Evolving Regulatory Policies
EPA has proposed a number of recent modifications in existing assessment approaches and new policies regarding assumptions or methods. Some policy actions have occurred in response to new scientific information whereas in other cases EPA has acted to better protect itself from legal actions or threats from pesticide opponents or to cater to the changing political climate. Since the draft chlorpyrifos human health assessment will be the first substantive assessment completed by EPA as part of Registration Review program, there are some key issues and areas to watch as EPA works toward a final chlorpyrifos human health assessment.
Consumer Exposure Assessment
For a number of years EPA has relied upon both field residue studies generated by registrants and residue monitoring data collected by USDA to prepare highly refined assessments of human dietary exposure to residues that may occur in food or water. EPA is in the process of revising its approach to estimating drinking water exposures. Rather than utilize real-world monitoring data, which shows no detections of chlorpyrifos residues in finished water delivered to customers, the Agency is considering using worst-case computer modeling estimates as a more conservative estimate of potential drinking water exposures.
Bystander Exposures to Airborne Pesticide Residues
In the past, EPA assessments included consideration of inhalation exposures to consumers following residential uses and to farmworkers and pest control operators during handling and application of pesticides. EPA now intends to consider also bystander exposures due to inhalation of airborne residues resulting from spray drift or evaporation from treated crops. The Agency’s proposed methodology for estimating bystander exposure to airborne residues was reviewed by the EPA Scientific Advisory Panel during December of 2009, and application of the finalized policy is awaited.
Farmworker Exposure Assessment
In association with a new “Environmental Justice” policy initiative, EPA during December of 2009 announced several proposed changes in how farmworker exposure assessments would be conducted. These changes included aggregating workplace and consumer exposures and adopting more conservative assumptions to account for teen workers and children of farmworkers who may be present in and around agricultural fields. Announcement of these proposed changes prompted a significant amount of public feedback, including concerns with implications of labor codes, and EPA has yet to announce the final approaches it will employ.
Expanded Application of the FQPA Uncertainty Factor
One particularly controversial aspect of EPA’s proposed farmworker exposure assessment policy change concerned expansion of provisions of the Food Quality Protection Act to farmworker assessments. The FQPA uncertainty factor was mandated for consideration by EPA when reviewing food residue tolerances to account for potential differences in sensitivity of infants and adults for exposures to certain pesticides. EPA announced during December of 2009 its intention of using the FQPA factor to drive more conservative assessments for children and pregnant women present in and around agricultural fields, but few details have emerged on how EPA would determine where this factor would be needed or how it would be applied.
Assessment of Epidemiology Research Studies
Epidemiology studies are surveys of human population and health records which attempt to correlate observed health outcomes with potential causative factors. Through a series of statistical analyses these studies attempt to determine any differences in health effects that may be correlated to pesticide exposures. There are many confounding factors involved in interpreting such studies including simultaneous exposure to multiple chemicals and situations and difficulties with documenting exposures, and EPA’s proposed approach was reviewed by the Scientific Advisory Panel during February of 2010. The Panel advised EPA to develop significant revisions in their approach, and the crop protection industry has recently petitioned EPA to take action regarding recommended improvements.
