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Radon risk

Sources of Rn-222 (radon) in bedrock

Uranium U-238 is present in all rock types in different concentrations. By its radioactive decay, radon Rn-222 is generated and released from rocks and soils. Some of the rocks like granites or black shales contain increased concentration of uranium. Therefore the risk of radon release and penetration into houses built on these rock types is higher. Radon in the indoor environment decays to daughter products, which are metallic isotopes of polonium and bismuth. The daughter products are bound to aerosol particles and are accumulated in the lungs. In higher concentrations they can increase the probability of lung cancer. The rocks and soils are the main source of radon compared to building materials and water in the Czech Republic. Therefore the attention is given to detecting rock types with higher radon potential

Mostly crystalline and granitic rocks with primarily enhanced concentration of uranium form the bedrock of the Czech Republic. Uranium is bound both in the form of anomalous accumulations – uranium deposits (of local impact) and in the form of rock forming minerals (e.g. zircon) which substantially contribute to radon release from bedrock. The highest uranium and subsequently radon concentrations are detected in the granitoid rocks of Variscan age (namely syenites - durbachites), forming plutonic bodies with large areal extent. Zirconium minerals are also concentrated in neovolcanites – mainly phonolitic and trachytic rocks. The radiometric pattern of the state territory is presented in the gamma dose rate map of the Czech Republic (M. Manová, M. Matolín 1998, Czech Geological Survey).

Radiometric map of the Czech Republic 1 : 500 000, Manova and Matolin 1998, CGS

Radiometric map of the Czech Republic 1 : 500,000. Gamma dose rate (nGy/h). (Authors: Manova and Matolin 1998, CGS)