Re-colonisation and recovery of populations of dogwhelks Nucella lapillus (L.) on shores formerly subject to severe TBT contamination.

Dogwhelks Nucella lapillus became locally extinct on some shores adjacent to areas of high shipping/boating activity during the period of high tributyltin (TBT) contamination in the 1980s and early 1990s. However, the species has now re-colonised sites at which extinction occurred on the Isle of Cumbrae, the northeast coast of England, the Shetland Isles and southwest England. There have also been substantial declines in the severity of imposex on adjacent shores where the species has persisted during this period. Re-colonisation and recovery can be attributed to two measures: regulations prohibiting the use of TBT-based paints on vessels < 25 m in length and the development of slow-releasing, self-polishing copolymer paints. Nevertheless, the International Maritime Organisation has now imposed a total ban on the use of TBT-based paints as antifoulants. This is almost certain to result in the use of paints containing alternative biocides and there is widespread concern that there is relatively little information on which to assess their likely environmental impacts. They could cause substantial environmental damage.

A review and assessment of tributyltin contamination in the North Sea, based on surveys of butyltin tissue burdens and imposex/intersex in four species of neogastropods.

It is evident from measures of butyltin tissue burdens and imposex or intersex in neogastropods that tributyltin (TBT) contamination of coastal waters and open parts of the North Sea is now low. It has been declining for at least the past decade. This is probably due to two measures. First, regulations prohibiting the use of TBT-based paints on small boats and fish farms have reduced inputs of TBT from these sources so that they are now negligible (except possibly where the regulations are flaunted). Second, there is evidence from sites, where commercial vessels are the sole source of TBT, that the adoption of TBT SPC paints has been effective in reducing environmental levels of these contaminants. However, poor dockyard practices, allowing TBT-contaminated wastes, including paint flakes, to accumulate in sediments have left a legacy of hot-spots of contamination in some ports. The impact is localised so that TBT contamination is low in coastal areas immediately adjacent to ports.