Determinations of soil radioactivity, indoor radon concentration levels and their correlation in Oke-Ogun area, Southwestern Nigeria

Indoor radon concentration measurements in 116 rooms and gamma activity measurements in the soil samples around the rooms were carried out in Oke-Ogun area (Southwestern, Nigeria). The mean activity concentrations of 40K, 232Th, and 238U in the soil were 3±5, 25±7 and 212±99 Bqkg−1, respectively. The mean absorbed dose rate (D) and the effective dose estimated were 44±8 nGy h−1 and 45±8 μSv y−1, respectively. Radon concentrations in the rooms varied from 148 Bqm−3 to 627 Bqm−3 with mean of 282±99 Bqm−3. The estimated mean annual effective dose is 7±2 mSv y−1. It is therefore advisable for the inhabitants of the study area to ventilate their houses regularly, to reduce the possible risk of contracting lung cancer. Radon concentration in the rooms surveyed show a good correlation (R² = 0.702) with 238U/226Ra activity in soil samples.