Trichloroethylene carcinogenic potency

Current U.S. regulatory policy regarding the carcinogenic potential of trichloroethylene (TCE) in humans is conflicting. Weight-of-evidence considerations show either no or inconsistent associations between chronic TCE exposure and excess human cancer risk. Occupational exposure limits are so great (538,000 mug/m(3)) that daily absorbed doses are greater than the rodent no observed adverse effect level (NOAEL). Using the regulatory strength-of-evidence approach, recommended ambient air concentration limits (1.1 mug/m(3)) are derived using the default linearized multistage model. The latter assumes a radiomimetic mode of action, a highly questionable assumption in light of published TCE mechanism of action data. Given the current state of U.S. regulatory policy on this material, credible analyses of the data are needed from neutral nongovernmental organizations.