Total National Emissions
of Nitrogen Oxides, 1970-2006*
(million short tons)
The transportation sector accounted for over half of the nation’s nitrogen oxide (NOx) emissions in
2006, with the majority coming from highway vehicles. For details on the highway emissions of NOx,
see Table 12.5 [Transportation Energy Data Book]
| Source category | 1970 |
1980 |
1990 |
1995 |
2000 |
2006 |
Percent |
|---|---|---|---|---|---|---|---|
Highway vehicles |
12.62 |
11.49 |
9.59 |
8.88 |
8.39 |
6.60 |
36.2% |
Other off-highway |
2.65 |
3.35 |
3.78 |
4.11 |
4.17 |
4.02 |
22.1% |
Transportation total |
15.28 |
14.84 |
13.37 |
12.99 |
12.56 |
10.62 |
58.3% |
Stationary fuel combustion total |
10.06 |
11.32 |
10.89 |
10.83 |
8.82 |
6.43 |
35.3% |
Industrial processes total |
0.78 |
0.56 |
0.80 |
0.77 |
0.81 |
0.89 |
4.9% |
Waste disposal and recycling total |
0.44 |
0.11 |
0.09 |
0.10 |
0.13 |
0.11 |
0.6% |
Miscellaneous total |
0.33 |
0.25 |
0.37 |
0.27 |
0.28 |
0.18 |
1.0% |
Total of all sources |
26.89 |
27.08 |
25.52 |
24.96 |
22.60 |
18.23 |
100.0% |
Source: U.S. Environmental Protection Agency, National Emission Inventory Air Pollutant Emission Trends website: www.epa.gov/ttn/chief/trends
(Additional resources: www.epa.gov/oar/oaqps)
*The sums of subcategories may not equal total due to rounding
