• Rule Summary
• Rule History
• Additional Resources

Rule Summary

On June 2, 2010, EPA strengthened the primary National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (SO₂). The revised standard will improve public health protection, especially for children, the elderly, and people with asthma. These groups are susceptible to the health problems associated with breathing SO₂.

EPA revised the primary SO₂ standard by establishing a new 1-hour standard at a level of 75 parts per billion (ppb). EPA’s evaluation of the scientific information and the risks posed by breathing SO₂ indicate that this new 1-hour standard will protect public health by reducing people’s exposure to high short-term (5-minutes to 24-hours) concentrations of SO₂.

Rule History

01/26/2011 – Denial of Petitions to Reconsider

06/22/2010 – Final Revision to Sulfur Dioxide Primary National Ambient Air Quality Standards (NAAQS)

12/08/2009 – Proposed Revision to Sulfur Dioxide Primary National Ambient Air Quality Standards (NAAQS)

Additional Resources

Regulatory Impact Analysis (RIA) for the Proposed Revisions to the Sulfur Dioxide National Ambient Air Quality Standards (NAAQS)

Fact Sheets and Additional Information Regarding the 2010 Revision to the Primary National Ambient Air Quality Standards (NAAQS) for Sulfur Dioxide

Scientific and Technical Documents Supporting the primary NAAQS for SO₂

Related Rules

Secondary National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide (NO₂) and Sulfur Dioxide (SO₂)