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Ionising radiation

Environmental Radioactivity - Medicine - Occupational Radiation Protection - Nuclear Hazards Defence

Ionisierende Strahlung

What is radon?

  • Radon occurs everywhere in the environment. It forms in the ground as a result of the radioactive decay of natural uranium which is present in many rocks in the ground.
  • Radon is a very mobile, radioactive noble gas that cannot be seen, smelled or tasted.
  • According to recent findings, five to ten per cent of the lung cancer cases in the German population can be attributed to the exposure to radon in buildings. Thus, radon is the second leading cause of lung cancer.

Radon is formed from natural uranium in the ground and in rocks and can accumulate in buildings. There it enhances the residents’ risk of getting lung cancer.

Radon is a very mobile, radioactive noble gas that cannot be seen, smelled or tasted. Radon is released from all materials containing uranium. It occurs everywhere in the world.

The major part of the radiation emanated from natural radiation sources to which the German population is exposed can be attributed to radon.

Radon as part of the uranium-238 decay chain

Diagram of the radon decay chain Radon decay chainDecay chain of radon-222

As intermediate product of the uranium-238 decay chain which occurs in all soils and rocks, radon is formed from radium-226.

The isotopes (special variants) radon-219 (historically termed "actinon"), radon-220 ("thoron") and radon-222 (radon) are part of the natural decay chains of

  • Uranium-235 (uranium-actinium chain)
  • Thorium-232 (thorium chain), and
  • Uranium-238 (uranium-radium chain).

They are themselves radioactive, i.e. their nuclei decay with time, emanating radiation.
If "radon" is mentioned at www.bfs.de, it is always meant to be radon-222 from the uranium-radium chain.

Exposure to radon

Radon is a radioactive element. The nucleus of radioactive elements is instable and decays. During this decay radiation is formed.

The half-life of radon is 3.8 days. This means that – irrespective of the radon concentration level – half of the amount of radon has decayed into its decay products within four days.

Short-lived radon decay products are isotopes of polonium, bismuth, and lead. These are also radioactive and have a very short half-life. Their nuclei decay within only a few minutes, emitting alpha radiation that may damage human tissue.

The radioactive radon decay products accumulate in aerosols (very fine particles in the air), which are inhaled. When the radon decay products decay in the lung, they emanate radiation. This radiation can damage cells in the lung tissue, thus causing lung cancer.

Radon risk in buildings

Via pores, gaps and cracks, radon is released from the ground and rocks – and also gets into buildings. There, radon accumulates indoors.

According to recent findings, five to ten per cent of the lung cancer cases in the German population are caused by the exposure to radon in buildings. Thus, radon is – second to smoking - the leading cause of lung cancer.

Various protection measures help reduce the radon concentration in a building.

State of 2018.11.21

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