Characterizing Personal Fine and Ultrafine Particle Exposures among Inner-City Children with Asthma

Abstract

The PEAK study aims to determine the association of particle size, microenvironment (ME) and peak exposure with respiratory effects in children with asthma. 25 children aged 8-17 with asthma were each followed for 4 consecutive days. Children’s personal PM2.5 (particles with diameter less than 2.5 μm) and ultrafine particle (UFP, diameter less than 0.1 μm) exposures were measured at high spatiotemporal resolutions using a backpack containing personal PM2.5 and UFP (expressed as LDSA, lung-deposited surface area) monitors and a GPS for geographic location (logging interval= 10 seconds). Information about means of transportation used, places visited, and activities at home that may have resulted in high exposures were also obtained. Exposures were partitioned into five MEs: Home, School, Vehicle transport, Pedestrian transport, and Other. PM2.5 and UFP cumulative exposures were dominated by Home. Mean UFP exposure intensities while in Pedestrian transport and Vehicle transport were both greater than 1 and higher than PM2.5. Exposure intensities while in Pedestrian transport were also greater than Vehicle transport. Correlations between PM2.5 and LDSA concentrations were examined to evaluate the need for personal UFP exposure monitoring in addition to the commonly-monitored PM2.5. The highest and lowest mean PM2.5/LDSA correlation coefficients belonged to Home (r=0.47) and Vehicle transport (r=0.15). Home pollutant correlations were particularly weak (high UFP and low PM2.5) during evening hours and coincided with common household activities such as cooking, cleaning, and burning candles/incense. Our findings suggest that UFP exposure is only weakly to moderately correlated with fine PM exposure, suggesting that personal exposure monitoring at high spatiotemporal resolutions and including UFP to personal exposure monitoring campaigns, may be important to fully understand the effect of particulate exposures in susceptible populations such as children with asthma.