An Assessment of the Carcinogenic Potential of Trichloroethylene Exposures in Humans. A. L. Lavin, C. F. Jacobson, and J. M. DeSesso, Mitretek Systems
Controversy regarding the potential of trichloroethylene (TCE) to cause cancer in humans has led to an ongoing evaluation by the United States Environmental Protection Agency. Laboratory animal studies have shown that chronic, high-dose exposures to TCE are associated with liver and lung tumors in mice, and with kidney tumors in rats. Most human epidemiological studies, however, have failed to demonstrate a link between human TCE exposures and these cancer endpoints. Recent studies by a group in Germany have suggested an association between TCE and kidney cancer, but these studies are flawed and await independent confirmation. A review of the mechanistic data related to TCE metabolism suggests that the discrepancy between the results of animal studies and human findings can be explained by (1) large differences in TCE exposure levels between experimental animals and humans, and (2) species-specific differences in TCE metabolism. Based on a critical assessment of these data, it can be concluded that humans exposed to TCE at environmentally relevant concentrations are not at increased risk for developing cancers of the lung or liver. In addition, while the epidemiological results to date for kidney cancer must be considered incomplete and are not clear-cut, the animal data suggest that kidney tumors are not likely at environmentally relevant exposures. Our conclusions lead us to suggest that the regulatory levels currently used for environmental cleanup of TCE (5 microg/L) could be substantially raised with no increased risk to human health.
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