Asian Journal of Engineering and Technology (ISSN: 2321 – 2462) Volume 04 – Issue 04, August 2016 Asian Online Journals (www.ajouronline.com ) 76 Assessment of Radioactivity of Some Surface Soils in Gboko Local Government Area of Benue State and Health Implications, North Central Nigeria D. T. Ayaakaa * , T. Sombo, and E. U. Utah Department of Physics, Federal University of Agriculture P.M.B 2373, Makurdi, Benue State, Nigeria * Corresponding author’s email: ayakadalton [AT] gmail.com ____________________________________________________________________________________________________________ ABSTRACT---- The activity concentrations of some radionuclides in soil samples were collected from10 locations in Gboko local government of Benue State have been determined using the Gamma ray Spectroscopy (Model No: 3M3/3). The soil activity ranges from 58.88 to 64.49Bq/Kg for 40 K, 3.33 to 5.31Bq/Kg for 238 U and 4.66 to 8.25Bq/Kg for 232 Th respectively for the urban areas. In the rural areas, the activity concentration ranges from 55.42 to 66.26Bq/Kg for 40 K, 3.77 to 5.55Bq/Kg for 238 U and 4.21 to 10.02Bq/Kg for 232 Th respectively. The mean absorbed dose rate in air ranges from 6.78nGy/h in Gboko – East to 9.37nGy/h in Mkar - Hill while the annual effective dose for the same areas varied from 0.01mSv/y in three sites to 0.01mSv/y in Mkar - Hill. The estimated absorbed dose rate in air varied from 6.73nGy/h in BCC to 10.28nGy/h in Gboko – Poly with annual absorbed dose of 0.01mSv/y in BCC to 0.03mSv/y in Ape - Inumbu. The results showed that, the annual effective dose rate is much lower than 0.1mSv/y maximum permissible limit recommended for humans by WHO, (2009). It is also lower than the safe limit of 0.07mSv/y permitted by UNSCEAR,( 2009) for individual members of the public. This reach work indicated that the samples soil may have not been impacted radio logically. Keywords---- Geology, Sample Soil, Gamma spectroscopy, Ionization, Specific Activities, Absorbed dose and Annual effective ____________________________________________________________________________________________ 1. INTRODUCTION Living things are continuously exposed to natural radionuclides occurring from within and outside the atmosphere. The exposure is due to natural occurring radioactive materials NORM (Ionizing radiation) in the soil, rocks and cosmic rays entering the earth’s surface from outer space and the internal exposure from the radioactive elements through food, water and air. The natural terrestrial component is due to decay series of 238 U, 232 Th and non-series of 40 K that are present in the environment and this exist in various geological formations (Ajayi et al., 2013). Measured/estimated exposure to natural radiation from naturally occurring radionuclides has become environmental concern to the public in Nigeria and national authorities of many other countries because of the incomparable health implication caused by these radionuclides. (Tchokossa et al 2006., Ajayi et al 2009., Diab et al 2008., Fatima et al., 2008). It has become established that radiation is part of the natural environment and it is estimated that approximately 80% of all human exposure comes from naturally occurring radioactive material (NORM). To estimate the terrestrial gamma dose rate for outdoor occupation, it is very important to evaluate the natural radioactivity level in soils (Mokobia et al., 2000). The knowledge of the distribution and of the behavior of the radionuclides in soil, in particular of the uranium isotopes and its daughter products is essential in understanding several aspects of the natural radiation environment, as the exchange of radionuclides between the soil solid matrix surface and ground surface waters, the uptake of radioactive nuclides by vegetation, the upper soil layers and the atmosphere (Avwiri et al., 2012). EPA (2005) on environments, health and safety online reported that the more radiation dose a person receives the greater the chance of developing chronic health effect like cancer, heart disease, mutation, hematological depression incidence, eye cataracts, leukemia and chromosome aberrations and death. This may be hidden until many years after the radiation doses are received between (10-40years).