Age-Specific Radiological Risk of ²²²Rn in Drinking Water Wells Along the Sultandağı Fault Zone (Türkiye): A One-Year Monitoring Study

Background: Radon in drinking water is a potential source of ionizing radiation exposure, yet long-term monitoring data from active tectonic regions remain limited. This study investigated ²²²Rn activity concentrations in drinking-water wells along the Sultandağı Fault (Afyonkarahisar, Türkiye) and assessed age-dependent radiological risks. Methods: ²²²Rn concentrations were measured at two-week intervals in 15 drinking-water wells between June 2021 and June 2022 using a WG-1001 water–gas separation system and an AB-5R radiation monitor. Annual effective dose (AED) and excess lifetime cancer risk (ELCR) were calculated for infants, children, and adults. Results: ²²²Rn concentrations ranged from 0.05 to 26.64 Bq L⁻¹, with a mean of 6.12 ± 2.79 Bq L⁻¹. Only one well exceeded the USEPA guideline level (11.1 Bq L⁻¹), whereas all measurements remained below the WHO reference level (100 Bq L⁻¹). Seasonal mean concentrations varied between 5.48 ± 2.53 and 7.08 ± 3.32 Bq L⁻¹. Mean AED values were 35.94, 13.17, and 15.63 μSv y⁻¹ for infants, children, and adults, respectively. Corresponding ELCR values were 1.26 × 10⁻⁴, 0.46 × 10⁻⁴, and 0.55 × 10⁻⁴. Conclusions: The results indicate generally low radiological risk from radon in drinking water within the study area, although elevated values were observed in some wells. Higher age-specific dose and risk estimates were obtained for infants. These findings provide long-term data on groundwater ²²²Rn variability in an active fault zone and support regional radiological risk assessment.