A study published in Science suggests that the global fish trade may increase the risk of per- and polyfluoroalkyl (PFAS) exposure worldwide—bringing seafood laden with “forever chemicals” to regions with low levels of environmental pollution.

There is a mounting body of evidence pointing to the health harms of dietary exposure to PFAS. Called “forever chemicals” due to their inability to break down in the environment or the human body, PFAS are used in industrial processes and consumer products, and have been linked to cancers, liver and heart damage, immune and developmental damage to infants and children, and other effects. PFAS are known to be taken up by food animals and crops from the environment.

For the present study, a team of researchers from China, Hong Kong, and North America—led by Wenhui Qiu, Ph.D. of the Southern University of Science and Technology—analyzed two decades of seawater monitoring data covering 3,126 locations around the world, using marine food web models to analyze PFAS concentrations in 212 edible marine fish species. The study integrated global data on PFAS pollution in the environment, bioaccumulation models in food webs, fish consumption, and trade, including more than 99 percent of global marine fish production.

Global State of PFAS Contamination in Seafood

Overall, the researchers determined that PFAS levels are closely related to the history of pollution and dilution capacity in marine regions. Significantly higher PFAS concentrations were found in predatory species higher up on the food chain.

Globally, the median concentration of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS)—two pervasive PFAS of concern for public health—in marine fish was 0.34 nanograms per gram of wet weight (ng/g WW). The median level was notably higher in Asia, reaching 1.03 ng/g WW. At the high end, some marine fish species from Saudi Arabia and Thailand had PFAS concentrations of 11.72 ng/g WW and 6.06 ng/g WW, respectively.

PFOS Restrictions Shown to be Effective in Reducing Risk

Importantly, the study found that the global hazard index for PFOS fell by 72 percent after restrictions were imposed in 2009 by the Stockholm Convention, suggesting the effectiveness of regulatory efforts to mitigate PFAS pollution; however, unregulated long-chain PFAS continue to pose elevated risks, the researchers warn.

European Fish Exports Expose Consumers Worldwide to PFAS

The global median estimated daily intake (EDI) of PFOA and PFOS was also mapped based on the data, indicating higher EDIs in North America, Oceana and Europe. Importantly, in global trade, high-risk fish species like cod, herring, sea bass, salmon, tuna, and swordfish are mainly sourced from Europe and exported to other markets, exposing consumers in regions with lower levels of PFAS pollution to “forever chemicals” through contaminated imported fish.

For example, the study found that, in Italy, only 11.71 percent of fish is imported from Sweden, but these imports account for 35.82 percent of Italians’ PFOA/PFOS intake. Conversely, domestically caught fish accounts for 28.02 percent of Italian consumption but only 5.23 percent of PFOA/PFOS exposure. Similar patterns were seen in other countries, including the UK and Columbia.

Fish Characteristics that Increase PFAS Contamination Risk

In addition to the mapping exercise, researchers from the City University of Hong Kong tested locally caught fish for PFAS to determine contamination levels and trends. The team found that certain species, including blackspot threadfin, daggertooth pike conger, Indian thryssa, and burrowing goby, contained relatively high PFAS concentrations.

The researchers noted that three categories of fish tend to pose higher risk of PFAS exposure to consumers:

• Predatory species higher up on the food chain
• Species high in fat (e.g., salmon, herring, sardines)
• Bottom-dwelling species.

The researchers warn that vulnerable populations such as the elderly, those who are pregnant, and those with chronic illnesses should be especially selective in their seafood choices to minimize PFAS-related risks.