Irradiation is the process by which an item is exposed to radiation. The exposure can be intentional, sometimes to serve a specific purpose, or it can be accidental. In common usage the term refers specifically to ionizing radiation, and to a level of radiation that will serve that specific purpose, rather than radiation exposure to normal levels of background radiation or abnormal levels of radiation due to accidental exposure. This term also applies to 'non-ionizing radiation as microwaves or to low frequency (50/60 Hz power supply), high frequency (as cellular phones, radio and TV transmissions).
If administered at appropriate levels, all of these forms of radiation can be used to sterilize objects, a technique used in the production of medical instruments and disposables, such as syringes as well as in the disinfestation and sterilization of food. Small doses of ionizing radiation (electron beam processing, X-rays and gamma rays) may be used to kill bacteria in food, or other organic material, including blood. Irradiation also includes (by the principle) microwave heating.
It is also used in cancer therapy.
Irradiation can furthermore be used in cross-linking of plastics or to improve material qualities of semi-precious stones. Due to its efficiency, electron beam processing is often used in the irradiation treatment of polymer-based products to improve the mechanical, thermal, and chemical properties, and often adding unique properties. Cross-linked polyethylene pipe (PEX), high-temperature products such as tubing and gaskets, wire and cable jacket curing, curing of composite materials, and crosslinking of tires are a few examples. Irradiation is also employed to prevent sprouting of certain cereals, onions, potatoes and garlic.
During the 2001 anthrax attacks, the US Postal Service irradiated mail to protect members of the US government and other possible targets. This can be of some concern to people, including artists; according to the ART in Embassies programme "incoming mail is irradiated, and the process destroys slides, transparencies and disks."
Furthermore, irradiated silver dimes were sold at the American Museum of Atomic Energy, Oakridge, TN. The dimes, Mercury and Roosevelt, were exposed to radiation. The person had the opportunity to buy the encased coins at the museum. Also, the coins were sold at the New York World's Fair, 1964-1965.