Assessment of carcinogenic risk from indoor radon exposure influenced by geological structures in the mountains of southern Caspian Sea

Indoor radon exposure is the main form of radon exposure that causes health consequences including lung cancer. The aim of this study was to investigate indoor radon concentration affected by different geological characteristics in a mountainous area. For this purpose, three areas close to each other in the mountains of northern Iran, which were different in terms of the presence of hot springs, were studied. Sampling and analysis of indoor radon concentration was done in twelve buildings in summer and winter. The results showed that the average concentration of radon in the studied buildings was 124.5 Bq m^-3, which was higher than the reference dose suggested by World Health Organization (WHO) (100 Bq m^-3) and lower than reference dose suggested by U.S. Environmental Protection Agency (EPA) (150 Bq m^-3). The average indoor radon concentration in areas with many hot springs, few hot springs, and no hot springs were 144.9 Bq m^-3, 130.45 Bq m^-3, and 98.06 Bq m^-3, respectively. The average Excess Lifetime Cancer Risk in the studied area was 9.700E-03, but Excess Lifetime Cancer Risk was 16.4% and 4.7% higher than the average in the areas that had many hot springs and few hot springs, respectively. High indoor radon concentration in hot spring areas and the carcinogenic risk caused by exposure to it should be controlled by concentration reduction techniques such as vent pipes and adequate ventilation, regular monitoring, and radon-resistant materials.