Korea eats more seafood, per head, than almost anywhere else on earth — roughly three times the global average — and its population carries the serum chemistry to prove it.
A new study published in Scientific Reports has found that the chemical burden associated with seafood consumption is far from uniform across different varieties, with finfish emerging as the principal source of persistent pollutant exposure among Korean adults, while seaweed and crustaceans appear to carry no measurable independent risk of that kind. The findings have implications not only for dietary guidance in Korea but for how regulators and researchers elsewhere approach the increasingly complex question of seafood safety.
The nutritional case for seafood has long been strong. Regular consumption is associated with reduced cardiovascular mortality, and the category delivers selenium, long-chain fatty acids, iodine, and high-quality protein in quantities difficult to replicate elsewhere in the diet. Yet seafood also accumulates both lipophilic and protein-binding persistent chemicals from the marine environment, and population-level studies have repeatedly linked fish intake to elevated serum concentrations of per- and polyfluoroalkyl substances (PFAS) — a class of synthetic compounds whose regulatory journey has been notably slow. Perfluorooctanesulfonic acid entered the Stockholm Convention only in 2009, and perfluorooctanoic acid followed a full decade later in 2019.
Korean adults already exhibit higher serum PFAS levels than their counterparts in France or the United States, a pattern that prior domestic research had begun to connect with dietary habits, particularly crustacean consumption and the use of food-contact materials. What had been missing was a systematic disaggregation of risk across all major seafood categories. This study, drawing on data from the Korean National Environmental Health Survey cycle 5 — conducted between 2021 and 2023 across 93 districts — attempts precisely that.
The researchers examined 4,279 participants, of whom 1,564 formed the subsample with serum measurements. That subsample was tested for 25 persistent organic pollutants and five PFAS, while participants reported their intake frequency across six distinct seafood categories: finfish, shellfish, crustaceans, seaweed, large predatory fish such as sharks and tuna, and other marine products including squid and sea cucumbers. The median total seafood consumption ran to approximately 14 servings per month, and those in the highest intake tertile tended to be older and less likely to smoke.
The contaminant picture that emerged from the analysis is notably differentiated. Each doubling of finfish intake was associated with serum PFAS concentrations between 4.4% and 14.1% higher, blood mercury 13.2% higher, and six of the seven measured serum polychlorinated biphenyls (PCBs) between 4.8% and 13% higher. Shellfish showed a more selective profile: each doubling of consumption corresponded to 9.4% higher PFOA and roughly 6% higher PFOS and PFNA, but carried no significant association with chlorinated compounds. Other marine products were linked to a 6% increase in blood mercury per doubling of intake. Crustaceans, seaweed, and large predatory fish, meanwhile, showed no positive independent associations with any of the measured contaminants — and seaweed was actually inversely associated with certain chlorinated compounds and blood mercury, a finding that merits further investigation. The low frequency with which participants consumed large predatory fish, only 3.1% ate them at least weekly, limits confident interpretation of that particular result.
The study’s primary health outcome was γ-glutamyl transferase (GGT), a liver enzyme whose elevation is a recognised marker of hepatic stress and metabolic dysfunction. A simultaneous quartile increment across all 16 contaminants in the model was associated with a modest 0.9% increase in GGT, driven principally by the PFAS component, and a 0.15-point increase in the fatty liver index, with organochlorine pesticides showing the strongest class-specific association. Taken in isolation, a one-quartile increase in PFAS corresponded to a 2.8% higher GGT, while the equivalent increase in PCBs was associated with a 1.2% rise. The full contaminant mixture showed a statistically significant association with higher GGT in men but not in women, a sex-specific pattern the study does not fully resolve.
Mediation analysis revealed that finfish intake itself was not directly and significantly associated with GGT, but that a positive indirect pathway operated through PFAS — a finding observed in both sexes. A negative, statistically uncertain non-mediated component also appeared in the model, which the authors cautiously suggest might reflect a nutritional benefit of finfish consumption, though they were unable to test this because the study did not measure nutrient intake. That gap is a genuine limitation, and one that illustrates a broader difficulty in nutritional epidemiology: disentangling the protective effects of a food from the hazards it simultaneously carries.
The study’s cross-sectional design, its reliance on self-reported intake frequency, and its inability to identify individual fish species all preclude causal inference and rule out species-specific dietary advice on the basis of these data alone. These are honest and important caveats. What the research does establish with reasonable confidence is that the persistent chemical burden associated with seafood consumption in Korea is concentrated in finfish, that shellfish carries a more limited and PFAS-specific signal, and that seaweed appears largely benign on this particular dimension of risk. The implication for both dietary guidance and regulatory assessment is that treating seafood as a single category understates the variation in chemical exposure that different consumption patterns actually produce. In a country where seafood is not a supplement to the diet but a central pillar of it, that distinction is anything but academic.