The Environmental Protection Agency may have to back off its proposed mitigation measures for atrazine because of serious questions about research on the herbicide’s impacts on aquatic life.

A scientific advisory panel, or SAP, assigned to examine EPA’s use of 11 studies on atrazine’s ecological impacts appeared to largely agree with the agency that the studies are flawed and should either no longer be considered or used in a more limited fashionin EPA’s proposed revisions to the 2020 atrazine registration review decision.

“We're really happy,” an industry official told Agri-Pulse. “We think it's going our way.”

The panel of scientists met over three days last month to discuss the 11 studies on atrazine’s effects on aquatic life that had been questioned by atrazine manufacturer and registrant Syngenta as well as grower groups.

The agency concluded in a “white paper” in July that the two studies that have received the most criticism should be tossed and that others had limited utility in determining the herbicide's impacts.

“I believe that SAP is going to stick to what EPA asked,” said Greg Krissek, co-chair of the Triazine Network, which advocates for continued use of atrazine.

The panel may in fact go further than EPA’s recommendations in limiting use of the papers, said Krissek, who expects there will be some “give and take” between the panel and EPA as the final report is developed. “But I want to see it in writing first,” he said.

Greg-Krissek-300.jpgGreg Krissek, Triazine Network

The SAP members “talked significantly about not using the two studies that we thought were the most problematic,” the industry official said.

Growers and the groups representing them, as well as Syngenta and others, testified before the SAP at last month's meeting to express their concerns about the potential loss of the herbicide, which they said would be the practical result of proposed mitigation measures.

At issue is EPA’s use of 3.4 parts per billion, or ppb, as the concentration-equivalent level of concern, a level that the industry has said is way too low. EPA says the CE-LOC is the “atrazine concentration level that triggers required monitoring and/or mitigation to protect aquatic plant communities.”

During the Trump administration, EPA raised the level to 15 ppb. But in an interim registration decision issued last year, EPA said that limit wasn't justified by the science and that the agency was keeping the 3.4 ppb level.

Continued complaints from industry stakeholders led to the convening of the SAP, where scientists mostly agreed with EPA that the studies suffer from various flaws.

It’s not clear what the new CE-LOC might be, but Krissek said “to the best of our mathematical projections, adopting the white paper’s recommendations should mean any CE-LOC will be higher” than 3.4 ppb. 

Focusing solely on “high-quality data” would yield a higher CE-LOC, said Jeff Giddings of Compliance Services International, in representing Syngenta at the SAP.

“As you refine the data and focus on the high-quality data … the [LOC] increases,” he said.

A higher CE-LOC would likely lead to EPA requiring growers to implement fewer practices to reduce atrazine runoff. 

As it stands, EPA has proposed requiring sorghum, field corn and sweet corn growers in watersheds with atrazine levels above 3.4 ppb (about 18% of all watersheds in the U.S.) to choose from a “picklist” of practices — among them cover crops, contour buffer strips, terrace farming or field borders — depending on the crop.

Sweet corn has five picklist practices, and sorghum and field corn each have twelve.

EPA is also proposing to allow higher rates in southern field corn production as well as an annual limit of 8 pounds/year for sugarcane production in Florida, and 4 pounds/year in Louisiana and Texas (with no picklist requirements).

Although the SAP was not convened to consider EPA’s modeling or the picklist, “they are linked to the use of the 11 poor quality studies that you are considering,” said Brent Rogers, president of the Kansas Corn Growers Association.

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“I strongly agree with EPA’s white paper findings,” which he said recommended excluding “the worst of these studies.”

“Atrazine is a critical component of weed management for U.S. corn farmers and has been for many decades,” said National Corn Growers Association President Tom Haag. “Atrazine is used on approximately 90 percent of all corn acres each year.” 

Haag called the picklist “unusable,” and said “no-till farming offers numerous environmental benefits in the form of reduced soil erosion” and improved water quality.

Tom HaagTom Haag, NCGA

At this point, the picklist is “just kind of hanging out there” until EPA determines a new CE-LOC number, which will influence the maps EPA comes up with to show where mitigation should take place, Krissek said. 

Another Kansas producer, sorghum grower Amy France, said the “loss of atrazine would only worsen the conservation challenges facing farmers and lead to increased rates of tillage on the dry and windy High Plains like here in Western Kansas.”

The abandonment of no-till or reduced-till practices would lead to increased greenhouse gas emissions, both from fields that have been tilled and the equipment used to till them, growers say.

EPA’s white paper said two studies should be excluded entirely, including one, known as Lampert, whose results were questionable because of “solvent bias” — that is, questions about whether ethanol was used to dissolve the atrazine before testing it.

Scientific advisory panels in 2007, 2009 and 2012 all recommended that the study be excluded. 

Another study that examined the effects of atrazine on wetland species also had been flagged for removal by the 2012 SAP.

The Detenbeck study involved “exposing organisms to atrazine at different concentrations in a step-by-step fashion,” SAP member Paul Sibley, an environmental sciences professor at the University of Guelph in Ontario, Canada.

But “while this approach might have been chosen for logistical or practical reasons, it does not accurately mimic the real-world conditions of atrazine exposure,” he said. “Atrazine exposure in the environment is seldom characterized by such a stepwise increase in concentration. Instead, organisms are exposed to varying concentrations of atrazine over time,” which makes the study design “inherently unrealistic.”

The Center for Food Safety said in comments to the agency that the studies at issue have been reviewed “ad nauseam.”

“In contrast to both this EPA scientific assessment and the 2012 SAP, this Scientific Advisory Panel is being asked, unfairly, to respond to an extremely narrow set of questions without regard to the bigger picture,” CFS said. “We urge the SAP to conduct the requested analysis in the broader light of the mountain of evidence demonstrating the broad-scale harms of atrazine to aquatic plant communities as well as aquatic and terrestrial animals and terrestrial plants.”

The SAP is scheduled to complete its written report by November.

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