Airborne concentrations of PM2.5 and diesel exhaust particles on Harlem sidewalks: A community-based pilot study

Residents of the dense urban core neighborhoods of New York City (NYC) have expressed increasing concern about the potential human health impacts of d iesel vehicle emissions. We measured concentrations of particulate matter l ess than or equal to 2.5 mu m in aerodynamic diameter (PM2.5) and diesel ex haust particles (DEP) on sidewalks in Harlem, NYC, and tested whether spati al variations in concentrations were related to local diesel traffic densit y. Eight-hour (1000-1800 hr) air samples for PM2.5 and elemental carbon (EC ) were collected for 5 days in July 1996 on sidewalks adjacent to four geog raphically distinct Harlem intersections. Samples were taken using portable monitors worn by study staff. Simultaneous traffic counts for diesel truck s, buses, cars, and pedestrians were carried out at each intersection on gr eater than or equal to 2 of the 5 sampling days. Eight-hour diesel vehicle counts ranged from 61 to 2,467 across the four sires. Mean concentrations o f PM2.5 exhibited only modest site-to-site variation (37-47 mu g/m(3)), ref lecting the importance of broader regional sources of PM2.5. In contrast, E C concentrations varied 4-fold across sites (from 1.5 to 6 mu g/m(3)), and were associated with bus and truck counts on adjacent streets and, at one s ite, with the presence of a bus depot. A high correlation (r = 0.95) was ob served between EC concentrations measured analytically and a blackness meas urement based on PM2.5 filter reflectance, suggesting the utility of the ta tter as a surrogate measure of DEP in future community-based studies. These results show that local diesel sources in Harlem create spatial variations in sidewalk concentrations of DEP. The study also demonstrates the feasibi lity of a new paradigm for community-based research involving full and acti ve partnership between academic scientists and community-based organization s.