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What’s New with MATS?

Posted: March 10th, 2022

Authors: Wesley H. 

On February 9th, the U.S. Environmental Protection Agency (U.S. EPA) published a proposed finding related to the National Emission Standards for Hazardous Air Pollutants (NESHAP) for Coal- and Oil-Fired Electric Generating Units (EGUs), commonly known as the Mercury and Air Toxics Standards (MATS). U.S. EPA proposes to revoke the May 22, 2020 determination that it is not appropriate or necessary to regulate hazardous air pollutant (HAP) emissions from coal- and oil-fired EGUs. A quick history of MATS and a description of the proposed rule are provided below.

Why Does U.S. EPA Need to Make this Determination?

As part of the Clean Air Act Amendments (CAAA) of 1990, Congress added Section 112, which required U.S. EPA to develop regulations to limit the emissions of 187 HAPs from various source categories.  Because another section of the CAAA, the Acid Rain Program, required criteria pollutant reduction from EGUs, Congress directed the U.S. EPA to regulate HAPs from EGUs only if it deemed it “appropriate and necessary” to do so.

This determination has been a point of contention for many years, and the U.S. EPA has gone back and forth on its determination as administrations have changed. U.S. EPA originally determined in 2000 that it was appropriate and necessary to regulate HAPs from EGUs and reaffirmed its conclusion in 2012 when it finalized the MATS rule, which requires coal and oil- fired EGUs to meet certain HAP emissions standards. Many aspects of the decision were challenged in court and in 2015, the U.S. Supreme Court, in Michigan v. EPA, held that the U.S. EPA did not account for the cost of the emissions standards in its determination to regulate HAPs from coal- and oil-fired EGUs. In response to the Supreme Court ruling, the following year the U. S. EPA issued a supplemental finding that, after considering cost, again concluded that regulating HAPs from coal and oil-fired EGUs through MATS was appropriate and necessary.  However, after petitions for review and a change in administration, the U.S. EPA reversed this decision in 2020, stating that the cost of compliance outweighs the emissions benefits from the regulation, and that it is not appropriate or necessary to regulate HAPs from EGUs. U.S. EPA also performed its required risk and technology review (RTR) and concluded that remaining risks from EGUs were acceptable and that there were no changes in technology that required revisions to the standards. The 2020 final action did not result in any revisions to MATS and the rule remains in place.

Why is U.S. EPA Reviewing MATS Again?

In January 2021, President Biden signed Executive Order 13990 that instructed the U.S. EPA to review the 2020 MATS final action (the appropriate and necessary finding and the RTR) and to propose a rule that revises or revokes the action. The U.S. EPA has reviewed the 2020 final action and concluded that it remains appropriate and necessary to regulate HAP emissions from EGUs. As part of their review, they evaluated HAP risk in the context of environmental justice, as required by various executive orders issues by the administration, particularly in the context of mortality risk for subsistence fishers (i.e., people who obtain a substantial portion of their dietary needs from self-caught fish). They also determined that they overestimated the cost of the rule in 2011 when they were developing it. The U.S. EPA has found that the benefits associated with regulating HAP emissions from EGUs outweigh the costs of complying with MATS. 

What’s Next with MATS?

At this time, the U.S. EPA is not proposing any changes to the existing emissions standards for MATS, and existing EGUs should not expect any impacts from this particular action. However, U.S. EPA is soliciting information to inform its re-evaluation of the 2020 MATS RTR. The agency is requesting information on the actual cost and performance of new, improved, or additional control technologies that may result in cost-effective reductions of HAP emissions from EGUs. Information on technologies and practices for monitoring HAP emissions and for controlling emissions during startup and shutdown is also being sought in an effort to identify whether there are cost-effective operational improvements that could be required as a result of the technology review. The U.S. EPA will evaluate this information and will issue a separate ruling to present the results of its review of the 2020 MATS RTR.

If you are currently subject to MATS, as of today there are no additional requirements or economic impacts resulting from this proposal. However, we will have to wait and see if the Agency proposes revisions to the rule as a result of its review of the 2020 MATS RTR. If you have any additional questions, please reach out to me Wesley Hill at whill@all4inc.com.


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