The U.S. Environmental Protection Agency has finalised registrations for three new pesticide active ingredients — epyrifenacil, diflufenican and trifludimoxazin — covering corn, soybeans, wheat, canola, peanuts and citrus, the agency confirmed.

The approvals give U.S. growers additional chemistry for herbicide-resistant weeds, including Palmer amaranth. They also reopen a regulatory argument: whether any of the three compounds should be classified as PFAS, the so-called "forever chemicals."

"Farmers are dedicated to caring for our land and natural resources, so new tools that help us do that are important," said American Farm Bureau Federation President Zippy Duvall, who also welcomed EPA Administrator Lee Zeldin's pledge of comprehensive vetting on new pesticide reviews.

"Pesticides undergo years of rigorous testing, with very few making it through the approval process," Duvall said. "These new products, backed by the best available science, will enable farmers to do more with less."

What did EPA approve?

Each active ingredient targets a defined set of crops:

• Epyrifenacil — canola, field corn, soybeans and wheat
• Diflufenican — corn and soybeans
• Trifludimoxazin — citrus, corn, peanuts, soybeans and other crops

EPA said the three products help farmers control economically damaging, herbicide-resistant weeds such as Palmer amaranth while supporting regenerative, soil-health practices such as no-till. The agency describes no-till as an alternative to intensive tillage that would otherwise increase runoff and erosion.

Why are the registrations being challenged on PFAS?

The controversy stems from differing definitions of what counts as a PFAS chemical under U.S. and international frameworks.

Environmental groups argue the compounds should be classified as per- and polyfluoroalkyl substances. Their reasoning rests on a broader Organisation for Economic Co-operation and Development definition of PFAS as chemicals containing carbon-fluorine bonds.

"They're all breaking down into things that are going to stick around forever," said Nathan Donley, environmental health science director at the Center for Biological Diversity.

EPA disagrees. The agency's office of pollution prevention and toxics finalised its PFAS definition in 2023, after a public rulemaking. That rule sets the threshold at two or more fluorinated carbons, deliberately excluding single-fluorinated-carbon molecules from the regulatory PFAS category.

The new products are each single-fluorinated-carbon compounds, the agency noted. By EPA's own definition, they do not fall within PFAS.

What did the risk assessment cover?

Before registration, EPA evaluated each active ingredient for human health and environmental risks. The agency concluded the products "do not pose unreasonable risks to human health or the environment."

For trifludimoxazin, EPA recorded "suggestive evidence" of carcinogenic potential based on animal studies, with additional rat findings on thyroid and liver effects. Label use restrictions, the agency concluded, are sufficient to protect human health.

Epyrifenacil produced liver and blood effects in animal testing. EPA set the dietary limit on the epyrifenacil label roughly 1,800 times lower than the doses at which any TFA-related effect could occur.

TFA, or trifluoroacetic acid, is a breakdown product that EPA included in its review alongside the parent compounds.

What should farmers and agronomists watch next?

State-level pesticide registrations and product label clearances now determine when each active ingredient reaches retailers. Growers planning future weed-control programmes should confirm label status with their state department of agriculture and seek in-field trial data on Palmer amaranth and waterhemp control before full-scale adoption.