Bioaccessibility and Health Risk Assessment of Cu, Cd, and Zn in "Colored" Oysters

Bioaccessibility describes the fraction of contaminants released from the food matrix into the digestive tracts of humans, which is beneficial for improving the health risk assessment of contaminants. In this study, the bioaccessibilities of cadmium (Cd), copper (Cu), and zinc (Zn) in two severely contaminated green oyster (Crassostrea angulate) and blue oyster (Crassostrea hongkongensis) populations were investigated. A human health risk assessment of these metals was then performed based on bioaccessibility measurements. Among the three metals, the bioaccessibility was the highest for Cu (42-95%), and Cd and Zn had comparable bioaccessibility (13-58%). There was no major difference in the bioaccessibility between green and blue oysters. A significant correlation between the tissue Cu and Zn concentrations was found in these highly contaminated oysters. A health risk assessment showed that all three metals in both oyster species seriously exceeded the levels recommended by the United States Environmental Protection Agency. Thus, oysters from these locations, and the metals contained therein, presented quite high risks for human consumption, which should be a great cause of concern. A significant relationship was only found between metal bioaccessibility and its tissue concentration instead of between metal bioaccessibility and subcellular distribution. In addition, a significant relationship was only observed between metal health risks and its tissue concentration. The influence of metal bioaccessibilities on the health risks was limited. This may suggest that in the case of the colored oysters examined in this study, metal concentration instead of metal subcellular distribution could be the driving factor of the metal bioaccessibility, and metal concentration, instead of metal bioaccessibility, could be the driving factor of the metal health risks.