Fine particulate concentrations on sidewalks in five Southern California cities

Abstract This research provides an exploratory examination of the factors associated with fine particle concentrations in intersection and sidewalk microenvironments in five study areas in the Los Angeles region. The study areas range from low-density, auto-oriented development patterns to dense urban areas with mid- and high-rise buildings. Average concentrations of FP DT (fine particle concentrations measured with DustTrak Aerosol Monitors) ranged from about 20 to 70 μg m −3 across study areas during stationary and mobile (walking) monitoring in morning, midday, and evening periods. Results suggest that fine particle concentrations are highly variable on urban sidewalks. A regression analysis shows that concentrations are associated with traffic and the proximate built environment characteristics after accounting for meteorological factors, time of day, and location in the region. Regressions show higher concentrations were associated with lower wind speeds and higher temperatures, higher adjacent passenger vehicle traffic, higher ambient concentrations, and street canyons with buildings of over five stories. Locations in street canyons with 2–5 story buildings and with more paving and open space had lower concentrations after accounting for other factors. The associations with traffic and built environment variables explained a small amount of the variation in FP DT concentrations, suggesting that future research should examine the relative role of localized traffic and built environment characteristics compared to regional ambient concentrations and meteorology.