A landmark international study, co-led by researchers from City University of Hong Kong (CityU), has uncovered significant health risks linked to the consumption of seafood contaminated with “forever chemicals.” Published in the prestigious journal Science, the research highlights an alarming trend of Per- and Polyfluoroalkyl Substances (PFAS) pollution crossing borders through the global fish trade, exposing consumers in relatively pristine regions, including Hong Kong, to high concentrations of these dangerous compounds, potentially increasing risks of cancer and reproductive harm.
The team, which included Professor Lam Mei-yi from CityU’s State Key Laboratory of Marine Environmental Health, analyzed two decades of global seawater monitoring data alongside 212 edible marine species. Their findings confirm PFAS, a class of synthetic chemicals used ubiquitously in consumer products, are migrating through the oceanic food chain. Crucially, the data demonstrated a phenomenon of “cross-border risk transfer,” where countries with lower local pollution levels may incur greater exposure simply by relying on imports from highly contaminated geographical zones.
Understanding the Global and Local Risk Landscape
PFAS are notorious for their chemical stability, earning them the moniker “forever chemicals” because they rarely break down in the environment. These substances accumulate in the human body over time through drinking water and the food chain, where high exposure levels are associated with several severe health impacts, including increased incidence of prostate, kidney, and testicular cancers; impaired fertility and developmental delays in children; and compromised immune function.
The research reveals marked regional differences in contamination. Asia, a major seafood consumer, showed a concerning median PFAS concentration of 1.03 ng/g in marine fish, significantly higher than the global average of 0.34 ng/g. Within this area, coastal waters near countries like Saudi Arabia and Thailand exhibited particularly high contamination levels.
However, the risk is not limited to locally caught fish. The study identified several high-risk imported species—including salmon, tuna, swordfish, cod, herring, and perch—often sourced from Europe and other heavily polluted regions. A stark example of risk transfer involves Italy, where imports from Sweden accounted for only 11.7% of its total fish supply yet contributed 35.8% of the total estimated PFAS intake for the Italian population.
Hong Kong Consumers Advised on Specific Species
While Hong Kong’s overall PFAS risk remains low, the CityU team conducted localized testing that flagged four specific, commonly consumed local fish species with notably elevated PFAS concentrations. These include:
- Threadfin (Sixfinger threadfin/Ma Yu): A common, highly valued local fish.
- Pikes eel
- Yellow croaker
- Red seabream (a bottom-dwelling fish)
Based on their research, the experts categorized three broad groups of fish that tend to accumulate the highest levels of PFAS and should be consumed with greater caution:
- High Trophic Level Predators: Such as swordfish and tuna, where pollutants are magnified through the food chain (bioaccumulation).
- High-Fat Fish: Including salmon and herring, as PFAS chemicals exhibit lipophilic tendencies.
- Benthic (Bottom-Dwelling) Fish: Like red seabream, which are more likely to ingest contaminants concentrated in marine sediments.
Expert Recommendations for Mitigating Exposure
Professor Lam stressed that public panic is unwarranted, but consumers must remain vigilant, particularly vulnerable groups like pregnant women, young children, the elderly, and those with chronic illnesses.
The expert advice centers on diversification and careful selection to manage dietary exposure:
- Diversify Your Diet: Rotate various food sources to prevent the continuous accumulation of single-source pollutants in the body.
- Limit High-Risk Imports: Restrict the intake of high-fat and high trophic level predatory species, especially those known to originate from heavily contaminated waters.
- Review Local Consumption: Adjust consumption habits based on the locally tested species, such as limiting frequent intake of Threadfin and the three other identified local fish.
This groundbreaking research underscores the necessity of coordinated international efforts to monitor and regulate the use of PFAS. For Hong Kong consumers, the study serves as an actionable food safety alert, empowering residents to make more informed choices at the seafood counter.