Bioaccumulation of Heavy Metals in Mollusca Species and Assessment of Potential Risks to Human Health

Along the Alexandria coast of the Egyptian Mediterranean Sea, five edible species of bivalve molluscs and one gastropoda species (Mactra coralline, Ruditapes decussates, Paphia undulate, Venerupis rhomboids, Crista pectinata and Coralliophila meyendorffi) were analyzed for content of metals (Cadmium, Chromium, Lead, Cobalt and Nickel) in the muscle and in the sediments where they live. The potential health risks of metals to humans via consumption of seafood were assessed by estimated daily intake and target hazard quotient. Significant positive correlations (p < 0.05) were obtained between tissue concentrations for all pairs of metals, with the exception of Cadmium. Significant positive correlations were also obtained for the concentrations of Cd and Ni in tissues of all studied species relative to their concentrations in surface sediments. However, correlations between tissue and sediment concentrations for Chromium, Lead and Cobalt were negative. Ruditapes decussates and C. meyendorffi had the highest values for the summed target hazard quotient and may pose a potential risk to local inhabitants through their consumption in the diet. The potential risk would arise from exposure to high tissue concentrations of Cd and Pb, which exceeded published guidelines for safety of seafood products in some cases. Chromium contributed a considerable fraction of the total target hazard quotient for all metals combined, but did not exceed the published guidelines. Cobalt and Ni did not contribute greatly overall to the target hazard quotient, except in the case of Ni in V. rhomboids.