Tributyltin (TBT) is an aggressive biocide that has been used in anti-fouling ship paints since the 1970s. The toxicity of TBT prevents the growth of algae, barnacles and other marine organisms on the ship's hull. TBT leaches from the paint and enters the marine environment. TBT accumulates in the sediment, in particular in areas with many ship movements, like harbours and ports. In addition, on shipping lanes in the open sea, the toxic effects of TBT are observed. Triphenyltin (TPT) has also been used as anti-fouling, but its major use is as fungicide in agriculture, especially potato cultures. It is believed that TPT causes similar effects as TBT. As well as being degradation products of TBT, mono- and dibutyltins are widely used as additives, mainly in PVC plastics but also in some other products. They have been found to leach from PVC products like drinking water pipes and from other applications. Though less toxic then TBT, they are still significantly hazardous chemicals.

TBT is responsible for the disruption of the endocrine system of marine shellfish leading to the development of male sex characteristics in female marine snails. TBT also impairs the immune system of organisms and shellfish develop shell malformations after exposure to extremely low levels of TBT in the seawater. Recent studies conducted by the Dutch Institute for Marine Research and the Free University (VU) of Amsterdam reveal that sperm whales that live and feed in the deep ocean far from ports and shipping lanes have appreciable amounts of TBT and its breakdown products in their bodies. This indicates that TBT may be widely dispersed in the marine environment, including the deep oceans where sperm whales normally live and feed.

TBT and its degradation products have been isolated from a wide range of marine environmental samples. In many cases, a relationship between levels of environmental contamination and the intensity of shipping traffic can be detected. TBT has been found in the tissues of cetaceans, seals, sea otters and water birds in a wide range of locations around the world. Tissues and sediments sampled from areas with heavy shipping activity show the highest levels of contamination.

Three companies produce TBT. The world's largest producer is the German chemical company Witco that has 75% of the world market. On the European market almost all TBT (99%) comes from Witco. The remaining 1-percentage comes from A. Song Woun, a Korean producer that has 5% of the global market share. Atochem produces TBT in the USA and has 20% of the world market, but no market share in the EU. The EU production of TBT is around 3000 tonnes annually. The global production is therefore around 4000 tonnes. The EU consumption is around 1300 tonnes.

Several paint producers manufacture TBT ship paints by incorporating the chemical in the paint. The largest producer on the world market is the British company International Paint that is owned by Akzo Nobel. Other global players are Sigma Coatings in the Netherlands, Hempel in Denmark, Jotun in Norway, Chugoku in Japan and Ameron in the US. Market shares are listed in Table 1.

TABLE 1. Global market share of TBT paint producers (Source: EU draft risk Assessment report 1998)

The main trend in the TBT paints industry during the last years is a shift away from free association paints towards self-polishing TBT paints. The free association paint has a shorter life span and leads to higher emissions. Globally, the number of ships is increasing. Within the EU it is decreasing since more and more flags of convenience are used.

There are several alternative products on the market. In some alternative anti-fouling systems, TBT has been replaced by another biocide. Examples of other biocides that are used in antifouling paints are Irgarol, which is an atrazine biocide, zineb, ziram and thiram. The TBT problem is replaced by another problem. An alternative that has been on the market for a long time, already before TBT was introduced, is copper-based anti-fouling paint. Copper is less harmful to the marine environment compared to TBT and is proposed as intermediate alternative by most IMO-countries.

An alternative system that does not depend on toxic chemicals is the biocide-free so-called non-stick system. When applied properly, the ship’s hull becomes too smooth for algae, barnacles and other marine organisms to attach themselves to the surface. International Paint is one of the companies that have a non-stick system on the market. International paint is world leader for both TBT paints and for non-stick-paints.

A less well known alternative is SealCoat, produced by the company with the same name. The skin of a seal inspires this Swedish finding. Because of the structure of the seal's skin, no organisms grow on it. The same structure can be created on the hull of a ship by small flexible particles.

This means that for the short term there are alternatives for TBT available that are less/non-toxic, depending on ship demands. Toxic-free alternatives for all ship demands need to be further developed. Greenpeace does not use TBT on its vessels. On the Rainbow Warrior, a biocide-free non-stick paint has been applied. The other Greenpeace ships regularly undertake Arctic expeditions and use a copper-based paint since the non-stick paint is not suitable for heavy ice conditions (pack ice), because the paint surface is not strong enough. The ice damages the paint surface and subsequently the smoothness is lost and this enhances the settlement of organisms.

Adverse effects on the farming of oysters and other effects already resulted in a ban on TBT on ships < 25 m in France in 1982. The USA and the UK followed in 1988 and many other European countries around 1990. The Marine Environment Protection Committee (MEPC) proclaimed a worldwide recommendation of the International Maritime Organisation (IMO) to ban TBT in 1990. The General Assembly of the IMO decided in 1998 that the environment committee (MEPC) should work on a global legal instrument to ban TBT. It was also decided that the ban, if possibly, should be effective in 2003 when it comes to the application of TBT paint and in 2008 when it concerns the presence of TBT paints on a ship.

Last June the MEPC started to work on this legal instrument. The MEPC agreed to propose to the General Assembly to organize a specific diplomatic conference where the final decision on the TBT ban will be taken. If the General Assembly agrees with this proposal, the diplomatic conference may take place in 2000 or 2001. This next meeting of the General Assembly will be held this November.

However, there is still opposition from several IMO parties, from the TBT industry, organized in an Organisation called ORTEP, and from some shipping companies.

In 1998, 15 European ministers and the EU Environment Commissioner gathered at their OSPAR ministerial meeting agreed to phase out all losses of all hazardous substances into the environment within one generation (by 2020). Organotins were listed by the OSPAR on the list for priority action for which a programme of measures should be developed by 2003. The Dutch have taken the lead for developing a programme of measures to eliminate Organotins that include TBT at the last OSPAR plenary meeting in June 1999 in Hull.

• A global stop on all releases of TBT and other Organotins into the environment;
• Priority should be given to ban TBT as anti fouling for all types of vessels, thereby shifting towards biocide-free anti-fouling paints within the time frame proposed by the IMO, or rather sooner as alternatives are available;
• Other Organotin compounds, including mono- and di-butyltin and triphenyltin compounds should be phased out accordingly.
• Organotins are just one example of the many hazardous substances still produced and in use. Ultimately -by 2020 at the latest- production and use of all these hazardous substances should be phased out.

Amsterdam, September 1999