Figure 5-8 Index of Key Air Pollutant Emissions from U.S. Transportation: 1990–2012

Excel

Index: 1990 = 1.0

Year Carbon monoxide Nitrogen oxide Volatile organic compounds PM-10 PM-2.5 Sulfur 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 1.91
2004 0.48 0.72 0.47 0.51 0.43 0.36 1.92
2005 0.44 0.67 0.43 0.50 0.42 0.29 1.91
2006 0.40 0.70 0.40 0.65 0.58 0.27 1.57
2007 0.36 0.72 0.36 0.81 0.75 0.25 1.23
2008 0.32 0.74 0.32 0.96 0.91 0.23 0.89
2009 0.31 0.70 0.31 0.93 0.86 0.19 0.84
2010 0.29 0.62 0.28 0.87 0.76 0.13 0.75
2011 0.26 0.52 0.25 0.80 0.64 0.07 0.63
2012 0.22 0.41 0.21 0.74 0.53 0.03 0.51

KEY: PM-10 = airborne particulates of less than 10 microns; PM-2.5 = airborne particulates of less than 2.5 microns.

NOTES: Not all graph scales are comparable. The indices are calculated using data on emissions from highway vehicles only. Particulate matters include PM without condensibles. Ammonia data for 2003 through 2005 are revised. Data for 2006 through 2008 are revised.

SOURCE: U.S. Environmental Protection Agency, Clearinghouse for Inventories and Emissions Factors, 1970 - 2012 Average annual emissions (all criteria pollutants), available at http://www.epa.gov/ttn/chief/trends/index.html as of January 2013.