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The list of isotopes that contribute to natural radiation can be divided into those materials which come from the ground (terrestrial sources – the vast majority) and those which are produced as a result of the interaction of atmospheric gases with cosmic rays (cosmogenic).

NORM levels are typically expressed in one of two ways: Becquerels per kilogram (or gram) indicates level of radioactivity generally or due to a particular isotope, while parts per million (ppm) indicates the concentration of a specific radioisotope in the material.

For most human activities involving minerals and raw materials, the levels of exposure to these radionuclides are not significantly greater than normal background levels and are not of concern for radiation protection.

However, certain work activities can give rise to significantly enhanced exposures that may need to be controlled by regulation.

A 70 kg person has 4400 Bq of K-40 – and 3000 Bq of carbon-14.) Cosmogenic NORM is formed as a result of interactions between certain gases in the Earth’s atmosphere and cosmic rays, and is only relevant to this paper due to flying being a common mode of transport.

Since most cosmic radiation is deflected by the Earth’s magnetic field or absorbed by the atmosphere, very little reaches the Earth’s surface and cosmogenic radionuclides contribute more to dose at low altitudes than cosmic rays as such.

(Humans have about 65 Bq/kg of K-40 and along with those foods are therefore correspondingly radioactive to a small degree.However, the term is used more specifically for all naturally occurring radioactive materials where human activities have increased the potential for exposure compared with the unaltered situation.Concentrations of actual radionuclides may or may not have been increased; if they have, the term Technologically-Enhanced (TENORM) may be used.Excluding uranium mining and all associated fuel cycle activities, industries known to have NORM issues include: Another NORM issue relates to radon exposure in homes, particularly those built on granitic ground.Occupational health issues include the exposure of flight crew to higher levels of cosmic radiation, the exposure of tour guides to radon in caves, exposure of miners to radon underground, and exposure of workers in the oil & gas and mineral sands industries to elevated radiation levels in the materials they handle.

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