FACT SHEET

Mercury and Air Toxics Standards for Power Plants:

Reaffirmation of the Appropriate and Necessary Finding

On February 15, 2023, the Environmental Protection Agency (EPA) reaffirmed that it
remains appropriate and necessary to regulate hazardous air pollutants (HAP), including
mercury, from power plants after considering cost.

o This action revokes a 2020 finding that it was not appropriate and necessary to
regulate coal- and oil-fired power plants under Clean Air Act (CAA) section 112,
which covers toxic air pollutants.

EPA reviewed the 2020 finding and considered updated information on both the public
health burden associated with HAP emissions from coal- and oil-fired power plants as well
as the costs associated with reducing those emissions under the Mercury and Air Toxics
Standards (MATS).

After weighing the public risks posed by these emissions to all Americans and to particularly
exposed and sensitive populations against the costs of reducing this harmful pollution, EPA
concludes that it remains appropriate and necessary to regulate these emissions.

This action ensures that coal- and oil-fired power plants continue to control emissions of
hazardous air pollution and that the agency properly interprets the CAA to protect the
public from hazardous air emissions.

The review that led to this final action was directed by President Biden's January 20, 2021,
Executive Order 13990, "Protecting Public Health and the Environment and Restoring
Science to Tackle the Climate Crisis."

o This Executive Order directed EPA to review and consider publishing a proposed
action to suspend, revise, or rescind the May 22, 2020, final action known as the
MATS Supplemental Finding and Residual Risk and Technology Review (RTR). EPA
proposed to revoke the 2020 finding in February 2022.

Executive Order 13990 also directed EPA to re-evaluate the MATS Risk and Technology
Review. EPA is planning to issue a separate proposal based on the Agency's assessment of
the RTR.

Prior to MATS, power plants were the largest domestic source of mercury and other air
toxic pollutants such as hydrogen chloride and selenium. They were also among the largest
domestic emitters of arsenic, chromium, cobalt, nickel, hydrogen cyanide, beryllium, and
cadmium. These sources also emitted significant amounts of sulfur dioxide, nitrogen oxides,
and particulates.

EPA finalized MATS in 2012 and required sources to meet emissions reduction standards by
2016. The rule, along with significant changes in the power sector, has been extremely
effective in keeping HAP from power plants out of the air. Between 2010 and 2017 mercury

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emissions from power plants within the U.S. were reduced by 86%, non-mercury metal
emissions were reduced by 81%, and acid gases emissions were reduced by 96%.

• Controlling HAP emissions from power plants improves public health for all Americans by
reducing fatal heart attacks, reducing cancer risks, avoiding neurodevelopmental delays in
children, and by helping to restore certain ecosystems people and businesses value. These
public health improvements are especially important for children and particularly
vulnerable segments of the population such as indigenous communities, low-income
communities, and people of color who regularly consume the fish they catch.

BACKGROUND

•	On April 12, 2012, EPA re-affirmed its 2000 finding that it is appropriate and necessary to
regulate coal- and oil-fired EGUs for HAP and promulgated National Emission Standards for
Hazardous Air Pollutants for that source category, commonly known as the Mercury and Air
Toxics Standards or MATS.

•	In 2015, the U.S. Supreme Court, in Michigan v. EPA, held that the Agency had erred by not
taking cost into consideration when making its determination that regulation of HAP
emissions from coal- and oil-fired EGUs under section 112 of the CAA is appropriate and
necessary.

•	On April 25, 2016, EPA issued a supplemental finding in response to the Michigan decision
and found that, after a consideration of costs, it remained appropriate and necessary to
regulate HAP emissions from coal- and oil-fired EGUs.

•	On May 22, 2020, EPA reversed that determination, finding that, after weighing the costs of
compliance against certain benefits of regulation, it is not appropriate and necessary to
regulate coal- and oil-fired EGUs under section 112 of the CAA.

•	The May 22, 2020, final action also included a RTR of MATS.

•	On February 9, 2022, EPA proposed to revoke the May 22, 2020 finding that it is not
appropriate and necessary to regulate coal- and oil-fired EGUs under CAA section 112, and
to reaffirm the Agency's April 25, 2016 finding that it remains appropriate and necessary to
regulate HAP emissions from EGUs after considering cost.

FOR MORE INFORMATION

•	Interested parties can download a copy of the final rule at Mercury and / cs
Standards.

•	Today's action and other background information are also available electronically on EPA's
electronic public docket system.

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