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Ionising radiation

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

Ionisierende Strahlung
radon, soil air, transport

What is radon?

Apart from the radionuclides of minor importance to radiation exposure to man, the earth’s crust contains the natural radionuclides uranium-238, uranium-235, thorium-232, and potassium-40. The radioactive noble gas radon-222 (half-life 3.8 days) is produced as intermediate product of the uranium-238 decay chain from radium-226. It is colourless, odourless and flavourless. In Germany, radon makes the largest contribution to the radiation exposure to the population due to natural radiation sources.

radon, soil air, transport

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.

Radon protection

Measures to provide protection against radon

It is reasonable to refurbish buildings with a radon exposure above an annual mean value of 100 becquerel per cubic metre compartment air. Such values are mainly measured in regions with high natural radon concentration in the soil. Persons staying in rooms with enhanced radon contents in the air over years, have a higher risk of contracting lung cancer. It is often sufficient to take small measures to reduce the radon concentration.

Map of Germany with indicated radon concentrationSource: (according to Menzler et. al.)

Radon in buildings

From the subsoil, radon reaches outside air and enters dwellings. The radon levels indoors depend on the formation of radon within the ground, the materials on the site, their properties relevant for radon transport, and the construction method. The annual mean value of radon concentrations indoors averages 50 Becquerel per cubic meter (Bq/m³).

Health effects

Radon can accumulate in the ambient air of closed rooms. Particularly harmful are its short-lived progeny which can deposit in the respiratory tract. Alpha radiation that accrues during decay can promote lung cancer. According to statistical risk calculations, nearly 1,900 deaths yearly are due to indoor radon in Germany. Within the European Union, 20,000 deaths yearly can be attributed to indoor radon.

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