Excerpt from the introduction:

Food irradiation is the process of exposing food to high levels of ionizing radiation. The practice has been in existence since the 1950s, but has been more widely used in recent years.

Irradiation has three main purposes: to eradicate pests such as fruit flies on harvested crops, extend the shelf life of food, and kill disease-causing microorganisms, such as E. coli, Salmonella and Listeria monocytogenes found in meat, eggs and other foods. In order to eradicate these microorganisms, higher doses of radiation and greater exposure times are needed than for pest control or shelf life extension. The radiation dose limit in the United States is the equivalent of up to 1 billion chest X-rays.

Irradiation facilities use either gamma rays, X-rays or electron beams. Gamma rays are emitted by the radioactive isotope cobalt-60. Electron beams, or e-beams, are produced by linear accelerators with a maximum energy of 10 million electron volts (MeV). X-rays have a maximum of 5 MeV.

Of the three varieties, X-rays are capable of penetrating most deeply into food, but the process is extremely expensive and energy intensive, so large amounts of food would have to be irradiated to make it affordable. Therefore, cobalt-60 irradiation is most widely used in the food industry. However, the radioactivity of cobalt-60 has been a concern for neighbors living in close proximity to these irradiation facilities.

The increasing construction of irradiation facilities around the world could have a direct effect on international trade. Pests, such as fruit flies, have been a barrier to trade for countries producing tropical fruits and vegetables. Irradiation may provide a means for eradicating pests, making exotic produce eligible for export to the United States. Internationally, the United States is perceived as a market for irradiated food. In 2006, trade agreements on food irradiation were signed between the United States and various countries around the world. This trend is expected to continue.