Trichloroethane, Trichloroethylene, and Tetrachloroethylene
Trichloroethane and trichloroethylene are widely used solvents that are ingredients in many products, including typewriter correction fluid (“Wite-Out”), color film cleaners, insecticides, spot removers, fabric-cleaning solutions, adhesives, and paint removers. They are used extensively in industry as degreasers. Trichloroethane is available in two isomeric forms, 1,1,2-trichloroethane and 1,1,1-trichloroethane, with the latter (also known as methyl chloroform) the more common. Tetrachloroethylene (perchloroethylene) is another related solvent that is used widely in the dry cleaning industry.
Mechanism of toxicity
These solvents act as respiratory and CNS depressants and skin and mucous membrane irritants. As a result of their high lipid solubility and CNS penetration, they have rapid anesthetic action, and both tricholorethylene and trichloroethane were used for this purpose medically until the advent of safer agents. Peak blood levels occur within minutes of inhalation exposure or 1–2 hours after ingestion. Their proposed mechanism of action includes neuronal calcium channel blockade and gamma-aminobutyric acid (GABA) stimulation.
Trichloroethane, trichloroethylene, their metabolite trichloroethanol, and tetrachloroethylene may sensitize the myocardium to the arrhythmogenic effects of catecholamines.
Trichloroethylene or a metabolite may act to inhibit acetaldehyde dehydrogenase, blocking the metabolism of ethanol and causing “degreaser’s flush.”
Carcinogenicity. The National Institute of Occupational Safety & Health (NIOSH) and the International Agency for Research on Cancer (IARC) consider tetrachloroethylene and trichloroethylene probable carcinogens (Group 2A). Although 1,1,2-trichloroethane is a NIOSH-suspected carcinogen, there is insufficient evidence to label 1,1,1-trichloroethane a carcinogen.
Toxic dose
Trichloroethane.
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