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Radon in buildings
Radon inside a building
From the subsoil, radon enters the atmosphere and also buildings. Indoors, radon is therefore present everywhere. Old buildings are more often affected than new ones, buildings with basement more often than buildings without basement.
A significant portion of the lung cancer cases among the German population is caused by exposure to radon and its decay products in buildings.
Influencing factors for indoor radon
Various factors influence the level of the indoor radon concentration of a building:
Amount of radon in the building subsoilShow / Hide
Higher radon concentrations in the subsoil often also increase the radon concentrations inside the buildings built upon it.
Typically, the relation of radon in indoor air to radon in soil air is approximately one to five per thousand. This results in indoor radon concentrations above 100 becquerel per cubic metre in about 10 to 50 percent of the buildings if radon concentrations in soil are 100,000 becquerel per cubic metre.
In areas where the radon concentration in the soil is under 20,000 becquerel per cubic metre, increased indoor radon concentrations can only be expected in less than one percent of the buildings.
Transport characteristics of the building subsoilShow / Hide
Tightness of a buildingShow / Hide
Due to its construction and use, there are practically always differences in pressure between the interior of a building and its subsoil. If a building is not tight against the subsoil it is built on, radon can enter the building more easily. A vacuum inside the building leads to radon being sucked from the subsoil into the building.
Constructional differences in pressure result, for example, from the height of a building: Greater height of a house results in a slight vacuum in the lowermost storey, which has a suction effect ("chimney effect"). Usage-depending differences in pressure occur when the indoor air is warmer than the outdoor air, thus creating a vacuum in the lower storeys.
Radon-containing soil air can generally enter a building (also newer ones) via cable ducts and leaks in the masonry (cracks, absence of insulation) or in the floor slab/basement floor.
Amount of radon in building material and drinking waterShow / Hide
Compared with the share of radon entering a building from the subsoil, the share of radon being released into a building from building material and drinking water is generally rather small.
Air-exchange rates of interior spacesShow / Hide
The more intensively a building is ventilated on account of its design or use, the more difficult it is for radon to accumulate there.
One example of design-related ventilation would be that the windows are very permeable or that outside air is supplied by a ventilation system. Use-related ventilation means that the residents actively open windows and doors frequently to air the rooms.
Location of rooms inside a buildingShow / Hide
The farther away from the surface a room is located, the less radon generally enters the room.
Radon concentrations in dwellings
Due to the different influencing factors, radon concentrations in living spaces differ significantly in Germany:
- In Germany, the annual mean of the radon concentration to which people are exposed in living spaces averages around 65 becquerel per cubic metre.
- According to current projections, about 10.5 million people in Germany are exposed to a radon concentration in the living space of more than 100 becquerels per cubic metre,
- of which almost 2 million people are even exposed to a radon concentration above the reference value of 300 becquerels per cubic metre.
Radon concentrations of more than 1,000 becquerels per cubic metre are also possible, but rarely occur.
The actual levels of indoor radon concentrations can only be determined by measurements.
Protection against the effects of radon
In particular the short-lived decay products of radon, which can deposit in the respiratory tract when inhaling radon-containing air, pose a risk to health. The radiation generating during their decay can promote the development of lung cancer.
There is no indication of a threshold below which radon would be harmless. For every 100 becquerel per cubic meter of long-term radon concentration in the room air, the risk of lung cancer increases by around 16 percent. Therefore, the radon concentration in living spaces should be reduced as far as this can be achieved with reasonable effort.
For people staying in radon-containing interior rooms for a short time only, the exposure is relatively low. Rooms where people stay only for a relatively short period of time are, for example, basement or box rooms.
Various measures help reduce the concentration of radon in a building and thus protect oneself against the exposure to radon and its decay products.
Where does radon occur indoors in Germany?
In the North German Plain, high indoor radon concentrations occur only rarely; they are more frequent in the German low mountain ranges and in the Alpine foreland. In the latter areas, uranium and radium-226, during whose decay radon is formed, are more frequent; the permeability of the soil there is often higher.
The Federal Office for Radiation Protection (BfS) provides a map at municipality level showing how indoor radon concentrations to which people are exposed in their living spaces vary regionally.
State of 2024.11.25
