Mercury bioaccessibility in fish and seafood: Effect of method, cooking and trophic level on consumption risk assessment

The bioaccessible Hg fraction in fish and seafood commonly present in the Mediterranean diet was assessed through three distinct in vitro extraction schemes. Each extraction method provided different results, highlighting the lack of a universal methodology to estimate mercury (Hg) bioaccessibility in those matrices. Bioaccessible Hg fractions ranged from 10 to nearly 90% of total mercury (T-Hg) and increased in predator species (Swordfish - Xiphias gladius, Blue Shark - Prionace glauca and Tuna - Thunnus sp.). Among the three extractions tested, the Unified Bioaccessibility Method (UBM) provided the highest estimation of Hg bioaccessibility for consumers. The tested cooking procedures (frying, grilling and steaming) considerably reduced the bioaccessible fraction. Results indicate that bioaccessible Hg found in ingested fish and seafood is far below the levels set by the current safety risk assessment legislation. These findings highlight the importance of integrating bioaccessibility measurements in food safety legislation.