In every issue of WebMD the Magazine, we ask our experts to answer readers' questions about a wide range of topics. In our September 2011 issue, we asked WebMD's nutrition expert about the usefulness and safety of microwave covers.
Q: At work, we're supposed to use plastic covers to keep the microwave clean. Are they safe?
A: Microwave covers are inexpensive, and they're dishwasher-safe and reusable, which makes them even cheaper (and green). Some are just a flat sheet of plastic, while others are dome-shaped. Most brands come in several sizes to fit different sizes of plates and dishes. Many are made of plastic that the FDA has approved for microwave use.
Plastic microwave covers are meant to replace the plastic wrap that many people use to cover their food in the microwave to keep it from splattering. The FDA says that plastic wrap labeled "microwave safe" is indeed safe. But if plastic wrap -- even microwave-safe plastic wrap -- touches food, especially food with high fat content, it can melt as well as cause steam burns when unwrapped.
Chemicals can also leach into the food if plastic wrap or plastic covers make contact with the food being heated. The FDA says those chemicals aren't dangerous, but your safest bet is to check labels carefully and only use plastic wrap and covers specifically approved for microwaves.
Want an easier solution? Cover your food with a ceramic plate or with a piece of biodegradable wax paper or paper towel.
source : Are Microwave Covers Safe?