Table 4-45: Estimated National Emissions of Sulfur Dioxide (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	2000	2001
Total all sources	31.22	28.04	25.93	23.31	22.52	22.26	22.69	22.81	23.08	22.38	22.08	21.77	21.35	18.62	18.39	18.84	18.95	17.65	16.32	15.79
Transportation, total	0.51	0.57	0.63	0.69	0.71	0.72	0.72	0.73	0.73	0.70	0.66	0.63	0.60	0.56	0.53	0.53	0.53	0.54	0.49	0.49
On-road vehicles	0.27	0.33	0.39	0.45	0.47	0.48	0.49	0.50	0.50	0.47	0.44	0.40	0.37	0.34	0.30	0.30	0.30	0.30	0.26	0.26
Off-road, total	0.24	0.24	0.24	0.24	0.24	0.24	0.24	0.23	0.23	0.23	0.23	0.23	0.23	0.23	0.23	0.23	0.23	0.24	0.23	0.22
Aircraft	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01	<0.01
Railroads	0.07	0.07	0.07	0.06	0.06	0.05	0.05	0.05	0.06	0.06	0.06	0.06	0.06	0.06	0.06	0.06	0.06	0.06	0.06	0.06
Marine vessels	0.16	0.16	0.16	0.17	0.18	0.18	0.18	0.17	0.17	0.17	0.16	0.16	0.16	0.16	0.16	0.16	0.17	0.18	0.16	0.16
Nontransportation, total	30.70	27.47	25.30	22.61	21.81	21.54	21.97	22.08	22.34	21.68	21.42	21.14	20.75	18.06	17.86	18.31	18.41	17.11	15.83	15.30
Fuel combustion	23.46	22.66	21.39	20.02	19.43	19.43	19.76	19.92	20.29	19.80	19.49	19.24	18.89	16.23	16.25	16.65	16.75	15.51	14.20	13.63
Industrial processesa	7.09	4.68	3.77	2.43	2.22	1.94	2.02	1.97	1.86	1.68	1.71	1.65	1.62	1.59	1.37	1.43	1.43	1.32	1.36	1.41
Waste disposal and recycling	<0.01	0.05	0.03	0.03	0.04	0.03	0.04	0.04	0.04	0.04	0.04	0.07	0.06	0.05	0.03	0.03	0.03	0.03	0.03	0.04
Miscellaneousb	0.15	0.08	0.10	0.13	0.13	0.14	0.16	0.15	0.15	0.16	0.17	0.17	0.19	0.19	0.20	0.20	0.20	0.24	0.23	0.23

KEY: R = revised.

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

^b Miscellaneous comprises nontransportation-related fugitive dust, agriculture and forestry, nonroad gasoline, nonroad diesel, other nonroad sources and other miscellaneous combustion 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 and, therefore, some estimates in this table may not match estimates produced in previous reports. The most recent revision of these estimates is based on Version 2 of the 1999 National Emissions Inventory (NEI) and provides a generally consistent time trend of the estimates. However, state-submitted data on mobile sources is only reflected in the estimates for 1999 and the EPA plans to correct this inconsistency in future publications.

Numbers may not add to totals due to rounding.

SOURCE

1970-2001: U.S. Environmental Protection Agency, Clearinghouse for Inventories and Emissions Factors (CHIEF), Current Emission Trends Summaries, available at Internet website http://www.epa.gov/ttn/chief/trends/ as of Aug. 14, 2003.