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EXPOSURE ASSESSMENT FROM THE NERL RESEARCH TRIANGLE PARK PARTICULATE MATTER PANEL STUDY
Citation:
Williams, R W., A W. Rea, J C. Suggs, K W. Leovic, A F. Vette, L S. Sheldon, C. Rodes, J. Thornburg, A. Ejire, AND W. Sanders Jr. EXPOSURE ASSESSMENT FROM THE NERL RESEARCH TRIANGLE PARK PARTICULATE MATTER PANEL STUDY. Presented at NCCU Environmental Seminar, Durham, NC, October 1, 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:
The U.S. Environmental Protection Agency performed a particulate matter (PM) exposure assessment based on data from the National Exposure Research Laboratory (NERL) Research Triangle Park (RTP) Particulate Matter (PM) Panel Study. This study was a one-year investigation of PM and related co-pollutants involving two distinct subpopulations living within the RTP area of North Carolina. Primary goals were to characterize the relationships between ambient and residential PM measures to those obtained from personal exposure monitoring and estimate ambient source contributions to personal and indoor mass concentrations. A total of 35 participants were involved in personal PM2.5 exposure monitoring. Participating were 27 nonsmoking hypertensive African-Americans living in a low-moderate SES neighborhood (SE Raleigh, NC) and a multi-racial cohort of eight individuals having implanted cardiac defibrillators (Chapel Hill, NC). The volunteers were monitored for seven consecutive days during four consecutive seasonal periods (summer 2000, fall 2000, winter 2001, spring 2001). Results indicated that daily personal PM2.5 mass concentrations were typically higher than their associated residential or ambient measurements (e.g., hypertensive cohort mean personal = 27.6, indoor = 21.7 , outdoor = 18.9, ambient = 18.9 ug/m3). Individual PM2.5 personal exposure concentrations were observed to range from 4 to 218 ug/m3 during the entire study period. Mean observed correlations between personal PM2.5 exposures and other ambient-based measurements varied significantly by season (r = 0.3 to 0.8). Factors influencing these variations are being investigated. Ambient PM2.5 mass concentrations were determined to be highly representative of those obtained from outside each residence regardless of season or distance (r > 0.8). PM2.5 personal cloud estimates for both cohorts averaged ~ 10 ug/m3 across the study. Mixed effects modeling indicates that ambient sources accounted for approximately 50% of the personal PM2.5 mass concentrations. Ranges of these estimates will be presented along with other summary findings.
This work has been funded wholly by the United States Environmental Protection Agency under contract #68-D-99-012 to the Research Triangle Institute and assistance agreement #CR-828186-01-0 to Shaw University. It has been subjected to Agency review and approved for publication.