Assessment of Metal Levels in Sediments and Oyster ( Crassostrea gigas ) Tissues from Shidugawa Bay, a Closed Japanese Aquaculture Environment

Metals are used as alternatives of antifouling paints in aquaculture and toxic to cultured fish and shellfish. To assess antifouling paints, metal levels in sediment and in oyster ( Crassostrea gigas ) collected from a Japanese aquaculture were investigated. Elevated metal concentrations in sediment were found in the part of the aquaculture with high density of fish nets, and significantly positive correlations among the metals in sediments indicated that source(s) of these metals were common. The levels of metals were slightly higher in oyster tissues collected near bottom than near surface of seawater of the aquaculture. The levels of Cr, Ni, and As in dry oyster tissues from the aquaculture were higher than those from most Japanese coastal areas, while Cu, Zn, and Pb in dry basis were lower than those from other areas. Estimated daily intake (EDI) for men and women followed the order of Zn > Cu > As>Cd > Cr > Ni > Pb. Non-carcinogenic health hazard (HQ) and hazard index values (total HQ) of Cd, Cr, Ni, Cu, Zn, As, Cd, and Pb were lower than 1, indicating that women and men would experience no risks of studied metals if they ingested the oysters collected from Shidugawa Bay, but target cancer risk (TR) of As suggested that oyster may pose potential health risk for adult men and women via oyster consumption. Thus, continuous monitoring of trace elements in sediments and seafoods influenced by antifouling paints should be recommended.