Natural and artificial sources of ionising radiation

Natural sources

Around 2/3 of exposure to ionising radiation is due to natural sources. Natural sources of ionising radiation include:

  • Cosmic radiation
    This comes from space and increases rapidly with altitude: the dose received by a mountain dweller who lives at an altitude of 1,000 metres is 20 % higher than the dose to which a person living by the sea is exposed.
  • Terrestrial or telluric radiation
    Human beings are constantly exposed to this form of the radiation, which comes from the ground. It is also found in building materials made from materials extracted from the ground.
  • Radioactivity in the air: radon
    Radon is a naturally occurring radioactive gas that is odourless, colourless and inert. It is the main source of natural radiation, and is produced from the decay of uranium, which is naturally found in the earth's crust (soil, rocks and water).
  • Radioactivity in the human body

    The human body is radioactive to the extent that humans eat, drink and breathe radioactive substances that occur naturally in our environment. These substances are constantly being absorbed by the human body and penetrating tissue, organs and bones.

    The human body typically contains around 40 g of potassium.
    Approximately 1/1000 of these 40 g is potassium-40, a radioactive isotope of potassium.

    The level of radiation in the human body is in the region of 120 Bq/kg, i.e. 8,400 Bq for a person weighing 70 kg.

How can we protect ourselves against radioactivity?

There are 3 golden rules when it comes to protecting ourselves from radioactivity. The effects of radiation are reduced with:

  • distance: the further away the source of radiation, the lower the dose received;
  • use of a protective screen: in the event of a nuclear accident, for example, sheltering in a house acts as a protective screen against ionising radiation;
  • the duration of exposure: the shorter the period of exposure, the smaller the dose received.

Artificial sources

Around 1/3 of exposure to ionising radiation comes from artificial sources. 

Sources of artificial exposure include:

  • medical origin

    Medical imaging examinations (radiology and nuclear medicine) and medical treatments, such as radiotherapy, use ionising radiation and account for most of the artificial exposure.

  • non-medical origin

    Certain industrial applications, nuclear facilities and fallout from past events account for a small proportion of the artificial exposure to ionising radiation.

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