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AN ALTERNATIVE METHOD FOR ESTABLISHING TEFS FOR DIXON-LIKE COMPOUNDS. PART 2. DEVELOPMENT OF AN APPROACH TO QUANTITATIVELY WEIGHT THE UNDERLYING POTENCY DATA
Citation:
HAWS, L. C., M. J. DEVITO, L. S. BIRNBAUM, N. J. WALKER, P. K. SCOTT, K. M. UNICE, M. A. HARRIS, W. H. FARLAND, B. L. FINLEY, AND D. STASKAL. AN ALTERNATIVE METHOD FOR ESTABLISHING TEFS FOR DIXON-LIKE COMPOUNDS. PART 2. DEVELOPMENT OF AN APPROACH TO QUANTITATIVELY WEIGHT THE UNDERLYING POTENCY DATA. Presented at 26th International Symposium on Halogenated Persistent Organic Pollutants, Oslo, NORWAY, August 21 - 25, 2006.
Description:
The current approach for evaluating potential health risks associated with exposure to mixtures of polychlorinated dibenzo-p-dixoins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (PCBs) [hereafter referred to as "dioxin-like compounds"] is based on the toxic equivalency factor (TEF) methodology. In accordance with this methodology, each PCDD, PCDF, and PCB congener believed to exhibit dioxin-like activity has been assigned a TEF based on comparison to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The current TEFs represent consensus-based values recommended the World Health Organization (WHO). In assigning TEFs to each congener, the WHO expert panel employed scientific judgment and a qualitative weighting scheme whereby individual relative estimates of potency (REPs) from in vivo studies were given greater weight than in vitro studies and/or quantitative structure activity relationship (QSAR) data; chronic studies were given greater weight than subchronic studies, which were given greater weight than subacute studies, which were given more weight than acute studies; and Ah-mediated toxic responses were given more weight than biochemical responses (e.g., enzyme induction).