Carcinogenicity Risk Assessment of 1,3-Butadiene Based on Occupational Studies. J. Liccione and E. Anderson, Sciences International, Inc., King Street Station, 1800 Diagonal Road, Suite 500, Alexandria, VA 22314
Recently, the Environmental Protection Agency evaluated the available data pertaining to the potential carcinogenicity of 1,3-butadiene ("Health Risk Assessment of 1,3-Butadiene," EPA 1998). The EPA draft risk assessment derives a cancer risk estimate for 1,3-butadiene based on one epidemiology study. In this regard, EPA’s cancer unit risk estimate for 1,3-butadiene was based on estimates of the excess leukemia mortality in styrene-butadiene rubber workers as reported in the retrospective follow-up study of men employed in the styrene-butadiene rubber industry in the United States and Canada (Delzell et al. 1995). While the cancer risk assessment is a substantial improvement over the Agency’s earlier risk assessment (EPA 1985), there are uncertainties associated with the with the Delzell et al. study, as well as the epidemiological database as a whole. Uncertainties of concern include inadequate and/or limited exposure estimates, inconsistent in the findings of mortality from leukemia between cohort and case-control studies, inconsistent definition of lymphatic and hematopoietic cancers, and potential confounding exposures to other chemicals. Moreover, the issue of whether or not epidemiological causality criteria are fulfilled by the epidemiologic evidence remains controversial. The uncertainties of the epidemiological database on 1,3-butadiene, and its impact on the cancer risk assessment of this chemical, will be addressed in this session.
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