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Drinking Water and Pesticides

Pesticides have the potential to contaminate drinking water supplies in both agricultural and urban settings. Under the Safe Drinking Water Act (1974), the U.S. EPA and other federal agencies monitor and regulate drinking water supplies. Many contaminants of drinking water occur at very low concentrations. Whether the contaminants pose a health risk depends on how toxic the pesticides are, how much is in the water, and how much exposure occurs on a daily basis.

Did you know?

• Public water systems are required to test drinking water for certain contaminants regularly. Testing for private well water is encouraged, but not required.
• Although the EPA regulates and monitors several drinking water contaminants, many pesticides are not regulated contaminants.
• When pesticides contaminate water, the levels often vary widely from month to month, and from season to season.
• Occasionally pesticides are used in canals, rivers, lakes and streams to control pests such as mosquitoes, weeds or invasive fish.
• Public drinking water systems use pesticides like chlorine to kill bacteria, viruses and other organisms, making the water safe to drink.
• Point-of-use devices like charcoal filters and reverse-osmosis treatments can be used to remove or minimize pesticides in drinking water.

Keep these tips in mind to prevent pesticide contamination of water supplies:

• Always read the label carefully before each and every use. Pay particular attention to the Environmental Hazards section of the label.
• Choose pesticides that are short-lived in the environment rather than pesticides that can persist for a long time after they have been applied.
• Select pesticides that do not move easily into groundwater once they have been applied.
• Don't apply pesticides when it is raining or about to rain.
• Avoid applying excess pesticides to hard surfaces like sidewalks and driveways where rain can wash them into storm drains.
• Where possible, leave an untreated area (a buffer strip) along waterways and drainage area.
• When cleaning out sprayers or other pesticide application equipment, make sure the rinse water won't contaminate waterways.
• Never dispose of any pesticide down storm drains or into sewer systems. Pesticides are considered hazardous waste and must be disposed of properly.

Additional Resources:

• Ground Water and Drinking Water - Environmental Protection Agency (EPA)
• Consumer Confidence Reports (annual drinking water quality) - Environmental Protection Agency (EPA)
• EPA Non-Regulatory Health-Based Drinking Water Levels - Environmental Protection Agency (EPA)
• Drinking Water Contaminants Fact Sheet - Environmental Protection Agency (EPA)
• Safe Drinking Water Act - Environmental Protection Agency (EPA)
• Safe Drinking Water Information - Environmental Protection Agency (EPA)
• How EPA Regulates Drinking Water Contaminants - Environmental Protection Agency (EPA)
• Pesticides and Water Quality - Purdue University
• Pesticides and Water Quality - U.S. Geological Survey (USGS)

Drinking Water from Wells:

• Private Drinking Water Wells - Environmental Protection Agency (EPA)
• Protect Your Private Well (infographic) - Environmental Protection Agency (EPA)
• Potential Well Water Contaminants and Their Impacts - Environmental Protection Agency (EPA)
• Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991–2004 - U.S. Geological Survey (USGS)
• Pesticides in the Nation's Streams and Ground Water, 1999-2001 - U.S. Geological Survey (USGS)

If you have questions about this, or any pesticide-related topic, please call NPIC at 800-858-7378 (8:00am - 12:00pm PST), or email at npic@ace.orst.edu.