Radon in building materials

Building material

Every building material from mineral raw material or natural rock– depending on the geological origin – contains a natural share of uranium and radium. When uranium and radium decay, radon and its decay products are formed and released from the building material into the building.

According to recent findings, approximately six per cent of the lung cancer cases in the German population can be attributed to exposure to radon in buildings. Thus, radon is one of the most important causes of lung cancer.

Building materials release rather small amounts of radon

The BfS examined market-standard building materials such as concrete, brick, aerated concrete, and sand-lime brick and also measured the level of radon they release (exhale). The building-material-related share is normally some few becquerel per cubic metre, in most cases clearly below 20 becquerel per cubic metre. Thus, building materials do generally not cause enhanced indoor radon concentrations.

How much radon is released from building material also depends on the material properties: For example, when bricks made from clay are fired at high temperatures, the pores in the clay close. That way, only small amounts of radon can be released subsequently. With unburnt material such as clay plaster, it must be assumed that more radon is released.

Legal provisions

Legal provisions to explicitly limit the release of radon from building materials do not exist. However, the contribution of radon from building materials should not significantly contribute to exceeding the reference values for radon.

Radioactivity content of building material is limited since January 1, 2019

Building materials, e.g. concrete bricks, usually consist of aggregate materials such as sand, gravel, clay, lime, concrete or similar materials. If residues from industrial processes – e.g. slags from metal smelting or sludges from water treatment, which contain more uranium and radium - are used as aggregate materials, the amount of radon can increase that gets from the building material into the building.

In its articles 133-135, the Radiation Protection Act provides for a limit of the radioactivity content of all building materials since January 1, 2019, that are used in the construction of residential and non-residential rooms. Since 2001, the Radiation Protection Ordinance had already prescribed a maximum percentage of residues from industrial processes in building materials. Since 2019, the monitoring of the radioactivity content also comprises natural mineral raw materials that may show enhanced levels of uranium and radium. This will also limit the level of radioactive radon that may be released during the decay of uranium and radium from building materials.