The physical and chemical characteristics of trichlorethylene are discussed together with its uses in industry and medical practice. Chemical and physical methods of the estimation of trichlorethylene in air have been described, including the use of gas detector tubes, which today is the method most commonly employed.
The metabolism of trichlorethylene was systematically investigated by Butler (1948), who in animals established the identity of the main metabolites appearing in the urine, Powell (1945a, b) having also done this in human subjects. The excretion of these metabolites has since been repeatedly investigated, but the intermediate breakdown products within the body as well as the organ mainly responsible still remain uncertain.
The acute toxicity of trichlorethylene, manifested preponderantly by central nervous system effects, came to be recognized during the second decade of this century, not long after its introduction as a substitute for benzol as a degreasant in Germany during the First World War. The recognition of a possible chronic toxic effect, characterized by a mild psycho-organic syndrome, came much later and is still not universally accepted. Damage to the trigeminal nerve after closed-circuit trichlorethylene anaesthesia was observed soon after its introduction as a general anaesthetic 30 to 40 years ago, and it was shown to be due to breakdown to dichloracetylene in carbon dioxide absorbers. The pure substance seems otherwise not to have a specific effect on this nerve. The balance of opinion, based on human observations and on animal experiments, is against a severe toxic effect on the liver, although individual cases of liver damage in industrial workers have been reported. The sudden fatal collapse of young workers during mild exercise has on rare occasions been described, there being in most cases an element of heavy exposure. Investigations on man and animals indicate that pure trichlorethylene has no severe effect on other systems of the body.
Maximum permissible levels for trichlorethylene in air were reduced from 400 p.p.m. in 1947 to 200 p.p.m., and in 1961 there was a further reduction to 100 p.p.m., which, except in the Soviet Union, is at present accepted in most parts of the world.
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