Chemical Composition and Oxidative Potential of PM_2.5 in Ambient Air of Tehran

The carcinogenicity of air pollution has been well established and is considered a threat to humans worldwide. Researchers have concluded although the properties of particulate matter (PM) such as size, shape, and mass are of primary importance for the study of air quality, another parameter such as oxidation potential (OP) can be used to determine particle toxicity or the health consequences related to PM samples. Here, the present study examines the characteristics of PM_2.5 components and their associated oxidation potential in the ambient air of Tehran, Iran using the dithiothreitol (DTT) assay. This study also compares the values of OP, and chemical composition (e.g.; anions and cations, metalloids, and polycyclic aromatic hydrocarbons (PAHs)) in the ambient air of Tehran with other urban areas globally. Sampling was conducted for nine months during three seasons: spring, summer, and autumn, in the ambient air of Tehran city, the capital of Iran from 2021/4/17 to 2021/12/6. According to the US EPA's Sampling Schedule, a high-volume air sampler (operating at a flow rate of 1.415 m³/min) was employed for PM_2.5 on fiberglass filters once every six days. The average value of DTTv was equal to 0.8 ± 0.3 (nmol.min^-1m^-3). The average values of DTTm were equal to 0.017 ± 0.01 (nmol.min^-1 µg^-1). Although the values of DTTv and DTTm in Tehran were relatively tolerable compared to other parts of Asia, they were at a high level compared to European and American countries. Nonetheless, DTTv in autumn was significantly higher than in summer and spring, while DTTm was slightly higher in spring than summer.