The radionuclide activity data of riverbed sand samples collected from 15 different locations along the banks of Thenpennai River flows within Tiruvannamalai district of Tamilnadu, India were implemented to evaluate the radiological safety of the geographical area. The activity concentrations of natural radionuclides were determined using gamma ray spectrometry. The sand samples believed to be undisturbed, were collected from a number of locations at a depth of 5-20 cm from the surface. In this region, the mean activity concentrations for the radionuclides utilized to conduct the calculations were; 226Ra at 5.24 Bq/Kg, 232Th at 112.19 Bq/Kg, and 40K at 360.96 Bq/Kg. The radiation hazard for residents was assessed by radium equivalent activity (Raeq), indoor air absorbed dose rate (D), annual effective dose (AEDE) and excess lifetime cancer risk (ELCR). The results reported were all below the recommended maximum values. Therefore, the radiological hazards attributed to building materials under study are negligible. The use of sand in construction of dwellings is considered to be safe for inhabitants. © 2023 Elsevier B.V., All rights reserved.