Use of PFAS-tainted sludge as fertilizer raises cancer risk on farms, EPA says

Farm families that consume milk, eggs and beef they raise themselves face an increased risk of cancer if their fields were fertilized with PFAS-laced sewage sludge, the EPA reported this week.

The results do not suggest that the broader food supply is contaminated. The EPA identified risks for people consuming some animal products from their land, drinking well water and eating fish from polluted lakes. The draft study found an unacceptable cancer risk when two PFAS chemicals were present at low levels.

To those who have been tracking the sprawling pollution problems posed by PFAS chemicals, the findings were long overdue. The chemicals don’t break down in human bodies or the environment and have already been linked with some cancers and health risks. The EPA’s report relied on many prior studies that have shown the chemicals will migrate into soil and groundwater, and be absorbed into some plants, including pastures that cows graze.

“What’s surprising is it took [the EPA] so long to recognize it,” said Matt Simcik, a professor of environmental chemistry at the University of Minnesota.

Now, the question is whether the findings will push Minnesota toward tighter regulation of the use of biosolids — the sludge left behind after sewage treatment — as fertilizer.

The Minnesota Pollution Control Agency released a draft of its own biosolids proposal last October, modeled on similar measures in Michigan and Wisconsin. Utilities that produce the sludge would have to test it once a year before sending it to farm fields. Low levels would require no action. The highest concentrations would result in a ban on spreading the material.

The lowest category covers biosolids where PFOA and PFOS, the two most toxic PFAS chemicals, are found at under 19 parts per billion. That’s where most of the test results in Minnesota have landed so far, the MPCA said in a webinar last November, and in that case, the utility would not have to alert the land owner or farmer of the results.

The EPA report, however, found that cancer risk for farm families is elevated when those chemicals are in biosolids at just 1 part per billion — essentially, the limit of detection. The EPA found risks could exceed a 1-in-1000 chance of developing cancer.

“Our farmers should know what they’re spreading on their field, regardless of if it’s ... very minimal,” said Loren Dauer, public policy director for the Minnesota Farm Bureau Federation.

MPCA spokeswoman Becky Lentz wrote in an email that the agency will update its strategy with new information and that “the final strategy, which will be released soon, reflects feedback that PFAS levels should be communicated at all levels.”

Treating raw sewage with filters and bacteria leaves sludge that must be incinerated, sent to a landfill or spread on the ground. Most of the largest plants in Minnesota, like the Metropolitan Wastewater Treatment Plant in St. Paul, burn their sludge.

Of the 161,300 tons of sludge created across the state in 2018, 61% was burned and 19% was spread on farm fields, according to data reported by the MPCA. Smaller amounts were packaged and sold for domestic use, or sent to landfills.

Reusing the nutrient-rich material as fertilizer has long been promoted by the EPA, and the MPCA website encourages using the material “in a manner that protects human health and the environment.” The state has known since 2008 that spreading biosolids on land could lead to PFAS pollution, according to a report it released that year.

Some outstate communities, like Albert Lea, depend on sending their biosolids to local farmers. Steven Jahnke, director of public works, said the city’s wastewater plant was set up under this assumption, and 4 to 6 million gallons of material are sent to farms annually.

Finding an alternative way of disposing of the sludge would raise sewage rates for everybody on the system, he said, because they would have to truck it to an incinerator hours away, or to a landfill.

In 2023, Minnesota estimated that filtering out all that PFAS at the sewage plant would cost between $14 billion and $28 billion over two decades, an unmanageable sum. The MPCA has repeatedly said it is focusing on reducing the chemicals at the source, by banning it in products and investigating businesses that release it.

Perhaps the biggest unknown is whether some farm fields in Minnesota are already contaminated at high levels from repeatedly spreading sludge. Testing in Maine has turned up levels high enough that some farms have shut down entirely.

State researchers have been studying PFAS levels in soil and crops and are in the process of publishing the results in a peer-reviewed journal, Lentz said. But the MPCA is not proposing to test each farm field in Minnesota.

“I would think that for the landowner but also for the consumer, we need to know,” said Rep. Rick Hansen, DFL-South St. Paul, who supported the legislation that directed the MPCA to come up with a biosolids plan.

But others are more wary of the idea.

“We need to make sure that, if we go down the path of testing agricultural land, that we put safeguards in place to make sure that Minnesota farm families are protected” from being sued, said Darin Broton, executive director of the AgriGrowth Council.

The coalition represents individual farmers and agri-business giants like Cargill and CHS. Now, the council has concluded that “we should ban any biosolid with any detectable level of PFAS in it from being applied to ag land,” Broton said.

That’s what has essentially happened in Maine. But the landfill that now receives most of the state’s sludge is filling up, according to a state report.

Daniel Marx, an attorney and lobbyist with Flaherty & Hood who represents the Coalition of Greater Minnesota Cities, warned that an outright ban could raise costs. That includes farming operations and food manufacturers that send wastewater to city treatment plants outstate.

Marx said utilities largely supported the original strategy the MPCA proposed and worked with the agency to develop it. If all the material is sent to a landfill or incinerator instead, “You’re not reducing the risk, you’re just shifting the risk,” Marx said.

Sen. Aric Putnam, DFL-St. Cloud, said the state does need to warn farmers about the potential consequences of spreading biosolids repeatedly. But he was also uncertain about mandating testing.

“If you’re going to look for something, you need a strategy for what you do when you find it,” he said.