Assessment of potentially toxic metals contamination and human health risk in surface water impacted by chipwood factory effluents in Yirgalem, Ethiopia

Abstract Concentrations of potentially toxic metals (As, Cd, Hg, Pb, Ni, Cr, Fe, Co, Cu, Zn, Mn) in surface water receiving effluents from the Chipwood factory in Yirgalem, Ethiopia, were determined during February 2025 (dry season). Water samples were collected from two effluent-receiving sites (CZA1 and CZA2) and a reference site (RS). Metal concentrations were quantified using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) following acid digestion. Human health risks were assessed using Chronic Daily Intake (CDI), Hazard Quotient (HQ), Hazard Index (HI), Cancer Risk (CR), and Total Cancer Risk (TCR) indices for children and adults. Mean concentrations of Hg (CZA1: 18.3 ± 1.15 μg l −1 ; CZA2: 33.0 ± 1.00 μg l −1 ) and Mn (CZA1: 785.0 ± 3.61 μg l −1 ; CZA2: 1051.3 ± 6.51 μg l −1 ) exceeded their respective WHO drinking water and FAO irrigation water limits, while Fe (CZA1: 686.0 ± 4.36 μg l −1 ; CZA2: 899.0 ± 6.66 μg l −1 ) exceeded the WHO drinking water limit. HQ and HI results indicated significant non-carcinogenic risks for children and adults at CZA1 and CZA2, with Hg contributing most prominently. CR values for Cr, Ni, and As, and TCR values exceeded the USEPA threshold (1.0 × 10 −4 ), indicating potential lifetime carcinogenic risks. Children exhibited higher HI and TCR values than adults, indicating greater vulnerability. These findings highlight the need for wastewater treatment, continuous monitoring, and provide critical evidence for understanding industrial metal contamination risks in rapidly industrializing regions of East Africa.