What is radon?

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 radioactive 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

Decay 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, approximately six percent of the lung cancer cases in the German population are caused by the exposure to radon in buildings. Thus, radon is – after smoking - one of the most important causes of lung cancer.

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