Abstract
<title>Abstract</title> <p> This study assessed the excess lifetime cancer risk (ELCR) associated with environmental gamma radiation exposure among residents in densely populated areas of Ulaanbaatar city. Soil samples collected in 2025 from selected locations based on a 1-km grid sampling scheme were analyzed at the accredited gamma spectrometry laboratory of the Institute of Nuclear Science and Technology, National University of Mongolia. Based on the measurement results, the annual effective dose (E <sub>out</sub> ) and ELCR were calculated. Statistical analysis based on the Monte Carlo simulation method was conducted to evaluate the distribution characteristics of ELCR and its 95% confidence interval. The results showed that the mean ELCR in 2025 was estimated at (0.261 ± 0.035)×10⁻³. This value was lower than the internationally accepted reference level of 0.290 ×10⁻³, indicating a relatively low environmental gamma radiation risk in Ulaanbaatar City. The results provide updated baseline information for environmental radiation monitoring and future radiological risk assessment in Ulaanbaatar City. </p>