Long response here, but seems to be worth it. from Wiki:
Toxicity[edit]
The effects of antifouling paint go beyond the organisms that it is intended to kill. By poisoning barnacles, algae, and other organisms at the bottom of the food chain, TBT is biomagnified up the marine predators' food web. It has been shown to harmfully affect many layers of the ecosystem, including invertebrates and vertebrates, even humans. Toxic effects in some species occur at 1 nano-gram per liter of water.[8]
Bioaccumulation[edit]
Even with its ban, TBT presents a danger to the environment. One of the most problematic aspects of TBT is its accumulation in sediments and its long half life of about 2 years. TBT often bonds to suspended material and sediments to the bottom, where it can remain and be released for up to 30 years.[9]
Invertebrates[edit]
TBT has been shown to affect invertebrate development. One of the most studied organisms are marine snails, of which the dog whelk (Nucella lapillus) has often been used as an Indicator species.[10] TBT disrupts their endocrine system by inhibiting Cytochrome P450 molecule. Among its myriad functions, P450 converts androgen, which has male-hormone properties, into oestrogen, which has female-hormone properties. This inhibition leads to masculinization in females, because the androgen levels are higher than normal. Since fewer fertile females are then available for mating, the population begins to decline, thereby seriously impacting the balance of the ecosystem.[8][11]
Another indicator species is Chironomus riparius, a species of non-biting midge, which has been used to test the effects of TBT on development and reproduction at sublethal concentrations found in marine environments. It was found that only 0.05 ng/ml range is enough to have developmental effects on their larvae, and 10-100 ng/l was enough to seriously offset the female to male ratio in the population. At 10 ng/l females were at 55.6% of the population and 85.7% at 100 ng/l. These results are interesting because unlike the masculinization of the stengoglassan gastropods, this experiment shows feminization.[4]
Vertebrates[edit]
Vertebrates become affected by the waters contamined with TBT as well as by consuming organisms that have already been poisoned. Oryzias latipes, commonly called Japanese rice fish, has been used as a model vertebrate organism to test for effects of TBT at developmental stages of the embryo. It was observed that developmental rate was slowed by TBT in a concentration-related manner and that tail abnormalities occurred.[8]
Illustrating the infiltration of TBT in the food chain, one study showed that most samples of skipjack tuna tested positive for presence of TBT. Tuna from waters around developing Asian nations had particularly high levels of TBT. Regulation of TBT is not enforced in Asia as rigorously as in Europe or US.[12]
Studies have shown that TBT is detrimental to the immune system. Research shows that TBT reduces resistance to infection in fish which live on the seabed and are exposed to high levels of TBT. These areas tend to have silty sediment like harbours and estuaries.[5]
TBT compounds have been described to interfere with glucocorticoid metabolism in the liver, by inhibiting the activity of the enzyme 11beta-hydroxysteroiddehydrogenase type 2, which converts cortisol to cortisone.[4]
Mammals[edit]
Mammals, even humans, are exposed to TBT through their diet. TBT has been shown to lead to immunosuppression in sea-otters and dolphins. High levels of tributyltin have been detected in the livers of sea otters (Enhydra lutris) and stranded bottlenose dolphins.[13] In addition, otters dying of infectious causes tended to have higher levels of tissue butyltins than those dying of trauma or other causes.[14] TBT has also been blamed by hearing experts for causing hearing loss in mammalian top predators such as toothed whales. Because hearing is important for mating and predation in these animals, long term consequences could be drastic.[15][16]
