| Trichloroethylene Cancer Epidemiology: A Consideration of Select Issues Cheryl Siegel Scott and Weihsueh A. Chiu National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA Abstract
A large body of epidemiologic evidence exists for exploring causal associations between cancer and trichloroethylene (TCE) exposure. The U.S. Environmental Protection Agency 2001 draft TCE health risk assessment concluded that epidemiologic studies, on the whole, support associations between TCE exposure and excess risk of kidney cancer, liver cancer, and lymphomas, and, to a lesser extent, cervical cancer and prostate cancer. As part of a mini-monograph on key issues in the health risk assessment of TCE, this article reviews recently published scientific literature examining cancer and TCE exposure and identifies four issues that are key to interpreting the larger body of epidemiologic evidence: a) relative sensitivity of cancer incidence and mortality data ; b) different classifications of lymphomas, including non-Hodgkin lymphoma ; c) differences in data and methods for assigning TCE exposure status ; and d) different methods employed for causal inferences, including statistical or meta-analysis approaches. The recent epidemiologic studies substantially expand the epidemiologic database, with seven new studies available on kidney cancer and somewhat fewer studies available that examine possible associations at other sites. Overall, recently published studies appear to provide further support for the kidney, liver, and lymphatic systems as targets of TCE toxicity, suggesting, as do previous studies, modestly elevated (typically 1.5–2.0) site-specific relative risks, given exposure conditions in these studies. However, a number of challenging issues need to be considered before drawing causal conclusions about TCE exposure and cancer from these data. Key words: cancer, drinking water exposures, epidemiology, occupational exposures, risk assessment, trichloroethylene. Environ Health Perspect 114: 1471–1478 (2006) . doi:10.1289/ehp.8949 available via http://dx.doi.org/ [Online 9 May 2006]
This article is part of the mini-monograph "Trichloroethylene Health Risks: Key Scientific Issues." Address correspondence to C.S. Scott, U.S. EPA, 1200 Pennsylvania Ave. NW, Mail Code 8623D, Washington, DC 20460 USA. Telephone: (202) 564-3286. Fax: (202) 565-0078. E-mail: Scott.Cheryl@epa.gov We thank the TCE team, including J. Blancato, J. Caldwell, C. Chen, M. Evans, J. Jinot, N. Keshava, J. Lipscomb, M. Okino, F. Power, and J. Schaum for their insightfulness and constructive input. Special thanks go to P. Preuss, J. Vandenberg, D. Bussard, and P. White for supporting this work. The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. The authors declare they have no competing financial interests. Received 22 December 2005 ; accepted 4 May 2006.
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