CE Original Date: August 1, 1993
CE Expiration Date: February 28, 2007
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|The following is about exposure pathways.|
Toluene is a clear, colorless liquid with an aromatic odor. It is a natural constituent of crude oil and is produced from petroleum refining and coke-oven operations. At room temperature, toluene is both volatile and flammable. The odor threshold for toluene in air is low-about 80 parts per billion (ppb), which is about 500 times lower than the level permitted in the workplace. In water, it can be tasted and smelled at a level of 40 ppb. These levels are well below the concentrations at which adverse effects have been observed for short-term exposure. Because toluene is lipid soluble, it has a moderate tendency to bioaccumulate in the food chain. Synonyms for toluene include toluol, methylbenzene, phenylmethane, and methacide.
The principal source of toluene exposure for the general population is gasoline, which contains 5% to 7% toluene by weight. Toluene is released to the atmosphere during the production, transport, and combustion of gasoline. Not surprisingly, toluene concentrations are highest in areas of heavy traffic, near gasoline filling stations, and near refineries. Toluene is short-lived in ambient air because of its reactivity with other air pollutants.
Common household products and cigarette smoke are the principal sources of toluene indoors. Indoor air is often several times higher in toluene concentration than outside air. Cigarette smokers absorb about 80 to 100 micrograms (µg) of toluene per cigarette. Toluene-containing consumer products include household aerosols, paints, paint thinners, varnishes, shellac, rust inhibitors, adhesives and adhesive products, and solvent-based cleaning and sanitizing agents. Toluene is used as a solvent in cosmetic nail polishes at concentrations of up to 50%.
Industrial use of toluene as a solvent replacement for the more toxic benzene is increasing. In addition to the products mentioned previously, toluene is commonly used in some printing operations, leather tanning, and chemical processes.
Intentional inhalation of toluene makes it one of the most abused hydrocarbon solvents. Glues, paints, and solvent mixtures are the most commonly abused products.
Although most environmental toluene is released directly to the atmosphere, it is occasionally detected in drinking water supplies. Water contamination occurs because toluene is a common chemical in hazardous waste and sludge disposal sites, industrial effluents, and petroleum wastes. Nonetheless, drinking water levels of toluene are usually low relative to those of other volatile organic chemicals.
The patient brings you the spray paint can, which lists the following ingredients on the label: paint (pigment), petroleum distillates, and a minor amount of methanol. A call to the regional poison control center reveals that the petroleum distillates in this brand of paint are mostly toluene, with minor amounts of xylene. The patient asks you if this toluene is the same chemical that caused her hospitalization 2 years ago.
How will you answer the patient's question?
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