Naturally Occurring Radionuclides in Tiles Available in Ibadan, Nigeria, and the Associated Radiological Hazards.

Introduction: All building materials of natural origin contain some amounts of primordial radionuclides, 40K, 232Th, and 238U, as well as other radionuclides in the decay series of 232Th and 238U. Purpose: The use of tiles to beautify walls and floors in dwellings has become popular worldwide and in Nigeria in particular. However, not much has been done in assessing the impact of the use of floor and wall tiles on the radiation exposure of dwellers. In this study, radioisotopes of natural origin (226Ra, 232Th, and 40K) in selected ceramic tiles often used in Ibadan Southwest Nigeria were estimated and the associated radiological parameters evaluated. Methodology: Forty-five samples of different types of floor and wall tiles were obtained from local markets within the study area. Each of the 45 samples was pulverized and sealed in an airtight sample container for 4 weeks before analysis using a sodium iodide-based gamma-ray spectrometer. Results: The average values of 226Ra, 232Th, and 40K obtained were 44.28 ± 0.56, 84.71 ± 0.60, and 830.44 ± 0.63 Bqkg-1, respectively, which shows that they are greater than the corresponding estimated worldwide average concentration. Again, the estimated average values obtained for the radiological hazard parameters for equivalent activity due to radium and representative gamma-ray level index were found to be lower than the world averages. Similarly, the absorbed dose rates due to gamma-ray emission were found to be higher than the world common values. Conclusion: This study indicates that the use of these tiles will not be posing potential radiological risk if used in dwellings. However, construction works that requires the use of these tiles must be designed in such a way that the emission of dangerous radiation will not be a threat to the occupants.

Radon and Thoron; Radioactive Gases Lurking in Earthen Houses in Rural Kenya.

In this paper, documented studies on radon and thoron concentrations in earthen dwellings and 238U and 232Th concentrations in soil in Kenya are reviewed. High concentrations of the isotopes were recorded in the earthen dwellings despite being generally well ventilated. Mrima Hill in the Coast region recorded the highest thoron levels with a mean of 652 Bq m-3. Twenty five percent of dwellings had thoron concentration in excess of 1,000 Bq m-3. Notably high indoor radon levels were recorded in Taita Taveta also in the Coast region, and in Kenyatta University situated in Nairobi in the Central region of the country. Radon concentration in the Rift Valley region was found to be too low to contribute significantly to radiation exposure. Based on studies on the concentration of 238U and 232Th in soil, the Southwestern region of the country was anticipated to have elevated radon/thoron concentrations in earthen dwellings. Existing studies involving measurement of indoor radon and thoron, and 226Ra and 232Th in soil are relatively few and of a small scale. More extensive studies are therefore necessary not only to corroborate the risk projections but to also generate sufficient data to enable countrywide mapping of indoor radon/thoron risk-prone areas.