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 The sum of the three main sources of background radiation – cosmic, terrestrial and internal – is about 2.4 mSv and is the annual whole-body dose equivalent arising from natural radiation. It must be emphasized that this is a global average dose, which may vary. There are several studies looking into the impact of high background radiation doses on humans and the possible long-term consequences of chronic exposure to such doses.

With respect to man-made radiation, the most significant source of exposure to the public is from medical procedures, which includes diagnostic X-rays, nuclear medicine, and radiation therapy. Medical exposure accounts for the largest radiation exposure to the population, after the natural background radiation. The advances in medical investigations, the important role of prevention through early diagnosis and also the aging population, are all factors leading to an increase in the number of diagnostic procedures. It is, therefore, important to find the balance between radiological exposure and the associated benefit to the patient. In order to reduce the risks of any deleterious effects from medical exposure, this should be limited as much as possible, especially in children, who are more susceptible to radiation-induced adverse events than adults.

(Bezak et al. Johns and Cunningham’s The Physics of Radiology, 2021. Adaptado