Table 4-44 ,,,,,,,,,
Estimated National Emissions of Particulate Matter (PM-2.5)a (Million short tons),,,,,,,,,
,,,,,,,,,
,1990,1991,1992,1993,1994,1995,1996,1997,1998
Transportation,,,,,,,,,
On-road vehicles,0.28,0.29,0.28,0.26,0.26,0.23,0.22,0.21,0.20
Aircraft,0.03,0.03,0.03,0.03,0.03,0.03,0.03,0.03,0.03
Railroads,0.05,0.05,0.05,0.05,0.05,0.03,0.02,0.03,0.03
Marine vessels,R0.03,R0.03,R0.03,R0.03,R0.03,R0.03,R0.04,R0.04,0.04
Other off-roadb,R0.03,R0.03,R0.03,0.04,0.04,0.04,0.04,0.04,0.04
Transportation-related fugitive dust,,,,,,,,,
  Unpaved roads,1.69,1.68,1.64,1.72,1.71,1.56,1.82,R1.89,1.91
  Paved roads,0.56,0.60,0.61,0.62,0.63,0.59,0.60,R0.64,0.66
    Total transportation,2.67,2.71,2.67,R2.75,R2.75,R2.51,R2.77,R2.88,2.91
,,,,,,,,,
Nontransportation,,,,,,,,,
Fuel combustion,0.91,0.89,0.93,0.85,0.84,0.90,R0.86,R0.79,0.79,,,,,,,
Industrial processesc,0.56,0.57,0.58,0.50,0.50,0.50,R0.38,R0.39,0.39,,,,,,,
Waste disposal and recycling,0.23,0.24,0.24,0.29,0.27,0.25,R0.23,R0.24,0.24,,,,,,,
Miscellaneousd,3.59,3.32,R3.22,R2.95,R3.62,R3.04,R3.96,R4.21,4.06,,,,,,,
    Total nontransportation,5.29,5.02,R4.97,R4.59,R5.23,R4.69,R5.43,R5.63,5.49,,,,,,,
TOTAL,7.96,7.74,R7.65,R7.33,R7.98,R7.18,R8.19,R8.48,8.38,,,,,,,
a Particulate matter less than 2.5 microns in size.,,,,,,,,,,,,,,,,
"b  Other off-road comprises nonroad gasoline- and diesel-powered recreational, airport service and railway maintenance vehicles and ",,,,,,,,,,,,,,,,
recreational marine vessels.,,,,,,,,,,,,,,,,
"c  Industrial processes comprise chemical and allied product manufacturing, metals processing, petroleum and related industries, and other",,,,,,,,,,,,,,,,
 industrial processes; solvent utilization; and storage and transportation.,,,,,,,,,,,,,,,,
"d  Miscellaneous comprises nonroad gasoline- and diesel-powered construction, industrial, lawn and garden, farm, light-commercial, ",,,,,,,,,,,,,,,,
"logging vehicles and other non-road sources; geogenic sources, agriculture and forestry, cooling towers, nontransportation-related fugitive",,,,,,,,,,,,,,,,
"dust, wildfires, managed burning, and other fugitive dust and combustion (that could not accurately be allocated to specific source categories).",,,,,,,,,,,,,,,,
,,,,,,,,,,,,,,,,
KEY: R = revised,,,,,,,,,,,,,,,,
,,,,,,,,
"NOTES:  The emissions estimates shown here are those that are directly emitted, which represent only a portion of the total PM-2.5 emissions",,,,,,,,
" found in the air.  Secondary formation of fine particulates resulting from emissions of nitrogen oxide, sulfur dioxide, volatile organic ",,,,,,,,
"compounds, and other substances is also a significant source of PM-2.5.",,,,,,,,
,,,,,,,,
Numbers may not add to totals due to rounding.,,,,,,,,
,,,,,,,,
The methodologies used to estimate emissions constantly evolve and undergo major changes.  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 methodology changes have occurred.",,,,,,,,
,,,,,,,,
"SOURCES:  U.S. Environmental Protection Agency, National Air Pollutant Emission Trends: 1900-1998 (EPA-454/R-00-002)",,,,,,,,
"(Research Triangle Park, NC: March 2000), table A-6; also available at Internet site www.epa.gov/ttn/chief/trends98/emtrnd.html, as of ",,,,,,,,
"Aug. 8, 2000.",,,,,,,,