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Hazards in Microwaving Food

by Ron Kurtus (7 October 2008)

Although using a microwave oven to heat food does not cause harm to the food, there are other hazards of which you should be aware.

Heating food in non-microwave-safe plastic containers can result in the material leaching into the food. Also, heating food that should really be cooked can result in harmful bacteria such as salmonella not being killed.

You need to realize the proper way to use a microwave oven for heating your food.

Questions you may have include:

This lesson will answer those questions. Health Disclaimer

Microwaves heat food

A microwave oven works by sending electromagnetic radiation in the form of microwaves throughout the inside of the oven. A major property of microwaves is that they cause certain molecules—especially water and those in food—to vibrate and get warm. Some materials, such as those in dinner plates are not affected. On the other hand, metals will react with the microwaves and cause sparks. For that reason you do not want to place metal utensils or use metal plates in a microwave oven.

I once wanted to heat up some coffee that was in a fine china cup that had gold trim around the edges. After I put the cup in the microwave oven and turned on the power, I saw sparks flying from the gold trim.

By the time I was able to turn off the power, the microwaves had eaten off al the gold trim from this fancy cup. That was a lesson learned.

Since the microwaves simply vibrate the food molecules, they only heat up the material and do no harm. One mice thing about it is that the food is heated from the inside out.

Don't use plastic containers

You should never heat food in a microwave oven in plastic containers that are not designated as microwave safe. The microwaves will not only heat your food, but they will also heat the plastic to unsafe levels, such that plastic molecules will leach into your food.

Plastic is not meant for consumption, and residues in your food are unhealthy and even unsafe.

Mothers should be especially careful to make sure baby bottles are microwave safe, if they use a microwave oven to heat up the milk.

Watch for dangerous bacteria

A microwave oven tends to concentrate the waves in certain areas inside the oven. This results in food getting hot in some areas, while other areas are cool. Often the instructions in heating food—such as a frozen dinner—is to heat it a certain amount of time and let it sit for several minutes. The reason is to allow the heat to even out throughout the food.

Newer microwave ovens have a rotating tray to allow the microwaves to irradiate al areas more evenly.

A big problem in heating food that has not been properly cooked is that harmful bacteria such as E. coli, salmonella and listeria may still be active in the food. Although the microwaves will kill the harmful bacteria in the areas that are made hot, this will not be the case in the cooler areas of the food.

Thus, heating uncooked or incompletely cooked food in a microwave oven can result in you or your family getting ill from food poisoning. To prevent that hazard, only use the microwave over to reheat previously cooked food.


Microwave ovens heat food and liquids by vibrating their molecules. Dishes and microwave safe containers do not get hot from the microwaves. Heating food in plastic containers that are not microwave safe can result in the material leaching into the food. Heating food that has not been completely cooked can result in harmful bacteria such as E. coli, salmonella and listeria not being killed. You need to realize the proper way to use a microwave oven for heating your food.

Use precautions when preparing food

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