Natural gamma radiation exposure to humans can possess significant health risks when exposed either externally or internally. Though risks are not established at low doses, the exposure levels are set based on conservative approach. In this work, 22 bore-well rock samples were collected from the agricultural area of Dharmapuri district, Tamil Nadu to evaluate the radiation exposure to humans living in that area using a gamma-ray spectrometer. The results shows that, the activity concentration of 238U ranges from MDA to 87±2 Bq kg−1 with an average value of 25 Bq kg−1, and for 232Th it ranges from MDA to 10±2 Bq kg−1, and for the 40K it ranges from 167±9 to 669±10 Bq kg−1 with the mean value of 310 Bq kg−1. The various radiological parameters are calculated and compared with the world-recommended limit to assess the radiation hazards. To identify the relation among the natural radioisotopes, Pearson correlation analysis was performed between the radiological variables. It reveales that radionuclides 238U and 232Th strongly correlated with each other and radiological parameters. This implies that 238U and 232Th originated from the same source and 40K was derived from different sources.