Forensic GIS γ-Radiation Mapping and Associated Radiological Health Risk Assessment of the Premier Cities of Sapele, Oghara and Koko; South-South Nigeria

Abstract

The GIS mapping of the terrestrial γ -radiation levels and evaluation of the radiological health hazard to residents of Sapele, Oghara and Koko cities in Nigeria have been carried out, using a Digilert nuclear radiation survey meter, geographical positioning system (GPS) and arc ArcGIS software. In Sapele (4 zones), the measured average gamma radiation levels ranged from 0.011 ± 0.003 mR h − 1 to 0.014 ± 0.005 mR h − 1 , while in Oghara (5 zones), the average gamma radiation levels ranged from 0.013 ± 0.002 mR h − 1 to 0.026 ± 0.009 mR h − 1 and for Koko(4 zones), the values obtained ranged from 0.018 ± 0.003 mR h − 1 (1.54 ± 0.11 mSvy − 1 ) to 0.023 ± 0.008 mR h − 1 respectively, with overall mean value of 0.017 ± 0.006 mR h − 1 (1.43 ± 0.51 mSvy − 1 ) . The mean absorbed gamma dose rate for three cities of Sapele, Oghara and Koko are 106.50 ± 22.33 nGy h − 1 , 167.28 ± 22.59 nGy h − 1 and 176.80 ± 24.74 η Gyh − 1 respectively. The mean annual effective dose rate (AEDR) for the three cities is 0.13 ± 0.03 mSvy − 1 , 0.20 ± 0.07 mSvy − 1 and 0.22 ± 0.06 mSvy − 1 mSvy − 1 respectively , while the mean excess lifetime cancer risk (ELCR) values are (0.47, 0.72 and 0.77) x10−3 respectively. The results obtained in the cities indicate that the BIR levels, and corresponding estimated health risk parameters in Koko > Oghara > Sapele. The estimated effective dosage to organs shows that liver receiving the least dose of 0.07mSvy−1 (11%) while testes got the highest dose of 0.12 mSvy−1 (19%). The overall results obtained show that all the thirteen zones’ BIR levels and their estimated risk parameters exceeded their recommended limits for the public and were also higher than reported values in previous studies reviewed. The reported significant elevation of the obtained background ionizing radiation (BIR) values may not necessarily establish any immediate likelihood of radiological health risk, but call for caution on possible accumulative radiation effects in future on the residents of the study area.