xvEPA
United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA-450/4-87-001
Air
National Air Quality and
Emissions Trends Report
1985
CARBON MONOXIDE TREND. 1976-1985
(ANNUAL 2ND MAX 8-HR NONOVERUPPING AVG)
1976 1977 1978 1979 1980 1981 1982 1983 19&4 1985
o
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EPA-450/4-87-001
National Air Quality and
Emissions Trends Report, 1985
Monitoring and Data
Analysis Division
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 2771 1
iif, ' ~ ? """''- Action Ago
?:>-" on 5, L: V.- ;
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DISCLAIMER
This report has been reviewed by the Office of Air Quality Planning and Standards, U.S.
Environmental Protection Agency, and approved for publication. Approval does not signify that
the contents necessarily reflect the views and policies of the Agency, neither does mention of
trade names or commercial products constitute endorsement or recommendation for use.
EPA-450/4-87-001
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PREFACE
This is the thirteenth 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 Cathy Coats for typing the report.
The following people are recognized for their contributions to
each of the sections of the report as principal authors:
Section 1 - William F. Hunt, Jr. and Robert E. Nel igan
Section 2 - William F. Hunt, Jr. and Warren P. Freas
Section 3 - Thomas C. Curran, Robert B. Faoro, Neil H. Frank, and
Warren P. Freas
Section 4 - Warren P. Freas and Robert B. Faoro
Section 5 - Stan Sleva, Neil Berg, David Lutz, George Manire,
and Dennis Shipman
Also deserving special thanks are Bob Mersch, PEI, for preparing
the computer graphics, Chuck Mann, Jake Summers and Susan Kimbrough 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.
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CONTENTS
LIST OF FIGURES v11
LIST OF TABLES xv
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 2-2
2.2 TREND STATISTICS 2-5
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 3-10
3.3 TRENDS IN CARBON MONOXIDE 3-19
3.4 TRENDS IN NITROGEN DIOXIDE 3-26
3.5 TRENDS IN OZONE 3-31
3.6 TRENDS IN LEAD 3-38
3.7 REFERENCES 3-44
4. AIR QUALITY LEVELS IN METROPOLITAN STATISTICAL
AREAS 4-1
4.1 SUMMARY STATISTICS 4-1
4.2 AIR QUALITY MSA COMPARISONS 4-3
4.3 REFERENCES 4-5
5. TRENDS ANALYSES FOR 14 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 5-8
5.3 BALTIMORE, MARYLAND URBANIZED AREA 5-12
5.4 PHILADELPHIA, PENNSYLVANIA-NEW JERSEY URBANIZED
AREA 5-16
5.5 ATLANTA, GEORGIA URBANIZED AREA 5-20
5.6 CHICAGO, ILLINOIS-NORTHWESTERN INDIANA URBANIZED
AREA 5-24
5.7 DETROIT, MICHIGAN URBANIZED AREA 5-28
5.8 HOUSTON, TEXAS URBANIZED AREA 5-32
5.9 ST. LOUIS, MISSOURI-ILLINOIS URBANIZED AREA 5-36
5.10 DENVER, COLORADO URBANIZED AREA 5-40
5.11 LOS ANGELES-LONG BEACH, CALIFORNIA URBANIZED AREA. 5-44
5.12 PHOENIX, ARIZONA URBANIZED AREA 5-48
5.13 PORTLAND, OREGON-WASHINGTON URBANIZED AREA 5-52
5.14 SEATTLE-EVERETT, WASHINGTON URBANIZED AREA 5-56
5.15 AIR QUALITY TRENDS FOR FIVE GEOGRAPHIC AREAS 5-60
5.16 REFERENCES 5-64
vi
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FIGURES
Figures Page
1-1 Number of persons living In counties with air quality 1-2
levels above the primary National Ambient Air Quality
Standards in 1985 (based on 1980 population data).
1-2 Illustrations of plotting conventions for boxplots. 1-3
1-3 National boxplot trend in annual geometric mean 1-5
TSP concentrations, 1976-1985.
1-4 National trend in particulate emissions, 1976-1985. 1-6
1-5 United States map of the highest annual geometric mean 1-6
TSP concentration by MSA, 1985.
1-6 National boxplot trend in the annual average S02 1-7
concentrations, 1976-1985.
1-7 National boxplot trend in the second-highest 1-8
24-hour S02 concentrations, 1976-1985.
1-8 National trend in the composite average of the estimated 1-8
number of exceedances of the 24-hour S02 NAAQS, 1976-1985.
1-9 National trend in sulfur oxide emissions, 1976-1985. 1-9
1-10 United States map of the highest annual arithmetic mean 1-9
S02 concentration by MSA, 1985.
1-11 National boxplot trend in the second-highest nonoverl apping 1-10
8-hour average CO concentrations, 1976-1985.
1-12 National trend in the composite average of the estimated 1-11
number of exceedances of the 8-hour CO NAAQS, 1976-1985.
1-13 National trend in emissions of carbon monoxide, 1976-1985. 1-11
1-14 United States map of the highest second maximum nonoverlapping 1-12
8-hour average CO concentration by MSA, 1985.
1-15 National boxplot trend in the annual average N02 1-13
Concentrations, 1976-1985.
1-16 National trend in emissions of nitrogen oxides, 1976-1985. 1-14
1-17 United States map of the highest annual arithmetic mean 1-14
N02 concentration by MSA, 1985.
1-18 National boxplot trend in the second-highest daily maximum 1-15
1-hour 03 concentrations, 1976-1985.
vii
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1-19 National trend in the emissions of volatile organic 1-16
compounds, 1976-1985.
1-20 National trend in the composite average of the number 1-16
of daily exceedances of the 03 NAAQS in the 63
season, 1976-1985.
1-21 United States map of the highest second daily maximum 1-17
1-hour average 63 concentration by MSA, 1985.
1-22 National boxplot trend in maximum quarterly average Pb 1-18
concentrations, 1976-1985.
1-23 National trend in lead emissions, 1976-1985. 1-19
1-24 United States map of the highest maximum quarterly 1-19
average lead concentration by MSA, 1985.
2-1 Ten Regions of the U.S. Environmental Protection Agency 2-7
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, 1976-1985.
3-4 Boxplot comparisons of trends in annual geometric mean 3-6
total suspended particulate concentrations at 1400
sites, 1976-1985.
3-5 National trend in particulate emissions, 1976-1985. 3-8
3-6 Boxplot comparisons of trends in annual mean total suspended 3-9
particulate concentrations at 2094 sites, 1981-1985.
3-7 Regional comparison of the 1983, 1984, 1985 composite 3-9
average of the geometric mean total suspended
particulate concentration.
3-8 National trend in the composite average of the annual 3-11
average sulfur dioxide concentration at both NAMS and all
sites with 95 percent confidence intervals, 1976-1985.
3-9 National trend in the composite average of the second- 3-11
highest 24-hour sulfur dioxide concentration at both
NAMS and all sites with 95 percent confidence
intervals, 1976-1985.
v i i i
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3-10 National trend in the composite average of the estimated 3-12
number of exceedances of the 24-hour sulfur dioxide NAAQS
at both NAMS and all sites with confidence intervals,
1976-1985.
3-11 Boxplot comparisons of trends in annual mean sulfur 3-14
dioxide concentrations at 264 sites, 1976-1985.
3-12 Boxplot comparisons of trends in second highest 24-hour 3-14
average sulfur dioxide concentrations at 257 sites,
1976-1985.
3-13 National trend in sulfur oxide emissions, 1976-1985. 3-15
3-14 Boxplot comparisons of trends in annual mean sulfur 3-17
dioxide conncentrations at 547 sites, 1981-1985.
3-15 Regional comparison of the 1983, 1984, 1985 composite 3-17
average of the annual average sulfur dioxide concentration.
3-16 Regional boxplot comparisons of the annual average sulfur 3-18
dioxide concentrations in 1985.
3-17 National trend in the composite average of the second 3-20
highest nonoverl apping 8-hour average carbon monoxide
concentration at both NAMS and all sites with 95 percent
confidence intervals, 1976-1985.
3-18 Boxplot comparisons of trends in second highest non- 3-20
overlapping 8-hour average carbon monoxide concentrations
at 163 sites, 1976-1985.
3-19 National trend in the composite average of the estimated 3-22
number of exceedances of the 8-hour carbon monoxide
NAAQS, at both NAMS and all sites with 95 percent
confidence intervals, 1976-1985.
3-20 National trend in emissions of carbon monoxide, 1976-1985. 3-23
3-21 Boxplot comparisons of trends in second highest nonover- 3-24
lapping 8-hour average carbon monoxide concentrations
at 355 sites, 1981-1985.
3-22 Regional comparison of the 1983, 1984, 1985 composite 3-24
average of the second highest nonoverl apping 8-hour
average carbon monoxide concentration.
3-23 National trend in the composite average of nitrogen dioxide 3-27
concentration at both NAMS and all sites with 95 percent
confidence intervals, 1976-1985.
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3-24 Boxplot comparisons of trends in annual mean nitrogen 3-27
dioxide concentrations at 108 sites, 1976-1985.
3-25 National trend in emissions of nitrogen oxides, 1976-1985. 3-29
3-26 Boxplot comparisons of trends in annual mean nitrogen 3-30
dioxide concentrations at 243 sites, 1981-85.
3-27 Regional comparison of the 1983, 1984, 1985 composite 3-30
average of the annual mean nitrogen dioxide
concentration.
3-28 National trend in the composite average of the second 3-33
highest maximum 1-hour ozone concentration at both
NAMS and all sites with 95 percent confidence
intervals, 1976-1985.
3-29 Boxplot comparisons of trends in annual second highest 3-33
daily maximum 1-hour ozone concentrations at 183 sites,
1976-1985.
3-30 National trend in the composite average of the estimated 3-34
number of daily exceedances of the ozone NAAQS in the
ozone season at both NAMS and all sites with 95 percent
confidence intervals, 1976-1985.
3-31 National trend in emissions of volatile organic compounds, 3-35
1976-1985.
3-32 Boxplot comparisons of trends in annual second highest 3-36
daily maximum 1-hour ozone concentrations at 523
sites, 1981-1985.
3-33 Regional comparison of the 1983, 1984, 1985 composite 3-36
average of the second-highest daily 1-hour ozone
concentrations.
3-34 National trend in the composite average of the maximum 3-39
quarterly average lead concentration at 53 sites
and 7 NAMS sites with 95 percent confidence intervals,
1976-1985.
3-35 Boxplot comparisons of trends in maximum quarterly 3-39
average lead concentrations at 53 sites, 1976-1985.
3-36 National trend in lead emissions, 1976-1985. 3-41
3-37 Boxplot comparisons of trends in maximum quarterly 3-42
average lead concentrations at 241 sites, 1976-1985.
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3-38 Regional comparison of the 1983, 1984, 1985 composite 3-43
average of the maximum quarterly average lead
concentration.
4-1 Number of persons living In counties with air quality 4-2
levels above the national ambient air quality standards
In 1985 (Based on 1980 population data).
4-2 United States map of the highest annual geometric mean 4-6
suspended particulate concentration by MSA, 1985.
4-3 United States map of the highest annual arithmetic mean 4-16
sulfur dioxide concentration by MSA, 1985.
4-4 United States map of the highest second maximum 24-hour 4-26
average sulfur dioxide concentration by MSA, 1985.
4-5 United States map of the highest second maximum non- 4-36
overlapping 8-hour average carbon monoxide
concentration by MSA, 1985.
4-6 United States map of the highest annual arithmetic mean 4-46
nitrogen dioxide concentration by MSA, 1985.
4-7 United States map of the highest second daily maximum 4-56
1-hour average ozone concentration by MSA, 1985.
4-8 United States map of the highest maximum quarterly average 4-66
lead concentration by MSA, 1985.
5-1 Illustration of plotting conventions for ranges used 5-3
in urbanized area trend analysis.
5-2 Location of TSP, Pb, and SCfc monitoring sites in 5-5
Boston, MA, 1981-1985.
5-3 Location of 03, NOg , and CO monitoring sites in 5-6
Boston, MA, 1981-1985.
5-4 Air quality trends in the composite mean and range 5-7
of pollutant-specific statistics for the Boston,
MA Urbanized Area, 1981-1985.
5-5 Location of TSP, Pb, and SO? monitoring sites in New 5-9
York, NY-NJ, 1981-1985.
5-6 Location of 0, NO? , and CO monitoring sites in New 5-10
Location of 03, NOg, and CO monitoring sites in New
York, NY-NJ, 1981-1985.
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5-7 Air quality trends in the composite mean and range 5-11
of pollutant-specific statistics for the New York,
NY-NJ Urbanized Area, 1981-1985.
5-8 Location of TSP, Pb, and S02 monitoring sites in 5-13
Baltimore, MD, 1981-1985.
5-9 Location of 03, NOg, and CO monitoring sites in 5-14
Baltimore, MD, 1981-1985.
5-10 Air quality trends in the composite mean and range of 5-15
pollutant-specific statistics for the Baltimore, MD
Urbanized Area, 1981-1985.
5-11 Location of TSP, Pb, and S0£ monitoring sites in 5-17
Philadelphia, PA-NJ, 1981-1985.
5-12 Location of 03, N0£, and CO monitoring sites in 5-18
Phil del phi a, PA-NJ, 1981-1985.
5-13 Air quality trends in the composite mean and range of 5-19
pollutant-specific statistics for the Phil del phi a, PA-NJ
Urbanized Area, 1981-1985.
5-14 Location of TSP, Pb, and Sty monitoring sites in 5-21
Atlanta, GA, 1981-1985.
5-15 Location of 03, NCfc, and CO monitoring sites in 5-22
Atlanta, GA, 1981-1985.
5-16 Air quality trends in the composite mean and range of 5-23
pollutant-specific statistics for the Atlanta, GA
Urbanized Area, 1981-1985.
5-17 Location of TSP, Pb, and S02 monitoring sites in 5-25
Chicago, IL-IN, 1981-1985.
5-18 Location of 03, N0£, and CO monitoring sites in Chicago, 5-26
IL-IN, 1981-1985.
5-19 Air quality trends in the composite mean and range 5-27
of pollutant-specific statistics for the Chicago,
IL-IN Urbanized Area, 1981-1985.
5-20 Location of TSP, Pb, and S02 monitoring sites in
Detroit, MI, 1981-1985. 5-29
5-21 Location of 03, N02, and CO monitoring sites in 5-30
Detroit, MI, 1981-1985.
xii
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5-22 Air quality trends in the composite mean and range of 5-31
pollutant-specific statistics for the Detroit, MI
Urbanized Area, 1981-1985.
5-23 Location of TSP, Pb, and S02 monitoring sites in 5-33
Houston, TX, 1981-1985.
5-24 Location of 63, N0|2 , and CO monitoring sites in 5-34
Houston, TX, 1981-1985.
5-25 Air quality trends in the composite mean and range 5-35
of pollutant-specific statistics for the Houston,
TX Urbanized Area, 1981-1985.
5-26 Location of TSP, Pb, and S02 monitoring sites in 5-37
St. Louis, MO-IL, 1981-1985.
5-27 Location of 03, N0£ , and CO monitoring sites in 5-38
St. Louis, MO-IL, 1981-1985.
5-28 Air quality trends in the composite mean and range of 5-39
pollutant- specific statistics for the St. Louis, MO-IL
Urbanized Area, 1981-1985.
5-29 Location of TSP, Pb, and S0£ monitoring sites in 5-41
Denver, CO, 1981-1985.
5-30 Location of 03, NOg, and CO monitoring sites in 5-42
Denver, CO, 1981-1985.
5-31 Air quality trends in the composite mean and range 5-43
of pollutant-specific statistics for the Denver,
CO Urbanized Area, 1981-1985.
5-32 Location of TSP, Pb, and S02 monitoring sites in Los 5-45
Angeles-Long Beach, CA, 1981-1985.
5-33 Location of 03, NO^ , and CO monitoring sites in Los 5-46
Angeles-Long Beach, CA, 1981-1985.
5-34 Air quality trends in the composite mean and range of 5-47
pollutant- specific statistics for the Los Angeles-
Long Beach, CA Urbanized Area, 1981-1985.
5-35 Location of TSP, Pb. and SOp monitoring sites in Phoenix,
AZ, 1981-1985. 5-49
5-36 Location of 03, N02, and CO monitoring sites in Phoenix, 5-50
AZ, 1981-1985.
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5-37 Air quality trends in the composite mean and range of
pollutant-specific statistics for the Phoenix, AZ
Urbanized Area, 1981-1985. 5-51
5-38 Location of TSP, Pb, and $03 monitoring sites in 5-53
Portland, OR-WA, 1981-1985.
5-39 Location of 03, NOj?, and CO monitoring sites in Portland, 5-54
OR-WA, 1981-1985.
5-40 Air Quality Trends in the composite mean and range of 5-55
pollutant-specific statistics for the Portland, OR-WA
Urbanized Area, 1981-1985.
5-41 Location of TSP, Pb, and S02 monitoring sites in 5-57
Seattle, WA, 1981-1985.
5-42 Location of 03, N02, and CO monitoring sites in
Seattle, WA, 1981-1985. 5-58
5-43 Air quality trends in the composite mean and range of 5-59
pollutant-specific statistics for the Seattle, WA
Urbanized Area, 1981-1985.
XTV
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TABLES
Tables Page
2-1 National Ambient Air Quality Standards (NAAQS). 2-3
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
1976-1985.
3-2 National Sul fur Oxide Emission Estimates, 3-15
1976-1985.
3-3 National Carbon Monoxide Emission Estimates, 3-23
1976-1985.
3-4 National Nitrogen Oxide Emission Estimates, 3-29
1976-1985.
3-5 National Volatile Organic Compound 3-35
Emission Estimates, 1976-1985.
3-6 National Lead Emission Estimates, 1976-1985. 3-41
4-1 Air Quality Summary Statistics and Their 4-2
Associated National Ambient Air Quality
Standards (NAAQS)
4-2 Highest Annual Geometric Mean Suspended 4-7
Particulate Concentration by MSA, 1985.
4-3 Highest Annual Arithmetic Mean Sulfur Dioxide 4-17
Concentration by MSA, 1985.
4-4 Highest Second Maximum 24-hour Average Sulfur 4-27
Dioxide Concentration by MSA, 1985.
4-5 Highest Second Maximum Nonoverlapping 8-hour 4-37
Average Carbon Monoxide Concentration by MSA,
1985.
4-6 Highest Annual Arithmetic Mean Nitrogen Dioxide 4-47
Concentration by MSA, 1985.
4-7 Highest Second Daily Maximum 1-hour Average Ozone 4-57
Concentration by MSA, 1985.
xv
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4-8 Highest Maximum Quarterly Average Lead Concentration 4-67
by MSA, 1985.
5-1 Air Quality Trend Statistics and Their Associated 5-3
National Ambient Air Quality Standards (NAAQS)
5-2 Percent Change in Air Quality Trend Statistics 5-60
1981 to 1985.
xv i
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NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 1985
EXECUTIVE SUMMARY
1-1
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NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT. 1985
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 1985, 76.4 million people were living in counties with measured air
quality levels that violated the NAAQS for ozone (03) (Figure 1-1). This
compares with 47.8 million people for total suspended particulate (TSP), 39.6
million people for carbon monoxide (CO), 7.5 million people for nitrogen
dioxide (NO;?), 4.5 million people for lead (Pb) and 2.2 million people for
sulfur dioxide (SO^). 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.
pdutart
TSP
SO.
ininons of p6rsons
Figure 1-1. Number of persons living in counties with air quality levels above
the primary National Ambient Air Quality Standards in 1985 (Based
on 1980 population data).
1-2
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Nationally, long-term 10-year (1976 through 1985) improvements can be
seen for TSP, 562, CO, N02, OQ, and Pb. Similar improvements have been
documented in earlier air quality trends reports, 1-12 issued by EPA. The trend
in 03 is complicated by a major drop in measured concentration levels which
occurred between 1978 and 1979, largely due to a change in the 03 measurement
calibration procedure.13 Therefore, special attention is given to the
period after 1978, because the change in the calibration procedure is not an
influence during this time.
The 10-year trend (1976-1985) is complemented with a more recent 5-year
trend (1981-1985). The 5-year trend was introduced in last year's*2 report to
increase the number of sites available for trend analysis. Emphasis is
placed 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 1984 and 1985, all of the
pollutants declined with major decreases observed for both carbon monoxide,
10 percent, and lead, 32 percent.
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
-95thPERCEN71LE
90th PERCENTILE
75th PERCENflLE
COMPOSE AVERAGE
MEDIAN
25th PERCENTILE
KMh PERCENT1UE
5th PERCENTILE
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
1976 to 1985 or 4 out of 5 years in the period 1981 to 1985. 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 89
1 argest metropolitan statistical areas (MSA). In each map, a spike is
plotted at the city location on the map surface. This represents the
highest pollutant concentration, recorded in 1985, 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 1400 sites, decreased 24 percent between 1976 and 1985 (Figure 1-3).
This corresponds to a 24 percent decrease in estimated particulate emissions
for the same period (Figure 1-4). 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 fil ters. T1 »14»15 For this reason, the portion of the
Figure 1-3 graph corresponding to 1979-1981 is stippled, indicating the
uncertainty associated with these data. As reported in last year's trends
report,12 there was a slight increase in particulate levels between 1983 and
1984 due to a return of rainfall to more normal levels and an increase in
particulate emissions. Between 1984 and 1985, particulate levels declined
4 percent, while emissions declined 3 percent. An examination of regional
trends patterns indicates decreases in TSP were evident in most Regions
between 1984 and 1985. Two of the EPA Regions, Region V (the Great Lake
States) and Region VI (the South Central States) were among the group of
Regions showing the largest particulate air quality improvements and were
also the only Regions experiencing increases in precipitation. Correspondingly,
it is likely that some of these Regional improvements were due to 1985
being a wetter year. The most recent 1985 annual geometric mean TSP concen-
tration is plotted for the 89 largest MSA(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/m3 can be found throughout the Nation.
110
100-
90-
80-
70-
60-
50-
40-
30-
20-
10-
0
CONCENTRATION. UCVM*
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-3.
National boxplot trend in annual geometric mean TSP
concentrations, 1976 - 1985.
1-5
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15
TSP EMISSIONS, 10* METRIC TONS/YEAR
10H
SOURCE CATEGORY
SOUD WASTE ft MISC CD FUEL
COMBUSTION
B INDUSTRIAL PROCESSES M TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-4. National trend in participate emissions, 1976 - 1985.
Figure 1-5. United States map of the highest annual geometric mean
TSP concentration by MSA, 1985.
1-6
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Sulfur Dioxide (SO?) - Annual average S02 levels measured at 264 sites
with continuous S02 monitors decreased 42 percent from 1976 to 1985 (Figure
1-6). A comparable decrease of 44 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 95 percent (Figure 1-8). Corre-
spondingly, there was a 21 percent drop in sulfur oxide emissions (Figure
1-9). The difference between emissions and air quality can be attributed
to several factors. SOg 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 1984 and 1985, nationwide average
S02 levels decreased 5 percent. The decrease in ambient levels correspond
to a 3 percent decrease in sulfur oxide emissions. The most recent 1985
annual arithmetic mean S02 is plotted for the 89 largest MSA(s) (Figure
1-10). Among these large metropolitan areas, the higher concentrations are
found in the heavily populated Midwest and Northeast. All urban areas have
ambient air quality concentrations lower than the current annual standard
of (.03 ppm) 80 ug/m3. However, 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, and it does not reflect
violations of the 24-hour standard.
0.040
CONCENTRATION. PPM
0.033-
o.oso
0.023-
0.020
O.O15-
0.010-
O.OOS
O.OOO
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-6. National boxplot trend in annual average S02 concentrations,
1976 - 1985.
1-7
-------
0.25
CONCENTRATION, PPM
0.20-
0.15
o.io-
0.05-
o.oo
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-7. National boxplot trend in second highest 24-hour S02
concentrations, 1976 - 1985.
2.5
ESflMATQ) EMXHMNCCS
257 SITES
2-
1 .5-
1 -
0.5
0
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-8. National trend in the composite average of the estimated
number of exceedances of the 24-hour S02 NAAQS, 1976 - 1985.
1-8
-------
30
SOX EMISSIONS, 10* METRIC TONS/YEAR
SOURCE CATEGORY
Mouimui ftoco«5 n no. COMUSDON
10
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-9. National trend in sulfur oxide emissions, 1976 -
1985.
Figure 1-10. United States map of the highest annual arithmetic mean
SC>2 concentration by MSA, 1985.
1-9
-------
Carbon Monoxide (CO) - Nationally, the second highest non-overlapping
8-hour average CO levels at 163 sites decreased 36 percent between 1976 and
1985 (Figure 1-11). The median rate of improvement has been about 5 percent
per year, but the 1984-85 decrease was twice as large, about 10 percent.
The estimated number of exceedances of the 8-hour NAAQS decreased 92 percent
between 1976 and 1985 (Figure 1-12). CO emissions decreased 21 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 1984 and 1985, CO levels decreased 10 percent. This
is probably due to the continuing reductions in CO emissions brought about
by the Federal Motor Vehicle Control Program, the change in the vehicle mix
and the possible influence of meteorological conditions in some geographic
areas. The most recent 1985 highest second maximum nonoverlapping 8-hour
average CO concentration is plotted for the 89 largest MSA(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.
25
CONCENTRATION. PPM
20-
15-
10-
5-
0
I
1
1976 1377 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-11. National boxplot trend in the second highest nonoverlapping
8-hour average CO concentrations, 1976 - 1985.
1-10
-------
50
ESTIMATED 8-HOUR EXCEEDANCES
163 SITES
40-
30-
20-
10-
I I 1 1 1 1 1 1 1 1
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-12. National trend in the composite average of the estimated
number of exceedances of the 8-hour CO NAAQS, 1976 - 1985.
120
CO EMISSIONS. 10* METRIC TONS/YEAR
20
SOURCE CATEGORY
SOLD WASTE & MISC D FUEL
COMBUSTION
INDUSTRIAL PROCESSES m TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-13. National trend in emissions of carbon monoxide, 1976 - 1985,
1-11
-------
Figure 1-14. United States map of the highest second maximum nonoverl apping
8-hour average CO concentration by MSA, 1985.
1-12
-------
Nitrogen Dioxide (NO?) - Annual average NOg levels, measured at 108
sites, increased from 1976 to 1979, and decreased through 1985, except for
a slight increase in 1984 (Figure 1-15). The 1985 composite N02 average,
however, is 11 percent lower than the 1976 level indicating a downward
trend during the overall period. The trend in the estimated nationwide
emissions of nitrogen oxides is similar to the NO^ air quality trend.
Between 1976 and 1985, total nitrogen oxide emissions decreased by 1 percent,
and highway vehicle emissions, the source category likely impacting the
majority of N0£ monitoring sites, decreased by 4 percent (Figure 1-16).
Between 1984 and 1985, the N02 composite average decreased by 2 percent,
while the estimated emissions of nitrogen oxides increased by 2 percent.
This small year-to-year difference between the ambient levels and the
emissions percent change is likely not significant given the relatively
low ambient N02 levels. The most recent 1985 highest annual arithmetic
mean N0?_ concentration is plotted for the 89 largest MSA(s) (Figure 1-17).
Los Angeles, California is the only area in the country exceeding the air
quality standard of .053 ppm.
0.07
0.06-
0.05-
0.04-
0.03-
0.02
0.01-
0.00
CONCENTRATION, PPM
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-15. National boxplot trend in annual average N02 concentrations
1976 - 1985.
1-13
-------
30
NO. EMISSIONS, 10* METRIC TONS/YEAR
0
SOURCE CATEGORY
SOUD WASTE & MISC. Q FUEL COMBUSTION
INDUSTRIAL PROCESSES 721 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-16. National trend in emissions of nitrogen oxides, 1976 - 1985.
Figure 1-17.
United States map of the highest annual arithmetic mean
N02 concentration by MSA, 1985.
1-14
-------
Ozone (03) - Nationally, the composite average of the second highest
daily maximum 1-hour 03 values, recorded at 183 sites, decreased 19 percent
between 1976 and 1985 (Figure 1-18). Volatile organic compound (VOC) emis-
sions decreased 11 percent during the same period (Figure 1-19). Although
the 1985 composite average for the 163 trend sites is 19 percent lower than
the 1976 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 1-18 and 1-20 indicate data affected
by measurements taken prior to the calibration change. In the post
calibration period (1979 to 1985), 03 levels decreased 10 percent (Figure 1-18),
while VOC emissions decreased 12 percent. The estimated number of exceedances
of the 03 standard decreased 38 percent between 1979 and 1985. (Figure
1-20). The 03 trends in the 1980's show that the 1980 and 1983 values were
higher than those in 1981, 1982, 1984, and 1985. Previous trends reports
11,12 have discussed the likelihood that the higher 1983 levels were influenced
by meteorological conditions in that year that were more conducive to ozone
formation than conditions in adjacent years. While 1985 levels are similar
to 1984 levels, there was a slight improvement of 2 percent in the national
composite average between these 2 years. The most recent 1985 highest
second daily maximum 1-hour average 03 concentration is plotted for the 89
largest MSAs (Figure 1-21). Many of these areas did not meet the 0.12 ppm
standard in 1985. 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.
0.30
CONCENTRATION, PPM
0.25-
0.20-
0.15-
0.10
0.05-
0.00
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-18. National boxplot trend in the second highest daily maximum 1-hour
03 concentrations, 1976 - 1985.
1-15
-------
VOC EMISSIONS, 10* METRIC TONS/YEAR
SOURCE CATEGORY
SOUO WASTE ft MSC B INDUSTRIAL PROCESSES
FUEL COMBUSTION E23 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-19. National trend in emissions of volatile organic compounds,
1976 - 1985.
20
ESHMATED EXCEEDANCES
183 SITES
15
10-
I 1 1 1 1 1 1 1 I I
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-20. National trend in the composite average of the number of
daily exceedances of the 03 NAAQS in the 03 season, 1976 - 1985.
1-16
-------
Figure 1-21.
United States map of the highest second daily maximum 1-hour
average 03 concentration by MSA, 1985.
1-17
-------
Lead (Pb) - The composite maximum quarterly average of ambient Pb
levels, recorded at 53 urban sites, decreased 79 percent between 1976 and
1985 (Figure 1-22). Lead emissions declined 86 percent during the same
period (Figure 1-23). In order to increase the number of trend sites, the
1981 to 1985 time period was examined. A total of 241 trend sites (1981 to
1985) measured a 50 percent decline in Pb levels, corresponding to a 62
percent decrease in estimated Pb emissions. Between 1984 and 1985 ambient Pb
levels declined 32 percent, while Pb emissions are estimated to have declined
48 percent. This extremely large decrease in both air quality levels and
estimated emissions is largely due to the reduction of the lead content of
leaded gasoline. The most recent 1985 highest maximum quarterly average
lead concentration is plotted for the 89 largest MSAs (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^.
3.5
CONCENTRATION. UG^V
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-22. National boxplot trend in maximum quarterly average Pb
concentrations, 1976 - 1985.
1-18
-------
200
150
100-
LEAD EMESONS, 10s METRIC TONS/YEAR
CD FUEL
COMBUSTION
INDUSTRIAL PROCESSES tZ3 TRANSPORTATION
50-
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 1-23. National trend in lead emissions, 1976 - 1985.
Figure 1-24. United States map of the highest maximum quarterly average
lead concentration by MSA, 1985.
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-450/1-74-007. October 1974.
4. Monitoring and Air Quality Trends Report, 1974. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, 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
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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-450/4-84-029. April 1985.
12. National Air Quality and Emissions Trends Report, 1984. U. S.
Environmental Protection Agency, Office of Air Quality Planning and Standards.
Research Triangle Park, NC. Publication No. EPA-450/4-86-001. April 1986.
13. Federal Register. Vol. 43, June 22, 1978, pp 26971-26975.
14. Mauser, Thomas R., U. S. Environmental Protection Agency, memorandum
to Richard G. Rhoads, January 11, 1984.
15. Frank, N. H., "Nationwide Trends in Total Suspended Particulate
Matter and Associated Changes in the Measurement Process," Proceedings of
the APCA/ASQC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. October 1984.
1-21
-------
2. INTRODUCTION
This report focuses on both 10-year (1976-1985) and 5-year (1981-1985)
national air quality trends in each of the major pollutants as well as
Regional and, where appropriate, short-term air quality trends. The
national analyses are complemented in Section 5 with air quality trends
in selected urbanized areas for the period 1981 through 1985. In both
the national 5-year trend and the urbanized area trends, the shorter
time period was used to expand the number of sites available for trend
analysis. The areas that were examined are: Atlanta, GA; Baltimore, MD;
Boston, MA; Chicago, IL-Northwestern IN; Denver, CO; Detroit, MI; Houston,
TX; Los Angeles-Long Beach, CA; New York, NY-Northeastern NJ; Philadelphia,
PA-NJ; Phoenix, AZ; Portland, OR-WA; and St. Louis, MO-IL; Seattle, WA.
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. The ambient levels presented are averages of direct
measurements.
In addition to ambient air quality, trends are also presented for
annual nationwide emissions. These are estimates of the amount and kinds
of pollution being emitted by automobiles, factories, and other sources,
based upon the best available engineering calculations for a given time
period. The emission trends are taken from the EPA publication, National
Air Pollutant Emission Estimates, 1940-1985? and the reader is referred
to this publication for more detailed information. Except for lead
emissions which are reported in gigagrams (one thousand metric tons),
the emission data are reported as teragrams (one million metric tons)
emitted to the atmosphere per year.2
Air quality progress is measured by comparing the ambient air
pollution levels with the appropriate primary and secondary National
2-1
-------
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.
Section 4 of this report, "Air Quality Levels in Metropolitan
Statistical Areas (MSA'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
for the years 1983, 1984 and 1985 are presented for each of the pollutants
for all MSA's with populations exceeding 500,000.
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 report^, 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 population
oriented to special purpose monitoring. 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 1976 to 1985. 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
2-2
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TABLE 2-1. National Ambient Air Quality Standards (NAAQS)
POLLUTANT
TSP
CO
NO 2
03
Pb
PRIMARY (HEALTH RELATED)
AVERAGING TIME CONCENTRATION
Annual Geometric
Mean
24-hour
75 ug/m3
260 ug/m3
Annual Arithmetic (0.03 ppm)
80 ug/m3
Mean
24-hour
8-hour
1-hour
(0.14 ppm)
365 ug/nP
9 ppm
(10 mg/np)
35 ppm
(40 mg/m3)
Annual Arithmetic 0.053 ppm
Mean (100 ug/m3)
Maximum Daily 1-hour 0.12 pp
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.
2-3
-------
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, S02 and N02, 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 SOz and N02 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 criterion 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
hourly observations. This minor modification in the criteria resulted
in a 3 percent difference in the total number of S02 trend sites for
the 10 year trend evaluation of the annual arithmetic mean, 264 sites, as
opposed to 257 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.4 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.
2-4
-------
In calculating the national and urban area trend analyses, each site
was weighted equally. The report examines both 10-year (1976 to 1985)
and 5-year (1981 to 1985) trends. The 5-year trend period is introduced
to increase the number of trend sites available for analysis (Table
2-2). The trend from 1981 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 1981 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 - 4003 total trend sites
versus 2171 trends sites, respectively (Table 2-2). This 84 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, SOg,
CO, N02 and 03 and 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.5
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 NAAQS's.
Two types of standard-related statistics are used - peak statistics
(the second maximum 24-hour S02 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
arithmetic means for SCfc and NC£, 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.
2-5
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TABLE 2-2. Comparison of Number of Sites for 10-Year and 5-Year Air
Quality Trends
POLLUTANT
Total Suspended
Particulate (TSP)
NUMBER OF SITES
1976-85 TREND 1981-85 TREND
Sul fur Dioxide
Carbon Monoxide (CO)
Ozone (03)
Nitrogen Dioxide (N02)
Lead (Pb)
Total
1400
2094
264
163
183
108
53
547
355
523
243
241
2171
4003
% CHANGE IN THE
NUMBER OF TREND
SITES
1976-85 vs. 1981-85
+50%
+107%
+118%
+ 186%
+125%
+354%
+84%
2-6
-------
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2-7
-------
2.3 REFERENCES
1. Federal Register, Vol. 44, May 10, 1979, pp 27558-27604.
2. National Air Pollutant Emission Estimates, 1940-1985. U.S.
Environmental Protection Agency. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-86-018.
January 1987.
3. National Air Quality and Emission Trends Report, 1984. U.S.
Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-86-001.
April 1986.
4. Federal Register, Vol. 51, No. 53, March 19, 1986, pp 9597-9598.
5. 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 (1976-1985) and more recent
5-year (1981-1985) 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, boxpl otsl 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 boxpl ots 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 boxpl ots allow us to simultaneously compare
trends in the "cleaner", "typical" and "dirtier" sites.
3-1
-------
COMPOSITE MEAN OF AIR
POLLUTION STATISTIC
O
z
o
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
I
I
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
X-*-
I
05th PCRCENT1LC
'90th PERCEMTILE
'75th PERCENTIUE
'COMPOSITE AVERAGE
"MEDIAN
'25th PERCCNTILE
KHhPERCENTJLE
5th 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 1981 through 1985. The recent 5-year trend was introduced
in last year's report? to increase the number of sites available for
analysis. Emphasis is placed 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.
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 1983, 1984 and 1985 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 number 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, with the exception of
lead emissions which are reported as gigagrams (one thousand metric
tons).8 These are estimates of the amount and kinds of pollution
being generated by automobiles, factories, and other sources.
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/rr?) not to be exceeded, while the 24-hour standard
i s 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: 1976-85
The 10-year trend in average TSP levels, 1976 to 1985, is shown in
Figure 3-3 for 1400 sites geographically distributed throughout
the Nation and for the subset of 357 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 1976-1981, followed by a sizeable decrease between
1981 and 1982 and stable levels between 1982 and 1985. The NAMS
sites show higher composite levels than the sites for the Nation in
general, but appear to show a similar pattern. Both curves display
their lowest values in 1985. The composite average of TSP levels
measured at 1400 sites, distributed throughout the Nation, decreased 24
percent during the 1976 to 1985 time period and the NAMS decreased 23
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.9,10,11 f0r 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 1985,
however, the long-term (8-year) improvement in TSP is estimated to be
25 percent. This is based on 1178 sites which measured TSP in both
years.
3-5
-------
CONCENTRATION, UQ/U*
70 -
60-
50-
40-
30-
20-
10-
n
T T- T
* * . M I
^r
r*^r-i--rT:rsSvs.. :
^.-.^ -^«-^^ . -^^
"^^^
>
, ^T f
.^
NAMS SITES (357) ALL SITESjWOpl
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-3. National trend in the composite average of the geometric
mean total suspended participate at both NAMS and all sites
with 95 percent confidence intervals, 1976-1985.
110
CONCENTRATION. UQA4*
100-
90-
80-
70-
60-
50-
40-
30-
20-
10-
0
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-4. Boxpl ot comparisons of trends in annual geometric mean
total suspended particul ate concentrations at 1400 sites,
1976-1985.
3-6
-------
Figures 3-3 and 3-4 present two different displays of the air
quality trend at the 1400 TSP sites, nationally, over the 1976-1985 time
period. Both permit evaluation of the 1978 and 1985 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 1985 as well as the 1982
to 1984 levels are all significantly lower than those of 1978. Moreover
1985 is significantly lower than the 1982 to 1984 period. This difference is
discussed in more detail in Section 3.1.2. 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
1985.
Nationwide TSP emission trends show an overall decrease of 24
percent from 1976 to 1985. (See Table 3-1 and Figure 3-5). 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.8
3.1.2 Recent TSP Trends: 1981-85
Figure 3-6 presents a boxplot display of the 1981-1985 TSP data
base which represents 2094 monitoring sites. The large decrease
following 1981 is attributed to the change in monitoring filters
discussed in Section 3.1.1. A more practical analysis focuses on the
last few years. Figure 3-7 presents a bar chart of regional average
TSP. It shows a mixed pattern among the last 3 years, but decreases in
TSP were evident in most regions between 1984 and 1985. This supports
the decrease seen in national average levels of 4 percent and emission
reductions of 3 percent. Only three Regions (I, IX and X) displayed an
increase in average TSP. In four of the regions with decreases (III,
V, VI and VII), 1985 regional TSP levels were in fact at a 10-year
minimum.
Short term variability in air pollution is often due to meteorology.
Among all meteorological parameters, precipitation has been shown to
have had the greatest influence on particulate air quality. Rainfall
has the effect of reducing re-entrainment of particles and washing
particles out of the air. An examination of regional precipitation
patterns shows that the three regions with 1984-1985 TSP increases were
also the only regions which experienced more than a 20 percent decrease
in total precipitation, relative to normal.12 Reduced precipitation
probably contributed to air quality degradation in these areas. On the
other hand, Regions V and VI were the only regions experiencing increases
in precipitation and were among the group showing the largest particulate
air quality improvements. Correspondingly, it is likely that some of
these regional improvements were due to 1985 being a wetter year.
3-7
-------
Table 3-1. National Particulate Emission Estimates, 1976-1985.
(mill ion metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983
Source Category
Transportation
Fuel Combustion
Industrial
Processes
Sol id Waste
Mi scellaneous
Total
1984
1.3 1.4 1.4 1.4 1.3 1.3 1.3 1.3 1.3 1.3
2.5 2.5 2.5 2.4 2.4 2.3 2.2 2.0 2.1 2.1
4.4 3.9 3.9 3.8 3.2 3.0 2.5 2.3 2.7 2.7
0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.3 0.3 0.3
1.0 0.8 0.8 0.9 1.1 0.9 0.7 1.1 0.9 0.8
9.6 9.0 9.0 8.9 8.4 7.9 7.1 7.0 7.3 7.3
TSP EMISSIONS, K)* METRIC TONS/YEAR
10-
SOURCE CATEGORY
SOLID WASTE ft MBC E3 FUEL
COMBUSTION
Of INDUSTRIAL PROCESSES EZ3 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-5. National trend in particulate emissions, 1976-1985.
3-8
-------
110
100 -|
90-
80-
70-
60-
50-
40-
30-
20-
10-
0
CONCENTRATION,
1981
1982
1983
1984
1985
Figure 3-6. Boxpl ot comparisons of trends in annual mean total suspended
particul ate concentrations at 2094 sites, 1981-1985.
CONCENTRATION,
BU -
70-
60-
50-
40-
30-
20-
10 -
COMPOSFTE AVERAGE
ZB 1983 1984 £3 1985
a
9
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/
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/
/
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/
/
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/
/
f
/
/
/
EPA REGION I II II IV V VI VII VIII IX X
NO. OF SITES 111 122 240 335 584 203 124 116 173 86
Figure 3-7. Regional comparison of the 1983, 1984, 1985 composite average
of the geometric mean total suspended particul ate concentration.
3-9
-------
3.2 TRENDS IN SULFUR DIOXIDE
Ambient sulfur dioxide (SOz) 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 (80 ug/nr) , a
24-hour level of 0.14 ppm (365 ug/m3) and a 3-hour level of 0.50 ppm (1300
ug/m3). The first two standards are primary (heal th-rel ated) standards,
while the 3-hour NAAQS is a secondary ( we 1 fare- 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 SOp 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: 1976-85
The long-term trend in ambient S02, 1976 to 1985, is graphically
presented in Figures 3-8 to 3-10. 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 4 years. Nationally, the annual mean S02,
examined at 264 sites, decreased at a median rate of approximately
5 percent per year; this resulted in an overall change of about 42
percent (Figure 3-8). The subset of 94 NAMS recorded higher average
concentrations but declined at a slightly higher rate of 6 percent per year.
The annual second highest 24-hour values displayed a similar decline
between 1976 and 1985. Nationally, among 257 stations with adequate
trend data, the median rate of change was 6 percent per year with an
overall decline of 44 percent (Figure 3-9). The 89 NAMS exhibited a
similar rate of improvement for an overall change of 43 percent.
The estimated number of exceedances also showed declines for the NAMS
as well as the composite of all sites (Figure 3-10). The vast majority
of SQ2 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 95 percent from 1976 to 1985.
3-10
-------
0.035
CONCENTRATION, PPM
0.030
0.025-
0.020-
0.015-
0.010-
0.005-
0.000
NAAQS-
MAMS SITES (94) a AJJ^SITESJ[264l
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-8. National trend in the composite average of the annual average
sulfur dioxide concentration at both NAMS and all sites with
95 percent confidence intervals, 1976-1985.
0.16
CONCENTRATION, PPM
O.U
0.12-
0.10-
0.08-
0.06-
0.04-
0.02-
0.00
NAAQS
NAMS SITES (89) Q ALLSITK_(257
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-9. National trend in the composite average of the second-
highest 24-hour sul fur dioxide concentration at both NAMS
and all sites with 95 percent confidence intervals, 1976-
1985.
3-11
-------
2.5
ESTWATED EXCEEDANCES
2-
1 .5
1 -
0.5-
0
NAMS SITES (89) n ALL_SITES^257^
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985.
Figure 3-10. National trend in the composite average of the estimated
number of exceedances of the 24-hour sul fur dioxide NAAQS
at both NAMS and all sites with confidence intervals,
1976-1985.
-------
The statistical significance of these long-term trends is graphically
illustrated on Figures 3-8 to 3-10 with the 95 percent confidence
intervals included on these figures. For both annual averages and peak
24-hour values, the S02 levels in 1985 are the lowest in 10 years but are
statistically indistinguishable among the last 4 years. 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 (1976-1978).
The inter-site variability for annual mean and annual second highest
24-hour S02 concentrations is graphically displayed in Figures 3-11 and
3-12. These figures show that higher concentrations decreased more rapidly
and the concentration range among sites has also diminished from the 1970's
to the 1980's.
Nationally, sulfur oxide emissions decreased 21 percent from
1976 to 1985 (Figure 3-13 and Table 3-2), reflecting the installation
of flue gas desul furization 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 plants.8
The disparity between the 42 percent decrease in S02 air quality
and the 21 percent decrease in 502 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 264 trend sites used in the
analysis of average S02 levels, two-thirds 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.^ Comparable SO? trends
have also been demonstrated for monitors located in the vicinity of
nonferrous smelters which produce some of the highest SO;? concentrations
observed nationally.7 Smelter sources represent a majority of S02
emissions in the intermountain region of the western U.S.
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
3-13
-------
0.040
CONCENTRATION. PPM
0.035-
0.030
0.023-
0.020-
0.015-
0.010
0.005
0.000
NAAQS-
X- 1
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-11. Boxpl ot comparisons of trends in annual mean sulfur dioxide
concentrations at 264 sites, 1976-1985.
0.25
CONCENTRATION, PPM
0.20-
0.15-
o.io-
0.05-
0.00
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-12. Boxpl ot comparisons of trends in second highest 24-hour
average sulfur dioxide concentrations at 257 sites,
1976-1985.
3-14
-------
Table 3-2.
Source Category
Transportation
Fuel Combustion
Industrial
Processes
Sol id Waste
Mi scellaneous
Total
National Sulfur Oxide Emission Estimates, 1976-1985.
(million metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983
4.6
0.0
0.0
4.4
0.0
0.0
4.1
0.0
0.0
4.1
0.0
0.0
3.5
0.0
0.0
3.7
0.0
0.0
3.1
0.0
0.0
3.1
0.0
0.0
1984 198
0.7 0.8 0.8 0.9 0.9 0.9 0.8 0.8 0.8 0.8
20.9 21.1 19.5 19.5 18.7 17.8 17.3 16.7 17.4 17.0
3.1 2.9
0.0 0.0
0.0 0.0
26.2 26.3 24.4 24.5 23.2 22.4 21.3 20.5 21.3 20.7
30
SO. EMISSIONS, 106 METRIC TONS/YEAR
SOURCE CATEGORY
INDUSTRIAL HOCOSO OB FUO. COMIUST10N G3 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-13. National trend in sulfur oxide emissions, 1976-1985.
3-15
-------
of facilities. Fifty-three individual plants in 14 states account for
one-half of all power plant emissions.13 jn addition, the 200 highest
S02 emitters account for more than 85 percent of all S0£ power plant
emissions.13*14 These 200 plants account for 57 percent of all S02
emissions, nationally.
Another factor which may account for differences in S02 emissions and
ambient air quality is stack height. The height at which SOg is released
into the atmosphere has been increasing at industrial sources and power
plants.15»16 This 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.
3.2.2. Recent SO? Trends: 1981-85
Figure 3-14 presents short-term S02 trends for annual mean concen-
trations. The boxplot display for the 1981-1985 data, based on 547
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 $62 monitoring sites in areas with
medium to low concentration levels. The 5-year trend shown in Figure
3-14 shows a continued decline in S02 concentrations. Air quality
levels decreased 5 percent, corresponding to a 3 percent decrease in
emissions.
Regional changes in composite average $03 concentrations for the
last 3 years, 1983-1985 are shown in Figure 3-15. Most regions
decreased slightly between 1984 and 1985.
Some of the regions with the lowest average $03 also contain some
of the highest S02 concentrations recorded nationally. This phenomenon
which is due to S02 in the vicinity of nonferrous smelters, is evident
in Figure 3-16 which shows the 1985 intra-regional concentration distri-
butions. Region IX, for example, displays a low overall average concen-
tration as mentioned previously, but also has the highest peak concen-
tration levels in the Nation because of the Arizona smelters. Similarly,
large intra-regional variability in S02 concentrations is seen in
Regions VI,VIII and X because of monitors located in the vicinity of
smelters.
3-16
-------
0.040
CONCENTRATION, PPM
0.035-
0.030
0.025-
0.020
0.015-
0.010-
0.005
0.000
NAAQS
1981
1982
1983
1984
1985
Figure 3-14. Boxplot comparisons of trends in annual mean sulfur dioxide
concentrations at 547 sites, 1981-1985.
CONCENTRATION, PPM
EPA REGION I
NO. OF SITES 43
o.uie-
0.014-
0.012-
0.010-
0.008-
O.006-
0.004-
0.002-
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COMPOSITE AVERAGE
23 1983 1984 ED 1985
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47 71
IV V
73 T73
VI
38
VII
T7
VI
13
IX
59
X
13
Figure 3-15. Regional comparison of the 1983, 1984, 1985 composite
average of the annual average sulfur dioxide concentration
3-1;
-------
CONCENTRATION
0.040
0.035-
0.030-
0.025-
0.020-
0.015
0.010
0.005-
0.000
i
X
V
EPA REGION I II III IV V VI VII VIII IX X
NO. OF SITES 43 47 71 73 173 38 17 13 59 13
Figure 3-16. Regional boxpl ot comparisons of the annual average sulfur
dioxide concentrations in 1985.
3-18
-------
3.3 TRENDS IN CARBON MONOXIDE
Carbon monoxide (CO) is a colorless, odorless, and poisonous gas
produced by incomplete burning of carbon in fuels. Transportation
sources account for over two-thirds of the nationwide CO emissions with
the largest contribution due to highway motor vehicles. 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. This analysis concentrates on the
8-hour average results because the 8-hour standard is generally the
more restrictive limit.
Trends sites were selected using the procedures presented in
Section 2.1. This resulted in a data base of 163 sites for the 1976-85
10-year time period and a data base of 355 sites for the 1981-85 5-year
time period. There were 45 NAMS sites included in the 10-year data
base and 102 NAMS sites in the 5-year data base. This approximate two-
fold increase in the number of trend sites available for the more recent
time period is consistent with the improvement in size and stability of
current ambient CO monitoring programs.
3.3.1 Ten Year CO Trends: 1976-85
Figure 3-17 presents the national 1976-85 composite average
trend for the second highest non-overlapping 8-hour CO value for the
163 long-term trend sites and the subset of 45 NAMS sites. During this
10-year period, the national composite average decreased by 36 percent
with a 33 percent decrease for the NAMS subset. The median rate of
improvement has been about 5 percent per year but the 1984-85 decrease
was twice as large, about 10 percent. The confidence intervals in
Figure 3-17 emphasize this overall improvement in CO levels with the
concentrations in more recent years being significantly less than those
in the earlier years. Eighty-six percent of these trend sites showed
long-term improvement in the 1976-85 time period. The same trend is
presented in Figure 3-18 but the boxplot provides more information on
the distribution of ambient CO levels from year to year at the 163 long-
term trend sites. Although certain percentiles show year to year
fluctuations, the general long-term improvement is clear.
The 10-year trend in the composite average of the estimated number
of exceedances of the 8-hour CO NAAQS is shown in Figure 3-19. This
exceedance rate was adjusted to account for incomplete sampling. The
trend in exceedances shows long-term improvement but the rates are much
more pronounced than those for the second maximums. The composite
average for estimated exceedances improved 92 percent between 1976 and
1985 for the 163 long-term trend sites while the subset of 45 NAMS had
a similar decrease of 89 percent. These percentage improvements for
exceedances are typically much larger than those found for peak
concentrations, such as the annual second maximum. The percentage
change for the second maximums are more likely to reflect the percentage
change in emission levels.
3-19
-------
16
CONCENTRATION, PPM
14-
12-
10-
8-
6-
4-
2-
0
NAAQS
NAMS STTES (45) a ALL STTESJ163)
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-17. National trend in the composite average of the second highest
nonoverl apping 8-hour average carbon monoxide concentration
at both NAMS and all sites with 9b percent confidence
intervals, 1976-1985.
25
CONCENTRATION, PPM
20-
15-
10-
5-
-*
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-18. Boxpl ot comparisons of trends in second highest nonoverl apping
8-hour average carbon monoxide concentrations at 163 sites,
1976-1985.
3-20
-------
National carbon monoxide emission estimates for 1976 through 1985
are presented in Table 3-3 and depicted graphically in Figure 3-20.8
These estimates show a 21 percent decrease between 1976 and 1985.
Emissions from transportation sources, which accounted for about 70
percent of the total CO emissions in 1975, are estimated to have
decreased by 26 percent during this 10-year period. These reductions
in CO emissions occurred even though vehicle miles of travel are
estimated to have increased by 26 percent between 1976 and 1985. This
indicates that the Federal Motor Vehicle Control Program (FMVCP)
has been effective on the national scale with controls more than offsetting
the growth during this period. The difficulty with comparing these air
quality and emission changes is that the emission changes reflect
national totals while the ambient CO monitors are frequently located to
identify potential problems. Therefore, the mix of vehicles and the
change in vehicle miles of travel in the area around a typical CO
monitoring site may differ from the national averages.
3.3.2 Five-Year CO Trends: 1981-85
This section examines ambient CO trends for the 5-year time
period 1981-85. As discussed in section 2.1, this allows the use of a
larger data base, 355 sites versus 163, because the historical data
completeness criterion is restricted to the 1981-85 time period so that
newer monitoring sites can qualify for inclusion. Figure 3-21 displays
the 5-year ambient CO trend in terms of the second highest non-
overlapping 8-hour averages. The composite average showed 17 percent
improvement between 1981 and 1985 and the boxplot presentation indicates
that this type of improvement was seen generally across all levels.
Thirty-two percent of these sites had second high values above the
level of the 8-hour CO standard in 1981 compared to 18 percent in 1985.
The 1984-85 improvement is also clear with a 10 percent decrease in the
national composite between these 2 years. At over one-half of these
sites, the 1985 value was the lowest for the past 5 years while only 14
percent had their high in 1985.
As shown in Table 3-3, total CO emissions are estimated to have
decreased 8 percent between 1981 and 1985. The transportation category,
and the subset of highway vehicles, also decreased by 8 percent.
Between 1984 and 1985, total CO emissions decreased by 3 percent with
transportation sources decreasing by 2 percent. This suggests that
the 10 percent improvement in CO air quality between 1984 and 1985
may be influenced in part by other factors such as meteorological conditions
or localized control measures. The 1986 data should provide additional
information on the strength of this improvement.
3-21
-------
50
ESIBMIED fr-HOUR OCOIMNCCS
40-
30-
20-
10
NAMS SITES (45) a ALL SITES (165)
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-19. 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 95 percent
confidence intervals, 1976-1985.
3-22
-------
Table 3-3. National Carbon Monoxide Emission Estimates, 1976-1985.
(million metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983 1984
Source Category
Transportation
Fuel Combustion
Total
1985
64.1 61.0 60.3 55.9 52.6 51.6 48.1 48.3 48.4 47.5
4.7 5.1 5.8 6.6 7.3 7.5 8.0 7.9 8.1 8.1
Industrial
Processes
Solid Waste
Mi scellaneous
7.
2.
7.
1
7
1
7.3
2.6
5.8
7.1
2.5
5.7
7.1
2.3
6.5
6.3
2.2
7.6
5.9
2.1
6.4
4.4
2.0
4.9
4.4
1.9
7.7
4.8
1.9
6.3
4.6
2.0
5.3
85.8 81.8 81.4 78.3 76.0 73.4 67.4 70.3 69.6 67.5
120
CO EMISSIONS, 10* METRIC TONS/YEAR
100 H
80
SOURCE CATEGORY
SOLID WASTE & M6C E3 FUEL
COMBUSTION
B INDUSTRIAL PROCESSES E3 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-20. National trend in emissions of carbon monoxide, 1976-1985.
3-23
-------
25
CONCENTRATION, PPM
20-
15
10
0
""
NAAQS-
-X-
1981
1982
1983
1984
1985
Figure 3-21.
Boxpl ot comparisons of trends in second highest nonoverl apping
8-hour average carbon monoxide concentrations at 355 sites,
1981-1985.
CONCENTRATION, PPM
13-
12-
11 -
10-
9-
8-
7-
6-
5-
4-
3 -
2-
1 -
n -
COMPOSITE AVERAGE
ZB 1983 1984 D 1985
n
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EPA REGION
NO. OF SITES
I
U
26
III
41
IV
53
V
52
VI
26
VII
t7
VHI
16
IX
79
X
31
Figure 3-22.
Regional comparison of the 1983, 1984, 1985 composite average
of the second highest nonoverl apping 8-hour average carbon
monoxide concentration.
3-24
-------
Composite regional averages for 1983-85 are presented in Figure 3-22
for the second highest non-overlapping 8-hour averages. The improvement
between 1984 and 1985 was widespread with only the southwest and far-
west departing from this pattern. These regional graphs are primarily
intended to depict relative change during this time period rather than
typical levels in each region. 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. Therefore, this graph is not intended to be
indicative of regional differences in absolute concentration levels.
3-25
-------
3.4 TRENDS IN NITROGEN DIOXIDE
Nitrogen dioxide (NOg), a yellowish, brown gas, is present in
urban atmospheres through emissions from two major sources; transportation
and stationary fuel combustion. The major mechani sm for the formation
of N0£ in the atmosphere is the oxidation of the primary air pollutant,
nitric oxide. NO^ 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
108 sites for the 1976-85 ten-year period and 243 sites for the 1981-85
5-year data base. Eleven of the long-term trend sites are NAMS while 46
NAMS are included in the 1981-85 data base. The size of the long-term
data base has been decreasing each successive year as low concentration
sites are discontinued or as NOg bubblers are replaced with continuous
instruments. In this latter case, data from these two different methods
are not merged. Only 33 of the 108 long-term trend sites are N02 bubblers.
3.4.1 Ten-year NO? Trends: 1976-85
The composite average long-term trend for the nitrogen dioxide mean
concentration at the 108 trend sites, and the 11 NAMS sites, is shown in
Figure 3-23. Nationally, at all sites, annual average NO? levels increased
from 1976 to 1979, decreased through 1985, except for a slight increase
in 1984. The 1985 composite average N02 level is 11 percent lower than
the 1976 level, indicating a downward trend during this period. Of the 108
trends sites, only 11 are designated as NAMS. This is to be expected
because NO? does not present a significant air quality problem in most
areas at tnis time. Also, NAMS for N0p_ are only located in urban areas
with populations of 1,000,000 or greater. The composite averages of the
NAMS, which are located in eight large metropolitan areas, are higher
than those of all sites. Comparing 1985 data to the 1976 levels shows an
11 percent decrease in the composite average for all trends sites and a
14 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 10-year trends completeness criteria and the generally
low levels of recorded N02 annual mean concentrations, with respect to the
level of the N02 NAAQS.
3-26
-------
0.06
CONCENTRATION, PPM
0.05-
0.04-
0.03-
0.02-
0.01-
0.00
NAAQS-
NAMS SITES (11) DALLJ(TES£08)
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-23. National trend in the composite average of nitrogen
dioxide concentration at both NAMS and all sites with 95
percent confidence intervals, 1976-1985.
0.07
CONCENTRATION, PPM
0.06-
0.05-
0.04-
0.03
0.02-
0.01 -
.i~-. JNAAQS
JL
0.00
'A ' i 1
A
1
1976 1377 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-24. Boxpl ot comparisons of trends in annual mean nitrogen
dioxide concentrations at 108 sites, 1976-1985.
3-27
-------
In Figure 3-23, 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 historical trends criteria, there are significant differences
among the composite means of the 108 long-term trends sites. Although the
1984 and 1985 composite mean N02 levels are not significantly different
from one another, they are significantly less than the earlier years
1977 through 1980.
Long-term trends'in NC£ annual average concentrations are also displayed
in Figure 3-24 with the use of boxplots. The improvement in the composite
average between 1979 and 1985 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 1976 through 1978 and generally decreasing until 1984.
Between 1976 and 1985 total nitrogen oxide emissions decreased by 1
percent, but highway vehicle emissions, the source category likely impacting
the majority of urban NOz sites, decreased by 4 percent. Figure 3-25 shows
that the two primary source categories of nitrogen oxide emissions are
fuel combustion and transportation.
3.4.2 Five-year NO? Trends: 1981-85
Figure 3-26 uses the boxplot presentation to display recent trends
in nitrogen dioxide annual mean concentrations for the years 1981-85.
Focusing on the past five years, rather than the last ten years, more than
doubles the number of sites, from 108 to 243, available for the analysis.
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 composite average N02 level at the 243 trend sites decreased 5
percent between 1981 and 1985. During this same period, nitrogen oxide
emissions decreased by 1 percent. Between 1984 and 1985, the NOg composite
average decreased 2 percent, while nitrogen oxide emissions recorded a 2
percent increase. This small year-to-year difference between the ambient
and emissions percent change is likely not significant given the
relatively low ambient N02 levels.
Regional trends in the composite average N02 concentrations for the
years 1983-85 are displayed in Figure 3-27 using bar graphs. As indicated
in the figure, Regions I and IX recorded the highest composite averages
during the past 3 years. The pattern of the year-to-year changes is
mixed among the regions, however, with seven of the ten regions; showing
decreases between 1984 and 1985.
3-28
-------
Table 3-4.
Source Category
Transportation
Fuel Combustion
Industrial
Processes
Solid Waste
Mi scellaneous
Total
National Nitrogen Oxides Emission Estimates, 1976-1985.
(million metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983 1984
9.3 9.5 9.7 9.5 9.2 9.3
10.0 10.4 10.3 10.5 10.1 10.0
0.7
0.1
0.2
0.7
0.1
0.2
0.8
0.1
0.2
0.8
0.1
0.2
0.7
0.1
0.2
0.6
0.1
0.2
8.9
9.8
0.5
0.1
0.1
8.6 8.7 8.
9.6 10.2 10.
0.5
0.1
0.2
0.6 0.
0.1 0.
0.2 0.
20.3 21.0 21.1 21.0 20.3 20.3 19.5 19.1 19.7 20.
30
NCL EMISSIONS, 106 METRIC TONS/YEAR
25-
20-
15-
10-
5-
SOURCE CATEGORY
SOUD WASTE & MISC. E3 FUEL COMBUSTION
D INDUSTRIAL PROCESSES E3 TRANSPORTATION
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-25. National trend in nitrogen oxides emissions, 1976-1985.
3-29
-------
CONCENTRATION, PPM
o.u/ -
0.06-
0.05-
0.04-
0.03-
0.02-
0.01 -
n nr>_
1
ill:
*
||
ll
||
:: [:.U H
Iff
1981
1982
1983
1984
1985
Figure 3-26. Boxpl ot comparisons of trends in annual mean nitrogen
dioxide concentrations at 243 sites, 1981-1985.
CONCENTRATION, PPM
O.O4U-
0.035-
0.030-
0.025-
0.020-
0.015-
0.010-
0.005-
i
p
i
i
t
t
',
. !
; \
' \
: \
t i
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COMPOSITE AVERAGE
^1983 1984 01985
p
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+
t
EPA REGION I N M IV V VI VII VII DC X
NO. OF SITES 6 8431649359 16592
Figure 3-27. Regional comparison of 1983, 1984, 1985 composite average
of the annual mean nitrogen dioxide concentration.
3-30
-------
3.5 TRENDS IN OZONE
Ozone (03) continues to be a major concern for large urban areas
throughout the nation. Ozone is not emitted directly by specific
sources but is formed in the air by chemical reactions between nitrogen
oxides and volatile organic compounds (VOC's) which come from sources
such as gasoline vapors, chemical solvents, and combustion products of
various fuels. These reactions are stimulated by sunlight and
temperature so that peak ozone levels typically occur during the warmer
times of the year. The strong seasonal ity of ozone levels makes it
possible for areas to limit their ozone monitoring to 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. May through October is
typical but States in the south and southwest may monitor the entire
year. More northern states would have shorter ozone seasons such as
May through September for North Dakota. This analysis uses these
ozone seasons on a State by State basis to ensure that the data
completeness requirements are applied to the relevant portions of the
year.
The 03 NAAQS is defined in terms of the daily maximum, that is,
the highest hourly average 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 analysis.
The trends site selection process, discussed in Section 2.1,
resulted in 183 sites being selected for the 1976-85 period and 523
sites qualifying for the 1981-85 5-year data base. Sixty-five of the
long-term trends sites were NAMS while 196 NAMS sites were included in
the 5-year trends data base. In both cases, the 5-year data base is
about three times as large as the 10-year data base which reflects the
improvement in ambient ozone monitoring networks.
3.5.1. Ten-Year Ozone Trends: 1976-85
Figure 3-28 displays the 10-year composite average trend for
the second high day during the ozone season for the 183 trends sites
and the subset of 65 NAMS sites. While the 1985 composite average for
the 183 trend sites is 19 percent lower than the 1976 average, the
interpretation of this decrease is complicated by a calibration change
for ozone measurements that occurred in the 1978-79 time period.17
The stippled portion of Figure 3-31 indicates data affected by
measurements taken prior to the calibration change. This complication
has been discussed in previous reports.7,9 Part of the problem in
quantifying exactly how much of the 1978-79 decrease is due to the
calibration change is that not all agencies made the change at the same
time and for some States the data prior to 1979 already accounted for
3-31
-------
the calibration change. Therefore, trend comparisons involving data
prior to 1979 should be viewed with caution and an awareness of the
possible effect of the calibration change. Comparing the 1985 and 1979
levels shows a 10 percent decrease in the composite average for all
trend sites and also for the subset of MAMS.
The 10-year trend for the annual second highest daily maximum for
the 183 site data base is displayed in Figure 3-29 using the boxplot
presentation. Again, the pre-1979 values are affected by the calibration
change, but the patterns from 1979 on are reasonably consistent across
all percentiles. Perhaps the most obvious feature is that the 1979,
1980, and 1983 levels are similar and higher than those for 1981, 1982,
1984, and 1985. The 1985 levels are lower than those in the other
years. Figure 3-30 presents the 1976-85 trend for the composite average
number of ozone exceedances. This 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. The stippled area again indicates
the time period when comparisons would be affected by the calibration
change so that the 63 percent decrease between 1976 and 1985 incorporates
the effect of the calibration change. Between 1979 and 1985 the
expected number of exceedances decreased 38 percent for the 183 sites
with a 42 percent decrease for the subset of NAMS sites. As with the
second maximum, the 1985 values are the lowest with the 1979, 1980, and
1983 values being higher than those for 1981, 1982, 1984, and 1985.
Table 3-5 and Figure 3-31 display the 1976-85 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 11 percent between 1976 and 1985.8 As shown in Table
3-5, the annual total for each year of the 1980's is less than any of
the annual totals for the 1976-79 period. Between 1976 and 1985, VOC
emissions from transportation sources are estimated to have decreased
30 percent despite a 26 percent increase in vehicle miles of travel
during this same time period. While most of the source categories
showed long term improvement, the fuel combustion component increased.
Fuel combustion accounted for 5 percent of the total VOC emissions in
1976 compared to 12 percent in 1985.
3.5.2 Five-Year Ozone Trends: 1981-85
By restricting the analysis to the 1981-85 time period, it is
possible to expand the trends data base to include 523 sites. Figure
3-32 uses a boxplot presentation of the annual second maximum daily
value at these sites. Although the national composite average decreased
5 percent between 1981 and 1985, the more obvious feature of this graph
is that 1983 levels were much higher than those of the other four
years. Previous reports?,9 have discussed the likelihood that these higher
3-32
-------
0.18
CONCENTRATION, PPM
0.10-
0.08-
0.06-
0.04-
O.02-
0.00
NAMS SITES (65) CD
1 1 [i 1 1 1 1 1 1
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-28. 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, 1976-1985.
0.30
CONCENTRATION, PPM
0.25-
0.20-
0.15-
0.10-
0.05-
0.00
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-29. Boxpl ot comparisons of trends in annual second highest daily
maximum 1-hour ozone concentration at 183 sites, 1976-1985.
3-33
-------
20
NO. OF EXGEEDANCES
15-
10-
5-
NAMS SITES (65) a ALL_SITlS^183l_
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-30.
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, 1976-1985.
3-34
-------
Table 3-5. National Volatile Organic Compound Emission Estimates, 1976-1985.
(million metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983 1984
Source Category
198
Transportation
Fuel Combustion
Industrial
Processes
Non-Industrial
Organic Solvent
Use
Sol id Waste
Mi scellaneous
10.3 10.0
1.2 1.4
9.7 8.9 8.2 7.9 7.4 7.3 7.3 7.2
1.6 1.9 2.2 2.3 2.5 2.6 2.6 2.6
8.7 9.1 9.7 9.6 9.0 8.1 7.3 7.7 8.6 8.6
1.9 1.9
0.8 0.8
1.0 0.8
1.9
0.8
0.8
2.0
0.7
0.9
1.9
0.6
1.0
1.6
0.6
0.9
1.5
0.6
0.7
1.6
0.6
1.1
1.8 1.6
0.6 0.6
0.9 0.7
Total
24.0 23.9 24.5 24.1 22.8 21.5 20.0 20.8 21.8 21.3
35
VOC EMISSIONS, 10* METRIC TONS/YEAR
15
10-1
5
SOURCE CATEGORY
SOUD WASTE 4 MISC E3 INDUSTRIAL PROCESSES
B FUEL COMBUSTION E2 TRANSPORTATION
-_- :._= --=
us =
=; = _ ; "
:.r I ::- -":
SH *.»**!* X" 2" -
^1 = =;=_ j^_ ;==- _| --.
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-31. National trend in emissions of volatile organic compounds, 1976-1985.
3-35
-------
0.30
CONCENTRATION, PPM
0.25H
0.20H
0.15H
o.ioH
o.osH
o.oo
1981
1982
1983
1984
1985
Figure 3-32. Boxpl ot comparisons of trends in annual second highest
daily maximum 1-hour ozone concentrations at 523 sites,
1981-1985.
CONCENTRATION, PPM
o.zo-
0.16-
0.12-
0.08-
0.04-
a
E
DMPOSTE AVERAGE
a 1983 1984 Z3 1985
i
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EPA REGION I II HI
NO. OF SITES 23 27 72
IV V VI VH VI IX X
78 107 52 21 15 113 15
Figure 3-33. Regional comparison of the 1983, 1984, 1985 composite
average of the second-highest daily 1-hour ozone
concentrations.
3-36
-------
1983 levels were influenced by meteorological conditions in that year
that were more conducive to ozone formation than conditions in adjacent
years. While 1985 levels are similar to 1984, there was a slight
improvement of 2 percent in the national composite average between
these 2 years.
As shown in Table 3-5, total VOC emissions are estimated to have
decreased by only 1 percent between 1981 and 1985. Transportation
sources decreased by 9 percent during this period. Between 1984 and
1985 both total VOC emissions and the transportation component showed
a decrease of approximately 2 percent which is similar to the ambient
air quality improvement.
Figure 3-33 presents a regional comparison for 1983, 1984, and
1985 of the composite average second highest daily maximum 1-hour ozone
concentration. For nine of the ten EPA Regions, 1983 was the highest
of these 3 years. The only exception to this pattern was in Region X,
the northwest. The 1985 levels were also lower than those of 1984 for
most parts of the country.
3-37
-------
3.6 TRENDS IN LEAD
Lead (Pb) gasoline additives, non-ferrous smelters, and battery plants
are the most significant contributors to atmospheric Pb emissions.
Transportation sources in 1985 alone contribute about 73 percent of the annual
emissions, down from 87 percent in 1984. The reasons for this drop are
noted be! ow.
Prior to promulgation of the Pb standard in October 1978!,18 two air
pollution control programs were implemented by EPA that have resulted in
lower ambient Pb levels. First, regulations were issued in the early
1970's which required the Pb content of all gasoline to be gradually
reduced over a period of many years. Most recently the Pb content of
leaded gasoline pool was to be 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. In 1985 unleaded
gasoline sales accounted for 65 percent of the total gasoline market.
Additionally, Pb emissions from stationary sources have been substantially
reduced by control programs oriented toward attainment of the TSP and
Pb ambient standards. The overall effect of these three control programs
has been a major reduction in the amount of Pb in the ambient air.
3.6.1 Long-term Lead Trends: 1976-85
Previous trend analyses of ambient Pb data!9,20 were based almost
excl usively 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 Pb. The sites were
predominantly located in the central business districts of larger American
cities. In September 1981, ambient Pb monitoring regulations were
promulgated.21 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 1976 to 1985 time period. A year was included as
"valid" if at least 3 of the 4 quarterly averages were available. A
total of only 53 urban-oriented sites, representing nineteen states,
met the data completeness criteria. Only seven of these sites were NAMS
sites, thereby, making a NAMS trend determination tentative. Twenty-seven
of the trend sites were located in the States of Arizona, Pennsylvania
and Texas. A total of 241 sites satisfied a trend criteria for the
1981-85 period, which required 4 out of 5 years in the 1981 to 1985 time
period.
The mean of the composite maximum quarterly averages and their
respective 95 percent confidence intervals are shown in Figure 3-34 for
both the 53 urban sites and 7 NAMS sites (1976-1985). There was a 79
percent overall (1976-85) decrease for the 53 urban sites. The confidence
3-38
-------
2.2-
CONCENTRATION.
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-34. National trend in the composite average of the maximum
quarterly average lead concentration at 53 sites and
7 NAMS sites (1976-1985) with 95 percent confidence
intervals.
3.5
CONCENTRATION. UQ/U*
2.5-
2-
1.5
1 -
0.5-
0
I
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-35. Boxpl ot comparisons of trends in maximum quarterly average
lead concentrations at 53 sites, 1976-1985.
3-39
-------
intervals for these sites indicate that the 1976-79 averages are significantly
different from the 1980-85 averages. Moreover, the 1985 average is
statistically different from all averages prior to 1983. The 1985 average
percentage-wise shows a 32 percent decrease from 1984. This is the
largest percentage decrease for any two consecutive years except for
1979-80 when the decrease also was 30 percent. The reduction of Pb in
gasoline from 1.0 grams/gal Ion to 0.5 grams/gal Ion is probably the principal
reason for this drop together with the increasing sales of unleaded
gasoline. Because of the small number of NAMS sites (7) with 8 years of
data, the confidence intervals are wide. However, the 1984 and 1985
averages are still significantly different from averages in the 1976-79
time period. Figure 3-35 shows boxplot comparisons of the maximum quarterly
average Pb concentrations at the 53 urban oriented Pb trend sites (1976-85).
This figure like the previous one shows the dramatic improvement in
ambient Pb concentrations for the entire distribution of trend sites.
Like the composite average concentration since 1977, most of the percent!les
also show a monotonically decreasing pattern.
A slightly larger sample of 53 urban-oriented sites qualified as
trend sites for the 1976-85 time period as compared with 36 sites for the
1975-84 time period in last year's report.7 Because of the small number
of 1976-85 trend sites relative to the 1981-85 trend sites more importance
should be given to the 5-year (1981-85) trend.
The 1976-85 trends in total lead emissions based on information from
the National Emissions Data System8 is shown in Figure 3-36. Table 3-6
summarizes the Pb emissions data as well. The drop (1976-85) in Pb
emissions was 86 percent. This compares with a 79 percent decrease
(1976-85) in ambient Pb noted above. The drop in Pb consumption
and subsequent Pb emissions since 1976 was brought about because of the
increased use of unleaded gasoline in catalyst equipped cars and the
reduced Pb content in leaded gasoline as noted above. The results of
these reductions in 1985 amounted to a 48 percent reduction nationwide in
total Pb emissions from 1984 levels. In 1985 unleaded gasoline sales
represented 65 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: 1981-85
Ambient Pb trends were also studied over the shorter time period
1981-85 (Figure 3-37). A total of 241 urban sites from 43 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 50
percent in average Pb concentrations over this time period. This corresponds
to reductions in Pb emissions of 62 percent. Even this larger group of
sites was disproportionately weighted by sites in California and Pennsylvania.
These states accounted for 35 percent of the 241 sites represented.
3-40
-------
Table 3.6. National Lead Emission Estimates, 1976-1985.
(thousand metric tons/year)
1976 1977 1978 1979 1980 1981 1982 1983
Source Category
1984
Transportation
Fuel Combustion
Industrial
Processes
Sol id Waste
Total
132.4 124.2 112.4 94.6 59.4 46.4 46.9 40.7 34.7 15.4
8.3 7.2 6.1 4.9 3.9 2.8 1.7 0.6 0.5 0.5
8.1 5.7 5.4 5.2 3.6 3.0 2.7 2.4 2.3 2.3
4.3 4.1 4.0 4.0 3.7 3.7 3.1 2.6 2.6 2.8
153.1 141.2 127.9 108.7 70.6 55.9 54.4 46.3 40.1 21.0
200
150-
100-
LEAD EMISSIONS, 103 METRIC TONS/YEAR
SOURCE CATEGORY
SOLID WASTE
FUEL
COMBUSTION
INDUSTRIAL PROCESSES EZJ TRANSPORTATION
50-
1976 1977 1978 1979 1980 1981 1982 1983 1984 1985
Figure 3-36. National trend in lead emissions, 1976-1985.
3-41
-------
3.5
CONCENTRATION, UQA43
3-
2.5-
2-
1.5
1 -
0.5-
0
NAAQS-
"K r***-,
-Ml
1981
1982 1983 1984 1985
Figure 3-37. Boxpl ot comparisons of trends in maximum quarterly average
lead concentrations at 241 sites, 1976-1985.
3-42
-------
Figure 3-38 shows 1983, 84 and 85 composite average Pb concentrations
by EPA region. The number of sites vary dramatically from 1 site in
Region VIII to 68 sites in Region IX. Only in the case of Regions III,
IV, V, VI, and IX can reasonable comparisons be made, since each region
has at least 19 sites. The 1983 and 1984 levels are fairly comparable
between these five regions with slightly higher Pb averages in Regions IV
and VI followed by Region V, Region IX and lower levels in Region III.
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 all regions show the
expected improvement in Pb concentrations over the 1983-85 time period.
For the eight 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, and Region II where the 1984 average is slightly
higher than in 1983.
1.8
CONCENTRATION, UQ/U*
1.6-
1.4-
1.2-
1 -
0.8-
0.6-
0.4-
0.2-
COMPOSTTE AVERAGE
eza «83 1984 a was
\
EPA REGION I II III IV V VI VII VI IX X
NO. OF SITES fl 114927391913 1683
Figure 3-38.
Regional comparison of the 1983, 1984, 1985 composite
average of the maximum quarterly average lead
concentration.
3-43
-------
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," Transactions
of the APCA/ASQC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. 1985.
7. National Air Quality and Emissions Trends Report, 1984. U. S.
Environmental Protection Agency, Office of Air Quality Planning" and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-86-001.
April 1986.
8. National Air Pollutant Emission Estimates, 1940-1985. U. S.
Environmental Protection Agency. Office of Air Quality Planning and
Standards, Research Triangle Park, NC. Publication No. EPA 450/4-86-018.
January 1987.
9. 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.
10. 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.
11. Hauser, R. T., U. S. Environmental Protection Agency, "Impact
of Filter Change on TSP Trends," memorandum to R. G. Rhoads, January 11, 1984.
12. 1985 Update to Analysis of Precipitation Variables for the
Contiguous United States, 1981 to 1984. PEI Associates, Inc., Durham,
NC. Report prepared for Neil H. Frank, U. S. Environmental Protection
Agency, Contract No. 68-02-4335. November 1986.
3-44
-------
13. National Acid Precipitation Assessment Program (NAPAP), 1980 NAPAP
Data Base, Version 3.0. September 1984.
14. 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.
15. Koerber, W. M., "Trends in S02 Emissions and Associated
Release Height for Ohio River Valley Power Plants," presented at the
75th Annual Meeting of the Air Pollution Control Association, New
Orleans, LA. June 1982.
16. Bergesen, C. Utility Data Institute, Inc., letter to F. William
Brownell, Esq., Hunter and Williams, February 21, 1985.
17. Federal Register. Vol. 43, June 22, 1978, pp. 26971-26975.
18. Federal Register, Vol. 43, October 5, 1978, pp. 46246-46277.
19. 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.
20. W. Hunt, "Experimental Design in Air Quality Management," Andrews
Memorial Technical Supplement, American Society for Quality Control, 1984.
21. Federal Register, Vol. 46, September 3, 1981, pp 44159-44172.
3-45
-------
4. AIR QUALITY LEVELS IN METROPOLITAN STATISTICAL AREAS
The Tables In this section summarize air quality levels by
Metropolitan Statistical Area (MSA) for MSA's with 1984 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 4-1) were exceeded by measured air quality in 1985
(Figure 4-1). Clearly, 03 is the most pervasive air pollution problem in 1985
in the United States with an estimated 76.4 million people living in counties
which exceeded the 03 standard. TSP follows with 47.8 million people,
CO with 39.6 million people, N0£ with 7.5 million people, lead with 4.5
million people and S02 with 2.2 million people.
In the MSA 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 MSA's
and from year-to-year. The higher air quality levels measured in the MSA
are summarized for the years 1983, 1984 and 1985.
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
MSA(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 MSA summaries, the air quality levels reported are
the highest levels measured within the MSA(s). All available sites in an
MSA are used in these summaries. In the case of 05, the problem as stated
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
second highest 24-hour average
second highest nonoverlapping
8-hour average
PRIMARY NAAQS
75 ug/m3
0.03 ppm
0.14 ppm
9 ppm
Nitrogen Dioxide
Ozone
Lead
annual arithmetic mean
second highest daily maximum
1-hour average
maximum quarterly average
ug/m3 = micrograms per cubic meter
ppm = parts per million
TSP
SO.
40 50
milfons of parsons
i
60
r
70
80 90
0.053 ppm
0.12 ppm
1.5 ug/m3
Figure 4-1. Number of persons living in counties with air quality levels
above the primary national ambient air quality standards in
1985 (based on 1980 population data).
4-2
-------
earlier is pervasive and the high values associated with the pollutant
can reflect a large part of the MSA. However, in many cases peak ozone
concentrations occur downwind of major urban areas, e.g. peak ozone levels
attributed to the Chicago metropolitan area are recorded in and near Racine,
Wisconsin. In contrast, the high CO values are generally highly localized
and reflect downtown areas with heavy traffic. The scale of measurement
for the pollutants - TSP, S02 and NOj? - fall somewhere in between. Finally,
while lead measurements generally reflect lead concentrations near roadways
in the MSA, if the monitor is located near a point source of lead emissions it
can produce readings substantially higher. Such is the case in several
MSAs. If the lead monitor is located near a point 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 MSA has three ozone monitors in 1985 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 MSA for 1985.
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 MSA COMPARISONS
In each of the following MSA air quality summaries, the MSA's are
grouped according to population starting with the largest MSA - New York,
NY-NJ and continuing to the smallest MSA with a population in excess of
500,000, New Haven-Meriden, Connecticut. The population groupings and the
number of MSA's contained within each are as follows: 17 MSA's have
populations in excess of 2 million, 27 MSA's have populations between 1
and 2 million and 45 MSA's have populations between 0.5 and 1 million.
The population statistics are based on the 1984 Metropolitan Statistical
Areas estimates.2
Air quality maps of the United States are introduced to show at a
glance how air quality varies among the 89 MSA's. Figures 4-2 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 1985, 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:
*A chemical composite measurement can be either a measurement for an
entire month or an entire quarter.
4-3
-------
Figure 4-2. United States Map of the Highest Annual Geometric Mean
Suspended Particulate Concentration by MSA. The map for particulate matter
displays the maximum annual geometric mean TSP concentration in 1985 for
large metropolitan areas. 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/m3 can be
found throughout the Nation.
Table 4-2. Highest Annual Geometric Mean Suspended Parti cul ate
Concentration by MSA, 1983-85.
Figure 4-3. United States Map of the Highest Annual Arithmetic Mean
Sulfur Dioxide Concentration by MSA, 1985. The map for sulfur dioxide
shows maximum annual mean concentrations in 1985. Among these large
metropolitan areas, the higher concentrations are found in the heavily
populated Midwest and Northeast. The peak SC>2 mean concentration occurs in
Pittsburgh, PA at an individual site near a large steel complex, however,
all urban areas have ambient air quality concentrations lower than the
current annual standard of 80 ug/m3 (.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 MSA, 1983-85.
Figure 4-4. United States Map of the Highest Second Maximum 24-hour
Average Sulfur Dioxide Concentration by MSA, 1985. The map for sulfur
dioxide shows the highest second highest maximum 24-hour average sulfur
dioxide concentration by MSA in 1985. The highest concentration is found
in the Syracuse, NY MSA at a large chemical plant located in Solvay, NY.
The second highest concentrations occur in Pittsburgh, PA at an individual
site near a large steel company. Both concentrations exceed the level of
the short-term standard. All other urban areas have Icwer ambient concentra-
tions below the 24-hour NAAQS of 0.14 parts per million.
Table 4-4. Highest Second Maximum 24-hour Average Sulfur Dioxide
Concentration by MSA, 1983-85.
Figure 4-5. United States Map of the Highest Second Maximum Nonoverlapping
8-hour Average Carbon Monoxide Concentration by MSA, 1985. The map for
carbon monoxide shows peak metropolitan concentrations in terms of the
second highest annual 8-hour value recorded in 1985. 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.
Table 4-5. Highest Second Maximum Nonoverlapping 8-hour Average Carbon
Monoxide Concentration by MSA, 1983-85.
4-4
-------
Figure 4-6. United States Map of the Highest Annual Arithmetic Mean
Nitrogen Dioxide Concentration by MSA, 1985. The map for nitrogen dioxide
displays the maximum annual mean measured in the Nation's largest metropolitan
areas during 1985. Los Angeles, California is the only area in the country
exceeding the air quality standard of .053 ppm.
Table 4-6. Highest Annual Arithmetic Mean Nitrogen Dioxide Concentration
by MSA, 1983-85.
Figure 4-7. United States Map of the Highest Second Daily Maximum
1-hour Average Ozone Concentrations by MSA, 1985. The ozone map shows the
second highest daily maximum concentration in the 89 largest metropolitan
areas. As shown, slightly over half of these areas did not meet the 0.12
ppm standard in 1985. 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 Concentratio
by MSA, 1983-85.
Figure 4-8. United States Map of the Highest Maximum Quarterly Average
Lead Concentration by MSA, 1985. 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/mX
Table 4-8. Highest Maximum Quarterly Average Lead Concentration by MSA,
1983-85.
The air quality summaries follow:
4.3 REFERENCES
1. Federal Register, Vol. 51, No. 53, March 19, 1986.
2. Statistical Abstract of the United States, 1986, U. S. Department
of Commerce, U. S. Bureau of the Census, Appendix II.
4-5
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5. TRENDS ANALYSES FOR 14 URBANIZED AREAS
This chapter presents trends in ambient air quality for the period
1981 - 1985 in 14 urbanized areas. The urbanized areas included in these
analyses are Atlanta, GA; Baltimore, MD; Boston, MA; Chicago, IL-Northwestern
IN; Denver, CO; Detroit, MI; Houston, TX; Los Angeles-Long Beach, CA; New
York, NY-Northeastern NO; Philadelphia, PA-NJ; Phoenix, AZ; Portland,
OR-WA; Seattle, 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, $03, CO, NO?, 03, and Pb. The urbanized areas were grouped
into five broad geographic areas: East, Midwest, South, Southwest, and North-
west. Composite averages were then calculated for each pollutant and
compared to the national averages.
The air quality data used for the trend statistics in this section were
obtained from the EPA National Aerometric Data Bank (NADB). Additionally,
limited data were taken from State annual reports. The monitoring sites used
for the trends analyses were required to satisfy the historical continuity
criteria of 4 out of 5 years of data in the period 1981 to 1985 except for
lead which required 1 valid quarter per year. Furthermore, 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 focus on the period 1981 through
1985 which complements the 5-year national trends analyses in Section 3.
The national trends analyses also include a 10-year trend (1976 to 1985).
Although some of the 14 urbanized areas had sufficient data to prepare
area trends for the 10-year period (1976 to 1985), several of the urbanized
areas did not have sufficient data to meet the 8 of 10-year data completeness
criteria. Therefore, only the 5-year trend is presented.
The air quality trends in this chapter are based on monitoring sites
located within the boundaries of the urbanized areas (except for 03) as
described in the 1980 Census of Population Report prepared hy the U.S.
Bureau of Census.1 The report defines 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 analyses.
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 1981-1985 and which were used in the trends analyses.
5-1
-------
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 analyses. For
1981-1985, the maximum and minimum values as well as the composite average
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 trends analyses for the 14 cities. It should
also be noted on the TSP trends plots for all cities, except Houston, that
the composite averages for 1981-1982 are connected by dotted lines. As
previously explained in Section 3.1.1, EPA has found that TSP data col-
lected in 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 sources, and meteorological characteristics
also need to be taken into consideration.
5-2
-------
(HIGHEST AIR QUALITY STATISTIC AMONG TREND SITES
'COMPOSITE 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 0.03 ppm
(80 ug/m3)
Carbon Monoxide second highest nonoverlapping 9 ppm
8-hour average (10 mg/m3)
Nitrogen Dioxide annual arithmetic mean 0.053 ppm
(100 ug/m3)
Ozone second highest daily maximum 0.12 ppm
1-hour average (235 ug/m3)
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
-------
5.1 BOSTON. MASSACHUSETTS URBANIZED AREA
Boston 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 a>l of Suffolk County and the greater portion of Norfolk County
plus portions of Plymouth, Middlesex, Essex, and Worcester Counties. The
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, and the trends graphs are displayed in Figure
5-4.
5-4
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5-7
-------
5.2 NEW YORK. NEW YORK-NORTHEASTERN NEW JERSEY URBANIZED AREA
New York 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 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 making it the leading manufacturing area in the United
States. Its 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.
New York 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 trends graphs
for the pollutants are shown in Figure 5-7 and depict the trends for 1981-
1985.
5-8
-------
e TSP site used in trend analysis
A Pb site used in trend analysis
Q SO2 site used in trend analysis
° TSP, Pb, and SO2 site used in trend analysis
Figure 5-5. Location of TSP, Pb, and 502 Monitoring Sites in New York, NY - NJ 1981 -1985
5-9
-------
Urbanized Area
City Area
03 cite used in trend analysis
A NC>2 *ite used in trend analysis
n CO site used in trend analysis
0 03. NOj. and CO site used in trend analysis
Figure 5-6. Location of 03, NC>2, and CO Monitoring Sites in New York, NY - NJ 1981-1985
5-10
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5.3 BALTIMORE, MARYLAND URBANIZED AREA
The Baltimore, MD urbanized area is the 14th largest in the United
States and had a 1980 population of 1,755,477. The area extends approxi-
mately 40 miles north to south and 32 miles east to west and includes 523
square miles. The urbanized area is comprised of Baltimore independent
city, and parts of Anne Arundel, Baltimore, Harford, and Howard counties.
Baltimore is one of the busiest seaports in the United States with
access to the sea through both the Chesapeake Bay and the Chesapeake and
Delaware Canal. It is located farther west than other seaports in the
Northeast and because of the economics of lower transportation costs,
Baltimore is one of the principal transportation routes between the East
Coast and the Midwest. Its major industries are shipbuilding, steel produc-
tion, chemical and fertilizer production, copper refining, sugar refining,
transportation, and production of aluminum, electronic equipment, and
numerous other small industrial products.
The area is near the average path of the low pressure systems which
move across the country, and cause frequent changes in wind direction which
contribute to the variable character of the weather. Mountains to the west
and the bay and ocean to the east produce a net effect of more equable
climate compared with other continental locations farther inland at the
same latitude. The rainfall distribution throughout the year is rather
uniform and averages about 43 inches per year.
Figures 5-8 and 5-9 show the locations of the monitoring sites used
in the trends analyses, and Figure 5-10 shows the trends graphs for the
pollutants.
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5.4 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 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.
The prevailing winds of the area are from the southwest in the summer
and from the northwest during the winter. Maritime air and the proximity
to the Delaware River contribute to high humidity and temperatures during
the summer months. The average rainfall is around 42 inches per year.
Figures 5-11 and 5-12 show the locations of the monitoring sites used
in the trends analyses, and Figure 5-13 depicts the trends graphs for the
pollutants.
5-16
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5.5 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 is the most
populous between Washington, D.C. 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 majority 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 between 1970 and 1980.
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 trends graphs are
provided in Figures 5-14 and 5-15. The trends graphs are shown in Figure
5-16.
5-20
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5.6 CHICAGO, ILLINOIS-NORTHWESTERN INDIANA URBANIZED AREA
The Chicago urbanized area covers approximately 1300 square miles and
includes 6,77Q,000 people. It is the third largest area in the nation in
terms of popufation with approximately 75 percent of the population living
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 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 terns 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 5-17 and 5-18 show the locations of the monitors used in the
trends analyses and Figure 5-19 shows the trends for all the pollutants in
the urbanized area.
5-24
-------
Urbanized Area
City Area
TSP site used in trend analysis
A Pb site used in trend analysis
D SO2 site used in trend analysis
0 TSP. Pb, and SO2 site used in trend analysts
ILLINOIS INDIANA
Figure 5-17. Location of TSP, Pb, andSO2 Monitoring Sites in Chicago, IL - IN 1981-1985
5-25
-------
Urbanized Area
City Area
03 site used in trend analysis
A NC>2 she used in trend analysis
D CO site used in trend analysis
° 03. NO2. and CO site used in trend analysis
ILLINOIS INDIANA
Figure 5-18. Location of 03, NO2, and CO Monitoring Sites in Chicago, IL - IN 1981 -1985
5-26
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5.7 DETROIT. MICHIGAN URBANIZED AREA
The Detroit urbanized area is the fifth largest in the United States
with a 1980 population of 3,809,327. The urbanized area includes Macomb,
Monroe, Oakland, and Wayne Counties with a total land area of approximately
870 square miles. Slightly less than 60 percent of the urban area population
lives in Wayne with the remainder about equally divided among Macomb and
Oakland Counties.
Economically, Detroit is a major center for the manufacturing of
automobiles, trucks, and other heavy equipment. As such it has developed iron
and steel facilities as well as other manufacturing to support the principal
industries. Because of Detroit's location between Lake Huron and Lake Erie
and its manufactured goods, it has become a major seaport in foreign trade.
Detroit is located in a relatively flat plain between Lake Huron and
Lake Erie which serves to moderate the predominately continental climate
with relatively warm summers and cold winters. Annual precipitation is
approximately 31 inches per year.
Figures 5-20 and 5-21 show the locations of the monitors used in the
trends analyses and Figure 5-22 shows the trends for all the pollutants in
the urbanized area.
5-28
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5-31
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5.8 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 5-23 shows the location of the TSP, Pb, and S02 sites used in
the trends analyses. Figure 5-24 shows the location of the 03, N02, and CO
sites used in the trends analyses with Figure 5-25 showing the trends of
the six pollutants during the study period.
5-32
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5-35
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5.9 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.
The urbanized area is divided by the Mississippi River, the boundary
between Missouri and Illinois. The Missouri River branches from the
Mississippi just north of the urbanized area and further subdivides the
urbanized area's northwest section. The area is centrally located with
commerce and the distribution of goods playing an important part in the
area's economy. 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 5-26 shows the location of the TSP, Pb, and S02 sites used in
the trends analyses with Figure 5-27 showing the location of the 03, N02,
and CO sites used in the trends analyses. Figure 5-28 depicts the trends
of the six pollutants during the study period.
5-36
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5-39
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5.10 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 with the Rocky Mountains just to its west.
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 5-29 and 5-30 show the locations of the monitors used in the
trends analyses, and Figure 5-31 show the trends graphs for the pollutants.
5-40
-------
5-41
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5-42
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5.11 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 area has
a population tff 9,479,436 according to the 1980 census 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.
Figures 5-32 and 5-33 show the location of the monitors used in the
trends analyses. Figure 5-34 shows the trends of the six pollutants during
the study period.
5-44
-------
5-45
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5-46
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5-47
-------
5.12 PHOENIX, ARIZONA URBANIZED AREA
The Phoenix urbanized area is one of the fastest growing major
urbanized areas in the country. The population increased by 65 percent
between the 1970 and 1980 census from 863,357 to 1,409,442. The urbanized
area extends 51 miles east to west and 32 miles north to south. The city
of Phoenix itself has a population of 789,704.
The Phoenix urbanized area is in the Sunbelt and has moderate to warm
winters and hot summers. The "Valley of the Sun" as the area is called
averages sunshine 86 percent of all the possible sunshine hours with only
7 inches of rain per year. Mountainous terrain is located to the north,
east and south of Phoenix. The differential cooling of the desert and the
mountains coupled with a nightime drainage wind flow pattern causes pollutants
to be transported away from Phoenix during the day only to return later
during the night.
The "Valley of the Sun" is primarily a tourist area with approximately
6 million visitors annually. Accordingly, the economy is primarily
commercial and service oriented. Although tourism is high, among the 75
largest metropolitan areas, Phoenix has the smallest number of miles of
freeways.
Figures 5-35 and 5-36 show the locations of the monitors used in the
trends analyses and Figure 5-37 illustrates the trends for all the pollutants
in the urbanized area.
5-48
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5-51
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5.13 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 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 monitoring sites used in the trends analyses
are shown in Figures 5-38 and 5-39. The trends graphs for all pollutants
are shown in Figure 5-40.
5-52
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5-53
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5.14 SEATTLE-EVERETT, WASHINGTON URBANIZED AREA
The Seattle-Everett urbanized area, which includes Seattle, Everett,
Bellevue, and. other smaller towns, ranks 20th nationally in population
size with a 1980 population of 1,391,535. Tacoma, while adjacent to
Seattle, is a separate urbanized area and is not included. The area covers
approximately 410 square miles and most of the population (approximately 85
percent) live in King county with the remainder in Snohomish county.
Seattle's location on the side of the Puget Sound with a good harbor
and ready access to the Pacific ocean made the city an ideal location for
commerce to-develop in the timber trades. Based on the early timber trade,
Seattle has grown to be a major port city in foreign trade, leading to
growth in manufactured products and development of other transportation
facilities.
Seattle is located inland from the Pacific Ocean between 100 to 150
miles and surrounded on three sides by the Cascade and Olympic mountain
ranges which moderate the Pacific maritime and continental climates. The
sheltering from the climates to the east and west of the mountain ranges
provide a rather mild winter and summer. Annual precipitation is approxi-
mately 34 inches, most of which falls during the period between October and
March.
Figures 5-41 and 5-42 show the locations of the monitors used in the
trends analyses and Figure 5-43 depicts the trends for all the pollutants
in the urbanized area.
5-56
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KITSAP
CO
SNOHOMISH CO
TP SITE USED IN TREND ANALYSIS
A Pb SITE USED IN TREND ANALYSIS
D SO2 SITE USED IN TREND ANALYSIS
O TSP Pb, and SO2 SITE USED IN TREND ANALYSIS
Figure5-41 Location of TSP Pb. and SC>2 Monitoring Sites in Seattle WA 1981 1985
5-57
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KITSAP
CO
O3 SITE USED IN TREND ANALYSIS
ANO2 SITE USED IN TREND ANALYSIS
DCO SITE USED IN TREND ANALYSIS
OO3. N02. and CO SITE USED IN TREND ANALYSIS
PIERCE CO
I J 4 MILES
13 MILES I \
Figure 5-42 Location of 03, NC>2. and CO Monitoring Sites in Seattle WA 1981-1985
5-58
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5-59
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5.15 AIR QUALITY TRENDS FOR FIVE GEOGRAPHICAL AREAS
The previous subsections included year to year individual urbanized
area 1981 to 1985 trends for the six criteria pollutants. Table 5-2 was
developed from these trends and presents a pollutant specific summary of
the overall change in concentration levels for each of the 14 urbanized
areas. These 14 areas were grouped according to five arbitrarily arranged
geographic areas: East, Midwest, South, Southwest, and Northwest. The
breakdown by urbanized area is as follows:
East - Boston, New York, Baltimore, Philadelphia
Midwest - Chicago, Detroit, St. Louis
South - Atlanta, Houston
Southwest - Denver, Los Angeles, Phoenix
Northwest - Portland, Seattle
Composite geographic area averages of the overall 5-year change in
quality concentrations were then prepared and compared to the national
averages. The following discussion addresses these findings.
air
Table 5-2. Percent Change In Air Quality Trend Statistics 1981 To 1985
East
Midwest
South
Southwest
Northwest
National
Boston
New York
Philadelphia
Baltimore
Detroit
Chicago
St. Louis
Atlanta
Houston
Denver
Phoenix
Los Angeles
Portland
Seattle
TSP
-18
-15
-25
-27
+ 8
+ 2
Pb
-49
-60
-56
-54*
-45*
-76
SO?
-15
CO
-17
-27
-18
+14
-24
-35
-24
0
-10
-26
-16
NO?
- 5
-16*
-23
- 9
°a
- 3
- 6
- 9
-19
-13
-54*
-64*
+ 6
-53
-26
-16
-21
-26
-23
-18
-29
-20
0
+ 1
- 2
+ 9
+33
- 8
- 5
- 5
-24
+ 4
+ 3
-17
-33
-10
-18
-15
-63
-66
-42
-63
-65
-
+16
-31
-41
-24
-33
-16
-13
-32
- 8
-
-22
+ 3
_
-14
- 4
- 3
-12
- 6
0
-18
- 6
-13
Weighted
Average**
-17
-50
-15
-20
*Extrapolated 5-year trend based on 4 years of data.
**Weighted by number of monitors in each city for comparison
to national average.
-12
- 4
5-60
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5.15.1 TSP TRENDS
Four of the five areas are compatible with the 18 percent national
decrease in TSP, with the East and the Southwest averaging 12 percent and
14 percent decreases, respectively. On the other hand, the Midwest and the
South exceeded the national percentage decrease with values of 22 percent
and 25 percent, respectively. The Northwest Region had increases in TSP of
2 percent in Seattle and 8 percent in Portland over the same 5-year period.
All of the overall increases occurred because of higher TSP levels in 1985.
The winter of 1985 was the coldest on record in the Pacific Northwest with
a 17 percent increase in heating degree days over 1984. Also 1985 was the
dryest year in a century with a 35 percent decrease over 1984 in the number
of hours with precipitation. The abnormally cold year led to increased
wood burning and road sanding. In Portland, there was also a 2.5 percent
increase in average daily traffic volume. The Northwest also had a generally
higher level of economic growth than in past years. All these factors tend
to re-enforce the higher levels of TSP recorded in 1985 in the Pacific Northwest,
5.15.2 Pb TRENDS
The similarities between the magnitude of the decreases in lead concen-
trations in all the large urbanized areas across all geographic divisions
is remarkable. Boston, New York, St. Louis, and Portland had 4 years of
relatively complete data and the 5-year trend is based on extrapolating the
4-year trend to a fifth year. With the exception of Philadelphia, which
had a 6 percent increase, most of the rest of the urbanized areas had decreases
in the 50 to 60 percent range. The East had the lowest decrease with 41
percent, the Midwest, South, Southwest, and Northwest experienced average
decreases of 57, 65, 57, and 60 percent, respectively compared to the
national average of 49 percent. The higher levels and large decrease in
Seattle (76 percent) were driven by one site located across the street from
a lead point source which discontinued operations in 1984. There is another
lead site about 0.4 miles away on the other side of the source which does
not show similar elevated values. If the source oriented site is not used,
the 5-year trend in Seattle reduces to 53 percent. In Philadelphia, the
composite Pb average concentration increased 6 percent from 1981 to 1985
compared to the national decrease of 49 percent. This upward trend is
attributed to a source oriented Pb sampler which is located near a plant
which manufactures lead oxide pigment for paint. The seven traffic oriented
sites show an average decrease from 1981 to 1985 of 13 percent. This decrease
which is considerably less than the national trend of 49 percent is attributed
to one site which showed an 80 percent increase from 1982 to 1985. This
site is downwind of a major interstate highway and major construction
during this period has occurred around the site. It is speculated that
re-entrained dust containing deposited Pb particles are the major cause of
the increased levels of this site. As stated earlier in the report, between
1984 and 1985, the emissions of lead nationally were reduced by 48 percent.
This reduction was a combination of a drop in the lead allowed in gasoline
and an increase in unleaded gasoline sales. This drop in emissions was
accompanied by a 32 percent decrease in ambient lead levels nationally and
a 34 percent average decrease in lead levels within the 14 city subset
between 1984 and 1985. The range of the decreases within the 14 cities was
between 1.6 percent in Seattle to 53 percent in Atlanta.
5-61
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5.15.3 SO? TRENDS
The composite average of the five individual geographic areas
showed an 11 percent decrease compared to a 15 percent decrease in the
national average. The East and Midwest had a 22 and a 10 percent decrease,
respectively. The Southwest exceeded the national trend with an average
decrease of 32 percent while the Northwest had a substantially lower decrease
of 5 percent. The high decrease in the Southwest for the 1981 - 1985 time
period was driven by the one site in Phoenix which recorded a 41 percent
decrease for that area. Although the values in the Southwest are among the
lowest in the county, the large percent decrease is believed to come from a
general lowering of S02 background levels due to the reduction of emissions
from the smelting industry in the Southwest over the last 5 years.
The Northwest had only a modest 5 percent decrease with no change at
all recorded over the last 5 years in Portland. The S02 levels from Portland
however are the lowest in the 14 cities analyzed and tend to fluctuate
around the minimal detectable levels of the instruments. The only urbanized
areas in which there was an increasing trend were St. Louis and Houston.
The 14 percent increase in St. Louis is attributable to an economic upturn
in the early 1980's and continuing at least through 1984. Although the S02
levels in Houston are among the lowest of the 14 cities in the analysis,
the 16 percent increase is believed to be a result of the general conversion
of industrial boilers in the city from natural gases to fuel oil over the
last few years.
5.15.4 CO TRENDS
Similar to the other pollutant primarily attributable to motor vehicle
emissions (lead), the trends in CO are remarkably uniform within a geographic
area when compared to the national average. The East, Midwest, South, South-
west, and Northwest areas decreased by 23, 28, 24, 17 and 21 percent,
respectively. The overall five area composite decrease of 20 percent is
close to the national composite average decrease of 17 percent.
Upon closer inspection of the figures, it is apparent that for most
cities a good share of the 5-year decrease was caused by the decrease
between 1984 and 1985. Although some cities showed an increase from 1984
to 1985, the average decrease of all 14 cities was 12.3 percent. The range
of change was from +23 percent in Los Angeles to -34 percent in Baltimore.
This compares with the already noted national composite average decrease
between 1984 and 1985 of 10 percent. Also it is of interest to note that
for the first time six major urbanized areas had no measured violations of the
CO NAAQS at the sites used in this trends analyses. Since the national CO
emissions only dropped 3 percent between 1984 and 1985, the improvement is
believed to possibly be a combination of meteorological conditions, localized
control measures, the change in the vehicle mix, traffic patterns, and
vehicle miles traveled in the vicinity of the monitors.
5-62
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5.15.5 NO? TRENDS
Data for the N02 trends analyses were the most sparse of all. The one
Phoenix N02 site showed an 81 percent increase if 1981 to 1985 data were
used and a 35 percent decrease if 1982 to 1985 data were used. As a result
it was decided not to use the Phoenix N02 data in the regional area N02
analyses. The urbanized areas of Atlanta and Portland had no sites which met
the trend criteria. The remaining 11 areas yielded the following area
trends.
In the East, the composite average was a 2 percent increase with
Baltimore measuring the highest increase (9 percent) over the 1981 to 1985
time period. The other areas all showed a higher decrease than the national
average of 5 percent with a 16 percent decrease in the Midwest, a 22 percent
decrease in the South (Houston only), a 6 percent decrease in the Southwest
and an 18 percent decrease in the Northwest (Seattle only). There is no
readily discernible reason as to why the N02 concentrations in Baltimore
increased 9 percent from 1981 to 1985.
5.15.6 03 TRENDS
The average decrease of the five geographic areas is 4 percent which
is almost identical to the national average of 3 percent. The East shows
an increase in 03 of 4 percent while the rest of the areas show decreases.
The Midwest, South, Southwest and Northwest show decreases of 7, 4, 6 and
10 percent, respectively. Upon closer examination two cities stand out,
Detroit and Boston, which drive the averages for the respective geographic
region. The 24 percent improvement in Detroit can be explained by summertime
meteorology in 1984 and 1985 which was conducive to the suppression of 03
levels. Almost all of the 24 percent decrease occurred between 1983 and
1984. The trend in Boston, based on only two sites, is driven by unusally
low values in 1981. Using 1981 to 1985 data the increase is 33 percent;
using 1982 to 1985 data the increase is only 8 percent; and using 1983 to
1985 data the trend decreases by 15 percent.
5-63
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5.16 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/ASQC Specialty Conference, "Quality Assurance in Air Pollution
Measurement," Boulder, CO. October 1984.
5-64
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA 450/4-87-001
2.
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
National Air Quality and Emissions Trends Report, 1985
5. REPORT DATE
February 1Q87
6. PERFORMING ORGANIZATION CODE
7. AUTHORS vJ. i-'. Hunt, Jr. (tdltor), T. C. Curran,
R. B. Faoro, N. H. Frank, W. Freas, C. Mann, R. E. Neligar
S. Sleva, N. Berg, D. Lutz, G. Mam're, & D. Shipman
8. PERFORMING ORGANIZATION REPORT NO.
9. 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 W. Freas and R. Mersch, PEI and the typing
by H. Hinton and C. Coats.
16 ABSTRACfnis report presents national and regional trends in air quality from 1976
through 1985 for total suspended particulate, sulfur dioxide, carbon monoxide,
nitrogen dioxide, ozone and lead. Air pollution trends were also examined
for the 5-year period (1981-85) 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. 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 Metropolitan
Statistical Areas (MSA'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 1983, 1984 and 1985.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
Air Pollution Trends
Emission Trends
Carbon Monoxide
Nitrogen Dioxide
Ozone
Sulfur Dioxide
Air Pol lution
Metropolitan
Statistical Area (MSA)
Air Quality Standarc s
National Air Monitorfing
Stations (NAMS)
b.IDENTIFIERS/OPEN ENDEDTERMS
c. COS AT I E;ield/Group
Total
Lead
Suspended Particulates
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (This Report)
Unclassified
21. NO. OF PAGES
L
20. SECURITY CLASS (This page I
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
frUSGPO 1987-727-408/40269
5-65
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