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Cross-State Air Pollution Rule (CSAPR)

Basic Information

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On July 6, 2011, the US Environmental Protection Agency (EPA) finalized a rule that protects the health of millions of Americans by helping states reduce air pollution and attain the 1997 ozone and fine particle and 2006 fine particle National Ambient Air Quality Standards (NAAQS). This rule, known as the Cross-State Air Pollution Rule (CSAPR), requires states to significantly improve air quality by reducing power plant emissions that cross state lines and contribute to ozone and fine particle pollution in other states. In a separate, but related, regulatory action, EPA finalized a supplemental rulemaking on December 15, 2011 to require five states - Iowa, Michigan, Missouri, Oklahoma, and Wisconsin - to make summertime NOX reductions under the CSAPR ozone season control program. CSAPR requires a total of 28 states to reduce annual SO2 emissions, annual NOX emissions and/or ozone season NOX emissions to assist in attaining clean air standards. To speed implementation, EPA is adopting federal implementation plans, or FIPs, for each of the states covered by this rule. EPA encourages States to replace these FIPs with State Implementation Plans, or SIPs. On February 7, 2012 and June 5, 2012, EPA issued two sets of minor adjustments to the Cross-State Air Pollution Rule (CSAPR).

EPA, states, tribes and local governments all play important roles in reaching clean air goals. With this rule, the Agency is renewing its commitment to implement the Clean Air Act's "good neighbor" provision, which requires states to address the problem of interstate transport of air pollution. At the same time, states, tribes, and local agencies continue to work on local pollution control measures.

Cross-State Air Pollution Rule States

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Map of States covered by the Cross-State Air Pollution Rule (CSAPR)

The CSAPR requires 23 states to reduce annual SO2 and NOX emissions to help downwind areas attain the 24-Hour and/or Annual PM2.5 NAAQS. Twenty-five states are required to reduce ozone season NOX emissions to help downwind areas attain the 1997 8-Hour Ozone NAAQS. The rule fully addresses all upwind states' transport obligations under the 1997 annual PM2.5 and 2006 24-hour PM2.5 standards. For 14 states, it will also fully address upwind state transport obligations under the 1997 ozone NAAQS. For the rest of the upwind states covered by the CSAPR ozone program, the rule makes a substantial "down payment" on emission reductions while EPA continues to evaluate what, if any, additional emission reductions might be needed.

The final CSAPR divides the states required to reduce SO2 into two groups. Both groups must reduce their SO2 emissions in Phase I. Group 1 states must make additional reductions in SO2 emissions for Phase II in order to eliminate their significant contribution to air quality problems in downwind areas.

Annual Public Health and Environmental Benefits

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Map that shows the health benefits of the Cross-State Air Pollution Rule (CSAPR) including mortality avoided and monitized benefits

The Cross-State Air Pollution Rule will help avoid tens of thousands of premature deaths and illnesses, achieving billions of dollars in public health benefits. The required emissions reductions will annually avoid:

  • 13,000 to 34,000 premature deaths
  • 15,000 nonfatal heart attacks
  • 19,000 hospital and emergency room visits
  • 1.8 million lost work days or school absences
  • 400,000 aggravated asthma attacks
(see EPA's Regulatory Impact Analysis.)

Pollution reductions will also lead to improvements in visibility in national and state parks, and increased protection for sensitive ecosystems including Adirondack lakes and Appalachian streams, coastal waters and estuaries, and forests.

Air Quality Improvements

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The Cross-State Air Pollution Rule will improve air quality in thousands of counties throughout the eastern, central, and southern U.S. - counties that are home to over 75% of the U.S. population. State, local and federal actions have already improved air quality so that many counties meet the National Ambient Air Quality Standards for ozone and fine particle pollution. Many areas have already been brought into attainment with these standards. This rule will help bring several more areas into attainment and help many more areas continue to meet the level of the standards.

Most of the counties with monitors in the region covered by the CSAPR are projected to meet the 1997 and 2006 ozone and fine particle standards under CSAPR. View a PDF: Impacts of the CSAPR on Counties with Monitors Projected to have Ozone and/or Fine Particle Air Quality Problems. (PDF 8pp 143 kb)

Emission Reductions

Bar chart showing a decrease in SO2, NOx and NOx Ozone Season emisisons from 2005 to 2014

CSAPR will take effect starting January 1, 2015 for SO2 and annual NOX reductions and May 1, 2015 for ozone season NOX reductions. Significant additional SO2 emission reductions in Group 1 states will be required in Phase II. Compared to 2005, EPA estimates that by Phase II this rule, along with other federal rules, will lower power plant annual emissions in the CSAPR region by:

  • 6.4 million tons per year of SO2 - a 73 percent reduction
  • 1.4 million tons per year of NOX - a 54 percent reduction
  • Including 340,000 tons per year of NOX during the ozone season
  • (see EPA's Regulatory Impact Analysis.)

Air Quality Improvements and Emission Reductions at a Low Cost

The final rule yields $120 to $280 billion in annual health and welfare benefits in Phase II, which far outweigh the estimated annual costs of CSAPR of $800 million, along with the roughly $1.6 billion per year in capital investments already under way as a result of CAIR. (see EPA's Regulatory Impact Analysis.

The high benefits and low costs of the rule are achieved through implementing an air quality-assured trading program for states in the CSAPR region. EPA sets a pollution limit (or budget) for each of the states covered by this rule. The rule allows sources in each state to meet those budgets in any way they see fit, including unlimited trading of emissions allowances between power plants within the same state. Interstate trading is also permitted. However, CSAPR Phase II includes provisions to assure that each state will meet its pollution control obligations. This structure reduces the cost of complying with the rule while ensuring that each state eliminates the SO2 and NOX emissions that significantly contribute to downwind nonattainment or interfere with maintenance of the 1997 and 2006 NAAQS.

The Cross-State Air Pollution Rule (CSAPR) and the Clean Air Interstate Rule (CAIR)

This rule replaces a 2005 rule known as the Clean Air Interstate Rule (CAIR). A December 2008 court decision kept the requirements of CAIR in place temporarily, but directed EPA to issue a new rule to implement the Clean Air Act requirements concerning the transport of air pollution across state boundaries. This Cross-State Air Pollution Rule is designed to implement these Clean Air Act requirements and respond to the court's concerns. The CSAPR takes effect January 1, 2015; CAIR will be implemented through the 2014 compliance periods, and then replaced by the CSAPR.

In Phase II, power plants in states common to both the Cross-State Air Pollution Rule and CAIR will achieve annual SO2 emissions around 1.8 million tons lower and annual NOX emissions around 76,000 tons lower than what would have been achieved at that time under CAIR.

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