22440 Federal Register / Vol. 75, No. 81 / Wednesday, April 28, 2010 / Proposed Rules 

ENVIRONMENTAL PROTECTION 

AGENCY 

40 CFR Part 87 

[EPA–HQ–OAR–2007–0294; FRL–9141–7] 

RIN 2060–AP79 

Advance Notice of Proposed 

Rulemaking on Lead Emissions From 

Piston-Engine Aircraft Using Leaded 

Aviation Gasoline 

AGENCY: Environmental Protection 

Agency (EPA). 

ACTION: Advance notice of proposed 

rulemaking. 

SUMMARY: EPA is issuing this Advance 

Notice of Proposed Rulemaking (ANPR) 

to describe information currently 

available and information being 

collected that will be used by the 

Administrator to issue a subsequent 

proposal regarding whether, in the 

Administrator’s judgment, aircraft lead 

emissions from aircraft using leaded 

aviation gasoline (avgas) cause or 

contribute to air pollution which may 

reasonably be anticipated to endanger 

public health or welfare. In this ANPR 

we describe and request comment on 

the data available for evaluating lead 

emissions, ambient concentrations and 

potential exposure to lead from the 

continued use of leaded avgas in pistonengine powered aircraft. We also 

describe and request comment on 

additional information being collected 

that will inform any future action. 

This ANPR is being issued to further 

respond to a petition submitted by 

Friends of the Earth (FOE) in 2006. 

Emissions of lead from piston-engine 

aircraft using leaded avgas comprise 

approximately half of the national 

inventory of lead emitted to air. There 

are almost 20,000 airport facilities in the 

U.S. at which leaded avgas may be used. 

EPA has long-standing concerns 

regarding exposure to lead, particularly 

during childhood. The most recent 

review and revision of the National 

Ambient Air Quality Standard (NAAQS) 

for lead, promulgated in 2008, found 

that serious health effects occur at much 

lower levels of lead in blood than 

previously identified and did not 

identify a safe level of lead exposure. 

DATES: Comments must be received on 

or before June 28, 2010. 

ADDRESSES: Submit your comments, 

identified by Docket ID No. EPA–HQ– 

OAR–2007–0294, by one of the 

following methods: 

• http://www.regulations.gov: Follow 

the on-line instructions for submitting 

comments. 

• E-mail: a-and-r-docket@epa.gov. 

• Fax: (202) 566–9744. 

• Mail: Environmental Protection 

Agency, Mail Code: 6102T, 1200 

Pennsylvania Ave., NW., Washington, 

DC 20460. Please include two copies. 

• Hand Delivery: EPA Docket Center 

(Air Docket), U.S. Environmental 

Protection Agency, EPA West Building, 

1301 Constitution Avenue, NW., Room: 

3334 Mail Code: 2822T, Washington, 

DC. Such deliveries are only accepted 

during the Docket’s normal hours of 

operation, and special arrangements 

should be made for deliveries of boxed 

information. 

Instructions: Direct your comments to 

Docket ID No. EPA–HQ–OAR–2007– 

0294. EPA’s policy is that all comments 

received will be included in the public 

docket without change and may be 

made available online at http:// 

www.regulations.gov, including any 

personal information provided, unless 

the comment includes information 

claimed to be Confidential Business 

Information (CBI) or other information 

whose disclosure is restricted by statute. 

Do not submit information that you 

consider to be CBI or otherwise 

protected through http:// 

www.regulations.gov or e-mail. The 

http://www.regulations.gov Web site is 

an ‘‘anonymous access’’ system, which 

means EPA will not know your identity 

or contact information unless you 

provide it in the body of your comment. 

If you send an e-mail comment directly 

to EPA without going through http:// 

www.regulations.gov your e-mail 

address will be automatically captured 

and included as part of the comment 

that is placed in the public docket and 

made available on the Internet. If you 

submit an electronic comment, EPA 

recommends that you include your 

name and other contact information in 

the body of your comment and with any 

disk or CD–ROM you submit. If EPA 

cannot read your comment due to 

technical difficulties and cannot contact 

you for clarification, EPA may not be 

able to consider your comment. 

Electronic files should avoid the use of 

special characters, any form of 

encryption, and be free of any defects or 

viruses. For additional information 

about EPA’s public docket visit the EPA 

Docket Center homepage at http:// 

www.epa.gov/epahome/dockets.htm. 

Docket: All documents in the docket 

are listed in the http:// 

www.regulations.gov index. Although 

listed in the index, some information is 

not publicly available, e.g., CBI or other 

information whose disclosure is 

restricted by statute. Certain other 

material, such as copyrighted material, 

will be publicly available only in hard 

copy. Publicly available docket 

materials are available either 

electronically in http:// 

www.regulations.gov or in hard copy at 

the EPA Docket Center, EPA/DC, EPA 

West, Room 3334, 1301 Constitution 

Avenue, NW., Washington, DC. The 

Public Reading Room is open from 8:30 

a.m. to 4:30 p.m., Monday through 

Friday, excluding legal holidays. The 

telephone number for the Public 

Reading Room is (202) 566–1744, and 

the telephone number for the Air Docket 

is (202) 566–1742. 

FOR FURTHER INFORMATION CONTACT: 

Marion Hoyer, Assessment and 

Standards Division, Office of 

Transportation and Air Quality, 2000 

Traverwood Drive, Ann Arbor, MI 

48105; telephone number: (734) 214– 

4513; fax number: (734) 214–4821; 

e-mail address: hoyer.marion@epa.gov. 

SUPPLEMENTARY INFORMATION: 

I. General Information 

A. What should I consider as I prepare 

my comments for EPA? 

1. Submitting CBI. Do not submit this 

information to EPA through http:// 

www.regulations.gov or e-mail. Clearly 

mark the part or all of the information 

that you claim to be CBI. For CBI 

information in a disk or CD ROM that 

you mail to EPA, mark the outside of the 

disk or CD ROM as CBI and then 

identify electronically within the disk or 

CD ROM the specific information that is 

claimed as CBI. In addition to one 

complete version of the comment that 

includes information claimed as CBI, a 

copy of the comment that does not 

contain the information claimed as CBI 

must be submitted for inclusion in the 

public docket. Information so marked 

will not be disclosed except in 

accordance with procedures set forth in 

40 CFR Part 2. 

2. Tips for Preparing Your Comments. 

When submitting comments, remember 

to: 

• Identify the rulemaking by docket 

number and other identifying 

information (subject heading, Federal 

Register date and page number). 

• Follow directions—The agency may 

ask you to respond to specific questions 

or organize comments by referencing a 

Code of Federal Regulations (CFR) part 

or section number. 

• Explain why you agree or disagree, 

suggest alternatives, and substitute 

language for your requested changes. 

• Describe any assumptions and 

provide any technical information and/ 

or data that you used. 

• If you estimate potential costs or 

burdens, explain how you arrived at 

your estimate in sufficient detail to 

allow for it to be reproduced. 


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1See docket item EPA–HQ–OAR–2007–0294– 

0003. 

2U.S. Environmental Protection Agency (2006) 

Air Quality Criteria for Lead. Washington, DC, EPA/ 

600/R–5/144aF. Available online at: http:// 

www.epa.gov/ncea/. 3National Ambient Air Quality Standards for 

Lead 73 FR 66965 (Nov. 12, 2008). 

• Provide specific examples to 

illustrate your concerns, and suggest 

alternatives. 

• Explain your views as clearly as 

possible, avoiding the use of profanity 

or personal threats. 

• Make sure to submit your 

comments by the comment period 

deadline identified. 

Table of Contents 

I. Overview 

A. Background on Leaded Aviation 

Gasoline 

B. Background Information Regarding 

General Aviation and Use of PistonEngine Aircraft 

C. Background on the Petition and EPA’s 

Response 

D. Statutory Authority 

1. Background 

2. Regulatory Authority for Emission 

Standards 

3. Regulatory Authority for Fuel Standards 

E. Federal Actions To Reduce Lead 

Exposure 

II. Health and Welfare Effects of Lead 

A. Multimedia and Multi-Pathway 

Exposure Considerations 

B. Health Effects Information 

1. Blood Lead 

2. Health Effects 

3. At-Risk Populations and Life Stages 

C. Welfare Effects 

1. Terrestrial Ecosystems 

2. Aquatic Ecosystems 

III. Lead Emissions from Piston-Engine 

Aircraft 

A. Inventory of Lead from Piston-Engine 

Powered Aircraft 

1. National Emissions of Lead from PistonEngine Aircraft 

2. Airport-Specific Emissions of Lead from 

Piston-Engine Aircraft 

B. Projections for Future Growth 

IV. Lead Concentrations in the Vicinity of 

Airports 

A. Chemical and Physical Properties of 

Lead Emitted by Piston-Engine Aircraft 

B. Summary of Airport Lead Monitoring 

and Modeling Studies 

1. Summary of Airport Lead Monitoring 

Studies 

2. Summary of Airport Lead Modeling 

Studies 

V. Exposure to Lead from Piston-Engine 

Aircraft and Potential for Impacts 

A. Exposure to Lead Emissions from 

Piston-Engine Aircraft 

1. Population Residing Near Airports 

2. Children Attending School Near 

Airports 

3. Agricultural Activities 

4. Pilots, Student-Trainees, Passengers 

5. Bioaccumulation of Lead in Aquatic 

Organisms 

B. Related Exposures of Concern 

1. Lead Contribution to Ambient 

Particulate Matter 

2. Ethylene Dibromide 

3. Non-Exhaust Exposure to Tetraethyl 

Lead 

VI. Additional Information Available for the 

NPRM to Evaluate the Potential for 

Public Health and Welfare Impacts and 

Considerations Regarding Engine 

Emission Standards 

A. The Lead NAAQS and Lead Emissions 

from Piston-Engine Aircraft 

1. Monitoring Lead at Airports to Evaluate 

Ambient Concentrations to Which Lead 

Emissions from Piston-Engine Aircraft 

Contribute 

2. Evaluating the Contribution of Lead 

Emissions from Piston-Engine Aircraft to 

Areas Approaching or Exceeding the 

Lead NAAQS 

B. Additional Information EPA Is 

Collecting to Evaluate Ambient Lead 

Concentrations Attributable to Emissions 

from Piston-Engine Aircraft 

C. Considerations Regarding Engine 

Emission Standards 

VII. Statutory and Executive Order Reviews 

I. Overview 

EPA is publishing this ANPR in 

further response to a petition submitted 

by Friends of the Earth (FOE) entitled 

‘‘Petition for Rulemaking Seeking the 

Regulation of Lead Emissions From 

General Aviation Aircraft Under § 231 of 

the Clean Air Act.’’ 1 In the petition, FOE 

requests that the Administrator of EPA: 

(1) Make a finding that lead emissions 

from general aviation aircraft endanger 

public health and welfare and issue a 

proposed emission standard for lead 

from general aviation aircraft under the 

Clean Air Act (CAA) or, alternatively, 

(2) if the Administrator of EPA believes 

that insufficient information exists to 

make such a finding, commence a study 

and investigation of the health and 

environmental impacts of lead 

emissions from general aviation aircraft, 

including impacts to humans, animals 

and ecosystems under the CAA and 

issue a public report on the findings of 

the study and investigation. Section I.C 

of this notice discusses the background 

on the petition and EPA’s response to 

date and Section I.D discusses EPA’s 

statutory authority under section 231(a) 

of the CAA. Under the CAA, if, in the 

Administrator’s judgment, lead 

emissions from the use of leaded avgas 

cause or contribute to air pollution 

which may reasonably be anticipated to 

endanger public health or welfare, then 

EPA would be required under our 

statutory authority to prescribe 

standards to control the emissions of 

lead from piston-engine aircraft. In 

promulgating such standards, the EPA 

would be required to consult with the 

Federal Aviation Administration (FAA), 

and could not change standards if doing 

so would significantly increase noise 

and adversely affect safety. FAA would 

then be required, after consultation with 

EPA, to prescribe regulations to insure 

compliance with any standards to 

control the emissions of lead from 

piston-engine aircraft. Under 49 U.S.C. 

44714, FAA would also be required to 

prescribe standards for the composition 

or chemical or physical properties of 

piston-engine fuel or fuel additives to 

control or eliminate aircraft lead 

emissions. 

In this notice, we discuss our analysis 

of the relevant information and issues to 

date, and we seek further public input 

regarding FOE’s petition. For the 

purposes of this notice, we will refer to 

the positive or negative exercise of 

judgment as to whether lead emissions 

from aircraft engines resulting from the 

use of aviation gasoline (avgas) cause or 

contribute to air pollution which may 

reasonably be anticipated to endanger 

public health or welfare as the 

‘‘endangerment finding’’ and the ‘‘cause 

or contribute finding.’’ This short-hand 

use of ‘‘endangerment finding’’ and 

‘‘cause or contribute finding’’ is strictly 

for purposes of simplifying the 

discussion, and should not be read as 

implying that EPA considers the 

exercise of the Administrator’s 

judgment to require a formal ‘‘finding’’ 

or ‘‘determination.’’ 

In 2006, EPA completed the Air 

Quality Criteria Document (AQCD) for 

Lead, which critically assesses and 

integrates relevant scientific information 

regarding the health effects of lead.2

EPA concluded that the latest evidence 

indicates adverse health effects, most 

notably among children, are occurring at 

much lower levels than previously 

considered. In 2008, EPA decreased the 

level of the primary National Ambient 

Air Quality Standard (NAAQS) for lead 

from 1.5 micrograms per cubic meter 

(μg/m3) to 0.15 μg/m3 in order to 

provide increased protection for 

children and other at-risk populations 

against an array of adverse health 

effects, most notably neurological effects 

in children, including neurocognitive 

and neurobehavioral effects.3

Neurotoxic effects in children and 

cardiovascular effects in adults are 

among those best substantiated as 

occurring at blood lead concentrations 

as low as 5 to 10 μg/dL (or possibly 

lower); and these categories are 

currently clearly of greatest public 

health concern (AQCD for Lead, p. 8– 

60). The U.S. Centers for Disease 

Control and Prevention (CDC) 

concluded in 2005 that no ‘‘safe’’ 

threshold for blood lead has been 

identified, and emphasized the 


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4Centers for Disease Control and Prevention 

(2005) Preventing lead poisoning in young children: 

a statement by the Centers for Disease Control and 

Prevention. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service. 

August. 

5Advisory Committee on Childhood Lead 

Poisoning Prevention (ACCLPP) (2007) Interpreting 

and managing blood lead levels <10 ug/dL in 

children and reducing childhood exposures to lead: 

Recommendations of CDC’s Advisory Committee on 

Childhood Lead Poisoning Prevention. Morbidity 

and Mortality Weekly Report. 56(RR–8). November 

2, 2007. 

6U.S. Environmental Protection Agency 

Electronic Report on the Environment. Available at: 

http://cfpub.epa.gov/eroe. Updated in December 

2009 using the 2005 National Emissions Inventory. 

7See ‘‘Prohibition on Gasoline Containing Lead or 

Lead Additives for Highway Use’’ 61 FR 3832 (Feb. 

2, 1996). 

8Commercial aircraft include those used for 

scheduled service transporting passengers, freight, 

or both. Air taxis fly scheduled and for-hire service 

carrying passengers, freight or both, but they 

usually are smaller aircraft than those operated by 

commercial air carriers. General aviation includes 

most other aircraft (fixed and rotary wing) used for 

recreational flying, business, and personal 

transportation. 

9ChevronTexaco (2006) Aviation Fuels Technical 

Review. FTR–3. Available online at: http://

www.chevronglobalaviation.com/docs/ 

aviation_tech_review.pdf. 

10ASTM International (2007) Standard 

Specification for Aviation Gasolines D910–06. 

11Ogston, A.R. (1981) A Short History of Aviation 

Gasoline Development, 1903–1980. Society of 

Automotive Engineers. Paper number 810848. 

importance of preventative measures.4 5

To provide increased protection against 

lead-related welfare effects, in 2008 EPA 

revised the secondary standard to be 

identical in all respects to the revised 

primary standard. Section II of this 

ANPR provides more detail regarding 

health and welfare effects of lead. 

Given the recent findings of the 

science summarized by EPA in the 

AQCD for Lead as well as the findings 

of the CDC, the Agency is concerned 

about the potential for health and 

welfare effects from exposure to lead 

emissions from aircraft engines using 

leaded avgas. On a national basis, 

emissions of lead from aircraft engines 

using leaded avgas are the largest single 

source category for emissions of lead to 

air, comprising approximately half of 

the national inventory.6 There are 

almost 20,000 airport facilities in the 

U.S. at which leaded avgas may be used, 

and in some areas of the country there 

are densely populated residential 

developments immediately adjacent to 

these airport facilities. As described in 

Section V, we estimate that up to 16 

million people reside and three million 

children attend school in close 

proximity to airport facilities servicing 

piston-engine aircraft that are operating 

on leaded avgas. 

Exposure to lead occurs through 

multiple routes (e.g., inhalation, 

ingestion and dermal adsorption), and 

lead emitted to the atmosphere can 

contribute to lead levels in multiple 

media (e.g., air, soil and water). The 

lead monitoring studies conducted at or 

near airports, described in Section IV of 

this ANPR, indicate that lead levels in 

ambient air on and near airports 

servicing piston-engine aircraft are 

higher than lead levels in areas not 

directly influenced by a lead source. In 

addition, the emissions of lead from 

these engines are also expected to 

distribute widely through the 

environment. This is in part due to the 

emission of lead at various altitudes 

during aircraft operations as well as the 

fine particle size of lead emitted by 

piston engines. Continued use of leaded 

avgas provides an ongoing source of 

new lead that is deposited in various 

environmental media and participates 

in long term cycling mechanisms in the 

environment, thus adding to the pool of 

lead available for uptake by humans and 

biota. We expect the lead from avgas to 

be bioavailable in the same way as the 

lead emitted by motor vehicles in the 

past, which was well documented to 

contribute to blood levels through both 

ingestion and inhalation. 

As noted in Section II of this ANPR, 

once deposited to surfaces, lead can 

subsequently be resuspended into the 

ambient air and, because of the 

persistence of lead, emissions of this 

metal contribute to environmental 

media concentrations for many years 

into the future. Lead that is a soil or dust 

contaminant today may have been 

airborne yesterday or many years ago. 

Therefore lead emissions from pistonengine aircraft could contribute to 

increased lead exposure and risk 

currently or at some time in the future. 

Section VI of this ANPR provides an 

overview of additional information that 

will be available for the NPRM to 

evaluate the potential for public health 

and welfare impacts from lead emitted 

by piston-engine aircraft. These 

additional data will come from lead 

monitoring being planned to satisfy 

requirements of the Lead NAAQS, air 

quality modeling planned at EPA and 

any information submitted to EPA 

during the comment period for this 

ANPR. 

The remainder of this section 

provides background on leaded avgas, 

FOE’s petition and EPA’s response to 

the petition to date, and statutory 

authority over emissions, fuel for 

aircraft and Federal actions to reduce 

lead exposure. Section II provides a 

discussion of the health and welfare 

effects of lead. Sections III, IV and V 

describe the emissions of lead from 

avgas, ambient lead concentration in the 

vicinity of airports and potential 

exposure to lead from leaded avgas, 

respectively. In Section VI, we describe 

the additional information EPA is 

collecting and considerations regarding 

engine emission standards. Section VII 

contains information on statutory and 

executive order reviews covering this 

action. 

A. Background on Leaded Aviation 

Gasoline 

In 1996, EPA promulgated regulations 

that banned the use of leaded gasoline 

in highway vehicles.7 The addition of 

lead to fuel used in piston-engine 

powered aircraft was not banned in this 

action, and the use of leaded avgas is 

the largest remaining source category of 

lead emissions. Lead is not added to jet 

fuel that is used in commercial aircraft, 

most military aircraft, or other turbineengine powered aircraft. Most pistonengine aircraft fall into the categories of 

either general aviation (GA) or air taxi 

(AT). GA and AT aircraft include a 

diverse set of aircraft types and engine 

models and are used in a wide variety 

of applications.8

Lead is added to fuel for pistonengine aircraft in the form of tetraethyl 

lead (TEL). This lead additive helps 

boost fuel octane, prevents knock, and 

prevents valve seat recession and 

subsequent loss of compression for 

engines without hardened valves. There 

are two main types of leaded avgas: 100 

Octane, which can contain up to 4.24 

grams of lead per gallon; and 100 

Octane Low Lead (100 LL), which can 

contain up to 2.12 grams of lead per 

gallon. Currently, 100LL is the most 

commonly available and most 

commonly used type of avgas.9 10 TEL 

was first used in piston-engine aircraft 

in 1927.11 Into the 1950s commercial 

and military aircraft in the U.S. operated 

on 100 Octane leaded avgas, but in 

subsequent years, the commercial and 

military aircraft fleet largely converted 

to jet turbine-engine propelled aircraft. 

However, the use of avgas containing 4 

grams of lead per gallon continued in 

piston-engine aircraft until the early 

1970s when 100LL became the 

dominant leaded fuel in use. Currently, 

very little 100 Octane is supplied in the 

U.S. and we use the lead content of 

100LL (2.12 grams per gallon) to 

characterize the lead available from 

avgas. 

Since lead is a persistent pollutant, it 

is important to characterize the 

historical use of this fuel. 


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12 In this ANPR and in EPA’s National Emissions 

Inventory, the use of the unit tons refers to short 

tons. 

13Oak Ridge National Laboratory (2009) 

Transportation Energy Data Book: Edition 28. 

Available at: http://cta.ornl.gov/data. Table A.7. 

14 Department of Energy Information 

Administration. Fuel production volume data 

obtained from http://tonto.eia.doe.gov/dnav/pet/

hist/mgaupus1A.htm accessed June 2009. 

15U.S. Department of Transportation Federal 

Aviation Administration Aviation Policy and Plans. 

FAA Aerospace Forecast Fiscal Years 2009–2025. 

p.81. Available at: http://www.faa.gov/ 

data_research/aviation/aerospace_forecasts/2009– 

2025/media/2009%20Forecast%20Doc.pdf. This 

document provides historical data for 2000–2008 as 

well as forecast data. 

16 General Aviation Manufacturers Association 

(2008) General Aviation Statistical Databook & 

Industry Outlook. Available online at: http://

www.gama.aero/files/2008_general_

aviation_statistical_databook__

indust_499b0dc37b.pdf. 

Approximately 14.6 billion gallons of 

leaded avgas have been consumed in the 

U.S. between 1970 and 2007. If this fuel 

was all 100LL, it would account for 

approximately 34,000 tons 12 of lead 

emitted to the air.13 In terms of the 

potential impacts from long-term use of 

leaded avgas at and near airports, older 

facilities would be expected to have a 

legacy of lead, particularly those that 

supported military and commercial 

aircraft operating on 100 Octane. Over 

3,000 of the 20,000 airport facilities in 

the U.S. are at least 50 years old and 

some airports have been in operation 

since the early 1900s. 

The Department of Energy’s (DOE’s) 

Energy Information Administration 

(EIA) provides information on the 

volume of leaded avgas supplied in the 

U.S.14 The Department of 

Transportation’s (DOT’s) FAA provides 

information on the volume of leaded 

avgas consumed in the U.S.15 EPA has 

historically used the DOE EIA avgas fuel 

volumes supplied to calculate national 

lead inventories from the consumption 

of leaded avgas. We are currently 

evaluating methods used by DOE and 

DOT to calculate annual avgas supply 

and consumption volumes. In this 

document, we provide avgas fuel 

volume data supplied by DOE and DOT 

and we note the source of the data for 

clarity. Over the past ten years, DOE 

estimates of the volume of leaded avgas 

supplied has ranged from 326 million 

gallons in 1999 to 235 million gallons in 

2008 (Figure 1). Applying the 

concentration of lead in 100LL (2.12 

grams of lead per gallon), the total 

quantity of lead supplied in avgas in the 

nation has ranged from 762 tons in 1999 

to 550 tons in 2008 (a 28% decrease 

over that time period). The decrease in 

fuel consumption is attributed to the 

decrease in piston-engine aircraft 

activity over that time period and not 

due to a shift to unleaded fuel. There are 

currently over 200,000 piston-engine 

aircraft in the U.S. that continue to 

consume leaded avgas and 

approximately 2,000 new piston-engine 

aircraft requiring leaded avgas are 

manufactured annually.16 As described 

in Section III.B of this ANPR, there is a 

slight growth in the activity of general 

aviation aircraft projected to 2025. 


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17 General Aviation Manufacturers Association 

(2008) General Aviation Statistical Databook and 

Industry Outlook, p.30. Retrieved on August 17, 

2009 from: http://www.gama.aero/files/

2008_general_aviation_statistical_databook__

indust_499b0dc37b.pdf. 

18 General Aviation Manufacturers Association 

(2008) General Aviation Statistical Databook and 

Industry Outlook, p.30. Retrieved on August 17, 

2009 from: http://www.gama.aero/files/

2008_general_aviation_statistical

_databook__indust_499b0dc37b.pdf. 

19 General Accounting Office Report to 

Congressional Requesters (2001) General Aviation 

Status of the Industry, Related Infrastructure, and 

Safety Issues. GAO–01–916. 

20 General Aviation Manufacturers Association 

(2008) General Aviation Statistical Databook and 

Industry Outlook, pp.51–55. Retrieved on August 

17, 2009 from: http://www.gama.aero/files/

2008_general_aviation_statistical_databook

__indust_499b0dc37b.pdf. 

21An electronic report can be generated from the 

NASR database and is available for download from 

the Internet at the following Web site. http://

www.faa.gov/airports_airtraffic/airports/ 

airport_safety/airportdata_5010/. This database is 

updated every 56 days. 

22FOE letter dated December 12, 2003 submitted 

to EPA Docket EPA–HQ–OAR–2002–0030. 

23See ‘‘Petition Requesting Rulemaking To Limit 

Lead Emissions from General Aviation Aircraft; 

Request for Comments’’ 72 FR 64570 (Nov. 16, 

2007). 

24See, e.g., Ethyl Corp. v. EPA, 541 F.2d 1, 6 (DC 

Cir.), cert. denied 426 U.S. 941 (1976); see also 

Massachusetts v. EPA, 549 U.S. 497, 506, n.7 

(2007). 

25See, ‘‘Endangerment and Cause or Contribute 

Findings for Greenhouse Gases under Section 

202(a) of the Clean Air Act; Final Rule,’’ 74 FR 

66496, 66505 (Dec. 15, 2009); see also, ‘‘Proposed 

Endangerment and Cause or Contribute Findings for 

Greenhouse Gases Under Section 202(a) of the 

Clean Air Act,’’ 74 FR 18886, 18890–94 (April 24, 

2009); see also ‘‘Regulating Greenhouse Gas 

Emissions Under the Clean Air Act; Advance Notice 

of Proposed Rulemaking,’’ 73 FR 44354, 44421–23 

(July 30, 2008). 

B. Background Information Regarding 

General Aviation and Use of PistonEngine Aircraft 

In the U.S., general aviation aircraft 

fly over 27 million hours and carry 166 

million passengers annually.17

Approximately 66 percent of hours 

flown by general aviation are conducted 

by piston-engine aircraft.18 Aircraft in 

the general aviation fleet are used for 

personal transportation (36 percent), 

instructional flying (19 percent), 

corporate uses (11 percent), business (11 

percent), air taxi and air tours (8 

percent) and the remainder include 

hours spent in other applications such 

as aerial observation and aerial 

application.19 According to the 2008 

General Aviation Statistical Databook & 

Industry Outlook report by the General 

Aviation Manufacturers Association 

(GAMA) there were 578,541 pilots in 

the United States in 2008.20 According 

to GAMA, in 2008, the number of active 

single-engine piston-powered aircraft 

was 144,220 and the number of active 

twin-engine piston-powered aircraft was 

18,385. In 2008, 1,791 new pistonengine aircraft were manufactured in 

the U.S. 

FAA’s Office of Air Traffic provides a 

complete listing of operational airport 

facilities in the National Airspace 

System Resources (NASR) database.21 In 

2008, there were 19,896 airport facilities 

in the U.S., the vast majority of which 

are expected to have activity by pistonengine aircraft that operate on leaded 

avgas. FAA’s National Plan of Integrated 

Airport Systems identifies 

approximately 3,400 airports that are 

significant to national air transportation. 

C. Background on the Petition and 

EPA’s Response 

In a 2003 letter to the EPA, FOE 

initially raised the issue of the potential 

for endangerment caused or contributed 

to by lead emissions from the use of 

leaded avgas.22 In 2006, FOE filed a 

petition with EPA requesting that the 

Administrator find endangerment or, if 

there was insufficient information to 

find endangerment, commence a study 

of lead emissions from piston-engine 

aircraft. In 2007, the EPA issued a 

Federal Register notice on the petition 

requesting comments and information 

related to a wide range of issues 

regarding the use of leaded avgas and 

potential public health and welfare 

exposure issues.23 We sought comments 

regarding exposure to lead from avgas 

combustion, emissions of lead, fuel 

options, and piston-engine technology. 

The comments received to date are 

publicly available in the docket (EPA– 

HQ–OAR–2007–0294). The majority of 

comments received concerned the 

nature of the industry and fuel supply 

issues. The commenters did not supply 

information regarding health or 

exposure issues. In 2008, the EPA 

initiated a lead study which will 

improve the manner in which EPA 

models emissions from piston-engine 

aircraft. This study is described in 

further detail in Section VI of this 

document. At the time we received 

FOE’s petition, the EPA was in the 

process of a full re-evaluation of the 

science supporting the lead NAAQS. 

Information from that re-evaluation and 

the relationship between the new lead 

standard and the emissions of lead from 

piston-engine aircraft are discussed in 

this ANPR. 

D. Statutory Authority 

1. Background 

Section 231 of the CAA sets forth 

EPA’s authority to regulate aircraft 

emissions of air pollution. As described 

further in Section I.D.2 of this ANPR, 

Section 231(a)(2)(A) requires EPA to, 

from time to time, issue proposed 

emission standards applicable to the 

emission of any air pollutant from any 

class or classes of aircraft engines 

which, in the Administrator’s judgment, 

cause or contribute to air pollution 

which may reasonably be anticipated to 

endanger public health or welfare. EPA 

has broad authority in exercising its 

judgment regarding whether emissions 

from certain sources cause or contribute 

to air pollution which may reasonably 

be anticipated to endanger public health 

or welfare.24 EPA has discussed its 

‘‘endangerment finding’’ authority at 

length in recent notices for greenhouse 

gases published in the Federal Register, 

and we refer readers to those notices for 

detailed discussions of the analytical 

and legal framework.25

In 1976, EPA listed lead under CAA 

section 108, making it what is called a 

‘‘criteria pollutant.’’ As part of the listing 

decision, EPA determined that lead was 

an air pollutant which, in the 

Administrator’s judgment, has an 

adverse effect on public health or 

welfare under then section 108(a). Once 

lead was listed, EPA issued primary and 

secondary NAAQS that the 

Administrator determined were 

requisite to protect public health with 

an adequate margin of safety and to 

protect public welfare from any known 

or anticipated adverse effects. Section 

109(b)(1) and (2). As discussed 

elsewhere in this notice, EPA issued the 

first NAAQS for lead in 1978, and 

recently revised the lead NAAQS by 

reducing the level of the standard from 

1.5 μg/m3 to 0.15 μg/m3, measured over 

a 3-month averaging period. These 

actions are part of the context for the 

issues before EPA under section 231(a). 

The first part of the endangerment test 

concerns identification of air pollution 

which may reasonably be anticipated to 

endanger public health or welfare. The 

CAA defines both ‘‘air pollutant’’ and 

‘‘welfare.’’ Air pollutant is defined in 

CAA section 302(g) as: ‘‘Any air 

pollution agent or combination of such 

agents, including any physical, 

chemical, biological, radioactive 

(including source material, special 

nuclear material, and byproduct 

material) substance or matter which is 

emitted into or otherwise enters the 

ambient air. Such term includes any 

precursors to the formation of any air 

pollutant, to the extent the 

Administrator has identified such 

precursor or precursors for the 

particular purpose for which the term 

‘air pollutant’ is used.’’ Lead fits within 


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26See ‘‘National Ambient Air Quality Standards 

for Lead’’ 73 FR 66970–67007 (Nov. 12, 2008). 

27See ‘‘National Ambient Air Quality Standards 

for Lead’’ 73 FR 67007–67012 (Nov. 12, 2008). 

28See, e.g., CAA sections 111(b); 213(a)(2), (4). 

29See, e.g., 66 FR 5001 (January 18, 2001) (heavy 

duty engine and diesel sulfur rule). 

30See, e.g., 67 FR 68242 (November 8, 2002) 

(snowmobile rule). 

31Bluewater Network v. EPA, 370 F.3d 1, 15 (DC 

Cir. 2004) (For Fairbanks, this contribution was 

equivalent to 1.2 percent of the total daily CO 

inventory for 2001). 

32NACAA v. EPA, 489 F.3d 1221, 1229–30 (DC 

Cir. 2007). 

this capacious definition, and has long 

been regulated as an air pollutant by 

EPA under the CAA (see Section I.E. of 

this ANPR). 

There is no definition of public health 

in the CAA. The U.S. Supreme Court 

has discussed the concept in the context 

of whether costs can be considered 

when setting NAAQS. Whitman v. 

American Trucking Ass’n, 531 U.S. 457 

(2001). In Whitman, the Court imbued 

the term with its most natural meaning: 

‘‘the health of the public.’’ Id., at 466. 

When considering public health, EPA 

has looked at morbidity, including acute 

and chronic health effects, as well as 

mortality. EPA has long regulated 

emissions of lead air pollution due to 

their adverse impacts on public health 

(see section I.E. of this ANPR). Exposure 

to lead causes ‘‘a broad array of 

deleterious effects on multiple organ 

systems,’’ among children and adults 

(AQCD for Lead, p.8–24 and Section 

8.4.1). Of particular concern are the 

neurotoxic effects of lead in young 

children.26 See Section II of this ANPR 

for a more complete overview of the 

public health effects of lead. 

Regarding ‘‘welfare,’’ CAA section 

302(h) states that ‘‘[a]ll language 

referring to effects on welfare includes, 

but is not limited to, effects on soils, 

water, crops, vegetation, man-made 

materials, animals, wildlife, weather, 

visibility, and climate, damage to and 

deterioration of property, and hazards to 

transportation, as well as effects on 

economic values and on personal 

comfort and well-being, whether caused 

by transformation, conversion, or 

combination with other air pollutants.’’ 

This definition is quite broad, and may 

include effects other than those listed 

here as effects on welfare. Welfare 

effects caused by lead have been 

evaluated by EPA and were the basis for 

establishing the secondary lead 

standard.27

By instructing the Administrator to 

consider whether emissions of an air 

pollutant cause or contribute to air 

pollution, the statute is clear that she 

need not find that emissions from any 

one sector or group of sources are the 

sole or even the major part of an air 

pollution problem. Moreover, section 

231(a) does not contain a modifier on its 

use of the term contribute. Unlike some 

other CAA provisions, it does not 

require ‘‘significant’’ contribution.28

Congress made it clear that the 

Administrator is to exercise her 

judgment in determining contribution, 

and authorized regulatory controls to 

address air pollution even if the air 

pollution problem results from a wide 

variety of sources. The cause or 

contribute test is designed to authorize 

EPA to identify and then address what 

may well be many different sectors or 

groups of sources that are each part of 

an air pollution problem. 

Section 231(a)(2) refers to 

contribution and does not specify that 

the contribution must be significant 

before an affirmative finding can be 

made. Any finding of a ‘‘contribution’’ 

requires some threshold to be met; a 

truly trivial or de minimis 

‘‘contribution’’ might not count as such. 

In the past, the Administrator has 

evaluated the emissions of the source or 

sources in different ways, based on the 

particular circumstances involved. In 

some mobile source rulemakings, the 

Administrator has used the percent of 

emissions from the regulated mobile 

source category compared to the total 

mobile source inventory for that air 

pollutant as the best way to evaluate 

contribution.29 In other instances the 

Administrator has looked at the percent 

of emissions compared to the total 

nonattainment area inventory of the air 

pollution at issue.30 EPA has found that 

air pollutant emissions that amount to 

1.2 percent of the total inventory met 

the statutory test for contribution, 

triggering EPA’s regulatory authority.31

2. Regulatory Authority for Emission 

Standards 

Section 231 of the CAA sets forth 

EPA’s authority to regulate aircraft 

emissions of air pollution. Section 

231(a)(2)(A) requires EPA to, from time 

to time, issue proposed emission 

standards applicable to the emission of 

any air pollutant from any class or 

classes of aircraft engines which, in the 

Administrator’s judgment, cause or 

contribute to air pollution which may 

reasonably be anticipated to endanger 

public health or welfare. Section 

231(a)(2)(B)(i) directs EPA to consult 

with FAA on aircraft engine emission 

standards, and section 231(a)(2)(B)(ii) 

provides that EPA shall not change the 

aircraft engine emission standards if 

such change would significantly 

increase noise and adversely affect 

safety. Section 231(a)(3) directs EPA to 

issue final regulations with such 

modifications as the Administrator 

‘‘deems appropriate.’’ 

In setting or revising standards, 

section 231(b) provides that EPA shall 

have them take effect after such period 

as EPA finds necessary (after 

consultation with the Secretary of 

Transportation) to permit the 

development and application of the 

requisite technology, giving appropriate 

consideration to the cost of compliance 

within such period. Section 231(c) then 

states that EPA’s regulations regarding 

aircraft shall not apply if disapproved 

by the President, after notice and 

opportunity for public hearing, on the 

basis of a finding by DOT that such 

regulations would create a hazard to 

aircraft safety. Section 232 directs DOT 

to issue and implement regulations to 

insure compliance with EPA’s 

standards, while section 233 pre-empts 

States and local governments from 

adopting or enforcing any aircraft 

emission standards that are not identical 

to EPA’s standards. 

In recently reviewing this statutory 

scheme, the U.S. Court of Appeals for 

the District of Columbia Circuit ruled 

that it constitutes a ‘‘both explicit and 

extraordinarily broad’’ delegation of 

‘‘expansive authority to EPA to enact 

appropriate regulations applicable to the 

emissions of air pollutants from aircraft 

engines.’’ 32

3. Regulatory Authority for Fuel 

Standards 

Section 211(c) of the CAA allows EPA 

to regulate fuels used in motor vehicles 

and nonroad vehicles or engines where 

emission products of the fuel either: (1) 

Cause or contribute to air pollution that 

reasonably may be anticipated to 

endanger public health or welfare, or (2) 

will impair to a significant degree the 

performance of any emission control 

device or system which is in general 

use, or which the Administrator finds 

has been developed to a point where in 

a reasonable time it will be in general 

use were such a regulation to be 

promulgated. This section of the CAA 

was used to eliminate lead from fuel 

used in motor vehicles. EPA’s authority 

to regulate fuels is limited to those fuels 

used in motor vehicles, motor vehicle 

engines, or nonroad engines or vehicles, 

under CAA section 211(c)(1). The CAA 

defines ‘‘motor vehicle,’’ ‘‘nonroad 

engine,’’ and ‘‘nonroad vehicle’’ in 

section 216 for purposes of part A of 

title II of the CAA. Part A is also where 

the authority to regulate fuels under 

section 211 resides. However, EPA’s 

authority to regulate aircraft resides in 


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33See http://www.epa.gov/airtrends/lead.html. 

34 ‘‘Regulation of Fuels and Fuel Additives’’ 38 FR 

1254 (Dec. 4, 1973). 

35 ‘‘Regulation of Fuels and Fuel Additives; 

Gasoline Lead Content’’ 50 FR 9386 (March 7, 1985). 

36 ‘‘Prohibition on Gasoline Containing Lead or 

Lead Additives for Highway Use’’ 61 FR 3832 (Feb. 

2, 1996). 

37 ‘‘Prohibition on Gasoline Containing Lead or 

Lead Additives for Highway Use’’ 61 FR 3834 (Feb. 

2, 1996). 

38These fuel volume estimates are from the 

Department of Energy Information Administration. 

http://tonto.eia.doe.gov/dnav/pet/hist/ 

mgaupus1A.htm. 

39U.S. Environmental Protection Agency (2008) 

EPA’s Report on the Environment EPA/600/R–07/ 

045F. Available at: http://www.epa.gov/roe/. 

40 ‘‘National Emission Standards for Hazardous 

Air Pollutants From Secondary Lead Smelting’’ 60 

FR 32587 (June 23, 1995). 

41 ‘‘National Emission Standards for Hazardous 

Air Pollutants From Secondary Lead Smelting’’ 62 

FR 32209 (June 13, 1997). 

42 ‘‘National Emission Standards for Hazardous 

Air Pollutants for Primary Lead Smelting’’ 64 FR 

30194 (June 4, 1999). 

43 ‘‘Standards of Performance for New Stationary 

Sources and Emission Guidelines for Existing 

Sources: Municipal Waste Combustors’’ 60 FR 

65387 (Dec. 19, 1995). 

44 ‘‘Emission Guidelines for Existing Sources and 

Standards of Performance for New Stationary 

Sources’’ 62 FR 45124 (Aug. 25, 1997). 

45 ‘‘Standards of Performance for New Stationary 

Sources and Emission Guidelines for Existing 

Sources: Large Municipal Waste Combustors’’ 71 FR 

27324–27348 (May 10, 2006). 

46Centers for Disease Control and Prevention 

(2005) Preventing lead poisoning in young children: 

a statement by the Centers for Disease Control and 

Prevention. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service. 

August. 

47Advisory Committee on Childhood Lead 

Poisoning Prevention (2007) Interpreting and 

managing blood lead levels <10 μg/dL in children 

and reducing childhood exposures to lead: 

part B of title II, and therefore the 

definitions of section 216 do not apply 

to aircraft. This means that aircraft are 

not ‘‘nonroad vehicles,’’ and aircraft 

engines are not ‘‘nonroad engines.’’ 

Consequently, EPA’s authority to 

regulate fuels under section 211 does 

not extend to fuels used exclusively in 

aircraft, such as leaded avgas, that are 

not also used in motor vehicles or 

nonroad vehicles or engines (excluding 

fuel used in vehicles exclusively). 

Instead, fuels used exclusively in 

aircraft engines are to be regulated by 

the FAA. Title 49 (49 U.S.C. 44714) 

requires that ‘‘the Administrator of the 

Federal Aviation Administration shall 

prescribe (1) standards for the 

composition or chemical or physical 

properties of an aircraft fuel or fuel 

additive to control or eliminate aircraft 

emissions the Administrator of the 

Environmental Protection Agency 

decides under section 231 of the Clean 

Air Act (42 U.S.C. 7571) endanger the 

public health or welfare; and (2) 

regulations providing for carrying out 

and enforcing those standards.’’ 

E. Federal Actions To Reduce Lead 

Exposure 

The U.S. has made tremendous 

progress in reducing lead concentrations 

in the outdoor air. Nationwide, average 

concentrations of lead in the air have 

dropped 91 percent between 1980 and 

2008.33 Much of this dramatic 

improvement occurred as a result of the 

permanent phase-out of lead in motor 

vehicle gasoline discussed in this 

section of the ANPR. However, lead 

continues to be emitted into the air from 

many different types of stationary 

sources and piston-engine aircraft as 

well as certain high performance 

engines such as race cars. 

Federal programs provide for 

nationwide reductions in emissions of 

lead and other air pollutants through 

several provisions in the CAA. In the 

early 1970s, EPA issued regulations 

regarding lead in gasoline in order to 

accomplish two purposes.34 First, EPA 

issued regulations designed to ensure 

the availability of unleaded gasoline for 

use in motor vehicles equipped with 

emission control systems such as 

catalytic converters. EPA had 

determined that lead additives would 

impair to a significant degree the 

performance of emission control 

systems. Second, EPA issued 

regulations designed to gradually reduce 

the content of lead in leaded gasoline, 

because EPA found that lead emissions 

from motor vehicles presented a 

significant risk of harm to the health of 

urban population groups, especially 

children. Children are at a sensitive life 

stage with regard to the adverse health 

effects of lead. In 1985, EPA, noting the 

significant reduction in adverse health 

effects, mainly among pre-school age 

children, that would result from 

reductions in lead content in gasoline, 

promulgated additional regulations to 

decrease the allowable concentration of 

lead in gasoline for motor vehicles to 

0.10 grams per gallon.35 In 1990 

Congress added section 211(n) to the 

CAA which provides that after 

December 31, 1995, it shall be unlawful 

to sell any gasoline for use in any motor 

vehicle which contains lead or lead 

additives. In 1996, EPA incorporated the 

CAA statutory ban on gasoline 

containing lead or lead additives for 

highway use into the Agency’s existing 

regulations on the lead content of 

gasoline.36 In this regulation, it was 

noted that the petroleum industry may 

continue to make and market gasoline 

produced with lead additives for all 

remaining uses, including use as fuel in 

aircraft, racing cars, and nonroad 

engines such as farm equipment engines 

and marine engines, to the extent 

otherwise allowed by law.37

In fact, there have been no regulatory 

limits placed on the production and 

consumption of leaded avgas, and, as 

noted in Section I.A of this ANPR, 

emissions of lead from piston-engine 

aircraft account for an increasing 

fraction of the lead emissions to air (e.g., 

accounting for approximately half the 

national inventory of lead emission in 

2005). This is in spite of the decrease in 

the supply of leaded avgas nationally 

from 374 million gallons (875 tons of 

lead) in 1990 to 235 million gallons (550 

tons of lead) in 2008.38 The decrease in 

fuel consumption is attributed to the 

decrease in piston-engine aircraft 

activity over that time period and not 

due to a shift to unleaded fuel. There are 

over 200,000 piston-engine aircraft in 

the U.S. that continue to consume 

leaded avgas and approximately 2,000 

new piston-engine aircraft requiring 

leaded avgas are manufactured 

annually. Projected growth for this 

industry is discussed in Section III.B. 

Significant reductions in emission of 

lead from stationary sources have been 

achieved between 1985 and 2002, 

totaling almost 2,000 tons of lead.39

Regulations promulgated in 1995, 1997 

and 1999 controlled emissions of lead 

from primary and secondary lead 

smelters, contributing to these 

reductions.40 41 42 Currently, metal 

industry emissions of lead comprise 

23% of the national inventory (298 

tons). Additional reductions in the 

emission of lead have been 

accomplished through controls on waste 

incineration and other stationary 

sources.43 44 45 These standards have 

been set at ‘‘maximum achievable 

control technology’’ (MACT) levels, and 

under CAA sections 112 and 129 EPA 

must revisit these standards in the 

future to determine whether they are 

sufficiently stringent to provide an 

ample margin of safety to protect public 

health and prevent an adverse 

environmental effect. 

As lead is a multimedia pollutant, a 

broad range of Federal programs beyond 

those that focus on air pollution control 

provide for nationwide reductions in 

environmental releases and human 

exposures. In addition, the U.S. Centers 

for Disease Control and Prevention 

(CDC) programs provide for the tracking 

of children’s blood lead levels 

nationally and provide guidance on 

levels at which medical and 

environmental case management 

activities should be implemented.46 47 In 


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Recommendations of CDC’s Advisory Committee on 

Childhood Lead Poisoning Prevention. Morbidity 

and Mortality Weekly Report. 56(RR–8). November 

2, 2007. 48Alliance to End Childhood Lead Poisoning 

(1991) The First Comprehensive National 

Conference; Final Report. October 6, 7, 8, 1991. 49Co-chaired by the Secretary of the HHS and the 

Administrator of the EPA, the Task Force consisted 

of representatives from 16 Federal departments and 

agencies. 

50See, e.g., 66 FR 58258. 

51See, e.g., ‘‘Implementation of the MercuryContaining and Rechargeable Battery Management 

Act’’ http://www.epa.gov/epaoswer/hazwaste/ 

recycle/battery.pdf and ‘‘Municipal Solid Waste 

Generation, Recycling, and Disposal in the United 

States: Facts and Figures for 2005’’ http:// 

www.epa.gov/epaoswer/osw/conserve/resources/ 

msw-2005.pdf. 

52http://www.epa.gov/owm/. 

53U.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. 

54http://www.epa.gov/epawaste/rcc/index.htm. 

55http://www.epa.gov/epawaste/hazard/ 

wastemin/. 

56http://www.epa.gov/epawaste/partnerships/ 

plugin/index.htm. 

57http://www.epa.gov/epawaste/nonhaz/ 

municipal/backyard/index.htm. 

58http://www.epa.gov/ord/. 

59National Ambient Air Quality Standards for 

Lead 73 FR 66970–67007 (Nov. 12, 2008) Section 

II.A. 

60U.S. Environmental Protection Agency Review 

of the National Ambient Air Quality Standards for 

Lead: Policy Assessment of Scientific and Technical 

Information OAQPS Staff Paper (2007) Chapter 2. 

EPA–452/R–07–013 November. 

61U.S. Environmental Protection Agency Air 

Quality Criteria for Lead (2006) Volume I: Chapters 

2 & 3. EPA/600/R–5/144aF. October. 

1991, the Secretary of the U.S. 

Department of Health and Human 

Services (HHS) characterized lead 

poisoning as the ‘‘number one 

environmental threat to the health of 

children in the United States.’’ 48 In 

1997, President Clinton created, by 

Executive Order 13045, the President’s 

Task Force on Environmental Health 

Risks and Safety Risks to Children in 

response to increased awareness that 

children face disproportionate risks 

from environmental health and safety 

hazards (62 FR 19885).49 By Executive 

Orders issued in October 2001 and April 

2003, President Bush extended the work 

for the Task Force for an additional 

three and a half years beyond its 

original charter (66 FR 52013 and 68 FR 

19931). The Task Force set a Federal 

goal of eliminating childhood lead 

poisoning by the year 2010, and 

reducing lead poisoning in children was 

identified as the Task Force’s top 

priority. 

Federal abatement programs provide 

for the reduction in human exposures 

and environmental releases from inplace materials containing lead (e.g., 

lead-based paint, urban soil and dust, 

and contaminated waste sites). Federal 

regulations on disposal of lead-based 

paint waste help facilitate the removal 

of lead-based paint from residences (68 

FR 36487). Further, in 1991, EPA 

lowered the maximum levels of lead 

permitted in public water systems from 

50 parts per billion (ppb) to 15 ppb 

measured at the consumer’s tap (56 FR 

26460). 

Federal programs to reduce exposure 

to lead in paint, dust, and soil are 

specified under the comprehensive 

Federal regulatory framework developed 

under the Residential Lead-Based Paint 

Hazard Reduction Act (Title X). Under 

Title X and Title IV of the Toxic 

Substances Control Act (TSCA), EPA 

has established regulations and 

associated programs with the goal of 

reducing exposure to lead via leadbased paint. For example, under Title IV 

of TSCA, EPA established standards 

identifying hazardous levels of lead in 

residential paint, dust, and soil in 2001. 

On March 31, 2008, the Agency issued 

a new rule (73 FR 21692) to further 

protect children from lead-based paint 

hazards resulting from renovation and 

repair work occurring in housing in 

which they live. 

Programs associated with the 

Comprehensive Environmental 

Response, Compensation, and Liability 

Act (CERCLA or Superfund) and 

Resource Conservation Recovery Act 

(RCRA) also implement abatement 

programs, reducing exposures to lead 

and other pollutants. For example, EPA 

determines and implements protective 

levels for lead in soil at Superfund sites 

and RCRA corrective action facilities. 

Federal programs, including those 

implementing RCRA, provide for 

management of hazardous substances in 

hazardous and municipal solid waste.50

Federal regulations concerning batteries 

in municipal solid waste control the 

collection and recycling or proper 

disposal of batteries containing lead.51

Similarly, Federal programs provide for 

the reduction in environmental releases 

of hazardous substances such as lead in 

the management of wastewater.52

A variety of Federal nonregulatory 

programs also provide for reduced 

environmental release of leadcontaining materials through voluntary 

measures and more general 

encouragement of pollution prevention, 

promotion of reuse and recycling, 

reduction of priority and toxic 

chemicals in products and waste, and 

conservation of energy and materials. 

These include the voluntary partnership 

between EPA and the National 

Association for Stock Car Auto Racing 

(NASCAR) which has achieved the goal 

of removing alkyl lead (organic forms of 

lead) from racing fuels used in the 

Nextel Cup, Busch and Craftsman Truck 

Series.53 Other programs include the 

Resource Conservation Challenge,54 the 

National Waste Minimization 

Program,55 ‘‘Plug in to eCycling’’ (a 

partnership between EPA and consumer 

electronics manufacturers and 

retailers),56 and activities to reduce the 

practice of backyard trash burning.57

In addition to the lead control 

programs summarized above, EPA’s 

research program, with other Federal 

agencies, identifies, encourages and 

conducts research needed to locate and 

assess serious risks and to develop 

methods and tools to characterize and 

help reduce risks. For example, EPA’s 

Integrated Exposure Uptake Biokinetic 

Model for Lead in Children (IEUBK 

model) and the Adult Lead 

Methodology are widely used and 

accepted as tools that provide guidance 

in evaluating site specific data. More 

recently, in recognition of the need for 

a single model that predicts lead 

concentrations in tissue for children and 

adults, EPA is developing the All Ages 

Lead Model (AALM) to provide 

researchers and risk assessors with a 

pharmacokinetic model capable of 

estimating blood, tissue, and bone 

concentrations of lead based on 

estimates of exposure over the lifetime 

of the individual. EPA research 

activities on substances including lead 

focus on better characterizing aspects of 

health and environmental effects, 

exposure, and control or management of 

environmental releases.58

II. Health and Welfare Effects of Lead 

A. Multimedia and Multi-Pathway 

Exposure Considerations 

This section briefly summarizes the 

information presented in the 2008 

NAAQS for Lead,59 the 2007 Lead Staff 

Paper 60 and the 2006 Air Quality 

Criteria Document for Lead (AQCD for 

Lead).61 Lead is an unusual pollutant in 

that the distribution of lead to different 

environmental media (e.g., air, soil, 

water) is important for evaluating public 

health and welfare effects. Lead emitted 

to the air can result in exposure via 

multiple pathways (e.g., inhalation, 

ingestion, dermal absorption). Some key 

multimedia and multi-pathway 

considerations for lead include the 

following: 

(1) Lead is emitted into the air from 

many sources encompassing a wide 


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62U.S. Environmental Protection Agency (2004) 

Air quality criteria for particulate matter. Research 

Triangle Park, NC: Office of Research and 

Development, National Center for Environmental 

Assessment; EPA report no. EPA–600/P–99/0028aF. 

63National Ambient Air Quality Standards for 

Lead 73 FR 66971 (Nov. 12, 2008), AQC for Lead, 

Section 2.5. 

64U.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. 

65Weathering of outdoor lead paint may also 

contribute to soil lead levels adjacent to the house. 

66National Ambient Air Quality Standards for 

Lead 73 FR 66965 (Nov. 12, 2008). 

67U.S. Environmental Protection Agency (2007) 

Review of the National Ambient Air Quality 

Standards for Lead: Policy Assessment of Scientific 

and Technical Information, OAQPS Staff Paper. 

EPA–452/R–07–013. Office of Air Quality Planning 

and Standards, Research Triangle Park. 

68Additionally, lead freely crosses the placenta 

resulting in continued fetal exposure throughout 

pregnancy, with that exposure increasing during the 

latter half of pregnancy (AQC for Lead, Section 

6.6.2). 

69Centers for Disease Control (1991) Preventing 

lead poisoning in young children: a statement by 

the Centers for Disease Control. Atlanta, GA: U.S. 

Department of Health and Human Services, Public 

Health Service; October 1. Available online at: 

http://wonder.cdc.gov/wonder/prevguid/p0000029/ 

p0000029.asp. 

70Centers for Disease Control and Prevention 

(2005) Preventing lead poisoning in young children: 

a statement by the Centers for Disease Control and 

Prevention. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service. 

August. 

71As described by the Advisory Committee on 

Childhood Lead Poisoning Prevention, ‘‘In 1991, 

CDC defined the blood lead level (BLL) that should 

prompt public health actions as 10 μg/dL. 

Concurrently, CDC also recognized that a BLL of 10 

μg/dL did not define a threshold for the harmful 

effects of lead. Research conducted since 1991 has 

strengthened the evidence that children’s physical 

and mental development can be affected at BLLS 

<10 μg/dL’’ (ACCLPP, 2007). 

72Advisory Committee on Childhood Lead 

Poisoning Prevention (2007) Interpreting and 

managing blood lead levels <10 μg/dL in children 

and reducing childhood exposures to lead: 

Recommendations of CDC’s Advisory Committee on 

Childhood Lead Poisoning Prevention. Morbidity 

and Mortality Weekly Report. 56(RR–8). November 

2, 2007. 

73This information documents a variation in 

mean blood lead levels across the various age 

groups monitored. For example, mean blood lead 

variety of stationary and mobile source 

types. Lead emitted to the air is 

predominantly in particulate form, with 

the particles occurring in various sizes. 

Once emitted, the particles can be 

transported long or short distances 

depending on their size, which 

influences the amount of time spent in 

the aerosol phase. In general, larger 

particles tend to deposit more quickly, 

within shorter distances from emissions 

points (e.g., kilometers), while smaller 

particles will remain in the aerosol 

phase and travel longer distances before 

depositing (e.g., hundreds to thousands 

of kilometers).62 As summarized in the 

AQCD for Lead, airborne concentrations 

of lead at sites near sources are much 

higher than at sites not known to be 

directly influenced by sources. 

(2) Once deposited to surfaces, lead 

can subsequently be resuspended into 

the ambient air and, because of the 

persistence of lead, emissions of this 

metal contribute to environmental 

media concentrations for many years 

into the future as it is cycled within and 

between environmental media such as 

soil, air and water. Lead that is a soil or 

dust contaminant today may have been 

airborne yesterday or many years ago.63

(3) Exposure to lead emitted into the 

ambient air can occur directly by 

inhalation, or indirectly by ingestion of 

lead-contaminated food, water or other 

materials including dust and soil. This 

occurs due to the environmental cycling 

of this persistent metal which, once 

emitted into the ambient air is 

distributed to other environmental 

media and can contribute to human 

exposures via indoor and outdoor dusts, 

outdoor soil, food and drinking water, 

as well as inhalation of air. Atmospheric 

deposition is estimated to comprise a 

significant proportion of lead in food 

(AQCD for Lead, p. 3–48). For example, 

livestock may be exposed to lead in 

vegetation (e.g., grasses and silage) and 

in surface soils via incidental ingestion 

of soil while grazing (USEPA 1986, 

Section 7.2.2.2.2).64 And dietary intake 

may be a predominant source of lead 

exposure among adults, greater than 

consumption of water and beverages or 

inhalation (73 FR 66971). These 

exposure pathways are described more 

fully in Section 8.2.2 of the AQCD for 

Lead. 

(4) Air-related exposure pathways are 

affected by changes to air quality, 

including changes in concentrations of 

lead in air and changes in atmospheric 

deposition of lead. Further, because of 

its persistence in the environment, lead 

deposited from the air may contribute to 

human and ecological exposures for 

years into the future as described above. 

Additionally, human exposures to 

lead include pathways that are not 

related to ambient air concentrations. 

The pathways of human exposure to 

lead that are not air-related include 

ingestion of indoor lead paint,65 lead in 

diet as a result of inadvertent additions 

during food processing, and lead in 

drinking water attributable to lead in 

distribution systems, as well as other 

generally less prevalent pathways, as 

described in the AQCD for Lead (pp. 3– 

50 to 3–51). 

B. Health Effects Information 

In 2008, EPA decreased the level of 

the primary (health-based) NAAQS for 

Lead from 1.5 μg/m3 to 0.15 μg/m3 in 

order to provide increased protection for 

children and other at-risk populations 

against an array of adverse health 

effects, most notably neurological effects 

in children, including neurocognitive 

and neurobehavioral effects.66 This 

section summarizes information 

provided in the numerous recent 

documents summarizing health and 

welfare effects from exposure to lead, 

including the AQCD for Lead, CDC 

documents, the EPA Staff Paper 67 and 

the proposed and final NAAQS for 

Lead. First, the use of blood lead as a 

measure of exposure to lead is described 

followed by a brief summary of the 

broad array of lead-induced health 

effects. Particular focus is given here to 

the effects of lead on the developing 

nervous system in children since this is 

among the most sensitive endpoints 

identified for this toxic metal. The 

section ends with a description of atrisk populations and life stages. 

1. Blood Lead 

Lead enters the body most commonly 

via the respiratory system and/or 

gastrointestinal tract, from which it is 

quickly absorbed into the blood stream 

and distributed throughout the body.68

Less commonly, lead, particularly 

organic forms of lead such as alkyl lead, 

can be absorbed through the skin 

(AQCD for Lead, page 4–12). Blood lead 

levels are extensively used as an index 

or biomarker of exposure by national 

and international health agencies, as 

well as in epidemiological (AQCD for 

Lead, Sections 4.3.1.3 and 8.3.2) and 

toxicological studies of lead health 

effects and dose-response relationships 

(AQCD for Lead, Chapter 5). The U.S. 

CDC, and its predecessor agencies, has 

for many years used blood lead level as 

a metric for identifying children at risk 

of adverse health effects and for 

specifying particular public health 

recommendations.69 Most recently, in 

2005, with consideration of a review of 

the evidence by their advisory 

committee, CDC revised their statement 

on Preventing Lead Poisoning in Young 

Children.70 CDC specifically recognized 

the evidence of adverse health effects in 

children with blood lead levels below 

10 μg/dL,71 the data demonstrating that 

no ‘‘safe’’ threshold for blood lead had 

been identified, and emphasized the 

importance of preventative measures.72

Since 1976, the CDC has been 

monitoring blood lead levels in multiple 

age groups nationally through the 

National Health and Nutrition 

Examination Survey (NHANES).73 The 


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levels in 2001–2002 for ages 1–5, 6–11, 12–19 and 

greater than or equal to 20 years of age, are 1.70, 

1.25, 0.94, and 1.56 μg/dL, respectively (AQC for 

Lead, p. 4–22). 

74Axelrad, D., U.S. EPA (November 4, 2009) Email message to Marion Hoyer, U.S. EPA. Available 

in docket number EPA–HQ–OAR–2007–0294. 

75U.S. Environmental Protection Agency (2007) 

Framework for Metals Risk Assessment. Office of 

the Science Advisor. EPA 120/R–07/001. 

76U.S. Environmental Protection Agency, 

Integrated Risk Information System (IRIS) (1993) 

IRIS Summary for Lead and compounds (CASRN 

7439–92–1), Available online at: http:// 

www.epa.gov/ncea/iris/subst/0277.htm. 

77 International Agency for Research on Cancer 

(IARC) (2006) Inorganic and organic lead 

compounds. Lyon, France: International Agency for 

Research on Cancer. IARC monographs on the 

evaluation of the carcinogenic risk of chemicals to 

humans: volume 87. Available online at: http:// 

monographs.iarc.fr/ENG/Monographs/vol87/ 

index.php. 

78National Toxicology Program (2003) Report on 

carcinogens background document for lead and lead 

compounds. Research Triangle Park, NC: U.S. 

Department of Health and Human Services. 

Available online at: http://ntp.niehs.nih.gov/ntp/ 

newhomeroc/roc11/Lead-Public.pdf. 

79National Toxicology Program. (2004) Lead 

(CAS no. 7439–92–1) and lead compounds. In: 

Report on carcinogens, eleventh edition. Research 

Triangle Park, NC: U.S. Department of Health and 

Human Services. Available online at: http:// 

ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/ 

s101lead.pdf. 

80At mean blood lead levels, in children, on the 

order of 10 μg/dL, and somewhat lower, 

associations have been found with effects to the 

immune system, including altered macrophage 

activation, increased IgE levels and associated 

increased risk for autoimmunity and asthma (AQC 

for Lead, Sections 5.9, 6.8, and 8.4.6). 

81With regard to blood lead levels in individual 

children associated with particular neurological 

effects, the AQC for Lead states ‘‘Collectively, the 

prospective cohort and cross-sectional studies offer 

evidence that exposure to lead affects the 

intellectual attainment of preschool and school age 

children at blood lead levels <10 μg/dL (most 

clearly in the 5 to 10 μg/dL range, but, less 

definitively, possibly lower).’’ (p. 6–269) 

82Epidemiological studies have consistently 

demonstrated associations between lead exposure 

and enhanced risk of deleterious cardiovascular 

outcomes, including increased blood pressure and 

incidence of hypertension. A meta-analysis of 

numerous studies estimates that a doubling of 

blood-lead level (e.g., from 5 to 10 μg/dL) is 

associated with ∼1.0 mm Hg increase in systolic 

blood pressure and ∼0.6 mm Hg increase in 

diastolic pressure (AQC for Lead, p. E–10). 

NHANES information has documented 

the dramatic decline in mean blood lead 

levels in the U.S. population that has 

occurred since the 1970s and that 

coincides with regulations regarding 

leaded motor vehicle fuels, leaded 

paint, and lead-containing plumbing 

materials that have reduced lead 

exposure among the general population 

(AQCD for Lead, Sections 4.3.1.3 and 

8.3.3). 

While blood lead levels in the U.S. 

general population, including geometric 

mean levels in children aged 1–5 have 

declined significantly, levels have been 

found to vary among children of 

different socioeconomic status (SES) 

and other demographic characteristics 

(AQCD for Lead, p. 4–21), as well as by 

age.74 Racial/ethnic and income 

disparities in blood lead levels in 

children persist. For example, blood 

lead levels for lower income and 

African American children are higher 

than those for the general population. 

The spectrum of health effects 

discussed in the following section is 

relevant for all forms of lead that enter 

the blood stream. Once in the blood 

stream, lead bioaccumulates in the 

body, with the bone serving as a large, 

long-term storage compartment. Soft 

tissues (e.g., kidney, liver, brain, etc.) 

serve as smaller compartments, in 

which lead may be more mobile (AQCD 

for Lead, Sections 4.3.1.4 and 8.3.1). 

During childhood development, bone 

represents approximately 70% of a 

child’s body burden of lead, and this 

accumulation continues through 

adulthood, when more than 90% of the 

total lead body burden is stored in the 

bone (AQCD for Lead, Section 4.2.2). 

Lead in bone can be mobilized during 

critical periods including pregnancy 

and lactation (AQCD for Lead, Section 

5.8.6). 

2. Health Effects 

Lead, as with mercury and arsenic, 

has no known biological function.75

Lead has been demonstrated to exert ‘‘a 

broad array of deleterious effects on 

multiple organ systems via widely 

diverse mechanisms of action’’ (AQCD 

for Lead, p. 8–24 and Section 8.4.1). 

This array of health effects includes 

effects on heme biosynthesis and related 

functions; neurological development 

and function; reproduction and physical 

development; kidney function; 

cardiovascular function; and immune 

function. The weight of evidence varies 

across this array of effects and is 

comprehensively described in the 

AQCD for Lead. There is also some 

evidence of lead carcinogenicity, 

primarily from animal studies, together 

with limited human evidence of 

suggestive associations (AQCD for Lead, 

Sections 5.6.2, 6.7, and 8.4.10). The U.S. 

EPA has listed lead under current EPA 

guidelines as a probable human 

carcinogen based on the available 

animal data (AQCD for Lead, p. 6– 

195).76 Inorganic lead has been 

classified as a probable human 

carcinogen by the International Agency 

for Research on Cancer (inorganic lead 

compounds), based mainly on sufficient 

animal evidence,77 and classified as 

reasonably anticipated to be a human 

carcinogen by the U.S. National 

Toxicology Program (lead and lead 

compounds) (AQCD for Lead, Section 

6.7.2).78 79

As described in the AQCD for Lead, 

the key effects associated with 

individual blood lead levels in children 

and adults in the range of 10 μg/dL and 

lower include neurological, 

hematological and immune 80 effects for 

children, and hematological, 

cardiovascular and renal effects for 

adults (AQCD for Lead, Tables 8–5 and 

8–6, pp. 8–60 to 8–62). As evident from 

the discussions in Chapters 5, 6 and 8 

of the AQCD for Lead, ‘‘neurotoxic 

effects in children and cardiovascular 

effects in adults are among those best 

substantiated as occurring at blood lead 

concentrations as low as 5 to 10 μg/dL 

(or possibly lower); and these categories 

are currently clearly of greatest public 

health concern’’ (AQCD for Lead, p. 8– 

60).81 82 The AQCD for Lead states, 

‘‘There is no level of lead exposure that 

can yet be identified, with confidence, 

as clearly not being associated with 

some risk of deleterious health effects’’ 

(AQCD for Lead, p. 8–63). 

While adults are susceptible to lead 

effects at lower blood lead levels than 

previously understood (e.g., AQCD for 

Lead, p. 8–25), among the wide variety 

of health endpoints associated with lead 

exposures, there is general consensus 

that the developing nervous system in 

children is among the, if not the, most 

sensitive. Blood lead levels in U.S. 

children have decreased notably since 

the late 1970s. Studies evaluating 

current blood lead levels in children 

have reported associations with 

neurodevelopment effects (AQCD for 

Lead, Chapter 6). Functional 

manifestations of lead neurotoxicity 

during childhood include sensory, 

motor, cognitive and behavioral 

impacts. Numerous epidemiological 

studies have reported neurocognitive, 

neurobehavioral, sensory, and motor 

function effects in children with blood 

lead levels below 10 μg/dL (AQCD Lead, 

Sections 6.2 and 8.4). 

Cognitive effects associated with lead 

exposures that have been observed in 

epidemiological studies have included 

decrements in intelligence test results, 

such as the widely used IQ score, and 

in academic achievement as assessed by 

various standardized tests as well as by 

class ranking and graduation rates 

(AQCD for Lead, Section 6.2.16 and pp 

8–29 to 8–30). As noted in the AQCD for 

Lead with regard to the latter, 

‘‘Associations between lead exposure 

and academic achievement observed in 

the above-noted studies were significant 

even after adjusting for IQ, suggesting 

that lead-sensitive neuropsychological 

processing and learning factors not 


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83As an example, the AQC for Lead states 

‘‘although an increase of a few mmHg in blood 

pressure might not be of concern for an individual’s 

well-being, the same increase in the population 

mean might be associated with substantial increases 

in the percentages of individuals with values that 

are sufficiently extreme that they exceed the criteria 

used to diagnose hypertension’’ (AQC for Lead, p. 

8–77). 

84For example, for a population mean IQ of 100 

(and standard deviation of 15), 2.3% of the 

population would score above 130, but a shift of the 

population to a mean of 95 results in only 0.99% 

of the population scoring above 130 (AQC for Lead, 

pp. 8–81 to 8–82). 

85U.S. EPA (2005) Guidance on Selecting Age 

Groups for Monitoring and Assessing Childhood 

Exposure to Environmental Contaminants. EPA/ 

630/P–03/003F. 

86U.S. EPA (2006) A Framework for Assessing 

Health Risks of Environmental Exposures to 

Children. EPA/600/R–05/093A. 

87U.S. EPA (2008) Child-Specific Exposure 

Factors Handbook. EPA/600/R–06/096F. 

reflected by global intelligence indices 

might contribute to reduced 

performance on academic tasks’’ (AQCD 

for Lead, pp 8–29 to 8–30). 

With regard to potential implications 

of lead effects on IQ, the AQCD for Lead 

recognizes the ‘‘critical’’ distinction 

between population and individual risk, 

identifying issues regarding declines in 

IQ for an individual and for the 

population. The AQCD for Lead further 

states that a ‘‘point estimate indicating a 

modest mean change on a health index 

at the individual level can have 

substantial implications at the 

population level’’ (AQCD for Lead, p. 8– 

77).83 A downward shift in the mean IQ 

value is associated with both substantial 

decreases in percentages achieving very 

high scores and substantial increases in 

the percentage of individuals achieving 

very low scores (AQCD for Lead, p. 8– 

81).84 For an individual functioning in 

the low IQ range due to the influence of 

developmental risk factors other than 

lead, a lead-associated IQ decline of 

several points might be sufficient to 

drop that individual into the range 

associated with increased risk of 

educational, vocational, and social 

failure (AQCD for Lead, p. 8–77). 

Other cognitive effects observed in 

studies of children have included 

decrements in attention, executive 

functions, language, memory, learning 

and visuospatial processing (AQCD for 

Lead, Sections 5.3.5, 6.2.5 and 8.4.2.1), 

with attention and executive function 

effects associated with lead exposures 

indexed by blood lead levels below 10 

μg/dL (AQCD for Lead, Section 6.2.5 

and pp. 8–30 to 8–31). The evidence for 

the role of lead in this suite of effects 

includes experimental animal findings 

(discussed in the AQCD for Lead, 

Section 8.4.2.1; p. 8–31), which provide 

strong biological plausibility of lead 

effects on learning ability, memory and 

attention (AQCD for Lead, Section 

5.3.5), as well as associated mechanistic 

findings. 

The persistence of such lead-induced 

effects is described in the AQCD for 

Lead (e.g., AQCD for Lead Sections 

5.3.5, 6.2.11, and 8.5.2). The persistence 

or irreversibility of such effects can be 

the result of damage occurring without 

adequate repair offsets or of the 

persistence of lead in the body (AQCD 

for Lead, Section 8.5.2). It is 

additionally important to note that there 

may be long-term consequences of such 

deficits over a lifetime. Poor academic 

skills and achievement can have 

‘‘enduring and important effects on 

objective parameters of success in real 

life,’’ as well as increased risk of 

antisocial and delinquent behavior 

(AQCD for Lead, Section 6.2.16). 

The current evidence reviewed in the 

AQCD for Lead with regard to the 

quantitative relationship between 

neurocognitive decrement, such as IQ, 

and blood lead levels indicates that the 

slope for lead effects on IQ is nonlinear 

and is steeper at lower blood lead levels, 

such that each μg/dL increase in blood 

lead may have a greater effect on IQ at 

lower blood lead levels (e.g., below 10 

μg/dL) than at higher levels (AQCD for 

Lead, Section 6.2.13; pp. 8–63 to 8–64; 

Figure 8–7). As noted in the AQCD for 

Lead, a number of examples of non- or 

supralinear dose-response relationships 

exist in toxicology (AQCD for Lead, pp. 

6–76 and 8–38 to 8–39). With regard to 

the effects of lead on 

neurodevelopmental outcomes such as 

IQ, the AQCD for Lead suggests that 

initial neurodevelopmental effects at 

lower lead levels may be disrupting very 

different biological mechanisms (e.g., 

early developmental processes in the 

central nervous system) than more 

severe effects of high exposures that 

result in symptomatic lead poisoning 

and frank mental retardation (AQCD for 

Lead, p. 6–76). The AQCD for Lead 

describes this issue in detail with regard 

to lead (summarized in AQCD for Lead 

at p. 8–39). Various findings within the 

toxicological evidence, presented in the 

AQCD for Lead, provide biologic 

plausibility for a steeper IQ loss at low 

blood lead levels, with a potential 

explanation being that the predominant 

mechanism at very low blood lead 

levels is rapidly saturated and that a 

different, less-rapidly-saturated process 

becomes predominant at blood lead 

levels greater than 10 μg/dL. 

3. At-Risk Populations and Life Stages 

Individuals potentially at risk from 

exposure to environmental pollutants 

include those with increased 

susceptibility and vulnerability. The 

terms ‘‘susceptibility’’ and 

‘‘vulnerability’’ have been used to 

characterize those with a greater 

likelihood of an adverse outcome given 

a specific exposure in comparison with 

the general population. This increased 

likelihood of response to a pollutant can 

result from a multitude of factors, 

including genetic or developmental 

factors, life stages (i.e., childhood or old 

age), gender differences, or preexisting 

disease states. In addition, new 

attention has been paid to the concept 

of some population groups having 

increased responses to pollution-related 

effects due to factors including 

socioeconomic status (SES) (e.g., 

reduced access to health care, poor 

nutritional status) or particularly 

elevated exposure levels. 

EPA uses the term ‘‘life stage’’ to refer 

to a distinguishable time frame in an 

individual’s life characterized by unique 

and relatively stable behavioral and/or 

physiological characteristics that are 

associated with development and 

growth. To recognize the rapid changes 

that occur during childhood related to 

physiology, metabolism, anatomy and 

behavior that can impact exposure and 

risk to environmental hazards, EPA now 

views childhood as a sequence of life 

stages, from conception through fetal 

development, infancy, and adolescence. 

EPA published several exposure and 

risk assessment guidance documents 

beginning in 2005,85 86 87 in which we 

emphasized the importance of 

considering the potential for increased 

sensitivity of different life stages or age 

groups in addition to that of groups that 

form a fixed portion of the population 

based on characteristics such as preexisting disease, gender, socioeconomic 

status, geographical location, culture/ 

ethnicity, or genetic make-up. 

Physiological, behavioral and 

demographic factors contribute to 

increased risk of lead-related health 

effects. Children are at increased risk of 

lead-related health effects due to various 

factors that enhance their exposures 

(e.g., via the hand-to-mouth activity that 

is prevalent in very young children, 

AQCD for Lead, Section 4.4.3) and 

susceptibility. While children are 

considered to be at a period of 

maximum exposure around 18–27 

months, the current evidence has found 

even stronger associations between 

blood lead levels at school age and IQ 

at school age. The evidence ‘‘supports 

the idea that lead exposure continues to 

be toxic to children as they reach school 

age, and [does] not lend support to the 

interpretation that all the damage is 

done by the time the child reaches 2 to 


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88U.S. Environmental Protection Agency (2007) 

Review of the National Ambient Air Quality 

Standards for Lead: Policy Assessment of Scientific 

and Technical Information, OAQPS Staff Paper. 

EPA–452/R–07–013. Office of Air Quality Planning 

and Standards, Research Triangle Park. 

89See 73 FR 66973 (November 12, 2008). 

90U.S. Environmental Protection Agency (2007) 

Review of the National Ambient Air Quality 

Standards for Lead: Policy Assessment of Scientific 

and Technical Information, OAQPS Staff Paper. 

EPA–452/R–07–013. Office of Air Quality Planning 

and Standards, Research Triangle Park. 

91U.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. 

3 years of age’’ (AQCD for Lead, Section 

6.2.12). Physiological factors that can 

affect risk of lead-related effects in 

children include genetic 

polymorphisms and nutritional status. 

Children with particular genetic 

polymorphisms (e.g., presence of the daminolevulinic acid dehydratase-2 

[ALAD–2] allele) have increased 

sensitivity to lead toxicity, which may 

be due to increased susceptibility to the 

same internal dose and/or to increased 

internal dose associated with the same 

exposure (AQCD for Lead, p. 8–71, 

Sections 6.3.5, 6.4.7.3 and 6.3.6). Some 

children may have blood lead levels 

higher than those otherwise associated 

with a given lead exposure (AQCD for 

Lead, Section 8.5.3) as a result of 

nutritional status (e.g., iron deficiency, 

calcium intake), as well as genetic and 

other factors (AQCD for Lead, Chapter 4 

and Sections 3.4, 5.3.7 and 8.5.3). 

Demographic factors that can affect 

risk of lead-related effects in children 

include residential location, poverty, 

and race. As noted in previous EPA 

actions on lead, situations of elevated 

exposure, such as residing near sources 

of ambient lead, as well as 

socioeconomic factors, such as reduced 

access to health care or low 

socioeconomic status can also 

contribute to increased blood lead levels 

and increased risk of associated health 

effects from air-related lead.88

Additionally, as described in the 

NAAQS for Lead, children in poverty 

and black, non-Hispanic children have 

notably higher blood lead levels than do 

economically well-off children and 

white children, in general.89

C. Welfare Effects 

Lead is persistent in the environment 

and accumulates in soils, aquatic 

systems (including sediments), and 

some biological tissues of plants, 

animals and other organisms, thereby 

providing long-term, multi-pathway 

exposures to organisms and ecosystems. 

In 2008, EPA established a secondary 

lead standard of 0.15 ug/m3. This 

standard is intended to protect the 

public welfare from known or 

anticipated adverse effects associated 

with the presence of lead in the ambient 

air. This section provides a summary of 

information regarding welfare effects of 

lead, focusing on terrestrial and aquatic 

ecosystems. This information is largely 

drawn from the 2006 AQCD for Lead, 

Chapter 6 of the Office of Air Quality 

Planning and Standards Staff Paper on 

Lead (SP) 90 and the Lead NAAQS. 

1. Terrestrial Ecosystems 

Lead is removed from the atmosphere 

and deposited on soil and other surfaces 

via wet or dry deposition. In soils, most 

lead is retained via the formation of 

stable solid phase compounds, 

precipitates, or complexes with organic 

matter. Thus, terrestrial ecosystems 

remain primarily sinks for lead but 

amounts retained in various soil layers 

vary based on forest type, climate, and 

litter cycling (AQCD for Lead, Section 

7.1). Once in the soil, the migration and 

distribution of lead is controlled by a 

multitude of factors including pH, 

precipitation, litter composition and 

other factors, which in turn, govern the 

rate at which lead is bound to organic 

materials in the soil (AQCD for Lead, 

Section 2.3.5, and Section AX 7.1.4.1). 

Lead exists in the environment in 

different forms which vary widely in 

their ability to cause adverse effects on 

ecosystems and organisms. Many forms 

of lead in the ambient air are quite 

insoluble and thus not easily leached to 

underground water once deposited to 

surfaces. However, leaching may occur 

under acidic conditions, where lead 

concentrations are extremely high, or in 

the presence of substances (e.g., soluble 

organic matter, high concentrations of 

chlorides or sulfates) that form 

relatively soluble complexes with lead 

(AQCD for Lead, Section 2.3.5). 

Plants take up lead via their foliage 

and through their root systems. The rate 

of plant uptake from soil varies by plant 

species, soil conditions, and lead 

species. Most lead in plants is stored in 

roots, and very little is stored in fruits. 

Metals that are applied to soil as salts 

(usually as sulfate, chloride, or nitrate 

salt) are accumulated more readily than 

the same quantity of metal added via 

sewage sludge, flue dust, or fly ash 

(AQCD for Lead, Section 2.3.7). 

Surface deposition of lead onto plants 

may represent a significant contribution 

to the total lead in and on the plant, as 

has been observed for plants near 

smelters and along roadsides (AQCD for 

Lead, page E–19). Atmospheric 

deposition of lead also contributes to 

lead in vegetation as a result of contact 

with above-ground portions of the plant 

(AQCD for Lead, pp. 7–9 and AXZ7–39; 

USEPA, 1986, Sections 6.5.3 and 

7.2.2.2.1). Wildlife may subsequently be 

exposed to lead in vegetation (e.g., 

grasses and silage) and in surface soils 

via incidental ingestion of soil while 

grazing (USEPA 1986, Section 

7.2.2.2.2).91

By far, the majority of air-related lead 

found in natural terrestrial ecosystems 

was deposited in the past during the use 

of lead additives in motor vehicle 

gasoline. Many sites receiving lead 

predominantly through long-range 

transport of gasoline-derived small 

particles have accumulated large 

amounts of lead in soils (AQCD for 

Lead, p. AX7–98). There is little 

evidence that terrestrial sites exposed as 

a result of this long range transport of 

lead have experienced significant effects 

on ecosystem structure or function 

(AQCD for Lead, Section AX7.1.4.2 and 

p. AX7–98). Strong complexation of 

lead by organic matter in soil may 

explain why few ecological effects have 

been observed (AQCD for Lead, p. AX7– 

98). Studies have shown decreasing 

levels of lead in vegetation, which 

appears to correlate with decreases in 

atmospheric deposition of lead resulting 

from the removal of lead additives to 

motor vehicle gasoline (AQCD for Lead, 

Section AX 7.1.4.2). 

The deposition of gasoline-derived 

lead into forest soils has produced a 

legacy of slow moving lead that remains 

bound to organic materials despite 

dramatic reductions in the use of leaded 

additives to motor vehicle fuels. Current 

levels of lead in soil vary widely 

depending on the source of lead but in 

all ecosystems lead concentrations 

exceed natural background levels. For 

areas influenced by point sources of air 

lead, concentrations of lead in soil may 

exceed by many orders of magnitude the 

concentrations which are considered 

harmful to laboratory organisms. 

Adverse effects in terrestrial organisms 

associated with lead include 

neurological, physiological and 

behavioral effects which may influence 

ecosystem structure and functioning (73 

FR 67008). 

2. Aquatic Ecosystems 

Atmospheric lead enters aquatic 

ecosystems primarily through 

deposition (wet and dry) and the 

erosion and runoff of soils containing 

lead. While overall deposition rates of 

atmospheric lead have decreased 

dramatically since the removal of lead 

additives from motor vehicle gasoline, 


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92AQC for Lead I. 7–24: (Vink, 2002; Rainbow, 

1996). 

93AQC for Lead AX7.2.3.1. 

94AQC for Lead page 232, Annex 7. 

95AQC for Lead page 232, Annex 7. 

96http://www.epa.gov/air/data/neidb.html. 

97 DOE Energy Information Administration. Fuel 

production volume data obtained from http:// 

tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm 

accessed November 2006. 98ChevronTexaco (2006) Aviation Fuels 

Technical Review. FTR–3. Available online at: 

http://www.chevronglobalaviation.com/docs/ 

aviation_tech_review.pdf. 

99ASTM International (2007) Standard 

Specification for Aviation Gasolines D910–06. 

100U.S. Environmental Protection Agency (2008) 

Lead Emissions from the Use of Leaded Aviation 

Gasoline in the United States, Technical Support 

Document. EPA420–R–08–020. Available online at: 

http://www.epa.gov/otaq/aviation.htm. 

lead continues to accumulate and may 

be re-exposed in sediments and water 

bodies throughout the United States 

(AQCD for Lead, Section 2.3.6). 

Several physical and chemical factors 

govern the fate and bioavailability of 

lead in aquatic systems. A significant 

portion of lead remains bound to 

suspended particulate matter in the 

water column and eventually settles 

into the substrate. Species, pH, salinity, 

temperature, turbulence and other 

factors govern the bioavailability of lead 

in surface waters (AQCD for Lead, 

Section 7.2.2). Lead can bioaccumulate 

in the tissues of aquatic organisms 

through ingestion of food and water, 

and adsorption from water, and can 

subsequently lead to adverse effects if 

tissue levels are sufficiently high.92 The 

accumulation of lead is influenced by 

pH and decreasing pH favors 

bioavailability and bioaccumulation. 

Organisms that bioaccumulate lead with 

little excretion must partition the metal 

such that it has limited bioavailability, 

otherwise toxicity will occur if a 

sufficiently high concentration is 

reached.93 The general symptoms of 

lead toxicity in fish include production 

of excess mucus, lordosis, anemia, 

darkening of the dorsal tail region, 

degeneration of the caudal fin, 

destruction of spinal neurons, 

aminolevulinic acid dehydratase 

(ALAD) inhibition, growth inhibition, 

renal pathology, reproductive effects, 

growth inhibition, and mortality.94

Toxicity in fish has been closely 

correlated with duration of lead 

exposure and uptake.95

Lead exists in the aquatic 

environment in various forms and under 

various chemical and physical 

parameters which determine the ability 

of lead to cause adverse effects either 

from dissolved lead in the water column 

or lead in sediment. Current levels of 

lead in water and sediment vary widely 

depending on the source of lead. 

Conditions exist in which adverse 

effects to organisms and thereby 

ecosystems may be anticipated given 

experimental results. It is unlikely that 

dissolved lead in surface water 

constitutes a threat to ecosystems that 

are not directly influenced by point 

sources. For lead in sediment, the 

evidence regarding the effects is less 

clear. It is likely that some areas with 

long-term historical deposition of lead 

to sediment from a variety of sources as 

well as areas influenced by point 

sources have the potential for adverse 

effects to aquatic communities. The long 

residence time of lead in sediment and 

its ability to be resuspended by 

turbulence make lead likely to be a 

factor for consideration regarding 

potential risk to aquatic systems for the 

foreseeable future (73 FR 67008). 

III. Lead Emissions From Piston-Engine 

Aircraft 

Currently, lead emitted by pistonengine aircraft operating on leaded 

avgas is the largest source of lead to the 

air, contributing about 50% of the 

National Emission Inventory in 2005. 

This section describes the draft 2008 

avgas lead inventory which is currently 

undergoing review by State, local and 

Tribal air agencies. We describe and 

request comment on input data used to 

derive airport-specific lead inventories. 

This section ends with a summary of 

data forecasting the potential growth of 

the industry using leaded avgas. 

A. Inventory of Lead From Piston-Engine 

Powered Aircraft 

Every three years, the EPA prepares a 

National Emissions Inventory (NEI) of 

air emissions of criteria pollutants and 

hazardous air pollutants with input 

from numerous State, local, and Tribal 

air agencies and from industry.96 For the 

purposes of this ANPR, EPA is 

describing piston-engine aircraft lead 

information provided in the draft 2008 

NEI as well as information from the 

final 2005 NEI. We have chosen to 

describe the draft 2008 NEI for the 

following reasons: (1) This is the first 

version of the NEI that will include 

airport-specific lead inventories that use 

our most recently developed methods 

for estimating lead (described below); 

(2) this inventory is the first NEI to 

include approximately 20,000 airport 

facilities in the U.S.; and (3) to increase 

awareness of the opportunity for State, 

local, and Tribal governments and 

industry to review this draft NEI and 

provide information that could improve 

airport lead inventories. Comments and 

data can be supplied to EPA for the 

2008 NEI until mid-2010. While we are 

describing the draft 2008 NEI for pistonengine aircraft emissions of lead, we do 

not have draft inventory estimates for 

2008 for all sources of lead. The 2008 

NEI will be final in 2010. 

1. National Emissions of Lead From 

Piston-Engine Aircraft 

To calculate the national avgas lead 

inventory, the volume of leaded avgas 

produced in a given year is multiplied 

by the concentration of lead in the avgas 

and by the fraction of lead emitted from 

a combustion system operating on 

leaded fuel (to account for the lead that 

is retained in the engine, engine oil and/ 

or exhaust system). For example, the 

volume of avgas produced in the U.S. in 

2008 according to DOE was 235,326,000 

gallons.97 The concentration of lead in 

avgas ([Pb] in the equation below) can 

be one of four levels (ranging from 0.14 

to 1.12 grams of lead per liter or 0.53 to 

4.24 grams of lead per gallon) as 

specified by the American Society for 

Testing and Materials (ASTM). By far 

the most common avgas supplied is 

‘‘100 Low Lead’’ or 100LL which has a 

maximum lead concentration specified 

by ASTM of 0.56 grams per liter or 2.12 

grams per gallon.98 99 A fraction of lead 

is retained in the engine, engine oil and/ 

or exhaust system which we currently 

estimate at 5%.100

For 2008, using DOE fuel volume 

estimates, the national estimate of lead 

emissions from the consumption of 

avgas is 522 tons as calculated 

according to the following equation: 

(,, 235 326 000 gal)(2.12 g Pb/gal)(0.95)

907,185 g/short ton = 522 short tons Pb


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101U.S. Department of Transportation Federal 

Aviation Administration Aviation Policy and Plans. 

FAA Aerospace Forecast Fiscal Years 2009–2025. 

p.81. Available at: http://www.faa.gov/ 

data_research/aviation/aerospace_forecasts/2009- 

2025/media/2009%20Forecast%20Doc.pdf. This 

document provides historical data for 2000–2008 as 

well as forecast data. 

102ChevronTexaco (2006) Aviation Fuels 

Technical Review p. 44. Available online at: 

http://www.chevronglobalaviation.com/docs/ 

aviation_tech_review.pdf. 

103EDMS is available online at: http:// 

www.faa.gov/about/office_org/ 

headquarters_offices/aep/models/edms_model/. 

As described in the Overview section 

of this ANPR, DOT’s FAA also provides 

estimates of annual avgas fuel 

consumption. For 2008, DOT estimates 

351,000,000 gallons of avgas were 

consumed. Consumption of this volume 

of avgas equates to a national lead 

emissions estimate for this source of 779 

short tons. DOT fuel volume data are 

derived from FAA estimates of pistonengine activity annually.101 We are 

working to identify the source(s) of the 

information used to derive DOE fuel 

volume estimates. In the draft 2008 NEI, 

we are using DOT fuel volume 

estimates. 

We currently cannot estimate the 

fraction of total lead emissions these 

estimates comprise since the inventories 

for all other sources of lead to air are not 

yet in the draft 2008 NEI. In 2005, lead 

from avgas comprised about 50% of the 

national lead inventory for emissions to 

air. As point source emissions of lead 

have decreased, lead emissions from 

piston-engine aircraft have become the 

largest single source of lead to air 

(Figure 2). These lead emissions 

estimates do not include evaporative 

losses of lead and minimal military 

aircraft data. Few military aircraft are 

piston-engine powered and consume 

leaded avgas.102 Military aircraft data 

are supplied by States, and data 

provided to EPA during the 2008 NEI 

review will be included in the final 

2008 inventory. 

2. Airport-Specific Emissions of Lead 

From Piston-Engine Aircraft 

Aircraft gaseous and particulate 

matter (PM) emissions are calculated 

through the FAA’s Emissions and 

Dispersion Modeling System (EDMS).103

This modeling system was designed to 

develop emission inventories for the 

purpose of assessing potential air 

quality impacts of airport operations 

and proposed airport development 

projects. Lead emissions from pistonengine aircraft are not included in 

EDMS. To estimate airport-specific lead 

inventories we use engine data and 

other attributes of general aviation (GA) 

and air taxi (AT) that are used in EDMS 

for GA and AT and we use methods 

similar to those in EDMS that are 

described in an EPA Technical Support 

Document (TSD) and briefly 


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104U.S. Environmental Protection Agency (2008) 

Lead Emissions from the Use of Leaded Aviation 

Gasoline in the United States, Technical Support 

Document. EPA420–R–08–020. Available online at: 

http://www.epa.gov/otaq/aviation.htm. 

105The FAA GAATA is a database collected from 

surveys of pilots flying aircraft used for general 

aviation and air taxi activity. For more information 

on the GAATA, see Appendix A, online at: 

http://www.faa.gov/data_statistics/ 

aviation_data_statistics/general_aviation/. 

106There are about 194,000 piston-engine aircraft 

in the U.S. general aviation and air taxi fleet 

(175,000 single-engine and 19,000 twin-engine 

aircraft) according to FAA’s 2005 GAATA Survey. 

107EPA understands that EDMS 5.0.2 has a 

limited list of piston engines, but these are 

currently the best data available. 

108U.S. Environmental Protection Agency (1992) 

Procedures for Emission Inventory Preparation, 

Volume IV: Mobile Sources, EPA–450/4–81–026d 

(Revised). 

109The information used to develop this estimate 

is from the following references: (a) Todd L. 

Petersen, Petersen Aviation, Inc, Aviation Oil Lead 

Content Analysis, Report Number EPA 1–2008, 

January 2, 2008, available at William J. Hughes 

Technical Center Technical Reference and Research 

Library at http://actlibrary.tc.faa.gov/ and (b) E-mail 

from Theo Rindlisbacher of Switzerland Federal 

Office of Civil Aviation to Bryan Manning of U.S. 

EPA, regarding lead retained in engine, September 

28, 2007. 

summarized here.104 The data required 

to estimate airport-specific lead 

inventories includes the landing and 

take-off (LTO) activity of piston-engine 

aircraft at a facility; fuel consumption 

rates by these aircraft during the various 

modes of the landing and take-off cycle; 

the time spent in each mode of the LTO 

(taxi/idle-out, takeoff, climb-out, 

approach, and taxi/idle-in); the 

concentration of lead in the fuel; and 

the retention of lead in the engine and 

oil. The equation used to calculate 

airport-specific lead emissions during 

the LTO cycle is below, followed by a 

description of each of the input 

parameters. 

LTO Pb (tons) -engine LTO gal/LTO)([Pb])( -P = ( )( piston avgas 1 b retention)

907,185 g/short ton

Piston-engine LTO: Most pistonengine aircraft fall into the categories of 

either GA or AT. Some GA and AT 

activity is conducted by turboprop and 

turbojet aircraft which do not use leaded 

avgas. There are no national databases 

that provide airport-specific LTO 

activity data for piston-engine aircraft 

separately from turbojet and turboprop 

aircraft. The fraction of GA and AT 

aircraft that use piston engines will vary 

by airport. However, in the absence of 

airport-specific data, EPA calculated a 

national default estimate using FAA’s 

GA and AT Activity (GAATA) 

Survey.105 The 2005 GAATA Survey 

reports that approximately 72% of all 

GA and AT LTOs are from piston-engine 

aircraft which use avgas, and about 28% 

are turboprop and turbojet powered 

which use jet fuel, such as Jet A.106 Lead 

is not added to jet fuel. Therefore, to 

calculate piston-engine aircraft LTO as 

input for this equation, the total GA 

plus AT LTOs are multiplied by 0.72. 

Avgas use (gal/LTO): Piston-engine 

aircraft can have either one or two 

engines. EDMS version 5.0.2 contains 

information on the amount of avgas 

used per LTO for some single and twinengine aircraft. The proportion of 

piston-engine LTOs conducted by 

single- versus twin-engine aircraft was 

taken from the FAA’s GAATA Survey 

for 2005 (90% of LTOs are conducted by 

aircraft having one engine and 10% of 

LTOs by aircraft having two engines). 

Since twin-engine aircraft have higher 

fuel consumption rates than those with 

single engines, a weighted average LTO 

fuel usage rate was established to apply 

to the population of piston-engine 

aircraft as a whole. For the single-engine 

aircraft, the average amount of fuel 

consumed per LTO was determined 

from the six types of single pistonengine aircraft within EDMS.107 This 

was accomplished by averaging the 

single-engine EDMS outputs for fuel 

consumed per LTO using the EDMS 

scenario property of ICAO/USEPA 

Default—Times in Mode (TIM), with a 

16 minute taxi-in/taxi-out time 

according to EPA’s Procedures for 

Emission Inventory Preparation, 

Volume IV: Mobile Sources, 1992.108

This gives a value of 16.96 pounds of 

fuel per LTO (lbs/LTO). Next, the 

average single-engine consumption rate 

was divided by the average density of 

100LL avgas, 6 pounds per gallon (lbs/ 

gal), producing an average fuel usage for 

single-engine piston aircraft of 2.83 

gallons per LTO (gal/LTO). This same 

calculation was performed for the two 

twin-engine piston aircraft within 

EDMS, producing an average LTO fuel 

usage rate for twin-engine piston aircraft 

of 9.12 gal/LTO. 

Using these single- and twin-engine 

piston aircraft fuel consumption rates, a 

weighted average fuel usage rate per 

LTO was computed by multiplying the 

average fuel usage rate for single-engine 

aircraft (2.83 gal/LTO) by the fleet 

percentage of single-engine aircraft 

LTOs (90%). Next, the twin-engine 

piston aircraft average fuel usage rate 

(9.12 gal/LTO) was multiplied by the 

fleet percentage of twin-engine aircraft 

LTOs (10%). By summing the results of 

the single- and twin-engine aircraft 

usage rates, the overall weighted average 

fuel usage rate per LTO of 3.46 gal/LTO 

is obtained. 

Concentration of lead in fuel, [Pb]: 

The maximum lead concentration 

specified by ASTM for 100LL is 0.56 

grams per liter or 2.12 grams per gallon. 

This amount of lead is normally added 

to assure that the required lean and rich 

mixture knock values are achieved. As 

noted above, 100 Octane (containing 

1.12 grams of lead per liter or 4.24 

grams of lead per gallon) is used by a 

small number of piston-engine aircraft. 

We currently do not include estimates 

of lead emissions using 100 Octane and 

we are requesting comment on the 

airport facilities where 100 Octane is 

used and the LTO activity associated 

with the use of this fuel. 

Retention of lead in engine and oil (1– 

Pb Retention): Recent data collected 

from aircraft piston engines operating 

on leaded avgas suggests that about 5% 

of the lead from the fuel is retained in 

the engine and engine oil.109 Thus the 

emitted fraction is 0.95. 

Multiplying the lead concentration in 

100LL avgas by the weighted average 

fuel usage rate produces an overall 

average value of 7.34 grams of lead per 

LTO (g Pb/LTO) for piston engines: 3.46 

gal/LTO × 2.12 g Pb/gal = 7.34 g Pb/ 

LTO. The denominator is a unit 

conversion factor used to express the 

lead inventory in units of short tons. 

Applying these parameters in the 

equation above yields the following 

equation: 


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110U.S. EPA (March 2010) Memorandum from 

Meredith Pedde to docket EPA–HQ–OAR–2007– 

0294, titled, ‘‘Calculating Aviation Gasoline Lead 

Emissions in the 2008 NEI.’’ pp.8–9. 

111An aircraft operation is defined as any landing 

or take-off event, therefore, to calculate LTOs, 

operations are divided by two. Most data sources 

from FAA report aircraft activity in numbers of 

operations which, for the purposes of calculating 

lead emissions using the method described in the 

TSD, need to be converted to LTO events. 

112An electronic report can be generated from the 

NASR database and is available for download from 

the Internet at the following Web site. http:// 

www.faa.gov/airports_airtraffic/airports/ 

airport_safety/airportdata_5010/. This database is 

updated every 56 days. 

113Stolport is an airport designed with STOL 

(Short Take-Off and Landing) operations in mind, 

normally having a short single runway. 

114http://aspm.faa.gov/main/taf.asp. 

115 In the absence of updated information from 

States, local authorities or Tribes, we are using the 

LTO data provided in the FAA database. 

116No Commuter, GA Itinerant, GA Local, or Air 

Taxi operations data. 

117U.S. EPA (March 2010) Memorandum from 

Meredith Pedde to docket EPA–HQ–OAR–2007– 

0294, titled, ‘‘Calculating Aviation Gasoline Lead 

Emissions in the 2008 NEI.’’ 

118Federal 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. 

119Hoekstra, M. (April 2000) Model for 

Estimating General Aviation Operations at NonTowered Airports. Prepared for FAA Office of 

Aviation Policy and Plans. 

120 GRA, Inc. ‘‘Review of TAF Methods,’’ Final 

Report, prepared for FAA Office of Aviation Policy 

and Plans under Work Order 45, Contract No. 

DTFA01–93–C–00066, February 25, 1998. 

121U.S. EPA (March 2010) Memorandum from 

Meredith Pedde to docket EPA–HQ–OAR–2007– 

0294, titled, ‘‘Calculating Aviation Gasoline Lead 

Emissions in the 2008 NEI.’’ 

Pb (tons) piston-engine LTO)(7.34 g Pb/LTO)(0.95)

907,185 = (g/short ton

which simplifies to: Pb = (piston-engine 

LTO) (7.7 × 10¥6 short tons) or 7 grams 

of lead per LTO where piston-engine 

LTO = (GA LTO + AT LTO)(0.72). EPA 

used similar methods to estimate lead 

emissions from piston-engine powered 

helicopters which are described 

separately.110 We currently estimate 

there are 6 grams of lead emitted by 

piston-engine helicopters per LTO. 

Lead emitted during the LTO cycle is 

assigned to the airport facility where the 

aircraft operations occur.111 FAA’s 

Office of Air Traffic provides a complete 

listing of operational airport facilities in 

the National Airspace System Resources 

(NASR) database.112 In 2008, there were 

19,896 airport facilities in the U.S., the 

vast majority of which are expected to 

have activity by piston-engine aircraft 

that operate on leaded avgas. There are 

seven types of airport facilities: airports, 

balloonports, seaplane bases, 

gliderports, heliports, stolports,113 and 

ultralight facilities. Among these, 

balloonports are the only facilities not 

expected to have piston-engine aircraft 

activity. 

Preparing airport-specific lead 

inventories requires information 

regarding LTO activity. 

These activity data are reported to the 

FAA for only a small subset of the 

approximately 20,000 facilities in the 

U.S. EPA obtains LTO information for 

approximately 3,400 facilities from 

FAA’s Terminal Area Forecast (TAF) 

database that is prepared by FAA’s 

Office of Aviation Policy and Plans.114

The TAF database currently includes 

information for airports in FAA’s 

National Plan of Integrated Airport 

Systems (NPIAS), which identifies 

airports that are significant to national 

air transportation. For airports not listed 

in the TAF, operations data are obtained 

from the NASR database, where 

available. Operations data provided by 

the NASR database may be self-reported 

by airport operators through data 

collection accomplished by airport 

inspectors who work for the State 

Aviation Agency, or operations data can 

be obtained through other means.115

We are using the January 15, 2009 

version of the NASR database to 

evaluate airport lead emissions 

inventories for 2008. Using the TAF 

database as the primary source of LTO 

information and the NASR as a 

secondary source, we have LTO activity 

data for approximately 5,600 airport 

facilities. There are approximately 

14,000 facilities in the NASR database 

for which there are no LTO activity 

data.116 We developed methods based 

on previous work conducted by the 

FAA to estimate LTO activity at the 

remaining airport and heliport facilities. 

We are requesting comment on these 

methods which are described here 

briefly. The details regarding the 

method described here are available in 

the docket.117

The FAA has used regression models 

to estimate operations at facilities where 

operations data are not available.118 119

In this work and other work, FAA 

identified characteristics of small 

towered airports for which there were 

statistically significant relationships 

with operations at these airports.120

Regression models based on the airport 

characteristics were then used to 

estimate general aviation operations for 

a set of non-towered airports. The 

airport characteristics identified by the 

FAA and used to estimate general 

aviation operations at small airports 

include: the number and type of aircraft 

based at the facility (i.e., ‘‘based 

aircraft’’), population in the vicinity of 

the airport, airport regional prominence, 

per capita income, region of the country, 

and the presence of certificated flight 

schools. We were able to obtain data 

from the NASR and the U.S. Census 

Bureau to evaluate relationships 

between several airport characteristics 

and LTO activity. LTO estimates were 

derived using different models 

depending on data availability. 

The number of based aircraft and 

county population in which the airport 

is located were the most highly 

significant and positive regressors to 

LTO activity that our analysis 

provided.121 The regression equation for 

based aircraft and county population is: 

LTOs = 1248 + 203.04*Aircraft + 

0.0019*County Population with an R2 = 

0.64. For approximately 7,800 facilities 

that do not report LTO activity to FAA, 

we used based aircraft and county 

population to estimate activity. We 

request comment on the method we are 

using to estimate LTO activity at these 

airport facilities. 

To estimate LTO activity at the airport 

facilities that do not report based 

aircraft, we used a regression equation 

based on county population and region 

of the country. The regression equation 

using county population and regression 

of the country is: LTOs = 6200.2 + 

0.0087*county population— 

175.07*West State ¥ 5567.3*Alaska + 

854.83*Northeast with an R2 = 0.15. 

This equation has a low correlation 

coefficient and we are exploring 

additional options for estimating LTO 

activity at these facilities for which very 

little information is reported to the 

FAA. We request comment on applying 

the regression equation above and 

alternative methods to estimate LTO 

activity at these facilities. 

For heliports, which comprise 

approximately 5,500 facilities in the 

NASR database, we had insufficient 

information on which to develop a 

regression equation and are currently 

using the median of activity (141 LTOs/ 

year) at heliports for which we have 

LTO activity data. Nationally, 25% of 

helicopters are piston-engine powered 

and therefore use leaded avgas. The 

FAA and EPA have limited information 


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122All documentation for use in preparing 2008 

emission inventories can be found on the NEI/EIS 

Implementation Web site: http://www.epa.gov/ttn/ 

chief/net/neip/index.html. 

123FAA Aerospace Forecast Fiscal Years 2009– 

2025. Available online at: http://www.faa.gov/ 

data_research/aviation. 

124 General Aviation Manufacturers Association 

(2008) General Aviation Statistical Databook and 

Industry Outlook, pp.51–55. Available online at: 

http://www.gama.aero/files/2008_general_

aviation_statistical_databook__indust

_499b0dc37b.pdf. 

125Except for sport pilots, an active pilot is a 

person with a pilot certificate with a valid medical 

certificate. Source: FAA 2008–2025 Aerospace 

Forecast. 

126U.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. 127U.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. 128Federal 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. 129ChevronTexaco (2006) Aviation Fuels 

Technical Review pp. 64–65. Available online at: 

http://www.chevronglobalaviation.com/docs/ 

aviation_tech_review.pdf. 

130U.S. Environmental Protection Agency (1986) 

Air Quality Criteria for Lead. Volume 2 Section 

regarding the specific heliports that 

have activity by piston-engine 

helicopters. We are requesting 

information regarding heliport facilities 

at which piston-engine powered aircraft 

operate and the activity of these aircraft. 

The draft 2008 NEI is the first 

inventory for which we are 

implementing the use of LTO-based lead 

estimates at almost 20,000 airport 

facilities and we are expecting State, 

local and Tribal air agency review of 

these data to improve our current 

estimates. The specific information on 

which we are requesting data include: 

(1) The fraction of GA and AT LTO 

activity reported to FAA that is 

conducted by piston-engine versus jetengine powered aircraft, (2) airportspecific LTO activity for single- versus 

twin-engine piston-powered aircraft, (3) 

fuel consumption rates for the pistonengine aircraft operating at each airport, 

(4) the time spent in each mode of 

operation including run-up checks 

conducted by piston-engine aircraft 

prior to take-off, and (5) the 

concentration of lead in fuel delivered 

to individual airports. Methods for 

providing information to EPA as part of 

the review process involved in 

finalizing the 2008 NEI are available.122

The discussion above pertains only to 

lead emissions during the LTO cycle. 

Lead emitted outside the LTO cycle 

occurs during aircraft cruise mode and 

portions of the climb-out and approach 

modes. This part of an aircraft operation 

emits lead at various altitudes as well as 

close to and away from airports. We are 

developing methods to estimate lead 

emissions outside the LTO cycle which 

we anticipate will be available in 2010. 

B. Projections for Future Growth 

The FAA publishes an annual forecast 

of the number of piston-engine powered 

aircraft, hours flown, the consumption 

of avgas, the numbers of pilots and 

student pilots.123 The most recent 

forecast is for the years 2009 through 

2025. The General Aviation 

Manufacturers Association (GAMA) 

reproduces the FAA forecast in their 

annual statistical databook.124

According to the GAMA summary, the 

number of active single-engine pistonpowered aircraft is projected to increase 

annually at a 0.5% growth rate, with the 

aircraft population increasing from 

144,220 in 2008 to 157,400 in 2025. The 

number of active twin-engine pistonpowered aircraft is projected to decrease 

0.9% annually, with aircraft population 

decreasing from 18,385 in 2008 to 

15,650 in 2025. The piston-powered 

helicopter population is expected to 

grow 4.7% annually from a population 

of 3,970 in 2008 to 8,295 in 2025. 

The FAA forecast predicts the number 

of hours flown in single-engine pistonpowered aircraft is projected to increase 

0.5% yearly from 2008 to 2025); the 

number of hours flown in twin-engine 

piston-powered aircraft is projected to 

decrease 1.5% annually and the number 

of hours flown in piston-powered 

rotocraft is projected to increase 3.9% 

annually. The changes in numbers of 

piston aircraft and hours flown is 

generally reflected in the consumption 

of leaded avgas. For the years 2008 

through 2025, DOT’s FAA estimates no 

change in the volume of leaded avgas 

consumed by single-engine aircraft in 

the U.S. (204 million gallons in 2008 

and 2025), a 1.9% decrease in leaded 

avgas consumed by multi-engine aircraft 

(from a baseline of 108 million gallons 

in 2008 to 78 million gallons in 2025), 

and a 3.8% annual increase in the 

volume of leaded avgas consumed by 

piston-powered helicopters (from a 

baseline of 13 million gallons in 2008 to 

24 million gallons in 2025). For 2025, 

the forecast volume of leaded avgas is 

348 million gallons. Consumption of 

this volume of fuel would release 773 

tons of lead to the air in 2025. 

The number of active pilots flying 

general aviation aircraft (excluding air 

transport pilots) is projected to be 

slightly over half a million in 2025, 

representing a yearly increase of 0.7% 

over the forecast period.125 The student 

pilot population is forecast to increase 

at a slightly higher rate of 1.0% yearly 

for a 2025 total slightly over 100,000. 

Private pilots and sport pilots are also 

projected to increase yearly (0.2% 

yearly increase in the number of private 

pilots). EPA is requesting comments on 

the forecast information presented in 

this section and on the uncertainty in 

these projections. 

IV. Lead Concentrations in the Vicinity 

of Airports 

This section summarizes information 

regarding the chemical and physical 

properties of lead emitted by pistonengine 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

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 


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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. 

131U.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. 

132U.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. 

133U.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. 

134South 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. 

136Environment Canada (2000) Airborne 

Particulate Matter, Lead and Manganese at 

Buttonville Airport. Toronto, Ontario, 

Canada:Conor Pacific Environmental Technologies 

for Environmental Protection Service, Ontario 

Region. 

137Tetra Tech, Inc. (2007) Destin Airport Air 

Sampling Project Executive Summary. Prepared for 

City of Destin, Florida. 

138Tetra Tech, Inc. (2008) Destin, Florida Airport 

Sampling Report. October 2008. Prepared for City 

of Destin, Florida. 

139Piazza, 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 

140U.S. Environmental Protection Agency (2009) 

2002 National-Scale Air Toxics Assessment 

(NATA). Available online at: http://www.epa.gov/ 

ttn/atw/nata2002/index.html. 

141South 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. 

142As 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. 

undergo compositional changes upon 

cooling and mixing with the ambient air 

as well as during transport; the watersolubility of these lead-bearing particles 

increases with a shift toward smaller 

mean particle size (USEPA 1977, 

Section 6.2.2.1). Lead halides from 

automobile exhaust break down rapidly 

in the atmosphere, via redox reactions 

in the presence of atmospheric acids 

(AQCD for Lead, page E–17). 

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 pistonengine 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). 

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 × 106 to 

8.6 × 106 particles per cm3 and using a 

specific density for soot of 1.2, the 

authors estimated the mass 

concentration of particulate emissions 

as approximately 10,000 μg/m3. 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). 

Due to their small size (i.e., typically 

less than one micron in diameter), leadbearing particles emitted by piston 

engines may disperse widely in the 

environment. However, lead emitted 

during LTO, particularly during groundbased operations such as start-up, idle, 

preflight run-up checks, taxi and takeoff 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 pistonengine 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. 

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 


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143A 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. 

144These distances were measured using Google 

Earth Pro software. 

145EPA 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. 

146U.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. 147Hu, 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. 148These 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. 

149Average concentrations reported in this study 

include three days of short-duration sampling so 

the average is not used for comparison here. 

150These distances were measured using Google 

Earth Pro software. 

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) μg/ 

m3.143 The maximum quarterly average 

concentration of lead in total suspended 

particulate matter (TSP) was 0.10 μg/m3, 

67% of the 2008 Lead NAAQS of 0.15 

μg/m3. 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 μg/m3. 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 

μg/m3 (winter) and 0.03 μg/m3

(spring).144 At a distance of one 

kilometer in the prevailing downwind 

direction from the maximum impact 

site, lead concentrations were 0.004 μg/ 

m3 and 0.008 μg/m3 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 onand 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

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). 

At the Van Nuys Airport, lead 

monitoring in ambient air was 

conducted at six sites for two threemonth 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 μg/m3 which was 

four-fold higher than the regional 

background level of 0.008 μg/m3

measured during the same time period 

at a site over 2.5 kilometers from the 

north end of the Van Nuys Airport. 

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 μg/m3 and the 

maximum 24-hour lead concentration 

was 0.13 μg/m3. One sample, collected 

for 11 hours, measured 0.30 μg/m3. The 

maximum concentration observed over 

a 24-hour period at the airport during 

this study (0.13 μg/m3) was 11 times 

higher than the lead concentration 

reported for the downtown Toronto, 

Canada background site during the same 

time period (0.012 μg/m3).149 The 

average lead concentration reported for 

the downtown Toronto site was 0.007 

μg/m3. 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. 

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 μg/m3 and downwind 

concentrations averaged 0.030 μg/m3. 

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 μg/m3

and 0.005 μg/m3 in April and July, 

respectively, and the average urban 


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151Murphy, 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. 

152U.S. Environmental Protection Agency (2009) 

2002 National-Scale Air Toxics Assessment 

(NATA). Available online at: http://www.epa.gov/ 

ttn/atw/nata2002/tables.html. 

153Piazza, 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. 

154Levin, 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. 

background lead concentration was 

0.003 and 0.004 μg/m3 in April and July, 

respectively. 

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. 

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 μg/g 

which was not substantially higher than 

the lead concentrations in soil samples 

at the two urban background sites (29 

and 31 μg/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. 

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

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 pistonengine aircraft. 

V. Exposure to Lead From PistonEngine 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 pistonengine 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. 

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 


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155U.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.’’ 

156Federal 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. 

157Obtained from: http://www.epa.gov/ttn/fera/ 

human_hem_censusandmet.html. 

158FAA 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). 

159ASTM International (2005) ASTM F2507–05 

Standard Specification for Recreational Airpark 

Design 

160http://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. 

161http://livingwithyourplane.com/about/ has a 

directory of over 600 residential airparks. 

162U.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. 

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 nearsource 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 pistonengine 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. 

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 pistonengine activity at heliports. 

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

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 


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163U.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.’’ 

164Public 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. 

165U.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. 

lead effects on IQ is nonlinear and is 

steeper at lower blood lead levels, such 

that each μg/dL increase in blood lead 

may have a greater effect on IQ at lower 

blood lead levels (e.g., below 10 μg/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. 

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 pistonengine 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. 

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 

schools within 

1 km of an 

airport 

Number of students who attend schools 

within 1 km of 

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 

Indian 

Asian/Pacific 

Islander 

Black, NonHispanic Hispanic White, NonHispanic Total students* 

All Schools within 1 

km of an airport.

Number ................. 46,861 154,408 597,223 764,704 1,646,882 3,290,763 

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 


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166United 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. 

167The 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/. 

168National 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. 

169National Agricultural Aviation Association: 

‘‘History.’’ Retrieved from: http:// 

www.agaviation.org/history.htm on August 13, 

2009. 

170U.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. 

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. 

172Harpole, 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. 

173Petersen, 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. 

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. 

177See http://flighttraining.aopa.org/. 

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. 

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

As discussed in Section II.C.1, surface 

deposition of lead onto plants may 

represent a significant contribution to 

the total lead in and on the plant. Lead 

halides, the primary form of lead 

emitted by engines operating on leaded 

fuel, are slightly water soluble. They 

therefore may be more readily absorbed 

by plants than other forms of inorganic 

lead. Atmospheric deposition of lead 

also contributes to lead in vegetation as 

a result of contact with above-ground 

portions of the plant (AQCD for Lead, 

pp. 7–9 and AXZ7–39; USEPA, 1986, 

Sections 6.5.3 and 7.2.2.2.1). Livestock 

may subsequently be exposed to lead in 

vegetation (e.g., grasses and silage) and 

in surface soils via incidental ingestion 

of soil while grazing (USEPA 1986, 

Section 7.2.2.2.2).170 The lead 

concentration of plants ingested by 

animals is primarily a result of 

atmospheric deposition of lead particles 

onto plant surfaces rather than the 

uptake of soil lead through plant roots. 

Some of the highest levels of lead 

exposure among livestock have been 

attributed to grazing near major sources 

such as smelters (AQCD for Lead, 

Section 2.3.8). Atmospheric deposition 

is estimated to comprise a significant 

proportion of lead in food (AQCD for 

Lead, p. 3–48) and dietary intake may be 

a predominant source of lead exposure 

among adults (greater than consumption 

of water and beverages or inhalation (73 

FR 66971)). 

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. 

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 


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178Federal 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/. 179Federal 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/. 180Federal Aviation Administration (FAA). ‘‘Pilot 

Schools—Search’’. Retrieved on August 17, 2009 

from: http://av-info.faa.gov/PilotSchool.asp. 181U.S. Environmental Protection Agency, ‘‘The 

Great Waters Program.’’ Retrieved on August 17, 

2009 from: http://www.epa.gov/air/oaqps/ 

gr8water/. 

182U.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. 

183U.S. Environmental Protection Agency, ‘‘The 

National Listing of Fish Advisories.’’ Retrieved on 

August 17, 2009 from: http://www.epa.gov/ 

waterscience/fish/advisories/. 

184 In some instances States supply individual 

fish tissue sample results and in some instances 

States supply averages of multiple fish tissue 

sample results. 

185State-specific fish advisories for lead can be 

downloaded from: http://oaspub.epa.gov/nlfwa/ 

nlfwa.bld_qry?p_type=advrpt&p_loc=on. 

186U.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. 

187U.S. Environmental Protection Agency, ‘‘Lead 

Fishing.’’. Retrieved on August 17, 2009 from: 

http://www.epa.gov/owow/fish/animals.html. 

188See Docket ID Number EPA–HQ–OAR–2006– 

0735. The Tribes that submitted comments were: 

Continued 

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. 

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 costeffective 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

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. 

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 inflight emissions are greatly dispersed in 

the environment and have been 

providing a source of lead to the 

environment for over 80 years. 

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 


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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. 

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

190U.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. 

191U.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. 

192National 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. 

193Thomas VM; Bedford JA; Cicerone RJ. (1997) 

Bromine emissions from leaded gasoline. Geophys 

Res Letters 24(11):1371–1374. 

194Chevron Material Safety Data Sheet for 

aviation gasoline. Available online at: http:// 

www.chevronglobalaviation.com/docs/ 

aviation_gas.doc. 

195Sigsby, J.E.; Dropkin, D.L.; Bradow, R.L.; Lang, 

J.M. (1982) Automotive Emissions of Ethylene 

Dibromide. SAE Technical Paper Series 820786. 

196U.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. 

197U.S. Environmental Protection Agency, 

‘‘Drinking Water Contaminants’’ Available online at: 

http://www.epa.gov/safewater/contaminants/ 

index.html. 

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 pistonengine aircraft on aquatic environments. 

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 μg/m3) and a 24-hour standard (35 

μg/m3). 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. 

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 × 10¥4 to 6 × 10¥4

per μg/m3. 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 × 10¥5 to 6 × 10¥5

per μg/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 μg/m3 based on 

the critical effect of nasal inflammation 

and a reference dose for chronic 

ingestion of 9 μg 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.¥ 

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 lightduty 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 pistonengine aircraft as well as the emissions 

associated with refueling and pre-flight 

fuel checks. 

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 μg/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

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 


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198U.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. 

199U.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. 

200U.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 

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. 

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). 

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 sourceoriented monitors. EPA Regional 

Administrators may waive the sourceoriented 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/m3. 

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, sourceoriented 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 


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201The petition is available at: http:// 

www.epa.gov/air/lead/pdfs/OAR.09.000.7687.pdf. 

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). 

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 PistonEngine Aircraft Contribute 

Among the estimated 135 sourceoriented 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 μg/m3. 

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, state EPA region 

County population (2000 

Census) 

Design value, 

2006–2008 

(μg/m3) 

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 


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202U.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 PistonEngine Powered Aircraft.’’ Docket number EPA– 

HQ–OAR–2007–0294. 

203The 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 postprocessor 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. 

204The report from this study is posted at 

http://www.epa.gov/otaq/aviation.htm. 

TABLE 3—COUNTIES WITH MAXIMUM ROLLING QUARTERLY AVERAGE LEAD CONCENTRATIONS EXCEEDING THE 2008 LEAD

NAAQS—Continued 

County, state EPA region 

County population (2000 

Census) 

Design value, 

2006–2008 

(μg/m3) 

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 sourceoriented 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 μg/m3. 

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 localscale gradient in lead concentrations onand near airport facilities with pistonengine 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 localscale 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 pistonengine 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

As part of this work, we collected air, 

soil and house dust samples for lead 

analysis in order to conduct a model-tomonitor evaluation, and to evaluate the 

potential for lead emissions from pistonengine 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 pistonengine 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 pistonengine 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 


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205 72 FR 64570 (Nov. 16, 2007); EPA Docket 

EPA–HQ–OAR–2007–0294. 

(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. 

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 


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