EPA-450/1-76-002
November 1976
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1975
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-450/1-76-002
November 1976
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1975
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-450/1-76-002
NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1975
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 1976
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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, RTF, 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 Management, 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 organiza-
tions - 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-450/1-76-002
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CONTENTS
Page
1. INTRODUCTION AND OVERVIEW I
I.I General Overview !
1.2 References 2
2. FEWER PEOPLE EXPOSED TO ADVERSE AIR POLLUTION IN TWO
LARGEST METROPOLITAN AREAS 3
2.1 Major Decrease in Population Exposed to High
Paniculate Levels in the New York-New Jersey-
Connecticut Air Quality Control Region 3
2.1.1 Methodology 3
2.1.2 TSP Air Quality Patterns 4
2.1.3 Changes in Population Exposed. 6
2.1.4 Conclusion '..... 11
2.2 Major Reduction in Percent of Time Metropolitan Los
Angeles Population is Exposed to Photochemical
Pollution 11
2.2.1 Methodology II
2.2.2 Changes in Population Exposed to Oxidants 13
2.2.3 Changes in Population Exposed to Nitrogen
Dioxide .'. 15
2.3 References for Section 2 18
3. NATIONAL AND REGIONAL TRENDS IN CRITERIA POLLUTANTS 25
3.1 Trends in Total Suspended Particulates .. 25
3. I.I TSP Trends (1971-1975) ...'.' 25
3.1.2 Changes in TSP Levels in 1974-1975 28
3.1.3 Population Exposure Trends 29
3.1.4 TSP Trends in Selected Cities , .....29
3.2 Trends in Sulfur Dioxide '........ 30
3.2.1 Sulfur Dioxide Trends (1971-1975) , 32
3.2.2 Recent Changes in Sulfur Dioxide Levels 33
3.2.3 Sulfur Dioxide Trends in Selected Cities 33
3.3 Trends in Carbon Monoxide 34
3.3.1 Data Base and Trend Techniques 34
3.3.2 CO Trends From 1970 to 1975 35
3.4 Trends in Oxidants 36
3.4.1 Data Base and Trend Techniques 36
3.4.2 Oxidant Trends in California 36
3.4.3 Oxidant/Ozone Trends in Areas Outside of
California 40
iii
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Page
3.5 Trends in Nitrogen Dioxide 40
3.5.1 Data Base and Trend Techniques , 40
3.5,2 Nitrogen Dioxide Trends in California 40
3.5.3 New Jersey, Colorado, Illinois, and Oregon 42
3.6 References for Section 3 43
4. NATIONWIDE EMISSION ESTIMATES, 1970-1975 .47
4.1 Emission Trends 47
4.2 References for Section 4 53
IV
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LIST OF TABLES
Table page
2-1 Number of People Living in Areas Exceeding National
Ambient Air Quality Standard for Total Suspended
Paniculate in Study Area in 1971 and 1974 ............................................... 9
2-2 Percent of Population Living in Areas Exceeding 24-Hour
National Ambient Air Quality Standard for Total Sus-
pended Paniculate .................................. . .................................. 10
2-3 Comparison of Trends in Total Suspended Particulate
Air Quality Measures in New York-New Jersey-Connecticut
Air Quality Control Region ........................ . ............................ . ....... 1 1
2^ Violations of NAAQS for Oxidant from 1965 to 1975 in
Los Angeles Air Basin .......................... , ...................................... 18
2-5 Trend in Violations of California 1-Hour Standard for
Nitrogen Dioxide and Average Duration ................................................. 23
3-1 Number and Percent of California Monitoring Sites
Showing Indicated Trends in 90th Percentile of i-Hour
Average CO Concentrations, 1970-1975 ................. . ................................ 35
3-2 Number and Percent of Non-California Monitoring Sites
Showing Indicated Trends in 90th Percentile of 8-Hour
Average CO Concentrations, 1970-1975 .............................. .... ................ 35
3-3 Summary of Trends in Annual Average of Daily 1-Hour
Maximum Oxidant Levels in Los Angeles Basin ........................................... 36
3-4 Summary of Trends in Third-Quarter Average of Daily
1-Hour Oxidant Levels in Los Angeles Basin ................................. .,.,...,..,.. 37
3-5 Summary of Trends in Number of Days 1-Hour Oxidant
Levels Exceeded 200 pig/ m-1 by Quarter in Los Angeles
Basin , ......... .... .......... .... .............. . ................. . ................... 37
3-6 Summary of Trends in Number of Third-Quarter Days
1-Hour Oxidant Levels Exceeded Two and Three Times
NAAQS for Oxidants in Los Angeles Basin, 1970-1975 ..................................... 37
3-7 Percent of Oxidant Trends Due to Atmospheric Dispersion
and Reactive Hydrocarbon Emissions in Los Angeles,
1966-1975 ........ , ........................ ............... ....... ..... . ............... 39
3-8 Average High Hour Oxidant Concentrations for Days With
Comparable Temperature and Inversion Conditions (April
Through October Oxidant Smog Seasons, 1962-1974) ..... ........... ..... . ................ 4*
3-9 Summary of Trends in Annual Average of Daily Maximum
1-Hour Oxidant Levels in San Diego Air Basin ........................................... 42
4-1 Summary of National Emission Estimates, 1970-1975 ................... . .................. 47
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Table Page
4-3 Nationwide Emission Estimates, 1971 , ,. 49
4-4 Nationwide Emission Estimates, 1972 50
4-5 Nationwide Emission Estimates, 1973 51
4-6 Nationwide Emission Estimates, 1974 ,, 52
4-7 Nationwide Emission Estimates, 1975 (Preliminary) 53
V!
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LIST OF FIGURES
Figure Page
2-1 Population Pattern in 1970 for New York-New Jersey-
Connecticut Air Quality Control Region 4
2-2 Location of 103 Total Suspended Paniculate Monitors
in Study Area , 5
2-3 Standardized Network of Receptor Points in Study Area .. 6
2-4 Isopleths of Annual Geometric Mean Concentrations of
Total Suspended Paniculate in 1971 , 7
2-5 Isopleths of Annual Geometric Mean Concentrations of
Total Suspended Paniculate in 1974 ................ , .................................... 7
2-6 Percent of Daily Total Suspended Paniculate Concentrations
Exceeding NAAQS ( 150 jug/m3) in 1971 .................................................. 8
2-7 Percent of Daily Total Suspended Particulate Concentrations
Exceeding NAAQS ( 150 Mg/m*) in 1974 ............ . ...... . .................... . . ........ 8
2-8 Decrease in Population Exposed to Total Suspended
Paniculate in New York-New Jersey-Connecticut Air
Quality Control Region From 1971 to 1974 ---- , . ................. ..... ................... 9
2-9 Population Exposed Daily to Total Suspended Particulate
Above 150jtg/m3 in New York-New Jersey-Connecticut Air
Quality Control Region ....... . ............... . .................. . ..................... 10
2-10 Population Density of Los Angeles Air Basin in 1970 ....... . ............................. 12
2-1 1 Locations of Nitrogen Dioxide and Oxidant Trend Sites
in Los Angeles Air Basin ................. . ............................................ 13
2-12 Standard Demographic Network for Trend Analysis in Los
Angeles Air Basin [[[ 13
2-13 Percent of Days on Which NAAQS for Oxidant was Exceeded
During Five 2-Year Periods ............ .... .............. . ........... . .......... . ---- . . 14
2-14 Average Duration on Days When NAAQS for Oxidant was
Exceeded During Five 2- Year Periods [[[ '6
2-15 Changes in Population Exposure to Oxidant During Five
2-Year Periods [[[ . . ..... .17
2-16 Nitrogen Dioxide Annual Mean Concentration for Five
2-Year Periods ....... . ..................................... . ......................... 19
2-17 Changes in Total Population Exposed to Nitrogen Dioxide
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Figure Page
2-19 Average Duration on Days When California 1-Hour Standard
was Exceeded During Five 2-Year Periods ,,.-.. 22
3-1 Sample Illustration of Plotting Conventions for Box
Plots 26
3-2 Trends of Annual Mean Total Suspended Paniculate Con-
centrations from 1971 to 1975 at 1792 Sampling Sites 26
3-3 Frequency Distributions in 1971 and 1975 for Total
Suspended Paniculate Trend Sites (Semi-Log Scale) 27
3-4 Percent of Total Suspended Particulate Sites Changing
by More than 5 ^g - 1971-1972 versus 1973-1975 by t&S^j
Concentration Range "... 27
li
3-5 Change in Percent of Sites in Nation Exceeding 24-Hour f^H^s
Primary Total Suspended Particulate Standard for a £>-'."
Given Number of Days in 1971 and 1975 (Computed Using . |g^j
Lognormal Distribution and Standard Geometric Deviation t.'/fS-i
of 1.6) 28 i|:|;
X -. %.;*
3-6 Changes by More Than 10% for Total Suspended Particulate |vf>.->
During 1974/1975 , , 29 ff|j
3-7 Percent of Population Exposed to Annual Mean Total .uK;:
Suspended Particulate in Excess of 75 ^g/ mj (NAAQS) from fS$&
1970 Through 1974 , , 30 |g|
3-8 Trend in National Population Exposure Expressed as
Annual Mean Total Suspended Particulate 30
3-9 Percent of Values Above Secondary Total Suspended
Particulate Standard for Selected Cities 31
3-10 Sulfur Dioxide Trends 1971-1975 (545 Sites), Annual pH
Averages 32 _ *;g%:'-
=KS£:*
i^yV^?
3-11 90th Percentile Trends for Sulfur Dioxide by Geographical "5-SSS
Region (1971-1975) 33 ?B;
SKXJJ>;
3-12 Recent Changes by More than 10% for Sulfur Dioxide .§§£§
(1974/1975) 34 tffB
3-13 Composite Average Sulfur Dioxide Trends (and Number of p|i
Sites) for Dominant SM-SA's in Each Region 34 v-WS
psfe
%-s-y;
3-14 Atmospheric Ventilation and Reactive Hydrocarbon Emissions f4f::
in Los Angeles County over 10-Year Period 38 Hip
^pSjjj|«
3-15 Oxidant Trends Adjusted for Meteorology .- 39
3-16 Annual Mean Nitrogen Dioxide Levels in the Los Angeles tfts;
Basin , 42 Ig',:
3-17 Annual Average of Daily Maximum 1-Hour NC>2 (4-Year f-s₯%
Running Mean) in the Los Angeles Basin 43 T .v
viii /Zv':
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Figure Page
3-18 Comparison of 1971 and 1975 Annual Mean Levels of
Nitrogen Dioxide in New Jersey , 44
4-1 Calculated Total Emissions of Criteria Pollutants by
Source Category, 1970 through 1975 (A: Transportation,
B: Stationary Source Fuel Combustion, C: Industrial
Processes. D: Solid Waste, E: Miscellaneous) 54
IX
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NATIONAL AIR QUALITY
AND EMISSIONS TRENDS REPORT,
1975
1. INTRODUCTION AND OVERVIEW
1.1 GENERAL OVERVIEW
Considerable progress has been made in achieving compliance with the National Ambient Air Quality
Standards (NAAQS) for total suspended parttculate, sulfur dioxide, carbon monoxide, and oxidants. In
contrast, however, trends for nitrogen dioxide are mixed. The 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.
Pollutant measurements are compared with standards in this report. Data for analysis were obtained
from the U.S. Environmental Protection Agency's National Aerometric Data Bank (NADB). These data are
gathered primarily from state and local air pollution control agencies through their monitoring activities.
This is the fifth report on air pollution trends issued by the Environmental Protection Agency. '^ Unlike
past reports, this report treats only trends in air quality (section 3} and emissions (section 4). The air quality
appendices contained in past reports '~4 identified the Air Quality Control Region, the site location and
number, and also contained air quality summary statistics by pollutant. This type of information will be
published in a separate report.
In this report the change in the number of people exposed to air quality levels above the National Ambient
Air Quality Standards (NAAQS) is emphasized. Changes in population exposure to air quality levels are
discussed for two selected areas: the New York-New Jersey-Connecticut Air Connecticut Air Quality Control
Region, accounting for 17 million people, and the Los Angeles Air Basin, accounting for 8 million people. In
the New York-New Jersey-Connecticut Study, emphasis was focused on the change in population exposed to
total suspended paniculate levels above the NAAQS. Changes in the population exposed to ozone and
nitrogen dioxide levels above the NAAQS were stressed in the Los Angeles study.
The major findings of the investigations are as follows:
I. Based on data collected at approximately 1800 monitoring sites, the estimated number of people in the
nation exposed to total suspended particulate levels in excess of the annual primary standard decreased
from 73 million in 1970 to 49 million in 1974. This improvement indicates that 24 million fewer people
were exposed to levels above the standard.
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2. As a result of switching to cleaner fuels and implementing participate control measures, approximately 7
million fewer people in the New York-New Jersey-Connecticut Air Quality Control Region were exposed
to total suspended participate concentrations in excess of the primary health standard of 75 micrograms p2) above the 1-hour California welfare standard of 470 jug/m3 on an average of 25
days per year in 1965 and 1966, 27 days per year in 1969 and 1970, and 18 days per year in 1973 and 1974.
These data show improvement in the past 5 years.
4. The most recent sulfur dioxide (SO2) ambient air data from 545 monitoring sites show that conentrations
in urban areas have decreased by an average of 30 percent since 1970. The improvement occurred rapidly
in the 1970-1973 period and then leveled off as many areas came into compliance. Major point sources
located outside of urban areas, such as non-ferrous smelters, pose the greatest threat to achievement of
the NAAQS for sulfur dioxide at the present time.
5, Improvement was noted at approximately 80 percent of the sites measuring carbon monoxide (CO)
throughout the nation. The rate of improvement was more pronounced in California, where the CO
emission standards are more stringent.
6. Data from sites monitoring oxidant showed considerable improvement in the Los Angeles Basin, the San
Francisco Bay Area, and the San Diego Air Basin.
7. A preliminary analysis of short-term trends (1973-1975) suggests a decline in summer oxidant/ozone
violations in the eastern part of the United States (eight sites decreasing and three sites increasing) and a
general increase in metropolitan Denver (five sites increasing). There are too few sites with sufficient
historical data in the remainder of the nation to characterize trends.
8. Nitrogen dioxide level trends vary geographically. A significant decline occurred in the Los Angeles Basin
Between 1971-1975, but in the San Francisco Bay Area, as many sites increased as decreased. Recent
declines have occurred in three cities in New Jersey and in Denver, Colorado. No significant trend for
nitrogen dioxide was found in the two other cities examined, Chicago, Illinois, and Portland, Oregon.
1.2 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. Environmental 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. Environmental 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. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Research Triangle Park, N.C. Publication Nb. EPA-450/1-76-001.
February 1976.
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2. FEWER PEOPLE EXPOSED TO ADVERSE AIR
POLLUTION IN TWO LARGEST METROPOLITAN AREAS
The number of people exposed to certain levels of air pollution has changed dramatically during the
1970*s. In the past, trends in air quality have been reported'"^ in terms of means, percentiles, and/or
maximum pollutant concentrations, all of which are statistically derived from air monitoring data. Trends in
these pollutant concentration statistics are reasonable measures of progress; however, they do not directly
indicate improvement in terms of the number of people being exposed to levels above the primary NAAQS.
Because the purpose of primary standards (health-related) is the protection of public health, studies have been
undertaken in two geographical areas-^to measure the impact of emission control plans on population groups
exposed to air pollution levels above the NAAQS. Both air quality data and population data are factored into this
"population exposure" approach.
Population exposure analyses were conducted for the New York-New Jersey-Connecticut Air Quality
Control Region (AQCR) and the Los Angeles Air Basin. These two 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 103 suspended
paniculate monitors, which have provided sufficient historical data to examine trends. The Los Angeles Basin
contains a population of 8 million people and has extensive oxidant and nitrogen dioxide monitoring
networks. The analysis in New York, therefore, focuses on the change in population exposure to total
suspended paniculate levels between 1971 and 1974, and the Los Angeles analysis examines the change in
population exposed to oxidant and nitrogen dioxide levels from 1965 through 1974. Both analyses required
the merging of local population and air quality data to compute several measures of pollutant exposure. In
order to accomplish this task, 1970 population data for both areas were "gridded" into a network of
population receptor points; each point represented a subset -of the areas' total population. A spatial
interpolation procedure5 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 is discussed in the following sections.
2,1 MAJOR DECREASE IN POPULATION EXPOSED TO HIGH PARTICIPATE
LEVELS IN THE NEW YORK-NEW JERSEY-CONNECTICUT AIR QUALITY
CONTROL REGION
The change in number of people exposed to total suspended particulate matter in the New York-New
Jersey-Connecticut AQCR was examined for the period from 1971 through 1974. Overall, significant
progress has been made in reducing population exposure to annual average TSP levels. As a result of
switching to cleaner fuels and implementing particulate control measures, typical annual concentration levels
were reduced 25 percent. This improvement is shown to have resulted in 71 percent fewer people living in areas
exposed to concentration in excess of the annual primary health standard of 75/ug/ m-'. In addition, progress
has been made in reducing the number of repeated exposures to high daily concentrations.
2.1.1 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
within the study area is depicted in Figure 2-1. The most densely populated areas are found in the urban core
consisting of most of New York City and parts of eastern New Jersey, where TSP concentrations are also
generally the highest.
Figure 2-2 presents the location of the 103 TSP monitors that provided the air quality data for this
analysis. Two years, 197J and 1974, were selected to demonstrate the change in population exposure over
time. Each of these monitoring sites produced a valid* year of data in 1971 and 1974.
'A valid year of data is based on a minimum of five 24-hour average values per calendar quarter.
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<2000
2000 7000
>7000
Figure 2- J. Population pattern in 1970 for New York - New Jersey - Connecticut Air Quality Control Region.
A network of 2,15 receptor points was used to interface the air quality and population dala. Each receptor
poini represented a subset of the total population, as well asasubset oftheless mobile but susceptible school-
age and elderly populations. This network, displayed in Figure 2-3, provides complete area coverage, and
more detail is afforded densely populated areas. The TSP air quality of each grid point of the 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.
2.1.2 TSP Air Quality Patterns
Spatial air quality patterns are described in terms of annual concentrations and the frequency that daily
concentrations exceed the daily welfare standard (150-yug mj). The secondary standard was used because it
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NEW YORK
NEW JERSEY
Figure 2-2. Location of 103 total suspended paniculate monitors in study area.
was violated more frequently than the primary standard and was, therefore, more illustrative of change in
TSP levels overtime. Trends in air quality patterns are demonstrated by comparison of isopleth maps in 197!
and 1974.
Isopleths of average TSP during 1971 are shown in Figure 2-4. The highest concentration levels are found
in the central portion of the region. Nineteen percent of the total land area in this region was exposed to annual
average concentrations greater than the primary N A AQS. The corresponding spatial distribution during 1974
is shown in Figure 2-5. As can be seen, there was an overall reduction in TSP levels throughout the region
between 1971 and 1974. The land area exposed to concentrations in excess of the annual primary standard has
been reduced to less than 4 percent of the Air Quality Control Region.
Daily exposure patterns are described in terms of isopleth maps that contour areas of the region that
exceed 150MS/m-' for a given percent of the days. Figures 2-6 and 2-7 show these contours for 1971 and 1974.
In 1971 almost one-third of the total area exceeded the standard 5 percent of the time, but by 1974 this area
had been reduced 50 percent.
5
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NEW YORK
NEW JERSEY
Figure 2-3. Standarized network of receptor points in study area.
2.1.3 Changes in Population Exposed
Trends in population exposure were evaluated in terms of {I) annual averages and (2) the frequency of
occurrence of daily TSP concentrations in excess of ISQug/m1. These concentration statistics were used to
determine the cumulative number of people associated with a particular annual average concentration or
frequency of occurrence. These population exposure distributions were then compared for 1971 and 1974.
The population exposure distribution for 1971 and 1974 for annual averages is shown in Figure 2-8. For
example, 58 percent of the total population in 1971 was residing in areas wherein annual TSP levels were
exceeding the primary annual TSP standard of 75Mg/ m-1. By contrast, in 1974, TSP levels had decreased to the
point that only 17 percent of the population was exposed to annual concentrations above the primary annual
NAAQS.
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AREAS WHERE ANNUAL MEAN TOTAL
SUSPENDED PARTICULATE CDNCEN-
TRATION EXCEEDS ANNUAL PRIMARY
STANDARD Of 75pg/m3
so
AREAS WHERE ANNUAL MEAN TOTAL
SUSPENDED PARTICULATE CONCEN-
TRATION EXCEEDS ANNDAl PRIMARY
STANDARD OF JS«ta3
NOTE: ISOPt-ETH MAPS ARE BASED ON SPATIAL INTERPOLATION FROM DATA MEASURED
AT 103 MONITORING SITES. LOCAL TSP MAY VARY BECAUSE OF METEOROLOGY, TOPOG-
RAPHY, AND EMISSIONS,
Figure 2-4. Isopleihs of annual geometric mean concentrations
of total suspended paniculate in 197L
Figure 2-5. Isopleihs of annual geometric mean concentrations
of total suspended particular in 1974.
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NEW YORK
NEW YORK
AREAS WHERE DAILY TOTAL SUSPEND-
ED CONCENTRATIONS EXCEED SECOND-
ARY NAAOS AT LEAST Ss OF THE TIME
AREAS WHERE DAILY TOTAL SUSPEND-
ED CONCENTRATION EXCEED SECOND
ARY NAAOS AT LEAST 5* OF THE TIME
NOTE: ISOPLETH MAPS ARE BASED ON SPATIAL INTERPOLATION FROM DATA MEASURED
AT 103 MONITORING SITES. LOCAL TSP MAY VARY BECAUSE OF METEOROLOGY, TOPOG-
RAPHY, AND EMISSIONS.
Figure 2-6. Percent of daily total suspended paniculate concentrations
exceeding NAAQS (ISOngfm3) in 1971.
Figure 2-7. Percent of daily total suspended particulate concentrations
exceeding NAAQS (ISOns/m*) in 1974.
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100
140
TSP ANNUAL CONCENTRATION, jig
Figure 2-8, Decrease in population exposed to total suspended particulate in New York - New Jersey
Connecticut Air Quality Control Region from 1971 10 1974.
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, the elderly, and school-age children.
The population exposure distributions for daily averages are shown in Figure 2-9 for 1971 and 1974. In
1971, 58 percent of the population lived in areas exposed to I50Mg/m3 more often than 5 percent of the days,
In 1974, however, only 15 percent of the population was exposed that often to this level. Table 2-2 shows the
population exposure distribution for various exposure frequencies in terms of the percent improvement from
1971 to 1974. As would be expected, fewer people are affected by the higher frequencies of exposure. Also, the
improvement in terms of the percent reduction in population exposure becomes larger for the higher exposure
frequencies.
Table 2-1. NUMBER OF PEOPLE LIVING IN AREAS EXCEEDING NATIONAL
AMBIENT AIR QUALITY STANDARD FOR TOTAL SUSPENDED
PARTICULATE IN STUDY AREA IN 1971 AND 1974a
Population
category
Total population
School age
Elderly
Total
population
17,000,000
3,900,000
1,800,000
Percent of category
population
1971
58
53
64
1974
17
14
20
Percent reduction in
population exposed to
levels above annual
primary NAAQS for TSP
71
74
69
aAnnual NAAQS for total suspended particulate is 75 micrograms per cubic meter.
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10 15 20
PERCENT OF DAYS ABOVE 150 jig/n
25
30
35
Figure 2.9, Population exposed daily to total suspended particulate above"ISOMg'/m3 in New York - New
Jersey - Connecticut Air Quality Control Region.
Table 2-2. PERCENT OF POPULATION LIVING IN AREAS EXCEEDING
24-HOUR NATIONAL AMBIENT AIR QUALITY STANDARD
FOR TOTAL SUSPENDED PARTICULATE
Exposure
frequency
At least 1 day
> 5% of days
>10% of days
> 15% of days
Percent of total
population
1971
86
57
32
19
1974
72
15
4
1
Percent
improvement
17
74
86
95
10
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2.1.4 Conclusion
The discussion above shows that TSP air quality improvements can be described in terms of a number of
separate but related indicators. Four of these trend indicators are; (I)changes in annual averages, (2) changes
in the percent of days exceeding I SO jug/ rnj. (3) changes in the percent of people exposed to the annual standard,
and (4) changes in the percent of people living where 5 percent or more days exceed 150 jug/ mj. Table 2-3 is a
summary of the improvement in TSP by each of the four types of indicators.
Table 2-3. COMPARISON OF TRENDS IN TOTAL SUSPENDED
PARTICULATE AIR QUALITY MEASURES IN NEW YORK-NEW JERSEY-
CONNECTICUT AIR QUALITY CONTROL REGION
Air quality measure
Mean of annual averages
Percent days exceeding daily
NAAQS{150/ig/m3)
Percent of people living where
annual averages exceed 75 #g/m3
Percent of people living where
5% or more of days exceed
IBOjigAn3
1971
79/ag/m3
7.7%
58%
57%
1974
61 jug/nr>3
3.0%
17%
15%
Percent
change
23
61
71
74
The improvement is largely due to the success of emission control plans. Examination of meteorological
data suggests that with the exception of precipitation, 1971 appears meteorologically similar to 1974. In 1971,
there was approximately 20 percent more precipitation than in 1974, Since precipitation tends to remove
particles from the air, it might be expected that the additional precipitation would lower TSP levels slightly
compared to 1974, ifemissions were equal. Thus, the improvement in the air quality indicators shown in Table
2-3 can logically be attributed to the success of the emission control plans.
2.2 MAJOR REDUCTION IN PERCENT OF TIME METROPOLITAN LOS ANGELES
POPULATION IS EXPOSED TO PHOTOCHEMICAL POLLUTION
An analysis similar to that for the New York area was made to.examine the change in population
exposure to oxidantsand nitrogen dioxide in the Los Angeles Air Basin. Air quality data collected from 1965
through 1974 were grouped into 2-year intervals to preserve historical continuity among the trend sites.6 The
analysis showed a considerable reduction in the percent of days the 1-hour primary health standard for
oxidant was violated. People in the Basin were exposed to a concentration above the standard on an average
of 176 days peryearin 1965 and 1966, 144 days per year in 1969 and 1970, and 105 days per year in 1973and
1974. Analysis of nitrogen dioxide data also showed some improvement; people were exposed to a
concentration above the 1-hourCalifornia welfare standard of470 yg/m-1 on an average of 25 days per year in 1965
and 1966, 27 days per year in 1969 and 1970, and 18 days peryearin 1973 and 1974. 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. In addition, progress has been made in the duration of exposure,
particularly in the case of oxidants.
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 census data, A population of 7.9 million was associated with the
oxidanl monitoring data, and the nitrogen dioxide monitoring network was judged to represent 6.5 million
people. Figure 2-10 depicts the spatial variation of the population density over the study area. Figure 2-11
presents the location of the ten monitoring sites that provided the air quality data for this analysis.
II
-------
Figure 2-10. Population density of £os Angeles Air Basin in 1970.
-------
O N02 SITES
O,* 0X1DANT SITES
Figure 2-11. Locations of nitrogen dioxide and oxidani trend sites in Los Angeles Air Basin.
The air quality and population data were interfaced by using a standardized network of 57 receptor points
for the oxidant analysis and 45 receptor points for the nitrogen dioxide analysis (Figure 2-12). The
standardized network 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 was estimated from the actual
monitoring data by spatial interpolation. The estimates of population and air quality were then used to
characterize the region.
2.2.2 Changes in Population Exposed to Oxidants
Daily exposure patterns are displayed on isopleth maps to indicate areas of the region that exceed the I -
hour oxidant standard of 160Mg/mJ for a given percent of the days (Figure 2-13). In 1965 and 1966 more than
O N02 RECEPTOR POINTS
O, OXIDANT RECEPTOR POINTS
Figure 2-12. Standard demographic network for trend analysis in Los Angeles Air Basin.
-------
1965/1966
1967/1968
1969/1970
1971/1972
1973/1974
<20%
>50%
Figure 2-13. Percent of days on which NAAQSfor oxidani was ex-
ceeded during five 2-year periods.
-------
half of the Basin violated the standard more than 50 percent of the days and the rest of the regional least 20
percent "of the days. In 1973 and 1974 the area where the standard was violated more than 50 percent of the
days decreased' to a small area around Azusa. The area where the standard was violated less frequently than 20
percent of the ways appeared in the southern half of the region.
For the days on which the oxidant primary standard was violated, the average number of hours of
violation per day was examined for the 10-year period (Figure 2-14), In 1965 and 1966 the average duration
was longer than 6 hours per day in the inland areas and longer than 3 hours per day in the coastal areas. By the
end of the 10-year period of interest, the average duration in a majority of the inland areas was shorter than 6
hours per day, but still longer than 3 hours per day in some of the coastal areas.
Figure 2-15 depicts the improvements in population exposure to oxidant levels from 1965 through 1974.
Each vertical bar with different hatch marks indicates the percentages of the population exposed to a
concentration above the standard at various percentages of days. For example, in 1965 and 1966,53 percent of
the population was exposed to a concentration above the standard on at least 50 percent of the days. In 1973
and 1974 the percentage of the population with the same exposure dropped to less than 5 percent. The second
group of veritical bars represents the percent of the population exceeding a level twice as high as the standard.
The third group is for three times the oxidant standard.
The region-wide trends in population exposure to oxidant are summarized in Table 2-4. People in the
study region were exposed to a concentration above the standard on an average of 176 days per year during
1965 and 1966, 144 days per year in 1969 and 1970, and 105 days per year in 1973 and 1974. The average
duration of such exposure also decreased from 5.1 hours per dayin 1965 and 1966 to 4.6 hours per day in 1969
and 1970 and to 4.3 hours per day in 1973 and 1974. The trends are similar for values greater than twice the
standard.
The improvement seen in oxidant levels can be explained by meteorological conditions and emission
trends. The overall 10-year decline in oxidants ceflects the steady reduction in reactive hydrocarbon
emissions, but some of the declines during the period can be associated with meteorological cycles. The high
oxidant levels during the period 1965 through 1970 were associated with an unusually high number of days
with poor dispersion. The meteorological cycle reversed itselfduring the period 1971 through 1974 when more
days had good dispersion conditions.
Table 2-4 shows that the 1971 and 1972 annual average of the daily hourly duration is the lowest of the 10-
year period. These 2 years had the fewest hourly excursions of the primary 1-hour standard and twice the
standard during their third quarters. The third quarter is the most important quarter in the oxidant season
since the highest oxidant concentrations and the most frequent violations of the standard occur during that
time of the year. A reduction in the 1971 and 1972 third-quarter concentrations and hourly violations of the
standard resulted in the lowest annual average of the daily hourly duration. During the third quarters of 1971
and 1972, more days had a higher-than-average wind speed than during third quarters of the other 8 years.
A more detailed discussion of the effects of meteorology and emissions on oxidant trends in the Los
Angeles Basin is presented in section 3,4.2
2.2.3 Changes in Population Exposed to Nitrogen Dioxide
Isopleth maps for nitrogen dioxide annual mean concentrations are shown in Figure 2-16. Over much of
the study region the annual average primary N A AQS of 100MS/ m-' was violated throughout the entire 10-year
period. The air quality has improved recently, however. From I967through 1972 concentrations greater than
l30Mg./m-' occurred in the majority of the heavily populated areas, but in 1973 and 1974 such levels were
confined to the San Fernando Valley.
Figure 2-17 depicts the percentages of the population exposed to selected annual average levels of
nitrogen dioxide. For example, the percentage ofthe population exposed to 13Qjug; m-' or higher annual mean
15
-------
1365/1966
1971/1972
1967/1968
1973/1974
L
1969/197 D
Figure 2-14, Average duration on days when NAAQSfor oxidant
was exceeded during five 2-year periods.
-------
NAAQS
1965/66
1967/68
1969/70
1971/72
1973/74
TRIPLE WAAQS
20 40 60
PERCENT OF TOTAL POPULATION
EXAMPLE: IN 1965/68 ABOUT 53% OF THE TOTAL POPULATION WAS
EXPOSED TO OXIDANT LEVELS ABOVE THE NAAQS (160pg/m3 FOR
1 HOUR) MORE THAN 50% OF THE DAYS PER YEAR. IN THE SAME
PERIOD ABOUT 44% OF THE TOTAL POPULATION WAS EXPOSED TO
OXIDANT LEVELS AT TWICE THE NAAQS FOR AT LEAST 20% OF THE
DAYS PER YEAR, BUT LESS THAN 10% OF THE DAYS PER YEAR,
P = % OF DAYS
Figure 2-15. Changes in population exposure to oxidani during five 2-year periods.
n
-------
Table 2-4. VIOLATIONS OF NAAQS FOROX1DANT FROM 1965 TO 1975
IN LOS ANGELES AIR BASIN
Index
Avg No. of days per year
exceeding 160^g/m3
(8pphm)
Avg daily duration,3 hr
Avg No. of days per year
exceeding 320 /ug/m3
(16 pphm)
Avg daily duration,'3 hr
1965 and
1966
176
5.1
70
3.1
1967 and
1968
162
4.8
59
3.1
1969 and
1970
144
4.6
45
2.8
1971 and
1972
109
3.8
26
2.1
1973 and
1974
105
4.3
26
2.9
average daily duration is the average number of hours per day above the oxidant NAAQS.
The average daily duration is the average number of hours per day the oxidarit level was twice the NAAQS.
concentration changed from 19 percent in 1965 and 1966 to 70 percent in 1969 and 1970, and back lo 33
percent in 1973 and 1974. In contrast, virtually everyone was exposed to annual average nitrogen dioxide
levels above the primary standard of 100 figlw? between 1969 and 1974.
The isopleth maps of the percent of days the 1-hour California "welfare" standard of 470 jug/ mj was
violated are shown in Figure 2-18. The area exceeding the standard more frequently than 6 percent of the days
was approximately matched with the area of the City of Los Angeles in 1965 and 1966. extended toalmost the
entire study region from 1967 through 1972, and was confined to the San Fernando Valley in 1973 and 1974.
The isopleth maps of the average hourly duration for days that the California I-hour standard was
exceeded are shown in Figure 2-19. The area with an average duration longer than 3 hours per day was
confined to the north-central part of the San Fernando Valley in 1965 and 1966, extended to the majority of
the study region from 1967 through 1972 and shrank to the Los Angeles downtown area in 1973 and 1974.
The region-wide trends in population exposure to nitrogen dioxide are summarized in Table 2-5. People
in the study region were exposed to a concentration above the I -hour California standard of 470 ^g rn' on an
average of 25 days per year in 1965 and 1966, 27 days per year in 1969and 1970, and 18 days per year in 1973
and 1974. The average duration of such exposure changed from 2.6 hours per day in 1965 and 1966 to 3.0
hours per day in 1969 and 1970 and to 2.5 hours per day in !973 and 1974.
The increasing (1965-1970) and decreasing (1971-1974) trends displayed in the population exposure
statistics correspond to trends m oxides of nitrogen emissions. Emissions increased by 275 tons per day
between 1966 and 1970 and are only now decreasing because of the emission standards for nitrogen dioxide
for 1971 and later-model cars.?
2.3 REFERENCES FOR SECTION 2
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. Environmental Protection Agency, Off ice of Air
Quality Planning and Standards. Research Triangle Park, N.C. Publication No. EPA^SO/ i-73-004.
December 1973.
3. 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.
18
-------
1965/1986
1S71/1972
1967/1988
1973/1974
1969/1970
AREA NOT INCLUDED IN STUDY.
Figure 2-16. Nitrogen dioxide annual mean concentration for five
2-year periods.
-------
1961/66
1967/68
1969/70
1S73/74
iii
I
_L
J_
20 40 60
PERCENT OF TOTAL POPULATION
80
100
EXAMPLE: DURING 1965/66 ABOUT 91% OF THE POPULATION
WAS EXPOSED TO CONCENTRATIONS BETWEEN 100 AND 130
jug/m3. ABOUT 19% WERE EXPOSED TO CONCENTRATIONS
ABOVE 130 Ai8/m3. THE NAAO.S IS 100 jug/m3 ANNUAL AVERAGE.
ANNUAL MEAN
CONCENTRATION,
<100
100-130
Figure 2-17. Changes in total population-exposed to nitrogen, dioxide during five 2-year periods.
4. Monitoring and Air Quality Trends Report, 1974. U.S. Environmental Protection Agency, Officeof Air
Quality Planning and Standards. Research Triangle Park, N.C. Publication No. EPA-450/1-76-001.
February 1976.
5. Horie, Yuji and Arthur C. Stern. Analysis of Population Exposure to Air Polluiion 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.
6. Horie, Yuji and A. Chaplin. Analysis of Population Exposure to Oxidants and Nitrogen Dioxide in the
Los Angeles Basin. Technology Service Corporation, Santa Monica, California. Prepared for' the
Monitoring and Data Analysis Division, U.S. Environmental Protection Agency. August 5, 1976.
7, 1974 Profile of Air Pollution Control, County of Los Angeles, Air Pollution Control District, Los
Angeles, California.
-------
1965/1966
1971/1972
1967/1968
1973/1974
1968/1970
*A'REA KOT INCLUDED IN STUDY.
Figure 2-18. Percent of days on which California 1-hr standard was
exceeded during five 2-year periods.
-------
1965/1966
1971/1972 !
1967/1968
1973/1974;
1969/1970
<2hr
AREA NOT INCLUDED IN STUDY.
Figure 2-19. Average duration on days when California I-hr standard
was exceeded during Jive 2-year periods.
-------
Table 2-5. TREND IN VIOLATIONS OF CALIFORNIA 1-HOUR STANDARD
FOR NITROGEN DIOXIDE AND AVERAGE DURATION a
-------
3. NATIONAL AND REGIONAL TRENDS
IN CRITERIA POLLUTANTS
The "criteria" pollutants are total suspended partieulaies, sulfur dioxide, oxidants, carbon monoxide, and
nitrogen dioxide. The pollutant trends are discussed below on a national and on a regional basis. Obviously,
there are many ways of looking al trends in air quality. The evaluation herein is a discussion of trends with
respect to Ihe National Ambient Air Quality Standards since the passage of the Clean Air Act of 1970.
3.1 TRENDS IN TOTAL SUSPENDED PARTICIPATE
The general improvement in ambient air quality with respect to total suspended paniculate discussed in
previous reports!"4 is continuing. Trends since 1971 indicate a general improvement of 4 percent per year
based upon data from approximately 1800 sites. There have been some geographical differences with
Northeast and Great Lakes areas improving at even higher rates. Trends in some of the Western states have
been fairly stable, probably due to fugitive (wind blown) dust and to some extent due to secondary particulates
caused by photochemical reactions in areas such as Los Angeles and San Francisco.
The overall reduction of ambient total suspended paniculate means that 33 percent fewer people are
exposed to annual mean levels in excess of the primary standard. Further improvements in TSP air quality
levels are anticipated. The present rate of progress may not be sustained since fewer traditional sources remain
to be controlled and since fugitive dust and reentrained urban particulates are more difficult to control.
Even though improvements have been made, a significant ambient TSP problem still remains. The most
recent data show that approximately 50 percent of the state and local monitoring stations have annual
averages in excess of the secondary annual TSP air quality standard. Approximately 30 percent of the nation's
population is still living in areas above the long-term primary annual standard. On July I, 1976, calls were
made for State Implementation Plan (SIP) revisions that would require states to adopt new regulations for areas
where problems exist.
To provide a better understanding of the improvement inTSP levels, it is useful to consider the patterns n,
emissions during the same time period. For the purposes of this report, a brief consideration of emission
trends will suffice, but more detailed information is available elsewhere. 5 Emissions may be described as
either "potential" or "actual." Potential emissions are those that would have occurred without any controls
whereas actual emissions reflect the reductions resulting from controls. The reason for this distinction
becomes apparent when one considers the net improvement in TSP levels. During the 1970-1974 penxJ
potential emissions of particulates from stationary sources increased an estimated 20 percent from industrial
growth. Without additional controls, therefore, TSP levels would not have remained constant but would have
deteriorated further. The reason for the observed net improvement in TSP levels is that the degree of control
increased from 69 percent to 82 percent during this time so that actual emissions were reduced. In fact, in [974
approximately 26 million tons per year of particulates was being controlled that was not controlled in 1970.-*
The data used in the analyses of TSP trends were obtained from EPA's National Aeromelric Data Bank,
Most of these data are collected by state and local agencies and sent to EPA. This section treats four categories of
trends: (1) trends from 1971 to 1975, (2) recent changes in 1974 and 1975, (3) trends in population exposure,
and (4) trends in specific cities.
3.1.1 TSP THENDS IN 1971-1975
in order to present a variety of information in one figure, a modified version of the graphical technique
known as a Box Plot6 [$ used In this section and in the next. These graphs present the 10th, 25th, 5vi!:
(median), 75th, and 90th percentiles of the data, as well as the composite average. The 10th and 2i;:i
percentiles depict the "cleaner" sites. The 75th and 90th depict the "dirtier" sites, and the median and average
describe the "typical" sites. For example, 90 percent of the sites would have concentrations lower than the 9dth
-------
percentile. Also, the ranges of the 10th and 90th percentiles, and the 25th and TSthpercentiles indicate what
"most" of the sites are doing. Although the average and median both characterize typical behavior, the median
has the advantage of not being affected by a few extremely high observations. Figure 3-1 shows how this
information is plotted.
1
I
90TH PERCENTILE
-75TH PERCENTILE
-COMPOSITE AVERAGE
-MEDIAN
-2STH PERCENTILE
-10TH PERCENTILE
Figure 3-1. Sample illustration of plotting conventions
for box plots.
In Figure 3-2, the general improvement in TSP levels is seen in all parameters; however, the use of the Box
Plot technique highlights the more pronounced improvement in the higher concentration ranges. The cleaner
sites are also improving, but the pattern is more stable. The improvement in the composite average is due
primarily to decreases at the higher sites rather than to uniform reductions at all sites. This pattern is
consistent with the pollution control programs in effect. Those sites that already meet the ambient air quality
standards are not so much concerned with further reductions but rather with maintaining their air quality.
110-
100-
90-
70-
Sfl-
4D-
30-
20-
10-
! }
^ rn 1 i f
r-L, _L
o^ ^_^^
T I T T
1971 1972 1973 1974 1975
YEAR
Figure 3-2. Trends of annual mean total suspended paniculate
concentrations from 1971 to 1975 at 1792 sampling sites.
26
-------
While Figure 3-2 shows year-by-year improvement in TSP levels. Figure 3-3 contrasts the frequency
distributions of these sites in 1971 and 1975. The shaded area indicates improvement for all perccntiles. For
example, in 1971 approximately 37 percent of these sites exceeded the primary standard of 75Mg/ m1, but by
1975 only 23 percent were in excess. A greater percentage of sites in the higher concentration ranges show
improvements, and sites in the lower ranges are more stable. Figure 3-4 indicates the percent of sites increasing
40 50 60 70 80 90 100 110 120 130 140 160
CONCENTRATION, pg/m3
Figure 3-3, Frequency distributions in 1971 and 1975 for total suspended paniculate trend sites (semi-log
scale).
a t-
<5
DC y_
z a
SCE
I ty
100(220}"
75-100(432)
o
u
iO-7S(723)
0-10(417)
0
NO CHANGE
I
10 20 30 40 50 60 70 80
90 100
MEASUREMENT SITES, %
'NUMBER OF SITES PER CONCENTRATION RANGE CATEGORY INDICATED IN ( ).
Figure 3-4, Percent oj tal suspended paniculate sites changing by more than 5MS, / 971 -1972 versus 1973
1975 by concentratiat. ange.
-------
or decreasing by S^g/ m3 rordil'ferent concentration ranges. While improvement has been made in all seasons,
ihe lirsl and second quarters have shown the most consistent progress.
Although improvement in TSP levels has occurred throughout broad geographic areas, the West has not
followed this general pattern. The median in the West has been fairly stable but the 90th percentile value has
been somewhat erratic. This may be due to regional differences in the nature of the TSP problem. In some
areas of the West, wind-blown dust is a major determinant of TSP levels. In addition, in areas such as Los
Angeles, secondary particulates are important. Neither of these factors is easily controlled by standard particulate
control measures.
The improvements discussed so far have been presented in terms of changes in annual mean levels.
Another important aspect of the TSP problem is the peak values during the year. During the 1971-1975 time
period many sites increased their sampling frequency and thus complicated the analysis of trends in peak
values. To compensate for this change, the number of days the primary standard was exceeded was estimated
using the lognormal distribution. These formulas are commonly used in air'pollution data analysis and are
reasonably accurate for TSP7 Figure 3-5 was obtained by using the geometric means of the actual data and
an assumed standard geometric deviation of 1.6 and 365 days of sampling. Although based upon estimated
values, this technique is a convenient means of depicting expected improvement from 1971 to 1975 in terms of
peak values.
KC/J
«SC >
Q
-------
SHORT-TERM CHANGiS
IN MEANS
NO CHANGE
SHORT-TERM CHANGES
IN PEAKS
NO CHANGE
10
I
20
40
I
60
60
i
70
I
80
I
90
MEASUREMENT SITES, %
Figure 3-6. Changes by more than 10% for total suspended paniculate during 1974 j1975.
outnumbered increases by more than 3 lo 1. For the case of peak values, the short-term trend also shows more
decreases than increases.
3.1.3 Population Exposure Trends
Section 2 presented trends in population exposure for selected cities. Although this section is primarily
concerned with trends in actual air quality, the data base for TSP is sufficiently dense to permit at least a
preliminary analysis of nationwide trends in population exposure. The nature of the data base does not lend
itself to a detailed analysis as done for selected cities so certain simplifying assumptions were introduced and
1970 census data were used with TSP data from 1970 to 1974. The data are separately examined among
counties in Standard Metropolitan Statistical Areas (SMSA) and the total non-SMSA portions of each AQCR. One
hundred sixty-four million people were considered to live in areas represented by the approximately 1800 TSP
monitors, which had sufficient historical data during the 1970-1974 time period.The percent of population
exposed to a given concentration is assumed to be proportional to the percent of monitoring sites at which this
concentration is exceeded for each area.
Out of 164 million people considered in this analysis, the portion of the population exposed to
concentrations in excess of the primary standard of 75 #g/ mj decreased from 45 percent in 1970 to 30 percent
in 1974. This trend in reduced nationwide population exposure is pictured in Figure 3-7.
Reduced exposures generally occurred at all concentration levels. This is demonstrated by Figure 3-K,
which presents the change, in nationwide population exposure for three concentration levels: 60, 75, and 90
MS- m-1.
100
3.J.4 TSP Trends in Selected Cities
While the previous sections have discussed general trends, the purpose of this section is to highlight
specific cities to illustrate the progress made on a local level. Ten cities were chosen on the basis of available
historical data and broad geographic representation.
While composite averages show a fairly steady change .from year to year, another way lo view these same
data is shown in Figure 3-9. This figure displays the percent of observations that were above the secondary
TSP standard (I50Mg/m-') in selected areas, emphasizing the effect of control measures on high values, in
many cases the improvement is more pronounced than is apparent from the composite average. Forexamplc,
in the New York City area (N.Y.-N.J.-Conn. AQCR). there were 103 sites during this time period. While the
composite average of these sites dropped from 79 to 61 MSf m-'. the percent of limes the secondary standard v as
exceeded decreased from 7.7 percent lo 3.0 percent. Although the composite average showed a 22 pert-.m
improvement, the fraction of times the secondary standard was exceeded showed a 61 percent improvement
Though presentations like Figure 3-9 are useful to indicate relative change within an area, and therein
trends, such a presentation cannot necessarily be used to rank cities. Local monitoring networks may di;-^
-------
YEAR r
1970
1
1072 j
I
i
1
tfl73
1974
PERCENT
45
43
37
32
30
EACH SYMBOL REPRESENTS 8.2 MILLION PEOPLE
(5% OF 164 MILLION BASE)
Figure 3-7. Percent of population exposed to annual mean total
suspended paniculate in excess o/75Mg/mJ (NAAQS)from 1970
through 1974,
CONCENTRATION,/Jg/m3
1970
1974
Figure 3-8. Trend in national population exposure expressed as annual -neon total
suspended paniculate.
appreciably in character; and within a given area there may be appreciable gradients in
discussed in section 2.1 for the New York City area.
i levels, as was
3.2 TRENDS IN SULFUR DIOXIDE
A comparison of the most recent data with those for other recent years sh
concentrations inurbanareashavedecreasedbyanaverageof30percentsince 1970. !
ulfur dioxide
oTSPIevcIs,
30
-------
BOSTON, MA 1970
(3 SITES) 1975
NEW YORK (AQCR) 1971
(103 SITES) 1975
WASHINGTON, DC 1971
(S SITES) 1975
CHARLOTTE, NC 1971
(8 SITES) 1975
DETROIT, Ml 1971
(7 SITES) 1975
CHICAGO, IL 1970
(18 SITES) 1975
DENVER, CO 1971
(6 SITES) 1975
ALBUQUERQUE, NM 1971
(6 SITES) 1975
LOS ANGELES (AQCR) 1971
(11 SITES) 1975
PORTLAND, OR
(5 SITES)
1972
1975
I
I
5 10 15 20 25
VALUES ABOVE SECONDARY STANDARD,%
3D
Figure 3-9. Percent of values above secondary total suspended paniculate standard for
selected cities.
which have shown consistent improvement from year to year, sulfur dioxide levels improved rapidly in the
1970-1973 period and then leveled off as many areas came into compliance with the standards. The data
available through 1975 indicate that sulfur dioxide levels have been relatively stable for the nation as a whole
over the past year. Trends in ambient sulfur dioxide appear to have leveled off or in some cases increased
slightly, apparently because of the failure or .inability to use clean fuels in some areas of the country. For
example, in Los Angeles, ambient sulfur dioxide levels are low but have increased because of recent fuel
shifting associated with natural gas curtailments. A similar pattern appears in parts of the Northeast, where,
for example, data from Boston show slight increases in ambient sulfur dioxide levels during the past year.
From a national perspective, the urban sulfur dioxide problem has diminished so that only a few monitors
in a small number of u: ban areas are exceeding sulfur dioxide NA AQS. Major point sources located outside
of urban areas, such a:> smelters, pose the greatest threat to violation of sulfur dioxide NAAQS at the present
31
-------
lime, A combination of special-purpose ambient monitoring and modeling indicates that sulfur dioxide
,\AAQS are being exceeded around many of these sources.
I he data used in theanalyseso! suifurdioxide Irendswere selected on the basisot historical completeness
during die 1971-1975 time period. As discussed in the overview, there lias been nationwide improvement in
sulfur dioxide levels during the early 1970's; however, an important aspect nationally is that almost 90 percent
of these decreasing-trend sites are in populous areas.
1 he decreasing trend of sulfur dioxide emissions should noi be taken to mean that sulfur dioxide is no
longer a problem. What has happened is that the nature of the sulfur dioxide problem in this country has
changed in the past few years. In the late 1960's many cities had high sulfur dioxide levels. Pollution abatement
has been quite successful in our cities, and sulfur dioxide levels have improved dn-.matically. In many
localities, however, major sulfur oxide sources are located away from urban areas. Sulfur dioxide levels
around these sources are not adequately reflected in the trend data base. Thus, the do\\ nward trends in sulfur
dioxide represent only one part of the total picture. Although substantial improvement has been generally
made in the more heavily populated areas, suflur dioxide is still a problem in some areas.
In many cases, the isolated nature of these non-urban sources makes long-term trend monitoring
difficult, in general, the primary concern with these sources is to monitor the surrounding air for compliance
with the applicable air quality standards. This can be done effectively through special studies at much lower
cost than would be required to maintain trend sites continuously for several years. Moreover, such long-term
trend sites would yield information only for one particular source and be of limited use in assessment of
pollution nationwide,
3.2.1 Sulfur Dioxide Trends (1971-1975)
The Box Plot technique was also used to illustrate sulfur dioxide trends during the 1971-1975 period
(Figure 3-10). For sulfur dioxide the general stabilization is much more pronounced. Despite the overall
improvement in ambient sulfur dioxide levels, it is evident that a leveling off has occurred during the past few
years. The use of the Box Plot technique, however, reveals fairly consistent progress for the sites measuring
higher concentrations. This is emphasized by the decreasing size of the boxes in successive years as the range of
sullur dioxide concentrations decreases. This stabilization of sulfur dioxide at relatively low levels is evidence
60-,
50-
40
S 20-
10-
T T T I T
1171 1972 1973 1974 1971
YEAR
Figure 3-10. Sulfur dioxide trends 1971-1975 (545 .tiles), annual averages.
32
-------
ol the progress made in abatement of sulfur oxide emissions in cities across the nation. As would be expected.
the majority of sites showed improvement during this time period. 11" only those sites with annual averages
greater than 50 percent of the sulfur dioxide standard in 1971-1972 are considered, the results are even more
striking. Over 80 percent of these sites showed improvement during this time period.
Figure 3-11 shows the 90th percentiles for various geographical areas during the 1971-1975 period. The
West is omitted from this graph because it had only 33 sites. (The Los Angeles area is discussed as one of the
"selected cities.") The 90th percentiles for regions except the West indicate the general suflur dioxide
improvement during this period. This figure also points out the higher levels in the northern cities due to
emissions associated with space heating.
80-
70-
60-
50-
SI40-1
30-
20-
10-
NORTHCENTRAL
NORTHEAST
SOUTH
MIDWEST
I I I I I
1971 1972 1973 1974 1975
YEAR
Figure 3-11. 90th percent He trends for sulfur dioxide hy
geographical region (1971-1975),
3.2,2 Recent Changes in Sulfur Dioxide Levels
Figure 3-12 summarizes the number of increases and decreases in sulfur dioxide levels during the past 2
years for quarterly means and peak values. In bolh cases, more sites showed improvement rather than
increases, but the number of sites with no change prevented the emergence of any overall trend, Howeu-r, for
those sites with values greater than 50 percent of the primary sulfur dioxide standards. I he majoriu show
slum-term improvement in bolh means and peak levels.
3.2,3 Sulfur Dioxide Trends in Selected Cities
Because of the recent increases and decreases in sulfur dioxide levels nationally, it is useful to present the
patterns in selected areas in more detail. This is done in Figure 3-13 for the Standard Metropolitan Statistical
Areas with the most sites in each geographical region. This graph illustrates the varied patterns in trends in the
following categories: continued improvement (Chicago), general improvement hut currently stable (Houston).
stable (Nashville), overall general improvement but evidence of trend reversal (Boston).and general increase (Los
Angeles). The major problem for cities is the availability of low-sulfur fuels. In certain areas increases in sulfin
dioxide have been anticipated because of insufficient supplies of low sulfur fuels.
-------
SHORT-TERM CHANGES
IN MEANS
NO CHANGE
SHORT-TERM CHANGES
IN PEAK VALUES
NO CHANGE
10 20 30 40 50 60
MEASUREMENT SITES, %
70
80
90
100
Figure 3-12. Recent changes by more than 10% for sulfur dioxide (1974/1975J.
u
o
u
50-
40-
30-j
20-
LOS ANGELES (11)
* CHICAGO (40)
. BOSTON (17)
10-
0
*ii i j ii r "', r~ | ^ Hi "
1971 1972 1913 1974
HOUSTON (19)
1975
YEAR
Figure 3-13. Composite average sulfur dioxide trends (and number of sites) for dominant
SMS A's in each region.
3.3 TRENDS IN CARBON MONOXIDE
The primary source of carbon monoxide (CO) emissions in most cities is the automobile. Nationally,
approximately 75 percent of the CO emissions are attributed to transportation sources: but in certain areas,
such as Los Angeles, these sources may contribute as much as 99 percent. Any location with sufficient traffic
density may be viewed as having a potential CO problem. The problem may be very localized, perhaps at just a
few street corners, or it may be widespread throughout the center-city area and near major commuter
corridors. Improvements in ambient CO levels are directly related to the comro! of automotive emissions.
3.3.1 Data Base and Trend Techniques
As indicated in previous reports 3-4 historical data i'orCO are inadcqu.au
this analysis, all CO data from EPA's National Aerometrie Data Bank were .
34
i. .-.>.s national trends. For
..CIK*. 10 select sites having
-------
current data. Any site with 4,000 or more hourly values {out of a possible 8760 per year) for at least 3 years was
used ifit also had data from 1975, As a result of this screening process, 102 sites were selected from 24 states.
OI these, 42 were located in California, which is indicati%;e of the well-established air quality'monitoring
program in that state. More than half (34 out of 60) of the sites outside California had data for only 3 years.
Because 3 years of data are usually not sufficient to characterize trends, the approach used in this analysis is to
examine the patterns of groups of sites to present a general picture of CO trends rather than concentrating on
spccilic sites. Non-parametric regression^ was used to assess the sign of the trend at each site, as well as the
signilicance level. The 90th percentile of the 8-hour CO data was used to reflect peak concentrations and yet
introduce more stability than the maximum or second highest value. In addition, the 8-hour average primary
CO standard is the one that is most frequently violated.
3.3.2 CO Trends From 1970 to 1975
CO trends are evaluated by presenting the results for the State of California and comparing these patterns
with those from the rest of the nation. In this way, the extensive California data base provides a convenient
frame of reference for CO trends on the national level.
The CO trends for California are summarized in Table 3-1, and those for the rest of the nation are shown
in Table 3-2. In both cases, the overall picture clearly indicates improve ..^nt. For those sites with data for 3 or
more years, the 81 percent improvement of the California sites agrees closely with the 78 percent showing
improvement for the rest of the country.
Table 3-1. NUMBER AND PERCENT OF CALIFORNIA MONITORING SITES
SHOWING INDICATED TRENDS IN 90TH PERCENTILE OF 8-HOUR
AVERAGE CO CONCENTRATIONS, 1970-1975
Years of data
5 or more
4 or more
3 or more
Down
14(70%)
27 (79%)
34 (81%)
No change
2(10%)
2 (6%)
2 (5%)
Up
4 (20%)
5 (15%)
6 (14%)
Total
20
34
42
Table 3-2. NUMBER AND PERCENT OF NON-CALIFORNIA MONITORING
SITES SHOWING INDICATED TRENDS IN 9QTH PERCENTILE OF 8-HOUR
AVERAGE CO CONCENTRATIONS, 1970-1975
Years of data
5 or more
4 or more
3 or more
Down
12 (75%)
20 (77%)
47 (78%)
No change
0
0
0
Up
4 (25%)
6(23%)
13 (22%)
Total
16
26
60
Because of the variability associated with trends based upon only 3 years of data, more meaningful,
conclusions can bedrav-n from those sites with 4 or more years of data. As shown in the tables, the percent of
sites showing improvement is still inclose agreement (79 percent and 77percent)and basically the same as lor
all data. The California trends are much more pronounced; 44 percent of the sites have statistically significant
improvements, as opposed to 27 percent for the rest of the nation. Also, the rate of improvement appears
greater in California w , a median rate of around 7 percent per year versus 5 percent for the rest of the nation.
The general applicabili* of these median rales is limited by the extent of the data bases, but they do illustrate
35
-------
thai the California trends are more pronounced. With respect to trends in the rest of the nation, there was no
particular geographical clustering, and all arenas of the country had sites showing improvement,
j ;
Another way of determining CO hv6{$ is^'o measure the earboxyhemoglobin level in the blood ofpeople
breathing air polluted with CO. In a sensc,~lhe blood of each individual provides an indicator of his or her
exposure to CO. Reductions in CO emissions should reduce carboxyhemoglobin body-burden in the general
public. Although these types of data are limited, there have beenstudies of carboxyhemoglobin levels in blood
donors.
Trends for Chicago using 1970 and 1974 CO emissions were compared with the mean percent
carboxyhemoglobin fornonsmokers for the same time frame. Carboxyhemoglobin was reduced by 25 percent
(2.04 to 1.53 percent and the weighed average CO emissions declined by 22,8 percent ItM 1 This relatively close
agreement suggests that the CO emission controls are being effective in improving carboxyhemoglobin levels
in the general public.
3.4 TRENDS IN OXIDANTS
The extensive monitoring network of the State of California is reflected in the trend analysis that follows.
Analysis of trends in other parts of the country is impaired by changes in analytical methods, the change from
measuring total oxidants to ozone, or the lack of a monitoring network. Oxidant data for many years were
examined for the Los Angeles Basin, the San Francisco Bay Area, and the San Diego Basin. For areas outside
of California, recent oxidant/ozone trends (1973-1975) were examined.
3.4.1 Data Base and Trend Techniques
For the Los Angeles Basin, five parameters were used to characterize Basinwide oxidant trends: (I) third-
quarter average of hourly data, (2) annual average of daily maximum 1-hour data, (3) the number of days
when levels exceeded the Federal Episode Alert Criteria for oxidants of 200 fJ-gj m3. (4 and 5) the numbers of
third-quarter days exceeding two and three times the N AAQS for oxidants of 160MS/ m3. Oxidant trends in
San Francisco are based on the average daily maximum value for days with comparable meteorology during
the oxidant season. For the San Diego Basin, the annual average of daily maximum 1-hour data was used to
characterize oxidant trends. Data for these analyses were obtained from EPA's National Aerometric Data
Bank and supplemented by publications of the Los Angeles Air Pollution Control District, 12-14 the San
Diego Air resources Board, 15 and the Bay Area Air Pollution Control District. l6
3.4.2 Oxidant Trends in California
The trends in oxidants in California are presented for the most recent 5 years (197 [ to 1975) and for longer
periods up to 10 years. For the Los Angeles Basin, oxidant trends are summarized in Tables 3-3 through 3-6.
The data indicate long-term improvement, with average high-hour oxidant levels declining 31 percent and
average third-quarter concentrations dropping 23 percent.
Table 3-3. SUMMARY OF TRENDS IN ANNUAL AVERAGE OF DAILY
1-HQUR MAXIMUM OXIDANT LEVELS IN LOS ANGELES BASIN
Length of data record
5 years (1971-1975)
10 years (1966-1975)
Number of sites
Down
3(22%)a
9 (31%)
No change
5
0
Up
1 (7%)
0
Total
9
9
3 Numbers in parentheses are percent change in concentration between base year and 1975.
Since 1971, however, the improvement is not so pronounced. Even though annual average daily
maximum levels have declined 22 percent, fewer sites have declined (3 versus 9) in the 5-year versus the 10-year
period. Also, third-quarter average levels have remained unchanged between 1971 and 1975. Similarly, there
36
-------
Table 3-4. SUMMARY OF TRENDS IN THIRD-QUARTER AVERAGE OF
DAILY 1-HOUR OXIDANT LEVELS IN LQjS ANGELES BASIN
Length of data record
5 years (1971-1975)
9 years (1967-1975)
Number^jf sites
Down
0
6(23%)
No change
3
3
Up
0
0
Total
9
9
Table 3-5. SUMMARY OF TRENDS IN NUMBER OF DAYS 1-HOUR OXIDANT
LEVELS EXCEEDED 200 jug/m3 BY QUARTER IN LOS ANGELES BASIN
Length of
data record
5 years
(1971-1975)
10 years
(1966-1975)
Quarter
1st
no
change
down
2nd
no
.change
down
3rd
no
change
no
change
4th
no
change
down
Annual
no
change
down
Table 3-6. SUMMARY OF TRENDS IN NUMBER OF THIRD-QUARTER DAYS
l-HOUR OXIDANT LEVELS EXCEEDED TWO AND THREE TIMES NAAQS
FOR OXIDANT IN LOS ANGELES BASIN, 1970-1975
Number of sites
2 X NAAQS
3 X NAAQS
Down
3
2
No change
8
8
Up
0
1
Total
11
11
is a long-term decline in the total number of days exceeding 200 jug/ m-1 (0.10 ppm) annually, but there is no
change in the past 5 years. While no long-term or short-term change has occurred in the number of third-
quarter days in violation of the 200-/ig/m3 alert level, some improvement has occurred at higher concentration
levels, as indicated by Table 3-6. This is important since the third quarter is the season of greatest
photochemical activity and highest I-hour oxidant concentrations.
The overall 10-year decline in oxidant levels and the absence of a trend in the recent 5-year data maybe
explained by examining hydrocarbon emission trends and meteorological conditions. The annual number of
days with poor atmospheric ventilation 12 (mixing) in the Basin is shown in Figure 3-14. The figure reveals
that during the period 1966 through 1970 an above normal number of days had poor ventilation, but
beginning in 1971 the cycle reversed and fewer than normal of these days occurred. Superimposed upon this is
the steady reduction of reactive hydrocarbon emissions^ seen in Figure 3-14. The results of correlating the
observed meteorology and emissions with the annual average of daily maximum 1-hour oxidants and the
number of days above 200Mg/m3 are shown in Table 3-7. The 10-year oxidant trend is, then, partially
explained by hydrocarbon emissions and atmospheric ventilation. Emissions were found to account for at
least twice as much of the oxidant trend as the meteorology.
37
-------
U)
00
1900
1700
1500
>>
as
1
I 1300
t/f
z
o
1 1100
BOO
700
000
VENTILATION
NORMAL \-/. V-
REACTIVE HYDROCARBONS
(HYDROCARBON EMISSIONS WERE
AVAILABLE FOR 1965,1970,1973,
AND 1i74. DATA FOR OTHER YEARS
WERE DETERMINED BY LINEAR IN-
TERPOLATION OR EXTRAPOLATION.)
1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975
YEAR
Figure 3-14. Atmospheric ventilation and reactive hydrocarbon emissions in Los Angeles County over 10-
year period.
12D
too
20
-------
Table 3-7. PERCENT OF OXIDANT TRENDS DUE "TO ATMOSPHERIC
DISPERSION AND REACTIVE HYDROCARBOliiMISSIONS
IN LOS ANGELES, 1966-1975
Area of Basin
Percent
Azusa - Pasadena - Pomona a
Burbank - Reseda a
Los Angeles, downtown - West Los Angeles
Lennox - Long Beach3
Basinwide
91
80
78
91
95
Annual average of daily 1-hour maximum oxidant concentrations.
''Annual number of days oxidant levels exceeded 200 jzg/m3.
The observed oxidant levels were adjusted for abnormal meteorology using a simple linear model.
Examples of the observed and adjusted trends in Figure 3-15 indicate that adjusting for the meteorology tends
to smooth oxidant trends to follow emission trends more closely. Looking at the meteorological data in
Figure 3-14, it can be seen that atmospheric ventilation induced higher oxidant levels between 1966 and 1970
and lower oxidaat levels from 1971 through 1974.
300
«>
"I 280
p 260
cc
u
2
O
o
a
x
o
240
220
200
180
OBSERVED AIR QUALITY
A ADJUSTED AIR QUALITY
AIR QUALITY AS A FUNCTION
OF EMISSIONS
NUMBER OF DAYS
ABOVE 200 MQ/
(BASINWIDE TOTAL)
ANNUAL AVERAGE OF
DAILY 1-HOUR MAXIMUM
(AZUSA,PASADENA,
POMONA COMPOSITE)
280
260 "I
240
220
cc
UJ
200
180
1B65 . 1967 1S6i 1i71 1973 1971
YEAR
Figure J-/J. Oxidant trends adjusted for meteorology.
39
-------
Comparing the observed and adjusted oxidant levels reveals that abnormal meteorology has altered
annual oxidant levels up to 14 percent per year in 1972 and about 2.5 percent for the 10-year period. The
analysis shows how recent meteorological patterns may have masked the continuous decline in oxidant levels
during the past 5 years and thus have caused the lack of any trend at many sites during this period.
Table 3-8 summarizes both long- and short-term oxidant trends in the San Francisco Bay Area for days
with comparable meteorology during the oxidant seasons. The data were obtained from a report prepared by
the Bay Area Air Pollution Control District.16 Restricting the analysis to days with similar temperature and
inversion conditions minimizes the effect of year-to-year variation due solely to meteorology. As shown in
Table 3-8, all long-term trends and five of the seven short-term trends indicate improvement. Although there
are two short-term increases, neither is statistically significant. All but one of the 13-year improvements were
significant. Oxidant trends in the San Diego Basin are summarized in Table 3-9. In this region of California,
annual average daily oxidant maxima declined 40 percent during the past 10 years; however, recent increases
nearly equal recent declines. No change has, therefore, occurred during the past 5 years in the San Diego
Basin.
3.4.3 Oxidant/Ozone Trends in Areas Outside of California
Ten states outside of California contain sites with at least 3 consecutive years of current oxidant/ ozone
data. Although 3 years of data are insufficient to determine trends at a specific location, the data may provide
information on the tendency of trends in oxidant/ozone level.
For this analysis, third-quarter oxidant data were analyzed at 21 sites in the ten states where sufficient
data are available. Only third-quarter data were analyzed since this represents the season of highest
photochemical activity. The percent of days when the oxidant/ozone standard (160 Mg/ m' I-hour value) was
equalled or exceeded was used to reflect the frequency of violations and yet provide more stability than either
the percent of hours exceeding the standard or the maximum and second-high value. A non-parametric
regression technique was used to indicate the sign of the trend and significance level at each site.
Although none of the trends were statistically significant, as might be expected from the limited amount
of data, a geographic clustering of similar trend signs is apparent. The results indicate a decreasing tendency in
summer oxidant/ ozone violations in the eastern cities (8 sites down, 3 sites up) and an increase at sites in the
Denver area (5 sites up). Unfortunately, the limited number of sites precludes any firm conclusions about
regional trends. The analysis does provide, however, an initial oxidant/ ozone data base, which will continue
to grow as more years of data become available.
3.5 TRENDS IN NITROGEN DIOXIDE
Examination of existing nitrogen dioxide data for potential trend sites indicates that sufficient data are
available for trend evaluations at sites in California, New Jersey, Illinois, Colorado, and Oregon.
3.5.1 Data Base and Trend Techniques
For the Los Angeles Basin, three parameters were used to characterize Basinwide nitrogen dioxide
trends: annual average of hourly data, annual average of daily maximum I-hour data, and the number of days
when nitrogen dioxide levels exceeded the State of California I-hour nitrogen dioxide standard of 470^K/mJ
(0.25 ppm). The annual average of daily maximum 1-hour data was examined in the San Diego Basin, while
the annual mean of nitrogen dioxide was used for the San Francisco Bay Area and all sites outside California.
The California data were obtained from the same sources as the oxidant data in section 3.4 12-15
3.5.2 Nitrogen Dioxide Trends in California
In the Los Angeles Basin, trends in all three parameters indicate an overall Basinwide decline in nitrogen
dioxideduring the period 1971 through 1975. Figures 3-l6and 3-!7show the decline in the Basinwide mean
of the annual average of all hourly data and the annual average of daily maximum values, respectively. A long-
term decline in the geographic variability of nitrogen dioxide levels is also evident. The numberof days
exceeding the California short-term standard does not show as clear a trend. The minimum for the period
1965 through 1975 was reached in 1973; however, since then there has been an increase of about 10 days per
year. This rise is mainly attributable to increases during the fourth quarter, which is (he season of high daily
nitrogen dioxide concentrations at most sites in the Basin.
40
-------
Table 3-8, AVERAGE HIGH-HOUR OXIDANT CONCENTRATIONS FOR DAYS WITH COMPARABLE TEMPERATURE AND INVERSION CONDITIONS
(APRIL THROUGH OCTOBER OXIDANT SMOG SEASONS, 1962-1974)16
Monitoring
stations
San Francisco (SF)
San Leandro (SL)
San Jose (SJ)
Redwood City (RCJ
Walnut Creek (WC>
San Rafael (SRI
BAAPCDb
average
Ln/ermorec
Average high-hour oxidant concentration (Kl), ppm
1962
0.14
0.13
0.11
0.13
0.10
0.08
0.12
(NO)
1i63
0,12
0.16
0.17
0.10
0.11
0.09
0.12
(NO!
1964
0.15
0.19
0.14
0.10
0.10
0.07
0.13
(NDI
1965
0.09
0.19
0.16
0.14
0.11
0.08
0.13
(ND)
1966
0.08
0.14
0.11
0.10
0.10
0.07
0.10
(ND)
1967
O.OB
0.12
0.13
0.09
0.13
0.07
0.10
0.13
1968
0.05
0.11
0.13
0.08
0.10
0.06
0.9
0.18
1969
0.04
0.12
0.13
0.09
0.13
0.07
0.10
0.18
1970
0.07
0.12
0.12
0.08
0.09
0.08
0.09
0,13
1971
0.05
0.11
0.08
0.07
0.09
0.07
0.08
0.11
1972
0,03
0.10
0.10
0.08
0.09
0.05
0.08
0.09
1973
0.04
0.11
0.11
0.07
008
0.05
0.08
0.12
1974
0.05
0.10
0.16
0.07
0.08
0.06
0.09
0.13
13 yr
0.08
0.13
0.13
0.09
0.10
0.07
0.10
0.13
Oxidant trend
direction
1970-74
only
- (NS)a
-INS)
-HNS)
-(MS)
(ND)
-INS)
-(MS)
+(NS!
All
data
(ND)a
(ND)
INS)
(ND)
(NO)
(ND)
(NO)
-(IMS)
aNS - Not Significant, ND - No Data
"For Benchmark stations above with 13 years of record.
cStation with 8 years of record.
-------
Table 3-9, SUMMARY OF TRENDS IN ANNUAL AVERAGE OF DAILY MAXIMUM
1-HOUR OXIDANT LEVELS IN SAN DIEGO AIR BASIN
Length of
data record
5 years (1971-1975)
10 years (1966-1975)
Down
1 (35%)
3 (40%)
No change
1
0
Up
1 (36%)
0
Total
3
3
Numbers in parentheses are present change in concentration between the base year and 1975.
220
o 5 180
a 2
140
o
u
100
HIGHEST MEAN
I
I
I
1968 1969 1i70 1371 1972 1973 1974 197S
YEAR
Figure 3-16, Annual mean nitrogen dioxide levels in the Los Angeles Basin.
Examination of the annual average nitrogen dioxide concentrations at six sites in the San Francisco Bay
Area indicates that increases equalled declines during the period 1971 through 1975. Mean nitrogen dioxide
levels during these years remained at about 5UMg/ mj, which is half of the NAAQS for nitrogen dioxide. In the
San Diego Basin the annual average of daily maximum nitrogen dioxide at the downtown site indicates no
significant trend in nitrogen dioxide between 1971 and 1975.
3-5.3 New Jersey, Colorado, Illinois, and Oregon
The annual average nitrogen dioxide concentrations were examined for three sites in New Jersey for the
period 1969 to 1975. The most striking feature of the data is the reduction in nitrogen dioxide levels from mid-
1973 through mid-1975 at the high concentration sites: Newark, Bayonne, and Camden. These improvements
may be a reflection of the 1973-1974 fuel crisis coupled with the 1974-1975 economic recession. Both events
may have been responsible for reduced emissions in these cities. The decline in nitrogen dioxide levels between
1971 and 1975 is shown in Figure 3-18. Trends for these cities project levels below the annual standard for New
Jersey.
Recent annual average nitrogen dioxide trends in Denver are similar to trends at the New Jersey sites. The
39 percent decrease from mid-1973 through mid-1975 in Denver is comparable to the 39 percent decrease in
Bayonne and the 26 percent decrease in Newark during the same period. In contras*- long-term trends in
Portland, Oregon, show a steady increase in nitrogen dioxide concentrations di "ig 1972 and 1973.
Evidently, the increase was temporarily interrupted during the 1973-1974 fuel crisis s nee nitrogen dioxide
42
-------
PI
EC
t-
UJ
z
o
u
CM
O
340
320
300
280
260
240
220
200
180
I I I T
HIGHEST AVERAGE
BASINWIDE
MEAN (S SITES)
LOWEST AVERAGE
J_
I
I
I
I
1970 1S71
1972
YEAR
1973 1974
1975
figure 3-17. Annual average of daily maximum 1-hour NO2
(4-year running mean) in the Los Angeles Basin.
levels receded in early 1974. Recent data indicate a return to higher concentrations, although levels are stilt far
below the annual standard. With only slightly more than 4 years of data, it is difficult to see clearly whether
emission trends or meteorology are most affecting nitrogen dioxide levels in Portland. At the Chicago
Continuous Air M onitoring Program (CAM P) site nitrogen dioxide levels have fluctuated considerably since
1969. No clear long-term trend is evident, but concentration levels at this site remain above the annual
standard.
3.6 EEFERENCES FOR SECTION 3
1. The National Air Monitoring Program: Air Quality and Emissions Trends - Annual Report, Volumes I
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.
1. Monitoring and Air Quality Trends Reports, 1972. U.S. Environmental Protection Agency, Off ice 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. Environmental Protection Agency, Officeof Air
Quality Planning and Standards. Research Triangle Park, N.C. Publication No. EPA-450/1-74-007.
October 1974.
43
-------
1 140
120
100
S 80
o
X
60
UJ
o 40
20
NEWARK
BAYONNE
CAMDEN
1971 1975
1971 1975
1171 1975
Figure 3-18, Comparison of 1971 and 1975 annual mean levels of nitrogen dioxide in
New Jersey.
4, 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,
5. Participate and Sulfur Oxide Emission Reductions Achieved Nationwide for Selected Industrial Source
Categories, 1970-1974. U.S. Environmental Protection Agency, Office of Enforcement, Washington,
D.C. EPA-340/1-76-001, January 1976.
6. Turkey, J.W. Exploratory Data Analysis - Limited Preliminary Edition, Vol. 1, Chapter 5. Addison-
Wesley Publishing Co., Reading, Mass.
7. Larsen, R. A Mathematical Model for Relating Air Quality Measurements to Air Quality Standards,
U.S. Environmental Protection Agency, Office of Air Programs, Research Triangle Park, N.C,, AP-89,
November 1971.
8, Freas, Warren and T.C. Curran. Application of Nonparametric Regression for Air Quality Trends (in
preparation).
9. Stewart, Richard D., E.D. Baretta, L.R. Platte, E. Stewart, J.H. Kalbfleisch, B. Van Yserloo, and A.A.
Rimm, Carboxyhemoglobin Levels in American Blood Donors, Journal of the American Medical
Association, Vol. 229, August 26, 1974.
10. Stewart, C.L. Hake, A.J. Wu, and J.H. Kalbfleisch, Carboxyhemoglobin Trend in Chicago Blood
Donors, 1970-1975, E.P.A. Scientific Seminar on Automotive Pollutants, February 10, 1975. EPA-
600/9-75-003.
11. Expected Decline in Carboxyhemoglobin Levels as Related to Automobile Carbon Monoxide Emission
Standards, Economics and Science Planning, Supported by the National Science Foundation under
Grant No. STP75-21384, October 1, 1975.
12. Lunche, R.G. Air Quality and Meteorology 1974 Annual Report. County of Los Angeles Air Pollution
Control District, 1975.
44
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13. California Air Quality Data, Vol. VII, No. 1, 2, and 3. 1975 California Air Resources Board, Technical
Services Division.
14. Personal Communications with Jack Paskind, Technical Services Division, California Air Resources
Board.
15. Simeroth, D. and D. Koeberlein. Air Quality in (he San Diego Air Basin, State of California Air
Resources Board. August 1974.
16. Information Bulletin 3-25-75; A Study of Oxidant Concentration Trends, Technical Services Division,
Bay Area Air Pollution Control District.
-------
4. NATIONWIDE EMISSION ESTIMATES, 1970-1975
Estimates of nationwide emissions for 1970 through 1975 were determined from newly calculated,
internally consistent sets of figures based on the most current emission factors and on a more inclusive list of
source categories than those previously used.' Consequently, the emission estimates presented here
supercede any previously published estimates for the years since 1970,2 Obviously, previously published
estimates of emissions for years prior to 1970 will also lack strict continuity with these figures for the 1970
through 1975 period.
Table 4-1 summarizes the total emissions for particulates, sulfur oxides, nitrogen oxides, hydrocarbons,
and carbon monoxide from 1970 through 1975. Tables 4-2 through 4-7 summarize each of the pollutants on a
yearly basis and identify the major categories and several subcategories responsible for significant
contributions to the national totals.
Table 4-1. SUMMARY OF NATIONAL EMISSION ESTIMATES, 1970-1975
(I06tons/yr)
Year
1970
1971
1972
1973
1974
1975
Particulates
26.8
24.9
' 23.4
21.9
20,3
18.0
SOX
34.2
32.3
36.7
35.6
34.1
32.9
NOX
22.7
23.4
24.6
25.7
25.0
24.2
HC
33.9 '
33.3
34.1
34.0
32.9
30.9
CO
113.7
113.7
115.8
111.5
103,3
96.2
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, while emission inventories include all man-made particulates, suspended and settled. Sulfur dioxide
and nitrogen dioxide ambient air monitors measure only those two specific compounds, not all the oxides of
sulfur and nitrogen 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. 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 hydrocarbons are not reported because a reliable method has not yet
been developed for the continuous monitoring of this large and diverse class of compounds. Consequenlly,
monitoring is not required.
4.1 EMISSION TRENDS
Paniculate emissions from 1970 to 1975 (Figure 4-1) have been reduced primarily because of installation
of control equipment on industrial processes, a decrease in coal combustion by non-utility stationary sources,
installation of control equipment by electric utilities that burn coal, and a decrease in the burning of solid
wastes. The extent of the emission reduction by industrial processes is increased as the result of economic
47
-------
Table 4-2. NATIONWIDE EMISSION ESTIMATES, 1970
i106 tons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refinning
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coal refuse burning
Structural fires
Organic solvents
Oil and gas production
and marketing
Total
Particulates
1.3
0.8
0.5
9.7
4.5
5.2
13.6
0.3
0.1
2.0
8.4
2.8
1.2
1.0
0.4
0.2
0.3
0.1
<0.1
0
0
26.8
sox
0.7
0.3
0.4
26.6
19.2
7.4
6.7
0.8
0.7
4.5
0.6
0.1
0.1
0.1
0
0
0
0.1
0
0
0
34.2
NOX
9.3
7.0
2.3
12.3
5.7
6.6
0.6
0.2
0.3
0
0.1
<0.1
0.3
0.2
0.1
<0.1
<0.1
0.1
<0.1
0
0
22.7
HC
14.1
12.3
1.8
1.6
0.1
1.5
3.6
1.8
0.8
0.2
0
0.8
1.9
12.7
O.B
0.2
0.3
0.1
0
7.8
3.7
33.9
CO
88.0
77.4
10.6
1.5
0.2
1.3
11.5
4.3
2.2
3.7
0
1.3
6.8
5.9
3.3
0.6
1.6
0.3
0.1
0
0
113.7
recession which curtailed production by a large number of industries. This is particularly evident in the
emission reduction from 1974 to I975, which is shown.
Total emissions of sulfur oxides are estimated to have declined slightly from I972 through I975 (Figure 4-
I). Monitoring results show that ambient levels in the relatively well-monitored urban areas have declined
markedly in recent years (see Section 3), which suggests a significant shift in the use of higher sulfur fuels by
urban sources to a growing number of sources in relatively sparsely monitored areas. It has also been
estimated 2 that sulfur oxide emissions from electric-power-generating plants increased through at least I973.
These plants contribute some 70 percent of the sulfur oxide emissions in the stationary source category.
Clearly, there has been a substantial decrease of sulfur dioxide in the urban areas according to the airquality
data.
Trends in oxides of nitrogen emissions (Figure 4-1) have increased primarily because of increased
amounts of fuel consumed by electric utilities. To a lesser extent, nitrogen oxide emissions from highway and
non-highway mobile sources have also increased. The increase in nitrogen oxide emissions from highway
mobile sources is due to growth in vehicle-miles traveled (VMT), as well as the implementation of control
measures for CO and hydrocarbons, which have resulted inslightincreasesinnitrogen oxide emissions above
precontrolled levels. For light-duty vehicles nitrogen oxide emission rates per VMT have been reduced since
1972 so that emissions from this category, the mobile source category with the greatest amount of emissions,
have been effectively constant from 1972 to 1975.
Total hydrocarbon emission trends (Figure 4-1) have not changed appreciably during the period from
1970 to 1975. While significant reductions in the HC emissions from highway mobile sources have been
achieved, Ihese decreases in emissions have been offset by increases in industrial process emissions and
48
-------
Table 4-3. NATIONWIDE EMISSION ESTIMATES, 1971
(106 tons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coat refuse burning
Structural fires
Organic solvents
Oil and gas production
and marketing
Total
Particulates
1.3
0.8
0.5
8.8
4.3
4.5
12.8
0.2
0.1
1.6
7.9
3.0
0.9
1.1
0.6
0.2
0.2
0.1
<0.1
0
0
24.9
sox
0.7
0.3
0.4
25.2
18.7
6.5
6.2
0.8
0.7
4.0
0.6
0.1
0.1
0.1
0
0
0
0.1
0
0
0
32.3
NOX
9.8
7.5
2.3
12.5
6.0
6.5
0.6
0,2
0.3
0
0.1
0
0.3
0.2
0.1
<0.1
<0.1
0.1
<0.1
0
0
23.4
HC
13.7
12.0
1.7
1.7
0.1
1.6
3,5
1.7
0.8
0.2
0
0.8
1.5
12.9
0.9
0.2
0.3
0.1
0
7.5
3.9
33.3
CO
88.5
78.1
10.4
1.4
0.2
1.2
11.2
4.3
2.3
3.4
0
1.2
5.2
7.4
5.0
0.6
1.4
0.3
0.1
0
0
113.7
evaporative losses from organic solvent use and petroleum product marketing. These increases reflect
increased consumption of gasoline and distillate fuels for motor vehicle use and increased solvent use for
surface coating, degreasing, and a variety of other uses.
CO emissions have decreased (Figure 4-1) mainly because of the controls applied to highway motor
vehicles and decrease in burning of solid wastes. Industrial process emissions have also been reduced by
decreases in production and the obsolescence of certain high-polluting industrial processes, such as carbon
black manufacture by the channel process.
49
-------
Table 4-4. NATIONWIDE EMISSION ESTIMATES, 1972
(106 tons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coal refuse burning
Structural fires
Organic solvents
'Oil and gas production
and marketing
Total
Particulates
1.3
0.9
0.4
8.1
4.0
4.1
12.3
0.2
0.1
1.7
7,4
2.9
0-8
0.9
0.4
0.2
0.2
0.1
<0.1
0
0
23.4
sox
0.7
0.3
0.4
28.9
21.3
7.6
6.9
0.9
0.8
4.5
0.6
0.1
0.1
0.1
0
0
0
0.1
0
0
0
36.7
NOX
10.4
7.9
2.5
13.1
6.5
6.6
0.7
0.3
0.3
0
0.1
0
0.2
0.2
0.1
<0.1
<0.1
0.1
<0.1
0
0
24.6
HC
14.0
12.2
1.8
1.7
0.1
1.6
3.8
1.8
1.0
0.2
0
0.8
1.2
13.4
0.6
0.2
0.2
<0.1
0
8,4
4.0
34.1
CO
93.5
83.2
10.3
1.4
0.2
1.2
11.2
4.1
2.3
3.6
0
1.2
4.4
5.3
3.5
0,5
0.9
0.3
0.1
0
0
115.8
50
-------
Table 4-5. NATIONWIDE EMISSION ESTIMATES, 1973
(106 tons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coal refuse burning
Structural fires
Organic solvents
Oil and gas production
and marketing
Total
Particulates
1.3
0.9
0.4
7.5
3.7
' 3.8
11.7
0.2
0.1
1.6
7.0
2.8
0.7
0.7
0.4
0.1
0.1
0.1
<0.1
0
'0
21.9
SOX
0.7
0.4
0.3
28.0
22.0
6.0
6.7
0.9
0.9
4,1
0.7
0.1
0.1
0.1
0
0
0
0.1
0
0
0
35.6
NOX
10.9
8.1
2.8
13.7
7.0
6.7
0.7
0.3
0.3
0
0.1
0
0.2
0.2
0.1
0
0
0.1
0
0
0
25.7
HC
13.7
11.8
1.9
1.7
0.1
1.6
3.7
1.8
0,9
0.2
0
. 0.8
1.1
13.8
0.5
0.2
0.1
0.1
0
8.7
4.2
34.0
CO
90,3
80.0
10.3
1.4
0.3
1.1
11.5
4.4
2,4
3.5
0
1.2
4.0
4.3
2,7
0.5
0.7
0.3
0,1
0
0
111,5
53
-------
Table 4-6, NATIONWIDE EMISSION ESTIMATES, 1974
(106 tons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coal refuse burning
Structural fires
Organic solvents
Oil and gas production
and marketing
Total
Particulates
1.3
0.9
0.4
7.0
3,4
3.6
10.6
0.2
0.1
1.5
6.3
2.5
0.6
0.8
0.5
0.1
0.1
0.1
<0.1
0
0
20.3
SQX
0.8
0.4
0.4
26.8
21.1
5,7
6.3
1.0
0.9
3.7
0.7
<0.1
0.1
0.1
0
0
0
0.1
0
0
0
34.1
NOX
10.6
8.1
2.5
13.3
6.9
6.4
0.7
0.3
0.3
0
0.1
0
0.2
0.2
0.1
<0.1
<0.1
0.1
<0.1
0
0
25.0
HC
12.5
10.9
1.6
1.7
0.1
1.6
3.7
1.8
0.9
0.2
0
0.8
1.0
14.0
0.6
0.2
0.1
0.1
0
8.9
4.1
32.9
CO
82.1
72.8
9.3
1.4
0.3
1.1
11.0
4.1
2.5
3.3
0
1.1
3.5
5.3
3.8
0.5
0.6
0.3
0.1
0
0
103.3
52
-------
Table 4-7. NATIONWIDE EMISSION ESTIMATES, 1975 (PRELIMINARY)
(106 lons/yr)
Source category
Transportation
Highway
Non-highway
Stationary fuel combustion
Electric utilities
Other
Industrial processes
Chemicals
Petroleum refining
Metals
Mineral products
Other
Solid waste
Miscellaneous
Forest wildfires
Forest managed burning
Agricultural burning
Coal refuse burning
Structural fires
Organic solvents
Oil and gas production
and marketing
Total
Particulates
1.3
0.9
0.4
6.6
3.5
3.1
8.7
0.2
0.1
1.3
4.5
2.6
0.6
0.8
0.4
0.1
0.1
0.1
0.1
0
0
18.0
SOX
0.8
0.4
0.4
26.3
21.0
5.3
5.7
1.0
0.9
3.2
0.6
<0.1
<0.1
0.1
0
0
0
0.1
0
0
0
32.9
NOX
10.7
8.2
2.5
12.4
6.8
5.6
0.7
0.3
0.3
0
0.1
<0.1
0.2
0.2
0.1
<0.1
<0.1
0.1
<0.1
0
0
24.2
HC
11.7
10.0
1.7
1.4
0.1
1.3
3.5
1.6
0.9
0.2
0
0.8
0.9
13.4
0.6
0.2
0.1
0.1
<0.1
8.3
4.2
30.9
CO
77.4
67.8
9.6
1.2
0.3
0.9
9.4
3.3
2,2
2.8
0
1.1
3.3
4.9
3.3
0.5
0.6
0.3
0.1
0
0
96.2
4.2 REFERENCES FOR SECTION 4
1.
2.
3.
Mann,C.O. OAQPSData File of Nationwide Emissions. (1970-1975). U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards. Research Triangle Park, N. C. August 1976. (These reports
are standard computer reports available from the National Air Data Branchj Monitoring and Data Analysis
Division, OAQPS.)
Monitoring and Air Quality Trends Report, 1974. U.S. Environmental Protection Agency, Office of Air
Quality Planning and Standards. Research Traingle Park, N.C. Publication No. EPA-450/1-76-001.
February 1976.
Position Paper on Regulation of Atmospheric Sulfates. U.S. Environmental Protection Agency, Office
of Air Quality Planning and Standards. Research Triangle Park, N.C. Publication No. EPA-450 " 75-
007. September 1975. 87p.
-------
40
30
A 20
10
D&E
70 71
40
3D
« 20
10
70 71
PARTICIPATE MATTER -
72 73
YEAR
74 78
1 I I
NITROGEN OXIDES
J_
72 73
YEAR
74 75
40
30
10
I I I I
70 71
40
3D
20
10
_ D&E
70 71
SULFUR OXIDES
72 73
YEAH
HYDROCARBONS
I
71 73
YEAR
74 75
74 78
120
110
100
90
80
70
60
SO
40
30
20
10
70 71
CARBON MONOXIDE
I
I
72 73
YEAR
74 75
Figure 4.L Calculated total emmissions of criteria pollutants by source category, 1970 through 1975 (A: Transportation, B:
Stationary Source Fuel Combustion, C: Industrial Processes, D: Solid Waste, E: Miscellaneous),
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-450/1-76-002
3. RECIPIENT'S ACCESSIOWNO.
4. TITLE AND SUBTITLE
National Air Quality and Emissions Trends Report, 1975
5. REPORT DATE
November 1976
6. PERFORMING ORGANIZATION CODE
7, AUTHOFUS)
W. F, Hunt, Jr. (Editor), T. C. Curran,
!. Frank, W. Cox, R. Neliqan, N. Possiel, C. Mann
8, PERFORMING ORGANIZATION REPO'RT 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 1925
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
emphasized. Changes in air quality
the New York-New Jersey-Connecticut
16. ABSTRACT
This report presents national and regional trends in air quality through 1975 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
levels are discussed for two selected areas:
Air Quality Control Region, accounting for 17 million people}and the Los Angeles
Basin, accounting for 8 million people. Both areas show considerable improvement
in reducing adverse pollution levels. The trend 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 1970-1975 are also presented.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b. IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution Trends
Emission Trends
Carbon Monoxide
Nitrogen Dioxide
Oxidants
Sulfur Dioxide
Total Suspended P ciculates
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF
:ss
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
55 -frl), S. GOVERNMENT PRINTING OFFICE:. 1976 - ";.11-110/305
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