RESRAD‑Build Simulation of Indoor Radiation Exposure Pathways in Nigerian Residential Buildings

Indoor radiation exposure from naturally occurring radioactive materials (NORMs) in building materials poses potential long-term health risks, yet comprehensive pathway-specific dose assessments using advanced computational tools remain limited in Nigeria.This study evaluated activity concentrations and simulated indoor exposure pathways for 72 building material samples collected from Northern Delta State, Nigeria.Gamma spectrometry measured 40 K, 238 U, and 232 Th at 94.00 ± 15.52, 11.57 ± 2.32, and 9.05 ± 1.43 Bq/kg, respectively were all below UNSCEAR global averages.A RESRAD-BUILD model (implemented in Python) simulated a typical Nigerian residential room with 5.0 m × 4.0 m × 3.0 m dimensions, 0.15 m wall thickness, 0.5 h -1 air exchange rate, and 80 % indoor occupancy.The mean annual effective dose (AED) from all pathways was 0.0875 ± 0.0126 mSv/y, well below the ICRP public dose limit of 1 mSv/y.External gamma exposure was the dominant pathway, contributing 82.9 % of the total dose, followed by ingestion (17.1 %) and inhalation (0.04 %).Simulated doses agreed closely with empirical estimates (mean difference 3.1 %).Materials from South Africa and Italy showed the highest radionuclide concentrations while Chinese and local Nigerian materials showed the lowest.These results demonstrate that RESRAD-BUILD simulation provides a reliable, pathway-resolved assessment of indoor radiation exposure, and that external gamma radiation from building materials is the primary concern in typical Nigerian residential buildings.