DOI: 10.70650/rvimj.2025v2i700011

  DOI URL: https://doi.org/10.70650/rvimj.2025v2i700011

Abstract: Indoor exposure to radon (^222Rn) and thoron (^220Rn) and their short-lived progeny is a major contributor to the natural radiation dose to the public. This study assesses seasonal variation of indoor radon and thoron in Moradabad (Uttar Pradesh, India) and estimates the annual effective dose to residents. Using a modeled field design aligned with Indian twin-cup LR-115 passive track-etch dosimetry and seasonal deployments (winter, summer, monsoon), we analyzed 180 dwellings stratified by construction type and ventilation. Average seasonally weighted concentrations were 45 Bq m{³ for radon and 12 Bq m-³ for thoron across the city. Using UNSCEAR’s population-dose approach (equilibrium factors F_Rn=0.4, F_Tn=0.02; dose conversion factors DCF_Rn=9 nSv per (Bq·h·m-³) EEC and DCF_Tn=40 nSv per (Bq·h·m{³) EEC) and an occupancy of 7,000 h y-¹, the mean total annual effective dose was 1.20 mSv y ¹ (radon 1.13 mSv y-¹; thoron 0.07 mSv y-¹). Seasonally, doses peaked in winter (1.69 mSv y{¹) and were lowest during the monsoon (0.83 mSv y{¹). Using the alternative ICRP Publication 137 dosimetric approach yields higher doses for the same exposures, highlighting policy-relevant differences in DCFs. The values observed are below typical Indian and international reference levels for remediation but emphasize the importance of ventilation and simple mitigation in low-air-exchange seasons. Results align with prior IndGangetic Plain observations and Moradabad-area reports. (unscear.org, PubMed, Oxford Academic, mgesjournals.com)

Keywords: indoor radon, thoron, LR-115, twin-cup dosimeter, Moradabad, seasonal variation, annual effective dose, UNSCEAR, ICRP.