Irradiation exposes food to extremely high doses of ionizing radiation
in order to kill bacteria. This process destroys essential nutrients
and hastens their depletion during storage and cooking. Irradiation
also creates known toxins and carcinogens in food, such as benzene and
toluene, and a new class of chemicals, called "unique radiolytic
products" some of which the FDA has never tested for safety.
Research on irradiated foods has linked them to a wide range of health
problems in humans and animals, including reproductive dysfunction,
genotoxicity, cytotoxicity, fatal internal bleeding, and, in some cases,
cancer. There is no research on the health effects of consuming
irradiated foods over a long period of time, and no population has ever
consumed irradiated foods as a substantial part of their diet.
Food irradiation also perpetuates the unsanitary environment found in
many feedlots and slaughterhouses, where animals wallow in their own
filth and are slaughtered at extremely fast linespeeds. Workers in
these facilities are often the victims of numerous accidents that result
in serious injury or even death. By treating food after it has been
processed, irradiation will only allow these conditions to continue and
even worsen, increasing the likelihood that meat will be contaminated by
excrement and other carriers of dangerous pathogens, and risking the
lives of workers.
(I'm not sure where I got this from)