Assessment of indoor radon concentrations and exposure dose in selected occupational buildings and dwellings in Kampala Capital City Authority, Uganda

Abstract

Radon exposure is recognised as a serious public health issue resulting from its pronounced effect association with lung cancer, especially in enclosed environments where its concentration can rise significantly. While much of the existing research has concentrated on radon levels in dwelling settings, there is a noticeable gap in studies examining radon exposure in workplaces particularly in fast-developing urban centres like Kampala Capital City Authority. This research aimed to bridge that gap by investigating radon dose levels and assessing the potential radiological risks faced by both employees and inhabitants in selected occupational and dwelling structures located within five administrative divisions of Kampala Capital City Authority. To achieve this, radon levels were monitored at 20 different sites comprising 10 workplaces and 10 dwellings using the Radon Sentinel Model 1030, a continuous radon monitoring instrument. ²²²Rn levels measured in occupational structures varied between 8.7 ± 1.5 to 95.8 ± 8.0 Bq/m³, with a mean concentration of 30.8 ± 4.5 Bq/m³. Significantly elevated readings were observed in storage zones with limited ventilation, where values exceeded the WHO’s recommended ceiling of 100 Bq/m³, reaching a maximum of 194.8 ± 21.2 Bq/m³. In residential buildings, 222 Rn levels spanned from 15.3 ± 2.3 to 188.2 ± 8.2 Bq/m³, with an average of 71.7 ± 17.5 Bq/m³. Several household measurements surpassed the WHO reference threshold. The corresponding annual ED estimates were 0.32 ± 0.05 mSv/year for occupational environments and 0.75 ± 0.18 mSv/year for dwelling settings—both remaining within the internationally endorsed public exposure limit of 1.0 mSv/year. Additional radiological parameters were analysed including the annual equivalent dose to lung tissue, the calculated excess lifetime risk of cancer, and the projected number of LCC attributable to 222 Rn exposure. Overall, the indoor 222 Rn concentrations recorded across the surveyed sites were relatively moderate and are not expected to present substantial health risks. Nevertheless, routine monitoring is advised to account for seasonal fluctuations and maintain long-term radiological safety for occupants of the building.