What type of substance is it?
Tributyltin compounds are man-made organic substances containing the metal tin. They are used as pesticides and biocides in marine antifouling paints and in wood preservatives. They are usually colourless to yellow liquids, with an unpleasant odour and are not very soluble in water. Some of these compounds can be toxic to wildlife, especially fish, molluscs and other water dwelling organisms. They have been found to build up over time in the tissues of living organisms.
How is it released?
Release of tributyltin compounds is primarily from their use in wood preservatives and in marine antifouling paints on ships, quays, buoys etc. and potentially from their manufacture, transport and use. There are no natural sources.
Detailed information
Scientific name:
Tributyltin hydride, tributyltin fluoride, tributyltin chloride, etc.; C12H27SnX (where X = H, F, Cl, etc.); tributyltin oxide, C24H54Sn2O
Other names:
TBT; tributyltin hydride; tributyltin oxide (TBTO); bis (tributyltin) oxide; tributyltin fluoride; tributyltin chloride; tributyltin acetate; tributyltin acrylate; tributyltin methacrylate
CAS Number:
56-35-9 (oxide); 4808-30-4 (sulphide); 7437-35-6 (adipate); 2155-70-6 (methacrylate); 1983-10-4 (fluoride); 56-36-0 (acetate)
The only known practical alternatives to tributyltin and the similar triphenyltin compounds known for their use in antifouling paints are cuprous oxide paints. These are less effective and cannot be used on vessels with aluminium hulls because the copper in the paint is incompatible with aluminium. Newer antifouling paints contain TBT bound in a resin that slowly degrades, releasing the TBT in a controlled, steady rate and can last for several years (depending on the thickness of the original application). Other advantages claimed for this 'self polishing' coating are constant reactivation of antifouling properties and even a reduction of fuel costs over and above the savings resulting from a clean hull by providing a surface that becomes smoother with time.
Major uses of tributyl tin compounds are as underwater antifouling agents (protect from algal and barnacle growths, etc.) in boat/ship paints, quays, buoys, crab pots and fish nets, and as fungicides in wood preservatives. They have also been used as a preservative in textiles, paper, leather and glass. Other uses include as insecticides, biocides and rodent repellents, as antioxidants, curing agents, corrosion inhibitors, and in flame resistant polyester. Tributyltin methacrylate is used as a stabiliser for the plastic polyvinyl chloride, PVC..
Tributyltin compounds are usually colourless to yellow liquids, which have a weak but unpleasant odour. They are not very soluble in water but may be soluble in hot water.
Where is it released?
Releases of tributyltin compounds to the environment occur primarily by gradual leaching from antifouling paints, wood preservatives and potentially from their manufacture, transport and storage. High levels of TBT compounds have been found in water, sediment and biota near to pleasure boating activity, especially in or near marinas, boat yards and dry docks, where boat numbers are highest and paint is applied or removed. There are no natural sources of release to the environment.
Local environmental effects
They are toxic to fish and other marine life and contact with other wildlife should also be avoided. There is evidence for marine contamination and tributyltin compounds bioaccumulate in organisms. Tributyltin compounds are not very soluble in water but tend to bind well to particles/sediment where they can persist for some time. High levels of TBT compounds have been found in water, sediment and biota near to pleasure boating activity, especially in or near marinas, boat yards and dry docks. Exposure of land animals to TBT is l largely limited to its use in wood preservatives.
Global environmental effects
No significant global impacts are considered likely.
Possible health concerns
Excessive exposure to tributyl tin oxide may affect the digestive system, eye, immune system, lung and skin. The Environment Agency aims to ensure that environmental exposures are too low to harm human health.
Legislation
Why was this substance selected for the Pollution Inventory?
Included in : UK Surface Waters (Dangerous Substances) (Classification) Regulations reporting requirements; European Union Water Framework Directive (WFD) Priority list substances; Substances of potential environmental concern of national significance.
Standard risk phrases for the pure substance
The standard risk phrases provided here are generally those used by suppliers of chemicals to describe substances - for example on packaging materials. The most important source of these phrases are the CHIP Regulations - Chemicals (Hazard Information and Packaging for Supply) - provided by the Health and Safety Executive. Some substances do not have CHIP risk phrases and in these circumstances we have used other risk phrases, the sources of which are indicated.
CHIP Phrase(s) : T: Toxic; Xn: Harmful; Xi: Irritant; N: Dangerous for the Environment; R21: Harmful in contact with skin; R25: Toxic if swallowed; R36/38: Irritating to eyes and skin; R48/23/25: Toxic: danger of serious damage to health by prolonged exposure through inhalation and if swallowed; R50/53: Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment
Controlling legislation and international agreements
The EC Dangerous Substances Directive (and Daughter Directives) established an environmental quality standard for TBT which must be met in surface waters. This standard has effectively been superceded by the Environmental Quality Standards Directive (2008/105/EC)* which designates TBT compounds as a Priority Hazardous Substance. Member States must aim to achieve a more stringent environmental quality standard, and seek to reduce and eliminate all emissions, losses and discharges. The Environment Agency has produced a pollution reduction plan which sets out how we aim to do this.
TBT compounds are included on the red list and as such are substances for priority action on their control under the OSPAR and Helsinki Conventions – relating to protection of the marine environment, specifically that of the North Atlantic and Baltic seas
The use of TBT in antifouling paints is restricted in many countries. Restrictions on the supply and use of organostannic compounds in anti-fouling paints on vessels (and equipment intended to be fully or partially submerged) are contained in Annex 17 of the EU REACH Regulation (as amended). These restrictions apply to all EU Member States. International agreement not to use TBT antifouling paints on state flagged ships, or on ships entering state waters, has been reached through the International Convention on the Control of Harmful Anti-fouling Systems on Ships. Implemented in the EU by Regulation 782/2003, the relevant domestic legislation for this agreement is covered by the Merchant Shipping (Anti-fouling Systems) Regulations 2009. All vessels entering UK waters / ports need to provide a certificate that declares either that the hull is free from TBT, or that the TBT anti-fouling system has been coated to prevent leaching into the aquatic environment.
* The EQS Directive is a daughter Directive of the Water Framework Directive.
These factsheets have been compiled to provide users with information on the Pollution Inventory substances and represent our best efforts to summarise a large number of disparate and sometimes conflicting data sources. We emphasise that this information describes potential hazards rather than actual effects and that the Environment Agency seeks to regulate releases to minimise emissions and hence any risk of detrimental effects occurring.
