Tributyltin Concentration in Waters of the Chesapeake Bay

Tributyltin (TBT) has been analyzed in unfiltered water samples from the Chesapeake Bay (USA) from 1984 to 1989. Areas with large numbers of recreational vessels and one area with a high density of commercial and naval craft were targeted because of the likely input of TBT from these sources. The latter area also contained several large ship repair facilities that could contribute the antifouling agent. The range of TBT concentrations found at any one station was large with highest levels associated with times of peak usage. Concentrations in excess of 100 ng l-1 were common in some areas. The state and federal restrictions on TBT use appear to have partially achieved their desired effect of reducing water concentrations. While only one data set is extensive enough to show statistically significant downward trends, all sets visually indicate a decrease. A model that fits the most extensive data set indicates an 8–30% per year decrease in water TBT concentration for stations near boating activities.