Mercury and selenium concentrations in the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons of NW Mexico: health risk assessment
Abstract Mercury (Hg) and selenium (Se) concentrations in the soft tissue of the oysters Saccostrea palmula and Crassostrea corteziensis from four coastal lagoons (Altata, Macapule, Navachiste, El Colorado) of Northwest Mexico were determined. A total of 2520 specimens of S. palmula and 3780 of C. corteziensis (72.15 ± 4.95 and 73.57 ± 5.31 mm, respectively) were sampled seasonally from summer 2019 to spring 2020. The higher Hg concentration (wet weight) for S. palmula (0.13 ± 0.03–0.11 ± 0.02 µg g−1) and C. corteziensis (0.12 ± 0.02–0.11 ± 0.03 µg g−1) were obtained in summer−autumn 2019; Hg level was similar among the coastal lagoons and did not exceed the limit established by Mexican legislation and by the Food and Drug Agency. The higher Se concentration occurred in spring 2020 for both oyster species in El Colorado lagoon (4.55 ± 0.02 and 4.08 ± 0.05 µg g−1, respectively). The Se/Hg molar ratio of S. palmula and C. corteziensis ranged from 48.76–149.59 and 31.72–155.37, respectively; while the Se health benefit value was 19.23–42.28 and 17.82–35.30, respectively. The hazard quotient for Hg -estimated as methylmercury- and Se in both species of oyster was below 1. The high molar ratio obtained (Se/Hg > 1) indicates that the concentration of Se was sufficient to neutralize the possible toxicity of the Hg, therefore, the consumption of S. palmula and C. corteziensis from the four coastal lagoons studied does not represent a risk.