The Toxic Hazards of Industrial and Occupational Chemicals

¹ This chapter and Table IV-3 were originally conceived and created by Frank J. Mycroft, PhD.

Basic information on the toxicity of many of the most commonly encountered and toxicologically significant industrial chemicals is provided in Table IV-3. The table is intended to expedite the recognition of potentially hazardous exposure situations and therefore provides information such as vapor pressures, warning properties, physical appearance, occupational exposure standards and guidelines, and hazard classification codes, which may also be useful in the assessment of an exposure situation. Table IV-3 is divided into three columns: health hazards, exposure guidelines, and comments. To use the table correctly, it is important to understand the scope and limitations of the information it provides.

The chemicals included in Table IV-3 were selected on the basis of the following criteria: (1) toxic potential, (2) prevalence of use, (3) public health concern, and (4) availability of adequate toxicologic, regulatory, and physical and chemical property information. Several governmental and industrial sources of information were used. Chemicals have been omitted when little to no toxicologic information could be found, when there are no regulatory standards, or when chemicals have very limited use. Chemicals that were of specific interest, those with existing exposure recommendations, and those of frequent use (even if of low toxicity) generally were included.

Health hazard information. The health hazards section of Table IV-3 focuses primarily on the basic hazards associated with possible inhalation or skin exposure to chemicals in the workplace, and is based predominantly on the extant occupational health literature. Indeed, much of our understanding of the potential effects of chemicals on human health is derived from occupational exposures, the levels of which are typically many times greater than those of environmental exposures. Moreover, the information in Table IV-3 emphasizes acute health effects. Much more is known about the acute effects of chemicals on human health than about their chronic effects. The rapid onset of symptoms after exposure makes the causal association more readily apparent for acute health effects. Nonetheless, table entries are also informed by nonoccupational human exposure data when relevant (eg, from outbreaks of consumer product exposures) and from experimental animal toxicology. The latter is critical to carcinogenesis assessment, a major chronic exposure endpoint in contradistinction to the acute exposure effects noted earlier.
1. The table is not a comprehensive source of the toxicology and medical information needed to manage a severely symptomatic or poisoned patient. Medical management information and advice for specific poisonings, where applicable, are found in Section I (see “Emergency Evaluation and Treatment,”, and “Decontamination,”) and Section II (see “Caustic and Corrosive Agents,”; “Gases, Irritant,”; and “Hydrocarbons,”).
2. Hydrocarbons, which are defined broadly as chemicals containing carbon and hydrogen, account for the majority of substances in Table IV-3. Hydrocarbons have a wide range of chemical structures and, not surprisingly, a variety of toxic effects. There are a few common features of hydrocarbon exposure, and the reader is directed to Section II, Hydrocarbons, for information on general diagnosis and treatment. Some common features of hydrocarbon toxicity include the following:
  1. Skin. Dermatitis caused by defatting or removal of oils in the skin is common, especially with prolonged contact. Some hydrocarbon agents also can cause frank chemical burns.
  2. Arrhythmias. Many hydrocarbons, most notably fluorinated, chlorinated, and aromatic compounds, can sensitize the heart to the arrhythmogenic effects of epinephrine, resulting in premature ventricular contractions (PVCs), ventricular tachycardia, or fibrillation. Even simple aliphatic compounds such as butane can have this effect.
    1. Because arrhythmias may not occur immediately, cardiac monitoring for 24 hours is recommended for all victims who have had significant hydrocarbon exposure (eg, associated with syncope or coma).
    2. Ventricular arrhythmias preferably are treated with a beta-adrenergic blocker (eg, esmolol or propranolol). The use of epinephrine and other catecholamines should be avoided in the acutely hydrocarbon intoxicated patient, as these can precipitate arrhythmia.
  3. Pulmonary aspiration of most hydrocarbons, especially those with relatively high volatility and low viscosity (eg, gasoline, kerosene, and naphtha), can cause severe chemical pneumonitis.
3. Carcinogens and Reproductive Hazards. To broaden the scope of the table, findings from human and animal studies relating to the carcinogenic or reproductive toxicity of a chemical are included when available. The International Agency for Research on Cancer (IARC) is the foremost authority in evaluating the carcinogenic potential of chemical agents for humans. The overall IARC evaluations are provided, when available, in the health hazards section of the table. The following IARC ratings are based primarily on human and animal data:
  1. IARC Group 1 substances are considered human carcinogens; generally, there is sufficient epidemiologic information to support a causal association between exposure and human cancer.
  2. IARC Group 2 compounds are suspected of being carcinogenic to humans, based on a combination of data from animal and human studies. IARC Group 2 is subdivided into two parts:
    1. An IARC 2A rating indicates that a chemical is probably carcinogenic to humans. Most often, there is limited evidence of carcinogenicity in humans combined with sufficient evidence of carcinogenicity in animals.
    2. IARC 2B indicates that a chemical is possibly carcinogenic to humans. This category may be used when there is limited evidence from epidemiologic studies and less than sufficient evidence for carcinogenicity in animals. It also may be used when there is inadequate evidence of carcinogenicity in humans and sufficient evidence in animals.
  3. IARC Group 3 substances cannot be classified in regard to their carcinogenic potential for humans because of inadequate data.
  4. IARC Group 4 substances are probably not carcinogenic to humans.
  5. If a chemical is described in the table as carcinogenic but an IARC category is not given, IARC may not have classified the chemical at all or other sources consider it carcinogenic.
  6. Substances identified as reproductive toxicants are suspected to lead to adverse outcomes in human pregnancy based on clinical reports, epidemiologic investigation, or experimental animal data.
4. Problems in assessing health hazards. The nature and magnitude of the health hazards associated with occupational or environmental exposures to any chemical depend on its intrinsic toxicity and the conditions of exposure.
  1. Characterization of these hazards is often difficult. Important considerations include the potency of the agent, route of exposure, level and temporal pattern of exposure, increased susceptibility (which may be genetic or due to other factors), overall health status, and lifestyle factors that may alter individual sensitivities (eg, alcohol consumption may cause “degreaser's flush” in workers exposed to trichloroethylene). Despite their value in estimating the likelihood and potential severity of an effect, quantitative measurements of the level of exposure associated with an adverse effect often are unavailable.
  2. Hazard characterizations cannot address undiscovered or unappreciated health effects. The limited information available on the health effects of most chemicals makes this a major concern. For example, among the millions of compounds known to science, only about 100,000 are listed in the Registry of the Toxic Effects of Chemical Substances (RTECS) published by the National Institute for Occupational Safety and Health (NIOSH). Of these substances, fewer than 5,000 have any toxicity studies relating to their potential tumorigenic or reproductive effects in animals or humans. Because of these gaps, the absence of information does not imply the absence of hazard.
  3. The predictive value of animal findings for humans is sometimes uncertain. For many effects, however, there is considerable concordance between test animals and humans.
  4. The developmental toxicity information presented in Table IV-3 is not a sufficient basis upon which to make clinical judgments regarding whether a given exposure may affect a pregnancy adversely. For most chemicals known to have adverse effects on fetal development in test animals, there are insufficient data in humans. In general, so little is known about the effects of substances on fetal development that it is prudent to manage all chemical exposures conservatively. The information here is presented solely to identify those compounds for which available data further indicate the need to control exposures.
Exposure guidelines
1. Threshold limit values (TLVs) are workplace exposure guidelines established by the American Conference of Governmental Industrial Hygienists (ACGIH), a professional nongovernmental organization. Although the ACGIH has no legally mandated regulatory authority, its recommendations are highly regarded and widely followed by the occupational health and safety community. The toxicologic basis for each TLV varies. A TLV may be based on such diverse effects as respiratory sensitization, sensory irritation, narcosis, or asphyxia, to list but a few adverse endpoints. The Documentation of the Threshold Limit Values and Biological Exposure Indices, which is published and regularly updated by the ACGIH and describes in detail the rationale for each value, should be consulted for specific information on the toxicologic significance of any particular TLV. Common units for a TLV are parts of a chemical per million parts of air (ppm) or milligrams of a chemical per cubic meter of air (mg/m³). At standard temperature and pressure, TLV values in ppm can be converted to their equivalent concentrations in mg/m³ by multiplying the TLV in ppm by the molecular weight (MW) in milligrams of the chemical and dividing the result by 22.4 (1 mole of gas displaces 22.4 L of air at standard temperature and pressure):
  1. The threshold limit value time-weighted average (TLV-TWA) refers to airborne contaminants and is the time-weighted average concentration to which, per ACGIH findings, workers may be exposed repeatedly during a normal 8-hour workday and 40-hour workweek without an adverse effect. Unless otherwise indicated in Table IV-3, the values listed under the ACGIH TLV heading are the TLV-TWAs. Note that work days longer than 8 hours even below the TLV could nonetheless constitute excessive exposure.
  2. The threshold limit value-ceiling (TLV-C) is the airborne concentration that should not be exceeded during any part of a working exposure. Ceiling guidelines often are set for rapidly acting agents for which an 8-hour time-weighted average exposure limit would be inappropriate. TLV-Cs are listed under the ACGIH TLV heading and are indicated by “(C).”
  3. The threshold limit value-short-term exposure limit (TLV-STEL) is a time-weighted average exposure that should not be exceeded over any 15-minute period and no more than 4 times in an 8-hour workday. The TLV-STEL is set to avoid irritation, chronic adverse effects, impaired work performance, or injury.
  4. Compounds for which skin contact is a significant route of exposure are designated with “S.” This can refer to potential local corrosive effects or systemic toxicity due to skin absorption.
2. Occupational Safety and Health Administration (OSHA) regulations are legally binding standards for exposure to airborne contaminants that are set and enforced by OSHA, an agency of the federal government.
  1. The permissible exposure limit (PEL) set by OSHA is closely analogous to the ACGIH TLV-TWA. In fact, when OSHA was established in 1971, it formally adopted the 1969 ACGIH TLVs for nearly all of its PELs. In 1988, OSHA updated the majority of its PELs by adopting the 1986 TLVs. These revised PELs were printed in the 1990 edition of this manual. However, in early 1993, the 1988 PEL revisions were voided as a result of legal challenges and the earlier (1969) values were restored. These restored values cannot be assumed to reliably protect worker health.
  2. Substances that are specifically regulated as carcinogens by OSHA are indicated by “OSHA CA.” For these carcinogens, additional regulations apply. The notation “NIOSH CA” identifies the chemicals that the National Institute for Occupational Safety and Health (NIOSH) recommends be treated as potential human carcinogens.
  3. Some states operate their own occupational health and safety programs in cooperation with OSHA. In these states, stricter standards may apply or the state may establish standards for a substance with no Federal OSHA PEL whatsoever. California, in particular, has several such standards—where relevant, these are referred to in Table IV-3.
  4. The NIOSH (nonlegally binding) corollary to the OSHA PEL is the recommended exposure limit (REL). For NIOSH RELs, the time-weighted average is the concentration for up to a 10-hour workday (as opposed to 8 hours for OSHA) during a 40-hour work. For NIOSH, a short-term exposure limit is generally a 15-minute TWA exposure that should not be exceeded at any time during a workday (but can be specified as even shorter). A NIOSH ceiling value is a level recommended not be exceeded at any time. There are many compounds for which the NIOSH REL is lower than the OSHA PEL. NIOSH RELs are generally close to the ACGIH TLVs. In Table IV-3, NIOSH RELs are presented only for selected compounds, in particular those where the REL is ten times less permissive than the corresponding PEL or where there is no PEL at all. A NIOSH table with exposure limits for 677 compounds can be accessed at http://www.cdc.gov/niosh/npg/pgintrod.html.
3. Immediately dangerous to life or health (IDLH) represents “a maximum concentration from which one could escape within 30 minutes without any escape-impairing symptoms or any irreversible health effects.” The IDLH values originally were set jointly by OSHA and NIOSH for the purpose of respirator selection. They have been updated subsequently by NIOSH.
4. Acute Exposure Guideline Levels (AEGLs) were developed by the National Academy of Sciences, and are intended to predict how members of the general public (including children and the elderly) would be affected if they are exposed to a particular hazardous chemical in an emergency response situation.
  1. AEGL-1 levels might produce notable discomfort, or irritation; however, the effects are expected to be transient and not disabling.
  2. AEGL-2 levels could produce irreversible or other serious, long-lasting effects or impair the ability to escape.
  3. AEGL-3 levels could cause life-threatening health effects or death.
  4. AEGLs have been calculated for each of 5 exposure periods: 10 minutes, 30 minutes, 1 hour, 4 hours, and 8 hours.
  5. Table IV-3 provides the 10-minute AEGL-3 for approximately 175 substances. For other time periods and exposure levels, see the EPA website https://www.epa.gov/aegl/about-acute-exposure-guideline-levels-aegls.
The “Comments” column of Table IV-3 provides supplementary information on the physical and chemical properties of substances that would be helpful in assessing their health hazards, including physical state and appearance, vapor pressures, warning properties, and potential breakdown products. It also includes, where applicable, a brief notation of common uses and exposure scenarios.
1. Information on the physical state and appearance of a compound may help in its identification and indicate whether dusts, mists, vapors, or gases are likely means of airborne exposure. Note: For many products, for example, pesticides, the appearance and some hazardous properties may vary with the formulation.
2. The vapor pressure of a substance helps determine its potential maximum air concentration and influences the degree of inhalation exposure or airborne contamination. Vapor pressures fluctuate greatly with temperature.
  1. Substances with high vapor pressures tend to volatilize more quickly and can reach higher maximum air concentrations than substances with low vapor pressures. Some substances have such low vapor pressures that airborne contamination is a threat only if they are mechanically or otherwise dispersed, for example, as an aerosol.
  2. A substance with a saturated air concentration below its TLV does not pose a significant vapor inhalation hazard (but this would be irrelevant to aerosol generation or skin exposure). Vapor pressure can be converted roughly to saturated air concentration expressed in parts per million by multiplying by a factor of 1,300. This is equivalent to dividing by 760 mm Hg and then multiplying the result by 1 million to adjust for the original unit of parts per million (a pressure of 1 atmosphere equals 760 mm Hg):
3. Warning properties such as odor and sensory irritation can be valuable indicators of exposure. However, because of olfactory fatigue and individual differences in odor thresholds, the sense of smell is often unreliable in detecting many compounds. There is no correlation between the quality of an odor and its toxicity. Pleasant-smelling compounds are not necessarily less toxic than foul-smelling ones.
  1. The warning property assessments in the table are based on OSHA evaluations. For the purpose of this manual, chemicals described as having good warning properties can be detected by smell or irritation at levels below the TLV by most individuals. Chemicals described as having adequate warning properties can be detected at air levels near the TLV. Chemicals described as having poor warning properties can be detected only at levels significantly above the TLV or not at all.
  2. Reported values for odor threshold in the literature vary greatly for many chemicals and are therefore frequently uncertain. These differences make assessments of warning qualities difficult.
4. Thermal breakdown products. Under fire conditions, many organic substances break down to other toxic substances. The amounts, kinds, and distribution of breakdown products vary with the fire conditions and are not easily modeled. Information on the likely thermal decomposition products is included because of their importance in the assessment of health hazards under fire conditions.
  1. In general, incomplete combustion of any organic material will produce some carbon monoxide.
  2. The partial combustion of compounds containing sulfur, nitrogen, or phosphorus atoms will also release their oxides (Nitrogen Oxides, and Phosphorus).
  3. Compounds with chlorine atoms will release some hydrogen chloride or chlorine when exposed to high temperatures or fire; some chlorinated compounds may also generate phosgene. Bromine-containing compounds can break down into hydrogen bromide and bromine, as well as other brominated byproducts.
  4. Compounds containing the fluorine atom are similarly likely to break down to yield some hydrogen fluoride or even more toxic fluorine-containing byproducts.
  5. Some compounds (eg, polyurethane) that contain an unsaturated carbon-nitrogen bond will release cyanide during decomposition.
  6. Polychlorinated aromatic compounds may yield polychlorinated dibenzodioxins and polychlorinated dibenzofurans (Dioxins) when heated.
  7. In addition, smoke from a chemical fire is likely to contain large amounts of the volatilized original chemical and still other well recognized (eg, acrolein) and poorly characterized products of partial breakdown.
  8. The thermal breakdown product information in Table IV-3 is derived primarily from data found in the literature and the general considerations described immediately above.
Summary.Table IV-3 provides basic information that describes the potential health hazards associated with exposure to several hundred chemicals. The table is not a comprehensive listing of all the possible health hazards for each chemical. The information compiled here comes from a wide variety of sources and focuses on the more likely or commonly reported health effects. The table is intended primarily to guide users in the quick qualitative assessment of common toxic hazards. Its application to specific situations requires skill. Contact a regional poison control center (1-800-222-1222) or medical toxicologist for expert assistance in managing specific emergency exposures.

TABLE IV-3. HEALTH HAZARD SUMMARIES FOR INDUSTRIAL AND OCCUPATIONAL CHEMICALS

IARC = International Agency for Research on Cancer overall classification: 1 = known human carcinogen; 2A = probable human carcinogen; 2B = possible human carcinogen; 3 = inadequate data available. TLV = American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value 8-hour time-weighted average (TLV-TWA) air concentration. ppm = parts of chemical per million parts of air. mg/m³ = milligrams of chemical per cubic meter of air. mppcf = million particles of dust per cubic foot of air. (C) = ceiling air concentration (TLV-C) that should not be exceeded at any time. (STEL) = Short-term (15-minute) exposure limit. S = Skin absorption can be significant route of exposure.		SEN = Potential for worker sensitization as a result of dermal contact or inhalation exposure. NIOSH CA = Judged by the National Institute for Occupational Safety and Health (NIOSH) to be a known or suspected human carcinogen. OSHA CA = Regulated by the Occupational Safety & Health Administration (OSHA) as an occupational carcinogen. IDLH = Immediately Dangerous to Life or Health air concentration. 10-min AEGL3 = EPA Acute Exposure Guideline Level. The 10-min AEGL3 is the air level likely to cause life-threatening effects or death after a 10-minute exposure.
Health Hazard Summaries	ACGIH TLV	IDLH	Comments
Acephate (AP, [CAS: 30560-19-1]): Widely available organophosphorus insecticide considered to have low mammalian toxicity. Metabolized extensively to methamidophos, which is more toxic.			White or transparent solid, soluble in water with a strong odor similar to mercaptan. Vapor pressure is 1.7 × 10^-6 mm Hg at 24°C.
Acetaldehyde (CAS: 75-07-0): Corrosive; severe burns to eyes and skin may occur. Vapors strongly irritating to eyes and respiratory tract; evidence for adverse effects on fetal development in animals. A carcinogen in test animals (IARC 2B). NIOSH CA.	25 ppm (C)	2,000 ppm	Colorless liquid. Fruity odor and irritation are both adequate warning properties. Vapor pressure is 750 mm Hg at 20°C (68°F). Highly flammable. Carcinogenicity associated with consumption of alcoholic beverages.
Acetic acid (vinegar acid [CAS: 64-19-7]): Concentrated solutions are corrosive; severe burns to eyes and skin may occur. Vapors strongly irritating to eyes and respiratory tract.	10 ppm	50 ppm	Colorless liquid. Pungent, vinegar-like odor and irritation both occur near the TLV and are adequate warning properties. Vapor pressure is 11 mm Hg at 20°C (68°F). Flammable.
Acetic anhydride (CAS: 108-24-7): Corrosive; severe burns to eyes and skin may result. Dermal sensitization has been reported. Vapors highly irritating to eyes and respiratory tract.	1 ppm	200 ppm	Colorless liquid. Odor and irritation both occur below the TLV and are good warning properties. Vapor pressure is 4 mm Hg at 20°C (68°F). Flammable. Evolves heat upon contact with water.
Acetone (dimethyl ketone, 2-propanone [CAS: 67-64-1]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels. Eye irritation and headache are common symptoms of moderate overexposure.	250 ppm	2,500 ppm	Colorless liquid with a sharp, aromatic odor. Eye irritation is an adequate warning property. Vapor pressure is 266 mm Hg at 25°C (77°F). Highly flammable.
Acetonitrile (methyl cyanide, cyanomethane, ethanenitrile [CAS: 75-05-8]): Vapors mildly irritating to eyes and respiratory tract. Inhibits several metabolic enzyme systems. Dermal absorption occurs. Metabolized to cyanide; fatalities have resulted. Symptoms include headache, nausea, vomiting, weakness, and stupor. Limited evidence for adverse effects on fetal development in test animals given large doses.	20 ppm, S	500 ppm 10-min AEGL3: 240 ppm	Colorless liquid. Ether-like odor, detectable at the TLV, is an adequate warning property. Vapor pressure is 73 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen and cyanide. May be found in products for removing sculptured nails.
Acetophenone (phenyl methyl ketone [CAS: 98-86-2]): Direct contact irritating to eyes and skin. A CNS depressant at high levels.	10 ppm		Widely used in industry (eg, textile coatings).
Acetylene [CAS: 74-86-2]: Compressed gas used in welding and cutting of metals; previously used as a general anesthetic in the 1920s. An explosive hazard and simple asphyxiant.			Colorless gas with a faint to garlic-like odor. NIOSH recommended exposure limit (REL) 2,500 ppm (ceiling).
Acetylene tetrabromide (tetrabromoethane [CAS: 79-27-6]): Direct contact is irritating to eyes and skin. Vapors irritating to eyes and respiratory tract. Dermal absorption occurs. Highly hepatotoxic; liver injury can result from low-level exposures.	0.1 ppm	8 ppm	Viscous, pale yellow liquid. Pungent, chloroform-like odor. Vapor pressure is less than 0.1 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen bromide and carbonyl bromide.
Acetylsalicyclic acid [CAS: 50-78-2] Skin and eye irritant. Systemic toxicity (see Salicylates).	5 mg/m³		Odorless, colorless to white, crystalline powder.
Acrolein (acryaldehyde, 2-propenal [CAS: 107-02-8]): Highly corrosive; severe burns to eyes or skin may result. Vapors extremely irritating to eyes, skin, and respiratory tract; pulmonary edema has been reported. Permanent pulmonary function changes may result; see Gases, Irritant (IARC 3).	0.1 ppm (C), S	2 ppm 10-min AEGL3: 6.2 ppm	Colorless to yellow liquid. Unpleasant odor. Eye irritation occurs at low levels and provides a good warning property. Formed in the pyrolysis of many substances. Vapor pressure is 214 mm Hg at 20°C (68°F). Highly flammable. Common combustion byproduct in fire smoke.
Acrylamide (propenamide, acrylic amide [CAS: 79-06-1]): Concentrated solutions are slightly irritating. Well absorbed by all routes. A potent neurotoxin causing peripheral neuropathy. Contact dermatitis also reported. Testicular toxicity in test animals. A carcinogen in test animals (IARC 2A), NIOSH CA.	0.03 mg/m³, S	60 mg/m³	Colorless solid. Vapor pressure is 0.007 mm Hg at 20°C (68°F). Not flammable. Decomposes around 80°C (176°F). Breakdown products include oxides of nitrogen. Monomer used in the synthesis of polyacrylamide plastics.
Acrylic acid (propenoic acid [CAS: 79-10-7]): Corrosive; severe burns may result. Vapors highly irritating to eyes, skin, and respiratory tract. Limited evidence of adverse effects on fetal development at high doses in test animals. Based on structural analogies, compounds containing the acrylate moiety may be carcinogens (IARC 3).	2 ppm, S		Colorless liquid with characteristic acrid odor. Vapor pressure is 31 mm Hg at 25°C (77°F). Flammable. Inhibitor added to prevent explosive self-polymerization. Odor threshold near 1 ppm.
Acrylonitrile (cyanoethylene, vinyl cyanide, propenenitrile [CAS: 107-13-1]): Direct contact can be strongly irritating to eyes and skin. Well absorbed by all routes. A CNS depressant at high levels. Metabolized to cyanide. Moderate acute overexposure will produce headache, weakness, nausea, and vomiting. Evidence of adverse effects on fetal development at high doses in animals. A carcinogen in test animals with limited epidemiologic evidence for carcinogenicity in humans (IARC 2B), OSHA CA. NIOSH CA.	2 ppm, S	85 ppm 10-min AEGL3: 130 ppm	Colorless liquid with a mild odor. Odor threshold near 10 ppm. Vapor pressure is 83 mm Hg at 20°C (68°F). Flammable. Polymerizes rapidly. Thermal decomposition products include hydrogen cyanide and oxides of nitrogen. Used in the manufacture of ABS (acrylonitrile butadiene styrene) and SAN (styrene acrylonitrile) resins.
Alachlor (CAS: 15972-60-8): Not an eye irritant. Slightly irritating to the skin. A skin sensitizer.	1 mg/m³, SEN		Widely used as an herbicide. Colorless crystals. Vapor pressure is 0.000022 mm Hg at 25°C (77°F).
Aldicarb (CAS: 116-06-3): A potent carbamate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed dermally. IARC 3.			Widely used pesticide whose systemic absorption by fruits has caused human poisonings.
Aldrin (CAS: 309-00-2):Chlorinated insecticide. Minor skin irritant. Convulsant. Hepatotoxin. Well absorbed dermally. Limited evidence for carcinogenicity in test animals (IARC 2A), NIOSH CA.	0.05 mg/m³, S	25 mg/m³	Tan to dark brown solid. A mild chemical odor. Vapor pressure is 0.000006 mm Hg at 20°C (68°F). Not flammable but breaks down, yielding hydrogen chloride gas. Most uses have been banned in the US.
Allyl alcohol (2-propen-1-ol [CAS: 107-18-6]): Strongly irritating to eyes and skin; severe burns may result. Vapors highly irritating to eyes and respiratory tract. Systemic poisoning can result from dermal exposures. May cause liver and kidney injury.	0.5 ppm, S	20 ppm 10-min AEGL3: 87 ppm	Colorless liquid. Mustard-like odor and irritation occur near the TLV and serve as good warning properties. Vapor pressure is 17 mm Hg at 20°C (68°F). Flammable. Used in chemical synthesis and as a pesticide.
Allyl chloride (3-chloro-1-propene [CAS: 107-05-1]): Highly irritating to eyes, skin and respiratory tract. Well absorbed by the skin, producing both superficial and penetrating irritation and pain. Causes liver and kidney injury and neurotoxicity in test animals. Chronic exposures have been associated with reports of human peripheral neuropathy (IARC 3).	1 ppm, S	250 ppm	Colorless, yellow, or purple liquid. Pungent, disagreeable odor and irritation occur only at levels far above the TLV. Vapor pressure is 295 mm Hg at 20°C (68°F). Highly flammable. Breakdown products include hydrogen chloride and phosgene. Used as a chemical intermediate and in the synthesis of epichlorohydrin and glycerin.
Allyl glycidyl ether (AGE [CAS: 106-92-3]): Highly irritating to eyes and skin; severe burns may result. Vapors irritating to eyes and respiratory tract. Sensitization dermatitis has been reported. Hematopoietic and testicular toxicity occurs in test animals at modest doses. Well absorbed through the skin.	1 ppm	50 ppm	Colorless liquid. Unpleasant odor. Vapor pressure is 2 mm Hg at 20°C (68°F). Flammable. California OSHA PEL is 0.2 ppm.
Allyl propyl disulfide (onion oil [CAS: 2179-59-1]): Mucous membrane irritant and lacrimator.	0.5 ppm, SEN		Liquid with a pungent, irritating odor. A synthetic flavorant and food additive. Thermal breakdown products include sulfur oxide fumes.
alpha-Alumina (aluminum oxide [CAS: 1344-28-1]): Irritant dust with suspected fibrogenic potential; nanoparticles may have additional effects.	1 mg/m³		“McIntyre's powder,” predominantly aluminum oxide, was formerly administered intentionally as an inhalant to silica-exposed miners to prevent lung disease but was later discontinued for lack of efficacy.
Aluminum metal (CAS: 7429-90-5): Dusts can cause mild eye and respiratory tract irritation. Long-term inhalation of large amounts of fine aluminum powders or fumes from aluminum ore (bauxite) has been associated with reports of pulmonary fibrosis (Shaver disease). Acute exposures in aluminum refining (“pot room”) have been associated with asthma-like responses. Industrial processes used to produce aluminum have been associated with an increased incidence of cancer in workers. Nonoccupational exposure with renal insufficiency is associated with potential neurotoxicity.	1 mg/m³		Oxidizes readily. Fine powders and flakes are flammable and explosive when mixed with air. Reacts with acids and caustic solutions to produce flammable hydrogen gas. Bauxite ore can contain trace beryllium.
Aluminum phosphide (CAS: 20859-73-8): Effects caused by phosphine gas that is produced on contact with moisture. Severe respiratory tract irritant. See “Phosphides,”.		10-min AEGL3: 7.2 ppm	Used as a structural fumigant (including in dwellings, silos, boxcars) as dry powder or pellet, similar to zinc phosphide. Bystander exposures can occur.
4-Aminodiphenyl (p-aminobiphenyl, p-phenylaniline [CAS: 92-67-1]): Causes methemoglobinemia. Potent bladder carcinogen in humans (IARC 1). OSHA CA. NIOSH CA.	S		Colorless crystals. Formerly used as a rubber antioxidant and as a dye intermediate. Present in cigarette smoke.
2-Aminopyridine (CAS: 504-29-0): Mild irritant. Potent CNS convulsant in humans. Very well absorbed by inhalation and skin contact. Signs and symptoms include headache, dizziness, nausea, elevated blood pressure, and convulsions.	0.5 ppm	5 ppm	Colorless solid with a distinctive odor and a very low vapor pressure at 20°C (68°F). Combustible. Much of the human experience is derived from its use as a pharmaceutical treatment in selected neurologic conditions.
Amitrole (3-amino-1,2,4-triazole [CAS: 61-82-5]): Mild irritant. Well absorbed by inhalation and skin contact. Overexposure can cause acute lung injury. Shows antithyroid activity in test animals. Evidence of adverse effects on fetal development in test animals at high doses. A carcinogen in test animals (IARC 3), NIOSH CA.	0.2 mg/m³		Used as an herbicide. Crystalline solid. Appearance and some hazardous properties vary with the formulation.
Ammonia (CAS: 7664-41-7): Corrosive; severe burns to eyes and skin result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema has been reported. Severe responses are associated with anhydrous ammonia or with concentrated ammonia solutions.	25 ppm	300 ppm 10-min AEGL3: 2,700 ppm	Colorless gas or aqueous solution. Pungent odor and irritation are good warning properties. Anhydrous ammonia is flammable. Breakdown products include oxides of nitrogen. Although widely used in industry, concentrated forms are most frequently encountered in agriculture and from its use as a refrigerant.
Ammonium chloride (CAS: 12125-02-9): Skin, eye, and respiratory tract irritant.	10 mg/m³		Finely divided, odorless, white particulate. Decomposes on heating or burning, producing toxic and irritating fumes (nitrogen oxides, ammonia and hydrogen chloride). A large amount of fume may be generated in galvanizing operations.
n-Amyl acetate (CAS: 628-63-7): Defats the skin, producing a dermatitis. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at very high levels. Reversible liver and kidney injury may occur at very high exposures.	50 ppm	1,000 ppm	Colorless liquid. Its banana-like odor, detectable below the TLV, is a good warning property. Vapor pressure is 4 mm Hg at 20°C (68°F). Flammable.
sec-Amyl acetate (alpha-methylbutyl acetate [CAS: 626-38-0]): Defats the skin, producing a dermatitis. Vapors irritating to eyes and respiratory tract. A CNS depressant at very high levels. Reversible liver and kidney injury may occur at high-level exposures.	50 ppm	1,000 ppm	Colorless liquid. A fruity odor occurs below the TLV and is a good warning property. Vapor pressure is 7 mm Hg at 20°C (68°F). Flammable.
Aniline (aminobenzene, phenylamine [CAS: 62-53-3]): Mildly irritating to eyes upon direct contact, with corneal injury possible. Potent inducer of methemoglobinemia. Well absorbed via inhalation and dermal routes. Limited evidence of carcinogenicity in test animals (IARC 2A), NIOSH CA.	2 ppm, S	100 ppm 10-min AEGL3: 120 ppm	Colorless to brown viscous liquid. Distinctive amine odor and mild eye irritation occur well below the TLV and are good warning properties. Vapor pressure is 0.6 mm Hg at 20°C (68°F). Combustible. Breakdown products include oxides of nitrogen.
o-Anisidine (o-methoxyaniline [CAS: 29191-52-4]): Mild skin sensitizer causing dermatitis. Causes methemoglobinemia. Well absorbed through skin. Headaches and vertigo are signs of exposure. Possible liver and kidney injury. A carcinogen in test animals (IARC 2B), NIOSH CA.	0.5 mg/m³, S	50 mg/m³	Colorless, red, or yellow liquid with the fishy odor of amines. Vapor pressure is less than 0.1 mm Hg at 20°C (68°F). Combustible. Primarily used in the dyestuffs industry.
Antimony and salts (antimony trichloride, antimony pentachloride [CAS: 7440-36-0]): Dusts and fumes irritating to eyes, skin, and respiratory tract. Toxicity through contamination with silica or arsenic may occur. Antimony trioxide (CAS: 1309-64-4) is carcinogenic in test animals, with limited evidence for carcinogenicity among antimony trioxide production workers (IARC 2B). See also Antimony and Stibine.	0.5 mg/m³ (as Sb)	50 mg/m³ (as Sb)	The metal is silver-white and has a very low vapor pressure. Some chloride salts release HCl upon contact with air.
ANTU (alpha-naphthylthiourea [CAS: 86-88-4]): Well-absorbed by skin contact and inhalation. Pulmonary edema and liver injury may result from ingestion. Repeated exposures can injure the thyroid and adrenals. Possible trace contamination with alpha₂-naphthylamine, a suspected carcinogen (IARC 3).	0.3 mg/m³, S	100 mg/m³	Colorless to gray solid powder. Odorless. A rodenticide. Breakdown products include oxides of nitrogen and sulfur dioxide.
Argon (CAS: 7440-37-1): Simple asphyxiant.			Inert gas that is colorless, odorless, and heavier than air. Bulk displacement of oxygen could occur in a confined space release.
Arsenic (CAS: 7440-38-2): Irritating to eyes and skin; hyperpigmentation, hyperkeratoses, and skin cancers have been described. A general cellular poison. May cause bone marrow suppression, peripheral neuropathy, and gastrointestinal, liver, and cardiac injury. Some arsenic compounds have adverse effects on fetal development in test animals. Exposure linked to skin, respiratory tract, and liver cancer in workers (IARC 1), OSHA CA, NIOSH CA. See also Arsenic.	0.01 mg/m³ (as As)	5 mg/m³ (as As)	Elemental forms vary in appearance. Crystals are gray. Amorphous forms may be yellow or black. Vapor pressure is very low—about 1 mm Hg at 372°C (701°F).
Arsine (CAS: 7784-42-1): Extremely toxic hemolytic agent. Symptoms include abdominal pain, jaundice, hemoglobinuria, and renal failure. Low-level chronic exposures reported to cause anemia. See also Arsine. NIOSH CA.	0.005 ppm	3 ppm 10-min AEGL3: 0.91 ppm	Colorless gas with an unpleasant garlic-like odor. Flammable. Breakdown products include arsenic trioxide and arsenic fumes. Used in the semiconductor industry and also produced as a byproduct in metal refining or when arsenic is treated with acids.
Asbestos (chrysotile, amosite, crocidolite, tremolite, anthophyllite): Effects of exposure include asbestosis (fibrosis of the lung), lung cancer, mesothelioma, and possible digestive tract cancer (IARC 1). Signs of toxicity are usually delayed at least 15-30 years. OSHA CA, NIOSH CA. See also Asbestos.	0.1 fibers per cm³ (respirable fibers)		Exposure can occur not only through the primary use of asbestos but also through deconstruction and demolition work at prior asbestos use sites.
Asphalt fumes (CAS: 8052-42-4): Vapors and fumes irritating to eyes, skin, and respiratory tract. Skin contact can produce hyperpigmentation, dermatitis, or photosensitization. Some constituents are carcinogenic in test animals (IARC 2B), NIOSH CA.	0.5 mg/m³		Smoke with an acrid odor. Asphalt is a complex mixture of parrafinic, aromatic, and heterocyclic hydrocarbons formed by the evaporation of lighter hydrocarbons from petroleum and the partial oxidation of the residue.
Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine [CAS: 1912-24-9]): Skin and eye irritant. IARC 3.	2 mg/m³		Colorless crystals with a negligible vapor pressure. Slightly sensitive to light. The most heavily used triazine herbicide.
Azinphos-methyl (Guthion [CAS: 86-50-0]): Low-potency organophosphate anticholinesterase insecticide (Organophosphorus and Carbamate Insecticides).	0.2 mg/m³, S, SEN	10 mg/m³	Brown, waxy solid with a negligible vapor pressure. Not combustible. Breakdown products include sulfur dioxide, oxides of nitrogen, and phosphoric acid.
Barium and soluble compounds (CAS: 7440-39-3): Powders irritating to eyes, skin, and respiratory tract. Although not typical of workplace exposures, ingestion of soluble barium salts (as opposed to the insoluble medical compounds used in radiography) is associated with muscle paralysis. See also Barium.	0.5 mg/m³ (as Ba)	50 mg/m³ (as Ba)	Most soluble barium compounds (eg, barium chloride, barium carbonate) are odorless white solids. Elemental barium spontaneously ignites on contact with air and reacts with water to form flammable hydrogen gas. Barium carbonate is a rodenticide; barium styphnate is an explosive propellant.
Benomyl (methyl 1-[butylcarbamoyl]-2-benzimidazo-lecarbamate, Benlate [CAS: 17804-35-2]): A carbamate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Mildly irritating to eyes and skin. Of low systemic toxicity in test animals by all routes. Evidence of adverse effects on fetal development in test animals.	1 mg/m³, SEN		White crystalline solid with a negligible vapor pressure at 20°C (68°F). Fungicide and miticide. Appearance and some hazardous properties vary with the formulation.
Benzene (CAS: 71-43-2): Vapors mildly irritating to eyes and respiratory tract. Well-absorbed by all routes. A CNS depressant at high levels. Symptoms include headache, nausea, tremors, cardiac arrhythmias, and coma. Chronic exposure is causally associated with hematopoietic system depression, aplastic anemia, and leukemia (IARC 1), OSHA CA, NIOSH CA. See also Benzene.	0.5 ppm, S	500 ppm	Colorless liquid. Aromatic hydrocarbon odor near 50 ppm. Vapor pressure is 75 mm Hg at 20°C (68°F). Flammable. The generic term “benzine” is often used for gasoline or gasoline-like solvents and may not equate with benzene-containing materials.
Benzidine (p-diaminodiphenyl [CAS: 92-87-5]): Extremely well absorbed by inhalation and through skin. Causes bladder cancer in exposed workers (IARC 1), OSHA CA, NIOSH CA.	S		White or reddish solid crystals. Breakdown products include oxides of nitrogen. Found in dyestuffs, rubber industry, and analytic laboratories.
Benzoyl peroxide (CAS: 94-36-0): Dusts cause skin, eye, and respiratory tract irritation. A skin sensitizer. IARC 3.	5 mg/m³	1,500 mg/m³	White granules or crystalline solids with a very faint odor. Vapor pressure is negligible at 20°C (68°F). Strong oxidizer, reacting with combustible materials. Decomposes at 75°C (167°F). Unstable and explosive at high temperatures.
Benzyl chloride (alpha-chlorotoluene, [chloromethyl] benzene [CAS: 100-44-7]): Highly irritating to skin and eyes. A potent lacrimator. Vapors highly irritating to respiratory tract. Symptoms include weakness, headache, and irritability. May injure liver. Limited evidence for carcinogenicity and adverse effects on fetal development in test animals (IARC 2A).	1 ppm	10 ppm	Colorless liquid with a pungent odor near 1 ppm. Vapor pressure is 0.9 mm Hg at 20°C (68°F). Combustible. Breakdown products include phosgene and hydrogen chloride.
Beryllium (CAS: 7440-41-7): Very high acute exposure to dusts and fumes causes eye, skin, and respiratory tract irritation. More importantly, chronic low-level exposure to beryllium oxide dusts can produce an interstitial lung disease (berylliosis or chronic beryllium disease), a sarcoid-like condition that also can have extrapulmonary manifestations. Carcinogen in test animals. Limited evidence of carcinogenicity in humans (IARC 1), NIOSH CA.	0.00005 ppm S, SEN	4 mg/m³ (as Be)	Silver-white metal or dusts. Reacts with some acids to produce flammable hydrogen gas. Exposures have occurred in nuclear and aerospace workers; may be present in any specialty metal alloy or metal ceramic manufacturing process; trace amounts naturally occur in bauxite, leading to exposure in aluminum smelting; dental technicians may also be exposed.
Biphenyl (diphenyl [CAS: 92-52-4]): Fumes mildly irritating to eyes. Chronic overexposures can cause bronchitis and liver injury. Peripheral neuropathy and CNS injury have also been reported.	0.2 ppm	100 mg/m³	White crystals. Unusual but pleasant odor. Combustible. Previously used as antimold treatment for paper (eg, in wrapping citrus). An outbreak of parkinsonism has been reported in this context.
Bisphenol A (BPA [CAS: 80-05-7]): Chronic exposure through food and environmental contamination may cause adverse reproductive and developmental effects, potentially as an “endocrine disruptor.” NIOSH CA.			Widely used industrially as a starting material for carbonate plastics, in the formulation of epoxy resins, and as an additive to other plastics. Exposure occurs through migration of residual unreacted BPA.
Borates (anhydrous sodium tetraborate, borax [CAS: 1303-96-4]): Contact with dusts is highly irritating to eyes, skin, and respiratory tract. Contact with tissue moisture may cause thermal burns because hydration of borates generates heat. See also Boric Acid, Borates, and Boron.	2 mg/m³		White or light gray solid crystals. Odorless.
Boron oxide (boric anhydride, boric oxide [CAS: 1303-86-2]): Contact with moisture generates boric acid. Direct eye or skin contact with dusts is irritating. Occupational inhalation exposure has caused respiratory tract irritation. Evidence for adverse effects on the testes in animals.	10 mg/m³	2,000 mg/m³	Colorless glassy granules, flakes, or powder. Odorless. Not combustible.
Boron tribromide (CAS: 10294-33-4): Corrosive; decomposed by tissue moisture to hydrogen bromide and boric acid. Severe skin and eye burns may result from direct contact. Vapors highly irritating to eyes and respiratory tract.	1 ppm (C)	10-min AEGL3: 250 ppm	Colorless fuming liquid. Reacts with water, forming hydrogen bromide and boric acid. Vapor pressure is 40 mm Hg at 14°C (57°F).
Boron trifluoride (CAS: 7637-07-2): Corrosive; decomposed by tissue moisture to hydrogen fluoride and boric acid. Severe skin and eye burns may result. Vapors highly irritating to eyes, skin, and respiratory tract.	0.7 ppm (C)	25 ppm 10-min AEGL3: 110 mg/m³	Colorless gas. Odor threshold near 2 mg/m³. Dense, white, irritating fumes produced on contact with moist air. These fumes contain boric acid and hydrogen fluoride.
Bromine (CAS: 7726-95-6): Corrosive; severe skin and eye burns may result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema may result. Measles-like eruptions may appear on the skin several hours after a severe exposure.	0.1 ppm	3 ppm 10-min AEGL3: 19 ppm	Heavy red-brown fuming liquid. Odor and irritation thresholds are below the TLV and are adequate warning properties. Vapor pressure is 175 mm Hg at 20°C (68°F). Not combustible. Used as an alternative to chlorine in water purification (eg, hot tubs).
Bromine pentafluoride (CAS: 7789-30-2): Corrosive; severe skin and eye burns may result. Vapors extremely irritating to eyes and respiratory tract. Chronic overexposures caused severe liver and kidney injury in test animals.	0.1 ppm	10-min AEGL3: 79 ppm	Pale yellow liquid. Pungent odor. Not combustible. Highly reactive, igniting most organic materials and corroding many metals. Highly reactive with acids. Breakdown products include bromine and fluorine.
Bromoform (tribromomethane [CAS: 75-25-2]): Vapors highly irritating to eyes and respiratory tract. Well absorbed by inhalation and skin contact. CNS depressant. Liver and kidney injury may occur. Two preliminary tests indicate that it may be an animal carcinogen (IARC 3).	0.5 ppm	850 ppm	Colorless to yellow liquid. Chloroform-like odor and irritation are adequate warning properties. Vapor pressure is 5 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen bromide and bromine.
1-Bromopropane (n-propyl bromide, 1-BP [CAS: 106-94-5]): Experimental reproductive and hepatotoxin. Human neurotoxin. A carcinogen in test animals (IARC 2B).	0.1 ppm	46,000 ppm	Vapor pressure is 111 mm Hg at 25°C (77°F). Used as alternative to ozone-depleting solvents in dry cleaning and spray adhesives. Documented neurotoxicity following occupational exposure in adhesive use.
1,3-Butadiene (CAS: 106-99-0): Vapors mildly irritating. A CNS depressant at very high levels. Evidence of adverse effects on reproductive organs and fetal development in test animals. A very potent carcinogen in test animals; evidence of carcinogenicity in exposed workers (IARC 1), OSHA CA, NIOSH CA.	2 ppm	20,000 ppm	Colorless gas. Mild aromatic odor is a good warning property. Readily polymerizes. Inhibitor added to prevent peroxide formation. Used in the formation of styrene-butadiene and ABS (acrylonitrile butadiene styrene) plastics. California OSHA PEL is 1 ppm.
2-Butoxyethanol (ethylene glycol monobutyl ether, butyl cellosolve [CAS: 111-76-2]): Liquid very irritating to eyes and slightly irritating to skin. Vapors irritating to eyes and respiratory tract. Mild CNS depressant. A hemolytic agent in test animals. Well absorbed dermally. Liver and kidney toxicity in test animals. Reproductive toxicity much less than that of certain other glycol ethers, such as ethylene glycol monomethyl ether. See also Ethylene Glycol and Other Glycols. IARC 3.	20 ppm	700 ppm	Colorless liquid with a mild ether-like odor. Irritation occurs below the TLV and is a good warning property. Vapor pressure is 0.6 mm Hg at 20°C (68°F). Flammable.
n-Butyl acetate (CAS: 123-86-4): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Limited evidence for adverse effects on fetal development in test animals.	150 ppm (proposed 50 ppm)	17,000 ppm	Colorless liquid. Fruity odor is a good warning property. Vapor pressure is 10 mm Hg at 20°C (68°F). Flammable.
sec-Butyl acetate (2-butanol acetate [CAS: 105-46-4]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	200 ppm (proposed 50 ppm)	1,700 ppm
tert-Butyl acetate (tert-butyl ester of acetic acid [CAS: 540-88-5]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	200 ppm (proposed 50 ppm)	1,500 ppm
n-Butyl acrylate (CAS: 141-32-2): Highly irritating to skin and eyes; corneal necrosis may result. Vapors highly irritating to eyes and respiratory tract. Based on structural analogies, compounds containing the acrylate moiety may be carcinogens (IARC 3).	2 ppm, SEN		Colorless liquid. Odor threshold near 0.05 ppm. Vapor pressure is 3.2 mm Hg at 20°C (68°F). Flammable. Contains inhibitor to prevent polymerization.
n-Butyl alcohol (CAS: 71-36-3): Irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at very high levels. Chronic occupational overexposures associated with hearing loss and vestibular impairment.	20 ppm	1,400 ppm	Colorless liquid. Strong odor and irritation occur below the TLV and are both good warning properties. Flammable.
sec-Butyl alcohol (CAS: 78-92-2): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels.	100 ppm	2,000 ppm	Colorless liquid. Pleasant odor occurs well below the TLV and is an adequate warning property. Vapor pressure is 13 mm Hg at 20°C (68°F). Flammable.
tert-Butyl alcohol (CAS: 75-65-0): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels.	100 ppm	1,600 ppm	Colorless liquid. Camphor-like odor and irritation occur slightly below the TLV and are good warning properties. Vapor pressure is 31 mm Hg at 20°C (68°F). Flammable.
n-Butylamine (CAS: 109-73-9): Caustic alkali. Liquid highly irritating to eyes and skin upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract. May cause histamine release.	5 ppm (C), S	300 ppm	Colorless liquid. Ammonia-like or fishlike odor occurs below the TLV and is an adequate warning property. Vapor pressure is about 82 mm Hg at 20°C (68°F). Flammable.
tert-Butyl chromate (CAS: 1189-85-1): Liquid highly irritating to eyes and skin; severe burns may result. Vapors or mists irritating to eyes and respiratory tract. A liver and kidney toxin. By analogy to other Cr VI compounds, a possible carcinogen. No IARC evaluation, NIOSH CA. See Chromium.	0.1 mg/m³ (C) (as CrO₃), S	15 mg/m³ (as Cr VI)	Liquid. Reacts with moisture.
n-Butyl glycidyl ether (BGE, glycidylbutylether, 1,2-epoxy-3-butoxy propane [CAS: 2426-08-6]): Liquid irritating to eyes and skin. Vapors irritating to the respiratory tract and cause GI distress. A CNS depressant. Causes sensitization dermatitis upon repeated exposures. Testicular atrophy and hematopoietic injury at modest doses in test animals. IARC 2B.	3 ppm, S, SEN	250 ppm	Colorless liquid. Vapor pressure is 3 mm Hg at 20°C (68°F). Used in epoxy formulations.
n-Butyl lactate (CAS: 138-22-7): Vapors irritating to eyes and respiratory tract. Workers have complained of sleepiness, headache, coughing, nausea, and vomiting.	5 ppm		Colorless liquid. Vapor pressure is 0.4 mm Hg at 20°C (68°F). Combustible.
n-Butyl mercaptan (butanethiol [CAS: 109-79-5]): Vapors mildly irritating to eyes and respiratory tract. Pulmonary edema occurred at high exposure levels in test animals. A CNS depressant at very high levels. Limited evidence for adverse effects on fetal development in test animals at high doses.	0.5 ppm	500 ppm	Colorless liquid. Strong, offensive, garlic-like odor. Vapor pressure is 35 mm Hg at 20°C (68°F). Flammable.
*o-sec-Butylphenol (CAS: 89-72-5):* Irritating to skin upon direct, prolonged contact; burns have resulted. Vapors mildly irritating to eyes and respiratory tract.	5 ppm, S		A liquid.
*p-tert-Butyltoluene (CAS: 98-51-1):* Mild skin irritant upon direct contact. Defatting agent causing dermatitis. Vapors irritating to eyes and respiratory tract. A CNS depressant. Limited evidence of adverse effects on fetal development in test animals at high doses.	1 ppm	100 ppm	Colorless liquid. Gasoline-like odor and irritation occur below the TLV and are both good warning properties. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Combustible.
gamma-Butyrolactone (CAS: 96-48-0): Because of metabolism to gamma-hydroxybutyric acid (GHB), CNS and respiratory depression may occur. IARC 3.			Industrial solvent. Contained in some “acetone-free” nail polish removers (now restricted in US because it is a GHB precursor). Vapor pressure 1.5 mm Hg at 20°C (68°F).
Cadmium and compounds (CAS 7440-43-9): Acute fumes and dust exposures can injure the respiratory tract; pulmonary edema can occur. Chronic exposures associated primarily with kidney injury and lung injury. Adverse effects on the testes and on fetal development in test animals. Cadmium and some of its compounds are carcinogenic in test animals. Limited direct evidence for carcinogenicity in humans (IARC 1), OSHA CA, NIOSH CA. See also Cadmium.	0.01 mg/m³ (total dust, as Cd), 0.002 mg/m³ (respirable dust)	9 mg/m³ (dust and fumes, as Cd)	Compounds vary in color. Give off fumes when heated or burned. Generally poor warning properties. Metal has a vapor pressure of about 1 mm Hg at 394°C (741°F) and reacts with acids to produce flammable hydrogen gas. “Silver solder” typically contains cadmium. California OSHA PEL is 0.005 mg/m³.
Calcium cyanamide (calcium carbimide, lime nitrogen [CAS: 156-62-7]): Dusts highly irritating to eyes, skin, and respiratory tract. Causes sensitization dermatitis. Systemic symptoms include nausea, fatigue, headache, chest pain, and shivering. A disulfiram-like interaction with alcohol,“cyanamide flush,” may occur in exposed workers.	0.5 mg/m³		Gray crystalline material. Reacts with water, generating ammonia and flammable acetylene. In addition to industrial exposure, used as a pharmaceutical alcohol aversive agent.
Calcium hydroxide (hydrated lime, caustic lime [CAS: 1305-62-0]):Corrosive; severe eye and skin burns may result. Dusts moderately irritating to eyes and respiratory tract.	5 mg/m³		White, deliquescent crystalline powder. Odorless.
Calcium oxide (lime, quicklime, burnt lime [CAS: 1305-78-8]):Corrosive. Exothermic reactions with moisture. Highly irritating to eyes and skin upon direct contact. Dusts highly irritating to skin, eyes, and respiratory tract.	2 mg/m³	25 mg/m³	White or gray solid powder. Odorless. Hydration generates heat.
Camphor, synthetic (CAS: 76-22-2): Irritating to eyes and skin upon direct contact. Vapors irritating to eyes and nose; may cause loss of sense of smell. A convulsant at higher doses. See also Camphor and Other Essential Oils.	2 ppm	200 mg/m³	Colorless, glassy solid. Sharp, obnoxious, aromatic odor near the TLV is an adequate warning property. Vapor pressure is 0.18 mm Hg at 20°C (68°F). Combustible.
Caprolactam (CAS: 105-60-2): Highly irritating to eyes and skin upon direct contact. Vapors, dusts, and fumes highly irritating to eyes and respiratory tract. Convulsant activity in test animals. IARC 3.	5 mg/m³		White solid crystals. Unpleasant odor. Vapor pressure is 6 mm Hg at 120°C (248°F). Thermal breakdown products include oxides of nitrogen. Used in the production of Nylon 6; off-gassing of caprolactam from the polymerized product can be detected.
Captafol (Difolatan [CAS: 2425-06-1]): Dusts irritating to eyes, skin, and respiratory tract. A skin and respiratory tract sensitizer. May cause photoallergy dermatitis. Evidence for carcinogenicity in animal tests (IARC 2A), NIOSH CA.	0.1 mg/m³, S		White solid crystals. Distinctive, pungent odor. Fungicide. Thermal breakdown products include hydrogen chloride and oxides of nitrogen or sulfur.
Carbaryl (1-naphthyl N-methylcarbamate, sevin [CAS: 63-25-2]): A carbamate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Evidence of adverse effects on fetal development in test animals at high doses. IARC 3.	0.5 mg/m³, S	100 mg/m³	Colorless, white or gray solid. Odorless. Vapor pressure is 0.005 mm Hg at 20°C (68°F). Breakdown products include oxides of nitrogen and methylamine.
Carbofuran (2,3-dihydro-2,2'-dimethyl-7-benzofuranylmethyl-carbamate, Furadan [CAS: 1563-66-2]): A carbamate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Not well absorbed by skin contact.	0.1 mg/m³		White solid crystals. Odorless. Vapor pressure is 0.00005 mm Hg at 33°C (91°F). Thermal breakdown products include oxides of nitrogen.
Carbon black (CAS: 1333-86-4): Causes eye and respiratory irritation. A lung carcinogen in test animals (IARC 2B), NIOSH CA.	3 mg/m³		Extremely fine powdery forms of elemental carbon; may have adsorbed polycyclic organic hydrocarbons.
Carbon dioxide (carbonic acid, dry ice [CAS: 124-38-9]): Acute asphyxiant and CNS depressant. Exposure to high levels can produce tachypnea, shortness of breath, headache and other neurologic symptoms and signs, including coma.	5,000 ppm	40,000 ppm	Colorless, odorless gas. Nonflammable. Heavier than air. Exposure can occur through natural sources (geologic, including coal mines) and through man-made activities (industrial fermentation, dry ice sublimation). Enclosed space hazard.
Carbon disulfide (CAS: 75-15-0): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant causing coma at high concentrations. Well absorbed by all routes. Acute symptoms include headache, dizziness, nervousness, and fatigue. Neuropathies, parkinsonian syndromes, and psychosis may occur. A liver and kidney toxin. An atherogenic agent causing stroke and heart disease. Adversely affects male and female reproductive systems in test animals and humans. Evidence for adverse effects on fetal development in test animals. See also Carbon Disulfide.	1 ppm, S	500 ppm 10-min AEGL3: 600 ppm	Colorless to pale yellow liquid. Disagreeable odor occurs below the TLV and is a good warning property. Vapor pressure is 300 mm Hg at 20°C (68 F). Highly flammable. Major use is in viscose manufacture but is also used in chemical synthesis and as an industrial solvent. It was used in the past as an agricultural fumigant. It is one of the environmental breakdown products of the agricultural chemical metam sodium and is a metabolite of the pharmaceutical disulfiram.
Carbon monoxide (CAS: 630-08-0): Binds to hemoglobin, forming carboxyhemoglobin and causing cellular hypoxia. Persons with heart disease are more susceptible. Signs and symptoms include headache, dizziness, coma, and convulsions. Permanent CNS impairment and adverse effects on fetal development may occur after severe poisoning. See also Carbon Monoxide.	25 ppm	1,200 ppm 10-min AEGL3: 1,700 ppm	Colorless, odorless gas. No warning properties. Important sources of exposure include the indoor use of internal combustion engines, structural fires, and faulty space heaters. It is also an ambient air criteria pollutant regulated by the US Environmental Protection Agency. The solvent methlylene chloride and the antiseptic iodoform are both metabolized to carbon monoxide.
Carbon tetrabromide (tetrabromomethane [CAS: 558-13-4]): Highly irritating to eyes upon direct contact. Vapors highly irritating to eyes and respiratory tract. The liver and kidneys are also likely target organs.	0.1 ppm		White to yellow-brown solid. Vapor pressure is 40 mm Hg at 96°C (204°F). Nonflammable; thermal breakdown products may include hydrogen bromide and bromine.
Carbon tetrachloride (tetrachloromethane [CAS 56-23-5]): Mildly irritating upon direct contact. A CNS depressant. May cause cardiac arrhythmias. Highly toxic to kidney and liver. Alcohol abuse increases risk for liver toxicity. A carcinogen in test animals (IARC 2B), NIOSH CA. See also Carbon Tetrachloride and Chloroform.	5 ppm, S	200 ppm 10 min AEGL3: 700 ppm	Colorless. Ether-like odor is a poor warning property (odor threshold is near 20 ppm). Vapor pressure is 91 mm Hg at 20°C (68°F). Not combustible. Breakdown products include hydrogen chloride, chlorine gas, and phosgene. Can contaminate antique fire extinguishers.
Carbonyl bromide (carbonyl dibromide, bromophosgene[CAS 593-95-3]): Bromide analogue of carbonyl chloride (phosgene). Presumed to be potentially highly irritating to respiratory tract.			Potential thermal breakdown byproduct of multiple bromine-containing organic compounds.
Carbonyl fluoride (COF₂ [CAS: 353-50-4]): Extremely irritating to eyes and respiratory tract; pulmonary edema may result. Toxicity results from its hydrolysis to hydrofluoric acid.	2 ppm	10-min AEGL3: 1.0	Colorless, odorless gas. Decomposes upon contact with water to produce hydrofluoric acid. Can be a combustion byproduct of polyfluorocarbons.
Catechol (1,2-benzenediol, pyrocatechol [CAS: 120-80-9]): Highly irritating upon direct contact; severe eye and deep skin burns result. Well absorbed by skin. Systemic toxicity similar to that of phenol; however, catechol may be more likely to cause convulsions and hypertension. At high doses, renal and liver injury may occur. IARC 2B.	5 ppm, S		Colorless solid crystals. Used in industrial chemical synthesis of pesticides and other organic chemicals.
Cerium (oxide or salt): Rare earth element. Fume and dust exposure associated with human interstitial lung disease.			Component of “rouge” used in glass polishing; fume from arc lamp use (historical) and specialty applications. Proposed diesel fuel additive.
Cesium hydroxide (cesium hydrate [CAS: 21351-79-1]):Corrosive. Highly irritating upon direct contact; severe burns may result. Dusts are irritating to eyes and respiratory tract.	2 mg/m³		Colorless or yellow crystals that absorb moisture. Negligible vapor pressure.
Chloramine (monochloramine [CAS: 10599-90-3]): Vapors irritating to eyes and respiratory tract, can cause chemical pneumonitis (Gases, Irritant). Liquid is a skin irritant. Closely related moieties include dichloramine and trichloramine (nitrogen trichloride). IARC 3.			Colorless or yellow liquid at 25°C, highly water-soluble. Often a mixture of mono-, di-, and trichloramines, produced when bleach and ammonia cleaners are combined or when urine comes in contact with chlorinated water. Small amounts off-gas from chlorinated public swimming pools. Occupational exposures include produce washing/packaging and water disinfection.
Chlordane (CAS: 57-74-9): Irritating to skin. A CNS convulsant. Skin absorption is rapid and has caused convulsions and death. Hepatotoxic. Evidence of carcinogenicity in test animals (IARC 2B), NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.	0.5 mg/m³, S	100 mg/m³	Viscous amber liquid. Formulations vary in appearance. A chlorine-like odor. Vapor pressure is 0.00001 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride, phosgene, and chlorine gas. Pesticide use banned in the US since 1976.
Chlorinated camphene (toxaphene [CAS: 8001-35-2]): Moderately irritating upon direct contact. Acute toxicity includes nausea, confusion, tremors, and convulsions. Well-absorbed by skin. Potential liver and kidney injury. IARC 2B, NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.	0.5 mg/m³, S	200 mg/m³	Waxy amber-colored solid. Formulations vary in appearance. Turpentine-like odor. Vapor pressure is about 0.3 mm Hg at 20°C (68°F). Pesticide use banned in the US since 1990.
Chlorinated diphenyl oxide (CAS: 55720-99-5): Chloracne may result from even small exposures. A hepatotoxin in chronically exposed test animals. Signs and symptoms include gastrointestinal upset, jaundice, and fatigue. See also “Dioxins”.	0.5 mg/m³	5 mg/m³	Waxy solid or liquid. Vapor pressure is 0.00006 mm Hg at 20°C (68°F).
Chlorine (CAS: 7782-50-5): Extremely irritating to eyes, skin, and respiratory tract; severe burns and pulmonary edema may occur. Symptoms include lacrimation, sore throat, headache, coughing, and wheezing. High concentrations may cause rapid tissue swelling and airway obstruction through laryngeal edema. Can lead to irritant-induced asthma. See also Chlorine.	0.1 ppm	10 ppm 10-min AEGL3: 40 ppm	Amber liquid or greenish-yellow gas, heavier than air. Irritating odor and irritation occur near the TLV and are both good warning properties. Can be formed when acid cleaners are mixed with hypochlorite bleach cleaners. Major releases can occur through transportation and water treatment mishaps and in industrial bleaching.
Chlorine dioxide (chlorine peroxide [CAS: 10049-04-4]): Extremely irritating to eyes and respiratory tract. Symptoms and signs are those of chlorine gas (see also Chlorine), although chlorine dioxide is more potent.	0.1 ppm	5 ppm	Yellow-green or orange gas or liquid. Sharp odor at the TLV is a good warning property. Reacts with water to produce perchloric acid. Decomposes explosively in sunlight, with heat, or with shock to produce chlorine gas. Bleaching agent widely used in paper industry.
Chlorine trifluoride (chlorine fluoride [CAS: 7790-91-2]): Upon contact with moist tissues, hydrolyzes to chlorine, hydrogen fluoride, and chlorine dioxide. Extremely irritating to eyes, skin, and respiratory tract; severe burns or delayed pulmonary edema can result.	0.1 ppm (C)	20 ppm 10-min AEGL3: 84 ppm	Greenish-yellow or colorless liquid or gas or white solid. Has a suffocating, sweet odor near 0.1 ppm. Not combustible. Water-reactive, yielding hydrogen fluoride and chlorine gas. Used as incendiary and rocket fuel additive.
Chloroacetaldehyde (CAS: 107-20-0): Extremely corrosive upon direct contact; severe burns will result. Vapors extremely irritating to eyes, skin, and respiratory tract.	1 ppm (C)	45 ppm 10-min AEGL3: 44 ppm	Colorless liquid with a pungent, irritating odor. Vapor pressure is 100 mm Hg at 20°C (68°F). Combustible. Readily polymerizes. Thermal breakdown products include phosgene and hydrogen chloride.
alpha-Chloroacetophenone (tear gas, chemical Mace [CAS: 532-27-4]): Extremely irritating to mucous membranes and respiratory tract. With extremely high inhalational exposures, lower respiratory injury is possible. A potent skin sensitizer. See also Warfare Agents—Chemical.	0.05 ppm	15 mg/m³	Sharp, irritating odor and irritation occur near the TLV and are adequate warning properties. Vapor pressure is 0.012 mm Hg at 20°C (68°F). Mace is a common crowd control agent.
Chlorobenzene (monochlorobenzene [CAS: 108-90-7]): Irritating; skin burns may result from prolonged contact. Vapors irritating to eyes and respiratory tract. A CNS depressant. May cause methemoglobinemia. Prolonged exposure to high levels has caused lung, liver, and kidney injury in test animals.	10 ppm	1,000 ppm	Colorless liquid. Aromatic odor occurs below the TLV and is a good warning property. Vapor pressure is 8.8 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include hydrogen chloride and phosgene.
o-Chlorobenzylidene malononitrile (tear gas, OCBM, CS [CAS: 2698-41-1]): Highly irritating on direct contact; severe burns may result. Aerosols and vapors very irritating to mucous membranes and upper respiratory tract. With extremely high inhalational exposures, lower respiratory injury is possible. Potent skin sensitizer. Symptoms include headache, nausea and vomiting, severe eye and nose irritation, excess salivation, and coughing. See also Warfare Agents—Chemical.	0.05 ppm (C), S	2 mg/m³ 10-min AEGL3: 8.8 ppm	White solid crystals. Pepper-like odor at 0.005 mg/m³. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). CS is a common crowd control agent.
Chlorobromomethane (bromochloromethane, Halon 1011 [CAS: 74-97-5]): Irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. Disorientation, nausea, headache, seizures, and coma have been reported at high exposure. Chronic high doses caused liver and kidney injury in test animals.	200 ppm	2,000 ppm	Colorless to pale yellow liquid. Sweet, pleasant odor detectable far below the TLV. Vapor pressure is 117 mm Hg at 20°C (68°F). Thermal breakdown products include hydrogen chloride, hydrogen bromide, and phosgene.
Chlorodifluoromethane (Freon 22 [CAS: 75-45-6]): Irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. High-level exposure may cause arrhythmias. There is evidence at high doses for adverse effects on fetal development in test animals. IARC 3. See also Freons and Halons.	1,000 ppm		Colorless, almost odorless gas. Nonflammable. Thermal breakdown products may include hydrogen fluoride. Widely used commercial refrigerant (eg, in seafood industry).
Chloroform (trichloromethane [CAS: 67-66-3]): Mildly irritating upon direct contact; dermatitis may result from prolonged exposure. Vapors slightly irritating to eyes and respiratory tract. A CNS depressant. High levels (15,000-20,000 ppm) can cause coma and cardiac arrhythmias. Can produce liver and kidney damage. Limited evidence of adverse effects on fetal development in test animals. A carcinogen in test animals (IARC 2B), NIOSH CA. See also Carbon Tetrachloride and Chloroform.	10 ppm	500 ppm 10-min AEGL3: 4,000 ppm	Colorless liquid. Pleasant, sweet odor. Not combustible. Vapor pressure is 160 mm Hg at 20°C (68°F). Thermal breakdown products include hydrogen chloride, phosgene, and chlorine gas. California OSHA PEL is 2 ppm.
bis-Chloromethyl ether (BCME [CAS: 542-88-1]): A human lung carcinogen (IARC 1), OSHA CA, NIOSH CA.	0.001 ppm	10-min AEGL3: 0.23 ppm	Colorless liquid with a suffocating odor. Vapor pressure is 100 mm Hg at 20°C (68°F). Used in the manufacture of ion-exchange resins. Can be formed when formaldehyde is mixed with hydrochloric acid.
Chloromethyl methyl ether (CMME, methyl chloromethyl ether [CAS: 107-30-2]): Vapors irritating to eyes and respiratory tract. Workers at increased risk for lung cancer, possibly owing to contamination of CMME with 1-7% BCME (IARC 1). OSHA CA. NIOSH CA.		10-min AEGL3: 2.6 ppm	Combustible. Breakdown products include oxides of nitrogen and hydrogen chloride. Used in the manufacture of ion-exchange resins.
4-Chloro-2-methylphenoxyacetic acid (MCPA [CAS: 2698-38-6]): GI irritant with less toxicity than related phenoxherbicides 2,4-D and mecoprop (Chlorophenoxy Herbicides (2,4-D)).			White crystalline solid.
1-Chloro-1-nitropropane (CAS: 600-25-9): Based on animal studies, vapors highly irritating to eyes and respiratory tract and may cause pulmonary edema. High levels may cause injury to cardiac muscle, liver, and kidney.	2 ppm	100 ppm	Colorless liquid. Unpleasant odor and tearing occur near the TLV and are good warning properties. Vapor pressure is 5.8 mm Hg at 20°C (68°F). Used as a fungicide.
Chloropentafluoroethane (fluorocarbon 115 [CAS: 76-15-3]): Irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. Produces coma and cardiac arrhythmias, but only at very high levels in test animals. See also Freons and Halons.	1,000 ppm		Colorless, odorless gas. Thermal breakdown products include hydrogen fluoride and hydrogen chloride.
Chloropicrin (trichloronitromethane [CAS: 76-06-2]): Extremely irritating upon direct contact; severe burns may result. Vapors extremely irritating to eyes, skin, and respiratory tract; delayed pulmonary edema has been reported. Kidney and liver injuries have been observed in test animals.	0.1 ppm	2 ppm	Colorless, oily liquid. Sharp, penetrating odor and tearing occur near the TLV and are good warning properties. Vapor pressure is 20 mm Hg at 20°C (68°F). Breakdown products include oxides of nitrogen, phosgene, nitrosyl chloride, and chlorine gas. Used as a fumigant and also as an additive for its warning properties. Historically, used as a World War I chemical warfare agent.
beta-Chloroprene (2-chloro-1,3-butadiene [CAS: 126-99-8]): Irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Liver and kidneys are major target organs. Limited evidence for adverse effects on fetal development and male reproduction in test animals. Equivocal evidence of carcinogenicity in test animals (IARC 2B). NIOSH CA.	10 ppm, S	300 ppm	Colorless liquid with an ether-like odor. Vapor pressure is 179 mm Hg at 20°C (68°F). Highly flammable. Breakdown products include hydrogen chloride. Used in making neoprene.
para-Chlorobenzotrifluoride (PCBTF) [CAS: 98-56-6]: Irritant of the skin, eyes and respiratory system. High vapor concentrations cause anesthesia. Thermal decomposition products include fumes of hydrogen fluoride, hydrogen chloride and possibly organic fluorides. IARC 2B.			Clear colorless liquid with an aromatic odor. A “green” solvent that is exempt from the EPA's stricter Clean Air Act Regulation. A common solvent in low VOC paint and ink formulations.
o-Chlorotoluene (2-chloro-1-methylbenzene [CAS: 95-49-8]): In test animals, direct contact produced skin and eye irritation; high vapor exposures resulted in tremors, convulsions, and coma. By analogy to toluene and chlorinated compounds, may cause cardiac arrhythmias.	50 ppm		Colorless liquid. Vapor pressure is 10 mm Hg at 43°C (109°F). Flammable.
Chlorpyrifos (Dursban [CAS: 2921-88-2]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Peripheral neuropathy and dermatitis reported. Sodium 3,5,6-trichloropyridin-2-ol (STCP) is an important intermediate for synthesizing chlorpyrifos and has caused poisoning including chloracne and peripheral nerve damage.	0.1 mg/m³, S		White solid crystals. Vapor pressure is 0.00002 mm Hg at 25°C (77°F). Agricultural pesticide.
Chromic acid and chromates (chromium trioxide, sodium dichromate, potassium chromate): Highly irritating upon direct contact; severe eye and skin ulceration (chrome ulcers) may result. Dusts and mists highly irritating to eyes and respiratory tract. Skin and respiratory sensitization (asthma) may occur. Chromium trioxide is a teratogen in test animals. Certain hexavalent chromium compounds are carcinogenic in test animals and humans (IARC 1). Chromium III compounds and chromium metal are less strongly associated with cancer (IARC 3). NIOSH CA. See also Chromium.	0.003 mg/m³ (Cr III compounds), 0.0005 mg/m³ (water-soluble Cr VI compounds), 0.0002 mg/m³ (insoluble Cr IV compounds)	15 mg/m³ (Cr VI)	Soluble chromate compounds are water-reactive. Chromates are common components of cement in concrete fabrication. Hexavalent chromium exposure can occur in metal plating and in making and welding chrome containing (eg, stainless) steel. Selected yellow pigments and glazes can contain hexavalent chromium.
Chromium metal and insoluble chromium salts: Irritating upon direct contact with skin and eyes; dermatitis may result. Ferrochrome alloys possibly associated with pneumonoconiotic changes. OSHA CA (Cr VI). See also Chromium.	0.5 mg/m³ (metal, as Cr), 0.01 mg/m³ (Cr VI compounds, as Cr)	250 mg/m³ (Cr II compounds), 25 mg/m³ (Cr III compounds), 250 mg/m³ (Cr metal)	Chromium metal, silver luster; copper chromite, greenish-blue solid. Odorless
Chromyl chloride (CAS: 14977-61-8): Highly irritating upon direct contact; severe burns may result. Mists and vapors highly irritating to eyes and respiratory tract. Certain hexavalent chromium VI compounds are carcinogenic in test animals and humans. NIOSH CA. See also Chromium.	0.025 ppm		Dark red fuming liquid. Water-reactive, yielding hydrogen chloride, chlorine gas, chromic acid, and chromic chloride.
Coal tar pitch volatiles (particulate polycyclic aromatic hydrocarbons [CAS: 65996-93-2]): Irritating upon direct contact. Contact dermatitis, acne, hypermelanosis, and photosensitization may occur. Fumes irritating to eyes and respiratory tract. A carcinogen in test animals and humans (IARC 1), NIOSH CA.	0.2 mg/m³	80 mg/m³	A complex mixture composed of a high percentage of polycyclic aromatic hydrocarbons. A smoky odor. Combustible. Creosote is an important source of exposure.
Citric acid (CAS 77-92-9): Irritating upon direct contact. Aereosols irritating to eyes and respiratory tract. If ingested, irritating to gastrointestinal tract.	10 pg/m³		Naturally occurring but common industrial chemical including at high concentrations.
Cobalt and compounds: Dusts irritating to eyes, skin, and sensitization may occur. Fumes and dusts irritate the respiratory tract; chronic interstitial pneumonitis and respiratory tract sensitization reported. Cardiotoxicity is associated with ingestion but has not been well documented with occupational exposures. Cobalt is also ototoxic. Evidence of carcinogenicity in test animals (IARC 2B).	0.02 mg/m³ (elemental and inorganic compounds, as Co)	20 mg/m³ (as Co)	Elemental cobalt is a black or gray, odorless solid with a negligible vapor pressure. “Hard metal” used in specialty grinding and cutting is a tungsten carbide-cobalt amalgam and causes a specific (giant cell) pneumonitis pattern. Exposure-related illness through dysfunction of metal-on-metal cobalt-containing hip prostheses has occurred.
Cobalt hydrocarbonyl (CAS: 16842-03-8): In animal testing, overexposure produces symptoms similar to those of nickel carbonyl and iron pentacarbonyl. Effects include headache, nausea, vomiting, dizziness, fever, and pulmonary edema.	0.1 mg/m³ (as Co)		Flammable gas.
Copper fumes, dusts, and salts: Irritation upon direct contact varies with the compound. The salts are more irritating and can cause corneal ulceration. Allergic contact dermatitis is rare. Dusts and mists irritating to the respiratory tract; nasal ulceration has been described. Ingestion can cause severe gastroenteritis, hepatic injury, and hemolysis. See also Copper.	1 mg/m³ (dusts and mists, as Cu), 0.2 mg/m³(fumes, as Cu)	100 mg/m³ (as Cu)	Salts vary in color. Generally odorless. Agricultural pesticidal applications, especially as copper sulfate (blue vitriol). California OSHA PEL is 0.1 mg/m³.
Cotton dust: Chronic exposure causes a respiratory syndrome called byssinosis. Symptoms include cough and wheezing, which typically appear on the first day of the workweek and continue for a few days or all week, although they may subside within an hour after the affected individual leaves work. Can lead to irreversible obstructive airway disease. A flulike illness similar to metal fume fever also occurs among cotton workers (“Monday morning fever”).	0.1 mg/m³ (thoracic fraction)	100 mg/m³	Cotton textile manufacture is the principal source of exposure. “Card room” work (an early stage in cotton thread production) is the most significant source of exposure.
Creosote (coal tar creosote [CAS: 8001-58-9]): A primary irritant, photosensitizer, and corrosive. Direct eye contact can cause severe keratitis and corneal scarring. Prolonged skin contact can cause chemical acne, pigmentation changes, and severe penetrating burns. Exposure to the fumes or vapors causes irritation of mucous membranes and the respiratory tract. Systemic toxicity results from phenolic and cresolic constituents. Liver and kidney injury may occur with heavy exposure. A carcinogen in test animals. Some evidence for carcinogenicity in humans (IARC 2A), NIOSH CA. See also “Phenol and Related Compounds,”.			Oily, dark liquid. Appearance and some hazardous properties vary with the formulation. Sharp, penetrating, smoky odor. Combustible. Creosote is produced by the fractional distillation of coal tar but also can be derived from other fossil fuel sources. See entry on coal tar pitch volatiles. Plant-derived “creosote” is a different material that was used as a medicinal agent in the past and does not have the same carcinogenic potential.
Cresol (methylphenol, cresylic acid, hydroxymethylbenzene [CAS: 1319-77-3]): Corrosive. Skin and eye contact can cause severe burns. Exposure may be prolonged owing to local anesthetic action on skin. Well absorbed by all routes. Dermal absorption is a major route of systemic poisoning. Induces methemoglobinemia. CNS depressant. Symptoms include headache, nausea and vomiting, tinnitus, dizziness, weakness, and confusion. Severe lung, liver, and kidney injury may occur. See also “Phenol and Related Compounds,”.	20 mg/m³, S	250 ppm	Colorless, yellow, or pink liquid with a phenolic odor. Vapor pressure is 0.2 mm Hg at 20°C (68°F). Combustible.
Crotonaldehyde (2-butenal [CAS: 4170-30-3]): Highly irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract; delayed pulmonary edema may occur. Evidence for carcinogenicity in test animals (IARC 3).	0.3 ppm (C), S	50 ppm 10-min AEGL3: 44 ppm	Colorless to straw-colored liquid. Pungent, irritating odor occurs below the TLV and is an adequate warning property. Has been used as a warning agent in fuel gases. Vapor pressure is 30 mm Hg at 20°C (68°F). Flammable. Polymerizes when heated.
*Crufomate (4-tert-butyl-2-chlorophenyl N-methyl O-methylphosphoramidate [CAS: 299-86-5]):* An organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	5 mg/m³		Crystals or yellow oil. Pungent odor. Flammable. Agricultural pesticide.
Cumene (isopropylbenzene [CAS: 98-82-8]): Mildly irritating upon direct contact. A CNS depressant at moderate levels. Well absorbed through skin. Adverse effects in fetal development in rats at high doses. IARC 2B.	50 ppm	900 ppm	Colorless liquid. Sharp, aromatic odor below the TLV is a good warning property. Vapor pressure is 8 mm Hg at 20°C (68°F). Flammable.
Cyanamide (carbodiimide [CAS: 420-04-2]): Causes transient vasomotor flushing. Highly irritating and caustic to eyes and skin. Has a disulfiram-like interaction with alcohol, producing flushing, headache, and dyspnea (Disulfiram).	2 mg/m³		Combustible. Thermal breakdown products include oxides of nitrogen. Used as an agricultural chemical for plant growth regulation.
Cyanide salts (sodium cyanide, potassium cyanide): Potent and rapidly fatal metabolic asphyxiants that inhibit cytochrome oxidase and stop cellular respiration. Well absorbed through skin; caustic action can promote dermal absorption. See also Cyanide.	5 mg/m³ (C) (as cyanide), S	25 mg/m³ (as cyanide)	Solids. Mild, almond-like odor. In presence of moisture or acids, hydrogen cyanide may be released. Odor is a poor indicator of exposure to hydrogen cyanide. May be generated in fires from the pyrolysis of such products as polyurethane and polyacrylonitrile. Cyanide salts are used in metal plating and metal pickling operations.
Cyanogen (dicyan, oxalonitrile [CAS: 460-19-5]): Hydrolyzes to release hydrogen cyanide and cyanic acid. Toxicity similar to that of hydrogen cyanide. Vapors irritating to eyes and respiratory tract.	10 ppm [proposed: 5 ppm (C)]	10-min AEGL3: 150 ppm	Colorless gas. Pungent, almond-like odor. Breaks down on contact with water to yield hydrogen cyanide and cyanate. Flammable.
Cyanogen chloride (CAS: 506-77-4): Vapors extremely irritating to eyes and respiratory tract; pulmonary edema may result. Cyanide interferes with cellular respiration.	0.3 ppm (C)		Colorless liquid or gas with a pungent odor. Thermal breakdown products include hydrogen cyanide and hydrogen chloride. Formed by reaction with hypochlorite in the treatment of cyanide-containing wastewater.
Cyclohexane (CAS: 110-82-7): Mildly irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Chronically exposed test animals developed liver and kidney injury.	100 ppm	1,300 ppm	Colorless liquid with a sweet, chloroform-like odor. Vapor pressure is 95 mm Hg at 20°C (68°F). Highly flammable. Organic solvent; principal industrial use in production of caprolactam.
Cyclohexanol (CAS: 108-93-0): Irritating upon direct contact. Vapors irritating to eyes and respiratory tract. Well absorbed by skin. A CNS depressant at high levels. Based on animal tests, it may injure the liver and kidneys at high doses.	50 ppm, S	400 ppm	Colorless, viscous liquid. Mild camphor-like odor. Irritation occurs near the TLV and is a good warning property. Vapor pressure is 1 mm Hg at 20°C (68°F). Combustible.
Cyclohexanone (CAS: 108-94-1): Irritating upon direct contact. Vapors irritate the eyes and respiratory tract. A CNS depressant at very high levels. Chronic, moderate doses caused slight liver injury in test animals. IARC 3.	20 ppm, S	700 ppm	Clear to pale yellow liquid with peppermint-like odor. Vapor pressure is 2 mm Hg at 20°C (68°F). Flammable. A nylon industry chemical precursor.
Cyclohexene (1,2,3,4-tetrahydrobenzene [CAS: 110-83-8]): By structural analogy to cyclohexane, may cause respiratory tract irritation. A CNS depressant.	20 ppm	2,000 ppm	Colorless liquid with a sweet odor. Vapor pressure is 67 mm Hg at 20°C (68°F). Flammable. Readily forms peroxides and polymerizes.
Cyclohexylamine (aminocyclohexane [CAS: 108-91-8]): Corrosive and highly irritating upon direct contact. Vapors highly irritating to eyes and respiratory tract. Pharmacologically active, possessing sympathomimetic activity. Weak methemoglobin-forming activity (Methemoglobinemia). Very limited evidence for adverse effects on reproduction in test animals. Animal studies suggest brain, liver, and kidneys are target organs.	10 ppm	10-min AEGL3: 38 ppm	Liquid with an obnoxious, fishy odor. Flammable.
Cyclonite (RDX, trinitro-trimethylene-triamine, hexogen [CAS: 121-82-4]): Induces methemoglobinemia. Dermal and inhalation exposures affect the CNS with symptoms of confusion, headache, nausea, vomiting, multiple seizures, and coma.	0.5 mg/m³, S		Explosive crystalline solid, principal ingredient in the plastic explosive C-4. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Exposure occurs among munitions workers and military personnel.
Cyclopentadiene [CAS: 542-92-7]): Mildly irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Animal studies suggest some potential for kidney and liver injury at high doses.	75 ppm	750 ppm	Colorless liquid. Sweet, turpentine-like odor. Irritation occurs near the TLV and is a good warning property. Vapor pressure is high at 20°C (68°F). Flammable.
Cyclopentane (CAS: 287-92-3]): Mildly irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at very high levels. Solvent mixtures containing cyclopentane have caused peripheral neuropathy, although this may have been related to n-hexane in combination.	600 ppm		Colorless liquid with a faint hydrocarbon odor. Vapor pressure is about 400 mm Hg at 31°C (88°F). Flammable.
Cyclotetramethylene-tetranitramine (HMX, octogen [CAS: 26914-41-0]): Dermally absorbed. Causes seizures in humans. Induces methemoglobinemia in animals (human data limited).			White powder. Odorless. Explosive. Chemically related to RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine). May be as potent a cause of seizures, but not as widely manufactured as RDX.
DDT (dichlorodiphenyltrichloroethane [CAS: 50-29-3]): Dusts irritating to eyes. Ingestion may cause tremor and convulsions. Chronic low-level exposure results in bioaccumulation. A carcinogen in test animals (IARC 2A), NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.	1 mg/m³	500 mg/m³	Colorless, white, or yellow solid crystals with a faint aromatic odor. Vapor pressure is 0.0000002 mm Hg at 20°C (68°F). Combustible. Banned for use in the US in 1973.
Decaborane (CAS: 17702-41-9): A potent CNS toxin. Symptoms include headache, dizziness, nausea, loss of coordination, and fatigue. Symptoms may be delayed in onset for 1-2 days; convulsions occur in more severe poisonings. Systemic poisonings can result from dermal absorption. Animal studies suggest a potential for liver and kidney injury.	0.05 ppm, S	15 mg/m³	Colorless solid crystals with a pungent odor. Vapor pressure is 0.05 mm Hg at 25°C (77°F). Combustible. Reacts with water to produce flammable hydrogen gas. Used as a rocket fuel additive and as a rubber vulcanization agent.
Demeton (Systox, mercaptophos [CAS: 8065-48-3]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	0.05 mg/m³, S	10 mg/m³	A sulfur-like odor. A very low vapor pressure at 20°C (68°F). Thermal breakdown products include oxides of sulfur. Agricultural pesticide.
Diacetone alcohol (4-hydroxy-4-methyl-2 pentanone [CAS: 123-42-2]): Irritating upon direct contact. Vapors very irritating to eyes and respiratory tract. A CNS depressant at high levels. Possibly some hemolytic activity.	50 ppm	1,800 ppm	Colorless liquid with an agreeable odor. Vapor pressure is 0.8 mm Hg at 20°C (68°F). Flammable.
Diacetyl (CAS: 625-34-3): Eye, skin, and respiratory irritant. One of several alpha diketone flavoring agents found to cause respiratory toxicity, producing constrictive bronchiolitis in occupationally exposed workers (“popcorn workers' lung”).	0.01 ppm		Vapor pressure is 56.8 mm Hg at 25°C (77°F). Artificial butter flavoring agent. Removed from US microwavable popcorn but still in use industrially and as an additive to other products.
1,2-diacetylbenzene (1,2-DAB [CAS: 704-00-7]): Putative active metabolite of the organic solvent 1,2-diethylbenzene; forms blue-colored polymeric protein adducts and induces the formation of amyotrophic lateral sclerosis (ALS)-like giant, intraspinal neurofilamentous axonal swellings in an experimental animal model.			Yellow to light brown crystalline powder. The parent compound, 1,2-diethylbenzene, is used as an industrial solvent.
Diazinon (O,O-diethyl O-2-isopropyl-4-methyl-6-pyrimidinyl thiophosphate [CAS: 333-41-5]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed dermally. Evidence of adverse reproductive effects in experimental testing. IARC 2A.	0.01 mg/m³ (inhalable fractionand vapor), S		Commercial grades are yellow to brown liquids with a faint odor. Vapor pressure is 0.00014 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen and sulfur. Agricultural pesticide.
Diazomethane (azimethylene, diazirine [CAS: 334-88-3]): Extremely irritating to eyes and respiratory tract; pulmonary edema has been reported. Immediate symptoms include cough, chest pain, and respiratory distress. A potent methylating agent and respiratory sensitizer. IARC 3.	0.2 ppm	2 ppm	Yellow gas with a musty odor. Air mixtures and compressed liquids can be explosive when heated or shocked. Used as a methylating agent in chemical synthesis.
Diborane (boron hydride [CAS: 19287-45-7]): Extremely irritating to the respiratory tract; pulmonary edema may result. Repeated exposures have been associated with headache, fatigue, and dizziness; muscle weakness or tremors; and chills or fever. Animal studies suggest the liver and kidney are also target organs.	0.1 ppm	15 ppm 10-min AEGL3: 7.3 ppm	Colorless gas. Obnoxious, nauseatingly sweet odor. Highly flammable. Water-reactive; ignites spontaneously with moist air at room temperatures. A strong reducing agent. Breakdown products include boron oxide fumes. Used in microelectronics industry. Reacts violently with halogenated extinguishing agents.
1,2-Dibromo-3-chloropropane (DBCP [CAS: 96-12-8]): Irritant of eyes and respiratory tract. Has caused sterility (aspermia, oligospermia) in overexposed men. Well absorbed by skin contact and inhalation. A carcinogen in test animals (IARC 2B), OSHA CA, NIOSH CA.			Brown liquid with a pungent odor. Combustible. Thermal breakdown products include hydrogen bromide and hydrogen chloride. Banned as a pesticide in the US.
1,2-Dibromo-2,2-dichloroethyl dimethyl phosphate (naled, Dibrom [CAS: 300-76-5]): An organophosphate anticholinesterase agent (Organophosphorus and Carbamate Insecticides). Highly irritating upon contact; eye injury is likely. Dermal sensitization can occur. Well absorbed dermally; localized muscular twitching results within minutes of contact.	0.1 mg/m³, S, SEN	200 mg/m³	Has a pungent odor. Vapor pressure is 0.002 mm Hg at 20°C (68°F). Not combustible. Breaks down to dichlorvos. Thermal breakdown products include hydrogen bromide, hydrogen chloride, and phosphoric acid. Agricultural pesticide.
Dibutyl phosphate (di-n-butyl phosphate [CAS: 107-66-4]): A moderately strong acid likely to be irritating upon direct contact. Vapors and mists are irritating to the respiratory tract and have been associated with headache at low levels.	5 mg/m³, S	30 ppm	Colorless to brown liquid. Odorless. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Decomposes at 100°C (212°F) to produce phosphoric acid fumes.
Dibutyl phthalate (CAS: 84-74-2): Mildly irritating upon direct contact. Ingestion has produced nausea, dizziness, photophobia, and lacrimation but no permanent effects. Adverse effects on fetal development and male reproduction in test animals at very high doses.	5 mg/m³	4,000 mg/m³	Colorless, oily liquid with a faint aromatic odor. Vapor pressure is less than 0.01 mm Hg at 20°C (68°F). Combustible.
1, 2-Dichloroacetylene (CAS: 7572-29-4): Vapors extremely irritating to eyes and respiratory tract; pulmonary edema may result. CNS toxicity includes nausea and vomiting, headache, involvement of trigeminal nerve and facial muscles, and outbreaks of facial herpes. Limited evidence for carcinogenicity in test animals (IARC 3), NIOSH CA.	0.1 ppm (C)		Colorless liquid. Can be formed as a breakdown product of certain chlorinated organic compounds.
o-Dichlorobenzene (1,2-dichlorobenzene [CAS: 95-50-1]): Irritating upon direct contact; skin blisters and hyperpigmentation may result from prolonged contact. Vapor irritating to eyes and respiratory tract. Highly hepatotoxic in test animals. Evidence for adverse effects on male reproduction, but limited evidence of carcinogenicity in test animals (IARC 3).	25 ppm	200 ppm	Colorless to pale yellow liquid. Aromatic odor and eye irritation occur well below the TLV and are adequate warning properties. Thermal breakdown products include hydrogen chloride and chlorine gas.
p-Dichlorobenzene (1,4-dichlorobenzene [CAS: 106-46-7]): Irritating upon direct contact with the solid. Vapors irritating to eyes and respiratory tract. Systemic effects include headache, nausea, vomiting, and liver injury. The ortho isomer is more toxic to the liver. A carcinogen in test animals (IARC 2B), NIOSH CA.	10 ppm	150 ppm	Colorless or white solid. Mothball odor and irritation occur near the TLV and are adequate warning properties. Vapor pressure is 0.4 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include hydrogen chloride. Used as a deodorizer and moth repellent. Industrially, used as a chemical intermediate for dyes and polyphenylene sulfide resin.
3,3'-Dichlorobenzidine (CAS: 91-94-1): Well absorbed by the dermal route. Animal studies suggest that severe eye injury and respiratory tract irritation may occur. A potent carcinogen in test animals (IARC 2B), OSHA CA, NIOSH CA.	S		Crystalline needles with a faint odor.
Dichlorodifluoromethane (Freon 12, fluorocarbon 12 [CAS: 75-71-8]): Mild eye and respiratory tract irritant. Extremely high exposures can cause coma and cardiac arrhythmias. See also Freons and Halons.	1,000 ppm	15,000 ppm	Colorless gas. Ether-like odor is a poor warning property. Vapor pressure is 5.7 mm Hg at 20°C (68°F). Not combustible. Decomposes slowly on contact with water or heat to produce hydrogen chloride, hydrogen fluoride, and phosgene.
1,3-Dichloro-5,5-dimethylhydantoin (Halane, Dactin [CAS: 118-52-5]): Releases hypochlorous acid and chlorine gas on contact with moisture. Direct contact with the dust or concentrated solutions irritating to eyes, skin, and respiratory tract.	0.2 mg/m³	5 mg/m³	White solid with a chlorine-like odor. Odor and eye irritation occur below the TLV and are adequate warning properties. Not combustible. Thermal breakdown products include hydrogen chloride, phosgene, oxides of nitrogen, and chlorine gas.
1,1-Dichloroethane (ethylidene chloride [CAS: 75-34-3]): Mild eye and skin irritant. Vapors irritating to the respiratory tract. A CNS depressant at high levels. By analogy with its 1,2-isomer, may cause arrhythmias. Animal studies suggest some potential for kidney and liver injury.	100 ppm	3,000 ppm	Colorless, oily liquid. Chloroform-like odor occurs at the TLV. Vapor pressure is 182 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include vinyl chloride, hydrogen chloride, and phosgene.
1,2-Dichloroethane (ethylene dichloride [CAS: 107-06-2]): Irritating upon prolonged contact; burns may occur. Well absorbed dermally. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels; may be associated with chronic toxic encephalopathy. Can cause cardiac arrhythmias. Severe liver and kidney injury has been reported. A carcinogen in test animals (IARC 2B), NIOSH CA.	10 ppm	50 ppm	Odor threshold near 50 ppm. Flammable. Thermal breakdown products include hydrogen chloride and phosgene. A widely used industrial solvent.
1,1-Dichloroethylene (vinylidine chloride [CAS: 75-35-4]): Irritating upon direct contact. Vapors very irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. In test animals, damages the liver and kidneys. Limited evidence of carcinogenicity in test animals (IARC 2B), NIOSH CA.	5 ppm		Colorless liquid. Sweet, ether-like or chloroform-like odor occurs below the TLV and is a good warning property. Polymerizes readily. Also used as a copolymer with vinyl chloride.
1,2-Dichloroethylene (1,2-dichloroethene, acetylene dichloride [CAS: 540-59-0]): Vapors mildly irritating to respiratory tract. A CNS depressant at high levels; once used as an anesthetic agent. May cause cardiac arrhythmias. Mildly hepatotoxic.	200 ppm	1,000 ppm	Colorless liquid with a slightly acrid, ether-like or chloroform-like odor. Vapor pressure is about 220 mm Hg at 20°C (68°F). Thermal breakdown products include hydrogen chloride and phosgene.
Dichloroethyl ether (bis[2-chloroethyl] ether, dichloroethyl oxide [CAS: 111-44-4]): Irritating upon direct contact; corneal injury may result. Vapors highly irritating to respiratory tract. A CNS depressant at high levels. Dermal absorption occurs. Animal studies suggest the liver and kidneys are also target organs at high exposures. Limited evidence for carcinogenicity in test animals (IARC 3), NIOSH CA.	5 ppm, S	100 ppm	Colorless liquid. Obnoxious, chlorinated solvent odor occurs at the TLV and is a good warning property. Flammable. Breaks down on contact with water. Thermal breakdown products include hydrogen chloride.
Dichlorofluoromethane (fluorocarbon 21, Freon 21, Halon 112 [CAS: 75-43-4]): Animal studies suggest much greater hepatotoxicity than with most common chlorofluorocarbons. Causes CNS depression, respiratory irritation, and cardiac arrhythmias at very high air levels. Evidence for adverse effects on fetal development in test animals at high levels. See also Freons and Halons.	10 ppm	5,000 ppm	Colorless liquid or gas with a faint ether-like odor. Thermal breakdown products include hydrogen chloride, hydrogen fluoride, and phosgene.
1,1-Dichloro-1-nitroethane [CAS: 594-72-9]): Based on animal studies, highly irritating upon direct contact. Vapors highly irritating to eyes, skin, and respiratory tract; pulmonary edema may result. In test animals, lethal doses also injured the liver, heart, and kidneys.	2 ppm	25 ppm	Colorless liquid. Obnoxious odor and tearing occur only at dangerous levels and are poor warning properties. Vapor pressure is 15 mm Hg at 20°C (68°F).
2,4-Dichlorophenol [CAS: 120-83-2]: Extremely toxic, but the mechanism of action in human fatalities has not been determined.			Odor threshold near 0.2 ppm. Used as a chemical precursor in the manufacture of 2,4-dichlorophenoxyacetic acid (2,4-D). Exposure occurs through unintended releases in industrial settings.
2,4-Dichlorophenoxyacetic acid (2,4-D [CAS: 94-75-9]): Direct skin contact can produce a rash. Overexposed workers have manifested peripheral neuropathy. Severe rhabdomyolysis and minor liver and kidney injury may occur. Adverse effects on fetal development at high doses in test animals. Weak epidemiologic associations of phenoxy herbicides with soft-tissue sarcomas (IARC 2B). See also Chlorophenoxy Herbicides (2,4-D).	10 mg/m³, S	100 mg/m³	White to yellow crystals. Appearance and some hazardous properties vary with the formulation. Odorless. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include hydrogen chloride and phosgene. Used as an herbicide.
1,3-Dichloropropene (1,3-dichloropropylene, Telone [CAS: 542-75-6]): Based on animal studies, irritating upon direct contact. Well absorbed dermally. Vapors irritating to eyes and respiratory tract. In test animals, moderate doses caused severe injuries to the liver, pancreas, and kidneys. A carcinogen in test animals (IARC 2B), NIOSH CA.	1 ppm, S		Colorless or straw-colored liquid. Sharp, chloroform-like odor. Polymerizes readily. Dissolves in water and evaporates easily. Vapor pressure is 28 mm Hg at 25°C (77°F). Thermal breakdown products include hydrogen chloride and phosgene. A soil fumigant pesticide widely used in the US.
2,2-Dichloropropionic acid (CAS: 75-99-0): Corrosive upon direct contact with concentrate; severe burns may result. Vapors mildly irritating to eyes and respiratory tract.	5 mg/m³		Colorless liquid. The sodium salt is a solid.
Dichlorotetrafluoroethane (fluorocarbon 114, Freon 114 [CAS: 76-14-2]): Vapors may sensitize the myocardium to arrhythmogenic effects of epinephrine at modestly high air levels (25,000 ppm). Other effects at higher levels (100,000-200,000 ppm) include respiratory irritation and CNS depression. See also Freons and Halons.	1,000 ppm	15,000 ppm	Colorless gas with a mild ether-like odor. Thermal breakdown products include hydrogen chloride, hydrogen fluoride, and phosgene.
Dichlorvos (DDVP, 2,2-dichlorovinyl diethyl phosphate [CAS: 62-73-7]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Peripheral neuropathy reported. Extremely well absorbed through skin. Evidence of carcinogenicity in test animals (IARC 2B).	0.1 mg/m³, S, SEN	100 mg/m³	Colorless to amber liquid with a slight chemical odor. Vapor pressure is 0.032 mm Hg at 32°C (90°F). Pesticide in indoor “pest strips”; overexposure from misuse can occur.
*Dicrotophos (dimethyl cis-2-dimethylcarbamoyl-1-methylvinyl phosphate, Bidrin [CAS: 141-66-2]):* An organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Dermal absorption occurs.	0.05 mg/m³, S		Brown liquid with a mild ester odor. Agricultural pesticide.
Dieldrin (CAS: 60-57-1): Minor skin irritant. Potent convulsant and hepatotoxin. Dermal absorption is a major route of systemic poisoning. Overexposures produce headache, dizziness, twitching, and convulsions. Limited evidence for adverse effects on fetal development and carcinogenicity in test animals (IARC 2A), NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.	0.1 mg/m³, S	50 mg/m³	Light brown solid flakes with a mild chemical odor. Appearance and some hazardous properties vary with the formulation. Vapor pressure is 0.0000002 mm Hg at 32°C (90°F). Not combustible. Agricultural pesticide.
Diesel exhaust: A respiratory irritant. May act as an adjuvant to immunologic sensitization. Animal and human epidemiologic studies provide evidence of pulmonary carcinogenicity (IARC 1), NIOSH CA.	100 mg/m³, S (uncombusted liquid)		Diesel engines emit a complex mixture of gases, vapors, and respirable particulates, including many polycyclic aromatic and nitroaromatic hydrocarbons and oxides of nitrogen, sulfur, and carbon, including carbon monoxide.
Diethylamine (CAS: 109-89-7): Corrosive. Highly irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema may occur. Subacute animal studies suggest liver and heart may be target organs.	5 ppm, S	200 ppm	Colorless liquid. Fishy, ammonia-like odor occurs below the TLV and is a good warning property. Vapor pressure is 195 mm Hg at 20°C (68°F). Highly flammable. Thermal breakdown products include oxides of nitrogen. Corrosion inhibitor and other industrial applications.
*2-Diethylaminoethanol (N,N-diethylthanolamine, DEAE [CAS: 100-37-8]):* Based on animal studies, highly irritating upon direct contact and a skin sensitizer. Vapors likely irritating to eyes, skin, and respiratory tract. Has been associated with irritant-induced asthma. Reports of nausea and vomiting after a momentary exposure to 100 ppm.	2 ppm, S	100 ppm	Colorless liquid. Weak to nauseating ammonia odor. Flammable. Thermal breakdown products include oxides of nitrogen. Corrosion inhibitor.
Diethylenetriamine (DETA [CAS: 111-40-0]): Corrosive; highly irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract. Dermal and respiratory sensitization can occur.	1 ppm, S		Viscous yellow liquid with an ammonia-like odor. Vapor pressure is 0.37 mm Hg at 20°C (68 F). Combustible. Thermal breakdown products include oxides of nitrogen.
Diethyl ketone (3-pentanone [CAS: 96-22-0]): Mildly irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract.	200 ppm		Colorless liquid with an acetone-like odor. Flammable.
Diethyl sulfate (CAS: 64-67-5): Strong eye and respiratory tract irritant. Sufficient evidence of carcinogenicity in test animals, limited evidence (laryngeal cancer) in humans (IARC 2A).			An alkylating agent. Colorless oily liquid with a peppermint odor.
Difluorodibromomethane (dibromodifluoromethane, Freon 12B2 [CAS: 75-61-6]): Based on animal tests, vapors irritate the respiratory tract. A CNS depressant. By analogy to other freons, may cause cardiac arrhythmias. In test animals, high-level chronic exposures caused lung, liver, and CNS injury. See also Freons and Halons.	100 ppm	2,000 ppm	Heavy, volatile, colorless liquid with an obnoxious, distinctive odor. Vapor pressure is 620 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen bromide and hydrogen fluoride.
Diglycidyl ether (di[2,3-epoxypropyl]-ether, DGE [CAS: 2238-07-5]): Extremely irritating upon direct contact; severe burns result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema may result. Testicular atrophy and adverse effects on the hematopoietic system at low doses in test animals. CNS depression also noted. An alkylating agent and a carcinogen in test animals. No IARC evaluation. NIOSH CA.	0.01 ppm	10 ppm	Colorless liquid with a very irritating odor. Vapor pressure is 0.09 mm Hg at 25°C (77°F). Used in the epoxy industry.
Diisobutyl ketone (2,6-dimethyl-4-heptanone [CAS: 108-83-8]): Mildly irritating upon direct contact. Vapors mildly irritate eyes and respiratory tract. A CNS depressant at high levels.	25 ppm	500 ppm	Colorless liquid with a weak, ether-like odor. Vapor pressure is 1.7 mm Hg at 20°C (68°F).
Diisopropylamine (CAS: 108-18-9): Corrosive. Highly irritating upon direct contact; severe burns may result. Vapors very irritating to eyes and respiratory tract. Workers exposed to levels of 25-50 ppm have reported hazy vision, nausea, and headache.	5 ppm, S	200 ppm	Colorless liquid with an ammonia-like odor. Vapor pressure is 60 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen.
Dimethoate (phosphorodithiolate [CAS 60-51-5]): Organophosphate anticholinesterase agent (see Organophosphorus and Carbamate Insecticides). Suspect human teratogen.			White, crystalline solid with a camphor-like odor. Thermal breakdown to nitrogen, phosphorous, and sulfur oxides. Agricultural pesticide.
Dimethyl acetamide (DMAC [CAS: 127-19-5]): Potent hepatotoxin similar to dimethylformamide (DMF). DMAC has also caused hallucinations. Inhalation and skin contact are major routes of absorption. Limited evidence for adverse effects on fetal development in test animals at high doses.	10 ppm, S	300 ppm	Colorless liquid with a weak ammonia-like odor. Vapor pressure is 1.5 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen. Widely used industrial solvent, especially in film and fiber applications.
Dimethylamine (DMA [CAS: 124-40-3]): Corrosive upon direct contact; severe burns may result. Vapors extremely irritating to eyes and respiratory tract. Animal studies suggest liver is a target organ.	5 ppm, S	500 ppm	Colorless liquid or gas. Fishy or ammonia-like odor far below TLV is a good warning property. Flammable. Thermal breakdown products include oxides of nitrogen.
Dimethylamine borane (DMAB [CAS: 74-94-2]): Eye, skin, and respiratory tract irritant. Absorbed through intact skin. Potent CNS and peripheral neurotoxin.			Vapor pressure is 266 mm Hg at 25°C (77°F). Used as reducing agent for nonelectric plating of semiconductors in the microelectronics industry.
4-Dimethylaminophenol (CAS: 619-60-3): Potent oxidizer used to induce methemoglobinemia in some countries outside the US (see Methemoglobinemia).
N,N-Dimethylaniline (CAS: 121-69-7): Causes methemoglobinemia. A CNS depressant. Well absorbed dermally. Limited evidence for carcinogenicity in test animals (IARC 3).	5 ppm, S	100 ppm	Straw-colored to brown liquid with an amine-like odor. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen.
Dimethylcarbamoyl chloride (CAS: 79-44-7): Expected to be extremely irritating upon direct contact or by inhalation. A carcinogen in test animals (IARC 2A), NIOSH CA.	0.005 ppm, S		Liquid. Rapidly reacts with moisture to yield carbon dioxide, dimethylamine and hydrogen chloride.
N,N-Dimethylformamide (DMF [CAS: 68-12-2]): Dermally well absorbed. Symptoms of overexposure include abdominal pain, nausea, and vomiting. Potent hepatotoxin in humans. Interferes with ethanol to cause disulfiram-like reactions. Limited human evidence for testicular cancer (IARC 2A). Limited evidence for adverse effects on fetal development in animals.	5 ppm, S	500 ppm 10-min AEGL3: 970 ppm	Colorless to pale yellow liquid. Faint ammonia-like odor is a poor warning property (odor threshold is near the TLV). Vapor pressure is 2.7 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. Multiple industrial applications as a solvent, in particular in coatings and artificial leather manufacturing.
1,1-Dimethylhydrazine (DMH, UDMH [CAS: 57-14-7]): Corrosive upon direct contact; severe burns may result. Vapors extremely irritating to eyes and respiratory tract; pulmonary edema may occur. Well absorbed through the skin. May cause methemoglobinemia and hemolysis. A potent hepatotoxin; a carcinogen in test animals (IARC 2B), NIOSH CA.	0.01 ppm, S	15 ppm 10-min AEGL3: 65 ppm	Colorless liquid with yellow fumes. Amine odor. Vapor pressure is 1.3 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Rocket fuel additive. “Aerozine 50” is a 50:50 mix of UDMH and hydrazine.
Dimethylmercury (mercury dimethyl [CAS: 593-74-8]): Extremely toxic liquid readily absorbed by inhalation or across intact skin; as little as 1-2 drops on a latex glove caused death in a research chemist. Neurotoxic effects include progressive ataxia, dysarthria, visual and auditory dysfunction, and coma. See also “Mercury,”.	0.01 mg/m³, S (alkyl Hg compounds as a class)		Colorless liquid with a weak, sweet odor. Density 3.2 g/mL Vapor pressure 50-82 mm Hg at 20°C (68°F). Permeable through latex, neoprene, and butyl rubber gloves. (OSHA recommends Silver Shield laminate gloves under outer gloves.)
Dimethyl sulfate (CAS: 77-78-1): Powerful vesicant action; hydrolyzes to sulfuric acid and methanol. Extremely irritating upon direct contact; severe burns have resulted. Vapors irritating to eyes and respiratory tract; delayed pulmonary edema may result. Skin absorption is rapid. Nervous system toxicity also manifested. A carcinogen in test animals (IARC 2A), NIOSH CA.	0.1 ppm, S	7 ppm	Colorless, oily liquid. Very mild onion odor is barely perceptible and a poor warning property. Vapor pressure is 0.5 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include sulfur oxides. Methylating agent used in chemical synthesis.
N,N-Dimethyl-p-toluidine (CAS: 99-97-8): Oxidizing agent causing methemoglobinemia, presumably through its metabolite p-methylphenylhydroxylamine. A carcinogen in test animals (IARC 2B).			Used as a polymerization accelerator for ethyl methacrylate monomer. Exposure has occurred through artificial (sculpted) nail application.
Dinitrobenzene [CAS: 528-29-0 (ortho); 100-25-4 (para)]: May stain tissues yellow upon direct contact. Vapors are irritating to respiratory tract. Potent inducer of methemoglobinemia. Chronic exposures may result in anemia and liver damage. Injures testes in test animals. Very well absorbed through the skin.	0.15 ppm, S	50 mg/m³	Pale yellow crystals. Explosive; detonated by heat or shock. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Munitions and other industrial applications.
Dinitro-o-cresol (2-methyl-4,6-dinitrophenol [CAS: 534-52-1]): Highly toxic; uncouples oxidative phosphorylation, increasing metabolic rate and leading to fatigue, sweating, rapid breathing, tachycardia, and fever. Liver and kidney injury may occur. Symptoms may last for days, as it is excreted very slowly. May induce methemoglobinemia. Poisonings may result from dermal exposure. Yellow-stained skin may mark exposure.	0.2 mg/m³, S	5 mg/m³	Yellow solid crystals. Odorless. Dust is explosive. Vapor pressure is 0.00005 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen.
2,4-Dinitrophenol (CAS: 25550-58-7): Potent uncoupler of oxidative phosphorylation. Initial findings include hypertension, fever, dyspnea, and tachypnea. May cause methemoglobinemia and harm liver and kidneys. May stain skin at point of contact. Limited evidence for adverse effects on fetal development. See also Pentachlorophenol and Dinitrophenol.			Industrial chemical and pesticide. Abused as a chemical dietary supplement for weight loss and in body building. Fatal hyperthermia has been reported.
2,4-Dinitrotoluene (DNT [CAS: 25321-14-6]): May cause methemoglobinemia. Uncouples oxidative phosphorylation, leading to increased metabolic rate and hyperthermia, tachycardia, and fatigue. A hepatotoxin. May cause vasodilation; headache and drop in blood pressure are common. Cessation of exposure may precipitate angina pectoris in pharmacologically dependent workers. Well absorbed by all routes. May stain skin yellow. Injures testes in animals and, possibly, exposed workers. A carcinogen in test animals, NIOSH CA.	0.2 mg/m³, S	50 mg/m³	Orange-yellow solid (pure) or oily liquid with a characteristic odor. Explosive. Thermal breakdown products include oxides of nitrogen. Vapor pressure is 1 mm Hg at 20°C (68°F). Exposure encountered in the munitions industry.
1,4-Dioxane (1,4-diethylene dioxide [CAS: 123-91-1]): Vapors irritating to eyes and respiratory tract. Inhalation or dermal exposures may cause gastrointestinal upset and liver and kidney injury. A carcinogen in test animals (IARC 2B), NIOSH CA.	20 ppm, S	500 ppm	Colorless liquid. Mild ether-like odor occurs only at dangerous levels and is a poor warning property. Vapor pressure is 29 mm Hg at 20°C (68°F). Flammable. Industrial solvent and chemical additive stabilizer for chlorinated solvents. California OSHA PEL is 0.28 ppm.
*Dioxathion (2,3-p-dioxanedithiol S,S-bis [O,O-diethyl phosphorodithioate] [CAS: 78-34-2]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed dermally.	0.1 mg/m³, S		Amber liquid. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include oxides of sulfur. Agricultural pesticide.
Dipropylene glycol methyl ether (DPGME [CAS: 34590-94-8]): Mildly irritating to eyes upon direct contact. A CNS depressant at very high levels.	100 ppm, S	600 ppm	Colorless liquid with a mild ether-like odor. Nasal irritation is a good warning property. Vapor pressure is 0.3 mm Hg at 20°C (68°F). Combustible.
Diquat (1,1-ethylene-2,2'-dipyridinium dibromide, Reglone, Dextrone [CAS: 85-00-7]): Mucosal irritant; corrosive in high concentrations. Acute renal failure and liver injury may occur. Chronic feeding studies caused cataracts in test animals. Although pulmonary edema may occur, unlike with paraquat, pulmonary fibrosis has not been shown with human diquat exposures. See also Paraquat and Diquat.	0.5 mg/m³ (total dust, inhalable fraction), 0.1 mg/m³ (respirable dust), S		Yellow solid crystals. Appearance and some hazardous properties vary with the formulation. Nonspecific contact herbicide.
Disulfiram (tetraethylthiuram disulfide, Antabuse [CAS: 97-77-8]): Inhibits aldehyde dehydrogenase, an enzyme involved in ethanol metabolism. Exposure to disulfiram and alcohol will produce flushing, headache, and hypotension. Disulfiram may also interact with other industrial solvents that share metabolic pathways with ethanol. Limited evidence for adverse effects on fetal development in test animals. IARC 3. See also Disulfiram.	2 mg/m³		Crystalline solid. Thermal breakdown products include oxides of sulfur. Metabolic pathways include carbon disulfide. Disulfiram and related compounds have been used in rubber industry vulcanization.
*Disulfoton (O,O-diethyl-S-ethylmercapto ethyl dithiophosphate [CAS: 298-04-4]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Dermally well absorbed.	0.05 mg/m³, S		Vapor pressure is 0.00018 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur.
Divinylbenzene (DVB, diethylene benzene, vinylstyrene [CAS: 1321-74-0]): Mildly irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. CNS depressant. May be metabolized to a neurotoxin 1,2-diacetylbenzene.	10 ppm		Pale yellow liquid. Combustible. Must contain inhibitor to prevent explosive polymerization.
Endosulfan (CAS: 115-29-7): Inhalation and skin absorption are major routes of exposure. Symptoms include nausea, confusion, twitching, and convulsions. Animal studies suggest liver and kidney injury from very high exposures. Limited evidence for adverse effects on male reproduction and fetal development in animal studies. See also Chlorinated Hydrocarbon Pesticides.	0.1 mg/m³, S		Chlorinated hydrocarbon insecticide. Tan, waxy solid with a mild sulfur dioxide odor. Thermal breakdown products include oxides of sulfur and hydrogen chloride.
Endrin (CAS: 72-20-8): Endrin is the stereoisomer of dieldrin, and its toxicity is very similar. Well absorbed through skin. Overexposure may produce headache, dizziness, nausea, confusion, twitching, and convulsions. Adverse effects on fetal development in test animals. IARC 3. See also Chlorinated Hydrocarbon Pesticides.	0.1 mg/m³, S	2 mg/m³	Colorless, white, or tan solid. A mild chemical odor and negligible vapor pressure of 0.0000002 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride.
Environmental tobacco smoke: Passive smoking causes respiratory irritation and small reductions in lung function. It increases severity and frequency of asthmatic attacks in children. May cause coughing, phlegm production, chest discomfort, and reduced lung function in adults. Causes developmental toxicity in infants and children and reproductive toxicity in female adults. Epidemiologic studies show passive smoking causes lung and other cancers (IARC 1).			Secondhand smoke is now the preferred term for this form of tobacco smoke exposure. Thirdhand smoke exposure refers to the re-release of tobacco byproducts after deposition on surfaces.
Epichlorohydrin (chloropropylene oxide [CAS: 106-89-8]): Extremely irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema has been reported. Other effects include nausea, vomiting, and abdominal pain. Sensitization reported (contact dermatitis). Animal studies suggest potential for liver and kidney injury. High doses reduce fertility in test animals. A carcinogen in test animals (IARC 2A), NIOSH CA.	0.5 ppm, S	75 ppm 10-min AEGL3: 570 ppm	Colorless liquid. The irritating, chloroform-like odor is detectable only at extremely high exposures and is a poor warning property. Vapor pressure is 13 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include hydrogen chloride and phosgene. Used in epoxy manufacturing.
*EPN (O-ethyl O-p-nitrophenyl phenylphosphonothioate [CAS: 210464-5]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	0.1 mg/m³, S	5 mg/m³	Yellow solid or brown liquid. Vapor pressure is 0.0003 mm Hg at 100°C (212°F). Agricultural pesticide.
Ethanolamine (2-aminoethanol [CAS: 141-43-5]): Highly irritating upon direct contact; severe burns may result. Animal studies suggest that at high levels, vapors are irritating to eyes and respiratory tract; liver and kidney injury may occur. Limited evidence for adverse effects on fetal development in animal studies.	3 ppm	30 ppm	Colorless liquid. A mild ammonia-like odor occurs at the TLV and is an adequate warning property. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen.
Ethion (phosphorodithioic acid [CAS: 563-12-2]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed dermally.	0.05 mg/m³, S		Colorless, odorless liquid when pure. Technical products have an objectionable odor. Vapor pressure is 0.000002 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur. Agricultural pesticide.
2-Ethoxyethanol (ethylene glycol monoethyl ether, EGEE, cellosolve [CAS: 110-80-5]): Mildly irritating on direct contact. Skin contact is a major route of absorption. Overexposures may reduce sperm counts in men. A potent teratogen in both rats and rabbits. Large doses cause lung, liver, testes, kidney, and spleen injury in test animals. See also Ethylene Glycol and Other Glycols.	5 ppm, S	500 ppm	Colorless liquid. Very mild, sweet odor occurs only at very high levels and is a poor warning property. Vapor pressure is 4 mm Hg at 20°C (68°F).
2-Ethoxyethyl acetate (ethylene glycol monoethyl ether acetate, cellosolve acetate): Mildly irritating upon direct contact. May produce CNS depression and kidney injury. Skin contact is a major route of absorption. Metabolized to 2-ethoxyethanol. Adverse effects on fertility and fetal development in animals. See also Ethylene Glycol and Other Glycols.	5 ppm, S	500 ppm	Colorless liquid. Mild ether-like odor occurs at the TLV and is a good warning property. Flammable.
Ethyl acetate (CAS: 141-78-6): Slightly irritating to eyes and skin. Vapors irritating to eyes and respiratory tract. A CNS depressant at very high levels. Metabolized to ethanol and acetic acid, so may have some of the fetotoxic potential of ethanol.	400 ppm	2,000 ppm	Colorless liquid. Fruity odor occurs at the TLV and is a good warning property. Vapor pressure is 76 mm Hg at 20°C (68°F). Flammable.
Ethyl acrylate (CAS: 140-88-5): Extremely irritating upon direct contact; severe burns may result. A skin sensitizer. Vapors highly irritating to eyes and respiratory tract. In animal tests, heart, liver, and kidney damage was observed at high doses. A carcinogen in test animals (IARC 2B), NIOSH CA.	5 ppm	300 ppm	Colorless liquid. Acrid odor occurs below the TLV and is a good warning property. Vapor pressure is 29.5 mm Hg at 20°C (68°F). Flammable. Contains an inhibitor to prevent dangerous self-polymerization.
Ethyl alcohol (alcohol, grain alcohol, ethanol, EtOH [CAS: 64-17-5]): At high levels, vapors irritating to eyes and respiratory tract. A CNS depressant at high levels of exposure. Strong evidence for adverse effects on fetal development in test animals and humans with chronic ingestion (fetal alcohol syndrome). IARC 1. See also Ethanol.	1,000 ppm (STEL)	3,300 ppm	Colorless liquid with a mild, sweet odor. Odor threshold near 1,800 ppm. Vapor pressure is 43 mm Hg at 20°C (68°F). Flammable.
Ethylamine (CAS: 75-04-7): Corrosive upon direct contact; severe burns may result. Vapors highly irritating to eyes, skin, and respiratory tract; delayed pulmonary edema may result. Animal studies suggest potential for liver and kidney injury at moderate doses.	5 ppm, S	600 ppm	Colorless liquid or gas with an ammonia-like odor. Highly flammable. Thermal breakdown products include oxides of nitrogen.
Ethyl amyl ketone (5-methyl-3-heptanone [CAS: 541-85-5]): Irritating to eyes upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	10 ppm	100 ppm	Colorless liquid with a strong, distinctive odor. Flammable.
Ethylbenzene (CAS: 100-41-4): Mildly irritating to eyes upon direct contact. May cause skin burns upon prolonged contact. Dermally well absorbed. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels of exposure. IARC 2B.	20 ppm	800 ppm	Colorless liquid. Aromatic odor and irritation occur at levels close to the TLV and are adequate warning properties. Vapor pressure is 7.1 mm Hg at 20°C (68°F). Flammable. California OSHA PEL is 5 ppm.
Ethyl bromide (bromoethane [CAS: 74-96-4]): Irritating to skin upon direct contact. Irritating to respiratory tract. A CNS depressant at high levels and may cause cardiac arrhythmias. Former use as an anesthetic agent was discontinued because of fatal liver, kidney, and myocardial injury. Evidence for carcinogenicity in test animals (IARC 3).	5 ppm, S	2,000 ppm	Colorless to yellow liquid. Ether-like odor detectable only at high, dangerous levels. Vapor pressure is 375 mm Hg at 20°C (68°F). Highly flammable. Thermal breakdown products include hydrogen bromide and bromine gas.
Ethyl butyl ketone (3-heptanone [CAS: 106-35-4]): Mildly irritating to eyes upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	50 ppm	1,000 ppm	Colorless liquid. Fruity odor is a good warning property. Vapor pressure is 4 mm Hg at 20°C (68°F). Flammable.
Ethyl chloride (CAS: 75-00-3): Mildly irritating to eyes and respiratory tract. A CNS depressant at high levels; has caused cardiac arrhythmias at anesthetic doses. Animal studies suggest the kidneys and liver are target organs at high doses. Structurally similar to the carcinogenic chloroethanes. IARC 3.	100 ppm, S	3,800 ppm	Colorless liquid or gas with a pungent, ether-like odor. Highly flammable. Thermal breakdown products include hydrogen chloride and phosgene.
Ethylene chlorohydrin (2-chloroethanol [CAS: 107-07-3]): Skin contact extremely hazardous because it is not irritating and absorption is rapid. Vapors irritating to eyes and respiratory tract; pulmonary edema has been reported. Systemic effects include CNS depression, cardiomyopathy, shock, and liver and kidney damage.	1 ppm (C), S	7 ppm 10-min AEGL3: 6.4 ppm	Colorless liquid with a weak ether-like odor. Vapor pressure is 5 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include hydrogen chloride and phosgene. Industrial intermediate in chemical synthesis but can be created de novo during ethylene oxide sterilization of certain plastics.
Ethylenediamine (CAS: 107-15-3): Highly irritating upon direct contact; burns may result. Respiratory and dermal sensitization may occur. Vapors irritating to eyes and respiratory tract. Animal studies suggest potential for kidney injury at high doses.	10 ppm, S	1,000 ppm 10-min AEGL3: 25 ppm	Colorless viscous liquid or solid. Ammonia-like odor occurs at the PEL and may be an adequate warning property. Vapor pressure is 10 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. Widely used in industrial chemical and pharmaceutical synthesis.
Ethylene dibromide (1,2-dibromoethane, EDB [CAS: 106-93-4]): Highly irritating upon direct contact; severe burns result. Highly toxic by all routes. Vapors highly irritating to eyes and respiratory tract. Severe liver and kidney injury may occur. A CNS depressant. Adverse effects on the testes in animals and possibly humans. A carcinogen in test animals (IARC 2A), NIOSH CA.	S	100 ppm	Colorless liquid or solid. Mild, sweet odor is a poor warning property. Vapor pressure is 11 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen bromide and bromine gas. Chemical intermediate used in organic synthesis. Formerly widely used as a pesticide but now banned in the US except for limited fumigant applications.
Ethylene glycol (antifreeze [CAS: 107-21-1]): A CNS depressant. Metabolized to glycolic, oxalic and other acids; severe acidosis and renal failure may result. Precipitation of calcium oxalate crystals in tissues can cause extensive injury. Adversely affects fetal development in animal studies at very high doses. Not well absorbed dermally. See also Ethylene Glycol and Other Glycols.	25 ppm		Colorless viscous liquid. Odorless with a very low vapor pressure.
Ethylene glycol dinitrate (EGDN [CAS: 628-96-6]): Causes vasodilation similarly to other nitrate compounds (see Nitrates and Nitrites). Headache, hypotension, flushing, palpitation, delirium, and CNS depression may occur. Well absorbed by all routes. Tolerance and dependence may develop to vasodilator effects; cessation after repeated exposures may cause angina pectoris. Can induce methemoglobinemia.	0.05 ppm, S	75 mg/m³	Yellow oily liquid. Vapor pressure is 0.05 mm Hg at 20°C (68°F). Explosive. Historically, a munitions manufacturing chemical.
Ethyleneimine (aziridine [CAS: 151-56-4]): Strong caustic. Highly irritating upon direct contact; severe burns may result. Vapors irritating to eyes and respiratory tract; delayed-onset pulmonary edema may occur. Overexposures have resulted in nausea, vomiting, headache, and dizziness. Well absorbed dermally. Similar compounds are potent sensitizers. A carcinogen in animal studies (IARC 2B), OSHA CA, NIOSH CA.	0.5 ppm, S	100 ppm 10-min AEGL3: 51 ppm	Colorless liquid with an amine-like odor. Vapor pressure is 160 mm Hg at 20°C (68°F). Flammable. Contains inhibitor to prevent explosive self-polymerization. Explosive derivatives can be formed with exposure to silver. Aziridine-derived polyfunctional amines are widely used as hardeners and cross-linking agents in various reactive products.
Ethylene oxide (CAS: 75-21-8): Highly irritating upon direct contact. Vapors irritating to eyes and respiratory tract; delayed pulmonary edema has been reported. CNS depressant at very high levels. Chronic overexposures can cause peripheral neuropathy and possible permanent CNS impairment. Adverse effects on fetal development and fertility in test animals and limited evidence in humans. IARC 1, OSHA CA, NIOSH CA. See also Ethylene Oxide.	1 ppm	800 ppm 10-min AEGL3: 360 ppm	Colorless. Highly flammable. Ether-like odor is a poor warning property. Important source of exposures has been instrument sterilization operations in health care industry.
Ethyl ether (diethyl ether, ether [CAS: 60-29-7]): Vapors irritating to eyes and respiratory tract. A CNS depressant and anesthetic agent; tolerance may develop to this effect. Overexposure produces nausea, headache, dizziness, anesthesia, and respiratory arrest. Evidence for adverse effects on fetal development in test animals.	400 ppm	1,900 ppm	Colorless liquid. Ether-like odor occurs at low levels and is a good warning property. Vapor pressure is 439 mm Hg at 20°C (68°F). Highly flammable. No longer used as a general anesthetic.
Ethyl formate (CAS: 109-94-4): Slightly irritating to the skin upon direct contact. Vapors mildly irritating to eyes and upper respiratory tract. In test animals, very high levels caused rapid narcosis and pulmonary edema.	100 ppm (STEL)	1,500 ppm	Colorless liquid. Fruity odor and irritation occur near the TLV and are good warning properties. Vapor pressure is 194 mm Hg at 20°C (68°F). Highly flammable.
Ethyl methylacrylate monomer (CAS: 97-63-2): Irritant and sensitizing agent.			Precursor of ethyl methacrylate polymers. Flammable.
Ethyl mercaptan (ethanethiol [CAS: 75-08-1]): Vapors mildly irritating to eyes and respiratory tract. Respiratory paralysis and CNS depression at very high levels. Headache, nausea, and vomiting likely owing to strong odor.	0.5 ppm	500 ppm 10-min AEGL3: 450 ppm	Colorless liquid. Penetrating, offensive, mercaptan-like odor. Vapor pressure is 442 mm Hg at 20°C (68°F).
N-Ethylmorpholine (CAS: 100-74-3): Irritating to eyes upon direct contact. Vapors irritating to eyes and respiratory tract. Workers exposed to levels near the TLV reported drowsiness and temporary visual disturbances, including corneal edema. Animal testing suggests potential for skin absorption.	5 ppm, S	100 ppm	Colorless liquid with ammonia-like odor. Vapor pressure is 5 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen.
Ethyl silicate (tetraethyl orthosilicate, tetraethoxysilane [CAS: 78-10-4]): Irritating upon direct contact. Vapors irritating to eyes and respiratory tract. In subchronic animal testing, high vapor levels produced liver, lung, and kidney damage and delayed-onset pulmonary edema.	10 ppm	700 ppm	Colorless liquid. Faint alcohol-like odor and irritation are good warning properties. Vapor pressure is 2 mm Hg at 20°C (68°F). Flammable.
Etidronic acid (1-hydroxyethylidene 1,1-diphosphonic acid, HEDP [CAS: 2809-21-4]): Inadvertent ingestion in an industrial setting has caused renal failure.			A bisphosphonate used in detergents, corrosion inhibition in water cooling and boilers, cosmetics and medical treatment. Available in powder and liquid forms. The liquid form is clear and colorless with a slight odor.
Fenamiphos (phenamiphos [CAS: 22224-92-6]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed dermally.	0.05 mg/m³, S		Tan, waxy solid. Vapor pressure is 0.000001 mm Hg at 30°C (86°F). Agricultural pesticide.
*Fensulfothion (O,O-diethyl O-[4-(methylsulfinyl) phenyl] phosphorothioate [CAS: 115-90-2])*: An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	0.01 mg/m³, S		Brown liquid. Agricultural pesticide.
*Fenthion (O,O-dimethyl O-[3-methyl-4-(methylthio)phenyl] phosphorothioate [CAS: 55-38-9]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Highly lipid-soluble; toxicity may be prolonged. Dermal absorption is rapid.	0.05 mg/m³, S		Yellow to tan viscous liquid with a mild garlic-like odor. Vapor pressure is 0.00003 mm Hg at 20°C (68°F). Agricultural pesticide.
Ferbam (ferric dimethyldithiocarbamate [CAS: 14484-64-1]): Thiocarbamates do not act through cholinesterase inhibition. Dusts irritating upon direct contact; causes dermatitis in persons sensitized to sulfur. Dusts are mild respiratory tract irritants. Limited evidence for adverse effects on fetal development in test animals. IARC 3.	5 mg/m³	800 mg/m³	Odorless, black solid. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include oxides of nitrogen and sulfur. Used as a fungicide.
Ferrovanadium dust (CAS: 12604-58-9): Mild irritant of eyes and respiratory tract.	1 mg/m³	500 mg/m³	Odorless, dark-colored powders.
Fipronil (CAS: 120068-37-3): Phenylpyrazole insecticide; blocks GABA-gated chloride channels and can cause seizures. Mild irritant of eyes and respiratory tract.			Used to kill crickets, fire ants, fleas, ticks, termites, and roaches. Registered for use in more than 50 consumer products.
Fluoride dust (as fluoride): Irritating to eyes and respiratory tract. Workers exposed to levels 10 mg/m³ experienced nasal irritation and bleeding. Chronic overexposures may result in skin rashes. Fluorosis, a bone disease caused by chronic high-level fluoride ingestion, is not associated with occupational dust inhalation. See also Fluoride.	2.5 mg/m³ (as F)	250 mg/m³ (as F)	Appearance varies with the compound. Sodium fluoride is a colorless to blue solid.
Fluorine (CAS: 7782-41-4): Rapidly reacts with moisture to form ozone and hydrofluoric acid. Severe eye, skin, and respiratory tract irritant; penetrating burns and pulmonary edema have resulted. Systemic hypocalcemia can occur with fluorine or hydrogen fluoride exposure. See also Gases, Irritant.	1 ppm	25 ppm 10-min AEGL3: 36 ppm	Pale yellow gas. Sharp odor is a poor warning property. Highly reactive; will ignite many oxidizable materials. Uses include rocket fuel oxidizer.
Fonofos (O-ethyl-S-phenyl ethylphosphonothiolothionate, Dyfonate [CAS: 944-22-9]): A highly toxic organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	0.1 mg/m³, S		Vapor pressure is 0.00021 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur. Agricultural pesticide.
Formaldehyde (formic aldehyde, methanal, HCHO [CAS: 50-00-0]): Highly irritating to eyes upon direct contact. Irritating to skin; may cause sensitization dermatitis. Vapors highly irritating to eyes and respiratory tract. Sensitization may occur. IARC 1, OSHA CA, NIOSH CA. See also Formaldehyde.	0.3 ppm (C), SEN	20 ppm	Colorless gas with a suffocating odor. Odor threshold near 1 ppm. Combustible. Aqueous solutions (formalin) often contain methanol. Formaldehyde off-gassing can occur from formaldehyde-containing materials such as insulation and particle board.
Formamide (methanamide [CAS: 75-12-7]): In animal tests, mildly irritating upon direct contact. Adverse effects on fetal development in test animals at very high doses.	10 ppm, S		Clear, viscous liquid. Odorless. Vapor pressure is 2 mm Hg at 70°C (158°F). Combustible. Thermal breakdown products include oxides of nitrogen.
Formic acid (CAS: 64-18-6): Corrosive; severe burns may result from contact of eyes and skin with concentrated acid. Vapors highly irritating to eyes and respiratory tract. Ingestion may produce severe metabolic acidosis. See “Methanol,”.	5 ppm	30 ppm	Colorless liquid. Pungent odor and irritation occur near the TLV and are adequate warning properties. Vapor pressure is 30 mm Hg at 20°C (68°F). Combustible.
Furfural (bran oil [CAS: 98-01-1]): Highly irritating upon direct contact; burns may result. Vapors highly irritating to eyes and respiratory tract; pulmonary edema may result. Animal studies indicate the liver is a target organ. Hyperreflexia and convulsions occur at large doses in test animals. IARC 3.	2 ppm, S	100 ppm	Colorless to light brown liquid. Almond-like odor occurs below the TLV and is a good warning property. Vapor pressure is 2 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen.
Furfuryl alcohol (CAS: 98-00-0): Dermal absorption occurs. Vapors irritating to eyes and respiratory tract. A CNS depressant at high air levels.	10 ppm, S	75 ppm	Clear, colorless liquid. Upon exposure to light and air, color changes to red or brown. Vapor pressure is 0.53 mm Hg at 20°C (68°F). Combustible.
Gadolinium (CAS: 7440-54-2): Nephrogenic systemic sclerosis (fibrosis) in humans.			Used as a medical contrast agent in magnetic resonance imaging.
Gasoline (CAS: 8006-61-9): Although exact composition varies, the acute toxicity of all gasoline mixes is similar. Vapors irritating to eyes and respiratory tract at high levels. CNS symptoms include incoordination, dizziness, headaches, and nausea. Benzene (generally <1%) is one significant chronic health hazard. Other additives, such as ethylene dibromide and tetraethyl and tetramethyl lead, may be absorbed through the skin. Very limited evidence for carcinogenicity in test animals (IARC 2B). NIOSH CA. See also Hydrocarbons.	300 ppm		Clear to amber liquid with a characteristic odor. Highly flammable. Gasoline is sometimes used inappropriately as a solvent. Substance abuse via inhalation can occur.
Germanium tetrahydride (CAS: 7782-65-2): A hemolytic agent with effects similar to but less potent than those of arsine in animals. Symptoms include abdominal pain, hematuria, anemia, and jaundice.	0.2 ppm		Colorless gas. Highly flammable.
Glutaraldehyde (1,5-pentandial [CAS: 111-30-8]): The purity and therefore the toxicity vary widely. Allergic dermatitis may occur. Highly irritating on contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract; respiratory sensitization or irritant-induced asthma may occur. In animal studies, the liver is a target organ at high doses. See Antiseptics and Disinfectants.	0.05 ppm (C), SEN		Colorless solid crystals. Odor threshold near 0.2 ppm. Vapor pressure is 0.0152 mm Hg at 20°C (68°F). Can undergo hazardous self-polymerization. Commonly used as a sterilizing agent in medical settings, widely replacing ethylene oxide.
Glycidol (2,3-epoxy-1-propanol [CAS: 556-52-5]): Highly irritating to eyes on contact; burns may result. Moderately irritating to skin and respiratory tract. Evidence for carcinogenicity and testicular toxicity in test animals (IARC 2A).	2 ppm	150 ppm	Colorless liquid. Vapor pressure is 0.9 mm Hg at 25°C (77°F). Combustible.
Glyphosate (CAS: 1071-83-6): Intentional self-poisoning has caused acute noncardiogenic pulmonary edema, renal failure; toxic effects may result from the surfactant component rather than from glyphosate itself. IARC 2A. See also Glyphosate.			White or colorless solid. Odorless or slight amine odor; negligible vapor pressure. Stable to light and heat. Agricultural herbicide.
Halothane (CAS: 151-67-7): Potential to cause hepatitis and may be teratogenic in occupationally exposed workers.	50 ppm		Clear, colorless liquid with a sweetish, pleasant odor; inhalation anesthetic.
Hafnium (CAS: 7440-58-6): Based on animal studies, dusts are mildly irritating to eyes and skin. Liver injury may occur at very high doses.	0.5 mg/m³	50 mg/m³	The metal is a gray solid. Other compounds vary in appearance.
Heptachlor (CAS: 76-44-8): Skin absorption is rapid and has caused convulsions and death. Hepatotoxic. Stored in fatty tissues. Limited evidence for adverse effects on fetal development in test animals at high doses. A carcinogen in test animals (IARC 2B). NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.	0.05 mg/m³, S	35 mg/m³	White or light tan, waxy solid with a camphor-like odor. Vapor pressure is 0.0003 mm Hg at 20°C (68°F). Thermal breakdown products include hydrogen chloride. Not combustible. Pesticide use banned by EPA in 1988.
n-Heptane (CAS: 142-82-5): Vapors only slightly irritating to eyes and respiratory tract. May cause euphoria, vertigo, CNS depression, and cardiac arrhythmias at high levels.	400 ppm	750 ppm	Colorless clear liquid. Mild gasoline-like odor occurs below the TLV and is a good warning property. Vapor pressure is 40 mm Hg at 20°C (68°F). Flammable. Industrial solvent also widely used in consumer products.
Hexachlorobutadiene (CAS: 87-68-3): Based on animal studies, rapid dermal absorption is expected. The kidney is the major target organ but also hepatotoxic in animal studies. A carcinogen in test animals (nonetheless, IARC 3), NIOSH CA.	0.02 ppm, S		Heavy, colorless liquid. Thermal breakdown products include hydrogen chloride and phosgene. Solvent and byproduct in industrial chemical synthesis.
Hexachlorocyclopentadiene (CAS: 77-47-4): Vapors extremely irritating to eyes and respiratory tract; lacrimation and salivation. In animal studies, a potent kidney and liver toxin. At higher levels, the brain, heart, and adrenal glands were affected. Tremors occurred at high doses.	0.01 ppm		Yellow to amber liquid with a pungent odor. Vapor pressure is 0.08 mm Hg at 20°C (68°F). Not combustible.
Hexachloroethane (perchloroethane [CAS: 67-72-1]): Hot fumes irritating to eyes, skin, and mucous membranes. Based on animal studies, causes CNS depression and kidney and liver injury at high doses. Limited evidence of carcinogenicity in test animals (IARC 2B), NIOSH CA.	1 ppm, S	300 ppm	White solid with a camphor-like odor. Vapor pressure is 0.22 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include phosgene, chlorine gas, and hydrogen chloride.
Hexamethylene diisocyanate [CAS: 822-06-0]: Irritating to eyes, skin and respiratory system.			Pale yellow liquid with a strong odor. As with other isocyanates, a polyurethane precursor.
Hexachloronaphthalene (Halowax 1014 [CAS: 1335-87-1]): Based on historical workplace experience, a potent toxin causing severe chloracne and severe, occasionally fatal liver injury. See Dioxins. Skin absorption can occur.	0.2 mg/m³, S	2 mg/m³	Light yellow solid with an aromatic odor. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Not combustible.
Hexamethylphosphoramide (CAS: 680-31-9): Low-level exposures produced nasal cavity cancer in rats (IARC 2B). Adverse effects on the testes in test animals. NIOSH CA.	S		Colorless liquid with an aromatic odor. Vapor pressure is 0.07 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen.
n-Hexane (normal hexane [CAS: 110-54-3]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels, producing headache, dizziness, and GI upset. Occupational overexposures have resulted in peripheral neuropathy and color vision impairment; methyl ethyl ketone potentiates this toxicity. Testicular toxicity in animal studies.	50 ppm, S	1,100 ppm 10-min AEGL3: 12,000 ppm	Colorless, clear liquid with a mild gasoline odor. Vapor pressure is 124 mm Hg at 20°C (68°F). Highly flammable. Previously a widely used solvent, in particular in rubber cement type glues.
Hexane isomers (other than n-hexane, isohexane,2,3-demethylbutane): Vapors mildly irritating to eyes and respiratory tract. CNS depressant at high levels, producing headache, dizziness, and GI upset.	500 ppm		Colorless liquids with a mild petroleum odor. Vapor pressures are high at 20°C (68°F). Highly flammable.
sec-Hexyl acetate (1,3-dimethylbutyl acetate[CAS: 108-84-9]): At low levels, vapors irritating to eyes and respiratory tract. Based on animal studies, a CNS depressant at high levels.	50 ppm	500 ppm	Colorless liquid. Unpleasant fruity odor and irritation are both good warning properties. Vapor pressure is 4 mm Hg at 20°C (68°F). Flammable.
Hexylene glycol (2-methyl-2,4-pentanediol[CAS: 107-41-5]): Irritating upon direct contact; vapors irritating to eyes and respiratory tract. A CNS depressant at very high doses in animal studies.	25 ppm (C)		Liquid with a faint sweet odor. Vapor pressure is 0.05 mm Hg at 20°C (68°F). Combustible.
Hydrazine (diamine [CAS: 302-01-2]): Corrosive upon direct contact; severe burns result. Vapors extremely irritating to eyes and respiratory tract; pulmonary edema may occur. Highly hepatotoxic. A convulsant and hemolytic agent. Kidneys are also target organs. Well absorbed by all routes. Limited human evidence of lung cancer (IARC 2A), NIOSH CA.	0.01 ppm, S	50 ppm 10-min AEGL3: 64 ppm	Colorless, fuming, viscous liquid with an amine odor. Vapor pressure is 10 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. Used as a rocket fuel and in some military jet systems. Toxicity treated with pyridoxine.
Hydrogen bromide (HBr [CAS: 10035-10-6]): Direct contact with concentrated solutions may cause corrosive acid burns. Vapors highly irritating to eyes and respiratory tract; pulmonary edema may result.	2 ppm (C)	30 ppm 10-min AEGL3: 740 ppm	Colorless gas or pressurized liquid. Acrid odor and irritation occur near the TLV and are adequate warning properties. Not combustible.
Hydrogen chloride (hydrochloric acid, muriatic acid, HCl[CAS: 7647-01-0]): Direct contact with concentrated solutions may cause corrosive acid burns. Vapors highly irritating to eyes and respiratory tract; pulmonary edema has resulted. IARC 3. See Gases, Irritant.	2 ppm (C)	50 ppm 10-min AEGL3: 620 ppm	Colorless gas with a pungent, choking odor. Irritation occurs near the TLV and is a good warning property. Not combustible. Contact with water, including atmospheric humidity, leads to formation of hydrochloric acid.
Hydrogen cyanide (hydrocyanic acid, prussic acid, HCN[CAS: 74-90-8]): A rapidly acting, potent metabolic asphyxiant that inhibits cytochrome oxidase and stops cellular respiration. See also Cyanide.	4.7 ppm (C), S	50 ppm 10-min AEGL3: 27 ppm	Colorless to pale blue liquid or colorless gas with a sweet, bitter almond smell that is an inadequate warning property, even for those sensitive to it. Vapor pressure is 620 mm Hg at 20°C (68°F). Cyanide salts will release HCN gas with exposure to acids or heat.
Hydrogen fluoride (hydrofluoric acid, HF [CAS: 7664-39-3]): Produces severe, penetrating burns to eyes, skin, and deeper tissues upon direct contact with solutions. Onset of pain and erythema may be delayed as much as 12-16 hours. As a gas, highly irritating to the eyes and respiratory tract; pulmonary edema has resulted. Severe hypocalcemia may occur with overexposure. See Hydrogen Fluoride and Hydrofluoric Acid.	0.5 ppm (C) (as F), S	30 ppm 10-min AEGL3: 170 ppm	Colorless fuming liquid or gas. Irritation occurs at levels below the TLV and is an adequate warning property. Vapor pressure is 760 mm Hg at 20°C (68°F). Not combustible. Concentrated HF is used in the microelectronics industry. Over-the-counter rust-removing products may contain HF, but generally at lower concentrations (<10%).
Hydrogen peroxide (CAS: 7722-84-1): A strong oxidizing agent. Direct contact with concentrated solutions can produce severe eye damage and skin irritation, including erythema and vesicle formation. Vapors irritating to eyes, skin, mucous membranes, and respiratory tract. See also Antiseptics and Disinfectants. IARC 3.	1 ppm	75 ppm	Colorless liquid with a slightly sharp, distinctive odor. Vapor pressure is 5 mm Hg at 30°C (86°F). Because of instability, usually found in aqueous solutions (3% for home use, higher in some “health food” products and in industry). Not combustible but a very powerful oxidizing agent.
Hydrogen selenide (CAS: 7783-07-5): Vapors extremely irritating to eyes and respiratory tract. Systemic symptoms from low-level exposure include nausea and vomiting, fatigue, metallic taste in mouth, and a garlicky breath odor. Animal studies indicate hepatotoxicity.	0.05 ppm	1 ppm 10-min AEGL3: 0.67 ppm	Colorless gas. The strongly offensive odor and irritation occur only at levels far above the TLV and are poor warning properties. Flammable. Water-reactive.
Hydrogen sulfide (sewer gas [CAS: 7783-06-4]): Vapors irritating to eyes and respiratory tract. At higher levels, a potent, rapid systemic toxin causing cellular asphyxia and death. Systemic effects of low-level exposure include headache, cough, nausea, and vomiting. See also Hydrogen Sulfide.	1 ppm	100 ppm 10-min AEGL3: 76 ppm	Colorless gas. Although the strong rotten egg odor can be detected at very low levels, olfactory fatigue occurs. Odor is therefore a poor warning property. Flammable. Produced by the decay of organic material, as may occur in sewers, manure pits, and fish processing. Fossil fuel production or storage also may generate the gas.
Hydroquinone (1,4-dihydroxybenzene [CAS: 123-31-9]): Highly irritating to eyes upon direct contact. Chronic occupational exposures may cause discoloration and opacification of the cornea. Systemic effects from ingestion include tinnitus, headache, dizziness, GI upset, and CNS excitation. May cause methemoglobinemia. Limited evidence of carcinogenicity in test animals (IARC 3).	1 mg/m³, SEN	50 mg/m³	White solid crystals. Vapor pressure is less than 0.001 mm Hg at 20°C (68°F). Combustible. Used in photographic development and as an industrial reducing agent; over-the-counter use as a skin depigmenting agent.
2-Hydroxypropyl acrylate (propylene glycol acrylate, HPA [CAS: 999-61-1]): Highly irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract. Based on structural analogies, compounds containing the acrylate moiety may be carcinogens. No IARC evaluation.	0.5 ppm, S, SEN		Combustible liquid.
Indene (CAS: 95-13-6): Repeated direct contact with the skin has produced dermatitis but no systemic effects. Vapors probably irritating to eyes and respiratory tract. Based on animal studies, high air levels may cause liver and kidney damage.	5 ppm		Colorless liquid. Polycyclic hydrocarbon used industrially in the manufacture of selected polymers.
Indoxacarb (CAS: 173584-44-6): An oxadiazine insecticide that blocks neuronal voltage-dependent sodium channels. Intentional ingestion has resulted in methemoglobinemia and acute kidney injury.			White powder with low water solubility. Vapor pressure is negligible. Used as broad spectrum insecticide in cotton, vegetables, and fruit; introduced as a new “reduced risk” pesticide to replace organophosphates.
Indium (CAS: 7440-74-6): Based on animal studies, the soluble salts are extremely irritating to eyes upon direct contact. Dusts irritating to eyes and respiratory tract. Linked to occupationally related interstitial lung disease, including pulmonary fibrosis and alveolar proteinosis.	0.1 mg/m³		Appearance varies with the compound. The elemental metal is a silver-white lustrous solid. Indium-tin oxide is a sintered metal combination used in flat screen displays.
Iodine (CAS: 7553-56-2): Extremely irritating upon direct contact; severe burns result. Rarely, a skin sensitizer. Vapors extremely irritating and corrosive to eyes and respiratory tract. Medicinal use of iodine-containing drugs has been associated with fetal goiter. Iodine causes adverse effects on fetal development in test animals. See also Iodine.	0.01 ppm		Violet-colored solid crystals. Sharp, characteristic odor is a poor warning property. Vapor pressure is 0.3 mm Hg at 20°C (68°F). Not combustible.
Iron oxide fume (CAS: 1309-37-1): Fumes and dusts can produce a benign pneumoconiosis (siderosis) manifested by chest radiographic opacities. Fume is associated epidemiologically with infectious pneumonia. IARC 3.	5 mg/m³	2,500 mg/m³ (as Fe)	Red-brown fume with a metallic taste. Vapor pressure is negligible at 20°C (68°F). Welders on mild steel are the principal exposure group.
Iron pentacarbonyl (iron carbonyl [CAS: 13463-40-6]): Acute toxicity resembles that of nickel carbonyl. Inhalation of vapors can cause lung and systemic injury without warning signs. Symptoms of overexposure include headache, nausea and vomiting, and dizziness. Symptoms of severe poisoning are fever, extreme weakness, and pulmonary edema; effects may be delayed for up to 36 hours.	0.1 ppm	0.4 ppm 10-min AEGL3: 0.23 ppm	Colorless to yellow viscous liquid. Vapor pressure is 40 mm Hg at 30.3°C (86.5°F). Highly flammable. Used in specialized chemical synthesis applications, including nanotubule formation.
Isoamyl acetate (banana oil, 3-methyl butyl acetate [CAS: 123-92-2]): May be irritating to skin upon prolonged contact. Vapors mildly irritating to eyes and respiratory tract. Symptoms in men exposed to 950 ppm for 0.5 hour included headache, weakness, dyspnea, and irritation of the nose and throat. A CNS depressant at high doses in test animals. Extrapyramidal syndrome (reversible) in one human case report.	50 ppm	1,000 ppm	Colorless liquid. Banana- or pearlike odor and irritation occur at low levels and are good warning properties. Vapor pressure is 4 mm Hg at 20°C (68°F). Flammable. Often used to test respirator fit, including in military recruits.
Isoamyl alcohol (3-methyl-1-butanol, isopentanol [CAS: 123-51-3]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	100 ppm	500 ppm	Colorless liquid. Irritating alcohol-like odor and irritation are good warning properties. Vapor pressure is 2 mm Hg at 20°C (68°F). Flammable.
Isobutyl acetate (2-methylpropyl acetate [CAS: 110-19-0]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels.	50 ppm	1,300 ppm	Colorless liquid. Pleasant fruity odor is a good warning property. Vapor pressure is 13 mm Hg at 20°C (68°F). Flammable.
Isobutyl alcohol (2-methyl-1 propanol [CAS: 78-83-1]): A CNS depressant at high levels.	50 ppm	1,600 ppm	Colorless liquid. Mild characteristic odor is a good warning property. Vapor pressure is 9 mm Hg at 20°C (68°F). Flammable.
Isophorone (trimethylcyclohexenone [CAS: 78-59-1]): Vapors irritating to eyes and respiratory tract. Workers exposed to 5-8 ppm experienced fatigue and malaise after 1 month. Higher exposures result in nausea, headache, dizziness, and a feeling of suffocation at 200-400 ppm. Limited evidence for adverse effects on fetal development in test animals.	5 ppm (C)	200 ppm	Colorless liquid with a camphor-like odor. Vapor pressure is 0.2 mm Hg at 20°C (68°F). Flammable. California OSHA PEL is 4 ppm.
Isophorone diisocyanate (CAS: 4098-71-9): Based on animal studies, extremely irritating upon direct contact; severe burns may result. By analogy with other isocyanates, vapors or mists likely to be potent respiratory sensitizers, causing asthma. See also Isocyanates.	0.005 ppm		Colorless to pale yellow liquid. Vapor pressure is 0.0003 mm Hg at 20°C (68°F). Possible thermal breakdown products include oxides of nitrogen and hydrogen cyanide.
2-lsopropoxyethanol (isopropyl cellosolve, ethylene glycol monoisopropyl ether [CAS: 109-59-1]): Defatting agent causing dermatitis. May cause hemolysis.	25 ppm, S		Clear colorless liquid with a characteristic odor.
Isopropyl acetate (CAS: 108-21-4): Vapors irritating to the eyes and respiratory tract. A weak CNS depressant.	100 ppm	1,800 ppm	Colorless liquid. Fruity odor and irritation are good warning properties. Vapor pressure is 43 mm Hg at 20°C (68°F). Flammable.
Isopropyl alcohol (isopropanol, 2-propanol [CAS: 67-63-0]): Vapors produce mild eye and respiratory tract irritation. High exposures can produce CNS depression. See also Isopropyl Alcohol. IARC 3.	200 ppm	2,000 ppm	Rubbing alcohol. Sharp odor and irritation are adequate warning properties. Vapor pressure is 33 mm Hg at 20°C (68°F). Flammable.
Isopropylamine (2-aminopropane [CAS: 75-31-0]): Corrosive upon direct contact; severe burns may result. Vapors highly irritating to the eyes and respiratory tract. Exposure to vapors can cause transient corneal edema.	5 ppm	750 ppm	Colorless liquid. Strong ammonia odor and irritation are good warning properties. Vapor pressure is 478 mm Hg at 20°C (68°F). Highly flammable. Thermal breakdown products include oxides of nitrogen.
Isopropyl ether (diisopropyl ether [CAS: 108-20-3]): A skin irritant upon prolonged contact with liquid. Vapors mildly irritating to the eyes and respiratory tract. A CNS depressant.	250 ppm	1,400 ppm	Colorless liquid. Offensive and sharp ether-like odor and irritation are good warning properties. Vapor pressure is 119 mm Hg at 20°C (68°F). Highly flammable. Contact with air causes formation of explosive peroxides.
Isopropyl glycidyl ether (CAS: 4016-14-2): Irritating upon direct contact. Allergic dermatitis may occur. Vapors irritating to eyes and respiratory tract. In animals, a CNS depressant at high oral doses; chronic exposures produced liver injury. Some glycidyl ethers possess hematopoietic and testicular toxicity.	50 ppm	400 ppm	Flammable. Vapor pressure is 9.4 mm Hg at 25°C (77°F).
Kepone (chlordecone [CAS: 143-50-0]): Potent neurotoxin; overexposure causes slurred speech, memory impairment, incoordination, weakness, tremor, and convulsions. Causes infertility in males. Hepatotoxic. Well absorbed by all routes. A carcinogen in test animals (IARC 2B), NIOSH CA. See also Chlorinated Hydrocarbon Pesticides.			A solid. Banned pesticide, not manufactured in the US since 1978.
Kerosene (CAS 8008-20-6; 64742-81-0): Mixture of medium-length aliphatic hydrocarbons. Reported to cause encephalopathy (“solvent syndrome”) in those chronically exposed.	200 mg/m³		Colorless to yellowish, oily liquid with a strong, characteristic odor; used in cooking and lighting fuels and jet fuel.
Ketene (ethenone [CAS: 463-51-4]): Vapors extremely irritating to the eyes and respiratory tract, leading to pulmonary edema. Toxicity similar to that of phosgene, of which it is the nonchlorinated analog. Human exposure data limited.	0.5 ppm	5 ppm 10-min AEGL3: 0.24 ppm	Colorless gas with a sharp odor. Acetylating agent. Water-reactive. Auto reacts to form the ketene dimer, which is also toxic.
Lanthanum (oxide or salt [CAS:7439-91-0]): Rare earth element. Fume and dust exposure may be associated with human interstitial lung disease (cerium co-exposure).			Various industrial and research applications.
Lead (inorganic compounds, dusts, and fumes): Toxic to CNS and peripheral nerves, kidneys, and hematopoietic system. Toxicity may result from acute or chronic exposures. Inhalation and ingestion are the major routes of absorption. Symptoms and signs include abdominal pain, anemia, mood or personality changes, and peripheral neuropathy. Encephalopathy may develop with high blood levels. Adversely affects reproductive functions in men and women. Adverse effects on fetal development in test animals. IARC 2A. See also Lead.	0.05 mg/m³	100 mg/m³ (as Pb)	The elemental metal is dark gray. Vapor pressure is low, about 2 mm Hg at 1,000°C (1,832°F). Major industrial sources include smelting, battery manufacture, radiator repair, and glass and ceramic processing. Construction and renovation work involving old leaded paint is another major source. Hobbyists and craft workers can also be exposed to lead (eg, stained glass window making). Environmental pollution (contaminated water, air, and foodstuffs) is an important source of exposure, and lead is found in some traditional (eg, Ayurvedic, Hispanic, Chinese) medicines.
Lead arsenate (CAS: 10102-48-4): Symptoms include abdominal pain, headache, vomiting, diarrhea, nausea, itching, and lethargy. Suspected carcinogen. Liver and kidney damage may also occur. IARC 2A. See “Lead,”, and “Arsenic,”.			White powder often dyed pink. Not combustible. No specific TLV for lead arsenate; use the value for inorganic lead (0.05 mg/m³).
Lead chromate (chrome yellow [CAS: 7758-97-6]): Toxicity may result from both the chromium and the lead components. Lead chromate is a suspected human carcinogen owing to the carcinogenicity of hexavalent chromium (IARC 1) and inorganic lead compounds. See “Lead,”, and “Chromium,”.	0.05 mg/m³ (as Pb), 0.012 mg/m³ (as Cr)		Yellow pigment in powder or crystal form.
Lindane (gamma-hexachlorocyclohexane [CAS: 58-89-9]): A CNS stimulant and convulsant. Vapors irritating to the eyes and mucous membranes and produce severe headaches and nausea. Well absorbed by all routes. Animal feeding studies have resulted in lung, liver, and kidney damage. May injure bone marrow. IARC 1 (non-Hodgkin lymphoma). See also Chlorinated Hydrocarbon Pesticides.	0.5 mg/m³, S	50 mg/m³	White crystalline substance with a musty odor if impure. Not combustible. Vapor is 0.0000094 mm Hg at 20°C (68°F). Use as a pesticide restricted by EPA to certified applicators. No longer licensed in the US as a topical scabicide.
Lithium hydride (CAS: 7580-67-8): Strong vesicant and alkaline corrosive. Extremely irritating upon direct contact; severe burns result. Dusts extremely irritating to eyes and respiratory tract; pulmonary edema may develop. Symptoms of systemic toxicity include nausea, tremors, confusion, blurring of vision, and coma.	0.05 mg/m³ (C)	0.5 mg/m³	Off-white, translucent solid powder that darkens on exposure. Odorless. Very water-reactive, yielding highly flammable hydrogen gas and caustic lithium hydroxide. Finely dispersed powder may ignite spontaneously. California OSHA PEL is 0.025 mg/m³.
LPG (liquefied petroleum gas [CAS: 68476-85-7]): A simple asphyxiant and possible CNS depressant. Flammability dangers greatly outweigh toxicity concerns. See also “Hydrocarbons,”.	1,000 ppm	2,000 ppm	Colorless gas. An odorant usually is added because the pure product is odorless. Highly flammable.
Magnesium oxide fume (CAS: 1309-48-4): Slightly irritating to eyes and upper respiratory tract. There is little evidence to support magnesium oxide as a cause of metal fume fever.	10 mg/m³	750 mg/m³	White fume.
*Malathion (O,O-dimethyl dithiophosphate of diethyl mercaptosuccinate [CAS: 121-75-5]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). May cause skin sensitization. Absorbed dermally. IARC 2A.	1 mg/m³, S	250 mg/m³	Colorless to brown liquid with mild skunklike odor. Vapor pressure is 0.00004 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur and phosphorus. Agricultural pesticide.
Maleic anhydride (2,5-furandione [CAS: 108-31-6]): Extremely irritating upon direct contact; severe burns may result. Vapors and mists extremely irritating to eyes, skin, and respiratory tract. A skin and respiratory tract sensitizer (asthma). IARC 3.	0.01 mg/m³, SEN	10 mg/m³	Colorless to white solid. Strong, penetrating odor. Eye irritation occurs at the TLV and is an adequate warning property. Vapor pressure is 0.16 mm Hg at 20°C (68°F). Combustible.
Mancozeb (CAS: 1018-01-7): Manganese-containing dithiocarbmate fungicide. Based on animal testing and human experience, low acute toxicity. Produces dermatitis in some individuals.			Yellow powder. Odorless. Negligible vapor pressure. Decomposes at high temperature. A related manganese-containing herbicide, maneb, has been associated with parkinsonism.
Manganese compounds and fume (CAS: 7439-96-5): Chronic overexposure results in a CNS toxicity manifested as psychosis, which may be followed by development of parkinsonism (manganism). See also Manganese.	0.02 mg/m³ (elemental inhalable fraction, as Mn), 0.1 mg/m³ (as Mn)	500 mg/m³ (as Mn)	Elemental metal is a gray, hard, brittle solid. Other compounds vary in appearance. Exposure occurs in mining and milling of the metal, in ferromanganese steel production, and through electric arc welding.
Manganese cyclopentadienyl tricarbonyl (MCT [CAS: 12079-65-1]): MCT is an organic manganese compound used as a gasoline antiknock additive. See “Manganese,”.	0.1 mg/m³ (as Mn), S		MCT is used in Canada but is still under EPA review in the US. Ultrafine manganese is a combustion byproduct.
Mecoprop (MCPP [CAS: 93-65-2]): See “Chlorophenoxy Herbicides,”. IARC 2B.			Colorless or white crystals and flakes. Agricultural pesticide (herbicide).
Melamine (CAS: 108-78-1): Eye and respiratory tract irritant. Animal tests and ingestion of contaminated pet food produce kidney damage and failure. IARC 2B.			Colorless or white crystals and flakes. Sublimes. Decomposition produces cyanide and nitrogen oxides. In addition to occupational exposures, the public has been exposed through contaminated food.
Mercury, elemental and inorganic (quicksilver [CAS: 7439-97-6], calomel [CAS: 10112-91-1]): Acute exposures to high vapor levels cause toxic pneumonitis and pulmonary edema. Well absorbed by inhalation. Skin contact can produce irritation and sensitization dermatitis. Mercury salts but not metallic mercury are toxic to the kidneys. High acute or chronic overexposures can result in CNS toxicity, chronic renal disease, and peripheral neuropathy. Some inorganic mercury compounds have adverse effects on fetal development in test animals. See also Mercury. IARC 3.	0.025 mg/m³, S	10 mg/m³	Elemental metal is a dense, silvery liquid. Odorless. Vapor pressure is 0.0012 mm Hg at 20°C (68°F). Sources of exposure include small-scale gold refining or recycling operations by hobbyists and mercury-containing instruments. Vacuuming spilled mercury can lead to high airborne levels. Skin absoption of mercurous chloride, a common adulterant of skin lightening products, can lead to systemic Hg poisoning.
Mercury, organic (alkyl) compounds (methyl mercury, methylmercury iodide, dimethylmercury, diethyl mercury, ethylmercuric chloride, phenylmercuric acetate): Well absorbed by all routes. Slow excretion may allow accumulation to occur. Readily crosses blood-brain barrier and placenta. Can cause kidney damage, organic brain disease, and peripheral neuropathy. Some compounds are extremely toxic. Methylmercury is teratogenic in humans. See also Mercury.	0.01 mg/m³ (as Hg), S	2 mg/m³ (as Hg)	Colorless liquids or solids. Many alkyl compounds have a disagreeable odor. Inorganic mercury can be converted to alkyl mercury compounds in the environment. Can accumulate in food chain. Historically, methyl mercury was used as a grain treatment pesticide. Phenylmercuric acetate use as a fungicide was banned from indoor paints in 1990. Systemic toxicity from methylmercury iodide contamination of a skin lightening cream has been reported.
Mesityl oxide (4-methyl-3-penten-2-one [CAS: 141-79-7]): Causes dermatitis upon prolonged contact. Vapors very irritating to eyes and respiratory tract. Based on animal tests, a CNS depressant and injures kidney and liver at high levels.	15 ppm	1,400 ppm	Colorless viscous liquid with a strong odor. Irritation is an adequate warning property. Vapor pressure is 8 mm Hg at 20°C (68°F). Flammable. Readily forms peroxides.
Metaldehyde (CAS: 108-62-3). Pesticide for molluscs (snails and slugs) and common cause of poisoning in household pets; human ingestions reported, including seizures and fatalties.			Solid material. Also commonly used as a camping stove fuel.
Metam sodium (sodium methydithiocarbamate [CAS: 137-42-8]): Skin, eye, mucous membrane, and respiratory tract irritant. Reacts with water to yield methyl isothiocyanate, an irritant that has been associated with asthma. Carbon disulfide is also a breakdown product.			Olive green to light yellow liquid with fairly strong sulfur-like odor. Miscible in water. Boiling point 110°C. Vapor pressure 21 mm Hg at 25°C (77°F). Combustion may release oxides of sulfur and nitrogen. Soil pesticide.
Methacrylic acid (2-methylpropenoic acid [CAS: 79-41-4]): Corrosive upon direct contact; severe burns result. Vapors highly irritating to eyes and, possibly, respiratory tract. Based on structural analogies, compounds containing the acrylate moiety may be carcinogens. No IARC evaluation.	20 ppm		Liquid with an acrid, disagreeable odor. Vapor pressure is less than 0.1 mm Hg at 20°C (68°F). Combustible. Polymerizes above 15°C (59°F), emitting toxic gases.
Methamidophos (CAS: 10265-92-6): Irritating to the skin and eyes; can be absorbed dermally. Organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides) that can also cause delayed peripheral neuropathy.			Colorless crystals with a mercaptan-like odor. Not water soluble; soluble in toluene, n-hexane, and 2-propanol. Oxidation produces toxic phosphorus oxides. Flammable and toxic phosphine gas produced in contact with strong reducing agents. Agricultural pesticide.
Methomyl (S-methyl-N-[(methylcarbamoyl)oxy] thioacetimidate, Lannate, Nudrin [CAS: 16752-77-5]): A carbamate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).	0.2 mg/m³ (inhalable faction and vapors), S		A slight sulfur odor. Vapor pressure is 0.00005 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen and sulfur. Agricultural pesticide.
Methoxychlor (dimethoxy-DDT, 2,2-bis(p-methoxyphenol)-1,1,1-trichloroethane [CAS: 72-43-5]): Organochlorine (p186). Convulsant at very high doses in test animals. Limited evidence for adverse effects on male reproduction and fetal development in test animals at high doses. IARC 3, NIOSH CA.	10 mg/m³	5,000 mg/m³	Colorless to tan solid with a mild fruity odor. Appearance and some hazardous properties vary with the formulation. Vapor pressure is very low at 20°C (68°F). Agricultural pesticide.
2-Methoxyethanol (ethylene glycol monomethyl ether, methyl cellosolve [CAS: 109-86-4]): Workplace overexposures have resulted in depression of the hematopoietic system and encephalopathy. Symptoms include disorientation, lethargy, and anorexia. Well absorbed dermally. Animal testing revealed testicular atrophy and teratogenicity at low doses. Overexposure associated with reduced sperm counts in workers. See also Ethylene Glycol and Other Glycols.	0.1 ppm, S	200 ppm	Clear, colorless liquid with a faint odor. Vapor pressure is 6 mm Hg at 20°C (68°F). Flammable. Industrial solvent.
2-Methoxyethyl acetate (ethylene glycol monomethyl ether acetate, methyl cellosolve acetate [CAS: 110-49-6]): Mildly irritating to eyes upon direct contact. Dermally well absorbed. Vapors slightly irritating to the respiratory tract. A CNS depressant at high levels. Based on animal studies, may cause kidney damage, leukopenia, testicular atrophy, and birth defects. See also Ethylene Glycol and Other Glycols.	0.1 ppm, S	200 ppm	Colorless liquid with a mild, pleasant odor. Flammable. Industrial solvent.
Methyl acetate (CAS: 79-20-9): Vapors moderately irritating to the eyes and respiratory tract. A CNS depressant at high levels. Hydrolyzed to methanol in the body with possible consequent toxicity similar to that of methanol.	200 ppm	3,100 ppm	Colorless liquid with a pleasant, fruity odor that is a good warning property. Vapor pressure is 173 mm Hg at 20°C (68°F). Flammable.
Methyl acetylene (propyne [CAS: 74-99-7]): A CNS depressant and respiratory irritant at very high air concentrations in test animals.	1,000 ppm	1,700 ppm	Colorless gas with sweet odor. Flammable.
Methyl acrylate (2-propenoic acid methyl ester [CAS: 96-33-3]): Methacrylic acid. Highly irritating upon direct contact; severe burns may result. A sensitizer. Vapors highly irritating to the eyes and respiratory tract. Based on structural analogies, compounds containing the acrylate moiety may be carcinogens (IARC 2B).	2 ppm, S, SEN	250 ppm	Colorless liquid with a sharp, fruity odor. Vapor pressure is 68.2 mm Hg at 20°C (68°F). Inhibitor included to prevent violent polymerization. Exposure can occur through artificial (sculpted) nail application.
Methylacrylonitrile (2-methyl-2-propenenitrile, methacrylonitrile, 2-cyanopropene [CAS: 126-98-7]): Mildly irritating upon direct contact. Well absorbed dermally. Metabolized to cyanide. In animal tests, acute inhalation at high levels caused death without signs of irritation. Lower levels produced convulsions and loss of motor control.	1 ppm, S	10-min AEGL3: 3.9 ppm	Liquid. Vapor pressure is 40 mm Hg at 13°C (55°F). Industrial polymer.
Methylal (dimethoxymethane [CAS: 109-87-5]): Mildly irritating to eyes and respiratory tract. A CNS depressant at very high levels. Animal studies suggest a potential to injure heart, liver, kidneys, and lungs at very high air levels.	1,000 ppm	2,200 ppm	Colorless liquid with pungent, chloroform-like odor. Highly flammable.
Methyl alcohol (methanol, wood alcohol [CAS: 67-56-1]): Mildly irritating to eyes and skin. Systemic toxicity may result from absorption by all routes. Toxic metabolites are formate and formaldehyde. Signs and symptoms include headache, nausea, abdominal pain, dizziness, shortness of breath, metabolic acidosis, and coma. Visual disturbances range from blurred vision to blindness. See also Methanol.	200 ppm, S	6,000 ppm	Colorless liquid with a distinctive, sharp odor that is a poor warning property. Flammable. Found in fuels, solvents, windshield fluids and antifreezes.
Methylamine (CAS: 74-89-5): Corrosive. Vapors highly irritating to eyes, skin, and respiratory tract; severe burns and pulmonary edema may result.	5 ppm	100 ppm 10-min AEGL3: 910 ppm	Colorless gas with a fishy or ammonia-like odor. Odor is a poor warning property owing to olfactory fatigue. Flammable. Used in a variety of organic synthesis applications, including methamphetamine production.
Methyl-n-amyl ketone (2-heptanone [CAS: 110-43-0]): Vapors are irritating to eyes and respiratory tract. A CNS depressant. Flammable.	50 ppm	800 ppm	Colorless or white liquid with a fruity odor. Vapor pressure is 2.6 mm Hg at 20°C (68°F).
N-Methylaniline (CAS: 100-61-8): A potent inducer of methemoglobinemia. Well absorbed by all routes. Animal studies suggest potential for liver and kidney injury.	0.5 ppm, S		Yellow to light brown liquid with a weak ammonia-like odor. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen.
Methyl bromide (bromomethane [CAS: 74-83-9]): Causes severe irritation and burns upon direct contact. Vapors irritating to the lung; pulmonary edema may result. The CNS, liver, and kidneys are major target organs; acute poisoning causes nausea, vomiting, delirium, and convulsions. Both inhalation and skin exposure may cause systemic toxicity. Chronic exposures associated with peripheral neuropathy in humans. Evidence for adverse effects on fetal development in test animals. Limited evidence of carcinogenicity in test animals (IARC 3), NIOSH CA. See also Methyl Bromide.	1 ppm, S	250 ppm 10-min AEGL3: 3,300 ppm	Colorless liquid or gas with a mild chloroform-like odor that is a poor warning property. Chloropicrin, a lacrimator, often is added as a warning agent. Methyl bromide has been widely used as a fumigant in agriculture and in structural pesticide control but is being phased out because of its ozone-depleting potential.
Methyl n-butyl ketone (MBK, 2-hexanone [CAS: 591-78-6]): Vapors irritating to eyes and respiratory tract at high levels. A CNS depressant at high doses. Causes peripheral neuropathy by a mechanism thought to be the same as that of n-hexane. Well absorbed by all routes. Testicular toxicity in animal studies.	5 ppm, S	1,600 ppm	Colorless liquid with an acetone-like odor. Vapor pressure is 3.8 mm Hg at 20°C (68°F). Flammable. NIOSH-recommended exposure limit is 1 ppm. California OSHA PEL is 1 ppm.
Methyl chloride (chloromethane [CAS: 74-87-3]): Symptoms include headache, confusion, ataxia, convulsions, and coma. Liver, kidneys, and bone marrow are other target organs. Evidence for adverse effects on both the testes and fetal development. IARC 3, NIOSH CA.	50 ppm, S	2,000 ppm 10-min AEGL3: 3,800 ppm	Colorless gas with a mild, sweet odor that is a poor warning property. Highly flammable. Industrial chemical also formerly used as an anesthetic and refrigerant.
Methyl-2-cyanoacrylate (CAS: 137-05-3): Vapors irritating to the eyes and upper respiratory tract. May act as a sensitizer (skin and lungs). A strong and fast-acting glue that can cause body parts to adhere to each other or surfaces. Direct contact with the eyes may result in mechanical injury if the immediate bonding of the eyelids is followed by forced separation.	0.2 ppm		Colorless viscous liquid. Commonly, this compound and related substances are known as “super glues.”
Methylcyclohexane (CAS: 108-87-2): Irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Based on animal studies, liver and kidney injury may occur at chronic high doses.	400 ppm	1,200 ppm	Colorless liquid with a faint benzene-like odor. Vapor pressure is 37 mm Hg at 20°C (68°F). Highly flammable.
o-Methylcyclohexanone (CAS: 583-60-8): Based on animal studies, irritating upon direct contact. Dermal absorption occurs. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels.	50 ppm, S	600 ppm	Colorless liquid with mild peppermint odor. Irritation is a good warning property. Vapor pressure is about 1 mm Hg at 20°C (68°F). Flammable.
*Methyl demeton (O,O-dimethyl 2-ethylmercaptoethyl thiophosphate [CAS: 8022-00-2]):* An organophosphate-type cholinesterase inhibitor. See Organophosphorus and Carbamate Insecticides.	0.5 mg/m³, S		Colorless to pale yellow liquid with an unpleasant odor. Vapor pressure is 0.00036 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur and phosphorus. Agricultural pesticide.
4,4'-Methylene-bis(2-chloroaniline) (MOCA [CAS: 101-14-4]): A human carcinogen (IARC 1), NIOSH CA. Dermal absorption occurs.	0.01 ppm, S		Tan solid. Thermal breakdown products include oxides of nitrogen and hydrogen chloride.
Methylene bis (4-cyclohexylisocyanate, dmdi, 4-HMDI [CAS: 5124-30-1]): A strong irritant and skin and respiratory tract sensitizer (asthma).	0.005 ppm		White to pale yellow solid flakes. Odorless. Possible thermal breakdown products include oxides of nitrogen and hydrogen cyanide. Precursor component of polyurethanes.
Methylene bisphenyl isocyanate (4,4-diphenylmethane diisocyanate, MDI [CAS: 101-68-8]): Irritating upon direct contact. Vapors and dusts highly irritating to eyes and respiratory tract. Potent respiratory tract sensitizer (asthma). IARC 3.	0.005 ppm	75 mg/m³	White to pale yellow flakes. Odorless. Vapor pressure is 0.05 mm Hg at 20°C (68°F). Possible thermal breakdown products include oxides of nitrogen and hydrogen cyanide. Precursor component of polyurethanes.
Methylene chloride (methylene dichloride, dichloromethane [CAS: 75-09-2]): Irritating upon prolonged direct contact. Dermal absorption occurs. Vapors irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. Liver and kidney injury at high concentrations. Converted to carbon monoxide in the body with resultant carboxyhemoglobin formation. A carcinogen in test animals (IARC 2A), OSHA CA, NIOSH CA. See also Methylene Chloride.	50 ppm	2,300 ppm 10-min AEGL3: 12,000 ppm	Heavy colorless liquid with a chloroform-like odor that is a poor warning property. Vapor pressure is 350 mm Hg at 20°C (68°F). Possible thermal breakdown products include phosgene and hydrogen chloride. Methylene chloride is a solvent with many industrial and commercial uses (eg, paint strippers, carburetor cleaners).
4,4-Methylene dianiline (4,4'-diaminodiphenylmethane [CAS: 101-77-9]): Vapors highly irritating to eyes and respiratory tract. Hepatotoxicity (cholestatic jaundice) observed in overexposed workers. Systemic toxicity may result from inhalation, ingestion, or skin contact. Methemoglobinemia, kidney injury, retinal injury, and evidence of carcinogenicity in animals (IARC 2B), OSHA CA, NIOSH CA.	0.1 ppm, S		Light brown solid crystals with a faint amine odor. Combustible. Thermal breakdown products include oxides of nitrogen. Used in synthesis of isocyanate and other polymer production. Historically, large-scale exposure incident occurred from contaminated foodstuffs (Epping jaundice).
Methylene iodide (iodoform [CAS: 75-47-8]): Severe liver toxin. Causes CNS impairment associated with elevated iodide levels. Metabolized to carbon monoxide. Elevated carboxyhemoglobin (COHb) noted following heavy acute ingestion. Iodide toxicity with chronic application to wounds and nonintact skin.	0.6 ppm	100 ppm	Colorless liquid. Acrid ether-like odor. Vapor pressure is 400 mm Hg at 25°C (77°F). Medical disinfectant.
Methyl ethyl ketone (2-butanone, MEK [CAS: 78-93-3]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Limited evidence for adverse effects on fetal development in test animals. Potentiates neurotoxicity of methyl butyl ketone and n-hexane.	200 ppm	3,000 ppm 10-min AEGL3: 10,000 ppm	Colorless liquid with a mild acetone odor. Vapor pressure is 77 mm Hg at 20°C (68°F). Flammable.
Methyl ethyl ketone peroxide (CAS: 1338-23-4): Based on chemical reactivity, highly irritating upon direct contact; severe burns may result. Vapors or mists likely to be highly irritating to the eyes and respiratory tract. Corrosive if ingested. In animal tests, overexposure resulted in liver, kidney, and lung damage.	0.2 ppm (C)		Colorless liquid with a characteristic odor. Shock-sensitive. Breaks down above 50°C (122°F). Explodes upon rapid heating. May contain additives such as dimethyl phthalate, cyclohexanone peroxide, and diallylphthalate to add stability. Used as a hardener in manufacture of resins and plastics, including fiberglass.
Methyl formate (CAS: 107-31-3): Vapors highly irritating to eyes and respiratory tract. A CNS depressant at high levels. Exposure has been associated with visual disturbances, including temporary blindness.	50 ppm, S	4,500 ppm	Colorless liquid with a pleasant odor at high levels. Odor is a poor warning property. Vapor pressure is 476 mm Hg at 20°C (68°F). Highly flammable.
Methylhydrazine (monomethylhydrazine [CAS: 60-34-4]): Similar to hydrazine in its toxicity. Vapors likely to be highly irritating to the eyes and respiratory tract. Causes methemoglobinemia. Potent hemolysin. Highly hepatotoxic. Causes kidney injury. A convulsant. A carcinogen in test animals. No IARC evaluation. NIOSH CA.	0.01 ppm, S	20 ppm 10-min AEGL3: 16 ppm	Colorless clear liquid. Vapor pressure is 36 mm Hg at 20°C (68°F). Flammable. Used as a rocket propellant like the related dimethyl hydrazine. Exposure to methylhydrazine can also occur from ingestion of false morel mushrooms.
Methyl iodide (iodomethane [CAS: 74-88-4]): An alkylating agent. Based on chemical properties, likely to be highly irritating upon direct contact; severe burns may result. Dermal absorption is likely. Vapors highly irritating to respiratory tract; pulmonary edema has resulted. Neurotoxic: signs and symptoms include nausea, vomiting, dizziness, slurred speech, visual disturbances, ataxia, tremor, irritability, convulsions, and coma. Delusions and hallucinations may persist following acute exposure. Severe hepatic injury may also occur. Limited evidence of carcinogenicity in test animals (IARC 3), NIOSH CA.	2 ppm, S	100 ppm 10-min AEGL3: 670 ppm	Colorless, yellow, red, or brown liquid. Not combustible. Vapor pressure is 375 mm Hg at 20°C (68°F). Thermal breakdown products include iodine and hydrogen iodide. Agricultural fumigant that was proposed as a replacement for methyl bromide, but withdrawn in US before widespread use.
Methyl isoamyl ketone (5-methyl-2-hexanone [CAS: 110-12-3]): By analogy to other aliphatic ketones, vapors are likely to be irritating to eyes and respiratory tract. Likely to be a CNS depressant.	20 ppm		Colorless liquid with a pleasant odor. Vapor pressure is 4.5 mm Hg at 20°C (68°F). Flammable.
Methyl isobutyl ketone (4-methyl-2-pentanone, hexone [CAS: 108-10-1]): Irritating to eyes upon direct contact. Vapors irritating to eyes and respiratory tract. Reported systemic symptoms in humans are weakness, dizziness, ataxia, nausea, vomiting, and headache. High-dose studies in animals suggest a potential for liver and kidney injury. IARC 2B.	20 ppm	500 ppm	Colorless liquid with a mild odor. Vapor pressure is 7.5 mm Hg at 25°C (77°F). Flammable.
Methyl isocyanate (MIC [CAS: 624-83-9]): Highly reactive; highly corrosive upon direct contact. Vapors extremely irritating to eyes, skin, and respiratory tract; severe burns and fatal pulmonary edema have resulted. A sensitizing agent. Toxicity is not related to cyanide. Evidence that severe poisonings have adverse effects on fetal development. See Isocyanates.	0.02 ppm, S	3 ppm 10-min AEGL3: 1.2 ppm	Colorless liquid with a sharp, disagreeable odor that is a poor warning property. Vapor pressure is 348 mm Hg at 20°C (68°F). Flammable. Reacts with water to release methylamine. Polymerizes upon heating. Thermal breakdown products include hydrogen cyanide and oxides of nitrogen. Used as a chemical intermediate in carbamate pesticide synthesis. MIC is not in urethanes.
Methyl mercaptan (CAS: 74-93-1): Causes delayed-onset pulmonary edema. CNS effects include narcosis and convulsions. Reported to have caused methemoglobinemia and hemolysis in a patient with G6PD deficiency.	0.5 ppm	150 ppm 10-min AEGL3: 120 ppm	Colorless liquid with an offensive rotten egg odor. Odor and irritation are good warning properties.
Methyl methacrylate (CAS: 80-62-6): Irritating upon direct contact. Vapors irritating to the eyes, skin, and respiratory tract. A sensitizer (asthma and dermatitis). At very high levels may produce headache, nausea, vomiting, or dizziness. Possible peripheral nerve toxicity. Limited evidence for adverse effects on fetal development in animal tests. Limited evidence for carcinogenicity (IARC 3).	50 ppm, SEN	1,000 ppm	Colorless liquid with a pungent, acrid, fruity odor. Vapor pressure is 35 mm Hg at 20°C (68°F). Flammable. Contains inhibitors to prevent self-polymerization. Used in resin polymers, including medical applications.
*Methyl parathion (O,O-dimethyl*O-p-nitrophenylphosphorothioate [CAS: 298-00-01): A highly potent organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). IARC 3.	0.02 mg/m³, S		Tan liquid with a strong garlic-like odor. Vapor pressure is 0.5 mm Hg at 20°C (68°F). Appearance may vary with formulation. Agricultural pesticide.
Methyl propyl ketone (2-pentanone [CAS: 107-87-9]): Vapors irritating to eyes and respiratory tract. Based on animal studies, a CNS depressant at high levels.	150 ppm (STEL)	1,500 ppm	Colorless liquid with a characteristic odor. Vapor pressure is 27 mm Hg at 20°C (68°F). Flammable.
Methyl silicate (tetramethoxy silane [CAS: 681-84-5]): Highly reactive; corrosive upon direct contact; severe burns may result. Vapors extremely irritating to eyes and respiratory tract; severe eye burns and pulmonary edema may result.	1 ppm	10-min AEGL3: 1.7 ppm	Colorless crystals. Reacts with water, forming silicic acid and methanol.
alpha-Methylstyrene (CAS: 98-83-9): Slightly irritating upon direct contact. Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. IARC 2B.	10 ppm	700 ppm	Colorless liquid with a characteristic odor. Irritation is an adequate warning property. Vapor pressure is 1.9 mm Hg at 20°C (68°F). Flammable.
*Methyl tert-butyl ether (MTBE [CAS: 1634-04-4]):* Vapors mildly irritating to eyes and respiratory tract. A CNS depressant; acute exposure at high levels can cause nausea, vomiting, dizziness, and sleepiness. Adverse effects on liver and kidney in test animals at high levels. Evidence for adverse effects on reproduction and carcinogenicity in test animals exposed to very high concentrations (IARC 3).	50 ppm		A volatile colorless liquid at room temperature. Odor threshold near 50 ppm. Gasoline additive banned in several states. Vapor pressure is 248 mm Hg at 25°C (77°F).
Metribuzin (4-amino-6-[1,1-dimethylethyl]-3-[methylthio]-1,2,4-triazin-5[4H]-one [CAS: 21087-64-9]): Human data available reveal no irritation or sensitization after dermal exposure. In animal testing, was poorly absorbed through the skin and produced no direct skin or eye irritation. Repeated high doses caused CNS depression and liver and thyroid effects.	5 mg/m³		Vapor pressure is 0.00001 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur and nitrogen. Agricultural pesticide (herbicide).
Mevinphos (2-carbomethoxy-1-methylvinyl dimethylphosphate, phosdrin [CAS: 7786-34-7]): An organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed by all routes. With repeated exposures to low levels, can accumulate to produce symptoms.	0.01 mg/m³, S	4 ppm	Colorless or yellow liquid with a faint odor. Vapor pressure is 0.0022 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include phosphoric acid mist. Agricultural pesticide.
Mica (CAS: 12001-25-2): Dusts may cause pneumoconiosis with chronic inhalation.	3 mg/m³	1,500 mg/m³	Colorless solid flakes or sheets. Odorless. Vapor pressure is negligible at 20°C (68°F). Noncombustible.
Monocrotophos (dimethyl 2-methylcarbamoyl-1-methylvinyl phosphate [CAS: 6923-22-4]): An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Limited human data indicate it is well absorbed through the skin but is rapidly metabolized and excreted.	0.05 mg/m³, S		Reddish-brown solid with a mild odor. Agricultural pesticide.
Morpholine (tetrahydro-1,4-oxazine [CAS: 110-91-8]): Corrosive; extremely irritating upon direct contact; severe burns may result. Well absorbed dermally. Vapors irritating to eyes and respiratory tract. Exposure to vapors has caused transient corneal edema. May cause severe liver and kidney injury. Inadequate carcinogenicity data (IARC 3).	20 ppm, S	1,400 ppm	Colorless liquid with mild ammonia-like odor. Vapor pressure is 7 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. Found in some consumer polish and wax products.
Monosodium methanearsonate (MSMA [CAS: 2163-80-6)]. Arsenical herbicide. Hepatoxin and auditory neurotoxin.			Light yellow liquid. Odorless.
Naphthalene (CAS: 91-20-3): Highly irritating to eyes upon direct contact. Vapors are irritating to eyes and may cause cataracts upon chronic exposure. Dermally well absorbed. May induce methemoglobinemia. Symptoms of overexposure include headache and nausea. Causes cataracts and retinal damage in animal studies. Suspected carcinogen (IARC 2B). See also Naphthalene and Paradichlorobenzene.	10 ppm, S	250 ppm	White to brown solid. The mothball odor and respiratory tract irritation are good warning properties. Current mothball formulations in the US do not contain naphthalene. Vapor pressure is 0.05 mm Hg at 20°C (68°F). Combustible. California OSHA PEL 0.1 ppm.
beta-Naphthylamine (2-aminonaphthalene [CAS:91-59-8]): Acute overexposures can cause methemoglobinemia or acute hemorrhagic cystitis. Well absorbed through skin. Known human bladder carcinogen (IARC 1), OSHA CA, NIOSH CA.			White to reddish crystals. Vapor pressure is 1 mm Hg at 108°C (226°F). Combustible. Former rubber industry chemical.
Neonicitinoids: imidacloprid [CAS 13821-41-3], clothianidin [CAS 210880], dinotefuran [CAS 165252-80-0], nitenpyram [CAS 150824-47-8] and thiamethoxam [CAS 153719-23-4]: Agonists at postsynaptic nicotinic acetylcholine receptors. Poor permeability of the blood-brain barrier. Clinical effects of exposure may resemble nicotine toxicity. Serious adverse effects such as respiratory failure, sedation, seizures, and rhabdomyolysis have been reported.			Agricultural pesticides. They are highly selective for the nicotinic receptors in insects compared with mammals.
Nickel carbonyl (nickel tetracarbonyl [CAS: 13463-39-3]): Inhalation of vapors can cause severe lung and systemic injury without irritant warning signs. Effects include headache, nausea, vomiting, fever, extreme weakness and ventilatory failure. Based on animal studies, liver and brain damage may occur. Adverse effects on fetal development in test animals. A carcinogen in test animals. No IARC evaluation. NIOSH CA.	0.05 ppm (as Ni), C	2 ppm (as Ni) 10-min AEGL3 : 0.46 ppm	Colorless liquid or gas. The musty odor is a poor warning property. Vapor pressure is 321 mm Hg at 20°C (68°F). Highly flammable. Exposures largely limited to nickel refining. Metal smelter byproduct. California OSHA PEL is 0.001 ppm.
Nickel metal and soluble inorganic salts (nickelchloride, nickel sulfate, nickel nitrate, nickel oxide): May cause a severe sensitization dermatitis, “nickel itch,” upon repeated contact. Fumes highly irritating to the respiratory tract. Some compounds have adverse effects on fetal development in test animals. Some compounds are human nasal and lung carcinogens (nickel compounds, IARC 1; nickel metal, IARC 2B), NIOSH CA.	1.5 mg/m³ (elemental); 0.1 mg/m³ (soluble compounds, as Ni); 0.2 mg/m³ (insoluble compounds, as Ni)	10 mg/m³ (as Ni)	Gray metallic powder or green solids. All forms are odorless.
Nicotine (CAS: 54-11-5): A potent nicotinic cholinergic receptor agonist. Well absorbed by all routes of exposure. Symptoms include dizziness, confusion, weakness, nausea and vomiting, tachycardia and hypertension, tremors, convulsions, and muscle paralysis. Death from respiratory paralysis can be very rapid. Adverse effects on fetal development in animal studies. See also Nicotine.	0.5 mg/m³, S	5 mg/m³	Pale yellow to dark brown viscous liquid with a fishy or amine-like odor. Vapor pressure is 0.0425 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen. A widely used pesticide. Dermal absorption can occur in tobacco harvesters (“green tobacco illness”). California OSHA PEL 0.075 ppm.
Nitric acid (aqua fortis, engraver's acid [CAS: 7697-37-2]): Concentrated solutions corrosive to eyes and skin; very severe penetrating burns result. Vapors highly irritating to eyes and respiratory tract; acute lung injury has resulted. Chronic inhalation exposure can produce bronchitis and erosion of the teeth.	2 ppm	25 ppm 10-min AEGL3: 170 ppm	Colorless, yellow, or red fuming liquid with an acrid, suffocating odor near 1 ppm. Vapor pressure is approximately 62 mm Hg at 25°C (77°F). Not combustible. Interaction with organic materials or selected metals can release nitrogen dioxide. Home exposures have occurred in hobbyists.
Nitric oxide (NO, nitrogen monoxide [CAS: 10102-43-9]): Nitric oxide slowly converts to nitrogen dioxide in air; eye and mucous membrane irritation and pulmonary edema are likely from nitrogen dioxide. Overexposures have been reported to result in acute and chronic obstructive airway disease. Based on animal studies, may cause methemoglobinemia. See also Nitrogen Oxides.	25 ppm	100 ppm	Colorless or brown gas. The sharp, sweet odor occurs below the TLV and is a good warning property.
p-Nitroaniline (CAS: 100-01-6): Irritating to eyes upon direct contact; may injure cornea. Well absorbed by all routes. Over-exposure results in headache, weakness, respiratory distress, and methemoglobinemia. Liver damage may also occur.	3 mg/m³, S	300 mg/m³	Yellow solid with an ammonia-like odor that is a poor warning property. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen.
Nitrobenzene (CAS: 98-95-3): Irritating upon direct contact; sensitization dermatitis may occur. Well absorbed by all routes. Causes methemoglobinemia. Symptoms include headache, cyanosis, weakness, and gastrointestinal upset. May injure liver. Injures testes in animals. Limited evidence for adverse effects on fetal development in animals. IARC 2B.	1 ppm, S	200 ppm	Pale yellow to dark brown viscous liquid. Shoe polish-like odor is a good warning property. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen. Used industrially in the manufacture of aniline.
p-Nitrochlorobenzene (CAS: 100-00-5): Irritating upon direct contact; sensitization dermatitis may occur upon repeated exposures. Well absorbed by all routes. Causes methemoglobinemia. Symptoms include headache, cyanosis, weakness, and gastrointestinal upset. May cause liver and kidney injury. NIOSH CA.	0.1 ppm, S	100 mg/m³	Yellow solid with a sweet odor. Vapor pressure is 0.009 mm Hg at 25°C (77°F). Combustible. Thermal breakdown products include oxides of nitrogen and hydrogen chloride.
4-Nitrodiphenyl (4-nitrobiphenyl [CAS: 92-93-3]): Extremely well absorbed through skin. Produces bladder cancer in dogs and rabbits. Metabolized to 4-aminodiphenyl, which is a potent carcinogen in humans. Inadequate carcinogenicity data (IARC 3). OSHA CA, NIOSH CA.	S		White solid with a sweet odor. Thermal breakdown products include oxides of nitrogen.
Nitroethane (CAS: 79-24-3): Based on high-exposure studies in animals, vapors are irritating to the respiratory tract. A CNS depressant. Can cause methemoglobinemia. Causes liver injury at high levels of exposure in test animals. A structurally similar compound, 2-nitropropane, is a carcinogen. No IARC evaluation.	100 ppm	1,000 ppm	Colorless viscous liquid with a fruity odor that is a poor warning property. Vapor pressure is 15.6 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. In addition to industrial applications, exposure has occurred use in consumer products (nail polish remover).
Nitrogen dioxide (CAS: 10102-44-0): Gases and vapors irritating to eyes and respiratory tract; fatal pulmonary edema has resulted. Initial symptoms include cough and dyspnea. Pulmonary edema may appear after a delay of several hours. The acute phase may be followed by a fatal secondary stage, with fever and chills, dyspnea, cyanosis, and delayed-onset proliferative bronchiolitis. See Nitrogen Oxides.	0.2 ppm	20 ppm 10-min AEGL3: 170 ppm	Dark brown fuming liquid or gas. Pungent odor and irritation occur only slightly above the TLV and are adequate warning properties. Vapor pressure is 720 mm Hg at 20°C (68°F). Important exposures include structural fires, silage (silo filling), gas-shielded (MIG [metal inert gas] or TIG [tungsten inert gas]) welding, and the interaction of nitric acid with other materials. The related dinitrogen tetroxide [CAS: 10544-72-6] is in equilibrium with nitrogen dioxide and is also highly toxic.
Nitrogen trifluoride (nitrogen fluoride [CAS: 7783-54-2]): Vapors may cause eye irritation. Based on animal studies, may cause methemoglobinemia and liver and kidney damage.	10 ppm	1,000 ppm	Colorless gas with a moldy odor that is a poor warning property. Not combustible. Highly reactive and explosive under a number of conditions.
Nitroglycerin (glycerol trinitrate [CAS: 55-63-0]): Causes vasodilation, including vasodilation of coronary arteries. Headache and drop in blood pressure are common. Well absorbed by all routes. Tolerance to vasodilation can occur; cessation of exposure may precipitate angina pectoris in pharmacologically dependent workers. See also Nitrates and Nitrites.	0.05 ppm, S	75 mg/m³	Pale yellow viscous liquid. Vapor pressure is 0.00026 mm Hg at 20°C (68°F). Highly explosive. Exposure can occur among munitions and pharmaceutical workers.
Nitromethane (CAS: 75-52-5): Based on high-dose animal studies, causes respiratory tract irritation, liver and kidney injury, and CNS depression with ataxia, weakness, convulsions, and, possibly, methemoglobinemia. Associated with an outbreak of human peripheral neuropathy. A suspected carcinogen (IARC 2B).	20 ppm	750 ppm	Colorless liquid with a faint fruity odor that is a poor warning property. Vapor pressure is 27.8 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Used as an industrial chemical and as a fuel in model engines. Can interfere with some clinical assays for creatinine. California OSHA PEL is 2 ppm.
1-Nitropropane (CAS: 108-03-2): Vapors mildly irritating to eyes and respiratory tract. Liver and kidney injury may occur.	25 ppm	1,000 ppm	Colorless liquid with a faint fruity odor that is a poor warning property. Vapor pressure is 27.8 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen.
2-Nitropropane (CAS: 79-46-9): Mildly irritating, CNS depressant at high exposures. Highly hepatotoxic; fatalities have resulted. Renal toxicity also occurs. Well absorbed by all routes. Limited evidence for adverse effects on fetal development in test animals. A carcinogen in test animals (IARC 2B). NIOSH CA.	10 ppm	100 ppm	Colorless liquid. Vapor pressure is 12.9 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen. A chemical solvent that has been used in commercial products.
N-Nitrosodimethylamine (dimethylnitrosamine [CAS:62-75-9]): Overexposed workers had severe liver damage. Based on animal studies, well absorbed by all routes. A potent animal carcinogen producing liver, kidney, and lung cancers (IARC 2A). OSHA CA. NIOSH CA.	S		Yellow viscous liquid. Combustible. Industrial intermediate in selected processes (eg, dimethyl hydrazine synthesis) and an environmental contaminant.
*Nitrotoluene (o-, m-, p-nitrotoluene [CAS: 99-08-1]):* Weak inducer of methemoglobinemia. By analogy to structurally similar compounds, dermal absorption is likely. Inadequate carcinogenicity data (IARC 3).	2 ppm, S	200 ppm	o-Nitrotoluene and m-nitrotoluene, yellow liquid or solid; p-nitrotoluene, yellow solid. All isomers have a weak, aromatic odor. Vapor pressure is approximately 0.15 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Intermediate in synthesis of dyestuffs and explosives.
Nitrous oxide (CAS: 10024-97-2): A CNS depressant. Hematopoietic effects from chronic exposure include megaloblastic anemia. Substance abuse has resulted in neuropathy. May have an adverse effect on human fertility and fetal development. See also Nitrous Oxide.	50 ppm		Colorless gas. Sweet odor. Not combustible. Widely used as an anesthetic gas in dentistry, and a popular inhalant chemical of abuse (“laughing gas”).
Octachloronaphthalene (Halowax 1051 [CAS: 2234-13-1]): By analogy to other chlorinated naphthalenes, workers overexposed by inhalation or skin contact may experience chloracne and liver damage. For chloracne, see also “Dioxins,”.	0.1 mg/m³, S	0.1 mg/m³ (effective IDLH)	Pale yellow solid with an aromatic odor. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride.
Octane (CAS: 111-65-9): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at very high concentrations.	300 ppm	1,000 ppm	Colorless liquid. Gasoline-like odor and irritation are good warning properties. Vapor pressure is 11 mm Hg at 20°C (68°F). Flammable.
Osmium tetroxide (osmic acid [CAS: 20816-12-0]): Corrosive upon direct contact; severe burns may result. Fumes are highly irritating to eyes and respiratory tract. Based on high-dose animal studies, bone marrow injury and kidney damage may occur.	0.0002 ppm (as Os)	1 mg/m³ (as Os)	Colorless to pale yellow solid with a sharp and irritating odor like that of chlorine. Vapor pressure is 7 mm Hg at 20°C (68°F). Not combustible. Catalyst and laboratory reagent.
Oxalic acid (ethanedioic acid [CAS: 144-62-7]): A strong acid; corrosive to eyes and to skin upon direct contact. Fumes irritating to respiratory tract. Highly toxic upon ingestion; precipitation of calcium oxalate crystals can cause hypocalcemia and renal damage. See also Oxalic Acid.	1 mg/m³	500 mg/m³	Colorless or white solid. Odorless. Vapor pressure is less than 0.001 mm Hg at 20°C (68°F).
Oxygen difluoride (oxygen fluoride, fluorine monoxide[CAS: 7783-41-7]): Extremely irritating to the eyes, skin, and respiratory tract. Effects similar to those of hydrofluoric acid. Based on animal studies, may also injure kidneys, internal genitalia, and other organs. Workers have experienced severe headaches after low-level exposures.	0.05 ppm (C)	0.5 ppm 10-min AEGL3: 1.3 ppm	Colorless gas with a strong and foul odor. Olfactory fatigue is common, so odor is a poor warning property. A strong oxidizing agent.
Ozone (triatomic oxygen [CAS: 10028-15-6]): Irritating to eyes and respiratory tract. Pulmonary edema has been reported. See also Gases, Irritant.	0.05 ppm (heavy work), 0.08 ppm (moderate work), 0.1 ppm (light work), 0.2 ppm (≤2 h)	5 ppm	Colorless or bluish gas. Sharp, distinctive odor is an adequate warning property. A strong oxidizing agent. Gas-shielded and specialty welding are potential sources of exposure, in addition to water purification and industrial bleaching operations.
Paraquat (1,1-dimethyl-4,4'-bipyridinium dichloride [CAS:4687-14-7]): Extremely irritating upon direct contact; severe corrosive burns may result. Well absorbed through skin. A potent toxin causing acute multiple-organ failure as well as progressive fatal pulmonary fibrosis after overexposure. See also Paraquat and Diquat.	0.05 mg/m³	1 mg/m³	Odorless white to yellow solid. Vapor pressure is negligible at 20°C (68°F). Not combustible. Thermal breakdown products include oxides of nitrogen and sulfur and hydrogen chloride. Although widely used as an agricultural herbicide, most deaths occur as a result of intentional ingestion.
*Parathion (O,O-diethyl O-p-nitrophenyl phosphorothioate[CAS: 56-38-2]):* Highly potent organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Systemic toxicity has resulted from inhalation, ingestion, and dermal exposures. Evidence for adverse effects on fetal development in test animals at high doses. IARC 2B.	0.05 mg/m³, S	10 mg/m³	Yellow to dark brown liquid with garlic-like odor. Odor threshold of 0.04 ppm suggests it has good warning properties. Vapor pressure is 0.0004 mm Hg at 20°C (68°F). Thermal breakdown products include oxides of sulfur, nitrogen, and phosphorus. In the field, weathering/oxidation can convert parathion to paraoxon, an even more toxic organophosphate. Agricultural pesticide.
Pentaborane (CAS: 19624-22-7): Highly irritating upon direct contact; severe burns may result. Vapors irritating to the respiratory tract. A potent CNS toxin: symptoms include headache, nausea, weakness, confusion, hyperexcitability, tremors, seizures, and coma. Residual CNS effects may persist. Liver and kidney injury may also occur.	0.005 ppm	1 ppm 10-min AEGL3: 2.0 ppm	Colorless liquid. Vapor pressure is 171 mm Hg at 20°C (68°F). The pungent sour milk odor occurring only at air levels well above the TLV is a poor warning property. May ignite spontaneously. Reacts violently with halogenated extinguishing media. Thermal breakdown products include boron acids. Used as a dopant in the microelectronics industry.
Pentachloronaphthalene (Halowax 1013 [CAS: 1321-64-8]): Chloracne results from prolonged skin contact or inhalation. May cause severe, potentially fatal liver injury or necrosis by all routes of exposure.	0.5 mg/m³, S		Pale yellow waxy solid with a pleasant aromatic odor. Odor threshold not known. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride fumes.
Pentachlorophenol (Penta, PCP [CAS: 87-86-5]): Irritating upon direct contact; burns may result. Vapors irritating to eyes and respiratory tract. A potent metabolic poison; uncouples oxidative phosphorylation. Well absorbed by all routes. Evidence for adverse effects on fetal development and carcinogenicity in test animals (IARC1). See also Pentachlorophenol and Dinitrophenol. Case reports have associated PCP with bone marrow toxicity.	0.5 mg/m³, S	2.5 mg/m³	Eye and nose irritation occur slightly above the TLV and are good warning properties. Vapor pressure is 0.0002 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride, chlorinated phenols, and octachlorodibenzodioxin. Has been widely used as a wood preservative. Trace dioxin contamination can lead to chloracne.
Pentane (n-pentane [CAS: 109-66-0]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels.	1,000 ppm	1,500 ppm	Colorless liquid with a gasoline-like odor that is an adequate warning property. Vapor pressure is 426 mm Hg at 20°C (68°F). Flammable. California OSHA PEL is 600 ppm.
Perfluoroallyl chloride (PFAC, [CAS: 79-47-0]). Severe inhalation irritant with human fatalities.			Colorless gas with a similar chemical structure to allyl chloride. Used in polymers and elastomers as a precursor to (chlorodifluoromethyl) trifluorooxirane.
Petroleum distillates (petroleum naphtha, petroleumether): Vapors irritating to eyes and respiratory tract. A CNS depressant. If n-hexane, benzene, or other toxic contaminants are present, those hazards should be addressed. See also Hydrocarbons.		1,100 ppm	Colorless liquid. Kerosene-like odor at levels below the TLV serves as a warning property. Highly flammable. Vapor pressure is about 40 mm Hg at 20°C (68°F).
Phenol (carbolic acid, hydroxybenzene [CAS: 108-95-2]): Corrosive acid and protein denaturant. Direct eye or skin contact causes severe tissue damage or blindness. Deep skin burns can occur without warning pain. Systemic toxicity by all routes; percutaneous absorption of vapor occurs. Vapors highly irritating to eyes and respiratory tract. Symptoms include nausea, vomiting, cardiac arrhythmias, circulatory collapse, convulsions, and coma. Toxic to liver and kidney. A tumor promoter; however, inadequate carcinogenicity data (IARC 3). See also Phenol and Related Compounds.	5 ppm, S	250 ppm	Colorless to pink crystalline solid, or viscous liquid. Its odor has been described as distinct, acrid, and aromatic or as sweet and tarry. As the odor is detected at or below the TLV, it is a good warning property. Vapor pressure is 0.36 mm Hg at 20°C (68°F). Combustible.
Phenylenediamine (p-aminoaniline, paraphenylenediamine, PPD [CAS: 106-50-3]): Irritating upon direct contact. May cause skin and respiratory tract sensitization. Inflammatory reactions of larynx and pharynx have been noted often in exposed workers. Systemic toxicity includes angioedema, convulsions, coma, hemolysis, methemoglobinemia, rhabdomyolysis, myocarditis, renal and hepatic injury. Inadequate carcinogenicity data (IARC 3).	0.1 mg/m³	25 mg/m³	White to light purple or brown solid, depending on degree of oxidation. Combustible. Thermal breakdown products include oxides of nitrogen. Industrial chemical intermediate. Also present in some inexpensive hair dyes and henna substitutes (“black henna”).
Phenyl ether (diphenyl ether [CAS: 101-84-8]): Mildly irritating upon prolonged direct contact. Vapors irritating to eyes and respiratory tract. Based on high-dose experiments in animals, liver and kidney damage may occur after ingestion.	1 ppm	100 ppm	Colorless liquid or solid. Mildly disagreeable odor detected below the TLV serves as a good warning property. Vapor pressure is 0.02 mm Hg at 25°C (77°F). Combustible.
Phenyl glycidyl ether (PGE, 1,2-epoxy-3-phenoxypropane[CAS: 122-60-1]): Irritating upon direct contact. A skin sensitizer. Based on animal studies, vapors are very irritating to eyes and respiratory tract. In high-dose animal studies, a CNS depressant producing injury to liver, kidneys, spleen, testes, thymus, and hematopoietic system. A carcinogen in test animals (IARC 2B), NIOSH CA.	0.1 ppm, S, SEN	100 ppm	Colorless liquid with an unpleasant, sweet odor. Vapor pressure is 0.01 mm Hg at 20°C (68°F). Combustible. Readily forms peroxides.
Phenylhydrazine (CAS: 100-63-0): A strong base and corrosive upon direct contact. A potent skin sensitizer. Dermal absorption occurs. Vapors very irritating to eyes and respiratory tract. Causes hemolysis in animals, with secondary kidney damage. Limited evidence of carcinogenicity in test animals. No IARC evaluation. NIOSH CA.	0.1 ppm, S	15 ppm	Pale yellow crystals or oily liquid with a weakly aromatic odor. Darkens upon exposure to air and light. Vapor pressure is less than 0.1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen. Used industrially in dye synthesis.
Phenylphosphine (CAS: 638-21-1): In animals, subchronic inhalation at 2 ppm caused loss of appetite, diarrhea, tremor, hemolytic anemia, dermatitis, and irreversible testicular degeneration.	0.05 ppm (C)		Crystalline solid. Spontaneously combustible at high air concentrations.
*Phorate (O,O-diethyl S-(ethylthio)methyl phosphorodithioate, Thimet, Timet [CAS: 298-02-2]):* An organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed by all routes.	0.05 mg/m³, S		Clear liquid. Vapor pressure is 0.002 mm Hg at 20°C (68°F). Agricultural pesticide.
Phosgene (carbonyl chloride, COCl₂[CAS: 75-44-5]): Extremely irritating to the lower respiratory tract. Exposure can be insidious because irritation and smell are inadequate as warning properties for pulmonary injury. Higher levels cause irritation of the eyes, skin, and mucous membranes. See also Phosgene.	0.1 ppm	2 ppm 10-min AEGL3: 3.6 ppm	Colorless gas. Sweet haylike odor at low concentrations; sharp and pungent odor at high concentrations. Dangerous concentrations may not be detected by odor. Chemical synthesis intermediate; can be a breakdown product of chlorinated organic compounds subjected to heat or ultraviolet light.
Phosmet (imidan, phthalophos [CAS: 732-11-6]): Organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides).			Thermal breakdown to nitrogen, phosphorus and sulfur oxides. Agricultural pesticide.
Phosphine (hydrogen phosphide [CAS: 7803-51-2]): Extremely irritating to the respiratory tract; fatal pulmonary edema has resulted. A multisystem poison. Symptoms in moderately overexposed workers included diarrhea, nausea, vomiting, cough, headache, and dizziness. See also Phosphine and Phosphides.	0.05 ppm	50 ppm 10-min AEGL3: 7.2 ppm	Colorless gas. A fishy or garlic-like odor detected well below the TLV is considered to be a good warning property. May ignite spontaneously on contact with air. A common fumigant, generated on site (eg, in grain storage and other enclosed spaces) by aluminum or zinc phosphide and atmospheric moisture.
Phosphoric acid (CAS: 7664-38-2): A strong corrosive acid; severe burns may result from direct contact. Mist or vapors irritating to eyes and respiratory tract.	1 mg/m³	1,000 mg/m³	Colorless, syrupy, odorless liquid. Solidifies at temperatures below 20°C (68°F). Vapor pressure is 0.03 mm Hg at 20°C (68°F). Not combustible.
Phosphorus (yellow phosphorus, white phosphorus, P [CAS: 7723-14-0]): Severe, penetrating burns may result upon direct contact. Material may ignite upon contact with skin. Fumes irritating to eyes and respiratory tract; pulmonary edema may occur. Potent hepatotoxin. Systemic symptoms include abdominal pain, jaundice, and garlic odor on the breath. Historically, chronic poisoning caused jaw bone necrosis (“phossy jaw”). See also Phosphorus.	0.1 mg/m³ (yellow phosphorus)	5 mg/m³	White to yellow, waxy or crystalline solid with acrid fumes. Flammable. Vapor pressure is 0.026 mm Hg at 20°C (68°F). Ignites spontaneously on contact with air. Thermal breakdown products include phosphoric acid fumes. Historical exposures involved the match industry, which has long since substituted other forms of phosphorus. Current uses include munitions (including some fireworks) and pesticides.
Phosphorus oxychloride (CAS: 10025-87-3): Highly corrosive upon direct contact. Fumes extremely irritating to eyes and respiratory tract; can cause acute lung injury. Systemic effects include headache, dizziness, and dyspnea. Kidney toxicity may occur.	0.1 ppm	10-min AEGL3: 1.1 ppm	Clear colorless to pale yellow, fuming liquid possessing a pungent odor. Vapor pressure is 40 mm Hg at 27.3°C (81°F). Not combustible. Reacts with moisture to release phosphoric and hydrochloric acids.
Phosphorus pentachloride (CAS: 10026-13-8): Highly corrosive upon direct contact. Fumes extremely irritating to eyes and respiratory tract; can cause acute lung injury.	0.1 ppm	70 mg/m³	Pale yellow solid with a hydrochloric acid-like odor. Not combustible. Reacts with moisture to release phosphoric and hydrochloric acids.
Phosphorus pentasulfide (CAS: 1314-80-3): Rapidly reacts with moisture and moist tissues to form hydrogen sulfide and phosphoric acid. Severe burns may result from prolonged contact with tissues. Dusts or fumes extremely irritating to eyes and respiratory tract. Systemic toxicology is caused predominantly by hydrogen sulfide.	1 mg/m³	250 mg/m³	Greenish-yellow solid with odor of rotten eggs. Olfactory fatigue reduces value of smell as a warning property. Thermal breakdown products include sulfur dioxide, hydrogen sulfide, phosphorus pentoxide, and phosphoric acid fumes. Ignites spontaneously in the presence of moisture. Industrial intermediate including in the production of selected pesticides.
Phosphorus trichloride (CAS: 7719-12-2): Highly corrosive upon direct contact. Fumes extremely irritating to eyes and respiratory tract; can cause acute lung injury.	0.2 ppm	25 ppm 10-min AEGL3: 7.0 ppm	Fuming colorless to yellow liquid. Irritation provides a good warning property. Vapor pressure is 100 mm Hg at 20°C (68°F). Not combustible. Reacts with moisture to release phosphoric and hydrochloric acids.
Phthalic anhydride (phthalic acid anhydride [CAS:85-44-9]): Extremely irritating upon direct contact; chemical burns occur after prolonged contact. Dusts and vapors extremely irritating to respiratory tract. A potent skin and respiratory tract sensitizer (asthma).	0.002 ppm, SEN	60 mg/m³	White crystalline solid with choking odor at very high air concentrations. Vapor pressure is 0.05 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include phthalic acid fumes.
Picloram (4-amino-3,5,6-trichloropicolinic acid [CAS:1918-02-1]): Dusts mildly irritating to skin, eyes, and respiratory tract. Has low oral toxicity in test animals. Limited evidence of carcinogenicity in animals (IARC 3).	10 mg/m³		White powder possessing a bleachlike odor. Vapor pressure is 0.0000006 mm Hg at 35°C (95°F). Thermal breakdown products include oxides of nitrogen and hydrogen chloride. Also used as an herbicide in combination with 2,4-D.
Picric acid (2,4,6-trinitrophenol [CAS: 88-89-1]): Irritating upon direct contact. Dust stains skin yellow and can cause sensitization dermatitis. Symptoms of low-level exposure are headache, dizziness, and gastrointestinal upset. May induce methemoglobinemia. Ingestion can cause hemolysis, nephritis, and hepatitis. Staining of the aqueous humor can give vision a yellow hue. A weak uncoupler of oxidative phosphorylation.	0.1 mg/m³	75 mg/m³	Pale yellow crystalline solid or paste. Odorless. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Decomposes explosively above 120°C (248°F). May detonate when shocked. Contact with metals, ammonia, or calcium compounds can form salts that are much more sensitive to shock detonation. Exposure can occur in munitions manufacturing (historically a major source of exposure).
Pindone (Pival, 2-pivaloyl-1,3-indanedione (CAS:83-26-1]): A vitamin K antagonist anticoagulant (Warfarin and Superwarfarins).	0.1 mg/m³	100 mg/m³	Bright yellow crystalline substance.
Piperazine dihydrochloride (CAS: 142-64-3): Irritating upon direct contact; burns may result. A moderate skin and respiratory sensitizer. Nausea, vomiting, and diarrhea are side effects of medicinal use. Overdose has caused confusion, lethargy, coma, and seizures.	0.03 ppm SEN		White crystalline solid with a mild fishy odor. This and other piperazine salts have been used as an antihelminthic (ascaricide); human use discontinued in the US.
Piperidine (CAS: 110-89-4): Highly irritating upon direct contact; severe burns may result. Vapors irritating to eyes and respiratory tract. Neurotoxic. Small doses initially stimulate autonomic ganglia; larger doses depress them. A 30- to 60-mg/kg dose may produce symptoms in humans.		10-min AEGL3: 370 ppm	Flammable. Widely used industrial intermediate including in pharmaceutical synthesis.
Platinum-soluble salts (sodium chloroplatinate, ammoniumchloroplatinate, platinum tetrachloride): Sensitizers causing asthma and dermatitis. Metallic platinum does not share these effects. Soluble platinum compounds are also highly irritating to eyes, mucous membranes, and respiratory tract.	0.002 mg/m³ (as Pt)		Appearance varies with the compound. Thermal breakdown products of some chloride salts include chlorine gas. Used as industrial catalysts and in specialized photographic applications.
Polychlorinated biphenyls (chlorodiphenyls, Aroclor 1242, PCBs; 42% chlorine, CAS:53469-21-9; 54% chlorine, CAS: 11097-69-1): Exposure to high concentrations is irritating to eyes, nose, and throat. Chronically overexposed workers have chloracne and liver injury. Reported symptoms are anorexia, gastrointestinal upset, and peripheral neuropathy. Some health effects may be caused by contaminants or thermal decomposition products. Adverse effects on fetal development and fertility in test animals. A carcinogen in test animals (IARC 2A), NIOSH CA. See also Polychlorinated Biphenyls (PCBs).	1 mg/m³ (42% chlorine), S 0.5 mg/m³ (54% chlorine), S	5 mg/m³ (42% or 54% chlorine)	42% chlorinated: a colorless to dark brown liquid with a slight hydrocarbon odor and a vapor pressure of 0.001 mm Hg at 20°C (68°F). 54% chlorinated: light yellow oily liquid with a slight hydrocarbon odor and a vapor pressure of 0.00006 mm Hg at 20°C (68°F). Thermal breakdown products include chlorinated dibenzofurans and chlorodibenzo dioxins. Although no longer used, old transformers may still contain PCBs.
Polytetrafluoroethylene decomposition products: Overexposures result in polymer fume fever, a disease with flulike symptoms that include chills, fever, and cough. See also Table IV-2. Perfluoroisobutylene (PFIB [CAS: 382-21-8] has produced severe lung injury and death in occupational exposure acting similarly to, but approximately 10 times as potent as phosgene.	0.01 ppm (for PFIB)		Produced in the production (PFIB) and in pyrolysis of Teflon and related materials (PFIN, carbonyl fluoride and others).
Polyvinyl chloride decomposition products: Irritating to the respiratory tract.			Produced by the high-temperature partial breakdown of polyvinyl chloride plastics. Decomposition products include hydrochloric acid. Plasticizers and other additives and their breakdown products may also be released.
Portland cement (a mixture of mostly tricalcium silicateand dicalcium silicate with some alumina, calciumaluminate, and iron oxide): Alkaline irritant of the eyes, nose, and skin; corrosive burns may occur. Long-term heavy exposure has been associated with dermatitis and bronchitis.	1 mg/m³ (with no asbestos and <1% crystalline silica)	5,000 mg/m³	Gray powder. Odorless. Portland cement manufacture is typically is associated with sulfur dioxide exposure. Concrete is a combination of cement (typically with chromate as an additive) and aggregate (with sand as a potential source of silica exposure). May contain chromates (see Chromium).
Potassium hydroxide (KOH [CAS: 1310-58-3]): A caustic alkali causing severe burns upon direct contact. Exposure to dust or mist causes eye, nose, and respiratory tract irritation. See also Caustic and Corrosive Agents.	2 mg/m³ (C)		White solid that absorbs moisture. Vapor pressure is negligible at 20°C (68°F). Gives off heat and a corrosive mist when in contact with water.
Potassium permanganate (CAS: 7722-64-7): Powerful oxidizer. Contact with tissues produces necrosis, and ingestion is often fatal owing to multiple-organ failure. Eye contact produces severe damage. Exposure can cause manganese toxicity (see Antiseptics and Disinfectants).	(proposed: 0.02 mg/m³ [respirable fraction, as Mn])		Purple-gray crystals. Strong oxidizer. Contamination of potassium permanganate-treated illicit drugs has led to manganese toxicity following injection abuse.
Propane (CAS: 74-98-6): Simple asphyxiant. See also “Hydrocarbons,”.		2,100 ppm 10-min AEGL3: 33,000 ppm	Highly flammable.
Propanil (CAS: 709-98-8). Chloracne and methemoglobinemia reported in a study of workers in a pesticide plant producing propanil, the former likely from dioxin contamination (see Dioxins).			Colorless, white, or light brown odorless solid. Agricultural pesticide (herbicide).
Propargyl alcohol (2-propyn-1-ol [CAS: 107-19-7]): Irritating to skin upon direct contact. Dermally well absorbed. A CNS depressant. Causes liver and kidney injury in test animals.	1 ppm, S	10-min AEGL3: 130 ppm	Light to straw-colored liquid with a geranium-like odor. Vapor pressure is 11.6 mm Hg at 20°C (68°F). Flammable.
Propionic acid (CAS: 79-09-4): Irritating to eyes and skin upon direct contact with concentrated solutions; burns may result. Vapors irritating to eyes, skin, and respiratory tract.	10 ppm		Colorless oily liquid with a pungent, somewhat rancid odor. Vapor pressure is 10 mm Hg at 39.7°C (103.5°F). Flammable.
Propoxur (o-isopropoxyphenyl-N-methylcarbamate, DDVP,Baygon [CAS: 114-26-1]): A carbamate anticholinesterase insecticide (Organophosphorus and Carbamate Insecticides). Limited evidence for adverse effects on fetal development in test animals.	0.5 mg/m³		White crystalline solid with a faint characteristic odor. Vapor pressure is 0.01 mm Hg at 120°C (248°F). Common insecticide found in many consumer pesticide formulations.
n-Propyl acetate (CAS: 109-60-4): Vapors irritating to eyes and respiratory tract. Excessive inhalation may cause weakness, nausea, and chest tightness. Based on high-exposure studies in test animals, a CNS depressant.	200 ppm	1,700 ppm	Colorless liquid. Mild fruity odor and irritant properties provide good warning properties. Vapor pressure is 25 mm Hg at 20°C (68°F). Flammable.
Propyl alcohol (1-propanol [CAS: 71-23-8]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. See also “Isopropyl Alcohol,”.	100 ppm	800 ppm	Colorless volatile liquid. Vapor pressure is 15 mm Hg at 20°C (68°F). Mild alcohol-like odor is an adequate warning property.
Propylene dichloride (1,2-dichloropropane [CAS: 78-87-5]): Vapors very irritating to eyes and respiratory tract. Causes CNS depression and severe liver and kidney damage at modest doses in animal studies. Testicular toxicity at high doses in test animals. IARC 1. NIOSH CA.	10 ppm, SEN	400 ppm	Colorless liquid. Chloroform-like odor is considered an adequate warning property. Vapor pressure is 40 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include hydrogen chloride. Industrial chemical intermediate; no longer used as an agricultural nematocide or industrial solvent in the US.
Propylene glycol dinitrate (1,2-propylene glycol dinitrate,PGDN [CAS: 6423-43-4]): Chemically similar to nitroglycerin (see Nitrates and Nitrites). Mildly irritating upon direct contact. Dermal absorption occurs. May cause methemoglobinemia. Potential neurotoxic effects. Causes vasodilation, including vasodilation in coronary arteries and systemic hypotension. Headache common. Tolerance to vasodilation can occur; cessation of exposure may precipitate angina pectoris in pharmacologically dependent workers.	0.05 ppm, S	10-min AEGL3: 16 ppm	Colorless liquid with an unpleasant odor. Thermal breakdown products include oxides of nitrogen. Principal use as a torpedo fuel propellant (component of Otto Fuel II); military personnel comprise the primary at-risk group.
Propylene glycol monomethyl ether (1-methoxy-2-propanol[CAS: 107-98-2]): Vapors very irritating to the eyes and possibly the respiratory tract. A mild CNS depressant.	50 ppm		Colorless, flammable liquid.
Propylene imine (2-methylaziridine [CAS: 75-55-8]): Highly irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract. May also injure liver and kidneys. Well absorbed dermally. A carcinogen in test animals (IARC 2B), NIOSH CA.	0.2 ppm, S	100 ppm 10-min AEGL3: 170 ppm	A fuming colorless liquid with a strong ammonia-like odor. Flammable. Thermal breakdown products include oxides of nitrogen. Alkylating agent used in polymer synthesis and other industrial applications.
Propylene oxide (2-epoxypropane [CAS: 75-56-9]): Highly irritating upon direct contact; severe burns result. Vapors highly irritating to eyes and respiratory tract. Based on high-dose animal studies, may cause CNS depression and peripheral neuropathy. A carcinogen in test animals (IARC 2B), NIOSH CA.	2 ppm, SEN	400 ppm 10-min AEGL3: 1,300 ppm	Colorless liquid. Its sweet, ether-like odor is considered to be an adequate warning property. Vapor pressure is 442 mm Hg at 20°C (68°F). Highly flammable. Polymerizes violently.
n-Propyl nitrate (nitric acid n-propyl ester [CAS: 627-13-4]): Vasodilator causing headaches and hypotension. Causes methemoglobinemia. See also “Nitrates and Nitrites,”.	25 ppm	500 ppm	Pale yellow liquid with an unpleasant sweet odor. Vapor pressure is 18 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen.
Pyrethrum (pyrethrin I or II; cinerin I or II; jasmolin I or II): Dusts cause primary contact dermatitis and skin and respiratory tract sensitization (asthma). Of very low systemic toxicity. See also Pyrethrins and Pyrethroids.	5 mg/m³	5,000 mg/m³	Vapor pressure is negligible at 20°C (68°F). Combustible. Widely used insecticide including in consumer products.
Pyridine (CAS: 110-86-1): Irritating upon prolonged direct contact; occasional reports of skin sensitization. Vapors irritating to eyes and respiratory tract. A CNS depressant. Causes methemoglobinemia. Chronic ingestion of small amounts has caused fatal liver and kidney injury. Workers exposed to 6-12 ppm have experienced headache, dizziness, and gastrointestinal upset. Dermally well absorbed. Inadequate carcinogenicity data (IARC 3).	1 ppm	1,000 ppm	Colorless or yellow liquid with a nauseating odor and a definite “taste” that serves as a good warning property. Vapor pressure is 18 mm Hg at 20°C (68°F). Flammable. Thermal breakdown products include oxides of nitrogen and cyanide. Large scale industrial chemical used in chemical synthesis, including pharmaceuticals.
Pyrogallol (1,2,3-trihydroxybenzene; pyrogallic acid [CAS:87-66-1]): Highly irritating upon direct contact; severe burns may result. Potent reducing agent and general cellular poison. Causes methemoglobinemia. Attacks heart, lungs, liver, kidneys, red blood cells, bone marrow, and muscle. Causes sensitization dermatitis. Deaths have resulted from the topical application of salves containing pyrogallol.			White to gray odorless solid.
Quinone (1,4-cyclohexadienedione, p-benzoquinone [CAS:106-51-4]): A severe irritant of the eyes and respiratory tract. May induce methemoglobinemia. Acute overexposure to dust or vapors can cause conjunctival irritation and discoloration, corneal edema, ulceration, and scarring. Chronic exposures can permanently reduce visual acuity. Skin contact can cause irritation, ulceration, and pigmentation changes. Inadequate carcinogenicity data (IARC 3).	0.1 ppm	100 mg/m³	Pale yellow crystalline solid. The acrid odor is not a reliable warning property. Vapor pressure is 0.1 mm Hg at 20°C (68°F). Sublimes when heated.
Resorcinol (1,3-dihydroxybenzene [CAS: 108-46-3]): Corrosive acid and protein denaturant; extremely irritating upon direct contact; severe burns result. May cause methemoglobinemia. A sensitizer. Dermally well absorbed. See also “Phenol and Related Compounds,”. Inadequate carcinogenicity data (IARC 3).	10 ppm		White crystalline solid with a faint odor. May turn pink on contact with air. Vapor pressure is 1 mm Hg at 108°C (226°F). Combustible.
Rhodium (soluble salts): Respiratory irritant. Mild eye irritant. Acts as contact dermatitis allergen and as potential asthma-causing agent.	0.01 mg/m³		Vapor pressure is less than 0.1 mm Hg at 25°C (77°F). Used in specialty metal (jewelry) plating and as a catalyst.
*Ronnel (O,O-dimethyl-O-(2,4,5-trichlorophenyl)phosphorothioate, Fenchlorphos [CAS: 299-84-3]):* One of the least toxic organophosphate anticholinesterase insecticides (Organophosphorus and Carbamate Insecticides).	5 mg/m³	300 mg/m³	Vapor pressure is 0.0008 mm Hg at 20°C (68°F). Not combustible. Unstable above 149°C (300°F); harmful gases such as sulfur dioxide, dimethyl sulfide, and trichlorophenol may be released. Agricultural pesticide.
Rotenone (tubatoxin, cube root, derris root, derrin [CAS:83-79-4]): Irritating upon direct contact or inhlation. A metabolic poison; depresses cellular respiration and inhibits mitotic spindle formation. Ingestion of large doses numbs oral mucosa and causes nausea and vomiting, muscle tremors, and convulsions. Associated with parkinsonism in epidemiological studies. Chronic exposure caused liver and kidney damage in animals. Limited evidence for adverse effects on fetal development in animals at high doses.	5 mg/m³	2,500 mg/m³	White to red crystalline solid. Vapor pressure is negligible at 20°C (68°F). A natural pesticide extracted from plants such as cube, derris, and timbo. Odorless. Decomposes upon contact with air or light. Unstable to alkali.
Sarin (GB [CAS: 107-44-8]): Extremely toxic chemical warfare nerve agent by all routes of contact. Readily absorbed via respiratory tract and skin and eyes. A potent cholinesterase inhibitor with rapid onset of symptoms. Vapors highly irritating.		10-min AEGL3: 0.064 ppm	Clear, colorless liquid. Odorless. Most volatile of nerve agents. Vapor pressure is 2.1 mm Hg at 20°C (68°F). Not flammable. Chemical warfare agent.
Selenium and inorganic compounds (as selenium): Fumes, dusts, and vapors irritating to eyes, skin, and respiratory tract; pulmonary edema may occur. Many compounds are well absorbed dermally. A general cellular poison. Chronic intoxication causes depression, nervousness, dermatitis, gastrointestinal upset, metallic taste in mouth and garlicky odor of breath, excessive caries, and loss of fingernails or hair. The liver and kidneys are also target organs. Some selenium compounds have been found to cause birth defects and cancers in test animals; inadequate carcinogenicity data (IARC 3). See also Selenium.	0.2 mg/m³ (as Se)	1 mg/m³ (as Se)	Elemental selenium is a black, gray, or red crystalline or amorphous solid and is odorless. Used as bluing agent in weapons maintenance. Selenium shampoos can cause elevated hair levels on hair heavy metals screens. Can be an important environmental contaminant.
Selenium dioxide (selenium oxide [CAS: 7446-08-4]): Strong vesicant; severe burns result from direct contact. Converted to selenious acid in the presence of moisture. Well absorbed dermally. Fumes and dusts very irritating to eyes and respiratory tract. See also Selenium.			White solid. Reacts with water to form selenious acid.
Selenium hexafluoride (CAS: 7783-79-1): Vesicant. Reacts with moisture to form selenium acids and hydrofluoric acid; severe HF burns may result from direct contact. Fumes highly irritating to eyes and respiratory tract; pulmonary edema and lung injury may result.	0.05 ppm	2 ppm	Colorless gas. Not combustible.
Selenium oxychloride (CAS: 7791-23-3): Strong vesicant. Direct contact can cause severe burns. Dermally well absorbed. Fumes extremely irritating to eyes and respiratory tract; delayed pulmonary edema and lung injury may result.			Colorless to yellow liquid. Hydrogen chloride and selenious acid fumes produced on contact with moisture.
Silica, amorphous (diatomaceous earth, precipitated andgel silica): Possesses little or no potential to cause silicosis. Most sources of amorphous silica contain quartz (see entry for crystalline silica, below). If greater than 1% quartz is present, the quartz hazard must be addressed. When diatomaceous earth is strongly heated (calcined) with limestone, it becomes crystalline and can cause silicosis. Amorphous silica has been associated with lung fibrosis, but the role of crystalline silica contamination remains controversial. For silicates, as opposed to silica (below), there are inadequate carcinogenicity data (IARC 3).		3,000 mg/m³	White to gray powders. Odorless with a negligible vapor pressure. The TLV for dusts is 10 mg/m³ if no asbestos and less than 1% quartz are present.
Silica, crystalline (quartz, fused amorphous silica,cristobolite, tridymite, tripoli [CAS: 14464-46-1]): Inhalation of dusts causes silicosis, a progressive, fibrotic scarring of the lungs. Individuals with silicosis are much more susceptible to tuberculosis. Crystalline silica is a human carcinogen (IARC 1), NIOSH CA.	0.025 mg/m³	25 mg/m³ (cristobolite, tridymite), 50 mg/m³ (quartz, tripoli)	Colorless, odorless solid with a negligible vapor pressure. A component of many mineral dusts. Exposure can occur in a variety of occupational settings, including sand blasting, secondary concrete work, stone cutting (including synthetic/artificial stone materials containing silica), and mining and quarrying.
Silicon (CAS: 7440-21-3): A nuisance dust that does not cause pulmonary fibrosis. Parenteral exposure has been associated with systemic toxicity.			Gray to black, lustrous, needle-like crystals. Vapor pressure is negligible at 20°C (68°F).
Silicon tetrachloride (tetrachlorosilane [CAS: 10026-04-7]): Generates hydrochloric acid vapor upon contact with moisture; severe burns may result. Extremely irritating to eyes and respiratory tract; pulmonary edema and lung injury may result.		10-min AEGL3: 160 ppm	Odor threshold near 0.75 ppm. Not combustible.
Silver (CAS: 7440-22-4): Silver compounds cause argyria, a blue-gray discoloration of tissues, which may be generalized throughout the viscera or localized to the conjunctivae, nasal septum, and gums. Some silver salts are corrosive upon direct contact with tissues.	0.01 mg/m³ (soluble compounds, as Ag), 0.1 mg/m³ (metal)	10 mg/m³ (Ag compounds, as Ag)	Compounds vary in appearance. Silver nitrate is a strong oxidizer. Heavy systemic exposure is typically through intentional chronic ingestion as an alternative self-treatment rather than occupational inhalation.
Sodium azide (hydrazoic acid, sodium salt, NaN₃ [CAS:26628-22-8]): Potent cellular toxin; inhibits cytochrome oxidase. Eye irritation, bronchitis, headache, hypotension, and collapse have been reported in overexposed workers. See also Azide, Sodium.	0.29 mg/m³ (C) (as sodium azide), 0.11 ppm (C) (as hydrazoic acid vapor)		White, odorless, crystalline solid. Present in some motor vehicle air bag systems.
Sodium bisulfide (NaSH [CAS: 16721-80-5]): Decomposes in the presence of water to form hydrogen sulfide and sodium hydroxide (Caustic and Corrosive Agents). Highly corrosive and irritating to eyes, skin, and respiratory tract.			White crystalline substance with a slight odor of sulfur dioxide.
Sodium bisulfite (sodium hydrogen sulfite, NaHSO₃[CAS: 7631-90-5]): Irritating to eyes, skin, and respiratory tract. Hypersensitivity reactions (angioedema, bronchospasm, or anaphylaxis) may occur.	5 mg/m³		White crystalline solid with a slight sulfur dioxide odor and disagreeable taste. Widely used as a food and chemical preservative.
Sodium fluoroacetate (compound 1080 [CAS: 62-74-8]): A highly toxic metabolic poison. Metabolized to fluorocitrate, which prevents the oxidation of acetate in the Krebs cycle. Human lethal oral dose ranges from 2 to 10 mg/kg. See also Fluoroacetate.	0.05 mg/m³, S	2.5 mg/m³	Fluffy white solid or a fine white powder. Sometimes dyed black. Hygroscopic. Odorless. Vapor pressure is negligible at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen fluoride. Has been used as a rodenticide.
Sodium hydroxide (NaOH [CAS: 1310-73-2]): A caustic alkali; may cause severe burns. Fumes or mists are highly irritating to eyes, skin, and respiratory tract. See also Caustic and Corrosive Agents.	2 mg/m³ (C)	10 mg/m³	White solid that absorbs moisture. Odorless. Emits great amount of heat upon solution in water. Soda lye is an aqueous solution.
Sodium metabisulfite (sodium pyrosulfite [CAS:7681-57-4]): Very irritating to eyes and skin upon direct contact. Dusts irritating to eyes and respiratory tract; pulmonary edema may result. Hypersensitivity reactions may occur.	5 mg/m³		White powder or crystalline material with a slight odor of sulfur dioxide. Reacts to form sulfur dioxide in the presence of moisture.
Soman (GD [96-64-0]): Extremely toxic chemical warfare nerve agent by all routes of contact. Readily absorbed via respiratory tract and skin and eyes. A potent cholinesterase inhibitor with rapid onset of symptoms. Vapors highly irritating.		10-min AEGL3: 0.049 ppm	Clear, colorless liquid. Slight camphor-like odor that is not an adequate indication of exposure. Vapor pressure is 0.4 mm Hg at 25°C (77°F).
Stibine (antimony hydride [CAS: 7803-52-3]): A potent hemolytic agent similar to arsine. Gases irritating to the lung; pulmonary edema may occur. Liver and kidneys are secondary target organs. See also Antimony and Stibine.	0.1 ppm	5 ppm	Colorless gas. Odor similar to that of hydrogen sulfide but may not be a reliable warning property. Formed when acid solutions of antimony are treated with zinc or strong reducing agents. Used in the microelectronics industry.
Stoddard solvent (mineral spirits, a mixture of aliphaticand aromatic hydrocarbons [CAS: 8052-41-3]): Dermal absorption can occur. Vapors irritating to eyes and respiratory tract. A CNS depressant. Chronic overexposures associated with headache, fatigue, bone marrow hypoplasia, and jaundice. May contain a small amount of benzene. See also “Hydrocarbons,”.	100 ppm	20,000 mg/m³	Colorless liquid. Kerosene-like odor and irritation are good warning properties. Vapor pressure is approximately 2 mm Hg at 20°C (68°F). Flammable.
Strychnine (CAS: 57-24-9): Neurotoxin binds to inhibitory, postsynaptic glycine receptors, which results in excessive motor neuron activity causing muscular hyperrigidity leading to respiratory impairment or paralysis. See also Strychnine.	0.15 mg/m³	3 mg/m³	White solid. Odorless. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include oxides of nitrogen. Commonly used as a rodenticide (gopher bait).
Styrene monomer (vinylbenzene [CAS: 100-42-5]): Irritating upon direct contact. Dermal absorption occurs. Vapors irritating to respiratory tract. A CNS depressant. Symptoms include headache, nausea, dizziness, and fatigue. Cases of peripheral neuropathy have been reported. Neurotoxic in animal studies. Limited evidence for adverse effects on fetal development. Animal and potential human carcinogen (IARC 2A).	20 ppm	700 ppm	Colorless viscous liquid. Sweet aromatic odor at low concentrations is an adequate warning property. Odor at high levels is acrid. Vapor pressure is 4.5 mm Hg at 20°C (68°F). Flammable. Inhibitor must be included to avoid explosive polymerization. Used in SBR (styrene butadiene rubber), ABS (acrylonitrile butadiene styrene), and SAN (styrene acrylonitrile) polymers.
*Subtilisins (proteolytic enzymes of Bacillus subtilis* [CAS:1395-21-7]):** Primary skin and respiratory tract irritants. Potent sensitizers causing asthma.	0.06 mcg/m³ (C)		Light-colored powder. Occupational asthma was associated with introduction into detergent in a powder formulation.
Sulfur dioxide (CAS: 7446-09-5): Forms sulfurous acid upon contact with moisture. Strongly irritating to eyes and skin; burns may result. Extremely irritating to the respiratory tract; has caused obstruction of the upper airways and pulmonary edema. Persons with asthma are of documented increased sensitivity to the bronchoconstrictive effects of sulfur dioxide air pollution. Inadequate carcinogenicity data (IARC 3). See also Sulfur Dioxide.	0.25 ppm (STEL)	100 ppm 10-min AEGL3: 30 ppm	Colorless gas. Pungent, suffocating odor with a “taste” and irritative effects that are good warning properties. Criteria air pollutant. Fossil fuel burning is a major environmental source. Byproduct of smelting and other industrial processes. Prior use as a refrigerant with potential exposure from antique refrigerators.
Sulfur hexafluoride (CAS: 2551-62-4): Considered to be essentially a nontoxic gas. Asphyxiation by the displacement of air is suggested as the greatest hazard.	1,000 ppm		Odorless, colorless dense gas. May be contaminated with other fluorides of sulfur, including the highly toxic sulfur pentafluoride, which release HF or oxyfluorides on contact with moisture.
Sulfuric acid (oil of vitriol, H₂SO₄ [CAS: 7664-93-9]): Highly corrosive upon direct contact; severe burns may result. Breakdown may release sulfur dioxide. Exposure to the mist can irritate the eyes, skin, and respiratory tract.	0.2 mg/m³	15 mg/m³	Colorless to dark brown heavy, oily liquid. Odorless. Eye irritation may be an adequate warning property. A strong oxidizer. Addition of water creates strong exothermic reaction. Vapor pressure is less than 0.001 mm Hg at 20°C (68°F). California OSHA PEL is 0.1 mg/m³.
Sulfur monochloride (CAS: 10025-67-9): Forms hydrochloric acid and sulfur dioxide upon contact with water; direct contact can cause burns. Vapors highly irritating to the eyes, skin, and respiratory tract.	1 ppm (C)	5 ppm	Fuming, amber to red oily liquid with a pungent, irritating, sickening odor. Eye irritation is a good warning property. Vapor pressure is 6.8 mm Hg at 20°C (68°F). Combustible. Breakdown products include hydrogen sulfide, hydrogen chloride, and sulfur dioxide.
Sulfur pentafluoride (disulfur decafluoride [CAS:5714-22-7]): Vapors are extremely irritating to the respiratory tract, and acute lung injury may occur; causes pulmonary edema at low levels (0.5 ppm) in test animals.	0.001 ppm (C)	1 ppm	Colorless liquid or vapor with a sulfur dioxide-like odor. Vapor pressure is 561 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include sulfur dioxide and hydrogen fluoride.
Sulfur tetrafluoride (SF₄ [CAS: 7783-60-0]): Readily hydrolyzed by moisture to form sulfur dioxide and hydrogen fluoride. Extremely irritating to the respiratory tract; pulmonary edema and lung injury may occur. Vapors also highly irritating to eyes and skin.	0.1 ppm (C)		Colorless gas. Reacts with moisture to form sulfur dioxide and hydrogen fluoride. Used for electrical insultaton. Potent greenhouse gas.
Sulfuryl fluoride (Vikane, SO₂ F₂ [CAS: 2699-79-8]): Irritating to eyes and respiratory tract; fatal pulmonary edema has resulted. Acute high exposure causes tremors and convulsions in test animals. Chronic exposures may cause kidney and liver injury and elevated fluoride. See also Fluoride.	5 ppm	200 ppm 10-min AEGL3: 81 ppm	Colorless, odorless gas with no warning properties. Chloropicrin, a lacrimator, often is added to provide a warning property. Thermal breakdown products include sulfur dioxide and hydrogen fluoride. A widely used structural pesticide fumigant, and poisoning can occur from inappropriate early reentry.
Sulprofos (O-ethyl O-[4-(methylthio)phenyl]S-propylphosphorodithioate [CAS: 35400-43-2]): An organophosphate anticholinesterase insecticide (Organophosphorus and Carbamate Insecticides).	0.1 mg/m³, S		Tan-colored liquid with a characteristic sulfide odor. Agricultural pesticide.
Tabun (GA [CAS: 77-81-6]): Extremely toxic chemical warfare nerve agent by all routes of contact. Readily absorbed via respiratory tract and skin and eyes. A potent cholinesterase inhibitor with rapid onset of symptoms. Vapors are highly irritating.		10-min AEGL3: 0.11 ppm	Clear, colorless liquid. Slight fruity odor that is not an adequate indication of exposure. Vapor pressure is 0.037 mm Hg at 20°C (68°F).
Talc, containing no asbestos fibers or crystalline silica(CAS: 14807-96-6): A tissue irritant. Pulmonary inhalation may cause pneumonitis; parenteral injection can also cause lung disease. Inadequate carcinogenicity data (IARC 3).	2 mg/m³	1,000 mg/m³	Used in many industries and in cosmetics.
Tantalum compounds (as Ta): Of low acute toxicity. Dusts mildly irritating to the lungs.		2,500 mg/m³ (metal and oxide dusts, as Ta)	Metal is a gray-black solid, platinum-white if polished. Odorless. Tantalum pentoxide is a colorless solid. Used in aerospace and other specialty alloys.
Tellurium and compounds (as Te): Reports of sleepiness, nausea, metallic taste, and garlicky odor on breath and perspiration with workplace exposures. Neuropathy has been noted in high-dose studies. Hydrogen telluride causes pulmonary irritation and hemolysis; however, its ready decomposition reduces likelihood of a toxic exposure. Some tellurium compounds are fetotoxic or teratogenic in test animals.	0.1 mg/m³ (as Te)	25 mg/m³ (as Te)	Metallic tellurium is a solid with a silver-white or grayish luster. Used in specialty alloys and in the semiconductor industry.
Tellurium hexafluoride (CAS: 7783-80-4): Slowly hydrolyzes to release hydrofluoric acid and telluric acid. Extremely irritating to the eyes and respiratory tract; pulmonary edema may occur. Has caused headaches, dyspnea, and garlicky odor on the breath of overexposed workers.	0.02 ppm	1 ppm 10-min AEGL3: 0.029 ppm	Colorless gas. Offensive odor. Not combustible. Thermal breakdown products include hydrogen fluoride.
*Temephos (Abate, O,O,O',O'-tetramethyl*O,O-thiodi-p-phenylene phosphorothioate [CAS:3383-96-8]): Primary irritant of eyes, skin, and respiratory tract; a moderately toxic organophosphate-type cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Well absorbed by all routes.	1 mg/m³, S		Colorless or white crystals; liquid above 87° F. Not water soluble; soluble in toluene, ether, and hexane. Very low vapor pressure. Agricultural pesticide.
Terphenyls (diphenyl benzenes, triphenyls [CAS:26140-60-3]): Irritating upon direct contact. Vapors and mists irritating to respiratory tract; pulmonary edema has occurred at very high levels in test animals. Animal studies also suggest a slight potential for liver and kidney injury.	5 mg/m³ (C)	500 mg/m³	White to light yellow crystalline solids. Irritation is a possible warning property. Vapor pressure is very low at 20°C (68°F). Combustible. Commercial grades are mixtures of o-, m-, and p-isomers. California OSHA PEL is 0.5 ppm.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD [CAS1746-01-6]): A potent form of acne (chloracne) is a specific marker of exposure. Human carcinogen (IARC 1), NIOSH CA. See also “Dioxins,”.			White crystalline solid. A toxic contaminant of numerous chlorinated herbicides, including 2,4,5-T and 2,4-D.
1,1,1,2-Tetrachloro-2,2-difluoroethane (halocarbon 112a;refrigerant 112a [CAS: 76-11-9]): Of low acute toxicity. Very high air levels irritating to the eyes and respiratory tract. A CNS depressant at high levels. By anology to other freons, may cause cardiac arrhythmias. High-dose studies in animals suggest possible kidney and liver in jury. See also Freons and Halons.	100 ppm	2,000 ppm	Colorless liquid or solid with a slight ether-like odor. Vapor pressure is 40 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and hydrogen fluoride.
1,1,2,2-Tetrachloro-1,2-difluoroethane (halocarbon 112;refrigerant 112 [CAS: 76-12-0]): Of low acute toxicity. Once used as an antihelminthic. Very high air levels cause CNS depression. Vapors mildly irritating. By analogy to other freons, may cause cardiac arrhythmias. See also Freons and Halons.	50 ppm	2,000 ppm	Colorless liquid or solid with a slight ether-like odor. Odor is of unknown value as a warning property. Vapor pressure is 40 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and hydrogen fluoride.
1,1,2,2-Tetrachloroethane (acetylene tetrachloride [CAS:79-34-5]): Dermal absorption may cause systemic toxicity. Vapors irritating to the eyes and respiratory tract. A CNS depressant. By analogy to other (Trichloroethane, Trichloroethylene, and Tetrachloroethylene) chlorinated ethane derivatives, may cause cardiac arrhythmias. May cause hepatic or renal injury. Inadequate evidence of carcinogenicity in test animals (IARC 2B), NIOSH CA.	1 ppm, S	100 ppm	Colorless to light yellow liquid. Sweet, suffocating, chloroform-like odor is a good warning property. Vapor pressure is 8 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and phosgene. Prior heavy use as a solvent in the US.
Tetrachloroethylene (perchloroethylene, PERC [CAS: 127-18-4]): Irritating upon prolonged contact; mild burns may result. Vapors irritating to eyes and respiratory tract. A CNS depressant. By analogy to trichloroethylene and other chlorinated solvents, may cause arrhythmias. May cause liver and kidney injury. Chronic overexposure may cause short-term memory loss and personality changes. Limited evidence of adverse effects on male reproductive function and fetal development in test animals. Evidence for carcinogenicity in test animals (IARC 2A), NIOSH CA. See also Trichloroethane, Trichloroethylene, and Tetrachloroethylene.	25 ppm	150 ppm	Colorless liquid. Chloroform-like or ether-like odor and eye irritation are adequate warning properties. Vapor pressure is 14 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include phosgene and hydrochloric acid. Used in the dry cleaning industry.
Tetrachloronaphthalene (Halowax [CAS: 1335-88-2]): Causes chloracne and jaundice. Stored in body fat. Dermal absorption occurs. For chloracne, see also “Dioxins,”.	2 mg/m³	20 mg/m³ (effective IDLH)	White to light yellow solid. Aromatic odor of unknown value as a warning property. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Thermal breakdown products include hydrogen chloride and phosgene.
Tetraethyl dithionopyrophosphate (TEDP, sulfotepp [CAS:3689-24-5]): An organophosphate anticholinesterase insecticide (Organophosphorus and Carbamate Insecticides). Well absorbed dermally.	0.1 mg/m³, S	10 mg/m³	Yellow liquid with garlic odor. Not combustible. Thermal breakdown products include sulfur dioxide and phosphoric acid mist. Agricultural pesticide.
Tetraethyl lead (CAS: 78-00-2): A potent CNS toxin. Dermally well absorbed. Can cause psychosis, mania, convulsions, and coma. Reports of reduced sperm counts and impotence in overexposed workers. See also “Lead,”.	0.1 mg/m³ (as Pb), S	40 mg/m³ (as Pb)	Colorless liquid. May be dyed blue, red, or orange. Slight musty odor of unknown value as a warning property. Vapor pressure is 0.2 mm Hg at 20°C (68°F). Combustible. Decomposes in light. As a gasoline additive, largely phased out. California OSHA PEL is 0.075 mg/m³.
Tetraethyl pyrophosphate (TEPP [CAS: 107-49-3]): A potent organophosphate cholinesterase inhibitor (Organophosphorus and Carbamate Insecticides). Rapidly absorbed through skin.	0.01 mg/m³, S	5 mg/m³	Colorless to amber liquid with a faint fruity odor. Slowly hydrolyzed in water. Vapor pressure is 1 mm Hg at 140°C (284°F). Not combustible. Thermal breakdown products include phosphoric acid mist. California OSHA PEL is 0.004 ppm.
Tetrahydrofuran (THF, diethylene oxide [CAS: 109-99-9]): Mildly irritating upon direct contact. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant at high levels. A liver and kidney toxin at high doses in test animals. IARC 2B.	50 ppm, S	20,000 ppm	Colorless liquid. The ether-like odor is detectable well below the TLV and provides a good warning property. Flammable. Vapor pressure is 145 mm Hg at 20°C (68°F).
Tetrahydrothiophene (THT [CAS: 110-01-0]): Eye and respiratory tract irritant. Case report association with severe airway obstruction.			Pale yellow or clear liquid with pungent, objectionable odor. Vapor pressure is 18 mm Hg at 25°C (77°F). Highly flammable. Used as an odorant (eg, added to natural gas).
Tetramethyl lead (CAS: 75-74-1): A potent CNS toxin thought to be similar to tetraethyl lead. See also “Lead,”.	0.15 mg/m³ (as Pb), S	40 mg/m³ (as Pb)	Colorless liquid. May be dyed red, orange, or blue. Slight musty odor is of unknown value as a warning property. Vapor pressure is 22 mm Hg at 20°C (68°F). California OSHA PEL is 0.075 mg/m³.
Tetramethyl succinonitrile (TMSN [CAS: 3333-52-6]): A potent neurotoxin. Headaches, nausea, dizziness, convulsions, and coma have occurred in overexposed workers.	0.5 ppm, S	5 ppm	Colorless, odorless solid. Thermal breakdown products include oxides of nitrogen.
Tetramethylammonium hydroxide (TMAH [CAS: 75-59-2): A corrosive substance that can cause injury to the skin, eyes, and respiratory tract. Exposure has resulted in human fatalities.			A very strong base that forms corrosive alkaline solutions. Used in semiconductor manufacturing.
Tetranitromethane (CAS: 509-14-8): Highly irritating upon direct contact; mild burns may result. Vapors extremely irritating to eyes and respiratory tract; pulmonary edema has been reported. May cause methemoglobinemia. Liver, kidney, and CNS injury in test animals at high doses. Overexposure associated with headaches, fatigue, dyspnea. See also Nitrates and Nitrites. A carcinogen in animal tests (IARC 2B).	0.005 ppm	4 ppm 10-min AEGL3: 2.2 ppm	Colorless to light yellow liquid or solid with a pungent, acrid odor. Irritative effects are a good warning property. Vapor pressure is 8.4 mm Hg at 20°C (68°F). Not combustible. A weak explosive and oxidizer. Highly explosive in the presence of impurities.
Tetryl (nitramine, 2,4,6-trinitrophenylmethylnitramine[CAS: 479-45-8]): Causes skin sensitization with dermatitis. Dusts extremely irritating to the eyes and respiratory tract. Stains tissues bright yellow. May injure the liver and kidneys. Overexposures also associated with malaise, headache, nausea, and vomiting.	1.5 mg/m³	750 mg/m³	White to yellow solid. Odorless. A strong oxidizer. Vapor pressure is much less than 1 mm Hg at 20°C (68°F). Explosive used in detonators and primers.
Texanol (2,2,4-trimethyl 1,3-pentanediol monoisobutyrate [CAS: 25265-77-4]): Mild potential eye, nose and throat irritant.			Volatile organic compound that is a common additive to water-based paints.
Thallium (CAS: 7440-28-0) and soluble compounds(thallium sulfate, thallium acetate, thallium nitrate): A potent toxin causing diverse chronic effects, including psychosis, peripheral neuropathy, optic neuritis, alopecia, abdominal pain, irritability, and weight loss. Liver and kidney injury may occur. Ingestion causes severe hemorrhagic gastroenteritis. Absorption possible by all routes. See also Thallium.	0.02 mg/m³ (inhalable fraction, as Tl), S	15 mg/m³ (as Tl)	Appearance varies with the compound. The elemental form is a bluish-white ductile heavy metal with a negligible vapor pressure. Thallium has been used as a rodenticide.
Thioglycolic acid (mercaptoacetic acid [CAS: 68-11-1]): Skin or eye contact with concentrated acid causes severe burns. Vapors irritating to eyes and respiratory tract.	1 ppm, S		Colorless liquid. Unpleasant mercaptan-like odor. Vapor pressure is 10 mm Hg at 18°C (64°F). Found in some cold wave and depilatory formulations.
Thiram (tetramethylthiuram disulfide [CAS: 137-26-8]): Dusts mildly irritating to eyes, skin, and respiratory tract. A moderate allergen and a potent skin sensitizer. Has disulfiram-like effects in exposed persons who consume alcohol. An experimental goitrogen. Adverse effects on fetal development in test animals at very high doses. Inadequate carcinogenicity data (IARC 3).	0.05 mg/m³, SEN	100 mg/m³	White to yellow powder with a characteristic odor. May be dyed blue. Vapor pressure is negligible at 20°C (68°F). Thermal breakdown products include sulfur dioxide and carbon disulfide. Used in rubber manufacture (vulcanization) and as a fungicide.
Tilmicosin phosphate (Micotil 300 [CAS: 137330-13-3]): Severe allergen and acute human cardiotoxin.			Yellow to amber liquid. Veterinary antibiotic. Has been used for intentional self-poisoning.
Tin, metal and inorganic compounds: Dusts irritating to the eyes, nose, throat, and skin. Prolonged inhalation may cause chest radiographic abnormalities. Some compounds react with water to form acids (tin tetrachloride, stannous chloride, and stannous sulfate) or bases (sodium and potassium stannate).	2 mg/m³ (as Sn)	100 mg/m³ (as Sn)	Metallic tin is odorless with a dull, silvery color.
Tin, organic compounds: Highly irritating upon direct contact; burns may result. Dusts, fumes, or vapors highly irritating to the eyes and respiratory tract. Triethyltin is a potent neurotoxin; triphenyltin acetate is highly hepatotoxic. Trialkyltins are the most toxic, followed in order by the dialkyltins and monoalkyltins. Within each of these classes, the ethyltin compounds are the most toxic. All are well absorbed dermally.	0.1 mg/m³, S (as Sn)	25 mg/m³ (as Sn)	There are many kinds of organotin compounds: mono-, di-, tri-, and tetra-alkyltin and -aryltin compounds exist. Combustible. Organic tin compounds are used in some polymers and paints (as a mildewcide).
Titanium dioxide (CAS: 13463-67-7): A mild pulmonary irritant. IARC 2B, NIOSH CA.	10 mg/m³	5,000 mg/m³	White odorless powder. Rutile is a common crystalline form. Vapor pressure is negligible.
Tolidine (o-tolidine, 3,3'-dimethylbenzidine [CAS:119-93-7]): A carcinogen in test animals (IARC 2B), NIOSH CA.	S		White to reddish solid. Oxides of nitrogen are among thermal breakdown products. Nanoparticle preparations have widespread applications including consumer products.
Toluene (toluol, methylbenzene [CAS: 108-88-3]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant; may cause brain, kidney, and muscle damage with frequent intentional abuse. May cause cardiac arrhythmias. Liver and kidney injury with heavy exposures. Abusive sniffing during pregnancy associated with birth defects. Inadequate carcinogenicity data (IARC 3). See also Toluene and Xylene.	20 ppm, S	500 ppm 10-min AEGL3: 10,000 ppm	Colorless liquid. Aromatic, benzene-like odor detectable at very low levels. Irritation serves as a good warning property. Vapor pressure is 22 mm Hg at 20°C (68°F). Flammable. Common industrial solvent also found in many consumer products (eg, adhesives, strippers).
Toluene-2,4-diisocyanate (TDI [CAS: 584-84-9]): A potent respiratory tract sensitizer (asthma) and potent irritant of the eyes, skin, and respiratory tract. Pulmonary edema has resulted with higher exposures. A carcinogen in test animals (IARC 2B), NIOSH CA. See also Isocyanates.	0.001 ppm, S, SEN	2.5 ppm 10-min AEGL3: 0.65 ppm	Colorless needles or a liquid with a sharp, pungent odor near 0.01 ppm. Vapor pressure is approximately 0.04 mm Hg at 20°C (68°F). Combustible. Precursor material for polyurethane; exposure to TDI may occur during polymerization including in field applications.
o-Toluidine (2-methylaniline [CAS: 95-53-4]): A corrosive alkali; can cause severe burns. May cause methemoglobinemia. Dermal absorption occurs. A human carcinogen (IARC 1), NIOSH CA.	2 ppm, S	50 ppm	Colorless to pale yellow liquid. The weak aromatic odor is thought to be a good warning property. Vapor pressure is less than 1 mm Hg at 20°C (68°F).
m-Toluidine (3-methylaniline [CAS: 108-44-1]): A corrosive alkali; can cause severe burns. May cause methemoglobinemia. Dermal absorption occurs.	2 ppm, S		Pale yellow liquid. Vapor pressure is less than 1 mm Hg at 20°C (68°F).
p-Toluidine (4-methylaniline [CAS: 106-49-0]): A corrosive alkali; can cause severe burns. May cause methemoglobinemia. Dermal absorption occurs. A carcinogen in test animals, NIOSH CA.	2 ppm, S		White solid. Vapor pressure is 1 mm Hg at 20°C (68°F).
Tributyl phosphate (CAS: 126-73-8): Highly irritating upon direct contact; causes severe eye injury and skin irritation. Vapors or mists irritating to the eyes and respiratory tract; high exposure in test animals caused pulmonary edema. Weak anticholinesterase activity. Headache and nausea are reported.	5 mg/m³	30 ppm	Colorless to pale yellow liquid. Odorless. Vapor pressure is very low at 20°C (68°F). Combustible. Thermal breakdown products include phosphoric acid fume.
Trichloroacetic acid (CAS: 76-03-9): A strong acid. A protein denaturant. Corrosive to eyes and skin upon direct contact. Insufficient data for carcinogenicity (IARC 2B).	0.5 ppm		Deliquescent crystalline solid. Vapor pressure is 1 mm Hg at 51°C (128.3°F). Thermal breakdown products include hydrochloric acid and phosgene.
1,2,4-Trichlorobenzene (CAS: 120-82-1): Prolonged or repeated contact can cause skin and eye irritation. Vapors irritating to the eyes, skin, and respiratory tract. High-dose animal exposures injure the liver, kidneys, lungs, and CNS. Does not cause chloracne.	5 ppm (C)		A colorless liquid with an unpleasant, mothball-like odor. Vapor pressure is 1 mm Hg at 38.4°C (101.1°F). Combustible. Thermal breakdown products include hydrogen chloride and phosgene.
1,1,1-Trichloroethane (methyl chloroform, TCA [CAS:71-55-6]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. Some dermal absorption occurs. Liver and kidney injury may occur. See also Trichloroethane, Trichloroethylene, and Tetrachloroethylene. IARC 3.	350 ppm	700 ppm	Colorless liquid. Odor threshold near 350 ppm. Vapor pressure is 100 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and phosgene. Widely used chlorinated solvent.
1,1,2-Trichloroethane (CAS: 79-00-5): Dermal absorption may occur. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. Causes liver and kidney injury in test animals. Limited evidence for carcinogenicity in test animals (IARC 3), NIOSH CA. See also Trichloroethane, Trichloroethylene, and Tetrachloroethylene.	10 ppm, S	100 ppm	Colorless liquid. Sweet, chloroform-like odor is of unknown value as a warning property. Vapor pressure is 19 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include phosgene and hydrochloric acid.
Trichloroethylene (trichloroethene, TCE [CAS: 79-01-6]): Dermal absorption may occur. Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. May cause cranial and peripheral neuropathy and liver damage. Has a disulfiram-like effect, “degreasers' flush” (Trichloroethane, Trichloroethylene, and Tetrachloroethylene). Reported to cause liver and lung cancers in mice (IARC 1), NIOSH CA. See also Trichloroethane, Trichloroethylene, and Tetrachloroethylene.	10 ppm	1,000 ppm	Colorless liquid. Sweet chloroform-like odor near 100 ppm. Vapor pressure is 58 mm Hg at 20°C (68°F). Not combustible at room temperature. Decomposition products include hydrogen chloride and phosgene. Widely used chlorinated solvent.
Trichlorofluoromethane (Freon 11 [CAS: 75-69-4]): Vapors mildly irritating to eyes and respiratory tract. A CNS depressant. May cause cardiac arrhythmias. See also Freons and Halons.	1,000 ppm (C)	2,000 ppm	Colorless liquid or gas at room temperature. Vapor pressure is 690 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and hydrogen fluoride.
Trichloronaphthalene (Halowax [CAS: 1321-65-9]): Causes chloracne. A hepatotoxin at low doses, causing jaundice. Stored in body fat. Systemic toxicity may occur after dermal exposure. For chloracne, see also “Dioxins,”.	5 mg/m³, S	20 mg/m³ (effective IDLH)	Colorless to pale yellow solid with an aromatic odor of uncertain value as a warning property. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Flammable. Decomposition products include phosgene and hydrogen chloride.
2,4,5-Trichlorophenoxyacetic acid (2,4,5-T [CAS:93-76-5]): Moderately irritating to eyes, skin, and respiratory tract. Ingestion can cause gastroenteritis and injury to the CNS, muscle, kidney, and liver. A weak uncoupler of oxidative phosphorylation. Polychlorinated dibenzodioxin (dioxin) compounds are contaminants. There are reports of sarcomas occurring in applicators. Adverse effects on fetal development in test animals.	10 mg/m³	250 mg/m³	Colorless to tan solid. Appearance and some hazardous properties vary with the formulation. Odorless. Vapor pressure is negligible at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride and dioxins. An herbicide once widely used as a defoliant and in Vietnam (“Agent Orange”).
1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113 [CAS:76-13-1]): Vapors mildly irritating to eyes and mucous membranes. Very high air levels cause CNS depression and may injure the liver. May cause cardiac arrhythmias at air concentrations as low as 2,000 ppm in test animals. See also Freons and Halons.	1,000 ppm	2,000 ppm	Colorless liquid. Sweet, chloroform-like odor occurs only at very high concentrations and is a poor warning property. Vapor pressure is 284 mm Hg at 20°C (68°F). Not combustible. Thermal breakdown products include hydrogen chloride, hydrogen fluoride, and phosgene.
Triethylamine (CAS: 121-44-8): An alkaline corrosive; highly irritating to eyes and skin; severe burns may occur. Vapors very irritating to eyes and respiratory tract; pulmonary edema may occur. High doses in animals cause heart, liver, and kidney injury. CNS stimulation possibly resulting from inhibition of monoamine oxidase (see Monoamine Oxidase Inhibitors).	0.5 ppm, S	200 ppm	Colorless liquid with a fishy, ammonia-like odor of unknown value as a warning property. Vapor pressure is 54 mm Hg at 20°C (68°F). Flammable. Industrial chemical but also used as an insect “anesthetic” in research and other applications.
Trifluorobromomethane (Halon 1301; Freon 13B1 [CAS:75-63-8]): Extremely high air levels (150,000-200,000 ppm) can cause CNS depression and cardiac arrhythmias. See also Freons and Halons.	1,000 ppm	40,000 ppm	Colorless gas with a weak ether-like odor at high levels and poor warning properties. Not combustible.
Trifluoromethane (Freon 23 [CAS: 75-46-7]): Vapors mildly irritating to the eyes and mucous membranes. Very high air levels cause CNS depression and cardiac arrhythmias. See also Freons and Halons.			Not combustible. Thermal breakdown products include hydrogen fluoride.
Trimellitic anhydride (TMAN [CAS: 552-30-7]): Dusts and vapors extremely irritating to eyes, nose, throat, skin, and respiratory tract. Potent respiratory sensitizer (asthma). Can also cause diffuse lung hemorrhage (and subsequent pulmonary hemosiderosis).	0.0005 mg/m³, S, SEN		Colorless solid. Hydrolyzes to trimellitic acid in aqueous solutions. Vapor pressure is 0.000004 mm Hg at 25°C (77°F). TMAN is an important component of certain epoxy formulations.
Trimethylamine (CAS: 75-50-3): An alkaline corrosive; highly irritating upon direct contact; severe burns may occur. Vapors very irritating to respiratory tract.	5 ppm		Highly flammable gas with a pungent, fishy, ammonia-like odor near 0.1 ppm. May be used as a warning agent in natural gas.
Trimethyl phosphite (phosphorous acid trimethylester [CAS:121-45-9]): Very irritating upon direct contact; severe burns may result. Vapors highly irritating to respiratory tract. Cataracts have developed in test animals exposed to high air levels. Evidence for adverse effects on fetal development in test animals.	2 ppm		Colorless liquid with a characteristic strong, fishy, or ammonia-like odor. Hydrolyzed in water. Vapor pressure is 24 mm Hg at 25°C (77°F). Combustible.
Trinitrotoluene (2,4,6-trinitrotoluene, TNT [CAS:118-96-7]): Irritating upon direct contact. Stains tissues yellow. Causes sensitization dermatitis. Vapors irritating to respiratory tract. May cause liver injury, methemoglobinemia. Occupational overexposure associated with cataracts. Causes vasodilation, including vasodilation in coronary arteries. Headache and drop in blood pressure are common. Well absorbed by all routes. Tolerance to vasodilation can occur; cessation of exposure may precipitate angina pectoris in pharmacologically dependent workers. See also “Nitrates and Nitrites,”. Inadequate carcinogenicity data (IARC 3).	0.1 mg/m³, S	500 mg/m³	White to light yellow crystalline solid. Odorless. Vapor pressure is 0.05 mm Hg at 85°C (185°F). Explosive upon heating or shock. Exposure can occur among munitions workers.
Triorthocresyl phosphate (TOCP [CAS: 78-30-8]): Inhibits acetylcholinesterase (Organophosphorus and Carbamate Insecticides). Potent neurotoxin causing delayed, partially reversible peripheral neuropathy by all routes.	0.02 mg/m³, S	40 mg/m³	Colorless viscous liquid. Odorless. Not combustible. Although an anticholinesterase inhibitor, it is widely used as a chemical additive and in chemical synthesis. Exposure has occurred through contaminated foodstuffs.
Triphenyl phosphate (CAS: 115-86-6): Weak anticholinesterase activity in humans (Organophosphorus and Carbamate Insecticides). Delayed neuropathy reported in test animals.	3 mg/m³	1,000 mg/m³	Colorless solid. Faint phenolic odor. Not combustible. Thermal breakdown products include phosphoric acid fumes.
Tungsten and compounds: Few reports of human toxicity. Some salts may release acid upon contact with moisture. Chronic exposure to tungsten carbide-cobalt amalgams in the hard metals industry may be associated with fibrotic lung disease.	5 mg/m³ (insoluble compounds), 1 mg/m³ (soluble compounds)		Elemental tungsten is a gray, hard, brittle metal. Finely divided powders are flammable. Hard metal is used in specialty saw blades and in diamond cutting, among other applications.
Turpentine (CAS: 8006-64-2): Irritating to eyes upon direct contact. Dermal sensitizer. Dermal absorption occurs. Vapors irritating to respiratory tract. A CNS depressant at high air levels. See also “Hydrocarbons,”.	20 ppm, SEN	800 ppm	Colorless to pale yellow liquid with a characteristic paintlike odor that serves as a good warning property. Vapor pressure is 5 mm Hg at 20°C (68°F). Flammable.
Uranium compounds: Many salts are irritating to the respiratory tract; soluble salts are potent kidney toxins. Uranium is a weakly radioactive element (alpha emitter); decays to the radionuclide thorium 230. Uranium has the potential to cause radiation injury to the lungs, tracheobronchial lymph nodes, bone marrow, and skin. NIOSH CA.	0.2 mg/m³ (soluble and insoluble compounds, as U)	10 mg/m³	Dense, silver-white, lustrous metal. Finely divided powders are pyrophoric. Radioactive (see Radiation (Ionizing)). Depleted uranium-containing weaponry has been investigated as a potential source of exposure (eg, through retained shrapnel).
Valeraldehyde (pentanal [CAS: 110-62-3]): Very irritating to eyes and skin; severe burns may result. Vapors highly irritating to the eyes and respiratory tract.	50 ppm		Colorless liquid with a fruity odor. Flammable.
Vanadium pentoxide (CAS: 1314-62-1): Dusts or fumes highly irritating to eyes, skin, and respiratory tract. Acute overexposures have been associated with persistent bronchitis and asthma-like responses (“boilermakers' asthma”). Sensitization dermatitis reported. Low-level exposure may cause a greenish discoloration of the tongue, metallic taste, and cough. IARC 2B.	0.05 mg/m³	35 mg/m³ (as V)	Yellow-orange to rust-brown crystalline powder or dark gray flakes. Odorless. Not combustible.
Vinyl acetate (CAS: 108-05-4): Highly irritating upon direct contact; severe skin and eye burns may result. Vapors irritating to the eyes and respiratory tract. Mild CNS depressant at high levels. Limited evidence for adverse effects on male reproduction in test animals at high doses. IARC 2B.	10 ppm	10-min AEGL3: 230 ppm	Volatile liquid with a pleasant fruity odor at low levels. Vapor pressure is 115 mm Hg at 25°C (77°F). Flammable. Polymerizes readily. Must contain inhibitor to prevent auto-polymerization.
Vinyl bromide (CAS: 593-60-2): At high air levels, an eye and respiratory tract irritant and CNS depressant; a kidney and liver toxin. Animal carcinogen (IARC 2A). NIOSH CA.	0.5 ppm		Colorless, highly flammable gas with a distinctive odor.
Vinyl chloride (CAS: 75-01-4): An eye and respiratory tract irritant at high air levels. Degeneration of distal phalanges with “acro-osteolysis,” Raynaud disease, and scleroderma has been associated with heavy workplace overexposures. A CNS depressant at high levels, formerly used as an anesthetic. May cause cardiac arrhythmias. Causes angiosarcoma of the liver in humans (IARC 1). OSHA CA. NIOSH CA.	1 ppm	10-min AEGL3: 12,000 ppm	Colorless, highly flammable gas with a sweet ether-like odor. Polymerizes readily. Current potential exposure is limited to vinyl chloride synthesis and polymerization to PVC.
Vinyl cyclohexene dioxide (vinylhexane dioxide [CAS: 106-87-6]): Moderately irritating upon direct contact; severe burns may result. Vapors highly irritating to eyes and respiratory tract. Testicular atrophy, leukemia, and necrosis of the thymus in test animals. Topical application causes skin cancer in animal studies (IARC 2B), NIOSH CA.	0.1 ppm, S		Colorless liquid. Vapor pressure is 0.1 mm Hg at 20°C (68°F).
Vinyl toluene (methylstyrene [CAS: 25013-15-4]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. Hepatic, renal, and hematologic toxicities at high doses in test animals. Limited evidence for adverse effects on the developing fetus. Inadequate carcinogenicity data (IARC 3).	50 ppm	400 ppm	Colorless liquid. Strong, unpleasant odor is considered to be an adequate warning property. Vapor pressure is 1.1 mm Hg at 20°C (68°F). Flammable. Inhibitor added to prevent explosive auto-polymerization.
VM&P naphtha (varnish makers' and printers' naphtha; ligroin [CAS: 8032-32-4]): Vapors irritating to eyes and respiratory tract. A CNS depressant at high levels. May contain a small amount of benzene. See also “Hydrocarbons,”.			Colorless volatile liquid. Common solvent.
VX (CAS 50782-69-9): Extremely toxic chemical warfare nerve agent by all routes of contact. Readily absorbed via respiratory tract and skin and eyes. A potent cholinesterase inhibitor with rapid onset of symptoms. Vapors highly irritating.		10-min AEGL3: 0.0027 ppm	Colorless or amber liquid. Least volatile of the chemical nerve agents: vapor pressure is 0.007 mm Hg at 25°C (77°F). Odor is not an adequate warning of exposure. Flammability unknown.
Warfarin (CAS: 81-81-2): An anticoagulant by ingestion. Medicinal doses associated with adverse effects on fetal development in test animals and humans. See also Warfarin and Superwarfarins.	0.1 mg/m³	100 mg/m³	Colorless crystalline substance. Odorless. Used as a rodenticide and pharmaceutical anticoagulant. Exposure is typically from inadvertent or deliberate ingestion rather than through workplace contamination.
*Xylene (mixture of o-, m-,* and p-dimethylbenzenes [CAS: 1330-20-7]):** Vapors irritating to eyes and respiratory tract. A CNS depressant. By analogy to toluene and benzene, may cause cardiac arrhythmias. May injure kidneys. Limited evidence for adverse effects on fetal development in test animals at very high doses. Inadequate carcinogenicity data (IARC 3). See also Toluene and Xylene.	100 ppm	900 ppm 10-min AEGL3: 7,200 ppm	Colorless liquid or solid. Weak, somewhat sweet aromatic odor. Irritant effects are adequate warning properties. Vapor pressure is approximately 8 mm Hg at 20°C (68°F). Flammable.
Xylidine (dimethylaniline [CAS: 1300-73-8]): May cause methemoglobinemia. Dermal absorption may occur. Liver and kidney damage seen in test animals.	0.5 ppm, S	50 ppm	Pale yellow to brown liquid. Weak, aromatic amine odor is an adequate warning property. Vapor pressure is less than 1 mm Hg at 20°C (68°F). Combustible. Thermal breakdown products include oxides of nitrogen. Used in chemical synthesis including in the dye industry.
Yttrium and compounds (yttrium metal, yttrium nitratehexahydrate, yttrium chloride, yttrium oxide): Dusts may be irritating to the eyes and respiratory tract.	1 mg/m³ (as Y)	500 mg/m³ (as Y)	Appearance varies with compound.
Zinc chloride (CAS: 7646-85-7): Caustic and highly irritating upon direct contact; severe burns may result. Ulceration of exposed skin from exposure to fumes has been reported. Fumes extremely irritating to respiratory tract; pulmonary edema and acute lung injury have resulted.	1 mg/m³	50 mg/m³	White powder or colorless crystals that absorb moisture. The fume is white and has an acrid odor. Exposure is principally through smoke bombs.
Zinc chromates (basic zinc chromate, ZnCrO₄; zincpotassium chromate, KZn₂ (CrO₄); zinc yellow): Contains hexavalent chromium, which is associated with lung cancer in workers. See also Chromium.	0.01 mg/m³ (as Cr)		Basic zinc chromate is a yellow pigment; dichromates are orange.
Zinc oxide (CAS: 1314-13-2): Fumes irritating to the respiratory tract. Causes metal fume fever. Symptoms include headache, fever, chills, and muscle aches.	2 mg/m³	500 mg/m³	A white or yellowish-white powder. Fumes of zinc oxide are formed when elemental zinc is heated above its melting point. Principal exposure is through brass foundries or welding on galvanized steel.
Zirconium compounds (zirconium oxide, ZrO₂; zirconiumoxychloride, ZrOCl; zirconium tetrachloride, ZrCl₄): Zirconium compounds are generally of low toxicity. Some compounds are irritating; zirconium tetrachloride releases HCl upon contact with moisture. Granulomata caused by the use of deodorants containing zirconium have been observed. Dermal sensitization has not been reported.	5 mg/m³ (as Zr)	50 mg/m³ (as Zr)	The elemental form is a bluish-black powder or a grayish-white, lustrous metal. The finely divided powder can be flammable.

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Introduction