Health risks in association with indoor radon, thoron and progeny exposure, and contribution of thoron progeny to total inhalation dose in Bangui city, Central African Republic

Measurement of radon, thoron, and their progeny was conducted in 49 dwellings in Bangui city, Central African Republic, followed by the annual inhalation dose assessment. The measurements were performed by passive-type radon–thoron discriminative detectors and thoron progeny monitors exposed for a 3-month period. The geometric means of indoor radon, thoron, radon progeny and thoron progeny concentrations (geometric standard deviations, GSDs) were 123 Bq m–3 (1.2), 76 Bq m⁠–⁠3 (3.0), 49 Bq m–3 (1.2), 5.2 Bq m–3 (2.5), respectively. The average value of the equilibrium factor of thoron, the total annual effective dose, excess lifetime cancer risk (ELCR) × 10–3, and lung cancer cases (LCC) × 10–9 measured in 49 dwellings were 0.10 ± 0.07, 4.12 ± 0.93 mSv y–1, 12.28 ± 2.78 and 74.2 ± 16.8, respectively. The contribution of thoron and its progeny to the total inhalation dose varies from 5 to 64 % with an average value of 34 %. Total annual effective doses for indoor radon, thoron and their progeny be much lower than the International Commission of Radiological Protection (ICRP) recommended range of 3–10 mSv y–1 and the World Health Organization's (WHO) limit of 10 mSv y–1. The findings suggest that indoor radon, thoron, and their progeny concentrations in Bangui dwellings are within safe limits, supporting the need for continued monitoring and public awareness programmes to maintain low exposure levels and mitigate potential long-term health risks, particularly lung cancer, in line with global radiation protection guidelines.