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THE USE OF LIGHT SCATTERING DATA TO ESTIMATE THE CONTRIBUTION OF INDOOR- AND OUTDOOR-GENERATED PARTICLES TO INDOOR AIR
Citation:
Allen, R., T. V. Larson, L A. Wallace, AND L. S. Liu. THE USE OF LIGHT SCATTERING DATA TO ESTIMATE THE CONTRIBUTION OF INDOOR- AND OUTDOOR-GENERATED PARTICLES TO INDOOR AIR. Presented at International Society of Exposure Analysis 2002 Conference, Vancouver, Canada, August 11-15, 2002.
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:
Many epidemiologic studies have shown an association between adverse health effects and particulate concentrations measured at centrally located sites. Other studies have been conducted to examine relationships between personal exposures and central site measurements. Few studies quantify the contribution of indoor and outdoor sources to personal exposures, as particles in these two environments differ in sources and composition, and exhibit temporal and between-residence variability. This study is a subset of a larger exposure assessment study conducted between October 99 and May 01. Subjects were recruited throughout the metropolitan Seattle area, including 67 elderly and 18 pediatric asthmatics. Particle mass and light scattering were monitored on 19 subjects and at 85 residences, including 42 apartments or group homes, and 43 private homes. This paper uses a censoring technique to identify and remove indoor sources from the continuous light scattering measurements. We then apply a mass balance model to the censored time series data to estimate the contribution of indoor- and outdoor-generated particles to indoor air and to personal air. The real-time personal exposure measurements are combined with the real-time indoor and outdoor particle measurements, time-activity-location information, potential particle events, and home ventilation logs to determine the contributions from various indoor and outdoor particle sources to total personal PM exposure. The particle infiltration efficiency averages 0.53 plus/minus 0.25 and differs significantly across dwelling types and by season. Despite having higher outdoor particle concentrations and spending more time outdoors, the pediatric subjects, as compared to elderly subjects, have no higher exposure to ambient particles.
This paper has been reviewed in accordance with US Environmental Protection Agency's peer and administrative review policies and approved for publication.