FACT SHEET 

Supplemental Proposal for Reducing Interstate Transport

 of Fine Particulate Matter and Ozone 

(Clean Air Interstate Rule) 

ACTION 

• On May 18, 2004, the Environmental Protection Agency proposed additional details and 

rule text supplementing its January 2004 proposal to reduce interstate transport of fine 

particulate matter and ozone. 

• The proposed Clean Air Interstate Rule is an important component of EPA’s efforts to 

implement the more protective national fine particle and 8-hour ozone air quality 

standards. When combined with the recently completed Clean Air Nonroad Diesel Rule 

and other national control programs, the reductions required by this final rule will allow 

most areas of the country to meet these standards without having to impose additional 

local controls. 

• The Clean Air Interstate Rule would require 29 eastern states and the District of 

Columbia to significantly reduce and permanently cap emissions of sulfur dioxide (SO2) 

and/or nitrogen oxides (NOx). In 2015, NOx emissions from the power sector would be 

65% below today’s levels. SO2 emissions from that sector would be 50% below current 

levels by 2015 and approximately 70% below current levels when fully implemented. 

< SO2 and NOx contribute to the formation of fine particles and ground-level 

ozone, pollutants that, together, are associated with thousands of premature deaths 

and illnesses each year. 

< Reducing emissions of these pollutants will significantly address these health 

issues, in addition to improving visibility and protecting sensitive ecosystems. 

EPA’s modeling predicts that when combined with existing emissions reduction 

requirements, this rule would help approximately 90% of “nonattainment areas” 

meet national air quality standards for ozone and particle pollution. 

< By addressing air pollutants from electric utilities in a cost-effective fashion, 

EPA’s Clean Air Interstate Rule proposal would protect public health and the 

environment without interfering with the steady flow of affordable energy for 

American consumers and businesses. 

• Each of the 29 states affected by the program and the District of Columbia must submit a 

plan to EPA that demonstrates it will meet its assigned statewide SO2 and/or NOx 

emissions budget (i.e., emissions reduction requirements). 

• States can meet the emissions reduction requirements by either: 

< joining the EPA-managed cap-and-trade programs for power plants, or 

< achieving reductions through other emissions control measures. 
• This supplemental proposal provides additional details and rule language for 

implementing the Clean Air Interstate Rule. These details include specifics on EPA’s 

model cap-and-trade program for power plants that states may adopt to achieve required 

emissions reductions. 

• EPA will take comment on this supplemental proposal for 45 days after it is published in 

the Federal Register. EPA will hold a public hearing in Alexandria, Virginia on June 3, 

2004 to hear oral testimony on the supplemental proposal. 

• After carefully considering all comments received, EPA expects to complete the Clean 

Air Interstate Rule this year. 

HIGHLIGHTS OF THE SUPPLEMENTAL PROPOSAL 

• EPA is proposing regulatory text for model multi-state cap and trade programs to reduce 

power plant emissions of SO2 and NOx. 

• EPA also outlines criteria which states choosing to control non-electric generators must 

follow. 

• EPA in partnership with states would administer the region-wide cap-and-trade programs. 

• States that would be subject to this rule may choose to adopt this cap and trade program – 

either reference it or repeat it verbatim in their state laws – to meet the proposed SO2 and 

NOx emissions reductions from power plants in a flexible and cost-effective manner. 

• States would be responsible for allocating emissions allowances and taking the lead in 

pursuing enforcement actions. 

• EPA would be responsible for assigning the state emissions budgets, reviewing and 

approving state plans to achieve required reductions, and administering the emissions and 

allowance tracking systems. 

• EPA is proposing its determination that the emissions reductions under this proposed 

rule, if achieved by power plants under the model cap-and-trade programs, would satisfy 

the best available retrofit technology (BART) requirements of the regional haze program 

as a “better than BART” alternative. The SO2 and NOx emissions model trading 

programs are expected to achieve greater emission reductions from power plants and on 

average, greater visibility improvements in impacted Class I areas compared to sourcespecific BART. 

• In this proposal, EPA is also clarifying unclear language and correcting minor errors from 

the original proposal. 
BACKGROUND 

• On January 30, 2004, EPA initially proposed the Interstate Air Quality Rule (69 FR 

4566), now called the Clean Air Interstate Rule (CAIR). This rule would require 29 

states and the District of Columbia to develop plans to reduce sulfur dioxide (SO2) and/or 

nitrogen oxides (NOx) emissions from facilities that emit these pollutants. 

• Sulfur dioxide is a “precursor” or pollutant that reacts in the atmosphere to form PM2.5. 

NOx is a precursor to both ozone and PM2.5 formation. Reducing upwind precursor 

emissions will assist downwind PM2.5 and 8-hour ozone nonattainment areas in meeting 

national air quality standards. 

• Affected states significantly contribute to a downwind state’s inability to meet national air 

quality standards for fine particle pollution (PM2.5) and/or 8-hour ozone. 

• The proposed Clean Air Interstate Rule would reduce SO2 emissions by 5.6 million tons 

per year when the rules are fully implemented (approximately 70 percent below current 

levels). NOx emissions would be cut by 1.8 million tons annually in 2015 (about 65 

percent below today's levels). 

• The states that would be covered by this rule are (states listed are controlling for both 

particle pollution and ozone unless otherwise noted): 

Alabama

Arkansas

Connecticut (ozone only)

Delaware

Florida (particle pollution only)

Georgia

Illinois

Indiana

Iowa

Kansas (particle pollution only)

Kentucky

Louisiana

Maryland

Massachusetts

Michigan

Minnesota (particle pollution only) 

Mississippi 

Missouri

 New Jersey 

New York 

North Carolina 

Ohio 

Pennsylvania 

South Carolina 

Tennessee 

Texas (particle pollution only) 

Virginia 

West Virginia 

Wisconsin 

District of Columbia 

ADDITIONAL INFORMATION 

• For information on today’s supplemental proposal and the proposed Clean Air Interstate 

Rule (formerly the Interstate Air Quality Rule) issued in January 2004, visit 

www.epa.gov/interstateairquality.