California is stepping up efforts to eliminate sources of pyrethroid concentrations in its waterways
In June 2017, the California Regional Water Quality Control Board and the Central Valley Region (Central Valley RWQCB) passed an amendment to the basin plan for the Sacramento River and San Joaquin River basins to control pyrethroid pesticide discharges. The change sets out controls for pyrethroid discharges, including prohibiting pyrethroid pesticide discharges above certain concentrations, maximum total daily exposure (TMDL) for pyrethroid pesticides, recommendations for government regulation of pyrethroids, and potential monitoring requirements.
Synthetic pyrethroids are the most common forms of commercially available urban pesticides for ants, termites, and flying insects currently being used for non-agricultural purposes due to the move away from historical bans on previously used DDT, chlorpyrifos, and diazinon pesticides. They are also commonly used in California for fruit and nut trees, row crops, rice, nurseries, and cityscapes. The California Department of Pesticide Regulations (DPR) is tracking trends in pesticide use and has shown an increase in the use of pyrethroids for certain crops, including almonds, tomatoes and grapes. In 2017, the last year data from DPR is available, pyrethroids were used on 16% more acreage for almonds, 17% more acreage for tomatoes and 30% more acreage for grapes. Pesticide drift during application and surface water runoff can lead to contamination and subsequent build-up of sediment in adjacent waterways. Pyrethroids tend to be hydrophobic and are sparingly soluble in water. They have a high affinity for the soil and are strongly sorbed on the sediments of natural water systems.
Due to their current use and extreme effectiveness against target organisms, municipal urban and agricultural runoff has resulted in increased toxicity in downstream receiving waters. Because pyrethroid pesticides are widely used for pest control in urban and residential areas, pyrethroids have been found in alarming levels in lakes, rivers and streams in the San Joaquin and Sacramento river basins that drained from urban and agricultural land uses. In order to address the identified impairment of surface water, the Central Valley RWQCB recently requested the approval of the Municipal Separate Storm Sewer System (MS4) in the affected watersheds to discharge pyrethroid pesticides from urban MS4 runoffs by issuing an order under Section Manage 13383 of the California Water Code Section 13383 allows the state or regional agency to establish monitoring and reporting requirements for discharges into navigable waters. In 2020, MS4 permits in the Sacramento and San Joaquin River basins received an RWQCB contract for the Central Valley to develop and implement either a Baseline Monitoring Plan or a Pyrethroid Management Plan. Ultimately, the permits can choose their preferred route to conform to the arrangement. Both approaches have advantages and disadvantages, and the best course of action is different for each community.
Basic monitoring plan
A basic monitoring program is intended to determine whether the discharges from the responsibility of a certain committee in the downstream waters exceed the water quality standards for pyrethroid pesticides. To conduct a monitoring program, the MS4 permits in the Sacramento and San Joaquin River basins can develop a basic monitoring plan that includes a plan to monitor the Surface Water Environmental Monitoring Program (SWAMP) (QAPP). The baseline monitoring plan and QAPP should describe the program objectives, monitoring locations, sampling methods, data quality objectives, laboratory methods and detection limits, and other relevant data as a guide for baseline monitoring.
Should an MS4 committee elect to conduct baseline monitoring, multiple rainy weather sampling events and at least one dry weather event are likely to be required. For example, the CVRWQB letter states that water or MS4 runoff monitoring should be done four times a year, including three rainy weather events (i.e. after the first flush, after winter, after spring runoff) and one dry weather event. In addition, water column and sediment toxicity monitoring should be performed four times per year to be consistent with monitoring events for pyrethroid chemistry and organic carbon received by water.
While some municipalities may have the staff and technical expertise to perform basic monitoring with their own in-house staff, many cities lack the resources to take rainwater samples in wet weather. Often this type of labor-intensive fieldwork has to be outsourced, which can result in higher costs for the city. Monitoring rainy weather also carries the risk of false starts or predicted rain events that may not occur and increase costs.
However, portions of the Sacramento and San Joaquin Rivers’ drainage basins are located in the mountains and foothills and consist of mostly rural communities. Some permits, particularly those covered by the Phase II Small MS4 permit, may make a small contribution to exceeding water quality standards for pyrethroids. Due to the lack of dense urban areas, such communities can benefit from basic monitoring in the long term if there is reason to believe that the monitoring shows that these permits do not exceed pyrethroid pesticide standards. Such a demonstration would allow a committee to forego developing and implementing a pyrethroid management plan in the future. If the baseline monitoring is exceeded, a pyrethroid management plan would still be required.
Pyrethoid management plan
Instead of developing and implementing a basic monitoring plan, the permits can go straight to development and implement a pyrethroid management plan. Nationwide studies, including a review of urban water catchment pyrethroid monitoring data developed by the California Stormwater Quality Association (CASQA), have shown that urban rainwater is known to contain pyrethroids in amounts above those set out in the Central Valley’s RWQCB basin plan Prohibition triggers lie. In deciding to develop a pyrethroid management plan rather than basic monitoring of discharges in wet and dry weather, a committee recognizes that “the data available is considered representative of their discharges”. In some communities, it may be uncomfortable to take responsibility for exceedances without evidence gathered from base surveillance.
A pyrethroid management plan must identify a number of management practices that can reasonably be expected to be effective in lowering pyrethroid levels in MS4 discharges. Management practices for municipal stormwater discharges may include awareness raising and public outreach activities, such as: B. the promotion of a reduced and proper use of pesticides, the reduction of municipal runoff through the implementation of the Low Impact Development (LID), the use of an integrated pest management and the support of the pollution prevention through pesticides regulation process. At this time, future trend monitoring and program effectiveness assessment is not specifically required as part of a management plan, but it is possible that some kind of monitoring will be required in the future to detect improvements in surface water pyrethroid levels.
If a committee suspects that its municipal discharges may be contributing to surpluses in the water quality standard for pyrethroids, it is likely more economical to proceed directly to developing a management plan for the use of pyrethroids for pest control. However, if historical data to monitor water quality are not available, especially in rural areas, it will be difficult for permits to assess their potential impact on the aquatic environment or the effectiveness of their program.
View outside the Central Valley
While the Central Valley RWQCB may be the latest agency to issue ordinances to combat pyrethroid pesticide excesses of water quality standards, its widespread use for structural pest control in urban areas and for agricultural purposes has continued to affect water catchment areas across California historically performed with other pesticides. Municipalities can be proactive by implementing inclusive pest management that focuses on long-term pest prevention or damage through a combination of techniques such as biological control, habitat manipulation, and the use of resistant plants instead of chemical pesticides. The University of California’s Nationwide Integrated Pest Control Program (UC IPM) is a useful resource for residents, breeders, land managers, community leaders, and other professional pest controllers to learn how to prevent and resolve pest problems with minimal unintended consequences. Pesticides can be used in ways that protect human health and the environment if they are selected and applied appropriately after considering ecosystem-based strategies.
SWELL:
Central Valley Regional Water Quality Control Board. Proposed Changes to the Sacramento River and San Joaquin River Basin Water Quality Control Plan to Control Pyrethroid Pesticide Discharge Final Staff Report. June 2017.
Pulupa, Patrick. Patrick Pulupa to Jered Reinking. July 13, 2020. Arrangement for filing technical reports and surveillance reports under Sections 13267 and 13383 of the California Water Code.
UC Research and Education Program for Sustainable Agriculture. 2017. “Integrated Pest Management (IPM).” What is sustainable agriculture? UC Department of Agriculture and Natural Resources.
