Toxicity and Degradation Studies of Tributyltin (TBT) and Dibutyltln (DBT) in the Aquatic Environment

A laboratory study on Crassostrea gigas spat showed the no effect concentration for the shell thickening response to TBT was between 2-20 ng l^-1for a 49 day exposure period. C. gigas spat relaid at 8 locations on the Crouch estuary showed the estuary to be highly contaminated with TBT. A graded response in TBT tissue residue, meat weight and shell thickening occurred away from high density moorings. Commercially viable oyster growth was observed only at the mouth of the estuary some 6 km from the area of high density moorings. DBT was not acutely toxic to fish, crustacea and polycheates at concentrations up to g l^-1DBT (100 times more than the highest measured environmental concentrations). DBT was toxic to C. gigas spat in a 49 day exposure study at g l^-1. Measurements of the degradation of TBT and DBT gave half-life values of 6 days for TBT in freshwater at C, and extrapolated values of 60 days for TBT and 90 days for DBT in seawater at C.