Irradiation

Irradiation is the process whereby an item is exposed to radiation. In common usage the term refers specifically to ionizing radiation, and to a level of radiation that will be destructive to life, rather than simply exposure to normal levels of radiation, or background radiation.

This may happen as the result of a specific nuclear event at a given point. For example, a nuclear bomb being detonated will irradiate a specific area. This is one measure of the destructive power of nuclear bombs. Neutron bombs are specifically designed to irradiate an area, and minimise the mechanical damage to that area. The idea is that all living things will be killed or disabled, but that the resources of the place (buildings, vehicles and the like) will not be destroyed. In practice this is not practical as objects (especially metals) which have been irradiated with neutrons will themselves become radioactive (this is the principle behind neutron activation analysis).

Some forms of radiation will not induce objects to become radioactive. One example of this is gamma rays. Gamma rays are very short wavelength electromagnetic radiation, and are extremely energetic and hostile to life. If used at the correct doses, they can be used to sterilise objects, and this technique is used in the production of medical instruments and disposables, such as syringes.

There has been controversy about the practice of irradiating food. By irradiating the food, some or all microbes in it are killed (depending on dose). This prolongs the life of the food greatly, but can have the disadvantage of killing beneficial microbes. Some foods (for example, fish) are irradiated at a low dose to avoid killing all spoilage bacteria so that if the food is stored improperly it will begin to smell bad long before botulism bacteria could reach harmful levels (botulism bacteria are hard to kill, except at such high doses of radiation that the taste of these foods changes). Other foods (e.g., herbs and spices) are irradiated at such high doses (30 kilo-grays or more) that they are completely sterilized. Most foods are irradiated at doses between these levels. It has also been claimed that irradiation can delay the ripening of fruits and vegetables and replace the need for pesticides.

Some consumers are concerned that irradiation, by killing all bacteria in food, can serve to disguise very poor food-handling procedures that could lead to other kinds of contamination. Other consumers are simply afraid of anything to do with radiation.

Further resources

See also: Deinococcus radiodurans

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