DESCRIPTION

Formaldehyde is an industrial and medical chemical used as a preservative and as an intermediary in many industrial processes.

FORMS AND USES

• Formaldehyde (methyl aldehyde, methylene oxide, formic aldehyde) is sold as an aqueous solution with concentrations varying from 37% to 56% formaldehyde by weight, with varying amounts of methanol added to retard polymerization (maximum methanol concentration is 15%).
• Medical uses of formaldehyde include antiseptics, disinfectants, tissue fixative, and embalming agents.
• Formaldehyde is used in the textile industry to attain a permanent press, wrinkle-free finish on textiles.
• Urea formaldehyde foam insulation releases formaldehyde vapor.
• Formaldehyde is a by-product of tobacco combustion.

TOXIC DOSE

• Formaldehyde solution (2%) can cause dermal or eye burns.
• Ingestion of a few gulps of 37% solution has caused death.

PATHOPHYSIOLOGY

• Formaldehyde is a direct mucosal irritant, causing rapid burning and lacrimation, as well as stimulating bronchospasm.
• Formaldehyde is rapidly metabolized to formic acid, which produces metabolic acidosis.
• The methanol contained in aqueous formaldehyde is metabolized to formic acid and contributes to the acidosis.
• Tissue necrosis with lactate production further contributes to the acidosis.

EPIDEMIOLOGY

• Ingestion of formaldehyde is rare, occupational exposure is common, and low level environmental exposure is ubiquitous.
• Toxic effects following ingestion or high-concentration dermal exposure can be severe.
• Ingestion, massive skin exposure, or inhalation of high concentrations may result in death.

CAUSES

• Ingestion of formaldehyde is usually intentional; occupational exposure is usually accidental.
• Child neglect should be considered if the patient is under 1 year of age; attempted suicide if the patient is over 6 years of age.

RISK FACTORS

Occupational formaldehyde exposures occur in the textile industry (crease-resistant finishers, fur processors, hide preservers, textile mordanters, printers, waterproofers); life sciences (anatomists, students, biologists, embalmers, histology technicians, pathologists, taxidermists); rubber and cement production (bookbinders, cosmetic formulators, electrical insulation manufacturers, glue and adhesive makers); plywood, particle board, or paper manufacturing; furniture manufacturing; and disinfectant manufacturing.

WORKPLACE STANDARDS

• OSHA: not listed.
• NIOSH REL TWA is 0.016; ceiling value is 0.1 ppm.
• ACGIH: TLV ceiling is 0.3 ppm.

Section Outline:

• DESCRIPTION
• FORMS AND USES
• TOXIC DOSE
• PATHOPHYSIOLOGY
• EPIDEMIOLOGY
• CAUSES
• RISK FACTORS
• WORKPLACE STANDARDS

DIFFERENTIAL DIAGNOSIS

• Other toxic agents that cause acute respiratory irritation include acetylene, ammonia, carbon disulfide, chloramine, chlorine, fluorine, hydrogen chloride or fluoride, and sulfur dioxide, among others.
• Other gastrointestinal irritants include strong acids or alkali.

SIGNS AND SYMPTOMS

Formaldehyde inhalation produces acute onset of respiratory irritant symptoms, and ingestion produces symptoms of acute caustic ingestion. In general, toxic effects of inhalation are less severe than those of ingestion.

Vital Signs

• Patients who have sustained significant exposure are usually anxious, as well as tachypneic and tachycardic from pain.
• In severe cases, patients present in shock with hypovolemia and hypotension.

HEENT

• Inhalation of low concentrations produces mucosal burning sensation and lacrimation.
• Inhalation of high concentrations causes mucosal burning with choking, coughing, sore throat, drooling, and difficulty in swallowing.
• Chronic inhalation causes headache, nausea and flulike symptoms.
• Ingestion may cause ulceration of the mouth, nasopharynx, esophagus, and respiratory mucosa.

Dermatologic

Acute exposure can cause dermatitis in sensitive individuals.

Pulmonary

• Respiratory effects of acute vapor inhalation are dependent on the concentration and duration of exposure.
• Prolonged high-dose exposure may cause parenchymal irritation with cough, chest pain, dyspnea, and wheezing.

Cardiovascular

Profound acidosis may cause hypotension.

Gastrointestinal

• Caustic gastrointestinal effects include hemorrhage, perforation, tissue fixation, and subsequent stricture formation.
• Severe vomiting and massive hematemesis may occur.

Renal

• Nephritis or acute tubular necrosis may develop following acute exposure.
• Chronic high-dose exposure may cause glomerulonephropathy.

Fluids and Electrolytes

Intravascular volume loss may result from massive fluid shift into injured tissues and potentially severe metabolic acidosis.

Neurologic

Limited inhalation exposure may produce headache and lightheadedness, whereas higher concentrations will have direct CNS depressant effects.

PROCEDURES AND LABORATORY TESTS

Essential Tests

• No tests may be needed for minimally symptomatic skin or inhalation exposure to formaldehyde.
• In cases of ingestion, the following should be obtained:
  • Serum electrolytes, BUN, creatinine to assess fluid shifts, monitor renal function, and assess acidosis
  • Complete blood count to assess blood loss
  • Serum liver function tests, coagulation studies in severe cases to assess injury
  • Arterial blood gas to assess acidosis and potential airway compromise

Recommended Tests

• In cases of serious skin or high-concentration formaldehyde inhalation exposure, the same tests as described as essential for ingestion should be undertaken.
• ECG, serum acetaminophen, and aspirin levels should be obtained to detect occult ingestion.
• Gastrointestinal endoscopy should be performed following ingestion to evaluate for burns.
• Pulmonary peak flows should be monitored to follow progress of bronchospasm.
• Chest radiography may be useful in the hypoxic patient to evaluate pulmonary injury or possible gastric perforation.
• Gastric contrast studies should be performed to evaluate stricture formation.

Not Recommended Tests

Serum formic acid and formaldehyde levels are not clinically useful.

Section Outline:

• DIFFERENTIAL DIAGNOSIS
• SIGNS AND SYMPTOMS
  • Vital Signs
  • HEENT
  • Dermatologic
  • Pulmonary
  • Cardiovascular
  • Gastrointestinal
  • Renal
  • Fluids and Electrolytes
  • Neurologic
• PROCEDURES AND LABORATORY TESTS
  • Essential Tests
  • Recommended Tests
  • Not Recommended Tests

• Following ingestion, treatment should focus on stabilization and resuscitation of patients with gastrointestinal hemorrhage and shock.
• Supportive care with appropriate airway management is vital.
• Dose and time of exposure must be determined for all substances involved.
• Vomiting and massive hematemesis may require emergent gastrectomy.

DIRECTING PATIENT COURSE

The health-care provider should call a poison control center when:

• Respiratory or gastrointestinal symptoms of formaldehyde poisoning are present.
• Signs and symptoms are not consistent with formaldehyde poisoning.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

The patient should be referred to a health-care facility when:

• Any toxic effects develop.
• Attempted suicide or homicide is possible.
• The patient or caregiver seems unreliable.
• Coingestant, drug interaction, or underlying disease presents an unusual problem.

Admission Considerations

Inpatient management is warranted in the following circumstances:

• Inhalation. Patients with hypoxia or apparent pulmonary injury, or those who remain symptomatic after a 6-hour observation period.
• Ingestion. All patients, unless they are asymptomatic after a trivial ingestion of a low-concentration formaldehyde solution.

DECONTAMINATION

Out of Hospital

• Inhalation. The patient should be removed from source of formaldehyde exposure.
• Ingestion
  • Emesis should not be induced, because of its potential for caustic injury.
  • Administer 4 to 6 ounces of milk or water to alert patients to reduce the corrosive effects.
• Dermal or ocular exposure. The exposed area should be irrigated with copious amounts of water.

In Hospital

• Ingestion
  • Gastric lavage should be avoided because of its potential for caustic injury or perforation.
  • Activated charcoal should also be avoided because it may interfere with endoscopy.
• Inhalation. Supplemental oxygen should be administered.
• Dermal or ocular exposure. The exposed area should be irrigated with copious amounts of water.

ANTIDOTES

There is no specific antidote for formaldehyde toxicity.

ADJUNCTIVE TREATMENT

• Immediate hemodialysis should be considered for severe acute ingestion to remove formaldehyde, formic acid, and methanol.
• Bronchospasm
  • Albuterol 0.15 mg/kg (maximum of 10 mg) in saline with humidified oxygen via nebulizer every 20 to 30 minutes
    • If the peak respiratory flow rate is greater than 90% after the initial dose, additional doses may not be needed.
    • The patient should be continually monitored for response.
  • Methylprednisolone 60 to 125 mg (1-1.5 mg/kg) given intravenously (children 1-2 mg/kg) every 6 to 8 hours; this dosage may be decreased to a single daily dose and tapered.
• Hypotension is treated with isotonic fluid infusion, the Trendelenburg position, and vasopressor if needed; dopamine is preferred, norepinephrine for refractory hypotension.

Section Outline:

• DIRECTING PATIENT COURSE
  • Admission Considerations
• DECONTAMINATION
  • Out of Hospital
  • In Hospital
• ANTIDOTES
• ADJUNCTIVE TREATMENT

PATIENT MONITORING

• Formaldehyde ingestion. Hemodynamic and respiratory function should be monitored continuously during treatment, and follow-up should include monitoring for possible stricture formation.
• Formaldehyde inhalation. Pulmonary function should be monitored continuously during treatment, and follow-up should include serial pulmonary function tests.

EXPECTED COURSE AND PROGNOSIS

• Formaldehyde ingestion is characterized by rapid onset of severe gastrointestinal effects that stabilize within hours with therapy.
• Gastrointestinal scarring, stricture, and dysfunction may occur following ingestion.
• Minor inhalational exposure resolves within hours.
• Severe inhalational exposure may lead to reactive airway disease.
• Formaldehyde hypersensitivity following toxic exposure has been reported.

DISCHARGE CRITERIA AND INSTRUCTIONS

• From the emergency department
  • Formaldehyde inhalation. Asymptomatic patients with normal vital signs may be discharged 6 hours after an acute exposure.
  • Formaldehyde ingestion. Asymptomatic patients who have ingested trivial amounts of low-concentration solution may be discharged following psychiatric evaluation, if needed.
• From the hospital. Patients may be discharged when toxic effects resolve or stabilize, following psychiatric evaluation, if needed.

Section Outline:

• PATIENT MONITORING
• EXPECTED COURSE AND PROGNOSIS
• DISCHARGE CRITERIA AND INSTRUCTIONS

• Hypersensitivity testing may be needed in susceptible individuals.
• The health-care provider should monitor for gastrointestinal dysfunction following ingestion.

Poisoning by agents primarily affecting skin and mucous membrane, ophthalmological, otorhinolaryngological, and dental drugs.

See Also: SECTION II, Caustics-Acidic and Hypotension chapters.

RECOMMENDED READING

Burge PS, Harries MG, Lam WK, et al. Occupational asthma due to formaldehyde. Thorax 1985;40:255-260.

Ellenhorn MJ. Antiseptics and Disinfectants. In: Ellenhorn MJ, et al., eds. Ellenhorn's medical toxicology: diagnosis and treatment of human poisoning, 2nd ed. Baltimore: Williams & Wilkins, 1997:1214-1217.

Gunby P. Fact or fiction about formaldehyde? JAMA 1980;243:1697-1703.

Author: Gerald F. O'Malley

Reviewer: Luke Yip