investigation of radon concentration in water samples from the industrial area of igbesa, ogun state, nigeria‎

Rn-222 is a naturally occurring radioactive gas that poses health risks primarily through inhalation of its decay products; dissolved radon in drinking water contributes to internal exposure via ingestion and, more significantly, through degassing into indoor air, where it increases airborne radon concentrations. in typical scenarios, waterborne radon contributes approximately 10% to the total effective dose via ingestion and up to 90% via transfer to indoor air in homes with high water usage. this study investigates levels of radon (rn-222) in 20 water samples collected from boreholes, wells, and the surin river within igbesa, ogun state, nigeria, in may 2025. the levels were measured with lr-115 type ii solid-state nuclear track detectors with levels of 5.7 ± 1.3 bq.l^-1 (sample w7, water from well) to 39.7 ± 8.3 bq.l^-1 (sample w16, surin river), and a mean of 13.535 ± 2.505 bq.l^-1. annual effective dose (aed) ranged from 0.0146 to 0.1016 msv.y⁻¹, and excess lifetime cancer risk (elcr) ranged between 0.0512 × 10⁻³ to 0.3557 × 10⁻³, both below international safety limits. the average concentration is above nigeria's recommended limit of 11.1 bq.l^-1 for potable water, particularly from the surin river that accumulates industrial effluents, suggesting effects of industrial wastes or geological activities. even though the levels fall below the world health organization's (who) 100 bq.l^-1 threshold, the breach of the nigerian limit in a few samples indicates real health issues for consumers of un-treated water, necessitating continuous surveillance.