Cracking the Code

• The coding system used on food containers corresponds with the type of plastic they're made of. Not all plastics are food-safe. Chemicals used in the manufacture of certain plastics include dioxins, adipates, and phthalates, all known carcinogens. Bisphenol-A, a hormonal disruptor, is found in some plastics and can pass to the food, especially when it is reheated or cooked in the container. According to the Natural Resources Defense Council website, you should choose plastic food containers that display any of the following codes: 1 (PET), 2 (HDPE), 4 (LDPE), or 5 (PP), as none of them leach any chemicals they are made of into food.

What to Avoid

• Polycarbonate plastics marked 7 (PC) or 7 ("other") typically contain bisphenol-A. Polystyrene coded as 6PS also contains toxic chemicals, and the styrene itself is listed as a human carcinogen by the World Health Organization's International Agency for Research on Cancer. Some clear plastic food containers are made of PVC plastic and bear the code 3 (PVC). PVC releases dioxins when it's manufactured and when it's heated. With more manufacturers now producing safer food storage containers, one way to reduce the risk of exposure is to look for labels that read "BPA-free," as they do not contain any bisphenol-A.