Assessment of Terrestrial Gamma Radiation and Radiological Health Risk in Oleh and Ozoro, Delta State, Nigeria

This study presents an evaluation of terrestrial gamma radiation and associated radiological health risks across eight urban zones in Oleh and Ozoro, Delta State, Nigeria. Background ionizing radiation (BIR) and absorbed dose rate (ADR) measurements were conducted across four zones per town, yielding mean ADR values of 83.08 ± 10.63 nGyh⁻¹ in Oleh and 91.05 ± 12.54 nGyh⁻¹ in Ozoro. The corresponding annual effective dose equivalent (AEDE) values-0.103 ± 0.013 mSvy⁻¹ and 0.112 ± 0.016 mSvy⁻¹, respectively were significantly below the UNSCEAR global average of 0.41 mSvy⁻¹, indicating compliance with international radiological safety standards. Excess lifetime cancer risk (ELCR) estimates ranged from 0.332 ± 0.077 × 10⁻³ to 0.445 ± 0.074 × 10⁻³, with a pooled mean of 0.376 ± 0.055 × 10⁻³, marginally exceeding the UNSCEAR reference value but remaining within tolerable stochastic risk limits. Organ-specific dose analysis revealed elevated exposure in radiosensitive tissues, notably the testes and bone marrow. Statistical robustness was confirmed through Monte Carlo simulations, Bayesian inference, and Bootstrap resampling, all of which demonstrated convergence and internal consistency. The findings suggest moderate radiological exposure across the study area, with localized variations attributable to anthropogenic activity and lithologic composition. Routine monitoring and targeted public health interventions are recommended to sustain environmental safety.