Because PFAS — the so-called "forever chemicals" — persist for extensive periods, they can continue to move through the environment. New research from the Great Lakes shows they travel through entire food webs, accumulating from algae and other small organisms to top predators and ultimately reaching people through what they eat.
What's happening?
To trace that movement, researchers at the University of Notre Dame compiled over four decades of previous studies and nearly 2,500 samples from algae, fish, birds, and other organisms, Grist reported.
Published this spring in the Journal of Environmental Quality, the meta-analysis found that PFAS levels generally increase with higher positions in the food chain.
As Grist reported, the researchers examined six PFAS compounds that are frequently measured. They found especially high levels in predators such as salmon and eagles, while algae and plants had the smallest concentrations, likely because of their short life cycles.
"What we're finding is that the food web itself is a vehicle for transferring these chemicals from one organism to another," Gary Lamberti, an aquatic science professor and co-author of the study, told Grist.
The study also pointed to an encouraging development. PFOS, one of the best-known PFAS, has declined sharply in the lower Great Lakes since industries began voluntarily phasing it out in the early 2000s, though similar declines have not been observed in the upper lakes.
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Why does it matter?
Across the United States, PFAS exposure is so common that measurable amounts are believed to be present in the blood of nearly everyone.
According to Grist, PFAS have been found in human blood, tissues, livers, kidneys, and lungs, and they are linked to serious health problems such as reduced fertility and cancer.
Exposure can happen through multiple pathways, but food is one of the most direct. If contaminated fish and wildlife carry high concentrations, that can affect what is considered safe for families to catch, cook, and eat.
Warnings about PFAS in fish have already led to consumption advisories in multiple states, including North Carolina, Wisconsin, Montana, and Pennsylvania. Michigan, which borders four of the Great Lakes, has tested fish for PFAS since 2012 and issues annual "safe fish" guidance, according to Grist.
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"If we can understand what the PFAS levels are in the food web, we can better communicate the risk of consuming those potentially toxic food sources," Katherine Manz, an environmental health professor at the University of Michigan who was not involved in the study, told Grist.
What's being done?
Researchers found that PFOS concentrations fell in Lake Erie and Lake Ontario after their use slowed.
Still, tracking and cleanup remain challenging. The upper Great Lakes hold water far longer — on the order of 60 to 170 years, versus about two to seven years for Lake Erie and Lake Ontario, according to Grist — than the lower lakes, which may explain why PFOS levels there have not declined as much.
Testing methods are improving as well. "It's like a chicken-and-an-egg situation," Vernon Lalone, CEO of Wave Lumina, a Michigan startup working on a rapid PFAS test for water and soil, told Grist. "You've got to have an analytical method that's robust and reliable enough to measure these things before you can regulate them at certain limits."
Lamberti offered a cautiously hopeful conclusion: "If we stop manufacturing these chemicals, they will eventually reduce in concentration in the food web. That's kind of good news for how we can manage these chemicals."
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