What is sulfur dioxide?
Sulfur dioxide (SO2) is one of a group of highly reactive gases called sulfur oxides (SOX). Exposure to SO2 can affect the respiratory system, especially for people with asthma, at elevated ventilation rates. Studies also show connections between short-term exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in populations at risk including children, the elderly, and asthmatics. Further, SOX can also react with other compounds in the atmosphere to form small particles that can cause or worsen respiratory disease and aggravate existing heart disease.
The largest source of SO2 emissions is fossil-fuel combustion at power plants and other industrial facilities. Smaller sources of SO2 emissions include extraction of metal from ore and burning of high-sulfur fuels by locomotives, large ships, and non-road equipment.
2010 SO2 National Ambient Air Quality Standards (NAAQS)
The United States Environmental Protection Agency (EPA) strengthened the SO2 primary NAAQS on on June 2, 2010 (75 FR 35520).
The new 75 parts per billion (ppb) one-hour primary standard became effective August 23, 2010. The EPA expects the one-hour standard to protect the public from exposure to high short-term concentrations and to protect communities located close to coal-fired power plants, industrial boilers, petroleum refineries, metal processing plants, and diesel exhaust. The EPA revoked previously existing SO2 annual and 24-hour primary standards, effective one year after area designations are final, because the EPA expects the new one-hour standard to provide sufficient protection.
State Implementation Plans (SIPs) to fulfill Federal Clean Air Act, §110(a)(1) and (2) infrastructure requirements are due to the EPA by June 2, 2013. Attainment demonstration SIPs showing the standard will be met in nonattainment areas by August 2017, are due to the EPA by February 2014.
For more information on the new EPA one-hour SO2 standard, please visit the EPA's Web page: Primary NAAQS for Sulfur Dioxide
Latest Planning Activities to Address SO2
Last updated: 5/10/2012
SO2 Implementation - Stakeholder Outreach by the EPA
The EPA is convening three meetings with stakeholders (states, tribes, environmental and public health organizations, and industry representatives) to discuss issues associated with the implementation of the SO2 standard. The discussions will focus on monitoring, modeling and implementation issues. These issues will be outlined in a white paper that will be provided at http://www.epa.gov/air/sulfurdioxide/implement.html in mid-May 2012.
Schedule for Stakeholder Discussions:
- Session 1: Environmental and Public Health Organization Representatives, May 30, 2012, Washington, DC
- Session 2: State and Tribal Representatives, May 31, 2012, Research Triangle Park, NC
- Session 3: Industry Representatives, June 1, 2012, Research Triangle Park, NC
For more information about these meetings, please contact Carolyn Childers with the EPA at (919) 541-5604.
Letter from the EPA on 2010 SO2 NAAQS Implementation
On April 12, 2012, the EPA sent a letter to states and tribes updating its requirements and plans for implementing the 2010 SO2 primary NAAQS.
Designation Recommendation for 2010 One-hour SO2 Primary NAAQS
On June 2, 2011, Texas recommended area designations for the new SO2 primary NAAQS to the EPA. Based on 2010 regulatory design values, nonattainment designation was recommended for Jefferson County, attainment designations were recommended for Dallas, Ellis, El Paso, Galveston, Gregg, Harris, Kaufman, McLennan, and Nueces Counties; and unclassifiable designations were recommended for all remaining counties.
Public Meetings
In January 2011, the TCEQ hosted meetings in Austin and Port Arthur to present information on the 2010 SO2 NAAQS and area designation requirements for Texas.
TCEQ Petition for Reconsideration of the Final Rule
On August 23, 2010, the TCEQ submitted a Petition for Reconsideration, asking the EPA to reconsider and stay the adoption and implementation of the final rule of the primary NAAQS for SO2. On January 18, 2011, the EPA filed a Denial of the Petitions to Reconsider the Final Rule Promulgating the Primary NAAQS for Sulfur Dioxide and Respondent’s Motion to Govern Further Proceedings in the United States Court of Appeals for the District of Columbia Circuit. Oral argument for this litigation is set for May 3, 2012.
Texas’ Attainment Status for the SO2 NAAQS
Texas currently has no areas designated nonattainment for any SO2 air quality standard. The EPA is currently working on developing area designations under the 2010 SO2 NAAQS. Nonattainment designations are expected for areas with monitored air quality data showing violations of the standard. All other areas are expected to be designated unclassifiable.
Related Web pages and publications
Get more information on the Texas SIP and contact the TCEQ
TCEQ SIP Contacts
