Farmworker advocates, environmental organizations and public health groups have taken the U.S. Environmental Protection Agency to court over its approval of a new pesticide containing per- and polyfluoroalkyl substances (PFAS), arguing the regulator failed to follow its own cancer risk assessment standards and underestimated potential threats to human health.
On December 30, 2025, Farmworker Justice, Pesticide Action & Agroecology Network North America, and the Center for Food Safety filed a legal challenge in the Ninth Circuit Court of Appeals, seeking to overturn the EPA’s approval of five pesticide products containing the fungicide cyclobutrifluram.
The contested approvals, granted by the Environmental Protection Agency on November 3, 2025, allow cyclobutrifluram to be used on romaine lettuce, as a seed treatment for cotton and soybeans, and across a range of non-food applications, including turfgrass on lawns, sports fields and parks, as well as ornamental plants such as Christmas trees.
Cyclobutrifluram belongs to the PFAS class of chemicals, often referred to as “forever chemicals” due to their resistance to environmental breakdown. According to the groups, the fungicide can persist in soil for years, migrate into surface water and groundwater, and ultimately contaminate drinking water supplies. They also argue that EPA lacks sufficient data on the toxicity of the chemical’s breakdown products.
The court filing points to evidence from long-term animal studies showing that cyclobutrifluram induced tumors in rodents, including liver cancer in male mice and thyroid tumors—both malignant and benign—in male and female rats. While animal testing is a standard method for evaluating potential cancer risks of pesticides, the petitioners say the EPA improperly discounted these findings.
The thyroid gland plays a critical role in regulating metabolism, brain development and fertility, and disruptions to the endocrine system have been linked to birth defects, reproductive harm and certain cancers, particularly among farmworkers and others with high levels of exposure to agricultural chemicals.
In their petition, the organizations argue that the EPA violated its own Guidelines for Carcinogen Risk Assessment by dismissing what they describe as clear evidence of carcinogenicity and by failing to evaluate cumulative risks from exposure to cyclobutrifluram alongside other similar pesticides. They are asking the court to rule that the approval violates the Federal Insecticide, Fungicide, and Rodenticide Act and to order the agency to reverse its decision.
“EPA has a duty to protect people from dangerous pesticides and it is disgraceful for the EPA to expose farmworkers and farming communities to a new pesticide without fully assessing the risks to human health,” said Lori Johnson, Legal Director of Farmworker Justice.
The groups say their concerns were raised repeatedly during the regulatory review process but were largely dismissed. They argue the EPA minimized certain risks, such as the fungicide’s potential to cause cancer, while ignoring others altogether, including the cumulative impact of multiple pesticide exposures.
Amy van Saun, senior attorney with Center for Food Safety and counsel for the petitioners, said: “Our federal agencies are not above our laws, and federal law does not allow EPA to ignore its own guidelines for assessing the cancer risk of pesticides. Yet here EPA did so again when approving this new PFAS fungicide cyclobutrifluram: EPA cannot abdicate its responsibility to protect people who work around these toxins and our children from cancer-causing or endocrine-disrupting pesticides.”
Concerns also extend beyond agricultural workers to the general public. Because cyclobutrifluram is approved for use on lawns, parks and sports fields, the groups warn that children could face additional exposure while playing on treated surfaces.
“We need farming communities and kids everywhere to be protected from cancer-causing pesticides,” said Allison Davis, Executive Director of Pesticide Action & Agroecology Network. “EPA should be considering the cumulative risks of exposure to pesticides, especially in frontline communities that face the brunt of pesticide exposures.”
The legal challenge highlights broader scientific concerns about fungicides that inhibit succinate dehydrogenase (SDH), an enzyme present not only in fungi and nematodes but also in humans. Researchers have warned that SDH-inhibiting fungicides may be linked to tumor development, particularly thyroid tumors.
Despite these concerns, the EPA concluded that cyclobutrifluram is “not likely to be carcinogenic to humans,” a determination the petitioners say allowed the agency to avoid assessing multiple routes of human exposure, especially those affecting farmworkers.
The case now places the EPA’s pesticide approval process under renewed scrutiny, as the court considers whether the agency met its legal obligations to fully evaluate health risks before allowing a new PFAS-based pesticide onto the market.
