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Tin, Zinc and Selenium: Metals in Cosmetics and Personal Care Products

Contact Author Jurij J. Hostynek and Howard I. Maibach, University of California
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This is the sixth article in a series discussing the 17 metal compounds listed in the CTFA International Cosmetic Ingredient Dictionary1 and the CIR Compendium.2 The present article discusses tin, zinc and selenium.

Tin

Exposure to tin and tin salts as they occur naturally in the environment poses no significant toxicological hazard to the general public, although a potential for human sensitization has been recognized. Significant accumulation of the metal or its salts in the organism is unlikely due to their poor solubility and minimal absorption from the respiratory and GI tracts. Tin fluoride has been used for many years in toothpaste and topical solutions, but the instability of the aqueous solutions appears to be a major disadvantage.

Exposure to tin and tin salts as they occur naturally in the environment poses no significant toxicological hazard to the general public, although the potential for human sensitization has been recognized. Significant accumulation of the metal or its salts in the organism is unlikely due to their poor solubility and minimal absorption from the respiratory and GI tracts. Tin fluoride has been used for many years in toothpaste and topical solutions, but the instability of the aqueous solutions appears to be a major disadvantage.

Organotin compounds, however, appear to be absorbed through the skin of humans and animals, resulting in tissue irritation and systemic toxicity. Cutaneous absorption of organotin compounds has been recognized as presenting a significant risk of systemic toxicity, and particular care is recommended to avoid direct skin contact in the work environment. No quantitative data are available on the rate of human skin absorption of any tin compounds.

General toxicology: Tin is considered a relatively nontoxic element; the main route of exposure to the metal is through nutritional intake, although even by that route it is minimally absorbed.3

Organotin compounds, on the other hand, represent a serious toxicological hazard. They are of anthropogenic origin, with the exception of methylations, which, like methylmercury, may also be produced by environmental biomethylation.4

Toxicity of organotins is due to their action as inhibitors of energy production in cells, interfering with mitochondrial oxidative phosphorylation. They also appear responsible for the apoptosis of immune cells, resulting in immunotoxicity. Evidence was provided in recent studies that tributyltin interferes with normal hormonal equilibria, and with steroid metabolism in particular.5-8

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