Radiological Assessment and Statistical Approaches of Natural Radionuclides in Soil Samples Related to Phosphate Ore Activities in the site of Dagbati, Southern Region of Togo

Distribution studies of U-238, Ra-226, Th-232 , and K-40 in soil, statistical analysis of activity concentrations, and radiological safety assessment were carried out in the phosphate ore site of Dagbati, southern region of Togo. The measurements were done using high purity germanium (HPGe) detector gamma-ray spectrometer. High values of activity concentrations of U-238 and Ra-226 measured were partially attributed to the nature of rocks and the geological structure of the studied area. Twenty-two out of 30 (73.33%) of soil samples presented values above the recommended limit for gamma-ray absorbed dose rate. Although the annual effective dose equivalent mean value of 0.68 mSv year(-1) (0.54 for indoor and 0.14 for outdoor) was below the recommended limit, more than 73% of soil samples were above. Similarly, external and internal hazard's indices, gamma level index, and excess lifetime cancer risk vary from 0.06 to 1.69, 0.09 to 3.20, 0.15 to 4.19, and 0.00004 to 0.00123, respectively, with more than 73% soil samples having values above the recommended limit. These are indications that long-term exposure to natural radiation may lead to cancer risk. However, considering the level of uranium in soil samples, the mass exhalation rate of radon was investigated and the mean value of 1450 mBq kg(-1) h(-1) obtained is lower than the safe value of 57,600 mBq kg(-1) h(-1). Therefore, using phosphate mining soil as building material is safe in terms of radon exposition but might lead to radiation exposure and further an increase of cancer incidence for the population.