Natural radioactivity measurements in soil, external dose and radiological hazard assessment in the uranium and thorium bearing region of Lolodorf, Cameroon

The level of natural radioactivity has been evaluated for soil samples collected from the uranium and thorium bearing region of Lolodorf in the southwestern Cameroon. Specific activities of ²²⁶Ra, ²³²Th and ⁴⁰K in these soil samples were determined using γ-ray spectrometry with sodium iodide (NaI(Tl)) detector. The specific activities for the whole study areas where consist of five inhabited localities were compared with the world average and permissible recommended limits. Specific activities of ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 5-120, 2-170 and 50-253 Bq kg^-1, with average values of 22±2, 37±6 and 98±7 Bq kg^-1, respectively. The average values of absorbed dose rate in air (D_a), external effective dose (E_ext), radium equivalent activity (Ra_eq), external hazard index (H_ext) and representative level index (I_γ) were 36.7±5.0 nGy h^-1, 0.29±0.04 mSv y^-1, 83±14 Bq kg^-1, 0.22±0.03 and 0.58±0.10 respectively, which, were lower than their recommended values. Although this study shows that radioactivity level is normal in the study areas, except some areas where the uranium and potassium anomalies had been found by previous investigations, the possibility of developing cancer cases among individuals must not be neglected. The soil from the sampling areas in this study can be used safely as building materials apart from some points within Ngombas and Kribi. (author)