Human health risks from multiple exposure pathways of potentially toxic elements in nickel-copper mine tailings, Central Botswana

Legacy tailings from decommissioned mines are known to negatively impact human health and environmental quality. In this study, potentially toxic elements (PTEs) including Cr, Cu, Ni, Pb, and Zn concentrations in tailings from a Selebi-Phikwe mine, Botswana, were assessed for contamination and health risk via multiple exposure pathways in adults and children. Tailings samples from the defunct mine were analyzed for total elemental composition using inductively coupled plasma-optical emission spectrometry. The results show a decreasing order of mean content of Co (2106 mg/kg) > Ni (1805 mg/kg) > Cr (139 mg/kg) > Co (97 mg/kg) > Zn (53 mg/kg) > Pb (14 mg/kg). The I-geo values show varying degrees of Cr, Cu, Ni, and Zn contamination. Dermal contact (54.5%) was the primary exposure pathway of noncarcinogenic risk for adults, and oral ingestion (95.7%) was the primary exposure route for children. The PTEs posed very low to no noncarcinogenic risks. As a single element, the mean hazard index (HI) for adults and children followed a similar trend: Cr > Cu > Ni > Pb > Zn. However, the carcinogenic risk of Cr, Cu, Ni, and Pb exposure in children was high and unacceptable. For adults, the carcinogenic risks of Cr, Cu, and Ni were high and unacceptable. Overall, children were generally more vulnerable to the adverse effects of PTE exposure. A study of this nature is essential for routine environmental monitoring and assessment and fundamental for planning and reinforcing existing pollution control measures.