Assessment of Radioactivity Levels in Bottled Drinking Water Consumed by Different Age Groups of People in Kampala City, Uganda

Abstract

The activity concentrations of natural radionuclides in drinking water may be enhanced depending on the geological strata from which it is extracted. The demand and consumption of bottled drinking water is increasing every year in Uganda mainly in Kampala city. Therefore, the study was purposed to assess the levels of natural radioactivity using a gamma spectrometer in commonly bottled drinking water in Kampala City. The mean specific activities for Ra-226, Th-232, and K-40 in bottled drinking water were 4.45±0.20, 1.32±0.27, and 46.33±0.24 Bq/l respectively which exceeded the specific World Health Organization recommended guidance level of 1.0 Bq/l except for K-40. The mean activity concentrations were however comparable to the mean concentration of tap water used in Kampala City, that is 4.00±0.16, 1.4±0.19, and 47.05±0.21 Bq/l for Ra-226, Th-232, and K-40 respectively. The annual effective dose contributed by two radionuclides of Ra-226 and Th-232 in the bottled water exceeded the maximum dose limit of 0.1 mSv/y recommended by the World Health Organization (WHO). The mean estimated excess lifetime cancer risk due to Ra-226 (0.00177) exceeded the recommended limit of 0.001 while that due to Th-232 (0.0001) was below the recommended limit. Therefore, the main contributor to the total annual ingestion dose was Ra-226. Due to the high solubility and toxicity of Ra-226, there is a significant concern warranting further investigation. Finally, the results from the study revealed that there was not any trace of contamination from artificial radionuclides in the bottled drinking water manufactured and consumed within Kampala City. With the growing populational demand for bottled drinking water, it's recommended that radioactivity levels comply with the WHO recommended radioactivity levels. Therefore, this study contributes to the revision of standards and development of regulations for radiological protection of the public and the environment from risks of radiation exposure associated with bottled drinking water.