The second most commonly used weedkiller in America has been found in tap water across the Midwest — and it was banned in Europe over 20 years ago. In January 2025, rather than tightening protections, the EPA raised the allowable level of this herbicide in US drinking water.
The chemical is atrazine. According to Simply Younger’s review of the regulatory and toxicological evidence, if you live anywhere near corn country, there is a reasonable chance it is in your water right now.
Key Takeaways
- Atrazine is the second most widely used herbicide in America — approximately 70–80 million pounds applied annually, primarily across Midwest corn fields. It is highly water-soluble and detected in 90% of Midwest water systems tested by the NRDC.
- The EU banned atrazine in 2004 under its precautionary principle. In January 2025, the US EPA moved in the opposite direction and raised the allowable level in drinking water.
- Atrazine is an endocrine disruptor that activates the enzyme aromatase, converting androgens to oestrogens. Research linked it to feminisation in amphibians at concentrations below the US legal limit.
- According to Simply Younger, annual water quality reports may not capture seasonal spikes — atrazine levels in agricultural communities can exceed legal limits 3–7x during spring runoff windows.
- Activated carbon filtration reduces atrazine effectively. Reverse osmosis provides the most comprehensive removal alongside PFAS, arsenic, and nitrates.
What Is Atrazine?
Atrazine is an agricultural herbicide used extensively on corn crops across the United States. Approximately 70–80 million pounds are applied annually across the Corn Belt. It is highly water-soluble and persistent — when applied to fields, rainfall washes it into streams, rivers, and groundwater. It accumulates in surface water that feeds municipal water supplies. In the Midwest, atrazine has become one of the most consistently detected agricultural chemicals in drinking water.
Why Did Europe Ban Atrazine?
The European Union banned atrazine in 2003, effective 2004. The EU’s assessment found atrazine could not be kept below 0.1 micrograms per litre in European groundwater — the EU’s universal pesticide limit in drinking water — and that evidence of endocrine-disrupting and carcinogenic properties was sufficient to justify removal from the market. The EU applies a blanket precautionary standard: no pesticide above 0.1 μg/L in drinking water, regardless of which one it is. This represents a fundamentally different regulatory philosophy to the US approach.
What Did the EPA Do in January 2025?
Rather than tightening the US standard, the EPA in January 2025 raised the allowable level of atrazine in drinking water — moving in the opposite direction to the scientific evidence. The decision reflects the structural dynamics of US pesticide regulation, where agricultural industry interests, economic impact assessments, and technical achievability all factor into regulatory outcomes alongside toxicological evidence.
How Widespread Is Atrazine in US Drinking Water?
The NRDC found atrazine in 90% of Midwest water systems tested. The Environmental Working Group’s tap water database shows that in some Corn Belt communities, atrazine levels spike 3–7x above the legal limit during late spring and early summer — immediately following spring application when the first heavy rains wash the herbicide into waterways. Annual water quality reports may not capture these peak concentrations. Atrazine has also been detected in water supplies across more than 30 states.
What Does Atrazine Do to the Human Body?
Atrazine is an endocrine disruptor. Its primary mechanism involves the enzyme aromatase, which converts androgens (male sex hormones) into oestrogens. Atrazine activates aromatase, increasing oestrogen production relative to androgen levels. Research by Dr. Tyrone Hayes at UC Berkeley demonstrated that atrazine exposure at concentrations found in natural water sources caused sexual demasculinisation and feminisation in male frogs — including both male and female reproductive organs in the same individual — at concentrations below the US legal limit.
In human research, epidemiological studies have linked atrazine to reduced sperm quality and testosterone in agricultural workers, adverse birth outcomes in communities with elevated water levels, and potential associations with ovarian cancer and non-Hodgkin’s lymphoma. Atrazine has been classified as a possible human carcinogen.
Why Is Atrazine Still Legal in the US?
The US sets compound-specific MCLs based on cost-benefit analysis that incorporates economic impact and agricultural dependency alongside toxicological evidence. Atrazine is deeply embedded in US corn production economics — cheap, effective, and difficult to replace without significant changes to farming practice. These economic factors carry weight in the US regulatory process in a way they do not in the EU’s precautionary framework.
How to Reduce Atrazine Exposure
- Check the EWG tap water database at ewg.org/tapwater using your zip code to see whether atrazine has been detected and at what levels.
- Be aware of seasonal spikes. Late spring and early summer represent the highest-risk window in agricultural regions.
- Activated carbon filtration reduces atrazine effectively. Solid block carbon performs better than pitcher filters.
- Reverse osmosis provides comprehensive removal alongside PFAS, arsenic, nitrates, and other contaminants carbon alone may not fully address.
- Private well owners should test annually — especially in spring — as wells in agricultural regions are particularly vulnerable.
Do you know what herbicides are in your water?
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Frequently Asked Questions
Why was atrazine banned in Europe but not the US?
The EU uses a precautionary principle: if a substance cannot be kept below 0.1 μg/L in drinking water, it is banned regardless of economic impact. The US sets compound-specific limits based on cost-benefit analysis that weights agricultural and economic factors alongside toxicological evidence. Different regulatory philosophies produce different outcomes.
Is atrazine an endocrine disruptor?
Yes. Atrazine activates the enzyme aromatase, which converts androgens to oestrogens, disrupting hormonal balance. Research has demonstrated feminisation effects in amphibians at concentrations below the US legal limit and has linked atrazine exposure to reduced testosterone and sperm quality in agricultural workers.
Does atrazine cause cancer?
Atrazine is classified as a possible human carcinogen. Epidemiological studies have found associations with ovarian cancer and non-Hodgkin’s lymphoma. The endocrine disruption mechanism — elevated oestrogen exposure — is a biologically plausible pathway for hormone-sensitive cancers. The evidence is consistent in direction but not definitive.
What filter removes atrazine from water?
Activated carbon filters — particularly solid block carbon — reduce atrazine effectively. Reverse osmosis provides the most comprehensive removal. Check NSF certifications for your specific filter model.
How do I know if atrazine is in my tap water?
Check the EWG tap water database at ewg.org/tapwater using your zip code. Request your utility’s Consumer Confidence Report. If you are in a Corn Belt state on a private well, arrange a certified laboratory water test — especially in spring after field application.
This article is for general informational purposes only and is not medical advice. Always consult a qualified healthcare professional if you have concerns about your health or water quality.
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