Reheating in plastic containers is bad: True or false? If the container isn’t designed to be microwaved (for example, the ones used for takeout), it could contain bisphenol A (BPA), which recently rendered many water bottles obsolete. “Studies have shown microwaving causes BPA to leach into food,” says Consumers Union toxicologist Urvashi Rangan. The chemical has links to diabetes and reproductive and metabolic disorders, and it’s not always obvious which plastics contain BPA, so unless you’ve bought the container yourself, better to reheat in paper, ceramic, or Pyrex.