Assessment of Annual Effective Dose Associated with Radon in Drinking Water from Gold and Bismuth Mining area of Edu, Kwara, North-central Nigeria

The aim of this paper is to assess the radon concentration of surface and ground waters around Bismuth mining site located in Edu, Kwara State, Nigeria, in order to ascertain its radiological risk. Seventeen (17) water samples were collected and analyzed for radon concentration using a calibrated Rad7-Active Electronic Detector Durridge. The Radon concentration for surface water ranged from 16.23 +/- 3.45 Bq/l to 24.71 +/- 4.51 Bq/l with a mean of 19.14 +/- 3.98 Bq/l while that of ground water ranged from 21.59 +/- 3.29 to 27.93 +/- 5.74 Bq/l with a mean of 24.16 +/- 4.21 Bq/l. The concentration results were used to estimate the annual effective doses. The mean total annual effective dose obtained by summing the dose due to inhalation and ingestion for surface water samples were 187.97 mu Svy(-1), 257.84 mu Svy(-1) and 292.77 mu Svy(-1) for adult, children and infants respectively. Also, the mean effective doses for ground water samples were of 237.25 mu Svy(-1), 325.44 mu Svy(-1) and 369.53 mu Svy(-1) for adult, children and infants respectively. Both the radon concentration and the effective dose due to its inhalation and ingestion were higher than the recommended limit of 11.1 Bq/l and 100 mu Svy(-1) respectively for all samples. Therefore, consumption of the water in this area poses serious health risk as the water is not safe for all age groups considered. Therefore, it is advised that the water from both sources be treated before consumption.