Radiological health risk assessment of water samples from Lake Edward, Rukungiri District, Uganda

Abstract

This study evaluated the radiological quality and associated health risks of water from Lake Edward, located in Rukungiri District, Uganda. Water samples were collected from sixteen locations grouped into four zones representing fishing, farming, domestic/livestock, and control areas. Gross alpha and gross beta activities were measured as preliminary indicators of radiological water quality, while activity concentrations of naturally occurring radionuclides (226Ra, 228Ra, and 40K) were determined using gamma-ray spectrometry. Radiological health risks were assessed by estimating the annual effective dose (AED) from water ingestion for adults and children, excess lifetime cancer risk (ELCR), and radiological hazard index (HI) in accordance with guidelines recommended by the International Commission on Radiological Protection and the World Health Organization. The mean gross alpha activity ranged from 0.16 ± 0.07 Bq L⁻1 in the fishing zone to 0.66 ± 0.05 Bq L⁻1 in the farming zone, while gross beta activity ranged from 0.22 ± 0.03 to 0.75 ± 0.05 Bq L⁻1 across the study area. Most samples complied with WHO guideline limits for drinking water, although a few locations in the farming zone showed elevated alpha and beta activities. The activity concentrations of 226Ra, 228Ra, and 40K ranged from below detection limit to 0.28 ± 0.03 Bq L⁻1, 0.21 ± 0.03 Bq L⁻1, and 0.44 ± 0.06 Bq L⁻1, respectively, with higher concentrations observed in agriculturally influenced areas. The calculated AED ranged from 0.022 to 0.128 mSv y⁻1 for adults and from 0.010 to 0.065 mSv y⁻1 for children. Two locations within the farming zone exceeded the WHO screening level of 0.1 mSv y⁻1 for adults. The estimated ELCR values were within internationally acceptable limits, although the hazard index exceeded unity at selected sampling points, indicating potential long-term radiological concern. Overall, the results suggest that water from Lake Edward generally presents low radiological risk for consumption; however, localized elevations in radionuclide concentrations associated with agricultural activities were observed. This study provides essential baseline radiological data for Lake Edward and highlights the need for routine monitoring and improved land-use management to ensure the long-term radiological safety of water resources in the region.