FAQ: microwave safety

Microwaves are great for convenience, but there are things you should be aware of before you cook certain foods or in certain ways. Here are the answers to some frequently asked questions.

No. Years of studies have found that microwave ovens leak too little radiation to be a health hazard. Just be sure that your microwave never operates while the door is open. If it does, its safety switch is broken and needs repair.

Yes, but the FDA cautions that you shouldn't let plastic wrap touch the food, since it can melt or allow chemicals to leach into the food.The bad news is that several terrible-sounding substances can seep from plastic wrap into your food during microwaving. These include diethylhexyl adipate, or DEHA, polyvinyl chloride and polyethylene.

The less-bad news is that animal studies have found that the tiny amounts of these substances that you ingest from microwaved foods are well below toxic levels and probably harmless. At least that's the current official verdict. To be safe, keep plastic wrap from touching the food. If you're still worried, use glass or china in the microwave instead of plastic.

Use only containers clearly marked as "microwave safe," since you can be sure they've been tested. Many plastic containers that are labelled as safe still allow minuscule amounts of the aforementioned chemicals to seep into food during microwaving but, again, this is not dangerous to your health. Never use old yogurt, margarine or other packaged food containers in the microwave, since they can allow larger amounts of chemicals to seep into your food.

Have you ever heated water for tea in the microwave and had it boil over in a furious froth when you added a tea bag or sugar? That's thanks to a phenomenon called superheated water, or water that's heated past the boiling point. Oddly enough, the water remains eerily still while in the microwave. It's a function of physics, partly due to the smooth container remaining cooler than the water (as microwave ovens heat only the water, while kettles and pots on a flame heat the container as well).

To lessen the odds of creating superheated water, put a wooden coffee stirrer or a spoonful of sugar or salt in the cup before microwaving.

Brown bags are definite microwave no-nos; they can contain contaminants and tiny metal shards that can ignite.

Yes. microwaves can't penetrate aluminum foil, so some advanced chefs use foil to shield certain parts of food that may cook too quickly (such as the wings on a Cornish game hen). According to the FDA, if you use new, smooth foil (creases can promote sparking), keep the amount small (no more than a hand's width) and place the foil at least five centimetres (two inches) away from the wall of the microwave to prevent burning, all should go well.

No. If you had your pacemaker installed more than 25 years ago, ask your doctor if it's safeguarded against microwaves. Otherwise, if it's a current model, passing by or hovering near the oven while it operates poses no threat.