Radiological hazard levels due to gamma emmiting radionuclides in natural water bodies in selected sub-counties of Mubende district

Abstract

This study was carried out to investigate the health hazard levels due to gamma rays emitted by radionuclides in natural water bodies in selected sub-counties in Mubende District. Owing to the interaction between underground water wells with the mineral rich geological components of the landscape; and the link that the minerals have with gamma emitting radionuclides, the population of Mubende is exposed to unknown levels of ionizing radiation. In the study, a representative of 60 natural water samples from the sub-counties of Bukuya, K.asambya, Kassanda and Kitumbi were analyzed for radiological hazard levels using a NaI (Tl) gamma-ray detector. Specific activities due to 226Ra, 232Th, 238 U, and 40 K. were obtained and then used to calculate the absorbed dose rates, annual effective dose equivalents and the radiological health hazard indices. To ensure quality control, the samples were collected from the sites in rinsed empty mineral water bottles which were sealed and labeled. They were transp01ied in paper boxes whose background radiation emissions were measured with an identifier. The mean Specific Activities in Bq/kg due to 226Ra, 232Th, 238U and 40K obtained from the laboratory investigations were 103.10 ± 2.59, 80.69 ± 1.33, 24.94 ± 0.42 and 16.02 ± 1.32, respectively. The mean absorbed dose rate was 97.45 nGyh-1 which was higher than the published reference value of 55 nGyh-1. The mean Annual Effective Dose Equivalent was 0.30 mSv year -1, above the reference level of 0.12 mSv year-1. The calculated radium equivalent was 219.50 Bqkg-1, below the reference level of 370 Bqkg-1 The mean external hazard index was 0.60 while the mean internal hazard index was 0.88. Though the Specific Activities, the mean absorbed dose rate and the annual effective dose equivalent were higher than reference values, the radiological hazard indices indicate that consuming these waters did not pose a significant threat to the health of the population but precautions should be taken against high radiation water sources. The study recommended that background radiation emissions in these sites of water collection be done by Uganda Atomic Energy Council (AEC) in collaboration with Uganda National Bureau of Standards (UNBS) and National water and sewerage cooperation (NWSC). In addition, it also recommended for periodic monitoring of the radioactivity levels due to the gamma emitting radionuclides in the natural and drinking waters of the district. Finally, the study recommended that a research be carried out on radiation hazard levels posed by water bodies this study did not look at in Mubende district.