The hormone-disrupting herbicide atrazine is contaminating nearly 25%, or about 860,000 miles, of all continental US rivers at levels that can harm wildlife and may threaten human health, a new review of federal records has found.
The waterways cover over 20% of surface drinking water intakes across the country, and over 675,000 private and commercial wells.
Atrazine can have severe impacts on human and animal hormones, especially for developing children. It was found to “chemically castrate” frogs, and cause some to change sexes. The herbicide is so dangerous that it has been effectively banned in 60 countries, including the European Union, since 2003. Litigation in the US seeks to strike down its approval, but it remains the second most widely used pesticide here, with about 70m pounds sprayed on the nation’s cropland annually.
The report, compiled by the Center for Biological Diversity, which advocates for stricter pesticide regulations, marks the first time anyone has analyzed all the EPA’s atrazine records and identified the threat’s extent.
“The problem is vast,” Nathan Donley, a report co-author and environmental health science director at the Center for Biological Diversity, told the Guardian. “Everyone recognizes this is a big problem, but the EPA has utterly failed to do anything about it for the last three or four decades.”
Atrazine is primarily used on commodity crops like corn, sugarcane and sorghum. The research around its health impacts is robust, and it is classified as a probable carcinogen by the International Agency for Cancer Research. It is an endocrine disruptor that is especially dangerous for developing fetuses and children at even very low levels of exposure, and is linked to impaired fetal growth, pre-term birth, birth defects and low birth weight.
Atrazine can be particularly harmful to reproductive systems, and is linked to the “feminization” of the male gonads, irregular menstrual cycles, lower sperm counts, poor semen quality and lower fecundity in men and women.
In animals, it also causes liver, kidney and heart damage. Exposure at levels as low as 0.1 parts per billion (ppb) in water has been shown to harm reproductive organ development in frogs, potentially leading to population decline. The current allowable level of atrazine in human drinking water is 30 times higher, at 3 ppb.
It was “no surprise that the pollution is so widespread”, said Tyrone Hayes, a University of California, Berkeley pesticides researcher who discovered atrazine’s impact on frogs’ reproduction systems in the early aughts. He was also in the late 1990s hired by Novartis, which produced atrazine until it was bought by Syngenta, to study the chemical.
“At the time it was known that atrazine was the most common pesticide contaminant in drinking water, rain, surface water and groundwater. You name it – atrazine was there,” Hayes told the Guardian. He noted it also travels via the atmosphere, and the US government found atrazine sprayed in Kansas can rain down on Minnesota.
“The effects are very clear, and in my opinion there is no safe level at which atrazine can be used because it is active in amphibians at 0.1 ppb, and there can be atrazine at 100 times that in rainfall,” Hayes added.
The Center for Biological Diversity and other public health groups have sued over the EPA’s approval of atrazine, and in 2020 the agency said it would put together a plan to address the water pollution, Donley said. A 2024 draft he reviewed showed an inadequate plan that “is not worth the paper that it’s printed on”, Donley said, and it is likely that the lawsuit will resume once the final plan is published.
The EPA has failed to act, Donley said, because atrazine is chemical giant Syngenta’s flagship product, widely used, and profitable. Analysts estimate $2-3bn in US sales in 2025.
“It’s the one of the most powerful pesticide industry lobbies behind glyphosate, because of the amount of money being made, and it’s the result of political malfeasance,” Donley said.
The EPA and Syngenta did not immediately respond to a request for comment.
Among five hotspots where pollution is most concentrated are the Chesapeake Bay region, the midwest corn belt, Florida’s Lake Okeechobee, the lower Mississippi River and the Texas Gulf coast.
The report highlights the unique risks in each area. In the midwest corn belt, including Kansas, Nebraska, Iowa, Missouri, Illinois, Indiana and Ohio, over two-thirds of river miles are contaminated, EPA records show, and that covers about half of the region’s wells and 68% of its drinking-water treatment facilities intakes. States in this region have rapidly rising early-onset cancer diagnoses compared with the rest of the country.
This high level of contamination in the Chesapeake Bay watershed largely stems from the high concentration of corn grown in the region, which is home to 18 million people and more than 3,600 species of plants and animals. Meanwhile, atrazine-contaminated watersheds run nearly the entire length of the lower Mississippi River, many at concentrations more than five times the level the EPA has found harmful to aquatic ecosystems.
“We need to follow the lead of over 60 countries around the world and ban atrazine once and for all,” Donley said. “Failing to do so will mean disease, death and dirty water in America for decades to come.”
