Ionizing radiation (X-rays, gamma rays, or beta particles with sufficient energy to strip electrons from molecules and produce ions) can produce birth defects, mutations, and cancer. These adverse health effects are usually associated with high dose levels delivered at high dose rates. Such a combination is not ordinarily encountered in food.
Previous radioactive contamination of foods has involved relatively small quantities of radioactive elements which have delivered low dose rates.
In these situations, the effects of the radiation exposure on health are extremely difficult to evaluate. High dose rates (100 million to 1 billion times background) are estimated to produce 2,600 ionization events per second in cells.
Background radiation levels are estimated to produce less than one ionization in the cell nucleus per day. Because cells have the capacity to repair damage to their genetic material, repair of ionization damage may occur at low radiation exposure.
Higher exposures may overwhelm the cells’ repair capacity. Whether any effects are observed in such cases depends on several factors. These include the dose delivered to the tissues, the nature of the emissions, and the metabolism of the cell. The following examples illustrate these points: Strontium-90 in food arouses most concern not only because of its long half-life but also because it behaves in the body in a manner somewhat similar to calcium.
The replacement of bone calcium with strontium-go exposes tissues and cells covering the bone to radiation, In addition, bone marrow is subject to the ionizing radiation from the strontium-go.
Thus, cancer of the bone-forming and bone-covering tissue as well as leukaemia of the bone marrow blood-forming cells can possibly result. Iodine is concentrated by the thyroid gland. Radioiodine’s produced in atmospheric nuclear detonations or released from nuclear power stations are also taken up and concentrated by the thyroid, increasing the risk of thyroid cancer.
Tritium, or radioactive hydrogen, combines chemically with oxygen to form water. Tritium derived from food would be widely distributed throughout the body exposing all tissues to radiation.