South Carolina Department of Health and Environmental Control

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Air Pollutants and Monitoring - Criteria Pollutants

• General
  Information
• National Ambient Air Quality Standards
• Boundaries & Designations
• State Implementation Plan
• Monitoring for SO₂

Boundaries and Designations for Sulfur Dioxide (SO₂)

The federal Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to identify areas in each state using these three designations:

• Attainment - area meets a National Ambient Air Quality Standard (standard)
• Nonattainment - area does not meet (or is contributing to nearby areas in not meeting) a standard
• Unclassifiable - there is not enough data to designate the area under a new or revised standard

EPA sets boundaries for areas designated nonattainment and unclassifiable based on recommendations from the states. States use ambient air monitoring networks, emissions inventories, EPA guidance, and other relevant information to make these recommendations. Furthermore, states and EPA request public input during the process.

See EPA's website for a list or maps of nonattainment areas, and an overview of the designation process.

Designation Process

On February 6, 2013, EPA issued a letter to SC indicating that it would not designate any areas of the state for the new 1-hour SO₂ standard. The EPA also announced that it would be working on developing an updated strategy for accurately identifying SO₂ levels throughout the country which will focus on modeling and/or monitoring sources which emit SO₂ above a certain threshold. Under this anticipated approach, EPA expects states to identify sources by early 2015, and provide modeling demonstrations or establish monitoring networks by late 2015. Those sources which are modeled would be designated 18 months after modeling demonstrations are submitted (December 2017) and attainment SIPs would be due August 2019. Those sources that are monitored would be designated after three years of monitored data is obtained (expected in December 2020) and attainment SIPs would be due August 2022. For more information, please visit EPA's SO₂ designations page.

For more information, background, and updates on how EPA plans to implement the new 1-hour SO₂ standard (including the designation process) please visit DHEC's SO₂ implementation page.

• Letter from EPA not designating any areas of SC for the 1-hour SO₂ Standard
• Extension of the Deadline for Area Designations for the 2010 Primary Sulfur Dioxide (SO₂) Air Quality Standard
• SO₂ Boundary Recommendations (submitted to EPA June 2, 2011)
• Guidance submitted by EPA regarding designation recommendations

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