Characteristics of gaseous and particulate air pollutants at four different urban hotspots in Tehran, Iran

Abstract This study reports a characterization of outdoor gaseous and particulate pollutants and their associated health effects in four different urban hotspots in Tehran, Iran during winter and summer. Buses, taxis, and cars are prominent sources of toxic pollutants in Tehran. There is a significant level of exposure to emissions from diesel buses in bus terminals, especially with boarding, disembarking, and waiting. Mean concentrations (µg/m3) in summer and winter, respectively, ranged from 10 to 20.67 and 17 to 21 for PM1, 52.50 to 79.19 and 58.33 to 85.33 for PM2.5, 64.50 to 102 and 78.83 to 125.83 for PM7, 130.17 to 204.67 and 157 to 231.67 for PM10, 261 to 409.50 and 305.83 to 458.83 for TSP, and 372.50 to 418.33 vs. 351.27 to 373.47 for CO2 (ppm). Particulate concentrations were higher in winter, especially the first three days of the week, assisted in part by the shallower mixing layer height as compared to summer. Mean hazard quotient (HQ) values for both PM2.5 and PM10 in both seasons for bus terminals in three scenarios ranged between 0.81 and 4.96, which exceeded reference levels (1