EPA’s Latest Atrazine Proposal; Comment Period Now Closed

UPDATED: Comment period is now closed. We appreciate the comments that were submitted by growers and grower organizations. 

EPA’s updated atrazine proposal, released December 2024, contained positive changes for growers, but concerns remain. As part of the atrazine registration review process that started in 2013, ended in 2020, and in an unprecedented move, was reopened in 2022, the Environmental Protection Agency (EPA) is accepting comments on its memorandum to the Interim Registration Review Decision.  The EPA comment period was open until April 4, 2025.

Low-Quality Studies Removed, but Some Remain

• The proposal affirms the proposed aquatic level of concern (CELOC) at 9.7 parts per billion, an improvement over the previously proposed 3.4 ppb.
• The 9.7 ppb CELOC was achieved after a Scientific Advisory Panel (SAP) recommended removal of several low-quality studies. However, other studies were not included in the SAP. Notably, one low-quality study (Pannard) was not included although growers requested its addition to the panel’s consideration.
• If the Pannard study had been considered by the SAP and removed, the CELOC would be estimated at 12 parts per billion. This would have removed millions of acres from mitigation requirements.

Mitigation Model Still Flawed

• EPA continues to use a deeply flawed model to predict atrazine runoff. Although the CELOC nearly tripled, 68% of U.S. corn acres would still be out of compliance and required to implement one or more mitigation practices. At the ultra-low 3.4 ppb CELOC, 72% of corn acres were impacted. Although the level of concern has tripled, the number of corn acres impacted was only marginally reduced—from 72% to 68%.
• EPA’s model uses a 95% Prediction Interval from WARP instead of the Standard Median Output to create the mitigation watershed maps. This substantially overpredicts actual real-world monitoring data.
• The result is 68% of corn acres requiring mitigation vs. 13% of corn acres if proper modeling was used.

Costly Mitigation Requirements—Improved, but Still Concerning

• In a positive move, EPA made significant changes to the mitigation proposal, bringing the atrazine mitigations into alignment with the 2023 Final Herbicide Strategy.
• EPA broadened its mitigation picklist from 12 practices to over 40 options by making it consistent with the Herbicide Strategy picklist.
• Depending on location, the farmer would need 0 points, 3 points, or 6 points of mitigation practices to use atrazine. The points can be accrued by implementing any combination of nearly 40 practices listed on the EPA Mitigation Menu Website.

Decreased Application Rate

• EPA’ caps the maximum annual use rate at 2 lbs./ac, down from the current rate of 2.5 lbs./ac.

The Triazine Network remains concerned that far too many growers will be required to implement costly mitigations due to the inclusion of a flawed study, a flawed methodology that lacks corresponding data, and a hyper-conservative strategy for determining which watersheds exceed the 9.7 ppb CELOC. While the comment period is now closed, growers and organizations can view submitted comments at Docket ID: EPA-HQ-OPP-2013-0266,  at www.regulations.gov.

Resources

View Listing of Counties (by state) and mitigations. 

Graphic: The Mitigation Map is very similar to the map EPA created in 2022. In 2022, 70 percent of U.S. corn acres were impacted. In the 2024 proposal, although the aquatic level of concern was nearly tripled, the percent of acres impacted only dropped by 3 percent to 67 percent of all corn acres impacted.