In times of danger of severe international conflicts with fear of the use of atomic weapons and accidents in nuclear power plants, a so-called "Disaster Medicine" has been created to reduce the damage in affected populations and territories. Radionuclide contamination in terrestrial ecosystems has nowadays reached a dangerous level. The most frequent and studied artificial radionuclides are iodine (131-I) and cesium (137-Cs and 134-Cs), which are both on the rise in the world. In humans, these elements are captured and metabolized by the thyroid, pancreas, mammary and salivary glands, cerebrospinal fluid and brain, thymus and numerous other organs and excrete with stool and urine. In organs, these radionuclides are a serious danger that can cause cancers, and through inflammatory, carcinogenic and necrotic mechanisms also thyroiditis, pancreatitis and functional deficiencies as well as diabetes mellitus, hypothyroidism and mental damage. The Author reports autoradiographic and scintigraphic studies describing some, little-known, damage to organs caused by radionuclides and in particular, pancreatic and thyroid cancer, chronic pancreatitis, thyroiditis and diabetes mellitus, whose incidence rate is gradually rising worldwide. Some methods of radionuclide removal and cancer prevention are also suggested.