WASHINGTON— Center for Food Safety, the Center for Biological Diversity, and Pesticide Action & Agroecology Network North America have sued the Trump administration over the registration of trifludimoxazin, a potent PFAS pesticide that breaks down into long-lived, PFAS byproducts.

PFAS, or perfluoroalkyl and polyfluoroalkyl substances, are a class of chemicals characterized by ultra-strong carbon-fluorine bonds that are highly resistant to break down. Trifludimoxazin takes years to decades to break down. The groups’ lawsuit was filed Friday in the 9th U.S. Circuit Court of Appeals.

The Environmental Protection Agency has approved the use of trifludimoxazin on many crops, including corn, wheat, oats, soybeans, oranges, apples, peanuts and almonds, despite acknowledging the chemical’s potential harms to wildlife and human health.

“Trifludimoxazin is a likely human carcinogen that belongs to a family of weedkillers that also causes reproductive harm, birth defects and neurological deficits in animal studies,” said Bill Freese, science director at Center for Food Safety. “As if the health threats weren’t enough, this incredibly potent herbicide can drift to stunt crops and wild plants hundreds of yards from a sprayed field, while runoff threatens wetland plants. Potent biocides like this have no business on the American landscape.”

The EPA acknowledges that trifludimoxazin causes thyroid tumors in rodent studies but did not assess the cancer risk to farmworkers who use the pesticide or to people exposed to trifludimoxazin-contaminated food or water.

Spray drift is likely to result in widespread harm to native plants and crops grown for food. Trifludimoxazin is 10 times more toxic to plants than dicamba, the herbicide whose rampant drift and runoff has caused unprecedented damage across many millions of acres of crops since 2017.

“While everyone’s distracted by the Trump administration’s erratic actions on the world stage, it keeps approving dangerous forever pesticides right here on our own soil,” said Nathan Donley, environmental health science director at the Center for Biological Diversity. “It’s unconscionable, immoral and illegal. Our kids and grandkids deserve better than to be saddled with pollution that never goes away.”

“Continuing to register new herbicides like trifludimoxazin keeps farmers on the pesticide treadmill and perpetuates the problem of herbicide resistance in weeds,” said Emily Marquez, Ph.D, staff scientist with Petitioner Pesticide Action & Agroecology Network North America. “The potential for PFAS pesticides to contaminate water and soil wherever they are used is highly concerning for the health and livelihoods of people in farming communities.”

Trifludimoxazin is one of many currently registered herbicides that kill plants by shutting down an enzyme (protoporpyhyrinogen oxidase, or PPO) that is also present in people. Even though animal research demonstrates these “PPO inhibitors” have common adverse effects on the liver and cause birth defects in fetuses exposed in utero, the EPA has refused to conduct a cumulative risk assessment of trifludimoxazin and other PPO inhibitors as required by law. This is especially concerning because two of the products approved by the EPA contain trifludimoxazin combined with saflufenacil, a second PPO inhibitor, meaning simultaneous exposure to both for workers.

Background

Trifludimoxazin was originally approved by the EPA in 2021 for nationwide use on corn, soy, fruit and nut crops. Center for Food Safety and the Center for Biological Diversity sued, saying this approval violated the federal Insecticide, Fungicide, and Rodenticide Act and the Endangered Species Act. That lawsuit noted the EPA’s finding that the herbicide had the potential to cause cancer, and that it would “likely cause severe harm" to many threatened and endangered fish, including endangered populations of Chinook salmon and steelhead trout, Atlantic sturgeon and smalltooth sawfish.

In response to the lawsuit, the pesticide company voluntarily agreed to stop the manufacture and sale of the pesticide in 2022. Despite these harms, Trump’s EPA proposed registering trifludimoxazin again for widespread use in 2025 and issued the approval in June 2026. Trifludimoxazin is the fifth PFAS pesticide approved under the second Trump administration.