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About the County Emissions Map - Criteria Air Pollutants
What does the map tell me?
ACounty Emissions Map indicates the amount or the density of criteria air pollutant emissions of every county in the selected geographic area. Emission amounts come from EPA's National Emission Inventory (NEI) database. Emission density is calculated as emission amount per square mile of land within each county.
A County Emissions Map groups counties in seven ranges of pollutant emissions amount or density, and shades each county to indicate its range. The first range is zero; counties in this range have no emissions of the selected pollutant. The other six ranges are based on nationwide percentiles, listed in the table below, of emissions amount or density. Nationwide percentiles are calculated separately for each combination of the selection criteria described below in How Can I Customize the Map, excluding counties with zero emissions.
| Shading Color of Range | Minimum Value in Range | Maximum Value in Range |
|---|---|---|
| White | Zero (or no value provided) | |
| Cyan | Smallest nonzero value | 10-th percentile |
| Green | Above 10-th percentile | 25-th percentile |
| Gold | Above 25-th percentile | 50-th percentile |
| Rose | Above 50-th percentile | 75-th percentile |
| Red | Above 75-th percentile | 90-th percentile |
| Brown | Above 90-th percentile | Highest value |
To generate a County Emissions map, choose a pollutant, year, and emissions value (amount or density). You also may choose a source type or source category, thereby selecting a subset of emission sources in each county.
What does the map look like?
This image is a typical County Emissions map: carbon monoxide emissions for a state. Map shading colors indicate how each county's CO emissions rank compared with all U.S. counties.
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.
- Pollutant Emitted (required)
- Emissions of the pollutant you select are displayed in the map.
Choose one of the criteria air pollutants or precursors, or their
total:
- CO - Carbon monoxide
- NOx - Nitrogen oxides
- VOC - Volatile organic compounds
- SO2 - Sulfur dioxide
- PM2.5 - Particulate matter (size < 2.5 micrometers)
- PM10 - Particulate matter (size < 10 micrometers)
- NH3 - Ammonia
- Total - Sum of the six criteria air pollutants (PM2.5 is a fraction of PM10)
- Year of Data (required)
- The calendar year of pollutant emissions displayed in the map. Choose
one of the available years. EPA compiles a national emissions inventory
at 3-year intervals (1996, 1999, ...) and updates the National Emission
Inventory database two to three years after the inventory year. EPA
estimates aggregate county pollutant emissions for years between inventories,
using factors such as economic activity and vehicle miles traveled.
- Map Shading Value (required)
- The type of emissions value represented by map shading colors:
- Amount - quantity of pollutant emissions in a county, in tons per year
- Density - pollutant emissions per unit of county land area, in tons per square mile per year
- Source Type (optional)
- Selects emissions from sources classified as either point or nonpoint. Point sources are stationary sources whose emissions are reported
individually. Generally, point sources are industrial or commercial
enterprises, such as power plants and factories. Nonpoint sources are:
- Mobile sources - onroad and nonroad vehicles, aircraft, railway locomotives, and marine vessels;
- Small stationary sources, such as homes and offices, whose emissions are not individually reported but are estimated from aggregate fuel consumption or similar information;
- Diffuse pollution sources, such as wildfires and agricultural tilling.
- Source Category (optional)
- Selects emissions from sources associated with a particular type of activity or industry. The available choices are "Tier-1" categories defined for the National Emission Trends Report.