10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Descriptive Characterization of Personal Exposure to Fine and Ultrafine Particle Among Inner-City Children with Asthma
Ehsan Majd, KIRSTEN KOEHLER, Meredith McCormack, Nadia Hansel, Johns Hopkins School of Public Health
Abstract Number: 84 Working Group: Aerosol Exposure
Abstract Introduction: It is yet to be determined which property (size, chemical composition, morphology) of particulate matter (PM) air pollution contributes most to its adverse respiratory effects. However, recent toxicological findings point to the potentially greater role of the smaller fraction of PM, known as ultrafine particles (UFP, particles with diameter less than ~0.1 μm). Recent advances in sensor technologies has facilitated the assessment of personal exposure to UFP at high spatial and temporal resolutions; an important step towards a better characterization of PM exposure and informing effective practices and policies to mitigate its harmful effects.
Methods: In this work we characterized personal PM2.5 (particles with diameter less than 2.5 μm) and UFP exposures of 25 children aged 8-17 with asthma for 4 consecutive days at high spatial and temporal resolutions, aiming to answer two questions: 1) is personal exposure monitoring necessary for UFP in addition to PM2.5? 2) is it necessary to monitor personal exposures at high temporal resolution? Personal PM2.5 and UFP (expressed as LDSA, lung-deposited surface area) monitors were placed inside a backpack, which also contained a GPS and a data logger for collecting real-time information on geographic location, temperature, relative humidity, acceleration and light intensity at 10-sec intervals. Information about means of transportation used, places visited, and activities at home that may have resulted in high exposures were also obtained. We partitioned the measured personal exposures into five microenvironments (ME): home, school, vehicle commute, walk, and other (for the visited places other than home and school) and examined the distribution of exposures in each of them for different averaging times. We also calculated and examined the correlation coefficients between PM2.5 and UFP exposures across the MEs.
Results: Among the MEs, both PM2.5 and UFP exposures were dominated by home. Unlike PM2.5, time-weighted averages of UFP exposure were high for vehicle commute (35±31 μm2/cm3) and walk (20±11 μm2/cm3) relative to home (37±23 μm2/cm3), despite very small fractions of time spent in these MEs (averages of 1% and 2%, respectively compared to 73% for home). Mean exposures did not vary much by changing the averaging times, but we observed drastic decreases in maximum PM2.5 and UFP exposures by increasing the averaging time from 1 to 5 min for vehicle commute and other. Correlation between UFP and PM2.5 exposures were generally high at home (R=0.72) and poor in other MEs. However, we observed several cases of weak correlations for home (high UFP and low PM2.5), which occurred during the evening hours and coincided with common household activities, such as cooking and cleaning (sweeping, vacuuming, and using chemical cleaners).
Conclusions: Our findings suggest the importance of personal exposure monitoring at high temporal resolution and accounting for short peaks in urban environments. Moreover, we observed that personal UFP exposure was much more sensitive than PM2.5 to activities inside an ME, as well as moving from one ME to another. Therefore, and considering its potentially greater health risks, we believe it is crucial to include UFP as one of the major variables of interest to personal exposure monitoring campaigns, especially for more susceptible population such as children with asthma.