Aggregate exposures under the Food Quality Protection Act: An approach using chlorpyrifos

The Food Quality Protection Act of 1996 (Public Law 104-170, August 3, 1996), which amended the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug, and Cosmetic Act (FFDCA), requires that the EPA evaluate pesticide safety in light of potential aggregate exposures from both nondietary and dietary routes. As with any new legislation, there has been considerable discussion and challenges presented within the regulatory and scientific communities regarding the effective implementation of this act as it relates to the determination of aggregate exposures. This paper describes a novel methodology incorporating personal exposure factors, route-specific exposure measurements, and usage information to characterize potential aggregate exposures to a widely used pesticide, chlorpyrifos. A calendar model framework has been developed to describe potential multipathway exposures to individuals. The model assimilates information regarding the typical use patterns of chlorpyrifos-containing pesticides in concert with quantitative exposure and dose measurements to estimate the probability and magnitude of exposures to members of the U.S. population. Studies measuring 3,5,6-trichloropyridinol, the primary metabolite of chlorpyrifos, in the urine of individuals within the United States show that aggregate exposures derived from this approach are consistent with actual population-based exposures to chlorpyrifos. According to this assessment, potential health risks attributed to exposure to chlorpyrifos are low when compared to relevant toxicological end points.