摘要：More than 23 million workers worldwide are occupationally exposed to ionizing radiation and all people inthe world are exposed to environmental radiation. The meanexposure, that is the mean annual dose of per person, isdominated by medical applications and exposure to naturalsources. Due to recent developments in healthcare, e.g. theincreasing application of ionising radiation in medical imaging with relative high doses like CT, and modern high doseapplications (for example CT angiography), the exposure dueto medical application has risen. Additionally, the changes inliving conditions increase the exposure to natural radioactivity also: More living time is spent in buildings or in anurban environment, which causes higher exposure to Naturally Occurring Radioactive Materials (NORM) in buildingmaterials and higher exposure to radon. The level of radonactivity concentration in buildings is far higher than in the environment (outdoor). This effect is often amplified by modern energy-efficient buildings which reduce the air exchangeand thus increase the radon indoor activity concentration. Insummary both medical application of ionizing radiation andnatural sources are responsible for the increase of the meanannual exposure of the population.
