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MASS CONCENTRATION RELATIONSHIPS FROM THE NERL RTP PARTICULATE MATTER PANEL STUDY
Citation:
Williams, R W., A W. Rea, J C. Suggs, K W. Leovic, A F. Vette, L S. Sheldon, C. E. Rodes, J. Thornburg, A. Ejire, AND W. Sanders Jr. MASS CONCENTRATION RELATIONSHIPS FROM THE NERL RTP PARTICULATE MATTER PANEL STUDY. Presented at 11th Annual Meeting of the International Society of Exposure Analysis, Charleston, SC, November 4-8, 2001.
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 National Exposure Research Laboratory's (NERL) Research Triangle Park (RTP) Particulate Matter (PM) Panel Study has completed a one-year investigation of personal, residential and ambient PM-related mass concentrations in two potentially susceptible subpopulations. PM2.5, PM10 and PMcoarse measurements were routinely conducted as part of the study. Personal exposures were characterized for only the PM2.5 size fraction. A total of 35 individuals participated. The first cohort consisted of 8 members with implanted cardiac defibrilators. The second cohort consisted of 27 African-Americans with controlled hypertension and living in a low/moderate socio-economic-status neighborhood. All of the participants were at least 50 years of age, non-smokers, and lived independently in their own residence in the RTP, NC area. The exposure assessment for both groups was conducted in identical manner. Each participant and their residence (indoor/outdoor) was monitored for 7 consecutive days during each of four seasonal periods (summer 2000, fall 2000, winter 2001, spring 2001). Daily diaries were used to determine the participant's activity patterns.
Preliminary results from the first two seasons indicated that daily personal PM2.5 mass concentrations were typically higher than matched residential or ambient measurements (e.g., fall African-American cohort mean personal = 23.9, indoor = 21.5 , outdoor = 19.1 , ambient = 20.2 ug/m3). The maximum PM2.5 personal exposure concentration observed during the first half of the study for either cohort was 99 ug/m3. PM2.5 mass concentrations were determined to represent approximately 60-90% of the total outdoor PM10 mass. Associations between personal PM2.5 exposures and ambient mass concentrations varied between seasons and increased significantly for both cohorts (e.g., summer cardiac defibrilator cohort r2 = 0.08, fall r2= 0.52). Higher residential air exchange values during the fall appear to be responsible for this finding. Residential outdoor PM2.5 mass concentrations from all homes highly correlated with those from the ambient site even over distances of up to 70 km (r > 0.85). PM2.5 personal cloud estimates for the first two seasons for both cohorts averaged ~ 9 ug/m3. PM mass concentration data and exposure relationships from all four seasons will be discussed at the time of presentation.
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.