TABLE 15-1a  Change in Air Pollutant Emissions by Type: 1992–2002,,,,,,,,,,,
"1992 = 100
",,,,,,,,,,,
All modes,1992,1993,1994,1995,1996,1997,1998,1999,2000,2001,2002
Carbon monoxide,100,95,90,85,80,77,75,71,70,65,62
Nitrogen oxides,100,99,98,97,96,96,95,91,92,87,82
Volatile organic compounds,100,95,90,84,79,77,76,74,70,66,62
PM-10,100,97,94,91,88,85,82,78,75,71,69
PM-2.5 ,100,97,94,90,86,83,79,75,71,67,65
Lead,100,94,93,97,90,90,89,92,97,N,N
Ammonia,100,107,114,122,127,141,137,143,147,149,154
"
KEY:  N = data are nonexistent; PM-10 = particulate matter of 10 microns in diameter or smaller; PM-2.5 = particulate matter of 2.5 microns in diameter or smaller. ",,,,,,,,,,,
"NOTE: To make it easier to compare data of differing magnitudes over time, the Bureau of Transportation Statistics divided the data for all years in each category (see table 15-1b) by the initial year value and multiplied the result by 100. ",,,,,,,,,,,
"
SOURCE: U.S. Department of Transportation, Research and Innovative Technoloy Administration, Bureau of Transportation Statistics, calculations using data in table 15-1b.   ",,,,,,,,,,,