There is a statistical correlation between radon activity concentration in the air and the harmful effect of exposure to radon and its short-lived decay products. Radon activity concentration in air is measured in becquerels per cubic metre (Bq/m3). One becquerel per cubic metre corresponds to 1 radioactive decay per second and per cubic metre of air. Exposure to elevated radon activity concentrations increases the probability of developing lung cancer compared to exposure to lower concentrations. The relative risk of lung cancer increases, meaning that the risk increases in relation to the personal lung cancer risk of an individual. Smokers, in particular, generally have a higher risk of lung cancer, which can lead to a high absolute lung cancer risk in combination with exposure to radon. Radon in and of itself is enough to increase the probability of non-smokers developing lung cancer, depending on the duration of exposure. The average radon activity concentration in recreation rooms in Germany is 50 Bq/m3.
It is impossible to prevent radon ingress entirely. However, at concentration levels above the reference level of 300 Bq/m³ in recreation rooms it should be considered whether proportionate measures to reduce the radon concentration can be taken. Thus, a reference level is not a limit value that cannot be exceeded. The reference level of 300 Bq/m³ generally ensures a good level of health protection, but it may be reasonable to consider taking measures to further reduce the radon concentration to below the reference level in frequently used rooms.
More information on the risks of radon exposure is available on the BfS website: