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CHEMICAL AND BIOCHEMICAL PROPERTIES
<br />GENERAL
<br />The chemical, physical, and biochemical properties of inorganic tin
<br />compounds differ dramatically from those of representative organotin
<br />compounds. There is general agreement that inorganic tins are not highly
<br />toxic due to their poor absorption and rapid turnover rate in tissues and to
<br />their being essential for growth in at least one species (rat). Of the 260
<br />known organotin compounds, all but a few are manufactured, and 36 are listed
<br />as toxic (Watanabe 1980). Most authorities agree on several points regarding
<br />organotin compounds: information concerning the mechanism of toxic action is
<br />incomplete; there is no evidence of carcinogenicity; trialkyltin compounds are
<br />the most toxic; and there are large differences in resistance between and
<br />within species.
<br />INORGANIC TIN
<br />Elemental tin has an atomic number of 50, an atomic mass of 118.69, and
<br />exists in three allo8ropic forms: white tin at room temperature, nonmetallic
<br />grey tin at <13.3 C, and brittle tin at >161°C. White tin is a stable
<br />silveg-white, lustrous, soft metal with a density of 7.27, a melting point of
<br />231.9 C, and a boiling point of 2,507 C. Tin has 10 stable isotopes (Sn-112,
<br />-114, -115, -116, -117, -118, -119, -120, -122, and -124), the most for any
<br />element. Inorganic tin compounds exist in the +2 (stannous) and +4 (stannic)
<br />oxidation states. Stannous compounds are generally more polar than stannic
<br />compounds, are unstable in dilute aqueous solutions, are easily oxidized, and
<br />normally contain some Sn+4. Stannic oxide occults naturally as the mineral
<br />cassiterite, has a melting point of 1,127 C, and has wide application in
<br />industry. Additional information on inorganic tin chemistry is listed in
<br />Zuckerman et al. (1978), WHO (1980), and Davies and Smith (1982).
<br />Signs of inorganic tin poisoning in mammals include local effects such as
<br />vomiting, diarrhea, and eye and nose irritation; however, these vary
<br />considerably among species (WHO 1980). The major systemic effects include
<br />ataxia, twitching of limbs, weakness of limbs, paralysis, growth retardation,
<br />decreased hemoglobin levels, and--at extremely high doses--testicular
<br />degeneration, pancreatic atrophy, formation of spongy brain white matter, and
<br />kidney necrosis. In humans, symptoms of inorganic tin intoxication include
<br />nausea, vomiting, diarrhea, stomach ache, fatigue, and headache. The lowest
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