Indoor radon concentrations in dwellings and public buildings in the western districts of the Orenburg region with increased respiratory system cancer morbidity rates

Introduction: The paper presents results of a radon survey conducted in 2021-2022 in existing dwellings and public buildings in 31 settlements of three districts of the western part of the Orenburg region (Buguruslanskiy, Buzulukskiy and Matveevskiy districts). Since exposure to radon and its progeny is the second leading cause of lung cancer after tobacco smoking, the selection of the districts for the survey was based on average standardized trachea, bronchi, and lung cancer morbidity rates in the districts of the Orenburg region for 2009–2018. Materials and Methods: The survey was conducted using solid-state nuclear track detectors in 31 settlements of the districts, where 83.5 % to 90.9 % of the population of each district live (9 settlements in Buguruslanskiy district, 9 in Buzulukskiy district, and 13 in Matveevskiy district). Results and Discussion: The results of measurements: taken in 51 dwellings and 45 public buildings in three districts showed that in 45 dwellings and 25 public buildings indoor radon concentrations do not exceed the established hygienic norm (action level) of 200 Bq/m3 (EEC) adopted in Russia for existing buildings. In six dwellings the action level is exceeded; in 20 public buildings with non-round-the-clock occupancy, additional measurements using instant or continuous methods during building operating hours are required. The highest values of annual average indoor radon EEC were obtained in the settlements of the Matveevskiy district: 745 Bq/m 3 in Starokutlumbet'evo and 643 Bq/m 3 in Kuz'kino. The largest number and percentage of exceedances of the established action level were also found in the settlements of the Matveevskiy district. Conclusion: The principle applied in the selection of districts for priority survey, based on the analysis of average standardized trachea, bronchi, and lung cancer morbidity rates, proved its effectiveness: the highest levels of indoor radon concentration were found in the district with the highest trachea, bronchi, and lung cancer morbidity rate in the Orenburg region.