Facts of LifeWhat do you know about Napthalene? [Archives:2005/835/Health]

April 21 2005

Moth repellants, insecticides, smokeless powder, solvents, and lubricants are many products that are used in our daily life. Those and many other chemically synthetic products are manufactured using a hydrocarbon called naphthalene directly or as an intermediate in the manufacture process.

Naphthalene, also referred to as naphthene, naphthalin, tar camphor, aldocarbon, or mothballs, is a white solid that exhibits a typical mothball odor at ambient temperature.

Having a molecular weight of 128.19, naphthalene is a polycyclic aromatic hydrocarbon composed of two fused benzene rings with the empirical formula of C10H8. It has a melting point of 80.5 C, a boiling point of 218 C, a vapor pressure of 0.082 mm Hg at 25 C.

Naphthalene is almost insoluble in water, but is soluble in benzene, toluene, ether, and several other organic solvents. It is flammable; the vapors and dusts can produce explosive mixtures with air.

It occurs in crude oil, from which it may be recovered directly as white flakes; it can also be isolated from cracked petroleum, coke-oven emissions, or from high-temperature carbonization of bituminous coal.

Naphthalene is used directly as a moth repellant, insecticide, anthelmintic, and intestinal antiseptic and is also used as an intermediate for the manufacture of synthetic resins, celluloid, lampblack, smokeless powder, solvents, and lubricants.

Most of the naphthalene entering the environment is released directly to the air from sources such as burning of fossil fuels and use of naphthalene-containing mothballs. Other sources include urban air pollution and cigarette smoke.

Small amounts of naphthalene are released to the aqueous environment as a result of discharges from coal tar production and distillation. In the atmosphere, naphthalene undergoes a number of degradation processes including reaction with photo chemically produced hydroxyl radicals.

In natural waters and soils, volatilization and biodegradation are major removal processes. Naphthalene has a short half-life and is not thought to bioaccumulate over time processes.

Absorption of naphthalene by the oral, inhalation, and dermal routes can be inferred in humans from the systemic toxic effects of the compound. However, the rate and extent of absorption is not known. An oral study with rats suggests that the rate of absorption remains fairly constant at doses up to 200 mg/kg.

Data on the tissue distribution of naphthalene in humans are very limited. Naphthalene or its metabolites can cross the placenta in humans in amounts sufficient to cause fetal toxicity. Oral and intraperitoneal studies with animals showed that naphthalene distributes to several tissues.

Following oral exposure, naphthalene was detected in the fat, liver, lungs, and heart of swine; in the liver and milk of dairy cows;

and in the liver, kidneys, lungs, fat, and yolk of laying pullets.

Naphthol was found in the urine of patients four days after naphthalene ingestion; smaller amounts were detected at five days and none thereafter.

Reasons for concern

Naphthalene has many critical effects when introduced to the body. Target organs that might be affected include the vital ones; the liver and kidneys as well as many others. Some of those significant and noteworthy effects are showed as follows:

1. Blood: Hemolytic anemia associated with decreased hemoglobin.

2. Gastrointestinal tract: Nausea, vomiting, abdominal pain, and diarrhea.

3. Nervous system: Confusion, listlessness and lethargy, muscle twitching, convulsions, decreased responses to painful stimuli and coma.

4. Liver: Jaundice, enlarged liver, and increased serum enzyme activity.

5. Kidneys: Increased creatinine and blood urea nitrogen levels, proteinuria and hemoglobinuria.

6. Eyes: Restricted visual fields and cataracts.

7. Reproduction: Hemolytic anemia has been reported in infants whose mothers were exposed to naphthalene during pregnancy.