Figure 15 Index of Key Air Pollutant Emissions from U.S. Transportation: 1975-2000

Figure 15 Index of Key Air Pollutant Emissions from U.S. Transportation: 1975-2000

(Index: 1975= 1.0, 1990 = 1.0 for PM-2.5 and ammonia)

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Year CO NOx VOC PM-10 PM-2.5 Ammonia Lead
1975 1.00 1.00 1.00 1.00     1.00
1976 1.00 1.03 0.96 1.00     1.08
1977 1.01 1.05 0.97 1.00     1.01
1978 1.02 1.08 0.93 0.99     0.84
1979 0.96 1.05 0.87 0.95     0.74
1980 0.94 1.04 0.87 0.92     0.48
1981 0.92 1.01 0.85 0.83     0.34
1982 0.92 0.99 0.86 0.81     0.32
1983 0.95 0.99 0.88 0.80     0.25
1984 0.95 0.99 0.88 0.84     0.23
1985 0.94 1.02 0.91 0.89     0.14
1986 0.88 0.94 0.83 0.83     0.08
1987 0.86 0.93 0.80 0.89     0.03
1988 0.87 0.99 0.82 0.93     0.02
1989 0.82 1.01 0.72 0.94     0.01
1990 0.73 0.99 0.66 0.93 1.00 1.00 0.01
1991 0.78 1.03 0.68 0.94 1.01 1.05 0.00
1992 0.76 1.05 0.64 0.94 1.00 1.10 0.00
1993 0.77 1.07 0.65 0.89 0.94 1.16 0.00
1994 0.78 1.09 0.67 0.88 0.92 1.23 0.00
1995 0.69 1.08 0.60 0.79 0.82 1.33 0.00
1996 0.73 1.20 0.62 0.87 0.96 1.23 0.00
1997 0.72 1.22 0.61 0.85 0.93 1.37 0.00
1998 0.71 1.21 0.61 0.82 0.89 1.35 0.00
1999 0.68 1.19 0.60 0.79 0.85 1.36 0.00
2000 0.66 1.14 0.57 0.75 0.80 1.38 0.00

Key: PM-10 and PM-2.5 = airborne particulates of less than 10 microns or 2.5 microns in diameter, respectively.

Note: Transportation emissions include all onroad mobile sources and the following nonroad mobile sources: recreational vehicles and boats, airport service equipment, aircraft, commercial marine vessels, and railroads. Other nonroad sources, e.g., farming equipment, are not included. Lead estimates include onroad mobile sources only.

Source: U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, National Air Pollutant Trends, available at http://www.epa.gov/ttn/chief/trends/index.html, as of September 2002.