A new analysis of more than four decades of Great Lakes data has mapped how PFAS, the long-lasting industrial compounds known as “forever chemicals,” accumulate through aquatic food webs and reach the fish that people catch and eat. The study, from the University of Notre Dame, was published this spring in the Journal of Environmental Quality.
Researchers synthesized 50 earlier studies containing roughly 2,500 biological measurements to track PFAS across species over a 42-year period, according to Notre Dame. The team said it focused on organisms rather than water or sediment, examining everything from algae and microbes up to top predators such as salmon and bald eagles.
“What we’re finding is that the food web itself is a vehicle for transferring these chemicals from one organism to another,” Gary Lamberti, a Notre Dame aquatic science professor emeritus and a study co-author, told Grist. “So it’s a more holistic view than we’ve known before.”
PFAS, or per- and polyfluoroalkyl substances, resist breaking down because their carbon-fluorine bonds are among the strongest in chemistry, Notre Dame said. As a result, the compounds build up in soil and water, and when algae absorb them the chemicals pass to the insects and fish that feed on them. The concentration rises at each step of the food chain and peaks in top predators, a process called biomagnification. Grist reported that algae and plants carried the lowest concentrations because they grow and die quickly, while predators had the highest.
Different lakes, different trends
The researchers examined six of the most commonly detected PFAS compounds, though the National Institutes of Health counts nearly 15,000 types. One compound, perfluorooctanesulfonic acid, or PFOS, was phased out of production between 2000 and 2002 and declined across the study period, Notre Dame said.
The declines were concentrated in the lower lakes, Erie and Ontario, which Grist reported are likely home to the heavy industries that used the chemicals. The team found little to no decline of PFOS in the larger upper lakes, Superior, Michigan and Huron. Notre Dame said the lowest contamination levels appeared in Lake Superior and the highest in Lake Ontario, a pattern Lamberti attributed to population and manufacturing density as well as the greater size and depth of the upper lakes.
The lakes also hold their water, and their contaminants, for very different lengths of time. Notre Dame said the average time a drop of water spends in a lake ranges from less than three years in Lake Erie to about 200 years in Lake Superior. “Unfortunately, the Great Lakes hold onto their water and contaminants for a very long time, meaning that there’s ample time for toxins to be taken up by the biota,” Lamberti said.
Lead author Peter Martin, a 2024 Notre Dame graduate now pursuing a doctorate at Michigan State University, began the work as a junior and used it for his senior honors thesis, the university said. “Each lake had its own specific temporal pattern,” Martin said. Co-principal investigator Daniele De Almeida Miranda added that biomagnification is not linear, noting that a bird eating a fish carries a different PFAS load than a fish because birds do not exchange the chemicals with water.
A public health question for a region
PFAS have been detected in human tissue, including blood, liver, kidneys and lungs, and the CDC reports that nearly all people in the United States likely have measurable levels in their blood. The National Institute of Environmental Health Sciences links the chemicals to health effects ranging from decreased fertility to certain cancers, and says diet is one route of exposure.
PFAS levels in fish have prompted consumption advisories in several states. Michigan, which borders four of the five Great Lakes, has tested fish for PFAS since 2012 and issues annual “safe fish” guidance. The NOAA reports that more than 30 million people rely on the Great Lakes for drinking water.
Katherine Manz, an environmental health professor at the University of Michigan who was not involved in the study, told Grist that understanding PFAS levels in the food web can improve how officials communicate risk. There is no national ban on PFAS, though a patchwork of federal rules restricts certain compounds and some manufacturers have voluntarily phased out others. Lamberti said more compounds continue to be developed that go untested for toxicity, and that a phased-out chemical such as PFOS “is still there, and will be around for decades.”
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