The Tin Rating is based on the occurence and concentration of tin in components of a product. For polymer materials, tin is used as a serrogate, indicating the likely prescence of organic tin or organotins. Levels below 100 ppm were deemed to be LOW. Products with tin between greater then 100 ppm were assigned a MEDIUM level. Tin in the form of organotins are used as stabilizers in PVC (vinyl) products, particularly in rigid PVC products (Modern Plastics Handbook 2000). They are also used as catalysts in silicone production. Organic tin compounds often consist of one, two, or three organic molecules attached to an atom of tin. Those with one or two organic molecules are often used to stabilize PVC plastic and are more likely to be present in children's toys, whereas those with three organic molecules are primarily used as pesticides. (Modern Plastics Handbook 2000)
Note: Two voluntary, third-party product standards specify limits for extractable tin in various materials. OKOE-TEX 100 standard for textiles and leather and the TUV Rheinland Group TOXPROOF & SG standards for textiles, leather and plastics restrict extractable tin to 1 ppm and non-detect respectively.