While Maine is leading the nation by setting limits for the chemicals and testing sludge to see if it meets them, local environmentalists fear that the state’s levels — 2.5 parts per billion for PFOA, 5.2 ppb for PFOS, and 1,900 ppb for PFBS — may not be stringent enough. “They’re probably about 10 times weaker than they should be,” said Mike Belliveau, executive director of the Environmental Health Strategy Center in Portland. “Even low parts-per-billion levels of PFAS in sludge can threaten the health of the food supply.”

In March, the state announced that it would temporarily halt the land application of sludge and begin the testing, after milk from a dairy farm in Arundel, Maine, was found to be contaminated with PFAS that had likely come from sludge that the farmers had spread on their land as fertilizer. These results, which have not yet been published or reported, are from the first round of testing. An additional 28 samples were collected but the results of their testing are not yet available.

All sewage sludge recently tested by the Maine Department of Environmental Protection was contaminated with PFAS chemicals, according to documents obtained by The Intercept. The state tested the sludge, solid waste that remains after the treatment of domestic and industrial water, for the presence of three “ forever chemicals ”: PFOA , PFOS, and PFBS . Of 44 samples taken from Maine farms and other facilities that distribute compost made from the sludge, all contained at least one of the PFAS chemicals. In all but two of the samples, the chemicals exceeded safety thresholds for sludge that Maine set early last year.

David Burns, director of the Bureau of Remediation and Waste Management at the Maine DEP, said that the state set the safety thresholds for sludge based on available toxicological information and that it chose those three chemicals because more is known about them than other PFAS. He said Maine will probably screen sludge for more compounds in the future.

Burns also said that, at farms where sludge has been found to have elevated PFAS levels, the state has authorized testing of the soil where it would be spread. If those tests “exceed a screening level, they’re prohibited from spreading the sludge on those sites,” he said. “But some sites have not exceeded the level so we’ve been able to authorize spreading.”

The evidence of widespread sludge contamination comes just days after a Food and Drug Administration study revealed that PFAS chemicals were also found in food. The investigation, which was conducted by FDA chemists but made public by the Environmental Defense Fund and the Environmental Working Group, detected 16 PFAS chemicals in food samples collected from grocery stores in the mid-Atlantic region. Among them were PFOS, which was in almost half of the meat and seafood products (ground turkey, tilapia, and shrimp had particularly high levels); PFBA, which was found in pineapple; and PFHxS in sweet potato. A slice of chocolate cake with icing was found to have extremely high levels of a chemical called PFPeA.

All PFAS chemicals persist indefinitely in the environment, and many have been shown to harm people. PFOA and PFOS, the two best-known in the class, have been linked to developmental, reproductive, and immune effects, as well as cancers, thyroid disease, and obesity — among other health problems. PFBS, which 3M introduced in 2003 as a replacement for PFOS, also accumulates in the blood and livers of rats, according to a report the company sent to the Environmental Protection Agency in 2008. Another adverse incident report from 3M showed that PFBS affects the livers of mice, as well as their cholesterol and fat levels. And according to a 2015 report from the Danish Environmental Protection Agency, PFBS affects both placental cells and neurodevelopment, and has been found in particularly high levels in children with asthma.

While the FDA says it is “working to better understand the potential dietary exposure to PFAS,” researchers have already clearly shown that vegetables can absorb PFAS chemicals from the soil into their leaves. And the EPA has noted that diet is likely the primary source of human exposure to PFOS.

Indeed, though the EPA has failed to set PFAS standards for sludge, the agency has long been aware of the problem. As The Intercept reported in 2015, the agency knew back in 2009 that sludge from a wastewater treatment facility in Decatur, Alabama, contained PFOA and PFOS. From there, the toxic sludge made its way to nearby fields and, for 12 years, had been spread across 5,000 acres of local grazing land. Later testing confirmed that the chemicals had contaminated animals and humans in the rural area.