Radiological risk assessment of drinking water sources around the Osukuru phosphate mining area, Tororo district, Uganda.
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Date
2026
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Busitema University
Abstract
Phosphate mining and processing at Osukuru mines in Tororo District, Uganda, release naturally occurring radioactive materials (NORM) into the environment, potentially contaminating drinking water and posing long-term health risks such as cancer, kidney damage, and bone disorders. This study quantified radionuclide concentrations in local water sources, compared them with WHO and EPA safe limits, and assessed radiological risks. Fifteen (15) water samples were analyzed using High-Purity Germanium (HPGe) gamma spectrometry with Gamma Vision software. Activity concentrations of 226Ra, 232Th, and 40K ranged from (0.11 to 0.22) BqL⁻¹, (0.13 to 0.37) BqL⁻¹, and (6.08 ± 3.04 to 10.67 ± 3.80) BqL⁻¹, respectively. The mean values were 0.16 Bq L⁻¹ (226Ra), 0.211 BqL⁻¹ (232Th), and (8.98 ± 3.47) BqL⁻¹ (40K). Notably, in all samples, 232Th exceeded the WHO screening level of 0.1 BqL⁻¹, while 226Ra were lower than WHO safe limits of 1.0 BqL⁻¹ and 40K remained within the safe limit except for S8, S9, S11 and S14. Mean hazard indices for external hazard (0.0031), internal hazard (0.00352), and gamma index (0.005) were all less than 1, indicating low dose levels. The mean annual gonadal equivalent dose (AGED) was (4.18 ± 1.09) μSvy⁻¹, mean radium equivalent activity (Raeq) (1.15 ± 0.27), absorbed dose rate (0.58 ± 0.14) nGyh⁻¹, mean excess lifetime cancer risk (ELCR) (2.48 × 10⁻⁶ ± 0.001), which was lower than the global limit of 2.9 𝑥 10−4 and mean annual effective dose rate (7.08 × 10⁻⁴) mSvy⁻¹ was lower than WHO dose limit of 0.1 mSvy⁻¹. Although the calculated radiological risk indices indicate low risks, the study recommended heavy metal and radionuclide combined assessment, establishment of local radiological surveillance, seasonal studies, groundwater modelling, and routine monitoring because 232Th concentrations exceeded WHO screening levels of 0.1BqL−1. This could be attributed to the mining and processing of phosphate ore for fertilizer production, or the radioactive wastes entering the water bodies.
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Citation
Egau, H. (2026). Radiological risk assessment of drinking water sources around the Osukuru phosphate mining area, Tororo District, Uganda. [Unpublished dissertation]. Busitema University.