Radioactivity and toxic element concentrations in soil and food crops from a copper mining area in Uganda: environmental and public health implications

Abstract

Mining activities can lead to the accumulation of radionuclides and metallic elements in surrounding soils, posing risks to food safety and human health. This study assessed radioactivity and contamination with toxic elements in 18 soil and food crop samples from the Kilembe copper mining area in Western Uganda to evaluate potential public health impacts. The samples were analysed for 226Ra, 232Th, and 40K using high-purity germanium (HPGe) gamma spectrometry, while concentrations of Cr, Cu, Co, Ni, Pb, and As were determined using inductively coupled plasma mass spectrometry (ICP-MS). The mean activity concentrations of 226Ra, 232Th, and 40K in soils were 71.16 ± 40.87, 50.85 ± 9.01, and 823.70 ± 231.58 Bq kg−1, respectively, all exceeding world averages. In food crops, 40K levels (1066.51 ± 224.71 Bq kg−1) were also elevated. The estimated annual committed effective dose exceeded the ICRP safety limit of 1 mSv y−1 for infants and children, while the excess lifetime cancer risk surpassed the 2.9 × 10−4 threshold for all age groups. Annual organ-specific dose estimates revealed increased risks to the gastrointestinal tract and bone surfaces. Metallic element analysis showed high concentrations of Cu (541.05 ± 389.83 mg kg−1) and Pb (64.99 ± 32.93 mg kg−1) in soils, with Pb levels in crops exceeding the WHO/FAO limit by 20 %. The health hazard indices for Cu, Pb, and As were above unity in both children and adults, indicating significant non-carcinogenic risks. Total cancer risks from Pb and As were (2.91 ± 1.27) × 10−3 (children) and (1.67 ± 0.73) × 10−3 (adults), which exceeded acceptable thresholds. Statistical analysis indicated shared geochemical behaviour of radionuclides and metals in soils, but distinct uptake pathways in food crops. These findings highlight the need for environmental monitoring, mining waste remediation, and regulating food sources to reduce radiological and chemical health risks in the study area.