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Air Pollution from Ozone

General information on ozone, and TCEQ planning that addresses the ozone National Ambient Air Quality Standards (NAAQS).

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What is ozone? How is it formed? Why should we be concerned about this air pollutant?

Latest air quality planning that addresses the ozone NAAQS

Last updated: 10/30/2019

New Executive Director's Recommended 2015 Eight-Hour Ozone National Ambient Air Quality Standard (NAAQS) Emissions Inventory (EI) SIP Revision for the Houston-Galveston-Brazoria (HGB), Dallas-Fort Worth (DFW), and Bexar County Nonattainment Areas

On November 20, 2019, the commission will consider proposal of the executive director's recommended 2015 Eight-Hour Ozone NAAQS EI SIP Revision for the HGB, DFW, and Bexar County Nonattainment Areas (Non-Rule Project No. 2019-111-SIP-NR). The executive director's proposed SIP revision would satisfy Federal Clean Air Act (FCAA), §172(c)(3) and §182(a)(1) EI reporting requirements for areas designated nonattainment for the 2015 eight-hour ozone NAAQS. The revision would also include a certification statement to confirm that the emissions statements and nonattainment new source review requirements have been met for the HGB, DFW, and Bexar County 2015 eight-hour ozone nonattainment areas.

Infrastructure and Transport SIP Revisions for the 2015 Ozone Standard

On August 8, 2018, the commission adopted two revisions to the Texas SIP for the 2015 ozone NAAQS: the 2015 Ozone NAAQS Infrastructure SIP Revision (Non-Rule Project No. 2017-040-SIP-NR) and the 2015 Ozone NAAQS Transport SIP Revision (Non-Rule Project No. 2017-039-SIP-NR). Infrastructure and Transport SIP revisions for the 2015 ozone NAAQS were due to the United States Environmental Protection Agency (EPA) by October 1, 2018.

Proposed Infrastructure and Transport SIP Revisions for the 2015 Ozone Standard

On March 7, 2018, the commission approved proposal of two revisions to the Texas SIP for the 2015 ozone NAAQS: the 2015 Ozone NAAQS Infrastructure SIP Revision (Non-Rule Project No. 2017-040-SIP-NR) and the 2015 Ozone NAAQS Transport SIP Revision (Non-Rule Project No. 2017-039-SIP-NR). Infrastructure and Transport SIP revisions for the 2015 ozone NAAQS are due to the United States Environmental Protection Agency (EPA) by October 1, 2018. A public hearing for both SIP revisions was held at 2:00 p.m. on April 10, 2018 at the Texas Commission on Environmental Quality, 12100 Park 35 Circle, Building E, Room 201S.

The proposed 2015 Ozone NAAQS Infrastructure SIP revision would outline the requirements of FCAA, §110(a)(2)(A) through (C) and (E) through (M) and the Texas provisions supporting the requirements. These requirements include basic program elements such as enforceable emission limitations and control measures, air quality monitoring and modeling, a permitting program, adequate funding and personnel, authority under state law to carry out the plan, emissions reporting, emergency powers, public participation, and fee collection.

The proposed 2015 Ozone NAAQS Transport SIP revision would document how the transport elements listed in FCAA, §110(a)(2)(D) are currently addressed in the Texas SIP. This SIP revision would provide a detailed technical demonstration and other supporting information to meet the interstate transport requirements of FCAA, §110(a)(2)(D)(i) and (ii).

The 2015 Ozone NAAQS

On October 1, 2015, the EPA revised the primary and secondary NAAQS for ozone to an eight-hour standard of 0.070 parts per million (ppm), or 70 parts per billion (ppb) (80 FR 65292Exit the TCEQ). The 2015 eight-hour ozone NAAQS became effective on December 28, 2015. The EPA designated six Houston-Galveston-Brazoria (HGB) area counties (Brazoria, Chambers, Fort Bed, Galveston, Harris, and Montgomery) and nine Dallas-Fort Worth (DFW) area counties (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Tarrant, and Wise) as nonattainment for the 2015 eight-hour ozone NAAQS, effective August 3, 2018 (83 FR 25766Exit the TCEQ). The EPA designated Bexar County as nonattainment for the 2015 eight-hour ozone NAAQS, effective September 24, 2018 (83 FR 35136Exit the TCEQ). Each of the three nonattainment areas in Texas were assigned a marginal classification. Under the marginal classification, the DFW and HGB areas are required to meet the 2015 eight-hour ozone NAAQS by the end of 2020 to meet an attainment date of August 3, 2021, while Bexar County must meet an attainment date of September 24, 2021. 

For more information on the 2015 ozone standard, see:

For more information on Texas' state designation recommendations for the 2015 ozone NAAQS, see:

Emissions Inventory (EI) SIP Revision for the 2008 Eight-Hour Ozone Standard for the Houston-Galveston-Brazoria (HGB) and Dallas-Fort Worth (DFW) Areas

On July 2, 2014, the commission adopted the EI SIP revision for the 2008 Eight-Hour Ozone Standard (Non-Rule Project No. 2013-016-SIP-NR). This SIP revision satisfies the FCAA, §172 and §182 requirements for the HGB and DFW nonattainment areas under the 2008 eight-hour ozone standard. The SIP revision includes 2011 emissions inventories for ozone precursors (volatile organic compounds and nitrogen oxides) from point, area, on-road mobile, non-road mobile, and biogenic emissions source categories as the base year emissions inventories for the HGB and DFW areas. The nonattainment area base year EI submission was due no later than 24 months from the July 20, 2012 effective date of designations under the 2008 eight-hour ozone standard, July 20, 2014.

Infrastructure and Transport SIP Revision for the 2008 Ozone Standard

On December 5, 2012, the commission adopted the FCAA, §110(a)(1) and (2) Infrastructure and Transport SIP Revision for the 2008 Ozone NAAQS (Non-Rule Project No. 2012-004-SIP-NR). This SIP revision outlines the requirements of FCAA, §110(a)(2)(A) through (M) and the Texas provisions supporting the requirements. These requirements include basic program elements such as enforceable emission limitations and control measures, air quality monitoring and modeling, a permitting program, adequate funding and personnel, authority under state law to carry out the plan, emissions reporting, emergency powers, public participation, and fee collection. This SIP revision also includes a technical demonstration to support that Texas meets the interstate transport requirements of FCAA, §110(a)(2)(D)(i)(I).

A public hearing was held on September 25, 2012 at the Texas Commission on Environmental Quality headquarters in Austin. The public comment period was from August 24 through September 28, 2012. Comments were submitted by the United States Environmental Protection Agency, Alamo Area Council of Governments, Public Citizen, and four individuals. 

The 2008 Ozone Standard

On March 27, 2008, the EPA lowered the primary and secondary eight-hour ozone NAAQS to 0.075 parts per million (73 FR 16436Exit the TCEQ). On May 21, 2012, the EPA published in the Federal Register final designations for the 2008 eight-hour ozone standard, effective July 20, 2012 (77 FR 30088Exit the TCEQ). The Dallas-Fort Worth (DFW) area (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, Tarrant, and Wise Counties) was designated moderate nonattainment and the Houston-Galveston-Brazoria (HGB) area (Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller Counties) was designated marginal nonattainment.

On May 21, 2012, the EPA also published in the Federal Register a final rule to establish classification thresholds, establish December 31 of each relevant calendar year as the attainment date for each classification, and revoke the 1997 eight-hour ozone NAAQS for purposes of transportation conformity (77 FR 30160Exit the TCEQ). On March 6, 2015, the EPA published a final SIP requirements rule for implementing the 2008 eight-hour ozone NAAQS (80 FR 12264Exit the TCEQ). On February 16, 2018, the United States Court of Appeals for the District of Columbia Circuit issued an opinion in the case South Coast Air Quality Management District vs. EPA, 882 F.3d 1138 (D.C. Cir. 2018)Exit the TCEQ. The court’s decision vacated parts of the EPA’s final 2008 eight-hour ozone standard SIP requirements rule, including the redesignation substitute, removal of anti-backsliding requirements for areas designated nonattainment under the 1997 eight-hour ozone NAAQS, waiving requirements for transportation conformity for maintenance areas under the 1997 eight-hour ozone NAAQS, and elimination of the requirement to submit a second 10-year maintenance plan.

The HGB area was reclassified from marginal to moderate nonattainment on December 14, 2016 (81 FR 90207Exit the TCEQ). On August 23, 2019, the EPA reclassified the DFW and HGB areas from moderate to serious nonattainment for the 2008 eight-hour ozone NAAQS (84 FR 44238Exit the TCEQ). The attainment date for serious nonattainment areas is July 20, 2021 with a 2020 attainment year.

For more information on the TCEQ's designation recommendation process for the 2008 ozone NAAQS, see:

Related webpages and publications

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