EPA proposal for pesticide tied to reproductive harm lands back with Trump

US environmental regulators are planning to change allowable levels of a weedkiller linked with reproductive health problems to a concentration critics say discounts years of documented health and environmental risks — potentially marking a new battlefront within the Trump administration.

The proposal by the Environmental Protection Agency (EPA), which was put forth in late 2024 under the Biden administration, would allow concentrations of the herbicide atrazine up to 9.7 parts per billion (ppb) in streams and lakes before any mitigation efforts were required.

That is nearly three times higher than the level of 3.4 ppb proposed by the EPA in 2016 and reiterated by the agency as proper in 2022. But it is lower than a level pushed for under the prior Trump administration. It is also lower than the longtime benchmark of 10 ppb that was in place from 2011-2019, and lower than atrazine maker Syngenta says is necessary.

The agency’s move has been met with outrage by environmental health advocates who say industry influence is overriding solid science, and years of fighting to reduce atrazine contamination of waterways is in jeopardy.

“It’s a punch in the gut for all the people who have worked to protect us from this incredibly harmful poison,” said Nathan Donley, environmental health science director with the Center for Biological Diversity.

Atrazine is a widely used weed killing chemical that is popular with farmers, particularly those growing corn, and the chemical has been found to heavily contaminate drinking water supplies around the country, raising concerns for human health. The chemical has been banned for use as an herbicide in European Union since 2003.

Research has shown that atrazine is an endocrine disruptor that can affect the sexual development of frogs — chemically castrating make frogs and feminizing male amphibians. The effects are seen at exposure to levels well below 1 ppb — over 10 times lower than the new proposed threshold for environmental safety, known as the CE-LOC, or concentration equivalent level of concern.

In a wide variety of species, including mammals, atrazine causes androgens, or masculinizing chemicals, to be converted to estrogen. It has also been linked with an increased risk of various cancers, pre-term birth, birth defects, and diminished immune function.

Syngenta, the primary manufacturer of atrazine didn’t immediately respond to a request for comment. But the company’s website states that atrazine is well studied, good for the environment and not dangerous.

“There is no link between atrazine and endocrine disruption at real-world exposure levels,” the company states.

Though public health advocates say the new allowable level is too high to truly be protective, the EPA’s most recent position disagrees. Before Biden left office, EPA spokesman Remmington Belford noted in a statement sent in response to questions that the new CE-LOC proposal followed a 2023 scientific advisory panel re-evaluation of a subset of studies on the topic.

“EPA does not anticipate any human health risks of concern from atrazine exposure to surface water and drinking water,” Belford added.

The EPA is currently taking public comments on the proposal. The comment period ends Feb. 18, though the agency says comments must be received by Feb. 3.

It is unclear if the proposal will be impacted by changes in administration at the EPA under the newly inaugurated President Donald Trump. But the prior Trump administration sparked an uproar when it attempted to raise the CE-LOC to 15 ppb.

EPA scientists reported administrative meddling forced them to discount scientific findings to support that level, and the measure was successfully challenged in court.

Back and forth

As defined, the CE-LOC is supposed to provide a limit that protects fish, invertebrates and amphibians in the aquatic ecosystem. But agreeing on where that level should be has been a drawn-out battle pitting Syngenta and supporters pushing for higher levels against health and environmental advocates pushing for lower levels.

The EPA has whipsawed back and forth on the question amid political changes in EPA leadership.

In a 2022 letter from EPA Assistant Administrator Michal Freedhoff to an industry advocacy group, Freedhoff cited “confusion” over the changing agency positions on the matter. She said the 15 ppb undertaken by the first Trump administration represented a “policy decision” but the best data on the issue – as analyzed in 2016 before Trump took office and again during the Biden administration – supported the 3.4 ppb.

It is not clear why the agency moved from 3.4 ppb to the 9.7 ppb before Biden left office, but many suspect corporate pressure as a possible culprit.

Syngenta has a long history of seeking to influence regulatory findings regarding atrazine and other pesticide products and using secretive tactics to discount independent science, and some observers say pressure from the company and its supporters is a key factor in the EPA changing positions. Syngenta is one of the world’s largest agrochemical companies and is owned by ChemChina, a Chinese state-owned chemical giant.

Internal records disclosed through litigation more than a decade ago show the company has a history of deploying multiple tactics to silence criticism of atrazine, including investigating scientists on an EPA advisory panel, harassing a scientist studying atrazine, and other measures, such as recruiting “third-party allies” to support the safety of its products while appearing to be independent of the company.

Similar tactics have been used by Syngenta to downplay the risks of its paraquat weed killers, The New Lede revealed after obtaining thousands of internal company records.

Researcher Tyrone Hayes, an ecotoxicologist and developmental biologist at UC-Berkeley who has studied atrazine for nearly 30 years, said that the move by the EPA to allow such a high level of atrazine into the water is inexplicable, given the evidence of atrazine harm to the environment. Industry pressure is the only reasonable explanation for the agency action, he said.

Jason Rohr, a researcher who has studied atrazine at the University of Notre Dame, said the latest move by the EPA to set a benchmark at 9.7 is “a little disappointing.”

“I would have expected [the EPA] to go in the opposite direction, for there to be more regulations and restrictions, especially in the last decade with all we’ve learned,” he said.

In a 2021 paper, Rohr wrote that the story of atrazine “represents a textbook example of manufacturing uncertainty & bending science to delay undesired regulatory decisions.”

The paper chronicles how Syngenta and other industry groups regularly “bent science” toward favorable outcomes; attacked and denied science perceived as harmful to their interests; harassed scientists such as Hayes and generally “manufactured uncertainty” to delay or prevent regulations.

Besides atrazine’s endocrine-disrupting effects, it suppresses the activity of aquatic plants and algae, which form the basis of the entire food web. “Atrazine, like many herbicides, will suppress primary productivity, [which] has potential to have cascading effects on all other organisms,” Rohr said.

Mitigation measures

The CE-LOC is the average concentration of atrazine found in water bodies that “when exceeded, presents a greater than 50% chance of negatively affecting” an aquatic environment, according to the EPA. It is primarily meant to protect aquatic plants, which atrazine, an herbicide, directly suppresses — but it’s also supposed to be set at a level that doesn’t hurt animals.

The proposal on atrazine is part of a broader plan to implement a suite of mitigation measures  meant to reduce harms associated with atrazine. Along with altering the CE-LOC, the EPA proposal includes a point-based “mitigation menu” meant to promote measures that reduce runoff, such as leaving farm fields untilled.

How many points farmers need varies by area, and includes factors that EPA has tried to take into account, such as community atrazine use, quantity of rainfall, and soil type.

In some areas, farmers only need three “points” to be comply with the proposed label’s instructions; in other areas it’s five. Practicing no-till yields three points — but that is not in itself sufficient to eliminate the risk of runoff, critics charge.

(Featured image by Getty Images for Unsplash+.)