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.
---------------------------------------------------------------------------

    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

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 <IP_ADDRESS>). 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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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

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\
---------------------------------------------------------------------------

    \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).
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \149\ Average concentrations reported in this study include
three days of short-duration sampling so the average is not used for
comparison here.
---------------------------------------------------------------------------

    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

background lead concentration was 0.003 and 0.004 [mu]g/m\3\ in April
and July, respectively.
---------------------------------------------------------------------------

    \150\ These distances were measured using Google Earth Pro
software.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \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

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

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

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 <IP_ADDRESS>.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
<IP_ADDRESS>.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)).
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    \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

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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/.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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.
---------------------------------------------------------------------------

    \189\ http://www.epa.gov/pmdesignations/.
---------------------------------------------------------------------------

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.-
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

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.
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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).
---------------------------------------------------------------------------

    \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
---------------------------------------------------------------------------

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

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).
---------------------------------------------------------------------------

    \201\ The petition is available at: http://www.epa.gov/air/lead/pdfs/OAR.09.000.7687.pdf.
---------------------------------------------------------------------------

    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
----------------------------------------------------------------------------------------------------------------
                                                                                County       Design value,
                          County, state                             EPA region      population       2006-2008
                                                                                (2000 Census)   ([mu]g/m\3\)
----------------------------------------------------------------------------------------------------------------
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

Sullivan, TN....................................................               4         153,048            0.26
Beaver, PA......................................................               3         181,412            0.20
Cuyahoga, OH....................................................               5       1,393,978            0.17
----------------------------------------------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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

(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.
---------------------------------------------------------------------------

    \205\ 72 FR 64570 (Nov. 16, 2007); EPA Docket EPA-HQ-OAR-2007-
0294.
---------------------------------------------------------------------------

    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