California Data to Inform Priority-Setting and Risk Assessment of Pesticides
As noted in Chapter 3, the committee judges that the California Department of Pesticide Regulation (DPR) may be able to rely more on the toxicologic assessments performed by the US Environmental Protection Agency (EPA) and therefore direct more resources toward obtaining California-specific data on pesticide uses, exposure, and illnesses. Focus on the latter will allow DPR to factor California-specific data into its risk assessments—such as information on cropping patterns, agricultural practices, agricultural–urban boundaries, characteristics of agricultural workers, and population demographics—to a greater extent. The purpose of this chapter is to identify where further data-gathering by DPR might help to improve its priority-setting and risk-assessment processes.
PESTICIDE-EXPOSURE INFORMATION
In many circumstances, EPA and DPR use generic exposure scenarios and national estimates in their exposure assessments of pesticides. For example, in estimating exposure to pesticides, they use sources of data on pesticide residues, such as the US Department of Agriculture (USDA) Pesticide Data Program; on dietary intakes, such as the USDA Continuing Survey of Food Intake by Individuals and the National Health and Nutrition Examination Survey (NHANES); on specific handler exposure scenarios, such as the Pesticide Handler Exposure Database, the Agricultural Handlers Exposure Database, and the Outdoor Residential Exposure Task Force; and on other relevant issues such as Agricultural Reentry Task Force Transfer Coefficients. DPR supplements exposure assessments with California-specific information, which the committee judges to be the most valuable contribution to DPR’s risk-assessment process. California routinely collects data on agricultural and other pesticide uses, air concentrations of pesticides, and reports of human pesticide-related illnesses.
California Pesticide Use and Ambient-Air Concentrations
California was the first state to require reporting of agricultural pesticide use. The Pesticide Use Reporting (PUR) program is recognized as one of the most comprehensive in the nation. All agricultural pesticide use must be reported monthly to county agricultural commissioners, who report the data to DPR. The reporting requirements also include pesticide applications in public areas, rangeland, and pastures; postharvest pesticide treatments of agricultural commodities; and pesticide treatments in poultry and fish production and in some livestock applications. Data are typically compiled into square-mile areas (meridian–township–range sections), but initiatives have been undertaken to encourage the use of geospatial information systems to improve the spatial resolution of pesticide applications to smaller areas, such as field sites. Pesticide applications in home and garden use and in most industrial and institutional uses are excluded from the
reporting requirements (DPR 2013). Although it would be difficult to obtain accurate information on personal home use, it might be possible to collect some information by expanding PUR reporting requirements to cover all licensed pesticide appliers, including those who perform applications for nonagricultural purposes at homes, institutions, and industries. There appears to be no requirement to report the use of pesticide-treated seeds.
The California Air Resources Board (ARB) collects measurements of ambient pollutants from over 40 sites in the state. DPR and ARB monitor pesticides that have been deemed toxic air contaminants. Two types of monitoring data are collected: on ambient monitoring and on application-site monitoring. Ambient monitoring is performed in selected communities to measure pesticide concentrations over several weeks or months, and application-site monitoring is performed in the immediate vicinity of specific pesticide applications to measure concentrations over hours or days.
PUR and ARB data have been used by DPR and other researchers to evaluate the agricultural use of pesticides and ambient concentrations (e.g., Harnly et al. 2005; Li et al. 2005) and to evaluate the predictive capability of exposure models (e.g., Cryer 2005; van Wesenbeeck et al. 2011). Most recently, the California Environmental Health Tracking Program studied agricultural pesticide use near public schools (CEHTP 2014). PUR data have also been used by researchers to investigate the relationship between pesticide exposure and a variety of health outcomes, such as fetal death (Bell et al. 2001a,b), lowered birth weight (Gemmill et al. 2013), birth defects (Shaw et al. 2014; Yang et al. 2014), childhood autism (Roberts et al. 2007), Parkinson disease (Costello et al. 2009; Manthripragada et al. 2010), and childhood and adult cancers (Gunier et al. 2001; Clary and Ritz 2003; Marusek et al. 2006). Although epidemiologic studies do not establish causal relationships, they might be used to identify potential health outcomes of concern.
California Dietary Intake
The use of NHANES data and other national or generic sources of data on dietary consumption may not accurately reflect the dietary patterns of the state, in that they do not take into account demographics, seasonal availability of produce, or other factors specific to California. There are a number of dietary studies of California residents, which might provide confirmatory evidence of the adequacy of NHANES data for risk-assessment purposes. For example, the committee found a few California-specific surveys from the Centers for Disease Control and Prevention (CDC 2010, 2012) and the California Department of Public Health (CDPH 2010, 2011a,b) that provide broad characterizations of Californians’ consumption of fruits and vegetables.
Similar to the need to incorporate or use California-specific information on dietary consumption, DPR should seek ways to leverage its programs and expertise to generate state-specific information on drinking-water intake patterns to reflect source-water typography and meteorology, demographics, or spatiotemporal patterns relevant to an exposure assessment. To the extent possible, DPR should partner with other agencies and organizations to obtain state-specific estimates of drinking-water consumption and the concentrations of evaluated pesticides in drinking water to develop customized and site-specific exposure assessments for this pathway.
California Worker Scenarios
Because of the types of agriculture in California and its climatic conditions, general nationwide assumptions about seasonal use of pesticides, the number of growing seasons, and working conditions may not be appropriate for DPR’s assessments. The demographics of the agricultural workforce may also be substantially different from nationwide estimates. The committee heard from stakeholders representing agricultural workers that workers may work over 10 hours per day during the growing season, work with labor-intensive crops, may not have accessibility to showers, and may be adolescents (Katten 2014). Although susceptible populations, such
as pregnant women and children, are routinely considered in most risk assessments, less consideration has been given to risks to adolescent workers. Adolescents are prohibited from handling pesticides, but they could have exposures different from those estimated for worker bystanders. Thus, better characterization of the worker population and working conditions would help DPR in tailoring its risk assessments.
EPA has an initiative under way to revise its risk-assessment methods for workers, children of workers in agricultural fields, and pesticides that have no food uses (EPA 2009). Proposed changes include consideration of adolescent workers and of workers and their children who may accompany them to work. This presents an opportunity for DPR to collaborate with EPA on these important issues.
Other California Exposure Information
California began an environmental-contaminant biomonitoring program in 2006, and several pesticides are monitored. The program is a collaborative effort of the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment and Department of Toxic Substances Control. Several biomonitoring studies of pesticide exposure have been conducted in California. They have examined contemporary exposures of agricultural workers, other adults, and potentially susceptible subpopulations (such as pregnant women and children) primarily to organophosphates. Estimates have been based on samples of urine (e.g., Castorina et al. 2003; Bradman et al. 2005, 2007; Trunnelle et al. 2014a), breast milk (e.g., Weldon et al. 2011), blood (e.g., Huen et al. 2012), teeth (e.g., Gunier et al. 2013), and amniotic fluid (e.g., Bradman et al. 2003). A number of the studies are going on now and are being conducted in collaboration with the California Biomonitoring Program. In addition, a workgroup of EPA’s Pesticide Program Dialogue Committee (21st Century Toxicology/New Integrated Testing Strategies Workgroup) is developing a priority list of pesticides for biomarker research, working to identify how existing data relevant to diagnosing overexposure to pesticides can be made more accessible, and working to identify opportunities for additional information (EPA 2014).
California-specific data on environmental exposure to pesticides are also being collected. Some data are available on pesticide residues on foliar samples, soil, dust, surface or hand wipes, and other environmental materials (e.g., DPR 2009; Harnly et al. 2009; PANA 2010; Gunier et al. 2011; Trunelle et al. 2014b). The evaluations have been performed in homes, in schools, and in the field. It might be useful for DPR to review the scientific literature periodically for relevant information and new developments that could inform its exposure assessments.
Surveillance of Pesticide-Related Illness
Since 1971, California has been mandated through DPR to maintain the Pesticide Illness Surveillance Program (PISP), the oldest and largest program of its kind in the United States. Cases of human pesticide-related illness are required to be reported within 24 hours of examination. Cases are reported by five mechanisms: a clinician reports a suspected case to a local health officer, who files an illness report; a clinician calls the California Poison Control System; the worker-compensation system identifies cases; a clinician files a Doctor’s First Report of Occupational Illness and Injury form (DPR 2003); or a clinician reports a case on line through the California Reportable Disease Information Exchange system (CDPH 2014). Pesticide-poisoning cases are investigated by the county agricultural commissioner who is responsible for the county in which the poisoning occurred. Another source of case ascertainment is the cholinesterase monitoring program; DPR regulations require employers to provide medical monitoring of workers who regularly handle organophosphate or carbamate insecticides (OEHHA 2007; DPR 2011).
The following steps are necessary for illness cases to be successfully reported: the affected person must be seen by a clinical provider, the clinician recognizes the condition as a pesticide-related event, the clinician is aware of the requirement to report, the clinician files a report, and the receiving agency records and documents the case. Employees, supervisors, and any members of the public can also bring cases to the attention of the county commissioners. The surveillance program probably underreports the number of pesticide-related illnesses in the state because access to health care for many workers may be inadequate, workers may be reluctant to report illnesses, and clinicians may not have the appropriate training to identify a case as pesticide-related or be aware of the need to report cases. Some cases may also be misclassifications of illnesses unrelated to pesticide exposure.
PISP data can affect the risk-assessment process by affecting priority-setting among active ingredients; pesticides shown to have higher numbers of human health incidents related to their use may be assigned priorities before an equivalent pesticide that has less history of pesticide-related illnesses (S. Koshlukova, DPR, Sacramento, CA, personal communication, May 16, 2014). In addition, PISP data can aid in problem formulation regarding specific pesticides and may confirm risk-assessment findings. CDPH is considering linking data from the PUR and PISP databases to investigate possible correlations (P. English, Environmental Health Investigations Branch, personal communication, July 8, 2014). In the future, opportunities for collecting data on pesticide-related illness from medical records might come from the recent passage of the Health Information Technology for Economic and Clinical Health Act, which promotes the adoption and “meaningful use” of health-information technology.
The committee judges that DPR’s risk-assessment process could best be improved by more data collection and better characterization of pesticide exposure in the state. Programs are already in place to collect state-specific data, and the efforts might be expanded and coordinated with other departments to fill data gaps.
Recommendations:
• Consideration should be given to expanding PUR reporting requirements to include licensed pesticide appliers, who would include those who perform applications for nonagricultural purposes in homes, institutions, and industries if not already required to so. The resulting data would help to fill gaps in information about exposure from those types of pesticide uses.
• If resources allow, PUR data should be reviewed in relation to air-monitoring data and surveillance data on pesticide-related illness to determine whether any patterns are evident and to judge the accuracy of exposure assumptions or models.
• The integration of a component based on a geospatial-information system into the PUR program should continue to be encouraged.
• Because surveillance programs like PISP rarely capture more than a moderate percentage of cases, consideration should be given to improving the reporting of pesticide-related illness, for example, by improving training of clinicians, expanding the means by which cases can be reported, searching electronic health records, and possibly expanding the use of biomarkers. More accurate data on pesticide-related illness will support better priority-setting and aid in the development of problem formulation for conducting risk assessments of specific pesticides.
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