In the United States, PFAS chemicals are so ubiquitous — found in everything from frying pans to skincare — that nearly all of the country’s population likely has measurable levels of the so-called ‘forever chemicals’ in their blood. It’s only in the last few decades that the public and scientists started untangling the health and ecological risks associated with some of the manufactured compounds, which earned their nickname because they don’t break down easily in the environment. Now, new research from the University of Notre Dame has deepened our understanding of how PFAS can filter through ecosystems and move up the food chain to get to people. The peer-reviewed study, published this spring in the Journal of Environmental Quality, focused on the Great Lakes. The researchers analyzed 42 years of studies and combined nearly 2,500 samples of algae, fish, birds, and other organisms, in what’s called a meta-analysis to identify trends in PFAS distribution. PFAS have been linked to a range of health issues, and the chemicals have been identified in human tissue, including in the bloodstream, liver, kidneys, and lungs. Known health risks range from decreased fertility to a higher prevalence of certain cancers. People can be exposed to PFAS in several ways, including through the food they eat. ‘What we’re finding is that the food web itself is a vehicle for transferring these chemicals from one organism to another,’ said Gary Lamberti, aquatic science professor at Notre Dame and a study co-author. ‘So it’s a more holistic view than we’ve known before.’ The Great Lakes study focused on six of the PFAS chemicals most commonly tested for, but there are more than 15,000 types out there, according to the National Institutes of Health. Researchers identified a dramatic decrease over the last two decades of one PFAS chemical known as PFOS, following a voluntary phaseout by industries in the early 2000s. ‘If we stop manufacturing these chemicals, they will eventually reduce in concentration in the food web,’ Lamberti said. ‘That’s kind of good news for how we can manage these chemicals.’ Those declines were seen in the lower Great Lakes — Ontario and Erie — likely because these areas are home to the heavy industries that used the chemicals. But there was little to no decline in PFOS in the upper lakes Superior, Michigan, and Huron, most likely because the water bodies are larger than the lower lakes. In contrast to the shallower Erie and Ontario lakes, which flush out their water about every 2 to 7 years, water can stay in the upper lakes anywhere from about 60 to 170 years. The study also confirmed that these chemicals increase in concentration as they travel up the food chain. Algae and plants have the lowest concentration, according to the study, because they grow and die quickly. But predators like salmon and eagles had the highest concentration because they’re eating a large amount of prey that have a lot of accumulated PFAS. Read Next Trump’s EPA vows to fight ‘forever chemicals’ — by loosening regulations Zoya Teirstein Potentially dangerous levels of these chemicals in fish have prompted warnings by state officials across the country on how much is safe to eat, including in North Carolina, Wisconsin, Montana, and Pennsylvania. Michigan, which borders 4 of the 6 Great Lakes, has been testing fish for PFAS since 2012 and issues ‘safe fish’ guidelines annually. ‘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,’ said Katherine Manz, an environmental health professor at the University of Michigan who was not involved in the study. While it was easy to find PFAS data on salmon, trout, and some birds, Lamberti said, the information on the ‘less glamorous’ smaller fish, invertebrates, and algae was harder to come by. Tools to analyze the range of these chemicals are still evolving, said Vernon Lalone, CEO of Wave Lumina, a Michigan-based startup that’s developing a rapid testing kit for PFAS in water and soil. ‘It’s like a chicken-and-an-egg situation,’ said Lalone, who wasn’t involved in the study. ‘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 said there’s still plenty of questions about how these chemicals will shift in waterways as temperatures rise due to climate change, ice formation shifts, and as industries introduce new chemicals. But he’s optimistic — his study shows that when forever chemicals are removed from production, food webs eventually cycle them out. There is no national ban on PFAS, but a patchwork of federal regulations restricts certain chemicals, and some manufacturers have phased out other PFAS compounds voluntarily. ‘That’s what we need to be thinking about with these chemicals,’ Lamberti said, ‘how we’re going to remove them from the production and find substitutes for them to do the right thing.’ This story was originally published by Grist with the headline New research traces how ‘forever chemicals’ move through the Great Lakes and into people on Jul 6, 2026.