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About the Nonattainment Areas Map - Criteria Air Pollutants

What does the map tell me?

A Nonattainment Areas Map identifies counties where air pollution levels persistently have exceeded national air quality standards established by the Clean Air Act, and nearby counties whose pollutant emissions contributed to the elevated levels.

EPA uses six "criteria pollutants" as indicators of air quality, and has established for each of them a maximum concentration above which adverse effects on human health may occur. These threshold concentrations are called National Ambient Air Quality Standards (NAAQS). When an area does not meet the air quality standard for one of the criteria pollutants, or when an area contributes to bad air quality in a neighboring area, it may be subject to the formal rule-making process which designates it as nonattainment. In addition, the rule specifies what air pollution reduction measures an area must adopt, and when the area must reach attainment. The Green Book Web site has detailed information about nonattainment areas.

Each county in a Nonattainment Areas Map is shaded to indicate its nonattainment status with respect to the pollutant you selected. Counties that are meeting air quality standards for that pollutant are not shaded (or, they are shaded with the background color of the map). Counties that contain a nonattainment area, and whole counties that are nonattainment areas, are shaded.

A bar chart beside the map shows the total population of the geographic area in the map, as of year 2000. Segments of the bar, which are shaded like the map, indicate the aggregate population of area types in the map: part-county and whole-county nonattainment areas, and counties (and parts of counties) that are attaining the air quality standard. The relative sizes of the bar segments illustrate the fraction of the population living in nonattainment areas. You may use the View Data function to see the population of individual counties - the county total and the population within nonattainment areas.

To generate a Nonattainment Areas map, choose a pollutant. You may optionally include geographic features in a map.

If you generate a map using the default settings, placing your mouse pointer on a nonattainment county displays the county's name. Placing your mouse pointer on a segment of the bar chart displays the aggregate population of the corresponding areas in the map.

What does the map look like?

The sample map shows California counties designated nonattainment with regard to the national air quality standard for ozone (8-hour average concentration). Map shading identifies counties that are partly or wholly nonattainment. A bar chart beside the map shows the aggregate population of whole- and part-county nonattainment areas. The balance of the state population, indicated by the unshaded (white) bar segment, live in areas that attained the air quality standard. The sample map also includes optional geographic features: Class I areas (green outlines) and major cities.

How can I customize the map?

Geographic Area
The name of the geographic area previously selected is displayed here. You can click on "change" to choose a different area.

Nonattainment Pollutant   (required)
Counties containing nonattainment areas for the pollutant you choose are included in the map. You may choose any one of the criteria air pollutants. The default pollutant is carbon monoxide. At present, there are no nitrogen dioxide nonattainment areas.
  • CO - Carbon monoxide
  • NO2 - Nitrogen dioxide
  • O3 - Ozone (1-hour)
  • O3 - Ozone (8-hour)
  • SO2 - Sulfur dioxide
  • PM2.5 - Particulate matter (diameter <2.5 micrometers)
  • PM10 - Particulate matter (diameter <10 micrometers)
  • Pb - Lead

Empty Map   (optional)
Select this option to generate a map even if the geographic coverage contains no nonattainment areas for the selected pollutant. Without this option selected, a map is produced only when the geographic coverage has at least one nonattainment area.

Geographic Features   (optional)
Enhances a map with features such as city locations, highways, and national park outlines. Without this option selected, the map includes standard features: state outlines and nonattainment counties.

 

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