Naphthalene and paradichlorobenzene are common ingredients in diaper pail and toilet bowl deodorizers, insecticides, and mothballs. Both compounds have a similar pungent odor and are clear-to-white crystalline substances; therefore, they are difficult to distinguish visually. Naphthalene is no longer commonly used because it largely has been replaced by the less toxic paradichlorobenzene. While formulations and sizes vary, most moth repellent products contain nearly 100% naphthalene or paradichlorobenzene.

Both compounds sublimate into vapor upon opening. They are well absorbed by ingestion, dermal exposure, and through inhalation, however the oral and dermal routes are most commonly associated with toxicity. Both compounds cause GI upset, and both may cause CNS stimulation. In addition, naphthalene may produce hemolysis and methemoglobinemia, especially in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency.

1. Naphthalene. As little as 250-500 mg may produce hemolysis in a patient with G6PD deficiency. The amount necessary to produce lethargy or seizures is not known but may be as little as 1-2 g. Several infants developed serious poisoning from clothes and bedding that had been stored in naphthalene mothballs. The LD₅₀ is 1.8 g/kg in adult rats.
2. Paradichlorobenzene is much less toxic than naphthalene; up to 20-g ingestions have been well tolerated in adults. The oral LD₅₀ for adult rats is 3.8 g/kg.
3. Pharmacokinetics. Both compounds are rapidly absorbed orally or by inhalation.

Acute ingestion usually causes prompt nausea and vomiting. Both compounds are volatile, and inhalation of vapors may cause eye, nose, and throat irritation.

1. Naphthalene.
   1. Agitation, headaches, confusion, lethargy, and seizures may occur with naphthalene ingestion.
   2. Hemolytic anemia and methemoglobinemia, particularly in children following ingestion and in patients with G6PD deficiency, is well documented.
   3. Nausea, vomiting, diarrhea (occasionally bloody), hematuria, and jaundice (as a consequence of hemolysis) have also been noted.
2. Paradichlorobenzene
   1. Acute ingestions of small amounts in children are virtually always innocuous.
   2. Exposure to the vapor can cause ocular irritation and GI upset.
   3. Prolonged direct contact can cause a burning sensation to the skin. Paradichlorobenzene decomposes to hydrochloric acid; this may explain some of its irritant effects.
   4. Unlike naphthalene, hematologic effects are rarely reported in acute or chronic exposure.
   5. A single case report from the 1950s reports hepatic necrosis and death in two people living in a home saturated with paradichlorobenzene for several months; other symptoms included headaches, clumsiness, slurred speech, diarrhea, and weight loss. No air measurements were taken and no other possible causes of their symptoms were discussed.
   6. Chronic ingestions have been linked to leukoencephalopathy.

Usually is based on a history of ingestion and the characteristic “mothball” smell around the mouth and in the vomitus. Differentiation between naphthalene and paradichlorobenzene by odor or color is difficult. In an in vitro x-ray study, paradichlorobenzene was radiopaque but naphthalene was not visible. In a saturated salt solution (about 1 tablespoon of salt in 4 oz of water), naphthalene will float and paradichlorobenzene will sink.

1. Specific levels. Serum and urine testing is not widely available. Paradichlorobenzene breakdown products (2,5-dichlorophenol) can be found in the urine and blood. Similarly, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, or their breakdown products can be found in samples of urine, stool, blood, milk, or body fat. Elevated levels indicate that a patient was exposed but are not correlated with clinical outcome.
2. Other useful laboratory studies include CBC, hepatic aminotransferases and, if hemolysis is suspected, haptoglobin, free hemoglobin, and urine dipstick for occult blood (positive with hemoglobinuria), creatine kinase, and G6PD testing.

1. Emergency and supportive measures
   1. Maintain an open airway and assist ventilation if necessary.
   2. Treat coma and seizures if they occur.
   3. Treat hemolysis and resulting hemoglobinuria, if they occur, by intravenous hydration and urinary alkalinization (see “Rhabdomyolysis,”).
2. Specific drugs and antidotes. There is no specific antidote.
3. Decontamination
   1. Naphthalene. Administer activated charcoal orally if conditions are appropriate (see Table I-37,). Gastric lavage is not necessary after small-to-moderate ingestions if activated charcoal can be given. Do not induce vomiting because of risk for lethargy and seizures. Do not administer milk, fats, or oil, which may enhance absorption.
   2. Paradichlorobenzene. Gut emptying and charcoal are not necessary unless a massive dose has been ingested. Do not administer milk, fats, or oils, which may enhance absorption.
   3. Inhalation. With either agent, remove the victim from exposure; fresh air is all that is required.
4. Enhanced elimination. There is no role for these procedures.