Study shows PFAS levels dropping in Great Lakes fish
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A recent study conducted by researchers at the U.S. Environmental Protection Agency lab in Duluth found that PFAS chemicals – often known as “forever chemicals” because they don’t break down in the environment – have steadily declined in Great Lakes fish over the past two decades.
It’s a rare bit of good news in the fight against the growing problem of PFAS contamination, which has been found in lakes and rivers around Minnesota and has seeped into some drinking water systems. Epidemiological studies have shown that PFAS exposure in humans can weaken immunity and increase the risk for certain types of cancer, kidney and liver disease, and birth defects.
"It's great news for people who are catching fish in the Great Lakes, or who care about the health of the Great Lakes,” said lead author Sarah Balgooyen, a former research chemist at the Duluth lab who’s now at the Colorado School of Mines. “We know these fish are safer to eat than they were even 10 years ago."
Companies have manufactured per- and polyfluoroalkyl substances, known as PFAS chemicals, since the 1930s and 40s. They’re used in a wide range of consumer products, from carpet and cosmetics to clothing and cookware, and were key ingredients in famous brand names such as Teflon and Gore-Tex. They were prized for their ability to repel water and resist heat.
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Monitoring for the chemicals in the environment didn’t start until the late 1990s, when scientists began to realize that the chemicals could be harmful to humans and the environment.
But researchers at the U.S. Environmental Protection Agency lab in Duluth devised a way to essentially go back in time, to measure PFAS accumulations in fish going back to the 1970s.
They were able to do that because the EPA has collected samples of lake trout and walleye from all five Great Lakes for more than 50 years. They collected them initially to measure levels of contaminants like PCBs, DDT and mercury. PFAS was not even on their radar at the time.
The scientists tested the frozen samples, and found that PFAS concentrations in the fish steadily increased until the early 2000s. But between 2008 and 2012 they began to sharply drop. The study is published in the Journal of Great Lakes Research.
That decline began after many industries began phasing out the use of some of the PFAS chemicals, particularly those known as “long-chain” PFAS, which persist longer in the environment. For example, one of the most widely used chemicals, PFOS, was phased out by 3M between 2000 and 2002.
PFOA, used in products ranging from Teflon cookware to stain-resistant carpets and firefighting foam, was gradually phased out beginning in 2006.
“So really what we’re seeing is these lakes readily responding to those changes in industry,” explained Balgooyen.
She said the findings aren’t totally unexpected. Studies have shown that PFAS levels in human blood have also been decreasing as their presence in consumer products drops.
But PFAS isn’t going away. Rather, they’re getting flushed through the Great Lakes and the St. Lawrence Seaway into the oceans, which Balgooyen calls “that final sink of aqueous contamination.”
Researchers also caution that even reduced levels of PFAS in fish can still be harmful to human health.
The Minnesota Department of Health recommends limiting fish consumption in more than 50 lakes and rivers around the state because of PFAS contamination in fish. That includes a recommendation to not eat more than one serving per week of rainbow smelt from Lake Superior.
“We don't know exactly what levels are safe,” said Gary Ankley, one of the study’s co-authors who retired last year as a toxicologist at the Duluth EPA lab after 37 years, in the midst of the Trump administration’s steep budget cuts to the agency. He’s now an adjunct professor at the University of Minnesota Duluth.
“Research is still ongoing,” added Ankley. “It’s encouraging that they have decreased over time. But it's very much an open-ended story at this point, and in terms of saying whether the levels that are out there now are going to be problematic in terms of human health or ecological effects, we're still not entirely certain about that.”
Ankley said it’s also unclear whether PFAS levels in Great Lakes fish will continue to go down, or whether they’ll plateau at a certain level and remain in and contaminate the water for decades to come. “No one knows where we are on that decline curve,” he said.
They are, after all, nicknamed “forever chemicals” because they don’t break down quickly and remain in the environment for such a long period of time.
