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DESIGNING STUDIES AND COLLECTING DATA USEFUL FOR CUMULATIVE RISK ASSESSMENT
Citation:
Simmons, J E., C. Gennings, M. Casey, M. J. Plewa, E. D. Wagner, W. H. Carter, A McDonald, Y M. Sey, AND L K. Teuschler. DESIGNING STUDIES AND COLLECTING DATA USEFUL FOR CUMULATIVE RISK ASSESSMENT. Presented at Society of Toxicology 42nd Annual Meeting, Salt Lake City, Utah, March 9-13, 2003.
Description:
DESIGNING STUDIES AND COLLECTING DATA USEFUL FOR CUMULATIVE RISK ASSESSMENT. J E Simmons1, C Gennings2, M Casey2, M J Plewa3, E D Wagner3, W H Carter, Jr.2, A McDonald1,Y M Sey1, L K Teuschler3 1NHEERL, ORD, U.S. EPA, RTP NC, USA; 2VCU, Richmond, VA, USA;3Univ. Illinois, Urbana, IL, USA; 4 NCEA, ORD, U.S. EPA, Cincinnati, OH, USA.
Humans are exposed to very complex environmental mixtures. In contrast to this reality, most laboratory investigations of mixtures, with the exception of mutagenicity assays, have focused on mixtures comprised of a few chemicals. Over the past decade, great advances have been made in component-based assessment of simple mixtures with development of appropriate, efficient and novel experimental designs, statistical methods and risk assessment techniques. These gains have increased greatly our ability to collect data useful for risk assessment. Additionally, these methods and approaches have been used to assess experimentally the validity of risk assessment assumptions. This is illustrated by experiments with the four trihalomethanes -chloroform, bromoform, bromodichloromethane and chlorodibromomethane ? disinfection byproducts (DBPs) formed during chemical disinfection of drinking water. In low-dose regions, dose-additive hepatotoxicity was observed in mice; in high-dose regions, the mixtures were additive or antagonistic, but not synergistic. Similar gains need to be made for complex mixtures. Component-based approaches that use information on the individual chemicals contained in the mixture are not by themselves sufficient for complex, environmental mixtures because significant portions of the mixture mass are unidentified. Joint theoretical and experimental work to extend these methods is needed and can only be successful by the combined collaborative efforts of toxicologists, statisticians and risk assessors. An effort is in progress for a more complex chemical mixture, including power and sample-size estimates, and methods to determine the portion of any observed toxicity attributable to the unidentified fraction of the mixture. In summary, experimental methods and techniques are described and illustrated for collection of data useful for risk assessment. (This abstract does not reflect EPA policy