High percentage of butyltin residues in total tin in the livers of cetaceans from Japanese coastal waters

There have been few reports on quantitative discussion of organic tin compo unds based on total tin in environmental media and biota. The present study determined concentrations of total tin (Sigma Sn = organic + inorganic) an d butyltin compounds (Sigma BTs = MBT + DBT + TBT) in the livers of cetacea ns collected from Japanese coastal waters in order to estimate the ratio of Sigma BTs:Sigma Sn and to elucidate the role of anthropogenic butyltins in the view of total tin accumulation in these higher trophic organisms. Addi tionally, some cetacean species from open seas and oceans were also subject ed to analyses for comparison purposes. Higher concentrations of Sigma Sn a nd Sigma BTs were found in coastal species than in offshore species, indica ting greater input of tin compounds in coastal waters surrounding Japan. Si gma Sn concentrations increased with an increase in Sigma BTs residues in a ll species analyzed (r = 0.95, p < 0.001). Furthermore, Sigma BTs made up c onsiderably higher percentages of the hepatic Sigma Sn in coastal species, with up to 74% in finless porpoise (Neophocaena phocaenoides) and 90% in bo ttlenose dolphin (Tursiops troncatus). These findings suggest that hepatic tin in coastal cetaceans predominantly exists in organic form such as butyl tin compounds, implying that tin residues in marine mammals reflect mostly the input from anthropogenic sources. Despite some similar features expecte d between the residues of tin and mercury, anthropogenic exposure to tin co mpounds seems to be more apparent than exposure to mercury, which generally originates from natural exposure.