Outdoor ²²²Rn-concentrations in Germany – part 1 – natural background

To determine the natural radiation exposure due to outdoor radon (²²²Rn) and its short-lived decay products in Germany, the Federal Office for Radiation Protection (BfS) conducted a measuring programme over three years. The annual mean radon concentration at 1.5 m above ground level was measured with solid-state track etch detectors at 173 measuring points in an even grid with a grid length of approx. 50 km. Furthermore, annual mean values of the equilibrium-equivalent radon concentration (EEC) and the equilibrium factor were estimated on the basis of the activity concentrations of ²¹⁴Pb and ²¹⁴Bi measured at 27 stations of the German Meteorological Service (DWD). Our study yielded a spatial mean outdoor radon concentration for Germany of 9 ± 1 Bq m⁻³ (median: 8 (−0.5/+1.0) Bq m⁻³), with regional means varying from 4.5 Bq m⁻³ in Hamburg to 14 Bq m⁻³ in Bavaria. The determined EEC are in a range from 1.4 to 11 Bq m⁻³. - Highlights: • Outdoor radon background concentrations (²²²Rn) were measured in Germany. • Measurements were carried out at 173 locations over three years. • EEC and the equilibrium factor were estimated at 27 measuring points. • Effective dose due to outdoor radon was determined