Fielder, RJ; Lowing, RK; Shillaker, RO
Toxicity to animals. Trichloroethylene has low acute toxicity to animals. Exposure of rats or mice to concentrations of the order of 10 000 ppm for four hours resulted in the death of 50% of the animals. The corresponding figure for a single oral dose was about 5 g/kg. In inhalation studies full anaesthesia was produced at concentrations of about 5000 ppm and above. Inhalation studies; mild liver damage; 400-500 ppm; 3000 ppm; central nervous system; 1000 ppm. The mutagenicity of trichloroethylene has been investigated in a number of short-term tests. Positive results were obtained when trichloroethylene was tested using certain microorganisms (yeasts), indicating that the compound can produce point mutations. Positive results were also obtained when trichloroethylene was investigated using the micronucleus test, suggesting that the compound can produce chromosome abnormalities. A number of long-term animal studies have been carried out to investigate the carcinogenicity of tricholoroethylene, using both the inhalation and the oral route. No evidence of any significant carcinogenic effect was noted in the studies in rat and hamster. However the standard of this work was inadequate to base any conclusions on the negative result obtained. Hepatocellular carcinoma. No evidence of any teratogenic effects were noted when pregnant rats or mice were exposed to trichloroethylene by inhalation. Some fetotoxic effects, indicative of delayed development, were noted in rats, but only at a relatively high concentration (1800 ppm). Toxicity to man. The principal effect after acute exposure to trichlorethylene is depression of the CNS, exposure to high concentrations (about 5000 ppm and above) producing narcosis and, in extreme cases, coma and death. Recovery from narcosis is usually uneventful, with no serius sequelae, and the compound has been used as an anaesthetic for short operations. Exposure of volunteers to 500-1000 ppm trichloroethylene under controlled conditions, resulted in some symptoms of CNS distrubance (dizziness, lightheadedness, lethargy) and some impairment in performance of a number of behavioural tests designed to measure visual-motor response. No signs of toxicity, nor any impairment in performance, were in general noted in subjects exposed to 300 ppm or less trichloroethylene. The most prevalent toxic effect noted in surveys of workers occupationally exposed to trichloroethylene involves the CNS. Symptoms of CNS distrubance (fatigue, headaches, dizziness, inability to concentrate) have frequently been noted in workers exposed to average levels of trichloroethylene estimated to be about 100-200 ppm. More severe 'pre-narcotic' symptoms (feelings of inebriation, visual disturbances) occurred in workers exposed to mean trichloroethylene levels of 200-300 pmm. Prolonged exposur to a level which produces toxic symptoms may also result in hearing defects. Mild liver dysfunction. There is no evidence to suggest that exposure to trichloroethylene is associated with an increased incidence of cancer in man but this aspect has not been adequately investigated. There is no evidence to indicate that exposure to trichloroethylene has produced any adverse effects in the offspring of women workers exposed to the material; increased incidence of menstrual disorders in female workers, and of decreased libido in male workers. (Shortened.)