GIS mapping of impact of industrial activities on the terrestrial background ionizing radiation levels of Ughelli metropolis and its environs, Nigeria

The assessment of industrial activities and effluents on the external background ionizing radiation (BIR) levels of Ughelli metropolis and its environs has been conducted, using a digilert 100 nuclear radiation monitor and geographical positioning system for GIS mapping. The monitoring of the terrestrial BIR levels was carried out for 2 years (from May 2013 to June 2015) in 21 locations within the city and 21 other major villages/towns in Ughelli North local government area of Delta state. Measured exposure rate in Ughelli metropolis revealed a mean value of 15.20 ± 2.80 µRh⁻¹ (1.28 ± 0.23 mSvy⁻¹), while a mean value of 15.19 ± 2.70 µRh⁻¹ (1.28 ± 0.23 mSvy⁻¹) was obtained in the villages/towns. The estimated mean outdoor absorbed dose rate for the Ughelli metropolis and Ughelli environs is 132.16 ± 24.36 ηGyh⁻¹ and 132.15 ± 23.50 ηGyh⁻¹, respectively. The mean annual effective dose equivalent is 0.16 ± 0.03 mSvy⁻¹) while the mean excess life cancer risk is (0.56 ± 0.11) × 10⁻³ mSvy⁻¹. GIS maps of the study area revealing the BIR distribution and higher radiation levels were recorded in areas/communities where there are industrial activities and oil and gas facilities. The overall results of the measured exposure rates and the estimated radiological indices show that 73.5% of the sampled location exceeded their permissible limits. The mean equivalent dose rate obtained is higher than the safe exposure limit of 1.0 mSvy⁻¹) recommended by UNSCEAR, and the mean radiation exposure levels in the study area is well above the normal background radiation level of 13.00 µRh⁻¹ which shows that the studied area is radiologically contaminated. Though these values obtained may not cause immediate health hazard, there is the likelihood of long-term accumulating health side effects on the residents of some of these locations and communities sampled. Recommendations are made on the possible ways of reducing the impacts on the populace.