Microwaving plastic: Does it release dioxins?

Dioxins are cancer-causing substances most often found in soil, water and animal fat. Brush fires and forest fires naturally release dioxins into the air. So, too, does the uncontrolled burning of household trash. Certain chemical and industrial processes also may form small amounts of dioxins. Although stories have circulated for years that freezing or microwaving plastic food containers or wraps causes them to release dioxins, this isn't thought to be true.

Still, it's important to follow general safety guidelines when you're heating food in the microwave. For example:

• Use microwave-safe containers. Use containers or wraps specifically labeled as "microwave-safe." Don't use margarine tubs, carryout containers, or paper or plastic grocery bags.
• Check product labels. When you heat packaged foods, follow the microwave instructions printed on the label. If instructions aren't given, transfer the food to a plate or container that you know is microwave-safe.
• Don't allow plastic wrap to touch the food. Leave a small gap between the plastic wrap and the food while it's being heated.