It turns out even plastics that are BPA-free may interfere with your body’s estrogen levels. Many were already aware that plastics with BPA (bisphenol A) could pose health risks. As a result, many consumers seek out BPA-free items, especially ones for small children like baby bottles and sippy cups. However, a study in Environmental Health tested the resins—the raw materials that make up the plastics—of 14 different BPA-free types. Four of the plastics release chemicals that mimic estrogen, and it seems like the resins themselves may be the problem. Polystyrene, the resin used in Styrofoam and several types of food and beverage containers, was found to consistently seep estrogen when 11 samples of it were exposed to intense steam or ultraviolet rays.