Bioaccumulation and Chronic Toxicity of Bis(tributyltin) Oxide (TBTO): Tests with a Saltwater Fish

Abstract

The accumulation and depuration of bis(tributyltin) oxide (TBTO), a widely used active ingredient in antifouling paints, and its acute and chronic toxicity to sheepshead minnows (Cyprinodon variegatus) were determined. Equilibrium between the concentration of carbon-14-labeled-TBTO in seawater and in fish tissues was not reached after 58 days of exposure. The maximum observed bioconcentration factor in whole fish was ×2600. The maximum observed bioconcentration factors for the muscle, viscera, and remains were ×1810, ×4580, and ×2120, respectively. Sheepshead minnows depurated 52 percent of the 14C-TBTO within 7 days and 74 percent after 28 days. The 21-day median lethal concentration (LC50) for sheepshead minnows exposed to TBTO was 0.96 ppb. The only statistically significant effect observed in the life-cycle test was mortality of the F0 fish in the mean measured TBTO concentration of 4.8 ppb. There was an obvious concentration-response relationship in mortality of the F1 fish, although, no statistically significant differences in mortality were detected between the control and the TBTO-exposed treatments. The surviving F1 fish exhibited no signs of abnormal development, nor was growth decreased as a result of F0 exposure to TBTO concentrations <-1.0 ppb. Tissue samples from the life-cycle test, analyzed for total tin, confirmed the bioconcentration of TBTO, showed the accumulation to be concentration dependent, and indicated that the fish were actively metabolizing TBTO into its lower and less toxic alkyl moieties.