A hybrid approach for assessing source-oriented health risk and evaluating mitigation measures of potential toxic elements in road dust from mining areas

Among various environment media, road dust in mining areas can serve as both a sink and a significant source of mining-related potentially toxic elements (PTEs), due to transportation leakage and resuspension caused by wind and traffic disturbances. However, the routine applications of deterministic parameters and total concentrations of pollutants may result in either underestimation or overestimation of the health risk posed by road dust. In this study, a hybrid approach combining bioaccessibility assays, Positive Matrix Factorization (PMF), traffic emission and dispersion model, and Monte Carlo simulation (MCS) was applied to evaluate source-oriented health risk and efficiency of mitigation measures. The geo-accumulation index (I_geo) of Ba, Pb, Cd, Mn, and Zn exceeded 3, indicating the presence of anthropogenic pollution. The results of PMF revealed that mine-associated source contributed to 86.7% of PTEs. When considering the bioaccessibility of PTEs, the mean hazard index (HI) for children still exceeded 1, indicating appreciable non-carcinogenic risks, with the mine-associated source being the major contributor. The inhalation was recognized as the primary exposure route, and the animal model indicated that PTEs in mining dust tend to accumulate in various organs following inhalation exposure. The results further revealed that a four-fold increase of road contact time resulted in an up to 2.5-fold increase in health risks. Mitigation measures involving the control of silt loading (sL) on road and the passage duration of large vehicles (e.g., only passable at night) were suggested. 'Clean' level of sL (0.5 g/m²) or 'medium' level of sL (5 g/m²) combined with 'low' level of vehicle weights (2 tons) could reduce the risks to acceptable levels. Collectively, the results indicated that road dust in mining and tailing regions can act as a hotspot for mining-originated PTEs reaching populations living around, highlighting the need for effective mitigation strategies to reduce dust resuspension.