Risk assessment under FQPA: case study with chlorpyrifos

Key science policies have had significant impact on the evolving implementation of the Food Quality and Protection Act (FQPA) (PL 104-170, 1996) by the US Environmental Protection Agency (EPA). The impact offour of these policies will be examined using the risk assessment for chlorpyrifos as a case study. These policies are selection of a regulatory endpoint, use of animal data without consideration of human data for setting the reference dose, a 10 FQPA safety factor and use of the 99.9 percentile of modeled consumer exposure in the acute dietary assessment. Each of these policy decisions had individual impact that was then compounded as cumulative impact on the revised risk assessment for chlorpyrifos conducted by the US EPA in 2000 [Federal Register Notice 65(159) (2000) 49982]. But embedded within each science policy, there are assumptions which may be too conservative and which together have resulted in a very large multiplicative reduction in the allowable exposure limits for chlorpyrifos in the US. These new exposure limits are quite different from other regulatory standards around the world. There is third party opposition to many of these policies and many believe the understanding of the relationship between exposure and what is known about human and animal responses to chlorpyrifos has been clouded. These changes in policy insert a new level of conservatism into the scientific statement of risk and create confusion that threatens to weaken the credibility of the regulatory process.