Cadmium, copper, lead and zinc in cultured oysters under two contrasting climatic conditions in coastal lagoons from SE Gulf of California, Mexico

In order to determine the metal concentrations in cultured oysters from four coastal lagoons from SE Gulf of California, several individuals of Crassostrea gigas and C. corteziensis were collected and their cadmium, copper, lead and zinc levels were measured by atomic absorption spectrometry after acid digestion. The concentration of metals in oyster soft tissue was Zn > Cu > Cd > Pb. In two lagoons, Cd concentrations (10.1–13.5 μg g⁻¹ dw) exceeded the maximum level allowed according to the Official Mexican Standard (NOM-031-SSA1-1993), which is equivalent to the WHO recommended Cd levels in organisms used for human consumption.