Microwave ovens are a ubiquitous kitchen appliance, and they are valued for their ability to heat or cook food much more quickly than conventional ovens or toasters. The somewhat mysterious heating abilities of microwaves have been fodder for urban legends regarding the safety of the appliances, particularly concerning the dangers of staring into a microwave while it is operating. Evidence regarding the risk of staring into microwaves is mixed among members of the scientific and health communities.
The basis for the mythology regarding microwaves and eye damage lies in the way in which microwaves heat food. Microwaves heat or cook food through dielectric heating. A transformer in the microwave transfers energy into a device that changes electric energy into microwave radiation, and the microwaves are then directed evenly to the food. The microwaves heat up water and fat molecules in the food for even heating. Microwave radiation is different from the radiation from more dangerous waves found in X-rays because microwaves cannot electrically charge substances like cells.
Chronic exposure to microwaves has been linked to an increased risk of cataracts, according to a 1984 study published by the National Radiological Protection Board. Eyes are vulnerable to damage because they have limited access to your body's blood supply and therefore do not have access to methods for quick healing or cooling. The specific threshold for exposure has not been identified as of 2010, but chronic occupational exposure and acute exposure for at least three hours are currently linked to eye injuries as a result of microwaves.
No scientific study has found that realistic household exposure to microwaves is linked to eye damage or more serious health risks, like cancer. If you have a standard residential microwave, there is no evidence to suggest that staring into the microwave during an average heating time should produce any acute or chronic effects, according to the World Health Organization. Studies that have linked microwaves to health problems examined chronic exposure over several years and looked at high levels of exposure due to occupational hazards or direct exposure. If your microwave is fully functional without any major leaks, infrequently staring into a microwave will not cause any serious or lasting damage.
To prevent injuries to eyes, microwave manufacturers are held to strict safety standards. The microwaves that are produced inside your microwave oven are securely kept within the confines of the heating box. The U.S. Food and Drug Adminstration is the governing body responsible for setting exposure limits, and 2010 guidelines instruct manufacturers to ensure that the amount of microwave radiation that can leak from a microwave must remain below 5 milliwatts per square centimeter, a threshold determined to be well below the minimum exposure limit for protecting health.