FACT SHEET

Pollutant-Specific Significant Contribution Finding for Greenhouse Gas Emissions

from New, Modified, and Reconstructed Stationary Sources: Electric Utility Generating Units,
and Process for Determining Significance of Other NSPS Source Categories

ACTION

•	On January 7, 2021, the U.S. Environmental Protection Agency (EPA) provided a framework
for criteria for making a significant contribution finding (SCF) for greenhouse gas (GHG)
emissions from a source category, for the purpose of regulating those emissions under
section 111(b) of the Clean Air Act (CAA).

•	CAA section 111(b)(1)(A) states that "[The Administrator] shall include a category of sources
[for regulation] if in his judgment it causes, or contributes significantly to, air pollution
which may reasonably be anticipated to endanger public health or welfare." In an earlier
rulemaking, EPA concluded that the Agency must make a pollutant-specific finding that such
pollutant "contributes significantly to" air pollution that endangers public health or welfare.

•	EPA's framework sets an emissions threshold of 3 percent of total gross U.S. GHG emissions
(as measured in carbon dioxide equivalent, i.e., CChe) from a stationary source category as
the primary criterion in making a pollutant-specific significance determination for purposes
of CAA section 111(b).

•	The framework for a clear emissions threshold provides certainty regarding EPA's process
and gives regulated entities insight into EPA's approach to making a determination of
significance under this part of the CAA.

•	The framework provides that source categories can only be considered to contribute
significantly to dangerous air pollution due to their GHG emissions if the amount of those
emissions exceeds 3 percent of total U.S. GHG emissions. For certain source categories that
emit above this threshold, the framework also provides secondary criteria that can be used
to further evaluate whether a source category contributes significantly.

•	In this action, EPA is also determining that the electric utility generating units (EGU) source
category contributes significantly to dangerous air pollution because GHG emissions from
the EGU source category (which includes utility boilers, gasification units, and stationary
combustion turbines) are substantially above the 3-percent threshold. The EGU source
category represents over 25 percent of total U.S. GHG emissions.

•	A source category's significance determination may be reevaluated in the future as the GHG
emissions and secondary criteria for that source category may change over time.

•	The criteria provided in the framework only apply to GHGs in the context of EPA's significant
contribution finding under CAA section 111(b)(1)(A). This final rule does not discuss criteria
for making a significant contribution finding for pollutants other than GHGs.

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BACKGROUND

•	Section 111(b) of the CAA provides authority to address emissions from new, modified, and
reconstructed power plants, recognizing different approaches are available at different
stages of construction.

•	In 2015, EPA issued final new source performance standards (NSPS) to regulate GHGs from
new power plants under CAA section 111(b), as well as a final rule known as the Clean
Power Plan (CPP) to regulate GHGs from existing power plants under CAA section 111(d).

•	On March 28, 2017, President Trump signed the Energy Independence Executive Order (EO
13783) which called for, among other things, a review of the final rules to regulate GHGs
from power plants and, if appropriate, reconsideration proceedings to suspend, revise, or
rescind the rules.

•	In August 2018, EPA proposed to repeal the CPP and replace it with the Affordable Clean
Energy (ACE) Rule, which regulates GHGs from existing power plants under CAA section
111(d). EPA finalized the repeal of the CPP and promulgated ACE in July 2019.

•	In December 2018, EPA proposed revisions to the GHG NSPS from new, modified, and
reconstructed fossil fuel-fired power plants. EPA held one public hearing and received more
than 142,000 comments on the proposal.

o In the December 2018 proposal, EPA solicited comment on whether to make a

pollutant-specific significant contribution finding for GHG emissions from EGUs, which
is the subject of this final action.

o The remainder of the 2018 proposal was dedicated to the issue of the determination
of the best system of emission reduction for newly constructed, modified, and
reconstructed coal-fired EGUs. EPA is not addressing that aspect of the proposal, or
related comments, in this final rulemaking. These issues will be addressed in a future
EPA action.

•	In the 2020 Oil and Gas Rule, EPA finalized its position that the CAA requires the Agency to
make a pollutant-specific significant contribution finding for a source category before
setting performance standards for that pollutant, unless the Agency addressed the pollutant
when it initially listed the source category.

FOR MORE INFORMATION

•	Interested parties can download a copy of the final rule notice from EPA's website at the
following address: https://www.epa.gov/stationary-sources-air~pollution/nsps-ghg~
emissions-new-mod if ied~and~reconstructed~electric~utility.

•	Today's action and other background information are also available electronically at
https://www.regulations.gov/, EPA's electronic public docket and comment system.
Materials for this action can be accessed using Docket ID No. EPA-HQ-OAR-2013-0495.

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•	Out of an abundance of caution for members of the public and our staff, the EPA Docket
Center and Reading Room are closed to the public, with limited exceptions, to reduce the
risk of transmitting COVID-19. Our Docket Center staff will continue to provide remote
customer service via email, phone and webform.

•	For further information on EPA Docket Center services and their current status, please visit
us online at https://www.epa.eov/dockets.

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