4 new pesticides ignite debate over PFAS definition

The US Environmental Protection Agency is doubling down on efforts to decrease a backlog of new pesticide active ingredients waiting for EPA approval to enter the marketplace. Since April, the agency has proposed registering four of them—cyclobutrifluram, diflufenican, isocycloseram, and trifludimoxazin.

All four pesticides contain a fully fluorinated methyl or methylene group, raising concerns that they will persist in soil and water for many years. Environmental groups argue that the chemicals are per- and polyfluoroalkyl substances (PFAS) under the definition recommended by the Organisation for Economic Co-operation and Development (OECD) in 2021. PFAS are notoriously difficult to remove from the environment, and some of them are toxic at extremely low levels. 

The proposed active ingredients have half-lives of over 3 years, which means that half of what is sprayed today will still be contaminating soil and water in 3 years, at the time of the next US presidential election, Nathan Donley, environmental health science director at the Center for Biological Diversity, said during a meeting of the EPA’s Pesticide Program Dialogue Committee (PPDC) on June 17. Donley is a member of the PPDC, representing the environmental group’s perspective.

“It’s like PFAS pollution on steroids these past few months,” he said, referring to the EPA’s plan to approve the four pesticides. The EPA’s pesticides office “appears to have absolutely no plan to account for the fact that actives are getting more persistent and fluorinated breakdown products are essentially going to be around forever.” 

The proposed pesticide active ingredients can degrade into trifluoroacetic acid, which persists in the environment for more than 100 years, Donley noted. Saying that is not a toxicological concern, as the EPA did in its risk assessments of the four chemicals, is “completely out of touch with reality,” he said.

The EPA’s proposed registrations have stirred up a debate over the definition of PFAS. The EPA’s Office of Pesticide Programs considers PFAS to be chemicals containing at least two saturated, fully fluorinated carbons, either CF₂ or CF₃. The OECD defines PFAS as any chemical with at least one saturated CF₂ or CF₃. The European Union has adopted a definition that is closer to that recommended by the OECD.

Under the EPA’s definition, the four proposed pesticides are not considered to be PFAS, Ed Messina, director of the EPA’s pesticides office, said at the PPDC meeting. The risk assessments for the four chemicals are available for public review and show how the agency arrived at its conclusions, he noted. Interested parties can challenge those assessments, and the EPA will respond, he said. The public comment periods for two of the chemicals have already closed, but the EPA is still accepting comments on diflufenican until July 7 and trifludimoxazin until July 11.

EPA’s pesticide review goals

The EPA hopes to register about 30 new pesticide active ingredients by the end of September, Messina said. It remains to be seen how many of those are fluorinated. The agency is also striving to complete its review of about 40 new uses of existing pesticides, to ensure they comply with requirements under the Endangered Species Act and those related to testing for endocrine disruption, Messina said.

Completing reviews of older pesticides that are up for reregistration is also a big priority for the EPA’s pesticides office. About 800 of these reviews are due by October 2026, Messina said. Draft risk assessments have been completed for about 92% of those cases, he added. The agency hopes to complete them all by the deadline, he said.

The EPA is also boosting data visualizations to make it easier to share performance metrics related to pesticide decisions with industry and the public. For example, the agency has revised an application called MyPest, which allows pesticide registrants to monitor the progress of their submissions in real time. The data visualizations are among several process improvements aimed at accelerating the speed and enhancing the timeliness of pesticide reviews, Messina said.

Marc Lame, emeritus professor in the Paul H. O’Neill School of Public and Environmental Affairs at Indiana University noted at the PPDC meeting that the EPA’s remarks at the meeting left out goals related to environmental and health protection. Lame is a member of the PPDC. Absent from the EPA’s presentation was any mention of compliance, enforcement, technical assistance, or environmental stewardship programs, he said. Does this mean that the EPA is “just a permit shop at this point?” he asked. He also questioned whether the administration’s goal of cooperative federalism would transfer such responsibilities to state and local regulators.

The big priority of the EPA’s pesticides office is reforming the permitting process, Messina responded. But clean air, land, and water are also some of the administration’s top goals, he said. The pesticides office is committed to understanding the human health and environmental risks of pesticides, including whether they can disrupt the endocrine system or harm endangered species, he said.