Comparative toxicokinetics of tributyltin in five marine species and its utility in predicting bioaccumulation and acute toxicity

The acute toxic response (LC50), bioconcentration factor (BCF), lethal tissue residue (LR50), uptake clearance constant (k(1)), and elimination rate constant (k(2)) for tributyltin (TBT) were examined and compared in four marine invertebrate and one marine fish species. The toxic response and BCFs were vastly different among the species when exposed to the dissolved compound, which was reflected in their unequal uptake clearance and elimination rate constants. Based on the dual-rate constant approach for a one compartment, first-order kinetic model (1CFOK), predicted values for both the acute toxic response and BCF based on these toxicokinetic constants were matched closely by observed values. Additionally, a strong correlation between the LC50 and BCF was found, which was expected based on their relationship to the balance between uptake and elimination and a consistent LR50 (lethal residue causing 50% mortality) among species. Predictions were made about the time to steady-state tissue concentrations with k(2) values and how this would affect the results of the standard 10 day toxicity bioassay. Because acute TBT toxicity occurs at tissue concentrations 100 times lower than compounds exhibiting a narcosis mode of action, tributyltin is very toxic at low environmental concentrations, especially to organisms that have high uptake clearance and low elimination rate constants. Making predictions about toxicity based on uptake clearance and elimination rate constants in conjunction with the critical body residue will be helpful when choosing sensitive organisms for determining water and sediment quality criteria.