Table 4-41: Estimated National Emissions of Nitrogen Oxides

Table 4-41: Estimated National Emissions of Nitrogen Oxides

(Million short tons)

Excel | CSV

  1970 1975 1980 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999
TOTAL all sources 20.93 22.63 24.38 23.20 22.81 23.07 24.12 23.89 R24.17 R24.34 R24.73 R25.11 R25.47 R25.05 R26.05 R26.35 R26.02 25.39
Transportation                                    
On-road vehicles 7.39 8.65 8.62 8.09 7.77 7.65 7.66 7.68 R7.21 R7.56 R7.76 R7.96 R8.18 R7.96 R8.79 R8.92 R8.82 8.59
Off-road                                    
Aircraft 0.07 0.09 0.11 0.12 0.12 0.13 0.13 0.14 0.16 0.16 0.16 0.16 0.16 0.17 0.17 0.17 0.17 0.18
Railroads 0.50 0.59 0.73 0.81 0.83 0.85 0.90 0.92 0.93 0.93 0.95 0.95 0.95 0.99 R1.18 R1.22 R1.22 1.20
Marine vessels 0.17 0.21 0.47 0.56 0.60 0.63 0.70 0.75 0.94 1.00 0.96 0.92 0.93 0.94 R0.97 R0.99 R1.00 1.01
Other off-roada 0.04 0.04 0.04 0.06 0.06 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.09 0.09 0.09 0.10
Total transportation 8.17 9.58 9.97 9.64 9.38 9.33 9.46 9.56 R9.32 R9.71 R9.90 R10.06 R10.30 R10.13 R11.20 R11.39 R11.30 11.07
Nontransportation                                    
Fuel combustion 10.06 10.49 11.32 10.05 9.87 10.01 10.47 10.54 10.89 R10.78 10.93 11.11 11.02 10.83 R10.52 R10.58 R10.40 10.03
Industrial processesb 0.78 0.54 0.56 0.80 0.79 0.76 0.78 0.77 0.80 0.72 0.76 0.74 0.77 0.77 R0.80 R0.84 R0.85 0.85
Waste disposal and recycling 0.44 0.16 0.11 0.09 0.09 0.09 0.09 0.08 0.09 0.10 0.10 0.12 0.11 0.10 0.10 0.10 0.10 0.09
Miscellaneousc 1.49 1.88 2.43 2.62 2.68 2.88 3.33 2.94 3.07 3.03 3.05 3.08 3.29 3.22 R3.42 R3.45 R3.38 3.35
Total nontransportation 12.77 13.07 14.42 13.56 13.43 13.74 14.67 14.33 14.85 R14.63 14.84 15.05 15.19 14.92 R14.85 R14.96 R14.72 14.32

KEY: R = Revised.

a Other off-road comprises nonroad gasoline- and diesel-powered recreational, airport service and railway maintenance vehicles, and recreational marine vessels.

b Industrial processes comprises chemical and allied product manufacturing, metals processing, petroleum and related industries, and other industrial processes; and solvent utilization, storage, and transport.

c Miscellaneous comprises nonroad gasoline- and diesel-powered construction, industrial, lawn and garden, farm, light-commercial, logging vehicles, and other nonroad sources; health services, cooling towers, fugitive dust; and other combustion sources that could not be accurately allocated to specific source categories.

NOTES: The methodologies used to estimate emissions constantly evolve and undergo major changes. These improved methods are often used to revise estimates for previous years. Therefore, some estimates in this table may not match estimates produced in previous reports, and some trends may not be consistent across years in which major changes in methodology have occurred.

Numbers may not add to totals due to rounding.

SOURCES: 1970-1985,1989-1999: U.S. Environmental Protection Agency, National Air Quality and Emissions Trends Report: 1999 (EPA-454/R-01-004) (Research Triangle Park, NC: March 2001), table A-4; available at Internet website http://www.epa.gov/oar/aqtrnd99/toc.html as of Sept. 5, 2001.

1988:Ibid, National Air Pollutant Emission Trends: 1900-1998 (EPA-454/R-00-002) (Research Triangle Park, NC: March 2000), table A-2; available at Internet website http://www.epa.gov/ttn/chief/trends/trends98/browse.html as of Sept. 5, 2001.

1986-87: Ibid, National Emission Trends source reports database; available at Internet website www.epa.gov/air/data/nettier.html as of Sept. 5, 2001.