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THE CONTRIBUTION OF PARTICLE RESUSPENSION TO INDOOR AND PERSONAL AIR CONCENTRATIONS
Citation:
Sheldon, L S., A W. Rea, A F. Vette, C HowardReed, R W. Williams, V R. Highsmith, C. E. Rodes, AND P. A. Lawless. THE CONTRIBUTION OF PARTICLE RESUSPENSION TO INDOOR AND PERSONAL AIR CONCENTRATIONS. Presented at ISEA 2000 Exposure Analysis in the 21st Century: Integrating Science, Policy and Quality of Life, Monterey Peninsula, CA, October 24-27, 2000.
Impact/Purpose:
The primary study objectives are:
1.To quantify personal exposures and indoor air concentrations for PM/gases for potentially sensitive individuals (cross sectional, inter- and intrapersonal).
2.To describe (magnitude and variability) the relationships between personal exposure, and indoor, outdoor and ambient air concentrations for PM/gases for different sensitive cohorts. These cohorts represent subjects of opportunity and relationships established will not be used to extrapolate to the general population.
3.To examine the inter- and intrapersonal variability in the relationship between personal exposures, and indoor, outdoor, and ambient air concentrations for PM/gases for sensitive individuals.
4.To identify and model the factors that contribute to the inter- and intrapersonal variability in the relationships between personal exposures and indoor, outdoor, and ambient air concentrations for PM/gases.
5.To determine the contribution of ambient concentrations to indoor air/personal exposures for PM/gases.
6.To examine the effects of air shed (location, season), population demographics, and residential setting (apartment vs stand-alone homes) on the relationship between personal exposure and indoor, outdoor, and ambient air concentrations for PM/gases.
Description:
An association has been demonstrated between ambient PM concentrations and human morbidity/mortality. However, little is known regarding the most important sources of PM exposure, inter- and intrapersonal variability in exposure, and the relationship between personal exposure and exposure estimates based on field site measurements. NERL is conducting several longitudinal Panel Studies to address these uncertainties and to evaluate the important determinates of PM exposure. As part of this effort, research is underway to evaluate the contributions to personal exposure from indoor sources and resuspended ambient particles. This paper focuses on the impacts of particle resuspension.
Panel study monitoring included personal exposure measurements of PM 2.5 mass. Both PM 2.5 and PM 10 mass measurements were also taken at ambient, outdoor, and indoor locations. Nephelometers (MIE, Inc. personalDataRam) were used to collect real-time PM 2.5 data concurrently with personal and indoor samples. Nephelometer data were downloaded each day and used to query participants about those activities that were responsible for elevated PM concentrations. Although the nephelometers did not provide accurate mass measurements, this approach provided a valuable qualitative measure of personal and indoor sources of PM. Real-time particle counts in the fine and ultrafine size range were measured both indoors and outdoors for selected microenvironments using SMPS, LASX, and APS instruments. Information on housing characteristics and activities were also collected.
Combining results from the two real-time measurement techniques provided valuable information on particle resuspension. The nephelometer and time activity data were used to determine the relative contribution of particle resuspension on personal and indoor air concentrations. The SMPS, LSX, and APS instruments were used to evaluate the size distribution of resuspended particles. Results suggest that a substantial portion of the PM in both personal and indoor air can result from particle resuspension. In addition, resuspension results in predominately coarse mode particles. Additional work is underway to identify the nature of the particles associated with resuspension.
This work has been funded wholly by the United States Environmental Protection Agency under contract #68-D-99-012 to the Research Triangle Institute. It has been subjected to Agency review and approved for publication.