Trace metals in bivalve molluscs from Thailand

Capture fisheries and aquaculture provide a large quantity of bivalve molluscs for human consumption in Thailand each year. The existing information on trace elements in these bivalves is fragmentary and contradictory. This paper reports data for eight metals (cadmium, chromium, copper, iron, lead, nickel, mercury and zinc) in the four major species marketed. These are the clam Pahia undulata, the cockle Anadara granosa, the green mussel Perna viridis and the rock oyster Crassostrea commercialis. The bivalves analysed were taken at markets or in the field to cover as many of the major sources as possible. The results indicate no major threat to public health from trace elements in these species from Thailand and lend confidence to the expansion of aquaculture operations. In particular, the levels of lead found in the samples analysed are considerably lower than those previously reported by other authors.