Radioactivity has been present on Earth since its formation; natural radionuclides are either cosmic or terrestrial in origin. Thus, man has been exposed to ionizing radiation since always. Artificial radionuclides have appeared with the development of medical, industrial and military radioactivity applications.
The harmful effects of ionizing radiation were demonstrated shortly after the discovery of radioactivity. And even if they are not completely characterized (especially at low doses), it is still necessary to be protected against ionizing radiation, and to establish the health monitoring of persons potentially exposed. These are mainly workers exposed in their normal working conditions, and patients exposed during a medical procedure using ionizing radiation. This monitoring notably includes dose assessments.