Radioactivity concentration variation with depth and assessment of workers' doses in selected mining sites

Mining workers are exposed to radiation in the process of extracting minerals from the earth crust. In this research, activity concentration of the radionuclides in samples collected at different depths in Komu (0–220 ft) and Olode (0–30 ft) mining sites, Oyo State, Nigeria and the associated workers' radiological risks were assessed. Gemstones from these sites are mined for local and international markets. The radionuclide contents of the samples were determined using Gamma spectroscopy technique. At Komu, 238U and 232Th concentrations, with few exceptions, increased with depth while that of 40K had no defined pattern. At Olode site, 238U and 232Th concentrations decreased with depth while that of 40K was almost constant. Internal hazard indices at Komu in some cases indicated an unacceptable level of risk to workers. Workers' doses would have been underestimated by between 12 and 55% if the activity concentrations of samples in the pit were not included in the calculation.