United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
March 1981
Air
National
Air Pollutant
Emission Estimates,
1970—1979

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                                    EPA-450/4-81-010
         National  Air Pollutant
Emission Estimates,  1970 — 1979
              Monitoring and Data Analysis Division
            U.S. ENVIRONMENTAL PROTECTION AGENCY
               Office of Air. Noise, and Radiation
            Office of Air Quality Planning and Standards
            Research Triangle Park, North Carolina 27711

                     March 1981

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This report is published by the U.S. Environmental Protection Agency to
report information of general interest in the field of air pollution . Copies
are available free of charge to Federal employees, current contractors and
grantees, and nonprofit organizations - as supplies permit - from the Library
Services Office  (MD-35), U.S. Environmental Protection Agency. Research
Triangle Park,  North Carolina 27711;  or,  for a fee, from the National Technical
Information Service,  5285 Port Royal Road, Springfield,  Virginia 22161.

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                             ABSTRACT
  This report presents estimates of trends  in  nationwide air
pollutant emissions for the five major pollutants: particulates,
sulfur oxides, nitrogen oxides, volatile organic compounds, and
carbon monoxide.  Estimates are presented for  each year from 1970
through 1979.  Emission estimates are broken down according to
major classifications of air pollution sources.  A short analysis
of trends is given, along with a discussion of methods used to
develop the data.

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                             CONTENTS


Section                                                      Page

  LIST OF TABLES	.  . .  •	vii

  LIST OF FIGURES	viii


1.SUMMARY 	   1

2.NATIONWIDE EMISSION TRENDS, 1970-1979	   3

  2.1 Particulates	   3

  2.2 Sulfur Oxides	   3

  2.3 Nitrogen Oxides	   3

  2.4 Volatile Organic Compounds	   3

  2.5 Carbon Monoxide .	   4

3.METHODS	21

  3.1  Transportation	22
       3.1.1 Motor Vehicles	22
       3.1.2 Aircraft	22
       3.1.3 Railroads	23
       3.1.4 Vessels	23
       3.1.5 Nonhighway Use  of Motor Fuels	23

  3.2  Fuel  Combustion in Stationary Sources	23
       3.2.1 Coal	23
       3.2.2 Fuel Oil	24
       3.2.3 Natural Gas	24
       3.2.4 Other Fuels	24

  3.3  Industrial Processes  	  24

  3.4  Solid Waste Disposal	  25

  3.5  Miscellaneous Sources	25
       3.5.1 Forest Fires	25
       3.5.2 Agricultural Burning 	  25
       3.5.3 Coal Refuse Burning. ....	26
       3.5.4 Structural  Fires 	  26
       3.5.5 Nonindustrial Organic Solvent Use	  26

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                       CONTENTS (continued)
                                                             Page
4.ANALYSIS OF TRENDS	27
  4.1 Participates	29
  4.2 Sulfur Oxides	30
  4.3 Nitrogen Oxides	31
  4.4 Volatile Organic Compounds	31
  4.5 Carbon Monoxide	31
5.REFERENCES	36
  TECHNICAL REPORT DATA AND ABSTRACT	37

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                               LIST OF TABLES

Table                                                                   Page
  1.  Summary of National  Emission Estimates  	   2
  2.  National  Estimates of Participate Emissions	   5
  3.  National  Estimates of Sulfur Oxide Emissions 	   6
  4.  National  Estimates of Nitrogen Oxide Emissions 	   7
  5.  National  Estimates of Volatile Organic  Compound Emissions	   8
  6.  National  Estimates of Carbon Monoxide Emissions	   9
  7.  Nitrogen Oxide Emissions from Highway Vehicles	  10
  8.  Volatile Organic Compound Emissions from Highway Vehicles	11
  9.  Carbon Monoxide Emissions from Highway  Vehicles	12
  10. Particulate Emissions from Fuel Combustion 	  13
  11. Sulfur Oxide Emissions from Fuel Combustion	14
  12. Nitrogen Oxide Emissions from Fuel Combustion	15
  13. Particulate Emissions from Industrial Processes	16
  14. Sulfur Oxide Emissions from Industrial  Processes 	  17
  15. Nitrogen Oxide Emissions from Industrial  Processes 	  18
  16. Volatile Organic Compound Emissions from Industrial  Processes.  .  . .19
  17. Carbon Monoxide Emissions from Industrial  Processes	20
  18. Theoretical 1979 National Emission Estimates with 1970 Level  of
      Control	28
                                   VII

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                          LIST OF FIGURES

Figure                                                       Page
1.  Highway Vehicle NOx Emissions Estimates 	  33
2.  Highway Vehicle VOC Emissions Estimates 	  34
3.  Highway Vehicle CO Emission Estimates 	  35
                            viii

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             NATIONAL AIR POLLUTANT EMISSION ESTIMATES

                             1970-1979


                            1.  SUMMARY

  Table 1 summarizes estimated national emissions for each year.
As shown in the table, estimated participate emissions (TSP) have
decreased substantially, emissions of  sulfur oxides (SOx), volatile
organic compounds (VOC), and carbon monoxide (CO) have declined
slightly, while nitrogen oxide emissions (NOx) have increased.

  These data entirely replace those published earlier for 1970-1976
in EPA report National Air Pollutant Emissions Estimates 1940-1976
(EPA-450/1-78-003), for 1970-1977 in the National Air Quality
Monitoring, and Emissions Trends Report, 1977 (EPA-450/2-78-052)
and for 1970-1978 in National Air Pollutant Emission Estimates,
1970-1978 (EPA-450/480-002).Because  of modifications in
methodology and use of more refined emission factors, data from
this report should not be compared with data in these earlier
reports.

  Reporting of emissions on a nationwide basis, while useful as  a
general indicator of pollutant levels, has definite limitations.
National totals or averages are not the best guide for estimating
trends for particular localities.  Yet, it is important that some
criteria be established for measurement of national progress in  the
control of air pollutant emissions.  The emission estimates
presented herein represent calculated  estimates based on standard
emission inventory procedures.  Since  these data are estimates only
and do not represent the results of any program for the measurement
of actual emissions, their accuracy is somewhat limited.
Similarly, it would' not necessarily be expected that these emission
estimates would be in agreement with emission estimates derived
through a different emission inventory procedure.  The principal
objective of compiling these data is to identify probable overall
changes in emissions on a national scale.  It should be recognized
that these estimated national trends in emissions may not be
representative of local trends in emissions or air quality.

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                                  TABLE  1

                 SUMMARY  OF  NATIONAL  EMISSION  ESTIMATES
Year

1970
1971
1972
1973
1274
1975
1976
1977
1978
1979

Change 1970-
       1979
 TSP
 21.0
 19.2
 17.0
 15.8
 14.0
 11.6
 10.6
  9.9
  9.7
  9.5
-54.8%
      TERAGRAMS/YEAR

 SOX          NOX
 28.3
 26.9
 27.4
 28.5
 26.7
 25.2
 25.9
 25.4
 24.3
 24.5
-13.4%
 19.1
 19.6
 20.7
 21.2
 20.8
 20.2
 21.8
 22.4
 22.7
 22.6
418.3%
              VOC
 27.7
 27.0
 27.4
 26.8
 25.5
 23.4
 24,
 24,
 25,
 24.6
-11.2%
 CO

112.9
112.6
110.
108.
102.
.7
,1
.4
 98.0
 99.4
 96.4
 94.9
 91.4
-19.0%
Note:  One teragram equals  1012  grams  (106 metric tons) or
approximately 1.1  x 10° short  tons.

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                 2.  NATIONWIDE EMISSION TRENDS,  1970-1979


  Tables 2 through 6 show trends in the emissions  of  each  pollutant
according to major source categories.  More detailed  breakdowns  of the
emissions from highway vehicles are given  in Tables 7  through  9,  for
stationary source fuel combustion  in Tables 10 through 12,  and for
industrial processes in Tables 13  through  17.

  In the industrial process tables the Standard  Industrial  Classification
(SIC) in which the process is included is  shown.   These  designations  are
not intended to represent the complete emissions  for  all SIC categories and
serve only to identify and classify the industrial  processes shown.

  In all tables data are reported  in metric units,  either  as teragrams
(lp!2 grams) or gigagrams (10" grams) per  year.   One  teragram
equals approximately 1.1 x 10^ short tons  and one  gigagram  equals
approximately 1.1 x 10^ short tons.

2.1 Particulates

  Particulates emissions result primarily  from fuel combustion in
stationary sources and from industrial processes.   From  1970 through  1979,
total particulate emissions have decreased by 55  percent.   This  substantial
decrease is due primarily to installation  of control  equipment  on in-
dustrial processes and coal-fired  stationary fuel  combustion sources.   In
addition, particulate emissions have decreased because of  less burning of
solid waste.

2.2 Sulfur Oxides

  Sulfur oxide emissions occur mostly from stationary  source fuel
combustion. In addition, sulfur oxide emissions  from  industrial  processes
are significant.  From 1970 to 1979, emissions of  sulfur oxides  decreased
by 13 percent.  This decrease relates primarily  to  decreased emissions from
primary nonferrous smelters and sulfuric acid manufacturing plants.
Emissions from stationary source fuel combustion  have  decreased  slightly
due to expanded use of fuels with  low sulfur contents  and  installations of
flue gas desulfurization systems by electric utilities.

2.3 Nitrogen Oxides

  Emissions of nitrogen oxides are produced almost  entirely by fuel
combustion by stationary sources and transportation sources, Nitro-
gen oxide emissions increased about 18 percent from 1970 to 1979.  This
increase is due to increased motor vehicle travel  and  increased  fuel  use by
electric utilities.  The nationl recession in 1975  resulted in
significantly less industrial activity and corresponding NOX emissions.

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2.4 Volatile Organic Compounds

  Volatile  organic  compound emissions  decreased  slightly,  by  about  11
percent.  As a  result of the Federal motor vehicle  control  program,
emissions from  highway vehicles  decreased  by 30  percent.   In  addition,
emissions from  miscellaneous organic solvent use decreased, mainly  due  to
the substitution  of water-based  emulsified asphalts for those liquified
with petroleum  distillates.  However,  emissions  from industrial  processes
increased.  This  increase partially offsets the  decreases  in  emissions  for
other source categories, resulting  in  an overall  minor change in total
emissions.

2.5 Carbon Monoxide

  Carbon monoxide emissions occur largely  from transportation sources.   As
a result of the Federal  motor vehicle  control  program, emissions from
highway vehicles  decreased by 16  percent from 1970  to 1979.   Industrial
process emissions decreased mainly  in  the  carbon black (obsolescence of the
channel process) and petrole.um refining industries  (increased use of CO
boilers on catalytic cracking unit  catalyst regenerations).   Emissions  from
the burning of  solid waste and agricultural  materials also declined
substantially.

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                                                            TABLE 2

                                       NATIONAL ESTIMATES OF PARTICIPATE EMISSIONS
     SOURCE CATEGORY
Transportation
  Highway vehicles
  Aircraft
  Railroads
  Vessels
  Other off-highway vehicles
  Transportation Total

Stationary Source Fuel Combustion
  Electric Utilities
  Industrial
  Commercial-Institutional
  Residential
  Fuel Combustion Total

Industrial processes

Solid waste disposal
  Incineration
  Open burning
  Solid Waste Total

Miscellaneous
  Forest fires
  Other Burning
  Misc. Organic Solvent
  Miscellaneous Total
 1970
 0.9
 0.1
 0.1
 1.3
10.2
 0.4
 0.7
 1.1
 TERAGRAMS/YEAR

1971      1972
 9.6
 0.4
 0.5
 0.9
 9.4
 0.3
 0.4
 0.7
         1973
          1974
         1975    1976    1977   1978   1979
1.0
0.1
0.1
0.1
0.1
1.4
1.0
0.1
0.1
0.1
0.1
1.4
1.1
0.1
0.1
0.1
0.1
1.5
1.1
0.1
0.1
0.1
0.1
1.5
1.0
0.1
0.1
0.0
0.1
1.3
1.1
0.1
0.1
0.0
0.1
1.4
1.1
0.1
0.1
0.0
0.1
1.4
1.1
0.1
0.1
0.0
0.1
1.4
1.1
0.1
0.1
0.0
0.1
1.4
4.1
2.8
0.2
0.2
7.3
3.6
2.1
0.2
0.2
6.1
2.9
1.4
0.2
0.1
4.6
2.9
1.1
0.2
0.1
4.3
 8.5
 0.3
 0.3
 0.6
                                      2.6
                                      1.0
                                      0.2
                                      0.1
                                      3.9
 7.0
 0.3
 0.3
 0.6
2.4
0.8
0.2
0.1
3.5
1.9
0.7
0.2
0.1
2.9
1.8
0.7
0.2
0.2
2.9
1.7
0.6
0.2
0.2
2.7
1.5
0.6
0.2
0.2
2.5
 5.5
 0.3
 0.3
 0.6
0.7
0.4
0.0
1.1
0.9
0.3
0.0
1.2
0.7
0.2
0.0
0.9
0.7
0.2
0.0
0.9
0.8
0.2
0.0
1.0
0.6
0.1
0.0
0.7
4.9    4.4
0.2
0.2
0.4
                                                       0.9
                                                       0.1
                                                       0.0
                                                       1.0
0.2
0.2
0.4
                                                     0.7
                                                     0.1
                                                     0.0
                                                     0.8
        4.4
0.2
0.2
0.4
                                                    0.7
                                                    0.1
                                                    0.0
                                                    0.8
       4.3
0.2
0.2
0.4
                                                  0.8
                                                  0.1
                                                  0.0
                                                  0.9
Total
21.0
19.0
17.0
15.8
14.0
11.6    10.6
       9.9
        9.7    9.5

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                                                          TABLE 3

                                        NATIONAL ESTIMATES OF SULFUR OXIDE EMISSIONS
     SOURCE CATEGORY

Transportation
  Highway Vehicles
  Aircraft
  Railroads
  Vessels
  Other Off-highway Vehicles
  Transportation Total

Stationary Source Fuel Combustion
  Electric Utilities
  Industrial
  Commercial-Institutional
  Residential
  Fuel Combustion Total

Industrial Processes

Solid Waste Disposal
  Incineration
  Open Burning
  Solid Waste Total

Miscellaneous
  Forest Fires
  Other Burning
  Miscellaneous Organic Solvent
  Miscellaneous Total
              TERAGRAMS/YEAR

1970    1971    1972    1973    1974    1975
 6.4
 0.0
 0.0
 0.0
5.9
0.0
0.0
0.0
                                       1976    1977    1978    1979
0.3
0.0
0.1
0.2
0.1
0.7
0.3
0.0
Q.i
q.i
0.1
.0.6
0.3
0.0
0.1
0.1
0.1
0.6
0.3
0.0
0.1
0.1
0.1
0.6
0.3
0.0
0.1
0.1
0.1
0.6
0.3
0.0
0.1
0.1
0.1
0.6
0.4
0.0
0.1
0.2
0.1
0.8
0.4
0.0
0.1
0.2
0.1
0.8
0.4
0.0
0.1
0.2
0.1
0.8
0.4
0.0
0.1
0.2
0.1
0.8
15.6
3.6
1.3
0.6
21.1
15.4
3.0
1.3
0.6
20.3
15.6
2.9
1.3
0.4
20.2
17.0
2.6
1.3
0.4
21.3
16.5
2.3
1.2
0.4
20.4
16.5
2.2
1.0
0.3
20.0
17.1
2.1
1.2
0.3
20.7
16.9
2.0
1.1
0.3
20.3
16.0
2.0
1.1
0.3
19.4
16.0
2.3
1.0
0.3
19.6
6.5
0.0
0.0
0.0
6.5
0.0
0.0
0.0
5.7
0.0
0.0
0.0
4.6
0.0
0.0
0.0
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.4
0.0
0.1
0.2
0.1
0.8
17.1
2.1
1.2
0.3
20.7
4.4
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.4
0.0
0.1
0.2
0.1
0.8
16.9
2.0
1.1
0.3
20.3
4.3
0.0
0.0
0.0
0.0
0.0
0.0
0.0
4.1
0.0
0.0
0.0
4.1
0.0
0.0
0.0
Total
28.3    26.9
       27.4
       28.5    26.7    25.2    25.9    25.4    24.3
                                               24.5

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                                                          TABLE 4

                                       NATIONAL ESTIMATES OF NITROGEN OXIDE EMISSIONS
     SOURCE CATEGORY

Transportation
  Highway Vehicles
  Aircraft
  Railroads
  Vessels
  Other Off-highway Vehicles
  Transportation Total

Stationary Source Fuel Combustion
  Electric Utilities
  Industrial
  Commercial-Insitutional
  Residential
  Fuel Combustion Total

Industrial Processes
                ^

Solid Waste Disposal
  Incineration
  Open Burning
  Solid Waste Total

Miscellaneous
  Forest Fires  .
  Other Burning >
  Misc. Organic Solvent
  Miscellaneous Total
            TERAGRAMS/YEAR

1970 :   1971    1972    .1973   1974    1975
 0.8
 0.1
 0.3
 0.4
0.8
0.1
0.2
0.3
                                      1976    1977    1978    1979
5.2
o.i -
0.6
0.1
1.2
7.2
5.7
0.1
0.6
0.1
1.2
7.7
6.3
0.1
0.7
0.1
1.2
8.4
6.6
0.1
0.7
0.1
1.2
8.7
6.4
0.1
0.7
0.1
1.3
8.6
6.4
0.1
0.7
0.1
1.3
8.6
6.7
0.1
0.7
0.1
1.4
9.0
6.8
. 0.1
0.7
• 0.1
1.4
9.1
6.9
0.1
0.7
0.2
1.5
9.4
6.7
0.1
0.7
0.2
1.5
9.2
 0.8
 0.1
 0.1
 0.2
6.6
0.1
0.7
0.1
1.2
8.7
6.2
4.4
0.5
0.4
11.5
0.8
0.0
0.1
0.1
0.1
0.0
0.0
0.1
6.4
0.1
0.7
0.1
1.3
8.6
6.1
4.2
0.5
0.3
11.1
0.8
0.0
0.1
0.1
0.2
0.0
0.0
0.2
5.1
4.4
0.5
0.4
10.4
5.3
4.3
0.5
0.4
10.5
5.7
4.4
0.5
0.4
11.0
6.2
4.4
0.5
0.4
11.5
6.1
4.2
0.5
0.3
11.1
6.1
3.9
0.4 ,
0.3
10.7
6.6
4.2
0.5
0.4
11.7
7.1
, 4.2
0.5
0.4
12.2
7.1
4.2
0.5
0.4
12.2
7.5
4.1
0.4
0.3
12.3
                                0.7
                                0.0
                                0.1
                                0.1
0.8
0.0
0.1
0.1
0.8
0.0
0.1
0.1
0.8
0.0
0.1
0.1
0.8
0.0
0.1
0.1
0.2
0.1
0.0
0.3
0.2
0.1
0.0
0.3
0.2
0.1
0.0
0.3
0.1
0.0
0.0
0.1
0.2
0.0
0.0
0.2
0.1
0.0
0.0
0.1
0.2
o.o •
0.0
0.2
0.2
0.0
0.0
0.2
0.2
0.0
0.0
0.2
0.2
0.0
0.0
0.2
Total
19.1
19.6
20.7
               21.2   20.8    20.2    21.8    22.4    22.7
                       22.6

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                                                          TABLE 5

                                 NATIONAL ESTIMATES OF VOLATILE ORGANIC COMPOUND EMISSIONS
     SOURCE CATEGORY

Transportation
  Highway Vehicles
  Aircraft
  Railroads
  Vessels
  Other Off-highway Vehicles
  Transportation Total

Stationary Source Fuel  Combustion
  Electric Utilities
  Industrial
  Commercial-Institutional
  Residential
  Fuel Combustion Total

Industrial Processes

Solid Waste Disposal
  Incineration
  Open Burning
  Solid Waste Total

Miscellaneous
  Forest Fires
  Other Burning
  Misc. Organic Solvent
  Miscellaneous Total
1970
 0.5
 1.3
 1.8
 0.7
 0.3
 2.2
 3.2
      TERAGRAMS/YEAR

1971     1972    1973
 0.5
 1.0
 1.5
 0.9
 0.3
 2.0
 3.2
                1974    1975    1976    1977    1978    1979
10.6
0.3
0.2
0.4
0.6
12.1
10.5
0.3
Q.2
Q.4
Q.6
12.0
10.5
0.3
0.2
0.4
0.6
12.0
10.0
0.2
0.2
0.4
0.6
11.4
9.2
0.2
0.2
0.4
0.6
10.6
8.8
0.2
0.2
0.4
0.6
10.2
8.6
0.2
0.2
0.5
0.6
10.1
8.3
0.2
0.2
0.5
0.6
9.8
8.0
0.2
0.2
0.5
0.6
9.5
7.2
0.2
0.2
0.5
0.7
8.8
0.1
0.1
0.0
0.1
0.3
0.1
0.1
0.0
0.1
0.3
0.1
0.1
0.0
0.1
0.3
0.1
0.1
0.0
0.1
0.3
0.1
0.1
0.0
0.1
0.3
0.1
0.1
0.0
0.0
0.2
0.1
0.1
0.0
0.0
0.2
0.1
0.1
0.0
0.0
0.2
0.1
0.1
0.0
0.0
0.2
0.1
0.1
0.0
0.0
0.2
10.3    10.0    11.0    11.3
 0.4
 0.7
 1.1
0.4
0.6
1.0
                        10.9
0.4
0.5
0.9
                         9.8    10.7
0.4
0.5
0.9
0.4
0.4
0.8
                               11.2
0.4
0.4
0.8
                               12.3
0.4
0.4
0.8
                               12.4
0.4
0.4
0.8
0.7
0.2
2.1
3.0
0.6
0.2
2.0
2.8
0.7
0.2
1.9
2.8
0.5
0.1
1.7
2.3
0.9
0.1
1.6
2.6
0.7
0.1
1.6
2.4
0.7
0.1
1.8
2.6
0.7
0.1
1.6
2.4
Total
27.7
27.0
27.4    26.8
       25.5
       23.4
       24.4    24.4    25.4    24.6

-------
                                                          TABLE 6

                                      NATIONAL ESTIMATES OF CARBON MONOXIDE EMISSIONS
     SOURCE CATEGORY

Transportation
  Highway Vehicles
  Aircraft
  Railroads
  Vessels
  Other Off-highway Vehicles
  Transporation Total

Stationary Source Fuel Combustion
  Electric Utilities
  Industrial
  Commercial-Institutional
  Residential
  Fuel Combustion Total

Industrial Processes

Solid Waste Disposal
  Incineration
  Open Burning
  Solid Waste Total

Miscellaneous
  Forest Fires
  Other Burning
  Misc. Organic Solvent
  Miscellaneous Total
 1970
 79.0
  0.9
  0.3
  1.2
  7.3
 88.7
  0.2
  0.5
  0.1
      TERAGRAMS/YEAR

1971     1972    1973
  9.0
  2.7
  3.7
  6.4
  5.1
  1.9
  0.0
  7.0
1974    1975    1976    1977    1978
                                                71.4
                                                 0.8
                                                 0.3
                                                 1.5
                                                 5.7
                                                79.7
1979
79.4
0.9
0.2
1.3
7.0
88.8
0.2
0.5
0.1
0.9
1.7
8.8
2.3
2.7
5.0
6.7
1.6
0.0
8.3
80.9
0.8
0.3
1.3
6.8
90.1
0.3
0.5
0.1
0.7
1.6
8.4
2.2
2.1
4.3
5.2
1.1
0.0
6.3
79.7
0.8
0.3
1.4
6.6
88.8
0.3
0.5
0.1
0.6
1.5
8.6
2.1
1.7
3.8
4.5
0.9
0.0
5.4
74.6
0.8
0.3
1.4
5.8
82.9
0.3
0.5
0.1
0.6
1.5
8.1
1.9
1.5
3.4
5.6
0.9
0.0
6.5
73.5
0.8
0.2
1.4
5.7
81.6
0.3
0.5
0.1
0.7
1.6
6.9
1.8
1.3
3.1
4.0
0.8
0.0
4.8
73.0
0.8
0.3
1.5
5.8
81.4
0.3
0.5
0.1
0.7
1.6
6.6
1.5
1.2
2.7
6.4
0.7
0.0
7.1
                                                 0.8
                                                 1.7

                                                 6.6
                                                 1.5
                                                 1.1
                                                 2.6
                                                 5.1
                                                 0.7
                                                 0.0
                                                 5.8
70.3
0.9
0.3
1.6
5.5
78.6
0.3
0.5
0.1
0.9
1.8
6.3
1.4
1.1
2.5
5.0
0.7
0.0
5.7
65.9
0.9
0.3
1.5
5.9
74.5
0.3
0.5
0.1
1.0
1.9
6.3
1.4
1.1
2.5
5.5
0.7
0.0
6.2
Total
112.9   112.6   110.7   108.1    102.4    98.0    99.4    96.4    94.9     91.4

-------
                                                          TABLE  7

                                       NITROGEN  OXIDE  EMISSIONS  FROM HIGHWAY  VEHICLES
     SOURCE CATEGORY
Gasoline-powered Vehicles
  Passenger cars
  Light Duty Trucks-1
  Light Duty Trucks-2
  Heavy Duty Trucks
  Motorcycles

Diesel-powered Vehicles
  Passenger Cars
  Heavy Duty Trucks

Total
 1970
    (GIGAGRAMS/YEAR)

1971     1972    1973
1974    1975    1976    1977    1978    1979
3,240
380
160
490
0
3,490
420
180
52Q
P
3,760
500
220
540
0
3,940
510
240
560
0
3,730
490
250
550
0
3,750
460
260
550
0
3,820
510
330
560
0
3,810
510
380
560
0
3,710
490
440
540
0
3,390
460
450
520
10
    000000000       10
  960   1,040   1,250   1,300   1,340   1,410   1,470   1,590    1,740    1,900

5,230   5,650   6,270   6,550   6,360   6,430   6,690   6,850    6,920    6,740
                                                                10

-------
                                                          TABLE  8

                                 VOLATILE ORGANIC COMPOUND EMISSIONS  FROM HIGHWAY  VEHICLES
     SOURCE CATEGORY

Gasoline-powered Vehicles
  Passenger Cars
  Light Duty Trucks-1
  Light Duty Trucks-2
  Heavy Duty Trucks
  Motorcycles

Diesel-powered Vehicles
  Passenger Cars
  Heavy Duty Trucks

Total
          GIGAGRAMS/YEAR

  1970    1971     1972    1973
1974    1975    1976    1977     1978     1979
8,320
920
310
900
90
0
110
8,230
920
300
820
130
0
120
8,030
1,000
330
810
150
0
140
7,650
930
330
770
180
0
150
6,920
880
340
690
200
0
140
6,640
790
360
690
200
0
150
6,260
810
470
700
200
0
160
5,890
770
540
680
200
0
170
5,610
700
630
640
210
0
180
4,930
620
630
640
170
0
200
10,650  10,520  10,460  10,010   9,170   8,830    8,600    8,250    7,970   7,190
                                                                11

-------
                                                          TABLE 9

                                      CARBON MONOXIDE EMISSIONS ROM HIGHWAY VEHICLES


                                                        (GIGAGRAMS/YEAR)

     SOURCE CATEGORY                       1970    1971     1972    1973    1974    1975    1976    1977    1978    1979

Gasoline-powered Vehicles
  Passenger cars                          61,050  61,640  61,740  60,560  56,100  54,950  52,780  50,800  49,620  45,330
  Light Duty Trucks-1                      6,150   6,180   6,950   6,680   6,490   5,920   6,340   6,090   5,750   5,310
  Light Duty Trucks-2                      2,050   1,940   2,160   2,160   2,230   2,460   3,280   3,800   4,480   4,580
  Heavy Duty Trucks                        9,100   8,820   9,130   9,240   8,700   9,050   9,480   9,530   9,270   9,460
  Motorcycles                                290     440     500     570     650     660     660     660     680     570

Diesel-powered Vehicles
  Passenger Cars                               000000000      10
  Heavy Duty Trucks                          330     360     430     450     420     440     470     500     550     610

Total                                     78,970  79,380  80,910  79,660  74,590  73,480  73,010  71,380  70,350  65,870
                                                                12

-------
                                                          TABLE 10

                              PARTICIPATE EMISSIONS FROM FUEL COMBUSTION IN STATIONARY SOURCES
     SOURCE CATEGORY

Coal
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Coal Total

Fuel Oil
  Electric Utilities
  Industrial
  Resi denti al/Commerical
  Fuel Oil Total

Natural Gas
  Electric Utilities
  Industrial
  Resi dent i al/Commerci al
  Natural Gas Total

Wood
  Industrial
  Residential
  Wood Total

Other Fuels
  Industrial
  Residential
  Other Fuels Total

Fuel Combustion Total
           (GIGAGRAMS/YEAR)

1970    1971     1972    1973    1974    1975    1976
1977    1978    1979
3,960
2,360
210
6,530
no
50
100
260
20
40
30
90
310
50
360
40
10
50
3,470
1,640
200
5,310
110
40
100
250
20
40
30
90
290
50
340
40
10
50
2,780
980
160
3,920
110
50
110
270
20
40
30
90
270
40
310
40
10
50
2,750
750
160
3,660
130
50
100
280
20
40
30
90
250
40
290
40
10
50
2,490
580
160
3,230
130
50
90
270
20
40
30
90
250
40
290
40
10
50
2,290
490
130
2,910
110
30
80
220
10
30
30
70
200
60
260
40
10
50
1,740
420
110
2,270
120
50
90
260
10
30
40
80
190
60
250
40
10
50
1,600
350
110
2,060
140
60
90
290
10
30
30
70
190
80
270
30
10
40
1,570
350
110
2,030
140
50
80
270
10
30
30
70
180
100
280
30
10
40
1,400
360
100
1,860
120
50
80
250
20
30
30
80
170
120
290
30
10
40
7,290   6,040   4,640   4,370   3,930   3,510   2,910   2,730   2,690   2,520
                                                                13

-------
                                                          TABLE 11

                             SULFUR OXIDE EMISSIONS FROM FUEL COMBUSTION  IN  STATIONARY  SOURCES


                                                      (GIGARAMS/YEAR)

     SOURCE CATEGORY                       1970    1971    1972    1973    1974     1975    1976     1977     1978     1979

Coal
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Coal Total

Fuel Oil
  Electric Utilities
  Industrial
  Resi denti al/Conmerci al
  Fuel Oil Total

Natural Gas
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Natural Gas Total

Wood
  Industrial
  Residential
  Wood Total

Other Fuel
  Industrial
  Residential
  Other Fuels Total

Fuel Combustion Total
14,150
2,790
510
17,450
1,440
620
1,400
3,460
0
0
0
0
30
0
30
110
20
130
21 ,070

13,910
2,280
480
16,67,0
1,450
590
1,340
3,380
0
0
0
0
30
0
30
90
20
no
20,190

14,260
2,150
340
16,750
1,370
640
1,390
3,400
0
0
0
0
30
0
30
100
10
no
20', 290

15,490
1,870
300
17,660
1,560
660
1,310
3,530
0
0
0
0
20
0
20
90
10
100
21,310
14
15,010
1,560
300
16,870
1,520
650
1,320
3,490
0
0
0
0
30
0
30
100
10
no
20,500

15,120
1,590
220
16,930
1,360
460
1,070
2,890
0
0
0
0
30
0
30
90
10
100
19,950

15,690
1,330
220
17,240
1,430
620
1,230
3,280
0
0
0
0
30
0
30
120
10
130
20,680

15,270
1,140
250
16,660
1,620
750
1,210
3,580
0
0
0
0
30
0
30
120
10
130
20,400

14,330
1,190
250
15,770
1,660
660
1,110
3,430
0
0
0
0
30
0
30
no
10
120
19,350

14,520
1.540
230
16,290
1,440
620
1,020
3,080
0
0
0
0
30
0
30
120
10
130
19,530


-------
                                                          TABLE 12

                            NITROGEN OXIDE EMISSIONS FROM FUEL COMBUSTION IN STATIONARY SOURCES
     SOURCE CATEGORY

Coal
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Coal Total

Fuel Oil
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Fuel Oil Total

Natural Gas
  Electric Utilities
  Industrial
  Resi denti al/Commerci al
  Natural Gas Total

Mood
  Industrial
  Residential
  Wood Total

Other Fuels
  Industrial
  Residential
  Other Fuels Total

Fuel Combustion Total
 1970
     (GIGAGRAMS/YEAR)

1971     1972    1973    1974
1975    1976    1977    1978
1979
3,380
680
40
4,100
650
160
440
1,250
1,070
3,290
310
4,670
180
0
180
60
50
110
3,460
550
40
4,050
780
160
440
1 ,380
1,090
3,380
320
4,790
170
0
170
50
50
100
3,690
530
40
4,260
950
170
450
1,570
1,090
3,440
330
4,860
170
0
170
60
50
110
4,090
470
40
4,600
1,110
190
450
1,750
990
3,510
320
4,820
160
0
160
50
50
100
4,130
440
50
4,620
1,050
180
410
1,640
940
3,360
310
4,610
170
0
170
60
40
100
4,270
470
40
4,780
980
140
380
1,500
860
3,040
320
4,220
190
0
190
60
40
100
4,710
430
40
5,180
1,050
200
430
1,680
840
3,270
330
4,440
200
0
200
70
40
110
5,030
410
40
5,480
1,220
230
420
1,870
870
3,270
310
4,450
190
0
190
70
40
110
5,070
420
50
5,540
1,150
220
410
1,780
870
3,250
320
4,440
200
0
200
60
40
100
5,560
460
50
6,070
980
210
380
1,570
960
3,180
330
4,470
210
0
210
70
30
100
10,310  10,490  10,970  11,430  11,140  10,790  11,610  12,100  12,060  12,420
                                                             15

-------
                                                          TABLE 13

                                      PARTICULATE EMISSIONS FROM INDUSTRIAL PROCESSES
     SOURCE CATEGORY (SIC)

Cattle Feed lots (0211)
Cotton Ginning (0724)
Metallic Ore Mining (10)
Coal Mining (1211)
Crushed Stone (142)
Sand and Gravel  (144)
Clays (145)
Potash/Phosphate Rock (1474,1475)
Feed and Grain Milling (204)
Lumber and Plywood (24)
Pulp Mills (261,262)
Chemicals (28)
Petroleum Refining (2911)
Asphalt Paving and Roofing (295)
Glass (321,322)
Cement (3241)
Brick and Tile (3251)
Concrete, Lime,  Gypsum (327)
Clay Sintering (3295)
Iron and Steel (3312)
Ferroalloys (3313)
Iron and Steel Foundries(332)
Primary Nonferrous Smelters(333)
Secondary Nonferrous Smelters(334,336)
Grain Elevators(4421,5153)

Total
  1970
     (GIGAGRAMS/YEAR)

1971     1972    1973    1974
1975    1976    1977   1978    1979
20
20
580
350
1,220
50
500
40
80
80
520
250
70
570
50
1,390
1,080
540
90
1,250
160
200
320
50
670
20
20
530
300
1,140
50
420
40
80
80
460
210
70
560
50
1,360
1,170
440
90
1,040
140
200
300
60
790
20
30
530
300
1,090
50
360
40 .
80
90
440
210
70
560
50
1,340
1,180
410
90
1,050
150
180
280
50
730
20
20
550
280
1,060
50
300
40
70
90
310
180
80
600
50
990
1,070
390
90
960
160
160
250
50
720
20
20
530
250
880
50
170
40
60
80
330
160
80
520
50
850
500
340
70
840
150
130
200
50
570
20
20
470
250
690
40
90
30
60
70
180
130
70
330
40
690
400
280
40
630
90
80
170
50
590
20
20
440
260
590
40
70
30
50
80
150
140
60
250
50
700
260
230
20
550
80
80
140
50
550
20
30
350
260
510
50
50
30
50
90
150
130
60
160
50
650
270
180
20
490
70
70
100
40
500
20
20
390
250
550
50
60
30
50
90
90
130
50
170
50
660
300
180
10
500
60
60
100
40
500
20
30
390
280
570
50
50
30
50
80
100
120
50
170
40
620
240
150
10
470
40
60
90
50
540
10,190   9,620   9,380   8,540   6,940   5,510   4,910   4,380   4,410  4,300
                                                             16

-------
                                                          TABLE 14

                                      SULFUR OXIDE EMISSIONS FROM INDUSTRIAL PROCESSES
     SOURCE CATEGORY

Natural Gas Production (1311)
Pulp Mills (261,262)
Sulfuric Acid (2819)
Carbon Black(2895)
Petroluem Refining (2911)
Glass(321,322)
Cement(3241)
Lime(3274)
Iron and Steel (3312)
Primary Copper (3331)
Primary Lead and Zinc (3332, 3333)
Primary Aluminum(3334)
Secondary Lead (3341)

Total
 1970
     (GIGAGRAMS/YEAR)

1971     1972    1973    1974
1975    1976    1977    1978    1979
100
70
540
0
620
20
580
30
300
3,650
410
70
20
100
70
530
0
660
20
580
30
230
3,220
360
70
20
120
70
570
10
690
20
600
30
270
3,740
310
70
20
150
70
570
10
760
30
610
30
290
3,690
190
80
20
160
70
440
10
750
30
580
30
280
3,080
160
80
20
160
70
330
10
730
30
490
30
240
2,290
110
60
20
130
80
250
10
700
30
530
30
250
2,220
110
70
30
120
80
260
10
720
30
580
30
230
2,070
90
80
30
130
80
260
10
720
30
630
30
220
1,930
0
80
30
120
80
250
10
680
30
680
30
230
1,870
0
80
30
6,420   5,890   6,520   6,500   5,690   4,570   4,440   4,330   4,150   4,090
                                                             17

-------
                                                          TABLE 15

                                     NITROGEN OXIDE EMISSIONS FROM INDUSTRIAL PROCESSES


                                                        (GIGAGRAMS/YEAR)

     SOURCE CATEGORY                       1970    1971     1972    1973    1974    1975    1976    1977    1978    1979

Pulp Mi 11s(261,262)                           20      20       30      30      30      20      30      30      30      30
Organic Chemicals(286)                       60      60       60      70      60      60      50      50      50      60
Ammonia(2873)                                40      40       40      40      40      40      40      50      40      50
Nitric Acid(2873)                           180     170      170     170     160     140     140     130     120     120
Petroleum Refining (2911)                   310     310      320     330     330     320     330     350     350     340
Glass(321,322)                               40      40       50      50      50      50      50      60      60      60
Cement (3241)                                 90      90      100     100     100      80      90      90     100     100
Iron and Steel(3312)                         50      40       50      50      50      40      40      40      40      40

Total                                       790     770      820     840     820     750     770     800     790     800
                                                             18

-------
                                                          TABLE 16

                               VOLATILE ORGANIC COMPOUND EMISSIONS FROM INDUSTRIAL PROCESSES
     SOURCE CATEGORY
Crude Oil Production, Storage, and
  Transfer(l311,4463)
Food and Beverages(20)
Text lies(22)
Graphic Arts(27)
Plastics(2821,3079)
Organic Chemicals(286)
Other Chemicals(28)
Petroleum Refining(2911)
Rubber Tires(3011)
Glass(321,322)
Iron and Steel(3312)
Petroleum Product Storage and
  Transfer(5171,5541)
Dry Cleaning(721)
Adhesives1
Degreasing1
Solvent Extraction Processes1
Surface Coating1
Other Organic Solvent Use1

Total
  1970
     (GIGAGRAMS/YEAR)

1971     1972    1973    1974
1975    1976    1977    1978
1979
590
120
180
280
400
890
570
720
100
50
110
1,670
280
460
560
230
1,730
1,370
590
120
180
260
390
950
500
760
110
50
80
1,740
270
430
510
220
1,610
1,270
600
120
180
300
450
1,060
480
790
110
50
100
1,830
300
490
500
240
1,880
1,480
600
120
180
310
470
1,150
490
820
110
50
110
1,890
300
500
520
240
1,930
1,540
580
130
180
280
460
1,210
460
850
110
50
100
1,830
280
460
470
220
1,780
1,470
570
130
170
240
390
1,070
370
880
90
50
90
1,840
250
400
400
190
1,470
1,210
580
130
170
270
450
1,280
430
880
90
60
100
1,890
260
440
420
200
1,650
1,380
600
140
150
280
480
1,390
450
. 940
120
60
90
1,900
270
460
420
220
1,810
1,460
610
140
180
330
560
1,500
450
960
110
70
90
1,940
320
550
460
260
2,200
1,530
610
150
190
340
590
1,580
460
960
100
60
90
1,810
330
560
460
260
2,230
1,640
10,310  10,040  10,960  11,330  10,920   9,810  10,680  11,240   12,260   12,420
^This is a general category which includes process emissions from organic solvent use in a wide variety of industries.
Thus no specific SIC is given.
                                                             19

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                                                          TABLE 17

                                          CARBON MONOXIDE EMISSIONS FROM INDUSTRIAL PROCESSES
     SOURCE CATEGORY

Pulp Mills (261,262)
Inorganic Pigments(2816)
Charcoal(2861)
Organic Chemicals(286)
Ammonia(2873)
Carbon Black(2895)
Petroleum Refining(2911)
Asphalt Roofing(2952)
Iron and Steel(3312)
Iron Foundries(3321)
Primary Aluminum(3334)

Total
 1970
     (GIGAGRAMS/YEAR)

1971     1972    1973    1974
1975    1976    1977    1978
1979
550
20
60
340
100
2,600
1,990
10
1,620
1,090
590
550
20
60
360
110
2,380
2,050
10
1,470
1,160
580
590
20
60
420
110
1,780
2,080
10
1,560
1,180
610
610
20
60
440
110
1,890
2,120
10
1,580
1,060
670
610
30
50
460
110
1,680
2,040
10
1,460
920
730
550
20
30
470
120
1,410
2,030
10
1,100
590
580
620
30
30
450
120
1,550
1,340
10
1,180
590
630
630
30
30
500
130
1,760
1,180
10
1,160
470
680
650
30
30
540
120
1,630
880
10
1,210
440
720
700
30
30
560
130
1,610
850
10
1,200
400
750
8,970   8,750   8,420   8,570   8,100   6,910   6,550   6,580   6,260   6,270
                                                             20

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                            3.  METHODS

  The generation of  an emission  inventory involves  many steps to
achieve the desired  result, which  is  to  estimate the  amount of
emissions for  selected pollutants  in  a defined  geographical area.
Ideally, nationwide  emission  estimates should  result  from a sum-
mation of county, state, and  regional data in  which each component
is reported separately.  The  National Emissions Data  System (NEDS)
uses this procedure.  The methods  used to prepare data  for this
publication are as similar as  possible to those used  for NEDS data
preparation.   Since  NEDS uses  a  more  detailed  procedure involving
calculation of emissions for  individual  sources and summation of
these individual emission totals to  produce national  totals,  there
is a much greater chance for  errors  or omissions to occur in  the
NEDS data.  Because  of the basic similarity of  techniques, dis-
crepancies between national totals reported herein  and  those  given
in NEDS reports are  due largely  to incomplete  data  reporting  and
errors in the  NEDS data.  The  quality of NEDS data  over time  has
improved so that the differences between NEDS  emission  reports for
1977 and later years and national  emission totals determined  by the
procedure used for this publication  are  not as  great  as in earlier
NEDS reports.  Moreover, historical  NEDS data  are not revised to
account for updated  emission  factors, errors or omissions in  the
data.  As a result annual NEDS  publications do  not  necessarily
represent a consistent trend  in  estimated emissions.

  Because it is impossible to  test every pollutant  source indivi-
dually, particularly area sources, an estimating procedure must be
used.  In order to do this, however,  one must  either  estimate the
emissions directly or estimate  the magnitude of other variables
that can then  be related to emissions.   These  indicators include
fuel consumption, vehicle miles, population, sales, tons of refuse
burned, raw materials'processed, etc., which are then multiplied by
appropriate emission factors  to  obtain emission estimates.

  The limitations and applicability  of emission factors must  be
understood.  In general, emission  factors are  not precise indi-
cators of emissions  from a single  source; rather, they  are quan-
titative estimates of the average  rate of pollutant released  as a
result of some activity.  They  are most  valid when  applied to a
large number of sources and processes.   If their limitations  are
recognized, emission factors  are extremely useful  in  determining
emission levels.  A detailed  discussion  of emission factors and
related information  is contained in Reference 2.  The emission
factor thus relates  quantity  of  pollutants emitted  to indicators
such as those  noted  above, and  is  a  practical  approach  for
determining estimates of emissions from  various source  categories.
                                  21

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  A discussion  of trends is meaningful  only when there is a common
basis  for  evaluation.   It was necessary,  therefore,  to quantify
emissions  using the same criteria for each year.  This meant using
the same estimation techniques,  using equal or equivalent data
sources, covering the  same pollutant sources,  and using compatible
estimates  of  pollutant control  levels from year to year.   Estimates
for previous  years were updated  using current  emission factors and
including  the most recent information .available.  The criteria used
in calculating  emissions was the same for all  years.

  The  methodology used in generation of emission estimates for
individual  source categories follows.

3.1 Transportation

3.1.1  Motor Vehicles

  Emission  estimates from gasoline-and  diesel-powered motor
vehicles were based upon vehicle-mile tabulations and emission
factors.   Seven vehicle categories  are  considered; light  duty
gasoline (mostly passenger cars), light duty diesel  passenger cars,
light  duty  trucks (trucks less than 6000  pounds in weight), light
duty trucks 6000 to 8500 pounds  in  weight, heavy duty gasoline
trucks and  buses, and  heavy duty diesel  trucks and buses, and
motorcycles.  The emission factors  used are based on  the  latest
available  data  from Reference 3.   The MOBILE 2 model, developed  by
the EPA Office  of Mobile Source  Air Pollution  Control  was used to
calculate  emission factors.  The factors  are based on national
average conditions and do not include corrections for specific
geographical  areas to  account for local  model  year distributions,
altitude,  temperature, or hot/cold  vehicle operation  differences.
For each of these variables, only national  averages  were  considered
in the emission factors.   Average speed is taken into account on a
nationwide  basis according to the published distribution  of
vehicle-miles travelled (VMT) for urban and rural  fractions.  These
data are published in  Reference  4.   For rural  VMT, the average
speed  is considered to be 45 miles  per  hour, and for  urban VMT,
19.6 miles  per  hour.

3.1.2  Aircraft

  Aircraft  emissions are based on emission factors and air-
craft  activity  statistics reported  by the Federal  Aviation
Administration.5  Emissions are  based on  the number  of
landing-takeoff (LTD)  cycles. Any  emissions in cruise mode,
                                  22

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which is defined to be above 3000  feet  (1000 meters)  are ignored.
Average emission factors, which  take  into  account  the national  mix
of aircraft types for general  aviation, military,  and commercial
aircraft, are used to compute  the  emissions.

3.1.3 Railroads

  The Department of Energy  reports  consumption  of  diesel  fuel  and
residual fuel oil by railroads.^   Average  emission factors
applicable to diesel fuel consumption were used to calculate
emissions.  The average  sulfur content  of  each  fuel was  used to
estimate SOX emissions.

3.1.4. Vessels

  Vessel use of diesel fuel, residual oil,  and  coal  is reported by
the Department of Energy.6,/   Gasoline  use is based on national
boat and motor registrations,  coupled with a use factor  (gallons/
motor/year) from Reference  8.  Emission factors from  AP-42^  are
used to compute emissions.  Since AP-42 does not contain an
emission factor for coal use by  vessels, an average emission factor
for coal combustion in boilers was  used.

3.1.5 Nonhighway Use of  Motor  Fuels

  Gasoline and diesel fuel  are consumed by off-highway vehicles.
The fuel use is divided  into seven  categories;  farm tractors,  other
farm machinery, construction equipment, industrial machinery,  small
general  utility engines  such as  lawnmowers and  snowthrowers, snow-
mobiles, and motorcycles.   Fuel  use is  estimated for  each category
from estimated equipment population and an annual  use factor of
gallons per unit per year.°

3.2 Fuel Combustion in Stationary  Sources

3.2.1  Coal

  Bituminous coal, lignite, and  anthracite coal  use are  reported by
the Department of Energy.7  Most coal is consumed  by  electric
utilities.  Average emission factors and the sulfur content  of  each
type of coal were used to estimate  emissions.   Degree of particu-
late control was based on a report  by Midwest Research Institute^
together with data from  NEDS10.  Sulfur content data  for electric
utilities are available  from the Department of  Energyll.  Sulfur
contents for other categories  are  based on NEDS data.
                                  23

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3.2.2 Fuel Oil

  Distillate  oil,  residual  oil,  and kerosene are consumed by
stationary sources nationwide.   Consumption by user category is
reported  by the  Department  of Energy.6  Average emission fac-
tors and  the  sulfur content of each fuel  were used  to estimate
emissions.

3.2.3 Natural Gas

  Natural gas consumption data are also reported by the Department
of Energy.12  Liquefied petroleum gas  (LPG) use is  also in-
cluded with natural  gas for the  purpose of estimating emissions.
Average emission factors from AP-42^ were used to calculate  the
emission  estimates.

3.2.4 Other Fuels

  Consumption of wood,  coke, coke-oven gas, and bagasse is based  on
data reported in NEDS.10 Average emission factors  were used to
calculate emissions,  which  are relatively minor on  a national
basis.

3.3 Industrial Processes

  In addition to fuel  combustion, certain other industrial pro-
cesses generate  and  emit varying quantities of pollutants into the
air.  The lack of  published national  data on production, type of
equipment, and controls, as well  as an absence of emission factors,
makes it  impossible  to  include estimates  of emissions from all
industrial process sources.

  Production  data  for industries that  are known to  produce the
great majority of  emissions were derived  from literature data.
Generally, the Minerals Yearbook,13 published by the Bureau  of
Mines, and Current Industrial  Reports,14  published  by the
Bureau of the Census,  provide adequate data for most industries.
Average emission factors were applied  to  production  data to  obtain
emissions.  Control  efficiencies applicable to various processes
were estimated on  the  basis of published  reports^ and from NEDS
data.l°

  For the purposes of this  report, petroleum product storage and
marketing operations  (gasoline,  crude  oil, and distillate fuel  oil
storage and transfer, gasoline bulk terminals and bulk plants,  re-
tail gasoline service  stations)  are included as industrial
processes.  Also included as industrial  processes are industrial
surface coating  and  degreasing operations, graphic  arts (printing
and publishing), and  dry cleaning operations.   All  of these  proces-
ses involve the  use  of  organic solvents.   Emissions  from the con-
sumption  of organic  solvents are estimated based on  data reported
in reference  15.   It  is assumed  that all  solvents consumed are
eventually released  as  air  pollution.
                                  24

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3.4 Solid Waste Disposal

  A study conducted  in  1968 on  solid  waste  collection and disposal
practices^ was the  basis for estimating  emissions from solid
waste disposal.  Results of this  study  indicate that  the average
collection rate of solid waste  is  about 5.5 pounds per capita per
day in the United States.  It has  been  stated  that a  conservative
estimate of the total generation  rate is  10 pounds per capita per
day.  The results of this survey  were updated  based on data re-
ported in NEDS and used to estimate,  by disposal  method, the
quantities of solid waste generated.  Average  emission factors were
applied to these totals to obtain  estimates of total  emissions from
the disposal of solid wastes.

3.5 Miscellaneous Sources

3.5.1 Forest Fires

  The Forest Service of the Department  of Agriculture publishes
information on the number of forest fires and  the acreage
burned.17  Estimates of the amount of material  burned per acre
are made to estimate the total  amount of  material burned.  Similiar
estimates are made to account for  managed burning of  forest areas.
Average emission factors were applied to  the quantities of
materials burned to  calculate emissions.

3.5.2 Agricultural Burning

  A studylS was conducted by EPA  to obtain  from local  agri-
cultural and pollution  control  agencies estimates of  the number of
acres and estimated  quantity of material  burned per acre in
agricultural burning operations.   These data have been updated and
used to estimate agricultural burning emissions,  based on average
emission factors.
                                 25

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3.5.3 Coal Refuse

  Estimates  of  the  number  of  burning  coal-refuse  piles  existing  in
the United States are  made in reports by the  Bureau  of  Mines.1"
Their publication presents a  detailed discussion  of  the nature,
origin, and  extent  of  this source  of  pollution.   Rough  estimates  of
the quantity of emissions  were  obtained  using this  information by
applying average emission  factors  for coal  combustion.   It  was
assumed that  the number  of burning refuse piles decreased to  a
negligible amount by 1975.

3.5.4 Structural Fires

  The United  States Department  of  Commerce  publishes, in their
statistical  abstracts, information on the number  and types  of
structures damaged  by  fire^O.   Emissions were estimated by
applying average emission  factors  for wood  combustion to these
totals.

3.5.5 Nonindustrial Organic Solvent Use

  This category includes nonindustrial sales  of surface coatings
(primarily for  architectural  coating)  solvent evaporation from
consumer products (aerosols,  space deodorants, polishes,
toiletries,  etc.),  use of  volatile organic  compounds as general
cleaning solvents,  paint removers, and liquefaction  of  asphalt
paving compounds, and  other undefined end uses.   Total  national
organic solvent use is estimated from chemical production reports
of the U.S.  Tariff  Commission^ together with estimates of the
portion of total production for use as solvent for each
chemical.15   jt is  assumed that all solvent production  is equal
to the amount necessary  to make up for solvent lost  through
evaporation.  Estimated- emissions from organic solvent use by
industrial processes and selected  nonindustrial solvent use
categories were obtained from Reference  15.  Solvent use not
accounted for by industrial processes is reported as nonindustrial
organic solvent use, with  annual estimates  adjusted  according to
solvent production  levels.
                                 26

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                       4. Analysis of Trends

  National trends  in air pollutant emissions are  a  function  of  a
number of factors.  Air pollution control measures  and  economic
conditions have the strongest impact on total  emissions.   National
emission trends do not provide any insight  into the distribution or
concentration of air pollution sources within  the United  States.
Therefore, local emission trends do not necessarily coincide with
national emission  trends.  Based on the national  implementation of
control measures for some classes of sources,  such  as  highway motor
vehicles, it is reasonable to infer that  for most localities, the
national trend in  emissions reasonably approximates local  trends in
emissions for the  same class of sources.

  In addition to the fact that national emission  trends do not
measure local changes in emission densities, national  emission  trends
may not be consistent with air quality trends  because  of  the impact of
meteorological factors on air quality data.  Also,  the  estimates for
TSP, SOx, and NOx  emissions include more  substances than  are routinely
measured by ambient air monitoring equipment.  For  example,
high-volume air samplers collect only suspended particulates
approximately 0.3  to 100 micro-meters in  diameter,  but  TSP emission
inventories include both suspended and settled particulates  generated
by man's activities.  Likewise sulfur dioxide  (SO?)  and nitrogen
dioxide (NO?) ambient air monitors measure  only those  two
compounds while oxides of sulfur (SOx) and  nitrogen (NOx)  are included
in the emission estimates.  In each case, the  substance measured by
the ambient air monitor is the most prevalent  constitutent of its
pollutant class or is acknowledged to be  its most representative
indicator.  Estimates of oxidant emissions  are not  provided  because
most oxidant species are secondary pollutants  generated by
photochemical reactions in the atmosphere.  Emission estimates  of VOC,
a major ingredient in oxidant-producing reactions,  were developed from
current emission factors.2.3  Generally,  excluded from  VOC
estimates were emissions of methane, ethane, methyl  chloroform, and
other compounds which are considered to be  of  negligible  photochemical
reactivity.  Organic species were identified based  on Reference 22.
If no data were available for a source category,  the total hydrocarbon
emission factor from Reference 2 was used.  Highway vehicle  emissions
were estimated as  nonmethane VOC's.3

  The following sections discuss the most important  factors
influencing the emission trends for each  pollutant.
                                 27

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                                 TABLE 18

               THEORETICAL 1979 NATIONAL EMISSION  ESTIMATES
                     BASED ON  1970  LEVEL OF  CONTROL


                             (TERA6RAMS/YEAR)

Source Category                TSP      SOX        NOX        VOC        CO
Transportation
Highway Vehicles
Non-Highway
Transportation Total
Stationary Source Fuel
Combustion
Electric Utlities
Industrial
Resi denti al /Commerci al
Fuel Combustion Total
Industrial Processes(SIC)
Mining Operations
(10,12,13,14)
Food and Agricultural
(02,07,20)
Wood Products(24,26)
Chemical s(28)
Petroleum Refining(29)
Metal s(33)
Mineral Products(32)
Miscellaneous
Industrial Processes Total
Solid Waste
Miscellaneous
Total
1979 Actual Emissions
(Table 1)
Theoretical 1979 Emissions
As A Percentage of 1970
Actual Emissions
1970 Actual Emissions
(Table 1)
Theoretical 1979 Emissions
As A Percentage of 1970
Actual Emissions


1.3
0.3
1.6


6.7
2.1
0.5
9.3

3.1

1.3

0.7
0.3
0.1
1.8
4.2
0.0
11.5
1.1
1.2
24.7

9.5


260%

21.0


118%


0.4
0.4
0.8


25.5
2.8
1.5
29.8

0.3

0.0

0.1
0.8
0.9
3.7
0.8
0.0
6.6
0.0
0.1
37.3

24.5


152%

28.3


132%
28

7.6
2.5
10.1


7.5
4.1
0.7
12.3

0.0

0.0

0.0
0.3
0.3
0.1
0.2
0.0
0.9
0.4
0.3
24.0

22.6


106%

19.1


126%


14.6
1.6
16.2


0.1
0.1
0.0
0.2

0.6

0.1

0.0
2.8
1.0
0.1
0.1
8.3
13.0
1.9
3.3
34.6

24.4


142%

27.7


125%


107.9
8.7
116.6


0.3
0.5
1.1
1.9

0.0

0.0

0.7
3.0
2.3
3.5
0.0
0.0
9.5
6.9
7.4
142.3

91.4


156%

112.9


126%


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4.1 Particulates

  Particulate emissions result primarily from  fuel  combustion  in
stationary sources and from industrial processes.   Substantial
reductions in particulate emissions have occurred  because  of the
installation of control equipment on these sources.  The extent of
the reduction is most evident from the data  in Table 18 which  shows
theoretical 1979 national emission estimates,  assuming that pol-
lutant control levels did not change since 1970.   Overall, particulate
emissions would have increased by about 18 percent  if the  extent  of
particulate control had not increased.  In reality, as shown in Table
1, particulate emissions decreased about 55  percent.  Thus, 1979
actual particulate emissions were less than  half of what they  would
have been without control efforts.

  More specifically, with no change in the level of control,
emissions from fuel combustion in stationary sources would have
increased from 7.3 teragrams to 9.3 teragrams, a 27 percent increase.
In fact, particulate emissions decreased to  2.5 teragrams, a 66 per-
cent decrease.  The electric utility sector  has the largest potential
for particulate emissions.  This is due to the extensive use of coal-
fired boilers to generate electricity.  In 1970, electric  utilities
consumed approximately 321 million tons of coal.   By 1979, this total
had increased to about 527 million tons.  Despite  this extensive
increase in coal consumption, particulate emissions from electric
utilities decreased 63 percent.  Improvement or installation of
control equipment on existing sources and New  Source Performance
Standards (NSPS) requirements for new facilities can be credited  with
the achievement of this emission reduction.  Particulate emissions
from other stationary fuel combustion sectors  have also decreased.
Additional control equipment has been installed on industrial  and
commercial coal-fired boilers.  In addition, the actual consumption of
coal by these and the residential sector declined  from 1970 to 1979.

  Particulate emissions from industrial processes  also decreased
because of installation of additional controls.  As noted  in the
tables, with no change in the level of control, increases  in in-
dustrial production would have caused a slight increase in emis-
sions from 10.2 to 11.5 teragrams.  In fact, industrial process
particulate emissions decreased 58 percent to 4.3  teragrams.
Substantial reductions were achieved in mineral products (cement,
crushed stone, brick, lime, etc.) and primary metal industries, most
notably in iron and steel production.
                                  29

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  A caveat  that  should be noted with respect to these participate
emission  estimates is that fugitive particulate (emissions from
unconfined  sources such as storage piles, material  loading,  etc.)
emissions are  incompletely accounted for in the emission totals.
Rough  estimates  of industrial  process fugitive emissions are
included  for  some industries.   Area source fugitive dust emissions
(unpaved  roads,  construction activities, etc.) are  not included at
all.   Similarly, natural  sources of particulates,  such as wind
erosion or  dust, are not  included.  (An exception  is forest  fires,
some of which  result from natural  causes).  In total, these
fugitive  emissions may amount  to a considerable portion of total
particulate emissions.  The controls applied to these sources  have
so far been minimal.  Due to the lack of adequate  emission factors
and emission  inventory techniques  for these sources, fugitive
particulate emissions have not been included in most emission
inventories.   As additional data become available,  it is expected
that estimates of fugitive particulate emissions will  be included
in future reports.

4.2 Sulfur  oxides

  Fuel combustion by stationary sources produces most sulfur oxide
emissions.  In addition,  certain industrial  processes, such  as
smelting  of copper,  lead, and  zinc ores, sulfuric  acid manu-
facturing,  and other industries also produce sulfur oxide emis-
sions.  Significant  emission reductions from industrial  processes
have occurred, mostly from non-ferrous smelters and sulfuric acid
plants.  By-product  recovery of sulfuric acid at smelters has  in-
creased since  1970.   As a result sulfur oxide emissions that previ-
ously  would have been released to  the atmosphere are recovered as
sulfuric  acid.   Since 1972 new sulfuric acid manufacturing plants
have been subject to New  Source Performance Standards requirements.
These  rules have contributed to decreased emissions as new plants
built  to meet  new product demands  or replace old facilities  must
meet more stringent  emission limitations than old  facilities.

  As shown  in  the tables, sulfur oxide emissions from electric
utilities account for more than half of total  emissions.
Combustion  of  sulfur-bearing fuels, chiefly coal and residual  fuel
oil, is responsible.   Between  1970 and 1979 utility use of coal
increased about  64  percent and residual  oil  use increased about
50 percent.  Emissions from utilities have increased only slightly,
because fuels  with  lower  sulfur content have been  used to the
extent that they were available.   Flue gas desulfurization systems
have seen only limited use to  date, but by the late 1970's enough
units  were  in  service to  prevent additional  increases  in electric
utlity emissions.   1979 electric utility emissions  would have  been
approximately  5  percent higher without the operation of flue gas
desulfurization  controls.  The theoretical  1979 National  emission
estimates given  in Table  18 for stationary fuel  combustion sources
are based on 1979 fuel  amounts but 1970 average sulfur contents.
On this basis, electric utility emissions would have increased 64
percent.  In fact,  emissions increased only 3 percent.   Sulfur
oxide  emissions  from other fuel  combustion sectors  decreased,
primarily due  to less coal  burning by these consumers.


                                  30

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4.3 Nitrogen oxides

  Nitrogen oxide emissions result almost entirely from
transportation.and stationary fuel combustion  sources.   Only
limited controls have been applied to sources  of NOx  emissions.
Table 18 shows that with the 1970 control level, national  NOx
emissions would have been only 6 percent higher than  actual 1979
emissions. The emissions from stationary fuel  combustion sources
reflect the actual growth in fuel consumption.  For mobile sources,
NOx emissions were controlled as a result of the Federal  Motor
Vehicle Control Program (FMVCP).  Nitrogen oxide emissions from
highway vehicles would have increased 46 percent, had there been  no
change in control level since 1970.  The estimates of actual NOx
emissions show a 29 percent increase.

4.4 Volatile organic compounds

  Emissions of VOC decreased primarily due to  motor vehicle
controls and less burning of solid waste.  Had controls  not been
implemented, a substantial increase  in emissions from highway
vehicles would have occurred.  From  1970 to 1979 vehicle-miles of
travel in the U.S. increased by about 37 percent.4  A
comparable increase in emissions would have occurred  had 1970
control levels remained unchanged.   As a result of the controls put
in place, VOC emissions from highway vehicles  actually decreased
32 percent.  VOC emissions also decreased due  to the  substitution
of water-based emulsified asphalts (used for road paving)  for
asphalts liquefied with petroluem distillates  (cutback asphalts).
This is reflected in the decreased emissions reported for
miscellaneous organic solvent use.

  These decreases were offset by increases in  industrial  process
emissions so that overall, total VOC emissions were reduced only
slightly.  Emissions from petroleum  refining and chemical  pro-
duction increased due to expanded production of organic  chemicals
and petroleum products.  Emissions from petroleum product storage
and marketing also increased due to  increase demand for  gasoline
and other petroleum products.

4.5 Carbon monoxide

  Carbon monoxide emissions occur mainly from  highway vehicles.
From 1970 through 1972, emissions from highway vehicles  increased.
In 1973, CO emissions decreased and  subsequently have decreased
further through 1979.  Overall, from 1970 to 1979, highway vehicle
emissions decreased 6 percent.  This trend is  the result of the
competing forces of growth in motor  vehicle-miles travelled (VMT)
and controls to limit CO emissions from motor  vehicles.   From 1970
through 1972, controls had a limited effect in reducing  emissions.
                                   31

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From 1973 on,  the  control  measures  have  been  successful  in reducing
emissions despite  growth  in  VMT.  For  1974  and  1979  sharp re-
ductions in emissions  from the  previous  years occur  because of
decline in VMT for these  years.   Overall, 1979  VMT is  still  37
percent higher than in 1970.   If  no controls  other than  those  in
place in 1970  had  been implemented, highway vehicle  emissions would
have increased in  proportion  to the growth  in VMT.

  Figures 1,2,  and 3  show the  trend  in  estimated actual  emissions
from highway vehicles  along with  estimated  emissions for two other
theoretical scenarios.  The  estimated  emissions  with constant 1970
emission factors show  the expected  emissions  if  there  were no
Federal Motor  Vehicle  Control  Program.   In  this  case substantial
increases in emissions occur  as a result of growth in  VMT.  The
estimated emissions with  constant 1970 VMT  show  the  predicted
effects of FMVCP if no growth  in  VMT occur.  The substantial
emission reductions that  occur  in this case may  apply  to areas with
congested traffic  volumes where VMT had  reached  a practical  growth
limit by 1970, so  that  no future  growth  in  VMT was possible.  This
situation may  exist in  central  business  districts or other loca-
tions in major metropolitan  areas.

  CO emissions from other sources either decreased or  remained
about the same from 1970  to  1979.   The most sizeable reductions
resulted from  decreased burning of  solid waste  and agricultural
materials.
                                  32

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Highway Vehicle
NO  Emissions  (10b MT/yr)
  "
        7.5
        7.0
        6.5
        6.C
        5.5
        5.0
        4.5
        4.0
        0.0
                                                                    Emissions with
                                                               Constant 1970 Emission
                                                                       Factors
                                                                  Estimated  Actual
                                                                     Emissions
                                                               Emissions with
                                                                    Constant 1970 VMT
           .'1970  1971   1972  T973   1974   1975  1976  1977  1978  1979

                   Figure 1.  Highway Vehicle NOX Emissions Estimates
                                              33

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Highway? Vehicle
VCfC' Emissions
(TO-6 MT/yr)
      15


      14


      13


      12


      11


      10


       5
       8
   ssions  with Constant
1970 Emission  Factors
                                                                    Estimated Actual
                                                                         Emissions
                                        Emissions with
                                        Constant 1970 VMT
            1970  1971   1972   1973  1974  1975   1976   1977   1978  1979  1980  1981

                      Figure  2.  Highway Vehicle VOC Emissions Estimates
                            34

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Highway
Vehicle
  CO
    -  110
Emissions
 (106 MT/yi
       100
        90
        80
        70
        60
        50
                                                                Emissions  with
                                                             Constant 1970 Emission
                                                                    Factors
                                                                   Estimated Actual
                                                                     Emissions
Emissions with
Constant 1S70 VMT
        40
        30
              1970  1971  1972  1973  1974  1975  1976  1977  1978  1979
               Figure 3.  Highway Vehicle CO Emissions estimates
                                                 35

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                              5. References

 *1.National Emissions Report, National Emissions Data System (NEDS).NADB,
    OAQPS.US Environmental Protection Agency,Research Triangle Park.NC.
    Publication No.EPA-450/4-80-005.March 1980.
  2.Compilation of Air Pollutant Emission Factors,Third Edition (Inclu-
    ding Supplements 1-10).US Environmental Protection Agency,Research
    Triangle Park,NC.Publication No.AP-42.
  3.Mobile 2 Users's Guide and Supporting Background Documentation (Draft)
    US Environmental Protection Agency, Office of Mobile Source Air
    Pollution Control, Ann Arbor, Michigan.1979
 *4.Highway Statistics.Federal Highway Administration,US Department of
    Transportation,Washington,DC.1979.
 *5.FAA Air Traffic Activity.Federal Aviation Administration,US
    Department of Transportation,Washington,DC.1979.
 *6.Energy Data Reports,Sales of Fuel Oil and Kerosine,Energy Infor-
    mation Administration,US Department of Energy,Washington,DC 1979.
 *7.Energy Data Reports,Bituminous Coal and Lignite Distribution,
    Energy Information Administration,US Department of Energy,
    Washington,DC 1979.
  8.Exhaust Emissions from Uncontrolled Vehicles and Related Equipment
    Using Internal Combustion Engines.Southwest Research Institute,
    San Antonio,TX.Prepared for US Environmental Protection Agency,
    Research Triangle Park,NC.EPA Contract No.EHS 70-108.Oct 1973.
  9.Particulate Pollutant Systems Study.Midwest Research Institute,Kansas
    City,MO.Prepared for US Environmental Protection Agency,Research
    Triangle Park,NC.Natural Air Pollution Control Administration
    Contract No.CPA 22-69-104.May 1971.
 10.Standard Computer Retrievals from the National Emissions Data System
    (NEDS).Unpublished computer report available from NADB,OAQPS,US
    Environmental Protection Agency, Research Triangle Park.NC.
*11.Energy Data Reports, Cost and Quality of Fuels for Electric  Utility
    Plants-1979, Energy Information Administration, US Department of Energy,
    Washington, D.C. Publication No. DOE/EIA-0191(79).June 1980.
*12.Energy Data Reports.Natural  Gas Production and Consumption,Energy
    Information Administration,U.S. Department of Energy,Washington,D.C.
    1979.
*13.Minerals Yearbook.Bureau of Mines, US Department of the Interior,
    Washington,DC.
*14.Current Industrial Reports.Bureau of the Census,US Department of Com-
    merce, Washington,DC.
 15.Ends Use of Solvents Containing Volatile Organic Compounds,  The
    Research Corporation of New England, Wethersfield, CT.EPA Publication
    EPA-450/3-79-032, May 1979.
 16.1968 National Survey of Community Solid Waste Practices.Public Health
    Service,US Department of Health,Education,and Wei fare,Cincinnati,
    OH.PHS Publication No.1867.1968.
*These publications are issued periodically.  The most recent publication
available when this document was prepared is cited.
                                       36

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*17.Wildfire Statistics.Forest Service,US Department of Agriculture,
    Washington,DC 1977.
 18.Emissions Inventory from Forest Wildfires,Forest Managed Burns,
    and Agricultural Burns.US Environmental  Protection Agency,
    Research Triangle Park,NC 27711.Publication No.EPA-450/3-74-062.
    November 1974.
 19.Coal Refuse Fires,An Environmental  Hazard.Bureau of Mines,US
    Department of the Interior,Washington,DC.Information Circular
    8515.1971.
*20.Statistical Abstract of the United  States.Bureau of the Census, US
    Department of Commerce,Washington,DC. 1977 (98th ed.)
*21.Synthetic Organic Chemicals,US Production and Sales.US Tariff
    Commission,Washington,DC.
 22.Volatile Organic Compound (VOC) Species  Data Manual Second Edition,US
    Environmental Protection Agency,Research Triangle Park,NC.Publication
    No.EPA-450/4-80-015.July 1980.
 23.Standard Industrial Classification  Manual 1972, Executive Office of
    the President, Office of Management and  Budget, Washington, D.C.
*These publications are issued periodically.   The most recent publication
available when this document was prepared is  cited.
                                        37

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                                    TECHNICAL REPORT DATA
                             (Please read Instructions on the reverse before completing)
 1. REPORT NO.
  EPA-450/4-81-010
                                                            3. RECIPIENT'S ACCESSIONiNO.
4. TITLE AND SUBTITLE

  National Air  Pollutant Emission Estimates, 1970-1979
5. REPORT DATE

  March 1981
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)

  Monitoring  and Data Analysis  Division
                                                            8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
  U.S. Environmental Protection Agency
  Office of  Air, Noise and Radiation
  Office of  Air Quality Planning and Standards
  Research Triangle Park, North Carolina  27711
                                                            10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
 12. SPONSORING AGENCY NAME AND ADDRESS
                                                            13. TYPE OF REPORT AND PERIOD COVERED
                                                              Final - 1970-1979
                                                            14. SPONSORING AGENCY CODE
 15. SUPPLEMENTARY NOTES
 16. ABSTRACT
  This report presents estimates of trends in  nationwide air pollutant
  emissions  for the five major pollutants:  sulfur oxides, particulates,
  carbon monoxide, hydrocarbons, and nitrogen  oxides.   Estimates are
  broken down according to  major types of air  pollutant sources.  A short
  analysis of emission trends is given, along  with a discussion of methods
  used to develop the data.
 7.
                                KEY WORDS AND DOCUMENT ANALYSIS
                  DESCRIPTORS
                                              b.IDENTIFIERS/OPEN ENDEDTERMS
             c.  COSATI Field/Group
  trends,  emissions,  inventory, air
  pollutants, nationwide,  sulfur
  oxides,  carbon monoxide,  particulates,
  hydrocarbons, nitrogen  oxides,
  controllable emissions,  miscellaneous
  sources
 3. DISTRIBUTION STATEMENT
  Release  unlimited
                                               19. SECURITY CLASS (ThisReport)
                                                 Unclassified
              21. NO. OF PAGES
                    44
                                               20. SECURITY CLASS (Thispage)
                                                 Unclassified
                                                                         22. PRICE
EPA Form 2220-1 (9-73)

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