[Federal Register Volume 87, Number 23 (Thursday, February 3, 2022)]
[Proposed Rules]
[Pages 6324-6362]
[FR Doc No: 2022-01150]

Vol. 87

Thursday,

No. 23

February 3, 2022

Part III

 Environmental Protection Agency

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40 CFR Parts 87, 1030, and 1031

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Control of Air Pollution From Aircraft Engines: Emission Standards and
Test Procedures; Proposed Rule

Federal Register / Vol. 87 , No. 23 / Thursday, February 3, 2022 /
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 87, 1030, and 1031

[EPA-HQ-OAR-2019-0660; FRL-7558-01-OAR]
RIN 2060-AU69

Control of Air Pollution From Aircraft Engines: Emission
Standards and Test Procedures

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: The Environmental Protection Agency (EPA) is proposing
particulate matter (PM) emission standards and test procedures
applicable to certain classes of engines used by civil subsonic jet
airplanes (those engines with rated output of greater than 26.7
kilonewtons (kN)) to replace the existing smoke standard for aircraft.
These proposed standards and test procedures are equivalent to the
engine standards adopted by the United Nations' International Civil
Aviation Organization (ICAO) in 2017 and 2020 and would apply to both
new type design aircraft engines and in-production aircraft engines.
The EPA, as well as the United States Federal Aviation Administration
(FAA), actively participated in the ICAO proceedings in which these
requirements were developed. These proposed standards would reflect the
importance of the control of PM emissions and U.S. efforts to secure
the highest practicable degree of uniformity in aviation regulations
and standards. Additionally, the EPA is proposing to migrate,
modernize, and streamline the existing regulations into a new part. As
part of this update, the EPA is also proposing to align with ICAO by
applying the smoke number standards to engines less than or equal to
26.7 kilonewtons rated output used in supersonic airplanes.

DATES: Comments on this proposal must be received on or before April 4,
2022.
    Public hearing: EPA will announce the public hearing date and
location for this proposal in a supplemental Federal Register document.

ADDRESSES:
    Comments: EPA solicits comments on all aspects of the proposed
standards.
    Written comments: Submit your comments, identified by Docket ID No.
EPA-HQ-OAR-2019-0660, at https://www.regulations.gov. Follow the online
instructions for submitting comments. Once submitted, comments cannot
be edited or removed from Regulations.gov. The EPA may publish any
comment received to its public docket. Do not submit electronically any
information you consider to be Confidential Business Information (CBI)
or other information whose disclosure is restricted by statute.
Multimedia submissions (audio, video, etc.) must be accompanied by a
written comment. The written comment is considered the official comment
and should include discussion of all points you wish to make. The EPA
will generally not consider comments or comment contents located
outside of the primary submission (i.e., on the web, cloud, or other
file sharing system). For additional submission methods, the full EPA
public comment policy, information about CBI or multimedia submissions,
and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa-dockets.
    The EPA is temporarily suspending its Docket Center and Reading
Room for public visitors, 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. We
encourage the public to submit comments via https://www.regulations.gov
as there may be a delay in processing mail and faxes. For further
information and updates on EPA Docket Center services, please visit us
online at https://www.epa.gov/dockets.
    The EPA continues to carefully and continuously monitor information
from the Centers for Disease Control and Prevention (CDC), local area
health departments, and our Federal partners so that we can respond
rapidly as conditions change regarding COVID-19.
    Docket: EPA has established a docket for the action under Docket ID
No. EPA-HQ-OAR-2019-0660. All documents in the docket are listed on the
www.regulations.gov website. Although listed in the index, some
information is not publicly available, e.g., confidential business
information or other information whose disclosure is restricted by
statute. Certain other material, such as copyrighted material is not
placed on the internet and will be publicly available only in hard copy
form. Publicly available docket materials are available either
electronically through www.regulations.gov or in hard copy at the
following location:
    Air and Radiation Docket and Information Center, EPA Docket Center,
EPA/DC, EPA WJC West Building, 1301 Constitution Ave. NW, Room 3334,
Washington, DC.
    Out of an abundance of caution for members of the public and our
staff, the EPA Docket Center and Reading Room was closed to public
visitors on March 31, 2020, to reduce the risk of transmitting COVID-
19. Our Docket Center staff will continue to provide remote customer
service via email, phone, and webform. We encourage the public to
submit comments via https://www.regulations.gov or email, as there is a
temporary suspension of mail delivery to EPA, and no hand deliveries
are currently accepted. For further information on EPA Docket Center
services and the current status, please visit us online at https://www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Bryan Manning, Office of
Transportation and Air Quality, Assessment and Standards Division
(ASD), Environmental Protection Agency, 2000 Traverwood Drive, Ann
Arbor, MI 48105; telephone number:<PHONE_NUMBER>; email address:
[email protected].

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information
    A. Does this action apply to me?
    B. Executive Summary
    1. Summary of the Major Provisions of the Proposed Regulatory
Action
    2. Purpose of the Proposed Regulatory Action
    3. Environmental Justice
II. Introduction: Context for This Proposed Action
    A. EPA Statutory Authority and Responsibilities Under the Clean
Air Act
    B. The Role of the United States in International Aircraft
Agreements
    C. The Relationship Between EPA's Regulation of Aircraft Engine
Emissions and International Standards
III. Particulate Matter Impacts on Air Quality and Health
    A. Background on Particulate Matter
    B. Health Effects of Particulate Matter
    C. Environmental Effects of Particulate Matter
    1. Deposition of Metallic and Organic Constituents of PM
    2. Materials Damage and Soiling
    D. Near-Source Impacts on Air Quality and Public Health
    E. Contribution of Aircraft Emissions to PM in Selected Areas
    F. Other Pollutants Emitted by Aircraft
    G. Environmental Justice
IV. Details for the Proposed Rule
    A. PM Mass Standards for Aircraft Engines
    1. Applicability of Standards
    2. New Type nvPM Mass Numerical Emission Limits for Aircraft
Engines
    3. In Production nvPM Mass Numerical Emission Limits for
Aircraft Engines
    4. Graphical representation of nvPM Mass Numerical Emission
Limits
    B. PM Number Standards for Aircraft Engines
    1. Applicability of Standards

    2. New Type nvPM Number Numerical Emission Limits for Aircraft
Engines
    3. In Production nvPM Number Numerical Emission Limits for
Aircraft Engines
    4. Graphical representation of nvPM Number Numerical Emission
Limits
    C. PM Mass Concentration Standard for Aircraft Engines
    1. PM Mass Concentration Standard
    2. Graphical Representation of nvPM Mass Concentration Numerical
Emission Limit
    D. Test and Measurement Procedures
    1. Aircraft Engine PM Emissions Metrics
    2. Test Procedure
    3. Test Duty Cycles
    4. Characteristic Level
    5. Derivative Engines for Emissions Certification Purposes
    E. Annual Reporting Requirement
V. Aggregate PM Inventory Impacts
    A. Aircraft Engine PM Emissions for Modeling
    1. Baseline PM Emission Indices
    2. Measured nvPM EIs for Inventory Modeling
    3. Improvements to Calculated EIs
    B. Baseline PM Emission Inventory
    C. Projected Reductions in PM Emissions
VI. Technological Feasibility and Economic Impacts
    A. Market Considerations
    B. Conceptual Framework for Technology
    C. Technological Feasibility
    D. Costs Associated With the Proposed Rule
    E. Summary of Benefits and Costs
VII. Technical Amendments
    A. Migration of Regulatory Text to New Part
    B. Deletion of Unnecessary Provisions
    C. Other Technical Amendments and Minor Changes
VIII. Statutory Authority and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From
Environmental Health Risks and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That
Significantly Affect Energy Supply, Distribution or Use
    I. National Technology Transfer and Advancement Act (NTTAA)
    J. Executive Order 12898: Federal Actions To Address
Environmental Justice in Minority Populations and Low-Income
Populations

I. General Information

A. Does this action apply to me?

    This proposed action would affect companies that design and or
manufacture civil subsonic jet aircraft engines with a rated output of
greater than 26.7 kN and those that design and or manufacturer civil
jet engines for use on supersonic airplanes with a rated output at or
below 26.7 kN. These affected entities include the following:

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                                                        Examples of
           Category              NAICS code \a\    potentially affected
                                                         entities
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Industry......................           336412   Manufacturers of new
                                                   aircraft engines.
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\a\ North American Industry Classification System (NAICS).

    This table lists the types of entities that EPA is now aware could
potentially be affected by this action. Other types of entities not
listed in the table could also be regulated. To determine whether your
activities are regulated by this action, you should carefully examine
the relevant applicability criteria in 40 CFR parts 87 and 1031. If you
have any questions regarding the applicability of this action to a
particular entity, consult the person listed in the preceding FOR
FURTHER INFORMATION CONTACT section.
    For consistency purposes across the United States Code of Federal
Regulations (CFR), common definitions for the words ``airplane,''
``aircraft,'' ``aircraft engine,'' and ``civil aircraft'' are found in
Title 14 CFR part 1, and are used as appropriate throughout this new
proposed regulation under 40 CFR parts 87 and 1031.

B. Executive Summary

1. Summary of the Major Provisions of the Proposed Regulatory Action
    The EPA is proposing to regulate PM emissions from covered aircraft
engines through the adoption of domestic PM regulations that match the
ICAO PM standards, which would be implemented and enforced in the U.S.
The proposed standards would apply to new type design and in-production
aircraft engines with rated output (maximum thrust available for
takeoff) of greater than 26.7 kN used by civil subsonic jet airplanes:
Those engines generally used in commercial passenger and freight
aircraft, as well as larger business jets. The EPA is proposing to
adopt three different forms of PM standards: A PM mass standard in
milligrams per kilonewton (mg/kN), a PM number standard in number of
particles per kilonewton (#/kN), and a PM mass concentration standard
in micrograms per cubic meter ([mu]g/m\3\). The applicable dates and
coverage of these standards would vary, as described in the following
paragraphs, and more fully in in IV.A, IV.B, and IV.C respectively.
    First, the EPA is proposing PM engine emissions standards, in the
form of both PM mass (mg/kN) and PM number (#/kN), for new type designs
and in-production aircraft turbofan and turbojet engines with rated
output greater than 26.7 kN. The proposed standards for in-production
engines would apply to those engines that would be manufactured on or
after January 1, 2023, even if type certificated before that date. The
proposed standards for new type designs would apply to those engines
whose initial type certification application was submitted on or after
January 1, 2023. The in-production standards would have different
emission levels limits than would the standards for new type designs.
The different emission levels limits for new type designs and in-
production engines would depend on the rated output of the engines.
Compliance with the proposed PM mass and number standards would be done
in accordance with the standard landing and take-off (LTO) test cycle,
which is currently used for demonstrating compliance with gaseous
emission standards (oxides of nitrogen (NOX), hydrocarbons
(HC), and carbon monoxide (CO) standards) for the covered engines.
    Second, the EPA is proposing a PM engine emissions standard in the
form of maximum mass concentration ([mu]g/m\3\) for in-production
aircraft turbofan and turbojet engines with rated output greater than
26.7 kN manufactured on or after January 1, 2023.\1\ Compliance with
the PM mass concentration standard would be done using the same test
data that is developed to demonstrate compliance with the LTO-based PM
mass and number standards. The proposed PM mass concentration standard
would apply to the highest concentration of PM measured across the
engine operating thrust range, not

just at one of the four LTO thrust settings.
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    \1\ The implementation date for ICAO's PM maximum mass
concentration standards is on or after January 1, 2020. The final
rulemaking that would follow this proposed rulemaking for these
standards is expected to be completed before January 1, 2023. Thus,
the standards would have an implementation date of January 1, 2023
(instead of January 1, 2020).
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    The proposed PM mass concentration standard was developed by ICAO
to provide, through a PM mass measurement, the equivalent smoke opacity
or visibility control as afforded by the existing smoke number standard
for the covered engines. Thus, the EPA is also proposing to no longer
apply the existing smoke number standard for new engines that would be
subject to the proposed PM mass concentration standard after January 1,
2023, but the EPA is maintaining smoke number standards for new engines
not covered by the PM mass concentration standard (e.g., in-production
aircraft turbofan and turbojet engines with rated output less than or
equal to 26.7 kN) and for engines already manufactured. This proposed
approach would essentially change the existing standard for covered
engines from being based on a smoke measurement to a PM measurement.
    Third, the EPA is proposing testing and measurement procedures for
the PM emission standards and various updates to the existing gaseous
exhaust emissions test procedures. These proposed test procedure
provisions would implement the recent additions and amendments to
ICAO's regulations, which are codified in ICAO Annex 16, Volume II. As
we have historically done, we propose to incorporate these test
procedure additions and amendments to the ICAO Annex 16, Volume II into
our regulations by reference.
    The proposed aircraft engine PM standards, test procedures and
associated regulatory requirements are equivalent to the international
PM standards and test procedures adopted by ICAO in 2017 and 2020 and
promulgated in Annex 16, Volume II.\2\ The United States and other
member States of ICAO, as well as the world's aircraft engine
manufacturers and other interested stakeholders, participated in the
deliberations leading up to ICAO's adoption of the international
aircraft engine PM emission standards.
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    \2\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed
November 15, 2021). The ICAO Annex 16 Volume II is found on page 17
of the ICAO Products & Services Catalog, English Edition of the 2021
catalog, and it is copyright protected; Order No. AN16-2. The ICAO
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of
January 1, 2021. Amendment 10 is also found on page 17 of this ICAO
catalog, and it is copyright protected; Order No. AN 16-2/E/12.
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    In addition to the PM standards just discussed, the EPA is
proposing to migrate the existing aircraft engine emissions regulations
from 40 CFR part 87 to a new 40 CFR part 1031, and all the aircraft
engine standards and requirements described earlier would be specified
in this new part 1031. Along with this migration, the EPA is proposing
to restructure the regulations to allow for better ease of use and
allow for more efficient future updates. The EPA is also proposing to
delete some unnecessary definitions and regulatory provisions. Finally,
the EPA is proposing several other minor technical amendments to the
regulations, including applying smoke number standards to engines of
less than or equal to 26.7 kilonewtons (kN) rated output used in
supersonic airplanes.
2. Purpose of the Proposed Regulatory Action
    In developing these proposed standards, the EPA took into
consideration the importance of both controlling PM emissions and
international harmonization of aviation requirements. In addition, the
EPA gave significant weight to the U.S.'s treaty obligations under the
Chicago Convention, as discussed in Section II.B, in determining the
need for and appropriate levels of PM standards. These considerations
led the EPA to propose standards for PM emissions from certain classes
of covered aircraft engines that are equivalent in scope, stringency,
and effective date to the PM standards adopted by ICAO.
    The new ICAO aircraft PM emission standards will take effect on
January 1, 2023 but will not apply in the U.S. unless adopted into
domestic law. One of the core functions of ICAO is to adopt Standards
and Recommended Practices on a wide range of aviation-related matters,
including aircraft emissions. As a member State of ICAO, the United
States actively participates in the development of new environmental
standards, within ICAO's Committee on Aviation Environmental Protection
(CAEP), including the PM standards adopted by ICAO in both 2017 and
2020. Due to the international nature of the aviation industry, there
is an advantage to working within ICAO, in order to secure the highest
practicable degree of uniformity in international aviation regulations
and standards. Uniformity in international aviation regulations and
standards is a goal of the Chicago Convention, because it ensures that
passengers and the public can expect similar levels of protection for
safety and human health and the environment regardless of manufacturer,
airline, or point of origin of a flight. Further, it helps reduce
barriers in the global aviation market, benefiting both U.S. aircraft
engine manufacturers and consumers.
    When developing new emissions standards, ICAO/CAEP seeks to capture
the technological advances made in the control of emissions through the
adoption of anti-backsliding standards reflecting the current state of
technology. The PM standards the EPA is proposing were developed using
this approach. Thus, the adoption of these aviation standards into U.S.
law would simultaneously prevent aircraft engine PM levels from
increasing beyond their current levels, align U.S. domestic standards
with the ICAO standards for international harmonization, and help the
U.S. meet its treaty obligations under the Chicago Convention.
    These proposed standards would also allow U.S. manufacturers of
covered aircraft engines to remain competitive in the global
marketplace (as described later in the introductory text of Section
IV). In the absence of U.S. standards implementing the ICAO aircraft
engine PM emission standards, U.S. civil aircraft engine manufacturers
could be forced to seek PM emissions certification from an aviation
certification authority of another country (not the FAA) in order to
market and operate their aircraft engines internationally. U.S.
manufacturers could be at a significant disadvantage if the U.S. fails
to adopt standards that are at least as stringent as the ICAO standards
for PM emissions. The ICAO aircraft engine PM emission standards have
been or are being adopted by other ICAO member states that certify
aircraft engines. The proposed action to adopt in the U.S. PM standards
that match the ICAO standards would help ensure international
consistency and acceptance of U.S. manufactured engines worldwide.
3. Environmental Justice
    Executive Orders 12898 (59 FR 7629, February 16, 1994) and 14008
(86 FR 7619, February 1, 2021) direct federal agencies, to the greatest
extent practicable and permitted by law, to make achieving
environmental justice (EJ) part of their mission by identifying and
addressing, as appropriate, disproportionately high and adverse human
health or environmental effects of their programs, policies, and
activities on minority populations and low-income populations in the
United States. Section III.G discusses these executive orders in
greater detail, along with the potential environmental justice concerns
associated with exposure to aircraft PM near airports. EPA defines
environmental justice as the fair

treatment and meaningful involvement of all people regardless of race,
color, national origin, or income with respect to the development,
implementation, and enforcement of environmental laws, regulations, and
policies.
    Studies have reported that many communities in close proximity to
airports are disproportionately represented by people of color and low-
income populations (as described later in Section III.G). In an action
separate from this proposed rulemaking, EPA will be conducting an
analysis of the communities residing near airports where jet aircraft
operate in order to more fully understand disproportionately high and
adverse human health or environmental effects on people of color, low-
income populations and/or indigenous peoples. The results of this
analysis could help inform additional policies to reduce pollution in
communities living in close proximity to airports.
    As described in Section V.C, while newer aircraft engines typically
have significantly lower emissions than existing aircraft engines, the
proposed standards in this action are technology-following in order to
align with ICAO's standards and are not expected to, in and of
themselves, result in further reductions in PM from these engines.
Therefore, we do not anticipate an improvement in air quality for those
who live near airports where these aircraft operate.

II. Introduction: Context for This Proposed Action

    EPA has been regulating PM emissions from aircraft engines since
the 1970s when the first smoke number standards were adopted. This
section provides context for the proposed rule, which proposes three PM
standards for aircraft engines. This section includes a description of
EPA's statutory authority, the United States' role in ICAO and
developing international emission standards, and the relationship
between United States' standards and ICAO's international standards.

A. EPA Statutory Authority and Responsibilities Under the Clean Air Act

    Section 231(a)(2)(A) of the Clean Air Act (CAA) directs the
Administrator of EPA to, from time to time, propose aircraft engine
emission standards applicable to the emission of any air pollutant from
classes of aircraft engines which in his or her judgment causes or
contributes to air pollution that may reasonably be anticipated to
endanger public health or welfare. (See 42 U.S.C. 7571(a)(2)(A)). CAA
section 231(a)(2)(B) directs the EPA to consult with the Administrator
of the Federal Aviation Administration (FAA) on such standards, and it
prohibits the EPA from changing aircraft emission standards if such a
change would significantly increase noise and adversely affect safety.
(See 42 U.S.C. 7571(a)(2)(B)(i)-(ii)). CAA section 231(a)(3) provides
that after we provide notice and an opportunity for a public hearing on
standards, the Administrator shall issue such standards ``with such
modifications as he deems appropriate.'' (See 42 U.S.C. 7571(a)(3)). In
addition, under CAA section 231(b) the EPA is required to ensure, in
consultation with the U.S. Department of Transportation (DOT), that the
effective date of any standard provides the necessary time to permit
the development and application of the requisite technology, giving
appropriate consideration to the cost of compliance. (See 42 U.S.C.
7571(b)).
    Consistent with its longstanding approach and D.C. Circuit
precedent,\3\ the EPA interprets its authority under CAA section 231 as
providing the Administrator wide discretion in determining what
standards are appropriate, after consideration of the factors specified
in the statute and other relevant factors, such as applicable
international standards. We are not compelled under CAA section 231 to
obtain the ``greatest degree of emission reduction achievable'' as per
sections 213(a)(3) and 202(a)(3)(A) of the CAA, and so the EPA does not
interpret the Act as requiring the agency to give subordinate status to
factors such as cost, safety, and noise in determining what standards
are reasonable for aircraft engines. Rather, the EPA has greater
flexibility under section 231 in determining what standard is most
reasonable for aircraft engines. Thus, as in past rulemakings, EPA
notes its authority under the CAA to issue reasonable aircraft engine
standards with either technology-following or technology-forcing
results, provided that, in either scenario, the Agency has a reasonable
basis after considering all the relevant factors for setting the
standard.\4\ Once EPA adopts standards, CAA section 232 then directs
the Secretary of Transportation to prescribe regulations to ensure
compliance with the EPA's standards. (See 42 U.S.C. 7572). Finally,
section 233 of the CAA vests the authority to promulgate emission
standards for aircraft or aircraft engines only in the Federal
Government. States are preempted from adopting or enforcing any
standard respecting aircraft or aircraft engine emissions unless such
standard is identical to the EPA's standards. (See 42 U.S.C. 7573).
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    \3\ The U.S. Court of Appeals for the D.C. Circuit has held that
CAA section 231 confers an ``extraordinarily broad'' degree of
discretion on EPA to ``weigh various factors'' and adopt aircraft
engine emission standards as the Agency determines are reasonable.
Nat'l Ass'n of Clean Air Agencies v. EPA, 489 F.3d 1221, 1229-30
(D.C. Cir. 2007) (NACAA).
    \4\ See 70 FR 69664, 69676 (November 17, 2005).
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B. The Role of the United States in International Aircraft Agreements

    The Convention on International Civil Aviation (commonly known as
the `Chicago Convention') was signed in 1944 at the Diplomatic
Conference held in Chicago. It was ratified by the United States on
August 9, 1946. The Chicago Convention establishes the legal framework
for the development of international civil aviation. The primary
objective is ``that international civil aviation may be developed in a
safe and orderly manner and that international air transport services
may be established on the basis of equality of opportunity and operated
soundly and economically.'' \5\ In 1947, ICAO was established, and
later in that same year, ICAO became a specialized agency of the United
Nations (UN). ICAO sets international standards for aviation safety,
security, efficiency, capacity, and environmental protection and serves
as the forum for cooperation in all fields of international civil
aviation. ICAO works with the Chicago Convention's member States and
global aviation organizations to develop international Standards and
Recommended Practices (SARPs), which member States reference when
developing their domestic civil aviation regulations. The United States
is one of 193 currently participating ICAO member States.6 7
ICAO standards are not self-implementing. They must first be adopted
into domestic law to be legally binding in any member State.
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    \5\ ICAO, 2006: Convention on International Civil Aviation,
Ninth Edition, Document 7300/9. Available at: https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July 20, 2021).
    \6\ Members of ICAO's Assembly are generally termed member
States or contracting States. These terms are used interchangeably
throughout this preamble.
    \7\ There are currently 193 contracting states according to
ICAO's website: https://www.icao.int/MemberStates/Member%20States.English.pdf (last accessed July 12, 2021).
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    In the interest of global harmonization and international air
commerce, the Chicago Convention urges its member States to
``collaborate in securing the highest practicable degree of uniformity
in regulations, standards, procedures and organization in relation to
aircraft, [. . .] in all matters which such uniformity will facilitate
and improve

air navigation.'' \8\ The Chicago Convention also recognizes that
member States may adopt national standards that are more or less
stringent than those agreed upon by ICAO or standards that are
different in character or that comply with the ICAO standards by other
means. Any member State that finds it impracticable to comply in all
respects with any international standard or procedure, or that
determines it is necessary to adopt regulations or practices differing
in any particular respect from those established by an international
standard, is required to give notification to ICAO of the differences
between its own practice and that established by the international
standard.\9\
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    \8\ ICAO, 2006: Convention on International Civil Aviation,
Article 37, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July
20, 2021).
    \9\ ICAO, 2006: Doc 7300-Convention on International Civil
Aviation, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July
20, 2021).
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    ICAO's work on the environment focuses primarily on those problems
that benefit most from a common and coordinated approach on a worldwide
basis, namely aircraft noise and engine emissions. SARPs for the
certification of aircraft noise and aircraft engine emissions are
covered by Annex 16 of the Chicago Convention. To continue to address
aviation environmental issues, in 2004, ICAO established three
environmental goals: (1) Limit or reduce the number of people affected
by significant aircraft noise; (2) limit or reduce the impact of
aviation emissions on local air quality; and (3) limit or reduce the
impact of aviation greenhouse gas (GHG) emissions on the global
climate.
    The Chicago Convention has a number of other features that govern
international commerce. First, member States that wish to use aircraft
in international transportation must adopt emission standards that are
at least as stringent as ICAO's standards if they want to ensure
recognition of their airworthiness certificates by other member States.
Member States may ban the use of any aircraft within their airspace
that does not meet ICAO standards.\10\ Second, the Chicago Convention
indicates that member States are required to recognize the
airworthiness certificates issued or rendered valid by the contracting
State in which the aircraft is registered provided the requirements
under which the certificates were issued are equal to or above ICAO's
minimum standards.\11\ Third, to ensure that international commerce is
not unreasonably constrained, a member State that cannot meet or deems
it necessary to adopt regulations differing from the international
standard is obligated to notify ICAO of the differences between its
domestic regulations and ICAO standards.\12\
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    \10\ ICAO, 2006: Convention on International Civil Aviation,
Article 33, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July
20, 2021).
    \11\ ICAO, 2006: Convention on International Civil Aviation,
Article 33, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July
20, 2021).
    \12\ ICAO, 2006: Convention on International Civil Aviation,
Article 38, Ninth Edition, Document 7300/9. Available at https://www.icao.int/publications/Documents/7300_9ed.pdf (last accessed July
20, 2021).
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    ICAO's Committee on Aviation Environmental Protection (CAEP), which
consists of members and observers from States, intergovernmental and
non-governmental organizations representing the aviation industry and
environmental interests, undertakes ICAO's technical work in the
environmental field. The Committee is responsible for evaluating,
researching, and recommending measures to the ICAO Council that address
the environmental impacts of international civil aviation. CAEP's terms
of reference indicate that ``CAEP's assessments and proposals are
pursued taking into account: Technical feasibility; environmental
benefit; economic reasonableness; interdependencies of measures (for
example, among others, measures taken to minimize noise and emissions);
developments in other fields; and international and national
programs.'' \13\ The ICAO Council reviews and adopts the
recommendations made by CAEP. It then reports to the ICAO Assembly, the
highest body of the organization, where the main policies on aviation
environmental protection are adopted and translated into Assembly
Resolutions. If ICAO adopts a CAEP proposal for a new environmental
standard, it then becomes part of ICAO standards and recommended
practices (Annex 16 to the Chicago Convention).\14\ \15\
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    \13\ ICAO: CAEP Terms of Reference. Available at https://www.icao.int/environmental-protection/Pages/Caep.aspx#ToR (last
accessed July 20, 2021).
    \14\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed
November 15, 2021). The ICAO Annex 16 Volume II is found on page 17
of the ICAO Products & Services English Edition of the 2021 catalog,
and it is copyright protected; Order No. AN16-2. The ICAO Annex 16,
Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.
Amendment 10 is also found on page 17 of this ICAO catalog, and it
is copyright protected; Order No. AN 16-2/E/12.
    \15\ CAEP develops new emission standards based on an assessment
of the technical feasibility, cost, and environmental benefit of
potential requirements.
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    The FAA plays an active role in ICAO/CAEP, including serving as the
representative (member) of the United States at annual ICAO/CAEP
Steering Group meetings, as well as the ICAO/CAEP triennial meetings,
and contributing technical expertise to CAEP's working groups. The EPA
serves as an advisor to the U.S. member at the annual ICAO/CAEP
Steering Group and triennial ICAO/CAEP meetings, while also
contributing technical expertise to CAEP's working groups and assisting
and advising the FAA on aviation emissions, technology, and
environmental policy matters. In turn, the FAA assists and advises the
EPA on aviation environmental issues, technology, and airworthiness
certification matters.
    CAEP's predecessor at ICAO, the Committee on Aircraft Engine
Emissions (CAEE), adopted the first international SARPs for aircraft
engine emissions which were proposed in 1981.\16\ These standards
limited aircraft engine emissions of hydrocarbons (HC), carbon monoxide
(CO), and oxides of nitrogen (NOX). The 1981 standards
applied to newly manufactured engines, which are those engines
manufactured after the effective date of the regulations--also referred
to as in-production engines. In 1993, ICAO adopted a CAEP/2 proposal to
tighten the original NOX standard by 20 percent and amend
the test procedures.\17\ These 1993 standards applied both to newly
certificated turbofan engines (those engine models that received their
initial type certificate after the effective date of the

regulations, also referred to as new type design engines) and to in-
production engines; the standards had different effective dates for
newly certificated engines and in-production engines. In 1995, CAEP/3
recommended a further tightening of the NOX standards by 16
percent and additional test procedure amendments, but in 1997 the ICAO
Council rejected this stringency proposal and approved only the test
procedure amendments. At the CAEP/4 meeting in 1998, the Committee
adopted a similar 16 percent NOX reduction proposal, which
ICAO approved in 1998. Unlike the CAEP/2 standards, the CAEP/4
standards applied only to new type design engines after December 31,
2003, and not to in-production engines, leaving the CAEP/2 standards
applicable to in-production engines. In 2004, CAEP/6 recommended a 12
percent NOX reduction, which ICAO approved in 2005.\18\ \19\
The CAEP/6 standards applied to new engine designs certificated after
December 31, 2007, again leaving the CAEP/2 standards in place for in-
production engines before January 1, 2013. In 2010, CAEP/8 recommended
a further tightening of the NOX standards by 15 percent for
new engine designs certificated after December 31, 2013.\20\ \21\ The
Committee also recommended that the CAEP/6 standards be applied to in-
production engines on or after January 1, 2013, which cut off the
production of CAEP/2 and CAEP/4 compliant engines with the exception of
spare engines; ICAO adopted these as standards in 2011.\22\
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    \16\ ICAO, 2017: Aircraft Engine Emissions: Foreword,
International Standards and Recommended Practices, Environmental
Protection, Annex 16, Volume II, Fourth Edition, July 2017.
Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021). The ICAO Annex 16
Volume II is found on page 17 of the ICAO Products & Services
English Edition 2021 catalog and is copyright protected; Order No.
AN16-2. The ICAO Annex 16, Volume II, Fourth Edition, includes
Amendment 10 of January 1, 2021. Amendment 10 is also found on page
17 of this ICAO catalog, and it is copyright protected; Order No. AN
16-2/E/12.
    \17\ CAEP conducts its work triennially. Each 3-year work cycle
is numbered sequentially and that identifier is used to
differentiate the results from one CAEP meeting to another by
convention. The first technical meeting on aircraft emission
standards was CAEP's predecessor, i.e., CAEE. The first meeting of
CAEP, therefore, is referred to as CAEP/2.
    \18\ CAEP/5 did not address new aircraft engine emission
standards.
    \19\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017. Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed
June 16, 2021). The ICAO Annex 16 Volume II is found on page 17 of
the ICAO Products & Services Catalog, English Edition of the 2021
catalog, and it is copyright protected; Order No. AN16-2. The ICAO
Annex 16, Volume II, Fourth Edition, includes Amendment 10 of
January 1, 2021. Amendment 10 is also found on page 17 of this ICAO
catalog, and it is copyright protected; Order No. AN 16-2/E/12.
    \20\ CAEP/7 did not address new aircraft engine emission
standards.
    \21\ ICAO, 2010: Committee on Aviation Environmental Protection
(CAEP), Report of the Eighth Meeting, Montreal, February 1-12, 2010,
CAEP/8-WP/80 Available in Docket EPA-HQ-OAR-2010-0687.
    \22\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017, Amendment 10. CAEP/8
corresponds to Amendment 7 effective on July 18, 2011. Available at
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on
page 17 of the ICAO Products & Services Catalog, English Edition of
the 2021 catalog, and it is copyright protected; Order No. AN16-2.
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10
of January 1, 2021. Amendment 10 is also found on page 17 of this
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
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    At the CAEP/10 meeting in 2016, the Committee agreed to the first
airplane CO2 emission standards, which ICAO approved in
2017. The CAEP/10 CO2 standards apply to new type design
airplanes for which the application for a type certificate will be
submitted on or after January 1, 2020, some modified in-production
airplanes on or after January 1, 2023, and all applicable in-production
airplanes manufactured on or after January 1, 2028.
    At the CAEP/10 and CAEP/11 meetings in 2016 and 2019, the Committee
agreed to three different forms of international PM standards for
aircraft engines. Maximum PM mass concentration standards were agreed
to at CAEP/10, and PM mass and number standards were agreed to at CAEP/
11. ICAO adopted the PM maximum mass concentration standards in 2017
and the PM mass and number standards in 2020. The CAEP/10 PM standards
apply to in-production engines on or after January 1, 2020, and the
CAEP/11 PM standards apply to new-type and in-production engines on or
after January 1, 2023. In addition to CAEP/10 agreeing to a maximum PM
mass concentration standard, CAEP/10 adopted a reporting requirement
where aircraft engine manufacturers were required to provide PM mass
concentration, PM mass, and PM number emissions data--and other related
parameters--by January 1, 2020 for in-production engines.\23\
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    \23\ More specifically, the international PM standard applies to
all turbofan and turbojet engines of a type or model, and their
derivative versions, with a rated output greater than 26.7 kN and
whose date of manufacture of the individual engine is on or after
January 1, 2020 (or those engines manufactured on or after January
1, 2020).
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C. The Relationship Between EPA's Regulation of Aircraft Engine
Emissions and International Standards

    Domestically, as required by the CAA, the EPA has been engaged in
reducing harmful air pollution from aircraft engines for over 40 years,
regulating gaseous exhaust emissions, smoke, and fuel venting from
engines.\24\ We have periodically revised these regulations.\25\ The
EPA's actions to regulate certain pollutants emitted from aircraft
engines come directly from the authority in section 231 of the CAA, and
we have aligned the U.S. emissions requirements with those promulgated
by ICAO. As described above in Section II.B, the ICAO/CAEP terms of
reference includes technical feasibility.\26\ Technical feasibility has
been interpreted by CAEP as technology demonstrated to be safe and
airworthy and available for application over a sufficient range of
newly certificated aircraft.\27\ This interpretation resulted in all
previous ICAO emission standards, and the EPA's standards reflecting
them, being anti-backsliding standards (i.e., the standards would not
reduce aircraft PM emissions below current levels of engine emissions),
which are technology following.
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    \24\ U.S. EPA, 1973: Emission Standards and Test Procedures for
Aircraft; Final Rule, 38 FR 19088 (July 17, 1973).
    \25\ The following are the most recent EPA rulemakings that
revised these regulations. U.S. EPA, 1997: Control of Air Pollution
from Aircraft and Aircraft Engines; Emission Standards and Test
Procedures; Final Rule, 62 FR 25355 (May 8, 1997). U.S. EPA, 2005:
Control of Air Pollution from Aircraft and Aircraft Engines;
Emission Standards and Test Procedures; Final Rule, 70 FR 69664
(November 17, 2005). U.S. EPA, 2012: Control of Air Pollution from
Aircraft and Aircraft Engines; Emission Standards and Test
Procedures; Final Rule, 77 FR 36342 (June 18, 2012). U.S. EPA, 2021:
Control of Air Pollution From Airplanes and Airplane Engines: GHG
Emission Standards and Test Procedures; Final Rule, 86 FR 2136
(January 11, 2021).
    \26\ ICAO: CAEP Terms of Reference. Available at https://www.icao.int/environmental-protection/Pages/Caep.aspx#ToR (last
accessed July 20, 2021).
    \27\ ICAO, 2019: Report of the Eleventh Meeting, Montreal, 4-15
February 2019, Committee on Aviation Environmental Protection,
Document 10126, CAEP11. It is found on page 26 of the English
Edition of the ICAO Products & Services 2021 Catalog and is
copyright protected: Order No. 10126. For purchase and available at:
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed June 21, 2021). The statement on technological feasibility
is located in Appendix C of Agenda Item 3 of this report (see page
3C-4, paragraph 2.2).
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    For many years the EPA has regulated aircraft engine PM emissions
through the use of smoke number standards.\28\ Since setting the
original smoke number standards in 1973, the EPA has periodically
revised these standards. The EPA amended its smoke standards to align
with ICAO's smoke standards in 1982 \29\ and again in 1984.\30\
Additionally, EPA has amended the test procedures for measuring smoke

emissions \31\ and modified the effective dates and compliance schedule
for smoke emissions standards periodically.\32\ Now, we are proposing
to adopt three different forms of aircraft engine PM standards: A PM
mass concentration standard ([mu]g/m\3\), a PM mass standard (mg/kN),
and PM number standard (#/kN). These proposed aircraft engine PM
emission standards are a different way of regulating and/or measuring
\33\ aircraft engine PM emissions in comparison to smoke number
emission standards.
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    \28\ U.S. EPA, 40 CFR 87.1. ``Smoke means the matter in exhaust
emissions that obscures the transmission of light, as measured by
the test procedures specified in subpart G of this part.'' ``Smoke
number means a dimensionless value quantifying smoke emission as
calculated according to ICAO Annex 16.''
    \29\ U.S. EPA, Control of Air Pollution From Aircraft and
Aircraft Engines; Emission Standards and Test Procedures, Final
Rule, 47 FR 58462, December 30, 1982.
    \30\ U.S. EPA, Control of Air Pollution From Aircraft and
Aircraft Engines; Smoke Emission Standard, Final Rule, 49 FR 31873,
August 9, 1984 (bifurcating EPA's smoke standard for new engines
into two regimes--one for engines with rated output less than 26.7
kilonewtons and one for engines with rated output equal to or
greater than 26.7 kilonewtons).
    \31\ U.S. EPA, Control of Air Pollution From Aircraft and
Aircraft Engines; Emission Standards and Test Procedures, Final
Rule, 62 FR 25356, May 8, 1997 (harmonizing EPA procedures with
recent amendments to ICAO test procedures); U.S. EPA, Control of Air
Pollution From Aircraft and Aircraft Engines; Emission Standards and
Test Procedures, Final Rule, 70 FR 69664, November 17, 2005 (same);
U.S. EPA, Control of Air Pollution From Aircraft and Aircraft
Engines; Emission Standards and Test Procedures, Final Rule, 77 FR
36342, June 18, 2012.
    \32\ U.S. EPA, Amendment to Standards, Final Rule, 43 FR 12614,
March 24, 1978 (setting back by two years the effective date for all
gaseous emissions standards for newly manufactured aircraft and
aircraft gas turbine engines); U.S. EPA, Control of Air Pollution
from Aircraft and Aircraft Engines; Extension of Compliance Date for
Emission Standards Applicable to JT3D Engines, Final Rule, 44 FR
64266, November 6, 1979 (extending the final compliance date for
smoke emission standards applicable to the JT3D aircraft engines by
roughly 3.5 years); U.S. EPA, Control of Air Pollution from
Aircraft; Amendment to Standards, Final Rule, 45 FR 86946, December
31, 1980 (setting back by two years the effective date for all
gaseous emissions standards which would otherwise have been
effective on January 1,1981, for aircraft gas turbine engines); U.S.
EPA, Control of Air Pollution from Aircraft and Aircraft Engines,
Final Rule, 46 FR 2044, January 8, 1981 (extending the applicability
of the temporary exemption provision of the standards for smoke and
fuel venting emissions from some in-use aircraft engines); U.S. EPA,
Control of Air Pollution From Aircraft and Aircraft Engines; Smoke
Emission Standard, Final Rule, 48 FR 46481, October 12, 1983
(staying the smoke regulations for new turbojet and turbofan engines
rated below 26.7 kN thrust).
    \33\ Also, as described in Section IV.D, the proposed PM
standards employ a different method for measuring aircraft engine PM
emissions compared to the historical smoke number emission
standards.
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    Internationally, the EPA and the FAA have worked within the
standard-setting process of ICAO (CAEP and its predecessor, CAEE) since
the 1970's to help establish international emission standards and
related requirements, which individual member States adopt into
domestic law and regulations. Historically, under this approach,
international emission standards have first been adopted by ICAO, and
subsequently the EPA has initiated rulemakings under CAA section 231 to
establish domestic standards that are harmonized with ICAO's standards.
After EPA promulgates aircraft engine emission standards, CAA section
232 requires the FAA to issue regulations to ensure compliance with the
EPA aircraft engine emission standards when certificating aircraft
pursuant to its authority under Title 49 of the United States Code.
This proposed rule would continue this historical rulemaking approach.
    The EPA and FAA worked from 2009 to 2019 within the ICAO/CAEP
standard setting process on the development of the three different
forms of international aircraft engine PM emission standards (a PM mass
concentration standard, a PM mass standard, and a PM particle number
standard). In this action, we are proposing to adopt PM standards
equivalent to ICAO's three different forms of aircraft engine PM
emission standards. Adoption of the proposed standards would meet the
United States' obligations under the Chicago Convention and would also
ensure global acceptance of FAA airworthiness certification.
    In December 2018, the EPA issued an information collection request
(ICR) that matches the CAEP/10 p.m. reporting requirements described
earlier.\34\ In addition to the PM standards, the proposed rulemaking
would codify the reporting requirements implemented by this 2018 EPA
ICR into the EPA regulations, as described later in Section IV.E. Also,
in a similar time frame as this proposed rulemaking, EPA will be
renewing this ICR (the ICR needs to be renewed triennially).
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    \34\ 83 FR 44621, August 31, 2018. U.S. EPA, Aircraft Engines--
Supplemental Information Related to Exhaust Emissions (Renewal), OMB
Control Number 2060-0680, ICR Reference Number<PHONE_NUMBER>-08,
December 17, 2018.
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III. Particulate Matter Impacts on Air Quality and Health

A. Background on Particulate Matter

    Particulate matter (PM) is a highly complex mixture of solid
particles and liquid droplets distributed among numerous atmospheric
gases which interact with solid and liquid phases. Particles range in
size from those smaller than 1 nanometer (10-9 meter) to
over 100 micrometers ([mu]m, or 10-6 meter) in diameter (for
reference, a typical strand of human hair is 70 [mu]m in diameter and a
grain of salt is about 100 [mu]m). Atmospheric particles can be grouped
into several classes according to their aerodynamic and physical sizes.
Generally, the three broad classes of particles include ultrafine
particles (UFPs, generally considered as particulates with a diameter
less than or equal to 0.1 [mu]m (typically based on physical size,
thermal diffusivity or electrical mobility)), ``fine'' particles
(PM2.5; particles with a nominal mean aerodynamic diameter
less than or equal to 2.5 [mu]m), and ``thoracic'' particles
(PM10; particles with a nominal mean aerodynamic diameter
less than or equal to 10 [mu]m). Particles that fall within the size
range between PM2.5 and PM10, are referred to as
``thoracic coarse particles'' (PM10-2.5, particles with a
nominal mean aerodynamic diameter less than or equal to 10 [mu]m and
greater than 2.5 [mu]m).
    Particles span many sizes and shapes and may consist of hundreds of
different chemicals. Particles are emitted directly from sources and
are also formed through atmospheric chemical reactions between PM
precursors; the former are often referred to as ``primary'' particles,
and the latter as ``secondary'' particles. Particle concentration and
composition varies by time of year and location, and, in addition to
differences in source emissions, is affected by several weather-related
factors, such as temperature, clouds, humidity, and wind. Ambient
levels of PM are also impacted by particles' ability to shift between
solid/liquid and gaseous phases, which is influenced by concentration,
meteorology, and especially temperature.
    Fine particles are produced primarily by combustion processes and
by transformations of gaseous emissions (e.g., sulfur oxides
(SOX), nitrogen oxides (NOX) and volatile organic
compounds (VOCs)) in the atmosphere. The chemical and physical
properties of PM2.5 may vary greatly with time, region,
meteorology, and source category. Thus, PM2.5 may include a
complex mixture of different components including sulfates, nitrates,
organic compounds, elemental carbon, and metal compounds. These
particles can remain in the atmosphere for days to weeks and travel
through the atmosphere hundreds to thousands of kilometers.
    Particulate matter is comprised of both volatile and non-volatile
PM. PM emitted from the engine is known as non-volatile PM (nvPM), and
PM formed from transformation of an engine's gaseous emissions are
defined as volatile PM.\35\ Because of the

difficulty in measuring volatile PM, which is formed in the engine's
exhaust plume and is significantly influenced by ambient conditions,
the EPA is proposing standards only for the emission of nvPM.
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    \35\ The ICAO 2019 Environmental Report, Available at https://www.icao.int/environmental-protection/Documents/ICAO-ENV-Report2019-F1-WEB%20(1).pdf (last accessed September 1, 2021). See pages 98,
100, and 101 for a description of non-volatile PM and volatile PM.
     ``During the combustion of hydrocarbon-based fuels, aircraft
engines generate gaseous and particulate matter (PM) emissions. At
the engine exhaust, particulate emissions consist mainly of
ultrafine soot or black carbon emissions. These particles, referred
to as ``non-volatile'' PM (nvPM), are present at high temperatures,
in the engine exhaust. Compared to conventional diesel engines, gas
turbine engines emit non-volatile particles of smaller mean
diameter. Their characteristic size ranges roughly from 15 to 60
nanometers (nm; 1nm = 1/100,000 of a millimeter). These particles
are invisible to the human eye and are ultrafine.'' (See page 98.)
    ``Additionally, gaseous emissions from engines can also condense
to produce new particles (i.e., volatile particulate matter--vPM) or
coat the emitted soot particles. Gaseous emissions species react
chemically with ambient chemical constituents in the atmosphere to
produce the so called secondary particulate matter. Volatile
particulate matter is dependent on these gaseous precursor
emissions. While these precursors are controlled by gaseous emission
certification and the fuel composition (e.g., sulfur content) for
aircraft gas turbine engines, the volatile particulate matter is
also dependent on the ambient air background composition.'' (See
pages 100 and 101.)
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B. Health Effects of Particulate Matter

    Scientific studies show exposure to ambient PM is associated with a
broad range of health effects. These health effects are discussed in
detail in the Integrated Science Assessment for Particulate Matter (PM
ISA), which was finalized in December 2019.\36\ The PM ISA concludes
that human exposures to ambient PM2.5 are associated with a
number of adverse health effects and characterizes the weight of
evidence for broad health categories (e.g., cardiovascular effects,
respiratory effects, etc.).\37\ The PM ISA additionally notes that
stratified analyses (i.e., analyses that directly compare PM-related
health effects across groups) provide strong evidence for racial and
ethnic differences in PM2.5 exposures and in
PM2.5-related health risk. As described in Section III.D,
concentrations of PM increase with proximity to an airport. Further,
studies described in Section III.G report that many communities in
close proximity to airports are disproportionately represented by
people of color and low-income populations.
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    \36\ U.S. EPA. Integrated Science Assessment (ISA) for
Particulate Matter (Final Report, 2019). U.S. Environmental
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \37\ The causal framework draws upon the assessment and
integration of evidence from across epidemiological, controlled
human exposure, and toxicological studies, and the related
uncertainties that ultimately influence our understanding of the
evidence. This framework employs a five-level hierarchy that
classifies the overall weight of evidence and causality using the
following categorizations: Causal relationship, likely to be causal
relationship, suggestive of a causal relationship, inadequate to
infer a causal relationship, and not likely to be a causal
relationship (U.S. EPA. (2009). Integrated Science Assessment for
Particulate Matter (Final Report). U.S. Environmental Protection
Agency, Washington, DC, EPA/600/R-08/139F, Table 1-3).
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    EPA has concluded that recent evidence in combination with evidence
evaluated in the 2009 p.m. ISA supports a ``causal relationship''
between both long- and short-term exposures to PM2.5 and
mortality and cardiovascular effects and a ``likely to be causal
relationship'' between long- and short-term PM2.5 exposures
and respiratory effects.\38\ Additionally, recent experimental and
epidemiologic studies provide evidence supporting a ``likely to be
causal relationship'' between long-term PM2.5 exposure and
nervous system effects, and long-term PM2.5 exposure and
cancer. In addition, EPA noted that there was more limited and
uncertain evidence for long-term PM2.5 exposure and
reproductive and developmental effects (i.e., male/female reproduction
and fertility; pregnancy and birth outcomes), long- and short-term
exposures and metabolic effects, and short-term exposure and nervous
system effects resulting in the ISA concluding ``suggestive of, but not
sufficient to infer, a causal relationship.''
---------------------------------------------------------------------------

    \38\ Short term exposures are usually defined as less than 24
hours duration.
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    More detailed information on the health effects of PM can be found
in a memorandum to the docket.\39\
---------------------------------------------------------------------------

    \39\ Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660,
``Health and environmental effects of non-GHG pollutants emitted by
turbine engine aircraft,'' August 23, 2021.
---------------------------------------------------------------------------

C. Environmental Effects of Particulate Matter

    Environmental effects that can result from particulate matter
emissions include visibility degradation, plant and ecosystem effects,
deposition effects, and materials damage and soiling. These effects are
briefly summarized here and discussed in more detail in the memo to the
docket cited above.
    PM2.5 emissions also adversely impact visibility.\40\ In
the Clean Air Act Amendments of 1977, Congress recognized visibility's
value to society by establishing a national goal to protect national
parks and wilderness areas from visibility impairment caused by manmade
pollution.\41\ In 1999, EPA finalized the regional haze program (64 FR
35714) to protect the visibility in Mandatory Class I Federal areas.
There are 156 national parks, forests and wilderness areas categorized
as Mandatory Class I Federal areas (62 FR 38680-38681, July 18, 1997).
These areas are defined in CAA section 162 as those national parks
exceeding 6,000 acres, wilderness areas and memorial parks exceeding
5,000 acres, and all international parks which were in existence on
August 7, 1977. EPA has also concluded that PM2.5 causes
adverse effects on visibility in other areas that are not targeted by
the Regional Haze Rule, such as urban areas, depending on
PM2.5 concentrations and other factors such as dry chemical
composition and relative humidity (i.e., an indicator of the water
composition of the particles). EPA established the secondary 24-hour
PM2.5 NAAQS in 1997 and has retained the standard in
subsequent reviews.\42\ This standard is expected to provide protection
against visibility effects through attainment of the existing secondary
standards for PM2.5. EPA is reconsidering the 2020 decision,
as announced on June 10, 2021.\43\
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    \40\ U.S. EPA. Integrated Science Assessment (ISA) for
Particulate Matter (Final Report, 2019). U.S. Environmental
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \41\ See Section 169(a) of the Clean Air Act.
    \42\ In the 2012 review of the PM NAAQS, the EPA eliminated the
option for spatial averaging for the 24-hour PM2.5
standard (78 FR 3086, January 15, 2013).
    \43\ https://www.epa.gov/newsreleases/epa-reexamine-health-standards-harmful-soot-previous-administration-left-unchanged.
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1. Deposition of Metallic and Organic Constituents of PM
    Several significant ecological effects are associated with
deposition of chemical constituents of ambient PM such as metals and
organics.\44\ Like all internal combustion engines, turbine engines
covered by this rule may emit trace amounts of metals due to fuel
contamination or engine wear. Ecological effects of PM include direct
effects to metabolic processes of plant foliage; contribution to total
metal loading resulting in alteration of soil biogeochemistry and
microbiology, plant and animal growth and reproduction; and
contribution to total organics loading resulting in bioaccumulation and
biomagnification.
---------------------------------------------------------------------------

    \44\ U.S. Environmental Protection Agency (U.S. EPA). 2018.
Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides
of Sulfur and Particulate Matter Ecological Criteria Second External
Review Draft). EPA-600-R-18-097. Washington, DC. December. Available
on the internet at https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=340671.
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2. Materials Damage and Soiling
    Deposition of PM is associated with both physical damage (materials
damage effects) and impaired aesthetic qualities (soiling effects). Wet
and dry deposition of PM can physically affect materials, adding to the
effects of natural weathering processes, by potentially promoting or
accelerating the corrosion of metals, by degrading paints and by

deteriorating building materials such as stone, concrete and
marble.\45\
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    \45\ U.S. Environmental Protection Agency (U.S. EPA). 2018.
Integrated Science Assessment (ISA) for Oxides of Nitrogen, Oxides
of Sulfur and Particulate Matter Ecological Criteria Second External
Review Draft). EPA-600-R-18-097. Washington, DC. December. Available
on the internet at https://cfpub.epa.gov/ncea/isa/recordisplay.cfm?deid=340671.
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D. Near-Source Impacts on Air Quality and Public Health

    Airport activity can adversely impact air quality in the vicinity
of airports. Furthermore, these adverse impacts may disproportionately
impact sensitive subpopulations. A recent study by Yim et al. (2015)
assessed global, regional, and local health impacts of civil aviation
emissions, using modeling tools that address environmental impacts at
different spatial scales.\46\ The study attributed approximately 16,000
premature deaths per year globally to global aviation emissions, with
87 percent attributable to PM2.5. The study concludes that
about a third of these mortalities are attributable to PM2.5
exposures within 20 kilometers of an airport. Another study focused on
the continental United States estimated 210 deaths per year
attributable to PM2.5 from aircraft.\47\ While there are
considerable uncertainties associated with such estimates, these
results suggest that in addition to the contributions of
PM2.5 emissions to regional air quality, impacts on public
health of these emissions in the vicinity of airports are an important
public health concern.
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    \46\ Yim, S.H.L., Lee, G.L., Lee, I.H., Allrogen, F., Ashok, A.,
Caiazzo, F., Eatham, S.D., Malina, R., Barrett, S. R.H. 2015.
Global, regional, and local health impacts of civil aviation
emissions. Environ. Res. Lett. 10: 034001. https://iopscience.iop.org/article/10.1088/1748-9326/10/3/034001.
    \47\ Brunelle-Yeung, E., Masek, T., Rojo, J., Levy, J.,
Arunachalam, S., Miller, S., Barrett, S., Kuhn, S., Waitz, I. 2014.
Assessing the impact of aviation environmental policies on public
health. Transport Policy 34: 21-28. https://www.sciencedirect.com/science/article/pii/S0967070X14000468?via%3Dihub.
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    A significant body of research has addressed pollutant levels and
potential health effects in the vicinity of airports. Much of this
research was synthesized in a 2015 report published by the Airport
Cooperative Research Program (ACRP), conducted by the Transportation
Research Board.\48\ The report concluded that PM2.5
concentrations in and around airports vary considerably, ranging from
``relatively low levels to those that are close to the NAAQS, and in
some cases, exceeding the standards.'' \49\
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    \48\ Kim, B., Nakada, K., Wayson, R., Christie, S., Paling, C.,
Bennett, M., Raper, D., Raps, V., Levy, J., Roof, C. 2015.
Understanding Airport Air Quality and Public Health Studies Related
to Airports. Airport Cooperative Research Program, ACRP Report 135.
https://trid.trb.org/view/1364659.
    \49\ Kim, B., Nakada, K., Wayson, R., Christie, S., Paling, C.,
Bennett, M., Raper, D., Raps, V., Levy, J., Roof, C. 2015.
Understanding Airport Air Quality and Public Health Studies Related
to Airports. Airport Cooperative Research Program, ACRP Report 135,
p. 39. https://trid.trb.org/view/1364659.
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    Furthermore, the report states (p. 40) that ``existing studies
indicate that ultrafine particle concentrations are highly elevated at
an airport (i.e., near a runway) with particle counts that can be
orders of magnitude higher than background with some persistence many
meters downwind (e.g., 600 m). Finally, the report concludes that
PM2.5 dominates overall health risks posed by airport
emissions. Moreover, one recently published study concluded that
emissions from aircraft play an etiologic role in pre-term births,
independent of noise and traffic-related air pollution exposures.\50\
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    \50\ Wing, S.E., Larson, T.V., Hudda, N., Boonyarattaphan, S.,
Fruin, S., Ritz, B. 2020. Preterm birth among infants exposed to in
utero ultrafine particles from aircraft emissions. Environ. Health
Perspect. 128, https://doi.org/10.1289/EHP5732.
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    Since the publication of the 2015 ACRP literature review, a number
of studies conducted in the U. S. have been published which concluded
that ultrafine particle number concentrations were elevated downwind of
commercial airports, and that proximity to an airport also increased
particle number concentrations within residences. Hudda et al.
investigated ultrafine particle number concentrations (PNC) inside and
outside 16 residences in the Boston metropolitan area. They found
elevated outdoor PNC within several kilometers of the airport. They
also found that aviation-related PNC infiltrated indoors and resulted
in significantly higher indoor PNC.\51\ In another study in the
vicinity of Logan airport, Hudda et al. analyzed PNC impacts of
aviation activities.\52\ They found that, at sites 4.0 and 7.3 km from
the airport, average PNCs were 2 and 1.33-fold higher, respectively,
when winds were from the direction of the airport compared to other
directions, indicating that aviation impacts on PNC extend many
kilometers downwind of Logan airport. Stacey (2019) conducted a
literature survey and concluded that the literature consistently
reports that particle numbers close to airports are significantly
higher than locations distant and upwind of airports, and that the
particle size distribution is different from traditional road traffic,
with more extremely fine particles.\53\ Similar findings have been
published from European studies.54 55 56 57 58 59  Results
of a monitoring study of communities near Seattle-Tacoma International
Airport also found higher levels of ultrafine PM near the airport, and
an impacted area larger than at near-roadway sites.\60\ The PM
associated with aircraft landing activity was also smaller in size,
with lower black carbon concentrations than near-roadway samples. As
discussed above, PM2.5 exposures are associated with a
number of serious, adverse health effects. Further, the PM attributable
to aircraft emissions has been associated with potential adverse health
impacts.61 62 For example, He et al.

(2018) found that particle composition, size distribution and
internalized amount of particles near airports all contributed to
promotion of reactive organic species in bronchial epithelial cells.
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    \51\ Hudda, N., Simon, N.C., Zamore, W., Durant, J.L. 2018.
Aviation-related impacts on ultrafine number concentrations outside
and inside residences near an airport. Environ. Sci. Technol. 52:
1765-1772. https://pubs.acs.org/doi/abs/10.1021/acs.est.7b05593.
    \52\ Hudda, N., Simon, M.C., Zamore, W., Brugge, D., Durant,
J.L. 2016. Aviation emissions impact ultrafine particle
concentrations in the greater Boston area. Environ. Sci. Technol.
50: 8514-8521. https://pubs.acs.org/doi/abs/10.1021/acs.est.6b01815.
    \53\ Stacey, B. 2019. Measurement of ultrafine particles at
airports: A review. Atmos. Environ. 198: 463-477. https://www.sciencedirect.com/science/article/pii/S1352231018307313.
    \54\ Masiol M, Harrison RM. Quantification of air quality
impacts of London Heathrow Airport (UK) from 2005 to 2012. Atmos
Environ 2017;116:308-19. https://doi.org/10.1016/j.atmosenv.2015.06.048.
    \55\ Keuken, M.P., Moerman, M., Zandveld, P., Henzing, J.S.,
Hoek, G., 2015. Total and size-resolved particle number and black
carbon concentrations in urban areas near Schiphol airport (the
Netherlands). Atmos. Environ. 104: 132-142. https://www.sciencedirect.com/science/article/pii/S1352231015000175?via%3Dihub.
    \56\ Pirhadi, M., Mousavi, A., Sowlat, M.H., Janssen, N.A.H.,
Cassee, F.R., Sioutas, C., 2020. Relative contributions of a major
international airport activities and other urban sources to the
particle number concentrations (PNCs) at a nearby monitoring site.
Environ. Pollut, 260: 114027. https://www.sciencedirect.com/science/article/pii/S0269749119344987?via%3Dihub.
    \57\ Stacey, B., Harrison, R.M., Pope, F., 2020. Evaluation of
ultrafine particle concentrations and size distributions at London
Heathrow Airport. Atmos. Environ., 222: 117148. https://www.sciencedirect.com/science/article/pii/S1352231019307873?via%3Dihub.
    \58\ Ungeheuer, F., Pinxteren, D., Vogel, A. 2021.
Identification and source attribution of organic compounds in
ultrafine particles near Frankfurt International Airport. Atmos.
Chem. Phys. 21: 3763-3775. https://doi.org/10.5194/acp-21-3763-2021.
    \59\ Zhang, X., Karl, M. Zhang, L. Wang, J., 2020. Influence of
Aviation Emission on the Particle Number Concentration near Zurich
Airport. Environ. Sci. Technol. 54: 14161-14171. https://doi.org/10.1021/acs.est.0c02249.
    \60\ University of Washington. 2019. Mobile Observations of
Ultrafine Particles: The Mov-UP study report. https://deohs.washington.edu/mov-up.
    \61\ Habre. R., Zhou, H., Eckel, S., Enebish, T., Fruin, S.,
Bastain, T., Rappaport, E. Gilliland, F. 2018. Short-term effects of
airport-associated ultrafine particle exposure on lung function and
inflammation in adults with asthma. Environment International 118:
48-59. https://doi.org/10.1016/j.envint.2018.05.031.
    \62\ He, R.W., Shirmohammadi, F., Gerlofs-Nijland, M.E.,
Sioutas, C., & Cassee, F.R. 2018. Pro-inflammatory responses to
PM(0.25) from airport and urban traffic emissions. The Science of
the total environment, 640-641, 997-100. https://www.sciencedirect.com/science/article/pii/S0048969718320394?via%3Dihub.
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    Because of these potential impacts, a systematic literature review
was recently conducted to identify peer-reviewed literature on air
quality near commercial airports and assess the quality of the
studies.\63\ The systematic review identified seventy studies for
evaluation. These studies consistently showed that particulate matter,
in the form of ultrafine PM (UFP), is elevated in and around airports.
Furthermore, many studies showed elevated levels of black carbon,
criteria pollutants, and polycyclic aromatic hydrocarbons as well.
Finally, the systematic review, while not focused on health effects,
identified a limited number of references reporting adverse health
effects impacts, including increased rates of premature death, pre-term
births, decreased lung function, oxidative DNA damage and childhood
leukemia. More research is needed linking particle size distributions
to specific airport activities, and proximity to airports,
characterizing relationships between different pollutants, evaluating
long-term impacts, and improving our understanding of health effects.
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    \63\ Riley, K., Cook, R., Carr, E., Manning, B. 2021. A
Systematic Review of The Impact of Commercial Aircraft Activity on
Air Quality Near Airports. City and Environment Interactions,
100066. https://doi.org/10.1016/j.cacint.2021.100066.
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    A systematic review of health effects associated with exposure to
jet engine emissions in the vicinity of airports was also recently
published.\64\ This study concluded that literature on health effects
was sparse, but jet engine emissions have physicochemical properties
similar to diesel exhaust particles, and that exposure to jet engine
emissions is associated with similar adverse health effects as exposure
to diesel exhaust particles and other traffic emissions. A 2010
systematic review by the Health Effects Institute (HEI) concluded that
evidence was sufficient to support a causal relationship between
exposure to traffic-related air pollution and exacerbation of asthma
among children, and suggestive of a causal relationship for childhood
asthma, non-asthma respiratory symptoms, impaired lung function and
cardiovascular mortality.\65\
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    \64\ Bendtsen, K. M., Bengtsen, E., Saber, A., Vogel, U. 2021. A
review of health effects associated with exposure to jet engine
emissions in and around airports. Environ. Health 20:10. https://doi.org/10.1186/s12940-020-00690-y.
    \65\ Health Effects institute. ``Special Report 17: A Special
Report of the Institute's Panel on the Health Effects of Traffic-
Related Air Pollution.'' January, 2010. https://www.healtheffects.org/publication/traffic-related-air-pollution-critical-review-literature-emissions-exposure-and-health.
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E. Contribution of Aircraft Emissions to PM in Selected Areas

    This section provides background on the contribution of aircraft
engine emissions to local PM concentrations. In some areas with large
commercial airports, turbine engine aircraft can make a significant
contribution to ambient PM2.5. To evaluate these potential
impacts, we identified the 25 airports where commercial aircraft
operations are the greatest, based on data for 2017 from the Federal
Aviation Administration (FAA) Air Traffic Data System (ATADS).\66\
These 25 commercial airports are located in 24 counties and 22
metropolitan statistical areas (MSAs). We compared the contributions of
these airports to emissions at both the county and MSA levels.
Comparisons at both scales provide a fuller picture of how airports are
impacting local air quality. Figure III-1 depicts the contribution to
county-level PM2.5 direct emissions from all turbine
aircraft in that county with rated output of greater than 26.7 kN.
Emissions data were obtained from the EPA 2017 National Emissions
Inventory (NEI).\67\ The contributions of engines greater than 26.7 kN
rated output to total turbine engine emissions at individual airports
were estimated based on FAA data.\68\ At the county level,
contributions to total mobile source PM2.5 emissions range
from less than 1 to almost 14 percent. However, it should be noted that
two airports cross county lines--Hartsfield-Jackson Atlanta
International Airport (Clayton and Fulton counties) and O'Hare (Cook
and DuPage counties). For those airports, percentages are calculated
for the sum of the two counties. In addition, five of these counties
are in nonattainment for either the PM2.5 or PM10
standard. When emissions from these airports are considered as part of
the entire MSA, the contribution is much smaller. Figure III-2 depicts
the contributions at the metropolitan statistical area (MSA) instead of
the county level, and contributions across airports range from 0.4 to 3
percent. Details of this analysis are described in a memorandum to the
docket.\69\
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    \66\ https://aspm.faa.gov/opsnet/sys/main.asp.
    \67\ 2017 National Emissions Inventory: Aviation Component,
Eastern Research Group, Inc., July 25, 2019, EPA Contract No. EP-C-
17-011, Work Order No. 2-19. Available at https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-data
(last accessed on June 27, 2021). See section 3.2 for airports and
aircraft related emissions in the Technical Supporting Document for
the 2017 National Emissions Inventory, January 2021 Updated Release.
Available at https://www.epa.gov/sites/production/files/2021-02/documents/nei2017_tsd_full_jan2021.pdf (last accessed on June 27,
2021).
    \68\ These data were obtained using radar-informed data from the
FAA Enhanced Traffic Management System (ETMS). The annual fuel burn
and emissions inventories at selected top US airports were based on
the 2015 FAA flight operations database. The fraction of total PM
emissions from aircraft covered by the proposed PM standards is
based on the ratio of total PM emissions from flights by engines
with thrust rating >26.7 kN compared to PM emissions from the whole
fleet at each airport.
    \69\ Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, July
28, 2021, '' Estimation of 2017 Emissions Contributions of Turbine
Aircraft >26.7 kN to NOX and PM2.5 as a
Percentage of All Mobile PM2.5 for the Counties and MSAs
in Which the Airport Resides, 25 Largest Carrier Operations.''
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F. Other Pollutants Emitted by Aircraft

    In addition to particulate matter, a number of other criteria
pollutants are emitted by the aircraft which are the subject of this
proposed rule. These pollutants, which are not covered by the rule,
include nitrogen oxides (NOX), including nitrogen dioxide
(NO2), volatile organic compounds (VOC), carbon monoxide
(CO), and sulfur dioxide (SO2). Aircraft also contribute to
ambient levels of hazardous air pollutants (HAP), compounds that are
known or suspected human or animal carcinogens, or that have noncancer
health effects. These compounds include, but are not limited to,
benzene, 1,3-butadiene, formaldehyde, acetaldehyde, acrolein,
polycyclic organic matter (POM), and certain metals. Some POM and HAP
metals are components of PM2.5 mass measured in turbine
engine aircraft emissions.\70\
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    \70\ Kinsey, J.S., Hays, M.D., Dong, Y., Williams, D.C. Logan,
R. 2011. Chemical characterization of the fine particle emissions
from commercial aircraft engines during the aircraft particle
emissions experiment (APEX) 1-3. Environ. Sci. Technol. 45:3415-
3421. https://pubs.acs.org/doi/10.1021/es103880d.
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    The term polycyclic organic matter (POM) defines a broad class of
compounds that includes the polycyclic aromatic hydrocarbon compounds
(PAHs). POM compounds are formed primarily from combustion and are
present in the atmosphere in gas and particulate form. Metal compounds
emitted from aircraft turbine engine combustion include chromium,
manganese, and nickel. Several POM compounds, as well as hexavalent
chromium, manganese compounds and nickel compounds are included in the
National Air Toxics Assessment, based on potential carcinogenic
risk.\71\ In addition, as mentioned previously, deposition of metallic
compounds can have ecological effects. Impacts of POM and metals are
further discussed in the memorandum to the docket referenced above.
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    \71\ https://www.epa.gov/national-air-toxics-assessment.
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G. Environmental Justice

    Executive Order 12898 (59 FR 7629, February 16, 1994) establishes
federal executive policy on environmental justice. It directs federal
agencies, to the greatest extent practicable and permitted by law, to
make achieving environmental justice part of their mission by
identifying and addressing, as appropriate, disproportionately high and
adverse human health or environmental effects of their programs,
policies, and activities on minority populations and low-income
populations in the United States. EPA defines environmental justice as
the fair treatment and meaningful involvement of all people regardless
of race, color, national origin, or income with respect to the
development, implementation, and enforcement of environmental laws,
regulations, and policies.\72\
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    \72\ Fair treatment means that ``no group of people should bear
a disproportionate burden of environmental harms and risks,
including those resulting from the negative environmental
consequences of industrial, governmental and commercial operations
or programs and policies.'' Meaningful involvement occurs when ``(1)
potentially affected populations have an appropriate opportunity to
participate in decisions about a proposed activity [e.g.,
rulemaking] that will affect their environment and/or health; (2)
the public's contribution can influence [the EPA's rulemaking]
decision; (3) the concerns of all participants involved will be
considered in the decision-making process; and (4) [the EPA will]
seek out and facilitate the involvement of those potentially
affected'' A potential EJ concern is defined as ``the actual or
potential lack of fair treatment or meaningful involvement of
minority populations, low-income populations, tribes, and indigenous
peoples in the development, implementation and enforcement of
environmental laws, regulations and policies.'' See ``Guidance on
Considering Environmental Justice During the Development of an
Action.'' Environmental Protection Agency, https://www.epa.gov/environmentaljustice.
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    Executive Order 14008 (86 FR 7619, February 1, 2021) also calls on
federal agencies to make achieving environmental justice part of their
missions ``by developing programs, policies, and activities to address
the disproportionately high and adverse human health, environmental,
climate-related and other cumulative impacts on disadvantaged
communities, as well as the accompanying economic challenges of such
impacts.'' It also declares a policy ``to secure environmental justice
and spur economic opportunity for disadvantaged communities that have
been historically marginalized and overburdened by pollution and under-
investment in housing, transportation, water and wastewater
infrastructure and health care.'' Under Executive Order 13563, federal
agencies may consider equity, human dignity, fairness, and
distributional considerations, where appropriate and permitted by law.
    EPA's June 2016 ``Technical Guidance for Assessing Environmental
Justice in Regulatory Analysis'' provides recommendations on conducting
the highest quality analysis feasible, recognizing that data
limitations, time and resource constraints, and analytic challenges
will vary by media and regulatory context.\73\
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    \73\ ``Technical Guidance for Assessing Environmental Justice in
Regulatory Analysis.'' Epa.gov, Environmental Protection Agency,
https://www.epa.gov/sites/production/files/2016-06/documents/ejtg_5_6_16_v5.1.pdf (June 2016).
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    When assessing the potential for disproportionately high and
adverse health or environmental impacts of regulatory actions on
minority populations, low-income populations, tribes, and/or indigenous
peoples, the EPA strives to answer three broad questions: (1) Is there
evidence of potential EJ concerns in the baseline (the state of the
world absent the regulatory action)? Assessing the baseline will allow
the EPA to determine whether pre-existing disparities are associated
with the pollutant(s) under consideration (e.g., if the effects of the
pollutant(s) are more concentrated in some population groups). (2) Is
there evidence of potential EJ concerns for the regulatory option(s)
under consideration? Specifically, how are the pollutant(s) and its
effects distributed for the regulatory options under consideration?
And, (3) do the regulatory option(s) under consideration exacerbate or
mitigate EJ concerns relative to the baseline? It is not always
possible to quantitatively assess these questions.
    EPA's 2016 Technical Guidance does not prescribe or recommend a
specific approach or methodology for conducting an environmental
justice analysis, though a key consideration is consistency with the
assumptions underlying other parts of the regulatory analysis when
evaluating the baseline and regulatory options. Where applicable and
practicable, the Agency endeavors to conduct such an analysis. Going
forward, EPA is committed to conducting environmental justice analysis
for rulemakings based on a framework similar to what is outlined in
EPA's Technical Guidance, in addition to investigating ways to further
weave environmental justice into the fabric of the rulemaking process.

    Numerous studies have found that environmental hazards such as air
pollution are more prevalent in areas where people of color and low-
income populations represent a higher fraction of the population
compared with the general population, including near transportation
sources.74 75 76 77 78
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    \74\ Rowangould, G.M. (2013) A census of the near-roadway
population: Public health and environmental justice considerations.
Trans Res D 25: 59-67. https://dx.doi.org/10.1016/j.trd.2013.08.003.
    \75\ Marshall, J.D., Swor, K.R., Nguyen, N.P. (2014)
Prioritizing environmental justice and equality: Diesel emissions in
Southern California. Environ Sci Technol 48: 4063-4068. https://doi.org/10.1021/es405167f.
    \76\ Marshall, J.D. (2000) Environmental inequality: Air
pollution exposures in California's South Coast Air Basin. Atmos
Environ 21: 5499-5503. https://doi.org/10.1016/j.atmosenv.2008.02.005.
    \77\ Tessum, C.W., Paolella, D.A., Chambliss, SE, Apte, J.S.,
Hill, J.D., Marshall, J.D. (2021) PM2.5 polluters
disproportionately and systemically affect people of color in the
United States. Science Advances 7:eabf4491. https://www.science.org/doi/10.1126/sciadv.abf4491.
    \78\ Mohai, P., Pellow, D., Roberts Timmons, J. (2009)
Environmental justice. Annual Reviews 34: 405-430. https://doi.org/10.1146/annurev-environ-082508-094348.
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    As described in Section III.D, concentrations of PM increase with
proximity to an airport. Air pollution can disproportionately impact
sensitive subpopulations near airports. Henry et al. (2019) studied
impacts of several California airports on surrounding schools and found
that over 65,000 students spend 1 to 6 hours a day during the academic
year being exposed to airport pollution, and the percentage of impacted
students was higher for those who were economically disadvantaged.\79\
Rissman et al. (2013) studied PM2.5 at the Hartsfield-
Jackson Atlanta International Airport and found that the relationship
between minority population percentages and aircraft-derived PM was
found to grow stronger as concentrations increased.\80\
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    \79\ Henry, R.C., Mohan, S., Yazdani, S. (2019) Estimating
potential air quality impact of airports on children attending the
surrounding schools. Atmospheric Environment, 212: 128-135. https://www.sciencedirect.com/science/article/pii/S1352231019303516?via%3Dihub.
    \80\ Rissman, J., Arunachalam, S., BenDor, T., West, J.J. (2013)
Equity and health impacts of aircraft emissions at the Hartfield-
Jackson Atlanta International Airport, Landscape and Urban Planning
120: 234-247. https://www.sciencedirect.com/science/article/pii/S0169204613001382.
---------------------------------------------------------------------------

    Additional studies have reported that many communities in close
proximity to airports are disproportionately represented by minorities
and low-income populations. McNair (2020) describes nineteen major
airports that underwent capacity expansion projects between 2000 and
2010, thirteen of which met characteristics of race, ethnicity,
nationality and/or income that indicate a disproportionate impact on
these residents.\81\ Woodburn (2017) reports on changes in communities
near airports from 1970-2010, finding suggestive evidence that at many
hub airports over time, the presence of marginalized groups residing in
close proximity to airports increased.\82\
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    \81\ McNair, A. (2020) Investigation of environmental justice
analysis in airport planning practice from 2000 to 2010. Transp.
Research Part D 81:102286. https://www.sciencedirect.com/science/article/pii/S1361920919311149?via%3Dihub.
    \82\ Woodburn, A. (2017) Investigating neighborhood change in
airport-adjacent communities in multiairport regions from 1970 to
2010. Journal of the Transportation Research Board, 2626, 1-8.
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    Although not being conducted as part of this rulemaking, EPA is
conducting a demographic analysis to explore whether populations living
nearest the busiest runways show patterns of racial and socioeconomic
disparity.\83\ This will help characterize the state of environmental
justice concerns and inform potential future actions. Finely resolved
population data (i.e., 30 square meters) will be paired with census
block group demographic characteristics to evaluate if people of color,
children, indigenous populations, and low-income populations are
disproportionately living near airport runways compared to populations
living further away. The results of this analysis could help inform
additional policies to reduce pollution in communities living in close
proximity to airports.
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    \83\ EPA anticipates that the results of the study will be
released publicly in a separate document from the final rule.
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    In summary, the proposed in-production standards for both PM mass
and PM number are levels that all aircraft engines in production
currently meet in order to align with ICAO's standards. Thus, the
proposed standards are not expected to result in emission reductions,
beyond the business-as-usual fleet turnover that would occur absent of
the proposed standards. Therefore, we do not anticipate an improvement
in air quality for those who live near airports where these aircraft
operate.

IV. Details for the Proposed Rule

    In considering what PM emissions standards for aircraft engines are
appropriate to adopt under section 231 of the CAA, EPA, after
consultation with FAA, took into consideration the importance of both
controlling PM emissions and international harmonization of aviation
requirements. In addition, the EPA gave significant weight to the
U.S.'s treaty obligations under the Chicago Convention in determining
the need for and appropriate levels of PM standards. These
considerations led the EPA to propose aircraft engine PM standards
based on engine standards adopted by ICAO. When developing the PM
standards, ICAO looked at three different methods of measuring the
amount of PM emitted. The first is PM mass, or a measure of the total
weight of the particles produced over the test cycle. This is how the
EPA has historically set PM emissions standards for other sectors.
Second, ICAO considered PM number, or the number of particles produced
by the engine over the test cycle. These are two different methods of
measuring the same pollutant, PM, but each provides distinct and
valuable information. Third, ICAO developed PM mass concentration
standards, as a replacement to the existing standards based on smoke
number.
    EPA's proposed action consists of three key parts: (1) A proposal
for PM mass and number emissions standards for aircraft gas turbine
engines, (2) a change in test procedure and form of the existing
standards--from smoke number to PM mass concentration, and (3) new
testing and measurement procedures for the PM emission standards and
various updates to the existing gaseous exhaust emissions test
procedures.
    Sections IV.A through IV.C describe the proposed mass, number, and
mass concentration standards for aircraft engines. Section IV.D
describes the proposed test procedures and measurement procedures
associated with the PM standards. Section IV.E presents information
related to the proposed reporting requirements.
    As discussed above in Section III.A, PM2.5 consists of
both volatile and nonvolatile PM, although only nonvolatile PM would be
covered by the proposed standards. Only nonvolatile PM is present at
the engine exit because the exhaust temperature is too high for
volatile PM to form. The volatile PM (or secondary PM) is formed as the
engine exhaust plume cools and mixes with the ambient air. The result
of this is that the volatile PM is significantly influenced by the
ambient conditions (or ambient air background composition). Because of
this complexity, a test procedure to measure volatile PM has not yet
been developed for aircraft engines. In order to directly measure
nonvolatile PM, ICAO agreed to adopt a measurement procedure, as
described below in Section IV.D, which is based on conditions that
prevent the formation of volatile PM upstream of the measurement
instruments. The intent of

this approach is to improve the consistency and repeatability of the
nvPM measurement procedure.
    Due to the international nature of the aviation industry, there is
an advantage to working within ICAO, in order to secure the highest
practicable degree of uniformity in international aviation regulations
and standards. Uniformity in international aviation regulations and
standards is a goal of the Chicago Convention, because it ensures that
passengers and the public can expect similar levels of protection for
safety and human health and the environment regardless of manufacturer,
airline, or point of origin of a flight. Further, it helps prevent
barriers in the global aviation market, benefiting both U.S. aircraft
engine manufacturers and consumers.
    When developing new emissions standards, ICAO/CAEP seeks to capture
the technological advances made in the control of emissions through the
adoption of anti-backsliding standards reflecting the current state of
technology. The PM standards the EPA is proposing were developed using
this approach. Thus, the adoption of these aircraft engine standards
into U.S. law would simultaneously prevent aircraft engine PM levels
from increasing beyond their current levels, align U.S. domestic
standards with the ICAO standards for international harmonization, and
help the U.S. meet its treaty obligations under the Chicago Convention.
    These proposed standards would also allow U.S. manufacturers of
covered aircraft engines to remain competitive in the global
marketplace. The ICAO aircraft engine PM emission standards have been,
or are being, adopted by other ICAO member states that certify aircraft
engines. In the absence of U.S. standards implementing the ICAO
aircraft engine PM emission standards, the U.S. would not be able to
certify aircraft engines to the PM standards. In this case, U.S. civil
aircraft engine manufacturers could be forced to seek PM emissions
certification from an aviation certification authority of another
country in order to market and operate their aircraft engines
internationally. Foreign certification authorities may not have the
resources to certify aircraft engines from U.S. manufacturers in a
timely manner, which could lead to delays in these engines being
certified. Thus, U.S. manufacturers could be at a disadvantage if the
U.S. does not adopt standards that are at least as stringent as the
ICAO standards for PM emissions. The proposed action to adopt in the
U.S. PM standards that match the ICAO standards would help ensure
international consistency and acceptance of U.S. manufactured engines
worldwide.
    The EPA considered whether to propose standards more stringent than
the ICAO standards. As noted above, the EPA considered both the need
for emissions reductions and the international nature of the aircraft
industry and air travel in evaluating whether to propose more stringent
standards. These considerations have historically led the EPA to adopt
international standards developed through ICAO. The EPA concluded that
proposing to adopt the ICAO PM standards in place of more stringent
standards is appropriate in part because international uniformity and
regulatory certainty are important elements of these proposed
standards. This is especially true for these proposed standards because
they change our approach to regulating aircraft PM emissions from past
smoke measurements to the measurement of nvPM mass and number for the
first time. It is appropriate to gain experience from the
implementation of these nvPM standards before considering whether to
adopt more stringent nvPM mass and/or number standards, or whether
another approach to PM regulation would better address the health risks
of PM emissions from aircraft engines. Additionally, the U.S.
Government played a significant role in the development of these
proposed standards. The EPA believes that international cooperation on
aircraft emissions brings substantial benefits overall to the United
States. Having invested significant effort to develop these standards
and obtain international consensus for ICAO to adopt these standards, a
decision by the United States to deviate from them might well undermine
future efforts by the United States to seek international consensus on
aircraft emissions standards. For these reasons, EPA placed significant
weight on international regulatory uniformity and certainty and is
proposing standards that match the standards which EPA worked to
develop and adopt at ICAO, and is not proposing more stringent
standards.

A. PM Mass Standards for Aircraft Engines

1. Applicability of Standards
    These proposed standards for PM mass, like the ICAO standards,
would apply to all subsonic turbofan and turbojet engines of a type or
model with a rated output (maximum thrust available for takeoff)
greater than 26.7 kN whose date of manufacture is on or after January
1, 2023.\84\ These proposed standards would not apply to engines
manufactured prior to this applicability date.
---------------------------------------------------------------------------

    \84\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017, III-4-3 & III-4-4pp.
Available at https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last accessed November 15, 2021). The ICAO Annex 16
Volume II is found on page 17 of the ICAO Products & Services
Catalog, English Edition of the 2021 catalog, and it is copyright
protected; Order No. AN16-2. The ICAO Annex 16, Volume II, Fourth
Edition, includes Amendment 10 of January 1, 2021. Amendment 10 is
also found on page 17 of this ICAO catalog, and it is copyright
protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    The level of the proposed standard would vary based on when the
initial type certification application is submitted.\85\ Engines for
which the type certificate application was first submitted on or after
January 1, 2023 would be subject to the new type level in Section
IV.A.2 below. These engines are new engines that have not been
previously certificated.
---------------------------------------------------------------------------

    \85\ In most cases, the engine manufacturer applies to FAA for
the type certification; however, in some cases the applicant may be
different than the manufacturer (e.g., designer).
---------------------------------------------------------------------------

    Engines manufactured on or after January 1, 2023 would be subject
to the in-production level, in Section IV.A.3 below.

2. New Type nvPM Mass Numerical Emission Limits for Aircraft Engines
    Aircraft engines with a rated output (rO), maximum thrust available
for take-off, greater than 26.7 kN and whose initial type certification
application is submitted to the FAA on or after January 1, 2023 shall
not exceed the level, as defined by Equation IV-1. As described in
Section IV.D, the nvPM Mass limit is based on mg of PM divided by kN of
thrust, as determined over the LTO cycle.
[GRAPHIC] [TIFF OMITTED] TP03FE22.029

3. In Production nvPM Mass Numerical Emission Limits for Aircraft
Engines

    Aircraft engines that are manufactured on or after January 1, 2023
shall not exceed the level, as defined by Equation IV-2.
[GRAPHIC] [TIFF OMITTED] TP03FE22.030

4. Graphical Representation of nvPM Mass Numerical Emission Limits

    Figure IV-1 shows how the proposed nvPM mass emission limits
compare to known in-production engines.
    Data shown in this figure is from the ICAO Engine Emissions
Databank (EEDB).86 87
---------------------------------------------------------------------------

    \86\ ICAO Aircraft Engine Emissions Databank, July 20, 2021,
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft-engine-emissions-databank.
    \87\ Note, EPA ICR number 2427.06 ``Aircraft Engines--
Supplemental information related to Exhaust Emissions'' also
collects aircraft nvPM data. In the interest of using the most up to
date information, the ICAO EDB was used because it has been updated
more recently than EPA data. The EPA should be receiving new data
from this ICR in Feb. 2022.
[GRAPHIC] [TIFF OMITTED] TP03FE22.031

B. PM Number Standards for Aircraft Engines

1. Applicability of Standards

    These proposed standards for PM number, like the ICAO standards,
would apply to all subsonic turbofan and turbojet engines of a type or
model with a rated output greater than 26.7 kN whose date of
manufacture is on or after January 1, 2023.\88\ These proposed
standards would not apply to engines manufactured prior to this
applicability date.
    The level of the proposed standard would vary based on when the
initial type certification application is submitted. Engines for which
the type

certificate application was first submitted on or after January 1, 2023
would be subject to the new type level in Section IV.B.2 below. These
are new engines that have not been previously certificated.
    Engines manufactured on or after January 1, 2023 would be subject
to the in-production level, in IV.B.3 below.

2. New Type nvPM Number Numerical Emission Limits for Aircraft Engines

    Aircraft engines with a rated output greater than 26.7 kN and whose
initial type certification application is submitted to the FAA on or
after January 1, 2023 shall not exceed the level, as defined by
Equation IV-3. As described in Section IV.D, the nvPM number limit is
based on number of particles divided by kN of thrust, as determined
over the LTO cycle.
[GRAPHIC] [TIFF OMITTED] TP03FE22.032

3. In Production nvPM Number Numerical Emission Limits for Aircraft
Engines

    Aircraft engines that are manufactured on or after January 1, 2023
shall not exceed the level, as defined by Equation IV-4.
[GRAPHIC] [TIFF OMITTED] TP03FE22.033

4. Graphical Representation of nvPM Number Numerical Emission Limits

    Figure IV-2 shows how the proposed nvPM number emission limits
compare to known in-production engines. Data shown in this figure is
from the ICA O Engine Emissions Databank (EEDB).\89\
---------------------------------------------------------------------------

    \88\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017, III-4-4pp. Available at
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on
page 17 of the ICAO Products & Services Catalog, English Edition of
the 2021 catalog, and it is copyright protected; Order No. AN16-2.
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10
of January 1, 2021. Amendment 10 is also found on page 17 of this
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
    \89\ ICAO Aircraft Engine Emissions Databank, July 20, 2021,
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft/-engine-emissions/-databank (last accessed
November 15, 2021).
[GRAPHIC] [TIFF OMITTED] TP03FE22.034

C. PM Mass Concentration Standard for Aircraft Engines

    The current smoke number-based standards were adopted to reduce the
visible smoke emitted by aircraft engines. Smoke number is quantified
by measuring the opacity of a filter after soot has been collected upon
it during the test procedure. Another means of quantifying the smoke
from an engine exhaust is through PM mass concentration
(PMmc).
    ICAO developed a PM mass concentration standard during the CAEP/10
cycle and adopted it in 2017. This PM mass concentration standard was
developed to provide equivalent exhaust visibility control as the
existing smoke number standard starting on January 1, 2020. With the
EPA's involvement, the ICAO PM mass concentration limit line was
developed using measured smoke number and PM mass concentration data
from several engines to derive a smoke number-to-PM mass concentration
correlation. This correlation was then used to transform the existing
smoke number-based limit line into a generally equivalent PM mass
concentration limit line, which was ultimately adopted by ICAO as the
CAEP/10 PM mass concentration standard. The intention when the
equivalent PM mass concentration standard was adopted was that
equivalent visibility control would be maintained and testing would
coincide with the PM mass and PM number measurement, thus removing the
need to separately test and measure smoke number.
    While the ICAO PM mass concentration standard was intended to have
equivalent visibility control as the existing SN standard, the method
used to derive it was based on limited data and needed to be confirmed
for regulatory purposes. Additional analysis was conducted during the
CAEP/11 cycle to confirm this equivalence. The EPA followed this work
as it progressed, provided input during the process, and ultimately
concurred with the results.\90\ The analysis, based on aerosol optical
theory and visibility criterion, demonstrated with a high level of
confidence that the ICAO PM mass concentration standard did indeed
provide equivalent visibility control as the existing smoke number
standard. This provided the justification for ICAO to agree to end
applicability of the existing smoke number standard for engines subject
to the PM mass concentration standard, effective January 1, 2023.
---------------------------------------------------------------------------

    \90\ ICAO, 2019: Report of Eleventh Meeting, Montreal, 4-15
February 2019, Committee on Aviation Environmental Protection,
Document 10126, CAEP/11. It is found on page 26 of the English
Edition of the ICAO Products & Services 2021 Catalog and is
copyright protected; Order No. 10126. For purchase available at:
https://www.icao.int/publications/Pages/catalogue.aspx (last
accessed November 15, 2021). The analysis performed to confirm the
equivalence of the PM mass concentration standard and the SN
standard is located in Appendix C (starting on page 3C-33) of this
report.
---------------------------------------------------------------------------

1. PM Mass Concentration Standard
    The EPA is proposing to adopt a PM mass concentration standard for
all aircraft engines with rated output greater than 26.7 kN and
manufactured on or after January 1, 2023.\91\ This proposed standard
has the same form, test procedures, and stringency as the CAEP/10 PM
mass concentration standard adopted by ICAO in 2017. However, the
applicability date proposed here is different than that agreed to by
ICAO. The proposed PM mass concentration standard is based on the
maximum concentration of PM emitted by the engine at any thrust
setting, measured in micrograms ([micro]g) per meter cubed (m\3\). This
is similar to the current smoke standard, which is also based on the
measured maximum at any thrust setting. Section IV.D describes the
measurement procedure. Like the LTO-based PM mass and PM number
standards discussed above, this is based on the measurement of nvPM
only, not total PM emissions.
---------------------------------------------------------------------------

    \91\ ICAO, 2017: Aircraft Engine Emissions, International
Standards and Recommended Practices, Environmental Protection, Annex
16, Volume II, Fourth Edition, July 2017, III-4-3. Available at
https://www.icao.int/publications/catalogue/cat_2021_en.pdf (last
accessed November 15, 2021). The ICAO Annex 16 Volume II is found on
page 17 of the ICAO Products & Services Catalog, English Edition of
the 2021 catalog, and it is copyright protected; Order No. AN16-2.
The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10
of January 1, 2021. Amendment 10 is also found on page 17 of this
ICAO catalog, and it is copyright protected; Order No. AN 16-2/E/12.
---------------------------------------------------------------------------

    To determine compliance with the proposed PM mass concentration
standard, the maximum nvPM mass concentration [[mu]g/m\3\] would be
obtained from measurement at sufficient thrust settings such that the
emission maximum can be determined. The maximum value would then be
converted to a characteristic level in accordance with the procedures
in ICAO Annex 16, Volume II, Appendix 6. The resultant characteristic
level must not exceed the regulatory level determined from the
following formula:
[GRAPHIC] [TIFF OMITTED] TP03FE22.035

    Engines certificated under the new PM mass concentration standard
would not need to certify smoke number values and would not be subject
to in-use smoke standards. It is important to note that other smoke
number standards remain in effect for in-production aircraft turbofan
and turbojet engines at or below 26.7 kN rated output and for in-
production turboprop engines. Also, the in-use smoke standards will
continue to apply to some already manufactured aircraft engines that
were certified to smoke number standards.
2. Graphical Representation of nvPM Mass Concentration Numerical
Emission Limit
    Figure IV-3 shows how the proposed nvPM mass concentration emission
limits compare to known in-production engines. Data shown in this
figure is from the ICAO Engine Emissions Databank EEDB).\92\
---------------------------------------------------------------------------

    \92\ ICAO Aircraft Engine Emissions Databank, July 20, 2021,
``edb-emissions-databank v28C (web).xlsx'', European Union Aviation
Safety Agency (EASA), https://www.easa.europa.eu/domains/environment/icao-aircraft/-engine-emissions/-databank.

---------------------------------------------------------------------------

[GRAPHIC] [TIFF OMITTED] TP03FE22.036

D. Test and Measurement Procedures

1. Aircraft Engine PM Emissions Metrics
    When developing the PM standards, ICAO looked at three different
methods of measuring the amount of PM emitted. The first is PM mass, or
a measure of the total weight of the particles produced over the test
cycle. This is how the EPA has historically measured PM emissions
subject to standards for other sectors. Second, ICAO considered PM
number, or the number of particles produced by the engine over the test
cycle. These are two different methods of measuring the same pollutant,
PM, but each provides valuable information. Third, ICAO developed PM
mass concentration standards, as an alternative to the existing
visibility standards based on smoke.
    The EPA proposes to incorporate by reference the metrics agreed at
ICAO and incorporated into Annex 16 Volume II, to measure PM mass
(Equation IV-6) and PM number (Equation IV-7). These metrics are based
on a measurement of the nvPM emissions, as measured at the instrument,
over the LTO cycle and is normalized by the rated output of the engine
(rO).
[GRAPHIC] [TIFF OMITTED] TP03FE22.037

    The EPA proposes the PM mass concentration standard be based on the
maximum mass concentration, in micrograms per meter cubed, produced by
the engine at any thrust setting.
    Regulatory compliance with the emissions standards is based on the
product of Equation IV-6 or Equation

IV-7 or mass concentration divided by a correction factor in Table IV-
2, to obtain the characteristic level that is used to determine
compliance with emissions standards (see IV.D.4 below).
2. Test Procedure
    The emission test and measurement procedures adopted by ICAO were
produced in conjunction with the Society of Automotive Engineers (SAE)
E-31 Aircraft Exhaust Emissions Measurement Committee.\93\ These
procedures were developed in SAE E-31 in close consultation between
government and industry, and subsequently they were adopted by ICAO and
incorporated into ICAO Annex 16, Volume II.
---------------------------------------------------------------------------

    \93\ ``E-31 Committee was formed to develop and maintain
cognizance of standards for measurement of emissions from aircraft
powerplants and to promote a rational and uniform approach to the
measurement of emissions form aircraft engines and combustion
systems to support the practical assessment of the industry. The E-
31 Committee, in its operation uses an Executive Committee,
Membership Panel, Subcommittees and working technical panels as
required to achieve its objectives.''
    (See https://www.sae.org/works/committeeHome./do?comtID=TEAE31,
last accessed November 15, 2021).
---------------------------------------------------------------------------

    These procedures build off the existing aircraft engine measurement
system for gaseous pollutants. At least 3 engine tests need to be
conducted to determine the emissions rates. These tests can be
conducted on a single engine or multiple engines.\94\ A representative
sample of the engine exhaust is sampled at the engine exhaust exit. The
exhaust then travels through a heated sample line where it is diluted
and kept at a constant temperature prior to reaching the measurement
instruments.
---------------------------------------------------------------------------

    \94\ All three tests could be conducted on a single engine. Or
two tests could be conducted on one engine and one test on a second
engine. Or three separate engines could each be tested a single
time.
---------------------------------------------------------------------------

    The methodology for measuring PM from aircraft engines differs from
other test procedures for mobile source PM2.5 standards in
two ways. First, as discussed above, the procedure is designed to
measure only the nonvolatile component of PM. The measurement of
volatile PM is very dependent on the environment where it is measured.
The practical development of a standardized method of measuring
volatile PM has proved challenging. Therefore, the development of a
procedure for nvPM was prioritized and the result is proposed here
today.
    Second, the sample is measured continuously rather than being
collected on a filter and measured after the test. This approach was
taken primarily for the practical reasons that, due to high dilution
rates leading to relatively low concentrations of PM in the sample,
collecting enough particulate on a filter to analyze has the potential
to take hours. Given the high fuel flow rates of these engines, such
lengthy test modes would be very expensive. Additionally, because of
the high volume of air required to run a jet engine and the extreme
engine exhaust temperatures, it is not possible to collect the full
exhaust stream in a controlled manner as is done for other mobile
source PM2.5 measurements.
    Included in the proposed procedures, to be incorporated by
reference, are measurement system specifications and requirements,
instrument specifications and calibration requirements, fuel
specifications, and corrections for fuel composition, dilution, and
thermophoretic losses in the collection part of the sampling system.
    To create a uniform sampling system design that works across gas
turbine engine testing facilities, the test procedure calls for a 35-
meter sample line. This results in a significant portion of the PM
being lost in the sample lines, on the order of 50 percent for PM mass
and 90 percent for PM number. These particle losses in the sampling
system are not corrected for in the regulatory compliance levels
(standards). Compliance with the standard is based on the measurement
at the instruments rather than the exit plane of the engine
(instruments are 35 meters from engine exit). This is due to the lack
of robustness of the sampling system particle loss correction
methodology and that a more stringent standard at the instrument will
lead to a reduction in the nvPM emissions at the engine exit plane. A
correction methodology has been developed to better estimate the actual
PM emitted into the atmosphere. This correction is described below in
Section V.A.2.
3. Test Duty Cycles
    Mass and number PM emissions are proposed to be measured over the
Landing and Take-Off (LTO) cycle shown in Table IV-1. This is the same
duty cycle used today to measure gaseous emissions from aircraft
engines and is intended to represent operations and flight under an
altitude of 3,000 feet near an airport. Due to challenges in measuring
at these exact conditions and atmospheric and fuel corrections that
need to be applied after testing; it is not necessary to measure
exactly at these points. Emissions rates for each mode can be
calculated by testing the engine(s) over a sufficient range of thrust
settings such that the emission rates at each condition in Table IV-1
can be determined.

 Table IV-1--Landing and Take-Off Cycle Thrust Settings and Time in Mode
                                  \95\
------------------------------------------------------------------------
                                                              Time in
           LTO operating mode             Thrust setting  operating mode
                                            Percent rO       (minutes)
------------------------------------------------------------------------
Take-off................................             100             0.7
Climb...................................              85             2.2
Approach................................              30             4.0
Taxi/ground idle........................               7            26.0
------------------------------------------------------------------------

    The existing smoke number standard was adopted to reduce the
visible smoke emitted from aircraft engines. Smoke number has been
determined by measuring the visibility or opacity of a filter after
soot has been collected upon it during the test procedure. Another
means of measuring this visibility is by direct measurement of the
particulate matter mass concentration. By measuring visibility based on
mass concentration rather than smoke

number, the number of tests needed can be reduced, and mass
concentration data can be collected concurrently with other PM