BPA is short for bisphenol A. It's a chemical found in the plastic of food containers and in drinking cans. It's not safe to have food in because the chemicals can get into your food, and once you eat them, it can mess with your endocrine system, or your hormones. It has been reported that BPA has been linked to reproductive disorders, heart disease, Type 2 diabetes, and can deteriorate the quality of women's eggs.
BPA is found in water bottles, which is why it is important to use re-usable water bottles that are BPA free. You can save money by not buying bottled water and instead drinking form the tap as well as save yourself from a harmful chemical like BPA.