ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 87 [EPA - HQ - OAR- 2007 - 0294; FRL _XXXX - X ] RIN 2060 - AP79 Advance Notice of Proposed Rulemaking on Lead Emissions from Piston - Engine Aircraft Using Leaded Aviation Gasoline AGENCY: Environmental Protection Agency (EP A). 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 propos al 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 reasonabl y be anticipated to endanger public health or welfare . In this ANPR we describe and request comment on the data available for evaluating lead emissions, ambient concentrations and potential exposure to lead from the continued use of leaded avgas in piston - engine powered aircraft. We also describe and reque st 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 leade d 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 concerns2

regarding exposure to lead, particularl y 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 identi fy

a safe level of lead exposure. DATES: Comments must be received on or before [Insert date 60 day s after publication in the Federal Register] . ADDRESSES: Submit your comments, identified by Docket ID No. EPA - HQ - OAR - 2007 - 0294, by one of the following methods:

 www.regulations.gov : Follow the on - line instructions for submitting comments.

 Email: a - and - r - docket@epa.gov

 Fax: (202) 566 - 9744

 Mail: Environme ntal 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, R oom: 3334 Mail Code: 2822T, Washington, DC. Such deliveries are onl y 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 - 200 7 - 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 www.regulations.gov , including an y personal information p rovided, unless the comment includes information claimed to be Confidential Business Information (CBI)3

or other information whose disclosure is restricted by statute. Do not submit information that y ou consider to be CBI or otherwise protected through www. regulations.gov or e - mail. The www.regulations.gov website is an “anony mous access” s ys tem, which means EPA will not know y our identity

or contact information unless you provide it in the body of y our comment. If yo u send an e - mail comment directly to EPA without going through www.regulations.gov y our 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 s ubmit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with an y disk or CD - ROM y ou submit. I f EPA cannot read y our comment due to technical difficulties and cannot contact you f or clarification, EPA may not be able to consider yo ur comment. Electronic files should avoid the use of special characters, any form of encry ption, 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 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 b y statute. Certain other material, such as copyrighted material, will be publicly

available only

in hard copy . Publicly

available docket materials are available either electronica lly

in www.regulations.gov or in hard cop y 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 holiday s. The telephone number for the Public Reading Room is (202) 566 - 1744, and the telephone number for the Air Docket is (202) 566 - 1742 .4

FOR FURTHER INFORMATION CONTACT: Marion Ho ye r, Assessment and Standards Divisio n, Office of Transportation and Air Qualit y, 2000 Traverwood Drive, Ann Arbor, MI, 48105; telephone number: (734) 214 - 4513; fax number: (734) 214 - 4939; email address: hoy er.marion@epa.gov . SUPPLEMENTARY INFOR MATION: 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 www.regulations.gov or e - mail. Clearl y mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that y ou 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 co mplete version of the comment that includes information claimed as CBI, a cop y 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:

• Id entify

the rulemaking by

docket number and other identifying information (subject heading, Federal Register date and page number).5

• 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

y ou agree or disagree, suggest alternatives, and substitute language for your requested changes.

• Describe an y assumptions and provide an y technical information and/or data that yo u used.

• If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to b e reproduced.

• Provide specific examples to illustrate y our concerns, and suggest alternatives.

• Explain your views as clearl y as possible, avoiding the use of profanity or personal threats.

• Make sure to submit y our comments by the comment period deadline id entified.6

Table of Contents I. Overview A. Background on Leaded Aviation Gasoline B. Background on the Petition and EPA’s Response C. Statutory

Authority 1. Background 2. Regulatory

Authority

for Emission Standards 3. Regulatory

Authority

for Fuel S tandards D . Federal Actions to Reduce Lead Exposure II. Health and Welfare Effects of Lead A. Multimedia and Multi - P athway Exposure Considerations B. Health Effects 1. Blood Lead 2. Hea lth Effects 3. At - R isk P opulations and Life Stages C. Welfare Effe cts 1. Terrestrial Ecos ys tems 2. Aquatic Ecos ys tems I II . L ead Emissions from Piston - Engine Aircraft A. Inventory

of Lead from Piston - Engine Powered Aircraft 1. National Emissions of Lead from Piston - Engine Aircraft 2. Airport - S pecific E missions of L ead from Piston - Engine Aircraft7

B . Industry

Projections for Future Growth

I V. Lead Concentrations in the Vicinity of Airports A. Chemical and Phy sical Properties of Lead Emitted by Piston - Engine Aircraft B. Summary

of Airport Lead Monitoring and Modeling Stu dies 1. Summary

of Airport Lead Monitoring Studies 2. Summary

of Airport Lead Modeling Studies V. Exposure to L ead from Piston - Engine Aircraft and Potential for Impacts A. Exposure to L ead Emissions from Piston - Engine Aircraft 1. Population Residing within One Kilometer of Airports 2 . Children Attending School Near Airports 3 . Farming Activities 4 . Pilots, Student - Trainees, Passengers 5 . Fish Advisories for Lead B . Related Exposures of Concern 1. L ead Contribut ion to Ambient P articulate M atter 2. Ethylene Dibromide 3. Non - E xhaust E xposure to Tetraethyl Lead VI . Additional Information Available for the NPRM to Evaluat e the Potential for Public Health & Welfare Impacts and Considerations Regarding Engine Emission Standards A. The Lead NAAQS and L ea d Emissions from Piston - Engine Aircraft 1. Monitoring Lead at Airports to Evaluate Ambient Concentrations to Which8 Lead Emissions from Piston - Engine Aircraft Contribute 2. Evaluating the Contribution of L ead 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 VI I. 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 § 23 1 of the Clean Air Act.” 1 Inthe petition, F O E 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, alternativel y, 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 emissi ons from general aviation aircraft, including impacts to humans, animals and ecos ys tems under the CAA and issue a public report on the findings of the study and investigation. Section I .B of this notice discusses the background on the petition and EPA’s r esponse to date, and Section I.C discusses EPA’s

1 See docket item EPA - HQ - OAR - 2007 - 0294 - 0003.9

statutory authorit y under section 231(a) of the CAA. Under the CAA, i f, 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 t o consult with the Federal Aviation Administration (FAA) , and could not change standards if doing so would significantl y increase noise and adversel y affect safety. FAA would then be required, after consultation with EPA, to prescribe regulations to insur e compliance with any standards to control the emissions of lead from piston - engine aircraft. Under 49 USC 44714, FAA would also be required to prescribe standards for the composition or chemical or phy sical properties of piston - engine fuel or fuel additi ves to control or eliminate aircraft lead emissions. In this notice, we discuss our anal ys is 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

reasonabl y be anticipated to endanger public health or welfare a s the “endangerment finding” and the “cause or contribute finding.” This short - hand use of “endangerment finding” and “cause or contribute finding” is strictl y for purposes of simplifying the discussion, and should not be read as implying that EPA conside rs the exercise of the Administrator’s judgment to require a formal “finding” or “determination.” In 200 6 , EPA completed the Air Quality Criteria Document (AQC D ) for Lead, which critically assesses and integrates relevant scientific information regardin g the health effects of10

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  g/m 3 to 0.15  g/m 3 in order to provide increased protection for children and other at risk populations against an array of adverse health effects, most notably neurological effects in children, includi ng 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 categor ies are currently clearl y 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 importance o f 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 re garding 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 lea d emissions from aircraft engines using leaded avgas. On a national basis, emissions of lead from aircraft engines using leaded avgas are the largest single

2 U.S. Environmental Protection Agency (2006) Air Quality Criteria for Lead. Washington, DC, EPA/600/R 5/144aF. Available online at: www.epa.gov/ncea/ 3 National Ambient Air Quality Standards for Lead 73 FR 66965 (Nov. 12, 2008). 4 Centers for Disease Control and Prevention (2005) Prev enting lead poisoning in young children: a statement by the Centers for Disease Control and Prevention. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. August. 5 Advisory Committee on Childhood Lead Poisoning Prevention (A CCLPP) (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, 2007.11

source category

for emissions of lead to air, comprising approximately half of the national invent ory . 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 dens ely

populated re sidential developments immediately

adjacent to these airport facilities. As described in Sectio n 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 data described in Section IV of this ANPR indicate that lead levels in ambient air on and near airport s 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 env ironmental media and participates in long term cy cling 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 v ehicles 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, o nce deposited to surfaces, lead can subsequently be resuspended into the ambient air and, because of the persistence of lead, emissions of this metal 6 U.S. Environmental Protection Agency Electronic Report on the Environment. Available at: http://cfpub.epa.gov/eroe . Updated in December 2009 using the 2005 National Emissions Inventory.12

contribute to environmental media concentrations for man y ye ars into the future. Lead that is a soil or dust contaminant today may have been airborne y esterday or man y years ago. Therefore lead emission s from piston - engine aircraft could contribute to increased lead exposure and risk currentl y 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 potentia l 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 subm itted 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 actio ns to reduce lead exposure . Section II provides a discussion of the health and welfare effects of lead . Section s II I , IV and V describe the emissions of lead from avgas, ambient lead concentration in the vicinity of airports and potential exposure to lea d from leaded avgas, respectivel y. In Section VI, we describe the additional information EPA is collecting and considerations regarding engine emission standards. S ection VII contains information on statutory and executive order review s covering this act ion . 

### A. Background on Leaded Aviation Gasoline

In 19 96 , EPA promulgated regulations that banned the use of leaded gasoline in highway13

vehicles . 7 The addition of lead to fuel used in piston - engine powered aircraft was not banned in this action , and th e use of leaded avgas is the largest remaining source category of lead emissions . Lead is not added to jet fuel that is used in commercial aircraft, most military aircraft, or other turbine - engine powered aircraft . Most piston - engine aircraft fall into the categories of either general aviation (GA) or air taxi (AT). GA and AT aircraft include a diverse set of aircraft ty pes and engine models and are used in a wide variety of applications. 8

L ead is added to fuel for piston - engine aircraft in the form o f tetraeth yl lead (TEL). This lead additive helps boost fuel octane, prevent s knock, and prevent s valve seat recession and subsequent loss of compression for engines without hardened valves. T here are two main ty pes 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 t ype of avgas. 9 , 10 TELwas 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 y ears, the commercial and military aircraft fleet largel y 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 earl y 19 7 0s 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

7 See “ Prohibition on Gasoline Containing Lead or Lead Additives for Highway Use ” 61 FR 3832 (Feb. 2, 1996) . 8 Commercial aircraft include those used for scheduled service transporting passengers, freight, or both. Air taxis fly scheduled and for - hire se rvice 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 tr ansportation. 9 ChevronTexaco (200 6 ) Aviation Fuels Technical Review. FTR - 3. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf 10 AST M International (2005) Annual Book of ASTM Standards Section 5: Petroleum Products, Lubricants, and Fossil Fuels Volume 05.01 Petroleum Products and Lubricants (I): D 56

– D 3230. 11 Ogston, A.R. (1981) A Short History of Aviation Gasoline Development, 1903 - 1980. Society of Automotive Engineers. Paper number 810848.14

avgas. Over 3,000 of the 20,000 airport facilities in the U.S. are at least 50 y ears old and some airports have been in operation since the earl y 1900s. These older facilities would be expected to have a legacy

of lead, particularly

those that supported military and commercial aircraft operating on 100 Octane. 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 ac count for approximately

34,000 tons 12 of lead emitted to the air. 13 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 sold 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 sales volumes . Inthis document, we provide avgas fuel volume data supplied by DOE and DOT and we note the source of the data for clarit y . Over the past ten y ears, DOE estimates of the volume of leaded avgas supplied have ranged from 326 million gallons in 1999 to 235 million gallons in 2008. 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 7 62 tons in 1999 to 55 0 tons in 2008 (a 2 8 % 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 12 In this ANPR and in EPA’s National Emissions Inventory, the use of the unit tons refers to short tons. 13 Oak Ridge National Laboratory (2009) Transportation Energy Data Book: Edition 28. Avai lable at: cta.ornl.gov/data. Table A.7. 14 D epartment of Energy Energy Information Administration. Fuel production volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus 1A .htm accessed June 2009 . 15 U.S. Department of Transportation Federal Aviation Administration Aviation Policy and Plans. FAA Aerospace Forecast Fiscal Years 2009 - 2025. p.81. Available at: http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009 - 2025/media/2009%20Forecast%20Doc.pdf This document provides historical data for 2000 - 2008 as w ell as forecast data.15

current ly 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 gr owth in the activity of general aviation aircraft projected to 2025.

Av gas Pb, 1 999-2008

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 Ye arThousand Barrels of AvgasSupplied

0 98 196 294 393 491 589 687 785 883Tons of Pb from Avgas

Figure 1. Tons of Lead Supplied in Aviation Gasoline Annually from 1999

– 2008. Source: DOE Energy Information Administration 

### B. Background on the Petition and EPA’s Response In a 2003 letter to the EPA, F OE initially raised the issue of the potential for 16 General Aviation Manufacturers Association (2008) General Aviation Statistical Databook & Industry Outlook. Available online at: htt p://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf .16

endangerment caused or contributed to by lead emissions from the use of leaded avgas . 17 In 2006, FOE filed a petition with EPA requesting that the Administrator find endangerment or, if there was insufficient info rmation to find endangerment, commence a study of lead emissions from piston - engine aircraft . In2007 , the EPA issued a Federal Register n otice on the p etition requesting comments and information related to a wide range o f issues regarding the use of leaded avgas and potential public health and welfare exposure issues . 18 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 publicl y available in the docket (EPA HQ - OAR - 2007 - 0294 ). The majority of comments received concerned the nature of the industry and fuel suppl y issues. The comment e rs did not supply information regarding health or exposure issues . In2008, 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 VIof this document. At the time we received FOE’s petition, the EPA was in the p rocess 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. 

### C. Statut ory Authority

1. Background Section 231 of the CAA sets forth EPA’s authority to regulate aircraft emissions of air 17 FOE letter dated December 12, 2003 submitted to EPA Docket EPA - HQ - OAR - 2002 - 0030. 18 See “Petition Requesting Rulemaking To Limit Lead Emissions from General Aviatio n Aircraft; Request for Comments” 72 FR 64570 (Nov. 16, 2007).17

pollution. As described further in Section I.C.2 of this ANPR, Section 231(a)(2)(A) requires EPA to, from time to time, issue proposed e mission standards applicable to the emission of any air pollutant from an y 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 we lfare. 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. 19 EPA has discussed its “endangerment finding” authority

at length in recent notices published in the Federal Register, and we refer readers to those notices for detailed discussions of the anal yt ical and legal framework. 20 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 s ection 108(a). Once lead was listed, EPA i ssued primary and secondary NAAQS that the Administrator determined were requisite to protect public health with an adequate margin of safet y and to protect public welfare from an y known or anticipated adverse effects. Section 109(b)(1) and (2). As discu ssed 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 to 0.15 micrograms per cubic meter, measured over a 3 - month averaging period. These actions are part of the context for the issues before EPA under section 231(a).

19 See, e.g., Ethyl Corp. v. EPA , 541 F.2d 1, 6 (D.C. Cir.), cert. denied 426 U.S. 941 (1976); see also Massachusetts v. EPA , 549 U.S. 497, 506, n.7 (2007). 20 See , “Endangerment and Cause or C ontribute 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; Ad vance Notice of Proposed Rule ma king ,” 73 FR 44354, 44421 - 23 (July 30, 2008).18

The first part of the endangerment test concerns identification of air pollution which may reasonabl y be anticipated to endanger public health or welfare. The CAA defines both “air poll utant” and “welfare.” Air pollutant is defined in CAA section 302(g) as: “Any air pollution agent or combination of such agents, including an y physical, chemical, biological, radioactive (including source material, special nuclear material, and by product material) substance or matter which is emitted into or otherwise enters the ambient air. Such term includes any precursors to the formation of an y air pollutant, to the extent the Administrator has identified such precursor or precursors for the particul ar purpose for which the term ‘air pollutant’ is used.” Lead fits within this capacious definition, and has long been regulated as an air pollutant b y EPA under the CAA (see Section I.D. 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 h ealth 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 publ ic health (see section I .D. of this ANPR). Exposure to lead causes “a broad array of deleterious effects on multiple organ s ys tems,” 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 y oung19

children. 21 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, e ffects on soils, water, crops, vegetation, man - made materials, animals, wildlife, weather, visibility , and climate, damage to and deterioration of propert y, and hazards to transportation, as well as effects on economic values and on personal comfort and we ll - being, whether caused b y 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 b y lead have been evaluated b y EPA and were the basis for establishing the secondary lead standard. 22 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 emissio ns 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. 23 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 variet y of so urces. T he cause or contribute test is designed to authorize EPA to identify and then address what may well be man y different sectors or groups of sources that are each part of an air pollution problem.

21 See “National Ambient Air Quality Standards for Lead” 73 FR 66970 - 67007 (Nov. 12, 2008) 22 See “National Ambient Air Quality Standards for Lead” 73 FR 67007 - 67012 (Nov. 12, 2008). 23 See, e.g., CAA sections 111(b); 213(a)(2), (4).20

S ection 231(a)(2) refers to contribution and does n ot 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 Admi nistrator has evaluated the emissions of the source or sources in different way s, based on the particular circumstances involved. In some mobile source rulemakings, the Administrator has used the percent of emissions from the regulated mobile source categ ory compared to the total mobile source inventory for that air pollutant as the best way to evaluate contribution. 24 Inother instances the Administrator has looked at the percent of emissions compared to the total nonattainment area inventory of the air p ollution at issue. 25 EPA has found that air pollutant emissions that amount to 1.2 percent of the total inventory met the statutory test for contribut ion, triggering EPA’s regulatory authority . 26

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 an y air pollutant from an y class or classes of aircraft engines which, in the Administrator’s judgment, cause or contribute to air pollution which may reasonabl y be anticipated to endanger public health or welfare. Section 231(a)(2)(B)(i) directs EPA to consult with FAA on aircraft engine emission st andards, and section 231(a)(2)(B)(ii)

24 See, e.g., 66 FR 5001 (January 18, 2001) (heavy duty engine and diesel sulfur ru le). 25 See, e.g., 67 FR 68242 (November 8, 2002) (snowmobile rule). 26 Bluew ater Netw ork v. EPA , 370 F.3d 1, 15 (D.C. Cir. 2004) (For Fairbanks, this contribution w as equivalent to 1.2 percent of the total daily CO inventory for 2001).21

provides that EPA shall not change the aircraft engine emission standards if such change would significantl y increase noise and adversel y affect safety. Section 231(a)(3) directs EPA to issue final regulations with su ch 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

th e 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 safet y. Section 232 directs DOT to issue and implement regulations to insure compliance with EPA’s stand ards, while section 233 pre - empts states and local governments from adopting or enforcing an y 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 authorit y to EPA to enact appropriate regulations applicable to the emissions of air pollutants from aircraft engines.” 27 3. Regulatory Autho rity for Fuel Standards Section 211(c) of the CAA allows EPA to regulate fuels used in motor vehicles and

27 NACAA v. EPA , 489 F.3d 1221, 1229 - 30 (D.C. Cir. 2007).22

nonroad vehicles or engines where emission products of the fuel either: (1) cause or contribute to air pollution that reasonably may be anticipated t o endanger public health or welfare, or (2) will impair to a significant degree the performance of any emission control device or s ys tem which is in general use, or which the Administrator finds has been developed to a point where in a reasonable time it w ill 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 und er section 211 resides. However, EPA’s authority to regulate aircraft resides in 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.” Consequentl y, 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 b y the FAA. Title 49 (49 U.S.C. 44714) requires that “the Administrator of the Federal Aviation Administration shall prescribe (1) standards for the composi tion or chemical or phy sical 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 pu

blic health or welfare; and (2) regulations providing for carrying out and enforcing those standards.”23



### D. Federal Actions to Reduce Lead Exposure The U.S. has made tremendous progress in reducing lead concentrations in the outdoor air. Nationwide, avera ge concentrations of lead in the air have dropped 91 percent between 1980 and 2008. 28 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 man y different t ypes 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 othe r air pollutants through several provisions in the CAA. Inthe early 1970s, EPA issued regulations regarding lead in gasoline in order to accomplish two purposes. 29 First, EPA issued regulations designed to ensure the availability of unleaded gasoline for use in motor vehicles equipped with emission control sy stems such as cataly tic converters. EPA had determined that lead additives would impair to a significant degree the performance of emission control sy stems. Second, EPA issued regulations designed t o graduall y 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 group s, 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 regul ations to decrease the allowable concentration of lead in gasoline for motor vehicles to 0.10 grams per gallon. 30 In1990

28 See http://www.epa.gov/airtrends/lead.html 29 “Regulation of Fuels and Fuel Additives” 38 FR 1254 (Dec. 4, 1973) 30 “Regulation of Fuels and Fuel Additives; Gasoline Lead Content” 50 FR 9386 (March 7, 1985)24

Congress added section 211(n) to the CAA which provides that after December 31, 1995, it shall be unlawful to sell an y gasoline for us e in an y 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. 31 In this r egulation, 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 b y law. 32 In fact, there have been no regulatory limits placed on the production and consumption of leaded avgas , and , as noted in S ection 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 emi ssion in 2005). This is in spite of the decrease in the suppl y of leaded avgas nationall y from 374 million gallons (875 tons of lead) in 1990 to 23 5 million gallons (5 50 tons of lead) in 2008. 33 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 pist on - 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 S ection III.B. S ignificant redu ctions in emission of lead from stationary source s have been achieved 31 “ Prohibit ion on Gasoline Containing Lead or Lead Additives for Highway Use” 61 FR 3832 (Feb. 2, 1996) 32 “ Prohibition on Gasoline Containing Lead or Lead Additives for Highway Use” 61 FR 3834 (Feb. 2, 1996) 33 These fuel volume estimates are from the Departement of E nergy Energy Information Administration. http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm25

between 1985 and 200 2 , totaling almost 2,000 tons of lead . 34 Regulations promulgated in 1995, 1997 and 1999 controll ed emissions of lead from primary and secondary

lead smelters, contrib uting to these reductions . 35 , 36 , 37 Currentl y, 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 station ary sources. 38 , 39 , 40 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 bey ond those that focus on air pollution control provide for nationwide reductions in envi ronmental 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 nationall y and provide guidance on levels at which medical and environmental c ase management activities should be implemented. 41 , 42 In1991, the Secretary of the U.S. Department of Health and Human Services

34 U.S. Environmental Protection Agency (2008) EPA’s Report on the Environment EPA/600/R - 07/ 045F. Available at: http://www.epa.gov/roe/ 35 “National Emission Standards for Hazardous Air Pollutants From Secondary Lead Smelting ” 60 FR 32587 (June 23, 1995) 36 “National Emission Standards for Hazardous Air Pollutants From Secondary Lead Smelting ” 62 F R 32209 (June 13, 1997) 37 “National Emission Standards for Hazardous Air Pollutants for Primary Lead Smelting ” 64 FR 30194 (June 4, 1999) 38 “ Standards of Performance for Municipal Waste Combustors and Emission Guidelines ” 60 FR 65387 (Dec. 19, 1995) 39 “ Em ission Guidelines for Existing Sources and Standards of Performance for New Stationary Sources ” 62 FR 45124 (Aug. 25, 1997) 40 “ Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources: Large Municipal Waste Combustor s ” 71 FR 27324 - 27348 (May 10, 2006) 41 Centers for Disease Control and Prevention (2005) Preventing lead poisoning in young children: a statement by the Centers for Disease Control and Prevention. Atlanta, GA: U.S. Department of Health and Human Services, P ublic Health Service. August.26

(HHS) characterized lead poisoning as the “number one environmental threat to the health of children in the United States . ” 43 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 saf

et y hazards (62 FR 19885). 44 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 y ears bey ond its original charter (66 FR 52013 and 68 FR 19931). The Task Force set a Federal goal of eliminating childhood lead poisoning b y the ye ar 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 environment al releases from in - place materials containing lead (e.g., lead - based paint, urban soil and dust, and contaminated waste sites). Federal regulations on disposal of lead - based paint waste help facilitate the removal of lead - based paint from residences (68 FR 36487). Further, in 1991, EPA lowered the maximum levels of lead permitted in public water sy stems 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

42 Advisory 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 Chi ldhood Lead Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR - 8). November 2, 2007. 43 Alliance to End Childhood Lead Poisoning ( 1991 ) The First Comprehensive National Conference; Final Report. October 6, 7, 8, 1991. 44 Co - chaired by the Se cretary of the HHS and the Administrator of the EPA, the Task Force consisted of representatives from 16 Federal departments and agencies.27

Control Act (TSCA), EPA has established regulations and associated programs with the goal of reducing exposure to lead via lead - based paint. For example, under Title IV of TSCA, EPA established standards identifying hazardous levels of lead in residential paint, d ust, 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, C ompensation, and L iability

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 . 45 Federal regulations concerning batteries in munic ipal solid waste control the collection and recy cling or proper disposal of batteries containing lead . 46 Similarly , Federal programs provide for the reduction in environmental releases of hazardous substances such as lead in the management of wastewater. 47 A variet y of federal nonregulatory programs also provide for reduced environmental release of lead - containing materials through voluntary measures and more general encouragement of pollution prevention, promotion of reuse and recycling, reduction of priority

45 See, e.g., 66 FR 58258. 46 See, e.g., “Implementation of the Mercury - Containing and Rechargeable Battery Management Act” http://www.epa.gov/epaoswer/hazwaste/recycle/battery.pdf and “Municipal Solid Waste Generation, Recycling, and Disposal in the United States: Facts and Figures for 2005” http://www.epa.gov/epaoswer/osw / conserve/resources/msw - 2005.pdf. 47 http://www.epa.gov/owm/28

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. 48 Other programs include the Resource Conservation Challenge, 49 the National Waste Minimization Program, 50 “Plug in to eCy cling” (a partnership between EPA and consumer electronics manufacturers and retailers ) , 51 and activities to reduce the practice of backyard trash burning. 52 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 M ethodology 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 tissues 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 acti vities on substances including lead focus on better characterizing aspects of health and environmental effects, exposure, and control or management of environmental releases. 53

48 U.S. Environmental Protection Agency Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT national action plan for alkyl - Pb. Washington, DC. Available online at: http://www.epa.gov/

pbt/pubs/A lkyl_lead_action_plan_final.pdf 49 http://www.epa.gov/epaoswer/osw/conserve/index.htm 50 http://www.epa.g ov/epaoswer/hazwaste/minimize/leadtire.htm 51 http://www.epa.gov/epaoswer/hazwaste/recycle/electron/crt.htm#crts 52 http://www.epa.gov/msw/backyard/pubs.htm 53 http://www.epa.gov/ord/researchaccomplishments/index.html29



## II. Health and We lfar e Effects of Lead A. Multim edia and Multi - P athway Exposure Considerations This section briefl y summarizes the information presented in th e 2008 NAAQS for Lead , 54 the 2007 Lead Staff Paper 55 and the 2006 Air Quality Criteria Document for Lead ( AQCD for Lead) . 56 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 . L ead emitted to the air can result in exposure via multip le p athway s (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 man y sources encompassing a wide variety of stationary and mobile source t ypes. 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 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 aerosol phase and

54 National Ambient Air Quality Standards for Lead 73 FR 66970 - 67007 (Nov. 12, 2 008) Section II.A. 55 U.S. Environmental Protection Agency Review of the National Ambient Air Quality Standards for Lead: Policy Assessment of Scientific and Technical Information OAQPS Staff Paper ( 2007) Chapter 2. EPA - 452/R - 07 - 013 November. 56 U.S. Envir onmental Protection Agency (2006) Air Quality Criteria for Lead . Volume I: Chapters 2 & 3. EPA/600/R - 5/144aF. October.30

travel longer distances before depositing (e.g., hundreds to thousands of kilometers) . 57 As summarized in the AQCD for Lead, airborne concentrations of lead at site s near sources are much higher than at sites not known to be directl y influenced b y sources. (2) Once deposited to surfaces, lead can subsequently be resuspended into the ambient air and, because of the pers istence of lead , emissions of this metal contribute to environmental media concentrations for many ye ars into the future. Lead that is a soil or dust contaminant today may have been airborne y esterday or man y ye ars ago . 58 (3) Exposure to lead emitted int o the ambient air can occur directl y b y 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). 59 And dietary intake may be a predominant source of lead exposure among adults, greater than consumption of water and beverages or inhalation (73

57 U.S. Environmental Protection Agency (2004) Air Quality Criteria for Particulate Matter. Research Triangle Park, NC: Office of Resear ch and Development, National Center for Environmental As sessment ; EPA report no. EPA - 600/P - 99 / 0 028aF. 58 National Ambient Air Quality Standards for Lead 73 FR 66971 (Nov. 12, 2008) , AQC for Lead, Section 2.5. 59 U.S. Environmental Protection Agency (1986) Ai r Quality Cr iteria for L ead. 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 - 142378.31

FR 66971). These exposure pathway s are described more full y in S ection 8.2.2 of the AQCD for Lead. (4) Air - related exposur e pathway s 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 ye ars into the future. Additionally , human exposures to lead include pathway s that are not related to ambient air concentrations. The pathway s of human exposure to lead that are not air - related include ingestion of in door lead paint, 60 lead in diet as a result of inadvertent additions during food processing, and lead in drinking water attributable to lead in distribution sy stems, as well as other generall y less prevalent pathways, as described in the AQCD for Lead (pp. 3 - 50 to 3 - 51). 

### B. Health Effects Inform ation In 2008, EPA decreased the level of the primary (health - based) NAAQS for L ead from 1.5  g/m 3 to 0.15  g/m 3 in order to provide increased protection for children and other at - risk populations against an array o f adverse health effects, most notably neurological effects in children, including neurocognitive and neurobehavioral effects. 61 This section summarizes information provided in the numerous recent documents summarizing health and welfare effects

60 Weathering of outdoor lead paint may also contribute to soil lead levels adjacent to the house . 61 National Ambient Air Quality Standards for Lead 73 FR 66965 (Nov. 12, 2008).32

from expos ure to lead, including the AQCD for Lead , CDC documents , the EPA Staff Paper 62 and the proposed and final NAAQS for Lead . First, the use of blood lead as a measure of exposure to lead is described , followed b y a brief summary of the broad array

of lead - in duced health effects . Particular focus is given here to the effects of lead on the developing nervous sy stem in children since this is among the most sensitive endpoint s identified for this toxic metal . The section ends with a description of at - risk popu lations and life stages . 1. Blood Lead Lead enters the bod y most commonly via the respiratory sy stem and

/or gastrointestinal tract, from which it is quickly absorbed into the blood stream and distributed throughout the body . 63 Less commonly, lead , part icularl y organic forms of lead such as akyl lead, can be absorbed through the skin (AQCD for Lead, page 4 - 12) . Blood lead levels are extensivel y used as an index or biomarker of exposure by national and international health agencies, as well as in epidemi ological ( 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, have for man y years used blood lead level as a me tric for identifying children at risk of adverse health effects and for specifying particular public health recommendations. 64 Most recentl y, in 2005, with consideration of a review of the evidence b y their advisory

committee, CDC revised their statement o n Preventing Lead Poisoning in Young

62 U.S. Environmental Protection Agency (200 7 ) Review of the National Ambient Air Quality St andards 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. 63 Additionally, lead freely crosses the placenta resulting in continue d fetal exposure throughout pregnancy, with that exposure increasing during the latter half of pregnancy ( AQCD for Lead , S ection 6.6.2). 64 Centers for Disease Control (1991) Preventing lead poisoning in young childr en: a statement by the Center s for Diseas e Control. Atlanta, GA: U.S. Department of H ealth and Human Services, Public Health Service; October 1. Available online at: http://wonder.cdc.gov/wonder/prevguid/p0000029/p0000029.asp33

Children . 65 CDC specifically recognized the evidence of adverse health effects in children with blood lead levels below 10 μg/dL , 66 the data demonstrating that no “safe” threshold for blood lead had been identified, and emphasiz ed the importance of preventative measures . 67 Since 1976, the CDC has been monitoring blood lead levels in multiple age groups nationally

through the National Health and Nutrition Examination Survey (NHANES). 68 The NHANES information has document ed 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 significantl y, 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. 69 R acial/ethnic and income disparities in blood lead levels in children

65 Centers for Disease Control and Prevention (2005) Preventing lead po isoning 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. 66 As described by the Advisory Committee on Childhood Lead Poisoning Prevent ion, “In 1991, CDC defined the blood lead level (BLL) that should prompt public health actions as 10 μg/d L. Concurrently, CDC also recognized that a BLL of 10 μg/d L 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 BLL S <10 μg/d L” (ACCLPP, 2007). 67 Advisory 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 Chil dhood Lead Poisoning Prevention. Morbidity and Mortality Weekly Report. 56(RR - 8). November 2, 2007. 68 This information documents a variation in mean blood lead levels across the various age groups monitored. For example, mean blood lead levels in 2001 - 20 02 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 ( AQCD for Lead , p. 4 - 22). 69 Axelrad, D. 2009. E - mail message to Marion Hoyer, U.S. EPA. November 4, 2009. Docket number EPA - HQ OA R - 2007 - 0294.34

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, l ead bioaccumulates in the body , with the bone serving as a large, long - term storage compartment . S oft tissues (e.g., kidney , liver, brain, etc . ) serve as smaller compartments, in which lead may be more mobile ( AQCD for Lead, S ections 4.3.1.4 and 8.3.1). During childhood development, bone represents approximately 70% of a child’s bod y 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 , S ection 4.2.2). Lead i n bone can be mobilized during critical periods including pregnancy and lactation ( AQCD for Lead, S ection 5.8.6). 2 . Health Effects Lead, as with mercury

and arsenic, has no known biological function. 70 Lead has been demonstrated to exert “a broad array of deleterious effects on multiple organ sy stems via widel y diverse mechanisms of action” ( AQCD for Lead , p. 8 - 24 and S ection 8.4.1). This array of health effects includes effects on heme biosy nthesis and related functions; neurological development and f unction; reproduction and phy sical development; kidney function; cardiovascular function; and immune function. The weight of evidence varies across this array of effects and is comprehensivel y described in the AQCD for Lead . There is also some evidence o f lead carcinogenicity , primarily from animal studies, together with limited human evidence of 70 U.S. Environmental Protection Agency (2007) Framework for Metals Risk Assessment. Office of the Science Ad visor. EPA 120/R - 07/001.35

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 carcinog en based on the available animal data ( AQCD for Lead, p. 6 - 195). 71 In organic l ead has been classified as a probable human carcinogen b y the International Agency for Research on Cancer (inorganic lead compounds), based mainly on sufficient animal evidence, 72 and classified a s reasonabl y anticipated to be a human carcinogen b y the U.S. National Toxicology Program (lead and lead compounds) ( AQCD for Lead, Section 6.7.2) . 73 , 74 As described in the AQCD for Lead , the key effects associated with individual blood lea d levels in children and adults in the range of 10 μg/dLand lower include neurological, hematological and immune 75 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 possi bly lower); and these categories are currently clearl y of greatest public health concern” ( AQCD for Lead , p. 8 - 60). 76 , 77 T he AQCD for Lead

71 U.S. Environmental Protection Agency, Integrated Risk Information System (IRIS) (1993) IRIS Summary for Lea d and compounds (CASRN 7439 - 92 - 1 ), Available online at: http://www.epa.gov/ncea/iris/subst/0277.htm . 72 International Agency for Research on Cancer (IARC) (2005) Inorganic and organic lead compoun ds. 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 . 73 National Toxicology Program (2003) Report on carcinogens background document for lead and lead compounds. Research Triangle Park, NC: U.S. Department of Health and Human Services. Available online at: http://ntp.niehs.nih.gov/ntp/newhomeroc/roc11/Lead - Public.pdf 74 National Toxicology Program. (2004) Lead (CAS no. 7439 - 92 - 1) and lead compounds. In: Report on carcinogens, eleventh edition. Research Triangle Park, NC: U.S. Department of Health and Human Services. Available online at: http://ntp.niehs.nih.gov/ntp/roc/eleventh/profiles/s101lead.pdf. 75 At mean blood lead levels, in children, on the order of 10 μg/dL, and some what 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 D for Lead , Sections 5.9, 6.8, and 8.4.6). 76 With regard to blood lead levels in individual children associated with particular neurological effects, the AQCD for Lead states “Collectively, the prospective cohort and cross - sectional studies offer evidence th at exposure to lead36

state s , “There is no level of lead exposure that can y et be identified, with confidence, as clearl y not being associated with some risk of deleterious health effects” ( AQCD for Lead , p. 8 - 63). While a dults are susceptible to lead effects at lower blood lead levels than previously understood (e.g., AQCD for Lead , p. 8 - 25) , among the wide variet y of health endpoints ass ociated with lead exposures, there is general consensus that the developing nervous sy stem in children is among the, if not the, most sensitive. B lood lead levels in U.S. children have decreased notabl y since the late 1970s . S tudies evalu ating current bl ood 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 epidemiol ogical 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 widel y 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 , S ection 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 expos ure and academic achievement observed in the above - noted studies were significant even after adjusting 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) 77 Epidemiological studies have consis tently 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 (AQCD for Lead, p. E - 10) .37

for IQ, suggesting that lead - sensitive neurops yc hological processing and learning factors not reflected b y global intelligence indices might contribute t o reduced performance on academic tasks” ( AQCD for Lead , pp 8 - 29 to 8 - 30). With regard to potential implications of lead effects on I Q, the AQCD for Lead recognizes the “critical” distinction between population and individual risk, identifying issues re garding 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). 78 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). 79 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 increa sed 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 leve ls below 10 μg/dL( AQCD for Lead ,

78 As an example, the AQCD for Lead states “although an increase of a few mmHg in bl ood 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 cr iteria used to diagnose hypertension” (AQCD for Lead, p. 8 - 77). 79 For example, for a population mean IQ of 100 (and standard deviation of 15), 2.3% of the population would score above 130, but a shift of the population to a mean of 95 results in only 0.99% of the population scoring above 130 (AQCD for Lead, pp. 8 - 81 to 8 - 82).38

S ection 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 , S ection 8.4.2.1; p. 8 - 31), which provide strong biolog ical plausibility of lead effects on learning abilit y, memory and attention ( AQCD for Lead , S ection 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 , S ection 8.5.2). It is additionally impo rtant 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 antisocia l and delinquent behavior ( AQCD for Lead , S ection 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 l ead 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 , S ection 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 o utcome s 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 nervous39

sy stem) than more severe effects of high exposures that result in sy mptomatic 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 P opulations and Life Stages Individuals potentiall y atrisk 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 like lihood 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.

EP A 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 phy siological characteristics that are associated with development and growth. To recognize the r apid changes that occur40

during childhood related to phy siology , 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, in fancy , and adolescence. EPA published several exposure and risk assessment guidance documents beginning in 2005, 80 81 82 in which we emphasized the importance of considering the potential for increased sensitivity of different life stages or age groups in ad dition to that of groups that form a fixed portion of the population b ased on characteristics such as pre - existing disease, gender, socioeconomic status, geographical l ocation, culture/ethnicity , or genetic make - up. Phy siological, behavioral and demograph ic 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 yo ung children, AQCD for Lead , S ection 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 b y the time the child reaches 2 to 3 y ears of age” ( AQCD for Lead , S ection 6.2.12). Ph ys iological factors that can affect risk of lead - related effects in children include genetic poly morphisms and nutritional status. C hildren with particular genetic poly morphisms (e.g., presence of the δ aminolevulinic a cid deh ydratase - 2 [ALAD - 2] allele) h ave increased sensitivity to lead toxicity ,

80 US EPA (2005) Guidance on Selecting Age Groups for Monitoring and Assessing Childhood Exposure to Environmental Contaminants. EPA/630/P - 03/003F . 81 US EPA (2006) A Frame wo rk for Asses sing Health Risks of Environmental Exposures to Children. EPA/600/R 05/093F. 82 US EPA (2008) Child - Specific Exposure Factors Handbook. EPA/600/R - 06/096F.41

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) . S ome children may have blood lead levels higher than those otherwise associated with a given lead exposure ( AQCD for Lead , S ection 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, s ituations 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 associ ated health effects from air - related lead. 83 Additionally , as described in the NAAQS for Lead, children in povert y and black, non - Hispanic children have notably

higher blood lead levels than do economicall y well - off children and white children, in general . 84 

### C. Welfare Effects Lead is persistent in the environment and accumulates in soils, aquatic sy stems (including sediments), and some biological tissues of plants, animals and other organisms, thereb y providing long - term, multi - pathway exposures to org anisms and ecos ys tems. In2008, EPA

83 U.S. Environmental Protection Agency (200 7 ) 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. 84 See 73 FR 66973 (November 12, 2009).42

established a secondary

lead standard of 0.15 ug/m 3

. This standard is intended to protect the public welfare from known or anticipated adverse effects associated with the presence of lead in the ambient air. This sect ion provides a summary of information regarding welfare effects of lead, focusing on terrestrial and aquatic ecos ys tems . This information is largel y drawn from the 2006 AQCD for Lead , Chapter 6 of the Office of Air Quality Planning and Standards Staff Pap er on L ead (SP) 85 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. Insoils, most lead is retained via the formation of stable solid phase compounds , precipitates, or complexes with organic matter. Thus, t errestrial ecos ys tems remain primaril y sinks for lead but amounts retained in various soil lay ers vary based on forest ty

pe, climate, and litter cy cling ( AQCD for Lead , S ection 7.1). Once in the so il, the migration and distribution of lead is controlled b y 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 , S ec tion 2.3.5 , and S ection AX 7.1.4.1). Lead exists in the environment in different forms which vary widely in their ability

to cause adverse effects on ecos ys tems and organisms. Many forms of lead in the ambient air are quite insoluble and thus not easil y leached to underground water once deposited to surfaces . However, leaching may

occur under acidic conditions, where lead concentrations are extremel y

85 U.S. Environmental Protection Agency (20 0 7 ) 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.43

high, or in the presence of substances (e.g., soluble organic matter, high concentrations of chlorides or sulfates) that form relativel y soluble complexes with lead ( AQCD for Lead, S ection 2.3.5) . Plants take up lead via their foliage and through their root s ys tems. The rate of plant uptake from soil varies by plant species , soil conditions, and lead spec ies. 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 sludg e, flue dust, or fl y ash ( AQCD for Lead, S ection 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 subseque ntly

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). 86 By far, the majorit y of air - related lead found in natural terrestrial ecos ys tems was de posited in the past during the use of lead additives in motor vehicle gasoline. Man y 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

86 U.S. Environmental Prot ection Agency (1986) Air Q uality C riteria for L ead. 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 - 142378.44

evidence that terrestrial sites exposed as a result of this long range transport of lead have experienced significant effects on ecos ys tem structure or function ( AQCD for Lead , S ection AX7.1.4.2 and p. AX7 - 98). Strong complexation o f lead b y 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 , S ection 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 ecos ys tems lead concentrations exceed natural background levels. For areas influenced b y poi nt sources of air lead, concentrations of lead in soil may exceed b y many orders of magnitude the concentrations which are considered harmful to laboratory organisms. Adverse effects in terrestrial organisms associated with lead include neurological, phy s iological and behavioral effects which may influence ecos ys tem structure and functioning (73 FR 67008) . 2. Aquatic Ecosystems Atmospheric lead enters aquatic ecosy stems primarily through deposition (wet and dry) and the erosion and runoff of soils contai ning lead. While overall deposition rates of atmospheric lead have decreased dramaticall y since the removal of lead additives from motor45

vehicle gasoline, lead continues to accumulate and may be re - exposed in sediments and water bodies throughout the Unit ed States ( AQCD for Lead , S ection 2.3.6). Several ph ys ical and chemical factors govern the fate and bioavailability of lead in aquatic s ys tems. 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). Le ad can bioaccumulate in the tissues of aquatic organisms through ingestio n of food and water, and adsorption from water, and can subsequently lead to adverse effects if tissue levels are sufficiently high. 87 The accumulation of lead is influenced b y 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 sufficientl y high concentration is reached. 88 The general sy mptoms 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 deh ydratase (ALAD) inhibition, growth inhibition, renal pathology, reproductive effects, growth inhib ition, and mortality . 89 Toxicity in fish has been closely

correlated with duration of lead exposure and uptake. 90

87 U.S. Environmental Protection Agency (2006) Air Quality Criteria for Lead . EPA/600/R - 5/144aF. October. Volume I. pp. 7 - 24: (Vink, 2002; Rainbow , 1996). 88 U.S. Environmental Protection Agency (2006) Air Quality Criteria for Lead . EPA/600/R - 5/144aF. October . Section AX7.2.3.1. 89 U.S. Environmental Protection Agency (2006) Air Quality Criteria for Lead . EPA/600/R - 5/144aF. October . p. 232, Annex 7 . 90 U.S. Environmental Protection Agency (2006) Air Quality Criteria for Lead . EPA/600/R - 5/144aF . October . P . 232, Annex 7.46

Lead exists in the aquatic environment in various forms and under various chemical and phy sical parameters which determine the abilit y 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

widel y depending on the source of lead . Conditions exist in which adverse effects to organisms and thereb y eco sy stems may be anticipated given experimental results. It is unlikely that dissolved lead in surface water constitutes a threat to ecosy stems that are not directly influenced by

point sources. For lead in sediment, the evidence regarding the effects is l ess clear. Itis likel y 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 s ys tems for the foreseeable future (73 FR 67008) . 

## III. Lead Emissions fr omA viation Gasoline Curre ntly , lead emi tted by piston - engine aircraft operating on leaded avgas is the largest source of lead to the air , contributing about 50% of the National Emission Inventory in 2005 . This section describes the draft 2008 avgas lead inventory which is current ly undergoing review by state, local and tribal air agenc i es . 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.47



### A. Inventory of Lead from Piston - Engine Powered Aircraft Every three y ears, the EPA prepares a National Emissions Inventory (NEI ) of air emissions of criteria pollutants and hazardous air pollutants w ith input from numerous state, local , and tribal air agen ci es and from industry . 91 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 th e 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 recentl y developed methods for estimating lead (described below) ; 2) this inventory

is the first NEIto include a pproximately 20,000 airport facilities in the U.S. ; and 3) t o increase awareness of the opportunity for state, local, and tribal governments and industry to review this draft NEI and provide information that could imp rov e airport lead inventories. Comment s and data can be supplied to EPA for the 2008 NEI until mid - 2010. While we are describing the draft 2008 NEI for piston - engine aircraft emissions of lead, we do not have draft inventory

estimates for 2008 for all sources of lead. The 2008 NEI will be fi nal in 2010. 

### 1. National Emissions of Lead f rom Piston - Engine Aircraft To calculate the national avgas lead inventory , the volume of leaded avgas produced in a given ye ar is multiplied by the concentration of lead in the avgas and by the fraction of lea d emitted from a combustion sy stem operating on leaded fuel ( to account for the lead that is retained in the engine, engine oil and/or exhaust sy stem ) . For example, the volume of avgas

91 Information regarding EPA’s National Emissions Inventory is available from: http://www.epa.gov/air/data/neidb.html .48

produced in the U.S. in 2008 according to DOE was 235,326,000 gallons. 92 The concentration of lead in avgas ([Pb] in the equation below) can be one of four levels (ranging from 0.14 to 1.12 grams of lead per liter) as specified b y the American Society for Testing and Materials (ASTM). By far the most common avgas supplied i s “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. 93 , 94 A fraction of lead is retained in the engine, engine oil and/or exhaust sy stem which we currentl y estimate at 5%. 95 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) = 522 short tons Pb

907,1 8 5 g/ short ton 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 . Consumpt ion of this volume of avgas equates to a nat ional lead emissions estimate for this source of 779 short tons. DOT fuel volume data are derived from FAA estimates of piston - engine activity

annually . 96 We are working to identify the source(s) of the information

92 DOE Energy Information Administration. Fuel production volume data obtained from http://tonto.eia.doe.gov/dnav/pet/hist/mgaupus1A.htm accessed November 2006. 93 ChevronTexaco (200 6 ) Aviation Fuels Technical Review. FTR - 3. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf 94 ASTM International (2005) Annual Book of ASTM Standards Section 5: Petroleum Products, Lubricants, and Fossil Fuels Volume 05.01 Petroleum Products and Lubricants (I): D 56

– D 3230. 95 U.S. Environmental Protection Agency (2008) Lead Emis sions from the Use of Leaded Aviation Gasoline in the United States, Technical Support Document. EPA420 - R - 08 - 020. Available online at: www.epa.gov/otaq/aviation.htm . 96 U.S. Department of Transportation Federal Aviation Administration Aviation Policy and Plans. FAA Aerospace Forecast Fiscal Years 2009 - 2025. p.81. Available at:49

used to d eriv e DOE fuel volume estimate s. Inthe draft 2008 NEI, we are using DOT fuel volume estimates. We currentl y cannot estimate the fraction of total lead emissions th ese estimates comprise since the inventories for all other sources of lead to air are not y et 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. 97 Military aircraft data are supplied by

states , and data provided t o EPA during the 2008 NEI review will be included in the final 2008 inventory .

http://www.faa.gov/data_research/aviation/aerospace_forecasts/2009 - 2025/media/2009%20Forecast%20Doc.pdf This document provide s historical data for 2000 - 2008 as w ell as forecast data. 97 ChevronTexaco (2006) Aviation Fuels Technical Review p. 44. Available online at: http://www.chevronglobalaviation .com /docs/aviation_tech_review.pdf .50 0 100 200 300 400 500 600 700 800

1999 2002 2005 2008 Yea rTons of Lead from Avgas

0% 10% 20% 30% 40% 50% 60%% Contribution of Avgas toTotal Lead

Tons o f L ead fro m Avgas % C o nt ri but io n ofAvg as to T ot al L ead Figure 2. The Increasing Contribution of L ead from Aviation Gasoline to the Total Inventory of Lead Emissions to Air Annually (the total lead inventory

for 2008 will be avai lable in 2010). Fuel volume data is from DOE’s Energy Information Administration. 

### 2. Airport - Specific Emissions of Lead f rom Piston - Engine Aircraft Aircraft gaseous and particulate matter (PM) emissions are calculated through the FAA’s Emissions and Dis persion Modeling S ys tem ( EDMS ) . 98 This modeling sy stem was designed to develop emission inventories for the purpose of assessing potential air quality impacts of airport

98 EDMS is available online at: http://www.faa.gov/about/office_org/headquarters_offices/aep/models/edms_model/51

operations and proposed airport development projects. Lead emissions from piston - engi ne aircraft are not included in EDMS . To estimate airport - specific lead inventories we use engine data and other attributes of GA and 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 briefl y summarized here. 99 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 cy cle ; 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 equat ion used to calculate airport - specific lead emissions during the LTO cy cle is below, followed b y a description of each of the input parameters.

LTO Pb ( tons ) = (piston - engine LTO)(avgas gal/LTO)([Pb])(1 - Pb retention) 907,18 5 g/ short ton Piston - engine LTO : Most piston - engine aircraft fall into the categories of either general aviation (GA) or air taxi (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 calculat ed a national default estimate

99 U.S. Environmental Protection Agency (2008) Lead Emissions from the Use of Leaded Aviation Gasoline in the United States, Technical Support Document. EPA420 - R - 08 - 020. Available online at: www.epa.gov/otaq/aviation.htm .52

using FAA’s GA and AT Activity (GAATA) Survey . 100 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 whi ch use jet fuel, such as Jet A. 101 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/L TO) : Piston - engine aircraft can have either one or two engines. EDMS version 5.0.2 contains information on the amount of avgas used per LTO for some single and twin - engine aircraft. The proportion of piston - engine L TOs conducted b y s ingle - versus twin engine aircraft was taken from the FAA’s GAATA Survey for 2005 (90% of L TOs are conducted b y aircraft having one engine and 10% of L TOs 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 ty pes of single piston - engine aircraft within EDMS. 102 This was accomp lished by averaging the single - engine EDMS outputs for fuel consumed per LTO using the EDMS scenario propert y 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 Preparati on, Volume IV: Mobile Sources , 1992. 103 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 100 The FAA GAATA is a database collected from surveys of pilots flying aircraft used fo r general aviation and air taxi activity. For more information on the GAAT A, see Appendix A , online at : http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/ 101 There are about 194,000 piston - engine aircraft in the U.S. general aviation and air taxi fleet (175,000 single engine and 19,000 twin - engine aircraft) according to FAA’s 2005 GAATA Survey. 102 EPA understands that EDMS 5.0.2 has a limited list of piston engines, but these are currently the best data available. 103 U.S. Environmental Protection Agency (1992) Procedures for Emission Inventory Preparation, Volume IV: Mobile Sources , EPA - 450/4 - 81 - 026d (Revised).53

average densit y of 100LL avgas, 6 pounds per gallon (lbs/gal), producing an average fu el usage for single - engine piston aircraft of 2.83 gallons per L TO (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/L TO . Using these single - and twin - engine piston aircraft fuel consumption rates, a weighted average fuel usage rate per LTO was computed b y multiplying the average fuel usage rate for single - engine aircraft (2.83 gal/LTO) b y the fleet percentage of single - engine aircraft LTOs (90%). Next, the twin - engine piston aircraft average fuel usage rate (9.12 gal/L TO) 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] : T he maximum lead concentration specified b y 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 4.24 grams of lead per gallon is used by a small number of piston - engine aircraft . We currentl y 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.54

Retention of lead in engine and oil (1 - Pb Retention) : Recent d ata collected from a ircraft piston engines operating on leaded avgas suggests that about 5% of the lead from the fuel is retained in the engine and engine oil. 104 Thus the emitted fraction is 0.95. Multiplying th e lead concentration in 100LL avgas by the weighted average fu el usage rate produces an overall average value of 7.34 grams of lead per LTO (g Pb/L TO) for piston engines: 3.46 gal/L TO x 2.12 g Pb/gal = 7.34 g Pb/L TO. The denominator is a unit conversion factor used to express the lead inventory in units of short ton s. Applying these parameters in the equation above yields the following equation:

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

907,185 g/ short ton which simplifies to: Pb = (piston - engine LTO) (7. 7 X 10 - 6 short tons) or 7 grams of lead per LTO where piston - engine LTO = (GA LTO + AT L TO)(0.72) . EPA used similar methods to estimate lead emissions from piston - engine powered helicopters which are described separately . 105 We currently estimate there are 6 grams of lead emitted by piston - engine helic opters per LTO. L ead emitted during the LTO cy cle is assigned to the airport facility where the aircraft 104 The information used to develop this estimate is from the following references: (a) Todd L. Petersen, Petersen Aviation, Inc, Aviation Oil Lead Content Analysis , Report Number EPA 1 - 2008, January 2, 2008, available at William J. Hughes Technical Center Technical Reference and Research Library at http://actlibrary.tc.faa.gov/ and (b) E - ma il from Theo Rindlisbacher of Switzerl and Federal Office of Civil Aviation to Bryan Manning of U.S. EPA, regarding lead retained in engine, September 28, 2007. 105 U.S. Environmental Protection Agency (2009) Calculating Aviation Gasoline Lead Emissions in the 2008 NEI. Available at: www.epa.gov/ otaq/aviation.htm. pp.8 - 9.55

operations occur. 106 FAA’s Office of Air Traffic provides a complete listing of operational airport facilities in the National Airspace Sy stem Resourc es (NASR) database. 107 In 2008, there we re 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 t yp es of airport facilities: airports, ballo onports, seaplane bases, gliderports, heliports, stolports, 108 and ultralight facilities. Among these, balloonports are the onl y facilities not expected to have piston - engine aircraft activity . Preparing airport - specific lead inventories requires information regarding LTO activity . T hese activity

data are reported to the FAA for only a small subset of the approximate ly 20,000 facilities in the U.S. EPA obtains L TO 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. 109 The TAF database currently includes information for airports in FAA’s National Plan of Integrated Airport Sy stems (NPIAS), which identifies airports that are significant to national ai r transportation. For airports not listed in the TAF , operations data are obtained from the NASR database , where available. O perations data provided by the NASR database may

be self - reported by

airport operators through data collection accomplished by ai rport inspectors who work for the State Aviation Agency , or operations data can be obtained

106 An aircraft operation is defined as any landing or take - off event, therefore, to calculate LTOs, operations are divided by two. Most data sources from FAA report aircraft activity in numbers of operations which, for the purpos es of calculating lead emissions using the method described in the TSD, need to be converted to LTO events. 107 An electronic report can be generated from the NASR database and is available for dow nload from the internet at the following website. . http://www.faa.gov/airports_airtraffic/airports/airport_safety/airportdata_5010/ This database is updated every 56 days. 108 Stolport is an airport designed with STOL (S hort Take - Off and Landing) operations in mind, normally having a short single runway . 109 These data are available from: http://aspm.faa.gov/main/taf.asp .56

through other means. 110 We are using the January 15, 2009 version of the NASR database to evaluate airport lead emissions inventories for 2008 . Using the TAF data base as the primary

source of LTO information and the NASR as a secondary source, we have LTO activity data for approximately 5,6 00 airport facilities . There are approximately 14, 000 facilities in the NASR database for which there are no LTO activity data . 111 We developed methods based on previous work conducted b y the FAA to estimate LT O activit y 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. 112 The FAA has used regression models to estimate operations at facilities where operations data are not available. 113 , 114 In this work and other work, FAA identified characteristics of small towered airports for which there were statisticall y significant relationships with operations at these airports. 115 Regression models based on the airport characteristics were then used to estimate general aviation operations for a set of non - towered airports. The airport char acteristics identified by

the FAA and used to estimate general aviation operations at small airports include: the number and t ype of aircraft based at the facility (i.e., ‘based aircraft ’ ) , population in the vicinity of the airport, airport regional promin ence, per capita income, region of the country , and 110 In the absence of updated information from States, local authorities or Tribes, w e are using the LTO data provided in the FAA database. 111 No Commuter, GA Itinerant, GA Local, or Air Taxi operations data. 112 U.S. Environmental Protection Agency (2009) Calculating Aviation Gasoline Lead Emissions in the 2008 NEI. Available at www.epa.gov/otaq/aviation.htm 113 Federal Aviation Administration, Office of Aviation Policy and Plans, Statistics and Forecast Branch. ( July 2001 ) Model for Estimating General Aviation Operations at Non - towered Airports Using Tow ered and Non tow ered Airport Data. Prepared by GRA, Inc. 114 Hoekstra, M. (April, 2000) Model for Estimating General Aviation Ope rations at Non - Towered Airports. P repared for FAA Office of Aviation Policy and Plans. 115 GRA, Inc. “Review of TAF Methods,” Final Report, prepared for FAA Office of Aviation Policy and Pl ans under Work Order 45, Contract No. DTFA01 - 93 - C - 00066, February 25, 1998.57

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 regressor s to LTO activity that our anal ys is p rovided. 116 The regression equation for based aircraft and county population is: L TOs = 1248 + 203.04*Aircraft + 0.0019*County Population with an R2 = 0.64. F or approximately 7,8 00 facilities that do not report L TO 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 e quation based on count y population and region of the country. The regression equation using count y 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 an alternative methods to estimate L TO activit y 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 currentl y us in g 116 The derivation of these regression equations is described in the document titled “Calculating Aviation Gasoline Lead Emissions in the 2008 NEI.” Available at www.epa.gov/otaq/avi ation.htm.58

the median of activity

(141 L TOs/ ye ar) 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 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 incl ude : 1) the fraction of GA and AT LTO activity reported to FAA that is conducted by piston - engine versus jet - engine powered aircraft, 2) airport - specific LTO activity

for single - versus twin - engine piston - powered aircraft, 3) fuel consumption rates for th e piston - engine aircraft operating at each airport, 4) the time spent in each mode of operation including run - up checks conducted by piston - engine aircraft prior to take - off, 5) the concentration of lead in fuel delivered to individual airports. Methods f or providing information to EPA as part of the review process involved in finalizing the 2008 NEI are available. 117 The discussion above pertains only to lead emissions during the LTO cy cle. L ead emitted outside the L TO cy cle occurs during aircraft cruis e 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 L TO cy cle which we anticipate will be available in 20 10 .

117 All documentation for use in preparing 2008 emission inventories can by found on the NEI/EIS Implementation website : http://www.epa.gov/ttn/chief/net/neip/index.html.59



### 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 . 118 The most recent forecast is for the y ears 200 9 through 2025. The General Aviation Manufacturers Association (GAMA) reproduces the FAA forecast in their annual statistical databook . 119 According to the GAMA summary , the number of active single - engine piston - powered aircr aft is projected to inc rease annually at a 0.5% growth rate, with the aircraft population increasing from 144,220 in 2008 to 157,400 in 2025. The number of active twin - engine piston - powered aircraft is projected to decrease 0.9% annuall y, with aircraft po pulation 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 - engin e piston - powered aircraft is projected to increase 0 . 5 % ye arl y from 2008 to 20 2 5) ; the number of hours flown in twin - engine piston - powered aircraft is projected to decrease 1. 5 % annuall y and the number of hours flown in piston - powered rotocraft is projecte d 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 ye ars 200 8 through 2025, DOT’s FAA estimates no change in the volume of leaded avgas consumed by sin gle - engine aircraft in the U.S. ( 204 million gallons in 200 8 and 2025), a 1. 9 % decrease in leaded avgas consumed by multi - engine aircraft (from a baseline of

118 FAA Aero space Forecast Fiscal Years 200 9

–2025 . Available online at: http://www.faa.gov/data_research/aviation 119 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.pdf60

108 million gallons in 2008 to 78 million gallons in 2025), and a 3 .8% annual increase in the vol ume 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 3 4 8 million gallons. Consumption of this volume of fuel would relea se 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 slightl y over half a million in 2025, representing a yearl y increase of 0.7% over the forecast period. 120 The student pilot population is forecast to increase at a slightly higher rate of 1.0% yearl y for a 2025 total slightly over 100,000. Private pilots and sport pilots are also projected to increase ye arly (0.2% y earl y increase in the number of private p ilots). 

## IV . Lead Concentrations in the Vi cinity of Airports

This section summarizes information regarding the chemical and phy sical properties of lead emitted b y piston - engine aircraft and monitoring and modeling studies regarding ambient and soil lead concentrations in the vicinity of airports where piston - engine aircraft operate. 

### A. Chem ical and Physical Properties of Lead Em itted by Piston - Engine Aircraft

Information regarding lead emissions from engines operating on leaded fuel is summarized in prior AQCDs for Lead. The chemical form of lead added to avgas (i.e., tetraeth yl 120 Except for sport pilots, an active pilot is a person with a pilot certificate with a valid medical certificate. Source: FAA 200 9 - 2025 Aerospace Forecast . Available online at: http://www.faa.gov/data_research/aviation61

lead) and the lead scavenger, eth yl ene dibromide, are the same compounds used in leaded gasoline for motor vehicles in the past . Therefore, the summary of the science regard ing 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) publish ed a study of piston - engine aircraft emissions including measurements of lead. 121 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 plug s and if the deposits become thick enough, the engine can be damaged. Eth yl ene dibromide reacts with the lead oxide, converting it to brominated lead and lead ox yb romides. 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. 122 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 . 123 L ead halides under go compositional changes upon cooling and mixing with the ambient air as well as during transport ; the water - solubility of these lead - bearing particles increase s with a shift toward smaller mean particle size (USEPA 19 77 , S ection 6.2.2.1 ). Lead h alides from automobile exhaust break down rapidly in the atmosphere, via redox reactions in the presence of atmospheric acids ( AQCD for Lead, page E - 17). 121 Federal Office of Civil Aviation Environmental Affairs (2007) Aircraft Piston Engine Emissions Summary Report. 33 - 05 - 003 Piston Engine Emissions_Swiss FOCA_Summary. Report_070612_rit. Available online at: http://www.bazl.admin.ch . 122 ChevronTexaco (2006) Aviation Fuels Technical Review pp. 64 - 65. Available online at: http://www.chevronglobalaviation.com/docs/aviation_tech_review.pdf . 123 U.S. Environmental Protection Ag ency (1986) Air quality C riteria for L ead. Volume 2 Section Chapters 5 & 6. Research Triangle Park, NC: Office of Health and Environmental Assessment, Environmental Criteria and Assessment Office; EPA report no. EPA - 600/8 - 83/028aF - dF. 4v. Available from: N TIS, Springfield, VA; PB87 - 142378.62

A small fraction of unc ombusted alkyl lead was measured in the exhaust of motor vehicles operating with leaded gasoline and is therefore likely to be present in the exhaust from piston - engine aircraft. 124 Alkyl lead is the general term for organic lead compounds and includes the lead additives tetramethyl lead and tetraethyl lead. Tetraeth yl lead is a highl y volatile compound and therefore, a portion of tetraethyl lead in fuel exposed to air will partition into the vapor phase. Tetraeth yl lead can enter the atmosphere from avgas distribution sy stems, refueling operations, fuel check pre - flight procedures and evaporative losses from the aircraft . 125 Tetra eth yl lead ha s an atmospheric residence time ranging from a few hours to a few day s. Tetraeth yl lead reacts with the hy droxyl rad ical in the gas - phase to form a variet y of products that include ionic trialkyl lead, dialkyl lead and metallic lead. Trialkyl lead is slow to react with the hydrox yl radical and is quite persistent in the atmosphere ( AQCD for Lead, page 2 - 5). Particle s 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 0.10 8 microns under different power conditions. The particle number concentration ranged from 5.7x10 6 to 8.6x10 6 particles per cm 3 and using a specific density for soot of 1.2, the authors estimated the mass concentration of particulate emissions as approximately 10,000  g/m 3

. The authors noted that these particle emission rates are comparable to those from a t ypical diesel passenger car engine without a particle filter (FOCA, S ection 2.2.3.a) . 124 U.S. Environmental Protection Agency Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT national action plan for alkyl - Pb. Washington, DC. Available online at: http://www.epa.gov/pbt/pubs/A lkyl_ lead_action_plan_final.pdf 125 U.S. Environmental Protection Agency Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT national action plan for alkyl - Pb. Washington, DC. p. 12. Available online at: http://www.epa.gov/pbt/pubs/A lkyl_le ad_action_plan_final.pdf63

A significant fraction of particles in the submicron size rang e are deposit ed and ret ained in the lower respiratory

sy stem of humans and animals ( AQCD for PM, page 6 - 108) . 126 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, lead - bearing particles emitted by piston engines may disperse widely in the environment. However, lead emitted during LTO, particularly during ground based operations such as start - up, idle, preflight run - up checks, taxi and take - off may depo sit 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 ope rations for decades , including ye ars when lead concentrations in avgas were twice as high as current levels. We seek comment on the chemical and ph ys ical form of lead emissions from piston - engine aircraft as well as dispersion and deposition patterns that may influence the risk for local - scale impacts. 

### B. Summ ary ofAirport Lead Monitoring and Modeling Studies L ead concentrations in ambient air have been reported for samples collected on or near five airports: the Santa Monica municipal airport in Sant a Monica, CA , the Van Nu ys airport in Van Nu ys , CA, the Chicago O’Hare airport in IL, the Toronto Buttonville municipal airport in

126 U.S. Environmental Protection Agency (2004) Air Quality Criteria for Particulate Matter (AQCD). Volume II Document No. EPA600/P - 99/002bF. Washington, DC: U.S. Environmental Protection Agency. Available online at: http://cfpub.epa .gov/ncea/cfm/recordisplay.cfm?deid=87903 .64

Ontario, Canada , and the Destin airport in Destin, FL . 127 , 128 , 129 , 130 , 131 Air quality modeling of lead emissions from piston - engin e aircraft has been conducted as part of EPA’s National Air Toxics Assessment and in one study . 132 , 133 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 in formation 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 propert y served man y purposes and therefore used different criteria for determining sample locations, sample durations, sample collection methods, and collection of important metadata (e.g., activit y of piston - engine aircraft and aircraft engine ty pe). This section summarizes results fro m these studies .

127 South Coast Air Quality Management District (2007) Community - Scale Air Toxics Monitoring

– Sun Valley Neighborhood and General Aviation Airports. Presented by Dr. Philip Fine at the U.S. EPA Air Toxics Data Ana lysis Workshop - Chicago, IL. October 2 - 4, 2007. 128 Illinois Environmental Protection Agency Bureau of Air ( 2002 ) Chicago O’Hare Airport Air Toxic Monitoring Program June

– December, 2000. 129 Environment Canada ( 2000 ) Airborne Particulate Matter, Lead and Manganese at Buttonville Airport. Toronto, Ontario, Canada:Conor Pacific Environmental Technologies for Environmental Protection Service, Ontario Region. 130 Tetra Tech, Inc. (2007) Destin Airport Air Sampling Project Executive Summary. Prepared for City of Destin, Florida. 131 Tetra Tech, Inc. (2008) Destin, Florida Airport Sampling Report. October 2008. Prepared for City of Destin, Florida. 132 Piazza, B for the Los Angeles Unified School District Environmental Health and Safety Branch (1999) Santa Monica Muni cipal 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 133 U.S. Environmental Protection Agency (2009) 2002 National - Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn/atw/nata2002/index.html65

Ambient monitoring studies at and near airports have shown an increase in lead levels in ambient air at or near airports with piston - engine activity . The stud y at the Santa Monica A irport 134 is the only

study to date in which a lead moni tor was sited at an area of anticipated maximum concentration for a period of time that provides ambient concentrations relevant for comparison t o the Lead NAAQS. 135 Inthis study where monitors were placed in locations to identify the gradient in lead conc entrations 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 - 20 07 . At the monitor placed near the runway blast fence (i.e., the maximum impact site) on the Santa Monica A irport propert y, the quarterly average concentrations of lead in total suspended particulate matter ( TSP ) were 0.08 ( w inter) and 0.10 ( s pring)  g/m 3

. 136 T he maximum quarterly

average concentration of lead in total suspended particulate matter (TSP) was 0.10  g/m 3 , 67% of the 2008 Lead NAAQS of 0.15  g/m 3 . This suggests that ambient air lead concentrations at similar airports with more piston - engine ac tivity than the Santa Monica A irport may be higher, and could further approach or exceed 0.15  g/m 3

. At a neighborhood site, 70 meters in the prevailing downwind direction from the maximum impact site, quarterl y average concentrations of lead in TSP were 0.02  g/m 3 (winter) and 0.03  g/m 3 (spring). 137 At a distance of one kilometer in the prevailing downwind direction from the maximum impact site, lead concentrations were 0.004  g/m 3 and 0.008  g/m 3 in winter and spring, respectivel y (these 134 South Coast Air Quality Management District (2007) Community - Scale Air Toxics Monitoring

– Sun Valley Neighborhood and General Aviation Airports. Presente d 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. 135 As with other lead source s, 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 dow nwind of the take - of

f strip near the “blast fence.” http://www.epa.gov/ttnamti1/files/ambient/pb/NetworkDesignQA.pdf 136 A low - volume sampler w as used at this site which EPA expects w ould yield com parable results to a high - volume sampler, the later of which is the current method used to collect samples for comparison with the Lead NAAQS. 137 These distances were measured using Google Earth Pro softw are.66

concentrations are considered the background lead concentration) . The study conducted at the Santa Monica Airport reported concentrations of ambient lead that were highest at on - and near airport areas downwind from the emissions of piston - engine aircraft. These data su ggest 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. 138 As with other emissions from internal combustion engines, lead emitted b y piston - engine aircraft are largely

in the submicron and even ultrafine size fraction ; therefore, analogies to grad ients in ultrafine PM are relevant . A s summarized in EPA’s 2009 Integrated Science Assessment for Particulate Matter, ultrafine particulate number counts decrease exponentially with distance from roadway s. 139 A recent stud y at the Santa Monica Airport reported increased ultrafine PM in a neighborhood downwind from aircraft operations that were conducted b y jet and piston - engine aircraft. 140 The EPA is conducting modeling and monitoring studies to further evaluate the gradient in lead concentrations with distance from airport s (see Section VI .B of this ANPR). At the Van Nu ys Airport, lead monitoring in ambient air was conducted at s ix sites for two three - month periods. Le ad monitoring for this study included locations of ambient air on airport property . H owever, monitors were not sited in the area anticipated to experience the

138 EPA notes that additional information regarding this study at the Santa Monica Airport may become available. If additional information does become available, EPA will take this information into account in the NPRM. 139 U.S. Environmental Protection Agency (2009) Integrated Science Assessment for Particulate Matter. Second External Review Draft. EPA/600/R - 08/139B. p. 3 - 110. Available online at: http://cfpub.epa.gov/ncea/ cfm/recordisplay.cfm?deid=210586 140 Hu, S., Fruin, S., Kozaw a, 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 - 8045.67

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. 141 T he highest quarterly concentration of lead observed at the Van Nu ys Airport was at the monitor located over one kilometer away fr o m the maximum impact site and the lead concentration at this site was 0.03  g/m 3 which was four - fold higher than the regional background level o f 0.008  g/m 3 measured during the same time period at a site over 2.5 kilometers from the north end of the Van Nu ys Airport . At the Toronto Buttonville M unicipal A irport, ten 24 - hour PM 10 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 ) . PM 10 is particulate matter less than ten microns in aerod ynamic diameter. The average lead concentration among the airport monitors ( which inclu d es three samples that were taken for less than a 12 - hour period ) , was 0.03  g/m 3 and the maximum 24 - hour lead concentration was 0. 1 3  g/m 3 . O ne sample, collected for 11 hours , measured 0.30  g/m 3

. The maximum concentration observed over a 24 - hour period at the airport during this study (0. 1 3  g/m 3 ) was 11 times higher than the lead concentration reported for the downtown Toronto, Canada background site during the same time period (0.012  g/m 3 ) . 142 The average lead concentrati on reported for the downtown Toronto site was 0.007  g/m 3

. The total particulate matter mass in PM 10 was also measured in this study , and at the airport, the average mass of lead in PM 10 was 0. 15 % of the total PM 10 mass. At the downtown Toronto site, the average mass of lead in PM 10 was 0.04% of

141 These distances were measured using Google Earth Pro softw are. Prevailing wind direction, which determines the direction in which the majority of aircraft depart, is provided in the SCAQMD presentation of these data. 142 Average concentrations reported in this study include three days of short - duration sampling so the average is not used for comparison here.68

the total PM 10 mass. The study report e d 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 downwin d of the Chicago O’Hare Airport on sixteen day s 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 i n areas adjacent to airport propert y, two monitoring sites were deploy ed on different sides of the airport : one in Bensenville, IL and the other in Schiller Park, IL. For five day s 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 day s were, on average 8 8 % higher than lead concentrations measured at the upwind site. Lead concentrations at the upwind site over the five day s averaged 0.016  g/m 3 and downwind concentrations averaged 0.030  g/m 3

. This study demonstrates the potential for operations on airport propert y to impact ambient lead concentrations downwind. Lead TSP samples were collected for four day s in April 2007 and for three day s 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. 143 The average lead concentration among the four residential locations was 0.004  g/m 3 and 0.005  g/m 3 in April and July , respectively , and the average urban background lead concentration was 0 .003 and 0.004  g/m 3 in April and July , respectively . 143 These distances were measured using Google Earth Pro softw are.69

In addition to these airport - specific studies, a uthors evaluatin g 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 . 144 At some airports, piston - engine a ircraft activity conducted for recreational purposes can increase greatl y 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 co ncentrations 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 e valuate the influence of this variability in activity on ambient lead c oncentrations. We have identified no studies evaluating the potential contribution of piston - engine aircraft emissions on vegetation. We have identified o nly one study

that reports soil concentrations on airport propert y where piston - engine aircraft ar e 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  g/ g which was not substantially higher than the lead concentrations in soil samples at the two urban background sites ( 29 and 31  g/g ) . We are seeking comments on the potential for piston - engine aircraft emissions to impact local soil lead

144 Murphy, D.M., Capps, S.L., Daniel, J.S., Frost, G.J., and White, W.H. (2008) Wee kly patterns of aerosol in the United States. Atmos . Chem. Phys., 8, 2729

–2739.70

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 Natio nal Air Toxics Assessment (NATA ) as nonroad sources of lead. 145 Ambient l ead concentration s and exposures t o 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. The contribution of piston - engine aircraft emissions to state inventories and ambient lead concentrations are described in a memo to the docket for this ANPR. 146 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 VIof this ANPR, the E PA is currentl y conducting a study to model the local - scale v ariability in ambient lead concentrations attributable to piston - engine activity at a case study

airport. This project will include collection of air monitoring data for use in evaluating model performance. In the NPRM, we will describe the results of th e modeling study with NATA results for this airport and previous modeling work . 147

145 U.S. Environmental Protection Agency (2009) 2002 National - Scale Air Toxics Assessment (NATA). Available online at: http://www.epa.gov/ttn /atw/nata2002/tables.html. 146 Mem o f

rom Meredith Pedde to docket EPA - HQ - OAR - 2007 - 0294 titled ‘Summary Statistics of Piston - engine Aircraft Lead Emissions in EPA’s 2002 National Air Toxics Assessment (NATA).’ 147 Piazza, B for the Los Angeles Unified School District Environmental Health and S afety 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:71

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 . 

## V. Exposur e to Lead fr omA viation Gasoline and Potential for Im pacts The continued use of lead in avgas b y piston - engine aircraft is a significant source of lead to the environment. Piston - engine aircraft emissions of lead occur at ground level as well as at flying altitude. Consequently , lead from this source is concentrated near airports but is also deposited over a large geographic area potentially contri buting 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 envir onment posing a potential risk to future generations In this section we discuss a variet y of exposure pathway s and scenarios b y which the general population and environment may experience an increase in lead exposure from emissions of lead b y piston - engin e aircraft. This section also describes the potential for public health and welfare effects from exposure to compounds associate d with the continued use of tetraethyl lead in fuel , such as the contribution of lead to ambient particulate matter, emissions of ethylene http://yosemite.epa.gov/oar/CommunityAssessment.nsf/6ce396ab3fa98ee485256db0004acd94/$FILE/Santa_Monica .pdf72

dibromide and non - exhaust exposure to tetraethyl lead. We are seeking comments and information on these exposure scenarios as well as additional exposure pathway s and scenarios . 

### A. Exposure to Lead Em itted by Piston - Engine Aircraft Piston - en gine 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. L e ad particles can deposit to soil, water, vegetation and other surfaces or remain airborne for some time following emissions. Inth is section we discuss potentially exposed populations which include people living or attending schools near airports and pilo ts. Additional pathway s by which people and animals could be exposed to lead emissions from piston - engine aircraft are those associated with agricultural applications of these aircraft and piston - engine activity at seaport and inland waterway s. L ead from aviation gasoline has been identified as a potential source of contamination for local communities. 148 As described below, man y general aviation airports are located in densely populated areas. GA airport facilities were ty pically built in sparsely

populated areas , man y of which are now heavily

populated or are experiencing increased residential development. This development include s dense residential neighborhoods, schools, businesses, and recreational facilities. Airports can function as a center of man y forms of activity in a community. Airports are

148 Levin, R.; Brow

n, MJ; Kashtoc k, ME ; Jacobs, DE; Whelan, EA; Rodm an, J; Schock, MR; Padilla, A; Sinks , T. (2008) US Children’s Lead Exposures, 2008: Implications for Prevention. Environ. Health Perspec. 116:1285 - 1293.73

often surrounded b y 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 advanta ge of the ease of transport and pilot training/recreation offered by quick access to an airport . Man y airports offer on - site tours to the general public, educational classes, and recreational opportunities that can present near - source exposure scenarios. Airports are especiall y attractive to young children , and programs at some airports are focu sed on this population and provide outdoor observation facilities and picnic facilities for families to observe aircraft operations. M any general aviation airport s offer instructional fl yi ng 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, f ireworks display s, air shows and c ommunity

meals . Man y ai rport facilities provide activities which bring people from the general public in close proximity to lead emissions from piston - engine aircraft and piston engine helicopt e rs. 

### 1. Population Residing Near Airports

To evaluate the number of people who might be exposed to elevated lead levels due to emissions from pisto n - engine aircraft , EPA calculated the number of people that live within one kilometer of the centroid of an airport. The centroid of the airport is defined here as the latitude and longitude coordinate provided b y airports to FAA. 149 Th e s e coordinate s ty pically identif y a location in the center of the runway or runway

area. For some airports, nearby residences ar e 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

149 Federal Aviation Administration. Airport Data (5010) & Contact In formation, Airport Facilities Data. Retrieved on August 13, 2009 from: http://www.faa.gov/airports/airport_safety/airportdata_5010/menu/index.cfm74

airports such as those servicing primarily commercial aircraft activity . For airport facilities with o ne runway th at is approximately one kilometer in length , this method will generall y include people residing within approximately 500 meters from the ends of the runway and may include residences up to approximately 9 00 meters from the sides of the runway . T he limited ambient lead monitoring data near airports presented in Section IV of this ANPR suggests that for some airports this anal ys is will underestimate the actual number of people potentially exposed to elevated levels of ambient lead from piston - engine powered aircraft. We plan to revise this anal ys is for the NPRM using a graphical interface sy stem that will allow us to evaluate the number of people living within uniform distances of aircraft activity . Using 2000 U . S . Census Data 150 at the block level, EPA estim ates that 16 million people live within one kilometer of the centroid of the 19,896 air port facilities which includes airports, seaplane bases, heliports, stolports, ultralight facilities and glider ports . There are currentl y 5,567 heliports in this analy sis, 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 currentl y have limited information regarding which heliport fac ilities have piston - engine activity and we are seeking comment on piston - engine activity at heliports. There are several pathways b y which people may be exposed to lead associated with the use of piston - engine aircraft. These include inhalation of ambie nt 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 track ed into interior spaces . There is also the potential for ingestion of lead emitted by piston engine

150 Obtained from : http://www.epa.gov/ttn/fera/human_hem_censusandmet.html .75

aircraft emission s to deposit on edible plants and produce being cultivated in locations near a irports. Consequently , there is the potential for exposure to lead emitted by piston - engine aircraf t 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 hav e information on the potential significance of this exposure pathway and we are seeking comment on information and anal ys es 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 communit ies or residential airpark s. Some residential airparks are private while others have public services and facilities. Some residential airparks are specificall y d esigned as airport communities with driveway s leading from aircraft hang ars 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 . 151 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. 152 Some residential airparks provide taxiway s for access to the runway , some provide streets separate from taxiway s, and some share automobile and aircraft traffic on the same thoroughfares . A variety of re sources list the location and services offered by residential

151 FAA officially defines “through - the - fence” as those activities permitted by an airport sponsor through an agreement that permits access to the public landing area by independent entities or operations offering an aeronautical activity or to ow ners 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.o rg/whatsnew/region/airportOps0712.pdf ) 152 ASTM International (2005) ASTM F2507

– 05 Standard Specification for Recreational Airpark Design.76

airpar ks in the U.S. and estimates of the number of residential airparks range from 300 to 600. 153 , 154 Insome cases, records are maintained on ly for those residential parks that have five or more homes or lots. Exposure modeling at the EPA indicates that, for the 20 highest air emi ssion sources , local emissions are significantly related to local blood lead levels . 155 We are aware of no studies evaluating blood lead levels among people who live in close proximity to airports with piston engine activit y or those f

or whom lead emissions from piston engines may elevate their exposure via other exposure pathway s . As noted in Section II.B.2, the current evidence indicates that the slope for lead effects on IQ is nonlinear and is steeper at lower blood lead levels, suc h 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 informatio n regarding blood lead concentrations in children living near airports and the extent to which these emissions cause or contribute to an y increases in blood lead levels . 

### 2 . Children Attending School N ear Airports As noted in Section II.B.2 of this ANPR, while adults are susceptible to lead effects at lower blood lead levels than previousl y understood (e.g., AQCD for Lead, p. 8 - 25), there is general consensus that the developing nervous s ys tem in children is among the, if not the , most sensitive health end

points . A lso , as noted in Section II.B.3, while children are considered to be

153 www.airparks.com maintains a list of airparks that have five or more hom es/lots. The list can be updated by the public and as of July 31, 2009, lists 326 residential airparks. 154 http://livingwithyourplane.com/about/ has a directory of over 600 residential airparks. 155 U.S . E nvironmental P rotection A gency ( 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 .77

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 b y the time the child reaches 2 to 3 y ears of age” ( AQCD for Lead, Sec tion 6.2.12). Accordingl y, school - age children are an at - risk population for lead exposures. This section discusses potential exposures of children at school to lead associated with piston - engine aircraft. During the school year, students spend many hours a day at school, which usually includes time on school playgrounds and on school athletic fields . Those children attending schools in close proximity to piston - engine activity m a y 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 3) . 156 These children rep resent 6% of the total U.S. student population. Table 3 . Numbers of Public and Private Schools and School Children Attending Schools Located w ithin O ne 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

156 Public School Data available for 2006 - 2007 from: http://nces.ed.gov/ccd/bat/ ; Private School Data available for 2 007 - 2008: http://nces.ed.gov/surveys/pss/pssdata.asp .78 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 povert y 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 d ata from the Department of Education that provides this information. These data indicate that m inorities are overrepresented at schools that are located within one kilometer from the centroid of an airport. For example, Hispanic students repres ent 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 4 ). Black students represent 18% of students at schools located within one kilometer of an airport , whereas b lack students rep resent 16% of the student population in the U.S. (T able 4 ). Table 4 . Racial Distribution at Schools w ithin O ne Kilometer of the C entroid of an A irport and the Racial Distribution at all U.S. Schools .

American Indian / Alaskan Indian Asian /

Pacific Islander Black,

Non Hispanic Hispanic White, Non Hispanic Total

Students *79

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 % *T his 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 roadway s, airports, ports, rail yards) are likel y to have lower income than the g eneral population . 157 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 progr am. Children from families with incomes at or below 130 percent of the poverty level are eligible for free meals. Those with incomes between 130 percent and 185 percent of the povert y level are eligible for reduced - price meals. 158 Free and reduced lunch e ligibility is onl y tracked b y 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

157 U.S. Environmental Protection Agency (2007) Regulatory Impact Analysis for the Regulation to Control Hazardous Air Pollutant Emissions fro m Mobile Sources. Chapter 3, p. 3 - 122. 158 United States Department of Agriculture: Food and Nutrition Service, National School Lunch Program Fact Sheet. Obtained from: http:/ /www.fns.usda.gov/cnd/Lunch/AboutLunch/NSLPFactSheet.pdf , August 3, 2009. For the period July 1, 2008, through June 30, 2009, 130 percent of the poverty level is $27,560 for a family of four; 185 percent is $39,220 .80

are el ig ible for either free or reduced lunches, whereas n ationall y, 41% of students at public schools are eligible for either free or reduced lunches. As this anal ys is demonstrates, those living in the vicinity

of airports are more likel y to be low - income hous eholds 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 concentration s 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 variet y of agricultural a ctivities 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 A ctivity (GAATA) Survey annuall y 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 . 159 , 160 According to the results of the 2007 G AATA Survey (the most recent), aerial application in agriculture and forestry represented 5% of all hours flown by gener al aviation aircraft in 2007. Of the total aerial application hours flown in 2007 (1.41 million hours), 60% of the hours were flown b y piston - engine aircraft. Aerial a pplication

159 The FAA GAATA is a database collecte d from surveys of pilots flying aircraft used for general aviation and air taxi activity. For more information on the GAAT A, see Appendix A at http://www.faa.gov/data_statistics/aviation_data_statistics/general_aviation/ . 160 National Agricultural Aviation Association : “Help the Aerial Application Industry by completing the 2008 General Aviation Activity Survey.” Retrieved from: http://www.agaviation.org/2008%20GenAvnSurvey.htm on August 13 , 2009.81

activity includes crop and timber production, which involve fertilizer and p esticide 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. 161 As discussed in Section II.C.1, surface de position 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 b y engines operating on leaded fuel, are slightl y water soluble . They therefore may be more readil y absorbed by plant s 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). 162 The l ead concentration of plants ingested b y anim als is primarily a result of atmospheric deposition of lead particles onto plant surfaces rather than the uptake of soil lead through plant roots . S ome of the highest levels of lead exposure among livestock have been attributed to grazing near major sourc es 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) ) .

161 National Agricultural Aviation Association : “History”. Retrieved from: http://www.agaviation.org/history.htm on August 13, 2009. 162 U.S. Environmental Protection Agency (1986) Air Q uality C riteria for L ead. 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 - 142378.82

D epending on wind conditions, an aircraft involved in aerial application may fl y onl y 4 inches to 12 feet above the crops. 163 , 164 , 165 The low fl yi ng 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 directl y depositing on vegetation and surrounding soil. We h ave not identified an y data or analy ses 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 p assengers and pilots access their aircraft in areas that are ty pically in close proximity

to runway s. Therefore, these individuals walk near and breathe the air near locations where aircraft are idling, conducting r un - up checks, taxiing, taking off, and l anding. In the U.S., general aviation aircraft fl y over 27 million hours and carry 166 million passengers annuall y. 166 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 163 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 164 Harpole, T. (3 - 1 - 2007) “That Old - Tim e Profession” Air & Space Magazine. Retrieved on August 12, 2009 from: http://www.airspacemag.com/history - of - flight/old_time_profession.html 165 Petersen, R. “So you want to be a spray pilot”. AgAir Update. Retrieved on October 9, 2009 from: http://www.agairupdate.com/aau/wannabe/pilot.html 166 General Aviation Manufactu rers Association (2008) General Aviation Statistical Databook and Industry Outlook. Available at: http://www.gama.aero/files/2008_general_aviation_statistical_databook__indust_499b0dc37b.pdf83

hours, 11 percent are for business , eight percent are air taxi and air tours and the remainder include hours spend in other applications such as aerial observation and aerial application. 167 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. 168 Among the pilot population, 75,382 were student pilots , comprising 13% of the total p ilot population. The majority of initial pilot training is conducted in piston - engine aircraft. 169 There is no age minimum for pilots to begin tak ing fl yi ng lessons. 170 The minimum age for conducting a solo flight is 16 y ears 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 y ear old age group and 11,562 student pilots in the 16 - 19 y ears old age group. G AMA reports that in 2008 there are 3,846 private pilots in the 16 - 19 y ears old age group. According to the FAA there are more than 500 flight training schools. 171 , 172 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

167 General Accounting Office Report to Congressional Requesters (2 001) General Aviation Status of the Industry, Related Infrastructure, and Safety Issues. GAO - 01 - 916. 168 GAMA 2008 General Aviation Statistical Databook & Industry Outlook report . Retrieved on August 17, 2009 from: http://www.gama.aero/files/2008_general_av iation_statistical_databook__in dust_499b0dc37b.pdf 169 See http://flighttraining.aopa.org/learntofly/aircraft/ 170 Federal Aviation Administration (FAA). “ Becom e a Pilot

— Student Pilot's Certificate Requirements .” Retrieved on August 17, 2009 from http://www.faa.gov/pilots/become/student_cert/ . 171 Federal Aviation Administration (FAA). “ Ty pes of Pilot Schools & Choosing a Pilot School ”. Retrieved on August 17, 2009 from http://www.faa.gov/training_testing/training/pilot_schools/ . 172 Federal Aviation Administration (FAA). “ Pilot Schools - Search”. Retrieved on August 17, 2009 from http://av info.faa.gov/PilotS chool.asp .84

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

As discussed in Section II.C.2 of this ANPR , l ead 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 o n 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). 173 Alkyl lead, in particular, has been identified by

EPA as a Level I Persistent, Bioaccumulative, and Toxic (PBT) pollutant. Level I substances are targeted for virtual elimination through pollution prevention and other incentive - based actions that phase out their use, generation or release in a cost - effective manner within the most e xpedient time - frame. 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. 174 We are concerned about the potential for lead emissions fro m piston - engine aircraft to be a source o f 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 provid es 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 173 U.S. Environmental Protection Agency, “The Great Waters Program”. Retrieved on August 17, 2009 from http://www.epa.gov/air/oaqps/gr8w ater/ . 174 U.S. Environmental Protection Agency Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT national action plan for alkyl - Pb. Washington, DC. Available online at: http://www.epa.gov/pbt/pubs/A lkyl_lead_action_plan_final.pdf85

seaplane facilities, man y 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. L ead emissions from seaplane facilities as well as airports and heliports near water bodies can enter the aquatic ecosy stem by either deposition from ambient air or runoff of lead deposited to surface soils . As noted in Section I V.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 i nto w ater than other inorganic forms of lead . The EPA Office of Water maintains a database of the National L isting of Fish Advisories (NLFA) which is made available on the Internet to provide information regarding locall y - issued fish advisories and safe eatin g guidelines. 175 States, territories, and tribes ( collectively referred to here as "states") provide this information to EPA every y ear. The most recent ye ar for which data are available is 200 8 . St ates provide information regarding contaminant levels of bioaccumulative toxins measured in fish including lead, mercury , pol ychl orinated biphen yl s (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 an y m easureable 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 anal yt ical

175 U.S. Environmental Protection Agency, “The National Listing of Fish Advisories”. Retrieved on August 17, 200 9 from http://www.epa.gov/waterscience/fish/advisories/ .86

detection limit in 1 , 000 fish samples 176 and among the fish in which measureable lead concentrations were reported, the concentrations of lead ranged from 5 ppb to 60,400 ppb . 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 0.11ppm in 1984. 177 The decrease in mean lead concentrations was attributed primari ly to re d uctions in the lead content of motor vehicle gasoline. S ources of contamination of lead to waterway s frequently noted include lead gunshot, lead sinkers, and Superfund sites. 178 Lead emissions from piston - engine aircr aft 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 ti ssue lead concentrations at water bodies throughout the U.S. due to the emission of lead in flight. These in - flight emissions are greatl y 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 L acs Band of Ojibwe submitted comments to the L ead NAAQS docket noting the importance of fish consumption in their diet. 179 The Fond du Lac Band of Lake Superior Chippewa also noted in their comments , “As a reservation with municipal airport within its

176 In some instances states supply individual fish tissue sample results and in some instances states supply averages of multiple fish tissue sample results. 177 U.S. Environmental Protection Agency (20 00) 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: www.epa.gov/waterscience/fish/advice/volume1/index.html 178 U.S. Environmental Protection Agency, “Lead Fishing”. Retrieved on August 17, 2009 from http://www.epa.gov/owow/fish/animals.html . 179 See Docket ID Number EPA - HQ - OAR - 2006 - 0735. The tribes that submitted comments were: The Bad River Band of Lake Superior Tribe of Chippew a Indians, The Quapaw Tribe of Oklahoma, The Leech Lake Band of Ojibw e, The Lone Pine Paiute - Shoshone Reservation, The Fond du Lac Band of Lake Superior Chippew a, and The Mille Lacs Band of Ojibw e.87

exterior boundaries with two schools and tribal housing in close proximity to the airport (one half mile), leaded aircraft f uel 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 Re servation there are seven prop plane airports with many private air strips scattered throughout the area.” EPA is requesting comment on an y information regarding the potential impact of lead emissions from piston - engine aircraft on aquatic environments.



### B. Related Exposure

s 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 A gency . Among these issues are 1) the contribution of lead emissions to ambient PM, especiall y in areas in nonattainment with the PM 2.5 NAAQS, 2) the emissions of ethylene dibromide to the environment and 3) the evaporative emissions of tetraeth yl lead. 

### 1. Lead Contribut ion to Ambient P articulate M atter As discussed in Section IV.A of this ANPR , lead emitted by piston engines is expected to be predominantl y in the particle phase and will contribute to ambient PM . There are two U.S. National Ambient Air Quality Standards (NAAQS) for PM 2.5 : an annual standard (15 μg/m 3 ) and a 24 - hour standard (35 μg/m 3 ). As of March 4, 2009 there are 39 1997 PM 2.5 nonattainment areas. Area designations for the 2006 24 - hour PM 2.5 NAAQS were promulgated in 2009 for 3188

areas. 180 All of these nonattainment are as 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 facilitie s 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% o f the mobile source PM 2.5 inventory in these areas. In each of f our areas designated as nonattainment with the PM 2.5 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 PM 2.5 concentrations exceeding the 24 - hour PM 2.5 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 Sy stem 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 i ngestion. 181 EPA developed an inhalation reference concentration, ingestion dose and cancer unit risk estimates for inhalation and ingestion of ethylene dibromide. 182 Evidence of nasal tumors, hemangiosarcomas and mesotheliomas in rodents was used b y EPA to develop inhalation unit risk estimates (central tendency estimates

180 Information regarding PM designations is available at: http://www.epa.gov/pmdesignations/ . 181 U.S. Environmental Protection Agency (2004) Integrated Risk Information System (IRIS), IRIS Summary for 1,2 - dibromoethane CASRN 106 - 93 - 4. Available online at: http://www.epa. gov/ncea/iris/subst/0361.htm . 182 U.S. Environmental Protection Agency (2004) Integrated Risk Information System (IRIS), Toxicological Review of 1,2 - dibromoethane in support of summary information on the Integrated Risk Information System. Available online at: http://www.epa.gov/ncea/iris/toxreviews/0361 - tr.pdf89

and 95% upper bound estimates) of 3 x10 - 4 to 6x10 - 4 per μg/m 3

. Evidence of forestomach tumors, hemangiosarcomas, thy roid 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 x10 - 5 to 6x10 - 5 per μg/L assuming consumption of 2 Lof water per day by a 70 kg human. EPA developed a reference concentration for chronic inhalation of 9 μg/m 3 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. 183 T he International Agency

for Research on Cancer (IARC) has classified ethylene dibromide as a Group 2A carcinogen: probably car cinogenic 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. 184 The concentration of eth yl ene dibromide in leaded avgas is listed as less than 4 milliliters per gallon (<9 grams per gallon). 185 Since eth yl ene dibromide was measured in the exhaust and evaporative emissions from light - duty vehicles in the U.S. when they were operated on leaded fuel containing ethylene dibromide w e anticipate piston - engine aircraft are currently a source of ethylene dibromide to air. 186 Measurements of eth yl ene dibromide have not been made that

183 National Toxicology Program (NTP) (2005). 11 th Report on Carcinogens. Public Health Service, U.S. Department of Health and Human Services, Research Triangle Park, NC. Available from: http://ntp se rver.niehs.nih.gov. 184 Thomas VM; Bedford JA; Cicerone RJ. (1997) Bromine emissions from leaded gasoline. Geophys Res Letters 24(11):1371 - 1374. 185 Chevron Material Safety Data Sheet for aviation gasoline. Available online at: http://www.chevronglobalaviation .com /docs/aviation_gas.doc 186 Sigsby, J.E.; Dropkin, D.L.; Bradow , R.L.; Lang, J.M. (1982) Automotive Emissions of Ethylene Dibromide. SAE Technical Paper Series 820786.90

would allow estimation of the exhaust and evaporative emissions from piston - engine aircraft as well as the emissions associated with refueling and pre - flight fuel checks. 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. 187 The EPA established a Maximum Concentration Level (MCL ) of 0.05  g/L for ethylene dibromide , which is 100 - fold lower than the MCLfor benzene and 300 - fold lower than the MCLfor lead. The MCLis the highest level of a contaminant that is allowed in drinking water and is an enforceable drinking water standard. 188 The EPA Office of Underground Storage Tanks (OUST) and Office of Research and Development’s Nat ional Risk Management Research Laboratory (NRMRL) in association with the Association of State and Territorial Solid Waste Management Officials (ATSWMO) have formed a team to evaluate the potential for public health and welfare effects attributable to ethylene dibromide from past or present fuel leaks and spills. 189 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

187 U.S. Environmental Protection Agency Office of Research and Development (2008) Natura l Attenuation of the Lead Scavengers 1,2 - Dibrom oethane (EDB) and 1,2 - Dichloroethane (1,2 - DCA) at Motor Fuel Release Sites and Im plications for Risk Management, Chapter 2. EPA 600/R - 08/107. Available online at: www. epa.gov/ada . 188 U.S. Environmental Protection Agency, “Drinking Water Contaminants” Available online at: http://www.epa.gov/safe wa ter/contaminants/index.html 189 U.S. Environmental Protection Agency Office of Research and Development (2008) Natural Attenuation of the Lead Scavengers 1,2 - Dibrom oethane (EDB) and 1,2 - Dichloroethane (1,2 - DCA) at Motor Fuel Release Sites and Im plications for Risk Management. p.3. EPA 600/R - 08/107. Available online at: www.epa.gov/ada .91

dibromide was detected in 54 samples, 43 of which had ethylene dibromide concentrations above the MCL . 190 These sites did not include anal ys is of groundwater at airports. While not the focus of this ANPR , ethylene dibromide exposure from inhalation or ingestion pathway s is an ongoing concern for EPA , and reduct ion in the use of leaded gasoline containing ethylene dibromide may reduce exposure and risk to public health and welfare from ethylene dibromide . 

### 3. Non - E xhaust Exposure to Tetraethyl Lead

Tetraeth yl lead is a volatile component of leaded avgas. The l argest source of tetraeth yl 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 c ontaminants by draining a small amount of fuel from each tank sump before flight and after refueling. This fuel is frequentl y 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 b y direct photoly sis, reaction with ozone, and by reaction with hydrox yl compounds. Therefore, depending on ambient conditi ons, alkyl lead may exist in the atmosphere for hours to day s. 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 190 U.S. Environmental Protection Agency Office of Research and Development (2008) Natural Attenuation of the Lead Scavengers 1,2 - Dibrom oethane (EDB) and 1,2 - Dichloroethane (1,2 - DCA) at Motor Fuel Release Sites and Im plications for Risk Management. p.4. EPA 600/R - 08/107. Available online at: www.epa.gov/ada .92

possible derma l 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 pisto n - engine aircraft, the PBT National Action Plan for Alkyl - lead 191 noted that aviation fuel attendants and mechanics are potentiall y 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 lipo philic 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 waterway s 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 Inform ation Av ailable for the NPRM to Evaluate the Potential for

Public Health & We lfar e Im pacts 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

191 U.S. Environmental Protection Agency Persistent, Bioaccumulative, and Toxic Pollutants (PBT) Program (2002) PBT national action plan for alkyl - Pb. Washington, DC. Page 14. Available online at: http://www.epa.gov/pbt/pubs/A lkyl_lead_action_plan_final.pdf93

Administrator to subsequently e xercise her judgment regarding whether aircraft lead emissions from avgas use cause or contribute to air pollution which may reasonabl y 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 an y information submitted to EPA during the comment period for this ANPR . 

### A. The Lead NAAQS and Lead Em issions from Piston - E ngine Aircraft

On Nove mber 12, 2008, when EPA promulgated revisions to the L ead 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 describ e 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 L ead NAAQS may provide additional data on the potential for lead emissions from pist on - engine aircraft to cause or contribute to ambient air concentrations that exceed the 2008 L ead NAAQS. Acknowledging that the existing monitoring network for lead is not sufficient to determine whether man y areas of the country would meet the 2008 L ea d 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 m aximum impact areas where lead emissions are greater than or equal to one ton or more per ye ar. We refer to these monitors as94

source - oriented monitors. EPA Regional Administrators may waive the source - oriented monitoring requirements if the monitoring ag ency can demonstrate that emissions from the source will not contribute to maximum air lead concentrations greater than 50 percent of the revised standard, or 0.075 ug/m 3 . EPA estimated that approximately 135 facilities emit lead at levels over the one to n emission threshold, making them subject to the lead monitoring requirements. Lead monitors are operating at a small number of these sources (described in Section VI.A.2 below). For the remainder, source - oriented monitors are to be operational b y 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 - oriente d monitors. Following promulgation of the 2008 L ead NAAQS and monitoring requirements, the Natural Resources Defense Council, the Missouri Coalition for the Environment Foundation, Phy sicians for Social Responsibility , and the Coalition to End Childhood Le ad Poisoning (Petitioners) petitioned EPA for reconsideration of the lead emission rate at which we required monitoring (the “emission threshold,” currentl y 1.0 tpy). 192 EPA granted the petition to reconsider aspects of the monitoring requirements and pr oposed revisions to lead ambient air monitoring requirements in December 2009 ( 74 FR 69050 ) . Also as part of promulgating the 2008 L ead NAAQS, EPA described the approach for implementing the revised standards and provided an implementation timeline. EPA will use

192 The petition is available at: http://www.epa.gov/air/lead/pdfs/OAR.09.000.7687.pdf95

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 attainm ent, nonattainment, or unclassifiable in October 2009. States update their recommendations to EPA in October 2010 using an y 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 ye ars after desi gnation. Additional information regarding the lead standard implementation is available at www.epa.gov/air/lead/actions.html and in the 2008 L ead NAAQS (73 FR 67030 - 67043). 1. Monitoring Lead at Airports to Evaluate Ambient Concentrations to Which Lead Emissions from Piston -

Engine Aircraft Contribute Among the e stimated 135 source - oriented lead monitoring sites, there are f our airports where we expect lead monitoring to begin in January 2010. T hese airports are the Van Nuy s A irport in Van Nu ys , CA; the Phoenix Deer Valley A irport in Phoenix, AZ; the Centennial A irport in Englewood, CO; and the Day tona Beach International A irport in Day tona Beach, FL . In each of these areas, we will, as data bec omes available, evaluate the impact of lead emissio ns from piston - engine aircraft o n air quality .96

2. Evaluating the Contribution of Lead Emissions from Piston - Engine Aircraft to Areas Approaching or Exceeding the Lead NAAQS In this section we discuss av ailable 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 L ead NAAQS. This evaluation may include the following: 1) areas currentl y out of attainment or designated as maintenance with the 1978 L ead NAAQS; 2) areas with current lead monitors that are out of attainment with the 2008 L ead NAAQS; and 3) locations that will have new lead monitors t o meet the 2008 L ead 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 qualit y. The EPA is retain ing the 1978 L ead NAAQS until one y ear after designations for the 2008 L ead 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 demonstrati ons for the new standards. Onl y two areas, East Helena, MT (including Lewis and Clark counties), and part of Jefferson County in Herculaneum, MO, are designated nonattainment with the 1978 L ead NAAQS. The industrial facility causing nonattainment with th e L ead NAAQS in the East Helena area closed in 2001. Eleven areas are designated as maintenance areas, onl y three of which currentl y have lead monitors. These three locations (Iron C ounty , MO, Dakota C ounty MN, and Collin C ounty , TX) have lead monitors w ith design value97

concentrations exceeding the 2008 L ead NAAQS. The design value is the highest “rolling” three month average over a three - ye ar period that is relevant for comparison to the level of the 2008 L ead NAAQS. Implementation of the 2008 L ead N AAQS is underway , and we have not y et designated areas under it. When EPA promulgated the 2008 L ead NAAQS, EPA provided a list of 18 counties with design values exceeding the 2008 lead standard of 0.15 μg/m 3 . Using more recent data from EPA’s Air Quality Sy stem, there are 14 sites at which design values exceed the 2008 L ead NAAQS (Table 6). Over 4.6 million people live in the counties where design values are greater than the 2008 L ead NAAQS. After EPA designates areas that currently have sufficient lead monitoring data , no later than October 15, 2010, w e 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 6. Counties with Maximum Rolling Quarterly Average Lead Concentrations Exceeding the 2008 Lead NAAQS. County , State EPA Region County Population (2000 Census) Design Val ue, 2006 -

2008 (  g/m 3 ) Jefferson, MO 7 198,099 2.89 Iron, MO 7 10,697 2.46 Delaware, IN 5 118,769 2.1698

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 3 73,638 0.36 Madison, IL 5 258,941 0.28 Lo gan, OH 5 46,005 0.27 Sullivan, TN 4 153,048 0.26 Beaver, PA 3 181,412 0.20 Cuy ahoga, 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, b y 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 runway s 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 fr om piston - engine aircraft and other sources of ambient lead. The EPA will be conducting modeling anal ys es to evaluate the contribution of these lead emissions to nonattainment areas and areas that may be approaching nonattainment concentrations. Lead emi tted by piston - engine aircraft fl yi ng through nonattainment areas may99

also contribute to lead measured in the nonattainment area. These emissions would be potentially

challenging to quantify , although a series of scoping analy ses could be conducted. We s eek comment on characterizing the contribution of lead emissions from piston - engine aircraft fl yi ng through areas that are not attaining the 2008 L ead NAAQS and the potential contribution of piston - engine lead emissions that may be transported into lead no nattainment areas. As noted above, approximately 13 5 new lead monitors will begin collecting ambient lead samples starting in January 2010 in order to satisfy

the source - oriented monitoring requirements of the 2008 L ead 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 L ead NAAQS of 0.15  g/m 3

. 

### B. Additional Information EPA is Collecting to Evaluate Am bient Lead Concentrations Attributable to Em ission s from Piston - Engine Aircraft In 2008 EPA initiated a study to provide information regarding the local - scale gradient in lead concentrations on - and near airport facilities with piston - engine powered aircraft a ctivity . 193 This study

is focused mainly

on developing an approach for modeling lead emissions from piston - engine aircraft using the Meteorological Society (AMS)/EPA Regulatory

Model (AERMOD), and evaluating it using air quality measurements. For purposes of local - scale

193 Mem orandum to the docket HQ - EPA - OAR - 2007 - 0294 titled “ Work Plan for Air Quality Modeling and Monitoring of Lead.” Emissions from Piston - Engine Pow ered Aircraft .” Docket number EPA - HQ - OAR - 2007 - 0294.100

dispersion modeling, AERMOD is EPA’s preferred model. 194 Th e approach being developed includes apportion ing lead emitted during landing and take - off to different altitudes in order to characterize emi ssions during these modes of operation in a realistic manner. In addition, this modeling study

includes anal ys is of the spatial and temporal emissions from piston - engine aircraft during the other modes of aircraft operation (e.g., taxi, run - up check, take - off, landing). The modeling results will include an evaluation of the relative contributions of all known source s of lead to the local ambient air, including piston - engine aircraft, local traffic, resuspended road dust, and industrial sources with in 20 km of the airport selected for our case stu dy . As part of this work underway , we are collecting air, soil and house dust samples for lead anal ys is in order to conduct a model - to - monitor evaluation, and to evaluate the potential for lead emissions from piston - engine aircraft to create a gradient i n 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 stud y conducted b y the SCAQMD discussed in Section IV .B of this ANPR in 2005 - 2007. Inaddition, there are no major point sources of lead i n close proximity to the airport, simplifying the model development and interpretation of monitoring results . The study

at the Santa Monica A irport will be complete in 2010. 195 This model ing approach will be used to evaluate potential for exceed ance of the Lead

194 The EPA provides modeling guidance for AERMOD at www.epa.gov/ttn /scram/guidanceindex.htm and www.epa.gov/scram001/dispersion_prefree.htm#aermod . A post - processor for AERMOD that reads model output and calculates rolling 3 - mo nth averages for th e 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 . 195 When this study is finalized, the report will be posted at www.epa.gov/otaq/aviation.htm.101

NAAQS on airport property and surrounding areas, as well as providing an approach to characterize the contribution of lead emissions from piston - engine aircraft to areas with ambient lead concentrations currently exceeding the 2008 Lead NAAQS. This modeling approach will also allow us to quantify

the changes in ambient lead concentrations following the implementation of different piston - engine control strategie s . 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 n ear or attending school near general aviation activity . We request comment on all information EPA is collecting to evaluate ambient lead concentrations attributable to emissions from piston - engine aircraft and risk posed by emissions of lead from piston - e ngine aircraft.



### C . Considerations Regarding Engine Em ission 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 c onsidering 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 aviati on gasoline. One option to consider, for example, could be an emissions standard (established under 40 CFR 87) that would require all newl y - manufactured general aviation piston engines to be able to operate with appropriate reliability

and durability

on unleaded aviation gasoline by some future date. Such a102

standard might require that new engines used in aircraft would have to receive an FAA ty pe certificate that reflects achievement of these requirements under FAA regulations set forth at 14 CFR parts 33 /34. Be yond 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 sign ificant logistical challenge, and in some cases a technical chall enge 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 ai rframes. Given the potentially large number of affected aircraft and the potential complexities involved, a program affecting in - use aircraft engines would need careful consideration b y both EPA and FAA and the two agencies would need to work together in considering an y 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 b y engine manufacturers (OEMs), independent shops, and in the field by certified power plant mechanics are performed to fully mee t the intent of a possible program without compromising the safet y of those aircraft and engines. EPA also asks for comment on potential problems with this approach including suggested modifications,103

improvements, or other approaches. Finall y, EPA request s comment on how market incentives might be developed to encourage modification to run on unleaded aviation gasoline as part of a regulatory

requirement.



### VII. Statut ory 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 Or der 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 appl y 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 Actio ns 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 any104

subsequent rulemaking. Dated_____________

________________________ ___________ Lisa P. Jackson, Ad ministrator Advance Notice of Proposed Rulemaking on Lead Emissions from Piston - Engine Aircraft Using Leaded Aviation Gasoline page 104 of 104