[Federal Register Volume 75, Number 81 (Wednesday, April 28, 2010)]
[Proposed Rules]
[Pages 22440-22468]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2010-9603]
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Part II
Environmental Protection Agency
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40 CFR Part 87
Advance Notice of Proposed Rulemaking on Lead Emissions From Piston-
Engine Aircraft Using Leaded Aviation Gasoline; Proposed Rule
Federal Register / Vol. 75 , No. 81 / Wednesday, April 28, 2010 /
Proposed Rules
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ENVIRONMENTAL PROTECTION AGENCY
40 CFR Part 87
[EPA-HQ-OAR-2007-0294; FRL-9141-7]
RIN 2060-AP79
Advance Notice of Proposed Rulemaking on Lead Emissions From
Piston-Engine Aircraft Using Leaded Aviation Gasoline
AGENCY: Environmental Protection Agency (EPA).
ACTION: Advance notice of proposed rulemaking.
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SUMMARY: EPA is issuing this Advance Notice of Proposed Rulemaking
(ANPR) to describe information currently available and information
being collected that will be used by the Administrator to issue a
subsequent proposal regarding whether, in the Administrator's judgment,
aircraft lead emissions from aircraft using leaded aviation gasoline
(avgas) cause or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare. In this ANPR we
describe and request comment on the data available for evaluating lead
emissions, ambient concentrations and potential exposure to lead from
the continued use of leaded avgas in piston-engine powered aircraft. We
also describe and request comment on additional information being
collected that will inform any future action.
This ANPR is being issued to further respond to a petition
submitted by Friends of the Earth (FOE) in 2006. Emissions of lead from
piston-engine aircraft using leaded avgas comprise approximately half
of the national inventory of lead emitted to air. There are almost
20,000 airport facilities in the U.S. at which leaded avgas may be
used. EPA has long-standing concerns regarding exposure to lead,
particularly during childhood. The most recent review and revision of
the National Ambient Air Quality Standard (NAAQS) for lead, promulgated
in 2008, found that serious health effects occur at much lower levels
of lead in blood than previously identified and did not identify a safe
level of lead exposure.
DATES: Comments must be received on or before June 28, 2010.
ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2007-0294, by one of the following methods:
http://www.regulations.gov: Follow the on-line
instructions for submitting comments.
E-mail: [email protected].
Fax: (202) 566-9744.
Mail: Environmental Protection Agency, Mail Code: 6102T,
1200 Pennsylvania Ave., NW., Washington, DC 20460. Please include two
copies.
Hand Delivery: EPA Docket Center (Air Docket), U.S.
Environmental Protection Agency, EPA West Building, 1301 Constitution
Avenue, NW., Room: 3334 Mail Code: 2822T, Washington, DC. Such
deliveries are only accepted during the Docket's normal hours of
operation, and special arrangements should be made for deliveries of
boxed information.
Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2007-0294. EPA's policy is that all comments received will be included
in the public docket without change and may be made available online at
http://www.regulations.gov, including any personal information
provided, unless the comment includes information claimed to be
Confidential Business Information (CBI) or other information whose
disclosure is restricted by statute. Do not submit information that you
consider to be CBI or otherwise protected through http://www.regulations.gov or e-mail. The http://www.regulations.gov Web site
is an ``anonymous access'' system, which means EPA will not know your
identity or contact information unless you provide it in the body of
your comment. If you send an e-mail comment directly to EPA without
going through http://www.regulations.gov your e-mail address will be
automatically captured and included as part of the comment that is
placed in the public docket and made available on the Internet. If you
submit an electronic comment, EPA recommends that you include your name
and other contact information in the body of your comment and with any
disk or CD-ROM you submit. If EPA cannot read your comment due to
technical difficulties and cannot contact you for clarification, EPA
may not be able to consider your comment. Electronic files should avoid
the use of special characters, any form of encryption, and be free of
any defects or viruses. For additional information about EPA's public
docket visit the EPA Docket Center homepage at http://www.epa.gov/epahome/dockets.htm.
Docket: All documents in the docket are listed in the http://www.regulations.gov index. Although listed in the index, some
information is not publicly available, e.g., CBI or other information
whose disclosure is restricted by statute. Certain other material, such
as copyrighted material, will be publicly available only in hard copy.
Publicly available docket materials are available either electronically
in http://www.regulations.gov or in hard copy at the EPA Docket Center,
EPA/DC, EPA West, Room 3334, 1301 Constitution Avenue, NW., Washington,
DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday
through Friday, excluding legal holidays. The telephone number for the
Public Reading Room is (202) 566-1744, and the telephone number for the
Air Docket is (202) 566-1742.
FOR FURTHER INFORMATION CONTACT: Marion Hoyer, Assessment and Standards
Division, Office of Transportation and Air Quality, 2000 Traverwood
Drive, Ann Arbor, MI 48105; telephone number: (734) 214-4513; fax
number: (734) 214-4821; e-mail address: [email protected].
SUPPLEMENTARY INFORMATION:
I. General Information
A. What should I consider as I prepare my comments for EPA?
1. Submitting CBI. Do not submit this information to EPA through
http://www.regulations.gov or e-mail. Clearly mark the part or all of
the information that you claim to be CBI. For CBI information in a disk
or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM
as CBI and then identify electronically within the disk or CD ROM the
specific information that is claimed as CBI. In addition to one
complete version of the comment that includes information claimed as
CBI, a copy of the comment that does not contain the information
claimed as CBI must be submitted for inclusion in the public docket.
Information so marked will not be disclosed except in accordance with
procedures set forth in 40 CFR Part 2.
2. Tips for Preparing Your Comments. When submitting comments,
remember to:
Identify the rulemaking by docket number and other
identifying information (subject heading, Federal Register date and
page number).
Follow directions--The agency may ask you to respond to
specific questions or organize comments by referencing a Code of
Federal Regulations (CFR) part or section number.
Explain why you agree or disagree, suggest alternatives,
and substitute language for your requested changes.
Describe any assumptions and provide any technical
information and/or data that you used.
If you estimate potential costs or burdens, explain how
you arrived at your estimate in sufficient detail to allow for it to be
reproduced.
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Provide specific examples to illustrate your concerns, and
suggest alternatives.
Explain your views as clearly as possible, avoiding the
use of profanity or personal threats.
Make sure to submit your comments by the comment period
deadline identified.
Table of Contents
I. Overview
A. Background on Leaded Aviation Gasoline
B. Background Information Regarding General Aviation and Use of
Piston-Engine Aircraft
C. Background on the Petition and EPA's Response
D. Statutory Authority
1. Background
2. Regulatory Authority for Emission Standards
3. Regulatory Authority for Fuel Standards
E. Federal Actions To Reduce Lead Exposure
II. Health and Welfare Effects of Lead
A. Multimedia and Multi-Pathway Exposure Considerations
B. Health Effects Information
1. Blood Lead
2. Health Effects
3. At-Risk Populations and Life Stages
C. Welfare Effects
1. Terrestrial Ecosystems
2. Aquatic Ecosystems
III. Lead Emissions from Piston-Engine Aircraft
A. Inventory of Lead from Piston-Engine Powered Aircraft
1. National Emissions of Lead from Piston-Engine Aircraft
2. Airport-Specific Emissions of Lead from Piston-Engine
Aircraft
B. Projections for Future Growth
IV. Lead Concentrations in the Vicinity of Airports
A. Chemical and Physical Properties of Lead Emitted by Piston-
Engine Aircraft
B. Summary of Airport Lead Monitoring and Modeling Studies
1. Summary of Airport Lead Monitoring Studies
2. Summary of Airport Lead Modeling Studies
V. Exposure to Lead from Piston-Engine Aircraft and Potential for
Impacts
A. Exposure to Lead Emissions from Piston-Engine Aircraft
1. Population Residing Near Airports
2. Children Attending School Near Airports
3. Agricultural Activities
4. Pilots, Student-Trainees, Passengers
5. Bioaccumulation of Lead in Aquatic Organisms
B. Related Exposures of Concern
1. Lead Contribution to Ambient Particulate Matter
2. Ethylene Dibromide
3. Non-Exhaust Exposure to Tetraethyl Lead
VI. Additional Information Available for the NPRM to Evaluate the
Potential for Public Health and Welfare Impacts and Considerations
Regarding Engine Emission Standards
A. The Lead NAAQS and Lead Emissions from Piston-Engine Aircraft
1. Monitoring Lead at Airports to Evaluate Ambient
Concentrations to Which Lead Emissions from Piston-Engine Aircraft
Contribute
2. Evaluating the Contribution of Lead Emissions from Piston-
Engine Aircraft to Areas Approaching or Exceeding the Lead NAAQS
B. Additional Information EPA Is Collecting to Evaluate Ambient
Lead Concentrations Attributable to Emissions from Piston-Engine
Aircraft
C. Considerations Regarding Engine Emission Standards
VII. Statutory and Executive Order Reviews
I. Overview
EPA is publishing this ANPR in further response to a petition
submitted by Friends of the Earth (FOE) entitled ``Petition for
Rulemaking Seeking the Regulation of Lead Emissions From General
Aviation Aircraft Under Sec. 231 of the Clean Air Act.'' \1\ In the
petition, FOE requests that the Administrator of EPA: (1) Make a
finding that lead emissions from general aviation aircraft endanger
public health and welfare and issue a proposed emission standard for
lead from general aviation aircraft under the Clean Air Act (CAA) or,
alternatively, (2) if the Administrator of EPA believes that
insufficient information exists to make such a finding, commence a
study and investigation of the health and environmental impacts of lead
emissions from general aviation aircraft, including impacts to humans,
animals and ecosystems under the CAA and issue a public report on the
findings of the study and investigation. Section I.C of this notice
discusses the background on the petition and EPA's response to date and
Section I.D discusses EPA's statutory authority under section 231(a) of
the CAA. Under the CAA, if, in the Administrator's judgment, lead
emissions from the use of leaded avgas cause or contribute to air
pollution which may reasonably be anticipated to endanger public health
or welfare, then EPA would be required under our statutory authority to
prescribe standards to control the emissions of lead from piston-engine
aircraft. In promulgating such standards, the EPA would be required to
consult with the Federal Aviation Administration (FAA), and could not
change standards if doing so would significantly increase noise and
adversely affect safety. FAA would then be required, after consultation
with EPA, to prescribe regulations to insure compliance with any
standards to control the emissions of lead from piston-engine aircraft.
Under 49 U.S.C. 44714, FAA would also be required to prescribe
standards for the composition or chemical or physical properties of
piston-engine fuel or fuel additives to control or eliminate aircraft
lead emissions.
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\1\ See docket item EPA-HQ-OAR-2007-0294-0003.
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In this notice, we discuss our analysis of the relevant information
and issues to date, and we seek further public input regarding FOE's
petition. For the purposes of this notice, we will refer to the
positive or negative exercise of judgment as to whether lead emissions
from aircraft engines resulting from the use of aviation gasoline
(avgas) cause or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare as the ``endangerment
finding'' and the ``cause or contribute finding.'' This short-hand use
of ``endangerment finding'' and ``cause or contribute finding'' is
strictly for purposes of simplifying the discussion, and should not be
read as implying that EPA considers the exercise of the Administrator's
judgment to require a formal ``finding'' or ``determination.''
In 2006, EPA completed the Air Quality Criteria Document (AQCD) for
Lead, which critically assesses and integrates relevant scientific
information regarding the health effects of lead.\2\ EPA concluded that
the latest evidence indicates adverse health effects, most notably
among children, are occurring at much lower levels than previously
considered. In 2008, EPA decreased the level of the primary National
Ambient Air Quality Standard (NAAQS) for lead from 1.5 micrograms per
cubic meter ([mu]g/m\3\) to 0.15 [mu]g/m\3\ in order to provide
increased protection for children and other at-risk populations against
an array of adverse health effects, most notably neurological effects
in children, including neurocognitive and neurobehavioral effects.\3\
Neurotoxic effects in children and cardiovascular effects in adults are
among those best substantiated as occurring at blood lead
concentrations as low as 5 to 10 [mu]g/dL (or possibly lower); and
these categories are currently clearly of greatest public health
concern (AQCD for Lead, p. 8-60). The U.S. Centers for Disease Control
and Prevention (CDC) concluded in 2005 that no ``safe'' threshold for
blood lead has been identified, and emphasized the
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importance of preventative measures.4 5 To provide increased
protection against lead-related welfare effects, in 2008 EPA revised
the secondary standard to be identical in all respects to the revised
primary standard. Section II of this ANPR provides more detail
regarding health and welfare effects of lead.
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\2\ U.S. Environmental Protection Agency (2006) Air Quality
Criteria for Lead. Washington, DC, EPA/600/R-5/144aF. Available
online at: http://www.epa.gov/ncea/.
\3\ National Ambient Air Quality Standards for Lead 73 FR 66965
(Nov. 12, 2008).
\4\ Centers for Disease Control and Prevention (2005) Preventing
lead poisoning in young children: a statement by the Centers for
Disease Control and Prevention. Atlanta, GA: U.S. Department of
Health and Human Services, Public Health Service. August.
\5\ Advisory Committee on Childhood Lead Poisoning Prevention
(ACCLPP) (2007) Interpreting and managing blood lead levels <10 ug/
dL in children and reducing childhood exposures to lead:
Recommendations of CDC's Advisory Committee on Childhood Lead
Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR-
8). November 2, 2007.
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Given the recent findings of the science summarized by EPA in the
AQCD for Lead as well as the findings of the CDC, the Agency is
concerned about the potential for health and welfare effects from
exposure to lead emissions from aircraft engines using leaded avgas. On
a national basis, emissions of lead from aircraft engines using leaded
avgas are the largest single source category for emissions of lead to
air, comprising approximately half of the national inventory.\6\ There
are almost 20,000 airport facilities in the U.S. at which leaded avgas
may be used, and in some areas of the country there are densely
populated residential developments immediately adjacent to these
airport facilities. As described in Section V, we estimate that up to
16 million people reside and three million children attend school in
close proximity to airport facilities servicing piston-engine aircraft
that are operating on leaded avgas.
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\6\ U.S. Environmental Protection Agency Electronic Report on
the Environment. Available at: http://cfpub.epa.gov/eroe. Updated in
December 2009 using the 2005 National Emissions Inventory.
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Exposure to lead occurs through multiple routes (e.g., inhalation,
ingestion and dermal adsorption), and lead emitted to the atmosphere
can contribute to lead levels in multiple media (e.g., air, soil and
water). The lead monitoring studies conducted at or near airports,
described in Section IV of this ANPR, indicate that lead levels in
ambient air on and near airports servicing piston-engine aircraft are
higher than lead levels in areas not directly influenced by a lead
source. In addition, the emissions of lead from these engines are also
expected to distribute widely through the environment. This is in part
due to the emission of lead at various altitudes during aircraft
operations as well as the fine particle size of lead emitted by piston
engines. Continued use of leaded avgas provides an ongoing source of
new lead that is deposited in various environmental media and
participates in long term cycling mechanisms in the environment, thus
adding to the pool of lead available for uptake by humans and biota. We
expect the lead from avgas to be bioavailable in the same way as the
lead emitted by motor vehicles in the past, which was well documented
to contribute to blood levels through both ingestion and inhalation.
As noted in Section II of this ANPR, once deposited to surfaces,
lead can subsequently be resuspended into the ambient air and, because
of the persistence of lead, emissions of this metal contribute to
environmental media concentrations for many years into the future. Lead
that is a soil or dust contaminant today may have been airborne
yesterday or many years ago. Therefore lead emissions from piston-
engine aircraft could contribute to increased lead exposure and risk
currently or at some time in the future.
Section VI of this ANPR provides an overview of additional
information that will be available for the NPRM to evaluate the
potential for public health and welfare impacts from lead emitted by
piston-engine aircraft. These additional data will come from lead
monitoring being planned to satisfy requirements of the Lead NAAQS, air
quality modeling planned at EPA and any information submitted to EPA
during the comment period for this ANPR.
The remainder of this section provides background on leaded avgas,
FOE's petition and EPA's response to the petition to date, and
statutory authority over emissions, fuel for aircraft and Federal
actions to reduce lead exposure. Section II provides a discussion of
the health and welfare effects of lead. Sections III, IV and V describe
the emissions of lead from avgas, ambient lead concentration in the
vicinity of airports and potential exposure to lead from leaded avgas,
respectively. In Section VI, we describe the additional information EPA
is collecting and considerations regarding engine emission standards.
Section VII contains information on statutory and executive order
reviews covering this action.
A. Background on Leaded Aviation Gasoline
In 1996, EPA promulgated regulations that banned the use of leaded
gasoline in highway vehicles.\7\ The addition of lead to fuel used in
piston-engine powered aircraft was not banned in this action, and the
use of leaded avgas is the largest remaining source category of lead
emissions. Lead is not added to jet fuel that is used in commercial
aircraft, most military aircraft, or other turbine-engine powered
aircraft. Most piston-engine aircraft fall into the categories of
either general aviation (GA) or air taxi (AT). GA and AT aircraft
include a diverse set of aircraft types and engine models and are used
in a wide variety of applications.\8\
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\7\ See ``Prohibition on Gasoline Containing Lead or Lead
Additives for Highway Use'' 61 FR 3832 (Feb. 2, 1996).
\8\ Commercial aircraft include those used for scheduled service
transporting passengers, freight, or both. Air taxis fly scheduled
and for-hire service carrying passengers, freight or both, but they
usually are smaller aircraft than those operated by commercial air
carriers. General aviation includes most other aircraft (fixed and
rotary wing) used for recreational flying, business, and personal
transportation.
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Lead is added to fuel for piston-engine aircraft in the form of
tetraethyl lead (TEL). This lead additive helps boost fuel octane,
prevents knock, and prevents valve seat recession and subsequent loss
of compression for engines without hardened valves. There are two main
types of leaded avgas: 100 Octane, which can contain up to 4.24 grams
of lead per gallon; and 100 Octane Low Lead (100 LL), which can contain
up to 2.12 grams of lead per gallon. Currently, 100LL is the most
commonly available and most commonly used type of avgas.9 10
TEL was first used in piston-engine aircraft in 1927.\11\ Into the
1950s commercial and military aircraft in the U.S. operated on 100
Octane leaded avgas, but in subsequent years, the commercial and
military aircraft fleet largely converted to jet turbine-engine
propelled aircraft. However, the use of avgas containing 4 grams of
lead per gallon continued in piston-engine aircraft until the early
1970s when 100LL became the dominant leaded fuel in use. Currently,
very little 100 Octane is supplied in the U.S. and we use the lead
content of 100LL (2.12 grams per gallon) to characterize the lead
available from avgas.
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\9\ ChevronTexaco (2006) Aviation Fuels Technical Review. FTR-3.
Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
\10\ ASTM International (2007) Standard Specification for
Aviation Gasolines D910-06.
\11\ Ogston, A.R. (1981) A Short History of Aviation Gasoline
Development, 1903-1980. Society of Automotive Engineers. Paper
number 810848.
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Since lead is a persistent pollutant, it is important to
characterize the historical use of this fuel.
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Approximately 14.6 billion gallons of leaded avgas have been consumed
in the U.S. between 1970 and 2007. If this fuel was all 100LL, it would
account for approximately 34,000 tons \12\ of lead emitted to the
air.\13\ In terms of the potential impacts from long-term use of leaded
avgas at and near airports, older facilities would be expected to have
a legacy of lead, particularly those that supported military and
commercial aircraft operating on 100 Octane. Over 3,000 of the 20,000
airport facilities in the U.S. are at least 50 years old and some
airports have been in operation since the early 1900s.
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\12\ In this ANPR and in EPA's National Emissions Inventory, the
use of the unit tons refers to short tons.
\13\ Oak Ridge National Laboratory (2009) Transportation Energy
Data Book: Edition 28. Available at: http://cta.ornl.gov/data. Table
A.7.
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The Department of Energy's (DOE's) Energy Information
Administration (EIA) provides information on the volume of leaded avgas
supplied in the U.S.\14\ The Department of Transportation's (DOT's) FAA
provides information on the volume of leaded avgas consumed in the
U.S.\15\ EPA has historically used the DOE EIA avgas fuel volumes
supplied to calculate national lead inventories from the consumption of
leaded avgas. We are currently evaluating methods used by DOE and DOT
to calculate annual avgas supply and consumption volumes. In this
document, we provide avgas fuel volume data supplied by DOE and DOT and
we note the source of the data for clarity. Over the past ten years,
DOE estimates of the volume of leaded avgas supplied has ranged from
326 million gallons in 1999 to 235 million gallons in 2008 (Figure 1).
Applying the concentration of lead in 100LL (2.12 grams of lead per
gallon), the total quantity of lead supplied in avgas in the nation has
ranged from 762 tons in 1999 to 550 tons in 2008 (a 28% decrease over
that time period). The decrease in fuel consumption is attributed to
the decrease in piston-engine aircraft activity over that time period
and not due to a shift to unleaded fuel. There are currently over
200,000 piston-engine aircraft in the U.S. that continue to consume
leaded avgas and approximately 2,000 new piston-engine aircraft
requiring leaded avgas are manufactured annually.\16\ As described in
Section III.B of this ANPR, there is a slight growth in the activity of
general aviation aircraft projected to 2025.
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\14\ Department of Energy Information Administration. Fuel
production volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm accessed June 2009.
\15\ U.S. Department of Transportation Federal Aviation
Administration Aviation Policy and Plans. FAA Aerospace Forecast
Fiscal Years 2009-2025. p.81. Available at: http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009-2025/media/2009%20Forecast%20Doc.pdf. This document provides historical data
for 2000-2008 as well as forecast data.
\16\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook & Industry Outlook. Available online
at: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
[GRAPHIC] [TIFF OMITTED] TP28AP10.014
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B. Background Information Regarding General Aviation and Use of Piston-
Engine Aircraft
In the U.S., general aviation aircraft fly over 27 million hours
and carry 166 million passengers annually.\17\ Approximately 66 percent
of hours flown by general aviation are conducted by piston-engine
aircraft.\18\ Aircraft in the general aviation fleet are used for
personal transportation (36 percent), instructional flying (19
percent), corporate uses (11 percent), business (11 percent), air taxi
and air tours (8 percent) and the remainder include hours spent in
other applications such as aerial observation and aerial
application.\19\ According to the 2008 General Aviation Statistical
Databook & Industry Outlook report by the General Aviation
Manufacturers Association (GAMA) there were 578,541 pilots in the
United States in 2008.\20\ According to GAMA, in 2008, the number of
active single-engine piston-powered aircraft was 144,220 and the number
of active twin-engine piston-powered aircraft was 18,385. In 2008,
1,791 new piston-engine aircraft were manufactured in the U.S.
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\17\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook and Industry Outlook, p.30. Retrieved
on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
\18\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook and Industry Outlook, p.30. Retrieved
on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
\19\ General Accounting Office Report to Congressional
Requesters (2001) General Aviation Status of the Industry, Related
Infrastructure, and Safety Issues. GAO-01-916.
\20\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook and Industry Outlook, pp.51-55.
Retrieved on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
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FAA's Office of Air Traffic provides a complete listing of
operational airport facilities in the National Airspace System
Resources (NASR) database.\21\ In 2008, there were 19,896 airport
facilities in the U.S., the vast majority of which are expected to have
activity by piston-engine aircraft that operate on leaded avgas. FAA's
National Plan of Integrated Airport Systems identifies approximately
3,400 airports that are significant to national air transportation.
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\21\ An electronic report can be generated from the NASR
database and is available for download from the Internet at the
following Web site. http://www.faa.gov/airports_airtraffic/airports/airport_safety/airportdata_5010/. This database is
updated every 56 days.
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C. Background on the Petition and EPA's Response
In a 2003 letter to the EPA, FOE initially raised the issue of the
potential for endangerment caused or contributed to by lead emissions
from the use of leaded avgas.\22\ In 2006, FOE filed a petition with
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.\23\ We sought comments regarding exposure to lead from avgas
combustion, emissions of lead, fuel options, and piston-engine
technology. The comments received to date are publicly available in the
docket (EPA-HQ-OAR-2007-0294). The majority of comments received
concerned the nature of the industry and fuel supply issues. The
commenters did not supply information regarding health or exposure
issues. In 2008, the EPA initiated a lead study which will improve the
manner in which EPA models emissions from piston-engine aircraft. This
study is described in further detail in Section VI of this document. At
the time we received FOE's petition, the EPA was in the process of a
full re-evaluation of the science supporting the lead NAAQS.
Information from that re-evaluation and the relationship between the
new lead standard and the emissions of lead from piston-engine aircraft
are discussed in this ANPR.
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\22\ FOE letter dated December 12, 2003 submitted to EPA Docket
EPA-HQ-OAR-2002-0030.
\23\ See ``Petition Requesting Rulemaking To Limit Lead
Emissions from General Aviation Aircraft; Request for Comments'' 72
FR 64570 (Nov. 16, 2007).
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D. Statutory Authority
1. Background
Section 231 of the CAA sets forth EPA's authority to regulate
aircraft emissions of air pollution. As described further in Section
I.D.2 of this ANPR, Section 231(a)(2)(A) requires EPA to, 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 the Administrator's judgment, cause or contribute to air pollution
which may reasonably be anticipated to endanger public health or
welfare. EPA has broad authority in exercising its judgment regarding
whether emissions from certain sources cause or contribute to air
pollution which may reasonably be anticipated to endanger public health
or welfare.\24\ EPA has discussed its ``endangerment finding''
authority at length in recent notices for greenhouse gases published in
the Federal Register, and we refer readers to those notices for
detailed discussions of the analytical and legal framework.\25\
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\24\ See, e.g., Ethyl Corp. v. EPA, 541 F.2d 1, 6 (DC Cir.),
cert. denied 426 U.S. 941 (1976); see also Massachusetts v. EPA, 549
U.S. 497, 506, n.7 (2007).
\25\ See, ``Endangerment and Cause or Contribute Findings for
Greenhouse Gases under Section 202(a) of the Clean Air Act; Final
Rule,'' 74 FR 66496, 66505 (Dec. 15, 2009); see also, ``Proposed
Endangerment and Cause or Contribute Findings for Greenhouse Gases
Under Section 202(a) of the Clean Air Act,'' 74 FR 18886, 18890-94
(April 24, 2009); see also ``Regulating Greenhouse Gas Emissions
Under the Clean Air Act; Advance Notice of Proposed Rulemaking,'' 73
FR 44354, 44421-23 (July 30, 2008).
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In 1976, EPA listed lead under CAA section 108, making it what is
called a ``criteria pollutant.'' As part of the listing decision, EPA
determined that lead was an air pollutant which, in the Administrator's
judgment, has an adverse effect on public health or welfare under then
section 108(a). Once lead was listed, EPA issued primary and secondary
NAAQS that the Administrator determined were requisite to protect
public health with an adequate margin of safety and to protect public
welfare from any known or anticipated adverse effects. Section
109(b)(1) and (2). As discussed elsewhere in this notice, EPA issued
the first NAAQS for lead in 1978, and recently revised the lead NAAQS
by reducing the level of the standard from 1.5 [mu]g/m\3\ to 0.15
[mu]g/m\3\, measured over a 3-month averaging period. These actions are
part of the context for the issues before EPA under section 231(a).
The first part of the endangerment test concerns identification of
air pollution which may reasonably be anticipated to endanger public
health or welfare. The CAA defines both ``air pollutant'' and
``welfare.'' Air pollutant is defined in CAA section 302(g) as: ``Any
air pollution agent or combination of such agents, including any
physical, chemical, biological, radioactive (including source material,
special nuclear material, and byproduct material) substance or matter
which is emitted into or otherwise enters the ambient air. Such term
includes any precursors to the formation of any air pollutant, to the
extent the Administrator has identified such precursor or precursors
for the particular purpose for which the term `air pollutant' is
used.'' Lead fits within
[[Page 22445]]
this capacious definition, and has long been regulated as an air
pollutant by EPA under the CAA (see Section I.E. of this ANPR).
There is no definition of public health in the CAA. The U.S.
Supreme Court has discussed the concept 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.
When considering public health, EPA has looked at morbidity, including
acute and chronic health effects, as well as mortality. EPA has long
regulated emissions of lead air pollution due to their adverse impacts
on public health (see section I.E. of this ANPR). Exposure to lead
causes ``a broad array of deleterious effects on multiple organ
systems,'' among children and adults (AQCD for Lead, p.8-24 and Section
8.4.1). Of particular concern are the neurotoxic effects of lead in
young children.\26\ See Section II of this ANPR for a more complete
overview of the public health effects of lead.
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\26\ See ``National Ambient Air Quality Standards for Lead'' 73
FR 66970-67007 (Nov. 12, 2008).
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Regarding ``welfare,'' CAA section 302(h) states that ``[a]ll
language referring to effects on welfare includes, but is not limited
to, effects on soils, water, crops, vegetation, man-made 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.'' This definition is quite broad, and may include
effects other than those listed here as effects on welfare. Welfare
effects caused by lead have been evaluated by EPA and were the basis
for establishing the secondary lead standard.\27\
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\27\ See ``National Ambient Air Quality Standards for Lead'' 73
FR 67007-67012 (Nov. 12, 2008).
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By instructing the Administrator to consider whether emissions of
an air pollutant cause or contribute to air pollution, the statute is
clear that she need not find that emissions from any one sector or
group of sources are the sole or even the major part of an air
pollution problem. Moreover, section 231(a) does not contain a modifier
on its use of the term contribute. Unlike some other CAA provisions, it
does not require ``significant'' contribution.\28\ Congress made it
clear that the Administrator is to exercise her 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. The cause or contribute test is designed to authorize EPA
to identify and then address what may well be many different sectors or
groups of sources that are each part of an air pollution problem.
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\28\ See, e.g., CAA sections 111(b); 213(a)(2), (4).
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Section 231(a)(2) refers to contribution and does not specify that
the contribution must be significant before an affirmative finding can
be made. Any finding of a ``contribution'' requires some threshold to
be met; a truly trivial or de minimis ``contribution'' might not count
as such. In the past, the Administrator has evaluated the emissions of
the source or sources in different ways, based on the particular
circumstances involved. In some mobile source rulemakings, the
Administrator has used the percent of emissions from the regulated
mobile source category compared to the total mobile source inventory
for that air pollutant as the best way to evaluate contribution.\29\ In
other instances the Administrator has looked at the percent of
emissions compared to the total nonattainment area inventory of the air
pollution at issue.\30\ EPA has found that air pollutant emissions that
amount to 1.2 percent of the total inventory met the statutory test for
contribution, triggering EPA's regulatory authority.\31\
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\29\ See, e.g., 66 FR 5001 (January 18, 2001) (heavy duty engine
and diesel sulfur rule).
\30\ See, e.g., 67 FR 68242 (November 8, 2002) (snowmobile
rule).
\31\ Bluewater Network v. EPA, 370 F.3d 1, 15 (DC Cir. 2004)
(For Fairbanks, this contribution was equivalent to 1.2 percent of
the total daily CO inventory for 2001).
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2. Regulatory Authority for Emission Standards
Section 231 of the CAA sets forth EPA's authority to regulate
aircraft emissions of air pollution. Section 231(a)(2)(A) requires EPA
to, 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 the Administrator's judgment, cause or contribute to
air pollution which may reasonably be anticipated to endanger public
health or welfare. Section 231(a)(2)(B)(i) directs EPA to consult with
FAA on aircraft engine emission standards, and section 231(a)(2)(B)(ii)
provides that EPA shall not change the aircraft engine emission
standards if such change would significantly increase noise and
adversely affect safety. Section 231(a)(3) directs EPA to issue final
regulations with such modifications as the Administrator ``deems
appropriate.''
In setting or revising standards, section 231(b) provides that EPA
shall have them take effect after such period as EPA finds necessary
(after consultation with the Secretary of Transportation) to permit the
development and application of the requisite technology, giving
appropriate consideration to the cost of compliance within such period.
Section 231(c) then states that EPA's regulations regarding aircraft
shall not apply if disapproved by the President, after notice and
opportunity for public hearing, on the basis of a finding by DOT that
such regulations would create a hazard to aircraft safety. Section 232
directs DOT to issue and implement regulations to insure compliance
with EPA's standards, while section 233 pre-empts States and local
governments from adopting or enforcing any aircraft emission standards
that are not identical to EPA's standards.
In recently reviewing this statutory scheme, the U.S. Court of
Appeals for the District of Columbia Circuit ruled that it constitutes
a ``both explicit and extraordinarily broad'' delegation of ``expansive
authority to EPA to enact appropriate regulations applicable to the
emissions of air pollutants from aircraft engines.'' \32\
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\32\ NACAA v. EPA, 489 F.3d 1221, 1229-30 (DC Cir. 2007).
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3. Regulatory Authority for Fuel Standards
Section 211(c) of the CAA allows EPA to regulate fuels used in
motor vehicles and nonroad vehicles or engines where emission products
of the fuel either: (1) Cause or contribute to air pollution that
reasonably may be anticipated to endanger public health or welfare, or
(2) will impair to a significant degree the performance of any emission
control device or system which is in general use, or which the
Administrator finds has been developed to a point where in a reasonable
time it will be in general use were such a regulation to be
promulgated. This section of the CAA was used to eliminate lead from
fuel used in motor vehicles. EPA's authority to regulate fuels is
limited to those fuels used in motor vehicles, motor vehicle engines,
or nonroad engines or vehicles, under CAA section 211(c)(1). The CAA
defines ``motor vehicle,'' ``nonroad engine,'' and ``nonroad vehicle''
in section 216 for purposes of part A of title II of the CAA. Part A is
also where the authority to regulate fuels under section 211 resides.
However, EPA's authority to regulate aircraft resides in
[[Page 22446]]
part B of title II, and therefore the definitions of section 216 do not
apply to aircraft. This means that aircraft are not ``nonroad
vehicles,'' and aircraft engines are not ``nonroad engines.''
Consequently, EPA's authority to regulate fuels under section 211 does
not extend to fuels used exclusively in aircraft, such as leaded avgas,
that are not also used in motor vehicles or nonroad vehicles or engines
(excluding fuel used in vehicles exclusively).
Instead, fuels used exclusively in aircraft engines are to be
regulated by the FAA. Title 49 (49 U.S.C. 44714) requires that ``the
Administrator of the Federal Aviation Administration shall prescribe
(1) standards for the composition or chemical or physical properties of
an aircraft fuel or fuel additive to control or eliminate aircraft
emissions the Administrator of the Environmental Protection Agency
decides under section 231 of the Clean Air Act (42 U.S.C. 7571)
endanger the public health or welfare; and (2) regulations providing
for carrying out and enforcing those standards.''
E. Federal Actions To Reduce Lead Exposure
The U.S. has made tremendous progress in reducing lead
concentrations in the outdoor air. Nationwide, average concentrations
of lead in the air have dropped 91 percent between 1980 and 2008.\33\
Much of this dramatic improvement occurred as a result of the permanent
phase-out of lead in motor vehicle gasoline discussed in this section
of the ANPR. However, lead continues to be emitted into the air from
many different types of stationary sources and piston-engine aircraft
as well as certain high performance engines such as race cars.
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\33\ See http://www.epa.gov/airtrends/lead.html.
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Federal programs provide for nationwide reductions in emissions of
lead and other air pollutants through several provisions in the CAA. In
the early 1970s, EPA issued regulations regarding lead in gasoline in
order to accomplish two purposes.\34\ First, EPA issued regulations
designed to ensure the availability of unleaded gasoline for use in
motor vehicles equipped with emission control systems such as catalytic
converters. EPA had determined that lead additives would impair to a
significant degree the performance of emission control systems. Second,
EPA issued regulations designed to gradually reduce the content of lead
in leaded gasoline, because EPA found that lead emissions from motor
vehicles presented a significant risk of harm to the health of urban
population groups, especially children. Children are at a sensitive
life stage with regard to the adverse health effects of lead. In 1985,
EPA, noting the significant reduction in adverse health effects, mainly
among pre-school age children, that would result from reductions in
lead content in gasoline, promulgated additional regulations to
decrease the allowable concentration of lead in gasoline for motor
vehicles to 0.10 grams per gallon.\35\ In 1990 Congress added section
211(n) to the CAA which provides that after December 31, 1995, it shall
be unlawful to sell any gasoline for use in any motor vehicle which
contains lead or lead additives. In 1996, EPA incorporated the CAA
statutory ban on gasoline containing lead or lead additives for highway
use into the Agency's existing regulations on the lead content of
gasoline.\36\ In this regulation, it was noted that the petroleum
industry may continue to make and market gasoline produced with lead
additives for all remaining uses, including use as fuel in aircraft,
racing cars, and nonroad engines such as farm equipment engines and
marine engines, to the extent otherwise allowed by law.\37\
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\34\ ``Regulation of Fuels and Fuel Additives'' 38 FR 1254 (Dec.
4, 1973).
\35\ ``Regulation of Fuels and Fuel Additives; Gasoline Lead
Content'' 50 FR 9386 (March 7, 1985).
\36\ ``Prohibition on Gasoline Containing Lead or Lead Additives
for Highway Use'' 61 FR 3832 (Feb. 2, 1996).
\37\ ``Prohibition on Gasoline Containing Lead or Lead Additives
for Highway Use'' 61 FR 3834 (Feb. 2, 1996).
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In fact, there have been no regulatory limits placed on the
production and consumption of leaded avgas, and, as noted in Section
I.A of this ANPR, emissions of lead from piston-engine aircraft account
for an increasing fraction of the lead emissions to air (e.g.,
accounting for approximately half the national inventory of lead
emission in 2005). This is in spite of the decrease in the supply of
leaded avgas nationally from 374 million gallons (875 tons of lead) in
1990 to 235 million gallons (550 tons of lead) in 2008.\38\ The
decrease in fuel consumption is attributed to the decrease in piston-
engine aircraft activity over that time period and not due to a shift
to unleaded fuel. There are over 200,000 piston-engine aircraft in the
U.S. that continue to consume leaded avgas and approximately 2,000 new
piston-engine aircraft requiring leaded avgas are manufactured
annually. Projected growth for this industry is discussed in Section
III.B.
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\38\ These fuel volume estimates are from the Department of
Energy Information Administration. http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm.
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Significant reductions in emission of lead from stationary sources
have been achieved between 1985 and 2002, totaling almost 2,000 tons of
lead.\39\ Regulations promulgated in 1995, 1997 and 1999 controlled
emissions of lead from primary and secondary lead smelters,
contributing to these reductions.40 41 42 Currently, metal
industry emissions of lead comprise 23% of the national inventory (298
tons). Additional reductions in the emission of lead have been
accomplished through controls on waste incineration and other
stationary sources.43 44 45 These standards have been set at
``maximum achievable control technology'' (MACT) levels, and under CAA
sections 112 and 129 EPA must revisit these standards in the future to
determine whether they are sufficiently stringent to provide an ample
margin of safety to protect public health and prevent an adverse
environmental effect.
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\39\ U.S. Environmental Protection Agency (2008) EPA's Report on
the Environment EPA/600/R-07/045F. Available at: http://www.epa.gov/roe/.
\40\ ``National Emission Standards for Hazardous Air Pollutants
From Secondary Lead Smelting'' 60 FR 32587 (June 23, 1995).
\41\ ``National Emission Standards for Hazardous Air Pollutants
From Secondary Lead Smelting'' 62 FR 32209 (June 13, 1997).
\42\ ``National Emission Standards for Hazardous Air Pollutants
for Primary Lead Smelting'' 64 FR 30194 (June 4, 1999).
\43\ ``Standards of Performance for New Stationary Sources and
Emission Guidelines for Existing Sources: Municipal Waste
Combustors'' 60 FR 65387 (Dec. 19, 1995).
\44\ ``Emission Guidelines for Existing Sources and Standards of
Performance for New Stationary Sources'' 62 FR 45124 (Aug. 25,
1997).
\45\ ``Standards of Performance for New Stationary Sources and
Emission Guidelines for Existing Sources: Large Municipal Waste
Combustors'' 71 FR 27324-27348 (May 10, 2006).
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As lead is a multimedia pollutant, a broad range of Federal
programs beyond those that focus on air pollution control provide for
nationwide reductions in environmental releases and human exposures. In
addition, the U.S. Centers for Disease Control and Prevention (CDC)
programs provide for the tracking of children's blood lead levels
nationally and provide guidance on levels at which medical and
environmental case management activities should be
implemented.46 47 In
[[Page 22447]]
1991, the Secretary of the U.S. Department of Health and Human Services
(HHS) characterized lead poisoning as the ``number one environmental
threat to the health of children in the United States.'' \48\ In 1997,
President Clinton created, by Executive Order 13045, the President's
Task Force on Environmental Health Risks and Safety Risks to Children
in response to increased awareness that children face disproportionate
risks from environmental health and safety hazards (62 FR 19885).\49\
By Executive Orders issued in October 2001 and April 2003, President
Bush extended the work for the Task Force for an additional three and a
half years beyond its original charter (66 FR 52013 and 68 FR 19931).
The Task Force set a Federal goal of eliminating childhood lead
poisoning by the year 2010, and reducing lead poisoning in children was
identified as the Task Force's top priority.
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\46\ Centers for Disease Control and Prevention (2005)
Preventing lead poisoning in young children: a statement by the
Centers for Disease Control and Prevention. Atlanta, GA: U.S.
Department of Health and Human Services, Public Health Service.
August.
\47\ Advisory Committee on Childhood Lead Poisoning Prevention
(2007) Interpreting and managing blood lead levels <10 [micro]g/dL
in children and reducing childhood exposures to lead:
Recommendations of CDC's Advisory Committee on Childhood Lead
Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR-
8). November 2, 2007.
\48\ Alliance to End Childhood Lead Poisoning (1991) The First
Comprehensive National Conference; Final Report. October 6, 7, 8,
1991.
\49\ Co-chaired by the Secretary of the HHS and the
Administrator of the EPA, the Task Force consisted of
representatives from 16 Federal departments and agencies.
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Federal abatement programs provide for the reduction in human
exposures and environmental releases from in-place materials containing
lead (e.g., lead-based paint, urban soil and dust, and contaminated
waste sites). Federal regulations on disposal of lead-based paint waste
help facilitate the removal of lead-based paint from residences (68 FR
36487). Further, in 1991, EPA lowered the maximum levels of lead
permitted in public water systems from 50 parts per billion (ppb) to 15
ppb measured at the consumer's tap (56 FR 26460).
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 and Title IV of the Toxic Substances Control
Act (TSCA), EPA has established regulations and associated programs
with the goal of reducing exposure to lead via lead-based paint. For
example, under Title IV of TSCA, EPA established standards identifying
hazardous levels of lead in residential paint, dust, and soil in 2001.
On March 31, 2008, the Agency issued a new rule (73 FR 21692) to
further protect children from lead-based paint hazards resulting from
renovation and repair work occurring in housing in which they live.
Programs associated with the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA or Superfund) and Resource
Conservation Recovery Act (RCRA) also implement abatement programs,
reducing exposures to lead and other pollutants. For example, EPA
determines and implements protective levels for lead in soil at
Superfund sites and RCRA corrective action facilities. Federal
programs, including those implementing RCRA, provide for management of
hazardous substances in hazardous and municipal solid waste.\50\
Federal regulations concerning batteries in municipal solid waste
control the collection and recycling or proper disposal of batteries
containing lead.\51\ Similarly, Federal programs provide for the
reduction in environmental releases of hazardous substances such as
lead in the management of wastewater.\52\
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\50\ See, e.g., 66 FR 58258.
\51\ See, e.g., ``Implementation of the Mercury-Containing and
Rechargeable Battery Management Act'' http://www.epa.gov/epaoswer/hazwaste/recycle/battery.pdf and ``Municipal Solid Waste Generation,
Recycling, and Disposal in the United States: Facts and Figures for
2005'' http://www.epa.gov/epaoswer/osw/conserve/resources/msw-2005.pdf.
\52\ http://www.epa.gov/owm/.
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A variety of Federal nonregulatory programs also provide for
reduced environmental release of lead-containing materials through
voluntary measures and more general encouragement of pollution
prevention, promotion of reuse and recycling, reduction of priority and
toxic chemicals in products and waste, and conservation of energy and
materials. These include the voluntary partnership between EPA and the
National Association for Stock Car Auto Racing (NASCAR) which has
achieved the goal of removing alkyl lead (organic forms of lead) from
racing fuels used in the Nextel Cup, Busch and Craftsman Truck
Series.\53\ Other programs include the Resource Conservation
Challenge,\54\ the National Waste Minimization Program,\55\ ``Plug in
to eCycling'' (a partnership between EPA and consumer electronics
manufacturers and retailers),\56\ and activities to reduce the practice
of backyard trash burning.\57\
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\53\ U.S. Environmental Protection Agency Persistent,
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT
national action plan for alkyl-Pb. Washington, DC. Available online
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
\54\ http://www.epa.gov/epawaste/rcc/index.htm.
\55\ http://www.epa.gov/epawaste/hazard/wastemin/.
\56\ http://www.epa.gov/epawaste/partnerships/plugin/index.htm.
\57\ http://www.epa.gov/epawaste/nonhaz/municipal/backyard/index.htm.
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In addition to the lead control programs summarized above, EPA's
research program, with other Federal agencies, identifies, encourages
and conducts research needed to locate and assess serious risks and to
develop methods and tools to characterize and help reduce risks. For
example, EPA's Integrated Exposure Uptake Biokinetic Model for Lead in
Children (IEUBK model) and the Adult Lead Methodology are widely used
and accepted as tools that provide guidance in evaluating site specific
data. More recently, in recognition of the need for a single model that
predicts lead concentrations in tissue for children and adults, EPA is
developing the All Ages Lead Model (AALM) to provide researchers and
risk assessors with a pharmacokinetic model capable of estimating
blood, tissue, and bone concentrations of lead based on estimates of
exposure over the lifetime of the individual. EPA research activities
on substances including lead focus on better characterizing aspects of
health and environmental effects, exposure, and control or management
of environmental releases.\58\
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\58\ http://www.epa.gov/ord/.
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II. Health and Welfare Effects of Lead
A. Multimedia and Multi-Pathway Exposure Considerations
This section briefly summarizes the information presented in the
2008 NAAQS for Lead,\59\ the 2007 Lead Staff Paper \60\ and the 2006
Air Quality Criteria Document for Lead (AQCD for Lead).\61\ Lead is an
unusual pollutant in that the distribution of lead to different
environmental media (e.g., air, soil, water) is important for
evaluating public health and welfare effects. Lead emitted to the air
can result in exposure via multiple pathways (e.g., inhalation,
ingestion, dermal absorption). Some key multimedia and multi-pathway
considerations for lead include the following:
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\59\ National Ambient Air Quality Standards for Lead 73 FR
66970-67007 (Nov. 12, 2008) Section II.A.
\60\ U.S. Environmental Protection Agency Review of the National
Ambient Air Quality Standards for Lead: Policy Assessment of
Scientific and Technical Information OAQPS Staff Paper (2007)
Chapter 2. EPA-452/R-07-013 November.
\61\ U.S. Environmental Protection Agency Air Quality Criteria
for Lead (2006) Volume I: Chapters 2 & 3. EPA/600/R-5/144aF.
October.
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(1) Lead is emitted into the air from many sources encompassing a
wide
[[Page 22448]]
variety of stationary and mobile source types. Lead emitted to the air
is predominantly in particulate form, with the particles occurring in
various sizes. Once emitted, the particles can be transported long or
short distances depending on their size, which influences the amount of
time spent in the aerosol phase. In general, larger particles tend to
deposit more quickly, within shorter distances from emissions points
(e.g., kilometers), while smaller particles will remain in the aerosol
phase and travel longer distances before depositing (e.g., hundreds to
thousands of kilometers).\62\ As summarized in the AQCD for Lead,
airborne concentrations of lead at sites near sources are much higher
than at sites not known to be directly influenced by sources.
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\62\ U.S. Environmental Protection Agency (2004) Air quality
criteria for particulate matter. Research Triangle Park, NC: Office
of Research and Development, National Center for Environmental
Assessment; EPA report no. EPA-600/P-99/0028aF.
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(2) Once deposited to surfaces, lead can subsequently be
resuspended into the ambient air and, because of the persistence of
lead, emissions of this metal contribute to environmental media
concentrations for many years into the future as it is cycled within
and between environmental media such as soil, air and water. Lead that
is a soil or dust contaminant today may have been airborne yesterday or
many years ago.\63\
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\63\ National Ambient Air Quality Standards for Lead 73 FR 66971
(Nov. 12, 2008), AQC for Lead, Section 2.5.
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(3) Exposure to lead emitted into the ambient air can occur
directly by inhalation, or indirectly by ingestion of lead-contaminated
food, water or other materials including dust and soil. This occurs due
to the environmental cycling of this persistent metal which, once
emitted into the ambient air is distributed to other environmental
media and can contribute to human exposures via indoor and outdoor
dusts, outdoor soil, food and drinking water, as well as inhalation of
air. Atmospheric deposition is estimated to comprise a significant
proportion of lead in food (AQCD for Lead, p. 3-48). For example,
livestock may be exposed to lead in vegetation (e.g., grasses and
silage) and in surface soils via incidental ingestion of soil while
grazing (USEPA 1986, Section 7.2.2.2.2).\64\ And dietary intake may be
a predominant source of lead exposure among adults, greater than
consumption of water and beverages or inhalation (73 FR 66971). These
exposure pathways are described more fully in Section 8.2.2 of the AQCD
for Lead.
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\64\ U.S. Environmental Protection Agency (1986) Air quality
criteria for lead. Research Triangle Park, NC: Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from:
NTIS, Springfield, VA; PB87-142378.
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(4) Air-related exposure pathways are affected by changes to air
quality, including changes in concentrations of lead in air and changes
in atmospheric deposition of lead. Further, because of its persistence
in the environment, lead deposited from the air may contribute to human
and ecological exposures for years into the future as described above.
Additionally, human exposures to lead include pathways that are not
related to ambient air concentrations. The pathways of human exposure
to lead that are not air-related include ingestion of indoor lead
paint,\65\ lead in diet as a result of inadvertent additions during
food processing, and lead in drinking water attributable to lead in
distribution systems, as well as other generally less prevalent
pathways, as described in the AQCD for Lead (pp. 3-50 to 3-51).
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\65\ Weathering of outdoor lead paint may also contribute to
soil lead levels adjacent to the house.
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B. Health Effects Information
In 2008, EPA decreased the level of the primary (health-based)
NAAQS for Lead from 1.5 [mu]g/m\3\ to 0.15 [mu]g/m\3\ in order to
provide increased protection for children and other at-risk populations
against an array of adverse health effects, most notably neurological
effects in children, including neurocognitive and neurobehavioral
effects.\66\ This section summarizes information provided in the
numerous recent documents summarizing health and welfare effects from
exposure to lead, including the AQCD for Lead, CDC documents, the EPA
Staff Paper \67\ and the proposed and final NAAQS for Lead. First, the
use of blood lead as a measure of exposure to lead is described
followed by a brief summary of the broad array of lead-induced health
effects. Particular focus is given here to the effects of lead on the
developing nervous system in children since this is among the most
sensitive endpoints identified for this toxic metal. The section ends
with a description of at-risk populations and life stages.
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\66\ National Ambient Air Quality Standards for Lead 73 FR 66965
(Nov. 12, 2008).
\67\ U.S. Environmental Protection Agency (2007) Review of the
National Ambient Air Quality Standards for Lead: Policy Assessment
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research
Triangle Park.
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1. Blood Lead
Lead enters the body most commonly via the respiratory system and/
or gastrointestinal tract, from which it is quickly absorbed into the
blood stream and distributed throughout the body.\68\ Less commonly,
lead, particularly organic forms of lead such as alkyl lead, can be
absorbed through the skin (AQCD for Lead, page 4-12). Blood lead levels
are extensively used as an index or biomarker of exposure by national
and international health agencies, as well as in epidemiological (AQCD
for Lead, Sections 4.3.1.3 and 8.3.2) and toxicological studies of lead
health effects and dose-response relationships (AQCD for Lead, Chapter
5). The U.S. CDC, and its predecessor agencies, has for many years used
blood lead level as a metric for identifying children at risk of
adverse health effects and for specifying particular public health
recommendations.\69\ Most recently, in 2005, with consideration of a
review of the evidence by their advisory committee, CDC revised their
statement on Preventing Lead Poisoning in Young Children.\70\ CDC
specifically recognized the evidence of adverse health effects in
children with blood lead levels below 10 [mu]g/dL,\71\ the data
demonstrating that no ``safe'' threshold for blood lead had been
identified, and emphasized the importance of preventative measures.\72\
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\68\ Additionally, lead freely crosses the placenta resulting in
continued fetal exposure throughout pregnancy, with that exposure
increasing during the latter half of pregnancy (AQC for Lead,
Section 6.6.2).
\69\ Centers for Disease Control (1991) Preventing lead
poisoning in young children: a statement by the Centers for Disease
Control. Atlanta, GA: U.S. Department of Health and Human Services,
Public Health Service; October 1. Available online at: http://wonder.cdc.gov/wonder/prevguid/p0000029/p0000029.asp.
\70\ Centers for Disease Control and Prevention (2005)
Preventing lead poisoning in young children: a statement by the
Centers for Disease Control and Prevention. Atlanta, GA: U.S.
Department of Health and Human Services, Public Health Service.
August.
\71\ As described by the Advisory Committee on Childhood Lead
Poisoning Prevention, ``In 1991, CDC defined the blood lead level
(BLL) that should prompt public health actions as 10 [mu]g/dL.
Concurrently, CDC also recognized that a BLL of 10 [mu]g/dL did not
define a threshold for the harmful effects of lead. Research
conducted since 1991 has strengthened the evidence that children's
physical and mental development can be affected at BLLS <10 [mu]g/
dL'' (ACCLPP, 2007).
\72\ Advisory Committee on Childhood Lead Poisoning Prevention
(2007) Interpreting and managing blood lead levels <10 [mu]g/dL in
children and reducing childhood exposures to lead: Recommendations
of CDC's Advisory Committee on Childhood Lead Poisoning Prevention.
Morbidity and Mortality Weekly Report. 56(RR-8). November 2, 2007.
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Since 1976, the CDC has been monitoring blood lead levels in
multiple age groups nationally through the National Health and
Nutrition Examination Survey (NHANES).\73\ The
[[Page 22449]]
NHANES information has documented the dramatic decline in mean blood
lead levels in the U.S. population that has occurred since the 1970s
and that coincides with regulations regarding leaded motor vehicle
fuels, leaded paint, and lead-containing plumbing materials that have
reduced lead exposure among the general population (AQCD for Lead,
Sections 4.3.1.3 and 8.3.3).
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\73\ This information documents a variation in mean blood lead
levels across the various age groups monitored. For example, mean
blood lead levels in 2001-2002 for ages 1-5, 6-11, 12-19 and greater
than or equal to 20 years of age, are 1.70, 1.25, 0.94, and 1.56
[mu]g/dL, respectively (AQC for Lead, p. 4-22).
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While blood lead levels in the U.S. general population, including
geometric mean levels in children aged 1-5 have declined significantly,
levels have been found to vary among children of different
socioeconomic status (SES) and other demographic characteristics (AQCD
for Lead, p. 4-21), as well as by age.\74\ Racial/ethnic and income
disparities in blood lead levels in children persist. For example,
blood lead levels for lower income and African American children are
higher than those for the general population.
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\74\ Axelrad, D., U.S. EPA (November 4, 2009) E-mail message to
Marion Hoyer, U.S. EPA. Available in docket number EPA-HQ-OAR-2007-
0294.
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The spectrum of health effects discussed in the following section
is relevant for all forms of lead that enter the blood stream. Once in
the blood stream, lead bioaccumulates in the body, with the bone
serving as a large, long-term storage compartment. Soft tissues (e.g.,
kidney, liver, brain, etc.) serve as smaller compartments, in which
lead may be more mobile (AQCD for Lead, Sections 4.3.1.4 and 8.3.1).
During childhood development, bone represents approximately 70% of a
child's body burden of lead, and this accumulation continues through
adulthood, when more than 90% of the total lead body burden is stored
in the bone (AQCD for Lead, Section 4.2.2). Lead in bone can be
mobilized during critical periods including pregnancy and lactation
(AQCD for Lead, Section 5.8.6).
2. Health Effects
Lead, as with mercury and arsenic, has no known biological
function.\75\ Lead has been demonstrated to exert ``a broad array of
deleterious effects on multiple organ systems via widely diverse
mechanisms of action'' (AQCD for Lead, p. 8-24 and Section 8.4.1). This
array of health effects includes effects on heme biosynthesis and
related functions; neurological development and function; reproduction
and physical development; kidney function; cardiovascular function; and
immune function. The weight of evidence varies across this array of
effects and is comprehensively described in the AQCD for Lead. There is
also some evidence of lead carcinogenicity, primarily from animal
studies, together with limited human evidence of suggestive
associations (AQCD for Lead, Sections 5.6.2, 6.7, and 8.4.10). The U.S.
EPA has listed lead under current EPA guidelines as a probable human
carcinogen based on the available animal data (AQCD for Lead, p. 6-
195).\76\ Inorganic lead has been classified as a probable human
carcinogen by the International Agency for Research on Cancer
(inorganic lead compounds), based mainly on sufficient animal
evidence,\77\ and classified as reasonably anticipated to be a human
carcinogen by the U.S. National Toxicology Program (lead and lead
compounds) (AQCD for Lead, Section 6.7.2).78 79
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\75\ U.S. Environmental Protection Agency (2007) Framework for
Metals Risk Assessment. Office of the Science Advisor. EPA 120/R-07/
001.
\76\ U.S. Environmental Protection Agency, Integrated Risk
Information System (IRIS) (1993) IRIS Summary for Lead and compounds
(CASRN 7439-92-1), Available online at: http://www.epa.gov/ncea/iris/subst/0277.htm.
\77\ International Agency for Research on Cancer (IARC) (2006)
Inorganic and organic lead compounds. Lyon, France: International
Agency for Research on Cancer. IARC monographs on the evaluation of
the carcinogenic risk of chemicals to humans: volume 87. Available
online at: http://monographs.iarc.fr/ENG/Monographs/vol87/index.php.
\78\ National Toxicology Program (2003) Report on carcinogens
background document for lead and lead compounds. Research Triangle
Park, NC: U.S. Department of Health and Human Services. Available
online at: http://ntp.niehs.nih.gov/ntp/newhomeroc/roc11/Lead-Public.pdf.
\79\ National Toxicology Program. (2004) Lead (CAS no. 7439-92-
1) and lead compounds. In: Report on carcinogens, eleventh edition.
Research Triangle Park, NC: U.S. Department of Health and Human
Services. Available online at: http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s101lead.pdf.
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As described in the AQCD for Lead, the key effects associated with
individual blood lead levels in children and adults in the range of 10
[mu]g/dL and lower include neurological, hematological and immune \80\
effects for children, and hematological, cardiovascular and renal
effects for adults (AQCD for Lead, Tables 8-5 and 8-6, pp. 8-60 to 8-
62). As evident from the discussions in Chapters 5, 6 and 8 of the AQCD
for Lead, ``neurotoxic effects in children and cardiovascular effects
in adults are among those best substantiated as occurring at blood lead
concentrations as low as 5 to 10 [mu]g/dL (or possibly lower); and
these categories are currently clearly of greatest public health
concern'' (AQCD for Lead, p. 8-60).81 82 The AQCD for Lead
states, ``There is no level of lead exposure that can yet be
identified, with confidence, as clearly not being associated with some
risk of deleterious health effects'' (AQCD for Lead, p. 8-63).
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\80\ At mean blood lead levels, in children, on the order of 10
[mu]g/dL, and somewhat lower, associations have been found with
effects to the immune system, including altered macrophage
activation, increased IgE levels and associated increased risk for
autoimmunity and asthma (AQC for Lead, Sections 5.9, 6.8, and
8.4.6).
\81\ With regard to blood lead levels in individual children
associated with particular neurological effects, the AQC for Lead
states ``Collectively, the prospective cohort and cross-sectional
studies offer evidence that exposure to lead affects the
intellectual attainment of preschool and school age children at
blood lead levels <10 [mu]g/dL (most clearly in the 5 to 10 [mu]g/dL
range, but, less definitively, possibly lower).'' (p. 6-269)
\82\ Epidemiological studies have consistently demonstrated
associations between lead exposure and enhanced risk of deleterious
cardiovascular outcomes, including increased blood pressure and
incidence of hypertension. A meta-analysis of numerous studies
estimates that a doubling of blood-lead level (e.g., from 5 to 10
[mu]g/dL) is associated with ~1.0 mm Hg increase in systolic blood
pressure and ~0.6 mm Hg increase in diastolic pressure (AQC for
Lead, p. E-10).
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While adults are susceptible to lead effects at lower blood lead
levels than previously understood (e.g., AQCD for Lead, p. 8-25), among
the wide variety of health endpoints associated with lead exposures,
there is general consensus that the developing nervous system in
children is among the, if not the, most sensitive. Blood lead levels in
U.S. children have decreased notably since the late 1970s. Studies
evaluating current blood lead levels in children have reported
associations with neurodevelopment effects (AQCD for Lead, Chapter 6).
Functional manifestations of lead neurotoxicity during childhood
include sensory, motor, cognitive and behavioral impacts. Numerous
epidemiological studies have reported neurocognitive, neurobehavioral,
sensory, and motor function effects in children with blood lead levels
below 10 [mu]g/dL (AQCD Lead, Sections 6.2 and 8.4).
Cognitive effects associated with lead exposures that have been
observed in epidemiological studies have included decrements in
intelligence test results, such as the widely used IQ score, and in
academic achievement as assessed by various standardized tests as well
as by class ranking and graduation rates (AQCD for Lead, Section 6.2.16
and pp 8-29 to 8-30). As noted in the AQCD for Lead with regard to the
latter, ``Associations between lead exposure and academic achievement
observed in the above-noted studies were significant even after
adjusting for IQ, suggesting that lead-sensitive neuropsychological
processing and learning factors not
[[Page 22450]]
reflected by global intelligence indices might contribute to reduced
performance on academic tasks'' (AQCD for Lead, pp 8-29 to 8-30).
With regard to potential implications of lead effects on IQ, the
AQCD for Lead recognizes the ``critical'' distinction between
population and individual risk, identifying issues regarding declines
in IQ for an individual and for the population. The AQCD for Lead
further states that a ``point estimate indicating a modest mean change
on a health index at the individual level can have substantial
implications at the population level'' (AQCD for Lead, p. 8-77).\83\ A
downward shift in the mean IQ value is associated with both substantial
decreases in percentages achieving very high scores and substantial
increases in the percentage of individuals achieving very low scores
(AQCD for Lead, p. 8-81).\84\ For an individual functioning in the low
IQ range due to the influence of developmental risk factors other than
lead, a lead-associated IQ decline of several points might be
sufficient to drop that individual into the range associated with
increased risk of educational, vocational, and social failure (AQCD for
Lead, p. 8-77).
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\83\ As an example, the AQC for Lead states ``although an
increase of a few mmHg in blood pressure might not be of concern for
an individual's well-being, the same increase in the population mean
might be associated with substantial increases in the percentages of
individuals with values that are sufficiently extreme that they
exceed the criteria used to diagnose hypertension'' (AQC for Lead,
p. 8-77).
\84\ For example, for a population mean IQ of 100 (and standard
deviation of 15), 2.3% of the population would score above 130, but
a shift of the population to a mean of 95 results in only 0.99% of
the population scoring above 130 (AQC for Lead, pp. 8-81 to 8-82).
---------------------------------------------------------------------------
Other cognitive effects observed in studies of children have
included decrements in attention, executive functions, language,
memory, learning and visuospatial processing (AQCD for Lead, Sections
5.3.5, 6.2.5 and 8.4.2.1), with attention and executive function
effects associated with lead exposures indexed by blood lead levels
below 10 [mu]g/dL (AQCD for Lead, Section 6.2.5 and pp. 8-30 to 8-31).
The evidence for the role of lead in this suite of effects includes
experimental animal findings (discussed in the AQCD for Lead, Section
8.4.2.1; p. 8-31), which provide strong biological plausibility of lead
effects on learning ability, memory and attention (AQCD for Lead,
Section 5.3.5), as well as associated mechanistic findings.
The persistence of such lead-induced effects is described in the
AQCD for Lead (e.g., AQCD for Lead Sections 5.3.5, 6.2.11, and 8.5.2).
The persistence or irreversibility of such effects can be the result of
damage occurring without adequate repair offsets or of the persistence
of lead in the body (AQCD for Lead, Section 8.5.2). It is additionally
important to note that there may be long-term consequences of such
deficits over a lifetime. Poor academic skills and achievement can have
``enduring and important effects on objective parameters of success in
real life,'' as well as increased risk of antisocial and delinquent
behavior (AQCD for Lead, Section 6.2.16).
The current evidence reviewed in the AQCD for Lead with regard to
the quantitative relationship between neurocognitive decrement, such as
IQ, and blood lead levels indicates that the slope for lead effects on
IQ is nonlinear and is steeper at lower blood lead levels, such that
each [mu]g/dL increase in blood lead may have a greater effect on IQ at
lower blood lead levels (e.g., below 10 [mu]g/dL) than at higher levels
(AQCD for Lead, Section 6.2.13; pp. 8-63 to 8-64; Figure 8-7). As noted
in the AQCD for Lead, a number of examples of non- or supralinear dose-
response relationships exist in toxicology (AQCD for Lead, pp. 6-76 and
8-38 to 8-39). With regard to the effects of lead on neurodevelopmental
outcomes such as IQ, the AQCD for Lead suggests that initial
neurodevelopmental effects at lower lead levels may be disrupting very
different biological mechanisms (e.g., early developmental processes in
the central nervous system) than more severe effects of high exposures
that result in symptomatic lead poisoning and frank mental retardation
(AQCD for Lead, p. 6-76). The AQCD for Lead describes this issue in
detail with regard to lead (summarized in AQCD for Lead at p. 8-39).
Various findings within the toxicological evidence, presented in the
AQCD for Lead, provide biologic plausibility for a steeper IQ loss at
low blood lead levels, with a potential explanation being that the
predominant mechanism at very low blood lead levels is rapidly
saturated and that a different, less-rapidly-saturated process becomes
predominant at blood lead levels greater than 10 [mu]g/dL.
3. At-Risk Populations and Life Stages
Individuals potentially at risk from exposure to environmental
pollutants include those with increased susceptibility and
vulnerability. The terms ``susceptibility'' and ``vulnerability'' have
been used to characterize those with a greater likelihood of an adverse
outcome given a specific exposure in comparison with the general
population. This increased likelihood of response to a pollutant can
result from a multitude of factors, including genetic or developmental
factors, life stages (i.e., childhood or old age), gender differences,
or preexisting disease states. In addition, new attention has been paid
to the concept of some population groups having increased responses to
pollution-related effects due to factors including socioeconomic status
(SES) (e.g., reduced access to health care, poor nutritional status) or
particularly elevated exposure levels.
EPA uses the term ``life stage'' to refer to a distinguishable time
frame in an individual's life characterized by unique and relatively
stable behavioral and/or physiological characteristics that are
associated with development and growth. To recognize the rapid changes
that occur during childhood related to physiology, metabolism, anatomy
and behavior that can impact exposure and risk to environmental
hazards, EPA now views childhood as a sequence of life stages, from
conception through fetal development, infancy, and adolescence. EPA
published several exposure and risk assessment guidance documents
beginning in 2005,85 86 87 in which we emphasized the
importance of considering the potential for increased sensitivity of
different life stages or age groups in addition to that of groups that
form a fixed portion of the population based on characteristics such as
pre-existing disease, gender, socioeconomic status, geographical
location, culture/ethnicity, or genetic make-up.
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\85\ U.S. EPA (2005) Guidance on Selecting Age Groups for
Monitoring and Assessing Childhood Exposure to Environmental
Contaminants. EPA/630/P-03/003F.
\86\ U.S. EPA (2006) A Framework for Assessing Health Risks of
Environmental Exposures to Children. EPA/600/R-05/093A.
\87\ U.S. EPA (2008) Child-Specific Exposure Factors Handbook.
EPA/600/R-06/096F.
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Physiological, behavioral and demographic factors contribute to
increased risk of lead-related health effects. Children are at
increased risk of lead-related health effects due to various factors
that enhance their exposures (e.g., via the hand-to-mouth activity that
is prevalent in very young children, AQCD for Lead, Section 4.4.3) and
susceptibility. While children are considered to be at a period of
maximum exposure around 18-27 months, the current evidence has found
even stronger associations between blood lead levels at school age and
IQ at school age. The evidence ``supports the idea that lead exposure
continues to be toxic to children as they reach school age, and [does]
not lend support to the interpretation that all the damage is done by
the time the child reaches 2 to
[[Page 22451]]
3 years of age'' (AQCD for Lead, Section 6.2.12). Physiological factors
that can affect risk of lead-related effects in children include
genetic polymorphisms and nutritional status. Children with particular
genetic polymorphisms (e.g., presence of the [delta]-aminolevulinic
acid dehydratase-2 [ALAD-2] allele) have increased sensitivity to lead
toxicity, which may be due to increased susceptibility to the same
internal dose and/or to increased internal dose associated with the
same exposure (AQCD for Lead, p. 8-71, Sections 6.3.5, 6.4.7.3 and
6.3.6). Some children may have blood lead levels higher than those
otherwise associated with a given lead exposure (AQCD for Lead, Section
8.5.3) as a result of nutritional status (e.g., iron deficiency,
calcium intake), as well as genetic and other factors (AQCD for Lead,
Chapter 4 and Sections 3.4, 5.3.7 and 8.5.3).
Demographic factors that can affect risk of lead-related effects in
children include residential location, poverty, and race. As noted in
previous EPA actions on lead, situations of elevated exposure, such as
residing near sources of ambient lead, as well as socioeconomic
factors, such as reduced access to health care or low socioeconomic
status can also contribute to increased blood lead levels and increased
risk of associated health effects from air-related lead.\88\
Additionally, as described in the NAAQS for Lead, children in poverty
and black, non-Hispanic children have notably higher blood lead levels
than do economically well-off children and white children, in
general.\89\
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\88\ U.S. Environmental Protection Agency (2007) Review of the
National Ambient Air Quality Standards for Lead: Policy Assessment
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research
Triangle Park.
\89\ See 73 FR 66973 (November 12, 2008).
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C. Welfare Effects
Lead is persistent in the environment and accumulates in soils,
aquatic systems (including sediments), and some biological tissues of
plants, animals and other organisms, thereby providing long-term,
multi-pathway exposures to organisms and ecosystems. In 2008, EPA
established a secondary lead standard of 0.15 ug/m\3\. This standard is
intended to protect the public welfare from known or anticipated
adverse effects associated with the presence of lead in the ambient
air. This section provides a summary of information regarding welfare
effects of lead, focusing on terrestrial and aquatic ecosystems. This
information is largely drawn from the 2006 AQCD for Lead, Chapter 6 of
the Office of Air Quality Planning and Standards Staff Paper on Lead
(SP) \90\ and the Lead NAAQS.
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\90\ U.S. Environmental Protection Agency (2007) Review of the
National Ambient Air Quality Standards for Lead: Policy Assessment
of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/
R-07-013. Office of Air Quality Planning and Standards, Research
Triangle Park.
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1. Terrestrial Ecosystems
Lead is removed from the atmosphere and deposited on soil and other
surfaces via wet or dry deposition. In soils, most lead is retained via
the formation of stable solid phase compounds, precipitates, or
complexes with organic matter. Thus, terrestrial ecosystems remain
primarily sinks for lead but amounts retained in various soil layers
vary based on forest type, climate, and litter cycling (AQCD for Lead,
Section 7.1). Once in the soil, the migration and distribution of lead
is controlled by a multitude of factors including pH, precipitation,
litter composition and other factors, which in turn, govern the rate at
which lead is bound to organic materials in the soil (AQCD for Lead,
Section 2.3.5, and Section AX 7.1.4.1).
Lead exists in the environment in different forms which vary widely
in their ability to cause adverse effects on ecosystems and organisms.
Many forms of lead in the ambient air are quite insoluble and thus not
easily leached to underground water once deposited to surfaces.
However, leaching may occur under acidic conditions, where lead
concentrations are extremely high, or in the presence of substances
(e.g., soluble organic matter, high concentrations of chlorides or
sulfates) that form relatively soluble complexes with lead (AQCD for
Lead, Section 2.3.5).
Plants take up lead via their foliage and through their root
systems. The rate of plant uptake from soil varies by plant species,
soil conditions, and lead species. Most lead in plants is stored in
roots, and very little is stored in fruits. Metals that are applied to
soil as salts (usually as sulfate, chloride, or nitrate salt) are
accumulated more readily than the same quantity of metal added via
sewage sludge, flue dust, or fly ash (AQCD for Lead, Section 2.3.7).
Surface deposition of lead onto plants may represent a significant
contribution to the total lead in and on the plant, as has been
observed for plants near smelters and along roadsides (AQCD for Lead,
page E-19). Atmospheric deposition of lead also contributes to lead in
vegetation as a result of contact with above-ground portions of the
plant (AQCD for Lead, pp. 7-9 and AXZ7-39; USEPA, 1986, Sections 6.5.3
and 7.2.2.2.1). Wildlife may subsequently be exposed to lead in
vegetation (e.g., grasses and silage) and in surface soils via
incidental ingestion of soil while grazing (USEPA 1986, Section
7.2.2.2.2).\91\
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\91\ U.S. Environmental Protection Agency (1986) Air quality
Criteria for Lead. Research Triangle Park, NC: Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from:
NTIS, Springfield, VA; PB87-142378.
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By far, the majority of air-related lead found in natural
terrestrial ecosystems was deposited in the past during the use of lead
additives in motor vehicle gasoline. Many sites receiving lead
predominantly through long-range transport of gasoline-derived small
particles have accumulated large amounts of lead in soils (AQCD for
Lead, p. AX7-98). There is little evidence that terrestrial sites
exposed as a result of this long range transport of lead have
experienced significant effects on ecosystem structure or function
(AQCD for Lead, Section AX7.1.4.2 and p. AX7-98). Strong complexation
of lead by organic matter in soil may explain why few ecological
effects have been observed (AQCD for Lead, p. AX7-98). Studies have
shown decreasing levels of lead in vegetation, which appears to
correlate with decreases in atmospheric deposition of lead resulting
from the removal of lead additives to motor vehicle gasoline (AQCD for
Lead, Section AX 7.1.4.2).
The deposition of gasoline-derived lead into forest soils has
produced a legacy of slow moving lead that remains bound to organic
materials despite dramatic reductions in the use of leaded additives to
motor vehicle fuels. Current levels of lead in soil vary widely
depending on the source of lead but in all ecosystems lead
concentrations exceed natural background levels. For areas influenced
by point sources of air lead, concentrations of lead in soil may exceed
by many orders of magnitude the concentrations which are considered
harmful to laboratory organisms. Adverse effects in terrestrial
organisms associated with lead include neurological, physiological and
behavioral effects which may influence ecosystem structure and
functioning (73 FR 67008).
2. Aquatic Ecosystems
Atmospheric lead enters aquatic ecosystems primarily through
deposition (wet and dry) and the erosion and runoff of soils containing
lead. While overall deposition rates of atmospheric lead have decreased
dramatically since the removal of lead additives from motor vehicle
gasoline,
[[Page 22452]]
lead continues to accumulate and may be re-exposed in sediments and
water bodies throughout the United States (AQCD for Lead, Section
2.3.6).
Several physical and chemical factors govern the fate and
bioavailability of lead in aquatic systems. A significant portion of
lead remains bound to suspended particulate matter in the water column
and eventually settles into the substrate. Species, pH, salinity,
temperature, turbulence and other factors govern the bioavailability of
lead in surface waters (AQCD for Lead, Section 7.2.2). Lead can
bioaccumulate in the tissues of aquatic organisms through ingestion of
food and water, and adsorption from water, and can subsequently lead to
adverse effects if tissue levels are sufficiently high.\92\ The
accumulation of lead is influenced by pH and decreasing pH favors
bioavailability and bioaccumulation. Organisms that bioaccumulate lead
with little excretion must partition the metal such that it has limited
bioavailability, otherwise toxicity will occur if a sufficiently high
concentration is reached.\93\ The general symptoms of lead toxicity in
fish include production of excess mucus, lordosis, anemia, darkening of
the dorsal tail region, degeneration of the caudal fin, destruction of
spinal neurons, aminolevulinic acid dehydratase (ALAD) inhibition,
growth inhibition, renal pathology, reproductive effects, growth
inhibition, and mortality.\94\ Toxicity in fish has been closely
correlated with duration of lead exposure and uptake.\95\
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\92\ AQC for Lead I. 7-24: (Vink, 2002; Rainbow, 1996).
\93\ AQC for Lead AX7.2.3.1.
\94\ AQC for Lead page 232, Annex 7.
\95\ AQC for Lead page 232, Annex 7.
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Lead exists in the aquatic environment in various forms and under
various chemical and physical parameters which determine the ability of
lead to cause adverse effects either from dissolved lead in the water
column or lead in sediment. Current levels of lead in water and
sediment vary widely depending on the source of lead. Conditions exist
in which adverse effects to organisms and thereby ecosystems may be
anticipated given experimental results. It is unlikely that dissolved
lead in surface water constitutes a threat to ecosystems that are not
directly influenced by point sources. For lead in sediment, the
evidence regarding the effects is less clear. It is likely that some
areas with long-term historical deposition of lead to sediment from a
variety of sources as well as areas influenced by point sources have
the potential for adverse effects to aquatic communities. The long
residence time of lead in sediment and its ability to be resuspended by
turbulence make lead likely to be a factor for consideration regarding
potential risk to aquatic systems for the foreseeable future (73 FR
67008).
III. Lead Emissions From Piston-Engine Aircraft
Currently, lead emitted by piston-engine aircraft operating on
leaded avgas is the largest source of lead to the air, contributing
about 50% of the National Emission Inventory in 2005. This section
describes the draft 2008 avgas lead inventory which is currently
undergoing review by State, local and Tribal air agencies. We describe
and request comment on input data used to derive airport-specific lead
inventories. This section ends with a summary of data forecasting the
potential growth of the industry using leaded avgas.
A. Inventory of Lead From Piston-Engine Powered Aircraft
Every three years, the EPA prepares a National Emissions Inventory
(NEI) of air emissions of criteria pollutants and hazardous air
pollutants with input from numerous State, local, and Tribal air
agencies and from industry.\96\ For the purposes of this ANPR, EPA is
describing piston-engine aircraft lead information provided in the
draft 2008 NEI as well as information from the final 2005 NEI. We have
chosen to describe the draft 2008 NEI for the following reasons: (1)
This is the first version of the NEI that will include airport-specific
lead inventories that use our most recently developed methods for
estimating lead (described below); (2) this inventory is the first NEI
to include approximately 20,000 airport facilities in the U.S.; and (3)
to increase awareness of the opportunity for State, local, and Tribal
governments and industry to review this draft NEI and provide
information that could improve airport lead inventories. Comments and
data can be supplied to EPA for the 2008 NEI until mid-2010. While we
are describing the draft 2008 NEI for piston-engine aircraft emissions
of lead, we do not have draft inventory estimates for 2008 for all
sources of lead. The 2008 NEI will be final in 2010.
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\96\ http://www.epa.gov/air/data/neidb.html.
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1. National Emissions of Lead From Piston-Engine Aircraft
To calculate the national avgas lead inventory, the volume of
leaded avgas produced in a given year is multiplied by the
concentration of lead in the avgas and by the fraction of lead emitted
from a combustion system operating on leaded fuel (to account for the
lead that is retained in the engine, engine oil and/or exhaust system).
For example, the volume of avgas produced in the U.S. in 2008 according
to DOE was 235,326,000 gallons.\97\ The concentration of lead in avgas
([Pb] in the equation below) can be one of four levels (ranging from
0.14 to 1.12 grams of lead per liter or 0.53 to 4.24 grams of lead per
gallon) as specified by the American Society for Testing and Materials
(ASTM). By far the most common avgas supplied is ``100 Low Lead'' or
100LL which has a maximum lead concentration specified by ASTM of 0.56
grams per liter or 2.12 grams per gallon.98 99 A fraction of
lead is retained in the engine, engine oil and/or exhaust system which
we currently estimate at 5%.\100\
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\97\ DOE Energy Information Administration. Fuel production
volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm accessed November 2006.
\98\ ChevronTexaco (2006) Aviation Fuels Technical Review. FTR-
3. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
\99\ ASTM International (2007) Standard Specification for
Aviation Gasolines D910-06.
\100\ U.S. Environmental Protection Agency (2008) Lead Emissions
from the Use of Leaded Aviation Gasoline in the United States,
Technical Support Document. EPA420-R-08-020. Available online at:
http://www.epa.gov/otaq/aviation.htm.
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For 2008, using DOE fuel volume estimates, the national estimate of
lead emissions from the consumption of avgas is 522 tons as calculated
according to the following equation:
[GRAPHIC] [TIFF OMITTED] TP28AP10.015
[[Page 22453]]
As described in the Overview section of this ANPR, DOT's FAA also
provides estimates of annual avgas fuel consumption. For 2008, DOT
estimates 351,000,000 gallons of avgas were consumed. Consumption of
this volume of avgas equates to a national lead emissions estimate for
this source of 779 short tons. DOT fuel volume data are derived from
FAA estimates of piston-engine activity annually.\101\ We are working
to identify the source(s) of the information used to derive DOE fuel
volume estimates. In the draft 2008 NEI, we are using DOT fuel volume
estimates.
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\101\ U.S. Department of Transportation Federal Aviation
Administration Aviation Policy and Plans. FAA Aerospace Forecast
Fiscal Years 2009-2025. p.81. Available at: http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009-2025/media/2009%20Forecast%20Doc.pdf. This document provides historical data
for 2000-2008 as well as forecast data.
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We currently cannot estimate the fraction of total lead emissions
these estimates comprise since the inventories for all other sources of
lead to air are not yet in the draft 2008 NEI. In 2005, lead from avgas
comprised about 50% of the national lead inventory for emissions to
air. As point source emissions of lead have decreased, lead emissions
from piston-engine aircraft have become the largest single source of
lead to air (Figure 2). These lead emissions estimates do not include
evaporative losses of lead and minimal military aircraft data. Few
military aircraft are piston-engine powered and consume leaded
avgas.\102\ Military aircraft data are supplied by States, and data
provided to EPA during the 2008 NEI review will be included in the
final 2008 inventory.
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\102\ ChevronTexaco (2006) Aviation Fuels Technical Review p.
44. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
[GRAPHIC] [TIFF OMITTED] TP28AP10.016
2. Airport-Specific Emissions of Lead From Piston-Engine Aircraft
Aircraft gaseous and particulate matter (PM) emissions are
calculated through the FAA's Emissions and Dispersion Modeling System
(EDMS).\103\ This modeling system was designed to develop emission
inventories for the purpose of assessing potential air quality impacts
of airport operations and proposed airport development projects. Lead
emissions from piston-engine aircraft are not included in EDMS. To
estimate airport-specific lead inventories we use engine data and other
attributes of general aviation (GA) and air taxi (AT) that are used in
EDMS for GA and AT and we use methods similar to those in EDMS that are
described in an EPA Technical Support Document (TSD) and briefly
[[Page 22454]]
summarized here.\104\ The data required to estimate airport-specific
lead inventories includes the landing and take-off (LTO) activity of
piston-engine aircraft at a facility; fuel consumption rates by these
aircraft during the various modes of the landing and take-off cycle;
the time spent in each mode of the LTO (taxi/idle-out, takeoff, climb-
out, approach, and taxi/idle-in); the concentration of lead in the
fuel; and the retention of lead in the engine and oil. The equation
used to calculate airport-specific lead emissions during the LTO cycle
is below, followed by a description of each of the input parameters.
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\103\ EDMS is available online at: http://www.faa.gov/about/office_org/headquarters_offices/aep/models/edms_model/.
\104\ U.S. Environmental Protection Agency (2008) Lead Emissions
from the Use of Leaded Aviation Gasoline in the United States,
Technical Support Document. EPA420-R-08-020. Available online at:
http://www.epa.gov/otaq/aviation.htm.
[GRAPHIC] [TIFF OMITTED] TP28AP10.017
Piston-engine LTO: Most piston-engine aircraft fall into the
categories of either GA or AT. Some GA and AT activity is conducted by
turboprop and turbojet aircraft which do not use leaded avgas. There
are no national databases that provide airport-specific LTO activity
data for piston-engine aircraft separately from turbojet and turboprop
aircraft. The fraction of GA and AT aircraft that use piston engines
will vary by airport. However, in the absence of airport-specific data,
EPA calculated a national default estimate using FAA's GA and AT
Activity (GAATA) Survey.\105\ The 2005 GAATA Survey reports that
approximately 72% of all GA and AT LTOs are from piston-engine aircraft
which use avgas, and about 28% are turboprop and turbojet powered which
use jet fuel, such as Jet A.\106\ Lead is not added to jet fuel.
Therefore, to calculate piston-engine aircraft LTO as input for this
equation, the total GA plus AT LTOs are multiplied by 0.72.
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\105\ The FAA GAATA is a database collected from surveys of
pilots flying aircraft used for general aviation and air taxi
activity. For more information on the GAATA, see Appendix A, online
at: http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/.
\106\ There are about 194,000 piston-engine aircraft in the U.S.
general aviation and air taxi fleet (175,000 single-engine and
19,000 twin-engine aircraft) according to FAA's 2005 GAATA Survey.
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Avgas use (gal/LTO): Piston-engine aircraft can have either one or
two engines. EDMS version 5.0.2 contains information on the amount of
avgas used per LTO for some single and twin-engine aircraft. The
proportion of piston-engine LTOs conducted by single- versus twin-
engine aircraft was taken from the FAA's GAATA Survey for 2005 (90% of
LTOs are conducted by aircraft having one engine and 10% of LTOs by
aircraft having two engines). Since twin-engine aircraft have higher
fuel consumption rates than those with single engines, a weighted
average LTO fuel usage rate was established to apply to the population
of piston-engine aircraft as a whole. For the single-engine aircraft,
the average amount of fuel consumed per LTO was determined from the six
types of single piston-engine aircraft within EDMS.\107\ This was
accomplished by averaging the single-engine EDMS outputs for fuel
consumed per LTO using the EDMS scenario property of ICAO/USEPA
Default--Times in Mode (TIM), with a 16 minute taxi-in/taxi-out time
according to EPA's Procedures for Emission Inventory Preparation,
Volume IV: Mobile Sources, 1992.\108\ This gives a value of 16.96
pounds of fuel per LTO (lbs/LTO). Next, the average single-engine
consumption rate was divided by the average density of 100LL avgas, 6
pounds per gallon (lbs/gal), producing an average fuel usage for
single-engine piston aircraft of 2.83 gallons per LTO (gal/LTO). This
same calculation was performed for the two twin-engine piston aircraft
within EDMS, producing an average LTO fuel usage rate for twin-engine
piston aircraft of 9.12 gal/LTO.
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\107\ EPA understands that EDMS 5.0.2 has a limited list of
piston engines, but these are currently the best data available.
\108\ U.S. Environmental Protection Agency (1992) Procedures for
Emission Inventory Preparation, Volume IV: Mobile Sources, EPA-450/
4-81-026d (Revised).
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Using these single- and twin-engine piston aircraft fuel
consumption rates, a weighted average fuel usage rate per LTO was
computed by multiplying the average fuel usage rate for single-engine
aircraft (2.83 gal/LTO) by the fleet percentage of single-engine
aircraft LTOs (90%). Next, the twin-engine piston aircraft average fuel
usage rate (9.12 gal/LTO) was multiplied by the fleet percentage of
twin-engine aircraft LTOs (10%). By summing the results of the single-
and twin-engine aircraft usage rates, the overall weighted average fuel
usage rate per LTO of 3.46 gal/LTO is obtained.
Concentration of lead in fuel, [Pb]: The maximum lead concentration
specified by ASTM for 100LL is 0.56 grams per liter or 2.12 grams per
gallon. This amount of lead is normally added to assure that the
required lean and rich mixture knock values are achieved. As noted
above, 100 Octane (containing 1.12 grams of lead per liter or 4.24
grams of lead per gallon) is used by a small number of piston-engine
aircraft. We currently do not include estimates of lead emissions using
100 Octane and we are requesting comment on the airport facilities
where 100 Octane is used and the LTO activity associated with the use
of this fuel.
Retention of lead in engine and oil (1-Pb Retention): Recent data
collected from aircraft piston engines operating on leaded avgas
suggests that about 5% of the lead from the fuel is retained in the
engine and engine oil.\109\ Thus the emitted fraction is 0.95.
---------------------------------------------------------------------------
\109\ The information used to develop this estimate is from the
following references: (a) Todd L. Petersen, Petersen Aviation, Inc,
Aviation Oil Lead Content Analysis, Report Number EPA 1-2008,
January 2, 2008, available at William J. Hughes Technical Center
Technical Reference and Research Library at http://actlibrary.tc.faa.gov/ and (b) E-mail from Theo Rindlisbacher of
Switzerland Federal Office of Civil Aviation to Bryan Manning of
U.S. EPA, regarding lead retained in engine, September 28, 2007.
---------------------------------------------------------------------------
Multiplying the lead concentration in 100LL avgas by the weighted
average fuel usage rate produces an overall average value of 7.34 grams
of lead per LTO (g Pb/LTO) for piston engines: 3.46 gal/LTO x 2.12 g
Pb/gal = 7.34 g Pb/LTO. The denominator is a unit conversion factor
used to express the lead inventory in units of short tons.
Applying these parameters in the equation above yields the
following equation:
[[Page 22455]]
[GRAPHIC] [TIFF OMITTED] TP28AP10.018
which simplifies to: Pb = (piston-engine LTO) (7.7 x 10-6
short tons) or 7 grams of lead per LTO where piston-engine LTO = (GA
LTO + AT LTO)(0.72). EPA used similar methods to estimate lead
emissions from piston-engine powered helicopters which are described
separately.\110\ We currently estimate there are 6 grams of lead
emitted by piston-engine helicopters per LTO.
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\110\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline
Lead Emissions in the 2008 NEI.'' pp.8-9.
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Lead emitted during the LTO cycle is assigned to the airport
facility where the aircraft operations occur.\111\ FAA's Office of Air
Traffic provides a complete listing of operational airport facilities
in the National Airspace System Resources (NASR) database.\112\ In
2008, there were 19,896 airport facilities in the U.S., the vast
majority of which are expected to have activity by piston-engine
aircraft that operate on leaded avgas. There are seven types of airport
facilities: airports, balloonports, seaplane bases, gliderports,
heliports, stolports,\113\ and ultralight facilities. Among these,
balloonports are the only facilities not expected to have piston-engine
aircraft activity.
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\111\ An aircraft operation is defined as any landing or take-
off event, therefore, to calculate LTOs, operations are divided by
two. Most data sources from FAA report aircraft activity in numbers
of operations which, for the purposes of calculating lead emissions
using the method described in the TSD, need to be converted to LTO
events.
\112\ An electronic report can be generated from the NASR
database and is available for download from the Internet at the
following Web site. http://www.faa.gov/airports_airtraffic/airports/airport_safety/airportdata_5010/. This database is
updated every 56 days.
\113\ Stolport is an airport designed with STOL (Short Take-Off
and Landing) operations in mind, normally having a short single
runway.
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Preparing airport-specific lead inventories requires information
regarding LTO activity.
These activity data are reported to the FAA for only a small subset
of the approximately 20,000 facilities in the U.S. EPA obtains LTO
information for approximately 3,400 facilities from FAA's Terminal Area
Forecast (TAF) database that is prepared by FAA's Office of Aviation
Policy and Plans.\114\ The TAF database currently includes information
for airports in FAA's National Plan of Integrated Airport Systems
(NPIAS), which identifies airports that are significant to national air
transportation. For airports not listed in the TAF, operations data are
obtained from the NASR database, where available. Operations data
provided by the NASR database may be self-reported by airport operators
through data collection accomplished by airport inspectors who work for
the State Aviation Agency, or operations data can be obtained through
other means.\115\
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\114\ http://aspm.faa.gov/main/taf.asp.
\115\ In the absence of updated information from States, local
authorities or Tribes, we are using the LTO data provided in the FAA
database.
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We are using the January 15, 2009 version of the NASR database to
evaluate airport lead emissions inventories for 2008. Using the TAF
database as the primary source of LTO information and the NASR as a
secondary source, we have LTO activity data for approximately 5,600
airport facilities. There are approximately 14,000 facilities in the
NASR database for which there are no LTO activity data.\116\ We
developed methods based on previous work conducted by the FAA to
estimate LTO activity at the remaining airport and heliport facilities.
We are requesting comment on these methods which are described here
briefly. The details regarding the method described here are available
in the docket.\117\
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\116\ No Commuter, GA Itinerant, GA Local, or Air Taxi
operations data.
\117\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline
Lead Emissions in the 2008 NEI.''
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The FAA has used regression models to estimate operations at
facilities where operations data are not available.118 119
In this work and other work, FAA identified characteristics of small
towered airports for which there were statistically significant
relationships with operations at these airports.\120\ Regression models
based on the airport characteristics were then used to estimate general
aviation operations for a set of non-towered airports. The airport
characteristics identified by the FAA and used to estimate general
aviation operations at small airports include: the number and type of
aircraft based at the facility (i.e., ``based aircraft''), population
in the vicinity of the airport, airport regional prominence, per capita
income, region of the country, and the presence of certificated flight
schools. We were able to obtain data from the NASR and the U.S. Census
Bureau to evaluate relationships between several airport
characteristics and LTO activity. LTO estimates were derived using
different models depending on data availability.
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\118\ Federal Aviation Administration, Office of Aviation Policy
and Plans, Statistics and Forecast Branch. (July 2001) Model for
Estimating General Aviation Operations at Non-Towered Airports Using
Towered and Non-towered Airport Data. Prepared by GRA, Inc.
\119\ Hoekstra, M. (April 2000) Model for Estimating General
Aviation Operations at Non-Towered Airports. Prepared for FAA Office
of Aviation Policy and Plans.
\120\ GRA, Inc. ``Review of TAF Methods,'' Final Report,
prepared for FAA Office of Aviation Policy and Plans under Work
Order 45, Contract No. DTFA01-93-C-00066, February 25, 1998.
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The number of based aircraft and county population in which the
airport is located were the most highly significant and positive
regressors to LTO activity that our analysis provided.\121\ The
regression equation for based aircraft and county population is: LTOs =
1248 + 203.04*Aircraft + 0.0019*County Population with an R\2\ = 0.64.
For approximately 7,800 facilities that do not report LTO activity to
FAA, we used based aircraft and county population to estimate activity.
We request comment on the method we are using to estimate LTO activity
at these airport facilities.
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\121\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to
docket EPA-HQ-OAR-2007-0294, titled, ``Calculating Aviation Gasoline
Lead Emissions in the 2008 NEI.''
---------------------------------------------------------------------------
To estimate LTO activity at the airport facilities that do not
report based aircraft, we used a regression equation based on county
population and region of the country. The regression equation using
county population and regression of the country is: LTOs = 6200.2 +
0.0087*county population--175.07*West State - 5567.3*Alaska +
854.83*Northeast with an R\2\ = 0.15. This equation has a low
correlation coefficient and we are exploring additional options for
estimating LTO activity at these facilities for which very little
information is reported to the FAA. We request comment on applying the
regression equation above and alternative methods to estimate LTO
activity at these facilities.
For heliports, which comprise approximately 5,500 facilities in the
NASR database, we had insufficient information on which to develop a
regression equation and are currently using the median of activity (141
LTOs/year) at heliports for which we have LTO activity data.
Nationally, 25% of helicopters are piston-engine powered and therefore
use leaded avgas. The FAA and EPA have limited information
[[Page 22456]]
regarding the specific heliports that have activity by piston-engine
helicopters. We are requesting information regarding heliport
facilities at which piston-engine powered aircraft operate and the
activity of these aircraft.
The draft 2008 NEI is the first inventory for which we are
implementing the use of LTO-based lead estimates at almost 20,000
airport facilities and we are expecting State, local and Tribal air
agency review of these data to improve our current estimates. The
specific information on which we are requesting data include: (1) The
fraction of GA and AT LTO activity reported to FAA that is conducted by
piston-engine versus jet-engine powered aircraft, (2) airport-specific
LTO activity for single- versus twin-engine piston-powered aircraft,
(3) fuel consumption rates for the piston-engine aircraft operating at
each airport, (4) the time spent in each mode of operation including
run-up checks conducted by piston-engine aircraft prior to take-off,
and (5) the concentration of lead in fuel delivered to individual
airports. Methods for providing information to EPA as part of the
review process involved in finalizing the 2008 NEI are available.\122\
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\122\ All documentation for use in preparing 2008 emission
inventories can be found on the NEI/EIS Implementation Web site:
http://www.epa.gov/ttn/chief/net/neip/index.html.
---------------------------------------------------------------------------
The discussion above pertains only to lead emissions during the LTO
cycle. Lead emitted outside the LTO cycle occurs during aircraft cruise
mode and portions of the climb-out and approach modes. This part of an
aircraft operation emits lead at various altitudes as well as close to
and away from airports. We are developing methods to estimate lead
emissions outside the LTO cycle which we anticipate will be available
in 2010.
B. Projections for Future Growth
The FAA publishes an annual forecast of the number of piston-engine
powered aircraft, hours flown, the consumption of avgas, the numbers of
pilots and student pilots.\123\ The most recent forecast is for the
years 2009 through 2025. The General Aviation Manufacturers Association
(GAMA) reproduces the FAA forecast in their annual statistical
databook.\124\ According to the GAMA summary, the number of active
single-engine piston-powered aircraft is projected to increase annually
at a 0.5% growth rate, with the aircraft population increasing from
144,220 in 2008 to 157,400 in 2025. The number of active twin-engine
piston-powered aircraft is projected to decrease 0.9% annually, with
aircraft population decreasing from 18,385 in 2008 to 15,650 in 2025.
The piston-powered helicopter population is expected to grow 4.7%
annually from a population of 3,970 in 2008 to 8,295 in 2025.
---------------------------------------------------------------------------
\123\ FAA Aerospace Forecast Fiscal Years 2009-2025. Available
online at: http://www.faa.gov/data_research/aviation.
\124\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook and Industry Outlook, pp.51-55.
Available online at: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf.
---------------------------------------------------------------------------
The FAA forecast predicts the number of hours flown in single-
engine piston-powered aircraft is projected to increase 0.5% yearly
from 2008 to 2025); the number of hours flown in twin-engine piston-
powered aircraft is projected to decrease 1.5% annually and the number
of hours flown in piston-powered rotocraft is projected to increase
3.9% annually. The changes in numbers of piston aircraft and hours
flown is generally reflected in the consumption of leaded avgas. For
the years 2008 through 2025, DOT's FAA estimates no change in the
volume of leaded avgas consumed by single-engine aircraft in the U.S.
(204 million gallons in 2008 and 2025), a 1.9% decrease in leaded avgas
consumed by multi-engine aircraft (from a baseline of 108 million
gallons in 2008 to 78 million gallons in 2025), and a 3.8% annual
increase in the volume of leaded avgas consumed by piston-powered
helicopters (from a baseline of 13 million gallons in 2008 to 24
million gallons in 2025). For 2025, the forecast volume of leaded avgas
is 348 million gallons. Consumption of this volume of fuel would
release 773 tons of lead to the air in 2025.
The number of active pilots flying general aviation aircraft
(excluding air transport pilots) is projected to be slightly over half
a million in 2025, representing a yearly increase of 0.7% over the
forecast period.\125\ The student pilot population is forecast to
increase at a slightly higher rate of 1.0% yearly for a 2025 total
slightly over 100,000. Private pilots and sport pilots are also
projected to increase yearly (0.2% yearly increase in the number of
private pilots). EPA is requesting comments on the forecast information
presented in this section and on the uncertainty in these projections.
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\125\ Except for sport pilots, an active pilot is a person with
a pilot certificate with a valid medical certificate. Source: FAA
2008-2025 Aerospace Forecast.
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IV. Lead Concentrations in the Vicinity of Airports
This section summarizes information regarding the chemical and
physical properties of lead emitted by piston-engine aircraft and
monitoring and modeling studies regarding ambient and soil lead
concentrations in the vicinity of airports where piston-engine aircraft
operate.
A. Chemical and Physical Properties of Lead Emitted by Piston-Engine
Aircraft
Information regarding lead emissions from engines operating on
leaded fuel is summarized in prior AQCDs for Lead.126 127
The chemical form of lead added to avgas (i.e., tetraethyl lead) and
the lead scavenger, ethylene dibromide, are the same compounds 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 AQCD for Lead are relevant to
understanding some of the properties of lead emitted from piston-engine
aircraft. In addition, the Swiss Federal Office of Civil Aviation
(FOCA) published a study of piston-engine aircraft emissions including
measurements of lead.\128\
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\126\ U.S. Environmental Protection Agency (1977) Air Quality
Criteria for Lead. Research Triangle Park, NC: Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office; EPA report no. EPA-600/8-77-017. Available at: http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_pr.html.
\127\ U.S. Environmental Protection Agency (1986) Air Quality
Criteria for Lead. Research Triangle Park, NC: Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available at:
http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_pr.html.
\128\ Federal Office of Civil Aviation Environmental Affairs
(2007) Aircraft Piston Engine Emissions Summary Report. 33-05-003
Piston Engine Emissions--Swiss FOCA--Summary. Report--070612--rit.
Available online at: http://www.bazl.admin.ch.
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When leaded avgas is combusted, the lead is oxidized to form lead
oxide. In the absence of a 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 halogenated forms of lead are volatile at the high temperatures
experienced under combustion conditions and are therefore exhausted
from the engine along with the other combustion by-products.\129\ Upon
cooling to ambient temperatures these brominated lead compounds are
converted to particulate matter. In addition to lead halides, ammonium
salts of lead halides were also emitted by motor vehicles.\130\ Lead
halides
[[Page 22457]]
undergo compositional changes upon cooling and mixing with the ambient
air as well as during transport; the water-solubility of these lead-
bearing particles increases with a shift toward smaller mean particle
size (USEPA 1977, Section 6.2.2.1). Lead halides from automobile
exhaust break down rapidly in the atmosphere, via redox reactions in
the presence of atmospheric acids (AQCD for Lead, page E-17).
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\129\ ChevronTexaco (2006) Aviation Fuels Technical Review pp.
64-65. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf.
\130\ U.S. Environmental Protection Agency (1986) Air Quality
Criteria for Lead. Volume 2 Section Chapters 5 & 6. Research
Triangle Park, NC: Office of Health and Environmental Assessment,
Environmental Criteria and Assessment Office; EPA report no. EPA-
600/8-83/028aF-dF. 4v. Available from: NTIS, Springfield, VA; PB87-
142378.
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A small fraction of uncombusted alkyl lead was measured in the
exhaust of motor vehicles operating with leaded gasoline and is
therefore likely to be present in the exhaust from piston-engine
aircraft.\131\ Alkyl lead is the general term for organic lead
compounds and includes the lead additives tetramethyl lead and
tetraethyl lead. 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. Tetraethyl lead can enter the
atmosphere from avgas distribution systems, refueling operations, fuel
check pre-flight procedures and evaporative losses from the
aircraft.\132\ 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 (AQCD for Lead, page 2-5).
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\131\ U.S. Environmental Protection Agency Persistent,
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT
national action plan for alkyl-Pb. Washington, DC. Available online
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
\132\ U.S. Environmental Protection Agency Persistent,
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT
national action plan for alkyl-Pb. Washington, DC. p. 12. Available
online at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
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Particles emitted by piston-engine aircraft are in the submicron
size range (less than one micron in diameter). 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. The particle number concentration ranged
from 5.7 x 10\6\ to 8.6 x 10\6\ particles per cm\3\ and using a
specific density for soot of 1.2, the authors estimated the mass
concentration of particulate emissions as approximately 10,000 [mu]g/
m\3\. The authors noted that these particle emission rates are
comparable to those from a typical diesel passenger car engine without
a particle filter (FOCA, Section 2.2.3.a).
A significant fraction of particles in the submicron size range are
deposited and retained in the lower respiratory system of humans and
animals (AQCD for PM, page 6-108).\133\ The 1986 AQCD for Lead
concludes that lead deposited in the lower respiratory tract is totally
absorbed (USEPA 1986, page 10-2).
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\133\ U.S. Environmental Protection Agency (2004) Air Quality
Criteria for Particulate Matter (AQCD). Volume II Document No.
EPA600/P-99/002bF. Washington, DC: U.S. Environmental Protection
Agency. Available online at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=87903.
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Due to their small size (i.e., typically less than one micron in
diameter), lead-bearing particles emitted by piston engines may
disperse widely in the environment. However, lead emitted during LTO,
particularly during ground-based operations such as start-up, idle,
preflight run-up checks, taxi and take-off may deposit to the local
environment. Meteorological factors (e.g., wind speed, convection,
rain, humidity) will influence local deposition rates. As discussed in
the overview section of this ANPR, many airports in the country have
been home to piston-engine operations for decades, including years when
lead concentrations in avgas were twice as high as current levels. We
seek comment on the chemical and physical form of lead emissions from
piston-engine aircraft as well as dispersion and deposition patterns
that may influence the risk for local-scale impacts.
B. Summary of Airport Lead Monitoring and Modeling Studies
Lead concentrations in ambient air have been reported for samples
collected on or near five airports: the Santa Monica municipal airport
in Santa Monica, CA, the Van Nuys airport in Van Nuys, CA, the Chicago
O'Hare airport in IL, the Toronto Buttonville municipal airport in
Ontario, Canada, and the Destin airport in Destin,
FL.134 135 136 137 138 Air quality modeling of lead
emissions from piston-engine aircraft has been conducted as part of
EPA's National Air Toxics Assessment and in one
study.139 140 As discussed in Section VI.A of this ANPR,
State and local agencies are initiating lead monitoring at four
airports in 2010 that will provide additional information regarding the
air quality impact of lead emissions from piston-engine aircraft.
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\134\ South Coast Air Quality Management District (2007)
Community-Scale Air Toxics Monitoring--Sun Valley Neighborhood and
General Aviation Airports. Presented by Dr. Philip Fine at the U.S.
EPA Air Toxics Data Analysis Workshop--Chicago, IL. October 2-4,
2007.
\135\ Illinois Environmental Protection Agency Bureau of Air
(2002) Chicago O'Hare Airport Air Toxic Monitoring Program June-
December, 2000.
\136\ 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.
\137\ Tetra Tech, Inc. (2007) Destin Airport Air Sampling
Project Executive Summary. Prepared for City of Destin, Florida.
\138\ Tetra Tech, Inc. (2008) Destin, Florida Airport Sampling
Report. October 2008. Prepared for City of Destin, Florida.
\139\ Piazza, B for the Los Angeles Unified School District
Environmental Health and Safety Branch (1999) Santa Monica Municipal
Airport: A Report on the Generation and Downwind Extent of Emissions
Generated from Aircraft and Ground Support Operations. Report
Prepared for The Santa Monica Airport Working Group. Available
online at: http://yosemite.epa.gov/oar/CommunityAssessment.nsf/
6ce396ab3fa98ee485256db0004acd94/$FILE/Santa--Monica.pdf
\140\ U.S. Environmental Protection Agency (2009) 2002 National-
Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn/atw/nata2002/index.html.
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1. Summary of Airport Lead Monitoring Studies
The ambient air monitoring studies reporting lead concentrations on
and near airport property served many purposes and therefore used
different criteria for determining sample locations, sample durations,
sample collection methods, and collection of important metadata (e.g.,
activity of piston-engine aircraft and aircraft engine type). This
section summarizes results from these studies.
Ambient monitoring studies at and near airports indicate that lead
levels in ambient air at or near airports with piston-engine activity
are higher than lead levels in areas not directly influenced by a lead
source. The study at the Santa Monica Airport \141\ is the only study
to date in which a lead monitor was sited at an area of anticipated
maximum concentration for a period of time that provides ambient
concentrations relevant for comparison to the Lead NAAQS.\142\ In this
study where monitors were placed in
[[Page 22458]]
locations to identify the gradient in lead concentrations with distance
from piston-engine activity, ambient lead increased with increasing
proximity to the airport. Lead monitors were located at seven sites
around the Santa Monica Airport for two three-month periods, in Spring
2006 and Winter 2006-2007. At the monitor placed near the runway blast
fence (i.e., the maximum impact site) on the Santa Monica Airport
property, the quarterly average concentrations of lead in total
suspended particulate matter (TSP) were 0.08 (winter) and 0.10 (spring)
[mu]g/m\3\.\143\ The maximum quarterly average concentration of lead in
total suspended particulate matter (TSP) was 0.10 [mu]g/m\3\, 67% of
the 2008 Lead NAAQS of 0.15 [mu]g/m\3\. This suggests that ambient air
lead concentrations at similar airports with more piston-engine
activity than the Santa Monica Airport may be higher, and could further
approach or exceed 0.15 [mu]g/m\3\. At a neighborhood site, 70 meters
in the prevailing downwind direction from the maximum impact site,
quarterly average concentrations of lead in TSP were 0.02 [mu]g/m\3\
(winter) and 0.03 [mu]g/m\3\ (spring).\144\ At a distance of one
kilometer in the prevailing downwind direction from the maximum impact
site, lead concentrations were 0.004 [mu]g/m\3\ and 0.008 [mu]g/m\3\ in
winter and spring, respectively (these concentrations are considered
the background lead concentration). The study conducted at the Santa
Monica Airport reported concentrations of ambient lead that were
highest at on- and near airport areas downwind from the emissions of
piston-engine aircraft. These data suggest that piston-engine activity
can increase ambient lead concentrations in downwind neighborhood
sites, resulting in levels that are four to five times higher than
background levels and maximum impact site concentrations that are up to
25 times higher than background lead levels.\145\
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\141\ South Coast Air Quality Management District (2007)
Community-Scale Air Toxics Monitoring--Sun Valley Neighborhood and
General Aviation Airports. Presented by Dr. Philip Fine at the U.S.
EPA Air Toxics Data Analysis Workshop--Chicago, IL. October 2-4,
2007. This presentation includes lead monitoring data collected at
and near the Santa Monica Airport and the Van Nuys Airport.
\142\ As with other lead sources, source-oriented monitors for
airports should be sited in ambient air at the location of predicted
maximum lead concentration. Typically, the location of maximum lead
concentration will be downwind of the take off strip near the
``blast fence.'' http://www.epa.gov/ttnamti1/files/ambient/pb/NetworkDesignQA.pdf.
\143\ A low-volume sampler was used at this site which EPA
expects would yield comparable results to a high-volume sampler, the
latter of which is the current method used to collect samples for
comparison with the Lead NAAQS.
\144\ These distances were measured using Google Earth Pro
software.
\145\ EPA notes that additional information regarding this study
at the Santa Monica Airport may become available. If additional
information does become available, EPA will take this information
into account in the NPRM.
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As with other emissions from internal combustion engines, lead
emitted by piston-engine aircraft are largely in the submicron and even
ultrafine size fraction; therefore, analogies to gradients in ultrafine
PM are relevant. As summarized in EPA's 2009 Integrated Science
Assessment for Particulate Matter, ultrafine particulate number counts
decrease exponentially with distance from roadways.\146\ A recent study
at the Santa Monica Airport reported increased ultrafine PM in a
neighborhood downwind from aircraft operations that were conducted by
jet and piston-engine aircraft.\147\ The EPA is conducting modeling and
monitoring studies to further evaluate the gradient in lead
concentrations with distance from airports (see Section VI.B of this
ANPR).
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\146\ U.S. Environmental Protection Agency (2009) Integrated
Science Assessment for Particulate Matter. Second External Review
Draft. EPA/600/R-08/139B. p. 3-110. Available online at: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=210586.
\147\ Hu, S., Fruin, S., Kozawa, K., Mara, S., Winer, A.M.,
Paulson, S.E. (2009) Aircraft Emission Impacts in a Neighborhood
Adjacent to a General Aviation Airport in Southern California.
Environ. Sci. Technol. 43:8039-8045.
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At the Van Nuys Airport, lead monitoring in ambient air was
conducted at six sites for two three-month periods. Lead monitoring for
this study included locations of ambient air on airport property.
However, monitors were not sited in the area anticipated to experience
the maximum impact from piston-engine aircraft emissions. The
monitoring site that was in closest proximity to the maximum impact
area was more than one kilometer downwind from the maximum impact
site.\148\ The highest quarterly concentration of lead observed at the
Van Nuys Airport was at the monitor located over one kilometer away
from the maximum impact site and the lead concentration at this site
was 0.03 [mu]g/m\3\ which was four-fold higher than the regional
background level of 0.008 [mu]g/m\3\ measured during the same time
period at a site over 2.5 kilometers from the north end of the Van Nuys
Airport.
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\148\ These distances were measured using Google Earth Pro
software. Prevailing wind direction, which determines the direction
in which the majority of aircraft depart, is provided in the SCAQMD
presentation of these data.
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At the Toronto Buttonville Municipal Airport, ten 24-hour
PM10 samples were collected at four sites at the airport (as
close as 15 meters from the runway) and one urban background site in
downtown Toronto (located about 10 kilometers west, southwest of the
airport). PM10 is particulate matter less than ten microns
in aerodynamic diameter. The average lead concentration among the
airport monitors (which includes three samples that were taken for less
than a 12-hour period), was 0.03 [mu]g/m\3\ and the maximum 24-hour
lead concentration was 0.13 [mu]g/m\3\. One sample, collected for 11
hours, measured 0.30 [mu]g/m\3\. The maximum concentration observed
over a 24-hour period at the airport during this study (0.13 [mu]g/
m\3\) was 11 times higher than the lead concentration reported for the
downtown Toronto, Canada background site during the same time period
(0.012 [mu]g/m\3\).\149\ The average lead concentration reported for
the downtown Toronto site was 0.007 [mu]g/m\3\. The total particulate
matter mass in PM10 was also measured in this study, and at
the airport, the average mass of lead in PM10 was 0.15% of
the total PM10 mass. At the downtown Toronto site, the
average mass of lead in PM10 was 0.04% of the total
PM10 mass. The study reported that the use of leaded avgas
at the airport was evident in enhanced airborne lead levels.
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\149\ Average concentrations reported in this study include
three days of short-duration sampling so the average is not used for
comparison here.
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Lead and other hazardous air pollutants were measured at sites
upwind and downwind of the Chicago O'Hare Airport on sixteen days
during the period from June through December, 2000. In order to assess
the potential impact of airport operations on ambient concentrations of
lead and other pollutants in areas adjacent to airport property, two
monitoring sites were deployed on different sides of the airport: one
in Bensenville, IL and the other in Schiller Park, IL. For five days
during the sampling campaign, the prevailing wind direction provided
samples that were collected simultaneously upwind and downwind of the
airport. Lead concentrations measured at the downwind site on these
five days were, on average, 88% higher than lead concentrations
measured at the upwind site. Lead concentrations at the upwind site
over the five days averaged 0.016 [mu]g/m\3\ and downwind
concentrations averaged 0.030 [mu]g/m\3\. This study demonstrates the
potential for operations on airport property to impact ambient lead
concentrations downwind.
Lead TSP samples were collected for four days in April 2007 and for
three days in July 2008 near the Destin Airport in Destin, FL. Twelve-
hour TSP samples (AM and PM) were collected at four residential
locations ranging from 200 meters to 400 meters from the runway at the
Destin Airport and at two urban background locations which were 1.4
kilometers and 2.7 kilometers from the airport.\150\ The average lead
concentration among the four residential locations was 0.004 [mu]g/m\3\
and 0.005 [mu]g/m\3\ in April and July, respectively, and the average
urban
[[Page 22459]]
background lead concentration was 0.003 and 0.004 [mu]g/m\3\ in April
and July, respectively.
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\150\ These distances were measured using Google Earth Pro
software.
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In addition to these airport-specific studies, authors evaluating
ambient 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
reported a weekend increase in ambient lead that the authors attributed
to weekend increases in piston-engine powered general aviation
activity.\151\ At some airports, piston-engine aircraft activity
conducted for recreational purposes can increase greatly on weekends
and can also change seasonally with weather conditions. These peaks in
activity are important to capture because they may have a strong
influence on long-term average concentrations in an area. However, the
current database for ambient lead concentrations at maximum impact
sites at airports is severely limited and does not allow us to
quantitatively evaluate the influence of this variability in activity
on ambient lead concentrations.
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\151\ Murphy, D.M., Capps, S.L., Daniel, J.S., Frost, G.J., and
White, W.H. (2008) Weekly patterns of aerosol in the United States.
Atmos. Chem. Phys., 8, 2729-2739.
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We have identified no studies evaluating the potential contribution
of piston-engine aircraft emissions on vegetation. We have identified
only one study that reports soil concentrations on airport property
where piston-engine aircraft are active. The air monitoring study
conducted at the Toronto Buttonville airport in Ontario, Canada
reported lead concentrations in soil samples collected at eight
locations at the airport and two locations at the urban background
site. Soil samples that were collected at the Toronto Buttonville
airport had lead concentrations ranging from 22-46 [mu]g/g which was
not substantially higher than the lead concentrations in soil samples
at the two urban background sites (29 and 31 [mu]g/g). We are seeking
comments on the potential for piston-engine aircraft emissions to
impact local soil lead concentrations.
2. Summary of Airport Lead Modeling Studies
Lead emissions from piston-engine aircraft at 3,410 airports were
included in the recently released 2002 National Air Toxics Assessment
(NATA) as nonroad sources of lead.\152\ Ambient lead concentrations and
exposures to lead are modeled for area, point and nonroad sources.
Nonroad sources include only lead emissions from piston-engine
aircraft. Lead emission rates are based on the lead concentration in
fuel and not direct emission measurements. For the NPRM we will
summarize modeling results from the 2005 NATA which will incorporate
all 20,000 airport facilities discussed in Section III of this ANPR.
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\152\ U.S. Environmental Protection Agency (2009) 2002 National-
Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn/atw/nata2002/tables.html.
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As discussed in Section VI of this ANPR, the EPA has conducted a
study to develop a modeling approach to evaluate the local-scale
variability in ambient lead concentrations attributable to piston-
engine activity at a case study airport. This project includes
collection of air monitoring data for use in evaluating model
performance. In the NPRM, we will describe the results of the modeling
study with NATA results for this airport and previous modeling
work.\153\
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\153\ Piazza, B for the Los Angeles Unified School District
Environmental Health and Safety Branch (1999) Santa Monica Municipal
Airport: A Report on the Generation and Downwind Extent of Emissions
Generated from Aircraft and Ground Support Operations. Report
Prepared for The Santa Monica Airport Working Group. Available
online at: http://yosemite.epa.gov/oar/CommunityAssessment.nsf/
6ce396ab3fa98ee485256db0004acd94/$FILE/Santa--Monica.pdf.
---------------------------------------------------------------------------
We are requesting comment on the availability of additional
monitoring or modeling studies that evaluate the air quality impact of
lead emissions from piston-engine aircraft as well as potential impacts
on soil, house dust, surface water or other environmental media. We
also request comment on the availability of studies that assess the
potential public health and welfare impacts of lead emissions from
piston-engine aircraft.
V. Exposure to Lead From Piston-Engine Aircraft and Potential for
Impacts
The continued use of lead in avgas by piston-engine aircraft is a
significant source of current lead emissions to the environment.
Piston-engine aircraft emissions of lead occur at ground level as well
as at flying altitude. Lead from this source is thus concentrated near
airports and is also deposited over a large geographic area potentially
contributing to higher ambient concentrations in many communities.
Numerous groups within the population may be at risk of exposure to
lead in fresh emissions from piston-engine aircraft, resuspended dust
or other routes. Further, lead accumulates in the environment posing a
potential risk to future generations
In this section we discuss a variety of exposure pathways and
scenarios by which the general population and environment may
experience an increase in lead exposure from emissions of lead by
piston-engine aircraft. This section also describes the potential for
public health and welfare effects from exposure to compounds associated
with the continued use of tetraethyl lead in fuel, such as the
contribution of lead to ambient particulate matter, emissions of
ethylene dibromide and non-exhaust exposure to tetraethyl lead. We are
seeking comments and information on these exposure scenarios as well as
additional exposure pathways and scenarios.
A. Exposure to Lead Emissions From Piston-Engine Aircraft
Piston-engine aircraft emissions of lead occur at ground level as
well as at altitudes, resulting in areas of more concentrated ambient
air exposure, as discussed in Section IV, and can also be distributed
over large geographic areas due to in-flight emissions. Lead particles
can deposit to soil, water, vegetation and other surfaces or remain
airborne for some time following emissions. In this section we discuss
potentially exposed populations which include people living or
attending schools near airports and pilots. Additional pathways by
which people and animals could be exposed to lead emissions from
piston-engine aircraft are those associated with agricultural
applications of these aircraft and piston-engine activity at seaport
and inland waterways.
Lead from aviation gasoline has been identified as a potential
source of contamination for local communities.\154\ As described below,
many general aviation airports are located in densely populated areas.
GA airport facilities were typically built in sparsely populated areas,
many of which are now heavily populated or are experiencing increased
residential development. This development includes dense residential
neighborhoods, schools, businesses, and recreational facilities.
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\154\ Levin, R.; Brown, MJ; Kashtock, ME; Jacobs, DE; Whelan,
EA; Rodman, J; Schock, MR; Padilla, A; Sinks, T. (2008) Lead
Exposures in U.S. Children, 2008: Implications for Prevention.
Environ. Health Perspec. 116:1285-1293.
---------------------------------------------------------------------------
Airports can function as a center of many forms of activity in a
community. In EPA's initial research, EPA has found that airports are
often surrounded by a variety of land uses including recreational sport
facilities (e.g., baseball diamonds, soccer fields, golf courses, and
swimming pools) and residential communities that take
[[Page 22460]]
advantage of the ease of transport and pilot training/recreation
offered by quick access to an airport. Many airports offer on-site
tours to the general public, educational classes, and recreational
opportunities that can present near-source exposure scenarios. Airports
are especially attractive to young children, and programs at some
airports are focused on this population and provide outdoor observation
facilities and picnic facilities for families to observe aircraft
operations. Many general aviation airports offer instructional flying
and/or clubs where children 14 years of age and older as well as adults
can learn to fly in rental aircraft. Airport facilities also host
community-friendly activities such as antique sales, fireworks
displays, air shows and community meals. Many airport facilities
provide activities which bring people from the general public in close
proximity to lead emissions from piston-engine aircraft and piston-
engine helicopters. EPA is requesting information regarding national
databases that provide information regarding recreational fields and
community gardens in close proximity to airports.
1. Population Residing Near Airports
To evaluate the number of people who might be exposed to elevated
lead levels due to emissions from piston-engine aircraft, EPA
calculated the number of people that live within one kilometer of the
centroid of an airport.\155\ The centroid of the airport is defined
here as the latitude and longitude coordinate provided by airports to
FAA.\156\ These coordinates typically identify a location in the center
of the runway or runway area. For some airports, nearby residences are
outside the one kilometer distance from the airport centroid. This is
the case for residences near airports that have runways that are longer
than two kilometers and for residences near large airports such as
those servicing primarily commercial aircraft activity. For airport
facilities with one runway that is approximately one kilometer in
length, this method will generally include people residing within
approximately 500 meters from the ends of the runway and may include
residences up to approximately 900 meters from the sides of the runway.
The limited ambient lead monitoring data near airports presented in
Section IV of this ANPR suggests that for some airports this analysis
will underestimate the actual number of people potentially exposed to
elevated levels of ambient lead from piston-engine powered aircraft.
This is because the analysis will include very little of the nearby
population for airports that have a large footprint. We plan to revise
this analysis for the NPRM using a graphical interface system that will
allow us to evaluate the number of people living within uniform
distances of aircraft activity.
---------------------------------------------------------------------------
\155\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to
docket EPA-HQ-OAR-2007-0294, titled, ``Evaluation of People Living
Within 1 km of U.S Airport Facilities.''
\156\ Federal Aviation Administration. Airport Data (5010) &
Contact Information, Airport Facilities Data. Retrieved on August
13, 2009 from: http://www.faa.gov/airports/airport_safety/airportdata_5010/menu/index.cfm.
---------------------------------------------------------------------------
Using 2000 U.S. Census Data \157\ at the block level, EPA estimates
that 16 million people live within one kilometer of the centroid of the
19,896 airport facilities which includes airports, seaplane bases,
heliports, stolports, ultralight facilities and glider ports. There are
currently 5,567 heliports in this analysis, which can be in densely
populated areas. Fourteen of the 16 million people living within one
kilometer of the centroid of an airport facility live within one
kilometer of a heliport. We currently have limited information
regarding which heliport facilities have piston-engine activity and we
are seeking comment on piston-engine activity at heliports.
---------------------------------------------------------------------------
\157\ Obtained from: http://www.epa.gov/ttn/fera/human_hem_censusandmet.html.
---------------------------------------------------------------------------
There are several pathways by which people may be exposed to lead
associated with the use of piston-engine aircraft. These include
inhalation of ambient airborne lead as well as incidental ingestion of
ambient lead through contact with indoor or outdoor surfaces to which
ambient lead has deposited. Additionally, ambient lead deposited to
outdoor soil can be tracked into interior spaces. There is also the
potential for ingestion of lead emitted by piston engine aircraft
emissions to deposit on edible plants and produce being cultivated in
locations near airports. Consequently, there is the potential for
exposure to lead emitted by piston-engine aircraft via ingestion for
those consuming vegetables grown near airports that service piston-
engine aircraft. In addition to personal gardens, community gardens are
sometimes sited near airports as these areas can have undeveloped
available land. We do not have information on the potential
significance of this exposure pathway and we are seeking comment on
information and analyses that could inform this issue.
In some cases, pilots and their families choose to live in close
proximity to an airstrip. These communities intentionally placed near
airports are known as airport communities, fly-in communities or
residential airparks. Some residential airparks are private while
others have public services and facilities. Some residential airparks
are specifically designed as airport communities with driveways leading
from aircraft hangars or tie-downs onto the airstrip, while other
residential airparks allow apartments to be built in the airplane
hangar. Other residential airparks are developed by the addition of a
neighborhood immediately adjacent to a commercial airport. FAA terms
this a ``through-the-fence'' operation.\158\ Homes are required to be
at least 45 meters from the runway centerline and can be built along
one or both sides of the runway.\159\ Some residential airparks provide
taxiways for access to the runway, some provide streets separate from
taxiways, and some share automobile and aircraft traffic on the same
thoroughfares. A variety of resources list the location and services
offered by residential airparks in the U.S. and estimates of the number
of residential airparks range from 300 to 600.160 161
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\158\ FAA officially defines ``through-the-fence'' as those
activities permitted by an airport sponsor through an agreement that
permits access to the public landing area by independent entities or
operations offering an aeronautical activity or to owners of
aircraft based on land adjacent to, but not part of, the airport
property. The obligation to make an airport available for the use
and benefit of the public does not impose any requirement for the
airport sponsor to permit ground access by aircraft from adjacent
property. (http://www.aopa.org/whatsnew/region/airportOps0712.pdf).
\159\ ASTM International (2005) ASTM F2507-05 Standard
Specification for Recreational Airpark Design
\160\ http://www.airparks.com maintains a list of airparks that
have five or more homes/lots. The list can be updated by the public
and as of July 31, 2009, lists 326 residential airparks.
\161\ http://livingwithyourplane.com/about/ has a directory of
over 600 residential airparks.
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In some cases, records are maintained only for those residential
parks that have five or more homes or lots.
Exposure modeling at the EPA indicates that, for the 20 highest air
emission sources, local emissions are significantly related to local
blood lead levels.\162\ We are aware of no studies evaluating blood
lead levels among people who live in close proximity to airports with
piston-engine activity or those for whom lead emissions from piston
engines may elevate their exposure via other exposure pathways. As
noted in Section II.B.2, the current evidence indicates that the slope
for
[[Page 22461]]
lead effects on IQ is nonlinear and is steeper at lower blood lead
levels, such that each [mu]g/dL increase in blood lead may have a
greater effect on IQ at lower blood lead levels (e.g., below 10 [mu]g/
dL) than at higher levels (AQCD for Lead, Section 6.2.13; pp. 8-63 to
8-64; Figure 8-7). We are therefore seeking comment and information
regarding blood lead concentrations in children living near airports
and the extent to which these emissions cause or contribute to any
increases in blood lead levels.
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\162\ U.S. Environmental Protection Agency (2007) Pilot Study of
Targeting Elevated Blood Lead Levels in Children (Draft Final
Report). Washington DC: U.S. EPA Office of Pollution Prevention and
Toxics. http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=195303.
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2. Children Attending School Near Airports
As noted in Section II.B.2 of this ANPR, while adults are
susceptible to lead effects at lower blood lead levels than previously
understood (e.g., AQCD for Lead, p. 8-25), there is general consensus
that the developing nervous system in children is among the, if not
the, most sensitive health endpoints. Also, as noted in Section II.B.3,
while children are considered to be at a period of maximum exposure
around 18-27 months, the current evidence has found even stronger
associations between blood lead levels at school age and IQ at school
age. The evidence ``supports the idea that lead exposure continues to
be toxic to children as they reach school age, and [does] not lend
support to the interpretation that all the damage is done by the time
the child reaches 2 to 3 years of age'' (AQCD for Lead, Section
6.2.12). Accordingly, school-age children are an at-risk population for
lead exposures. This section discusses potential exposures of children
at school to lead associated with piston-engine aircraft.
During the school year, students spend many hours a day at school,
which usually includes time on school playgrounds and on school
athletic fields. Those children attending schools in close proximity to
piston-engine activity may have increased exposure to lead. Using data
from the U.S. Department of Education's National Center for Education
Statistics, EPA calculated that there are 8,637 schools located within
one kilometer of the centroid of an airport in the U.S., at which over
3 million children are in attendance (Table 1).163 164 These
children represent 6% of the total U.S. student population.
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\163\ U.S. EPA (March 2010) Memorandum from Meredith Pedde to
docket EPA-HQ-OAR-2007-0294, titled, ``Identification of Schools
Within 1 km of U.S Airport Facilities.''
\164\ Public School Data available for 2006-2007: http://nces.ed.gov/ccd/bat/; Private School Data available for 2007-2008:
http://nces.ed.gov/surveys/pss/pssdata.asp.
Table 1--Numbers of Public and Private Schools and School Children
Attending Schools Located Within One Kilometer of the Centroid of an
Airport Servicing Piston-engine Aircraft
------------------------------------------------------------------------
Number of
Number of students who
schools within attend schools
1 km of an within 1 km of
airport an airport
------------------------------------------------------------------------
Private Schools......................... 2,185 420,824
Public Schools.......................... 6,452 2,869,939
-------------------------------
All Schools......................... 8,637 3,290,763
------------------------------------------------------------------------
Section II.B.1 notes that children in poverty and black, non-
Hispanic children have notably higher blood lead levels than do
economically well-off children and white children, in general. To
evaluate potential ethnic and economic disparities among children
attending schools close to airports compared with the general
population, we used data from the Department of Education that provides
this information. These data indicate that minorities are
overrepresented at schools that are located within one kilometer from
the centroid of an airport. For example, Hispanic students represent
23% of students at schools located within one kilometer of an airport,
whereas Hispanic students represent 19% of students in all U.S. schools
(Table 2). Black students represent 18% of students at schools located
within one kilometer of an airport, whereas black students represent
16% of the student population in the U.S. (Table 2).
Table 2--Racial Distribution at Schools Within One Kilometer of the Centroid of an Airport and the Racial Distribution at all U.S. Schools
--------------------------------------------------------------------------------------------------------------------------------------------------------
American
Indian/Alaskan Asian/Pacific Black, Non- Hispanic White, Non- Total
Indian Islander Hispanic Hispanic students*
--------------------------------------------------------------------------------------------------------------------------------------------------------
All Schools within 1 km of an Number.............. 46,861 154,408 597,223 764,704 1,646,882 3,290,763
airport.
Percent............. 1% 5% 18% 23% 50%
All U.S. Schools.................. Number.............. 632,237 2,581,822 8,696,565 10,525,763 30,664,231 54,271,986
Percent............. 1% 5% 16% 19% 57%
--------------------------------------------------------------------------------------------------------------------------------------------------------
* This table includes only those children that identify as one of the five races/ethnicities. A small fraction of students identify as mixed race or
`other' and they are not included here, therefore the percent of students does not total 100%.
In general, housing and income data suggest that people living in
close proximity to major transportation sources (i.e., major roadways,
airports, ports, railyards) are likely to have lower income than the
general population.\165\ To evaluate the socioeconomic status of
students who attend schools near airports, EPA evaluated the number of
students who are eligible for the U.S. Department of Agriculture's free
or reduced school lunch program. Children
[[Page 22462]]
from families with incomes at or below 130 percent of the poverty level
are eligible for free meals. Those with incomes between 130 percent and
185 percent of the poverty level are eligible for reduced-price
meals.\166\ Free and reduced lunch eligibility is only tracked by the
U.S. Department of Education's National Center for Education Statistics
for students who attend public schools. At public schools that are
located within one kilometer of the centroid of an airport, 47% of
students are eligible for either free or reduced lunches, whereas
nationally, 41% of students at public schools are eligible for either
free or reduced lunches. As this analysis demonstrates, those living in
the vicinity of airports are more likely to be low-income households
and minority residents.
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\165\ U.S. Environmental Protection Agency (2007) Regulatory
Impact Analysis for the Regulation to Control Hazardous Air
Pollutant Emissions from Mobile Sources. Chapter 3, p. 3-122.
\166\ United States Department of Agriculture: Food and
Nutrition Service, National School Lunch Program Fact Sheet.
Obtained from: http://www.fns.usda.gov/cnd/Lunch/AboutLunch/NSLPFactSheet.pdf, August 3, 2009. For the period July 1, 2008,
through June 30, 2009, 130 percent of the poverty level is $27,560
for a family of four; 185 percent is $39,220.
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We are aware of no studies evaluating blood lead levels among
children attending school in close proximity to airports with piston-
engine activity. We are seeking comment and information regarding blood
lead concentrations in children who attend schools in close proximity
to airports and the extent to which these emissions cause or contribute
to any increases in blood lead levels.
3. Agricultural Activities
Piston-engine aircraft are used in a variety of agricultural
activities that may introduce lead into the human diet as well as
contribute to lead in the environment. The FAA conducts the General
Aviation and Air Taxi Activity (GAATA) Survey annually to obtain
information on the general aviation and air taxi fleet, the number of
hours flown, and the reasons people use general aviation and air taxi
aircraft.167 168 According to the results of the 2007 GAATA
Survey (the most recent), aerial application in agriculture and
forestry represented 5% of all hours flown by general aviation aircraft
in 2007. Of the total aerial application hours flown in 2007 (1.41
million hours), 60% of the hours were flown by piston-engine aircraft.
Aerial application activity includes crop and timber production, which
involve fertilizer and pesticide application and seeding cropland. The
National Agricultural Aviation Association estimates that there are
approximately 3,200 aerial application professional operators and
pilots in the United States.\169\
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\167\ The FAA GAATA is a database collected from surveys of
pilots flying aircraft used for general aviation and air taxi
activity. For more information on the GAATA, see Appendix A at
http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/.
\168\ National Agricultural Aviation Association: ``Help the
Aerial Application Industry by completing the 2008 General Aviation
Activity Survey.'' Retrieved from: http://www.agaviation.org/2008%20GenAvnSurvey.htm on August 13, 2009.
\169\ National Agricultural Aviation Association: ``History.''
Retrieved from: http://www.agaviation.org/history.htm on August 13,
2009.
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As discussed in Section II.C.1, surface deposition of lead onto
plants may represent a significant contribution to the total lead in
and on the plant. Lead halides, the primary form of lead emitted by
engines operating on leaded fuel, are slightly water soluble. They
therefore may be more readily absorbed by plants than other forms of
inorganic lead. Atmospheric deposition of lead also contributes to lead
in vegetation as a result of contact with above-ground portions of the
plant (AQCD for Lead, pp. 7-9 and AXZ7-39; USEPA, 1986, Sections 6.5.3
and 7.2.2.2.1). 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 (USEPA 1986, Section
7.2.2.2.2).\170\ The lead concentration of plants ingested by animals
is primarily a result of atmospheric deposition of lead particles onto
plant surfaces rather than the uptake of soil lead through plant roots.
Some of the highest levels of lead exposure among livestock have been
attributed to grazing near major sources such as smelters (AQCD for
Lead, Section 2.3.8). Atmospheric deposition is estimated to comprise a
significant proportion of lead in food (AQCD for Lead, p. 3-48) and
dietary intake may be a predominant source of lead exposure among
adults (greater than consumption of water and beverages or inhalation
(73 FR 66971)).
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\170\ U.S. Environmental Protection Agency (1986) Air Quality
Criteria for Lead. Research Triangle Park, NC: Office of Health and
Environmental Assessment, Environmental Criteria and Assessment
Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from:
NTIS, Springfield, VA; PB87-142378.
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Depending on wind conditions, an aircraft involved in aerial
application may fly only 4 inches to 12 feet above the
crops.171 172 173 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. We have not
identified any data or analyses regarding the contribution of piston-
engine aircraft lead emissions to lead concentrations in or on plant
tissues, in livestock or the dose that this might deliver to the human
population. We are seeking comments on the potential significance of
this exposure pathway.
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\171\ Xiong, Chao. (9-23-2007) ``Future for Crop Dusters is up
in the Air''. The Star Tribune. Retrieved on August 12, 2009 from:
http://www.startribune.com/local/11606661.html.
\172\ Harpole, T. (3-1-2007) ``That Old-Time Profession'' Air &
Space Magazine. Retrieved on August 12, 2009 from: http://www.airspacemag.com/history-of-flight/old_time_profession.html.
\173\ Petersen, R. ``So you want to be a spray pilot''. AgAir
Update. Retrieved on October 9, 2009 from: http://www.agairupdate.com/aau/wannabe/pilot.html.
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4. Pilots, Student-Trainees, Passengers
Pilots, student-trainees, and passengers are all potentially
exposed to lead emissions from piston-engine aircraft that use leaded
avgas. General aviation passengers and pilots access their aircraft in
areas that are typically in close proximity to runways. Therefore,
these individuals walk near and breathe the air near locations where
aircraft are idling, conducting run-up checks, taxiing, taking off, and
landing.
In the U.S., general aviation aircraft fly over 27 million hours
and carry 166 million passengers annually.\174\ Approximately 36
percent of the hours flown by general aviation are for personal
transportation, 19 percent are instructional flight hours, 11 percent
are corporate flight hours, 11 percent are for business, eight percent
are air taxi and air tours and the remainder include hours spent in
other applications such as aerial observation and aerial
application.\175\ According to the 2008 General Aviation Statistical
Databook & Industry Outlook report by the General Aviation
Manufacturers Association (GAMA) there were 578,541 pilots in the
United States in 2008.\176\ Among the pilot population, 75,382 were
student pilots, comprising 13% of the total pilot population. The
majority of initial pilot training is conducted in piston-engine
aircraft.\177\ There is no age minimum for
[[Page 22463]]
pilots to begin taking flying lessons.\178\ The minimum age for
conducting a solo flight is 16 years and a pilot certificate cannot be
issued until 17 years of age. According to the 2008 General Aviation
Statistical Databook & Industry Outlook report by the GAMA, there are
190 student pilots in the 14-15 year old age group and 11,562 student
pilots in the 16-19 years old age group. GAMA reports that in 2008
there are 3,846 private pilots in the 16-19 years old age group.
According to the FAA there are more than 500 flight training
schools.179 180 The requirement for a private pilot
certificate is 40 hours in a non-approved school, and 35 hours in an
approved school. However, most people obtain 60 to 75 hours of training
before earning their pilot certificate.
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\174\ General Aviation Manufacturers Association (2008) General
Aviation Statistical Databook and Industry Outlook. Available at:
http://www.gama.aero/files/2008_general_aviation_statistical_databook_indust_499b0dc37b.pdf.
\175\ General Accounting Office Report to Congressional
Requesters (2001) General Aviation Status of the Industry, Related
Infrastructure, and Safety Issues. GAO-01-916.
\176\ GAMA 2008 General Aviation Statistical Databook & Industry
Outlook report. Retrieved on August 17, 2009 from: http://www.gama.aero/files/2008_general_aviation_statistical_databook_indust_499b0dc37b.pdf.
\177\ See http://flighttraining.aopa.org/.
\178\ Federal Aviation Administration (FAA). ``Become a Pilot--
Student Pilot's Certificate Requirements.'' Retrieved on August 17,
2009 from: http://www.faa.gov/pilots/become/student_cert/.
\179\ Federal Aviation Administration (FAA). ``Types of Pilot
Schools & Choosing a Pilot School''. Retrieved on August 17, 2009
from: http://www.faa.gov/training_testing/training/pilot_schools/.
\180\ Federal Aviation Administration (FAA). ``Pilot Schools--
Search''. Retrieved on August 17, 2009 from: http://av-info.faa.gov/PilotSchool.asp.
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The general public for whom flying is a recreational activity may
be the most highly exposed population to lead emissions from piston-
engine activity. In addition to their inhalation exposure to engine
exhaust emissions, pilots can be exposed to evaporative emissions of
TEL during aircraft fueling, and fuel sump checks during preflight
inspections.
5. Bioaccumulation of Lead in Aquatic Organisms
As discussed in Section II.C.2 of this ANPR, lead bioaccumulates in
the tissues of aquatic organisms through ingestion of food and water.
Because of the potential for significant deposition of lead compounds
to water bodies, EPA researches and reports on the atmospheric
deposition of lead compounds to the Great Waters (the Great Waters
include the Great Lakes, Lake Champlain, Chesapeake Bay and many U.S.
coastal estuaries).\181\ Alkyl lead, in particular, has been identified
by EPA as a Level I Persistent, Bioaccumulative, and Toxic (PBT)
pollutant. Level I substances are targeted for virtual elimination
through pollution prevention and other incentive-based actions that
phase out their use, generation or release in a cost-effective manner
within the most expedient timeframe. In 2002, EPA issued the PBT
National Action Plan for Alkyl-lead to promote further voluntary
reductions of use and exposure to alkyl lead compounds, including
leaded avgas.\182\
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\181\ U.S. Environmental Protection Agency, ``The Great Waters
Program.'' Retrieved on August 17, 2009 from: http://www.epa.gov/air/oaqps/gr8water/ gr8water/.
\182\ U.S. Environmental Protection Agency Persistent,
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT
national action plan for alkyl-Pb. Washington, DC. Available online
at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf.
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We are interested in the potential for lead emissions from piston-
engine aircraft to be a source of lead pollution to aquatic organisms.
Among the approximately 20,000 airport facilities in the United States
there are 448 seaplane facilities. Landing and take-off activity by
aircraft 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. In addition to seaplane
facilities, many airports and heliports are located very close to
rivers, lakes and streams, which can provide a direct pathway for
emission of organic and inorganic lead to the air near/above inland
waters. Lead emissions from 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. As noted in Section IV.A, lead halides (the primary form of lead
emitted by engines operating on leaded fuel) are slightly water-soluble
and may be more readily dissolved into water than other inorganic forms
of lead.
The EPA Office of Water maintains a database of the National
Listing of Fish Advisories (NLFA) which is made available on the
Internet to provide information regarding locally-issued fish
advisories and safe eating guidelines.\183\ States, territories, and
Tribes (collectively referred to here as ``States'') provide this
information to EPA every year. The most recent year for which data are
available is 2008. States provide information regarding contaminant
levels of bioaccumulative toxins measured in fish including lead,
mercury, polychlorinated biphenyls (PCBs) and dioxin. Based on these
data states issue fish consumption advisories that provide information
regarding water bodies for which fish tissue concentrations of these
pollutants are found by the State criteria to be safe or unsafe for
consumption. The EPA recommends that if fish are detected as having any
measureable level of accumulated lead in their tissues that this is
cause for concern for all consumers, but especially for children and
pregnant or nursing women, and that issuing an advisory is prudent.
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\183\ U.S. Environmental Protection Agency, ``The National
Listing of Fish Advisories.'' Retrieved on August 17, 2009 from:
http://www.epa.gov/waterscience/fish/advisories/.
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The 2008 NLFA database includes data on lead concentrations in over
23,000 fish from over 1,000 lakes and streams. Among these fish, lead
concentrations were above the analytical detection limit in 1,000 fish
samples \184\ and among the fish in which measureable lead
concentrations were reported, the concentrations of lead ranged from 5
ppb to 60,400 ppb.\185\ States do not provide information regarding the
source of contamination in water bodies where fish tissue
concentrations of lead are above detection limits. Lead concentrations
in fish tissue samples declined from mean concentrations of 0.28 ppm in
1976 to 0.11 ppm in 1984.\186\ The decrease in mean lead concentrations
was attributed primarily to reductions in the lead content of motor
vehicle gasoline. Sources of contamination of lead to waterways
frequently noted include lead gunshot, lead sinkers, and Superfund
sites.\187\ Lead emissions from piston-engine aircraft may contribute
to fish tissue lead concentrations in water bodies that are in close
proximity to piston-engine aircraft activity. In one case, a State
reported lead contaminated fish in a lake on airport property. Piston-
engine aircraft emissions of lead also have the potential to contribute
to fish tissue lead concentrations at water bodies throughout the U.S.
due to the emission of lead in-flight. These in-flight emissions are
greatly dispersed in the environment and have been providing a source
of lead to the environment for over 80 years.
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\184\ In some instances States supply individual fish tissue
sample results and in some instances States supply averages of
multiple fish tissue sample results.
\185\ State-specific fish advisories for lead can be downloaded
from: http://oaspub.epa.gov/nlfwa/nlfwa.bld_qry?p_type=advrpt&p_loc=on.
\186\ U.S. Environmental Protection Agency (2000) Guidance for
Assessing Chemical Contaminant Data for Use in Fish Advisories.
Volume 1: Fish Sampling and Analysis. EPA 823-B-00-007. p. 4-59.
Available online at: http://www.epa.gov/waterscience/fish/advice/volume1/index.html.
\187\ U.S. Environmental Protection Agency, ``Lead Fishing.''.
Retrieved on August 17, 2009 from: http://www.epa.gov/owow/fish/animals.html.
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The Fond du Lac Band of Lake Superior Chippewa, the Leech Lake Band
of Ojibwe and the Mille Lacs Band of Ojibwe submitted comments to the
Lead NAAQS docket noting the importance of fish consumption in their
diet.\188\ The Fond du Lac Band of Lake
[[Page 22464]]
Superior Chippewa also noted in their comments, ``As a reservation with
a municipal airport within its exterior boundaries with two schools and
Tribal housing in close proximity to the airport (one half mile),
leaded aircraft fuel is a concern.'' The Leech Lake Band of Ojibwe
noted in their comments, ``Along with the concerns over the emission
inventory, the Tribes have great concern regarding the amount of lead
from ``small'' prop engine airports. On or very near the Leech Lake
Reservation there are seven prop plane airports with many private air
strips scattered throughout the area.'' EPA is requesting comment on
any information regarding the potential impact of lead emissions from
piston-engine aircraft on aquatic environments.
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\188\ 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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B. Related Exposures of Concern
While the subject of this ANPR is focused on the emissions of lead
from piston-engine aircraft, the use of tetraethyl lead in fuel
contributes to additional public health and welfare issues that are
also of concern to the Agency. Among these issues are: (1) The
contribution of lead emissions to ambient PM, especially in areas in
nonattainment with the PM2.5 NAAQS; (2) the emissions of
ethylene dibromide to the environment; and (3) the evaporative
emissions of tetraethyl lead.
1. Lead Contribution to Ambient Particulate Matter
As discussed in Section IV.A of this ANPR, lead emitted by piston
engines is expected to be predominantly in the particle phase and will
contribute to ambient PM. There are two U.S. National Ambient Air
Quality Standards (NAAQS) for PM2.5: an annual standard (15
[mu]g/m\3\) and a 24-hour standard (35 [mu]g/m\3\). As of March 4, 2009
there are 39 1997 PM2.5 nonattainment areas. Area
designations for the 2006 24-hour PM2.5 NAAQS were
promulgated in 2009 for 31 areas.\189\ All of these nonattainment areas
have at least one airport servicing aircraft using leaded avgas and
most nonattainment areas have several airport facilities. The Los
Angeles-South Coast Air Basin has 343 airport facilities which have a
cumulative lead inventory of 15.0 tons. The contribution of PM-lead to
these nonattainment areas ranges from 0.001 to 0.7% of the mobile
source PM2.5 inventory in these areas. In each of four areas
designated as nonattainment with the PM2.5 annual standard,
there is at least one lead monitor at which design values for 2006-2008
are greater than the 2008 Lead NAAQS and two of these counties have
PM2.5 concentrations exceeding the 24-hour PM2.5
NAAQS. Reductions in lead emissions in these counties would help bring
the area into attainment.
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\189\ http://www.epa.gov/pmdesignations/.
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2. Ethylene Dibromide
As noted in Section IV.A, ethylene dibromide (1,2-dibromoethane) is
added to leaded avgas to scavenge lead in order to prevent the
deposition of lead oxide to valves and spark plugs. Emissions of
ethylene dibromide are a concern to the EPA. Ethylene dibromide is
classified in EPA's Integrated Risk Information System database as
likely to be carcinogenic to humans, and a number of chronic noncancer
effects have been observed in animals and humans exposed to ethylene
dibromide by inhalation and ingestion.\190\ EPA developed an inhalation
reference concentration, ingestion dose and cancer unit risk estimates
for inhalation and ingestion of ethylene dibromide.\191\ Evidence of
nasal tumors, hemangiosarcomas and mesotheliomas in rodents was used by
EPA to develop inhalation unit risk estimates (central tendency
estimates and 95% upper bound estimates) of 3 x 10-\4\ to 6
x 10-\4\ per [mu]g/m\3\. Evidence of forestomach tumors,
hemangiosarcomas, thyroid follicular cell adenomas or carcinomas was
used by EPA to develop drinking water unit risk estimates (central
tendency estimates and 95% upper bound estimates) of 3 x
10-\5\ to 6 x 10-\5\ per [mu]g/L assuming
consumption of 2 L of water per day by a 70 kg human. EPA developed a
reference concentration for chronic inhalation of 9 [mu]g/m\3\ based on
the critical effect of nasal inflammation and a reference dose for
chronic ingestion of 9 [mu]g per kg per day based on the critical
effects of testicular atrophy, liver peliosis, and adrenal cortical
degeneration. The National Toxicology Program listed ethylene dibromide
as ``reasonably anticipated to be a human carcinogen'' in the Eleventh
Report on Carcinogens in 2005.\192\ The International Agency for
Research on Cancer (IARC) has classified ethylene dibromide as a Group
2A carcinogen: probably carcinogenic to humans.-
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\190\ U.S. Environmental Protection Agency (2004) Integrated
Risk Information System (IRIS), IRIS Summary for 1,2-dibromoethane
CASRN 106-93-4. Available online at: http://www.epa.gov/ncea/iris/subst/0361.htm.
\191\ U.S. Environmental Protection Agency (2004) Integrated
Risk Information System (IRIS), Toxicological Review of 1,2-
dibromoethane in support of summary information on the Integrated
Risk Information System. Available online at: http://www.epa.gov/ncea/iris/toxreviews/0361tr.pdf.
\192\ National Toxicology Program (NTP) (2005) 11th Report on
Carcinogens. Public Health Service, U.S. Department of Health and
Human Services, Research Triangle Park, NC. Available from: http://ntp-server.niehs.nih.gov.
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In the additive package used to dose fuel with lead, ethylene
dibromide is added to achieve a lead-to-bromine atom ratio of 1:2 and a
bromine-to-lead weight ratio of 1:2.\193\ The concentration of ethylene
dibromide in leaded avgas is listed as less than 4 milliliters per
gallon (<9 grams per gallon).\194\ Since ethylene dibromide was
measured in the exhaust and evaporative emissions from light-duty
vehicles in the U.S. when they were operated on leaded fuel containing
ethylene dibromide we anticipate piston-engine aircraft are currently a
source of ethylene dibromide to air.\195\ Measurements of ethylene
dibromide have not been made that would allow estimation of the exhaust
and evaporative emissions from piston-engine aircraft as well as the
emissions associated with refueling and pre-flight fuel checks.
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\193\ Thomas VM; Bedford JA; Cicerone RJ. (1997) Bromine
emissions from leaded gasoline. Geophys Res Letters 24(11):1371-
1374.
\194\ Chevron Material Safety Data Sheet for aviation gasoline.
Available online at: http://www.chevronglobalaviation.com/docs/aviation_gas.doc.
\195\ Sigsby, J.E.; Dropkin, D.L.; Bradow, R.L.; Lang, J.M.
(1982) Automotive Emissions of Ethylene Dibromide. SAE Technical
Paper Series 820786.
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In addition to contributing to ambient concentrations, ethylene
dibromide may also enter underground aquifers via leaking underground
storage tanks or fuel spills. Studies demonstrate that ethylene
dibromide may persist for long periods of time in certain groundwater
environments.\196\ The EPA established a Maximum Concentration Level
(MCL) of 0.05 [mu]g/L for ethylene dibromide, which is 100-fold lower
than the MCL for benzene and 300-fold lower than the MCL for lead. The
MCL is the highest level of a contaminant that is allowed in drinking
water and is an enforceable drinking water standard.\197\
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\196\ U.S. Environmental Protection Agency Office of Research
and Development (2008) Natural Attenuation of the Lead Scavengers
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor
Fuel Release Sites and Implications for Risk Management, Chapter 2.
EPA 600/R-08/107. Available online at: http://www.epa.gov/ada.
\197\ U.S. Environmental Protection Agency, ``Drinking Water
Contaminants'' Available online at: http://www.epa.gov/safewater/contaminants/index.html.
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The EPA Office of Underground Storage Tanks (OUST) and Office of
Research and Development's National Risk Management Research Laboratory
(NRMRL) in association with the Association of State and Territorial
[[Page 22465]]
Solid Waste Management Officials (ATSWMO) have formed a team to
evaluate the potential for public health and welfare effects
attributable to ethylene dibromide from past or present fuel leaks and
spills.\198\ Among the goals of the EPA/ATSWMO team is to develop
information on the distribution of ethylene dibromide in groundwater at
leaking underground storage tank sites in States that do not routinely
monitor this contaminant. Water samples for this study were provided by
State agencies to EPA between October 2005 and July 2007. Of the 802
groundwater samples provided from 102 sites, ethylene dibromide was
detected in 54 samples, 43 of which had ethylene dibromide
concentrations above the MCL.\199\ These sites did not include analysis
of groundwater at airports.
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\198\ U.S. Environmental Protection Agency Office of Research
and Development (2008) Natural Attenuation of the Lead Scavengers
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor
Fuel Release Sites and Implications for Risk Management. p.3. EPA
600/R-08/107. Available online at: http://www.epa.gov/ada.
\199\ U.S. Environmental Protection Agency Office of Research
and Development (2008) Natural Attenuation of the Lead Scavengers
1,2-Dibromoethan (EDB) and 1,2-Dichloroethane (1,2-DCA) at Motor
Fuel Release Sites and Implications for Risk Management. p.4. EPA
600/R-08/107. Available online at: http://www.epa.gov/ada.
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While not the focus of this ANPR, ethylene dibromide exposure from
inhalation or ingestion pathways is an ongoing concern for EPA, and
reduction in the use of leaded gasoline containing ethylene dibromide
may reduce exposure and risk to public health and welfare from ethylene
dibromide.
3. Non-Exhaust Exposure to Tetraethyl Lead
Tetraethyl lead is a volatile component of leaded avgas. The
largest source of tetraethyl lead exposure is expected to originate
from evaporative emissions associated with fuel production, fuel
distribution, aircraft refueling, pre-flight fuel checks, accidental
spills, and fuel tank venting. Pilots check fuel for contaminants by
draining a small amount of fuel from each tank sump before flight and
after refueling. This fuel is frequently deposited onto the tarmac
after the fuel check. EPA is interested in data regarding this practice
and any estimates of lead emitted to the air by evaporation of the
alkyl lead in the fuel deposited on the tarmac. Alkyl lead becomes
oxidized in the atmosphere by direct photolysis, reaction with ozone,
and by reaction with hydroxyl compounds. Therefore, depending on
ambient conditions, alkyl lead may exist in the atmosphere for hours to
days.
Pilots, aviation fuel attendants and mechanics are likely to be
among the most highly exposed population to alkyl lead. These
populations are at risk due to both inhalation and possible dermal
exposure. Absorption of inhaled alkyl lead into the bloodstream is
higher than that for inorganic lead compounds which are generally in
particulate form (AQCD for Lead, Section 4.2.1). In addition to
exposure to lead in the exhaust emissions from piston-engine aircraft,
the PBT National Action Plan for Alkyl-lead \200\ noted that aviation
fuel attendants and mechanics are potentially exposed to alkyl lead
emissions due to inhalation of alkyl lead compounds released to the air
during fueling, via evaporative emissions from spills, or via
evaporative emissions from unused gasoline remaining in the engine or
fuel tanks. Further, these populations are also at risk because of
possible dermal absorption of gasoline containing alkyl lead compounds.
Due to the lipophilic nature of alkyl lead and its ability to permeate
biological membranes, alkyl lead is absorbed rapidly and extensively
through the skin (AQCD for Lead, page 4-12). In addition to direct
human exposure, runoff and deposition of alkyl lead to waterways would
increase the amount of lead available for uptake by aquatic plants and
animals (see Section V.A.7 of this ANPR for more information).
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\200\ U.S. Environmental Protection Agency Persistent,
Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT
national action plan for alkyl-Pb. Washington, DC. Page 14.
Available online at: http://www.epa.gov/pbt/pubs/Alkyl_lead_action_plan_final.pdf
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VI. Additional Information Available for the NPRM To Evaluate the
Potential for Public Health and Welfare Impacts and Considerations
Regarding Engine Emission Standards
As noted in the Overview section of this ANPR, in this action we
are describing information currently available and information being
collected that will be used by the Administrator to subsequently
exercise her judgment regarding whether aircraft lead emissions from
avgas use cause or contribute to air pollution which may reasonably be
anticipated to endanger public health or welfare. These additional data
will come from lead monitoring being planned to satisfy requirements of
the Lead NAAQS, air quality modeling planned at EPA that is described
below and any information submitted to EPA during the comment period
for this ANPR.
A. The Lead NAAQS and Lead Emissions From Piston-Engine Aircraft
On November 12, 2008, when EPA promulgated revisions to the Lead
NAAQS, EPA also adopted revisions to ambient air monitoring
requirements for lead, described the approach for implementing the
revised standards, and provided an implementation timeline. We describe
each of these activities as well as more recent activities below. This
section also discusses the most current information available regarding
how implementation of the Lead NAAQS may provide additional data on the
potential for lead emissions from piston-engine aircraft to cause or
contribute to ambient air concentrations that exceed the 2008 Lead
NAAQS.
Acknowledging that the existing monitoring network for lead is not
sufficient to determine whether many areas of the country would meet
the 2008 Lead NAAQS, the EPA re-designed the nation's lead monitoring
network to allow assessment of compliance with the revised lead
standard. Lead monitoring requirements promulgated in 2008 stipulate
that, at a minimum, monitoring agencies must place monitors at maximum
impact areas where lead emissions are greater than or equal to one ton
or more per year. We refer to these monitors as source-oriented
monitors. EPA Regional Administrators may waive the source-oriented
monitoring requirements if the monitoring agency can demonstrate that
emissions from the source will not contribute to maximum air lead
concentrations greater than 50 percent of the revised standard, or
0.075 ug/m\3\. EPA estimated that approximately 135 facilities emit
lead at levels over the one ton emission threshold, making them subject
to the lead monitoring requirements. Lead monitors are operating at a
small number of these sources (described in Section VI.A.2 below). For
the remainder, source-oriented monitors are to be operational by
January 1, 2010.
EPA also required monitors to be operated in each of the 101 urban
areas with populations greater than 500,000 in order to gather
information on the general population's exposure to lead in air. We
refer to these monitors as population-oriented monitors.
Following promulgation of the 2008 Lead NAAQS and monitoring
requirements, the Natural Resources Defense Council, the Missouri
Coalition for the Environment Foundation, Physicians for Social
Responsibility, and the Coalition to End Childhood Lead Poisoning
(Petitioners) petitioned
[[Page 22466]]
EPA for reconsideration of the lead emission rate at which we required
monitoring (the ``emission threshold,'' currently 1.0 tpy).\201\ EPA
granted the petition to reconsider aspects of the monitoring
requirements and proposed revisions to lead ambient air monitoring
requirements in December 2009 (74 FR 69050).
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\201\ The petition is available at: http://www.epa.gov/air/lead/pdfs/OAR.09.000.7687.pdf.
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Also as part of promulgating the 2008 Lead NAAQS, EPA described the
approach for implementing the revised standards and provided an
implementation timeline. EPA will use county boundaries as the
presumptive boundaries for nonattainment areas, and adjustments to
boundaries will be made on case-by-case bases. States in which there is
sufficient monitoring data made recommendations for areas to be
designated attainment, nonattainment, or unclassifiable in October
2009. States update their recommendations to EPA in October 2010 using
any additional monitoring data available from the increased source-
oriented monitoring network described above. Final designations of all
attainment, nonattainment and unclassifiable areas will be effective no
later than January 2012. Where data are sufficient from the currently
existing lead monitoring network, we expect that initial designations
will be effective January 2011. States are directed to submit State
Implementation Plans (SIPs) no later than eighteen months after
designation, outlining how they will reduce pollution to meet the lead
standards. States are required to attain the standards no later than
five years after designation. Additional information regarding the lead
standard implementation is available at http://www.epa.gov/air/lead/actions.html and in the 2008 Lead NAAQS (73 FR 67030-67043).
1. Monitoring Lead at Airports To Evaluate Ambient Concentrations to
Which Lead Emissions From Piston-Engine Aircraft Contribute
Among the estimated 135 source-oriented lead monitoring sites,
there are four airports where we expect lead monitoring to begin in
January 2010. These airports are the Van Nuys Airport in Van Nuys, CA;
the Phoenix Deer Valley Airport in Phoenix, AZ; the Centennial Airport
in Englewood, CO; and the Daytona Beach International Airport in
Daytona Beach, FL. In each of these areas, we will, as data becomes
available, evaluate the impact of lead emissions from piston-engine
aircraft on air quality.
2. Evaluating the Contribution of Lead Emissions From Piston-Engine
Aircraft to Areas Approaching or Exceeding the Lead NAAQS
In this section we discuss available information and information
that will become available in 2010 that can be used to evaluate the
potential for lead emissions from piston-engine aircraft to contribute
to ambient concentrations in areas exceeding the Lead NAAQS. This
evaluation may include the following: (1) Areas currently out of
attainment or designated as maintenance with the 1978 Lead NAAQS; (2)
areas with current lead monitors that are out of attainment with the
2008 Lead NAAQS; and (3) locations that will have new lead monitors to
meet the 2008 Lead NAAQS source-oriented monitoring requirements. In
each of these areas, we will, as data become available, evaluate the
contribution of lead emissions from piston-engine aircraft to lead
inventories and air quality.
The EPA is retaining the 1978 Lead NAAQS until one year after
designations for the 2008 Lead NAAQS, except in current nonattainment
areas. In those areas, EPA will retain the 1978 standard until the area
submits, and EPA approves, attainment and/or maintenance demonstrations
for the new standards. Only two areas, East Helena, MT (including Lewis
and Clark counties), and part of Jefferson County in Herculaneum, MO,
are designated nonattainment with the 1978 Lead NAAQS. The industrial
facility causing nonattainment with the Lead NAAQS in the East Helena
area closed in 2001. Eleven areas are designated as maintenance areas,
only three of which currently have lead monitors. These three locations
(Iron County, MO, Dakota County MN, and Collin County, TX) have lead
monitors with design value concentrations exceeding the 2008 Lead
NAAQS. The design value is the highest ``rolling'' three month average
over a three-year period that is relevant for comparison to the level
of the 2008 Lead NAAQS.
Implementation of the 2008 Lead NAAQS is underway, and we have not
yet designated areas under it. When EPA promulgated the 2008 Lead
NAAQS, EPA provided a list of 18 counties with design values exceeding
the 2008 lead standard of 0.15 [micro]g/m\3\. Using more recent data
from EPA's Air Quality System, there are 14 sites at which design
values exceed the 2008 Lead NAAQS (Table 3). Over 4.6 million people
live in the counties where design values are greater than the 2008 Lead
NAAQS. After EPA designates areas that currently have sufficient lead
monitoring data, no later than October 15, 2010, we will evaluate the
contribution of lead emissions from piston-engine aircraft to lead
inventories in nonattainment, maintenance and in some cases,
unclassifiable areas, depending on the presence of point sources of
lead and the status of ambient lead monitoring in those areas.
Table 3--Counties With Maximum Rolling Quarterly Average Lead Concentrations Exceeding the 2008 Lead NAAQS
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County Design value,
County, state EPA region population 2006-2008
(2000 Census) ([mu]g/m\3\)
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Jefferson, MO................................................... 7 198,099 2.89
Iron, MO........................................................ 7 10,697 2.46
Delaware, IN.................................................... 5 118,769 2.16
Hillsborough, FL................................................ 4 998,948 1.77
Collin, TX...................................................... 6 491,675 1.26
Pike, AL........................................................ 4 29,605 1.21
Dakota, MN...................................................... 5 355,904 0.70
Fulton, OH...................................................... 5 42,084 0.69
Berks, PA....................................................... 3 373,638 0.36
Madison, IL..................................................... 5 258,941 0.28
Logan, OH....................................................... 5 46,005 0.27
[[Page 22467]]
Sullivan, TN.................................................... 4 153,048 0.26
Beaver, PA...................................................... 3 181,412 0.20
Cuyahoga, OH.................................................... 5 1,393,978 0.17
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Lead emissions from piston-engine aircraft operating at airports
outside nonattainment areas can also contribute to lead measured in the
nonattainment area. In addition, other sources of lead that do not, by
themselves, exceed the lead emission monitoring threshold may be
located near airports. For example, at some airports in the U.S., race
track venues are located immediately adjacent to runways where piston-
engine aircraft operate. We are seeking information regarding ambient
concentrations of lead that can result from the combined emissions of
leaded fuel used in some race vehicles, lead emissions from piston-
engine aircraft and other sources of ambient lead.
The EPA intends to conduct modeling analyses to evaluate the
contribution of these lead emissions to nonattainment areas and areas
that may be approaching nonattainment concentrations. Lead emitted by
piston-engine aircraft flying through nonattainment areas may also
contribute to lead measured in the nonattainment area. These emissions
would be potentially challenging to quantify, although a series of
scoping analyses could be conducted. We seek comment on characterizing
the contribution of lead emissions from piston-engine aircraft flying
through areas that are not attaining the 2008 Lead NAAQS and the
potential contribution of piston-engine lead emissions that may be
transported into lead nonattainment areas.
As noted above, approximately 135 new lead monitors will begin
collecting ambient lead samples starting in January 2010 in order to
satisfy the source-oriented monitoring requirements of the 2008 Lead
NAAQS. In the NPRM we will discuss the potential contribution of lead
from piston-engine aircraft to these areas where the ambient data
suggest lead concentrations are close to or exceeding the 2008 Lead
NAAQS of 0.15 [mu]g/m\3\.
B. Additional Information EPA Is Collecting To Evaluate Ambient Lead
Concentrations Attributable to Emissions From Piston-Engine Aircraft
In 2008 EPA initiated a study to provide information regarding the
local-scale gradient in lead concentrations on- and near airport
facilities with piston-engine powered aircraft activity.\202\ This
study focused mainly on developing an approach for modeling lead
emissions from piston-engine aircraft using the Meteorological Society
(AMS)/EPA Regulatory Model (AERMOD), and evaluating it using air
quality measurements. For purposes of local-scale dispersion modeling,
AERMOD is EPA's preferred model.\203\ The approach developed includes
apportioning lead emitted during landing and take-off to different
altitudes in order to characterize emissions during these modes of
operation in a realistic manner. In addition, this modeling study
includes analysis of the spatial and temporal emissions from piston-
engine aircraft during the other modes of aircraft operation (e.g.,
taxi, run-up check, take-off, landing). The modeling results include an
evaluation of the relative contributions of all known sources of lead
to the local ambient air, including piston-engine aircraft, local
traffic, resuspended road dust, and industrial sources within 20 km of
the airport selected for our case study. The EPA study at the Santa
Monica Airport was recently completed.\204\
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\202\ U.S. EPA (March 2010) Memorandum from Marion Hoyer to the
docket EPA-HQ-OAR-2007-0294, titled, ``Work Plan for Air Quality
Modeling and Monitoring of Lead Emissions from Piston-Engine Powered
Aircraft.'' Docket number EPA-HQ-OAR-2007-0294.
\203\ The EPA provides modeling guidance for AERMOD at http://www.epa.gov/ttn/scram/guidanceindex.htm and http://www.epa.gov/scram001/dispersion_prefree.htm#aermod. A post-processor for AERMOD
that reads model output and calculates rolling 3-month averages for
the period modeled to provide lead concentrations that can be
compared with the Lead NAAQS is available online at: http://www.epa.gov/ttn/amtic/files/ambient/pb/leadpost.zip.
\204\ The report from this study is posted at http://www.epa.gov/otaq/aviation.htm.
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As part of this work, we collected air, soil and house dust samples
for lead analysis in order to conduct a model-to-monitor evaluation,
and to evaluate the potential for lead emissions from piston-engine
aircraft to create a gradient in air, soil and house dust
concentrations of lead in proximity to the airport activities.
We selected the Santa Monica municipal airport for this study
because of the data available from the monitoring study conducted by
the SCAQMD in 2005-2007 discussed in Section IV.B of this ANPR. In
addition, there are no major point sources of lead in close proximity
to the airport, simplifying the model development and interpretation of
monitoring results.
EPA intends to use this modeling approach to evaluate potential for
exceedance of the Lead NAAQS on airport property and surrounding areas,
as well as providing an approach to characterize the contribution of
lead emissions from piston-engine aircraft to areas with ambient lead
concentrations currently exceeding the 2008 Lead NAAQS. This modeling
approach will also allow us to quantify the changes in ambient lead
concentrations following the implementation of different piston-engine
control strategies. The application of this modeling approach to a
case-study airport could also be used as input to conduct a risk
assessment evaluating the potential contribution of lead from piston-
engine emissions on blood lead levels and IQ deficits for those living
near or attending school near general aviation activity.
We request comment on all information EPA is collecting to evaluate
ambient lead concentrations attributable to emissions from piston-
engine aircraft and risk posed by emissions of lead from piston-engine
aircraft.
C. Considerations Regarding Engine Emission Standards
A positive endangerment and cause or contribute finding with
respect to the emissions of lead from general aviation aircraft would
trigger EPA's duty to set emission standards. In considering emission
standards, EPA would consider controlling emissions from piston engines
using aviation gasoline in aircraft. In cooperation with FAA, EPA would
evaluate the technical feasibility of a possible phase-down or
elimination of leaded aviation gasoline. One option to consider, for
example, could be an emissions standard
[[Page 22468]]
(established under 40 CFR 87) that would require all newly-manufactured
general aviation piston engines to be able to operate with appropriate
reliability and durability on unleaded aviation gasoline by some future
date. Such a standard might require that new engines used in aircraft
would have to receive an FAA type certificate that reflects achievement
of these requirements under FAA regulations set forth at 14 CFR parts
33/34.
Beyond this, EPA recognizes that there is a big challenge in
dealing with the in-use fleet. Converting in-use aircraft/engines to
operate on unleaded aviation gasoline would be a significant logistical
challenge, and in some cases a technical challenge as well. In many
cases, the implementation of this concept might depend upon efforts and
actions of aircraft and engine manufacturers in identifying the
necessary modifications and developing hardware as necessary. Depending
on timing, these engines might need to be able to operate on either
leaded or unleaded aviation gasoline, or a blend thereof. EPA
recognizes that in many cases these modifications could trigger the
need for FAA regulatory approval of the modifications for both the
engines and airframes. Given the potentially large number of affected
aircraft and the potential complexities involved, a program affecting
in-use aircraft engines would need careful consideration by both EPA
and FAA and the two agencies would need to work together in considering
any potential program affecting the in-use fleet.
EPA requests comment on this outline of approaches for
transitioning the fleet to unleaded aviation gasoline, as well as
potential implementation dates, if EPA were to trigger the duty to set
emission standards. Comment is also requested on how a program could be
best structured to assure that conversions conducted by engine
manufacturers (OEMs), independent shops, and in the field by certified
power plant mechanics are performed to fully meet the intent of a
possible program without compromising the safety of those aircraft and
engines. EPA also asks for comment on potential problems with this
approach including suggested modifications, improvements, or other
approaches. EPA is requesting comment on potential implications for
international import and export of piston engines and aviation fuel, as
well as potential impacts on international transport. Finally, EPA
requests comment on how market incentives might be developed to
encourage modification to run on unleaded aviation gasoline as part of
a regulatory requirement.
As part of the responses to the Federal Register notice EPA
published in November 2007 entitled ``Petition Requesting Rulemaking to
Limit Lead Emissions from General Aviation Aircraft,'' EPA received a
number of comments addressing both technology and fuel-based options as
potential measures to reduce or eliminate lead in avgas.\205\ In
addition to these comments, EPA is aware of completed and ongoing work
done under the auspices of the Coordinating Research Council and more
recent viewpoints and efforts put forth by industry trade associations,
airframe/engine manufacturers, specialty vendors, aviation user groups,
and other innovators. The work and perspectives of these groups on
technology and avgas fuel quality options are important, and EPA asks
for further comment reflecting any new data on technology developments,
fuel formulation approaches, or other technical viewpoints.
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\205\ 72 FR 64570 (Nov. 16, 2007); EPA Docket EPA-HQ-OAR-2007-
0294.
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According to Department of Energy data, annual demand for aviation
gasoline is very small in comparison to motor gasoline yet its use is
as geographically widespread. This of course creates challenges for
supply, distribution, and storage. EPA asks for comment on the avgas
refining locations and practices, supply (including imports and
exports, if any), details on distribution to terminals and airports,
and storage practices for avgas at terminals and airports across the
country. EPA is also interested in comments on progress and timeframes
for developing alternatives to current leaded avgas and how these might
be integrated into the fuel supply and distribution system.
VII. Statutory and Executive Order Reviews
Under Executive Order 12866, entitled Regulatory Planning and
Review (58 FR 51735, October 4, 1993), this is a ``significant
regulatory action'' because of the cross-agency nature of this issue.
Accordingly, EPA submitted this action to the Office of Management and
Budget (OMB) for review under Executive Order 12866 and any changes
made in response to OMB recommendations have been documented in the
docket for this action. Because this action does not propose or impose
any requirements, other statutory and Executive Order reviews that
apply to rulemaking do not apply. Should EPA subsequently determine to
pursue a rulemaking, EPA will address the statues and Executive Orders
as applicable to that rulemaking.
Nevertheless, the Agency welcomes comments and/or information that
would help the Agency to assess any of the following: Tribal
implications pursuant to Executive Order 13175, entitled Consultation
and Coordination with Indian Tribal Governments (65 FR 67249, November
6, 2000); environmental health or safety effects on children pursuant
to Executive Order 13045, entitled Protection of Children from
Environmental Health Risks and Safety Risks (62 FR 19885, April 23,
1997) and human health or environmental effects on minority or low-
income populations pursuant to Executive Order 12898, entitled Federal
Actions to Address Environmental Justice in Minority Populations and
Low-Income Populations (59 FR 7629, February 16, 1994). The Agency will
consider such comments during the development of any subsequent
rulemaking.
Dated: April 20, 2010.
Lisa P. Jackson,
Administrator.
[FR Doc. 2010-9603 Filed 4-27-10; 8:45 am]
BILLING CODE 6560-50-P