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 is 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 the elderly, individuals with cardiovascular disease, and African-Americans living in an environmental justice neighborhood. Select populations living in Baltimore, MD, Fresno, CA, and Research Triangle Park, NC are involved. Data from personal exposures, ambient, outdoor residential, and indoor residential locations measurements of PM 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), season, or other factors such as socio-economic status classification. Data from one study performed over the course of one year and involving over 30 participants estimated that approximately 46% of one's personal PM mass concentration exposure is of ambient origin.
Keywords:
PARTICULATE MATTER, AMBIENT, PERSONAL PM CONCENTRATIONS, SUSCEPTIBLE POPULATION, ENVIRONMENTAL JUSTICE , INDOOR ENVIRONMENTS,
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Project Information:
Progress
:Field monitoring has been completed for all of the studies (Baltimore [summer 1998], Fresno [spring and summer 1999], and Research Triangle Park [spring 2001]). Data validation and analysis from PM mass concentration measurements associated with the Research Triangle Park study have been completed and a database developed. PM mass concentration and select PM species or related co-pollutants data associated with the Baltimore and Fresno studies have been summarized and published in numerous peer reviewed journal articles. In addition, two key APM reports (NERL-PM-APM1, NERL-PM-APM21) and two supplemental interim milestone technical reports have been completed and made available to client institutions. These are summarized below. Chemical (elemental) analysis of samples from the Research Triangle Park study has been initiated and is expected to be completed during FY2003. Additional journal articles summarizing new findings from the multiple studies and preliminary PM mass data from the Research Triangle Park study will be submitted to numerous journals during 2003. 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 in 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 of work performed under this task have been reported in numerous presentations and publications. Walsh, D. Effects of particulate matter on the heart rate variability of elderly residents in an east coast retirement community: the Baltimor
Relevance
: The work being performed under this task directly responds to the NRC Research Topic 1: Outdoor Measures verses 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 a fundamental understanding how these many factors interplay in defining individual exposures. In 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. 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/NHEERL ( John Creason), EPA/NCEA -(Les Grant) for criteria document review, EPA/OAQPS (John Bachmann/Ted Palma), EPA/OTAQ (Rich Baldauf), NRC, Scientific community
Project IDs:
ID Code
:5676
Project type
:OMIS