The U.S. EPA adjusted the concentration limit for Atrazine to 9.7µg/L for aquatic organisms

Recently, the U.S. Environmental Protection Agency (EPA) announced that the concentration level of Atrazine adversely affecting aquatic plants has been updated to 9.7µg/L. The new standard, based on the results of an August 2023 review, will be used to make new regulatory decisions to protect aquatic plants, fish, invertebrates and amphibians.

Atrazine is one of the most widely used herbicides in the United States, primarily to control annual broadleaf and gramineous weeds in crops such as corn, sorghum and sugar cane. In addition, the product is also registered for use in macadamia nuts, guava, fallow fields and lawns.

The revision stems from a complicated regulatory history. In 2016, EPA determined the level of Atrazine negatively affecting the aquatic environment to be 3.4µg/L; In September 2020, the EPA raised that level to 15µg/L based on a policy rather than a scientific decision. Subsequently, the EPA faced a lawsuit alleging violations of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA); In August 2023, EPA convened a meeting of the FIFRA Scientific Advisory Panel to evaluate 11 studies used to calculate safe concentrations of Atrazine. After considering the recommendations of the Scientific Advisory Panel and re-evaluating two additional studies, EPA recalculated the safe concentration of Atrazine to 9.7µg/L.