EPA-450/1-77-002
DECEMBER 1977
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1976
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U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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EPA-450/1-77-002
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1976
MONITORING AND DATA ANALYSIS DIVISION
MONITORING AND REPORTS BRANCH
U,S, ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF AIR AND WASTE MANAGEMENT
OFFICE OF AIR QUALITY PLANNING AND STANDARDS
MONITORING AND DATA ANALYSIS DIVISION.,
RESEARCH TRIANGLE PARK/ NORTH CAROLINA 27711
NOVEMBER 1977
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The Office of Air and Waste Management of the Environmental Protection Agency
would like to thank the EPA Regional Offices and the many state and local
agencies that have contributed to air quality data. Thanks also are extended
to the Environmental Monitoring and Support Laboratory, RTP, for providing
air quality data from the National Air Surveillance Network
This report has been reviewed by the Monitoring and Data Analysis Division,
Office of Air Quality Planning and Standards, Office of Air and Waste Manage-
ment, Environmental Protection Agency, and approved for publication. Mention
of trade names or commercial products does not constitute endorsement or
recommendation for use. Copies are available free of charge to Federal
employees, current contractors and grantees, and nonprofit organizations -
as supplies permit - from the Office of Library Services, Environmental
Protection Agency, Research Triangle Park, North Carolina 27711; or copies
may be purchased from the Superintendent of Documents, U.S. Government
Printing Office, Washington, D.C. 20460.
Publication No. EPA-450/1-77-002
ii
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, CONTENTS
Page
1. INTRODUCTION AND OVERVIEW 1
1.1 General Overview 1
1.2 Acknowledgement 4
1.3 References 4
2. FEWER PEOPLE EXPOSED TO ADVERSE AIR POLLUTION IN
MAJOR METROPOLITAN AREAS 5
2.1 Major Decrease in Population Exposed to High
Participate Levels in New York, Chicago and Denver 6
2.1.1 Major Decrease in Population Exposed to High
Particulate Levels in New York-New Jersey-
Connecticut Air Quality Control Region 7
2.1.1.1 Methodology 7
2.1.1.2 TSP Air Quality Pattern 11
2.1.1.3 Changes in Population Exposed 11
2.1.2 Major Decrease in Population Exposed to High
Particulate Levels in the City of Chicago 14
2.1.2.1 Methodology 14
2.1.2.2 TSP Air Quality Patterns 16
2.1.2.3 Changes in Population Exposed 19
2.1.3 Decrease in Population Exposed to High Particulate
Levels in the Metropolitan Denver Area 19
2.1.3.1 TSP Air Quality Pattern 23
2.1.3.2 Changes in Population Exposed 28
2.2 Metropolitan Los Angeles Shows Long-Term Improvement in
Population Exposed to High Photochemical Levels 28
2.2.1 Methodology 30
2.2.2 Changes in Population Exposed to Oxidants 33
2.2.3 Changes in Population Exposed to Nitrogen Dioxide 33
2.3 Acknowledgement --36
2.4 References-- --39
3. NATIONAL AND REGIONAL TRENDS IN CRITERIA POLLUTANTS 40
3.1 Trends in Total Suspended Particulate 41
3.1.1 Long-Term TSP Trends: 1970-1976- 41
3.1.2 Short-Term TSP Trends: 1975-1976 44
3.2 Trends in Sulfur Dioxide 53
3.3 Trends in Carbon Monoxide 55
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LIST OF TABLES v
Table Page
2.1 Number of People Living in Areas Exceeding National Ambient
Air Quality Standard for Total Suspended Particulate in New
York-New Jersey-Connecticut Air Quality Region in 1970, 1973
and 1976. -------------------------------------------------------- 15
2.2 Number of People Living in Areas Exceeding National Ambient
Air Quality Standard for Total Suspended Particulate in
Chicago in 1970 and 1976 ----------------------------------------- 21
2.3 Comparison of Average Number of Days with Poor Dispersion and
Average Number of Days Violating NAAQS for Oxidants -------------- 35
2.4 Comparison of Average Number of Days with Poor Dispersion and
Average Number of Days Violating the California 1-Hour Welfare
Standard of 470
3.1 Percent of Monitoring Sites Showing Indicated Trends in 90th
Percentile of 8-Hour Average CO Concentrations 1970-1976- ..... ---60
3.2 Oxidant/Ozone Trends in 90th Percentile of Annual Hourly
Observations 1970-1976- ..... ---- ..... ------- ........ - ...... ---- 64
3.3 Oxidant/Ozone Trends (1970-1976) By EPA Region ..... ......... 65
3.4 Nitrogen Dioxide Trends in Annual Arithmetric Mean 1970-1976 ----- 68
5.1 Summary of National Emission Estimates, 1970-1976 (10 Metric
tons/yr) --------------------------------------------------------- 76
5.2 Nationwide Emission Estimates, 1970 (106 metric tons/year) ------- '8
5.3 Nationwide Emission Estimates, 1971 (106 metric tons/year) ------- 79
5.4 Nationwide Emission Estimates, 1972 (106 metric tons/year) ------- 80
5.5 Nationwide Emission Estimates, 1973 (10^ metric tons/year) ------- 81
5.6 Nationwide Emission Estimates, 1974 (1Q6 metric tons/year) ------- 82
5.7 Nationwide Emission Estimates, 1975 (10 metric tons/year) ------- 83
5.8 Nationwide Emission Estimates, 1976 (106 metric tons/year) ------- 84
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Page
3.4 Trends in Photochemical Oxidants- 61
3.5 Trends in Nitrogen Dioxide-- 67
3.6 Acknowledgement-- 67
3.7 References--- 70
4. AIR QUALITY MAPS OF THE UNITED STATES 72
4.1 Total Suspended Participate Air Quality Map 72
4.2 Sulfur Dioxide Air Quality Map- 73
4.3 Photochemical Oxidant Air Quality Map 74
4.4 Acknowledgment 74
4.5 References 75
5. NATIONWIDE EMISSION ESTIMATES, 1970-1976 -76
5.1 Detailed Annual Emission Estimates 77
5.2 Emission Trends 84
5.3 Acknowledgement- 86
5.4 References 86
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LIST OF FIGURES
FIGURE PAGE
2-1 Population Pattern in 1970 for the New York-New Jersey-Connecticut
Air Quality Control Region 8
2-2 Location of 161 Total Suspended Particulate monitors in the New York-
New Jersey-Connecticut Air Quality Control Region 9
2-3 Network of artificial receptors points in the New York Study Area 10
2-4 Isopleth of annual geometric mean concentrations of Total Suspended
Particulate in 1970, 1973, 1976 12
2-5 Decrease in population exposed to Total Suspended Particulate in
New York-New Jersey-Connecticut Air Quality Control Region from
1970 to 1976 13
2-6 Population Pattern in 1970 for the city of Chicago 17
2-7 Locations of 161 Total Suspended Particulate monitors in the city
of Chicago 17
2-8 Network of receptor points in the city of Chicago 17
2-9 Annual Mean TSP in the city of Chicago, 1970,1976 18
2-10 Population exposure distribution for the city of Chicago 20
2-lla Metropolitan Denver study area --22
2-llb Population density pattern in Metropolitan Denver, in 1970 -24
2-12 Location of TSP monitors in Metropolitan Denvei -25
2-13 Receptor network in Metropolitan Denver area 26
2-14 Annual mean TSP in Metropolitan Denver, 1970 and 1975 27
2-15 Population exposure distribution for Denver, 1970 and 1975 29
2-16 Population density of Los Angeles Air Basin in 1970 31
2-17 Locations of Nitrogen Dioxide and Oxidant trend sites in Los
Angeles Air Basin 32
2-18 Standard demographic network for trend analysis in Los Angeles Basin--32
2-19 Percent of days on which NAAQS for Oxidant was exceeded during six
2-year periods 34
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FIGURE PAGE
2-20 Percent of days on which California 1-hour standard was exceeded
during six 2-year periods in Metropolitan Los Angeles 37
wr I
3-2
3-3
3-4
3-5
3-6
3-7
3-8
3-9
3-10
3-11
3-12
3-13
3-14
3-15
^unip i v. i i luj^i uuiun u i piu^uiny <-UIIVCII L 1 Ulli IUI UUA [J 1 U Ui - -
Trends of annual mean Total Suspended Parti cul ate concentrations from
1970 to 197fi at ? 350 ^amnlinn citpc:--
Trends of peak daily Total Suspended Particulate concentrations from
1970 tn 1 97fi at 9 15D <;amn1inn
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NATIONAL AIR QUALITY
AND
EMISSIONS TRENDS REPORT, 1976
1. INTRODUCTION AND OVERVIEW
1.1 GENERAL OVERVIEW
Long-term progress (1970-1976) can be seen in achieving compliance
with the National Ambient Air Quality Standards (NAAQS) nationally for
total suspended particulate, sulfur dioxide, and carbon monoxide, and
for photochemical oxidants in California. In the short-term, however,
some reversals have taken place for total suspended particulate with
many areas experiencing increases between 1975 and 1976. Where photo-
chemical oxidants are measured outside California, the trend appears
basically stable over the 1973-1976 period. Nitrogen dioxide trends are
stable in California; nationally, however, nitrogen dioxide levels tend
to be increasing based mostly on three years of data. There are still
insufficient data, however, to draw any definite conclusions on nitrogen
dioxide levels outside California.
Air quality progress is measured by comparing the ambient air
pollution levels with appropriate primary and secondary NAAQS for each
of the pollutants. Primary standards protect the public health, and
secondary standards protect the public welfare as measured by effects
of pollution on vegetation, materials and visibility. The standards
are further categorized for long- or short-term exposure. Long-term
standards specify an annual mean that may not be exceeded; short-term
standards specify upper limit values for 1-, 3-, 8-, or 24-hour averages
that may not be exceeded more than once per year.
Data for analysis in this report were obtained primarily from the
U.S. Environmental Protection Agency's National Aerometric Data Bank (NADB)
These data are gathered primarily from State and local air polluton control
agencies through their monitoring activities.
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This is the sixth report on air pollution trends issued by the
U.S. Environmental Protection Agency. The report updates the
population exposure analyses for the New York-New Jersey-Connecticut
Air Quality Control Region, accounting for 17 million people and the
c
Los Angeles Air Basin, accounting for 8 million people. Population
exposure analyses are also featured for the City of Chicago and
Metropolitan Denver. Changes in the population exposed to ozone
and nitrogen dioxide levels above the standard were stressed in the
Los Angeles study, while changes in the population exposed to total
suspended particulate levels above the NAAQS are examined in the other
cities.
A major feature of this report is the presentation of multi-color
air quality maps for total suspended particulate, sulfur dioxide, and
photochemical oxidants. These maps are included to respond to the often
asked question: "How does air quality vary across the United States?"
The major findings of these investigations are as follows:
1. The general long-term improvement in total suspended particulate
reversed itself between 1975 and 1976 with many areas experiencing
increases. The likely explanation for this phenomenon is
meteorological. Large areas of the country experienced droi ght
during 1976. These extremely dry soil conditions increased
the likelihood of wind-blown dust contributing to ambient
particulate levels.
2. A major decrease was observed in the population exposed to
high particulate levels in Metropolitan New York, Chicago,
and Denver. The greatest improvement occurred in the New York-
New Jersey-Connecticut Air Quality Control Region, where the
percentage of the population exposed to particulate levels
above the annual primary health standard decreased from
60 percent in 1970 to 0 percent in 1976. Similarly, Chicago
decreased from 100 percent in 1970 to 64 percent in 1976;
while Denver decreased from 83 percent in 1970 to 74 percent
in 1975.
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3. The long-term improvement in the Los Angeles Basin in the
percentage of days when the 1-hour oxidant standard was
violated, reversed itself in 1975 and 1976. People in
the Basin were exposed to a concentration above the standard
on an average of 176 days per year in 1965 and 1966, 105 days
per year in 1973 and 1974, and 112 days in 1975 and 1976.
This slight degradation over the last four years appears to
be due to an increase in the number of days with poor meteoro-
logical dispersion.
4. The early 1970's saw dramatic decreases in ambient sulfur
dioxide levels in the Nation's urbanized areas. Since then
national trends have been much more stable and violations of
the sulfur dioxide standard are generally confined to areas
around specific sulfur oxide sources. In contrast to TSP,
levels between 1975 and 1976 are relatively stable. Of the
722 sulfur dioxide trend sites, 11 percent increased, 12 percent
decreased and 76 percent remained stable between 1975 and 1976.
5. Approximately three-fourths of the 202 carbon monoxide trend sites
showed improvement. California sites had a slightly higher rate of
improvement; 7 percent per year in California versus 6 percenl per
year outside California for sites with four or more years of rata.
In 1976, 49 percent of the sites report their all-time-low 90'h
percentile values.
6. Photochemical oxidant ranks today as one of the most serious
and pervasive air pollution problems in this country. In
1975, 86 percent of the ozone sites reporting to the NADB
exceeded the NAAQS of 160 yg/m3. The California sites were
basically stable during the 1970-1976 period, while the
non-California sites show a slight tendency for increasing
patterns with 55 sites "up" and 46 sites "down."
7. Nitrogen dioxide trends are stable in California, but outside
of California there is a preponderence of increasing patterns
with twice as many sites showing "up" patterns than "down"
patterns (154 versus 77 sites). Since most of these sites
have only 3 years of data, there is still insufficient
historical data to draw any definite conclusions on nitrogen
dioxide trends outside California.
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1.2 ACKNOWLEDGMENT
The Monitoring and Data Analysis Division would like to acknowledge
William F. Hunt, Jr., for the overall management, coordination and
direction given in assembling this report.
1.3 REFERENCES FOR SECTION 1
1. The National Air Monitoring Program: Air Quality and Emissions
Trends - Annual Report, Volumes 1 and 2. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, N.C. Publication No. EPA-450/1-73-001 a
and b. July 1973.
2. Monitoring and Air Quality Trends Reports, 1972. U.S. Environ-
mental Protection Agency, Office of Air Quality Planning and
Standards. Research Triangle Park, N.C. Publication No.
EPA-450/1-73-004. December 1973.
3. Monitoring and Air Quality Trends Report, 1973. U.S. Environ-
mental Protection Agency, Office of Air Quality Planning and
Standards. Research Triangle Park, N.C. Publication No.
EPA-450/1-74-007. October 1974.
4. Monitoring and Air Quality Trends Report, 1974. U.S. Enviroi-
mental Protection Agency, Office of Air Quality Planning and
Standards. Research Triangle Park, N.C. Publication No.
EPA-450/1-76-001. February 1976.
5. National Air Quality and Emission Trends Report, 1975. U.S.
Environmental Protection Agency, Office of Air Quality Planning
and Standards. Research Triangle Park, N.C. Publication No.
EPA-450/1-76-002. November 1976.
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2. FEWER PEOPLE EXPOSED TO ADVERSE AIR POLLUTION
IN MAJOR METROPOLITAN AREAS
In the National Air Quality and Emissions Trends Report, 1975,
the trends in the population exposure were examined for two major
metropolitan areas - the New York-New Jersey-Connecticut Air Quality
Control Region (AQCR) and the Los Angeles Air Basin. In this report,
these analyses are extended through 1976, and population exposure
trends in Chicago and Denver are reported as well. The population
exposure analyses examine improvements in terms of decreases in the
numbers of people being exposed to pollutant levels above the National
Ambient Air Quality Standards (NAAQS). Because the purpose of primary
standards (health-related) is the protection of public health, these
studies have been undertaken, in cooperation with EPA's Regional
Offices, to measure the effectiveness of emission control plans in
reducing air pollution levels below the NAAQS. Both air quality data
and population data are factored into this "population exposure"
approach.
The change in population exposure to high particulate levels
was determined for the New York-New Jersey-Connecticut AQCR and the
cities of Chicago and Denver. Photochemical oxidants and nitrogen
dioxide were examined in the Los Angeles Basin. These areas were
selected because they are among the nation's largest metropolitan areas
and also have extensive air monitoring networks. The New York-New Jersey-
Connecticut AQCR accounts for 17 million people and has a total of 161
suspended particulate monitors, which provide sufficient historical data
to examine trends. Chicago accounts for 3.4 million people and has 16
sites with historical data; Denver has a population of 1 million and 19
sites for conducting trends. The Los Angeles Air Basin has a population
of 8 million people and has extensive oxidant and nitrogen dioxide
monitoring networks.
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For each metropolitan area, the time period analyzed was based
on availability and completeness of air quality data. In the population
studies related to particulate, the data for New York and Chicago were
sufficiently complete to permit examination of individual years. In
the Denver analysis, 3-year average periods were employed to make the
best use of available data. For the population study of oxidants and nitro-
gen dioxide in Los Angeles, a 12-year period could be examined because of
the long-term monitoring program in that city.
Meteorology is recognized to be an important factor affecting air
quality trends. Where possible, meteorological variables were included
to aid in the interpretation of the results.
The analyses required the merging of a local population and air
quality data to compute several measures of pollutant exposure. In
order to accomplish this task, 1970 population data for all areas were
"gridded" into a network of population receptor points; each point
represented a subset of the areas' total population. A spatial
2
interpolation procedure was then employed to estimate the air quality
at each population receptor point. This procedure yielded estimates of
population exposure for the total population by place of residence. The
progress in reducing both the number of people exposed and the frequency
of exposure to pollutant levels above the NAAQS levels are discussed in
the following section.
2.1 MAJOR DECREASE IN POPULATION EXPOSED TO HIGH PARTICULATE LEVELS
IN NEW YORK, CHICAGO AND DENVER
The greatest long-term improvement occurred in the New York-New Jersey-
Connecticut Air Quality Control Region, where the proportion of the
population exposed to concentrations in excess of the annual primary health
standard of 75 yg/m3 decreased from 66 percent to 0 between 1970 and 1976.
Considerable progress was also seen in Chicago; tne proportion of the
population exposed to TSP levels greater than the annual primary standard
fell from 100 percent in 1970 to 64 percent in 1976. In Denver, the per-
centage of the exposed population dropped from 83 percent in 1970 to 74
percent in 1975.
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2.1.1 Major Decrease In Population Exposed to High Participate Levels
in New York-New Jersey-Connecticut Air Quality Control Region
The change in number of people exposed to total suspended particu-
late (TSP) matter in the New York-New Jersey-Connecticut AQCR was
examined for the period from 1970 to 1976. Overall, significant progress
has been made in reducing population exposure to annual average TSP levels
within the AQCR. Switching to cleaner fuels and implementing particulate
control measures has reduced annual concentration levels by 30 percent.
This improvement means that no one lives in areas exposed to concentrations
in excess of the annual primary health standard of 75 yg/m3.
2.1.1.1 Methodology
Air quality data produced by the TSP monitoring network in the Tri-
State Region were examined, together with demographic statistics, to
determine the change in resident populations exposed to ambient air
pollution of various levels. In 1970, about 17 million people were
living in the study area. Population density in 1970 is depicted in
Figure 2-1. The most densely populated areas were found in the urban
core composed of most of New York City and parts of northeastern New
Jersey. TSP concentrations are generally the highest in these areas.
Figure 2-2 presents the locations of the 161 TSP monitors that
provided the air quality data for this analysis. Three years, 1970,
1973 and 1976 were selected to demonstrate the change in population
exposure over time. At least 107 monitoring sites produced a valid*
year of data in each of these years. TSP estimates for other sites
were obtained by considering the relative annual changes among all 161
TSP monitors during 1970-1976.
A network of 215 receptor points was used to interface the a.ir
quality and population data. Each receptor point represented a subset
of the total population, as well as subsets of the less mobile but
susceptible school-age and elderly populations. This network, displayed
in Figure 2-3, provides complete area coverage, with more detail afforded
densely populated areas. The TSP air quality of each grid point of the
*A valid year of data is based on a minimum of five 24-hour-average
values per calendar quarter.
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2000 7000
>7000
Figure 2-1. Population pattern in 1970 for New York - New Jersey - Connecticut Air Quality
Control Region.
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Figure 2-2. Location of 161 total suspended particulate monitors in the New York - New Jersey
Connecticut Air Quality Control Region.
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10
NEW YORK
NEW JERSEY
Figure 2-3. Network of artificial receptors points in the New York study area.
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11
network was estimated from the actual monitoring data by spatial
interpolation. The estimates of population and air quality were then
used to characterize the region.
2.1.1.2 TSP Air Quality Pattern
Isopleths of average TSP during 1970, 1973 and 1976 are shown -
Figure 2-4. In 1970, approximately 21 percent of the region had TSF
concentrations greater than the primary NAAQS. The affected areas
included New York City and adjacent populated parts of New Jersey,
New York State and Connecticut. At the same time, 51 percent of the
land area exhibited TSP concentrations over the secondary TSP "welfare"
standard of 60 yg/m3.
By 1973, substantial reductions in TSP could be seen. The land
area exposed to concentrations in excess of the annual primary standard
has been reduced to 2 percent of the Air Quality Control Region. The
affected areas were mostly in the central portion of the region con-
sisting of parts of New York City and adjacent New Jersey. The area
with concentrations above the secondary standard was also reduced; the
affected area constituted about 15 percent of the AQCR.
In 1976, only one TSP monitoring site in Jersey City, N.J.,
produced an annual TSP concentration above the primary standard. The
reported concentration was 78 yg/m3. Because this monitor was adjacent
to monitors measuring lower concentrations, Figure 2-4 does not show any
areas above the primary standard. The land area subjected to concentra-
tions above the secondary standard has also continued to shrink. The
affected area is less than 7 percent of the AQCR.
2.1.1.3 Changes in Population Exposed
Trends in population exposure were evaluated in terms of annual
averages. These concentration statistics were used to determine the
cumulative number of people associated with a particular annual average
concentration. These population exposure distributions were then compared
for 1970, 1973 and 1976 (Figure 2-5).
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12
t
N
1976
AREA WHERE TOTAL SUSPENDED
PARTICULATE CONCENTRATION
IS:
I I <60/ig/m3
60-75 ^g/m3
>75A<9/m3
Figure 2-4. Isopleth of annual geometric mean concentrations of total suspended
particulate in 1970, 1973, 1976.
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The data show that 60 percent of the total population in 1970
was living in areas where annual TSP levels exceeded the primary
TSP standard of 75 yg/m3. By contrast, in 1973 TSP levels had decreased
to the point that only 12 percent of the population was exposed to
annual concentrations above the primary annual NAAQS. The analysis shows
that in 1976, no people were living in areas where levels exceeded the
primary annual NAAQS.
Table 2-1 shows the population exposure for two subpopulations,
the elderly and school-age children. A slightly higher proportion of
the elderly population is living in areas of higher annual TSP levels
but the overall rates of progress are similar for the total population.
Typical concentration exposures decreased from 78 yg/m3 in 1970,
to 61 yg/m3 in 1973 and to 55 yg/m3 in 1976. This represents an overall
improvement of 30 percent in average concentration exposure. An examination
of meteorological data indicated that the total annual precipitation in
1973 was 57 inches and in 1976, 41 inches. Since precipitation tends to
remove particles from the air and the last year had 28 percent less
precipitation, the improvement can be mainly attributed to the success
of emission control plans and local economic factors.
2.1.2 Major Decrease in Population Exposed to High Particulate Levels
in the City of Chicago
The change in the number of people exposed to total suspended
particulate matter in the City of Chicago was examined for the period
from 1970 to 1976. The analysis showed an overall reduction in average
TSP levels of 26 percent. This improvement resulted in 36 percent fewer
people exposed to annual TSP levels above the annual primary health
standard of 75 yg/m3.
2.1.2.1 Methodology
Air quality data produced by the TSP monitoring network operated by
the City of Chicago were examined together with demographic statistics
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15
Table 2.1 Number of People Living in Areas Exceeding National Ambient
Air Quality Standard for Total Suspended Particulate in New
York-New Jersey-Connecticut Air Quality Control Region in
1970, 1973 and 1976.
Population
Category
Total Population
School -age
Elderly
Total
Population
17,000,000
3,900,000
1,800,000
Percent of Category
Population
1970 1973 1976
60
55
66
12
10
14
0
0
0
Percent Reduction
Between
1970 and 1976
100
100
100
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16
to determine the change in resident population exposed to ambient air
pollution of various levels. In 1970, about 3.4 million people were
living in Chicago. Population density within the study area is depicted
in Figure 2-6. Separate population estimates were used for 1970 and
1975. According to the estimates obtained from the University of
Illinois, the study area population exhibited less than a 10 percent
decrease during this period. Consequently, the spatial distribution
showed little change.
Figure 2-7 presents the locations of 16 TSP monitors that provided
the air quality for this analysis. Each monitor produced a valid year
of data in 1970 and 1976.
A network of 75 receptor points were used to interface air
quality and population data. The receptor points were placed at the
center of the "community areas'J within the City of Chicago. A community
area is an aggregate of adjacent census tracts with similar residential
characteristics. Each receptor point represented a subset of the total
population, as well as a subset of the less mobile, but susceptible,
school-age and elderly populations. The network is displayed in Figure 2-8.
The TSP air quality at each receptor point of the network was estimated from
the actual monitoring data by spatial interpolation. The estimates o"
population and air quality were then used to characterize the study aiea.
2.1.2.2 TSP Air Quality Pattern
Isopleths of average TSP during 1970 and 1976 are shown in Figure 2-9.
In 1970, the entire city was above the TSP primary NAAQS. The highest TSP
concentrations are found in the highly industrialized Calumet region of
Southeast Chicago. High concentrations are also found in downtown Chicago,
extending westward into the adjoining industrial areas.
In the 1976 isopleths, a substantial city-wide decrease in TSP
levels can be seen. About one-third of the city is now below the primary
TSP NAAQS. These areas include the North and South Central parts of
Chicago. Both are areas of moderate population density.
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2.1.2.3 Changes in Population Exposed
Frequency distributions of population exposure were obtained by
comparing the community area population with the corresponding estimates
of annual mean TSP. The distributions for 1970 and 1976 are compared in
Figure 2-10, which shows that the percent of population residing in
Chicago with annual TSP above the primary NAAQS decreased from 100
percent in 1970 to 64 percent in 1976. This represents a 36 percent
decrease.
Table 2-2 shows population exposure for two subpopulations,
the elderly and school-age children. A slightly higher proportion of
the school-age population is living in areas of higher annual TSP levels.
Typical exposure decreased from 104 yg/m3 in 1970 to 77 yg/m3 in
1976. This represents an overall improvement of 26 percent in average
concentration exposure. This improvement is largely due to the success
of the emission control efforts.
An examination of meteorological data indicated that total annual
precipitation was 46 inches in 1970 and 34 inches in 1976 and that
average wind speed was the same for both years. Since precipitation
removes particulates from the air and the least polluted-year had 26
percent less precipitation, one could reasonably conclude that pollution
control efforts were responsible for this improvement.
2.1.3 Decrease in Population Exposed to High Particulate Levels in the
Metropolitan Denver Area
The change in the number of people exposed to total suspended
particulate matter in the Metropolitan Denver area were examined for
the period from 1970 to 1975. The analysis showed an overall improvement
of 10 percent in the exposure to annual average TSP.
The study region, a subset of the Metropolitan Denver Standard
Metropolitan Statistical Area (SMSA), consists of Denver County and the
populated parts of Adams, Jefferson, and Arapahoe Counties. The study
area is shown in Figure 2-lla. The population in the 231 census tracts
-------
20
40
60 75 80 100
ANNUAL TSP CONCENTRATIONS, jug/m3
120
Figure 2-10. Population exposure distribution for the city of Chicago.
-------
Table 2-2. Number of People Living in Areas Exceeding National Ambient
Air Quality Standard for Total Suspended Particulate in
Chicago in 1970 and 1976
Population
Category
Total Population
School-age
Elderly
Total
Population
3,357,000
735,000
356,000
Percent of Category
Population
1970 1976
100
100
100
64
70
54
Percent Reduction
Between
1970 and 1976
36
30
46
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that comprise the study area was 1.06 million in 1970. This represents
86 percent of the people in the Metropolitan Denver SMSA. The spatial
distribution of the population density is shown in Figure 2-llb. The
study area population increased to 1.27 million in 1975; the growth
occurred in suburban areas. Population data for 1970 obtained from
the Bureau of the Census were based on total population by census
tract. Corresponding estimates for 1975 were obtained from the Denver
Regional Council of Governments.
Air quality data were provided by 19 TSP monitoring stations.
(Figure 2-12.) Thirteen of these monitors provided data for both 1970
and 1975 air quality, while three additional monitors were used in
each time period to provide supplementary detail. Representative esti-
mates of annual mean TSP for 1970 and 1975 were obtained by averaging
available data for the two time periods: 1969-1971 and 1974-1976,
respectively. This was primarily done to minimize possible short-term
meteorological effects.
A network of 231 receptor points derived from the population
centroids of the census tract was used to interface the air quality and
population data for 1970 and 1975. This network is displayed in Figure 2-13,
The census tracts provided estimates of population as well as land are. .
The TSP air quality at each receptor point of the network was estimate'
from the actual monitoring data by spatial interpolation. The estimate
of population and air quality were then used to characterize the study
area.
2.1 .3.1 TSP Air Quality Pattern
Spatial patterns of the air quality for 1970 and 1975 were established
by using the data at the individual monitoring stations and supplementary
information estimated at the artificial receptor network (Figure 2-14).
In 1970 most of the study area was exposed to annual TSP above the
primary NAAQS. The highest TSP concentrations are found in the central
-------
24
PEOPLE PER SQUARE MILE
| | <1,000
, ji&i&i 1,000- 5,000
5,000-10,000
>10,000
Figure 2-11b. Population density pattern in Metropolitan Denver, in 1970.
-------
25
MONITORING STATIONS
-$ BOTH 1970 & 1975
# 1970 ONLY
1975 ONLY
Figure 2-12. Location of TSP monitors in Metropolitan Denver.
-------
Figure 2-13. Receptor network in Metropolitan Denver area.
-------
90
AREA WHERE ANNUAL
MEAN TOTAL SUSPENDED
PARTICULATE CONCEN-
TRATION IS:
< 75 A g/mj
75-90 /, j/m3
90-105 ^g/m
1975
Figure 2-14. Annual mean TSP in Metropolitan Denver, 1970 and 1975.
-------
28
City of Denver and extend northward down the Platte River Valley. Most
of the areas with levels below the primary NAAQS were in the southeastern
part of Denver County and suburban areas of Arapahoe County. A moderate
decrease in TSP levels was observed throughout the region The areas
below the primary NAAQS in 1975 have grown to include more of the eastern
portions of Jefferson County.
2.1.3.2 Changes in Population Exposed
Frequency distributions of population exposure were obtained by
comparing the census tract populations with the corresponding estimates
of annual mean TSP. The distributions for 1970 and 1975, shown in
Figure 2-15, reveal that the percent of population residing in aredb
with annual TSP above the primary NAAQS decreased from 83 percent in
1970 to 74 percent in 1975. This represents ^1 11 percent improvement.
Typical concentration exposures decreased 10 percent from 96 ug/m3 in
1970 to 86 ug/m3 in 1975. Both of these indicators show similar- improve-
ment to annual TSP in the Metropolitan Denver Area.
2.2 METROPOLITAN LOS ANGELES SHOWS LONG-TERM IMPROVEMENT IN POPULATK N
EXPOSED TO HIGH PHOTOCHEMICAL LEVELS
Changes in the exposure of the Los Angeles Basin population to
photochemical oxidants and nitrogen dioxide were first presented in the
National Air Quality and Emission Trends Report, 1975. This section
updates that analysis through 1976. Air quality data collected from
1965 through 1976 were grouped into 2-year intervals to preserve historical
continuity among the trend sites. The analysis showed a considerable
reduction in the percent of days the 1-hour primary health standard for
oxidants was violated. People in the Los Angeles Basin were exposed
to concentrations above the standard on an average of 186 days per year
in 1965 and 1966, 14^ days per year in 1969 and 1970, 105 days per year
in 1973 and 1974, and 112 days per year in 1975 and 1976. The slight
-------
60
75 9Q 105 120
ANNUAL TSP CONCENTRATION, j
135
150
Figure 2-15. Population exposure distributions for Denver, 1970 and 1975.
-------
30
degradation between the 1973/1974 period and the 1975/1976 period may
be due to an increase in the number of days with poor dispersion*.
Analysis of nitrogen dioxide data showed some improvement; people were
exposed to a concentration above the 1-hour California welfare standard
of 470 yg/m3 on an average of 25 days per year in 1965 and 1966, 27
days per year in 1969 and 1970, and 19 days per year in 1975 and 1976.
Although the California standard is related to visibility, it served
as a convenient reference point to evaluate population exposure to hourly
concentrations of nitrogen dioxide.
2.2.1 Methodology
Air quality data collected at ten air monitoring stations measuring
oxidants and eight measuring nitrogen dioxide were examined together with
population statistics prepared by the Southern California Association
of Governments (SCAG) and with the 1970 censu; data. /\ population of
7.9 million was associated with the oxidant mcnitoring data, and the
nitrogen dioxide monitoring network was judges to represent 6.5 million
people. Figure 2-16 depicts the spatial vari. tion of ;he population
density over the study area. Figure 2-17 pre ents the location of the
ten monitoring sites that provided the air quality data for the analys:s.
The air quality and population data were interfaced by using a
standardized network of 57 receptor points for the oxidant analysis am
45 receptor points for the nitrogen dioxide analysis (Figure 2-18).
The standardized netv;ork provides complete area coverage, but more detail
is given to areas of high population density. Each standard network
point thus represents a local population as well as its air quality. The
oxidant and nitrogen dioxide air quality of each grid point of the standardized
network were estimated from the actual monitoring data by spatial interpolation.
The estimates of population and air quality were then used to characterize
the region.
*A day with poor dispersion is defined as a day with severely restricted
mixing, moving inversion base height less than 1500 feet, maximum
mixing height less than or equal to 3500 feet, wind speed less than or
equal to 5 mph from 0600 to 1200 PSI.
-------
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ON02 SITES
O,*OXIDANT SITES
Figure 2-17. Locations of nitrogen dioxide and oxidant trend sites in Los Angeles Air Basin.
O N02 RECEPTOR POINTS
O,« OXIDANT RECEPTOR POINTS
Figure 2-18. Standard demographic network for trend analysis in Los Angeles Air Basin.
-------
33
2.2.2 Changes in Population Exposed to Oxidants
Daily exposure patterns are displayed on isopleth maps to indicate
areas of the region that exceed the 1-hour oxidant standard of 160 ug/m3
for a given percent of the days (Figure 2-19). A long-term improvement
can be seen over the 12-year period from 1965 through 1976. In 1965
and 1966, more than half of the Los Angeles Basin violated the standard
more than 50 percent of the days and the rest of the region at least 20
percent of the days. The greatest overall improvement was in 1973 and 1974
when the standard was violated more than 50 percent of the days only
in a small area around Azusa. In 1975 and 1976, areas around Burbank
and San Bernardino also violated the standard more than 50 percent of
the days. These same areas violated the standard in excess of 45 percent
of the days in 1973 and 1974. An examination of days with poor dispersion
shows an increase in the 1975/1976 period over the 1973/1974 period
(Table 2-3). This, in part, explains the slight deterioration in oxidant
air quality between the two time periods.
The region-wide trends in population exposure to oxidant are summarized
in Table 2-3. People in the study region were exposed to concentrations
above the standard on an average of 176 days per year during 1965 and
1966, 144 days per year in 1969 and 1970, 105 days per year in 1973 am
1974, and 112 days in 1975 and 1976. The trends are similar for valuef
greater than twice the standard. Of interest is the lack of oxidant
improvement between 1971 and 1976. When the three, 2-year periods are
compared, the average number of days on which the oxidant standard was
violated correlates well with the average number of days with poor
dispersion. This suggests that changes in the number of days violating
the oxidant NAAQS over the 1971-1976 period may be due to meteorology.
2.2.3 Changes in Population Exposed to Nitrogen Dioxide
The National Air Quality and Emissions Trends Report, 1975 reported
that much of the study region violated the annual average primary NAAQS
of 100 yg/m3 through out the 10-year period, 1965-1974. This was also
true in 1975 and 1976.
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This report focuses on the percent of days the 1-hour California
"welfare" standard of 470 [jg/m3 was violated (Figure 2-20). A major
question is 'Why didn't the improvement in N02 from 1971/1972 to 1973/1974
continue into 1975/1976?" Table 2-4 compares the average number of days
with poor dispersion versus the average number of days per year exceeding
the 1-hour California standard. Although 1975/1976 had a typical
number of poor dispersion days, when compared with earlier years, days
with poor dispersion were significantly highly in 1975/1976 than in
1973/1974. The lack of N02 improvement from 1973/1974 to 1975/1976 could
be due to meteorology coming back to normal in 1975/1976 after unusually
good conditions in 1973/1974. The relatively more severe meteorological
condition of 1975/1976 may have disguised the effect of N02 emission
reductions that took place between 1973/1974 ind 1975/1976.
The effect of the long-term nitrogen oxide control strategy may
also have been temporarily distorted by the gasoline crisis in the
winter of 1973/1974. Not only was meteorology unusually good in 1973/
1974 but also NC^air quality in 1973/1974 benefited slightly from the
gasoline shortage. A fairer test of recent N0? trends would be to compare
1975/1976 with 1971/1972; in this case, we see improvement in both the
isopleth maps and the average number of days violating the California
welfare standard - 33 days in 1971 and 1972 versus 19 days in 1975
and 1976.
2.3 ACKNOWLEDGMENT
The Monitoring and Data Analysis Division would like to recognize
the contributions of Neil Frank, William F. Hunt, Jr., Jim Capel, and
Margaret Swann of the Division in assembling this section. The section
would not have been possible without support received from EPA Regional
Offices. Specifically, the Division would like to recognize Lew Heckman,
Region II; Stephen Goranson and Linda Larson, Region V; Barry Levene,
Region VIII; and Coe Owen, Region IX.
-------
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2.4 REFERENCES FOR SECTION 2
1. National Air Qualtiy and Emissions Trends Report. 1975,
U.S. Environmental Protection Agency, Office of Air Quality
Planning and Standards, Research Triangle Park, N.C.
Publication No. EPA-450/1-76-002. November 1976.
2. Horie, Yuji and Arthur C. Stern. Analysis of Population
Exposure to Air Pollution in New York-New Jersey-Connecticut
Tri-State Region. U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research
Triangle Park, N.C. Publication No. EPA-450/3-76-027.
March 1976.
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40
3. NATIONAL AND REGIONAL TRENDS IN CRITERIA POLLUTANTS
Trends in ambient levels of total suspended participate, sulfur dioxide,
carbon monoxide, oxidantb, and nitrogen dioxide are reported in this section.
Each of these criteria pollutants is discussed individually; the extent of
the analysis varies according to the amount of available historical data.
In contrast to Section 2, which dealt with specific urban areas, this section
focuses upon national trends and trends over broad geographic regions. (Section
4 of this report presents maps illustrating the concentration ranges of several
pollutants in various parts of the country.)
Considerable thought has been given to various ways to improve the nation's
ambient air quality monitoring programs. The recent activities of the Standing
Air Monitoring Work Group (SAMWG) have served as a focal point for new ideas.
This work group, composed of representatives from EPA and State and local air
monitoring agencies, has developed a comprehensive strategy document for ambient
air quality monitoring. Because many elements of the SAMWG strategy document
will affect future trend analyses, some of these points are mentioned here so
that interested readers will be made aware of anticipated improvements in the
nation's air monitoring programs.
The most obvious change will be the designation of specific Nationa Air
Quality Stations (NAQTS) for the criteria pollutants. These NAQTS sites
would primarily be determined by the population of the area. For total
suspended particulate and sulfur dioxide, the allocation would be on the
basis of population and pollutant concentration. Selected for the primary
purpose of long-term trends analyses, these measuring stations will provide
more consistent data bases from one year to the next and also ensure adequate
geographical coverage. Obviously, these NAQTS sites would not be the only com-
ponent of an air monitoring program. There are a variety of purposes for ambient
monitoring programs, and, therefore, it will be necessary to supplement these
NAQTS sites with other types of monitoring stations. Other items of note in
the SAMWG strategy document relate to quality assurance, increased continuous
monitoring, and adherence to standardized siting criteria, all of which will
improve the ambient air quality data bases and thereby serve to improve
subsequent trend analyses. Readers interested in the details of the SAMWG recom-
mendations are referred to the strategy document.
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41
3.1 TRENDS IN TOTAL SUSPENDED PARTICIPATE
The general long-term improvement in ambient air quality with respect
2-6
to total suspended particulate (TSP) has been discussed in previous reports.
During the 1970's, there has been nationwide improvement in TSP concentrations,
but many areas experienced increases between 1975 and 1976. This section
discusses national and regional TSP trends during the 1970-1976 time period
with particular attention given to comparisons between 1975 and 1976.
The data used in these analyses were obtained from EPA's National
Aerometric Data Bank. The vast majority of the data were collected by State
and local agencies through their air monitoring programs and then submitted
to EPA. All sites having four consecutive quarters of data from 1970-1973
and also from 1974 through 1976 were included in these analyses. This selection
criterion was used to ensure balanced seasonality and a comparable data base
from the beginning to the end of the time period. Sufficient data to satisfy
this selection criterion were available from 2,350 sites, although a site
would need only a minimum of 2 years of data to qualify for selection, 70
percent of these 2,350 sites had at least 4 complete years of data during the
1970-1976 time period.
As in last year's Trends Report, a modified version of the graphical
technique known as a box-plot is used to display trends. This plotting
technique depicts several characteristics of the data simultaneously. Fi
-------
42
r
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90TH PERCENTILE
75TH PERCENTILE
COMPOS TE AVERAGE
MEDIAN
25TH PERCENTILE
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Figure 3-1. Sample illustration of plotting conventions
for box plots.
-------
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slightly less than 4 percent per year, with more marked improvement in the
Northeast and Great Lakes regions. Figure 3-3 displays trends in peak
values at these same sites and shows a similar pattern during this
time period. It should be noted that sampling frequencies at many of
these sites were increased during this time period. While increasing sampling
frequencies would not alter trends in annual means, it could be expected to
result in an artificial increase on the order of 2 to 3 percent per year
for the peak values during this time period. Even with this contribution,
however, the general pattern in Figure 3-3 shows improvement through 1975.
Also apparent in both graphs is the trend reversal in 1976, which is discussed
in more detail in the following section dealing with short-term changes.
Knowledge of geographical differences in long-term TSP trends provides back-
ground information that is useful in considering the short-term changes.
Figure 3-4 displays 1970-1976 trends for each EPA Region and provides
a convenient presentation of trends by geographical area. Although all
areas had improved TSP levels in the 1970-1976 time period, trends in the
western areas of the country were generally less pronounced. In many cases,
this geographical variation is attributable to a difference in the nature
of TSP problems from one area to another. In some locations, wind-blown dust
is an important component of TSP levels and is more difficult to control than
emissions from traditional sources.
As would be expected from these graphs, improvement was fairly consistent
from 1970 to 1976, with 72 percent of the sites having decreases in ambient
TSP levels. Because air pollution control strategies are designed to reduce
levels at locations exceeding the National Ambient Air Quality Standards,
more pronounced improvement would be expected for the sites with higher con-
centrations. For those sites with 1970-1973 averages above the annual
primary standard, 81 percent showed improvement. For sites in this category,
improvements outnumbered increases by at least a 2 to 1 margin in all regions
of the country. Using nonparametric regression, 27 percent of these higher
concentration sites shows statistically significant improvement while only 1
percent of these sites had statistically significant increases.
3.1.2 Short-Term TSP Trends: 1975-1976
In many areas of the country, the general downward trend in TSP levels
in the early 1970's was followed by a reversal in 1976. This was apparent
in Figure 3-2 and 3-3 for the nation, but is more obvious in some of the
-------
45
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1975
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Figure 3-3. Trends of peak daily total suspended particulate concentrations from 1970 to 1976
at 2,350 sampling sites.
-------
45
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-------
47
regional graphs in Figure 3-4. Based upon changes between comparable
quarters in 1975 and 1976 for these TSP trend sites, 53 percent of those
comparisons showed increases. Over half the States had more increases
than decreases between Iy75 and 1976. The Southeast, Midwest and West
generally recorded increases.
The widespread pattern of these increases suggests that some common
factor was involved. Because no general increases in particulate emissions
throughout these areas occurred in 1976, and there were not widespread
changes in sampling methodology, meteorological conditions would be the
likely candidate for explaining these increases. In fact, many State
agencies ranging from the Midwest to Washington and California have cited
8-14
meteorology as the main reason for these TSP increases in 1976. Large
areas of the country experienced drought during 1976, and these extremely
dry soil conditions increased the likelihood of wind-blown dust contributing
to ambient TSP levels.
Figure 3-5 illustrates the geographical areas affected by drought in
1976. This map was constructed by integrating the Palmer Index throughout
1976. The Palmer Index, a reasonable indicator of overall soil moisture
conditions, reflects both rainfall and evapotranspiration. This map shows
that dry soil conditions existed in those general areas that had TSP increases,
Specific days that had high TSP concentrations may also be examined to sts
whether the dry conditions contributed to these values.
Such an analysis was done in the Midwest by EPA's Region V with the
15
cooperation of the State agencies in Region V and also Iowa. Figure 3-6
illustrates TSP isopleths in this area for October 15, 1976. Elevated TSP
levels were recorded throughout this area. On this particular day, dry
soil conditions and strong winds combined to increase the likelihood of
wind-blown dust. These meteorological factors also coincided with fall
harvesting, which increased the likelihood of wind-blown soil particles.
This explanation of these high levels were also supported by microscopic
15
examination of the high-volume filters for this day.
*0btained from the Weekly Weather and Crop Bulletin
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49
150**
Figure 3-6. Isopleths of total suspended particulate concentrations
and Iowa for October 15, 1976.
in EPA Region V
-------
50
An even more dramatic example of the impact of wind-blown dust over
a broad geographic area occurred in February, 1977, in the Southeast.
Although this incident took place in 1977 rather than 1976, it illustrates
the potential impact that dust storms can have. Extremely high TSP
values were recorded on February 24, 1977, throughout this area, and an
analysis was conducted by personnel of EPA's Region IV office with the
cooperation of State and local air pollution agencies in the Southeast
as well as the National Weather Service Forecast Office (NOAA) in
Birmingham, Alabama. Figure 3-7 shows TSP concentration isopleths
in EPA Region IV for February 24, and is indicative of the extremely high
values in this area for that day. The basic cause was wind erosion of
the soil. Figure 3-8 graphically depicts a satellite view of the dust
storm at successive points in time from February 23-25, 1977. Extremely
dry soil conditions in the Central Plains and the development of a strong
frontal system resulted in dust being stirred up and eventually transported
east. Meteorological conditions that were likely to cause dust storms
coincided with widespread cultivation for farming, and the end result was
widespread transport of wind-blown dust throughout a broad geographical
area. It should be noted that the concentration levels reported during
this storm were extremely unusual for this area and represent historically
high values that are not at all typical of the normal TSP ranges in the ^egion.
In discussing the 1975-1976 increases, it should be noted that some areas
continued to improve in 1976. For example, the continued progress in the New
York area was presented in Section 2. Nationally, for those trend sites with
complete 1975 and 1976 data, 54 percent of the sites above the primary standard in
1975, showed improvement in 1976. In general, the short-term 1975-1976
did not appreciably affect status with respect to the primary standards. For
those sites located in highly populated areas (SMSA's), 5 percent went from
above 75 yg/m3 (the primary standard) to below, while another 5 percent crossed
in the opposite direction for net change of zero. For those sites located
outside these populated areas, however, 8 percent crossed in the increasing
direction while only 3 percent dropped below the standard so that there was
a net increase. This seems consistent with the meteorological contribution
to these increases in that the urbanized areas showed a lesser impact.
-------
51
Figure 3-7. Isopleths of total suspended particulate concentrations
east for February 24, 1977.
in the south-
-------
52
-------
53
3.2 TRENDS IN SULFUR DIOXIDE
The entire sulfur dioxide picture has changed in the 1970's. The
early 1970's saw dramatic decreases in ambient sulfur dioxide levels in
2-6
the nation's urbanized areas. " Since then the national trends have
been much more stable, and violations of the sulfur dioxide standard are
generally confined to areas around specific sulfur oxide sources.
Sites for this analysis were obtained using the same selection
criteria discussed in Section 3.1 for TSP. For sulfur dioxide, 722 sites
had sufficient historical data to qualify as sulfur dioxide trend sites.
Less than 10 percent of these sites had data in 1970-1971, when sulfur
dioxide levels were rapidly reduced in many areas; therefore, graphs
are presented only for the 1972-1976 time period. All data were used
when examining changes, however. Those readers interested in the earlier
2-6
time period are referred to previous reports.
Figure 3-9 displays a box-plot of nationwide sulfur dioxide trends
for annual means. The graph shows general improvement with relatively
stable behavior in the low to middle ranges. In discussing changes in
ambient sulfur dioxide levels, it is useful to consider sites with annual
averages of less than 26 yg/m3 (0.01 ppm) as a separate category. These
sites have annual means less than one-third of the annual primary standard.
Because the annual means are so low, artificial trends can be introduced
merely by changes in the manner of reporting individual values below the
minimum detectable limit of the monitoring instrument. For a similar
reason, changes of less than 5 yg/m3 are treated as "no change" in this
analysis.
In comparing changes between 1970-1973 and 1974-1976, 64 percent
of the sites remained below 26 yg/m3 throughout. For the other sites,
51 percent showed improvement and 23 percent reported increases, In
contrast to TSP, changes between 1975 and 1976 are relatively stable with
11 percent of the sites increasing, 12 percent decreasing, and 76 percent
either showing no change or remaining below 26 yg/m3. As in the case of
TSP, meteorology is likely to have an effect on short-term changes. For
-------
54
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Figure 3-9. Trends of annual mean sulfur dioxide concentrations from 1972-1976 a,
722 sampling sites.
-------
55
sulfur dioxide, heating degree-days are an important meteorological para-
meter and reflect fuel usage for space heating. Short-term increases may
be due, therefore, to changes in emissions associated with varying meteorology.
This type of effect was seen in Minnesota, where sulfur dioxide levels in
the fall quarter of 1976 were 17 percent higher than the corresponding
quarterly averages for 1973-1975, but at the same time heating degree-days
12
increased 23 percent due to colder weather.
Urban sulfur dioxide levels have traditionally been higher in the
Northeast and Great Lakes areas where emissions are associated with space
heating. Figure 3-10 and 3-11 display the general improvement in sulfur
dioxide levels in those areas. The New England States had no violations
of the sulfur dioxide standards in 1976. There has also been improvement
in portions of the Great Lakes States. For example, the Michigan Department
of Natural Resources reported only four counties with violations of the
sulfur dioxide standards in 1976. For Illinois, 1976 was the first year
in the history of the Illinois EPA that no monitoring site in their State
q
violated the sulfur dioxide annual primary standard.
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As discussed in previous reports, " the general improvement in sulfur
dioxide levels is indicative of trends in urban areas. At the present time,
the remaining sulfur dioxide problems are primarily associated with specific
sources impacting their surrounding areas. These situations are more
commonly investigated by special studies rather than long-term trend moni-
toring programs.
3.3 TRENDS IN CARBON MONOXIDE
There has been general improvement in carbon monoxide (CO) levels
5 6
through 1976. As discussed in previous reports, ' the historical data
base for CO is very limited compared to those for TSP and sulfur dioxide.
The nationwide data base for CO continues to expand, an indication of the
increased monitoring activities of State and local agencies during the 1970's.
For example, in last year's trends report 102 sites had 3 or more years of
-------
56
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25
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! T
1970
1971
1972
1973
YEAR
1974
1975
1976
Figure 3-10. Trends of annual mean sulfur dioxide concentrations in New England from 1970-
1976 (60 sites).
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57
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Figure 3-11. Trends of annual mean sulfur dioxide concentrations in the Great Lakes area from
1970 to 1976 (160 sites).
-------
58
data while 202 sites meet this criteria for this year's report. The State
of California with its well established monitoring program remains the
major contributor to the CO data base with 59 sites qualifying as trends
sites.
Changes in CO levels were determined for each site by nonparametric
regression. The parameter used was the annual 90th percent!le of the
8-hour CO averages. The 8-hour averages rather than hourly averages are
used because the 8-hour standard is more frequently exceeded. The choice
of the 90th percentile is somewhat of a compromise. A desirable trend
parameter should reflect whether consistent progress is being made with
respect to the standards; however, the maximum or second highest 8-hour
value may fluctuate from year to year because of unusual meteorology or
a few traffic jams so that progress being made in reducing the extent of
the CO problem is masked. The percent of time that the 8-hour standard
is exceeded is also a useful parameter, but for those sites that are very
close to the standard, this can occassionally be misleading. For example,
a site with only one violation one year and two the next would show a 100
percent increase, but would not really be indicative of that dramatic a
deterioration. The 90th percentile means that only 10 percent of the 8-hour
averages were higher. It is more stable as a trend indicator than the
maximum and yet still indicates what changes are occurring in the higher
8-hour averages at the site. Figure 3-12 indicates the relationship among
the maximum, the 90th percentile, and the percent of time above the standard
for 8-hour averages for the downtown Los Angeles site. This illustrates
that 90th percentile changes are consistent with the patterns seen in the
other parameters.
During the 1970-1976 period, approximately three-fourths of these CO
sites showed improvement. Table 3-1 summarizes these changes for all sites
and also for just those sites with five or more years of data. Both the
California and nonCalifornia sites had approximately the same percentage
of increases and decreases. However, the California sites had a slightly
higher median rate of improvement; 7 percent per year in California versus
6 percent per year outside California for sites with 4 years or more data.
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59
120
100
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60
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A MAXIMUM 8-HOUR VALUE
D 90th PERCENTILE
O PERCENTOFTIME STANDARD EXCEEDED
1970
1971
1972
1973
YEAR
1974
1975
1976
Figure 3-12. Sample graph of trends in three CO parameters (expressed as percent of 1970 value )
for Los Angeles, California.
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60
Table 3-1 PERCENT OF MONITORING SITES SHOWING INDICATED
TRENDS IN 90th PERCENTILE OF 8-HOUR AVERAGE CO
CONCENTRATIONS 1970-1976
Years of data
3 or more
5 or more
Number of sites
202
75
%
down
74
79
% no
change
5
5
%
up
20
16
-------
61
In comparing 1975 and 1976 values, 52 percent of the sites showed
improvement, 39 percent had increases, and 9 percent were unchanged. In
fact, 49 percent of the sites reported their all time low value in 1976.
The State of New Jersey has had an aggressive program to reduce
automobile related pollution. A part of this program is an inspection/
maintenance program to ensure that exhaust emission standards are being
met. Figure 3-13 was prepared by the New Jersey Department of Environ-
mental Protection to illustrate the progress made in reducing New Jersey
18
CO levels from 1972 through 1977. The dates for the initiation of the
two phases of their inspection/maintenance program are shown. Gasoline
consumption for New Jersey is also shown indicating that CO levels
continue to improve despite an overall increase in gasoline consumption.
3.4 TRENDS IN PHOTOCHEMICAL OXIDANTS
Photochemical oxidant air pollution, expressed as ozone (O^), ranks
today as one of the most serious and pervasive air pollution problems
in this country. In 1975, about 85 percent (356 of 416) of the 03 sites
reporting to the National Aerometric Data Bank exceeded the National
Ambient Air Quality Standard (NAAQS) of 160 yg/m3 not to be exceeded more
than 1- hour per year.
In previous reports, 0^ trends assessment has been primarily limited
to California sites since they were the only ones with sufficient historical
data. Enough nonCalifornia sites are now available for trend purposes so
that a preliminary but not a complete assessment of nationwide 03 trends
can be made. In order to qualify as a trend site, a site must have at least
3 years of data with at least 4,000 observations per year in the 1970-1976
period with the further stipulation that the 1970-1973 and 1974-1976 period
each have at least 1 year of data. Nationally, 174 sites representing 34
States met this criteria - 62 in California and 112 in the remainder of the
country.
The analysis of 03 trends was done using a nonparametric regression
procedure. This same procedure is also used for determining trends in
the other pollutants. The trend analysis is based on the annual rate of
change of the 90th percentile of the annual hourly observations. The
statistic was chosen because it is more stable than either using the
highest hourly value, and yet it still reflects the upper tail of the 0^
annual frequency distribution.
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MONTHLY MOVING AVERAGES FOR 18 MONITORING SITES
Figure 3-13. Carbon monoxide air quality and gasoline consumption by motor vehicles for New Jersey.
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63
Table 3-2 shows the distribution of California and nonCalifornia sites
into three categories of trend direction (down, no change, up). This
represents merely a tabulation of the overall trend tendencies for those
sites satisfying our trend criteria. Overall, the California sites do
not show any predominate trend direction, instead the sites are about
equally distributed between the three trend categories; Regional trends
in Los Angeles and San Francisco were also mixed with no clear patterns.
The overall picture obtained from the California sites, particularly in
Los Angeles, is one of a steady unchanging pattern of 03 concentrations
from 1970-1976.
The nonCalifornia sites show a slight tendency for increasing
patterns with 55 sites up and 46 sites down. Table 3-3 indicates that
the greater frequency of up patterns occur in Regions IV, V, VI and VII.
For the most part, these sites represent only 3 years of data, therefore,
assessing the significance of these patterns is difficult. Future trend
analysis will assess the validity of these findings.
Figure 3-14 shows the trend in the Bay Area Air Pollution Control
District (BAAPCD) of the average highest hour oxidant concentrations for
19
days with comparable temperature and inversion conditions. By just
looking at comparable days in terms of meteorology in this way, the varying
affects of meteorology from year to year are greatly reduced. The BAAPCD
average of six sites shows a stable pattern over the 1970-1976 period
varying from 135 yg/m3 in 1970 and 117 ug/m3 in 1976. Section 2.2 of
this report discusses the longer-term improvement in the population exposed
to high 03 levels in the Los Angeles Metropolitan Area.
Data from 174 sites were analyzed for 03 trends over the time period
1970-1976. Sites in California did not show any consistent overall trend
patterns. Trends in the Los Angeles and San Francisco areas were judged as
stable over this time period.
Data from nonCalifornia sites was restricted for the most part to
only 3 years of data (77 out of 112 sites). There was a little more
tendency for the nonCalifornia sites to show increasing trend patterns.
However, the data still remains too limited in both the number of years
reporting and from a geographic standpoint to determine whether these
patterns are real.
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64
Table 3-2 OXIDANT/OZONE TRENDS IN 90th PERCENTILE OF ANNUAL
HOURLY OBSERVATIONS 1970 - 1976
Direction of
trend
Down
No change
Up
Total
California sites
24
16
22
62
NonCalifornia
sites
46
11
55
112
Total
70
29
75
174
-------
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300
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O SAN JOSE, CALIF.
OSAN FRANSISCO, CALIF,.
A 6 SITE AVERAGE, BAAPCD
1970
1976
Figure 3-14. Average daily maximum-hour oxidant concentrations for days in April-October having
comparable temperatures and inversions in the Bay Area Air Pollution Control District (BAAPCD).
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67
3.5 TRENDS IN NITROGEN DIOXIDE
Trends in the annual mean concentrations of nitrogen dioxide were
investigated for 276 sites throughout the country for the period 1970-1976.
Forty-two of these sites were located in California. Sites were selected
for the trend analysis if they had at least 3 years of data with at least
4,000 observations per year in the study period. At least 1 year had to
be in both the 1970-1973 and 1974-1976 periods of time in order for a
site to pass the trend criteria.
Table 3-4 summarizes the N02 trend patterns observed at the 276
sites. Among the 42 California sites, 19 were in the down and 19 in
the up categories. The nonCalifornia sites, on the other hand, show
almost twice as many sites (145 to 77) with up than down patterns. Most
of the nonCalifornia sites (228 out of the 234) however, had only 3 years
of data so that it is impossible now to draw any definite conclusions
from these findings.
Figure 3-15 shows the trends in N02 in the Los Angeles and San
Francisco areas. The Los Angeles average of nine sites shows a decline
in N02 concentrations overall for the 1970-1976 period, with a reversal
of this pattern occurring in 1975 and 1976. The highest site in the L.A.
Basin (Burbank) and the lowest site (Azusa) are also plotted. The San
Francisco sites, on the other hand, show a more stable pattern. The
average represents six sites in the San Francisco area.
3.6 ACKNOWLEDGMENTS
The Monitoring and Data Analysis Division wishes to acknowledge the
contributions of Tom Curran and Bob Faoro in the preparation of Section 3.
as well as the contributions made by EPA's Regional Offices during the review
process. Special mention should be made of the contributions of Barry Gilbert
(EPA-Region IV); and Ed Klappenbach and Steve Goranson (EPA-Region V) for their
special studies. Of course, the largest debt of gratitude is due the many
State and local agencies whose monitoring programs and reports make this
type of analysis possible.
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68
Table 3-4. NITROGEN DIOXIDE TRENDS IN ANNUAL ARITHMETIC MEAN 1970-1976
Direction of
trend
Down
No
Up
Total
California
sites
19
4
19
42
Non-California
sites
77
12
145
234
Total
96
16
164
276
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-------
70
3.7 REFERENCES FOR SECTION 3
1. Air Monitoring Strategy for State Implementation Plans, prepared
by the Standing Air Monitoring Work Group, May 1977.
2. The National Air Monitoring Program: Air Quality and Emissions Trends -
Annual Report, Volumes 1 and 2. U.S. Environmental Protection Agency,
Office of A1r Quality Planning and Standards, Research Triangle Park, N.C.
Publication No EPA-450/1-73-001 a and b. July 1973.
3. Monitoring and Air Quality Trends Reports, 1972. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, N.C. Publication No. EPA-450/1-73-004.
4. Monitoring and Air Quality Trends Report, 1973. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, N.C. Publication No. EPA-450/1-74-007.
October 1974.
5. Monitoring and Air Quality Trends Report, 1974. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, N.C. Publication No. EPA-450/1-76-001.
February, 1976.
6. National Air Quality and Emissions Trends Report, 1975. U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, N.C. Publication No. EPA 450/1-76-002. November 1976.
7. Tukey, J.W. Exploratory Data Analysis. Addison-Wesley Publishing Co.
Reading, Mass. 1977.
8. California Air Quality Data, Vol VIII No. 3. 1976 California Air
Resources Board.
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71
9. 1976 Annual Air Quality Report, Illinois Environmental Protection
Agency. Springfield, Illinois.
10. 1976 Iowa Air Quality Report, Iowa Department of Environmental Quality.
Des Moines, Iowa. August 1977.
11. 1976 Air Quality Report. Michigan Department of Natural Resources,
Lansing, Michigan.
12. Minnesota A1r Quality 1971-1976. Minnesota Pollution Control Agency.
Roseville, Minnesota. February 1977.
13. Washington State Air Monitoring Data for 1976. Washington State
Department of Ecology. Olympia, Washington. May 1977.
14. 1976 Air Quality Data Report, State of Wisconsin Department of Natural
Resources
15. KlappenbacH, E.W. and Goranson, S.K. "Long Range Transport of Particulates:
Case Study, October 15. 1976." Presented at the 70th Annual Meeting of
Air Pollution Control Association, Toronto, Ontario, Canada. June 1977
16. Air Quality Data In Region IV During the Texas-Oklahoma Dust Storm
Assembled by Barry Gilbert, Air Programs Branch. Region IV-EPA
Atlanta, Georgia.
17. 1976 Annual Report on Air Quality in New England. U.S. Environmental Protection
Region I Surveillance and Analysis Division, Lexington, Mass. May 1977.
18. New Jersey Department of Environmental Protection Annual Report: July 1, 1976-
June 30, 1977. New Jersey Department of Environmental Protection,
Trenton, New Jersey ( in preparation).
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72
4. AIR QUALITY MAPS OF UNITED STATES
This section deals with a special topic, the geographical variations
in air quality across the United States. Three multi-color air quality maps
are presented, one dealing with total suspended particulate (TSP) a second
with sulfur dioxide (SOp) and a third with photochemical oxidants (03). The
maps are provided to respond to the often asked question: "How does air
quality vary across the United States?"
Each of the maps indicates pollutant-specific summary statistics by
county for the United States. The summary statistics relate to appropriate
pollutant-specific National Ambient Air Quality Standards (NAAQS). In order
to make the greatest use of available air quality data, the highest yearly
statistic occurring within a county over the period 1974-1976 was used.
The TSP and SCL air quality maps reflect data that were available from the
U.S. Environmental Protection Agency's National Aerometric Data Bank (NADB)
in September 1977. These data were supplemented with updated information
from State reports, which were provided by the Regional Offices. The 0^ map
reflects information on the NADB as of mid-October, supplemented with informa-
tion obtained from a special report on 0, data.
These maps should not be used to determine non-attainment areas because
the maps have been created to reflect the highest measured ambient concentra-
tions in the 3-year period, and more current information may show that the
counties are or are not violating standards. Such is the case in the counties
encompassing the Metropolitan New York City area. The TSP map shows air
quality exceeding the annual mean NAAQS based on 1974 data, but the population
exposure analysis in Section 2.1 shows that only one site in New Jersey was
violating the annual primary NAAQS in 1976. The reader must keep in mind
that corrective action may have been already taken in other situations as
well. A discussion of the pollutant specific maps follows.
4.1 TOTAL SUSPENDED PARTICULATE AIR QUALITY MAP
The highest annual geometric mean measured in a county in the period
1974-1976 was used as the summary statistic. The annual mean was selected
because it is less likely to be influenced by fugitive dust than would be
a second-high 24-hour average. The four color categories compare the worst
-------
73
annual TSP mean to levels above and below the primary annual geometric
mean NAAQS of 75 yg/m3, which is not to be exceeded. Counties colored in blue
recorded measurements less than one-half the annual standard, while
counties colored in green reflect a TSP annual mean greater than one-half
the annual NAAQS but less than the annual standard. Counties colored in
yellow reflect a high TSP value clearly violating the standard, but less
than or equal to 100 yg/m3, while counties in red reflect a high TSP
Value exceeding 100 yg/m3.
A total of 1197 counties had one or more annual means during the
1974-1976 period so that they could be displayed on the map. Of these,
355 had annual means clearly violating the annual primary NAAQS. The
counties with TSP levels exceeding the annual NAAQS, can be found throughout
the United States. The southwestern corner of the United States, made up
of California, Arizona and part of New Mexico, appears to have extensive
violations. This, to some extent, is due to the nature of the analysis,
for this part of the country comprises the counties with the largest land
area. San Bernadino County, California, for example, is larger in land
area than the combined States of Massachussetts, Connecticut and Rhode Island.
Since the analysis is based on the worst annual mean measured in the county,
greater attention is drawn to the air quality in these large counties.
4.2 SULFUR DIOXIDE AIR QUALITY MAPS
The second maximum 24-hour average measured in a county in the period
i
1974-1976 was used as the summary statistic. This relates to the short-term
24-hour average standard of 365 yg/m3, which is not to be exceeded more than
once per year. This was used instead of the annual mean, which could be com-
pared to the SCU annual mean primary NAAQS, because many S0? monitors did not
collect sufficient data to meet the NADB validity criteria for calculating
an annual mean. The criteria requires that at least 75 percent of the total
possible data be available to calculate an annual mean. Further, the 24-hour
average NAAQS is more likely to be violated than the annual standard.
An examination of the sulfur dioxide map indicates that most areas
of the country are not showing violations of the short-term NAAQS. Of the 834
counties with SOp data, 60 had second maximum 24-hour averages exceeding
the 24-hour primary standard. Most of these occurred in the industrial
areas of the Mid-West Other violations can be seen in the western part of the
United States where the principal sources are smelting operations.
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74
4.3 PHOTOCHEMICAL OXIDANT AIR QUALITY MAP
The second daily maximum 1-hour average occurring within a county
in the 1974-1976 time period was used for photochemical oxidants. This
relates to the 1-hour average 03 NAAQS of 160 yg/m3 which is not to be
exceeded more than once per year. The second daily maximum 1-hour average
is a more stable statistic for geographical comparisons than the second
highest hourly average observed within a year. The latter can be more
easily influenced by a day with unusually abnormal meteorological condi-
tions that are conducive to high 0- levels. As indicated earlier, the
03 maps reflect information available on the NADB as of mid-October 1977,
supplemented with information obtained from a special report on 03 data
collected in rural areas. ^
Counties with a second daily maximum 1-hour average less than the
NAAQS are colored in blue, while counties colored in purple show 03
measurements greater than one but less than two times the NAAQS. Pink
counties show second daily maximum 1-hour averages greater than two times
the standards, but less than three times the standard, while red counties
have 0, measurements in excess of three times the NAAQS.
From the map, it can be seen that the 03 problem is widespread and
standards are being violated in most areas where 03 is being measured.
The counties in which monitoring is taking place represent 50.2 percent
of the population of the United States. Approximately 99 percent of these
people live in counties where the photochemical oxidant standard was
violated. The counties colored in blue, for the most part, are in remote
rural areas and their second daily maximum 1-hour measurements are close
to the standard.
4.4 ACKNOWLEDGMENT
The Monitoring and Data Analysis Division would like to recognize the
contributions made by William F. Hunt, Jr., Robert B. Faoro, Virginia
Henderson, Jerome Mersch, Hersh Rorex, Warren Freas, Thomas Curran, Sherry
Olson, Margaret Swann, James Capel, and Jeff Smith. Mr. Charles Keadle
of the Office of Administration deserves special recognition for the art
work he prepared. The section would not have been possible without support
-------
75
received from the Regional Offices. Specifically, the Division would like
to recognize Jean Kelleher, Region I; Lew Heckman, Region II; Sandor Kovacs,
Region III, Barry Gilbert, Region IV; Steve Goranson and Linda Larson,
Region V; Miquel Flores, Region VI, Charles Whitmore, Region VII, Barry
Levene, Region VIII, Coe Owen, Region IX, and George Hoffer, Region X.
4.5 REFERENCES
1. "Compilation and Evaluation of Privately Collected Ambient
Ozone Data West of the Mississippi River," prepared by PEDCo
Environmental, Inc., Kansas City, Missouri for the U.S.
Environmental Protection Agency, Monitoring and Data Analysis
Division, Research Triangle Park, N.C. 27711, April 1977.
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76
5. NATIONWIDE EMISSION ESTIMATES, 1970-1976
Table 5-1 summarizes estimated national emissions of total suspended
particulates (TSP), sulfur oxides (SO ), nitrogen oxides (NO ), hydrocarbons
X X
(HC), and carbon monoxide (CO). Because of modifications in methodology
and use of more refined emission factors, data from the following tables
should not be compared with data in previous reports.
Table 5-1 SUMMARY OF NATIONAL EMISSION ESTIMATES, 1970-1976
(10^ metric tons/yr)
Year
1970
1971
1972
1973
1974
1975
1976
TSP
22.6
21.4
20.3
19.9
17.5
14.4
13.4
sox
29.1
27.9
28.8
29.7
28.2
25.7
26.9
NOX
20.4
21.3
22.2
22.9
22.6
22.2
23.0
HC
29.7
29.3
29.7
29.8
28.6
26.2
27.9
CO
99.8
100.2
102.0
98.3
91.5
85.9
87.2
Two distinctions between these emission estimates and ambient pollutant
measurements should be noted. First, the emission estimates for particulates,
sulfur oxides, and nitrogen oxides embrace a broader range of substances
than are measured by routine ambient air monitoring equipment. The high-
volume air sampler collects only the particulates suspended in air that
range from approximately 0.3 to 100 micrometers in diameter, but emission
inventories include both suspended and settled particulates generated by
man's activities. Sulfur dioxide and nitrogen dioxide ambient air monitors
measure only those two specific compounds; not all the oxides of sulfur and
nitrogen which are included in the emission estimates. In each case, however
the compound actually measured is the most prevalent constituent of its
pollutant class or is acknowledged to be its most representative indicator.
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77
Second, the tables of estimated emissions include hydrocarbons but not
oxidants. Obviously, oxidant emissions would not be meaningful because
the overwhelming majority of oxidants are so-called secondary pollutants
generated by photochemical reactions in the atmosphere. Emissions of
hydrocarbons are important because hydrocarbons are a major ingredient
for those oxidant-producing reactions; yet, ambient measurements of hydro-
carbon are not reported because a reliable method has not yet been developed
for the continuous monitoring of this large and diverse class of compounds.
Consequently, monitoring is not required. Hydrocarbon emission estimates
reported herein are basically for total hydrocarbons, as defined by cur-
2
rently available emission factors . Sources that emit only methane are
generally not included. Sources that emit a mixture of hydrocarbons,
including methane, would include methane in the total hydrocarbon emission
estimates.
5.1 DETAILED ANNUAL EMISSION ESTIMATES
Tables 5-2 through 5-8 present annual emission estimates according
to major source categories. These data are estimated from published data
on fuel use and industrial production, and other EPA data, such as air
pollutant emission factors and available information on the extent of air
JC
pollution controls employed ~ .
The "Transportation" category includes emissions from all mobile sources.
Highway vehicles include passenger cars, trucks, and buses. Non-highway
vehicles include aircraft, railroads, vessels, and miscellaneous mobile
engines such as farm equipment, industrial and construction machinery,
lawnmowers, and snowmobiles.
"Stationary Fuel Combustion" is defined to be all fuel use in stationary
combustion equipment such as boilers and stationary internal combustion
engines. Emissions are shown for electric utility power plants, industrial
establishments, and other fuel consumers (residential, commercial, govern-
mental, schools).
"Industrial Processes" include emissions resulting from operation of
process equipment by manufacturing industries. In addition, the categories
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78
Table 5-2. NATIONWIDE EMISSION ESTIMATES, 1970
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
TOTAL
TSP
0,7
0.4
7.1
4.1
2.6
0.4
0.3
0.1
2.1
7.7
0
0
2.2
0.9
0.5
0.3
0.1
0
0
22.6
S0x
0.7
0.3
0.4
22.3
15.7
4,6
2.0
5.9
0,5
0.6
4.1
0.5
0.1
0
0.1
0,1
0,1
0
0
0.1
0
0
29.1
NOX
8.4
6.3
2,1
10.9
5.1
5.1
0.7
0.6
0.2
0.3
0
0.1
0
0
0
0,3
0.2
0.1
0
0.1
0
0
20.4
HC
12.6
11,1
1.5
1.5
0.1
1,3
0.1
8.5
1.5
0.7
0.2
0
2.7
2.7
0.7
1.7
5.4
0.7
0.3
0.1
0
4.3
29.7
CO
79.2
69.7
9.5
1.2 -.
0.2
0.5
0.5
8.0
3.0
2.0
2.1
0
0
0
0.9
6.1
5.3
3.5
1.4
0.3
0.1
0
99.8
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
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79
Table 5-3. NATIONWIDE EMISSION ESTIMATES, 1971
(Id6 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
TOTAL
TSP
1.1
0.7
0.4
6.6
4.0
2.2
0.4
11.8
0.3
0.1
1.9
7.3
0
0
2.2
0.8
1.1
0.7
0.2
0.1
0.1
0
21.4
S0x
0.7
Q.3
0.4
21.5
15.6
4.0
1.9
5.5
0.5
0.6
3.6
0.6
0.1
0
0.1
0.1
0.1
0
0
0.1
0
0
27.9
N0x
8.9
6.7
2.2
11.2
5.4
5.1
0.7
0.6
0.2
0.3
0
0.1
0
0
0
0.3
0.3
0.2
0
0.1
0
0
21.3
HC
12.3
10.8
1.5
1.5
0.1
1.3
0.1
8.5
1.4
0.7
0.2
0
2.8
2.7
0.7
1.4
5.6
1.0
0.3
Q.I
0
4.2
29.3
CO
79.6
70.3
9.3
1.2
0.2
0.5
0.5
7.9
2.7
2.1
2.2
0
0
0
0.9
4.7
6.8
5.1
1.3
0.3
0.1
0
100.2
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
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80
Table 5-4. NATIONWIDE EMISSION ESTIMATES, 1972
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metal s
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
.
TSP
1.2
0.8
0.4
6.4
4.0
2.0
0.4
11.1
0.3
0.1
1.9
6.7
0
0
2.1
0.7
0.9
0.5
0.2
0.1
0.1
0
20.3
S0x
0.7
0.3
0.4
21.8
16.0
4.0
1.8
6.1
0.6
0.7
4.0
0.6
0.1
0
0.1
0.1
0.1
0
0
0.1
0
0
28.8
N0y
A
9.4
7.1
2.3
11.7
5.9
5.1
0.7
0.7
0.3
0.3
0
0.1
0
0
0
0.2
0.2
0.1
0
0.1
0
0
22.2
HC
12.6
11.0
1.6
1.5
0.1
1.3
0.1
8.9
1.5
0.7
0.2
0
2.9
2.9
0.7
1.1
5.6
0.7
0.2
0.1
0
4.6
29.7
CO
84.0
74.8
9.2
1.3
0.3
0.5
0.5
7.9
2.6
2.1
2.2
0
0
0
1.0
4.0
4.8
3.6
0.8
0.3
0.1
0
102.0
TOTAL _.' _ _ - ' - -I
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
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81
Table 5-5. NATIONWIDE EMISSION ESTIMATES, 1973
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
TOTAL
TSP
1.2
0.8
0.4
6.5
4.3
1.8
0.4
10.9
0.3
0.1
2.1
6.3
0
0
2.1
0.6
0.7
0.4
0.1
0.1
0.1
0
19.9
S0x
0.8
0.4
0.4
22.9
17.5
3.7
1.7
5.8
0.5
0.8
3.7
0.6
0.1
0
0.1
0.1
0.1
0
0
0.1
0
0
29.7
NOY HC CO
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82
Table 5-6. NATIONWIDE EMISSION ESTIMATES, 1974
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use"
TOTAL
TSP
1.2
0.8
0.4
5.6
3.8
1.4
0.4
9.4
0.3
0.1
1.9
5.4
0
0
1.7
0.5
0.8
0.5
0.1
0.1
0.1
0
17.5
SOx
0.8
0.4
0.4
21.9
17.0
3.3
1.6
5.3
0.4
0.8
3.3
0.6
0.1
0
0.1
0.1
0.1
0
0
0.1
0
0
28.2
NOX
9.6
7.3
2.3
11.9
6.2
5.0
0.7
0.7
0.3
0.3
0
0.1
0
0
0
0.2
0.2
0.1
0
0.1
0
0
22.6
HC
11.3
9.8
1.5
1.5
0.1
1.3
0.1
9.2
1.6
0.8
0.2
0
2.9
2.9
0.8
0.9
5.7
0.6
0.3
0.1
0
4.7
28.6
CO
74.0
65.6
8.4
1.3
0.3
0.5
0.5
8.2
2.5
2.3
2.4
0
0
0
1.0
3.2
4.8
3.9
0.5
0.3
0.1
0
91.5
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
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83
Table 5-7. NATIONWIDE EMISSION ESTIMATES, 1975
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
X
Stationary fuel cgp&ustion
El ectn> utilities
Industrial
xx Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metal s
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
TOTAL
TSP
1.2
0.8
0.4
5.3
3.9
1.1
0.3
6.9
0.2
0.1
1.3
3.7
0
0
1.6
0.4
0.6
0.3
0.1
0.1
0.1
0
14.4
x
0.8
0.4
0.4
20.6
16.7
2.5
1.4
4.2
0.3
0.7
2.5
0.5
0.1
0
0.1
0
0.1
0
0
0.1
0
0
25.7
x
9.9
7.6
2.3
11.2
6.1
4.5
0.6
0.7
0.3
0.3
0
0.1
0
0
0
0.2
0.2
0.1
0
0.1
0
0
22.2
HC
10.9
9.4
1.5
1.4
0.1
1.2
0.1
8.5
1.5
0.8
0,2
0
2.9
2.4
0.7
0.8
4.6
0.4
0.1
0.1
0
4.0
26.2
CO
71.5
63.3
8.2
1.2
0.3
0.5
0.4
7.1
2.2
2.3
1.7
0
0
o
0.9
2.9
3.2
2.3
0.5
0.3
0.1
0
85.9
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
-------
Table 5-8. NATIONWIDE EMISSION ESTIMATES, 1976
(10 metric tons/year)
Source category
Transportation
Highway vehicles
Non-highway vehicles
Stationary fuel combustion
Electric utilities
Industrial
Residential, commercial & institutional
Industrial processes
Chemicals
Petroleum refining
Metal s
Mineral products
Oil & gas production and marketing
Industrial organic solvent use
Other processes
Solid waste
Miscellaneous
Forest wildfires and managed burning
Agricultural burning
Coal refuse burning
Structural fires
Miscellaneous organic solvent use
TOTAL
TSP
1.2
0.8
0.4
4.6
3.2
1.1
0.3
6.3
0.3
0.1
1.3
3.2
0
0
1.4
0.4
0.9
0.6
0.1
0.1
0.1
0
13.4
S0x
0.8
0.4
0.4
21.9
17.6
2.6
1.7
4.1
0.3
0.7
2.4
0.5
0.1
0
0.1
0
0.1
0
0
0.1
0
0
26.9
N0x
10.1
7.8
2.3
11.8
6.6
4.5
0.7
0.7
0.3
0.3
0
0.1
0
0
0
0.1
0.3
0.2
0
0.1
0
0
23.0
HC
10.8
9.3
1.5
1.4
0.1
1.2
0.1
9.4
1.6
0.9
0.2
0
3.0
2.9
0.8
0.8
5.5
0.8
0.1
0.1
0
4.5
27.9
CO
69.7
61.4
8.3
1.2
0.3
0.5
0.4
7.8
2.4
2.4
1.9
0
0
0
1.1
2.8
5.7
4.8
0.5
0.3
0.1
0
87.2
Note: A zero in Tables 5-2 through 5-8 indicates emissions of less than 50,000
metric tons per year.
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85
"Oil and Gas Production and Marketing" (crude oil and natural gas production,
petroleum storage tanks and transfer facilities, gasoline service stations)
and "Industrial Organic Solvent Use" (surface coating and degreasing of
manufactured products, printing and publishing) are included under industrial
processes. "Other processes" represents combined emissions from pulp and
paper, wood products, agricultural, rubber and plastics, and textile indus-
tries. "Solid Waste" includes emissions from combustion of waste in municipal
and other incinerators, and open burning of domestic and municipal refuse.
"Miscellaneous" includes emissions from combustion of forest, agricul-
tural and coal refuse materials and structural fires. Also included are
estimated emissions from consumption of organic solvents not accounted for
in industrial processing operations. This includes trade sales of surface
coatings, dry cleaning, cutback asphalt paving, and other commercial and
domestic consumption of organic solvents.
5.2 EMISSION TRENDS
Overall, from data in Table 5-1, it can be determined that from 1970
through 1976, emissions of particulates decreased by 40 percent; sulfur
oxides decreased by 8 percent; nitrogen oxides increased by 13 percent;
hydrocarbons decreased by 6 percent; and carbon monoxide decreased by 13
percent. Since these data are only calculated estimates of emissions on a
nationwide scale, trends in emissions for local areas may be entirely
different. Nevertheless, national emission estimates should be indicative
of the overall general trend in the quantities of air pollutants released
to the atmosphere.
Particulate emissions from 1970 to 1976 have been substantially reduced
by installation of control equipment on industrial processes and large sta-
tionary fuel combustion sources that burn coal. In addition, particulate
emissions have decreased because of lower quantities of coal consumed by
small industrial and other fuel combustion sources, and less burning of
solid waste.
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86
Sulfur oxide emissions have been reduced slightly from 1970 to 1976.
Emissions from stationary fuel combustion sources have remained about con-
stant while industrial process emissions have been reduced by increased
recovery of sulfur at primary non-ferrous smelters. Emissions from electric
utility fuel consumption have increased because of increased coal consumption.
The increase is moderated by the use of coals with lower average sulfur
content. Sulfur oxides emissions from other fuel combustion sectors have
decreased because of less coal use by these sources.
Nitrogen oxide emissions have increased, predominantly because of
increased highway vehicle travel and increased fuel combustion by electric
utilities. Emissions from other sources have not changed significantly.
Hydrocarbon emissions have been reduced slightly from controls imple-
mented on highway vehicles. Despite substantial growth in motor vehicle
travel, there has been a net reduction in hydrocarbon emissions. Stationary
source emissions have remained about constant. Increased industrial process
emissions have been balanced by decreased emissions from burning of solid
waste.
Carbon monoxide emissions have decreased primarily because of highway
vehicle controls and less burning of solid waste. Emissions from other
source categories have not changed appreciably.
Emissions in 1975 were generally lower than those in 1976 because of
economic conditions in 1975 that reduced industrial production. Increased
emissions from 1975 to 1976 reflect the effects of economic recovery. At
the same time, increased levels of control are being applied by major sources
so that particulate emissions actually decreased from 1975 to 1976 and
increases in emissions of other pollutants were relatively small.
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87
5.3 ACKNOWLEDGMENT
The Monitoring and Data Analysis Division would like to recognize
Charles Mann for assembling this section of the report.
A;'r Qiality _and Emission Trends Report, 1975.
hi1' vo'.i'ienu; rVr ruction Agency, Office of Air Quality P'icm.i.hy
::i:l Stanc1a--'dr, . Research Triangle Park, N.C, Publication No.
li'V 'ISO/ 1- ; 5-UJ2. November 1976.
;'o vildtloi-' of Alf Pollutant Emission Factors ^ LPA Publication
/P-i;?, Third Edition (including Supplements 1-7), U.S. Environ-
mental P-I.O: :^on Agency, Research Triangle Park, N.C. August V*TI
ildnn, C.O. OAQPS Data Files of Nationwide Emissions, 1970-1976.
Unpublished documents, National Air Data Branch, Monitoring and
Jata Analysis Division, U.S. Environmental Protection Agency,
Research Triangle Park, N.C., November 1977.
Data from Compliance Data System, Division of Stationary Source:
Enforcement, U.S. Environmental Protection Agency, Washington, D.f,
June 1977
Data from Energy Data System, Energy Strategies Branch, Strategies
and Air Standards Division, U.S. Environmental Protection Agency,
Research Triangle Park, N.C. April 1977
Data from National Emissions Data System, National Air Data
Branch, Monitoring and Data Analysis Division, U.S. Environmental
Protection Agency, Research Triangle Park, N.C. November 1977.
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28
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/1-76-002
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
National Air Quality and Emission Trends Report, 1976
5. REPORT DATE
December. 1977
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
W.F. Hunt, Jr., (Editor), T.C. Curran, N. Frank,
R. Faoro, W. Cox, R. Neligan and C. Mann
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Waste Management
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
Annual 1976
14. SPONSORING AGENCY CODE
5. SUPPLEMENTARY NOTES Special mention should be made of the contributions of Lew Heckman,
Reg. II, Barry Gilbert, Reg. TV; Steve Goranson, Linda Larson and Ed KTappenbach,
Reg. V; and. Barry LeVene, Reg. VIII.
16. ABSTRACT
"T|iis'report presents national and regional trends in air quality through
1976 for total suspended particulate, sulfur dioxide, carbon monoxide, nitrogen
dioxide and oxidants. The change in the number of people exposed to air quality
levels above the National Ambient Air Quality Standards is emphasized for four major
metropolitan areas: the New York-New Jersey-Connecticut Air Quality Control Region;
the Los Angeles Basin; the City of Chicago and Metropolitan Denver. . All areas show
long-term improvement' in reducing adverse pollution levels. A major feature of this
report is the presentation of multi-color air quality maps for total suspended parti-
culate, sulfur dioxide and photochemical oxidants. The maps are included to respond
to the often asked question: "How does air quality vary across the United States?"
The analyses in this report are based on the data collected through the extensive
monitoring activities conducted by Federal, State and local air pollution control
agencies. Nationwide emissions for the period 1970-1976 are also presented.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution Trends
Emission Trends
Carbon Monoxide
Nitrogen Dioxide
Sulfur Dioxide
Total Suspended Particulates
Air Pollution Maps
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (TflisReport)
Unclassified
21. NO. OF PAGES
o 88
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
88
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