Indoor and Outdoor Aerosol Exposures at Schools and their Associations with Local Vehicular Traffic

SERGEY A GRINSHPUN (1), Heather Hochstetler (1), Michael Yermakov (1), Tiina Reponen (1), and Patrick H. Ryan (1)

(1) Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio

     Abstract Number: 308
     Last modified: May 5, 2010

Abstract
While children’s exposure to traffic-related particles has received considerable attention, few studies have addressed the effect of diesel exhaust from school buses on air quality at schools. Additionally, there is a lack of data about the association between indoor and outdoor aerosol characteristics in schools. The present study was conducted to determine the indoor and outdoor mass concentrations and elemental compositions of PM2.5 aerosol at four urban schools with 5-39 diesel-powered school buses transporting students daily. Indoor and outdoor particle number concentrations and size distributions (starting from 10 nm) at each school were determined using real-time aerosol instruments. The number concentration of ambient aerosol was found to be affected by the school bus traffic. The PM2.5 filter-collected samples revealed presence of elemental carbon (EC) and other traffic-related elements at levels that suggest some influence of diesel particles. At the same time, no statistically significant association was identified between the ratio of mass concentrations of elemental-to-organic carbon (EC/OC) in the ambient air and the number of school bus arrivals and departures. Statistically significant associations were found between indoor and outdoor values of the mass concentration of airborne EC (R$^2 = 0.66), EC/OC ratio (R$^2 = 0.43), and the particle number concentration (R$^2 = 0.72) that is primarily influenced by ultrafine particles. This suggests efficient penetration of traffic-originated particles from outdoor to indoor environments. The results indicate that particles generated by the diesel exhaust from school buses affect the number concentration but make only a minor contribution to the mass of outdoor PM2.5 aerosol at these selected schools.

The study is presently supported in parts by the National Institute of Environmental Health Sciences, the University of Cincinnati’s Research Council, and the Center for Sustainable Urban Environments.