Judith A. Wakefield

October 26, 2003


Plastics in the Microwave Oven


Stories about the dangers of chemicals leaching from plastic into microwave-oven-heated food have been circulating on the internet for years. The original rumor was that dioxins in plastic containers could migrate into fatty food when fatty foods was heated in plastic containers. The story has gotten all mixed up and the one who made the accusations was discovered not to even be a medical doctor. The actual issue was plasticizers migrating during microwaving of foods, not dioxins.

Plastic materials used in microwavaveable and dual-ovenable food containers such as those used to hold TV dinners must undergo testing and receive pre-market approval by FDA before they can be marketed for their intended use.

One chemical called diethylhexyl adipate (DEHA) has received a lot of media attention. DEHA is a plasticizer, a substance added to some plastics to make them flexible. DEHA exposure may occur when eating certain foods where the plastic wrap touches the food, especially fatty foods such as meat and cheese. But the levels are very low. The levels of the plasticizer that might be consumed as a result of plastic film use are well below the levels showing no toxic effect in animal studies. It is recommended that you use only wraps labeled for microwave use. Microwave-safe plastic wrap should be placed loosely over food so that steam can escape, and should not directly touch your food. Some plastic wraps have labels indicating that there should be a one-inch or greater space between the plastic and the food during microwave heating.


Other claims have asserted that plastics contain dioxins, a group of contaminants labeled as a "likely human carcinogen" by the Environmental Protection Agency. "The FDA has seen no evidence that plastic containers can produce dioxins when heated in the microwave. In fact, most, if not all, plastic containers would not even have the correct chemical composition to form dioxins," Dr. Edward Machuga says. Heís with the FDAís center for Food Safety and Applied Nutrition.

Dr. Machuga recommends that we should be sure to use any plastics for their intended purpose and in accordance with directions. If you donít find instructions for microwave use, you should use a different plate or container that you know is microwave-safe. Such containers are made to withstand high temperatures, others arenít. Glass, ceramic containers, and all plastics should be labeled for microwave oven use.

For example, carry out containers from restaurants, whipped topping bowls, margarine tubs and other one-time use containers should not be used in the microwave, according to the American Plastics Council. Inappropriate containers may melt or warp, which can increase the likelihood of spills and burns or cause harmful chemicals to migrate into the food. Also discard containers that hold prepared microwaveable meals after you use them - they are meant for one-time use. If the container is labeled that it is a type one or two plastic, put it with your plastics for recycling.

Always read directions, but generally, microwave-safe plastic wraps, wax paper, cooking bags, parchment paper, and white microwave-safe paper towels are safe for use. Covering food helps protect against contamination, keeps moisture in, and allows food to cook evenly. Never use thin plastic storage bags, brown paper or plastic grocery bags, newspapers, or aluminum foil in the microwave. Microwave plastic wraps, wax paper, cooking bags, parchment paper, and white microwave-safe paper towels are safe to use.

The real important point to remember is to only use plastic containers meant for microwave heating. Saving and using plastic containers that refrigerated foods came in to heat foods in the microwave oven is not a good idea. Donít save and re-use these containers, that were only meant for storage of cold foods. Read the label on your plastic wrap and be sure it is labeled for microwave oven use before you use it.