United States
Environmental Protection
Agency
Off ice of Air'Quality
Planning and Standards
Research Triangle Park, NC 27711
October 1996
EPA-454/F-96-008
Air
and
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The overall quality of our nation's air continues to improve.
This brochure highlights the U.S. Environmental Protection
Agency's (EPA's) most recent evaluation of status and trends
in our nation's air quality.
® Emissions of the six principal air pollutants increased
significantly between 1900 and 1970. This includes
emissions of carbon monoxide, lead, nitrogen dioxide,
volatile organic compounds, particulate matter, and sulfur
dioxide. However, since passage of the 1970 Clean Air
Act Amendments, emissions of all of these pollutants
have declined, in some cases dramatically.
® Economic growth and environmental protection can go
hand-in-hand. Between 1970 and 1995, total combined
emissions of the six principal pollutants decreased while
gross domestic product, population, and total vehicle
miles traveled all increased significantly.
• In 1995, Phase I of EPA's Acid Rain Program alone
reduced sulfur dioxide emissions from affected power
plants by 5.6 million tons compared to 1980 levels. This
was 39 percent below the level anticipated under the
1990 Amendments to the Clean Air Act.
• Newly available monitoring data'showed significant
reductions in benzene concentrations and other toxic air
pollutants from 1994 to 1995. At sites where these data
were available, the median reduction for benzene was
approximately 38 percent. Early analysis indicates this
reduction may be a result of reduced vehicle emissions
due to the use of reformulated gasoline.
® Short-term trends between 1994 and 1995 showed a
slight increase in monitored concentration levels of ozone.
Monitored concentration levels of carbon monoxide,
nitrogen dioxide, particulate matter, and sulfur dioxide
continued to decrease, while lead remained unchanged.
During this same 1 -year period, emissions of all six
principal air pollutants decreased.
® Despite the improvements in air quality since 1970,
nearly 80 million people lived in counties where air quality
levels exceeded the national air quality standards for at
least one of the six principal pollutants in 1995.
® Air pollution, such as ground-level ozone, acid rain, and
air toxics, also significantly affects ecosystems. For
example, ground-level ozone is responsible for
approximately 1 to 2 billion dollars in reduced agricultural
crops each year. In addition, certain toxic pollutants (like
some metals and organic chemicals) that are emitted
from industrial sources can be deposited into water
bodies and magnify through the food web, adversely
affecting fish-eating animals and humans.
® Over the past several years, the American public has
become conscious of other air pollution issues such as
protection of the stratospheric ozone layer and the effect
of global warming on the Earth's climate. EPA continues
to work with States, industry, and other partners to find
cost-effective and innovative ways to solve air pollution
problems.
Background
Air pollution causes a wide variety of health effects that range
from eye irritation, to heart and lung damage, to premature
death. It can also impair visibility and reduce crop production,
as well as damage ecosystems, national parks, wilderness
areas, and water bodies.
Air pollution comes from many different sources. "Stationary
sources" such as factories, power plants, and smelters —
"mobile sources" including cars, buses, planes, trucks, and
trains — and "natural sources" such as wildfires, windblown
dust, and volcanic eruptions — all contribute to air pollution.
The Clean Air Act provides the principal framework for
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national, State, Tribal, and local efforts to protect air quality. Under the
Clean Air Act, which was last amended in 1990, EPA has a number of
responsibilities, including:
• Setting National Ambient Air Quality Standards (NAAQS) for
pollutants considered harmful to public health and the
environment.
® Ensuring that these air quality standards are met or attained (in ;
cooperation with States) through national standards and ;
strategies to control air pollutant emissions from automobiles,
factories, and other sources.
• Reducing emissions of sulfur dioxide and nitrogen oxides that ;
cause acid rain.
• Limiting use of chemicals that damage the stratospheric ozone
layer in order to prevent increased levels of harmful ultraviolet :
radiation.
• Ensuring that sources of toxic air pollutants are well controlled.
The Clean Air Act established two types of National Ambient Air Quality
Standards. Primary standards set limits to protect public health, including
the.health of "sensitive" populations such as asthmatics, children, and the
elderly. Secondary air quality standards set limits to protect public welfare,
including protection against decreased visibility and damage to animals,
crops, vegetation, and buildings.
EPA has set national air quality standards for six principal pollutants (referred ;
to as "criteria" pollutants): carbon monoxide (CO), lead (Pb), nitrogen dioxide ?
(NCy, ozone (63), particulate matter (PM-10), and sulfur dioxide (802). :
[Note: The pollutant ozone is not emitted directly to the air, but is formed j
when sunlight acts on emissions of nitrogen oxides (NOX) and volatile ;
organic compounds (VOC).] :
The Clean Air Act Amendments of 1990 also identified 189 "toxic" air ;
pollutants for regulation. Air toxics are those pollutants^that are known :
or suspected to cause cancer or other serious health effects (such as
birth or developmental defects). The Clean Air Act contains j
requirements for reducing air toxic emissions from industrial factories ;
and other sources. :
EPA also has responsibility for setting standards to reduce chemicals :
that destroy the stratospheric ozone layer and pollutants that cause
acid rain and visibility impairment. This brochure provides an overview
of trends in these air pollution problems, as well as global warming
issues and the processes EPA has developed for controlling pollutants that
contribute to global warming.
IN OF NITROGEN
(1900-1590)
i
Without the passage of the Clean Air Act
Amendments in 1970, emissions would have
increased at a higher rate.
1-910
1930
1950
1970
1990
IN ©F VOLATILE
ORGAJttO COMPOUNDS
(1900-1990)
Without the passage of the Clean Air Act
Amendments in 1970, emissions would have
continued to increase.
1910
1930
1-950
1970
1990
TREND IN EMISSIONS OF SUUFUR4DQDES.
(1900-1990)
50
40
30
20
10
0
Without the passage of the Clean Air Act
Amendments in 1970, emissions would have
continued to increase.
1910
1930
-------
Six
For the past 23 years, EPA has
examined air pollution trends of
each of the six principal pollutants
in this country. EPA examines changes in air pollution levels
over time and summarizes the current air pollution status
annually in two comprehensive technical documents titled
National Air Quality and Emissions Trends Report and National
Air Pollutant Emission Trends. The following sections
summarize trends in air quality and emissions during the last
10 years.
Long-Term
Before the Clean Air Act was signed into law in 1963, the 20th
century had witnessed a significant and continued increase in
air pollution levels. Although efforts made during the 1960's
by State and local air pollution agencies in certain polluted
cities in the Northeast helped reduce pollution in some local
areas, emissions continued to increase on a national level.
Between 1900 and 1970, emissions of nitrogen oxides
increased 690 percent, volatile organic compounds increased
260 percent, and sulfur dioxide increased 210 percent.
Emissions of these pollutants have decreased significantly
since the passage of the 1970 Clean Air Act Amendments.
Without pollution controls resulting from these Amendments,
emissions would have continued to increase as illustrated in
the charts on page 2.
©f Air Quality
EPA tracks two kinds of trends: air based
on actual measurements of pollutant concentrations in the air
at selected monitoring sites throughout the country, and
©missions based on engineering estimates of the total
tonnage of these pollutants released into the air annually.
However, starting in 1994, under the Acid Rain Program, EPA
began tracking emissions of sulfur dioxide and nitrogen oxides
based on data from continuous emission monitors for the
electric utility industry.
Each year, EPA gathers and analyzes air quality concentration
data from more than 4,000 monitoring stations around the
country. Monitoring stations are operated by State, Tribal, and
local government agencies as well as some Federal agencies,
including EPA. Trends are derived by averaging direct
measurements from these monitoring sites on a yearly basis.
During the last 10 years (1986 through 1995), air quality has
continued to improve as shown in the chart below.
IN
(1986-1995)*
37%
78%
14%
6%
22%
37%
* PM-10 measurements began in 1988.
The most notable improvements are a 78 percent decrease in
lead concentrations and a 37 percent decrease in both
carbon monoxide and sulfur dioxide concentrations.
Improvements in measured concentrations are also noted for
the other principal pollutants including nitrogen dioxide,
ozone, and particulate matter during this same timeframe.
EPA estimates nationwide emissions trends based on
engineering calculations of the amounts and types of
pollutants emitted by automobiles, factories, and other
sources. Emissions trends are based on many factors,
including the level of industrial activity, technology
developments, fuel consumption, vehicle miles traveled, and
other activities that cause air pollution. Emissions trends also
reflect changes in air pollution regulations and installation of
emissions controls. Over the last 10-year period, emissions
have shown improvement (decreased) for all principal air
pollutants as shown in the chart below.
IN
(1986-1995)*
16%
32%
3%
9%
17%
18%
* PM-10 emissions are estimated between 1988 and 1995.
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Between 1970 and 1995, total emissions of the six principal air
pollutants decreased 29 percent. As illustrated in the chart to
the right, decreases in the individual pollutants ranged from 25
percent for VOC to 98 percent for lead. NOX emissions
increased 6 percent over the same time period due to increases
in fuel combustion. At the same time, as indicated in the charts
below, U.S. population increased 28 percent, vehicle miles
traveled increased 116 percent, and gross domestic product
increased 99 percent.
Comparison of 1970 and 1995 Emissions
(28% decrease for aSB pollutants)
Million Tons/Year Thousand Tons/Year
150 _, , 250
Although some areas of the U.S. are experiencing air pollution problems,
overall air pollution continues to decline, despite extensive national growth.
1995
199Q
1980
1970-
500- 1000 1500- 2000 2500
0 50 100 ISO 200 250 300-
Mmon People
d 1000 2000 3000 4000 5000 6000 7000
Bison Dollars-
Since 1970, the U.S. has experienced extensive national growth.
10
20
50
30 40
Million Peop'e
In 1995, nearly 80 million people lived in counties with monitored air
quality levels above national health-based air quality standards.
The dramatic improvements in emissions and air quality
occurred simultaneously with significant increases in
economic growth and population. The improvements are a
result of effective implementation of clean air laws and
regulations, as well as improvements in the efficiency of
industrial technologies.
As seen in the chart to the left, despite great progress in air
quality improvement, in 1995 nearly 80 million people
nationwide lived in counties with monitored air quality levels
above the primary national air quality standards.
The highest number for ozone (nearly 71 million) is attributed to
the hot weather conditions in 1995, which were conducive to
ozone formation.
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Six
©I the P©ilytants Carbon monoxide
is a colorless, odorless, poisonous gas formed when carbon
in fuels is not burned completely. It is a byproduct of highway
vehicle exhaust, which contributes about 60 percent of all CO
emissions nationwide. In cities, automobile exhaust can cause
as much as 95 percent of all CO emissions. These emissions
can result in high concentrations of CO, particularly in local
areas with heavy traffic congestion. Other sources of CO
emissions include industrial processes and fuel combustion in
sources such as boilers and incinerators. Despite an overall
downward trend in concentrations and emissions of CO,
some metropolitan areas still experience high levels of CO.
Health and Enwironmental Carbon monoxide
enters the bloodstream and reduces oxygen delivery to the
body's organs and tissues. The health threat from exposure to
CO is most serious for those who suffer from cardiovascular
disease. Healthy individuals are also affected, but only at
higher levels of exposure. Exposure to elevated CO levels is
associated with visual impairment, reduced work capacity,
reduced manual dexterity, poor learning ability, and difficulty in
performing complex tasks. EPA's health-based national air
quality standard for CO is 9 parts per million (ppm) measured
as an annual second-maximum 8-hour average concentration.
Trends In Long-term
improvements continued between 1986 and 1995. National
average CO concentrations decreased 37 percent while CO
emissions decreased 16 percent. Long-term air quality
improvement in CO occurred despite a 31 percent increase in
vehicle miles traveled in the U.S. during the past 10 years.
Between 1994 and 1995, national average CO concentrations
decreased 10 percent, while total CO emissions decreased
7 percent. Transportation sources (includes highway and
off-highway vehicles) now account for 81 percent of national
total CO emissions.
Annual 2nd Maiimym S-H©yr
37%
Concentration, ppm
15
10
-r-90th Percentile
* -Mean
^Median
JLlOth Percentile
334 Sites
NAAQS
86 87 88 89 90 91 92 93 94 95
16%
Th©ysaod Short Tons Per Year
140,000
120,000
El Transportation 0 Miscellaneous
86 87 88 89 90 91 92 93 94 95
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(Pb)
Hatyre ©f the P@llytants Smelters and battery
plants are the major sources of lead in the air. The highest
concentrations of lead are found in the vicinity of nonferrous
smelters and other stationary sources of lead emissions.
Health Exposure to lead mainly occurs through
inhalation of air and ingestion of lead in food, paint, water, soil, or
dust. Lead accumulates in the body in blood, bone, and soft
tissue. Because it is not readily excreted, lead can also affect the
kidneys, liver, nervous system, and other organs. Excessive
exposure to lead may cause anemia, kidney disease,
reproductive disorders, and 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 other processes in
the body. Fetuses and children are especially susceptible to low
doses of lead, often suffering central nervous system damage or
slowed growth. Recent studies show that lead may be a factor in
high blood pressure and subsequent heart disease in middle-
aged white males. Lead may also contribute to osteoporosis in
post-menopausal women. EPA's health-based national air quality
standard for lead is 1.5 micrograms per cubic meter (|ig/m3)
measured as an annual maximum quarterly average
concentration.
Trends In Lewelss Between 1986 and 1995, average
lead concentrations in urban areas throughout the country
decreased 78 percent while total lead emissions decreased 32
percent. These reductions are a direct result of the use of
Pb
Annyal Maximum Quarterly
78%
no
Concentration, yg/m3
2.0
1.5
1.0
0.5
0.0
T-9Qth Pereentile
4 -Mean
- -Median
J-10th Pereentile
189 Sites
NAAQS
86 87 88 89 90 91 92 93 94 95
b
>:
Short Tons Per Year
8,000
6,000
EU Fuel Combustion
H Industrial Processing
fEB Transportation
4,000
2,000
86 87 88 89 90 91 92 93 94 95
unleaded gasoline in automobiles. The large reduction in lead
emissions from transportation sources has changed the nature of
the pollution problem for lead in the U.S. While there are still
violations of the lead air quality standard, they tend to occur near
large industrial sources such as lead smelters. Between 1994
and 1995, lead emissions decreased 1 percent while national
average lead concentrations remained unchanged.
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\
• j
•-' Hatyre and S@yr©es ©f the Pollutants Nitrogen dioxide
belongs to a family of highly reactive gases called nitrogen
oxides (NOX). These gases form when fuel is burned at high
temperatures, and come principally from motor vehicle
exhaust and stationary sources such as electric utilities and
industrial boilers. A suffocating, brownish gas, nitrogen dioxide
is a strong oxidizing agent that reacts in the air to form
corrosive nitric acid, as well as toxic organic nitrates. It also
plays a major role in the atmospheric reactions that produce
ground-level ozone (or smog).
En¥ir©nsin©sital Nitrogen dioxide can
irritate the lungs and lower resistance to respiratory infections
such as influenza. The effects of short-term exposure are still
unclear, but continued or frequent exposure to concentrations
that are typically much higher than those normally found in the
ambient air may cause increased incidence of acute respiratory
illness in children. EPA's health-based national air quality
standard for NO2 is 0.053 ppm (measured as an annual
arithmetic mean concentration). Nitrogen oxides contribute to
ozone formation and can have adverse effects on both
terrestrial and aquatic ecosystems. Nitrogen oxides in the air
can significantly contribute to a number of environmental effects
such as acid rain and eutrophication in coastal waters like the
Chesapeake Bay. Eutrophication occurs when a body of water
suffers an increase in nutrients that leads to a reduction in the
amount of oxygen in the water, producing an environment that
is destructive to fish and other animal life.
Trends in nitrogen Dioxide Levels: Nationally, annual
NO2 concentrations remained relatively constant throughout
the 1980's, followed by decreasing concentrations in the
1990's. Average NO2 concentrations in 1995 were 14 percent
lower than the average concentrations recorded in 1986. The
two primary sources of the NOX emissions in 1995 were fuel
combustion (46 percent) and transportation (49 percent).
Between 1986 and 1995, emissions from fuel combustion
decreased 6 percent, and emissions from highway vehicles
decreased 2 percent. Overall, national total NOX emissions
decreased 3 percent. Additionally, 1995 is the fourth year in a
row that all monitoring locations across the nation, including
Los Angeles, met the Federal NO2 air quality standard.
Annual Arithmetic
'
1 5%
Concentration, ppm
0.07
0.06
0.05
0.04
0.03
OAO
.uz
0.01
0.00
-90th Percentile 21 2 Sites
-Mean
-Median
_1 Oth Percentile NAAOS
>< —
.
s
*
^•— .
1
\
86 87 88 89 90 91 92 93 94 95
Thousand Short Tons Per Year
30,000
25,000
20,000
15,000
10,000
5,000
C3 Fuel Combustion H industrial Processing
E3 Transportation 0 Miscellaneous
87 88 89 90 91 92 93 94 95
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(03)
and S@yrees of the Pollutant: Ground-level ozone (the
primary constituent of smog) is the most complex, difficult to control,
and pervasive of the six principal air pollutants. Unlike other
pollutants, ozone is not emitted directly into the air by specific
sources. Ozone is created by sunlight acting on NOX and VOC in the
air. There are thousands of types of sources of these gases. Some of
the common sources include gasoline vapors, chemical solvents,
combustion products of fuels, and consumer products. Emissions of
NOX and VOC from motor vehicles and stationary sources can be
carried hundreds of miles from their origins and result in high ozone
concentrations over very large regions.
Health Environmental Scientific evidence indicates
that ground-level ozone not only affects people with impaired
respiratory systems (such as asthmatics), but healthy adults and
children. Exposure to ozone for 6 to 7 hours, even at relatively low
concentrations, significantly reduces lung function and induces
respiratory inflammation in normal, healthy people during periods of
moderate exercise. It can be accompanied by symptoms such as
chest pain, coughing, nausea, and pulmonary congestion. Recent
studies provide evidence of an association between elevated ozone
levels and increases in hospital admissions for respiratory problems in
several U.S. cities. Results from animal studies indicate that repeated
exposure to high levels of ozone for several months or more can
produce permanent structural damage in the lungs. EPA's health-
based national air quality standard for ozone is currently set at
0.12 ppm (measured as the second daily 1 -hour maximum
concentration). Ozone is responsible for approximately 1 to 2 billion
dollars of agricultural crop yield loss in the U.S. each year. Ozone also
damages forest ecosystems in California and the eastern U.S. New
scientific studies indicate that ozone causes adverse health and
environmental effects at lower concentrations and longer periods of
exposure than the current standards. As a result, EPA is reviewing
whether revisions to the current ozone NAAQS are warranted.
Trends in Levels: Trends in ozone concentrations are
influenced by year-to-year changes in meteorological conditions as
well as changes in emissions. National ozone concentrations in
1995 were 6 percent lower than those in 1986. However, between
1994 and 1995, national ozone concentrations increased 4
percent. Because of the hot, dry summer, meteorological
conditions in 1995 were conducive to ozone formation, especially
from the Midwest and Gulf States to the eastern U.S. Emissions of
VOC (which contribute to ozone formation) decreased 9 percent
between 1986 and 1995 and 2 percent between 1994 and 1995.
Based on air quality monitoring data, over 70 million people lived in
counties with air quality levels above EPA's health-based national
air quality standard for ozone in 1995.
In 1994, EPA established a new monitoring network to gather further
data on causes of ozone air pollution. This network of monitors,
called Photochemical Assessment Monitoring Stations (PAMS), is
Annual 2nd Daily 1-Hour Maximum
1 4%
Concentration, ppm
0.25
0.20
0.15
0.10
0.05
0.00
T~90th Percentile
A _Mean
--Median
-_10th Percentile
573 Sites
4-4
NAAQS
86 87 88 89 90 91 92 93 94 95
15: 2%
Thousand Short T©ns Per Year
35,000
30,000
25,000
20,000
15,000
10,000
5,000
CU Fuel Combustion H Industrial Processing
G3 Transportation E3 Miscellaneous
86 87
89 90 91 92 93 94 95
located in ozone nonattainment areas of the U.S. which are classified
as "serious," "severe," or "extreme." Concentration data were
collected in 22 areas for ozone, NOX, and a variety of VOC (including
several toxic air pollutants) that form ozone. The majority of the PAMS
sites showed decreases in the monitored concentrations of toxic air
pollutants and ozone-forming VOC.
8
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} Hature and Sources of the P@llytants Particulate matter is
'' the term for solid or liquid particles found in the air. Some
particles are large or dark enough to be seen as soot or smoke.
Others are so small they can be detected only with an electron
microscope. Because particles originate from a variety of mobile
and stationary sources (diesel trucks, woodstoves, power
plants, etc.), their chemical and physical compositions vary
widely. Particulate matter can be directly emitted or can be
formed in the atmosphere when gaseous pollutants such as
SO2 and NOX react to form fine particles.
Health and Environmental In 1987, EPA replaced
the earlier Total Suspended Particulate (TSP) air quality standard
with a PM-10 standard. The new standard focuses on smaller
particles that are likely responsible for adverse health effects
because of their ability to reach the lower regions of the
respiratory tract. The PM-10 standard includes particles with a
diameter of 10 micrometers or
cvw ^vxx-, |ess (0.0004 inches or one-
v v**«&w&sH seventh the width of a human
hair). EPA's health-based
national air quality standard for
PM-10 is 50 fig/m3 (measured
as an annual mean) and 150
jig/m^ (measured as a daily
concentration). Major concerns
for human health from exposure
to PM-10 include: effects on
breathing and respiratory
systems, damage to lung
tissue, cancer, and premature death. The elderly, children, and
people with chronic lung disease, influenza, or asthma, are
especially sensitive to the effects of particulate matter. Acidic
PM-10 can also damage human-made materials and is a major
cause of reduced visibility in many parts of the U.S. New
scientific studies suggest that fine particles (smaller than 2.5
micrometers in diameter) may cause serious adverse health
effects. As a result, EPA is considering setting a new standard
for PM-2.5. In addition, EPA is reviewing whether revisions to
the current PM-10 standards are warranted.
Trends in PM-10 Air monitoring networks were
changed in 1987 to measure PM-10 (replacing the earlier TSP
monitors). Between 1988 and 1995, average PM-10
concentrations decreased 22 percent. Short-term trends
between 1994 and 1995 showed a decrease of 4 percent in
monitored PM-10 concentration levels.
Emissions of PM-10 shown in the chart are based on estimates
from fuel combustion sources, industrial processes, and
Annual Arithmetic
Concentration, ug/m3
70
60
CO
40
30
20
10
0
I
-90th Percentile 955 Qi\es
_Mean
-Median
_1 Oth Percentile
NAAQS
i n
&, j.
~ i\* i
^ 4 * i-
J * * — -fc
1
i
I
I
88 89 90 91 92 93 94 95
,
Thousand Short Tons Per Year
3,500
3,000
2,500
2,000
1,500
1,000
500
0
88 89 90 91 92 93 94 95
*Omits natural and miscellaneous sources.
transportation sources, which account for only 6 percent of the
total PM-10 emissions nationwide. Between 1988 and 1995,
PM-10 emissions for these sources decreased 17 percent.
Short-term emissions trends between 1994 and 1995 showed
a 6 percent decrease.
The emissions estimates presented above do not include
emissions from natural and miscellaneous sources which are
fugitive dust (unpaved and paved roads), agricultural and
forestry activities, wind erosion, wildfires and managed burning.
These emissions estimates also do not account for particulate
matter that is secondarily formed in the atmosphere from
gaseous pollutants (e.g., SC>2 and NOX).
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Nature and Soyrees of the Pollutant: Sulfur dioxide
belongs to the family of gases called sulfur oxides (SOX).
These gases are formed when fuel containing sulfur (mainly
coal and oil) is burned, and during metal smelting and other
industrial processes.
Health and Environmental The major health
concerns associated with exposure to high concentrations of
862 include effects on breathing, respiratory illness,
alterations in pulmonary defenses, and aggravation of existing
cardiovascular disease. Children, the elderly, and people with
asthma, cardiovascular disease or chronic lung disease (such
as bronchitis or emphysema), are most susceptible to
adverse health effects associated with exposure to 862-
EPA's health-based national air quality standard for SO2 is
0.03 ppm (measured on an annual arithmetic mean
concentration) and 0.14 ppm (measured over 24 hours).
862 is a precursor to sulfates, which are associated with
acidification of lakes and streams, accelerated corrosion of
buildings and monuments, reduced visibility, and adverse
health effects.
Trends in Sulfyr Between 1986 and
1995, national SC>2 concentrations decreased 37 percent
and SO2 emissions decreased 18 percent. Between 1994
SO2
Annual Arithmetic Mean
37%
Concentration, ppm
0.04
0.03
0.02
0.01
0.00
-r-90th Percentile
Mean
4-yedian
U_1 Oth Percentile
473 Sites
NAAQS
86 87 88 89 90 91 92 93 94 95
Thousand Short Tons Per Year
30,000
25,000
20,000
15,000
10,000
5,000
87 88 89 90 91 92 93 94 95
and 1995, national SO^ concentrations decreased 17
percent and SC>2 emissions decreased 13 percent. These
significant decreases in concentrations and emissions reflect
the success of the first year of the Acid Rain Program. While
national 862 air quality levels have improved, EPA remains
concerned about short-term peak SO2 concentrations. As a
result, EPA proposed a program for States, industry, and
communities to use in evaluating and addressing peak
concentrations that could occur near some industrial
sources.
10
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©f the Problems Acidic deposition or
"acid rain" occurs when emissions of sulfur dioxide (802) and
oxides of nitrogen (NOX) in the atmosphere react with water,
oxygen, and oxidants to form acidic compounds. These
compounds fall to the Earth in either dry form (gas and
particles) or wet form (rain, snow, and fog). Some are carried by
the wind, sometimes hundreds of miles, across State and
national borders. In the U.S., about 70 percent of annual SO2
emissions and 30 percent of NOX emissions are produced by
electric utility plants that burn fossil fuels.
Coal-fired electric utilities and
other sourees fiiat Mm fossil fuels
emit sulfur dioxide aeid nitrogen enisles.
Health and Environmental Before falling to Earth,
SC>2 and NOX gases and related particulate matter (sulfates
and nitrates) contribute to poor visibility and impact public
health. Major human health concerns associated with their
exposure include effects on breathing and the respiratory
system, damage to lung tissue, cancer, and premature death. In
the environment, acid rain raises the acid levels of lakes and
streams (making the water unsuitable for some fish and other
wildlife) and damages trees at high elevations. It also speeds up
the decay of buildings, statues, and sculptures, including those
that are part of our national heritage.
Program Straefyre The overall goal of EPA's
Acid Rain Program is to improve public health and the
environment by reducing emissions of SC>2 and NOX. In order
to accomplish its goals cost-effectively, the program employs
both innovative and traditional approaches for controlling air
pollution and encourages energy efficiency and pollution
prevention.
Specifically, to achieve its goal of reducing annual SO2
emissions by 10 million tons between 1980 and 2010, the 1990
Clean Air Act Amendments require a two-phase tightening of
the restrictions on fossil fuel-fired power plants. Phase I began
in 1995 and affected 445 electric utility units, including the
biggest and dirtiest in the country. Phase II, which begins in the
year 2000, will tighten the annual SO2 emission limits for these
plants and also set restrictions on smaller, cleaner plants fired
by coal, oil, and gas. The Clean Air Act also requires significant
reductions in NOX emissions beginning in 1996, most of which
will be achieved by requiring coal-fired utility boilers to install
low-NOx burner technologies and meet new emissions
standards.
Reductions in SO2 and NOX will decrease levels of sulfates,
nitrates, and ground-level ozone (smog), leading to
improvements in public health and other benefits such as better
water quality in lakes and streams. Visibility will also improve,
enhancing the beauty of our country's scenic vistas, including
those in national parks. Likewise, damage to the trees that
populate mountain ridges from Maine to Georgia will be
reduced, and deterioration of our historic buildings and
monuments will be slowed.
Emissions Trends? Emissions
reductions have been significantly greater in 1995, the first year
of compliance with EPA's Acid Rain Program. As shown below,
for the 445 electric utility units participating in Phase I of the
Acid Rain Program, actual emissions measured by continuous
emission monitoring systems were reduced by more than half
relative to 1980 levels, plummeting from 10.9 to 5.3 million tons.
These emissions were 3.4 million tons (or 39 percent) below the
1995 allowable emissions level of 8.7 million tons required by
the Clean Air Act.
SO2 EMISSIONS
445 Phase S Affected Utility Units
1985
1990
1995
In 19955 emissions at Phase I affected utility ousts
were 3.4 mission tons below their required level.
11
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According to a recent study released by the U.S. Geological
Survey, reductions in SO2 emissions resulted in less acidic rain
in 1995. In the study, 1995 precipitation data were compared
with reference data from 1983 through 1994. As shown in the
map below, the study reports a 10 to 25 percent drop in wet
deposition sulfate concentration and rainfall acidity, particularly
at some sites located in the Midwest, Northeast, and Mid-
Atlantic Regions. These areas are some of the most acid-
sensitive regions of the country. Some areas on the map show
increases in sulfate levels. These are attributed to drought
conditions that occurred during 1995. Had rainfall conditions
•been more normal in 1995, even greater reductions in sulfate
levels might have occurred.
The Acid Rain Program has also led to improvements in SO2
concentrations and emissions. Between 1994 and 1995,
national SC>2 concentrations decreased 17 percent and SC>2
emissions (all sources combined) decreased 13 percent.
In In
Source: U.S. Geological Survey #96-0346
(National Atmospheric Deposition Program/National Trends Network)
0 5
10
The level ofsulfates in rain is an indicator of acidity. A 10 to 25 percent decrease in sulfate levels in rainfall
was observed in 1995, particularly in some of the most acid-sensitive regions of the U.S.
12
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Shenandoah National Park under a range of pollution conditions.
Visibility in cleaner areas is more sensitive to increases in
pollution than degraded environments.
Hature ©f the Problems Visibility impairment
occurs as a result of the scattering and absorption of light by
particles and gases in the atmosphere. It is most simply
described as the haze which obscures the clarity, color, texture,
and form of what we see. The same particles which are linked
to serious health effects [sulfates, nitrates, organic carbon, soot
(elemental carbon), and soil dust] can significantly affect our
ability to see.
High relative humidity can significantly increase the effect of
pollution on visibility. Some particles, such as sulfates,
accumulate water and grow to sizes at which they are more
efficient at scattering light and creating haze. Poor summer
visibility in the eastern U.S. is primarily the result of high suifate
concentrations exposed to high humidity levels.
The same amount of pollution can have dramatically different
effects on visibility, depending on existing conditions. This is
illustrated by the photographs above which characterize visibility in
Shenandoah National Park under a range of conditions. The top
left photograph represents a "clear" day at Shenandoah (80 miles
visual range). These conditions are close to naturally-occurring
visibility (i.e., without human-made pollution). An average day at
Shenandoah is represented by the top right photograph (18 miles
visual range), and is the result of an additional 10 ug/m3 of fine
particles in the atmosphere. The two lower photographs illustrate
the change in visual range that occurs by adding 10 ug/m3 of fine
particles to the area when the air is already degraded. It shows
that small amounts of air pollution in cleaner areas can have
dramatic effects on visibility impairment, it also implies that more
emission reductions may be needed in heavily degraded
environments to make noticeable differences.
Long-Term Trendss Visibility impairment has been analyzed
using data collected since 1960 at 280 monitoring stations
located at airports across the country. At these stations,
measurements of visual range (the maximum distance at which
an observer can discern the outline of an object) were
recorded. The following maps show the amount of haze during
the summer months of'1970, 1980, and 1990. The dark blue
color represents the best visibility and red represents the worst
visibility. Overall, the maps show that visibility impairment in the
eastern U.S. increased greatly between 1970 and 1980 and
decreased slightly between 1980 and 1990. This follows the
overall trend in emissions of sulfur oxides, which are a major
source of fine particles and reduced visibility.
FT'--.
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Maps of haze from airport visual data (July-September) show the amount
of summertime haze (visibility impairment) during 1970,1980, and 1990.
Haze in the eastern U.S. increased significantly between 1970 and 1980,
and decreased slightly between 1980 and 1990.
13
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Visibility Monitoring Networks In 1987, a visibility monitoring
network was established as a cooperative effort between EPA,
States, National Park Service, U.S. Forest Service, Bureau of Land
Management, and U.S. Fish and Wildlife Service. The network is
designed to track progress toward the Clean Air Act's national
goal of remedying existing and preventing future visibility
impairment in national parks and wilderness areas. The network
is the largest in the country devoted to fully characterizing visibility.
It also provides information for determining the types of pollutants
and sources primarily responsible for reduced visibility.
In many parts of the U.S., sulfates are the largest single
contributor to haze. Data from this monitoring network reveal that
sulfates account for approximately two-thirds of the visibility
reduction in the Appalachian Mountains in the East. Organic
carbon, the next-largest contributor, causes about 15 percent of
visibility reduction, in most areas of the western U.S. and Alaska,
sulfates and organic particles contribute equally to haze. In
southern California, nitrate particles are the greatest contributor
to haze.
Programs t© Impiwe Visibility: In April 1994, EPA began
developing a new regional haze program to address visibility
impairment in national parks and wilderness areas. This program will
introduce new approaches to monitoring and modeling regional
haze as well as define a policy for achieving "reasonable progress"
toward the reduction of visibility impairment.
The program will build on efforts of the Grand Canyon Visibility
Transport Commission, which was established to options
for improving visibility impairment, particularly for protection of
national parks and wilderness areas on the Colorado Plateau. In
June 1996, this Commission issued its report, Recommendations
for Improving Western Vistas. Some of the recommendations in
its report include:
® Continuing implementation of Clean Air Act requirements for
reducing SO2 emissions from stationary sources through the
year 2000. After 2000, establish SO2 emission targets and a
plan for an emissions cap and trading program.
® Decreasing mobile source emissions through a mix of
national, regional, and local strategies.
® Minimizing visibility impairment caused by controlled burning.
® Improving regional monitoring and emissions tracking
capabilities.
Other air quality programs are expected to lead to emission
reductions that will improve visibility in certain regions of the
country. The Acid Rain Program has achieved significant
reductions in SO2 emissions, which are expected to lead to
improvements in visibility impairment caused by sulfate haze,
particularly in the eastern U.S. Better controls on NOX sources
also can improve regional visibility conditions. Other programs,
such as EPA's NAAQS, mobile source and woodstove programs
to reduce particulate emissions, can benefit areas impacted by
visibility impairment.
Grand Canyon National Park under a range of visibility conditions.
14
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AIR
Hatyre and S@yre©ss Toxic air pollutants are those
pollutants known or suspected to cause cancer or other
serious health effects, such as birth defects or reproductive
effects. Examples of toxic air pollutants include dioxins,
benzene, arsenic, beryllium, mercury, and vinyl chloride. The
Clean Air Act currently lists 188* toxic air pollutants to be
regulated by EPA. They are emitted from all types of sources,
including motor vehicles and stationary sources, such as
manufacturing plants.
Control of toxic air pollutants differs in focus from control of the
six principal pollutants for which EPA has established national
air quality standards (discussed earlier). For the six principal
pollutants, a variety of control strategies are used in geographic
areas where national air quality standards have been violated.
In contrast, for toxic air pollutants, EPA has focused on
identifying all major industrial sources that emit these pollutants
and developing national technology-based performance
standards to significantly reduce their emissions. The objective
is to ensure that major sources of toxic air pollution are well
controlled regardless of geographic location.
EPA's toxic air pollutant program and the NAAQS program
complement each other. Many toxic air pollutants are emitted in
the form of particulates or as VOC. Control programs to meet
the NAAQS for ozone and PM-10 also reduce toxic air pollutant
emissions. Likewise, emission requirements under the toxic air
pollutants program can significantly help achieve the NAAQS
for ozone and PM-10. For example, EPA's final toxic air
pollutant regulation for organic chemical manufacturing is
expected to reduce VOC emissions (which form ground-level
ozone or smog) by an amount equivalent to removing millions
of cars from the road.
*Caprolactam was recently removed from the list of toxic air pollutants.
The toxic air pollutant program is especially important in
reducing emissions at or near industrial locations and in
controlling pollutants that are toxic even when emitted in small
amounts. Companies handling toxic chemicals are required by
EPA to develop plans to prevent accidental releases and to
contain any releases in the event they should occur.
Heaitti Environmental At sufficient
concentrations and exposure durations, human health effects
from toxic air pollutants can include cancer, poisoning, and
rapid onset of sickness, such as nausea or difficulty in
breathing. Other less measurable effects include
immunological, neurological, reproductive, developmental, and
respiratory effects. Toxic air pollutants may also be deposited
onto soil or into lakes and streams, thereby affecting ecological
systems and eventually human health through consumption of
contaminated food (mainly freshwater fish).
Trends In ¥®xi© Air Pollytantss EPA will soon begin using
the National Toxics Inventory (NTI) to track nationwide
emissions trends for toxic air pollutants listed in the Clean Air
Act. NTI contains information on toxic emissions in 1990 of
approximately 8.8 billion pounds. As illustrated in the chart
below, NTI includes emissions from large industrial or "point"
sources, smaller stationary sources called "area" sources, and
mobile sources.
1990 National TotaS Toxle Air Pollutant Emissions by Source
(8.8 billion pounds)
Mobile Sources
39%
Large Industrial Complexes
(Point Sources)
30%
According to National Toxics Inventory data, area sources account for
31 percent of U.S. toxic emissions, mobile sources account for 39
percent, and point sources account for 30 percent.
15
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of
Parameter
2,2,4-Trimethylpentane
Acetalctehycte
Benzene
Ethflbenzene
Formaldehyde
M/PXylene
N-hexane
Q-xyiene
Styrene
Toluene
Number of
17
6
19
17
6
14
17
17
17
17
Median % Change ;
(all
-23
-14
-38
-23
+4
-21
-8
-18
-17
-23
VOC species shown above have high ozone forming potential and/or are toxic. Preliminary analysis of these VOC measured in 22 areas
showed concentration changes for several toxic air pollutants. The median percent change in concentrations ranged from 38 percent
reduction of benzene to 4 percent increase of formaldehyde.
NTI builds on emissions data from EPA's Toxic Release Inventory,
which reflects about half the total emissions from large industrial
point sources and about 14 percent of national total emissions.
As of October 1996, EPA has issued air toxics standards for 47
source categories, such as chemical plants, oil refineries,
aerospace manufacturers, and steel mills, as well as area sources
like dry cleaners, commercial sterilizers, secondary lead smelters,
and chromium electroplating. When these standards are fully
implemented, toxic emissions from stationary sources should be
reduced by approximately 35 percent. Toxic emissions from point
sources have already declined, a trend that is expected to
continue as the result of emissions standards. By the year 2005,
EPA projects that the toxic air pollutant program will reduce toxic
emissions by 75 percent. Because controls for toxic air pollutants
also reduce VOC and PM-10 emissions, over the next 10 years,
the program should realize reductions in VOC and PM-10
emissions of more than 4 billion pounds per year.
Preliminary analysis of specific VOC measured in urban locations
classified as "serious," "severe," or "extreme" ozone
nonattainment (PAMS network - see "Ozone" section) indicate
that ambient concentration levels of certain toxic VOC appear to
be declining. For example, as illustrated in the above table,
benzene levels showed a significant decline between 1994 and
1995 (approximately 38 percent), possibly as a result of the use
of reformulated gasoline in those areas. It should be noted that
RAMS measurements have only been taken for 3 years and that
continued efforts in the PAMS program are expected to provide
more confidence in evaluating the long-term trends of benzene
and other toxic VOC.
16
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This figure compares satellite measurements of ozone levels over North America. Each color band represents an area with a similar
amount of ozone overhead; lower levels ofdobson units indicate less protective ozone overhead. Ozone trends are based on detailed
statistical analysis of large data sets, and not on simple graphs like these.
of the The stratosphere,
located about 6 to 30 miles above the Earth, contains a layer of
ozone gas that protects living organisms from harmful ultraviolet
radiation (UV-b) from the Sun. Over the past 2 decades, however,
this protective shield has been damaged. Each year, an "ozone
hole" forms over the Antarctic, and ozone levels fall to 70 percent
below normal. Even over the U.S., ozone levels are about 5
percent below normal in the summer and 10 percent below
normal in the winter. The figure above shows ozone levels over
North America in dobson units (DU) in March 1979 and March
1994. One hundred DU of ozone would form a layer 1 millimeter
thick at the Earth's surface. Each color band represents an area
with a similar amount of ozone overhead. Comparing the colors
of the bands over a particular city, such as Seattle, shows lower
ozone levels in 1994 than in 1979. This figure is a snapshot in
time that shows one example of reduced ozone levels. Long-term
trends are based on numerous data taken over several years,
as opposed to single observations.
As the ozone layer thins, more UV-b radiation reaches the Earth.
In 1996, scientists demonstrated for the first time that UV-b levels
over most populated areas have increased. Scientists have
linked several substances associated with human activities to
ozone depletion, including the use of chlorofluorocarbons (CFCs),
halons, carbon tetrachloride, and methyl chloroform. These
chemicals are emitted from home air conditioners, foam
cushions, and many other products. Strong winds carry them
through the lower part of the atmosphere, called the troposphere,
and into the stratosphere. There, strong solar radiation
chlorine and bromine atoms that attack protective ozone
molecules. Scientists estimate that one chlorine atom can
destroy 100,000 ozone molecules.
Some UV-b reaches the
Earth's surface even with normal ozone levels. However, since
the ozone layer normally absorbs most UV-b radiation from the
Sun, ozone depletion is expected to lead to increases in harmful
effects associated with UV-b radiation. In humans, UV-b is linked
to skin cancer, including melanoma, the form of skin cancer with
the highest fatality rate. It also causes cataracts and suppression
of the immune system.
The effects of UV-b radiation on plant and aquatic ecosystems are
not well understood. However, the growth of certain food plants
can be slowed by excessive UV-b radiation. In addition, some
scientists suggest that marine phytoplankton, which are the base
of the ocean food chain, are already under stress from UV-b
radiation. This stress could have adverse consequences for
human food supplies from the oceans. Because they absorb
CO2 from the atmosphere,'significant harm to phytoplankton
populations could increase global warming (see following section
on "Global Warming and Climate Change").
Programs t© the Lasers In
1987, 27 countries signed the Montreal Protocol, a landmark
treaty that recognized the international nature of ozone depletion
and committed the world to limiting the production of ozone-
depleting substances. Today, over 150 nations have signed the
protocol, which has been strengthened twice and now calls for
the elimination of these chemicals.
The 1990 Clean Air Act Amendments established a U.S. regulatory
program to protect the stratospheric ozone layer. In January 1996,
U.S. production of many ozone-depleting substances virtually
17
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UV-b by Latitude
6SN: 6.8%
55N: 7.3%
45N: 5.0%
35N: 3.9%
2SN: 1.2%
15N: 0.1%
Equator
153:2.3%
25S: 2.6%
35S: 2.9%
45S: 5.5%
55S: 9.9%
653:11.0%
A 1996 study using satellite-based analyses of UV-b trends demonstrated that UV-b levels had increased at ground level This figure shows the
percent increases in average annual UV-b reaching the surface over the past 10 years. UV-b incidence is strongly dependent on latitude. At
latitudes that cover the U.S., UV-b levels are 4 to 5 percent higher than they were 10 years ago.
ended, including CFCs, carbon tetrachloride, and methyl
chloroform. Production of halons ended in January 1994.
EPA regulations control the handling and emissions of CFCs and
the use of substitutes. Many new products that are either
harmless or less damaging to the ozone layer are now gaining
popularity. For example, computer-makers are using ozone-safe
solvents to clean circuit boards, and automobile manufacturers
are using HFC-134a, an ozone-safe refrigerant, in new motor
vehicle air conditioners. In some sectors, the transition away from
ozone-depleting substances has already been completed.
Trends in Depletions Scientific
evidence shows that the approach taken under the Montreal
Protocol has been effective. In 1995, measurements showed that
the tropospheric concentrations of methyl chloroform had started
to fall, indicating that emissions had been greatly reduced.
Tropospheric concentrations of other ozone-depleting
substances, like CFCs, are also beginning to decrease. It takes
several years for these substances to reach the stratosphere and
release chlorine and bromine. For this reason, stratospheric
chlorine levels are expected to continue to rise, peak between
1997 and 1999, and then slowly decline. Because of the stability
of most ozone-depleting substances, chlorine will be released into
the stratosphere for many years, and the ozone layer will not fully
recover until well into the next century.
In 1996, scientists developed a new technique allowing them to
draw conclusions about UV-b radiation at ground level. According
to satellite-based trend analyses, major populated areas have
experienced increasing UV-b levels over the past 15 years. As
shown by the figure above, at latitudes that cover the U.S., UV-b
levels are 4 to 5 percent higher than they were 10 years ago.
18
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The Earth's climate is fueled by the Sun.
Most of the Sun's energy, called solar radiation, is absorbed by
the Earth, but some is reflected back into space. A natural layer of
atmospheric gases absorbs a portion of this reflected solar
radiation, eventually releasing some of it into space, but forcing
much of it back to Earth. There it warms the Earth's surface
creating what is known as the natural "greenhouse effect," as
illustrated in the diagram below. Without the natural greenhouse
effect, the Earth's average temperature would be much colder,
and the planet would be covered with ice.
Recent.scientific evidence shows that the greenhouse effect is
being increased by release of certain gases to the atmosphere
that cause the Earth's temperature to rise. This is called "global
warming." Carbon dioxide (CCy accounts for about 85 percent
of greenhouse gases released in the U.S. CO2 emissions are
largely due to the combustion of fossil fuels in electric power
generation. Methane (CH^) emissions, which result from
agricultural activities, landfills, and other sources, are the second
largest contributor to greenhouse gases in the U:S.
Industrial applications such as foam production, refrigeration, dry
cleaning, chemical manufacturing, and semiconductor
manufacturing produce other greenhouse gas emissions such as
hydrofluorocarbons (MFCs). Smelting of aluminum produces
another greenhouse gas called perfluorinated compounds (PFCs).
Emissions of NOX and VOC from automobile exhaust and
industrial processes contribute to the formation of ground-level
ozone or smog, also a greenhouse gas.
0
C
I
Some solar radiation
is reflected by the Earth
and the atmosphere.
Some of the infrared
radiation passes through
the atmosphere, and
some is absorbed and
re-emitted in all directions
by greenhouse gas molecules.
The effect of this is to
warm the Earth's surface and
the lower atmosphere.
passes
through
the clear
atmosphere
The greenhouse effect is being accelerated by releases of certain gases to the atmosphere
that are causing the Earth's temperature to rise.
19
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Health and Greenhouse gas
emissions could cause a 1.8 to 6.3° Fahrenheit rise in
temperature during the next century, if atmospheric levels are
not reduced. Although this change may appear small, it could
produce extreme weather events, such as droughts and floods;
threaten coastal resources and wetlands by raising sea level;
and increase the risk of certain diseases by producing new
breeding sites for pests and pathogens. Agricultural regions and
woodlands are also susceptible to changes in climate that
could result in increased insect populations and plant disease.
This degradation of natural ecosystems could lead to reduced
biological diversity.
International Over 150 world leaders have
responded to the early warnings of climate change. In 1988, the
Intergovernmental Panel on Climate Change (IPCC) was
formed, and in 1992, these 150 countries signed a treaty
known as the "Framework Convention on Climate Change"
(FCCC) to stabilize atmospheric greenhouse gases. Early
indications suggest that most countries are not on track to
meet the year 2000 target for reducing emissions of
greenhouse gases, and further, that holding emissions at 1990
levels will not prevent or solve the problem. In 1997, the FCCC
will meet in Japan, where agreement may be reached on a
legally binding international pact to prevent or reduce the risk of
climate change.
UnSn Programs t© Mitigate Climate The United
States adopted a Climate Change Action Plan in 1993 to
reduce greenhouse gas emissions. Hundreds of companies
and nonprofit organizations are working together to effectively
reduce their emissions. The Plan involves 50 programs
implemented by EPA, the Department of Energy, the
Department of Agriculture, and other Government agencies.
EPA's voluntary pollution prevention programs seek to prevent
greenhouse gas emissions through partnerships with business,
government, and other groups by stimulating investments in
energy-efficient technology and practices. Combined, EPA's
voluntary pollution prevention programs to reduce greenhouse
gas emissions have over 2,000 partners. Since 1992,
participants in these programs have prevented the release of
over 2.5 million tons of greenhouse gas emissions.
Lights Star
Buildings Program
Energy Star Programs
' Natural Gas Star, AgStar, and
Landfill Methane Outreach Programs
Voluntary Aluminum
Industrial Partnership
Climate Wise Program
Energy-efficient lighting, heating,
air conditioning, and ventilation
Commercial and residential energy-efficient
products and effective product labeling
Cost-effective reduction of
methane emissions
Reduction of perfluorinated
compound emissions
Company-specific emissions
reduction plans
EPA's voluntary pollution prevention programs are reducing greenhouse gas emissions
through partnerships with industry and others.
20
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Since EPA was established in 1970, air quality in the U.S. has
improved tremendously. Many of these improvements can be
attributed to pollution control programs instituted under the
Clean Air Act, State and local laws, and actions by industry.
Because air pollution problems continue in many parts of the
country, EPA and States continue to seek innovative and more
cost-effective programs to further reduce emissions. Market-
based programs like emissions trading provide incentives for
industry to develop new pollution control technologies or
pollution prevention approaches. Through continued
partnership with the regulated community, environmental
groups, State, Tribal, and local governments, and concerned
citizens, EPA is working to develop effective common-sense
control strategies to improve our nation's air quality.
F@r Further lnf©rmati®ns
Calls (919)541-5285
National Air Pollutant Emission Trends,
1900-1995 (EPA-454/R-96-007)
(919)541=5558
National Air Quality and Emissions Trends,
1995 (EPA-454/R-96-005)
internet Userss EPA Homepage at: (http://www.epa.gov)
Tills brochyr© is CMI the internet at:
(http ://www. epa.gov/oar/aqtrnd95. html)
Technology transfer Network (TTN)
® Access by modern, dial: (919) 541-5742
(for modems up to 14,400 bps)
® Access by Internet: (http://ttnwww.rtpnc.epa.gov)
Add (202) 233-9620
Strat®splierl© H@tl!n©s (800) 296-1996
Energy Star Hotlines (888) STAR-YES
GO . Carbon Monoxide
Pb Lead
NO2, NOX Nitrogen Dioxide, Nitrogen Oxides
03 Ozone
PM-10 Particulate Matter (10 micrometers
in diameter or less)
SO2, SOX Sulfur Dioxide, Sulfur Oxides
Other
CH4 Methane
CO2 Carbon Dioxide
CFCs Chlorofluorocarbons
DU Dobson Unit(s)
EPA Environmental Protection Agency
FGC© Framework Convention on Climate Change
HFGs Hydrofluorocarbons
1PG© Intergovernmental Panel on Climate Change
National Ambient Air Quality Standard [
PAHS Photochemical Assessment Monitoring
Stations
NTI National Toxics Inventory
PFCs Perfluorinated Carbons
TRI Toxic Release Inventory
TSP Total Suspended Particulates
¥©G Volatile Organic Compounds
Q
I
U.S. Environmental Protection Apencv
Regions, Library (PL-12J)
// West Jackson Bcuievard l?fh
o, IL 60604-3590
* tf W*,
Chicagc
21
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