A radiation accident involves a non-routine overexposure to ionizing radiation, as a result either of dispersal of radioactive material or of being too close to a radioactive source. This could occur, for example, following a major accident at a nuclear facility, in industrial or medical settings because of lack of appropriate occupational or patient safety, following loss or theft of radioactive material, or as a result of a deliberate malicious act. Exposure to ionizing radiation can pose a substantial health risk, with the type and level of risk depending on the duration and amount of exposure.