The soft pliable properties of tin are exploited in many manufacturing and other situations. It is used as a resistant coating for mild steel, to produce so called ‘tin plate’ widely used to produce containers, and as a component, usually with lead, of soft solders. Some ceramic pigments are prepared from compounds of tin and tin-fluoride derivatives are added to toothpastes.
Organotin compounds such as tributyl tin have anti-microbial properties and are used to prevent growth of moulds and bacteria on materials such as paper, wood, plastics, stone etc. Inclusion of organotins in marine paints to reduce the fouling of boats and other structures, has led to many situations of environmental toxicity.
Toxicity
Inorganic tin compounds are relatively innocuous. Prolonged exposures to dust and fumes can cause a pneumoconiosis but there are few other features associated with occupational activities. Effects on haem metabolism have been well described; and Sn++ is a powerful inducer of haem oxygenase.
Unlike arsine, the gaseous tin hydride does not cause haemolysis, but it does produce a profound neurotoxicity.
The toxicity of organic tin compounds has been extensively investigated. Metabolism and effects are markedly structure dependent and little toxicity is associated with monoalkyl tin compounds. The di- and trialkyl compounds are reactive but toxicity is influenced by alkyl chain length. Dermal exposure produces acute irritation with evidence for absorption and systemic symptoms such as anaemia, renal and hepatocellular damage. Triethyl tin uncouples oxidative phosphorylation and inhibits mitochondrial ATPase. Release of catecholamines may be responsible for the hyperglycaemia, blood pressure response and piloerection. Immunotoxicity involving the thymus is another aspect of the toxicity of the organotin compounds.
Laboratory Indices of Exposure
Urinary excretion of tin is the appropriate test for monitoring exposure to inorganic compounds. Haematological investigations can also be included.
There are no recommendations concerning monitoring of exposure to organotin compounds. Metabolic studies have resulted in the development of complex procedures for the separation of mono- di- and tri-alkyl derivatives in tissue specimens, but it is unclear if measurement of these species in other situations is of value. Determination of total tin in blood and urine is likely to give the most useful information concerning recent exposure and absorption.
References:
Schramel P, Wendler I, Angerer J. Determination of metals (Sb, Bi, Pb, Cd, Hg, Pd, Pt, Te, Tl, Sn and W) in urine samples by inductively coupled plasma-mass spectrometry. Int Arch Occup Environm Health 1997; 69: 219-23