Surface Water Protection Program for Pesticide Use in California - ACS Axial | ACS Publications

Surface Water Protection Program for Pesticide Use in California

The increasing use of the newer pesticides such as the pyrethroids, neonicotinoids, and fipronil has resulted in their ubiquitous occurrence in surface waters and led to observations of adverse effects on aquatic organisms. The widespread contamination has stimulated active discussions and research on monitoring, aquatic toxicology, risk assessment, modeling, mitigation, and regulatory efforts to minimize contamination and protect environmental integrity.

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 and the monitoring programs in Minnesota, Washington, North Dakota, Oregon, and California. California likely has the most comprehensive and sustained surface water 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. The California Department of Pesticide Regulation (CDPR) conducted its first surface water monitoring study in 1981 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.


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. 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.


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). 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.


Pesticides detected at high frequencies and at concentrations exceeding U.S. Environmental Protection Agency (EPA) aquatic life benchmarks are targeted for mitigation actions. Collaborative educational and outreach events are initiated to pesticide users for taking measures to mitigate pesticide runoff. More specifically, engaging 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. 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.

This post is an excerpt from Pesticides in Surface Water: Monitoring, Modeling, Risk Assessment, and Management‘.

Editors: Kean S. Goh, Jay Gan, Dirk F. Young, Yuzhou Luo
Publication Date (Web): March 26, 2019
Copyright © 2019 American Chemical Society

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