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.
Atomic nuclei contain protons and neutrons. The stability of a nucleus depends upon the number of protons and neutrons are nearly equal, then the nucleus is stable. The nuclei in which the number of neutrons is more than the number of protons are unstable.
Radioactive rays are penetrating and ionizing and can therefore destroy living cells. Small does of radiation over an extended period may cause cancer and eventually death.