Analysis of heavy metals in cow milk from the vicinity of Hawassa industrial zone reveals potential risks in human health
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Abstract
The incidence of milk contamination linked with environmental pollution has increased over the years. But little is known about heavy metal contamination of milk in developing countries like Ethiopia where research in environmental pollution is still in its infancy. This study aimed to determine concentrations of ten heavy metals (Cr, Ni, Cu, Zn, As, Cd, Pb, Fe, Co and Mn) in domestically produced cow milk from Hawassa Industrial Zone (HIZ), Ethiopia and assess the associated human health risks from milk consumption. Estimated Daily Intake (EDI), Target Hazard Quotients (THQ), Hazard Index (HI) and Target Cancer Risk (TCR) were used as indices to evaluate potential human health risks from milk consumption. Average concentrations of metals in milk from Industrial (IZ) and Nonindustrial Zone (NIZ) decreased in the order Zn>Fe>Mn>Cu>Cr>Ni>Pb>As>Co>Cd and Zn>Fe>Mn>Cu>Cr>As>Ni>Pb>Co>Cd, respectively. Mean concentrations of Zn (5093.33+223.49 µg kg-1), Fe (592.0+63.19 µg kg-1) and Cu (77.78+13.94 µg kg-1) in milk from IZ as well as Zn (3953.33+63.15 µg kg-1) and Cu (63.0+9.78 µg kg-1) in milk from NIZ were above the maximum tolerance limits proposed by International Dairy Federations. From the results of human health risk assessments, it was concluded that effects of all heavy metals put together may affect human health as indicated by the elevated HI. Effluents from industries in HIZ are assumed to be the main sources of the heavy metals. Therefore, awareness creation of farmers and policy interventions with respect to waste disposal are recommended to protect the health of the ecosystem and the public.