For the first time, the Environmental Protection Agency on Tuesday warned that “forever chemicals” present in sewage sludge that is used as fertilizer can pose human health risks.

In an extensive study, the agency said that while the general food supply isn’t threatened, the risk from contaminated fertilizer could in some cases exceed the EPA’s safety thresholds “sometimes by several orders of magnitude.”

A growing body of research has shown that the sludge can be contaminated with synthetic chemicals known as per- and polyfluoroalkyl substances, or PFAS, which are used widely in everyday items like nonstick cookware and stain-resistant carpets. The chemicals, which are linked to a range of illnesses including an increased risk of cancer, do not break down in the environment, and, when tainted sludge is used as fertilizer on farmland, can contaminate the soil, groundwater, crops and livestock.

The EPA has for decades encouraged the use of sludge from treated wastewater as inexpensive fertilizer with no limits on how much PFAS it can contain. But the agency’s new draft risk assessment sets a potential new course. If finalized, it could mark what could be the first step toward regulating PFAS in the sludge used as fertilizer, which the industry calls biosolids. The agency currently regulates certain heavy metals and pathogens in sewage sludge used as fertilizer, but not PFAS.

The Biden administration has tackled PFAS contamination elsewhere, setting limits on PFAS in drinking water for the first time and designating two kinds of PFAS as hazardous under the nation’s Superfund cleanup law. Those rules came after the agency said in 2023 that there is no safe level of exposure to those two PFAS.

The EPA’s risk study comes as farmers across the country have been discovering PFAS on their land.

In Maine, the first and only state that is systematically testing its farmland for PFAS, dozens of dairy farms have been found to be contaminated. In Texas, a group of ranchers sued the provider of sludge fertilizer last year after a neighboring farm used the fertilizer on its fields. County investigators found several types of PFAS in the ranchers’ soil, water, crops and livestock, and the ranchers have since sued the EPA, accusing the agency of failing to regulate PFAS in biosolids. In Michigan, state officials shut down a farm where tests found particularly high concentrations in the soil and in cattle that grazed on the land.

The EPA hasn’t changed its policy of promoting sludge fertilizer, which has benefits along with the risks. It is rich in nutrients, and spreading it on fields cuts down on the need to incinerate it or put it in landfills, which would have other environmental costs.

The agency said in its new assessment that at farms that used contaminated sludge, the highest human risks involved drinking milk from pasture-raised cows raised on a contaminated farm, from drinking contaminated water, from eating eggs from pasture-raised hens or beef from cattle raised on contaminated land, or from eating fish from lakes and ponds contaminated with runoff.