Health information, not medical advice. Guidance differs for infants, pregnancy, and existing conditions. Test your own water and speak to a doctor or your local health authority. We may earn a commission when you buy through our links; it never affects our scores.
The short answer
Atrazine in water comes from a weed killer used mainly on corn, sorghum, and sugarcane, and it reaches drinking water through runoff from treated fields. The EPA’s enforceable limit is 0.003 mg/L (3 µg/L), and long-term exposure above that level is linked to cardiovascular and reproductive problems (EPA). Some of the highest stream levels have been found in corn-growing Midwestern states. Granular activated carbon is the most commonly used treatment, and NSF lists an atrazine reduction claim under NSF/ANSI 53. There is no evidence that boiling removes it.
Where does atrazine in water come from?
Atrazine is an herbicide used to control annual broadleaf and grass weeds, used most on corn, sorghum, and sugarcane. In drinking water, its source is runoff from herbicide used on row crops.
USGS sampling found that atrazine levels in agricultural streams tracked where it was used, with some of the highest concentrations in corn-growing areas of Illinois, Indiana, Iowa, Nebraska, and Ohio. A study of 149 streams in 10 Midwestern states found atrazine was the most frequently detected and most persistent herbicide measured, and its seasonal pattern suggested that the aquifers feeding many of those streams were contaminated with herbicides. In a 1992 to 1995 study of the Western Lake Michigan drainages in Wisconsin and Michigan, atrazine was detected in all stream samples and in more than half of groundwater samples (USGS Circular 1156).
Is atrazine in water harmful?
People who drink water with atrazine above the EPA limit over many years could have problems with the cardiovascular system or reproduction. Oregon’s health authority says drinking water with high levels over a long time can cause cardiovascular system and reproductive problems, and that children and the elderly are particularly susceptible.
Agencies base their limits on different animal findings. The WHO’s guideline rests on suppression of the luteinizing hormone surge in a rat study. Health Canada bases its limit on reduced offspring body weight in a rat reproduction study and considers it protective for bottle-fed infants. Its 1993 document classifies atrazine as possibly carcinogenic to humans, found the human evidence on ovarian cancer inadequate, and found no clear increase in lymphoma risk.
The cancer picture has since shifted. In November 2025, IARC classified atrazine as “probably carcinogenic to humans” (Group 2A), citing limited human evidence, including positive associations with a subtype of non-Hodgkin lymphoma, and sufficient evidence in animals.
What are the limits for atrazine in drinking water?
The limits differ widely, and the US limit is the strictest of the three.
| Agency | Value | What it’s for |
|---|---|---|
| EPA | 0.003 mg/L (3 µg/L) | MCL (maximum contaminant level), enforceable for public water systems; the MCLG (maximum contaminant level goal), a health goal, is also 0.003 mg/L |
| Health Canada | 0.005 mg/L (5 µg/L) | Maximum acceptable concentration for atrazine plus its N-dealkylated metabolites |
| WHO | 0.1 mg/L (100 µg/L) | Guideline for atrazine and its chloro-s-triazine metabolites; a separate 0.2 mg/L guideline covers hydroxyatrazine |
What is the EPA doing about atrazine now?
Atrazine remains under EPA registration review. The current interim decision dates from September 2020, and the agency says it will proceed with a revised interim decision after reviewing comments on its proposed revisions. In July 2024 it revised its level of concern for aquatic plant communities to 9.7 µg/L, up from 3.4 µg/L, and in December 2024 it proposed updated mitigation measures to reduce exposure to non-target species and protect listed species. That proposal was published for public comment in December 2024.
In October 2025 the agency released the U.S. Fish and Wildlife Service’s draft biological opinions for atrazine and simazine for a 60-day public comment period. The EPA said the final Fish and Wildlife Service opinions were due by March 31, 2026. As of September 2026, the EPA had not posted a final opinion or a revised interim decision.
How do you test for atrazine?
The EPA limit applies to public water systems. For a private well, Minnesota recommends using an accredited laboratory, and says nitrate above 3 mg/L in well water suggests additional testing may be a good idea, because if nitrate is present, pesticides may be as well. See our well water guide.
How do you remove atrazine from water?
- Activated carbon: Granular activated carbon filtration is the most commonly used treatment, and the WHO says 0.1 µg/L can be achieved using granular or powdered activated carbon. For private wells, options include central treatment at the well or where water enters the home, or a point-of-use filter at the kitchen sink, but treatment may not work if levels are very high and the equipment must be carefully maintained.
- Other methods: Reverse osmosis, ion exchange, ozone oxidation, and ultraviolet radiation have also been used successfully to remove atrazine, per Health Canada.
- Boiling: There is no evidence that boiling removes atrazine.
Health Canada says home activated charcoal units should be used only on microbiologically safe water, flushed well before each use, and have their filters changed often, because they can themselves become a source of chemical and microbial contamination.
Look for certification. NSF’s listings include “Atrazine Reduction” as a health-effects claim under NSF/ANSI 53. Not every NSF/ANSI 53 filter carries it, so check the listing for the atrazine claim specifically. See our guide to NSF certification and how to choose a water filter.
Which filters are certified for atrazine?
Few of the filters we review carry an atrazine certification we could confirm. The one below does, with the certifier and standard on the card. It’s a refrigerator filter, so it only fits the fridges that take it.
Frigidaire PureSource Ultra II
Common questions
Does boiling remove atrazine?
Oregon’s health authority says there is no evidence that boiling removes atrazine.
Is 3 ppb the same as the EPA limit?
Yes. The limit is 0.003 mg/L, which equals 3 µg/L, or 3 ppb.
Does a carbon filter remove atrazine?
Activated carbon is the most commonly used treatment, and granular or powdered activated carbon can reduce atrazine to 0.1 µg/L. For a home filter, look for the NSF/ANSI 53 atrazine reduction claim on the certifier’s listing.
Has the EPA banned atrazine?
No. Atrazine is in an ongoing registration review, with a September 2020 interim decision in place and a revised interim decision still to come.
Why is the WHO limit so much higher than the EPA’s?
The agencies use different studies and assumptions. The WHO’s 0.1 mg/L is based on suppression of a hormone surge in rats, with a safety factor of 100, while Health Canada’s 0.005 mg/L uses a 1,000-fold uncertainty factor on a rat reproduction study. The EPA’s limit and goal are both 0.003 mg/L.
Sources
Prices as of November 1, 2026. Product prices and availability are accurate as of the date/time indicated and are subject to change. As an Amazon Associate we earn from qualifying purchases.