Health Risks Assessment of Natural Radionuclides Distribution in Soil and Edible Plant Samples Within Otukpo LGA in Benue State, Nigeria

Abstract

The activity concentration of natural radionuclides and their potential radiological health hazards have been analysed in soil and edible plant samples collected from various sections of the Otukpo Local Government Area of Benue State. The activity concentration of naturally occurring radionuclides (U238, Th232 and K40) in each of the ten randomly selected samples of soil and edible plants was analysed using a High Purity Germanium Detector Gamma ray spectrometer with a model NaI(Ti) situated at the Nigeria Institute for Radiation Protection, University of Ibadan, Nigeria. The mean concentration activity of soil samples for U238, Th232 and K40 was 25.7000  6.215, 45.400  5.564 and 174.100  21.001 Bq/kg while the corresponding average activity concentration of the plant samples was found to be 27.800  4.479, 35.400  556 and 136.600  14.100 Bq/kg respectively in order of K40  Th232  U238. Radiological parameters such as radium equivalent (Raeq), internal health indices (Hin) and external health indices (Hex), indoor annual effective dose rate (AEDRin) and outdoor annual effective dose rate (AEDRout), gamma index (I) and alpha index (I), and excess lifetime cancer risks (ELCR) were determined in the sampled soil and plants to assess their health impacts. The results of the evaluated health indices were found to be reasonably lower than the permissible threshold prescribed by ICRP and may not pose any immediate health threat to the consumers. Annual effective dose (AEDing) and the excess lifetime cancer risks due to ingestion of the plant samples ranged from 0.252 – 0.631 mSv/yr and 0.009 – 0.022  103 respectively, with the Azadurachta Indica having the maximum value. The calculated average values for ADEing and ELCR for ingestion of the plant samples were found to be 0.002 mSv/yr and 0.001, respectively, which were far below the recommended safe limits of 1.0 mSv/y and 0.29  103 respectively, indicating an insignificant possibility of radiological risks accruing from continuous consumption of plants cultivated on the sample soil. The average value of the natural radionuclide soil to plant transfer factor follows the order Th232  U238  K40. This signifies a conceivable high bio-accumulation of the radionuclides on plants, with the possibility of causing radiological health risks due to long-term consumption of the plants, and therefore should be regularly monitored.

Keywords