Determinants of exposure to ultrafine particulate matter, black carbon, and PM2.5 in common travel modes in Istanbul

Abstract

The personal exposure concentrations of ultrafine particles (UFPs), black carbon (BC), and particulate matter with an aerodynamic diameter ≤2.5 μm (PM2.5) were measured in often-used transport vehicles and routes in Istanbul, Turkey. Exposure to these pollutants were estimated for four different travel modes (bus, metrobus, car, light rail) and five travel routes. Pollutant measurements were simultaneously conducted in the vehicles, and the relationship between pollutant concentrations, meteorological variables, and environmental factors were investigated. The seasonal statistically correlation results indicated that the relation between the meteorological variables and in-vehicle pollutant concentrations were variable with the seasonal differences. UFP concentrations were significantly higher in winter, while in-vehicle BC concentrations were significantly higher in summer. No significant difference was found between the summer and winter in-vehicle PM2.5 concentrations for bus, metrobus and light-rail. There was a significant positive correlation between UFP and BC with transport over roads. The highest average concentrations of UFP, BC, and PM2.5 were observed when car windows were open while traveling, and wind speed negatively affected pollutant concentrations and accounted for between 1 and 29% of their variability. Atmospheric pressure was significantly negatively correlated with BC but positively correlated with UFP and PM2.5. Humidity was a significant factor for UFP (1–12%) and PM2.5 (0–10%), but was not a factor for BC. The pollutant concentrations at the station/platform were the common significant factor for those concentrations in buses, metrobuses and light rail; the variability was determined between 4 and 66% for BC, 3 and 36% for UFP, and 1 and 75% for PM2.5. The time of day was also significant for BC (variation of 3–10%) and UFP (variation of 2–10%) for bus, metrobus, and car trips. The highest average exposures per kilometer for all pollutants was in buses, with exposure levels of UFP, BC, and PM2.5 at 12.3 × 108 particles km−1, 0.40 μg km−1, and 1.33 μg km−1, respectively, while the lowest average exposures per kilometer for all pollutants were in the car with the windows closed and on light rail. It was observed that the metrobus near the highway provided the least concentrations of pollutant exposure.