Final Report: Assessing Human Exposures to Particulate and Gaseous Air Pollutants

EPA Grant Number: R827353C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R827353
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EPA Harvard Center for Ambient Particle Health Effects
Center Director: Koutrakis, Petros
Title: Assessing Human Exposures to Particulate and Gaseous Air Pollutants
Investigators: Koutrakis, Petros , Suh, Helen H. , Brown, Kathleen Ward , Sarnat, Jeremy
Institution: Harvard University
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Amount: Refer to main center abstract for funding details.
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air

Objective:

Theme I: Assessing Particle Exposures for Health Effects Studies: A large data set on personal exposures and indoor and outdoor concentrations was collected for panels of susceptible individuals across the U.S. (Sarnat, et al., 2000; Sarnat, et al., 2001; Sarnat, et al., 2002; Koutrakis, et al., 2005). These investigations suggest that personal exposures to PM2.5 of ambient origin are highly correlated with outdoor concentrations. However, the regression slopes of personal exposures on outdoor concentrations, which are usually less than one, vary substantially depending on house characteristics, season, and city climatic conditions. The strong correlations between personal and ambient concentrations were unique to PM2.5, as personal exposures to O3, SO2 and NO2 were substantially lower than, and weakly correlated with, corresponding outdoor concentrations (Sarnat, et al., 2005).

The primary focus of Theme I was to assess human exposures to particles and gaseous co-pollutants in order to better understand their heath effects. As such, research conducted as part of Theme I contained five main objectives:

  1. to characterize the inter- and intra- variability in personal particulate and gaseous exposures;
  2. to identify factors affecting the relationship between personal exposures and outdoor levels;
  3. to determine the contribution of outdoor and indoor particles to personal particulate exposures;
  4. to quantify the effect of measurement error for fine particles and their co-pollutants (coarse mass and the criteria gases) on risk estimates from epidemiological studies; and
  5. to differentiate the health effects of particles from outdoor and indoor sources.

These objectives were addressed by three inter-related research projects, which made use of our database of personal, indoor, and outdoor particulate and gaseous exposures.

A central research objective of this group of projects was the examination of relationships between ambient particles and gases and corresponding personal exposures. The primary objectives of this work were to characterize exposures to PM2.5 and its major components and to assess the relative importance of several error sources to our ability to estimate exposures from ambient fine particle concentrations. These objectives were addressed using measurements of personal particulate exposures and corresponding indoor, outdoor, and ambient concentrations that were made for several cohorts of sensitive individuals. These data were specifically used to examine the impact of geographic location on the relationships between personal particulate and gaseous exposures; to evaluate the ability of ambient, home outdoor and home indoor pollutant concentrations to serve as proxies of personal exposure; and to determine how housing characteristics and activity patterns affect the relationships between personal exposures and ambient concentrations. The current findings indicate that geographical differences, ventilation of the home, time spent outdoors and local traffic sources may affect the ability of ambient concentrations to serve as proxies for personal exposures.

Summary/Accomplishments (Outputs/Outcomes):

Pooling results from the Boston and Baltimore panel studies, we assessed whether the contribution of ambient particles on personal exposures varied by city, season and cohort. No cohort effect was found on the attenuation factors, which suggests that subjects from each cohort (i.e., seniors, children, chronic obstructive pulmonary disease (COPD) patients) were exposed to the same fraction of ambient PM2.5, given the same concentrations of ambient PM2.5. A report detailing these findings was published in 2005 (Koutrakis, et al., 2005). In one paper, we analyzed data from a Baltimore multiple pollutant exposure assessment to examine the role of ambient pollutant concentrations in PM2.5 epidemiologic models (Sarnat, et al., 2001). Since the Baltimore analysis was the first to examine relationships between personal exposures and ambient concentrations for PM2.5 and gaseous pollutants, it was important to conduct a similar analysis for other cities. We conducted an analysis including personal exposure and ambient concentration multi-pollutant data from the Boston panel study. Results from the Boston analysis, which includes both data from Baltimore and Boston, provide further evidence that the ambient gaseous pollutant concentrations are better surrogates of personal PM2.5 exposures, especially personal exposures to PM2.5 of ambient origin, than their respective personal exposures. These findings suggest that using ambient gas concentrations in multiple-pollutant health effects models along with PM2.5 may not be appropriate, since both the ambient gaseous and PM2.5 concentrations are serving as surrogates for PM2.5 exposures. In addition, the robustness of these findings was demonstrated by using various analytical methods and model structures. A paper entitled, “Relationships among Personal Exposures and Ambient Concentrations of Particulate and Gaseous Pollutants and their Implications for Particle Health Effects Studies,” was published in April 2005 in Epidemiology.

An additional panel study conducted in Boston found ambient particulate sulfate (SO42-) to be strongly correlated with corresponding personal exposures and home indoor concentrations for individuals not using humidifiers, a source of indoor SO42-. Correlations between ambient SO42- and personal exposures, however, varied by subject and by season. Associations with outdoor SO42- concentrations were similar to those for ambient concentrations. Ambient elemental carbon (EC) and PM2.5 concentrations were more weakly associated with corresponding personal and indoor levels, as compared to SO42-, likely due to the contributions of indoor and other local EC and PM2.5 sources.

In addition, this study found infiltration of outdoor pollutants into the home to be a key factor determining the contribution of ambient pollution to personal exposures, due to the large proportion of time individuals spend in their residences. High indoor-outdoor SO42- correlations indicated that home indoor and home outdoor levels correlated consistently regardless of the differences in the absolute levels in the two microenvironments. The significantly weaker associations for EC and PM2.5 compared to SO42- indicate that personal and household activities likely play an important role in determining personal exposures and can weaken associations with outdoor or ambient concentrations.

For EC, substantial spatial variation in outdoor concentrations was found, with this spatial variation lessening the ability of ambient concentrations to act as proxies of personal EC exposures. These results suggest that placement of outdoor EC monitors closer to participants’ homes may reduce exposure error in epidemiological studies of EC and other traffic-related particles. Infiltration was also shown to impact the ability of ambient concentrations to reflect exposures, as a strong seasonal difference in infiltration was found, where greater ventilation during the summer may have resulted in significantly higher personal exposures to particles originating from ambient sources. In contrast in the winter, lower infiltration can result in a greater contribution of indoor sources to personal exposures to EC and PM2.5.

A number of exposure and source factors were also found to affect personal exposures, particularly ventilation, time spent outdoors, time spent in transit and proximity to a major roadway. As indicated in previous panel studies, ventilation was a significant exposure modifier primarily during summer with open windows in the home approximately doubling the personal-ambient slopes for all pollutants, except NO2. While ventilation increased exposures to pollutants generated outdoors, there was evidence in this study of large impacts from indoor sources particularly at low ventilation rates. Subjects that spent more than an hour outdoors during summer had significantly increased personal exposures compared to individuals that spent less than that time outdoors, but the overall effect on personal exposures differed by pollutant with the greatest difference seen for EC. Living close to a major road was associated with higher traffic-related pollutants—EC, PM2.5 and NO2. This study also associated humidifiers using tap water with the highest personal and indoor SO42- and PM2.5 levels measured in the study. Other residence-specific location factors, including traffic density, population density, and percentage urban land use, were not significant modifiers of the personal-ambient association for any of the pollutants.

This analysis also indicated that open window status provided more consistent model results than air exchange rate (AER) in this study. The inconsistent results for AER may be due to the fact that many of the homes measured were apartments. As a result, the AER method could not differentiate between make-up air from outdoors or from neighboring apartments. Imprecision in the AER method also cannot be ruled out as contributing to this finding. As a result, future studies that include personal or indoor exposure measures may consider open windows as a better indicator of air exchange with outdoors in apartments or multi-unit buildings over a 24-hour period.

The results also indicated that infiltration into homes during the one-week monitoring period was remarkably consistent, given the various housing types measured. While the inter-home variability in infiltration ratios was substantial, infiltration ratios for a given home varied little over the week. Minimal intra-home variation in infiltration ratios is important given the complexity and difficulty of conducting large-scale personal exposure studies. A better understanding of how some housing, activity and source factors affect personal-ambient relationships may allow us to better estimate personal exposures in future health assessment studies.

Conclusions:

Determining how well ambient monitors estimate personal exposures is especially important, given the recent generation of combined health and exposure studies on small panels of individuals. For these studies, more accurate estimates of exposures are needed to provide sufficient power to examine PM-associated impacts on intermediate health outcomes, such as heart rate variability and blood inflammation markers (Dubowsky, et al., 2006). In addition to assessing ambient concentrations, an assessment of ventilation conditions in the homes will likely provide a good indicator of the amount of outdoor pollution contributing to exposures in these studies.

References:

Dubowsky SD, Suh H, Schwartz J, Coull BA, Gold DR. Diabetes, obesity, and hypertension may enhance associations between air pollution and markers of systemic inflammation. Environmental Health Perspectives 2006;114(7):992-998.

Koutrakis P, Suh H, Sarnat J, Brown K, Coull B, Schwartz J. Characterization of particulate and gas exposures of sensitive subpopulations living in Baltimore and Boston. Health Effects Institute, Research Report. Boston, MA, Health Effects Institute, 2005.

Sarnat JA, Brown KW, Schwartz J, Coull BA, Koutrakis P. Ambient gas concentrations and personal particulate matter exposures: implications for studying the health effects of particles. Epidemiology 2005;16(3):385-395.

Sarnat JA, Koutrakis P, Suh H. Assessing the relationship between personal particulate and gaseous exposures of senior citizens living in Baltimore. Journal of the Air & Waste Management Association 2000;50(7):1184-1198.

Sarnat JA, Long CM, Koutrakis P, Coull BA, Schwartz J, Suh HH. Using sulfur as a tracer of outdoor fine particulate matter. Environmental Science & Technology 2002;36(24):5305-5314.

Sarnat JA, Schwartz J, Catalano P, Suh H. Gaseous pollutants in particulate matter epidemiology: confounders or surrogates? Environmental Health Perspectives 2001;109(10):1053-1061.


Journal Articles on this Report : 6 Displayed | Download in RIS Format

Other subproject views: All 6 publications 6 publications in selected types All 6 journal articles
Other center views: All 200 publications 198 publications in selected types All 197 journal articles
Type Citation Sub Project Document Sources
Journal Article Sarnat JA, Koutrakis P, Suh HH. Assessing the relationship between personal particulate and gaseous exposures of senior citizens living in Baltimore, MD. Journal of the Air & Waste Management Association 2000;50(7):1184-1198. R827353 (Final)
R827353C001 (2000)
R827353C001 (2001)
R827353C001 (2002)
R827353C001 (2003)
R827353C001 (2004)
R827353C001 (Final)
  • Abstract from PubMed
  • Full-text: Taylor&Francis-Full Text PDF
    Exit
  • Abstract: Taylor&Francis-Abstract
    Exit
  • Journal Article Sarnat JA, Schwartz J, Catalano PJ, Suh HH. Gaseous pollutants in particulate matter epidemiology:confounders or surrogates? Environmental Health Perspectives 2001;109(10):1053-1061. R827353 (Final)
    R827353C001 (2001)
    R827353C001 (2002)
    R827353C001 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Journal Article Sarnat JA, Long CM, Koutrakis P, Coull BA, Schwartz J, Suh HH. Using sulfur as a tracer of outdoor fine particulate matter. Environmental Science & Technology 2002;36(24):5305-5314. R827353 (Final)
    R827353C001 (2001)
    R827353C001 (Final)
  • Abstract from PubMed
  • Full-text: ES&T-Full Text HTML
    Exit
  • Abstract: ES&T-Abstract
    Exit
  • Other: ES&T-Full Text PDF
    Exit
  • Journal Article Sarnat JA, Brown KW, Schwartz J, Coull BA, Koutrakis P. Ambient gas concentrations and personal particulate matter exposures:implications for studying the health effects of particles. Epidemiology 2005;16(3):385-395. R827353 (Final)
    R827353C001 (2003)
    R827353C001 (2004)
    R827353C001 (Final)
  • Abstract from PubMed
  • Full-text: Epidemiology-Full Text HTML
    Exit
  • Abstract: Epidemiology-Abstract
    Exit
  • Other: Epidemiology-Full Text PDF
    Exit
  • Journal Article Sarnat SE, Coull BA, Ruiz PA, Koutrakis P, Suh HH. The influences of ambient particle composition and size on particle infiltration in Los Angeles, CA, residences. Journal of the Air & Waste Management Association 2006;56(2):186-196. R827353 (Final)
    R827353C001 (Final)
  • Abstract from PubMed
  • Full-text: Taylor&Francis-Full Text PDF
    Exit
  • Abstract: Taylor&Francis-Abstract
    Exit
  • Journal Article Sarnat SE, Coull BA, Schwartz J, Gold DR, Suh HH. Factors affecting the association between ambient concentrations and personal exposures to particles and gases. Environmental Health Perspectives 2006;114(5):649-654. R827353 (Final)
    R827353C001 (Final)
    R826780 (Final)
  • Full-text from PubMed
  • Abstract from PubMed
  • Associated PubMed link
  • Supplemental Keywords:

    RFA, Health, Scientific Discipline, Air, Air Pollution Monitoring, particulate matter, Toxicology, air toxics, Environmental Chemistry, Epidemiology, Risk Assessments, Environmental Microbiology, Environmental Monitoring, indoor air, Atmospheric Sciences, Molecular Biology/Genetics, Biology, ambient air quality, monitoring, particle size, particulates, risk assessment, sensitive populations, chemical exposure, air pollutants, cardiopulmonary responses, human health effects, indoor exposure, lung, ambient air monitoring, exposure and effects, ambient air, ambient measurement methods, exposure, pulmonary disease, developmental effects, epidemelogy, respiratory disease, COPD, air pollution, ambient monitoring, children, particle exposure, chronic effects, human exposure, inhalation, pulmonary, particulate exposure, ambient particle health effects, inhaled, PM, inhalation toxicology, cardiopulmonary, indoor air quality, human health, air quality, cardiovascular disease, dosimetry, exposure assessment, human health risk, respiratory, measurement methods

    Relevant Websites:

    http://www.hsph.harvard.edu/epacenter/epa_center_99-05/index.html Exit

    Progress and Final Reports:

    Original Abstract
  • 1999 Progress Report
  • 2000 Progress Report
  • 2001 Progress Report
  • 2002 Progress Report
  • 2003 Progress Report
  • 2004 Progress Report

  • Main Center Abstract and Reports:

    R827353    EPA Harvard Center for Ambient Particle Health Effects

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827353C001 Assessing Human Exposures to Particulate and Gaseous Air Pollutants
    R827353C002 Quantifying Exposure Error and its Effect on Epidemiological Studies
    R827353C003 St. Louis Bus, Steubenville and Atlanta Studies
    R827353C004 Examining Conditions That Predispose Towards Acute Adverse Effects of Particulate Exposures
    R827353C005 Assessing Life-Shortening Associated with Exposure to Particulate Matter
    R827353C006 Investigating Chronic Effects of Exposure to Particulate Matter
    R827353C007 Determining the Effects of Particle Characteristics on Respiratory Health of Children
    R827353C008 Differentiating the Roles of Particle Size, Particle Composition, and Gaseous Co-Pollutants on Cardiac Ischemia
    R827353C009 Assessing Deposition of Ambient Particles in the Lung
    R827353C010 Relating Changes in Blood Viscosity, Other Clotting Parameters, Heart Rate, and Heart Rate Variability to Particulate and Criteria Gas Exposures
    R827353C011 Studies of Oxidant Mechanisms
    R827353C012 Modeling Relationships Between Mobile Source Particle Emissions and Population Exposures
    R827353C013 Toxicological Evaluation of Realistic Emissions of Source Aerosols (TERESA) Study
    R827353C014 Identifying the Physical and Chemical Properties of Particulate Matter Responsible for the Observed Adverse Health Effects
    R827353C015 Research Coordination Core
    R827353C016 Analytical and Facilities Core
    R827353C017 Technology Development and Transfer Core