Organotin compounds

The substance
These compounds are generally man-made chemicals. Physical properties, including odour and appearance, will depend on the specific compound. Triphenyltin compounds tend to be colourless solids with low vapour pressures, and have a low solubility in water. Tributyltin oxide is a colourless liquid that is slightly soluble in water. Dibutyltin chloride is a white solid that is soluble in hot water.

Use
Of the various organotins, the di-substituted and tri-substituted compounds are the most widely used. Disubstituted compounds are used as stabilisers in plastics, including polyvinyl chloride (PVC) water pipes, and are added to polyurethane foams and silicones to increase their strength. Tri-substituted compounds are and have been used in the preservation of materials (wood, stone, textiles), as fungicides, miticides and disinfectants, as bactericides in cooling water, and in antifouling paints. Specifically, tributyltins have been used as molluscicides, disinfectants, antifoulings on boats and ships, in wood preservatives, as slimicides on masonry, and as biocides. Triphenyltins are used as fungicides on crops such as potatoes and sugar beet, and in the past were also used in paints for ships and boats. The use of organotins in antifouling systems and as biocides in the marine environment gets more and more restricted under European Community legislation.

Major emissions
In the past, one of the main sources of release into the marine environment was of triphenyltins and tributyltins which had been used in paints for ships and boats. Other sources of organotins release include the industries that they are used in, particularly the chemical industry, and through their application, for instance, in paint and wood preservative products. The disposal of products containing organotins into landfill can also lead to release into the environment.

Impacts on human health and environment
Excessive exposure to some organic tin compounds may cause adverse health effects on the brain, eye, immune system, lung, skin and the unborn child, and may cause cancer. Most local environmental concerns arise from organotin pollution in the marine environment. Two of the most hazardous compounds in this environment are tributyltin and triphenyltin. Tributyltin (TBT) is very toxic to algae, molluscs, crustacea and fish. TBT has been identified as an endocrine disrupting substance with observable effects in gastropods molluscs and suggested effects in marine mammals. It is also thought to impair the immune system of organisms and lead to shellfish developing shell malformations. Triphenyltin may have similar effects. TBT is listed as priority hazardous substance in the Water Framework Directive.

Emission to water reporting threshold: 50 kg/year

Data source: European Pollutant Emission Register