EPA Shares Fish and Wildlife Service’s Draft Biological Opinions for Atrazine and Simazine for Public Comment
Released October 7, 2025
The U.S. Environmental Protection Agency (EPA) is releasing and seeking public comment on the U.S. Fish and Wildlife Service’s (FWS) draft biological opinions (BiOp) for the pesticides atrazine and simazine. Atrazine and simazine are two widely used herbicides in the United States. The FWS draft biological opinions for atrazine and simazine are available on EPA’s Biological Opinions Webpage and public comments may be submitted to docket number EPA-HQ-OPP-2020-0514 at www.regulations.gov. The draft biological opinions will be available for public comment for 60 days.
Under the Endangered Species Act (ESA), EPA must ensure that its actions, including pesticide registration actions, are not likely to jeopardize federally listed endangered or threatened species, or adversely modify their designated critical habitats. When EPA determines in a biological evaluation that use of a pesticide product may affect listed species or critical habitats, EPA must initiate formal consultation with FWS, the National Marine Fisheries Service (NMFS), or both (the Services). In response, the Service(s) may develop a biological opinion for EPA’s consideration that determines whether the pesticide will jeopardize listed species or adversely modify critical habitats.
EPA initiated formal consultation with the Services upon completing biological evaluations for these pesticides. The draft biological opinions being released for public comment are part of the ongoing formal consultation with FWS.
FWS Biological Opinions
During the consultations, EPA, FWS and the atrazine and simazine registrants worked together to identify drift and runoff mitigation options consistent with EPA’s Herbicide Strategy. This mitigation also reflects scientific analyses and subsequent updates contained in the final Insecticide Strategy that are relevant to the Herbicide Strategy (e.g., updated spray drift buffer distances). Having Herbicide Strategy mitigations available for consideration helped facilitate a more efficient consultation, leading FWS to conclude that the proposed actions for atrazine and simazine are not likely to jeopardize or adversely modify the majority of species and critical habitats for which EPA made Likely to Adversely Affect determinations in the 2021 biological evaluations. In addition, implementation of label changes to which the registrants voluntarily committed before the biological evaluations, along with label changes agreed to during the development of the draft BiOps, supported a more efficient consultation.
These draft BiOps do not include any likely jeopardy/adverse modification (J/AM) determinations. There are a limited number of species and critical habitats where FWS has not yet made a J/AM determination (either likely or not) and FWS has identified a need for further consideration of these species prior to making a determination. These species may be exposed to pesticides when visiting or residing on treated agricultural fields or non-agricultural use sites (e.g., residential turf), which are scenarios not addressed by the Herbicide Strategy. As the consultation continues, before finalizing the BiOps, additional information on the remaining species and critical habitats that are under consideration may be collected to determine if atrazine and simazine are likely to jeopardize the continued existence of these species or adversely modify their designated critical habitats and, if so, identify any additional mitigations needed to reduce exposures and avoid J/AM. FWS, EPA, and the U.S. Department of Agriculture will continue to work with the registrants before the BiOps are finalized to identify any remaining mitigation that may be needed to ensure that the uses of atrazine and simazine are not likely to jeopardize listed species or adversely modify designated critical habitats.
Next Steps
After the 60-day public comment period, EPA will provide FWS with the comments received for consideration before FWS finalizes the biological opinions. EPA intends to continue working with FWS and the registrants prior to FWS’s final BiOps to ensure that the proposed mitigations are technologically and economically feasible. The final atrazine and simazine BiOps are scheduled to be completed by March 31, 2026, as required by a federal court order. Following completion of the final FWS biological opinions, EPA plans to implement the mitigation measures described in the FWS final biological opinions. The final NMFS biological opinion is scheduled for 2030.
Furthermore, EPA has completed its obligations for atrazine and simazine under the Federal Food, Drug, and Cosmetic Act to evaluate how the pesticides may affect estrogen, androgen, and thyroid systems.
Once EPA has completed consultation with the Services, the agency will complete final decisions on atrazine and simazine.