Experimental and Monte Carlo-based health risk assessment of seasonal radon exposure in groundwater and soil of Meghalaya, India

This study examines seasonal changes in radon levels in groundwater and soil, and their related health risks, in Baridua Village, Meghalaya, India. Groundwater and soil samples were collected during summer (Aug-Sep 2024) and winter (Jan-Feb 2025). Radon in water was measured using emanometry technique, while soil radon, radium content, and exhalation rates were determined with LR-115 detectors. Groundwater radon was significantly higher in summer (57.87 Bq L^{- 1}) than in winter (29.30 Bq L^{- 1}), with 93% of summer samples exceeding the USEPA safe limit of 11.1 Bq L^{- 1}. The mean soil radon concentrations were 938.57 Bq m^{- 3} in summer and 777.14 Bq m^{- 3} in winter, suggesting relatively small variations. Soil radium content and exhalation rates were observed to be below the global average values. During summer, total effective doses due to radon in water exceeded the WHO guideline of 100 µSv y^{- 1}, with average values of 137.72 µSv y^{- 1} for adults and 147.46 µSv y^{- 1} for children. Monte Carlo simulations indicated a 48.91% chance that children may exceed this dose. Soil radon contributed little to alpha radiation dose, with only a 0.73% probability of exceeding the limit under worst-case conditions.