Methods for Risk Assessment of Pesticides in the Diet. B. E. Mileson, S. S. Olin, J. A. Foran, E. Julien, L. Barraj, and B. Petersen, ILSI Risk Science Institute, 1126 16th St. N.W., Washington, DC 20036; and Novigen Sciences, Inc., 1730 Rhode Island Ave. N.W., Washington, DC 20036
The Food Quality Protection Act of 1996 requires the EPA to consider the cumulative effects of exposure to pesticides that act by a common mechanism of toxicity when assessing tolerances for pesticide chemical residues. While the goal of assessing cumulative effects is desirable, methods of risk assessment for multiple chemicals that act by a common mechanism of toxicity are poorly developed. In this analysis we evaluate current methods for risk assessment of exposure to multiple chemicals using anticholinesterase organophosphorus (OP) pesticides in the diet as an example. We used a probabilistic approach to assess exposure to OP pesticides, integrated with each of three standard methods to assess the risks due to exposure to multiple noncarcinogenic chemicals. These methods are: the hazard index (HI), toxicity equivalency factor (TEF), and margin of exposure (MOE). EPA Reference doses were the basis for the HI approach, and a consistent data set of no observed adverse effect levels (NOAELs) for inhibition of acetylcholinesterase in rat brain was the basis for the TEF and MOE approaches. Exposure to the U.S. population and three subpopulations of children was characterized using food consumption data from the USDA’s Continuing Surveys of Food Intake by Individuals (CSFII), and residues on fruits and vegetables reported by the Pesticide Data Program (PDP). The resulting distributions reflect the exposure and combined toxicity of the OP pesticides as estimated by the HI, the TEF, and the MOE methods. The distributions represent the range of population exposure on any given single day, and provide no information about chronic exposure. Additional data and analysis methods are needed to improve risk assessment of multiple chemicals including: chronic food consumption patterns, mechanistic data for chemicals, incorporation of a temporal component and mechanistic data in distributional analyses. The gaps in data and analysis methods suggest that caution must be used in interpreting the distributions of exposure and toxicity of OP pesticides in the diet.
This work was supported by the ILSI North America Food Toxicology and Safety Assessment Committee.
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