An assessment of the carcinogenic potential of trichloroethylene in humans

Controversy surrounds the assessments of carcinogenic potential associated with human exposure to trichloroethylene (TCE). The American Conference of Governmental Industrial Hygienists states that TCE is "not suspected to be a human carcinogen." In contrast, the International Agency for Research on Cancer has classified TCE as a probable human carcinogen, based primarily o n the results of animal toxicity studies. Chronic high-dose TCE exposures c ause hepatic and pulmonary tumors in mice and renal tumors in rats. Human e pidemiology studies, however, do not support a causal association between e xposure to TCE at environmentally relevant levels and cancers of the lung, liver, or kidney. The apparent discrepancy between the animal data and the human data can be explained by (1) differences in TCE exposure levels. betw een laboratory animals and humans, (2) species-specific differences in TCE metabolism, and (3) other species-specific mechanisms involved in the devel opment of cancer in rodents. This paper critically assesses the experimenta l and epidemiological data relevant to the carcinogenic potential of TCE. F rom the analysis, we conclude that TCE exposure at concentrations likely to be encountered in most environmental media is not likely to cause liver, l ung, or kidney cancers in humans.