BTS | Table 4-41: Estimated National Emissions of Nitrogen Oxides

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Table 4-41: Estimated National Emissions of Nitrogen Oxides

(Million short tons)

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	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-road^a	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 processes^b	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
Miscellaneous^c	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.