Acid Rain Progra

2005 PROGRESS REPO
Summary ....................................................................................................2

Origins of the Acid Rain Program ................................................................4

SO2 Emission Reductions ............................................................................5

SO2 Program Compliance ...........................................................................7

SO2 Allowance Market ................................................................................8

SO2 Compliance Options ..........................................................................10

NOx Emission Reductions and Compliance................................................11

Emission Monitoring and Reporting ..........................................................13

Status and Trends in Air Quality, Acid Deposition, and Ecological Effects ......14

Air Quality ................................................................................................17

Acid Deposition ........................................................................................20

Recovery of Acidified Lakes and Streams....................................................22

Quantifying Costs and Benefits of the Acid Rain Program...........................24

Further National Controls to Protect Human Health and the Environment.....26

Online Information, Data, and Resources ..................................................27

Endnotes ..................................................................................................28

EPA-430-R-06-015

Clean Air Markets Division

Office of Air and Radiation

U.S. Environmental Protection Agency

October 2006
(ARP), status of implementation, and progress toward

achieving environmental goals.

The Acid Rain Program 2005 Progress Report updates

data reported in previous years, specifically:

• Sulfur dioxide (SO2) emissions, allowance market

information, and program compliance.

• Nitrogen oxides (NOx) emissions and program

compliance.

• Status and trends in acid deposition, air quality, and

ecological effects.

• Future programs that build on the ARP to further

address environmental quality.

The Acid Rain Program 2005 Progress Report includes

special sections on fuel switching, EPA’s framework for

accountability, program costs and benefits, surface water

quality monitoring, impact assessment, environmental 

justice, and new rules.

For more information on the ARP, including additional information on SO2 and NOx emissions, acid 

deposition monitoring, environmental effects of acid 

deposition, and detailed unit-level emissions data, please

visit EPA’s Clean Air Markets Web site at

<www.epa.gov/airmarkets>.
yy, 

x 

volatile organic compounds (VOCs) to form

ground-level ozone (smog).The U.S. electric power

industry accounts for approximately 67 percent of

total U.S. SO2 emissions and 22 percent of total

U.S. NOx emissions from man-made sources.1

The Acid Rain Program (ARP) was created

under Title IV of the 1990 Clean Air Act

Amendments to reduce the adverse effects of acid

deposition through reductions in annual emissions

of SO2 and NOx.The act calls for SO2 reductions

of 10 million tons from 1980 emission levels, largely achieved through a market-based cap and trade

program, which utilizes emission caps to permanently limit the level of SO2 emissions from power

plants. NOx reductions are achieved through a 

program closer to a more traditional, rate-based

regulatory system.The NOx program is designed to

achieve a 2 million ton reduction from what NOx

emission levels were projected to be in the year

2000 without implementation of Title IV.

Since the start of the ARP in 1995, reductions

in SO2 and NOx emissions from the power sector

have contributed to significant air quality and

environmental and human health improvements.

The SO2 program affected 3,456 operating 

generating units in 2005 (with most emissio

duced by about 1,100 coal-fired units).The 

program applied to a subset of 982 operatin

fired units in 2005.

The 2005 compliance year marked the

eleventh year of the program. During this pe

the ARP has:

• Reduced SO2 emissions by more than 5

lion tons from 1990 levels, or about 35 p

of total power sector emissions. Compar

1980 levels, SO2 emissions from power p

have dropped by more than 7 million to

about 41 percent.

• Cut NOx emissions by about 3 million to

from 1990 levels, so that emissions in 200

less than half the level anticipated withou

program. Other efforts, such as the NOx 

Trading Program in the eastern United S

also contributed significantly to this reduc
emissions data ever developed and made those

data available and accessible through comprehensive electronic data reporting and Webbased tools for agencies, researchers, affected

sources, and the public.

• Delivered pioneering e-government results, automating

administrative processes,

reducing paper use, and providing online systems for

doing business with EPA.

• Achieved extremely high

compliance levels. No units

operating in the ARP during

2005 were found out of compliance with the allowance

holding requirements.

• Reduced implementation

costs by allowing sources to

choose cost-effective compliance strategies.

After 11 years of implementation, monitoring,

and assessment, the ARP has proven to be an effective and efficient means of meeting emission reduction goals under the Clean Air Act. A 2005 study2

estimated the program’s benefits at $122 billion

annually in 2010, while cost estimates are around

$3 billion annually (in 2000$). Despite the program’s historic and projected benefits, however,

EPA analyses of recent studies of human health,

data from long-term monitoring networks, and

ecological assessments have revealed the need for

additional emission reductions to protect human

health and continue ecological recovery and protection. EPA recognized the need for further SO2

and NOx controls on the power industry to address

transport problems many states face in efforts to

CAIR in March 2005 to address transport o

particles and ozone in the eastern United St

CAVR to improve visibility in national park

wilderness areas; and CAMR to reduce nati

mercury emissions from co

fired power plants. Starting 

2009 and 2010, CAIR esta

regional caps on SO2 and 

emissions for affected easte

states.Annual SO2 emissio

capped at 3.7 million tons 

2010 and 2.6 million tons 

2015.Annual NOx emissio

capped at 1.5 million tons 

2009 and 1.3 million tons 

2015. CAIR will operate c

rently with the ARP.

CAVR addresses SO2 a

NOx emissions from non-

states located in the West a

parts of New England. Aff

sources under CAVR mus

reduce SO2 and NOx emissions impairing v

in national parks and wilderness areas. Notab

EPA has proposed to allow power plants and 

stationary sources to establish regional cap a

trade programs to accomplish these reductio

CAMR establishes a national cap on me

emissions beginning in 2010 and utilizes a m

based cap and trade program.Additionally, n

existing coal-fired power plants—the nation

largest sources of mercury emissions—will b

required to meet standards of performance t

limit mercury emissions.These programs wi

as a key component of strategies to protect h

health and the environment across the Unite

States into the next decade.
g p

compounds hundreds of miles,

often across state and national borders, where they impair air quality

and damage public health, acidify

lakes and streams, harm sensitive

forests and coastal ecosystems,

degrade visibility, and accelerate

the decay of building materials.

The Acid Rain Program

(ARP), established under Title IV

of the 1990 Clean Air Act

Amendments, requires major

reductions of SO2 and NOx emissions from the electric power

industry.The SO2 program sets a permanent cap

on the total amount of SO2 that may be emitted

by electric generating units in the contiguous

United States.The program is phased in, with the

final 2010 SO2 cap set at 8.95 million tons, a level

of about one-half of the emissions from the power

sector in 1980.

As seen in Figure 1, emissions of both SO2 and

NOx have dropped markedly under the ARP

while combustion of fossil fuel, measured as “heat

input,” for electricity generation has increased significantly.

Using a market-based cap and trade mechanism to reduce SO2 emissions allows flexibility for

individual combustion units to select their own

methods of compliance. Currently, one allowance

provides a regulated unit limited authorization to

emit one ton of SO2.The Clean Air Act allocates

allowances to regulated units based on historic 

fuel consumption and specific emission rates prior

to the start of the program.The total allowa

allocated for each year equal the SO2 emissi

The program encourages early reductions by

allowing sources to bank unused allowances 

year and use them in a later year.

The ARP has closer to a traditional appr

to achieve NOx emission reductions. Rate-b

limits apply to most of the coal-fired electric 

boilers subject to the ARP.

The ARP is composed of two phases for 

and NOx. Phase I applied primarily to the la

coal-fired electric generation sources from 1

through 1999 for SO2 and from 1996 throu

1999 for NOx. Phase II for both pollutants b

in 2000. In 2005, the SO2 Phase II requirem

applied to 3,456 operating units; the Phase I

requirements applied to 982 of those operat

units that are >_ 25 megawatts and burned co

between 1990 and 1995.

Heat Input

SO2 Emissions

Electricity Net Generation

Average Retail Price of Electricity

NOx Emissions

-50%

-40%

-30%

-20%

-10%

0%

Percent Cha

1990 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 

Year

* Generation from fossil fuel-fired plants. 

** Constant year 2000 dollars adjusted for inflation. 

Source: Energy Information Administration, Annual Energy Review, 2005 (electrici

tion, retail price); EPA (heat input, emissions), 2005
(including industrial and commercial boilers and the metals and 

9.4 9.3 8.7

5.3 5.4 5.5 5.3 4.9

17.3

16.1 15.7

11.9 12.5

13.0 13.1

12.5

11.2 10.6 10.2 10.6 10.3 10.2

8.7 8.3

7.1 7.0

9.6 9.5 10.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

All Affected Sources

Phase II (2000 on) Sources

Phase I (1995-1999) Sources

Allowances Allocated 

7.0

9.5 9.5 9.5

1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

SO2 Emissions (million tons)

Year

Figure 2: SO2 Emissions from Acid Rain Program Sources

✧ In 1995, the first 

year of implement

tion, SO2 emission

decreased by 24 

percent—nearly 

4 million tons—fro

1990 levels.

✧ During the past

decade, SO2 emissions dropped an

additional 14 perc

from 1995 levels

despite a 24 perce

increase in power

generation (based 

heat input).

✧ In 2005, SO2 emis

sions from all ARP

units totaled 10.2

million tons, a 35

percent decrease

from 1990 levels

(15.7 million tons

✧ Until SO2 allowanc

prices began to

increase in 2004 in

anticipation of EPA

2005 Clean Air

Interstate Rule

(CAIR), prices gene

ally remained unde

$200/ton, well belo

expected control co

for the program. 0

5

10

15

20

25

8.7

11.7

13.4

15.0

16.6

21.6

19.9

18.8

18.2

17.1

16.4

SO2 Emissions (million tons)

Year

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005

Allowances Allocated that Year

Unused Allowances from 

Previous Year (bank)

Actual Emissions from Affected Sources

Figure 3: SO2 Emissions and the Allowance Bank, 1995-2005

Source: EPA, 2006

Source: EPA, 2006
with more than 6.8 million unused allowances carried over (or banked) from prior years, there were

nearly 16.4 million allowances available for use in

2005. Sources emitted 10.2 million tons of SO2 in

2005, somewhat more than the allowances allocated for the year, but far less than the total

allowances available (see Figure 3).4

The number of banked allowances dropped from

6.8 million available for 2005 compliance to 6.2 million available for 2006 and future years, a 10 percent

reduction of the total bank. In the next several years,

industry anticipation of stringent emission requirements under the Clean Air Interstate Rule (CAIR) is

expected to encourage sources to pursue additional

reductions.While these reductions will result in an

increase in banked allowances, tighter retirement

ratios under CAIR will lead to depletion of the bank

and further emission reductions. In 2010, the total

number of Title IV allowances allocated annually

drops to 8.95 million (about half of the emissions

from the power industry in 1980) and remains statutorily fixed at that annual level permanently.Table 1

explains in more detail the origin of the allowances

that were available for use in 2005, and Table 2 on

page 7 shows how those allowances were used.

The states with the highest emitting sources in

1990 have seen the greatest SO2 reductions during

the ARP (see Figure 4). Most of these states are

upwind of the areas the ARP was designed to 

protect, and reductions have resulted in important 

environmental and health benefits over a large

regional scale. In addition, the states that reduced

emissions from 1990 to 2005 had total annual reductions of approximately 6 million tons, while the

states that increased emissions—largely attributable to

growth and not increases in emission rates—had

much smaller annual increases of approximately 

lization and em

rates specified i

Clean Air Act.

Allowance

Auction

250,000 The allowance 

tion provides

allowances to t

market that we

aside in a Spec

Allowance Rese

when the initia

allowance alloc

was made. 

Opt-in

Allowances

97,678 Opt-in allowan

provided to un

entering the pro

voluntarily. The

were eight opt-

units in 2005. 

Total 2005

Allocation

9,539,575 

Total

Banked

Allowances**

6,845,477 Banked allowan

are those allow

accrued in acco

from previous y

which can be u

compliance in 2

or any future ye

Total 2005

Allowable

Emissions

16,385,052

Source: EPA, 2006

*In this report, the term “unit” means a fossil fuel-fired combu

serves a generator that provides electricity for sale. The vast maj

SO2 emissions under the program result from coal-fired generat

but oil and natural gas units are also included in the program. 

**Total banked allowances are adjusted from the 2004 Progress 

account for additional deductions made for electronic data rep

(EDR) resubmissions after 2004 reconciliation was completed.
Indiana, Kentucky,

Massachusetts, Missouri, New

York, Ohio, Pennsylvania,

Tennessee,West Virginia, and

Wisconsin.The states with the

greatest annual reductions were

in the Midwest and include

Ohio (1.1 million tons

reduced), Illinois, Indiana,

Missouri,Tennessee, and West

Virginia, each of which reduced

over 500,000 tons per year.

Scale: Largest bar equals

2.2 million tons of 

 emissions in Ohio, 1990

SO2

SO Emissions in 1990 2

SO Emissions in 1995 2

SO Emissions in 2000 2

SO Emissions in 2005 2

Source: EPA, 2006

Approximately 10.2 million

allowances were deducted from

sources’ accounts in 2005 to cover

emissions.Table 2 displays these

allowance deductions, as well as the

remaining banked allowances from

1995 through 2005. In 2005, all Acid

Rain Program (ARP) units were in

compliance with the allowance holding requirements and no excess emissions penalties were paid.5 Title IV

set a penalty of $2,000 per ton in

1990, which is adjusted annually for

inflation.The 2005 penalty level was

set at $3,042 per excess ton, but no

penalties were levied.The ARP’s cap

and trade approach offers emission

sources the flexibility to comply with

regulations using their choice of the

most cost-effective strategies available. Since the program’s inception,

the compliance rate has consistently

been extraordinarily high.

SO2 Program Compliance

TOTAL HELD ON MARCH 1, 2006* 16,3

Unit Accounts Subject to Reconciliation 13,10

Other Accounts** 3,28

TOTAL DEDUCTIONS 10,22

Emissions*** 10,22

Penalties (2006 Vintage) 

TOTAL BANKED 6,16

Unit Accounts Subject to Reconciliation 2,87

Other Accounts 3,28

Table 2: SO2 Allowance Reconciliation Summary, 2005

Source: EPA, 2006

* March 1, 2006, is the allowance transfer deadline, the point in time at which un

accounts were frozen and after which no transfers of 1995 through 2005 allowa

recorded. The freeze on these accounts was removed when annual reconciliation 

complete. 

** Other accounts include general accounts and unit accounts that are not subject 

ciliation. General accounts can be established in the Allowance Tracking System 

any utility, individual, or other organization.

*** Includes 310 allowances deducted from opt-in sources for reduced utilization. 
Other sources have been able to postpone or

reduce expenditures for control by purchasing

allowances from sources that controlled below

their allowance allocation level.The allowance

prices ultimately reflect

these flexible compliance

decisions. Economists refer

to this as the marginal cost

of compliance—the cost of

reducing the next ton of

SO2 emitted from the

power sector.

The cost of emission

allowances was initially

projected to be between

$250 and $500 per ton

during Phase I (1995 to

1999) and $500 to $1,000

per ton in Phase II (beyond 2000). As shown in

Figure 5, actual allowance prices were in the $100

to $200 range, with a low of $65 in 1996. Even as

the more stringent Phase II requirements became

effective in 2000, prices were generally below the

$200 per allowance mark until they started to rise

at the end of 2003. Market observers believe that

the lower than expected prices early in the program were due primarily to reduced compliance

costs.The availability of low-cost, low-sulfur 

coal resulted in larger than expected emission

reductions, which increased the supply of

allowances and put downward pressure on the

market. In addition, technological innovation

reduced the expected marginal costs of scrubbers

by over 40 percent from original estimates.These

cost and emission reductions led to a large bank of

allowances from Phase I that were available for

to initial uncertainty as EPA finalized the C

Air Interstate Rule (CAIR). CAIR requires 

ther SO2 reductions from sources in many e

states beginning in 2010.These additional re

tions cause an incre

the expected margi

cost of compliance 

future years. Becaus

allowances are bank

today for use in fut

years, estimates of fu

control costs impac

current market pric

allowances. Howeve

apparent overly con

tive reaction by buy

who wanted assuran

that they could cov

rent and future allow

needs, caused market prices to exceed EPA’s 

mate of future control costs. In the first half 

2006, however, allowance prices have fallen 

and were just over $600 per ton at the end o

2006.This price level is more consistent wit

where EPA has expected allowances to be to

given estimates of the marginal cost of redu

SO2 emissions under CAIR. EPA has seen

temporary run-ups in the allowance markets

before, with appropriate downward adjustme

buyers and sellers more completely assess ma

fundamentals. For instance, at the beginning 

compliance with the NOx Budget Program

EPA observed a similar pattern of market ru

followed by a self-correction.

In fact, current SO2 allowance market co

tions (as of September 2006) track closely w

EPA’s estimates.The current SO2 allowance 
approximately $360 per

allowance due to the 2:1 retirement ratio that applies to those

vintage allowances for sources

in the CAIR region.

July 2006 spot market prices

show that prices for the earlier

vintage are trading for $610 to

$740 per ton, and the later vintages (2010–2014) are trading for

$308 to $390 per ton.

In 2005, nearly 5,700 private

allowance transfers (moving

roughly 19.9 million allowances

of past, current, and future vintages) were recorded in the 

EPA Allowance Tracking System

(ATS).About 10 million 

(50 percent) were transferred in

economically significant transactions (i.e., between economically

unrelated parties).Transfers

between economically unrelated

parties are a better indicator of a

vibrant market than are transactions among the various units of

a given company. In the majority

of these transfers, allowances

were acquired by power companies. Figure 7 shows the annual

volume of SO2 allowances transferred under the ARP (excluding allocations, retirements, and

other transfers by EPA) since

official recording of transfers

began in 1994.

19

15.3 16.5

21.4 22.5

25.0

18.7

13.5

15.2

8.2

16.7

9.2

0

5

10

15

20

25

30

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2

Allowances (millions)

Year

Between economically related organizations.

Between economically unrelated organizations (significant transfers).

Figure 7: SO2 Allowances Transferred under the

Acid Rain Program

Source: EPA, 2006

$0

$200

1994199519961997199819992000200120022003200420052006

Price (

Year

Source: Cantor Fitzgerald Market Price Index, 2006

$721

$360

EPA Projected Allowance Price 

in 2010 (in 2006 Dollars) 

Up to 2010 Vintage 2010-2014 Vintage

July 2006 Spot 

Market Price Range*

2006 Vintage 2010 Vintage

$308

$390

$610

$740

* EPA analysis suggests that 2006 vintage allowances should be selling for ab

$600 per allowance and 2010 allowances should be about $300 per allowan

Source: EPA, 2006, and Evolution Markets, LLC, 2006

Figure 6: Actual and Forecast Allowance Prices 
p

December 2001, parties began to use a system

developed by EPA to allow online allowance

transfers. In 2005, account holders registered

about 98 percent of all private allowance transfers

through EPA’s online transfer system.6

Other Renewables

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

3,000,000

3,500,000

4,000,000

4,500,000

1990

1992

1994

1996

1998

2000

2002

2004

Gigawatt Hours

Year

Hydroelectric

Nuclear

Natural Gas

Petroleum

Coal

Figure 9: Net Electric Generation 

by Energy Source

Source: EPA, 2006

Since 1995, the majority of units affected by

the Acid Rain Program (ARP) have chosen to

comply with the emission reduction requirements

by using or blending low-sulfur coal, installing

SO2 and NOx controls such as scrubbers and

low-NOx burners, or purchasing allowances from

the market or using banked allowances.

According to the Energy Information

Administration, the 1987 repeal of the Power

Plant and Industrial Fuel Use Act prohibiting the

use of natural gas by new electric generating units

led to a large increase in natural gas generating

capacity through 2000.7 Additional factors

contributing to this increase were low natur

prices through the 1990s, the availability of

increasingly efficient natural gas technology 

form of advanced combined cycle units, the 

construction-to-operation time to build new 

bined cycle units, and the attractiveness of

natural gas as a trace SO2-emitting fuel sour

However, coal-fired generation grew fro

1990 to 2004, taking advantage of the exces

capacity available at existing plants.Today, co

remains the largest single fuel used for gener

electricity in the United States, at 50 percen

net generation in 2005 (see Figure 9).

SO2 Compliance Options

0

Year

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 200

Source: EPA, 2006.

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

Existing

pulverized

coal plant

retrofitted

with SCR and

FGD

Exisiting

pulverized

coal plant

w/o SCR and

FGD

New

pulverized

coal plant

with BACT

controls

New

combined

cycle plant

with BACT

controls

New

pulverize

coal pla

w/o BAC

control

Capital costs

Fuel costs

Var

Fixe

Cents per kWh (1995$)

Figure 10: Comparison of Electric Generation Cost

Base Load Coal-fired and Gas-fired Electric Genera

*Unit sizes used in this analysis are around 325 megawatts.

Source: EPA, 2006
These factors contributed to an economic situation where it became more economical in many

regions of the country to retrofit existing baseload

coal plants with scrubbers than to build new coalfired capacity to enhance existing load or to build

new coal-fired capacity where excess coal capacity

was available at existing plants.Where excess coalfired capacity was not an alternative, building new

combined cycle units was the cheapest alternative

to meet new load requirements (see Figure 10).

g

Virginia). For the most part, the

areas have been, and continue t

comparatively high users of natu

and oil and have the infrastructu

support natural gas-fired electric 

eration. In particular, the West South Centr

Pacific Contiguous regions, which contribu

over half of the electricity generated by nat

gas in the United States, have a long histor

oil and gas generation that precedes the im

mentation of the ARP in 1995 (see Figure 

Additionally, the West South Central and P

Contiguous regions have not traditionally b

heavily affected by the requirements of the 

Title IV of the 1990 Clean

Air Act Amendments requires

NOx emission reductions for

certain coal-fired electric generating units. Unlike the SO2 program, Congress applied

rate-based emission limits based

on a unit’s boiler type to achieve

NOx reductions (see Table 3).

The NOx emission limit is

expressed as pounds of NOx per

unit of heat input (lbs/million

British thermal units [mmBtu])

for each boiler subject to a NOx

limit. Owners can meet the

NOx limits for each individual

unit or meet group NOx limits

through averaging plans for

groups of units that share a 

common owner and designated

NOx Emission Reductions and Compliance

Source: EPA, 2006

Table 3: Number of NOx-Affected Title IV Units by Boiler T

and NOx Emission Limit

Coal-Fired Boiler Type Title IV Standard

Emission Limits

(lb/mmBtu)

Num

U

Phase I Group 1 Tangentially Fired 0.45 1

Phase I Group 1 Dry Bottom,

Wall-fired

0.50 1

Phase II Group 1 Tangentially Fired 0.40 3

Phase II Group 1 Dry Bottom,

Wall-fired

0.46 2

Cell Burners 0.68 3

Cyclones >155 MW 0.86 5

Wet Bottom >65 MW 0.84 2

Vertically Fired 0.80 2

Total n/a 9

New Engla

Middle Atlan

East North Cent

West North Cent

South Atlan

East South Centr

West South Cent

Mount

Pacific Contiguo

Source: Energy Information Administration, 2006
were projected to occur in

2000 absent the ARP (8.1 million tons).This goal was first

achieved in 2000 and has been

met every year thereafter,

including 2005. Figure 12

shows that NOx emissions from

all ARP sources were 3.6 million tons in 2005.This level is

4.5 million tons less than the

projected level in 2000 without

the ARP, or more than double

the Title IV NOx emission

reduction objective.These

reductions have been achieved

while the amount of fuel burned

to produce electricity at all ARP

units in 2005, as measured by

heat input, has increased 38 percent since 1990.While the ARP

was responsible for a large portion of these annual NOx reductions, other programs (such as

the Ozone Transport

Commission’s NOx Budget

Program, EPA’s NOx State

Implementation Plan (SIP) Call,

and regional NOx emission control programs) also contributed

significantly to the NOx reductions achieved by sources in

2005.

As with SO2, the states with the highest 

NOx-emitting sources in 1990 tended to see the

greatest power plant NOx emission reductions 

(see Figure 13).The sum of reductions in the 39

states and the District of Columbia that had lower

annual NOx emissions in 2005 than in 1990 

approximately 2.8 million tons, while the su

increases in the nine states that had higher a

NOx emissions in 2005 than in 1990 was m

smaller, about 61,000 tons. Eight of the 11 s

with NOx emission decreases of more than

100,000 tons were in the Ohio River Basin

0

1

1990 1995 1996 1997 1998 1999 2000 2001 2002 2003 200

Year

NOx E

NOx Program Affected Sources

Title IV Sources Not Affected by NOx Program

Source: E

NO Emissions in 1990 x

NO Emissions in 1995 x

NO Emissions in 2000 x

NO Emissions in 2005 x

Scale: Largest bar equals 500,000 

tons of NOx emissions in Ohio, 1990 

Note: 2005 NOx Budget Program 

states shaded in gray

Figure 13: State-by-State NOx Emission Levels for Acid Rain

Program Sources, 1990–2005

Source: EPA, 2006
method.The vast majority of

emissions are monitored with

CEMS while the alternatives

provide an efficient means of

monitoring emissions from the

large universe of units with

lower overall mass emission

levels (see Figures 14 and 15).

Since the program’s inception in 1995, emissions have

been continuously monitored

and reported, verified, and

recorded by EPA, and provided

to the public through EPA’s

Web site. Hourly emissions data

are reported for all affected

sources in quarterly electronic

reports, and EPA conducts

automated software audits that

perform rigorous checks to ensure the completeness, quality, and integrity of the emissions data.

CEMS and approved alternatives are a cornerstone

of the ARP’s accountability and transparency. All 

emissions data are available to the public at EPA’s

Clean Air Markets Data and Maps Web site at

<http://cfpub.epa.gov/gdm/>.The site also provides access to a variety of other data associated

with emission trading programs, including reports,

queries, maps, charts, and file downloads covering

source information, emissions, allowances, program

compliance, and air quality.

The emission monitoring requirements f

ARP are found in 40 CFR Part 75.These p

sions are also required for participation in th

Budget Trading Program, a NOx summer se

trading program implemented by many east

states in response to EPA’s 1998 NOx SIP C

The Part 75 requirements will also be used 

future to implement the Clean Air Interstate 

(CAIR) and the Clean Air Mercury Rule

(CAMR).

56

18 176

5

Coal Units w/ CEMS Waste Units w/CEMS Oil Units w/ CEMS

Oil Units w/o CEMS Gas Units w/o CEMS Gas Units w/ CEMS

96%

<0.1% 1% 2% <0.1% <0.3%

Coal Units w/ CEMS Waste Units w/CEMS Oil Units w/ CEMS

Oil Units w/o CEMS Gas Units w/o CEMS Gas Units w/ CEMS

Figure 15: Monitoring Methodology for the Acid Rain Pro

Total SO2 Mass

Source: EPA, 2006

Source: EPA, 2006
from acidification in fresh water lakes and streams, improvements 

bility, and reduced risk to forests, materials, and structures.Table 4 

the regional changes in key air quality and atmospheric deposition

measurements linked to the ARP’s SO2 and NOx emission reduc

Title IV has been quite suc

cessful in reducing

emissions of SO2 and NOx

from power generation.

These reductions have

improved air quality,

visibility, and human

health at a relatively low

cost compared to the

benefits generated. 

However, the report also

noted that several scientific

studies indicate that

recovery of acid-sensitive

ecosystems will require

40 to 80 percent further

emission reductions

beyond those anticipated

with full implementation of

Title IV. Power generation

currently contributes

approximately 67 percent

of the SO2 emissions and

22 percent of the NOx

emissions nationwide. Even

if all SO2 emissions from

power plants were eliminated, reductions from

other source categories

would be needed for

full protection of all acidsensitive ecosystems affected by acid deposition. 

To view the report, visit: 

<www.al.noaa.gov/AQRS/

reports/napapreport05.pdf>

Measurement Unit Region Average P

Ch

1989–1991 2003–2005

Wet Sulfate 

Deposition

kg/ha Mid-Atlantic

Midwest

Northeast

Southeast

27

23

23

18

20

16

14

15

Wet Sulfate 

Concentration

mg/L Mid-Atlantic

Midwest

Northeast

Southeast

2.4

2.3

1.9

1.3

1.6

1.6

1.1

1.1

Ambient Sulfur

Dioxide 

Concentration

μg/m3 Mid-Atlantic

Midwest

Northeast

Southeast

13

10

6.8

5.2

8.4

5.8

3.1

3.4

Ambient Sulfate

Concentration

μg/m3 Mid-Atlantic

Midwest

Northeast

Southeast

6.4

5.6

3.9

5.4

4.5

3.8

2.5

4.1

Wet Inorganic

Nitrogen 

Deposition

kg/ha Mid-Atlantic

Midwest

Northeast

Southeast

5.9

6.0

5.3

4.3

5.5

5.5

4.1

4.4

Wet Nitrate 

Concentration

mg/L Mid-Atlantic

Midwest

Northeast

Southeast

1.5

1.4

1.3

0.8

1.0

1.2

0.9

0.7

Ambient Nitrate

Concentration

μg/m3 Mid-Atlantic

Midwest

Northeast

Southeast

0.9

2.1

0.4

0.6

1.0

1.8

0.5

0.7

Total Ambient 

Nitrate Concentration (Nitrate +

Nitric acid)

μg/m3 Mid-Atlantic

Midwest

Northeast

Southeast

3.5

4.0

2.0

2.2

3.0

3.5

1.7

2.1

Table 4: Regional Changes in Air Quality and Deposition o

Sulfur and Nitrogen, 1989–1991 Versus 2003–2005

Source: Clean Air Status and Trends Network (CASTNET) and the National Atmospheric

Deposition Program/National Trends Network (NADP/NTN)

* Percent change is estimated from raw measurement data, not rounded; some of the me

ment data used to calculate percentages may be at or below detection limits.
p, 

action to achieve further progress. For ecosystem protection, the recommendations include

✧ Improving monitoring and tracking of ecosystems and science to support secondary or

alternative standards.

✧ Taking an “airshed” approach.

✧ Emphasizing results, accountability, and dynamic, data-based program adjustment.

EPA’s Clean Air Act Advisory Committee (CAAAC) expanded on the NAS recommendation

with further ecosystem-related recommendations, including the establishment of:

✧ A framework for accountability

✧ Benchmarks and measures of the ecological impacts of air pollution

✧ Effects of multiple pollutants

✧ Measures of ecosystem response

✧ Collaborative integrated assessments

✧ Critical loads and thresholds

Air Quality Management in the United States, National Academies Press: 

<www.nap.edu/catalog/10728.html>
groundlevel ozone, and other forms of atmospheric pollution. Established in 1987, CASTN

now consists of nearly 90 sites across the United States. EPA’s Office of Air and Radiation o

ates most of the monitoring stations; the National Park Service (NPS) funds and operates

approximately 30 stations in cooperation with EPA. Many CASTNET sites are approaching a

continuous 20-year data record, reflecting EPA’s commitment to long-term environmental m

toring. Public access to CASTNET data is available at <www.epa.gov/castnet>.

EPA also uses data from other ambient monitoring networks, including the State and Local

Ambient Monitoring and National Ambient Monitoring Systems (SLAMS/NAMS). These net

works are used to document attainment of National Ambient Air Quality Standards (NAAQ

and show trends in ambient air quality over time.

NADP/NTN is a nationwide, long-term network tracking the chemistry of precipitation.

NADP/NTN offers data on hydrogen (acidity measured as pH), sulfate, nitrate, ammonium, 

ride, and base cations. The network is a cooperative effort involving many groups, including t

State Agricultural Experiment Stations, U.S. Geological Survey, U.S. Department of Agricultur

EPA, NPS, National Oceanic and Atmospheric Administration (NOAA), and other governmen

and private entities. NADP/NTN has grown from 22 stations at the end of 1978 to more tha

sites spanning the continental United States, Alaska, Puerto Rico, and the Virgin Islands.

Chemicals Chemical

Species

Measured In Why are these measured by the networks?

Ambient Air Wet Deposition

SO2 Sulfur

Dioxide

X Primary precursor of wet and dry acid deposition; primary 

cursor to fine particles in many regions.

SO4

2- Sulfate Ion X X Major contributor to wet acid deposition; major compone

fine particles in the Midwest and eastern regions; can be tr

ported over large distances; formed from reaction of sulfur

dioxide in the atmosphere. 

NO3- Nitrates Ion X X Contributor to acid and nitrogen wet deposition; major co

ponent of fine particles in urban areas; formed from reacti

of NOx in the atmosphere.

HNO3 Nitric Acid X Strong acid and major component of dry nitrogen deposit

formed as a secondary product from NOx in the atmosphe

NH4

+ Ammonium

Ion

X X Contributor to wet and dry nitrogen deposition; major com

nent of fine particles; provides neutralizing role for acidic c

pounds; formed from ammonia gas in the atmosphere.

H+ Ionic

Hydrogen

X Indicator of acidity in precipitation; formed from reaction 

sulfate and nitrate in water.

Ca2

+

Mg2

+

K+

Na+

Calcium

Magnesium

Potassium

Sodium

X

X

X

X

X

X

X

X

These base cations neutralize acidic compounds in precipit

tion and the environment; also play a major role in plant n

tion and soil productivity.

Table 5: Air Quality and Acid Deposition Measurements
Figure 17a: Annual Mean Ambient Sulfur

Dioxide Concentration, 1989–1991*

Source: CASTNET

Figure 17b: Annual Mean Ambient Sulfur

Dioxide Concentration, 2003–2005

Source: CASTNET

monitored violation of the SO2 ambient air quality

standard since 2000. Based on EPA’s latest air quality

trends data located at <www.epa.gov/airtrends>,

the national composite average of SO2 annual mean

ambient concentrations decreased 48 percent

between 1990 and 2005, as shown in Figure 16.

The largest single-year reduction (21 percent)

occurred in the first year of the Acid Rain Program

(ARP), between 1994 and 1995.

These trends are consistent with the ambient

trends observed in Clean Air Status and Trends

Network (CASTNET). During the late 1990s,

following implementation of Phase I of the ARP,

dramatic regional improvements in SO2 and 

ambient sulfate concentrations were observed at

CASTNET sites throughout the eastern Un

States due to the large reductions in SO2 em

from ARP sources.Three-year mean annual 

concentrations of SO2 and sulfate from CAS

NET long-term monitoring sites are compa

from 1989 through 1991 and 2003 through 

in both tabular form (see Table 4 on page 14

graphically in maps (see Figures 17a through 

Conce

0.00

0.01

1980 1985 19901995 2000 

Year

10% of sites have concentrations below this line.

Source: EPA air emission trends, <www.epa.gov/airtrend

*Dots on all maps represent monitoring sites. Lack of shading for southern Florida on Figures 17a, 18a, and 19a indicates lack of monitoring 
Source: CASTNETSource: CASTNET

Figure 19a: Annual Mean Total Ambient 

Nitrate Concentration, 1989–1991

Source: CASTNET

Figure 19b: Annual Mean Total Ambient 

Nitrate Concentration, 2003–2005

Source: CASTNET
ambient sulfate concentrations, greater than 

7 micrograms per cubic meter (μg/m3

), were also

gy

declined, with the largest decreases observed 

the Ohio River Valley (see Figures 18a and 

Assessing Recent Monitoring Data—Sulfate

Air quality monitoring networks such as the Clean Air Status and Trends Network (CASTNET

report air concentration data for both primary (sulfur dioxide) and secondary (sulfate) pollu

tants as an indication of changes in power plant emissions. Continuous emission monitors o

fossil fuel-burning power plants at the unit or stack level provide the data for SO2 emissions

which show a national decrease from 2004 to 2005. Interestingly, ambient monitoring data 

CASTNET for 2005 show an increase in sulfate (SO4

2

) concentrations—an important constit

of fine particulate matter—across much of the eastern United States. This observed increase 

not correlate with the relatively steady or declining emissions data from regional sources and 

likely to be the result of year-to-year variations in meteorological conditions or other factors

Sulfate ion formation is the result of complex chemical and physical processes involving emi

sions from Acid Rain Program (ARP) sources, non-ARP sources (i.e., industrial processes, ag

culture and transportation), meteorological conditions, and other phenomena. EPA employ

range of analytical and assessment protocols to understand these processes, including mod

of source/receptor relationships, source apportionment, and atmospheric transport process

Although the ARP has achieved significant reductions in SO2 from coal-burning power plants—

35 percent since 1990—sulfate deposition and concentrations vary from year to year. This illus

the importance of long-term monitoring and accounting for annual variability to determine sta

and trends over time. Another steep reduction

in SO2 emissions is projected to be achieved by

the Clean Air Interstate Rule (CAIR), which wil

cap eastern SO2 emissions at 2.6 million tons i

2015, much lower than the ARP’s toughest cap

that starts in 2010. As with the ARP, this progr

is expected to result in significant emission red

tions. These reductions may be followed by pe

fluctuations in regional and source-specific

emissions as sources seek to comply with the c

as well as fluctuating signals from the air quali

and deposition monitoring networks.

Sulfate Concentrations

Source: CASTNET
agriculture).

In some areas, NOx levels can also be affected by

emissions transported via air currents over wide

y

sively, these improvements may be partly attrib

to added NOx controls installed for complian

the NOx Budget Trading Program.

National Atmospheric Deposition Program/

National Trends Network (NADP/NTN) monitoring data show significant improvements in most

deposition indicators. For example, wet sulfate

deposition—sulfate that falls to the earth through

rain, snow, and fog—has

decreased since the implementation of the Acid Rain

Program (ARP), particularly

throughout the early 1990s in

much of the Ohio River Valley

and northeastern United

States. Some of the greatest

reductions have occurred in

the mid-Appalachian region,

including Maryland, New

York,West Virginia,Virginia,

and most of Pennsylvania.

Other less dramatic reductions

have been observed across

much of New England,

portions of the southern

Appalachian Mountains, and

in some areas of the Midwest.

Between the 1989–1991

and 2003–2005 observation

periods, average decreases in wet deposition of

sulfate ranged from 36 percent in the Northeast to

19 percent in the Southeast (see Table 4 on page

14 and Figures 20a and 20b).Along with we

fate deposition, wet sulfate concentrations h

also decreased significantly. Since 1991, avera

levels decreased 40 percent in the Northeast

percent in the Mid-Atlantic, and 30 percent 

Midwest.A strong correl

between large-scale SO2 

sion reductions and large

reductions in sulfate conc

tions in precipitation has 

noted in the Northeast, o

the areas most affected by 

deposition.

A reduction in the lon

range transport of sulfate 

emission sources located i

Ohio River Valley is a pri

reason for reduced concen

tions of sulfate in precipit

in the Northeast.The red

in sulfate documented in 

Northeast, particularly acr

New England and portion

New York, were also affec

by SO2 emission reductio

eastern Canada. NADP data indicate that sim

reductions in precipitation acidity, expressed a

hydrogen ion (H+

) concentrations, occurred

concurrently with sulfate reductions.

Acid Deposition
Source: National Atmospheric Deposition Program

Figure 21a: Annual Mean Wet Inorganic

Nitrogen Deposition, 1989–1991

Figure 21b: Annual Mean Wet Inorgani

Nitrogen Deposition, 2003–2005

Reductions in nitrogen deposition recorded

since the early 1990s have been less dramatic

than those for sulfur.As noted earlier, emissions

from source categories other than ARP sources

significantly affect air concentrations and nitrogen

deposition. Inorganic nitrogen deposition dec

in the Mid-Atlantic and Midwest (8 percent) 

more significantly in the Northeast (23 perce

remained virtually unchanged in the Southea

Figures 21a and 21b).

Source: National Atmospheric Deposition Program

Source: National Atmospheric Deposition Program Source: National Atmospheric Deposition Program
United States. Climate

change, forest maturatio

logical disturbances (e.g

outbreaks), and land us

change can have an im

on ecosystems that are 

affected by acid deposi

Nevertheless, scientists 

demonstrated measurab

improvements in some 

and streams resulting fr

Acid Rain Program (A

Scientists studied lakes 

streams in four regions—

England, the Adirondac

Mountains, the norther

Appalachians (includin

Catskill Mountains), an

southern Appalachians

(including the Blue Ri

and found signs of reco

many, but not all, of tho

areas (see Figure 22).Th

signs of recovery includ

reductions in sulfate an

minum concentrations 

decreases in acidity.

The monitoring d

show that sulfate conc

tions are declining sub

tially in all but one of 

regions. Statistically sig

cant decreases in nitra

centrations are eviden

of the regions, althoug

magnitude of these ch

is small, especially in N

These measurements were plotted against time, and trends for

the given lake or stream during the 15-year period were then

calculated as the change in each of the measurements per year

(e.g., change in concentration of sulfate per year). Using the

trends calculated for each water body, median regional

changes were determined for each recovery measure. A negative value of the “slope of the regional trend” means that the

measure has been declining in the region, while a positive value

means it has been increasing. The greater the value of the

trend, the greater the yearly change in the measurement.

Movement toward recovery is indicated by positive trends in

acid neutralizing capacity (ANC) and negative trends in sulfate, nitrate,

hydrogen 

ion, and 

aluminum.

Negative

trends in

base cations

and positive

trends in

organic acids

can balance

out the

decreasing

trends in 

sulfate and

nitrate and prevent ANC from increasing. The results of these

regional trend analyses are shown in Figure 22 and Table 6. 

Increasing ANC was evident in two of the regions studied

(Adirondacks and northern Appalachians). One-quarter to

one-third of the lakes and streams in these regions previously

affected by acid rain are no longer acidic at base-flow conditions, although they are still highly sensitive to future changes

in deposition.

-5- -4 3 -2 -1 0 1 2

Sulfate

(μeq/L/yr)

Slope of Regional Trend

Nitrate

(μeq/L/yr)

ANC

(μeq/L/yr)

Hydrogen 

Ion (μeq/L/yr)

Base Cations

(μeq/L/yr)

So. Appalachian Streams (n=65)

No. Appalachian Streams (n=9)

Adirondack Lakes (n=49)

New England Lakes (n=21)

Figure 22: Regional Trends, Lakes and

Streams, 1990–2004

Source: EPA
England. It should be noted, however, that decreasing nitrate concentrations do not appear to be

related to the magnitude of changes in emissions

or deposition in these areas, but are likely a result

of ecosystem factors that are not yet fully understood.

As a result of declining sulfate (and to some

extent nitrate) concentrations, the acidity of lake

and stream water is decreasing in three of the four

regions. In the Adirondacks and northern

Appalachians, acid neutralizing capacity (ANC, an

indicator of aquatic ecosystem recovery) is increasing. For example, 48 out of 49 monitored

Adirondack lakes showed reductions in sulfate concentrations that coincide with reductions in atmospheric concentrations of sulfur.These decreases in

sulfate, as well as decreases in nitrate concentrations

that do not appear to be due to changes in atmospheric nitrogen deposition, have resulted in

increased pH and ANC as well as decreases in the

amount of toxic inorganic aluminum in Adirondack

lakes. In New England,ANC appears to be increasing only slightly, and is not statistically significant,

but hydrogen ion concentrations are declining.

Declining hydrogen ion concentrations represent an

increase in pH, which also is elevated by statistically

significant levels in the Adirondacks. In contrast,

increasing sulfate concentrations are evident in the

southern Appalachians.This regional increase may

be explained in part by the region’s soils, which can

store large amounts of sulfate delivered by deposition.When large amounts of sulfate have accu

lated in the soils over time, stream water sulfa

centrations can also continue increasing over 

Thus, despite decreasing sulfate in atmospher

osition, an increase in sulfate concentrations i

stream has been observed in that region.

Base cations are important because they 

the impact of sulfur and nitrogen deposition

cation concentrations in lakes and streams ar

expected to decrease when rates of atmosph

deposition decline, but if they decrease too m

they limit recovery in pH and ANC.While 

high rates of base cation decline in the north

Appalachians may be of concern, they do no

rently seem to be preventing recovery. How

their behavior in the future will bear watchi

Organic acids are natural forms of acidit

Lakes and streams vary widely in how much 

ral acidity they have, and increases in organi

like declining base cations, over time can lim

recovery. Organic acid concentrations are cu

increasing in many parts of the world, but th

cause is still being debated. Of the regions m

tored by EPA, only the Adirondacks are show

significant increases in organic acids, and the

increase may be responsible for 10 to 15 per

less recovery (in ANC) than expected. In or

fully understand and assess response and reco

of sensitive ecosystems to emission reduction 

grams, this area may require further investiga

Values show the slope of the regional trend (the median value for the trends in all of the sites in the region). Regional trends that are statistic

icant are shown in bold.

Source: EPA, 2004

Hydrogen (μeq/L/yr) -0.02 -0.26 -0.01 -0.0

Organic Acids (μeq/L/yr) +0.02 +0.15 -0.03 Insufficie

Aluminum (μg/L/yr) Insufficient data -4.72 Insufficient data Insufficie
A 2005 analysis10 of the annual benefits an

costs of the Acid Rain Program (ARP) updat

those of the National Acid Protection Assessm

Program (NAPAP) 1990 Integrated Assessme

and a 1995 EPA report11 by integrating scient

knowledge that has emerged since the 1990s

An expanded list of impacts has increased the 

program’s estimated benefits, while newer im

mentation strategies—unforeseen in 1990—h

lowered estimated costs.The estimated value 

program’s annual benefits in the year 2010 no

totals $122 billion (in 2000$).These benefits 

mostly from the prevention of health-related

impacts (such as premature deaths, illnesses, an

workdays missed due to illness), but also inclu

improved visibility in parks and other recreati

areas and ecosystem improvements.These ben

stem from the substantial difference that the A

expected to make in many areas meeting the

National Ambient Air Quality Standards (NA

by 2010 for fine particles less than 2.5 microm

in diameter (PM2.5) and ozone (see Figure 25

Notably, some significant benefits are not qua

such as the 20 percent reduction in mercury 

sions from coal-fired power plants; improvem

Quantifying Costs an

Benefits of the Acid

Rain Program

ailments.

– Visibility improvements in some parks.

✧ Many benefits are not included in

estimates:

– Mercury reductions.

– Acid rain environmental benefits.

– Remaining visibility benefits from

parks and urban areas.

– Others.

✧ Benefits from CAIR/CAMR for Canada

have not yet been quantified. 

0

50

100

150

200

250

300

350

400

2010 2020

Billions of Dollars (2006$)

Acid Rain: Canada

Acid Rain: United States

CAIR/CAMR:

United States

Year

Figure 23: Combined

Estimated Annual Benefits

for ARP, CAIR, and CAMR

Source: EPA, 2006, derived from Chestnut & Mills Analysis,

“A fresh look at the benefits and costs of the US acid rain

program” (Oct. 1, 2004) and EPA’s Multi-pollutant Regulatory

Analysis: CAIR, CAVR, CAMR (Oct. 2005). Acid Rain 2020

benefits extrapolated from 2010 estimates. Consumer

Price Index–Urban was used to convert 1999 dollars and 

2000 dollars to 2006 dollars.

pygpy p

atmospheric deposition. Because sulfate con

tions in streams are increasing strongly in th

region, many of the other chemical variables 

ANC and pH) show trends typical of acidify

conditions, rather than recovery.
Environmental Justice Analysis

In September 2005, EPA published a staff report evaluating

the public health benefits of the ARP, focusing on the

changes in exposure of minority and low-income populations to ambient concentrations of PM2.5 as a result of

the ARP. Analyses of SO2 and NOx emissions show that,

in general, the areas with highest emissions prior to the

program have also experienced the greatest emission

reductions. However, since the ARP does not mandate

reductions from specific sources, the exact effects of the

ARP on specific populations or localities are harder to

assess. To explore the potential environmental justice

issues related to the ARP, EPA investigated how trading

SO2 emissions under the ARP might affect minority and

low-income communities, and how trading SO2 emissions has impacted air quality at both regional and local

levels. In formulating this analysis of the ARP, EPA measured exposure to PM2.5 concentrations in relation to regional locations, population size, race, and income levels. This

investigation led EPA to the following conclusions: 

✧ There is no evidence that the cap and trade mechanism has led to increased human

exposure to air pollution.

✧ The ARP improved air quality substantially overall.

✧ The ARP improved air quality substantially for all population groups.

✧ No disproportionately high and adverse human health or environmental effects were fou

for minority or low-income groups. 

To view the complete report, visit <www.epa.gov/airmarkets/staff_analysis.pdf>.

NOx costs to be no more than $1 billion annually,

and likely less, from the limited analysis that has

been completed in this area.This leads to a more

than 40:1 benefit-cost ratio.Among the most

gg

24 for the combined estimated benefits of th

ARP, Clean Air Interstate Rule (CAIR), and

Clean Air Mercury Rule (CAMR).
ments in human health and

environmental protection.With

the Acid Rain Program (ARP),

the NOx SIP Call in the eastern

United States, and mobile source

rules covering new cars, trucks,

buses, and nonroad equipment,

states have critical controls to

help achieve ozone and fine

particle National Ambient Air

Quality Standards (NAAQS).

In the spring of 2005, EPA

promulgated a suite of air quality

rules designed to achieve additional reductions of SO2, NOx,

and mercury from power plants.

These rules include Clean Air

Interstate Rule (CAIR), Clean

Air Mercury Rule (CAMR),

and Clean Air Visibility Rule

(CAVR).14 See Figure 27 for an

implementation timeline.

EPA expects that the air

quality impacts of these regulations, coupled with recent rules

to reduce fine particles and NOx

from motor vehicles, will be

extensive. Figures 24-26 show

areas projected to attain the

NAAQS in 2010 and 2020 with

these regulations, compared to

today. Figure 24 shows ozone

and PM2.5 nonattainment areas

primarily occurring in eastern

states and California.As the new

rules are implemented, nonattainment is expected to decline

steadily, with 92 fewer areas by

Both PM and 

Nonattainmen

PM Only 

Nonattainmen

Ozone Only 

Nonattainmen

Source: EPA

Legend

Both PM a

Nonattainm

PM Only 

Nonattainm

Ozone Only 

Nonattainm

Nonattainm

Projected t

Figure 25: Projected Nonattainment Areas in 2010 After

Reductions From CAIR and Existing Clean Air Act Program

Source: EPA

Legend

Both PM and 

Nonattainmen

PM Only 

Nonattainmen

Ozone Only 

Nonattainmen

Nonattainmen

Projected to A

Figure 26: Projected Nonattainment Areas in 2020 After Red

From CAIR, CAVR, and Existing Clean Air Act Programs

Source: EP

Note: 129 areas currently designated as nonattainment for PM2.5 and/or 8-hour ozone

Note: Areas forecast to remain in nonattainment may need to adopt additional local or regi

to attain the standards by dates set pursuant to the Clean Air Act. These additional local or 

measures are not forecast here, and therefore this figure overstates the extent of expected no

Note: Areas forecast to remain in nonattainment may need to adopt additional local or regi

to attain the standards by dates set pursuant to the Clean Air Act. These additional local or r

measures are not forecast here, and therefore this figure overstates the extent of expected no
States develop SPs

(18 months)

Note: Dotted lines indicate a range of time. 

CAMR 

signed

CAMR and CAVR

SPs Due

(Nov 06)

Phase I : CAMR Hg Program 

(10)

Phase II : CAMR Hg Program 

Regional Haze (RH) (18) SIPs Due (Dec 07) CAVR BART Controls Required 

(5 years after RH SIPs approved)

CAVR

signed

health and the environment,

and helping states and local

communities meet NAAQS

for fine particles and ozone.

Source: EPA, 2006

About the Clean Air Markets Division

The availability and transparency of data, from emission

measurement to allowance trading to deposition monitoring,

is a cornerstone of effective cap and trade programs. The

Clean Air Markets Division 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, including the Acid

Rain Program (ARP).

<www.epa.gov/airmarkets>

Regulatory Information

To learn more about how emissions cap and trade 

programs work, see:

www.epa.gov/airmarkets/arp

Acid Rain Program

www.epa.gov/airmarkets/progsregs/noxview.html

NOx Budget Trading Program

www.epa.gov/airmarkets/capandtrade/index.html

General Cap and Trade Information

Also, See Recent Related Rulemakings:

www.epa.gov/cair

Clean Air Interstate Rule (CAIR)

www.epa.gov/CAMR/index.htm

Clean Air Mercury Rule (CAMR)

www.epa.gov/visibility

Clean Air Visibility Rule (CAVR)

http://www.epa.gov/airmarkets/cair/analyses/

naaqsattainment.pdf

CAIR, CAMR, CAVR and NAAQS Attainment

Progress and Results

Several reports have assessed the progress and results, and pr

future impacts of the Acid Rain Program.

www.sciencedirect.com/science/ journal/03014797

Chestnut, L. G., Mills, D. M. (2005, November). A fre

the benefits and costs of the U.S. acid rain program. Journal o

Environmental Management, Vol. 77, Issue 3, 252-256.

www.al.noaa.gov/AQRS/reports/napapreport05.pdf

2005 National Acid Precipitation Assessment Program Repo

Congress.

www.epa.gov/airmarkets/articles/adaq.html 

U.S. Environmental Protection Agency, Office of Air a

Radiation, Clean Air Markets Division. (2005, Septem

The Acid Rain Program and Environmental Justice: Staff Ana

www.rff.org/Documents/RFF-RPT-Adirondacks.pdf

Banzhaf, S., Burtraw, D., Evans, D., and Krupnick, A. 

September). Valuation of natural resource improvements in 

Adirondacks. Resources for the Future. 

www.adirondacklakessurvey.org

Jenkins, J., Roy, K., Driscoll, C., Beurkett, C. (2005, O

Acid rain and the Adirondacks: A Research Summary. Adiro

Lakes Survey Corporation. 

Emissions, Allowances, and Environmenta

For more information on emissions, allowances, and environm

data, see:

cfpub.epa.gov/gdm

EPA Clean Air Markets Data and Maps

www.epa.gov/castnet

Clean Air Status and Trends Network (CASTNET)

www.epa.gov/airmarkets/deposition/2005atlas.pdf

Atmosphere in Motion Results from the National Dep

Monitoring Networks: 2005 Atlas

nadp.sws.uiuc.edu

National Atmospheric Deposition Program/

National Trends Network

Online Information, Data, and Resources
6 Allowance transfers are posted and updated daily on <www.epa.gov/airmarkets>.

7 Gruenspecht, Howard. (2006, February 9). Deputy Administrator of the Energy Information Administration, Department of E

Statement before the Subcommittee on Clean Air, Climate Change, and Nuclear Safety of the Committee on Environment an

Works in the United States Senate. p.3.

8 Other programs such as the NOx SIP Call, the OTC NOx Budget Program, and state laws also contribute to reductions, espe

after 2000.

9 Monitoring data from the Temporally Integrated Monitoring of Ecosystems (TIME) and Long-Term Monitoring network.

10 Chestnut and Mills, 2005.

11 Human Health Benefits from Sulfate Reduction under Title IV of the 1990 Clean Air Act Amendments. EPA-430-R-95-010

12 See, for example:

Ellerman, D. (2003). Lessons from Phase 2 compliance with the U.S.Acid Rain Program. Cambridge, Massachusetts: MIT Center for 

and Environmental Policy Research.

Carlson, C.P., Burtraw, D., Cropper, M., and Palmer, K. SO2 control by electric utilities:What are the gains from trade? Journal 

Economy,Vol. 108, No. 6: 1292-1326.

Office of Management and Budget. (2003). Informing Regulatory Decisions: 2003 Report to Congress on the Costs and Benefits of Fe

Regulations and Unfunded Mandates on State, Local, and Tribal Entities. Office of Information and Regulatory Affairs.

<www.whitehouse.gov/omb/inforeg/2003_cost-ben_final_rpt.pdf>.

13 EPA estimates recognize that some switching to lower-sulfur coal (and accompanying emission reductions) would have occurr

absence of Title IV as railroad deregulation lowered the cost of transporting coal from Wyoming’s Powder River Basin electric 

plants in the Midwest and as plant operators adapted boilers to different types of coal.

14 CAIR (see <www.epa.gov/cair/index.html>), CAMR (see <www.epa.gov/air/mercuryrule>), CAVR (see <www.epa.gov/o

visibility/index.html>).

Recycled/Recyclable—Printed with Vegetable Oil Based Inks on 100% Postconsumer, Process Chlorine Free Recycled Paper

United States

Environmental Protection Agency

Office of Air and Radiation

Clean Air Markets Division

1200 Pennsylvania Avenue, NW (6204J)

Washington, DC 20460

EPA-430-R-06-015

October 2006

www.epa.gov/airmarkets