Radon

Radon is a noble gas which is colourless, odourless and flavourless, does not bind and escapes via cracks and gaps from the earth into the breathing air. Radon exists only as radioactive isotopes. Radon-222 is the isotope with the longest half-life of almost 4 days. It is a natural decay product of the uranium-radium series which exists all over the earth and contributes considerably to the natural environmental radioactivity.

In addition, the short-lived radon-220, traditionally called "Thoron", is also found. Because of its short half-life of only 55 seconds, it cannot move far.

The decay of radon triggers a whole chain of further decays. Radon and the similarly radioactive decay products can enter the lungs via the air we breathe and emit i.a. alpha radiation. Alpha radiation can damage the cells of the lung. These damages can favour the generation of cancer.