The microwave oven has certainly been the most controversial of all kitchen-related inventions. Much of the concern surrounding the safety of microwaves regards the amount of radiation given off by one. The word "radiation" is charged with all sorts of connotations for us, living as we do in an age of nuclear energy. A microwave oven does produce radiation when in operation, but it is important to define what radiation is, and what dangers it poses to humans, if any.
Scientifically speaking, radiation consists of any waves that form part of the electromagnetic spectrum. Visible light, radio and television signals, and the infrared beams used by remote controls are all forms of radiation. We are constantly surrounded by every type of radiation to some degree. As most people know, some forms of radiation, such as x-rays, can be dangerous or even fatal in large enough amounts. The radiation used by microwave ovens has a very long wavelength, so that it is not visible to our eyes. It is, however, at just the right wavelength to excite water molecules, thereby heating them, and this in turn heats whatever food is in the microwave.
The vast majority of microwave radiation produced by microwave ovens is contained within the oven itself while it is in operation. A small amount may escape, and this is normal and not a cause for concern. Any of the effects or hazards presented by microwave ovens are quite mild compared to more dangerous types of energy such as gamma rays and x-rays. The main result of the exposure of an object to microwaves is that it will be heated. Therefore, burns are the main hazard presented by microwaves, as is the case with anything else that uses heat to cook food.
It was the case at one time that small amounts of microwave leakage could interfere with heart pacemakers if someone with a pacemaker stood too close to a microwave for too long. Those who design pacemakers and the batteries they use have since corrected most of these problems, although there is no guarantee that a malfunctioning microwave could not pose some form of danger. Even though most microwaves are completely safe to use, more research will need to be done in order to determine what constitutes a safe level of microwave radiation. This may take some time, as it is difficult to study what the effects are of very low levels of radiation over a person's lifetime.