California's Department of Pesticide Regulation (DPR), a department of the California Environmental Protection Agency (CalEPA), is responsible for ensuring the protection of workers, public health, and the environment from effects associated with pesticide use in the state. Emphasis on pesticide risk assessment in California stems from the 1984 Birth Defect Prevention Act. The law prohibited DPR from registering new pesticides without a full complement of health studies and mandated that registrants of older pesticides (those registered before 1984) update their health-effects data to current standards. The law required DPR to identify adverse effects and to determine their importance in making registration decisions. Thus, risk assessment plays a critical role in DPR's evaluation of potential health hazards related to exposure to pesticides and is the basis of new regulations and other use restrictions.

The US Environmental Protection Agency (EPA) conducts comprehensive reviews of active ingredients in new pesticides before federal registration, and DPR allows federally approved active ingredients to be registered in California on a conditional or interim basis without a risk assessment provided that all data required by EPA have been submitted to the state. California may also require registrants to submit additional data to support registration. Priorities are then set for risk assessment of newly registered active ingredients and state-registered pesticides undergoing re-evaluation by DPR. DPR performs its own risk assessments so that California-specific concerns are addressed, including state-specific cropping patterns, climatic and cultural conditions, and worker practices. In addition, because residential areas are much closer to agricultural boundaries in California than in many other states, more emphasis is placed on risks posed by off-site movement of pesticides (Sokolow 2003; DPR 2011).

After registration, DPR has a process for continuous evaluation and re-evaluation to detect potential problems. California has one of the most extensive residue-monitoring programs in the nation; data are collected on residues from preharvest crops, postharvest of raw produce, postharvest commodities, and fresh produce in the marketplace. Exposure monitoring studies are conducted to collect data on pesticide exposure patterns and to assess the effectiveness of existing controls. DPR also has projects for monitoring air quality, groundwater, and surface water under field conditions specific to California. Potential health concerns are identified through investigations into pesticide illnesses and incidents and from mandatory registrant reports on adverse effects of registered products (DPR 2011). Data from those and other sources may trigger the need for a re-evaluation of a registered pesticide. Priorities for risk assessment of registered pesticides and new pesticides are set according to which ones pose the greatest risk to human health.

DPR's risk assessment consists of five steps: hazard identification, dose–response assessment, exposure assessment, risk characterization, and risk appraisal. The department's Medical Toxicology Branch conducts the hazard identification, and the Work Health and Safety Branch conducts the exposure assessment. DPR uses those evaluations to prepare a risk-characterization document for each pesticide. The documents undergo peer review that involves scientists in DPR, CalEPA's Office of Environmental Health Hazard Assessment, and EPA and other relevant experts. Some pesticides are also regulated under the Toxic Air Contaminant Act if their active ingredients could pose a health threat as air pollutants. The Toxic Air Contaminant Program focuses on the evaluation and control of pesticides in ambient community air (DPR 2011).

THE COMMITTEE'S TASK AND APPROACH

DPR arranged for an independent peer review of its human health risk-assessment practices to ensure that they are scientifically and technically credible and to identify ways to improve efficiency and productivity in the process so that risk assessments could be completed more quickly. The National Research Council has published guidance on various aspects of human health risk assessments that are highly relevant to this endeavor (NRC 2009, 2011, 2014). Thus, DPR asked the National Research Council to convene a committee of experts to review its risk-assessment practices. The charge to the committee is presented in Box 1-1.

BOX 1-1

Statement of Task. An ad hoc committee will conduct an independent scientific and technical evaluation of the CalEPA's risk-assessment process for pesticides. The committee will examine documents provided by DPR on the processes it uses for hazard identification, (more...)

To address its task, the committee held three meetings. Public data-gathering sessions were held at the first two meetings; the committee met with representatives of DPR, EPA's Office of Pesticide Programs, a worker-advocacy group, and pesticide registrants. Open-microphone sessions were held in both meetings to hear the views of other interested stakeholders. As specified in its charge, the committee focused on determining whether DPR's risk assessments are being performed in a scientifically credible manner. The committee reviewed guidance documents provided by DPR on how it sets priorities for risk assessments and how it conducts its exposure assessments and risk assessments. It also reviewed three pesticide-specific risk assessments for the purpose of understanding the procedures and practices of DPR, but it did not evaluate the adequacy of these individual assessments. A list of the documents that the committee considered is presented in Appendix B.