Annual effective dose of radon in groundwater samples for different age groups in Obuasi and Offinso in the Ashanti Region, Ghana

The study presents radon (222Rn) activity concentration in the groundwater samples and their annual effective dose exposure in Offinso and Obuasi in the Ashanti, Region for different age groups. Radon measurement was made using Durridge RAD-7 H2O technique. In Obuasi, mean 222Rn concentration in groundwater was 0.09 0.01 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant were 0.64 0.11 Sv yr−1, 1.28 0.21 Sv yr−1 and 4.46 0.73 Sv yr−1 respectively and the mean annual effective dose due to inhalation was 0.28 0.05 mSv yr−1 for the dry season whiles in the rainy season the mean 222Rn concentration in groundwater was 0.08 0.01 Bq l−1, the mean annual effective dose due to ingestion for adult, child and infant was 0.56 0.09 Sv yr−1, 1.13 0.18 Sv yr−1, 3.94 0.62 Sv yr−1 respectively and the annual effective dose due to inhalation was 0.24 0.04 mSv yr−1. In Offinso , the mean 222Rn concentration in groundwater was 0.14 0.05 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant was 1.03 0.37 Sv yr−1, 2.06 0.74 Sv yr−1, and 7.20 0.74 Sv yr−1 respectively and the mean annual inhalation dose a mean of 0.46 0.16 mSv yr−1 for the dry season. In the rainy season, the mean indoor 222Rn concentration in groundwater was 0.13 0.04 Bq l−1, mean annual effective dose due to ingestion for adult, child and infant was 1.26 0.31 Sv yr−1, 1.89 0.61 Sv yr−1 and 6.62 2.15 Sv yr−1 respectively and the mean annual effective dose due to inhalation was mean of 0.41 0.13 mSv yr−1. The mean annual effective doses of all the samples are lower than the reference level of 0.1 mSvyr−1 for drinking water of WHO and EU Council. It has been concluded that drinking water of the study area is generally safe as far as radon related health hazards are concerned apart from a few isolated cases. It has been found that radon levels within the region have a positive correlation with depth of the water sources.