Heavy Metals in Tasmanian Shellfish 2-The Influence of Heavy Metal Ratios on the Accumulation and Detoxification Mechanisms in Rats Fed Contaminated Oysters

The contamination of estuaries in Tasmania by ore processing plants and wolfram mines, and subsequent closure of oyster harvesting leases provided oysters, contaminated with different ratios of heavy metals, for the study of metal interactions. The high atomic ratios of zinc to cadmium (% 1200- 14OO: l) found at certain times in oysters in the Derwent estuary appeared to suppress food intake, growth and feed conversion in rats fed diets containing cadmium in excess of 15 pg g-' ( dry weight). Little cadmium was deposited in the usual target organs, the liver and kidney. Models for prediction of cadmium deposition in these organs based on the zinc and cadmium contents of the diet are discussed. From these models it can be seen that little cadmium would be deposited in target organs from ingestion of shellfish containing levels of metals permitted by health regulations, but the ratios of metals found in shellfish in the Derwent estuary may lead to the instability of metallothioneins in animals consuming the shellfish.