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Wendy Heiger-Bernays, PhD
Department of Environmental Health, BU School of Public Health
Boston University Superfund Research Program

Winter, 2014

Derivation of TCE Toxicity Values and Implications for Risk Management

Trichloroethylene (TCE) is a common contaminant in groundwater in the United States and countries where this degreasing agent was and is used.  In addition to exposures that occur through contact with contaminated water, vapor intrusion results in inhalation of TCE in residential and commercial buildings. In September, 2011, the U.S. Environmental Protection Agency (EPA) released its Final Assessment for TCE on the Integrated Risk Information System (IRIS) . EPA provides an oral cancer slope factor and inhalation unit risk value, but the non-cancer effects are of particular interest. This interest is based on the identification of developmental effects at very low doses. As a result, the non-cancer risk assessment may be the determinant in the management of TCE-contaminated environments. Two EPA regions and the Agency for Toxic Substances and Disease Registry have used the chronic RfC to assess shorter-term exposures. The Massachusetts Department of Environmental Protection is using the cardiac malformation endpoint in its assessment of Imminent Hazard evaluations for TCE in the indoor environment.

Multiple effects of TCE are observed in rodent studies, with some evidence from human TCE exposures in community studies. The basis for EPA’s Reference Concentration (RfC) is cardiac malformations in a fetal rat model (Johnson et al., 2003) and immune system developmental effects in mouse models. The RfC is derived from the relevant studies using benchmark dose modeling using PBPK model-predicted internal doses, and application of a single uncertainty factor to account for the use of the modeling from animal to humans. The resultant value is 0.002 mg/m3 (0.0004 ppm).

This presentation will discuss the derivation and critique of the EPA-derived RfC, use of the RfC for short-term exposures and a discussion of the implications of its use on site management and risk communication.

USEPA, Integrated Risk Information System. Trichloroethylene, 2011.

Johnson et al., (2003). Threshold of trichloroethylene contamination in maternal drinking waters affecting fetal heart development in the rat. Environ Health Perspect 111:289-292


Seminar will be held May 7, 2014 in Frankfort Kentucky at the KYDEP, noon.