United States
Environmental Protection
Agency
The Particle Pollution Report
missions rnroug
PM2.s Concentrations are Declining
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Printed on 100% recycled/recyclable process chlorine-free paper with 100% post-consumer fiber using vegetable-oil-based ink.
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EPA 454-R-04-002
December 2004
The Particle Pollution Report
Current Understanding of Air Quality and Emissions through 2003
Contract No. 68-D-02-065
Work Assignment No. 2-01
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Emissions, Monitoring, and Analysis Division
Research Triangle Park, North Carolina
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Introduction
Contents
Introduction ii
Major Findings 1
Understanding Particle Pollution 2
Particle Pollution Is... 2
Complex 2
A Continuum of Sizes 2
Made Up of Many Species 3
Seasonal 4
Both Local and Regional 8
Particle Pollution in 2003 10
PM10-PM2.5 12
Looking at Trends 13
PM10 National and Regional Trends 13
PM25 National and Regional Trends 14
25-year PM2 5 Trends 16
Rural Sulfate Trends 18
Explaining the Trends 20
Regional PM2 5 Trends in Three
Regions (1999-2003) 20
Effect of Meteorology 21
The PM25 Remainder 22
Control Programs 23
The Future 25
Upcoming PM25 Designations 26
PM2 5 and Other Pollutants 26
From the black puff of smoke from an old diesel bus to the
haze that obscures the view in our national parks, particle
pollution affects us all. This complex pollutant is present
year-round, both in our cities and in the countryside, and
it can cause health problems for millions of Americans.
EPA's national air quality standards for particle pollution
are designed to protect public health and the environment.
As this report shows, we are seeing progress: levels of particle
pollution are decreasing on a national scale. Yet millions
of people still live in areas of the country where particle
pollution levels exceed national air quality standards. This
harmful pollution affects not only people, but also visibility,
ecosystems, and man-made materials.
EPA considers fine particle pollution its most pressing air
quality problem, and the Agency is taking a number of steps
that will reduce particle emissions and formation. These
efforts range from EPA's Acid Rain program and regulations
reducing emissions from fuels and diesel engines, to imple-
mentation of the Agency's first fine particle standards and
a proposed rule to reduce particle-forming emissions from
power plants.
In this report, EPA
Explores characteristics of particle pollution in the
United States
Analyzes particle pollution for 2003 (the most recent
year of data)
Summarizes recent and long-term trends
Investigates the relationship between air quality and
emissions
Reviews some current programs and future prospects for
reducing particle pollution levels.
In addition, text boxes in this report present information
on more specialized areas of interest, such as the PM
Supersite project, episodic events, satellite monitoring, and
the relationship of particle pollution to other air pollutants.
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Major Findings
Air Quality Improvements
Particulate matter (PM) air quality has been
improving nationwide, both for PM2 5 and PM10.
PM2 5 concentrations
- in 2003 were the lowest since nationwide moni-
toring began in 1999
- have decreased 10% since 1999
- are about 30% lower than EPA estimates they
were 25 years ago.
PM10 concentrations
- in 2003 were the second lowest since nationwide
monitoring began in 1988
- have declined 7% since 1999
- have declined 31% since 1988.
In 2003, 62 million people lived in 97 U.S. coun-
ties with monitors showing particle pollution levels
higher than the PM2 5 air quality standards, the
PM10 standards, or both.
Monitored levels of both PM2 5 and PM10 generally
decreased the most in areas with the highest
concentrations. For example, PM2 5 levels decreased
20% in the Southeast from 1999 to 2003. The
Northwest showed a 39% decrease in PM10 levels
from 1988 to 2003.
Sources and Emissions
Sulfates, nitrates, and carbon compounds are the
major constituents of fine particle pollution.
Sulfates and nitrates form from atmospheric trans-
formation of sulfur dioxide and nitrogen oxide
gases. Carbon compounds can be directly emitted,
or they can form in the atmosphere from organic
vapors.
Approximately one-third of the PM2 5 improvement
observed in the eastern half of the country can be
attributed to reduced sulfates; a large portion of the
remaining PM2 5 improvement is attributable to
reductions in carbon-containing particles, especially
in the Industrial Midwest and the Southeast.
Power plant emissions of sulfur dioxide dropped
33% from 1990 to 2003, largely as a result of EPA's
Acid Rain program. These reductions yielded
significant regional reductions in sulfate concentra-
tions, reducing acid deposition and improving
visibility.
Nationwide, reductions in industrial and highway
vehicle emissions of fine particles and volatile
organic compounds appear to have contributed to
the improvement in PM2 5.
In the eastern half of the country
- regional pollution accounts for more than half of
the measured PM2 5. This regional pollution
comes from a variety of sources, including power
plants, and can be transported hundreds of miles.
- sulfates account for 25% to 55% of PM25 levels.
Sulfate levels are similar in urban and nearby rural
areas. Power plants are the largest contributor to
this sulfate formation.
In the Industrial Midwest, Northeast, and southern
California, nitrates make up a large portion of
PM2 5, especially in winter. Average nitrate concen-
trations in urban areas are generally higher than
nearby rural levels. Power plants and highway
vehicle emissions are large contributors to nitrate
formation.
EPA and states have put in place a number of
control programs that will continue to reduce
particle-forming emissions. EPA's 2004 Clean Air
Nonroad Diesel Rule will significantly reduce
emissions from nonroad diesel equipment across the
country. EPA's proposed Clean Air Interstate Rule
(proposed December 2003) will reduce PM-
forming emissions from power plants in the eastern
United States.
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Understanding Particle Pollution
Particle Pollution Is..
Complex
Perhaps no other pollutant is as complex as
particle pollution. Also called particulate matter
or PM, particle pollution is a mixture of solid
particles and liquid droplets found in the air.
Some particles, such as dust, dirt, soot, or smoke,
are large or dark enough to be seen with the
naked eye. Others are so small, they can only be
detected using an electron microscope.
These tiny particles come in many sizes and
shapes and can be made up of hundreds of
different chemicals. Some particles are emitted
directly from a source, while others form in
complicated chemical reactions in the atmos-
phere. And some can change back and forth
from gas to particle form. Particle pollution also
varies by time of year and by location and is
affected by several aspects of weather, such as
temperature, humidity, and wind.
A Continuum of Sizes
In general, particle pollution consists of a mixture
of larger materials, called "coarse particles," and
smaller particles, called "fine particles." Coarse
particles have diameters ranging from about
2.5 micrometers (urn) to more than 40 (am, while
fine particles, also known as known as PM2 5,
include particles with diameters equal to or
smaller than 2.5 um. EPA also monitors and
regulates PM10, which refers to particles less than
or equal to 10 um in diameter. PM10 includes
coarse particles that are "inhalable" particles
ranging in size from 2.5 to 10 um that can
penetrate the upper regions of the body's respira-
tory defense mechanisms. "Ultrafme" particles
are a subset of PM2.5, measuring less than 0.1 um
in diameter.
Figure 1. Comparison of PM sizes.
C PM2.5
<2.5 um in diameter
Human Hair
-70 um average diameter
90 um in diameter
Fine Beach Sand
e courtesy of EPA, Office of Research and Development
Note: In this report, particle size or diameter refers to a normalized measure called aerodynamic
diameter, which accounts for the irregular shape and varying density of most particles.
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Particle Pollution Is..
Made Up of Many Species
Particles are made up of different chemical
components. The major components, or species,
are carbon, sulfate and nitrate compounds, and
crustal materials such as soil and ash. The
different components that make up particle
pollution come from specific sources and are
often formed in the atmosphere (see "Sources
and Transport of Particle Pollution" on page 6).
The chemical makeup of particles varies across
the United States (see Figure 2). For example,
fine particles in the eastern half of the United
States contain more sulfates than those in the
West, while fine particles in southern California
contain more nitrates than other areas of the
country. Carbon is a substantial component of
fine particles everywhere. (For information on
the composition of ultrafme and coarse particles
in Los Angeles, see page 7.)
Figure 2. Average PM2.5 composition in urban areas by region, 2003.
WEST EAST
Northwest
Upper
Midwest
©
Southern
California
Southwest
Industrial
Midwest
Northeast
e
Southeast
^ Sulfates
^ Nitrates
<^ Carbon
^ Crustal
Circle size corresponds
to PM2 5 concentration.
Note: In this report, the term"sulfates" refers to ammonium sulfate and "nitrates" refers to ammonium nitrate. "Carbon" refers to
total carbonaceous mass, which is the sum of estimated organic carbon mass and elemental carbon. "Crustal" is estimated using the
IMPROVE equation for fine soil at vista.cira.colostate.edu/improve.
This report summarizes analysis results using the geographic areas shown in this map. The area definitions correspond to the regions
used in EPA's 1996 PM Criteria Document (www.epa.gov/ttn/naaqs).
In this report, "Hast" includes three regions: the Northeast, the Industrial Midwest, and the Southeast.
Health and Environmental Effects of Particulate Matter
Health Effects
Exposure to particles can lead to a variety of serious health
effects. The largest particles do not get very far into the lungs,
so they tend to cause fewer harmful health effects. Coarse
and fine particles pose the greatest problems because they
can get deep into the lungs, and some may even get into the
bloodstream. Scientific studies show links between these small
particles and numerous adverse health effects. Long-term
exposures to PM, such as those experienced by people living
for many years in areas with high particle levels, are associ-
ated with problems such as decreased lung function, develop-
ment of chronic bronchitis, and premature death. Short-term
exposures to particle pollution (hours or days) are associated
with a range of effects, including decreased lung function.
increased respiratory symptoms, cardiac arrythmias (heartbeat
irregularities), heart attacks, hospital admissions or emergency
room visits for heart or lung disease, and premature death.
Sensitive groups at greatest risk include people with heart or
lung disease, older adults, and children.
Environmental Effects
Fine particles are the major source of haze that reduces
visibility in many parts of the United States, including our
national parks. PM affects vegetation and ecosystems by
settling on soil and water, upsetting delicate nutrient and
chemical balances. PM also causes soiling and erosion damage
to structures, including culturally important objects such as
monuments and statues.
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Particle Pollution Is..
Seasonal
Fine particles often have a seasonal pattern. PM2 5
values in the eastern half of the United States are
typically higher in the third calendar quarter
(July-September) when sulfates are more readily
formed from sulfur dioxide (SO2) emissions from
power plants in that region. Fine particle concen-
trations tend to be higher in the fourth calendar
quarter in many areas of the West, in part because
fine particle nitrates are more readily formed in
cooler weather, and wood stove and fireplace use
produces more carbon.
The time of year also influences daily fine particle
patterns. Unlike daily ozone levels, which are
usually elevated in the summer, daily PM2 5 values
at some locations can be high at any time of the
year. Figure 4 shows 2003 PM2 5 levels for Fresno
and Baltimore. The colors in the background of
these charts correspond to the colors of the Air
Quality Index (AQI), EPA's tool for informing
the public about air pollution levels in their
communities. As the Fresno graphic illustrates,
fine particles can be elevated in the fall and
winter in some areas, while ozone is elevated
only in the summer. Contrast the Fresno graphic
with the Baltimore graphic, which shows PM
elevated year-round. Note: Elevated levels on
the AQI do not indicate that an area is violating
EPA's national air quality standards for any
particular pollutant. The AQI is designed to
help people reduce their individual exposure
to pollution.
Figure 3. Seasonal averages of PM2.5 concentration by region, 1999-2003.
25
|2°
Jr 15
(0
5
°- 5
0
Southern
California
25
I20
| 15
(0
°- 5
0
Northwest
25
20
25
-E2°
| 15
fD
>
°- 5
0
Southwest
o
Upper
Midwest
25
25
01
rf15
(0
^,10
°- 5
Southeast
^ 5
0
Industrial
Midwest
25
-E20
| 15
fD
Northeast
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Air Quality Index (AQI) - Particulate Matter
The AQI is an index for reporting daily air
quality. It tells how clean or polluted the
air is and what associated health effects
might be a concern. The AQI focuses on
health effects people may experience
within a few hours or days after
breathing polluted air. EPA calculates the
AQI for five major pollutants regulated
by the Clean Air Act: particulate matter.
ozone, carbon monoxide, sulfur dioxide.
and nitrogen dioxide. The AQI values for
particulate matter are shown here.
PM2.5
AQI (ug/m3)
0-50 00-154
'
51-100 15.5-40.4
101-150 40.5-65.4
1 151-200 65.5-150.4
^^^^^^^^^^^^^^^^^^^^H
I 201-300 150.5-250.4
PM10
(ug/m3)
0-54
55-154
155-254
255-354
^^^^^^^^^H
355-424
Air Quality Descriptor
Good
^^^^H ^^^^^^1
Moderate
Unhealthy for Sensitive Groups
Unhealthy
Very unhealthy
Figure 4. Daily PM2 5 and ozone AQI values, 2003.
Fresno, CA
Very Unhealthy
Unhealthy
Unhealthy for Sensitive Groups
Moderate
Good
JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN
Date
Baltimore, MD
Very Unhealthy
Unhealthy
Unhealthy for Sensitive Groups
Moderate
Good
JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC JAN
Date
0
0 ° Ozone
2.5
Note: These graphs represent data from Federal Reference Method monitors. They do not show data from all
monitors that report the Air Quality Index.
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Sources and Transport of Particle Pollution
Sources
Particulate matter includes both "primary" PM, which is
directly emitted into the air, and "secondary" PM, which forms
indirectly from fuel combustion and other sources. Generally,
coarse PM is made up of primary particles, while
fine PM is dominated by secondary particles.
Primary PM consists of carbon (soot) emitted from cars,
trucks, heavy equipment, forest fires, and burning waste
and crustal material from unpaved roads, stone crushing,
construction sites, and metallurgical operations.
Secondary PM forms in the atmosphere from gases. Some of
these reactions require sunlight and/or water vapor.
Secondary PM includes
Sulfates formed from sulfur dioxide emissions from
power plants and industrial facilities
Nitrates formed from nitrogen oxide emissions from cars,
trucks, and power plants
Carbon formed from reactive organic gas emissions from
cars, trucks, industrial facilities, forest fires, and biogenic
sources such as trees.
Note: For more information about the apportionment of
fine particles to their sources, go to wuw.epa.gov/oar/
oaqps/pm2 5 / docs.html
Transport
In the atmosphere, coarse and fine particles behave in
different ways. Larger coarse particles may settle out from the
air more rapidly than fine particles and usually will be found
relatively close to their emission sources. Fine particles,
however, can be transported long distances by wind and
weather and can be found in the air thousands of miles from
where they were formed.
Automobiles, Power Generation, and Other
Sources Contribute to Fine Particle Levels
Cars, trucks, heavy equipment,
wild fires, waste burning,
and biogenics
/ \
Suspended soil
and metallurgical
operations
Cars, trucks, and
power generation
Power
generation
Note: Ammonia from sources such as fertilizer and animal feed
operations contributes to the formation ofsulfates and nitrates
that exist in the atmosphere as ammonium sulfate and
ammonium nitrate.
Visibility
One of the most obvious effects of air pollution occurs both
in urban areas and at the country's best-known and most-
treasured national parks and wilderness areas. Visibility
impairment occurs when fine particles scatter and absorb light,
creating a haze that limits the distance we can see and that
degrades the color, clarity, and contrast of the view. The
particles that cause haze are the same particles that contribute
to serious health problems and environmental damage.
Visibility impairmentand the concentration of particles that
cause itgenerally is worse in the eastern United States than it
is in the West. Humidity can significantly increase visibility
impairment by causing some particles to become more efficient
at scattering light. Average relative humidity levels are higher
in the East (70% to 80%) than in the West (50% to 60%).
In the East, reduced visibility is mainly attributable to sulfates,
organic carbon, and nitrates. Poor summertime visibility is
primarily the result of high sulfate concentrations, combined
with high humidity. Sulfates, which dominate the composition
of these visibility-impairing particles, have been found to
contribute even more to light extinction than they do to fine
particle concentrations. In the West, organic carbon, nitrates,
and crustal material make up a larger portion of total particle
concentrations than they do in the East.
Through its 1999 regional haze rule, EPA, states, and other
federal agencies are working to improve visibility in 156
national parks and wilderness areas such as the Grand Canyon,
Yosemite, the Great Smokies, and Shenandoah. Five multistate
regional planning organizations are working together to
develop and implement regional haze reduction plans. For
more information, see www.epa.gov/airtrends/vis.html.
Yosemite National Park (California) under bad and good
visibility conditions. Visual range is iii kilometers (km) in
the left photo and greater than 208 km in the right photo.
Shenandoah National Park (Virginia) under bad and
good visibility conditions. Visual range is 25 km in the left
photo and i80 km in the right photo.
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PM Supersites
Ultrafine Particles (<0.1
Los Angeles, CA
(University of Southern California Site)
Feb Mar Apr May Jun
03 03 03 03 03
Oct Nov Dec Jan
02 02 02 03
Nitrates
D Sulfates
D Metals
D Organic Carbon
Elemental Carbon
Note: "Crustal materials" include windblown soil, industrial process emissions, sea salt, and jlyash from combustion.
After issuing the nation's first PM2.5 standards in 1997, EPA
developed the PM Supersites project, a monitoring research
program, to address a number of scientific issues associated
with particulate matter. Program goals focus on obtaining
atmospheric measurements to
Characterize PM, its constituents, atmospheric trans-
port, and source categories that affect PM in any
region
Compare and evaluate different PM measurement
methods (e.g., emerging sampling methods, routine
monitoring techniques)
Support exposure and health effects research
concerning the relationships between sources, ambient
PM concentrations, and human exposures and health
effects and the biological basis for these relationships.
EPA selected eight locations for Supersites, including Los
Angeles. Atmospheric measurements taken at the Los
Angeles site between October 2002 and September 2003
show that ultrafine particles make up a small portion of the
PM concentration compared to inhalable coarse and fine
particles. However, the number of ultrafine particles is signifi-
cantly larger than the number of coarse or fine particles. EPA
is studying this from a health perspective.
The Los Angeles data also show that coarse, fine, and ultra-
fine PM have different compositions. For each type of PM,
there is a difference in the relative amounts of nitrates,
sulfates, crustal materials, and carbon. Carbon, shown here
as organic and elemental carbon, makes up a large fraction
of ultrafine and fine PM in Los Angeles.
For more information, see
www.epa.gov/ttn/amtic/supersites.html and
www.epa.gov/ttn/amtic/laprog.html
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Particle Pollution Is..
Both Local and Regional
Both local and regional sources contribute to
particle pollution. Figure 5 shows how much of
the PM2 5 mass can be attributed to local versus
regional sources for 13 selected urban areas
(arranged west to east). In each of these urban
areas, monitoring sites were paired with nearby
rural sites. When the average rural concentration
is subtracted from the measured urban concen-
tration, the estimated local and regional contri-
butions become apparent.
In the East, regional pollution contributes more
than half of total PM25 concentrations. Rural
background PM2.5 concentrations are high in the
East and are somewhat uniform over large
geographic areas. These regional concentrations
come from emission sources such as power
plants, natural sources, and urban pollution and
can be transported hundreds of miles.
For the cities shown in Figure 5, local contribu-
tions range from 2 to 20 micrograms per cubic
meter (ug/m3), with the West generally showing
larger local contributions than the East. In the
East, local contributions are generally greatest in
cities with the highest annual average PM2 5
concentrations.
Figure 6 shows the local and regional contri-
butions for the major chemical components that
make up urban PM25: sulfates, carbon, and
nitrates. In the eastern United States, the local
contribution of sulfates is generally small. Most
sulfates in the East are converted from regional
SO2 emissions and are transported long distances
from their sources.
Carbon has the largest local contribution of the
three major chemical components. These local
emissions come from a combination of mobile
and stationary combustion sources. The regional
Figure 5. Local and regional contribution to urban PM2
Measured PM2 5 Concentration
Fresno
Missoula
Salt Lake City
Tulsa
St. Louis
Birmingham
Indianapolis
Atlanta
Cleveland
Charlotte
Richmond
Baltimore
New York City
WEST
| EAST
1
Contribution
D Local
I
0 5 10 15 20 25 30
Annual Average PM2 5 Concentration, [ig/m3
Note: Urban and nearby rural PM2S
concentrations suggest substantial
regional contributions to fine particles
in the East. The measured PM2 s
concentration is not necessarily the
maximum for each urban area.
Regional concentrations are derived
from the rural IMPROVE monitoring
network,
http://vista.cira.colostate.edu/improve.
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contribution, which varies from 30% to 60% of
the total carbon at urban locations, is from rural
emission sources such as vegetation and wildfires,
as well as region-wide sources such as cars and
trucks.
Nitrates represent only about 10% to 30% of
annual average PM2.5, and urban concentrations
are higher than the nearby regional levels. This is
likely due to local nitrogen sources such as cars,
trucks, and small stationary combustion sources.
Figure 6. Local and regional contribution of major PM2.s chemical components.
Sulfates
Carbon
Fresno
Missoula
Salt Lake City
Tulsa
St. Louis
Birmingham
Indianapolis
Atlanta
Cleveland
Charlotte
Richmond
Baltimore
New York City
zn
in
E] WEST
| EAST
II
1
II
n Regional
II Contribution
D Local
1
2 4 6 8 10
Annual Average Concentration
of Sulfates, [ig/m3
12
Fresno
Missoula
Salt Lake City
Tulsa
St. Louis
Birmingham
Indianapolis
Atlanta
Cleveland
Charlotte
Richmond
Baltimore
New York City
Nitrates
WEST
EAST
1 1
L~] Regional
Contribution
D Local
Contribution
2 46 8 10 12
Annual Average Concentration
of Carbon, [ig/m3
Fresno
Missoula
Salt Lake City
Tulsa
St. Louis
Birmingham
Indianapolis
Atlanta
Cleveland
Charlotte
Richmond
Baltimore
New York City
P
1 | WEST
LJ EAST
n
^
i
^
i i
~n
1 1 n Regional
1 1 Contribution
1 Local
1 1 Contribution
IE!
2 4 6 8 10 12
Annual Average Concentration
of Nitrates, [ig/m3
Note: Regional concentrations are
derived from the rural IMPROVE
monitoring network,
http://vista.dra.colostate.edu/improve.
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Particle Pollution in 2003
Nationally, fine particle concentrations in 2003
were the lowest since nationwide PM2 5 moni-
toring began in 1999. Compared with 2002, the
biggest decreases occurred in the Industrial
Midwest and parts of California areas with
relatively high PM25 concentrations. PM10 concen-
trations were slightly higher in 2003 than the
previous year, but they are still the second lowest
since nationwide PM10 monitoring began in 1988.
Although average concentrations have declined
nationally, many areas still exceed the level of
the PM standards. In 2003, monitors in 97
counties (home to 62 million people) showed
concentrations greater than the PM10 or PM2 5
national air quality standards. Thirty-seven
counties (21 million people) measured concen-
trations in excess of the national PM10 standards,
and 72 counties (53 million people) exceeded the
national PM2 5 standards. These numbers do not
include other areas outside of these counties that
might contribute to levels above the standards.
Figure 7 shows the range of PM10 concentrations
across the country in 2003. The highest concen-
trations were recorded in Inyo and Mono coun-
ties, California; El Paso County, Texas; and Dona
Ana County, New Mexico. Figure 8 shows the
Figure 7. PM1O concentrations, 2003 (second maximum 24-hour).
Concentration range (ng/m3)
D s54
D 55-154
155-354
>354
Note: Circle size corresponds
to PM2S concentration range.
Figure 8. PM2.s concentrations, 2003 (annual average).
Concentration range (ng/m3)
D s10
D 10.1 - 15
D 15.1 -20
>20
10
-------
range of 2003 PM2 5 annual averages across the
country. The highest annual averages occurred
in southern California and Pittsburgh. High
levels are also seen in many urban areas in the
Southeast, Northeast, and Industrial Midwest. See
www.epa.gov/airtrends/pm.html for county-level
maps of PM.
PM2 5 concentrations can reach unhealthy levels
even in areas that meet the annual standard. In
2003, there were 277 counties with at least
1 unhealthy day based on PM2 5 AQI values, as
shown in Figure 9. Nearly two-thirds of those
counties had annual averages below the level of
the standard. Figure 10 shows how several major
metropolitan areas fared in 2003 relative to
previous years. Most metropolitan areas had fewer
unhealthy PM2 5 days in 2003 compared to the
average from the previous 3 years, which reflects
the improvements observed in 2003.
Figure 9. PM2.5 AQI days above 100 (>40.5 ug/m3) in 2003.
Note: This map represents data from Federal Reference Method monitors. It does not show data from all monitors that
report the Air Quality Index. As such, it may not provide a complete pkture of days above the AQI in some cities.
Figure 10. Number of days with PM2 5 AQI levels above 100, 2003 versus average 2000-2002.
'* s if
Mi'is ^
^ 6 New York
r8 4 Cincir
^tzi
St. Louis 2,
L
Birm
l-^-i Salt Lake
Sacramento Denver
Washington, DC
4 Cincinnati
St. Louis ,, ^=L
,, Charlotte
11 9
;Tiingham
Number of days (2000-2002, average)
Number of days (2003)
11
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PM10 - PM,
Particulate matter varies greatly in size. "Coarse"
particles can be as large as 40 micrometers (jam)
in diameter or even larger. EPA's National
Ambient Air Quality Standards (NAAQS) for
participate matter, however, have focused on
particles that are 10 um in diameter or smaller.
These particles are the most likely to be inhaled
and can penetrate into the lower respiratory tract.
EPA has had air quality standards for particles
10 (am and smaller since 1987. In 1997, EPA also
established an NAAQS for fine particles those
particles 2.5 um in diameter or smaller. EPA is
now in the process of reviewing the PM
NAAQS.
As shown in Figure 11, the size distribution of
particles smaller than 10 um but larger than
2.5 um varies by geographic location. Levels of
PM10_2 5 are generally higher in the West, particu-
larly the Southwest. PM10_2.5 typically comprises
more than half of the PM10 mass in the West.
Data also suggest that concentrations of particles
between 2.5 and 10 um in size are lower in the
mid-Atlantic and Southeast. Overall, while
directly emitted PM2 5 and its precursors can
come from both local and regional sources, the
larger particles that are part of PM10 tend to
come from local sources.
Figure 11. Percent of 2003 annual average concentration of particles smaller
than 10 um but larger than 2.5 um, by region.
North- Southern South- Upper Ind. Mid- North- South-
west CA west Midwest west east east
D PM
10-2.5
n PM
2.5
National Standards for Particulate Matter
EPA first established National Ambient Air Quality Standards
(NAAQS) for total suspended particulate (TSP) in 1971.
When the standards were revised in 1987, TSP was replaced
by PM10. In 1997, EPA revised the primary (health) and
secondary (welfare) PM NAAQS by adding standards for
PM2 5. EPA added PM2 5 standards because fine particles
are more closely associated with serious health effects.
The NAAQS for PM10 and PM2.5 include both short-term
(24-hour) and long-term (annual) standards:
NAAQS
PM
PM.,
Short-term
(24-hour average)
Long-term
(annual average)
65 ug/m3
15 ug/m3
150 ug/m3
50 ug/m3
Compliance
Each PM standard carries a separate threshold for
compliance:
For the long-term standards for both PM2 5 and PM10,
compliance is determined based on the average of three
consecutive annual average values.
Compliance with the short-term PM2 5 standard is
determined by the 3-year average of the annual 98th
percentile of 24-hour concentrations.
The short-term standard for PM10 is not to be exceeded
more than once per year, averaged over 3 years.
EPA reviews the NAAQS on a regular basis. The standards
for PM-io and PM2 5 are currently under review, to be
completed in 2006.
Note: fjg/tn3 = micrograms per cubic meter.
12
-------
Looking at Trends
PM10 National and Regional Trends
Nationally, PM10 concentrations have decreased
31% since 1988, as shown in Figure 12.
Regionally, PM10 decreased most in areas with
historically higher concentrations the
Northwest (39%), the Southwest (33%), and
southern California (35%).
Programs aimed at reducing direct emissions of
particles have played an important role in
reducing PM10 concentrations, particularly in
western areas. Some examples of PM10 controls
include paving unpaved roads, replacing wood
and coal with cleaner-burning fuels like natural
gas, and using best management practices for
agricultural sources of resuspended soil.
Additionally, EPA's Acid Rain Program has
substantially reduced SO2 emissions from power
plants since 1995 in the eastern United States,
contributing to lower PM concentrations. Direct
emissions of PM10 have decreased approximately
25% nationally since 1988.
Figure 12. Regional and national trends in annual average PM10 concentrations and emissions,
1988-2003.
Annual Average PM10 Concentrations, 1988-2003
Northwest
|,39%
Southern
California
|.35%
Upper
Midwest
J.16%
Southwest
|,33%
26.5
Northeast
Industrial
Midwest
28.8
|,29%
24.3
4 29%
20.5
Southeast
4-25%
24.6
National Standard:
Regional Trend
National PM10 Air Quality
89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
1988-2003: 31 % decrease
1999-2003: 7% decrease
National Direct PM10 Emissions
D Transportation D Industrial Processes
Fuel Combustion
n 1996, EPA refined its
methods for estimating
emissions.
89 90 91 92 93 94 95 96 97 98 99 00 01 02 03
1988-2003: approximately 25% decrease
1999-2003: 3% decrease
13
-------
PM25 National and Regional Trends
PM25 concentrations have decreased 10% nation-
ally since 1999. Generally, PM25 has decreased
the most in regions with the highest concentra-
tions the Southeast (20%), southern California
(16%), and the Industrial Midwest (9%), as shown
in Figure 13. With the exception of the
Northeast, the remaining regions posted modest
declines in PM25 from 1999 to 2003.
A variety of local and national programs have
resulted in a 5% decrease in estimated direct
emissions of PM25 over the past 5 years. In addi-
tion, programs that reduce the gaseous emissions
that can form particles in the atmosphere have
yielded additional reductions. National programs
that affect regional emissions including
EPA's Acid Rain Program have contributed
to lower sulfate concentrations and, conse-
quently, to lower PM2 5 concentrations, partic-
ularly in the Industrial Midwest and Southeast.
National ozone-reduction programs designed
to reduce emissions of volatile organic
compounds (VOCs) and nitrogen oxides
(NOX) also have helped reduce carbon and
nitrates, both of which are components of
PM2.5. Nationally, SO2, NOX, and VOC emis-
sions decreased 9%, 9%, and 12%, respectively,
from 1999 to 2003. In eastern states affected
by the Acid Rain Program, sulfates decreased
7% over the same period.
14
-------
Figure 13. Regional and national trends in annual average PM2.s concentrations and emissions
related to PM2 5 formation, 1999-2003.
Annual Average PM2 5 Concentrations, 1999-2003
Upper
Midwest
415% 11~4~~ ~~I0.7
46%
Southern
California
2tL° _ 16.9 Snnthuwoct
116%
8.7 8.1
4?%
Industrial
Midwest
15.6 ^.|
49%
Southeast
15J ' ~.6
420%
Northeast
13.2 13..
National Standard: 15
Regional Trend
National PM2.s and Precursor Emissions
30
20
c
01
u
c
o
u
National PM2.5
Air Quality
780 Monitoring Sites
'90% of sites have
concentrations
below this line
10
14 Average
\
10% of sites have
concentrations
below this line
99 00 01 02 03\
. 10% Decrease
NOV
Only a subset of VOC
contributes to PM
0
99 00 01 02 03 99 00 01 02 03
I Fuel Combustion CD Industrial Processes D Transportation
Note: Ammonia is a contributor to PM2 s formation. However, because of uncertainty in ammonia
emission estimates, its trends are not shown here.
15
-------
25-Year PM2 5 Trends
Because EPA's national PM2 5 monitoring
network is just 5 years old, we use data from
older PM2 5 monitoring networks to assess
longer-term trends. Although the earlier
networks are more limited in geographic scope
and years of coverage, their data do provide
historical perspective. The maps in Figure 14
show how PM2 5 concentrations 25 years ago
compare with PM2 5 concentrations today in
39 major cities. Reductions vary among the 39
cities. Generally, the largest reductions occurred
in the areas with the highest concentrations. On
average, today's levels are about 30% lower than
they were 25 years ago.
The following examples, illustrated in Figure 14,
show how PM2 5 concentrations have improved
over the past 25 years in three cities. Figure 14
also shows PM10 concentrations for comparison
(where available). PM25 accounts for more than
half of the PM10 levels in these areas.
Los Angeles: PM2 5 concentrations have
decreased substantially since 1980. Although
concentrations have leveled off in recent
years, average PM2 5 levels in 2003 were the
lowest on record. Low-sulfur gasoline use
and ozone reduction programs designed to
control NOX and VOC emissions may have
contributed to the PM2 5 decrease observed
in the 1990s.
Washington, DC: PM2 5 concentrations are
currently (2003) at their lowest levels. The
relatively large drop from 1994 to 1995
corresponds to decreases in sulfates (21%) and
organic carbon (30%). The decrease in
sulfates is attributable in part to the Acid
Rain Program, which substantially reduced
SO2 emissions from power plants during this
time. The decrease in organic carbon is
attributable in part to the use of reformulated
gasoline.
Chicago: PM2 5 concentrations at this site
have dropped substantially since the early
1980s, reaching their lowest levels in 2003.
For additional information on long-term trends,
see www.epa.gov/airtrends/pm.html.
16
-------
Figure 14. Comparison of historical PM2.5 and PM1O annual average concentrations, 1979-2003.
Average Annual PM2 5 Concentrations, 1979-1983
Concentration range (ng/m3)
D < 15 [5 Cities]
D 15.1 -20 [13 Cities]
D 20.1 -25 [14 Cities]
25.1 -30 [5 Cities]
> 30 [2 Cities]
Source: Inhalable Paniculate Network
Average Annual PM2 5 Concentrations, 2001-2003
Concentration range (ng/m3)
< 15 [24 Cities]
D 15.1 -20 [13 Cities]
> 20 [2 Cities]
PM2 5 Annual Average Concentrations
Los Angeles, CA
£ 40
1
c 30
.0
(TJ
i- 20
c
OJ
o 10
u
0
, I
n !-
-i
, i
<*/
p
V
\A2
r
\
.
pr
**
',
N
S
p
PM25
79 81 83 85 87 89 91 93 95 97 99 01 03
50
c-30
O
i 20
o 10
u
Washington, DC
PM25 PM10
Incomplete Data
PM25
NAAQS
Level
79 81 83 85 87 89 91 93 95 97 99 01 03
Chicago, IL
50
£ 40
"oi
i
c 30
0
PM25 PM10
Incomplete Data
PM25
NAAQS
Level
79 81 83 85 87 89 91 93 95 97 99 01 03
Source: Federal Reference Method Network
Note: The 1979-1983 data are from the Inhalable Paniculate Network (IPN). The 1984-1999 data are from EPA's Air
Quality System. The 1999-2003 data are from the Federal Reference Method (FRM) network. The 1993-2003 data for
Washington, DC, are from the IMPROVE network.
17
-------
Rural Sulfate Trends
In the eastern half of the United States, sulfates
account for 25% to 55% of PM25 annually. Power
plants are the largest contributor to sulfate formation
in the East, where they were responsible for more than
75% of sulfur dioxide emissions in 2003.
In the East, power plants reduced sulfur dioxide emis-
sions 33% between 1990 and 2003. As Figure 15
shows, this downward trend matches well with the
trend in concentrations of rural sulfates (a 29%
decrease). Because sulfates have such a large regional
component (shown in Figure 6), these trends in sulfate
concentration can also be used to help explain urban
PM2 5 trends.
The reductions shown in Figure 15 are primarily
attributable to implementation of EPA's Acid Rain
program. Phase I compliance began in 1995, affecting
large coal-burning power plants in 21 eastern and
midwestern states. Phase II implementation began in
2000, tightening emission limits on the Phase I power
plants and setting restrictions on smaller coal-, oil-, and
gas-fired plants. As the figure shows, sulfur dioxide
emissions and sulfate concentrations decreased
following implementation of both phases. A slight
increase in SO2 emissions in the latter half of the 1990s
was likely due to power plants not affected until Phase
II began in 2000. The small increase from 2002 to 2003
resulted from increased electricity production by coal-
fired and oil-fired units. These units emit much more
SO2 than natural gas units that generated less power in
2003. This annual variation does not affect the total
limit on SO2 emissions under the Acid Rain Program.
(For more information, see www.epa.gov/air/oap.html
and www.epa.gov/acidrainreport/.)
Figure 15. Eastern annual trends of sulfur dioxide
emissions from power plants and sulfate concentrations.
15,000
2,2 10,000
5,000
0
i Sulfate Concentrations
SO2 Emissions from Power Plants
90 91 92 93 94 95 96 97 98 99 00 01 02 03
5 I
Cm
3 8 E
" 0)
ll
l/l
0
Episodic Events
PM concentrations can increase dramatically due to
human-caused or natural episodic events, such as biomass
burning, meteorological inversions, dust storms, and
volcanic and seismic activity. These events are rare,
affecting less than 1 % of reported PM2 5 concentrations
between 2001 and 2003. Episodic events can affect
people's short-term PM exposure, briefly pushing hourly
and daily PM levels into the unhealthy ranges of the Air
Quality Index. However, these events rarely have a signifi-
cant effect on annual or longer averages of PM.
Biomass burning can be either a human-initiated event, as
in the burning of vegetation for land clearing or land use
change, or a natural event, as in the wild fires resulting
from lightning. Biomass burning can significantly increase
PM levels in local areas and sometimes more distant areas.
Air currents can carry smoke from forest fires half-way
around the earth. Organic carbon compounds usually
dominate the PM2 5 concentration profile during these
fire episodes.
Topography and meteorological conditions make some
areas more susceptible to episodic events. In mountain
regions, temperature inversions sometimes trap polluted
air during the winter. Wintertime PM2 5 and PM10 can
be more than three times higher than other seasonal
averages. Woodstove smoke, containing large amounts
Satellite photo of forest fires, southern
California, October 27, 2003.
Note: Sulfate concentrations are from EPA's CASTNET
monitoring network, unvw.epa.gov/castnet
18
-------
of organic carbon, is often identified as a significant source
of the elevated wintertime PM concentrations.
Arid desert conditions in the southwestern United States
make this region more vulnerable to wind-blown dust than
other regions of the nation. Most dust events are caused
by passage of weather fronts and troughs and downmixing
of upper-level winds. Cyclone development and thunder-
storms result in the most dramatic dust clouds with the
lowest visibilities. Dust-related events are typically domi-
nated by large, coarse particles, but fine particle levels also
increase.
The effects of dust storms can also be seen globally. Giant
sand storms originating in the Sahara Desert can blow
across the Atlantic to South America, the Caribbean, and
the southeastern United States, transporting several
hundred million tons of dust each year. Movement of dust
from Africa has increased since 1970 because of an increase
of dry weather in the Saharan region. Satellite pictures
also confirm that sandstorms originating in China's Gobi
Desert occasionally cross the Pacific to the United States.
Transport from Africa typically occurs in the summer, and
transport from Asia typically occurs in the spring.
Temperature inversion. Salt Lake Valley, Utah,
January 13, 2004.
Dust storm. Phoenix, Arizona, August 19,1999.
Satellite photo of giant cloud of dust originating
in North Africa moving westward.
19
-------
Explaining the Trends
PM25 Trends in Three Regions
(1999-2003)
To better understand ambient air quality, it is
helpful to examine trends and the factors that
contribute to those trends in specific regions. This
section explores, in detail, trends in three regions in
the eastern half of the country from 1999 to 2003.
Figure 16 shows the 5-year regional trends in
urban PM2 5 and its major chemical constituents.
In the Southeast, PM2 5 declined sharply from
1999 to 2002, with little further change to 2003.
Overall, the Southeast shows a 20% decrease in
PM2.5 from 1999 to 2003. In the Industrial
Midwest, there is a gradual downward PM2 5
trend from 1999 to 2001 and a more pronounced
decrease from 2001 to 2003. Overall, PM2.5
decreased 9% over the 5-year period. In the
Northeast, PM25 increased slightly from 1999
through 2001, then decreased through 2003,
for an overall increase of 1%. Trends in PM
components indicate that reductions in sulfates
appear to be responsible for approximately one-
third of the reductions in PM2 5 in the Industrial
Midwest and the Southeast. Trends in sulfate
concentrations in the eastern United States match
well with trends in SO2 emissions from power
plants over the past 14 years (based on analyses
discussed in the previous section; see Figure 15).
Figure 17 shows that, on smaller sub regional
scales, the relationship between sulfate concentra-
tions and power plant SO2 emissions can vary
among the subregions. Although trends in sulfate
concentrations and SO2 emissions match best
overall in the Southeast (SO2 emissions down
15%, sulfate concentrations down 13%, from
1999 to 2003), the year-to-year comparisons for
the Industrial Midwest and the Northeast do not
show such a close match. Sulfur dioxide emis-
sions in the Industrial Midwest declined 19%,
while sulfate concentrations declined 5%. In the
Northeast, sulfur dioxide emissions were down
6%, and sulfate concentrations were up 3%.
These subregional differences may be caused by
several factors, the most important of which is
likely to be transport. As Figure 17 shows, the
ratio of sulfate concentrations to SO2 emissions is
higher in the Northeast than in the other
regions. This suggests that transport of emissions
20
Figure 16. Trends in PM2.5 and its chemical constituents, 1999-2003.
Southeast
16-
14-
12-
m
01 10
o
u
4-
2-
0-
PM,
115 PM2 5 Monitoring Sites
-20%
Sulfate
-13%
PM25 Remainder
(mostly carbon) -32%
Crustal
I . * * ! . t
Nitrate
+18%
1999 2000 2001 2002 2003
Year
Industrial Midwest
16-
14-
12-
"E
01 10
c
o
o
u
4-
2-
0-
PM,
119 PM2 5 Monitoring Sites
-9%
PM25 Remainder -17%
(mostly carbon)
Nitrate
-4%
Crustal
Northeast
16-
14-
12-
m
01 10
c
o
P 8-
6-
o
u
2-
o-
56 PM2 5 Monitoring Sites
Sulfate
+3%
PM25 Remainder
(mostly carbon)
Nitrate
+2%
Crustal
1999 2000 2001 2002 2003
Year
1999 2000 2001 2002 2003
Year
Note: Sulfate and nitrate concentrations from the CASTNET monitoring network were adjusted to represent mass in
PM2 5 and include ammonium as well as water. Trends for crustal were not available so constant values based on
20022003 data for each region were used. See www.epa.gov/airtrends/pm.htmlforfurther details.
-------
Figure 17. Meteorologically adjusted sulfate
concentrations, 1999-2003.
Northeast
Southeast
m
14-
C
o
IS 3-
-7 =
90 91 92 93 94
95 96 97
Year
00 01 02 03
Industrial Midwest
90 91 92 93 94 95 96 97
Year
00 01 02 03
] SO2 emissions from power plants -»- CASTNET sulfate concentrations
-A- Meteorologically adjusted sulfate concentrations
from other regions contributes to sulfate forma-
tion in the Northeast. Other factors that may
contribute to the subregional differences in these
trends include variations in meteorological condi-
tions that are important to sulfate formation and
transport, contributions to the Northeast from
Canada, and subregional differences in the contri-
butions of sources other than power plants.
Effect of Meteorology
Weather plays a role both in the atmospheric
formation of PM2 5 and in the quantity of emis-
sions that contribute to this pollution. For this
report, we examined the effect of meteorology
on sulfates, which are a major component of
PM2 5, especially in the eastern half of the United
States. To assess the effect of meteorology on
annual average sulfate concentrations, EPA has
conducted a preliminary analysis, adjusting sulfate
levels based on weather conditions. (The blue
line in Figure 17 represents measured sulfate
concentrations; the red line represents the meteo-
rologically adjusted sulfate concentrations.) One
of the main parameters driving these preliminary
adjustments is temperature. In the eastern half of
the United States, 1999, 2001, and 2003 were
near-normal meteorological years, so only
minimal adjustments to sulfate concentrations
were needed. In 2000, however, a cool summer
may well have caused sulfur dioxide emissions to
be lower than average, resulting in lower amounts
of sulfates in the air. Adjusting for weather in
2000 raised estimated sulfate levels in all three
regions to the level expected during a year with
average weather conditions.
Conversely, the summer of 2002 in the eastern
United States was one of the hottest in recent
years. Sulfur dioxide emissions were higher that
year, likely due (at least in part) to increased
demand for electricity for cooling. The meteoro-
logical adjustment for 2002 reduces the amount
of sulfates in all three regions to levels expected
during a normal meteorological year.
In two of the three regions, the variations in
power plant SO2 emissions (illustrated by the
yellow bars in Figure 17) generally correlate more
closely with the meteorologically adjusted sulfates
(the red line) than the unadjusted sulfates (the
blue line). In the Industrial Midwest, however,
adjusting for weather causes the sulfate trend to
move farther away from the sulfur dioxide emis-
sion trend in 2002-2003. More refined meteoro-
logical analyses and emission inventories are
necessary to fully understand these results.
21
-------
The PM25 Remainder
Figure 16 (page 20) also shows the estimated
trend in the "PM2.5 remainder" for each of the
three regions. The remainder is estimated by
subtracting all known PM2 5 components from
the total PM2 5 mass. Some uncertainties exist in
our interpretations of these data; however, the
PM2 5 remainder appears to consist mostly of
carbon-containing particles. Some small contri-
butions to the PM2 5 remainder trend shown in
Figure 16 include
Trends in crustal material
Local contributions for nitrates and sulfates
(see the discussion on pages 8 and 9)
Any changes in data quality or the operation
of EPA's PM2.5 Federal Reference Method
monitoring network during its first few years
of operation.
Despite the uncertainties, the reductions in the
PM2 5 remainder for the Industrial Midwest and
Southeast appear to be due, in large part, to
reductions in emissions that contribute to the
formation of carbon-containing particles. The
relative importance of various man-made emis-
sions sources to these trends is uncertain and may
vary by region and urban area. Important sources
of carbon-containing particles in urban air
include direct emissions from sources such as
motor vehicles, fuel combustion, and fires and
atmospheric transformation of certain organic
gases, including both regional biogenic emissions
and some components of man-made VOCs.
It is interesting to note that, in Figure 18, the
decrease in the estimated PM2 5 remainder corre-
sponds either to reductions in directly emitted
fine particles or reductions in man-made VOC
emissions. The Northeast region, however, shows
virtually no net change in PM2 5 or in any of its
estimated components. Yet both direct PM2 5
emissions and VOC emissions decreased from
1999 to 2003. EPA is continuing to conduct
research and analysis to better identify and
quantify key direct emission sources in addition
to the relative contribution of man-made VOC
emissions to atmospheric formation of carbon-
containing particles.
Figure 18. PM25 emission trends.
SO2 Emissions
£ 8,000
^ 7,000
3J 6,000
3
£ 5,000
I
£- 4,000
| 3,000
I 2,000
f 1.000
vo>
> 0
£ 8,000
^ 7,000
3J 6,000
3
£ 5,000
£ 4,000
| 3,000
I 2,000
f 1.000
0)
> 0
600
500
400
300
200
100
£ 600
o 500
§ 400
rf 300
o
'» 200
E
LLJ
^ 100
(a
0)
> 0
96 97 98 99 00 01 02 03
NOV Emissions
96 97 98 99 00 01 02 03
Direct PM2 5 Emissions
96 97 98 99 00 01 02 03
VOC Emissions
96 97 98 99 00
Year
Industrial Midwest * Northeast
01 02 03
Southeast
Percent Change in Emissions from
1999 to 2003
22
-------
For more details on the PM2 5 remainder, see
ww.epa.gov/airtrends/pm.html. For information
on EPA's monitoring networks, see
www.epa.gov/ttn/amtic/.
Control Programs
Many programs have been put in place to reduce
levels of particulate matter. Table 1 lists the major
emission control programs that have contributed
to reductions in PM since 1995 and will
continue to reduce PM in the future. These
programs control direct PM emissions and/or the
emissions that contribute to PM formation, such
as SO2, NOX, and VOCs. The control programs
consist of a series of regulations that reduce emis-
sions from many stationary and mobile source
sectors. For example, beginning in 2008, states
will be required to attain the National Ambient
Air Quality Standards for fine particles. EPA's
proposed Clean Air Interstate Rule (proposed
in December 2003) will help states meet those
requirements by reducing SO2 and NOX emis-
sions in the eastern United States thus reducing
particle pollution transported across state bound-
aries. Another regulation, the Best Available
Retrofit Technology (BART) program, will
require the older, existing power plants to control
PM emissions with retrofit pollution control
equipment. Also, national mobile source rules are
in place to strengthen the emission requirements
for virtually all types of mobile sources. Many
localities also have pollution reduction require-
ments for diesel engine retrofits as well as sulfur
limits in diesel and gasoline engines.
Table 1. A Selection of Emission Control Programs Contributing to PM Emission Reductions, 1995-2015
Program
Clean Air Nonroad
Diesel Rule
Clean Air Interstate Rule
(proposed December 2003)
Acid Rain Program
NOX SIP Call
Regional Haze Rule/
Best Available Retrofit
Technology
PM2 5 Implementation0
PM10 SIPs
(e.g., San Joaquin Valley)
Maximum Achievable
Control Technology
(MACT) Standardsd
Sector
Mobile sources
Electric Utilities
Electric Utilities
Electric Utilities
Electric Utilities'3
Stationary/Area/
Mobile sources
Stationary/Area/
Mobile sources
Stationary/Area
Direct PMa
Reductions
X
X
X
X
X
X
S02
Reductions
X
X
X
X
X
X
X
PM Precursors
NOX VOC
Reductions Reductions
X
X
X
X
X
X X
X X
X
Implementation
Date
2004-2015
2010-2015
1995-2010
2004
2013-2015
2008-2015
Ongoing
1996-2003
Various Mobile
Source Programs6
X
Ongoing
a Includes elemental and organic carbon, metals, and other direct emissions of PM.
b Also applies to industrial boiler and the other source categories also covered under Prevention of Significant Deterioration (PSD).
c Includes Reasonably Available Control Technology (RACT) and Reasonably Available Control Measures (RACM).
d Includes a variety of source categories such as Boilers and Process heaters. Pulp and Paper, Petroleum Refineries, various minerals and ores,
and others. While these standards are for hazardous air pollutants (HAPs) such as metals, measures to reduce HAPs in many cases also
reduce PM emissions.
e Includes such programs as onroad diesel and gasoline engines, nonroad gasoline engines. Low Sulfur Diesel and Gasoline Fuel Limits for
onroad and offroad engines. Motorcycles, Land-based recreational vehicles, and Marine diesel engines.
23
-------
Using Satellites to Track Particulate Matter
The most direct way to obtain surface concentration data
for particles is from the routine measurements made at surface
monitoring stations across the United States. This approach has
some limitations, however, because large regions of the country
do not have surface monitors, and coastal regions are often influ-
enced by polluted air approaching over water. In addition, pollu-
tion may be transported aloft, undetected by surface monitors,
and then descend to influence air at the ground. New work
being done through a collaborative partnership between EPA,
the National Aeronautics and Space Administration (NASA), and
the National Oceanic and Atmospheric Administration (NOAA)
uses satellite observations to augment the surface network
monitoring data with satellite data.
The NASA MODIS (Moderate Resolution Imaging Spectro-
radiometer) instruments on board the EOS (Earth Observing
System) satellites EOS-Terra and EOS-Aqua provide twice-daily
measurements of aerosol optical depth (AOD), a measure of how
much light airborne particles prevent from passing through a
column of atmosphere. Scientists use these measurements to
estimate the relative amount of aerosols suspended in the
atmosphere.
IDEA (Infusing satellite Data into Environmental
Applications) is a partnership between EPA, NASA, and
NOAA. These agencies are working to improve air
quality assessment, management, and prediction by
infusing satellite measurements from NASA into EPA
and NOAA analyses for public benefit.
Initial research shows that MODIS-derived data are suitable for
tracking air quality events on a regional scale and may be a good
surrogate for estimating the intensity of surface PM2.5 concentra-
tions. More research and data are needed to help show how
aerosol loads are distributed vertically in the atmosphere so that
MODIS-derived AOD can be put into the proper context. For
more information on the MODIS-derived AOD and PM2 5 pollu-
tion events, go to the Cooperative Institute for Meteorological
Satellite Studies/Space Science and Engineering Center at the
University of Wisconsin-Madison website: http://idea.ssec.wisc.edu.
Composites of MODIS-derived AOD (color) and cloud optical thickness (black-white) from September 5 to 8, 2003. The
majority of the high AOD seen in the images (yellow-red) was the result of several very large wildfires in western North
America from British Columbia to Oregon. MODIS-derived AOD tracked the movement of the plume, which eventually
affected surface PM2 5 concentrations throughout the midwestern United States.
24
-------
The Future
Figure 19. Projected emission reductions by 2015.
National and regional regulations will make
major reductions in ambient PM25 levels over the
next 10 to 20 years. In particular, the proposed
Clean Air Interstate Rule (CAIR) and the
existing NOX SIP Call, wiU reduce SO2 and NOX
emissions from certain electric generating units
and industrial boilers across the eastern half of the
United States. Regulations to implement the
ambient air quality standards for PM2 5 will
require direct PM2 5 and PM2 5 precursor controls
in nonattainment areas. New national mobile
source regulations affecting heavy-duty diesel
engines, highway vehicles, and other mobile
sources will reduce emissions of NOX, direct
PM2 5, SO2, and VOCs.
EPA estimates that current and proposed regula-
tions for stationary and mobile sources will cut
SO2 emissions by 6 million tons annually in 2015
from 2001 levels. NOX emissions will be cut
9 million tons annually in 2015 from 2001 levels.
VOC emissions will drop by 3 million tons, and
direct PM2 5 emissions will be cut by 200,000
tons in 2015, compared to 2001 levels. Figure 19
shows anticipated emission reductions. Most of
the SO2 reductions are associated with electric
generating sources, while NOX and VOC reduc-
tions for mobile sources are associated with
continuing improvements in onroad and nonroad
vehicles.
Models predicting the effect of these emission
reductions on air quality show that all areas in
the eastern United States will have lower PM2 5
concentrations in 2015 relative to present-day
conditions. In most cases, the predicted improve-
ment in PM25 ranges from 10% to 20%. EPA
estimates that the proposed CAIR combined
with existing regulations will bring the majority
of the counties in the East into attainment for the
PM2 5 standards. As Figure 20 shows, 99 eastern
counties are estimated to have exceeded the
annual PM25 standard in the 1999-2002 period,
but only 13 of those counties are projected to
exceed the PM25 standard by 2015. More infor-
mation on CAIR can be found at:
www. epa.gov/interstateairquality/.
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2001
2015
Figure 20. Estimated reduction in number of coun-
ties exceeding PM2 5 standards from 2001 (99) to
2015 (13), based on current programs plus the Clean
Air Interstate Rule as proposed in December 2003.
Ambient PM2.5,1999-2002
99 Counties Exceeding PM2.5 Standards
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Estimated PM2.5, 2015
13 Counties Exceeding PM2.5 Standards
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Upcoming PM2 5 Designations
EPA designates areas as attaining or not attaining
the National Ambient Air Quality Standards for
fine particulate matter (PM25). EPA designates an
area as "nonattainment" if it has violated the annual
or 24-hour national PM2 5 standard (assessed over
a 3-year period) or if it has contributed to a viola-
tion of one of the standards. Once designated,
nonattainment areas must take actions to improve
their PM2 5 air quality on a certain timeline.
Designations are a crucial first step in the efforts
of states, tribes, and local governments to reduce
harmful levels of fine particles. For more details on
PM2 5 designations, visit www.epa.gov/
pmdesignations.
Note: Designations are based on 3 years of data,
and the boundaries of defined nonattainment areas
may differ from the county boundaries used in
this report.
PM25 and Other Pollutants
Areas that experience PM2 5 concentrations that
exceed the National Ambient Air Quality
Standards can also have air quality problems associ-
ated with other pollutants. This association in the
presence of different pollutants is not unexpected.
A 2004 report by the National Academies of
Sciences (Air Quality Management in the United
States) indicates that air pollutants "often share
similar precursors and similar chemical reactions
once in the atmosphere." For example, nitrogen
oxides, which contribute to PM2 5 formation, are
also a key ingredient in ground-level ozone.
Pollutants may also be emitted from the same types
of sources. Industries that emit air toxics may also
emit chemicals that contribute to ozone or PM
formation. Data indicate that millions of people
likely live in areas where particle pollution levels
are elevated along with ozone and/or air toxics.
EPA will continue to analyze this information as
we work to protect public health across the
country.
26
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Acronyms
AOD
AQI
BART
CAA
CAIR
CASTNET
EOS
EPA
FRM
EIAP
IDEA
IMPROVE
IPN
km
MACT
MODIS
NAAQS
aerosol optical depth
Air Quality Index
best available retrofit technology
Clean Air Act
Clean Air Interstate Rule
Clean Air Status and Trends
Network
Earth Observing System
U.S. Environmental Protection
Agency
Federal Reference Method
hazardous air pollutants
Infusing satellite Data into
Environmental Applications
Interagency Monitoring of
Protected Visual Environments
Inhalable Particulate Network
kilometer
maximum achievable control
technology
moderate resolution imaging
spectroradiometer
National Ambient Air Quality
Standards
NASA National Aeronautics and Space
Administration
NOAA National Oceanic and Atmospheric
Administration
NOX oxides of nitrogen
PM particulate matter
PM10 particulate matter 10 |_im or less in
size
PM2 5 particulate matter (fine) 2.5 |_im or
less in size
PM10_2 5 particulate matter (coarse) between
10 and 2.5 |_im in size
PSD prevention of significant
deterioation
RACM reasonably available control
measures
RACT reasonably available control
technology
SIP State Implementation Plan
SO2 sulfur dioxide
TCM total carbonaceous mass
TSP total suspended particulate
|j,g/m3 micrograms per cubic meter
|j,m micrometers
VOC volatile organic compound
For Further Information
Web Sites
Additional technical information: www. epa.gov/airtrends/pm.html
Air Quality Index (AQI): www.epa.gov/airnow
Clean Air Interstate Rule: wwwepa.gov/interstateairquality/
CASTNET: www.epa.gov/castnet/
Emissions: www.epa.gov/ttn/chief/
EPA 1996 PM Criteria Document: www.epa.gov/ttn/naaqs
EPA Monitoring Networks: www.epa.gov/ttn/amtic/
Health and Ecological Effects: www.epa.gov/air/urbanair/pm/index.html
IMPROVE: vista.cira.colostate.edu/improve
National Academies: www4.nationalacademies.org/nas/nashome.nsf
Office of Air and Radiation: www.epa.gov/oar
Office of Air Quality Planning and Standards: www.epa.gov/oar/oaqps
Office of Atmospheric Programs: www.epa.gov/air/oap.html
Office of Transportation and Air Quality: www.epa.gov/otaq
Online Air Quality Data: wwwepa.gov/air/data/index.html
PM Supersites: www.epa.gov/ttn/amtic/supersites.html and www.epa.gov/ttn/amtic/laprog.html
PM2.5 Designations: www.epa.gov/pmdesignations
Report on Acid Rain: wwwepa.gov/acidrainreport/
Satellite information: idea.ssec.wisc.edu
Source apportionment: www.epa.gov/oar/oaqps/pm25/docs.html
Visibility: www.epa.gov/airtrends/vis.html
27
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