EWG's Tap Water Database



July 2017


Atrazine is one of the most widely and heavily used herbicides in American agriculture. The EPA estimates that about 70 million pounds are applied every year. From farm fields, atrazine seeps into streams, rivers and groundwater, and eventually ends up in drinking water. EWG data show that atrazine is the most commonly detected pesticide in tap water. In 2015, atrazine was found in water systems serving 30 million Americans in 28 states.

Water utilities struggle to remove atrazine from their supplies, particularly in the spring, when millions of pounds of the chemical are applied corn and soybean fields. In 2012, Syngenta, the herbicide’s sole manufacturer, settled for $105 million a lawsuit filed by more than 1,000 Midwestern water providers over costs to remove atrazine from drinking water – a figure some utilities said would not begin to cover the cost of removal.

Click here to see the nationwide testing results for atrazine.

Why is atrazine harmful?

Atrazine is a hormone disrupter that likely affects the human reproductive system at low doses, and poses the greatest risk during pregnancy and early childhood.

Atrazine resists degradation from heat or sunlight, posing a significant threat to water quality. Europe bans all pesticides in drinking water, leading to a 2003 phase out of atrazine. EWG and other advocates have called for a complete ban on atrazine in the U.S.

Atrazine is widely detected in groundwater, rivers and drinking water at concentrations that exceed the EPA’s ecological concern level of 3 parts per billion, or ppb. University of California, Berkeley, scientist Tyrone Hayes has reported that low-level exposures can cause male frogs to turn into egg-laying females.

What are the health guidelines for atrazine?

Federal laws allow up to 3 ppb of atrazine in treated tap water. The federal government also permits water suppliers to average atrazine measurements collected over a year, which means that the reported values underestimate intense spikes of elevated exposures during certain times of the year. Human epidemiological studies suggest that these legal standards are insufficient to protect public health.

In 1999 the California Office of Environmental Health Hazard Assessment set a public health goal of 0.15 parts per billion for atrazine in drinking water, based on a study finding increased rates of breast cancer in rats exposed to the chemical. California’s legal maximum for atrazine in tap water is 1 ppb.

How can atrazine affect people?

Research on the endocrine-disrupting potential of atrazine suggests that it acts by depressing the luteinizing hormone, leading to the increased production of estrogen and prolactin in females, and changes in testosterone levels in males. As the EPA summarized in a presentation to its Science Advisory Board in 2011, in studies of laboratory animals these hormonal changes delay puberty, alter the development and function of the breast and ovaries, damage testes and cause prostate inflammation.

In 2011, the EPA’s Science Advisory Panel concluded that atrazine could cause adverse health outcomes in people and rejected the EPA’s draft determination that atrazine is “not a likely human carcinogen,” cautioning that:

… the cancers for which there is suggestive evidence of carcinogenic potential include: ovarian cancer, non-Hodgkin’s lymphoma, hairy-cell leukemia and thyroid cancer. These cancer sites require follow-up studies. In addition, cancers for which there is inadequate evidence include: prostate cancer, breast cancer, liver cancer, esophageal cancers, and childhood cancers. These cancer sites also require follow-up studies. [Emphasis added.]

Based on recent human epidemiological studies, EWG questions the adequacy of the current 3 ppb federal drinking water limit for protecting human health. Atrazine concentrations in water vary by season, making it difficult to study its effects on people. Also, atrazine frequently co-occurs with nitrate, a fertilizer chemical, and the mixture of the chemicals could have a cumulative effect. Despite this complexity, studies suggest human health may be affected by low levels of atrazine in drinking water.

How much atrazine in drinking water is safe?

This question is not yet settled. As scientists continue to study endocrine disruptors, more and more information becomes available showing that these contaminants do not belong in water. As a provisional benchmark, EWG uses the California public health goal of 0.15 ppb and calls on water utilities to reduce atrazine in their water to below this level.

What should be done to reduce exposures to atrazine?

EWG calls on the federal government to protect all Americans from atrazine by capping the maximum allowable atrazine concentration well below the current federal legal limit of 3 ppb.

What can I do to address the risks of atrazine in my drinking water?

Use EWG’s Tap Water Database to see if your water system reported testing for atrazine, and if it was detected. If you don’t see your water provider or want to learn more about tests, contact your provider directly to ask if they test for atrazine or have detected it.

If you drink well water or are part of a small drinking water system, your water may not be tested for atrazine. The EPA requires more frequent atrazine monitoring for communities with known pollution problems. Find out if atrazine has been detected in your region by contacting nearby water utilities or your local public health department. If you live near cornfields or other agricultural lands, you may consider paying to have your water tested, but talk to local water experts about the best season to collect a water sample.

If any atrazine is detected in your water, install a water filter certified to remove atrazine. EWG recommends using filtered water for drinking while you are pregnant, mixing baby formula or giving drinking water to a young child.


Associated Press, Syngenta Pays Millions in Settlement to Farming States. The Topeka Capital-Journal, 2013. Available at

California Office of Environmental Health Hazard Assessment, Public Health Goal for Atrazine in Drinking Water. 1999. Available at

C. Chevrier et al., Urinary Biomarkers of Prenatal Atrazine Exposure and Adverse Birth Outcomes in the PELAGIE Birth Cohort. Environmental Health Perspectives, 2011, 119(7):1034-1041.

L.A. Cragin et al., Menstrual Cycle Characteristics and Reproductive Hormone Levels in Women Exposed to Atrazine in Drinking Water. Environmental Research, 2011, 111(8):1293-1301.

Elizabeth Mendez, Presentation to the Scientific Advisory Panel. Atrazine Re-Evaluation: Scientific Considerations in Potential Sensitivity of Infants & Children. Environmental Protection Agency, Office of Pesticide Programs, Health Effects Division, July 26-29, 2011.

EPA Science Advisory Panel, Meeting Minutes of the FIFRA Scientific Advisory Panel meeting held July 26-28, 2011 on the Re-Evaluation of the Human Health Effects of Atrazine: Review of Non-Cancer Effects, Drinking Water Monitoring Frequency and Cancer Epidemiology. Oct. 26, 2011.

EPA, Office of Pesticides, Environmental Fate and Effects Division, Refined Ecological Risk Assessment for Atrazine. April 12, 2016. Available at

European Commission, Review Report for the Active Substance Atrazine. Finalized in the Standing Committee on the Food Chain and Animal Health at its meeting on Oct. 3, 2003 in support of a decision concerning the non-inclusion of atrazine in Annex I of Directive 91/414/EEC and the withdrawal of authorisation for plant protection products containing this active substance. European Commission Health and Consumer Protection Directorate-General, 2003, SANCO/10496/2003-final.

T. Hayes et al., Demasculinization and Feminization of Male Gonads by Atrazine: Consistent Effects Across Vertebrate Classes. Journal of Steroid Biochemistry and Molecular Biology, 2011, 127:64-73.

M.G. Rhoades et al., Atrazine and Nitrate in Public Drinking Water Supplies and Non-Hodgkin Lymphoma in Nebraska, USA. Environmental Health Insights, 2014, 7:15-27.

L.T. Stayner et al., Atrazine and Nitrate in Drinking Water and the Risk of Preterm Delivery and Low Birth Weight in Four Midwestern States. Environmental Research, 2017, 152:294-303.