BREATHING EASIER:
A REPORT ON AIR QUALITY
IN CALIFORNIA, ARIZONA, NEVADA & HAWAII
May 1995
U.S. ENVIRONMENTAL PROTECTION AGENCY, REGION 9
REGION 9
AIR MONITORING STATIONS
EPA 909-R-95-001
MAY 1995
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BREATHING EASIER:
A REPORT ON AIR QUALITY
IN CALIFORNIA, ARIZONA, NEVADA & HAWAII
May 1995
Prepared By:
U.S. Environmental Protection Agency
Region 9
Air and Toxics Division
75 Hawthorne Street (A-2-4)
San Francisco, CA 94105
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Table of Contents
EXECUTIVE SUMMARY ES-1
INTRODUCTION i
OZONE 1-1
PARTICULATE MATTER 2-1
CARBON MONOXIDE 3-1
NITROGEN DIOXIDE 4-1
SULFUR DIOXIDE 5-1
LEAD 6-1
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EXECUTIVE SUMMARY
WE'RE BREATHING EASIER:
A DECADE OF PROGRESS
TOWARD CLEANER AIR IN
THE WESTERN STATES
There has been a substantial
improvement in air quality in U.S. EPA's
western region -- California, Arizona,
Nevada, and Hawaii -- over the last ten
years. Despite an increase in auto travel
of almost 50% over the past decade, air
pollutant levels have decreased overall
by about one-third. Both the number of
days on which air pollution has exceeded
federal air quality standards, and the air
pollutant concentration levels have
decreased for the six major air pollutants
targeted for reduction under the federal
Clean Air Act.
Of the six pollutants, the greatest
reductions have been recorded for lead
(93%), followed by sulfur dioxide (34%),
and carbon monoxide (29%). The
tremendous reduction in lead levels has
resulted mostly from the phase-out of
lead in gasoline. Particulate matter,
nitrogen dioxide, and smog-forming
ground-level ozone present the most
serious remaining challenges. However,
all six pollutants are being steadily
reduced.
Long-Term (1984-93) Air Quality Trends
Ten-year trends show that air quality
has improved for ozone (O3), carbon
monoxide (CO), nitrogen dioxide (NO2),
sulfur dioxide (SO2), and lead (Pb).
Although particulate matter (PM10) has
only been monitored for six years, levels
have decreased during that period.
Changes in air pollutant levels
between 1984 and 1993 (the most recent
year for which complete data are
available) forall long-term monitoring sites
in California, Arizona, Nevada, and Hawaii
are as follows:
Lead (Pb): 93% decrease
Sulfur Dioxide (SO2): 34%
decrease
Carbon Monoxide (CO): 29%
decrease
Particulate Matter (PM10): 25%
decrease
Ozone (03): 18% decrease
Nitrogen Dioxide (NO2): 13%
decrease
Most Improved Areas
Many of the geographic areas that
failed to meet federal air quality standards
when the Clean Air Act Amendments were
passed in 1990 have improved enough to
meet the standards based on data from
more recentyears (1991, 1992, and 1993).
Areas in this "most improved" category,
for each of the six pollutants, are:
« Ground-level Ozone (O3): San
Francisco Bay Areaand Monterey
Bay, California; and Reno,
Nevada.
ES- 1
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Particulate Matter (PM10):
Sacramento, California; Ajo,
Rillito, Payson, Hayden, and
Miami, Arizona.
Carbon Monoxide (CO): San
Francisco Bay Area, San Diego,
Sacramento, Fresno, Stockton,
Modesto, Chico, Lake Tahoe, and
Reno.
Sulfur Dioxide (SO2): In earlier
years, violations had occurred
near nonferrous metal (copper)
smelters in Arizona, but none have
been recorded recently. The only
recent violations were from
naturally-occurring volcanic
emissions at Hawaii Volcanoes
National Park.
Nitrogen Dioxide (NO2): The only
violation of the standard was in
the South Coast Air Basin (Los
Angeles Area) in 1991. That area
met the standard in 1992 and
1993.
Lead (Pb): All areas met the
federal standard.
WHERE PROBLEMS REMAIN
Ground-level ozone (O3) violations
were recorded in most of Southern
California, the San Joaquin Valley,
the Sacramento Area, and
Phoenix.
Particulate matter(PM10) violations
were recorded in the South Coast
AirBasin, Southeast Desert, Great
Basin Valley, San Joaquin Valley,
Reno, Las Vegas, Phoenix and
some rural areas in Arizona.
Carbon monoxide (CO) violations
occurred in the South Coast Air
Basin, Phoenix, and Las Vegas.
REGION IX
AIR MONITORING STATIONS
Figure ESa - Air Monitoring Stations, 1991-1993.
ES-2
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INTRODUCTION
This report presents the last ten
years' air quality information for areas
within EPA Region 9, consisting of Ari-
zona, California, Hawaii, Nevada, and the
Pacific Islands. Current air quality
(through 1993) and ten-year trends are
presented for the six air pollutants for
which National Ambient Air Quality Stan-
dards (NAAQS) have been developed.
These air pollutants are carbon monoxide
(CO), ozone (O3), nitrogen dioxide (NO2),
sulfur dioxide (SO2), lead (Pb), and par-
ticulate matter with aerodynamic size of
10 microns or less (PM10). The Federal
standards are presented in Table 1. State
air quality standards may differ from the
NAAQS.
The air quality data for this report
were collected from several hundred moni-
toring sites throughout Region 9 by local,
state, and Federal agencies and private
organizations. Most of the data are stored
on EPA's Aerometric Information Retrieval
Systems (AIRS) data base. The data,
analysis methods, and emissions esti-
mates used in this report are taken from
EPA's annual "National Air Quality and
Emissions Trends Report", but are tai-
lored specifically to EPA Region 9. The
reader may refer to that document for
technical details and for air quality infor-
mation about areas outside of Region 9.
The information presented here is
organized by pollutant and is intended to
show general air quality and trends for
some areas in Region 9 and for the Re-
gion as a whole. In most cases, air quality
information is not presented for individual
monitors.
POLLUTANT
O3
PM-1O
CO
S02
PRIMARV
(HEALTH RELATED)
Type of
Average
Max. Daily
1 -hour Avg
Annual
Mean
24-hour
8-hour
1 -hour
Annual
Mean
Annual
Mean
2-4-Hour
Max
Quarterly
Average
Standard Level
Concentration
O.12 ppm
(236 ug/m3)
SO ug/m3
15O ug/m3
9 ppm
(1O mg/m3)
35 ppm
(4O mg/m3)
O.O63 ppm
(TOO |jg'm3)
SO ug/m3
(O.O3 ppm)
(O.14 ppm)
1 .5 U£)/m3
SECONDARY
(WELFARE RELATED)
Type of
Average
Standard Level
Concentration
Same as Primary Standard
Same as Primary Standard
Same as Primary Standard
No Secondary Standard
No Secondary Standard
Same as Rrlmary Standard
1 3OO ug/m3
(O.SO ppm)
Same as Primary Standard
ppm = parts per million; ppb = parts per billion;
mg/m3 = milligrams per cubic meter; ug/m3 = micrograms per cubic meter
Table 1
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OZONE
BACKGROUND and HEALTH EFFECTS
Ground-level ozone (O3) is the major
component of smog. While ozone in the
upper atmosphere benefits life by shield-
ing the earth from the sun's harmful ultra-
violet radiation, high concentrations of
ozone at ground level are a major health
and environmental concern. Ozone is not
emitted directly into the air, but is formed
through complex chemical reactions be-
tween precursor emissions of volatile or-
ganic compounds (VOC) and nitrogen
oxides (NOx) in the presence of sunlight.
These reactions are stimulated by sun-
light and temperature so that peak ozone
levels typically occur during the warmer
times of the year. Both VOC and NOx are
emitted by motor vehicles and industrial
sources.
The reactivity of ozone causes health
problems because it damages lung tis-
sue, reduces lung function, and sensi-
tizes the lungs to other irritants. Scien-
REGION IX
AIR MONITORING STATIONS
FOR
OZONE
1991-93
tific evidence indicates that ambient lev-
els of ozone not only affect people with
impaired respiratory systems, such as
asthmatics, but healthy adults and chil-
dren as well. Exposure to ozone for
several hours at relatively low concentra-
tions has been found to reduce lung func-
tion significantly in normal, healthy people
during exercise. This decrease in lung
function generally is accompanied by
symptoms including chest pain, cough-
ing, sneezing, and pulmonary conges-
tion. Ozone also damages agricultural
crops and forests.
The national health standard for O_
o
is defined in terms of the daily highest (1 -
houraverage) concentration. Ambient O3
concentrations should not exceed 120
ppb more than one day per year, based
on a three-year average.
RECENT OZONE AIR QUALITY
IN REGION 9
Forthethree-
year period 1991-
93, O3 was moni-
tored at 252 sites
in Region 9. Fig-
ure 1a shows the
geographic distri-
bution of O, moni-
o
tors throughout
the Region. In
general, more
monitors are lo-
cated in or near
urban areas than
in rural areas.
The 81 moni-
toring stations
Figure 1a
1 1
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where ozone pollution exceeded the
NAAQS during 1991-93 are shown on the
map in Figure 1 b as the vertical "spikes".
The height of each spike is proportional
to the number of days per year that the
NAAQS was exceeded. The most serious
O3 problem in the Region (and in the
nation) is in the South Coast Air Basin
(Los Angeles area). Other areas that
violated the O3 NAAQS include San Di-
ego and Ventura counties, the California
Southeast Desert, San Joaquin Valley,
Sacramento, and Phoenix.
LONG-TERM OZONE TRENDS: 1984-93
With respect to ozone, air quality
has improved over the last ten years in
most areas of Region 9. For the Region
as a whole, there were 124 long-term
monitors that operated for the ten-year
period. These monitors, as a group,
showed an 18% decrease in O3 concen-
trations between 1984 and 1993 (based
on the second highest daily 1-hour maxi-
mum concentration). This compares to a
12% decrease at 532 sites nationwide.
Figure 1 c shows the number of days
that the O3 Stage 1 ("smog alert") level of
200 ppb was reached in the six most
serious O3 pollution areas of Region 9.
Ozone air quality measured by this air
quality indicator has improved gradually
over the last ten years. The South Coast
had 97 Stage 1 days in 1984 compared to
23 in 1993. Likewise, the Southeast
Desert has improved from a high of 18
Stage 1 days in 1986 to one day in 1993.
Stage 1 days have not occurred at all in
the other four areas in several years.
Figure 1 d shows the number of days
in which ozone levels exceeded the O3
standard of 120 ppb for each of the last
10 years in various areas of the Region.
Note that the number of days is a "basin-
wide" composite from all O3 monitors in
an air basin. It represents the number of
days during the year that the O3 standard
was exceeded at one or more monitors.
The largest reduction in ozone pollu-
tion has been in the California South Coast
Air Basin. The standard was exceeded in
the Basin on 179 days at its worst in 1984.
In 1993, it was exceeded on only 124
days. The second-largest improvement
occurred in the California Southeast
Desert area, where the number of
exceedances decreased from 123 days
in 1988 to 76 days in 1993.
The trend toward fewer days above
the O3 NAAQS and Stage 1 smog alert
level has been accompanied by a trend in
lower O- concentrations. Peak O. con-
o J
centrations in each area of Region 9 that
had several long-term monitors showed
improving air quality. The percent de-
creases in peak O3 concentration between
1984 and 1993 were as follows:
% Decrease
In Peak
Concentration
27%
20%
20%
19%
18%
16%
13%
10%
6%
Area
South Coast
San Francisco
Bay Area
Ventura County
Southeast Desert
Sacramento - Metro
San Diego County
San Joaquin Valley
Santa Barbara Co.
Phoenix
The South Coast Air Basin had the
largest decrease in peak O3 concentra-
tions. There were 25 long-term O3 moni-
tors in the South Coast and the average
(second highest daily 1-hour) concentra-
tion at those sites decreased from 260
ppb in 1984 to 180 ppb in 1993.
1 -2
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Sogro - btror»tnc. informtinn
Figure Ib
Syrtcn (MRS)
EPA Region 9
Air Quality
OZONE
Frequency of
NAAQS Violations
1991-93
Air Quality Trends 1984-93
100
OZONE Stage 1 Days
Number of days O3 Stage 1 (200 ppb) reached.
Areas Classified
Serious to Extreme
South Coast
E. Desert Modified AQMA
San Joaquin Valley
San Diego County
i I
'34 '35 '36 '37
'39 '90 '91 '92 '93
Ventura County
Sacramento Metro
Figure Ic
Stage 1 = 200 ppb (1-hour
concentration).
Number of Stage 1 Days reached
at one or more locations.
1-18-95
1-3
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Air Quality Trends 1984-93
OZONE Exceedances
Number of days exceeding the O3 NAAQS.
Areas Classified
Serious to Extreme
South Coast
S.E. Desert Modified AQMA
San Joaquin Valley
San Diego County
Ventura County
Sacramento Metro
I I I I
88 '89 '90 '91 '92 '93
Areas Classified
Attainment to Moderate
Imperial County
Santa Barbara County
£r,.... ,<... <.... .C,.,-,.S.'l,* Monterey Bay
I/ Las Vegas
'84 '85 '86 '87 '88 '89 '90 '91 '92 '93
Number of days exceeding the NAAQS at one or more locations
NAAQS = 120 ppb (1-hour concentration).
NAAQS = National Ambient Air Quality Standard.
Figure Id
1-4
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PARTICULATE MATTER
BACKGROUND and HEALTH EFFECTS
Air pollutants called "particulate mat-
ter" include dust, dirt, soot, smoke, and
liquid droplets directly emitted into the air
by sources such as factories, power plants,
transportation sources, construction ac-
tivity, fires, and windblown dust. Particu-
lates are also formed in the atmosphere
by condensation ortransformation of emit-
ted gases such as sulfur dioxide, nitrogen
oxides, and volatile organic compounds
into tiny droplets.
Based on studies of human popula-
tions exposed to high concentrations of
particles (often in the presence of sulfur
dioxide) and on laboratory studies of ani-
mals and humans, the major concerns 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, dam-
age to lung tissue, carcinogenesis and
premature death. The majorsubgroupsof
the populations that appear likely to be
most sensitive to the effects of particulate
matter include individuals with chronic ob-
structive pulmonary cardiovascular dis-
ease, individuals with influenza, asthmat-
ics, the elderly, and children. Particulate
matter may injure crops, trees and shrubs,
and may cause damage to metal surfaces,
fabrics, etc. Fine particulates also impair
visibility by scattering light and reducing
the visual range in urban, rural, and wil-
derness areas. The haze caused by fine
particles can diminish crop yields by re-
ducing sunlight.
The current NAAQS for particulate
matter was established in 1987. The par-
ticulate size measurement used, known
as PM10, includes particles with an aero-
dynamic diameter of less than 10 microns.
These smaller particles are most likely
responsible for the adverse health effects
on humans because particles so small
can reach the thoracic or lower regions of
the respiratory tract. The PM10 annual
mean standard is 50 micrograms per cu-
bic meter of air (ug/m3). The 24-hour
standard is attained when the expected
number of days per calendar year above
150 ug/m3 is no more than one. EPA is
currently reviewing recent health effects
studies on fine particulates, and may re-
vise the PM10 NAAQS to focus on particles
smaller than ten microns. In addition,
EPA is considering standards for visibility
impairment and regional haze, which may
be part of the revised PM NAAQS or sepa-
rate standards.
RECENT PM^ AIR QUALITY IN REGION 9
For the three-year period 1991-93,
PM10 was monitored at 258 sites in Region
9. Figure 2a shows the geographic distri-
bution of PM10 monitors throughout the
Region.
The 51 PM10 sites that violated the
NAAQS during 1991-93 are shown on the
map in Figure 2b. The "spikes" represent
monitors with PM10 levels in violation of
the annual standard, and the height of
each spike shows the annual mean con-
centration for the site. The triangles on
the map show monitors that attained the
annual standard but exceeded the 24-
hour standard. The more serious PM10
problem areas in Region 9 are in the South
Coast Air Basin (Los Angeles area), San
Joaquin Valley, California's Southeast
2 1
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Figure 2a
REGION IX
AIR MONITORING STATIONS
PARTICULATES (PM1O)
1991-93
Desert and Great Basin Valley, Reno, Las
Vegas, Phoenix, and several areas near
the Mexican border.
LONG-TERM PM^ TRENDS: 1988-93
PM10 is the newest NAAQS pollut-
ant to be measured, with data going back
only to 1988 in most areas. Overall, PM10
annual mean concentrations have de-
creased by 25% in Region 9, based on
142 monitoring sites operating from 1988
through 1993. This compares to a 20%
decrease at 799 sites nationwide.
Figure 2c shows the 6-year PM10
changes for 22 areas in Region 9 from
1988 through 1993. For most of the ar-
eas, the number of exceedances of the
24-hourstandard has decreased overtime.
For example, the number of exceedances
in the San Joaquin Valley decreased from
13 days in 1990 to 4 days in 1993. Like-
wise, Paul Spur, a town in Arizona, im-
proved from 1 1 days above the standard
in 1989 to none in 1992 and 1993.
Figure 2d shows the trend in PM
3 10
concentrations since 1988. For most ar-
eas, the annual mean concentration has
decreased. The ten areas with the largest
percentage reduction in their annual mean
concentration are:
% Decrease in
Concentration
69%
62%
57%
50%
46%
45%
44%
41%
39%
38%
Area
Rillito, AZ
Payson, AZ
Paul Spur, AZ
Hayden, AZ
Ajo, AZ
Douglas, AZ
San Bernardino Co.
(Desert) CA
Owens Valley, CA
Nogales, AZ
Yuma, AZ
California's South Coast Air Basin
has the largest long-term PM10 monitoring
network, with 13 sites, and has shown an
overall 32% reduction in annual mean con-
centrations between 1988 and 1993.
2 -2
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CO
to
I
UJ
A= Site exceeds only the 24-hour NAAQS
EPA Region 9
Air Quality
PARTICULATES
( PM10 )
Severity of Annual NAAQS Violations
1991-93
7/94
Figure 2b
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Air Quality Trends 1988-93
PARTICULATE MATTER (PM10) Exceedances
Number of days exceeding the 24-hour PM,0 NAAQS.
15
Arizona and
Nevada
Nonattainment
Areas
Paul Spur
Reno
Payson
Las Vegas
Phoenix
Negates
Rillito
Yuma
Hayden/Miami
Bullhead City
Douglas
Ajo
'89
'90
'91
'92
i
'93
NAAQS = 150 ug/m3
(24-hour average
concentration).
Number of days
exceeding the NAAQS
at one or more
locations.
NAAQS = National
Ambient Air Quality
Standard.
California
Nonattainment
Areas
San Joaquin Valley
South Coast
Owens Valley
Coachella Valley
Imperial Valley
San Bernardino County Desert
Searles Valley
Mammoth Lakes
Sacramento County
Mono Basin
Figure 2c
2-4
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Air Quality Trends 1988-93
PARTICULATE MATTER (PM10) Concentrations
Composite annual mean concentrations.
'88
Arizona and
Nevada
Nonattainment
Areas
Paul Spur -57% (1 site)
Pay son -62% (1 site)
Nogales -39% (1 site)
Rillito-69%(1 site)
Douglas -45% (1 site)
Phoenix-21% (5 sites)
Yuma -38% (1 site)
Las Vegas -26% (5 sites)
Hayden/Miami-50% (1 site)
Reno-13% (3 sites)
Bullhead City-32% (1 site)
Ajo -46% (1 site)
'89
'93
- NAAQS = 50 ug/m3
(annual mean
concentration).
Percent change in
concentration
between 1988 and
1993 is based on
linear regression
analysis.
» NAAQS = National
Ambient Air Quality
Standard.
1
'88 '89 '90
California
Nonattainment
Areas
Imperial Valley -26% (2 sites)
South Coast -32% (13 sites)
San Joaquin Valley -17% (11 sites)
Coachella Valley -32% (3 sites)
San Bernardino County Desert -44% (2 sites)
Sacramento County -33% (6 sites)
Mammoth Lakes +13% (1 site)
Searles Valley -34% (3 sites)
Owens Valley -41% (3 sites)
Mono Basin +31 % (2 sites)
'92 '93
11-30-94
Figure 2d
2-5
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CARBON MONOXIDE
BACKGROUND and HEALTH EFFECTS
Carbon monoxide (CO) is a color-
less, odorless, and poisonous gas pro-
duced by incomplete combustion of car-
bon in fuels. Two-thirds of the nationwide
CO emissions are from transportation
sources, with the largest contribution com-
ing from highway motor vehicles.
Carbon monoxide enters the blood-
stream and reduces the delivery of oxy-
gen to the body's organs and tissues.
The health threat is most serious for those
who suffer from cardiovascular disease,
particularly those with angina or periph-
eral vascular disease. Exposure to el-
evated CO levels is associated with im-
pairment of visual perception, manual
dexterity, learning ability, and perfor-
mance of complex tasks.
The NAAQS for ambient CO specify
upper limits for both 1-hour and 8-hour
average levels that are not to be ex-
ceeded more than once per year. The 1 -
hour level is 35 ppm, and the 8-hour
average level is 9 ppm. This report fo-
cuses on the 8-hour standard because
the 1-hour standard is rarely exceeded.
RECENT CARBON MONOXIDE
AIR QUALITY IN REGION 9
Forthe two-year period 1992-93, CO
was monitored at 139 sites in Region 9.
Figure 3a shows the geographic distribu-
tions of CO monitors throughout the Re-
gion. In general, more monitors are lo-
cated in or near urban areas than in rural
areas.
REGION IX
AIR MONITORING STATIONS
FOR
CARBON MONOXIDE
1992-93
3- 1
rigure
-------
The five CO monitoring sites that
violated the NAAQS during 1992-93 are
shown on the map in Figure 3b. The
vertical "spikes" represent CO monitors
in violation, and the height of each spike
shows the number of violations. The
three areas with violations were the South
Coast Air Basin (Los Angeles area), Phoe-
nix, and Las Vegas. Three other areas
(Sacramento, Bakersfield, and South Lake
Tahoe) occassionally exceeded the
NAAQS but not often enough to cause a
violation.
LONG-TERM CO TRENDS: 1984-93
Carbon monoxide air quality has
greatly improved overthe lastten years in
all areas of Region 9. Overall, CO con-
centrations (second high 8-hour average)
have decreased by 29% in the Region
based on 81 sites operating from 1984
through 1993. This compares to a 37%
decrease at 314 sites nationwide. Much
of the CO air quality improvement can be
attributed to newer, cleaner-burning ve-
hicles and fuels, and state smog check
programs.
Figure 3c shows the number of days
with CO pollution above the standard for
each of the last 10 years for 14 areas of
the Region. Note that the number of days
is a composite from all CO monitors in an
air basin. It represents the number of
days during the year that the CO standard
was exceeded at one or more monitors.
Several areas have shown remark-
able reductions in CO exceedances dur-
ing the last ten years. The CO
exceedances in Phoenix decreased from
99 days in 1984 to one day in 1993. The
South Coast decreased from 76 days to
29. Las Vegas decreased from 54 days to
five. Lake Tahoe decreased from 42
days to none.
Peak CO concentrations (8-hour av-
erage) have also decreased substantially
during the last ten years in seven areas
that have several long-term monitors. The
percent decreases in CO concentrations
between 1984 and 1993 were as follows:
% Decrease
in Peak
Concentration
50%
43%
37%
27%
26%
20%
16%
Area
Lake Tahoe
Phoenix
Tucson
San Francisco
Bay Area
South Coast Air Basin
San Diego County
Sacramento
3-2
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Figure 3b
EPA Region 9
Air Quality
CARBON MONOXIDE
Frequency of 8-hour
NAAQS Violations
1992-93
Air Quality Trends 1984-93
CARBON MONOXIDE Exceedances
Number of days exceeding the 8-hour CO NAAQS.
Nonattainment
Areas
South Coast
Phoenix
Vegas
Lake Tahoe
Sacramento
Reno
Fresno
San Francisco Bay Area
Stockton
Modesto
San Diego County
Chico
Tucson
Bakersfield
'86 '87 '88 '89 '90 '91 '92 '93
NAAQS = 9 ppm (8-hour average
concentration).
Number of days exceeding the
NAAQS at one or more locations.
NAAQS = National Ambient Air
Quality Standard.
Figure 3c
3-3
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NITROGEN DIOXIDE
BACKGROUND and HEALTH EFFECTS
Nitrogen dioxide (NO2) is a brown-
ish, highly reactive gas which is present
in urban atmospheres. NO2 is formed in
the atmosphere from emissions of oxides
of nitrogen (NOx). NOx plays a major role,
together with volatile organic compounds,
in the atmospheric reactions that produce
ozone. NOx forms when fuel is burned at
high temperatures. The two major NOx
emission categories are transportation
sources (primarily motor vehicles) and
stationary fuel combustion sources, such
as electric utilities and industrial boilers.
The NAAQS is based on nitrogen
dioxide (NO2) because it is known to be
highly toxic to humans. Nitrogen dioxide
can irritate the lungs, cause bronchitis
and pneumonia, and lower resistance to
respiratory infections. Nitrogen oxides
are an important precursor to both ozone
and acidic precipitation, which harm both
terrestrial and aquatic ecosystems. The
NAAQS for NO2 is 53 ppb annual mean
concentration.
RECENT NO, AIR QUALITY IN REGION 9
&
Forthe two-year period 1992-93, NO2
was monitored at 135 sites in Region 9.
Figure 4a shows the geographic distribu-
tion of NO2 monitors throughout the Re-
gion. In general, more monitors are lo-
cated in or near urban areas than in rural
REGION IX
AIR MONITORING STATIONS
FOR
NITROGEN DIOXIDE
1992-93
4- 1
Figure 4a
-------
areas.
There were no sites that violated the
NO2 NAAQS in 1992 or 1993. In fact,
there were no violations anywhere in the
United States during this period. The
most recent violation occurred in the South
Coast Air Basin (Los Angeles area) in
1991.
LONG-TERM NO, TRENDS:
1984-93
Air quality with respect to nitrogen
dioxide has improved over the last ten
years in Region 9. For the Region as a
whole, there were 69 long-term monitors
that operated for the 10-year period.
These monitors, as a group, showed a
13% decrease in their annual mean NO0
concentrations between 1984 and 1993.
This compares with a 12% decrease at
201 sites nationwide.
Figure 4b shows the change in an-
nual mean concentration forsix sites since
1984. These sites represent the higher
NO2 concentrations found in the South
Coast, San Diego, San Joaquin Valley,
Bay Area, and Sacramento areas. Note
that all areas were well below the stan-
dard except for the South Coast Air Ba-
sin. However, the South Coast was below
the NO2 standard for the last two years.
Based on a composite of 17 long-term
sites in the South Coast, their annual
mean NO2 concentration decreased by
17% between 1984 and 1993.
Air Quality Trends 1984-93
NITROGEN DIOXIDE (NO2) Cpncentrations
Annual mean concentrations.
NAAQS - 53 ppb (annual mean
concentration).
NAAQS = National Ambient Air
Quality Standard.
Figure 4b
4-2
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SULFUR DIOXIDE
BACKGROUND and HEALTH EFFECTS
Ambient sulfur dioxide (SO2) results
largely from stationary sources that burn
coal and oil, refineries, pulp and paper
mills, and from nonferrous metal smelt-
ers.
SO2 affect
High concentrations of
breathing and may aggravate existing res-
piratory and cardiovascular disease.
Sensitive populations include asthmat-
ics, individuals with bronchitis or emphy-
sema, children, and the elderly. SO2 also
produces leaf damage to trees and agri-
cultural crops.
Sulfur dioxide and other oxides of
sulfur combine with oxygen to form sul-
fates and with water vapor to form aero-
sols of sulfurous and sulfuric acid. These
acid mists can irritate the respiratory sys-
tems of humans and animals and injure
plants. Particulate sulfates also reduce
visibility.
There are three NAAQS for SO2: an
annual arithmetic mean of 80 micrograms
per cubic meter of air (ug/m3), a 24-hour
level of 365 ug/m3 and a 3-hour level of
1300 ug/m3. The first two standards are
primary (health-related) standards, while
the 3-hour NAAQS is a secondary (wel-
fare-related) standard. For an air basin to
be classified as having attained the SO2
standard, the annual mean standard is
not to be exceeded, while the short-term
standards are not to be exceeded more
than once per year.
REGION IX
AIR MONITORING STATIONS
FOR
SULFUR DIOXIDE
1992-93
5- 1
Figure 5a
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RECENT sq AIR QUALITY IN REGION 9
g
For the two-year period 1992-93, SO2
was monitored at 88 sites in Region 9.
Figure 5a shows the geographic distribu-
tion of SO2 monitors throughout the Re-
gion. The only site in Region 9 which
violated the NAAQS during this period
was one monitor at Hawaii Volcanoes
National Park, which exceeded both the
24-hour and 3-hour standards. The
exceedances were due to natural SO2
emissions from volcanoes. The annual
standard was not violated at any monitor-
ing site.
LONG-TERM SO, TRENDS: 1984-93
There have been no exceedances of
the annual SO2 standard in Region 9 since
1984, and the trend in SO2 concentra-
tions has been downward for the last ten
years. For the Region as a whole, there
were 37 long-term monitors during that
period. These monitors, as a group,
showed a 34% decrease in annual SO2
concentrations between 1984 and 1993.
This compares to a 26% decrease at 474
sites nationwide.
Until the mid-1980's, the SO2 NAAQS
was exceeded at sites near nonferrous
metal smelters in Arizona. See Figure 5b
for the 10-year trends for both the 24-
hour and 3-hour standards. During the
last ten years, several smelters have
ceased operations. The currently operat-
ing smelters near the towns of Hayden,
Miami, and San Manuel have substan-
tially reduced their SO2 emissions, and
consequently the number of NAAQS vio-
lations has declined. For example, the
Miami area went from eleven exceedances
of the 24-hour standard in 1984 to none in
recent years. Likewise, for the 3-hour
standard, Miami went from 30
exceedances in 1984 to none in recent
years.
5-2
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Air Quality Trends 1984-93
SULFUR DIOXIDE Exceedances
Number of exceedances of the SQ> NAAQS.
12
24-hour Primary Standard
Hawaii Volcanoes N.R
Miami, AZ
Morenci, AZ
Douglas, AZ
Ajo, AZ
0 IfIII1III1
'84 '85 '86 '87 '88 '89 '90 '91 '92 '93
Hayden, AZ
San Manuel, AZ
Number of exceedances of the
NAAQS at one or more locations.
* NAAQS = National Ambient Air
Quality Standard.
3-hour Secondary Standard
(NAAQS = 1300jig/m3)
Hawaii Volcanoes N.R
Miami, AZ
Morenci, AZ
Douglas, AZ
I I I I I I
'84 '85 '86 '87 '88 '89 '90 '91 '92 '93
Ajo, AZ
Hayden, AZ
San Manuel, AZ
10-17-94
Figure 5b 5_3
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LEAD
BACKGROUND and HEALTH EFFECTS
Sincethemid-1970's, lead (Pb) emis-
sions have been reduced over 90% - the
most dramatic success thus far in the
nation's struggle for cleaner air. This has
been mainly the result of eliminating lead
from most gasoline sold in the U.S. The
virtual elimination of lead emissions from
transportation sources has changed the
nature of the ambient lead problem in the
United States from vehicle-related to one
associated with point stationary sources
such as smelters, battery plants, and solid
waste disposal. There are few such lead
point sources in Region 9.
Exposure to lead can occur through
multiple pathways, including inhalation of
air and ingestion of lead in food, water,
soil, or dust. Excessive lead exposure
can cause seizures, mental retardation
and/or behavioral disorders. Fetuses,
infants, and children are especially sus-
ceptible to low doses of lead, resulting in
central nervous system damage. The
NAAQS for Pb is 1.5 micrograms per
cubic meter of air (ug/m3) average con-
centration over a three-month period.
RECENT Pb AIR QUALITY IN REGION 9
For the two-year period 1992-93, Pb
was monitored at 54 sites in Region 9.
Figure 6a shows the geographic distribu-
tion of the Pb monitors throughout the
Region.
AIR MONITORING STATIONS
FOR
6- 1
Figure 6a
-------
There were no violations of the Pb
NAAQS at any sites during 1992-93. Lead
concentrations are now typically 10% of
the Federal standard or less. The only Pb
violation in the last ten years was mea-
sured at a special purpose monitor in
1991. The monitor is sited near a lead
smelter in Commerce, located in the South
Coast Air Basin. Anti-pollution measures
were subsequently put into place at this
source, and Pb emissions have been
greatly reduced.
LONG-TERM Pb TRENDS: 1984-93
Lead concentrations have been con-
tinually declining over the past ten years
throughout Region 9. The highest con-
centrations today are only a small frac-
tion of the Federal standard. For the
Region as a whole, there were 30 long-
term monitors that operated for the ten-
year period. These monitors, as a group,
showed an astounding 93% decrease in
maximum quarterly mean Pb concentra-
tions between 1984 and 1993. This com-
pares to an equally notable 89% decrease
at 204 sites nationwide.
Figure 6b shows the 10-year change
in Pb concentrations for the South Coast
Air Basin (Los Angeles area) and the San
Francisco Bay Area.
Air Quality Trends 1984-93
LEAD (Pb) Concentrations
Composite maximum quarterly mean concentrations.
South Coast
-91% (9 sites)
San Francisco Bay Area
-93% (13 sites)
0.0 |
'84 '85 '86 '87 '88
NAAQS = 1.5 |ig/m 3
(highest quarterly mean
concentration).
'90 '91 '92 '93
NAAQS = National
Ambient Air Quality
Standard.
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