TBT or not TBT?: That is the question

Abstract

The benefits which have accrued from the development of TBT‐based antifouling paints, and their use on boat hulls and mariculture cages, must be assessed against environmental costs. High concentrations of tributyltin (TBT) occurred in some coastal waters in areas of intensive shipping (or ship‐related) activity or mariculture during the period of unregulated use of TBT‐based paints, and there is evidence that they were harmful to marine life. For example, they were held responsible for the near collapse of oyster farming in France and declines in the populations of dogwhelks in British waters. However, regulations, which were introduced by many countries a decade or so ago, restricting the use of these antifoulants to vessels > 25 m in length, have been highly effective in reducing TBT contamination. Predictions that TBT was likely to have catastrophic effects on some marine life have not been fulfilled and the problem of serious pollution is now restricted largely to centres of commercial shipping activity, such as major ports and shipyards. Severe impact is even localised in Hong Kong, which is one of the busiest ports in the world, and where regulations are said to be ignored. The International Maritime Organisation (IMO) is currently considering draft regulations which will ban the application of TBT‐based antifoulants from the year 2003. TBT coatings will not be allowed on ships from 2008 onwards. It is argued that the introduction of these regulations is premature and should be delayed until a proven safe alternative is available. Additional regulations could reduce the ambient concentrations of TBT in the environment still further, as could the development of new technologies relating to, for example, waste water treatment, port facilities and the properties of paints.