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Assays / Trace
Metals/ Tin
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
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