62753 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
select the home retention option that 
they thought would be best for them. Under what circumstances, if any, should veterans retain opportunities to select from VA loss-mitigation options? How would giving veterans the ability to select from VA loss-mitigation options impact servicers? If VA were to switch to a prescribed order of loss- mitigation options that servicers must follow, what limitations, if any, should be placed on veterans’ ability to select from them? 
4. During the COVID–19 pandemic, 
certain loss-mitigation options were offered without the requirement of collecting financial information. Moving beyond the pandemic, under what circumstances should VA require servicers to collect financial information before a loss-mitigation option is selected? Under what circumstances might a trial payment plan serve as a substitute for the collection of financial information? 
Questions Related to Loan Deferment, 
VAPCP, and COVID–19 Refund Modifications 
5. How should VA develop a loan 
deferment option that would assist veterans without placing undue burden on servicers? For example, if VA were 
to incentivize a hybrid loan deferment/ repayment plan in which servicers would defer the missed principal and interest and establish a loan repayment plan for missed taxes and insurance, would that address potential concerns related to short-term lost income from deferring missed mortgage payments? For veterans, what consumer protection concerns should VA be aware of in considering a loan deferment loss- mitigation option? 
6. In what way(s), if any, should VA 
use the VAPCP and/or COVID–19 Refund Modification after the COVID– 19 national emergency? VA is particularly interested in data and evidence showing whether the VAPCP and/or COVID–19 Refund Modification programs have assisted veterans, servicers, and taxpayers. 
7. What challenges would exist for 
veterans, servicers, holders, and VA, if VA were to develop a loss-mitigation option similar to the VAPCP, but with a requirement for repayment at a low interest rate (rather than the zero percent interest rate under the VAPCP)? What hurdles might servicers face in executing such loan documents on behalf of VA? What if VA required servicers to service such loans on VA’s behalf? 
8. Would a low-interest second loan 
option similar to the VAPCP be more helpful to veterans and/or servicers than a loan deferment loss-mitigation option, and what data and evidence exist to support your response? What sort of financial evaluation would be appropriate to determine whether a low- interest second loan would be an appropriate loss-mitigation option for a veteran, as opposed to VA’s existing loss-mitigation options at 38 CFR 36.4319? 
9. What, if any, limitations should VA 
place on a deferment-style loss- mitigation option, including minimum/ maximum deferment amounts, lifetime uses, etc.? 
Questions Related to Incentive 
Payments 
10. What kind of incentive payment 
might be appropriate to make loan deferment a more viable option for servicers and VA? What kind of incentive payment might be appropriate for a loss-mitigation option similar to the VAPCP or COVID–19 Refund Modification? 
11. How could VA structure an 
incentive payment that does not encourage servicers to use one of these loss-mitigation options if more financially feasible options are available to assist the veteran? 
Questions Related to Investor 
Requirements 
12. What, if any, Government 
National Mortgage Association (Ginnie Mae) specific investor requirements should VA consider when evaluating changes to VA loss-mitigation options, including the introduction of a deferment-style loss-mitigation option? 
Executive Orders 12866 and 13563 
Executive Orders 12866 and 13563 
direct agencies to assess the costs and 
benefits of available regulatory alternatives and, when regulation is necessary, to select regulatory approaches that maximize net benefits (including potential economic, environmental, public health and safety effects, and other advantages; distributive impacts; and equity). Executive Order 13563 (Improving Regulation and Regulatory Review) emphasizes the importance of quantifying both costs and benefits, reducing costs, harmonizing rules, and promoting flexibility. The Office of Information and Regulatory Affairs has determined that this rule is a significant regulatory action under Executive Order 12866. The Regulatory Impact Analysis associated with this rulemaking can be found as a supporting document at www.regulations.gov. Signing Authority 
Denis McDonough, Secretary of 
Veterans Affairs, approved this 
document on October 11, 2022, and authorized the undersigned to sign and submit the document to the Office of the Federal Register for publication electronically as an official document of the Department of Veterans Affairs. 
Jeffrey M. Martin, 
Assistant Director, Office of Regulation Policy 
& Management, Office of General Counsel, Department of Veterans Affairs. 
[FR Doc. 2022–22414 Filed 10–14–22; 8:45 am] 
BILLING CODE 8320–01–P 
ENVIRONMENTAL PROTECTION 
AGENCY 
40 CFR Parts 87, 1031, and 1068 
[EPA–HQ–OAR–2022–0389; FRL–5934–01– 
OAR] 
RIN 2060–AT10 
Proposed Finding That Lead 
Emissions From Aircraft Engines That Operate on Leaded Fuel Cause or Contribute to Air Pollution That May Reasonably Be Anticipated To Endanger Public Health and Welfare 
AGENCY : Environmental Protection 
Agency (EPA). 
ACTION : Proposed action. 
SUMMARY : In this action, the 
Administrator is proposing to find that lead air pollution may reasonably be anticipated to endanger the public health and welfare within the meaning of section 231(a) of the Clean Air Act. The Administrator is also proposing to find that engine emissions of lead from certain aircraft cause or contribute to the 
lead air pollution that may reasonably be anticipated to endanger public health and welfare under section 231(a) of the Clean Air Act. 
DATES : 
Comments: Written comments must 
be received on or before January 17, 2023. 
Public Hearing: The EPA plans to 
hold a virtual public hearing on November 1, 2022. See 
SUPPLEMENTARY  
INFORMATION for information on 
registering for a public hearing. 
ADDRESSES : You may submit your 
comments, identified by Docket ID No. EPA–HQ–OAR–2022–0389, by any of the following methods: 
•Federal eRulemaking Portal: 
https://www.regulations.gov (our 
preferred method). Follow the online instructions for submitting comments. 
•Email: a-and-r-docket@epa.gov. 
Include Docket ID No. EPA–HQ–OAR– 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00015 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162754 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
1The FAA regulates ultralight vehicles under 14 
CFR part 103. 
2Rotorcraft encompass helicopters, gyroplanes, 
and any other heavier-than-air aircraft that depend 
principally for support in flight on the lift generated by one or more rotors. 2022–0389 in the subject line of the 
message. 
•Mail: U.S. Environmental 
Protection Agency, EPA Docket Center, OAR, Docket EPA–HQ–OAR–2022– 0389. Mail Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460. 
•Hand Delivery or Courier (by 
scheduled appointment only): EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. The Docket Center’s hours of operations are 8:30 a.m.–4:30 p.m., Monday–Friday (except federal holidays). 
Instructions: All submissions received 
must include the Docket ID No. for this action. Comments received may be posted without change to https://www.regulations.gov/, including any 
personal information provided. For detailed instructions on sending comments and additional information on the process for this action, see the ‘‘Public Participation’’ heading of the 
SUPPLEMENTARY INFORMATION section of 
this document. 
Public Hearing. EPA plans to hold a 
virtual public hearing for this action. Please refer to Participation in Virtual Public Hearing in the 
SUPPLEMENTARY  
INFORMATION section of this document 
for additional information. 
FOR FURTHER INFORMATION CONTACT : 
Marion Hoyer, Office of Transportation and Air Quality, Assessment and Standards Division (ASD), Environmental Protection Agency; Telephone number: (734) 214–4513; Email address: hoyer.marion@epa.gov. 
SUPPLEMENTARY INFORMATION : 
A. Public Participation 
Written Comments: Submit your 
comments, identified by Docket ID No. EPA–HQ–OAR–2022–0389, at https://www.regulations.gov (our preferred 
method), or the other methods identified in the 
ADDRESSES section of 
this document. Once submitted, comments cannot be edited or withdrawn from the docket. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI), Proprietary Business Information (PBI), or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (including such 
content located on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI, PBI, or multimedia submissions, and general guidance on making effective comments, please visit https://www.epa.gov/dockets/commenting-epa- dockets. 
Documents to which the EPA refers in 
this proposed action are available online at https://www.regulations.gov/ in the 
docket for this action (Docket EPA–HQ– OAR–2022–0389). To access reference documents in-person and for additional assistance, please refer to the following instructions. 
The EPA plans to hold a virtual 
hearing on November 1, 2022. This hearing will be held using Zoom. In order to attend the virtual public hearing, all attendees (including those who will not be presenting verbal testimony) must register in advance. Upon publication of this document in the Federal Register, the EPA will begin 
registering speakers for the hearing. To register to speak at the virtual hearing, please use the instructions at https://www.epa.gov/regulations-emissions- vehicles-and-engines/regulations-lead- emissions-aircraft. If you have questions 
regarding registration, consult the person listed in the preceding 
FOR 
FURTHER INFORMATION CONTACT section of 
this document. The last day to register to speak at the hearing will be October 31, 2022. Prior to the hearing, the EPA will post a general agenda that will list registered speakers in approximate order at: https://www.epa.gov/ regulations-emissions-vehicles-and- engines/regulations-lead-emissions- aircraft. The EPA will make every effort 
to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearings to run either ahead of schedule or behind schedule. 
The EPA anticipates that each 
commenter will have 5 minutes to 
provide oral testimony. The EPA recommends submitting the text of your oral testimony as written comments to the docket for this action. The EPA may ask clarifying questions during the oral presentations but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral testimony and supporting information presented at the public hearing. 
If you require the services of a 
translator or special accommodations such as audio description, please identify these needs when you register 
for the hearing no later than October 24, 2022. The EPA may not be able to arrange accommodations without advanced notice. 
B. General Information Does this action apply to me? 
Regulated Entities: In this action, the 
EPA is proposing to make endangerment 
and cause or contribute findings for the lead air pollution and engine emissions of lead from certain aircraft. The classes of aircraft engines and of aircraft relevant to this proposed action are referred to as ‘‘covered aircraft engines’’ and as ‘‘covered aircraft,’’ respectively throughout this document. Covered aircraft engines in this context means any aircraft engine that is capable of using leaded aviation gasoline. Covered aircraft in this context means all aircraft and ultralight vehicles
1equipped with 
covered engines. Covered aircraft would, for example, include smaller piston-engine aircraft such as the Cessna 172 (single-engine aircraft) and the Beechcraft Baron G58 (twin-engine aircraft), as well as the largest piston- engine aircraft—the Curtiss C–46 and the Douglas DC–6. Other examples of covered aircraft would include rotorcraft,
2such as the Robinson R44 
helicopter, light-sport aircraft, and ultralight vehicles equipped with piston engines. Because the majority of covered aircraft are piston-engine powered, this document focuses on those aircraft (in some contexts the EPA refers to these same engines as reciprocating engines). All such references and examples used in this document are covered aircraft as defined in this paragraph. 
The proposed findings in this action, 
if finalized, would not themselves apply new requirements to entities other than the EPA and the Federal Aviation Administration (FAA). Specifically, if the EPA issues final findings that lead emissions from covered aircraft engines cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare, then the EPA would, under section 231 of the Clean Air Act, promulgate aircraft engine emission standards for that air pollutant. In contrast to the findings, those standards would apply to and have an effect on other entities outside the federal government. Entities potentially interested in this proposed action include those that manufacture 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00016 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162755 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
3E.O. 13045. Protection of Children From 
Environmental Health Risks and Safety Risks. 62 FR 
19885 (April 23, 1997). 4EPA (2006) A Framework for Assessing Health 
Risks of Environmental Exposures to Children. 
EPA, Washington, DC, EPA/600/R–05/093F, 2006. 
5EPA. Memorandum: Issuance of EPA’s 2021 
Policy on Children’s Health. October 5, 2021. 
Available at https://www.epa.gov/system/files/ documents/2021-10/2021-policy-on-childrens- health.pdf. 
6EPA. ‘‘Childhood Lifestages relating to 
Children’s Environmental Health.’’ Oct. 25, 2021. Retrieved from https://www.epa.gov/children/ childhood-lifestages-relating-childrens- environmental-health on Nov. 22, 2021. 7EPA (2013) ISA for Lead. Executive Summary 
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxvii– 
lxxxviii. EPA/600/R–10/075F, 2013. See also, National Toxicology Program (NTP) (2012) NTP Monograph: Health Effects of Low-Level Lead. Available at https://ntp.niehs.nih.gov/go/36443. 
8EPA (2013) ISA for Lead. Executive Summary 
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxvii– lxxxviii. EPA/600/R–10/075F, 2013. 
9EPA (2013) ISA for Lead. Section 1.9.4. ‘‘Pb 
Exposure and Neurodevelopmental Deficits in Children.’’ p. I–75. EPA/600/R–10/075F, 2013. and sell covered aircraft engines and 
covered aircraft in the United States and those who own or operate covered aircraft. Categories that may be 
regulated in a future regulatory action include, but are not limited to, those listed here: 
Category NAICSacode SICbcode Examples of potentially affected entities 
Industry ................... 3364412 3724 Manufacturers of new aircraft engines. 
Industry ................... 336411 3721 Manufacturers of new aircraft. 
Industry ................... 481219 4522 Aircraft charter services (i.e., general purpose aircraft used for a variety of spe-
cialty air and flying services). Aviation clubs providing a variety of air transpor-
tation activities to the general public. 
Industry ................... 611512 8249 and 8299 Flight Training. 
aNorth American Industry Classification System (NAICS). 
bStandard Industrial Classification (SIC) code. 
This table is not intended to be 
exhaustive, but rather provides a guide 
for readers regarding potentially regulated entities likely to be interested in this proposed action. This table lists examples of the types of entities that the EPA is now aware of that could potentially have an interest in this proposed action. If the EPA issues final affirmative findings under section 231(a) of the Clean Air Act regarding lead, the EPA would then undertake a future notice and comment rulemaking to issue emission standards, and the FAA would be required to prescribe regulations to ensure compliance with these emissions standards pursuant to section 232 of the Clean Air Act. Such findings also would trigger the FAA’s statutory mandate pursuant to 49 U.S.C. 44714 to prescribe standards for the composition or chemical or physical properties of an aircraft fuel or fuel additive to control or eliminate aircraft emissions which EPA has decided endanger public health or welfare under section 231(a) of the Clean Air Act. Other types of entities not listed in the table could also be interested and potentially affected by subsequent 
actions at some future time. If you have any questions regarding the scope of this proposed action, consult the person listed in the preceding 
FOR FURTHER  
INFORMATION CONTACT section of this 
document. 
C. Children’s Health 
Executive Order 130453requires 
agencies to identify and assess health 
and safety risks that may disproportionately affect children and ensure that activities address disproportionate risks to children. Children may be more vulnerable to environmental exposures and/or the associated health effects, and therefore more at risk than adults. These risks to children may arise because infants and children generally eat more food, drink more water and breathe more air relative 
to their size than adults do, and consequently may be exposed to relatively higher amounts of contaminants. In addition, normal childhood activity, such as putting hands in mouths or playing on the ground, can result in exposures to contaminants that adults do not typically have. Furthermore, environmental contaminants may pose health risks specific to children because children’s bodies are still developing. For example, during periods of rapid growth such as fetal development, infancy and puberty, their developing systems and organs may be more easily harmed.
4 
Protecting children’s health from 
environmental risks is fundamental to the EPA’s mission. Since the inception of Executive Order 13045, the understanding of children’s environmental health has broadened to include conception, infancy, early childhood and through adolescence until 21 years of age.
5Because 
behavioral and physiological characteristics can affect children’s environmental health risks, childhood and children’s health is viewed with an understanding of the concept of ‘‘lifestages,’’ which recognize unique growth and developmental periods through which all humans pass.
6 
This document includes discussion 
and analysis that is focused particularly on children. For example, as described in Sections III.A and V of this document, the scientific evidence has long been established demonstrating that young children (due to rapid growth and development of the brain) are vulnerable to a range of neurological effects resulting from exposure to lead. Low levels of lead in young children’s blood have been linked to adverse effects on intellect, concentration, and academic achievement, and as the EPA has previously noted ‘‘there is no evidence of a threshold below which there are no harmful effects on cognition from [lead] exposure.’’
7Evidence 
suggests that while some neurocognitive effects of lead in children may be transient, some lead-related cognitive effects may be irreversible and persist into adulthood, potentially contributing to lower educational attainment and financial well-being.
8The 2013 Lead 
ISA notes that in epidemiologic studies, postnatal (early childhood) blood lead levels are consistently associated with cognitive function decrements in children and adolescents.
9In Section 
II.A.5 of this document, we describe the number of children living near and attending school near airports and provide a proximity analysis of the potential for greater representation of children in the near-airport environment compared with neighboring areas. 
D. Environmental Justice 
Executive Order 12898 establishes 
federal executive policy on 
environmental justice. It directs federal agencies, to the greatest extent practicable and permitted by law, to make achieving environmental justice part of their mission by identifying and addressing, as appropriate, disproportionately high and adverse human health or environmental effects 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00017 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162756 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
1059 FR 7629 (Feb. 16, 1994). 
11Fair 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 regulatory Agency’s 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, EPA’s Environmental Justice During the Development of an Action. Available at https://www.epa.gov/sites/ default/files/2015-06/documents/considering-ej-in- rulemaking-guide-final.pdf. See also https://
www.epa.gov/environmentaljustice. 
1286 FR 7619 (Feb. 1, 2021). 
1376 FR 3821 (Jan. 18, 2011). 14EPA (2013) ISA for Lead. Section 5.4. 
‘‘Summary.’’ pp. 5–40 through 5–42. EPA, 
Washington, DC, EPA/600/R–10/075F, 2013. 
15EPA (2022) ‘‘America’s Children and the 
Environment.’’ Summary of blood lead levels in children updated in 2022, available at https://www.epa.gov/americaschildrenenvironment/ biomonitoring-lead. Data source: Centers for Disease 
Control and Prevention, National Report on Human Exposure to Environmental Chemicals. Blood Lead (2011–2018). Updated March 2022. Available at https://www.cdc.gov/exposurereport/report/pdf/ cgroup2_ LBXBPB_ 2011-p.pdf. 
16EPA (2013) ISA for Lead. Section 1.9.1. ‘‘Public 
Health Significance.’’ p. 1–68; Section 1.9.5. ‘‘Reversibility and Persistence of Neurotoxic Effects of Pb.’’ p. 1–76. EPA, Washington, DC, EPA/600/R– 
10/075F, 2013. 
17EPA (2022) Technical Support Document (TSD) 
for the EPA’s Proposed Finding that Lead Emissions from Aircraft Engines that Operate on Leaded Fuel Cause or Contribute to Air Pollution that May Reasonably Be Anticipated to Endanger Public Health and Welfare. EPA, Washington, DC, EPA– 420–R–22–025, 2022. Available in the docket for this action. of their programs, policies, and 
activities on people of color populations and low-income populations in the United States.
10The EPA defines 
environmental justice as the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies.
11 
Executive Order 14008 also calls on 
federal agencies to make achieving environmental justice part of their missions ‘‘by developing programs, policies, and activities to address the disproportionately high and adverse human health, environmental, climate- related and other cumulative impacts on disadvantaged communities, as well as the accompanying economic challenges of such impacts.’’
12It also declares a 
policy ‘‘to secure environmental justice and spur economic opportunity for disadvantaged communities that have been historically marginalized and overburdened by pollution and under- investment in housing, transportation, water and wastewater infrastructure and health care.’’ Under Executive Order 13563, federal agencies may consider equity, human dignity, fairness, and distributional considerations, where appropriate and permitted by law.
13 
The United States has made 
substantial progress in reducing lead exposure, but disparities remain along racial, ethnic, and socioeconomic lines. For example, blood lead levels in children from low-income households remain higher than those in children from higher income households, and the most exposed Black children still have 
higher blood lead levels than the most exposed non-Hispanic White children.
14 15 Depending on the levels 
and associated risk, such blood lead levels may lead to lifelong health effects and barriers to social and economic well-being.
16 
In this action, the EPA is undertaking 
an evaluation, under section 231(a)(2)(A) of the Clean Air Act, of whether emissions of lead from engines in covered aircraft may cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare. We are not proposing emission standards at this time, and therefore, our consideration of environmental justice is focused on describing populations living near airports in the United States. Section II.A.5 of this document, and the Technical Support Document
17for this 
action describe the scientific evidence and analyses conducted by the EPA that provide information about the disparity in residential location for some low- income populations, people of color and some indigenous peoples in the United States, particularly Alaska Natives, with regard to their proximity to some airports where covered aircraft operate. The information presented in Section II.A.5 of this document indicates that there is a greater prevalence of people of color and of low-income populations within 500 meters or one kilometer of some airports compared with people living more distant. If such differences were to contribute to disproportionate and adverse impacts on people of color and low-income populations, they could indicate a potential environmental justice concern. 
Table of Contents 
I. Executive Summary II. Overview and Context for This Proposal 
A. Background Information Helpful to 
Understanding This Proposal 
1. Piston-Engine Aircraft and the Use of 
Leaded Aviation Gasoline 
2. Emissions of Lead From Piston-Engine 
Aircraft 
3. Concentrations of Lead in Air 
Attributable to Emissions From Piston- 
Engine Aircraft 
4. Fate and Transport of Emissions of Lead 
From Piston-Engine Aircraft 
5. Consideration of Environmental Justice 
and Children in Populations Residing Near Airports 
B. Federal Actions To Reduce Lead 
Exposure 
C. History of Lead Endangerment Petitions 
for Rulemaking and the EPA Responses 
III. Legal Framework for This Action 
A. Statutory Text and Basis for This 
Proposal 
B. Considerations for the Endangerment 
and Cause or Contribute Analyses Under Section 231(a)(2)(A) 
C. Regulatory Authority for Emission 
Standards 
IV. The Proposed Endangerment Finding 
Under CAA Section 231 
A. Scientific Basis of the Endangerment 
Finding 
1. Lead Air Pollution 2. Health Effects and Lead Air Pollution 3. Welfare Effects and Lead Air Pollution B. Proposed Endangerment Finding 
V. The Proposed Cause or Contribute Finding 
Under CAA Section 231 
A. Proposed Definition of the Air Pollutant B. The Data Used To Evaluate the Proposed 
Cause or Contribute Finding 
C. Proposed Cause or Contribution Finding 
for Lead 
VI. Statutory Authority and Executive Order 
Reviews 
A. Executive Order 12866: Regulatory 
Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review 
B. Paperwork Reduction Act (PRA) C. Regulatory Flexibility Act (RFA) D. Unfunded Mandates Reform Act 
(UMRA) 
E. Executive Order 13132: Federalism 
F. Executive Order 13175: Consultation 
and Coordination With Indian Tribal Governments 
G. Executive Order 13045: Protection of 
Children From Environmental Health Risks and Safety Risks 
H. Executive Order 13211: Actions 
Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use 
I. National Technology Transfer and 
Advancement Act (NTTAA) 
J. Executive Order 12898: Federal Actions 
To Address Environmental Justice in Minority Populations and Low-Income Populations 
K. Determination Under Section 307(d) 
VII. Statutory Provisions and Legal Authority 
I. Executive Summary 
Pursuant to section 231(a)(2)(A) of the 
Clean Air Act (CAA or Act), the 
Administrator proposes to find that 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00018 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162757 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
18As noted in Section IV.A of this notice, the lead 
air pollution that we are considering in this 
proposed finding can occur as elemental lead or in lead-containing compounds. 
19EPA (2013) ISA for Lead. EPA, Washington, 
DC, EPA/600/R–10/075F, 2013. 
20EPA (2006) AQC for Lead. EPA, Washington, 
DC, EPA/600/R–5/144aF, 2006. 
21EPA (1986) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–83/028aF–dF, 1986. 
22EPA (1977) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
23As noted in Section V.A of this notice, the lead 
air pollutant we are considering in this proposed finding can occur as elemental lead or in lead- containing compounds. 24Under section 108(a)(2) of the CAA, air quality 
criteria are intended to ‘‘accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare which may be expected from the presence of [a] pollutant in the ambient air . . . .’’ Section 109 of the CAA directs the Administrator to propose and promulgate ‘‘primary’’ and ‘‘secondary’’ NAAQS for pollutants for which air quality criteria are issued. Under CAA section 109(d)(1), EPA must periodically complete a thorough review of the air quality criteria and the NAAQS and make such revisions as may be appropriate in accordance with sections 108 and 109(b) of the CAA. A fuller description of these legislative requirements can be found, for example, in the ISA (see 2013 Lead ISA, p. lxix). 
25Section 109(b)(1) defines a primary standard as 
one ‘‘the attainment and maintenance of which in the judgment of the Administrator, based on such criteria and allowing an adequate margin of safety, are requisite to protect the public health.’’ A secondary standard, as defined in section 109(b)(2), must ‘‘specify a level of air quality the attainment and maintenance of which, in the judgment of the Administrator, based on such criteria, is requisite to protect the public welfare from any known or anticipated adverse effects associated with the presence of [the] pollutant in the ambient air.’’ 26EPA (2013) ISA for Lead. EPA, Washington, 
DC, EPA/600/R–10/075F, 2013. 
27EPA (1977) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
28EPA (1986) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386), 
1986. 
29EPA (2006) AQC for Lead. EPA, Washington, 
DC, EPA/600/R–5/144aF, 2006. 
30EPA (2013) ISA for Lead. Section 3.1.1. 
‘‘Pathways for Pb Exposure.’’ p. 3–1. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
31EPA (2013) ISA for Lead. Section 3.7.1. 
‘‘Exposure.’’ p. 3–144. EPA, Washington, DC, EPA/ 600/R–10/075F, 2013. 
32EPA (2013) ISA for Lead. Section 6.2. ‘‘Fate and 
Transport of Pb in Ecosystems.’’ p. 6–62. EPA, 
Washington, DC, EPA/600/R–10/075F, 2013. 
33EPA (2013) ISA for Lead. Section 2.3. ‘‘Fate and 
Transport of Pb.’’ p. 2–24. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
34EPA (2013) ISA for Lead. Section 1.2.1. 
‘‘Sources, Fate and Transport of Ambient Pb;’’ p. 1– 6. Section 2.3. ‘‘Fate and Transport of Pb.’’ p. 2–24. EPA, Washington, DC, EPA/600/R–10/075F, 2013. emissions of lead from covered aircraft 
engines cause or contribute to lead air 
pollution that may reasonably be anticipated to endanger public health and welfare. Covered aircraft would, for example, include smaller piston-engine aircraft such as the Cessna 172 (single- engine aircraft) and the Beechcraft Baron G58 (twin-engine aircraft), as well as the largest piston-engine aircraft—the Curtiss C–46 and the Douglas DC–6. Other examples of covered aircraft would include rotorcraft, such as the Robinson R44 helicopter, light-sport aircraft, and ultralight vehicles equipped with piston engines. 
For purposes of this action, the EPA 
is proposing to define the ‘‘air pollution’’ referred to in section 231(a)(2)(A) of the CAA as lead, which we also refer to as the lead air pollution in this document.
18In proposing to find 
that the lead air pollution may reasonably be anticipated to endanger the public health and welfare, the EPA relies on the extensive scientific evidence critically assessed in the 2013 Integrated Science Assessment for Lead (2013 Lead ISA) and the previous Air Quality Criteria Documents (AQCDs) for Lead, which the EPA prepared to serve as the scientific foundation for periodic reviews of the National Ambient Air Quality Standards (NAAQS) for lead.
19 20 21 22  
Further, for purposes of this action, 
the EPA is proposing to define the ‘‘air pollutant’’ referred to in CAA section 231(a)(2)(A) as lead, which we also refer to as the lead air pollutant in this document.
23Accordingly, the 
Administrator is proposing to find that emissions of the lead air pollutant from covered aircraft engines cause or contribute to the lead air pollution that may reasonably be anticipated to endanger public health and welfare under CAA section 231(a)(2)(A). 
In addition to the proposed findings 
and the science on which they are based, this document includes an overview and background context helpful to understanding the source sector in the context of this proposal, a brief summary of some of the federal actions focused on reducing lead exposures, and the legal framework for this action. 
II. Overview and Context for This 
Proposal 
We summarize here background 
information that provides additional context for this proposed action. This includes information on the population of aircraft that have piston engines, information on the use of leaded aviation gasoline (avgas) in covered aircraft, physical and chemical characteristics of lead emissions from engines used in covered aircraft, concentrations of lead in air from these engine emissions, and the fate and transport of lead emitted by engines used in such aircraft. We also include here an analysis of populations residing near and attending school near airports and an analysis of potential environmental justice implications with regard to residential proximity to runways where covered aircraft operate. This section ends with a description of a broad range of federal actions to reduce lead exposure from a variety of environmental media and a summary of citizen petitions for rulemaking regarding lead emissions from covered aircraft and the EPA responses. 
A. Background Information Helpful to 
Understanding This Proposal 
This proposal draws extensively from 
the EPA’s scientific assessments for lead, which are developed as part of the EPA’s periodic reviews of the air quality criteria
24for lead and the lead 
NAAQS.25These scientific assessments 
provide a comprehensive review, synthesis, and evaluation of the most 
policy-relevant science that builds upon the conclusions of previous assessments. In the information that follows, we discuss and describe scientific evidence summarized in the most recent assessment, the 2013 Lead ISA
26as well as information 
summarized in previous assessments, including the 1977, 1986, and 2006 AQCDs.
27 28 29  
As described in the 2013 Lead ISA, 
lead emitted to ambient air is transported through the air and is distributed from air to other environmental media through deposition.
30Lead emitted in the past 
can remain available for environmental or human exposure for extended time in some areas.
31Depending on the 
environment where it is deposited, it may to various extents be resuspended into the ambient air, integrated into the media on which it deposits, or transported in surface water runoff to other areas or nearby waterbodies.
32 
Lead in the environment today may have been airborne yesterday or emitted to the air long ago.
33Over time, lead 
that was initially emitted to air can become less available for environmental circulation by sequestration in soil, sediment and other reservoirs.
34 
The multimedia distribution of lead 
emitted into ambient air creates multiple air-related pathways of human and ecosystem exposure. These pathways may involve media other than air, including indoor and outdoor dust, soil, surface water and sediments, vegetation and biota. The human exposure pathways for lead emitted into air include inhalation of ambient air or ingestion of food, water or other materials, including dust and soil, that have been contaminated through a pathway involving lead deposition from 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00019 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162758 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
35EPA (2013) ISA for Lead. Section 3.1.1. 
‘‘Pathways for Pb Exposure.’’ p. 3–1. EPA, 
Washington, DC, EPA/600/R–10/075F, 2013. 
36EPA (2013) ISA for Lead. Sections 1.3. 
‘‘Exposure to Ambient Pb.’’ p. 1–11. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
37EPA (2013) ISA for Lead. Sections 3.4.1. ‘‘Pb in 
Blood.’’ p. 3–85; Section 5.4. ‘‘Summary.’’ p. 5–40. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
38EPA (2006) AQC for Lead. Chapter 3. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 
39EPA (1986) AQC for Lead. Section 1.11.3. EPA, 
Washington, DC, EPA–600/8–83/028aF-dF (NTIS 
PB87142386), 1986. 
40EPA (1977) AQC for Lead. Section 12.3.1.1. 
‘‘Air Exposures.’’ p. 12–10. EPA, Washington, DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
41EPA (1977) AQC for Lead. Section 12.3.1.2. 
‘‘Air Exposures.’’ p. 12–10. EPA, Washington, DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
42EPA (1977) AQC for Lead. Section 12.3.1.1. 
‘‘Air Exposures.’’ p. 12–10. EPA, Washington, DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
43Miranda et al., 2011. A Geospatial Analysis of 
the Effects of Aviation Gasoline on Childhood Blood Lead Levels. Environmental Health Perspectives. 119:1513–1516. 
44Zahran et al., 2017. The Effect of Leaded 
Aviation Gasoline on Blood Lead in Children. Journal of the Association of Environmental and Resource Economists. 4(2):575–610. 45Klemick et al., 2022. Cardiovascular Mortality 
and Leaded Aviation Fuel: Evidence from Piston- 
Engine Air Traffic in North Carolina. International 
Journal of Environmental Research and Public Health. 19(10):5941. 
46ASTM International (May 1, 2021) Standard 
Specification for Leaded Aviation Gasolines D910– 21. 
47National Academies of Sciences, Engineering, 
and Medicine (NAS). 2021. Options for Reducing Lead Emissions from Piston-Engine Aircraft. Washington, DC: The National Academies Press. https://doi.org/10.17226/26050. 
48Ogston 1981. A Short History of Aviation 
Gasoline Development, 1903–1980.Society of Automotive Engineers. p. 810848. 49U.S. Department of Commerce Civil 
Aeronautics Administration. Statistical Handbook of Aviation (Years 1930–1959). https:// babel.hathitrust.org/cgi/pt?id=mdp.39015027813032&view=1up&seq=899. 
50U.S. Department of Commerce Civil 
Aeronautics Administration. Statistical Handbook of Aviation (Years 1960–1971). https:// babel.hathitrust.org/cgi/ pt?id=mdp.39015004520279&view=1up&seq=9&skin=2021. 
51DOE. EIA. Petroleum and Other Liquids; 
Supply and Disposition. Aviation Gasoline in Annual Thousand Barrels. Fuel production volume data obtained from https://www.eia.gov/dnav/pet/ pet_sum_ snd_ a_eppv_ mbbl_ a_cur-1.htm and 
https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=C400000001&f=A on 
Dec., 30, 2021. 
52Department of Transportation (DOT). FAA. 
Aviation Policy and Plans. FAA Aerospace Forecast Fiscal Years 2009–2025. p. 81. Available at http:// 
www.faa.gov/data_ research/aviation/aerospace_
forecasts/2009-2025/media/ 2009%20Forecast%20Doc.pdf. This document 
provides historical data for 2000–2008 as well as forecast data. 
53DOT. FAA. Aviation Policy and Plans. Table 
23. p. 111. FAA Aerospace Forecast Fiscal Years 2021–2041. Available at https://www.faa.gov/sites/ faa.gov/files/data _research/aviation/aerospace_
forecasts/FY2021-41_ FAA_ Aerospace_ Forecast.pdf. ambient air.35Ambient air inhalation 
pathways include both inhalation of air 
outdoors and inhalation of ambient air that has infiltrated into indoor environments.
36The air-related 
ingestion pathways occur as a result of lead emissions to air being distributed to other environmental media, where humans can be exposed to it via contact with and ingestion of indoor and outdoor dusts, outdoor soil, food and drinking water. 
The scientific evidence documents 
exposure to many sources of lead emitted to the air that have resulted in higher blood lead levels, particularly for people living or working near sources, including stationary sources, such as mines and smelters, and mobile sources, such as cars and trucks when lead was a gasoline additive.
37 38 39 40 41 42  
Similarly, with regard to emissions from engines used in covered aircraft there have been studies reporting positive associations of children’s blood lead levels with proximity to airports and activity by covered aircraft,
43 44thus 
indicating potential for children’s exposure to lead from covered aircraft engine emissions. A recent study evaluating cardiovascular mortality rates in adults 65 and older living within a few kilometers and downwind of runways, while not evaluating blood lead levels, found higher mortality rates in adults living near single-runway airports in years with more piston- engine air traffic, but not in adults living near multi-runway airports, suggesting the potential for adverse adult health 
effects near some airports.
45 
1. Piston-Engine Aircraft and the Use of Leaded Aviation Gasoline 
Aircraft operating in the U.S. are 
largely powered by either turbine engines or piston engines, although other propulsion systems are in use and in development. Turbine-engine powered aircraft and a small percentage of piston-engine aircraft (i.e., those with 
diesel engines) operate on fuel that does not contain a lead additive. Covered aircraft, which are predominantly piston-engine powered aircraft, operate on leaded avgas. Examples of covered aircraft include smaller piston-powered aircraft such as the Cessna 172 (single- engine aircraft) and the Beechcraft Baron G58 (twin-engine aircraft), as well as the largest piston-engine aircraft—the Curtiss C–46 and the Douglas DC–6. Additionally, some rotorcraft, such as the Robinson R44 helicopter, light-sport aircraft, and ultralight vehicles can have piston engines that operate using leaded avgas. 
Lead is added to avgas in the form of 
tetraethyl lead. Tetraethyl lead helps boost fuel octane, prevents engine knock, and prevents valve seat recession and subsequent loss of compression for engines without hardened valves. There are three main types of leaded avgas: 100 Octane, which can contain up to 4.24 grams of lead per gallon (1.12 grams of lead per liter), 100 Octane Low Lead (100LL), which can contain up to 2.12 grams of lead per gallon (0.56 grams of lead per liter), and 100 Octane Very Low Lead (100VLL), which can contain up to 0.71 grams of lead per gallon (0.45 grams of lead per liter).
46 
Currently, 100LL is the most commonly available and most commonly used type of avgas.
47Tetraethyl lead was first used 
in piston-engine aircraft in 1927.48 
Commercial and military aircraft in the U.S. operated on 100 Octane leaded avgas into the 1950s, but in subsequent years, the commercial and military aircraft fleet largely converted to turbine-engine powered aircraft which do not use leaded avgas.
49 50The use of 
avgas containing approximately 4 grams of lead per gallon continued in piston- engine aircraft until the early 1970s when 100LL became the dominant leaded fuel in use. 
There are two sources of data from the 
federal government that provide annual estimates of the volume of leaded avgas supplied and consumed in the U.S.: the Department of Energy, Energy Information Administration (DOE EIA) provides information on the volume of leaded avgas supplied in the U.S.,
51and 
the FAA provides information on the volume of leaded avgas consumed in the U.S.
52Over the ten-year period from 
2011 through 2020, DOE estimates of the annual volume of leaded avgas supplied averaged 184 million gallons, with year-on-year fluctuations in fuel supplied ranging from a 25 percent increase to a 29 percent decrease. Over the same period, from 2011 through 2020, the FAA estimates of the annual volume of leaded avgas consumed averaged 196 million gallons, with year- on-year fluctuations in fuel consumed ranging from an eight percent increase to a 14 percent decrease. The FAA forecast for consumption of leaded avgas in the U.S. ranges from 185 million gallons in 2026 to 179 million gallons in 2041, a decrease of three percent in that period.
53As described 
later in this section, while the consumption of leaded avgas is expected to decrease three percent from 2026 to 2041, FAA projects increased activity at some airports and decreased activity at other airports out to 2045. 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00020 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162759 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
54See FAA. NASR. Available at https://
www.faa.gov/air_ traffic/flight_ info/aeronav/aero_
data/eNASR_ Browser/. 
55FAA (2020) National Plan of Integrated Airport 
Systems (NPIAS) 2021–2025 Published by the 
Secretary of Transportation Pursuant to Title 49 U.S. Code, Section 47103. Retrieved on Nov. 3, 2021 from: https://www.faa.gov/airports/planning _
capacity/npias/current/media/NPIAS-2021-2025- Narrative.pdf. 
56See FAA’s NASR. Available at https://
www.faa.gov/air_ traffic/flight_ info/aeronav/aero_
data/eNASR_ Browser/. 
57FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 1: Historical General Aviation and Air Taxi Measures. Table 1.1— General Aviation and Part 135 Number of Active Aircraft By Aircraft Type 2008–2019. Retrieved on Dec., 27, 2021 at https://www.faa.gov/data_research/aviation_ data_ statistics/general_ aviation/ 
CY2019/. Separately, FAA maintains a database of 
FAA-registered aircraft and as of January 6, 2022 there were 222,592 piston-engine aircraft registered with FAA. See: https://registry.faa.gov/ aircraftinquiry/. 
58FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 1: Historical General Aviation and Air Taxi Measures. Table 1.1— General Aviation and Part 135 Number of Active Aircraft By Aircraft Type 2008–2019. Retrieved on Dec., 27, 2021 at https://www.faa.gov/data_research/aviation_ data_ statistics/general_ aviation/ 
CY2019/. 
59General Aviation Manufacturers Association 
(GAMA) (2019) General Aviation Statistical Databook and Industry Outlook, p.27. Retrieved on October 7, 2021 from: https://gama.aero/wp- content/uploads/GAMA_ 2019Databook_ Final-2020- 
03-20.pdf. 
60GAMA (2019) General Aviation Statistical 
Databook and Industry Outlook, p.16. Retrieved on October 7, 2021 from: https://gama.aero/wp- 
content/uploads/GAMA_ 2019Databook_ Final-2020- 
03-20.pdf. 
61There are both fixed-wing and rotary-wing 
aircraft; and airplane is an engine-driven, fixed- wing aircraft and a rotorcraft is an engine-driven rotary-wing aircraft. 
62See FAA Aerospace Forecast Fiscal Years 
2021–2041. p. 28. Available at https://www.faa.gov/ sites/faa.gov/files/data_ research/aviation/ 
aerospace_ forecasts/FY2021-41_ FAA_ Aerospace_
Forecast.pdf. 
63FAA Aerospace Forecast Fiscal Years 2021– 
2041. Table 28. p. 116., and Table 29. p. 117. Available at https://www.faa.gov/sites/faa.gov/files/ data_ research/aviation/aerospace_ forecasts/ 
FY2021-41_ FAA_ Aerospace_ Forecast.pdf. 
64FAA. U.S. Civil Airmen Statistics. 2021 Active 
Civil Airman Statistics. Retrieved from https://
www.faa.gov/data_ research/aviation_ data_
statistics/civil_ airmen_ statistics on May 20, 2022. 
65FAA. U.S. Civil Airmen Statistics. 2021 Active 
Civil Airman Statistics. Retrieved from https://www.faa.gov/data_ research/aviation_ data_
statistics/civil_ airmen_ statistics on May 20, 2022. 
66FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 1: Historical General Aviation and Air Taxi Measures. Table 1.4— General Aviation and Part 135 Total Hours Flown By Actual Use 2008–2019 (Hours in Thousands). Retrieved on Dec., 27, 2021 at https://www.faa.gov/ data_ research/aviation_ data_ statistics/general_
aviation/CY2019/. 67FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 3: Primary and Actual 
Use. Table 3.2—General Aviation and Part 135 Total Hours Flown by Actual Use 2008–2019 (Hours in Thousands). Retrieved on Mar., 22, 2022 at https://www.faa.gov/data_ research/aviation_
data_ statistics/general_ aviation/CY2019/. 
68FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 3: Primary and Actual Use. Table 3.2—General Aviation and Part 135 Total Hours Flown by Actual Use 2008–2019 (Hours in Thousands). Retrieved on Mar., 22, 2022 at https://www.faa.gov/data_ research/aviation_
data_ statistics/general_ aviation/CY2019/. 
69FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 3: Primary and Actual Use. Table 1.3—General Aviation and Part 135 Total Hours Flown by Aircraft Type 2008–2019 (Hours in Thousands). Retrieved on Dec., 27, 2021 at https://www.faa.gov/data_ research/aviation_
data_ statistics/general_ aviation/CY2019/. 
70In 2012, the FAA Aerospace Forecast projected 
a 0.03 percent increase in hours flown by the piston-engine aircraft fleet for the period 2012 through 2032. FAA Aerospace Forecast Fiscal Years 2012–2032. p. 53. Available at https://www.faa.gov/ data_ research/aviation/aerospace_ forecasts/media/ 
2012%20FAA%20Aerospace%20Forecast.pdf. 
71See FAA’s Air Traffic Activity Data. Available 
at https://aspm.faa.gov/opsnet/sys/airport.asp. The FAA’s National Airspace System 
Resource (NASR)54provides a complete 
list of operational airport facilities in the 
U.S. Among the approximately 19,600 airports listed in the NASR, approximately 3,300 are included in the National Plan of Integrated Airport Systems (NPIAS) and support the majority of piston-engine aircraft activity that occurs annually in the U.S.
55While less aircraft activity occurs 
at the remaining 15,336 airports, that activity is conducted predominantly by piston-engine aircraft. Approximately 6,000 airports have been in operation since the early 1970s when the leaded fuel being used contained up to 4.24 grams of lead per gallon of avgas.
56The 
activity by piston-engine aircraft spans a range of purposes, as described further below. In Alaska this fleet of aircraft currently play a critical role in the transportation infrastructure. 
As of 2019, there were 171,934 piston- 
engine aircraft in the U.S.
57This total 
includes 128,926 single-engine aircraft, 
12,470 twin-engine aircraft, and 3,089 rotorcraft.
58The average age of single- 
engine aircraft in 2018 was 46.8 years and the average age of twin-engine aircraft in 2018 was 44.7 years old.
59In 
2019, 883 new piston-engine aircraft were manufactured in the U.S. some of which are exported.
60For the period from 2019 through 2041, the fleet of 
fixed wing61piston-engine aircraft is 
projected to decrease at an annual average rate of 0.9 percent, and the hours flown by these aircraft is projected to decrease 0.9 percent per year from 2019 to 2041.
62An annual 
average growth rate in the production of piston-engine powered rotorcraft of 0.9 percent is forecast, with a commensurate 1.9 percent increase in hours flown in that period by piston- engine powered rotorcraft.
63There were 
approximately 664,565 pilots certified to fly general aviation aircraft in the U.S. in 2021.
64This included 197,665 
student pilots and 466,900 non-student pilots. In addition, there were more than 301,000 FAA Non-Pilot Certificated mechanics.
65 
Piston-engine aircraft are used to 
conduct flights that are categorized as either general aviation or air taxi. General aviation flights are defined as all aviation other than military and those flights by scheduled commercial airlines. Air taxi flights are short duration flights made by small commercial aircraft on demand. The hours flown by aircraft in the general aviation fleet are comprised of personal and recreational transportation (67 percent), business (12 percent), instructional flying (8 percent), medical transportation (less than one percent), and the remainder includes hours spent in other applications such as aerial observation and aerial application.
66 
Aerial application for agricultural activity includes crop and timber production, which involve fertilizer and pesticide application and seeding cropland. In 2019, aerial application in agriculture represented 883,600 hours flown by general aviation aircraft, and approximately 17.5 percent of these total hours were flown by piston-engine aircraft.
67 
Approximately 71 percent of the 
hours flown that are categorized as general aviation activity are conducted by piston-engine aircraft, and 17 percent of the hours flown that are categorized as air taxi are conducted by piston- engine aircraft.
68From the period 2012 
through 2019, the total hours flown by piston-engine aircraft increased nine percent from 13.2 million hours in 2012 to 14.4 million hours in 2019.
69 70 
As noted earlier, the U.S. has a dense 
network of airports where piston-engine aircraft operate, and a small subset of those airports have air traffic control 
towers which collect daily counts of aircraft operations at the facility (one takeoff or landing event is termed an ‘‘operation’’). These daily operations are provided by the FAA in the Air Traffic Activity System (ATADS).
71The 
ATADS reports three categories of airport operations that can be conducted by piston-engine aircraft: Itinerant General Aviation, Local Civil, and Itinerant Air Taxi. The sum of Itinerant General Aviation and Local Civil at a facility is referred to as general aviation operations. Piston-engine aircraft operations in these categories are not reported separately from operations conducted by aircraft using other propulsion systems (e.g., turboprop). 
Because piston-engine aircraft activity generally comprises the majority of general aviation activity at an airport, 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00021 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162760 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
72Geidosch. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Past Trends and Future 
Projections in General Aviation Activity and Emissions. June 1, 2022. Docket ID EPA–HQ–2022– 0389. 
73FAA’s TAF Fiscal Years 2020–2045 describes 
the forecast method, data sources, and review process for the TAF estimates. The documentation for the TAF is available at https://taf.faa.gov/ Downloads/TAFSummaryFY2020-2045.pdf. 74The TAF is prepared to assist the FAA in 
meeting its planning, budgeting, and staffing requirements. In addition, state aviation authorities and other aviation planners use the TAF as a basis for planning airport improvements. The TAF is available on the internet. The TAF database can be accessed at: https://taf.faa.gov. 
75EPA (1977) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–77–017 (NTIS PB280411), 1977. 
76EPA (1986) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386), 1986. 
77EPA (2013) ISA for Lead. Section 2.2.2.1 ‘‘Pb 
Emissions from Piston-engine Aircraft Operating on Leaded Aviation Gasoline and Other Non-road Sources.’’ p. 2–10. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 78EPA (1986) AQC for Lead. EPA, Washington, 
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386), 
1986. 
79Griffith 2020. Electron microscopic 
characterization of exhaust particles containing lead 
dibromide beads expelled from aircraft burning leaded gasoline. Atmospheric Pollution Research 11:1481–1486. 
80EPA (1986) AQC for Lead. Volume 2: Chapters 
5 & 6. EPA, Washington, DC, EPA–600/8–83/028aF– dF (NTIS PB87142386), 1986. 
81EPA (2013) ISA for Lead. Table 2–1. ‘‘Pb 
Compounds Observed in the Environment.’’ p. 2– 8. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
82EPA (2013) ISA for Lead. Section 2.2.2.1 ‘‘Pb 
Emissions from Piston-engine Aircraft Operating on Leaded-Aviation Gasoline and Other Non-road Sources.’’ p. 2–10. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 
83Memorandum to Docket EPA–HQ–OAR–2022– 
0389. Potential Exposure to Non-exhaust Lead and Ethylene Dibromide. June 15, 2022. Docket ID EPA– HQ–2022–0389. general aviation activity is often used as 
a surrogate measure for understanding piston-engine activity. 
In order to understand the trend in 
airport-specific piston-engine activity in the past ten years, we evaluated the trend in general aviation activity. We calculated the average activity at each of the airports in ATADS over three-year periods for the years 2010 through 2012 and for the years 2017 through 2019. We focused this trend analysis on the airports in ATADS because these data are collected daily at an airport-specific control tower (in contrast with annual activity estimates provided at airports without control towers). There were 513 airports in ATADS for which data were available to determine annual average activity for both the 2010–2012 period and the 2017–2019 time period. The annual average operations by general aviation at each of these airports in the period 2010 through 2012 ranged from 31 to 346,415, with a median of 34,368; the annual average operations by general aviation in the period from 2017 through 2019 ranged from 2,370 to 396,554, with a median of 34,365. Of the 513 airports, 211 airports reported increased general aviation activity over the period evaluated.
72The increase in 
the average annual number of operations by general aviation aircraft at these 211 facilities ranged from 151 to 136,872 (an increase of two percent and 52 percent, respectively). 
While national consumption of leaded 
avgas is forecast to decrease three percent from 2026 to 2045, this change in fuel consumption is not expected to occur uniformly across airports in the U.S. The FAA produces the Terminal Area Forecast (TAF), which is the official forecast of aviation activity for the 3,300 U.S. airports that are in the NPIAS.
73For the 3,306 airports in the 
TAF, we compared the average activity by general aviation at each airport from 2017–2019 with the FAA forecast for general aviation activity at those airports in 2045. The FAA forecasts that activity by general aviation will decrease at 234 of the airports in the TAF, remain the same at 1,960 airports, and increase at 1,112 of the airports. To evaluate the magnitude of potential increases in activity for the same 513 airports for which we evaluated activity trends in the past ten years, we 
compared the 2017–2019 average general aviation activity at each of these airports with the forecasted activity for 2045 in the TAF.
74The annual 
operations estimated for the 513 airports in 2045 ranges from 2,914 to 427,821 with a median of 36,883. The TAF forecasts an increase in activity at 442 of the 513 airports out to 2045, with the increase in operations at those facilities ranging from 18 to 83,704 operations annually (an increase of 0.2 percent and 24 percent, respectively). 
2. Emissions of Lead From Piston- 
Engine Aircraft 
This section describes the physical 
and chemical characteristics of lead emitted by covered aircraft, and the national, state, county and airport- specific annual inventories of these engine emissions of lead. Information regarding lead emissions from motor vehicle engines operating on leaded fuel is summarized in prior AQCDs for Lead, and the 2013 Lead ISA also includes information on lead emissions from piston-engine aircraft.
75 76 77 Lead is 
added to avgas in the form of tetraethyl lead along with ethylene dibromide, both of which were used in leaded gasoline for motor vehicles in the past. Therefore, the summary of the science regarding emissions of lead from motor vehicles presented in the 1997 and 1986 AQCDs for Lead is relevant to understanding some of the properties of lead emitted from piston-engine aircraft and the atmospheric chemistry these emissions are expected to undergo. Recent studies relevant to understanding lead emissions from piston-engine aircraft have also been published and are discussed here. 
a. Physical and Chemical Characteristics 
of Lead Emitted by Piston-Engine Aircraft 
As with motor vehicle engines, when 
leaded avgas is combusted, the lead is oxidized to form lead oxide. In the 
absence of the ethylene dibromide lead scavenger in the fuel, lead oxide can collect on the valves and spark plugs, 
and if the deposits become thick enough, the engine can be damaged. Ethylene dibromide reacts with the lead oxide, converting it to brominated lead and lead oxybromides. These brominated forms of lead remain volatile at high combustion temperatures and are emitted from the engine along with the other combustion by-products.
78Upon cooling to ambient 
temperatures these brominated lead compounds are converted to particulate matter. The presence of lead dibromide particles in the exhaust from a piston- engine aircraft has been confirmed by Griffith (2020) and is the primary form of lead emitted by engines operating on leaded fuel.
79In addition to lead 
bromides, ammonium salts of other lead halides were also emitted by motor vehicles and would be expected in the exhaust of piston-engine aircraft.
80 
Uncombusted alkyl lead was also 
measured in the exhaust of motor vehicles operating on leaded gasoline and is therefore likely to be present in the exhaust from piston-engine aircraft.
81Alkyl lead is the general term 
used for organic lead compounds and includes the lead additive tetraethyl lead. Summarizing the available data regarding emissions of alkyl lead from piston-engine aircraft, the 2013 Lead ISA notes that lead in the exhaust that might be in organic form may potentially be 20 percent (as an upper bound estimate).
82In addition, 
tetraethyl lead is a highly volatile compound and therefore, a portion of tetraethyl lead in fuel exposed to air will partition into the vapor phase.
83 
Particles emitted by piston-engine 
aircraft are in the submicron size range (less than one micron in diameter). The Swiss Federal Office of Civil Aviation (FOCA) published a study of piston- engine aircraft emissions including 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00022 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162761 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
84Swiss FOCA (2007) Aircraft Piston Engine 
Emissions Summary Report. 33–05–003 Piston 
Engine Emissions_ Swiss FOCA_ Summary. Report_
070612_ rit. Available at https:// 
www.bazl.admin.ch/bazl/en/home/specialists/ regulations-and-guidelines/environment/pollutant- emissions/aircraft-engine-emissions/report- appendices-database-and-data-sheets.html. 
85Swiss FOCA (2007) Aircraft Piston Engine 
Emissions Summary Report. 33–05–003 Piston Engine Emissions_ Swiss FOCA_ Summary. Report_
070612_ rit. Section 2.2.3.a. Available at https:// 
www.bazl.admin.ch/bazl/en/home/specialists/ 
regulations-and-guidelines/environment/pollutant- emissions/aircraft-engine-emissions/report- appendices-database-and-data-sheets.html. 
86The lead inventories for 2008, 2011 and 2014 
are provided in the U.S. EPA (2018b) Report on the Environment Exhibit 2. Anthropogenic lead emissions in the U.S. Available at https://cfpub.epa.gov/roe/indicator.cfm?i=13#2. 
87EPA 2017 NEI. Available at https://
www.epa.gov/air-emissions-inventories/2017- national-emissions-inventory-nei-data. 
88Advance Notice of Proposed Rulemaking on 
Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline. 75 FR 2440 (April 28, 
2010). 
89Airport lead annual emissions data used were 
reported in the 2017 NEI. Available at https://www.epa.gov/air-emissions-inventories/2017- national-emissions-inventory-nei-data. The 
methods used to develop these inventories are described in EPA (2010) Calculating Piston-Engine Aircraft Airport Inventories for Lead for the 2008 NEI. EPA, Washington, DC, EPA–420–B–10–044, 2010. (Also available in the docket for this action, EPA–HQ–OAR–2022–0389). 
90The 2017 NEI utilized 2014 aircraft activity 
data to develop airport-specific lead inventories. Details can be found on page 3–17 of the document located here: https://www.epa.gov/sites/default/ files/2021-02/documents/nei2017_ tsd_full_
jan2021.pdf#page=70&zoom=100,68,633. 
91Lead emitted in-flight is assigned to states 
based on their overall fraction of total piston-engine aircraft operations. The state-level estimates of 
engine emissions of lead include both lead emitted in the landing and takeoff cycle as well as lead emitted in-flight. The method used to develop these estimates is described in EPA (2010) Calculating Piston-Engine Aircraft Airport Inventories for Lead for the 2008 NEI, available here: https://
nepis.epa.gov/Exe/ZyPDF.cgi/P1009I13.PDF?Dockey=P1009I13.PDF. 
92Airport lead annual emissions data used were 
reported in the 2017 NEI. Available at https://www.epa.gov/air-emissions-inventories/2017- 
national-emissions-inventory-nei-data. In addition 
to the triennial NEI, the EPA collects from state, local, and Tribal air agencies point source data for larger sources every year (see https://www.epa.gov/ air-emissions-inventories/air-emissions-reporting- requirements-aerr for specific emissions 
thresholds). While these data are not typically published as a new NEI, they are available publicly upon request and are also included in https://
www.epa.gov/air-emissions-modeling/emissions- modeling-platforms that are created for years other 
than the triennial NEI years. County estimates of lead emissions from non-aircraft sources used in this action are from the 2019 inventory. There are 3,012 counties and statistical equivalent areas where EPA estimates engine emissions of lead occur. 
93See EPA lead inventory data available at 
https://www.epa.gov/air-emissions-modeling/ emissions-modeling-platforms. measurements of lead.84The Swiss 
FOCA reported the mean particle 
diameter of particulate matter emitted by one single-engine piston-powered aircraft ranged from 0.049 to 0.108 microns under different power conditions (lead particles would be expected to be present, but these particles were not separately identified in this study). The particle number concentration ranged from 5.7x10
6to 
8.6x106particles per cm3. The authors 
noted that these particle emission rates are comparable to those from a typical diesel passenger car engine without a particle filter.
85Griffith (2020) collected 
exhaust particles from a piston-engine aircraft operating on leaded avgas and examined the particles using electron microscopy. Griffith reported that the mean diameter of particles collected in exhaust was 13 nanometers (0.013 microns) consisting of a 4 nanometer (0.004 micron) lead dibromide particle surrounded by hydrocarbons. 
b. Inventory of Lead Emitted by Piston- 
Engine Aircraft 
Lead emissions from covered aircraft 
are the largest single source of lead to air in the U.S. in recent years, contributing over 50 percent of lead emissions to air starting in 2008 (Table 1).
86In 2017, approximately 470 tons of 
lead were emitted by engines in piston- powered aircraft, which constituted 70 percent of the annual emissions of lead to air in that year.
87Lead is emitted at 
and near thousands of airports in the U.S. as described in Section II.A.1 of this document. The EPA’s method for developing airport-specific lead estimates is described in the EPA’s Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline
88and in the 
document titled ‘‘Calculating Piston- Engine Aircraft Airport Inventories for Lead for the 2008 National Emissions Inventory.’’
89The EPA’s National 
Emissions Inventory (NEI) reports airport estimates of lead emissions as well as estimates of lead emitted in- flight, which are allocated to states based on the fraction of piston-engine aircraft activity estimated for each state. These inventory data are briefly summarized here at the state, county, and airport level.
90 
TABLE 1—P ISTON -ENGINE EMISSIONS OF LEAD TO AIR 
2008 2011 2014 2017 
Piston-engine emissions of lead to air, tons ................................................... 560 490 460 470 
Total U.S. lead emissions, tons ....................................................................... 950 810 720 670 
Piston-engine emissions as a percent of the total U.S. lead inventory .......... 59% 60% 64% 70% 
At the state level, the EPA estimates 
of lead emissions from piston-engine 
aircraft range from 0.3 tons (Rhode Island) to 50.5 tons (California), 47 percent of which is emitted in the landing and takeoff cycle and 53 percent of which the EPA estimates is emitted in-flight, outside the landing and takeoff cycle.
91Among the counties in the U.S. 
where the EPA estimates engine emissions of lead from covered aircraft, lead inventories range from 0.00005 tons per year to 4.1 tons per year and constitute the only source of air-related 
lead in 1,140 counties (the county estimates of lead emissions include the lead emitted during the landing and 
takeoff cycle and not lead emitted in- flight).
92In the counties where engine 
emissions of lead from aircraft are the sole source of lead to these estimates, annual lead emissions from the landing and takeoff cycle ranged from 0.00015 to 0.74 tons. Among the 1,872 counties in the U.S. with multiple sources of lead, including engine emission from covered aircraft, the contribution of aircraft engine emissions ranges from 0.0006 to 0.26 tons, comprising 0.0065 to 99.98 percent of the county total, respectively. 
The EPA estimates that among the 
approximately 20,000 airports in the U.S., airport lead inventories range from 
0.00005 tons per year to 0.9 tons per year.
93In 2017, the EPA’s NEI includes 
638 airports where the EPA estimates engine emissions of lead from covered aircraft were 0.1 ton or more of lead annually. Using the FAA’s forecasted activity in 2045 for the approximately 3,300 airports in the NPIAS (as described in Section II.A.1 of this document), the EPA estimates airport- specific inventories may range from 0.00003 tons to 1.28 tons of lead (median of 0.03 tons), with 656 airports 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00023 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162762 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
94EPA used the method describe in EPA (2010) 
Calculating Piston-Engine Aircraft Airport 
Inventories for Lead for the 2008 NEI to estimate airport lead inventories in 2045. This document is available here: https://nepis.epa.gov/Exe/ ZyPDF.cgi/P1009I13.PDF?Dockey=P1009I13.PDF. 
95Geidosch. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Lead Emissions from the use of Leaded Aviation Gasoline from 1930 through 2020. June 1, 2022. Docket ID EPA–HQ–2022–0389. 
96Carr et. al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment, 45 (32), 5795–5804. DOI: https://dx.doi.org/10.1016/j.atmosenv.
2011.07.017. 
97Feinberg et. al., 2016. Modeling of Lead 
Concentrations and Hot Spots at General Aviation Airports. Journal of the Transportation Research 
Board, No. 2569, Transportation Research Board, 
Washington, DC, pp. 80–87. DOI: 10.3141/2569–09. 
98Municipality of Anchorage (2012). Merrill Field 
Lead Monitoring Report. Municipality of Anchorage Department of Health and Human Services. Anchorage, Alaska. Available at https://www.muni.org/Departments/health/Admin/environment/AirQ/Documents/Merrill%20Field%20Lead%20Monitoring%20Study_ 2012/Merrill
%20Field%20Lead%20Study%20Report%20-%20final.pdf. 
99Environment Canada (2000) Airborne 
Particulate Matter, Lead and Manganese at Buttonville Airport. Toronto, Ontario, Canada: Conor Pacific Environmental Technologies for Environmental Protection Service, Ontario Region. 
100Fine et. al., 2010. General Aviation Airport Air 
Monitoring Study. South Coast Air Quality Management District. Available at https://www.aqmd.gov/docs/default-source/air-quality/air-quality-monitoring-studies/general-aviation-study/study-of-air-toxins-near-van-nuys-and-santa-monica-airport.pdf. 
101Lead emitted from piston-engine aircraft in the 
particulate phase would also be measured in samples collected to evaluate total ambient PM
2.5 
concentrations. 102EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. EPA, Washington, DC, EPA–420–R–20–003, 2020. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG52.pdf. EPA responses to peer 
review comments on the report are available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YIWD.pdf. These documents are also available 
in the docket for this action (Docket EPA–HQ– OAR–2022–0389). 
103EPA (2022) Technical Support Document 
(TSD) for the EPA’s Proposed Finding that Lead Emissions from Aircraft Engines that Operate on Leaded Fuel Cause or Contribute to Air Pollution that May Reasonably Be Anticipated to Endanger Public Health and Welfare. EPA, Washington, DC, EPA–420–R–22–025, 2022. Available in the docket for this action. 
104These studies report monitored or modeled 
data for averaging times ranging from approximately 18 hours to three-month averages. 
105Carr et. al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment, 45 (32), 5795–5804. DOI: https://dx.doi.org/10.1016/j.atmosenv.
2011.07.017. 
106Heiken et. al., 2014. Quantifying Aircraft Lead 
Emissions at Airports. ACRP Report 133. Available at https://www.nap.edu/catalog/22142/quantifying-
aircraft-lead-emissions-at-airports. 
107Hudda et. al., 2022. Substantial Near-Field Air 
Quality Improvements at a General Aviation Airport Following a Runway Shortening. Environmental Science & Technology. DOI: 10.1021/ acs.est.1c06765. 
108Fine et. al., 2010. General Aviation Airport Air 
Monitoring Study. South Coast Air Quality Management District. Available at https://www.aqmd.gov/docs/default-source/air-quality/air-quality-monitoring-studies/general-aviation-study/study-of-air-toxins-near-van-nuys-and-santa-monica-airport.pdf. 
109EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. EPA, Washington, DC, EPA–420–R–20–003, 2020. 110EPA (2010) Development and Evaluation of an 
Air Quality Modeling Approach for Lead Emissions from Piston-Engine Aircraft Operating on Leaded Aviation Gasoline. EPA, Washington, DC, EPA– 420–R–10–007, 2010. https://nepis.epa.gov/Exe/ZyPDF.cgi/P1007H4Q.PDF?Dockey=P1007H4Q.PDF. 
111EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. EPA, Washington, DC, EPA–420–R–20–003, 2020. EPA responses to peer review comments on the report are available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YIWD.pdf. 
112Feinberg et. al., 2016. Modeling of Lead 
Concentrations and Hot Spots at General Aviation Airports. Journal of the Transportation Research 
Board, No. 2569, Transportation Research Board, 
Washington, DC, pp. 80–87. DOI: 10.3141/2569–09. 
113Feinberg et. al., 2016. Modeling of Lead 
Concentrations and Hot Spots at General Aviation Airports. Journal of the Transportation Research 
Board, No. 2569, Transportation Research Board, 
Washington, DC, pp. 80–87. DOI: 10.3141/2569–09. 
11473 FR 66965 (Nov. 12, 2008). 
11540 CFR 50.16 (Nov. 12, 2008). estimated to have inventories above 0.1 
tons in 2045.94 
We estimate that piston-engine 
aircraft have consumed approximately 38.6 billion gallons of leaded avgas in the U.S. since 1930, excluding military aircraft use of this fuel, emitting approximately 113,000 tons of lead to the air.
95 
3. Concentrations of Lead in Air Attributable to Emissions From Piston- Engine Aircraft 
In this section, we describe the 
concentrations of lead in air resulting from emissions of lead from covered aircraft. Air quality monitoring and modeling studies for lead at and near airports have identified elevated concentrations of lead in air from piston-engine aircraft exhaust at, and downwind of, airports where these aircraft are active.
96 97 98 99 100 101 This 
section provides a summary of the literature regarding the local-scale impact of aircraft emissions of lead on concentrations of lead at and near airports, with specific focus on the results of air monitoring for lead that the EPA required at a subset of airports and 
an analysis conducted by the EPA to estimate concentrations of lead at 13,000 airports in the U.S., titled ‘‘Model-extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports.’’
102 103  
Gradient studies evaluate how lead 
concentrations change with distance from an airport where piston-engine aircraft operate. These studies indicate that concentrations of lead in air are estimated to be one to two orders of magnitude higher at locations proximate to aircraft emissions, compared to nearby locations not impacted by a source of lead air emissions (concentrations for periods of approximately 18 hours to three-month 
averages).
104 105 106 107 108 109 The 
magnitude of lead concentrations at and near airports is highly influenced by the amount of aircraft activity (i.e., the 
number of take-off and landing operations, particularly if concentrated at one runway) and the time spent by aircraft in specific modes of operation. The most significant emissions in terms of ground-based activity, and therefore ground-level concentrations of lead in 
air, occur near the areas with greatest fuel consumption where the aircraft are stationary and running.
110 111 112 For 
piston-engine aircraft these areas are most commonly locations in which pilots conduct engine tests during run- up operations prior to take-off (e.g., magneto checks during the run-up operation mode). Run-up operations are conducted while the brakes are engaged so the aircraft is stationary and are often conducted adjacent to the runway end from which the aircraft will take off. Additional modes of operation by piston-engine aircraft, such as taxiing or idling near the runway, may result in additional hotspots of elevated lead concentration (e.g., start-up and idle, 
maintenance run-up).
113 
The lead NAAQS was revised in 
2008.114The 2008 decision revised the 
level, averaging time and form of the standards to establish the current primary and secondary standards, which are both 0.15 micrograms per cubic meter of air, in terms of consecutive three-month average of lead in total suspended particles.
115In 
conjunction with strengthening the lead NAAQS in 2008, the EPA enhanced the existing lead monitoring network by requiring monitors to be placed in areas with sources such as industrial facilities and airports with estimated lead emissions of 1.0 ton or more per year. Lead monitoring was conducted at two airports following from these requirements (Deer Valley Airport, AZ 
and the Van Nuys Airport, CA). In 2010, the EPA made further revisions to the monitoring requirements such that state and local air quality agencies are now required to monitor near industrial facilities with estimated lead emissions of 0.50 tons or more per year and at airports with estimated emissions of 1.0 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00024 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162763 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
11675 FR 81226 (Dec. 27, 2010). 
117EPA (2015) Program Overview: Airport Lead 
Monitoring. EPA, Washington, DC, EPA–420–F–15– 
003, 2015. Available at: https://nepis.epa.gov/Exe/ 
ZyPDF.cgi/P100LJDW.PDF?Dockey=P100LJDW.PDF. 
118EPA (2022) Technical Support Document 
(TSD) for the EPA’s Proposed Finding that Lead Emissions from Aircraft Engines that Operate on Leaded Fuel Cause or Contribute to Air Pollution that May Reasonably Be Anticipated to Endanger Public Health and Welfare. EPA, Washington, DC, EPA–420–R–22–025, 2022. Available in the docket for this action. 119A design value is a statistic that summarizes 
the air quality data for a given area in terms of the indicator, averaging time, and form of the standard. Design values can be compared to the level of the standard and are typically used to designate areas as meeting or not meeting the standard and assess progress towards meeting the NAAQS. 
120As noted earlier, when summarizing the 
available data regarding emissions of alkyl lead from piston-engine aircraft, the 2013 Lead ISA notes that an upper bound estimate of lead in the exhaust that might be in organic form may potentially be 20 percent (2013 Lead ISA, p. 2–10). Organic lead in engine exhaust would be expected to influence receptors within short distances of the point of emission from piston-engine aircraft. Airports with large flight schools and/or facilities with substantial delays for aircraft queued for takeoff could experience higher concentrations of alkyl lead in the vicinity of the aircraft exhaust. 
121The data in Table 2 represent concentrations 
measured at one location at each airport and monitors were not consistently placed in close proximity to the run-up areas. As described in Section II.A.3, monitored concentrations of lead in air near airports are highly influenced by proximity of the monitor to the run-up area. In addition to monitor placement, there are individual airport factors that can influence lead concentrations (e.g., the use of multiple run-up areas at an airport, fleet composition, and wind speed). The monitoring data reported in Table 2 reflect a range of lead concentrations indicative of the location at which measurements were made and the specific operations at an airport. 122EPA (2020) Model-Extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. 
EPA, Washington, DC, EPA–420–R–20–003, 2020. 
123EPA (2022) Technical Support Document 
(TSD) for the EPA’s Proposed Finding that Lead Emissions from Aircraft Engines that Operate on Leaded Fuel Cause or Contribute to Air Pollution that May Reasonably Be Anticipated to Endanger Public Health and Welfare. EPA, Washington, DC, EPA–420–R–22–025, 2022. Available in the docket for this action. 
124In this study, the EPA defined the maximum 
impact site as 15 meters downwind of the tailpipe of an aircraft conducting run-up operations in the area designated for these operations at a runway 
end. The maximum impact area was defined as approximately 50 meters surrounding the maximum impact site. 
125Prior to this model extrapolation study, the 
EPA developed and evaluated an air quality modeling approach (this study is available here: https://nepis.epa.gov/Exe/ZyPDF.cgi/P1007H4Q.PDF?Dockey=P1007H4Q.PDF), and subsequently applied the approach to a second airport and again performed an evaluation of the model output using air monitoring data (this second study is available here: https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG52.pdf). ton or more per year.116As part of this 
2010 requirement to expand lead 
monitoring, the EPA also required a one-year monitoring study of 15 additional airports with estimated lead emissions between 0.50 and 1.0 ton per year in an effort to better understand how these emissions affect concentrations of lead in the air at and near airports. Further, to help evaluate airport characteristics that could lead to ambient lead concentrations that approach or exceed the lead NAAQS, airports for this one-year monitoring study were selected based on factors such as the level of piston-engine aircraft activity and the predominant use of one runway due to wind patterns. 
As a result of these requirements, 
state and local air authorities collected and certified lead concentration data for at least one year at 17 airports with most monitors starting in 2012 and generally continuing through 2013. The data presented in Table 2 are based on the certified data for these sites and represent the maximum concentration monitored in a rolling three-month average for each location. 
117 118  
TABLE 2—L EADCONCENTRATIONS  
MONITORED AT 17 A IRPORTS IN THE  
U.S. 
Airport, State Lead 
design 
value,119 
μg/m3 
Auburn Municipal Airport, WA .. 0.06 
Brookhaven Airport, NY ............ 0.03 
Centennial Airport, CO ............. 0.02 
Deer Valley Airport, AZ ............ 0.04 
Gillespie Field, CA .................... 0.07 
Harvey Field, WA ..................... 0.02 
McClellan-Palomar Airport, CA 0.17 
Merrill Field, AK ........................ 0.07 
Nantucket Memorial Airport, 
MA ......................................... 0.01 
Oakland County International 
Airport, MI ............................. 0.02 
Palo Alto Airport, CA ................ 0.12 
Pryor Field Regional Airport, AL 0.01 
Reid-Hillview Airport, CA .......... 0.10 
Republic Airport, NY ................. 0.01 
San Carlos Airport, CA ............. 0.33 
Stinson Municipal, TX ............... 0.03 
Van Nuys Airport, CA ............... 0.06 Monitored lead concentrations 
violated the lead NAAQS at two airports in 2012: the McClellan-Palomar Airport and the San Carlos Airport. At both of these airports, monitors were located in close proximity to the area at the end of the runway most frequently used for pre-flight safety checks (i.e., run-up). 
Alkyl lead emitted by piston-engine aircraft would be expected to partition into the vapor phase and would not be collected by the monitoring conducted in this study, which is designed to quantitatively collect particulate forms of lead.
120 
Airport lead monitoring and modeling 
studies have identified the sharp decrease in lead concentrations with distance from the run-up area and therefore the importance of considering monitor placement relative to the run- up area when evaluating the maximum impact location attributable to lead emissions from piston-engine aircraft. The monitoring data in Table 2 reflect differences in monitor placement relative to the run-up area as well as other factors; this study also provided evidence that air lead concentrations at and downwind from airports could be influenced by factors such as the use of more than one run-up area, wind speed, and the number of operations conducted by single- versus twin-engine aircraft.
121 
The EPA recognized that the airport 
lead monitoring study provided a small sample of the potential locations where emissions of lead from piston-engine aircraft could potentially cause concentrations of lead in ambient air to 
exceed the lead NAAQS. Because we anticipated that additional airports and conditions could lead to exceedances of the lead NAAQS at and near airports where piston-engine aircraft operate, and in order to understand the range of lead concentrations at airports nationwide, we developed an analysis of 13,000 airports in the peer-reviewed report titled, ‘‘Model-extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports.’’
122 123  
This report provides estimated ranges of lead concentrations that may occur at and near airports where leaded avgas is used. The study extrapolated modeling results from one airport to estimate air lead concentrations at the maximum impact area near the run-up location for over 13,000 U.S. airports.
124The model- 
extrapolated lead estimates in this study indicate that some additional U.S. airports may have air lead concentrations above the NAAQS at this area of maximum impact. The report also indicates that, at the levels of activity analyzed at the 13,000 airports, estimated lead concentrations decrease to below the standard within 50 meters from the location of highest concentration. 
To estimate the potential ranges of 
lead concentrations at and downwind of the anticipated area of highest concentration at airports in the U.S., the relationship between piston-engine aircraft activity and lead concentration at and downwind of the maximum impact site at one airport was applied to piston-engine aircraft activity estimates for each U.S. airport.
125This approach 
for conducting a nationwide analysis of airports was selected due to the impact of piston-engine aircraft run-up 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00025 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162764 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
126EPA (2022) Technical Support Document 
(TSD) for the EPA’s Proposed Finding that Lead 
Emissions from Aircraft Engines that Operate on Leaded Fuel Cause or Contribute to Air Pollution that May Reasonably Be Anticipated to Endanger Public Health and Welfare. EPA, Washington, DC, EPA–420–R–22–025, 2022. Available in the docket for this action. 
127EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. Table 6. p. 53. EPA, Washington, DC, EPA–420–R– 20–003, 2020. 128See methods used in EPA (2020) Model- 
extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports. Table 2. p.23. EPA, Washington, DC, EPA–420–R–20–003, 2020. 
129EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports, Table 6. p.53. EPA, Washington, DC, EPA–420–R– 20–003, 2020. 
130Carr et. al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment 45: 5795–5804. 131EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. Table 6. p.53. EPA, Washington, DC, EPA–420–R– 20–003, 2020. EPA responses to peer review 
comments on the report are available here: https:// 
nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=
P100YIWD.pdf. 
132See EPA’s 2017 AirToxScreen. Available at 
https://www.epa.gov/AirToxScreen. 
133These concentration estimates are not used for 
comparison to the level of the Lead NAAQS due to different temporal averaging times and underlying assumptions in modeling. The AirToxScreen estimates are provided to help state, local and Tribal air agencies and the public identify which pollutants, emission sources and places they may wish to study further to better understand potential risks to public health from air toxics. There are uncertainties inherent in these estimates described by the EPA, some of which are relevant to these estimates of lead concentrations; however, these estimates provide perspective on the potential influence of piston-engine emissions of lead on air quality. See https://www.epa.gov/AirToxScreen/ 
airtoxscreen-limitations. operations on ground-level lead 
concentrations, which creates a maximum impact area that is expected to be generally consistent across airports. Specifically, these aircraft consistently take off into the wind and typically conduct run-up operations immediately adjacent to the take-off runway end, and thus, modeling lead concentrations from this source is constrained by variation in a few key parameters. These parameters include: (1) Total amount of piston-engine aircraft activity, (2) the proportion of activity conducted at one runway end, (3) the proportion of activity conducted by multi-piston-engine aircraft, (4) the duration of run-up operations, (5) the concentration of lead in avgas, (6) wind speed at the model airport relative to the extrapolated airport, and (7) additional meteorological, dispersion model, or operational parameters. These parameters were evaluated through sensitivity analyses as well as quantitative or qualitative uncertainty analyses. To generate robust concentration estimates, the EPA evaluated these parameters, conducted wind-speed correction of extrapolated estimates, and used airport-specific information regarding airport layout and prevailing wind directions for the 13,000 airports.
126 
Results of this national analysis show 
that model-extrapolated three-month average lead concentrations in the maximum impact area may potentially exceed the lead NAAQS at airports with activity ranging from 3,616–26,816 Landing and Take-Off events (LTOs) in a three-month period.
127The lead 
concentration estimates from this model-extrapolation approach account for lead engine emissions from aircraft only, and do not include other sources of air-related lead. The broad range in LTOs that may lead to concentrations of lead exceeding the lead NAAQS is due to the piston-engine aircraft fleet mix at individual airports such that airports where the fleet is dominated by twin- engine aircraft would potentially reach concentrations of lead exceeding the lead NAAQS with fewer LTOs compared with airports where single- engine aircraft dominate the piston- engine fleet.
128Model-extrapolated 
three-month average lead concentrations 
from aircraft engine emissions were estimated to extend to a distance of at least 500 meters from the maximum impact area at airports with activity ranging from 1,275–4,302 LTOs in that three-month period.
129In a separate 
modeling analysis at an airport at which hundreds of take-off and landing events by piston-engine aircraft occur per day, the EPA found that modeled 24-hour concentrations of lead were estimated above background extending almost 1,000 meters downwind from the runway.
130 
Model-extrapolated estimates of lead 
concentrations in the EPA report ‘‘Model-extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports’’ were compared with monitored values and show general agreement, suggesting that the extrapolation method presented in this report provides reasonable estimates of the range in concentrations of lead in air attributable to three-month activity periods of piston-engine aircraft at airports. The assessment included detailed evaluation of the potential impact of run-up duration, the concentration of lead in avgas, and the impact of meteorological parameters on model-extrapolated estimates of lead concentrations attributable to engine emissions of lead from piston-powered aircraft. Additionally, this study included a range of sensitivity analyses as well as quantitative and qualitative uncertainty analyses. The EPA invites comment on the approach used in this 
model-extrapolation analysis. 
The EPA’s model-extrapolation 
analysis of lead concentrations from engine emissions resulting from covered aircraft found that the lowest annual airport emissions of lead estimated to result in air lead concentrations approaching or potentially exceeding the NAAQS was 0.1 tons per year. There are key pieces of airport-specific data that are needed to fully evaluate the potential for piston-engine aircraft operating at an airport to cause concentrations of lead in the air to exceed the lead NAAQS, and the EPA’s report ‘‘Model-extrapolated Estimates of Airborne Lead Concentrations at U.S. 
Airports’’ provides quantitative and qualitative analyses of these factors.
131 
The EPA’s estimate of airports that have annual lead inventories of 0.1 ton or more are illustrative of, and provide one approach for an initial screening 
evaluation of locations where engine emissions of lead from aircraft increase localized lead concentrations in air. Airport-specific assessments would be needed to determine the magnitude of the potential range in lead concentrations at and downwind of each facility. 
As described in Section II.A.1 of this 
document, the FAA forecasts 0.9 percent decreases in piston-engine aircraft activity out to 2041, however these decreases are not projected to occur uniformly across airports. Among the more than 3,300 airports in the FAA TAF, the FAA forecasts both decreases and increases in general aviation, which is largely comprised of piston-engine aircraft. If the current conditions on which the forecast is based persist, then lead concentrations in the air may increase at the airports where general aviation activity is forecast to increase. 
In addition to airport-specific 
modeled estimates of lead concentrations, the EPA also provides annual estimates of lead concentrations for each census tract in the U.S. as part of the Air Toxics Screening Assessment (AirToxScreen).
132The census tract 
concentrations are averages of the area- weighted census block concentrations within the tract. Lead concentrations reported in the AirToxScreen are based on emissions estimates from anthropogenic and natural sources, including aircraft engine emissions.
133 
The 2017 AirToxScreen provides lead concentration estimates in air for 73,449 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00026 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162765 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
134As airports are generally in larger census 
blocks within a census tract, concentrations for 
airport blocks dominate the area-weighted average in cases where an airport is the predominant lead emissions source in a census tract. 
135Swiss FOCA (2007) Aircraft Piston Engine 
Emissions Summary Report. 33–05–003 Piston Engine Emissions_ Swiss FOCA_ Summary. Report_
070612_ rit. Available at https:// 
www.bazl.admin.ch/bazl/en/home/specialists/ regulations-and-guidelines/environment/pollutant- emissions/aircraft-engine-emissions/report- appendices-database-and-data-sheets.html. 
136Griffith 2020. Electron microscopic 
characterization of exhaust particles containing lead dibromide beads expelled from aircraft burning leaded gasoline. Atmospheric Pollution Research 11:1481–1486. 
137EPA (2013) ISA for Lead. Section 1.3. 
‘‘Exposure to Ambient Pb.’’ p. 1–11. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
138EPA (2006) AQC for Lead. Section E.6. p. 2– 
5. EPA, Washington, DC, EPA/600/R–5/144aF, 2006. 139EPA (1977) AQC for Lead. Section 6.2.2.1. 
EPA, Washington, DC, EPA–600/8–77–017, 1977. 
140EPA (2006) AQC for Lead. Section E.6. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 
141EPA (2006) AQC for Lead. Section 2. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 
142EPA (2013) ISA for Lead. Section 1.2.1. 
‘‘Sources, Fate and Transport of Ambient Pb;’’ p. 1– 6; and Section 2.3. ‘‘Fate and Transport of Pb.’’ p. 2–24 through 2–25. EPA, Washington, DC, EPA/ 600/R–10/075F, 2013. 
143Memorandum to Docket EPA–HQ–OAR– 
2022–0389. Deposition of Lead Emitted by Piston- engine Aircraft. June 15, 2022. Docket ID EPA–HQ– 2022–0389. 
144EPA (2013) ISA for Lead. Section 2.6.1. 
‘‘Soils.’’ p. 2–118. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 145EPA (2013) ISA for Lead. Chapter 6. 
‘‘Ecological Effects of Pb.’’ p. 6–57. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
146Murphy et al., 2008. Weekly patterns of 
aerosol in the United States. Atmospheric Chemistry and Physics. 8:2729–2739. 
147Lead concentrations collected as part of the 
Interagency Monitoring of Protected Visual Environments (IMPROVE) network and the National Oceanic and Atmospheric Administration (NOAA) monitoring sites. 
148Heiken et al., 2014. ACRP Web-Only 
Document 21: Quantifying Aircraft Lead Emissions at Airports. Contractor’s Final Report for ACRP 02– 34. Available at https://www.trb.org/Publications/ Blurbs/172599.aspx. census tracts in the U.S.134Lead 
emissions from piston-engine aircraft 
comprised more than 50 percent of these census block area-weighted lead concentrations in over half of the census tracts, which included tracts in all 50 states, as well as Puerto Rico and the Virgin Islands. 
4. Fate and Transport of Emissions of 
Lead From Piston-Engine Aircraft 
This section summarizes the chemical 
transformation that piston-engine aircraft lead emissions are anticipated to undergo in the atmosphere and describes what is known about the deposition of piston-engine aircraft lead, and potential impacts on soil, food, and aquatic environments. 
a. Atmospheric Chemistry and 
Transport of Emissions of Lead From Piston-Engine Aircraft 
Lead emitted by piston-engine aircraft 
can have impacts in the local environment and, due to their small size (i.e., typically less than one micron in 
diameter),
135 136 lead-bearing particles 
emitted by piston engines may disperse widely in the environment. However, lead emitted during the landing and takeoff cycle, particularly during ground-based operations such as start- up, idle, preflight run-up checks, taxi and the take-off roll on the runway, may deposit to the local environment and/or infiltrate into buildings.
137Depending 
on ambient conditions (e.g., ozone and 
hydroxyl concentrations in the atmosphere), alkyl lead may exist in the atmosphere for hours to days
138and 
may therefore be transported off airport property into nearby communities. 
Lead halides emitted by motor 
vehicles operating on leaded fuel were reported to undergo compositional changes upon cooling and mixing with the ambient air as well as during transport, and we would anticipate lead 
bromides emitted by piston-engine aircraft to behave similarly in the atmosphere. The water-solubility of these lead-bearing particles was reported to be higher for the smaller lead-bearing particles.
139Lead halides 
emitted in motor vehicle exhaust were reported to break down rapidly in the atmosphere via redox reactions in the presence of atmospheric acids.
140 
Tetraethyl lead has an atmospheric residence time ranging from a few hours to a few days. Tetraethyl lead reacts with the hydroxyl radical in the gas phase to form a variety of products that include ionic trialkyl lead, dialkyl lead and metallic lead. Trialkyl lead is slow to react with the hydroxyl radical and is quite persistent in the atmosphere.
141 
b. Deposition of Lead Emissions From Piston-Engine Aircraft and Soil Lead Concentrations to Which Piston-Engine Aircraft May Contribute 
Lead is removed from the atmosphere 
and deposited on soil, into aquatic systems and on other surfaces via wet or dry deposition.
142Meteorological 
factors (e.g., wind speed, convection, 
rain, humidity) influence local deposition rates. With regard to deposition of lead from aircraft engine emissions, the EPA modeled the deposition rate for aircraft lead emissions at one airport in a temperate climate in California with dry summer months. In this location, the average lead deposition rate from aircraft emissions of lead was 0.057 milligrams per square meter per year.
143 
Studies summarized in the 2013 Lead 
ISA suggest that soil is a reservoir for 
contemporary and historical emissions of lead to air.
144Once deposited to soil, 
lead can be absorbed onto organic material, can undergo chemical and physical transformation depending on a number of factors (e.g., pH of the soil 
and the soil organic content), and can participate in further cycling through air or other media.
145The extent of 
atmospheric deposition of lead from aircraft engine emissions would be expected to depend on a number of factors including the size of the particles emitted (smaller particles, such as those in aircraft emissions, have lower settling velocity and may travel farther distances before being deposited compared with larger particles), the temperature of the exhaust (the high temperature of the exhaust creates plume buoyancy), as well as meteorological factors (e.g., wind speed, precipitation rates). As a result of the size of the lead particulate matter emitted from piston-engine aircraft and as a result of these emissions occurring at various altitudes, lead emitted from these aircraft may distribute widely through the environment.
146Murphy et al. (2008) 
reported weekend increases in ambient lead monitored at remote locations in the U.S. that the authors attributed to weekend increases in piston-engine powered general aviation activity.
147 
Heiken et al. (2014) assessed air lead 
concentrations potentially attributable to resuspended lead that previously deposited onto soil relative to air lead concentrations resulting directly from aircraft engine emissions.
148Based on 
comparisons of lead concentrations in total suspended particulate (TSP) and fine particulate matter (PM
2.5) measured 
at the three airports, coarse particle lead was observed to account for about 20– 30 percent of the lead found in TSP. The authors noted that based on analysis of lead isotopes present in the air samples collected at these airports, the original source of the lead found in the coarse particle range appeared to be from aircraft exhaust emissions of lead that previously deposited to soil and were resuspended by wind or aircraft- induced turbulence. Results from lead isotope analysis in soil samples collected at the same three airports led the authors to conclude that lead emitted from piston-engine aircraft was not the dominant source of lead in soil in the samples measured at the airports they studied. The authors note the 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00027 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162766 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
149McCumber and Strevett 2017. A Geospatial 
Analysis of Soil Lead Concentrations Around 
Regional Oklahoma Airports. Chemosphere 167:62– 
70. 
150Kavouras et al., 2013. Bioavailable Lead in 
Topsoil Collected from General Aviation Airports. The Collegiate Aviation Review International 31(1):57–68. Available at https://doi.org/10.22488/ okstate.18.100438. 
151Heiken et al., 2014. ACRP Web-Only 
Document 21: Quantifying Aircraft Lead Emissions at Airports. Contractor’s Final Report for ACRP 02– 34. Available at https://www.trb.org/Publications/Blurbs/172599.aspx. 
152EPA (2010) Development and Evaluation of an 
Air Quality Modeling Approach for Lead Emissions from Piston-Engine Aircraft Operating on Leaded Aviation Gasoline. EPA, Washington, DC, EPA– 420–R–10–007, 2010. https://nepis.epa.gov/Exe/ZyPDF.cgi/P1007H4Q.PDF?Dockey=P1007H4Q.PDF. 
153Environment Canada (2000) Airborne 
Particulate Matter, Lead and Manganese at Buttonville Airport. Toronto, Ontario, Canada: Conor Pacific Environmental Technologies for Environmental Protection Service, Ontario Region. 
154Lejano and Ericson 2005. Tragedy of the 
Temporal Commons: Soil-Bound Lead and the Anachronicity of Risk. Journal of Environmental Planning and Management. 48(2):301–320. 
155EPA (2013) ISA for Lead. Section 3.1.3.3. 
‘‘Dietary Pb Exposure.’’ p. 3–20 through 3–24. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
156EPA (2006) AQC for Lead. Section 8.2.2. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 
157EPA (2006) AQC for Lead. Section 8.2.2. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 158O’Connor-Marer. Aerial Applicator’s Manual: 
A National Pesticide Applicator Certification Study 
Guide. p. 40. National Association of State Departments of Agriculture Research Foundation. Available at https://www.agaviation.org/Files/RelatedEntities/Aerial _Applicators_ Manual.pdf. 
159The additive used in the fuel to scavenge lead 
determines the chemical form of the lead halide emitted; because ethylene dibromide is added to leaded aviation gasoline used in piston-engine aircraft, the lead halide emitted is in the form of lead dibromide. 
160EPA (2006) AQC for Lead. pp. 7–9 and AXZ7– 
39. EPA, Washington, DC, EPA/600/R–5/144aF, 2006. 
161EPA (2006) AQC for Lead. p. AXZ7–39. EPA, 
Washington, DC, EPA/600/R–5/144aF, 2006. 
162EPA (1986) AQC for Lead. Sections 6.5.3. EPA, 
Washington, DC, EPA–600/8–83/028aF–dF (NTIS PB87142386), 1986. 
163EPA (1986) AQC for Lead. Section 
7.2.2.2.1.EPA, Washington, DC, EPA–600/8–83/ 028aF–dF (NTIS PB87142386), 1986. 
164EPA (1986) AQC for Lead. Section 7.2.2.2.2. 
EPA, Washington, DC, EPA–600/8–83/028aF–dF (NTIS PB87142386), 1986. 165EPA (2013) ISA for Lead. Section 6.4.2. 
‘‘Biogeochemistry and Chemical Effects of Pb in Freshwater and Saltwater Systems.’’ p. 6–147. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
166EPA (2002) Persistent, Bioaccumulative, and 
Toxic Pollutants (PBT) Program. PBT National Action Plan for Alkyl-Pb. Washington, DC. June. 2002. 
167See FAA’s NASR. Available at https://
www.faa.gov/air_ traffic/flight_ info/aeronav/aero_
data/eNASR_ Browser/. 
168National Academies of Sciences, Engineering, 
and Medicine 2014. Best Practices for General Aviation Aircraft Fuel-Tank Sampling. Washington, DC: The National Academies Press. https://doi.org/ 10.17226/22343. complex history of topsoil can create 
challenges in understanding the extent to which aircraft lead emissions impact soil lead concentrations at and near airports (e.g., the source of topsoil can 
change as a result of site renovation, construction, landscaping, natural events such as wildfire and hurricanes, and other activities). Concentrations of lead in soil at and near airports servicing piston-engine aircraft have been measured using a range of approaches.
149 150 151 152 153 154 Kavouras 
et al. (2013) collected soil samples at three airports and reported that construction at an airport involving removal and replacement of topsoil complicated interpretation of the findings at that airport and that the number of runways at an airport may influence resulting lead concentrations in soil (i.e., multiple runways may 
provide for more wide-spread dispersal of the lead over a larger area than that potentially affected at a single-runway airport). 
c. Potential for Lead Emissions From 
Piston-Engine Aircraft To Impact Agricultural Products 
Studies conducted near stationary 
sources of lead emissions (e.g., smelters) 
have shown that atmospheric lead sources can lead to contamination of agricultural products, such as vegetables.
155 156 In this way, air lead 
sources may contribute to dietary exposure pathways.
157As described in Section II.A.1 of this document, piston- engine aircraft are used in the application of pesticides, fertilizers and seeding crops for human and animal consumption and as such, provide a potential route of exposure for lead in food. To minimize drift of pesticides and other applications from the 
intended target, pilots are advised to maintain a height between eight and 12 feet above the target crop during application.
158The low flying height is 
needed to minimize the drift of the fertilizer and pesticide particles away from their intended target. An unintended consequence of this practice is that exhaust emissions of lead have a substantially increased potential for directly depositing on vegetation and surrounding soil. Lead halides, the primary form of lead emitted by engines operating on leaded fuel,
159are slightly 
water soluble and, therefore, may be more readily absorbed by plants than other forms of inorganic lead. 
The 2006 AQCD indicated that 
surface deposition of lead onto plants may be significant.
160Atmospheric 
deposition of lead provides a pathway for lead in vegetation as a result of contact with above-ground portions of the plant.
161 162 163 Livestock may 
subsequently be exposed to lead in vegetation (e.g., grasses and silage) and 
in surface soils via incidental ingestion of soil while grazing.
164 
d. Potential for Lead Emissions From Piston-Engine Aircraft To Impact Aquatic Ecosystems 
As discussed in Section 6.4 of the 
2013 Lead ISA, lead bioaccumulates in the tissues of aquatic organisms through ingestion of food and water or direct uptake from the environment (e.g., across membranes such as gills or skin).
165Alkyl lead, in particular, has 
been identified by the EPA as a 
Persistent, Bioaccumulative, and Toxic (PBT) pollutant.
166There are 527 
seaport facilities in the U.S., and landing and take-off activity by seaplanes at these facilities provides a direct pathway for emission of organic and inorganic lead to the air near/above inland waters and ocean seaports where these aircraft operate.
167Inland airports 
may also provide a direct pathway for emission of organic and inorganic lead to the air near/above inland waters. Lead emissions from piston-engine aircraft operating at seaplane facilities as well as airports and heliports near water bodies can enter the aquatic ecosystem by either deposition from ambient air or runoff of lead deposited to surface soils. 
In addition to deposition of lead from 
engine emissions by piston-powered aircraft, lead may enter aquatic systems from the pre-flight inspection of the fuel for contaminants that pilots conduct. While some pilots return the checked fuel to their fuel tank or dispose of it in a receptacle provided on the airfield, some pilots discard the fuel onto the tarmac, ground, or water, in the case of a fuel check being conducted on a seaplane. Lead in the fuel discarded to the environment may evaporate to the air and may be taken up by the surface on which it is discarded. Lead on tarmac or soil surfaces is available for runoff to surface water. Tetraethyl lead in the avgas directly discarded to water will be available for uptake and bioaccumulation in aquatic life. The National Academy of Sciences Airport Cooperative Research Program (ACRP) conducted a survey study of pilots’ fuel sampling and disposal practices. Among the 146 pilots responding to the survey, 36 percent indicated they discarded all fuel check samples to the ground regardless of contamination status and 19 percent of the pilots indicated they 
discarded only contaminated fuel to the ground.
168Leaded avgas discharged to 
the ground and water includes other 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00028 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162767 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
169Memorandum to Docket EPA–HQ–OAR– 
2022–0389. Potential Exposure to Non-exhaust Lead 
and Ethylene Dibromide. June 15, 2022. Docket ID EPA–HQ–2022–0389. 
170EPA (2013) ISA for Lead. Section 5.4. 
‘‘Summary.’’ p. 5–40. EPA, Washington, DC, EPA/ 600/R–10/075F, 2013. 
171EPA. America’s Children and the 
Environment. Summary of blood lead levels in children updated in 2022, available at https:// 
www.epa.gov/americaschildrenenvironment/ biomonitoring-lead. Data source: Centers for Disease 
Control and Prevention, National Report on Human Exposure to Environmental Chemicals. Blood Lead (2011–2018). Updated March 2022. Available at https://www.cdc.gov/exposurereport/report/pdf/cgroup2_ LBXBPB_ 2011-p.pdf. 
172The relative contribution of lead emissions 
from covered aircraft engines to these disparities 
has not been determined and is not a goal of the evaluation described here. 173Residential proximity to a source of a specific 
air pollutant(s) is a widely used surrogate measure to evaluate the potential for higher exposures to that pollutant (EPA Technical Guidance for Assessing Environmental Justice in Regulatory Analysis. 
Section 4.2.1). Data presented in Section II.A.3 demonstrate that lead concentrations in air near the runup area can exceed the lead NAAQS and concentrations decrease sharply with distance from the ground-based aircraft exhaust and vary with the amount of aircraft activity at an airport. Not all people living within 500 meters of a runway are expected to be equally exposed to lead. 
174Miranda et al., 2011. A Geospatial Analysis of 
the Effects of Aviation Gasoline on Childhood Blood Lead Levels. Environmental Health Perspectives. 119:1513–1516. 
175Zahran et al., 2017. The Effect of Leaded 
Aviation Gasoline on Blood Lead in Children. Journal of the Association of Environmental and Resource Economists. 4(2):575–610. 
176Rowangould 2013. A census of the near- 
roadway population: public health and environmental justice considerations. Transportation Research Part D 25:59–67. https:// 
dx.doi.org/10.1016/j.trd.2013.08.003. 
177Marshall et al., 2014. Prioritizing 
environmental justice and equality: diesel emissions in Southern California. Environmental Science & Technology 48: 4063–4068. https://
doi.org/10.1021/es405167f. 
178Marshall 2008. Environmental inequality: air 
pollution exposures in California’s South Coast Air Basin. Atmospheric Environment 21:5499–5503. 
https://doi.org/10.1016/j.atmosenv.2008.02.005. 
179Tessum et al., 2021. PM 2.5polluters 
disproportionately and systemically affect people of color in the United States. Science Advances 7:eabf4491. 
180Mohai et al., 2009. Environmental justice. 
Annual Reviews 34:405–430. Available at https://
doi.org/10.1146/annurev-environ-082508-094348. 
181McNair 2020. Investigation of environmental 
justice analysis in airport planning practice from 2000 to 2010. Transportation Research Part D 81:102286. 
182Woodburn 2017. Investigating neighborhood 
change in airport-adjacent communities in multiairport regions from 1970 to 2010. Journal of the Transportation Research Board, 2626, 1–8. 
183Rissman et al., 2013. Equity and health 
impacts of aircraft emissions at the Hartfield- Jackson Atlanta International Airport. Landscape and Urban Planning, 120: 234–247. hazardous fuel components such as 
ethylene dibromide.169 
5. Consideration of Environmental Justice and Children in Populations Residing Near Airports 
This section provides a description of 
how many people live in close proximity to airports where they may be exposed to airborne lead from aircraft engine emissions of lead (referred to here as the ‘‘near-airport’’ population). This section also provides the demographic composition of the near- airport population, with attention to implications related to environmental justice (EJ) and the population of children in this near-source environment. Consideration of EJ implications in the population living near airports is important because blood lead levels in children from low-income households remain higher than those in children from higher income households, and the most exposed Black children still have higher blood lead levels than the most exposed non- Hispanic White children.
170 171 172  
Executive Orders 12898 (59 FR 7629, 
February 16, 1994) and 14008 (86 FR 7619, February 1, 2021) direct Federal agencies, to the greatest extent practicable and permitted by law, to make achieving EJ part of their mission by identifying and addressing, as appropriate, disproportionately high and adverse human health or environmental effects of their programs, policies, and activities on people of color populations and low-income populations in the United States. The EPA defines environmental justice as the fair treatment and meaningful involvement of all people regardless of race, color, national origin, or income with respect to the development, implementation, and enforcement of environmental laws, regulations, and policies. For the reasons described in 
SUPPLEMENTARY INFORMATION Section D, 
our consideration of EJ implications here is focused on describing conditions relevant to the most recent year for which demographic data are available. The analysis described here provides information regarding whether some demographic groups are more highly represented in the near-airport environment compared with people who live farther from airports. Residential proximity to airports implies that there is an increased potential for exposure to lead from covered aircraft engine emissions.
173As 
described in Section II.A.3 of this document, several studies have measured higher concentrations of lead in air near airports with piston-engine aircraft activity. Additionally, as noted in Section II.A of this document, two studies have reported increased blood lead levels in children with increasing proximity to airports.
174 175  
We first summarize here the literature 
on disparity with regard to those who live in proximity to airports. Then we describe the analyses the EPA has conducted to evaluate potential disparity in the population groups living near runways where piston- engine aircraft operate compared to those living elsewhere. 
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.
176 177 178 179 180  The literature includes studies that have 
reported on communities in close proximity to airports that are disproportionately represented by people of color and low-income populations. McNair (2020) described nineteen major airports that underwent capacity expansion projects between 2000 and 2010, thirteen of which had a large concentration or presence of persons of color, foreign-born persons or low-income populations nearby.
181 
Woodburn (2017) reported 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.
182Rissman et al. (2013) 
reported that with increasing proximity to the Hartsfield-Jackson Atlanta International Airport, exposures to particulate matter were higher, and there were lower home values, income, education, and percentage of white residents.
183 
The EPA used two approaches to 
understand whether some members of the population (e.g., children five and 
under, people of color, indigenous populations, low-income populations) represent a larger share of the people living in proximity to airports where piston-engine aircraft operate compared 
with people who live farther away from these airports. In the first approach, we evaluated people living within, and children attending school within, 500 meters of all of the approximately 20,000 airports in the U.S., using methods described in the EPA’s report titled ‘‘National Analysis of the Populations Residing Near or Attending 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00029 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162768 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
184EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. 
EPA, Washington, DC, EPA–420–R–20–003, 2020. EPA responses to peer review comments on the report are available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YISM.pdf. 
185EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. EPA, Washington, DC, EPA–420–R–20–003, 2020. 
186Carr et. al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment, 45 (32), 5795–5804. DOI: https://dx.doi.org/10.1016/j.atmosenv.
2011.07.017. 
187We do not assume or expect that all people 
living within 500m or 1,000m of a runway are exposed to lead from piston-engine aircraft emissions, and the wide range of activity of piston- 
engine aircraft at airports nationwide suggests that exposure to lead from aircraft emissions is likely to vary widely. 
188In this analysis, we included populations 
living in census blocks that intersected the 500- meter buffer around each runway in the U.S. Potential uncertainties in this approach are described in our report National Analysis of the Populations Residing Near or Attending School Near U.S. Airports. EPA–420–R–20–001, available 
at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=
P100YG4A.pdf, and in the EPA responses to peer 
review comments on the report, available here: https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YISM.pdf. 
189EPA (2020) National Analysis of the 
Populations Residing Near or Attending School Near U.S. Airports. EPA–420–R–20–001. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=
P100YG4A.pdf. 
190Clarke. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Estimation of Population Size and Demographic Characteristics among People Living Near Airports by State in the United States. May 31, 2022. Docket ID EPA–HQ–2022–0389. 
191Clarke. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Estimation of Population Size and Demographic Characteristics among People Living Near Airports by State in the United States. May 31, 2022. Docket ID EPA–HQ–2022–0389. 
192These data are presented in tabular form for 
all states in this memorandum located in the docket: Clarke. Memorandum to Docket EPA–HQ– OAR–2022–0389. Estimation of Population Size and Demographic Characteristics among People Living Near Airports by State in the United States. May 31, 2022. Docket ID EPA–HQ–2022–0389. School Near U.S. Airports.’’184In the 
second approach, we evaluated people 
living near the NPIAS airports in the conterminous 48 states. As noted in Section II.A.1 of this document, the NPIAS airports support the majority of piston-engine aircraft activity that occurs in the U.S. Among the NPIAS airports, we compared the demographic composition of people living within one kilometer of runways with the demographic composition of people living at a distance of one to five kilometers from the same airports. 
The distances analyzed for those 
people living closest to airports (i.e., distances of 500 meters and 1,000 meters) were chosen for evaluation following from the air quality monitoring and modeling data presented in Section II.A.3 of this document. Specifically, the EPA’s modeling and monitoring data indicate that concentrations of lead from piston- engine aircraft emissions can be elevated above background levels at distances of 500 meters over a rolling three-month period. On individual days, concentrations of lead from piston- engine aircraft emissions can be elevated above background levels at distances of 1,000 meters on individual days downwind of a runway, depending on aircraft activity and prevailing wind direction.
185 186 187  
Because the U.S. has a dense network 
of airports, many of which have neighboring communities, we first quantified the number of people living and children attending school within 500 meters of the approximately 20,000 airports in the U.S. The results of this analysis are summarized at the national scale in the EPA’s report titled ‘‘National Analysis of the Populations Residing Near or Attending School Near U.S. Airports.’’
188From this analysis, 
the EPA estimates that approximately 5.2 million people live within 500 meters of an airport runway, 363,000 of whom are children age five and under. The EPA also estimates that 573 schools attended by 163,000 children in kindergarten through twelfth grade are within 500 meters of an airport runway.
189 
In order to identify potential 
disparities in the near-airport population, we first evaluated populations at the state level. Using the U.S. Census population data for each State in the U.S., we compared the percent of people by age, race and indigenous peoples (i.e., children five and under, Black, Asian, and Native American or Alaska Native) living within 500 meters of an airport runway with the percent by age, race, and indigenous peoples comprising the state population.
190Using the methodology 
described in Clarke (2022), the EPA identified states in which children, Black, Asian, and Native American or Alaska Native populations represent a greater fraction of the population compared with the percent of these groups in the state population.
191 
Results of this analysis are presented in the following tables.
192This state-level 
analysis presents summary information for a subset of potentially relevant demographic characteristics. We present data in this section regarding a wider array of demographic characteristics when evaluating populations living near NPIAS airports. 
Among children five and under, there 
were three states (Nevada, South Carolina, and South Dakota), in which the percent of children five and under living within 500 meters of a runway represent a greater fraction of the population by a difference of one percent or greater compared with the percent of children five and under in the state population (Table 3). 
TABLE 3—T HEPOPULATION OF CHILDREN FIVEYEARS AND UNDER WITHIN 500 M ETERS OF AN AIRPORT RUNWAY  
COMPARED TO THE STATE POPULATION OF CHILDREN FIVEYEARS AND UNDER  
State Percent of 
children aged 
five years and 
under within 
500 meters Percent of 
children aged 
five years and 
under within 
the state Number of 
children aged 
five years and 
under within 
500 meters Number of 
children aged 
five years and 
under in the 
state 
Nevada ............................................................................................................. 10 8 1,000 2 24,200 
South Carolina ................................................................................................. 9 8 400 361,400 
South Dakota ................................................................................................... 11 9 3,000 71,30 0 
There were nine states in which the 
Black population represented a greater fraction of the population living in the near-airport environment by a difference of one percent or greater compared with the state as a whole. These states were California, Kansas, Kentucky, Louisiana, Mississippi, Nevada, South Carolina, West Virginia, and Wisconsin (Table 4). 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00030 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162769 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
193For this analysis, we evaluated the 2,022 
airports with a population of greater than 100 
people inside the zero to one kilometer distance to avoid low population counts distorting the assessment of percent contributions of each group to the total population within the zero to one kilometer distance. 
194Kamal et.al., Memorandum to Docket EPA– 
HQ–OAR–2022–0389. Analysis of Potential Disparity in Residential Proximity to Airports in the Conterminous United States. May 24, 2022. Docket ID EPA–HQ–2022–0389. Methods used are described in this memo and include the use of block group resolution data to evaluate the 
representation of different demographic groups 
near-airport and for those living one to five kilometers away. TABLE 4—T HEBLACK POPULATION WITHIN 500 M ETERS OF AN AIRPORT RUNWAY AND THE BLACK POPULATION , BY 
STATE 
State Percent Black 
within 500 
meters Percent Black 
within the 
state Black 
population 
within 500 
meters Black 
population in 
the state 
California .......................................................................................................... 8 7 18,981 2,486,500 
Kansas ............................................................................................................. 8 6 1,240 17 3,300 
Kentucky .......................................................................................................... 9 8 3,152 342 ,800 
Louisiana .......................................................................................................... 46 32 14,669  1,463,000 
Mississippi ........................................................................................................ 46 37 8,542 1,103,100 
Nevada ............................................................................................................. 12 9 1,794 2 31,200 
South Carolina ................................................................................................. 31 28 10,066 1,3 02,900 
West Virginia .................................................................................................... 10 3 1,452 63, 900 
Wisconsin ......................................................................................................... 9 6 4,869 367 ,000 
There were three states with a greater 
fraction of Asians in the near-airport environment compared with the state as 
a whole by a difference of one percent or greater: Indiana, Maine, and New Hampshire (Table 5). 
TABLE 5—T HEASIAN POPULATION WITHIN 500 M ETERS OF AN AIRPORT RUNWAY AND THE ASIAN POPULATION , BYSTATE 
State Percent Asian 
within 500 
meters Percent Asian 
within the 
state Asian 
population 
within 500 
meters Asian 
population in 
the state 
Indiana ............................................................................................................. 4 2 1,681 1 05,500 
Maine ............................................................................................................... 2 1 406 13, 800 
New Hampshire ............................................................................................... 4 2 339 29,000 
Among Native Americans and Alaska 
Natives, there were five states (Alaska, Arizona, Delaware, South Dakota, and New Mexico) where the near-airport population had greater representation by Native Americans and Alaska Natives compared with the portion of the population they comprise at the state level by a difference of one percent or greater. In Alaska, as anticipated due to the critical nature of air travel for the transportation infrastructure in that state, the disparity in residential proximity to a runway was the largest; 16,000 Alaska Natives were estimated to live within 500 meters of a runway, representing 48 percent of the population within 500 meters of an airport runway compared with 15 percent of the Alaska state population (Table 6). 
TABLE 6—T HENATIVE AMERICAN AND ALASKA NATIVE POPULATION WITHIN 500 M ETERS OF AN AIRPORT RUNWAY AND  
THENATIVE AMERICAN AND ALASKA NATIVE POPULATION , BYSTATE 
State Percent Native 
American and 
Alaska Native 
within 500 
meters Percent Native 
American and 
Alaska Native 
within the 
state Native 
American and 
Alaska Native 
population 
within 500 
meters Native 
American and 
Alaska Native 
population in 
the state 
Alaska .............................................................................................................. 48 15 16,02 0 106,300 
Arizona ............................................................................................................. 18 5 5,017 335,300 
Delaware .......................................................................................................... 2 1 112 5,900  
New Mexico ..................................................................................................... 21 10 2,265 208, 900 
South Dakota ................................................................................................... 22 9 1,606 72,80 0 
In a separate analysis, the EPA 
focused on evaluating the potential for 
disparities in populations residing near the NPIAS airports. The EPA compared the demographic composition of people living within one kilometer of runways at 2,022 of the approximately 3,300 NPIAS airports with the demographic composition of people living at a distance of one to five kilometers from the same airports.
193 194 In this analysis, over one-fourth of airports (i.e., 515) 
were identified at which children under five were more highly represented in the zero to one kilometer distance compared with the percent of children under five living one to five kilometers away (Table 7). There were 666 airports where people of color had a greater presence in the zero to one kilometer area closest 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00031 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162770 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
195This analysis of 2,022 NPIAS airports did not 
include airports in Alaska. 
196Kamal et.al., Memorandum to Docket EPA– 
HQ–OAR–2022–0389. Analysis of Potential 
Disparity in Residential Proximity to Airports in the Conterminous United States. May 24, 2022. Docket ID EPA–HQ–2022–0389. 197Kamal et.al., Memorandum to Docket EPA– 
HQ–OAR–2022–0389. Analysis of Potential Disparity in Residential Proximity to Airports in the Conterminous United States. May 24, 2022. Docket ID EPA–HQ–2022–0389. 198Federal Lead Action Plan to Reduce 
Childhood Lead Exposures and Associated Health 
Impacts. (2018) President’s Task Force on Environmental Health Risks and Safety Risks to Children. Available at https://www.epa.gov/sites/ default/files/2018-12/documents/fedactionplan _
lead_ final.pdf. 
19941 FR 14921 (April 8, 1976). See also, e.g., 81 
FR at 71910 (Oct. 18, 2016) for a description of the history of the listing decision for lead under CAA section 108. 
20073 FR 66965 (Nov. 12, 2008). to airport runways than in populations 
farther away. There were 761 airports where people living at less than two- times the Federal Poverty Level represented a higher proportion of the overall population within one kilometer of airport runways compared with the proportion of people living at less than two-times the Federal Poverty Level 
among people living one to five kilometers away. 
TABLE 7—N UMBER OF AIRPORTS (AMONG THE 2,022 A IRPORTS EVALUATED ) WITHDISPARITY FOR CERTAIN DEMO-
GRAPHIC POPULATIONS WITHIN ONEKILOMETER OF AN AIRPORT RUNWAY IN RELATION TO THE COMPARISON POPU-
LATION BETWEEN ONE AND FIVEKILOMETERS FROM AN AIRPORT RUNWAY  
Demographic group Number of airports with disparitya 
Total airports 
with disparity Disparity 
1–5% Disparity 
5–10% Disparity 
10–20% Disparity 
20%+ 
Children under five years of age ......................................... 515 507 7 1 0 
People with income less than twice the Federal Poverty 
Level ................................................................................. 761 307 223 180 51 
People of Color (all races, ethnicities and indigenous peo-
ples) .................................................................................. 666 377 126 123 40 
Non-Hispanic Black .............................................................. 405 240 77 67 21 
Hispanic ............................................................................... 551 402 85 47 17 
Non-Hispanic Asian ............................................................. 268 243 18 4 3 
Non-Hispanic Native American or Alaska Native195........... 144 130 6 7 1 
Non-Hispanic Hawaiian or Pacific Islander ......................... 18 17 1 0 0 
Non-Hispanic Other Race .................................................... 11 11 0 0 0 
Non-Hispanic Two or More Races ...................................... 226 226 0 0 0 
To understand the extent of the 
potential disparity among the 2,022 
NPIAS airports, Table 7 provides information about the distribution in the percent differences in the proportion of children, individuals with incomes below two-times the Federal Poverty Level, and people of color living within one kilometer of a runway compared with those living one to five kilometers away. For children, Table 7 indicates that for the vast majority of these airports where there is a higher percentage of children represented in the near-airport population, differences are relatively small (e.g., less than five 
percent). For the airports where disparity is evident on the basis of poverty, race and ethnicity, the disparities are potentially large, ranging up to 42 percent for those with incomes below two-times the Federal Poverty Level, and up to 45 percent for people of color.
196 
There are uncertainties in the results 
provided here inherent to the proximity- based approach used. These uncertainties include the use of block group data to provide population numbers for each demographic group analyzed, and uncertainties in the Census data, including from the use of data from different analysis years (e.g., 2010 Census Data and 2018 income data). These uncertainties are described, and their implications discussed in Kamal et.al. (2022).
197 
The data summarized here indicate 
that there is a greater prevalence of children under five years of age, an at- risk population for lead effects, within 500 meters or one kilometer of some airports compared to more distant locations. This information also indicates that there is a greater prevalence of people of color and of low-income populations within 500 meters or one kilometer of some airports compared with people living more distant. If such differences were to contribute to disproportionate and adverse impacts on people of color and low-income populations, they could indicate a potential EJ concern. Given the number of children in close proximity to runways, including those in EJ populations, there is a potential for substantial implications for children’s health. The EPA invites comment on the potential EJ impacts of aircraft lead emissions from aircraft engines and on the potential impacts on children in close proximity to runways where piston-engine aircraft operate. 
B. Federal Actions To Reduce Lead 
Exposure 
The federal government has a 
longstanding commitment to programs to reduce exposure to lead, particularly for children. In December 2018, the President’s Task Force on Environmental Health Risks and Safety 
Risks to Children released the Federal Lead Action Plan, detailing the federal government’s commitments and actions to reduce lead exposure in children, some of which are described in this section.
198In this section, we describe 
some of the EPA’s actions to reduce lead exposures from air, water, lead-based paint, and contaminated sites. 
In 1976, the EPA listed lead under 
CAA section 108, making it what is called a ‘‘criteria air pollutant.’’
199Once 
lead was listed, the EPA issued primary and secondary NAAQS under sections 109(b)(1) and (2), respectively. The EPA issued the first NAAQS for lead in 1978 and revised the lead NAAQS in 2008 by reducing the level of the standard from 1.5 micrograms per cubic meter to 0.15 micrograms per cubic meter, and revising the averaging time and form to an average over a consecutive three- month period, as described in 40 CFR 50.16.
200The EPA’s 2016 Federal 
Register notice describes the Agency’s 
decision to retain the existing Lead 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00032 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162771 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
20181 FR 71912–71913 (Oct. 18, 2016). 
202Documents pertaining to the current review of 
the NAAQS for Lead can be found here: https://
www.epa.gov/naaqs/lead-pb-air-quality-standards. 
20377 FR 555 (Jan. 5, 2012). 
20478 FR 9112 (Feb. 7, 2013). 
205Effective in Jan. 2014, the amount of lead 
permitted in pipes, fittings, and fixtures was lowered. See, Section 1417 of the Safe Drinking 
Water Act: Prohibition on Use of Lead Pipes, 
Solder, and Flux at https://www.epa.gov/sdwa/use- lead-free-pipes-fittings-fixtures-solder-and-flux- drinking-water. 
20640 CFR 141 Subpart I (June 7, 1991). 
20740 CFR 141 Subpart I (June 7, 1991). 
20886 FR 4198. (Jan. 15, 2021). 
209E.O. 13990. Protecting Public Health and the 
Environment and Restoring Science to Tackle the Climate Crisis. 86 FR 7037 (Jan. 20, 2021). 
21086 FR 31939. (Dec. 17, 2021). 
211See https://www.epa.gov/ground-water-and- 
drinking-water/review-national-primary-drinking- water-regulation-lead-and-copper. Accessed on 
Nov. 30, 2021. 
21286 FR 31939 (Dec. 17, 2021). 21366 FR 1206 (Jan. 5, 2001). 
21484 FR 32632 (July 9, 2019). NAAQS.201The Lead NAAQS is 
currently undergoing review.202 
States are primarily responsible for 
ensuring attainment and maintenance of 
the NAAQS. Under section 110 of the Act and related provisions, states are to submit, for EPA review and, if appropriate, approval, state implementation plans that provide for the attainment and maintenance of such standards through control programs directed to sources of the pollutants involved. The states, in conjunction with the EPA, also administer the Prevention of Significant Deterioration program for these pollutants. 
Additional EPA programs to address 
lead in the environment include the Federal Motor Vehicle Control program under Title II of the Act, which involves controls for motor vehicles and nonroad engines and equipment; the new source performance standards under section 111 of the Act; and emissions standards for solid waste incineration units and the national emission standards for hazardous air pollutants (NESHAP) under sections 129 and 112 of the Act, respectively. 
The EPA has taken a number of 
actions associated with these air pollution control programs, including completion of several regulations requiring reductions in lead emissions from stationary sources regulated under the CAA sections 112 and 129. For example, in January 2012, the EPA updated the NESHAP for the secondary lead smelting source category.
203These 
amendments to the original maximum achievable control technology standards apply to facilities nationwide that use 
furnaces to recover lead from lead- bearing scrap, mainly from automobile batteries. Regulations completed in 2013 for commercial and industrial solid waste incineration units also require reductions in lead emissions.
204 
A broad range of Federal programs 
beyond those that focus on air pollution control provide for nationwide reductions in environmental releases and human exposures to lead. For example, pursuant to section 1417 of the Safe Drinking Water Act (SDWA), any pipe, pipe or plumbing fitting or fixture, solder, or flux for potable water applications may not be used in new installations or repairs or introduced into commerce unless it is considered ‘‘lead free’’ as defined by that Act.
205 Also under section 1412 of the SDWA, 
the EPA’s 1991 Lead and Copper Rule
206regulates lead in public 
drinking water systems through corrosion control and other utility actions which work together to minimize lead levels at the tap.
207On 
January 15, 2021, the agency published the Lead and Copper Rule Revisions (LCRR)
208and subsequently reviewed 
the rule in accordance with Executive Order 13990.
209While the LCRR took 
effect in December 2021, the agency concluded that there are significant opportunities to improve the LCRR.
210 
The EPA is developing a new proposed rule, the Lead and Copper Rule Improvements (LCRI),
211that would 
further strengthen the lead drinking 
water regulations. The EPA identified priority improvements for the LCRI: proactive and equitable lead service line replacement (LSLR), strengthening compliance tap sampling to better identify communities most at risk of lead in drinking water and to compel lead reduction actions, and reducing the complexity of the regulation through improvement of ‘‘methods to identify and trigger action in communities that are most at risk of elevated drinking water levels.’’
212The EPA intends to 
propose the LCRI and take final action on it prior to October 16, 2024. 
Federal programs to reduce exposure 
to lead in paint, dust, and soil are specified under the comprehensive federal regulatory framework developed under the Residential Lead-Based Paint Hazard Reduction Act (Title X). Under Title X (codified, in part, as Title IV of the Toxic Substances Control Act [TSCA]), the EPA has established regulations and associated programs in six categories: (1) Training, certification and work practice requirements for persons engaged in lead-based paint activities (abatement, inspection and risk assessment); accreditation of training providers; and authorization of state and Tribal lead-based paint programs; (2) training, certification, and work practice requirements for persons engaged in home renovation, repair and 
painting (RRP) activities; accreditation of RRP training providers; and authorization of state and Tribal RRP programs; (3) ensuring that, for most housing constructed before 1978, information about lead-based paint and lead-based paint hazards flows from sellers to purchasers, from landlords to tenants, and from renovators to owners and occupants; (4) establishing standards for identifying dangerous levels of lead in paint, dust and soil; (5) providing grant funding to establish and maintain state and Tribal lead-based paint programs; and (6) providing information on lead hazards to the public, including steps that people can take to protect themselves and their families from lead-based paint hazards. 
The most recent rules issued under 
Title IV of TSCA revised the dust-lead hazard standards (DLHS) and dust-lead clearance levels (DLCL) which were established in a 2001 final rule entitled ‘‘Identification of Dangerous Levels of Lead.’’
213The DLHS are incorporated 
into the requirements and risk assessment work practice standards in the EPA’s Lead-Based Paint Activities Rule, codified at 40 CFR part 745, subpart L. They provide the basis for risk assessors to determine whether dust-lead hazards are present in target housing (i.e., most pre-1978 housing) 
and child-occupied facilities (pre-1978 nonresidential properties where children 6 years of age or under spend a significant amount of time such as daycare centers and kindergartens). If dust-lead hazards are present, the risk assessor will identify acceptable options for controlling the hazards in the respective property, which may include abatements and/or interim controls. In July 2019, the EPA published a final rule revising the DLHS from 40 micrograms per square foot and 250 micrograms per square foot to 10 micrograms per square foot and 100 micrograms per square foot of lead in dust on floors and windowsills, respectively.
214The DLCL are used to 
evaluate the effectiveness of a cleaning following an abatement. If the dust-lead levels are not below the clearance levels, the components (i.e., floors, 
windowsills, troughs) represented by the failed sample(s) shall be recleaned 
and retested. In January 2021, the EPA published a final rule revising the DLCL to match the DLHS, lowering them from 40 micrograms per square foot and 250 micrograms per square foot to 10 micrograms per square foot and 100 micrograms per square foot on floors 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00033 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162772 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
21586 FR 983 (Jan. 7, 2021). 
21686 FR 7037 (Jan. 20, 2021). 
217For more information about the EPA’s 
CERCLA program, see www.epa.gov/superfund. 
218For more information about the EPA’s RCRA 
program, see https://www.epa.gov/rcra. 
219See https://www.epa.gov/regulations- 
emissions-vehicles-and-engines/petitions-and-epa- 
response-memorandums-related-lead. Accessed on 
Dec. 12, 2021. 220Friends of the Earth (formerly Bluewater 
Network) comment dated Dec. 12, 2003, submitted to EPA’s 68 FR 56226, published Sept. 30, 2003. 
221See 72 FR 64570 (Nov. 16, 2007). 
22275 FR 22440–68 (Apr. 28, 2010). 
223Petitioners filed a complaint in district court 
seeking to compel EPA to respond to their 2006 petition for rulemaking and to issue an endangerment finding and promulgate regulations. The EPA then issued its response to the petition, mooting that claim of the complaint. In response to EPA’s motion for summary judgment on the remaining claims, the court concluded that making the endangerment determination is not a nondiscretionary act or duty and thus that it lacked jurisdiction to grant the relief requested by plaintiffs. Friends of the Earth v. EPA, 934 F. Supp. 
2d 40, 55 (D.D.C. 2013). 
224The petition for reconsideration submitted to 
EPA by Friends of the Earth, Physicians for Social Responsibility, and Oregon Aviation Watch is available at https://www.epa.gov/sites/default/files/ 2016-09/documents/avgas-petition-reconsider-04- 21-14.pdf. 
225The 2015 EPA response to the 2014 petition 
for reconsideration is available at https://www.epa.gov/sites/default/files/2016-09/ documents/ltr-response-av-ld-foe-psr-oaw-2015-1- 23.pdf. 
226The 2021 petition is available at https://
www.epa.gov/system/files/documents/2022-01/ aviation-leaded-avgas-petition-exhibits-final-2021- 10-12.pdf. 
227EPA’s response to the 2021 petition is 
available at https://www.epa.gov/system/files/ documents/2022-01/ltr-response-aircraft-lead- petitions-aug-oct-2022-01-12.pdf. and windowsills, respectively.215The 
EPA is now reconsidering the 2019 and 
2021 rules in accordance with Executive Order 13990
216and in response to a 
May 2021 decision by U.S. Court of Appeals for the Ninth Circuit. 
Programs associated with the 
Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund)
217and 
Resource Conservation Recovery Act (RCRA)
218also implement removal and 
remedial response programs that reduce exposures to the release or threat of a release of lead and other hazardous substances. The EPA develops and implements protective levels for lead in soil at Superfund sites and, together with states, at RCRA corrective action facilities. The Office of Land and Emergency Management develops policy and guidance for addressing multimedia lead contamination and determining appropriate response actions at lead sites. Federal programs, including those implementing RCRA, provide for management of hazardous substances in hazardous and municipal solid waste (e.g., 66 FR 58258, 
November 20, 2001). 
C. History of Lead Endangerment 
Petitions for Rulemaking and the EPA Responses 
The Administrator’s proposed 
findings further respond to several citizen petitions on this subject including the following: petition for rulemaking submitted by Friends of the Earth in 2006, petition for rulemaking submitted by Friends of the Earth, Oregon Aviation Watch and Physicians for Social Responsibility in 2012, petition for reconsideration submitted by Friends of the Earth, Oregon Aviation Watch, and Physicians for Social Responsibility in 2014, and petition for rulemaking from Alaska Community Action on Toxics, Center for Environmental Health, Friends of the Earth, Montgomery-Gibbs Environmental Coalition, Oregon Aviation Watch, the County of Santa Clara, CA, and the Town of Middleton, WI in 2021. These petitions and the EPA’s responses are described here.
219 
In a 2003 letter to the EPA, Friends of 
the Earth initially raised the issue of the potential for lead emissions from the use of leaded avgas in general aviation aircraft using piston engines to cause or contribute to endangerment of public health or welfare.
220In 2006, Friends of 
the Earth filed a petition with the EPA requesting that the Administrator find endangerment or, if there was insufficient information to find endangerment, commence a study of lead emissions from piston-engine aircraft. In 2007, the EPA issued a Federal Register notice on the petition requesting comments and information related to a wide range of issues regarding the use of leaded avgas and potential public health and welfare exposure issues.
221The EPA did not 
receive new information to inform the evaluation of whether lead emissions from aircraft engines using leaded avgas cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. 
In 2010, the EPA further responded to 
the 2006 petition from Friends of the Earth by issuing an Advance Notice of Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded Aviation Gasoline (ANPR).
222In the ANPR, the EPA 
described information currently available and information being collected that would be used by the Administrator to issue a subsequent proposal regarding whether, in the Administrator’s judgment, aircraft lead emissions from aircraft using leaded avgas cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. After issuing the ANPR, the EPA continued the data collection and evaluation of information that is described in Sections II.A, IV and V of this action. 
In 2012, Friends of the Earth, 
Physicians for Social Responsibility, and Oregon Aviation Watch filed a new petition claiming that, among other things, the EPA had unreasonably delayed in responding to the 2006 petition from Friends of the Earth because it had failed to determine whether emissions of lead from general aviation aircraft engines cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare.
223The EPA responded to the 2012 petition with our plan for collecting the necessary information and conducting a proceeding under CAA section 231 regarding whether lead emissions from piston-engine aircraft cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare. Friends of the Earth, Physicians for Social Responsibility, and Oregon Aviation Watch submitted a petition for reconsideration in 2014
224to which the 
EPA responded in 2015.225 
In 2021, Alaska Community Action on 
Toxics, Center for Environmental Health, Friends of the Earth, Montgomery-Gibbs Environmental Coalition, Oregon Aviation Watch, the County of Santa Clara, CA, and the Town of Middleton, WI, again petitioned the EPA to conduct a proceeding under CAA section 231 regarding whether lead emissions from piston-engine aircraft cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare.
226The EPA 
responded in 2022 noting our intent to develop this proposal regarding whether lead emissions from piston-engine aircraft cause or contribute to air pollution that may reasonably be anticipated to endanger public health or welfare.
227 
III. Legal Framework for This Action 
In this action, the EPA is proposing to 
make two separate determinations—an endangerment finding and a cause or contribute finding—under section 231(a)(2)(A) of the Clean Air Act. The EPA has, most recently, finalized such findings under CAA section 231 for greenhouse gases (GHGs) in 2016 (2016 Findings), and in that action the EPA 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00034 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162773 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
228FR 54422–54475 (Aug. 15, 2016). 
229See e.g., 81 FR at 55434–54440 (Aug. 19, 
2016). 
23074 FR 66496, 66505–10 (Dec. 15, 2009). 
231Coalition for Responsible Regulation, Inc. v. 
EPA, 684 F.3d 102 (D.C. Cir. 2012) (CRR) 
(subsequent history omitted). 
23281 FR at 55434 (Aug. 19, 2016). 
23381 FR at 55434 (Aug. 19, 2016). 
234Regarding ‘‘welfare,’’ the CAA states that ‘‘[a]ll 
language referring to effects on welfare includes, 
but is not limited to, effects on soils, water, crops, vegetation, manmade materials, animals, wildlife, weather, visibility, and climate, damage to and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal comfort and well-being, whether caused by transformation, conversion, or combination with other air pollutants.’’ CAA section 302(h). Regarding ‘‘public health,’’ there is no definition of ‘‘public health’’ in the Clean Air Act. The Supreme Court has discussed the concept of ‘‘public health’’ in the context of whether costs can be considered when setting NAAQS. Whitman v. American Trucking Ass’n, 531 U.S. 457 (2001). 
In Whitman, the Court imbued the term with its 
most natural meaning: ‘‘the health of the public.’’ Id. at 466. 
235See Massachusetts v. EPA, 549 U.S. 497,533 
(2007) (interpreting an analogous provision in CAA section 202). 
236See 81 FR at 54435 (Aug. 19, 2016). 
237CRR, 684 F.3d at 122 (internal citations 
omitted) (June 26, 2012). 238CRR, 684 F.3d at 122 (internal citations 
omitted) (June 26, 2012). 
23981 FR at 54425 (Aug. 19, 2016). 
240See, e.g., Rulemaking for non-road 
compression-ignition engines under section 213(a)(4) of the CAA, Proposed Rule at 58 FR 28809, 28813–14 (May 17, 1993), Final Rule at 59 FR 31306, 31318 (June 17, 1994); Rulemaking for highway heavy-duty diesel engines and diesel sulfur fuel under sections 202(a) and 211(c) of the CAA, Proposed Rule at 65 FR 35430 (June 2, 2000), and Final Rule at 66 FR 5002 (Jan. 18, 2001). 
241As the Administrator is applying the 
provisions of CAA section 307(d) to this action under section 307(d)(1)(V), we need not determine whether those provisions would apply to this action under section 307(d)(1)(F). provided a detailed explanation of the 
legal framework for making such findings and the statutory interpretations and caselaw supporting its approach.
228In this proposal, the 
Administrator is using the same approach of applying a two-part test under section 231(a)(2)(A) as described in the 2016 Findings and is relying on the same interpretations supporting that approach, which are briefly described in this Section, and set forth in greater detail in the 2016 Findings.
229This is 
also the same approach that the EPA used in making endangerment and cause and contribute findings for GHGs under section 202(a) of the CAA in 2009 (2009 Findings),
230which was affirmed 
by the U.S. Court of Appeals for the D.C. Circuit in 2012.
231As explained further 
in the 2016 Findings, the text of the CAA section concerning aircraft emissions in section 231(a)(2)(A) mirrors the text of CAA section 202(a) that was the basis for the 2009 Findings.
232Accordingly, for the same 
reasons as discussed in the 2016 Findings, the EPA believes it is reasonable to use the same approach under section 231(a)(2)(A)’s similar text as was used under section 202(a) for the 2009 Findings, and it is proposing to act consistently with that framework for purposes of these proposed section 231 findings.
233As this approach has been 
previously discussed at length in the 2016 and 2009 Findings, the EPA provides only a brief description in this proposal. 
A. Statutory Text and Basis for This 
Proposal 
Section 231(a)(2)(A) of the CAA 
provides that the ‘‘The Administrator shall, from time to time, issue proposed emission standards applicable to the emission of any air pollutant from any class or classes of aircraft engines which in his judgment causes, or contributes to, air pollution which may reasonably be anticipated to endanger public health or welfare.’’
234In this proposal, the EPA is addressing the predicate for regulatory action under CAA section 231 through a two-part test, which as noted previously, is the same as the test used in the 2016 Findings and in the 2009 Findings. 
As the first step of the two-part test, 
the Administrator must decide whether, in his judgment, the air pollution under consideration may reasonably be anticipated to endanger public health or 
welfare. As the second step, the Administrator must decide whether, in his judgment, emissions of an air pollutant from certain classes of aircraft engines cause or contribute to this air pollution. If the Administrator answers both questions in the affirmative, he will issue standards under section 231.
235 
In accordance with the EPA’s 
interpretation of the text of section 231(a)(2)(A), as described in the 2016 Findings, the phrase ‘‘may reasonably be anticipated’’ and the term ‘‘endanger’’ in section 231(a)(2)(A) authorize, if not require, the Administrator to act to prevent harm and to act in conditions of uncertainty.
236They do not limit him to 
merely reacting to harm or to acting only when certainty has been achieved; indeed, the references to anticipation and to endangerment imply that the failure to look to the future or to less than certain risks would be to abjure the Administrator’s statutory responsibilities. As the D.C. Circuit explained, the language ‘‘may reasonably be anticipated to endanger public health or welfare’’ in CAA section 202(a) requires a ‘‘precautionary, forward-looking scientific judgment about the risks of a particular air pollutant, consistent with the CAA’s precautionary and preventive orientation.’’
237The court determined 
that ‘‘[r]equiring that the EPA find ‘certain’ endangerment of public health or welfare before regulating greenhouse gases would effectively prevent the EPA from doing the job that Congress gave it in [section] 202(a)—utilizing emission standards to prevent reasonably anticipated endangerment from maturing into concrete harm.’’
238The 
same language appears in section 231(a)(2)(A), and the same interpretation applies in that context. 
Moreover, by instructing the 
Administrator to consider whether emissions of an air pollutant cause or contribute to air pollution in the second part of the two-part test, the Act makes clear that he need not find that emissions from any one sector or class of sources are the sole or even the major part of the air pollution considered. This is clearly indicated by the use of the term ‘‘contribute.’’ Further, the phrase ‘‘in his judgment’’ authorizes the Administrator to weigh risks and to consider projections of future possibilities, while also recognizing uncertainties and extrapolating from existing data. 
Finally, when exercising his judgment 
in making both the endangerment and cause-or-contribute findings, the Administrator balances the likelihood and severity of effects. Notably, the phrase ‘‘in his judgment’’ modifies both ‘‘may reasonably be anticipated’’ and ‘‘cause or contribute.’’ 
Often, past endangerment and cause 
or contribute findings have been proposed concurrently with proposed standards under various sections of the CAA, including section 231.
239 
Comment has been taken on these proposed findings as part of the notice and comment process for the emission standards.
240However, there is no 
requirement that the Administrator propose the endangerment and cause or contribute findings concurrently with proposed standards and, most recently under section 231, the EPA made separate endangerment and cause or contribute findings for GHGs before proceeding to set standards. 
The Administrator is applying the 
rulemaking provisions of CAA section 307(d) to this action, pursuant to CAA section 307(d)(1)(V), which provides that the provisions of 307(d) apply to ‘‘such other actions as the Administrator may determine.’’
241Any subsequent 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00035 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162774 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
242See CRR, 684 F.3d at 117 (explaining two-part 
analysis under section 202(a)) (June 26, 2012). 
243See, e.g., 81 FR 54422, 54434–55435 (Aug. 15, 
2016). 
244See, e.g., 81 FR at 54437–54438 (September 4, 
2013). 
245See, e.g., 81 FR at 54437–54438 (Aug. 15, 
2016). 246See, e.g., 81 FR at 54437–54438 (Aug. 15, 
2016). 
247See 81 FR at 54437–54438 (Aug. 15, 2016). 
248See 81 FR at 54437–54438 (Aug. 15, 2016). 
249See 81 FR at 54437–54438 (Aug. 15, 2016). 
250CRR, 684 F.3d at 122–123 (June 26, 2012). 
251CRR, 684 F.3d at 122–123. (quoting Ethyl 
Corp., 541 F.2d at 18) (June 26, 2012). 
25281 FR at 54438 (Aug. 15, 2016). 
25381 FR at 54438 (Aug. 15, 2016). 25481 FR at 54438 (Aug. 15, 2016). 
255See 81 FR at 54462 (Aug. 15, 2016). standard setting rulemaking under CAA 
section 231 will also be subject to the notice and comment rulemaking procedures under CAA section 307(d), as provided in CAA section 307(d)(1)(F) (applying the provisions of CAA section 307(d) to the promulgation or revision of any aircraft emission standard under CAA section 231). Thus, these proposed findings will be subject to the same procedural requirements that would apply if the proposed findings were part of a standard-setting rulemaking. 
B. Considerations for the Endangerment 
and Cause or Contribute Analyses Under Section 231(a)(2)(A) 
In the context of this proposal, the 
EPA understands section 231(a)(2)(A) of the CAA to call for the Administrator to exercise his judgment and make two separate determinations: first, whether the relevant kind of air pollution (here, lead air pollution) may reasonably be anticipated to endanger public health or welfare, and second, whether emissions of any air pollutant from classes of the sources in question (here, any aircraft engine that is capable of using leaded aviation gasoline), cause or contribute to this air pollution.
242 
This analysis entails a scientific 
judgment by the Administrator about the potential risks posed by lead 
emissions to public health and welfare. In this proposed action, the EPA is using the same approach in making scientific judgments regarding endangerment as it has previously described in the 2016 Findings, and its analysis is guided by the same five principles that guided the Administrator’s analysis in those Findings.
243 
Similarly, the EPA is taking the same 
approach to the cause or contribute analysis as was previously explained in the 2016 Findings.
244For example, as 
previously noted, section 231(a)(2)(A)’s instruction to consider whether emissions of an air pollutant cause or contribute to air pollution makes clear that the Administrator need not find that emissions from any one sector or class of sources are the sole or even the major part of an air pollution problem.
245Moreover, like the CAA 
section 202(a) language that governed the 2009 Findings, the statutory language in section 231(a)(2)(A) does not contain a modifier on its use of the term ‘‘contribute.’’
246Unlike other CAA 
provisions, it does not require 
‘‘significant’’ contribution. Compare, e.g., CAA sections 111(b); 213(a)(2), (4). 
Congress made it clear that the Administrator is to exercise his judgment in determining contribution, and authorized regulatory controls to address air pollution even if the air pollution problem results from a wide variety of sources.
247While the 
endangerment test looks at the air pollution being considered as a whole and the risks it poses, the cause or contribute test is designed to authorize the EPA to identify and then address what may well be many different sectors, classes, or groups of sources that are each part of the problem.
248 
Moreover, as the EPA has previously 
explained, the Administrator has ample discretion in exercising his reasonable judgment and determining whether, under the circumstances presented, the cause or contribute criterion has been met.
249As noted in the 2016 Findings, 
in addressing provisions in section 202(a), the D.C. Circuit has explained that the Act at the endangerment finding step did not require the EPA to identify a precise numerical value or ‘‘a minimum threshold of risk or harm before determining whether an air pollutant endangers.’’
250Accordingly, 
the EPA ‘‘may base an endangerment 
finding on ‘a lesser risk of greater harm . . . or a greater risk of lesser harm’ or any combination in between.’’
251As the 
language in section 231(a)(2)(A) is analogous to that in section 202(a), it is reasonable to apply this interpretation to the endangerment determination under section 231(a)(2)(A).
252Moreover, 
the logic underlying this interpretation supports the general principle that under CAA section 231 the EPA is not required to identify a specific minimum threshold of contribution from potentially subject source categories in determining whether their emissions ‘‘cause or contribute’’ to the endangering air pollution.
253The 
reasonableness of this principle is further supported by the fact that section 231 does not impose on the EPA a requirement to find that such contribution is ‘‘significant,’’ let alone the sole or major cause of the 
endangering air pollution.
254 
Finally, as also described in the 2016 
Findings, there are a number of possible ways of assessing whether air pollutants cause or contribute to the air pollution which may reasonably be anticipated to endanger public health and welfare, and no single approach is required or has been used exclusively in previous cause or contribute determinations under title II of the CAA.
255 
C. Regulatory Authority for Emission Standards 
Though the EPA is not proposing 
standards in this action, should the EPA finalize these findings, the EPA would then proceed to propose emission standards under CAA section 231. As noted in Section III.A of this document, section 231(a)(2)(A) of the CAA 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 his or her judgment causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare. 
CAA section 231(a)(2)(B) further 
directs the EPA to consult with the Administrator of the FAA on such standards, and it prohibits the EPA from changing aircraft emission standards if such a change would significantly increase noise and adversely affect safety. CAA section 231(a)(3) provides that after we provide notice and an opportunity for a public hearing on standards, the Administrator shall issue such standards ‘‘with such modifications as he deems appropriate.’’ In addition, under CAA section 231(b), the EPA determines, in consultation with the U.S. Department of Transportation (DOT), that the effective date of any standard provides the necessary time to permit the development and application of the requisite technology, giving appropriate consideration to the cost of compliance. 
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, section 233 of the CAA vests the authority to promulgate emission standards for aircraft or aircraft engines only in the federal government. States are preempted from adopting or enforcing any standard respecting aircraft or aircraft engine 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00036 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162775 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
256CAA Section 233 (Dec. 31, 1970). 
257EPA (2013) ISA for Lead. Section 2.2. 
‘‘Sources of Atmospheric Pb.’’ p. 2–1. EPA, 
Washington, DC, EPA/600/R–10/075F, 2013. 
258EPA (2013) ISA for Lead. Executive Summary. 
‘‘Sources, Fate and Transport of Lead in the Environment, and the Resulting Human Exposure and Dose.’’ pp. lxxviii-lxxix. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
259The lead air pollution that we are considering 
in this proposed finding can occur as elemental lead or in lead-containing compounds, and this proposed definition of the air pollution recognizes that lead in air (whatever form it is found in, including in inorganic and organic compounds containing lead) has the potential to elicit public health and welfare effects. We note, for example, that the 2013 Lead ISA and 2008 AQCD described the toxicokinetics of inorganic and organic forms of lead and studies evaluating lead-related health effects commonly measure total lead level ( i.e., all 
forms of lead in various biomarker tissues such as blood). 260EPA (2013) ISA for Lead. EPA, Washington, 
DC, EPA/600/R–10/075F, 2013. 
261EPA (2006) AQC for Lead. EPA, Washington, 
DC, EPA/600/R–5/144aF, 2006. 
262EPA (2013) ISA for Lead. Section 5.4. 
‘‘Summary.’’ p. 5–40. EPA, Washington, DC, EPA/ 
600/R–10/075F, 2013. 
263The causal framework draws upon the 
assessment and integration of evidence from across 
scientific disciplines, spanning atmospheric chemistry, exposure, dosimetry and health effects studies (i.e., epidemiologic, controlled human 
exposure, and animal toxicological studies), and assessment of the related uncertainties and limitations that ultimately influence our understanding of the evidence. This framework employs a five-level hierarchy that classifies the overall weight-of-evidence with respect to the causal nature of relationships between criteria pollutant exposures and health and welfare effects using the following categorizations: causal relationship; likely to be causal relationship; suggestive of, but not sufficient to infer, a causal relationship; inadequate to infer the presence or absence of a causal relationship; and not likely to be a causal relationship. EPA (2013) ISA for Lead. Preamble Section. p. xliv. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 264EPA (2013) ISA for Lead. Table ES–1. 
‘‘Summary of causal determinations for the relationship between exposure to Pb and health effects.’’ pp. lxxxiii-lxxxvii. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
265EPA (2013) ISA for Lead. Table ES–1. 
‘‘Summary of causal determinations for the relationship between exposure to Pb and health effects.’’ p. lxxxiii and p. lxxxvi. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
266EPA (2013) ISA for Lead. Table ES–1. 
‘‘Summary of causal determinations for the relationship between exposure to Pb and health effects.’’ pp. lxxxiii-lxxxiv. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
267EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxvii- lxxxviii. EPA, Washington, DC, EPA/600/R–10/ 075F, 2013. emissions unless such standard is 
identical to the EPA’s standards.256 
IV. The Proposed Endangerment Finding Under CAA Section 231 
A. Scientific Basis of the Endangerment 
Finding 
1. Lead Air Pollution 
Lead is emitted and exists in the 
atmosphere in a variety of forms and 
compounds and is emitted by a wide range of sources.
257Lead is persistent in 
the environment. Atmospheric transport distances of airborne lead vary depending on its form and particle size, as discussed in Section II.A of this document, with coarse lead-bearing particles deposited to a greater extent near the source, while fine lead-bearing 
particles can be transported long distances before being deposited. Through atmospheric deposition, lead is distributed to other environmental media, including soils and surface water bodies.
258Lead is retained in soils and 
sediments, where it provides a historical record and, depending on several factors, can remain available in some areas for extended periods for environmental or human exposure, with any associated potential public health and public welfare impacts. 
For purposes of this action, the EPA 
is proposing to define the ‘‘air pollution’’ referred to in section 231(a)(2)(A) of the CAA as lead, which we also refer to as the lead air pollution in this document.
259 
2. Health Effects and Lead Air Pollution 
As noted in Section II.A of this 
document, in 2013, the EPA completed the Integrated Science Assessment for Lead which built on the findings of previous AQCDs for Lead. These documents critically assess and integrate relevant scientific information regarding the health and welfare effects of lead and have undergone extensive 
critical review by the EPA, the Clean Air Scientific Advisory Committee (CASAC), and the public. As such, these assessments provide the primary scientific and technical basis on which the Administrator is proposing to find that lead air pollution is reasonably anticipated to endanger public health and welfare.
260 261  
As summarized in Section II.A of this 
document, human exposure to lead that is emitted into the air can occur by multiple pathways. Ambient air inhalation pathways include both inhalation of air outdoors and inhalation of ambient air that has infiltrated into indoor environments. Additional exposure pathways may involve media other than air, including indoor and outdoor dust, soil, surface water and sediments, vegetation and biota. While the bioavailability of air- related lead is modified by several factors in the environment (e.g., the 
chemical form of lead, environmental fate of lead emitted to air), as described in Section II.A of this document, it is well-documented that exposures to air- related lead can result in increased blood lead levels, particularly for children living near air lead sources, who may have increased blood lead levels due to their proximity to these sources of exposure.
262 
As described in the EPA’s 2013 Lead 
ISA and in prior Criteria Documents, lead has been demonstrated to exert a broad array of deleterious effects on multiple organ systems. The 2013 Lead ISA characterizes the causal nature of relationships between lead exposure and health effects using a weight-of- evidence approach.
263We summarize 
here those health effects for which the EPA in the 2013 Lead ISA has concluded that the evidence supports a determination of either a ‘‘causal relationship,’’ or a ‘‘likely to be causal relationship,’’ or for which the evidence is ‘‘suggestive of a causal relationship’’ between lead exposure and a health effect.
264In the discussion that follows, 
we summarize findings regarding effects observed in children, effects observed in adults, and additional effects observed that are not specific to an age group. 
The EPA has concluded that there is 
a ‘‘causal relationship’’ between lead exposure during childhood (pre and postnatal) and a range of health effects in children, including the following: Cognitive function decrements; the group of externalizing behaviors comprising attention, increased impulsivity, and hyperactivity; and developmental effects (i.e., delayed 
pubertal onset).
265In addition, the EPA 
has concluded that the evidence 
supports a conclusion that there is a ‘‘likely to be causal relationship’’ between lead exposure and conduct disorders in children and young adults, internalizing behaviors such as depression, anxiety and withdrawn behavior, auditory function decrements, and fine and gross motor function decrements.
266 
Multiple epidemiologic studies 
conducted in diverse populations of children consistently demonstrate the harmful effects of lead exposure on cognitive function (as measured by decrements in intelligence quotient [IQ], decreased academic performance, and poorer performance on tests of executive function). These findings are supported by extensively documented toxicological evidence substantiating the plausibility of these findings in the epidemiological literature and provide information on the likely mechanisms underlying these neurotoxic effects.
267 
Intelligence quotient is a well- 
established, widely recognized and rigorously standardized measure of neurocognitive function which has been 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00037 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162776 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
268EPA (2013) ISA for Lead. Section 4.3.2. 
‘‘Cognitive Function.’’ p. 4–59. EPA, Washington, 
DC, EPA/600/R–10/075F, 2013. 
269EPA (2006) AQC for Lead. Sections 6.2.2 and 
8.4.2. EPA, Washington, DC, EPA/600/R–5/144aF, 2006. 
270EPA (2013) ISA for Lead. Section 4.3.2. 
‘‘Cognitive Function.’’ p. 4–59. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
271EPA (2013) ISA for Lead. Section 1.9.4. ‘‘Pb 
Exposure and Neurodevelopmental Deficits in Children.’’ p. 1–76. EPA, Washington, DC, EPA/ 600/R–10/075F, 2013. 
272EPA (2013) ISA for Lead. Section 1.9.4. ‘‘Pb 
Exposure and Neurodevelopmental Deficits in Children.’’ p. 1–76. EPA/600/R–10/075F, 2013. 
273EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxvii- lxxxviii. EPA, Washington, DC, EPA/600/R–10/ 075F, 2013. 
274EPA (2013) ISA for Lead. Section 1.9.5. 
‘‘Reversibility and Persistence of Neurotoxic Effects of Pb.’’ p. 1–76. EPA, Washington, DC, EPA/600/R– 
10/075F, 2013. 
275EPA (2013) ISA for Lead. Section 4.3.14. 
‘‘Public Health Significance of Associations between Pb Biomarkers and Neurodevelopmental Effects.’’ p. 4–279. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 
276EPA (2013) ISA for Lead. Section 1.9.1. 
‘‘Public Health Significance.’’ p. 1–68. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
277EPA (2013) ISA for Lead. Executive Summary. 
‘‘Public Health Significance.’’ p. xciii. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
278EPA (2013) ISA for Lead. Section 1.9.1. 
‘‘Public Health Significance.’’ p. 1–68. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
279EPA (2013) ISA for Lead. Section 1.9.1. 
‘‘Public Health Significance.’’ p. 1–68. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
280EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii. EPA/600/R–10/075F, 2013. 281EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii. EPA/600/R–10/075F, 2013. 
282EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii. EPA/600/R–10/075F, 2013. 
283EPA (2013) ISA for Lead. Executive Summary. 
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii. EPA/600/R–10/075F, 2013. 
284EPA (2013) ISA for Lead. Executive Summary. 
‘‘Public Health Significance.’’ p. xciii. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
285EPA (2013) ISA for Lead. Table ES–1. 
‘‘Summary of causal determinations for the 
relationship between exposure to Pb and health effects.’’ pp. lxxxiv-lxxxvii. EPA, Washington, DC, EPA/600/R–10/075F, 2013. used extensively as a measure of the 
negative effects of exposure to lead.
268 269 Examples of other measures 
of cognitive function negatively 
associated with lead exposure include measures of intelligence and cognitive development and cognitive abilities, such as learning, memory, and executive functions, as well as academic performance and achievement.
270 
In summarizing the evidence related 
to neurocognitive impacts of lead at different childhood lifestages, the 2013 Lead ISA notes that ‘‘in individual studies, postnatal (early childhood and concurrent [with IQ testing]) blood lead levels are also consistently associated with cognitive function decrements in children and adolescents.’’
271The 2013 
Lead ISA additionally notes that the findings from experimental animal studies indicate that lead exposures during multiple early lifestages and periods are observed to induce impairments in learning, and that these findings ‘‘are consistent with the understanding that the nervous system continues to develop (i.e., synaptogenesis and synaptic pruning remains active) throughout childhood and into adolescence.’’
272The 2013 
Lead ISA further notes that ‘‘it is clear that lead exposure in childhood presents a risk; further, there is no evidence of a threshold below which there are no harmful effects on cognition from lead exposure,’’ and additionally recognizes uncertainty about the lead exposures that are part of the effects and blood lead levels observed in epidemiologic studies (uncertainties which are greater in studies of older children and adults than in studies of younger children).
273Evidence suggests 
that while some neurocognitive effects of lead in children may be transient, some lead-related cognitive effects may be irreversible and persist into adulthood,
274potentially affecting lower educational attainment and financial 
well-being.275 
The 2013 Lead ISA concluded that 
neurodevelopmental effects in children were among the effects best substantiated as occurring at the lowest blood lead levels, and that these categories of effects were clearly of the greatest concern with regard to potential public health impact.
276For example, in 
considering population risk, the 2013 Lead ISA notes that ‘‘[s]mall shifts in the population mean IQ can be highly significant from a public health perspective’’.
277Specifically, if lead- 
related decrements are manifested uniformly across the range of IQ scores in a population, ‘‘a small shift in the population mean IQ may be significant from a public health perspective because such a shift could yield a larger proportion of individuals functioning in the low range of the IQ distribution, which is associated with increased risk of educational, vocational, and social failure’’ as well as a decrease in the proportion with high IQ scores.
278 
With regard to lead effects identified 
for the adult population, the 2013 Lead ISA concluded that there is a ‘‘causal relationship’’ between lead exposure and hypertension and coronary heart disease in adults. The 2013 Lead ISA concluded that cardiovascular effects in adults were those of greatest public health concern for adults because the evidence indicated that these effects occurred at the lowest blood lead levels, compared to other health effects, although the role of past versus current exposures to lead is unclear.
279 
With regard to evidence of 
cardiovascular effects and other effects of lead on adults, the 2013 Lead ISA notes that ‘‘[a] large body of evidence from both epidemiologic studies of adults and experimental studies in animals demonstrates the effect of long- term lead exposure on increased blood pressure and hypertension.’’
280In addition to its effect on blood pressure, ‘‘lead exposure can also lead to coronary heart disease and death from cardiovascular causes and is associated with cognitive function decrements, symptoms of depression and anxiety, and immune effects in adult humans.’’
281The extent to which the 
effects of lead on the cardiovascular system are reversible is not well- characterized. Additionally, the frequency, timing, level, and duration of lead exposure causing the effects observed in adults has not been pinpointed, and higher exposures earlier in life may play a role in the development of health effects measured later in life.
282The 2013 Lead ISA states 
that ‘‘[i]t is clear however, that lead exposure can result in harm to the cardiovascular system that is evident in adulthood and may also affect a broad array of organ systems.’’
283In 
summarizing the public health significance of lead on the adult population, the 2013 Lead ISA notes that ‘‘small lead-associated increases in the population mean blood pressure could result in an increase in the proportion of the population with hypertension that is significant from a public health perspective.’’
284 
In addition to the effects summarized 
here, the EPA has concluded there is a ‘‘likely to be causal relationship’’ between lead exposure and both cognitive function decrements and psychopathological effects in adults. The 2013 Lead ISA also concludes that there is a ‘‘causal relationship’’ between lead exposure and decreased red blood cell survival and function, altered heme synthesis, and male reproductive function. The EPA has also concluded there is a ‘‘likely to be causal relationship’’ between lead exposure and decreased host resistance, resulting in increased susceptibility to bacterial infection and suppressed delayed type hypersensitivity, and cancer.
285 
Additionally, the evidence is 
suggestive of lead exposure and some additional effects. These include auditory function decrements and 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00038 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162777 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
286EPA (2013) ISA for Lead. Table ES–1. 
‘‘Summary of causal determinations for the 
relationship between exposure to Pb and health effects.’’ pp. lxxxiv-lxxxvi. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
287EPA (2013) ISA for Lead. Chapter 5. 
‘‘Approach to Classifying Potential At-Risk Factors.’’ p. 5–2. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 
288EPA (2013) ISA for Lead. Section 5.4. 
‘‘Summary.’’ p. 5–44. EPA, Washington, DC, EPA/ 600/R–10/075F, 2013. 
289Causal determinations for ecological effects 
were based on integration of information on biogeochemistry, bioavailability, biological effects, and exposure-response relationships of lead in terrestrial, freshwater, and saltwater environments. This framework employs a five-level hierarchy that classifies the overall weight-of-evidence with respect to the causal nature of relationships between criteria pollutant exposures and health and welfare effects using the categorizations described in the 2013 Lead NAAQS. 290EPA (2013) ISA for Lead. Table ES–2. 
‘‘Schematic representation of the relationships between the various MOAs by which Pb exerts its effects.’’ p. lxxxii. EPA, Washington, DC, EPA/600/ R–10/075F, 2013. 
291EPA (2013) ISA for Lead. Table ES–2. 
‘‘Summary of causal determinations for the relationship between Pb exposure and effects on plants, invertebrates, and vertebrates.’’ p. xc. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
292EPA (2013) ISA for Lead. Table ES–2. 
‘‘Summary of causal determinations for the relationship between Pb exposure and effects on plants, invertebrates, and vertebrates.’’ p. xc. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
293EPA (2013) ISA for Lead. Table ES–2. 
‘‘Summary of causal determinations for the relationship between Pb exposure and effects on plants, invertebrates, and vertebrates.’’ p. xc. EPA, Washington, DC, EPA/600/R–10/075F, 2013. 
294EPA (2013) ISA for Lead. ‘‘Summary.’’ p. xcvi. 
EPA, Washington, DC, EPA/600/R–10/075F, 2013. subclinical atherosclerosis, reduced 
kidney function, birth outcomes (e.g., low birth weight, spontaneous abortion), and female reproductive function.
286 
The EPA has identified factors that 
may increase the risk of health effects of lead exposure due to susceptibility and/ or vulnerability; these are termed ‘‘at- risk’’ factors. The 2013 Lead ISA describes the systematic approach the EPA uses to evaluate the coherence of evidence to determine the biological plausibility of associations between at- risk factors and increased vulnerability and/or susceptibility. An overall weight of evidence is used to determine whether a specific factor results in a population being at increased risk of lead-related health effects.
287The 2013 
Lead ISA concludes that ‘‘there is adequate evidence that several factors— childhood, race/ethnicity, nutrition, residential factors, and proximity to lead sources—confer increased risk of lead-related health effects.’’
288 
3. Welfare Effects and Lead Air Pollution 
The 2013 Lead ISA characterizes the 
causal nature of relationships between lead exposure and welfare effects using a five-level hierarchy that classifies the overall weight-of-evidence.
289We 
summarize here the welfare effects for which the EPA has concluded that the evidence supports a determination of either a ‘‘causal relationship,’’ or a ‘‘likely to be causal relationship,’’ with exposure to lead, or that the evidence is ‘‘suggestive of a causal relationship’’ with lead exposure. The discussion that follows is organized to first provide a 
summary of the effects of lead in the terrestrial environment, followed by a summary of effects of lead in freshwater and saltwater ecosystems. The 2013 Lead ISA further describes the scales or levels at which these determinations between lead exposure and effects on plants, invertebrates, and vertebrates were made (i.e., community-level, 
ecosystem-level, population-level, organism-level or sub-organism level).
290 
In terrestrial environments, the EPA 
determined that ‘‘causal relationships’’ exist between lead exposure and reproductive and developmental effects in vertebrates and invertebrates, growth in plants, survival for invertebrates, hematological effects in vertebrates, and physiological stress in plants.
291The 
EPA also determined that there were ‘‘likely to be causal relationships’’ between lead exposure and community and ecosystem effects, growth in invertebrates, survival in vertebrates, neurobehavioral effects in invertebrates and vertebrates, and physiological stress in invertebrates and vertebrates. 
In freshwater environments, the EPA 
found that ‘‘causal relationships’’ exist between lead exposure and reproductive and developmental effects in vertebrates and invertebrates, growth in invertebrates, survival for vertebrates and invertebrates, and hematological effects in vertebrates. The EPA also determined that there were ‘‘likely to be causal relationships’’ between lead exposure and community and ecosystem effects, growth in plants, neurobehavioral effects in invertebrates and vertebrates, hematological effects in invertebrates, and physiological stress in plants, invertebrates, and vertebrates.
292 
The EPA also determined that the 
evidence for saltwater ecosystems was ‘‘suggestive of a causal relationship’’ between lead exposure and reproductive and developmental effects in invertebrates, hematological effects in vertebrates, and physiological stress in invertebrates.
293 
The 2013 Lead ISA concludes, ‘‘With 
regard to the ecological effects of lead, uptake of lead into fauna and subsequent effects on reproduction, growth and survival are established and are further supported by more recent 
evidence. These may lead to effects at the population, community, and ecosystem level of biological organization. In both terrestrial and aquatic organisms, gradients in response are observed with increasing concentration of lead and some studies report effects within the range of lead detected in environmental media over the past several decades. Specifically, effects on reproduction, growth, and survival in sensitive freshwater invertebrates are well-characterized from controlled studies at concentrations at or near lead concentrations occasionally encountered in U.S. fresh surface waters. Hematological and stress related responses in some terrestrial and aquatic species were also associated with elevated lead levels in polluted areas. However, in natural environments, modifying factors affect lead bioavailability and toxicity and there are considerable uncertainties associated with generalizing effects observed in controlled studies to effects at higher levels of biological organization. Furthermore, available studies on community and ecosystem- level effects are usually from contaminated areas where lead concentrations are much higher than typically encountered in the environment. The contribution of atmospheric lead to specific sites is not clear and the connection between air concentration of lead and ecosystem exposure continues to be poorly characterized.’’
294 
B. Proposed Endangerment Finding 
The Administrator proposes to find, 
for purposes of CAA section 231(a)(2)(A), that lead air pollution may reasonably be anticipated to endanger the public health and welfare. This proposal is based on consideration of the extensive scientific evidence, described in this section, that has been amassed over decades and rigorously peer reviewed by CASAC. 
V. The Proposed Cause or Contribute 
Finding Under CAA Section 231 
A. Proposed Definition of the Air 
Pollutant 
Under section 231, the Administrator 
is to determine whether emissions of any air pollutant from any class or classes of aircraft engines cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare. As in the 2016 Findings that the EPA made under 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00039 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162778 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
295The lead air pollutant we are considering in 
this proposed finding can occur as elemental lead 
or in lead-containing compounds, and this definition of the air pollutant recognizes the range of chemical forms of lead emitted by engines in covered aircraft. 296The lead inventories for 2008, 2011 and 2014 
are provided in the EPA (2018b) Report on the 
Environment Exhibit 2. Anthropogenic lead emissions in the U.S. Available at https://cfpub.epa.gov/roe/indicator.cfm?i=13#2. The lead 
inventories for 2017 are available at https://www.epa.gov/air-emissions-inventories/2017- 
national-emissions-inventory-nei-data#dataq. 
297Airport lead annual emissions data used were 
reported in the 2017 NEI. Available at https://www.epa.gov/air-emissions-inventories/2017- 
national-emissions-inventory-nei-data. In addition 
to the triennial NEI, the EPA collects from state, local, and Tribal air agencies point source data for larger sources every year (see https://www.epa.gov/ air-emissions-inventories/air-emissions-reporting- requirements-aerr for specific emissions 
thresholds). While these data are not typically published as a new NEI, they are available publicly upon request and are also included in https://
www.epa.gov/air-emissions-modeling/emissions- modeling-platforms, which are created for years 
other than the triennial NEI years. County estimates of lead emissions from non-aircraft sources used in this action are from the 2019 inventory. There are 3,012 counties and statistical equivalent areas where EPA estimates engine emissions of lead occur. 
298FAA. General Aviation and Part 135 Activity 
Surveys—CY 2019. Chapter 3: Primary and Actual Use. Table 1.3—General Aviation and Part 135 Total Hours Flown by Aircraft Type 2008–2019 (Hours in Thousands). Retrieved on Dec., 27, 2021 at https://www.faa.gov/data_ research/aviation_
data_ statistics/general_ aviation/CY2019/. 
299Geidosch. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Past Trends and Future Projections in General Aviation Activity and Emissions. June 1, 2022. Docket ID EPA–HQ–2022– 0389. 
300Geidosch. Memorandum to Docket EPA–HQ– 
OAR–2022–0389. Past Trends and Future Projections in General Aviation Activity and Emissions. June 1, 2022. Docket ID EPA–HQ–2022– 0389. 
301FAA TAF Fiscal Years 2020–2045 describes 
the forecast method, data sources, and review process for the TAF estimates. The documentation for the TAF is available at https://taf.faa.gov/ Downloads/TAFSummaryFY2020-2045.pdf. section 231 for greenhouse gases, in 
making this proposed cause or contribute finding under section 231(a)(2), the Administrator first defines the air pollutant being evaluated. The Administrator has reasonably and logically considered the relationship between the lead air pollution and the air pollutant when considering emissions of lead from engines used in covered aircraft. The Administrator proposes to define the air pollutant to match the proposed definition of the air pollution, such that the air pollutant analyzed for contribution would mirror the air pollution considered in the endangerment finding. Accordingly, for purposes of this action, the Administrator is proposing to define the ‘‘air pollutant’’ referred to in section 231(a)(2)(A) as lead, which we also refer to as the lead air pollutant in this document.
295As noted in Section II.A.2 
of this document, lead emitted to the air from covered aircraft engines is predominantly in particulate form as lead dibromide; however, some chemical compounds of lead that are expected in the exhaust from these engines, including alkyl lead compounds, would occur in the air in gaseous form. 
Under section 231(a), the 
Administrator is required to set ‘‘emission standards applicable to the emission of any air pollutant’’ from classes of aircraft engines that the Administrator determines causes or contributes to air pollution that may reasonably be anticipated to endanger public health or welfare. If the Administrator makes a final determination under section 231 that the emissions of the lead air pollutant from certain classes of aircraft engines cause or contribute to air pollution that may reasonably be anticipated to endanger public health and welfare, then he is called on to set standards applicable to the emission of this air pollutant. The term ‘‘standards applicable to the emission of any air pollutant’’ is not defined, and the Administrator has the discretion to interpret it in a reasonable manner to effectuate the purposes of section 231. We anticipate that the Administrator would consider a variety of factors in determining what approach to take in setting the standard or standards, and the EPA would provide notice and an opportunity to comment on the proposed standards before finalizing 
them. 
B. The Data Used To Evaluate the 
Proposed Cause or Contribute Finding 
The Administrator’s assessment of 
whether emissions from the engines used in covered aircraft cause or contribute to lead air pollution is informed by estimates of lead emissions from the covered aircraft, lead concentrations in air at and near airports that are attributable to lead emissions from piston engines used in covered aircraft, and potential future conditions. 
As used in this proposal, the term, 
‘‘covered aircraft’’ refers to all aircraft and ultralight vehicles equipped with covered engines which, in this context, means any aircraft engine that is capable of using leaded avgas. Examples of covered aircraft would include smaller piston-powered aircraft such as the Cessna 172 (single-engine aircraft) and the Beechcraft Baron G58 (twin-engine aircraft), as well as the largest piston- engine aircraft—the Curtiss C–46 and the Douglas DC–6. Other examples of covered aircraft would include rotorcraft, such as the Robinson R44 helicopter, light-sport aircraft, and ultralight vehicles equipped with piston engines. The vast majority of covered aircraft are piston-engine powered. 
In recent years, covered aircraft are 
estimated to be the largest single source of lead to air in the U.S. Since 2008, as described in Section II.A.2.b of this document, lead emissions from covered aircraft are estimated to have contributed over 50 percent of all lead emitted to the air nationally. The EPA estimates 470 tons of lead were emitted by covered aircraft in 2017, comprising 70 percent of lead emitted to air nationally that year.
296In approximately 
1,000 counties in the U.S., the EPA’s emissions inventory identifies covered aircraft as the sole source of lead emissions. Among the 1,872 counties in the U.S. for which the inventory identifies multiple sources of lead emissions, including engine emissions from covered aircraft, the contribution of aircraft engine emissions ranges from 0.0006 to 0.26 tons per year, comprising 0.0065 to 99.98 percent (respectively) of total lead emissions to air in those counties from covered aircraft.
297 Covered aircraft activity, as measured 
by the number of hours flown nationwide, increased nine percent in the period from 2012 through 2019.
298 
General aviation activity, largely conducted by covered aircraft, increased up to 52 percent at airports that are among the busiest in the U.S.
299In 
future years, while piston-engine aircraft activity overall is projected to decrease slightly, this change in activity is not projected to occur uniformly across airports in the U.S.; some airports are forecast to have increased activity by general aviation aircraft, the majority of which is conducted by piston-engine aircraft.
300Although there is some 
uncertainty in these projections, they indicate that lead emissions from covered aircraft may increase at some airports in the future.
301 
Additionally, engine emissions of 
lead from covered aircraft may deposit in the local environment and, due to the small size of the lead-bearing particles emitted by engines in covered aircraft, these particles may disperse widely in the environment. Therefore, because lead is a persistent pollutant in the environment, we anticipate current and future emissions of lead from covered aircraft engines may contribute to exposures and uptake by humans and biota into the future. 
In evaluating the contributions of 
engine emissions from covered aircraft 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00040 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162779 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
302Carr et. al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- 
field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment, 45 (32), 5795–5804. DOI: https://dx.doi.org/10.1016/j.atmosenv.
2011.07.017. 
303EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports. 
Table 6. EPA–420–R–20–003, 2020. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG52.pdf. 
304Carr et al., 2011. Development and evaluation 
of an air quality modeling approach to assess near- field impacts of lead emissions from piston-engine aircraft operating on leaded aviation gasoline. Atmospheric Environment, 45 (32), 5795–5804. DOI: https://dx.doi.org/10.1016/
j.atmosenv.2011.07.017. 
305Heiken et al., 2014. Quantifying Aircraft Lead 
Emissions at Airports. ACRP Report 133. Available at https://www.nap.edu/catalog/22142/quantifying- 
aircraft-lead-emissions-at-airports. 
306Hudda et al., 2022. Substantial Near-Field Air 
Quality Improvements at a General Aviation Airport Following a Runway Shortening. Environmental Science & Technology. DOI: 10.1021/ acs.est.1c06765. 
30773 FR 66965 (Nov. 12, 2008). 30875 FR 81226 (Dec. 27, 2010). 
309EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports 
Table 6. EPA–420–R–20–003, 2020. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=
P100YG52.pdf. 310EPA’s 2017 AirToxScreen is available at 
https://www.epa.gov/AirToxScreen. 
311South Coast Air Quality Management District 
(2012) Adoption of 2012 Lead SIP Los Angeles 
County by South Coast Governing Board, p.3–11, Table 3–3. Available at https://www.aqmd.gov/ home/air-quality/clean-air-plans/lead-state- implementation-plan. The South Coast Air Quality 
Management District identified 22 airports in the Los Angeles County-South Coast Air Basin nonattainment area; the Whiteman Airport is among those in the nonattainment area and the EPA estimated activity at this airport may increase lead concentrations to levels above the lead NAAQS in the report, Model-extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports. Table 7. EPA, Washington, DC, EPA–420–R–20– 003, 2020. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG52.pdf. 
312EPA provides updated information regarding 
nonattainment areas at this website: https:// www.epa.gov/green-book/green-book-lead-2008- area-information. to lead air pollution, as defined in 
Section V.A of this document, the EPA also considers lead concentrations in the ambient air—monitored concentrations, modeled concentrations, and model-extrapolated estimates of lead concentrations. Lead concentrations monitored in the ambient air typically quantify lead compounds collected as suspended particulate matter. The information gained from air monitoring and air quality modeling provides insight into how lead emissions from piston engines used in covered aircraft can affect lead concentrations in air. 
As described in Section II.A.3 of this 
document, the EPA has conducted air quality modeling at two airports and extrapolated modeled estimates of lead concentrations to 13,000 airports with piston-engine aircraft activity. These studies indicate that over a three-month averaging time (the averaging time for the Lead NAAQS), the engine emissions of lead from covered aircraft are estimated to contribute to air lead concentrations to a distance of at least 500 meters downwind from a runway.
302 303 Additional studies have 
reported that lead emissions from covered aircraft may have increased concentrations of lead in air by one to two orders of magnitude at locations proximate to aircraft emissions compared to nearby locations not impacted by a source of lead air emissions.
304 305 306  
In 2008 and 2010, the EPA enhanced 
the lead monitoring network by requiring monitors to be placed in areas with sources such as industrial facilities and airports, as described further in Section II.A.3 of this document.
307 308 As part of this 2010 requirement to expand lead monitoring nationally, the EPA required a 1-year monitoring study of 15 additional airports with estimated lead emissions between 0.50 and 1.0 ton per year in an effort to better understand how these emissions affect concentrations of lead in the air at and near airports. Further, to help evaluate airport characteristics that could lead to ambient lead concentrations that approach or exceed the lead NAAQS, airports for this 1-year monitoring study were selected based on factors such as the level of activity of covered aircraft and the predominant use of one runway due to wind patterns. Monitored lead concentrations in ambient air are highly sensitive to monitor location relative to the location of the run-up areas for piston-engine aircraft and other localized areas of elevated lead concentrations relative to the air monitor locations. 
The lead monitoring study at airports 
began in 2011. In 2012, air monitors were placed in close proximity to the run-up areas at the San Carlos Airport (starting on March 10, 2012) and the McClellan-Palomar Airport (starting on March 16, 2012). The concentrations of lead measured at both of these airports in 2012 were above the level of the lead NAAQS, with the highest measured levels of lead in total suspended particles over a rolling three-month average of 0.33 micrograms per cubic meter of air at the San Carlos Airport and 0.17 micrograms per cubic meter of air at the McClellan-Palomar Airport. These concentrations violate the primary and secondary lead NAAQS, which are set at a level of 0.15 micrograms per cubic meter of air measured in total suspended particles, as an average of three consecutive monthly concentrations. 
In recognition of the potential for lead 
concentrations to exceed the lead NAAQS in ambient air near the area of maximum concentration at airports, the EPA further conducted an assessment of airports nationwide, titled ‘‘Model- extrapolated Estimates of Airborne Lead Concentrations at U.S. Airports’’ and described in Section II.A.3 of this document.
309The model-extrapolated 
lead concentrations estimated in this study are attributable solely to emissions from engines in covered aircraft operating at the airports evaluated and did not include other sources of lead emissions to air. The EPA identified four airports with the potential for lead concentrations above the lead NAAQS due to lead emissions from engines used in covered aircraft. 
Additional information regarding the 
contribution of engine emissions of lead from covered aircraft to lead air pollution is provided by the EPA’s Air Toxics Screening Assessment. As described and summarized in Section II.A.3 of this document, the EPA’s Air Toxics Screening Assessment estimates that piston engines used in aircraft contribute more than 50 percent of the lead concentration in over half of the census tracts in the U.S.
310 
The EPA also notes that lead 
emissions from engines in covered aircraft are present in three of the ten areas in the U.S. currently designated as nonattainment for the 2008 lead NAAQS. These areas are Arecibo, PR, 
and Hayden, AZ, each of which include one airport servicing covered aircraft, and the Los Angeles County-South Coast Air Basin, CA, which contains at least 22 airports within its nonattainment area boundary.
311 312  
Although the lead emissions from aircraft are not the predominant source of airborne lead in these areas, the emissions from covered aircraft may increase ambient air lead concentrations in these areas. 
C. Proposed Cause or Contribution 
Finding for Lead 
Taking into consideration the data 
and information summarized in Section V of this document, the Administrator proposes to find that engine emissions of the lead air pollutant from covered aircraft cause or contribute to the lead air pollution that may reasonably be anticipated to endanger public health and welfare. In reaching this proposed conclusion, the Administrator notes that piston-engine aircraft operate on leaded avgas. That operation emits lead- 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00041 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162780 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
313The lead inventories for 2008, 2011 and 2014 
are provided in the U.S. EPA (2018b) Report on the 
Environment Exhibit 2. Anthropogenic lead emissions in the U.S. Available at https://cfpub.epa.gov/roe/indicator.cfm?i=13#2. The lead 
inventories for 2017 are available at https://www.epa.gov/air-emissions-inventories/2017- national-emissions-inventory-nei-data#dataq. 
314EPA (2020) Model-extrapolated Estimates of 
Airborne Lead Concentrations at U.S. Airports Table 7. EPA–420–R–20–003, 2020. Available at https://nepis.epa.gov/Exe/ZyPDF.cgi?Dockey=P100YG52.pdf. containing compounds into the air, 
contributing to lead air pollution in the environment. As explained in Section II.A of this document, once emitted from covered aircraft, lead may be transported and distributed to other environmental media, and present the potential for human exposure through air and non-air pathways before the lead is removed to deeper soils or waterbody sediments. In reaching this proposed finding, the Administrator takes into consideration different air quality scenarios in which emissions of the lead air pollutant from engines in covered aircraft may cause or contribute to lead air pollution. Among these considerations, he places weight on the fact that current lead emissions from covered aircraft are an important source of air-related lead in the environment and that engine emissions of lead from covered aircraft are the largest single source of lead to air in the U.S. in recent years. In this regard, he notes that these emissions contributed over 50 percent of lead emissions to air starting in 2008, when approximately 560 tons of lead was emitted by engines in covered aircraft, and more recently, in 2017, when approximately 470 tons of lead was emitted by engines in covered aircraft.
313 
Additionally, he takes into account 
the fact that in some situations lead emissions from covered aircraft have contributed and may continue to contribute to air quality that exceeds the lead NAAQS. The NAAQS are standards 
that have been set to protect public health, including the health of sensitive groups, with an adequate margin of safety, and to protect public welfare from any known or anticipated adverse effects associated with the presence of the pollutant in the ambient air. For example, the EPA’s monitoring data show that lead concentrations at two airports, McClellan-Palomar and San Carlos, violated the lead NAAQS. The EPA’s model-extrapolated estimates of lead also indicate that some U.S. airports may have air lead concentrations above the NAAQS in the area of maximum impact from operation of covered aircraft.
314Given that the 
lead NAAQS are established to protect public health and welfare, contributions 
to concentrations that exceed the lead NAAQS are of particular concern to the Administrator and add support for the proposed conclusion that lead emissions from engines in covered aircraft cause or contribute to the endangering air pollution. 
The Administrator is also concerned 
about the likelihood for these emissions to continue to be an important source of air-related lead in the environment in the future, if uncontrolled. While recognizing that national consumption of leaded avgas is forecast to decrease slightly from 2026 to 2041 commensurate with overall piston- engine aircraft activity, the Administrator also notes that these changes are not expected to occur uniformly across the U.S. For example, he takes note of the FAA forecasts for airport-specific aircraft activity out to 2045 that project decreases in activity by general aviation at some airports, while projecting increases at other airports. Although there is some uncertainty in these projections, they indicate that lead emissions from covered aircraft may increase at some airports in the future. Thus, even assuming that consumption of leaded avgas and general aviation activity decrease somewhat overall, as projected, the Administrator anticipates that current concerns about these sources of air-related lead will continue into the future, without controls. Accordingly, the Administrator is considering both current levels of emissions and anticipated future levels of emissions from covered aircraft. In doing so, the Administrator is proposing to find that current levels cause or contribute to pollution that may reasonably be anticipated to endanger public health and welfare. He also is taking into consideration the projections that some airports may see increases in activity while others see decreases, as well as the uncertainties in these predictions. The Administrator therefore considers all this information and data collectively to inform his judgment on whether lead emissions from covered aircraft cause or contribute to endangering air pollution. 
Accordingly, for all the reasons 
described, the Administrator proposes to conclude that emissions of the lead air pollutant from engines in covered aircraft cause or contribute to the lead air pollution that may reasonably be anticipated to endanger public health and welfare. VI. Statutory Authority and Executive 
Order Reviews 
Additional information about these 
statutes and Executive Orders can be found at https://www2.epa.gov/laws- regulations/laws-and-executive-orders. 
A. Executive Order 12866: Regulatory 
Planning and Review and Executive Order 13563: Improving Regulation and Regulatory Review 
This action is a ‘‘significant regulatory 
action’’ because of the cross-agency nature of this issue. Accordingly, it was submitted to the Office of Management and Budget (OMB) for review under Executive Order 12866. This action proposes a finding that emissions of the lead air pollutant from engines in covered aircraft cause or contribute to the lead air pollution that may be reasonably anticipated to endanger public health and welfare. Any changes made in response to OMB recommendations have been documented in the docket. 
B. Paperwork Reduction Act (PRA) 
This action does not impose an 
information collection burden under the 
PRA. The proposed endangerment and cause or contribute findings under CAA section 231(a)(2)(A) do not contain any information collection activities. 
C. Regulatory Flexibility Act (RFA) 
I certify that this action will not have 
a significant economic impact on a 
substantial number of small entities under the RFA. This action will not impose any requirements on small entities. The proposed endangerment and cause or contribute findings under CAA section 231(a)(2)(A) do not in-and- of-themselves impose any new requirements but rather set forth the Administrator’s proposed finding that emissions of the lead air pollutant from engines in covered aircraft cause or contribute to lead air pollution that may be reasonably anticipated to endanger public health and welfare. Accordingly, this action affords no opportunity for the EPA to fashion for small entities less burdensome compliance or reporting requirements or timetables or exemptions from all or part of the proposal. 
D. Unfunded Mandates Reform Act 
(UMRA) 
This action does not contain any 
unfunded mandate as described in UMRA, 2 U.S.C. 1531–1538 and does not significantly or uniquely affect small governments. The action imposes no enforceable duty on any state, local or Tribal governments or the private sector. 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00042 Fmt 4702 Sfmt 4702 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS162781 Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules 
315See Docket ID Number EPA–HQ–OAR–2006– 
0735. The Tribes that submitted comments were: 
The Bad River Band of Lake Superior Tribe of Chippewa Indians, The Quapaw Tribe of Oklahoma, The Leech Lake Band of Ojibwe, The Lone Pine Paiute-Shoshone Reservation, The Fond du Lac Band of Lake Superior Chippewa, and The Mille Lacs Band of Ojibwe. 
316EPA (2021) EPA Policy on Children’s Health. 
Available at https://www.epa.gov/system/files/ 
documents/2021-10/2021-policy-on-childrens- 
health.pdf. E. Executive Order 13132: Federalism 
This action does not have federalism 
implications. It will not have substantial 
direct effects on the states, on the relationship between the national government and the states, or on the distribution of power and responsibilities among the various levels of government. 
F. Executive Order 13175: Consultation 
and Coordination With Indian Tribal Governments 
This action does not have Tribal 
implications as specified in Executive Order 13175. The proposed endangerment and cause or contribute findings under CAA section 231(a)(2)(A) do not in-and-of-themselves impose any new requirements but rather set forth the Administrator’s proposed finding that emissions of the lead air pollutant from engines in covered aircraft cause or contribute to lead air pollution that may 
be reasonably anticipated to endanger public health and welfare. Thus, Executive Order 13175 does not apply to this action. 
Tribes have previously submitted 
comments to the EPA noting their concerns regarding potential impacts of lead emitted by piston-engine aircraft operating on leaded avgas at airports on, and near, their Reservation Land.
315The 
EPA plans to continue engaging with Tribal stakeholders on this issue and will offer a government-to-government consultation upon request. 
G. Executive Order 13045: Protection of 
Children From Environmental Health Risks and Safety Risks 
The EPA interprets E.O. 13045 (62 FR 
19885, April 23, 1997) as applying only to those regulatory actions that concern health or safety risks, such that the analysis required under section 5–501 of the E.O. has the potential to influence the regulation. This action is not subject to E.O. 13045 because it does not propose to establish an environmental standard intended to mitigate health or safety risks. Although the Administrator considered health and safety risks as part of the proposed endangerment and cause or contribute findings under CAA section 231(a)(2)(A), the proposed 
findings themselves, if finalized, would not impose a standard intended to mitigate those risks. While this action is not subject to Executive Order 13045 in this scenario, the Agency’s Policy on Children’s Health
316still applies. The 
Administrator considered lead exposure risks to children as part of this proposed endangerment finding under CAA section 231(a)(2)(A). This action’s discussion of the impacts of lead exposure on public health and welfare is found in Section IV of this document, and specific discussion with regard to children are contained in Supplemental Information Section C, as well as Sections II.A.5, and IV of this document. A copy of the documents pertaining to the impacts on children’s health from emissions of lead from piston-engine aircraft that the EPA references in this action have been placed in the public docket for this action (Docket EPA–HQ– OAR–2022–0389). 
H. Executive Order 13211: Actions 
Concerning Regulations That Significantly Affect Energy Supply, Distribution or Use 
This action is not a ‘‘significant 
energy action’’ because it is not likely to have a significant adverse effect on the supply, distribution or use of energy. Further, we have concluded that this action is not likely to have any adverse energy effects because the proposed endangerment and cause or contribute findings under section 231(a)(2)(A) do not in-and-of themselves impose any new requirements but rather set forth the Administrator’s proposed finding that emissions of the lead air pollutant from engines in covered aircraft cause or contribute to lead air pollution that may be reasonably anticipated to endanger public health and welfare. 
I. National Technology Transfer and 
Advancement Act (NTTAA) 
This action does not involve technical 
standards. 
J. Executive Order 12898: Federal 
Actions To Address Environmental Justice in Minority Populations and Low-Income Populations 
The EPA believes this action will not 
have potentially disproportionately high and adverse human health or environmental effects on people of 
color, low-income, or indigenous populations because this action does not affect the level of protection provided to human health or the environment. The Administrator considered the potential for lead exposure risks to people of color, low-income, and indigenous populations as part of this proposed endangerment finding under CAA section 231(a)(2)(A). This action’s discussion of lead exposure impacts on public health and welfare is found in Section IV of this document. Specific discussion focused on environmental justice with regard to people of color, low-income, and indigenous populations are found in Supplemental Information Section D, as well as Sections II.A.5, and Section IV of this document. A copy of the documents pertaining to the EPA’s analysis of potential environmental justice concerns related to this action have been placed in the public docket for this action (Docket EPA–HQ–OAR–2022– 0389). 
K. Determination Under Section 307(d) 
Section 307(d)(1)(V) of the CAA 
provides that the provisions of section 
307(d) apply to ‘‘such other actions as the administrator may determine.’’ Pursuant to section 307(d)(1)(V), the Administrator determines that this action is subject to the provisions of section 307(d). 
VII. Statutory Provisions and Legal 
Authority 
Statutory authority for this action 
comes from 42 U.S.C. 7571, 7601 and 7607. 
List of Subjects 40 CFR Parts 87 and 1031 
Environmental protection, Air 
pollution control, Aircraft, Aircraft 
engines. 
40 CFR Part 1068 
Environmental protection, 
Administrative practice and procedure, 
Confidential business information, Imports, Motor vehicle pollution, Penalties, Reporting and recordkeeping requirements, Warranties. 
Michael S. Regan, 
Administrator. 
[FR Doc. 2022–22223 Filed 10–14–22; 8:45 am] 
BILLING CODE 6560–50–P 
VerDate Sep<11>2014 17:04 Oct 14, 2022 Jkt 259001 PO 00000 Frm 00043 Fmt 4702 Sfmt 9990 E:\FR\FM\17OCP1.SGM 17OCP1lotter on DSK11XQN23PROD with PROPOSALS1