Assessment of geogenic natural radionuclide contents of soil samples collected from Ogun State, South western, Nigeria

Background: Natural radionuclides are always present in the environment. Human exposure to the background radiation is inevitable. It is therefore important to assess health risk associated with these radionuclides. Materials and Methods: The distribution of natural radionuclides U-238, Th-232 and K-40 in soil samples collected from all the twenty (20) local Governments headquarter areas in Ogun state, Nigeria were determined by gamma spectroscopy using a high-purity germanium detector. The measured concentrations were used in estimating the radiological risk pose to people living in these communities. Results: The activity concentrations measured ranged between 3 +/- 1 Bqkg(-1) (Otta) to 27 +/- 6 Bqkg(-1) (odeda) for U-238, 10 +/- 1 Bqkg(-1) (Otta) to 126 +/- 6 Bqkg(-1) (Ijebu Igbo) for Th-232 and 7 +/- 6 Bqkg(-1) (Aiyetoro) to 497 +/- 1 Bqkg(-1) (Odeda) for K-40. The mean radium equivalent calculated was 77.6 Bqkg(-1) which is lower than 370 Bqkg(-1) of the world average and the hazard indices calculated were lower than unity. Conclusion: The absorbed rate and annual effective dose estimated for most of the locations are in good agreement with world average values except for Akomoje, Ake-Abeokuta, Ogere, Ijebu-Igbo and Odeda.