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Radiation dose from natural sources is mainly from exposure to radon in the environment. Radon has its origin from uranium-bearing bedrocks and overburden. in the present study, assessment of the level of radon over the three lithological units upon which the residential areas of obafemiAwolowo University campus, ile-ife (oAU) was situated was carried out. Soil gas radon concentration measurement was carried out at a constant depth of 0.80 m across the three lithologies (granite gneiss, grey gneiss and mica schist) using a RAD7 electronic radon detector. A total of 138 in-situ soil gas radon measurements were carried out. obtained experimental data were analysed and summarised using descriptive and inferential statistics with statistical significance set at p < 0.05. A radon potential map was also developed using existing permeability data of the soils in the area. Soil radon concentration varied across the different lithologies ranging from 0.04 kBq/m 3-190 kBq/m 3 with a mean value of 14 kBq/m 3. The mean value of Rn-222 concentration obtained in the three lithologies are 3.5 ± 5.9, 11.5 ± 25.8 and 28.4 ± 37.4 kBq/m 3 for granite gneiss, grey gneiss and mica schist respectively. there is a statistically significant difference (p < 0.001) in the mean concentration of radon-222 measured on the three lithologies. the granite gneiss and grey gneiss lithologies have been designated into low radon index, while mica schist lithology has been designated as medium radon index. 34% of the sampled areas exhibit high radon risk based on Swedish risk criteria, thereby warranting protective actions.

Drinking water samples obtained from different groundwater sources in Ekiti State, Nigeria were assayed for radon concentration with the aid of a Durridge RAD7 electronic radon detector. In the three types of well considered, higher radon contents were found in hand-dug wells with manual pumps while hand-dug wells with removable covers presented the least radon content. The total annual effective dose incurred through the consumption of groundwater in the study area is found to be within the guideline value of 0.1 mSv recommended by European Union and WHO.

The quantitative evaluations of naturally occurring radioisotopes in environmental media have provided significant information on the geological and radiological characteristics of different environments around the world. In furtherance to a preliminary study within southwest Nigeria set out to determine the distribution of 222 Rn in groundwater and soil gas, the present study employed a well-shielded NaI(Tl) and RAD 7 detectors to determine activity concentrations of 226 Ra and 222 Rn in the media. Samples were collected from 100 sampling sites spatially distributed within the study area. Multivariate statistics were employed to extract the relationships between the activity concentrations of 226 Ra and 222 Rn in order to ascertain their origin and behavior in the basement complex geological area of southwest Nigeria. The mean activity concentration of 226 Ra falls below the world average value of 35 Bq kg −1 in soil as reported by UNSCEAR, and 222 Rn mean activity concentration is lower than 100 Bq l −1 recommended by WHO and European Commission as the criterion level in utility water for the members of the public. It can therefore be concluded that there is no significant radiological risks to the environment and human health due the presence of the measured radionuclides in soil and groundwater.

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