Made with Xara Talk to us and ask the expert  Welcome to Operational Radiation Safety “Πάν μέτρον άριστον” These various possible effects at the molecular, cellular and tissue level influence the overall outcome of a person exposed to radiation. The severity of any  immediate effect will depend on the total amount of exposure to radiation within a given period of time-termed the radiation dose. If a person is exposed to  very high levels of radiation for a significant period of time and the accumulated dose is high, a large number of cells can be killed. This represents serious  injury to the exposed person (e.g. skin burns, hair loss, sterility, damage to the blood-producing systems and the immune system). Depending on the dose,  the exposed person can recover from the injuries, particularly if good medical treatment is made available quickly. But at very high doses, recovery is not  possible, leading to death over days or weeks. At lower doses of radiation, below the levels associated with early onset of injury and death due to cell-killing, an exposed population may show an increased  incidence of certain types of cancer, years to decades later, compared with populations that were not exposed. In this respect ionizing radiation is a  carcinogen similar to cigarette smoke and the incidence of cancer in a population increases with the radiation dose received. In scientific studies on animals,  hereditary effects have been observed, but this has never been observed in human populations, though we can assume that it probably does occur in humans  to a small degree.