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Critical Issues of Exposure Assessment for Human Health Studies of Air Pollution

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Critical Issues of Exposure Assessment for Human Health Studies of Air Pollution SAMSI September 15, 2009 Michelle L. Bell Yale University * Linked with urban ... – PowerPoint PPT presentation

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Title: Critical Issues of Exposure Assessment for Human Health Studies of Air Pollution


1
Critical Issues of Exposure Assessment for Human
Health Studies of Air Pollution
SAMSI September 15, 2009
  • Michelle L. Bell
  • Yale University

2
Outline
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

3
Exposure Assessment for Studies of Air Pollution
and Health
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

4
Example Air Pollution and Health Effects Model
  • Time-series model / Acute exposure
  • Community-aggregated health data
  • Community-aggregated exposure data

5
Example Air Pollution and Health Effects Model
Estimated Air Pollution Exposure
6
Exposure Assessment for Studies of Air Pollution
and Health
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

7
Traditional Approaches to Exposure Assessment
  • Use of ambient monitors
  • cost-effective
  • can provide large sample size
  • not present in all times or locations of interest
  • locations based on regulatory, not scientific,
    purposes
  • obscures between-person differences
  • Personal monitors
  • individualized data
  • short timeframe
  • small population
  • logistical concerns

Source Louisville, KY government
Jiang and Bell EHP 2008
8
Traditional Approaches to Exposure Assessment
  • Use of ambient monitors
  • cost-effective
  • can provide large sample size
  • not present in all times or locations of interest
  • locations based on regulatory, not scientific,
    purposes
  • obscures between-person differences
  • Personal monitors
  • individualized data
  • measure pollutant characteristics of interest
  • short timeframe and small population
  • logistical concerns and expensive

9
Exposure Assessment for Studies of Air Pollution
and Health
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

10
Spatial Misalignment
  • Spatially heterogeneity in the concentration
    surface field
  • Mismatch between data used to estimate exposure
    and actual subjects locations

11
Correlation of PM2.5 components by distance
Peng and Bell Biostatistics Accepted
12
Spatial Disconnect in Data
13
Error Model
Pollution data measured at a single or multiple
fixed locations
Peng and Bell Biostatistics Accepted
14
Spatial Misalignment Adjustment
  • Monitor average ( ) good proxy for true
    value ( xt ) with good monitor coverage and/or
    low spatial heterogeneity
  • Spatial misalignment adjustments useful when
  • Pollutant very spatially heterogeneous (e.g., EC)
  • Poor monitor coverage within area of interest,
    but monitors elsewhere

15
Multi-Pollutant Concepts
  • Physiologically we respond to a complex mixture
    of air pollutants
  • Many studies focus on the effects of a single
    pollutant
  • Additional pollutants typically considered with
    respect to confounding, not complex effects
  • Air pollution policy set for single pollutants
  • Based on single pollutant science

16
Major Air Pollution Emissions Sources
Industrial Sources
Diesel
Domestic Sources
Gasoline
Power Generation
VEHICLE SOURCES
STATIONARY SOURCES
17
Particulate Matter
  • What is represented by an exposure estimate for
    PM?
  • Only pollutant regulated without regard to
    chemical form
  • May vary in
  • Size
  • Shape
  • Chemical structure
  • Water content
  • Acidity
  • Age
  • Etc.

18
Different chemical components by PM size
Different sources by PM size
19
PM as a Pollutant Mixture
PM2.5 sulfate (2000-2002)
Bell et al. EHP 2007
20
Bell et al. EHP 2007
21
PM2.5 and Medicare Hospital Admissions
Change in Hospital Admissions per 10 mg/m3 PM2.5
Ischemic Heart Disease
Heart Failure
Heart Rhythm
Respiratory Infection
COPD
Peripheral Vascular Disease
Cerebrovascular Disease
Dominici et al. JAMA 2006
22
Allow Temporal Variation in Effect Estimates
Based on Variation in Exposure
23
Season Interaction Model
  • Allows different effect estimates by season

Harmonic Model
  • Allows effect estimates to differ throughout the
    year

Bell et al. Am J Epidemiol 2008
24
Seasonal Variation in PM Total Mass Health Effect
Estimates
increase in CVD hospitalizations per 10 mg/m3
L0 PM2.5
Day of the year
Bell et al. Am J Epidemiol 2008
25
Exposure Assessment for Studies of Air Pollution
and Health
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

26
Example Air Quality Modeling to Estimate Exposure
  • CMAQ / MM5
  • Aug 15 18, 1995
  • 2,168 cells with 4 km horizontal resolution
  • 8 monitors for ozone

Bell Environ Int 2006
27
Bell and Ellis J Air Waste Manage Assoc 2003
28
County-level Exposure Estimates
1-Hour max O3 (ppb)
Monitor in county
Modeling estimates
Spatial interpolation of monitors
Bell Environ Int 2006
29
Individual-Level Exposure Estimates
1-Hour max O3 (ppb)
Nearest monitor
Bell Environ Int 2006
30
Ozone monitors in Georgia 2000
Persons / Sq. Mile
31
Example Traffic Modeling to Estimate Exposure
Holford et al. Statistics in Medicine Accepted
32
Estimated NO2 (traffic) Levels for New Haven
County Area (2002)
Holford et al. Statistics in Medicine Accepted
33
Exposure Assessment for Studies of Air Pollution
and Health
  • Basic health effects model
  • Methods of measuring exposure
  • Key challenges in assessing exposure
  • Spatial misalignment
  • Multiple pollutant exposures
  • Special case of particulate matter
  • Current and upcoming approaches to estimating
    exposure
  • Other challenges

34
Other Challenges
  • Other factors affecting certainty of monitor
    values
  • Detection limits of monitors
  • Measurement error (see co-located monitors)
  • Other factors that affect exposure and variation
    of exposure
  • Movement through the community
  • Indoor/outdoor activity patterns
  • Behaviors and activities (e.g., AC, jogging)
  • Differences between exposure and dose

35
Thank you
  • Key Collaborators
  • Francesca Dominici, Harvard University
  • Roger D. Peng, Johns Hopkins University
  • Keita Ebisu, Yale University
  • Sponsors
  • National Institute for Environmental Health
    Sciences (NIEHS)
  • Health Effects Institute
  • U.S. Environmental Protection Agency-sponsored
    Johns Hopkins Particulate Matter Research Center
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