KEY: CO = carbon monoxide; NOx = nitrogen oxides; VOC = volatile organic compounds;
PM-10 = particulate matter 10 microns in diameter or smaller; PM-2.5 = particulate
matter 2.5 microns in diameter or smaller.
SOURCE: U.S. Environmental Protection Agency, Office of Air Quality Planning
and Standards, “National Emission Inventory (NEI), Air Pollutant Emission Trends,”
available at http://www.epa.gov/ttn/chief/trends/,
as of January 2001.
