Do Microwaves Cause Cancer? (And 3 Other Microwave Myths)

In the United States, 97% of households have a microwave. But what misconceptions about our microwave use persist? Let’s take a look at 4 microwave myths that science has proven false.

Sabrina Stierwalt, PhD
5-minute read
Episode #281

The forms of radiation that are typically linked to cancer are those with high enough energies or frequencies to ionize—or remove electrons from—atoms or molecules, and thus are able to cause damage in our cells. High energy forms of radiation include X-rays, gamma rays, and some ultraviolet radiation.

Microwaves, by contrast, are a much lower energy form of radiation. So while they can cause molecules to vibrate, like the water molecules in our leftovers, they do not change the chemical structure of the food by ionizing it or through any other means. Our bodies are full of water and so just as with food, prolonged, intense exposure to microwave radiation will cause those water molecules in our bodies to vibrate and heat up their surroundings. Thus, it is definitely not a great idea to, say, warm yourself up in the microwave if you could fit inside of one.

However, unaltered, properly functioning microwaves do not emit microwaves unless the door is shut. And according to the American Cancer Society, the amount of radiation that is allowed to leak out of microwaves based on federal laws in the US is far below the level that could potentially cause harm. The metal mesh visible through the windows on most microwave doors further have holes that are small enough that the microwaves cannot escape but large enough that visible light can still pass through, or in other words, large enough so that you can still see inside to check on the progress of your lunch.

Until we know more, it may be safest to use a glass container to reheat your food.

Myth #4: As long as it’s not metal, it can go in the microwave.

We know that we can’t put a metal fork in the microwave because metals are great conductors of electricity. The atoms that make up that fork have electrons that are easily freed to move rapidly about the utensil ultimately refusing to let the microwave radiation be absorbed like it is in food. Instead, the microwaves are reflected which can cause electrical sparks between the metal fork and any other nearby conductor of electricity, like the wall of the microwave. These sparks can burn holes in the microwave, cause a fire, and even burn out the microwave.

But what about plastic containers? Certain plastics that contain lead, BPA (or bisphenol-A, a substance that makes clear, hard plastic), or phthalates (additives that make plastic softer and more flexible) are known for letting these harmful chemicals seep into food when heated. BPA and phthalates are thought to be endocrine disrupters that can upset our hormonal balances and so in the US, plastics containing certain threshold amounts of these materials are not dubbed “microwave safe” by the FDA.

However, in approving something for microwave use, the FDA also considers the surface area ratio of the plastic container to the food, how long the container will sit in the microwave, and how often the container is likely to be used. There also may be other potentially harmful substances or “plasticizers” that turn out to be potentially harmful like BPA but that we have not yet studied. So until we know more, it may be safest to use a glass container to reheat your food.

Until next time, this is Sabrina Stierwalt with Everyday Einstein’s Quick and Dirty Tips for helping you make sense of science. You can become a fan of Everyday Einstein on Facebook or follow me on Twitter, where I’m @QDTeinstein. If you have a question that you’d like to see on a future episode, send me an email at everydayeinstein@quickanddirtytips.com.

Image courtesy of shutterstock.


About the Author

Sabrina Stierwalt, PhD

Dr Sabrina Stierwalt earned a Ph.D. in Astronomy & Astrophysics from Cornell University and is now a Professor of Physics at Occidental College.

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