Critical issues of exposure assessment for human health studies of air pollution
This presentation is the property of its rightful owner.
Sponsored Links
1 / 35

Critical Issues of Exposure Assessment for Human Health Studies of Air Pollution PowerPoint PPT Presentation


  • 93 Views
  • Uploaded on
  • Presentation posted in: General

Critical Issues of Exposure Assessment for Human Health Studies of Air Pollution. SAMSI September 15, 2009. Michelle L. Bell Yale University. Outline. Basic health effects model Methods of measuring exposure Key challenges in assessing exposure Spatial misalignment

Download Presentation

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

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Critical issues of exposure assessment for human health studies of air pollution

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

SAMSI

September 15, 2009

Michelle L. Bell

Yale University


Outline

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


Exposure assessment for studies of air pollution and health

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


Critical issues of exposure assessment for human health studies of air pollution

Example Air Pollution and Health Effects Model

  • Time-series model / Acute exposure

  • Community-aggregated health data

  • Community-aggregated exposure data


Critical issues of exposure assessment for human health studies of air pollution

Example Air Pollution and Health Effects Model

Estimated Air Pollution Exposure


Exposure assessment for studies of air pollution and health1

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


Traditional approaches to exposure assessment

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


Traditional approaches to exposure assessment1

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


Exposure assessment for studies of air pollution and health2

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


Spatial misalignment

Spatial Misalignment

  • Spatially heterogeneity in the concentration surface field

  • Mismatch between data used to estimate exposure and actual subjects’ locations


Correlation of pm 2 5 components by distance

Correlation of PM2.5 components by distance

Peng and Bell Biostatistics Accepted


Spatial disconnect in data

Spatial Disconnect in Data

Pollution data measured at a single or multiple fixed locations

Health data aggregated over a spatial area

Weather data measured at a single or multiple fixed locations, that likely differ from the pollution monitor locations


Error model

Error Model

Pollution data measured at a single or multiple fixed locations

True pollution level over a spatial area

Peng and Bell Biostatistics Accepted


Spatial misalignment adjustment

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


Multi pollutant concepts

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


Major air pollution emissions sources

SO2

PM

Pb

NOx

CO

VOCs

Major Air Pollution Emissions Sources

Industrial Sources

Diesel

Domestic Sources

Gasoline

Power

Generation

VEHICLE

SOURCES

STATIONARY

SOURCES


Particulate matter

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.


Critical issues of exposure assessment for human health studies of air pollution

Different chemical components by PM size

Different sources by PM size


Critical issues of exposure assessment for human health studies of air pollution

<1.0 mg/m3

1.0 to 2.5

2.5 to 4.0

4.0 to 5.5

>5.5

PM as a Pollutant Mixture

PM2.5 sulfate (2000-2002)

Bell et al. EHP 2007


Critical issues of exposure assessment for human health studies of air pollution

Spring

Winter

Fall

Summer

<2 mg/m3

2 to 3

Seasonal sulfate PM2.5 averages for 187 U.S. counties, 2000-2005

3 to 4

4 to 5

>5

Bell et al. EHP 2007


Pm 2 5 and medicare hospital admissions

PM2.5 and Medicare Hospital Admissions

3

2

1

0

-1

West

East

-2

% 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


Allow temporal variation in effect estimates based on variation in exposure

Allow Temporal Variation in Effect Estimates Based on Variation in Exposure


Season interaction model

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


Critical issues of exposure assessment for human health studies of air pollution

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


Exposure assessment for studies of air pollution and health3

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


Example air quality modeling to estimate exposure

Domain 1

Domain 2

Domain 3

Domain 4

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


Critical issues of exposure assessment for human health studies of air pollution

Bell and Ellis J Air Waste Manage Assoc 2003


Critical issues of exposure assessment for human health studies of air pollution

> 180

170 to 180

160 to 170

150 to 160

140 to 150

130 to 140

120 to 130

110 to 120

100 to 110

<100

County-level Exposure Estimates

1-Hour max O3 (ppb)

Monitor in county

Modeling estimates

Spatial interpolation of monitors

Bell Environ Int 2006


Critical issues of exposure assessment for human health studies of air pollution

180+

170 to 180

160 to 170

150 to 160

140 to 150

130 to 140

120 to 130

110 to 120

100 to 110

<100

Modeling estimates

Individual-Level Exposure Estimates

1-Hour max O3 (ppb)

Nearest monitor

Bell Environ Int 2006


Ozone monitors in georgia 2000

< 50

51 to 75

75 to 150

151 to 250

251 to 500

501 to 1000

>1001

Ozone monitors in Georgia 2000

Persons / Sq. Mile


Example traffic modeling to estimate exposure

Example: Traffic Modeling to Estimate Exposure

Holford et al. Statistics in Medicine Accepted


Estimated no 2 traffic levels for new haven county area 2002

Estimated NO2 (traffic) Levels for New Haven County Area (2002)

Holford et al. Statistics in Medicine Accepted


Exposure assessment for studies of air pollution and health4

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


Other challenges

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


Thank you

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


  • Login