f/EPA
EPA-450/4-91-026
November 1991
United States Office of Air Quality
Environmental Protection Planning and Standards
Agency Technical Support Division
National Air Data Branch
Research Triangle Park, NC 27711
Air
National Air Pollutant
Emission Estimates
1940 -1990
\ \\.\\
Printed on Recycled Paper
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EPA Publication No. EPA-450/4-91-026
NATIONAL AIR POLLUTANT
EMISSION ESTIMATES
1940-1990
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
November 1991
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boi .:.-.!, 12th Floor
Chicago, IL 60604-:, »;-J
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This report is published by the U.S. Environmental Protection Agency (EPA) 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 Services, 5285 Port Royal Road, Springfield, Virginia 22161.
Questions or comments on the report may be directed to:
Mary Ann Stewart
EPA Project Officer
Mail Drop 14
Emission Inventory Branch
Technical Support Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
EPA Publication No. EPA-450/4-91-026
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FOREWORD
This document presents the most recent estimates of national and regional emissions of the
criteria air pollutants. The emissions of each pollutant are estimated for many different source
categories, which collectively account for nearly all anthropogenic emissions. The report presents the
total emissions from all 48 contiguous States, Alaska and Hawaii, and from ten different regions of the
country. The emission trends are updated annually.
This report represents the first of a series which will track the changes in national emissions
since the Clean Air Act Amendments of 1990. The emission trends are the net effect of many factors,
including changes in the nation's economy and in industrial activity, technology, consumption of fuels,
traffic, and other activities which cause air pollution. The trends also reflect changes in emissions as a
result of air pollution regulations and emission controls. These reports will serve as a measure of our
nation's progress in reducing air pollution as a result of mandatory and voluntary controls and of
continuous changes in national activity.
This report also reflects recent improvements in the way national and regional emissions are
calculated. Improvement in estimation methods is an on-going effort, and it is expected that future
reports will reflect this effort. The emission trends presented in this report are based on consistent
methods applied to all years.
in
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TABLE OF CONTENTS
Page
FOREWORD iii
TABLE OF CONTENTS iv
LIST OF FIGURES vi
LIST OF TABLES vii
ACKNOWLEDGEMENT viii
1.0 EXECUTIVE SUMMARY 1
1.1 Whafs New in This Report 1
1.1.1 Inclusion of PM-10 Emissions 1
1.1.2 Inclusion of Regional Emission Trends 1
1.1.3 Emissions Projections 3
1.1.4 Earlier Reporting 3
1.2 Emission Estimates for 1990 3
1.2.1 Paniculate Matter Emissions in 1990 3
1.2.2 Sulfur Oxide Emissions in 1990 5
1.2.3 Nitrogen Oxide Emissions in 1990 5
1.2.4 Volatile Organic Compound Emissions in 1990 5
1.2.5 Carbon Monoxide Emissions in 1990 6
1.2.6 Lead Emissions in 1990 6
2.0 NATIONAL EMISSION TRENDS, 1940 TO 1990 6
2.1 Summary of Total National Emission Estimates 6
2.2 Graphical Trend in Total National Emissions 6
2.3 Total National Emissions by Decade 14
2.4 National Emissions by Source Category 14
2.4.1 Emissions from Transportation Sources 14
2.4.2 Emissions from Stationary Fuel Combustion Sources 14
2.4.3 Emissions from Industrial Processes 14
2.4.4 Emissions from Fugitive Dust PM-10 Sources 14
3.0 REGIONAL EMISSION TRENDS, 1985 THROUGH 1990 14
4.0 METHODOLOGY 29
4.1 Calculation Procedure 29
4.1.1 Transportation 30
4.1.1.1 Highway Vehicles 30
4.1.1.2 Aircraft 31
4.1.1.3 Railroads 31
4.1.1.4 Vessels 31
4.1.1.5 Off Highway Vehicles 31
4.1.2 Stationary Source Fuel Combustion 32
4.1.2.1 Coal 32
4.1.2.2 Fuel Oil 32
iv
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4.1.2.3 Natural Gas 32
4.1.2.4 Wood and Other Fuels 32
4.1.3 Industrial Processes 32
4.1.3.1 Miscellaneous Industrial Processes for Lead 33
4.1.4 Solid Waste Disposal 33
4.1.5 Miscellaneous Sources 33
4.1.5.1 Forest Fires 33
4.1.5.2 Agricultural Burning 33
4.1.5.3 Coal Refuse Burning 33
4.1.5.4 Stmcture Fires 34
4.1.5.5 Nonindustrial Organic Solvent Use 34
4.1.6 Fugitive Dust PM-10 Sources 34
4.1.6.1 Unpaved Roads 34
4.1.6.2 Paved Road Resuspension 34
4.1.6.3 Wind Erosion 35
4.1.6.4 Agricultural Tilling 35
4.1.6.5 Construction Activities 35
4.1.6.6 Mining and Quarrying 35
4.2 Maintaining Consistency 36
4.3 National Emission Estimates for 1990 36
4.4 Regional Emission Estimates 37
5.0 ANALYSIS OF NATIONAL TRENDS, 1940 THROUGH 1990 37
5.1 Total Paniculate and PM-10 39
5.2 Sulfur Oxides 40
5.3 Nitrogen Oxides 41
5.4 Non-methane Volatile Organic Compounds 41
5.5 Carbon Monoxide 42
5.6 Lead 43
6.0 NATIONAL EMISSION PROJECTIONS 43
6.1 Future Trends in Sulfur Oxide Emissions 44
6.2 Future Trends in Nitrogen Oxide Emissions 46
6.3 Future Trends in Non-methane Volatile Organic Compound Emissions 47
6.4 Future Trends in Carbon Monoxide Emissions 49
7.0 SEASONAL EMISSION PROJECTIONS 50
8.0 REFERENCES 52
APPENDIX A - NATIONAL EMISSIONS BY SOURCE CATEGORY 55
APPENDIX B - NATIONAL EMISSIONS BY SUBCATEGORY 63
APPENDIX C - REGIONAL EMISSIONS 84
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LIST OF FIGURES
Number
1. Trend in Total Paniculate Matter Emissions from 1940 to 1990 for the United States
and by Source Category 7
2. Trend in Fugitive Dust PM-10 Emissions from 1985 to 1990 for the United States and
by Source Category 8
3. Trend in Sulfur Oxide Emissions from 1940 to 1990 for the United States and by
Source Category 9
4 Trend in Nitrogen Oxide Emissions from 1940 to 1990 for the United States and by
Source Category 10
5. Trend in Non-methane Volatile Organic Compound Emissions from 1940 to 1990 for
the United States and by Source Category 11
6. Trend in Carbon Monoxide Emissions from 1940 to 1990 for the United States and by
Source Category 12
7. Trend in Lead Emissions from 1970 to 1990 for the United States and by Source
Category 13
8. EPA Administrative Regions 20
9. Trend in Total Particulate Matter Emissions from 1985 to 1990 by Region 21
10. Trend in PM-10 Emissions from Point and Fugitive Process Sources by Region from
1985 to 1990 22
11. Trend in Sulfur Oxide Emissions from 1985 to 1990 by Region 23
12. Trend in Nitrogen Oxide Emissions from 1985 to 1990 by Region 24
13. Trend in Non-methane Volatile Organic Compound Emissions from 1985 to 1990 by
Region 25
14. Trend in Carbon Monoxide Emissions from 1985 to 1990 by Region 26
15. Trend in Lead Emissions from 1985 to 1990 by Region 27
16. Trend in Fugitive Dust PM-10 Emissions from 1985 to 1990 by Region 28
17. Projected Trend in Sulfur Oxide Emissions, 1990 to 2010 45
18. Projected Trend in Nitrogen Oxide Emissions, 1990 to 2010 47
19. Projected Trend in Non-methane Volatile Organic Compound Emissions, 1990 to 2010 ... 48
20. Projected Trend in Carbon Monoxide Emissions, 1990 to 2010 49
VI
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LIST OF TABLES
Number Page
1. Summary of Estimates of Nationwide Emissions 2
2. Major Source Categories 4
3. Total National Emissions of Total Particulate Matter, 1940-1990 15
4. Total National Emissions of Sulfur Oxides, 1940-1990 16
5. Total National Emissions of Nitrogen Oxides, 1940-1990 17
6. Total National Emissions of Non-methane Volatile Organic Compounds, 1940-1990 18
7. Total National Emissions of Carbon Monoxide, 1940-1990 19
8. Theoretical 1990 National Emissions Based on 1970 Controls 39
9. Total National Sulfur Oxide Emissions, 1980 to 2010 45
10. Total National Nitrogen Oxide Emissions, 1980 to 2010 46
11. Total National Volatile Organic Compound Emissions, 1980 to 2010 48
12. Total National Carbon Monoxide Emissions, 1980 to 2010 49
13. Comparison of Ozone Season and National Average Volatile Organic Compound Emissions .. 51
14. Comparison of Ozone Season and National Average Nitrogen Oxide Emissions 51
A-1. National Emissions Estimates of Total Particulate Matter 56
A-2. National Emissions Estimates of Sulfur Oxides 57
A-3. National Emissions Estimates of Nitrogen Oxides 58
A-4. National Emissions Estimates of Non-methane Volatile Organic Compounds 59
A-5. National Emissions Estimates of Carbon Monoxide 60
A-6. National Emissions Estimates of Lead 61
A-7. National Emissions Estimates of PM-10 62
B-1. Emissions of Total Particulate Matter from Transportation Sources 64
B-2. Emissions of Sulfur Oxides from Transportation Sources 65
B~3. Emissions of Nitrogen Oxides from Transportation Sources 66
B-4. Emissions of Volatile Organic Compound from Transportation Sources 67
B-5. Emissions of Carbon Monoxide from Transportation Sources 68
B-6. Emissions of PM-10 from Transportation Sources 69
B-7. Emissions of Total Particulate Matter from Fuel Combustion Sources 70
B-8. Emissions of Sulfur Oxides from Fuel Combustion Sources 71
B-9. Emissions of Nitrogen Oxides from Fuel Combustion Sources 72
B-10. Emissions of Volatile Organic Compound from Fuel Combustion Sources 73
B-11. Emissions of Carbon Monoxide from Fuel Combustion Sources 74
B-12. Emissions of PM-10 from Fuel Combustion Sources 75
B-13. Emissions of Total Particulate Matter from Industrial Processes 76
B-14. Emissions of Sulfur Oxides from Industrial Processes 77
B-15. Emissions of Nitrogen Oxides from Industrial Processes 78
B-16. Emissions of Volatile Organic Compound from Industrial Processes 79
B-17. Emissions of Carbon Monoxide from Industrial Processes 80
B-18. Emissions of Lead from Industrial Processes 81
B-19. Emissions of PM-10 from Industrial Processes 82
B-20. National Summary of Fugitive Dust PM-10 Emissions, 1985-1990 83
C-1. Regional Emissions Estimates of Total Particulate Matter 85
C-2. Regional Emissions Estimates of Sulfur Oxides 85
C-3. Regional Emissions Estimates of Nitrogen Oxides 86
C-4. Regional Emissions Estimates of Non-methane Volatile Organic Compounds 86
C-5. Regional Emissions Estimates of Carbon Monoxide 87
C-6. Regional Emissions Estimates of Lead 87
C-7. Regional Emissions Estimates of PM-10 from Point and Fugitive Process Sources 88
C-8. Regional Emissions Estimates of Fugitive Dust PM-10 88
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ACKNOWLEDGEMENT
This report was prepared with the help of many people. The EPA wishes to acknowledge the
assistance of William W. Frietsche of the National Air Data Branch, Mary Ann Stewart of the Emission
Inventory Branch, and Gerhard Gschwandtner, Patricia Carlson, and T. Allan Dean of E.H. Pechan &
Associates, Inc. in preparing the emission estimates and producing this report. Appreciation is also
extended to Evelyn S. Kimbrough and Charles O. Mann for helping develop much of the original trends
methodology. The agency wishes to acknowledge data and information provided by numerous people
from other agencies of Government and private institutions and organizations.
VIII
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1.0 EXECUTIVE SUMMARY
This report presents the U.S. Environmental Protection Agency's (EPA) latest estimates of national
and regional emissions for criteria air pollutants: total paniculate matter, including fine paniculate
matter (PM-10), sulfur oxides (SOX), nitrogen oxides (NOX), volatile organic compounds (VOC), carbon
monoxide (CO) and lead. Estimates are presented for the past fifty years; 1940 to 1990.
National emissions are estimated annually by the U.S. EPA based on statistical information
about each source category, emission factors and control efficiency. The estimates are made for over
450 individual source categories that include nearly all major sources of anthropogenic emissions. The
emission estimates for individual source categories are aggregated to show the emission trends at the
national and regional levels and by major source category.
Table 1 summarizes the total national emissions of each pollutant from 1940 to 1990. The
emissions are expressed in metric units; either teragrams (1012 grams) or gigagrams (109 grams) per
year. One teragram equals one million metric tons, or approximately 1.1 million short tons. (One short
ton equals 2,000 pounds.) One gigagram equals one thousand metric tons, or approximately 1.1
thousand short tons. Table 1 also presents the percentage change in total national emissions of each
pollutant for the past fifty, twenty and ten years and since 1989.
Emissions of SOX are expressed as weight equivalent sulfur dioxide and emissions of NOX are
expressed as weight equivalent nitrogen dioxide. The VOC emissions referred to in this report include
non-methane volatile organic compounds.
1.1 What's New in This Report
This report contains new information on the regional trends of all criteria pollutant emissions
including, for this first time, fugitive dust PM-10 emissions, from 1985 to 1990. (PM-10 includes
particulate matter less than 10 micrometers or less in diameter.) This report also presents emission
projections for the nation to the years 2000 and 2010, and comparison of ozone season and annual
daily average emissions of VOC and NOX. In addition, the report is being made available earlier this
year than in previous years as a result of an accelerated schedule and a revised method for updating
the emission trends.
1.1.1 Inclusion of PM-10 Emissions
PM-10 emissions were estimated in response to an EPA rule published on July 1, 1987,
establishing an ambient air quality standard for PM-10. This standard replaced the previously existing
standard for total suspended particulate matter. PM-10 emissions are estimated for the same point and
fugitive process source categories included in the total particulate emission estimates, and for fugitive
dust sources including agricultural tilling, construction activity, mining and quarrying, paved roads,
unpaved roads and wind erosion. Fugitive dust PM-10 sources had been omitted from previous
national emission estimates.
1.1.2 Inclusion of Regional Emission Trends
For the first time, the national emission trends have been disaggregated to show the emission
trends in different regions of the country. Essentially the same method was used for deriving the
national emission estimates, except that region-specific activity data were used for each source
category.
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1.1.3 Emissions Projections
National emissions of sulfur and nitrogen oxides, non-methane volatile organic compounds and
carbon monoxide are projected to the year 2000 and 2010. These projections are based on future
economic and activity growth projections and the expected emission reductions due to the
implementation of the Clean Air Act Amendments of 1990.
1.1.4 Earlier Reporting
In addition, emission trends are presented about four months earlier than in previous annual
reports. Where final information for a source category was not available for estimating emissions, the
1990 emissions estimate is based on the emission trend in the past seven years for that category.
Exceptions to this approach include highway vehicles, electric utilities, copper smelters, forest fires and
natural gas combustion sources for which actual data were available. As a result, the 1990 emission
estimates are considered preliminary. Final estimates for 1990 will be presented in the next annual
report.
1.2 Emission Estimates for 1990
In 1990, the U.S. economy operated at a slightly reduced level from 1989 because of the onset
of a recession. Coal consumption, a major source of sulfur oxides, increased, as did overall vehicular
traffic, a major source of volatile organic compounds, carbon monoxide and nitrogen oxides. Also,
more land was burned by forest fires in 1990 compared to 1989, resulting in slightly increased air
pollution. Industrial activity varied; some source categories increased production while others did not.
The net effect on total emissions of all of these changes and of continued emission reductions because
of control devices appears to be little changed in 1990 compared to 1989.
During 1990, the U.S. preparation for war in the Middle East was a major news item. The
increased activity in domestic military air and other related traffic appears to be a small fraction of
overall national traffic activity, resulting in no noticeable increase in national emissions. The following
sections present a brief description of the changes in total national emissions of each pollutant from
1989 to 1990.
1.2.1 Paniculate Matter Emissions in 1990
The total national emissions for total paniculate matter (TP), excluding fugitive dust, are
estimated to be 7.5 teragrams. The total national emissions of PM-10 from point and fugitive process
sources are estimated to be 6.4 teragrams and from fugitive dust sources are estimated to be 40.8
teragrams. Point and fugitive process sources include transportation, fuel combustion, industrial
processes, solid waste disposal, and miscellaneous. The major subcategories comprising these
sources are listed in Table 2.
Collectively, industrial processes appear to be the largest contributor to anthropogenic
emissions of TP. In 1989, industrial processes contributed 2.7 teragrams, compared to 2.8 teragrams
in 1990. In addition, as a result of more area burned by forest fires, especially in Alaska, national TP
emissions from forest fires increased from 0.8 teragrams in 1989 to 1.1 teragrams in 1990. The net
effect of these changes was an increase in total national emissions of 0.3 teragrams. Total national
PM-10 emissions increased from 6.1 teragrams in 1989 to 6.4 teragrams in 1990.
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TABLE 2. MAJOR SOURCE CATEGORIES
Category
Transportation
Stationary Source Fuel
Combustion
Industrial Processes
Solid Waste Disposal
Miscellaneous
Fugitive Dust PM-10 Sources
Subcategory
Highway Vehicles (Gasoline and Diesel-Powered)
Aircraft
Railroads
Vessels
Off Highway Vehicles and Machinery
Electric Utilities
Industrial Boilers
Commercial and Institutional Boilers and Furnaces
Residential Furnaces and Space Heaters
Chemical Manufacturing
Petroleum Refining
Primary and Secondary Metals
Iron and Steel Mills
Mineral Products
Food Production and Agriculture
Industrial Organic Solvent Use
Petroleum Product Production and Marketing
Incineration
Open Burning
Forest Fires
Other Burning (Agricultural Burning, Coal
Refuse Burning, and Structure Fires)
Miscellaneous Organic Solvents Evaporation
Paved Roads
Unpaved Roads
Agricultural Tilling
Construction Activity
Mining and Quarrying
Wind Erosion
Notes: Refer to Section 4.0 for a description of source categories.
For the purposes of this report, forest fires are considered
anthropogenic sources although some fires may be caused by nature.
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In 1990, total national fugitive dust PM-10 emissions are estimated to be about six times
greater than the total emissions from anthropogenic point and fugitive process sources. The total PM-
10 emissions from fugitive dust sources (agricultural tilling, construction, mining and quarrying, paved
roads and unpaved roads) is about the same in 1990 as for each of the five previous years. Reduced
wind erosion is largely responsible for the decrease in total fugitive dust PM-10 emissions from 1989 to
1990.
Unlike other fugitive dust sources, wind erosion can be highly variable. For example, the total
national emissions from wind erosion in 1987 are estimated to be 1.3 teragrams, compared to 15.9
teragrams in 1988. The lack of precipitation in 1988 prior to spring crop planting, especially in the
central and western U.S., contributed to greater wind erosion.
1.2.2 Sulfur Oxide Emissions in 1990
The total national emissions of SO, in 1990 are estimated to be 21.2 teragrams compared to
20.8 teragrams in 1989. The most significant change in SOX emissions since 1989 appears to have
occurred in the stationary source fuel combustion category. Greater consumption of coal by electric
utilities and industrial boilers in 1990 accounts for nearly all of the 0.4 teragram increase in total
emissions.
Consumption of fuel oil, another major source of SOX, is difficult to predict because fuel oil
deliveries and consumption have not followed a smooth trend in the past few years. Since the 1990
emissions from fuel oil combustion are based on extending the past trend, the resulting emission
estimate may noticeably affect the total.
1.2.3 Nitrogen Oxide Emissions in 1990
In 1990, the total national NOX emissions are estimated to be 19.6 teragrams compared to 19.8
teragrams in 1989. This decrease is due to a slight decrease in NOX emissions from highway vehicles
as older, less efficient automobiles are replaced with newer automobiles. Historically, for the past ten
years, national emissions of NO, have remained nearly constant despite increased vehicular traffic. For
example, in 1980, the total national emissions were 20.9 teragrams.
1.2.4 Volatile Organic Compound Emissions in 1990
In 1990, total national non-methane volatile organic compound (VOC) emissions were 18.7
teragrams compared to 18.5 teragrams in 1989. Highway vehicles continue to be a major source of
VOC and NOX. Vehicle miles travelled (VMT) increased from 2,107 x 109 miles in 1989 to 2,128 x 109
miles travelled in 1990, or 1 about percent. As a result of reduced gasoline volatility and continued
replacement of older automobiles, total non-methane VOC emissions from gasoline-powered highway
vehicles decreased by 1.6 percent from 1989 to 1990 according to the EPA calculations.
For 1980 to 1990, the EPA recently improved the method for calculating VOC emissions from
highway vehicles by including state and monthly ambient temperatures, gasoline volatility guideline
values and vehicle miles travelled. The effect of this improvement is that the total national VOC
emissions are 12 to 15 percent greater than before. These improvements are described in Section
4.1.1.1. It is possible that further improvements, including the use of actual gasoline volatility data and
vehicle speed data, may result in different estimates in the future. Recent tunnel studies and
measurements of tailpipe emissions suggest that actual VOC emissions from highway vehicles are
much higher than traditional estimates, but as of yet, these suggestions are unsubstantiated by
emission models.
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VOC emissions from forest fires increased from 0.8 teragrams in 1989 to 1.1 teragrams in 1990
as a result of one-third more land area burned. Most of this increase is a result of widespread fires in
Alaska.
1.2.5 Carbon Monoxide Emissions in 1990
In 1990, total national CO emissions are estimated to be 60.1 teragrams compared to 60.4
teragrams in 1989. From 1989 to 1990, the total emissions from transportation sources decreased by
2.4 teragrams. CO emissions from residential fuel combustion also decreased by 0.3 teragrams, while
emissions from forest fires increased by 2.3 teragrams due to more land area burned. All other source
contributions stayed about the same.
1.2.6 Lead Emissions in 1990
Total national lead emissions decreased from 7.2 gigagrams in 1989 to 7.1 gigagrams in 1990.
On a historic basis, lead emissions have changed little in recent years. The sharpest reductions
occurred in the 1970s and early 1980s when leaded gasoline was being replaced with unleaded
gasoline.
Historically, the greatest decreases in lead emissions occurred prior to the 1980s before the
introduction of unleaded gasoline. For example, in 1970, lead emissions from highway vehicles were
156.0 gigagrams, compared to 56.4 gigagrams in 1980. By 1990, the total emissions from highway
vehicles were only 2.0 gigagrams.
2.0 NATIONAL EMISSION TRENDS, 1940 TO 1990
This chapter presents the estimated national emission trends both graphically and numerically.
All estimates for 1990 are preliminary (as explained in Chapter 3.0) and may change in the future as
final information becomes available.
2.1 Summary of Total National Emission Estimates
Table 1 summarizes the total national emission estimates from 1940 to 1990 for each criteria
pollutant including both TP and PM-10. The estimates are presented for 1940, 1950, 1960, 1970, 1975
and for each year from 1980 to 1990. (National emission estimates are also available for each year
from 1970 to 1980, but are not included in this report. These estimates have been presented in earlier
reports in this series.)
2.2 Graphical Trend in Total National Emissions
Figures 1 through 7 show the trend in the total national emissions of each pollutant by major
source category. The major source categories include transportation sources, stationary source fuel
combustion, industrial processes, solid waste disposal, and miscellaneous. Figure 2 shows the trend in
fugitive dust PM-10 emissions from 1985 through 1990 and Figure 7 shows the trend in lead emissions
from 1970 to 1990. The trend of all other pollutants is shown from 1940 to 1990.
Fugitive dust is a significant component of TP, especially in arid parts of the country. Major
sources of fugitive dust PM-10 addressed in this report include agricultural tilling, construction activity,
mining and quarrying, paved roads, unpaved roads, and wind erosion.
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2.3 Total National Emissions by Decade
Tables 3 through 7 present the total national emission estimates for each pollutant, except
PM-10 and lead, for each decade from 1940 to 1990, by source category. Estimates of PM-10
emissions are available only for the past six years, and estimates of lead emissions are available only
for the past two decades.
2.4 National Emissions by Source Category
Tables A-1 through A-6 in Appendix A present the national emission estimates by source
category for 1970, 1975, 1979 and for each year from 1980 through 1990. Table A-6 presents the lead
emission estimates, and Table A-7 presents the emission estimates of PM-10 for point and fugitive
process sources from 1985 through 1990.
2.4.1 Emissions from Transportation Sources
Tables B-1 through B-6 in Appendix B present the national emission estimates in detail for the
transportation source category. Estimates are presented for each criteria pollutant except lead, which is
addressed in Table A-6 with other source categories. The estimates are presented for different types of
gasoline and diesel powered highway vehicles, aircraft, railroad locomotives, vessels, various machines
and other off highway vehicles.
2.4.2 Emissions from Stationary Fuel Combustion Sources
Tables B-7 through B-12 in Appendix B present emission estimates in detail for stationary fuel
combustion sources. Estimates are presented for use of coal, fuel oil, natural gas, wood and other fuels.
2.4.3 Emissions from Industrial Processes
Tables B-13 through B-19 in Appendix B present the national emissions in detail for industrial
processes. The Standard Industrial Classification (SIC) is shown for each process subcategory. These
estimates do not include all SIC categories, only those that are shown.
2.4.4 Emissions from Fugitive Dust PM-10 Sources
Table B-20 presents the estimated national fugitive dust emissions of PM-10 from 1985 to
1990. These estimates include emissions from paved and unpaved roadways, agricultural tilling,
construction activity, mining and quarrying, and wind erosion.
3.0 REGIONAL EMISSION TRENDS, 1985 THROUGH 1990
This chapter presents the results of estimating the total emissions by the ten EPA regions
shown in Figure 8. When comparing emissions from different regions, it is important to take into
account the size of the region, their population, economic activity, predominant types of industry, soil
type and other factors that affect air pollution.
Figures 9 through 16 show the trend in the total national emissions of each pollutant, including
PM-10, from 1985 through 1990 and by EPA Region. Regional emissions were estimated by source
category, in the same manner as for national emissions, but only the total regional emissions are
presented in this report. Total regional emissions are presented by pollutant in Tables C-1 through C-7
in Appendix C for each year.
14
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TABLE 3. TOTAL NATIONAL EMISSIONS OF
TOTAL PARTICULATE MATTER, 1940-1990
(Teragrams/Year)
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Off Highway
Transportation
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial-Institutional
Residential
Stationary Source Fuel Combustion
Industrial Processes
Iron and Steel Mills
Primary Metal Smelt ng
Secondary Metals
Mineral Products
Chemicals
Petroleum Refining
Wood Products
Food and Agriculture
Mining Operations
Industrial Processes
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Total
Total of All Sources
1940 1950 1960 1970 1980 1990
0.2
0.0
2.4
0.1
0.0
2.7
1.3
3.3
0.4
2.5
7.5
3.0
0.6
0.2
2.0
0.3
0.0
0.5
0.8
1.3
8.7
0.3
0.2
0.3
0.0
1.7
0.1
0.0
2.1
2.0
2.8
0.5
1.7
7.0
3.5
0.6
0.3
2.9
0.4
0.0
0.8
0.8
3.4
12.7
0.3
0.3
0.6
0.0
0.1
0.0
0.0
0.7
2.8
1.8
0.1
1.0
5.7
1.7
0.5
0.2
3.8
0.3
0.1
0.9
0.9
4.1
12.5
0.4
0.5
0.9
0.1
0.1
0.0
0.1
1.2
2.3
1.6
0.1
0.6
4.6
1.2
0.6
0.2
2.9
0.2
0.1
0.7
0.8
3.9
10.5
0.4
0.7
1.1
0.1
0.1
0.0
0.1
1.3
0.8
0.5
0.1
1.0
2.4
0.3
0.1
0.1
0.7
0.1
0.1
0.2
0.6
1.1
3.3
0.2
0.2
1.3
0.1
0.0
0.0
0.1
1.5
0.4
0.3
0.0
1.0
1.7
0.2
0.1
0.1
0.5
0.1
0.0
0.2
0.5
1.2
2.8
0.1
0.2
0.5 0.6
0.9
1.1 0.4
0.8 0.8 0.8 0.4 0.1
3.7 2.5 1.8 1.1
23.1 24.9 21.6 18.5 8.5
0.3
2.9 1.7 1.0 0.7 1.0 1.1
0.1
1.1 1.2
7.5
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total due to
rounding.
15
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TABLE 4. TOTAL NATIONAL EMISSIONS
OF SULFUR OXIDES, 1940-1990
(Teragrams/Year)
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Off Highway
Transportation Total
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial-Institutional
Residential
Fuel Combustion Total
Industrial Processes
Primary Metal Smelting
Pulp Mills
Chemicals
Petroleum Refining
Iron and Steel
Secondary Metals
Mineral Products
Natural Gas Processing
Industrial Processes Total
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Total
Total of All Sources
1940 1950 1960 1970 1980 1990
0.0
0.0
2.7
0.2
0.0
2.9
22
55
1.0
23
11.0
2.5
0.0
0.2
0.2
0.5
0.0
0.3
0.0
3.7
0.0
0.0
0.0
0.0
0.5
0.1
0.0
2.0
0.2
0.0
2.3
4.1
5.2
1.7
1.9
12.9
2.8
0.0
0.4
0.3
0.6
0.0
0.5
0.0
4.6
0.0
0.0
0.0
0.0
0.5
0.1
0.0
0.2
0.1
0.0
0.4
8.4
3.5
1.0
1.1
14.0
3.0
0.1
0.4
0.6
0.6
0.0
0.5
0.1
5.3
0.0
0.0
0.0
0.0
0.5
0.3
0.0
0.1
0.2
0.1
0.6
15.8
4.1
0.9
0.5
21.3
3.7
0.2
0.5
0.7
0.7
0.0
0.6
0.1
6.4
0.0
0.0
0.0
0.0
0.1
0.4
0.0
0.1
0.3
0.1
0.9
15.5
2.4
0.7
0.2
18.7
1.2
0.2
0.3
0.8
0.5
0.0
0.6
0.1
3.8
0.0
0.0
0.0
0.0
0.0
0.6
0.0
0.1
0.2
0.1
0.9
14.2
2.3
0.4
0.3
17.1
0.5
0.3
0.2
1.0
0.4
0.0
0.6
0.2
3.1
0.0
0.0
0.0
0.0
0.0
0.5 0.5 0.5 0.1 0.0 0.0
17.6 19.8 19.7 28.3 23.4 21.2
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total
due to rounding.
16
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TABLE 5. TOTAL NATIONAL EMISSIONS
OF NITROGEN OXIDES, 1940-1990
(Teragrams/Year)
1940 1950 1960 1970 1980 1990
1.4
0.0
0.6
0.1
0.2
2.2
0.0
0.9
0.1
0.4
3.8
0.0
0.7
0.1
0.5
6.3
0.1
0.6
0.1
0.8
7.9
0.1
0.8
0.2
1.0
5.6
0.1
0.5
0.2
1.1
2.3
0.6
2.3
0.2
0.3
3.4
3.6
5.1
8.0
2.9
0.3
0.3
4.7
3.7
0.3
0.4
3.9
0.3
0.4
0.2
0.0
0.1
0.1
0.3
0.1
0.1
0.2
0.5
0.1
0.2
0.3
0.7
0.1
0.3
9.8
1.2 2.3 4.4 6.4
3.1
0.3
0.4
0.7
0.0
0.1
0.4 0.1
7.5
7.3
3.3
0.2
0.4
6.7 9.1 10.1 11.2
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Off Highway
Transportation Total
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial-Institutional
Residential
Fuel Combustion Total
Industrial Processes
Petroleum Refining
Chemicals
Iron and Steel Mills
Pulp Mills
Mineral Products
Industrial Processes Total
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Total
Total of All Sources
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total
due to rounding.
0.1
0.0
0.0
0.0
0.1
0.1
0.0
0.1
0.0
0.1
0.2
0.1
0.1
0.0
0.1
0.2
0.2
0.1
0.0
0.2
0.2
0.2
0.1
0.0
0.2
0.2
0.1
0.0
0.0
0.2
0.6
0.0
0.1
0.1
0.7
0.2
0.9
6.9
0.4
0.2
0.6
9.4
0.2
0.2
0.4
13.0
0.2
0.1
0.3
18.5
0.2
0.0
0.2
20.9
0.2
0.0
0.3
19.6
17
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TABLE 6. TOTAL NATIONAL EMISSIONS OF
NON-METHANE VOLATILE ORGANIC
COMPOUNDS, 1940-1990
(Teragrams/Year)
1940 1950 1960 1970 1980 1990
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Off Highway
Transportation Total
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial- Institutional
Residential
Fuel Combustion Total
Industrial Processes
Chemicals
Petroleum Refining
Iron and Steel Mills
Mineral Products
Food and Agriculture
Industrial Organic Solvent Use
Petroleum Product Pioduction
and Marketing
Industrial Processes Total
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Organic Solvent Use
Miscellaneous Total
Total of All Sources
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total
due to rounding.
4.0
0.0
0.5
0.0
0.2
4.7
0.0
0.1
0.0
1.7
1.8
0.8
0.4
0.3
0.0
0.1
1.0
0.7
3.3
0.4
0.5
0.9
3.1
0.6
0.8
4.5
15.2
5.7
0.1
0.5
0.1
0.4
6.8
0.0
0.1
0.0
1.2
1.3
1.2
0.5
0.4
0.0
0.1
2.1
1.1
5.4
0.4
0.6
1.0
1.7
0.6
1.3
3.6
18.1
8.3
0.2
0.2
0.2
0.5
9.4
0.0
0.1
0.0
0.7
0.8
1.1
0.7
0.3
0.0
0.2
2.4
1.6
6.3
0.5
0.9
1.4
0.9
0.5
1.7
3.1
21.0
9.1
0.3
0.2
0.3
0.5
10.3
0.0
0.1
0.0
0.4
0.6
1.6
0.7
0.4
0.0
0.2
4.0
2.1
8.9
0.5
1.3
1.8
0.7
0.3
2.3
3.3
25.0
7.7
0.2
0.2
0.4
0.5
9.0
0.0
0.1
0.0
0.8
0.9
1.8
1.0
0.3
0.0
0.2
3.9
2.1
9.2
0.3
0.3
0.6
0.9
0.1
1.9
2.9
22.6
5.1
0.2
0.1
0.5
0.5
6.4
0.0
0.1
0.0
0.7
0.9
1.9
0.7
0.2
0.0
0.2
3.1
2.1
8.1
0.3
0.3
0.6
1.1
0.1
1.5
2.7
18.7
18
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TABLE 7. TOTAL NATIONAL EMISSIONS
OF CARBON MONOXIDE, 1940-1990
(Teragrams/Year)
1940 1950 1960 1970 1980 1990
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Oft Highway
Transportation Total
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial-Institutional
Residential
Fuel Combustion Total
Industrial Processes
Chemicals
Petroleum Refining
Iron and Steel Mills
Primary Metal Smelting
Secondary Metals
Pulp Mills
Industrial Processes Total
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Total
Total of All Sources
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total
due to rounding.
22.6
0.0
3.7
0.2
3.4
29.9
0.0
0.4
0.1
15.8
16.3
3.8
0.2
1.5
0.0
1.0
0.1
6.6
2.0
1.3
3.3
22.8
3.7
26.5
82.6
34.2
0.8
2.8
0.2
6.7
44.7
0.1
0.5
0.1
10.9
11.6
5.3
2.4
1.1
0.1
1.4
0.2
10.5
2.5
1.8
4.3
12.8
3.7
16.5
87.6
47.7
1.6
0.3
0.6
8.0
58.2
0.1
0.6
0.0
6.4
7.1
3.6
2.8
1.3
0.3
1.0
0.3
9.3
2.5
2.6
5.1
6.7
3.3
10.0
89.7
65.3
0.9
0.3
1.2
6.8
74.4
0.2
0.7
0.1
3.5
4.5
3.1
2.0
1.6
0.6
1.1
0.6
8.9
2.7
3.7
6.4
5.1
2.1
7.2
101.4
48.7
1.0
0.3
1.4
4.7
56.1
0.3
0.7
0.1
6.4
7.4
2.0
1.6
1.0
0.8
0.3
0.7
6.3
1.2
1.0
2.2
6.9
0.7
7.6
79.6
30.3
1.1
0.2
1.7
4.4
37.6
0.3
0.7
0.1
6.4
7.5
1.7
0.4
0.7
0.7
0.2
0.9
4.7
0.9
0.8
1.7
8.1
0.6
8.6
60.1
19
-------
E
0-
LU
CO
0>
1_
13
g>
LL
20
-------
21
-------
22
-------
23
-------
24
-------
25
-------
26
-------
27
-------
28
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The trends in regional emissions generally follow the trends in national emissions for most
source categories. This effect is largely due to the fact that each region has a diversity of source
categories which reflect the national diversity. Some source categories, however, such as forest fires,
prescribed burning, wind erosion and certain industrial processes, have significant regional effects and
do not necessarily follow national trends. These source categories will generally account for large
changes at the regional level from one year to the next.
4.0 METHODOLOGY
The estimation of national emissions by pollutant and by year involves many steps. Ideally,
national emission estimates should be the result of adding the emissions of each individual source in
the country. However, this is not possible, and therefore, reliable emission estimates must be based on
a "top-down" calculation approach.
The methods used to prepare the estimates presented in this report are as similar as possible
to those used for Aerometnc Information Retrieval System (AIRS) data preparation.1 To develop the
AIRS point source file, a complex calculation procedure must be followed which includes source-by-
source and plant-by-plant emissions calculations. Individual point source estimates are added to the
state level totals, and these are then added to the national level figures.
To develop the AIRS area source file, statistical information must be collected on each type of
area source. Area sources include many small sources (generally producing emissions of less than
100 tons per year) that are too numerous to account for individually. Residential fuel combustion and
solid waste disposal are examples of area sources.
In addition, fugitive dust emissions (emissions from unconfined sources such as storage piles,
material loading and wind erosion of land) must be estimated. These estimates are based on large-
scale data and various calculation procedures developed in recent years. Fugitive dust may include
paniculate matter of various size, but for the purposes of this report, is considered equivalent to PM-10.
4.1 Calculation Procedure
Since it is impossible to measure the emissions of every source individually, a "top-down"
estimating procedure must be used. The emissions are calculated either for individual sources or for
many sources combined, using indicators of emissions. Depending on the source category, these
indicators may include fuel consumption or deliveries, vehicle miles travelled, tons of refuse burned, raw
material processed, etc. When indicators are used, emission factors which relate the quantity of
emissions to the activity indicator must also be used.
Emission factors are not necessarily precise indicators of emissions. They are quantitative
estimates of the average rate of emissions from many sources combined. These factors are most valid
when applied to a large number of sources. If their limitations are recognized, emission factors are
extremely useful tools for estimating national emissions.
29
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The basic "top-down" calculation procedure for most source categories, excluding highway
vehicles and copper smelters, may be represented by the following equation:
I C \
E08 = AsxEFDsx 1 - -^ eq'1
P.s s p,s I 10Ql
where, £ = emissions
p = pollutant
s = source category
A = activity level
EF = emission factor
C = percent control efficiency
National activity data for individual source categories are obtained from many different
publications. Emission factors are generally obtained from the U.S. EPA's Compilation Of Air Pollutant
Emission Factors. AP-422, and from the EPA's mobile source emission factor model available at the
time of calculation, MOBILE4.3 (MOBILE4.1 was not available at the time, but will be used for updating
the emission trends next year.) The overall control efficiency of a source category is currently derived
from AIRS data. In the past, it was derived from the National Emissions Data System (NEDS),4 the
predecessor of AIRS, and from the 1985 National Acid Precipitation Assessment Program (NAPAP)
emission inventory.5
Exceptions to this approach include electric power plants, copper smelters and highway
vehicles. For power plants, SOX emissions are always calculated on a plant-by-plant basis. For copper
smelters from 1975 to 1990, SOX emissions are obtained from the plants directly through the respective
state air pollution agencies. For highway vehicles, emissions are calculated by state and month, using
a method described in Section 4.1.1.
The following sections describe the methodology used for estimating the annual emissions from
1940 to 1990 by major source category.
4.1.1 Transportation
This category includes gasoline and diesel-powered motor vehicles, aircraft, railroad, vessels
and nonhighway use of motor fuels.
4.1.1.1 Highway Vehicles-
Emissions from gasoline and diesel-powered motor vehicles are based upon vehicle miles
travelled (VMT) and emission factors. Eight vehicle categories are considered; gasoline-powered
automobiles, diesel-powered automobiles, light duty gasoline trucks (trucks less than 6,000 pounds in
weight), light duty gasoline trucks 6,000 to 8,500 pounds in weight, light duty diesel trucks, heavy duty
gasoline trucks and buses, heavy duty diesel trucks and buses, and motorcycles.
Emission factors for VOC, NOX and CO were obtained from the MOBILE4 model.3 This model
was designed to be used as a tool for estimating exhaust and running loss emissions from highway
vehicles in nonattainment areas and in urban air sheds. For VOCs, the model requires information on
ambient temperature, vehicle speeds, gasoline volatility, and other variables. For TP and PM-10,
30
-------
emission factors were obtained from AP-42. These emission factors account for tire wear, brake wear
and tailpipe exhaust emissions.
For years prior to 1980, the emissions were calculated on the national level only, assuming a
single average annual ambient temperature value, a single gasoline volatility value, a distribution of
vehicle speed and vehicle type, and a percentage of hot and cold starts. For 1980 and subsequent
years, the emissions were calculated on the state and monthly level using a new method.6 State
voluntary fuel volatility guidelines obtained from the American Society for Testing and Materials7 and
average monthly maximum and minimum temperatures in each state were put into MOBILE4. As a
result of using this new method, national VOC emissions estimates were about 12 to 15 percent higher
than previous estimates.
In both methods, average vehicle speed is based on the published distribution of VMT.8
Published VMT data are divided into three road categories, corresponding with assumed average
speeds of 55 miles per hour for interstates and other primary highways, 45 miles per hour for other
rural roads, and 19.6 miles per hour for urban streets. For 1940 and 1950, average speeds were
assumed to be 45, 35 and 19.6 miles per hour for these roadway classifications.
Lead emission estimates are based on gasoline consumption, gasoline lead content, percent
unleaded gasoline, and emission factors. The lead content of gasoline in 1970 was obtained from the
Bureau of Mines, U.S. Department of the Interior9, and for subsequent years, from AP-42. The percent
unleaded gasoline was obtained from the Energy Information Administration, U.S. Department of
Energy.10
4.1.1.2 Aircraft--
Emissions from aircraft are based on the number of landings and take-offs reported by the
Federal Aviation Administration11 and on AP-42 emission factors for various types of aircraft. Emissions
occurring when aircraft are above 3,000 feet are not included in the estimates. Average emission
factors are calculated which take into account the national mix of different types of aircraft used for
general aviation, military and commercial purposes.
4.1.1.3 Railroads--
Emissions from railroads are based on diesel and residual fuel oil consumption by railroads as
reported by the Energy Information Administration.12 Coal consumption by steam locomotives has been
negligible since 1955. Average emission factors were used that are applicable to each type of fuel. In
the case of sulfur oxides, the average sulfur content of each fuel was included in the emission factor.
4.1.1.4 Vessels-
The consumption of diesel fuel, residual oil and coal by vessels operating inside the U.S.
boundaries was obtained from the U.S. Department of Energy.10'12'13 Gasoline consumption is based on
national boat and motor registrations together with usage factors (gallons/motor/year)10, and marine
gasoline sales as reported by the U.S. Department of Transportation.8 The estimates of fuel
consumption are multiplied by AP-42 emission factors. In the case of coal-fired vessels, an average
emission factor for coal combustion in boilers was used.
4.1.1.5 Off Highway Vehicles-
This source category includes farm tractors, other farm machinery, construction equipment,
industrial machinery, small general utility engines such as lawn mowers and snowmobiles, and
31
-------
motorcycles. Fuel use is estimated for each subcategory from equipment population data and an
annual fuel use factor14 together with fuel deliveries of diesel fuel reported by the U.S. Department of
Energy12 for gasoline sales reported by the U.S. Department of Transportation8 for off-highway use.
4.1.2 Stationary Source Fuel Combustion
This major category includes the combustion of bituminous coal, lignite and anthracite coal, fuel
oil, natural gas, wood and other fuels.
4.1.2.1 Coal-
The consumption of bituminous coal, lignite and anthracite coal by various end users is
reported by the U.S. Department of Energy.13'15 Most coal is consumed by electric utilities. The
reported consumption by source category was multiplied by an average emission factor representative
of each category- In the case of sulfur oxide emissions, the emission factor included an average sulfur
content value for each type of coal consumed.16
In the case of electric utilities, the sulfur oxide emission factor was adjusted to account for the
amount of sulfur controlled by flue gas desulfurization systems, according to information reported by the
U.S. Department of Energy.16 In the case of particulate matter, an overall control efficiency was
obtained from AIRS for all power plants combined.
4.1.2.2 Fuel Oil--
Residual oil, distillate oil and kerosene are burned by electric utilities, industrial boilers,
commercial and institutional boilers, furnaces and residential heaters. The consumption of each fuel
type by end user is reported by the U.S. Department of Energy.12 Average emission factors and sulfur
content values are calculated and applied to the consumption data.
4.1.2.3 Natural Gas--
Natural gas consumption is also reported by the U.S. Department of Energy for various end-
user groups.17 AP-42 emission factors were used to calculate the emissions.
4.1.2.4 Wood and Other Fuels--
Consumption of wood has been estimated by the U.S. Department of Energy18'19 for wood
stoves and residential fireplaces. Consumption of bagasse is based on data reported in AIRS. Sales
of liquified petroleum gas are reported by the U.S. Department of Energy.10 Coke and coke-oven gas
consumption is obtained from the U.S. Department of Energy.6 These consumption values were
multiplied by appropriate emission factors obtained either from AP-42 or AIRS.
Lead emissions from the combustion of waste oil were based on information obtained from the
EPA's Office of Solid Waste. The amount of waste oil burned is assumed to remain constant, while the
lead content of waste oil has been assumed to decrease as a result of the general reduction in leaded
oil and petroleum products.
4.1.3 Industrial Processes
Production data for industries that produce the majority of emissions were obtained from
available publications. Generally, the Minerals Yearbook9 and Current Industrial Reports21, published by
the Bureau of Census, provide most of the necessary data. Average emission factors were applied to
32
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the various production data. Average nationwide control efficiency values for various processes were
obtained either from published reports22, the 1985 NAPAP emission inventory, AIRS or NEDS.
Petroleum product storage and petroleum marketing operations, including gasoline, crude oil and
distillate fuel oil storage and transfer, gasoline bulk terminals and bulk plants, and retail gasoline service
stations, are included as industrial processes. Also included are industrial surface coating and degreasing
operations, graphic arts (printing and publishing), and dry cleaners.
All of these processes involve the use of organic solvents. Emissions from the consumption of
organic solvents are estimated from information reported by the U.S. EPA.23 It is assumed that all solvents
consumed eventually evaporate, except in surface coating operations where some of the organic solvent
vapors are controlled. The control efficiency of surface coating operations is derived from AIRS.
4.1.3.1 Miscellaneous Industrial Processes for Lead--
Lead emissions from miscellaneous industrial processes include lead alkyl production (a major
source of lead) and other minor sources such as type metal production, can soldering, cable covering, and
miscellaneous sources. The lead alkyl production is based on information reported by the U.S.
International Trade Commission.24 Production information for other minor sources is obtained from the U.S.
Department of Energy.9
4.1.4 Solid Waste Disposal
The emissions from this category are based on an assumed solid waste generation rate of 5.5
pounds per capita per day. This value was originally based on a study of solid waste collection and
disposal practices.25 This value is adjusted each year based on information contained in AIRS. Average
emission factors are applied to the estimated quantities of solid waste disposal.
4.1.5 Miscellaneous Sources
This major source category includes forest fires, agricultural burning, coal refuse burning and
structure fires.
4.1.5.1 Forest Fires-
The U.S. Forest Service of the Department of Agriculture and the U.S. Department of the Interior
publish information on the number of forest fires, their location and the acreage burned each year. The
amount of forest biomass burned and controlled burning of forest areas each year are estimated by the
EPA per acre.26 Average emission factors were applied to the estimated quantities of materials burned.
4.1.5.2 Agricultural Buming-
A study was conducted by the U.S. EPA to obtain local agricultural and air pollution control agency
estimates of the number of acres and quantity of material burned per acre in agricultural burning
operations.26 These data have been updated and used to estimate emissions based on average emission
factors.
4.1.5.3 Coal Refuse Burning--
Estimates of the number of burning coal-refuse piles existing in the U.S. are reported by the Bureau
of Mines.27 This publication presents a detailed discussion of the nature, origin, and extent of this source of
33
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pollution. Rough estimates of the quantity of emissions were made using this information by applying
average emission factors for coal combustion. It should be noted that the number of coal-refuse piles had
decreased to negligible by 1975.
4.1.5.4 Structure Fires--
The U.S. Department of Commerce publishes information on the number and type of structures
damaged by fires each year.28 Emissions are estimated by applying average emission factors for wood
combustion to these statistics.
4.1.5.5 Nonindustrial Organic Solvent Use--
This source category includes nonindustrial sales of surface coatings for architectural coating,
and solvent evaporation from consumer products such as aerosols, deodorants, polishes, toiletries, etc.
This category also includes the use of organic compounds such as general cleaning solvents, paint
removers, liquification of asphalt paving compounds, and miscellaneous other. Total national organic
solvent use is estimated from chemical production reports together with estimates of the portion of total
production of each chemical for use as solvent.23'29 It is assumed that the quantity of all solvent
produced is equal to the quantity necessary to make up for solvent loss by evaporation.
4.1.6 Fugitive Dust PM-10 Sources
Estimates of fugitive dust PM-10 emissions were made for the following categories: unpaved
roads, wind erosion, agricultural tilling, construction, mining and quarrying, paved roads and burning.
An EPA study30 showed that emissions estimates at both the national and regional level for these
source categories would require either modification of existing PM-10 or TP emissions estimation
methods or development of new methodologies.31 As a result, new estimating methods were developed
for each category to predict the latest annual emissions. Predictive methods were necessary because
much of the necessary data were not available in time to estimate the 1990 emissions. A brief
description of the method for each source category follows.
4.1.6.1 Unpaved Roads--
Regional emissions from unpaved roads were determined using the method developed as part
of an EPA study to determine the feasibility of developing regional emissions estimates.30 The method
utilized is similar to that developed by NAPAP.31 Three minor modifications, relative to the NAPAP
method, were made in determining the emissions estimates for unpaved roads. First, the AP-42
emission factor for unpaved roads was utilized for all unpaved road surface types. Secondly, a plume
depletion factor was not applied to the emissions estimates. These first two modifications were made
to be consistent with the approach used for other source categories. AP-42 emission factors are
applied throughout to produce the emissions estimates. Plume depletion factors are not (and have not
ever been) applied to paniculate emissions from other paniculate sources. Thirdly, variable (not fixed)
values of vehicle speeds, weights, and number of wheels were used to develop the emission factor for
unpaved roads.
4.1.6.2 Paved Road Resuspension-
Regional PM-10 emissions from paved road resuspension were estimated by summing state-
level emission estimates. A "dry days" term was included in the AP-42 emission factor equation for
paved roads similar to the one used in the unpaved road emission factor, in an attempt to account for
the effect of precipitation.
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An empirical model was used to express the relationship between traffic volume and surface silt
loading. Surface silt loading values were determined for various paved road function classes by EPA
region. Average daily traffic volume was calculated by dividing the total VMT for a particular functional
class, year, and state and then dividing by the number of days in the year.
For the years 1985 to 1989 the total VMT (by EPA region and functional class) was obtained
from the Federal Highway Administration.8 VMT from paved roads were calculated by subtracting the
unpaved VMT from the total VMT. For 1990, the total VMT were obtained by EPA region, and rural
and urban VMT. The rural and urban VMT were further subdivided into functional classes using the
1989 VMT distribution.
4.1.6.3 Wind Erosion--
Regional PM-10 wind erosion emission estimates for agricultural lands were made by modifying
the NAPAP method for estimating wind erosion emissions. The original NAPAP method and the
method used here both develop an expectation of the dust flux based on the probability distribution of
wind energy. The method developed for this report uses the mean wind speed and information on
threshold friction velocity and information on precipitation to predict the wind erosion flux potential for
soils.
It should be noted that the emissions estimates developed as part of the NAPAP effort utilized
a 30 year wind record and thus represent a 30 year average emission estimate. The wind erosion
emission estimates developed for this report use state-level, year-specific wind and activity data.
4.1.6.4 Agricultural Tilling-
Regional PM-10 emissions from agricultural tilling were made using the AP-42 emission factor
equation for agricultural tilling with year-specific and state-level emission factor correction parameters
and activity data.
4.1.6.5 Construction Activities--
Regional PM-10 emissions were estimated using an emission factor for construction activity and
the total number of acres of land under construction in the nation. The average duration of construction
was also estimated.
4.1.6.6 Mining and Quarrying-
Regional PM-10 emissions estimates for mining and quarrying operations include the following
sources: 1) overburden removal, 2) drilling and blasting, 3) loading and unloading and 4) overburden
replacement. Transfer and conveyance operations, crushing and screening operations and storage and
travel on haul roads are not included in the estimates.
Metallic ore emissions were calculated by assuming that for the four operations listed above,
the PM-10 emission factors for copper ore processing operations apply to all metallic ores. Nonmetallic
ore and coal emissions were calculated by assuming that the PM-10 emission factors for western
surface coal mining apply to both nonmetallic ores and coal.
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4.2 Maintaining Consistency
When estimating national emission trends, it is important to follow a consistent methodology.
Should the emission factor for a source category change, for example, then the new factor must be
applied to all previous years. Similarly, if an activity indicator for a source category changes, as is
sometimes the case when preliminary figures are published, the new value must be used in the
calculations for that year. Also, if the calculation method changes for any source category, possibly as
a result of improving the method or as a result of a change in available data, the new method must be
applied to all previous years. In this way, the emission trends are consistent and the changes in
emissions from one year to the next are comparable.
4.3 National Emission Estimates for 1990
For 1990 only, the national emissions are based on preliminary estimates. For previous years,
the emissions estimates were based on final published statistics and information which became
available almost a year later. A method was developed for providing reliable estimates earlier than
before.
The 1990 estimates are based on the activity level, the emission factor for each pollutant and
the control efficiency of each source category during the past seven years. Although more than twenty
years of consecutive data are available in the EPA trends files, seven years of data were found to
provide the best basis for projecting the trend in these variables to the next year. The trend of each
variable was projected to 1990 using either a linear regression or a quadratic equation depending on
which method provided the best results when applied to 1989 data. The 1990 national emissions were
then calculated for each source category using equation 1 shown in Section 4.1.
When the projection method was applied to the seven years of data prior to 1989, the resulting
total national emission estimates were nearly identical to the estimates derived by the original method.
The percentage difference between the actual emissions and the estimates, as calculated for 1989 on
the national level, are summarized below:
Pollutant Percent Difference
Total Particulate Matter 0.6 %
Sulfur Dioxide -1.4%
Nitrogen Oxide -1.1 %
Non-methane Volatile Organic Compounds 0.7 %
Carbon Monoxide 0.8 %
Lead 4.6 %
PM-10 (Point and Fugitive Process Sources) 1.0 %
Note: A negative sign indicates the preliminary estimates
were less than the actual. A positive sign indicates the
estimates were greater than the actual.
The preliminary estimation method provides a reasonable indication of changes in annual total
national emissions. When combined with actual data for major source categories such as electric
utilities, highway vehicles and others, the method provides a reliable indication of trends.
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4.4 Regional Emission Estimates
For each source category, except industrial processes, state-level activity data were obtained
for 1985 through 1988. In most cases, state-level data were obtained directly from the same
references from which national data were obtained. The state-level activity data were aggregated to
the EPA regional level and the regional totals were used to develop regional fractions of the national
activity. These fractions were multiplied by the national emissions to obtain regional emission estimates
by source category. The regional emissions of all source categories were added to produce regional
total emissions.
In the case of industrial process categories, except copper smelters, the regional fractions were
obtained from the 1985 NAPAP emission inventory. The same fraction was used for each year from
1985 through 1990 because the changes in regional fractions for nonindustrial source categories were
found to be negligible from year to year.
5.0 ANALYSIS OF NATIONAL TRENDS, 1940 THROUGH 1990
National trends in air pollutant emissions are a function of a number of factors. Air pollution
control measures and economic conditions have the greatest 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. For this reason, regional emission trends were developed.
In this report, emissions of SOX are reported as the equivalent weight of sulfur dioxide (SO2),
which is the predominant sulfur oxide species. Some emissions of sulfur trioxide (SO3) are also
included, but are also expressed as the equivalent weight of SO2. Emissions of NO, include
predominantly nitric oxide (NO) and nitrogen dioxide (NO2). Other nitrogen oxides are probably emitted
in small amounts. In this report, NOX emissions are expressed as the equivalent weight of NO2.
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. No adjustments have been made to exclude ethane and other
photochemically reactive VOCs or to include chlorofluorocarbons. If no data were available for a
source category, the total non-methane hydrocarbon or the total hydrocarbon emission factor from AP-
42 was used. Highway vehicle emissions were estimated as non-methane VOCs.
The following sections of this chapter discuss the most important factors influencing the
emission trends of each pollutant. The analysis is divided into two parts; 1940 through 1970 when
significant changes in technology, activity patterns, and fuel use occurred, and 1970 through 1990 when
emissions were being controlled.
In the 1950s and 1960s, paniculate matter and smoke emissions were among the first
pollutants to be controlled by local air pollution abatement programs. A concerted effort to control the
emissions of other pollutants did not begin on the national level until the Clean Air Act of 1970. Since
then, considerable progress has been made in reducing emissions of SOX, NOX, VOC, CO, lead and
fine paniculate matter by installing emission control devices on automobiles, electric power plants,
industrial processes and other sources. In order to see the general effect of emission controls in the
past twenty years, the national emissions in 1970 are compared to the emissions in 1990, assuming the
same level of emission control and emission factors in 1990 as in 1970. Table 8 shows the theoretical
1990 emissions by source category.
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TABLE 8. THEORETICAL 1990 NATIONAL EMISSIONS
BASED ON 1970 CONTROLS
(Teragrams/Year)
Source Category
Transportation
Highway Vehicles
Non-Highway
Transportation Total
Stationary Source Fuel Combustion
TP SOX NOX VOC CO LEAD
1.8 0.6 12.1 20.5 107.9 200.1
0.2 0.4 1.9 1.3 7.5 4.8
2.0 0.9 14.0 21.9 115.4 205.0
Electric Utilities
Industrial
Residential/Commercial
Fuel Combustion Total
Industrial Processes (SIC)
Mining Operations (10,12,13,14)
Food and Agriculture (02,07,20)
Wood Products (24,26)
Chemicals (28)
Petroleum Refining (29)
Mineral Products (32)
Metals (33)
Miscellaneous
Industrial Processes Total
Solid Waste Disposal
Miscellaneous
Total
1990 actual emissions (from Table 1)
1970 actual emissions (from Table 1)
Ratio of theoretical 1990 emissions to
actual 1990 emissions
Ratio of theoretical 1990 emissions to
actual 1970 emissions
5.4
1.6
1.1
8.1
4.2
1.5
1.1
0.3
0.7
2.5
1.2
0.0
11.5
0.3
1.2
23.1
7.5
18.5
3.08
1,24
23.5
2.7
0.7
26.8
0.4
0.0
0.3
0.8
1.5
0.8
2.8
0.0
6.5
0.0
0.0
34.3
21.2
28.3
1.62
1.21
8.6
3.3
0.6
12.5
0.0
0.0
0.0
0.3
0.2
0.2
0.0
0.0
0.7
0.1
0.3
27.5
19.6
18.5
1.40
1.49
0.0
0.1
0.7
0.9
0.0
0.2
0.0
2.0
1.0
0.0
0.2
6.4
9.8
0.6
2.7
35.9
18.7
25.0
1.92
1.44
0.3
0.7
6.5
7.5
0.0
0.0
1.2
2.8
2.4
0.0
2.6
0.0
9.1
1.7
8.6
142.3
60.1
101.4
2.37
1.40
0.7
9.3
0.0
10.0
0.2
0.0
0.0
0.1
0.0
0.3
15.0
0.2
15.8
2.8
0.0
233.6
7.1
203.8
32.90
1.15
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Table 8 shows the approximate effect of emission controls since 1970. It should be noted that to
some extent, source category activity levels, emission factors and control efficiency are interrelated.
For example, industrial modernization and changes in technology may affect emission factors and may
result in cleaner, more energy efficient operations. Also, changes in technology and economic growth
patterns may affect source category activity levels. In addition, some emissions may be voluntarily
reduced as a result of increased awareness of environmental issues. Therefore, the information
presented in Table 8 provides insight into the effect of emission controls, but does not account for
changes in activity levels and emission factors as a result of changes in technology, economy and other
factors.
5.1 Total Paniculate and PM-10
1940-1970
The estimated TP emissions for 1940,1950 and 1960 were 25 to 17 percent higher than in
1970. Even though industrial production levels and the quantities of fuels consumed were lower than
the post-1970 period, emissions were generally uncontrolled before 1970, resulting in greater
emissions. In 1940 and 1950, TP emissions from coal combustion by railroads and from forest wildfires
were significant. In 1940, for example, railroads contributed about one-tenth of the total national
emissions and forest fires contributed about the same.
A large portion of the TP emissions from stationary source fuel combustion resulted from the
combustion of coal. In 1940, coal was consumed mostly by the industrial and residential sectors.
Since 1940, residential coal use has declined substantially, resulting in a corresponding reduction in
emissions. Industrial coal use has also declined, but not to the same extent. Emission controls used
by industrial coal consumers have increased over the years and by 1970 emissions had decreased to
about half the 1940 level.
Coal combustion by electric utilities has increased from 46 teragrams (51 million tons) in 1940
to 291 teragrams (321 million tons) in 1970. This increase in consumption has resulted in increased
emissions from 1940 to 1970. Since 1970, TP emissions from electric utilities have decreased, despite
continued increases in coal consumption, as a result of installing air pollution control equipment.
TP emissions from industrial processes increased from 1940 through 1950, primarily as a result
of increased industrial production. From 1950 through 1970, industrial output continued to grow, but
installation of pollution control equipment more than offset the increase in production.
1970-1990
Since 1970, TP emissions have decreased substantially as a result of air pollution control
efforts. As shown in Table 8, without emission controls added since 1970, TP emissions would have
increased by 24 percent from 1970 to 1990. In reality, TP emissions decreased about 60 percent from
1970 to 1990. The 1990 TP emissions were about a third of the possible emissions had there been no
additional controls in place since 1970. Since 1970, industrial processes have contributed most of the
anthropogenic TP emissions followed by stationary source fuel combustion, transportation sources and
other sources.
In 1970, industrial processes contributed 57 percent of the total and in 1990, only 37 percent
indicating considerable progress in reducing emissions. TP emissions from industrial processes have
been reduced substantially due to installation of improved control equipment mandated by air pollution
control programs. Since 1970, actual emissions from industrial processes declined by 73 percent.
Tables B-13 (TP) and B-19 (PM-10) show estimated emissions for specific processes.
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In 1970, stationary source fuel combustion contributed 25 percent of the total, and in 1990,
contributed 23 percent. In 1990, 62 percent of the TP emissions from stationary fuel combustion
sources originated from wood burning, compared to 14 percent in 1970. Today, wood stoves, wood
furnaces and fireplaces in residential homes account for 91 percent of the TP emissions from wood
burning.
Coal combustion by electric utilities has increased from an estimated 321 million tons in 1970 to
771 million tons in 1990 while TP emissions from electric utilities have decreased. Installation of
improved control equipment is largely responsible for this reduction. New facilities constructed in the
1970s were required to meet New Source Performance Standards.
Comments on Particulate Emission Estimates
Particulate emission controls have been mostly effective in reducing emissions of large and
intermediate size particles. The long-term trend in emissions of small particles is not known because
only a few years of data are presently available. It is unlikely, however, that small particle emissions
(PM-10) have been reduced to the same extent that total particulate emissions have been reduced. It
should be noted that some small particles may form in the atmosphere through various chemical and
physical processes. These particles are not included in the TP emission estimates.
5.2 Sulfur Oxides
1940-1970
From 1940 to 1970, SOX emissions increased 61 percent as a result of increased consumption
of fossil fuels. By 1970, coal combustion accounted for 82 percent of total SOX emissions from all
stationary fuel combustion sources. Emissions from industrial processes also increased, but to a lesser
extent. SOX emissions from other sources decreased, primarily as a result of the obsolescence of
coal-fired locomotives and less coal refuse burning.
1970- 1990
Since 1970, total SOX emissions have declined about 25 percent as a result of the use of
cleaner fuels with lower sulfur content, the use of flue gas desulfurization systems at some power
plants, and the increased use of emission control devices by industry. In particular, SOX emissions
have been sharply reduced at nonferrous smelters. By-product recovery of sulfuric acid at these
smelters has increased since 1970 resulting in recovered sulfuric acid not being emitted in the form of
SOX. In addition, new sulfuric acid manufacturing plants have been subject to New Source
Performance Standards since 1972. As new plants are built or modified, they must achieve more
stringent emission controls.
As shown in Figure 3, eledric utilities account for most of the total SOX emissions. From 1970
to 1990, coal consumption by electric utilities more than doubled, but total emissions decreased slightly
as a result of coal cleaning and blending with lower sulfur coal. Flue gas desulfurization systems have
been installed at new plants since the late 1970s and have been retrofitted on many existing plants.
These systems have substantially reduced emissions compared to what they otherwise might have
been. SOX emissions from other fuel combustion sectors have also generally decreased, primarily due
to less coal burning by industrial, commercial and residential consumers.
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The theoretical 1990 national emission estimates shown in Table 8 for stationary fuel
combustion sources are based on 1990 fuel consumption, fuel sulfur contents that represent 1970
average levels for fuel oil and an estimated average sulfur content of coal that would have been
consumed if there were no changes in air pollution regulations since 1970. It is estimated that the
average sulfur content of coal burned nationwide would have declined even without new air pollution
regulations due to the greater use of cleaner coal from the Western U.S., which generally has a lower
sulfur content than coal from the Eastern U.S. At the 1970 level of control, electric utility emissions
would have increased about 49 percent since 1970. In reality, electric utility SOX emissions decreased
by 10 percent from 1970 to 1990.
Comments on SOV Emission Estimates
SOX emissions have been identified as precursors of acidic precipitation and deposition. To
support Federal research activities on this subject, more detailed historical emissions estimates of SOX
have been developed. Interested readers may wish to review Reference 32, which contains state-level
estimates of SOX and NO, emissions from 1900 through 1980 and by source category together with
historic fuel consumption data.
5.3 Nitrogen Oxides
1940-1970
NOX emissions are emitted mostly by stationary fuel combustion sources and by motor vehicles.
From 1940 through 1970, NOX emissions increased steadily as a result of increased natural gas
combustion and an increase in gasoline consumption.
1970- 1990
Table 8 shows that with the 1970 control level, national NOX emissions would have been 40
percent greater than actual 1990 emissions. For electric utilities, New Source Performance Standards
have helped reduce the growth in NOX emissions even though NOX emissions from electric utilities
increased 66 percent from 1970 to 1990. For mobile sources, NOX emissions have been controlled as
a result of the Federal Motor Vehicle Control Program. Without this program, NOX emissions from
highway vehicles may have more than doubled. In reality, NOX emissions from highway vehicles
decreased 11 percent from 1970 to 1990.
5.4 Non-methane Volatile Organic Compounds
1940- 1970
From 1940 through 1970, non-methane VOC emissions increased about 65 percent. Major
increases in vehicular travel and industrial production were mostly responsible for this increase. Total
VOC emissions from transportation sources almost doubled from 1940 to 1970. In 1940, residential
fuel combustion and forest fires accounted for 32 percent of total national VOC emissions, but by 1970
their contribution had decreased to 4 percent.
1970- 1990
Since 1970, total national VOC emissions have decreased as a result of motor vehicle emission
controls and less open burning of solid waste. VOC emissions from gasoline and diesel powered
highway vehicles decreased 44 percent from 1970 to 1990. Table 8 presents the theoretical 1990
emissions assuming 1970 levels of control.
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Total national VOC emissions also have decreased since 1970 due to the substitution of water-
based emulsified asphalts for asphalts liquified with petroleum distillates. This reduction is reflected in
the decreased emissions reported for miscellaneous organic solvent use. Some of this decrease has
been partially offset by increases in industrial process emissions.
In the early 1970s, VOC emissions from industrial processes would have increased due to
higher production levels, particularly in petroleum refining, organic chemical production, and industrial
uses of organic solvents. Emission control devices and process changes have helped limit the growth
in emissions. Through the mid-1970s, emissions from petroleum product storage and marketing
operations actually increased as a result of increased demand for petroleum products, especially motor
gasoline. Since 1978, emissions from these sources have decreased as the result of more effective
control measures.
Comments on Non-methane VOC Emission Estimates
VOC and NOX are principal components in atmospheric chemical and physical reactions that
form ozone and other photochemical oxidants. VOC species that contribute mostly to the formation of
ozone are included in the total VOC emission estimates. Nonreactive compounds such as methane are
not included. Biogenic sources of organic compounds, such as trees and other vegetation, are also not
included at the present time. VOC from natural sources appears to exceed the amount of
anthropogenic emissions according to recent research, but the extent to which biogenic sources
contribute to oxidant formation has not been clearly established.
Historic emissions of non-methane VOC from anthropogenic sources have been estimated by
state from 1900 to 1985 in support of Federal research activities under NAPAP33, and by source
category.
5.5 Carbon Monoxide
1940-1970
In 1940, highway vehicles contributed about 27 percent of CO emissions while residential
combustion of fuel, forest fires, and miscellaneous burning contributed about 50 percent of the total CO
emissions. From 1940 through 1970, emissions from all types of highway vehicles combined nearly
tripled.
By 1970, highway vehicles accounted for 64 percent of the total CO emissions. Emissions from
industrial processes increased from 1940 to 1970 by about 35 percent. The largest increase occurred
in the petroleum refining sector, primarily as a result of increased refinery throughput to meet increased
demand for gasoline and other distillate products.
1970 - 1990
Since 1970, highway vehicles have been the largest single contributing source of CO
emissions. Figure 6 shows how the emissions from major highway vehicle subcategories have
changed. The implementation of the Federal Motor Vehicle Control Program has helped reduce CO
emissions since the early 1970s.
From 1970 through 1980, total vehicle miles travelled increased 36 percent, but because of
controls on new vehicles, total CO emissions from highway vehicles actually decreased 25 percent.
From 1980 through 1990 vehicle miles travelled increased about 35 percent, but as a result of pollution
controls and the disappearance of older uncontrolled vehicles, CO emissions from highway vehicles
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actually decreased 38 percent during this period. Without the implementation of vehicle emission
controls, CO emissions from highway vehicles would have increased more than threefold from 1970 to
1990.
CO emissions from stationary fuel combustion sources occur mainly in the residential sector.
These emissions decreased in the mid-1970s as residential consumers converted from fuel oil to natural
gas or electric heating. Part of this decrease has been offset by the increased use of residential wood
stoves and fireplaces. In 1990, residential wood combustion accounted for about 10 percent of total
national CO emissions.
CO emissions from other sources have also decreased. Emissions from solid waste disposal have
decreased as the result of regulating or prohibiting burning of solid waste in many areas of the country. CO
emissions from industrial processes have also declined since 1970 as a result of the obsolescence of
certain high-polluting processes such as the manufacture of carbon black by the channel process, and as a
result of installing more emission controls. Emissions from the burning of agricultural crop residues have
also decreased since 1970 as a result of less burning.
5.6 Lead
1970-1990
Total national lead emissions have also decreased sharply as a result of the Federal Motor Vehicle
Control Program. This program has resulted in the widespread use of catalytic converters on automobiles
to help reduce NOX, VOC, and CO emissions and the use of unleaded gasoline for vehicles with these
converters. From 1970 through 1975, gasoline consumption increased 16 percent, but because of the
decrease in the lead content of gasoline, lead emissions from highway vehicles decreased 24 percent.
From 1975 to 1990, the percent of unleaded gasoline sales increased from 13 to over 90 percent, and the
lead emissions from highway vehicles decreased about 99 percent (see Table A-6).
A major recent reduction in lead emissions occurred when the U.S. EPA required petroleum
refiners to lower the lead content of leaded gasoline to 0.5 grams per gallon in 1985 and 0.1 grams per
gallon in 1986. Previously, the lead content of leaded gasoline had been 1.1 grams per gallon or more.
In 1990, lead emissions from highway vehicles account for 29 percent of the total national lead
emissions. Industrial processes account for 31 percent of the total. Solid waste disposal accounts for an
additional 31 percent and stationary source fuel combustion accounts for the rest. These percentage
contributions are substantially different from the contribution in 1970 when highway vehicles accounted for
77 percent of the total.
6.0 NATIONAL EMISSION PROJECTIONS
Emission projections are important for examining the potential combined effect of the Clean Air Act
Amendments (CAAA) of 1990 and expected changes in the national economy and resulting pollution
generating activity. Projections have been made for the years 2000 and 2010 using currently available
information. The current emission projections for SOX, NOX, VOC and CO are described below together
with basic assumptions.
The projections for each pollutant show a decrease in total national emissions from 1990 to 2000.
The decreases are a result of the expected effect of the CAAA which imposes mandatory emission
reductions on a broad range of source categories. These mandatory reductions are expected to more than
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offset increases due to assumed economic growth. Implementation by States of discretionary measures
needed to meet ambient standards or progress requirements for VOC are accounted for.
In order to project emission trends it is necessary to predict economic growth, industrial activity,
fuel consumption and other factors. Therefore future trends are speculative and there may be a
significant level of uncertainty associated with them. Projected emission estimates will be updated
periodically using the most recent information on actual activity by each source category. As new
information becomes available emission trends will be updated and emission projections will be
recalculated.
6.1 Future Trends in Sulfur Oxide Emissions
Table 9 presents the current estimates of future total national SOX emissions, and SOX
emissions from electric utilities and other sources. The expected emission trends are shown in Figure
17. The estimated electric utility emissions are based on a model (AIRCOST-PC) which simulates
emissions according to current arid future emission standards and controls, electric utility generation
capacity and future demand for electricity.34 Electricity generation forecasts were obtained from the
U.S. Department of Energy.35 Nonutility SOX emissions are based on the 1985 NAPAP emission
inventory and earnings projections by source category as reported by the Bureau of Economic
Analysis36 and the estimated rate of retirement of existing sources.
Future SOX emissions will be significantly affected by the CAAA of 1990 with a projected
reduction of 10 million short tons (approximately 9.1 teragrams) from the 1980 emission level to be
achieved by 2010. SOX emissions from electric utilities will be subject to mandated reductions as part
of a two phase program beginning in 1995. While the second phase of mandated reductions begins in
2000, the effect of various special phase-in provisions will result in higher emissions in the early 2000s,
until by 2010 total allowable sulfur dioxide will be 8.9 million tons (approximately 8.1 teragrams). The
acid rain title limits the total allowable tons of sulfur dioxide from the utility sector but leaves plant by
plant compliance decisions to the industry. That is, acid rain control amendments will be implemented
using a market-based emissions allowance trading system which allows utility managers to decide
which combination of pollution control equipment, low sulfur fuel, energy conservation, emissions
dispatching and emissions allowances they feel is suitable to ensure compliance with the primary
prohibition against emitting sulfur dioxide in excess of the number of allowances held.
SOX emissions from nonutility point sources have declined from 1980 levels due to reduced
activity in steel production, nonferrous smelting and other heavy industrial processes which historically
were major sources. Emission reductions in the CAAA were based on the assumption that net
emission reductions, which occurred between 1980 and 1985, would not be offset by growth in future
years. The projections presented here are based on that assumption. Because of the uncertainty
associated with the emissions from these and other sources, the EPA will conduct a study of future
industrial SOX emissions.
Further reductions in SOX emissions are expected after 1990 as a result of motor vehicle diesel
fuel being limited to 0.05 percent sulfur (by weight). This limit is expected to produce about an 80
percent reduction in emissions per diesel-powered vehicle. Some of this reduction may be offset by the
expected increase in diesel fuel consumption over the next 10 to 20 years.
44
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TABLE 9. TOTAL NATIONAL SULFUR OXIDE EMISSIONS, 1980 TO 2010
(Teragrams/Year)
Electric Utilities
Nonutility, Point Sources
Other Sources
Total
1980
15.5
6.2
1.7
23.4
1990
14.2
5.4
1.6
21.2
2000
8.5
4.9
1.4
14.8
2010
8.1
5.1
1.1
14.3
J~ Other Sources
L Nonutility,
[ Point Sources
45
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6.2 Future Trends in Nitrogen Oxide Emissions
Table 10 presents the current estimates of future total NOX emissions and NOX emissions from
highway vehicles, industrial sources, electric utilities and all other sources. These expected emission
trends are shown in Figure 18. The projections account for the expected net effect of all provisions of
the CAM concerning NOX. These include the NOX emission limits prescribed for utility boilers under
the acid rain provisions, the Tier I automobile tailpipe standards, and application of technology based
requirements to nonutility boilers (generally greater than 100 tons/year) in ozone nonattainment areas
and the Northeast Ozone Transport Region. The estimates do not fully incorporate new source review
requirements such as offsets and lowest achievable emission rates in nonattainment areas, nor
additional controls required based on attainment demonstration modeling. They also do not attempt to
estimate the extent to which any areas might be exempted from NOX stationary source controls under
Section 182(f).
Projections of NOX emissions from highway vehicles are based on projected vehicle miles
travelled and MOBILE4.1 emission factors. These emission factors reflect current emission control
standards and Tier I motor vehicle emission standards of the CAAA. (Tier II standards are not reflected
because these are discretionary.) As a result of these standards, NOX emissions from highway vehicles
are expected to decrease by almost 50 percent from 1990 to 2000.
By 2000, all electric utility units with capacities greater than 25 megawatts are expected to meet
new emission limits imposed by the CAAA. Also, new or modified electric power units will be subject to
revised performance standards. As a result, NOX emissions from electric utilities are expected to
decrease by 16 percent in the next ten years. The analysis for utilities was performed under the
assumption that low NOX combustion technology would be employed to meet the NOX provisions of Title
IV. The 6.1 teragram estimate for electric utilities in 2000 is approximately 1.8 teragrams (2 million
short tons) less than what would have been emitted by utilities without controls implemented as a result
of the CAAA of 1990.
Estimates of future NOX emissions from industrial sources are based on state-level growth
factors and the expected application of reasonable available control technology where required. As a
result, a 10 percent reduction is expected in NOX emissions from industrial sources from 1990 to 2000.
This reduction may be more than offset by increases in emissions between 2000 and 2010. The future
trend of stationary source NOX emissions is presently uncertain because it is not known whether ozone
nonattainment areas will be exempt from the proposed new source review policy that requires lowest
achievable emission reductions and offsets for new major sources.
TABLE 10. TOTAL NATIONAL NITROGEN OXIDE EMISSIONS, 1980 TO 2010
(Teragrams/Year)
1980 1990 2000 2010
Electric Utilities 6.4 7.3 6.1 7.4
Industrial Sources * 3.8 3.9 3.5 4.1
Highway Vehicles 7.9 5.6 3.0 2.9
Other 2.8 2.8 3.0 3.2
Total 20.9 19.6 15.6 17.6
* Includes industrial fuel combustion and processes.
46
-------
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T Highway
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1980
1990
2000
2010
6.3 Future Trends in Non-methane Volatile Organic Compound Emissions
Table 11 presents the current estimates of future total national VOC emissions and VOC
emissions from highway vehicles. The expected emission trends are shown in Figure 19. These
estimates are also based on the Emission Reduction and Cost Analysis Model (ERCAM)37 which has
been used to analyze costs and benefits of the nonattainment and motor vehicle provisions in the
CAAA of 1990 in addition to projecting NOX emissions. The estimates are based on presumed growth
rates in population, industrial activity, and vehicle miles travelled. It is assumed that mandatory
emission control measures specified in the CAAA, such as tailpipe emission standards and prescribed
emission controls for point sources, will be implemented. It is also assumed that states will meet the
minimum emission control requirements and reductions as specified by the CAM in order to meet the
National Ambient Air Quality Standards for ozone. In reality, states may exceed the minimum
requirements, and therefore, future emissions may be overestimated.
Table 11 shows a 27 percent decrease in total national VOC emissions from 1990 to 2000.
This decrease is largely due to an expected 65 percent reduction in emissions from highway vehicles
as a result of continued fleet turnover and additional emission controls despite an expected 25 percent
increase in total vehicle miles travelled over this time period.
47
-------
From 2000 to 2010, the estimates are substantially more uncertain, but currently indicate that
total emissions will remain stable. Growth and development in attainment areas (areas meeting the
National Ambient Air Quality Standards for ozone), is expected to result in increased emissions. This
increase is expected to offset continued declines in nonattainment area emissions, especially those
where additional reductions will be needed after 2000.
TABLE 11. TOTAL NATIONAL NON-METHANE VOLATILE ORGANIC COMPOUND EMISSIONS,
1980 TO 2010
(Teragrams/Year)
Highway Vehicles
All Other Sources
Total
1980
7.7
14.9
22.6
1990
5.1
13.6
18.7
2000
1.6
11.6
13.2
2010
1.6
11.6
13.2
19* Projected Trer$ In NON-METHANE
48
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6.4 Future Trends in Carbon Monoxide Emissions
Table 12 presents the current estimates of future total national CO emissions and CO
emissions from highway vehicles. The expected emission trends are shown in Figure 20. These
estimates are also based on ERCAM. The projections show a 43 percent decrease by the year 2000 in
total CO emissions from highway vehicles as a result of continued fleet turnover and new measures
such as enhanced automobile inspection and maintenance programs, and the expected use of
oxygenated fuels in CO nonattainment areas.
TABLE 12. TOTAL NATIONAL CARBON MONOXIDE EMISSIONS, 1980 TO 2010
(Teragrams/Year)
Highway Vehicles
All Other Sources
Total
1980
48.7
30.9
79.6
1990
30.3
29.8
60.1
2000
17.1
25.8
42.9
2010
19.8
25.6
45.4
49
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7.0 SEASONAL EMISSION PROJECTIONS
A comparison of peak ozone season VOC emissions and annual average VOC emissions is
shown in Table 13. The peak ozone season is generally the summer months (June, July and August)
when ambient temperatures are generally high and contribute to increased formation of ozone in the
lower atmosphere. The 1990 CAAA measure progress toward attaining the ozone National Ambient Air
Quality Standards in terms of decreases in peak ozone season VOC emissions. VOC emissions are a
principal precursor to ozone which is commonly referred to as smog. Table 13 shows the 1987 base
year emissions and projected emissions for the year 2000 and 2010. The 1987 base year was chosen
since it is the mid-point of the ambient ozone concentration data used to determine the nonattainment
status of different areas of the country.
Table 13 shows that on a daily basis, peak ozone season VOC emissions are greater than
annual average emissions. Evaporative VOC emissions from motor vehicles increase with temperature
producing emissions during the ozone season that are higher than annual average emissions.
Nonmotor vehicle VOC emissions are lower during the ozone season than average annual emissions
due to decreases in residential wood burning, which is typically associated with wintertime heating.
Projection year differences in total VOC emissions narrow with time as the contribution of motor vehicle
emissions decreases due to more stringent emission controls. Control measures expected to reduce
evaporative motor vehicle VOC emissions include the new Federal evaporative test procedure, less
volatile gasoline, enhanced inspection procedures, and new vehicle refueling controls.
Table 14 provides a comparison of peak ozone season and annual average NOX emissions.
Peak ozone season NOX emissions are lower than annual average emissions because motor vehicle
NOX emissions decrease with increasing temperature. This analysis does not attempt to capture
seasonal variations in point source emissions. Nonmotor vehicle emissions shown in Table 14
therefore are identical for ozone season and annual average days. While demand for electricity may
be higher in the summer than in other seasons, and can produce corresponding peaks in emissions
from electric utilities, these peak demand periods can vary significantly by day and by location. Thus,
the values shown in Table 14 should not be considered representative of emissions in any specific
area. There is no reason to expect that industrial NOX emissions will vary significantly by season on the
national level.
50
-------
Table 13
Comparison of Peak Ozone Season and Annual Average VOC Emissions
(Gigagrams/Day)
Motor Vehicles
All Other Sources
Total
Peak
1987
24.5
35.4
59.9
Ozone Season
2000
7.6
29.4
37.0
2010
7.3
29.7
37.0
Annual Average
1987
15.9
37.3
53.2
2000
4.3
31.8
36.1
2010
4.4
31.8
36.2
Table 14
Comparison of Peak Ozone Season and Annual Average NOX Emissions
(Gigagrams/Day)
Motor Vehicles
All Other Sources
Total
Peak Ozone Season
1987 2000 2010
14.9 7.8 7.4
36.5 34.5 40.3
51.4 42.3 47.7
Annual Average
1987 2000 2010
16.9 8.2 7.9
36.5 34.5 40.3
53.4 42.7 48.2
Notes: The 1987 emission estimates are based on National Air Pollutant Emission Estimates 1940-
1989, EPA-450/4-91-004, March 1991. These estimates were adjusted to reflect peak ozone
season (generally June through August) conditions.
The projection year VOC emissions are from ERCAM-VOC model results. These results are
based on a September, 1991 analysis of the 1990 CAAA.
The projection year NOX emissions are from a September, 1991 analysis of the 1990 CAAA.
* Emission estimates for the years 2000 and 2010 reflect additional reductions needed for areas
to meet estimated 3 percent reductions or attainment targets. More reductions may be needed.
Some may come from NOX after 1996.
51
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8.0 REFERENCES
1. AIRS Facility Subsystem. National Air Data Branch, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC. March 1991.
2. Compilation Of Air Pollutant Emission Factors, Fourth Edition, and Supplements, AP-42. U.S.
Environmental Protection Agency, Research Triangle Park, NC.
3. User's Guide to MOBILE4 (Mobile Source Emissions Model). EPA-AA-TEB-89-01. Office of
Mobile Source, U.S. Environmental Protection Agency, Ann Arbor, Michigan. February 1989.
4. Standard Computer Retrievals from the National Emissions Data System (NEDS). Unpublished
computer report available from National Air Data Branch, Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency, Research Triangle Park, NC.
5. The 1985 NAPAP Emissions Inventory (Version 2): Development of the Annual Data and
Modeler's Tapes. EPA-600/7-89-012a. U.S. Environmental Protection Agency, Cincinnati, OH.
November 1989.
6. Feasibility of Including Regional and Temporal VOC Emissions Estimates in the EPA Emissions
Trends Report. EPA-450/4-91-005a. U.S. Environmental Protection Agency, Research
Triangle Park, NC. September 1990.
7. Annual Book of ASTM Standards (Section 5: "Petroleum Products, Lubricants, and Fossil
Fuels"; Volume 05:01: Petroleum Products and Lubricants (1)). D56-D1947. American Society
for Testing and Materials, Philadelphia, PA. 1988
8. Highway Statistics. Federal Highway Administration, U.S. Department of Transportation,
Washington, DC. Annual.
9. Minerals Yearbook. Bureau of Mines, U.S. Department of the Interior, Washington, DC.
Annual.
10. Petroleum Supply Annual. Energy Information Administration, U.S. Department of Energy,
Washington, DC. Annual.
11. FAA Air Traffic Activity. Federal Aviation Administration, U.S. Department of Transportation,
Washington, DC. Annual.
12. Petroleum Marketing Monthly. Energy Information Administration, U.S. Department of Energy,
Washington, DC. Monthly.
13. Coal Distribution January-December. Energy Information Administration, U.S. Department of
Energy, Washington, DC. Annual.
14. Exhaust Emissions from Uncontrolled Vehicles and Related Equipment Using Internal
Combustion Engines. EPA Contract No. EHS 70-108. Southwest Research Institute, San
Antonio, TX. October 1973.
52
-------
15. Electric Power Annual. Energy Information Administration, U.S. Department of Energy,
Washington, DC. Annual.
16. Cost and Quality of Fuels for Electric Utility Plants. Energy Information Administration, U.S.
Department of Energy, Washington, D.C. Annual.
17. Natural Gas Annual. Energy Information Administration, U.S. Department of Energy,
Washington, DC. Annual.
18. Estimates of U.S. Wood Energy Consumption from 1949 to 1981. DOE/EIA-0341. U.S.
Department of Energy, Washington, DC. August 1982.
19. Estimates of U.S. Wood Energy Consumption 1980-1983. DOE/EIA-0341 (83). U.S.
Department of Energy, Washington, DC. November 1984.
20. Quarterly Coal Report. Energy Information Administration, U.S. Department of Energy,
Washington, DC. Quarterly.
21. Current Industrial Reports. Bureau of the Census, U.S. Department of Commerce, Washington,
DC. Annual.
22. Particulate Pollutant Systems Study. National Air Pollution Control Administration Contract No.
CPA 22-69-104. Midwest Research Institute, Kansas City, MO. May 1971.
23. End Uses of Solvents Containing Volatile Organic Compounds. EPA-450/3-79-032. U.S.
Environmental Protection Agency, Research Triangle Park, NC. May 1979.
24. Synthetic Organic Chemicals, United States Production Sales. United States International
Trade Commission, Washington, DC 20436. Annual.
25. 1968 National Survey of Community Solid Waste Practices. PHS Publication No. 1867. Public
Health Service, U.S. Department of Health, Education, and Welfare, Cincinnati, OH. 1968.
26. Emissions Inventory from Forest Wildfires, Forest Managed Burns, and Agricultural Burns.
EPA-450/3-74-062. U.S. Environmental Protection Agency, Research Triangle Park, NC.
November 1974.
27. Coal Refuse Fires, An Environmental Hazard. Information Circular 8515. Bureau of Mines,
U.S. Department of the Interior, Washington, DC. 1971.
28. Statistical Abstract of the United States. Bureau of the Census, U.S. Department of Commerce,
Washington, DC. Annual.
29. Chemical and Engineering News, Facts and Figures Issue. American Chemical Society,
Washington, DC. Annual.
30. Feasibility of Including Fugitive PM-10 Emissions Estimates in the EPA Emissions Trends
Report. EPA-450/4-91-005b. U.S. Environmental Protection Agency, Research Triangle Park,
NC. September 1990.
53
-------
31. A.L William and G.J. Stensland, Uncertainties in Emission Factor Estimates of Dust from
Unpaved Roads. Paper No. 89-24.6, Annual Meeting of the Air and Waste Management
Association, Anaheim, CA. June 1989.
32. Historic Emissions of Sulfur and Nitrogen Oxides in the United States from 1900 to 1980.
EPA-600/7-85-009a and b. U.S. Environmental Protection Agency, Cincinnati, OH. April 1985.
33. Historic Emissions of Volatile Organic Compounds in the United States from 1900 to 1985.
EPA-600/7-88-008a. U.S. Environmental Protection Agency, Cincinnati, OH. May 1988.
34. AIRCOST/PC - Installation and Operating Instructions. E.H. Pechan & Associates, Inc.,
Springfield, VA. November 1988.
35. Annual Outlook for U.S. Electric Power, 1991-Projections Through 2010. Energy Information
Administration, U.S. Department of Energy, Washington, DC. July 1991.
36. Regional Projections to 2040, Volume 1: States. Bureau of Economic Analysis, U.S.
Department of Commerce, Washington, DC. June 1990.
37. ERCAM-VOC: Description and Application. E.H. Pechan & Associates, Inc., Springfield, VA.
March 1989.
54
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APPENDIX A - NATIONAL EMISSIONS BY SOURCE CATEGORY
55
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61
-------
TABLE A-7. NATIONAL EMISSIONS ESTIMATES
OFPM-10
(Teragrams/Year)
Source Category
Transportation
Highway Vehicles
Aircraft
Railroads
Vessels
Other Off Highway
Transportation Total
1985 1986 1987 1988 1989 1990
1.1
1.1
1.3 1.3
1.1 1.176
1.3
1.4
1.2
1.5
1.2
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
0.1
0.0
0.0
0.1
1.5
Stationary Source Fuel Combustion
Electric Utilities
Industrial
Commercial-Institutional
Residential
0.0 0.0 0.0 0.0
0.1
0.0
1.0
0.1
0.0
1.0
0.1
0.0
1.0
0.1
0.0
1.0
0.0 0.0
0.1
0.0
1.0
0.1
0.0
1.0
Fuel Combustion Total
1.1
1.1
1.1
1.1
1.1
1.1
Industrial Processes
2.7 2.5 2.4 2.6 2.6 2.7
Solid Waste Disposal
Incineration
Open Burning
Solid Waste Total
0.1
0.2
0.0
0.2
0.3 0.2
0.0
0.2
0.2
0.0
0.2
0.2
0.0
0.2
0.2
0.0
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0.2
Miscellaneous
Forest Fires
Other Burning
Miscellaneous Organic Solvent
Miscellaneous Total
0.6
0.1
0.0
0.7
0.5
0.1
0.0
0.6
0.1
0.0
0.5 0.7
0.9
0.1
0.0
1.0
0.6
0.1
0.0
0.8
0.1
0.0
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Total of All Sources
6.0 5.6 5.8 6.3 6.1 6.4
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal total due to
rounding.
62
-------
APPENDIX B - NATIONAL EMISSIONS BY SUBCATEGORY
63
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68
-------
TABLE B-6. EMISSIONS OFPM-10
FROM TRANSPORTATION SOURCES
(Gigagrams/Year)
Source Category 1985 1986 1987 1988 1989 1990
Highway Vehicles
Gasoline-powered
Passenger cars 506 514 536 566 590 596
Lighttrucks-1 96 106 117 121 127 128
Light trucks-2 62 61 63 66 69 70
Heavy duty vehicles 46 40 40 44 46 47
Motorcycles 334444
Total - Gasoline 714 725 759 801 835 844
Diesel-powered
Passenger cars 19 18 16 13 11 11
Lighttrucks 433444
Heavy duty vehicles 340 313 323 358 367 369
Total-Diesel 363 334 342 375 382 384
Highway Vehicle Total 1,076 1,059 1,101 1,176 1,218 1,228
Aircraft 75 80 77 77 79 78
Railroads 37 35 36 37 37 32
Vessels 16 16 17 17 17 17
Farm Machinery 69 71 67 76 69 72
Construction Machinery 19 21 19 21 20 21
Industrial Machinery 14 13 13 13 17 12
Other Off-highway Vehicles 444443
Transportation Total 1,309 1,300 1,334 1,422 1,461 1,464
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal
total due to rounding.
69
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EMISSIONS OF NITROGEN OXIDES
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(Gigagrams/Year)
1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
4,820 5,150 5,250 5,200 5,410 5,710 5,932 5,823 6,066 6,332 6,429 6,416
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TABLEB-12. EMISSIONS OF PM-10
FROM FUEL COMBUSTION SOURCES
(Gigagrams/Year)
Source Category 1985 1986 1987 1988 1989 1990
Coal
Electric Utilities 000000
Industrial 000000
Commercial-Institutional 000000
Residential 111111
Coal Total 211111
Fuel Oil
Electric Utilities 19 28 23 29 30 30
Industrial 16 18 17 14 13 11
Commercial-Institutional 8 9 9 10 8 8
Residential 344555
Fuel Oil Total 47 58 54 58 57 54
Natural Gas
Electric Utilities 444444
Industrial 16 15 15 18 18 18
Commercial-Institutional 222222
Residential 666666
Natural Gas Total 27 26 26 29 30 30
Wood
Industrial 55 52 62 80 88 88
Residential 993 1,002 997 997 1,026 985
Wood Total 1,048 1,054 1,059 1,077 1,114 1,073
Other Fuels
Industrial 7 8 8 9 10 10
Residential 211111
Other Fuels Total 9 9 9 10 11 11
Fuel Combustion Total 1,132 1,149 1,149 1,176 1,214 1,168
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal
total due to rounding.
75
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TABLE B-19. EMISSIONS OF PM-10 FROM
INDUSTRIAL PROCESSES
(Gigagrams/Year)
Source Category
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
1985 1986 1987 1988 1989 1990
13
9
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231
455
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12
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117
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46
64
4
58
92
92
90
19
124
14
213
12
89
6
98
10
35
51
30
390
21
0
130
312
477
46
56
3
45
98
94
95
17
133
13
196
12
90
7
103
9
38
54
30
346
20
0
128
321
578
45
55
4
44
98
105
97
17
127
14
213
11
93
6
117
9
40
54
31
353
19
0
153
336
574
46
46
6
46
96
82
101
17
125
14
215
10
92
5
116
13
46
54
36
353
19
0
149
332
603
49
48
7
80
104
84
103
18
133
13
216
11
100
6
116
11
47
54
37
364
2,660 2,468 2,425 2,580 2,601 2,703
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal
total due to rounding. Numbers in brackets are Standard Industrial Codes.
82
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TABLE B-20. NATIONAL SUMMARY OF FUGITIVE
DUST PM-10 EMISSIONS, 1985-1990
(Teragrams/Year)
Source Category 1985 1986 1987 1988 1989 1990
Agricultural Tilling 6.2 6.3 6.4 6.4 6.3 6.3
Construction 11.5 10.7 11.0 10.6 10.2 9.1
Mining and Quarrying 0.3 0.3 0.3 0.3 0.3 0.3
Paved Roads 5.9 6.1 6.5 6.9 7.0 7.2
Unpaved Roads 13.3 13.3 12.7 14.2 13.9 14.1
Wind Erosion 3.2 8.5 1.3 15.9 10.7 3.8
Total 40.5 45.3 38.1 54.3 48.5 40.8
Note: 1990 emission estimates are preliminary. The sums of subcategories may not equal
total due to rounding.
83
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APPENDIX C - REGIONAL EMISSIONS
84
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TABLE C-1. REGIONAL EMISSIONS ESTIMATES
OF TOTAL PARTICULATE MATTER
(Teragrams/Year)
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
Total
1985
0.2
0.3
0.7
1.5
1.7
0.8
0.6
0.4
0.8
0.5
7.2
1986
0.2
0.2
0.7
1.4
1.6
0.7
0.5
0.3
0.7
0.4
6.7
1987
0.2
0.3
0.7
1.4
1.6
0.7
0.5
0.3
0.8
0.5
6.9
1988
0.2
0.3
0.7
1.5
1.7
0.7
0.6
0.6
0.7
0.5
7.5
1989
0.2
0.3
0.7
1.5
1.7
0.7
0.6
0.4
0.7
0.4
7.2
1990
0.2
0.3
0.7
1.4
1.7
0.7
0.5
0.4
0.7
0.9
7.5
Note: 1990 emission estimates are preliminary.
TABLE C-2. REGIONAL EMISSIONS ESTIMATES
OF SULFUR OXIDES
(Teragrams/Year)
Region
I
II
III
IV
V
VI
VII
VIII
IX
X
Total
1985
0.5
0.6
2.4
4.2
4.9
3.8
1.5
1.7
1.4
0.2
21.1
1986
0.3
0.5
3.0
4.2
4.9
3.5
1.4
1.4
1.4
0.3
20.9
1987
0.3
0.5
2.9
4.1
4.8
3.5
1.4
1.4
1.2
0.3
20.5
1988
0.4
0.5
2.8
3.9
4.7
3.6
1.5
1.6
1.3
0.3
20.6
1989
0.3
0.5
2.9
4.0
4.8
3.7
1.5
1.6
1.2
0.3
20.8
1990
0.3
0.5
2.9
4.1
4.9
3.7
1.5
1.7
1.3
0.3
21.2
Note: 1990 emission estimates are preliminary.
85
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TABLE C-3. REGIONAL EMISSIONS ESTIMATES
OF NITROGEN OXIDES
(Teragrams/Year)
Region 1985 1986 1987 1988 1989 1990
I
II
III
IV
V
VI
VII
VIII
IX
X
0.6
1.0
2.0
3.7
3.8
4.3
1.4
1.3
1.1
0.7
0.6
0.9
2.2
3.6
3.6
4.0
1.2
1.1
1.0
0.9
0.6
0.9
2.2
3.6
3.6
4.2
1.2
1.2
1.0
0.9
0.6
0.9
2.2
3.6
3.7
4.3
1.4
1.3
1.1
1.0
0.6
0.9
2.2
3.6
3.7
4.3
1.3
1.3
1.1
1.0
0.5
0.8
2.1
3.5
3.6
4.3
1.3
1.3
1.1
1.1
Total 19.9 19.1 19.4 20.0 19.8 19.6
Note: 1990 emission estimates are preliminary.
TABLE C-4. REGIONAL EMISSIONS ESTIMATES
OF NON-METHANE VOLATILE
ORGANIC COMPOUNDS
(Teragrams/Year)
Region 1985 1986 1987 1988 1989 1990
I 0.6 0.5 0.5 0.5 0.5 0.5
II
III
IV
V
VI
VII
VIII
IX
X
0.9
2.0
2.7
3.6
3.5
0.8
2.6
2.1
1.2
0.9
1.9
2.6
3.4
3.3
0.8
2.3
2.1
1.2
0.9
1.9
2.6
3.4
3.3
0.8
2.4
2.2
1.2
0.9
1.8
2.6
3.4
3.4
0.9
2.5
2.1
1.3
0.8
1.8
2.5
3.2
3.3
0.8
2.2
2.1
1.2
0.8
1.8
2.5
3.2
3.3
0.7
2.2
2.0
1.7
Total 20.1 19.0 19.3 19.4 18.5 18.7
Note: 1990 emission estimates are preliminary.
86
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TABLE C-5. REGIONAL EMISSIONS ESTIMATES
OF CARBON MONOXIDE
(Teragrams/Year)
Region 1985 1986 1987 1988 1989 1990
I
II
III
IV
V
VI
VII
VIII
IX
X
3.2
4.8
6.6
14.1
12.9
10.2
3.9
3.9
4.8
4.4
3.1
4.5
6.4
13.1
12.3
9.0
3.5
3.1
4.1
4.0
3.0
4.4
6.5
12.9
12.2
8.8
3.4
3.0
4.9
4.2
2.8
4.2
6.0
12.8
12.0
8.7
4.0
5.3
4.5
4.4
2.8
4.1
5.9
12.8
11.6
8.7
3.7
3.1
4.3
3.6
2.6
3.8
5.5
11.4
11.1
7.9
2.9
3.0
4.2
7.6
Total 68.7 63.2 63.4 64.7 60.4 60.1
Note: 1990 emission estimates are preliminary.
TABLE C-6. REGIONAL EMISSIONS ESTIMATES
OF LEAD
(Gigagrams/Year)
Region 1985 1986 1987 1988 1989 1990
I
II
III
IV
V
VI
VII
VIII
IX
X
1.1
1.9
2.0
3.8
4.5
2.7
1.9
0.8
0.7
0.7
0.4
0.9
0.7
1.3
2.1
0.9
1.1
0.3
0.5
0.3
0.4
0.8
0.6
1.2
2.0
0.9
1.1
0.3
0.5
0.2
0.3
0.8
0.6
1.2
1.9
0.8
1.0
0.3
0.4
0.2
0.3
0.7
0.5
1.1
1.9
0.7
1.1
0.3
0.4
0.2
0.3
0.6
0.5
1.1
1.8
0.7
1.0
0.3
0.4
0.2
Total 20.1 8.4 8.0 7.6 7.2 7.1
Note: 1990 emission estimates are preliminary.
87
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TABLE C-7. REGIONAL EMISSIONS ESTIMATES
OF PM-10 FROM POINT AND
FUGITIVE PROCESS SOURCES
(Teragrams/Year)
Region 1985 1986 1987 1988 1989 1990
I
II
III
IV
V
VI
VII
VIII
IX
X
Total
Note: 1990 emission estimates are preliminary.
0.2
0.2
0.5
1.3
1.4
0.6
0.5
0.3
0.6
0.4
6.0
0.2
0.2
0.5
1.2
1.4
0.5
_ 0.5
0.2
0.6
0.4
5.6
0.2
0.2
0.6
1.2
1.4
0.5
0.4
0.2
0.6
0.4
5.8
0.2
0.2
0.6
1.3
1.5
0.6
0.5
0.5
0.6
0.4
6.3
0.2
0.2
0.6
1.3
1.5
0.6
0.5
0.3
0.6
0.3
6.1
0.2
0.2
0.6
1.2
1.5
0.6
0.5
0.3
0.6
0.7
6.4
TABLE C-8. REGIONAL EMISSIONS ESTIMATES
OF FUGITIVE DUST PM-10
(Teragrams/Year)
Region 1985 1986 1987 1988 1989 1990
I
IV
V
VI
VII
VIII
IX
X
Total 40.5 45.3 38.1 54.3 48.5 40.8
Note: 1990 emission estimates are preliminary.
1.4
2.2
2.2
5.7
7.1
8.2
4.5
3.2
4.1
2.0
1.3
2.0
2.1
5.6
6.8
14.1
4.6
2.8
4.1
1.9
1.3
2.0
2.2
5.9
6.8
7.7
3.9
2.9
3.5
2.0
1.3
1.7
2.2
6.2
6.7
20.2
6.6
3.8
3.6
1.8
1.1
1.7
2.1
6.2
6.3
17.3
5.7
3.0
3.3
1.9
1.0
1.4
1.9
6.1
6.0
11.5
5.2
2.9
2.9
1.9
88
-ftU.S. Government Printing Office ; 1992 - 312-014/40054
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