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Atrazine Updates

Select an item below to learn about atrazine updates.

What Happened? Brief History What’s at Stake? Effectiveness, Safety and Stewardship EPA’s Current LOC of 15 PPB Implications EPA Docket Comments

Atrazine Regulatory Update
EPA’s Re-evaluation of the Current Atrazine CE-LOC
and Proposed Mitigation Measures

July 2024:

What Happened?

On July 8, 2024, the EPA provided an update on its re-evaluation which included recalculation of the atrazine concentration-equivalent level of concern (CE-LOC) to correct errors EPA made in deriving the Agency’s previously announced 3.4 ug/l (3.4 ppb) CE-LOC, as well as errors made in the Watershed Regressions for Pesticides (WARP-MP) analysis. The new atrazine CE-LOC announced is 9.7 ug/l (9.7 ppb). EPA Announces Update on Atrazine | US EPA

The CE-LOC is a 60-day average exposure level that EPA uses to assess potential risks to aquatic eco-systems (creeks, streams, rivers, etc.) and determine whether additional monitoring or label mitigation measures are required.

The atrazine CE-LOC revision announced in July 2024 follows the Agency’s re-evaluation of 13 microcosm and mesocosm (COSM) studies, 11 of which were the focus of the August 2023 FIFRA Scientific Advisory Panel (SAP) meeting. In addition, EPA announced some revisions to the WARP-MP model inputs and updated the watershed maps to reflect those changes.

While Syngenta generally supports the atrazine CE-LOC revision, we disagree with the continued inclusion and scoring of one study that has been widely criticized by the scientific community, the Pannard (COSM) study. The Pannard study is a very low-quality study with many confounding issues and poor methodology. Even though Syngenta and other stakeholders requested (in 2022 public comments) that the Pannard study and the Baxter study be included in the 2023 FIFRA SAP meeting for review, EPA refused to have the SAP re-evaluate the studies. Instead, they did their own internal review of the studies after the SAP meeting and decided to only rescore the Baxter study. The CE-LOC would be even higher >11.8 ug/L (>11.8 ppb) if the Pannard study had been excluded or scored correctly.

Additionally, Syngenta disagrees with the approach used to map and project potential watershed acres that would require mitigation measures for the CE-LOC level of 9.7 ppb, as it made negligible changes to the map from the prior 3.4 ppb CE-LOC calculations. Based on 20 years of intensive watershed monitoring in over 75 watersheds across the U.S., we know that atrazine only potentially exceeds the proposed CE-LOC of 9.7 ppb in all but the most highly vulnerable watersheds.

Brief History of the Atrazine CE-LOC

As part of an earlier atrazine re-registration action going back to 2003, EPA sought to establish an atrazine CE-LOC that was protective of aquatic life. The CE-LOC was derived from a complicated weight of evidence approach by EPA that considered all relevant COSM (microcosm or mesocosm aquatic “community”) studies. The studies came from academia, government (USGS), industry and private sources. EPA also convened multiple SAPs to help determine the appropriate LOC.

EPA’s CE-LOC was 18 ppb during 2004-2011 and 10 ppb (estimated) during 2011-2019. In 2012, EPA proposed lowering the CE-LOC to 4-7 ppb, but its rationale for doing so failed scientific peer review. Among other things, the 2012 SAP concluded that EPA had failed to address specific scientific recommendations of the 2007 and 2009 SAPs and that 11 of the COSM studies EPA relied on were either incorrectly scored as “effect” instead of “no effect” or were of such poor scientific quality that they should be excluded from the assessment.

In 2016, EPA published a draft Ecological Risk Assessment, where they proposed an atrazine CE-LOC of 3.4 ppb, despite detailed public comments and scientific critiques submitted by Syngenta, the Triazine Network, USDA, NASDA and other stakeholders, and SAP recommendations to the contrary. This proposed CE-LOC was not finalized or adopted by EPA. In fact, in June 2016 EPA stated it “will have atrazine's [draft] assessment peer reviewed by the Scientific Advisory Panel in 2017” - which it did not do.

In 2019, EPA issued a regulatory update that set the CE-LOC at 15 ppb, which was subsequently confirmed in the atrazine IRRD (2020). This CE-LOC was based on sound science, taking into account prior SAP recommendations and public comments submitted by the USDA and other stakeholders. In EPA’s IRRD, no significant label changes were proposed for atrazine related to use rates.

In November 2020, activist groups filed a lawsuit against EPA in the US Court of Appeals 9th Circuit, arguing that the atrazine IRRD should be vacated because, they allege, EPA neglected their responsibility under FIFRA to properly consider the risks of atrazine. The lawsuit did not mention or refer to the atrazine CE-LOC.

In August 2021, EPA asked the Court to grant a remand (stay, pause) without vacatur, so that EPA could “reconsider” the CE-LOC and the potential for further monitoring or mitigation.

On June 30, 2022, EPA announced it had re-evaluated the CE-LOC, and “determined” in its proposed revised interim registration review decision (IRRD) that the LOC is 3.4 ppb with additional label mitigation measures required for atrazine use. An LOC of 3.4 ppb would impact over 65 million acres of corn, sorghum and sugarcane (over 70% of all corn acres).

Anticipated EPA timeline for completing its re-evaluation

EPA has indicated that it plans to propose revised atrazine mitigation measures in September 2024, and to request public comment on the proposed measures.

EPA has also indicated that it plans to issue a revised IRRD for atrazine later this calendar year, and that it will require registrants to adopt and implement additional label mitigation measures for atrazine products, targeted at watershed areas where the Agency predicts exceedances of the atrazine CE-LOC.

Based on historical regulatory timelines, it’s unlikely that the Agency’s revised label mitigation measures for atrazine products would be implemented and in effect prior to calendar year 2026.

What’s at Stake?

Atrazine is a vital tool for farmers across the nation, and it is especially important to farmers who implement conservation tillage, or no-till farming, which plays a significant role in carbon sequestration. Farmers are committed to carbon-smart farming. However, if farmers are unable to effectively use atrazine, many acres will return to tillage and carbon savings will be greatly impacted. Syngenta and other stakeholders have repeatedly urged EPA not to adopt an unprecedented, significantly lower CE-LOC that lacks a solid scientific basis or to require additional, unnecessary label mitigation measures that would have significant, real-world negative impacts on growers and their use of products containing atrazine.

Effectiveness, Safety and Stewardship of Atrazine Products:

Atrazine’s effectiveness and safety is well documented throughout the United States and around the world, with more than 7,000 scientific studies conducted on the product. Atrazine plays a significant role in feeding the world, and it also contributes to protecting the environment and critical wildlife habitats.

Syngenta has been a leader in stewarding and promoting appropriate uses of atrazine products. As reflected in EPA’s IRRD in 2020, Syngenta proactively, voluntarily proposed label modifications for atrazine products that included removing certain uses (e.g., uses in Hawaii; roadside and conifer uses); requiring additional in - field downwind buffers; and requiring mandatory spray drift language. These label modifications were approved by EPA and adopted by all atrazine technical registrants.

You can download and read comments to the EPA docket from USDA, Syngenta, the Triazine Network and the National Association of State Departments of Agriculture at the links below: