Figure 1 - National Transportation Emissions Trends Index: 1970-1999

Figure 1 - National Transportation Emissions Trends Index: 1970-1999

(Index: 1970 = 1.0; 1990 = 1.0 for PM-2.5 and ammonia)

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Figure 1 - National Transportation Emissions Trends Index: 1970–1999. If you are a user with disability and cannot view this image, use the table version. If you need further assistance, call 800-853-1351.

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.