Background radiation

Last revised by Travis Fahrenhorst-Jones on 5 Jul 2023

Background radiation refers to exposure to ionizing radiation in day-to-day life, excluding occupational exposures. It is measured in millisieverts (mSv). Ionizing radiation occurs naturally in the environment 1,2:

  • radioactive gas (e.g. radon, thoron): 0.2-2.2 mSv/year

  • external terrestrial (e.g. building materials): 0.3-1 mSv/year

  • ingestion (i.e. diet): 0.2-1 mSv/year

  • cosmic radiation: 0.3-1 mSv/year

Geographic variables in background radiation include altitude (higher altitude results in higher cosmic radiation exposure) and percentage of radioactive gas in the atmosphere. The average background radiation is 1.5-2 mSv/year in Australia 1, 3.2 mSv/year in the United States 2, and 2.3 mSv/year in the United Kingdom 3.

Medical exposure is sometimes considered part of background radiation with average doses of 1.7 mSv (Australia) 1, and 2.7 mSv (UK) 3 to 3.0 mSv (United States) per person per year 2. These figures will vary dramatically depending on availability and technology.   

See also

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