Bioaccessibility of trace elements in fine and ultrafine atmospheric particles in an industrial environment

The lung bioaccessibility, defined as the solubility of metals in particulate matter within alveolar lung fluid, is an essential parameter in health risk assessment concerning the inhalation of airborne particles. This study aimed to estimate the pulmonary bioaccessibility of toxic metals present in various particle sizes in an industrial emission area. Using an in vitro method, fine and ultrafine particles collected from a Fe–Mn smelter environment were evaluated for their bioaccessibility using a simulated alveolar fluid (Gamble solution) and a four-step sequential extraction procedure for metal speciation. Findings indicated that the bioaccessibility of metals varied dramatically, with Fe being nearly insoluble (<1%) and Rb exhibiting extremely high solubility (>80%). Notably, finer particles (submicron and ultrafine) demonstrated greater bioaccessibility compared to coarser particles (>1 µm), likely due to their high surface area and concentration. Furthermore, bioaccessibility increased significantly in proximity to the smelter (within 800 m) due to interactions with other emissions, while such effects diminished at greater distances (2000 m) where urban aerosols diluted industrial emissions, except for Fe, which was more soluble in combustion-derived particles.