Radiological and elemental hazards of informal gold mining at OAU: health risk modelling with spectrometric and probabilistic indices.

This study investigates the environmental and radiological health risks associated with artisanal gold mining activities along the Opa River section of Obafemi Awolowo University (OAU), Ile-Ife, Nigeria. The research addresses a critical gap in understanding the long-term stochastic health effects of heavy metals and naturally occurring radionuclides in a vulnerable academic environment. Artisanal mining, though economically beneficial, has led to significant soil contamination, posing potential risks to over 40,000 campus residents and surrounding communities. The study evaluates the extent of contamination and quantifies associated health risks, aligning with Sustainable Development Goals (SDGs) 3, 6, 12, and 15. A total of 100 soil and mine tailing samples were collected and analysed using X-ray fluorescence (XRF) spectrometry for elemental composition and NaI(Tl) gamma spectrometry for radionuclide activity. Deterministic risk indices-including Hazard Quotient (HQ), Hazard Index (HI), Radium Equivalent (Raeq), and Gamma Index (Iᵧ)-were computed following USEPA and UNSCEAR guidelines. To address uncertainty in exposure parameters, a Monte Carlo Simulation (10,000 iterations) was employed to estimate Excess Lifetime Cancer Risk (ELCR). Results revealed elevated concentrations of lead (Pb: 267.94 µg/g), manganese (Mn: 4026.46 µg/g), and potassium-40 (40K: 511.10 Bq/kg). While deterministic indices remained below critical thresholds, probabilistic modelling indicated a worst-case ELCR of 2.04 × 10-4, suggesting up to 204 potential cancer cases per million individuals. The findings underscore the inadequacy of relying solely on deterministic models and highlight the need for probabilistic risk frameworks in environmental health assessments. The study advocates continuous environmental monitoring, site reclamation, and integration of Monte Carlo-based risk forecasting into national radiation safety policies to safeguard public health in mining-impacted academic environments.