5-2 Index of Key Air Pollutant Emissions from U.S. Transportation: 1990-2008

5-2 Index of Key Air Pollutant Emissions from U.S. Transportation: 1990-2008

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Index: 1990 = 1.0

Year Carbon monoxide Nitrogen oxide Volatile organic compounds PM-10 PM-2.5 Surfur dioxide Ammonia
1990 1.00 1.00 1.00 1.00 1.00 1.00 1.00
1991 0.95 0.99 0.94 0.96 0.95 0.93 1.09
1992 0.90 0.97 0.89 0.91 0.90 0.87 1.17
1993 0.86 0.96 0.83 0.87 0.85 0.80 1.26
1994 0.81 0.94 0.78 0.83 0.81 0.73 1.35
1995 0.76 0.93 0.72 0.79 0.76 0.67 1.43
1996 0.71 0.91 0.66 0.74 0.71 0.60 1.52
1997 0.69 0.92 0.64 0.71 0.67 0.60 1.71
1998 0.66 0.90 0.62 0.66 0.62 0.60 1.65
1999 0.62 0.87 0.61 0.62 0.57 0.60 1.72
2000 0.62 0.88 0.57 0.59 0.54 0.52 1.77
2001 0.58 0.81 0.53 0.55 0.49 0.49 1.79
2002 0.55 0.82 0.52 0.52 0.46 0.49 1.90
2003 0.51 0.77 0.50 0.52 0.45 0.42 1.92
2004 0.48 0.72 0.47 0.51 0.43 0.36 1.95
2005 0.44 0.68 0.44 0.50 0.42 0.29 1.98
2006 0.41 0.63 0.41 0.48 0.40 0.24 1.97
2007 0.38 0.59 0.39 0.46 0.37 0.18 1.98
2008 0.35 0.54 0.36 0.44 0.34 0.13 U

Key: PM-10 = airborne particulates of less than 10 microns; PM-2.5 = airborne particulates of less than 2.5 microns; U = unavailable.

Notes: The indexes are calculated using data on emissions from highway vehicles only. Particulate matters include PM without condensibles. The 2003 data are revised except carbon monoxide, nitrogen oxide, surfur dioxide, and ammonia. The 2004 data are revised except nitrogen oxide, sufur dioxide, and ammonia. The 2005 data are revised except carbon monoxide, surfur dioxide, and ammonia. The 2006 data are revised except carbon monoxide, volatile organic compounds, and ammonia. The 2007 data are revised except carbon monoxide, surfur dioxide, and ammonia.

Source: U.S. Environmental Protection Agency, Clearinghouse for Inventories and Emissions Factors (CHIEF), Current Emission Trends Summaries, available at http://www.epa.gov/ttn/chief/trends/index.html as of November 2010.