Trichloroethylene Health Risk Assessment: Synthesis and Characterization (External Review Draft)

Note: EPA has updated this document, but this version is provided as a courtesy to the public as a matter of public record.

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This assessment presents EPA's most current evaluation of the potential health risks from exposure to trichloroethylene (TCE). TCE exposure is associated with several adverse health effects, including neurotoxicity, immunotoxicity, developmental toxicity, liver toxicity, kidney toxicity, endocrine effects, and several forms of cancer. Mechanistic research indicates that TCE-induced carcinogenesis is complex, involving multiple carcinogenic metabolites acting through multiple modes of action. Under EPA's proposed (1996, 1999) cancer guidelines, TCE can be characterized as highly likely to produce cancer in humans.

For effects other than cancer, an oral reference dose (RfD) of 3x10^-4 mg/kg-d was based on critical effects in the liver, kidney, and developing fetus. An inhalation reference concentration (RfC) of 4x10^-2 mg/m³ was based on critical effects in the central nervous system, liver, and endocrine system. Several cancer slope factors were developed, with most between 2x10^-2 and 4x10^-1 per mg/kg-d. Several sources of uncertainty have been identified and quantified.

The mechanistic information suggests some risk factors that may make some populations more sensitive. There are suggestions that TCE could affect children and adults differently. In addition, several chemicals have the potential to alter TCE's metabolism and clearance and subsequent toxicity, conversely, TCE exposure can augment the toxicity of other chemicals. Widespread environmental exposure to some of TCE's metabolites makes it important to consider the cumulative effect of TCE along with other environmental contaminants.

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