2002 Progress Report: Exposure Characterization Error

EPA Grant Number: R827351C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R827351
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EPA NYU PM Center: Health Risks of PM Components
Center Director: N/A
Title: Exposure Characterization Error
Investigators: Ito, Kazuhiko
Institution: New York University School of Medicine
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Period Covered by this Report: June 1, 2002 through May 31, 2003
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air


The objectives of this project are to: (1) quantitatively characterize spatio-temporal error of particulate matter (PM) components and gaseous co-pollutants measured at routine regulatory-based air monitors as a function of site characteristics using the entire United States air monitoring network; (2) establish the relationship between the estimated error at a given monitoring site and the effect size/significance in mortality and morbidity models; and (3) evaluate the relative contribution of the error due to site-to-site and person-to-site variability. This project will test the validity of the prevailing hypothesis that the PM and gaseous co-pollutants data from a single air monitoring station can adequately reflect the population exposure for the entire city, and that resulting risk estimates and their significance are not biased.

Progress Summary:

Progress in Years 1-3 of the Project. We completed the analysis of nationwide PM10 and gaseous criteria pollutants. A manuscript has been submitted (Ito, et al., 2003). Spatial uniformity of temporal correlation was examined by computing monitor-to-monitor correlation using available multiple monitors for PM10 and gaseous pollutants (NO2, SO2, CO, and O3) for the nationwide data between 1988-1997. For each monitor, the median of temporal correlation with other monitors within the Air Quality Control Region (AQCR) was computed. The resulting median correlation was modeled as a function of qualitative site characteristics (i.e., land-use, location-setting, and monitoring-objective) and quantitative information (median separation distance, longitude/latitude, or regional indicators) for each pollutant. Generalized Additive Models (GAM) with stringent convergence criteria were used to fit the smooth function of the separation distance and regional variation. The intercepts of the models across pollutants showed the overall rank in monitor-to-monitor correlation on the average: O3, NO2, PM10, (0.7~0.8) > CO (~0.6) > SO2 (~0.4). Both the separation distance and regional variation were important predictors of the correlation. For PM10, for example, the correlation for the monitors along the East Coast was higher by ~0.1 than for the nationwide average. The qualitative monitor characteristics often were significant predictors of the variation in correlation, but their impacts were not substantial in magnitude for most categories. These results suggest that the apparent regional heterogeneity in PM effect estimates, as well as the differences in the significance of health outcome associations across pollutants, may in part be explained by the differences in monitor-to-monitor correlations by region and across pollutants.

In addition, we completed processing of weather and mortality data for the years 1985-1997 for the largest 88 United States cities, and conducted several analyses investigating the associations between air pollution and mortality in large cities. For New York City data, the role of contributing respiratory causes of death on the associations between the PM10 and the underlying (primary) nonrespiratory causes of death (circulatory and cancer) was investigated (DeLeon, et al., 2003). It was found that these nonrespiratory causes of death were associated more strongly with PM10 when the deaths had respiratory contributing causes. The implication is that past studies underestimated the role of respiratory diseases in PM-mortality associations.

Progress in Year 4 of the Project. We have made additional progress in two areas: (1) examination of exposure characterization error in the newly available PM2.5 speciation data, and (2) examination of influence of exposure characterization error in the PM10-mortality associations in New York City.

A large number of monitors started collecting chemical speciation data from PM2.5 filters in 2000 and 2001 in the United States. The data from this chemical speciation network may be useful for source-oriented evaluations of PM health effects. The aim was to examine the monitor-to-monitor correlation of each of the PM2.5 speciation components (i.e., trace element, ions, elemental, and organic carbon), as well as factor analysis-derived source-apportioned PM2.5 using data from multiple monitors. Data from three monitors in New York City that collected PM2.5 speciation data every third day (New York Botanical Gardens in the Bronx; Intermediate School 52 in the Bronx; and Queens College in Queens) were analyzed for the years 2001-2002. As expected, the highest temporal correlations across the three sites were found for the PM components that are related to secondary aerosols (e.g., S, with r ~ 0.9). Some of the components that are related to soil (e.g., Si) and residual oil burning (e.g., V) showed moderate correlation (r ~ 0.7). Although the number of factors obtained from each of the three monitors varied, they all qualitatively identified same source types. However, the estimated mean contributions to PM2.5 mass concentrations varied somewhat across the three locations, especially for the source types that likely are influenced by local emissions (i.e., traffic, incineration). The implication of these observations is that if a source-oriented evaluation of the health effects of PM components is conducted using data from a monitor to represent a whole city's population, then any potential effects from local sources may be masked.

To construct a framework for a systematic evaluation of the influence of exposure characterization error on the PM-mortality associations in the nationwide data, an initial evaluation of PM10-mortality associations was conducted using New York City daily mortality data and multiple monitors' data from a larger geographic boundary, the AQCR for New York-New Jersey-Connecticut Metropolitan area. Of the 56 monitors that operated, 25 monitors collected measurements on at least 78 percent of the every-sixth-day sampling days during 1989-1997, and were considered further for mortality analysis. The monitor-to-monitor correlation ranged from approximately 0.6 to 0.95. The 1-day lagged mortality association was most significant for 24 out of the 25 monitors, but the coefficients and significance varied. Generally, the regression coefficients were inversely proportional to the mean PM10 values of the monitor, indicating a constant bias (or "artifact") due to the concentration gradient across the area. These results suggest that the raw PM regression coefficient computed from a single or a few monitors may not be transferable to other locales without adjusting for a potential bias due to location of the monitor.

Future Activities:

During the next year, we will continue to construct a framework for a systematic evaluation of the influence of exposure characterization error on the PM-mortality associations in nationwide data.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 7 publications 7 publications in selected types All 7 journal articles
Other center views: All 112 publications 101 publications in selected types All 89 journal articles
Type Citation Sub Project Document Sources
Journal Article Ito K, Thurston GD, Nadas A, Lippmann M. Monitor-to-monitor temporal correlation of air pollution and weather variables in the North-Central U.S. Journal of Exposure Analysis & Environmental Epidemiology 2001;11(1):21-32. R827351 (Final)
R827351C001 (2000)
R827351C001 (2002)
R827351C001 (2003)
R827351C001 (Final)
R825271 (Final)
  • Abstract from PubMed
  • Full-text: JESEE-Full Text PDF
  • Abstract: JESEE-Abstract
  • Supplemental Keywords:

    air pollution, air pollutants, particles, particulate matter, PM, fine particles, PM2.5, PM components, air monitoring, exposure, gaseous criteria pollutants, NO2, nitrogen dioxide, SO2, sulfur dioxide, CO, carbon monoxide, O3, ozone, health effects, health outcomes, health risks, air pollution and mortality, urban air, New York City, New York, NY, New Jersey, NJ, Connecticut, CT, source apportionment, exposure assessment, exposure characterization, PM mortality., RFA, Health, Scientific Discipline, PHYSICAL ASPECTS, Air, ENVIRONMENTAL MANAGEMENT, particulate matter, Environmental Chemistry, Health Risk Assessment, Risk Assessments, Environmental Monitoring, Physical Processes, Atmospheric Sciences, Atmosphere, Risk Assessment, ambient air quality, atmospheric particulate matter, particulates, air toxics, atmospheric particles, chemical characteristics, toxicology, ambient air monitoring, airborne particulate matter, ozone, environmental risks, exposure, Sulfur dioxide, air pollution, aerosol composition, atmospheric aerosol particles, human exposure, ozone monitoring, PM, exposure assessment

    Relevant Websites:

    http://charlotte.med.nyu.edu/epa-pm-center/ Exit

    Progress and Final Reports:

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

  • Main Center Abstract and Reports:

    R827351    EPA NYU PM Center: Health Risks of PM Components

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827351C001 Exposure Characterization Error
    R827351C002 X-ray CT-based Assessment of Variations in Human Airway Geometry: Implications for Evaluation of Particle Deposition and Dose to Different Populations
    R827351C003 Asthma Susceptibility to PM2.5
    R827351C004 Health Effects of Ambient Air PM in Controlled Human Exposures
    R827351C005 Physicochemical Parameters of Combustion Generated Atmospheres as Determinants of PM Toxicity
    R827351C006 Effects of Particle-Associated Irritants on the Cardiovascular System
    R827351C007 Role of PM-Associated Transition Metals in Exacerbating Infectious Pneumoniae in Exposed Rats
    R827351C008 Immunomodulation by PM: Role of Metal Composition and Pulmonary Phagocyte Iron Status
    R827351C009 Health Risks of Particulate Matter Components: Center Service Core
    R827351C010 Lung Hypoxia as Potential Mechanisms for PM-Induced Health Effects
    R827351C011 Urban PM2.5 Surface Chemistry and Interactions with Bronchoalveolar Lavage Fluid (BALF)
    R827351C012 Subchronic PM2.5 Exposure Study at the NYU PM Center
    R827351C013 Long Term Health Effects of Concentrated Ambient PM2.5
    R827351C014 PM Components and NYC Respiratory and Cardiovascular Morbidity
    R827351C015 Development of a Real-Time Monitoring System for Acidity and Soluble Components in Airborne Particulate Matter
    R827351C016 Automated Real-Time Ambient Fine PM Monitoring System