Surface Water Protection Program for Pesticide Use in California

in surface water in the United States, namely the U.S. Geological Survey's .... products are not granted registration, PREM does allow SWPP scientists...
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Surface Water Protection Program for Pesticide Use in California Kean S. Goh,* Yuzhou Luo, and Nan Singhasemanon Surface Water Protection Program, California Department of Pesticide Regulation, Sacramento, California 95812, United States *E-mail: [email protected].

The mission of the California Department of Pesticide Regulation’s Surface Water Protection Program is to protect surface water from pesticide contamination resulting from the use of pesticides in agricultural and urban environments. The program relies on both preventive and responsive components to prevent adverse impacts of pesticide residues to humans and aquatic organisms. To achieve this mission, the program integrates the following key components: (1) the evaluation of pesticide products submitted for registration in California, (2) the monitoring of surface water and sediment for high use pesticides with high aquatic toxicity potential, (3) the modeling of fate and transport of pesticides to predict environmental exposures and aquatic risks, (4) the mitigation of any adverse impacts from legal use of registered pesticides, and (5) the promulgation of regulatory actions to implement use restrictions and/or best management practices. These program components overlap, operate interdependently, and feed back into each other in a continuous evaluation loop.

Introduction There are only a few programs that consistently monitor for pesticides in surface water in the United States, namely the U.S. Geological Survey’s National Water-Quality Assessment Program (1) and the monitoring programs in Minnesota (2), Washington (3), North Dakota (4), Oregon (5), and California (6). California likely has the most comprehensive and sustained surface water © 2019 American Chemical Society

protection program for pesticides, implemented to address the large amount of pesticide use (94.8 million kg in 2016) for agricultural and urban pest control and aimed to protect surface water quality for the benefit of human and aquatic health (7). The California Department of Pesticide Regulation (CDPR) conducted its first surface water monitoring study in 1981 (8) and officially established the Surface Water Protection Program (SWPP) in 2000. The SWPP has evolved to become a holistic scientific program that implements components of pollution prevention, monitoring, modeling, mitigation, research, education, outreach, and regulation. The program has a clear mission and vision to protect surface water quality under the general pesticide regulatory authorities and mandates in California. The mission is carried out by a team of seventeen highly trained multidisciplinary scientists with adequately sustained funding resources to support staffing, a state of the art pesticide analytical laboratory, university and research agency contracts, collaborations on areas such as aquatic toxicity assessment and testing, studies related to pesticide fate and transport, mitigation methodology, and aquatic risk assessment. This chapter highlights the key components of the program: prevention, monitoring, mitigation, education, outreach, and regulatory actions. Most of the components are covered in detail in separate chapters in this volume. These components are dynamic and interactive, and provide continuous evaluation of the status and success of the program in protecting surface water quality.

Regulatory Authority A regulatory program, even a scientific one, has to work under the authorities and mandates of federal and state laws and regulations. In California, water quality regulatory agencies are governed by the Federal Clean Water Act and the California Porter Cologne Act. The California State Water Resources Control Board and the nine Regional Water Quality Control Boards (collectively known as the Water Boards) administer these statutes to protect water quality. The Water Boards, through statewide water quality control plans or basin plans, can set water quality objectives and discharge requirements, list water bodies as impaired by toxicants such as pesticides on the Federal Clean Water Act Section 303(d) list, and implement total maximum daily loads. As California’s pesticide regulatory agency, the CDPR works under the umbrella of the Federal Insecticide, Fungicide, and Rodenticide Act and under the authority of the California Food and Agricultural Code. The CDPR’s SWPP specifically implements: 1.

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Section 11501(b), which is used to protect the environment from harmful pesticides by prohibiting, regulating, or ensuring proper stewardship of those pesticides. Section 12824, which endeavors to eliminate any pesticide that endangers the environment and develop an orderly program for the continuous evaluation of all registered pesticides.

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Section 14102, which prohibits or regulates the use of environmentally harmful materials, considers the effect of all such materials upon the environment, and takes all necessary steps to protect the environment. Section 14103, which establishes the criteria and regulations relating to environmental injury and protection.

These environmental protection authorities and mandates are further defined in the California Code of Regulations, including those relating to registration evaluation reviews and the formal CDPR reevaluation process. These regulatory activities are coordinated among the Water Boards and CDPR through a Management Agency Agreement (MAA) and the implementation plan associated with it. The MAA and the associated implementation plan coordinate pesticide water quality activities of mutual interest, facilitate communications and interactions, promote collaborative problem solving, assure the protection of water quality, and provide a framework to cooperatively respond to the presence of pesticides in surface water (9). Even though the original MAA and associated implementation plan were completed and signed in 1997, the CDPR and the Water Boards implemented revisions and updates to the documents in 2017 with expected completion in 2019 to more accurately reflect current programs and expectations.

Prevention A key component to protecting surface water quality is to prevent a new pesticide product that could adversely affect aquatic and benthic organisms from being used in California. The SWPP conducts evaluations during the pesticide registration process to identify products that could pose high adverse risks to the state’s aquatic environments when used according to the product label. The Pesticide Registration Evaluation Model (PREM) can be used to evaluate most pesticide products that the SWPP receives for potential impacts to aquatic and benthic organisms in order to protect the environment and human health (10). PREM is conducted in two stages: (1) initial screening, and (2) refined modeling with focus on aquatic application, rice application, urban scenarios, high risk agricultural use patterns, and pesticide degradates. Initial screening is based on chemical properties (e.g., soil adsorption coefficient, water solubility, and reaction half-lives), aquatic toxicity of the active ingredient (AI), and estuarine/marine species sensitivity. PREM quickly separates pesticides that are unlikely to be a surface water quality problem from those that may cause harm and require additional evaluation. Risk is further characterized using product-specific information (use pattern and application rate) and the model provides registration recommendations: (1) to support registration without conditions; (2) to support conditional registration with requests for analytical methods, additional data, or place the AI on a watch-list; or (3) not to support registration. The watch-list covers AIs that may contaminate surface water if used. Potential actions for the listed pesticides require an analytical method to facilitate post-use monitoring, flagging for reassessment if a new label is associated with a high-exposure use 3

pattern, and monitoring for surface water quality post-use. Although an important aspect of PREM and registration evaluations is to recommend that high risk products are not granted registration, PREM does allow SWPP scientists to consider potential changes to the product label that may allow the products to eventually be registered.

Monitoring Once a pesticide is registered for use in California, the use amount and its pattern is evaluated by running the Surface Water Monitoring Prioritization Model (SWMP) (11). SWMP is developed to prioritize pesticides for surface water monitoring in agricultural and urban areas of California. To generate the monitoring priority list of pesticide ingredients and their degradates, the model incorporates pesticide use and toxicity data, as well as chemical properties, monitoring results, and application information. Advanced options are also provided in the model for monitoring prioritization at various spatial and temporal scales, with user-defined months, years, counties, and watersheds. The model facilitates the automation of updating the monitoring priority lists in agricultural and urban areas of California. Two processes are defined in the prioritization: (1) pesticide ranking according to their use amounts and toxicity data, and (2) pesticide screening based on historical monitoring results, physicochemical properties, registered use sites, and application methods. The pesticide ranking process generates a preliminary priority list of pesticides in the areas of interest (use patterns, years, months, counties, and/or watersheds) and the pesticide screening process refines the priority list by identifying pesticides with relatively high risks to surface water quality. The top prioritized pesticides are candidates to be considered in surface water monitoring studies. Each year, the SWPP’s ongoing monitoring studies are evaluated by running SWMP by using the latest pesticide use reported for each region of interest and any newly reported aquatic toxicity information (12). The SWPP is able to capture pesticides with increasing use and high toxicity to be included in current or future monitoring. Currently, we monitor for regionally-prioritized pesticides in urban and agricultural areas of northern and southern California (13–16). All analytical method development and sample analyses are conducted by the California Department of Food and Agriculture’s Center for Analytical Chemistry. Monitoring data are uploaded to the SWPP’s publicly accessible surface water database and analyzed for trends of pesticide concentrations, effectiveness of mitigation measures, and regulatory actions (17).

Mitigation, Education, and Outreach We recognize the importance of pest management to protect human and animal health, produce crops, and protect structures. Our mission is to reduce risk while allowing viable pest management. Preventive actions include the ability to influence pesticide use patterns and instructions, including the addition of mitigation measures at the pesticide registration stage and the ability to determine 4

if further mitigation is needed once the pesticide has been used widely. Mitigation is a major component of the SWPP and was a subject of our previous ACS symposium book (18) and Chapters 21, 22, and 26 in this volume (19–21). Post-registration mitigation practices included changes in the use of directions, application methods, irrigation management, and installation of structures to prevent or ameliorate pesticide runoff: 1.

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Pesticide – for specific pest and site conditions, select an appropriate pesticide class, formulation, use rate, site of application, and timing of application. Application technology – calibrate application equipment, select proper nozzle type and spray particle size, reduce height of application, consider drift reduction agents or adjuvants. Environmental conditions – be cognizant of the location of sensitive water bodies and allow spray buffer, slope of the field, wind speed and direction. Irrigation management – use efficient irrigation methods such as microsprinkler and drip systems, and irrigate to crop evapotranspiration schedule. Physical control structures – consider installing a vegetated buffer, a vegetated ditch, and vegetated filter strips, water and sediment holding ponds, constructed wetlands, charcoal/woodchip filters, wood-chip bioreactors, etc.

Pesticides detected at high frequencies and at concentrations exceeding U.S. Environmental Protection Agency (EPA) aquatic life benchmarks are targeted for mitigation actions (22). We initiate collaborative educational and outreach events to pesticide users for taking measures to mitigate pesticide runoff. More specifically, we engage with the pesticide registrants and professional user groups on taking voluntary product stewardship measures and, when necessary, follow up with a formal reevaluation process or provide suggested label changes. Reevaluation entails requesting data from registrants, for example, to better identify the sources (use patterns and use sites), as well as the processes and pathways that can cause a pesticide to move off-site to contaminate surface water, and to conduct studies to evaluate and implement various mitigation measures to reduce pesticide runoff. Mitigation could be in the form of issuing permit conditions with use restrictions (particularly to address agricultural sources), product label changes by registrant, or regulations with restrictions including those related to limitation on application methods, timing of application, target sites, environmental conditions, formulation, a buffer zone to sensitive sites, for example. Reevaluations for surface water protection have been completed for copper antifouling paints, diazinon, chlorpyrifos, and pyrethroids. In addition, a negotiated mitigation measure through label changes for fipronil has been implemented (23).

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Regulatory Actions Reevaluation and data assessment processes resulted in five rulemaking actions: dormant spray restriction regulations for diazinon and chlorpyrifos (2003), urban surface water protection regulations for pyrethroids (2012), designation of chlorpyrifos as a California restricted material (2015), copper antifouling paints regulations (2018), and label changes on the urban uses of fipronil (2018). Dormant spray regulations only allow application to hydrologically-isolated sites or farms with water recirculating systems or holding ponds (72 h hold); otherwise, a written recommendation from a licensed pest control advisor is needed with a buffer zone (305 m) to sensitive sites and with wind speed limitations (4.8–16 km/h). We have completed evaluations of diazinon and chlorpyrifos use and surface water monitoring data, and concluded that uses of both AIs in recent years have decreased to levels that no longer pose significant risk to aquatic organisms. We determined that additional mitigation measures are not necessary at this time (24, 25). In 2012, the CDPR promulgated the urban surface water protection regulations for seventeen pyrethroids. The regulations were prompted by continued detections of pyrethroids in urban waterways at levels that are toxic to aquatic macroinvertebrates. In brief, the regulations restrict applications that are considered high risk for runoff. These restrictions include limiting perimeter band treatment to a 3-ft band or less from the base of a building outward and a 2-ft band or less above the grade level, prohibiting application during precipitation (except under eaves), prohibition of applications to storm drain or curbside gutter, and maintaining a 2-ft buffer adjacent to the sidewalk and driveway (26). Currently, surface water monitoring data shows a decline in bifenthrin concentrations in northern California and no change in southern California, but a slight increase in deltamethrin and cyfluthrin in both areas, respectively (27–29). In 2015, the CDPR designated chlorpyrifos as a restricted material and established recommended permit conditions, including one that was meant to specifically address surface water concerns: Incorporate or clean-up granules that are spilled during loading or are visible on the soil surface in turn areas. Although CDPR reviews of chlorpyrifos data in California’s Central Valley showed that recent years’ aquatic risks due to chlopyrifos were considered to be de minimis, concerns (particularly along the Central Coast) still necessitated additional mitigation. The copper antifouling paints reevaluation resulted in regulations that require the cancellation of existing paints for use on recreational vessels that have an adjusted daily mean copper release rate exceeding 9.5 µg/cm2 per day. This leach rate cap also applies to new paints registration submissions after July 1, 2018. Fipronil label changes to protect surface water quality included the following items: (1) prohibition of application to garage doors, driveways, vertical surfaces above the driveway and garage door, or to cracks and crevices leading or adjacent to the driveway; (2) prohibition of spray bandwidth greater than 6 in. out or up from where the ground meets the foundation; (3) limitation of the finished solution to a maximum of 0.03%; (4) prohibition of application during rain or when rain is 6

predicted within 48 h post-application; (5) prohibition of re-application at intervals less than 60 days; (6) limitation of application to a maximum of 4 times per year; and (7) prohibition of applications between November 1, 2018 and February 28, 2019.

Summary The SWPP’s wholistic surface water protection approach encompasses CDPR’s initial product registration and subsequent continuous evaluation process to effectively ensure the protection of human and environmental health in California. The SWPP employs predictive modeling to evaluate potential risks to prevent new pesticide products from adversely affecting aquatic life during the initial registration phase. As products become registered and used, the SWPP (in coordination with California Water Boards) monitors to assess possible adverse impacts. Data collected are compiled in the surface water database and are continuously analyzed by SWPP scientists. Occasionally, the risks associated with certain pesticides need to be addressed by CDPR using its pesticide regulatory framework. SWPP then works to evaluate suspected sources and pathways, ultimately resulting in mitigation recommendations that could involve label changes, permit conditions, and regulations. The SWPP continuously evaluates current and novel best management practices in the field and with statistical and modeling tools to ensure that practical pesticide runoff or drift mitigation measures can be discovered, validated, and implemented. Focused education and outreach are then conducted for user groups to help implement mitigation measures. SWPP relies again on its monitoring capabilities to evaluate the success of these measures and assess whether changes or improvements need to be made to ensure that surface water quality is protected.

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