PFAS in fish: 'eternal polluters' end up on our plates

The international trade in fish not only moves tons of food from one continent to another. It also circulates an invisible risk: that of PFAS, the so-called perpetual chemicals. That's according to a new study published in Science. In it, for the first time, a global map of exposure to these substances through the consumption of marine fish was drawn up.

PFAS are extremely persistent chemical compounds that have been used for decades in numerous industrial processes and everyday products. Just because they hardly degrade, they accumulate in ecosystems and in living organisms, including fish. As fish spread around the world, the contaminants travel with them and eventually end up on our plates.

The research

The research was coordinated by Wenhui Qiu of the Southern University of Science and Technology in Shenzhen, who worked with a large international team. The team took an innovative approach: it combined environmental data collected at more than 3,100 different sites between 2010 and 2021 with information on fish trade routes and dietary patterns in 44 countries.

The goal was to calculate the so-called 'estimated daily intake' (EDI): how much does an average inhabitant of a given country acquire through consumed fish, both from fish caught in their own waters and imported fish?

By doing this, researchers were able to estimate the presence of PFAS in 212 commonly eaten species of marine fish. They focused on two specific compounds: PFOA and PFOS, the most common contaminants. The result is a detailed picture, not only of where contamination is the highest, but more importantly of how human exposure to these compounds is 'redistributed' through the flow of global fisheries trade.

According to the study, the risk of exposure to PFAS through fish consumption is highest in North America, Oceania and Europe. Europe, in particular, emerges as one of the major nodes in this system.

The authors of the study explain that the European fisheries trade plays an important role in moving fish from more polluted areas to regions that would actually be less exposed from an environmental perspective. In other words, because of the global market, the risk is not limited to the most heavily polluted areas, but is 'exported' elsewhere.

One of the most innovative aspects of the study is precisely the focus on the role of international trade. What matters is not only where the fish are caught, but also where they are eaten. Countries with relatively less polluted waters may still face higher exposure simply because they import large quantities of fish.

The risks

As mentioned, the research focused primarily on two long-chain forms of PFAS: PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). In scientific literature, both are associated with negative health effects such as hormonal disturbances, immune system problems and increased risk of certain diseases.

The good news is that after restrictions introduced since 2009, the risk assessment for PFOS has decreased by 72% on average. Yet, long-chain forms of PFAS that are not yet regulated remain a concern, especially given their ability to accumulate over time.

Moreover, in most of the countries surveyed, the risk score remains below the threshold of one, the level above which specific measures become necessary. The main exceptions are Greenland and Denmark: there, exceeding the threshold is mainly related to dietary habits: in fact, per capita fish consumption is particularly high in these areas.

Not surprisingly, it also reveals a direct relationship between the amount of fish consumed and the risk score: the more fish you eat, the higher the exposure. Accordingly, the highest values are measured in northern European countries, which are also geographically closer to the areas where PFAS industrial production has historically been concentrated.

Note that the study certainly does not want to portray fish in a bad light. Fish is a valuable foodstuff, but the study reveals an often ignored reality: pollution knows no borders and follows the same routes as global trade.

Where do PFAS come from and what can you do about it?

The main route by which PFAS enter marine ecosystems, the researchers explain, is through freshwater: rivers and lakes drain discharges from industrial plants as well as from drinking and wastewater systems. As a result, the substances concentrate before they reach the sea. The problem is exacerbated by the fact that in inland waters, flow is much slower than in the oceans, which encourages accumulation.

Proximity to specific sources of pollution also plays a role. Concentrations in coastal waters are higher when there are factories that produce or use PFAS, or facilities that release large quantities, such as some military bases nearby.

Researchers say that reducing exposure to PFAS requires not only changing individual consumption patterns, but above all reducing the sources of pollution, tightening controls and regulating these substances more strictly.

Because as long as these 'eternal chemicals' are produced and released into the environment, they will continue to end up - silently - in the seas as well as on plates around the world.

Source: Science

(MP/©GreenMe.it/Translation and adaptation: The Global Lifestyle/Pic: Unsplash