Dose Assessment of Radon Levels in the South-Dayi District of the Volta Region, Ghana

Abstract

Background to the study Radon is a globally present and known radioactive gas with its ability to cause lung cancer as its major health implication. Ghana currently lacks national policies on radon gas and substantive radon vulnerability map largely due to lack of adequate baseline radon concentration data for the entire country. This thesis thus seeks to provide baseline radon data for the South-Dayi District, the effective dose assessment due to inhalation of the measured in-door concentrations with reference to the World Health Organization standards and the interpretation of any possible correlations that may exist between In-door, Soil and Altitude as variables. Methodology In this research, LR115 type II detectors, a type of Solid State Nuclear Track Detectors were deployed in 30 sites/homes within the South-Dayi District. The detectors were retrieved after specified periods and processed at the Nuclear Track Detection Laboratory of the Ghana Atomic Energy Commission to obtain the radon concentrations over the study period for both indoor and soil. For the measured indoor radon, appropriate computations were made to convert the concentrations to doses (absorbed, equivalent and effective dose to lungs). Results Indoor radon was found to range from 11.60 to 111.07 Bq/m3 with the mean value for the district being 34.90 ± 20.77 Bq/m3, a value lower than the mean global indoor concentration of 40 Bq/m3. Only one site recorded a value greater than the action level stated by the WHO. The values of 0.44 mS/yr, 8.80 mSv/yr and 1.01 mSv/yr were the mean annual; absorbed dose, equivalent dose and effective dose to lungs respectively for the populace of the district. The mean soil radon concentration for the district was 1.76 ± 0.89 KBq/m3 with values ranging from 0.38 to 3.93 KBq/m3. From the correlation analysis, R-squared values of 0.0719 and 0.0015 were obtained for indoor radon against soil radon and soil radon against altitude respectively. The above results thus signifying an extremely weak dependence of indoor radon on soil radon concentrations. The correlation analysis of indoor radon against altitude also indicates an extremely weak correlation with an R-squared value of 3*10-5. All the correlations obtained were positive. Conclusion The mean in-door radon concentration for the district over the study period was 34.90 ± 20.77 Bq/m3 while that for the soil was 1.76 ± 0.89 KBq/m3. R-squared values of 0.0719 and 0.0015 were obtained for indoor radon against soil radon and soil radon against altitude respectively whiles 3*10-5 was obtained as the R-squared for analysis of indoor radon against altitude. Though the mean indoor radon concentration for the district was below the reference level of 100 Bq/m3 as set by the World Health Organisation, radon still possess a threat to the populace since there is no safe threshold for radiation.