Study: Freshwater fish contain concerning levels of ‘forever chemical’

A large catch of smelt.
Captured smelt inside a cooler in May 2022 on Park Point on the shore of Lake Superior in Duluth. The annual tradition, that sees people wading into the lake at night with big nets to gather the smelt, shows no signs of abating even though Minnesota, Wisconsin and Michigan have placed advisories on eating smelt because of PFAS pollution.
Derek Montgomery for MPR News

A new study has found that eating locally-caught freshwater fish could expose people to concerning levels of a “forever chemical” known as PFOS.

The study, published in the journal Environmental Research, raises concerns about the risk to humans of ingesting the chemicals through food consumption. 

PFOS is perfluorooctane sulfonic acid, a synthetic chemical that’s part of a large class of compounds known as PFAS. They’re very durable, and don’t break down easily in the environment.

The researchers analyzed data from more than 500 samples of fish fillets collected from 2013 to 2015 by the U.S. Environmental Protection Agency.

Grow the Future of Public Media

MPR News is supported by Members. Gifts from individuals power everything you find here. Make a gift of any amount today to become a Member!

The researchers found fish with detectable levels of PFAS in all 48 continental U.S. states. 

“It wasn’t just in areas near industrial sources that we might expect to see contamination in nearby wildlife, but it was also in areas that were away from those sources,” said Tasha Stoiber, a senior scientist with the Environmental Working Group, which authored the study and advocates for stricter regulation of PFAS.

Phased-out PFOS most found

PFOS was the forever chemical found most often. It was manufactured for decades, including by Minnesota-based 3M, to make consumer products resistant to stains and grease, including Scotchgard. 

PFOS was phased out of production in the U.S. two decades ago, but has been found in the environment, soil, fish and wildlife. Exposure to the chemicals has been linked to negative human health impacts including high cholesterol, reduced immune response and thyroid problems.

The EWG researchers calculated that eating one fish a year was equal to ingesting water with PFOS at 48 parts per trillion for a month. That’s much higher than what the Minnesota Department of Health considers a safe level for drinking water.

“What's striking is that it doesn't take much exposure,” Stoiber said. “Even eating fish a couple of times a year could affect PFAS in your body.”

Minnesota’s health-based advisory levels for PFOS are 15 parts per trillion. That’s lower than the federal limit of 70 parts per trillion.

But due to growing concerns about the health impacts, last year the U.S. EPA recommended that the level of PFOS allowed in drinking water be lowered to 0.02 parts per trillion. The agency is expected to propose national drinking water regulations for certain PFAS soon.

The Minnesota Department of Health has issued fish consumption advisories for several Minnesota lakes because of PFOS levels. They include Bde Maka Ska, Lake Elmo and Lake Harriet in the Twin Cities metro.

In a statement, the health department said it has long worked with the state Pollution Control Agency and the Department of Natural Resources to analyze the amount of chemicals, including PFAS, in fish caught in the state’s waters.

“Fish are an important source of economical nutrition for many Minnesotans, but the amount of fish one eats should be balanced with the risks of eating fish that may be contaminated with harmful chemicals,” it stated.

The amount of contaminants in fish can vary greatly depending on the type and size of fish and where it’s caught, the health department said.

The department said it hasn’t had time to review the data or methods used in the report. But it said people are exposed to contaminants in fish in different ways than they are exposed to contaminants in drinking water, so comparing the two “is not scientifically sound.”

Stoiber said while there’s been a lot of attention paid to the health impacts to humans from drinking water containing PFAS, the study suggests that food also could be a key method of exposure to the chemicals.

In 2021, the Minnesota Legislature banned the use of PFAS in food packaging by next year.

Environmental justice concerns

Stoiber said the findings also raise environmental justice concerns for communities who depend on eating fish they catch in local rivers and lakes.

“There (are) certain populations and communities that are high frequency fish consumers, and this kind of exposure is going to impact them the most,” Stoiber said.

The researchers found median amounts of PFAS in freshwater fish were hundreds of times higher than the levels detected in commercially caught fish, she said

Stoiber said she knows the study’s findings will be difficult for people to hear, especially those who enjoy freshwater fishing and eating their catch. But she said the research highlights the need for national guidance on fish consumption.

“This is a consequence of the decades of unregulated use of these chemicals,” she said.