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.
Trichloroethane. The acute lethal oral dose to humans is reportedly between 0.5 and 5 mL/kg. The recommended workplace limits (ACGIH TLV-TWA) in air for the 1,1,1-trichloroethane and 1,1,2-trichloroethane isomers are 350 and 10 ppm, respectively, and the air levels considered immediately dangerous to life or health (IDLH) are 700 and 100 ppm, respectively. Anesthetic levels are in the range of 10,000–26,000 ppm. The odor is detectable by a majority of people at 500 ppm, but olfactory fatigue commonly occurs.
Trichloroethylene. The acute lethal oral dose is reported to be approximately 3–5 mL/kg. The recommended workplace limit (ACGIH TLV-TWA) is 50 ppm (269 mg/m3), and the air level considered immediately dangerous to life or health (IDLH) is 1000 ppm.
Tetrachloroethylene. The recommended workplace limit (ACGIH TLV-TWA) is 25 ppm (170 mg/m3), and the air level considered immediately dangerous to life or health (IDLH) is 150 ppm.
Clinical presentation. Toxicity may be a result of inhalation, skin contact, or ingestion.
Inhalation or ingestion may cause nausea, euphoria, headache, ataxia, dizziness, agitation, confusion, and lethargy and, if intoxication is significant, respiratory arrest, seizures, and coma. Hypotension and cardiac dysrhythmias may occur. Inhalational exposure may result in cough, dyspnea, and bronchospasm. With severe overdose, renal and hepatic injury may be apparent 1–2 days after exposure.
Local effects of exposure to liquid or vapors include irritation of the eyes, nose, and throat. Prolonged skin contact can cause a defatting dermatitis and, in the case of trichloroethane and tetrachloroethylene, may result in scleroderma-like skin changes.
Ingestion can produce GI irritation associated with nausea, ...