Radon outdoors in Germany

If radon escapes from soil and rocks into the atmosphere, it mixes very quickly with the outdoor air and usually occurs in low concentrations. The inhalation of radon outdoors causes a relatively low exposure to radiation. It is an unavoidable part of natural radiation exposure.

Estimations using representative measurement data

From 2003 to 2006, the Federal Office for Radiation Protection (BfS) calculated the radon concentration outdoors using a lattice-like grid of about 50 km spacing across the entire Federal Republic.

At 173 representative measurement points, solid state track detectors at a height of 1.5 metres each measured the radon concentration in the outdoor air over a period of 3 years. The German Metrological Service supported the BfS in this endeavour.

The result of the measurements: At breathing height (1.5 metres above the ground), radon occurs in low concentrations of generally 3 to 31 becquerels per cubic metre of air. The annual average in Germany is 9 becquerels per cubic metre of air.

The spatial distribution of radon concentration in Germany is shown by colour and was estimated based on averages of the regional measurements results over a 3-year measurement period.

Average radon concentrations in the ground-level atmosphere (outdoor air). How high the radon concentration actually is in a building at a certain location cannot be read from the map. Only a measurement can determine this. Read more: www.bfs.de/en-radon-measurement

Radon situation at specific locations can only be clarified by making measurements

The map shows that the radon concentration in the air near the soil rises from north to south. The reason for the amount of radon at breathing height ("air near the soil") depends on

• geology: radon arises during the decay of uranium and radium-226, which are present in all soils and rocks to a varying extent. The content of uranium and radium-226 in the soil is higher on average in the south than in the north.
• atmospheric conditions: in the north, bodies of low-radon air from the North and Baltic Sea areas reduce the radon concentration in the air near the soil; in addition, the air is mixed more strongly by the high wind speeds near the coast.

The values of radon concentration in the air near the soil help to assess the radon concentration in buildings. They also enable differentiation between geologically-influenced and human-caused (e.g. through mining) levels of radon and their contribution to the radiation exposure of people.

The map does not provide information about the radon concentration at a certain place. The actual level of outdoor radon at a given location can only be determined precisely by measurements of the near-surface air.