FACT SHEET
EPA's Proposal to Strengthen and Update the
Mercury and Air Toxics Standards for Power Plants

SUMMARY OF ACTION

•	On April 3, 2023, the Environmental Protection Agency (EPA) proposed to strengthen
and update the National Emission Standards for Hazardous Air Pollutants for Coal- and
Oil-Fired Electric Utility Steam Generating Units (EGUs), commonly known as the
Mercury and Air Toxics Standards (MATS) for power plants, to reflect recent
developments in control technologies and the performance of these plants.

•	This proposed rule reflects the most significant improvements and updates to MATS
since EPA first issued these standards in February 2012. It also fulfills EPA's responsibility
under the Clean Air Act to periodically re-evaluate its standards in light of advancements
in pollution control technologies to determine whether revisions are necessary.

•	The current MATS established standards to limit emissions of mercury; acid gas
hazardous air pollutants (HAP) such as hydrogen chloride (HCI) and hydrogen fluoride;
non-mercury HAP metals such as nickel, lead, and chromium; and organic HAP such as
formaldehyde and dioxin/furan from coal- and oil-fired power plants.

•	Combined with other changes affecting the power sector, MATS has driven sharp
reductions in harmful air toxic pollutants from coal- and oil-fired power plants. Industry-
reported emissions data, required by MATS, shows 2021 mercury emissions from coal-
fired EGUs were 90 percent lower than pre-MATS levels.1 Since 2010, acid gas HAP
emissions have been reduced by over 96 percent and emissions of the non-mercury
metals - including nickel, arsenic, and lead - have been reduced by more than 81
percent.

•	This proposal builds upon the highly successful and cost-effective health protections in
MATS. Based on its latest assessment of available control technologies, EPA is proposing
to further limit the emission of non-mercury HAP metals from existing coal-fired power
plants by significantly reducing the emission standard for filterable particulate matter
(fPM), which is designed to control non-mercury HAP metals. EPA is proposing a two-
thirds reduction in the fPM standard. Also, EPA is proposing to remove the low-emitting
EGU provisions for fPM and non-mercury HAP metals.

•	EPA is also proposing to tighten the emission limit for mercury for existing lignite-fired
power plants by 70 percent, to a level that is aligned with the mercury standard that
other coal-fired power plants have been achieving under the current MATS.

•	EPA's proposal would also strengthen emissions monitoring and compliance by
requiring coal-fired EGUs to comply with the fPM standard using PM continuous
emission monitoring systems (CEMS).

1 2021 Power Sector Programs Progress Report; available at

https://wyvw3.epa.Qov/airmarkets/proQress/reports/pdfs/2021 full report.odf and in the rulemaking docket.

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•	PM CEMS provide regulators, the public, and facility owners or operators with cost-
effective, accurate, and continuous emission measurements. This real-time, quality-
assured feedback can lead to improved control device and power plant operation, which
would reduce air pollutant emissions and exposure for local communities.

•	In addition, EPA is proposing to revise startup requirements in MATS to assure better
emissions performance during startup.

TECHNOLOGY REVIEW

•	EPA is proposing to strengthen some emission limits in MATS, based on its
determination that technologies and/or methods of operation are available to achieve
additional HAP control from coal-fired EGUs at reasonable costs.

•	EPA is proposing a more stringent standard for emissions of fPM - which serves as a
surrogate for the non-mercury HAP metals - from existing coal-fired EGUs. EPA is
proposing to revise the fPM emission standard from 0.030 pounds per million British
thermal units of heat input (Ib/MMBtu) to 0.010 Ib/MMBtu and is soliciting comment on
an even more stringent standard of 0.006 Ib/MMBtu or lower.

o Currently, 91% of coal-fired capacity without known retirement plans before the
proposed compliance period already have demonstrated an fPM emissions rate
at our below the EPA's proposed revision to the standard.

•	EPA is also proposing to tighten the standard for emissions of mercury from lignite-fired
EGUs.

o EPA is proposing that lignite-fired EGUs meet the same mercury emission

standard as EGUs firing other types of coal (i.e., bituminous and subbituminous),
which is 1.2 pounds per trillion British thermal units of heat input (1.2 Ib/TBtu) or
an alternative output-based standard of 0.013 pounds per gigawatt-hour electric
output. Lignite-fired EGUs are currently subject to a mercury emission standard
of 4.0 Ib/TBtu.

o EPA's review of information on current mercury emission levels and controls for
lignite-fired EGUs shows that lignite-fired EGUs can achieve the more stringent
mercury emission rate using available control technologies and/or improved
methods of operation at reasonable costs.

•	As noted above, EPA is also proposing to require that existing coal-fired EGUs utilize
continuous emissions monitoring systems (CEMS) to demonstrate compliance with the
fPM emission standard. EPA estimates that approximately two-thirds of the existing
coal-fired generating fleet does not currently utilize such systems.

•	Lastly, EPA is proposing to remove one of the two options for defining the startup
period for MATS-affected EGUs, based on its determination that this option is not widely
utilized or necessary and that removing it would better secure good emissions
performance during startup periods.

•	EPA requests public comment on all aspects of this proposed rule, including our
evaluation of the costs and efficacy of control option assumptions.

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•	Among other issues, EPA requests comment on whether we have accurately assessed
the variability of fPM emissions and requests information on the costs, pollution
reduction benefits, and cost-effectiveness of applying lower emission limits to sources
subject to MATS; and whether there are other factors the Agency should consider that
would support a more stringent emission limit.

RISK REVIEW

•	The results of the 2020 RTR showed that emissions of HAP from coal- and oil-fired
power plants have been reduced such that residual risk is at an acceptable level.

•	EPA has carefully reviewed the 2020 assessment of residual risk and has decided not to
propose any changes to the risk analysis in this action. EPA did not find any errors in the
2020 residual risk review, and has determined that the risk review was conducted using
approaches and methodologies that are consistent with prior residual risk analyses and
reviews for other industrial sectors.

•	Although EPA is not reopening the 2020 risk review, the proposed standards under this
technology review would achieve reductions in HAP emissions from power plants and
likely reduce HAP exposures to affected populations.

EMISSIONS CHANGES, BENEFITS AND COSTS

•	EPA projects that the proposed changes would result in the following emissions
reductions in the year 2035:

o 82 pounds of mercury;
o 800 tons of fine particulate matter (PM2.5);
o 8,800 tons of sulfur dioxide (SO2);
o 8,700 tons of nitrogen oxides (NOx); and
o 5 million tons of carbon dioxide (CO2).

•	As directed under Executive Order 12866 and consistent with EPA Guidelines for
Preparing Economic Analysis, EPA estimated health benefits, climate

•	benefits, compliance costs, and net benefits of the proposed revisions to the MATS rule
in a Regulatory Impact Analysis (RIA).

•	Present value: The present value of benefits and costs of this action are calculated over
the 10-year period from 2028 to 2037. EPA projects the present value of net benefits to
be $2.4 billion to $3.0 billion. This includes $1.2 billion to $1.9 billion in health benefits,
$1.4 billion in climate benefits, and compliance costs of $230 million to $330 million.

•	Annual value: EPA projects the estimated annualized value net benefits to be $300
million to $350 million. This includes $170 million to $220 million in health benefits,
$170 million in climate benefits, and compliances costs of $33 million to $38 million.

•	The potential benefits from reducing mercury and non-mercury metal HAP were not
monetized and are not included in these estimates. However, this proposal is projected
to reduce emissions of mercury and non-mercury metal HAP, which should help reduce
exposure to methylmercury for sub-populations that rely on subsistence fishing and

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reduce exposure to non-mercury metal HAP including carcinogens such as nickel,
arsenic, and hexavalent chromium, for residents living in the vicinity of these facilities.

POWER SECTOR EFFECTS

•	The power sector analysis supporting this action indicates that the proposed rule would
result in relatively minor impacts on the power sector.

o For example, EPA projects the proposed revisions to MATS would lead to small
national increases in energy prices. Retail electricity prices are projected to
increase in the contiguous U.S. by an average of less than 0.1 percent in 2028,
2030, and 2035. In 2035, the delivered natural gas price is anticipated to increase
by less than 0.1 percent in response to the proposed rule.

o In addition, EPA projects that, under the proposed rule about 500 megawatts of
coal-fired capacity would retire by 2028. Consistent with this small increase in
projected retirements, the Agency does not project coal production for use in
the power sector to change significantly by 2028.

•	Today's proposed rule is one part of a broader suite of actions that Administrator Regan
announced in March 2022 to protect communities across the nation from the various
health and environmental impacts of power plant pollution. EPA is committed to
developing these actions in a transparent and orderly way to provide regulatory
certainty and a long-term planning horizon that allows states, grid operators, and power
companies to make good investments and planning decisions, while preserving the
industry's ability to deliver reliable and affordable electricity.

BACKGROUND

•	Power plants are among the largest domestic sources of emissions of mercury and other
toxic air pollutants such as arsenic, chromium, cobalt, nickel, hydrogen chloride,
beryllium, and cadmium.

o Exposure to these HAP, at certain levels and duration, is associated with a variety
of adverse health effects, which may include irritation of the lung, skin, and
mucus membranes; detrimental effects on the central nervous system; damage
to the kidneys; alimentary effects such as nausea and vomiting; and cancer.

•	In addition to mercury emission standards, MATS also has an HCI emission standard,
which serves as a surrogate for all acid gas HAP; an emission standard for fPM, which
serves as a surrogate for the non-mercury HAP metals; and work practice standards that
require periodic combustion tune-ups to limit formation and emissions of organic HAP.
Coal-fired EGUs with operational add-on flue gas desulfurization (FGD) technology (e.g.,
wet scrubber, spray dryer absorber, dry sorbent injection) and SO2 CEMS can
demonstrate compliance with an alternative SO2 emission limit that serves as an
alternative surrogate for the acid gas HAP.

•	Section 112 of the Clean Air Act (CAA) requires EPA to regulate air toxics from listed
categories of industrial facilities in two phases.

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•	The first phase is "technology-based," where EPA develops standards for controlling the
emissions of air toxics from sources in an industry group or "source category" under
section 112(d) of the CAA. These maximum achievable control technology (MACT)
standards are based on emissions levels that are already being achieved by the best-
controlled and lower-emitting sources in an industry.

•	Within 8 years of setting the MACT standards, section 112(f)(2) of the CAA directs EPA
to assess the remaining health risks from each source category to determine whether
the standards protect public health with an ample margin of safety and protect against
adverse environmental effects. This second phase is a "risk-based" approach called
residual risk. Here, EPA must determine whether more health-protective standards are
necessary.

•	Also, at least every 8 years after setting MACT standards, section 112(d)(6) of the CAA
requires EPA to review and revise the standards, if necessary, to account for
improvements in air pollution controls and/or prevention.

•	This proposed action responds to President Biden's January 20, 2021, Executive Order
13990 "Protecting Human Health and the Environment and Restoring Science to Tackle
the Climate Crisis."

•	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, which included the MATS RTR.

•	In February 2023, EPA revoked the 2020 finding that it was not appropriate and
necessary to regulate coal- and oil-fired power plants under CAA section 112, based on a
number of factors that EPA must consider under the Clean Air Act including the
significant emissions of HAPs from these plants, the harmful health impacts of this
pollution on the public as a whole and on vulnerable communities and populations, and
the availability of cost-effective controls to reduce these emissions.

PUBLIC HEARING AND COMMENT

•	EPA will hold a virtual public hearing for this proposed action. Further details will be
announced at https://www.epa.gov/stationarv-sources~air~pollution/mercury-and~air~
toxics-standards.

•	EPA will accept comment on the proposal for 60 days after publication in the Federal
Register. Comments, identified by Docket ID No. EPA-HQ-OAR-2018-0794, may be
submitted by one of the following methods:

° Go to https://www.regulations.gov/ and follow the online instructions for

submitting comments,
o Send comments by email to a-and-r~docket@epa.gov. Attention Docket ID No.

EPA-HQ-OAR-2018-0794 in the subject line of the message,
o Fax your comments to: (202) 566-9744, Attention Docket ID No. EPA-HQ-OAR-
2018-0794.

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o Mail your comments to: EPA Docket Center, Environmental Protection Agency,
Mail Code: 28221T, 1200 Pennsylvania Ave, NW, Washington, DC 20460,
Attention Docket ID No. EPA-HQ-OAR-2018-0794.
o Deliver comments in person to: EPA Docket Center, 1301 Constitution Ave., NW,
Room 3334, Washington, DC. Note: In-person deliveries (including courier
deliveries) are only accepted during the Docket Center's normal hours of
operation. Special arrangements should be made for deliveries of boxed
information.

FOR MORE INFORMATION

•	Interested parties can download a copy of the proposed rule from EPA's website at the
following address: https://www.epa.gov/stationarv-sources~air~pollution/mercurv-and~
air-toxics-standards.

•	Today's proposed action and other background information are also available
electronically at https://www.reeulations.eov/, EPA's electronic public docket and
comment system.

o The Public Reading Room is located at the EPA Headquarters library, room
number 3334 in the EPA WJC West Building, 1301 Constitution Avenue, NW,
Washington, DC. Hours of operation are 8:30 a.m. to 4:30 p.m., eastern standard
time, Monday through Friday, excluding federal holidays,
o Visitors are required to show photographic identification, pass through a metal
detector, and sign the EPA visitor log. All visitor materials will be processed
through an X-ray machine as well. Visitors will be provided a badge that must be
visible at all times.

o Materials for this proposed action can be accessed using Docket ID No. EPA-HQ-
OAR-2018-0794.

•	For further technical information about the proposed rule, contact Sarah Benish, EPA's
Office of Air Quality Planning and Standards, at (919) 541-5620 or

benish.sarah@epa.eov.

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