Environmental Health Reports

Water Woes: An Analysis of Pesticide Concentrations in California Surface Water

11/28/2000

Executive Summary

As the new home of CALPIRG's environmental work, Environment California can be contacted with any questions regarding this report.

Analysis of recently released surface water sampling data compiled by the Department of Pesticide Regulation (DPR) reveals that many California surface water bodies suffer from toxic pesticide contamination that poses health threats to humans and aquatic life.

The database contains records of over 92,000 sampling tests from 133 locations on California creeks, rivers, drainage basins and sloughs—most of which are in the Central Valley. 1 The data result from 32 studies conducted over the last 10 years, principally by the California Department of Pesticide Regulation.2

Pesticide contamination is widespread in California’s waterways

The data reveal a pattern of pesticide pollution in California’s waterways.

• Of the 151 different pesticide active ingredients that were sampled for, 86 compounds (57%) were detected at least once.

• Pesticides were detected in nearly 8,500 samples (9% of all samples).

• Pesticides were detected in almost every waterway tested. Pesticides were detected in 128 of the 133 (96%) locations tested.

• Many water bodies produced widespread detections. Pesticides were detected in over 50% of tests in 13 locations where more than 10 tests were conducted.

Particularly hazardous pesticides were widely detected

• The five most frequently detected pesticide active ingredients were diuron, diazinon, simazine, chlorpyrifos and molinate.

• All five of these are particularly hazardous pesticides that have been linked to cancer, nervous system damage, endocrine (hormone) system disruption, and/or groundwater contamination.

Toxic pesticides are present at levels that threaten aquatic life and drinking water sources

• Of the nearly 8,500 positive detections in the DPR database, 4,349 (51%) exceeded safe levels for aquatic toxicity or drinking water consumption, according to criteria set by state or federal agencies.

• Certain pesticides frequently exceeded criteria. For example, diazinon exceeded criteria 98% of the time it was detected, chlorpyrifos 92%, molinate 33%, and simazine 12% of the time it was detected.

• Four pesticides, atrazine, molinate, simazine and carbofuran, were detected at levels that exceed California drinking water standards.3

• One hundred and 46 detections exceeded California drinking water standards or health goals.

Pesticides in surface water may pose a health threat to people who use that water for a drinking source or recreational activities. For example, approximately 20 million people in Southern California depend on the Delta for drinking water. Contaminated surface waters may also recharge underground aquifers that are widely used for drinking water in the Central Valley. Actual health risk will depend on the degree to which individuals are exposed to pesticides -- an analysis that is not attempted here.

While we know less about the health threat to humans from pesticide concentrations in surface water, we do know that widespread pesticide toxicity in waterways poses a clear threat to aquatic life, including important fisheries.

Recommendations

Although DPR's database is not a comprehensive set of all studies of surface water quality in California, its significant volume of data demonstrates the widespread contamination of the tested locations, corroborating the findings of many other studies.4 This persistent pesticide contamination in California's waters reflects the continued failure of the responsible agencies to take strong action for the protection of our aquatic resources.

Policymakers and regulating agencies should:

• Begin immediate phase out of pesticides that continually contaminate our waters at levels harmful to aquatic ecosystems and human health.

• Phase out the use of all pesticides linked to cancer, reproductive and developmental harm, acute toxicity, nervous system damage, or groundwater contamination. Pesticides that are suspected of disrupting the proper function of the endocrine (hormone) system should also be phased out. All of these pesticides threaten both humans and aquatic animals, and should be phased out as a class.

• Close loopholes for agricultural runoff of pesticides. Irrigation return flows and rinse waters are currently considered non-point sources of pollution, effectively exempting conventional agriculture from complying with the state clean water act. Agricultural entities that apply pesticides should be required to monitor their discharges into nearby waterways and apply for permits to discharge pesticides into our creeks, rivers, lakes and estuaries.

• Establish enforceable drinking water standards for all pesticides, and revise existing standards to make them fully protective of public health.

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