Bisphenol A (BPA) is a molecule used as a building block for many polymers, including polycarbonate plastic (which is widely used to manufacture baby bottles, water bottles, and medical equipment) and epoxy resins (used to coat the inside of food cans). It has been known since the 1930's, but only recently has it caused widespread conern as an endocrine disruptor, and possible carcinogen. it may also trigger fat-cell activity, leading to obesity. Many retailers have banned products using Bisphenol A in packaging manufacture.