Assessment of indoor radon (222Rn) levels and associated radiological risks in occupational buildings and dwellings in Kampala, Uganda

Abstract

Radon-222 (222Rn) is a naturally occurring radioactive gas and the second leading cause of lung cancer after smoking, posing a public health concern. Assessing indoor 222Rn levels in occupational and residential environments is essential for radiological risk evaluation. In this study, indoor 222Rn concentrations were measured using a continuous radon monitor (CRM) in 20 buildings across Kampala City, Uganda. In occupational buildings, 222Rn concentrations ranged from 8.7 ± 1.5 to 95.8 ± 8.0 Bq m−3, with a mean of 30.8 ± 4.5 Bq m−3. Poorly ventilated storage rooms showed elevated levels, with a maximum of 194.8 ± 21.2 Bq m−3, exceeding the WHO reference level of 100 Bq m−3. In dwellings, concentrations ranged from 15.3 ± 2.3 to 188.2 ± 8.2 Bq m−3, averaging 71.7 ± 17.5 Bq m−3. Some dwellings recorded values above the WHO threshold. The average annual effective doses were 0.32 ± 0.05 mSv y−1 in occupational buildings and 0.75 ± 0.18 mSv y−1 in dwellings, both below the recommended public limit of 1.0 mSv y−1. Additional radiological parameters, including annual equivalent dose, excess lifetime cancer risk and potential lung cancer cases, were also evaluated. Statistical analysis revealed a strong positive correlation between 222Rn concentrations and radiological hazard indices, as well as a positive correlation with indoor humidity and a weak negative correlation with temperature. These findings highlight the importance of controlling humidity and enhancing ventilation to mitigate indoor radon risks. Although indoor 222Rn levels in the surveyed buildings were generally low and unlikely to pose significant health risks, continued monitoring is recommended to capture seasonal variability and ensure long-term radiological protection for occupants.