Bisphenol A, better known as BPA, has inspired fear in the minds of the health conscious ever since researchers first expressed concern that the chemical may disrupt the human endocrine system in 2008. Now, more than a quarter of food brands offer at least some of their products in BPA-free packaging, according to a new study. But the research, published Wednesday by the Environmental Working Group (EWG), also demonstrates why people buying BPA-free products may not be getting the product they think.