Bioaccessibility, source and human health risk of Pb, Cd, Cu and Zn in windowsill dusts from an area affected by long-term Pb smelting

Non-ferrous metal smelting results in heterogenous spatial distribution of potentially toxic metals (PTM) near smelters. In this work, windowsill dusts were collected from smelting (SA) and urban (UJ) sub-areas of Jiyuan (a city affected by > 70 years of Pb smelting) to investigate PTM source and bioaccessibility. The < 10 mu m fraction of dusts were analyzed for total and bioaccessible Pb, Cd, Cu and Zn concentrations; bioaccessibility was analyzed by a three-stage assay (i.e., lung phase, gastric phase and gastrointestinal phase) using artificial lysosomal fluid (ALF, L phase) followed by simulated gastric and gastrointestinal fluids (G and GI phases). This assay mimicked the movement of particles phagocytosed by alveolar macrophages in the respiratory system, then transported up the oropharynx and subsequently swallowed and transported into the digestive system. Zinc had greater bioaccessible concentrations in L and GI phases than other metals, and the mean L phase bioaccessible PTM concentrations in SA were greater than in UJ. The mean L + GI phase bioaccessible concentrations of Pb, Cd, Cu and Zn in SA were 280, 79, 124 and 1458 mg kg(-1), while those in UJ were 215, 54, 116 and 598 mg kg(-1), respectively. The L phase extracted 87.7 to 98.8 % of PTM within the L + GI assay. Lead had a lower L + GI bioaccessibility than Cd, Cu and Zn (70-76 % vs. 82-92 %). Higher tolerable Cd carcinogenic risks based on bioaccessibility were found in SA sub-area than in UJ while no carcinogenic or non-carcinogenic risk was found for other metals. Lead isotopic ratios indicated that both Pb ore and smelting bottom ash contributed to dust Pb accumulation in SA, while coal burning, lead ore, Pb smelting bottom ash and diesel engine exhaust contributed to dust Pb accumulation in UJ. Overall, results indicated heterogenous distribution of PTM source and bioaccessibility in the vicinity of Pb smelters.