EVALUATION OF NATURAL EXPOSURE DOSE LEVELS FROM ENVIRONMENTAL RADIATION AT ORASHI RIVER, SOUTHERN NIGERIA.

Abstract

This paper presents the outcome of a baseline study initiated to evaluate the natural exposure dose rate in six locations of Orashi river, southern Nigeria using the Radalert Nuclear Radiation Monitor (Radalert 100) for measurement of Background Ionizing Radiation. The mean Background Ionizing Radiation (BIR) at different locations: Igovia, Okarki, Mbiama, Akinima, Joinkrama 3 and Oguta were 0.13±0.03, 0.14±0.01. 0.13±0.01, 0.17±0.02, 0.17±0.01 and 0.15±0.02 μSv/h respectively. The average results of the dose rate were within the safe recommended limit of 0.274 μSv/h. The Annual Effective Dose Equivalent (AEDE) ranged from 0.23 mSvy-1 at Igovia and Mbiama to 0.29 mSvy-1 at Akinima and JK3. The values of Annual Effective Dose Equivalent (AEDE) obtained from all the sites are lower than the permissible limit of 1.00 mSvy-1. The estimated average annual effective dose to different body organs such as the lungs, ovaries, testes, liver, kidney, bone marrow and whole body are 0.167±0.11, 0.151±0.02, 0.214±0.01, 0.120±0.04, 0.162±0.04, 0.180±0.01 and 0.177±0.03 mSvy-1 respectively. The results shows that the liver have the lowest sensitivity to radiation and lungs have the highest sensitivity to radiation. These values are below the International permissible limits of 1.0 mSvy-1 as stated by Agbalagba (2017) and Darwish et al. (2015). The values of Excess Life Cancer Risk (ELCR) are slightly higher than the permissible limits of 0.29×10-3. The values of Dose Rate, Annual Effective Dose Equivalent and Annual Effective Dose are in agreement with the permissible limit and do not pose any instant radiological health hazards on the residents of the area and the general public but may develop cancer in later years