Figure 17
Index of Key Air Pollutant Emissions from U.S. Transportation: 1980–2001

Index: 1980 = 1.0, 1990 = 1.0 for PM-2.5 and ammonia

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Key: PM-10 and PM-2.5 = airborne particulates of less than 10 microns or 2.5 microns, respectively.

Notes: Transportation emissions include all onroad mobile sources and the following nonroad mobile sources: recreational vehicles and boats, airport service equipment, aircraft, marine vessels, and railroads. Lead includes onroad mobile sources only. EPA discontinued lead emissions estimates in 2001. Trend lines shown differ from previous editions due to a new EPA estimating methodology.

Source: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Average Annual Emissions, All Criteria Pollutants 1970–2001, available at http://www.epa.gov/ttn/chief/trends/, as of August 2003.