Radiometric mapping of terrestrial gamma radiation and evaluation of radiological health risk on the residents in Nigeria state commercial and capital cities

Abstract

The radiometric mapping of the terrestrial ionizing radiation to evaluate the possible radiological health risk to residents of Agbor and Asaba metropolis have been conducted, using a digilert nuclear radiation monitor meter and geographical positioning system (GPS). The two monitored cities and environs were delineated into five zones. Measured zones mean outdoor background ionizing radiation (BIR) levels in Asaba ranged from 0.012 ± 0.003 mRh−1 (1.01 ± 0.27 mSvy−1 to 0.023 ± 0.009 mRh−1 (1.96 ± 0.82 mSvy−1) with total mean value of 0.018 ± 0.006 (1.52 ± 0.49 mSvy−1). In Agbor, zones mean outdoor BIR levels ranged from 0.012 ± 0.004 mRh−1 (1.01 ± 0.35 mSvy−1 to 0.019 ± 0.004 mRh−1 (1.58 ± 0.37 mSvy−1) with total mean value of 0.016 ± 0.004 (1.38 ± 0.38 mSvy−1). The mean outdoor absorbed dose rate for Asaba and Agbor are 158.34 ± 50.44 and 141.52 ± 29.58 respectively. The mean annual effective dose equivalent (AEDE) for the two cities are 0.19 ± 0.05 and 0.16 ± 0.05 mSvy−1, respectively, while the mean excess lifetime cancer risk (ELCR) are (0.69 ± 0.21 and 0.64 ± 0.17) × 10−3 mSvy−1, respectively. The estimated effective dosage to organs received shows that testes have the highest dose of 0.10 mSvy−1, with liver receiving the lowest dose of 0.06 mSvy−1. The study revealed that of the 100 sampling locations, 76 sampling sites outdoor radiation levels (76%) exceeded the World ambient standard levels of 0.013 mRh−1(1.0 mSvy−1). The overall results obtained shows elevation of BIR levels and all the estimated risk parameters except ELCR and effective doses to organs, above recommended limit for the public. However, these values obtained will not constitute any immediate radiological health risk to the residents of the study areas.