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Pesticides from agricultural runoff are among the most common contaminants in U.S. drinking water, particularly in farming regions. Learn about the health risks, which chemicals are most concerning, and how to protect your family.
Pesticides are chemicals used to kill or control pests, weeds, fungi, and insects in agricultural and residential settings. The term encompasses herbicides (weed killers), insecticides, fungicides, and other chemical agents. Over one billion pounds of pesticides are used in the United States each year.
These chemicals enter drinking water primarily through agricultural runoff, when rain or irrigation carries pesticides from fields into surface water and groundwater. USGS studies have found pesticides in 94% of sampled stream sites and 61% of shallow groundwater wells in agricultural areas.
Important: Pesticide contamination is most common in agricultural regions, particularly the Midwest Corn Belt, California's Central Valley, and areas with intensive farming. Private wells near farms are at higher risk than municipal supplies.
The most commonly detected herbicide in U.S. drinking water. Used primarily on corn crops. Linked to endocrine disruption, hormone interference, and reproductive issues.
The world's most widely used herbicide. Classified as a probable carcinogen by the WHO's cancer research agency. Used on GMO crops and for residential weed control.
A triazine herbicide related to atrazine. Used on corn, citrus, and for aquatic weed control. Associated with endocrine disruption.
One of the oldest and most widely used herbicides. A component of Agent Orange. Classified as possibly carcinogenic by WHO.
An organophosphate insecticide linked to developmental harm in children. Banned for residential use but still used agriculturally.
Children: Developing nervous systems are particularly sensitive to pesticide exposure. Studies link pesticide exposure to learning disabilities and ADHD.
Pregnant women: Pesticide exposure during pregnancy is associated with birth defects, low birth weight, and developmental delays.
Agricultural workers: Higher occupational exposure increases cancer risk and other chronic health effects.
| Pesticide | EPA MCL | MCLG | Health Concern |
|---|---|---|---|
| Atrazine | 3 ppb | 3 ppb | Cardiovascular, reproductive |
| Glyphosate | 700 ppb | 700 ppb | Kidney, reproductive (probable carcinogen) |
| Simazine | 4 ppb | 4 ppb | Cancer risk |
| 2,4-D | 70 ppb | 70 ppb | Liver, kidney, adrenal gland |
| Alachlor | 2 ppb | 0 ppb | Cancer, liver, kidney, eyes |
| Lindane | 0.2 ppb | 0.2 ppb | Liver, kidney, immune system |
Note: Many health organizations argue EPA limits are too high. EWG recommends much stricter guidelines based on newer research. Some pesticides like chlorpyrifos have no federal drinking water limit despite documented health effects.
Rain and irrigation water carry pesticides from treated fields into streams, rivers, and groundwater. This is by far the largest source of pesticide contamination in drinking water.
Pesticides applied to soil can percolate down through soil layers to contaminate aquifers. Some pesticides persist in groundwater for years or decades.
Aerial and ground spraying can carry pesticides beyond target areas, contaminating nearby water sources, particularly during windy conditions.
Lawn care, pest control, and golf course maintenance contribute to pesticide contamination in suburban areas, flowing into stormwater systems and groundwater.
Some banned pesticides like DDT and chlordane persist in soil and groundwater for decades. Agricultural areas may have legacy contamination from older chemicals.
Pesticide contamination is highest in agricultural regions. USGS studies consistently find the highest pesticide levels in these areas:
Iowa, Illinois, Indiana, Ohio, Nebraska - highest atrazine levels
Intensive agriculture, diverse pesticide use
Citrus and vegetable farming
Citrus, vegetables, high rainfall runoff
Apple orchards, wheat farming
Cotton, rice, soybean production
Private Wells: If you have a private well near agricultural land, regular pesticide testing is essential. Well depth, soil type, and proximity to fields affect risk.
The only reliable method. Labs use EPA-approved methods (like EPA 508 or 525) to detect multiple pesticides at low levels. Request a "pesticide scan" for comprehensive coverage.
Contact your state health department for certified lab lists, or call EPA: 800-426-4791.
Some mail-in test kits include pesticides, but coverage is limited compared to lab testing. May only test for a few common pesticides.
Municipal water systems test for regulated pesticides. Check your Consumer Confidence Report or search your city on our site to see what has been detected.
When to Test:
Activated carbon is highly effective for most pesticides, removing 90-99% of organic contaminants through adsorption. Available in whole-house and point-of-use systems.
Cost: $100-400 for under-sink; $1,000-3,000 for whole-house
Removes 90-98% of most pesticides. Point-of-use systems are common for drinking water. Often combined with carbon pre-filters for optimal pesticide removal.
Cost: $200-500 for under-sink + $50-100/year maintenance
Membrane filtration that removes many pesticides along with other contaminants. Less wastewater than RO but effective for pesticide reduction.
Does NOT Effectively Remove Pesticides:
Check your water quality report for pesticides. If you have a private well near agricultural land, get it tested for common pesticides.
A quality activated carbon filter or reverse osmosis system can remove most pesticides from drinking water. Look for NSF 53 certification.
Buying organic reduces pesticide use in your area. Support policies that protect water sources from agricultural runoff.
Choose organic lawn care and integrated pest management. Pesticides applied to your property can affect your own well and local water sources.
No. Boiling may actually concentrate some pesticides by evaporating water. Use carbon filtration or reverse osmosis to remove pesticides.
Organic farms don't use synthetic pesticides, but they may still be affected by pesticide drift or groundwater contamination from conventional neighbors.
It varies widely. Some pesticides break down in weeks, while others persist for years or decades. Atrazine and its breakdown products can remain in groundwater for many years.
Standard Brita filters provide limited pesticide reduction. For significant pesticide removal, use filters certified to NSF Standard 53 for pesticides, or reverse osmosis systems.
See what pesticides have been detected in your city's water supply.
This information is provided for educational purposes only and is not intended as medical advice. If you are concerned about pesticide exposure, consult with a healthcare provider. Water quality data is sourced from EPA and USGS databases. Private well owners should test their water through certified laboratories for accurate results.