Calculating Piston-Engine Aircraft
Airport Inventories for Lead for the
2008 National Emissions Inventory
&EPA
United States
Environmental Protection
Agency
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Calculating Piston-Engine Aircraft
Airport Inventories for Lead for the
2008 National Emissions Inventory
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
&EPA
United States
Environmental Protection
Agency
EPA-420-B-10-044
December 2010
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Calculating Piston-Engine Aircraft Airport Inventories for Lead for the 2008
National Emissions Inventory
December 2010
Section 1. Introduction
The main purpose of this document is to describe the methods the Environmental
Protection Agency (EPA) used to calculate airport lead (Pb) inventories for the 2008
National Emissions Inventory (NEI).l These methods focus on the development of
approaches to estimate piston-engine aircraft activity at airports in the U.S. since the
activity of this fleet is reported to the Federal Aviation Administration (FAA) as general
aviation (GA) or air taxi (AT) activity - categories that also include jet-engine aircraft
activity. The methods described here reflect improvements to the methods used in
developing the airport-specific piston-engine aircraft inventories in the 2002 NEI and the
2005 NEI.
Background information regarding the use of leaded aviation gasoline (avgas) in
piston-engine powered aircraft is available in other documents.2'3 Briefly, most piston-
engine aircraft operations fall into the categories of either GA or AT. Aircraft used in
GA and AT activities include a diverse set of aircraft types and engine models and are
used in a wide variety of applications.4 Lead emissions associated with GA and AT
aircraft stem from the use of one hundred octane low lead (100LL) avgas. The lead is
added to the fuel in the form of tetraethyl lead (TEL). This lead additive helps boost fuel
octane, prevent engine knock, and prevent valve seat recession and subsequent loss of
compression for engines without hardened valves. Today, 100LL is the most commonly
available type of aviation gasoline in the United States.5 Lead is not added to jet fuel that
is used in commercial aircraft, most military aircraft, or other turbine-engine powered
aircraft. Lead emissions from the use of leaded avgas comprised 45% of the national
inventory for emissions of lead in 2002.6
1 In this document '2008 NEF refers to 2008 NEI version 1 (January 2011), available at
http://www.epa.gov/ttn/chief/net/2008inventory.html
2 EPA (2007) Review of the National Ambient Air Quality Standards for Lead: Policy Assessment of
Scientific and Technical Information. OAQPS Staff Paper. EPA-452/R-07-013 November 2007. pp 2-8 and
2-9.
3FAA William J. Hughes Technical Center
http://www.tc.faa.gov/act4/insidethefence/2006/0609_06_AvFuels.htm
4 Commercial aircraft include those used for scheduled service transporting passengers, freight, or both.
Air taxis fly scheduled and for-hire service carrying passengers, freight or both, but they usually are smaller
aircraft than those operated by commercial air carriers. General aviation includes most other aircraft (fixed
and rotary wing) used for personal transportation, business, instructional flying, and aerial application.
5 ChevronTexaco (2005) Aviation Fuels Technical Review. FTR-3.
http://www.chevronglobalaviation.com/docs/aviation tech review.pdf
6 U.S. Environmental Protection Agency (2008) EPA's Report on the Environment EPA/600/R-07/045F.
Available at: http://www.epa.gov/roe
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This document is organized into eight sections. Section 2 describes the data we
use to calculate the national inventory for the amount of lead released to the air from the
combustion of leaded avgas. Section 3 describes the landing and takeoff data we use to
calculate airport-specific inventories for lead. Section 4 describes how we estimate
landing and takeoff data for the airport facilities that do not report it to the F AA. Section
5 describes the estimate of landing and takeoff activity occurring at heliports in the U.S.
Section 6 describes the methods used to calculate the airport-specific inventories for lead.
Section 7 describes data that would be needed to improve the estimates of airport-specific
inventories for lead and Section 8 describes the estimates of the amount of lead emitted
in-flight that are in the 2008 NEI.
In this document, units of tons (i.e., U.S. short tons) are used when discussing the
national and airport-specific lead inventory in order to be consistent with the manner in
which the NEI reports inventories for lead and other pollutants. The unit of grams is used
in describing the concentration of lead in avgas and in describing emission factors.
Conversion factors are provided for clarity.
Section 2. Calculating the National Avgas Lead Inventory
Because lead is a persistent pollutant and accumulates in the environment, we
include all lead emissions from piston-engine aircraft in the NEI - emissions occurring
during the landing and take-off cycle at airports as well as emissions occurring at
altitude.7 To calculate the national avgas lead inventory, we use information provided by
the U.S. Department of Transportation's (DOT's) Federal Aviation Administration
(FAA) regarding the volume of leaded avgas consumed in the U.S. in 2008.8 The U.S.
Department of Energy's (DOE's) Energy Information Administration (EIA) provides
information regarding the volume of leaded avgas produced in a given year. EPA has
historically used the DOE EIA avgas fuel volume produced to calculate national lead
inventories from the consumption of leaded avgas. However, since EPA uses DOT
airport activity and aircraft data, we are using the DOT fuel volume data in the 2008 NEI
to calculate the national lead inventory in order to use a consistent data source. In this
document, when we refer to avgas fuel volume data it is data supplied by DOT, except
where noted.
As demonstrated in the equation below, to calculate the annual emission of lead
from the consumption of leaded avgas, we multiply the volume of avgas used by the
concentration of lead in the avgas, minus the small amount of lead that is retained in the
engine, engine oil and/or exhaust system. The volume of avgas used in the U.S. in 2008
7 U.S. EPA, 2006. Air Quality: Criteria for Lead: 2006; EPA/600/R-5/144aF; U.S. Government Printing
Office, Washington, DC, October, 2006.
8 U. S. Department of Transportation Federal Aviation Administration Aviation Policy and Plans. FAA
Aerospace Forecast Fiscal Years 2010-2030. p.99. Available at:
http://www.faa.gov/data_research/aviation/aerospace_forecasts/2010-
2030/media/2010%20Forecast%20Doc.pdf This document provides historical data for 2000-2008 as well
as forecast data.
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was 248,100,000 gallons.9 The concentration of lead in avgas ([Pb] in the equation
below) can be one of four levels (ranging from 0.14 to 1.12 grams of lead per liter) as
specified by the American Society for Testing and Materials (ASTM). By far the most
common avgas supplied is "100 Low Lead" or 100LL. 10'u The maximum lead
concentration specified by ASTM for 100LL is 0.56 grams per liter or 2.12 grams per
gallon.12 A fraction of lead is retained in the engine, engine oil and/or exhaust system
which we currently estimate at 5%.13
For the 2008 NEI, the national estimate of lead emissions from the consumption
of avgas was 551 tons (see equation below).
(248.100.000 gaiy2.12gPb7gaiyo.95) = 551 tons Pb
907,180 g/ton
As described above, DOE's EIA also provides estimates of the annual volume of
leaded avgas produced in a given year. For 2008, the volume of avgas produced in the
U.S. was 5,603 thousand barrels or 235,326,000 gallons.14 Consumption of this volume
of avgas equates to a national lead emissions estimate for this source of 522 short tons.
Section 3. Landing and Takeoff Data Sources and Uses
Airport-specific inventories require information regarding landing and takeoff
(LTO) activity by aircraft type.15 According to FAA records, there are approximately
20,000 airport facilities in the U.S., the vast majority of which are expected to have
activity by piston-engine aircraft that operate on leaded avgas. Of these facilities, EPA's
NEI has in the past, reported emissions of lead (and other criteria pollutants and
9 U. S. Department of Transportation Federal Aviation Administration Aviation Policy and Plans. FAA
Aerospace Forecast Fiscal Years 2010-2030. p.99. Available at:
http://www.faa.gov/data_research/aviation/aerospace_forecasts/2010-
2030/media/2010%20Forecast%20Doc.pdf This document provides historical data for 2000-2008 as well
as forecast data.
10 ChevronTexaco (2005) Aviation Fuels Technical Review. FTR-3.
11 The 2008 General Aviation Statistical Databook & Industry Outlook report by General Aviation
Manufactures Association (GAMA) found that over 90% of avgas is 100LL.
12 ASTM International (2005) Annual Book of ASTM Standards Section 5: Petroleum Products,
Lubricants, and Fossil Fuels Volume 05.01 Petroleum Products and Lubricants (I): D 56 - D 3230.
13 The information used to develop this estimate is from the following references: (a) Todd L. Petersen,
Petersen Aviation, Inc, Aviation Oil Lead Content Analysis, Report # EPA 1-2008, January 2, 2008,
available at William J. Hughes Technical Center Technical Reference and Research Library at
http://actlibrary.tc.faa.gov/ and (b) E-mail from Theo Rindlisbacher of Switzerland Federal Office of Civil
Aviation to Bryan Manning of U.S. EPA, regarding lead retained in engine, September 28, 2007.
14 DOE Energy Information Administration. Fuel production volume data obtained from
http://tonto.eia.doe.gov/dnav/pet/hist/mgaupuslA.htm accessed November 2006.
15 An aircraft operation is defined as any landing or takeoff event, therefore, to calculate LTOs, operations
are divided by two. Most data sources from FAA report aircraft activity in numbers of operations which,
for the purposes of calculating lead emissions using the method described in this document, need to be
converted to LTO events.
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hazardous air pollutants) at 3,410 airports.16 While the 3,410 airport facilities are among
the most active in the U.S., they comprise only a small fraction of the total airport
facilities where leaded avgas is used.
FAA's Office of Air Traffic provides a complete listing of operational airport
facilities in the National Airspace System Resources (NASR) database. The electronic
NASR data report, referred to here as the 5010 airport data report, can be generated from
the NASR database and is available for download from the FAA website.1? This report is
updated every 56 days. EPA obtains airport information (including operations) for a
subset of the facilities in the NASR database from FAA's Terminal Area Forecast (TAP)
database that is prepared by FAA's Office of Aviation Policy and Plans.18 The TAP
database currently includes information for airports in FAA's National Plan of Integrated
Airport Systems (NPIAS), which identifies airports that are significant to national air
transportation. Approximately 500 of the airports that are in the TAP database have
either an FAA air traffic control tower or an FAA contract tower where controllers count
operations. The operations data from the control towers is reported to The Operations
Network (OPSNET)19 which is publically available in the Air Traffic Activity System
90
(ATADS) database. The operations data for the towered airports that is reported in
OPSNET and ATADS is then reported to the TAP database. The operations data for the
airports in the TAP database that do not have control towers represent estimates.21 The
operations supplied in the 5010 airport data report for facilities not reported in the TAP
may be self-reported by airport operators through data collection accomplished by airport
inspectors who work for the State Aviation Agency, or operations data can be obtained
through other means.22
The 5010 airport data report supplies the date that the associated operations data
represents.23 Because airports that are not in the TAP database submit data voluntarily to
FAA for the 5010 data report, many of the airports have operations data that represent
data for years earlier than 2008. Nationally, GA and AT piston-engine operations have
decreased in recent years,24 therefore EPA did not use operations data from years prior to
2008 as it is reported. Instead, EPA multiplied the older GA and AT piston-engine data
(Section 6 describes the method EPA used to calculate the number of piston-engine
16 These 3,410 facilities are the facilities for which the FAA's Terminal Area Forecast (TAP) database
provides information regarding aircraft activity. The TAP database is prepared by FAA's Office of
Aviation Policy and Plans and includes information for the airports in FAA's National Plan of Integrated
Airport Systems (NPIAS). One of the goals of the NPIAS is to identify airports that are significant to
national air transportation.
17 http://www.faa.gov/airports airtraffic/airports/airport safetv/airportdata_5010/
18 http://aspm.faa.gov/main/taf.asp
19 http://aspm.faa.gov/opsnet/sys/
20 http://aspm.faa.gov/opsnet/sys/Airport, asp
21 FAA's Terminal Area Forecast Summary (Fiscal Years 2009 - 2030), Appendix A (page 28)
http://www.faa.gov/data_research/aviation/taf_reports/media/TAF%20Summary%20Report%20FY%2020
09%20-%202030.pdf
22 In the absence of updated information from States, local authorities or Tribes, we are using the LTO data
provided in the FAA database.
23 The 12-month ending date on which annual operations data in the report is based.
24http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/
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operations from total GA and AT activity data) by scaling factors that were calculated by
dividing the 2008 national amount of avgas produced by the national amount of avgas
produced in the year the operations data represents.25 A table with the scaling factors is
provided in Appendix A. The national volume of avgas produced data comes from the
DOE, EIA website and is available for 1981 - 2009.26 For operations data older than
1981, EPA divided the 2008 national amount of avgas produced by the average of the
national amount of avgas produced from 1981 - 1989. Jet engines do not use avgas,
therefore EPA did not apply scaling factors to the turbine operations for data from years
prior to 2008.
EPA also obtains operations data from the T-100 segment data from the Bureau of
Transportation Statistics (BTS). The aircraft in the T-100 data are matched to aircraft in
the FAA's Emission and Dispersion Modeling System (EDMS) using the crosswalk table
developed for earlier versions of the NEI. Generally the T-100 data covers commercial
air carrier operations, but some AT activities are included in the data set that would
double count with the TAP data at the same airport. To correct for possible double
counting, first the AT LTOs included in the T-100 data were compiled using the aircraft
type data included in the aircraft make/models crosswalk.27 The resulting aggregated
LTOs were compared with the reported TAP LTOs for airports where there were
overlaps. The T-100 AT LTOs were then subtracted from the TAF AT data to ensure
that double counting was minimized. Note that if the T-100 AT value was larger than the
TAF value, the TAF value was set to zero to eliminate the possibility of negative LTOs in
the dataset.
The 2008 draft NEI was developed using the January 15, 2009 version of the
5010 airport data report. In that version of the report there were 19,925 airport facilities
in the U.S. that had submitted data to the FAA. Among these 19,925 facilities, 99
facilities were not relevant for the purposes of estimating lead emissions because they
9R
were either listed as closed (85) or they were balloonports (14). Therefore, lead
inventories were needed for 19,826 facilities. In the January 15, 2009 version of the 5010
airport data report there were 5,654 airport facilities for which operations data were
provided (many of which are facilities in FAA's TAF database).29 There were 14,172
facilities in the 5010 airport data report for which there were no operations data.30 As a
25 The FAA General Aviation and Air Taxi (Part 135) Activity Surveys (source of national level piston-
engine operations data) are only available annually, starting in 1999. Because there are airports with
operations data older than 1999, EPA used avgas product supplied data as a surrogate for piston-engine
operations to estimate the change in piston-engine activity over the last three decades.
26 http://tonto.eia.doe. gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=mgaupus 1 &f= A. DOT recently
changed the way they estimate fuel consumption data, so while EPA used DOT data to determine the 2008
national avgas lead inventory, for the purpose of calculating these scaling factors EPA used DOE's data in
order to have historical fuel data that is calculated in a consistent manner.
27 The T-100 data does not specify that the operations data is air taxi in nature; however, in discussions with
FAA, EPA determined that these flights are air taxi in nature and has assigned them in the 2008 NEI as
such.
28 Balloon craft do not use avgas
29 Either Commuter, GA Itinerant, GA Local, or Air Taxi operations data, as these operations can be
performed by piston-engine aircraft.
30 No Commuter, GA Itinerant, GA Local, or Air Taxi operations data.
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part of the review process for the draft 2008 NEI, EPA received updated airport data from
states and also looked at more recent versions of the 5010 airport data report to update the
status of airports, so the number of airports for which EPA estimated activity is slightly
lower in the 2008 NEI than in the draft 2008 NEI. The following section of this
document describes the method EPA used to estimate operations for the 14,132 airport
facilities in the 2008 NEI that do not have reported activity data.
As described in Section 1, most piston-engine aircraft fall into the categories of
either GA or AT. Some GA and AT activity is conducted by turboprop and turbojet
aircraft which do not used leaded avgas. There are no national databases that provide
airport-specific LTO activity data for piston-engine aircraft separately from turbojet and
turboprop aircraft. The databases described above report total GA and AT activity
conducted by both piston-engine and j et-engine aircraft. Part (a) in Section 6 describes
how we estimate piston-engine LTOs at airports in the 2008 NEI.
Section 4. Estimating LTOs at the 14,132 Airport Facilities with No LTO Data
FAA has used regression models to estimate operations at facilities where
operations data are not available.31'32 In this work and other work, FAA identified
characteristics of small towered airports for which there were statistically significant
relationships with operations at these airports.33 Regression models based on the airport
characteristics were then used to estimate general aviation operations for a set of non-
towered airports. The airport characteristics identified by FAA and used to estimate
general aviation operations at small airports include: the number of aircraft based at a
facility (termed 'based aircraft'), population in the vicinity of the airport, airport regional
prominence, per capita income, region, and the presence of certificated flight schools.
In the 2000 report titled 'Model for Estimating General Aviation Operations at
Non-towered Airports,' a model of GA annual activity was developed using information
from small towered airports to explain GA activity at towered and non-towered airports.
The model explained GA activity at the towered airports well (R2 of 0.75) but produced
higher estimates than state-supplied estimates for non-towered airports.34
The relevant data available in the 5010 airport data report for the purposes of
estimating airport operations include: facility type (airport, balloonport, seaplane base,
gliderport, heliport, stolport,35 ultralight); number of GA aircraft based at each airport by
31 Federal Aviation Administration, Office of Aviation Policy and Plans, Statistics and Forecast Branch.
July 2001. Model for Estimating General Aviation Operations at Non-towered Airports Using Towered
and Non-towered Airport Data. Prepared by GRA, Inc.
32 Mark Hoekstra, "Model for Estimating General Aviation Operations at Non-Towered Airports" prepared
for FAA Office of Aviation Policy and Plans, April 2000.
33 GRA, Inc. "Review of TAP Methods," Final Report, prepared for FAA Office of Aviation Policy and
Plans under Work Order 45, Contract No. DTFA01-93-C-00066, February 25, 1998.
34 The mean absolute difference between the model operations estimate and the state operations estimate
was 16,940 operations.
35
Stolport is an airport designed with STOL (Short Take-Off and Landing) operations in mind, normally
having a short single runway.
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type (glider, helicopter, jet engine, military, multi-engine, single engine, ultralight);
operations data (air taxi, commercial, commuter, GA itinerant, GA local, military)36; and
operations date (12-month ending date on which annual operations data is based).
Census data was also merged with the 5010 airport data report to give population data for
each airport's county.
Using the FAA work referenced above, we explored relationships among the
airport data variables that best predicted aircraft activity (LTOs). We found that based
aircraft was a highly significant and positive regressor to LTOs. Table 1 shows that for
facilities that did not have LTO data in the January 15, 2009 version of the 5010 airport
data report, 7,856 had based aircraft data while 6,316 did not have based aircraft data.37'
00
Therefore, as described below, LTO estimates were derived using different methods
depending on data availability.
Table 1: Contingency table describing the numbers of airport facilities that have or do
not have LTO data and/or based aircraft data for airport facilities in the January 15, 2009
version of the 5010 airport data report
HAVE LTO DATA
HAVE
BASED
AIRCRAFT
DATA
YES
NO
YES
4,872
782
5,654
NO
7,856
6,316
14,172
12,728
7,098
19,826
36 As explained in footnote 15, an aircraft operation is defined as any landing or takeoff event, therefore, to
calculate LTOs, operations are divided by two. The 5010 airport data report from FAA reports aircraft
activity in numbers of operations which, for the purposes of calculating Pb emissions using the method
described in the TSD, are converted to LTO events.
37 As described in Section 3, the number of facilities with no LTO data changed slightly from the draft 2008
NEI to the 2008 NEI. In the 2008 NEI, of the facilities that did not have reported activity data, 7,837
facilities reported based aircraft data and 6,295 did not report based aircraft data.
38 These numbers include data for the following types of facilities: airports, balloonports, seaplane bases,
gliderports, heliports, stolports, and ultralights.
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(a) Estimating LTOs at Facilities with Based Aircraft Data, but No LTO Data:
There are 6,414 facilities in the 2008 NEI (not including heliports) for which the
5010 airport data report supplies the number of based aircraft39 but not activity data to
which the regression equation (based aircraft vs. LTOs) could be applied. Using the
4,872 airports for which both LTO and aircraft data is known, the initial relationship
found between based aircraft and LTOs was:
Equation 1:
LTOs = 2494 + 208*aircraft R2 = 0.55
The FAA models found population to be another significant regressor. We used
the population of the county in which the airport is located as the population variable.
Adding county population to the model gave the following relationship:
Equation 2:
LTOs = 2204 + 194*aircraft + 0.0038*county population R2 = 0.56
EPA received numerous comments to the docket on its Advance Notice of
Proposed Rulemaking on Lead Emissions from Piston-Engine Aircraft Using Leaded
Aviation Gasoline40 indicating that aviation in Alaska is different than it is in the
continental U.S. Commenters pointed out that in Alaska, 82% of communities are not
accessible by road and rely on air transport for life sustaining goods and services.41
Commenters also noted that Alaskans travel by air eight times more often per capita than
those in the continental U.S. For those reasons, we added a dummy variable in equation
3 to identify whether or not an airport is located in Alaska. Because the relationship
between based aircraft and LTOs is likely different for Alaskan airports than it is for
airports that aren't in Alaska, we also added an interaction term to equation 3 (interaction
of an airport being in Alaska and its sum of based aircraft).
Equation 3:
LTOs = 1937 + 205*aircraft + 0.0038*county population + 566*Alaska -
108*(AlaskaXaircraft)
R2 = 0.58
After analyzing the data and plot for the data underlying equation 3, we found
many airport facilities identified as commercial airports for which based aircraft was
extremely low (i.e., less than 10), yet LTOs were quite high (i.e., anywhere from 100,000
39 Based aircraft for this purpose was limited to single- and multi-engine aircraft, helicopters, and
ultralights since these aircraft types can use leaded avgas.
40 U.S. Environmental Protection Agency (2010) Advance Notice of Proposed Rulemaking on Lead
Emissions From Piston-Engine Aircraft Using Leaded Aviation Gasoline. 75 FR 22440 (April 28, 2010).
41 Comments to the docket on EPA's Advance Notice of Proposed Rulemaking on Lead Emissions from
Piston-Engine Aircraft Using Leaded Aviation Gasoline from the Alaska Air Carriers Association (dated 18
June 2010; comment number OAR-2007-0294-0323.1) and Alaska Governor Parnell (dated 25 August
2010; comment number OAR-2007-0294-0403.1).
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to more than 200,000 LTOs/year).42 These facilities were removed from the regression
analysis. Additionally, for reasons described below, heliports were also removed from
the regression. The resulting relationship was:
Equation 4:
LTOs = 1293 + 203*aircraft + 0.0019*county population - 473*Alaska -
144*(AlaskaXaircraft)
R2 = 0.65
When equation 4 was applied to the 6,414 airport facilities that report based
aircraft data but not LTO activity, the resulting sum of LTOs was almost 15 million.
EPA estimates that the number of LTOs at the airports that do not report activity data
should approximate the number of LTOs from the bottom of the distribution of the set of
airports that report activity data to the 5010 airport data report but that are not in the TAP
database. The average number of LTOs per year from airports in the bottom 30% of the
set of airports that report activity data to the 5010 airport data report but that are not in
the TAP database is -63 LTOs/year. Multiplying 63 by the number of airports that do
not report activity data equals 549,050 LTOs.43 Therefore, EPA used equation 4 to
generate the distribution of LTOs at the individual airports that report based aircraft data
but not activity data and then applied a scaling factor of 0.0356 to those LTOs to obtain
the LTOs that are reported in the 2008 NEI.44 The sum of the LTOs from this set of
airports plus the sum of the LTOs at the airports that do not report either based aircraft or
activity data (described below in section (bj) sum to 549,050 LTOs. These LTOs are all
assigned to the GA, piston-engine category since they are assigned to smaller general
aviation airports that are assumed to have little to no air taxi or jet aircraft activity.
Equation 4 and the scaling factor were used to estimate LTO activity for the
2008 NEI at airport facilities that report based aircraft data but not activity data.
(b) Estimating LTOs at Facilities with Neither Based-Aircraft Data nor LTO Data:
There are 2,260 facilities (not including heliports) for which the 5010 airport data
report supplies neither the number of based aircraft nor activity data. In the absence of
data to establish a relationship to airport activity, we assign a default value of LTOs to
the GA, piston-engine category for each of these facilities.
42 From FAA's website, "Addresses for Commercial Service Airports", available at:
http://www.faa.gov/airports_airtraffic/airports/planning_capacity/passenger_allcargo_stats/addresses/media
/commercial_service_airports_addresses.xls
43 This rounded number is calculated by multiplying 63.298 LTOs/year by 8,674, which is the number of
airports that don't report activity data (6,414 don't report activity data and 2,260 facilities don't report
activity or based aircraft data).
44 The scaling factor was calculated by dividing 528,710 LTOs by 14,862,767 LTOS; the 528,710 LTOs are
equal to 549,050 LTOs minus 20,340 LTOs (20,340 LTOs represent the sum of LTOs assigned to the 2,260
facilities that don't report either activity data or based aircraft data - the derivation of LTO estimates for
these facilities is described in Section 4 (b)). The 14,862,767 LTOs are the sum of LTOs that result from
applying equation 4 to the 6,414 facilities with based aircraft data but no activity data.
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The default value was determined by evaluating GA LTOs that are reported at the
set of 2,471 facilities that report activity data to the 5010 airport data report but that are
not in the TAP set of airports. The average number of LTOs reported to the bottom ten
percent of these facilities (when sorted by total GA LTOs) was 9. These facilities are
assumed to most closely approximate the set of 2,260 facilities that do not report any
based aircraft or LTO data; therefore, we assigned 9 LTOs to the GA, piston-engine
category for these airport facilities for purposes of developing inventory estimates.
Section 5. Calculating LTOs at Heliports:
There were 5,559 heliport facilities in the January 15, 2009 FAA 5010 data report
that were operational. Of those, only 92 (or 2%) reported LTO data, and of those, only
31 reported both based aircraft and LTO data. Because of the limited information
regarding activity at heliports, some municipalities have hired contractors to survey
activity in their local area.45' 46
The summary statistics for LTO data provided at the 92 operational heliports is
presented in Table 2. These facilities report a wide range in activity from 3 LTOs/year to
more than 18,000 LTOs/year. Some facilities clearly have significant helicopter traffic
(i.e., thousands of LTOs/year) which is supported by the contractor summaries of heliport
activity in the Washington Metropolitan area. The little data available to us suggests that
the median helicopter activity is less than 200 LTOs/year. In the absence of more
information on which to base estimates of LTO activity, we assigned 141 LTOs (the
median of the reported heliport LTOs) to the GA category at all of the heliports which do
not report LTO data. The piston-engine fraction developed in Section 6 is applied to the
141 LTOs resulting in 51 LTOs assigned to the GA, piston-engine category and 90
assigned to the GA, turbine-engine category. This is an area of significant uncertainty in
the inventory and one for which EPA is seeking information from local agencies.
Table 2: Heliport LTO Data for those Reporting LTO Data in the January 15. 2009
Version of the 5010 Airport Data Report
18,250
3
1,123
141
50
Maximum LTOs
Minimum LTOs
Average LTOs
Median LTOs
Mode LTOs
45 Executive Summary: Regional Helicopter System Plan, Metropolitan Washington Area, prepared by
Edwards and Kelcey for the Metropolitan Washington Council of Governments, 2005.
46 Alaska Aviation Emission Inventory, prepared by Sierra Research, Inc. for Western Regional Air
Partnership, 2005.
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Section 6. Methodology for Estimating Airport-Specific Lead Emissions
In 2008, EPA developed a method to calculate lead emissions at airports where
piston-engine powered aircraft operate. 4? This method brings lead inventories into
alignment with the manner in which other criteria pollutants emitted by aircraft are
calculated. This method is described here with changes that were made from previous
methods (i.e., the method used to develop the 2002 inventory) and applied in developing
airport lead inventories for the 2008 NEI. In this section we first present the equation
used to calculate lead emitted during the LTO cycle then we describe each of the
components of the input data: we describe how we calculate piston-engine LTOs from
data available in FAA databases, we describe the derivation of the emission factor for the
amount of lead emitted during the LTO cycle, and we describe the estimate of the amount
of lead retained in the engine and oil that we do not include in the amount of lead
released to the air.
Historically, where aircraft specific activity data are available (such as T-100),
aircraft gaseous and particulate matter (PM) emissions have been calculated through the
FAA's EDMS.48 This modeling system was designed to develop emission inventories
for the purpose of assessing potential air quality impacts of airport operations and
proposed airport development projects. However, EDMS has a limited number of piston-
engine aircraft in its aircraft data and is currently not set up to calculate metal emissions
and thus, it is not a readily available tool for determining airport lead inventories related
to aircraft operations. In developing this approach to determine piston-engine aircraft
lead emissions, EPA relied upon the basic methodology employed in EDMS. This
requires as input the activity of piston-engine aircraft at a facility, fuel consumption rates
by these aircraft during the various modes of the LTO cycle and time in each mode
(taxi/idle-out, takeoff, climb-out, approach, and taxi/idle-in), the concentration of lead in
the fuel and the retention of lead in the engine and oil. The equation used to calculate
airport-specific lead emissions during the LTO cycle is below, followed by a description
of each of the input parameters.
LTO Pb (tons) = (piston-engine LTOYavgas Pb g/LTOVl-Pb retention)
907,180 g/ton
(a) Calculating Piston-engine L TO:
Piston-engine LTOs are used to calculate emissions of lead that are assigned to
the airport facility where the aircraft operations occur. An aircraft operation is defined as
any landing or takeoff event, therefore, to calculate LTOs, operations are divided by two.
Most data sources from FAA report aircraft activity in numbers of operations which, for
the purposes of calculating lead emissions, need to be converted to LTO events. We
47 U.S. EPA (2008) Lead Emissions from the Use of Leaded Aviation Gasoline in the United States,
Technical Support Document. EPA420-R-08-020. Available at: www.epa.gov/otaq/aviation.htm.
48 EDMS available from
http://www.faa.gov/about/office org/headauarters offices/aep/models/edms model/
11
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describe here the method used to estimate the fraction of GA and AT LTOs at an airport
that are conducted by piston-engine aircraft. These fractions are calculated separately
(one fraction for GA and one for AT). These fractions are multiplied by total LTOs
reported separately for GA and AT and then summed to arrive at the total LTOs
conducted by piston-engine aircraft at an airport.
One use of the 2008 NEI is to identify sources of lead, including airports, that
have inventories of 0.50 tons per year or more for the purposes of identifying locations
where lead monitoring may be required to evaluate compliance with the National
Ambient Air Quality Standard for Lead. To calculate the most airport-specific
inventories for airports that may potentially exceed this inventory threshold, we used a
more airport-specific surrogate for this subset of airports than the remainder of the
airports where we applied national default averages described below.
We used the fraction of based aircraft at an airport that are single- or multi-engine
to calculate the number of GA LTOs at an airport that were conducted by piston-engine
aircraft. The data regarding the population of based aircraft at an airport is available for a
subset of airports in the FAA 5010 master records data report described in Section 3. For
example, if an airport reports 150 single-engine aircraft, 20 multi-engine aircraft and a
total of 180 aircraft based at that facility, then the fraction of based aircraft we would use
as a surrogate for piston-engine aircraft is 94% ((150+20)7180). We then multiply the
total GA LTOs for that facility by 0.94 to calculate piston-engine LTOs.
We evaluated this surrogate by comparing the results of using it with piston-
engine aircraft operations reported for airports that supply this information in master
plans, airport layout plans, noise abatement studies and/or land use compatibility plans.
We could rarely find data from the same year for comparison purposes; however, for the
majority of airports, based aircraft and actual observed piston-engine aircraft activity
1 • 1 • 49
agreed within ten percent.
For the majority of airports in the 2008 NEI we used national average fractions of
GA and AT LTOs conducted by piston-engine aircraft that were derived using FAA's
General Aviation and Part 13550 Activity Surveys - CY 2008 (GAATA).51 Table 2.4 in
the 2008 GAATA Survey reports that approximately sixty-six percent (66%) of all GA
and AT LTOs are from piston-engine aircraft which use avgas, and about thirty-four
49 Documents used to evaluate the use of based aircraft include the following:
Airport Master Plan Update Prescott Municipal Airport (Ernest A Love Field) (2009) Available at:
www.cityofprescottnet/_d/amp_tablecontents.pdf
Gillespie field Airport Layout Plan Update Narrative Report (2005) Available at: www.co.san-
diego.ca.us/dpw/airports/powerpoints/pdalp.pdf
Land Use Compatibility Plan for the Grand Forks International Airport (2006) Available at:
www.gfkairport.com/authoritv/pdf/land use.pdf
McClellan-Palomar Land Use Compatibility Plan (Amended March 4, 2010) Available at:
www.ci.oceanside.ca.us/.../McClell an-Palomar_ALUCP_03-4-10_amendment.pdf
50 On-demand (air taxi) and commuter operations not covered by Part 121
51 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 2008 GAATA, see Appendix A at
http://www.faa.gov/data_research/aviation_data_statistics/general_aviation/CY2008/
12
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percent (34%) are turboprop and turbojet powered which use jet fuel, such as Jet A. The
LTO data in Table 2.4 in the 2008 GAATA Survey does not distinguish LTOs as GA or
AT, and thus does not allow us derive separate piston activity fractions for GA and AT.
We are using the number of hours flown by piston versus turboprop or turbojet
aircraft (reported in Table 1.4 in the 2008 GAATA Survey) to allow us to make separate
estimates of the fraction of GA activity conducted by piston aircraft and the fraction of
AT activity conducted by piston aircraft. We chose to use the fraction of hours flown by
piston-engine aircraft as a surrogate to calculate the fraction of LTOs flown by piston
aircraft since the overall (i.e., for GA and AT combined) piston percent of hours flown
(66.4%) is very close to the percent of LTOs that are piston (65.7%). Table 1.4 of the
2008 GAATA presents the total hours flown by aircraft type and separates GA from AT.
Seventy-three percent (73%) of all GA hours flown are by piston-engine aircraft while
twenty-eight percent (28%) of all GA hours flown are by turboprop and turbojet powered
aircraft.52 Twenty-three percent (23%) of all AT hours flown are by piston-engine
aircraft while seventy-seven percent (77%) of all AT hours flown are by turboprop and
turbojet powered aircraft. Approximately 5,000 of the total 20,000 airport facilities in the
U.S. are heliports at which only helicopters (rotocraft) operate. Therefore, EPA also
calculated the percent of rotocraft hours flown that are conducted by piston-engine
aircraft. Thirty-six percent (36%) of all GA rotocraft hours flown are by piston-engine
rotocraft while sixty-four percent (64%) of all GA rotocraft hours flown are by turboprop
and turbojet powered rotocraft. Two percent (2%) of all AT rotocraft hours flown are by
piston-engine rotocraft while ninety-eight percent (98%) of all AT rotocraft hours flown
are by turboprop and turbojet powered rotocraft. Table 3 identifies the piston and turbine
fractions that were used in the absence of airport-specific information to calculate piston-
engine operations at airports and heliports in the 2008 NEI.
Table 3: Piston and Turbine Activity Fractions used in the 2008 NEI
Piston
Powered
Turbine
Powered
Airports
GA
72.5%
27.5%
AT
23.1%
76.9%
Heli]
GA
36.1%
63.9%
ports
AT
2%
98%
Numbers in the text may not add to 100% due to rounding; the percentages in Table 3 are the values we
used to calculate the 2008 NEI.
13
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(b) Calculating the Piston-engine Aircraft Emission Factor: Grams of Lead Emitted per
LTO:
Piston-engine aircraft can have either one or two engines. EDMS version 5.0.2
contains information on the amount of avgas used per LTO for some single and twin-
engine aircraft. The proportion of piston-engine LTOs conducted by single- versus twin-
engine aircraft was taken from the FAA's GAATA Survey for 2008 (90% of LTOs are
conducted by aircraft having one engine and 10% of LTOs by aircraft having two
engines).53 Since twin-engine aircraft have higher fuel consumption rates than those with
single engines, a weighted-average LTO fuel usage rate was calculated to apply to the
population of piston-engine aircraft as a whole. For the single-engine aircraft, the
average amount of fuel consumed per LTO was determined from the six types of single
piston-engine aircraft within EDMS.54 This was calculated by averaging the single-
engine EDMS outputs for fuel consumed per LTO using the EDMS scenario property of
ICAO/USEPA Default - Times in Mode (TIM), with a 16 minute taxi-in/taxi-out time
according to EPA's Procedures for Emission Inventory Preparation, Volume IV: Mobile
Sources, 1992.55 This gives a value of 16.96 pounds of fuel per LTO (Ibs/LTO). The
average single-engine fuel consumption rate was divided by the average density of
100LL avgas, 6 pounds per gallon (Ibs/gal), producing an average fuel usage rate for
single-engine piston aircraft of 2.83 gallons per LTO (gal/LTO). This same calculation
was performed for the two twin-engine piston aircraft within EDMS, producing an
average LTO fuel usage rate for twin-engine piston aircraft of 9.12 gal/LTO.
Using these single- and twin-engine piston aircraft fuel consumption rates, a
weighted average fuel usage rate per LTO was computed by multiplying the average fuel
usage rate for single-engine aircraft (2.83 gal/LTO) by the fleet percentage of single-
engine aircraft LTOs (90%). Next, the twin-engine piston aircraft average fuel usage rate
(9.12 gal/LTO) was multiplied by the fleet percentage of twin-engine aircraft LTOs
(10%). By summing the results of the single- and twin-engine aircraft usage rates, the
overall weighted-average fuel usage rate per LTO of 3.46 gal/LTO was obtained.
To calculate the emission factor, the concentration of lead in fuel is multiplied by
the fuel consumption per LTO. The maximum lead concentration specified by ASTM for
100LL is 0.56 grams per liter or 2.12 grams per gallon. This amount of lead is normally
added to assure that the required lean and rich mixture knock values are achieved.
Multiplying this lead concentration in avgas by the weighted average fuel usage rate
produces an overall average value of 7.34 grams of lead per LTO (g Pb/LTO) for piston-
engines: 3.46 gal/LTO x 2.12 g Pb/gal = 7.34 g Pb/LTO.
53 The LTOs from the categories of 1-engine fixed wing piston, piston rotocraft, experimental total, and
light sport were summed to determine the total number of single-engine piston aircraft LTOs.
54 EPA understands that EDMS 5.0.2 has a limited list of piston-engines, but these are currently the best
data available.
55 U.S. EPA, Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources, EPA-450/4-
81026d (Revised), 1992.
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(c) Retention of Lead in Engine and Oil (1-Pb Retention):
Data collected from aircraft piston-engines operating on leaded avgas suggests
that about 5% of the lead from the fuel is retained in the engine and engine oil.56 Thus
the emitted fraction is 0.95. This information is used in calculating airport-specific lead
inventories and will be used to develop future national estimates of lead emitted from the
consumption of leaded avgas.
Applying these parameters in the equation above yields the following equation:
Pb(tons) =(piston-engine LTO) (7.34 g Pb/LTO) (0.95)
907,180 g/ton
which simplifies to:
Pb(tons) = (piston-engine LTO) (7.7 X 10'6)
Where piston-engine LTO57 = (GA LTO x 0.725) + (AT LTO x 0.231)
(d) Estimating Lead Emissions from Piston-Engine Helicopters:
The emission factor for helicopters (g Pb/LTO) was determined in the same
manner as described above for piston-engine fixed-wing aircraft. The concentration of
lead in avgas (2.12 g/gal) was multiplied by the weighted average fuel usage rate for four
types of Robinson helicopter engines.58 This produced an overall average emission
factor of 6.60 grams of lead per LTO (g Pb/LTO) for piston-engine powered helicopters.
There are no national databases that provide heliport-specific LTO activity data
for piston-engine powered helicopters separately from turbine-engine powered
helicopters. The 2008 FAA GA and Part 135 Activity (GAATA) Survey reports that
approximately 36% of all GA helicopter hours flown are by piston-engine aircraft which
use avgas, and about 64% are by turbine-engine powered which use jet fuel (which does
56 The information used to develop this estimate is from the following references: (a) Todd L. Petersen,
Petersen Aviation, Inc, Aviation Oil Lead Content Analysis, Report # EPA 1-2008, January 2, 2008,
available at William J. Hughes Technical Center Technical Reference and Research Library at
http://actlibrary.tc.faa.gov/ and (b) E-mail from Theo Rindlisbacher of Switzerland Federal Office of Civil
Aviation to Bryan Manning of U.S. EPA, regarding lead retained in engine, September 28, 2007.
57 This equation for piston-engine LTOs only applies to non-heliport facilities. See the text immediately
below for equations for calculating piston-engine LTOs and Pb emissions at heliports.
58 This was done using the following 4 engine types in EDMS 5.1: Robinson R22 IO-320-D IAD; Robinson
R22 IO-360-B; Robinson R22 O-320; Robinson R22 TSIO-360C. The fuel consumption rates were:
Robinson R22 IO-320-D1AD - 5.546 g Pb/LTO; Robinson R22 IO-360-B - 5.973 g Pb/LTO; Robinson
R22 O-320 - 6.276 g Pb/LTO; Robinson R22 TSIO-360C - 8.604 g Pb/LTO.
15
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not contain lead).59 The 2008 FAA GAATA Survey reports that approximately 2% of all
AT helicopter hours flown are by piston-engine aircraft which use avgas, and about 98%
are by turbine-engine powered rotocraft. We expect the fraction of helicopter activity
conducted by piston-engines to vary by heliport with some facilities having no piston-
engine powered helicopter activity and some hosting mainly or only piston-engine
powered helicopters. However, in the absence of heliport-specific data, the national
default estimates of 36% for GA and 2% for AT from the GAATA Survey were used.
Therefore, to calculate piston-engine aircraft LTO as input for this equation, the
helicopter GA LTOs were multiplied by 0.36 and helicopter AT LTOs were multiplied by
0.02.
Lead emitted at the heliport facility was calculated for the 2008 NEI using either
the LTO data provided in FAA databases or the estimate LTO activity in the following
equation (i.e., 141 LTOs):
Pb(tons) = (piston-engine helicopter LTO) (6.60 g Pb/LTO) (0.95)
907,180 g/ton
which simplifies to:
Pb(tons) = (piston-engine helicopter LTO) (6.9 X 10"6)
Where piston-engine helicopter LTO = (Helicopter GA LTO x 0.36) + (Helicopter AT
LTO x 0.02)
Section 7. Improving Airport-specific Lead Emissions Estimates
There are refinements to the methods described here that would improve airport-
specific inventories, most of which involve acquiring airport- and aircraft-specific input
data. The following information describes data inputs that could be used to generate
airport lead inventories tailored to specific airports or otherwise improve the estimates
using currently available data. State and local authorities might have, or be able to
collect, better information for some of these key data inputs.
State and local agencies might have access to airport-specific data that would
improve the national estimates of lead emissions per LTO. These improvements largely
involve replacing national average or default values with airport-specific data on the
activity of piston-engine aircraft. Three key data inputs are:
59 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/
16
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1) Airport-specific LTO activity for piston-powered aircraft, including the fraction
of piston-engine activity conducted by single- versus twin-engine aircraft. Some
airport facilities collect this information and states may use these data to
calculate airport-specific lead inventories. The activity data should be current
and updated on a regular schedule so that the data represents the inventory year
as closely as possible.
2) The time spent in each mode of the LTO cycle. EPA uses the EDMS scenario
property of ICAO/USEPA Default - Times in Mode, with a 16 minute taxi-
in/taxi-out time according to EPA's Procedures for Emission Inventory
Preparation, Volume IV: Mobile Sources, 1992. While some local authorities
have confirmed that these are the relevant times in mode at their airports for
piston aircraft, the applicability of these times in mode will vary by airport. EPA
has learned that one of the important factors in piston aircraft operation that is
currently not included in the time in mode or emissions estimates is the time and
fuel consumption during the pre-flight run-up checks conducted by piston-engine
aircraft prior to takeoff.
3) Other data inputs for the airport-specific lead inventory calculation for which
states or local authorities may provide airport-specific information include the
concentration of lead in the avgas supplied at an airport, and the fraction of lead
in fuel that is retained in the engine and oil, and aircraft-specific fuel
consumption rates by the piston-engine aircraft in specific modes of operation.
The accuracy of the based aircraft data on which equation 4 is modeled can be
improved. FAA recognizes the need to improve the integrity of the 5010 data report
based-aircraft counts for all of the GA airports and reliever airports in the NPIAS and is
currently in the process of improving the data collection and submission methods to
accomplish this task.60
Section 8. Lead emitted inflight (i.e., outside the LTO cycle):
Lead emissions, especially those at altitude, undergo dispersion and eventually
deposit to surfaces, and lead deposited to soil and water can remain available for uptake
by plants, animals and humans for long periods of time. Because lead is a persistent
pollutant, we are including all lead emissions - at airports and in-flight - in the NEI.61
For inventory purposes, lead emitted outside the LTO cycle occurs during aircraft
cruise mode and portions of the climb-out and approach modes above the mixing height
(typically 3,000 ft62). This part of an aircraft operation emits lead at various altitudes as
well as close to and away from airports. Because the precise area of lead emission and
deposition is not known for these flights, EPA is using a simplistic approach to allocate
60 National Based Aircraft Inventory Program:
http://www.basedaircraft.com/public/FrequentlyAskedQuestions.aspx. accessed 2/17/2009
61 U.S. EPA, 2006. Air Quality: Criteria for Lead: 2006; EPA/600/R-5/144aF; U.S. Government Printing
Office, Washington, DC, October, 2006.
62 According to EPA's Procedurees for Emission Inventory Preparation, Volume IV: Mobile Sources, 1992.
17
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these emissions for the purposes of the 2008 NEI. A brief explanation of the nature of
GA flights is provided here for context regarding emissions of lead in-flight.
FAA categorizes GA flights as either local area or itinerant operations and this
distinction plays a role in the area over which lead is emitted. Local operations are those
activities performed by aircraft operating in the local traffic pattern or within sight of the
airport, aircraft executing simulated instrument approaches or low passes at the airport,
and/or aircraft operating to or from the airport in a designated practice area located within
a 20-mile radius of the airport. Local operations are common for GA aircraft. This
includes applications such as recreational, proficiency and instructional flying as well as
many common general aerial support tasks. Emissions during local flying are more likely
to influence air and soil concentrations of lead in the vicinity of the airport because they
occur near the airport, often at altitudes below the mixing height.
Itinerant operations are all operations other than those described above as local
operations. An itinerant aircraft operation usually is one in which the aircraft departs
from one airport and lands at a different airport. Depending on air time and distance, an
itinerant flight is much more likely to involve departing the local flying area of the
originating airport and climbing to altitudes above the mixing height. It is reasonable
then, to generally expect that lead emitted outside the LTO cycle during itinerant
operations, in contrast with local operations, will be more widely dispersed and at greater
distances from the airport.
The portion of the national avgas lead emitted in flight (i.e., outside the LTO
cycle) is calculated by subtracting the sum of airport facility lead inventories from the
national avgas lead inventory. Even though FAA collects and reports information
regarding the fraction of GA operations that are local and itinerant, there is no practical
method to assign in-flight lead emissions to small geographic areas such as airports or
census tracts. And similar data is not available for AT operations, a portion of which are
conducted by piston-engine aircraft. Since the average duration of a piston-engine
aircraft flight is approximately an hour, an itinerant flight can traverse county lines.
Therefore, given the current data available, the best approach is to assign the out-of-LTO
cycle lead to the state where the flight originated.
In the 2008 NEI EPA allocated lead emissions that are calculated as being outside
the LTO cycle to states based on the state-specific fraction of national GA and AT piston-
engine LTO activity. The state-specific fractions were calculated by multiplying the
percent of GA and AT piston-engine LTO activity in each state by 296 tons, which is the
amount of lead we currently estimate is emitted outside of the LTO cycle nationwide.
Table 4 presents the total GA and AT piston-engine LTOs by state, the state-specific
faction of national GA and AT piston-engine LTO activity, and the out-of-LTO lead
emissions assigned to each state.
18
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Table 4: Out-of-LTO Lead Emissions by State
STATE
AK
AL
AR
AZ
CA
CO
CT
DC
DE
FL
GA
HI
IA
ID
IL
IN
KS
KY
LA
MA
MD
ME
MI
MN
MO
MS
MT
NC
ND
NE
NH
NJ
NM
NV
NY
OH
OK
OR
PA
Total GA
and AT
Piston
LTOs
660,133
671,026
638,875
1,430,302
3,881,357
780,426
226,807
28,833
84,617
2,751,015
750,876
138,432
281,961
430,812
920,908
566,583
459,720
280,378
622,011
714,159
436,861
228,302
880,818
647,876
389,551
461,383
270,311
743,004
214,139
221,681
173,355
466,961
309,657
298,712
999,738
1,180,583
575,402
596,730
954,839
Percent of
National GA
and AT Piston
LTOs (by state)
2.0%
2.0%
1.9%
4.3%
11.6%
2.3%
0.7%
0.1%
0.3%
8.3%
2.3%
0.4%
0.8%
1.3%
2.8%
1.7%
1.4%
0.8%
1.9%
2.1%
1.3%
0.7%
2.6%
1.9%
1.2%
1.4%
0.8%
2.2%
0.6%
0.7%
0.5%
1.4%
0.9%
0.9%
3.0%
3.5%
1.7%
1.8%
2.9%
OutofLTO
Pb emissions
(tons)
5.86
5.96
5.68
12.71
34.48
6.93
2.01
0.26
0.75
24.44
6.67
1.23
2.50
3.83
8.18
5.03
4.08
2.49
5.53
6.34
3.88
2.03
7.82
5.76
3.46
4.10
2.40
6.60
1.90
1.97
1.54
4.15
2.75
2.65
8.88
10.49
5.11
5.30
8.48
19
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PR
RI
SC
SD
TN
TX
UT
VA
VI
VT
WA
WI
WV
WY
80,728
45,348
506,650
228,198
535,913
2,422,722
299,471
502,559
25,763
88,318
1,189,142
778,320
143,393
106,190
0.2%
0.1%
1.5%
0.7%
1.6%
7.3%
0.9%
1.5%
0.1%
0.3%
3.6%
2.3%
0.4%
0.3%
0.72
0.40
4.50
2.03
4.76
21.52
2.66
4.46
0.23
0.78
10.56
6.91
1.27
0.94
For additional information or if you have questions regarding the methods described in
this document, please contact Meredith Pedde (pedde.meredith@epa.gov) or Marion
Hoyer (hoyer.marion@epa.gov).
20
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APPENDIX A
Table A-1: Scaling factors
Year
Before
198164
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
U.S. Product Supplied
of Aviation Gasoline
(Thousand Barrels)63
11,147
9,307
9,444
8,692
9,969
11,673
9,041
9,705
9,427
8,910
8,265
8,133
7,606
7,555
7,841
7,400
7,864
7,032
7,760
7,188
6,921
6,682
5,987
6,189
7,006
6,626
6,258
5,603
Ratio of
2008 to
YearX
0.57
0.50
0.60
0.59
0.64
0.56
0.48
0.62
0.58
0.59
0.63
0.68
0.69
0.74
0.74
0.71
0.76
0.71
0.80
0.72
0.78
0.81
0.84
0.94
0.91
0.80
0.85
0.90
1.00
63 Data from the Energy Information Administration's (EIA's) table, "U.S. Product Supplied of Aviation
Gasoline (Thousand Barrels)." Available at:
http://tonto.eia.doe.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=mgaupusl&f=A Accessed August 25,
2010.
64 EIA does not have data for volumes of avgas product supplied for years earlier than 1981. To calculate
the scaling factor to use for activity data from years before 1981, we used the ratio of 2008 avgas volume
product supplied to the average avgas volume supplied from 1981 to 1989.
21
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