Assessing cancer risk due to exposure to radionuclides in soil dust in mining areas of South Africa

Despite the environmental significance of airborne particulates generated from mine tailings, there is limited information on exposure of people living in the neighbourhoods adjacent to such sites. The main objective of the study was to assess cancer risk due to enhanced radionuclides present in dust samples and to evaluate the exposure risk of populations living in three mining areas in the Free State and West Rand in South Africa. Soil and dust samples were collected between January 2016 and March 2018 in different seasons for determination of the level of naturally occurring radioactive materials in the samples. The samples were prepared and sealed for 4 weeks to attain secular equilibrium of the 238U and 232Th and their respective progenies, and thereafter analysed using gamma spectroscopy. Radiological parameters were calculated from the activity of the radionuclides to estimate exposure risk. The absorbed dose rate in air ranged from 76 to 137, 50 to 133 and 19 to 75 (nGy hr-1) for areas A, B and C, respectively. The mean excess lifetime cancer risk in all three mines was lower than the world average of 1.45 × 10-3; accordingly, the cancer risk was found to be negligible. The findings revealed that most radiological parameters were within the accepted international values; thus the soils in the areas could be considered to be safe for the humans living there.