Cumulative Risk Assessment for Pesticide Regulation: A Risk Characterization Challenge. M. A. Fox and L. Abbott, US Department of Agriculture, DC
Cumulative risk assessment debuted as a tool for regulating pesticides this year. US EPA’s precedent-setting effort included refinements in toxicological data, dose-response modeling, and multiple-pathway exposure assessment. Risk characterization should clearly present the complexity associated with the refinements. We present an example comparing an organo-phosphate "single chemical" with a preliminary cumulative assessment that highlights aspects of the dietary exposure model and cumulative approach that influence risk estimates. Explanation of the cumulative risk assessment presents a risk characterization challenge. We outline the challenges raised by the example and other criteria from risk characterization documents. We used the index chemical, methamidophos and its parent acephate in example assessments. By choosing methamidophos we focus on components of the models rather than the other pesticides. By comparing the methamidophos "single" and cumulative assessments, we find differences in approach with potential to result in inconsistent regulatory action. For example, higher dietary exposure estimates result simply from using the Food Commodity Intake Database, new recipes developed by US EPA and USDA to translate foods into agricultural commodities, rather than using the proprietary recipe databases used in "single chemical" assessments. Subtle changes in assumptions between the assessments lead to evaluation of different commodities by the two models, again yielding a higher exposure estimate for the cumulative assessment. The Presidential-Congressional Commission on Risk Assessment and Risk Management identified critical elements of risk characterization including information on the risk assessment. Our example illustrates the pitfalls of lack of transparency in models and approaches. We evaluate the final organo-phosphate cumulative report in an effort to improve risk characterization concomitant with the progress of cumulative analysis.
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