The oxidative and neurotoxic potentials of the ambient PM_2.5 extracts: The efficient multi-solvent extraction method

The health effects of ambient air particulate matter with a diameter of ≤2.5 μm (PM_2.5) on the central nervous system are well known and the induced oxidative stress has been shown as their main neuropathologic outcome. Ambient air PM_2.5 sampling methods mostly use air sampler systems that collect PM_2.5 on filters, which is followed by a PM_2.5 extraction approach. Inefficient extraction may lead to compositional bias and unreal interpretation of the results. This study aimed to compare our proposed multi-solvent extraction (MSE) approach for PM_2.5 extraction with a conventional aqueous extraction (AqE) method using the analysis of oxidative effects and cytotoxicity in the human neuroblastoma SH-SY5Y cell line. Ambient PM_2.5 samples were collected from an urban traffic location in Tehran city, the capital of Iran, using a high-volume sampler. The developed MSE method was proved to have superior advantages over the AqE method including an increased extraction efficiency (as much as 96 against 48% for PM_ms and PM_aq, respectively), and decreased artifacts and compositional biases. Ambient PM_2.5, besides PM_ms and PM_aq were analyzed for water-soluble ions, metals, and major elements. Dithiothreitol, ascorbic acid, lipid peroxidation, and cell viability assays on SH-SY5Y cells represented the significantly higher oxidative potential for PM_ms compared to PM_aq. The increased cytotoxicity may occur because of the increased oxidative potential of PM_ms and possibly is associated with higher efficiency of the MSE over the AqE method for removal of total redox-active PM components.