Screening Urban Pesticide Use for Potential Water Quality Impacts
G. Fred Lee, Ph.D. PE, DEE
G. Fred Lee and Associates, El Macero, CA
June 1998
Diazinon and chlorpyrifos have been found to cause aquatic life toxicity in urban area stormwater runoff. This toxicity arises from the use of these pesticides by commercial applicators and the public for the control of structural and lawn and garden pests. At this time the Department of Pesticide Regulation (DPR) tracks commercial applicator use of pesticides in urban areas. However, there is no record kept of the public's use of pesticides that can be purchased over the counter without restrictions. It is estimated that in the Palo Alto, CA area, the amount of public use of the organophosphate pesticide diazinon is approximately equal to the commercial applicator use. In the Upper Newport Bay watershed of Orange County, CA, approximately 25,000 pounds of diazinon and chlorpyrifos are applied in urban areas each year by commercial applicators. It is estimated that approximately the same amount is applied by the public in these same areas. The application of these pesticides to residential properties causes stormwater runoff from the urban areas to be highly toxic to certain forms of freshwater and marine zooplankton which are likely important components of larval and other organism fish food.
Several years ago, as part of urban stormwater runoff water quality monitoring in the San Francisco Bay area, urban stormwater runoff was found to be toxic to certain forms of aquatic life. What was originally thought to be heavy metal-caused toxicity in urban stormwater runoff has been found to be OP pesticide-caused toxicity. Diazinon and chlorpyrifos have been found to be a significant cause of aquatic life toxicity in urban stormwater runoff throughout the state through the use of Toxicity Investigation Evaluations (TIEs). While diazinon and chlorpyrifos are some of the most commonly used pesticides in urban areas, there are other pesticides used in urban areas that could also be contributing to aquatic life toxicity. At this time, the regulatory agencies have been conducting a reactive approach toward evaluating the cause of aquatic life toxicity in urban stormwater runoff, where, when toxicity is found, TIEs are conducted to determine its cause. Because of the large amounts of pesticides used in urban areas for which there is essentially no information on whether these pesticides are causing aquatic life toxicity or other adverse impacts on aquatic life and other beneficial uses of the receiving waters for urban stormwater runoff, there is need to develop a systematic, proactive program to evaluate the potential for pesticides used in urban areas by commercial applicators and the public to cause aquatic life toxicity in stormwater runoff and fugitive irrigation water from urban residential, commercial, and industrial areas.
The proactive pesticide use/impact evaluation should consist of the following components.
These efforts should be funded by pesticide manufacturers and formulators, and the public who wish to use the pesticides in urban areas. The burden of proof for the safe use of pesticides in urban areas with respect to protecting receiving waters for urban area stormwater runoff should be on those who wish to manufacture, sell, and use pesticides, rather than is occurring now, on the environment. This proactive, more adequate screening of pesticides for potential environmental impacts should be designed to go beyond the conventional registration for pesticide use where the focus is on fully protecting the aquatic life and other beneficial uses of receiving waters associated with stormwater runoff from residential, commercial, and industrial properties located in urban areas.
Reference as: "Lee, G.F., 'Screening Urban Pesticide Use for Potential Water Quality Impacts,' G. Fred Lee & Associates, El Macero, CA, June (1998)."
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