Measurements of radioactivity levels in part of Ota Southwestern Nigeria: Implications for radiological hazards indices and excess lifetime cancer-risks

Super SPEC RS-125 radiation detector with large 2.0 x 2.0 NaI crystal and linear energy ranging from 0.80 MeV to 1.2 MeV was used to measure the activities of primordial nuclides and the radiation dose exposures rate in Iyana-Iyesi, Ota, southwestern Nigeria. The measured activities vary from 17±0.02 Bqkg-1 to 30.49 ±0.01 Bqkg-1 , 50.01 ±0.16 Bqkg-1 to 158.49±0.17 Bqkg-1 , and 406.9±0.42 Bqkg-1 to 1275.48±0.82 Bqkg-1 for238U,232Th and40K respectively. The acquired gamma radiation dose rate range from 138.696 ±2.06 (nGyh-1 ) to 350.103±7.21 (nGyh-1 ) with mean value of 148.22 (nGyh-1 ), almost three times higher than the recommended safe limit of 55 (nGyh-1 ). The measured activities and radiation dose rate were engaged to estimate the annual outdoor effective dose, gamma index, excess lifetime cancer risks and annual gonadal dose equivalent. It was observed from all the estimated parameters, those values in the study area are well above the recommended safe limit for normal background radiation. This suggest that the dwellers and those using the excavated geomaterials from this area for construction purposes are exposed to very high radiation from natural radionuclides. Further research to evaluate the mineralogy and geochemistry of the clay deposits in the area is highly recommended