BPA or Bisphenol A is a chemical found in plastics and which can behave similar to estrogen and other hormones in our bodies. Unlike phthalates, which are found in soft plastic products, BPA is found in hard plastics, like baby bottles. BPA is also found in other plastic containers, such as plastic water bottles.
You can identify plastics made with BPA by looking for the plastic identification number "7" inside the recycling symbol on their label.
The use of BPA has become controversial, as there is a concern that BPA can leach out of plastic and into baby formula, juice, food, and other substances inside plastic containers made with BPA.