Navigation and service

Ionising radiation

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

Ionisierende Strahlung

Radon in the soil

  • The radon arising in the soil partly reaches the surface and is released into the atmosphere. The exhalation rate strongly depends on the permeability of the soil and weather conditions (temperature, humidity, air pressure). Radon can also be dissolved in ground water and migrates in bedrock.
  • The radon map of Germany provides orientation as to the regional distribution of the radon concentration in the soil air one meter below the surface.
  • The "radon potential" enables conclusions to be drawn about the risk of increased indoor radon concentrations. It links the gas incidence in the soil to its permeability to create an assessment parameter.

Radon is a noble gas that is colorless, odorless and tasteless, does not bind itself and escapes through cracks and fissures from the soil into the breathing air. It only occurs in radioactive form and can cause lung cancer. Radon is the most common cause of this disease for non-smokers.

Radon release from the ground

Part of the radon originating from the decay of radium located in rocks and soil particles is emitted in the pore volume of soil and stones. Due to atmospheric conditions (temperature, air pressure, weather), the radon concentration in a depth of less than one meter varies considerably. With increasing depth, the radon concentration rises to a saturation value.

The permeability of the soil plays a decisive role. Generally, starting from a depth of one meter, the radon concentration in the soil air changes only in a minor way. Due to the half-life (circa 1,600 years) of Radium-226, the parent of radon, the radon soil air concentration is stable over a long term. If the radon concentration of a particular site is known, new measurements are only necessary after significant interventions done in the underground.

Cracks and rifts simplify the transport of radon in the underground. Therefore the local radon concentration can be much higher in the proximity of chasms, subsidences or boundaries between different rocks. Furthermore, radon can be dissolved in groundwater and transported through the geological underground.

© Bundesamt für Strahlenschutz