Natural radioactivity levels and their radiological hazard indices in selected laterite mining sites located in Northeast Nigeria have been investigated in this study. The activity concentrations Radium-²²⁶, Thorium-²³² and Potassium-⁴⁰ in laterite soil samples were determined using NaI (Tl) gamma-ray spectrometry while in situ background radiation measurements were obtained with the aid of a portable radiation survey meter. Using standard radiological assessment models recommended by the United Nations Scientific Committee on the Effects of Atomic Radiation and the International Commission on Radiological Protection, absorbed dose rate, annual effective dose equivalent, external hazard index, internal hazard index, and annual gonadal equivalent doses were evaluated.

The results showed significant differences in radionuclide content among the studied mining sites and the highest activity concentration was measured for Potassium-⁴⁰ in most of samples. The results revealed that in some locations, the gross beta and alpha radionuclide concentrations as well as the absorbed dose rates were above globally accepted average values indicating an increased level of environmental radioactivity attributed to mining activities. However, the derived values of annual effective dose and radiological hazard indexes were below safe limits internationally recommended. The study concludes that even if the evaluated mining sites are considered as radiologically safe, environmental surveillance and radiation protection measures must still be conducted to prevent possible exposure of considerable length.

Keywords: Dosimetry; Laterite; Mining; Radioactivity; Radionuclides.