U.S. census unit population exposures to ambient air pollutants.

Area of Science:

• Environmental Science
• Public Health
• Epidemiology
• Air Quality Monitoring

Background:

• Estimating ambient PM2.5 and ozone concentrations has advanced using various data sources and modeling, yielding gridded surfaces.
• Epidemiologic studies require population exposures at census geographic units (CGUs) for health data linkage and individual privacy.
• This study addresses the need for population exposure estimates to ambient PM2.5 and ozone for U.S. CGUs.

Purpose of the Study:

• To generate population exposure estimates for ambient fine particulate matter (PM2.5) and ozone at U.S. Census Geographic Units (CGUs).
• To provide data suitable for health impact assessments and public communication regarding air quality.

Main Methods:

• Converted U.S. EPA's 2001-2006 gridded air quality data to census block group (BG) level using spatial proximity.
• Employed a bottom-up strategy, aggregating BG estimates weighted by population distribution to derive CGU-level exposures.
• Validated BG daily estimates against monitoring data, showing good comparability.

Main Results:

• Daily BG estimates for PM2.5 deviated by an average of 2 μg/m³, and for ozone by 3 ppb, compared to observed values.
• Population exposures to PM2.5 and ozone exhibited significant geographic variation across the United States.
• In 2006, PM2.5 exposure estimates exceeded National Ambient Air Quality Standards (NAAQS) for at least 7 days in the West Coast, Northwest, and parts of the East.
• Ozone exposure estimates exceeded NAAQS for at least 7 days in most of California and some Eastern/Southeastern areas.

Conclusions:

• The generated population exposure estimates are valuable for health impact assessments via linkage studies.
• These data can aid in communicating air quality issues to the public and policymakers for intervention planning.