SACRAMENTO--Cal/EPA's Department of Pesticide Regulation (DPR) has released its 1997 report on ground water testing for pesticides. Based on 2,508 water well samples, the report showed 96 wells -- less than 4 percent -- had verified pesticide detections. All residues were below levels of health concern.

The annual report is required by the Pesticide Contamination Prevention Act of 1985 (AB 2021, Connelly). Among other provisions of the law, government agencies that test well water for pesticide residues must report the results to DPR. When pesticides are found in ground water as a result of agricultural use, DPR prohibits or restricts their further use in areas where they were detected. In addition, the Department uses the monitoring data to help develop pesticide use practices designed to prevent contamination of ground water by other chemicals.

The report summarizes results from ground water surveys that were submitted to DPR between July 1996 and June 1997. (Agencies are not required to report results immediately. The monitoring reflected in the report was done between 1989 and 1997.) The testing was done by DPR, the State Department of Health Services, State Department of Water Resources, Santa Clara County Water District, City of San Francisco, San Francisco Bay Regional Water Quality Control Board, East San Joaquin Water Conservation District, U.S. Forest Service, and Ciba-Geigy, Inc.

Samples were taken from 2,508 wells in 48 of California's 58 counties. While pesticide residues were detected and verified in 96 wells in seven counties, residues were all below levels of health concern. (See attached table for details on county detections.) The verified detections were made in 86 private drinking water wells, 7 public wells, and 3 non-drinking wells.

Most samples were analyzed for multiple chemicals. Overall, the tests targeted a total of 165 pesticide active ingredients and breakdown products. Of those, verified detections were made of seven herbicides (atrazine, bromacil, diuron, hexazinone, norflurazon, prometon, and simazine) and four breakdown products of herbicides. (See attached table for details.) This is the first time norflurazon and the herbicide breakdown product DACT have been found in California ground water.

In addition, three other agricultural chemicals were found that are recurring contaminants of ground water but have not been used in several years: DBCP, ethylene dibromide, and 1,2-D. There were also unconfirmed detections of six other pesticides that are no longer registered for agricultural use. DPR does not conduct follow-up sampling to verify these agricultural detections because there is no need to put use restrictions on agricultural chemicals no longer used.

Single copies of the Well Inventory Report can be obtained free from: Environmental Monitoring and Pest Management Branch, Department of Pesticide Regulation, 830 K Street, Sacramento, California 95814-3510, phone (916) 324-4100. The executive summary of the report is also available in the "Publications" section of DPR's Web page: http://www.cdpr.ca.gov.

Attached is background and information excerpted from the report

Summary (PDF)
Table2 (PDF)