A representative national indoor radon survey in Germany

Background: Radon is a carcinogenic indoor pollutant, which can cause lung cancer. Therefore, radon protection was included in national legislations and radon protection activities are carried out in Europe. Objective: In Germany a nationwide survey to measure levels of indoor radon concentration in residential buildings was conducted. Design: The survey was designed to represent the population. The measurements were taken for 6,000 households all over Germany for 12 months, with two measurements in each household with track etch detectors. The distribution follows administrative units (401 districts). In a first step, participants were acquired through a nationwide mailing with randomly chosen addresses. In a second step, more participants were brought in by specific advertising campaigns in local media. Results: Results of approx. 6,500 households (= approx. 13,000 individual readings) were included in the study. The intention of a population-representative survey could not fully be accomplished, but the areal distribution of the participating households corresponded satisfactorily to the intended district-based distribution. The radon concentrations follow a log-normal distribution. The Germany-wide median is 44 Bq/m3, the geometric mean 49 Bq/m3, and the arithmetic mean is higher at 77 Bq/m3. Discussion: The German reference level of 300 Bq/m3 is exceeded in about 3.5% of all measurements. Higher values, mainly due to geology, occur in the eastern and southern part of Germany. Known dependencies on building characteristics are confirmed, such as increased values in older buildings or on lower floors. Conclusions: This survey can serve as a profound data basis for following radon studies in Germany and for an estimation of exposure of the population due to radon.