Risk assessment of toxic metals in the tailings dam associated with an iron ore processing plant

This study was conducted to determine the concentrations of heavy metals in the tailings dam of an iron ore processing plant located in Central Iran and to evaluate their ecological and human health risks. A total of nine tailings samples were collected in autumn 2024 and combined into three composite samples for analysis. After acid digestion according to the USEPA protocol, concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb), and zinc (Zn) were determined using ICP–MS. Several contamination and risk indices, including the Contamination Factor (CF), Contamination Degree (CD), Geo-accumulation Index (Igeo), Ecological Risk Factor (Eri), Potential Ecological Risk Index (RI), Hazard Index (HI), and Carcinogenic Risk (CR), were calculated. The mean concentrations (± SD) of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn were (34.14 ± 3.14), (9.75 ± 7.18), (30.17 ± 6.81), (105 ± 25.91), (0.005 ± 0.002), (234.4 ± 124.9), (38.91 ± 12.46), and (84.38 ± 31.08) mg kg⁻¹, respectively. According to the Iranian Department of Environment standards and the Igeo index, most metals were within acceptable limits; however, cadmium showed elevated contamination levels and represented the primary ecological concern. The calculated CD and RI values were 44.1 and 1042.58, respectively, indicating a very high ecological risk category mainly driven by Cd accumulation. In contrast, the health risk assessment revealed that both HI and CR values remained within acceptable ranges, suggesting no significant adverse health effects for workers under current exposure conditions. Nevertheless, due to the limited number of samples, the findings should be interpreted as representative only of the sampled locations. Continuous environmental monitoring and appropriate management measures are therefore recommended to minimize potential long-term ecological impacts.