Setting Priorities Among Pesticides for Risk Assessment
The US Environmental Protection Agency (EPA) regulates all pesticides that are sold and distributed in the United States. After comprehensive scientific analyses and other assessments are performed and EPA grants a registration, registrants are required to comply with individual registration requirements imposed by a state to register the pesticide in the state. In California, all new pesticide active ingredients (AIs) are candidates for risk assessment, as are those already approved and undergoing re-evaluation because a potential health hazard has been identified. Under California statutory requirements, the Department of Pesticide Regulation (DPR) focuses its resources on the AIs that pose the greatest risks to human health. The AIs of greatest concern are identified through a priority-setting process, which was outlined by DPR in four documents provided to the committee: a description of the priority-setting process (DPR 2004), a master list of AIs under consideration (DPR 2011), and two examples of how candidates for risk assessment are selected from the master list (DPR 2007; Schreider 2014). The sections below summarize DPR’s priority-setting process and then the committee’s evaluation of the examples that it reviewed.
CALIFORNIA’S PRIORITY-SETTING PROCESS
The four documents provided by DPR on its priority-setting activities were informative in getting a general sense of the overall process, but some details had to be inferred, and inconsistencies were found among the documents. This section summarizes the committee’s understanding of DPR’s process.
DPR’s priorities for conducting risk assessments are focused on the AIs that pose the greatest risks to human health. The toxicology database required for federal registration under the Federal Insecticide, Fungicide, and Rodenticide Act is the primary source of toxicity information. Other reliable information is also considered in both priority-setting and risk assessment. If exposure data on AIs are not available at the priority-setting stage, estimates are based on the best available information. Box 2-1 provides a description of the candidate selection and priority-setting process. During the process, DPR has multiple opportunities to interact with staff of other California agencies, stakeholders, the public, and a scientific review panel.
Both new pesticides and state-registered pesticides are candidates for risk assessments. Reevaluation of registered pesticides is usually triggered by evidence of a potential human health hazard, such as from worker incidence reports or cases of environmental contamination, but may also be triggered by discovery that data on which DPR relied to register a product are incomplete, outdated, or based on other compelling information that suggests an adverse risk to people or the environment. DPR produces semiannual reports that describe the pesticides undergoing reevaluation and ones that were considered but were judged not to be in need of re-evaluation (DPR 2011).
BOX 2-1 DPR’s Candidate Selection and Priority-Setting Process for Pesticides
- High, Medium, Low Grouping: AIs are placed into groups of high, medium, or low priority for risk assessment by AEAP. PREC reviews the groupings.
- Candidate Pool: RAPWG selects and ranks a group of 10 candidates for risk-assessment initiation.
- Selection Process:
- 3.1. Recommended candidates: On the basis of staffing and other resources, DPR determines how many risk assessments can be initiated in the coming year.
- 3.2. Prioritization of candidate pool: Senior DPR scientists and branch chiefs make recommendations to upper management on the specific AIs that should enter the risk-assessment process.
- 3.3. Public consultation and scientific review: The recommendations are posted on DPR’s website, made available to interested parties, and reviewed by the PREC and SRP.
- Initiation of Risk Assessment:
- 4.1. After evaluating comments, DPR decides which AIs will enter the risk-assessment process.
- 4.2. Risk assessments are initiated through a formal notification process.
Source: Prepared by the committee on the basis of the processes outlined by DPR (2004, 2011) and Schreider (2014).
AIs are grouped into high-, medium-, and low-priority categories by an Adverse Effects Advisory Panel1 (AEAP) according to the criteria described in Box 2-2. All criteria are weighted equally, and a qualitative process is used to categorize AIs. AEAP meets periodically to update the groupings. Updates may include the addition of new AIs, the removal of AIs when registrations are canceled or when a risk assessment has been completed, and changes in categorizations
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1AEAP is composed of senior scientists in three DPR branches (Medical Toxicology, Worker Health and Safety, and Environmental Monitoring), the California Environmental Protection Agency Office of Environmental Health Hazard Assessment, and EPA.
BOX 2-2 Summary of Criteria Used by DPR to Set Priorities
The criteria used to set priorities among AIs for risk assessment and to identify the ones that could pose the greatest health risks can be divided into three categories of risk drivers: physical and chemical properties, toxicity, and exposure. Other factors that may affect priorities include eradication programs for new pests and regulatory actions by other state or federal agencies. DPR (2004) provides a more comprehensive description.
- Physical and chemical properties—such as vapor pressure, half-life, and solubility—are used to understand how and to what degree an AI might be released into the environment and be available for human exposure. Potential for bioaccumulation or bioconcentration is also considered.
- Toxicity considerations include the magnitude or severity of effects, the number of reported effects, the number of species affected, potency, dose–response information, and mechanism of action.
- Exposure considerations include types of potential exposure, use patterns, type of formulation, methods of application, and projected changes in use. Case reports from the Pesticide Illness Surveillance Program are also used as indicators of exposure potential.
Source: DPR (2004).
when new data on AIs become available. AEAP’s conclusions are reviewed by DPR’s Pesticide Registration and Evaluation Committee2 (PREC). A subset of 10 high-priority candidates for risk assessment are selected from the master list and ranked by the Risk Assessment Prioritization Work Group3 (RAPWG) annually. Focusing risk-assessment efforts on the top 10 candidates helps to minimize the possibility of investing assessment and management efforts on lower-risk compounds. Criteria described in Box 2-2 and scientific expertise in and detailed knowledge of pesticides are used to select 10 AIs (drawn primarily from the high-priority category). After the recommendations are approved by DPR management, a 45-day comment period is initiated and an announcement posted to DPR’s website. The announcement is also sent to interested parties, including a Scientific Review Panel (SRP),4 and is reviewed at a meeting of the PREC. After evaluating comments, DPR determines which AIs will enter the risk-assessment process. Risk assessments are initiated through a formal notification process.
The 2011 master list of candidates for risk assessment contains 323 AIs, of which 82 are categorized as of high priority, 143 moderate priority, and 98 low priority (DPR 2011). The criteria in Box 2-2 include a reasonable set of risk drivers for setting priorities, but the documentation
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2PREC includes representatives of California’s Departments of Public Health, Food and Agriculture, Industrial Relations, Resources Recycling and Recovery, and Fish and Game; the Structural Pest Control Board; the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment, State Water Resources Control Board, Air Resources Board, and Toxic Substances Control Department; the University of California; EPA, Region 9; the US Department of Agriculture; and the California Agricultural Commissioners and Sealers Association.
3RAPWG is composed of two DPR senior scientists in the Medical Toxicology Branch, two senior scientists in the Worker Health and Safety Branch, a senior scientist in the Environmental Monitoring Branch, and one representative each of the Office of Environmental Health Hazard Assessment and the Air Resources Board.
4A review panel of the Toxic Air Contaminants program, consisting of scientists in the University of California system.
supporting inclusion in the master list presents minimal information on studies that indicate possible adverse health effects. No details about the studies are provided, such as the specific health end point of concern, concentrations, test species, or route of exposure. The AIs are listed in alphabetic order in each category, so the master list reflects only a broad screening assessment of the AIs. The committee supports the broad categories used in DPR’s screening process but found that better documentation of the information used for making the categorizations is needed.
Examples of how 10 high-priority AIs were selected for risk assessment in 2007 and 2014 were reviewed. Both documents provide summaries of the meetings and activities of the RAPWG and the PREC that led to the selections. The process is somewhat subjective, relying on the expertise of the RAPWG members to identify the AIs of greatest concern, which are later reviewed by the PREC. The 2007 document provided the more substantive description of how the risk-assessment priority list was generated, describing the types of data considered by the RAPWG and the rationale for selection. The 2014 document provided only a brief description of pesticide uses and potential health effects and no clear basis of selection. Neither document provided a clear demonstration of how rankings were based on the evaluation criteria or an apparent way to reproduce DPR’s top-10 rankings. Furthermore, no information about why the remaining 70 or so high-priority AIs were not considered and selected is provided. Thus, there was no real ranking of AIs that would allow selection of the AIs that posed the highest risk.
DPR has a priority-setting process that focuses on identifying the AIs that potentially pose the greatest human health risks. The screening process used to categorize AIs into high-, medium-, and low-priority groups is practical given the large number of AIs that DPR must consider. The criteria used to select the top 10 AIs for risk assessment are reasonable and help to minimize the possibility that humans will incur excess risk during the time required to complete the assessment and make risk-management decisions. Strengths of the process include public consultation on the priority list and the involvement of scientific review and stakeholder groups (the AEAP, the RAPWG, the PREC, and the SRP) in the selection process. Periodic re-evaluation of the high-, medium-, and low-priority lists and the annual selection of the top 10 chemicals are also commendable.
Although the committee generally supports DPR’s priority-setting process, it identified several improvements that would help to make the process more transparent and defensible. First, better documentation of the evidence used to place AIs into high-, medium-, and low-priority categories is needed. Second, a more structured and objective ranking process would help to ensure that DPR is focusing on the most important AIs. The current processes used to select the top 10 AIs are fairly subjective and depend on the expertise and knowledge of the RAPWG members. Although documents describing the selection of the top candidates are available, the discussions are qualitative and do not explain how consideration of the criteria led to the ultimate ranking of the 10 candidates. A more formal approach to priority-setting would make the rankings more defensible, ensure that a consistent ranking approach is applied, help outside parties to understand how priorities are established, and provide a baseline description of the methods in case DPR decides to make modifications in the future.
Recommendations:
• DPR should update its 2004 documentation of its priority-setting process to provide more details so that the public can understand the process better. Flow diagrams would be helpful in documenting the steps in the process, identifying the staff and peer-review groups involved in each step, and indicating the opportunities for public input.
• DPR should provide more explicit documentation and support for how AIs are categorized into groups of high, medium, and low priority.
• DPR should develop a more objective and structured approach for ranking high-priority AIs on the basis of the criteria presented in Box 2-2 so that others could reasonably reproduce the rankings. One option to consider is the development of a scoring system to weight the different factors. Such a scheme could provide greater transparency in illustrating how the 10 high-priority candidates for risk assessments were selected. If such a scheme were developed, it would be important to have it peer-reviewed before implementation.
• DPR should continue to use California-specific data, such as information from the Pesticide Use Reporting program and the Pesticide Illness Surveillance Program, and perhaps collect additional data to help in setting priorities. (See Chapter 4 for recommendations on improving the collection of California-specific data.)
• For each document that sets risk-assessment priorities, DPR should disclose the names and affiliations of the members of the review group (the AEAP, the PREC, the RAPWG, and the SRP) involved in priority-setting to help to increase transparency in the review process.
DPR (Department of Pesticide Regulation). 2004. Process for Human Health Risk Assessment Prioritization and Initiation. Department of Pesticide Regulation, California Environmental Protection Agency. July 1, 2004 [online]. Available: http://www.cdpr.ca.gov/docs/risk/raprocess.pdf [accessed February 12, 2014].
DPR (Department of Pesticide Regulation). 2007. Final Notice on Active Ingredients Prioritized for Risk Assessment Initiation. Department of Pesticide Regulation, California Environmental Protection Agency. September 17, 2007 [online]. Available: http://www.cdpr.ca.gov/docs/risk/final_notice.pdf [accessed February 12, 2014].
DPR (Department of Pesticide Regulation). 2011. Prioritization and Status of Active Ingredients for Risk Characterization: Report # 52. Department of Pesticide Regulation, California Environmental Protection Agency. July 15, 2011 [online]. Available: http://www.cdpr.ca.gov/docs/dept/prec/2011/prec_letter_report_52_20110916.pdf [accessed February 12, 2014].
Schreider, J. 2014. Final Recommendations Regarding the List of Active Ingredients Prioritized for Risk Assessment Initiation. Memorandum to Marylou Verder-Carlos, Assistant Director, from Jay Schreider, Senior Toxicologist, Medical Toxicology Branch. Department of Pesticide Regulation, California Environmental Protection Agency. February 18, 2014 [online]. Available: http://www.cdpr.ca.gov/docs/risk/priot_wkgrp.pdf [accessed April 24, 2014].
