Seasonal Variations in Particle Exposure: A Study at an Indian Highway Toll Station Investigating Coarse, Fine, Ultrafine, and Black Carbon Particles

Particulate matter (PM_2.5 and PM₁₀), black carbon (BC), and ultrafine particle (UFP) exposures among toll station workers on a highway in India were measured in both summer and winter seasons. Results showed that toll workers inside the toll collection booths (T_inside) were exposed to higher concentrations of air pollutants than those working outside the booths (T_outside), except for UFP. The concentrations of PM_2.5 were higher during winter than summer: 152.3 > 86.1 µg m^-3 (T_inside) and 136.6 > 79.2 µg m^-3 (T_outside), while PM₁₀ concentrations were 205.8 > 169.5 µg m^-3 (T_inside) and 185.3 > 156.4 µg m^-3 (T_outside), and BC concentrations were 38.8 > 34.5 µg m^-3 (T_inside) and 22.2 > 18.5 µg m^-3 (T_outside). In contrast, UFP concentrations were higher at T_outside (31312 > 22000 pt cm^-3) than T_inside (21610 > 18000 pt cm^-3). The diurnal variation of pollutants showed higher concentrations in the evening hours due to increased traffic, low wind speed and less atmospheric dispersion. Further, a significant correlation was found between pollutants and meteorological parameters (temperature, relative humidity, wind speed, solar radiation and boundary layer height) and traffic volume. Using Multiple-path particle dosimetry model (MPPD), mass deposition in the lungs were determined. Mass deposition found to be higher inside the toll booths workers. The study also revealed that PM particles consisted of soot, mineral and fly ash, which are proxies of fresh exhaust emissions, re-suspended road dust, and industrial emissions, respectively. The presence of Si, Al, Ca and Pb, as confirmed by EDX analyses, indicated the sources of pollutants to be re-suspended road dust, brake/tire wear, and construction dust. The results underscore the importance of implementing policies to control air pollutant levels, especially in workplaces near busy roads.