Organotin and seals in the Dutch Wadden Sea

Already for decades the quality of the water in the Dutch Wadden Sea is an important issue for research, discussions and legislation. Although the amount of well-known pollutants has been decreasing an optimum has not been reached. The question if the present pollutions can cause immunosuppression for animals is still unknown. The concentrations of heavy metal and other pollutants like PCB?s have been decreasing. Never the less some substances are present higher than the maxima acceptable risk. One of these substances is organotin. Organotin represents a group of organic compounds that contain tin. Butyl and phenyl groups are the most well known. Examples of widely produced organotins are TBT (tributyltin) and TPT (triphenyltin). TBT is mainly used as paint additive in the shipping industry to prevent the fouling of ship hulls. TPT is also used in this matter but only in small amount. The major use was as fungicide in agriculture, especially potato culture. Although the use of TBT and TPT are prohibited for several years still quantities can be found in the environment. TBT and TPT seem to be comparable in toxicity and bioaccumulative behaviour but can be distinguished in degradability. TPT appeared to be more persistent than TBT for as well as in sediment as in organisms. Because their hydrophobic quality it is hard to solve in water and within a short period after release they are fixated to sediment and suspended matter. Earlier research has shown that imposex can occur already at concentrations as low as a billionth of gram per liter. Because of the large differences in doses effect relations between different trophic levels no assumption can be made that the concentration in which imposex occurs also establishes negative consequences for the harbour seal. In this report analyses of organotin in suspended matter and in harbour seal livers reported. Further more a research check is performed to find results of negative effects of organotin for sea mammals and other organisms.