Styrofoam containers package fast food, store leftovers from restaurants and wrap a variety of ready-to-eat foods at takeout restaurants. People tend to think of the squeaky white substance used to make disposable beverage containers when they think of styrofoam when, in fact, the styrofoam name covers some types of transparent plastic packaging as well. The name styrofoam is actually a genericized trademark owned by Dow Chemical Company for its range of polystyrene foam food packaging. People in other countries often know the material simply as polystyrene.
What is styrofoam
Styrofoam or polystyrene is a rigid vinyl polymer used in a nearly endless list of products, including food packaging, manufacturing, insulation and emergency buoyancy aids. The product contains thousands of tiny pieces of plastic bound together using free radical vinyl polymerisation, a chemical reaction used in the manufacture of many plastics. Chances are you come into contact with styrofoam products on a daily basis.
People concerned about microwaving styrofoam packaging fear chemicals from the polystyrene will leach into the food and pose a health risk. It's true -- many plastics are unsuitable for microwave use because they transfer dangerous levels of chemicals into food. However, most of these types of plastics are used outside the food industry and do not come into contact with food. Concerns often site the transfer of phthalates, chemical compounds known to cause reproductive problems in animals, and dioxin, a known carcinogen, as a health risk associated with microwaving styrofoam. Phthalates were banned from food packaging in the 1980s, and dioxin is not present in microwave-safe containers approved by the Food and Drug Administration (FDA).
Some, but not all, types of styrofoam are suitable for microwave use. The best way of staying safe is to read all instructions printed on the packaging. If the container says it's suitable for single use only, do not repeatedly microwave the plastic. Styrofoam products that the FDA has deemed safe through testing for food usually carry the "Microwave Safe" label.
It's always best to be cautious when it comes to microwaving plastics of any kind. Containers that do not have the "Microwave Safe" label are not inherently unsafe; the FDA simply has not tested the products. The American Plastics Councils says some unlabeled containers are made from microwave-safe plastics but might pose a melt risk because of their thin walls. If you are unsure, transfer your food to a microwave-safe ceramic bowl or other container.
- Harvard Medical School; "Harvard Health Publications: HEALTHbeat"; Nancy Ferrari; August 2006
- Health Canada; "Microwave Ovens and Food Safety"
- Harvard Medical School Family Health Guide; "Microwaving Food in Plastic: Dangerous or Not?"; July 2006
- Polymer Science Learning Center; Polystyrene
- Polymer Science Learning Center; Free Radical Polymerization