The first part of the Handbook contains concepts and definitions of radioactivity, the basic laws of radioactive decay, the interaction of nuclear radiation with a substance, the principles of detection, dosimetry and protection against nuclear radiation, radiotoxicity of radionuclides, radiation safety issues, including the organization of the radiation safety service, as well as tables in which nuclear physical properties for most radionuclides are given. The second part of the Handbook is devoted to the description of toxic (acute, chronic, local) effects on the human body of chemicals, measures for the prevention of poisoning, methods of personal protection and emergency care for poisoning. The third part provides hygienic standards (MPC, OBUV, ODC) of chemicals in the air of the working zone, atmospheric air of populated areas and in the water of water bodies.