Radon/Thoron and Progeny Concentrations in Dwellings: Influencing Factors and Lung Cancer Risk in the Rutile Bearing Area of Akonolinga, Cameroon

This paper reports the levels of radon (Rn), thoron (Tn), and their progeny (TnP) concentrations in dwellings; studies factors influencing these concentrations; and assesses the associated lung cancer risk in Akonolinga’s area in Cameroon, where rutile deposits have been identified but are not yet industrially exploited. Indoor Rn and Tn were determined using CR39-based detectors. Additionally, Rn in soil gas, 226Ra, and 232Th concentrations in soil were measured using Markus 10, high purity germanium detector (HPGe), respectively. On average, indoor Rn, Tn concentration, and the equilibrium equivalent Thoron concentration (EETC) or TnP were 39.5, 68.1, and 5.0 Bq m−3, respectively. Average concentrations of Rn in soil gas, 226Ra, and 232Th in soil were 24.3 kBq m−3, 17 Bq kg−1, and 27 Bq kg−1, respectively. Correlation analysis indicates that indoor radon and thoron levels were tightly linked with factors such as their precursor concentrations in soil, the building materials, dwelling architecture, and inhabitant living habits. Furthermore, it was observed that Rn and TnP were the major contributors to the inhalation effective dose, accounting for 39.6% and 56.7% of the total, respectively. The estimated excess lifetime cancer risk (ELCR) from the exposition to Rn and TnP was found to be 2.93 × 10−3 and 4.36 × 10−3, respectively, exceeding the global average, raising health concerns.