New map shows radon situation in homes

Map: Radon in the home

The radioactive gas radon: you can't see it, smell it, or taste it. It is present in small quantities in every building. Elevated radon levels pose a serious health risk because this indoor pollutant is one of the most common causes of lung cancer after smoking. A new map from the Federal Office for Radiation Protection (BfS) shows the average radon concentration to which people are estimated to be exposed in their homes.

Radon is formed in varying quantities in the ground throughout Germany. It can enter buildings through leaks in the floor area. According to calculations by the BfS, every person in Germany breathes in air with an average radon concentration of around 65 bequerel per cubic metre when they are at home.

The new map of the BfS shows whether the average value for the inhabitants of their own city or municipality is above or below the national average of 65 bequerel per cubic metre. The regional fluctuations in the average values range from less than 35 bequerel per cubic metre in western Lower Saxony to over 150 bequerel per cubic metre in many low mountain ranges and mountainous regions.

In densely built-up areas, the map often shows lower values than in the surrounding areas. This can be attributed to the settlement structure. In urban areas, a higher percentage of people live on higher floors than in rural areas – and the radon concentration in a building generally decreases with each floor upwards.

Dr. Inge Paulini

Only a radon measurement can provide clarity

"The sometimes very low average values do not mean that elevated radon levels cannot occur in your own community", warns BfS President Inge Paulini. "Even with a low average, high or very high radon concentrations of over 1,000 bequerel per cubic metre are possible in individual homes."

"There is no threshold below which radon is definitely harmless", says Paulini. If the legal reference value of 300 bequerel per cubic metre is exceeded, measures against radon are recommended – and even mandatory – in workplaces. In frequently used rooms, it may also make sense to consider measures to reduce the radon concentration below this value.

However, according to Paulini, you can take effective action against radon only if you know the radon concentration in your home. It cannot be read directly from the BfS map: "Only a radon measurement can provide clarity. It is simple and inexpensive. All you need is a little patience. For optimum results, the measurement should be carried out for a whole year."

Radon measuring device in a living room

Suitable radon measuring devices can be ordered from specialised laboratories and set up by yourself. These are small plastic containers. They require no power supply and emit neither light nor sound. At the end of the measurement period, the devices are sent back to the laboratory, which analyses the measurement and provides information on the results. The cost per measurement is €30–50. The BfS provides a list of providers who fulfil the quality standards for radon measurements at workplaces at www.bfs.de/radon-messen.

Basements and ground floors most frequently affected

If you spend a lot of time in buildings with an elevated radon concentration in the indoor air, the risk of developing lung cancer increases. How high the radon concentration is in a living space depends primarily on the amount of radon in the ground, the structure of the building, and the floor. Basements and ground floors are usually more affected than higher floors.

For the new map, the BfS used the results of radon measurements in living spaces throughout Germany. These were carried out by the BfS between 2019 and 2020 as part of a departmental research project of the Federal Ministry for the Environment and Consumer Protection (BMUV). The calculations also included data from building and population statistics as well as information on the characteristics of the local natural areas.

The map and further information on the methodology and notes on interpreting the map can be found at www.bfs.de/radon-karte-wohnungen.