TRIBUTYLTIN INPUTS TO THE NORTH-SEA FROM SHIPPING ACTIVITIES, AND POTENTIAL RISK OF BIOLOGICAL EFFECTS

The mechanisms leading to an annual input of tributyltin (TBT) to the North Sea from shipping are discussed. It is estimated that the gross annual input of TBT to the North Sea was 68 tonnes. A simple numerical model of the North Sea has been applied to the input data, and indica tes that the greatest risk of biological effects of TBT from commercia l vessels would be expected in areas of the south-eastern North Sea (N STF Areas 4, 5), and off eastern England (Area 3ii). Low intensity of impact was indicated in the northern (Areas 1, 2, 3i) and north-centra l (Area 7i) North Sea. The sensitivity of the model output to variatio ns in critical parameters of the behaviour and inputs of TBT are discu ssed, and are found to have minor effects on the overall conclusions. The estimates of relative risk of biological effects from TBT broadly reflect the impacts observed in dogwhelks (Nucella lapillus L.) in Nor th Sea coastal areas.