Source Apportionment and Age-Specific Radiological Health Risk from Drinking Water in an Active Coal Mining Region: A Case Study of Okaba, Nigeria

Access to clean water in mining regions is frequently compromised by contaminants, including naturally occurring radioactive materials. This study investigates radiological contamination of drinking water sources in the Okaba coalfield, Nigeria, where artisanal coal mining operations potentially mobilize radionuclides into surface and groundwater. Activity concentrations of 238U, 232Th, and 40K were quantified in 24 water samples using high-purity germanium gamma spectrometry. Results revealed significant radionuclide enrichment, with mean activity concentrations of 104.80 ± 15.2 Bq L−1 for 238U, 51.49 ± 8.7 Bq L−1 for 232Th, and 719.64 ± 89.4 Bq L−1 for 40K. These values substantially exceed global average concentrations for natural waters and are notably higher than those reported in other Nigerian mining regions. Radiological hazard indices, including radium equivalent activity (mean = 573.87 Bq L−1) and the internal hazard index (exceeding unity in 29% of samples), indicated significant potential health risks. Strong positive correlation between 238U and 232Th (r = 0.82, p < .01) and spatial analysis linking elevated concentrations to proximity to mining activities implicate anthropogenic mobilization as the primary source of uranium and thorium enrichment. Age-specific annual effective dose (AED) via ingestion exceeded the World Health Organization reference level of 0.1 mSv y−1 in 100% of samples for infants, 96% for children, and 92% for adults. Infants emerged as the most vulnerable cohort, with mean AED of 1.75 mSv y−1, approximately 17.5 times the guideline value. These findings underscore a serious public health concern and highlight the urgent need for targeted monitoring, remediation strategies, and policy interventions in artisanal and small-scale mining regions.