The Environmental Protection Agency on Feb. 20 issued a final rule to repeal amendments to the Mercury and Air Toxics Standards (MATS) National Emission Standards for Hazardous Air Pollutants (NESHAP) for Oil- and Coal-Fired Fossil Fuel-Fired power plants.
The final rule would restore the 2012 MATS standards and reinstate compliance flexibility, justified on the basis of cost-effectiveness, technical feasibility, and low residual risk from the source category, APPA reported.
EPA has repealed three core elements of the 2024 MATS amendments:
1. Filterable particulate matter (fPM) standard for existing coal-fired electric generating units (EGUs).
• Reverted from 0.010 lb/MMBtu (2024) back to 0.030 lb/MMBtu (2012).
2. Mandatory use of PM CEMS for fPM compliance
• Restored prior flexibility to use quarterly stack testing, PM continuous parametric monitoring systems, CPMS, or PM CEMS.
3. Tightened mercury (Hg) standard for lignite-fired EGUs
• Reverted from 1.2 lb/TBtu (2024) back to 4.0 lb/TBtu (2012).
EPA’s Repeal Rationale
EPA is basing its repeal on three primary findings:
• EPA concludes that the 2024 MATS Residual Risk and Technology Review (RTR) standards were not cost-effective, with costs exceeding those historically accepted under CAA for similar rules.
• EPA reaffirmed its 2020 residual risk review, which found cancer risks for coal and coal-fired EGUs were well below 1-in-1 million threshold. The 2012 MATS rule provides an ample margin of safety.
• EPA found the tighter mercury standard for lignite-fired units was not adequately supported by data across the full range of boiler designs and fuel characteristics.
Compliance and Monitoring Changes
EPA has restored EGU compliance options; the final rule now allows EGUs to demonstrate compliance using quarterly stack testing, PM CPMS, or PM CEMS. EPA no longer believes that the advantages of PM CEMS outweigh the increased cost of PM CEMS compared to PM CPMS and quarterly stack testing that were determined to be appropriate for demonstrating compliance with the fPM emission standard in the 2012 MATS Rule.
EPA is reinstating the LEE program for fPM and non Hg HAP metals, allowing sources with emissions below 50 percent of the applicable limit for three consecutive years to reduce the frequency of stack testing. Finally, the EPA is also updating the fPM measurement requirements that allow either an increased minimum volume per run or the collection of a minimum mass per run.
For public power utilities, the final rule helps balance affordability, reliability, and environmental protection.
By restoring proven standards and compliance options, EPA reduces regulatory burden while preserving emissions controls that have already delivered and will continue to provide substantial reductions in mercury and other hazardous air pollutants.
APPA submitted extensive technical comments on the proposed MATS RTR repeal, which the Agency used to support its final rule.
More information on the final rule is available on EPA’s website.
