EPA's NOX Reduction Program and Clean Air Interstate Rule
2009 Environmental and Health Results
Program Basics
The Clean Air Interstate Rule (CAIR) was designed to ad-
dress interstate transport of ozone and fine particulate
matter (PM25) pollution. To do so, CAIR required certain
states to limit emissions of nitrogen oxides (NOX) and sul-
fur dioxide (SC>2), which contribute to the formation of
ozone and PM2.5. CAIR developed three separate cap and
trade programs that could be used to achieve the required
reductions — the CAIR NOX ozone season trading program,
the CAIR annual NOX trading program, and the CAIR SC>2
trading program. The CAIR NOX ozone season and annual
programs began in 2009, while the CAIR SC>2 annual pro-
gram began in 2010. The reduction in ozone and PM2.5
formation resulting from implementation of the CAIR pro-
grams provides health benefits as well as improved visibil-
ity in national parks and improved ecosystem protection in
the eastern U.S.
2009 Progress Reports
EPA released a series of reports over several months sum-
marizing the first year of CAIR implementation, including
the transition from the ozone season NOX Budget Program
(NBP) to the CAIR NOX ozone season program. Previous
online reports presented and analyzed emission reduc-
tions, compliance results, and market activity in 2009. This
is the third and final report in the series and contains 2009
data on environmental results as well as analyses of the ef-
fects of reduced NOX emissions on ozone and nitrate lev-
els and reduced NOX and SC>2 emissions on PM2i5. Detailed
emission results and other facility and allowance data are
also publicly available on EPA's Data and Maps website at
. To view emission
and other facility information in an interactive format us-
ing Google Earth or a similar three-dimensional platform,
go to EPA's Interactive Mapping site at .
Litigation and Rules to Replace CAIR
On July 11, 2008, the U.S. Court of Appeals for the D.C. Cir-
cuit issued a ruling vacating CAIR in its entirety. EPA and
At a Glance: CAIR Benefits in 2009
Ozone: Ground-level ozone decreased under the first
year of the CAIR NOX ozone season program, continuing
the marked improvements achieved by the NOX SIP [State
Implementation Plan) Call program.
• Regional 1-hour ozone concentrations in CAIR states
decreased by an average of 16 percent between
2000-2002 [before implementation of the NBP) and
2007-2009 [under the NBP and first year of CAIR
NOX ozone season program implementation)
• Between 2002 and 2009, 8-hour average ozone
concentrations decreased by an average of 18 percent
across all states controlled for ozone under the CAIR
NOX ozone season program
• Based on data gathered from 2007-2009, 86 percent
of the original eastern nonattainment areas for the
8-hour ozone standard now have ozone air quality
that is better than the standard
Particulate Matter: The CAIR NOX annual program and
CAIR SC>2 program were established to reduce the inter-
state transport of fine particulate matter [PM2 5)
• Concentrations of PM2 5 have decreased by approxi-
mately 18 percent in the warm season [May through
September) and 12 percent in the cool season [Oc-
tober through April) across states controlled for PM
under the CAIR rules
• Based on data gathered from 2007-2009, 92 percent
of the areas in the east originally designated nonat-
tainment for the 24-hour average PM2 5 standard now
have PM2.s air quality that is better than the standard
Human Health Benefits: An estimated 10,000 to 26,000
lives are saved annually due to the reductions in PM2 5 from
the CAIR rules
other parties requested a rehearing, and on December 23,
2008, the Court revised its decision and remanded CAIR to
EPA without vacatur. This ruling leaves CAIR and the CAIR
Federal Implementation Plans (FIPs) — including the CAIR
trading programs — in place until EPA issues new rules to
replace CAIR.
United States
Environmental Protection
Agency
January 2011
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
EPA is committed to issuing rules to replace CAIR that will
help states address the interstate air emissions transport
problem in a timely way and that fully comply with the
requirements of the Clean Air Act and the opinions of the
D.C. Circuit. EPA has developed a proposed Transport Rule
which, if finalized as proposed, would replace CAIR after
the end of the 2011 control periods. The proposed rule was
signed in July 2010, and is available online at .
Ozone
Ozone pollution forms when NOX and volatile organic com-
pounds (VOCs) react in the presence of sunlight. Ozone it-
self is rarely emitted directly into the air. Major sources of
NOX and VOC emissions include motor vehicles, solvents,
industrial facilities, and electric power plants.
Meteorology plays a significant role in ozone formation.
Dry, hot, sunny days are most favorable for ozone pro-
duction. In general, ozone concentrations increase during
the daylight hours, peak in the afternoon when the tem-
perature and sunlight intensity are highest, and drop in the
evening. Because ground-level ozone concentrations are
highest when sunlight is most intense, the warm summer
months (May 1 to September 30) are known as the ozone
season.
Ozone Impacts on Human Health and Ecosystems
Exposure to ozone has been linked to a variety of health
effects, the severity of which depends on concentration,
length of exposure, and breathing rate. At levels found in
many urban areas, ozone can aggravate respiratory dis-
eases such as asthma, emphysema, and bronchitis, and can
increase susceptibility to respiratory infections. More seri-
ous effects include emergency department visits, hospital
admissions, and premature mortality.
Scientific evidence also continues to show that repeated
exposure to ozone damages sensitive vegetation, including
some tree, crop, and native plant species. Such effects can
include reduced growth and productivity, damaged foliage,
and increased susceptibility to disease, insect pests, and
other stresses (e.g., harsh weather). Ozone-related dam-
age can lead to ecosystem-level changes such as loss of
diversity.
For more information on the health and environmental ef-
fects of ground-level ozone, visit .
Ozone Standards
The Clean Air Act (CAA) requires EPA to set National Ambi-
ent Air Quality Standards (NAAQS) for ground-level ozone
and five other criteria pollutants. The CAA established
two types of national air quality standards for ground-
level ozone. Primary standards set limits to protect public
health, including the health of "sensitive" populations such
as asthmatics, children, and the elderly. Secondary stan-
dards set limits to protect public welfare, including protec-
tion against visibility impairment and damage to animals,
crops, vegetation, and buildings. The CAA requires EPA to
review the latest scientific information and standards ev-
ery five years.
In the 1970s, EPA established the NAAQS for ozone. A
1-hour standard of 0.08 parts per million (ppm) was set in
1971 and revised to 0.12 ppm in 1979. In 1997, a new, more
stringent 8-hour ozone standard of 0.08 ppm was promul-
gated, revising the 1979 standard. In March 2008, EPA
changed the 8-hour ozone standard to 0.075 ppm. Howev-
er, in September 2009, EPA announced it would reconsider
its 2008 decision. EPA is reconsidering the standards to
ensure they are clearly grounded in science, protect public
health with an adequate margin of safety, and are sufficient
to protect the environment. In January 2010, EPA proposed
stricter standards for ground-level ozone — in the range of
0.060 to 0.070 ppm measured over eight hours. As part of
Figure 1: Transition from the NBP to CAIR
• CAIR states controlled
for fine particles
• CAIR states controlled
for ozone
CAIR states controlled for both
^1 fine particles and ozone
Note: In a November 2009 rule, EPA stayed the effectiveness of
CAIR for Minnesota, which had previously been among the states
controlled for fine particles.
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
EPA's extensive review of the science, Administrator Jack-
son has asked the Clean Air Scientific Advisory Committee
(CASAC) for further interpretation of the epidemiological
and clinical studies they used to make their recommenda-
tion. To ensure EPA's decision is grounded in the best sci-
ence, EPA will review the input CASAC provides before the
new standard is selected. Given this ongoing scientific re-
view, EPA intends to set a final standard in the range rec-
ommended by the CASAC by the end of July 2011.
CAIR NOX Ozone Season Program
The CAIR NOX ozone season program was established to
reduce interstate transport of ozone during the summer
months and help eastern U.S. counties attain the 1997
ozone standard. The CAIR NOX ozone season program
applies to electric generating units (EGUs) as well as, in
some states, large industrial units that produce electricity
or steam primarily for internal use and were carried over
from the NBP. The CAIR NOX ozone season requirements
apply to all states from the former NBP except Rhode Is-
land, and to six additional eastern states (Arkansas, Flor-
ida, Iowa, Louisiana, Mississippi, and Wisconsin). In addi-
tion, while only parts of Alabama, Michigan, and Missouri
were in the NBP, the CAIR NOX ozone season requirements
apply to these states in their entirety. In Figure 1 on page 2
the states colored yellow and green are those that are sub-
ject to the CAIR NOX ozone season program.
CASTNET
The Clean Air Status and Trends Network (CASTNET)
is the only long-term monitoring network designed
to assess trends in regional (rural) ozone levels and
acidic dry deposition. Sites are equipped with an
ozone analyzer and a three-stage filter pack to collect
total weekly gaseous (i.e., nitric acid) and particulate
(i.e., nitrate) concentrations. Each site also measures
a suite of meteorological parameters which are used
to model dry deposition fluxes of the acidic pollut-
ants. Many of the monitoring sites have been running
continuously for over 15 years, making the network
ideal for long-term trends analyses. Regional trends
in ozone levels from CASTNET sites have been used to
assess emission reduction programs, such as the NBP
and Acid Rain Program (ARP). CASTNET data will now
be used to determine baselines and regional ozone
trends for CAIR and future reduction programs. Fig-
ure 2 shows the 59 CASTNET sites used in this report's
analysis of trends in rural ozone, sulfate and nitrate
concentrations. These sites met data completeness
criteria and are located in CAIR states or within 200
kilometers (km) of a CAIR state's border.
Figure 2: CASTNET Monitoring Stations
CASTNET Sites
^ EPA o National Park Service
EZI
ED
CAIR states controlled
for fine particles
CAIR states controlled
for ozone
CAIR states controlled for both
fine particles and ozone
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
The first year of implementation of the CAIR NOX ozone
season program was 2009. In 2009, there were 3,279 EGUs
and industrial facility units in the program and NOX emis-
sions from those sources were approximately 495,000
tons.
To better understand how the CAIR NOX ozone season
program affected ozone formation in the atmosphere, this
report examines changes in ozone concentrations before
and after implementation of CAIR. The report compares
regional and geographic trends in ozone levels to changes
in meteorological conditions (such as temperature) and
NOX emissions from CAIR sources. This report also ex-
plores changes in human health and forest ecosystems due
to ground-level ozone effects as well as changes in nitrate
concentration.
Measuring and Evaluating Changes in Ozone
Two long-term monitoring networks measure ozone lev-
els as well as meteorological and other air quality data
throughout the United States. Monitoring sites used for
regulatory compliance are located mainly in urban areas
and report data to EPAs Air Quality System (AQS). Sites
in EPAs Clean Air Status and Trends Network (CASTNET)
measure trends in ozone at rural sites. The changes in
eastern ozone concentrations presented in this report de-
Figure 3: Weekly Average of Maximum Ozone Season Daily Temperatures, 2006-2009
pict data from AQS and CASTNET monitoring sites located
within both CAIR and adjacent states. These analyses show
a range of ozone reductions based on the metric used and
the years examined.
Meteorological Effects on Environmental Trends
Detecting trends or causal effects in air quality requires
several data points or multiple-year averages because of
natural variability in environmental measurements and
meteorology. EPA uses a regression model for trends anal-
ysis that partially adjusts for the variability in weather.
Figure 3 shows the weekly average of maximum daily tem-
peratures during the NOX ozone season at CASTNET sites
included in the CAIR region that met the data complete-
ness criteria. During the first year of CAIR, 2009, the ozone
season months were cooler on average than those months
during the 2006-2008 time period, making it important
to account for meteorological effects when assessing any
trends in air pollution after CAIR was implemented (see
page 8 for an analysis of ozone trends using meteorologi-
cally adjusted data).
O
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0
30
25
20
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Q.
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£ 10
2006-2008
Source: EPA, 2010
May
Jun
Jul
Aug
Sep
Oct
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Changes in 1 -Hour Ozone Concentrations in the East
EPA examined changes in unadjusted regional 1-hour
ozone concentrations, as measured at urban (AQS) and ru-
ral (CASTNET) sites. Results demonstrate how NOX emis-
sion reduction policies have affected ozone concentrations
in the eastern United States. Figure 4 shows changes in
the 99th percentile of 1-hour ozone concentrations be-
tween 2000-2002 (before implementation of the NBP)
and 2007-2009 (under the NBP and first year of CAIR NOX
ozone season program implementation). Using this metric,
an overall regional reduction in ozone levels was observed
between these two time periods, with an average reduc-
tion in ozone concentrations in CAIR states of 16 percent.
This reduction represents the greatest three-year average
decrease in ozone concentrations since the NBP program
began in 2003.
Figure 4: Percent Change in 1-Hour Ozone Concentrations
during the Ozone Season, 2000-2002 versus 2007-2009
' •' ;• ,* V •- : •'•'• .'.Ozone
:• .'o-rS'- -
1 : ..-.- • v- ' 99th Percentlle
(% change)
.•>!.•-••'' • • " . | -14--10
$•'.'*••
•a
e-10
Source: EPA, 2010
Changes in Rural Ozone Concentrations
Rural ozone measurements are useful in assessing the im-
pacts on air quality resulting from regional NOX emission
reductions because these monitoring sites are typically
less affected by local sources of NOX (e.g., industrial, auto-
motive, and power generation sources) than urban mea-
surements. Consequently, the formation of ozone in these
areas is particularly sensitive to changes in levels of region-
al NOX emissions. The majority of reductions in rural ozone
concentrations can therefore be attributed to reductions
in regional NOX emissions and transported ozone. EPA in-
vestigated trends in both rolling 8-hour and 1-hour ozone
concentrations as measured at CASTNET monitoring sites
within the CAIR NOX ozone season region and in adjacent
states (states within 200 km of a CAIR NOX ozone season
state's borders).
Regional Trends in Ozone
An Autoregressive Integrated Moving Average (ARIMA)
model was used to determine the trend in ozone concen-
trations since the inception of various programs geared
towards reducing NOX emissions. The ARIMA model is an
advanced statistical analysis tool that can evaluate trends
over time (time series analysis). The average of the 99th
percentile of the 8-hour daily maximum ozone concentra-
tions (the highest daily levels of ozone) measured at CAST-
NET sites during the CAIR NOX ozone season was modeled
(Figure 5). The ARIMA model shows that between 1990
and 2003, the average of the 99th percentile of ozone con-
centration was 89 parts per billion (ppb). After 2004, the
year by which the majority of NBP affected states began
Figure 5: Shift in 8-Hour Seasonal Rural Ozone Concentra-
tions in the CAIR NOX Region, 1990-2009
1 IU
100
? 90
Q_
- 80
O
1 70
g 60
i so
i! 40
<§ 30
20
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n
0
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— I,
°
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
o Actual — Model Estimate D 95% Confidence Band
Note: Ozone concentration data are from CASTNET sites that met
completeness criteria and are located in and adjacent to the CAIR
NOX region.
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
compliance, a statistically significant shift occurred and a
new trend was established, with an average ozone level of
74 ppb. The ARIMA model shows a statistically significant,
17 percent (15 ppb) decrease in ozone concentrations be-
ginning at the start of the NBP, suggesting that this program
is a major contributor to these regional improvements in
ozone. In 2009, the first compliance year of the new CAIR
NOX programs, ozone concentrations were the lowest over
the 20-year period. Ozone concentrations were down 27
ppb (29 percent) in 2009 versus 1990.
The large improvements in ozone concentrations shown
in Figure 5 on page 5 result from the establishment of the
NBP in 2003, which CAIR now carries forward. Emission
controls in place primarily from the NBP are responsible
for these improvements. The significant decrease in ozone
levels evident in Figure 5 is not the result of the recent eco-
nomic downturn, given that the large drop in ozone con-
centrations predated the economic downturn. Moreover,
emission rates for fossil generation have declined remark-
ably to capped levels established under the NBP and have
been to shown to be binding in a viable trading market.
Site-Specific Changes in Rural Ozone
Changes in hourly ozone concentrations at CASTNET sites
located in or within 200 km of a state's border which par-
ticipates in the CAIR NOX ozone season program are shown
in Figure 6. The percent difference in the average of the
99th percentile for 2000-2002 versus 2007-2009 was
calculated for each site which met the completeness crite-
ria. The 99th percentile is used to represent the change in
extreme ozone concentrations. The largest reductions oc-
curred downwind of the Ohio River Valley where the great-
est reductions in NOX emissions were realized. There are
a total of 19 CASTNET sites with reductions greater than
20 percent. Abington, CT (ABT147) showed the great-
est decrease in 99th percentile average ozone concentra-
tion with a 31 percent reduction between 2000-2002 and
2007-2009. To determine whether the percent difference
was statistically significant, a p-value was calculated using
a Student's t-test. Sites with significant changes at the 90
percent confidence level are noted with a star.
Figure 6: Percent Difference in 99th Percentile Hourly Ozone Values during the Ozone Season, 2000-2002 versus 2007-2009
CAIR states controlled
for fine particles
CAIR states controlled
for ozone
CAIR states controlled for both
fine particles and ozone
Percent Difference
A Greater than 28%
21% to 28%
Q 14% to 21%
7% to 14%
Less than 7%
Significant Change
(at 90% confidence level)
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Figure 7: Changes in the Monthly Distribution of Ozone
Outside of the Ozone Season (January)
During the Ozone Season (June)
o>
e
o>
Q_
0 10 20 30 40 50 60
Ozone (ppb)
70 80 90 100
^ Ozone concentration 2000-2002
Source: EPA, 2010
Changes in the Monthly Distribution of Ozone
An additional statistical analysis shows that the monthly
distribution of 8-hour daily maximum ozone concentra-
tions has shifted to lower concentrations. This shift has oc-
curred in the CAIR region during the ozone season since
implementation of the NBP and CAIR program. Figure 7
depicts every 8-hour daily maximum value measured in
January and June (where January represents months out-
side the ozone season and June represents months within
the ozone season) for two time periods. The blue lines rep-
resent ozone concentrations before implementation of the
NBP and CAIR program (2000-2002), while the red lines
represent ozone concentrations after implementation of
the NBP and CAIR Program (2007-2009). The y-axis rep-
resents the percent of the total number of days in a month
with measurements at a specific ozone ppb level.
As the right-hand graph in Figure 7 shows, there is a no-
ticeable shift toward lower ozone concentration during
the ozone season (represented by the red arrow). As NOX
emission controls were turned on at sources subject to the
NBP and CAIR program, there have been fewer days with
high levels of ozone during the ozone season. In months
outside the ozone season (represented by the month of
January), there is little to no shift.
As Table 1 shows, the 99th percentile of 8-hour ozone
dropped by 6-15 ppb during the ozone season, while there
were very little (February and March) to no significant
changes in the months outside of the ozone season (except
for October).
0 10 20 30 40 50 60 70 80 90 100
Ozone (ppb)
Ozone concentration 2007-2009
The downward shift in the monthly distribution of ozone
levels in the CAIR region is indicative of broader, substan-
tial change in ozone concentrations due in significant part
to the NBP and CAIR programs.
Table 1: Shift in 8-Hour Ozone Concentration by Month,
2000-2002 versus 2007-2009
Change in 99th Percentile 8-Hour
Month Ozone Concentration
January
February
March
April
May
June
July
August
September
October
November
December
No statistically significant shift
Down 3 ppb
Down 2 ppb
No statistically significant shift
Down 6 ppb
Down 12 ppb
Down 15 ppb
Down 11 ppb
Down 7 ppb
Down 12 ppb
No statistically significant shift
No statistically significant shift
Note: Months within the ozone season are shaded.
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Changes in 8-Hour Ozone Concentrations
Daily maximum 8-hour ozone concentration data were as-
sessed from 70 urban AQS areas and 34 rural CASTNET
sites located in the CAIR NOX ozone season program region.
For a monitor or area to be included in this trend analysis,
it had to provide complete and valid data for 50 percent
of the ozone season days for each of the years from 1997-
2008. In addition, urban AQS areas often include more than
one monitoring site. In these cases, the site with the high-
est observed ozone concentration for each day was used.
Figure 8 shows the AQS and CASTNET monitoring sites in
the CAIR NOX ozone season program region that met these
completeness criteria.
Ozone Changes after Adjusting for Meteorology
As noted earlier, weather plays an important role in deter-
mining ozone levels. Accordingly, EPA uses a generalized
linear model to describe the relationship between daily
ozone and several meteorological parameters.1 The model
accounts for the variation in seasonal ozone across differ-
ent years by correcting for meteorological fluctuations.
The most important meteorological parameters consid-
ered in this model are daily maximum 1-hour tempera-
Figure 8: Location of Urban and Rural Ozone Monitoring Sites
) Urban area (AQS)
(Rural site (CASTNET)
CAIR states
| | controlled for
fine particles
CAIR states
controlled for
both fine particles
and ozone
CAIR states
I I controlled
for ozone
Note: Urban areas represent multiple monitoring sites.
Rural areas represent single monitoring sites.
Source: EPA, 2010
8
ture and midday (10 a.m. to 4 p.m.) relative humidity. This
methodology and the subsequent ozone estimates are pro-
vided by EPA's Office of Air Quality Planning and Standards
(OAQPS), Air Quality Assessment Division.
Figure 9 shows trends in the seasonal average daily maxi-
mum 8-hour ozone concentrations in the CAIR NOX ozone
season region before and after adjusting for the influence
of weather.2 For example, lower temperatures and higher
relative humidity in the CAIR NOX ozone season region
during the 2004 ozone season dampened ozone formation,
while higher temperatures and lower relative humidity
in the 2007 ozone season increased ozone formation. Re-
moving the effects of weather results in a higher-than ob-
served ozone estimate for 2004 and a lower-than observed
ozone estimate for 2007. The firstyear of CAIR, 2009, was a
cooler year than the 2006-2008 time period, however the
meteorologically-adjusted trend still indicates a decrease
in ozone concentrations. Therefore, decreases in ozone
concentrations in 2009 are due not only to cooler tempera-
tures, but also to emission reductions. Three-year averages
will be used in 2011 to assess the air quality impact of the
CAIR NOX reductions with more confidence.
Figure 9: Seasonal Average of 8-hour Ozone Concentrations in
CAIR States before and after Adjusting for Weather
70
60
50
.Q
Q.
S 40
c 30
8
c
o
20
o
N
O
10
Start of NBP
1997 1999 2001 2003 2005 2007 2009
^^^— Adjusted for Weather
• • • Unadjusted for Weather
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
A closer look at the meteorologically-adjusted ozone trends
since the start of the NBP in 2003 indicates that these re-
ductions are substantive and sustainable. The average
reduction in seasonal daily maximum 8-hour ozone con-
centrations measured in the CAIR NOX region in the 2000-
2002 and 2007-2009 time periods was about 9 percent. Af-
ter considering the influence of weather, the improvement
in daily maximum 8-hour ozone concentrations between
these three-year periods was 13.5 percent. A comparison
of single year meteorologically-adjusted ozone reveals an
18 percent reduction between 2002 and 2009.
Furthermore, the pace of these reductions has increased
since implementation of the NBP and subsequent CAIR
NOX ozone season program. Between 1997 and 2002,
ozone fell by 3 percent, while between 2002 and 2009,
ozone dropped by 18 percent. This is consistent with the
downward trend in NOX emissions.
Figure 10: NOX Emission Reductions and Adjusted Seasonal 8-hour Ozone Concentration Changes in CAIR NOX Ozone Season States
Linking Ozone and NOX Emissions
Figure 10 is a snapshot depicting the relationship between
reductions in NOX emissions from CAIR NOX ozone season
program sources and reductions in 8-hour average ozone
after implementation of the NBP and CAIR. As indicated
previously, between 2002 and 2009, ozone decreased
across all CAIR NOX ozone season program states (after ad-
justing for meteorology) by an average of 18 percent. The
largest reductions occurred in Tennessee, Illinois, Virginia,
Mississippi, North Carolina, Pennsylvania, and Connecticut.
Source: EPA, 2010
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Changes in Ozone Nonattainment Areas
In April 2004, EPA designated 126 areas as nonattainment
for the 8-hour ozone standard adopted in 1997, of which
113 designations took legal effect.3 These designations
were made using data from 2001-2003. Of those areas, 92
are in the East (as shown in Figure 11) and are home to
about 103 million people.4 Based on data gathered from
2007-2009, 86 of these original eastern nonattainment
areas show concentrations below the level of the 1997
ozone standard (0.08 ppm), indicating improvements in
ozone. Improvements in these 86 areas mean that 93 per-
cent of the original nonattainment areas in the East now
have ozone air quality that is better than the standard un-
der which they were originally designated nonattainment.
These improvements bring cleaner air to over 87 million
people. The majority of these areas have officially been re-
designated to attainment or maintenance, as described in
Section 107 of the Clean Air Act.
Figure 11: Changes in Nonattainment Areas in the CAIR
Region, 2001-2003 (Original Designations) versus 2007-2009
Attained 1997 8-hour ozone NAAQS (85 areas)
Above NAAQS, showing improvement (4 areas)
Incomplete data for 2007-2009 (2 areas)
CAIR States (controlled for PM and/or ozone)
Note: Previous NBP progress reports included Early Action Compact
(EAC) areas as areas of nonattainment. Those areas were switched
to attainment/unclassified status before the nonattainment desig-
nation took legal effect and are not included in this analysis of CAIR
nonattainment areas. For more information on EACs please visit
Source: EPA, 2010
Six of the original 92 areas in the East continue to exceed
the level of the standard. In the four largest of these areas,
however, ozone concentrations have fallen by an average
of 13 percent. Because of the reductions in these four ar-
eas, over 15 million Americans living in these areas are ex-
periencing better air quality. The other two areas do not
have sufficient recent ozone data to quantify their change
in ozone.
Given that the majority of relevant NOX emission reduc-
tions occurring after 2003 are attributable to the NBP and
CAIR, it is reasonable to conclude that these NOX reduction
programs have been a significant contributor to these im-
provements in ozone air quality.
Ozone Impacts on Forests
Air pollution can impact the environment and affect eco-
logical systems, leading to changes in the ecological com-
munity and influencing the diversity, health, and vigor of
individual species. Ground-level ozone has been shown in
numerous studies to have a strong effect on the health of
many plants, including a variety of commercial and ecolog-
ically important forest tree species throughout the United
States.5
When ozone is present in the air, it can enter a plant through
pores in its leaves known as stomata and cause significant
cellular damage. This damage can compromise the abil-
ity of the plant to produce sugars during photosynthesis.
The remaining energy resources of the plant are further
depleted as leaves attempt to repair or replace damaged
tissue. This loss of energy resources can lead to reduced
growth and/or reproduction and health of plants. Ozone
stress also increases the susceptibility of plants to disease,
insects, fungus, and other environmental stresses (e.g.,
harsh weather). Because ozone damage can also cause vis-
ible injury to leaves, it can reduce the aesthetic value of or-
namental vegetation and trees, and negatively affect scenic
vistas in protected natural areas.
Assessing the impact of ground-level ozone on forests in
the eastern United States involves understanding the risk
to tree species from ambient ozone concentrations and ac-
counting for the prevalence of those species within the for-
est. The more abundant ozone-sensitive tree species are in
a community, the larger the impact on the community as a
whole. As a way to quantify the risk to particular trees, sci-
entists have developed concentration-response (C-R) func-
tions which relate ozone exposure to tree response. Tree
seedling C-R functions are determined by exposing tree
seedlings to different ozone levels and measuring reduc-
tions in growth as "biomass loss." In areas where certain
species dominate the forest community, the biomass loss
10
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
from ozone can be significant. In this analysis, biomass loss
is used as an indicator for the effects of ozone on the forest
ecosystem.
Some of the common tree species in the eastern United
States that are sensitive to ozone are black cherry (Prunus
serotind), yellow or tulip-poplar (Liriodendron tulipiferd),
sugar maple [Acer saccharum), eastern white pine [Pinus
strobus), Virginia Pine [Pinus virginiand), red maple [Acer
rubrum), and quaking aspen [Populus trenuloides). To es-
timate the biomass loss for forest ecosystems across the
eastern United States, the biomass loss for each of the sev-
en tree species was calculated using the three-month, 12-
hour W126 exposure metric6 at each location, along with
each tree's individual C-R functions. The W126 exposure
metric was calculated using monitored ozone data from
CASTNET and AQS sites, and a three-year average was
used to minimize the effect of variations in meteorological
and soil moisture conditions. The biomass loss estimate
for each species was then multiplied by its prevalence in
the forest community using the U.S. Department of Agri-
culture (USDA) Forest Service IV index of tree abundance
calculated from Forest Inventory and Analysis (FLA) mea-
surements.7 This analysis compared two time periods:
2000-2002 (before the NBP) and 2007-2009 (under the
NBP and first year of the CAIR NOX ozone season program)
and demonstrates the benefit to forest ecosystems from
decreasing ozone concentrations during these two time
periods.
Since implementation of the NBP and CAIR, the number of
areas with significant biomass loss (more than 2 percent)8
due to ozone was 16 percent for the period of 2007-2009,
down from 37 percent for the period of 2000-2002 for all
seven tree species across their range in the East (see Fig-
ure 12). Of these seven species, the black cherry, yellow
poplar, eastern white pine, and quaking aspen are the most
sensitive to ozone. For these species' individual response,
Figure 12: Estimated Average Biomass Loss of Selected Species due to Ozone Exposure, 2000-2002 versus 2007-2009
Pre-NBP Implementation
Average Biomass Loss, 2000-2002
Post-NBP and CAIR Implementation
Average Biomass Loss, 2007-2009
Biomass (% Loss)
< 1%
1 to 3%
3 to 6%
6 to 9%
> 9 % (Max 23%)
1 to 3%
3 to 6%
6 to 9%
>9%(Max13.4%)
Source: EPA, 2010
11
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
the areas with significant biomass loss decreased on aver-
age by 17 percent, with quaking aspen and eastern white
pine showing the most improvement. The remaining three
tree species — red maple, sugar maple and Virginia pine —
are no longer predicted to experience significant biomass
loss across their range. While this change in biomass loss
cannot be exclusively attributed to the implementation of
the NBP and CAIR, it is likely that NOX emission reductions
and the corresponding decreases in ozone concentration
occurring under the NBP and CAIR contributed to this en-
vironmental improvement. Also, other environmental fac-
tors, such as soil moisture, that can affect ozone damage
were not considered in this analysis.9
Changes in Nitrate
NOX is emitted from a source as nitric oxide (NO) and ni-
trogen dioxide (NC^). Once in the air, several chemical re-
actions occur, depending on meteorological conditions and
concentrations of other pollutants in the atmosphere. NOX
contributes to the formation of many secondary pollutants,
including particulate nitrate (NOs), nitric acid (HNOs),
ozone, and organic compounds. For example, ozone is pro-
duced when N02, volatile organic compounds (VOCs), and
sunlight are present.
Generally, NOX is removed directly from the atmosphere by
dry deposition of nitric acid and particulate nitrates, and
wet deposition of dissolved nitrates. Nitrate deposition can
be harmful to sensitive ecosystems, vegetation, and water
bodies by causing eutrophication, changes in biological
communities, and an increased sensitivity to changes in
the environment. Because the majority of NOX in the CAIR
NOX region is removed from the atmosphere over a period
of four to nine days, nitrogen deposition from transported
NOX emissions may still affect areas that are considerable
distances from NOX emission sources.
As facilities install and use control technologies, reducing
the amount of NOX emitted in the CAIR NOX region, the
amount of NOX secondary pollutants also decreases. To
determine the trend in total nitrate since the inception of
various programs geared towards reducing NOX emissions,
an ARIMA model was used to assess changes in the aver-
age of median total nitrate concentrations as measured at
CASTNET sites located in the CAIR NOX region during the
ozone season (see Figure 13). The ARIMA model illustrates
that between 1990 and 2003, total nitrate concentrations
averaged about 3 ug/m3. After 2004, the year by which the
majority of NBP affected states began compliance, a statis-
tically significant shift occurred and a new trend was estab-
lished with an average concentration of 2 ug/m3. Similar
to the shift observed for ozone concentrations, the ARIMA
model shows a statistically significant, 33 percent (1 ug/
m3) decrease in total nitrate since the start of the NBP, sug-
gesting that the NBP was a significant contributor to these
improvements in total nitrate. In 2009, the first compliance
year of the new CAIR NOX programs, nitrate concentrations
were the lowest over the 20-year period.
Figure 13: Shift in Seasonal Nitrate Concentrations at Rural
Sites in the CAIR Region, 1990-2010
o
3.5
CO
£ 3.0
O)
n.
^ 2.5
o
I 2.0
1.5
0.5
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
o Actual — Model Estimate O 95% Confidence Band
Note: Total nitrate concentration data are from CASTNET sites that
met completeness criteria and are located in and adjacent to the
NBP region.
Source: EPA, 2010
12
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Particulate Matter
"Particulate matter," also known as particle pollution or
PM, is a complex mixture of extremely small particles and
liquid droplets. Particle pollution is made up of a number
of components, including acids (such as nitrates and sul-
fates), organic chemicals, metals, and soil or dust particles.
Fine particles (PM2 5) can form when gases emitted from
power plants, industrial sources, automobiles, and other
sources react in the air.
Particulate Matter Impacts on Human Health and Ecosystems
Particle pollution — especially fine particles — contains
microscopic solids or liquid droplets that are so small that
they can get deep into the lungs and cause serious health
problems. Numerous scientific studies have linked par-
ticle pollution exposure to a variety of problems, includ-
ing: increased respiratory symptoms, such as irritation of
the airways, coughing, or difficulty breathing; decreased
lung function; aggravated asthma; development of chronic
bronchitis; irregular heartbeat; nonfatal heart attacks; and
premature death in people with heart or lung disease.
Particles can be carried over long distances by wind and
then settle on ground or water. The effects of this settling
include: making lakes and streams acidic; changing the
nutrient balance in coastal waters and large river basins;
depleting the nutrients in soil; damaging sensitive forests
and farm crops; and affecting the diversity of ecosystems.
For more information on the health and environmental
effects of particulate matter, visit .
Particulate Matter Standards
The CAA requires EPA to set NAAQS for particle pollution.
The first PM standard for fine particles was set by EPA in
1997 at 65 micrograms per cubic meter (ug/m3) for 24-
hour exposure and at 15 ug/m3 for annual exposure. EPA
revised the air quality standards for particle pollution in
2006. The 2006 standards tighten the 24-hour fine particle
standard from the current level of 65 micrograms per cu-
bic meter (ug/m3) to 35 ug/m3, and retain the current an-
nual fine particle standard at 15 ug/m3.
CAIR Annual Programs
The CAIR NOX annual program and CAIR SC>2 program
were established to address the interstate transport of
PM2.5 pollution throughout the year and help eastern U.S.
counties attain the PM2.5 annual standard. These programs
generally apply to large electric generating units (EGUs) —
boilers, turbines, and combined cycle units used to gener-
ate electricity for sale. The CAIR annual programs apply in
all of the CAIR NOX ozone season states except Connecticut,
Massachusetts, and Arkansas, and also in Texas and Geor-
gia. In Figure 1 on page 2, the states colored blue and green
are those that are subject to the CAIR annual programs and
controlled for fine particles.
The first year of implementation of the CAIR NOX annual
program was 2009. In 2009, there were 3,321 EGUs in the
program and NOX emissions from those sources were ap-
proximately 1.3 million tons. Implementation of the CAIR
SC>2 program began in 2010. However, all the CAIR SC>2 pro-
gram facilities participated in a monitoring and reporting
training year in 2009. With the exception of a small num-
ber of facilities with pending applicability questions, all
participating units reported data in 2009. Their total SC>2
emissions in 2009 were approximately 5.0 million tons.
Several factors contributed to early reductions in SC>2 prior
to implementation of the CAIR SC>2 program in 2010. The
ability to use SC>2 allowances from the ARP to comply with
the CAIR SC>2 program served as a strong incentive from
2005-2009 for units subject to both programs to lower
SC>2 emissions in order to bank allowances for future use
under CAIR. For example, in 2009 37 EGUs subject to the
ARP added scrubbers to reduce SC>2 emissions. Thirty-four
of those units are also in the CAIR SC>2 program, suggest-
ing that the controls were installed to meet the emission
reductions that were required in 2010, the CAIR SC>2 pro-
gram's first compliance year. Another factor influencing
early SC>2 reductions was the recent economic downturn
that lowered demand for electric power. Between 2008
and 2009 there was a 7.5 percent drop in heat input, a sur-
rogate measure of electricity generation. Additionally, sev-
eral state programs and new source review (NSR) settle-
ments contributed to early SC>2 reductions.
To better understand how the CAIR annual programs will
affect PM2.s formation in the atmosphere, this report pres-
ents regional and geographic trends in PM2 5 levels prior to
implementation of any of the CAIR annual programs, and
for 2009, the first year of the CAIR NOX annual program
implementation.
13
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Measuring and Evaluating Changes in Particulate Matter
Average PM2i5 concentration data were assessed from
55 urban AQS areas located in the CAIR NOX annual pro-
gram region. For a monitor or area to be included in this
trend analysis, it had to provide complete and valid data
for at least 60 days in each of the years from 2001-2009.
In addition, urban AQS areas often include more than one
monitoring site. In these cases, the site with the highest ob-
served PM2.5 concentration for each day was used. Figure
14 shows the AQS monitoring sites in the CAIR NOX annual
program region that met these completeness criteria.
Trends in PM2.5 Concentrations
As with ozone, weather plays an important role in the for-
mation of PM (see Figure 3 for 2008 and 2009 weather
trends). EPA uses a statistical model to account for the
weather-related variability of PM2i5 concentrations to pro-
vide a more accurate assessment of the underlying trend in
the precursor emissions that cause PM2i5 formation. This
methodology and the subsequent PM2 5 estimates are pro-
vided by EPA's Office of Air Quality Planning and Standards
(OAQPS), Air Quality Assessment Division.
Figure 15 shows separate trends in PM2 5 concentrations in
the CAIR NOX annual program region for the warm months
(May to September) and cool months (October to April).
These separate graphs are shown due to the seasonal vari-
Figure 15: PM2.5 Seasonal Trends
Warm Season Trends
Figure 14: CAIR PM2.5 Monitoring Sites
2001
Source: EPA, 2010
2003 2005 2007 2009
— Adjusted for Weather
CAIR states
I I controlled
for fine particles
CAIR states
I I controlled
for ozone
CZI
CAIR states
controlled for
both fine particles
and ozone
Source: EPA, 2010
ability of the components that make up PM2 5 (explained
in more depth in the following section). After adjusting for
weather, PM2 5 concentrations have decreased by approxi-
mately 18 percent in the warm season and 12 percent in
the cool season between the 2001-2003 and 2007-2009
monitoring periods.
Cool Season Trends
18
16
14
12
10
0
2001 2003 2005
• Unadjusted for Weather
2007
2009
14
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Changes in PM2.5 Composition
The chemical composition of PM2i5 is characterized in
terms of five major components that generally comprise
the mass of PM2i5: sulfate, nitrate, organic carbon, elemen-
tal carbon, and crustal material. On average, sulfate is the
largest component by mass in the eastern U.S. and gener-
ally the largest sources of sulfate in the east are EGUs and
industrial boilers.
Composition of PM2i5 was analyzed in 91 metropolitan
and micropolitan areas (i.e., Core Based Statistical Areas)
within the CAIR region in 2005 and 2009. Results of this
analysis indicate that all of the areas studied, with com-
plete data, showed a decline in sulfate concentration as a
portion of PM2 5 between 2005 and 2009 (see Figure 16
for results in select cities). The CAIR annual SC>2 program
was not implemented until 2010, but results from the 2009
monitoring training year indicate that many sources made
emissions reductions early (see the Clean Air Interstate
Rule 2009 Emission, Compliance, and Market Analyses
report at ). Nitrate concentrations as a portion of PM2 5
decreased in about 87 percent of the areas between 2005
and 2009. In total, PM2 5 mass was down in all but two of
the areas studied (El Paso, Texas and Tallahassee, Florida).
Figure 16:2005 and 2009 Sulfate Concentration in PM2.5
\
2009
Scale: the largest bar
represents 6.28 pg/m3
in Pittsburgh, 2005.
CAIR states controlled
for fine particles
CAIR states controlled
for ozone
CAIR states controlled
for both fine particles
and ozone
Source: EPA, 2010
15
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Changes in PM2.s Nonattainment Areas
In January 2005, EPA designated 39 areas as nonattain-
ment for the annual average PM2.5 standard adopted in
1997, one of which was also designated nonattainment
for the 24-hour average PM2i5 standard.10 These designa-
tions were made using data from 2001-2003. Of those
areas, 36 are in the East (as shown in Figure 17) and are
home to about 88 million people.11 Based on data gathered
from 2007-2009, 33 of these original eastern areas show
concentrations below the level of the 1997 PM2i5 standard
(15.0 ug/m3), indicating improvements in PM2i5 air quality.
Improvements in these 33 areas mean that 92 percent of
the areas originally designated nonattainment in the East
now have PM2 5 air quality that is better than the standard
under which they were originally designated nonattain-
ment. These improvements bring cleaner air to over 69
million people. Many of these areas have applied to be offi-
cially redesignated to maintenance, as described in Section
107 of the CAA.
Three of the original 36 areas in the East continue to ex-
ceed the level of the PM25 standard. In two of these areas,
however, PM2 5 concentrations have fallen by an average
of 16 percent. Because of these reductions in PM2 5, over
800,000 Americans living in these areas are experiencing
better air quality. The other area does not have sufficient
recent PM2 5 data to quantify its change in air quality.
Figure 17: Changes in PM Nonattainment Areas in the CAIR
Region, 2001-2003 (Original Designations) versus 2007-2009
Attained 1997 Annual PM NAAQS (33 areas)
Above NAAQS, showing improvement (2 areas: Birmingham,
1 Alabama and Liberty-Clairton, Pennsylvania)
Incomplete data for 2007-2009 (1 area: Canton-Massillon, Ohio)
CAIR States controlled for PM and/or ozone are outlined.
Source: EPA, 2010
Given that the majority of relevant NOX and SC>2 emission
reductions occurring after 2003 are attributable to the
Acid Rain Program, NBP, and CAIR, it is reasonable to con-
clude that these emission reduction programs have been a
significant contributor to these improvements in PM2 5 air
quality.
Health Benefits
With 2009 ushering in the CAIR annual and ozone season
NOX programs, coupled with electricity generators pre-
paring for compliance with the CAIR annual SC>2 program,
2009 saw significant reductions in emissions of both NOX
and SC>2 by EGUs in the CAIR program. These reductions in
pollutants that are precursors to ground-level ozone and
ambient particulate matter can be expected to improve air
quality and human health.
Exposure to ground-level ozone and particulate matter has
been shown to adversely impact human health and wel-
fare. The 2009 PM2 5 Integrated Science Assessment12 and
the 2006 ozone criteria document13 identify the human
health effects associated with these ambient pollutants,
which include premature mortality and a variety of mor-
bidity effects associated with acute and chronic exposures.
PM welfare effects include visibility impairment and mate-
rials damage. Ozone welfare effects include damages to ag-
ricultural and forestry sectors. NOX welfare effects include
aquatic and terrestrial acidification and nutrient enrich-
ment.14 S02 welfare effects include aquatic and terrestrial
acidification and increased mercury methylation.14 Though
models exist for quantifying these ecosystem impacts, time
and resource constraints precluded quantifying those ef-
fects in this analysis.
Emission reductions for summer NOX were estimated as
the reduction in NOX emissions from CAIR units between
2008 and 2009, scaled by the reduction in heat input (to
account for reduced demand). It is difficult to discern emis-
sion reductions prior to 2008 because many states were
complying with the NBP at that time. S02 reductions attrib-
utable to CAIR were estimated as the difference between
2005 and 2009 monitored S02 emissions, scaled by the re-
duction in heat input (electricity demand) between those
two assessment years. While these two approaches differ,
they are both believed to be the most appropriate screen-
ing-level estimates available for each pollutant.
In order to assess the order of magnitude of CAIR benefits
in 2009, EPA performed a screening level assessment com-
bining reductions in S02 and NOX emissions that can large-
ly be attributed to CAIR with benefit per ton factors derived
from EPA's recent analysis of the proposed Transport Rule.
Summer NOX reductions were combined with summer NOX
16
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Table 2: Estimated Quantifiable PM2.5 Human Health Benefits
Largely Attributable to CAIR in 2009
Table 3: Estimated Quantifiable Ozone Human Health Benefits
Largely Attributable to CAIR in 2009
Incidences
PM2.5 Benefits Avoided Value (2006$)
Premature Mortality
Pope etal. (2002) (age > 30)
3% Discount Rate
7% Discount Rate
Laden etal. (2006) (age > 25)
3% Discount Rate
7% Discount Rate
Infant (<1 year)
Chronic Bronchitis
Non-fatal heart attacks (age > 18)
Hospital admissions — respiratory (all
ages)
Hospital admissions — cardiovascular
(all ages)
Emergency room visits for asthma (age
<18)
Acute Bronchitis (age 8-1 2)
Lower Respiratory Symptoms (age 7-14)
Upper Respiratory Symptoms (age 9-18)
Minor restricted-activity days (ages
18-65)
Lost work days (ages 18-65)
Asthma exacerbation (asthmatics 6-1 8)
10,000
26,000
43
6,400
15,000
2,400
5,100
9,600
15,000
170,000
130,000
7,400,000
1,200,000
160,000
$ 77,000,000,000
$ 71,000,000,000
$ 200,000,000,000
$ 180,000,000,000
$ 360,000,000
$ 2,900,000,000
$ 1,700,000,000
$ 33,000,000
$ 140,000,000
$ 3,500,000
$ 6,300,000
$ 3,200,000
$ 3,800,000
$ 440,000,000
$ 150,000,000
$ 8,600,000
Source: EPA, 2010
benefit per ton factors for ground-level ozone health end-
points to estimate CAIR benefits attributable to reductions
in ozone while annual SC>2 reductions were combined with
annual SC>2 benefit per ton factors for ambient PM2 5 health
endpoints to estimate CAIR benefits attributable to reduc-
tions in ambient PM2 5. Although annual reductions in NOX
would also contribute to reductions in PM2 5, EPA did not
develop annual NOX benefit per ton factors for ambient
PM25 for the proposed Transport Rule. Therefore, these
benefits were not quantified, adding to the conservative
scope of this assessment.
This analysis includes several independent estimates of the
relationship between premature mortality and exposure to
PM2 5 or ozone. The use of multiple estimates stems from
the conclusions of EPA's 2006 ozone criteria document13
and recommendations from the EPA Science Advisory
Board, the National Research Council, and the National
Academy of Sciences. For PM2 5 mortality, this analysis uses
two epidemiological studies, Pope et al. 2002 and Laden
et al. 2006 to represent the low end and high end respec-
Incidences
Ozone Benefits Avoided Value (2006$)
Premature Mortality
Multi-city and NMMAPS
Bell etal. (2004) (all ages)
Schwartz etal. (2005) (all ages)
Huang etal. (2005) (all ages)
Meta-analyses
Ito etal. (2005) (all ages)
Bell etal. (2005) (all ages)
Levy et al. (2005) (all ages)
Hospital admissions — respiratory (ages > 65)
Hospital admissions — respiratory (ages < 2)
Emergency room visits for asthma (all ages)
School absence days
Minor restricted-activity days (ages 18-65)
39
60
65
180
130
180
280
220
180
80,000
230,000
$ 320,000,000
$ 500,000,000
$ 540,000,000
$ 1,500,000,000
$ 1,100,000,000
$ 1,500,000,000
$ 6,700,000
$ 2,200,000
$ 65,000
$ 7,200,000
$ 14,000,000
Source: EPA, 2010
lively of premature mortality estimates. For ozone mortal-
ity, this analysis uses six epidemiological studies including:
three multi-city studies (including the National Morbidity,
Mortality and Air Pollution Study [NMMAPS]) and three
meta-analyses of multi-city and single-city studies. For
more information on the selected estimates, please refer to
EPA's Regulatory Impact Analysis for the Proposed Federal
Transport Rule at .
The results of this screening-level assessment, shown in
Table 2, indicate that the total assessed human health ben-
efits of CAIR in 2009 due to changes in PM2i5 from reduc-
tions in annual SC>2 emissions were between $83 and $200
billion annually using a 3 percent discount rate and be-
tween $76 and $190 billion annually using a 7 percent dis-
count rate (all benefits are cited in 2006 dollars).15 Benefits
from decreased ground-level ozone due to reductions in
summer NOX emissions attributable to CAIR are expected
to have added between $0.35 billion and $1.5 billion (see
Table 3). A majority of this monetized benefit comes from
incidences of premature mortality avoided — 10,000 to
26,000 incidences annually due to PM2i5 benefits and 39 to
180 incidences annually due to ozone benefits. Other end-
points evaluated in this assessment include nonfatal heart
attacks, hospital and emergency room visits, bronchitis,
and asthma.
17
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The Clean Air Interstate Rule: 2009 Environmental and Health Results
Notes
i Cox, W. M. & Chu, S.H. 1996. Assessment of interannual ozone variation in urban areas from a climatological perspective. Atmospheric Envi-
ronment 30:16, 2615-2625.
Camalier, L., Cox, W.M. & Dolwick, P. 2007. The effects of meteorology on ozone in urban areas and their use in assessing ozone trends. At-
mospheric Environment. 41:33, 7127-7137.
2 The seasonal average ozone concentration is calculated as the average of the daily maximum 8-hour ozone levels during the ozone season.
These results provide a combined seasonal average for NBP states and do not show variations in ozone concentrations for specific urban or
rural areas.
3 40 CFR Part 81. Designation of Areas for Air Quality Planning Purposes.
4 U.S. Census. 2000.
5 U.S. EPA. 2007. Review of the National Ambient Air Quality Standards for Ozone, Policy Assessment of Scientific and Technical Information.
OAQPS Staff Paper. EPA-452/R-07-003. This document is available in Docket EPA-HQ-OAR-2003-0190 and online at . Northeastern Research Station, USDA Forest Service.
8 Areas with more than 2 percent biomass loss are defined here as significant based on a consensus workshop on ozone effects, which re-
ported that a 2 percent annual biomass loss causes harm because of the potential for compounding effects over multiple years as short-term
negative effects on seedlings affect long-term forest health. See:
Heck, W.W. &Cowling E.B. 1997. The need for a long term cumulative secondary ozone standard - an ecological perspective. Environmental
Management, January, 23-33.
9 Chappelka, A.H. and Samuelson, L.J. 1998. Ambient ozone effects on forest trees of the eastern United States: A review. New Phytologist 139:
91-108.
1° 40 CFR Part 81. Designation of Areas for Air Quality Planning Purposes.
11 U.S. Census. 2000.
12 U.S. Environmental Protection Agency (U.S. EPA). 2009d. Integrated Science Assessment for Particulate Matter (Final Report). EPA-600-R-
08-139F. National Center for Environmental Assessment - RTF Division. December. Available on the Internet at .
13 U.S. Environmental Protection Agency (U.S. EPA). 2006a. Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final).
EPA/600/R-05/004aF-cF. Washington, DC: U.S. EPA. February. Available on the Internet at .
14 U.S. Environmental Protection Agency (U.S. EPA). 2008f. Integrated Science Assessment for Oxides of Nitrogen and Sulfur -Ecological Cri-
teria National (Final Report). National Center for Environmental Assessment, Research Triangle Park, NC. EPA/600/R-08/139. December.
Available on the Internet at .
15 Results reflect the use of 3 percent and 7 percent discount rates consistent with EPA and OMB guidelines. Further discussion of the choice of
discount rate appears in EPA's Guidelines for Preparing Economic Analyses. EPA 240-R-00-003. National Center for Environmental Econom-
ics, Office of Policy Economics and Innovation. Washington, DC. September. Available on the Internet at
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