The U.S. FDA differs from the corresponding agencies in other First World countries because it has a different standard for determining safety. Usually, a manufacturer has to prove a new chemical is safe before they can put it on the market. In the U.S., the standard is different. Unless a third party can prove to their satisfaction that the product is unsafe, the manufacturer can continue to sell it. This is why bisphenol-A, for example, is used in the lining of all canned foods in the U.S. and not in other countries. Although studies have repeatedly come out indicating that it binds to estrogen receptors and mimics estrogen in some ways, the FDA has claimed that no one study in humans has conclusively proven that BPA has effects. BPA studies are difficult in humans because it's impossible to shield a control group from exposure to it- virtually all foods sold in the U.S. are laced with it, with no labeling requirements whatsoever. China has banned the use of BPA, but still manufactures millions of tons for exports to the U.S.