United States
Environmental Protection
Agency
Office of Air Quality
Planning and Standards
Research Triangle Park NC 27711
EPA 454/R-04-026
October 1894
Air
National Air Quality and
Emissions Trends Report,
1993
95th Percentile = 44
90th Percentile = 38
75th Percentile = 30
Mean = 27
Median = 25
25th Percentile = 22
10th Percentile = 18
5th Percentile = 15
-1993 Particulate Matter-
Highest County Annual Mean
(micrograms per cubic meter)
•/J
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454/R-94-026
National Air Quality and
Emissions Trends Report,
1993
U.S. Environmental Protection Agency
Region 5, Library (PL-12J)
77 West Jackson Boulevard, 12th Floor
Chicago, 1L 60604-3590
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Air and Radiation
Office of Air Quality Planning and Standards
Technical Support Division
Research Triangle Park, North Carolina 27711
October 1994
Printed on recylced paper.
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About the Cover:
The graphical display presents both numerical and geographical distributions of annual mean
particulate matter (PM-10) concentrations across the United States for 1993. The boxplot
separates the data into quartiles, each represented by a different color. Arrows are drawn to
show the annual mean concentration at each quartile and at several other percentiles. The
adjacent maps are color-coded to correspond to the quartiles of the boxplot. Each dot on the
maps represents the site of the highest annual mean concentration (in ug/m^)for that county.
This graphical technique helps the reader discern spatial patterns in the paniculate matter
data. Note that the upper quartiles are dominated by sites located in the western part of the
country and the Ohio River Valley, while sites in the eastern United States more frequently
occur in the lower quartiles.
Disclaimer
This report has been reviewed and approved for publication by the Office of Air Quality Planning and
Standards, U.S. Environmental Protection Agency. Mention of trade names or commercial products
are not intended to constitute endorsement of recommendation for use.
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» X
Preface
This is the twenty-first annual report of air pollution trends issued by the U.S. Environmental Protec-
tion Agency. The report is prepared by the Technical Support Division and 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 the trends techniques, interpretations, conclusions, and
methods of presentation. Please forward any response to Mr. Warren P. Freas, (MD-14)
U.S. Environmental Protection Agency, Technical Support Division, Research Triangle Park, North
Carolina, 27711.
For additional air quality data, readers can access the Aerometric Information Retrieval System (AIRS)
Executive from the AIRS bulletin board on the Office of Air Quality Planning and Standards (OAQPS)
Technology Transfer Network (TTN). To gain access by modem, dial (919) 541-5742. To gain
access by internet, telnet ttnbbs.rtpnc.epa.gov. For help in accessing the OAQPS TTN, dial
(919) 541-5384.
Hi
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Contents
Chapter 1: Executive Summary 1
1.1 Introduction 1
1.2 Major Findings 2
Overview of Carbon Monoxide (CO) 2
Overview of Lead (Pb) 4
Overview of Nitrogen Dioxide (NO2) 6
Overview of Ozone (O3) 8
Overview of Paniculate Matter (PM-10) 10
Overview of Sulfur Dioxide (SO2) 12
1.3 Some Perspective 14
1.4 References 16
Chapter 2: Methodology 19
2.1 Air Quality Data Base 20
2.2 Air Quality Trend Statistics 20
2.3 Emission Estimates Methodology 22
2.4 References 23
Chapter 3: National and Regional Trends in NAAQS Pollutants 25
3.1 Trends in Carbon Monoxide 27
3.1.1 Long-term CO Trends: 1984-1993 27
3.1.2 Recent CO Trends: 1991-1993 31
3.2 Trends in Lead 32
3.2.1 Long-term Pb Trends: 1984-1993 32
3.2.2 Recent Pb Trends: 1991-1993 36
3.3 Trends in Nitrogen Dioxide 39
3.3.7 Long-term NO2 Trends: 1984-1993 39
3.3.2 Recent NO2 Trends: 1991-1993 39
3.4 Trends in Ozone 43
3.4.1 Long-term O3 Trends: 1984-1993 43
3.4.2 Recent O3 Trends: 1991-1993 47
3.4.3 Clean Air Act Update: 1991-1993 47
3.5 Trends in Paniculate Matter 49
3.5.1 PM-10 Air Quality Trends 49
3.5.2 PM-10 Emission Trends 52
Contents
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3.6 Trends in Sulfur Dioxide 55
3.6.1 Long-term SO., Trends: 1984-1993 55
3.6.2 Recent SO2 Trends: 1991-1993 56
3.7 Visibility 59
IMPROVE Monitoring Network 59
Airport Visual Range Data 60
Programs to Improve Visibility 61
3.8 References 64
Chapter 4: Air Toxics 67
4.1 Air Toxics and Their Effects 67
4.2 Emissions Trends: Extent of the Problem 68
Background—Data Sources and Limitations 68
Summary of Emissions 69
4.3 Air Toxics Regulations and Implementation Status 75
CAAA Requirements 75
Status Report on Air Toxics Regulations 75
MACT Standards: Source Category Profiles 76
Aerospace Manufacturing and Re-work Industry 77
Petroleum Refinery 77
Halogenated Solvent Cleaning 78
Magnetic Tape Manufacturing 78
Marine Vessel Loading Operations 79
Polymers and Resins II 79
Pulp, Paper, and Paperboard Industry Manufacturing Processes 80
Gasoline Distribution Industry (Stage I) 80
Secondary Lead Smelters 81
4.4 References 82
Chapter 5: Air Quality Status of Metropolitan Areas 83
5.1 Nonattainment Areas 83
5.2 Population Estimates for Counties Not Meeting NAAQS, 1993 96
5.3 Maps of Peak Air Quality Levels by County, 1993 98
5.4 Metropolitan Statistical Area (MSA) Air Quality Summary, 1993 105
5.5 References 106
Chapters: Selected Metropolitan Area Trends 119
6.1 The Pollutant Standards Index 119
6.2 Summary of PSI Analyses 121
6.3 References 126
vi • Contents
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Chapter?: International Air Pollution Perspective 127
7.1 Emissions 127
7.2 Ambient Concentrations 132
7.3 Ambient Concentration Regulations 137
7.4 References 139
Data Appendix 141
Contents • vii
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Figures
Figure 1-1. Comparison of 1970 and 1993 national total emissions 14
Figure 1-2. Number of persons living in counties with air quality levels not meeting the primary
NAAQS in 1993. (Based on 1990 population data and 1993 air quality data.) 15
Figure 2-1. Illustration of plotting convention of boxplots 21
Figure 2-2. Ten Regions of the U.S. Environmental Protection Agency. 22
Figure 3-1. Comparison of 1970 and 1993 national total emissions 26
Figure 3-2. Boxplot comparisons of trends in second-higest non-overlapping eight-hour
average carbon monoxide concentrations at 314 sites, 1984-1993 27
Figure 3-3. National trend in the composite average of the estimated number of exceedances of
the eight-hour CO NAAQS, at both NAMS and all sites with 95-percent confidence
intervals, 1984-1993 28
Figure 3-4. Comparison of trends in total national VMT and national highway vehicle carbon monoxide
emissions, 1984-1993 30
Figure 3-5. Regional comparisons of 1991,1992, and 1993 composite averages of the second
highest non-overlapping eight-hour average carbon monoxide concentrations 31
Figure 3-6. Boxplot comparisons of trends in maximum quarterly average lead concentrations
at 204 sites, 1984-1993 33
Figure 3-7. Comparison of national trends in the composite average of the maximum quarterly
average lead concentrations at urban and point-source oriented sites, 1984-1993. 34
Figure 3-8. Maximum quarterly mean lead concentrations in the vicinity of lead
point sources, 1993 34
Figure 3-9. Regional comparisons of the 1991,1992, and 1993 composite average of the maximum
quarterly average lead concentrations 36
Figure 3-10. Boxplot comparisons of trends in annual mean nitrogen dioxide concentrations at
201 sites, 1984-1993 40
Figure 3-11. Regional comparisons of 1991, 1992, and 1993 composite averages of the annual
mean nitrogen dioxide concentrations 42
Figure 3-12. Boxplot comparisons of trends in annual second-higest daily maximum one-hour ozone
concentration at 532 sites, 1984-1993 43
Figure 3-13. National trend in 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, 1984-1993.... 44
Figure 3-14. Comparison of meteorologically adjusted, and unadjusted, trends in the composite average
of the second-higest maximum one-hour ozone concentration for 43 MSAs, 1984-1993 45
Figure 3-15. Regional comparison of the 1991,1992, and 1993 composite averages of the
second highest daily one-hour ozone concentrations 47
Figure 3-16. Map depicting marginal ozone nonattainment areas meeting the ozone NAAQS during
the three-year compliance period, 1991-1993 48
Figure 3-17. Boxplot comparisons of trends in weighted annual mean PM-10 concentrations at 799 sites,
1988-1993 50
viii • Contents
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Figure 3-18. Boxplot comparisons of trends in the 90th percentile of 24-hour PM-10 concentrations
at 799 sites, 1988-1993 50
Figure 3-19. Regional comparisons of the 1991,1992, and 1993 composite averages of the
weighted annual mean PM-10 concentrations 51
Figure 3-20. Boxplot comparisons of trends in annual mean sulfur dioxide concentrations at 474 sites,
1984-1993 55
Figure 3-21. Boxplot comparisons of trends in second-higest 24-hour average sulfur dioxide
concentrations at 469 sites, 1984-1993 56
Figure 3-22. Regional comparisons of the 1991,1992, and 1993 composite averages of the annual
sulfur dioxide concentrations 58
Figure 3-23. Aerosol size distribution 59
Figure 3-24. Annual average light extinction 60
Figure 3-25. Visual range airport data monitoring sites 61
Figure 3-26. United States trends map for the 75th percentile of light extinction derived from airport
visual range data. (Q1 = January - March; Q2 = April - June) 62
Figure 3-27. United States trends map for the 75th percentile of light extinction derived from airport visual
range data. (Q3 = July - September; Q4 = October - December) 63
Figure 4-1. Top 10 hazardous air pollutants, 1988 basis 70
Figure 4-2. Industry categories reporting highest total HAP releases, 1988 basis 70
Figure 4-3. 1991 total air releases, HAP species by state, from TRI 71
Figure 4-4. 1992 total air releases, HAP species by state, from TRI 71
Figure 4-5. Percent change in HAP air releases from 1988 to 1992, from TRI 72
Figure 4-6. Percent change in HAP air releases from 1991 to 1992, from TRI 72
Figure 4-7. Changes in HAP air releases from 1988 to 1992 for top five states from 1988, from
TRI 73
Figure 4-8. Gridded map of TRI total air releases of HAPs, 1992 74
HAP Emissions from Aerospace Manufacturing 77
HAP Emissions from Petroleum Refinery 77
HAP Emissions from Halogenated Solvent Cleaning 78
HAP Emissions from Magnetic Tape Manufacturing 78
HAP Emissions from Marine Vessel Loading 79
HAP Emissions from Polymers and Resins II 79
HAP Emissions from Pulp, Paper, and Paperboard 80
HAP Emissions from Gasoline Distribution Industry (Stage I) 80
HAP Emissions from Secondary Lead Smelters 81
Figure 5-1. Example of multiple nonattainment (NA) areas within a larger NA area (two SO2 NA
areas inside the Pittsburgh-Beaver Valley ozone NA area, counted as one area) 89
Figure 5-2. Example of overlapping NA areas (Searles Valley PM-10 NA area partially overlaps the
San Joaquin Valley ozone NA area, counted as two areas) 89
Figure 5-3. Areas designated nonattainment for carbon monoxide 90
Figure 5-4. Areas designated nonattainment for lead 91
Figure 5-5. Area (Los Angeles) lesignated nonattainment for nitrogen dioxide 92
Figure 5-6. Areas designated nonattainment for ozone 93
Figure 5-7. Areas designated nonattainment for PM-10 Particulates, by emission type 94
Contents • ix
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Figure 5-8. Areas designated nonattainment for sulfur dioxide 95
Figure 5-9. Number of persons living in counties with air quality levels not meeting the primary
NAAQS in 1993. (Based on 1990 population data and 1993 air quality data.) 96
Figure 5-10. Carbon monoxide air quality concentrations, 1993—highest second maximum
eight-hour average 99
Figure 5-11. Lead air quality concentrations, 1993—highest quarterly average 100
Figure 5-12. Nitrogen dioxide air quality concentrations, 1993—highest arithmetic mean 101
Figure 5-13. Ozone air quality concentrations, 1993—highest second daily one-hour maximum 102
Figure 5-14. PM-10 air quality concentrations, 1993—highest second maximum 24-hour average 103
Figure 5-15. Sulfur dioxide air quality concentrations, 1993—highest second maximum 24-hour average.. 104
Figure 7-1. SOx emissions in 1000 metric tons/year for selected countries 127
Figure 7-2. Trend in annual average sulfur dioxide concentrations in selected cities of the world 134
Figure 7-3. Trend in annual second-higest 24-hour sulfur dioxide concentrations in selected
U.S. cities and Canadian cites, 1983-1991 134
Figure 7-4. Trend in annual average suspended paniculate concentrations in selected cities of
the world 135
Figure 7-5. Trend in annual geometric mean total suspended paniculate concentrations in selected
U.S. cities and Canadian cites, 1985-1991 135
Figure 7-6. Trend in annual second-higest one-hour ozone concentrations in selected U.S. cities and
Canadian cites, 1983-1991 136
Figure 7-7. Comparison of ambient levels of annual second daily maximum one-hour ozone,
annual average total suspended paniculate matter and sulfur dioxide concentrations
among selected cities 136
Contents
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Tables
Table 2-1. National Ambient Air Quality Standards (NAAQS) in Effect in 1993 19
Table 2-2. Number of Monitoring Sites 21
Table 3-1. National CO Emission Estimates, 1984-1993 29
Table 3-2. National Pb Emission Estimates, 1984-1993 36
Table 3-3. National NOx Emission Estimates, 1984-1993 41
Table 3-4. National Volatile Organic Compound Emission Estimates, 1984-1993 46
Table 3-5. National PM-10 Emission Estimates, 1985-1993, No Natural Source or Miscellaneous
Emissions 52
Table 3-6. Miscellaneous and Natural Source Paniculate Matter Emission Estimates, 1985-1993 53
Table 3-7. National Sulfur Oxides Emission Estimates, 1984-1993 57
Table 4-1. Summary of Previously Reported MACT Standards 76
Table 5-1. Nonattainment Areas for NAAQS Pollutants as of September 1994 83
Table 5-2. Simplified Nonattainment Areas List 85
Table 5-3. Number of Counties With at Least One Monitoring Site by Pollutant 98
Table 5-4. 1993 Metropolitan Statistical Area Air Quality Factbook Peak Statistics for Selected
Pollutants by MSA 108
Table 6-1. Comparison of Pollutant Standards Index (PSI) Values with Pollutant Concentrations,
Health Descriptions, and PSI Colors 120
Table 6-2 Number of PSI Days Greater than 100 at Trend Sites, 1984-93, and All Sites in 1993 122
Table 6-3. (Ozone Only) Number of PSI Days Greater Than 100 at Trend Sites, 1984-93, All Sites
in 1993 124
Table 7-1. Emissions of Sulfur Dioxide from Anthropogenic Sources in Selected Countries,
1980 and 1990. Total Emissions (103 Metric Tons per Year as SO2) 128
Table 7-2. Emissions of Nitrogen Oxides from Anthropogenic Sources in Selected Countries,
1980 and 1990. Total Emissions (103 Metric Tons per Year as NO2) 130
Table 7-3. Emissions of Particulates from Anthropogenic Sources in Selected Countries,
1980 and 1990. Total Emissions (103 Metric Tons per Year) 132
Table 7-4. Urban Trends in Annual Average Sulfur Dioxide Concentrations (ug/m3) 133
Table 7-5. Selected International Air Quality Standards and Guidelines (units in ug/m3) 138
Contents • xi
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Chapter 1: Executive Summary
1.1 Introduction
This is the twenty-first annual report
documenting air pollution trends
in the United States.1"20 The primary
emphasis of this report is on those
pollutants for which the U.S. Environ-
mental Protection Agency (EPA) has
established National Ambient Air
Quality Standards (NAAQS). EPA
set these standards to protect public
health and welfare. Primary stan-
dards are designed to protect public
health, while secondary standards
protect public welfare, such as the ef-
fects of air pollution on vegetation,
materials and visibility. Air toxics,
another set of pollutants regulated
under the Clean Air Act are also dis-
cussed. Air toxics are those pollut-
ants known to cause, or suspected of
causing, cancer or other serious health
effects, such as reproductive effects or
birth defects. Due to the limited
availability of ambient data for air
toxics, this report focuses on the
analysis of trends in hazardous air
pollutant emissions and the status of
regulatory development for the air
toxics provisions of the Clean Air Act
Amendments of 1990 (CAAA).
The analyses in this report focus
on comparisons with the primary
standards in effect in 1993, examines
changes in air pollution levels over
time, and summarizes the current air
pollution status. The six pollutants
with National Ambient Air Quality
Standards are: carbon monoxide
(CO), lead (Pb), nitrogen dioxide
(NO2), ozone (O3), particulate matter
(PM-10) whose aerodynamic size is
equal to or less than 10 microns, and
sulfur dioxide (SO2). It is important
to note that the discussions of ozone
in this report refer to ground level
(tropospheric) ozone and not to
stratospheric ozone. Stratospheric
ozone, which is miles above the earth,
acts as a protective screen from the
sun's ultraviolet rays. Ground level
ozone, which is in the air we breathe,
is a health and environmental concern
and is the primary ingredient of what
is commonly called smog.
This report tracks two kinds of
trends: air concentrations, based
on actual direct measurements of pol-
lutant concentrations in the air at se-
lected sites throughout the country;
and emissions, which are estimates of
the total tonnage of these pollutants
released into the air annually. The
emission trends are estimated using
best available engineering calcula-
tions. These are derived from many
factors, including the level of indus-
trial activity, technology changes, fuel
consumption, vehicle miles of travel,
and other activities that cause air pol-
lution. The trends also reflect
changes in air pollution regulations
and the installation of emission con-
trols. The estimates of emissions in
this report differ from those reported
last year because of improvements in
emission estimation methodologies.
Also note that the 1990 to 1993 emis-
sion estimates are preliminary, and
will be revised in the next report when
final data from ozone State Imple-
mentation Plans (SIPs) become avail-
able. Additional emission estimates
and a more detailed description of
the estimation methodology is con-
tained in a companion report, Na-
tional Air Pollutant Emission Trends,
1900-1993.2}
The first three chapters of this re-
port describe trends in the six
NAAQS pollutants. Chapter 3 also
contains information on visibility
trends throughout the country. Chap-
ter 4 presents information on air tox-
ics. Chapter 5 includes the status of
areas with respect to the NAAQS as
well as a listing of selected 1993 air
quality summary statistics for every
metropolitan statistical area (MSA) in
the nation. Chapter 6 presents trends
in the Pollutant Standards Index (PSI)
for 89 cities with populations of at
least one-half million. The PSI is
widely used in the air pollution field
to report daily air quality to the gen-
eral public. PSI index values are re-
ported in all metropolitan areas of the
United States with populations ex-
ceeding 200,000. Chapter 7 provides
an international air pollution perspec-
tive.
Chapter 1: Executive Summary • 1
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Section 1.2 Major Findings-CO
1.2 Major Findings
Carbon Monoxide (CO)
CO SUMMARY
Air Concentrations
1984-93: 37 percent decrease (8-hour second high at 314 sites)
i 97 percent decrease (8-hour exceedances at 314 sftes)
5 percent decrease (8-hour second high at 394 sites)
1992-93:
Emissions
1984-93:
1992-93:
15 percent decrease
1 percent increase
Overview
• Trends — Improvements contin-
ued with the 1984-93 10-year period
showing a 37-percent decrease in air
quality levels and a 15-percent reduc-
tion in total emissions. These air
quality improvements agree closely
with the estimated 24-percent reduc-
tion in highway vehicle emissions.
This is understandable given the fact
the urban CO monitoring network is
primarily mobile source oriented.
This progress occurred despite the
33-percent increase in miles of travel
in the United States during the past 10
years. Transportation sources ac-
counted for 77 percent of the nation's
total CO emissions in 1993. Esti-
mated nationwide CO emissions in-
creased one percent between 1992
and 1993. This increase in CO emis-
sions between 1992 and 1993 can be
largely attributed to three sources:
highway vehicles, off-highway ve-
hicles, and wildfires.
• Status — In November 1991,
EPA designated 42 areas as non-
attainment for CO. Based on the
magnitude of CO concentrations, 41
of these areas were classified as mod-
erate, and only one, Los Angeles, was
classified as serious. The 41 moder-
ate areas must meet the NAAQS by
December 31,1995, while Los Ange-
les has until December 31, 2000.
Since the original nonattainment area
designations, four areas have been re-
designated to attainment for the CO
NAAQS: Cleveland, OH; Duluth,
MN; Syracuse, NY; and Memphis,
TN.
• Some Details — The first major
clean fuels program under the 1990
Clean Air Act Amendments is the
oxygenated fuel program imple-
mented by state and local agencies
following EPA guidelines. Increasing
the oxygen content of gasoline re-
duces CO emissions by improving
fuel combustion, which is typically
less efficient at cold temperatures.
On November 1, 1992, new oxygen-
ated fuel programs began in 28 metro-
politan areas. These programs
generally run from November through
February.
2 • Chapter 1: Executive Summary
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Section 1.2 Major Findings-CO
CO TREND, 1984-1993
(ANNUAL 2ND MAX 8-HR AVG)
15
CONCENTRATION, PPM
10-
314 SITES
90% of sites have lower
2nd max 8-hr concentrations
than this line
10% of sites have lower
2nd max 8-hr concentrations
than this line
I I I I I I I I
84 85 86 87 88 89 90 91 92 93
CO EMISSIONS TREND
(1984-1993)
THOUSAND SHORT TONS PER YEAR
120,000-
100,000-
80,000 •
60,000 -
40,000 -
20,000 -
• Fuel Combustion Blndustrial Processes j|jTranspottaUon [jMiscellnneous
84 85 86 87 88 89 90 91 92 93
CO EFFECTS
Carbon monoxide enters the bloodstream and reduces oxygen delivery to the body's organs and tissues.
The health threat from carbon monoxide is most serious for those who suffer from cardiovascular
disease, particularly those with angina or peripheral vascular disease. Healthy individuals also are
affected but only at higher levels. Exposure to elevated carbon monoxide levels is associated with
impairment of visual perception, work capacity, manual dexterity, learning ability and performance of
complex tasks.
Chapter 1: Executive Summary • 3
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Section 1.2 Major Findings-Pb
Lead (Pb)
Pb SUMMARY
• Air Concentrations
1984-9$: 89 percent decrease (maximum quarterly average at 204 sites)
11 percent decrease (maximum quarterly average at 228 sites)
1992-93:
Emissions
1984-93:
1992-93:
88 percent decrease in total lead emissions
(96 percent decrease in lead emissions from transportation sources)
3 percent increase in total lead emissions
(3 percent decrease m lead emissions from transportation sources)
Overview
• Trends — Ambient lead (Pb) con-
centrations in urban areas throughout
the country have decreased 89 percent
since 1984. Total Pb emissions have
also dropped 88 percent since 1984
due primarily to reductions from auto-
motive sources. The drop in Pb
consumption and subsequent Pb emis-
sions was brought about by the in-
creased use of unleaded gasoline in
catalyst-equipped cars (99 percent of
the total gasoline market in 1993) and
the reduced Pb content in leaded
gasoline. The three-percent increase
in Pb emissions between 1992 and
1993 was due to the increase in emis-
sions from metab processing,
incineration operations, and man-
ufacturing. These are offset some-
what by the decreased emissions from
highway vehicles.
• Status — There are 13 areas that
have been designated as nonattain-
ment because of NAAQS violations
for lead.
• Some Details — The large reduc-
tion in lead emissions from transpor-
tation sources has changed the nature
of the ambient lead problem in the
United States. In 1984, estimated
lead emissions were 42,217 tons, and
91 percent was due to transportation
sources. By 1993, estimated lead
emissions dropped to 4,885 tons, and
transportation sources accounted for
31 percent due to the remaining frac-
tion of leaded gasoline sales. Current
lead nonattainment problems are as-
sociated with point sources, such as
smelters, battery plants, and solid
waste disposal. Consequently, EPA's
lead attainment strategy targets air-
borne emissions from these stationary
sources of lead. Monitoring networks
are being expanded around sources of
concern, followed by inspections of
any facility where violations of the
NAAQS are detected. Compliance
activities include negotiating consent
decrees, agreements, or state orders
for individual sources.
4 • Chapter 1: Executive Summary
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Section 1.2 Major Findings-Pb
PB TREND, 1984-1993
(ANNUAL MAX QRTLY AVG)
PB EMISSIONS TREND
(1984-1993)
21
CONCENTRATION, UG/M3
1.5-
1-
0.5-
204 SITES
NAAQS
90% of sites have lower
Max Quarterly Means
than this line
Max Quarterly Mearfs than this line
50,000
40,000 -
30,000 -
20,000 -
10,000-
SHORT TONS PER YEAR
0~l I I [ I I I I I
84 85 86 87 88 89 90 91 92 93
Fuel Combustion • Industrial Processes I \ Transportation
84 85 86 87 88 89 90 91 92 93
Pb EFFECTS
Exposure to lead can occur through multiple pathways, including inhalation of air and ingestion of lead
in food, water, soil, or dust. Lead accumulates in the body in blood, bone, and soft tissue. Because it
is not readily excreted, lead also affects the kidneys, liver, nervous system, and blood-forming organs.
Excessive exposure to lead may cause neurological impairments such as seizures, mental retardation,
and/or behavioral disorders. Even at low doses, lead exposure is associated with changes in fundamental
enzymatic, energy transfer, and homeostatic mechanisms in the body. Fetuses, infants, and children
are especially susceptible to low doses of lead, often suffering central nervous system damage. Recent
studies have also shown that lead may be a factor in high blood pressure and subsequent heart disease
in middle-aged white males.
Chapter 1: Executive Summary • 5
-------
Section 1.2 Major Findings-No;
Nitrogen Dioxide (NO2)
SUMMARY
Air Concentrations
1984-93: 12 percent decrease (annual mean at 201 sites)
1992-93: 2 percent decrease (annual mean at 269 sites)
Emissions: Nitrogen Oxides (NOJ
1984-93: 1 percent; Increase ;
1992-93: 2 percent increase
Overview
• Trends — Although relatively
constant throughout the early 1980s,
ambient NO2 levels have declined
steadily since the peak year of 1988.
NO2 air quality has improved 12 per-
cent since 1984. Nitrogen oxides
emissions are estimated to have in-
creased one percent since 1984, with
a three-percent increase in fuel com-
bustion emissions. The two primary
source categories of nitrogen oxide
emissions, and their contribution in
1993, are fuel combustion (50 per-
cent) and transportation (45 percent).
Since 1984, emissions from highway
vehicles are estimated to have de-
creased 11 percent, while fuel com-
bustion emissions increased three
percent. Approximately 76 percent of
the increase in NOX emissions be-
tween 1992 and 1993 is attributable
to increased emissions from coal-fired
electric utilities. The remainder of the
increase in emissions this year is due
to increased emissions from off-high-
way sources.
• Status — Currently, Los Angeles
is the only area designated as non-
attainment for NO2.
• Some Details — In recent years,
Los Angeles was identified as the
only location not meeting the Na-
tional Ambient Air Quality Standard
for nitrogen dioxide. However, this is
the second year in a row that all moni-
toring locations in Los Angeles have
met the federal NO2 standard.
State of the art air quality models
and improved knowledge of the ambi-
ent concentrations of VOCs and NOX
indicate that NOX control is necessary
for effective reduction of ozone in
many areas of the United States.
Thus, even though the NO2 standards
are now being met at all monitoring
locations throughout the country, NOX
emissions and their control are impor-
tant factors for addressing the current
widespread violations of the ozone
NAAQS.
6 • Chapter 1: Executive Summary
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Section 1.2 Major Findings-NO2
NO2 TREND, 1984-1993
(ANNUAL ARITHMETIC MEAN)
NOX EMISSIONS TREND
(1984-1993)
0.06
CONCENTRATION. PPM
0.05
0.04
0.03
0.02-
0.01
0.00
201 SITES
NAAQS
90% of sites have lower
Arith Mean concentrations
than this line
10% of sites have lower
Arith Mean concentrations
than this line
30,000
THOUSAND SHORT TONS PER YEAR
iiiiiIir^
84 85 86 87 88 89 90 91 92 93
25,000 -
20,000-
15,000-
10,000
5,000
84 85 86 87 88 89 90 91 92 93
Nitrogen dioxide can irritate the lungs and lower the resistance to respiratory infections such as influenza.
The effects of short-term exposure are still unclear, but continued or frequent exposure to concentrations
higher than those normally found in the ambient air may cause increased incidence of acute respiratory
disease in children. Nitrogen oxides are an important precursor to both ozone and acidic precipitation,
and may affect both terrestrial and aquatic ecosystems. Atmospheric deposition of NOX is a potentially
significant contributor to ecosystem effects including algal blooms in certain estuaries such as the
Chesapeake Bay. In some western areas NOX is an important precursor to particulate matter
concentrations.
Chapter 1: Executive Summary • 7
-------
Section 1.2 Major Findings-O3
Ozone (O3)
SUMMARY
• Air Concentrations
1984-93 12 percent decrease (second highest daily max 1-hour at 532 sites)
80 percent decrease (excsedanee days at 532 sites)
1992-93: 2 percent increase (second highest dally max 1 -hour at 722 sites)
• Emissions: Volatile Organic Compounds (VOC)
1984-93: Q percent decrease (+1 percent for NOX)
1992-93; 1 percent increase (+2 percent for NO*)
Overview
• Trends — Ground level ozone, the
primary constituent of smog, is a per-
vasive pollution problem for the
United States. Ambient trends are in-
fluenced by varying meteorological
conditions. Although meteorological
conditions in the east during 1993
were more conducive to O3 formation
than last year, the composite mean
level for 1993 was still the second
lowest composite average of the 10-
year trend period of 1984-93. The
lowest composite mean level was re-
corded in 1992, and the highest was
recorded in 1988. Recent control
measures include rules to lower fuel
volatility and lower NOX and VOC
emissions from tailpipes. Emission
estimates for VOCs, which contribute
to ozone formation, are estimated to
have improved by nine percent since
1984. However, these VOC emission
estimates represent annual totals,
while ozone is a warm weather prob-
lem. NOX emissions, the other major
precursor factor in ozone formation,
increased one percent between 1984
and 1993. Seasonal emissions inven-
tories are being developed for use in
future trends assessments.
• Status — In November 1991,
EPA designated 98 areas as non-
attainment for O3. Since these initial
nonattainment designations, seven ar-
eas have been redesignated as attain-
ment. EPA has announced plans to
review the ozone NAAQS and to ex-
amine options for implementing alter-
native NAAQS to ensure a smooth
transition if a decision is made to re-
vise the existing NAAQS. The
schedule for this review has been
published elsewhere.23
• Some Details — Year-to-year O3
trends are affected by changing me-
teorological conditions. The larger
improvement of 21 percent reported
last year between 1983 and 1992 was
due in part to 1983 being a relatively
high year for ozone, and 1992 being a
relatively low year. New statistical
techniques accounting for meteoro-
logical influences suggest an im-
provement of 12 percent for the
10-year period. This happens to
match the percent change for the am-
bient trend.
8 • Chapter 1: Executive Summary
-------
Section 1.2 Major Findings-O3
OZONE TREND, 1984-1993 VOC EMISSIONS TREND
(ANNUAL 2ND DAILY MAX HOUR) (1984 - 1993)
0.25
CONCENTRATION, PPM
0.20"
0.15
0.10-
0.05
0.00
532 SITES
90% of sites have lower
2nd max 1-hr concentrations
than this line
i- ^L-JjS**^y •••" X. •' :::v "•*• «*
MM-* w»i*«iS^l»»1IS^ *»«««** MKW,J*« « **'iLyf ^*^*!y*J**^1' "^^
••;'"; *A;;KvS :.„->'-,' -'"'(~* ^ -i' ""^^
10% of sites have lower
2nd max 1-hr concentrations
than this line
30,000
THOUSAND SHORT TONS PER YEAR
25,000"
20,000-
15,000-
10,000
5,000
I \ I [ I I I I
84 85 86 87 88 89 90 91 92 93
•Fuel Combustion llndustnal Processes |JTransportation ^Miscellaneous
84 85 86 87 88 89 90 91 92 93
0, EFFECTS
The reactivity of ozone with humans causes health problems because it damages lung tissue, reduces
lung function, and sensitizes the lungs to other irritants. Scientific evidence indicates that ambient
levels of ozone not only affect people with impaired respiratory systems, such as asthmatics, but
healthy adults and children as well. Exposure to ozone for six to seven hours at relatively low
concentrations has been found to significantly reduce lung function and induce respiratory inflammation
in normal, healthy people during periods of moderate exercise. This decrease in lung function often is
accompanied by such symptoms as chest pain, coughing, nausea, and pulmonary congestion. Recent
studies provide evidence of an association between elevated ambient O3 levels and increases in hospital
admissions for respiratory problems in several U.S. cities. Though less well established in humans,
animal studies have demonstrated that repeated exposure to ozone for months to years can produce
permanent structural damage in the lungs and accelerate the rate of lung function decline and aging of
the lungs. Ozone is responsible for several billion dollars of agricultural crop yield loss in the United
States each year. It also causes noticeable foliar damage in many crops and species of trees. Forest
and ecosystem studies indicate that damage is resulting from current ambient ozone levels.
Chapter 1: Executive Summary • 9
-------
Section 1.2 Major Findings-PM-10
Participate Matter (PM-10)
PM-10 SUMMARY
• Air Concentrations: Paniculate Matter (PM-10)
1988-93: 20 percent decrease (based on arithmetic mean at 799 sites)
1992-93: 3 percent decrease (based on arithmetic mean at 799 sites)
• Emissions: PM-10
1988-93: 10 percent decrease (excluding miscellaneous and natural sources)
1992-33: 2 percent decrease (excluding miscellaneous and natural sources)
Overview
• Trends — In 1987, EPA replaced
the earlier total suspended participate
(TSP) standard with a PM-10 stan-
dard. PM-10 focuses on smaller
particles that are likely to be respon-
sible for adverse health effects be-
cause of their ability to reach the
lower regions of the respiratory tract.
Ambient monitoring networks have
been revised to measure PM-10 rather
than TSP. PM-10 ambient levels de-
creased 20 percent between 1988 and
1993. PM-10 emissions from sources
historically included in inventories
are estimated to have decreased 10
percent since 1988. Progress in re-
ducing particulate matter emissions is
most noticeable in the areas of high-
way vehicles, particularly diesel
vehicles, and residential wood com-
bustion. Nationally, fugitive sources,
such as emissions from agricultural
tilling, construction, and unpaved
roads, contribute six to eight times
more PM-10 emissions than sources
historically included in emission in-
ventories.
• Status — In November 1991,
EPA designated 70 areas as non-
attainment for PM-10. During the
last two years an additional 13 areas
throughout the country have been des-
ignated as nonattainment for PM-10.
• Some Details — More and more
studies are being conducted across the
country to better understand the na-
ture of particulate matter—what it is
made up of, the effect of different size
particles, which sources it comes
from, how it varies in different geo-
graphical areas, and its effects on
health. Revisions to the ambient stan-
dards and changes to the current
monitoring network for particulate
matter are being considered in light of
the new information being discov-
ered.
10 • Chapter 1: Executive Summary
-------
Section 1.2 Major Findings-PM-10
PM-10 TREND, 1988-1993
(ANNUAL ARITHMETIC MEAN)
70
CONCENTRATION. UG/M3
60
50-
40-
30-
20-
10"
799 SITES
NAAQS
90% of sites have lower
Arith Mean concentrations
than this line
* • *• .-•.-
10% of sites have lower
Arith Mean concentrations
than this line
88
I
89
90
\
91
\
92
PM-10 EMISSIONS TREND
(no miscellaneous emissions)
(1988-1993)
THOUSAND SHORT TONS PER YEAR
4,000
3,000
2,000
1,000
93
Fuel Combustion • Industrial Processes (i;l Transportation
PM EFFECTS
Based on studies of human populations exposed to ambient particle pollution (sometimes in the presence
of sulfur dioxide) and laboratory studies of both animals and humans, the major areas of concern for
human health include: effects on breathing and respiratory symptoms, aggravation of existing respiratory
and cardiovascular disease, alterations in the body's defense systems against foreign materials, damage
to lung tissue, carcinogenesis, and premature mortality. The major subgroups of the population that
appear likely to be the most sensitive to the effects of particulate matter include individuals with chronic
obstructive pulmonary or cardiovascular disease, influenza, and asthma, as well as the elderly and
children. Particulate matter causes damage to materials and soiling. It is a major cause of visibility
impairment in many parts of the United States.
Chapter 1: Executive Summary • 11
-------
Section 1.2 Major Findings-SO2
Sulfur Dioxide (SO2)
SUMMARY
Air Concentrations
1984-93:
26 percent decrease (arithmetic mean at 474 sites)
36 percent decrease (24-hour second high at 469 sites)
1 percent decrease (arithmetic mean at 560 sites)
• Emissions: Sulfur Oxides (SO,)
1984-93: 6 percent decrease
1992-93: 1 percent Increase
Overview
• Trends — Since 1984, SOX emis-
sions decreased six percent, while
average SO2 air quality improved by
26 percent. This difference occurred
because the historical ambient moni-
toring networks are population-ori-
ented in urban areas while the
major emission sources tended to be
in less populated areas. The one-per-
cent increase in total SOX emissions
between 1992 and 1993 was the re-
sult of increased iuel usage (primarily
coal) in the electric utility sector.
This increase was largely offset by
decreased industrial fuel combustion
and highway vehicle emission esti-
mates.
• Status — Almost all monitors in
U.S. urban areas meet EPA's ambient
air quality standards for SO2. Disper-
sion models are commonly used to as-
sess ambient SO2 problems around
point sources because it is frequently
impractical to operate enough moni-
tors to provide a complete air quality
assessment. Currently, there are 47
areas designated nonattainment for
SO2. New regulations are being con-
sidered to target high short-term SO2
emitters for monitoring.
• Some Details — Four programs
make up the EPA's strategy to control
the emissions associated with SO2:
(1) the National Ambient Air Quality
Program, which sets the primary and
secondary standards discussed earlier
in this report; (2) the New Source
Performance Standards, which set
emission limits for new sources; (3)
the New Source Review/Prevention
of Significant Deterioration Program,
which protects air quality from dete-
riorating in clean areas by requiring
new major SO2 sources to conduct air
quality analyses before receiving a
permit; and (4) the Acid Rain Pro-
gram, which is set forth in Title IV of
the 1990 Clean Air Act Amendments.
12 • Chapter 1: Executive Summary
-------
Section 1.2 Major Findings-SO2
SO2 TREND, 1984-1993
(ANNUAL ARITHMETIC MEAN)
SOX EMISSIONS TREND
(1984-1993)
0.035
0.030
0.025
0.020
0.015-
0.010
0.005-
CONCENTRATION, PPM
0.000
474 SITES
NAAQS
90% of sites have lower
Arith Mean concentrations
than this line
Arith Mean concentrations
than this line
I I I I I I I I
84 85 86 87 88 89 90 91 92 93
30,000
25,000
20,000
15,000
10,000
5,000
THOUSAND SHORT TONS PER YEAR
• Fuel Combustion H Industrial Processes |<| Transportation
84 85 86 87 88 89 90 91 92 93
The major health effects of concern associated with exposure to high concentrations of sulfur dioxide
include effects on breathing, respiratory illness, alterations in the lungs'defenses, and aggravation of
existing respiratory and cardiovascular disease. The major subgroups of the population that are most
sensitive to sulfur dioxide include asthmatics and individuals with cardiovascular disease or chronic
lung disease (such as bronchitis or emphysema), as well as children and the elderly. Sulfur dioxide
also can produce foliar damage on trees and agricultural crops. Together, sulfur dioxide and nitrogen
oxides are the major precursors to acidic deposition (acid rain). This is associated with a number of
effects including acidification of lakes and streams, accelerated corrosion of buildings and monuments,
and visibility impairment.
Chapter 1: Executive Summary • 13
-------
Section 1.3 Some Perspective
1.3 Some Perspective
A 10-year period is convenient for
considering ambient pollution trends.
This is because of changes that oc-
curred in monitoring networks during
the early 1980s and changes over time
that routinely occur in the geographi-
cal distribution of monitors. Al-
though it is difficult to provide
ambient trends going back more than
10 years, it is important not to over-
look some of the earlier control efforts
in the air pollution field. While the
ambient monitoring trends and the
emission trends can be viewed as in-
dependent assessments of the underly-
ing pollutant trends, the emission
estimates can also be used to provide
information on longer time periods.
Figure 1-1 provides a convenient
summary of the 1970-93 emission
changes for all six NAAQS pollut-
ants. Lead emissions clearly recorded
the most impressive decrease of 98
percent, but improvements are also
seen for emissions of PM-10 (-78 per-
cent), SOX (-30 percent), CO (-24
percent), and VOCs (-24 percent).
Only NOX emissions showed an in-
crease (14 percent) between 1970 and
1993 levels. It is important to realize
that these reductions occurred even
during an increase in vehicle miles
travelled and industrial output. More
detailed information on these emis-
sion trends and the updated estimation
methodologies are contained in a
companion report.21
While progress has been made, it
is important not to lose sight of the
magnitude of the air pollution prob-
lem that still remains. Based upon
data submitted to EPA's data base,
approximately 59 million people in
the United States reside in counties
which did not meet at least one air
quality standard for the single year
1993. Ground level ozone is the most
common contributor with 51 million
people living in counties that ex-
ceeded the ozone standard in 1993.
This is the second consecutive year
that every monitoring site in the coun-
try met the nitrogen dioxide standard.
With respect to sulfur dioxide, it is
important to note that while almost all
monitoring sites are currently meeting
the NAAQS, sulfur dioxide problems
in the United States are now associ-
ated with point sources and are typi-
cally identified by modeling rather
than by routine ambient monitoring.
These population estimates are based
on a single year of data, 1993, and
only consider counties with monitor-
ing data for that pollutant. Chapter 5
discusses other approaches that would
yield different numbers.
140
120
100
80
60
40
20
MILLION SHORT TONS/YEAR
250
200
150
100
50
THOUSAND
SHORT TONS/YEAR
NOx
VOC
PM10
SOx
LEAD
1970 n 1993
Figure 1-1. Comparison of 1970 and 1993 national total emissions.
14 • Chapter 1: Executive Summary
-------
Section 1.3 Some Perspective
In 1991, EPA issued a rule for-
mally designating areas that did not
meet air quality standards.22 Based
upon these designations, EPA esti-
mated that 150 million people live in
nonattainment areas. This difference
between the 150 million and 59 mil-
lion population figures is because the
formal designations are based upon
multiple years of data, rather than just
one, to reflect a broader range of me-
teorological conditions. Also, the
boundaries used for nonattainment ar-
eas may consider other air quality re-
lated information, such as emission
inventories and modeling. They may
extend beyond those counties with
monitoring data to more folly charac-
terize the ozone problem and to facili-
tate the development of an adequate
control strategy. For the pollutant
lead, EPA's aggressive effort to better
characterize lead point sources has
resulted in new monitors that have
documented additional problem areas.
Finally, the designations were gener-
ally based on data from the years
1987-1989, which included the peak
ozone year of 1988.
Although this report emphasizes
those six pollutants for which there
are National Ambient Air Quality
Standards. There are other air pollut-
ants of concern, as evidenced by the
fourth chapter's discussion of air tox-
ics. Air toxics are chemicals known
or suspected of causing cancer or
other serious health effects (e.g., re-
productive effects). According to
EPA's Toxic Release Inventory, more
than 1.8 billion pounds of toxics were
released to the atmosphere in 1992 as
compared to 2.0 billion pounds in
1991 24,25 Further, estimated emis-
sions of hazardous air pollutants (189
compounds identified for regulatory
attention by the CAAA) declined
from approximately 1.5 billion
pounds in 1991 to roughly 1.3 billion
pounds in 1992. While control pro-
grams are designed to address the cri-
teria pollutants, they are also
expected to reduce air toxic releases
to some degree by reducing emissions
of particulates, volatile organic
chemicals and nitrogen oxides. Title
III of the CAAA provides specific
new tools to directly address releases
of hazardous air pollutants. EPA also
is implementing programs to reduce
emissions of pollutants contributing to
depletion of the stratospheric ozone
layer and acidic deposition.
40 60
millions of persons
80
100
Figure 1-2. Number of persons living in counties with air quality levels not meeting the primary NAAQS in 1993.
(Based on 1990 population data and 1993 air quality data.)
Chapter 1: Executive Summary • 15
-------
Section 1.4 References
1.4 References
1. The National Air Monitoring Program: Air Quality and Emissions Trends - Annual Report, EPA-
450/1-73-OOla and b, U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC 27711, July 1973.
2. Monitoring and Air Quality Trends Report, 1972, EPA-450/1 -73-004, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, December
1973.
3. Monitoring and Air Quality Trends Report, 1973, EPA-450/1-74-007, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, October
1974.
4. Monitoring and Air Quality Trends Report, 1974, EPA-450/1 -76-001, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February
1976.
5. National Air Quality and Emissions Trends Report, 1975, EPA-450/1 -76-002, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
2771 I.November 1976.
6. National Air Quality and Emissions Trends Report, 1976, EPA-450/1-77-002, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, December 1977.
7. National Air Quality and Emissions Trends Report, 1977, EPA-450/2-78-052, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, December 1978.
8. 1980 Ambient Assessment -AirPortion, EPA-450/4-81-014, U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, February 1981.
9. National Air Quality and Emissions Trends Report, 1981, EPA-450/4-83-011, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, April 1983.
10. National Air Quality and Emissions Trends Report, 1982, EPA-450/4-84-002, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, March 1984.
11. National Air Quality and Emissions Trends Report, 1983, EPA-450/4-84-029, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, April 1985.
12. National Air Quality and Emissions Trends Report, 1984, EPA-450/4-86-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, April 1986.
13. National Air Quality and Emissions Trends Report, 1985, EPA-450/4-87-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, February 1987.
14. National Air Quality and Emissions Trends Report, 1986, EPA-450/4-88-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, February 1988.
15. National Air Quality and Emissions Trends Report, 1987, EPA-450/4-89-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, March 1989.
16 • Chapter 1: Executive Summary
-------
Section 1.4 References
16. National Air Quality and Emissions Trends Report, 1988, EPA-450/4-90-002, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, March 1990.
17. National Air Quality and Emissions Trends Report, 1989, EPA-450/4-91-003, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, February 1991.
18. National Air Quality and Emissions Trends Report, 1990, EPA-450/4-91-023, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, November 1991.
19. National Air Quality and Emissions Trends Report, 1991, EPA-450/R-92-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, October 1992.
20. National Air Quality and Emissions Trends Report, 1992, EPA-454/R-93-031, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, October 1993.
21. National Air Pollutant Emission Estimates, 1900-1993, EPA-454/R-94-027, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC
27711, October 1994.
22. Federal Register, November 6, 1991.
23. Federal Register, February 3, 1994.
24. 1991 Toxics Release Inventory, EPA-745-R-93-003, U.S. Environmental Protection Agency, Office
of Pollution Prevention and Toxics, Washington, D.C. 20460, May 1993.
25. 1992 Toxics Release Inventory, EPA 745-R-94-001, U.S. Environmental Protection Agency, Office
of Pollution Prevention and Toxics, Washington, D.C. 20460, April 1994.
Chapter 1: Executive Summary • 17
-------
18 • Chapter 1: Executive Summary
-------
Chapter 2: Methodology
This report focuses on 10-year
(1984-93) national air quality trends
for each of the major pollutants estab-
lished by the National Ambient Air
Quality Standards (NAAQS). This
chapter presents many of the technical
details involved in these analyses.
Readers familiar with previous re-
ports may prefer initially to proceed
directly to the remaining sections.
The national analyses are comple-
mented in Chapter 6 with air quality
trends of specific metropolitan areas,
and in Chapter 7 with a perspective
on international air pollution.
The air quality trends statistics
displayed for a particular pollutant in
this report are closely related to
pollutant-specific NAAQS. Trends in
other air quality indicators are also
discussed for some pollutants.
NAAQS are currently in place for the
following six pollutants: carbon mon-
oxide (CO), lead (Pb), nitrogen diox-
ide (NO2), ozone (O3), particulate
matter whose aerodynamic size is
equal to or less than 10 microns (PM-
10), and sulfur dioxide (SO2). There
are two types of standards: primary
and secondary. Primary standards
protect against adverse health effects,
whereas secondary standards protect
against welfare effects like damage to
crops, vegetation, and buildings.
Table 2-1 lists the NAAQS for each
pollutant in terms of the level of the
standard and the averaging time that
Table 2-1. National Ambient Air Quality Standards (NAAQS) in Effect in 1993
Pollutant
Primary
(Health Related)
Secondary
(Welfare Related)
Type of
Average
CO
Pb
N02
03
PM-10
S02
8-houi*
1-houi*
Maximum
Quarterly
Average
Annual
Arithmetic
Mean
Maximum
Daily
1-hour
Average0
Annual
Arithmetic
Mean"
24-hourd
Annual
Arithmetic
Mean
24-hour"
Standard Level Type of Standard Level
Concentration' Average Concentration
9ppm
(10 mg/m3)
35ppm
(40 mg/m3)
1.5 |jg/m3
0.053 ppm
(100 Mg/m3)
0.12 ppm
(235 M9/m3)
50 Mg/m3
150 Mg/m3
80 pg/m3
(0.03 ppm)
365 Mg/m3
0.14 ppm
No Secondary Standard
No Secondary Standard
Same as Primary Standard
Same as Primary Standard
Same as Primary Standard
Same as Primary Standard
Same as Primary Standard
3-houi* 1300 M9/m3
(0.50 ppm)
• Parenthetical value is an approximately equivalent concentration.
b Not to be exceeded more than once per year.
c The standard is attained when the expected number of days per calendar year with maximum hourly average con-
centrations above 0.12 ppm is equal to or less than one, as determined according to Appendix H of the Ozone NAAQS.
" Particulate standards use PM-10 (particles less than 1Ou in diameter) as the indicator pollutant. The annual stan-
dard is attained when the expected annual arithmetic mean concentration is less than or equal to 50 ug/m3; the
24-hour standard is attained when the expected number of days per calendar year above 150 pg/m3 is equal to or
less than one; as determined according to Appendix K of the PM NAAQS.
Chapter 2: Background • 19
-------
Section 2.1 Air Quality Data Base
the standard represents. Some pollut-
ants (PM-10 and SO2) have standards
for both long-term (annual average)
and short-term (24-hour or less) aver-
aging times. The short-term stan-
dards are designed to protect against
acute, or short-term health effects,
while the long-term standards were
established to protect against chronic
health effects.
It is important to note that the dis-
cussion of ozone in this report refers
to ground level (tropospheric) ozone
and not to stratospheric ozone. Strato-
spheric ozone, which is miles above
the earth, provides a protective screen
from the sun's ultraviolet rays.
Ground level ozone, which is in the
air we breathe, can cause health and
environmental concerns. It also is the
primary ingredient of smog.
The ambient air quality data pre-
sented in this report were obtained
from EPA's Aerometric Information
Retrieval System (AIRS). These are
actual direct measurements of pollut-
ant concentrations at monitoring sta-
tions operated by state and local
governments throughout the nation.
EPA and other federal agencies oper-
ate some air quality monitoring sites
on a temporary basis as a part of air
pollution research studies. In 1993,
more than 4,400 monitoring sites re-
ported air quality data for one or more
of the six NAAQS pollutants to
AIRS. The vast majority of these
measurements represent the heavily
populated urban areas of the nation.
The national monitoring network
conforms to uniform criteria for moni-
tor siting, instrumentation, and qual-
ity assurance.1 Each monitoring site
is classified into one of three specific
categories. National Air Monitoring
Stations (NAMS) were established to
ensure a long-term national network
for urban area-oriented ambient
monitoring and to provide a system-
atic, consistent data base for air qual-
ity comparisons and trends analysis.
The State and Local Air Monitoring
Stations (SLAMS) allow state or lo-
cal governments to develop networks
tailored for their immediate monitor-
ing needs. Special Purpose Monitors
(SPMs) fulfill very specific or short-
term monitoring goals. Often SPMs
are used as source-oriented monitors
rather than monitors which reflect the
overall urban air quality. Data from
all three types of monitoring sites are
presented in this report.
2.1 Air Quality Data
Base
Monitoring sites are included in the
national 10-year trend analysis if they
have complete data for at least eight
of the 10 years 1984 to 1993. For
regional comparisons, the site had to
report data in each of the last three
years to be included in the analysis.
Data for each year had to satisfy an-
nual data completeness criteria appro-
priate to pollutant and measurement
methodology. Table 2-2 displays the
number of sites meeting the 10-year
trend completeness criteria. For PM-
10, whose monitoring network has
just been initiated over the last few
years, analyses are based on sites
with data in five of the six years dur-
ing the 1988-93 period.
The air quality data are divided
into two major groupings: 24-hour
measurements and continuous one-
hour measurements. The 24-hour
measurements are obtained from
monitoring instruments that produce
one measurement per 24-hour period.
They typically operate on a system-
atic sampling schedule of once every
six days, or 61 samples per year.
Such instruments are used to measure
PM-lOandPb. More frequent sam-
pling of PM-10 such as every other
day, or every day, is also common.
Only PM-10 weighted annual arith-
metic means that met the AIRS an-
nual summary criteria were selected
as valid means for trends purposes.2
The 24-hour Pb data were required to
have at least six samples per quarter
in at least three of the four calendar
quarters. Monthly composite Pb data
were used if at least two monthly
samples were available for at least
three of the four calendar quarters.
One-hour data are obtained from
continuously operating monitoring in-
struments that produce a measure-
ment every hour. This gives a
possible total of 8,760 hourly mea-
surements in a year. For continuous
hourly data, a valid annual mean for
trends requires at least 4,380 hourly
observations. The SO2 standard-re-
lated daily statistics required 183 or
more daily values. Because of the
different selection criteria, the number
of sites used to produce daily SO2 sta-
tistics may differ slightly from the
number of sites used to produce an-
nual SO2 statistics. Ozone sites met
the annual trends data completeness
requirement if they had at least 50
percent of the daily data available for
the ozone season, which typically
varies by state.3
The use of a moving 10-year win-
dow for trends yields a data base that
is more consistent with the current
monitoring network and also reflects
the period following promulgation of
uniform monitoring requirements. In
addition, this procedure increases the
total number of trend sites for the
10-year period relative to the data
bases used in the last annual report.4
2.2 Air Quality Trend
Statistics
The air quality statistics presented in
this report relate to the pollutant-spe-
cific NAAQS and comply with rec-
ommendations of the Intra-Agency
Task Force on Air Quality Indica-
tors.5 Although not directly related to
the NAAQS, more robust air quality
indicators are presented for some pol-
lutants to provide a consistency
check.
A composite average of each of
the trend statistics is used in the
graphical presentations that follow.
20 • Chapter 2: Background
-------
Section 2.2 Air Quality Trend Statistics
All sites are weighted equally in cal-
culating the composite average trend
statistic. Missing annual summary
statistics for the second through ninth
years for a site are estimated by linear
interpolation from the nearest years.
Missing end points are replaced with
the nearest valid year of data. There-
suiting data sets are statistically bal-
anced, allowing simple statistical
procedures and graphics to be easily
applied. This procedure is conserva-
tive since end-point rates of change
are dampened by the interpolated es-
timates.
This report uses statistical confi-
dence intervals around composite av-
erages to make comparisons between
years. If the confidence intervals for
any two years do not overlap, then the
composite averages of the two years
are significantly different. Ninety-
five percent confidence intervals for
composite averages of annual means
and of second maxima are calculated
from a two-way analysis of variance,
followed by an application of the
Tukey studentized range.6 The confi-
dence intervals for composite aver-
ages of estimated exceedances are
calculated by fitting Poisson distribu-
tions7 to the exceedances each year,
and then by applying the Bonferroni
multiple comparisons procedure.8
The utilization of these procedures is
explained elsewhere.9-10
Boxplots" are used to present air
quality trends because they have the
advantage of portraying several fea-
tures of the data simultaneously. Fig-
ure 2-1 illustrates the use of this
technique by presenting the percen-
tiles of the data as well as the com-
posite average. For example, 90
percent of the sites have concentra-
tions equal to or lower than the 90th
percentile.
Bar graphs are introduced for re-
gional comparisons with three-year
trend data. These comparisons are
based on the 10 EPA regions (Figure
2-2). The composite averages of the
appropriate air quality statistic of
Table 2-2. Number of Monitoring Sites
Pollutants
1993
Number of
Sites Reporting
1984-93
Number of
Trend Sites
CO
537
314
Pb
430
204
N0
377
201
925
532
PM-10
1508
799*
S02
692
474
Total
4469
2524
'Number of Trend Sites in 1988-93
95th PERCENTILE
90th PERCENTILE
X-*-
75th PERCENTILE
COMPOSITE AVERAGE
MEDIAN
25th PERCENTILE
10th PERCENTILE
5th PERCENTILE
Figure 2-1. Illustration of plotting convention of boxplots.
Chapter 2: Background • 21
-------
Section 2.3 Emission Estimates Methodology
1991,1992, and 1993 are presented.
The approach is simple, allowing the
reader, at a glance, to compare the
short-term changes in all 10 EPA re-
gions.
2.3 Emission
Estimates
Methodology
Trends are also presented for annual
nationwide emissions of CO, Pb, ni-
trogen oxides (NOJ, volatile organic
compounds (VOCs), PM-10, and sul-
fur oxides (SOX). These are estimates
of both the amount and kinds of pollu-
tion being emitted by automobiles,
factories, and other sources based on
best available engineering calcula-
tions. Because of changes in the
methodology used to obtain these
emissions estimates since last year,
these estimates have been recomputed
for each year. Thus, comparison of
the estimates for 1993 in this report
with earlier years in previous reports
is not appropriate. Also, the 1990 to
1993 emission estimates are prelimi-
nary, and may be revised in the next
annual report.
Changes have been made in the
emissions methodology. Updated
methodologies developed for Clean
Air Act modeling requirements are
used for the 1985 through 1993 emis-
sion estimates. The trends methodol-
ogy from previous trends reports is
used for the 1940 through 1984 pe-
riod. This difference will not be a
factor after this report since the 10-
year trends time period will begin in
post 1984.
Changes since last year include
use of the MOBILESa model, includ-
ing a version of the model specific to
California used to estimate highway
vehicle emissions. State and county
level estimates for vehicle miles trav-
elled (VMT) mix, in-use Reid vapor
pressure (RVP), oxygenated fuels,
and inspection/maintenance (I/M)
programs were updated. Updates
were made to the estimates of forest
fire emissions that are included in the
miscellaneous category. Also, the
methodology for PM-10 emissions
estimates has been revised since last
year. PM-10 emissions for 1985 to
the present are based on a 1990
county-level emission inventory
newly developed using methods simi-
lar to those developed for Clean Air
Act modeling requirements. Years
prior to and following 1990 were
backcast and forecast using economic
growth factors for most source cat-
egories. Some additional differences
arise from changing the source of
growth factors between 1991 and
1992.
All of these changes are part of a
broad effort to update and improve
emission estimates. Any significant
impacts from these changes in meth-
odology on emission estimates are de-
scribed in the individual pollutant
sections that follow in Chapter 3. For
more detailed information, the reader
should refer to a companion EPA pub-
lication, National A ir Pollutant Emis-
sion Trends, 1900-1993.12
9 0
Figure 2-2. Ten Regions of the U.S. Environmental Protection
22 • Chapter 2: Background
-------
Section 2.4 References
2.4 References
1. Ambient Air Quality Surveillance, 44 CFR 27558, May 10, 1979.
2. Aerometric Information Retrieval System (AIRS), Volume 2, U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park, NC, October 1993.
3. Ambient Air Quality Surveillance, 51 FR 9597, March 19, 1986.
4. National Air Quality and Emissions Trends Report, *1992, EPA-450/R-93-031, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
October 1993.
5. U.S. Environmental Protection Agency Infra-Agency Task Force Report on Air Quality Indicators,
EPA-450/4-81-015, U.S. Environmental Protection Agency, Office of Air Quality Planning and
Standards, Research Triangle Park, NC, February 1981.
6. B. J. Winer, Statistical Principles in Experimental Design, McGraw-Hill, NY, 1971.
7. N. L. Johnson and S. Kotz, Discrete Distributions, Wiley, NY, 1969.
8. R. G. Miller, Jr., Simultaneous Statistical Inference, Springer-Verlag, NY, 1981.
9. A. K. Pollack, 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.
10. A. K. Pollack and W. F. Hunt, Jr., "Analysis of Trends and Variability in Extreme and Annual
Average Sulfur Dioxide Concentrations," presented at the Air Pollution Control Association,
American Society for Quality Control Specialty Conference on Quality Assurance in Air Pollution
Measurements, Boulder, CO, 1985.
11. J. W. Tukey, Exploratory Data Analysis, Addison-Wesley Publishing Company, Reading, MA,
1977.
12. National Air Pollutant Emission Estimates, 1900-1993, EPA-454/R-94-027, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
October 1994.
Chapter 2: Background • 23
-------
24 • Chapter 2: Background
-------
Chapter 3: National and Regional
Trends in NAAQS
Pollutants
EPA has set National Ambient Air
Quality Standards (NAAQS) for six
pollutants considered harmful to
public health: carbon monoxide (CO),
lead (Pb), nitrogen dioxide (NO2),
ozone (O3), particulate matter (PM-
10), and sulfur dioxide (SO2). This
chapter focuses on both the 10-year
(1984-93) trends and the recent
changes in air quality and emissions
for the six NAAQS pollutants.
Changes since 1992, comparisons be-
tween all the trend sites, and the sub-
set of National Air Monitoring
Stations (NAMS) are highlighted.
The NAMS were established to pro-
vide a national network of monitoring
sites that could provide data for na-
tional trends and air quality assess-
ments. The primary objective for the
NAMS is to monitor areas where the
pollutant concentrations and popula-
tion exposures are expected to be
highest with respect to the NAAQS.
Trends are examined for both the na-
tion and the 10 EPA regions. This
chapter also presents a section on vis-
ibility, a topic related to several of the
NAAQS pollutants.
As in previous reports, the air
quality trends are presented by using
trend lines, confidence intervals, box-
plots, and bar graphs. See Chapter 2,
Section 2.2 for a detailed description
of confidence intervals and boxplot
procedures.
These long-term trends have em-
phasized air quality statistics that are
closely related to the NAAQS. For
many pollutants this tends to place an
emphasis on peak levels since these
levels are associated with the health
effects of concern. While these peak
summary statistics may be more
readily understood with respect to the
NAAQS, there is concern that they
may be too variable to be used as
trend indicators. This issue was ad-
dressed in an earlier report in re-
sponse to concerns raised about O3
trend indicators by a National Acad-
emy of Sciences (NAS) report.1 The
concern was whether trend results us-
ing a peak value type of summary sta-
tistic, such as the annual second
maximum, could be overly influenced
by data from just a few days and not
necessarily be representative of an
"overall" trend. Trends in alternative
summary statistics were compared
with the peak statistics to see if there
were sufficient differences to warrant
concern. As an example of alterna-
tive trends indicators, the NAS report
cited earlier EPA analyses which used
a comparison of different percentiles
and maximum values.2-3 The concen-
tration percentiles are statistically ro-
bust, in the sense that they are less
affected by a few extreme values.
Trends in various alternative CO, O3,
and NO2 summary statistics were
similar, however, there was a ten-
dency to show less percent improve-
ment (become flatter) for the lower
percentile indicators.4
Trends are also presented for
annual nationwide emissions of CO,
Pb, nitrogen oxides (NOX), volatile
organic compounds (VOCs), PM-10,
and sulfur oxides (SOX). These emis-
sions data are estimated using best
available engineering calculations.
The reader should refer to a compan-
ion report for a detailed description of
emission trends, source categories
and estimation procedures.5 Because
of changes in the methodology used to
obtain these emissions estimates since
last year, the estimates have been re-
computed for each year. Thus, com-
parison of the 1993 emission
estimates in this report to earlier years
in previous reports is not appropriate.
There have been changes in the emis-
sions methodology as discussed in
Chapter 2.
Because of changes that have
occurred in ambient monitoring
measurement methodology and the
change over time in the geographical
distribution of monitors, it is difficult
to provide ambient trends going back
more than 10 years. It is important,
however, not to overlook some of the
earlier control efforts in the air pollu-
tion field. While the ambient moni-
toring trends and the emission trends
Chapter 3: National and Regional Trends in NAAQS Pollutants • 25
-------
can be viewed as independent assess-
ments of underlying pollutant trends,
the emission estimates can also be
used to provide information on longer
time periods. Figure 3-1 provides a
convenient summary of the 1970-93
emission changes for all six NAAQS
pollutants. Pb emissions clearly re-
corded the most impressive decrease
of 98 percent but improvements are
also seen for emissions of PM-10 (-78
percent), SOX (-30 percent), CO (-24
percent), and VOCs (-24 percent).
Only NOX emissions showed an in-
crease (14 percent) between 1970 and
1993 levels. It is important to realize
that these reductions occurred even
with an increase in vehicle miles trav-
eled and industrial output.
This chapter covers the six criteria
pollutants which have NAAQS. The
chapter which follows focuses on the
189 air toxic pollutants established in
the 1990 Clean Air Act Amendments.
One program within EPA cuts across
both sets of air pollutants—the Permit
Program.
Title V of the 1990 Clean Air Act
Amendments requires states to de-
velop operating permit programs and
then submit them to EPA for ap-
proval. These operating permit pro-
grams require each major stationary
source (there are approximately
35,000 major sources) to obtain an
operating permit within one year of
the approval of the program by EPA.
An operating permit for a source will
describe each of the federally re-
quired air pollution control require-
ments that apply to the source. The
Act requires states to collect fees
from Title V sources to cover both the
direct and indirect costs of developing
and implementing the permit pro-
gram.
Since the Permit Program is still
in the initial stages of approving state
programs, there is not much to report
at this time. However, look to future
reports for information on the success
of this program.
140
120
100
80
60
40
20
0
MILLION SHORT TONS/YEAR
NOx
VOC
PM10
SOx
250
200
150
100
50
THOUSAND
SHORT TONS/YEAR
LEAD
1970 n 1993
Figure 3-1. Comparison of 1970 and 1993 national total emissions.
26 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.1 Trends in Carbon Monoxide
3.1 Trends in
Carbon Monoxide
Carbon monoxide (CO) is a colorless,
odorless and poisonous gas produced
by incomplete burning of carbon in
fuels. When CO enters the blood-
stream, it reduces the delivery of oxy-
gen to the body's organs and tissues.
Health threats are most serious for
those who suffer from cardiovascular
disease, particularly those with an-
gina or peripheral vascular disease.
Exposure to elevated CO levels can
cause impairment of visual percep-
tion, manual dexterity, learning abil-
ity, and performance of complex
tasks.
The NAAQS for ambient CO
specifies upper limits for both
one-hour and eight-hour averages that
are not to be exceeded more than once
per year. The one-hour level is 35
ppm, and the eight-hour level is nine
ppm. This trends analysis focuses on
eight-hour average results because the
eight-hour standard is generally a
more restrictive limit. Nationally,
there have not been any recorded
exceedances of the CO one-hour
NAAQS since 1990.
Trend sites were selected by using
the criteria presented in Chapter 2,
Section 2.1 which yielded a data base
of 314 sites for the 10-year 1984-93
period and a data base of 394 sites
for the three-year 1991-93 period.
Ninety-six NAMS sites were in-
cluded in the 10-year data base, and
115 in the three-year data base. Sev-
enty-seven percent of the nationwide
CO emissions are from transportation
sources. The largest emissions contri-
bution comes from highway motor
vehicles. Thus, the focus of CO
monitoring has been on traffic ori-
ented sites in urban areas where the
main source of CO is motor vehicle
exhaust. Other major CO sources are
wood-burning stoves, incinerators,
and industrial sources.
3.1.1 Long-term CO
Trends: 1984-1993
The 1984-93 composite national av-
erage trend is shown in Figure 3-2 for
the second highest non-overlapping
eight-hour CO concentration at 314
long-term trend sites. During this
10-year period, the national compos-
ite average of the annual second
highest eight-hour concentration de-
creased by 37 percent. The boxplot
presentation provides additional in-
formation on the year-to-year distri-
bution of ambient CO levels at these
long-term trend sites. The general
long-term improvement in ambient
CO levels is clear for all the percen-
tiles, but is especially notable at the
higher percentile concentrations. Al-
though not shown in Figure 3-2, the
composite average of the second high-
est non-overlapping eight-hour con-
centration at the subset of 96 NAMS
decreased by 35 percent. Nationally,
the median rate of improvement be-
tween 1984 and 1993 is four percent
per year for the 314 trend sites, as
well as for the subset of 96 NAMS.
Following the small upturn between
1985 and 1986, composite average
eight-hour CO levels have shown a
steady decline during the last seven
years. The regional median rates of
improvement varied from three to six
percent per year. The greatest im-
provement was seen in the Rocky
Mountain states with a decline in CO
levels of six percent per year. The
northeast states saw median rates of
decline of five percent per year, while
the Region 6 and 9 states recorded a
three percent per year decline in CO
levels. The 1993 composite average
15
CONCENTRATION, PPM
10-
5-
314 SITES
NAAQS
I I I I I I \\ \ \
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-2. Boxplot comparisons of trends in second highest non-overlapping
eight-hour average carbon monoxide concentrations at 314 sites,
1984-1993.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 27
-------
Section 3.1 Trends in Carbon Monoxide
is the lowest composite mean re-
corded since trends have been re-
ported, and is significantly lower than
the composite means for 1990 and
earlier years.
Figure 3-3 displays the 10-year
trend in the composite average of the
estimated number of NAAQS exceed-
ances of the eight-hour CO. This ex-
ceedance rate was adjusted to account
for incomplete sampling. The trend in
exceedances shows long-term im-
provement, but the rates of change are
much higher than those for the second
maximums. The composite average
of estimated exceedances decreased
97 percent between 1984 and 1993 at
the 314 long-term trend sites, while
the subset of 96 NAMS showed a 95-
percent decrease. These percentage
changes for exceedances are typically
much larger than those found for peak
concentrations due to the nature of the
exceedance statistic. The trend in an-
nual second maximum eight-hour val-
ues is more likely to reflect the change
in emission levels than the trend in
exceedances. For both curves, the
1993 composite average of the esti-
mated exceedances is significantly
lower than levels for 1990 and earlier
years. A tabulation of the composite
averages for the 314 trend sites and
the subset of 96 NAMS sites can be
found in the Data Appendix to this
report.
The 10-year 1984-93 trend in na-
tional CO emission estimates is
shown in Table 3-1. These estimates
show a 15-percent decrease in total
emissions between 1984 and 1993.
The estimates in this report differ
from those reported last year in sev-
eral ways. First, the MOBILESa
EST. 8-HR EXCEEDANCES
6-
2-
ALL SITES (314)
1 NAMS SITES (96)
T
T
T
T
T
T
T
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-3. National trend in the composite average of the estimated number of
exceedances of the eight-hour CO NAAQS, at both NAMS and all
sites with 95-percent confidence intervals, 1984-1993.
model was used to estimate highway
vehicle emissions, including revised
state and county level estimates for
vehicle miles traveled (VMT) mix,
in-use Reid Vapor Pressure (RVP),
oxygenated fuels, and inspection/
maintenance (I/M) programs. These
changes in methodology yielded
higher estimates for highway vehicle
CO emissions than reported last year.
For example, the revised highway ve-
hicle CO emissions estimate for 1984
is five percent higher, and the revised
estimate for 1992 emissions is eight
percent higher than reported previ-
ously. Updates were also made to the
estimates of forest fire emissions that
are included in the miscellaneous cat-
egory. These changes in methodology
and data updates yield a revised
emissions estimate for 1992 that is 11
percent higher than last year. The es-
timate for 1984 was revised upward
by only one percent. As a result of
these revised totals, the 10-year de-
cline in CO emissions is not as large
as reported last year.
28 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.1 Trends in Carbon Monoxide
Table 3-1 . National CO Emission Estimates, 1 984-1 993
(thousand short tons/year)
SOURCE
CATEGORY
Fuel Combustion -
Electric Utilities
Fuel Combustion -
Industrial
Fuel Combustion -
Other
Chemical and
Allied Product
Manufacturing
Metals Processing
Petroleum and
Related Industries
Other Industrial
Processes
Solvent Utilization
Storage and
Transport
Waste Disposal
and Recycling
Highway
Vehicles
Off-Highway
Natural Sources
Miscellaneous
Total
1984
316
732
6,760
2,082
1,734
383
908
0
0
2,028
78,881
13,427
0
7,011
114,262
1985
292
670
6,686
1,845
2,223
462
694
2
49
1,941
77,387
13,706
0
6,116
112,072
1986
291
650
6,571
1,853
2,079
451
715
2
51
1,916
73,347
13,984
0
6,161
108,070
1987
300
649
6,338
1,798
1,984
455
713
2
50
1,850
70,645
14,131
0
6,203
105,117
1988
313
669
6,172
1,917
2,101
441
711
2
56
1,806
71,081
14,500
0
6,332
106,100
1989
319
672
5,942
1,925
2,132
436
716
2
55
1,747
66,050
14,518
0
6,290
100,806
1990 1991
314 314
677 682
5,726 5,583
1,940 1,953
2,080 1,992
435 439
717 711
2 2
55 56
1,686 1,644
62,858 62,074
14,642 14,621
0 0
12,623 9,826
103,753 99,898
1992 1993
313 322
671 667
5,033 4,444
1,964 1,998
2,044 2,091
410 398
719 732
2 2
55 56
1,717 1,732
59,859 59,989
14,904 15,272
0 0
8,679 9,506
96,368 97,208
NOTE: The sums of sub-categories may not equal total due to rounding.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 29
-------
Section 3.1 Trends in Carbon Monoxide
Figure 3-4 contrasts the 10-year
increasing trend in vehicle miles trav-
eled (VMT) with the declining trend
in CO emissions from highway ve-
hicles. Emissions from highway ve-
hicles decreased 24 percent during the
1984-93 period, despite a 33-percent
increase in VMT.1 This indicates that
the Federal Motor Vehicle Control
Program (FMVCP) has been effective
on the national scale, with controls
more than offsetting growth during
this period.
While there is a general agree-
ment between the overall trends in air
quality and emissions, it is worth not-
ing that the emission changes reflect
estimated national totals, while ambi-
ent CO monitors are frequently lo-
cated to identify local problems. The
mix of vehicles and the change in
VMT in areas around specific CO
monitoring sites may differ from the
national averages.
Percent of 1984 Level
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Hwy CO Emissions Total VMT
Figure 3-4. Comparison of trends in total national VMT and national highway vehicle carbon monoxide emissions,
1984-1993.
30 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.1 Trends in Carbon Monoxide
3.1.2 Recent CO Trends:
1991-1993
This section describes ambient CO
changes during the last three years
(1991, 1992 and 1993) at sites that
recorded data in all three years. Be-
tween 1991 and 1993, the composite
average of the second highest
non-overlapping eight-hour average
CO concentration at 394 sites de-
creased by 12 percent, and decreased
by seven percent at 115 NAMS sites.
Between 1991 and 1993, the compos-
ite average of the estimated number of
exceedances of the eight-hour CO
NAAQS decreased by 55 percent at
the 394 trend sites and 63 percent at
the subset of 115 NAMS sites. Dur-
ing 1992 and 1993, the composite av-
erage of the second highest non-over-
lapping eight-hour average CO
concentration at the 394 trends sites
decreased five percent and the com-
posite number of estimated exceed-
ances decreased by 14 percent.
Estimated nationwide CO emissions
increased one percent between 1992
and 1993. The increase in CO emis-
sions between 1992 and 1993 can be
largely attributed to three sources:
highway vehicles (+2 percent), off-
highway (+2 percent), and wildfires
(+10 percent). The latter two catego-
ries typically do not impact urban CO
levels. These recent changes in emis-
sions should be viewed with caution
as the 1990 through 1993 emission
estimates are preliminary and subject
to revision in subsequent reports.
Figure 3-5 shows the composite
regional averages for the 1991-93
time period. Eight of the 10 regions
had 1993 composite mean levels that
were less than the corresponding
1991 and 1992 values. Increases in
composite mean CO levels were seen
in Regions 4 and 6. These regional
graphs are intended primarily to de-
pict relative change. Because the mix
of monitoring sites may vary from one
area to another, this graph is not in-
tended to indicate regional differences
in concentration levels.
12
CONCENTRATION, PPM
10-
8-
6-
4-
COMPOSITE AVERAGE
• 1991 E3 1992 l=l 1993
EPA REGION I
NO. OF SITES 24
Figure 3-5. Regional comparisons of 1991,1992, and 1993 composite averages of the second highest non-overlapping
eight-hour average carbon monoxide concentrations.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 31
-------
Section 3.2 Trends in Lead
3.2 Trends in Lead
Exposure to Pb can occur through
multiple pathways, including inhala-
tion of air and ingestion of Pb in food,
water, soil, or dust. Excessive Pb ex-
posure can cause seizures, mental re-
tardation and/or behavioral disorders.
A recent National Health and Nutri-
tion Examination Survey reported a
78-percent decrease in blood lead lev-
els from 12.8 to 2.8 ug/dL between
1976 and 1980 and from 1988 to
1991.6 This dramatic decline can be
attributed to the reduction of leaded
gasoline and to the removal of lead
from soldered cans. Although this
study shows great progress, infants
and young children are especially sus-
ceptible to low doses of Pb, and this
age group still shows the highest lev-
els.6 Low doses of Pb can lead to
central nervous system damage. Re-
cent studies have also shown that Pb
may be a factor in high blood pressure
and in subsequent heart disease in
middle-aged white males.
Lead (Pb) gasoline additives, non-
ferrous smelters, and battery plants
are the most significant contributors
to atmospheric Pb emissions. In 1993
transportation sources contributed 33
percent of the annual emissions, down
substantially from 81 percent in 1985.
Total Pb emissions from all sources
dropped from 20,100 tons in 1985 to
4,900 tons in 1993. The decrease in
Pb emissions from highway vehicles
accounts for essentially all of this de-
cline. The reasons for the decrease
are noted below.
Two air pollution control pro-
grams implemented by EPA before
promulgation of the Pb standard7 in
October 1978 have resulted in lower
ambient Pb levels. First, regulations
issued in the early 1970s required
gradual reduction of the Pb content of
all gasoline over a period of many
years. The Pb content of the leaded
gasoline pool was reduced from an
average of 1.0 gram/gallon, to 0.5
gram/gallon on July 1,1985, and still
further to 0.1 gram/gallon on January
1, 1986. Second, as part of EPA's
overall automotive emission control
program, unleaded gasoline was in-
troduced in 1975 for automobiles
equipped with catalytic control de-
vices. These devices reduce emis-
sions of CO, VOCs and NOX. In
1993, unleaded gasoline sales ac-
counted for 99 percent of the total
gasoline market. In contrast, the un-
leaded share of the gasoline market in
1984 was approximately 60 percent.
These programs have essentially
eliminated violations of the Pb stan-
dard in urban areas except those areas
with Pb point sources.
Programs are also in place to con-
trol Pb emissions from stationary
point sources. Lead emissions from
stationary sources have been substan-
tially reduced by control programs
oriented toward attainment of the
PM-10 and Pb ambient standards.
However, significant ambient prob-
lems still remain around some Pb
point sources, which are now the fo-
cus of new monitoring initiatives. Pb
emissions in 1993 from industrial
sources, e.g., primary and secondary
Pb smelters, dropped by about 91 per-
cent from levels reported in 1970.
Emissions of Pb from solid waste dis-
posal are down about 76 percent since
1970. In 1993, emissions from solid
waste disposal, industrial processes
and transportation were: 500,2,300,
and 1,600 short tons, respectively.
The overall effect of the control pro-
grams for these three categories has
been a major reduction in the amount
of Pb in the ambient air. Additional
reductions in Pb are anticipated as a
result of the Agency's Multimedia
Lead Strategy issued in February,
1991.8 The goal of the Lead Strategy
is to reduce Pb exposures to the full-
est extent practicable.
Early trend analyses of ambient
Pb data were based almost exclu-
sively on National Air Surveillance
Network (NASN) sites.9-10 These
sites were established in the 1960s to
monitor ambient air quality levels of
total suspended particulate (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 regula-
tions were promulgated, which estab-
lished the current monitoring
network.11
3.2.1 Long-term Pb
Trends: 1984-1993
As with other pollutants, the sites se-
lected for long-term trend analysis
had to satisfy annual data complete-
ness criteria of at least eight out of 10
years of data in the 1984 to 1993 pe-
riod. A year was included as "valid"
if at least three of the four quarterly
averages were available. As in the
1992 report, composite Pb data, i.e.,
individual 24-hour observations
composited by month or quarter and
measured by a single analysis, were
used in the trend analysis. Twenty-
two sites qualified for the 10-year
trend because of the additional com-
posite data.
A total of 204 urban-oriented sites
from 37 states and Puerto Rico met
the data completeness criteria.
Eighty-eight of these sites were
NAMS—the largest number of Pb
NAMS sites to qualify for the 10-year
trends. Twenty-six (13 percent) of
the 204 trend sites were located in
California. However, the Pb trend at
the California sites was identical to
the trend at the non-California sites.
Therefore, these sites did not distort
the overall trends. Other states with
10 or more trend sites included: Texas
(17), Illinois (16), Kansas (15), Ohio
(14), Pennsylvania (11), and Michi-
gan (10). Again, the Pb trend in each
of these states was very similar to the
national trend. Sites that were located
near Pb point sources, such as pri-
mary and secondary Pb smelters,
were excluded from the urban trend
analysis because the increased levels
32 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.2 Trends in Lead
at these sources could mask the un-
derlying urban trends. Trends at Pb
point-source oriented sites are dis-
cussed later in this section.
The means of (he composite maxi-
mum quarterly averages show an 89-
percent decrease (1984-93) at 204
urban-oriented sites in Figure 3-6.
The boxplot comparison in this figure
also shows dramatic improvement in
ambient Pb concentrations over the
entire distribution of trend sites.
Since 1984, the maximum quarterly
Pb averages and most of the percen-
tiles show a monotonically decreasing
pattern. The 204 urban-oriented sites
that qualified for the 1984-93 period
is almost the same number of sites
(203) that qualified for 1983-92.
Pb emissions over this 10-year
period also decreased. There was an
88-percent decrease in total Pb emis-
sions and a 96-percent decrease in
Pb emissions from transportation
sources.
Figure 3-7 shows the trend in av-
erage Pb concentrations for the
urban-oriented sites and for 66
point-source oriented sites that also
met the 10-year data completeness
criteria. Composite average ambient
Pb concentrations at the point-source
oriented sites located near industrial
sources of Pb, e.g., smelters and bat-
tery plants, improved 63 percent
compared to 89 percent at the urban-
oriented sites. The average at the
point-source oriented sites dropped in
magnitude from 1.5 to 0.6 ug/m3, a
0.9 ug/m3 difference, whereas the av-
erage at the urban sites dropped from
0.4 to 0.05 ug/m3. The improvement
at point-source oriented sites reflects
both industrial and automotive Pb
emission controls. However, some
industrial source reductions are due to
plant shutdowns. There are still sev-
eral urban areas where significant Pb
problems persist. The six Metropoli-
tan Statistical Areas (MSAs) shown
CONCENTRATION, UG/M3
I I I I I
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-6. Boxplot comparisons of trends in maximum quarterly average lead
concentrations at 204 sites, 1984-1993.
in Table 5-3 that are above the Pb
NAAQS in 1993 are all due to Pb
point sources. These MSAs are:
• Cleveland, OH;
• Indianapolis, IN;
• Memphis, TN-AL-MS;
• Omaha, NE-IA;
• Philadelphia, PA-NJ; and
• St Louis, MO-IL.
None of the monitoring sites re-
sponsible for 1993 Pb concentrations
above the NAAQS had sufficient his-
torical data to be included in the
point-source oriented trends discussed
above. The sites in these MSAs that
recorded Pb concentrations above the
NAAQS were sites situated near the
Pb point sources listed in EPA's Lead
Strategy. This strategy has an in-
creased target of 30 primary or sec-
ondary Pb smelters and three other
stationary sources for more intensive
Pb monitoring.
The map in Figure 3-8 shows the
highest quarterly average Pb concen-
trations that were recorded during
1993 in the vicinity of these sources.
At present, various types of enforce-
ment and/or regulatory actions are
being actively pursued by EPA, with
State involvement, for all Pb point
sources that have reported Pb levels
above the NAAQS. This is especially
the case, as indicated on the map in
Figure 3-8, where exceptionally high
Pb levels have been reported. The Pb
sources that reported the highest 1993
quarterly Pb averages in ug/m3 in-
clude: ASARCO Glover (23.59),
Master Metals (16.13), and Franklin
Smelting (11.23). Although signifi-
cant problems still remain, as indi-
cated by the map, there have been
some success stories on point source
Pb problems. Two examples are
highlighted later in this section.
Table 3-2 summarizes the Pb
emissions data. The 1984-93 drop in
total Pb emissions was 88 percent.
Reduced Pb emissions in the transpor-
tation category account for most of
Chapter 3: National and Regional Trends in NAAQS Pollutants • 33
-------
Section 3.2 Trends in Lead
this drop. Pb emissions from the
other categories show only small
changes over the 1984-93 time pe-
riod. The percent decrease in total Pb
emissions (89 percent) is equivalent
to the change in the average ambient
Pb concentrations. The drop in Pb
consumption and subsequent Pb emis-
sions since 1984 was brought about
by the increased use of unleaded
gasi "ine in cars equipped with cata-
lytic control devices and the reduced
Pb content in leaded gasoline. There-
suits of these actions in 1993
amounted to a 76-percent reduction
nationwide in total Pb emissions from
1985 levels. As noted previously, un-
leaded gasoline represented 99 per-
cent of 1993 total gasoline sales.
Although the good agreement among
the trends for Pb consumption, emis-
sions, and ambient levels are based
upon a limited geographical sample,
they do indicate that ambient urban
Pb levels are responding to the drop in
Pb emissions.
CONCENTRATION, UG/M 3
1-
o.si
Point Source Sites (66) Urban Sites (204)
NAAQS
1984 1985 1986 1987 1988 1989 1990 1991
1992
1993
Figure 3-7. Comparison of national trends in the composite average of the
maximum quarterly average lead concentrations at urban and
point-source oriented sites, 1984-1993.
23.59
16.13
11.23
Figure 3-8. Maximum quarterly mean lead concentrations in the vicinity of lead point sources, 1993.
34 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.2 Trends in Lead
Table 3-2. National Pb Emission Estimates, 1 984-1 993
(short tons/year)
SOURCE
CATEGORY 1984
Fuel Combustion -
Electric Utilities 88
Fuel Combustion -
Industrial 29
Fuel Combustion -
Other 424
Chemical and
Allied Product 133
Manufacturing
Metals Processing 1,919
Petroleum and
Related Industries 0
Other Industrial
Processes 483
Solvent Utilization 0
Storage and
Transport 0
Waste Disposal
and Recycling 901
Highway
Vehicles 35,930
Off-Highway 2,310
Natural Sources 0
Miscellaneous 0
Total 42,217
1985
64
30
421
118
2,097
0
316
0
0
871
15,978
229
0
0
20,124
NOTE:
1986
69
25
422
108
1,820
0
199
0
0
844
3,589
219
0
0
7,296
1987
64
22
425
123
1,818
0
202
0
0
844
3,121
222
0
0
6,840
1988
66
19
426
136
1,917
0
172
0
0
817
2,700
211
0
0
6,464
1989 1990 1991
67 64 61
18 18 18
420 418 416
136 136 132
2,153 2,138 1,939
000
173 169 167
000
000
765 804 582
2,161 1,690 1,519
207 197 186
000
000
6,099 5,635 5,020
1992 1993
59 62
18 18
414 417
93 109
2,042 2,118
0 0
54 54
0 0
0 0
416 518
1,452 1,383
193 206
0 0
0 0
4,741 4,885
The sums of sub-categories may not equal total due to rounding.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 35
-------
Section 3.2 Trends in Lead
The 10-year trend at the 66 point-
source oriented sites shows a much
larger decline in Pb concentrations
(-63 percent) than did Pb emissions
from industrial processes (-10 per-
cent). Improvement in Pb concentra-
tions at point-source oriented sites
reflects improvement at a relatively
small number of Pb sources. The
emission figures for industrial pro-
cesses represent all industrial sources
in the nation. It is interesting to note
that the Pb emissions from industrial
processes are lowest in 1986 (2,127
short tons), but rise slightly to 2,281
short tons in 1993. On the other
hand, the trend in point-source ori-
ented sites shows a decline over this
period, although there is a small in-
crease in average Pb concentrations
in 1988.
3.2.2 Recent Pb Trends:
1991-1993
Ambient Pb trends were also studied
over the shorter period 1991-93. A
total of 228 urban sites from 37 states
met the data requirement that a site
have data from all three years. In re-
cent years, the number of Pb sites
have dropped because of the elimina-
tion of some TSP monitors from state
and local air monitoring programs.
Pb measurements were obtained from
the TSP filters. Some monitors were
eliminated because of the change in
the particulate matter standard from
TSP to PM-10, while others were dis-
continued because of the very low Pb
concentrations measured at or below
the minimum detectable level in many
urban locations. Although some fur-
ther attrition may occur, the core net-
work of NAMS Pb sites together with
supplementary state and local sites
should be sufficient to assess national
ambient Pb trends. The three-year
data base (1991-93) showed an im-
provement of 11 percent in composite
average urban Pb concentrations.
The 1991 and 1993 Pb averages,
however, were extremely low: 0.063
and 0.047 ng/m3 respectively. Be-
tween 1991 and 1993, total Pb emis-
sions decreased three percent and Pb
emissions from transportation sources
dropped seven percent. Most of this
decrease in total nationwide Pb emis-
sions was due once again to the de-
crease in automotive Pb emissions.
Even this larger group of sites was
disproportionately weighted by sites
in California, Texas, Illinois, Kansas,
Ohio, and Pennsylvania. These states
had about 47 percent of the 228 sites
represented. The percent changes in
1991-93 average Pb concentrations
for these six states, however, were
very similar to the percent change for
the remaining sites. Apparently, the
contributions of these sites did not
distort the national trends. Although
urban Pb concentrations continue to
decline consistently, there are indica-
tions that the rate of the decline has
slowed down. Clearly, in some areas
urban Pb levels are so low that further
improvements have become difficult.
Indeed, as will be shown later, all
sections of the country are showing
declines in average Pb concentrations.
Ninety-three point-source oriented
sites showed a 14-percent decline in
average Pb levels over the 1991-93
time period. Thus, Pb concentrations
near Pb point sources, unlike the ur-
ban sites which showed an 18-percent
decrease, have improved to a lesser
extent over the last three years. Pb
emissions from industrial processes
also did not change much during the
1991-93 period. As expected, the av-
erage Pb levels at the point-source ori-
ented sites are much higher here than
CONCENTRATION, UG/M3
1.4-
1.2-
1 -
0.8-
0.6-
0.4-
0.2-
COMPOSITE AVERAGE
• 1991 • 1992 O 1993
•^ fc In an
EPA REGION I II I" IV V VI VII VIII IX X
NO. OF SITES 17 11 33 27 48 28 17 8 34 5
Figure 3-9. Regional comparisons of the 1991,1992, and 1993 composite
average of the maximum quarterly average lead concentrations.
36 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.2 Trends in Lead
at the urban sites. The 1992 and 1993
Pb point source averages were 0.84
and 0.73 ug/m3, respectively.
For the 10-year time period, how-
ever, the largest single year drop in
average Pb concentrations (37 per-
cent) occurred as expected between
1985 and 1986, because of the reduc-
tion in the Pb content in leaded gaso-
line. The 1993 composite average Pb
concentrations showed the more mod-
est decline of 11 percent from 1992
levels, while total Pb emissions in-
creased by three percent. There has
been a three-percent decrease in esti-
mated Pb emissions for the transporta-
tion category between 1992 and 1993,
while VMT increased one percent be-
tween 1992 and 1993. The Pb emis-
sions trend is expected to continue
downward, but at a slower rate, pri-
marily because the leaded gasoline
market is almost gone. Some major
petroleum companies have discontin-
ued refining leaded gasoline because
of the dwindling market.
Figure 3-9 shows 1991,1992 and
1993 composite average Pb concen-
trations by EPA region. Once again,
the larger three-year data base of 228
sites was used for this comparison.
The number of sites varies dramati-
cally by region from five in Region
10, to 48 in Region 5. In all regions
except Region 2, there was a decrease
in average Pb urban concentrations
between 1991 and 1993. These re-
sults confirm that average Pb concen-
trations in urban areas are continuing
to decrease throughout the country.
This is exactly what is to be expected
since the national air pollution control
program is now fully in place for Pb.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 37
-------
Section 3.2 Trends in Lead
LEAD SUCCESS STORIES
facility (formerly Pacific
'
38 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.3 Trends in Nitrogen Dioxide
3.3 Trends in
Nitrogen Dioxide
Nitrogen dioxide (NO2) is a brown-
ish, highly reactive gas that is present
in all urban atmospheres. NO2 can ir-
ritate the lungs, cause bronchitis and
pneumonia, and lower resistance to
respiratory infections. Nitrogen ox-
ides are an important precursor both
to O3 and acid rain, and may affect
both terrestrial and aquatic ecosys-
tems. The major mechanism for the
formation of NO2 in the atmosphere is
the oxidation of the primary air pol-
lutant nitric oxide (NO). NOX plays a
major role, together with VOCs, in
the atmospheric reactions that pro-
duce O3. NOX forms when fuel is
burned at high temperatures. The two
major emissions sources are transpor-
tation and stationary fuel combustion
sources such as electric utility and in-
dustrial boilers.
NO2 is measured using a continu-
ous monitoring instrument that can
collect as many as 8,760 hourly ob-
servations per year. Only annual
means based on at least 4,380 hourly
observations were considered in the
trends analyses that follow. A total of
201 sites were selected for the
10-year period, and 269 sites were
selected for the three-year data base.
3.3.1 Long-term NO2
Trends: 1984-1993
Figure 3-10 uses boxplots to display
the long-term trend in the annual av-
erage NO2 concentration at 201 trend
sites. The 1993 composite average of
the NO2 mean concentrations at the
201 trend sites was at its lowest level
in the past 10 years, and was 12 per-
cent lower than the 1984 level. The
middle quartiles for the years 1984 to
1989 are similar, followed by a de-
crease in levels beginning in 1990.
The upper percentiles, which gener-
ally reflect NO2 annual mean levels in
the Los Angeles metropolitan area,
also show improvement during the
last four years. The lower percentiles
show little change. NO2 composite
average levels for each year from
1984 through 1989 are statistically
indistinguishable based on 95-percent
confidence intervals about the com-
posite means. The difference between
the 1993 and 1984 composite average
levels is statistically significant, how-
ever. This is the fifth consecutive
year of continued improvement in
NO2 levels.
Previous reports have shown that
the level of the NO2 composite means
varied by metropolitan area size, with
the larger areas recording the higher
concentration levels.12 NAMS sites
for N02 are located only in large ur-
ban areas with populations of one
million or greater. Thus, it is not sur-
prising that the composite averages of
the NAMS are higher than those of
the 201 trend sites. Although the
overall trends are similar for both sets
of sites, greater improvement has
been recorded at the 45 NAMS sites.
At the subset of NAMS sites the 1993
composite average of the NO2 annual
mean concentration is 14 percent
lower than the composite average in
1984, as compared to the 12-percent
improvement for the 201 trend sites.
This difference for the NAMS sites
also is statistically significant. The
composite averages for both the 201
trend sites and the subset of 45
NAMS sites are listed in the Data
Appendix.
Table 3-3 presents the trend in es-
timated nationwide emissions of NOX.
Total 1993 NOX emissions are one
percent higher than 1984 emissions.
Table 3-3 shows that the two primary
source categories of NOX emissions
are fuel combustion and transporta-
tion, composing 50 percent and 45
percent, of total 1993 NOX emissions,
respectively. While fuel combustion
emissions (primarily from coal-fired
electric utilities) are three percent
higher in 1993 than in 1984, NOX
emissions from highway vehicles de-
creased 11 percent during this 10-
hour period. The good agreement
between the ambient trends and the
changes in NOX emissions from high-
way vehicles is expected because the
population-oriented urban monitors
are more likely to reflect transporta-
tion impacts rather than power plant
emissions.
The emissions estimates in this
report have been recomputed using
the MOBILESa emissions factor
model and with updated inputs at the
state and county level. The revised
1984 estimate of total NOX emissions
is one percent higher than last year's
estimate, while the revised 1992 total
is one percent lower.
As noted in a recent report pre-
pared by the National Research
Council (NRC), state of the art air
quality models and improved knowl-
edge of the ambient concentrations of
VOCs and NOX indicate that NOX
control is necessary for effective re-
duction of ozone in many areas of the
United States.1 The NRC report rec-
ommended that to substantially re-
duce ozone in many urban/suburban/
rural areas of the United States, the
control of NOX emissions will prob-
ably be necessary in addition to, or
instead of, the control of VOCs. Re-
gional modeling studies performed
subsequent to the NRC report have
tended to confirm the need to control
NOX emissions to reduce ozone in
many areas. Thus, even though the
NO2 standard is currently being met
in all locations throughout the coun-
try, NOX emissions and their control
are important factors for addressing
the current widespread violations of
the ozone NAAQS.
3.3.2 Recent NO2 Trends:
1991-1993
Between 1992 and 1993, the compos-
ite annual mean NO2 concentration, at
269 sites with complete data during
Chapter 3: National and Regional Trends in NAAQS Pollutants • 39
-------
Section 3.3 Trends in Nitrogen Dioxide
the last three years, decreased two
percent. This followed a three-per-
cent decrease in the composite mean
between 1991 and 1992. At the sub-
set of 53 NAMS, the composite mean
concentration decreased three percent
between 1992 and 1993. Los Ange-
les, CA, which met the NO2 NAAQS
for the first time in 1992 continued to
show improvement in 1993. Nation-
wide emissions of NOX are estimated
to have increased two percent be-
tween 1992 and 1993. Approxi-
mately 76 percent of the increase in
NOX emissions between 1992 and
1993 is attributable to increased
emissions from coal fired electric
utilities. The remainder of the in-
crease in emissions this year is due to
increased emissions from off-highway
sources. Highway vehicle emissions
were unchanged between 1992 and
1993.
Regional trends in the composite
average NO2 concentrations for the
years 1991-93 are displayed by bar
graphs in Figure 3-11. Region 10,
which did not have any NO2 sites
with data in all three years is not
shown. Five of the nine regions had
1993 composite means that were lower
than 1991 levels, but higher than 1992
levels. Only Region 2 continued to
record progress in reducing NO2 levels
in each of the last two years. In con-
trast, the 1993 composite mean NO2
levels in Regions 4 and 5 were higher
than both the 1991 and 1992 means.
However, all of the annual means are
well below the level of the air quality
standard.
These regional graphs are in-
tended primarily to depict relative
change. Because the mix of monitor-
ing sites may vary from one area to
another, this graph is not intended to
indicate regional differences in abso-
lute concentration levels.
0.06
CONCENTRATION, PPM
0.05 -
0.04-
0.03
0.02 -
0.01 -
0.00
201 SITES
NAAQS
I
I
I I I I I I I I I
1984 1985 1986 1987 1988 1989 1990 1991 1992
Figure 3-10. Boxplot comparisons of trends in annual mean nitrogen
concentrations at 201 sites, 1984-1993.
I
1993
dioxide
40 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.3 Trends in Nitrogen Dioxide
Table 3-3. National NOX Emission Estimates, 1 984-1 993
(thousand short tons/year)
SOURCE
CATEGORY 1984
Fuel Combustion -
Electric Utilities 7,268
Fuel Combustion -
Industrial 3,415
Fuel Combustion -
Other 670
Chemical and
Allied Product 161
Manufacturing
Metals Processing 54
Petroleum and
Related Industries 70
Other Industrial
Processes 203
Solvent Utilization 0
Storage and
Transport 0
Waste Disposal
and Recycling 90
Highway
Vehicles 8,387
Off-Highway 2,644
Natural Sources 0
Miscellaneous 210
Total 23,172
1985 1986
6,916 6,909
3,209 3,065
701 694
374 381
87 80
124 109
327 328
2 3
2 2
87 87
8,089 7,773
2,734 2,777
0 0
201 202
22,853 22,409
1987
7,128
3,063
710
371
76
101
320
3
2
85
7,662
2,664
0
203
22,386
1988
7,530
3,187
737
398
82
100
315
3
2
85
7,661
2,914
0
206
23,221
1989
7,607
3,209
730
395
83
97
311
3
2
84
7,682
2,844
0
205
23,250
1990 1991 1992
7,516 7,482 7,473
3,256 3,309 3,206
732 745 735
399 401 411
81 79 80
100 103 96
306 298 305
223
223
82 81 83
7,488 7,373 7,440
2,843 2,796 2,885
000
384 305 272
23,192 22,977 22,991
1993
7,782
3,176
732
414
82
95
314
3
3
84
7,437
2,986
0
296
23,402
NOTE: The sums of sub-categories may not equal total due to rounding.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 41
-------
Section 3.3 Trends in Nitrogen Dioxide
0.040
CONCENTRATION, PPM
COMPOSITE AVERAGE
• 1991 • 1992 O 1993
EPA REGION I II HI IV V VI VII VIII IX
NO. OF SITES 18 12 37 26 28 26 12 12 98
Figure 3-11. Regional comparisons of 1991,1992, and 1993 composite averages
of the annual mean nitrogen dioxide concentrations.
42 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.4 Trends in Ozone
3.4 Trends in Ozone
Ozone (O3) is a photochemical oxi-
dant and the major component of
smog. While O3 in the upper atmo-
sphere is beneficial to life by shield-
ing the earth from harmful ultraviolet
radiation from the sun, high concen-
trations of 03 at ground level are a
major health and environmental con-
cern. O3 is not emitted directly into
the air but is formed through complex
chemical reactions between precursor
emissions of VOCs and NOX in the
presence of sunlight. These reactions
are stimulated by sunlight and tem-
perature so that peak O3 levels occur
typically during the warmer times of
the year. Both VOCs and NOX are
emitted by transportation and indus-
trial sources. VOCs are emitted from
sources as diverse as autos, chemical
manufacturing and dry cleaners, paint
shops, and other sources using sol-
vents. NOX emissions also were dis-
cussed in the previous section.
The reactivity of O3 causes health
problems because it damages lung tis-
sue, reduces lung function, and sensi-
tizes the lungs to other irritants.
Scientific evidence indicates that am-
bient levels of O3 not only affect
people with impaired respiratory sys-
tems, such as asthmatics, but healthy
adults and children as well. Exposure
to O3 for several hours at relatively
low concentrations has been found to
significantly reduce lung function and
induce respiratory inflammation in
normal, healthy people during exer-
cise. This decrease in lung function
generally is accompanied by symp-
toms including chest pain, coughing,
sneezing and pulmonary congestion.
The O3 NAAQS is defined in
terms of the daily maximum, that is,
the highest hourly average for the day,
and it specifies that the expected num-
ber 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 dur-
ing the O3 season are considered in
this analysis. The strong seasonality
of O3 levels makes it possible for ar-
eas to limit their O3 monitoring to a
certain portion of the year, termed the
O3 season. Peak O3 concentrations
typically occur during hot, dry, stag-
nant summertime conditions, i.e., high
temperature and strong solar insola-
tion.13-14 The length of the O3 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. Northern states have shorter O3
seasons e.g., May through September
for North Dakota. This analysis uses
these O3 seasons to ensure that the
data completeness requirements apply
to the relevant portions of the year.
There are 532 sites in the
1984-93 long-term trends data base,
and 722 sites with data in each of the
last three years, 1991-93. The
NAMS compose 197 of the long-term
trends sites and 220 of the sites in the
three-year data base.
3.4.1 Long-term O3
Trends: 1984-1993
Figure 3-12 displays the 10-year
composite average and the inter-site
variability of the annual second high-
est daily maximum one-hour concen-
tration during the O3 season at 532
trend sites. The 1993 composite aver-
age for these sites is 12 percent lower
than the 1984 level, and 9 percent
lower for the subset of 197 NAMS.
The 1993 composite average is higher
than the 1992 level, which was the
lowest composite average of the past
10 years. However, the 1993 com-
posite average is still the second low-
est level during the past 10 years.
The distribution of second daily maxi-
mum one-hour concentrations in 1992
0.25
CONCENTRATION, PPM
0.20-
0.15-
0.10
0.05-
0.00
532 SITES
F T I
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-12. Boxplot comparisons of trends in annual second highest daily
maximum one-hour ozone concentration at 532 sites, 1984-1993.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 43
-------
Section 3.4 Trends in Ozone
is also lower than any other year. The
increase in the composite average be-
tween 1992 and 1993 is not statisti-
cally significant. The composite
averages and confidence intervals for
the 532 trend sites and the subset of
197 NAMS sites are provided in the
Data Appendix.
The interpretation of recent O3
trends is difficult due to the confound-
ing factors of meteorology and emis-
sion changes. Just as the increase in
1988 is attributed in part to meteoro-
logical conditions that were more
conducive to ozone formation than
prior years, the 1992 decrease is due
in part, to meteorological conditions
being less favorable for O3 formation
in 1992 than in other recent years.15-16
Meteorological conditions in 1993
were once again more favorable to
ozone formation, especially in the
east and southeastern areas of the
country.17 Also, since the peak year
of 1988, the volatility of gasoline has
been reduced by new regulations
which lowered national average sum-
mertime Reid Vapor Pressure (RVP)
in regular unleaded gasoline from
10.0 to 8.9 pounds per square inch
(psi) between 1988 and 1989.18-19-20
RVP was reduced an additional three
percent between 1989 and 1990.21
Figure 3-13 depicts the 1984-93
trend for the composite average num-
ber of O3 exceedances. This statistic
is adjusted for missing data, and it re-
flects the number of days that the O3
standard is exceeded during the O3
season. Since 1984, the expected
number of exceedances decreased 60
percent at the 532 long-term trend
sites and 57 percent at the subset of
197 NAMS. The composite averages
of O3 estimated exceedances for the
last five years (1989-93) are signifi-
cantly lower than those for the first
five years (1984-88) of this 10-year
period. Because O3 trends have not
shown a consistent directional pat-
tern, the percent change between the
endpoints for the 10-year period of
1984-93 has to be recognized as a
simplification. An approach that ac-
counts for meteorological variability
in ozone trends assessments is dis-
cussed below.
The main focus of this annual re-
port is to track the trends in the qual-
ity of air people are breathing when
outdoors, therefore, it makes sense to
use a summary statistic that clearly
relates to the O3 air quality standard.
Nevertheless, as noted in a National
Academy of Sciences (NAS) report, it
is difficult to assess O3 trends because
the year to year variability in meteo-
rological conditions can greatly influ-
ence peak ozone levels.1
Last year's report described
EPA's ongoing effort to develop tech-
niques for adjusting O3 trends for me-
teorological influences. The report
featured a statistical model in which
the frequency distribution of O3 con-
centrations is described as a function
of meteorological parameters.22 The
fitted distribution can be used to esti-
mate percentiles and threshold ex-
ceedance probabilities for the daily
maximum O3 concentration given a
fixed set of meteorological conditions
in each modeled city. Cox and Chu
test for a statistically significant trend
term to determine if an underlying
meteorologically adjusted trend can
be detected.22
The model has been used to calcu-
late "meteorologically adjusted" esti-
mates of the upper percentiles of daily
maximum concentrations in each
year. Figure 3-14 displays ambient
air quality trends, and meteorologi-
cally adjusted O3 trends for 43 metro-
politan areas. The "adjusted" trend
indicator shown in Figure 3-14 is the
composite mean of the meteorologi-
cally adjusted 99th percentile daily
maximum one-hour concentrations
across each of the 43 individual met-
12
NO. OF EXCEEDANCES
10
8-
6-
4-
2-
A ALL SITES (532)
NAMS SITES (197)
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-13. National trend in 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, 1984-1993.
44 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.4 Trends in Ozone
0.18
0.16-
0.14-
0.12
0.1
0.08-
0.06
0.04-
0.02
CONCENTRATION, PPM
Met Adjusted Trend-43 MSA's
(99th percentile daily max 1-hr cone.)
.. •.. Unadjusted Ozone Trend-43 MSA's
' • •.. (99th percentile daily max 1 -hr cone.)
National Composite Mean Ozone Trend
(Annual 2nd Daily Max 1-hr)
Actual (43 MSA's) Met Adjusted (43 MSA's) National (509 sites)
(99th Percentile) (99th Percentile) (2nd Daily Max 1-hr)
. 1 1 1 1 1 1 1 I I
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-14. Comparison of meteorologically adjusted, and unadjusted, trends in the composite average of the second
highest maximum one-hour ozone concentration for 43 MSAs, 1984-1993.
ropolitan areas. The smoothing intro-
duced by the meteorological adjust-
ment is especially evident in the peak
O3 year, 1988, which was followed
by years less conducive to O3 forma-
tion. The steady downward trend is
clear. The composite average of the
99th percentile daily maximum one-
hour concentrations in 1993 is 12 per-
cent lower than the 1984 level. This
composite trend captures the spatial
and temporal variability in meteoro-
logical conditions among these 43
metropolitan areas. As illustrated by
this figure, the composite trend in the
unadjusted 99th percentile daily
maximum one-hour concentration for
these 43 metropolitan areas tracks the
national composite O3 trend in the
second highest daily maximum one-
hour concentration. Thus, the meteo-
rologically adjusted trend is likely to
be a reasonable indicator of the com-
posite national O3 trend. Coinci-
dently, the 10-year percent change in
both the adjusted, and unadjusted,
composite average of 99th percentile
concentration for these 43 cities is
exactly the same percentage change
as the national second daily maxi-
mum one-hour trends statistic. That
is, both the meteorologically adjusted
99th percentile concentrations and the
standard trends indicator decreased
by 12 percent between 1984-93.
Table 3-4 lists the 1984-93 emis-
sion estimates for VOCs which, to-
gether with NOX shown earlier in
Table 3-3, are involved in the atmo-
spheric chemical and physical pro-
cesses that result in the formation of
O3. As noted in previous sections,
these emissions estimates have been
recomputed using new methodologies
including the MOBILESa model and
updated inputs at the state and county
level. These changes resulted in re-
vised estimates for 1984 total emis-
sions that are two percent lower and
1992 total emissions that are one per-
cent higher than reported last year.
Total VOC emissions are estimated to
have decreased nine percent between
1984 and 1993. During this same pe-
riod, NOX emissions, the other major
precursor of O3 formation, increased
one percent. Between 1984 and
1993, VOC emissions from highway
vehicles decreased 35 percent, despite
a 33-percent increase in VMT. These
VOC estimates are annual totals. Be-
cause O3 is predominately a warm
weather problem, seasonal emissions
inventories are being developed for
the current year, thereby enabling
seasonal comparisons of emission es-
timates in future reports.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 45
-------
Section 3.4 Trends in Ozone
Table 3-4. National Volatile Organic Compound Emission Estimates, 1 984-1 993
(thousand short tons/year)
SOURCE
CATEGORY
Fuel Combustion -
Electric Utilities
Fuel Combustion -
Industrial
Fuel Combustion -
Other
Chemical and
Allied Product
Manufacturing
Metals
Processing
Petroleum and
Related Industries
Other Industrial
Processes
Solvent Utilization
Storage and
Transport
Waste Disposal
and Recycling
Highway Vehicles
Off-Highway
Natural Sources
Miscellaneous
Total
1984
45
156
917
1,620
182
1,253
227
6,309
1,810
687
9,441
1,973
0
951
25,572
1985
32
248
508
1,579
76
797
439
5,779
1,836
2,310
9,376
2,008
0
428
25,417
NOTE:
1986
34
254
499
1,640
73
764
445
5,710
1,767
2,293
8,874
2,039
0
435
24,826
1987
34
249
482
1,633
70
752
460
5,828
1,893
2,256
8,201
2,038
0
440
24,338
1988
37
271
470
1,752
74
733
479
6,034
1,948
2,310
8,290
2,106
0
458
24,961
1989
37
266
452
1,748
74
731
476
6,053
1,856
2,290
7,192
2,103
0
453
23,731
1990 1991
36 36
266 270
437 426
1,771 1,778
72 69
737 745
478 475
6,063 6,064
1,861 1,868
2,262 2,217
6,854 6,499
2,120 2,123
0 0
1,320 937
24,276 23,508
1992
35
271
385
1,799
72
729
482
6,121
1,848
2,266
6,072
2,160
0
780
23,020
1993
36
271
341
1,811
74
720
486
6,249
1,861
2,271
6,094
2,207
0
893
23,312
The sums of sub-categories may not equal total due to rounding.
46 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.4 Trends in Ozone
3.4.2 Recent O3 Trends:
1991-1993
This section discusses ambient O3
changes during the three-year time
period, 1991-93. By focusing on this
three-year period, we are able to use
a larger data base of 722 sites meet-
ing the trends criteria, compared to
532 sites for the 10-year period.
This three-year period follows the
reduction in the volatility of gasoline,
RVP, that has occurred since 1988. A
recent modeling analysis of New
York City conditions estimated that
the impact of this RVP reduction was
a 25-percent reduction in VOC emis-
sions.23
Meteorological conditions in the
eastern half of the country were more
conducive to ozone formation during
Summer 1993 than in 1992. Summer
1993 had a temperature pattern that
consisted of unusually warm tempera-
tures over the eastern half of the coun-
try and unusually cold temperatures
over the western half, divided by a
line stretching roughly from the Great
Lakes to the southern Rockies.17
Based on average daily maximum
temperatures, the southeast had the
hottest July-August on record in
1993.17 Between 1992 and 1993,
composite mean O3 concentrations in-
creased two percent at the 722 sites
and four percent at the subset of 220
NAMS, but both composite means
were less than 1991 levels. Between
1992 and 1993, the composite aver-
age of the number of estimated ex-
ceedances of the O3 standard
decreased by 10 percent at the 722
sites, and 3 percent at the 220 NAMS.
Nationwide VOC emissions in-
creased one percent between 1992
and 1993. Beginning with this year's
revised estimate for 1992, and the
preliminary estimate for 1993, for the
first time since 1970, solvent utiliza-
tion VOC estimates exceed highway
emissions. The majority of the in-
crease in 1993 estimates relative to
1992 can be attributed to increased
solvent use.
As Figure 3-15 indicates, the
composite average of the second daily
maximum concentrations decreased in
five of the 10 regions between 1992
and 1993, and increased in the other
five Regions. The increases were re-
corded in the northeastern and middle
Atlantic states which is consistent
with the year-to-year changes in me-
teorological conditions described
above.
Except for the two west coast re-
gions, all the remaining eight regions
recorded increases in the composite
average of the number of estimated
exceedances between 1992 and 1993.
However, in six of these eight regions
the 1993 composite average number
of estimated exceedances was lower
than the 1991 level. In the national
trend, these regional increases were
offset by the 20-percent reduction in
exceedances recorded in Region 9
(primarily in southern California).
These regional graphs are in-
tended primarily to depict relative
change. Because the mix of monitor-
ing sites may vary from one area to
another, this graph is not intended to
indicate regional differences in abso-
lute concentration levels.
3.4.3 Clean Air Act
Update: 1991-1993
The three-year period that was the fo-
cus of the discussion of recent O3
changes also provides a key milestone
for implementation of the Clean Air
Act Amendments of 1990. The Act
requires that all of the 40 marginal
ozone nonattainment areas meet the
O3 NAAQS during the three-year
time period, 1991-93. Areas not
meeting the standard that have no
more than one exceedance of the
0.20
CONCENTRATION, PPM
0.16-
0.12-
0.08-
0.04
COMPOSITE AVERAGE
• 1991 Hi 1992 CD 1993
EPA REGION
NO. OF SITES
I
44
II
35
III
81
IV V
119 142
VI
70
VII
27
VIII
22
IX
171
X
11
Figure 3-15. Regional comparison of the 1991,1992, and 1993 composite
averages of the second-highest daily one-hour ozone
concentrations.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 47
-------
Section 3.4 Trends in Ozone
NAAQS during 1993 can request to
have this requirement extended for an
additional year.
Figure 3-16 displays the location
of the 33 marginal areas that had
three complete years of ambient
monitoring data showing compliance
with the standard. Only three of the
remaining seven marginal areas did
not meet the NAAQS by this date and
had more than one exceedance in
1993. The other four areas recorded
either less than two exceedances or
had incomplete data during this pe-
riod. The current air quality status of
ozone nonattainment areas is listed in
the annual air quality update.24
Figure 3-16. Map depicting marginal ozone nonattainment areas meeting the ozone NAAQS during the three-year
compliance period, 1991-1993.
48 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.5 Trends in Participate Matter
3.5 Trends in
Paniculate Matter
Air pollutants called participate mat-
ter include dust, dirt, soot, smoke and
liquid droplets directly emitted into
the air by sources such as factories,
power plants, cars, construction activ-
ity, fires and natural windblown dust.
Particles formed in the atmosphere by
condensation or the transformation of
emitted gases such as SO2 and VOCs
are also considered paniculate matter.
Based on studies of human popu-
lations exposed to high concentrations
of particles (sometimes in the pres-
ence of SO2), and laboratory studies
of animals and humans, there are ma-
jor effects of concern for human
health. These include effects on
breathing and respiratory symptoms,
aggravation of existing respiratory
and cardiovascular disease, alter-
ations in the body's defense systems
against foreign materials, damage to
lung tissue, carcinogenesis and pre-
mature death. The major subgroups
of the population that appear to be
most sensitive to the effects of par-
ticulate matter include individuals
with chronic obstructive pulmonary or
cardiovascular disease or influenza,
asthmatics, the elderly and children.
Particulate matter also soils and dam-
ages materials, and is a major cause
of visibility impairment in the United
States.
Annual and 24-hour National
Ambient Air Quality Standards
(NAAQS) for particulate matter were
first set in 1971. Total suspended
particulate (TSP) was the first indica-
tor used to represent suspended par-
ticles in the ambient air. Since July 1,
1987, however, EPA has used the in-
dicator PM-10, which includes only
those particles with aerodynamic di-
ameter smaller than 10 micrometers.
These smaller particles are likely re-
sponsible for most of the adverse
health effects of particulate matter
because of their ability to reach the
thoracic or lower regions of the respi-
ratory tract.
The PM-10 annual and 24-hour
standards specify an expected annual
arithmetic mean not to exceed 50 ug/m3
and an expected number of 24-hour
concentrations greater than 150 ug/
m3 per year not to exceed one.
Samples are collected at a frequency
of every day, every other day, or every
sixth day depending on the conditions
in a particular monitoring area.
Several instruments have been ap-
proved by EPA for sampling PM-10.
The first is a high volume sampler, or
Hi-Vol, with a size selective inlet
(SSI) that collects suspended particles
up to 10 microns in diameter. This
sampler uses an inert quartz filter.
The second instrument is a "dichoto-
mous" sampler. It uses a different
PM-10 inlet, operates at a lower flow
rate, and produces two separate
samples: 2.5 to 10 microns and less
than 2.5 microns, each collected on a
teflon filter. There are also some rela-
tively new particulate matter samplers
which have the capability of produc-
ing hourly values of PM-10 on a con-
tinuous basis. These continuous
samplers are beginning to be intro-
duced into monitoring networks
across the country, but it will be a few
more years before they produce
enough data to generate trends.
3.5.1 PM-10 Air Quality
Trends
Two statistics are used to show
PM-10 air quality trends in this re-
port: the weighted annual arithmetic
mean and the 90th percentile of
24-hour concentrations. The weighted
annual arithmetic mean is used to re-
flect average air quality over an ex-
tended period of time. It is called
"weighted" because an average is
first taken for each quarter of a year
and then the four quarterly averages
are averaged. This ensures that each
part of the year is weighted equally,
even if more measurements are taken
during one part of a year than another.
The 90th percentile statistic is used
because PM-10 sampling frequency
varies among sites and may change
from one year to the next at some
sites. This statistic is less sensitive to
changes in sampling frequency than
are the maximum or second maximum
peak values.
Most monitoring networks have
been producing data with approved
reference samplers since mid-1987.
Thus, the air quality data presented
here is for the six-year period from
1988 to 1993, with a sample of 799
trend sites.
Figures 3-17 and 3-18 display
boxplots of the concentration distri-
bution for the weighted annual arith-
metic mean and the 90th percentile of
24-hour concentrations, respectively.
The trend for the annual mean is
steadily downward with an overall 20
percent decrease over the six-year pe-
riod. The 90th percentile trend de-
creases 19 percent overall, but shows
virtually no change between 1992 and
1993.
Annual mean PM-10 concentra-
tions over the last three years for each
EPA region are shown in Figure 3-19.
Eight of the 10 regions improved in
each consecutive year, while Regions
3 and 10 experienced a slight increase
in 1993 values over 1992.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 49
-------
Section 3.5 Trends in Particulate Matter
110
CONCENTRATION, UG/M
100-
90-
80-
70-
60-
50-
40-
30-
20-
10-
799 SITES
I I I \ \ I
1988 1989 1990 1991 1992 1993
Figure 3-17. Boxplot comparisons of trends in weighted annual mean PM-10 concentrations at 799 sites, 1988-1993.
CONCENTRATION, UG/M
1988 1989 1990 1991 1992 1993
Figure 3-18. Boxplot comparisons of trends in the 90th percentile of 24-hour PM-10 concentrations at 799 sites, 1988-1993.
50 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.5 Trends in Particulate Matter
CONCENTRATION, UG/M3
bU-
50-
40-
30-
20-
10 —
-
1
*
i
4
$
f
I
;.
COMPOSITE AVERAGE
• 1991 H 1992 CD 1993
•
h
-i
,
>
^
r
>
~
I
'
|
a
j
t
-,
r
i*
1
^
^
i
i
*
£
i
i
-
'S
\,
i
i
£
i
i
i
i-
r
i
*
ts
?
EPA REGION I II HI IV V VI VII VIII IX X
NO. OF SITES 78 48 60 75 149 81 43 81 128 56
Figure 3-19. Regional comparisons of the 1991,1992, and 1993 composite averages of the weighted annual mean PM-10
concentrations.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 51
-------
Section 3.5 Trends in Particulate Matter
3.5.2 PM-10 Emission
Trends
Trends in PM-10 emissions are
shown in Table 3-5. The table does
not include those emissions in the
miscellaneous category such as fugi-
tive dust, wildfires, and agricultural
emissions. It also excludes natural
emissions such as wind erosion. Mis-
cellaneous and natural emissions are
presented separately in Table 3-6.
The numbers in Table 3-5 reflect
the new methodology used to compute
PM-10 emissions this year. Because
the new methods were only applied to
data from 1985 on, trends are pre-
sented for just the nine-year period
from 1985 to 1993. A discussion of
the new methodology appears in
Chapter 2.
Over the nine-year period from
1985 to 1993, total PM-10 emissions
decreased almost 10 percent. Catego-
ries which show a significant amount
of change are highway vehicles
(down 22 percent) and fuel combus-
tion—other (down 19 percent). By
far the largest contributor to PM-10
highway vehicle emissions are heavy
duty diesel vehicles. Since 1985,
emissions from these vehicles have
declined 34 percent. Within the fuel
combustion—other category, residen-
tial wood combustion emissions are
down 21 percent due to public educa-
Table 3-5. National PM-10 Emission Estimates, 1985-1993, No Natural Source or Miscellaneous Emissions
(thousand short tons/year)
SOURCE
CATEGORY
Fuel Combustion -
Electric Utilities
Fuel Combustion -
Industrial
Fuel Combustion -
Other
Chemical and
Allied Product
Manufacturing
Metals Processing
Petroleum and
Related Industries
Other Industrial
Processes
Solvent Utilization
Storage and
Transport
Waste Disposal
and Recycling
Highway Vehicles
Off-Highway
Total
1985
284
234
896
67
147
32
317
2
57
279
271
368
2,953
NOTE:
1986
289
231
902
68
137
31
321
2
56
275
265
372
2,949
1987
282
226
910
68
131
30
314
2
54
265
261
350
2,893
1988
278
230
918
73
141
29
314
2
54
259
256
387
2,942
1989
278
229
922
74
142
28
308
2
54
251
253
372
2,909
1990
291
228
930
74
140
28
306
2
54
242
239
372
2,907
1991
253
229
942
72
136
28
300
2
53
245
223
367
2,849
1992
255
223
819
75
137
27
303
2
53
246
210
379
2,729
1993
270
219
723
75
141
26
d11
2
55
248
197
395
2,661
The sums of sub-categories may not equal total due to rounding.
52 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.5 Trends in Particulate Matter
tion programs, restrictions on fire-
place and woodstove use in the home,
and positive incentives to reduce
burning.
Table 3-6 shows 1985-93 miscel-
laneous and natural source PM-10
emissions. Although these categories
actually contribute many times more
emissions than those listed in the pre-
vious table, they are presented in a
separate table because the year-to-year
variability which some of them ex-
hibit makes them more difficult to use
to show trends in PM-10.
Fugitive dust is the major con-
tributor to PM-10 emissions in the
miscellaneous category. Among the
road types, emissions from unpaved
roads have remained fairly steady,
while emissions from paved roads are
estimated to have increased almost 30
percent since 1985, most likely due to
increased vehicle traffic. Emissions
in the construction/mining and quar-
rying category have decreased an es-
timated 13 percent since 1985.
Agricultural activity is a smaller
contributor to the national total, but is
estimated to be the major source in
specific regions. The same may be
said for the categories of wildfires,
managed burning, and wind erosion;
these may make a significant contri-
bution to PM-10 emissions in certain
parts of the country, such as the west.
Because PM-10 emissions due to
wind erosion are very sensitive to re-
gional soil conditions and year-
to-year changes in total precipitation,
there can be considerable variability
from year to year. Accordingly, esti-
mated emissions from wind erosion
were extremely high for the drought
year of 1988 and extremely low for
the exceptionally wet year of 1993.17
Table 3-6. Miscellaneous and Natural Source Particulate Matter Emission Estimates, 1985-1993
(thousand short tons/year)
SOURCE
CATEGORY
Fugitive Dust
unpaved roads
paved roads
construction/
mining and
quarrying
Agriculture & Forestry
agricultural
crops
agricultural
livestock
Other Combustion
wildfires*
managed burning
other
Natural Sources
wind erosion
Total
1985
14,719
6,299
13,009
6,833
275
142
523
59
3,565
45,424
1986
14,672
6,555
12,139
6,899
285
142
530
59
9,390
50,671
1987
13,960
6,877
12,499
7,008
330
142
536
59
1,457
42,868
1988
15,626
7,365
12,008
7,090
376
142
555
59
17,509
60,730
1989
15,346
7,155
11,662
6,937
397
142
549
59
11,826
54,073
1990
15,661
7,299
10,396
6,999
381
717
546
59
4,192
46,250
1991
14,267
7,437
10,042
6,965
363
457
537
59
10,054
50,181
1992
14,540
7,621
10,899
6,852
386
341
547
59
4,655
45,900
1993
14,404
8,164
11,368
6,842
394
418
549
59
628
42,826
NOTE: The sums of siib-calegories may not equal total due to rounding.
'Actual data reflecting acres burned in 1985,1990,1991, and 1992. 1993 uses an average of 1990-1992 data.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 53
-------
Section 3.5 Trends in Participate Matter
PM-10 SUCCESS STORY
States hiave made significant progress in reducing emission levels in moderate PM-10
nonattainment areas since the enacBnent of the Clean AirActAmendments of 1990 (CAM), particularly
in urban areas which contain Industrial point sources. This success is due largely to State efforts to
adopt and implement Reasonably Available Control Technology (RACT) to control point source
emissions and Reasonably Available Control Measures (RACM) to control area source emissions.
Two nonattainment areas which have made remarkable progress toward attaining the PM-10
NAAQS are Gtiyahoga County and Jefferson County {Steubenville}, Ohio, To begin to analya:e their
problem with par&sulate matter* the State of Ohio first developed an emissions inventory, which is a
listing of major sources along wifo esSmates of how much pollutant they produce. The emissions
inventory indicated that Hie major sources of PM-10 emissions in Cuyahoga and Jefferson Counties
were stack emissions from steel mill point sources, fugitive emissions from process sources, and
fugitive dust from paved roads, tinpavecl roads, storage piles, and parking lots.
Next, the State of Ohio adopted and submitted, as a part of the State Implementation Plans
(SIPs) for the two areas, regulations which were designed to reduce paniculate matter emissions.
These regulations (mostly RACT requirements) subjected the steel mills and other major sources to
limits on mass emissions and visible emissions. Similarly, RACM requirements were imposed on
the area sources at these facilities. As examples, control measures for unpaved roads and parking
areas included the use of surface binding agents, and control measures for paved roads and parking
areas included frequent flushing and sweeping to remove paniculate matter from the road surface.
Example control measures for storage piles, such as piles of coal, included wetting them down or
enclosing them and venting tie emissions via a control device.
Ohio prepared an attainment demonstration using dispersion modeling to demonstrate that the
control strategies which they had adopted would enable boti Cuyahoga and Jefferson Counties to
attain the PM-10 NAAQS by December 31»1094. Whereas multiple violations were observed in
previous years, the data for 1992 to 1994 indicate that both the annual and 24-hour PM-10 standards
are being met in these areas.
54 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.6 Trends in Sulfur Dioxide
3.6 Trends in
Sulfur Dioxide
Ambient sulfur dioxide (SO2) results
largely from stationary source coal
and oil combustion, steel mills, refin-
eries, pulp and paper mills and from
nonferrous smelters. There are three
NAAQS for SO2:
• an annual arithmetic mean of
0.03 ppm (80 ug/m3);
• a 24-hour level of 0.14 ppm
(365 ug/m3); and
• a three-hour level of 0.50 ppm
(1300 ug/m3).
The first two standards are primary
(health-related) standards, while the
three-hour NAAQS is a secondary
(welfare-related) standard. The an-
nual mean standard is not to be ex-
ceeded, while the short-term
standards are not to be exceeded more
than once per year. Trend analyses
follow for the primary standards.
High concentrations of SO2 affect
breathing and may aggravate existing
respiratory and cardiovascular dis-
ease. Sensitive populations include
asthmatics, individuals with bronchi-
tis or emphysema, children and the
elderly. SO2 is also a primary con-
tributor to acid deposition, or acid
rain, which causes acidification of
lakes and streams and can damage
trees, crops, historic buildings, and
statues. In addition, sulfur com-
pounds in the air contribute to visibil-
ity impairment in large parts of the
country. This is especially noticeable
in national parks.
The trends in ambient concentra-
tions are derived from continuous
monitoring instruments which can
measure as many as 8,760 hourly val-
ues per year. The SO2 measurements
reported in this section are summa-
rized into a variety of statistics which
relate to the SO2 NAAQS. The statis-
tics reported here are for the annual
arithmetic mean concentration and the
second highest annual 24-hour aver-
age (measured midnight to midnight).
3.6.1 Long-term SO2
Trends: 1984-1993
The long-term trend in ambient SO2
from 1984 to 1993 is graphically rep-
resented in the boxplots of Figures
3-20 and 3-21. In each figure a
10-year downward trend is evident,
although the rate of decline has
slowed over the last few years. An-
nual mean SO2 measured at 474 sites
across the United States decreased at
a median rate of approximately three
percent per year, resulting in an over-
all decrease of 26 percent since 1984
(Figure 3-20). The annual second
highest 24-hour values examined at
469 sites showed a median rate of
change of four percent per year, with
an overall decline of 36 percent (Fig-
ure 3-21).
The 138 NAMS sites, which are a
subset of the full set of sites measur-
ing SO2, recorded higher average con-
centrations than the full set of all SO2
monitors, but declined at a faster me-
dian rate over the 10-year period. At
the NAMS sites, the average annual
mean concentration dropped about
four percent per year for a total de-
crease of 33 percent over 10 years,
while the second highest 24-hour val-
ues decreased five percent per year
and 39 percent overall.
The trend in nationwide emissions
of sulfur oxides (SOJ, broken down
by source category, is shown in Table
3-7. After a 25-percent decrease in
total emissions during the 1970s and
early 1980s, SOX emissions have re-
mained relatively unchanged in recent
years. The largest contributor to SOX
emissions has consistently been coal
burning power plants.
0.035
CONCENTRATION, PPM
0.030-
0.025-
0.020-
0.015-
0.010-
0.005-
0000
474 SITES
NAAQS
"li,
mum V)
i l l l I I I l I i
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
Figure 3-20. Boxplot comparisons of trends in annual mean sulfur dioxide
concentrations at 474 sites, 1984-1993.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 55
-------
Section 3.6 Trends in Sulfur Dioxide
Four programs make up the EPA's
strategy to control the emissions asso-
ciated with SO2:
• The National Ambient Air Qual-
ity Program, which sets the pri-
mary and secondary standards
discussed earlier in this report.
• The New Source Review/Preven-
tion of Significant Deterioration
Program, which protects air
quality from deteriorating in clean
areas by requiring new major SO2
sources to conduct air quality
analyses before receiving a
permit.
• New Source Performance Stan-
dards, which set emission limits
for new sources.
• The Acid Rain Program, which is
set forth in Title IV of the 1990
Clean Air Act Amendments.
The first three programs protect
air quality and public health on a lo-
cal level, while the Acid Rain Pro-
gram addresses the regional problem
of long range transport of SO2. The
primary goal of the Acid Rain Pro-
gram is to reduce annual SO2 emis-
sions by 10 million tons below 1980
levels by setting national emission
caps on utility and industrial sources.
The focus of this control program is a
system which assigns each facility a
number of allowances based on his-
toric fuel consumption and a re-
stricted emission rate. Each facility
may, if they have reduced their emis-
sions below their allotted number of
allowances, sell or trade their extra
allowances to other facilities who
need them. Or, the facility may bank
away any extra allowances they have
at the end of the year. Thus, the
0.15
CONCENTRATION, PPM
NAAQS,
469 SITES
0.10-
0.05-
0.00
I I I I I I I I IT^
1984 1985 1986 1987 1988 1989 1990 1991 1992 1993
sources are given a large amount of
flexibility in meeting the program's
requirements, which should reduce
the cost of compliance. This is the
first large-scale regulatory use of such
a market-based incentive.25
3.6.2 Recent SO2 Trends:
1991-1993
Nationally, SO2 measured in the am-
bient air showed improvement over
the last three years in both average
and peak 24-hour concentrations.
Annual mean concentrations and sec-
ond highest 24-hour SO2 concentra-
tions each decreased eight percent
between 1991 and 1993. Most re-
cently, the change between 1992 and
1993 showed an average annual mean
SO2 decrease of about one percent
and a decrease in second highest
24-hour SO2 concentrations of five
percent.
Figure 3-22 presents the regional
changes in composite annual average
SO2 concentrations for the last three
years, 1991-1993. Although four of
the regions show a slight increase in
1993 values over 1992, the increases
are more than offset by decreases in
the other six regions.
Figure 3-21. Boxplot comparisons of trends in second highest 24-hour average
sulfur dioxide concentrations at 469 sites, 1984-1993.
56 • Chapters: National and Regional Trends in NAAQS Pollutants
-------
Section 3.6 Trends in Sulfur Dioxide
Table 3-7. National Sulfur Oxides Emission Estimates, 1984-1993
(thousand short tons/year)
SOURCE
CATEGORY 1984 1985 1986 1987 1988 1989 1990 1991
Fuel Combustion -
Electric Utilities 16,023 16,273 15,701 15,715 15,990 16,218 15,898 15,784
Fuel Combustion -
Industrial 2,723 3,169 3,116 3,068 3,111 3,086 3,106 3,139
Fuel Combustion -
Other 728 578 611 663 660 623 597 608
Chemical and
Allied Product 229 456 432 425 449 440 440 442
Manufacturing
Metals
Processing 1,387 1,042 888 616 702 657 578 544
Petroleum and
Related Industries 707 505 469 445 443 429 440 444
Other Industrial
Processes 923 425 427 418 411 405 401 391
Solvent Utilization 0 1 1 1 1 1 1 1
Storage and
Transport 04445555
Waste Disposal
and Recycling 25 34 35 35 36 36 36 36
Highway Vehicles 445 446 449 457 468 480 480 478
Off-Highway 198 208 221 233 253 267 265 266
Miscellaneous 9 7 7 7 7 7 14 11
Total 23,396 23,148 22,361 22,085 22,535 22,653 22,261 22,149
1992 1993
15,417 15,836
2,947 2,830
600 600
447 460
557 580
417 409
401 413
1 1
5 5
37 37
483 438
273 278
10 11
21,592 21,888
NOTE: The sums of sub-categories may not equal total due to rounding.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 57
-------
Section 3.6 Trends in Sulfur Dioxide
nMf CONCENTRATION, PPM
0.014-
0.012-
0.010-
0.008-
0.006 -
0.004-
0.002 -
COMPOSITE AVERAGE
• 1991 01 1992 CH 1993
$
K
I
i.
&
a
I
I
EPA REGION I II
NO. OF SITES 63 43
1
1
1
1
i
1
4
PI
~f
]
I
-1
B-!
i
1
\
(
-i
III IV V VI VII VIII IX
80 71 140 38 27 32 54
i
*
X
12
Figure 3-22. Regional comparisons of the 1991,1992, and 1993 composite averages of the annual sulfur dioxide
concentrations.
58 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section3.7 Visibility
3.7 Visibility
Visibility impairment, which is most
simply described as the haze which
obscures the clarity, color, texture,
and form of what we see, is actually a
complex problem which relates, in
part, to several of the pollutants dis-
cussed earlier in this report. Because
the topic of visibility does not fit com-
pletely within the discussion of any
one of the NAAQS pollutants, it is
included here in its own section.
IMPROVE Monitoring
Network
Many parts of the United States are
experiencing visibility problems, but
perhaps it is most noticeable in our
national parks and wilderness areas.
Section 169A of the 1977 amend-
ments to the Clean Air Act estab-
lished as a national goal the
protection of visibility in these "Class
I" areas. In 1980, the National Park
Service (NFS), in cooperation with
the EPA, established a long-term vis-
ibility monitoring program at remote
locations throughout the nation.
Since then, the effort has been ex-
panded to incorporate the U.S. Forest
Service (USFS), the Fish and Wildlife
Service (FWS), the Bureau of Land
Management (BLM), the State and
Territorial Air Pollution Program As-
sociation (STAPPA), the Western
States Air Resource Council
(WESTAR), and the Northeast States
for Coordinated Air Use Management
(NESCAUM). Together, this col-
laborative visibility monitoring effort
is called IMPROVE, for Interagency
Monitoring of PROtected Visual En-
vironments.
IMPROVE is currently the largest
monitoring network in the U.S. that
fully characterizes visibility. Cam-
eras and special particulate matter
samplers are present at each location
to monitor characteristics that will
help to describe and define visibility
over time. Most sites also directly
monitor the optical characteristics of
the atmosphere.
Visibility impairment is caused by
aerosols, or gas mixtures and sus-
pended particles in the atmosphere
that cause light to be scattered or ab-
sorbed, thereby reducing visibility.
Knowledge of the chemistry and
physical properties of the aerosols re-
sponsible for visibility impairment
can provide insight into the causes of
the visibility problem.
As Figure 3-23 shows, the par-
ticles in aerosols can be divided into
two categories based on size. Coarse
particles, with diameters greater than
2.5 micrometers, have little effect on
visibility impairment per unit concen-
tration. Wind blown dust is the major
contributor of coarse particles. Fine
particles, on the other hand, with di-
ameters less than 2.5 micrometers,
contribute greatly to the scattering
and absorption of light (also called
light extinction) and cause poor vis-
ibility. The significant chemical spe-
cies in fine aerosols are sulfates,
nitrates, organic carbon, light-absorb-
ing carbon (LAC), and soil dust.
Figure 3-24, which presents data
collected by the IMPROVE monitor-
ing network, illustrates the relation-
ship between the type of aerosol and
reduction in visibility. The pie charts
show the relative contribution of each
fine aerosol component to total light
extinction, while the size of each pie
chart represents the measured amount
of light extinction. Sulfates are the
largest single contributor to light ex-
tinction in all states east of New
Mexico and in Hawaii. In the Appa-
lachian Mountains, sulfates account
for 68 percent of the visibility reduc-
tion. Organic carbon, the next largest
contributor, causes 16 percent of the
visibility reduction. In most areas of
the west and in Alaska, sulfates and
O
z
cc
UJ
o
CO
2.5 micrometers
FINE
COARSE
PARTICLE SIZE
Figure 3-23. Aerosol size distribution.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 59
-------
Section 3.7 Visibility
CASCADES
COASTAL MTNS.
NORTHEAST
SONORAN DESERT
WEST TEXAS
SULFATE
ORGANICS
SOIL
LAC
NITRATE
Figure 3-24. Annual average light extinction.
organics are relatively equal in their
contributions to light extinction. Ni-
trate is the single largest contributor
to light extinction only in southern
California. LAC, which appears in
green in the figure, is generally the
smallest contributor at all monitoring
sites.26
The pie charts are scaled to show
measured amounts of light extinction.
The greater the light extinction, the
poorer the visibility. The figure illus-
trates the difference in visibility be-
tween the eastern and the western
portions of the United States. The
highest extinction and lowest visibil-
ity occurs in the east and Great Lakes
area, while the west has noticeable
lower extinction and higher visibility,
with the exceptions of areas near Los
Angeles, San Francisco, and the Pa-
cific Northwest. Generally, the best
visibility has been reported in a broad
region including the Great Basin,
most of the Colorado Plateau, deserts
of the southwest, portions of the Cen-
tral Rockies and Great Plains, and in
Alaska.26
Airport Visual Range Data
Another way to look at visibility im-
pairment is to study the visibility data
which has been collected at airports
for over 30 years. These data, col-
lected at 280 stations across the
United States since 1960, are mea-
surements of visual range, or the
maximum distance at which an ob-
server can discern the outline of an
object. Visual range is related in-
versely to light extinction, or haze,
and can provide the means to show
long-term trends in visibility.
Figure 3-25 shows the location of
the airport visual range monitoring
sites. Figures 3-26 and 3-27 picture
United States haze patterns and trends
in 16 maps created from airport visual
range data. The maps show the 75th
percentile of light extinction, where
the cooler colors show better visibil-
ity (dark blue being the best visibility)
and the warmer colors show poorer
visibility (red is the worst visibility).
Four separate quarters of data are
used to represent seasonal patterns
(Ql is January, February, March; Q2
is April, May, June; and so on). The
years shown are five-year averages
centered around 1960, 1970, 1980,
and 1990. The following analysis of
the visibility trends represented by
these maps is based largely on a paper
by Husar, Elkins, and Wilson titled
"U.S. Visibility Trends, 1960-
The overall national view shows
two large contiguous haze regions,
one over the eastern United States and
another over the western Pacific
states. The two haze regions are di-
vided by a low-haze territory that
spans between the Rocky Mountains
and the Sierra-Cascade mountain
60 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.7 Visibility
Figure 3-25. Visual range airport data monitoring sites.
ranges. This general pattern is pre-
served over the 30-year period. How-
ever, notable trends have occurred
over both the western and the eastern
haze regions.
The haziness in the western Pa-
cific states covers all of the coastal
states, with California exhibiting the
highest values. In the 1960s a large
fraction of western California had low
visibility particularly during quarters
1 and 4. By the 1990s the magnitude
of the Pacific Coast haziness showed
a marked decline for all seasons.
The eastern haze region extends
from the East Coast to the Rocky
Mountains. The western boundary of
the eastern haze regions is remark-
ably constant over both the seasons
and the years. In fact, the mid-section
of the U.S. extending from the Rocky
Mountains to the Mississippi River
has changed little over the 30-year
history.
The most dynamic pattern can be
observed over the eastern United
States from the Mississippi River to
the East Coast. The eastern United
States shows a definitive seasonal
variation over the region, and there is
also a significant trend over the past
30 years. Furthermore, these sea-
sonal and long-term trends are differ-
ent for sub-regions within the eastern
United States, such as the Northeast,
the Mid-Atlantic states and the Gulf
states regions.
In the 1960s the highest extinction
values were recorded for the cold sea-
son, quarters 1 and 4, with signifi-
cantly lower values for the warm
quarters (Q2 and Q3). The remark-
able reduction in the cold season hazi-
ness and the strong increase during
the warm season has shifted the haze
peak from winter to summer. Conse-
quently, there was also a regional
shift in the highest haze pattern. In
the 1960s the worst haziness occurred
surrounding Lake Erie and the New
York-Washington megalopolis, dur-
ing the cold season. By the 1990s the
worst haziness had drifted southward
toward Tennessee and the Carolinas
and it now occurs in the summer sea-
son.
The decade of the 1980s shows
less change than the earlier decades.
However, there was a continued haze
reduction in the Northeast, north of
the Ohio River and east of the Missis-
sippi River. The southeastern United
States, as well as the Pacific states,
have remained virtually unchanged in
the 1980s.28
Programs to Improve
Visibility
In April of 1994 EPA announced that
it will begin work on a Regional Haze
Program to address visibility impair-
ment in Class I areas. This program
will develop technical approaches to
monitoring and modeling regional
haze as well as define the policy for
achieving "reasonable progress" to-
wards the national goal of eliminating
visibility impairment in these areas.
The program will be developed in co-
ordination with efforts of the Grand
Canyon Visibility Transport Commis-
sion, which has been developing rec-
ommendations for EPA with respect
to protection of the Class I areas on
the Colorado Plateau in the south-
western United States.
The Grand Canyon Visibility
Transport Commission's recommen-
dations are due to EPA in November,
1995. EPA is planning to respond to
those recommendations by proposing
its program within 18 months of re-
ceipt of the report. Current work on
the Regional Haze Program is focus-
sing on development of monitoring
and modeling guidance as well as
tools for policy assessment.
In addition to the Regional Haze
Program, there is a relationship be-
tween visibility impairment and the
Chapter 3: National and Regional Trends in NAAQS Pollutants • 61
-------
Section 3.7 Visibility
1960 Ql
-f
Figure 3-26. United States trends map for the 75th percentile of light extinction derived from airport visual range data.
(Q1 = January - March; Q2 = April - June).
62 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.7 Visibility
V--, 1960 Q3
Figure 3-27. United States trends map for the 75th percentile of light extinction derived from airport visual range data.
(Q3 = July - September; Q4 = October - December).
Chapter 3: National and Regional Trends in NAAQS Pollutants • 63
-------
Section 3.8 References
NAAQS pollutants which should also
lead to improvements in visibility.
Controls for sources such as electric
utilities, diesel vehicles, petroleum
and chemical industries, and residen-
tial wood burning may be designed
primarily for NAAQS pollutant prob-
lems but should also produce better
visibility. The Acid Rain provisions
resulting from the 1990 Clean Air Act
Amendments will reduce SOX and
NOX. This should result in visibility
improvements that can be tracked as
these emission reductions take effect
in the late 1990s.28
3.8 References
1. Rethinking the Ozone Problem in Urban and Regional Air Pollution, National Research Council,
National Academy Press, Washington, DC, December 1991.
2. Curran, T.C., "Trends in Ambient Ozone and Precursor Emissions in U.S. Urban Areas," Atmospheric
Ozone Research and Its Policy Implications, Amsterdam, The Netherlands, 1989.
3. Curran, T.C. and N.H. Frank, "Ambient Ozone Trends Using Alternative Indicators", Tropospheric
Ozone and the Environment, Los Angeles, CA, March 1990.
4. National Air Quality and Emissions Trends Report, 1991, EPA-450/R-92-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
October 1992.
5. National Air Pollutant Emission Estimates, 1900-1993, EPA-454/R-94-027, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
October 1994.
6. J. Pirkle, et al., "The Decline in Blood Lead Levels in The United States, The National Health and
Nutrition Examination Surveys," Journal of the American Medical Association, July 27, 1994.
7. National Primary and Secondary Ambient Air Quality Standards for Lead, 43 FR 46246, October
5, 1978.
8. Memorandum. Joseph S. Carra to Office Directors Lead Committee. Final Agency Lead Strategy.
February 26, 1991.
9. R. B. Faoro and T. B. McMutten, National Trends in Trace Metals Ambient Air. 1965-1974, EPA-450/
1-77-003, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards,
Research Triangle Park, NC, February 1977.
10. W. Hunt, "Experimental Design in Air Quality Management," Andrews Memorial Technical
Supplement, American Society for Quality Control, Milwaukee, WI, 1984.
11. Ambient Air Quality Surveillance, 46 FR 44159, September 3, 1981.
12. National Air Quality and Emissions Trends Report, 1989, EPA-450/4-91-003, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
February 1991.
13. D.J. Kolaz and R.L. Swinford, "How to Remove the Influence of Meteorology from the Chicago
Areas Ozone Trend," presented at the 83rd Annual AWMA Meeting, Pittsburgh, PA, June 1990.
14. Use of Meteorological Data in Air Quality Trend Analysis, EPA-450/3-78-024, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
May 1978.
64 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Section 3.8 References
15. National Air Quality and Emissions Trends Report, 1988, EPA-450/4-90-002, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
March 1990.
16. W.O. Brown and R. R. Heim, Jr., "Climate Variations Bulletin", Volume 4, No. 8, National Climatic
Data Center, NOAA, Asheville, NC, September 1992.
17. W.O. Brown, "Climate Variations Bulletin", Volume 5, No. 8, National Climatic Data Center,
NOAA, Asheville, NC, September 1993.
18. Volatility Regulations for Gasoline and Alcohol Blends Sold in Calendar Years 1989 and Beyond,
54 FR 11868, March 22, 1989.
19. National Fuel Survey: Motor Gasoline - Summer 1988, Motor Vehicle Manufacturers Association,
Washington, D.C., 1988.
20. National Fuel Survey: Gasoline and Diesel Fuel - Summer 1989, Motor Vehicle Manufacturers
Association, Washington, D.C., 1989.
21. National Fuel Survey: Motor Gasoline - Summer 1990, Motor Vehicle Manufacturers Association,
Washington, D.C., 1990.
22. W.M. Cox and S.H. Chu, "Meteorologically Adjusted Ozone Trends in Urban Areas: A Probabilistic
Approach", Tropospheric Ozone and the Environment II, Air and Waste Management Association,
Pittsburgh, PA, 1992.
23. EHPA NEWSLETTER, Vol. 9, No. 3, E.H. Pechan & Associates, Inc., Springfield, VA, Summer
1992.
24. Carbon Monoxide and Ozone Air Quality Update, 1993, U.S. Environmental Protection Agency,
Office of Air Quality Planning and Standards, Research Triangle Park, NC, October 1994.
25. EPA Programs to Control Sulfur Dioxide in the Atmosphere, EPA 430/F-93-005, U.S. Environmental
Protection Agency, Research Triangle Park, NC, March 1993.
26. IMPROVE, Spatial and Temporal Patterns and the Chemical Composition of the Haze in the United
States: An Analysis of Data from the IMPROVE Network, 1988-1991, CIRA Cooperative Institute
for Research in the Atmosphere, Colorado State University, CO, February 1993.
27. R.B. Husar, J.B. Elkins, and W.E. Wilson, "U.S. Visibility Trends, 1960-1992," Air and Waste
Management Association 87th Annual Meeting and Exhibition, Cincinnati, OH, 1994.
28. Effects of the Clean Air Act Amendments on Visibility in Class I Areas, EPA Report to Congress,
Draft, U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Research
Triangle Park, NC, August 1993.
Chapter 3: National and Regional Trends in NAAQS Pollutants • 65
-------
66 • Chapter 3: National and Regional Trends in NAAQS Pollutants
-------
Chapter 4: Air Toxics
Air toxics differ fundamentally from
the criteria air pollutants, discussed in
the previous chapter, for several prin-
ciple reasons. First, the term air tox-
ics refers to literally hundreds of
pollutants, i.e., 189 compounds ac-
cording to Clean Air Act Amend-
ments (CAAA) definition, compared
to the six criteria pollutants for which
there are National Ambient Air Qual-
ity Standards. Next, the ambient con-
centration data for air toxics is
significantly limited, both temporally
and spatially, relative to that collected
by the long-term, nationwide monitor-
ing network for criteria pollutants. In
addition, air toxics are generally ob-
served at low ambient concentrations
often at or below detection limits for
current monitoring instrumentation.
Further, air toxics tend to manifest
quite localized pollution problems as
opposed to the usual urban and re-
gional scale environmental issues as-
sociated with many criteria pollutants.
Finally, the regulation of hazardous
air pollutants (HAPs) is a relatively
recent venture in contrast to the level
of attention and time commitment
dedicated to criteria pollutants.
As a result of these inherent dis-
similarities, this chapter is structured
differently than that for criteria pollut-
ants. The contents include: (1) an in-
troductory explanation of air toxics
and their associated health and eco-
logical effects; (2) a summary and in-
terpretation of current HAP emissions
for the United States; and (3) a brief
description of air toxics provisions of
the CAAA with a report on the status
of regulatory development and imple-
mentation.
4.1 Air Toxics and
Their Effects
For purposes of this report, air toxics
are defined as the 189 hazardous air
pollutants (HAPs) identified in Title
III of the CAAA. The CAAA implies
that these compounds were selected
for regulation because they
"... present, or may present, a
threat of adverse human health
effects (including, but not limited
to, substances which are known to
be, or may reasonably be an-
ticipated to be, carcinogenic,
mutagenic, teratogenic, neuro-
toxic, which cause reproductive
dysfunction, or which are acutely
or chronically toxic) or adverse
environmental effects whether
through ambient concentrations,
bioaccumulation, deposition, or
otherwise, ..."'
Exposure to air toxics can result
in a variety of severe human health
effects as well as impacts to ecosys-
tems. The possible human health ef-
fects include cancer and many other
chronic and acute effects. Many of
the air toxics listed in the CAAA are
known to be human carcinogens, and
a number of EPA studies have con-
cluded that exposure to air toxics, es-
pecially in urban environments, may
result in an increased incidence of
cancer.
Air toxics can also result in a
number of serious non-cancer effects.
It is particularly difficult to character-
ize non-cancer health effects as they
may be manifested in many ways:
poisoning, or immediate illness; or
less-measurable effects such as im-
munological, neurological, reproduc-
tive, developmental, mutagenic, or
respiratory effects. These effects in
turn exhibit wide ranges of severity
and reversibility.
Inhalation is only one of several
pathways of human exposure to air
toxics. Other pathways, such as
bioaccumulation and deposition, may
also impose significant risk to the vi-
ability of ecological systems as well
as serve as alternative routes of expo-
sure to humans. Toxic particulate
matter may be deposited onto soil or
into water bodies affecting ecological
systems as well as human health. For
example, deposition to soil may result
in exposure to children playing out-
doors or in uptake by agricultural
crops. Air toxics deposited to surface
waters may be taken up by fish which
ultimately find their way to the mar-
ketplace.
Chapter 4: Air Toxics • 67
-------
Section 4.2 Emissions Trends: Extent of the Problem
4.2 Emissions
Trends: Extent of the
Problem
Background—Data
Sources and Limitations
As mentioned previously, there is no
national air quality monitoring pro-
gram for air toxics similar to that used
to collect data on criteria pollutants.
The development of comparable data
for air toxics is complicated by a
number of factors:
• the number of chemical com-
pounds involved;
• the number and variety of sources
emitting the compounds;
• the low concentrations sometimes
involved; and
• the potential for secondary forma-
tion of one hazardous compound
from other, often non-hazardous,
compounds.
The limitations of currently avail-
able data sources for air toxics im-
pede the Environmental Protection
Agency's (EPA's) ability to identify
trends in HAP emissions and ambient
air concentrations. Therefore, even
preliminary assessments of baseline
emissions are somewhat tentative.
This chapter utilizes two types of
estimates of air toxic emissions: (1)
summaries of releases of HAPs as
represented in EPA's Toxic Release
Inventory (TRI); and (2) engineering
estimates of emissions by specific
source category. The TRI summaries
provide both an indication of the trend
in air toxics emissions and an overall
picture of the hot spots within the na-
tion. The source-specific inventories
were derived, using formal informa-
tion-gathering letters and meetings
with industry, plant visits, and exist-
ing state and local information on the
sources, as single year estimates to
support EPA's rule-making under
Title III. Because the source category
estimates and the TRI data are not
collected in the same manner, these
estimates are not directly comparable.
The TRI is currently the primary
source of comprehensive information
on emissions of air toxics. Autho-
rized by the Emergency Planning and
Community Right to Know Act
(EPCRA) of 1986, the TRI requires
manufacturing facilities with 10 or
more employees meeting thresholds
for manufacturing, processing or oth-
erwise using listed chemicals (includ-
ing air toxics) to submit annual
reports to EPA on their releases. Data
for the TRI has been collected since
1987. The data from TRI are used in
this report to provide an indication of
trends in toxic emissions, because it is
the only air toxics inventory which is
regularly updated.
While TRI is the only database
available for assessing air toxic emis-
sion trends, there are significant limi-
tations in the inventory's portrayal of
overall HAP emissions. First, facili-
ties with Standard Industrial Classifi-
cation (SIC) codes outside the range
of 20 to 39 (the manufacturing SIC
range) are not required to report.
Therefore, HAP emissions from fa-
cilities such as mining operations,
electric utilities, and oil and gas pro-
duction operations are not represented
in the TRI due to this exemption. In
addition, emissions from small manu-
facturing facilities (those with fewer
than 10 employees) as well as mobile,
commercial, residential, and con-
sumer sources are not included in the
TRI. More comprehensive, single
year national inventories for specific
pollutants (prepared by EPA to sup-
port special studies called for by the
CAAA) have demonstrated that emis-
sions from these excluded source cat-
egories can be much more significant
than those from the manufacturing
sector for some toxic air pollutants.2
Next, TRI data are self-reported by
the emitting facilities, and TRI does
not require facilities to perform any
actual monitoring or testing to de-
velop their TRI estimates. The accu-
racy of the reported data may vary
from facility to facility and year to
year. Finally, the original TRI list
only required reporting for 173 of the
189 HAPs identified in the CAAA.
Efforts are underway to enhance
the TRI database by expanding both
the type of facilities which must re-
port their releases and the list of
chemicals which must be reported.
Two of the sixteen compounds omit-
ted from the original TRI list,
acetophenone and ethylidene dichlo-
ride, will be added for the 1994 re-
porting year. On January 12, 1994,
the following nine HAPs were pro-
posed for addition to the TRI:
• caprolactam;
• dimethyl formamide;
• hexamethy lene-1,6-diisocyanate;
• hexane;
• isophorone;
• mineral fibers;
• phosphine;
• polycyclic organic matter (polycy-
clic aromatic compounds); and
• triethylamine.
Currently, there are no plans to
add the remaining five HAPs to the
TRI because they are either produced
in quantities too low to meet the re-
porting thresholds or emitted by
sources which currently are not re-
quired to report to the Inventory.
These five HAPs are:
• 2,2,4-trimethylpentane;
• 2,3,7,8-tetrachlorodibenzo-
p-dioxin;
• coke oven emissions;
• p,p'-dichlorodiphenyldichloro-
ethylene (DDE); and
• radionuclides (including radon).
As more information is collected
on air toxic emissions, baseline emis-
sions estimates for air toxics will be
modified to more accurately gauge
the effectiveness of Title III regula-
tions in reducing air toxic emissions.
68 • Chapter 4: Air Toxics
-------
Section 4.2 Emissions Trends: Extent of the Problem
In summary, 173 of the 189 HAPs
(those included in the TRI database)
are included in the analyses within
this chapter. All references to HAPs
emissions in the following section are
to the sum of these compounds as re-
ported in the TRI.
Summary of Emissions
In 1992, aggregate HAP emissions in
the United States totaled 1.3 billion
pounds, down from 1.5 billion pounds
in 1991. This total represents a de-
crease of approximately 600 million
pounds (or 31 percent) from 1988
levels and a reduction of 120 million
pounds (or eight percent) from 1991
levels. As points of comparison, total
TRI air releases declined 32 percent
and nine percent, and total TRI
releases declined 35 percent and six
percent, respectively, during the same
time periods.3-4
Figure 4-1 compares annual TRI
emission estimates from 1988 to 1992
for the top 10 HAPs (based on 1988
levels). The estimates reveal a gen-
eral downward trend for all, but one
(carbon disulfide), of the listed pollut-
ants. In similar fashion, Figure 4-2
presents yearly HAP emissions for
the top 10 industry categories based
on 1988 releases. All industry cat-
egories show a net decline since 1988
and reductions in emissions from
1991 levels as well. The chemical
products industry has consistently
reported greater aggregate HAP emis-
sions to TRI than any other source
category.
Figures 4-3 and 4-4 show re-
ported air toxic emissions by state for
1991 and 1992, respectively. In 1992,
three states (New Mexico, North Da-
kota, and Wyoming) joined the three
states from 1991 reporting total HAP
emissions less than one million
pounds (Hawaii, Nevada, and Ver-
mont). In 1992, five states reported
HAP releases greater than 65 million
pounds down from, seven states in
1991 and thirteen in 1988.
Changes in the TRI estimates of
HAP emissions by state for the time
periods 1988 to 1992 and 1991 to
1992 are depicted in Figure 4-5 and
4-6, respectively. The total HAP
emissions of thirty-one states have de-
clined by greater than 25 percent from
1988 levels. However, five states re-
ported increases in net HAP emission
for the same time period, and eight
states estimate one year increases in
HAP releases since 1991.
Figure 4-7 illustrates the trend in
HAP releases for the five states with
the greatest emission levels based on
1988 estimates. All five show a net
reduction in HAP emissions over the
1988 to 1992 time period. For all
five, except Alabama, the net change
was greater than 25 percent from
1988 levels. Virginia reported the
largest decline in HAP emissions, 57
percent, for the five year period.
Figure 4-8 presents the same data
illustrated in Figure 4-4 (total HAP
emissions by state for 1992) but uti-
lizes a smaller grid scale to better re-
solve the geographic location of these
emissions.
Chapter 4: Air Toxics • 69
-------
Section 4.2 Emissions Trends: Extent of the Problem
300
Toluene 1,1,1-Trichloroethane *MEK Dichloromethane Hydrochloric Acid
Methanol Xyiene (mixed isomers) Chlorine Carbon Disuffide Trichloroethylene
'Methyl Ethyl Ketone
Figure 4-1. Top 10 hazardous air pollutants, 1988 basis.
o>
Chemical Products Trans. Equip. Electric & Electronic Prods. Machinery'
Primary Metals Rubber & Plastic Furniture & Fixtures
Paper Products Fabricated Metals Printing, Publishing
* except Electrical
Figure 4-2. Industry categories reporting highest total HAP releases, 1988 basis.
70 • Chapter 4: Air Toxics
-------
Section 4.2 Emissions Trends: Extent of the Problem
1991 HAP Air Releases
(mlBlon pounds)
• 65tolOO (7)
StSto 65 (9)
D25to 45 (5)
• 15 to 25 (6)
• 5 to 15 (10)
• Ito 5 (7)
• Oto 1 (6)
Figure 4*3. 1991 total air releases, HAP species by state, from TRI.
\
A
1992 HAP Air Releases
(pnHlon pounds)
• 66 to 100 (5)
045 to 65 (7)
D 26to AS (8)
• 15 to 25 (7)
• 5to 16 (9)
• 1 to 5 (8)
• Oto 1 (6)
Figure 4-4. 1992 total air releases, HAP species by state, from TRI.
Chapter 4: Air Toxics • 71
-------
Section 4.2 Emissions Trends: Extent of the Problem
Percent Change in HAP
Air Releases 1988-1992
H Increase (5)
@ Up to 25% decrease (15)
D 29% to 50% decrease (25)
D Greater than 50% decrease (5)
Figure 4-5. Percent change in HAP air releases from 1988 to 1992, from TRI.
Percent Change in HAP
Air Releases 1991 -1992
H Increase (8)
B Up to 25% decrease (39)
D Greater than 25% decrease (3)
Figure 4-6. Percent change in HAP air releases from 1991 to 1992, from TRI.
72 • Chapter 4: Air Toxics
-------
Section 4.2 Emissions Trends: Extent of the Problem
0
1988
1989
1990
1991
1992
TX -^UT
Figure 4-7. Changes in HAP air releases from 1988 to 1992 for top five states from 1988, from TRI.
Chapter 4: Air Toxics • 73
-------
Section 4.2 Emissions Trends: Extent of the Problem
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74 • Chapter 4: Air Toxics
-------
Section 4.3 Air Toxics Regulations and Implementation Status
4.3 Air Toxics
Regulations and
Implementation Status
CAAA Requirements
As noted above, the CAAA identified
189 HAPs to be regulated according
to a stringent schedule. The process
of regulation entails the development
of emission standards based upon the
Maximum Achievable Control Tech-
nology (MACT) for each source
category emitting hazardous air pol-
lutants. These emission standards
apply to all major sources (defined as
sources emitting at least 10 tons per
year of any one of the 189 listed
HAPs, or at least 25 tons a year of
any combination of HAPs).
Regulations must be developed
according to the following timetable:
• 25 percent of all source categories
by 1994;
• 50 percent of all source categories
by 1997;and
• all source categories by the year
2000.
Standards also must be developed
for "area sources" (any source that is
not defined as a major source), al-
though these can be based on gener-
ally available control technologies
(GACT). The CAAA also contain
incentives to encourage more rapid
pollutant reductions through an early
reduction program. This program
gives a six-year extension on meeting
MACT requirements to sources that
reduce emissions by 90 percent or
more (95 percent for toxic particu-
lates) before the proposal of the appli-
cable standard.
In addition, the CAAA provide for
"residual risk" standards to reduce
any risk remaining after MACT con-
trols have been implemented. This
program entails the development of
procedures for assessing residual risk,
its public health significance, and un-
certainties by 1996. The program
also requires EPA to promulgate re-
sidual risk standards for each source
category within eight years after
MACT standards were promulgated
if necessary to provide an ample mar-
gin of safety to protect the public
health.
Additional air toxics provisions
include: (1) provisions to provide as-
sistance to states developing their
own air toxics programs; (2) an acci-
dental release prevention program;
and (3) requirements to establish
monitoring stations. (For a complete
list, please refer to Section 112 of the
CAAA).
Status Report on Air
Toxics Regulations
EPA is in the process of meeting the
ambitious schedule for implementing
the CAAA's air toxics provisions.
Infrastructure programs such as defin-
ing and classifying major source cat-
egories, establishing the priority
schedule for MACT phase-in, devel-
oping guidance for the accidental re-
lease program, and establishing
general provisions for record-keeping
and reporting requirements, have
been completed and are either
approved or in various stages of the
review/approval process.
Several major regulatory actions
in the air toxics program have been
finalized or proposed in the past year:
• In February 1994, EPA finalized
the standard for the Synthetic Or-
ganic Chemical Manufacturing
Industry which requires reduc-
tions in emissions of 112 HAPs
and affects nearly 400 chemical
manufacturing plants across the
nation. This standard is projected
to reduce HAP emissions from
existing sources in this industry
by 80 percent, or an estimated
440,000 tons per year by 1998,
more than any other air toxics rule
to be issued under the CAAA.
This rule also is projected to re-
duce volatile organic compounds,
which react to form ozone, by 1.1
million tons per year.
• The control technology standards
for approximately 3,700 industrial
and large commercial dry cleaners
were finalized in September 1993.
These regulations are projected to
decrease emissions of perchloro-
ethylene by approximately 7,300
tons annually by 1996.
• In July 1994, EPA finalized the
standards for industrial cooling
towers.
• Regulatory negotiations by EPA
produced an agreement on regula-
tions to reduce toxic emissions
from steel industry coke ovens.
These regulations were finalized
in October 1993.
• EPA has proposed standards for
nine additional source categories,
all of which will be finalized next
year.
• EPA has initiated work on 77
additional emission standards.
These include the emission stan-
dards due four years after enact-
ment and several that are due
seven years after enactment.
• EPA announced the final rule for
the Early Reductions Program in
December 1992. By August
1994, EPA had received and initi-
ated review of 95 submittals, 40
of which remain active. If all of
these sources follow through, the
estimated reductions in HAPs
would total over 30 million
pounds. The EPA has also re-
ceived 19 title V specialty permits
for early reductions.
Special Studies: The EPA also is
conducting special studies assessing
the emissions and effects of toxic air
pollutants. Several of these programs
completed reports to Congress in the
past year, including:
• The Hydrogen Fluoride Study,
which assessed the potential im-
Chapter 4: Air Toxics • 75
-------
Section 4.3 AirToxics Regulations and Implementation Status
pacts of accidental releases of hy-
drogen fluoride at industrial facili-
ties;
The Hydrogen Sulfide Study,
which assessed the impacts of hy-
drogen sulfide releases from oil
and gas wells and pipelines;
The Atmospheric Deposition to
Great Lakes and Coastal Waters
(Great Waters) Study, which is the
first in a series of reports to Con-
gress, has established the ground-
work for considering the
regulation of air toxic emissions
(this is based on the potential of
air toxic emissions to pollute bod-
ies of water, persist in the environ-
ment, and bioaccumulate in the
food chain, thereby causing del-
eterious health effects); and
The National Academy of Sci-
ences Study on Risk Assessment
Methodology, a report prepared
by eminent scientists outside the
EPA in an effort to evaluate
the Agency's risk assessment
methods.
Other studies, which are continu-
ing in support of Clean Air Act man-
dates and which may affect the course
of further regulatory activity, include:
• the Urban Area Source Program
strategy;
• the Electric Utilities Steam Gen-
erating Unit study;
• the Mercury Study;
• the Residual Risk Report;
• the Coke Oven Production Tech-
nology Study; and
• the Publicly-Owned Treatment
Works (POTW) Study.
MACT Standards: Source
Category Profiles
As described above, the CAAA air
toxics provisions focus on source cat-
egories emitting large quantities of
various air toxics rather than on par-
ticular compounds. Table 4-1 dis-
plays a summary of MACT standards
proposed in prior years and described
in previous Trends reports. Brief pro-
files of the nine source categories for
which regulations were proposed dur-
ing the past year or are in the final
stages of development are presented
following the table.
Table 4-1. Summary of Previously Reported MACT Standards
MACT Source Category
Synthetic Organic Chemical Manufact. Industry
Perchloroethylene Dry Cleaning Facilities
Coke Oven Batteries
Ethylene Oxide Sterilization Facilities
Chromium Electroplating Operations
Industrial Process Cooling Towers
Total
HAP
Current
550,000
50,000
1,830
1,200
175
25
603,230
Tons/Year
After Reg.
110,000
42,700
320
100
2
0
153,122
Number of
Facilities
370
3,700
30
200
5,000
300
9,600
Date of
Proposal
12/92
11/91
12/92
03/94
11/93
08/93
Final
04/94
09/93
10/93
11/94
11/94
07/94
Primary Toxics Emitted
Up to 150 Different HAPs
Perchloroethylene
Polycyclic Organic Matter
Ethylene Oxide
Chromium
Chromium
76 • Chapter 4: Air Toxics
-------
Section 4.3 Air Toxics Regulations and Implementation Status
Aerospace Manufacturing
and Re-work Industry
Aerospace manufacturing and re-work facilities emit ap-
proximately 208,000 tons of HAPs annually from sources
including paint and coating operations, chemical stripping,
and clean-up solvents. Most of the HAPs emitted by this
industry are solvents such as methyl ethyl ketone, 1,1,1-
trichloroethane, toluene, and methylene chloride. Many of
the primers used for aerospace vehicles also contain heavy
metals such as chromium and cadmium. Research indi-
cates that possible health effects of these pollutants include
cancer as well as developmental, respiratory, and neuro-
logical effects.
EPA proposed the NESHAP to control HAP emissions
from this industry in June 1994. It is estimated that more
than 2,800 facilities will be subject to this regulation.
Expected emission reductions are projected to lower HAP
emissions by approximately 127,800 tons per year (a 60-
percent reduction). In addition, emissions of volatile or-
ganic compounds (VOCs) will be reduced by 89,000 tons
annually.
Petroleum Refinery
Petroleum refineries annually emit approximately 78,000
tons of HAPs including benzene, toluene, xylene, ethyl
benzene, methyl tert-butyl ether, 2,2,4 trimethyl pentane,
and hexane. These compounds are thought to contribute to
cancer, liver and kidney damage, and neurological and de-
velopmental effects. The greatest emission reductions for
this source category will result from requiring refiners to
implement an effective program of leak detection and re-
pair for pumps, valves, compressors and other equipment.
Additional significant reductions will occur by requiring
efficient emission controls on storage tanks, process vents
and waste water collection and treatment systems.
EPA proposed this NESHAP on June 30, 1994, and
expects to promulgate it by June 30,1995. All 192 petro-
leum refineries in the United States will be covered by the
rule. The regulations will reduce emissions of HAPs from
petroleum refineries by 54,000 tons annually, a 69-percent
reduction of current emissions. As an additional benefit,
VOC emissions will be reduced by 72 percent or 350,000
tons per year.
HAP Emissions from Aerospace Manufacturing
After
Regu-
lation
1990
HAP Emissions from Petroleum Refinery
After
Regu-
lation
50 100 150
tons per year (thousand)
200 250
1990
0 20 40 60 80
tons per year (thousand)
100
Chapter 4: Air Toxics • 77
-------
Section 4.3 Air Toxics Regulations and Implementation Status
Halogenated Solvent Cleaning
In 1990, the estimated HAP emissions from the haloge-
nated solvent cleaning industry totaled 141,400 tons.
These emissions included methylene chloride, perchloroet-
hylene, trichloroethylene, 1,1,1 trichloroethane, carbon tet-
rachloride, and chloroform. Most of these compounds are
suspected carcinogens, as shown in animal studies and
some human studies.
The EPA rule proposed in November 1993 is based on
equipment and work practices standards with an alterna-
tive compliance requirement based on an overall solvent
emissions limit. The final rule is scheduled to be promul-
gated on November 15, 1994. Approximately 25,400
batch vapor and in-line solvent cleaning machines, and
100,000 batch cold cleaning machines are affected by the
standards. The rule will reduce annual emissions of the
targeted air toxics by 88,400 tons (or 63 percent).
Magnetic Tape Manufacturing
The HAPs emitted from the magnetic tape manufacturing
industry are primarily solvents used in the coating process
including methyl ethyl ketone, methyl isobutyl ketone, and
toluene. These substances can cause developmental, neu-
rological and possibly respiratory effects. Some particu-
late HAP emissions may also occur during the transfer of
magnetic particles to the coating mix. Based on 1992 in-
formation, major sources are estimated to emit about 4,500
tons of HAPs annually.
In March 1993, the EPA proposed standards to reduce
these emissions. The final rule is scheduled for promulga-
tion in November 1994. For the majority of the emission
points in a facility, the proposed rule would require 95 per-
cent control. Most facilities are expected to achieve this
with a solvent recovery device, such as a carbon adsorber.
Other emission points would be required to meet work
practice or equipment specifications. The rule as proposed
would reduce HAP emissions to about 2,200 tons per year
(an approximate reduction of 50 percent).
HAP Emissions from Halogenated Solvent Cleaning
After
Regu-
lation
1990
HAP Emissions from Magnetic Tape Manufacturing
After
Regu-
lation
50 100 150
tons per year (thousand)
1992
200
1234
tons per year (thousand)
78 • Chapter 4: Air Toxics
-------
Section 4.3 AirToxics Regulations and Implementation Status
Marine Vessel Loading Operations
Marine vessel loading and unloading operations are be-
lieved to emit as many as 60 of the 189 HAPs. Air toxic
emissions from this industry include benzene (a known
human carcinogen), toluene (a possible contributor to neu-
rological effects), ethyl benzene (a possible contributor to
developmental effects), and xylene (a possible contributor
to neurological effects). Emissions at marine terminal
loading operations result from the displacement of vapors
as liquids are loaded into cargo holds either directly
through open-hatches or from pipe header systems which
collect the vapors and vent to atmosphere.
The EPA proposed the marine vessel rule in May 1994.
Approximately 350 facilities/emitting 8,000 metric tons of
HAPs in 1990 will be affected by the rule. Expected emis-
sion reductions resulting from the rule are projected to be
7,600 metric tons per year (or a 95-percent reduction).
Polymers and Resins II
The EPA proposed the NESHAP for epoxy resin produc-
tion and non-nylon polyamides production in May 1994.
The proposed rules affect manufacturers that produce ba-
sic liquid epoxy resin (three facilities) and wet strength
resins (17 facilities).
HAPs are emitted at these processes from vents, stor-
age tanks, waste water collection and treatment systems,
and equipment leaks. The predominant air toxic emitted is
epichlorohydrin which is a suspected carcinogen, based on
animal studies and some human studies. Estimated
baseline HAP emissions are 160 tons per year. The pro-
posed rules set HAP emissions limitations, which are
based on the amount of resin produced, and require opera-
tors to implement leak detection and repair programs for
control of equipment leaks. The estimated reduction in
HAP emissions is 110 tons per year (a reduction of ap-
proximately 70 percent).
HAP Emissions from Marine Vessel Loading
After
Regu-
lation
1990
HAP Emissions from Polymers and Resins II
After
Regu-
lation
2468
tons per year (thousand)
10
1990
50 100 150
tons per year
200
Chapter 4: AirToxics • 79
-------
Section 4.3 AirToxics Regulations and Implementation Status
Pulp, Paper, and Paperboard Industry
Manufacturing Processes
Pulp and paper mills emit HAPs, most notably chloroform
and methanol, to the air as well as discharge toxic and
other Clean Water Act pollutants, most notably dioxins
and furans, into the nation's waters. Chloroform caused
cancer in animal studies, and methanol resulted in repro-
ductive and developmental effects in animal studies. There
are about 160 chemical pulping mills contributing approxi-
mately 187,000 tons of HAPs per year from process vents
and evaporation from waste water units.
The air rule and effluent guidelines were proposed in
December 1993 and are estimated to reduce HAP emis-
sions by 132,000 tons per year and VOC emissions by
787,600 tons annually. Air emission reductions are
achieved by venting process equipment to combustion de-
vices and steam stripping certain waste water steams.
HAP controls for combustion sources at kraft mills will be
proposed in early 1994. Both HAP rules are planned to be
promulgated together with the effluent guidelines in early
1996.
HAP Emissions from Pulp, Paper, and Paperboard
After
Regu-
lation
1990
Gasoline Distribution Industry
(Stage I)
Gasoline vapor contains up to 11 hazardous air pollutants
(HAPs): benzene, toluene, ethylbenzene, naphthalene,
cumene, p-xylene, m-xylene, o-xylene, n-hexane, and 2-2-
4-trimethylpentane. In addition, methyl tert-butyl ether is
in gasolines reformulated and oxygenated to meet the
CAAA requirements for non attainment areas. These com-
pounds were found to contribute to cancer, liver and kid-
ney damage, as well as neurological and developmental
effects in animal studies and some human studies. Re-
sidual HAP and VOC emissions after current VOC control
measures are estimated to be 55,000 and 880,000 tons per
year, respectively. The potential major sources of HAPs in
the gasoline distribution network include about 380 me-
dium and large size gasoline bulk terminals, and about 20
large pipeline breakout stations. Emissions of HAPs from
these facilities occur during gasoline tank truck loading,
gasoline storage, and from leaking pumps, valves, flanges
and other equipment in gasoline service.
The HAP rule for major source terminals and pipeline
breakout stations was proposed in February 1994. This
regulation is estimated to reduce HAP and VOC emissions
by 2,970 and 48,400 tons annually, respectively.
HAP Emissions from Gasoline Distribution Industry (Stage I)
After
Regu-
lation
1990
50 100 150 200
tons per year (thousand)
250
10 20 30 40 50 60 70
tons per year (thousand)
80 • Chapter 4: Air Toxics
-------
Section 4.3 AirToxics Regulations and Implementation Status
Secondary Lead Smelters
There are about 23 secondary lead smelters in the United
States. These facilities provide the domestic capacity for
recycling automotive batteries. Secondary lead smelters
emit metallic HAPs, organic HAPs, and hydrochloric acid.
Some of the HAPs emitted, such as lead compounds, ar-
senic compounds, and 1,3-butadiene, are known or sus-
pected carcinogens. Total HAP emissions from this source
category are estimated at 2,900 tons per year.
National emission standards for these operations were
proposed in May 1994, and are expected to be promul-
gated by May 1995. The regulation would require control
of furnace combustion gases; process fugitive emission
sources including the furnace charging and tapping loca-
tions and emissions of lead fume from refining kettles; and
fugitive dust sources which are windblown or vehicular in-
duced emissions from storage piles, roadways, and other
areas of the facility. This NESHAP would result in emis-
sion reductions of 2,200 tons annually, or 75 percent of the
1990 baseline.
HAP Emissions from Secondary Lead Smelters
After
Regu-
lation
1990
0.5 1 1.5 2 2.5
tons per year (thousand)
3.5
Chapter 4: Air Toxics • 81
-------
Section 4.4 References
4.4 References
1. Clean Air Act Amendments of 1990, U.S. Code, vol. 42 sec. 7412(b)(2), 1990.
2. National Air Pollutant Emission Trends, 1900-1993, EPA-454-R-94-027, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, N.C.
27711.
3. 1992 Toxics Release Inventory, EPA-745-R-94-001, U.S. Environmental Protection Agency, Office
of Pollution Prevention and Toxics, Washington, D.C. 20460, April 1994.
4. 1991 Toxics Release Inventory, EPA-745-R-93-003, U.S. Environmental Protection Agency, Office
of Pollution Prevention and Toxics, Washington, D.C. .70460, May 1993.
82 • Chapter 4: Air Toxics
-------
Chapter 5: Air Quality Status
of Metropolitan Areas
This chapter provides some general
information on the current air quality
status of U.S. metropolitan areas.1
Several different summaries are pre-
sented. First, a simplified list of areas
designated nonattainment for the Na-
tional Ambient Air Quality Standards
(NAAQS) for carbon monoxide
(CO), lead (Pb), nitrogen dioxide
(NO2), ozone (O3), particulate matter
(PM-10), and sulfur dioxide (SO2) is
given. The list is followed by a set of
maps showing the locations of the
nonattainment areas for each pollut-
ant. Next, an estimate is provided of
the number of people living in coun-
ties which did not meet the NAAQS
based on a snapshot of 1993 air qual-
ity data. Pollutant-specific maps are
then presented to provide the reader
with a geographical view of how peak
1993 air quality levels varied
throughout counties in the United
States. Finally, a table is presented
that shows peak values for each Met-
ropolitan Statistical Area (MSA)
which had 1993 air quality monitor-
ing data.
5.1 Nonattainment
Areas
When an area does not meet the air
quality standard for one of the criteria
pollutants, it may be subject to the
formal rule-making process which
designates it as nonattainment. The
Clean Air Act Amendments (CAAA)
of 1990 further classify ozone, carbon
monoxide, and some particulate mat-
ter nonattainment areas based upon
the magnitude of the area's problem.
Nonattainment classifications may be
used to specify what air pollution re-
duction measures an area must adopt
and when the area must reach attain-
ment. The technical details underly-
ing these classifications are discussed
in the Code of Federal Regulations.2
Table 5-1 lists the number of non-
attainment areas for each pollutant as
of September 1994. Table 5-2 pro-
vides a simplified summary of indi-
vidual nonattainment areas listed al-
phabetically by state. A more de-
tailed listing is contained in the Code
of Federal Regulations, Part 81 (40
CFR 81). The population figures
listed with each nonattainment area
are based on figures from the 1990
Census. For nonattainment areas de-
fined as only partial counties, popula-
tion totals for just the nonattainment
area were used when available; oth-
erwise, whole county population to-
tals are shown. When a larger
nonattainment area encompassed a
smaller one, double-counting the
population was avoided by only
Table 5-1. Nonattainment Areas for NAAQS Pollutants as of September 1994
Pollutant
Number of
Nonattainment
Areas*
Carbon Monoxide (CO)
38
Lead (Pb)
13
Nitrogen Dioxide (NO)
Ozone (0'
93
Particulate Matter (PM-10)
Sulfur Dioxide (SO.)
47
* Unclassified areas are not included in the totals.
Chapter 5: Air Quality Status of Metropolitan Areas • 83
-------
Section 5.1 NonattainmentAreas
counting the population of the larger
area. Occasionally, two nonattainment
areas may only partially overlap. In
this case, these areas were counted as
two distinct nonattainment areas, and
the population was added accordingly
(see Figures 5-1 and 5-2).
The total number of nonattain-
ment areas has increased somewhat
since Table 5-2 was first published
last year. The largest change oc-
curred for PM-10 nonattainment ar-
eas, with an increase of 13 areas. SO2
added three nonattainment areas.
Two CO areas and one O3 area were
redesignated to attainment and were
dropped from the list. The number of
Pb and NO2 nonattainment areas re-
mained the same. It is worth mention-
ing that there are several areas,
especially for ozone but for other
pollutants as well, which have begun
the redesignation process but are not
included here because their redesig-
nations have not yet been finalized.
Since the original nonattainment
designations in 1991, five of the 98
ozone nonattainment areas have been
redesignated to attainment:
• Kansas City, KS-MO;
• Cherokee County, SC;
• Greensboro, NC;
• Knoxville, TN; and
• Raleigh-Durham, NC.
Of the 41 original CO nonattain-
ment areas in 1991, four areas have
been redesignated to attainment for
the CO NAAQS:
• Cleveland, OH;
• Duluth, MN;
• Syracuse, NY; and
• Memphis, TN.
The original number of PM-10
nonattainment areas has increased by
the following 13 areas:
• New York, NY;
• Weirton,WV;
• Thompson Falls, MT;
• Steamboat Springs, CO;
• Whitefish, MT (Flathead Co);
• Payson, AZ;
• Bullhead City, AZ;
• Sacramento Co, CA;
• San Bernadino Co, CA;
• Mono Basin, CA;
• Shoshone Co, ID;
• Oakridge, OR; and
• Lakeview, OR (Lake Co).
For SO2, seven of the original 51
nonattainment areas now meet the
NAAQS and have been redesignated
to attainment. These include:
• Colbert Co, AL;
• Green Bay, WI;
• Lauderdale Co, AL;
• Dane Co, WI;
• Milwaukee Co, WI;
• Washington Co, OH; and
• Morgan Co, OH..
Three new areas have been desig-
nated nonattainment for SO2:
• Warren, Pleasant, Glade, PA
(Warren Co, PA);
• Wierton, Butler, Clay, WV
(Hancock Co, WV); and
• Muscatine Co, LA.
The information contained in
Table 5-2 is depicted graphically in
Figure 5-3 through Figure 5-8. Each
map presents the location of the cur-
rent nonattainment areas for that cri-
teria pollutant. As in the case of the
table, this information was current as
of the end of September 1994.
84 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
Section 5.1 NonattainmentAreas
Table 5-2. Simplified Nonattainment Areas List3.
1
2
3
4
5
•*--*"• $ -'
->-".-T'-
•' "*''-ii ••'
:;'*<«»'
- 'So--
11
12
13
14
15
•:,-t^':.
;.A$>
?£*'
21
22
23
24
25
-. ;gg- '
;,i;lK-
;X§?
31
32
33
34
35
° .W."
.-'I?,
;,: $e-:
•JKJ
41
42
43
44
45
-:;'&
••>#;
51
52
53
54
55
''••Bfc •
'••'£•
Nto'',
61
62
63
64
65
". ;{jg'
' ;#
',.??.'
'70
STATE
AK
AK
AK
AL
AZ
°ASt-" v; "' ' >" .-
•ffe 1 '. ,,'**'•/' - t
^j"' -.'";<°: i-'.,' ','
./&; .\~~:" '••' ?"' '•'
'•*&•""' '• • ' "•'
AZ
AZ
AZ
AZ
AZ
,*?•>:•." •;;.':•.'•:
(SW?'!M-'-
'.tfA':"/.'"v''"':;
CA
CA
CA
CA
CA
'CA"'--" . .- • '-, "
;«^;:: -CK,..;,::.;;
fi?;-JS:
CA
CA
CA
CO
CO
..-co-.;"., .;:'-./-.!
• $o>x'v-:'";
-co'' ''•'•
CO
CO
CO
CT
DC-MD-VA
f"<*M''V-""j"
';:':H;:v":"-;
GU
GU
IA
ID
ID
,,10; \ , •,-',',
^•3:4'':
::lt '," -" " .-"'
IL
IL
IL
IL-IN
IN
Iff •
iN: \ 'v .
IM
IN
POLLUTANT(c) POPULATION(d)
AREA NAME(b) O3 CO SO2 PM10 Pb NO2 (1000s)
Anchorage . 1
Fairbanks . 1
Juneau
Birmingham 1
Ajo • 1
&uBh&icl City- ' - - - ' ! - * - ' ** • • ' , < - -
Douglas '.;'•'•'-'' !'' ,M ' - :. .4.,"' '•':'.* ' ~l-': 'i '.•
•SiSaBri^en. ,-;.-,', •. '' '' v ,..',...;.•.'-.• •'/•"• . - 2 ...
N(kfeie&'' '' "••' ' '• ;' • '••''.'' -' •''.'• • *' .-•'/.'•"
Paul Spur
Payson
Phoenix 1 1
Rillito
San Manuel - • 1
yw&ii •'•'-. \' :,.,/;;•/., v, ././ ,'v- ;'\- .. !' '<• ;•- -*',-'
^^^'•/."^•';''>>;.;'-; ; ;';1 =;::.;r-."'..' f '-y
:|B^4ife^W(^','"""",':: V"r'v: •"' -''• -••"•',"'•" ••''••' :• .'' .>' - ':-::
iatwtlWwe'Swih Shore , :','!-: •'' • '••'-• '-"1'. • ''
Los Angeles-South Coast Air Basin 1 1
Mammoth Lakes (in Mono Co.)
Mono Basin (in Mono Co.)
Monterey Bay 1
Owens Valley . . .
.^eiam^is-MWtf "'V :';;•••• ' " •' -1 ' 1 '*• " «.'•,'
'^^fc^'fC-;:;)';^';/^;^ ' ;;;.^;.,.-'->,,|'-J ;'M:--:. -';•
'J^r^^*^^Wa;«lii«itiropd<: '; " t, ' > '.'''., '" •' '.'. •' •'"
Searies Valley
Southeast Desert Modified AQMA 1
Ventura Co 1
Aspen
Canon City
.OoMNltoSM^ . :- . . ' ; , j',f -; .,;. f •-._,;• ? •• \ ~i ••',; i
•^S«%' -• ?V' ''•)•' •,''':='••'•.:!"•:->;•"•>,' •'• -:' i"^- . --C-?: »;
•twi«r '.•-,. "V; '"'•-.'' "' •"• •,': .-."'•"•:".. ;-'V- .. '.'.-'.,
jj^^tt^a^'; . • ' ' •' !•' ' ' ,• •'• '. 1 ' •' . . •
Pagosa Springs
Steamboat Springs
Telluride
Greater Connecticut 1 1
Washington 11 .
;^SS'i^«ja^W'pa^^*' .:''J !'•"•'•' •"•••'.'•' '-• ' ••;•- ••
;3^^^vf^sif^i^r.,;i ,;yr; ly^'y •'•''••',•• '.;''
Piti Power Plant .1
Tanguisson Power Plant . . 1
MuscatmeCo. . . 1
Boise
Sandpoint (in Bonner Co )
pinehurst . • - ". • ••,, • •••••- ..-.•;., .,-.». . '•
iJSKX/vOi •• '""^,':^:":: ^ •:>./' ';iS"' ''•>• '•
:'SSSE'.:--''-:': •''-''".''•'••' • ^''f'.':s.'> '•"•'' IV-'1
Jersey Co. 1
Oglesby
Peona . 1
Chicago-Gary-Lake County 1 . 1
Evansville 1
lndi$ftap<^s ,.\-1 -. -1' ' ,, , ,' ,1,^'-, ,; , - "\. 1,'- -
i&p9ri$C&- u - ' ' ',: !•!/ :'''%' ;s ' 1 • "'
•SnSl^^r ' • •,.,'• ,"•:.'• .' " : '* ';, '
:VigOCO. : ' ', ," - "' ' , ' 't "
1
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1
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-'f^-^v'.v' -•';.- ;'!-':x'-;
"•'••', : >'',-•';•'*'!-. v':;
1
3
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,-_»..,= '.>:); '-\-\'-{ ".'-..-'.
* u. '•.' ' „ j , - - •' ' ' j •
'* "' C *.s ' '.*'.'"''''
130
41
12
651
6
' ' " $ . x\" * ;,' /' '' " , -1' '^ '
•' ,:1$ '. ' : .; •"" "i,"'-; -''.,' '. •'.' ;" •'.'.'
S . ' i • •'••• ' : '' -; •'•.''. ' ,"•
•'••:"$''~: '•'./ •': . '- ''•-''•-' <-"•:'}. ., ''
•' ,'; i«;. -•-'•.'•-.''• '•;"'>' ' •'••:'-.'-':
1
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>4j8 :/-'; :> >fe%;=:'v^:;--'v
:'--!:S''--i!'-AN'-v'TS-''-!::?= *'••''
13513
10 (Pop Mono Co.)
(See Mono Co. above)
622
18
'•t<|99- -,'Y'V',;" ,' •.' .', -, ', • "'„•• , .
::iif '; ••'• '^^-A =-; ''-$ '••-' '
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«; %':^:',- V •;/'". -:*. ".V"* !•:;'•.', ."' ;,'•'',
• gg". ". •_ _ "., • •-,,' ,.-•_'• :•"'/ ;,, .
1
7
1
2470
3924
-'.iftj'>- -vV.'^l'.v-l'
'f^v^-'%;v^K1-*"-:'>-Vri'
145 (Pop Guam)
(See Guam above)
40
205
27
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18$* $*Oj>f^6i1iCQ4. ' '' ' ' ^ ^
21
4
. (See Peona Co. above)
7886
165
'• '797, ' '. , " ..'•••• ' •
;;io7 ;..;-;• V ,;-:''-'.' •;'
V1 '\T • ' ' s: -.-'.•• '.-•'•' '• •
- - *» , , - ,--
V106 •' •'.
Chapter 5: Air Quality Status of Metropolitan Areas • 85
-------
Section 5.1 NonattainmentAreas
Table 5-2. Simplified Nonattainment Areas List3 (cont.)
STATE
AREA NAME(b)
O3
POLLUTANT(c) POPULATION(d)
CO SO2 PM10 Pb NO2 (1000s)
71
72
73
74
75
,7g
= -,*?
/'7J
",?i
• 80
'si
82
83
84
85
-' 88
' •<&?•
88
,.te
' 90
91
92
93
94
95
;;|
101
102
103
104
105
iS
is
in
112
113
114
115
"116
' J1?
'31
i'tSs
121
122
123
124
125
'426
;,t&
^123
-12i
W
131
132
133
134
135
'J38
-ife
\$S0
IN
KY
KY
KY
KY
VK¥ -, ,
> ,,^Mft: ,- •
••/tA-'./ '.'< .',
'•".VA '".•'. "•
'"t(IA' " :
MA-NH
MD
MD
ME
ME
"'Mi'
ME: . -',
' - »»£' ; ' •'
, - 'JSflE,- ,* ,,' .
.'•''ME, =.,-/=••.
••'MI', '• - •-
Ml
Ml
MN
MN
MO
..".MO-:,/ •
MT
MT
MT
MT
MT
»syi h.
ftHiSS
"N'C
NC
NE
NH
NH
NJ '
: ' NM;:' ' • '
!:-8K/ /
"•",W • • ••
NV
NV
NY
NY
NY
r N5? : • • ,
'.'JNX " -' '
-, :=ifMWKJf •;
•' Off ' - - ''
OH " X
OH
OH
OH
OH
OH
•:OH
': • OH''
:i"W**, -.
,-; GH-PA ,.,•'
Wayne Co.
Edmonson Co.
Lexmgton-Fayette
Muhlenberg Co.
Owensboro
.,' .PssSieah ,' ,-,,','
• ' tietijiMt 'y • ' '.".'.".
Isl^ldRHEftoJUgfe °°- ,", ,-% • ,' ,
: , 1$R& £!J$i(l6SS, • - - ' ,- ^
• '^>rfi(8fleWl0(V:M^'-', ••
Boston-Lawrence-Worcester
Baltimore
Kent and Queen Anne Cos.
Hancock and Waldo Cos.
Knox and Lincoln Cos.
Lewtston-Aubum '
•Mllnookw ,'•
,-,-': ' Portland • •. .
'•'. ,,')Pi^qwe)^|: '' ._ ,
Detmtt-Ann Artjor , •
Grands Rapids
Muskegon
Minneapohs-St Paul
Olmsted Co.
Dent
z::$$*^',' ='•.' -.'
Lame Deer
Lewis & Clark
Libby
Missoula
Poison
i'tiSSonfaite^ .;/./•:''
/ A ,,' &**£»£&& ^^tt^tt^d- *' '. '- - '
,; - Mlaa?QMV"l9<**KunKl< " "
Raleigh-Durham
Winston-Salem
Douglas
Manchester
Portsmouth-Dover-Rochester
Atlantic City "''"
, ' ASbUcjaerciMi - ' - '
-. , ,,Aft$oiiiy ,,- , „ -, , ; ,
:, , • •CftrSr&t'StSpto&vyfey , "
Las Vegas
Reno
Albany-Schenectady-Troy
Buffalo-Niagara Falls
Essex Co. (White Mtn )
Jaffersort Co.
:". " Hj^gW^p^e," '
• ;Cifiibn • '• '
: Ctevsifflid-Aton-torain
Columbus
Coshocton Co.
Dayton-Springfield
Gailia Co.
Jefferson Co
Lake CO.
• -.Tote*)': - '
^, •* ^p^^r^tsd"^^^^ ' •
• - ' •Y0^i?g$ftMll''WdTi$i^$h&tQ!i
1
1 .....
1 .....
1
1 ...
• • • ' \',- . • , ' . ,-.••'. . '
: .-yi.. .-, -., ; ''.-,, /;-. ,-.:. './-.,.'.. .-• '. .'
•' -'",'* ;'{". -C--V .-'•'•;•.'•,-:;;••••, '..•'..' ".
'••'''"' •' i ':''.:,.-, •"'/. v: _' , " '•,,' •' -';',,.
. '• ' , i, ! - • ''-..'•'-.' • . :- .
11 ...
11
1 ...
1 . .
1 .....
1 . • . . . . . •
. • • , 1 : . '
r • •' , ' ,• • '•-.. '..'-. • • , -.
'••''•: -"..'-.-'.I' - : -' •" '
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1 .....
1 1 1 1 (g) .
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86 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
Section 5.1 NonattainmentAreas
Table 5-2. Simplified Nonattainment Areas List3 (cont.)
141
142
143
144
145
14i
148'
149
ISO
151
152
153
154
155
156
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139
160
161
162
163
164
165
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169
170
171
172
173
174
175
176
"177;
181
182
183
184
185
186',
: 189
-190
191
192
193
194
195
STATE
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OR
OR
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TN
TN
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TX
UT
UT
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WA
WA
WA
Wl
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WV
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AREA NAME(b)
Klamath Falls
Lakeview
LaGrande
Medford
Oakridge
SprfhgJtettMSBaane ., ' :- >: -
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Johnstown
Lancaster
Pittsburgh-Beaver Valley
Reading
Scranton-Wilkes-Batre ' ••
. Warren-Pleas.-Glade (in Warren Co)
York/-,' - - '.- '-. "• . ; , -
!-MD PniSa'delphla-Wilrnington-Trenton "-,,
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Providence (all of Rl)
Benton Co.
Fayette Co.
Humphreys Co.
MemipBs1" ': /, - ;.', „ '
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Houston-Galveston-Brazoria
Ogden
Salt Lake City
Tooele Co
, UttfcCo." \- - , . ,-- ,
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Spokane
Wallula
Yakima
Door Co.
KswawmCo. - " , , -
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Milwaukee-Racine '•,'•• ' -
OneldaCo, : •>- -' '- -,' •' •
Srieboygan
Walworth Co
Follansbee
Greenbner Co.
New Manchester Gr. (in Hancock Co)
Wier.-Butler-Clay (In Hancock Co) ;
HjiiiMingtefrAfeiartJ-'-r' >-'••• '•'•'•„'••': ,:
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POLLUTANT(c)
O3 CO SO2 PM10 Pb
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POPULATION(d)
NO2 (1000s)
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Chapter 5: Air Quality Status of Metropolitan Areas • 87
-------
Section 5.1 NonattainmentAreas
Table 5-2. Simplified Nonattainment Areas List3 (cont.)
Notes: (a) This is a simplified listing of Classified Nonattainment areas. Unclassified and transitional
nonattainment areas are not included. In certain cases, footnotes are used to clarify the areas
involved. For example, the lead nonattainment area listed within the Dallas-Fort Worth ozone
nonattainment area is in Frisco, Texas, which is not in Dallas county, but is within the designated
boundaries of the ozone nonattainment area. Readers interested in more detailed information should
use the official Federal Register citation (40 CFR 81).
(b) Names of nonattainment areas are listed alphabetically within each state. The largest city determines
which state is listed first in the case of multiple-city nonattainment areas. When a larger
nonattainment area, such as ozone, contains one or more smaller nonattainment areas, such as PM-
10 or lead, the common name for the larger nonattainment area is used.
(c) Nonattainment area status as of September, 1994.
(d) Population figures were obtained from 1990 census data. For nonattainment areas defined as only
partial counties, population figures for just the nonattainment area were used when these were
available. Otherwise, whole county population figures were used. When a larger nonattainment
area encompasses a smaller one, double-counting the population is avoided by only counting the
population of the larger nonattainment area. Note that several smaller nonattainment areas may be
inside one larger nonattainment area, as is the case in Figure 5-1, which is considered 1 nonattainment
area. Caution must be used in these cases, as population figures will not be representative of small
nonattainment areas for one pollutant inside larger nonattainment areas for another pollutant.
Occasionally, two nonattainment areas may only partially overlap, as in Figure 5-2. For the purpose
of this table, these are considered two distinct nonattainment areas.
(e) Lead nonattainment area is a portion of Jefferson county, Alabama.
(f) Lead nonattainment area is a portion of Franklin township, Marion county, Indiana.
(g) Lead nonattainment area is a portion of Dakota county, Minnesota.
(h) PM-10 nonattainment area is Granite City, Illinois, in Madison county.
(i) Lead nonattainment area is Herculaneum, Missouri in Jefferson county.
(j) Lead nonattainment area is a portion of Lewis and Clark county, Montana.
(k) Lead nonattainment area is a portion of Shelby county, Tennessee.
(1) Lead nonattainment area is a portion of Williamson county, Tennessee.
(m) Lead nonattainment area is Frisco, Texas, in Collin county.
88 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
Section 5.1 NonattainmentAreas
NA for O3
NA for SO2
Figure 5-1. Example of multiple nonattainment (NA) areas within a larger NA area (two S02 NA areas inside the Pittsburgh-
Beaver Valley ozone NA area, counted as one area).
NA for O3
NAforPM-10
Figure 5-2. Example of overlapping NA areas (Searles Valley PM-10 NA area partially overlaps the San Joaquin Valley
ozone NA area, counted as two areas).
Chapter 5: Air Quality Status of Metropolitan Areas • 89
-------
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Moderate > 12.7ppm
Moderate <= 12.7ppm
Designated Nonattainment Areas as of September 1994
Note: Unclassified areas are not shown.
Figure 5-3. Areas designated nonattainment for carbon monoxide.
-------
Section 5.1 NonattainmentAreas
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Chapter 5: Air Quality Status of Metropolitan Areas • 91
-------
Section 5.1 NonattainmentAreas
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92 • Chapter 5: Air Quality Status of Metropolitan Areas
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Note: Unclassified areas are not shown.
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-------
Section 5.1 NonattainmentAreas
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94 • Chapter 5: Air Quality Status of Metropolitan Areas
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Section 5.2 Population Estimates for Counties Not Meeting NAAQS, 1993
5.2 Population
Estimates for
Counties Not Meeting
NAAQS, 1993
Figure 5-9 provides an estimate of the
number of people living in counties in
which the levels of the primary
NAAQS were not met during 1993.
These estimates use a single-year in-
terpretation of the NAAQS to indi-
cate the current extent of the problem
for each pollutant. This single year
approach provides a convenient snap-
shot for the most recent year, but it
should be noted that attainment of
these standards requires more than
just one year of data to fully account
for variations in emissions and meteo-
rological conditions. The methodol-
ogy used to determine the counties not
meeting the single-year ozone
NAAQS was changed this year to use
the second daily maximum concentra-
tion rather than the number of esti-
mated exceedances. This change was
made in order to employ the same
methodology in these estimates as in
the county maps that follow. To re-
view the NAAQS for each pollutant,
see Chapter 2, Table 2-1.
Figure 5-9 demonstrates that O3
was the most pervasive air pollution
problem in 1993 for the United States
with an estimated 51.3 million people
living in counties which did not meet
the 03 standard. This estimate is an
increase of 8.7 million from last
year's revised estimate of 42.6 mil-
lion people for O3. Even with this in-
crease, the total is still the second
lowest population estimate during this
10-year period and is substantially
lower than the 112 million people liv-
ing in areas which did not meet the
ozone NAAQS in 1988. The increase
between 1992 and 1993 is likely due
in part to meteorological conditions
more conducive to O3 formation in
1993, especially in the eastern half of
the country.
Carbon monoxide has the next
largest total with 11.6 million, down
from last year's estimate of 14.3 mil-
lion. PM-10 follows with 9.4 million,
down significantly from 25.8 million
people in 1992. This decrease for
PM-10 is due to sixteen counties
which met the NAAQS in 1993, six
of which had large populations, in-
cluding Los Angeles, Chicago and
Phoenix. Pb is next with 5.5 million
and SO2 with 1.4 million people.
Both Pb and SO2 recorded small in-
creases. Finally, this is the second
consecutive year that no monitoring
violations of the NO2 NAAQS were
recorded.
A total of 59.1 million persons re-
sided in counties not meeting at least
one air quality standard during 1993
20 40 60
millions of persons
80
100
Figure 5-9. Number of persons living in counties with air quality levels not meeting the primary NAAQS in 1993. (Based on
1990 population data and 1993 air quality data.)
96 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
Section 5.2 Population Estimates for Counties Not Meeting NAAQS, 1993
(out of a total 1990 population of 249
million). This estimate is up 15 per-
cent from the revised estimate of 51.4
million people for 1992.
These population estimates are in-
tended to provide a relative measure
of the extent of the problem for each
pollutant in 1993. The limitations of
this single-year indicator should be
recognized. An individual living in a
county that violates an air quality
standard may not actually be exposed
to unhealthy air. For example, if CO
violations were confined to a traffic-
congested center city location during
evening rush hours in the winter, it is
possible that an individual may never
be in that area, or may be there only
at other times of the day or during
other seasons. The lead monitors
typically reflect the impact of lead
sources in the immediate vicinity of
the monitoring location and may not
be representative of county-wide air
quality. However, it is worth noting
that ozone, which appears to be the
most pervasive pollution problem by
this measure, is also the pollutant
most likely to have fairly uniform
concentrations throughout an area.
The limitations of using only a single
year of data were noted previously.
The assumptions and methodol-
ogy used in any population estimate
can, in some cases, yield a wide
swing in the estimate. For example,
while there are an estimated 51 mil-
lion people living in counties that had
1993 ozone data not meeting the
ozone NAAQS, there are an esti-
mated 140 million people living in
EPA designated ozone nonattainment
areas, based on air quality data from
the years 1987-89. Although these
numbers are properly qualified, with
such a large difference, it is important
to highlight some of the factors in-
volved in these estimates. The esti-
mate of 51 million people only
considers data from the single year,
1993, and only considers counties
with ozone monitoring data. Pres-
ently, counties with ozone monitors
contain 66 percent of the total U.S.
population (counties with monitors
for any pollutant comprise 77 per-
cent). In contrast, designated ozone
nonattainment areas are typically
based upon three years of data to en-
sure a broader representation of pos-
sible meteorological conditions. This
use of multiple years of data, rather
than a single year, is based on the pro-
cedure for determining attainment of
the ozone NAAQS.
Another difference is that the esti-
mate of 51 million people living in
counties with air quality levels not
meeting the ozone NAAQS only con-
siders counties that had ozone moni-
toring data for 1993. There were only
925 ozone monitors reporting in
1993. These monitors were located in
538 counties, which clearly falls far
short of the more than 3,100 counties
in the United States. This shortfall is
not as bad as it may initially appear
because it is often possible to take ad-
vantage of other air quality consider-
ations in interpreting the monitoring
data. This, in fact, is why other fac-
tors are considered in determining
nonattainment areas. Ozone tends to
be an area-wide problem with fairly
similar levels occurring across broad
regions. Because ozone is not simply
a localized hot-spot problem, effec-
tive ozone control strategies have to
incorporate a broad view of the prob-
lem. Nonattainment boundaries may
consider other air quality related in-
formation, such as emission invento-
ries and modeling, and may extend
beyond those counties with monitor-
ing data to more fully characterize the
ozone problem and to facilitate the
development of an adequate control
strategy.
Since the early 1970s, there has
been a growing awareness that ozone
and ozone precursors are transported
beyond the political jurisdiction of
source areas and affect air quality
levels at considerable distances
downwind. The transport of ozone
concentrations generated from urban
man-made emissions of precursors in
numerous areas to locations further
downwind can result in rather wide-
spread areas of elevated levels of
ozone across regional spatial scales.
Chapter 5: Air Quality Status of Metropolitan Areas • 97
-------
Section 5.3 Maps of Peak Air Quality Levels by County, 1993
5.3 Maps of Peak Air
Quality Levels by
County, 1993
This section presents air quality maps
that show how air quality varied
across the country during 1993. For
each pollutant, the maps display the
highest concentration recorded for
that air quality indicator among all
monitoring sites in the county. The
following annual air quality statistics
are displayed for each pollutant:
CO - The highest second maximum
eight-hour average concentration.
Pb - The highest quarterly average
concentration.
NO2 - The highest annual mean con-
centration.
O3 - The highest second daily maxi-
mum one-hour concentration.
PM-10 - The highest second maxi-
mum 24-hour average concentration.
SO - The highest second maximum
24-hour concentration.
These pollutant concentration
maps appear as Figures 5-10 through
5-15.
The bar chart accompanying each
map displays the number of people
living in counties within each pollut-
ant concentration range. For all of the
pollutants except PM-10, the sum of
the yellow and red bars equals the
height of the population bars in Figure
5-9 for the corresponding pollutant.
For PM-10, the map displays the sec-
ond highest 24-hour concentration in
the county, however, there are addi-
tional counties not shown on the map
that failed to meet the annual mean
standard in 1993. Thus, except for
PM-10, the reader can use these maps
to identify those counties not meeting
the NAAQS during 1993 that com-
pose the population estimate for each
pollutant.
The Pollutant Standards Index
(PSI) colors are employed in the fol-
lowing maps to provide a readily
identifiable and consistent color
scheme throughout. The PSI is a uni-
form air quality index used for the
daily reporting of air pollution con-
centrations in most major U.S. cities.
The "cooler" PSI colors (blue and
green) indicate air quality that is
"better" than the level of the corre-
sponding air quality standard. The
"warmer" colors (yellow, orange, red)
denote air quality levels that do not
meet the NAAQS for that pollutant.
A complete discussion of the PSI can
be found in the following chapter.
Table 5-3. Number of Counties With at Least One Monitoring Site by
Pollutant
Pollutant
Number of Counties With at
Least One Monitoring Site
Carbon Monoxide
250
Lead
187
Nitrogen Dioxide
213
Ozone
537
Paniculate Matter (PM-10)
647
Sulfur Dioxide
359
98 • Chapter 5: Air Quality Status of Metropolitan Areas
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Carbon Monoxide Air Quality Concentrations, 1993
Highest Second Max 8-Hour Average
en
CO
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Concentration (ppm)
- 15.4
Figure 5-10. Carbon monoxide air quality concentrations, 1993—highest second maximum eight-hour average.
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Highest Quarterly Average
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Figure 5-11. Lead air quality concentrations, 1993—highest quarterly average.
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Chapter 5: Air Quality Status of Metropolitan Areas • 103
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Sulfur Dioxide Air Quality Concentrations, 1993
Highest Second Max 24-Hour Average
01
CO
at
s-
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5
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Concentration (ug/m3)
81
I 81 - 365
366-800
Figure 5-15. Sulfur dioxide air quality concentrations, 1993—highest second maximum 24-hour average.
-------
Section 5.4 Metropolitan Statistical Area (MSA)Air Quality Summary, 1993
5.4 Metropolitan
Statistical Area (MSA)
Air Quality Summary,
1993
This section provides information for
general air pollution audiences on
1993 air quality levels in each MSA
in the United States. Generally, an
MSA is an area comprising a large
population center with adjacent com-
munities that have a high degree of
economic and social integration with
the urban center. MSAs contain a
central county(ies), and any adjacent
counties with at least 50 percent of
their population in the urbanized
area.1 Although MSAs compose
only 19 percent of the land area in the
United States, they account for 79
percent of the total population of 249
million in 1990.
At the end of this chapter, Table
5-4 presents a summary of the highest
air quality levels measured in each
MSA during 1993. Individual MSAs
are listed to provide more extensive
spatial coverage for large metropoli-
tan complexes. The MSA names and
population estimates have been re-
vised this year to reflect the 1993 re-
visions based on the most recent
census data. The 330 MSAs are
listed alphabetically, with the 1990
population estimate and air quality
statistics for each pollutant. Concen-
trations above the level of the respec-
tive NAAQS are shown in bold italic
type.
In the case of O3, the problem is
regional in scale, and the high values
associated with the pollutant can re-
flect a large part of the MSA. How-
ever in many cases, peak ozone
concentrations occur downwind of
major urban areas, e.g., peak ozone
levels attributed to the Chicago met-
ropolitan area are recorded in and
near Kenosha, Wisconsin. In con-
trast, high CO values generally are lo-
calized and reflect areas with heavy
traffic. The scale of measurement for
the pollutants — PM-10, SO2 and
NO2 — falls somewhere in between.
Finally, while Pb measurements gen-
erally reflect Pb concentrations near
roadways in the MSA, if a monitor is
located near a point source of lead
emissions it can produce readings
substantially higher. Such is the case
in several MSAs. Lead monitors lo-
cated near a point source are foot-
noted accordingly in Table 5-4.
The pollutant-specific statistics
reported in this section are for a single
year of data. For example, if an MSA
has three ozone monitors in 1993 with
second highest daily hourly maxima
of 0.15 ppm, 0.14 ppm and 0.12 ppm,
the highest of these, 0.15 ppm, would
be reported for that MSA. The asso-
ciated primary NAAQS concentra-
tions for each pollutant are
summarized in Table 2-1.
The same annual data complete-
ness criteria used in the air quality
trends data base for continuous data
were used here for the calculation of
annual means, i.e., 50 percent of the
required samples for SO2 and NO2. 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 ad-
vised that there are insufficient data to
calculate the annual mean. With re-
spect to the summary statistics on air
quality levels with averaging times
less than or equal to 24 hours, all sites
are included, even if they do not meet
the annual data completeness require-
ment.
For PM-10 and Pb, the arithmetic
mean statistics are based on 24-hour
measurements, which are typically
obtained from a systematic sampling
schedule. In contrast to the trends
analyses in Chapter 3 which used a
more relaxed indicator, only maxi-
mum quarterly average Pb concentra-
tions meeting the AIRS validity
criteria are displayed in Table 5-4.
Chapter 5: Air Quality Status of Metropolitan Areas • 105
-------
Section 5.5 References
5.5 References
1. Statistical Abstract of the United States, 1993, U.S. Department of Commerce, U.S. Bureau ofthe
Census, Appendix II.
2. Code of Federal Regulations, 40 CFR Part 81.
106 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
The reader is cautioned that this summary is not
adequate in itself to numerically rank MSAs ac-
cording to their air quality. The monitoring data
represent the quality of the air in the vicinity of the
monitoring site but may not necessarily represent
urban-wide air quality.
Chapter 5: Air Quality Status of Metropolitan Areas • 107
-------
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108 • Chapter 5: Air Quality Status of Metropolitan Areas
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BOULDER-LONGMONT, CO
BRAZORIA, TX
BREMERTON, WA
BRIDGEPORT, CT
BROCKTON, MA
BROWNSVitLE-HARUNSEN-aAN BENITO, TX
BRYAN-COLLEGE STATSON.TX • •
BUFFALO-NIAGARA FALLS, NY
BURLINGTON, VT
CAGUAS.PR
CANTON-MASSILLON, OH
CASPER, WY
CEDAR RAPIDS, IA
CHAMPAIGN-URBANA, IL
CHARLESTON-NORTH CHARLESTON, SC
CHARLESTON, WV
CHARLOTTE-6ASTONIA-ROCK HtLL, NC-SC
CHAHLOTTESVILLE, VA
CHATTANOOGA, TN-GA
CHEYENNE, WY
CHICAGO, IL
CHICO-PARADISE, CA
CINCINNATI, OH-KY-IN
CLARKSVILLE-HOPKINSVILLE, TN-KY
CLEVELAND-LORAIN-ELYRIA, OH
225,339
391 ,707
189,731
443,722
189,478
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13i4i39
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394,106
61 ,226
168,767
173,025
506,875
250,454
1,182,093
131,107
433,210
73,142
6,069,974
182,120
1 ,452,645
169,439
2,202,069
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CO = HIGHEST SECOND MAXIMUM NON-OVERLAPPING 8-HOUR CONCENTRATION (Applicable NAAQS is 9 ppm)
PB = HIGHEST QUARTERLY MAXIMUM CONCENTRATION (Applicable NAAQS is 1 5 ug/m3)
NO2 = HIGHEST ARITHMETIC MEAN CONCENTRATION (Applicable NAAQS is 0 053 ppm)
03 = HIGHEST SECOND DAILY MAXIMUM 1-HOUR CONCENTRATION (Applicable NAAQS is 0 12 ppm)
PM1 0 = HIGHEST WEIGHTED ANNUAL MEAN CONCENTRATION
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION
(Applicable NAAQS is 50 ug/m3)
(Applicable NAAQS
is150ug/m3)
SO2 = HIGHEST ANNUAL MEAN CONCENTRATION (Applicable NAAQS IS 0 03 ppm)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION
ND = INDICATES DATA NOT AVAILABLE
(Applicable NAAQS
isO 14 ppm)
IN = INDICATES INSUFFICIENT DATA TO CALCULATE SUMMARY STATISTIC
WTD
AM
UGM
PPM
=
=
WEIGHTED
ANNUAL MEAN
= UNITS ARE MICROGRAMS PER CUBIC METER
= UNITS ARE PARTS PER MILLION
(a) - Includes data flagged as a possible exceptional event
(b) - Impact from an industrial source in Leeds, AL Highest population onented site in Birmingham, AL is 0 07 ug/m3
(c) - Impact from an industrial source in Chicago, IL Highest population oriented site in Chicago, IL is 0 10 ug/m3
(d) - Impact from an industrial source in Cleveland, OH This facility has been shutdown. Highest site in Cleveland, OH is 0 10 ug/m3
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FORT MYERS-CAPE CORAL, FL
FORT PIERCE-PORT ST. LUCIE, FL
FORT SMITH, AR-OK
FORT WALTON BEACH, FL
FORT WAYNE, IN
GARY, IN
GLENS FALLS, NY
GOLDSBORO, NC
GRAND FORKS, ND-MN
GRAND RAPIDS-MUSKEGON-HOLLAND, Ml
SREENSSQRQ-WlNSTON-SAiEM-HiGtt POINT
GREENVILLE-SPARTANBURG-ANDERSON, SC
HAGERSTOWN, MD
HAMILTON-MIDDLETOWN, OH
HARRISBURG-LEBANON-CARLISLE, PA
HARTFORD, CT
335,113
251,071
175,911
143,776
363,811
604,526
118,539
78,143
70,683
688,399
640,861
121,393
291,479
587,986
767,841
ND
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in
CO = HIGHEST SECOND MAXIMUM NON-OVERLAPPING 8-HOUR CONCENTRATION (Applicable NAAQS is 9 ppm)
PB = HIGHEST QUARTERLY MAXIMUM CONCENTRATION (Applicable NAAQS is 1.5 ug/m3)
NO2 = HIGHEST ARITHMETIC MEAN CONCENTRATION (Applicable NAAQS is 0 053 ppm)
O3 = HIGHEST SECOND DAILY MAXIMUM 1-HOUR CONCENTRATION (Applicable NAAQS is 0.12 ppm)
PM10 = HIGHEST WEIGHTED ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 50 ug/m3)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 150 ug/m3)
S02 = HIGHEST ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 0 03 ppm)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 0 14 ppm)
ND = INDICATES DATA NOT AVAILABLE
IN = INDICATES INSUFFICIENT DATA TO CALCULATE SUMMARY STATISTIC
(e) - Impact from an industrial source in Columbus, GA.
(f) - Impact from an industrial source in Collin Co., TX Highest site in Dallas, TX is 0.14 ug/m3
WTD = WEIGHTED
AM = ANNUAL MEAN
UGM = UNITS ARE MICROGRAMS PER CUBIC METER
PPM = UNITS ARE PARTS PER MILLION
-------
Table 5-4. 1993 Metropolitan Statistical Area Air Quality Factbook Peak Statistics for Selected Pollutants by MSA (cont.)
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METBOROilTAN STATISTICAL AREA
HICKORY-MORGANTON, NC
HONOLULU, HI
HOUMA, LA
HOUSTON, TX
HUNTINGTON-ASHLAND, WV-KY-OH
HUNTSVltL&Al;- '• ••,'••
iNOIANAipQua, IN
JOWA ©TY, IA-
JAOKSW, Ml ,
JKoNspNiiMS" -:.," ,; • ,- -
JACKSON, TN
JACKSONVILLE, FL
JACKSONVILLE, NC
JAMESTOWN, NY
JANESVILLE-BELOIT, Wl
JERSEY -CITY, NJ : :
JOHNSON C[IY-KINeSPORT-SWSTOL, TN-VA
JOHNSTOWN, PA
JOfUN^MO
KALAMAZOO-BATTte CREEK, Mi
KANKAKEE, IL
KANSAS CITY, MO-KS
KENOSHA, Wl
KILLEEN-TEMPLE, TX
KNOXVILLE, TN
KOKQMQ, \H
LACROSSE,Wt-MN
LAFAYETTE, LA
LAFAYETTE, IN
LAKEqHARLES,LA
LAKELAND-WINTER HAVEN, FL
LANCASTER, PA
LANSING-EAST LANSING, Ml
LAREDO, TX
LAS CRUCES, NM
LAS VEGAS, NV-AZ
LAWRENCE KS
LAWRENCE, MA-NH
LAWTON,:OK
UEWISTON-AUBURN, ME
1980
POPULATION
221,700
836,231
182,842
3,301,937
312,529
238,912
' • 1 £49,822
•. , , 96,119
148,766
, ' ; 395,396
77,982
906,727
149,838
141,895
139,510
553,099
436,047
241,247
134,910
223,411
516,418
1,566,280
128,181
255,301
604,816
96,225
97,904
208,740
130,598
188,134
405,382
422,822
432,674
133,239
135,510
741,459
81,798
393,516
111,486
88,141
CO
8-HR
(PPM)
ND
4
ND
7
4
4
: 4
, ND
ND
6
ND
6
ND
ND
ND
8
7
4
ND
Z
ND
5
ND
ND
5
ND
ND
NO
NO
ND
ND
3
ND
ND
9
10
ND
ND
3
ND
m
QMAX
(UGM)
ND
0.01
ND
0.02
0.05
ND
2.te(s!
ND
ND
0.02
ND
0.07
ND
ND
ND
0,05
ND
0.06
ND
0.02
ND
0.03
ND
ND
ND
ND
ND
ND
ND
ND
ND
0.04
ND
ND
0.13
ND
ND
ND
ND
0.02
NO2
AM
(PPM)
ND
0004
ND
0.024
0.016
0.013
0.018
ND
ND,
ND
ND
0.015
ND
ND
ND
0.027
0.017
0.017
ND
0.015
ND
0.012
ND
ND
ND
ND
ND
ND
0.011
0.007
ND
0.015
ND
ND
ND
0.030
ND
ND
0.008
ND
OZONE
2ND MAX
(PPM)
0.09
006
0.10
0.20
0.12
0,11
0,11
~ND
ND
0,10
ND
0.12
ND
010
0.08
0,13
&13
0.10
ND
0.10
ND
011
0.13
ND
0.12
ND
ND
0.09
ND
0.11-
0.11
0.12
0.10
ND
0.73
0.11
ND
0.12
ND
ND
PM10
WTO AM
(UOM)
23
24
ND
32
33
. -25"
37
ND
, ND
'as.
24
28
23
IN
ND
34
, 25
•27
ND
24
ND
44
ND
16
40
ND
- ND
ND
IN
!N
ND
IN
ND
30
37
44
ND
!N-
IN
24
2NLTMAX
53
58
ND
89
79
56 ,
91
• ,,ND
,,ND
. ' ,61
56
61
43
52
ND
85
S7 •
83
ND ,
58
ND
97
ND
43
80
NO
• NO
ND ,
• 54
, 51 '
ND
68
ND
58
98
- 110
ND
' ,46'
.-88,
68
SO2
AM
0.004
0.002
ND
0.006
0.014
' - JN ,
0.01S ' -
ND
, ND, :
0.003 -
ND
0.004
ND
0.011
ND
0.011
O.OJO
0.015
ND
0.004
ND
0005
ND
ND
0.009
ND
ND
, ND,
0.005
• 0,005 '
0.004
0.007
ND
ND
0.011
ND
ND,
0.008 '
,ND-
•0.007,,-
- • 802-
24-HR:
(PPM)
0.017
0.017
ND
0.036
0.093
o;oir
0,055
N0
• ;.NC ',
,: OUJ10 - ,
ND
0047
ND
0.049
ND
0,035-
, 0.047 ' ,
0.049
' ND,
0.024
ND
0040
ND
ND
0.063
NO;
j®
ND
0.041
0.019
0.019
0.026
ND
ND
0.097
,ND
ND
:0,027
ND, . ,
O.OS8:, -,
-------
LEXINGTON, KY
LIMA, OH
LINCOLN, NE
LITTLE ROCK-NORTH LITTLE ROCK, AR
LONGVIEW-MARSHALL, TX
LOS ANSELES-LONQ- BEACH, CA
LOUtSViLLE KVMN
LOWELt,'«A-NH,
i,UBBOGK,TX - :
LYNdHBURG, VA
MACON, GA
MADISON, Wl
MANCHESTER, NH
MANSFIELD, OH
MAYAGUEZ, PR
MCALLEN-EDINBUBG-MISSION, TX
M6DFORD-ASHLAND, OR
MELSOURNE-TITUSVILLE-PAIM BAY, Ft
MEMPHIS, TN-AR-MS
o
3"
D)
•
MIAMI, FL
MIDDLESEX-SOMERSET-HUNTERDON, NJ
MILWAUKEE-WAUKESHA, Wl
MINNEAPOLIS-ST. PAUL, MN-WI
MOBILE, AL
348,428
154,340
213,641
513,117
162,431
'• 8,'S63ji84 '
•''ssKsej;
,-2^,667; ',
•222J3S • '
• 142,19S- -
281,103
367,085
147,809
126,137
133,497
383,545
146,389
398,978
981,747
178,403
3,192,582
1,019,835
1,432,149
2,464,124
476,923
7
ND
5
4
ND
•':'.,, 14
• 8 '
5
ND
ND
ND
5
5
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ND
6
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7
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0.57
ND
0.017
ND
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0.009
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- O'jfiSO-- ".'
0,014 -. - ,.
, ' ' NO i ,'' • •
',, ND:
• ' ND : - ,;
ND
ND
0.016
ND
ND
' . NO' '• ,
: ' m '
6.026' . "
0,015; '-
0.016
ND
0.024
0.024
ND
0.10
0.10
0.06
0.10
0.11
, aas : ; ' '-'
0.14 .
'I'NO, '-•
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ND
0.08
0.10
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' Ktri
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0,1*
0.11
0.12
0.11
0.09
0.10
25
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46
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60
75
96
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0.007
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0.006
ND
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0.003
0.009
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ND
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0.001
0.005
0.004
0.007
0.010
0.026
0.023
ND
0.017
ND
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0.018
0.056
ND
ND
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0.004
0.018
0.030
0.053
0.066
CO
o
o
•o
3
>
(D
CO = HIGHEST SECOND MAXIMUM NON-OVERLAPPING 8-HOUR CONCENTRATION (Applicable NAAQS is 9 ppm)
PB = HIGHEST QUARTERLY MAXIMUM CONCENTRATION (Applicable NAAQS is 1 5 ug/m3)
N02 = HIGHEST ARITHMETIC MEAN CONCENTRATION (Applicable NAAQS is 0 053 ppm)
O3 = HIGHEST SECOND DAILY MAXIMUM 1-HOUR CONCENTRATION (Applicable NAAQS is 0 12 ppm)
PM10 = HIGHEST WEIGHTED ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 50 ug/m3)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 150 ug/m3)
SO2 = HIGHEST ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 0 03 ppm)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 0 14 ppm)
ND = INDICATES DATA NOT AVAILABLE
IN = INDICATES INSUFFICIENT DATA TO CALCULATE SUMMARY STATISTIC
(g) - Impact from an industrial source in Indianapolis, IN Highest population oriented site in Indianapolis, IN is 0.04 ug/m3
(h) - Impact from an industrial source in Memphis, TN Highest population oriented site in Memphis, TN is 0 12 ug/m3.
WTD = WEIGHTED
AM = ANNUAL MEAN
UGM = UNITS ARE MICROGRAMS PER CUBIC METER
PPM = UNITS ARE PARTS PER MILLION
-------
Table 5-4. 1993 Metropolitan Statistical Area Air Quality Factbook Peak Statistics for Selected Pollutants by MSA (cont.)
o
3-
D>
-O
CD
Ol
O
SL
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5T
2.
S
c/>
,WTD*M::
MODESTO, CA
MONMOUTH-OCEAN, NJ
MONROE, LA
MONTGOMERY, AL
MUNCIE, IN
370,522
986,327
142,191
292,517
119,659
NEW BEDFORD, MA
NEW HAVEN-MERIDEN, CT
NEW LONDON-NORWICH, CT-RI
NEW ORLEANS, LA
NEW YORK, NY
ODESSA-MIDLAND, TX
OKLAHOMA CITY, OK
OLYMPIA, WA
OMAHA, NE-IA
ORANGE COUNTY, CA
PANAMA CiWj
PENSAOOW, PD ,
PEORIA-PEKIN, IL
PHILADELPHIA, PA-NJ
PHOENIX-MESA, AZ
PINE BLUFF, AR
PITTSBURGH, PA
PONCE. feR'r
175,641
638,220
266,819
1,238,816
8,546,846
118,934
958,839
161,238
618,262
2,410,556
344,406
339,172
4,856,881
2,122,101
85,487
2,056,705
', :i9,250
7
6
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ND
ND
ND
5
ND
5
7
7
• 5:
ND
8
5
7
7
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7
7
9
ND
5
ND
ND
ND
ND
ND
ND
ND
0.74
ND
0.26
ND
0.07
0.16
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ND
0.02
ND
5.07 G)
0.05
0.02
ND
0.03
7 7.20 (k)
0.06
ND
0.13
ND
ND
0,03
0.024
ND
0.009
ND
ND
ND
0.027
ND
0.019
0.043
;-;;ND*
0,881 :•
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ND
0.013
ND
ND
0.039
0,012'
0,6|2
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ND
ND
0.035
ND
ND
0.031
ND
' ND
IN
•• *
0.014
0.73
0.73
0.10
012
ND
0.13
0.09
0.75
0.13
0.11
0.12
0,12:: ,-
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ND
0.10
ND
0.07
0.17
0^11
ND,
0.12
0-11
0.08
0.74
0.73
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0.12
0,11
ND
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0.10
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IN
ND
27
23
ND
•:!?-,;
17
53
19
26
47
•34
ND
ND
21
IN
38
38
/ 27
26
IN
,1N
•IN
24
34
44
23
38
ND
30
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. * 34*
123
ND
81
48
ND
44
778
41
81
86
- ,?4,'
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ND;
ND
49
78
93
80
,48
, -75
,SO
•84
57
49
537
92
55
767
ND
68
91
•99-
' 39
ND
ND
0.004
ND
ND
.:, \Nff-•
ND
ND
0.011
ND
ND
ND
0.009
0.006
0.006
0.019
-, o-°SS -
' ••"»'"
ND
0.003
ND
0.002
0.002
0,0'pR
- 0,00»:
0,014
0.006
0.007
0.012
0.007
ND
0.021
HO
ND
O-*?'-
',0'.Q06-'-
'0^006' '
ND
0.044
0.019
0.025
0.052
'0,011>
ND
0.008
ND
0008
0.008
:,::ND '
0.065
aces
0.042
0.044
0.034
ND
0.755(1)
ND
,ND
-------
o
PROVIDENCE-FALL RIVER-WARWICK, RI-MA
PROVO-OREM, UT
PUEBLO, CO
PUNTA GORDA, FL
RACINE, Wl
RAL6JSH-DURHAM-CHAPEL HfU, NC
RAPttJ CITY; so . •
READING, PA" , .' .
REDDING, CA
RENO, m
RICHLAND-KENNEWICK-PASCO, WA
RICHMOND-PETERSBURG, VA
RIVERSIDE-SAN BERNARDINO, CA
ROANOKE, VA
ROCHESTER, MN
ROCHSSTiR, N¥
ROCKFORD, It
ROCKY MOUNT, NC
SACRAMENTO, CA
SASINAW-EWY CITY-MIDLAND, Ml
ST. CLOUD, MN
ST. JOSEPH, MO
ST. LOUIS, MO-IL
SALEM, OR
SALINAS, CA
1,141,510
263,590
123,051
110,975
175,034
'738,480
81,343 ,
336,523 • - .
' 147';036
254,667
150,033
865,640
2,588,793
224,477
106,470
1,002,410
283,719
133,235
1,481,102
399,320
190,921
83,083
2,444,099
278,024
355,660
5
10
ND
ND
4
7
ND
,4 .' •
2
?
ND
5
6
5
5
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ND
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5
9
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ND
0.04
ND
ND
0,04
0.03
ND
0.02
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ND
ND
5.45 (n)
ND
ND
0.022
0.026
ND
ND
ND
•"6,021
", ND •
ND >
ND
0.024
0.042
0.014
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ND
• ND
ND
0.022
0,009
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ND
0.024
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0.012
0.12
0.09
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ND
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0.13
0.23
0.10
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ND
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0.13
ND
0.09
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40
26
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26
73
32
20
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29
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32
44
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68
209
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60
172
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100
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55
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0.007
0.002
0.004
0.002
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0.001 , ,
ND
ND
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0.013
ND
ND
0.042
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ND
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^'"Otfi^V^ ' '
^.-•'^••'•^Kff^ 'v ^.
-•'•'»;Hfr:
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0.032
0.010
0.018
0.010
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0-005
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0.081
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in
CO = HIGHEST SECOND MAXIMUM NON-OVERLAPPING 8-HOUR CONCENTRATION (Applicable NAAQS is 9 ppm)
PB = HIGHEST QUARTERLY MAXIMUM CONCENTRATION (Applicable NAAQS is 1 5 ug/m3)
N02 = HIGHEST ARITHMETIC MEAN CONCENTRATION (Applicable NAAQS is 0 053 ppm)
O3 = HIGHEST SECOND DAILY MAXIMUM 1-HOUR CONCENTRATION (Applicable NAAQS is 0.12 ppm)
PM10 = HIGHEST WEIGHTED ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 50 ug/m3)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 150 ug/m3)
SO2 - HIGHEST ANNUAL MEAN CONCENTRATION (Applicable NAAQS is 0.03 ppm)
= HIGHEST SECOND MAXIMUM 24-HOUR CONCENTRATION (Applicable NAAQS is 0 14 ppm)
ND = INDICATES DATA NOT AVAILABLE
IN = INDICATES INSUFFICIENT DATA TO CALCULATE SUMMARY STATISTIC
(i) - Impact from an industrial source in Williamston Co , TN Highest population oriented site in Nashville, TN is 0 10 ug/m3
(I) - Impact from an industrial source in Omaha, NE Highest population oriented site in Omaha, AL is 0 02 ug/m3
(k) - Impact from an industrial source in Philadelphia, PA Highest population oriented site in Philadelphia, PA is 0 47 ug/m3
(I) - Impact from an industrial source
(m) - impact from an industrial source in Reading, PA Highest population oriented site in Reading, PA is 0,12 ug/m3.
(n) - Impact from an industrial source in Herculaneum, MO Highest population oriented site in St. Louis, MO is 0.05 ug/m3
WTD = WEIGHTED
AM = ANNUAL MEAN
UGM = UNITS ARE MICROGRAMS PER CUBIC METER
PPM = UNITS ARE PARTS PER MILLION
-------
8.
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03 cn co i- i-
116 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
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TRENTON, NJ
TUSCON, AZ
TULSA, OK
TUSCALOOSA, AL
TYLER, TX
UTICA-ROME, NY
VALLEJO-FAIRFIELD-NAPA, CA
VENTOftA, CA
V(CTOR1A,TX
VINEUND-MI1.LVILLE-BRIDGETON, NJ
VISALIA-TULARE-PORTERVILLE, CA
WACO, TX
WASHINGTON, DC-MD-VA-WV
WATERBURY, CT
WATERLOO-CEDAR FALLS, IA
WAUSAU.WI
WEST PALM BEACH-BOCA flATON, FL
WHEELING, WV-OH
WICHITA, KS
WICHITA FALLS, TX
WILLIAMSPORT, PA
WILMINGTON-NEWARK, DE-MD
WILMINGTON, NC
WORCESTER, MA-CT
YAKIMA, WA
YOLO, CA
YORK, PA
YOUNGSTOWN-WARREN, OH
YUBA CITY, CA
YUMA.AZ
325,824
666,880
708,954
150,522
151,309
316,633
451,186
669,016
74,361
138,053
311,921
189,731
3,000,504
221,629
146,611
115,400
863,518
159,301
485,270
122,378
118,710
578,587
120,284
320,006
188,823
381,288
417,848
492,619
122,643
106,895
ND
6
5
ND
ND
ND
7
4 ,
ND
ND
4
ND
8
ND
ND
ND
4
4
6
ND
ND
4
ND
6
8
ND
3
2
5
ND
ND
0.03
0.20
ND
ND
ND
0,02
ND
ND
ND
ND
ND
0.03
0.02
ND
ND
0.10
ND
0.02
ND
ND
002
ND
ND
ND
ND
0.04
ND
ND
ND
ND
0.028
0.017
ND
ND
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0,014,
01023
ND ;,
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0.023
ND
0.029
ND
ND
ND
0.013
ND
ND
ND
ND
0.019
ND
0.028
ND
ND
0,022
0,024
0.018
ND
0.14
0.10
0.12
ND
ND
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- 0.10', "
0.14' ••'•
' WO: '
0,12
0.15
ND
0.13
ND
ND
0.08 '.
0.12
0.11
0.08
ND
009
0.15
0 10
0.16
ND
ND
0.11
0.12
0,13
0.00
27
28
29
26
IN
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YND :
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53
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31
25
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24
29
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20
38
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31
36
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66
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67
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53
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58
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45
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77
84
69
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0.003
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0.011
0.006
ND
:'. ;i :'•>'•)&$'••
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'6,005 '.'
-. 'ito' '
0.006
0.015
0.003
0.007
ND
- -ND
0.008
"'0.812
ND
ND
ND
0.006
0.044
ND
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' 'ND'-'
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0.029
0.021
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0.060
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"0,032
~&.
-------
118 • Chapter 5: Air Quality Status of Metropolitan Areas
-------
Chapter 6: Selected Metropolitan
Area Trends
While most of this report discusses
trends on a national scale, great inter-
est exists in trends of air pollutants in
more localized areas. This chapter
presents 1984-93 air quality trends in
major urban areas. The areas se-
lected are the Primary Metropolitan
Statistical Areas (PMSA or MSA)
with populations of at least 500,000.
Urban area trends in the number
of unhealthy days as measured by the
Pollutant Standards Index (PSI) are
examined for all large metropolitan
areas. The air quality data used for
the trend statistics were obtained from
the EPA Aerometric Information Re-
trieval System (AIRS). This is the
fourth year that this report has pre-
sented trends in the PSI, which is used
locally in many areas to characterize
and publicly report air quality. Be-
cause the focus of this analysis is on
examining 10-year trends in the num-
ber of unhealthy days, the PSI values
are based on daily maximum pollutant
concentrations from the subset of am-
bient monitoring sites that met the 10-
year trends criteria of Chapter 2.
Thus, only sites which met the com-
pleteness criteria in at least eight of
the last 10 years are included in the
trends comparisons. It should also be
noted that no interpolation for missing
data is used in this chapter; this corre-
sponds with typical PSI reporting.
6.1 The Pollutant
Standards Index
The number of days when the PSI is
greater than 100 (the unhealthy
range) is used in this section as an air
quality indicator for describing urban
area trends. The PSI is widely used in
the air pollution field to report daily
air quality to the general public. PSI
index values are reported in all metro-
politan areas of the United States with
populations exceeding 200,000. The
index provides a uniform system of
measuring pollution levels for the ma-
jor air pollutants regulated under the
Clean Air Act. In addition, the PSI
advises the public about general
health effects associated with differ-
ent pollution levels, and describes
precautionary steps that may need to
be taken if levels rise into the un-
healthy range.1 The index integrates
information from five major pollut-
ants across an entire monitoring net-
work into a single number that
represents the worst daily air quality
experienced in an urban area. This is
accomplished by first computing a
separate sub-index for each pollutant
with data for the day. The daily PSI
value is determined by the pollutant
having the highest sub-index value
from all the monitoring values used
for that day. The index numbers are
on a scale of zero to 500. The most
important number on the scale is 100,
since this number corresponds to the
standard established under the Clean
Air Act. On days when two or more
pollutants exceed the standard (PSI
greater than 100), the pollutant with
the highest index is reported as the
PSI. Therefore, the PSI does not take
into account the possible adverse ef-
fects associated with combinations of
pollutants (synergism).1-2
The PSI places the maximum em-
phasis on acute health effects occur-
ring over very short time periods (24
hours or less) rather than chronic ef-
fects occurring over months or years.
It does not specifically account for
damage air pollutants can do to ani-
mals, vegetation, and materials such
as building surfaces and statues.
However, increased PSI levels gener-
ally reflect increased damage to the
environment.
The PSI is computed for PM-10,
SO2, CO, O3 and NO2 based on their
short-term National Ambient Air
Quality Standards (NAAQS), Federal
Episode Criteria and Significant
Harm Levels. Lead is the only major
pollutant not included in the index
because it does not have a short-term
NAAQS, a Federal Episode Criteria
or a Significant Harm Level.
Chapter 6: Selected Metropolitan Area Trends • 119
-------
Section 6.1 The Pollutant Standards Index
PSI estimates depend upon the
number of pollutants monitored and
the number of monitoring sites col-
lecting data. The more pollutants and
sites that are available in an area, the
better the estimate of the maximum
PSI for that day is likely to be. How-
ever, O3 accounts for most of the days
with a PSI above 100 and O3 air qual-
ity is relatively uniform over large ar-
eas so that a small number of sites
can still estimate maximum pollutant
concentrations. All of the included
cities had at least one CO trend site or
one O3 trend site. The typical one in
six day sampling schedule for most
PM-10 sites limits the number of days
that PM-10 can factor into the PSI de-
termination. Results for individual
years could be somewhat different if
data from all monitoring sites and all
pollutants were considered in an area.
This is illustrated for 1993, where the
number of PSI days from all monitor-
ing sites is compared to the results for
the subset of trend sites. Local agen-
cies may use only selected monitoring
sites to determine the PSI value so
that differences are possible between
the PSI values reported here and those
reported by the local agencies.
The PSI simplifies the presenta-
tion of air quality data by producing a
single dimensionless number ranging
from zero to 500. The PSI uses data
from all selected sites in the PMSA or
Consolidated Metropolitan Statistical
Area (CMSA) and combines different
air pollutants with different averaging
times, different units of concentration,
and more importantly, with different
NAAQS, Federal Episode Criteria
and Significant Harm Levels. Table
6-1 shows the five PSI categories and
health effect descriptor words. The
PSI is primarily used to report the
daily air quality of a large urban area
as a single number or descriptor
word. Frequently, the index is re-
ported as a regular feature on local
TV or radio news programs or in
newspapers.
Throughout this section, emphasis
is placed on CO and O3 which cause
most of the NAAQS violations in ur-
ban areas. Ozone presents unique
problems in summarizing values
across areas. The O3 pollution prob-
lem is regional in scale. High values
can represent an ozone problem over
a large area. Since it is a secondary
pollutant, peak O3 values can occur
downwind of the sources of precursor
pollutants.
Table 6-1. Comparison of Pollutant Standards Index (PSI) Values with Pollutant Concentrations, Health Descriptions, and
PSI Colors
INDEX
VALUE
500 ~
400
300 —
200
100
50
n
AIR
QUALITY
LEVEL
HARM
EMERGENCY
- WARNING —
— ALERT
NAAQS
NAAQS
POLLUTANT LEVELS
PMio
(24-hour)
ug/m3
600
500
420
350
150
50
n
SO 2
(24-hour)
ugftn3
2620
2100
1600
800
365
__ b
80
R
CO
(8-hour)
pom
50
40
30
15
9
4.5
0
°3
(1-hour)
pom
0.6
0.5
0.4
0.2
0.12
0.06
B
NO 2
(1-hour)
ppm
2.0
1.6
1.2
0.6
a
a
— a
HEALTH
EFFECT
DESCRIPTOR
HAZARDOUS
VERY
UNHEALTHFUL
UNHEALTHFUL
MODERATE
GOOD
PSI
COLORS
RED
ORANGE
YELLOW
GREEN
BLUE
aNo index values reported at concentration levels below those specified by "Alert Level" criteria.
b Annual primary NAAQS
120 • Chapter 6: Selected Metropolitan Area Trends
-------
Section 6.2 Summary of PSI Analyses
6.2 Summary of PSI
Analyses
Table 6-2 displays the number of PSI
days greater than 100 (unhealthful or
worse days) for the 10-year period,
1984-93, in 89 large metropolitan ar-
eas. For all practical purposes CO,
O3, PM-10 and SO2 are the only pol-
lutants that contribute to the PSI in
Table 6-2. NO2 rarely is a factor be-
cause it does not have a short-term
NAAQS and can only be included
when concentrations exceed one of
the Federal Episode Criteria or Sig-
nificant Harm Levels. Total sus-
pended particulates (TSP) is not
included in the index because the re-
vised particulate matter NAAQS is
for PM-10, not TSP. As noted above,
lead is not included in the index be-
cause it does not have a short-term
NAAQS or Federal Episode Criteria
and Significant Harm Levels.
Bakersfield, Pittsburgh, Riverside
and Salt Lake City are the only cities
where PSI days greater than 100 are
due to pollutants other than CO or O3.
For Pittsburgh, SO2 and PM-10 ac-
count for the additional days, while
PM-10 accounts for the additional
days in the other cities.
The first column in the table lists
the number of sites in each metropoli-
tan area that meet the 10-year trends
completeness criteria (eight of the last
10 years have valid data). The fol-
lowing 10 columns display the num-
ber of unhealthy days determined by
the subset of trends sites in each met-
ropolitan area. The two right most
columns show the number of corre-
sponding PSI days greater than 100,
using all active monitoring sites in
1993, not just the subset of 10-year
trend sites. Note that for all urban
areas there is close agreement be-
tween the two totals for 1993 of the
number of days when the PSI is
greater than 100 except in El Paso,
Fresno, Monmouth, and Wilmington-
Newark. The differences are attrib-
uted to currently active sites without
sufficient historical data to be used for
trends.
During the past decade, more than
half of the cities listed in Table 6-2
had days where O3 did not account for
all of the PSI greater than 100 days.
However, in 1993 only 13 cities had
days where the PSI was over 100 and
not due to ozone. These were: Chi-
cago, Denver, El Paso, Kansas City,
Las Vegas, Los Angeles, Nashville,
Omaha, Phoenix, Pittsburgh, River-
side-San Bernardino, Sacramento and
Salt Lake City. In most cases, CO or
PM-10 were the pollutants causing
high PSI with the exception noted
above for Pittsburgh. Also these in-
stances amounted to one to three days
with the exception of Los Angeles.
Because of the overall improvement
in CO levels (see Chapter 3, Section
3.1 in this report), CO accounts for
far less of these days in the latter half
of the 10-year period. In 1993, 90
percent of the days with PSI greater
than 100 days were due to O3.
As noted above, although the PSI
is based on five pollutants, ozone
tends to dominate the number of days
greater than 100 during the period
1984—93. This can be clearly seen in
Table 6-3 which presents the trend in
the number of PSI days greater than
100 based only on O3 monitoring
data. The two right most columns in
this table display the number of ozone
sites reporting data in 1993 and the
corresponding number of days with
the PSI greater than 100 based only
on 1993 O3 data. In this table, the im-
pact of the very hot and dry summer
of 1988 in the eastern United States
on O3 concentrations can clearly be
seen.
There are several assumptions
that are implicit in this PSI analysis.
Probably the most important is that
the monitoring data available for a
given area provide a reasonable esti-
mate of maximum short-term concen-
tration levels. The PSI procedure
uses the maximum concentration
which may not represent the air pollu-
tion exposure for the entire area. If
the downwind maximum concentra-
tion site for ozone is outside the
PMSA, these data are not used in this
analysis.
Note: Urban lead concentrations
have dropped dramatically over the
past 15 or so years. As a result, lead
violations now occur typically in the
vicinity of lead point sources (see
Chapter 3).
Chapter 6: Selected Metropolitan Area Trends • 121
-------
to
to
a
so
"S.
-.
a*
en
(D
CD
O
CD
Q_
CD
"
T3
5.
5T
2f
CD
D>
CD
Q.
100
1993
0
0
16
0
37
14
, 8
Q
5
,:. 3
0
0
6
1
1
4
"1
' 5
Z'
a
2
10
1
1
21
0
1
2
1
9
0
26
0
1
5
2
1
6
0
131
6
4
0
1
19 ' 0
CO
5'
3
co
I
3
10
•3
-------
Table 6-2. Number of PSI Days Greater Than 100 at Trend Sites, 1984-93, and All Sites in 1993
MSA
O
0)
CD
O)
W
CD_
CD
O
CD
Q.
O
ID
O
CD
0)
Q.
at
MINNEAPOLIS-ST. PAUL, MN-WI
MONMOUTH-OCEAN, NJ
NASHVILLE, TN
NASSAU-SUFFOLK, NY
NEW HAVEN-MERIDEN, CT
NEWORl£ANS;LA
NEW YORK, NY
NORFOLK-VIRGINIA BEACH-NgWPORT NEWS.VA-NC
OAKLAND, CA
OKLAHOMA CITY, OK
OMAHA, NE-IA
ORANGE COUNTY, CA
ORLANDO, FL
PHILADELPHIA, PA-NJ
PHOENIX-MESA, AZ
PITTSBURGH, PA
PORTLAND-VANCOUVER, OR-WA
PROVIDENCE-FAIL RIVER-WARWICK, RI-MA
RALEIGH-DURHAM-CHAPEL HILL, NC
RICHMOND-PETERSBURG, VA
RIVERSIDE-SAN BERNARDINO, CA
ROCHESTER, NY
SACRAMENTO, CA
ST. LOUIS, MO-IL
SALT LAKE CITY-OGDEN, UT
SAN ANTONIO, TX
SAN SEQO, CA
SAN FRANCISCO, CA
SANJOS£,CA
SAN JUAN-BAYAMON, PR
SCRANTON-WILKES-BARRE--HAZLETON, PA
SEATTLE-BELLEVUE-EVERETT, WA
SPRINGFIELD, MA
SYRACUSE, NY
TACOMA.WA ,
TAMPA-ST. PETERSBURG-CLEARWATER, FL
TOLEDO, OH
TUSCON.AZ ,
TULSA.OK
VENTURA, CA
WASHINGTON, DC-MD-VA-WV
WEST PALM BEACH-BOCA RATON, FL
WILMINGTON-NEWARK, DE-MD ____
«j
# trend
sites
11
2
11
4
8
9
32
; 11
,,'7
1?
8
9
8
4
29
16
23
'9
12
4
9
22
7
14
34
15
7
12
10
S
5
10
10
10
3
5
13
' 7
10
10
11
26
2
9
1984
21
2
27
2
24
. '8
.- : 96
- - • ' -'20
,. ' 0
12
14
1
69
0
31
107
' '15
4
26
29
2
164
0
70
22
20
2
51
Z
* 25
0
1
4
14
8
0
•3
3
' 7
10
23
30
0
5
1985
21
2
3
3
10
1
, , 61
, 21
1-
1 '
6
3
69
0
25
84
'9,
3
12
8
3
152
0
67
10
20
0
54
5
S7
0
1
24
11
17
• 12
5
0
3
5
19
15
0
8
1986
13
0
9
8
6
3
S3.
19
•:i
5
4
1
54
0
21
85
8
6
7
11
0
156
1
58
13
36
1
45
- 4
S
0
0
10
4
9
'3
5
;i
• i
4
60
12
0
6
1987
7
0
4
14
17
4
: 41 '
22
2
9
6
0
46
0
36
40
13
2
10
7
6
152
1
44
14
7
1
41
1
9
2
1
10
3
4
8
5
2
4
2
31
25
0
9
1988
1
0
15
10
16
2
;, -43
" 32
3
4
0
1
54
0
34
22
23
2
S
14
18
165
4
58
17
10
1
49
1
7
0
12
6
15
2
9
0
6
6
2
55
36
0
23
1989
5
0
4
6
7
1
' 16
4
•6"
2
2
1
53
0
19
30
9
0
2
2
0
155
0
45
12
15
0
61
0
13
0
1
4
2
2
, 4
1
1
2
2
46
7
0
4
1990
1
0
8
6
8
,0
.'"1?.
• - 8
0'
2
1
0
39
2
11
8
- 11
4
7~
3
1
128
1
39
8
6
0'
39
'1
5
0
0
2
2
1
, 1
''3
0
0
2
18
5
0
5
1991
0
0
1
12
19
0,
22
- 10'
" '. 1.
2
0
0
32
0
24
4
3
3
10
0
1
122
0
27
6
18
0
25
0
9
0
2
0
3
2
• , r
0
1'
0.
2
39
16
0
9
1992
1
0
1
2
2
1' ,
, ; 4
•• ' 5 '
2
'1
0
0
37
0
3
8
1
2
, 2
0
2
128
0
12
2
9
0
19
0
1
0
0
0
2
0
1
- 1
0
0
1
10
2
0
2
1993
0
0
3
4
T-
' - 2
:;,-:\e
;•: . 2
'-"3
3
0
1
17
0
20
',6
1 '5
. 0
-' 1
0
4
115
0
6
5
3
0
' ~14
0
1
0
0
0
7
0
0
0
, , 2
- •: o
1
16
12
0
3
Total* PSI > 100
sites 1 993
18
4
16
8
8
' '":1|
' ','.""13
• ' : -13
. '' ,19
10
11
9
8
29
- '-23
-.38
' ;is
' '12
11
10
29
0
9
3
6
11
' '',"-; 2
,; /::.--:2
::,,:,-,', '4-
'..•'' 3
0
1
17
0
31
, ' " ?
,9
; ' : * 0
: 1
0
8
123
7 0
25 9
42
17
,,7'
•:ie;
10
11
11
11
13
6
3
' •- /o
14,
," , - 0
: " 1
0
0
0
13 ! 7
6
, ' 8,
- 19,
10
15
• ' fi-
ll
0
: 0
•i ' • o
''.', ' •' 2
, : ' ' • 0
••,•'• i
18
32 14
6
13
2
9
ho
CO
-------
Table 6-3. (Ozone Only) Number of PSI Days Greater Than 100 at Trend Sites, 1984-93, and All Sites in 1993
O
zr
to
•o
5T
en
CD
o
CD
a.
o
T3
a
3
a.
in
MSA
ALBANY-SCHENECTADY-TROY, NY
ALLENTOWN-BETHLEHEM-EASTON, PA
ATLANTA, GA
AUSTIN-SAN MARCOS, TX
BAKERSFIELD, CA
BALTIMORE, MD
BATON ROUGE, LA
BERGEN-PASSAIC, NJ
BIRMINGHAM, AL
BOSTON, MA-NH
BUFFALO- NIAGARA FALLS, NY
CHARLESTON-NORTH CHARLESTON, SC
CHARLOTTE-GASTONIA-ROCKHILL, NC-SC
CHICAGO, IL
CINCINNATI, OH -KY- IN
CLEVELAND- LORAIN-ELYRIA, OH
COLUMBUS, OH
DALLAS, TX
DAYTON -SPRINGFIELD, OH
DENVER, CO
DETROIT, Ml
EL PASO, TX
FORT LAUDERDALE, FL
FORT WORTH-ARLINGTON, TX
FRESNO, CA
GARY, IN
GRAND RAPIDS-MUSKEGON-HOLLAND, Ml
GREENSBORO — WINSTON-SALEM — HIGH POINT, NC
HARRISBURG-LEBANON-CARUSLE, PA
HARTFORD, CT
HONOLULU, HI
HOUSTON, TX
INDIANAPOLIS, IN
JACKSONVILLE, FL
JERSEY CITY, NJ
KANSAS CITY, MO-KS
KNOXVILLE, TN
LAS VEGAS, NV-AZ
LITTLE ROCK-NORTH LITTLE ROCK, AR
LOS ANGELES-LONG BEACH, CA
LOUISVILLE, KY-IN
MEMPHIS, TN-AR-MS
MIAMI, FL
MIDDLESEX-SOMERSET-HUNTERDON, NJ
MILWAUKEE-WAUKESHA, Wl
# trend
sites
1
3
2
2
3
6
3
1
4
2
1
2
4
13
7
6
2
3
3
5
7
3
1
2
2
4
2
2
3
3
1
11
3
2
1
5
3
2
1
8
4
3
3
2
4
1984
1
5
8
0
26
19
11
4
2
7
0
0
5
9
2
3
Q
11
1
a
4
9
0
12
18
9
2
0
1
19
1
49
1
0
7
11
0
0
0
152
13
2
0
14
7
1985
2
2
9
2
27
13
8
8
3
3
2
0
1
8
2
1
0
14
0
1
1
10
0
8
21
2
4
0
1
11
0
48
2
2
13
3
0
1
0
154
4
4
3
15
5
1986
0
2
17
0
33
19
5
2
5
2
0
2
9
6
6
2
1
5
2
3
3
11
0
5
24
5
4
3
0
2
0
43
0
0
4
3
0
0
1
159
9
6
4
7
9
1987
0
5
19
0
45
26
10
12
6
4
2
0
10
14
10
7
1
8
2
4
6
12
0
2
28
6
9
1
4
8
0
52
1
1
12
2
0
0
1
145
3
5
4
9
12
1988
1
15
15
0
54
38
10
18
15
12
14
0
17
20
23
20
4
3
14
4
16
3
0
4
11
12
18
11
13
23
0
48
7
2
17
3
5
2
0
165
20
8
4
24
19
1989
0
0
3
0
28
7
9
2
0
2
1
0
2
2
2
2
0
3
3
0
10
10
1
2
21
0
8
0
0
7
0
34
2
0
2
1
0
1
0
138
1
2
3
7
8
1990
0
0
16
0
22
11
18
3
5
1
1
0
3
0
6
1
1
5
1
0
3
4
0
4
12
2
5
1
2
7
0
48
1
0
7
2
2
0
1
118
4
4
1
10
2
1991
0
2
5
0
23
20
6
3
0
3
0
0
2
7
7
5
3
0
1
0
7
5
0
7
18
3
8
0
0
12
0
40
0
0
7
1
O
0
0
111
5
0
2
8
10
1992
0
0
4
0
4
4
2
0
2
1
0
0
0
3
0
0
0
2
0
0
0
6
0
2
16
1
0
0
0
8
0
30
0
0
1
1
0
0
0
130
0
0
0
3
0
1993
0
0
14
0
28
12
3
0
5
3
0
0
4
0
1
1
0
4
2
0
2
4
0
1
13
0
1
2
1
9
0
26
0
1
5
1
1
0
0
102
5
1
0
1
0
Total #
sites
3
3
4
2
6
7
7
1
6
5
1
2
6
17
7
7
4
6
4
10
10
4
3
2
6
4
4
6
3
3
1
11
8
3
1
e
5
4
2
10
6
4
4
2
7
PSI > 100
1993
0
0
16
0
37
14
7
0
5
3
0
0
6
0
1
1
1
5
2
0
2
4
1
1
20
0
1
2
1
9
0
26
0
1
5
1
1
0
0
102
5
1
0
1
0
CD
a
o
3
O)
I
0)
T3
CO
2L
•<
u
-------
Section 6.2 Summary of PSI Analyses
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Chapter 6: Selected Metropolitan Area Trends • 125
-------
Section 6.3 References
6.3 References
1. Measuring Air Quality, The Pollutant Standards Index, EPA-451/K-94-001, U.S. Environmental
Protection Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC,
February 1994.
2. Code of Federal Regulations, 40 CFR Part 58, Appendix G.
126 • Chapter 6: Selected Metropolitan Area Trends
-------
Chapter 7: International Air
Pollution Perspective
This chapter discusses air pollution
emissions, trend patterns, levels for
selected countries and cities around
the world, and ambient concentration
regulations for international and na-
tional entities. Because the form of air
quality standards and goals may differ
among countries, common air quality
statistics have been selected for com-
parison purposes. Definitions and
monitoring methods may vary from
country to country; therefore, com-
parisons among nations are subject to
caution. Trends observed within each
country may be more reliable than
comparisons between countries.
7.1 Emissions
As a result of human activities involv-
ing stationary and mobile sources,
world-wide anthropogenic emissions
of SOX (reported as SO2) are currently
estimated to be approximately 99 mil-
lion metric tons.1 Fossil fuel combus-
tion accounts for approximately 90
percent of the global human-induced
SOX emissions.2 Over the past few
decades, global SOX emissions have
increased by approximately four per-
cent per year, corresponding to the in-
crease in world energy consumption.
Recent data indicate that emis-
sions of SOX have been significantly
reduced in many developed countries
(Figure 7-1). Table 7-1 provides ad-
ditional comparative information on
SO2 emissions. The table describes
the emissions of SOX from anthropo-
genic sources in selected countries in
1980 and 1990; the total emissions are
reported as 103 metric tons per year as
SO2. Because the manner in which
emission estimates were generated
may vary from country to country,
comparisons among nations are sub-
ject to caution.
About 90 percent of the human-in-
duced emissions originate in the
Northern Hemisphere. The United
States and countries within the former
Soviet Union are the two biggest
sources.3 For example, in 1970, the
United States emitted approximately
28 million metric tons of SO2, which
had been reduced to approximately 20
million metric tons by 1993.4 Coun-
tries within the former Soviet Union
emitted approximately 20 million met-
ric tons in 1981 compared to approxi-
mately 17 million metric tons in
1990.5 Much less information is
available for emission trends in devel-
oping countries. However, there are
indications that SOX emissions are in-
creasing in these developing areas and
SOX pollution is evident in countries
such as China, India (see Table 7-1)
and Mexico.2-3'5'6
In 1990, it was estimated that,
worldwide, 68 million metric tons of
nitrogen oxides (reported as NO2)
en
<
(A
LJU
Z
o
o
I
6000-,
5000-
4000-
3000-
2000-
1000-
United Kingdom
Finland
Hong Kongv
Norway
1970
1975
1980
1985
1990
Figure 7-1. S0x emissions in 1000 metric tons/year for selected countries.
Source: UNEP 1991a.
Chapter?: International Air Pollution Perspective • 127
-------
Section 7.1 Emissions
Table 7-1 . Emissions of sulfur dioxide from anthropogenic sources in selected
countries, 1980 and
1990. Total
emissions (1 03 metric tons per year as SO2)
Region/Country
NORTH AMERICA
Canada
USA
ASIA1
Afghanistan
Bangladesh
Brunei
Cambodia
China
China, Taiwan
Hong Kong
India
Indonesia
Israel
Japan
Korea
Korea, Dem.
Kuwait
Laos
Macao
Malaysia
Maldives
Mongolia
Myanmar
Nepal
Pakistan
Philippines
Qatar
Singapore
Sri Lanka
Thailand
Turkey
Viet Nam
EUROPE
Albania
Austria
Belgium
Bulgaria
Czechoslovakia
1980
4,643
21,256
8.5
57
0.9
1.3
13,370
1,040
166
2,010
329
308
1,600
271
1,920
450
1.4
3.0
272
-
65
31
4.9
198
1,040
122
30
420
276
34
50
390
828
1,034
3,100
1990
3,800
18,321
11
49
1.1
2.9
19,990
605
150
3,070
485
273
1,140
333
1,290
465
1.7
8.4
263
0.3
101
30
11
381
370
159
155
28
612
398
39
50
98
420
1,030
2,564
Per capita
1990
(kg year1)
143.3
84.7
3.9
0.5
4.4
0.3
17.7
29.8
25.9
3.7
2.7
58.6
9.2
7.9
59.3
222.5
0.4
18.9
14.7
1.5
49.4
0.7
0.6
3.4
6.0
430.8
51.7
1.7
11.2
7.2
0.6
0
13.1
42.3
114.6
177.1
% Change
1980-1990
-18
-13
29
-14
22
123
50
-42
-10
53
47
-11
-29
23
-33
3
21
180
-3
-
55
-3
124
92
-64
27
-7
46
44
15
-75
-49
0
-17
128 • Chapter 7: International Air Pollution Perspective
-------
Section 7.1 Emissions
Table 7-1. Emissions of sulfur dioxide from anthropogenic sources in selected countries, 1980 and
emissions (103
Region/country
Denmark
Finland
France
German. Dem. Rep.
Germany, Fed. Rep.
Greece
Hungary
Iceland
Ireland
Italy
Luxembourg
Netherlands
Norway
Poland
Portugal
Romania
Spain
Sweden
Switzerland
UK
Yugoslavia
USSR
Armenia
Azerbaijan
Belarus
Estonia
Georgia
Kazakhstan
Kyrgyzstan
Latvia
Lithuania
Moldova
Russia
Tajikistan
Turkmenistan
Ukraine
Uzbekistan
metric tons per year as SO2) (cont.)
1980
448
584
3,338
4,264
3,194
400
1,632
6
222
3,800
24
466
142
4,100
266
1,800
3,250
514
126
4,898
1,300
141
119
740
462
59
1,607
62
60
228
289
12,123
7
5
3,850
298
1990
266
256
1,206
5,242
1,002
500
1,010
6
168
2,406
10
238
60
3,210
212
1,800
2,190
204
62
3,774
1,480
73
90
562
192
76
1,484
56
54
143
231
10,166
17
22
2,782
542
Per capita
1990
(kg year1)
52.0
51.5
21.5
314.9
16.6
50.3
95.7
24.8
45.2
42.0
32.7
16.1
14.2
83.5
20.6
45.6
56.7
24.5
9.5
66.3
62.1
20.9
12.4
54.6
121.3
13.9
87.0
12.4
20.0
38.0
52.9
68.2
3.0
5.8
53.3
25.2
1990. Total
% Change
1980-1990
-41
-56
-64
23
-69
25
-38
0
-24
-37
-58
-49
-58
-22
-20
0
-33
-60
-51
-23
14
-48
-24
-24
-58
29
-8
-10
-10
-37
-20
-16
143
340
-28
82
Source: UNEP (1993) except for USA data (U.S. EPA, 1993).
1ln Asia, 1987 data were reported for all countries except for Turkey.
Chapter 7: International Air Pollution Perspective • 129
-------
Section 7.1 Emissions
were emitted into the atmosphere as a
result of human activities.1 Nitrogen
oxides are primarily emitted by fossil
fuel combustion, with the transport
sector typically accounting for be-
tween one-third and one-half of national
emissions.7 During the past 20 years,
trends in natural emissions have been
mixed. Table 7-2 summarizes the emis-
sions of NOX from anthropogenic
sources in selected countries.
In 1990, global emissions of sus-
pended particulate matter were esti-
mated to be approximately 57 million
metric tons per year.7 However, esti-
mates vary widely. The United Na-
tions Environment Program (UNEP)
has estimated the global total to be
closer to 135 million metric tons.3
Despite increased coal combustion, in
many industrialized countries, particu-
late emissions have decreased because
of cleaner burning techniques.3 Table
7-3 provides additional information
on particulate emissions to allow
for comparisons among countries.
Although, as already noted, the per-
cent change within each country may
be more reliable than comparisons
between countries. For Eastern Europe
and other developing countries,
although information is scarce, particu-
late emissions appear to be increasing.3
For more information on emission
estimates for Europe, Canada and
Mexico, the reader is directed to the
report, National Air Pollutant Emis-
sion Trends, 1900-1993* This com-
panion report summarizes emissions
estimates prepared by the European
Communities, European Environment
Agency Task Force that are broken
down by emission category. The
report also contains international
greenhouse gas emission estimates.
Table 7-2. Emissions of nitrogen oxides from anthropogenic sources in selected countries, 1980 and 1990. Total
emissions (103 metric tons per year at N02).
Region/Country
NORTH AMERICA
Canada
USA
ASIA1
Afghanistan
Bangladesh
Brunei
Cambodia
China
China, Taiwan
Hong Kong
India
Indonesia
Israel
Japan
Korea
Korea, Dem.
Laos
Macao
Malaysia
Mongolia
Myanmar
Nepal
Pakistan
Philippines
Singapore
Sri Lanka
Thailand
Turkey
Viet Nam
1980
1,959
19,160
22
58
4
9
4,910
225
88
1,670
465
80
2,130
365
383
8
3
126
49
47
21
164
184
67
31
255
175
88
1990
1,943
19,087
30
66
11
12
7,370
325
99
2,560
639
148
1,940
555
468
9
5
177
72
45
50
231
184
88
37
384
175
99
Per capita
1990
(kg year1)
73.3
79.8
1.8
0.6
44.2
1.4
6.5
16.0
17.1
3.1
3.6
31.8
15.7
13.1
21.5
2.2
11.3
9.9
35.3
1.1
2.6
2.1
3.0
29.3
2.2
7.0
3.0
1.5
% Change
1980-1990
-1
0
36
14
175
33
50
44
12
53
37
85
-9
52
22
12
67
40
47
-4
138
41
0
31
19
51
0
12
130 • Chapter 7: International Air Pollution Perspective
-------
Section 7.1 Emissions
Table 7-2. Emissions of nitrogen oxides from anthropogenic sources in selected countries, 1980 and 1990. Total
emissions (103 metric tons per year at N02). (cont.)
Region/Country
EUROPE
Albania
Austria
Belgium
Bulgaria
Czechoslovakia2
Denmark
Finland
France
German. Dem. Rep.2
Germany, Fed. Rep.2
Greece
Hungary
Iceland
Ireland
Italy
Luxembourg
Netherlands
Norway
Poland
Portugal
Romania
Spain
Sweden
Switzerland
UK
Yugoslavia
USSR
Armenia
Azerbaijan
Belarus
Estonia
Georgia
Kazakhstan
Kyrgyzstan
Latvia
Lithuania
Moldova
Russia
Tajikistan
Turkmenistan
Ukraine
Uzbekistan
Source: UNEP (1993) except for USA data (U.S. EPA,
1980
9
233
317
150
1,204
245
264
1,823
630
2,980
746
273
13
73
1,480
23
553
185
1,500
166
390
950
398
196
2,422
350
16
50
98
46
40
169
11
10
30
51
2,578
6
15
841
80
1993).
1990
9
209
300
150
1,122
254
290
1,742
705
2,707
746
238
12
135
1,755
15
529
212
1,280
142
390
950
373
184
2,690
420
23
59
101
20
24
330
12
14
35
39
3,050
8
35
761
117
Per capita
1990
(kg year1)
2.8
27.9
30.2
16.8
71.3
49.6
58.3
31.0
42.3
44.7
75.1
22.6
49.8
36.3
30.6
40.9
35.9
50.1
33.3
13.8
16.8
24.2
23.2
28.2
47.3
17.6
6.5
8.1
9.8
12.6
4.3
19.4
2.7
5.3
9.4
8.9
20.5
1.5
9.0
14.6
5.5
% Change
1980-1990
0
-10
-5
0
-7
4
10
-4
12
-9
0
-13
-8
85
19
-35
-4
15
-15
-14
0
0
-6
-6
11
20
44
18
3
-56
-40
95
9
40
17
-24
18
33
133
-10
46
1ln Asia, 1987 data were reported for all countries except for Turkey.
21 989 data used.
Chapter?: International Air Pollution Perspective • 131
-------
Section 7.2 Ambient Concentrations
Table 7-3. Emissions of particulates from anthropogenic sources in selected countries, 1980 and 1990. Total emissions
(103 metric tons per year).
Region/Country
NORTH AMERICA
Canada
USA"
EUROPE
Austria
France
Germany
Hungary
Ireland
Italy
Netherlands
Norway
Switzerland
UK
1980
1,907
5,512
79
427
3,190
576
94
433
158
24
28
560
1990
1,855a
2,637
39
276
2,275
343C
105
501 c
72
21
20
473
% Change
1980-1990
-3
-18
-51
-35
-29
-40
-12
16
-54
-12
-29
-16
a Source: M. Deslauriers, Environment Canada, Ottawa.
b EPA's National Air Pollutant Emissions Trends, 1993; PM-10 total emissions excluding miscellaneous and natural sources.
1989 data cited.
Source: Except where noted, OECD (1993).
7.2 Ambient
Concentrations
On a global scale, in general, declin-
ing annual average SO2 levels over
time correspond with declining emis-
sion trends (Figure 7-1). Trends in
SO2 annual average concentration
levels for selected cities are displayed
in Table 7-4.8 Again, the focus
should be more on the direction of
change, rather than on a comparison
of absolute levels, because monitor-
ing methods and siting objectives may
vary among countries. Figure 7-2
presents a comparison of SO2 annual
average concentrations in selected cit-
ies in the world. Figure 7-3 compares
the second-highest 24-hour sulfur di-
oxide concentrations at two sites in
the United States, a site in New York
and one in Chicago, with concentra-
tions experienced at sites in Montreal
(Quebec), Toronto (Ontario), and
Winnipeg (Manitoba), Canada.9
Similar to trend estimates for SO2
concentrations, suspended particulate
matter annual average concentrations
in cities are declining in many of the
world's industrialized cities. Urban
particulate matter concentrations have
declined in the Organization for Eco-
nomic Cooperation and Development
(OECD) countries from annual aver-
age concentrations of between 50 and
100 ng/m3 in the early 1970s, to lev-
els between 20 and 60 ug/m3 on an
annual basis.1 However, suspended
particulate matter concentrations in
many of the developing countries are
high when compared to some of the
more industrialized cities (Figure 7-
4). A comparison of the annual geo-
metric mean suspended particulate
matter concentrations between New
York and Chicago in the United States
and Hamilton (Ontario), Montreal
(Quebec), and Vancouver (British
Columbia) in Canada is illustrated in
Figure 7-5.
Hourly average values of O3 vary
from year to year, depending on fac-
tors such as precursor emissions and
meteorological conditions. Although
surface O3 measurements are made in
many countries, O3 has not been rou-
tinely summarized on an international
basis. In many OECD countries, O3
levels exceed the recommended stan-
dards. In Japan, hourly average con-
centrations of 235 ng/m3 (0.12 ppm)
are exceeded on a few days of the
year, mostly in the Tokyo and Osaka
areas8. Mexico City has experienced
some of the highest O3 hourly average
concentrations in the world. For the
period 1986-1991, at some locations
in Mexico City, maximum hourly av-
erage concentrations have at times
132 • Chapter 7: International Air Pollution Perspective
-------
Section 7.2 Ambient Concentrations
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-------
Section 7.2 Ambient Concentrations
600
CONCENTRATION, UG/M 3
500
400-
300-
200-
100-
0-
Mexico City
^Beijing
-B-
•Q London
l l l l l l l l I r
1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990
Figure 7-4. Trend in annual average suspended particulate concentrations of selected cities of the world.
Source: UNEP/WHO, 1992a; UNEP/WHO, 1992b.
90n
80-
70-
2 5.
DC z
2 60-
Q <
QJ QC
50-
40-
30
Chicago
1984 1985 1986 1987 1988 1989 1990 1991 1992
Figure 7-5. Trend in annual geometric mean total suspended particulate concentrations in selected U.S. cities and
Canadian cites, 1985-1991. Source: J. Dann, Environment Canada; AIRS database.
Chapter 7: International Air Pollution Perspective • 135
-------
Section 7.2 Ambient Concentrations
Ozone - 2nd maximum hour (ppm)
1985 M 1986 D 1987 Q 1988
1989 • 1990 0 1991 R] 1992
0.1-
0.0
Los Angeles, Ca Houston, TX New York, NY Quebec, due. Ottawa, Ont. Toronto, Ont Vancouver, BC
Figure 7-6. Trend in annual second highest one-hour ozone concentrations in selected U.S. cities and Canadian cites,
1983-1991. Source: T. Dann. Environment Canada; AIRS database.
Megacities
Athens-
Bangkok -
Beijing -
Bombay-
Buenos Aires -
Cairo-
Calcutta-
Caracas-
Christchurch-
Delhi-
Hong Kong-
Jakarta-
Karachi-
London-
Los Angeles -
Madrid-
Manila-
Moscow-
New York City-
Rio De Janeiro-
Sao Paulo-
Seoul-
Shanghai-
Shenyang-
Tokyo-
Toronto-
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H SO2
n oc
(
0 200 400 600 800 1000 1200
Micrograms per Cubic Meter
Figure 7-7. Comparison of ambient levels of annual second daily maximum one-hour ozone, annual average total
suspended particulate matter and sulfur dioxide concentrations among selected cities.
Source: UNEP/WHO, 1992a; UNEP/WHO, 1992b; Varshney and Aggarwal, 1992; UNEP/WHO, 1993; AIRS
database.
136 • Chapter 7: International Air Pollution Perspective
-------
Section 7.3 Ambient Concentration Regulations
exceeded 0.450 ppm.10 In March
1992, similar high hourly average
values were reported. These values
are higher than those that normally
occur in Los Angeles, California. In
general, 03 levels at urban locations
are lower in Canada than in the
United States. The lower O3 levels in
Canada may be associated with the
country's geographical location, i.e.,
lower temperature and solar radiation.
Figure 7-6 shows a comparison of the
second highest daily maximum O3
levels between some selected sites in
the United States and in Canada. The
year 1988 was conducive for high O3
concentrations in the eastern and
midwestern United States and parts of
Canada.
Concentrations for suspended par-
ticulate matter, sulfur dioxide, and
ozone vary substantially among cities
in the world. Figure 7-7 presents a
summary of the extent of these varia-
tions. The concentration information
presented in the figure was derived
from several sources.1'2-3'9-11'12'13-14-18
Ambient Pb levels have shown a
significant decline in the past decade.
Between 1984 and 1993, the compos-
ite average of the maximum quarterly
mean concentration decreased by 89
percent in the United States, with
even larger reductions in the early
1980s. In Canada, a very similar
trend in ambient Pb concentrations
has been observed. Composite aver-
age Pb concentrations declined over
95 percent for the 1974-1990 time
period.15 Also, average ambient Pb
concentrations in Tokyo, Japan16 have
dropped from around 1.0 ug/m3 in
1967 to approximately 0.1 ug/m3 in
1985 a 90-percent improvement.
7.3 Ambient
Concentration
Regulations
Most countries regulate ambient con-
centration of pollutants to protect its
citizens and their environment. The
averaging times, number of exceed-
ances, and units for these regulations
vary across countries. For purposes
of comparisons, a sampling of na-
tional regulations is summarized in
Table 7-5. The table lists selected
standards from certain countries.
The most common pollutants having
ambient air quality standards world-
wide are presented for each country.
However, these countries may have
other standards for pollutants that are
particular to their dominant industries
that are not presented here. It should
also be pointed out that different
countries treat standards very differ-
ently.17 In some cases, the standards
are a legislated requirement in which
specific steps must be taken when the
standards are not met. In other cases,
the standards serve as guidelines or
goals which put ambient monitoring
data into a perspective relative to
health risks or environmental degra-
dation. However, no specific steps
are taken when these limits are not
met. The regulations described are
subject to change and the information
in the tables was available at time of
publication by the sources cited. The
World Health Organization guide-
lines are listed in the table. No en-
tries are provided in the TSP columns
for the United States because the cur-
rent form of the standard is PM-10.
Chapter 7: International Air Pollution Perspective • 137
-------
Section 7.3 Ambient Concentration Regulations
Table 7-5. Selected International Air Quality Standards and Guidelines (units in ug/m3)
Country
Australia
Belgium
Brazil
Canada
Finland
France
Germany
Israel
Italy
Japan
Kuwait
Malaysia
Mexico
Netherlands
Saudi Arabia
South Africa
United Kingdom
United States
WHO
S02
Annual
Average
60
40-60
80
30
40
40-60
140
60
40-60
79
80
80
40-60
80
40-60
so
Daily
Average
100-150
365*
150
100-150
280
100-150
105
157*
105
350
500
400
265
100-150
365*
100-150
TSP
Annual
Average
90
40-60
60
150
75
90
90
60-90
TSP
Daily
Average
100-150
240*
120
200
350*
260
275
150
150-230
Ozone
Hourly
Average
240*
160*
100
118
157
200
220
120
290
240
235**
100-200
* Allowable exceedance: One per year
** The standard is attained when the expected number of days per year with maximum hourly average concentrations above 0.12 ppm
(235 ug rrr3) is equal to or less than one.
Source: International Union of Air Pollution Prevention Associations, 1991;Cochranetal., 1992; UNEP/WHO, 1992a.
138 • Chapter 7: International Air Pollution Perspective
-------
Section 7.4 References
7.4 References
1. "The State of the Environment," OECD, Published by the Organization for Economic Co-operation
and Development, Paris, 1991.
2. "Assessment of Urban Air Quality," GEMS, Published by the United Nations Environment Program
and the World Health Organization, Global Environment Monitoring System, Nairobi, Kenya, 1988.
3. "Urban Air Pollution," UNEP, 199la, UNEP/GEMS Environment Library No 4., United Nations
Environment Program, Nairobi, Kenya, 1991.
4. National Air Pollutant Emission Trends, 1900-1993,454/R-94-027, U.S. Environmental Protection
Agency, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711, 1994.
5. "Environmental Data Report 1993-94," UNEP, UNEP/GEMS Monitoring and Assessment Research
Centre, London, United Kingdom, Blackwell Publishers, Oxford, England, 1993.
6. "Environmental Data Report 1991 -92," UNEP. 1991 b, UNEP/GEMS Monitoring and Assessment
Research Centre, London, United Kingdom, Blackwell Publishers, Oxford, England, 1991.
7. "The State of the Environment 1972-92," UNEP, UNEP/GCSS HI/2, Published by the United Nations
Environment Program, Nairobi, Kenya, 1992.
8. "OECD Environmental Data-Compendium 1993," OECD, Organization for Economic Co-operation
and Development, Paris, 1993.
9. Dann, T, Data provided from Dann, T., "Environment Canada to A.S. Lefohn," A.S.L. & Associates,
Helena, MT, March 17, 1992, March 17, 1993.
10. Cicero-Fernandez, P., Guzman, I., and Moucheron-Hemmer, M., "Ozone trends and meteorology
in Mexico City: An exploratory analysis," Presented at the 86th Annual Meeting & Exhibition of
Air and Waste Management Association, Denver, Colorado, June 13-18, 1993.
11. Aerometric Information Retrieval Systems (AIRS), U.S. Environmental Protection Agency, Office
of Air Quality Planning and Standards, Research Triangle Park, NC, June 1994.
12. Romieu, I., Weitzenfeld, H., and Finkelman, J., Urban air pollution in Latin America and the
Caribbean, Journal of the A ir Waste Management Association 41:1166-1171, 1991.
13. "Urban Air Pollution in Megacities of the World," UNEP/WHO, 1992a, Published by the World
Health Organization and United Nations Environment Program, Blackwell Publishers, Oxford,
England, 1992.
14. "City Air Quality Trends," UNEP/WHO, 1992b, Published by the United Nations Environment
Program, Nairobi, Kenya, 1992.
15. Personal communication, T. Furmanczyk, Environment Canada, to R. Faoro. U.S. Environmental
Protection Agency, September 9, 1992.
16. Hazardous Air Pollutants Project Country Report of Japan, Organization For Economic Co-operation
and Development, Paris, France, March, 1991.
17. Cochran, L.S., Pielke, R.A., and Kovacs, E., Journal of the Air Waste Management Association,
42:1567-1572, 1992.
18. Varshney, C.K., Aggarwal, M., "Ozone pollution in the urban atmosphere of Delhi," Atmos, Environ,
268:291-294, 1992.
Chapter 7: International Air Pollution Perspective • 139
-------
140 • Chapter/: International Air Pollution Perspective
-------
Data Appendix
-------
T3
CD
Q.
x"
TREND STATISTICS USED IN THE 1993 TRENDS REPORT - MEANS
DATA TAKEN OFF OF AIRS ON JULY 8, 1994
Pollutant
Carbon Monoxide
•
"
"
•
"
? f" ', "1j' '•„«'•
Arith. Mean
»
"
& v^t'% ^ i ttr t^mt t i>
2nd.Max.Day
11
»
Exceed.Days
"
„,,.»,".•,.;,,«..,«•%,««•
Wgt Arith. Mean
11
2nd Max 24-Hr
«
90th %tile
11 S ' 5iill ' ::i 1 1'3 ',, i
Arith. Mean
•
•
2nd.Max.24hr.
•
•
Units
PPM
"
"
8hrs.
"
"
UG/M3
11
«
11
11
'•\ lil ti *«*V
PPM
"
11
;K«t *;«>•
PPM*
11
»
DAYS
11
"-,,,,. :>•>
UG/M3
"
11
11
11
!*ij«.,j/-.j»
PPM
»
11
PPM
»
»
#of
Sites
314
96
394
314
96
394
204
88
228
66
93
»t '-' i'~<
201
45
269
*•' * I -, *' '
532
197
722
532
197
722
799
255
799
255
799 ^
sfi};*?
474
138
560
469
138
552
Sites
Type
ALL
NAMS
ALL
ALL
NAMS
ALL
ALL
NAMS
ALL
PBPT"
PBPT"
"\ V' * ' »',
ALL
NAMS
ALL
:"*»'' iC
ALL
NAMS
ALL
ALL
NAMS
ALL
All
NAMS
ALL
NAMS
ALL,,
»;*;;*
ALL
NAMS
ALL
ALL
NAMS
ALL
1984
7.69
8.27
3.38
5.46
0.423
0.514
1.543
;,:.;;;'; *>?
0.0220
0.0272
t'liitP
0.1252
0.1219
6.35
5.23
r;.-'»''
0.1197
0.1188
5.22
4.34
,-.
0.0091
0.0106
0.0447
0.0457
1987
6.69
7.17
1.48
1.96
0.156
0.129
0.973
• :'* " _*'_
0.0220
0.0273
.,; ; ,j°-t ,
0.1261
0.1232
5.75
4.71
•< -if •-
0.0089
0.0101
0.0412
0.0431
1988
6.38
6.79
1.23
1.96
0.103
0.098
1.048
';',•!•'•"
0.0223
0.0270
- • • • *
0.1364
0.1352
8.02
7.28
33.2
36.9
79.7
84.7
55.8
"' ' ? ',", ™ *
0.0091
0.0104
0.0438
0.0454
1989
6.34
6.76
1.25
2.00
0.080
0.079
0.691
*' ' ,'' * ',, '-
0.0219
0.0266
''* ,_. 'f\'s . » '•
0.1169
0.1142
4.29
3.27
33.0
36.6
81.9
87.3
55.5
' '" " i V ,, '•*;'
0.0199
0.0241
0.0186
' , ' - •-/,
0.1071
0.1063
0.1049
2.91
2.34
2.64
27.2
30.2
65.4
71.5
44.8
0.0074
0.0081
0.0072
0.0333
0.0350
0.0333
1993
4.88
5.34
4.82
0.11
0.27
0.18
0.045
0.046
0.047
0.569
0.726
''-. '' •>, ' '
0.0194
0.0234
0.0183
';«:•'"''' :
0.1097
0.1104
0.1072
2.55
2.26
2.38
26.4
29.6
65.0
71.2
45.0
*",;,>",
0.0073
0.0078
0.0071
0.0319
0.0316
0.0317
% CHANGE
1984-93
-37%
-35%
-97%
-95%
-89%
-91%
-63%
'"••• •• '•'*.- ''
-12%
-14%
:;.»','- ', i » - ';s, ;; ,".-",
-12%
-9%
-60%
-57%
-20% *
-20% *
-18% *
-16% *
-19% *
*; ' ' ' ' ' ' ' \ '*
-26%
-33%
-36%
-39%
% CHANGE
1992-93
-5%
-14%
-11%
-9%
• •'•',*; '-
-2%
'•• • ,:,', 1 -
2%
-10%
-3%
-2%
-1%
-0%
0%
-1%
-5%
* FOR PM10 THE % CHANGE REFERS TO THE 1988-93 TIME PERIOD
" SITES LOCATED IN THE VICINITY OF LEAD POINT SOURCES
-------
T3
T3
(D
Q.
EMISSIONS STATISTICS USED IN THE 1993 TRENDS REPORT
NATIONAL EMISSION ESTIMATES (MILLION SHORT TONS/YEAR)"
Pollutant
1970
1984
1992
1993
1970-93
1984-93
**
***
* 1988 TOTAL EMISSIONS ESTIMATE (TO COINCIDE WITH THE AIR QUALITY PERCENT CHANGE)
LEAD EMISSIONS ARE IN THOUSANDS OF SHORT TONS/YEAR
PM10 EMISSIONS ESTIMATES EXCLUDE THE MISCELLANEOUS CATEGORY
1992-93
Carbon Monoxide
Lead"
Nitrogen Oxides
VOC
PM10"*
Sulfur Oxides
128.079
219.471
20.625
30.646
11.999
31 .096
114.262
42.217
23.172
25.572
2.942 *
23.396
96.368
4.741
22.991
23.020
2.729
21.592
97.208
4.885
23.402
23.312
2.661
21.888
-24%
-98%
13%
-24%
-78%
-30%
-15%
-88%
1%
-9%
-10%*
-6%
1%
'...', 3%
2%
"l%
-2%
1%
U
-------
144 • Data Appendix
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA 454/R-94-026
I. RECIPIENT'S ACCESSION NO
.. TITLE AND SUBTITLE
5. REPORT DATE
National Air Quality and Emissions Trends Report, 1993
6. PERFORMING ORGANIZATION CODE
. AUTHOR(S)
T. Curran, T. Fitz-Simons, W. Freas, J. Hemby
D. Mintz, S. Nizich, B. Parzygnat, M. Wayland
8. PERFORMING ORGANIZATION REPORT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Air and Radiation
Office of Air Quality Planning and Standards
Research Triangle Park, NC 27711
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report presents national and regional trends in air quality from 1984 through
1993 for particulate matter, sulfur dioxide, carbon monoxide, nitrogen dioxide, ozone
and lead. Air quality trends are also presented for 89 metropolitan areas. Both
national and regional trends in each of these 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 availabl j
engineering calculations; the ambient levels presented are averages of direct measure-
ments. International comparisons of air quality and emissions are contained in this
report. The topics of air toxics and visibility are also addressed.
This report also includes a section called Air Quality Status of Metropolitan Areas.
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 for the single year 1993. Air quality statistics are presented for each
of the pollutants for all MSAs with data in 1993.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Air Pollution Trends
Emission Trends
Carbon Monoxide
Nitrogen Dioxide
Ozone
Sulfur Dioxide
Total Suspended
Parti ml at--
Visibility
Particulate Matter
Air Pollution
Air Quality Standards
National Air Monitoring
Stations (NAMS)
Air Toxics
Pollutant Standards
Indox
18. DISTRIBUTION STATEMENT
Release Unlimited
19. SECURITY CLASS (Tins Report)
!1. NO OF PAGES
157
20 SECURITY CLASS (Tins page)
22 PRICE
EPA Form 2220-1 (Rev. 4-77) PREVIOUS EDITION is OBSOLETE
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