Uranium contamination of milk from cattle in the uranium-mining area in Siavonga District of Zambia: a preliminary human health risk assessment

Background Contamination of cow milk with uranium (U) is attracting global attention owing to U’s radio-toxicity and chemical toxicity in humans and animals. Concentrations of U in 223 cow milk samples from indigenous breeds reared in the proximity of a U mine in Zambia were measured using the inductively coupled mass spectrometry, and the human health risks from exposure to U through milk consumption were assessed. Results Milk from cattle reared in the U-mining area showed a significantly higher U-mean concentration (0.83 ± 0.64 µg/L; t = 9.95; tα = 0.05, p > 0.05) than milk from cattle reared in the non-mining area (0.08 µg/L ± 0.05). Among the residents of the U-mining area, the mean estimated daily intake (EDI), the target hazard quotients (THQs) and the target carcinogenic risks (TCRs) were all significantly (p < 0.05) elevated than among the residents of the non-mining area. Conclusions Since the EDIs, THQs and TCRs and the U level in the cow milk were all within the World Health Organization’s and the United States Environmental Protection Agency’s permissible limits of 0.6 µg/kg-bw/day, < 1, < 10–4 and 30 µg/L, respectively. The current study, therefore, has insufficient evidence to implicate U exposure through consumption of cow milk in any non-carcinogenic or carcinogenic human health complications that are currently prevailing in the study area. Graphic abstract