Regulators and scientists have looked at PFAS, also known as forever chemicals, contamination in local water supplies. However, for a team of researchers led by Chunmia Zheng of the Eastern Institute of Technology in China, there is a critical blind spot. They turned their attention to the global fish trade to examine how the movement of fish across borders transports contaminants from industrial and polluted regions.
Why Clean Seas Do Not Guarantee Safe Fish: How International Fish Markets Reshape PFAS Chemical Exposure Risks
A study analyzed global fish trade flows and mapped 212 marine species. Results revealed that forever chemicals are hitchhiking across the globe via international trade routes.
Overview
Forever chemicals are a large class of persistent industrial chemicals that resist degradation and accumulate in the environment and living organisms. These chemicals include legacy compounds like perfluorooctanoic acid or PFOA and perfluorooctane sulfonate or PFOS. Both are widely used in manufacturing, firefighting foams, and consumer products.
Nonetheless, because forever chemicals persist in the environment, they also enter the marine food chain and are further consumed by humans. Most people would think that they are safe from pollution if they live in a country with clean water and strict environmental laws. The researchers realized that people rarely eat only fish caught near where they live.
Previous studies also typically linked chemical risk to local waters and assumed that pollution and exposure to contaminants occur in the same place. Modern seafood markets are global. This means fish caught in one ocean region or seawater area are often consumed thousands of kilometers away. Ignoring trade would misrepresent real human exposure to PFAS.
But PFAS are especially suited to exploring cross-border chemical exposure because they persist in fish tissues and remain stable during processing, freezing, and transport. Specifically, once fish are contaminated. The chemicals travel unchanged through supply chains. This makes trade a major pathway for spreading exposure beyond a geographic scope.
Main Findings
Zheng and his team of marine scientists, engineers, and environmental scientists gathered existing measurements of PFAS chemicals found in marine fish. They then looked at how much fish people eat in different countries using national dietary statistics. Global fish trade records were examined to determine how fish are consumed. The following are the findings:
• Global Median Intake
The median daily intake of C8-PFAS from marine fish is 0.023 ng/kg/day. Marine fish consumption is a significant source of legacy PFAS exposure. Even moderate consumption can contribute meaningfully to long-term chemical intake because forever chemicals accumulate in fish tissue and resist breakdown.
• High-Risk Regions
People in North America, Oceania, and Europe have the highest exposure levels. It is worth underscoring the fact that high-income nations generally have a median daily intake of EDI 0.068 ng/kg/day. This is significantly higher than the global average. The trend comes from dietary habits and seafood imports that drive consumption.
• The Baltic Problem
The researchers highlighted specific areas, like the Baltic Sea in Europe. Fish, like salmon and herring, from these areas have very high levels of PFAS. Because these fish are exported to neighboring countries, those neighboring countries see a spike in chemical exposure, even if their own local waters are clean.
• Catch Versus Consumption
International fish trade strongly reshapes PFAS exposure patterns by moving contaminated fish from polluted regions to distant consumer markets. This disconnect means countries with cleaner marine environments can still experience elevated exposure. Pollution sources and health risks are geographically separated.
Takeaways
International fish trade redistributes PFAS exposure risks across regions. Countries with relatively clean coastal waters can still face high PFAS intake because they import fish from areas with greater contamination. Trade thus decouples exposure to toxic forever chemicals from the quality of the environment and the regulatory strength of a particular nation.
The study underscores trade as a risk redistributor and the paradox in food safety. To be specific, a country might have very strict environmental laws and clean local waters, yet its population can still face high PFAS risks because they import fish from regions with heavy industrial runoff. The researchers argue that current food-safety frameworks are too local.
Despite regulatory actions, legacy PFAS remain of concern. The study notes that PFOS hazard indices have declined by around 72 percent following phase-outs and regulations since 2009, thus indicating that actionable regulations can reduce human risk. However, many long-chain and unregulated forever chemicals still pose elevated exposure potential.
Nevertheless, based on their findings, Zheng and his team recommend the need to set global limits on PFAS in seafood specifically for international trade. They added that regulations need to shift toward managing and considering PFAS as a class of chemicals to prevent replacing one toxic chemical with another slightly different but equally dangerous one.
FURTHER READING AND REFERENCE
- Qiu, W., Yang, G., Cao, L., Niu, S., Li, Y., Fang, D., Dong, Z., Magnuson, J. T., Schlenk, D., Leung, K. M. Y., Zheng, Y., Zeng, Z., Feng, L., Zhang, X., Zhang, Y., Fan, W., Huang, T., Ma, J., Wu, M., … Zheng, C. 2025. “Risks of Per- and Polyfluoroalkyl Substance Exposure Through Marine Fish Consumption.” Science. 390(6779): 1305-1309. DOI: 1126/science.adr0351