United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/4-86-001
April 1986
Air
National Air Quality and
Emissions Trends Report,
1984
1975 1978 1977 1978 1979 1980 1981 1982 1983 1984
TtAR
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EPA-450/4-86-001
NATIONAL AIR QUALITY AND EMISSIONS
TRENDS REPORT, 1984
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
U.S. Environrren"l Pr lection Agency
Region V, I,;:/x '
230 South [:..-: ' v:_;-3t :"
Chicago, Illinois 60504 -..^
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DISCLAIMER
This report has been reviewed by the Office of Air Quality Planning
and Standards, Environmental Protection Agency, and approved for publication.
Mention of trade names or commercial products is not intended to constitute
endorsement or recommendation for use.
US. . -* *
Agency
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PREFACE
This is the twelfth annual report of air pollution trends issued by
the Monitoring and Data Analysis Division of the U. S. Environmental
Protection Agency. The report is directed toward both the technical
air pollution audience and the interested general public. The Division
solicits comments on this report and welcomes suggestions on our trend
techniques, interpretations, conclusions, and methods of presentation.
Please forward any response to William F. Hunt, Jr., (MD-14) U. S.
Environmental Protection Agency, Monitoring and Data Analysis Division,
Research Triangle Park, N. C. 27711.
The Monitoring and Data Analysis Division would like to acknowledge
William F. Hunt, Jr., for the overall management, coordination, and
direction given in assembling this report. Special mention should also
be given to Helen Hinton and Jo Harris for typing the report.
The following people are recognized for their contributions to
each of the sections of the report as principal authors:
- William F. Hunt, Jr. and Robert E. Neligan
- William F. Hunt, Jr.
- Thomas C. Curran, Robert B. Faoro, Neil H. Frank, and
Warren Freas
- William F. Hunt, Jr. and Robert B. Faoro
- Stan Sleva, Neil Berg, David Lutz, George Manire,
and Dennis Shipman
Also deserving special thanks are Karen Nelson for assembling the
air quality data base and preparing the computer graphics, Chuck Mann
and Jake Summers for the emission trend analyses, George Duggan for the
population exposure estimates, and David Henderson and Coe Owen of EPA
Region IX for providing us with their computer software to generate the
air quality maps of the United States used in this report.
Section 1
Section 2
Section 3
Section 4
Section 5
i n
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CONTENTS
LIST OF FIGURES vii
LIST OF TABLES xvii
1. EXECUTIVE SUMMARY 1-1
1.1 INTRODUCTION 1-2
1.2 MAJOR FINDINGS 1-5
1.3 REFERENCES 1-20
2. INTRODUCTION 2-1
2.1 DATABASE 2-3
2.2 TREND STATISTICS 2-4
2.3 REFERENCES 2-8
3. NATIONAL AND REGIONAL TRENDS IN CRITERIA POLLUTANTS.... 3-1
3.1 TRENDS IN TOTAL SUSPENDED PARTICULATE 3-5
3.2 TRENDS IN SULFUR DIOXIDE 3-11
3.3 TRENDS IN CARBON MONOXIDE 3-21
3.4 TRENDS IN NITROGEN DIOXIDE 3-27
3.5 TRENDS IN OZONE 3-33
3.6 TRENDS IN LEAD 3-41
3.7 REFERENCES 3-47
4. AIR QUALITY LEVELS IN STANDARD METROPOLITAN STATISTICAL
AREAS 4-1
4.1 SUMMARY STATISTICS 4-1
4.2 AIR QUALITY SMSA COMPARISONS 4-3
4.3 REFERENCES 4-5
5. TREND ANALYSIS FOR TEN URBANIZED AREAS 5-1
5.1 BOSTON, MASSACHUSETTS URBANIZED AREA 5-4
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5.2 NEW YORK, NEW YORK-NORTHEASTERN NEW JERSEY URBANIZED
AREA 5-9
5.3 PHILADELPHIA, PENNSYLVANIA-NEW JERSEY URBANIZED
AREA 5-14
5.4 ATLANTA, GEORGIA URBANIZED AREA 5-19
5.5 CHICAGO, ILLINOIS-NORTHWESTERN INDIANA URBANIZED
AREA 5-24
5.6 HOUSTON, TEXAS URBANIZED AREA 5-29
5.7 ST. LOUIS, MISSOURI-ILLINOIS URBANIZED AREA 5-34
5.8 DENVER, COLORADO URBANIZED AREA 5-39
5.9 LOS ANGELES-LONG BEACH, CALIFORNIA URBANIZED AREA. 5-44
5.10 PORTLAND, OREGON-WASHINGTON URBANIZED AREA 5-49
5.11 REFERENCES 5-55
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FIGURES
Figures Page
1-1 National Trend in the Composite Average of the Geometric 1-2
Mean Total Suspended Participate at Both NAMS and All Sites,
1975-1983.
1-2 National Trend in Participate Emissions, 1975-1983. 1-3
1-3 National Trend in the Annual Average Sulfur Dioxide 1-5
Concentration at Both NAMS and All Sites, 1975-1983.
1-4 National Trend in the Composite Average of the Second-Highest 1-6
24-hour Sulfur Dioxide Concentration at Both NAMS and
All Sites, 1975-1983.
1-5 National Trend in the Composite Average of the Estimated 1-6
Number of Exceedances of the 24-hour Sulfur Dioxide NAAQS
at Both NAMS and All Sites, 1975-1983.
1-6 National Trend in Sulfur Oxide Emissions, 1975-1983. 1-7
1-7 National Trend in the Composite Average of the Second-Highest 1-8
Nonoverlapping 8-hour Average Carbon Monoxide Concentration
at Both NAMS and All Sites, 1975-1983.
1-8 National Trend in the Composite Average of the Estimated 1-8
Number of Exceedances of the 8-hour Carbon Monoxide NAAQS
at Both NAMS and All Sites, 1975-1983.
1-9 National Trend in Emissions of Carbon Monoxide, 1975-1983. 1-9
1-10 National Trend in the Composite Average of Nitrogen Dioxide 1-9
Concentration at Both NAMS and All Sites, 1975-1983.
1-11 National Trend in Emissions of Nitrogen Oxides, 1975-1983. 1-10
1-12 National Trend in the Composite Average of the Second-Highest 1-11
Daily Maximum 1-hour Ozone Concentration at Both NAMS and All
Sites, 1975-1983.
1-13 National Trend in the Emissions of Volatile Organic 1-11
Compounds, 1975-1983.
1-14 National Trend in the Composite Average of the Number 1-12
of Daily Exceedances of the Ozone NAAQS in the Ozone
Season at Both NAMS and All Sites, 1975-1983.
1-15 National Trend in Maximum Quarterly Average Lead Levels at 61 1-13
Sites (1975-1983) and 138 Sites (1980-1983).
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1-16 Lead Consumed in Gasoline, 1975-1983. 1-14
(Sales to the Military Excluded)
1-17 National Trend in Lead Emissions, 1975-1983. 1-14
1-18 National Boxplot Trend in Second Highest Daily Maximum
1-Hour 03 Concentrations, 1975-1984. 1-15
1-19 National Trend in Emissions of Volatile Organic
Compounds, 1975-1984. 1-16
1-20 National Trend in the Composite Average of the Number
of Daily Exceedances of the 03 NAAQS in the 03 Season,
1975-1984. 1-16
1-21 United States Map of the Highest Second Daily Maximum
1-Hour Average 03 Concentration by SMSA, 1984. 1-17
1-22 National Boxplot Trend in Maximum Quarterly Average
Pb Concentrations, 1975-1984. 1-18
1-23 National Trend in Lead Emissions, 1975-1984. 1-19
1-24 United States Map of the Highest Maximum Quarterly
Average Lead Concentration by SMSA, 1984. 1-19
viii
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Figures Page
2-1 Ten Regions of the U.S. Environmental Protection 2-5
Agency
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Figures Page
3-1 Sample Illustration of Use of Confidence Intervals to 3-2
Determine Statistically Significant Change.
3-2 Illustration of Plotting Conventions for Boxplots. 3-3
3-3 National Trend in the Composite Average of the Geometric 3-6
Mean Total Suspended Particulate at Both NAMS and All
Sites with 95 Percent Confidence Intervals, 1975-1984.
3-4 Boxplot Comparisons of Trends in Annual Geometric Mean 3-6
Total Suspended Particulate Concentrations at 1510
Sites, 1975-1984.
3-5 National Trend in Particulate Emissions, 1975-1984. 3-8
3-6 Annual Nationwide Area - Weighted Total Precipitation 3-9
Compared to Long-term TSP Trends, 1975-1984.
3-7 Comparison of Long-term and Recent Trends in Annual 3-10
Geometric Mean Total Suspended Particulate Concentrations.
3-8 Regional Comparison of the 1982, 1983, 1984 Composite 3-10
Average of the Geometric Mean Total Suspended
Particulate Concentration.
3-9 National Trend in the Composite Average of the Annual 3-13
Average Sulfur Dioxide Concentration at Both NAMS and All
Sites with 95% Confidence Intervals, 1975-1984.
3-10 National Trend in the Composite Average of the Second- 3-13
Highest 24-hour Sulfur Dioxide Concentration at Both
NAMS and all sites with 95 Percent Confidence
Intervals, 1975-1984.
3-11 National Trend in the Composite Average of the Estimated 3-14
Number of Exceedances of the 24-hour Sulfur Dioxide NAAQS
at Both NAMS and all Sites with Confidence Intervals,
1975-1984.
3-12 Boxplot Comparisons of Trends in Annual Mean Sulfur 3-15
Dioxide Concentrations at 229 Sites, 1975-1984.
3-13 Regional Comparisons of Trends in Second Highest 24-hour 3-15
Average Sulfur Dioxide Concentrations at 224 Sites,
1975-1984.
3-14 National Trend in Sulfur Oxide Emissions, 1975-1984. 3-16
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Figures Page
3-15 National Smelter Emissions vs. Air Quality Trends, 1975- 3-18
1984.
3-16 Comparison of Long-term and Recent Trends in Annual 3-18
Average Sulfur dioxide Concentrations.
3-17 Regional Comparison of the 1982, 1983, 1984 Composite 3-19
Average of the Annual Average Sulfur Dioxide Concentration.
3-18 Regional Boxplot Comparisons of the Annual Avrage Sulfur 3-19
Dioxide Concentrations in 1984.
3-19 National Trend in the Composite Average of the Second 3-22
Highest Nonoverlapping 8-hour Average Carbon Monoxide
Concentration at both NAMS and All Sites With 95 Percent
Confidence Intervals, 1975-1984.
3-20 Boxplot Comparisons of Trends in Second Highest Non- 3-22
overlapping 8-hour Average Carbon Monoxide Concentrations
at 157 Sites, 1975-1984.
3-21 National Trend in the Composite Average of the Estimated 3-23
Number of Exceedances of the 8-hour Carbon Monoxide
NAAQS, at both NAMS and all Sites with 95 Percent
Confidence Intervals, 1975-1984.
3-22 National Trend in Emissions of Carbon Monoxide, 1975-1984. 3-25
3-23 Comparison of Long-term and Recent Trends in Second Highest 3-26
Nonoverlapping 8-hour Average Carbon Monoxide Concentrations.
3-24 Regional Comparison of the 1982, 1983, 1984 Composite 3-26
Average of the Second Highest Nonoverlapping 8-hour
Average Carbon Monoxide Concentration.
3-25 National Trend in the Composite Average of Nitrogen Dioxide 3-28
Concentration at both NAMS and all Sites with 95 Percent
Confidence Intervals, 1975-1984.
3-26 Boxplot Comparisons of Trends in Annual Mean Nitrogen 3-28
Dioxide Concentrations at 119 Sites, 1975-1984.
3-27 National Trend in Emissions of Nitrogen Oxides, 1975-1984. 3-30
3-28 Comparison of Long-term and Recent Trends in Annual Mean 3-31
Nitrogen Dioxide Concentrations.
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Figures Page
3-29 National Trend in the Composite Average of Nitrogen 3-31
Dioxide Concentration at both NAMS and all Sites with
95 Percent Confidence Intervals, 1980-1984.
3-30 Regional Comparison of the 1982, 1983, 1984 Composite 3-32
Average of the Annual Mean Nitrogen Dioxide
Concentration.
3-31 National Trend in the Composite Average of the Second 3-35
Highest Maximum 1-hour Ozone Concentration at both
NAMS and all Sites with 95 Percent Confidence
Intervals, 1975-1984.
3-32 Boxplot Comparisons of Trends in Annual Second Highest 3-35
Daily Maximum 1-hour Ozone Concentrations at 163 Sites,
1975-1984.
3-33 National Trend in the Composite Average of the Estimated 3-36
Number of Daily Exceedances of the Ozone NAAQS in the
Ozone Season at both NAMS and all Sites with 95 Percent
Confidence Intervals, 1975-1984.
3-34 National Trend in Emissions of Volatile Organic Compounds, 3-37
1974-1985.
3-35 Comparison of Long-term and Recent Trends in Annual 3-38
Second Highest Daily Maximum 1-hour Ozone Concentrations.
3-36 Regional Comparison of the 1982, 1983, 1984 Composite 3-38
Average of the Second-highest Daily 1-hour Ozone
Concentrations.
3-37 National Trend in the Composite Average of the Maximum 3-42
Quarterly Average Lead Concentration at 36 Sites (1975-
1984) and 147 Sites (1980-1984) with 95 Percent
Confidence Intervals.
3-38 Boxplot Comparisons of Trends in Maximum Quarterly 3-42
Average Lead Concentrations at 36 Sites, 1975-1984.
3-39 National Trend in Lead Emissions, 1975-1984. 3-44
3-40 Comparisons of Long-term and Recent Trends in Maximum 3-45
Quarterly Average Lead Concentrations.
xn
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Figures
3-41 National Trend in the Composite Average of the Maximum
Quarterly Average Lead Concentration at both NAMS and
all Sites with 95 Percent Confidence Intervals, 1980-
1984.
3-42 Regional Comparison of the 1982, 1983, 1984 Composite 3-46
Average of the Maximum Quarterly Average Lead
Concentration.
xm
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Figures Page
4-1 Nunber of Persons Living in Counties with Air Quality 4-2
Levels Above the National Ambient Air Quality Standards
in 1984 (Based on 1980 Population Data).
4-2 United States Map of the Highest Annual Geometric Mean 4-6
Suspended Particulate Concentration by SMSA, 1984.
4-3 United States Map of the Highest Annual Arithmetic Mean 4-15
Sulfur Dioxide Concentration by SMSA, 1984.
4-4 United States Map of the Highest Second Maximum 24-Hour 4-24
Average Sulfur Dioxide Concentration by SMSA, 1984.
4-5 United States Map of the Highest Second Maximum Non- 4-33
overlapping 8-Hour Average Carbon Monoxide
Concentration by SMSA, 1984.
4-6 United States Map of the Highest Annual Arithmetic Mean 4-42
Nitrogen Dioxide Concentration by SMSA, 1984.
4-7 United States Map of the Highest Second Daily Maximum 4-51
1-Hour Average Ozone Concentration by SMSA, 1984.
4-8 United States Map of the Highest Maximum Quarterly Average 4-60
Lead Concentration by SMSA, 1984
xiv
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Figures Page
5-1 Illustration of Plotting Conventions for Ranges Used 5-3
in Urbanized Area Trend Analysis.
5-2 Location of TSP, Pb, and S02 Monitoring Sites in 5-6
Boston, MA, 1980-1984.
5-3 Location of 03, N02, and CO Monitoring Sites in 5-7
Boston, MA, 1980-1984.
5-4 Air Quality Trends in the Composite Mean and Range 5-8
of Pollutant-Specific Statistics for the Boston,
MA Urbanized Area, 1980-1984.
5-5 Location of TSP, Pb, and S02 Monitoring Sites in New 5-11
York, NY-NJ, 1980-1984.
5-6 Location of 03, NOg, and CO Monitoring Sites in New 5-11
York, NY-NJ, 1980-1984.
5-7 Air Quality Trends in the Composite Mean and Range 5-13
of Pollutant-Specific Statistics for the New York,
NY-NJ Urbanized Area, 1980-1984.
5-8 Location of TSP, Pb, and S02 Monitoring Sites in 5-16
Philadelphia, PA-NJ, 1980-1984.
5-9 Location of 03, N02, and CO Monitoring Sites in 5-17
Philadelphia, PA-NJ, 1980-1984.
5-10 Air Quality Trends in the Composite Mean and Range of 5-18
Pollutant-Specific Statistics for the Philadelphia,
PA-NJ Urbanized Area, 1980-1984.
5-11 Location of TSP, Pb, and S02 Monitoring Sites in 5-21
Atlanta, GA, 1980-1984.
5-12 Location of 03, N02, and CO Monitoring Sites in Atlanta, 5-22
GA, 1980-1984.
5-13 Air Quality Trends in the Composite Mean and Range of 5-23
Pollutant-Specific Statistics for the Atlanta, GA
Urbanized Area, 1980-1984.
5-14 Location of TSP, Pb, and S02 Monitoring Sites in 5-26
Chicago, IL-IN, 1980-1984.
5-15 Location of 03, N02, and CO Monitoring Sites in Chicago, 5-27
IL, 1980-1984.
xv
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Figures Page
5-16 Air Quality Trends in the Composite Mean and Range 5-28
of Pollutant-Specific Statistics for the Chicago,
IL-IN Urbanized Area, 1980-1983.
5-17 Location of TSP, Pb, and S02 Monitoring Sites in 5-31
Houston, TX, 1980-1983.
5-18 Location of 03, N02, and CO Monitoring Sites in 5-32
Houston, TX, 1980-1983.
5-19 Air Quality Trends in the Composite Mean and Range 5-33
of Pollutant-Specific Statistics for the Houston,
TX Urbanized Area, 1980-1983.
5-20 Location of TSP, Pb, and S02 Monitoring Sites in 5-36
St. Louis, MO-IL, 1980-1983.
5-21 Location of 03, N02, and CO Monitoring Sites in 5-37
St. Louis, MO-IL, 1980-1983.
5-22 Air Quality Trends in the Composite Mean and Range of 5-38
Pollutant-Specific Statistics for the St. Louis, MO-IL
Urbanized Area, 1980-1983.
5-23 Location of TSP, Pb, and S02 Monitoring Sites in 5-41
Denver, CO, 1980-1983.
5-24 Location of 03, N02, and CO Monitoring Sites in 5-42
Denver, CO, 1980-1983.
5-25 Air Quality Trends in the Composite Mean and Range 5-43
of Pollutant-Specific Statistics for the Denver,
CO Urbanized Area, 1980-1983.
5-26 Location of TSP, Pb, and S02 Monitoring Sites in Los 5-46
Angeles, CA, 1980-1983.
5-27 Location of 03, N02, and CO Monitoring Sites in Los 5-47
Angeles, CA, 1980-1983.
5-28 Air Quality Trends in the Composite Mean and Range of 5-48
Pollutant-Specific Statistics for the Los Angeles-
Long Beach, CA Urbanized Area, 1980-1983.
5-29 Location of TSP, Pb, and S02 Monitoring Sites in 5-52
Portland, OR-WA, 1980-1983.
xvi
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Figures Page
5-30 Location of 03, N02, and CO Monitoring Sites in Portland, 5-53
OR-WA, 1980-1983.
5-31 Air Quality Trends in the Composite Mean and Range of 5-54
Pollutant-Specific Statistics for the Portland, OR-WA
Urbanized Area, 1980-1983.
xv ii
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TABLES
Tables Page
2-1 National Ambient Air Quality Standards (NAAQS). 2-2
2-2 Comparison of Number of Sites for 10-Year and 2-6
5-Year Air Quality Trends
3-1 National Particulate Emission Estimates, 3-8
1975-1984.
3-2 National Sulfur Oxide Emission Estimates, 3-16
1975-1984.
3-3 National Carbon Monoxide Emission Estimates, 3-25
1975-1984.
3-4 National Nitrogen Oxide Emission Estimates, 3-30
1975-1984.
3-5 National Volatile Organic Compound Oxide 3-37
Emission Estimates, 1975-1984.
3-6 National Lead Emission Estimates, 1975-1984. 3-44
4-1 Number of Persons Living in Counties with Air 4-2
Quality Levels Abve the National Ambient Air
Quality Standards in 1984 (Based on 1980
Popul ation Data.
4-2 Highest Annual Geometric Mean Suspended 4-7
Particulate Concentration by SMSA, 1984.
4-3 Highest Annual Arithmetic Mean Sulfur Dioxide 4-16
Concentration by SMSA, 1984.
4-4 Highest Second Maximum 24-hour Average Sulfur 4-25
Dioxide Concentration by SMSA, 1984.
4-5 Highest Second Maximum Nonoverlapping 8-hour 4-34
Average Carbon Monoxide Concentration by SMSA,
1984.
4-6 Highest Annual Arithmetic Mean Nitrogen Dioxide 4-43
Concentration by SMSA, 1984.
4-7 Highest Second Daily Maximum 1-hour Average Ozone 4-52
Concentration by SMSA, 1984.
xviii
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Tables Page
4-8 Highest Maximum Quarterly Average Lead Concentration 4-61
by SMSA, 1982.
5-1 Air Quality Trend Statistics and Their Associated 5-
National Ambient Air Quality Standards (NAAQS)
xix
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NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 1984
EXECUTIVE SUMMARY
1-1
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NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 1984
1. EXECUTIVE SUMMARY
1.1 INTRODUCTION
While considerable progress has been made controlling air pollution,
it still remains a serious public health problem. In order to protect the
public health and welfare, the U.S. Environmental Protection Agency (EPA)
has promulgated National Ambient Air Quality Standards (NAAQS). Primary
standards protect the public health, while secondary standards protect the
public welfare, as measured by the effects of air pollution on vegetation,
materials and visibility. This report will focus on comparisons to the
primary standards to examine both changes in air pollution levels over
time, as well as current air pollution status.
In 1984, 79.2 million people were living in counties with measured air
quality levels, that violated the NAAQS for ozone (03) (Figure 1-1). This
compares with 61.3 million people for carbon monoxide (CO), 32.6 million
people for total suspended particulate (TSP), 7.5 million people for nitrogen
dioxide (N02), 4.7 million people for lead (Pb) and 1.7 million people for
sulfur dioxide (S02). While millions of people continue to breathe air
that is in violation of the NAAQS, considerable progress is being made in reduc-
ing air pollution levels.
TSP
SO2
1
I
CO '1613
ilhiliiiiiliililiililiiiiiiiiiliiliiUiiii
NO2
OZONE
7 5
.
i iU. iUii liiiiiiihil. iUn ililUi Ui.i.i i
79 2
4 7
20 40 60
MILLIONS OF PERSONS
80
100
Figure l-l.
Number of persons living in counties with air quality levels above
the primary National Ambient Air Quality Standards in 1984 (Based
on I960 population data).
I-2
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Nationally, long-term 10-year (1975 through
seen for TSP, S02, CO, N02, 03, and Pb. Similar
documented in earlier air quality trends reports
in 03 is complicated by a major drop in measured
occurred between 1978 and 1979, largely due to a
1984) improvements can be
improvements have been
I'll issued by EPA. The trend
concentration levels which
change in the 03 measurement
calibration procedure.12 Therefore, special attention is given to the
period after 1979, because the change in the calibration procedure is not an
influence during this time.
The 10-year trend (1975-1984) is complemented with a more recent 5-year
trend (1980-1984). The 5-year trend is being introduced in this report to
increase the number of sites available for trend analysis. Future trends
reports will focus on the post-1980 period to take advantage of the larger
number of sites and the fact that the data from the post-1980 period should
be of the highest quality, with sites meeting uniform siting criteria and
high standards of quality assurance. Nationally, improvements can be seen
for all the pollutants during the 5-year period. Between 1983 and 1984,
however, TSP, S02 and N02 showed slight increases, while CO showed a slight
decline, Pb a more substantial decline, and 03 declined from its 1983 level to
the levels of 1981 and 1982.
The trends in ambient air quality, that follow, are presented as
boxplots, which display the 5th, 10th, 25th, 50th (median), 75th, 90th and
95th percentiles of the data, as well as the composite average (Figure 1-2).
The 5th, 10th and 25th percentiles depict the "cleaner" sites, while the
75th, 90th and 95th depict the dirtier sites and the median and average
describe the "typical" sites. The use of the boxplots allow us to simul-
taneously compare trends in the "cleaner", "typical" and "dirtier" sites.
I
-TSHlPCRCCHTlLE
~ COMPOSITE AVERAGE
Figure 1-2. Illustrations of plotting conventions for boxplots,
1-3
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All of the ambient air quality trend analyses are based on monitoring
sites which recorded at least 8 of the 10 years of data in the period
1975 to 1984 or 4 out of 5 years in the period 1980 to 1984. Each year
had to satisfy an annual data completeness criteria, which is discussed
in Section 2.1, Data Base.
Finally, the Executive Summary also contains air quality maps of the
United States to show at a glance how air quality varies among the 80
largest standard metropolitan statistical areas (SMSA). In each map, a
spike is plotted at the city location on the map surface. This represents
the highest pollutant concentration, recorded in 1984, corresponding to the
appropriate air quality standard. Each spike is projected onto a backdrop
facilitating comparison with the level of the standard. This also provides
an east-west profile of concentration variability throughout the country.
1-4
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1.2 MAJOR FINDINGS
Total Suspended Particulate (TSP ) - Annual average TSP levels, measured
at 1344 sites, decreased 20 percent between 1975 and 1984 (Figure 1-3).
This corresponds to a 33 percent decrease in estimated particulate emissions
for the same period (Figure 1-4). TSP air quality levels generally do not
improve in direct proportion to estimated emissions reductions, because air
quality levels are influenced by factors such as natural dust, reintrained
street dust, construction activity, etc., which are not included in the
emissions estimates. EPA has found that the TSP data collected during the
years 1979-1981 may be biased high due to the glass fiber filter used during
these years, and that most of the large apparent 2-year decrease in pollutant
concentrations between 1981 and 1982 can be attributed to a change in these
f liters J ' »13, 14 por ^\-(]S reason, the portion of the Figure 1-3 graph
corresponding to 1979-1981 is stippled, indicating the uncertainty associated
with these data. TSP decreased between 1982 and 1983, while rainfall
increased. Then in 1984, the TSP levels increased 2 percent over the 1983
levels, following a return of rainfall to more normal levels and an increase
in particulate emissions. The most recent 1984 annual geometric mean TSP
concentration is plotted for the 80 largest SMSA(s) (Figure 1-5). The highest
concentrations are generally found in the industrial Midwest and arid areas
of the West. The east-west profile shows that levels above the current
standard of 75 ug/m^ can be found throughout the Nation.
too
to
80
70-
JO
20
to
0
1975 1976 1977 1978 1979 I960 1981 1982 1983 1984
YEAR
Figure 1-3. National boxplot trend in annual geometric mean TSP
concentrations, 1975 - 1984.
1-5
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15
TSP EMISSIONS, 106 METRIC TONSAEAR
SOURCE CATEGORY
SOUD WASTE & MISC a FUEL
COMBUSTION
ra INDUSTRIAL PROCESSES E3 TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-4. National trend in participate emissions, 1975 - 1984.
Figure 1-5. United States map of the highest annual geometric mean
TSP concentration by SMSA, 1984.
1-6
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Sulfur Dioxide (S02) - Annual average S02 levels measured at 229 sites
with continuous S02 monitors decreased 36 percent from 1975 to 1984 (Figure
1-6). A comparable decrease of 41 percent was observed in the trend in the
composite average of the second maximum 24-hour averages (Figure 1-7). An
even greater improvement was observed in the estimated number of exceedances
of the 24-hour standard, which decreased 93 percent (Figure 1-8). Corre-
spondingly, there was a 16 percent drop in sulfur oxide emissions (Figure
1-9). The difference between emissions and air quality can be attributed
to several factors. S02 monitors are mostly urban population-oriented and
as such do not monitor many of the major emitters which tend to be located
in more rural areas. The residential and commercial areas, where most
monitors are located, have shown sulfur oxide emission decreases comparable
to S02 air quality improvement. Between 1983 and 1984, nationwide average
S02 levels increased 2 percent. The increase in ambient levels correspond
to a 4 percent increase in sulfur oxide emissions, which reflects increased
fuel consumption. The most recent 1984 annual arithmetic mean S02 is
plotted for the 80 largest SMSA(s) (Figure 1-10). Among these large
metropolitan areas, the higher concentrations are found in the heavily
populated Midwest and Northeast. The peak S02 mean concentration occurs in
Pittsburgh, PA at an individual site near a large steel complex. All other
urban areas have lower ambient air quality concentrations, well within the
current annual standard of 80 ug/m^ (.03 ppm). Because this map only
represents areas with population greater than one half million, it does not
reflect air quality in the vicinity of smelters or large power plants in
rural areas.
0.040
0.015-
0.030-
0.029-
0.020-
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 1-6. National boxplot trend in annual average S02 concentrations,
1975 - 1984.
1-7
-------
(US
0.00
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 1-7. National boxplot trend in second highest 24-hour S02
concentrations, 1975 - 1984.
2.5
o
I
lii
o
2
ts
o
in
1975 1976 1977 (978 1979 1880 1981 1982 1*83 <9S4
YEAR
Figure 1-8. National trend in the composite average of the estimated
number of exceedances of the 24-hour S02 NAAQS, 1975 - 1984,
1-8
-------
S0y EMISSIONS, 106 METRIC TONS/YEAR
SOURCE CATEGORY
INDUSTRIAL PROCESSES HE FUEL COMBUSTION
0
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-9. National trend in sulfur oxide emissions, 1975 - 1984.
Figure 1-10.
United States map of the highest annual arithmetic mean
S02 concentration by SMSA, 1984.
1-9
-------
Carbon Monoxide (CO) - Nationally, the second highest non-overlapping
8-hour average CO levels at 157 sites decreased 34 percent between 1975 and
1984 (Figure 1-11). Although the median rate of improvement has been approx-
imately 5 percent per year, this rate is less pronounced in the last few
years. The estimated number of exceedances of the 8-hour NAAQS decreased
88 percent between 1975 and 1984 (Figure 1-12). CO emissions decreased 14
percent during the same period (Figure 1-13). Because CO monitors are
typically located to identify potential problems, they are likely to be
placed in traffic saturated areas that may not experience significant
increases in vehicle miles of travel. As a result, the air quality levels
at these locations generally improve at a rate faster than the nationwide
reduction in emissions. Between 1983 and 1984, CO levels decreased only 1
percent. This leveling off appears to be consistent with CO emissions for
the highway vehicle portion of the transportation category which showed a 1
percent decrease between 1983 and 1984. The most recent 1984 highest second
maximum nonoverlapping 8-hour average CO concentration is plotted for the
80 largest SMSA(s) (Figure 1-14). The east-west profile indicates that
many of these urban areas in all geographic regions have air quality at or
exceeding the 9 ppm level of the standard.
u
I
o
OB
1
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 1-11. National boxplot trend in second highest nonoverlapping
8-hour average CO concentrations, 1975 - 1984.
1-10
-------
50
8
2 so
8
cc
o
I
Legend
1975 1*7$ 1977 1978 1979 1980 1961 19S2 19*3 1984
YEAR
Figure 1-12. National trend in the composite average of the estimated
number of exceedances of the 8-hour CO NAAQS, 1975 - 1984.
125
CO EMISSIONS, 106 METRIC TONS/YEAR
100-
75-
SOURCE CATEGORY
SOUD WASTE ft MISC CD FUEL
COMBUSTION
INDUSTRIAL PROCESSES E! TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-13. National trend in emissions of carbon monoxide, 1975 - 1984.
1-11
-------
Figure 1-14. United States map of the highest second maximum nonoverlapping
8-hour average CO concentration by SMSA, 1984.
1-12
-------
Nitrogen Dioxide (NO?) - Annual average N02 levels, measured at 119
sites, increased from 1975 to 1979, decreased through 1983 and then recorded
a slight increase in 1984 (Figure 1-15). The 1984 composite N02 average,
however, is ]0 percent lower than the 1975 level indicating a downward
trend during the overall period. The trend in the estimated nationwide
emissions of nitrogen oxides (NOX) is similar to the N02 air quality trend.
Between 1975 and 1984, total nitrogen oxide emissions increased by 3 percent,
but highway vehicle emissions, the source category likely impacting the
majority of N02 monitoring sites, decreased by 4 percent (Figure 1-16).
Between 1983 and 1984, the N02 composite average increased by 2 percent,
while the estimated emissions of nitrogen oxides increased by 3 percent.
The most recent 1984 highest annual arithmetic mean NO^ concentration is
plotted for the 80 largest SMSA(s) (Figure 1-17). Los Angeles, California
is the only area in the country exceeding the air quality standard of .053 ppm.
0.07
0.04
§0.0,
B
0.04-
0.03
0.01-
O.OO
1975 1976 1977 1878 1979 1980 1981 1982 1983 1984
YEAR
Figure 1-15.
National boxplot trend in annual average N02 concentrations
1975 - 1984.
1-13
-------
30
NCL EMISSIONS, 106 METRIC TONS/YEAR
25-
20-
15-
10-
5-
SOURCE CATEGORY
CH FUEL COMBUSTION
SOLID WASTE &
MISC.
INDUSTRIAL PROCESSES ^ TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-16. National trend in emissions of nitrogen oxides, 1975 - 1984,
Figure 1-17.
United States map of the highest annual arithmetic mean
NC>2 concentration by SMSA, 1984.
1-14
-------
Ozone (03) - Nationally, the composite average of the second highest
daily maximum 1-hour 03 values, recorded at 163 sites, decreased 17 percent
between 197b and 1984 (Figure 1-18). Volatile organic compound (VOC) emis-
sions decreased 6 percent during the same period (Figure 1-19). Although
the 1984 composite average for the 163 trend sites is 17 percent lower than
the 1975 average, the interpretation of this decrease is complicated by a
calibration change for 03 measurements that occurred in the 1978-79 time
period. The stippled portion of Figures 1-19 and 1-20 indicate data affected
by measurements taken prior to the calibration change. In the post
calibration period (1979 to 1984), 03 levels decreased 7 percent (Figure 1-18),
while VOC emissions decreased 10 percent. The estimated number of exceedances'
of the 03 standard decreased 36 percent (Figure 1-20). The 03 trends in
the 1980's show that the 1980 and 1983 values were higher than those in
1981 1982 and 1984. The previously reported increase between 1982 and
I983H was followed by a decrease of approximately 10 percent between 1983
and 1984. The magnitude of the 1982-83 increase and 1983-84 decrease was
likely attributable to meteorological conditions that were more conducive
to 03 formation in 1983. The 1984 ambient ozone levels are very similar to
the 1981-82 levels. This occurred despite an estimated national growth
of almost 200 billion vehicle miles of travel between 1980 and 198415 and
an expansion of economic activity in 1984. The most recent 1984 highest
second daily maximum 1-hour average 03 concentration is plotted for the 80
largest SMSAs (Figure 1-21). Slightly over half of these areas did not
meet the 0.12 ppm standard in 1984, The highest concentrations are observed
in Southern California, but high levels also persist in the Texas Gulf
Coast, Northeast corridor, and other heavily populated regions.
O.JO
0.23
0.20
o.e-
0.03-
0.00
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure
1-18. National boxplot trend in second highest daily maximum 1-hour
03 concentrations, 1976 - 1984.
1-15
-------
40
VOC EMISSIONS, 10' METRIC
30-
20
10-
SOURCE CATEGORY
I SOUD WASTE, FUEL C3 TRANSPORTATION
COMBUSTION ft MISC
I NONINDUSTRIAL CZ3 INDUSTRIAL PROCESSES
ORGANIC SOLVENT
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-19. National trend in emissions of volatile organic compounds,
197b - 1984.
20
15-
I
Legend
UTS
m*
vn im
um raao
YEAR
we*
»«2 »» »*«
Figure 1-20.
National trend in the composite average of the number of
daily exceedances of the 03 NAAQS in the 03 season, 1975 - 1984,
1-16
-------
Figure 1-21. United States map of the highest second daily maximum 1-hour
average 1)3 concentration by SMSA, 1984.
1-17
-------
Lead (Pb) - The composite maximum quarterly average of ambient Pb
levels, recorded at 36 urban sites, decreased 70 percent between 1975 and
1984 (Fiyure 1-22). Lead emissions declined 72 percent during the same
period (Figure 1-23). In order to increase the number of trend sites, the
1980 to 1984 time period was examined. A total of 147 trend sites (1980 to
1984) from 23 States measured a 45 percent decline in Pb levels, correspond-
ing to a 43 percent decrease in estimated Pb emissions. Between 1983 and
1984 ambient Pb levels declined 7 percent, while Pb emissions are estimated
to have declined 13 percent. The decrease in ambient Pb levels results
from three main EPA control programs. Regulations issued in the early 1970's
resulted in the Pb content of all gasoline being gradually reduced over the
period of years. Secondly, unleaded gasoline was introduced in 1975 for
use in automobiles equipped with catalytic control devices. Third, Pb
emissions from stationary sources have been reduced by both the TSP and Pb
control programs. The most recent 1984 highest maximum quarterly average
lead concentration is plotted for the 80 largest SMSAs (Figure 1-24). The
highest concentrations are found throughout the country in cities containing
nonferrous smelters or other point sources of lead. Because of the switch
to unleaded gasoline, other areas, primarily affected by automotive lead
emissions, show levels below the current standard of 1.5 ug/m^.
J.S
s-
o>
at
1.5
2
Z
0.5
V V
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 1-22.
National boxplot trend in maximum quarterly average Pb
concentrations, 1975 - 1984.
1-18
-------
200
LEAD EMISSIONS, 106 METRIC TONS/YEAR
FUEL
COMBUSTION
INDUSTRIAL PROCESSES E3 TRANSPORTATION
150-
100-
50-
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 1-23. National trend in lead emissions, 1975 - 1984.
Figure 1-24.
United States map of the highest maximum quarterly average
lead concentration by SMSA, 1984.
1-19
-------
1.3 REFERENCES
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, NC. Publication No. EPA-450/l-73-001a and b. July 1973.
2. Monitoring and Air Quality Trends Report, 1972. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, NC. 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, NC. Publication No. EPA-4bO/l-74-007. October 1974.
4. Monitoring and Air Quality Trends Report, 1974. t). S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA 450/1-76-001. February
1976.
5. National Air Quality and Emission Trends Report, 1975. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA 450/1-76-002. November 1976.
6. National Air Quality and Emission Trends Report, 1976. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/1-77-002. December 1977.
7. National Air Quality, Monitoring, and Emissions Trends Reports,
1977. U. S. Environmental Protection Agency, Office of Air Quality Planning
and Standards, Research Triangle Park, NC. Publication No. EPA-450/2-78-052.
December 1978. »
8. 1980 Ambient Assessment - Air Portion. U. S. Environmental Protection
Agency, Office of Air Quality Planning and Standards. Research Triangle
Park, NC. Publication No. EPA-450/4-81-014. February 1981.
9. National Air Quality and Emissions Trends Report, 1981. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/4-83-011. April 1983.
10. National Air Quality and Emissions Trends Report, 1982. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/4-84-002. March 1984.
1-20
-------
11. National Air Quality and Emissions Trends Report, 1983. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, NC. Publication No. EPA-45U/4-84-U29. April 1985.
12. Federal Register, Vol. 43, June 22, 1978, pp 26971-26975.
13. Mauser, Thomas R., U. S. Environmental Protection Agency, memorandum
to Richard G. Rhoads, January 11, 1984.
14. Frank, N. H., "Nationwide Trends in Total Suspended Particulate
Matter and Associated Changes in the Meaurement Process," Proceedings of
the APCA/ASQC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. October 1984.
15. Highway Statistics 1984, U. S. Department of Transportation,
Federal Highway Administration, Washington, D. C. Publication No. HHP-41/
10-8b(3M)QE. October 1985.
1-21
-------
2. INTRODUCTION
This report focuses on both 10-year (1975-1984) and 5-year (1980-1984)
national air quality trends in each of the major pollutants as well as
Regional and, where appropriate, short-tenn air quality trends. The
national analyses are complimented in Section 5 with air quality trends
in selected urbanized areas for the period 1980 through 1984. In both
the national 5-year trend and the urbanized area trends, the shorter
time period was used to expand the nirnber of sites available for trend
analysis. The areas that were examined are: Atlanta, GA; Boston, MA;
Chicago, IL-Northwestern IN; Denver, CO; Houston, TX; Los Angeles-Long
Beach, CA; New York, NY-Northeastern NO; Philadelphia, PA-NJ; Portland,
OR-WA; and St. Louis, MO-IL.
The national air quality trends are presented for all sites and the
National Air Monitoring Station (NAMS) sites. The NAMS were established
through monitoring regulations promulgated in May 1979^ to provide
accurate and timely data to the U. S. Environmental Protection Agency
(EPA) from a national air monitoring network. The NAMS are located in
areas with high pollutant concentrations and high population exposure.
These stations meet uniform criteria for siting, quality assurance,
equivalent analytical methodology, sampling intervals, and instrument
selection to assure consistent data reporting among the States. Other
sites operated by the State and local air pollution control agencies,
such as the State and Local Air Monitoring Stations (SLAMS) and Special
Purpose Monitors (SPM), in general, also meet the same rigid criteria,
except that in addition to being located in the area of highest concen-
tration and high population exposure, they are located in other areas
as well.
In addition to ambient air quality, trends are also presented for
annual nationwide emissions. These emissions are estimated using the
best available engineering calculations; the ambient levels presented
are averages of direct measurements. The emission trends are taken
from the EPA publication, National Air Pollutant Emission Estimates,
1940-19842 and the reader is referred to this publicat ion for more
detailed information.
Air quality progress is measured by comparing the ambient air
pollution levels with the appropriate primary and secondary National
Ambient Air Quality Standards (NAAQS) for each of the pollutants (Table
2-1). Primary standards protect the public health; 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 or quarterly mean that may not be exceeded; short-term standards
specify upper limit values for 1-, 3-, 8-, or 24-hour averages. With
the exception of the pollutant ozone, the short-term standards are not
to be exceeded more than once per year. The ozone standard requires
that the expected number of days per calendar year with daily maximum
hourly concentrations exceeding 0.12 parts per million (ppm) be less
than or equal to one.
2-1
-------
TABLE 2-1. National Ambient Air Quality Standards (NAAQS)
POLLUTANT
TSP
SOc
N02
Pb
PRIMARY (HEALTH RELATED)
AVERAGING TIME CONCENTRATION
Annual Geometric
Mean
24-hour
Annual Arithmetic
Mean
24-hour
8-hour
1-hour
75 ug/m3
260 ug/m3
(0.03 ppm)
80 ug/m3
(0.14 ppm)
365 ug/m-3
9 ppm
(10 mg/rrH)
(35 ppm}
40 mg/m-*
Annual Arithmetic 0.053 ppm
Mean (100 ug/m3)
Maximum Daily 1-hour 0.12 ppm
Average (235 ug/m3)
Maximum Quarterly 1.5 ug/m3
Average
SECONDARY (WELFARE RELATED)
AVERAGING TIME CONCENTRATION
Annual Geometric
Mean
24-hour
3-hour
60 ug/m3''
150 ug/m3
1300 ug/m3
(0.50 ppm)
No Secondary Standard**
No Secondary Standard
Same as Primary
Same as Primary
Same as Primary
*This annual geometric mean is a guide to be used in assessing
implementation plans to achieve the 24-hour standard of 150 ug/m3.
**Because no standards appear to be requisite to protect the public
welfare from any known or anticipated adverse effects from ambient
CO exposures, EPA rescinded the existing secondary standards.
Section 4 of this report, "Air Quality Levels in Standard
Metropolitan Statistical Areas (SMSA's);" provides interested members of
the air pollution control community, the private sector and the general
public with greatly simplified air pollution information. Air quality
statistics are presented for each of the pollutants for all SMSA's with
populations exceeding 500,000 for the years 1982, 1983 and 1984.
2-2
-------
2.1 DATA BASE
The ambient air quality data used in this report were obtained
from EPA's National Aerometric Data Bank (NADB). Air quality data are
submitted to the NADB by both State and local governments, as well as
federal agencies. At the present time, there are over 250 million air
pollution measurements on the NADB, the vast majority of which represent
the more heavily populated urban areas of the Nation.
As in last year's report3, the size of the available air quality
trends data base has been expanded by merging data at sites which have
experienced changes in the agency operating the site, the instrument
used, or a change in the project code, such as a change from residential
to commercial. A discussion of the impact of the merging of the air
quality data is presented in each of the individual pollutant discussions.
In order for a monitoring site to have been included in the national
10-year trend analysis, the site had to contain at least 8 out of the
10 years of data in the period 1975 to 1984. For the national 5-year
trend and urban area analyses, the site had to contain 4 out of 5 years
of data to be included as a trend site. Each year with data had to
satisfy an annual data completeness criterion. To begin with, the air
quality data are divided into two major groupings -- 24-hour measurements
and continuous 1-hour measurements. The 24-hour measurements are
obtained from monitoring instruments that produce one measurement per
24-hour period and are operated on a systematic sampling schedule of
once every 6 days or 61 samples per year. Such instruments are used to
measure TSP, S02, N02, and Pb. For these measurement methods, the NADB
defines a valid quarter's record as one consisting of at least five sample
measurements representively distributed among the months of that quarter.
Distributions of measurements that show no samples in 2 months of a
quarter or that show no samples in 1 month and only one sample in
another month are judged unacceptable for calculating a representative
estimate of the mean. A valid annual mean for TSP, S0£ and N0£, measured
with this type of sampler, requires four valid quarters to satisfy the NADB
criteria. For the pollutant lead, the data used has to satisfy the
criteria for a valid quarter in at least 3 of the 4 possible quarters
in a year for the national trend.
The 1-hour data are obtained from monitoring instruments that
operate continuously, producing a measurement every hour for a possible
total of 8760 hourly measurements in a year. For continuous hourly
data, a valid annual mean for SOg and NO? requires at least 4380 hourly
observations. This same annual data completeness criteria of at least
4380 hourly values was required for the CO standard related statistics -
the second maximum nonoverlapping 8-hour average and the estimated
number of exceedances of the 8-hour average CO standard.
A slightly different criteria was used for the S02 standard related
daily statistics - the second daily maximum 24-hour average and the
estimated number of daily exceedances of the S02 standard. Instead of
requiring 4380 or more hourly values, 182 or more daily values were
required. A valid day is defined as one consisting of at least 18
2-3
-------
hourly observations. This minor modification in the criteria resulted
in a 2 percent difference in the total number of SOg trend sites for
the 10 year trend evaluation of the annual arithmetic mean, 229 sites, as
opposed to 224 trend sites for the evaluation of both the second maximium
daily average and the estimated number of standard exceedances. There
was no difference in the number of S02 trend sites for the 5 year trend
period. Each statistic - annual arithmetic mean, the second maximum daily
average and the estimated number of exceedances - had the same number
of trend sites.
Finally, because of the seasonal nature of ozone, both the
second daily maximum 1-hour value and the estimated number of exceedances
of the 03 NAAQS were calculated for the ozone season, which varies by
State.^ For example, in California the ozone season is defined as 12
months, January through December, while in New Jersey it is defined as 7
months, April through October. In order for a site to be included it
had to have at least 50 percent of the daily data in the ozone season.
For all the pollutants, the site must satisfy the annual completeness
criterion, specified above, in at least 8 out of 10 years to be included
in the 10-year air quality trends data base and 4 out of 5 years in
both the 5-year trend and urbanized area trend data bases. The shorter
time period was used in the urbanized area analyses to expand the
number of sites available for trend analyses.
In calculating the national and urban area trend analyses each site
was weighted equally. The report examines both 10-year (1975 to 1984)
and 5-year (1980 to 1984) trends. The 5-year trend period is being
introduced at this time to increase the number of trend sites available
for analysis (Table 2-2). The trend from 1980 on reflects the period
following the promulgation of the monitoring regulations.1 The
regulations required uniform siting of monitors and placed greater
emphasis on quality assurance. In general, the data from the post 1980
period should be of the highest quality. As would be expected, there are
considerably more trend sites for the 5-year period than the 10-year
period - 3697 total trend sites versus 2048 trends sites, respectively
(Table 2-2). This 81 percent increase in the number of trends sites
for the 5-year period over the 10-year period reflects the greater
utilization of the ambient air quality data that is achieved by examining
the shorter time period. Trend sites can be found in all EPA Regions
(Figure 2-1) for TSP, S02, CO, N02 and 03 and nine EPA Regions for
lead for the 5-year period.
2.2 TREND STATISTICS
The air quality analyses presented in this report comply with the
recommendations of the Intra-Agency Task Force on Air Quality Indicators.6
This task force was established in January 1980 to recommend standardized
air quality indicators and statistical methodologies for presenting air
quality status and trends. The Task Force report was published in
February 1981. The air quality statistics used in these pollutant-
specific trend analyses relate directly to the appropriate NAAQS1s.
Two types of standard-related statistics are used - peak statistics
2-4
-------
*!/ RICO,
VIRGIN
ISLANDS
HAWAII.
GUAM
Figure 2-1. Ten regions of the U. S. Environmental Protection Agency.
2-5
-------
(the second maximum 24-hour S0£ average, the second maximum nonoverlapping
8-hour CO average, and the second daily maximum 1-hour 03 average) and
long-term averages (the annual geometric mean for TSP, the annual
TABLE 2-2. Comparison of Number of Sites for 10-Year and 5-Year Air
Quality Trends
POLLUTANT
Total Suspended
Particulate (TSP)
Sulfur Dioxide (S02)
Carbon Monoxide (CO)
Ozone ()3)
Nitrogen Dioxide (N02)
Lead (Pb)
Total
NUMBER OF SITES
1975-84 TREND 1980-84 TREND
1344
2048
229
157
163
119
36
2048
477
309
480
236
147
3697
% CHANGE IN THE
NUMBER OF TREND
SITES
1975-84 vs. 1980-84
+52%
+108%
+96%
+ 194%
+98%
+308%
+81%
2-6
-------
arithmetic means for S02 and N02, and the quarterly arithmetic mean for
lead). In the case of the peak statistics, the second maximum value is used,
because this is the value which traditionally has been used to determine
whether or not a site has or has not violated an air quality standard
in a particular year, and, therefore, the second maximum value is of
significant importance. A composite average of each of these statistics
is used, by averaging each statistic over all available trend sites, in
the graphical presentations which follow.
In addition to the standard related statistics, other statistics are
used, when appropriate, to further clarify observed air quality trends.
Particular attention is given to the estimated number of exceedances of
the short-term NAAQS's. The estimated number of exceedances is the
measured number of exceedances adjusted to account for incomplete sampling.
The emission data are reported as teragrams (one million metric
tons) emitted to the atmosphere per year.2 These are estimates of the
amount and kinds of pollution being generated by automobiles, factories,
and other sources, based upon the best available engineering calculations
for a given time period. More detailed information on the calculation of
emissions data is presented in Reference 2.
2-
-------
2.3 REFERENCES
1. Federal Register, Vol. 44, May 10, 1979, pp 27558-27604
2. National Air Pollutant Emission Estimates, 1940-1984. U.S.
Environmental Protection Agency. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-85-014.
January 1986.
3. National Air Quality and Emission Trends Report, 1983. U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA-450/4-84-029.
April 1985.
4. Rhoads, Richard G., U. S. Environmental Protection Agency,
memorandum to the Director of the Environmental Services Divisions and
Air and Waste Management Divisions, EPA Regions I through X, December 15,
1982.
5. Dixon, W. J. and F. J. Massey (1957). Introduction to Statistical
Analysis, McGraw-Hill, NY. 1957.
6. U.S. Environmental Protection Agency Intra-Agency Task Force
Report on Air Quality Indicators.U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park, NC.
Publication No. EPA-450/81-015. February 1981.
2-8
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3. NATIONAL AND REGIONAL TRENDS IN CRITERIA POLLUTANTS
This chapter focuses on both 10-year (1975-1984) and more recent
5-year (1980-1984) trends in each of the six major pollutants, as well
as short term air quality trends. Comparisons are made between all the
trend sites and the subset of NAMS. Trends are examined for both the
Nation and the ten EPA Regions.
The air quality trends data base has been expanded for all pollutants
by merging data at sites which have experienced changes in the agency
operating the site, the instrument used, or the designation of the
project code, such as residential to commercial. The impact of merging
the air quality data is discussed in each of the individual pollutant
sections.
The air quality trends information is presented using trend lines,
confidence intervals, boxplotsl and bar graphs. This report presents
statistical confidence intervals to facilitate a better understanding
of measured changes in air quality. Confidence intervals are placed
around composite averages, which are based on sites that satisfy annual
data completeness requirements. The confidence intervals can be used
to make comparisons between years; if the confidence intervals for any
2 years do not overlap, then the composite averages of the 2 years are
significantly different (Figure 3-1). Ninety-five percent confidence
intervals for composite averages of annual means (arithmetic and geometric)
and second maxima were calculated from a two-way analysis of variance
followed by an application of the Tukey Studentized Range.2 The confidence
intervals for composite averages of estimated exceedances were calculated
by fitting Poisson distributions^ to the exceedances each year and then
applying the Bonferroni multiple comparisons procedure.4 The utilization
of these procedures is explained in publications by Pollack, Hunt and
Curran5 and Pollack and Hunt.6
The boxplots have the advantage of displaying, simultaneously,
several features of the data. Figure 3-2 illustrates the use of this
technique in presenting the 5th, 10th, 25th, 50th (median), 75th, 90th
and 95th percentiles of the data, as well as the composite average.
The 5th, 10th and 25th percentiles depict the "cleaner" sites. The
75th, 90th and 95th 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 90th percentile. Although
the average and median both characterize typical behavior, the median
has the advantage of not being affected by a few extremely high
observations. The use of the boxplots allow us to simultaneously compare
trends in the "cleaner", "typical" and "dirtier" sites.
3-1
-------
COMPOSITE MEAN OF AIR
POLLUTION STATISTIC
o
H-4
«C
I
z
UJ
O
Z
o
o
o
O.
95% CONFIDENCE
INTERVAL ABOUT
COMPOSITE MEAN
RELATIONSHIPS: (MULTIPLE COMPARISONS)
YEAR 4 IS SIGNIFICANTLY LESS THAN
' YEARS 1, 2, AND 3
NEITHER YEARS 1 AND 2 NOR 2 AND 3 ARE
SIGNIFICANTLY DIFFERENT FROM ONE ANOTHER
YEARS 1 AND 3 ARE SIGNIFICANTLY
DIFFERENT FROM ONE ANOTHER
_L
I
YEAR 1
YEAR 2
YEAR 3
YEAR 4
Figure 3-1. Sample illustration of use of confidence intervals to
determine statistically significant change.
3-2
-------
I
I
«9th PERCENTILE
90thPCRCENTILE
-75th PERCENT1LE
'COMPOSITE AVERAGE
MCDUN
25lhPERCCNTILE
'10th PERCENTILE
»h PERCENTILE
Figure 3-2. Illustration of plotting conventions for box plots.
3-3
-------
Boxplots of all trend sites are presented for each year in the 10-
year trend. In the recent 5-year trend, the boxplots are presented for
the years 1980 through 1984. Superimposed upon this presentation is
the trend line from the 10-year period. The recent 5-year trend is
being introduced at this time to increase the nunber of sites available
for analysis. Future trends reports will focus on the post-1980 period
to take advantage of the larger nunber of sites and the fact that the
data from the post-1980 period should be of the highest quality, with
sites meeting uniform siting criteria and high standards of quality
assurance.
Bar graphs are used for the Regional comparisons with the 5-year
trend data base. The composite average of the appropriate air quality
statistic of the years 1982, 1983 and 1984 are presented. The approach
is simple and it allows the reader at a glance to compare the short-term
trend in all ten EPA Regions.
In addition to the standard related statistics, other statistics
are used, when appropriate, to further clarify observed air quality
trends. Particular attention is given to the estimated number of
exceedances of the short-term NAAQS's. The estimated number of
exceedances is the measured nunber of exceedances adjusted to account
for incomplete sampling.
Finally, trends are also presented for annual nationwide emissions.
These emissions data are estimated using the best available engineering
calculations. The emission data are reported as teragrams (one million
metric tons) emitted to the atmosphere per year.? These are estimates
of the amount and kinds of pollution being generated by automobiles,
factories, and other sources, based upon the best available engineering
calculations for a given time period.
3-4
-------
3.1 TRENDS IN TOTAL SUSPENDED PARTICULATE
Total Suspended Participate (TSP) is a measure of suspended particles
in the ambient air. These particles originate from a variety of stationary
and mobile sources. TSP is measured using a high volume sampler which
simply measures the total ambient particle concentration from suspended
particles ranging up to approximately 45 microns in diameter. It does
not provide additional information regarding particle size. There are
both annual geometric mean and 24-hour National Ambient Air Quality
Standards for TSP. The annual geometric mean standard is 75 micrograms
per cubic meter (ug/m3) not to be exceeded, while the 24-hour standard
is 260 ug/m3 not to be exceeded more than once per year. Because the
annual mean is a more stable estimator of air quality, given the EPA
recommended sampling frequency of once every 6 days, only the annual
mean is used as a trend statistic.
3.1.1 Long-Term TSP Trends: 1975-84
The 10-year trend in average TSP levels, 1975 to 1984, is shown in
Figure 3-3 for over 1300 sites geographically distributed throughout
the Nation and for the subset of 325 National Air Monitoring Stations
(NAMS) which are located in the large urban areas. The TSP levels are
expressed in terms of the composite average annual geometric mean.
The curves shown in Figure 3-3 indicate a very slight decrease in
composite levels from 1975-1981, followed by a sizeable decrease between
1981 and 1982 and stable levels between 1982 and 1984. The NAMS
sites show higher composite levels than the sites for the Nation in
general, but appear to show a similar pattern. The composite average
of TSP levels measured at 1344 sites, distributed throughout the Nation,
decreased 20 percent during the 1975 to 1984 time period and the NAMS
decreased 22 percent. From the curves in Figure 3-3, it appears that
most of this decrease occurred between the measured levels of 1981 and
1982. EPA has found, however, that the TSP data collected during the
years 1979-1981 may be biased high due to the glass fiber filter used
during these years, and that most of the large apparent 2-year decrease
in pollutant concentrations between 1981 and 1982 can be attributed to
a change in these filters.8.9*10 For this reason, the portion of the
Figure 3-3 graph corresponding to 1979-1981 is stippled, indicating
the uncertainty associated with these data. Due to the change in TSP
filters, the pattern of the yearly change in TSP between 1978 and 1982
is difficult to assess. On the basis of comparable filters used in
1978 and 1984, however, the long-term (7-year) improvement in TSP is
estimated to be 19 percent. This is based on 1251 sites which measured
TSP in both years.
3-5
-------
0
70
to
so
50
20
W79
71 MO IM1 M2
YEAR
Figure 3-3. National trend in the composite average of the geometric
mean total suspended particulate at both NAMS and all sites
with 95 percent confidence intervals, 1975-1984.
1M
WO
to
to
70-
8
30-
20
W
u
T
t975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-4. Boxplot comparisons of trends in annual geometric mean
total suspended particulate concentrations at 1344 sites,
1975-1984.
3-6
-------
Figures 3-3 and 3-4 present two different displays of the air
quality trend at the 1344 TSP sites, nationally, over the 1975-1984 time
period. Both permit evaluation of the 1978 and 1984 TSP levels in the
context of the 10 year period, which is used for all pollutants. With
95 percent confidence intervals developed for the composite annual
estimates (Figure 3-3), it can be seen that the 1984 as well as the 1982
and 1983 levels are all significantly lower than those of 1978. The
data do not show statistically significant variation among these last 3
years. In Figure 3-4, boxplots present the entire national concentration
distribution by year and show that a decrease occurred in every percentile
level between 1978 and 1984.
Nationwide TSP emission trends show an overall decrease of
33 percent from 1975 to 1984. (See Table 3-1 and Figure 3-5). Since
1978, however, the particulate matter emissions have decreased
24 percent which is comparable to the decrease in ambient TSP
levels. The reduction in particulate emissions occurred primarily
because of the reductions in industrial processes. This is attributed
to a combination of installation of control equipment and reduced
industrial activity. Other areas of TSP emission reductions include
reduced coal burning by non-utility users and installation of control
equipment by electric utilities that burn coal.''
The trend in particulate emissions would not be expected to agree with
the trend in ambient TSP levels due to the unaccounted for natural TSP
background and uninventoried emissions sources such as reentrained
dust. The apparent agreement between the ambient air quality and
emissions data may be due in part to the favorable role of meteorology
in recent years. An analysis of meteorological conditions for this period
indicates a potential for lower TSP concentrations due to abnormally
high precipitation, particularly in 1982 and 1983. Rainfall has the
effect of minimizing fugitive dust entrainment and washing particles
out of the air.
Figure 3-6 compares the trend in TSP with the annual percent
deviation from normal precipitation. Qualitatively, the change in
annual precipitation H tends to generally agree with the annual change in
TSP concentrations. For example, the increase in TSP due to drought
conditions in 1976 has been previously reported.12 The decrease in TSP
in 1982 has also been attributed, in part, to increased precipitation.13
The relationship between TSP and rainfall also appears to correspond to the
year to year variability in TSP during 1982-1984. TSP decreased between
1982 and 1983, while rainfall increased. Then in 1984, the TSP increased
following a return of rainfall to more normal levels. The effect of
rainfall on TSP concentrations was particularly important in California
which experienced a State-wide increase in TSP levels in 1984. This
change in TSP was examined in Southern California and was attributed to
unusually low TSP concentrations in 1983 (particularly March and April)
due to unusually rainy and unstable meteorological conditions.I4
3-7
-------
Table 3-1. National Participate Emission Estimates, 1975-1984.
(mil 1 ion metric tons/year)
1975 1976 1977 1978 1979 1980 1981 1982
Source Category
Transportation 1.4 1.4 1.4
2.5 2.5
4.4 4.0
0.4 0.4
1.0 0.8
9.7 9.1
1.4
Fuel Combustion 2.7
Industrial Processes 5.0
Solid Waste 0.6
Miscellaneous 0.7
Total 10.4
1983 1984
1.4
2.6
4.0
0.4
0.8
9.2
1.4
2.5
3.8
0.4
0.9
9.0
1.4
2.4
3.2
0.4
1.1
8.5
1.4
2.4
2.8
0.4
0.9
7.9
1.3
2.2
2.4
0.4
0.7
7.0
1.2
1.9
2.2
0.3
1.1
6.7
1.3
2.0
2.5
0.3
0.9
7.0
15
TSP EMISSIONS, 106 METRIC TONSAEAR
SOURCE CATEGORY
SOUD WASTE & MISC
99 INDUSTRIAL PROCESSES
O FUEL
COMBUSTION
E23 TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-5. National trend in particulate emissions, 1975-1984.
3-8
-------
Figure 3-6. Annual nationwide area - weighted total precipitation
compared to long-term TSP trends, 1975-84.
to
WET YEARS
DRY YEARS
1975 1976 1977 1978 1979 1980 19B1 1982 1983 1984
YEAR
3.1.2 Recent TSP Trends: 1980-84
The change in monitoring filters discussed in Section 3.1.1
complicates the evaluation of recent 5-year trends. Since future trends
reports will be focusing on trends in the 1980's, however, Figure 3-7
presents a boxplot display of 1980-1984 TSP data base which represents
over 2000 monitoring sites. These boxplots are superimposed on the
longer 10 year trend line showing the remarkable similarity in composite
average levels and insensitivity of the TSP data base to a 50 percent
increase in monitoring sites. This lays the groundwork for a transition
to this data base for future trends reports.
A more practical analysis of recent trends in TSP focuses on the
regional variability among the last 3 years, 1982-1984. Figure 3-8
shows that within each Region all 3 years had similar TSP levels with
1983 predominantly displaying a 3 year minimum. This is consistent
with the trend in the national composite levels and emission trends
(Figure 3-5 and 3-7). The largest 2 year changes in ambient TSP levels
consisted of a 7 percent decrease between 1982 and 1983 in Region VI
and a 9 percent and 11 percent increase between 1983 and 1984 in Regions
VIII and IX, respectively. The Region VI decrease is attributed to a
delay in utilization of the new EPA monitoring filters at some sites in
Texas while the increases in the Western Regions is due to changes in
precipitation discussed previously.
3-9
-------
100-
90-
« SO-
4
? 70
z"
o
1 -
PC
S so
2
8 -0-
0.
P 30-
20
10
-TERM TREND!
SITES 1
*
f
!«
1
H
*f
»
T
SHORT-TERM TREND
2048 SITES
ITIT
''*« it i
V( x 5H
ITT
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-7. Comparison of long-term and recent trends in annual geometric
mean total suspended particulate concentrations.
o
8 so
EPA REGION I
NO. OF SITES 113
Legend
I 1982 COMPOSITE AVERAGE
I 1983 COMPOSITE AVERAGE
I 1984 COMPOSITE AVERAGE
Figure 3-8. Regional comparison of the 1982, 1983, 1984 composite average
of the geometric mean total suspended particulate concentration
3-10
-------
3.2 TRENDS IN SULFUR DIOXIDE
Ambient sulfur dioxide (SC^) results primarily from stationary
source coal and oil combustion and from nonferrous smelters. There are
three NAAQS for SC^: an annual arthmetic mean of 0.03 ppm, a 24-hour
level of 0.14 ppm and a 3-hour level of 0.50 ppm. The first two standards
are primary (health-related) standards, while the 3-hour NAAQS is a
secondary (welfare-related) standard. The annual standard is not to be
exceeded, while the short-term standards are not to be exceeded more
than once per year. The trend analyses which follow are presented for
the primary standards.
The trends in ambient concentrations are derived from continuous
monitoring instruments which can measure as many as 8760 hourly values
per year. The S02 measurements reported in this section are summarized
into a variety of summary statistics which relate to the S02 NAAQS.
The statistics on which ambient trends will be reported are the annual
arithmetic mean concentration, the second highest annual 24-hour average
(measured midnight to midnight), and the expected annual number of
24-hour exceedances of the 24-hour standard of 0.14 ppm.
3.2.1 Long-term SO? Trends: 1975-84
The long-term trend in ambient S02, 1975 to 1984, is graphically
presented in Figures 3-9 to 3-11. In each figure, the trend at the
NAMS is contrasted with the trend at all sites. For each of the statistics
presented, a steady downward trend is evident through 1982, with some
leveling off over the last 3 years. Nationally, the annual mean S02,
examined at 229 sites, decreased at a median rate of approximately
5 percent per year; this resulted in an overall change of about 36
percent (Figure 3-9). The subset of 81 NAMS recorded higher average
concentrations but declined at a higher rate of 7 percent per year.
The annual second highest 24-hour values displayed a similar decline
between 1975 and 1984. Nationally, among 224 stations with adequate
trend data, the median rate of change was 5 percent per year with an
overall decline of 41 percent (Figure 3-10). The 78 NAMS exhibited a
similar rate of improvement for an overall change of 35 percent.
The estimated number of exceedances also showed declines for the NAMS
as well as the composite of all sites (Figure 3-11). The vast majority
of S02 sites, however, do not show any exceedances of the 24-hour
NAAQS. Most of the exceedances as well as the bulk of the improvements
occurred at source oriented sites including a few smelter sites in
particular. The national composite estimated number of exceedances
decreased 93 percent from 1975 to 1984. The apparent increase in
exceedances for the NAMS during the beginning of the trend period is
largely due to a NAMS site in Salt Lake City, Utah which is influenced
by a nearby smelter. There is considerable variability in the number
of exceedances at this site with the number of exceedances in 1976
being considerably greater than other years. This single site has
caused the trend at the NAMS sites to peak in 1976.
3-11
-------
The statistical significance of these long-term trends is graphically
illustrated on Figures 3-9 to 3-11 with the 95 percent confidence
intervals included on these figures. For both annual averages and peak
24-hour values, the S02 levels in 1984 are statistically different than
levels observed during the 1970's. For expected exceedances of the 24-
hour standard with its more rapid decline and higher variability, current
levels are only statistically different than average exceedances in earlier
years (1975-1978).
The inter-site variability for annual mean and annual second highest
24-hour S02 concentrations is graphically displayed in Figures 3-12 and
3-13. These figures show that higher concentrations decreased more rapidly
and the concentration range among sites has also diminished.
Nationally, sulfur oxide emissions decreased 16 percent from
1975 to 1984 (Figure 3-14 and Table 3-2). These emissions increased
from 1975 to 1976 due to improved economic conditions, but decreased
since then reflecting the installation of flue gas desulfurization
controls at coal-fired electric generating stations and a reduction in
the average sulfur content of fuels consumed. Emissions from other
stationary source fuel combustion sectors also declined, mainly due to
decreased combustion of coal by these consumers. Sulfur oxide emissions
from industrial processes are also significant. Emissions from industrial
processes have declined, primarily as the result of controls implemented
to reduce emissions from nonferrous smelters and sulfuric acid manufacturing
pi ants. ^
The disparity between the 36 percent decrease in S02 air quality
and the 16 percent decrease in S02 emissions can be attributed to
several factors. S02 monitors are mostly urban population-oriented and
as such do not monitor many of the major emitters which tend to be
located in more rural areas. Anong the 229 trend sites used in the
analysis of average S02 levels, 67 percent are categorized as population-
oriented. The remaining sites include those monitors in the vicinity of
large power plants, nonferrous smelters and other industrial sources
such as paper mills and steel producing facilities.
The residential and commercial areas, where most monitors are located,
have shown sulfur oxide emission decreases comparable to S02 air quality
improvement. These decreases in sulfur oxide emissions are due to a
combination of energy conservation measures and the use of cleaner
fuels in the residential and commercial areas.7
Although one-third of the trend sites are categorized as source-
oriented, the majority of S02 emissions are dominated by large point
sources. Two-thirds of all national S02 emissions are generated by
electric utilities (94 percent of which come from coal fired power plants).
The majority of these emissions, however, are produced by a small number
of facilities. Fifty-three individual plants in 14 states account for
one-half of all power plant emissions. 15 in addition, the 200 highest
S02 emitters account for more than 85 percent of all S02 power plant
emissions. ' These 200 plants account for 57 percent of all S02
emissions, nationally.
3-12
-------
ooss
0030
O
O
0.0*
CM
O
in
0.04
'NAAOS
i97« raao
YEAR
1*82
19*3 19*4
Figure 3-10.
National trend in the composite average of the second-
highest 24-hour sulfur dioxide concentration at both NAMS
and all sites with 95 percent confidence intervals, 1975-
1984.
3-13
-------
I/I
UJ
O
-------
0.040
0.035
8
0.030-
0.029
0.020-
O O.OtS
Q
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-12. Boxplot comparisons of trends in annual mean sulfur dioxide
concentrations at 229 sites, 1975-1984.
OJ3
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-13. Boxplot comparisons of trends in second highest 24-hour
average sulfur dioxide concentrations at 224 sites,
1975-1984.
3-15
-------
Table 3-2. National Sulfur Oxide Emission Estimates, 1975-1984.
(mill ion metric tons/year)
1975
Source Category
Transportation 0.6
Fuel Combustion 20.3
Industrial Processes 4.7
Solid Waste 0.0
Miscellaneous 0.0
Total 25.6
1976 1977 1978 1979 1980 1981 1982 1983 1984
0.7
20.9
4.6
0.0
0.0
26.2
0.
21.
4.
0.
0.
26.
8
1
4
0
0
3
0.8
19.6
4.1
0.0
0.0
24.5
0
19
4
0
0
24
.9
.4
.2
.0
.0
.5
0.9
18.8
3.5
0.0
0.0
23.2
0.8
17.8
3.7
0.0
0.0
22.3
0.
17.
3.
0.
0.
21.
8
3
2
0
0
3
0.8
16.7
3.1
0.0
0.0
20.6
0.9
17.3
3.1
0.0
0.0
21.4
SOX EMISSIONS, 106 METRIC TONS/YEAR
SOURCE CATEGORY
INDUSTRIAL PROCESSES OB FUEL COMBUSTION
0
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-14. National trend in sulfur oxide emissions, 1975 - 1984.
3-16
-------
Another factor which may account for differences in $03 emissions and
ambient air quality is stack height. The height at which S02 is released
into the atmosphere has been increasing at industrial sources and power
plants. 17,18 jn-js can permit ground level concentrations to decrease at a
faster rate than emissions. Under these circumstances, concentrations can, in
fact, decrease even if emissions increase.
The influence of particular source reductions on air quality is
presented for nonferrous smelters. These sources represent a majority
of S02 emissions in the intermountain region of the western U.S. (from
the Sierra crest to the continental divide). Monitors in the vicinity
of smelters tend to produce some of the highest S02 concentrations
observed nationally. Figure 3-15 compares the SOg air quality and
emission trends for smelters. It shows that these S02 concentrations,
represented by 17 monitoring sites, are higher and decreased at a
substantially faster rate than S02 nationally. The smelter sites have
experienced a 52 percent decrease in ambient concentrations, corresponding
to a 55 percent decrease in smelter emissions. The smelter decrease is
attributed to cutbacks in production or plant closings. Both smelter
trends track very well and show the increase in 1981 for both emissions
and ambient air quality which was recently reported by Opperheimer et.
al. for S02 emissions and western U.S. Regional sulfate concentrations.
3.2.2. Recent S02 Trends: 1980-84
Figure 3-16 presents a comparison of long and short-term S02 trends
for annual mean concentrations. The boxplot display for the 1980-1984
data, based on 477 sites, indicate a similar decrease over the same 5-
year period included in the long-term trends, but with lower average
concentrations. This is attributed to inclusion of new S02 monitoring
sites in areas with medium to low concentration levels. The 5-year
trend shown in Figure 3-16 matches the national emission trend in Figure
3-14. In particular, 1983 had the lowest S0£ levels. Air quality levels
increased 2 percent while emissions increased 4 percent. The small
increases from 1983 to 1984 may be attributed to an increase in fuel
combustion, which was only partially offset by new S02 controls.
Regional changes in composite average S02 concentrations for the
last 3 years, 1982-1984 are shown in Figure 3-17. Although most Regions
increased slightly between 1983 and 1984, annual changes are small and
no consistent pattern is apparent nationwide over the last 3 years.
The southern and western Regions (Regions IV, VI, VIII, and IX) maintain
their status of recording the lowest overall average concentrations in
recent years.
Although these Regions display relatively low overall average
concentrations, they also contain some of the highest S02 concentrations
recorded nationally. This phenomenon which is due to S02 in the vicinity
3-17
-------
0.04
0.0 J-
0.02
rf
0.01-
-
o
2
1975 1976 1977 1978 1979 I960 1981 1982 1983 1984
YEAR
Figure 3-15. National smelter emissions vs. air quality trends, 1975-1984.
0.040
0.030-
O.O75-
O 0.020
O
0.010
NAAOS
SHORT-TERM TREND
477 SITES
(LONG-TERM TREND I
228 SITES
1
1 Jl
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-16. Comparison of long-term and recent trends in annual average
sulfur dioxide concentrations.
3-18
-------
O.OH-
0 014-
0012
z- o.oio
o
fj
E 0 DOS
o
z
o
O o 006
0
0.004 -
0.002
',
EPA REGION
i
'
'
/
/
'
-
/
/
/
s
/
/
/
/
'
'
X
'
,
/
/
/
/
/
-,
/
/
/
/
/
/
^
/
/
/
/
/
7
'
J
/
'
'
'
/
,,
^
^
JK
1"
H
Legend
E2 19B2 COMPOSITE
'
II III IV
NO. OF SITES 36 44 63 72
1 t»B3 COMPOSnt
AVER Ad
AVCRAGI
a 1984 COMPOSITE AVERAGI
^1 ^
V VI
139 30
p
E
E i
E
W
-
/
/
S
f
f
/
t
'
]
f
ri
/
,
!
/ i
\
i
^ !
' !
*
n
/
/
»
*
t
t
f
f
VII VIII IX X
15 10 54 14
Figure 3-17. Regional comparison of the 1982, 1983, 1984 composite
average of the annual average sulfur dioxide concentration
0.010
O.OZS
0.020
o o.oo
o
0.010'
0.009
0.000-
1
1
EPHREGION I II III IV V VI VII VIII IX X
NO. OF SITES 36 44 63 72 139 30 15 10 54 14
Figure 3-18. Regional boxplot comparisons of the annual average sulfur
dioxide concentrations in 1984.
3-19
-------
of nonferrous smelters, 1s evident In Figure 3-18 which shows the 1984
Intra-reglonal concentration distributions. Region IX, for example,
displays a low overall average concentration as mentioned previously,
but also has the highest peak concentration levels in the Nation because
of the Arizona smelters. Similarly, large intra-regional variability
1n SOg concentrations is seen in Regions VI and X because of monitors
located in the vicinity of smelters.
3-20
-------
3.3 TRENDS IN CARBON MONOXIDE
Carbon monoxide (CO) is a colorless, odorless, and poisonous gas
produced by incomplete burning of carbon in fuels. Over two-thirds of
of the nationwide CO emissions are from transportation sources and
highway motor vehicle are the largest contributing source of these CO
emissions. The NAAQS for ambient CO specifies upper limits that are not
to be exceeded more than once per year for two different averaging times:
a 1-hour level of 35 ppm and an 8-hour level of 9 ppm. Because the 8-
hour standard is generally more restrictive, this trends analysis emphasizes
the 8-hour average results.
The trends site selection process, discussed in Section 2.1, resulted
in a data base of 157 sites for the 1975-84 long-term period and a data
base of 309 sites for the 1980-84 recent trends time period. Forty of
the long-term trends sites were NAMS while 90 NAMS qualified for inclusion
in the recent trends data base. This approximate doubling of the data
base between the long-term and recent trends time periods is indicative
of the improvement in size and stability of current ambient CO monitoring
programs.
3.3.1 Long-term CO Trends: 1975-84
Figure 3-19 presents the national 1975-84 composite average trend
for the second highest non-overlapping 8-hour CO value for the 157 long-
term trend sites and the subset of 40 NAMS sites. The national composite
decreased by 34 percent between 1975 and 1984, while there was a 30 percent
decrease for the NAMS subset. Although the median rate of improvement has
been approximately 5 percent per year, this rate is less pronounced in
the last few years. The confidence intervals in Figure 3-19 show that
ambient concentrations in the more recent years are significantly less
than the earlier years. During this time period, 87 percent of the trend
sites showed long-term improvement.
Figure 3-20 displays the same trend but uses the boxplot presentation
to provide more information on the distribution of ambient CO levels from
year to year at the 157 long-term trend sites. The general long-term
improvement is evident although certain percentiles show year to year
fluctuations.
The long-term composite average trend in the estimated number of
exceedances of the 8-hour CO NAAQS is shown in Figure 3-21. This exceedance
rate was adjusted to account for incomplete sampling and the pattern is
generally consistent with the trends in the second maximum i.e. long-term
improvement followed by a levelling off in the past few years. The rate
of improvement is more pronounced for this exceedance statistic with an
88 percent decrease between 1975 and 1984 for the 157 site data base
and a 79 percent decrease for the subset of 40 NAMS. The NAMS sites show
a recent increase but, as indicated by the confidence intervals, this is
not statistically significant.
3-21
-------
z
o
o
2
O
O
O
2-
O
o
m
I* <{>
Legend
NA_M_S_ SITES {40)
3 ALL SITES (157)
1975 1976 1977 1978 1979 1980 1981 1982 19SJ 1984
YEAR
Figure 3-19.
National trend in the composite average of the second
highest nonoverlapping 8-hour average carbon monoxide
concentration at both NAMS and all sites with 95 percent
confidence intervals, 1975-1984.
20
V
W75 1976 1377 W78 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-20.
Boxplot comparisons of trends in second highest nonoverlapping
8-hour average carbon monoxide concentrations at 157 sites,
1975-1984.
3-22
-------
o
z
o
£ 30
o
o
o
I
<
Legend
I NAMS SITES (40)
J AU SlTtS ^157)
1979 1980
YEAR
Figure 3-21.
National trend in the composite average of the estimated
number of exceedances of the 8-hour carbon monoxide NAAQS,
at both NAMS and all sites with 9b percent confidence
intervals, 1976-1984.
3-23
-------
National carbon monoxide emission estimates for 1975 through 1984
are presented in Table 3-3 and depicted graphically in Figure 3-22.7
These estimates show a 14 percent decrease in total CO emissions
between 1975 and 1984. Emissions from transportation sources, which
account for approximately 70 percent of the total emissions in 1984, are
estimated to have decreased 22 percent during this same 1975-84 time
period. These emission decreases occurred even though vehicle miles of
travel are estimated to have increased by almost 30 percent over this
time period. Therefore, the CO emission control program has been effective
on the national scale in that emission controls have more than offset growth
during this period. In comparing air quality and emission changes for
CO, it should be noted that the emission changes reflect national totals
while the ambient CO monitors are typically located to identify potential
problems. Therefore, these monitors are likely to be placed in traffic
saturated areas that may not experience significant increases in vehicle
miles of travel. As a result, the air quality levels at such locations
would be expected to improve at a faster rate than the nationwide reduction
in emissions.
3.3.2 Recent CO Trends: 1980-84
Figure 3-23 uses an expanded data set to display ambient CO trends
for the 1980-84 period in terms of the second highest non-overlapping
8-hour averages. As noted in Section 2.1, the larger data set, 309 versus
157 sites, is a result of restricting the historical data completeness
criterion to only the 1980's so that newer monitoring sites can qualify
for inclusion. In Figure 3-23, the previously discussed long-term
composite average for the 157 long-term trends sites is superimposed on a
boxplot presentation for the 309 sites used for recent trends. There is
less than a 5 percent difference between the composite averages of the
two data sets and there is general agreement in the trends. Both data
sets show consistent year to year improvement but the rate of improvement
appears to be decreasing. The recent trends data shows a 10 percent
improvement between 1980 and 1984 but the improvement between 1983 and
1984 was only 1 percent. This recent leveling off in air quality appears
to be consistent with the CO emissions presented in Table 3-3. For
example, while the transportation category showed a 22 percent decrease
between 1975 and 1984, there has been less than a 1 percent change between
1982 and 1984. Although not presented explicitly in Table 3-3, the
highway vehicle portion of the transportation category is estimated to
have decreased by 1 percent between 1983 and 1984.
Year-to-year changes in composite regional averages for 1982-84 are
shown in Figure 3-24. With the levelling off in CO improvement that was
seen for the most recent years, it is not surprising that regional patterns
are mixed. It should be noted that these regional graphs are primarily
intended to depict relative change during this time period and not typical
levels in each Region. Because the mix of monitoring sites may vary from
one area to another, with one set of sites dominated by center-city
monitors in large urban areas while another set of sites may represent a
more diversified mix, this graph is not intended to be indicative of
regional differences in absolute concentration levels.
3-24
-------
Table 3-3. National Carbon Monoxide Emission Estimates, 1975-1984.
(million metric tons/year)
1975
Source Category
Transportation 62.0
Fuel Combustion 4.4
Industrial Processes 6.9
Solid Waste 3.1
Miscellaneous 4.8
Total 81.2
1976 1977 1978 1979 1980 1981 1982 1983 1984
64.3
4.7
7.1
2.7
7.1
85.9
61
5
7
2
5
81
.1
.2
.2
.6
.8
.9
60.4
5.8
7.1
2.5
5.7
81.5
55.9
6.6
7.1
2.3
6.5
78.4
52.7
7.4
6.3
2.2
7.6
76.2
51.
7.
5.
2.
6.
73.
6
5
9
1
4
5
48.1
8.0
4.4
2.0
4.9
67.4
48.
8.
4.
1.
7.
70.
4
0
4
9
7
4
48.5
8.3
4.9
1.9
6.3
69.9
125
CO EMISSIONS, 10* METRIC TONS/YEAR
100-
75-
SOURCE CATEGORY
I SOUO WASTE ft MBC E3 FUEL
COMBUSTION
MOUSTRUL PROCESSES EJ TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-22. National trend in emissions of carbon monoxide, 1975-1984.
3-25
-------
I-
5-
SHOKT-TERM TREND
KM SITES
[LONG-TERM TREND!
C7 SITES I
NAAOS"
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-23.
Comparison of long-term and recent trends in second highest
nonoverlapping 8-hour average carbon monoxide concentrations
a-
11-
10-
i -
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Legend
Va 1982 COMPOSITE AVERAGE
1983 COMPOSITE AVERAGE
CZ) 1984 COMPOSITE AVERAGE
\ \
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DC X
NO. OF STIES 13 24 24 44 49 21 16 15 72 31
Figure 3-24.
Regional comparison of the 1982, 1983, 1984 composite average
of the second highest nonoverlapping 8-hour average carbon
monoxide concentration.
3-26
-------
3.4 TRENDS IN NITROGEN DIOXIDE
Nitrogen dioxide (N02), a yellowish, brown gas, is present in
urban atmospheres through emissions from two major sources; transportation
and stationary fuel combustion. The major mechanism for the formation
of N02 in the atmosphere is the oxidation of the primary air pollutant,
nitric oxide. N02 is measured using either a continuous monitoring
instrument, which can collect as many as 8760 hourly values a year,
or a 24-hour bubbler, which collects one measurement per 24-hour period.
Both monitors are used to compare annual average concentrations with the
N02 standard of 0.053 parts per million.
In order to expand the size of the available trends data base, data
were merged at sites which experienced changes in the agency operating the
site, the instrument used, or the designation of the project code, such as
population oriented or duplicate sampling. The merging was accomplished
by treating the bubbler and continuous hourly data separately. For example,
if a monitor at a given site was changed from a 24-hour bubbler to a
continuous hourly monitor, the data would not be merged. If, however,
a monitor at a given site changed from one type of continuous instrument
to another type of continuous instrument, the data would be merged.
The trends site selection process, described in Section 2.1, yielded
119 sites for the 1975-84 long-term period and 236 sites for the 1980-84
recent trends data base. Twelve of the long-term trend sites are MAMS
while 36 NAMS are included in the 1980-84 data base. The size of the
long-term data base has been decreasing each successive year as low
concentration sites are discontinued or as N02 bubblers are replaced
with continuous instruments. In this latter case, data from these two
different methods are not merged.
3.4.1 Long-term N02 Trends: 1975-84
The composite average long-term trend for the nitrogen dioxide mean
concentration at the 119 trend sites, and the 12 NAMS sites, is shown in
Figure 3-25. Nationally, at all sites, annual average N02 levels increased
from 1975 to 1979, decreased through 1983 and then recorded a slight increase
in 1984. However, the 1984 composite average N02 level is 10 percent
lower than the 1975 level, indicating a downward trend during this period.
Of the 119 trends sites, only 12 are designated as NAMS. This is to be
expected because N02 does not present a significant air quality problem
in most areas at this time. Also, NAMS for N02 are only located in urban
areas of populations of 1,000,000 or greater. Except for 1980, the composite
averages of the NAMS are higher than those of all sites. Comparing 1984
data to the 1975 levels shows a 10 percent decrease in the composite
average for all trends sites and a 12 percent decrease for the NAMS. The
discrepancy between the all sites and NAMS year to year changes may be
attributed to both the small number of NAMS meeting the long-term trends
criteria and the generally low levels of recorded N02 annual mean
concentrations.
3-27
-------
0.05
O
o
O
8
z
NAAQS
Legend
NAMS snts (12)
AU STCS (119)
1*75
n itao
YEAR
l»81 I»S2 1M1 19S4
Figure 3-25. National trend in the composite average of nitrogen
dioxide concentration at both NAMS and all sites with 95
percent confidence intervals, 1975-1984.
0.07
O.M
0.05
0.04
0.0 J
0.02
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-26. Boxplot comparisons of trends in annual mean nitrogen
dioxide concentrations at 119 sites, 1975-1984.
3-28
-------
In Figure 3-25, the 95 percent confidence intervals about the composite
means allow for comparisons among the years. While there are no significant
differences among the years for the NAMS, because there are so few sites
meeting the historial trends criteria, there are significant differences
among the composite means of the 119 long-term trends sites. Although the
1983 and 1984 composite mean N0;> levels are not significantly different
from one another, they are significantly less than the earlier years 1978,
1979 and 1980.
Long-term trends in N02 annual average concentrations are also displayed
in Figure 3-26 with the use of boxplots. The improvement in the composite
average between 1979 and 1984 can also be seen in the the upper percentiles.
The lower percentiles show little change, however.
The trend in the estimated nationwide emissions of nitrogen oxides (NOX)
is similar to the N02 air quality trend. Table 3-4 shows NOX emissions
increasing from 1975 through 1979 and generally decreasing until 1984.
Between 1975 and 1984 total nitrogen oxide emissions increased by 3
percent, but highway vehicle emissions, the source category likely impacting
the majority of N02 sites, decreased by 4 percent. Figure 3-27 shows
that the two primary source categories of nitrogen oxide emissions are
fuel combustion and transportation.
3.4.2 Recent NO? Trends: 1980-84
Figure 3-28 uses the boxplot presentation to display recent trends
in nitrogen dioxide annual mean concentrations for the years 1980-84.
Focusing on the past five years, rather than the last ten years, almost
doubles the number of sites, from 119 to 236, available for the analysis.
Superimposed upon this presentation is the long-term N0£ trend line from
the period 1975-84. As indicated by this figure, although the composite
means from the recent period are lower than the long-term means, the
trends are consistent for the two data bases.
The recent trend in the composite average of N02 concentrations at
both NAMS and all sites is shown in Figure 3-29 with 95 percent intervals
about the composite mean. The composite average N02 level at the 236 trend
sites decreased 7 percent between 1980 and 1984. During this same period,
nitrogen oxide emissions decreased by 3 percent. Between 1983 and 1984, the
N02 composite average increased 2 percent, while nitrogen oxide emissions
recorded a 3 percent increase. In contrast to the 1975-84 data base, the
recent 5-year trends data base shows greater consistency between the NAMS
and all sites trends. The subset of 33 NAMS show higher composite mean
levels than the 236 sites in the data base. However, neither site group
recorded significantly different N02 composite average levels during the
last 3 years.
Regional trends in the composite average N02 concentrations for the
years 1980-84 are displayed in Figure 3-30 using bar graphs. As indicated
in the figure, Regions I through III, V and IX consistently record the
highest composite averages. The pattern of the year-to-year changes is
mixed among the regions, however, eight of the ten Regions showed increases
between 1983 and 1984.
3-.29
-------
Table 3-4.
Source Category
Transportation
Fuel Combustion
Industrial Processes
Sol id Waste
Mi scellaneous
Total
National Nitrogen Oxide Emission Estimates, 1975-1984
(mill ion metric tons/year)
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
8.9 9.3 9.5 9.7 9.6 9.2 9.3 8.9 8.6 8.7
9.4 10.0 10.5 10.3 10.5 10.2 10.2 10.0 9.6 10.1
0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.6 0.6 0.6
0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1
0.1 0.2 0.2 0.2 0.2 0.2 0.2 0.1 0.2 0.2
19.2 20.3 21.0 21.0 21.1 20.4 20.5 19.7 19.1 19.7
30
N0y EMISSIONS, 106 METRIC TONS/YEAR
25-
20-
15-
10
SOURCE CATEGORY
CD FUEL COMBUSTION
SOUD WASTE &
MISC.
INDUSTRIAL PROCESSES Z2 TRANSPORTATION
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-27. National trend in emissions of nitrogen oxides, 1975-1984.
3-.30
-------
0.07
O.M-
0.05
0.04-
0.03
0.02
0.01-
0.00
-TCTKTWNO
SITES
NAAOS*
TCRM TREND
119 SlftS |
I
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-28. Comparison of long-term and recent trends in annual mean
nitrogen dioxide concentrations.
0.01
0.03
0.04-
O
0.03-
8
0.02-
0.01-
0.00
1M1
YEAR
Figure 3-29.
National trend in the composite average of nitrogen dioxide
concentration at both NAMS and all sites with 95 percent
confidence intervals, 1980-84.
3-31
-------
0.035-
OOJO-
z 0.025
3-
o
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5
2. 0.015-
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0005
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EPA REGION
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Legend
C3 1982 COMPOSITE AVERAGE
M 1983 COMPOSITE
C2 t»84 COMPOSITE
II III IV
NO. OF SITES 4 10 43 27
T
^^
AVERAGE
AVERAGE
m^ ^
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V VI VII VIII IX X
35
36
7 T7 55 2
Figure 3-30.
Regional comparison of the 1982, 1983, 1984 composite
average of the annual mean nitrogen dioxide concentration,
3-:32
-------
3.5 TRENDS IN OZONE
Ozone (03) is a major pollution concern for large urban areas
throughout the Nation. In contrast to the other criteria pollutants
described in this report, ozone is not emitted directly by specific
sources but is formed in the air by chemical reactions between nitrogen
oxides and volatile organic compounds. These come from sources such as
gasoline vapors, chemical solvents, and combustion products of various
fuels. Because these reactions are stimulated by sunlight and temperature,
peak ozone levels typically occur during the warmer times of the year.
The strong seasonal patterns for ozone make it possible for areas to
concentrate their ozone monitoring during a certain portion of the
year, termed the ozone season. The length of the ozone season varies
from one area of the country to another. While May through October is
fairly typical, States in the south and southwest may monitor the
entire year while the more northern States would have a shorter season,
such as May through September for North Dakota. This trends analysis
uses these 03 seasons on a State basis to ensure that the data completeness
requirements are applied to the relevant portions of the year.
The NAAQS for 03 is defined in terms of the daily maximum, that
is, the highest hourly value for the day, and specifies that the expected
number of days per year with values greater than 0.12 ppm should not be
greater than one. Both the annual second highest daily maximum and the
number of daily exceedances during the ozone season are considered in
this trends analysis.
The trends sites selection process, discussed in Section 2.1,
resulted in 163 sites being selected for the 1975-84 long-term period
and 480 sites qualifying for the 1980-84 recent trends data base.
Sixty of the long-term trends sites were NAMS while 175 NAMS sites were
included in the recent trends data base. For the NAMS and all sites,
the recent trends data base is approximately three times larger than
the long-term trends data base. This is consistent with the expected
improvement in the size and stability of current ambient ozone monitoring
networks.
3.5.1 Long-term 0^: 1975-84
The composite average long-term trend for the second high day
during the ozone season is shown in Figure 3-31 for the 163 trends
sites and the subset of 60 NAMS. Although the 1984 composite average
for the 163 trends sites is 17 percent lower than the 1975 average, the
interpretation of this decrease is complicated by a calibration change
for ozone measurements that occurred in the 1978-79 time period.20
The stippled portion of the Figure indicates data affected by measurements
taken prior to the calibration change. As noted in earlier reports, it
is difficult to quantify exactly how much of the 1978-79 decrease is
due to the calibration change.^ Not all agencies made the
change at the same time and, in fact, for some States such as California
the 1975-78 data already accounted for the change resulting from the new
3-33
-------
calibration procedure. Therefore, trend comparisons involving data
prior to 1979 should be viewed with caution and an awareness of the
affect of the calibration change. Comparing the 1984 data with 1979
shows a 7 percent decrease in the composite average for all trends
sites and also for the subset of NAMS. However, the general trend has
been somewhat mixed as discussed in the following section on recent
trends.
Long-term ozone trends are also displayed in Figures 3-32 and
3-33. Figure 3-32 uses the boxplot presentation for the annual second
highest daily maximum while Figure 3-33 presents the composite average
number of ozone exceedances. This latter statistic is adjusted for
missing data and reflects the number of days that the level of the
ozone standard is exceeded during the ozone season. Again, the stippled
area indicates the time period when comparisons would be affected by
the calibration change so that the 62 percent decrease in the number of
exceedances between 1975 and 1984 incorporates the effect of the
calibration change. Between 1979 and 1984 the expected number of
exceedances decreased 36 percent at the 163 trends sites with a decrease
of 32 percent at the subset of NAMS sites. Both Figures 3-31 and 3-33
illustrate the agreement between the trends at the NAMS sites and those
for the larger data base.
Table 3-5 and Figure 3-34 display the 1975-84 emission trends for
Volatile Organic Compounds (VOC) which, along with nitrogen oxides, are
involved in the atmospheric chemical and physical processes that result
in the formation of 03. Total VOC emissions are estimated to have decreased
6 percent between 1975 and 1984.7 As shown in Table 3-5 the annual
total for each year of the 1980's is less than the annual totals for the
1975-79 period. Emissions from transportation sources decreased by 30
percent during the 1975-84 period even though vehicle miles of travel
increased by 29 percent. Fuel combustion VOC emissions showed consistent
growth accounting for less than 5 percent of the total emissions in
1975 but more than 10 percent of the total in 1984. The more recent
emission patterns are discussed in the following section.
3.5.2 Recent 0^ Trends: 1980-84
Focusing on ozone trends in the 1980's permits the use of a
larger data base that reflects the improved status of current ambient
monitoring networks. Figure 3-35 uses a boxplot presentation for the
short-term ozone trends data base and also displays the previously
discussed long-term trends. Trends in the 1980's are reasonably consistent
for both data bases although the composite average and median are
slightly lower for the larger data base. The short-term data base showed
a 9 percent improvement for the national composite average second maximum.
The basic pattern, for both data sets, is that 1980 and 1983 values
were higher than those in 1981, 1982, and 1984. The previously reported
3-34
-------
0.18
O.tt-
O.M-
0.12
O
8
O
o
o.os
0.06
"NAAOS
1875 1S7« W77 W78
1i7t It
YEAR
1MI 1M2 1983 IM4
Figure 3-31.
National trend in the composite average of the second
highest maximum 1-hour ozone concentration at both
NAMS and all sites with 95 percent confidence intervals,
1975-1984.
o.so
0.25
0.20-
O.B-
0.00
1975 1976 1977 1978 1979 1980 19*1 1982 1983 1944
YEAR
Figure 3-32. Boxplot comparisons of trends in annual second highest
daily maximum 1-hour ozone concentrations at 163 sites,
1975-1984.
3-35
-------
20
IB-
Lagand
MAMS SUB (eo)
ALL SITES 063^.
M77
YEAR
Ml IM2 IMS ISM
Figure 3-33.
National trend in the composite average of the estimated
number of daily exceedances of the ozone NAAQS in the
ozone season at both NAMS and all sites with 95 percent
confidence intervals, 1975-1984.
3-36
-------
Table 3-5. Volatile Organic Compound National Emission
Estimates, 1975-1984.
1975
Source Category
Transportation 10.3
Fuel Combustion 1.0
Industrial Processes 8.1
Nonindustrial Organic 1.9
Solvent Use
Solid Waste
Mi scellaneous
Total
0.9
0.6
22.8
1976
10.4
1.2
8.7
1.9
0.8
1.0
24.0
(mill ion metric tons/year)
1977 1978 1979 1980 1981
10.0
1.4
9.0
1.9
0.8
0.8
23.9
9.8
1.6
9.6
1.9
0.8
0.8
24.5
8.9
1.9
9.5
2.0
0.7
0.9
23.9
8.2
2.1
8.9
1.9
0.6
1.0
22.7
8.0
2.3
8.0
1.6
0.6
0.9
21.4
1982 1983 1984
7.5
2.5
7.1
1.5
0.6
0.7
19.9
7.2
2.5
7.5
1.6
0.6
1.1
20.5
7.2
2.6
8.4
1.8
0.6
0.9
21.5
40
VOC EMISSIONS, 10' METRIC TONS/YEAR
30-
20
10-
SOURCE CATEGORY
SOLID WASTE,
COMBUSTION ft MISC
NONINDUSTRIAL
ORGANIC SOLVENT
I3 TRANSPORTATION
EZ3 INDUSTRIAL PROCESSES
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-34. National trend in emissions of volatile organic compounds,
1975-1984.
3-37
-------
0.30
0.29
0.20
0.19
O.W
0.00
SHORT-TERM TREND
460 sires
JDDNG-TERM TREND
KJ SITES I
NAAOS'
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-35. Comparison of long-term and recent trends in annual
second highest daily maximum 1-hour ozone concentrations
0 18-
^ 012
Z
O
F.
UJ
O
0
o
LJ
g 0 06
M
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EPA REGION
NO. OF SITES 2
, ;
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VZA 1982 COMPOSITE AVERACf
i 1963 COMPOSITE AVERAGI
CZ] 1984 COMPOSITE AVERAGI
II III IV V VI
3 27 62 69 101 43
)
VII
20
L $
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n /
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:
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VIII IX X
13 108 14
Figure 3-36.
Regional comparison of the 1982, 1983, 1984 composite
average of the second-highest daily 1-hour ozone
concentration.
3-38
-------
increase between 1982 and 1983 was followed by a decrease of approximately
10 percent between 1983 and 1984 so that the 1984 values are similar to
those reported in 1981 and 1982.10 /\t approximately one-third of these
sites, the 1984 value was the lowest annual second maximum for the
1980's, while only 10 percent had their highest value for the 1980's in
1984.
As noted in last year's trends report,10 the magnitude of the 1982-83
increase was likely attributable in part to meteorological conditions that
were more conducive to ozone formation in 1983. The addition of the
1984 data lends further support to this explanation because average
ambient ozone levels in 1984 were 10 percent less than 1983 even though
VOC emissions are estimated to have increased by 5 percent between
these 2 years. A study of the Chicago area for 1977-83 developed a
meteorological index for ozone potential and concluded that 1983 had
more ozone conducive days than 1981 and 1982 so that the ozone increase
in 1983 was reasonable.^ This same index also showed that 1984 had
fewer ozone conducive days than 1983 which would be consistent with a
decrease in ozone levels between 1983 and 1984.22 /\ different meteorological
index was examined in an ozone trends analysis for the Los Angeles area
and concluded that the ozone potential for 1982 in that area was the
lowest of any year in the 1956-84 time period.^ The difficulties of
extending these meteorological explanations and indices to broader
geographical areas has been discussed previously.10 However, to provide
additional insight on the ozone trend, a simplified ozone potential
index was considered using meteorological information on temperature,
wind speed, and cloud cover. These data were obtained from the National
Climatic Data Center for ten different cities: New York, Philadelphia,
Atlanta, Cincinnati, St. Louis, Houston, Minneapolis, Denver, Los
Angeles, and Portland. Ambient ozone data from nearby monitoring sites
were used to determine site-specific cut-off values for the meteorological
variables.23 For each site, individual yearly index values were normalized
by dividing by the 1979-84 average for that site and then the average for
the year was computed for the monitors in that area. These individual
city results could then be averaged to obtain a national composite
ozone potential index. In view of the oversimplifications involved,
this approach should be viewed with caution but, even though the index
is likely to be inadequate for an individual city, the relative change
in the overall index from year to year may be useful. In this case,
the index is consistent with the explanation that 1983 was more conducive
for ozone formation than either 1982 or 1984. Again, because of the
simplifications involved, these results should be viewed as only
suggestive rather than definitive but they do agree with the hypothesis
that 1983 ozone levels were higher than 1982 and 1984 in part because
of the differences in meteorological conditions for those years.
Total VOC emissions are estimated to have decreased by 5 percent
between 1980 and 1984, as shown in Table 3-5, with a 12 percent decrease for
transportation sources.? Between 1983 and 1984, total VOC emissions
3-39
-------
are estimated to have increased by 5 percent primarily due to an increase
in the industrial process portion. The major component affecting this
estimated increase was related to organic solvents.
Figure 3-36 displays the composite average second highest daily
maximum ozone value by EPA Region for the years 1982-84. This graph
illustrates how widespread the low-high-low pattern was with 1983 being
the highest of the 3-year period. This pattern occurred in nine of
the ten Regions with only the Pacific Northwest departing from this pattern
Because of the complexity of recent ozone trends, it is probably
useful to briefly summarize the patterns. Just as the 1982-83 increase
in ozone levels was thought to be partly attributable to meteorological
conditions in 1983 being more favorable for ozone formation, the 1983-
84 decrease should also be viewed as being in part a result of the 1983
meteorological conditions. Total VOC emissions are estimated to have
decreased 5 percent in the 1980's with transportation sources showing
12 percent improvement and industrial processes decreasing by 6 percent.
However, industrial process emissions are estimated to have increased
between 1983 and 1984. The 1983-84 improvement in ambient ozone levels
is likely due in part to the year to year differences in meteorological
conditions. The 1984 ambient ozone levels are very similar to the 1981-
82 levels. This occurred despite an estimated national growth of almost
200 billion vehicle miles of travel between 1980 and 1984, an increase
of 13 percent.24
3-40
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3.6 TRENDS IN LEAD
Lead (Pb) gasoline additives, non-ferrous smelters, and battery plants
are the most significant contributors to atmospheric lead emissions.
Transportation sources alone contribute about 80 percent of the annual
emissions.
Prior to promulgation of the lead standard in October 1978,25 two air
pollution control programs were implemented by EPA that have resulted in
lower ambient lead levels. First, regulations were issued in the early
1970's which required the lead content of all gasoline to be gradually
reduced over a period of many years. Most recently the lead content of
leaded gasoline was reduced from an average of 1.0 grams/gallon to 0.5
grams/gallon on July 1, 1985 and still further to 0.1 grams/gallon on
January 1, 1986. Second, as part of EPA's overall automotive emission
control program, unleaded gasoline was introduced in 1975 for use in
automobiles equipped with catalytic control devices which reduced emissions
of carbon monoxide, hydrocarbons and nitrogen oxides. Additionally, lead
emissions from stationary sources have been substantially reduced by
control programs oriented toward attainment of the TSP and lead ambient
standards. The overall effect of these three control programs has been a
major reduction in the amount of lead in the ambient air.
3.6.1 Long-term Lead Trends: 1975-84
Previous trend analyses of ambient Pb data26,27 were based almost
exclusively on National Air Surveillance Network (NASN) sites. These
sites were established in the 1960's to monitor ambient air quality levels
of TSP and associated trace metals, including lead. The sites'were
predominantly located in the central business districts of larger American
cities. In October 1980, new ambient Pb monitoring regulations were
promulgated.29 The siting criteria in the regulations resulted in the
elimination of many of the old historic TSP monitoring sites as being
unsuitable sites for the measurement of ambient Pb concentrations.
As with the other pollutants the trend sites that were selected had
to satisfy an annual data completeness criterion of at least 8 out of 10
years of data in the 1975 to 1984 time period. A year was included as
"valid" if at least 3 of the 4 quarterly averages were available. A
total of only 36 urban-oriented sites, representing just eight states,
met the data completeness criteria. Only six of these sites were NAMS
sites, thereby, making a NAMS trend determination impossible. Twenty-seven
of the trend sites were located in the States of Arizona, Pennsylvania
and Texas. A total of 147 sites satisfied a trend criteria for the
1980-84 period, which required 4 out of 5 years in the 1980 to 1984 time
period.
The mean of the composite maximum quarterly averages and their
respective 95 percent confidence intervals are shown in Figure 3-37 for
both 36 urban sites (1975-1984) and 147 sites (1980-1984). There was a
70 percent overall (1975-84) decrease. The confidence intervals
indicate that the 1975-78 averages are significantly different from the
1980-84 averages. The decrease was 38 and 45 percent in the mean (1980-84)
respectively for the 36 sites or the larger sample of 147 sites. For
3-41
-------
o
1.2-
8 °8
0.4
0.2
0
Figure 3-37.
} E
,-U
Legend
ALL SITES
1980-84 (147)
D ALL SITES
1975-8^(36)
NAAOS-
1*75 1*76
1*76
<*7« 1*80
YEAR
1*82
1184
National trend in the composite average of the maximum
quarterly average lead concentration at 36 sites (1975-
1984) and 147 sites (1980-1984) with 95 percent confidence
intervals.
3-
2.3-
1.5
O
2
X
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
YEAR
Figure 3-38. Boxplot comparisons of trends in maximum quarterly average
lead concentrations at 36 sites, 1975-1984.
3-42
-------
the larger sample of trend sites covering the 1980-84 period, the 1983
and 84 means are statistically different from the 1980-82 means. Thus,
the downward trend in ambient Pb levels is continuing. The box plots are
shown in Figure 3-38 for the 1975-84 period. All percentiles basically
show the same overall downward pattern as the mean.
In last year's report^, a larger sample of 61 urban-oriented sites
qualified as trend sites for the 1975-83 time period. The loss of 25
sites qualifying to describe the 10-year (1975-84) trend was due to
incomplete or missing data in 1984. Fourteen of the 25 sites came from
data contributed by the State of Texas which appears to be discontinuing
many of their long-term Pb sites. Because of the small number of 1975-84
trend sites relative to the 1980-84 trend sites more importance should be
given to the 5-year (1980-84) trend.
The 1975-84 trends in total lead emissions based on information from
the National Emissions Data System7 is shown in Figure 3-39. Table 3-6
summarizes the lead emissions data as well. The drop (1975-84) in lead
emissions was 72 percent. This compares with a 70 percent decrease
(1975-84) in ambient lead noted above. The drop in lead consumption
since 1975 was brought about because of the increased use of unleaded
gasoline in catalyst equipped cars and the reduced lead content in other
gasoline. In 1984 unleaded gasoline sales represented about 60 percent
of the total gasoline sales. Although the good agreement between the
trend in lead consumption, emissions, and ambient levels may be more
fortuitous than real due to the imbalanced national sample of trend
sites, it does show that ambient urban Pb levels are responding to the
drop in lead emissions.
3.6.2 Recent Lead Trends: 1980-84
Ambient Pb trends as noted above were also studied over the shorter
term period 1980-84 (Figure 3-40). A total of 147 urban sites from 23
states met the minimum data requirement of at least 4 out of the 5 years
of data. This larger and more representative set of sites showed an
improvement of 45 percent over this time period. This corresponds to
reductions in lead emissions of 43 percent. Even this larger group of
sites was disproportionately weighted by sites in California and Pennsylvania.
These states accounted for 52 percent of the 147 sites represented.
Ambient lead levels have decreased in each of these states. Also shown
is Figure 3-41 is the Pb trend at the 21 NAMS and for the entire sample
of 147 trend sites. The short-term Pb trend at 21 NAMS sites is very
similar to the trend for all sites although the Pb levels are higher,
because NAMS sites are located only in the larger cities and in areas of
maximum Pb emissions. Interestingly, the decrease in ambient lead levels
is so pronounced, that the 21 NAMS, while few in number, show statistically
significant decreases with the 1983 and 1984 composite averages significantly
less than the 1980 composite average.
3-43
-------
Table 3-6. National Lead Emission Estimates, 1975-1984
(mill ion metric tons/year)
Source Category
Transportation
Fuel Combustion
Industrial Process
Sol id Waste
Total
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
22.6
9.3
10.3
4.8
47.0
132.4
8.3
8.1
4.3
153.1
124.2
7.2
5.7
4.1
141.2
112.4
6.1
5.4
4.0
127.9
94.
4.
5.
4.
108.
6
9
2
0
7
59.4
4.0
3.6
3.7
70.7
46.4
2.8
3.0
3.7
55.9
46.
1.
2.
3.
54.
9
7
7
1
4
40.7
0.6
2.4
2.6
46.3
34.7
0.5
2.3
2.6
40.1
200
LEAD EMISSIONS, 10* METRIC TONS/YEAR
150-
100-
SOURCE CATEGORY
ED FUEL
COMBUSTION
INDUSTRIAL PROCESSES E2 TRANSPORTATION
50-
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-39. National trend in lead emissions, 1975-1984.
3-44
-------
3.5
2.S-
SHORT-TERM TREND
147 SITES
NAAOS*
JUONC-TERM TRD40
3S SITES
1975 1976 1977 1978 1979 1980 1981 1982 1983 1984
Figure 3-40. Comparison of long-term and recent trends in maximun
quarterly average lead concentrations.
OJ-
NAAOS
1
1M1
1M2
YEAR
IMS
Figure 3-41. National trend in the composite average of the maximum
quarterly average lead concentration at both NAMS and
all sites with 95 percent confidence intervals, 1980-1984.
3-45
-------
Figure 3-42 shows 1982, 83 and 84 composite average Pb concentrations
by EPA region. The number of sites vary dramatically from no sites in
Region VIII and only one site in Region II to 58 sites in Region IX.
To a large extent then the regional differences noted results from this
disparity in the number and types of sites represented and do not represent
true differences. Only in the case of Regions III, V, and IX can somewhat
reasonable comparisons be made. The influence of a single lead point
source at a site in St. Paul, Minnesota in 1982 greatly inflates this
composite average in Region V and results in the dramatic improvement in
subsequent years. The 1983 and 1984 levels are fairly comparable between
these three regions with slightly higher Pb averages in Region IX followed
by Region V and lower levels in Region III. This ordering seems reasonable
due to the fact that Regions IX and V are heavily weighted respectively by
sites in the larger cities of Los Angeles and Chicago.
The sites in Region III represent more of a cross section of the
entire region, that is smaller cities which account for its lower Pb levels.
Another point to note from this figure is that most regions show the
expected improvement in Pb concentrations over the 1982-84 time period.
For the three regions with 10 or more sites there is improvement in each of
the 3 years with the exception of Region III where the 1983 and 1984
means are the same.
o
o
o
IE
0.6
0.2
Legend
1982 COMPOSITE AVERAGE
I 1983 COMPOSITE AVERAGE
CS 1984 COMPOSITE AVERAGE
EPA REGION I
NO. OF SITES 6
IV
8
V
24
VI
8
VIII
0
IX
58
Figure 3-42. Regional comparison of the 1982, 1983, 1984 composite
average of the maximum quarterly average lead
concentration.
3-46
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3.7 REFERENCES
1. Tukey, J. W., Exploratory .Data Analysis. Addison-Wesley Publishing
Company, Reading, MA, 1977.
2. Winer, B. J., Statistical Principles in Experimental Design. McGraw-
Hill, NY, 1971.
3. Johnson, N. L., and S. Kotz, Discrete Distributions. Wiley, NY, 1969,
4. Miller, R. G., Jr., Simultaneous Statistical Inference. Springer-
Veriag, NY, 1981.
5. Pollack, A. K., W. F. Hunt, Jr., and T. C. Curran, "Analysis of
Variance Applied to National Ozone Air Quality Trends," presented at
the 77th Annual Meeting of the Air Pollution Control Association, San
Francisco, CA, June 1984.
6. A. Pollack and W. Hunt, "Analysis of Trends and Variability in
Extreme and Annual Average Sulfur Dioxide Concentrations," Transactgions
of the APCA/ASQC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. 1985.
7. National Air Pollutant Emission Estimates, 1940-1984. U. S.
Environmental Protection Agency. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA-450/4-85-014,
January 1986.
8. Frank, N. H., "Nationwide Trends in Total Suspended Particulate
Matter and Associated Changes in the Measurement Process," Transactions
of the APCA/ASQC Specialty Conference, "Quality Assurance in Air
Pollution Measurement," Boulder, CO. 1985.
9. Hauser, R. T., U. S. Environmental Protection Agency, "Impact
of Filter Change on TSP Trends," memorandum to R. G. Rhoads, January 11, 1984.
10. National Air Quality and Emissions Trends Report, 1983. U. S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-84-029.
April 1985.
11. Steigerwald, J., Analysis of Precipitation Variables for the
Continental United States. PEI Associates, Inc., Durham, NC. Report
prepared for Neil H. Frank, U. S. Environmental Protection Agency,
Contract No. 68-02-3855. September 1985.
12. National Air Quality and Emissions Trends Report, 1976. U. S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/1-77-022.
December 1977.
13. Wijnberg, L., T. Johnson, J. Steigerwald, J. Capel and R. Paul.
Analysis of Possible Causes of Decreased TSP Levels, 1981 to 1982.
PEI Associates, Inc., Durham, NC. Report prepared for Neil H. Frank, U. S.
Environmental Protection Agency, Contract No. 68-02-3855. July 1985.
3-47
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14. Davidson, A., M. Haggan and P. Wong. Air Quality Trends in
the South Coast Air Basin, 1975-1984. South Coast Air Quality Management
District, El Monte, CA. August 1985.
15. National Acid Precipitation Assessment Program (NAPAP), 1980 NAPAP
Data Base, Version 3.0. September 1984.
16. Pechan, E. and J. Wilson, Jr. "Estimates of 1973-1982 Annual
Sulfur Oxide Emissions from Electric Utilities." J. Air Poll. Control Assoc.
Vol. 34, No. 10. pp 1075-1078. September 1984.
17. Koerber, W. M., "Trends in S02 Emissions and Associated
Release Height for Ohio River Valley Power Plants," presented at the
7bth Annual Meeting of the Air Pollution Control Association, New
Orleans, LA. June 1982.
18. Bergesen, C. Utility Data Institute, Int., letter to F. William
Brownell, Esq., Hunter and Williams, February 21, 1985.
19. Oppenheimer, M., C. Epstein and R. Yuhnke, "Acid Deposition, Smelter
Emissions and the Linearity Issue in the Western United States." Science,
Vol. 229, pp. 859-862, August 30, 1985.
20. Federal Register, Vol. 43, June 22, 1978, pp. 26971-26975.
21. Sweitzer, T. A. and D. J. Kolaz, "An Assessment of the Influence
of Meteorology on the Trend of Ozone Concentrations in the Chicago
Area," Transactions of the APCA/ASQC Specialty Conference, "Quality
Assurance in Air Pollution Measurement," Boulder, CO. 1985.
22. Kolaz, D., Illinois Environmental Protection Agency, personal
communication with T. Curran, U. S. Environmental Protection Agency,
October 15, 1985.
23. Pollack, A. and M. Moezzi. "Application of a Simple Meteorological
Index of Ambient Ozone Potential to Ten Cities." Systems Applications, Inc.,
San Rafael, CA. December 1985.
24. Highway Statistics 1984, U. S. Department of Transportation,
Federal Highway Administration, Washington, D. C. Publication No. HHP-41/
10-85(3M)QE. October 1985.
25. Federal Register, Vol. 45, October 10, 1980, pp. 67564-67575.
26. Faoro, R. B. and T. B. McMullen, National Trends in Trace Metals
Ambient Air, 1965-1974. U. S. Environmental Protection Agency, Office of
Air Quality Planning and Standards. Research Triangle Park, NC.
Publication No. EPA-450/1-77-003. February 1977.
27. W. Hunt, "Experimental Design in Air Quality Management," Andrews
Memorial Technical Supplement, American Society for Quality Control, 1984.
3-48
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4. AIR QUALITY LEVELS IN STANDARD METROPOLITAN STATISTICAL AREAS
The Tables in this section summarize air quality levels by Standard
Metropolitan Statistical Area (SMSA) for SMSA's with populations greater
than 500,000. These summaries are complemented with an analysis of the
number of people living in counties in which pollutant specific primary
health NAAQS(s) (Table 1-1) were exceeded by measured air quality in 1984
(Figure 1-1). Clearly, 03 is the most pervasive air pollution problem in
the United States with an estimated 79.2 million people living in counties
which exceeded the 03 standard. CO follows with 61.3 million people, TSP
with 32.6 million people, N02 with 7.5 million people, lead with 4.7 million
people and S0£ with 1.7 million people.
In the SMSA summary tables which follow, the air quality statistics
relate to pollutant-specific NAAQS. The purpose of these summaries is to
provide the reader with information on how air quality varies among SMSA's
and from year-to-year. The higher air quality levels measured in the SMSA
are summarized for the years 1982, 1983 and 1984.
The reader is cautioned that these summaries are not sufficient in
themselves to adequately rank or compare the SMSA's according to their
air quality. To properly rank the air pollution severity in' different
SMSA(s), data on population characteristics, daily population mobility,
transportation patterns, industrial composition, emission inventories,
meteorological factors and, most important, the spatial representativeness
of the monitoring sites would also be needed.
The same annual data completeness criterion used in the air quality
trends data base was used here for the calculation of annual means. (See
Section 2.1). If some data have been collected at one or more sites, but
none of these sites meet the annual data completeness criteria, then the
reader will be advised that there are insufficient data to calculate the
annual mean.
With respect to the summary statistics for air quality levels with
averaging times less than or equal to 24-hours, measured with continuous
monitoring instruments, a footnote will be placed next to the level if the
volume of annual data is less than 4380 hours for CO, less than 183 days
for S02 or less than 50 percent of the days during the ozone season for
ozone, which varies by State. 1 For example, in California the ozone season
is defined as 12 months, January through December, while in New Jersey it is
defined as 7 months, April through October.
4.1 SUMMARY STATISTICS
In the following SMSA summaries, the air quality levels reported are
the highest levels measured within the SMSA(s). All available sites in an
SMSA are used in these summaries. In the case of 03, the problem as stated
earlier is pervasive and the high values associated with the pollutant
can reflect a large part of the SMSA. In contrast, the high CO values are
generally highly localized and reflect downtown areas with heavy traffic.
4-1
-------
Table 4-1. Air Quality Summary Statistics and Their
Associated National Ambient Air Quality Standards (NAAQS)
POLLUTANT
Total Suspended Particulate
Sulfur Dioxide
Carbon Monoxide
STATISTICS
annual geometric mean
annual arithmetic mean
PRIMARY NAAQS
75
0.03 ppm
second highest 24-hour average 0.14 ppm
second highest nonoverlapping 9 ppm
8-hour average
Nitrogen Dioxide
Ozone
Lead
annual arithmetic mean 0.053 ppm
second highest datly maximum 0.12 ppm
1-hour average
maximum quarterly average 1.5ug/m3
ug/m3 = micrograms per cubic meter
ppm = parts per million
j linlj ikuliiliiiiiUiili Iknln lillkiii IhJu
TSP
so2 11.7
co
NO2
OZONE
40 60
MILLIONS OF PERSONS
Figure 4-1 Number of persons living in counties with air quality levels above the
National Ambient Air Quality Standards in 1 984 (Based on 1980 population data)
100
4-2
-------
The scale of measurement for the pollutants - TSP, S0£ and N02 - fall
somewhere in between. Finally, while lead measurements generally reflect
lead concentrations near roadways in the SMSA, if the monitor is located
near a source of lead emissions it can produce readings substantially
higher. Such is the case in several SMSAs. If the lead monitor is located
near a source it will be footnoted accordingly in Table 4-8.
The pollutant-specific statistics reported are summarized in Table
4-1, along with their associated primary NAAQS concentrations. For example,
if an SMSA has three ozone monitors in 1982 with second highest daily
hourly maxima of .15 ppm, .14 ppm and .12 ppm, the highest of these, .15
ppm, would be reported for that SMSA for 1982.
In the case of Pb, the quarterly average is based either on as many as
90 24-hour measurements or one or more chemical composite measurements.*
Most of the maximum quarterly Pb averages are based on multiple 24-hour
measurements. If the maximum quarterly average is based on a chemical
composite, it is footnoted accordingly.
4.2 AIR QUALITY SMSA COMPARISONS
In each of the following SMSA air quality summaries, the SMSA's are
grouped according to population starting with the largest SMSA - New York,
NY-NJ and continuing to the smallest SMSA with a population in excess of
500,000, Long Branch - Asbury Park, NJ. The population groupings and the
number of SMSA's contained within each are as follows: 16 SMSA's have
populations in excess of 2 million, 23 SMSA's have populations between 1
and 2 million and 41 SMSA's have populations between 0.5 and 1 million.
The population statistics are based on the 1980 census.
Air quality maps of the United States are introduced to show at a
glance how air quality varies among the 80 SMSA's. Figures 4-1 through 4-7
appear just before the appropriate table summarizing the same air pollution
specific statistic. In each map, a spike is plotted at the city location
on the map surface. This represents the highest pollutant concentration,
recorded in 1984, corresponding to the appropriate air quality standard.
Each spike is also projected onto a backdrop facilitating comparison with
the level of the standard. This also provides an east-west profile of
concentration variability throughout the country.
The air quality summary statistics are summarized in the following
figures and tables:
Figure 4-2. United States Map of the Highest Annual Geometric Mean
Suspended Particulate Concentration by SMSA. The map for particulate matter
displays the maximum annual geometric mean TSP concentration in 1984 for
large metropolitan areas. The highest concentrations are generally found
*A chemical composite measurement can be either a measurement for an
entire month or an entire quarter.
4-3
-------
in the industrial Midwest and arid areas of the West. The east-west
profile shows that levels above the current standard of 75 ug/m^ can be
found throughout the Nation.
Table 4-2. Highest Annual Geometric Mean Suspended Particulate
Concentration by SMSA, 1981-83.
Figure 4-3. United States Map of the Highest Annual Arithmetic Mean
Sulfur Dioxide Concentration by SMSA, 1983. The map for sulfur dioxide
shows maximum annual mean concentrations in 1984. Among these large
metropolitan areas, the higher concentrations are found in the heavily
populated Midwest and Northeast. The peak S02 mean concentration occurs in
Pittsburgh, PA at an individual site near a large steel complex. All other
urban areas have lower ambient air quality concentrations, well within
the current annual standard of 80 ug/m^ (.03 ppm). Because this map only
represents areas with population greater than one half million, it does not
reflect air quality in the vicinity of smelters or large power plants in
rural areas.
Table 4-3. Highest Annual Arithmetic Mean Sulfur Dioxide Concentration
by SMSA, 1981-83.
Figure 4-4. United States Map of the Highest Second Maximum 24-hour
Average Sulfur Dioxide Concentration by SMSA, 1983. The map for sulfur
dioxide shows the highest second highest maximim 24-hour average sulfur
dioxide concentration by SMSA in 1984. The highest concentration occurs in
Pittsburgh, PA at an individual site near a large steel company. This
concentration exceeds the level of the short-term standard. All other
urban areas have lower ambient concentrations below the 24-hour NAAQS
of 0.14 parts per million.
Table 4-4. Highest Second Maximum 24-hour Average Sulfur Dioxide
Concentration by SMSA, 1981-83.
Figure 4-5. United States Map of the Highest Second Maximum Nonoverlapping
8-hour Average Carbon Monoxide Concentration by SMSA, 1983. The map for
carbon monoxide shows peak metropolitan concentrations in terms of the
second highest annual 8-hour value recorded in 1984. The east-west profile
indicate that many of these urban areas in all geographic regions have air
quality at or exceeding the 9 ppm level of the standard.
Table 4-5. Highest Second Maximum Nonoverlapping 8-hour Average Carbon
Monoxide Concentration by SMSA, 1981-83.
Figure 4-6. United States Map of the Highest Annual Arithmetic Mean
Nitrogen Dioxide Concentration by SMSA, 1983. The map for nitrogen dioxide
displays the maximum annual mean measured in the Nation's largest metropolitan
areas during 1984. Los Angeles, California is the only area in the country
exceeding the air quality standard of .053 ppm.
4-4
-------
Table 4-6. Highest Annual Arithmetic Mean Nitrogen Dioxide Concentration
by SMSA, 1981-83.
Figure 4-7. United States Map of the Highest Second Daily Maximum
1-hour Average Ozone Concentrations by SMSA, 1983. The ozone map shows the
second highest daily maximum concentration in the 80 largest metropolitan
areas. As shown, slightly over half of these areas did not meet the 0.12
ppm standard in 1984. The highest concentrations are observed in Southern
California, but high levels also persist in the Texas Gulf Coast, northeast
corridor, and other heavily populated regions.
Table 4-7. Highest Second Daily Maximum 1-hour Average Ozone Concentration
by SMSA, 1981-83.
Figure 4-8. United States Map of the Highest Maximum Quarterly Average
Lead Concentration by SMSA, 1983. The map for lead displays maximum
quarterly average concentrations in the Nation's largest metropolitan areas.
The highest concentrations are found throughout the country in cities
containing nonferrous smelters or other point sources of lead. Because of
the switch to unleaded gasoline, other areas, primarily affected by automotive
lead emissions, show levels below the current standard of 1.5 ug/rn^.
Table 4-8. Highest Maximum Quarterly Average Lead Concentration by SMSA,
1981-83.
The air quality summaries follow:
4.3 REFERENCES
1. Rhoads, Richard G., U. S. Environmental Protection Agency, memorandum
to Director of the Environmental Services Divisions and Air and Waste
Management Divisions, EPA Regions I through X, 15 December 1982.
4-5
-------
4-6
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5. TREND ANALYSIS FOR TEN URBANIZED AREAS
This chapter presents trends in ambient air quality for 1980 through
1984 in ten urbanized areas. The ten urbanized areas included in this
analysis are Atlanta, GA; Boston, MA; Chicago, IL-Northwestern IN; Denver,
CO; Houston, TX; Los Angeles-Long Beach, CA; New York, NY-Northeastern NJ;
Philadelphia, PA-NJ; Portland, OR-WA; and St. Louis, MO-IL. These cities
were selected because they were among the largest cities in each of the
EPA Regions. Where sufficient data were available, trends are presented
for the criteria pollutants TSP, S02, CO, N02, 03, and Pb.
The air quality data used for the trend statistics in this section were
obtained from the EPA National Aerometric Data Bank (NADB). Additionally,
some data were taken from State annual reports. The monitoring sites used
for the trend analysis were required to satisfy the historical continuity
criteria of 4 out of 5 years of data in the period 1980 to 1984. Further-
more, each year with data generally had to meet the annual data completeness
criteria as described in Section 2.1.
The urbanized area air quality trends focuses on the period 1980 through
1984. This complements the national trend analyses in Section 3 which exam-
ines both a 10-year trend (1975 to 1984) and a 5-year trend (1980 to 1984).
Although some of the ten urbanized areas had sufficient data to prepare
area trends for the ten year period (1975 to 1984), several of the urbanized
areas did not have sufficient data to meet the 8 of 10 year data completeness
criteria. As a result of this situation and considering the fact that the
ten urbanized areas began establishing fixed long-term National Air Monitoring
Stations in 1980, it was decided to begin the urbanized area trends analysis
in 1980.
The trends analyses are based on monitoring sites located within the
boundaries of the urbanized areas (except for 03) included in the 1980
Census of Population Report prepared by the U.S. Bureau of Census.^ The
report describes an urbanized area as consisting of a central city or cities,
and surrounding closely settled territory (urban fringe). Since the maximum
03 concentrations generally occur downwind of an urbanized area, the downwind
sites located outside of the urbanized area boundaries were also used in the
trends analysis.
Maps of the appropriate urbanized area are included as part of the
discussions on urban area trends. The maps include county and urban area
boundaries and were obtained from the Bureau of Census maps, while the city
boundaries are the best estimates of the actual city borders. The locations
of the monitoring sites shown on the maps are for sites having at least 4
years of data during 1980-1984 and which were used in the trend analysis.
The maps are presented for illustrative purposes to show the spatial distri-
bution of monitoring sites.
Figure 5-1 shows the plotting convention used in trends analysis. For
1980-1984, the maximum and minimum values as well as the composite average
5-1
-------
of the sites used in the trends are shown. The maximum and minimum values
are measured concentrations, while interpolated values for missing years
were used to calculate the appropriate average. Table 5-1 shows the air
quality statistics used in the trend analyses for the ten cities. It
should also be noted on the TSP trend plots for all cities, except Houston,
that the composite averages for 1980-1982 are connected by dotted lines.
As previously explained in Section 3.1.1, EPA has found that TSP data col-
lected in 1980 and 1981 may be biased high due to the glass fiber filter
used during these years. The apparent decrease in TSP concentrations
between 1981 and 1982 can be partially attributed to a change in the filters.
In Houston during 1981 and 1982, a combination of several different types
of filters were used which may have resulted in an unknown bias.2
The air quality data and trends presented in this section should not
be used to make direct city to city comparisons since the mix, configuration,
and number of sites comprising the area network are different. Furthermore,
other parameters such as population density, transportation patterns, indus-
trial composition, emission inventories, and meteorological characteristics
also need to be taken into consideration.
5-2
-------
IHIGHEST AIR QUALITY STATISTIC AMONG TREND SITES
j
ICOMPOSITE AVERAGE OF ALL TREND SITES
"LOWEST AIR QUALITY STATISTIC AMONG TREND SITES
FIGURE 5-1. ILLUSTRATION OF PLOTTING CONVENTIONS FOR RANGES USED IN
URBANIZED AREA TREND ANALYSIS.
Table 5-1. Air Quality Trend Statistics and Their
Associated National Ambient Air Quality Standards (NAAQS)
POLLUTANT TREND STATISTICS PRIMARY NAAQS
CONCENTRATION
Total Suspended Particulate annual geometric mean 75 ug/m3
Sulfur Dioxide annual arithmetic mean 80 ug/m3
(0.03 ppm)
Carbon Monoxide second highest nonoverlapping 10 mg/m3
8-hour average (9 ppm)
Nitrogen Dioxide annual arithmetic mean 100 ug/m3
(0.053 ppm)
Ozone second highest daily maximum 235 ug/m3
1-hour average (0.12 ppm)
Lead maximum quarterly average 1.5 ug/m3
ug/m3 = micrograms per cubic meter
ppm = parts per million
mg/m3 = milligrams per cubic meter
5-3
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5.1 BOSTON, MASSACHUSETTS URBANIZED AREA
The Boston urbanized area, located in the eastern part of the State,
is the largest urbanized area in the State of Massachusetts and the eighth
largest in the United States with a 1980 population of 2,678,762. It
includes all of Suffolk County and the greater portion of Norfolk County
plus portions of Plymouth, Middlesex, Essex, and Worcester Counties. The
urbanized area extends about 51 miles east to west and about 46 miles north
to south at the greatest distances.
The Boston basin, a territory within a range of hills, has rolling
topographical physical features, and is split by the Charles and Mystic Rivers,
Because of the confinement, many tall buildings and light industrial, commer-
cial, and residential land use complexes are in close proximity of each other.
Numerous small factories and a great diversification of industries are found
in this area including electrical, food, printing and publishing, transporta-
tion equipment, fabricated metal, and rubber products. Boston is the chief
United States' Atlantic Ocean fishing port. A large network of railroads and
truck lines serve this port.
The meteorology of the area is complex. Prevailing winds are from the
northwest in the winter and southwest in the summer. During the summer, the
land, sea-breeze effect allows pollutants to be transported out over the sea
and then returned to the inland area.
The locations of the monitors used in the pollutant trend graphs are
provided in Figure 5-2 and 5-3. The trend graphs are displayed in Figure
5-4.
5.1.1 TSP Trends
Twenty-two sites were operated during the period 1980-1984; six sites
had 4 or more years of valid data. There was a 22 percent decline in the
highest TSP levels and an 18 percent decline in the composite average concen-
trations comparing the 1980 to the 1984 levels. The trend is similar to
the national trend of 21 percent. The lowest TSP concentrations were mea-
sured at a site in a residential area while the highest concentrations were
measured in the industrial areas of Boston. Unlike the national trend,
there was no decrease in the geometric mean from 1981 to 1982. As noted in
Section 3.1.1, some of the national decrease in TSP from 1981 to 1982 may
be attributed to a change in the filters. In the case of the Boston urban-
ized area, the lack of a decrease may be due to the drier conditions in the
northeast in 1982 than in 1981.3
5.1.2 Pb Trends
There were six sites that reported data during the years of 1980-1984;
however, no site met the completeness criteria; therefore, no trend is
possible for the Boston area.
5-4
-------
5.1.3 $02 Trends
Nineteen S02 sites were operated between 1980 and 1984. Figure 5-4
shows the trend for five sites meeting the trend criteria. Comparing the
1980 composite annual mean to the 1984 value, there was a 21 percent decline
while the decline seen at the national level is 15 percent. The higher rate
of decline in the S02 levels for Boston may be related to meteorology and
fuel conservation. The highest levels were measured at a site located in
the industrial area of Boston and the lowest levels were measured at a site
located in a residential area of Medfield.
5.1.4 03 Trends
Figure 5-3 shows the trends for the two sites having 4 years of complete
data out of the ten sites that operated during the period 1980-1984. The
trends in the 03 levels fluctuated during this period; however, the composite
average levels showed increases of 4 percent between 1980 and 1984 and 21
percent between 1982 and 1983. Meteorology in 1983 may have partially
affected the higher 03 levels during this year.
5.1.5 NO? Trends
Seven sites reported N02 data during the period 1980-1984, and two
sites had 4 or more years of valid data. Comparing the 1980 to the 1984
levels, there was a 4 percent decline in the composite average levels or
slightly over one-half of the national average of 7 percent. The highest
NO? levels were measured at a site located in an industrial area. The rate
of decline in the N0£ levels for Boston from 1980 to 1983 is 38%. This is
contrasted by a 73 percent increase from 1983 to 1984. The reason for this
increase is not apparent; and since it was determined from only two sites,
it is difficult to draw conclusions from these data.
5.1.6 CO Trends
Three of the ten sites that operated during the period 1980-1984 met
the criteria of having 4 years of complete data. The data reported from
these three sites indicate an increase of 1 percent in the CO levels in
this urbanized area. In contrast, there was a 10 percent decline at the
national level. Composite average levels showed an increase of 1 percent
between 1980 and 1984. From 1980 to 1982, there was a dramatic 60% increase
in the trend statistic. This upward trend is attributed to urban redevelop-
ment and traffic rerouting as the monitors were in areas where traffic
volume increased significantly. Since 1982, the neighborhoods around the
monitors have stabilized, and there has been a 37% decrease from 1982 to
1984. Generally, the highest levels were measured in heavy commercial
areas of Boston and the lowest levels were measured in a light commercial
and residential complex area of Boston. Although there was little change
in the second highest nonoverlapping 8-hour average, there was a general
improvement in the annual average CO levels between 1980 and 1984.4
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5.2 NEW YORK. NEW YORK-NORTHEASTERN NEW JERSEY URBANIZED AREA
The New York urbanized area is the largest urbanized area in the
United States with a 1980 population of 15,590,274. It includes all of
Essex, Hudson, and Union Counties in New Jersey; all of Bronx, Kings,
Nassau, New York, Queens, and Richmond Counties in New York; parts of
Bergen, Middlesex, Monmonth, Morris, Ocean, Passaic, Somerset, and Sussex
Counties in New Jersey; and parts of Putnam, Rockland, Suffolk, and
Westchester Counties in New York. At its greatest distance, the urbanized
area extends about 105 miles east to west and about 110 miles north to south.
The urbanized area is located at the mouth of the Hudson River in the
northeastern part of the United States. As a major ocean port, it is the
busiest in the United States. Industries have concentrated in the urbanized
area because of the proximity to major markets and the easy access to trans-
portation facilites. This urbanized area is the leading manufacturing area
in the United States. The largest manufacturing industries are apparel and
other finished products; printing, publishing, and allied industries; food
products; machinery; chemical and allied products; fabricated metal products;
textile products; leather and leather products; paper products; auto and
aircraft production; and shipbuilding.
The urbanized area is close to the path of most frontal systems which
move across the United States. Extremes of hot weather which may last up
to 1 week are associated with air masses moving over land from a Bermuda
high pressure system. Extremes in cold weather are from rapidly moving
outbreaks of cold air moving southeastward from the Hudson Bay region.
The average rainfall is around 41 inches per year.
The maps showing the locations of the monitoring sites used in the
trend analysis are shown in Figure 5-5 and Figure 5-6. The trend graphs
for the pollutants are shown in Figure 5-7 and depict the trends for 1980-
1984. However, this 5-year period is not indicative of the overall air
quality progress achieved prior to 1980.
5.2.1 TSP Trends
There were 105 sampling sites (52 in New Jersey and 53 in New York)
that reported TSP data during 1980-1984, and of these 105 sites, 38 met the
4 out of 5-year data completeness criteria (17 in New Jersey and 21 in New
York). Figure 5-5 shows the location of the 38 sites, and Figure 5-7 shows
the trend graph of the 38 sites for 1980-1984 in which the composite average
decreased 13 percent as compared to the national average of 21 percent for
the same period. The highest measured concentrations were in the heavily
industrialized areas of New Jersey and the lowest concentrations were in
the residential areas of Long Island. Some of the decrease from 1981 to
1982 can be attributed to a change in the filters (see Section 3.1.1).
5.2.2 Pb Trends
Pb was sampled at 23 sites during 1980-1984. No site met the data
completeness criteria and no trends are depicted for Pb. The available
5-9
-------
data show maximum quarterly concentrations for 1984 of around 0.5 to 1.0
ug/m3 at traffic-oriented sites and 0.3 to 0.7 at non-traffic oriented
sites. The highest concentrations during 1980-1984 were measured in New
Brunswick, NJ near a battery manufacturing facility (1.73 ug/m3 in 1984.)
5.2.3 $02 Trends
There were 54 sites which reported some data in the period 1980-1984,
but only 19 sites met the data completeness criteria. The S02 levels
increased 1 percent as compared to the national average of a 15 percent
decrease (Figure 5-7). The highest concentrations during the period were
measured in New York County (Manhattan) and are attributed to apartment
buildings using oil for heating. While the overall annual mean levels
increased 1 percent, the composite New York City borough sites decreased
about 8 percent, the remaining New York county sites increased 11 percent
and the composite of the New Jersey sites increased 9 percent.
5.2.4 03 Trends
A total of 27 sites monitored for 03 during 1980-1984 and 10 of these
sites met the criteria for completeness and were used in the trend analysis.
The trends follow the national pattern in that there was a decrease for
1980-1982, an increase in 1983, and a decrease in 1984. From 1980-1984,
the New York 03 levels decreased 10 percent while the national levels
decreased 9 percent for the same period. The composite average concentra-
tions were above the NAAQS for each year during 1980-1984, and except for
1982, all the minimum trend sites were also above the NAAQS.
5.2.5 NO? Trends
The N02 trends for five sites that met the completeness criteria in
the urbanized area show the same concentrations for 1980 and 1981, an increase
in 1982, and similar levels through 1984. The five sites are a subset of
the 21 sites that reported data for 1980-1984. The overall trend for
1980-1984 was a 6 percent increase, which is the reverse of the national
decline of 7 percent. Part of this increase has been attributed to the
decline in usage of the mass transit system and an increase in vehicular
traffic.
5.2.6 CO Trends
There were 24 sites which measured CO during 1980-1984 and 11 sites
met the data completeness criteria. The CO composite average increased 2
percent as compared to the national decrease of 10 percent for the same
period. The highest concentrations were measured in street canyons in
Manhattan, Jersey City, and Elizabeth. The New Jersey portion of the
urbanized area increased 6 percent from 1980 to 1984 while the New York
portion decreased 6 percent.
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5.3 PHILADELPHIA, PENNSYLVANIA-NEW JERSEY URBANIZED AREA
The Philadelphia, PA-NJ urbanized area is the fourth largest in the
United States with a 1980 population of 4,112,933. It includes all of
Philadelphia County plus portions of Bucks, Chester, Delaware, and Montgomery
Counties in Pennsylvania and portions, of Burlington, Camden, and Gloucester
Counties in New Jersey. The urbanized area stretches about 65 miles east
to west and about 50 miles north to south at its greatest distances.
Philadelphia is located in the southeastern corner of Pennsylvania on
the Delaware River where the Schuylkill River flows into the Delaware. The
Atlantic Ocean is 85 to 90 miles down the Delaware River. Philadelphia
handles more shipping than any other port in the United States except for
New York. The industrial growth of Philadelphia was due to its proximity
to coal, petroleum, water power, and other natural resources. The leading
industries in Philadelphia are manufacturing of textiles, carpets, clothing,
paper, chemicals, glassware, oil refining, metalworking, ship building,
sugar refining, printing, and publishing.
Concerning the meteorology of the urbanized area, the prevailing winds
are from the southwest in the summer and from the northwest during the win-
ter. Maritime air and the proximity to the Delaware River contribute to
high humidity and temperatures during the summer months. The average rain-
fall is around 42 inches per year.
Figures 5-8 and 5-9 show the locations of the monitoring sites used in
the trend analysis, and Figure 5-10 depicts the trend graphs for the pollu-
tants.
5.3.1 TSP Trends
Figure 5-8 shows the location of 26 of the 37 sampling sites which
met the data completeness criteria during 1980-1983. The TSP trend shown
in Figure 5-10 is almost the same as the national trend in that the decrease
in Philadelphia for 1980-1984 was 19 percent compared to the national
decrease of 21 percent. The decrease for Philadelphia County was 15 per-
cent while the remaining sites in Pennsylvania and New Jersey each showed
a 24 percent decrease. Also, the 16 percent decrease in TSP levels from
1981 to 1982 is about the same as the national trend which has been attri-
buted in part to the filters used for collecting the samples (see Section
3.1.1).
5.3.2 Pb Trends
There were 28 sites which sampled for Pb in the urbanized area during
1980-1984 and four of these sites are shown in the trend analysis. The com-
posite average of these sites show an increase each year for the 5-year
period. This upward trend is caused by one source-oriented Pb sampler
which is located close to a plant which manufactures lead oxide pigment for
paint. The three traffic oriented sites show a decrease from 1980 to 1984
of 24 percent. This compares with a 45 percent decrease in the national
trend.
5-14
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5.3.3 S02 Trends
The S02 concentrations were measured at 23 sites in the urbanized
area. Ten of these sites met the data completeness criteria and were used in
the trend analysis. The 20 percent decline from 1980 to 1984, while greater
than the national decrease of 15 percent, appears to be consistent with
Philadelphia's preliminary estimates of changes in emissions.5 Area sources
and refineries contributed to the S02 levels measured in the urbanized area.
5.3.4 03 Trends
Of the 11 sites that monitored 03 in the urbanized area during 1980-1984,
eight sites were selected for the trend analysis based on data completeness.
The sites follow the national trend in decreases from 1980-1982 followed by
an increase in 1983 and a decrease in 1984. The result was a 19 percent
overall decrease from 1980-1984, as compared to the national decrease of 9
percent.
5.3.5 N02 Trends
Twelve sites monitored N02 during 1980-1984, and the trends for the
seven sites meeting the completeness criteria are shown in Figure 5-9. The
highest arithmetic average and the composite average of the seven sites were
about the same for 1980-1984. The effect of mobile sources (which account
for about 50 percent of the nitrogen oxide emissions) on the N02 sites may
be the reason for the relatively unchanged N02 trends. Increasing traffic
densities in the vicinity of the sites and decreasing NOX emissions due to
the Federal Motor Vehicle Emission Control Program could account for the
stable trend.
5.3.6 CO Trends
Carbon monoxide was measured at 19 sites during 1980-1984 and six of
these were used in the trend analysis. The composite CO levels at the six
sites showed an increase from 1980 to 1981, decreases from 1981-1983, followed
by an increase in 1984. There was an overall decrease of 4 percent from
1980 to 1984 which compares to the national decrease of 10 percent. The
highest concentrations in 1982-1984 were from a microscale site which had
insufficient data to be included in the trend analysis.
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5.4 ATLANTA. GEORGIA URBANIZED AREA
Atlanta, the capital of Georgia and its largest city, is located in
the north-central part of the State. The urbanized area of Atlanta is the
most populous area between Washington, DC and New Orleans with a 1980
population of 1,613,357. The area extends into ten counties and measures
approximately 40 miles north to south and 35 miles east to west. The major-
ity of the people in the urbanized area live in Fulton, de Kalb, and Cobb
Counties. Approximately 500 square miles of land area are included in this
urbanized area.
The city is the financial and commerical capital of the southeast, the
transportation and commercial center of the region, and an important distri-
bution, manufacturing, educational, and medical center. Since its location
is at the southern extreme of the Appalachian Range, it has become the gate-
way through which most overland and air traffic must pass from the eastern
seaboard to the west. Atlanta is a rapidly growing and expanding area.
The population increased by 37 percent since 1970. Atlanta has moderate
summer and winter weather, with the summer winds from the northwest and the
winter winds fluctuating from southwest to northwest. In spite of abundant
rainfall, serious dry spells occur during most years.
The locations of the monitors used in the pollutant trend graphs are
provided in Figures 5-11 and 5-12. The trend graphs are shown in Figure
5-13.
5.4.1 TSP Trends
Nineteen sites were operating for some time during the period 1980-1984
and nine of the sites had at least 4 years of valid data. The general
location of these sites is shown on the map in Figure 5-11. Five of the
nine sites were within the Atlanta city limits.
The composite average for the nine sites used to indicate the TSP
trend for Atlanta showed a 16 percent decline, while the national decline
was 21 percent. The highest annual mean was below the primary NAAQS for
all years except 1981. The lower rate of air quality improvement compared
to the national level may be due to Atlanta's rapid growth and to the
long dry periods in 1982 and 1983. The higher TSP levels in 1980 and 1981
are probably due in part to the filters (Section 3.1.1). The highest
levels were measured at a site located in a heavy commercial area and the
lowest levels were measured at sites located in light commercial and
residential areas.
5.4.2 Pb Trends
One Atlanta Pb site reported data during the 5-year period between
1980 and 1984, and met the data completeness criteria. However, there were
no valid quarters reported for 1984 so the 1984 value was extrapolated from
the 1983 level. The location of the Pb site is shown on the map in Figure
5-11.
5-19
-------
The Pb levels showed a 16 percent decrease between 1980 and 1983,
while the national trend indicated a 43 percent decrease. The 1980 to
1983 Pb levels at the Atlanta site were similar to the national composite
levels. It is difficult to provide any conclusive statement about the Pb
trends due to the sparsity of data.
5.4.3 S02 Trends
Atlanta operated one monitor during 1980 to 1984 which was relocated
to a different site in 1982. Neither site met the data completeness criteria;
therefore, no trend analysis was conducted.
5.4.4 03 Trends
There were two NAMS 03 sites that met the criteria of having 4 or more
valid years of data and the general location of these sites is shown on the
map in Figure 5-12. For this urbanized area, the ozone season was assumed
to run from March to November. The composite average of the second highest
daily maximum hour was above the NAAQS for 4 out of the 5 years. Figure
5-13 shows the 03 trend of plus 11 percent overall and depicts a saw-tooth
pattern. The national trend was a minus 9 percent over 1980-1984. The
meteorology in 1983 may have been more favorable for ozone formation than in
1981 and 1982.
5.4.5 NO? Trends
There were seven sites (three continuous monitoring sites) operating
during the 1980-1984 study period, none of which met the data completeness
criteria required for inclusion in the trend analysis.
5.4.6 CO Trends
There were six sites in the urbanized area and five of these sites met
the criteria of 4 out of 5 valid years of data. The general location of
these CO trend sites is shown on the map in Figure 5-12. Data from these
five sites indicated an 18 percent decline in the Atlanta CO levels as com-
pared to 10 percent nationally during this period. The greater percentage
reduction than the national average could be attributed to the initiation
of an automotive inspection maintenance program in 1981.
5-20
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5.5 CHICAGO, ILLINOIS-NORTHWESTERN INDIANA URBANIZED AREA
The Chicago urbanized area covers approximately 1300 square miles and
includes 6,770,000 people. It is the third largest urbanized area in the
nation in terms of population. Approximately 75 percent of the urbanized
area population live in Cook County, the remaining 25 percent live in parts
of Lake, Du Page and Will Counties in Illinois and portions of Lake and
Porter Counties in Indiana.
The urbanized area runs from Waukegan (near the Wisconsin border)
around Lake Michigan to Chesterton, Indiana to the east. The southern and
western boundaries of the urbanized area are very irregular. To the south
the area extends as far as Crown Point, Indiana and Park Forest South in
Illinois. Similarly, the urban area extends as far west as Bartlett, West
Chicago, and Napierville, all in Illinois.
Economically, Chicago is a major center for transportation,
manufacturing, and commercial enterprises. In terms of transportation,
Chicago has the largest air and rail traffic in the country. Because of
Chicago's location and large manufacturing concerns, it has developed an
extensive highway network for local and through traffic. Additionally, the
port of Chicago on Lake Michigan has developed into an important inland
port for raw materials and port of transfer for the Great Lakes-Atlantic
trade. Among Chicago's chief manufactures are food products, primary
metals (steel) and both elecrical and nonelectrical machinery.
Chicago occupies a relatively flat plains area bounded by Lake Michigan
in the east. The climate is predominately continental with relatively warm
summers and cold winters. Temperature extremes are somewhat altered by
Lake Michigan and other Great Lakes. Annual precipitation is on the order
of 33 inches per year.
Figures 5-14 and 5-15 show the locations of the monitors used in the
trend analysis and Figure 5-16 shows the trends for all the pollutants in
the urbanized area.
5.5.1 TSP Trends
Figure 5-14 shows the approximate location of the TSP sampling
locations operated in the Chicago urbanized area between 1980 and 1984,
that were used in the TSP trend analysis. The TSP trend in Figure 5-16
shows the composite average of 52 out of 97 sites meeting the trend criteria
during the period between 1980-1984. The 25 percent decline in TSP values
for the urbanized area is similar to the 5 year national decline of 21
percent over this period (1980 to 1984). While some of this improvement
must be attributed to the change in filters, discussed in Section 3.1.1,
some also appear to be related to reductions in emissions.
5.5.2 Pb Trends
During the period between 1980 and 1984, 74 sites were operated for
lead in the Chicago urban area. Lead data for many of these sites have
5-24
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not been submitted to EPA; therefore the Illinois State Annual reports for
1980-1984 have been used as a supplemental source for lead data to develop
a Chicago area trend.6-10 There were 35 sites shown on Figure 5-14 having
at least 4 years of valid data during the period and used to compute the
composite average of highest quarterly lead concentration. The Chicago
trend for the period 1980 to 1984 shows the same 45 percent decline as the
5-year national trend for lead.
5.5.3 $02 Trends
Twenty-one $03 monitoring sites operated in the Chicago area of which
nine sites met the trend criteria with a minimum of 4 years of valid data.
These sites are shown on Figure 5-14. The composite average of S02 values
in Chicago has declined by approximately 17 percent between 1980 and 1984,
which is close to the national decline of 15 percent.
5.5.4 03 Trends
The 03 trend for Chicago is based on the six sites meeting the data
completeness criteria out of the 28 sites operated during the period. The
location of the trend sites is shown in Figure 5-15. The composite average
of second daily maximum hour concentrations for Chicago shows patterns very
similar to the national trend in that the composite averages decline each
year between 1980 and 1982 with a pronounced 26 percent increase occurring
between 1982 and 1983 followed by a pronounced decrease of 17 percent between
1983 and 1984 (Figure 5-16). As noted in Section 3.5.1, a meteorological
index was developed for Chicago, which suggests that the 1982-83 increase in
0^ levels is partly attributable to meteorology.*1
5.5.5 N02 Trends
During the period 1980 to 1984 there were 56 N02 monitoring sites
operated in the urban area, 17 of which were used for the Chicago N02 trend.
The location of these 15 sites is shown in Figure 5-15. Eight of the 56
sites utilized continuous monitors and the remaining 48 sites used bubblers.
The composite annual average concentrations for the Chicago area are similar
to the national trend for all sites. The composite average declined 23
percent for Chicago over the 5-year period, as compared to 7 percent for
the nation. There is no apparent reason for the comparatively larger
decline in the Chicago area.
5.5.6 CO Trends
The CO trends are based on 2 of the 13 sites operated during the period
which met the data completeness criteria. The location of these sites is
shown on Figure 5-15. During the time period, the CO composite averages
declined by nearly 10 percent from 1980 through 1982 and then increased
in 1983 followed by a sharp decline in 1984 for a net decline of 15 percent.
The increase for 1983 appears to be related to a severe air stagnation
episode occurring on February 28 and March 1, 1983.12
5-25
-------
WISCONSIN
Urbanized Area
City Area
TSP site used in trend analysis
A Pb site used in trend analysis
D SC>2 site used in trend analysis
° TSP, Pb, and SC>2 site used in trend analysis
KILOMETERS
e MILES
ILLINOIS INDIANA
FIGURE 5-14. LOCATION OF TSP, Pb, AND SO2 MONITORING SITES IN CHICAGO, IL-IN, 1980-1984.
5-26
-------
Urbanized Area
City Area
03 site used in trend analysis
A NC>2 site used in trend analysis
D CO site used in trend analysis
° 03, NC>2, and CO site used in trend analysis
KILOMETERS
6 MILES
ILLINOIS INDIANA
FIGURE 5-15. LOCATION OF 03, N02, AND CO MONITORING SITES IN CHICAGO, IL-IN, 1980-1984
5-27
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5-28
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5.6 HOUSTON, TEXAS URBANIZED AREA
The Houston urbanized area is the tenth largest in the United States
with a population of 2,412,664. It includes almost all of Harris County
and very small portions of six other counties. The urbanized area extends
about 55 miles east to west and 45 miles north to south and covers a total
of approximately 750 square miles. The City of Houston has a population of
1,595,138 and is located west of Galveston Bay about 50 miles inland from
the Gulf of Mexico.
Houston is a major seaport, particularly for petroleum products, and it
has many refinery and petrochemical complexes along the Houston Ship Chan-
nel, which runs approximately 20 miles from the Houston center city east
to Galveston Bay. The area is in the Sunbelt, has a mild climate moderated
by the Gulf of Mexico, and is one of the fastest growing of all the major
urbanized areas. The population has increased 44 percent since 1970.
Figure 5-17 shows the location of the TSP, Pb, and S0£ sites used in
the trend analysis. Figure 5-18 shows the location of the 03, NO?, and CO
sites used in the trend analysis. Figure 5-19 shows the trends of the six
pollutants during the study period.
5.6.1 TSP Trends
The Houston TSP trend was developed from 27 sites which met the data
completeness criteria out of the 54 sites which operated during the period.
Figure 5-17 shows the geographic distribution of the 27 sites which were
used in the TSP trend analysis. The TSP trend in Houston is similar to the
national trend with the first 2 years substantially higher than the last 3
years. The decrease is thought to be partially affected by a change in
filters (see Section 3.1.1), and the 24 percent drop from the first to the
last year is nearly identical with the 21 percent decrease found on a
national basis.
5.6.2 Pb Trends
The Pb trend in Houston shows a 58 percent decrease compared to a 45
percent drop nationally for the 1980-1984 period. This trend is based on
18 sites which met the data completeness criteria. The data for these
sites were obtained from the Houston Health Department.13
5.6.3 S02 Trends
The Houston S02 trend is based on 3 out of 13 sites which operated
during the study period. S02 concentrations which are well below the NAAQS
started and ended the 5-year period at the same level compared to the national
trend which shows a 15 percent decrease between 1980 and 1984. Between 1980
and 1983, Houston showed a 10 percent decline in SO? levels followed by a 10
percent increase in 1984.
5-29
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5.6.4 03 Trends
The pattern of the 03 concentration in the Houston area is identical
with the national average, 1980 and 1983 are high, while 1981, 1982 and
1984 are lower. Similar to the national trend, meteorology may have been
more favorable for ozone buildup in 1983 than in 1981, 1982 and 1984,
Nationally, between 1980 and 1984, there is a 9 percent decrease in 63
levels. In contrast, 11 of the 16 monitoring sites in Houston, meeting the
data completeness criteria, show a 25 percent decrease from 1980 to 1984.
5.6.5 N02 Trends
The Houston downward trend for N02 is almost three times greater than
the national average, a 20 percent reduction versus an 7 percent reduction.
This trend is based on 7 sites which met the data completeness criteria out
of a total of 40 sites which monitored N02 in the Houston area during the
1980-1984 study period.
5.6.6 CO Trends
The Houston CO trend shows a 2 percent increase in contrast to the 10
percent drop in the national average. This increase is probably reflective
of an increase in automobile traffic volume in the vicinity of the trend
sites. This trend is based on only two of the nine CO monitoring locations
which operated during the study period and which had enough data to meet the
data completeness criteria.
5-30
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5-33
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5.7 ST. LOUIS, MISSOURI-ILLINOIS URBANIZED AREA
The St. Louis MO/IL urbanized area is the llth largest in the United
States with a 1980 population of 1,848,590. This population reflects a
loss of 33,354 or 1.8 percent since the 1970 census. The urbanized area
includes all of St. Louis Independent city and parts of three counties in
Missouri including St. Louis County, and parts of three counties in Illinois.
Mississippi just
urbanized area's
commerce and the
area's economy.
The urbanized area is divided by the Mississippi River, the boundary
between Missouri and Illinois. The Missouri River branches from the
north of the urbanized area and further subdivides the
northwest section. The area is centrally located with
distribution of goods playing an important part in the
There is heavy industry on the Illinois side, especially
steel manufacturing, smelting, and chemical processing. Along the Misissippi
River, there are large numbers of fuel burning electric generating plants.
At its widest point, the urbanized area extends 48 miles east to west and
32 miles north to south, and encompasses approximately 509 square miles.
The areas continental climate is somewhat modified by its location
near the geographical center of the United States. The area enjoys four
distinct seasons with the cold air masses to the North in Canada and the
warm air masses to the South in the Gulf of Mexico alternating in control
of the weather.
Figure 5-20 shows the location of the TSP, Pb, and SO? sites used in
the trend analysis. Figure 5-21 shows the location of the 03, N02, and CO
sites used in the trend anslysis. Figure 5-22 shows the trends of the six
pollutants during the study period.
5.7.1 TSP Trends
The trend in St. Louis is derived from 22 sites out of a possible 33
which were operating during the period. Figure 5-20 shows the location of
the 22 sites used in the TSP trend analyses. The 24 percent decrease in
the annual geometric mean in St. Louis is similar to the 21 percent decrease
in the national composite average. The pattern is also similar with the
first 2 years distinctly higher than the last 3 years. A change in the
composition of the filter between 1981 and 1982 is felt to be the reason
for this decrease (see Section 3.1.1).
5.7.2 Pb Trends
Because no Pb data were reported to the EPA in 1980 and 1981 and only
three sites reported Pb data in 1982-1984, no Pb trend analysis is possible
for the St. Louis urbanized area. There were four sites that sampled lead
during 1980-1984; however, no site met the data completeness criteria. Six
sites on the Illinois side of the urban area reported Pb data to the Data
bank for the first time in 1984.
5-34
-------
5.7.3 SO? Trends
The trend in annual average SO? in St. Louis shows a 7 percent increase
over the period 1980-1984, while the national composite average has dropped
15 percent during the same period. The increase in St. Louis is believed
to be attributed to a general economic recovery in the area. The trend in
St. Louis is based on 8 out of a possible 17 sites operating during 1980-
1984.
5.7.4 03 Trends
The St. Louis 03 trend is based on 10 of 22 sites which operated during
the 1980-1984 period. These sites showed a 1 percent decrease between 1980
and 1984. The pattern over the 5-year period is similar to the national
trends, that is, high levels in 1980 and 1983 and lower levels in 1981 and
1982. Although 1984 levels were almost as high as 1980 levels, there was
a 6 percent decrease from 1983 to 1984 which is similar to the national
1983-1984 decrease of 9 percent. As with many sections of the rest of the
country, meteorological conditions may have been more favorable for ozone
formation in 1983 than in 1981 and 1982.
5.7.5 N02 Trends
The 21 percent decrease in the N02 trend is three times greater than
the 7 percent decrease on a national basis. This trend is based on only
5 out of 16 possible site locations meeting the data completeness criteria
required for inclusion in the trend analysis.
5.7.6 CO Trends
The trend in the St. Louis urbanized area is based on 5 of 14 sites
which had sufficient data to meet the criteria for trend analysis. The 6
percent decrease in the CO trend is comparable with the national 10 percent
decrease during the study period. This smaller decrease could be attributed
to the general economic recovery of the area even though there was a small
population loss in the urbanized area over the previous 10 years.
5-35
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5-38
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5.8 DENVER. COLORADO URBANIZED AREA
The Denver urbanized area had a 1980 population of 1,352,070 and
includes all of Denver County plus portions of Adams, Arapahoe, Boulder,
Douglas, and Jefferson Counties. At the maximum boundaries, the urbanized
area extends about 27 miles east to west and 26 miles north to south.
Denver, the capital of Colorado, is located at the western edge of the
great plains of the Midwest. The Rocky Mountains are just to the west of
the urbanized area. Denver is one of the highest cities in the United States
with an altitude of about 1 mile above sea level.
Although manufacturing is minimal compared to other cities of similar
populations, Denver does have manufacturing industries for rubber goods and
luggage. Other industries include food processing, milling, printing and
publishing, steel processing, machinery manufacture, and power generation.
Denver has a large stockyard and has the largest sheep market in the United
States. In recent years, many energy concerns have located their headquar-
ters in Denver.
The meteorology in Denver is unique in that air masses from at least
four different sources influence the weather in the urbanized area. These
sources are polar air from Canada and the far northwest, moist air from the
Gulf of Mexico, warm dry air from Mexico and the southwest, and Pacific air
modified by the passage overland. Since Denver is a long distance from any
moisture source and is separated from the Pacific source by high mountains,
Denver generally has low relative humidity and low average precipitation of
around 14 inches per year.
Figure 5-23 and 5-24 show the locations of the monitors used in the
trend analysis, and Figure 5-25 show the trend graphs for the pollutants.
5.8.1 TSP Trends
Fifteen sites sampled TSP in the urbanized area during 1980-1984 and
12 of these sites met the data completeness criteria and were used in the
trend analysis. Figure 5-16 shows the location of the 12 samplers used for
the trend. Figure 5-17 shows a plot of the trends for 1980-1984 in which
the composite average decreased 11 percent compared to the national decrease
of 21 percent for the same period. Some of the decrease between 1981 and
1982 has been attributed to the filters used for collecting the samples
(see Section 3.1.1). The TSP composite average was above the NAAQS for
each year during 1980-1984. The elevated TSP levels in Denver have been
attributed to the arid conditions and reentrainment of dust particles.
5.8.2 Pb Trends
There were ten sites in the urbanized area which sampled Pb during
1980-1984 and four sites met the data completeness criteria. The trend
from 1980 to 1984 in Denver decreased 38 percent compared to the national
5-39
-------
decline of 45 percent. The composite average of the four sites in Denver
is about twice as high as the national composite. This, like TSP measure-
ments, are believed to be caused in part by low rainfall conditions cited
previously resulting in more reentrainment of Pb particles in street dust.
5.8.3 S02 Trends
The S02 trends for the urbanized area were developed from two sites
out of the three sites which had data during 1980-1984. The trends for the
composite average show fluctuations with a decrease of 10 percent during
the period. The composite averages are about one-third of the NAAQS.
5.8.4 03 Trends
Five sites out of seven sites met completeness criteria and were used
in the trend analysis. The composite average for the five sites increased
each year during 1980-1983 followed by a decrease in 1984. The composite
average decreased 4 percent during 1980-1984 as compared to the national
average which decreased 9 percent.
5.8.5 N02 Trends
There were three sites that reported N02 data during 1980-1984, and
all three sites were used in the trend analysis. The composite average
decreased slightly from 1980-1982, increased in 1983, and decreased in 1984.
The composite average was the same in 1980 and 1984 as compared to the
national decline of 7 percent. The concentrations measured at a site in
Jowntown Denver continue to be among the highest in the nation due to
mobile and point sources.
5.8.6 CO Trends
The CO concentrations were measured at ten sites in the urbanized area
and four of these sites met the data completeness criteria and were used for
the trend analysis. The composite average showed an increase of 3 percent
from 1980 to 1984. The use of wood for home heating in air tight stoves in
recent years could contribute up to 10 percent of the measured CO concen-
trations. 14 The national composite average decreased 10 percent for the same
period. The composite average for each year was above the NAAQS.
5-40
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5.9 LOS ANGELES-LONG BEACH, CALIFORNIA URBANIZED AREA
The Los Angeles-Long Beach urbanized area is the second largest in
the United States both in terms of population and land area. The urbanized
area has a population of 9,479,436 according to the 1980 census figures and
measures 70 miles from east to west, and 71 miles across from north to south.
The area stretches 90 miles in its longest dimension, that is, northwest to
southeast and contains approximately 1,700 square miles. The urban area
comprises parts of Los Angeles, Orange, and San Bernardino Counties.
The urbanized area is a flat area bounded by the Pacific Ocean on the
west, and south and the San Gabriel and San Bernardino Mountains on the north
and east. The meteorology in the area is complex, with frequent occurrences
of strong persistent temperature inversions, particularly during the period
of May through October. The wind pattern is dominated by a land-sea breeze
circulation system that sometimes allows pollutants to be transported out
to sea at night, only to return inland during the ensuing daylight hours
with the onset of the sea breeze.
Although automotive sources comprise the bulk of the emissions, the
area has a lot of manufacturing and service related industries as well as
petroleum refining and production, chemical plants, fuel burning electric
utilities, and numerous industrial boilers which also contribute to the
pollution levels. The climate is mild and along with the high incidence of
sunlight and latitude of the area, is conducive to a year-long ozone season.
Figure 5-26 shows the location of the TSP, Pb, and S0£ sites used in
the trend analysis. Figure 5-27 shows the location of the 03, N02, and CO
sites used in the study. Figure 5-28 shows the trends of the six pollutants
during the study period.
5.9.1 TSP Trends
There were 22 sites operating at some time during 1980-1984 with 12
sites meeting the data completeness criteria which were used in the trend
analysis. The location of the sites is shown in Figure 5-26. The trend in
Los Angeles TSP is similar to the national trend. The TSP trend from
1980-1984 shows two higher years, 1980-1981, and 2 lower years, 1982-1983,
with 1984 returning to higher levels. This trend has been associated with
a change in the TSP filter media (Section 3.1.1). In fact the South Coast
Air Quality Management District 15 in their report eliminated the effect of
the filter change for their data by adjusting the TSP annual average downward
by 13 percent. If the effect of the filter change is removed, the data
shows a 5 percent increase over the 5-year period as opposed to the 9
percent decrease shown by the unadjusted data and presented in the report.
The relatively lower TSP averages in 1982 and 1983 have been attributed to
meteorological conditions, i.e., above average rainfall. Specifically, the
seemingly large increase in TSP levels from 1983 to 1984 of 21 percent has
been attributed to the unusually lower TSP concentrations recorded in March
and April of 1983 which, in turn, stemmed from unusually rainy and unstable
conditions during that periodl5.
5-44
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5.9.2 Pb Trends
Los Angeles, with its preponderance of automotive related pollution,
exceeded the national average of 45 percent reduction in Pb levels with a 60
percent drop of its own. This is based on 12 of the 20 sites which met the
data completeness criteria during 1980-1983. California has a more stringent
lead standard than the NAAQS, and both of these standards were met for all
sampling sites for the first time in 1983 and continued to be met in 1984.
5.9.3 SO? Trends
The drop in Los Angeles of 25 percent in annual average S02 levels is
well ahead of the 15 percent decline seen nationally. This trend is made
up of 15 monitors which met data completeness criteria of the 23 monitors
which operated during the period. The increased improvement is attributed
to having cleaner fuels and a major point source, a steel facility, shutting
down during the period.
5.9.4 03 Trends
The 03 trend in Los Angeles closely parallels the national 9 percent
reduction with an average drop of 11 percent over the 5-year period. The
trend is based on 18 of 25 sites which operated during this period. A
recent trend analysis conducted by the South Coast Air Quality Management
District indicates that 1982 was a year of record low meteorological ozone
forming potential, and that 1983 was a return to near normal meteorological
conditions.I6 An update of the analysis indicates that while 1984 had even
higher meteorological potential for ozone formation than 198315, the 11
percent decrease in 1984 may be partially due to efforts to reduce congestion
during the Olympic period which resulted in an estimated weather-adjusted
average reduction of 12 percent in basinwide ozone maxima.17
5.9.5 N02 Trends
Of the 21 sites operating in the Los Angeles area, 15 met the trends
criteria and were used in the analysis. The Los Angeles N02 levels decreased
10 percent, compared with an 7 percent reduction for the nation.
5.9.6 CO Trends
The decrease in the CO levels is 34 percent or slightly over three
times the national average of 10 percent. This trend is comprised of 16 of
the 20 sites operating during the 1980-1984 period. The percentage reduction
is thought to be greater than the national average because of the higher
automotive related pollution in Los Angeles relative to the rest of the
nation, and the stringency of their automotive control program.
5-45
-------
Urbanized Area
City Area
SAN BERNARDINO CO
PACIFIC OCEAN
TSP site used in trend analysis
A Pb site used in trend analysis
D SO2 site used in trend analysis
° TSP, Pb, and SC>2 site used in trend analysis
SAN DIEGO CO
FIGURE 5-26 LOCATION OF TSP, Pb, AND S02 MONITORING SITES IN LOS ANGELES, CA, 1980-1984
5-46
-------
LOS ANGELES CO
Urbanized Area
City Area
SAN BERNARDINO CO
PACIFIC OCEAN
03 site used in trend analysis
A NC>2 site used in trend analysis
D CO site used in trend analysis
° 03, NO2, and CO site used in trend analysis
SAN DIEGO CO
FIGURE 5-27. LOCATION OF 03, N02, AND CO MONITORING SITES IN LOS ANGELES, CA, 1980-1984
5-47
-------
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5.10 PORTLAND. OREGON-WASHINGTON URBANIZED AREA
The Portland urbanized area covers approximately 300 square miles and
includes over 1,020,000 people. Approximately 50 percent of the urbanized
area population live in Multnomah County, the remaining 50 percent live in
parts of Clackamas and Washington Counties in Oregon and part of Clark
County, Washington.
The urbanized area is roughly bounded by Hazel Dell and Orchards in
Washington to the north; Forest Grove, Oregon to the west; Troutdale and
Gresham to the east; and Beaver Creek to the south.
Until the 1940's, Portland was largely a commercial and transportation
center. With the introduction of relatively cheap hydroelectric power in
the 1940's, metallurgical and chemical industries augmented the ongoing
commerce of the area.
The Portland area is about 65 miles from the Pacific Ocean and is
partially shielded from the maritime climate of the Pacific Ocean by the
surrounding hills and mountains. The winds are generally southeasterly
during the winter and northwesterly during summer. The average precipitation
for the area is 37 inches and typically 88 percent of the rainfall occurs
in the months of October through May.
The locations of the TSP, Pb, and S02 sites used in the trend analysis
are shown in Figure 5-29, and the locations for 03, N02, and CO sites are
shown in Figure 5-30. The trend graphs for all pollutants are shown in
Figure 5-31.
5.10.1 TSP Trends
Figure 5-29 is a map showing the approximate location of the 15 TSP
sampling locations operated in the Portland urbanized area during the period
between 1980 and 1984 and met the trends criteria. During the period 1980
to 1984, 20 TSP sampling sites operated in the Portland area, and 15 of
these sites met the trend criteria and were used in the trend graphs for
Portland (Figure 5-31). The composite average has declined over the 5-year
period by approximately 34 percent which is nearly twice the national
decline of 21 percent for TSP. This has occurred because TSP values in
Portland during 1980 were greatly elevated due to the fallout from the Mt.
St. Helens volcanic eruption. If the 1980 TSP composite average is ignored,
the decline in TSP concentrations for 1981 through 1984 is approximately
6 percent or about one-half the national decline for the period 1981-1984.
Also, some of the decrease between 1981 and 1982 may have been caused by a
change in the filters (Section 3.1.1).
5.10.2 Pb Trends
The Pb data for the Portland area trend analysis includes the SAROAD
data base and Pb data from the 1984 Oregon Air Quality Annual Report pro-
duced by the State of Oregon.18 Figure 5-31 shows the composite average
5-49
-------
of maximum quarterly concentrations of Pb from the 6 of 14 sites which met
the 4-year trend criteria. The location of these 6 sites is shown on
Figure 5-29. The composite average for Pb in Portland has declined by 53
percent during the period compared to the national rate of 45 percent.
This difference may be attributed to a State regulation which prohibits the
customer from pumping his own gasoline resulting in a lower rate of fuel
switching.
5.10.3 SO? Trends
The S02 trend sites for Portland are shown on Figure 5-29. The
composite annual average for S02 represents the two of four S02 monitoring
sites in the Portland area with sufficient data to meet the data criteria
for the period 1981-1984. No site operating during 1980 met the trend
criteria; therefore, no value for 1980 S02 has been shown on Figure 5-31.
During the period 1981 to 1983, the S02 levels at these sites declined by
20 percent or about 5 percent more than the national decline of 15 percent.
Large point sources of S02 emissions are absent in the Portland area and
this is reflected in Portland annual average concentrations of S02 which
are less than one third of the S02 NAAQS.
5.10.4 03 Trends
The composite average for 03 for the Portland area is based on all
three of the sites operated during the period between 1980 and 1984. The
composite average for the area increased in 1981 over 1980 then declined
from 1982 through 1984 for a net increase of 11 percent between 1980 and 1983.
This is a different pattern from the national trend for ozone which has
shown a decline in average concentrations from 1980 through 1982 with a
pronounced increase in 1983. The reasons for Portland's departure from the
national pattern appear to be related to the local meteorology. Generally,
the high maximum 03 value trends correspond to the trend in the number of
air stagnation days during the spring and summer months. This decrease may
also be due in part to a lower rate of fuel switching due to the State law
prohibiting customers from pumping their own gas.
5.10.5 N02 Trends
The Portland urbanized area was not large enough at the time of the
1970 census to require NAMS N02 monitoring. However, there have been studies
at two N02 sites which were operated for a short period of time during 1980
and 1981. Although neither of the sites met the trend criteria and no trend
lines for N02 could be prepared, it appears that the N02 averages which are
about 30 to 50 percent of the NAAQS have remained stable since 1980.
5.10.6 CO Trends
The CO trend for Portland shown on Figure 5-31 is for the five of six
sites which met the trends criteria for the 1980 through 1984 period. These
sites are shown on Figure 5-30. The composite average declined by 17 per-
cent between 1980 and 1982, then showed a 12 percent increase for 1983 over
1982 and then declined again in 1984 for an overall decline of 27 percent
5-50
-------
over the period 1980-1984. The reduction of CO levels in Portland is more
than twice the national rate of 10 percent which may be attributed to the
State's CO control program. This is different than the national trend
which showed a decline for each of the years in the 5-year period. The
increase in CO concentrations during 1983 may in large part be attributable
to the temporary displacement of significant traffic volumes off Interstate
84 onto other surface and arterial street systems, elevating levels measured
at affected sites.
5-51
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5.11 REFERENCES
1. 1980 Census of Population, U.S. Bureau of Census, PC 80-1, U.S.
Government Printing Office, Washington, DC. December 1981.
2. Frank, N. H., "Nationwide Trends in Total Suspended Particulate Matter
and Associated Changes in the Measurement Process," Proceedings of the
APCA/ASOC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. October 1984.
3. Johnson, T., J. Steigerwald, L. Wijnberg, J. Cape! , and R. Paul,
Analysis of Possible Causes of an Observed Decrease in Particulate
Levels from 1981 to 1982. Prepared for EPA by PEDCo Environmental,
Inc., Cincinnati, OH.April 1984.
4. Beloin, N., et al., 1983 Annual Report on Air Quality in New England,
U.S. Environmental Protection Agency, Region I, Lexington, MA.
July 1984.
5. Ostrowski, R., Philadelphia Air Management Services, Personal Communication
with S. Sleva, March 1, 1985.
6. 1980 Annual Air Quality Report, Illinois Environmental Protection
Agency, Division of Air Pollution Control, Springfield, IL.
7. 1981 Annual Air Quality Report, Illinois Environmental Protection
Agency, Division of Air Pollution Control, Springfield, IL.
8. 1982 Annual Air Quality Report, Illinois Environmental Protection
Agency, Division of Air Pollution Control, Springfield, IL. June 1983.
9. 1983 Annual Air Quality Report, Illinois Environmental Protection
Agency, Division of Air Pollution Control, Springfield, IL.
10. 1984 Annual Air Quality Report, Illinois Environmental Protection
Agency, Division of Air Pollution Control, Springfield, IL.
11. Sweitzer, T. A. and D. J. Kolaz, "An Assessment of the Influence
of Meteorology on the Trend of Ozone Concentrations in the Chicago
Area," Proceedings of the APCA/ASQC Specialty Conference, "Quality
Assurance in Air Pollution Measurement," Boulder, CO. October 1984.
12. G">ranson. S., U.S. Environmental Protection Agency, Chicago, IL, Personal
Communication with D. Shipman, November 14, 1984.
13. McMullen, G., Houston Health Department, Personal Communication with
N. Berg, March 11, 1985.
5-55
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14. Colorado Air Quality Data Report 1984, Colorado Department of Health,
Air Pollution Control Division.
15. Davidson, A., M. Hoggan, and P. Wong, Air Quality Trends in the
South Coast Air Basin 1975-1984, South Coast Air Quality Management
District, El Monte, CA.August 1985.
16. Davidson, A. and M. Hoggan, Air Quality Trends in the South Coast
Air Basin 1975-1983, South Coast Air Quality Management District,
El Monte, CA. November 1984.
17. Davidson, A. and J. Cassmassi, Ozone Reductions During Olympic
Period due to Congestion Reducing Measures, Journal of the Air
Pollution Control Association, March 1985.
18. 1984 Oregon Air Quality Annual Report, Oregon Department of
Environmental Quality, Air Quality Control Division. July 1985.
5-56
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing]
1. REPORT NO.
EPA 450/4/-86-001
3 RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
National Air Quality and Emissions Trends Report, 1984
REPORT DATE
March 1986
6. PERFORMING ORGANIZATION CODE
7.AuTHOR(s) w. F. Hunt, Jr., (Editor), T. C. Curran,
R. B. Faoro, H. H. Frank, W. Freas, C. Mann, R. E. Neligar
S. Sleva, N. Berg, D. Lutz,- G. Hani re. and D. Shipman
8 PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
10 PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13 TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15 SUPPLEMENTARY NOTES
The computer graphics were prepared by K. Nelson and the typing by H. Hinton
and J. Harris.
16 ABSTRACT
This report presents national and regional trends in air quality from 1975
through 1984 for total suspended particulate, sulfur dioxide, carbon monoxide,
nitrogen dioxide, ozone and lead. Air pollution trends were also examined
for the 5-year period (1980-84) to take advantage of the larger number of
sites and the fact that the data from the post-1980 period should be of the
highest quality. Both national and regional trends in each of the major
pollutants are examined, as well as complimentary air quality trends in 1984.
National air quality trends are also presented for both the National Air
Monitoring Sites (NAMS) and other site categories. In addition to ambient
air quality, trends are also presented for annual nationwide emissions. These
emissions are estimated using the best available engineering calculations;
the ambient levels presented are averages of direct measurements.
This report also includes a section, Air Quality Levels in Standard
Metropolitan Statistical Areas (SMSA's). Its purpose is to provide interested
members of the air pollution control community, the private sector and the
general public with greatly simplified air pollution information. Air
quality statistics are presented for each of the pollutants for all SMSA's
with populations exceeding 500,000 for the years 1982, 1983 and 1984.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b IDENTIFIERS/OPEN ENDED TERMS
c. COSATI [ leld/Group
Air Pollution Trends
Emission Trends
Carbon Monoxide
Nitrogen Dioxide
Ozone
Sulfur Dioxide
tan
Air Pollution
Standard Metropolr
Statistical Area (S-1SA)
Air Quality Statistics
National Air Monitor
Stations (NAMS)
ing
Total
Lead
Suspended Particulates
18 DISTRIBUTION STATEMENT
Release Unlimited
19 SECURITY CLASS /This Report/
Unclassified
21 NO OF PAGES
20 SECURITY CLASS IThls page)
Unclassified
EPA Form 2220-1 (Rev. 4-77)
PREVIOUS EDITION IS OBSOLETE
5-57
*U.S. GOVERNMENT PRINTING OFFICE' 1986625-040/21522
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U.S. Environs-n' .1 Pr.t-sctlon Agency
Region V, I" .
230 Sci-fi ,-.-:.- --t
Chicaso. ill '" ""
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