Radiation Safety: Non-Ionizing Radiation
Non-ionizing radiation is electromagnetic radiation that ranges from extremely low frequency (ELF) radiation to ultraviolet light. Some typical sources of non-ionizing radiation include lasers, microwave ovens, and video display terminals (VDT). However, any electrical appliance or electrical wiring emits ELF radiation.
Non-Ionizing Radiation, OSHA
Radiofrequency and Microwave Radiation, OSHA
Radio Frequency Safety, Federal Communications Commission
Microwave Oven Radiation Safety
Microwave ovens are extensively used in the workplace for applications varying from heating snacks and coffee water to elaborate sample preparation procedures in the research laboratories. Persons using microwave ovens should be aware of the possible “radiation hazards” from damaged or altered microwaves that result in leaking microwave energy. Additionally we need to realize that radiation safety standards are in place to assure that properly operating ovens present no radiation risks.
Microwave radiation is a form of radiation that is related to visible light, X-rays and gamma rays. However, microwave radiation effects and hazards should not be confused with the much more energetic X-ray and gamma ray radiations. Microwave radiation has the proper frequency to interact with the water molecule and cause the heating of materials. Microwave ovens are effective for heating food because the microwave radiation causes water molecules to vibrate and produce heating. Microwaves are reflected by metals so the radiation is confined with the metal ovens and the microwaves pass through materials that are not electrical conductors, such as glass, paper and plastics.
The radiation risks to people from microwave ovens would result if excessive radiation were to escape or leak from the oven cavity. This leaking radiation could cause heating of human tissue resulting in burns if the radiation intensity is sufficient. The eyes are especially sensitive to heating from microwaves, but all body tissues can be heated and burned if the microwave radiation is sufficiently intense.
Another risk or hazard that has been attributed to microwave oven operation is the possible interference of heart pacemaker devices. There was the concern that microwave oven operations and microwave leakage radiation might interfere and alter the pulsing response of some pacemakers. This problem has been resolved with new pacemaker and battery design and the risk of malfunctioning pacemakers no longer exists from microwave oven operation. All microwave ovens produced since 1971 are covered by a federal radiation standard to assure that operating ovens are safe. This standard requires that radiation leakage be limited to less than five milliwatts per centimeter squared at two inches from the oven over the lifetime of the unit. This five milliwatts of radiation is extremely low and well below the level at which heating or burning of human tissue would occur. In addition, people are usually at much greater distances than two inches from operating microwave ovens, and the microwave exposure decreases with increasing distance from the oven. In order to assure the microwave radiation remains within the oven cavity, the standard requires that oven doors be interlocked during oven operation.
Injuries resulting from microwave oven use are the same type as those related to conventional ovens or cooking surfaces. Persons are burned by handling hot items or from spattering of hot grease or other liquids. Steam generated from items heated in microwave ovens can cause very serious and painful burns. Explosions may occur in microwave ovens, as in other ovens, from pressure built up in sealed containers or from ignition of volatile materials.
Microwave ovens that are modified or constructed for special purposes such as drying ovens in research laboratories may not have proper reflective shielding surrounding the cavity. Vent openings, disabling of interlocks or removal of doors and sides of the oven may result in dangerous levels of leakage of microwave radiation. Altering of modifying microwave ovens in any way is not recommended.
Radiation safety precautions for microwave operation are simple:
- Use ovens in accordance with manufacturers instructions.
- Never operate an oven that produces microwaves with the door open.
- Beware of heat and steam generated from foods or beverages heated in a microwave oven. Never look directly into a covered container as the cover is removed. Always allow the steam to escape first.