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 particulate matter (PM 2.5 and PM 10) concentrations and human morbidity/mortality. However, little is known regarding the most important sources of PM exposure, interpersonal and intrapersonal variability in exposure, and the relationship between personal exposure and ambient exposure estimates based on fixed site monitoring. The NERL in association with a series of cooperating universities are currently analyzing data from several recent longitudinal (10-28 day) panel studies to address these uncertainties and to evaluate the important determinants of PM exposure for different subpopulations, area of the country, air sheds, housing structures, and life styles. Exposure assessments are being performed on panel data involving among others, the elderly, individuals with cardiovascular disease, asthmatics, and healthy individuals living in Atlanta, Boston, Anaheim, Los Angeles, Seattle, and New York City. PM measurements data from personal exposures, ambient, outdoor residential, and indoor residential locations will be analyzed. Copollutants such as CO, ozone, NO2, metals, and elemental-organic carbon will also be incorporated into the analysis. Information on time/activity patterns and potential sources of PM exposure from all participating subjects in conjunction with real-time PM monitoring is being used to establish the influence of various sources (ambient, indoor, personal) on total personal PM exposures. Results to date indicate that personal PM mass concentration exposures for individual panelists can be highly dependent upon the contribution of non-ambient sources (such as the presence of cooking aerosols within a home). The contribution of PM of ambient origin to personal exposures in many of the studies would not appear to be dependent upon susceptibility (health status) while seasonality and geographical settings for residents of some cities (Seattle and Los Angeles) may be influencing factors. Results indicate that a substantial portion of the interpersonal differences in personal-ambient associations appears to be due to the varying impact of outdoor particles on indoor environments. Building type and ventilation strongly influence penetration of ambient PM. Since people spend >90% of their time indoors, understanding particle penetration into buildings will be critical in determining exposure to ambient PM. Until recently, particle penetration efficiencies were thought to be constant and often assumed to be 100%. Results from these studies show that penetration efficiencies can vary substantially by residences and by season and that geographical locality may be important factors. Preliminary findings concerning seasonality from west coast studies performed here stand in contrast to similar studies performed under TD 5676 in a number of east coast cities (Baltimore, Research Triangle Park) concerning this issue. For 30 residences in Seattle, estimated mean penetration efficiency was 56 +/- 8%. In Fresno for 60 apartments, the estimated mean was 25 +/- 17% in the winter and 49 +/- 38% in the spring showing the substantial impact that differences in building ventilation can have over different seasons.

Record Details:

Record Type:PROJECT

Start Date:10/01/1999

Completion Date:09/01/2003

Record ID: 56150

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Project Information:

Progress :Field monitoring has been completed for all of the studies except for Anaheim and the Seattle portion of the studies led by the New York University Medical Center. Field monitoring at these sites will be completed in FY2003. Data validation/analysis is ongoing. Summaries of PM mass concentration have been prepared and reported in APM-1 (September 2001) and a secondary report, APM-21 was completed in August 2002. Numerous technical presentations concerning these studies have been made at scientific conferences during 2000-2002. Specific findings to date indicate:

1.Personal exposure/ambient ratios have substantial intra- and inter-personal variability
2.Stronger personal-outdoor PM correlations exist when data are analyzed by individual, over time. Although, the degree of this association varies by individual, the results suggest that for certain individuals, ambient PM2.5 concentrations are appropriate surrogates for exposures.
3.For pooled analyses that use average exposure concentrations for multiple individuals on a single day, longitudinal correlations with the ambient site concentration are high. This suggests that for community epidemiological studies, ambient PM concentrations are appropriate surrogates for exposures. Associations were strongest for fine particle sulfate>PM2.5 mass > PM10 mass.
4.Correlations between personal exposure and ambient concentrations are high when there is limited activity and few indoor sources.
5.Personal exposures to ambient PM are not substantially different for healthy and susceptible populations.
6 Some of the interpersonal differences in personal-ambient associations may be due to spatial variability in outdoor PM concentrations. Results suggest that for the eastern U.S., outdoor PM concentrations are fairly homogenous. Alternatively, in Fresno correlations between the ambient site and an outdoor residential site were relatively weak (r2<0.5), presumably due to nearby mobile sources.
7. Since people spend >90% of their time indoors, understanding particle penetration into buildings is critical in determining exposure to ambient PM. Until recently particle penetration efficiencies were thought to be constant and often assumed to be 100%. Results from the current studies show that penetration efficiencies can vary substantially by residences and by season. In Fresno for 60 apartments, the estimated mean was 25?17% in the winter and 49?38% in the spring showing the substantial impact that differences in building ventilation can have over different seasons.
8. Results have verified that for fine PM mass and sulfate, the ambient monitoring site should serve as an adequate surrogate for exposure in community-based epidemiological studies.
9. Weak correlations were found between personal PM2.5 and ambient gaseous co-pollutant exposures, suggesting that the gaseous co-pollutants are unlikely confounders of PM2.5. Strong correlations between personal exposures to PM2.5 and ambient concentrations of the co-pollutants exist indicating that the gaseous co-pollutants may serve as appropriate surrogates of personal PM2.5 exposures.


Results from this task have been reported in a number of presentations and publications, including the following:

ABSTRACT/ORAL

University of Washington Research Group-Research Abstracts

Dills, R., Paulsen, M., Simpson, C., Liu, L.-J. S., and Kalman, D. Urinary biomarkers for atmospheric wood smoke exposure - a field study. 2000 PNWIS/AWMA 40th Annual Conference, Victoria, BC, Canada, Nov 8-10, 2000.

Larson, T., Allen, R., and Liu, L.-J. S. Indoor and outdoor contributions to indoor light scattering coefficient at ten residences in Seattle, WA. ISEA 2000 Annual Conference,Monterey, CA, Oct 24-27, 2000.

Larson, T., Tuttle, T., and Liu, L.-J. S. Measurement of indoor and outdoor PM2.5 andlight scattering coefficient at sel

Relevance :The work being conducted under this task directly responds to the NRC Research Topic 1: Outdoor Measures versus Actual Human Exposure, "What are the quantitative relationships between concentrations of particulate-matter and gaseous copollutants measured at stationary outdoor air monitoring sites, and the contributions of these concentrations to actual personal exposures, especially for potentially susceptible subpopulations and individuals?" (NRC, 1998). The studies were enhanced to provide data on chemical species of PM and copollutants. Data from these studies will be used as direct inputs into the future Air Quality Criteria Document for Particulate Matter. These studies are highly significant because an understanding of the relationship between the ambient PM2.5 mass data and personal PM exposure is, by most measures, fundamental to the credibility of the EPA regulatory program. The association between ambient PM concentrations and health outcomes in the population, despite the fact that people spend more time indoors than out, raises questions regarding exposure-response relationships. Concerns are more earnest for potentially susceptible subpopulations, who may well spend even more time indoors, or who may otherwise alter their exposures by their behaviors. Similarly, many factors may alter exposure by virtue of geographical setting, climate, building construction etc. and it is important to gain some fundamental understanding how these many factors interplay in defining individual exposures. With regard to protecting the most susceptible subgroups, it appears from the limited studies to date, that it is unlikely that disease state plays a major role in determining total personal exposure to PM of ambient origin - specifically the PM2.5 fraction. However, the individual time activity profiles, housing and other environmental factors would appear to have more significant influence on personal exposure. East coast and west coast seasonality differences may indicate significant influences of climate upon potential personal exposures. The role of specific PM constituents that may be responsible for the associations between ambient PM mass concentrations and epidemiological health effects has yet to be defined. It is therefore even more important to understand the ability of community-based measurements to accurately reflect exposures to the population.

Clients :
EPA/ORD (John Creason)- for planning future epidemiological field studies, EPA/ORD (Haluk Ozkaynak/Janet Burke) development of a valid and extensive human exposure database for use in exposure model development EPA/NCEA (Les Grant) - for criteria

Project IDs:

ID Code :3937

Project type :OMIS