Citation:

Wallace, L A. AND R W. Williams. CONTRIBUTION OF FINE PARTICLES OF OUTDOOR ORIGIN TO PERSONAL EXPOSURES: RESULTS OF A 37-PERSON PANEL STUDY IN NORTH CAROLINA. Presented at International Society of Exposure Analysis 14th Annual Conference, Philadelphia, PA, October 17-21, 2004.

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:

The US EPA carried out a study of personal exposures to PM2.5 for 37 persons with hypertension or cardiovascular disease in North Carolina. Personal, indoor (home) and outdoor (home and central site) 24-h samples were collected for 7 consecutive days in each of four seasons in 2000-2001. PM results from the study have been previously reported (Williams et al., 2003a,b). We have applied a method based on sulfur measurements to calculate the portion of indoor PM2.5 concentrations and personal exposure due to outdoor particles. Because sulfur has few sources indoors, it can be used as a marker for PM of outdoor origin. All filters (>2000 from the personal, indoor at home and outdoor near home samples) were analyzed by X-ray fluorescence for sulfur among other elements. The fraction of personal exposure due to outdoor particles measured near the homes ranged from 0.33 to 0.77, with a median of 0.53. R2 values for regressions of the outdoor-generated contribution to personal PM2.5 exposure vs. outdoor measurements at the central site ranged from 0.19 to 0.88, with a median value of 0.73.

Although this work was reviewed by EPA and approved for publication, it may not necessarily reflect official Agency policy.

Record Details: