Mercury and Air Toxics Standards

On this page:

• Rule Summary
• Rule History
• Additional Resources

Rule Summary

In the National Emission Standards for Hazardous Air Pollutants for Coal- and Oil-Fired Electric Utility Steam Generating Units (EGUs), also known as the Mercury and Air Toxics Standards or MATS, EPA set technology-based emissions standards for mercury and other hazardous air pollutants (HAP) emitted by units with a capacity of more than 25 megawatts. These standards reflect levels achieved by the best-performing sources and apply to existing and new EGUs. 

MATS, along with significant changes in the power sector, has achieved significant health and environmental benefits by reducing a broad range of hazardous air pollutants.  By 2017 mercury emissions had dropped by 86 percent - down to approximately 4 tons.  Acid gas HAP and non-mercury metals are down 96 percent and 81 percent respectively when compared to 2010 levels.  

Rule History

05/07/2024 - Final Rule - National Emission Standards for Hazardous Air Pollutants: Coal- and Oil-Fired Electric Utility Steam Generating Units Review of the Residual Risk and Technology Review

04/03/2023 - Proposed Rule - National Emission Standards for Hazardous Air Pollutants: Coal - and Oil-Fired Electric Utility Steam Generating Units Review of the Residual Risk and Technology Review

02/15/2023 - Final Revocation of the 2020 Reconsideration, and Affirmation of the Appropriate and Necessary Supplemental Finding

02/09/2022 - Proposed Revocation of the 2020 Reconsideration, and Affirmation of the Appropriate and Necessary Supplemental Finding

07/17/2020 - Final Electronic Reporting Provisions (85 FR 55744)

05/22/2020 - Final Supplemental Finding for MATS and Risk and Technology Review (85 FR 31286)

04/15/2020 - Final Subcategory for Certain Existing Electric Utility Steam Generating Units Firing Eastern Bituminous Coal Refuse for Emissions of Acid Gas Hazardous Air Pollutants (85 FR 20838)

04/03/2020 - Proposed Electronic Reporting Revisions (85 FR 20342)

12/27/2018 - Proposed Revised Supplemental Finding for MATS and Risk and Technology Review (84 FR 2670)

08/08/2016 - Denials of Petitions for Reconsideration – Startup and Shutdown Provisions

• Notice of Final Action Denying Reconsideration on the MATS Startup and Shutdown Provisions (81 FR 52346)
• Denial Document for Reconsideration of Certain Startup and Shutdown Issues; MATS

04/14/2016 - Final Supplemental Finding about MATS and Costs (81 FR 24420)

03/17/2016 - Final Technical Corrections (81 FR 20172)

11/20/2015 - Proposed Supplemental Finding about MATS and Costs (80 FR 75025)

04/21/2015 - Denial of Petitions for Reconsideration of Certain Issues (80 FR 24218)

03/09/2015 - Interim Final Electronic Reporting Requirements (80 FR 15510)

12/19/2014 - Proposed Technical Corrections (80 FR 8442)

11/07/2014 - Final Updates to the Startup and Shutdown Provisions (79 FR 68777) 

11/07/2014 - Direct Final Rule (79 FR 68795) with Parallel Proposal (79 FR 68840) on Electronic Reporting

03/28/2013 - Final Updates to the Standards for New Power Plants (78 FR 24073)

11/16/2012 - Reconsideration of Certain Standards for New Power Plants and Requirements for Startup and Shutdown Periods (77 FR 71323)

02/16/2012 - EPA Announces Final Mercury and Air Toxics Standards for Power Plants (77 FR 9304) 

05/03/2011 - EPA Announces Proposed Mercury and Air Toxics Standards for Power Plants (76 FR 24976)

Additional Resources

Learn more about mercury, products that contain it, and actions to reduce it.