Clean Air Interstate Rule, Acid Rain Program and Former NOx Budget Trading Program
The Clean Air Interstate Rule (CAIR) and the Acid Rain
Program (ARP) are both cap and trade programs de-
signed to reduce emissions of sulfur dioxide (S02) and
nitrogen oxides (N0X) from power plants.
The ARP, established under Title IV of the 1990 Clean Air
Act (CAA) Amendments, requires major emission reduc-
tions of S02 and NOx, the primary precursors of acid rain,
from the power sector. The S02 program sets a permanent
cap on the total amount of S02 that may be emitted by elec-
tric generating units (EGUs) in the contiguous United States.
The program is phased in, with the final 2010 S02 cap set at
8.95 million tons, a level of about one-half of the emissions
from the power sector in 1980. NOx reductions under the
ARP are achieved through a program that applies to a subset
of coal-fired EGUs and is closer to a traditional, rate-based
regulatory system. Since the program began in 1995, the
ARP has achieved significant emission reductions.
The NOx Budget Trading Program (NBP) operated from 2003
to 2008. The NBP was a cap and trade program that required
NOx emission reductions from power plants and industrial
units in the eastern U.S. during the summer months.
CAIR addresses regional interstate transport of ozone and fine
particle (PM2 .;) pollution. CAIR requires certain eastern states
to limit annual emissions of NOx and S02, which contribute to
the formation of ozone and PM2 5. It also requires certain states
to limit ozone season NOx emissions, which contribute to the
formation of smog during the summer ozone season (May
to September], CAIR includes three separate cap and trade
programs to achieve the required reductions: the CAIR NOx
ozone season trading program, the CAIR NOx annual trading
program, and the CAIR S02 annual trading program. The CAIR
NOx ozone season and annual programs began in 2009, while
the CAIR S02 annual program began in 2010. The reduction in
ozone and PM2 5 formation resulting from implementation of
CAIR provides health benefits as well as improved visibility in
national parks and improvements in freshwater aquatic eco-
systems in the eastern U.S.
At a Glance:
Environmental and Health Results in 2010
By reducing the precursors (S02 and NOx] to PM2S and
ozone formation, emission reductions achieved by the
ARP, NPB, and CAIR significantly benefit human health
and welfare.
Air Quality: Between 1989 to 1991 and 2008 to 2010,
average ambient sulfate concentrations have decreased by
51 percent in the Mid-Atlantic, 52 percent in the Midwest,
57 percent in the Northeast, and 48 percent in the South-
east. In CAIR states, average 1-hour ozone concentrations
decreased by 19 percent between the same three-year
periods.
Acid Deposition: Between the 1989 to 1991 and 2008 to
2010 observation periods, regional decreases in wet depo-
sition of sulfate across the Eastern United States averaged
51 percent.
Surface Water Chemistry: Levels of Acid Neutralizing Ca-
pacity (ANC), the ability of a water body to neutralize acid
deposition, have increased significantly from 1990 in lake
and stream long-term monitoring sites in the Adirondack
Mountains and the Northern Appalachian Plateau. These
increasing ANC levels indicate trends toward recovery
from acidification.
On July 6, 2011, EPA finalized the Cross-State Air Pollution
Rule (CSAPR) to replace CAIR. On December 30, 2011, the U.S.
Court of Appeals for the District of Columbia Circuit stayed the
CSAPR pending resolution of litigation challenging it. While the
stay is in effect, the EPA will not be implementing the CSAPR.
Pursuant to the Court's order, CAIR, which was to be replaced
by the CSAPR as of January 1, 2012, will be in effect until the
stay is lifted.
United States
Environmental Protection
Mm Agency
May 2012
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
This report is part of a series of reports summarizing progress
in 2010 under both CAIR and the ARP. EPA combined emis-
sions and compliance data for both CAIR and the ARP to more
holistically show reductions in power sector emissions of S02
and NOx and the effect of these regional programs on human
health and the environment. While several other programs
contribute to NOx and S02 emission reductions and improved
air quality (e.g., mobile source emission control programs),
this series of reports focuses on achievements related to emis-
sion reductions at power sector sources under CAIR, the ARP,
and the former NBP.
The first report in this series, released in October 2011, pre-
sented 2010 data on combined emission reductions and com-
pliance results for CAIR and the ARP. It also presented some
historic NBP emissions data and evaluated shared progress
under these programs in 2010 by analyzing emission reduc-
tions and market activity. This report, the second in the series,
provides further 2010 trends analysis by comparing changes
in emissions to changes in a variety of environmental indica-
tors, particularly in the eastern United States.
For more information on CAIR, please visit . For more information on the ARP,
please visit . For more
information on the NBP, please visit .
Figure 1 contains important milestones for CAIR, ARP, CSAPR,
and the former NBP.
CAIR Litigation and the Cross-State Air Pollution Rule
CAIR was finalized in 2005. However, in July 2008, the U.S.
Court of Appeals for the D.C. Circuit granted several petitions
for review of CAIR, finding significant flaws in the rule. Subse-
quently, in December 2008, the court issued a ruling to keep
CAIR and the CAIR Federal Implementation Plans (FIPs)—in-
cluding the CAIR trading programs—in place temporarily until
EPA issued new rules to replace the CAIR and the CAIR FIPs.
On July 6, 2011, EPA finalized the Cross-State Air Pollu-
tion Rule (CSAPR) to replace CAIR. This rule responds to the
court's concerns and fulfills the "good neighbor" provision of
the Clean Air Act by addressing the problem of air pollution
that is transported across state boundaries. The CSAPR will
require 28 states in the eastern half of the U.S. to improve air
quality significantly by reducing power plant emissions of S02
and NOx that cross state lines and contribute to smog (ground-
level ozone) and soot (fine particle pollution) in other states.
Figure 1: History of CAIR, ARP, CSAPR, and Former NBP
1990 - Clean Air Act
Amendments establish
Title IV Acid Rain
Program (ARP)
2005 - Clean Air
Interstate Rule (CAIR) is
finalized
2004 - NBP begins
for 11 additional states
2008 - NBP ends;
CAIR NOx programs
"training year"
2010- Full
implementation of the
ARP; CAIR S02 annual
program begins
2011 - Cross-State Air Pollution Rule
(CSAPR) is finalized
1990
1995 2C30
2000 - ARP Phase 2
begins
1995-ARP Phase 1
begins
2005
2007 - NBP begins
for 21st and final state
2010
2003 - NOx Budget
Trading Program (NBP)
begins for nine states
2009 - CAIR NOx ozone
season and NOx annual
program begins;
CAIRS02 program
"training year"
2015
2014-
required for 16 Group I states
in the CSAPR
2012* - CSAPR begins
* On December 30, 2011, the U.S. Court of Appeals for the District of Columbia Circuit stayed the CSAPR pending resolution of litigation challenging it. While the
stay is in effect, the EPA will not be implementing the CSAPR. Pursuant to the Court's order, CAIR, which was to be replaced by the CSAPR as of January 1, 2012,
will be in effect until the stay is lifted.
Source: EPA, 2011
2
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Figure 2: CAIR, ARP, and NBP States
NBP Outline
Q CAIR States controlled
for ozone (ozone season NOx)
1~1 CAIR States controlled for
both fine particles and ozone
(annual S02 and NOx, ozone
season NOx)
The ARP covers sources
in the lower 48 states.
g| CAIR States controlled for
fine particles (annual S02 and NOx)
Note: In November 2009, EPA finalized a rule staying the requirements of CAIR
S02 and NOx programs.
Source: EPA, 2011
On December 30, 2011, the U.S. Court of Appeals for the Dis-
trict of Columbia Circuit stayed the CSAPR pending resolution
of litigation challenging it. While the stay is in effect, the EPA
will not be implementing the CSAPR. Pursuant to the Court's
order, CAIR, which was to be replaced by the CSAPR as of Janu-
ary 1, 2012, will be in effect until the stay is lifted. Visit for more information.
CAIR, ARP, and NBP Affected States and Units
Affected States
The ARP is a nationwide program affecting large fossil fuel-
fired power plants across the country. CAIR covers 27 eastern
states and the District of Columbia (D.C.) and requires reduc-
tions in annual emissions of S02 and NOx from 24 states and
D.C. (to achieve improvements in fine particle pollution in
downwind areas) and emission reductions of NOx during the
ozone season from 25 states and D.C. (to achieve improve-
ments in ozone pollution in downwind areas). The former NBP
affected 20 eastern states and D.C. State coverage for CAIR,
ARP, and NBP is shown in Figure 2.
Minnesota. Minnesota is therefore not currently included in the CAIR annual
Air Quality
Sulfur Dioxide
S02 is one of a group of highly reactive gasses known as "oxides
of sulfur." The largest sources of S02 emissions are from fossil
fuel combustion at power plants (65 percent) and other indus-
trial facilities (16 percent). Smaller sources of S02 emissions
include industrial processes such as extracting metal from ore,
and the burning of high sulfur containing fuels by locomotives,
large ships, and non-road equipment. S02 is linked with a num-
ber of adverse effects on the respiratory system.
Data collected from monitoring networks show that the de-
cline in SO 2 emissions from the power industry has improved
air quality. Based on EPA's latest air trends data, the national
composite average of S02 annual mean ambient concentra-
tions decreased 83 percent between 1980 and 2010, as shown
in Figure 3 on page 4 (based on state, local, and EPA monitor-
ing sites located primarily in urban areas). The largest single-
year reduction (20.5 percent) occurred in the first year of the
ARP, between 1994 and 1995. The second largest single-year
reduction (20 percent) occurred recently between 2008 and
2009, just prior to the start of the CAIR S02 program. These
trends are consistent with the regional ambient air quality
trends observed in the Clean Air Status and Trends Network
(CASTNET).
3
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Dramatic regional improvements in S02 and ambient sulfate
concentrations were observed following implementation of
Phase I of the ARP during the late 1990s at CASTNET sites
throughout the eastern United States, and these improve-
ments continue today. Analyses of regional monitoring data
from CASTNET show the geographic pattern of S02 and air-
borne sulfate in the eastern United States. Three-year mean
annual concentrations of S02 and sulfate from CASTNET long-
term monitoring sites are compared from 1989 to 1991 (be-
fore implementation of the ARP) and 2008 to 2010 (most re-
cent available data) in tabular form in Table 1 on page 5.
The average annual ambient concentrations of S02 from 1989
to 1991 were highest in western Pennsylvania and along the
Ohio River Valley. There was a significant decline in those con-
centrations in nearly all affected areas after implementation of
the ARP and other programs.
Like S02 concentrations, the highest average annual ambient
sulfate concentrations from 1989 to 1991 were observed in
Figure 3: National S02 Air Quality, 1980-2010
- - ¦ National Ambient Air Average Concentration
Quality Standard
90% of sites have 10% of sites have
concentrations below this line concentrations be low this line
Source: EPA, 2011
About Long-term Ambient and Deposition Monitoring Networks
To evaluate the impact of emission reductions on the en-
vironment, scientists and policymakers use data collected
from long-term national monitoring networks such as CAST-
NET and the National Atmospheric Deposition Program/
National Deposition Trends Network (NADP/NTN). Data
from long-term regulatory networks, such as State and Local
Air Monitoring Stations (SLAMS) and Chemical Speciation
Network (CSN), are stored in EPA's Air Quality System (AQS)
database. These complementary, long-term monitoring net-
works provide information on a variety of indicators neces-
sary for tracking temporal and spatial trends in regional air
quality and acid deposition.
CASTNET provides long-term monitoring of air quality in
rural areas to determine trends in regional atmospheric
nitrogen, sulfur, and ozone concentrations and deposition
fluxes (the rate of particles and gases being deposited to a
surface) of sulfur and nitrogen pollutants in order to evalu-
ate the effectiveness of national and regional air pollution
control programs. CASTNET operates more than 80 regional
sites throughout the contiguous United States, Alaska, and
Canada. Sites are located in areas where urban influences
are minimal. Information and data from CASTNET are
available at the CASTNET website at .
AQS contains ambient air pollution data collected by
EPA, state, local, and tribal air pollution control agen-
cies from thousands of monitoring stations. AQS also
contains meteorological data, descriptive informa-
tion about each monitoring station (including its geo-
graphic location and its operator), and data quality as-
surance/quality control information. Information and
data from AQS are available at the Air Quality System
website at .
NADP/NTN is a nationwide, long-term network track-
ing the chemistry of precipitation. NADP/NTN pro-
vides concentration and wet deposition data on hy-
drogen ion (acidity as pH), sulfate, nitrate, ammonium,
chloride, and base cations. NADP/NTN has grown to
more than 250 sites spanning the continental United
States, Alaska, Puerto Rico, and the Virgin Islands. In-
formation and data from NADP/NTN are available at
the NADP's website at .
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Table 1: Regional Changes in Air Quality and Deposition of Sulfur and Nitrogen Compounds, 1989-1991 versus 2008-2010,
from Rural Monitoring Networks
Measurement
Region
Annual Average,
1989-1991
Annual Average,
2008-2010
Percent Change
Number of Sites
Ambient S02 Concentration
Mid-Atlantic
13
4
-69
12
(micrograms per cubic meter,
Midwest
11
3.5
-68
10
Hg/m3)
Northeast
5.5
1.3
-76
3
Southeast
5.1
1.7
-67
8
Ambient Particulate Sulfate
Mid-Atlantic
6.3
3.1
-51
12
Concentration ((jg/m3)
Midwest
5.8
2.8
-52
10
Northeast
3.5
1.5
-57
3
Southeast
5.4
2.8
-48
8
Ambient Total Nitrate
Mid-Atlantic
3.3
1.8
-45
12
Concentration (Nitrate + Nitric
Midwest
4.6
3.1
-33
10
Acid) (ng/m3)
Northeast
1.8
0.9
-50
3
Southeast
2.2
1.4
-36
8
Dry Inorganic Nitrogen Depo-
Mid-Atlantic
2.4
1.3
-46
10
sition (kilograms nitrogen per
Midwest
2.5
1.7
-32
7
hectare, kg-N/ha)
Northeast
1.8
0.8
-56
2
Southeast
0.7
0.5
-29
1
Total Inorganic Nitrogen
Mid-Atlantic
8.8
5.4
-39
10
Deposition (kg-N/ha)
Midwest
8.9
7.2
-19
7
Northeast
6.8
4
-41
2
Southeast
5.8
4.1
-29
1
Dry Sulfur Deposition
Mid-Atlantic
6.9
2.7
-61
10
(kilograms sulfur per hectare,
Midwest
7.2
2.7
-63
7
kg-S/ha)
Northeast
4.1
1.1
-73
2
Southeast
0.9
0.5
-44
1
Total Sulfur Deposition
Mid-Atlantic
17
7
-59
10
(kg-S/ha)
Midwest
16
8
-50
7
Northeast
11
4.1
-63
2
Southeast
8.8
4.3
-51
1
Wet Nitrogen Deposition from
Mid-Atlantic
6.2
3.9
-37
11
Inorganic Nitrogen (kg-N/ha)
Midwest
5.8
4.6
-21
27
Northeast
5.6
3.7
-34
17
Southeast
4.4
3.5
-20
23
Wet Sulfur Deposition from
Mid-Atlantic
9.2
4.1
-55
11
Sulfate (kg-S/ha)
Midwest
7.1
3.5
-51
27
Northeast
7.5
3.6
-52
17
Southeast
6.1
3.3
-46
23
Notes:
• Averages are the arithmetic mean of all sites in a region that were present and met the completeness criteria in both averaging periods. Thus, average concen-
trations for 1989 to 1991 may differ from past reports.
• Total deposition is estimated from raw measurement data, not rounded, and may not equal the sum of dry and wet deposition.
• Percent change and values in bold indicates that differences were statistically significant at the 95 percent confidence level. Changes that are not statistically
significant may be unduly influenced by measurements at only a few locations or large variability in measurements.
Source: EPA, 2011
5
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
western Pennsylvania and along the Ohio River Valley. Most of
the eastern United States experienced annual ambient sulfate
concentrations greater than 5 micrograms per cubic meter
(jig/m3).
Ambient sulfate concentrations have also decreased since the
program was implemented, with average concentrations de-
creasing by 48 to 57 percent in regions of the East (see Table 1
on page 5), Both the magnitude and spatial extent of the high-
est concentrations have dramatically declined, with the largest
decreases observed along the Ohio River Valley.
Nitrogen Oxides
NOx is a group of highly reactive gasses including nitrogen di-
oxide, nitrous acid, and nitric acid. In addition to contributing
to the formation of ground-level ozone and PM2 5, NOx is linked
with a number of adverse effects on the respiratory system.
Although the ARP and CAIR NOx programs have contributed to
significant NOx reductions, emissions from other sources (such
as motor vehicles and agriculture] contribute to ambient ni-
trate concentrations in many areas. Ambient nitrate levels can
also be affected by emissions transported via air currents over
wide regions.
From 2008 to 2010, reductions in NOx emissions during the
ozone season from power plants under the NOx SIP Call, ARP,
and CAIR have continued to contribute to significant regional
improvements in ambient total nitrate (W03- plus HN0 3) con-
centrations. For instance, annual mean ambient total nitrate
concentrations for 2008 to 2010 in the Mid-Atlantic region
were 45 percent less than the annual mean concentration in
1989 to 1991 (see Table 1 on page 5). These improvements can
be partly attributed to added NOx controls installed for compli-
ance with the NOx SIP Call and CAIR.
Acid Deposition
National Atmospheric Deposition Program/National Deposi-
tion Trends Network (NADP/NTN] monitoring data show sig-
nificant improvements in the primary acid deposition indica-
tors. For example, wet sulfate deposition (sulfate that falls to
the earth through rain, snow, and fog] has decreased since the
implementation of the ARP in much of the Ohio River Valley
and northeastern United States. Some of the greatest reduc-
tions have occurred in the mid-Appalachian region, including
Maryland, New York, West Virginia, Virginia, and most of Penn-
sylvania. Other less dramatic reductions have been observed
across much of New England, portions of the southern Appala-
chian Mountains, and some areas of the Midwest. Between the
1989 to 1991 and 2008 to 2010 observation periods, average
decreases in wet deposition of sulfate averaged more than 46
percent for the eastern United States (see Table 1 on page 5
and Figure 4).
Figure 4: Three-Year Mean Wet Sulfate Deposition
1989-1991
7*' ;
Wet S042"
(kg/ha)
¦"0
-4
-8
-12
-16
Source: EPA, 2011
6
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Along with wet sulfate deposition, wet sulfate concentrations
have also decreased by similar percentages. A strong correla-
tion between large-scale S02 emission reductions and large
reductions in sulfate concentrations in precipitation has been
noted in the Northeast, one of the areas most affected by acid
deposition. The reduction in total sulfur deposition (wet plus
dry] has been of similar magnitude as that of wet deposition
in the Mid-Atlantic and Midwest, with reductions of 59 and
50 percent, respectively (see Table 1 on page 5). Because con-
tinuous data records are available from only a few sites in the
Northeast and Southeast, it is unclear if the observed reduc-
tions in total deposition are representative for those regions.
A principal reason for reduced sulfate deposition in the North-
east is a reduction in the long-range transport of sulfate from
emission sources located in the Ohio River Valley. The reduc-
tions in sulfate documented in the Northeast, particularly
across New England and portions of New York, were also af-
fected by S02 emission reductions in eastern Canada. NADP
data indicate that similar reductions in precipitation acidity,
expressed as hydrogen ion (H+] concentrations, occurred con-
currently with sulfate reductions, with reductions of 30 to 40
percent over much of the East,
Interpolation of Wet Deposition Fluxes
Total deposition is calculated as the sum of the wet de-
position flux (as measured or interpolated by nearby
NADP/NTN sites) and dry deposition flux estimated by
the CASTNET measured pollutant concentration and
modeled deposition velocity. Historically, wet deposi-
tion has been interpolated over large areas in the West-
ern U.S. due to the sparse number of sites. This problem
is exacerbated due to the rugged terrain. CASTNET and
NADP are now using PRISM (Parameter-elevation Re-
gressions on Independent Slopes Model), a model which
uses point measurements, temperature and climatic fac-
tors to produce precipitation grids. The PRISM precipi-
tation data sets are used to interpolate wet deposition
between NADP/NTN sites. There has been a large im-
provement in the resolution of the graphs and improved
accuracy in the data output. All historical maps and data
will be updated using the new interpolation technique
and will be available on the CASTNET website.
Reductions in nitrogen deposition recorded since the early
1990s have been less pronounced than those for sulfur. As
noted earlier, emission changes from source categories other
than ARP sources significantly affect air concentrations and
deposition of nitrogen. Inorganic nitrogen in wet deposition
decreased commensurately in the Mid-Atlantic and Northeast
(see Figure 5).
Decreases in dry and total inorganic nitrogen deposition at
CASTNET sites have generally been greater than that of wet
deposition, with a 39 and 19 percent decrease in total nitrogen
deposition for the Mid-Atlantic and Midwest, respectively (see
Table 1 on page 5).
Figure 5: Three-Year Mean Wet Inorganic Nitrogen Deposition
1989-1991
Source: EPA, 2011
Inorganic
Nitrogen
(kg/ha)
-0.0
-1.0
-2.0
-3.0
-4.0
-5.0
-6.0
1
-7.0
|
-8.0
-9.0
1
->10.0
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Ozone
Ozone pollution forms when NOx and volatile organic com-
pounds (VOCs] react in the presence of sunlight. Ozone itself
is rarely emitted directly into the air. Major sources of NOx and
VOC emissions include motor vehicles, solvents, industrial fa-
cilities, and electric power plants.
Meteorology plays a significant role in ozone formation. Dry,
hot, sunny days are most favorable for ozone production. In
general, ozone concentrations increase during the daylight
hours, peak in the afternoon when the temperature and sun-
light 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 Septem-
ber 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 ef-
fects, the severity of which depends on concentration, length of
exposure, and breathing rate. At levels found in many urban ar-
eas, ozone can aggravate respiratory diseases such as asthma,
emphysema, and bronchitis, and can increase susceptibility to
respiratory infections. More serious effects include emergency
department visits, hospital admissions, and premature deaths.
Air pollution can impact the environment and affect ecologi-
cal systems, leading to changes in the biological community,
both in the diversity of species and in the health and vigor of
individual species.
For more information on the health and environmental effects
of ground-level ozone, visit EPA's Ground-level Ozone website
at .
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. 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 promulgated, revising the 1979 standard. In March
2008, EPA changed the 8-hour ozone standard to 0.075 ppm.
NO, Reduction Programs and Ozone
To better understand how the CAIR, NBP, and ARP NOx pro-
grams affected ozone formation in the atmosphere, this report
examines changes in ozone concentrations before and after
implementation of the NBP and CAIR. The report compares re-
gional and geographic trends in ozone levels to changes in me-
teorological conditions (such as temperature] and NOx emis-
sions from CAIR sources.
Measuring and Evaluating Changes in Ozone
Two long-term monitoring networks measure ozone levels as
well as meteorological and other air quality data throughout
the United States. Monitoring sites used for regulatory com-
pliance are located mainly in urban areas and report data to
EPA's Air Quality System (AQS}. CASTNET sites measure trends
in ozone at rural sites and these data are also reported to AQS.
The changes in eastern ozone concentrations presented in this
report depict 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.
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Meteorological Effects on Environmental Trends
Detecting trends or causal effects in air quality requires several
data points or multiple-year averages because of natural vari-
ability in environmental measurements and meteorology. EPA
uses a regression model for trends analysis that partially ad-
justs for the variability in weather. Figure 6 shows the weekly
average of maximum daily temperatures during the NOx ozone
season at CASTNET sites included in the CAIR region that
met the data completeness criteria. During the ozone season
months in 2010, the average of maximum daily temperatures
were typically higher than the three-year average from 2007
to 2009, making it important to account for meteorological ef-
fects when assessing any trends in air pollution after CAIR was
implemented (see "Changes in 8-Hour Ozone Concentrations,"
below, for an analysis of ozone trends using meteorologically
adjusted data).
Changes in Rural Ozone Concentrations
Rural ozone measurements are useful in assessing the impacts
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, automotive, and power
generation sources] than urban measurements. Consequently,
the formation of ozone in these areas is particularly sensitive
to changes in levels of regional NQX emissions. The majority
of reductions in rural ozone concentrations can therefore be
attributed to reductions in regional NOx emissions and trans-
ported ozone. EPA investigated 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).
Figure 6: Weekly Average of Maximum Ozone Season Daily
Temperatures, 2007-2010
Source: EPA, 2011
Figure 7: Percent Change in Unadjusted 1-Hour Ozone
Concentrations during the Ozone Season, 2000-2002 versus
2008-2010
Note: Data are from AQS and CASTNET monitoring sites with two or more
years of data within each three-year monitoring period.
Source: EPA, 2011
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 rural (CAST-
NET) sites. Results demonstrate how NOx emission reduction
policies have affected ozone concentrations in the eastern
United States. Figure 7 shows changes in the 99th percentile
of unadjusted 1-hour ozone concentrations between 2000 to
2002 (before implementation of the NBP) and 2008 to 2010
(under the last year of the NBP and first year two years of the
CAIR NOx ozone season program). Using this metric, an over-
all regional reduction in ozone levels was observed between
these two time periods, with an average reduction in ozone
concentrations in CAIR states of 19 percent. To date, this re-
duction represents the greatest three-year average decrease in
ozone concentrations since the NBP began in 2003.
9
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Regional Trends in Ozone
An Autoregressive Integrated Moving Average (ARIMA) model
was used to determine the trend in ozone concentrations 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 dai-
ly maximum ozone concentrations (the highest daily levels of
ozone) measured at CASTNET sites during the CAIR NOx ozone
season was modeled (Figure 8). The ARIMA model shows that
between 1990 and 2003, the average of the 99th percentile
of ozone concentration was 89 parts per billion (ppb). After
2004, the year by which the majority of NBP affected states
began compliance, a statistically significant shift occurred and
a new trend was established, with an average ozone level of
73 ppb. The ARIMA model shows a statistically significant, 18
percent (16 ppb) decrease in ozone concentrations beginning
at the start of the NBP, suggesting that this program is a major
contributor to these regional improvements in ozone. In 2010,
the second compliance year of the CAIR NOx programs, ozone
concentrations were at the second lowest over the 21-year pe-
riod. Ozone concentrations were down 22 ppb (24 percent) in
2010 versus 1990.
The large decrease in ozone concentrations shown in Figure
8 results in part 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 improve-
ments. The significant decrease in ozone levels evident in Fig-
ure 8 is not the result of the recent economic downturn, given
that the large drop in ozone concentrations predated the eco-
nomic downturn.
Figure 8: Shift in 8-Hour Seasonal Rural Ozone Concentrations
in the CAIR N0X Region, 1990-2010
1101—i r
100
g 40
<§ 30
20
10
0 -
1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010
o Actual — Model Estimate ~ 95% Confidence Band
Note: Ozone concentration data are from CASTNET sites that met complete-
ness criteria and are located in and adjacent to the CAIR NOx region.
Source: EPA, 2011
Changes in 8-Hour Ozone Concentrations
Daily maximum 8-hour ozone concentration data were as-
sessed from 84 urban AQS areas and 46 rural CASTNET sites
located in the CAIR NOx ozone season program region. As
noted earlier, weather plays an important role in determining
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 varia-
tion in seasonal ozone across different years by correcting for
meteorological fluctuations. The most important meteorologi-
cal parameters considered in this model are daily maximum
1-hour temperature and midday (10 a.m. to 4 p.m.) relative
humidity.
10
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Figure 9 shows trends in the seasonal average daily maximum
8-hour ozone concentrations in the CAIR NOx ozone season re-
gion 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 tempera-
tures and lower relative humidity in the 2007 ozone season
increased ozone formation. Removing the effects of weather
results in a higher-than observed ozone estimate for 2004
and a lower-than observed ozone estimate for 2007. The sec-
ond year of CAIR, 2010, was warmer than the 2007 to 2009
time period, however the meteorologically-adjusted trend
remained stable from 2009 to 2010. Therefore, the warmer
temperatures explain some of the increase in ozone concen-
trations in 2010. Three-year averages will be used in 2011 to
assess the air quality impact of the CAIR NOx reductions with
more confidence.
A closer look at the meteorologically-adjusted ozone trends
since the start of the NBP in 2003 indicates that these reduc-
tions are substantive and sustained. The average reduction in
seasonal daily maximum 8-hour ozone concentrations mea-
sured in the CAIR NOx region in the 2001 to 2003 and 2008
to 2010 time periods was about 12 percent. After consider-
ing the influence of weather, the improvement in daily maxi-
mum 8-hour ozone concentrations between these three-year
periods was almost 16 percent. A comparison of single year
meteorologically-adjusted ozone between 2001 and 2010 also
reveals a 16 percent reduction.
Figure 9: Seasonal Average of 8-hour Ozone Concentrations in
CAIR States before and after Adjusting for Weather
70
60
50
' 40
30
20
10
Start
of NBP
%
Start of
ZA\R
1
1 1 1 1 1
2001 2002 2003 2004 2005 2006 2007 2008 2009 2010
— Adjusted for Weather • « ¦ Unadjusted for Weather
Note: 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 2001 to 2010. In addition, urban AQS areas often in-
clude more than one monitoring site. In these cases, the site with the highest
observed ozone concentration for each day was used.
Furthermore, the pace of these reductions has increased with Source: epa, 2011
implementation of the NBP and subsequent CAIR NOx ozone
season program. Between 2001 and 2005, ozone fell by six
percent, while between 2005 and 2010, ozone dropped by
over ten percent. This is consistent with the general downward
trend in NOx emissions observed over this time period.
11
-------
CAIR, ARP, and Former NBP 2010 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 to 2003. Of those areas, 91 are in the
East (as shown in Figure 10) and are home to about 103 mil-
lion people.4 Based on data gathered from 2008 to 2010, 90 of
these original eastern nonattainment areas show concentra-
tions below the level of the 1997 ozone standard (0.08 ppm),
indicating improvements in ozone. Improvements in these 90
areas mean that over 98 percent of the original nonattainment
areas in the East now have ozone air quality that is better than
the standard under which they were originally designated
nonattainment. The Baltimore, Maryland area is the only one
of the original 91 areas in the East that continues to exceed the
level of the standard. In this area, however, ozone concentra-
tions have fallen by over 13 percent. Because of the reductions
in all 91 areas, millions of Americans living in these areas are
experiencing better air quality.
Given that the majority of power sector 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.
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 compo-
nents, including acids (such as nitrates and sulfates), organic
chemicals, metals, and soil or dust particles. Fine particles
(PM2 5) can form when gases emitted from power plants, in-
dustrial sources, automobiles, and other sources react in the
air.
Particulate Matter Impacts on Human Health and Ecosystems
Particle pollution — especially fine particles — contains mi-
croscopic 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 particle pollution ex-
posure to a variety of problems, including: increased respira-
tory symptoms, such as irritation of the airways, coughing, or
difficulty breathing; decreased lung function; aggravated asth-
ma; development of chronic bronchitis; irregular heartbeat;
nonfatal heart attacks; and premature death.
Figure 10: Changes in Nonattainment Areas in the CAIR
Region, 2001-2003 (Original Designations) versus 2008-2010
| | Attained 1997 8-hour ozone NAAQS (90 areas)
Above NAAQS, showing improvement (1 area)
| | CAIR States (controlled for PM and/or ozone)
Source: EPA, 2011
For more information on the health and environmental effects
of particulate matter, visit EPA's Particulate Matter website at
.
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 (|.ig/m3) measured as the three-
year average of the 98th percentile for 24-hour exposure, and
at 15 |.ig/m3 for annual exposure measured as the three-year
annual mean. 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
cubic meter (|.ig/m3) to 35 |.ig/m3, and retain the current an-
nual fine particle standard at 15 |.ig/m3.
12
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Figure 11: PM2 5 Seasonal Trends
Warm Season Trends
o
<
—I 1 1 1 1 1 1 1—
2001 2003 2005 2007 2009
Adjusted for Weather
18
16
14
12
10
8
6
4
2
Cool Season Trends
o 1 1 1 r
2001 2003 2005
m m Unadjusted for Weather
2007
2009
Note: 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 to
2010. In addition, urban AQS areas often include more than one monitoring site. In these cases, the site with the highest observed PM2.5 concentration for each
day was used.
Source: EPA, 2011
Annual Emission Reduction Programs and PM25
The CAIR NOx annual program and CAIR S02 program were es-
tablished to address the interstate transport of PM2 5 pollution
throughout the year and help eastern U.S. counties attain the
PM2 5 annual standard. To better understand how emission re-
ductions under CAIR and ARP affected the formation of PM2 5,
this report presents regional and geographic trends in PM2 5
levels prior to implementation of any of the CAIR annual pro-
grams, and for 2010. More information on emissions reduc-
tions achieved in 2010 under the CAIR annual programs and
ARP can be found in the CAIR, ARP, and Former NBP 2010 S02
and NOx Emissions, Compliance, and Market Analyses Report
at .
Trends in PM2 5 Concentrations
Average PM2 5 concentration data were assessed from 108 ur-
ban AQS areas located in the CAIR NOx and S02 annual pro-
gram region.
As with ozone, weather plays an important role in the forma-
tion of PM (see Figure 6 on page 9 for weather trends). For this
report, EPA uses a statistical model to account for the weather-
related variability of PM2 5 concentrations to provide a more
accurate assessment of the underlying trend in the precursor
emissions that cause PM2 5 formation.
Figure 11 shows separate trends in PM2 5 concentrations in the
CAIR NOx and S02 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 variability of
the components that make up PM2 5. After adjusting for weath-
er, PM2 5 concentrations have decreased by over 22 percent in
the warm season and 13 percent in the cool season between
the 2001 to 2003 and 2008 to 2010 monitoring periods.
13
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Changes in PM2 S Nonattainment Areas
In January 2005, EPA designated 39 areas as nonattainment
for the annual average PM25 standard adopted in 1997, one
of which was also designated nonattainment for the 24-hour
average PM25 standard.5 These designations were made using
data from 2001 to 2003. Of those areas, 36 are in the East (as
shown in Figure 12] and are home to about 88 million people.6
Based on data gathered from 2008 to 2010,34 of these original
eastern areas show concentrations below the level of the 1997
PM2 5 standard (15.0 jig/m3), indicating improvements in PM2 5
air quality. Improvements in these 34 areas mean that 94 per-
cent 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 nonattainment.
The Liberty-Clairton (Pennsylvania) area is the only one of
the original 36 areas in the East that continues to exceed the
level of the PM2 5 standard (see inset in Figure 12}. However,
PM25 concentrations in that area have fallen by almost 25
percent since the original designation. The Canton-Massillion
area does not have sufficient recent PM25 data to quantify its
change in air quality.
Given that the majority of power sector NOx and S02 emission
reductions occurring after 2003 are attributable to the Acid
Rain Program, NBP, and CAIR, it is reasonable to conclude that
these emission reduction programs have been a significant
contributor to these improvements in PM2 5 air quality.
Figure 12: Changes in PM Nonattainment Areas in the CAIR
Region, 2001-2003 (Original Designations) versus 2008-2010
Above NAAQS, showing improvement (1 area)
| Incomplete data for 2008-2010 (1 area)
CAIR States controlled for PM and/or ozone are outlined.
Source: EPA, 2011
14
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Health Benefits of the ARP, NBP, and CAIR
By reducing precursors (S02 and NO J to I'M;-, formation and a
precursor (NOx) to ground-level ozone formation, emission re-
ductions achieved by the ARP, NPB, and CAIR significantly ben-
efit human health and welfare, Exposure to PM25 and ozone
is linked to premature death as well as a variety of non-fatal
effects including heart attacks, hospital and emergency de-
partment visits for respiratory and cardiovascular symptoms,
acute bronchitis, aggravated asthma, and days when people
miss work or school.7,8 In addition to these impacts on human
health, PM;;S contributes to visibility impairment and materi-
als damage and ozone negatively impacts agriculture and for-
estry.
Moreover, S02 and NOx pollution contribute to aquatic and ter-
restrial acidification while NOx pollution can cause nutrient
enrichment and S02 deposition can lead to the conversion of
mercury to methylated mercury—a more toxic form of this po-
tent neurotoxin.9
Ecosystems
Improvements in Surface Water Chemistry
Acid rain resulting from S02 and NOx emissions negatively af-
fects the health of lakes and streams in the U.S. Surface water
chemistry provides direct indications of the potential effects of
acidic deposition on the overall health of aquatic ecosystems.
Two EPA-administered monitoring programs provide informa-
tion on the impacts of acidic deposition on otherwise protect-
ed aquatic systems: Temporally Integrated Monitoring of Eco-
systems (TIME] and Long-term Monitoring (LTM) programs.
These programs are designed to track changes in surface water
chemistry in the four acid sensitive regions shown in Figure
13: New England, the Adirondack Mountains, the Northern
Appalachian Plateau, and the central Appalachians (the Valley
and Ridge and Blue Ridge Provinces).
Table 2 on page 16 shows regional trends in acidification from
1990 (before implementation of the ARP) to 2009 (most re-
cent available data) in lakes and streams through the LTM pro-
gram. Five indicators of aquatic ecosystem response to emis-
Figure 13: Long-term Monitoring Program Sites
sion changes are presented: measured ions of sulfate, nitrate,
base cations (sum of calcium, magnesium, sodium, and potas-
sium ions), acid neutralizing capacity (ANC), and dissolved
organic carbon (DOC). These indicators provide information
regarding the surface water sensitivity to acidification. Trends
in these measured chemical receptors allow for the determi-
nation of whether the conditions of the water bodies are im-
proving and heading towards recovery or if the conditions are
still acidifying.
Sulfate is the primary negatively charged ion in most acid-sen-
sitive waters and has the potential to acidify drainage waters
and leach aluminum and base cations from the soils. Nitrate
has the same potential as sulfate to acidify drainage waters.
However, nitrogen is a limiting nutrient for plant growth and a
large portion of nitrogen inputs from deposition are quickly in-
corporated into plants as organic nitrogen, leaving less leach-
ing of nitrate into surface waters. Base cations are the positive-
ly charged ions in surface waters that buffer both sulfate and
nitrate ions, thereby preventing surface water acidification.
15
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
ANC is a measure of acidification, which results in the dimin-
ishing ability of surface waters to neutralize strong acids that
enter aquatic systems. Water bodies with ANC values less than
or equal to 0 microequivalents per liter (|.ieq/L) are defined
as being of acute concern for acidification. Lakes and streams
having springtime ANC values less than 50 |.ieq/L are gener-
ally considered of elevated concern for acidification. Lakes and
streams with ANC higher than 50 |.ieq/L are generally consid-
ered of moderate to low concern for acidification. When ANC
is low, and especially when it is negative, stream water pH is
also low (less than pH 6), and there may be adverse impacts
on fish and other animals essential for a healthy aquatic eco-
system. Movement toward recovery of an aquatic ecosystem is
indicated by increasing trends in ANC and decreasing trends
in sulfate and nitrate concentrations. Dissolved organic car-
bon (DOC) is essentially organic material that is an important
part of the acid-base chemistry of most low-ANC freshwater
systems. While a host of factors control DOC dynamics in sur-
face waters, increased concentrations of DOC can be indicative
of reduced acidification from acid deposition and/or a sign of
increased decomposition of organic matter in the watershed.
As seen in Table 2, significant improving trends in sulfate con-
centrations from 1990 to 2009 are found at nearly all monitor-
ing sites in New England, Adirondacks, and the Catskill moun-
tains/Northern Appalachian Plateau. However, in the Central
Appalachians only 12 percent of monitored streams showed
a decreasing sulfate trend, while 14 percent of monitored
streams actually increased, despite decreasing sulfate deposi-
tion. The highly weathered soils of the Central Appalachians
are able to store large amounts of deposited sulfate, but as
long-term sulfate deposition exhausts the soil's ability to store
more sulfate, a decreasing proportion of the deposited sulfate
is retained in the soil and an increasing proportion is exported
to surface waters.
Surface nitrate concentrations trends are decreasing at some
of the sites in all four regions, but some sites also indicate flat
or slightly increasing nitrate trends. Improving trends for ni-
trate concentration were noted at 37 percent of all monitored
sites, but this improvement may only be partially explained by
decreasing deposition. Ecosystem factors, such as vegetation
disturbances and soil retention are also known to contribute
to declining surface water nitrate concentrations.
Reductions in sulfate deposition levels likely result in many
of the improving ANC trends. From 1990 to 2009, monitoring
sites in the Adirondacks (60 percent), and the Cats kills/north-
ern Appalachian Plateau (55 percent) showed the strongest
improvement in ANC trends. However, sites in New England
(20 percent) and the Central Appalachians (17 percent) had
few sites with improving ANC trends. Relatively flat trends
in sulfate in the Central Appalachians likely account for why
so few sites have improving ANC. In New England, hydrology
and declining trends of base cation concentration may delay
the onset of recovery. Decreasing base cation levels can bal-
ance out reductions of sulfate and nitrate, thereby preventing
ANC from increasing. DOC is increasing at only 30 percent of all
monitored lakes and streams. This is likely linked to declines in
sulfate concentrations as well as warmer seasonal and annual
temperatures.
Table 2: Regional Trends in Sulfate, Nitrate, ANC, and DOC at Long-term Monitoring Sites, 1990-2009
Region
Water Bodies
Covered
% of Sites with
Improving Sulfate
Trend
% of Sites with
Improving Nitrate
Trend
% of Sites with
Improving ANC
Trend
% of Sites with
Improving Base
Catons Trend
% of Sites with
Improving DOC
Trend
Adirondack Mountains
50 lakes in NY
94%
48%
60%
74%
48% (29 sites)
Catskills/N. Appalachian
Plateau*
9 streams in NY and PA
80%
30%
55%
80%
25% (9 sites)
New England
26 lakes in ME andVT
96%
33%
20%
57%
26% (15 sites)
Central Appalachians
66 streams inVA
12%
50%
17%
12%
NA
Notes:
• Trends are determined by multivariate Mann-Kendall tests.
• Trends are significant at the 95 percent confidence interval (p < 0.05).
• DOC was only examined in low-ANC waterbodies (ANC less than 25 neq/L).
• DOC is not currently measured in Central Appalachian streams.
*Data for streams in N. Appalachian Plateau is only through 2008.
Source: EPA, 2011
16
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Critical Loads and Exceedances
Since the early 1980s, acidic deposition has acidified many
lakes and many miles of streams in the eastern United States,10
However, with the implementation of the ARP, CAIR, and other
emission reduction programs, acidic deposition has decreased
throughout the eastern United States as emissions of NOxand
S02 have declined (see CAIR, ARP, and Former NBP 2010 Emis-
sions, Compliance, and Market Analyses Report). The critical
load approach is an assessment tool that can be used to deter-
mine the degree to which air pollution may be affecting ecolog-
ical health. A critical load is a quantitative estimate of exposure
to one or more pollutants below which significant harmful ef-
fects on specific sensitive elements of the environment do not
occur according to present knowledge.11 This approach pro-
vides a useful lens through which to assess the results of emis-
sion reduction programs such as the ARP and CAIR.
Figure 14: Lake and Stream Exceedances of Estimated
Critical Loads for Total Nitrogen and Sulfur Deposition,
1989-1991 vs.2008-2010
Drawing on the methods from the peer-reviewed scientific lit-
erature,12, 13 critical loads were calculated for over 2,300 lakes
and streams using the Steady-State Water Chemistry (SSWC)
model. These critical load estimates represent only lakes and
streams where surface water samples have been collected
through programs such as National Surface Water Survey
(NSWS), Environmental Monitoring and Assessment Program
(EMAP), the TIME program, and the LTM program. The lakes
and streams associated with these programs consist of a sub-
set of lakes and streams that are located in areas most affected
by acid deposition, but are not intended to represent all lakes
in the eastern US.
For this particular analysis, the critical load represents the
combined deposition loads of sulfur and nitrogen to which a
lake or stream could be subjected and still have a calculated
ANC of 50 neq/L or higher. While a critical load can be calcu-
lated for any ANC level, this level was chosen because it tends
to support healthy aquatic ecosystems and protect most fish
and other aquatic organisms, although systems can become
episodically acidic and some sensitive species still may be lost.
Critical loads of combined total sulfur and nitrogen deposition
are expressed in terms of ionic charge balance as milliequiva-
lents per square meter per year (meq/m2/yr).
If pollutant exposure is less than the critical load, adverse
ecological effects (e.g., reduced reproductive success, stunted
growth, loss of biological diversity) are not anticipated, and
recovery is expected over time if an ecosystem has been dam-
aged by past exposure. A critical load exceedance is the mea-
sure of pollutant exposure above the critical load. This means
pollutant exposure is higher than, or "exceeds," the critical load
and the ecosystem continues to be exposed to damaging levels
of pollutants. In order to assess the extent to which regional
lake and stream ecosystems are protected by the emission re-
ductions achieved by the ARP and CAIR so far, this case study
compares the amount of deposition systems can receive—the
critical load—to measured deposition for the period before
implementation of the ARP (1989 to 1991) and for a recent
period after ARP and CAIR implementation (2008 to 2010).
Overall, this critical load analysis shows that emission reduc-
tions achieved by the ARP and CAIR so far have contributed
significantly to improved environmental conditions and in-
creased ecosystem protection in the eastern United States.
For the period from 2008 to 2010, 30 percent of the lakes and
streams examined received levels of combined sulfur and ni-
trogen deposition that exceeded the critical load (Figure 14).
This is an improvement when compared to the 1989 to 1991
17
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Figure 15: U.S. S02 Emissions and Sulfate Concentrations, 1990
Note: This example depicts 1990 S02 emissions from ARP sources along with
1990 sulfate concentration data as measured by the CASTNET monitoring
program.
Source: EPA, 2011
period, during which 55 percent of lakes and streams exceeded
the critical load. Areas with the largest concentration of lakes
where acid deposition currently is greater than—or exceeds—
estimated critical loads include the southern Adirondack
mountain region in New York, southern New Hampshire and
Vermont, Cape Cod Massachusetts, and along the Appalachian
Mountain spine from Pennsylvania to North Carolina.
Online Information, Data, and Resources
The availability and transparency of data, from emission mea-
surement to allowance trading to deposition monitoring, is a
cornerstone of effective cap and trade programs. CAMD, in the
Office of Air and Radiation's Office of Atmospheric Programs,
develops and manages programs for collecting these data and
assessing the effectiveness of cap and trade programs, includ-
ing the ARP, NBP, and CAIR. CAMD then makes these data avail-
able to the public in readily usable and interactive formats.
The CAMD website at provides a public
resource for general information on how market-based pro-
grams work and what they have accomplished, along with the
processes, information, and tools necessary to participate in
any of these market-based programs.
To increase data transparency, EPA has created supplementary
maps that allow the user to display air market program data
geospatially on an interactive 3D platform. Figure 15 and Fig-
Figure 16: U.S. S02 Emissions and Sulfate Concentrations, 2010
Note: This example depicts 2010 S02 emissions from ARP sources along with
2010 sulfate concentration data as measured by the CASTNET monitoring
program.
Source: EPA, 2011
ure 16 are examples of these maps. The maps come in the form
of a KMZ file (a compressed KML file) that is downloaded di-
rectly to the user's computer. Data can be explored in new and
meaningful ways by turning different layers on and off, over-
laying data points and satellite imagery, and using navigation
tools to change the view of the Earth's surface. KMZ/KML files
are supported by programs such as Google Earth, ESRI Arc Ex-
plorer, and NASA WorldWind View. These interactive mapping
applications provide a unique way to identify environmental
trends and track the progress of various EPA programs, such
as the ARP. For more information or to utilize this tool, visit the
Interactive Mapping website at .
In another effort to increase data transparency, EPA regularly
posts updates of quarterly S02 and NOx emissions data from
coal-fired power plants controlled under the ARP and other
programs to make it easy for the public to track changes in
emissions from these sources (available at the Quarterly Emis-
sions Tracking website at ). The data presented on the quarterly emis-
sions tracking website compare emissions, emission rates,
and heat input from power plant units in the ARP. These files
graphically and spatially compare quarterly emission data
from the most recent completed quarter of 2011 with data for
the same quarter from 2010.
18
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Figure 17: Motion Charts of Annual ARP Coal-fired Power Plant Emissions, S02 Emission Rates and
Heat Input over Time, 1990 and 2010
Source: EPA, 2011
Interactive motion charts are a key feature on the quarterly
tracking website. Figure 17 shows examples of motion charts
created to show changes in ARP S02 emissions and S02 emis-
sion rates over time (from 1990 to 2010}. These motion charts
show, historically, how coal-fired power plants have responded
to the ARP. Each circle on the motion chart represents a facil-
ity in the ARP with one or more units that burn coal to create
electricity. The size and color of these circles tell us some-
thing about the facility. To the right of the motion chart you
will find two legends. The color spectrum at the top represents
the emissions generated per unit of fuel (also known as the
S02 emission rate], with warmer colors (yellow through red)
representing a high emission rate and cooler colors (green
through blue] representing a low emission rate. The size of the
circle on the chart is proportional to the emissions from that
plant. On the interactive mapping website, the user can watch
this data move through time by clicking the play button.
19
-------
CAIR, ARP, and Former NBP 2010 Environmental and Health Results
Notes
1. Cox, W. M. & Chu, S.H. 1996. Assessment of interannual
ozone variation in urban areas from a climatological per-
spective. Atmospheric Environment. 30:16, 2615-2625.
Camalier, L., Cox, W.M. & Dolwick, P. 2007. The effects of meteo-
rology on ozone in urban areas and their use in assessing ozone
trends. Atmospheric 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 aver-
age for CAIR ozone season 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. 40 CFR Part 81. Designation of Areas for Air Quality Planning
Purposes.
6. U.S. Census. 2000.
7. U.S. Environmental Protection Agency (U.S. EPA]. 2009. In-
tegrated Science Assessment for Particulate Matter (Final
Report]. EPA-600-R-08-139F. National Center for Environ-
mental Assessment - RTP Division. December. Available on
the Internet at .
8. U.S. Environmental Protection Agency (U.S. EPA]. 2006. 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 .
9. U.S. Environmental Protection Agency (U.S. EPA]. 2008. In-
tegrated Science Assessment for Oxides of Nitrogen and
Sulfur Ecological Criteria (Final Report]. National Center
for Environmental Assessment, Research Triangle Park,
NC. EPA/600/R-08/139. December. Available on the In-
ternet at .
10. Stoddard, J. L.;etal. (2003] Response ofSurface Water Chemistry
to the Clean Air Act Amendments of 1990; EPA/620/R-03/001;
U.S. EPA: Washington, DC.
11. Nilsson, J. & Grennfelt, P. (Eds] (1988] Critical loads for sulphur
and nitrogen. UNECE/Nordic Council workshop report, Skok-
loster, Sweden. March 1988. Nordic Council of Ministers: Co-
penhagen.
12. EPA, 2008 and DuPont J., T.A. Clair, C. Gagnon, D.S. Jeffries,
J.S. Kahl, and S.J. Nelson, and J. M. Peckenham. (2005]. En-
vironmental Monitoring and Assessment 109: 275-291
13. Sullivan T.J., B.J. Cosby, J.R. Webb, R.L. Dennis, A.J. Bulger, and
F.A. Deviney, Jr. 2007. Streamwater acid-base chemistry and
critical loads of atmospheric sulfur deposition in Shenandoah
National Park, Virginia. Environmental Monitoringand Assess-
ment 137:85 99
20
------- |