Introduction to Human Health Risk Assessment
EPA has chosen to present two human health risk assessments of chlorfenapyr, one for cotton, and one for citrus. The reasons for doing so follow: The human health risk assessment for cotton was completed in 1997. It was based to some extent on the default assumptions (100% crop treated, tolerance level residues), and residues in drinking water were estimated using the methodology standard at that time. This risk assessment concluded that estimates of risk were not at levels of concern. However, because of continuing discussions about the ecological risk, the Agency has not come to a decision to register cotton.
A human health risk assessment for citrus (which also included cotton) was completed in 1998. It was a more highly refined risk assessment (anticipated residues, 100% crop treated), and residues in drinking water were estimated using a methodology different from the one used in the cotton risk assessment. In this document, the estimates of risk, which included both cotton and citrus, were not at levels of concern. However, because the risk assessment for citrus was more refined, and the drinking water residues were different, the estimates of risk are lower than those presented in the cotton risk assessment. In addition, the citrus human health risk assessment presents the Agencys current thinking on this compound. For these reasons, EPA decided to present both risk assessments. Applications for registration are pending for chlorfenapyr use on other crops. However, no other human health risk assessments for chlorfenapyr have been completed at this time.