KEY: CO = carbon monoxide; NOx = nitrogen oxides; VOC = volatile organic compounds; PM-10 = particulate matter of 10 microns in diameter or smaller.
NOTES: Percentages may not add to 100 because of independent rounding. EPA no longer estimates lead emissions. Modal shares in 2000 were: highway gasoline vehicles, 4.1%; aircraft, 95.9%. Highway gasoline includes light-duty gas vehicles and motorcycles, light-duty gas trucks, and heavy-duty gas vehicles. Highway diesel includes heavy-duty diesel vehicles, and light-duty diesel trucks and vehicles. Marine vessels include coal, diesel, residual oil, gasoline, and other. Other includes diesel and gasoline recreational vehicles, airport service, railway maintenance, and recreational marine service. This table does not include farm, construction, industrial, logging, light commercial, and lawn and garden equipment.
SOURCE: U.S. Department of Transportation, Research and Innovative Technology Administration, Bureau of Transportation Statististics calculations using data from U.S. Environmental Protection Agency (EPA), Office of Air Quality Planning and Standards, National Emissions Inventory, 2002 Air Pollutant Emission Trends, available at http://www.epa.gov/ttn/, as of March 2005.