Does microwave radiation make food cause cancer?

This page is for anyone who wonders whether microwave ovens or microwaved food can cause cancer. It explains what microwaves do, what FDA says, and the safety issues that are real.

Almost all the anxiety about microwave ovens comes from a single word. The same word is used for x-rays, for nuclear accidents, and for the thing that reheats your soup. Those are not the same thing.

FDA draws the line explicitly: microwaves are non-ionizing radiation, so they do not have the same risks as x-rays or other types of ionizing radiation.

Ionizing radiation carries enough energy to knock electrons loose and damage DNA. That is the property that makes it a cancer concern. Microwaves do not have it. FDA says their energy is changed to heat in food.

FDA's description is straightforward. The microwave energy is changed to heat as it is absorbed by food, and does not make food radioactive or contaminated.

FDA says the energy is changed to heat as the food absorbs it.

FDA also addresses the related worry about nutrients, noting that microwave cooking does not reduce the nutritional value of foods any more than conventional cooking does. All cooking changes food somewhat. Microwaving is not a special case.

Heat is heat. A microwave gets there by a different route than a stovetop, and the food ends up in the same place.

The second worry is about standing near the appliance while it runs.

Under federal rules, FDA limits leakage to 5 milliwatts of microwave radiation per square centimeter at approximately 2 inches from the oven surface. The agency describes this limit as far below the level known to harm people.

FDA also notes that a reading taken 20 inches from an oven would be about 1/100th of the reading at 2 inches. Exposure drops sharply as you move away.

There are real microwave safety issues, and they are not the ones the internet worries about.

FDA's own safety tips include:

• Do not run an oven if the door does not close firmly or is damaged.
• Use cookware made for microwave ovens.
• Do not heat water longer than the maker recommends.
• Do not stand directly against the oven while it runs.

None of these tips is about cancer.

Meanwhile, the appliance on your counter is covered by a federal leakage standard, and FDA says plainly that microwaving does not make food radioactive or contaminated.

The split between ionizing and non-ionizing radiation is worth remembering, because it applies far beyond the kitchen.

Ionizing radiation, as described above, can damage DNA. X-rays and CT scans fall into this group. That is why medical imaging involves weighing whether the information is worth the exposure.

Non-ionizing radiation does not have that energy. Microwaves sit here, as do radio waves and the signals from everyday household devices. FDA calls microwaves non-ionizing, so their risks are not the same as x-ray risks.

Whenever you meet a claim about radiation and cancer, first work out which type is meant. That clears up most of the confusion. The two categories share a word and very little else.