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INTRODUCTION

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, 10% in oil, was used as a scabicide in the past. Naphthalene is no longer commonly used because it largely has been replaced by the less toxic paradichlorobenzene.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.

MECHANISM OF TOXICITY

Both compounds sublimate into vapor and enter the atmosphere upon being opened, and are well absorbed through the GI and respiratory tracts. Both compounds cause GI upset, and both may cause CNS stimulation. In addition, naphthalene may produce hemolysis, especially in patients with glucose-6-phosphate dehydrogenase (G6PD) deficiency.

TOXIC DOSE

  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. Dermal absorption is believed to be very low.

CLINICAL PRESENTATION

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, particularly in children following ingestion and in patients with G6PD deficiency, has been 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, there is no clear evidence of hematologic effects even in chronic exposures.

    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.

DIAGNOSIS

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 ...

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