People who eat just one U.S. freshwater fish a year are likely to show a significant increase of a cancer-causing chemical in their bloodstream, new research warns.
An analysis of U.S. government data derived from more than 500 fish samples revealed that the majority of fish living in streams, rivers and lakes across the country are contaminated with per- and poly-fluoroalkyl substances (PFAS) at levels almost 300 times higher than found in fish from other sources, including ocean and farmed fish, according to the paper published recently in the journal Environmental Research.
Importantly, perfluorooctanesulfonic acid (PFOS), a type of PFAS known to be particularly harmful, was the largest contributor to total PFAS levels found in freshwater fish samples, averaging 74% of the total, according to the study.
The U.S. Environmental Protection Agency (EPA) considers PFOS specifically to be a hazardous substance that “may present a substantial danger to human health” due to its links to cancer and effects on reproductive, developmental, and cardiovascular health, and warns that the chemical “may present a substantial danger to human health.” Other PFAS have also been linked to cancer, immune deficiencies, thyroid disease, and other health problems.
The research found that eating one serving of fish at the median PFOS contamination level was equivalent to consuming one month’s worth of drinking water contaminated at 2,400 times the recommended health advisory limit set by the EPA. The study determined that “even occasional consumption” of wild, freshwater fish would likely be a significant source of exposure.
Freshwater fish represent an important U.S. food source, especially for people living on a low income. About 660,000 people in the U.S. eat fish they catch themselves three or more times per week.
“Consuming a single freshwater fish could measurably increase PFAS levels in your body,” said David Andrews, a senior scientist at the Environmental Working Group (EWG) and one of the authors of the paper. “These fish are incredibly contaminated.”
Many studies have shown that PFAS chemicals are pervasive in the environment and the new analysis underscores the growing understanding that humans and animals have little avenue for escaping contamination. The research paper found that fish from all 48 contiguous U.S. states showed PFAS contamination, and only one of the samples did not contain any detectable PFAS.
The study also found higher levels of PFAS among fish from the Great Lakes as compared to water bodies elsewhere, indicating that the Great Lakes are particularly vulnerable to contamination. According to Andrews, this could be because the water in the Great Lakes empties into the ocean much more slowly than other water bodies, aiding the accumulation of PFAS.
Heidi Pickard, a PhD candidate at Harvard University who studies PFAS in aquatic ecosystems and was not involved in the new study, said the results are likely an underestimate of the actual contamination present in fish, given the lack of ability to test for all of the thousands of PFAS chemicals and PFAS precursors — chemicals that break down to form PFAS once they enter the environment.
“We’re only starting to be able to measure and quantify [other PFAS compounds],” she said.
A Ubiquitous Pollutant
PFAS are also often referred to as “forever chemicals” because they do not break down in the environment and bioaccumulate, persisting in the bodies of humans and animals. There are more than 4,000 man-made PFAS compounds used by a variety of industries for such things as electronics manufacturing, oil recovery, paints, fire-fighting foams, cleaning products and non-stick cookware.
According to one nationwide study, 97% of Americans have detectable levels of PFAS in their blood, and the chemical is a ubiquitous pollutant in water and soil across the country.
The Biden Administration is implementing a series of steps to try to restrict PFAS from contaminating water, air, land, and food as well as to clean up PFAS pollution and speed up research on other PFAS issues.
The findings are “very concerning” to communities that frequently consume fish from local waterways, said Andrews. The general U.S. population varies greatly in their frequency of fish consumption; anglers, individuals living near water bodies, and immigrant communities coming from cultures with high fish consumption are usually considered the highest consumers.
These people are at higher risk of PFAS contamination; for example, a 2017 study found that higher consumption of fish and shellfish was associated with elevated levels of some PFAS. A 2022 study of Burmese immigrant anglers in New York State found elevated levels of PFOS in the anglers compared to the general population. Some people, said Pickard, rely on freshwater fish for subsistence and may not be able to afford substituting store-bought fish for locally caught fish.
Catching and eating fish is also a sovereign right for Indigenous tribal nations that “must be honored and respected,” according to the paper’s authors.
While the EPA recognizes that eating U.S. freshwater fish exposes fishers to PFOS, there are currently no federal fish consumption regulations to protect fishers from these or other PFAS chemicals. Only 14 of 50 states have implemented PFAS-specific fish consumption advisories, which does not reflect the full extent of the contamination problem, according to the research paper.
For example, many states in the Great Lakes region use guidelines set by the Great Lakes Consortium for Fish Consumption Advisories to determine regulations. Those guidelines are based on the Environmental Protection Agency’s 2016 drinking water standards.
In 2022, the EPA substantially lowered the drinking water standards — by about three orders of magnitude — with new interim guidelines. If fish advisories across the country were updated to reflect the EPA’s interim guidelines, nearly all fish from rivers, lakes and streams could be considered unsafe, according to the research paper.
Sean Strom, an environmental toxicologist at the Wisconsin Department of Natural Resources, said a lack of funding and scientific capacity among state agencies is likely hindering the creation of new consumption advisories. States that have been monitoring PFAS for longer are more able to enact public health measures in response to changing science, according to Strom.
There is growing evidence that PFAS are affecting other wildlife across the country. The results for freshwater fish, said Andrews, is “just scratching the surface” of the likely contamination by industrial chemicals happening in ecosystems worldwide.
Pickard agreed and said more research is needed to show how PFAS are impacting the lives and health of wildlife.
“We have a significant challenge in being able to assess ecological risk for all these PFAS and what that’s going to mean for species,” she said. “What are the biological effects going to be for them?”
Cleaning up the country’s water bodies is unlikely, according to Ranier Lohmann, a professor of marine chemistry who studies PFAS at the University of Rhode Island.
“There’s not an easy solution to widespread, low-level contamination,” he said.