A Dartmouth-led study suggests that people who frequently consume seafood may face an increased risk of exposure to PFAS, the family of ubiquitous and resistant human-derived toxins known as “forever chemicals.”
The findings emphasize the need for stricter public health guidelines establishing the amount of seafood people can safely consume to limit their exposure to perfluoroalkyl and polyfluoroalkyl substances, the researchers report in the journal Exposure and Health. This need is especially urgent for coastal regions like New England, where the legacy of industry and PFAS pollution collides with a cultural predilection for fish, the authors write.
“Our recommendation is not to not eat seafood: Shellfish are a great source of lean protein and omega fatty acids. But they are also a potentially underappreciated source of PFAS exposure in humans,” said Megan Romano, the study’s corresponding author and researcher. associate professor of epidemiology at Dartmouth’s Geisel School of Medicine.
“Understanding this risk-benefit relationship of seafood consumption is important for people making dietary decisions, especially for vulnerable populations, such as pregnant women and children,” Romano said.
The study combined an analysis of PFAS concentrations in fresh seafood with a statewide survey of dietary habits in New Hampshire. National data indicates that New Hampshire, along with all of New England, is among the nation’s top seafood consumers, which made the state ideal for understanding the extent of people’s exposure to PFAS through of fish and shellfish.
“Most existing research focuses on PFAS levels in freshwater species, which are not what people primarily eat,” said Romano, who studies the effects of PFAS and other endocrine-disrupting chemicals. in drinking water in New England communities. “We saw this as a knowledge gap in the literature, especially for a New England state where we know people love their seafood.”
The study also relied on New Hampshire’s extensive data on the sources and effects of PFAS, which are a staple of consumer products such as plastics and nonstick coatings. The molecular stability that makes PFAS versatile also makes them nearly indestructible, leading them to be called forever chemicals.
In humans, PFAS are associated with cancer, fetal abnormalities, high cholesterol, and thyroid, liver, and reproductive disorders. The chemicals have accumulated in soil, water and wildlife, and studies have shown that almost all Americans have measurable amounts in their blood.
“PFAS are not limited to manufacturing, firefighting foams or municipal waste streams — they are a decades-long global challenge,” said study co-author Jonathan Petali, a toxicologist with the New Hampshire Department of Environmental Services. “New Hampshire was one of the first states to identify PFAS in drinking water. We are a data-rich state due to years spent researching the impacts of PFAS and trying to mitigate exposure.”
The researchers measured the levels of 26 varieties of PFAS in samples of the most consumed marine species: cod, haddock, lobster, salmon, scallop, shrimp and tuna. The seafood studied was purchased fresh at a coastal New Hampshire market and originated from several regions.
Shrimp and lobster recorded the highest concentrations, with averages reaching 1.74 and 3.30 nanograms per gram of meat, respectively, for certain PFAS compounds, the researchers report. Individual concentrations of PFAS in other fish and shellfish generally measured less than one nanogram per gram.
Researchers report that the prevalence of PFAS in the environment makes it difficult to know exactly where and how the chemicals enter the marine food chain. Some shellfish may be especially vulnerable to the accumulation of PFAS in their flesh due to their feeding and living on the seafloor, as well as their proximity to nearshore sources of PFAS. Larger marine species can ingest PFAS by eating smaller species that, like shellfish, are prone to the compounds building up in their systems.
The study is supported by a survey of 1,829 New Hampshire residents that researchers conducted to measure how much seafood Granite Staters eat, and it’s a lot.
The survey found that men in New Hampshire eat just over an ounce of seafood per day and women eat just under an ounce. Both are higher than what the National Health and Nutrition Examination Survey found for men and women in the Northeast, and more than 1.5 times the national average for both. The daily intake for New Hampshire children ages 2 to 11 was about 0.2 ounces, the high end of the range for children nationwide.
About 95% of adults surveyed by the researchers reported eating seafood in the past year, and 94% of that group consumed fish or shellfish in the past month. More than two-thirds of respondents ate seafood in the past week.
But people in New Hampshire don’t eat seafood uniformly. More than half of the people who ate seafood the week before the survey lived on the state’s coast or near the Massachusetts border. More than 60% of people with household incomes less than $45,000 a year reported eating seafood at least once a week, while people with higher household incomes reported eating seafood less frequently.
Of the species the researchers tested for PFAS, more than 70% of adults who ate seafood once a month or more consumed shrimp, haddock, and salmon. Just over 54% of these adults ate lobster. Salmon, canned tuna, shrimp and haddock were the most consumed species among children.
There are federal guidelines for safe seafood consumption for mercury and other contaminants, but none for PFAS, said Celia Chen, a co-author of the study and a research professor in Dartmouth’s Department of Biological Sciences.
“Top predatory species, like tuna and sharks, are known to contain high concentrations of mercury, so we can use that knowledge to limit exposure. But it’s less clear for PFAS, especially if you start to look at how how different compounds behave in the environment,” said Chen, who leads several federally funded projects examining how and where PFAS accumulate in aquatic food webs in New Hampshire and Vermont.
Establishing safety guidelines would help protect people who are especially susceptible to contaminants, said Kathryn Crawford, first author of the study and assistant professor of environmental studies at Middlebury College.
“Warnings about shellfish consumption often provide advice for those people who are more conservative than the rest of the population,” said Crawford, who began the project as a postdoctoral researcher at Dartmouth’s Roman Laboratory. “People who eat a balanced diet with more typical, moderate amounts of seafood should be able to enjoy the health benefits of seafood without excessive risk of exposure to PFAS.”