Australian Journal of Education and Learning Research SCIE Journals Australian Society for Commerce Industry & Engineering www.scie.org.au 33 Evaluation of Radiological Hazard Associated With The Use of Majidun River Sediment as Building Material O. Sowole Department of Physics and Telecommunication, Tai Solarin University of Education, Ijagun, Ijebu-Ode, Ogun State, Nigeria E mail: segunsowole@yahoo.com Telephone: +2348023531317 Abstract The radioactivity concentrations of 40 K, 238 U and 232 Th in sediment samples of Majidun river at Ikorodu, Lagos State in Nigeria had been determined by gamma spectrometry using NaI (TI) detector coupled with a pre-amplifier base to a multiple channel analyzer (MCA), these were then used to determine the radiological indicators; radium equivalent activity, internal and external hazard indices, and absorbed dose rate which translated to the annual effective dose rate. 10 sediment samples were collected from Majidun river. The values of the radiological indicators were found to be within the limits recommended, indicating that the use of the sediment of the river as building material pose no radiological health hazard to the occupants of the buildings. Keywords: concentration, radionuclide, radiological indicators, absorbed dose rate. 1. Introduction The world is naturally radioactive, thereby exposing humans to naturally occurring quantities of radiation on a daily basis. The exposure of human beings to ionizing radiation from natural sources is a continuing and inescapable feature of life on earth. For most individuals, this exposure exceeds that from all man-made sources combined (UNSCEAR, 2000). Radionuclides are chemical elements with unstable atomic structures called radioactive isotopes. In many parts of the world, building materials containing radioactive materials have been used for generations. As individuals spend more than 80% of their time indoor, the internal and external radiation exposure from building materials creates prolonged exposure situation (ICRP, 1999). Radiation being energy emitted when a radionuclide decays. It can affect living tissue only when the energy is absorbed in that tissue. Radionuclides can be hazardous to living tissue when they are inside an organism where radiation released can be immediately absorbed. They may also be hazardous when they are outside of the organism but close enough for some radiation to be absorbed by the tissue. Radionuclides can be released into the air by human activities. They can also be created in the atmosphere by natural processes such as the interaction of cosmic radiation with nitrogen to produce radioactive Carbon-14. Radionuclides can be removed from the air in several ways. Particles settle out of the atmosphere if air currents cannot keep them suspended. Rain or snow can also remove them. When these particles are removed from the atmosphere; they may land in water, on soil, or on the surfaces of living and non-living things. The particles may return to the atmosphere by re-suspension, which occurs when wind or some other natural or human activity generates clouds of dust containing radionuclides (OEPA, 2005). The main external source of irradiation to the human body is represented by the gamma radiation emitted by naturally occurring radioisotopes, also called terrestrial environmental radiation. These radioisotopes, such as 40 K and the radionuclides from the 232 Th and 238 U series and their decay products, exist at trace levels in all ground formations. Therefore, natural environmental radioactivity and the associated external exposure due to gamma radiation depend primarily on the geological and geographical conditions, and appear at different levels in the soils of each different geological region (UNSCEAR, 1993; 2000). However, it has been observed that the type and concentration vary considerably depending on the soil type. The effects of the radiation emitted by different radionuclides depend on the overlining soil material (thickness and type), its chelating agents and physio-chemical properties