It's amazing how much we've come to rely on microwave ovens. Yet a vague distrust remains regarding how they work and what they do to the food cooked in them. Microwave ovens do leak radiation, but at very low levels that the FDA and most scientists believe are harmless. There are a few simple guidelines to follow to make microwave use safer, including avoiding certain plastics when reheating (see Plastic Containers).
Ovens with damaged doors and latches can leak more radiation than normal, so make sure your appliance is in good condition. If using plastic containers, cook only with those labeled "microwave-safe." Do not cover containers in the microwave with cling-type wrap, which is made of PVC; use unbleached paper towels instead.
When defrosting meats and cooking frozen foods, be sure to remove the manufacturer's packaging. Also, remove microwave-ready foods from their packaging before heating, as there are health concerns related to heating plastic.
The butter flavoring in some microwave popcorn -- and many other foods -- contains a chemical called diacetyl that has caused incurable lung disease in popcorn-factory workers and in one man who ate several bags of butter-flavored microwave popcorn every day for many years. Manufacturers have already started dropping the ingredient from their products.
Use only ceramic or glass cookware in your microwave (metal, of course, can cause electrical arcing). Use a microwave-safe plate or bowl, and, instead of wasting paper towels, cover it with a glass pot lid, like the ones that come with casserole dishes, to prevent spatters.
Use the microwave infrequently, if at all. Cook and reheat foods on a conventional stove or in the oven.