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

Federal RegisterNov 23, 2022

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 9, 87, 1030, and 1031

[EPA-HQ-OAR-2019-0660; FRL-7558-02-OAR]

RIN 2060-AU69

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

AGENCY:

Environmental Protection Agency (EPA)

ACTION:

Final rule.

SUMMARY:

The Environmental Protection Agency (EPA) is finalizing particulate matter (PM) emission standards and test procedures applicable to certain classes of engines used by civil subsonic jet airplanes (engines with rated output of greater than 26.7 kilonewtons (kN)) to replace the existing smoke standard for those engines. The EPA is adopting these standards under our authority in the Clean Air Act (CAA). These 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 will apply to both new type design aircraft engines and in-production aircraft engines. The EPA, as well as the U.S. Federal Aviation Administration (FAA), actively participated in the ICAO proceedings in which the ICAO requirements were developed. These standards 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 migrating, modernizing, and streamlining the existing regulations into a new part in the Code of Federal Regulations. As part of this update, the EPA is also aligning with ICAO by applying the smoke number standards to engines less than or equal to 26.7 kilonewtons rated output used on supersonic airplanes.

DATES:

This final rule is effective on December 23, 2022. The incorporation by reference of certain material listed in this rule is approved by the Director of the Federal Register as of December 23, 2022.

ADDRESSES:

The EPA has established a docket for this 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 EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC. The Docket Center's hours of operations are 8:30 a.m.-4:30 p.m., Monday-Friday (except Federal Holidays). For further information on the EPA Docket Center services and the current status, see:

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: (734) 214-4832; email address:

manning.bryan@epa.gov.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. General Information

A. Does this action apply to me?

B. Executive Summary

C. EPA Future Work on Aircraft Engine PM Standards Beyond the Scope of This Final Rule

D. Judicial Review, Administrative Reconsideration, and Severability

II. Introduction: Context for This Action

A. The 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 the 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

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 of the Rule

A. PM Mass Standards for Aircraft Engines

B. PM Number Standards for Aircraft Engines

C. PM Mass Concentration Standard for Aircraft Engines

D. Test and Measurement Procedures

E. Annual Reporting Requirement

F. Response to Key Comments

V. Aggregate PM Inventory Methodology and Impacts

A. Aircraft Engine PM Emissions Modeling Methodologies

B. 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 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) and 1 CFR Part 51

J. Executive Order 12898: Federal Actions To Address Environmental Justice in Minority Populations and Low-Income Populations

K. Congressional Review Act

I. General Information

A. Does this action apply to me?

This action will potentially 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 manufacture civil jet engines with a rated output at or below 26.7 kN for use on supersonic airplanes. These potentially affected entities include the following:

see also NACAA,

489 F.3d at 1229-30.

Thus, as in past rulemakings, the 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.

Once the EPA adopts standards, CAA section 232 then directs the Secretary of Transportation to prescribe regulations to ensure compliance with the EPA's standards.

Finally, CAA section 233 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

70 FR 69664, 69676 (November 17, 2005); 86 FR 2136, 2139-2140 (January 11, 2021).

42 U.S.C. 7572.

42 U.S.C. 7573.

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.”

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.

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ICAO standards are not self-implementing. They must first be adopted into domestic law to be legally binding in any member State.

ICAO, 2006:

Convention on International Civil Aviation, Ninth Edition,

Document 7300/9. Available at:

http://www.icao.int/publications/Documents/7300_9ed.pdf

(last accessed October 31, 2022).

Members of ICAO's Assembly are generally termed member States or contracting States.

There are currently 193 contracting States (member States) according to ICAO's website. The list of ICAO member States is available in the docket for this rulemaking under document identification number EPA-HQ-OAR-2019-0660-0011.

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.”

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.

ICAO, 2006: Convention on International Civil Aviation, Article 37, Ninth Edition, Document 7300/9.

Id.

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.

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.

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.

Id., Article 33.

Id.

Id., Article 38.

ICAO's Committee on Aviation Environmental Protection (CAEP), which consists of members and observers from States as well as 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.”

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).

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ICAO: CAEP Terms of Reference. A copy of the CAEP Terms of reference is available in the docket for this rulemaking under document identification number EPA-HQ-OAR-2019-0660-0006.

ICAO, 2017:

Aircraft Engine Emissions,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017. The ICAO Annex 16 Volume II is found on page 17 of the ICAO Products & Services English Edition of the 2022 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.

CAEP develops new emission standards based on an assessment of the technical feasibility, cost, and environmental benefit of potential requirements.

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.

These standards limited aircraft engine emissions of HC, CO, and NO

. 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 NO

standard by 20 percent and amend the test procedures.

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 NO

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 NO

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 NO

reduction, which ICAO approved in 2005.

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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 NO

standards by 15 percent for new engine designs certificated after December 31, 2013.

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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.

ICAO, 2017:

Aircraft Engine Emissions: Foreword,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

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.

CAEP/5 did not address new aircraft engine emission standards.

ICAO, 2017:

Aircraft Engine Emissions,

CAEP/7 did not address new aircraft engine emission standards.

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.

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. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

At the CAEP/10 meeting in 2016, the Committee agreed to the first airplane

carbon dioxide (CO

) emission standards, which ICAO approved in 2017. The CAEP/10 CO

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.

More specifically, the international PM maximum mass concentration 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).

C. The Relationship Between the 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.

We have periodically revised these regulations.

The EPA's actions to regulate certain pollutants emitted from aircraft engines come directly from the authority in CAA section 231, and we have aligned the U.S. emission requirements with those adopted by ICAO. As described in Section II.B, the ICAO/CAEP terms of reference includes technical feasibility.

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.

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 engine emission levels), which are technology-following.

Emission Standards and Test Procedures for Aircraft; Final Rule, 38 FR 19088 (July 17, 1973).

The following are the most recent EPA rulemakings that revised these regulations. Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures; Final Rule, 62 FR 25355 (May 8, 1997); Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures; Final Rule, 70 FR 69664 (November 17, 2005); Control of Air Pollution from Aircraft and Aircraft Engines; Emission Standards and Test Procedures; Final Rule, 77 FR 36342 (June 18, 2012); Control of Air Pollution From Airplanes and Airplane Engines: GHG Emission Standards and Test Procedures; Final Rule, 86 FR 2136 (January 11, 2021).

ICAO: CAEP Terms of Reference. Available in the docket for this rulemaking under document identification number EPA-HQ-OAR-2019-0660-0006.

ICAO, 2019:

Report of the Eleventh Meeting,

Montreal, 4-15 February 2019, Committee on Aviation Environmental Protection, Document 10126, CAEP/11. It is found on page 27 of the English Edition of the ICAO Products & Services 2022 Catalog and is copyright protected: Order No. 10126. The statement on technological feasibility is located in Appendix C of Agenda Item 3 of this report (see page 3C-4, paragraph 2.2).

For many years the EPA has regulated aircraft engine PM emissions with smoke number standards.

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

and again in 1984.

Additionally, the EPA has amended the test procedures for measuring smoke emissions

and modified the effective dates and compliance schedule for smoke emission standards periodically.

Now, we are adopting three different forms of aircraft engine PM standards: a PM mass concentration standard (μg/m

), a PM mass standard (mg/kN), and PM number standard (#/kN). These aircraft engine PM emission standards are a different way of regulating and/or measuring

aircraft engine PM emissions in comparison to smoke number emission standards.

See 40 CFR 87.1 (July 1, 2021). “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.”

Control of Air Pollution From Aircraft and Aircraft Engines; Emission Standards and Test Procedures, Final Rule, 47 FR 58462 (December 30, 1982).

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).

62 FR 25356 (harmonizing EPA procedures with recent amendments to ICAO test procedures); 70 FR 69664 (same); 77 FR 36342.

Amendment to Standards, Final Rule, 43 FR 12614 (March 24, 1978) (setting back by two years the effective date for all gaseous emission standards for newly manufactured aircraft and aircraft gas turbine engines); 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); 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 emission standards which would otherwise have been effective on January 1,1981, for aircraft gas turbine engines); 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); 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).

Also, as described in Section IV.D, the final PM standards employ a different method for measuring aircraft engine PM emissions compared to the historical smoke number emission standards.

Internationally, the EPA and the FAA have worked within the standard-setting process of ICAO (CAEP and its predecessor, CAEE) since the 1970s 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 the 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 U.S. Code. This rulemaking will 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 adopting PM standards equivalent to ICAO's three different forms of aircraft engine PM emission standards. Adoption of these standards will meet

the United States' obligations under the Chicago Convention and will also help ensure global acceptance of FAA airworthiness certification.

In December 2018, the EPA issued an information collection request (ICR) that matches the CAEP/10 PM reporting requirements described in Section II.B.

In addition to the PM standards, this rulemaking codifies the reporting requirements implemented by this 2018 EPA ICR into the EPA regulations, as described in Section IV.E. Also, in a similar time frame as this rulemaking, the EPA will be renewing this ICR (the ICR needs to be renewed triennially).

Information Collection Request Submitted to OMB for Review and Approval; Comment Request; Aircraft Engines—Supplemental Information Related to Exhaust Emissions (Renewal), 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 201809-2060-08, December 17, 2018.

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 (µm, or 10

−6

meter) in diameter. For reference, a typical strand of human hair is 70 μm in diameter and a grain of salt is about 100 μm. 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 μm (typically based on physical size, thermal diffusivity or electrical mobility)), “fine” particles (PM

2.5

; particles with a nominal mean aerodynamic diameter less than or equal to 2.5 μm), and “thoracic” particles (PM

; particles with a nominal mean aerodynamic diameter less than or equal to 10 μm). Particles that fall within the size range between PM

2.5

and PM

, are referred to as “thoracic coarse particles” (PM

10-2.5

, particles with a nominal mean aerodynamic diameter less than or equal to 10 μm and greater than 2.5 μm).

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 (SO

), NO

and volatile organic compounds (VOCs)) in the atmosphere. The chemical and physical properties of PM

2.5

may vary greatly with time, region, meteorology, and source category. Thus, PM

2.5

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.

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 adopting standards only for the emission of nvPM.

ICAO 2019 Environmental Report. This document is available in the docket for this rulemaking under document identification number EPA-HQ-OAR-2019-0660-0022. 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. . . . These particles are invisible to the human eye and are ultrafine.” (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 emissions 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.” (pages 100 and 101.)

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 U.S. EPA's Integrated Science Assessment for Particulate Matter (PM ISA), which was finalized in December 2019 (2019 PM ISA), with a more targeted evaluation of studies published since the literature cutoff date of the 2019 PM ISA in the Supplement to the Integrated Science Assessment for PM (Supplement).

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Further discussion of PM-related health effects can also be found in the 2022 Policy Assessment for the review of the PM National Ambient Air Quality Standards (NAAQS).

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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.

U.S. EPA. Supplement to the 2019 Integrated Science Assessment for Particulate Matter (Final Report, 2022). U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-22/028, 2022.

U.S. EPA. Policy Assessment for the Reconsideration of the National Ambient Air Quality Standards for Particulate Matter (Final Report, 2022). U.S. Environmental Protection Agency, Washington, DC, EPA-452/R-22-004, 2022.

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.

The 2019 PM ISA concludes that human exposures to ambient PM

2.5

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.).

The 2019 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 PM

2.5

exposures and in PM

2.5

-related health risk. Recent studies evaluated in the Supplement support the conclusion of the 2019 PM ISA with respect to disparities in both PM

2.5

exposure and health risk by race and ethnicity and provide additional support for

disparities for lower socioeconomic status populations. 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.

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).

The EPA has concluded that recent evidence in combination with evidence evaluated in the 2009 PM ISA supports a “causal relationship” between both long- and short-term exposures to PM

2.5

and mortality and cardiovascular effects and a “likely to be causal relationship” between long- and short-term PM

2.5

exposures and respiratory effects.

Additionally, recent experimental and epidemiologic studies provide evidence supporting a “likely to be causal relationship” between long-term PM

2.5

exposure and nervous system effects, and long-term PM

2.5

exposure and cancer. Because of remaining uncertainties and limitations in the evidence base, the EPA determined a “suggestive of, but not sufficient to infer, a causal relationship” for long-term PM

2.5

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.

Short term exposures are usually defined as less than 24 hours duration.

More detailed information on the health effects of PM can be found in a memorandum to the docket.

The EPA is reconsidering a 2020 decision to retain the PM NAAQS.

U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, “Health and environmental effects of non-GHG pollutants emitted by turbine engine aircraft—final rule version,” August 11, 2022.

Id., p. 6.

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 in Section III.B.

2.5

emissions also adversely impact visibility.

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.

In 1999, the EPA finalized the regional haze program 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.

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. The EPA has also concluded that PM

2.5

causes adverse effects on visibility in other areas that are not targeted by the Regional Haze Rule, such as urban areas, depending on PM

2.5

concentrations and other factors such as dry chemical composition and relative humidity (

i.e.,

an indicator of the water composition of the particles). The secondary (welfare-based) PM NAAQS provide protection against visibility effects. In recent PM NAAQS reviews, EPA evaluated a target level of protection for visibility impairment that is expected to be met through attainment of the existing secondary PM standards.

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.

See CAA section 169(a).

Regional Haze Regulations; Final Rule, 64 FR 35714 (July 1, 1999).

National Ambient Air Quality Standards for Particulate Matter; Final Rule, 62 FR 38652 (July 18, 1997).

Cook, op. cit., p. 6.

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.

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.

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.

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.

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.

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.

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.

The study attributed approximately 16,000 premature deaths per year globally to global aviation emissions, with 87 percent attributable to PM

2.5

. The study concludes that about a third of these mortalities are attributable to PM

2.5

exposures within 20 kilometers of an airport. Another study focused on the continental United States estimated 210 deaths per year attributable to PM

2.5

from aircraft activity at airports.

While there are considerable uncertainties associated with such estimates, these results suggest that in addition to the contributions of PM

2.5

emissions to regional air quality, impacts on public health of these emissions in the vicinity of airports are an important public health concern.

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.

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.

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.

The

report concluded that PM

2.5

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.”

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.

Id.

Furthermore, the report states 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 PM

2.5

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.

Id. at 40.

Id. at 41.

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(4).

Since the publication of the 2015 ACRP literature review, a number of studies conducted in the United States 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.

In another study in the vicinity of Logan airport, Hudda et al. analyzed PNC impacts of aviation activities.

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.

Similar findings have been published from European studies.

78 79 80 81 82 83

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.

The PM associated with aircraft landing activity was also smaller in size, with lower black carbon concentrations than near-roadway samples. As discussed in Section III.B, PM

2.5

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.

85 86

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.

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: pp. 1765-1772.

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: pp. 8514-8521.

Stacey, B. 2019. Measurement of ultrafine particles at airports: A review. Atmos. Environ. 198: pp. 463-477.

Masiol M., Harrison R.M. Quantification of air quality impacts of London Heathrow Airport (UK) from 2005 to 2012. Atmos Environ 2017; 116:308-19.

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: pp. 132-142.

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.

Stacey, B., Harrison, R.M., Pope, F., 2020. Evaluation of ultrafine particle concentrations and size distributions at London Heathrow Airport. Atmos. Environ., 222: 117148.

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: pp. 3763-3775.

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: pp. 14161-14171.

University of Washington. 2019. Mobile Observations of Ultrafine Particles: The Mov-UP study report.

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: pp. 48-59.

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,

pp. 997-100.

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.

The systematic review identified seventy studies for evaluation. These studies consistently showed that particulate matter, in the form of 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 deoxyribonucleic acid (DNA) damage and childhood leukemia. As indicated in the proposal, 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.

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.

A systematic review of health effects associated with exposure to jet engine emissions in the vicinity of airports was also recently published.

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.

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.

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.

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 PM

2.5

. To evaluate these potential impacts, we identified the 25 airports where commercial aircraft operations are the greatest, based on data for 2017 from the FAA Air Traffic Data System (ATADS). 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 PM

2.5

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).

Inventory estimates for turbine engine aircraft were adjusted to account for an improved methodology for estimating PM from nvPM measurements. This adjustment is described in detail in Section V.B. 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.

At the county level, contributions to total mobile source PM

2.5

emissions range from less than 1 to about 16 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 PM

2.5

or PM

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 about 0.5 to 3 percent. Details of this analysis are described in a memorandum to the docket.

2017 National Emissions Inventory: Aviation Component, Eastern Research Group, Inc., June 25, 2020, EPA Contract No. EP-C-17-011, Work Order No. 2-19. 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. It should be noted that while identification of the 25 airports with the greatest commercial activity uses 2017 ATADS data, the 2017 NEI relies on 2014 ATADS data.

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 final PM standards is based on the ratio of total PM emissions from flights by engines with thrust rating greater than 26.7 kN compared to PM emissions from the whole fleet at each airport.

U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, “Estimation of 2017 Emissions Contributions of Turbine Aircraft >26.7 kN to NO

and PM

2.5

as a Percentage of All Mobile PM

2.5

for the Counties and MSAs in Which the Airport Resides, 25 Largest Carrier Operations—Final Rule,” June 14, 2022.

BILLING CODE 6560-50-P

ER23NO22.165

Figure III-1

ER23NO22.166

BILLING CODE 6560-50-C

Figure III-2

F. Other Pollutants Emitted by Aircraft

In addition to particulate matter, a number of other criteria pollutants are emitted by the aircraft subject to this final rule. These pollutants, which are not covered by the rule, include NO

, including nitrogen dioxide (NO

), VOC, CO, and sulfur dioxide (SO

). 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 PM

2.5

mass measured in turbine engine aircraft emissions.

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.

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.

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 in Section III.B.

U.S. EPA, Air Toxics Screening Assessment.

G. Environmental Justice

The 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.

“Technical Guidance for Assessing Environmental Justice in Regulatory Analysis.” Environmental Protection Agency (June 2016).

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.

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.

The 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, the EPA is committed to conducting environmental justice analysis for rulemakings based on a framework similar to what is outlined in the 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.

100

101

Rowangould, G.M. (2013) A census of the near-roadway population: public health and environmental justice considerations. Trans Res D 25: pp. 59-67.

Marshall, J.D., Swor, K.R., Nguyen, N.P. (2014) Prioritizing environmental justice and equality: diesel emissions in Southern California. Environ Sci Technol 48: pp. 4063-4068.

Marshall, J.D. (2000) Environmental inequality: air pollution exposures in California's South Coast Air Basin. Atmos Environ 21: pp. 5499-5503.

100

Tessum, C.W., Paolella, D.A., Chambliss, SE, Apte, J.S., Hill, J.D., Marshall, J.D. (2021) PM

2.5

polluters disproportionately and systemically affect people of color in the United States. Science Advances 7:eabf4491.

101

Mohai, P., Pellow, D., Roberts Timmons, J. (2009) Environmental justice. Annual Reviews 34: pp. 405-430.

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.

102

Rissman et al. (2013) studied PM

2.5

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.

103

102

Henry, R.C., Mohan, S., Yazdani, S. (2019) Estimating potential air quality impact of airports on children attending the surrounding schools. Atmospheric Environment, 212: pp. 128-135.

103

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: pp. 234-247.

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.

104

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.

105

104

McNair, A. (2020) Investigation of environmental justice analysis in airport planning practice from 2000 to 2010. Transp. Research Part D 81:102286.

105

Woodburn, A. (2017) Investigating neighborhood change in airport-adjacent communities in multiairport regions from 1970 to 2010. Journal of the Transportation Research Board, 2626, pp. 1-8.

Although not being conducted as part of this rulemaking, the EPA is conducting a demographic analysis to explore whether populations living nearest the busiest runways show patterns of racial and socioeconomic disparity.

106

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.

106

EPA anticipates that the results of the study will be released publicly in a separate document from the final rule.

The final in-production standards for both PM mass and PM number are levels that all aircraft engines in production currently meet to align with ICAO's standards. Thus, the final standards are not expected to result in emission reductions, beyond the business-as-usual fleet turnover that would occur absent the final standards. Therefore, we do not anticipate an improvement in air quality for those who live near airports where these aircraft operate, beyond what may occur as a result of fleet turnover and from any reductions in emissions from other sectors contributing to air quality near airports.

Response to comments on Section III of this action can be found in the Response to Comments document. In addition, all website addresses for references cited in this section are provided in a memorandum to the docket.

107

U.S. EPA, Cook, R. Memorandum to Docket EPA-HQ-OAR-2019-0660, “Web addresses for references cited in Section III of the preamble for Control of Air Pollution from Aircraft Engines: Emission Standards and Test Procedures; Final Rule,” November 9, 2022.

IV. Details of the Final Rule

In determining what final PM standards are appropriate under CAA section 231 and after consultation with FAA, the EPA considered the level of standards that could be met with the application of requisite technology within the necessary period of time that would allow the United States to meet its obligations under the Chicago Convention to at least match the ICAO standards, and gave appropriate consideration to the cost of compliance within this period. This determination also took into account the requirement that EPA's revised standards not significantly increase noise and adversely affect safety. The EPA considered the statutory requirements in CAA section 231 and other relevant factors as described in Section VI of both the proposed rule and this final rule, and we concluded that it was reasonable and appropriate to finalize the new PM standards that match the international standards in scope, stringency, and effective date. The EPA has consulted with FAA and believes sufficient lead time has been provided since the technology has already been developed and implemented by manufacturers to comply with the new PM standards. Also, as described in Section IV.F.1, the EPA is confident that the final standards will not significantly increase noise and adversely affect

safety. Further, as described in Section VI.D, the EPA does not project any costs associated with these standards because all in-production engines meet the in-production standards, nearly all in-production engines meet the new type design standard, and future new type designs are expected to meet the new type design standard. In addition to the statutory requirements of CAA section 231, the EPA, after consultation with FAA, also took into consideration the importance of controlling PM emissions, international harmonization of aviation requirements, and the international nature of the aircraft industry. The EPA gave significant weight to the United States' treaty obligations under the Chicago Convention in determining the need for and appropriate levels of PM standards. U.S. manufacturers could be at a significant disadvantage if the United States fails to adopt standards by the international implementation date. Also, given the short timeframe from this final action and the international implementation date, there would not be enough lead time for manufacturers to respond to more stringent standards that would require them to develop and implement new technologies.

These considerations led the EPA to determine that adopting aircraft engine PM standards based on engine standards adopted by ICAO is appropriate at this time. When developing the PM standards, ICAO adopted 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 emission standards for other sectors. The second is 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.

The EPA's final action will apply to subsonic turbofan and turbojet engines of a type or model with a rated output (maximum thrust available for takeoff) greater than 26.7 kN, hereinafter referred to as covered engines, and consists of three key parts: (1) PM mass and number emission standards for covered engines, (2) a change in test procedure and form of the existing standards for covered engines—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 final mass, number, and mass concentration standards for aircraft engines. Section IV.D describes the test procedures and measurement procedures associated with the PM standards. Section IV.E presents information related to the reporting requirements.

As discussed in Section III.A, PM

2.5

consists of both volatile and non-volatile PM (nvPM), although only non-volatile PM will be covered by the adopted standards. Only non-volatile 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. To directly measure non-volatile PM, ICAO agreed to adopt a measurement procedure, as described 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 non-volatile PM measurement procedure.

Due to the international nature of the aviation industry, there is an advantage to working within ICAO 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 emission 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 adopting were developed using this approach. Thus, the adoption of these aircraft engine standards into U.S. law will simultaneously prevent aircraft engine PM levels from increasing beyond their current levels, align U.S. domestic standards with the ICAO standards for international harmonization, meet the United States' treaty obligations under the Chicago Convention.

These standards will 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 United States 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 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 United States does not adopt standards that are at least as stringent as the ICAO standards for PM emissions. This action to adopt, in the United States, PM standards that match the ICAO standards will 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. See 87 FR 6324, 6337 (February 3, 2022). As noted in the preceding paragraphs, the EPA, after consultation with FAA, considered the statutory requirements under CAA section 231, the importance of controlling PM emissions, international harmonization of aviation requirements, the international nature of the aircraft industry and air travel, and the United States' obligations under the Chicago Convention in evaluating which stringency of standards to propose. These considerations have historically led the EPA to adopt international standards developed through ICAO. The EPA concluded that proposing and now adopting standards equivalent to 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 standards. This is especially true for these final standards because they change our approach to regulating aircraft PM emissions from past smoke measurements to the measurement of nvPM mass concentration, nvPM mass, and nvPM 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 nvPM 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, through the FAA, State Department, and the EPA, played a significant role in the development of these standards through a multi-year process. The EPA believes that international cooperation on aircraft emissions brings substantial benefits overall to the United States. Given that the EPA and FAA invested significant effort and considerable resources 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 emission standards. For these reasons, the EPA placed significant weight on international regulatory uniformity and certainty and is finalizing standards that match the standards which the EPA worked to develop and adopt at ICAO.

A. PM Mass Standards for Aircraft Engines

1. Applicability of Standards

These standards for PM mass, like the ICAO standards, will apply to covered engines whose date of manufacture is on or after January 1, 2023.

108

These standards will not apply to engines manufactured prior to this applicability date.

108

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. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

109

In most cases, the engine manufacturer applies to the FAA for the type certification; however, in some cases the applicant may be different than the manufacturer (

e.g.,

designer).

The level of the standard will vary based on when the initial type certification application is submitted.

109

Covered engines for which the type certificate application was first submitted on or after January 1, 2023 will be subject to the new type level in Section IV.A.2. These engines are new engines that have not been previously certificated.

Covered engines manufactured on or after January 1, 2023 will be subject to the in-production level, in Section IV.A.3.

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

Covered engines 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 milligram (mg) of PM, as determined over the LTO cycle, divided by kN of rated output (rO).

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

Covered engines that are manufactured on or after January 1, 2023 shall not exceed the level, as defined by Equation IV-2.

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4. Graphical Representation of nvPM Mass Numerical Emission Limits

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

110

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.

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Figure IV-1—nvPM mass standards compared to in-production engine LTO emission rates

B. PM Number Standards for Aircraft Engines

1. Applicability of Standards

These standards for PM number, like the ICAO standards, will apply to covered engines whose date of manufacture is on or after January 1, 2023.

111

These standards will not apply to engines manufactured prior to this applicability date.

111

ICAO, 2017:

Aircraft Engine Emissions,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017, III-4-4pp. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

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

Covered engines manufactured on or after January 1, 2023 will be subject to the in-production level, in Section IV.B.3.

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

Covered engines 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, as determined over the LTO cycle, divided by kN of rO.

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

Covered engines that are manufactured on or after January 1, 2023 shall not exceed the level, as defined by Equation IV-4.

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4. Graphical Representation of nvPM Number Numerical Emission Limits

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

112

ICAO Aircraft Engine Emissions Databank, July 20, 2021, “edb-emissions-databank v28C (web).xlsx,” European Union Aviation Safety Agency (EASA).

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Figure IV-2—nvPM number standards compared to in-production engine LTO emission rates

C. PM Mass Concentration Standard for Aircraft Engines

The previous 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 (PM

ICAO developed a PM mass concentration standard during the CAEP/10 cycle and adopted it in 2017.

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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 p.m. 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. 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.

113

ICAO, 2016: Tenth Meeting Committee on Aviation Environmental Protection Report, Doc 10069, CAEP/10.

While the ICAO PM mass concentration standard was intended to have equivalent visibility control as the existing smoke number 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.

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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.

114

ICAO, 2019:

Report of Eleventh Meeting, Montreal, 4-15 February 2019, Committee on Aviation Environmental Protection,

Document 10126, CAEP/11. 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 adopting a PM mass concentration standard for all covered engines manufactured on or after January 1, 2023.

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This standard has the same form, test procedures, and stringency as the CAEP/10 p.m. mass concentration standard adopted by ICAO in 2017. Note, the applicability date of the mass concentration standard, finalized in this action, represents a delay from the January 1, 2020 date agreed to by ICAO

116

. The PM mass concentration standard is based on the maximum concentration of PM emitted by the engine at any thrust setting, measured in micrograms (µg) per meter cubed (m

). This is similar to the previous 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 in Section IV.A and Section IV.B (and described in the introductory paragraphs of Section IV), this is based on the measurement of nvPM only, not total PM emissions.

115

ICAO, 2017:

Aircraft Engine Emissions,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017, III-4-3. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

116

A second component of the CAEP/10 agreement was data collection by January 1, 2020, so the EPA implemented domestically by updating the Aircraft Engine Emission ICR (EPA ICR Number 2427.04, OMB Control Number 2060-0680) on December 31, 2018 to include PM emission data.

To determine compliance with the PM mass concentration standard, the maximum nvPM mass concentration [μg/m

] will be obtained from measurements at sufficient thrust settings such that the emission maximum can be determined. The maximum value will 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:

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Engines certificated under the new PM mass concentration standard will not need to certify smoke number values and will not be subject to in-use smoke standards. It is important to note that other smoke number standards remain in effect for turbofan and turbojet aircraft engines at or below 26.7 kN rated output and for 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. In this final rule, the EPA did not reexamine or reopen the existing smoke number standards. Any comments we received on the existing smoke number standards are beyond the scope of this rulemaking.

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The EPA proposed to extend the applicability of the smoke standards to engines of less than or equal to 26.7 kilonewtons (kN) rated output used in supersonic airplanes, and so the single comment received on the extended applicability is within the scope of this rulemaking and is responded to in the Response to Comments document.

2. Graphical Representation of nvPM Mass Concentration Numerical Emission Limit

Figure IV-3 shows how the nvPM mass concentration emission limits compare to known in-production engines, which all were certified to the previous smoke standard. Data shown in this figure is from the ICAO Engine Emissions Databank (EEDB).

118

ICAO Aircraft Engine Emissions Databank, July 20, 2021, “edb-emissions-databank v28C (web).xlsx,” European Union Aviation Safety Agency (EASA).

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Figure IV-3—nvPM Mass Concentration Standard

D. Test and Measurement Procedures

1. Aircraft Engine PM Emissions Metrics

When developing the PM standards, ICAO adopted 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. The second is 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 is incorporating 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).

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The EPA is adopting the PM mass concentration standard based on the maximum mass concentration, in micrograms per meter cubed, produced by the engine at any thrust setting.

Regulatory compliance with the emission standards is based on the product of Equation IV-6 or Equation IV-7 or mass concentration divided by the appropriate factor from Table IV-2, to obtain the characteristic level that is used to determine compliance with emission standards (see Section IV.D.4).

2. Test Procedure

The EPA is incorporating by reference the PM test and measurement procedures in ICAO Annex 16, Volume II. These procedures were developed in conjunction with the Society of Automotive Engineers (SAE) E-31 Aircraft Exhaust Emissions

Measurement Committee

119

in close consultation between government and industry, and subsequently they were adopted by ICAO and incorporated into ICAO Annex 16, Volume II.

119

The E-31 Committee develops and maintains standards for measurement of emissions from aircraft engines. (See

https://www.sae.org/works/committeeHome.do?comtID=TEAE31,

last accessed October 31, 2022).

These procedures build off the existing ICAO Annex 16, Volume II aircraft engine measurement procedures for gaseous pollutants. As described in the Annex 16, at least three engine tests need to be conducted to determine the emissions rates. These tests can be conducted on a single engine or multiple engines.

120

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.

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For example, 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 certain other EPA test procedures for mobile source PM

2.5

standards in two ways. First, as discussed in the introductory paragraphs of Section IV, the procedure is designed to measure only the non-volatile 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 from aircraft engines has proved challenging. Therefore, the development of a procedure for measuring nvPM was prioritized by ICAO and SAE E-31and the result is adopted in this final rule.

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 PM

2.5

measurements.

Included in the procedures now incorporated by reference by the EPA 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 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 in Section V.A.2.

3. Test Duty Cycles

Mass and number PM emissions are measured over the LTO cycle shown in Table IV-1. This is the same duty cycle used 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. 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

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LTO operating mode

Thrust setting

percent rO

Time in

operating

mode minutes

Take-off

100

0.7

Climb

2.2

Approach

4.0

Taxi/ground idle

26.0

The

previous 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 measurements. Like the previous smoke standard, the PM mass concentration standard is be based on the maximum value at any thrust setting. The engine(s) will be tested over a sufficient range of thrust settings that the maximum can be determined. This maximum could be at any thrust setting and is not limited to the LTO thrust points in Table IV-1.

121

ICAO, 2017:

Aircraft Engine Emissions,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017, III-4-2. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

The EPA is incorporating by reference ICAO's Annex 16 to the Convention on International Civil Aviation, Environmental Protection, Volume II—Aircraft Engine Emissions, Fourth Edition, July 2017.

4. Characteristic Level

EPA is incorporating by reference Appendix 6 to ICAO Annex 16, Volume II—International Standards and Recommended Practices for correcting engine measurements to characteristic value. Like existing gaseous standards, compliance with the PM standards adopted in this action is based on the characteristic level of the engine. The characteristic level is a statistical

method of accounting for engine-to-engine variation in the measurement based on the number of engines tested. A minimum of three engine emissions tests is needed to determine the engine type's emissions rates for compliance with emission standards. The more engines that are used for testing increases the confidence that the emissions rate measured is from a typical engine rather than a high or low engine.

Table IV-2 is reproduced from Annex 16 Volume II Appendix 6 Table A6-1 and shows how these factors change based on the number of engines tested.

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As the number of engines tested increases, the factor also increases resulting in a smaller adjustment and reflecting the increased confidence that the emissions rate is reflective of the average engine off the production line. In this way, there is an incentive to test more engines to reduce the characteristic adjustment while also increasing confidence that the measured emissions rate is representative of the typical production engine.

122

ICAO, 2017:

Aircraft Engine Emissions,

International Standards and Recommended Practices, Environmental Protection, Annex 16, Volume II, Fourth Edition, July 2017, App 6-2pp. The ICAO Annex 16, Volume II, Fourth Edition, includes Amendment 10 of January 1, 2021.

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For PM mass and PM number, the characteristic level is based on the mean of all engines tested, and appropriately corrected, divided by the factor corresponding to the number of engine tests performed in Table IV-1. For PM mass concentration, the characteristic level is based on the mean of the maximum values of all engines tested, and appropriately corrected, divided by the factor corresponding to the number of engine tests performed in Table IV-2.

For example, an engine type where three measurements were obtained from the same engine has an nvPM mass metric value of 100 mg/kN (mean metric value of all engine tests). The nvPM LTO mass factor (or nvPM mass characteristic factor) from Table IV-2 for three engines is 0.7194. The metric value, with applicable corrections applied, is then divided by the factor to obtain the characteristic level of the engine. Therefore, the resulting characteristic level for this engine type, to determine compliance with the nvPM mass standard is 139.005 mg/kN. If instead three engines are each tested once, the characteristic factor would be 0.8858 and the nvPM mass characteristic level to determine compliance with the standard would be 112.892 mg/kN.

An engine type's characteristic level can also be further improved by testing additional engines. For example, if 10 separate engines were tested of the same type, the nvPM mass characteristic factor becomes 0.9375. The resulting characteristic level (assuming the average nvPM mass metric value remains 100 mg/kN) would be 106.667 mg/kN. This approach could be used if an engine exceeds the standard at the time it is initially tested or there is a desire to increase the margin to the standard for whatever reason. Table IV-3 shows these three different examples for nvPM LTO Mass.

Table IV-3—Impact of the Number of Engines Tested on Resulting Characteristic Level

Number of engines tested

Number of

tests per

engine

Measured nvPM

LTO Mass

(mg/kN)

Characteristic

factor

Characteristic

level

(mg/kN)

100

0.7194

139.005

100

0.8858

112.892

100

0.9375

106.667

5. Derivative Engines for Emissions Certification Purposes

Aircraft engine types can remain in production for many years and be subject to numerous modifications during their production life. As part of the certification process for any change, the type certificate applicant will need to show if the change will have an impact the engine emissions. While some of these changes could impact engine emissions rates, many of them will not. To simplify the certification process and reduce burden on both type certificate applicant and certification authorities, ICAO developed criteria to determine whether there has been an emissions change that requires new testing. Such criteria already exist at ICAO and in the EPA regulations for gaseous and smoke standards.

ICAO recommends

123

that if the characteristic level for an engine was type certificated at a level that is at or above 80 percent of the PM mass, PM number, or PM mass concentration standard, the type certificate applicant would be required to test the proposed derivative engine. If the engine is below 80 percent of the standard, engineering analysis can be used to determine new emission rates for the proposed derivative engines. The EPA is implementing these ICAO recommended practices in this final rule as the regulatory standard in the United States.

123

ICAO, 2020, Environmental Technical Manual, Doc 9501, Volume II—Procedures for the Emissions Certification of aircraft Engines, Fourth Edition, Section 2, Part III, Chapter 2.

ICAO evaluated the measurement uncertainty to develop criteria for determining if a proposed derivative engine's emissions are similar to the previously certificated engine's emissions. The EPA is adopting these ICAO criteria in this final rule.

124

Id.

For PM mass measurements described in Section IV.A, the following values apply:

• 80 mg/kN if the characteristic level for nvPM

mass

emissions is below 400 mg/kN.

• ±20% of the characteristic level if the characteristic level for nvPM

mass

emissions is greater than or equal to 400 mg/kN.

For PM number measurements, described in Section IV.B, the following values apply:

• 4×10

particles/kN if the characteristic level for nvPM

num

emissions is below 2×10

particles/kN.

• ±20% of the characteristic level if the characteristic level for nvPM

num

emissions is greater than or equal to 2×10

particles/kN.

For PM mass concentration measurements described in Section IV.C, the following values apply:

• ±200 μg/m

if the characteristic level of maximum nvPM mass concentration is below 1,000 μg/m

• ±20% of the characteristic level if the characteristic level for maximum nvPM mass concentration is at or above 1,000 μg/m

If a type certificate applicant can demonstrate that the engine's emissions are within these ranges, then new emissions rates will not need to be developed and the proposed derivative engine for emissions certification purposes will keep the existing emissions rates.

If the engine is not determined to be a derivative engine for emissions certification purposes, the type certificate applicant will need to certify the new emission rates for the engine.

E. Annual Reporting Requirement

In 2012, the EPA adopted an annual reporting requirement as part of a rulemaking to adopt updated aircraft engine NO

standards.

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This provision, adopted into 40 CFR 87.42, requires the manufacturers of covered engines to annually report data to the EPA which includes information on engine identification and characteristics, emissions data for all regulated pollutants, and production volumes. In 2018, the EPA issued an information collection request (ICR) which renewed the existing ICR and added PM information to the list of required data.

126

127

However, that 2018 ICR was not part of a rulemaking effort, and the new PM reporting requirements were not incorporated into the CFR at that time. Further, that 2018 ICR is currently being renewed (in an action separate from this rulemaking), and the EPA is including as part of that effort some additional data elements to the ICR (specifically, the emission indices for HC, CO, and NO

at each mode of the LTO cycle).

128

129

The EPA is now formally incorporating all aspects of that ICR, as proposed to be renewed, into 40 CFR 1031.150. It is important to note that the incorporation of the PM reporting requirements into the CFR will not create a new requirement for the manufacturers of aircraft engines. Rather, it will simply incorporate the existing reporting requirements (as proposed to be amended and renewed in a separate action) into the CFR for ease of use by having all the reporting requirements readily available in the CFR.

125

77 FR 36342 (June 18, 2012).

126

83 FR 44621 (August 31, 2018).

127

U.S. EPA,

Aircraft Engines—Supplemental Information Related to Exhaust Emissions (Renewal)

, OMB Control Number 2060-0680, ICR Reference Number 201809-2060-08, December 17, 2018. Available at

https://www.reginfo.gov/public/do/PRAViewICR?ref_nbr=201809-2060-008,

last accessed June 8, 2022.

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Proposed Information Collection Request; Comment Request; Air Emissions Reporting Requirements (Renewal); EPA ICR No. 2170.08, OMB Control No. 2060-0580, 86 FR 24614 (May 7, 2021).

129

Documentation and Public comments are available at:

https://www.regulations.gov/docket/EPA-HQ-OAR-2016-0546,

last accessed June 8, 2022.

The EPA uses the collection of information to help conduct technology assessments, develop aircraft emission inventories (for current and future inventories), and inform our policy decisions—including future standard-setting actions. The information enables the EPA to further understand the characteristics of aircraft engines that are subject to emission standards—and engines subject to the PM emission standards—and engines' impact on emission inventories. In addition, the information helps the EPA set appropriate and achievable emission standards and related requirements for aircraft engines. Annually updated information helps in assessing technology trends and their impacts on national emissions inventories. Also, it assists the EPA to stay abreast of developments in the aircraft engine industry.

As discussed in Section VII, the EPA is finalizing the proposal to migrate the existing 40 CFR part 87 regulatory text to a new 40 CFR part 1031. This effort includes clarifying portions of the regulatory text for ease of use. In the old 40 CFR 87.42(c)(6), the regulatory text did not specifically spell out some required data, but instead relied on incorporation by reference of ICAO Annex 16, Volume II's data reporting requirements and listed the data from this Annex that is not required by the EPA's reporting requirement. For future ease of use, 40 CFR 1031.150 explicitly lists all the required items rather than continuing the incorporation by reference approach in the existing reporting regulations. Finally, the EPA is incorporating by reference Appendix 8 of Annex 16, Volume II, which outlines procedures used to estimate measurement system losses, which are a required element of the reporting provisions.

F. Response to Key Comments

The EPA received numerous comments on the proposed rulemaking

which are summarized in the Response to Comments document along with the EPA's responses to those comments. Comments in their entirety are available in the docket for this rulemaking action. The following sections summarize the comments related to the stringency of the standards and the EPA's response to these comments. Some adverse comments are addressed more fully in the Response to Comments document.

1. Comments in Support of the Proposed Standards

Comment summary:

Some commenters stated that the proposed standards adhere to the statutory requirements of CAA section 231. They say that the proposed standards are well supported by an extensive administrative record. The commenters point out that the D.C. Circuit ruled in 2007 that CAA section 231 confers a broad degree of discretion on the EPA in setting aircraft engine emission standards.

130

National Association of Clean Air Agencies

EPA,

489 F.3d 1221, 1229-30 (D.C. Cir. 2007) (“When Congress enacted § 231 providing that the Administrator could, `from time to time,' act `in his judgment,' as `he deems appropriate,' it conferred broad discretion to the Administrator to weigh various factors in arriving at appropriate standards.”).

Response:

EPA is finalizing the standards as proposed. We agree that the proposed standards, as well as the final standards, satisfy our statutory obligations and are well-supported. The EPA acknowledges that the D.C. Circuit recognized the EPA's broad authority in CAA section 231

in National Association of Clean Air Agencies

EPA,

489 F.3d 1221, 1229-30 (D.C. Cir. 2007) (

NACAA

Comment summary:

Several commenters expressed their support of the EPA adopting PM standards that match the international PM standards because doing so is vital to the competitiveness of U.S. industry and regulatory certainty. They say it would protect U.S. jobs and strengthen the U.S. aviation industry by ensuring the global acceptance of U.S.-manufactured aircraft engines. They also say it will make sure U.S.-manufactured aircraft engines are available to aircraft manufacturers and U.S. airlines, while enabling U.S. airlines to obtain aircraft and aircraft engines at market-driven, competitive prices.

Response:

The EPA agrees this rule has the benefit of helping to ensure the acceptance of U.S.-manufactured aircraft engines by member States, aircraft (airframe) manufacturers, and airlines around the world. The EPA notes that under the terms of the Chicago Convention, ICAO member States must recognize as valid certificates of airworthiness issued by other ICAO member States, provided the requirements under which such certificates were issued are as least as stringent as the minimum ICAO standards.

131

ICAO, 2006:

Convention on International Civil Aviation,

Article 33, Ninth Edition, Document 7300/9.

Comment summary:

Some commenters urged the EPA to promptly issue the final rule with the standards matching the international standards. They say that this EPA rulemaking and the subsequent FAA certification rulemaking must be completed to start the certification process in the United States. Thus, they believe that prompt EPA action is necessary to provide sufficient time for FAA to promulgate their certification rulemaking and U.S. aircraft engine manufacturers to conduct the lengthy and expensive steps to demonstrate compliance with the standards, for all aircraft engines that will be in-production in 2023. They note that January 1, 2023, is the implementation date for the ICAO standards.

Response:

The EPA acknowledges that the international effective date for the ICAO mass concentration standards was January 1, 2020, and that the international effective date for the mass and number standards is January 1, 2023. The EPA also acknowledges that FAA will need to conduct a separate, subsequent certification rulemaking process to implement the EPA's PM standards finalized in this action.

In this action, the EPA is aiming to minimize disruption by finalizing this action before the January 1, 2023, the international effective date of the PM mass and number standards.

For comparison, the EPA notes the EPA finalized the domestic GHG standards for airplanes on January 11, 2021, after the international effective date for new type planes;

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however, disruption was avoided in practice because no manufacturers applied to FAA for a type certificate for a new type design airplane between January 1, 2020, and January 11, 2021.

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CAEP/10 airplane CO

standards apply to new type design airplanes for which the application for a type certificate was or 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.

Comment summary:

Some commenters state that the proposed standards are identical to ICAO's aircraft engine PM standards and that adopting them is consistent with the 1944 Chicago Convention treaty obligations. They say that these standards continue the long collaborative tradition between the EPA and ICAO. The commenters say that the objective of the Chicago Convention is to foster global cooperation and encourage an atmosphere where international civil aviation could be developed in a safe and orderly manner, while being operated soundly and economically. The commenters say that, with both the FAA and the EPA playing key leadership roles, it was only after significant deliberation and technical and economic analyses that CAEP agreed to the ICAO PM standards. The commenters say that the EPA's adoption of standards that align with ICAO standards supports international harmonization and regulatory uniformity.

Response:

The EPA agrees adopting the PM standards in this action satisfies the United States' treaty obligations under the Chicago Convention. The EPA also agrees that the EPA and the FAA had key leadership roles in the ICAO PM standard-setting process, and the EPA recognizes the significant deliberations and economic analyses that occurred in CAEP. The EPA agrees that this action promotes international cooperation and harmonization.

Comment summary:

Some commenters say that the standards are consistent with the CAEP terms of reference which provide that standards be technologically feasible, economically reasonable, environmentally beneficial, and balanced against interdependencies (aircraft noise and competing emission reductions of other pollutants, such as NO

). The commenters say that the CAEP terms of reference align well with the considerations in CAA section 231, and ICAO's assessment of each of the criteria of the terms of reference is directly related to the decisions the EPA must make when issuing aircraft engine emission standards. The commenters assert that CAA section 231(b) requires that aircraft engine emission standards allow sufficient lead time for the development of the necessary technology, while giving consideration of the cost to comply within this time period.

Response:

The EPA agrees that the final standards are consistent with the CAEP terms of reference and that the standards also meet the requirements of CAA section 231. The EPA would not adopt ICAO standards domestically without exercising the Agency's own independent evaluation of appropriate domestic standards under CAA section 231, which is what the EPA has done in

this rulemaking. Any domestic aircraft engine standards adopted by the EPA must comport with the requirements in CAA section 231.

Comment summary:

Some commenters say that CAA section 231(a)(2)(B)(ii) expressly prohibits changes in aircraft engine emission standards that “would significantly increase noise and adversely affect safety.” The commenters point out that, as the EPA describes in the proposed rulemaking, ICAO/CAEP evaluates “technological feasibility” using the Technology Readiness Level (“TRL”) scale and deems technologies that have attained TRL8 (defined as the “actual system completed and `flight qualified' through test and demonstration”) to be “technologically feasible.” Therefore, the commenters conclude, the use of TRL8 to evaluate “technological feasibility” makes sure aircraft engine emission standards reflect what technologies can safely deliver, instead of hypothetical “technology forcing” standards that could pose a potential threat to air safety.

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Any reference to technology-forcing standards in this rulemaking is not based on the level of the final PM standards, but it is intended to respond to comments.

Response:

The EPA agrees that TRL8

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is an adequate and appropriate criteria for identifying proven technologies that are demonstrably safe and of an acceptable noise level for purposes of this rulemaking. The EPA relies on TRL8 to support the PM standards finalized in this rule because TRL8 was used to justify the PM standards by ICAO, as described in Section VI.B. ICAO treats TRL8 as a proxy for what is technologically feasible in the course of establishing new international standards. This conservative approach allows ICAO to ensure that all technology being considered is safe and of acceptable noise level without having to conduct additional evaluation of specific technologies. The EPA agrees this use of TRL8 is a valid means for ICAO to develop standards that will, by definition, be based on technologies that have been proven safe, of acceptable noise level, and technologically feasible. The EPA also agrees that ICAO's use of TRL8 means that technologies considered have been proven safe and of an acceptable noise level, and therefore, that the final PM standards do not adversely affect safety and do not significantly increase noise. In setting the international standards, ICAO considered the emissions performance of aircraft engines assumed to be in-production on the implementation date for the PM mass and number standards, January 1, 2023. Thus, the technology was already demonstrated to be safe and of acceptable noise levels for these standards, and ICAO did not view that a new safety and noise analysis was necessary.

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As described in Section VI.B, TRL is a measure of Technology Readiness Level. CAEP has defined TRL8 as the “actual system completed and `flight qualified' through test and demonstration.” TRL is a scale from 1 to 9, TRL1 is the conceptual principle, and TRL9 is the “actual system `flight proven' on operational flight.” The TRL scale was originally developed by NASA. ICF International,

Analysis of CO

-Reducing Technologies for Aircraft,

Final Report, EPA Contract Number EP-C-12-011, see page 40, March 17, 2015.

However, in the EPA's view, ICAO's use of TRL8 to define technological feasibility is not the only means to ensure a standard does not adversely affect safety and does not significantly increase noise. The EPA does not view TRL8 to represent the most stringent level of technology that could be required in an EPA aircraft standard setting rulemaking. Nor does the EPA agree with the premise that standards based on technology below TRL8 would necessarily be technology forcing or inherently have a negative effect on safety and noise. In establishing U.S. aircraft engine emission standards, the EPA is not constrained to ICAO's definition of technological feasibility in assessing appropriate aircraft engine standards under CAA section 231(a).

See NACAA,

489 F.3d at 1229-30. In fact, the EPA has adopted technology-forcing standards under CAA section 231 in the past and found them to be safe and not to significantly increase noise.

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In the future, if the EPA were to consider setting emission standards based on technology that was not yet at TRL8 or not expected to be at TRL8 by the implementation date of the standards,

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the Agency, just as it did in this action, in consultation with the FAA, would evaluate the safety and noise impact (also lead time and cost) of such standards before making a determination in this regard. CAA section 231(a)(2)(B) and (a)(3). Any assessment of safety and noise (also lead time and cost) in the context of hypothetical technology-forcing standards would have to occur in the context of the specific standards under consideration.

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See

38 FR 19088 (July 17, 1973); 41 FR 34722 (August 16, 1976).

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As described in Section VI.B, for the ICAO PM standard setting, ICAO referred to technical feasibility as any technology demonstrated to be safe and airworthy proven to Technology Readiness Level 8 and available for application over a sufficient range of newly certificated aircraft. This means that the ICAO analysis that informed the international standard considered the emissions performance of aircraft engines assumed to be in-production on the ICAO implementation date for the PM mass and number standards, January 1, 2023.

2. Comments in Support of More Stringent Standards

Comment summary:

Several commenters were dissatisfied with the level of stringency of the PM standards. One commenter argued that CAA section 231 requires the EPA to adopt technology-forcing standards. Other comments argued CAA section 231 requires the EPA to set standards according to expectations of the development of technology over time. Some commenters say that, at a minimum, the EPA should establish standards that reduce emissions based on available engine technology. A number of commenters supported these arguments by pointing to the text of the statute, the underlying legislative intent, legislative history, and the purpose of the CAA.

Response:

The statutory-based arguments presented by commenters that the level of stringency of the PM standards are not authorized by CAA section 231 import requirements into the statute that do not exist.

As described in Section II.A, CAA section 231(a)(2)(A) directs the Administrator of the 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 the Administrator's judgment causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare. CAA section 231(a)(3) provides that after the EPA proposes standards, the Administrator shall issue such standards “with such modifications as he deems appropriate.” CAA section 231(b) requires that any emission standards “take effect after such period as the Administrator finds necessary . . . to permit the development and application of the requisite technology, giving appropriate consideration to the cost of compliance during such period.” The D.C. Circuit has held that the delegation of authority in CAA section 231 “is both explicit and extraordinarily broad” and that the text confers “broad discretion . . . to weigh various factors in arriving at appropriate standards.”

NACAA,

489 F.3d 1221, 1229-30.

The statutory language of CAA section 231 is not identical to other provisions in the CAA that direct the EPA to establish technology-based standards. CAA section 231(a) states that the EPA must “issue proposed emission standards applicable to the emission of any air pollutant” from aircraft engines

and to finalize “such regulations” with those modifications the EPA “deems appropriate.” CAA section 231(a)(2)(A) and (a)(3). This language is in contrast to Congress' direction in other parts of the Act, where it required the EPA to set standards that achieve a particular degree of emission reduction or environmental or public health protection. For example, in setting technology-based emission standards for hazardous air pollutants under CAA section 112(d)(2) and (3), the EPA must “require the maximum degree of reduction . . . that the Administrator . . . determines is achievable,” taking into account cost and non-air quality health and environmental impacts. CAA section 112(d)(2). Those standards also “shall not be less stringent than” explicitly prescribed levels. CAA section 112(d)(3). Health- and environmental quality-based NAAQS under CAA section 109 must be set at levels “requisite to protect the public health” and “requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of [the] air pollutant in the ambient air.” CAA section 109(b)(1) and (2). When regulating certain pollutants from motor vehicles and nonroad engine emissions under CAA sections 202(a)(3) and 213(a)(3) and (5), the EPA's standards must “reflect the greatest degree of emission reduction achievable . . . , giving appropriate consideration to cost, energy, and safety factors associated with the application of such technology.” CAA sections 202(a)(3) and 213(a)(3) and (5).

CAA section 231 lacks comparable language requiring it to meet a particular threshold of protectiveness, emission reduction, or technological stringency, despite this clear evidence that Congress knew how to impose such obligations when it wished.

See generally

CAA section 231. “Where Congress uses certain language in one part of a statute and different language in another, it is generally presumed that Congress acts intentionally.”

Nat'l Fed'n of Indep. Bus.

Sebelius,

567 U.S. 519, 544 (2012);

Sosa

Alvarez-Machain,

542 U.S. 692, 711 n.9 (2004) (citing a treatise on statutory construction and calling this principle the “usual rule” of judicial interpretation). In certain respects, the EPA's authority is broader than it is under other CAA provisions, in that the EPA is not required in setting aircraft emission standards to achieve a specified degree of emissions reduction.

Some commenters also presented a textual comparison of the House and Senate bills to conclude that Congress intended for CAA section 231 to be based on a consideration of pollution impacts and technological feasibility because the final CAA section 231(a)(1) required the EPA to conduct a study within 90 days after December 31, 1970 of air pollutants from aircraft to determine impact on air quality and technological feasibility of controlling such pollutants. S. Rep. No. 91-1196, at 24, 1 Leg. Hist. at 424; H.R. Rep. No. 91-1783, at 55 (Conf. Rep.). One commenter alleged this means “the necessary premise [is] that such study should inform the standards themselves.”

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However, the study requirement in CAA section 231(a)(1) does not establish a requirement for aircraft engine standards to be forward-looking technology-based regulation. That provision required EPA to conduct a one-time “study and investigation” “to determine” the extent of aircraft emissions' impacts on air quality and the feasibility of controlling them “[w]ithin 90 days after December 31, 1970.” The single study required in CAA section 231(a)(1) is not a continuing obligation that pertains to each exercise of the standard-setting authority under CAA section 231(a)(2) and (3), which contain no discussion of technological feasibility and under which standards are set and may be revised “from time to time.”

Cf. Sierra Club,

325 F.3d 374, 377 (D.C. Cir. 2003) (holding that a provision requiring EPA to set standards “based on” such a study did not make the validity of the standards dependent on their connection to that study).

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Comments of California, Connecticut, Illinois, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Vermont, Washington, and Wisconsin at 13. See also Comment of Sierra Club at 7-8.

The commenters also quoted to a Senate report accompanying the CAA 1970 amendment Senate bill to suggest CAA section 231 requires standards to be based on the degree of harm caused by aircraft pollution and the technology that can be developed in the future to reduce it. The statement cited by commenters from the Senate Report does not constrain the EPA where the plain text of the statute does not, and where Congress knew how, but declined, to make such constraints mandatory on the Agency. “Congress' authoritative statement is the statutory text, not the legislative history.”

Chamber of Com. Of U.S.

Whiting,

563 U.S. 582, 599 (2011) (quoting

Exxon Mobil Corp.

Allapattah Services, Inc.,

545 U.S. 546, 568 (2005) (internal quotation marks omitted). Further, the

NACAA

Court rejected an argument that similar statements in the 1970 Senate Report established Congress' intent that the EPA prioritize forward-looking standards.

NACAA,

489 F.3d at 1229-30;

Sierra Club

EPA,

325 F.3d 374, 379-380 (D.C. Cir. 2003).

The EPA's interpretation of CAA section 231 is not categorically at odds with the Clean Air Act's general protective purpose. The Act's general goal of reducing air pollution does not, in itself, prescribe regulatory factors for specific programs, nor does it restrict the EPA's discretion as to how best effectuate that goal in a specific action or in a regulatory program over time. Accordingly, while the EPA's discretion under CAA section 231 would allow it to select more stringent standards when appropriate, it does not mandate that the EPA elevate pollution reduction over all relevant factors in the consideration of any particular aircraft standard.

See NACAA,

489 F.3d at 1229-30.

The final PM standards fall squarely within the EPA's statutory authority under CAA section 231 to promulgate. As described in Section I.B.2 and the introductory text of Section IV, in proposing and adopting the final PM standards, the EPA considered the statutory requirements of CAA section 231. The EPA also took into account the need to control PM emissions, the importance of international harmonization, avoiding adverse impacts that could result from delaying adoption of PM standards at least as stringent as ICAO's PM standards, and gaining experience from the novel approach to implementing PM standards. Further, based on the EPA's independent view that technology at the TRL8 has been demonstrated to be safe and of an acceptable noise-level, the EPA is confident that the final standards will not significantly increase noise or adversely affect safety. The EPA reached the same conclusion as ICAO that a new noise and safety analysis was not necessary. For the same reasons, the EPA believes sufficient lead time has been provided since the technology has already been developed. Costs information for the standards is described in Section VI.D. Based on this assessment, the EPA concludes that it is reasonable to finalize PM standards that match the international standards in scope, stringency, and effective date.

Additional legal issues raised by these comments are addressed in the Response to Comments document.

Comment summary:

Some commenters claim the EPA has an obligation to consider the feasibility, costs, and benefits of more stringent standards, including technology-forcing standards, or at least explain why it did

not do so. A few commenters proposed suggestions to alternative PM controls such as de-rated takeoff, accelerated implementation of Optimized Profile Descents, reduced power during taxiing, improved taxi time, and reduced usage of auxiliary power units (APUs).

Response:

The focused scope of the EPA's proposed PM standards was informed by the January 1, 2023, international effective date for the mass and number PM standards, as well as the other considerations identified elsewhere throughout this preamble. The EPA does not believe it would be feasible to repropose more stringent PM standards and also meet the international effective date of the new mass and number standards. Should the United States miss the January 1, 2023, deadline, U.S. airplane and engine manufacturers could be forced to seek PM emissions certification from an aviation certification of another country to market and operate their airplanes and engines internationally. The United States would also miss its obligations under the Chicago Convention.

The EPA believes that the limited scope of the proposal is permissible under CAA section 231 and, based on the plain language of the statute, disagrees with the premise that the statute requires the Agency to propose multiple levels of stringency of standards. To the extent commenters identified specific alternative levels of stringency they woul

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