Environmental Health Reports

Toxics on Tap: Pesticides in California Drinking Water Sources

3/12/1999

Executive Summary

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

Pesticides are in the water supply of many California communities. The drinking water in some areas is unquestionably hazardous to the health of the residents who drink it. In other areas, evidence is strong that the risks are high, although the state has not adopted guidelines to protect public health based on the latest research. In many places, testing is so inadequate that nobody knows what is in the public water supply.

State agencies have blindfolded themselves by establishing regulations and procedures which prevent them from getting a clear picture of the extent of pesticide contamination. In some ways, they have clearly lacked the political will to take action. In other respects, these agencies simply lack the resources to protect public health effectively.

Pesticides are regularly detected in drinking water sources throughout California

Analysis of the databases maintained by the agencies studying California water quality shows that pesticide detections are common. One hundred one pesticides and related compounds have been detected in the state’s drinking water sources over the past 10ten years. Thirty-one have been detected in more than ten sources, and seven in more than 100 sources.

Pesticide contamination is worst in the Central Valley, but occurs throughout the state. Pesticides have been detected in the sources of water suppliers serving 16.5 million people in 46 of California’s 58 counties over the past ten years. Only 40 of the 600 water suppliers that have detected pesticides in their water sources use the expensive treatment facilities that effectively reduce the concentration of pesticides in water.

Many Californians are exposed to pesticides in drinking water at levels that threaten their health

Two pesticides—DBCP and EDB—have repeatedly been detected throughout the state at concentrations higher than state-established Maximum Contaminant Levels (MCLs). Both of these are soil fumigants that have long been banned, but both continue to persist in the water in many areas.

Other pesticides are detected above the level believed to cause a significant health risk, but below the maximum level allowed by law. The Public Health Goals (PHGs) of ten of the 19 pesticides for which the Office of Environmental Health Hazard Assessment has revised its risk assessment in the past two years are lower than the MCLs. Seven of these ten pesticides have been detected above the PHG but below the MCL. Most notable among these are atrazine, an herbicide still in use, and DBCP.

New evidence demonstrates that much of California’s public water supply is at higher risk than existing standards indicate

New studies show that Californians are also at risk from the many pesticides for which state agencies have not performed an official risk assessment or for which assessments are many years old. Data published by the U.S. Environmental Protection Agency (EPA) on carcinogens shows that simazine, diuron, and molinate are hazardous at concentrations lower than the levels at which these herbicides are detected in California. Other pesticides which are detected with some frequency warrant strict health standards, based on their cancer-causing effects as determined by EPA.

Regulators evaluate the health effects of exposure to pesticides one pesticide at a time. In reality, we are exposed to a multitude of pesticides. While numerous studies have given qualitative proof that negative effects are compounded by multiple contaminants working together, few studies have resulted in hard numbers to quantify those compounded effects. Rather than building an extra margin of safety into their assessments for this uncertainty, California regulators continue to ignore it altogether.

State regulatory agencies have failed to protect Californians adequately from pesticides in drinking water

The Department of Pesticide Regulation (DPR) is the state agency charged with overseeing pesticide use to prevent contamination of drinking water sources. Under previous administrations, DPR’s commitment to this mission has been weak at best—the regulations DPR put in place to implement pollution prevention laws have been ineffective, and work has proceeded very slowly. Decisions by upper management at DPR have prevented the rest of the department from doing their jobs effectively.

In 1986, California legislators passed the Pesticide Contamination Prevention Act. Its stated purpose was “to prevent further pesticide pollution of the groundwater aquifers of this state which may be used for drinking water supplies.” The law gave DPR the responsibility of identifying potential contaminants, checking for them in groundwater, and limiting their use when they are found. DPR has come up short in each of the four main requirements of the Act:

• The restrictions placed on the pesticides known to pollute groundwater have been ineffective at preventing further contamination. DPR placed restrictions on seven pesticides from 1986–90 due to their detection in groundwater, yet each of those pesticides has continued to be detected since then. No other pesticides were restricted due to groundwater contamination until 1997, when use of norflurazon was restricted slightly.

• DPR has delayed identifying and evaluating pesticides likely to contaminate groundwater. Thirteen years after creating a priority list for groundwater monitoring, DPR has satisfied the testing requirements for only 19 of the 63 pesticides on the list. • DPR does not follow up on all detections reported by other agencies. According to DPR’s database, DPR never attempted to follow up on thousands of detections reported by other agencies. The detections that were followed up on were not resampled until an average of 25 months after the initial detection.

• DPR does not collect all available data on groundwater testing for pesticides. Over 9,000 records of pesticide detections by the Department of Health Services and the U.S. EPA are not in the DPR database. This includes detections of over 100 pesticides, some of which were detected above health standards.

The California Department of Health Services (DHS) is the state agency charged with overseeing water suppliers to protect public health from exposure to unsafe levels of pesticides in drinking water. Their efforts fall short in three main areas:

• The maximum level of contamination allowed in drinking water for some pesticides is higher than the level believed to cause a significant health risk. For some pesticides, this is due to provisions in the law which allow DHS, after a cost-benefit analysis, to adopt standards much weaker than an analysis of health effects alone would dictate. For other pesticides, this is due to the slow pace at which DHS accepts new scientific understanding. For 15 of the 27 pesticides which currently have enforceable standards, those standards allow for significant risk to public health. In addition, according to studies approved by U.S. EPA, standards should be set for other pesticides which are not currently regulated, including 29 pesticides believed to have carcinogenic effects.

• DHS ignores valuable data in their assessments of the extent of pesticide contamination of drinking water sources. DHS sets weak statewide reporting limits based on the minimum technological standards for laboratories, and instructs labs not to report detections at concentrations below those limits. Detections below those levels by more sensitive instrumentation are treated as non-detections. Some reporting limits are higher than levels believed to cause a significant health risk. Only six of the 27 regulated pesticides have reporting limits low enough to identify contamination problems that are approaching dangerous levels.

• DHS does not force many small water suppliers to comply with minimum testing requirements. Over 1,700 water suppliers, serving nearly two million people, have never tested for pesticides, according to the DHS water quality database. Most of these are small rural water suppliers, which are often the most vulnerable to pesticide contamination.

Legal protections are not as strong for surface water as they are for groundwater. Although pesticide contamination of surface water sources has been widespread throughout the past 20 years, no formal mechanism for addressing this problem was in place until two years ago. In 1997, DPR, together with the State Water Resources Control Board, devised regulations to control polluted run-off. These new regulations are now about to be used for the first time for just one pesticide.

Recommendations

Recommendations for the Department of Pesticide Regulation

• Phase out the use of all pesticides that are continually contaminating drinking water sources. Atrazine, bromacil, diuron, molinate, and simazine have been plaguing California drinking water sources for years. Use restrictions have not been effective at ending contamination. All are suspected or known human carcinogens for which there is no safe use.

• Protect groundwater effectively by beginning to honor the spirit of the Pesticide Contamination Prevention Act. The intent of this act was to prevent all future pesticide contamination of groundwater, yet DPR in the Wilson Administration hid behind a regulatory system which allowed contamination to continue. In its current revision of these regulations, DPR should implement a system which is effective at prevention.

• Take decisive action for the protection of surface water. Pesticide contamination of surface water is not controlled as strictly as groundwater. DPR should create a system for surface water for the purpose of preventing all future contamination.

• Increase emphasis on the encouragement of least-toxic pest control methods. Alternatives to synthetic pesticides have been proven successful, and should be encouraged to spread as rapidly as possible. If all of the environmental and social costs associated with heavy use of synthetic pesticides were taken into account, and if least-toxic pest control methods were given the amount of support now given to the use of chemical pesticides, use of least-toxic methods by California growers would increase exponentially.

Recommendations for the Department of Health Services

• Revise Maximum Contaminant Levels to make them fully protective of public health. As the new Public Health Goals show that MCLs allow levels of contamination that may harm human health, DHS should act quickly to correct this shortcoming. DHS should also adopt health standards for pesticides that are not currently regulated but have been shown to be a potential threat to public health.

• Stop ignoring valuable data in assessing the extent of pesticide contamination. Discarding pesticide detections below weak reporting limits skews DHS’s understanding of the extent of the problem and affects their choice of solutions.

• Do not allow small water suppliers to slip through the regulatory cracks. Since small, rural water suppliers are generally more vulnerable to pesticide contamination, it is a severe health risk to allow them to pump out untested drinking water. 9

Recommendations for individuals

• Call or write Governor Davis to express your concern about pesticide contamination of drinking water sources.

• Get information from your local water utility to determine if pesticide contamination of drinking water is a problem in your community.

• Call on your local school system and local government to stop using toxic pesticides.

• Convince local authorities to maintain the roadsides in your community without the use of pesticides.

• Buy organic foods.

• Use least-toxic pest control methods at home.

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