Note: EPA no longer updates this information, but it may be useful for historical purposes. See

http://www.epa.gov/airtransport/ for information about the Transport Rule, EPA's response to the

Court remand of CAIR which will replace CAIR when final.

You are here: EPA Home Air & Radiation Clean Air Interstate Rule Basic Information

Basic Information

Basic Facts on CAIR

Cap and Trade Basics

Why Control SO2 and NOx?

CAIR Timeline

CAIR Nonattainment Maps

EPA Press Release

Basic Facts on CAIR

Citing significant health and clean air benefits, EPA finalized the Clean Air Interstate Rule

(CAIR) on March 10, 2005. This rule will result in the deepest cuts in sulfur dioxide (SO2) and

nitrogen oxides (NOx) in more that a decade.

The December 23, 2008 ruling leaves CAIR and the CAIR FIPs -- including the CAIR

trading programs -- in place until EPA issues a new rule to replace CAIR in accordance

with the July 11, 2008 decision. Read the court decision (PDF) (4pp, 22k). EPA informed

the Court that development and finalization of a replacement rule could take about two

years.

The U.S. Court of Appeals for the D.C. Circuit has ruled on petitions for review of the

Clean Air Interstate Rule (CAIR) and CAIR Federal Implementation Plans (FIPs),

including their provisions establishing the CAIR NOX annual and ozone season and SO2

trading programs. On July 11, 2008, the Court issued an opinion vacating and

remanding these rules; however, parties to the litigation requested rehearing of

aspects of the Court's decision, including the vacatur of the rules. On December 23,

2008, the Court granted rehearing only to the extent that it remanded the rules to EPA

without vacating them.

On March 10, 2005, the Environmental Protec tion Agency (EPA) announced the Clean

Air Interstate Rule (CAIR), a rule that will achieve the largest reduc tion in air pollution

in more than a decade. This action, called the "Interstate Air Quality Rule" when it was

proposed in January 2004, offers steep and sustained reductions in air pollution as well

as dramatic health benefits at more than 25 times greater than the cost by 2015.

Through the use of the proven cap-and-trade approach, CAIR achieves substantial

reductions of sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions and is a powerful

component of the Administration's plan to help over 450 counties in the eastern U.S.

meet EPA’s protective air quality standards for ozone or fine particles.

SO2 and NOx contribute to the formation of fine particles and NOx contributes to the

formation of ground-level ozone. Fine particles and ozone are associated with

thousands of premature deaths and illnesses each year. Additionally, these pollutants

reduce visibility and damage sensitive ecosystems.

By the year 2015, the Clean Air Interstate Rule will result in:

-- $85 to $100 billion in annual health benefits, annually preventing 17,000 premature

deaths, millions of lost work and school days, and tens of thousands of non- fatal heart

attacks and hospital admissions.

-- nearly $2 billion in annual visibility benefits in southeastern national parks, such as

Great Smoky and Shenandoah.

-- significant regional reduc tions in sulfur and nitrogen deposition, reducing the number

of acidic lakes and streams in the eastern U.S.

Clean Air Interstate Rule

http://www.epa.gov/cair/basic.html

Last updated on Friday, July 09, 2010

3/15/2011 EPA: Clean Air Interstate Rule - Basic ...

http://www.epa.gov/cair/basic.html 1/3
CAIR covers 28 eastern states and the District of Columbia. In this rule, EPA finds that

SO2 and NOx emissions from 25 states and the District of Columbia contribute to

unhealthy levels of fine particles in downwind states. In addition, NOx emissions in 25

eastern states and the Distric t of Columbia contribute to unhealthy levels of 8-hour

ozone in other downwind states. (See map on the Where You Live page for information

on affected states)

Based on an assessment of the emissions contributing to interstate transport of air pollution

and available control measures, EPA has determined that achieving required reductions in the

identified states by controlling emissions from power plants is highly cost effec tive.

States must achieve the required emission reduc tions using one of two compliance

options: 1) meet the state’s emission budget by requiring power plants to participate in

an EPA-administered interstate cap and trade system that caps emissions in two

stages, or 2) meet an individual state emissions budget through measures of the

state’s choosing.

CAIR provides a Federal framework requiring states to reduce emissions of SO2 and

NOx. EPA anticipates that states will achieve this primarily by reducing emissions from

the power generation sector. These reductions will be substantial and cost-effective,

so in many areas, the reductions are large enough to meet the air quality standards.

The Clean Air Ac t requires that states meet the new national, health-based air quality

standards for ozone and PM2.5 standards by requiring reductions from many types of

sources. Some areas may need to take additional local ac tions. CAIR reductions will

lessen the need for additional local controls.

This final rule provides cleaner air while allowing for continued economic growth. By

enabling states to address air pollutants from power plants in a cost effective fashion,

this rule will protect public health and the environment without interfering with the

steady flow of affordable energy for American consumers and businesses.

If states choose to meet their emissions reductions requirements by controlling power

plant emissions through an interstate cap and trade program, EPA’s modeling shows

that:

In 2010, CAIR will reduce SO2 emissions by 4.3 million tons -- 45% lower than

2003 levels, across states covered by the rule. By 2015, CAIR will reduce SO2

emissions by 5.4 million tons, or 57%, from 2003 levels in these states. At full

implementation, CAIR will reduce power plant SO2 emissions in affected states to

just 2.5 million tons, 73% below 2003 emissions levels.

CAIR also will achieve significant NOx reductions across states covered by the

rule. In 2009, CAIR will reduce NOx emissions by 1.7 million tons or 53% from

2003 levels. In 2015, CAIR will reduce power plant NOx emissions by 2 million

tons, achieving a regional emissions level of 1.3 million tons, a 61% reduction

from 2003 levels.

In 1990, national SO2 emissions from power plants were 15.7 million tons

compared to 3.5 million tons that will be achieved with CAIR. In 1990, national

NOx emissions from power plants were 6.7 million tons, compared to 2.2 million

tons that will be achieved with CAIR.

In upcoming but closely related ac tion, EPA will impose the first ever federallymandated requirements that coal-fired electric utilities reduce their emissions of

mercury. Together the Clean Air Mercury Rule and the Clean Air Interstate Rule create

a multi-pollutant strategy to reduce emissions throughout the United States.

The Bush Administration continues to believe that the President’s Clear Skies legislation

is a more efficient, effec tive, long-term mechanism to achieve large-scale national

reductions. Clear Skies legislation applies nationwide and is modeled on the highly

successful Acid Rain Program. The Agency remains committed to working with Congress

to pass legislation.

Cap and Trade Basics

The Clean Air Interstate Rule establishes a cap-and-trade system for SO2 and NOx

based on EPA's proven Acid Rain Program. The Acid Rain Program has produced

remarkable and demonstrable results, reducing SO2 emissions faster and cheaper than

anticipated, and resulting in wide-ranging environmental improvements.

3/15/2011 EPA: Clean Air Interstate Rule - Basic ...

http://www.epa.gov/cair/basic.html 2/3
EPA already allocated emission "allowances" for SO2 to sources subject to the Acid

Rain Program. These allowances will be used in the CAIR model SO2 trading program.

For the model NOx trading programs, EPA will provide emission "allowances" for NOx to

each state, according to the state budget. The states will allocate those allowances

to sources (or other entities), which can trade them. As a result, sources are able to

choose from many compliance alternatives, including: installing pollution control

equipment; switching fuels; or buying excess allowances from other sources that have

reduced their emissions.

Because each source must hold sufficient allowances to cover its emissions each year,

the limited number of allowances available ensures required reductions are achieved.

The mandatory emission caps, stringent emissions monitoring and reporting

requirements with significant automatic penalties for noncompliance, ensure that

human health and environmental goals are achieved and sustained.

The flexibility of allowance trading creates financial incentives for elec tricity generators

to look for new and low-cost ways to reduce emissions and improve the effec tiveness

of pollution control equipment.

Why Control SO2 and NOx?

Why EPA is Addressing Emissions of SO2 and NOx

EPA established more protective fine particle and 8-hour ozone national air quality

standards in 1997. Litigation and the need to establish a nationwide air monitoring

system for fine particles delayed the implementation of these standards, but

implementation is now moving forward. Areas not meeting these standards, known as

“nonattainment” areas, were designated in 2004. These state and local governments

are moving forward with plans to protect public health by attaining the standards as

quickly as possible.

Sulfur dioxide (SO2) and nitrogen oxides (NOx) contribute to the formation of fine

particles (PM) and NOx contributes to the formation of ground-level ozone.

Many sources contribute to levels of fine particle pollution and ozone that exceed

national air quality standards. Some of these pollutants may originate hundreds or

thousands of miles from the areas where violations are detected. The Clean Air Act's

"good neighbor provisions" require states to eliminate emissions that substantially

contribute to dirty air in downwind states.

Under the Clean Air Act, states are required to submit plans to EPA within three years

after the Agency revises a national air quality standard. Among other requirements,

these plans must limit emissions in states that contribute significantly to unhealthy air

downwind.

Although states have not yet developed plans for meeting the national air quality

standards for fine particle pollution and 8-hour ozone, EPA's analyses show that even

substantial local emission controls still would leave many areas in the eastern US with

unhealthy air in 2010.

By limiting emissions of SO2 and NOx on a regional scale, the Clean Air Interstate Rule

will help all areas in the eastern US achieve healthier air quality at reduced costs than

a strategy that relies solely on local controls.

CAIR Timeline

Promulgate CAIR Rule 2005

State Implementation Plans Due 2006

Phase I Cap in Place for NOx 2009

Phase I Cap in Place for SO2 2010

Phase II Cap in Place for NOx and SO2 2015

3/15/2011 EPA: Clean Air Interstate Rule - Basic ...

http://www.epa.gov/cair/basic.html 3/3