About the Emissions by Category Report - Criteria Air Pollutants

What does the report tell me?

The Emissions by Category report lists aggregate annual emissions of criteria air pollutants from sources in "tier-1" and "tier-2" categories defined by EPA. (These terms are defined later.) This report includes emissions from all types of sources:

point - factories, power plants, refineries, and other large facilities
nonpoint (formerly area) - small businesses, offices and residences, wildfires, dirt roads
mobile - roadway vehicles, construction equipment, trains, airplanes, ships

While point sources are identified individually, nonpoint sources are not. Rather, their emissions are estimated in aggregate based on fuel use and similar measures. Emissions from mobile sources are estimated from miles traveled. EPA computes aggregate emissions from nonpoint and mobile sources for each county, and (for this report) sums each county's point source emissions. The report gives two emissions values: point sources and the sum of nonpoint and mobile sources.

To get a better picture of what industries and activities are responsible for emissions, EPA defined 14 major types of sources (tier-1 categories) and 84 subtypes (tier-2 categories). The most detailed form of the Emissions by Category report lists aggregate nonpoint+mobile and point emissions for each tier-2 category for each county. You can create less detailed reports by omitting report columns, as described below in the How can I customize section. For example, you can produce reports that give total emissions by geographic area, with no breakdown by source categories.

The Emissions by Category report provides data for more years than other AirData emissions reports. EPA uses factors such as annual economic activity to estimate county aggregate emissions for years between emission inventories, which are compiled every three years. The Emissions by Category report gives you the capability to obtain year-to-year changes in aggregate emissions, compared with every-three-years data in the other AirData emissions reports.

Due to changes in EPA emission inventory procedures, 1999 emissions may not be directly comparable with prior years, especially with regard to particulate matter emissions.

What does the report look like?

The example report shows emissions of coarse particulate matter (PM10, particles up to 10 micrometers in diameter) and sulfur dioxide (SO2) in years 1998 and 1999. The report has the default level of summarization, which aggregates emissions by tier-1 category within each county. The grand total line gives total emissions for all categories and counties in the report. The red down-arrow button in the PM10 point source emissions column indicates that values in that column determine the order of report rows, and they are in descending order.

How can I customize the report?

Sort Order

You can use the SORT buttons in each report column to change the order of rows in the report. The default sort order is ascending tier-1 category, ascending county, or ascending state, depending on which columns are included in the report.

Detail or Summary

This is always a summary report; it always lists the aggregate emissions of similar sources. Omitting optional report columns can change the level of summarization in the report by grouping sources in different ways. The default report groups sources by tier-1 category within county; the report includes a row for each year and tier-1 category present in each county included in the report. The table below describes the types of summarization you may achieve by selecting various combinations of optional report columns. Note that if you select (include) the tier-2 report column, the tier-1 report column also is included.

Report Columns Selected (Included)	Emissions Summarized By...
Tier-1, Tier-2, County*, State	Tier-2 category by year within county (most detailed)
Tier-1, County*, State	Tier-1 category by year within county (default)
Tier-1, Tier-2, State	Tier-2 category by year within state
Tier-1, State	Tier-1 category by year within state
Tier-1	Tier-1 category totals by year for the entire geographic scope of the report (no breakdown by geography)
Tier-1, Tier-2	Tier-2 category totals by year for the entire geographic scope of the report (no breakdown by geography)
County*, State	County totals by year (no breakdown by category)
State	State totals by year (no breakdown by category)
(None)	Not allowed
* Including either County or County Code report column (or both) has the same effect on data summarization.

Pollutant - Single or Multiple

If you select a single pollutant, the report includes aggregate emissions of that one pollutant, and displays one pair of report columns for nonpoint- and point-source emissions. If you select multiple pollutants, the report includes aggregate emissions of each of them, and displays multiple pairs of columns for each pollutant's nonpoint- and point-source emissions.

Year - Single or Multiple

The report includes a row for every combination of geographic area, category, and year in which there were emissions. If you select a single year, the number of rows is the number of geographic areas and categories having emissions in that year. If you select multiple years, there are (normally) multiple rows for each geographic area and category.

What do the report columns mean?

Row #: Sequence number of report rows (lines). Sequence numbers are not associated with particular rows; they simply enumerate the rows of a report from first to last. Thus, choosing an alternate sort order for a report would change the sequence numbers associated with particular rows.
State: Postal abbreviation for the state or territory in which a source is located. [ Details ]
County: Name of the county (or equivalent jurisdiction) in which a source is located.
County Code: Code for the county (or equivalent jurisdiction) in which a source is located, consisting of 2-digit FIPS state code and 3-digit FIPS county code. FIPS is the acronym for Federal Information Processing Standards, which defines codes used in most U.S. government information systems.
Tier 1: Name a major category of air pollution emission sources. There are 14 tier-1 categories, which group sources by type of industry or pollution-producing activity.
Tier 2: Name of a sub-category of air pollution emission sources. There are 84 tier-2 categories.
Year: The calendar year in which pollutant emissions occurred. This column is displayed only when you select multiple years for the report. If you select a single year, it is shown in the report title.
Point Source Emissions: The sum of all point source emissions, in short tons, in the geographic area and source category represented by a row of the report. (A short ton is 2000 pounds.)
Nonpoint+Mobile Source Emissions: The sum of all nonpoint and mobile source emissions, in short tons, in the geographic area and source category represented by a row of the report. (A short ton is 2000 pounds.)