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, 62753-62781 [2022-22223]
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
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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 lossmitigation 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 lossmitigation 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
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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 lowinterest 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 lossmitigation option, including minimum/
maximum deferment amounts, lifetime
uses, etc.?
62753
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
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.
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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
Environmental Protection
Agency (EPA).
ACTION: Proposed action.
AGENCY:
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–
SUMMARY:
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
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:
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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
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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-epadockets.
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-emissionsvehicles-and-engines/regulations-leademissions-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-andengines/regulations-lead-emissionsaircraft. 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
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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 1 equipped 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 pistonengine aircraft—the Curtiss C–46 and
the Douglas DC–6. Other examples of
covered aircraft would include
rotorcraft,2 such 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
1 The FAA regulates ultralight vehicles under 14
CFR part 103.
2 Rotorcraft 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.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
and sell covered aircraft engines and
covered aircraft in the United States and
those who own or operate covered
NAICS a code
Category
aircraft. Categories that may be
regulated in a future regulatory action
SIC b code
Industry ...................
Industry ...................
Industry ...................
3364412
336411
481219
3724
3721
4522
Industry ...................
611512
8249 and 8299
62755
include, but are not limited to, those
listed here:
Examples of potentially affected entities
Manufacturers of new aircraft engines.
Manufacturers of new aircraft.
Aircraft charter services (i.e., general purpose aircraft used for a variety of specialty air and flying services). Aviation clubs providing a variety of air transportation activities to the general public.
Flight Training.
a North
American Industry Classification System (NAICS).
b Standard Industrial Classification (SIC) code.
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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 13045 3 requires
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
3 E.O. 13045. Protection of Children From
Environmental Health Risks and Safety Risks. 62 FR
19885 (April 23, 1997).
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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.5 Because
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
4 EPA (2006) A Framework for Assessing Health
Risks of Environmental Exposures to Children.
EPA, Washington, DC, EPA/600/R–05/093F, 2006.
5 EPA. 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-childrenshealth.pdf.
6 EPA. ‘‘Childhood Lifestages relating to
Children’s Environmental Health.’’ Oct. 25, 2021.
Retrieved from https://www.epa.gov/children/
childhood-lifestages-relating-childrensenvironmental-health on Nov. 22, 2021.
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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.’’ 7 Evidence
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.8 The 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.9 In 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
7 EPA (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.
8 EPA (2013) ISA for Lead. Executive Summary
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxvii–
lxxxviii. EPA/600/R–10/075F, 2013.
9 EPA (2013) ISA for Lead. Section 1.9.4. ‘‘Pb
Exposure and Neurodevelopmental Deficits in
Children.’’ p. I–75. EPA/600/R–10/075F, 2013.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
of their programs, policies, and
activities on people of color populations
and low-income populations in the
United States.10 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.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, climaterelated and other cumulative impacts on
disadvantaged communities, as well as
the accompanying economic challenges
of such impacts.’’ 12 It also declares a
policy ‘‘to secure environmental justice
and spur economic opportunity for
disadvantaged communities that have
been historically marginalized and
overburdened by pollution and underinvestment 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
10 59
FR 7629 (Feb. 16, 1994).
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-inrulemaking-guide-final.pdf. See also https://
www.epa.gov/environmentaljustice.
12 86 FR 7619 (Feb. 1, 2021).
13 76 FR 3821 (Jan. 18, 2011).
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11 Fair
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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 17 for this
action describe the scientific evidence
and analyses conducted by the EPA that
provide information about the disparity
in residential location for some lowincome 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
14 EPA (2013) ISA for Lead. Section 5.4.
‘‘Summary.’’ pp. 5–40 through 5–42. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
15 EPA (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.
16 EPA (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.
17 EPA (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.
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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 PistonEngine 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
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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 (singleengine 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.18 In 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.23 Accordingly, 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
18 As 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.
19 EPA (2013) ISA for Lead. EPA, Washington,
DC, EPA/600/R–10/075F, 2013.
20 EPA (2006) AQC for Lead. EPA, Washington,
DC, EPA/600/R–5/144aF, 2006.
21 EPA (1986) AQC for Lead. EPA, Washington,
DC, EPA–600/8–83/028aF–dF, 1986.
22 EPA (1977) AQC for Lead. EPA, Washington,
DC, EPA–600/8–77–017 (NTIS PB280411), 1977.
23 As 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 leadcontaining compounds.
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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 24 for lead and the lead
NAAQS.25 These scientific assessments
provide a comprehensive review,
24 Under 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).
25 Section 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.’’
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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 26 as 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.30 Lead emitted in the past
can remain available for environmental
or human exposure for extended time in
some areas.31 Depending 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.33 Over 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
26 EPA (2013) ISA for Lead. EPA, Washington,
DC, EPA/600/R–10/075F, 2013.
27 EPA (1977) AQC for Lead. EPA, Washington,
DC, EPA–600/8–77–017 (NTIS PB280411), 1977.
28 EPA (1986) AQC for Lead. EPA, Washington,
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386),
1986.
29 EPA (2006) AQC for Lead. EPA, Washington,
DC, EPA/600/R–5/144aF, 2006.
30 EPA (2013) ISA for Lead. Section 3.1.1.
‘‘Pathways for Pb Exposure.’’ p. 3–1. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
31 EPA (2013) ISA for Lead. Section 3.7.1.
‘‘Exposure.’’ p. 3–144. EPA, Washington, DC, EPA/
600/R–10/075F, 2013.
32 EPA (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.
33 EPA (2013) ISA for Lead. Section 2.3. ‘‘Fate and
Transport of Pb.’’ p. 2–24. EPA, Washington, DC,
EPA/600/R–10/075F, 2013.
34 EPA (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.
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ambient air.35 Ambient air inhalation
pathways include both inhalation of air
outdoors and inhalation of ambient air
that has infiltrated into indoor
environments.36 The 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 44 thus
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 pistonengine air traffic, but not in adults living
near multi-runway airports, suggesting
35 EPA (2013) ISA for Lead. Section 3.1.1.
‘‘Pathways for Pb Exposure.’’ p. 3–1. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
36 EPA (2013) ISA for Lead. Sections 1.3.
‘‘Exposure to Ambient Pb.’’ p. 1–11. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
37 EPA (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.
38 EPA (2006) AQC for Lead. Chapter 3. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
39 EPA (1986) AQC for Lead. Section 1.11.3. EPA,
Washington, DC, EPA–600/8–83/028aF-dF (NTIS
PB87142386), 1986.
40 EPA (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.
41 EPA (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.
42 EPA (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.
43 Miranda et al., 2011. A Geospatial Analysis of
the Effects of Aviation Gasoline on Childhood
Blood Lead Levels. Environmental Health
Perspectives. 119:1513–1516.
44 Zahran 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.
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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 (singleengine 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.47 Tetraethyl 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
45 Klemick et al., 2022. Cardiovascular Mortality
and Leaded Aviation Fuel: Evidence from PistonEngine Air Traffic in North Carolina. International
Journal of Environmental Research and Public
Health. 19(10):5941.
46 ASTM International (May 1, 2021) Standard
Specification for Leaded Aviation Gasolines D910–
21.
47 National 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.
48 Ogston 1981. A Short History of Aviation
Gasoline Development, 1903–1980.Society of
Automotive Engineers. p. 810848.
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do not use leaded avgas.49 50 The use of
avgas containing approximately 4 grams
of lead per gallon continued in pistonengine 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.,51 and
the FAA provides information on the
volume of leaded avgas consumed in the
U.S.52 Over 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 yearon-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.53 As 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.
49 U.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.
50 U.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.
51 DOE. 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.
52 Department of Transportation (DOT). FAA.
Aviation Policy and Plans. FAA Aerospace Forecast
Fiscal Years 2009–2025. p. 81. Available at https://
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.
53 DOT. 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.
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The FAA’s National Airspace System
Resource (NASR) 54 provides 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.55 While 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.56 The
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 pistonengine aircraft in the U.S.57 This total
includes 128,926 single-engine aircraft,
12,470 twin-engine aircraft, and 3,089
rotorcraft.58 The average age of singleengine aircraft in 2018 was 46.8 years
and the average age of twin-engine
aircraft in 2018 was 44.7 years old.59 In
2019, 883 new piston-engine aircraft
were manufactured in the U.S. some of
which are exported.60 For the period
54 See FAA. NASR. Available at https://
www.faa.gov/air_traffic/flight_info/aeronav/aero_
data/eNASR_Browser/.
55 FAA (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-2021-2025Narrative.pdf.
56 See FAA’s NASR. Available at https://
www.faa.gov/air_traffic/flight_info/aeronav/aero_
data/eNASR_Browser/.
57 FAA. 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/.
58 FAA. 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/.
59 General Aviation Manufacturers Association
(GAMA) (2019) General Aviation Statistical
Databook and Industry Outlook, p.27. Retrieved on
October 7, 2021 from: https://gama.aero/wpcontent/uploads/GAMA_2019Databook_Final-202003-20.pdf.
60 GAMA (2019) General Aviation Statistical
Databook and Industry Outlook, p.16. Retrieved on
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from 2019 through 2041, the fleet of
fixed wing 61 piston-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 2041.62 An 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 pistonengine powered rotorcraft.63 There were
approximately 664,565 pilots certified
to fly general aviation aircraft in the
U.S. in 2021.64 This 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
October 7, 2021 from: https://gama.aero/wpcontent/uploads/GAMA_2019Databook_Final-202003-20.pdf.
61 There are both fixed-wing and rotary-wing
aircraft; and airplane is an engine-driven, fixedwing aircraft and a rotorcraft is an engine-driven
rotary-wing aircraft.
62 See 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.
63 FAA 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.
64 FAA. 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.
65 FAA. 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.
66 FAA. 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/.
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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 pistonengine aircraft.68 From 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).71 The
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,
67 FAA. 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/.
68 FAA. 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/.
69 FAA. 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/.
70 In 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.
71 See FAA’s Air Traffic Activity Data. Available
at https://aspm.faa.gov/opsnet/sys/airport.asp.
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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.72 The 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.73 For 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
72 Geidosch. 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.
73 FAA’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.
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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.74 The 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 PistonEngine Aircraft
This section describes the physical
and chemical characteristics of lead
emitted by covered aircraft, and the
national, state, county and airportspecific 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
74 The 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.
75 EPA (1977) AQC for Lead. EPA, Washington,
DC, EPA–600/8–77–017 (NTIS PB280411), 1977.
76 EPA (1986) AQC for Lead. EPA, Washington,
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386),
1986.
77 EPA (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.
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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.78 Upon cooling to ambient
temperatures these brominated lead
compounds are converted to particulate
matter. The presence of lead dibromide
particles in the exhaust from a pistonengine aircraft has been confirmed by
Griffith (2020) and is the primary form
of lead emitted by engines operating on
leaded fuel.79 In 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.81 Alkyl 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).82 In 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 pistonengine aircraft emissions including
78 EPA (1986) AQC for Lead. EPA, Washington,
DC, EPA–600/8–83/028aF–dF (NTIS PB87142386),
1986.
79 Griffith 2020. Electron microscopic
characterization of exhaust particles containing lead
dibromide beads expelled from aircraft burning
leaded gasoline. Atmospheric Pollution Research
11:1481–1486.
80 EPA (1986) AQC for Lead. Volume 2: Chapters
5 & 6. EPA, Washington, DC, EPA–600/8–83/028aF–
dF (NTIS PB87142386), 1986.
81 EPA (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.
82 EPA (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.
83 Memorandum 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.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
measurements of lead.84 The 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 5.7x106 to
8.6x106 particles 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.85 Griffith (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 PistonEngine 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).86 In 2017, approximately 470 tons of
lead were emitted by engines in pistonpowered aircraft, which constituted 70
percent of the annual emissions of lead
to air in that year.87 Lead is emitted at
and near thousands of airports in the
U.S. as described in Section II.A.1 of
62761
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 88 and in the
document titled ‘‘Calculating PistonEngine Aircraft Airport Inventories for
Lead for the 2008 National Emissions
Inventory.’’ 89 The EPA’s National
Emissions Inventory (NEI) reports
airport estimates of lead emissions as
well as estimates of lead emitted inflight, 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—PISTON-ENGINE EMISSIONS OF LEAD TO AIR
2008
lotter on DSK11XQN23PROD with PROPOSALS1
Piston-engine emissions of lead to air, tons ...................................................
Total U.S. lead emissions, tons .......................................................................
Piston-engine emissions as a percent of the total U.S. lead inventory ..........
2011
560
950
59%
2014
490
810
60%
2017
460
720
64%
470
670
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.91 Among 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 inflight).92 In 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.93 In 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 airportspecific inventories may range from
0.00003 tons to 1.28 tons of lead
(median of 0.03 tons), with 656 airports
84 Swiss 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/pollutantemissions/aircraft-engine-emissions/reportappendices-database-and-data-sheets.html.
85 Swiss 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/pollutantemissions/aircraft-engine-emissions/reportappendices-database-and-data-sheets.html.
86 The 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.
87 EPA 2017 NEI. Available at https://
www.epa.gov/air-emissions-inventories/2017national-emissions-inventory-nei-data.
88 Advance Notice of Proposed Rulemaking on
Lead Emissions from Piston-Engine Aircraft Using
Leaded Aviation Gasoline. 75 FR 2440 (April 28,
2010).
89 Airport lead annual emissions data used were
reported in the 2017 NEI. Available at https://
www.epa.gov/air-emissions-inventories/2017national-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).
90 The 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.
91 Lead 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.
92 Airport lead annual emissions data used were
reported in the 2017 NEI. Available at https://
www.epa.gov/air-emissions-inventories/2017national-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-reportingrequirements-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/emissionsmodeling-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.
93 See EPA lead inventory data available at
https://www.epa.gov/air-emissions-modeling/
emissions-modeling-platforms.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
3. Concentrations of Lead in Air
Attributable to Emissions From PistonEngine 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
94 EPA 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.
95 Geidosch. 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.
96 Carr et. al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield 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.
97 Feinberg 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.
98 Municipality 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-%20
final.pdf.
99 Environment Canada (2000) Airborne
Particulate Matter, Lead and Manganese at
Buttonville Airport. Toronto, Ontario, Canada:
Conor Pacific Environmental Technologies for
Environmental Protection Service, Ontario Region.
100 Fine 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/airquality-monitoring-studies/general-aviation-study/
study-of-air-toxins-near-van-nuys-and-santamonica-airport.pdf.
101 Lead emitted from piston-engine aircraft in the
particulate phase would also be measured in
samples collected to evaluate total ambient PM2.5
concentrations.
102 EPA (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).
103 EPA (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.
104 These studies report monitored or modeled
data for averaging times ranging from
approximately 18 hours to three-month averages.
105 Carr et. al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield 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.
106 Heiken et. al., 2014. Quantifying Aircraft Lead
Emissions at Airports. ACRP Report 133. Available
at https://www.nap.edu/catalog/22142/quantifyingaircraft-lead-emissions-at-airports.
107 Hudda 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.
108 Fine 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/airquality-monitoring-studies/general-aviation-study/
study-of-air-toxins-near-van-nuys-and-santamonica-airport.pdf.
109 EPA (2020) Model-extrapolated Estimates of
Airborne Lead Concentrations at U.S. Airports.
EPA, Washington, DC, EPA–420–R–20–003, 2020.
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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
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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 runup 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
2008.114 The 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.115 In
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
110 EPA (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=P1007
H4Q.PDF.
111 EPA (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.
112 Feinberg 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.
113 Feinberg 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.
114 73 FR 66965 (Nov. 12, 2008).
115 40 CFR 50.16 (Nov. 12, 2008).
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ton or more per year.116 As 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—LEAD CONCENTRATIONS
MONITORED AT 17 AIRPORTS IN THE
U.S.
Airport, State
Lead
design
value,119
μg/m3
Auburn Municipal Airport, WA ..
Brookhaven Airport, NY ............
Centennial Airport, CO .............
Deer Valley Airport, AZ ............
Gillespie Field, CA ....................
Harvey Field, WA .....................
McClellan-Palomar Airport, CA
Merrill Field, AK ........................
Nantucket Memorial Airport,
MA .........................................
Oakland County International
Airport, MI .............................
Palo Alto Airport, CA ................
Pryor Field Regional Airport, AL
Reid-Hillview Airport, CA ..........
Republic Airport, NY .................
San Carlos Airport, CA .............
Stinson Municipal, TX ...............
Van Nuys Airport, CA ...............
0.06
0.03
0.02
0.04
0.07
0.02
0.17
0.07
0.01
0.02
0.12
0.01
0.10
0.01
0.33
0.03
0.06
116 75
FR 81226 (Dec. 27, 2010).
(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.
118 EPA (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.
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117 EPA
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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 runup 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
119 A 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.
120 As 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.
121 The 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.
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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.124 The modelextrapolated 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.125 This approach
for conducting a nationwide analysis of
airports was selected due to the impact
of piston-engine aircraft run-up
122 EPA (2020) Model-Extrapolated Estimates of
Airborne Lead Concentrations at U.S. Airports.
EPA, Washington, DC, EPA–420–R–20–003, 2020.
123 EPA (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.
124 In 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.
125 Prior 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).
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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.127 The 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 twinengine aircraft would potentially reach
concentrations of lead exceeding the
lead NAAQS with fewer LTOs
compared with airports where singleengine aircraft dominate the piston-
lotter on DSK11XQN23PROD with PROPOSALS1
126 EPA
(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.
127 EPA (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.
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engine fleet.128 Model-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.129 In 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
128 See methods used in EPA (2020) Modelextrapolated Estimates of Airborne Lead
Concentrations at U.S. Airports. Table 2. p.23. EPA,
Washington, DC, EPA–420–R–20–003, 2020.
129 EPA (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.
130 Carr et. al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield impacts of lead emissions from piston-engine
aircraft operating on leaded aviation gasoline.
Atmospheric Environment 45: 5795–5804.
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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).132 The census tract
concentrations are averages of the areaweighted 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
131 EPA (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.
132 See EPA’s 2017 AirToxScreen. Available at
https://www.epa.gov/AirToxScreen.
133 These 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.
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census tracts in the U.S.134 Lead
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.
lotter on DSK11XQN23PROD with PROPOSALS1
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 startup, 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.137 Depending
on ambient conditions (e.g., ozone and
hydroxyl concentrations in the
atmosphere), alkyl lead may exist in the
atmosphere for hours to days 138 and
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
134 As 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.
135 Swiss 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/pollutantemissions/aircraft-engine-emissions/reportappendices-database-and-data-sheets.html.
136 Griffith 2020. Electron microscopic
characterization of exhaust particles containing lead
dibromide beads expelled from aircraft burning
leaded gasoline. Atmospheric Pollution Research
11:1481–1486.
137 EPA (2013) ISA for Lead. Section 1.3.
‘‘Exposure to Ambient Pb.’’ p. 1–11. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
138 EPA (2006) AQC for Lead. Section E.6. p. 2–
5. EPA, Washington, DC, EPA/600/R–5/144aF,
2006.
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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.139 Lead 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.142 Meteorological
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.144 Once 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
139 EPA (1977) AQC for Lead. Section 6.2.2.1.
EPA, Washington, DC, EPA–600/8–77–017, 1977.
140 EPA (2006) AQC for Lead. Section E.6. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
141 EPA (2006) AQC for Lead. Section 2. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
142 EPA (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.
143 Memorandum to Docket EPA–HQ–OAR–
2022–0389. Deposition of Lead Emitted by Pistonengine Aircraft. June 15, 2022. Docket ID EPA–HQ–
2022–0389.
144 EPA (2013) ISA for Lead. Section 2.6.1.
‘‘Soils.’’ p. 2–118. EPA, Washington, DC, EPA/600/
R–10/075F, 2013.
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or other media.145 The 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.146 Murphy 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.148 Based on
comparisons of lead concentrations in
total suspended particulate (TSP) and
fine particulate matter (PM2.5) 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 aircraftinduced 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
145 EPA (2013) ISA for Lead. Chapter 6.
‘‘Ecological Effects of Pb.’’ p. 6–57. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
146 Murphy et al., 2008. Weekly patterns of
aerosol in the United States. Atmospheric
Chemistry and Physics. 8:2729–2739.
147 Lead concentrations collected as part of the
Interagency Monitoring of Protected Visual
Environments (IMPROVE) network and the
National Oceanic and Atmospheric Administration
(NOAA) monitoring sites.
148 Heiken 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.
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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).
lotter on DSK11XQN23PROD with PROPOSALS1
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.157 As described in
149 McCumber and Strevett 2017. A Geospatial
Analysis of Soil Lead Concentrations Around
Regional Oklahoma Airports. Chemosphere 167:62–
70.
150 Kavouras 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.
151 Heiken 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.
152 EPA (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.
153 Environment Canada (2000) Airborne
Particulate Matter, Lead and Manganese at
Buttonville Airport. Toronto, Ontario, Canada:
Conor Pacific Environmental Technologies for
Environmental Protection Service, Ontario Region.
154 Lejano 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.
155 EPA (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.
156 EPA (2006) AQC for Lead. Section 8.2.2. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
157 EPA (2006) AQC for Lead. Section 8.2.2. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
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Section II.A.1 of this document, pistonengine 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.158 The 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,159 are 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.160 Atmospheric
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
158 O’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.
159 The 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.
160 EPA (2006) AQC for Lead. pp. 7–9 and AXZ7–
39. EPA, Washington, DC, EPA/600/R–5/144aF,
2006.
161 EPA (2006) AQC for Lead. p. AXZ7–39. EPA,
Washington, DC, EPA/600/R–5/144aF, 2006.
162 EPA (1986) AQC for Lead. Sections 6.5.3. EPA,
Washington, DC, EPA–600/8–83/028aF–dF (NTIS
PB87142386), 1986.
163 EPA (1986) AQC for Lead. Section
7.2.2.2.1.EPA, Washington, DC, EPA–600/8–83/
028aF–dF (NTIS PB87142386), 1986.
164 EPA (1986) AQC for Lead. Section 7.2.2.2.2.
EPA, Washington, DC, EPA–600/8–83/028aF–dF
(NTIS PB87142386), 1986.
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skin).165 Alkyl lead, in particular, has
been identified by the EPA as a
Persistent, Bioaccumulative, and Toxic
(PBT) pollutant.166 There 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.167 Inland 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.168 Leaded avgas discharged to
the ground and water includes other
165 EPA (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.
166 EPA (2002) Persistent, Bioaccumulative, and
Toxic Pollutants (PBT) Program. PBT National
Action Plan for Alkyl-Pb. Washington, DC. June.
2002.
167 See FAA’s NASR. Available at https://
www.faa.gov/air_traffic/flight_info/aeronav/aero_
data/eNASR_Browser/.
168 National 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.
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hazardous fuel components such as
ethylene dibromide.169
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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 nearairport 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 nonHispanic 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.
169 Memorandum 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.
170 EPA (2013) ISA for Lead. Section 5.4.
‘‘Summary.’’ p. 5–40. EPA, Washington, DC, EPA/
600/R–10/075F, 2013.
171 EPA. 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.
172 The 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.
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For the reasons described in
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.173 As
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 pistonengine 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
SUPPLEMENTARY INFORMATION
173 Residential 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.
174 Miranda et al., 2011. A Geospatial Analysis of
the Effects of Aviation Gasoline on Childhood
Blood Lead Levels. Environmental Health
Perspectives. 119:1513–1516.
175 Zahran 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.
176 Rowangould 2013. A census of the nearroadway 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.
177 Marshall et al., 2014. Prioritizing
environmental justice and equality: diesel
emissions in Southern California. Environmental
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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.182 Rissman 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
Science & Technology 48: 4063–4068. https://
doi.org/10.1021/es405167f.
178 Marshall 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.
179 Tessum et al., 2021. PM
2.5 polluters
disproportionately and systemically affect people of
color in the United States. Science Advances
7:eabf4491.
180 Mohai et al., 2009. Environmental justice.
Annual Reviews 34:405–430. Available at https://
doi.org/10.1146/annurev-environ-082508-094348.
181 McNair 2020. Investigation of environmental
justice analysis in airport planning practice from
2000 to 2010. Transportation Research Part D
81:102286.
182 Woodburn 2017. Investigating neighborhood
change in airport-adjacent communities in
multiairport regions from 1970 to 2010. Journal of
the Transportation Research Board, 2626, 1–8.
183 Rissman et al., 2013. Equity and health
impacts of aircraft emissions at the HartfieldJackson Atlanta International Airport. Landscape
and Urban Planning, 120: 234–247.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
School Near U.S. Airports.’’ 184 In 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 pistonengine 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 pistonengine 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.’’ 188 From 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.190 Using 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.192 This 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—THE POPULATION OF CHILDREN FIVE YEARS AND UNDER WITHIN 500 METERS OF AN AIRPORT RUNWAY
COMPARED TO THE STATE POPULATION OF CHILDREN FIVE YEARS 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
10
9
11
8
8
9
1,000
400
3,000
224,200
361,400
71,300
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Nevada .............................................................................................................
South Carolina .................................................................................................
South Dakota ...................................................................................................
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).
184 EPA (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.
185 EPA (2020) Model-extrapolated Estimates of
Airborne Lead Concentrations at U.S. Airports.
EPA, Washington, DC, EPA–420–R–20–003, 2020.
186 Carr et. al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield 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.
187 We 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 pistonengine aircraft at airports nationwide suggests that
exposure to lead from aircraft emissions is likely to
vary widely.
188 In this analysis, we included populations
living in census blocks that intersected the 500meter 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.
189 EPA (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.
190 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.
191 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.
192 These 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.
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62769
TABLE 4—THE BLACK POPULATION WITHIN 500 METERS OF AN AIRPORT RUNWAY AND THE BLACK POPULATION, BY
STATE
State
Percent Black
within 500
meters
Percent Black
within the
state
8
8
9
46
46
12
31
10
9
7
6
8
32
37
9
28
3
6
California ..........................................................................................................
Kansas .............................................................................................................
Kentucky ..........................................................................................................
Louisiana ..........................................................................................................
Mississippi ........................................................................................................
Nevada .............................................................................................................
South Carolina .................................................................................................
West Virginia ....................................................................................................
Wisconsin .........................................................................................................
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
Black
population
within 500
meters
18,981
1,240
3,152
14,669
8,542
1,794
10,066
1,452
4,869
Black
population in
the state
2,486,500
173,300
342,800
1,463,000
1,103,100
231,200
1,302,900
63,900
367,000
or greater: Indiana, Maine, and New
Hampshire (Table 5).
TABLE 5—THE ASIAN POPULATION WITHIN 500 METERS OF AN AIRPORT RUNWAY AND THE ASIAN POPULATION, BY STATE
State
Percent Asian
within 500
meters
Percent Asian
within the
state
4
2
4
2
1
2
Indiana .............................................................................................................
Maine ...............................................................................................................
New Hampshire ...............................................................................................
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
Asian
population
within 500
meters
1,681
406
339
Asian
population in
the state
105,500
13,800
29,000
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).
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;
TABLE 6—THE NATIVE AMERICAN AND ALASKA NATIVE POPULATION WITHIN 500 METERS OF AN AIRPORT RUNWAY AND
THE NATIVE AMERICAN AND ALASKA NATIVE POPULATION, BY STATE
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
48
18
2
21
22
15
5
1
10
9
16,020
5,017
112
2,265
1,606
106,300
335,300
5,900
208,900
72,800
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Alaska ..............................................................................................................
Arizona .............................................................................................................
Delaware ..........................................................................................................
New Mexico .....................................................................................................
South Dakota ...................................................................................................
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
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the same airports.193 194 In this analysis,
193 For 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.
194 Kamal 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
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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
representation of different demographic groups
near-airport and for those living one to five
kilometers away.
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Federal Register / Vol. 87, No. 199 / Monday, October 17, 2022 / Proposed Rules
to airport runways than in populations
farther away. There were 761 airports
where people living at less than twotimes 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—NUMBER OF AIRPORTS (AMONG THE 2,022 AIRPORTS EVALUATED) WITH DISPARITY FOR CERTAIN DEMOGRAPHIC POPULATIONS WITHIN ONE KILOMETER OF AN AIRPORT RUNWAY IN RELATION TO THE COMPARISON POPULATION BETWEEN ONE AND FIVE KILOMETERS FROM AN AIRPORT RUNWAY
Number of airports with disparity a
Demographic group
Total airports
with disparity
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Children under five years of age .........................................
People with income less than twice the Federal Poverty
Level .................................................................................
People of Color (all races, ethnicities and indigenous peoples) ..................................................................................
Non-Hispanic Black ..............................................................
Hispanic ...............................................................................
Non-Hispanic Asian .............................................................
Non-Hispanic Native American or Alaska Native 195 ...........
Non-Hispanic Hawaiian or Pacific Islander .........................
Non-Hispanic Other Race ....................................................
Non-Hispanic Two or More Races ......................................
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 proximitybased 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,
195 This analysis of 2,022 NPIAS airports did not
include airports in Alaska.
196 Kamal 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.
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Disparity
1–5%
7
1
0
761
307
223
180
51
666
405
551
268
144
18
11
226
377
240
402
243
130
17
11
226
126
77
85
18
6
1
0
0
123
67
47
4
7
0
0
0
40
21
17
3
1
0
0
0
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
197 Kamal 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.
Fmt 4702
Disparity
20%+
507
B. Federal Actions To Reduce Lead
Exposure
Frm 00032
Disparity
10–20%
515
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 atrisk 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.
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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.198 In 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.’’ 199 Once
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 threemonth period, as described in 40 CFR
50.16.200 The EPA’s 2016 Federal
Register notice describes the Agency’s
decision to retain the existing Lead
198 Federal 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.
199 41 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.
200 73 FR 66965 (Nov. 12, 2008).
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NAAQS.201 The 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.203 These
amendments to the original maximum
achievable control technology standards
apply to facilities nationwide that use
furnaces to recover lead from leadbearing 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
201 81
FR 71912–71913 (Oct. 18, 2016).
pertaining to the current review of
the NAAQS for Lead can be found here: https://
www.epa.gov/naaqs/lead-pb-air-quality-standards.
203 77 FR 555 (Jan. 5, 2012).
204 78 FR 9112 (Feb. 7, 2013).
205 Effective in Jan. 2014, the amount of lead
permitted in pipes, fittings, and fixtures was
202 Documents
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Also under section 1412 of the SDWA,
the EPA’s 1991 Lead and Copper
Rule 206 regulates lead in public
drinking water systems through
corrosion control and other utility
actions which work together to
minimize lead levels at the tap.207 On
January 15, 2021, the agency published
the Lead and Copper Rule Revisions
(LCRR) 208 and subsequently reviewed
the rule in accordance with Executive
Order 13990.209 While 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),211 that 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.’’ 212 The 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
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/uselead-free-pipes-fittings-fixtures-solder-and-fluxdrinking-water.
206 40 CFR 141 Subpart I (June 7, 1991).
207 40 CFR 141 Subpart I (June 7, 1991).
208 86 FR 4198. (Jan. 15, 2021).
209 E.O. 13990. Protecting Public Health and the
Environment and Restoring Science to Tackle the
Climate Crisis. 86 FR 7037 (Jan. 20, 2021).
210 86 FR 31939. (Dec. 17, 2021).
211 See https://www.epa.gov/ground-water-anddrinking-water/review-national-primary-drinkingwater-regulation-lead-and-copper. Accessed on
Nov. 30, 2021.
212 86 FR 31939 (Dec. 17, 2021).
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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.’’ 213 The 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.214 The 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
213 66
214 84
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FR 32632 (July 9, 2019).
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and windowsills, respectively.215 The
EPA is now reconsidering the 2019 and
2021 rules in accordance with Executive
Order 13990 216 and 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) 217 and
Resource Conservation Recovery Act
(RCRA) 218 also 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).
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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
215 86
FR 983 (Jan. 7, 2021).
216 86 FR 7037 (Jan. 20, 2021).
217 For more information about the EPA’s
CERCLA program, see www.epa.gov/superfund.
218 For more information about the EPA’s RCRA
program, see https://www.epa.gov/rcra.
219 See https://www.epa.gov/regulationsemissions-vehicles-and-engines/petitions-and-eparesponse-memorandums-related-lead. Accessed on
Dec. 12, 2021.
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use of leaded avgas in general aviation
aircraft using piston engines to cause or
contribute to endangerment of public
health or welfare.220 In 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.221 The 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).222 In 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.223 The EPA
220 Friends of the Earth (formerly Bluewater
Network) comment dated Dec. 12, 2003, submitted
to EPA’s 68 FR 56226, published Sept. 30, 2003.
221 See 72 FR 64570 (Nov. 16, 2007).
222 75 FR 22440–68 (Apr. 28, 2010).
223 Petitioners 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
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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 224 to 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.226 The 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
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).
224 The 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-0421-14.pdf.
225 The 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-2015-123.pdf.
226 The 2021 petition is available at https://
www.epa.gov/system/files/documents/2022-01/
aviation-leaded-avgas-petition-exhibits-final-202110-12.pdf.
227 EPA’s response to the 2021 petition is
available at https://www.epa.gov/system/files/
documents/2022-01/ltr-response-aircraft-leadpetitions-aug-oct-2022-01-12.pdf.
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provided a detailed explanation of the
legal framework for making such
findings and the statutory
interpretations and caselaw supporting
its approach.228 In 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.229 This 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),230 which was affirmed
by the U.S. Court of Appeals for the D.C.
Circuit in 2012.231 As 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.232 Accordingly, 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.233 As 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.’’ 234 In this proposal, the EPA
228 FR
54422–54475 (Aug. 15, 2016).
e.g., 81 FR at 55434–54440 (Aug. 19,
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229 See
2016).
230 74 FR 66496, 66505–10 (Dec. 15, 2009).
231 Coalition for Responsible Regulation, Inc. v.
EPA, 684 F.3d 102 (D.C. Cir. 2012) (CRR)
(subsequent history omitted).
232 81 FR at 55434 (Aug. 19, 2016).
233 81 FR at 55434 (Aug. 19, 2016).
234 Regarding ‘‘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
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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.236 They 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.’’ 237 The 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
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.
235 See Massachusetts v. EPA, 549 U.S. 497,533
(2007) (interpreting an analogous provision in CAA
section 202).
236 See 81 FR at 54435 (Aug. 19, 2016).
237 CRR, 684 F.3d at 122 (internal citations
omitted) (June 26, 2012).
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maturing into concrete harm.’’ 238 The
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.240 However, 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.’’ 241 Any subsequent
238 CRR, 684 F.3d at 122 (internal citations
omitted) (June 26, 2012).
239 81 FR at 54425 (Aug. 19, 2016).
240 See, 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).
241 As 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).
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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.244 For 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.245 Moreover, 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
242 See CRR, 684 F.3d at 117 (explaining two-part
analysis under section 202(a)) (June 26, 2012).
243 See, e.g., 81 FR 54422, 54434–55435 (Aug. 15,
2016).
244 See, e.g., 81 FR at 54437–54438 (September 4,
2013).
245 See, e.g., 81 FR at 54437–54438 (Aug. 15,
2016).
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term ‘‘contribute.’’ 246 Unlike 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.247 While 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.249 As 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.’’ 250 Accordingly,
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.’’ 251 As 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).252 Moreover,
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.253 The
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
246 See, e.g., 81 FR at 54437–54438 (Aug. 15,
2016).
247 See 81 FR at 54437–54438 (Aug. 15, 2016).
248 See 81 FR at 54437–54438 (Aug. 15, 2016).
249 See 81 FR at 54437–54438 (Aug. 15, 2016).
250 CRR, 684 F.3d at 122–123 (June 26, 2012).
251 CRR, 684 F.3d at 122–123. (quoting Ethyl
Corp., 541 F.2d at 18) (June 26, 2012).
252 81 FR at 54438 (Aug. 15, 2016).
253 81 FR at 54438 (Aug. 15, 2016).
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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
254 81
FR at 54438 (Aug. 15, 2016).
81 FR at 54462 (Aug. 15, 2016).
255 See
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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.257 Lead 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.258 Lead 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
256 CAA
Section 233 (Dec. 31, 1970).
(2013) ISA for Lead. Section 2.2.
‘‘Sources of Atmospheric Pb.’’ p. 2–1. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
258 EPA (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.
259 The 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).
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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 airrelated 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 airrelated 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-ofevidence approach.263 We summarize
here those health effects for which the
260 EPA (2013) ISA for Lead. EPA, Washington,
DC, EPA/600/R–10/075F, 2013.
261 EPA (2006) AQC for Lead. EPA, Washington,
DC, EPA/600/R–5/144aF, 2006.
262 EPA (2013) ISA for Lead. Section 5.4.
‘‘Summary.’’ p. 5–40. EPA, Washington, DC, EPA/
600/R–10/075F, 2013.
263 The 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.
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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.264 In 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).265 In 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 wellestablished, widely recognized and
rigorously standardized measure of
neurocognitive function which has been
264 EPA (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.
265 EPA (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.
266 EPA (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.
267 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxviilxxxviii. EPA, Washington, DC, EPA/600/R–10/
075F, 2013.
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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.’’ 271 The 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.’’ 272 The 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).273 Evidence 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,274 potentially 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.276 For 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’’.277 Specifically, if leadrelated 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 longterm lead exposure on increased blood
pressure and hypertension.’’ 280 In
268 EPA (2013) ISA for Lead. Section 4.3.2.
‘‘Cognitive Function.’’ p. 4–59. EPA, Washington,
DC, EPA/600/R–10/075F, 2013.
269 EPA (2006) AQC for Lead. Sections 6.2.2 and
8.4.2. EPA, Washington, DC, EPA/600/R–5/144aF,
2006.
270 EPA (2013) ISA for Lead. Section 4.3.2.
‘‘Cognitive Function.’’ p. 4–59. EPA, Washington,
DC, EPA/600/R–10/075F, 2013.
271 EPA (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.
272 EPA (2013) ISA for Lead. Section 1.9.4. ‘‘Pb
Exposure and Neurodevelopmental Deficits in
Children.’’ p. 1–76. EPA/600/R–10/075F, 2013.
273 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Children.’’ pp. lxxxviilxxxviii. EPA, Washington, DC, EPA/600/R–10/
075F, 2013.
274 EPA (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.
275 EPA (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.
276 EPA (2013) ISA for Lead. Section 1.9.1.
‘‘Public Health Significance.’’ p. 1–68. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
277 EPA (2013) ISA for Lead. Executive Summary.
‘‘Public Health Significance.’’ p. xciii. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
278 EPA (2013) ISA for Lead. Section 1.9.1.
‘‘Public Health Significance.’’ p. 1–68. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
279 EPA (2013) ISA for Lead. Section 1.9.1.
‘‘Public Health Significance.’’ p. 1–68. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
280 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii.
EPA/600/R–10/075F, 2013.
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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.’’ 281 The extent to which the
effects of lead on the cardiovascular
system are reversible is not wellcharacterized. 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.282 The 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.’’ 283 In
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
281 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii.
EPA/600/R–10/075F, 2013.
282 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii.
EPA/600/R–10/075F, 2013.
283 EPA (2013) ISA for Lead. Executive Summary.
‘‘Effects of Pb Exposure in Adults.’’ p. lxxxviii.
EPA/600/R–10/075F, 2013.
284 EPA (2013) ISA for Lead. Executive Summary.
‘‘Public Health Significance.’’ p. xciii. EPA,
Washington, DC, EPA/600/R–10/075F, 2013.
285 EPA (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.
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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 ‘‘atrisk’’ 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 atrisk 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.287 The 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
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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.289 We
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
286 EPA (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.
287 EPA (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.
288 EPA (2013) ISA for Lead. Section 5.4.
‘‘Summary.’’ p. 5–44. EPA, Washington, DC, EPA/
600/R–10/075F, 2013.
289 Causal 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.
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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.291 The
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
290 EPA (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.
291 EPA (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.
292 EPA (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.
293 EPA (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.
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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 ecosystemlevel 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
294 EPA (2013) ISA for Lead. ‘‘Summary.’’ p. xcvi.
EPA, Washington, DC, EPA/600/R–10/075F, 2013.
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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.295 As 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
295 The 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.
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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 pistonengine 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.296 In 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
296 The 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/2017national-emissions-inventory-nei-data#dataq.
297 Airport lead annual emissions data used were
reported in the 2017 NEI. Available at https://
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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.299 In
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.300 Although 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
www.epa.gov/air-emissions-inventories/2017national-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-reportingrequirements-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/emissionsmodeling-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.
298 FAA. 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/.
299 Geidosch. 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.
300 Geidosch. 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.
301 FAA 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.
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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
302 Carr et. al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield 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.
303 EPA (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.
304 Carr et al., 2011. Development and evaluation
of an air quality modeling approach to assess nearfield 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.
305 Heiken et al., 2014. Quantifying Aircraft Lead
Emissions at Airports. ACRP Report 133. Available
at https://www.nap.edu/catalog/22142/quantifyingaircraft-lead-emissions-at-airports.
306 Hudda 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.
307 73 FR 66965 (Nov. 12, 2008).
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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 ‘‘Modelextrapolated Estimates of Airborne Lead
Concentrations at U.S. Airports’’ and
described in Section II.A.3 of this
document.309 The 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
308 75
FR 81226 (Dec. 27, 2010).
(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.
309 EPA
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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 lead310 EPA’s 2017 AirToxScreen is available at
https://www.epa.gov/AirToxScreen.
311 South 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-stateimplementation-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.
312 EPA provides updated information regarding
nonattainment areas at this website: https://
www.epa.gov/green-book/green-book-lead-2008area-information.
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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.314 Given that the
lead NAAQS are established to protect
313 The 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/2017national-emissions-inventory-nei-data#dataq.
314 EPA (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.
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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 pistonengine 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.
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VI. Statutory Authority and Executive
Order Reviews
Additional information about these
statutes and Executive Orders can be
found at https://www2.epa.gov/lawsregulations/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-andof-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.
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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.315 The
EPA plans to continue engaging with
Tribal stakeholders on this issue and
will offer a government-to-government
consultation upon request.
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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
315 See 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.
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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 316 still 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.
62781
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
I. National Technology Transfer and
Advancement Act (NTTAA)
This action does not involve technical
standards.
Environmental protection, Air
pollution control, Aircraft, Aircraft
engines.
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 protection,
Administrative practice and procedure,
Confidential business information,
Imports, Motor vehicle pollution,
Penalties, Reporting and recordkeeping
requirements, Warranties.
316 EPA
(2021) EPA Policy on Children’s Health.
Available at https://www.epa.gov/system/files/
documents/2021-10/2021-policy-on-childrenshealth.pdf.
PO 00000
Frm 00043
Fmt 4702
Sfmt 9990
40 CFR Part 1068
Michael S. Regan,
Administrator.
[FR Doc. 2022–22223 Filed 10–14–22; 8:45 am]
BILLING CODE 6560–50–P
E:\FR\FM\17OCP1.SGM
17OCP1
]]>Agencies
[Federal Register Volume 87, Number 199 (Monday, October 17, 2022)]
[Proposed Rules]
[Pages 62753-62781]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-22223]
=======================================================================
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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.
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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: [email protected]. Include Docket ID No. EPA-
HQ-OAR-
[[Page 62754]]
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: [email protected].
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 \1\ equipped 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,\2\ such 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.
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\1\ The FAA regulates ultralight vehicles under 14 CFR part 103.
\2\ Rotorcraft 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.
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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
[[Page 62755]]
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:
----------------------------------------------------------------------------------------------------------------
Examples of potentially affected
Category NAICS \a\ code SIC \b\ code 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 specialty air
and flying services). Aviation
clubs providing a variety of
air transportation activities
to the general public.
Industry................................ 611512 8249 and 8299 Flight Training.
----------------------------------------------------------------------------------------------------------------
\a\ North American Industry Classification System (NAICS).
\b\ Standard 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 13045 \3\ requires 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\
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\3\ E.O. 13045. Protection of Children From Environmental Health
Risks and Safety Risks. 62 FR 19885 (April 23, 1997).
\4\ EPA (2006) A Framework for Assessing Health Risks of
Environmental Exposures to Children. EPA, Washington, DC, EPA/600/R-
05/093F, 2006.
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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.\5\ Because 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\
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\5\ EPA. 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.
\6\ EPA. ``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.
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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.'' \7\ Evidence
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.\8\ The 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.\9\ In 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.
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\7\ EPA (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.
\8\ EPA (2013) ISA for Lead. Executive Summary ``Effects of Pb
Exposure in Children.'' pp. lxxxvii-lxxxviii. EPA/600/R-10/075F,
2013.
\9\ EPA (2013) ISA for Lead. Section 1.9.4. ``Pb Exposure and
Neurodevelopmental Deficits in Children.'' p. I-75. EPA/600/R-10/
075F, 2013.
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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
[[Page 62756]]
of their programs, policies, and activities on people of color
populations and low-income populations in the United States.\10\ 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.\11\
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\10\ 59 FR 7629 (Feb. 16, 1994).
\11\ Fair treatment means that ``no group of people should bear
a disproportionate burden of environmental harms and risks,
including those resulting from the negative environmental
consequences of industrial, governmental and commercial operations
or programs and policies.'' Meaningful involvement occurs when ``1)
potentially affected populations have an appropriate opportunity to
participate in decisions about a proposed activity [e.g.,
rulemaking] that will affect their environment and/or health; 2) the
public's contribution can influence the 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.
---------------------------------------------------------------------------
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.'' \12\ It also
declares a policy ``to secure environmental justice and spur economic
opportunity for disadvantaged communities that have been historically
marginalized and overburdened by pollution and under-investment in
housing, transportation, water and wastewater infrastructure and health
care.'' Under Executive Order 13563, federal agencies may consider
equity, human dignity, fairness, and distributional considerations,
where appropriate and permitted by law.\13\
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\12\ 86 FR 7619 (Feb. 1, 2021).
\13\ 76 FR 3821 (Jan. 18, 2011).
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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\
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\14\ EPA (2013) ISA for Lead. Section 5.4. ``Summary.'' pp. 5-40
through 5-42. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\15\ EPA (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.
\16\ EPA (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.
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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
\17\ for 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.
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\17\ EPA (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.
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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
[[Page 62757]]
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.\18\ In 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\
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\18\ As 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.
\19\ EPA (2013) ISA for Lead. EPA, Washington, DC, EPA/600/R-10/
075F, 2013.
\20\ EPA (2006) AQC for Lead. EPA, Washington, DC, EPA/600/R-5/
144aF, 2006.
\21\ EPA (1986) AQC for Lead. EPA, Washington, DC, EPA-600/8-83/
028aF-dF, 1986.
\22\ EPA (1977) AQC for Lead. EPA, Washington, DC, EPA-600/8-77-
017 (NTIS PB280411), 1977.
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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.\23\ Accordingly, 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).
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\23\ As 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.
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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 \24\ for lead and the lead
NAAQS.\25\ These 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 \26\ as well as
information summarized in previous assessments, including the 1977,
1986, and 2006 AQCDs.\27\ \28\ \29\
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\24\ Under 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).
\25\ Section 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.''
\26\ EPA (2013) ISA for Lead. EPA, Washington, DC, EPA/600/R-10/
075F, 2013.
\27\ EPA (1977) AQC for Lead. EPA, Washington, DC, EPA-600/8-77-
017 (NTIS PB280411), 1977.
\28\ EPA (1986) AQC for Lead. EPA, Washington, DC, EPA-600/8-83/
028aF-dF (NTIS PB87142386), 1986.
\29\ EPA (2006) AQC for Lead. EPA, Washington, DC, EPA/600/R-5/
144aF, 2006.
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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.\30\ Lead emitted in the past
can remain available for environmental or human exposure for extended
time in some areas.\31\ Depending 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.\33\ Over time, lead that was initially emitted to air
can become less available for environmental circulation by
sequestration in soil, sediment and other reservoirs.\34\
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\30\ EPA (2013) ISA for Lead. Section 3.1.1. ``Pathways for Pb
Exposure.'' p. 3-1. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\31\ EPA (2013) ISA for Lead. Section 3.7.1. ``Exposure.'' p. 3-
144. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\32\ EPA (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.
\33\ EPA (2013) ISA for Lead. Section 2.3. ``Fate and Transport
of Pb.'' p. 2-24. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\34\ EPA (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.
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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
[[Page 62758]]
ambient air.\35\ Ambient air inhalation pathways include both
inhalation of air outdoors and inhalation of ambient air that has
infiltrated into indoor environments.\36\ The 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.
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\35\ EPA (2013) ISA for Lead. Section 3.1.1. ``Pathways for Pb
Exposure.'' p. 3-1. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\36\ EPA (2013) ISA for Lead. Sections 1.3. ``Exposure to
Ambient Pb.'' p. 1-11. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
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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 44
thus 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\
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\37\ EPA (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.
\38\ EPA (2006) AQC for Lead. Chapter 3. EPA, Washington, DC,
EPA/600/R-5/144aF, 2006.
\39\ EPA (1986) AQC for Lead. Section 1.11.3. EPA, Washington,
DC, EPA-600/8-83/028aF-dF (NTIS PB87142386), 1986.
\40\ EPA (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.
\41\ EPA (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.
\42\ EPA (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.
\43\ Miranda et al., 2011. A Geospatial Analysis of the Effects
of Aviation Gasoline on Childhood Blood Lead Levels. Environmental
Health Perspectives. 119:1513-1516.
\44\ Zahran 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.
\45\ Klemick 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.
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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.\47\ Tetraethyl 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 50 The 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.
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\46\ ASTM International (May 1, 2021) Standard Specification for
Leaded Aviation Gasolines D910-21.
\47\ National 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.
\48\ Ogston 1981. A Short History of Aviation Gasoline
Development, 1903-1980.Society of Automotive Engineers. p. 810848.
\49\ U.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.
\50\ U.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.
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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.,\51\ and the FAA provides information on the
volume of leaded avgas consumed in the U.S.\52\ Over 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.\53\ As 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.
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\51\ DOE. 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.
\52\ Department of Transportation (DOT). FAA. Aviation Policy
and Plans. FAA Aerospace Forecast Fiscal Years 2009-2025. p. 81.
Available at https://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.
\53\ DOT. 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.
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[[Page 62759]]
The FAA's National Airspace System Resource (NASR) \54\ provides 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.\55\ While 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.\56\ The
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.
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\54\ See FAA. NASR. Available at https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/eNASR_Browser/.
\55\ FAA (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.
\56\ See FAA's NASR. Available at https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/eNASR_Browser/.
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As of 2019, there were 171,934 piston-engine aircraft in the
U.S.\57\ This total includes 128,926 single-engine aircraft, 12,470
twin-engine aircraft, and 3,089 rotorcraft.\58\ The 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.\59\ In 2019, 883 new
piston-engine aircraft were manufactured in the U.S. some of which are
exported.\60\ For the period from 2019 through 2041, the fleet of fixed
wing \61\ piston-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.\62\ An
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.\63\ There were approximately 664,565 pilots certified to
fly general aviation aircraft in the U.S. in 2021.\64\ This 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\
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\57\ FAA. 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/.
\58\ FAA. 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/.
\59\ General 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.
\60\ GAMA (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.
\61\ There 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.
\62\ See 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.
\63\ FAA 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.
\64\ FAA. 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.
\65\ FAA. 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.
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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\
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\66\ FAA. 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/.
\67\ FAA. 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/.
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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.\68\ From 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
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\68\ FAA. 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/.
\69\ FAA. 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/.
\70\ In 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.
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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).\71\ The 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,
[[Page 62760]]
general aviation activity is often used as a surrogate measure for
understanding piston-engine activity.
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\71\ See FAA's Air Traffic Activity Data. Available at https://aspm.faa.gov/opsnet/sys/airport.asp.
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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.\72\ The 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).
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\72\ Geidosch. 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.
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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.\73\ For 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.\74\
The 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).
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\73\ FAA'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.
\74\ The 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.
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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.
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\75\ EPA (1977) AQC for Lead. EPA, Washington, DC, EPA-600/8-77-
017 (NTIS PB280411), 1977.
\76\ EPA (1986) AQC for Lead. EPA, Washington, DC, EPA-600/8-83/
028aF-dF (NTIS PB87142386), 1986.
\77\ EPA (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.
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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.\78\ Upon 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.\79\ In 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\
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\78\ EPA (1986) AQC for Lead. EPA, Washington, DC, EPA-600/8-83/
028aF-dF (NTIS PB87142386), 1986.
\79\ Griffith 2020. Electron microscopic characterization of
exhaust particles containing lead dibromide beads expelled from
aircraft burning leaded gasoline. Atmospheric Pollution Research
11:1481-1486.
\80\ EPA (1986) AQC for Lead. Volume 2: Chapters 5 & 6. EPA,
Washington, DC, EPA-600/8-83/028aF-dF (NTIS PB87142386), 1986.
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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.\81\ Alkyl 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).\82\ In
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\
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\81\ EPA (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.
\82\ EPA (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.
\83\ Memorandum 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.
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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
[[Page 62761]]
measurements of lead.\84\ The 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\6\ to 8.6x10\6\
particles per cm\3\. The authors noted that these particle emission
rates are comparable to those from a typical diesel passenger car
engine without a particle filter.\85\ Griffith (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.
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\84\ Swiss 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.
\85\ Swiss 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.
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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).\86\ In
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.\87\ Lead 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 \88\ and in the document titled ``Calculating Piston-
Engine Aircraft Airport Inventories for Lead for the 2008 National
Emissions Inventory.'' \89\ The 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\
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\86\ The 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.
\87\ EPA 2017 NEI. Available at https://www.epa.gov/air-emissions-inventories/2017-national-emissions-inventory-nei-data.
\88\ Advance Notice of Proposed Rulemaking on Lead Emissions
from Piston-Engine Aircraft Using Leaded Aviation Gasoline. 75 FR
2440 (April 28, 2010).
\89\ Airport 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).
\90\ The 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.
Table 1--Piston-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 59% 60% 64% 70%
total U.S. lead inventory......................
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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.\91\ Among 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).\92\ In 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.
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\91\ Lead 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.
\92\ Airport 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.
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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.\93\ In 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
[[Page 62762]]
estimated to have inventories above 0.1 tons in 2045.\94\
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\93\ See EPA lead inventory data available at https://www.epa.gov/air-emissions-modeling/emissions-modeling-platforms.
\94\ EPA 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.
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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\
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\95\ Geidosch. 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.
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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
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\96\ Carr 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.
\97\ Feinberg 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.
\98\ Municipality 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.
\99\ Environment Canada (2000) Airborne Particulate Matter, Lead
and Manganese at Buttonville Airport. Toronto, Ontario, Canada:
Conor Pacific Environmental Technologies for Environmental
Protection Service, Ontario Region.
\100\ Fine 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.
\101\ Lead emitted from piston-engine aircraft in the
particulate phase would also be measured in samples collected to
evaluate total ambient PM2.5 concentrations.
\102\ EPA (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).
\103\ EPA (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.
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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\
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\104\ These studies report monitored or modeled data for
averaging times ranging from approximately 18 hours to three-month
averages.
\105\ Carr 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.
\106\ Heiken 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.
\107\ Hudda 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.
\108\ Fine 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.
\109\ EPA (2020) Model-extrapolated Estimates of Airborne Lead
Concentrations at U.S. Airports. EPA, Washington, DC, EPA-420-R-20-
003, 2020.
\110\ EPA (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.
\111\ EPA (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.
\112\ Feinberg 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.
\113\ Feinberg 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.
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The lead NAAQS was revised in 2008.\114\ The 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.\115\ In 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
[[Page 62763]]
ton or more per year.\116\ As 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.
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\114\ 73 FR 66965 (Nov. 12, 2008).
\115\ 40 CFR 50.16 (Nov. 12, 2008).
\116\ 75 FR 81226 (Dec. 27, 2010).
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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
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\117\ EPA (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.
\118\ EPA (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.
Table 2--Lead Concentrations Monitored at 17 Airports in the U.S.
------------------------------------------------------------------------
Lead design
Airport, State value,\119\
[mu]g/m\3\
------------------------------------------------------------------------
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\
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\119\ A 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.
\120\ As 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.
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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\
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\121\ The 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.
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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.\124\ The 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.
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\122\ EPA (2020) Model-Extrapolated Estimates of Airborne Lead
Concentrations at U.S. Airports. EPA, Washington, DC, EPA-420-R-20-
003, 2020.
\123\ EPA (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.
\124\ In 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.
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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.\125\ This approach for conducting a nationwide
analysis of airports was selected due to the impact of piston-engine
aircraft run-up
[[Page 62764]]
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\
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\125\ Prior 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).
\126\ EPA (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.
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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.\127\ The 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.\128\ Model-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.\129\ In 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\
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\127\ EPA (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.
\128\ See 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.
\129\ EPA (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.
\130\ Carr 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.
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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.
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\131\ EPA (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.
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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).\132\ The 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
[[Page 62765]]
census tracts in the U.S.\134\ Lead 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.
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\132\ See EPA's 2017 AirToxScreen. Available at https://www.epa.gov/AirToxScreen.
\133\ These 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.
\134\ As 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.
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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.\137\ Depending on
ambient conditions (e.g., ozone and hydroxyl concentrations in the
atmosphere), alkyl lead may exist in the atmosphere for hours to days
\138\ and may therefore be transported off airport property into nearby
communities.
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\135\ Swiss 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.
\136\ Griffith 2020. Electron microscopic characterization of
exhaust particles containing lead dibromide beads expelled from
aircraft burning leaded gasoline. Atmospheric Pollution Research
11:1481-1486.
\137\ EPA (2013) ISA for Lead. Section 1.3. ``Exposure to
Ambient Pb.'' p. 1-11. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\138\ EPA (2006) AQC for Lead. Section E.6. p. 2-5. EPA,
Washington, DC, EPA/600/R-5/144aF, 2006.
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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.\139\ Lead 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\
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\139\ EPA (1977) AQC for Lead. Section 6.2.2.1. EPA, Washington,
DC, EPA-600/8-77-017, 1977.
\140\ EPA (2006) AQC for Lead. Section E.6. EPA, Washington, DC,
EPA/600/R-5/144aF, 2006.
\141\ EPA (2006) AQC for Lead. Section 2. EPA, Washington, DC,
EPA/600/R-5/144aF, 2006.
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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.\142\
Meteorological 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\
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\142\ EPA (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.
\143\ Memorandum to Docket EPA-HQ-OAR-2022-0389. Deposition of
Lead Emitted by Piston-engine Aircraft. June 15, 2022. Docket ID
EPA-HQ-2022-0389.
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Studies summarized in the 2013 Lead ISA suggest that soil is a
reservoir for contemporary and historical emissions of lead to
air.\144\ Once 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.\145\ The 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.\146\
Murphy 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\
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\144\ EPA (2013) ISA for Lead. Section 2.6.1. ``Soils.'' p. 2-
118. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\145\ EPA (2013) ISA for Lead. Chapter 6. ``Ecological Effects
of Pb.'' p. 6-57. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\146\ Murphy et al., 2008. Weekly patterns of aerosol in the
United States. Atmospheric Chemistry and Physics. 8:2729-2739.
\147\ Lead concentrations collected as part of the Interagency
Monitoring of Protected Visual Environments (IMPROVE) network and
the National Oceanic and Atmospheric Administration (NOAA)
monitoring sites.
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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.\148\ Based on comparisons of lead concentrations in
total suspended particulate (TSP) and fine particulate matter
(PM2.5) 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
[[Page 62766]]
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).
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\148\ Heiken 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.
\149\ McCumber and Strevett 2017. A Geospatial Analysis of Soil
Lead Concentrations Around Regional Oklahoma Airports. Chemosphere
167:62-70.
\150\ Kavouras 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.
\151\ Heiken 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.
\152\ EPA (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.
\153\ Environment Canada (2000) Airborne Particulate Matter,
Lead and Manganese at Buttonville Airport. Toronto, Ontario, Canada:
Conor Pacific Environmental Technologies for Environmental
Protection Service, Ontario Region.
\154\ Lejano 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.
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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.\157\ As 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.\158\ The 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,\159\
are slightly water soluble and, therefore, may be more readily absorbed
by plants than other forms of inorganic lead.
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\155\ EPA (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.
\156\ EPA (2006) AQC for Lead. Section 8.2.2. EPA, Washington,
DC, EPA/600/R-5/144aF, 2006.
\157\ EPA (2006) AQC for Lead. Section 8.2.2. EPA, Washington,
DC, EPA/600/R-5/144aF, 2006.
\158\ O'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.
\159\ The 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.
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The 2006 AQCD indicated that surface deposition of lead onto plants
may be significant.\160\ Atmospheric 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\
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\160\ EPA (2006) AQC for Lead. pp. 7-9 and AXZ7-39. EPA,
Washington, DC, EPA/600/R-5/144aF, 2006.
\161\ EPA (2006) AQC for Lead. p. AXZ7-39. EPA, Washington, DC,
EPA/600/R-5/144aF, 2006.
\162\ EPA (1986) AQC for Lead. Sections 6.5.3. EPA, Washington,
DC, EPA-600/8-83/028aF-dF (NTIS PB87142386), 1986.
\163\ EPA (1986) AQC for Lead. Section 7.2.2.2.1.EPA,
Washington, DC, EPA-600/8-83/028aF-dF (NTIS PB87142386), 1986.
\164\ EPA (1986) AQC for Lead. Section 7.2.2.2.2. EPA,
Washington, DC, EPA-600/8-83/028aF-dF (NTIS PB87142386), 1986.
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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).\165\ Alkyl lead, in particular, has
been identified by the EPA as a Persistent, Bioaccumulative, and Toxic
(PBT) pollutant.\166\ There 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.\167\ Inland 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.
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\165\ EPA (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.
\166\ EPA (2002) Persistent, Bioaccumulative, and Toxic
Pollutants (PBT) Program. PBT National Action Plan for Alkyl-Pb.
Washington, DC. June. 2002.
\167\ See FAA's NASR. Available at https://www.faa.gov/air_traffic/flight_info/aeronav/aero_data/eNASR_Browser/.
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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.\168\
Leaded avgas discharged to the ground and water includes other
[[Page 62767]]
hazardous fuel components such as ethylene dibromide.\169\
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\168\ National 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.
\169\ Memorandum 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.
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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\
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\170\ EPA (2013) ISA for Lead. Section 5.4. ``Summary.'' p. 5-
40. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\171\ EPA. 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.
\172\ The 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.
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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.\173\ As 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\
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\173\ Residential 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.
\174\ Miranda et al., 2011. A Geospatial Analysis of the Effects
of Aviation Gasoline on Childhood Blood Lead Levels. Environmental
Health Perspectives. 119:1513-1516.
\175\ Zahran 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.
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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.\182\ Rissman 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\
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\176\ Rowangould 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.
\177\ Marshall 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.
\178\ Marshall 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.
\179\ Tessum et al., 2021. PM2.5 polluters
disproportionately and systemically affect people of color in the
United States. Science Advances 7:eabf4491.
\180\ Mohai et al., 2009. Environmental justice. Annual Reviews
34:405-430. Available at https://doi.org/10.1146/annurev-environ-082508-094348.
\181\ McNair 2020. Investigation of environmental justice
analysis in airport planning practice from 2000 to 2010.
Transportation Research Part D 81:102286.
\182\ Woodburn 2017. Investigating neighborhood change in
airport-adjacent communities in multiairport regions from 1970 to
2010. Journal of the Transportation Research Board, 2626, 1-8.
\183\ Rissman et al., 2013. Equity and health impacts of
aircraft emissions at the Hartfield-Jackson Atlanta International
Airport. Landscape and Urban Planning, 120: 234-247.
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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
[[Page 62768]]
School Near U.S. Airports.'' \184\ In 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.
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\184\ EPA (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.
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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
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\185\ EPA (2020) Model-extrapolated Estimates of Airborne Lead
Concentrations at U.S. Airports. EPA, Washington, DC, EPA-420-R-20-
003, 2020.
\186\ Carr 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.
\187\ We 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.
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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.'' \188\ From 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\
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\188\ In 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.
\189\ EPA (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.
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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.\190\ Using 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.\192\ This 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.
---------------------------------------------------------------------------
\190\ 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.
\191\ 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.
\192\ These 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.
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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--The Population of Children Five Years and Under Within 500 Meters of an Airport Runway Compared to the
State Population of Children Five Years and Under
----------------------------------------------------------------------------------------------------------------
Percent of Percent of Number of Number of
children aged children aged children aged children aged
State five years and five years and five years and five years and
under within under within under within under in the
500 meters the state 500 meters state
----------------------------------------------------------------------------------------------------------------
Nevada.......................................... 10 8 1,000 224,200
South Carolina.................................. 9 8 400 361,400
South Dakota.................................... 11 9 3,000 71,300
----------------------------------------------------------------------------------------------------------------
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).
[[Page 62769]]
Table 4--The Black Population Within 500 Meters of an Airport Runway and the Black Population, by State
----------------------------------------------------------------------------------------------------------------
Black
Percent Black Percent Black population Black
State within 500 within the within 500 population in
meters state meters the state
----------------------------------------------------------------------------------------------------------------
California...................................... 8 7 18,981 2,486,500
Kansas.......................................... 8 6 1,240 173,300
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 1,794 231,200
South Carolina.................................. 31 28 10,066 1,302,900
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--The Asian Population Within 500 Meters of an Airport Runway and the Asian Population, by State
----------------------------------------------------------------------------------------------------------------
Asian
Percent Asian Percent Asian population Asian
State within 500 within the within 500 population in
meters state meters the state
----------------------------------------------------------------------------------------------------------------
Indiana......................................... 4 2 1,681 105,500
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--The Native American and Alaska Native Population Within 500 Meters of an Airport Runway and the Native
American and Alaska Native Population, by State
----------------------------------------------------------------------------------------------------------------
Native
Percent Native Percent Native American and Native
American and American and Alaska Native American and
State Alaska Native Alaska Native population Alaska Native
within 500 within the within 500 population in
meters state meters the state
----------------------------------------------------------------------------------------------------------------
Alaska.......................................... 48 15 16,020 106,300
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 72,800
----------------------------------------------------------------------------------------------------------------
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
[[Page 62770]]
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.
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\193\ For 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.
\194\ Kamal 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 7--Number of Airports (Among the 2,022 Airports Evaluated) With Disparity for Certain Demographic
Populations Within One Kilometer of an Airport Runway in Relation to the Comparison Population Between One and
Five Kilometers From an Airport Runway
----------------------------------------------------------------------------------------------------------------
Number of airports with disparity \a\
-------------------------------------------------------------------------------
Demographic group Total airports Disparity 5- Disparity 10-
with disparity Disparity 1-5% 10% 20% Disparity 20%+
----------------------------------------------------------------------------------------------------------------
Children under five years of age 515 507 7 1 0
People with income less than 761 307 223 180 51
twice the Federal Poverty Level
People of Color (all races, 666 377 126 123 40
ethnicities and indigenous
peoples).......................
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 144 130 6 7 1
Alaska Native \195\............
Non-Hispanic Hawaiian or Pacific 18 17 1 0 0
Islander.......................
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\
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\195\ This analysis of 2,022 NPIAS airports did not include
airports in Alaska.
\196\ Kamal 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.
---------------------------------------------------------------------------
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\
---------------------------------------------------------------------------
\197\ Kamal 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.
---------------------------------------------------------------------------
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.\198\ In this
section, we describe some of the EPA's actions to reduce lead exposures
from air, water, lead-based paint, and contaminated sites.
---------------------------------------------------------------------------
\198\ Federal 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.
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In 1976, the EPA listed lead under CAA section 108, making it what
is called a ``criteria air pollutant.'' \199\ Once 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.\200\ The
EPA's 2016 Federal Register notice describes the Agency's decision to
retain the existing Lead
[[Page 62771]]
NAAQS.\201\ The Lead NAAQS is currently undergoing review.\202\
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\199\ 41 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.
\200\ 73 FR 66965 (Nov. 12, 2008).
\201\ 81 FR 71912-71913 (Oct. 18, 2016).
\202\ Documents pertaining to the current review of the NAAQS
for Lead can be found here: https://www.epa.gov/naaqs/lead-pb-air-quality-standards.
---------------------------------------------------------------------------
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.\203\ These 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\
---------------------------------------------------------------------------
\203\ 77 FR 555 (Jan. 5, 2012).
\204\ 78 FR 9112 (Feb. 7, 2013).
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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
\206\ regulates lead in public drinking water systems through corrosion
control and other utility actions which work together to minimize lead
levels at the tap.\207\ On January 15, 2021, the agency published the
Lead and Copper Rule Revisions (LCRR) \208\ and subsequently reviewed
the rule in accordance with Executive Order 13990.\209\ While 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),\211\ that 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.'' \212\ The
EPA intends to propose the LCRI and take final action on it prior to
October 16, 2024.
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\205\ Effective 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.
\206\ 40 CFR 141 Subpart I (June 7, 1991).
\207\ 40 CFR 141 Subpart I (June 7, 1991).
\208\ 86 FR 4198. (Jan. 15, 2021).
\209\ E.O. 13990. Protecting Public Health and the Environment
and Restoring Science to Tackle the Climate Crisis. 86 FR 7037 (Jan.
20, 2021).
\210\ 86 FR 31939. (Dec. 17, 2021).
\211\ See https://www.epa.gov/ground-water-and-drinking-water/review-national-primary-drinking-water-regulation-lead-and-copper.
Accessed on Nov. 30, 2021.
\212\ 86 FR 31939 (Dec. 17, 2021).
---------------------------------------------------------------------------
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.'' \213\ The 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.\214\ The 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
[[Page 62772]]
and windowsills, respectively.\215\ The EPA is now reconsidering the
2019 and 2021 rules in accordance with Executive Order 13990 \216\ and
in response to a May 2021 decision by U.S. Court of Appeals for the
Ninth Circuit.
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\213\ 66 FR 1206 (Jan. 5, 2001).
\214\ 84 FR 32632 (July 9, 2019).
\215\ 86 FR 983 (Jan. 7, 2021).
\216\ 86 FR 7037 (Jan. 20, 2021).
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Programs associated with the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA or Superfund) \217\ and
Resource Conservation Recovery Act (RCRA) \218\ also 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).
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\217\ For more information about the EPA's CERCLA program, see
www.epa.gov/superfund.
\218\ For more information about the EPA's RCRA program, see
https://www.epa.gov/rcra.
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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\
---------------------------------------------------------------------------
\219\ See https://www.epa.gov/regulations-emissions-vehicles-and-engines/petitions-and-epa-response-memorandums-related-lead.
Accessed on Dec. 12, 2021.
---------------------------------------------------------------------------
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.\220\ In 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.\221\ The 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.
---------------------------------------------------------------------------
\220\ Friends of the Earth (formerly Bluewater Network) comment
dated Dec. 12, 2003, submitted to EPA's 68 FR 56226, published Sept.
30, 2003.
\221\ See 72 FR 64570 (Nov. 16, 2007).
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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).\222\ In 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.
---------------------------------------------------------------------------
\222\ 75 FR 22440-68 (Apr. 28, 2010).
---------------------------------------------------------------------------
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.\223\
The 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 \224\ to which the EPA responded in
2015.\225\
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\223\ Petitioners 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).
\224\ The 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.
\225\ The 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.
---------------------------------------------------------------------------
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.\226\ The 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\
---------------------------------------------------------------------------
\226\ The 2021 petition is available at https://www.epa.gov/system/files/documents/2022-01/aviation-leaded-avgas-petition-exhibits-final-2021-10-12.pdf.
\227\ EPA'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.
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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
[[Page 62773]]
provided a detailed explanation of the legal framework for making such
findings and the statutory interpretations and caselaw supporting its
approach.\228\ In 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.\229\ This 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),\230\ which was
affirmed by the U.S. Court of Appeals for the D.C. Circuit in
2012.\231\ As 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.\232\ Accordingly, 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.\233\ As this approach has been previously discussed at
length in the 2016 and 2009 Findings, the EPA provides only a brief
description in this proposal.
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\228\ FR 54422-54475 (Aug. 15, 2016).
\229\ See e.g., 81 FR at 55434-54440 (Aug. 19, 2016).
\230\ 74 FR 66496, 66505-10 (Dec. 15, 2009).
\231\ Coalition for Responsible Regulation, Inc. v. EPA, 684
F.3d 102 (D.C. Cir. 2012) (CRR) (subsequent history omitted).
\232\ 81 FR at 55434 (Aug. 19, 2016).
\233\ 81 FR at 55434 (Aug. 19, 2016).
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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.'' \234\ In 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.
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\234\ Regarding ``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.
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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\
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\235\ See Massachusetts v. EPA, 549 U.S. 497,533 (2007)
(interpreting an analogous provision in CAA section 202).
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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.\236\ They 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.'' \237\ The 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.'' \238\ The
same language appears in section 231(a)(2)(A), and the same
interpretation applies in that context.
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\236\ See 81 FR at 54435 (Aug. 19, 2016).
\237\ CRR, 684 F.3d at 122 (internal citations omitted) (June
26, 2012).
\238\ CRR, 684 F.3d at 122 (internal citations omitted) (June
26, 2012).
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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.\240\ However, 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.
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\239\ 81 FR at 54425 (Aug. 19, 2016).
\240\ See, 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).
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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.'' \241\ Any subsequent
[[Page 62774]]
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.
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\241\ As 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).
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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\
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\242\ See CRR, 684 F.3d at 117 (explaining two-part analysis
under section 202(a)) (June 26, 2012).
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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\
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\243\ See, e.g., 81 FR 54422, 54434-55435 (Aug. 15, 2016).
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Similarly, the EPA is taking the same approach to the cause or
contribute analysis as was previously explained in the 2016
Findings.\244\ For 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.\245\ Moreover,
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.'' \246\ Unlike 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.\247\ While 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\
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\244\ See, e.g., 81 FR at 54437-54438 (September 4, 2013).
\245\ See, e.g., 81 FR at 54437-54438 (Aug. 15, 2016).
\246\ See, e.g., 81 FR at 54437-54438 (Aug. 15, 2016).
\247\ See 81 FR at 54437-54438 (Aug. 15, 2016).
\248\ See 81 FR at 54437-54438 (Aug. 15, 2016).
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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.\249\ As 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.'' \250\ Accordingly, 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.'' \251\ As 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).\252\ Moreover, 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.\253\ The 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\
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\249\ See 81 FR at 54437-54438 (Aug. 15, 2016).
\250\ CRR, 684 F.3d at 122-123 (June 26, 2012).
\251\ CRR, 684 F.3d at 122-123. (quoting Ethyl Corp., 541 F.2d
at 18) (June 26, 2012).
\252\ 81 FR at 54438 (Aug. 15, 2016).
\253\ 81 FR at 54438 (Aug. 15, 2016).
\254\ 81 FR at 54438 (Aug. 15, 2016).
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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\
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\255\ See 81 FR at 54462 (Aug. 15, 2016).
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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
[[Page 62775]]
emissions unless such standard is identical to the EPA's
standards.\256\
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\256\ CAA Section 233 (Dec. 31, 1970).
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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.\257\ Lead 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.\258\
Lead 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.
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\257\ EPA (2013) ISA for Lead. Section 2.2. ``Sources of
Atmospheric Pb.'' p. 2-1. EPA, Washington, DC, EPA/600/R-10/075F,
2013.
\258\ EPA (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.
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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\
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\259\ The 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).
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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\
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\260\ EPA (2013) ISA for Lead. EPA, Washington, DC, EPA/600/R-
10/075F, 2013.
\261\ EPA (2006) AQC for Lead. EPA, Washington, DC, EPA/600/R-5/
144aF, 2006.
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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\
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\262\ EPA (2013) ISA for Lead. Section 5.4. ``Summary.'' p. 5-
40. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
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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.\263\ We
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.\264\ In 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.
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\263\ The 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.
\264\ EPA (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.
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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).\265\ In 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\
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\265\ EPA (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.
\266\ EPA (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.
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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\
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\267\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Children.'' pp. lxxxvii-lxxxviii. EPA, Washington,
DC, EPA/600/R-10/075F, 2013.
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Intelligence quotient is a well-established, widely recognized and
rigorously standardized measure of neurocognitive function which has
been
[[Page 62776]]
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\
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\268\ EPA (2013) ISA for Lead. Section 4.3.2. ``Cognitive
Function.'' p. 4-59. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
\269\ EPA (2006) AQC for Lead. Sections 6.2.2 and 8.4.2. EPA,
Washington, DC, EPA/600/R-5/144aF, 2006.
\270\ EPA (2013) ISA for Lead. Section 4.3.2. ``Cognitive
Function.'' p. 4-59. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
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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.'' \271\
The 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.'' \272\ The 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).\273\ Evidence 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,\274\ potentially affecting lower educational
attainment and financial well-being.\275\
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\271\ EPA (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.
\272\ EPA (2013) ISA for Lead. Section 1.9.4. ``Pb Exposure and
Neurodevelopmental Deficits in Children.'' p. 1-76. EPA/600/R-10/
075F, 2013.
\273\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Children.'' pp. lxxxvii-lxxxviii. EPA, Washington,
DC, EPA/600/R-10/075F, 2013.
\274\ EPA (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.
\275\ EPA (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.
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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.\276\ For 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''.\277\ Specifically, 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\
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\276\ EPA (2013) ISA for Lead. Section 1.9.1. ``Public Health
Significance.'' p. 1-68. EPA, Washington, DC, EPA/600/R-10/075F,
2013.
\277\ EPA (2013) ISA for Lead. Executive Summary. ``Public
Health Significance.'' p. xciii. EPA, Washington, DC, EPA/600/R-10/
075F, 2013.
\278\ EPA (2013) ISA for Lead. Section 1.9.1. ``Public Health
Significance.'' p. 1-68. EPA, Washington, DC, EPA/600/R-10/075F,
2013.
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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\
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\279\ EPA (2013) ISA for Lead. Section 1.9.1. ``Public Health
Significance.'' p. 1-68. EPA, Washington, DC, EPA/600/R-10/075F,
2013.
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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.'' \280\ In 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.'' \281\ The 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.\282\
The 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.'' \283\ In 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\
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\280\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Adults.'' p. lxxxviii. EPA/600/R-10/075F, 2013.
\281\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Adults.'' p. lxxxviii. EPA/600/R-10/075F, 2013.
\282\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Adults.'' p. lxxxviii. EPA/600/R-10/075F, 2013.
\283\ EPA (2013) ISA for Lead. Executive Summary. ``Effects of
Pb Exposure in Adults.'' p. lxxxviii. EPA/600/R-10/075F, 2013.
\284\ EPA (2013) ISA for Lead. Executive Summary. ``Public
Health Significance.'' p. xciii. EPA, Washington, DC, EPA/600/R-10/
075F, 2013.
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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\
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\285\ EPA (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.
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Additionally, the evidence is suggestive of lead exposure and some
additional effects. These include auditory function decrements and
[[Page 62777]]
subclinical atherosclerosis, reduced kidney function, birth outcomes
(e.g., low birth weight, spontaneous abortion), and female reproductive
function.\286\
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\286\ EPA (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.
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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.\287\ The 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\
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\287\ EPA (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.
\288\ EPA (2013) ISA for Lead. Section 5.4. ``Summary.'' p. 5-
44. EPA, Washington, DC, EPA/600/R-10/075F, 2013.
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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.\289\ We 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\
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\289\ Causal 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.
\290\ EPA (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.
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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.\291\ The 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.
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\291\ EPA (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.
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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\
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\292\ EPA (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.
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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\
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\293\ EPA (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.
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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\
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\294\ EPA (2013) ISA for Lead. ``Summary.'' p. xcvi. EPA,
Washington, DC, EPA/600/R-10/075F, 2013.
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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
[[Page 62778]]
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.\295\ As 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.
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\295\ The 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.
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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.\296\ In 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\
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\296\ The 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.
\297\ Airport 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.
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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.\299\ In 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.\300\ Although there is some uncertainty in these projections,
they indicate that lead emissions from covered aircraft may increase at
some airports in the future.\301\
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\298\ FAA. 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/.
\299\ Geidosch. 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.
\300\ Geidosch. 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.
\301\ FAA 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.
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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
[[Page 62779]]
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
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\302\ Carr 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.
\303\ EPA (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.
\304\ Carr 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.
\305\ Heiken 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.
\306\ Hudda 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.
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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.
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\307\ 73 FR 66965 (Nov. 12, 2008).
\308\ 75 FR 81226 (Dec. 27, 2010).
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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.\309\ The 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.
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\309\ EPA (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.
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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\
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\310\ EPA's 2017 AirToxScreen is available at https://www.epa.gov/AirToxScreen.
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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.
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\311\ South 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.
\312\ EPA provides updated information regarding nonattainment
areas at this website: https://www.epa.gov/green-book/green-book-lead-2008-area-information.
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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-
[[Page 62780]]
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\
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\313\ The 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.
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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.\314\ Given 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.
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\314\ EPA (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.
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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.
[[Page 62781]]
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.\315\ The EPA plans to continue engaging with Tribal
stakeholders on this issue and will offer a government-to-government
consultation upon request.
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\315\ See 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.
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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 \316\ still 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).
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\316\ EPA (2021) EPA Policy on Children's Health. Available at
https://www.epa.gov/system/files/documents/2021-10/2021-policy-on-childrens-health.pdf.
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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
