Warning Over Toxic ‘Forever Chemical’ Risk From High Seafood Diets

We’re often told to incorporate more fish and seafood into our diets. However, according to new research, eating too much fish may expose us to toxic forever chemicals.

PFAS, which stands for per- and polyfluorinated alkyl substances, are a class of chemicals that can be found in a range of everyday products, from toilet paper to food packaging, cosmetics and dental floss. According to the U.S. Agency for Toxic Substances and Disease Registry, these so-called “forever chemicals” can lead to increased blood cholesterol and blood pressure, reduced immunity, reproductive issues and an increased risk of certain cancers.

As their nickname suggests, these chemicals break down very slowly over time. As a result of their widespread use and their persistence in the environment, PFAS are found in soils, oceans and waterways around the world. Indeed, a study by the US Geological Survey in 2023 found that nearly half of the nation’s tap water was contaminated by some sort of PFAS.

This may be set to change after the Biden administration ushered in the first-ever national limits on PFAS concentrations in drinking water on Wednesday. However, it could still be several years before the results of these regulations come to fruition.

For now, forever chemicals are still widely prevalent in water bodies around the world. And, as a result, it is perhaps unsurprising that they have been detected in various species of fish.

“Most existing research focuses on PFAS levels in freshwater species, which are not what people primarily eat,” Megan Romano, an associate professor at Dartmouth College’s Giesel School of Medicine, said in a statement. “We saw that as a knowledge gap in the literature, especially for a New England state where we know people love their seafood.”

In a new study, published in the journal Exposure and Health, Romano and colleagues aimed to fill this gap by pairing data on the concentrations of PFAS in fresh seafood with statewide surveys on seafood eating habits in New Hampshire. New Hampshire is among the country’s top seafood consumers, making it an ideal state for understanding the extent of our exposure to PFAS through fish and shellfish.

To collect this data, the team measured PFAS levels in samples of the most consumed marine species in New Hampshire: cod, haddock, lobster, salmon, scallop, shrimp and tuna. Shrimp and lobster had the highest concentrations, averaging as high as 1.74 and 3.30 nanograms per gram of flesh, respectively.

It’s difficult to know exactly where and how these forever chemicals enter the marine food chain due to the prevalence of PFAS in aquatic environments. However, the researchers say that some shellfish may be particularly vulnerable to the buildup of PFAS in their flesh due to feeding and living on the seafloor, as well as their proximity to the coast where PFAS sources are likely to be more prevalent.

Co-author Celia Chen, a biology professor at Dartmouth College, said that this gap in our understanding made it difficult to create federal guidelines on the same consumption of seafood with regard to PFAS exposure.

“Top predator species such as tuna and sharks are known to contain high concentrations of mercury, so we can use that knowledge to limit exposure,” Chen said. “But it’s less clear for PFAS, especially if you start looking at how the different compounds behave in the environment.”

However, Romano added that, while PFAS are present in many seafood species, this should not deter people from including seafood in a balanced, healthy diet.

“Our recommendation isn’t to not eat seafood—seafood is a great source of lean protein and omega fatty acids,” she said. “But it also is a potentially underestimated source of PFAS exposure in humans. Understanding this risk-benefit trade-off for seafood consumption is important for people making decisions about diet, especially for vulnerable populations such as pregnant people and children.”

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