Radiological Hazard Assessment and Human Exposure to Natural Radionuclides in Soils of Udege Mbeki Mining Area, Nasarawa State, Nigeria

Abstract

Mining involves excavating soil with radioactive materials, which may get deposited in large amounts in the atmosphere or enter the food chain and cause harm to humans when inhaled or ingested. This study evaluated the risks of exposure to ionizing radiation from the primordial and most abundant radionuclides in the soil – radium-226, potassium-40, and thorium-232 in Udege Mbeki mining area of Nasarawa State, Nigeria. Twenty-one (21) soil samples were randomly collected in the mining site and analyzed using gamma ray spectrometer. The standards used to check for the calibration are the International Atomic Energy Agency (IAEA) gamma Spectrometric reference materials RGK-1 for K-40, RGU-1 for Ra-226 (Bi-214 peak) and RTG-1 for Th-232 (Ti-208). The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in the samples ranged from 12.7462 to 430.8147 Bq/kg, 38.4147 to 725.4748 Bq/kg, and 22.3092 to 395.5596 Bq/kg respectively. The estimated effective dose in the soil samples was averaged at 148.8091 mSvy^-1 in the dump, 67.1197 mSv/yr in the farmland, and 121.4909 mSv/yr in the surface soil. These values exceed ICRP's recommended reference level of 1 mSv/yr for public exposure and 20 mSv/yr for workers averaged over a period of five years. Also, with the mean external hazard index recorded at 1.314 and exceeding the recommended threshold limit of 1.0 we conclude that the mine is hazardous both for the public and for workers.