Natural Radioactivity and Background Radiation

Background radiation is a natural part of the environment. The largest source of background radiation exposure comes from the natural radioactivity in rocks and soil and the inhalation of naturally occurring radon that seeps from the ground into our buildings. We are also exposed to cosmic radiation and the natural radioactivity in food and in the body.

On average, Australians are exposed to about 1.5 mSv each year from natural sources, although for some the dose might be more than double that. On average, we also receive about 1.7 mSv per year from medical diagnoses and treatment.

Background radiation for Australia. Total natural 1.5 mSv per year (ARPANSA 2017)

ARPANSA’s estimate of humans exposure to radiation in Australia

Human’s exposure to ionising radiation (ARPANSA 2017
Source of exposure Exposure (per year)
One CT (computed tomography) scan to the chest 5 mSv
Cosmic radiation exposure of domestic airline pilot 2 mSv
Total natural radiation in Australia 1.5 mSv
Australian uranium mining workers 1 mSv
One return flight from Melbourne to London a year 0.11 mSv
One chest X-ray (2 views) a year 0.06 mSv
Nuclear fallout (from atmospheric tests in the 1950s and 1960s) 0.02 mSv

The background radiation dose is variable; it depends on local geology, materials used for dwellings and height above sea level.

In Australia the external terrestrial dose varies depending on the amount of uranium, thorium and potassium in the surface rocks and soils

Extract from RADIOMETRIC MAP OF AUSTRALIA (2009). Commonwealth of Australia 2009 and Geoscience Australia

The following table gives some idea to how background radiation varies worldwide.

World average of natural background ionising radiation (ARPANSA 2017)
Source of exposure Exposure (per year)
Inhalation (radon gas) 0.2-10 mSv
External terrestrial 0.3-1 mSv
Ingestion 0.2-1 mSv
Cosmic radiation 0.3-1 mSv
Total natural 1-13 mSv


Health effects of ionising radiation (ARPANSA 2017)
Dose range Effects on human health (including unborn child)
Up to 10 mSv No direct evidence of human health effects
10 – 1 000 mSv No early effects; increased incidence of certain cancers in exposed populations at higher doses
1 000 – 10 000 mSv Radiation sickness (risk of death); increased incidence of certain cancers in exposed populations
Above 10 000 mSv Fatal always

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