Evaluation of radon exhalation rate and excessive lifetime cancer risk in Dumpsites in Ondo city Southwestern Nigeria

Background: ondo city in ondo state nigeria includes ondo east and west could be described as a research city due to antecedent number of research institutes. materials and methods: dose due to radioactivity content of soil samples from sixteen waste dump sites in ondo, southwestern nigeria was determined using gamma-ray spectrometer in order to evaluate the radiation hazard health profile and excess lifetime cancer risk elcr. results: the weighted average value of radon emanation coefficient, mass exhalation rate, concentration in soil gas and surface exhalation rate were 10.5%, 15.2 μbq kg^- 1 s^-1, 2.2 kbq m^-3 and 18.8 mbq m^-1s^-1. the weighted mean concentrations obtained were 354 ± 53, 58±14 and 23 ± 2bq kg^-1 for ^40k, ^226ra and ^232th respectively. radium equivalent activity (119.11bq kg^-1), outdoor external dose (54.26 ngy h^-1), indoor external dose (107.04 ngy h^-1), and total average annual effective dose (0.59 msv y^-1) were obtained. from the measured γ-rays spectra, elemental concentrations were determined for ^232th (mean 5.8ppm), ^226ra (mean 4.8ppm) and ^40k (mean 1.1 %). thorium was lower than world average 7.4ppm by a factor of 1.3; radium was higher than the world average (2.8 ppm) by factor 1.7 while potassium was relatively equal to world average (1.3 %). conclusion: the total excess lifetime cancer risk elcr was found to be 1.95 x 10^-3 which was slightly higher than the world average. in addition, a good correlation was found between the radium concentration and radon exhalation rate in the area.