There has been a lot of work over the past few years to understand the bioactivity of these chemicals—to better understand which hormones the chemicals interact with in the body, and what adverse health outcomes might be correlated with exposure. In the past, people focused mainly on whether or not a chemical was immediately toxic. If it didn't make consumers sick or kill them shortly after use, it was probably fine. But in recent years, we’ve become more aware that some chemicals might not kill us immediately, but could set us up for health problems in the future. And recently, researchers have begun to examine the idea that chemicals in our environment might even affect our metabolism.