Three organizations are suing to overturn the federal government’s approval of the herbicide trifludimoxazin based on concerns that using the substance on farms threatens human and environmental health.
The US Environmental Protection Agency disputes those claims, countering that its scientists conducted a robust review and determined that the herbicide doesn’t present any unreasonable danger.
The Center for Food Safety, Center for Biological Diversity, and Pesticide Action & Agroecology Network North America have asked that the 9th US Circuit Court of Appeals review the EPA’s decision earlier this year to register trifludimoxazin for agricultural uses. The groups said in a press release that the herbicide breaks down into perfluoroalkyl and polyfluoroalkyl substances (PFAS), byproducts that are known as “forever chemicals” due to their resilience.
The nonprofit organizations also said that trifludimoxazin is likely a carcinogen in humans yet the agency neglected to assess the cancer risk to farmworkers who handle the pesticide or people who consume contaminated food or water.
EPA officials announced last year that the firm BASF was seeking registration of a menu of trifludimoxazine-containing products that would be used to control broad leaf weeds and grasses and the agency was seeking public comments on the proposal. The agency said at the time that risk assessments had not raised any concerns about effects on human or animal health, although the substance posed potential risks for plants downstream or in surrounding environments.
EPA officials said in a June 30 memorandum in support of trifludimoxazin registration that the agency’s Cancer Assessment Review Committee had determined that the herbicide has “suggestive evidence of carcinogenic potential,” although the agency’s full analysis found no dietary or aggregate risks of concern for human health. It also had not identified any concerning risks of harming animals through acute or chronic exposure, although the herbicide does present risks for plants as well as chronic exposure risks for bees and other invertebrates that forage on fields that are treated with trifludimoxazin-saflufenacil combination products.
Bill Freese, science director for the Center for Food Safety, said by email that trifludimoxazin has been connected with thyroid and liver tumors in rodent studies, and the EPA should have conducted an extensive cancer risk assessment. He said that it also has been connected with birth defects and reproductive harm in other animal studies.
In addition, Freese said that trifludimoxazin spray is likely to worsen conditions in already degraded natural environments near US farm fields, especially when it is disbursed by airplane. He noted that field runoff is another concern due to the herbicide’s toxicity to aquatic plants and fish downstream.
The EPA responded with a statement that it reviews each proposed pesticide for toxicity, environmental effects, bioaccumulation potential, endangered species impacts, and risk of effects on children and developing fetuses, and it only approves registration when agency scientists conclude that the substance “will not cause unreasonable adverse effects on human health or the environment.” The analysis includes examination of the concentrations of byproducts that people are likely to be exposed to as the substances degrade.
In the provided statement, the EPA also disputed some of the language used to describe trifludimoxazin. It said that calling the herbicide a “forever chemical” is unscientific and noted that trifludimoxazin falls outside of the agency’s definition of PFAS substances. Freese noted, though, that trifludimoxazin fits the Organization for Economic Cooperation and Development’s broader definition of a PFAS.
As for the lasting effects of product use, Freese said that trifludimoxazin degrades into byproducts that may persist in environments for hundreds of days to years and very little is known about their effects. Data on the toxicity of those degradation products is needed to determine whether a substance is hazardous.
BASF had registered trifludimoxazin with the EPA in May 2021, but the company withdrew its registrations in response to a lawsuit against the EPA on allegations that the agency failed to comply with requirements to assess the expected effects of the product on endangered species, the EPA said in its June 30 memo. The company included in its updated application mitigations to reduce unintended impacts, including limiting the product to agricultural uses, prohibiting distribution by aircraft onto peanuts and tree crops, setting a lower cap on application rates for many crops, and prohibiting use in Alaska, Hawaii, and US territories.
The EPA said that the mitigations to reduce runoff and spray drift will help to prevent harm to endangered species and critical habitats.
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