Radon levels in Groundwater from a uranium Rich District in Southern Tanzania

Water samples were collected from springs, rivers and wells from Namtumbo District Southern Tanzania, an area with proven commercially viable uranium deposits. Samples were collected from 39 water sources located in eight wards within Namtumbo District. Radon in water was quantified using an active radon monitor (AlphaGUARD) in conjunction with the AquaKIT accessory. Radon concentrations in water samples ranged from 0.2 to 86BqL−1; with a mean value of 28.1BqL−1; 11.3BqL-1 and 6.8BqL-1 for rivers, springs and wells, respectively. The measured radon concentrations in all collected samples were below the limit of 100 BqL−1as set by the World Health Organization (WHO). However, 42% of the samples exceeded the USEPA action level of 11.1BqL-1. The mean values of the annual effective dose due to ingestion of radon and due to the inhalation of radon released from water are 26.4 and 26.1 μSvy−1, respectively. In addition, the mean values of estimated total annual effective doses are found to be 6.3 μSvy−1. The mean value of total annual effective doses is found to be lower than the reference dose level of 100 μSvy−1 recommended by the WHO and the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The mean values of effective doses per annum to the lungs and stomach are 3.1 and 3.2μSv, respectively.