BPA, or Bisphenol A (CH3)2C(C6H4OH)2, is a chemical that is part of most epoxy resins and clear polycarbonate plastics used in a wide range of consumer and industrial products.
Most consumer product epoxy systems have resin manufactured using Bisphenol A, but this chemical is fully reacted during the manufacturing process, so there are only very tiny amounts left over. It's actually the hardener that determines whether a resin can be marketed as BPA-free.