Hong Kong consumers with a penchant for seafood and sashimi may need to exercise greater caution regarding their dietary choices. A landmark study recently published in the authoritative journal Science, co-authored by scholars from City University of Hong Kong (CityU), has shed light on the invisible threat of chemical pollution in the global marine food chain. The research reveals that “forever chemicals” are migrating across borders through the international seafood trade, potentially increasing cancer and reproductive health risks for diners.
The Global “Cross-Border” Transfer of Pollution
Led by Professor Leo Chan, Director of the State Key Laboratory of Marine Pollution at CityU, the research team analyzed two decades of global seawater monitoring data alongside 212 edible fish species. The findings illustrate a worrying trend: chemical pollution does not respect geographical boundaries.
The study identified Per- and Polyfluoroalkyl Substances (PFAS)—a group of synthetic chemicals used in non-stick cookware, waterproof clothing, and firefighting foams—as a primary concern. These substances are notoriously stable, earning them the moniker “forever chemicals” because they do not break down in the natural environment. Instead, they bioaccumulate in the food chain.
A critical discovery was the “cross-border transfer” of these toxins. Salmon, tuna, swordfish, cod, and halibut—staples in many Hong Kong diets—were identified as high-risk species, often sourced from polluted waters in Europe. The research highlighted a stark disparity in Italy, where a mere 11.7% of imported fish originating from Sweden accounted for 35.8% of the population’s total PFAS intake. This demonstrates that residents in relatively clean environments can still face high exposure risks through imported seafood. Notably, PFAS concentrations in Asian waters were found to be significantly higher than the global average, with severe contamination recorded in Saudi Arabia and Thailand.
Health Implications of PFAS Exposure
The danger of PFAS lies in its ability to enter the human body through water or the biological chain and persist indefinitely. Consuming contaminated fish can lead to severe long-term health consequences:
- Carcinogenic Risks: Studies link high PFAS exposure to increased rates of prostate, kidney, and testicular cancers.
- Reproductive and Developmental Issues: The chemicals can impair fertility, elevate hypertension risks in pregnant women, and cause developmental delays in children.
- Immune System Damage: PFAS can compromise the immune system and disrupt endocrine functions, reducing the body’s ability to fight infection.
Local Fish Species Under Scrutiny
While Hong Kong’s overall risk level remains relatively low, the CityU team detected elevated PFAS concentrations in four specific local fish varieties. Consumers are advised to moderate their consumption of Sixfinger Threadfin (locally known as “Ma Yau”), Eel, Yellow Drum, and Red Seabream.
Furthermore, the team categorized three types of fish that naturally accumulate higher levels of toxins due to their biological traits. Predatory fish at the top of the food chain, such as tuna and swordfish, accumulate toxins through biomagnification. High-fat fish, including salmon, retain more PFAS due to the chemical’s affinity for lipids. Lastly, bottom-dwelling fish that feed on sediment are exposed to settled pollutants.
Expert Recommendations for Consumers
Despite these alarming findings, Professor Chan urges the public not to panic but to remain vigilant. High-risk groups, including the elderly, pregnant women, young children, and individuals with chronic illnesses, should be particularly cautious. To minimize exposure without sacrificing nutrition, experts recommend the following:
- Diversify Your Diet: Avoid relying on a single source of protein. Rotating different types of ingredients prevents the accumulation of specific contaminants.
- Limit High-Risk Imports: Reduce the intake of high-fat or predatory fish species sourced from heavily industrialized regions.
- Informed Choices: When purchasing seafood, refer to risk lists and adjust consumption habits accordingly.
As the global appetite for seafood grows, understanding the provenance of our food becomes as crucial as its nutritional value. This study serves as a vital reminder that the health of our oceans is inextricably linked to the health of our plates.