According to The Green Guide , a website and magazine devoted to greener living and owned by the National Geographic Society, the safest plastics for repeated use in storing food are made from high-density polyethylene (HDPE, or plastic #2), low-density polyethylene (LDPE, or plastic #4) and polypropylene (PP, or plastic #5). Most Tupperware products are made of LDPE or PP, and as such are considered safe for repeated use storing food items and cycling through the dishwasher. Most food storage products from Glad, Hefty, Ziploc and Saran also pass The Green Guide's muster for health safety. But consumers should be aware of more than just a few "safe" brands, as most companies make several product lines featuring different types of plastics. While the vast majority of Tupperware products are considered safe, for example, some of its food storage containers use polycarbonate (plastic #7), which has been shown to leach the harmful hormone-disrupting chemical Bisphenol A (...