Organotins with four organic groups, e.g. tetrabutyltin, tetraoctyltin and tetraphenyltin, can be used as starting materials or catalysts. Organotins with three organic groups can be powerful fungicides and bactericides, depending on the organic group R. Tributyltins (e.g. TBTO, Incidin) are industrial biocides used in antifouling paints and in wood treatment and preservation. They find use as disinfectants and agents for destroying molluscs such as snails (molluscicides). Other uses include antifungal action in textiles and industrial water systems such as cooling tower and refrigeration water systems, wood pulp and paper mill systems, and breweries. They can also be used for the control of schistosomiasis (a chronic tropical disease). Triphenyltins (e.g. Fentin, Tinmate, Brestanol) are used as agricultural fungicides and in antifouling paints. Other organotins in this class include Plictran, Bay Bue 1452, Vendex and Torque which are used as miticides/acaricides (substances used for killing mites or ticks). Organotins with two organic groups, e.g. dimethyltin, dibutyltin and diestertins, can be used as PVC heat stabilisers, as catalysts, in polyurethane formation and silicon curing, and as heat stabilisers for rigid food-packaging PVC. Organotins with one organic group, e.g. methyltin, butyltin, octyltin and monoestertins, are employed as PVC heat stabilisers. Common uses for selected organotin compounds follow. Tributyltin oxide is used as a fungicide and pesticide in timber treatments. It has been used in antifouling paints but this application is now banned by international protocol. Triphenyltin acetate is used as an insect control agent and a fungicide. Triphenyltin chloride is used as a biocide and an intermediate. Triphenyltin hydroxide is used as a chemical to sterilise insects and as a fungicide. Fenbutatin oxide is used for the control of a wide range of mites which feed on plants. Azocyclotin is a long-acting acaricide for the control of spider mites on fruits (including citrus), vines, hops, cotton, vegetables and ornamentals. Cyhexatin is used as an acaricide/miticide.
Substance name: Organo-tin compounds
CASR number: Not applicable
Molecular formula: A large number of organotin compounds exist. Important organotin compounds can belong to any of four classes. These classes are related to the number of organic groups, namely tetraorganotins, triorganotins, diorganotins and monoorganotins.
Synonyms: Organotin compounds include tributyltin or tributylstannane (CASR# 688-73-3), tributyltin oxide or TBTO, tributylstannane, Metatin 50, Biomet (CASR# 56-35-9), triphenyltin (CASR# 668-34-8), triphenyltin acetate or fentin acetate, TPTA, triphenylstannium acetate, Batasan, Brestan, Libromatin, Lirostanol, Phenostat A, Phentinoacetate, Suzu (CASR# 900-95-8), triphenyltin hydroxide or fentin hydroxide, hydroxytriphenylstannane, hydroxytriphenyltin, triphenylstannium hydroxide, triphenyltin oxide, Haitin, Tubotin (CASR# 76-87-9), triphenyltin chloride or fentin chloride, TPTC, chlorotriphenylstannane, chlorotriphenyltin, triphenylchlorostannane, triphenylchlorotin, Aquatin, Brestanol, Phenostat-C, Tinmate (CASR# 639-58-7) fenbutatin oxide or Bendex, Neoxtanox, Osdaran, Torque, Vendex, Shell (CASR# 13356-08-6), azocyclotin or Bay Blue 1452, Peropal (CASR# 41083-11-8), and cyhexatin or TCTH, plictran, tricyclohexylhydroxystannane, tricyclohexylhydroxytin, tricyclohexylstannanol, tricyclohexylstannium hydroxide (CASR# 13121-70-5).
Organotin compounds vary in their physical properties. Properties of selected organotins follow.
- Tributyltin oxide is a thin colourless to yellow liquid with a weak odour. Its specific gravity is 1.17.
- Triphenyltin acetate is an off-white crystalline solid. It melts at 124-126°C.
- Triphenyltin chloride is a white crystalline solid which melts at 103-106°C.
- Triphenyltin hydroxide is an off-white powder which melts at 124-126°C.
- Fenbutatin oxide is a white crystalline solid which is extremely stable to heat, light and atmospheric oxygen. It melts at 138-139°C and its specific gravity is 1.29-1.33.
- Azocyclotin is a colourless crystalline solid which melts at 219°C.
- Cyhexatin is a white crystalline solid that melts at 195-198°C.
Organotin compounds vary in their chemical and biological properties. Most commercial organotins have a very low water solubility. Some general properties for different classes of organotins follow.
- Tetraorganotins are very stable. They are ineffective as biocides (substances that are capable of killing living organisms) and are relatively non-toxic. However, they can be slowly decomposed or metabolised to more toxic triorganotin compounds.
- Triorganotin compounds are generally more toxic than organotins in other classes. Trialkyltins with linear organic groups cannot be used as agricultural biocides due to their high toxicity to plants (phytotoxicity). Diorganotins show no antifungal activity. Their antibacterial and toxic activity is low, except for the diphenyl derivatives.
- Monoorganotins show no biocidal activity and have very low toxicity to mammals.
Major environmental implications are related to triorganotins used as agricultural and industrial biocides and to a lesser extent to the application of some diorganotin and monoorganotin compounds in rigid PVC. Properties for selected organotin compounds follow.
- Solubility of tributyltin oxide in water is less than 20 ppm. It mixes with organic solvents.
- Triphenyltin acetate does not mix with water. It is soluble in ether.
- Triphenyltin chloride reacts with water.
- Triphenyltin hydroxide does not mix with water.
- Fenbutatin oxide is a triorganotin compound and is almost insoluble in water (0.005 milligram/L at 23°C). It is soluble in acetone, benzene and dichloromethane.
- Azocyclotin is a triorganotin compound. Its solubility in water is less than 1 ppm.
- Cyhexatin is a triorganotin compound. Its solubility in water is less than 1 ppm at 25°C. It is slightly soluble in acetone and soluble in methanol and chloroform.
The National Pollutant Inventory (NPI) holds data for all sources of organo-tin compounds emissions in Australia.
Brief contact with dialkyltin and trialkyltin compounds causes irritation of the skin and the respiratory tract. Acute intoxications can cause vomiting, headache, visual defects and abnormal electrical activity of the brain. These symptoms are unlikely to occur if proper protective measures are taken. Some organotin compounds have been reported to display anti-tumour activity. Tributyltin compounds are moderately toxic via both ingestion and dermal absorption. The tributyltin compounds may be strongly irritating to the skin and skin exposure may result in chemical burns in severe cases. Mucous membranes such as the eyes and nasal passages may also become irritated upon exposure. Shipyard workers occupationally exposed to dusts and vapours of tributyltin developed irritated skin, dizziness, difficulty in breathing and flu-like symptoms.
Entering the body
Organotin compounds can be inhaled in commercial/industrial work environments where organotin compounds are produced or used. Ingestion is considered to be an unlikely route of entry in these environments. Some skin absorption may occur when direct contact with organotins takes place. Exposure for the general public is expected to be minimal.
Occupational exposure is the most likely point of exposure to organotin compounds. Following proper handling procedures will minimise any risk of harmful exposure. A potential source of organotins in food and beverages arises from the use of triorganotin agricultural biocides and of diorganotins as heat stabilisers in PVC packaging materials. It has been found that food normally does not contain any detectable triorganotin residues. In the unlikely event of food being contaminated with traces of triorganotins, normal processing of food will largely degrade any remaining organotins. Diorganotins may leach from the packaging on the food, but resulting concentrations are generally very low. It has been concluded that exposure to diorganotins used in PVC is small.
Workplace exposure standards
Safe Work Australia sets the workplace exposure standards for lead and compounds through the workplace exposure standards for airborne contaminants. These standards are only appropriate for use in workplaces and are not limited to any specific industry or operation. Make sure you understand how to interpret the standards before you use them.
- Maximum eight hour time weighted average (TWA): 0.1 mg/m3
- Maximum short term exposure limit (STEL): 0.2 mg/m3
- Maximum eight hour time weighted average (TWA): 5 mg/m3
Drinking water guidelines
The Australian Drinking Water Guidelines include the following guidelines for acceptable water quality:
- Data are inadequate to set a guideline value for drinking water.
- Maximum of 0.001 milligrams per litre of water for health purposes
There is no evidence of accumulation of organotin compounds in the environment. However, tributyltin and triphenyltin, both active ingredients of antifouling ship paints, appear to be highly toxic to many species of aquatic organisms at parts per million level or even lower. Non-target aquatic organisms such as crustaceans, molluscs, mussels, clams and oysters may suffer structural changes, growth retardation and death. Tributyltin oxide has been shown to inhibit cell survival of marine unicellular algae. Tributyltin may be an endocrine disruptor (a substance capable of interfering with natural body hormones), with the development of male characteristics in females observed in several snail species and oysters exposed to tributyltin. Generally, larvae of any species are more sensitive to tributyltin exposure than are adult organisms. Tributyltin tends to accumulate in oysters, mussels, crustaceans, molluscs, fish and algae. Freshwater species will bioaccumulate more tributyltin than will marine organisms. In mammals, high levels of tributyltin oxide can affect the endocrine glands, upsetting the hormone levels in the pituitary, gonad, and thyroid glands. Large doses of tributyltin have been shown to damage the reproductive and central nervous systems, bone structure and the liver bile duct of mammals. Tributyltin compounds can also damage the immune system. Tributyltin can be considered moderately toxic to birds. The acute toxicity of organotin compounds to mammals decreases in the order trialkyltins > dialkyltins > monoalkyltins. Ethyl derivatives are the most toxic amongst alkyl groups, with triethyltin acetate being the most toxic of all organotin compounds. Organotins appear to be less toxic with increasing chain length of the organic group, with trioctyltin chloride being virtually non-toxic to animals.
Entering the environment
Organotin compounds can be transported in water. Air contamination by organotins has not been reported so far.
Where it ends up
Organotins have a low water solubility and a strong tendency to adhere to suspended materials and sediments. Organotin particles ultimately settle to the bottom, making widespread surface water contamination unlikely. Organotin compounds appear to be moderately persistent with reported half-lives ranging from several days in freshwater to several weeks in seawater and estuarine locations, depending on the initial concentration. Organotins also adsorb strongly to soil. Although leaching from soil and transport in soil may be possible, it is unlikely to occur. Degradation of organotins to less toxic products (i.e. non-toxic inorganic tin) depends on the organotin compound and is generally accelerated by sunlight and higher temperatures. Microbial degradation is another important transformation mechanism. Biomethylation does not seem to be a significant pathway for the transformation of organotin species. As an example, degradation of tributyltin can take from several months to more than two years depending on the conditions.
Australian Water Quality Guidelines for Fresh and Marine Waters (ANZECC, 1992):
The guideline for tributyltin is 0.008 microgram/L (i.e. 0.000000008 g/L) in fresh waters and 0.002 microgram/L (i.e. 0.000000002 g/L) in marine waters respectively.
Organotin compounds may be released from industrial manufacture facilities (in industrial effluent or to air) or from spraying in agricultural applications.
Diffuse sources, and industry sources included in diffuse emissions data
Triorganotins may enter waterways from antifouling coatings, molluscicide formulations for the control of snails, by spraying of agricultural biocides and by soil leaching from fields sprayed with biocides. Biocidal applications are the major contributors to organotin compounds in the environment.
Organotin compounds are not found naturally.
Antifouling coatings on boats and other vessels.
Some antifouling paints, some fungicides, some bactericides, some products containing PVC plastic (e.g. PVC food-packaging) may contain organotin compounds.
Sources used in preparing this information
- Agency for Toxic Substances and Disease Registry (ATSDR), ToxFAQs (September 1995), Tin (accessed, June, 1999)
- Australian and New Zealand Environment and Conservation Council (ANZECC) (1992), Australian Water Quality Guidelines for Fresh and Marine Waters.
- ChemFinder WebServer Project (1995), Azocyclotin (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Cyhexatin (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Fenbutatin oxide (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Tributyltin (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Tributyltin oxide (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Triphenyltin (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Triphenyltin acetate (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Triphenyltin chloride (accessed, June, 1999)
- ChemFinder WebServer Project (1995), Triphenyltin hydroxide (accessed, June, 1999)
- EXTOXNET (Extension Toxicology Network) - Pesticide Information Profiles (June 1996), Tributyltin (TBT) (accessed, June, 1999)
- Integrated Risk Information System (IRIS, September 1, 1997), Tributyltin oxide (TBTO) (accessed, June, 1999)
- Merian, E. (editor, 1991), Metals and Their Compounds in the Environment – Occurrence, Analysis, and Biological Relevance, VCH.
- Technical Advisory Panel (1999), Final Report to the National Environment Protection Council.
- Worksafe Australia (1996), Hazardous Substances Database, Tributyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Tricyclohexyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Triethyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Trihexyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Trimethyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Trioctyltin (compounds) (accessed, June, 1999)
- Worksafe Australia (1996), Hazardous Substances Database, Triphenyltin (compounds) (accessed, June, 1999)
- Safe Work Australia, Workplace exposure standards for airborne contaminants, accessed January 2019.
- National Health and Medical Research Council (NHMRC), Australian Drinking Water Guidelines (2011) - Updated October 2017, accessed May 2018.