It too can be a verb or an adjective. It describes the 'act' of applying ionizing radiation to living things. In the case of food irradiation, negative ionizing energy is used to scramble food energy molecules and makes them worthless. Eat irradiated food and you will grow old and die early. Radioactive isotopes and waste products from the nuclear industry are the source of the fission energy that is used to 'irradiate' America's food supply.
Irradiation focuses on the 'act' involved, rather than on the 'effect' the act produces.
People think nuclear when they hear radiation. In the public eye, irradiation does NOT mean the same thing as radiation. The word irradiation is neither black nor white. The wise person avoids microwave radiation, refuses to eat 'freak' food and avoids subjecting their body to the effects of 110 volt alternating current energy radiating from computer terminals and fluorescent lights. There are several ways to neutralize the effects of negative energy radiation.