Assessment of Radon-222 in Borehole Water and Age-Based Dose Estimates in Misau, Dambam, and Darazo Local Government Areas of Bauchi State, Nigeria (Published)
Radon-222 (²²²Rn), a naturally occurring radioactive gas, poses potential health risks when present in drinking water sources, primarily through inhalation of released gas and, to a lesser extent, direct ingestion. This study assessed radon concentrations in 30 borehole water samples collected from Misau, Dambam, and Darazo Local Government Areas (LGAs) in central Bauchi State, Nigeria. Samples were analyzed using a Liquid Scintillation Counter (Tri-Carb LSA 1000) at the Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria. Radon concentrations (CRnw) ranged from 0.174 to 6.356 Bq/L across all sites, with LGA-specific means of 2.921 ± 1.084 Bq/L (Misau), 2.898 ± 1.660 Bq/L (Dambam), and 2.163 ± 1.021 Bq/L (Darazo). The overall mean was 2.660 ± 1.293 Bq/L. These values are well below the World Health Organization (WHO) and European Union reference level of 100 Bq/L and the U.S. Environmental Protection Agency (EPA) maximum contaminant level of 11 Bq/L. Annual effective doses (AED) due to ingestion were calculated for adults, children, and infants using age-specific water consumption rates and dose conversion factors. Mean AED values were 21.32 μSv/y (adults), 42.65 μSv/y (children), and 149.28 μSv/y (infants) in Misau; 21.15 μSv/y, 42.31 μSv/y, and 148.08 μSv/y in Dambam; and 15.78 μSv/y, 31.57 μSv/y, and 123.74 μSv/y in Darazo, all were far below the WHO reference dose level of 0.1 mSv/y (100 μSv/y) from drinking water. Results indicate negligible radiological risk, consistent with similar studies in Bauchi State and other Nigerian regions. Continuous monitoring is recommended due to geological variability in granite-rich terrains.
Keywords: Bauchi state, Borehole Water, Nigeria, Radon-222, annual effective dose, liquid scintillation counting