Tales of toxin-seeping plastic bowls and wraps flood the Internet, and the U.S. Food and Drug Administration (FDA) also warns against some plastics and containers. It's time to sort fiction from the facts.

THE PLASTIC PERSPECTIVE
Plastics and plastic wrap have gotten a bad rap. Years ago, studies showed that some of the toxic plasticizer in PVC plastic wrap leaked into hot, fatty foods, but manufacturers have since stopped making plastic wrap out of PVC. Today, wraps are fabricated out of polyethylene or other plastics that don't contain plasticizers or other additives that can leach into foods.

Any plastic or frozen dinner tray surface that comes into contact with food must be considered harmless before the FDA approves it, says Vickie Vaclavik, Ph.D., assistant clinical nutrition professor at University of Texas Southwestern Medical Center at Dallas. "Prior to approval, the FDA considers the amount of a substance expected to migrate into food and the toxicological concerns about the particular chemical."

"If there were risks - and I don't think there were - they'd be tiny," says Robert L. Wolke, Ph.D., professor emeritus of chemistry at University of Pittsburgh and author of What Einstein Told His Cook: Kitchen Science Explained (W.W. Norton & Company, 2002). According to Wolke, even if toxins existed in plastics, the amounts leached out would be minute because plastics are generally impermeable, hard, smooth, and not porous or prone to emitting chemicals.

WHAT TO AVOID
More troublesome than other plastics are the polystyrene containers many restaurants use for take-out food, not because of safety concerns but because they don't stand up to heat.

"There's no toxic danger, but if you throw them into the microwave you may find gooey melted plastic all over your food," Wolke says.

Metal in the microwave is a well-known no-no because it deflects microwaves, perhaps causing fire-igniting sparks. However, some frozen food manufacturers intentionally add a thin aluminum coating to the lid. This browns the food's surface without damaging the oven, Wolke says. You can even get away with small pieces of foil used to wrap less than one-fourth of the food - say, the bony end of a chicken drumstick - to prevent it from overcooking or drying out.

WHAT TO USE
The safest containers for the microwave? Glass. China and porcelain place a close second. Be wary of stoneware, artisan pottery, or china trimmed or painted with metallic paint. These pieces may contain tiny iron or other metal particles that could create sparks and possibly a fire, Wolke says.

Cardboard and paper towels generally are fine for reheating, but items with colored ink and recycled paper may contain particles of carbon, which may ignite the paper. Wolke considers an overturned plain paper plate the ideal cover for heating foods in a microwave. "Plates are perfectly safe and keep their shape without anything touching your food," he says. "They don't stretch, melt, or get gooey on food like plastic wrap - and fat doesn't spatter on the oven." Avoid paper plates that include metallic decorations.

A HOME TEST
Finally, when in doubt, you can test whether a container or wrap is really microwave-safe by putting a cup of tap water in a glass measuring cup. Place it in the microwave along with (but not touching) the utensil you're testing. Microwave both on high for one minute.

"If the utensil feels warm or hot, it is not microwave-safe because it contains metal in the material or glaze," says Sari Greaves, R.D., a certified nutritionist at NewYork-Presbyterian Hospital. "Do not use it. The utensil or oven might crack."

LEARN MORE: Visit www.fda.gov/cdrh/consumer/index.html and type "microwave" into the search box.

• Vent plastic covers during microwaving to reduce the odds of steam burns when removing the wrap.
• Use caution when heating water in the microwave. In some situations, the water can become "superheated" - reaching temperatures above 212°F without boiling - and suddenly erupt from the container.
• Be careful when microwaving foods with high concentrations of fat or sugar, which absorb microwave energy readily and can surprise you with their heat.
• Never warm a baby's bottle in the microwave; uneven heating may create unnoticed areas of scalding hot liquid.