EPA’s national and regional rules to reduce emissions of pollutants that form sulfur dioxide (SO₂) pollution help state and local governments meet the Agency’s national air quality standards. 

General Conformity

General Conformity Rule: This rule ensures that action taken by federal agencies in nonattainment and maintenance areas do not interfere with a state’s plan to meet national air standards.

Power Plants and Industries

Data Requirements Rule: To help identify maximum 1-hour SO₂ concentrations in ambient air, EPA’s Data Requirements Rule (DRR) directs air agencies to provide data to characterize current ambient SO₂ air quality through modeling or monitoring in areas with large sources of SO₂.

Requirements to Reduce the Interstate Transport of Air Pollution:  Interstate air pollution transport, or air transport, is a combination of local emissions and emissions from upwind sources of SO₂ and other pollutants that impact air quality in any given location.

EPA’s Acid Rain Program uses a combination of traditional requirements and a market-based cap and trade program to reduce power plant emissions of nitrogen oxides (NO_x) and sulfur dioxide (SO₂), which contribute both to acid rain and to fine particle formation.

Exceptional Events Rule Revisions and Supporting Guidance: Exceptional events are unusual or naturally occurring events that can affect air quality but are not reasonably controllable using techniques that tribal, state or local agencies may implement in order to attain and maintain the national air standards.

Mercury and Air Toxics Standards (MATS): Pollution control measures for power plants may help reduce SO₂ levels.

Mobile Sources

State and Local Transportation Resources: Learn how Transportation Conformity, travel efficiency strategies, and other tools help states to achieve air quality and transportation objectives.