RESUMO
Human exposure to indoor radon has been a subject of continuous concern due to its health implications, especially as it relates to lung cancer. Radon contaminates indoor air quality and poses a significant health threat if not abated/controlled. A seasonal indoor radon assessment of residential buildings of Obafemi Awolowo University was carried out to determine radon seasonal variability and to evaluate the cancer risk to the residents. AT-100 diffusion-based track detectors were deployed within living rooms and bedrooms for the radon measurement. During the rainy season, the average indoor radon concentration was 18.4 ± 10.1 Bq/m3, with higher concentrations observed in bedrooms compared to living rooms, whereas the average radon concentration was 19.0 ± 4.4 Bq/m3 in the dry season, with similar radon levels in living rooms and bedrooms. The potential alpha energy concentration values ranged from 1.62 to 7.57 mWL. The annual effective dose equivalent values were below the world average and recommended limits for public exposure. Of the three geological units underlying the residences, the buildings overlying the granite gneiss lithology have the highest radon concentrations with average value of 21.4 Bq/m3. The soil gas radon concentration to indoor radon concentration ratio over the granite gneiss lithology is 0.006. The estimated average lifetime cancer risk due to radon inhalation in the residences indicated a potential risk of cancer development in 178 persons in 100 000 population over a lifetime period. The average indoor radon concentrations were below the recommended limit, requiring no immediate remediation measures. Improved ventilation of residential apartments is recommended to minimize residents' risk to indoor radon.
RESUMO
BACKGROUND: Globally, radon is a natural contaminant that affects indoor air quality. Several epidemiological studies have implicated high radon levels in the causality of lung cancer. The study therefore determined the environmental level of radon in selective offices in the Obafemi Awolowo University, Ile-Ife. The study employed a descriptive cross-sectional design. A Pro 3-series radon detector was used to determine the radon levels in randomly selected offices. The instrument was set-up in each office and after 48 h, reading was taken and recorded on a proforma data sheet. The structural characteristics of the offices were also assessed by observation. RESULTS: The result revealed that the radon level obtained in the sampled offices ranged from 0.0 to 5.3 pCi/L (196 Bq/m(3)). The median concentration of radon obtained from sampled offices was 0.9 pCi/L. Almost all (95 %) of the offices had radon levels within the 'permissible' reference level recommended by World Health Organization. Radon levels also showed a statistically significant decline with height of office building with the mean concentration of radon in offices located on the basement, ground floor and first floor being 1.54 ± 1.32, 0.99 ± 0.56, 0.63 ± 0.41 pCi/L respectively, (F statistic 5.8, p < 0.001). CONCLUSION: The radon levels obtained in most assessed offices in Obafemi Awolowo University were found to be within the permissible reference levels. Mitigation measures should be put in place in the few offices above permissible levels.