Ionizing radiations are present in many aspects of life today, including both radiations occurring naturally in the environment such as from radionuclides found in air (radon decay products), soils, food, water and the human body, as well as cosmogenesis and cosmic rays and artificially produced radiations such as found in:
- medical uses of X-rays (kV tubes and MV accelerators), gamma rays from external beam/brachytherapy sources and from short-lived radionuclides used in nuclear medicine (99mTc, other SPECT, PET radionuclides), as well as other emerging techniques (e.g. hadron and neutron therapies),
- nuclear industry cycle, discharges and waste,
- radioactive fallout from nuclear industry emergencies and nuclear weapons testing,
- irradiation facilities using gamma sources (60Co, 137Cs) or electron accelerators for sterilization (food, medical equipment), industrial radiography or radiation processing for environmental remediation (flue gas, wastewater, sewage sludge),
- scientific research facilities for high-energy photon/particle beams, or low-energy X-ray photons in nanotechnology.
Consider the impact in healthcare:
- 35 million medical examinations per year using radionuclides,
- 4 billion X-ray examinations per year,
- 8 million radiotherapy treatments per year,
- 11 million workers professionally exposed to ionizing radiation per year (of whom 6.5 / 4.6 million are monitored for natural/artificial sources),
- 11000 clinical accelerators and 2300 60Co sources for external beam therapy,
- 2500 HDR /LDR brachytherapy facilities,
- Over 200 industrial gamma irradiators and 1300 industrial electron accelerators.
The direct impact of ionizing radiations on medical (diagnostics and therapy), environmental (natural and in emergencies) and nuclear industry activities, shows the need for a world-wide, harmonized system of quantities and units to assure the accuracy and comparability of their measurement.