Answer to Question #4076 Submitted to "Ask the Experts"

If irradiated food is not radioactive, then is it possible to detect whether a substance has been irradiated or not? If there are set maximum doses for irradiating food in different countries, how is it monitored/measured? What effects would an overdose have? What kind of chemical changes does irradation have on the food?

If irradiated food is not radioactive, then is it possible to detect whether a substance has been irradiated or not?

The Department of Health and Human Services, Centers for Disease Control and Prevention (CDC) states, "There are no (other) significant changes in the amino acid, fatty acid, or vitamin content of food. In fact, the changes induced by irradiation are so minimal that it is not easy to determine whether or not a food has been irradiated." The Health Physics Society writes that the Food and Drug Administration (FDA) regulates food irradiation; and a green "RADURA" symbol is internationally recognized as an indication of irradiated food and is displayed on foods offered for sale to the public.

If there are set maximum doses for irradiating food in different countries, how is it monitored/measured?

The CDC states, "The dose of irradiation is usually measured in a unit called the gray, abbreviated Gy. This is a measure of the amount of energy transferred to food, microbe, or other substance being irradiated. 10 kiloGrays, or 10,000 Grays, is the same as an older measure, the megarad. A single chest x ray has a dose of roughly a half of a milligray (a thousandth of a gray). To kill Salmonella., fresh chicken can be irradiated at up to 4.5 kilograys, which is about seven million times more irradiation than a single chest x ray. To measure the amount of irradiation something is exposed to, photographic film is exposed to the irradiation at the same time. The film fogs at a rate that is proportional to the irradiation level."

What effects would an overdose have?

An increase in the known effects, which are, according to the CDC, "The high energy ray is absorbed as it passes through food, and gives up its energy. The food is slightly warmed. Some treated foods may taste slightly different, just as pasteurized milk tastes slightly different from unpasteurized milk. If the food still has living cells, (such as seeds, or shellfish, or potatoes) they will be damaged or killed just as microbes are. This can be a useful effect. For example, it can be used to prolong the shelf life of potatoes by keeping them from sprouting. The energy can induce a few other changes. At levels approved for use on foods, levels of the vitamin thiamine are slightly reduced. This reduction is not enough to result in vitamin deficiency."

What kind of chemical changes does irradiation have on the food?

See the effects described above.

John P. Hageman, CHP