Radionuclide concentrations and excess lifetime cancer risk due to gamma radioactivity in tailing enriched soil around Maiganga coal mine, Northeast Nigeria

Backround: Human activities such as mining enhance the radioactivity levels above normal background which can lead to an incremental increase in the radiation risk to the population. Materials and Methods: 20 tailing enriched soil samples collected around Maiganga coal mine, Gombe, Northeast Nigeria were assessed for their Ra-226, Th-232 and K-40 contents using HPGe gamma -ray detector. Results: The mean activity values of 11.90 +/- 3.0, 17.72 +/- 3.6 and 70.44 +/- 20.4 Bq kg were obtained for Ra-226, Th-232 and K-40 respectively. These values were below the world average values documented by UNSCEAR. The ratio of (232)Tn :Ra-226 obtained was 1.5, which showed that 232Th activity was higher than the activity of Ra-226 while 40K recorded the highest activity concentration in the studied samples. Statistical analysis identified strong positive relationships among all radiological parameters and confirmed that Ra-226, Th-232 and K-40 were the major contributors to radiation dose. Radium equivalent activity (Raeq), absorbed gamma dose rate (D-R), annual effective dose (AEDE), activity utilization index (AUI), external and internal hazard indices (H-ex and Hin()), gamma representative index (I-psi r), annual gonadal dose (AGDE) and excess lifetime cancer risk (ELCR) were calculated to quantify the radiation risk to the public from exposure to Ra-226, Th-232 and K-40 in the studied samples. The mean values of these hazard parameters were within the acceptable limits provided for human safety and environmental protection. Conclusion: The use of the tailing enriched soil samples of Maiganga coal mine for any purpose whatsoever does not therefore pose any immediate radiological risk to the coal workers or the general public.