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NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
C H A P T E R 1
Executive Summary
http://www.epa.gov/oar/airtrends
This 28th National Air Quality and for the first time, brings special facilitate timely updates. A summary of
Emission Trends Report documents air attention to a series of special studies that information will be published each
pollution trends in the United States, of policy-relevant air quality issues summer as it has for the past several
focusing on the 20-year period from (see Chapter 6 and the Special years in EPA’s Latest Findings on National
1983 to 2002 or 1982 to 2001 if that is Studies section). Air Quality: Status and Trends. This
the most recent data available. This In the future, the detailed infor National Air Quality and Emissions Trends
document highlights the U.S. mation traditionally contained in this Report will no longer appear annually in
Environmental Protection Agency’s report will be provided on the Web hard copy. Expect future reports to focus
(EPA’s) most recent thorough assess at http://www.epa.gov/airtrends to on special studies as this report does.
ment of the nation’s air quality, and,
Comparison of Growth Areas and Emissions
200%
Gross Domestic Product
164%
150%
155%
Vehicle Miles Traveled
100%
Energy Consumption
50% 42%
38%
U.S. Population
0%
Aggregate Emissions
-48% (Six Principal Pollutants)
-50%
70 80 90 95 96 97 98 99 00 01 02
Between 1970 and 2002, gross domestic product increased 164 percent, vehicle miles traveled increased 155 percent, energy consumption
increased 42 percent, and U.S. population increased 38 percent. At the same time, total emissions of the six principal air pollutants
decreased 48 percent.
CHAPTER 1 • EXECUTIVE SUMMARY 1
NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
Highlights Comparison of 1970 and 2002 Emissions
• National air quality levels meas
ured at thousands of monitoring 200
250
stations across the country have 180 1970
2002
shown improvements over the 160 200
past 20 years for all six principal 140
Thousand Tons
Million Tons
pollutants. 120 150
• Since 1970, aggregate emissions of 100
the six principal pollutants have 80 100
been cut 48 percent. During that 60
same time, U.S. gross domestic 40 50
product increased 164 percent, 20
energy consumption increased 42 0
CO NOx VOC SO2 PM10
0
Pb
percent, and vehicle miles trav (-48%) (-17%) (-51%) (-52%) (-34%)a (-98%)b
eled increased 155 percent.
• Despite this progress, about 160 through a nationwide cap and parks, the 8-hour ozone levels
million tons of pollution are emit trade program. This will also have increased somewhat.
ted into the air each year in the reduce acid rain and improve visi • Ground-level ozone is not emitted
United States. Approximately 146 bility. Also, in May 2003, EPA pro directly into the air, but is formed
million people live in counties posed nonroad diesel engine regu in the atmosphere by the reaction
where monitored air in 2002 was lations that would help improve of volatile organic compounds
unhealthy at times because of PM and ozone air quality. By 2030, (VOCs) and NOx in the presence
high levels of at least one of the this program would reduce annu of heat and sunlight. Emissions of
six principal air pollutants. al emissions of PM by 95 percent, VOCs have decreased about 40
• The vast majority of areas that nitrogen oxides (NOx) by 90 per percent over the past 20 years.
experienced unhealthy air did so cent, and sulfur levels by 99 per However, regional-scale NOx
because of one or both of two pol- cent from these engines. reductions over the same period
lutants—ozone and particulate • Of the six tracked pollutants, are only 15 percent. More NOx
matter (PM). Important efforts to progress has been slowest for reductions will be necessary
control these pollutants include ground-level ozone. Over the past before more substantial ozone air
implementing more protective 20 years, almost all geographic quality improvements are real
National Ambient Air Quality areas experienced some progress ized. Some of these additional
Standards (NAAQS) for ozone in lowering ozone concentrations. reductions will result from exist
and PM and issuing rules to The Northeast and Pacific South ing and recently enacted NOx
reduce emissions from onroad west exhibited the greatest emission reduction programs and
transportation and stationary improvement. In particular, sub also, potentially, from the Clear
combustion sources. These rules stantial progress seen in Los Skies legislation, if enacted.
will bring reductions in emissions Angeles has continued through • The improvement in overall emis
over the next several years. 2002. However, the national aver sions since 1970 included in this
• Additional reductions will be age ozone (8-hour) levels have year’s findings reflect more accu
needed to provide clean air in the been fairly constant in other met rate estimates of VOC, NOx, PM,
future. For example, the Clear ropolitan areas. An analysis to and carbon monoxide (CO) releases
Skies legislation currently being adjust 8-hour ozone levels in met from highway vehicles and non-
considered in Congress would, if ropolitan areas to account for the road engines. Previous years’
enacted, mandate reductions of influence of meteorological condi findings underreported emissions
particle- and ozone-forming com tions shows the 10-year trend to for cars and trucks in the 1970s
pounds from power generators by be relatively unchanged. At the and 1980s. This year’s findings
70 percent from current levels same time, for many national incorporate improvements in
2 EXECUTIVE SUMMARY • CHAPTER 1
NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
EPA’s mobile source emission tons from 1990 levels. In addition, degreasing operations; mobile
models, which are based on actual recent actions to address emis sources such as cars, buses, planes,
emissions measurements from sions of toxic air pollutants from trucks, and trains; and natural
thousands of motor vehicles and motor vehicles as well as stringent sources such as windblown dust and
have been peer-reviewed. The new standards for heavy-duty trucks, wildfires.
mobile model better represents buses, and diesel fuel will elimi
average U.S. driving habits, such nate 95 percent of emissions of Under the Clean Air Act
as more rapid accelerations and diesel particulate matter.
EPA establishes air quality standards
faster highway speeds.
• Measurements have shown that to protect public health, including
• Sulfates formed primarily from atmospheric concentrations of the health of “sensitive” populations
sulfur dioxide (SO2) emissions methyl chloroform are falling, such as children, older adults, and
from coal-fired power plants are a indicating that emissions have people with asthma. EPA also sets
major component of fine particles been greatly reduced. Concentra limits to protect public welfare. This
(known as PM2.5) in the eastern tions of other ozone-depleting includes protecting ecosystems,
United States. SO2 emissions substances in the upper layers of including plants and animals, from
decreased approximately 33 per the atmosphere, like chlorofluoro harm, as well as protecting against
cent from 1983 to 2002. Nationally, carbons (CFCs), are also begin decreased visibility and damage to
average SO2 ambient concen ning to decrease. crops, vegetation, and buildings.
trations have been cut approxi EPA has set national air quality
mately 54 percent over the same standards for six principal air pollut
Air Pollution
period. Reductions in SO2 concen ants (also called the criteria
trations and emissions since 1990 The Concern
pollutants): nitrogen dioxide (NO2),
are primarily due to controls Exposure to air pollution is associat
ozone (O3), sulfur dioxide, particu
implemented under EPA’s Acid ed with numerous effects on human
late matter, carbon monoxide, and
Rain Program. Sulfate reductions health, including respiratory prob
lead (Pb). Four of these pollutants
since 1999 are partly responsible lems, hospitalization for heart or
(CO, Pb, NO2, and SO2) are emitted
for some improvement in ambient lung diseases, and even premature
directly from a variety of sources.
fine particle concentrations, partic death. Children are at greater risk
Ozone is not directly emitted, but is
ularly in the southeastern United because they are generally more
formed when NOx and VOCs react
States. active outdoors and their lungs are
in the presence of sunlight. PM can
still developing. The elderly and
• In many locations, EPA now has be directly emitted, or it can be
people with heart or lung diseases
4 years of air quality monitoring formed when emissions of nitrogen
are also more sensitive to some types
data for PM2.5. Areas across the oxides, sulfur oxides, ammonia,
of air pollution.
Southeast, Mid-Atlantic, Midwest organic compounds, and other gases
Air pollution can also significant
regions, and California have air react in the atmosphere.
ly affect ecosystems. For example,
quality that is unhealthy due to Each year EPA looks at the levels
ground-level ozone has been associ
particle pollution. Region-wide of these pollutants in the air and the
ated with reductions of agricultural
emissions from power plants and amounts of emissions from various
and commercial forest yields, and
motor vehicles are among the sources to see how both have
airborne releases of NOx are one of
largest contributors to the high changed over time and to summarize
the largest sources of nitrogen pollu
PM2.5 concentrations. the current status of air quality.
tion in certain waterbodies, such as
• Since 1990, many actions have the Chesapeake Bay.
been taken that will significantly Reporting Air Quality and
reduce air toxics across the coun The Causes Emissions Trends
try. Specifically, regulations for Air pollution comes from many Each year, air quality trends are cre
facilities such as chemical plants, different sources. These include large ated using measurements from moni
dry cleaners, coke ovens, and stationary sources such as factories, tors located across the country. The
incinerators will reduce emissions power plants, and smelters; smaller following table shows that the air
of toxic air pollution by 1.5 million sources such as dry cleaners and quality based on concentrations
CHAPTER 1 • EXECUTIVE SUMMARY 3
NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
Percent Change in Air Quality Methods for estimating emissions emissions mostly contribute to the
1983-2002 1993-2002 continue to improve. Today’s esti formation of ozone and particles, the
NO2 -21 -11 mates are different from last year’s deposition of acids, and visibility
a
O3 1-h -22 -2 estimates. One reason is because this impairment.
a
8-h -14 +4
year EPA used updated, peer- Despite great progress in air
SO2 -54 -39
PM10 — -13
reviewed models that estimate VOC, quality improvement, approximately
PM2.5 — -8
b NOx, CO, and PM emissions from 146 million people nationwide lived
CO -65 -42 highway vehicles and nonroad in counties with pollution levels
Pb -94 -57 engines and and better represent above the NAAQS in 2002. Out of
real-world conditions, such as more the 230 nonattainment areas identi
Percent Change in Emissions
rapid accelerations and faster high fied during the 1990 Clean Air Act
1983-2002 1993-2002 way speeds. The emissions estimates Amendments designation process,
NOx -15 -12 generated by the new highway vehi 124 areas remain. In these nonattain
VOC -40 -25 cle model are derived from actual ment areas, however, the severity of
SO2 -33 -31 tailpipe measurements from thou air pollution episodes has decreased.
PM10c -34d -22 sands of vehicles. Another change in
PM2.5c — -17 the reporting of emissions trends is The Clean Air Act
CO -41 -21 that emissions from wildfires and
The Clean Air Act provides the prin
Pbe -93 -5 prescribed burnings are not consid
cipal framework for national, state,
—Trend data not available.
ered in the estimates of emission
a Not statistically significant.
tribal, and local efforts to protect air
change. This is due to the large vari
b Based on percentage change from 1999.
quality. Improvements in air quality
c Includes only directly emitted particles.
ability in the year-to-year levels of
are the result of effective implemen
d Based on percentage change from 1985.
these emissions and the relatively
Emission estimates prior to 1985 are uncertain.
tation of clean air laws and regula
small impact these distant emissions
e Lead emissions are included in the toxic air tions, as well as efficient industrial
pollutant emissions inventory and are presented have on most monitoring locations.
technologies. Under the Clean Air
for 1982-2001. Because of the high degree of uncer
Act, EPA has a number of responsi
Negative numbers indicate improvements in tainty in predicting emissions for
bilities, including
air quality or reductions in emissions. Positive these fires, their emissions have not
been projected for 2002 for PM, CO, • Conducting periodic reviews of
numbers show where emissions have increased.
and VOCs. These emissions will be the NAAQS for the six principal
estimated when 2002 acres-burned pollutants that are considered
data become available. However, fire harmful to public health and the
of the principal pollutants has emissions are included in the emis environment.
improved nationally over the past sion graphics through 2001. As a • Ensuring that these air quality
20 years (1983–2002). result of these reporting changes, standards are met (in cooperation
EPA estimates nationwide emis some emissions trends have changed with the state, tribal, and local
sions of ambient air pollutants and significantly. For example, rather governments) through national
the pollutants they are formed from than describing no change in the standards and strategies to control
(their precursors). These estimates 20-year emission trend for CO, EPA air pollutant emissions from vehi
are based on actual monitored read now estimates a 41 percent decrease cles, factories, and other sources.
ings or engineering calculations of in CO emissions from 1983 to 2002. • Reducing emissions of SO2 and
the amounts and types of pollutants This estimated change in emissions is NOx that cause acid rain.
emitted by vehicles, factories, and supported by the trend in CO air
other sources. Emission estimates are quality. • Reducing air pollutants such as
based on many factors, including Emissions of air pollutants con PM, SOx, and NOx, which can
levels of industrial activity, techno tinue to play an important role in a reduce visibility across large
logical developments, fuel consump number of air quality issues. About regional areas, including many of
tion, vehicle miles traveled, and 160 million tons of pollution are the nation’s most treasured parks
other activities that cause air emitted into the atmosphere each and wilderness areas.
pollution. year in the United States. These
4 EXECUTIVE SUMMARY • CHAPTER 1
NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
• Ensuring that sources of toxic air Air Toxics
pollutants that may cause cancer
EPA has developed a National-Scale
and other adverse human health
Air Toxics Assessment, which is a
and environmental effects are well
nationwide analysis of air toxics. The
controlled and that the risks to
assessment uses computer modeling
public health and the environment
of the 1996 National Emissions
are substantially reduced.
Inventory (NEI) air toxics data as the
• Limiting the use of chemicals that basis for developing health risk
damage the stratospheric ozone estimates for 33 toxic air pollutants
layer in order to prevent increased (a subset of the Clean Air Act’s list of
levels of harmful ultraviolet radia 188 air toxics plus diesel PM). The
tion. highest ranking 20 percent of the
counties in terms of risk (622 coun
Criteria Pollutants — ties) contain almost three-fourths of
Metropolitan Area Trends the U.S. population. Three air toxics
(chromium, benzene, and formalde
Out of 263 metropolitan statistical hyde) appear to pose the greatest
areas, 34 have significant upward nationwide carcinogenic risk. One air
trends. Of these, only those trends toxic, acrolein, is estimated to pose
involving 8-hour ozone had values the highest potential nationwide for
over the level of the air quality significant chronic adverse effects
standard. other than cancer.
Of the five criteria pollutants used
to calculate the Air Quality Index
Special Studies
(AQI), only four (CO, O3, PM10, and
SO2) generally contribute to the AQI For the first time, a series of policy-
value. Nitrogen dioxide is rarely the relevant studies and exploratory
highest pollutant measured. analyses are summarized in this
Although five criteria pollutants can report (see Chapter 6). These studies
contribute to the AQI, the index is address analysis of PM concentra
usually driven mostly by ozone. tions, carbon monoxide trends, the
number of days above AQI levels of
Criteria Pollutants — 100 for the ozone NAAQS, the spa
tial variation of air pollutants, and a
Official Nonattainment
proposed new reporting technique
Areas for air quality data. The full reports
As of September 2002, there were a are also included in this Special
total of 124 classified nonattainment Studies edition.
areas on the condensed nonattain
ment list (see Table A-19). The areas
on the condensed list are displayed
alphabetically by state. There were,
as of September 2002, approximately
126 million people living in classified
areas designated as nonattainment
for at least one of the criteria pollut
ants.
CHAPTER 1 • EXECUTIVE SUMMARY 5
NATIONAL AIR QUALITY AND EMISSIONS TRENDS REPORT, 2003
6 EXECUTIVE SUMMARY • CHAPTER 1
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