by McCoy K

mythbuster graphic Microwave ovens are convenient, easy to use, and found in millions of kitchens across the United States. Microwaves are high frequency radio waves which are readily absorbed by materials containing water, such as foods and human tissues. When water molecules in food absorb microwave energy, they vibrate, causing the food to be heated and cooked.

In recent years, microwave ovens have received some negative attention, and information about their possible dangers has been widely circulated on the Internet. Some people are concerned that being exposed to microwave energy from microwave ovens may lead to health problems. There is also concern that materials in plastics used to cover or hold foods in the microwave may leach into foods, contaminating them with harmful toxins.

Despite these concerns, when microwave ovens and microwave-safe plastics are used according to their instructions, they are safe.

Evidence for the Health Claim

Human tissues exposed to microwaves could certainly be damaged by heat if sufficient microwave energy were to escape the confines of an operating oven. Other risks associated with microwave oven use include the following:

  • Substances used to make plastics that aren’t recommended for microwave use (eg, diethylhexyl adipate—DEHA) may leach into foods when they are used in the microwave oven.
  • Burns may result from handling hot materials that have been heated in the microwave.
  • Foods or liquids that are heated unevenly may have a tendency to explode, which can also cause burns.
  • Uneven cooking may also result in food safety risks if potentially dangerous microorganisms are not killed in parts of the food.

Evidence Against the Health Claim

Although there are theoretical risks associated with using microwave ovens, their design keeps you safe from the dangers of microwave energy. Microwave ovens are designed so that their high levels of energy are only produced when the door is shut and the oven is switched on. Once the microwave is off, there is no longer microwave energy in the food, and the oven is not transmitting microwaves. Therefore, the likelihood of being directly harmed by a normally operating oven is less likely. However, if the oven is damaged or dirty, it is possible that microwave leakage could occur.

As for microwave-safe plastics, such as food covers and plastic containers, the US Food and Drug Administration (FDA) requires that they be tested for their intended use before they are marketed. When these plastics are used in accordance with directions for their intended purpose, they are considered safe. While it is possible that some of the substances used to make the plastics may leach into foods, the FDA believes that the levels of these substances are well within the margin of safety.


When you use your microwave and microwave-safe plastics according to the manufacturers’ instructions, you are not in danger. Still, there are some precautions you can take when using a microwave oven to avoid exposure to microwaves, dangerous substances from plastics, burns, and food borne illness:

  • Check that the door closes properly on your microwave
  • Keep the door seals clean and make sure the seals are not damaged
  • Do not use a damaged microwave until it has been repaired by a qualified service engineer
  • If you are unsure whether a plastic is microwave-safe, use a different plate or container to heat the food
  • Do not use carry-out containers or margarine tubs in the microwave
  • Place plastics loosely over foods and avoid letting the plastics touch the food
  • Never use plastic storage bags, grocery bags, newspapers, or aluminum foil in the microwave
  • Make sure raw meats, like poultry and fish, are thoroughly cooked, and allow food to sit in the microwave for several minutes after cooking so that the heat distributes evenly


Electromagnetic fields and public health: microwave ovens. World Health Organization website. Available at:  . Accessed November 6, 2008.

Plastics and the microwave. US Food and Drug Administration website. Available at:  . Accessed November 6, 2008.

Image Credit: Nucleus Communications, Inc.