The book tells about the ecological consequences of the Chernobyl Disaster, radionuclide pollution, migration of radionuclides along the Dnipro River and the cascade of its reservoirs to the Black Sea, the dynamics of radionuclide accumulation, radiation doses and disturbances in terrestrial and aquatic ecosystems. The generalized results of research executed by experts from Ukraine, Belarus, Russia and other countries concerning early and long-term consequences of ionizing irradiation of a human body are given. Expanding the use of nuclear technology and sources of ionizing radiation not only strengthens the power of countries, but also creates risks for the civilization of the nuclear age. Tests of nuclear and thermonuclear weapons, the Chernobyl and Fukushima-1 disasters have led to the formation of previously unknown in the biosphere man-made radionuclide anomalies unsuitable for permanent human habitation. The book is intended for a wide range of readers.