- Researchers say freshwater fish caught in the United States have higher levels of “forever chemicals” than saltwater fish.
- These chemicals, commonly called PFAS, can cause health issues ranging from weakened immune systems to fertility problems to cancer risks.
- The water the fish swim in is contaminated by a variety of sources, including landfills and wastewater treatment facilities.
- Experts say the contamination of freshwater fish is everywhere, including pristine rural areas.
Making a meal of freshwater fish such as largemouth bass, lake trout, or catfish could come with an unwanted helping of a potentially harmful chemical called perfluorooctane sulfonic acid (PFOS).
A study published today by the Environmental Working Group (EWG) reports that eating just a single serving of freshwater fish caught in the United States could be the equivalent of drinking water contaminated with PFOS for a month.
Researchers estimated that freshwater fish average 48 parts per trillion of the chemical per serving.
The analysis of data gathered by the U.S. Environmental Protection Agency (EPA) found that the median amounts of PFOS and other chemicals classified as PFAS, or perfluorinated alkylated substances, were 280 times greater in freshwater fish than in some commercially caught fish.
Dr. Kevin C. Rose, an associate professor in the Department of Biological Sciences at Rensselaer Polytechnic Institute in New York, told Healthline that freshwater predator fish such as pike, trout, and bass are more likely to build up higher levels of chemical contaminants.
He added that top saltwater predators like swordfish and tuna contain potentially harmful levels of mercury contamination from eating other fish.
The researchers analyzed data from more than 500 samples of fish filets collected in the United States from 2013 to 2015 under monitoring programs by the EPA, the National Rivers and Streams Assessment, and the Great Lakes Human Health Fish Fillet Tissue Study.
The median level of total PFAS in fish filets was 9,500 nanograms per kilogram, with a median level of 11,800 nanograms per kilogram in the Great Lakes.
The federal government has not yet established guidelines for the safe consumption of PFAS, which are currently under study by the U.S. Food and Drug Administration (FDA).
However, the FDA has previously flagged for concern imported clams with PFAS levels of 10,000 nanograms per kilogram, according to EWG.
Some research suggests that exposure to these “forever chemicals” — used in everything from non-stick cookware to firefighting foam to clothing stain-prevention products such as Scotchgard — may cause fertility problems, raise cancer risks, suppress immunity, and interfere with natural hormones, among other effects.
“The harmful levels of these chemicals are not well established because we don’t know what the dangers are,” said Rose. “There’s not a lot of research, but raising consumer awareness could pressure manufacturers to reduce their use of PFAS, which could reduce exposure in the long run without the need for regulatory action.”
Scotchgard maker 3M, for example, has pledged to eliminate the manufacturing of PFAS by 2025.
“PFAS contaminate fish across the U.S., with higher levels in the Great Lakes and fish caught in urban areas,” said Tasha Stoiber, PhD, an EWG senior scientist and study co-author.
Stoiber told Healthline that possible sources of PFAS in fish could include runoff into lakes and streams in urban areas — where the report found especially high levels of contamination — leaching from landfills or discharge from wastewater treatment plants that don’t filter out PFAS.
But that doesn’t mean freshwater fish caught in more pristine areas are safe.
“PFAS are found in even the most remote parts of the world,” said Stoiber.
The fish selected for the EPA study were the ones that are most commonly caught and consumed, Stoiber said. Low-income and certain ethnic populations who traditionally catch freshwater fish to supplement their diet may be especially at risk of PFAS contamination, she said.
Stoiber called on the federal government to set standards for the safe consumption of PFAS, which she said was especially important given the widespread presence of the chemicals in the environment.
Meanwhile, she said, consumers can reduce their exposure to PFAS by filtering their drinking water, limiting how much freshwater fish they eat, and eating fish sold in stores that the study showed contain lower levels of PFAS.