Indoor Radon and Its Health Risk Assessment in Iran: A Comprehensive Review Study

Understanding radon-prone areas is vital to prevent radon-related health problems, enhance public safety, and ensure adherence to regulations aimed at minimizing radon exposure. We conducted a comprehensive review of cross-sectional studies reporting on residential radon exposure in Iran. Our review encompassed studies published until February 13, 2022. Out of the 966 articles initially identified, 37 studies were included in our analysis, which measured indoor radon levels in a total of 3480 residential buildings in Iran. Notably, the highest residential radon levels (Bq.m⁻³) were found in Mazandaran province, with the most hazardous recorded levels in Talesh Mahalleh (3235), followed by Ramsar (1299). Conversely, Tehran, the capital city of Iran, had the lowest recorded levels of residential radon, at 11.0 Bq.m⁻³. Remarkably, indoor radon concentration exceeded both the reference levels recommended by the World Health Organization (WHO) and the standard levels set by the U.S. Environmental Protection Agency (US.EPA), with approximately 51% and 26%, respectively. The mean effective doses received by Iranian residents were 5.0 mSv.y⁻¹ (0.3–81.7). Moreover, the mean excess lifetime cancer risk (ELCR) associated with indoor radon exposure was determined to be two per 1000 people. The annual incidence of lung cancer cases (LCCs) per million people attributed to indoor radon exposure in Iranian residential buildings ranged from 5.00E − 06 to 1.47E − 03. The included studies addressed a wide range of variables affecting radon levels, but they did not cover all factors comprehensively. These factors encompass the meteorological parameters, geological characteristics, building construction materials, building type, window type, occupancy information, and ventilation rates in enclosed spaces. The potential health risks associated with indoor radon exposure necessitate the implementation of effective control measures. These should include raising public awareness, revising construction regulations, enhancing ventilation systems, identifying high-risk areas, and conducting more comprehensive studies to better understand the factors that influence radon concentration.