Integrated Review Plan for the 

National Ambient Air Quality 

Standards for Lead

External Review Draft

 
[This page intentionally left blank.]

 
EPA-452/D-11-001 

March 2011 

Integrated Review Plan for the 

National Ambient Air Quality 

Standards for Lead 

 

External Review Draft 

U. S. Environmental Protection Agency 

National Center for Environmental Assessment 

Office of Research and Development 

and 

Office of Air Quality Planning and Standards 

Office of Air and Radiation 

Research Triangle Park, North Carolina 27711 
March 2011 Draft – Do Not Quote or Cite

DISCLAIMER

This draft integrated review plan for the national ambient air quality standards for lead 

serves as a public information document and as a management tool for the U.S. Environmental 

Protection Agency's National Center for Environmental Assessment and the Office of Air 

Quality Planning and Standards in conducting the review of the national ambient air quality 

standards for lead. The approach described in this draft plan may be modified for presentation in 

the final plan to reflect consultation with the Clean Air Scientific Advisory Committee and 

public comments. Subsequent modifications to the plan may result from information developed 

during this review, and in consideration of advice and comments received from the Clean Air 

Scientific Advisory Committee and the public during the course of the review. Mention of trade 

names or commercial products does not constitute endorsement or recommendation for use. 
March 2011 i Draft – Do Not Quote or Cite

TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................... 1-1 

1.1 LEGISLATIVE REQUIREMENTS ....................................................................... 1-1 

1.2 OVERVIEW OF THE NAAQS REVIEW PROCESS ........................................... 1-3 

1.3 REVIEW OF AIR QUALITY CRITERIA AND STANDARDS FOR LEAD ..... 1-8 

 1.4 SCOPE OF THE CURRENT REVIEW................................................1-10 

2. REVIEW SCHEDULE ........................................................................................................ 2-1

3. KEY POLICY-RELEVANT ISSUES ................................................................................. 3-1 

3.1 ISSUES RELATED TO THE PRIMARY NAAQS ............................................... 3-1 

3.2 ISSUES RELATED TO THE SECONDARY NAAQS ......................................... 3-2 

4. SCIENCE ASSESSMENT .................................................................................................. 4-1 

4.1 SCOPE AND ORGANIZATION ........................................................................... 4-1 

4.2 ASSESSMENT APPROACH ................................................................................. 4-2 

 4.2.1 Introduction .............................................................................................. 4-2 

 4.2.2 Literature Search and Identification of Relevant Studies ........................ 4-4 

 4.2.3 Criteria for Study Selection ..................................................................... 4-4 

 4.2.4 Quality Assurance .................................................................................... 4-6 

4.3 CONTENT AND ORGANIZATION OF THE ISA .............................................. 4-7 

4.4 CAUSAL DETERMINATIONS .......................................................................... 4-15 

4.5 SUPPLEMENTARY MATERIALS .................................................................... 4-15 

4.6 SCIENTIFIC AND PUBLIC REVIEW ................................................................ 4-16 

5. QUANTITATIVE RISK AND EXPOSURE ASSESSMENT ............................................ 5-1 

5.1 OVERVIEW OF ASSESSMENTS IN LAST REVIEW ........................................ 5-2 

 5.1.1 Human Exposure and Health Risk Assessments ..................................... 5-2 

 5.1.2 Ecological Risk Assessment .................................................................... 5-5 

5.2 CONSIDERATION OF QUANTITATIVE ASSESSMENTS FOR 

 THIS REVIEW ....................................................................................................... 5-7 

 5.2.1 Human Exposure and Health Risk Assessment ....................................... 5-7 

 5.2.2 Ecological Risk Assessment .................................................................. 5-11 

5.3 SCIENTIFIC AND PUBLIC REVIEW .................................................................. 5-12 

6. AMBIENT AIR MONITORING ......................................................................................... 6-1 

6.1 Consideration of Sampling and Analysis Methods .................................................... 6-1 

6.2 Consideration of Air Monitoring Network Requirements ......................................... 6-2 

7. POLICY ASSESSMENT AND RULEMAKING ............................................................... 7-1 

7.1 Policy Assessment .................................................................................................... 7-1 

7.2 Rulemaking ................................................................................................................ 7-3 

8. REFERENCES .................................................................................................................... 8-1 

APPENDIX A. INTEGRATED SCIENCE ASSESSMENT FOR LEAD – OUTLINE ............. A-1
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1 1 INTRODUCTION 

2 The U.S. Environmental Protection Agency (EPA) is conducting a review of the air 

3 quality criteria and the national ambient air quality standards (NAAQS) for lead (Pb). The 

4 purpose of this document is to communicate the plan for this review. This review will provide 

5 an integrative assessment of relevant scientific information for Pb and will focus on the basic 

elements of the NAAQS for Pb: the indicator,1 averaging time, form,2 6 and level. These 

7 elements, which together serve to define each ambient air quality standard, must be considered 

8 collectively in evaluating the protection to public health and public welfare afforded by the 

9 standards. 

10 This draft Integrated Review Plan (IRP) contains the plans for this review of the air 

11 quality criteria for Pb-related effects on public health and public welfare and of the current Pb 

12 NAAQS. This draft IRP is being released for the purpose of consulting with the Clean Air 

13 Scientific Advisory Committee (CASAC) and obtaining public comment on the Agency’s plans. 

14 The final IRP will be informed by comments received from the CASAC and the public. 

15 This document is organized into eight chapters. Chapter 1 presents background 

16 information on the review process, the legislative requirements for the review of the NAAQS, 

17 and past reviews of the NAAQS for Pb. Chapter 2 presents the current review schedule. 

18 Chapter 3 presents a set of policy-relevant questions that will serve to focus this review on the 

19 critical scientific and policy issues. Chapters 4 through 7 discuss the planned scope and 

20 organization of key assessment documents, the planned approaches for preparing the documents, 

21 specific monitoring considerations and plans for scientific and public review of the documents. 

22 Complete reference citations are provided in chapter 8. 

23 1.1 LEGISLATIVE REQUIREMENTS 

24 Two sections of the Clean Air Act (CAA) govern the establishment and revision of the 

25 NAAQS. Section 108 (42 U.S.C. section 7408) directs the Administrator to identify and list 

26 certain air pollutants and then to issue air quality criteria for those pollutants. The Administrator 

27 is to list those air pollutants that in her “judgment, cause or contribute to air pollution which may 

28 reasonably be anticipated to endanger public health or welfare;” “the presence of which in the 

29 ambient air results from numerous or diverse mobile or stationary sources;” and “for which . . . 

 1

 The “indicator” of a standard defines the chemical species or mixture that is to be measured in 

determining whether an area attains the standard. 

2

 The “form” of a standard defines the air quality statistic that is to be compared to the level of the standard 

in determining whether an area attains the standard. For example, the form of the annual PM2.5 NAAQS is the 3-

year average of the weighted annual mean PM2.5 concentrations, while the form of the current 3-month Pb NAAQS 

is a 3-month average concentration not to be exceeded during a 3-year period. 
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1 [the Administrator] plans to issue air quality criteria...” Air quality criteria are intended to 

2 “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all 

3 identifiable effects on public health or welfare which may be expected from the presence of [a] 

4 pollutant in the ambient air . . .” 42 U.S.C. § 7408(b). Section 109 (42 U.S.C. 7409) directs the 

5 Administrator to propose and promulgate “primary” and “secondary” NAAQS for pollutants for 

6 which air quality criteria are issued. Section 109(b)(1) defines a primary standard as one “the 

7 attainment and maintenance of which in the judgment of the Administrator, based on such 

criteria and allowing an adequate margin of safety, are requisite to protect the public health.”3 8 A 

9 secondary standard, as defined in section 109(b)(2), must “specify a level of air quality the 

10 attainment and maintenance of which, in the judgment of the Administrator, based on such 

11 criteria, is requisite to protect the public welfare from any known or anticipated adverse effects 

associated with the presence of [the] pollutant in the ambient air.”4 12 

13 The requirement that primary standards provide an adequate margin of safety was 

14 intended to address uncertainties associated with inconclusive scientific and technical 

15 information available at the time of standard setting. It was also intended to provide a reasonable 

16 degree of protection against hazards that research has not yet identified. See Lead Industries 

17 Association v. EPA, 647 F.2d 1130, 1154 (D.C. Cir 1980), cert. denied, 449 U.S. 1042 (1980); 

18 American Petroleum Institute v. Costle, 665 F.2d 1176, 1186 (D.C. Cir. 1981), cert. denied, 455 

19 U.S. 1034 (1982); American Farm Bureau Federation v. EPA, 559 F. 3d 512, 533 (D.C. Cir. 

20 2009); Association of Battery Recyclers v. EPA, 604 F. 3d 613, 617-18 (D.C. Cir. 2010). Both 

21 kinds of uncertainties are components of the risk associated with pollution at levels below those 

22 at which human health effects can be said to occur with reasonable scientific certainty. Thus, in 

23 selecting primary standards that provide an adequate margin of safety, the Administrator is 

24 seeking not only to prevent pollution levels that have been demonstrated to be harmful but also 

25 to prevent lower pollutant levels that may pose an unacceptable risk of harm, even if the risk is 

26 not precisely identified as to nature or degree. The CAA does not require the Administrator to 

27 establish a primary NAAQS at a zero-risk level or at background concentration levels, see Lead

28 Industries v. EPA, 647 F.2d at 1156 n.51, but rather at a level that reduces risk sufficiently so as 

29 to protect public health with an adequate margin of safety. 

 3

 The legislative history of section 109 indicates that a primary standard is to be set at “the maximum 

permissible ambient air level . . . which will protect the health of any [sensitive] group of the population,” and that 

for this purpose “reference should be made to a representative sample of persons comprising the sensitive group 

rather than to a single person in such a group” S. Rep. No. 91-1196, 91st Cong., 2d Sess. 10 (1970). 

4

 Welfare effects as defined in section 302(h) (42 U.S.C. § 7602(h)) include, but are not limited to, “effects 

on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility and climate, damage to 

and deterioration of property, and hazards to transportation, as well as effects on economic values and on personal 

comfort and well-being.” 
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1 In addressing the requirement for an adequate margin of safety, the EPA considers such 

2 factors as the nature and severity of the health effects involved, the size of sensitive population(s) 

3 at risk, and the kind and degree of the uncertainties that must be addressed. The selection of any 

4 particular approach to providing an adequate margin of safety is a policy choice left specifically 

5 to the Administrator’s judgment. See Lead Industries Association v. EPA, 647 F.2d at 1161-62; 

6 Whitman v. American Trucking Associations, 531 U.S. 457, 495 (2001). 

7 In setting primary and secondary standards that are “requisite” to protect public health 

8 and welfare, respectively, as provided in section 109(b), EPA’s task is to establish standards that 

9 are neither more nor less stringent than necessary for these purposes. In so doing, EPA may not 

10 consider the costs of implementing the standards. See generally, Whitman v. American Trucking 

11 Associations, 531 U.S. 457, 465-472, 475-76 (2001). Likewise, “[a]ttainability and 

12 technological feasibility are not relevant considerations in the promulgation of national ambient 

13 air quality standards.” American Petroleum Institute v. Costle, 665 F. 2d at 1185. 

14 Section 109(d)(1) requires that “not later than December 31, 1980, and at 5-year 

15 intervals thereafter, the Administrator shall complete a thorough review of the criteria 

16 published under section 108 and the national ambient air quality standards . . . and shall make 

17 such revisions in such criteria and standards and promulgate such new standards as may be 

18 appropriate . . . .” Section 109(d)(2) requires that an independent scientific review committee 

19 “shall complete a review of the criteria . . . and the national primary and secondary ambient air 

20 quality standards . . . and shall recommend to the Administrator any new . . . standards and 

21 revisions of existing criteria and standards as may be appropriate . . . .” Since the early 1980's, 

22 this independent review function has been performed by the Clean Air Scientific Advisory 

Committee (CASAC).5 23 

24 1.2 OVERVIEW OF THE NAAQS REVIEW PROCESS 

25 Since completion of the last Pb NAAQS review, the Agency has made a number of 

26 changes to the process for reviewing the NAAQS. The current process, which is being applied to 

27 this review of the NAAQS for Pb, has four major phases: (1) planning, (2) science assessment, 

28 (3) risk/exposure assessment, and (4) policy assessment and rulemaking. An overview of the 

process is illustrated in Figure 1-1 below and each of these phases is described in this section.6 29 

30 The Agency maintains a web site on which key documents developed for NAAQS reviews are 

31 made available (http://www.epa.gov/ttn/naaqs/). 

 5 Lists of CASAC members and of members of the CASAC Pb Review Panel are available at: 

http://yosemite.epa.gov/sab/sabproduct.nsf/WebCASAC/CommitteesandMembership?OpenDocument. 

6

 Information on changes to the NAAQS review process since the last Pb NAAQS review is available at: 

http://www.epa.gov/ttn/naaqs/review.html. 
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1 The planning phase of the NAAQS review process begins with a science policy 

2 workshop, which is intended to identify issues and questions to frame the review. Drawing from 

3 the workshop discussions, a draft IRP is prepared jointly by EPA’s National Center for 

4 Environmental Assessment (NCEA), within the Office of Research and Development (ORD), 

5 and EPA’s Office of Air Quality Planning and Standards (OAQPS), within the Office of Air and 

6 Radiation (OAR). The draft IRP is made available for consultation with CASAC and for public 

7 comment. The final IRP is prepared in consideration of CASAC and public comments. This 

8 document presents the current plan and specifies the schedule for the entire review, the process 

9 for conducting the review, and the key policy-relevant science issues that will guide the review. 

10 The second phase of the review, science assessment, involves the preparation of an 

11 Integrated Science Assessment (ISA) and supplementary materials. The ISA, prepared by 

12 NCEA, provides a concise review, synthesis, and evaluation of the most policy-relevant science, 

13 including key science judgments that are important to the design and scope of exposure and risk 

14 assessments, as well as other aspects of the NAAQS review. The ISA and its supplementary 

15 materials provide a comprehensive assessment of the current scientific literature pertaining to 

16 known and anticipated effects on public health and welfare associated with the presence of the 

17 pollutant in the ambient air, emphasizing information that has become available since the last air 

18 quality criteria review in order to reflect the current state of knowledge. As such, the ISA forms 

19 the scientific foundation for each NAAQS review and is intended to provide information useful 

20 in forming judgments about air quality indicator(s), form(s), averaging time(s) and level(s) for 

21 the NAAQS. Hence, the ISA and its associated materials function in the current NAAQS review 

22 process as the Air Quality Criteria Document (AQCD) did in the previous review process. The 

23 current review process generally includes production of a first and second draft ISA, both of 

24 which undergo CASAC and public review prior to completion of the final ISA. Section 4 below 

25 provides a more detailed description of the planned scope, organization and assessment approach 

26 for the ISA and its supporting materials. 

27 In the third phase, the risk/exposure assessment phase, OAQPS staff considers 

28 information and conclusions presented in the ISA, with regard to support provided for the 

29 development of quantitative assessments of the risks and/or exposures for health and/or welfare 

30 effects. As an initial step, staff prepares one or more planning documents that consider the 

31 extent to which newly available scientific evidence and tools/methodologies warrant the conduct 

32 of quantitative risk and exposure assessments. To the extent warranted, this document(s) 

33 outlines a general plan, including scope and methods, for conducting the assessments. This 

34 planning document(s) is generally prepared in conjunction with the first draft ISA and presented 

35 for consultation with CASAC and for public comment. As discussed in chapter 5 below, this 

36 planning document for the current Pb NAAQS review will focus on consideration of the newly 
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1 available data, methods and tools in light of areas of uncertainty in the assessments conducted for 

2 the last review and of the potential for new or updated assessments to provide notably different 

3 exposure and risk estimates with lower associated uncertainty. Comments received on the 

4 planning document(s) are considered in the Agency’s decision as to whether to conduct such 

5 assessments. When an assessment is performed, one or more drafts of each risk and exposure 

6 assessment document (REA) undergoes CASAC and public review, with the initial draft REA(s) 

7 generally being reviewed in conjunction with review of the second draft ISA, prior to completion 

8 of final REA(s). The REA provides concise presentations of methods, key results, observations, 

9 and related uncertainties. Chapter 5 discusses possible approaches being considered with regard 

10 to human health- and welfare-related assessments for this review. 

11 The review process ends with a policy assessment and rulemaking phase. Under the 

12 current NAAQS review process (Jackson, 2009), the EPA Administrator has reinstated the use of 

13 a Policy Assessment (PA). The PA, like the previous OAQPS Staff Paper, is a document that 

14 provides a transparent OAQPS staff analysis and staff conclusions regarding the adequacy of the 

15 current standards and potential alternatives that are appropriate to consider prior to the issuance 

16 of proposed and final rules. The PA integrates and interprets the information from the ISA and 

17 REA(s) to frame policy options for consideration by the Administrator. Such an evaluation of 

18 policy implications is intended to help ‘‘bridge the gap’’ between the Agency’s scientific 

19 assessments, presented in the ISA and REA(s), and the judgments required of the EPA 

20 Administrator in determining whether it is appropriate to retain or revise the NAAQS. In so 

21 doing, the PA is also intended to facilitate CASAC’s advice to the Agency and recommendations 

22 to the Administrator on the adequacy of the existing standards or revisions that may be 

23 appropriate to consider, as provided for in the CAA. In evaluating the adequacy of the current 

24 standards and, as appropriate, a range of alternative standards, the PA considers the available 

25 scientific evidence and, as available, quantitative risk-based analyses, together with related 

26 limitations and uncertainties. The PA focuses on the information that is most pertinent to 

27 evaluating the basic elements of national ambient air quality standards: indicator, averaging 

28 time, form, and level. One or more drafts of a PA are released for CASAC review and public 

29 comment prior to completion of the final PA. 

30 Following issuance of the final PA and consideration of conclusions presented therein, 

31 the Agency develops and publishes a notice of proposed rulemaking that communicates the 

32 Administrator’s proposed decisions regarding the standards review. A draft notice undergoes 

interagency review involving other federal agencies prior to publication.7 33 Materials upon which 

 7

 Where implementation of the proposed decision would have an annual effect on the economy of $100 

million or more, e.g., by necessitating the implementation of emissions controls, EPA develops and releases a draft 

regulatory impact analysis (RIA) concurrent with the notice of proposed rulemaking. This activity is conducted 
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1 this decision is based, including the documents described above, are made available to the public 

2 in the regulatory docket for the review. A public comment period, during which public hearings 

3 are generally held, follows publication of the notice of proposed rulemaking. Taking into 

account comments received on the proposed rule,8 4 the Agency develops a final rule which 

5 undergoes interagency review prior to publication to complete the rulemaking process. Chapter 

6 7 discusses the development of the PA and the rulemaking steps for this review. 

 under Executive Order 12866. The RIA is conducted completely independent of and, by statute, is not considered in 

decisions regarding the review of the NAAQS. 

8

When issuing the final rulemaking, the Agency responds to all significant comments on the proposed rule. 
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Figure 1-1. Overview of the NAAQS Review Process.

Workshop 

on sciencepolicy 

issues

de

s

Interagency 

review

CASAC consultation

and public comment

Peer-reviewed 

scientific studies

Agency decisionmaking and draft 

final notice

Public hearings 

and comments 

on proposal

Integrated Review 

Plan: timeline and 

key policy-relevant 

issues and scientific 

questions 

Integrated Science Assessment: 

concise evaluation and synthesis of most 

policy-relevant studies

CASAC review and public 

comment

Agency decisionmaking and draft 

proposal notice

Interagency 

review

Policy A

staff 

policy o

on inte

interp

informa

an

Risk/Exposure Assessment:

concise quantitative assessment 

focused on key results, 

observations, and uncertainties

EPA 

proposed 

decision on 

standards
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1 1.3 REVIEW OF AIR QUALITY CRITERIA AND STANDARDS FOR 

2 LEAD 

3 On October 5, 1978, EPA initially promulgated primary and secondary NAAQS for Pb 

4 under section 109 of the Act (43 FR 46246). Both primary and secondary standards were set at a 

level of 1.5 micrograms per cubic meter (μg/m3 5 ), measured as Pb in total suspended particles 

6 (Pb-TSP), not to be exceeded by the maximum arithmetic mean concentration averaged over a 

7 calendar quarter. These standards were based on the 1977 Air Quality Criteria for Lead (USEPA, 

8 1977). 

9 The first review of the Pb standards was initiated in the mid-1980s. The scientific 

10 assessment for that review is described in the 1986 Air Quality Criteria for Lead (USEPA, 

11 1986a), the associated Addendum (USEPA, 1986b) and the 1990 Supplement (USEPA, 1990a). 

12 As part of the review, the Agency designed and performed human exposure and health risk 

13 analyses (USEPA, 1989), the results of which were presented in a 1990 Staff Paper (USEPA, 

14 1990b). Based on the scientific assessment and the human exposure and health risk analyses, the 

15 1990 Staff Paper presented recommendations for consideration by the Administrator (USEPA, 

16 1990b). After consideration of the documents developed during the review and the significantly 

17 changed circumstances since Pb was listed in 1976, the Agency did not propose any revisions to 

18 the 1978 Pb NAAQS. In a parallel effort, the Agency developed the broad, multi-program, 

19 multimedia, integrated U.S. Strategy for Reducing Lead Exposure (USEPA, 1991). As part of 

20 implementing this strategy, the Agency focused efforts primarily on regulatory and remedial 

21 clean-up actions aimed at reducing Pb exposures from a variety of nonair sources judged to pose 

22 more extensive public health risks to U.S. populations, as well as on actions to reduce Pb 

23 emissions to air, such as bringing more areas into compliance with the existing Pb NAAQS 

24 (USEPA, 1991). 

25 The most recent review of the Pb air quality criteria and standards was initiated in 

26 November, 2004 (69 FR 64926) and the Agency’s plans for preparation of the Air Quality 

27 Criteria Document and conduct of the NAAQS review were contained in two documents: Project 

28 Work Plan for Revised Air Quality Criteria for Lead (USEPA, 2005); and Plan for Review of the 

National Ambient Air Quality Standards for Lead (USEPA 2006a).9 29 The schedule for 

30 completion of this review was governed by a judicial order in Missouri Coalition for the 

31 Environment v. EPA (No. 4:04CV00660 ERW, Sept. 14, 2005; and amended on April 29, 2008 

32 and July 1, 2008,), which specified a schedule for the review of duration substantially shorter 

33 than five years. 

 9

 In the current review, these two documents have been combined into an integrated plan (this document). 
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1 The scientific assessment for the review is described in the 2006 Air Quality Criteria for 

2 Lead (USEPA, 2006b), multiple drafts of which received review by CASAC and the public. 

3 EPA also conducted human exposure and health risk assessments and a pilot ecological risk 

4 assessment for the review, after consultation with CASAC and receiving public comment on a 

5 draft analysis plan (USEPA, 2006c). Drafts of these quantitative assessments were reviewed by 

6 CASAC and the public. The pilot ecological risk assessment was released in December 2006 

7 (ICF, 2006) and the final health risk assessment report was released in November 2007 (USEPA, 

8 2007a). The policy assessment based on both of these assessments, air quality analyses and key 

9 evidence from the AQCD was presented in the Staff Paper (USEPA, 2007b), a draft of which 

10 also received CASAC and public review. The final Staff Paper presented OAQPS staff’s 

11 evaluation of the public health and welfare policy implications of the key studies and scientific 

12 information contained in the Criteria Document and presented and interpreted results from the 

13 quantitative risk/exposure analyses conducted for this review. Based on this evaluation, the Staff 

14 Paper presented OAQPS staff recommendations that the Administrator give consideration to 

15 substantially revising the primary and secondary standards to a range of levels at or below 0.2 

micrograms per cubic meter (μg/m3 16 ). 

17 Immediately subsequent to completion of the Staff Paper, EPA issued an advance notice 

18 of proposed rulemaking (ANPR) that was signed by the Administrator on December 5, 2007 (72 

FR 71488).10 19 CASAC provided advice and recommendations to the Administrator with regard to 

20 the Pb NAAQS based on its review of the ANPR and the previously released final Staff Paper 

21 and Risk Assessment Report. The proposed decision on revisions to the Pb NAAQS was signed 

22 on May 1, 2008 and published in the Federal Register on May 20, 2008 (73 FR 29184). In 

23 addition to public comments on the proposal received during the public comment period, both 

24 written and oral at two public hearings, the CASAC Pb Panel provided advice and 

25 recommendations to the Administrator based on its review of the proposal notice. The final 

26 decision on revisions to the Pb NAAQS was signed on October 15, 2008 and published in the 

27 Federal Register on November 12, 2008 (73 FR 66964). 

28 The November 2008 notice described EPA’s revisions to the primary and secondary 

29 NAAQS for Pb. In consideration of the much-expanded health effects evidence on 

30 neurocognitive effects of Pb in children, EPA substantially revised the primary standard from a 

level of 1.5 micrograms per cubic meter (μg/m3

) to a level of 0.15 μg/m3 31 . EPA’s decision on the 

32 level for the standard was based on the weight of the scientific evidence and guided by an 

33 evidence-based framework that integrates evidence for relationships between Pb in air and Pb in 

 10 The ANPR was one of the features of the revised NAAQS review process that EPA instituted in 2006. In 

2009 (Jackson, 2009), this component of the process was replaced by reinstatement of the OAQPS policy 

assessment (previously termed the Staff Paper). 
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1 children’s blood and Pb in children’s blood and IQ loss. The level of 0.15 μg/m3 was estimated 

2 to protect against air Pb-related IQ loss in the most highly exposed children, those exposed at the 

3 level of the standard. Results of the quantitative risk assessment were judged supportive of the 

4 evidence-based framework estimates. The averaging time was revised to a rolling 3-month 

5 period with a maximum (not-to-be-exceeded) form, evaluated over a 3-year period. As 

6 compared to the previous averaging time of calendar quarter, this revision was considered to be 

7 more scientifically appropriate and more health protective. The rolling average gives equal 

8 weight to all three-month periods, and the new calculation method gives equal weight to each 

9 month within each three-month period. Further, the rolling average yields 12 three-month 

10 averages each year to be compared to the NAAQS versus four averages in each year for the 

11 block calendar quarters pertaining to the previous standard. The indicator of Pb in total 

12 suspended particles (Pb-TSP) was retained, reflecting the evidence that Pb particles of all sizes 

13 pose health risks. The secondary standard was revised to be identical in all respects to the 

revised primary standards.11 14 

15 Revisions to the NAAQS were accompanied by revisions to the data handling 

16 procedures, the treatment of exceptional events and the ambient air monitoring and reporting 

requirements, as well as emissions inventory reporting requirements.12 17 As described in chapter 6 

18 below, one aspect of the new data handling requirements is the allowance for the use of Pb-PM10

19 monitoring for Pb NAAQS attainment purposes in certain limited circumstances at non-source20 oriented sites. Subsequent to the 2008 rulemaking, additional revisions were made to the 

21 monitoring network requirements as described in chapter 6 below. 

22 1.4 SCOPE OF THE CURRENT REVIEW 

23 For the current review of the Pb standards, relevant scientific information will be 

24 assessed with regard to human exposures and health effects associated with exposure to ambient 

25 air-related Pb. The review will also assess any relevant scientific information associated with 

26 known or anticipated public welfare effects that may be identified. Unlike the other pollutants 

27 for which NAAQS are established, Pb is a multimedia pollutant. Lead emitted into ambient air 

28 may subsequently occur in multiple environmental media, contributing to multiple pathways of 

29 exposure for humans and ecological receptors. This multimedia distribution of and 

 11 The current NAAQS for Pb are specified at 40 CFR 50.16. 

12 The current federal regulatory measurement methods for Pb are specified in 40 CFR 50, Appendix G and 

40 CFR part 53. Consideration of ambient air measurements with regard to judging attainment of the standards is 

specified in 40 CFR 50, Appendix R. The Pb monitoring network requirements are specified in 40 CFR 58, 

Appendix D, section 4.5. Guidance on the approach for implementation of the new standards was described in the 

Federal Register notices for the proposed and final rules (73 FR 29184; 73 FR 66964). 
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1 multipathway exposure to air-related Pb has a key role in the Agency’s consideration of the Pb 

2 NAAQS. Some associated considerations include the following (73 FR 66971): 

3  Lead emitted into the air is predominantly in particulate form, which can be transported 

4 long or short distances depending on particle size. 

5  Once deposited out of the air, Pb can subsequently be resuspended in the ambient air and, 

6 because of the persistence of Pb, Pb emissions contribute to media concentrations for 

7 some years into the future. 

8  Exposure to Pb emitted into the ambient air (air-related Pb) can occur directly by 

9 inhalation, or indirectly by ingestion of Pb-contaminated food, water or other materials 

including dust and soil.13 10 These exposures occur as Pb emitted into the ambient air is 

11 distributed to other environmental media and can contribute to human exposures via 

12 indoor and outdoor dusts, outdoor soil, food and drinking water, as well as inhalation of 

13 air. 

14  Air-related exposure pathways are affected by changes to air quality, including changes 

15 in concentrations of Pb in air and changes in atmospheric deposition of Pb. Further, 

16 because of its persistence in the environment, Pb deposited from the air may contribute to 

17 human and ecological exposures for years into the future. Thus, the roles of both air 

18 concentration and air deposition in human exposure pathways, and the persistence of Pb 

19 once deposited, influence the dynamics of the response of the various Pb exposure 

20 pathways to changes in air quality. 

21 

22 The current review of the Pb standards builds on the substantial body of work done 

23 during the course of the last review. In addition to a comprehensive Air Quality Criteria 

24 Document, EPA staff designed and conducted a complex multimedia, multipathway health risk 

25 assessment involving case studies represented different ambient air Pb exposure circumstances, 

26 and an assessment of the available information on ecological impacts of Pb, including the 

27 consideration of potentially vulnerable ecosystems. These different types of information were 

28 evaluated in a Staff Paper and provided the basis for the notice of proposed rulemaking and for 

29 the substantial revisions made to the Pb NAAQS. In light of the extensive and detailed 

30 quantitative analysis of health risks in the last review, as well as the substantial revisions made to 

31 the standard and the period of time elapsed since then in which new data may have been 

32 collected, the information newly available in the current review will be considered with regard to 

33 the extent to which an update or expansion to the last quantitative risk assessment is warranted. 

 13 In general, air-related pathways include those pathways where Pb passes through ambient air on its path 

from a source to human exposure or to an ecological receptor. 
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1 2 REVIEW SCHEDULE 

2 In April 2010, EPA’s National Center for Environmental Assessment in Research 

3 Triangle Park, NC (NCEA-RTP) announced the initiation of the current periodic review of the 

4 air quality criteria for Pb and the Pb NAAQS and issued a call for information in the Federal 

5 Register (75 FR 20843). Also, as an initial step in the NAAQS review process described in 

6 Section 1.1 above, EPA invited a wide range of external and internal EPA experts, representing a 

7 variety of areas of expertise (e.g., epidemiology, human and animal toxicology, statistics, 

8 risk/exposure analysis, atmospheric science) to participate in a workshop to discuss the policy9 relevant science to inform development of this plan. This workshop was held May 10-11, 2010 

10 in Research Triangle Park, NC (75 FR 20843). This workshop provided an opportunity for the 

11 participants to broadly discuss the key policy-relevant issues around which EPA would structure 

12 the Pb NAAQS review and to discuss the most meaningful new science that would be available 

13 to inform our understanding of these issues. Based in part on the workshop discussions, EPA has 

14 developed this draft integrated review plan outlining the schedule, the process, and the key 

15 policy-relevant science issues that will guide the evaluation of the air quality criteria for Pb and 

16 the review of the primary and secondary Pb NAAQS. 

17 Table 2-1 outlines the schedule under which the Agency is currently conducting this 

18 review. The scopes of the review and of the key documents to be prepared during the review are 

19 discussed throughout the rest of this document. 
March 2011 2-2 Draft – Do Not Quote or Cite

Table 2-1. Proposed Schedule for Review of Ambient Air Quality Criteria and NAAQS for Pb.

Stage of Review Major Milestone Draft Target Dates 

Integrated Plan Literature Search Ongoing 

Federal Register Call for Information April 2010 

Workshop on science/policy issues May 2010 

Draft Integrated Review Plan (IRP) March 2011 

CASAC consultation on IRP May 5, 2011 

FinalIRP June 2011 

Science Assessment First draft of ISA End April 2011 

CASAC public meeting for review of first draft ISA July 20-21, 2011 

Second draft of ISA December 2011 

CASAC/public review of second draft ISA February/March 2012 

Final ISA June 2012 

Risk/Exposure 

Assessment 

Planning document June 2011 

CASAC public meeting for consultation on planning 

document 

July 21, 2011 

If warranted, 

First draft risk and/or exposure assessments 

(REA) 

January 2012 

CASAC/public review of first draft REA February/March 2012 

Second draft REA July 2012 

CASAC/public review of second draft REA September/October 2012 

Final REA January 2013 

Policy Assessment/ 

Rulemaking 

First draft of policy assessment (PA) 

CASAC/public review of first draft PA 

Second draft of PA 

CASAC/public review of second draft PA 

Final PA 

Notice of proposed rulemaking 

August 2012 

September 2012 

February 2013 

March 2013 

June 2013 

January 2014 

Notice of final rulemaking November 2014 

 1 

 2 
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1 3 KEY POLICY-RELEVANT ISSUES 

2 For our purposes in considering the overarching questions regarding the adequacy of the 

3 current Pb NAAQS, we have identified key policy-relevant issues to be addressed in this review. 

4 They are presented below as a series of policy-relevant questions that will frame our approach to 

5 considering whether the current primary and secondary NAAQS for Pb should be retained or 

6 revised. The ISA, REAs (if conducted), and PA developed in this new review will provide the 

7 basis for addressing these questions and will inform the Agency’s judgment as to the adequacy 

8 of the current primary and secondary standards for Pb, and decisions as to whether to retain or 

9 revise these standards. 

10 3.1 ISSUES RELATED TO THE PRIMARY NAAQS 

11 The first step in reviewing the adequacy of the current primary NAAQS is to consider 

12 whether the available body of scientific evidence, assessed in the ISA, and used as a basis for 

13 any analyses that might be presented in an REA, supports or calls into question the scientific 

14 conclusions reached in the last review regarding health effects related to exposure to ambient air15 related Pb. This evaluation of the available scientific evidence will focus on key policy-relevant 

16 issues by addressing a series of questions including the following: 

17  To what extent has new information altered the scientific support for the occurrence of 

18 health effects associated with exposure to levels of Pb found in the ambient air? 

19  To what extent has new information altered conclusions from previous reviews regarding 

20 the plausibility of adverse health effects caused by Pb exposure? 

21  To what extent does the evidence suggest that alternate dose indicators other than blood 

22 Pb levels should be evaluated to characterize the biological effect? 

23  At what levels of Pb exposure do health effects of concern occur? 

24  To what extent has new information altered scientific conclusions regarding the 

25 relationships between Pb in ambient air and Pb in children’s blood and between Pb in 

26 children’s blood and reduced IQ? 

27  Has new information altered our understanding of human subpopulations that are 

28 particularly sensitive to Pb exposures? Is there new or emerging evidence on health 

29 effects beyond neurocognitive endpoints in children that suggest additional sensitive 

30 subpopulations should be given increased focus in this review? 

31  To what extent is key scientific evidence becoming available to improve our 

32 understanding of the health effects associated with various time periods of Pb exposures, 

33 including not only daily, but also chronic (months to years) exposures? To what extent is 

34 critical research becoming available that could improve our understanding of the 

35 relationship between various health endpoints and different lag periods (e.g., single day, 

36 multi-day distributed lags)? 
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1  To what extent do any risk or exposure analyses developed for the review suggest that 

2 exposures of concern for Pb-related health effects are likely to occur with current ambient 

3 levels of Pb or with levels that just meet the Pb standard? If estimates are developed, are 

4 the estimated risks/exposures of sufficient magnitude such that the health effects might 

5 reasonably be judged to be important from a public health perspective? What are the 

6 important uncertainties associated with any risk/exposure estimates? 

7  To what extent have important uncertainties identified in the last review been reduced 

8 and/or have new uncertainties emerged? 

9  To what extent does newly available information reinforce or call into question any of the 

10 basic elements of the current Pb standard? 

11 If the evidence suggests that revision of the current standards might be appropriate, EPA 

12 will evaluate how the standards might be revised. Specifically, we will evaluate how the 

13 scientific information and assessments inform decisions regarding the basic elements of the Pb 

14 NAAQS: indicator, averaging time, level, and form. These elements will be considered 

15 collectively in evaluating the health protection afforded by the current or any alternative 

16 standards considered. Specific policy-relevant questions that will be addressed include: 

17  To what extent is there any new information that would support consideration of a 

18 different indicator for Pb? 

19  To what extent does the health effects evidence evaluated in the ISA, air quality analyses 

20 and, if available, the REA, provide support for considering different exposure indices or 

21 averaging times? 

22  To what extent do air quality analyses and other information provide support for 

23 consideration of alternative standard forms? 

24  What range of alternative standard levels should be considered based on the scientific 

25 evidence evaluated in the ISA, air quality analyses and, if available, REA? 

26  What are the important uncertainties and limitations in that evidence and assessments and 

27 how might those uncertainties and limitations be taken into consideration in identifying 

28 alternative standards for consideration? 

29 3.2 ISSUES RELATED TO THE SECONDARY NAAQS 

30 As with the review of the primary NAAQS, the first step in reviewing the adequacy of 

31 the current secondary NAAQS is to consider whether the available body of scientific evidence, 

32 assessed in the ISA, and used as a basis for any analyses that might be presented in an REA, 

33 supports or calls into question the scientific conclusions reached in the last review regarding 

34 welfare effects related to exposure to ambient air-related Pb. This evaluation of the available 

35 scientific evidence will focus on key policy-relevant issues by addressing a series of questions 

36 for each category of Pb-related welfare effects identified in the ISA as being associated with the 

37 presence of Pb in the ambient air, while taking into account multimedia, multipathway 

38 exposures: 
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1  To what extent does the available information demonstrate or suggest that Pb-related 

2 effects are occurring at current ambient conditions or at levels that would meet the 

3 current standard? 

4  To what extent does the available information inform judgments as to whether any 

5 observed or anticipated effects are adverse to public welfare? 

6  To what extent is the current secondary standard likely to be effective in achieving 

7 protection against any identified adverse effects? 

8  Are there new empirical data or modeling results that would enhance our understanding 

9 of the movement of lead in ecosystems, or improve our understanding of bioavailability 

10 and mechanisms of exposure? 

11  What new information is available about the nature of lead effects on aquatic 

12 ecosystems? What new evidence is there regarding critical loads for these systems? 

13  Does the newly available evidence alter the scientific support for lead effects on 

14 terrestrial or aquatic ecosystems associated with the levels of Pb found in ambient air? 

15  Does the newly available evidence indicate different exposure levels at which ecological 

16 receptors are expected to experience effects? 

17  What new information, methods or tools are available to inform or facilitate assessment 

18 of the accumulation and movement of air-deposited Pb through terrestrial and aquatic 

19 ecosystems over time? 

20  To what extent does newly available information reinforce or call into question any of the 

21 basic elements of the current Pb standard? 

22 To the extent that the evidence suggests that revision of the current secondary Pb 

23 NAAQS would be appropriate to consider, the staff then identifies ranges of standards (in terms 

24 of exposure indices, averaging times, levels, and forms) that would reflect a range of alternative 

25 policy judgments as to the degree of protection that is requisite to protect public welfare from 

26 known or anticipated adverse effects. In so doing, the staff addresses the following questions 

27 taking into account multimedia, multipathway exposures: 

28  Does the available information provide support for considering different Pb exposure 

29 indices? 

30  Does the available information provide support for considering different averaging times? 

31  What range of levels and forms of alternative standards is supported by the information, 

32 and what are the uncertainties and limitations in that information? 

33  To what extent do specific levels and forms of alternative standards reduce adverse 

34 impacts attributable to Pb, and what are the uncertainties in the estimated reductions? 
March 2011 4-1 Draft – Do Not Quote or Cite

1 4 SCIENCE ASSESSMENT 

2 4.1 SCOPE AND ORGANIZATION 

3 The science assessment for Pb will consist of the ISA as well as supplementary materials 

4 (see Section 4.5) if additional documentation is required to support information contained within 

5 the ISA. The ISA will critically evaluate and integrate the scientific information on the health 

6 and welfare effects associated with exposure to Pb. The ISA is not intended to provide a detailed 

7 literature review; but rather, will draw from the existing body of evidence to synthesize the 

8 current state of knowledge on the most relevant issues pertinent to the review of the NAAQS for 

9 Pb. The ISA provides an updated comprehensive assessment of the current scientific literature 

10 pertaining to known and anticipated effects on public health and welfare associated with the 

11 presence of Pb in the ambient air, thus revising the assessment available at the time of the last 

12 review. 

13 Discussions in the ISA will primarily focus on scientific evaluations that can inform the 

14 key policy questions described in Chapter 3 of this document. Although emphasis is placed on 

15 discussion of health and welfare effects information, other scientific information is also 

16 presented and evaluated in order to provide a better understanding of the sources of Pb to 

17 ambient air, measurement and concentrations of Pb in ambient air, its subsequent fate and 

18 transport in the environment, pathways of human and ecological exposure, and toxicokinetic 

19 characteristics of Pb in the human body, as well as the characterization of population exposures 

20 to Pb. 

21 The ISA will build on the conclusions of the last review of the air quality criteria for Pb, 

22 presented in the 2006 air quality criteria document (AQCD) (U.S. EPA, 2006), and focus on peer 

23 reviewed literature published thereafter and on any new interpretations of previous literature. 

24 The 2006 AQCD (U.S. EPA, 2006) evaluated literature published through December 2005. The 

25 ISA will begin with a discussion of major legal and historical aspects of prior review documents 

26 as well as key milestones and procedures for document preparation. In subsequent chapters, the 

27 results of recent scientific studies will be integrated with previous findings. Important older 

28 studies may be discussed in detail to reinforce key concepts and conclusions and/or if they are 

29 open to reinterpretation in light of newer data. Older studies also may be the primary focus in 

30 some areas of the document where research efforts have subsided, and these older studies remain 

31 the definitive works available in the literature. Emphasis will be placed on studies that examine 

32 effects associated with Pb concentrations relevant to current population and ecosystem 

33 exposures, and particularly those pertaining to Pb concentrations currently found in ambient air. 

34 Other studies may be included if they contain unique data, such as a previously unreported effect 
March 2011 4-2 Draft – Do Not Quote or Cite

1 or mechanism for an observed effect, or examine multiple concentrations to elucidate exposure2 response relationships. 

3 4.2 ASSESSMENT APPROACH 

4 4.2.1 Introduction 

5 The EPA’s National Center for Environmental Assessment in Research Triangle Park 

6 (NCEA-RTP) is responsible for preparing the ISA for Pb. In each NAAQS review, development 

7 of the science assessment begins with a “Call for Information” published in the Federal Register. 

8 This notice announces EPA’s initiation of activities in the preparation of the ISA for the specific 

9 NAAQS review and invites the public to assist through the submission of research studies in the 

10 identified subject areas. This and subsequent key components of the process currently followed 

11 for the development of an ISA (i.e., the standard protocol) are presented in Figure 4.1. How the 

12 ISA fits into the larger NAAQS review process is briefly described in section 1.2, the Overview 

13 of the NAAQS Review Process. Important aspects of the development of the ISA are described 

14 in the sections below, including the approach for searching the literature and identifying relevant 

15 publications and specific policy-relevant questions intended to guide the assessment. These 

16 responsibilities are undertaken by expert authors of the ISA chapters that include EPA staff with 

17 extensive knowledge in their respective fields and extramural scientists solicited by EPA for 

18 their expertise in specific fields. The process for scientific and public review of drafts of the ISA 

19 is described in Section 4.6. 
March 2011 4-3 Draft – Do Not Quote or Cite

1 

2 Figure 4-1. Standard steps in the development of Integrated Science Assessments (ISAs). 

3 
March 2011 4-4 Draft – Do Not Quote or Cite

1 4.2.2 Literature Search and Identification of Relevant Studies 

2 The NCEA-RTP will use a systematic approach to identify relevant studies for inclusion 

3 in the Pb assessment. The EPA has already published a Federal Register notice (75 FR 8934, 

4 February 26, 2010) to announce the initiation of this review and request information from the 

5 public. In addition to the call for information, publications will be identified through an ongoing 

6 literature search process that includes extensive computer database mining on specific topics in a 

7 variety of disciplines. Additional publications will be identified by EPA scientists by reviewing 

8 previous EPA reports and reviewing reference lists from key publications; studies also will be 

9 identified in the course of CASAC and public review. 

10 From the lists of publications broadly compiled from the search methods described above, 

11 EPA will identify relevant studies to be reviewed as part of the assessment. Epidemiologic 

12 studies, animal toxicological studies, and studies of ecological or welfare effects of Pb, including 

13 those related to exposure-response relationships, mode(s) of action (MOA), and susceptible 

14 populations and lifestages will be identified. Additionally, air quality and emissions data, studies 

15 on atmospheric chemistry, environmental fate and transport, as well as issues related to Pb 

16 toxicokinetics and exposure will also be identified. The assessment will include research 

17 published or accepted for publication since the 2006 air quality review and through 

18 approximately one month prior to the release of the second external review draft of the ISA (see 

19 Table 2-1). Studies published after that date may also be assessed if they provide new 

20 information that impacts one or more key scientific issues. Once identified, studies are reviewed 

21 with regard to quality assurance criteria described in section 4.2.3 below before including them 

22 in the assessment document. 

23 The combination of the approaches described here is expected produce the 

24 comprehensive collection of studies to be included in the assessment and from which the most 

25 informative and policy relevant studies will be selected for particular focus. 

26 4.2.3 Criteria for Study Selection 

27 In general, in assessing the scientific quality and relevance of health and environmental 

28 effects studies, the following quality assurance criteria are considered when selecting studies for 

29 inclusion in the ISA. 

30 1. Are the study populations, subjects, or animal models adequately selected and are they 

31 sufficiently well defined to allow for meaningful comparisons between study or exposure 

32 groups? 

33 2. Are the statistical analyses appropriate, properly performed, and properly interpreted? 

34 Are likely covariates adequately controlled or taken into account in the study design and 

35 statistical analysis? 

36 3. Are the air quality data, exposure, or dose metrics of adequate quality? 
March 2011 4-5 Draft – Do Not Quote or Cite

1 4. Are the health or welfare effect measurements meaningful and reliable? 

2 Studies published since the last air quality criteria review will be emphasized in the ISA; 

3 however, evidence from studies described in last assessment that are needed to characterize the 

4 current state of the science as well as new interpretations of older evidence will also will be 

5 included in the assessment. 

6 Among the studies included in the ISA, EPA will give particular focus to those 

7 containing information in the following areas: 

8 1. new studies with adequate data at the low end of the exposure distribution (e.g. <10 

9 μg/dL blood); 

10 2. new studies that provide quantitative effect estimates for populations or lifestages and 

11 concentrations of interest; 

12 3. Pb exposure or effects in susceptible populations and lifestages; 

13 4. issues related to the potential for confounding of study effects/responses by non-Pb 

14 exposure-related factors or variables, and to the modification of Pb-related effects; 

15 5. the timing (e.g., across/within specific lifestages) and duration of exposure associated 

16 with specific responses; 

17 6. concentration-response relationships for specific Pb-related effects; 

18 7. the interpretation of Pb biomarkers in epidemiological studies; and/or air-to-blood Pb or 

19 air-to-bone Pb relationships; 

20 8. studies that evaluate Pb as a component of a complex mixtures of pollutants. 

21 In selecting epidemiologic studies for inclusion in the present assessment, EPA will 

22 consider studies containing information on (1) recent or cumulative exposures relevant to current 

23 population exposure levels of Pb; (2) health endpoints that repeat or extend findings from earlier 

24 assessments as well as those not previously extensively researched; (3) populations and lifestages 

25 that are susceptible to Pb exposures; (4) issues related to potential confounding, and 

26 modification of effects; and/or (5) important methodological issues (e.g., timing and duration of 

27 exposure, concentration-response relationships, interpretation of biomarkers in epidemiological 

28 studies, and air-to-blood/bone relationships) related to Pb exposure effects. In selecting the most 

29 informative and policy relevant epidemiologic studies on which to give particular focus in the Pb 

30 ISA, emphasis will be placed on those most relevant to standard setting in the United States. 

31 Informative studies conducted in other countries will be discussed, as appropriate (e.g. studies 

32 for which the mean blood Pb level in the population studied is comparable to the current mean 

33 blood Pb level in the corresponding U.S. population). 

34 In reviewing new studies in the ISA that have evaluated the response of laboratory 

35 animals to Pb exposure, we will review studies that reveal the effects of Pb exposure within the 
March 2011 4-6 Draft – Do Not Quote or Cite

1 previously identified target biological systems (e.g. neurological, cardiovascular, renal, immune). 

2 Additionally, particular focus will be given to those studies that involve doses or body burdens 

3 that approximate human doses or body burden conditions relevant to current U.S. exposures. 

4 Studies at higher exposure or doses that result in body burdens above what is found in the current 

5 U.S. population will be discussed when the study can provide information relevant to potential 

6 mechanisms of action, information on exposure-response relationships, or otherwise improve our 

7 understanding of susceptible populations and lifestages. 

8 In reviewing informative studies of welfare effects, emphasis will be placed on recent 

9 studies that: (1) evaluate the occurrence of effects associated with Pb exposure at current ambient 

10 levels, with a particular focus on ambient levels resulting from ambient air Pb, and/or (2) 

11 investigate the effects of Pb on ecosystems at any scale. Studies conducted in geographical areas 

12 outside the U.S. will be included in the assessment if they contribute to the general knowledge of 

13 the effects of Pb irrespective of species or locality. As in the selection of health-related scientific 

14 studies, welfare-related studies will be selected that advance our understanding of mechanisms 

15 by which Pb directly affects terrestrial and aquatic biota. These mechanisms, as they pertain to 

16 Pb exposures of short or longer duration, will inform our understanding of indirect effects that Pb 

17 may exert more broadly on ecosystem structure, function and services. Key studies identified for 

18 welfare effects will be integrated into the discussion to inform our interpretation of the ecological 

19 literature and our characterization of uncertainties. 

20 The criteria described here provide generalized benchmarks to guide the inclusion in the 

21 ISA of the highest quality and most policy-relevant studies. Detailed critical analysis of all 

22 studies of the effects of Pb on health and welfare, especially in relation to the above criteria, is 

23 beyond the scope of this document. Since the last scientific review was completed within the 

24 past five years, it is expected that a considerable portion of the current ISA may be devoted to 

25 summarizing previously available evidence that contributed to the basis for the last rulemaking. 

26 4.2.4 Quality Assurance 

27 NCEA participates in the Agency-wide Quality Management System, which requires the 

28 development of a Quality Management Plan (QMP). Implementation of the NCEA QMP 

29 ensures that all data generated or used by NCEA scientists are “of the type and quality needed 

30 and expected for their intended use” and that all information disseminated by NCEA adheres to a 

31 high standard for quality including objectivity, utility and integrity. Quality assurance (QA) 

32 measures detailed in the QMP will be implemented beginning with the start of the current Pb 

33 review, including the development of the Pb ISA. 

34 The NCEA QA staff is responsible for the review and approval of quality-related 

35 documentation. NCEA scientists are responsible for the evaluation of all inputs to the ISA, 
March 2011 4-7 Draft – Do Not Quote or Cite

1 including primary (new) and secondary (existing) data, to ensure their quality is appropriate for 

2 their intended purpose. NCEA follows the Data Quality Objectives, which identify the most 

3 appropriate inputs to the science assessment, and provides QA instruction for researchers citing 

4 secondary information. The approaches utilized to search the literature and criteria for study 

5 selection were detailed in the two preceding subsections. Generally, NCEA scientists rely on 

6 scientific information found in peer-reviewed journal articles, books, and government reports. 

7 Where information is integrated or reduced from multiple sources to create new figures, tables, 

8 or summation, the data generated are considered to be new and subject to rigorous quality 

9 assurance measures to ensure their accuracy. 

10 4.3 CONTENT AND ORGANIZATION OF THE ISA 

11 Generally, the organization of the Pb ISA will be similar to the organization of the 

12 integrative synthesis chapter of the 2006 Pb AQCD (U.S. EPA, 2006) and recent assessments for 

13 other criteria pollutants (e.g. Carbon Monoxide (U.S. EPA, 2010)). 

14 The ISA for Pb will contain information relevant to considering whether it is appropriate 

15 to retain or revise the current ambient air Pb standards. Decisions on the specific content of the 

16 ISA will be guided by the series of policy-relevant questions outlined in Chapter 3 in addition to 

17 a set of policy-relevant questions more specifically related to scientific evidence that may 

18 become newly available in the current review process. These policy-relevant questions for the 

19 ISA are related to two overarching issues. The first issue is the extent to which new scientific 

20 evidence has become available that alters or substantiates the scientific evidence presented and 

21 evaluated in the last Pb NAAQS review. The second issue is whether uncertainties from the last 

22 air quality criteria review have been addressed and/or whether new uncertainties have emerged. 

23 The specific questions related to the review of the scientific literature for Pb that stem from these 

24 two issues were derived from the last Pb NAAQS review, as well as from discussions of the 

25 scientific evidence that occurred at the May 2010 Science Policy Workshop for the current 

26 review (75 FR 20843). These specific questions, which will guide decisions on content for the 

27 Pb ISA, are listed below by topic area.

Source to Exposure 

28 Ambient Air Sources and Multimedia Environmental Distribution: The ISA will present and 

29 evaluate current information related to sources of Pb to ambient air, ambient air concentrations 

30 and size distributions of Pb measured as a component of particulate matter. Note that gas phase 

31 Pb data are not available in the EPA Air Quality System (AQS) for assessment of Pb in the 

32 vicinity of gaseous Pb emissions where leaded gasoline is still used (e.g. airports, certain 

33 automotive racing facilities). The available information will be presented concerning sources of 
March 2011 4-8 Draft – Do Not Quote or Cite

1 freshly and previously emitted Pb including resuspension of previously deposited Pb. The ISA 

2 will evaluate relevant information concerning the transport and fate of Pb released into the air 

3 directly and via other environmental media (e.g., soil, surface and ground water). The ISA will 

4 discuss Pb fluxes into and distribution among different media. Where available, the ISA will 

5 draw from information in the literature about the bioavailability of Pb in different media to 

6 organisms based on the organisms’ biochemical characteristics. 

7 The assessment will also describe the distribution of air monitors in the federal regulatory 

8 Pb monitoring network and consider new studies that address the precision and accuracy of the 

9 Federal Reference and Federal Equivalent Methods (FRM and FEM, respectively) for Pb. The 

10 assessment will also consider information on the design of other air monitoring networks in 

11 which Pb measurements are taken, such as the Chemical Speciation Network (CSN), Interagency 

12 Monitoring of Protected Visual Environments (IMPROVE), and National Air Toxics Trends 

13 Stations (NATTS). Additionally, new information regarding Pb techniques for the analysis of 

14 particulate matter samples will be discussed. In reviewing the currently available evidence, we 

15 will consider the following specific questions: 

16 1. What new evidence is available on primary and secondary sources of Pb? 

17 2. What new information is available regarding the fate and transport of Pb in the 

18 environment? What new data exists to characterize atmospheric deposition and 

19 resuspension of Pb. 

20 3. What new information is available regarding monitoring Pb in the environment and 

21 analyzing Pb species within particulate matter samples? 

22 4. What data are available to characterize airborne Pb concentrations, spatial and temporal 

23 variability of concentrations, size distributions of Pb in the environment as a function of 

24 different sources of Pb, and covariation of Pb concentrations with other ambient air 

25 pollutant concentrations? 

26 Exposure: The ISA will compile and evaluate evidence developed since the last assessment that 

27 helps characterize the variability and uncertainty in the relationships between ambient Pb 

28 concentrations and exposures to Pb of humans and ecosystems relevant to the primary and 

29 secondary standards. A conceptual model of Pb exposure through various pathways, including 

30 exposure to airborne Pb and Pb deposited onto soil, as well as that which contributes to indoor 

31 dust and dietary exposures, will be discussed. EPA will also assess studies relevant to the 

32 assessment of errors in measurement or estimation of human exposure to Pb as well as the 

33 possibly differential exposures of some populations. The following questions will be considered 

34 during review of the available evidence: 

35 1. What new evidence is available on exposure to Pb through air-related pathways? Can air36 related pathways be disentangled from water- and soil-related pathways using available 

37 data? 
March 2011 4-9 Draft – Do Not Quote or Cite

1 2. What new evidence is available regarding observational studies of Pb exposure? How do 

2 these studies inform the assessment of exposure to air-related pathways? 

3 3. What new studies address susceptibility to elevated Pb exposure? 

4 Toxicokinetics, Biological Markers, and Models of Lead Burden in Humans 

The ISA will evaluate the literature relating to the toxicokinetics14 5 of Pb, including the 

6 application of available models to evaluate the storage of Pb in the body, biological markers of 

7 Pb that indicate exposure and body burden, and the quantification of Pb exposure or dose from 

8 air-related exposure pathways (e.g. air-to-blood ratios). During the last review, uncertainties 

9 were identified including the blood Pb-air Pb relationship in slope-factor models, and the 

10 interpretation of blood Pb and bone Pb concentrations reported in epidemiologic studies. The 

11 ISA will consider these key uncertainties and evaluate the extent to which new scientific 

12 evidence may inform our ability to characterize and/or reduce those uncertainties during the 

13 current review. In reviewing the currently available evidence, we will consider the following 

14 specific questions: 

15 1. What new evidence is available on biological and other factors that could affect the 

16 distribution and accumulation of Pb into blood and bone (e.g., age, nutrition, gender, 

17 race)? 

18 2. What new evidence is available on population and lifestage variability in Pb biokinetics? 

19 3. What new developments are available in biokinetic models that can be used for 

20 estimating impacts of multimedia human lead exposures on internal body burden, 

21 generally indicated by blood or bone Pb levels? Is there new evidence to inform our 

22 understanding of the response of blood Pb to changes in ambient air Pb and associated 

23 exposure pathways? 

24 4. What new evidence is available to characterize biomarkers of concurrent and cumulative 

25 exposures? What are the related uncertainties with interpreting biomarker data for 

26 exposure assessment? 

27 5. How and to what extent does previous or concurrent Pb exposure, including duration 

28 (e.g., acute, subchronic, chronic) and pattern (e.g., continuous low, extreme peak) impact 

29 blood Pb and bone Pb? 

30 6. What new evidence is available on the relationship between air Pb and blood Pb levels 

31 and uncertainties in that relationship? What new knowledge exists regarding the 

32 characterization of changes in this relationship when accounting for the multiple 

33 pathways of Pb exposure and body burden associated with Pb exposure? What does the 

34 current evidence indicate regarding variation in the relationship with variation in blood 

35 Pb levels or air Pb levels? 

 14 The phrase toxicokinetics refers generally to the quantitative aspects and timing of absorption, 

distribution, biotransformation and excretion of xenobiotic chemicals in the body. 
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1 7. To what extent does new scientific evidence increase our understanding of the 

2 contributions of Pb from different sources and exposure pathways to blood Pb levels or to 

3 other indicators of Pb body burden (e.g., contributions from various air-related pathways, 

4 including diet and indoor dust pathways)? 

Human Health Effects 

5 The ISA will evaluate the scientific literature related to neurological, cardiovascular, 

6 renal, immune, hematological and other health effects associated with exposures to Pb. Building 

7 upon the last review, EPA will continue to review the available epidemiologic and toxicological 

8 evidence related to these health effects and, to the extent data are available, additional endpoints 

9 (e.g., mortality, developmental, carcinogenic/mutagenic, and cellular outcomes). The results of 

10 new studies will be integrated with the previous findings and with any new interpretations of 

11 previous findings. The ISA will also integrate previous information on susceptible populations 

12 and lifestages (e.g., children, lactating women, and older adults) or factors affecting 

13 susceptibility (e.g., genetic polymorphisms and health status) with any new evidence on 

14 susceptibility factors, lifestages or populations. 

15 For a given type of health outcome, the ISA will fully integrate findings across the 

16 different disciplines to evaluate the strength, robustness and consistency of evidence, which 

17 contribute to EPA’s assessment of causal relationships. Integration will also entail using the 

18 toxicological findings to assess biological plausibility for the epidemiologic findings, including 

19 the coherence of epidemiologic observations with known mechanisms of toxicity. Efforts will be 

20 directed at identifying the lower blood Pb levels at which adverse effects are observed and at 

21 describing concentration-response relationships with a focus on Pb exposures at the lower end of 

22 the distribution. Concentration-response relationships also will be evaluated for comparability 

23 across the studies. Another area of focus includes assessment of the durations of exposure and 

24 specific developmental periods of exposure that are most strongly associated with particular 

25 health effects. The ISA will also assess the evidence for uncertainties related to these 

26 associations and evaluate information on the public health implications related to ambient Pb 

27 exposure. Grouped by topic area, some of the specific scientific questions that EPA will seek to 

28 address in the ISA are as follows: 

29 Health Endpoints: The ISA will evaluate health effects evidence for a multitude of outcomes 

30 assessed in epidemiologic and toxicological studies guided by the following questions: 

31 1. How do results of recent epidemiologic studies and current or new interpretations of 

32 previous findings expand our understanding of the relationship between body burdens 

33 of Pb and neurological effects in children and adults, including deficits in IQ, 

34 behavior, learning, and motor skills, as well as risk of neurodegenerative diseases? 

35 What new evidence is available on the potential clinical relevance of these effects? 
March 2011 4-11 Draft – Do Not Quote or Cite

1 Do recent studies expand the current understanding of concentration-response 

2 relationships pertinent to the range of Pb exposures currently experienced by the U.S. 

3 population? 

4 2. How do different indicators of Pb body burdens (e.g., Pb in blood or bone) compare 

5 in terms of their associations with adverse health outcomes? What do these findings 

6 contribute to the understanding of how effects may differ for more recent and 

7 cumulative lifetime exposure? 

8 3. What new epidemiological evidence is available on health outcomes associated with 

9 measures of Pb exposure in the elderly (e.g., total mortality and cardiovascular 

10 mortality)? What does such evidence indicate regarding the potential for different 

11 impacts of early-life, current, and cumulative lifetime Pb exposures? 

12 4. Within the epidemiologic literature, is there consistency between associations 

13 observed in children and adults and between related health outcomes (e.g., 

14 cardiovascular and renal)? 

15 5. Does new evidence from the literature on effects observed in adult animals in 

16 response to experimental exposures to Pb during development inform the 

17 understanding of populations and life stages that are susceptible to Pb exposure (e.g., 

18 children, elderly, obese)? Within the sensitive in utero period of development, is there 

19 evidence of Pb causing epigenetic changes or evidence of Pb effects differing 

20 between the sexes or genetic variants? 

21 6. For what Pb-induced health effects, is there sufficient evidence in multiple species to 

22 support a quantitative comparison of exposures that induce the effects? 

23 7. To what extent does exposure to Pb contribute to health effects in organ systems other 

24 than the neurological, cardiovascular, and renal systems (e.g., hepatic, 

25 gastrointestinal, skeletal)? Is there epidemiological evidence that Pb exposure is 

26 associated with new biological markers of effect (e.g. cortisol, brain imaging 

27 endpoints, glomerular filtration) that combined with mechanistic evidence may 

28 support conclusions regarding biological plausibility? 

29 8. What new evidence has become available to help discern how the effects of Pb 

30 exposure on a health outcome are modified when it occurs within mixtures that 

31 include other toxic metals, ambient pollutants, or other environmental exposures 

32 versus Pb alone (e.g., additive, synergistic, or antagonistic effects)? 

33 Uncertainties: The ISA will evaluate uncertainty in the scientific data, particularly in relation to 

34 observed epidemiologic findings and their consistency with toxicological studies in terms of 

35 observed effects and biological pathways. In this vein, the following questions will be 

36 considered: 

37 1. To what extent are the health effects observed in epidemiological studies attributable 

38 to exposure to Pb rather than co-exposures to other toxic metals or environmental 

39 contaminants? 

40 2. In epidemiologic studies, what are the uncertainties in Pb effect estimates due to 

41 potential confounding factors (e.g., demographic and lifestyle attributes, 
March 2011 4-12 Draft – Do Not Quote or Cite

1 socioeconomic status [SES], genetic susceptibility factors, occupational exposure, 

2 and access to medical care)? 

3 3. Based on the new body of evidence, what uncertainties remain regarding the nature 

4 and shape of concentration-response relationships (e.g., threshold, linear, nonlinear)? 

5 What evidence is newly available on the uncertainties related to other aspects of 

6 statistical model specification and how can it be used to assess the influence of these 

7 uncertainties on the results of epidemiologic studies? What evidence is available 

8 from toxicological studies of dose-response relationships? 

9 4. What uncertainties surround the evidence for long-term effects such as those that 

10 shorten life duration and/or affect the development or progression of disease? 

11 Biological Mechanism(s) or Modes of Action: In evaluating the current information from 

12 studies that investigate mechanisms for the health outcomes that have been associated with 

13 exposure to Pb, EPA will address the following questions in the ISA: 

14 1. To what extent is evidence now available regarding mechanisms for neurological 

15 effects associated with “lower” (< 10 μg/dL or < 5 μg/dL) blood Pb levels (e.g., 

16 oxidative stress)? What toxicological evidence is available on mechanisms and dose17 response relationships for other health outcomes (e.g., cardiovascular, renal, or 

18 immunological effects) or dose metrics, and is there coherence between this and 

19 epidemiologic findings for these endpoints? 

20 2. To what extent is key evidence now available regarding mechanisms of action and 

21 concentration-response relationships at various ages and developmental stages, 

22 including critical windows of exposure that result in different effects and/or effects at 

23 lower exposures? Are new animal models available to better characterize 

24 mechanisms of action at various lifestages? 

25 3. What mechanistic evidence is available on common modes of action that would help 

26 our understanding of health effects of exposure to Pb when it occurs within mixtures 

27 versus alone (e.g., evidence for additive, synergistic, or antagonistic effects)? 

28 Susceptible Populations and Lifestages: The ISA will examine the evidence for different health 

29 effects or outcomes to identify specific population groups that may have a greater likelihood of 

30 experiencing health effects related to Pb exposure. In identifying these groups, the ISA will 

31 consider a variety of defining factors including, but not limited to lifestage (e.g., childhood), 

32 lifestyle (e.g., smoking status, nutrition), genetic or developmental factors, race, sex, preexisting 

33 disease, access to health care, and factors affecting exposure to Pb such as neighborhood 

34 characteristics. In the ISA, the evaluation of susceptibility factors will consider the following 

35 issues: 

36 1. To what extent is key new evidence available that could inform the understanding of 

37 populations that are particularly susceptible to Pb exposures? What is known about 

38 genetic traits, pre-existing conditions (obesity), or other factors that affect susceptibility 

39 (sex)? To what extent is the strength of epidemiologic or toxicological evidence driven 

40 by effects observed in populations with increased susceptibility? 
March 2011 4-13 Draft – Do Not Quote or Cite

1 a. Is there evidence from new animal models of susceptibility factors that improves 

2 our characterization of susceptible populations and is there coherence between 

3 findings for these models and epidemiologic findings? 

4 2. To what extent is key evidence now available to inform our understanding of 

5 developmental lifestages that are particularly susceptible to Pb exposures? What is 

6 known about critical windows of exposure for Pb with regard to their impact on 

7 concentration-response relationships and/or effects elicited? 

8 a. To what extent is susceptibility to the effects of early life Pb exposure associated 

9 with the development and or persistence/progression of Pb effects in adults? Are 

10 there new animal models that follow these windows of susceptibility? 

11 b. Are new animal models available that may help us to characterize the critical 

12 windows of exposure to Pb and, is there coherence between findings from these 

13 models and epidemiologic findings? Do any of these models show differential 

14 responses by sex of the animal? 

15 3. What do the currently available studies indicate regarding the relationship between 

16 exposures to Pb and health effects in those with preexisting diseases (e.g., renal diseases) 

17 compared to healthy individuals? What medical conditions are identified as increasing 

18 susceptibility to Pb effects? What is the nature and time-course of the development of 

19 effects in previously healthy persons and in persons with pre-existing disease (e.g., 

20 cardiovascular disease)? What are the pathways and mechanisms through which Pb may 

21 be acting for these groups? 

22 Public Health Implications: The ISA will present concepts that integrate evidence on Pb-related 

23 health effects and consequent public health significance to assist in the assessment of the public 

24 health implications of exposure to Pb in ambient air. Development of these concepts may 

25 include consideration of estimates of the sizes of identified susceptible populations (e.g., adults 

26 with cardiovascular disease, children) and discussion of the public health significance of the 

27 magnitudes of change in health outcomes concluded to result from air-related Pb exposures. 

28 Ecological and Other Welfare Effects 

29 The ISA will evaluate the current literature related to effects of Pb exposures in aquatic 

30 and terrestrial ecosystems at all scales, as available. Evidence related to any other welfare 

31 effects (e.g. visibility, climate, materials) will be considered, if available. Publications will be 

32 evaluated for causal relationships between Pb at ambient levels and ecological effects. Studies at 

33 higher than ambient Pb exposures will be evaluated to the extent they can inform the 

34 interpretation of the effects of exposures that are currently widespread in the environment. In the 

35 last review, EPA recognized the persistence of Pb in the environment, and concluded that the 

36 combination of Pb accumulated from past deposition, and much smaller ongoing deposition 

37 continue to cause ecological effects in terrestrial and aquatic ecosystems (U.S. EPA, 2006). If 

38 available, new studies pertaining to the recycling of Pb in aquatic and terrestrial ecosystems, and 
March 2011 4-14 Draft – Do Not Quote or Cite

1 to the role of previously sequestered Pb in current ecosystem processes, including its 

2 contribution to total loading, will be discussed. This discussion will include evaluation of the 

3 effect of Pb on ecosystem productivity and of the potential effects of Pb on ecosystem services. 

4 Sources of Pb that are not relevant to consideration of air-related Pb (e.g. Pb shot) were not 

5 considered. Some scientific questions that EPA will seek to address in the ISA follow, grouped 

6 by topic area. 

7 Terrestrial Ecosystem Effects: 

8 1. What new information is available about the nature of the effects of Pb on terrestrial 

9 ecosystems, especially Pb that is relevant to air-related pathways? Is there new 

10 evidence of effects at current ecosystem loads? Is there new evidence that, in 

11 combination with the previously existing evidence, supports the development of 

12 critical loads for terrestrial ecosystems? 

13 2. Is there new information available for establishing specific exposure levels at which 

14 terrestrial ecological receptors are expected to experience effects? 

15 3. Are there new empirical data or modeling results that would improve our 

16 understanding of the movement of Pb in or through terrestrial systems, or would 

17 improve our understanding of Pb bioavailability and pathways of exposure for 

18 terrestrial organisms? 

19 4. Is there new evidence that contributes to a better understanding of the nature and 

20 magnitude of the potential effects of Pb on terrestrial ecosystem services? 

21 Aquatic Ecosystem Effects: 

22 1. What new information is available about the nature of the effects of Pb on aquatic 

23 ecosystems, especially Pb that is relevant to air-related pathways? Is there new 

24 evidence of effects at current ecosystem loads? Is there new evidence that, in 

25 combination with the previously existing evidence, supports the definition of critical 

26 loads for aquatic ecosystems? 

27 2. Is there new information available for establishing specific exposure levels at which 

28 aquatic ecological receptors are expected to experience effects? 

29 3. Are there new empirical data or modeling results that would improve our 

30 understanding of the movement of Pb in or through aquatic systems or would 

31 improve our understanding of Pb bioavailability and pathways of exposure for aquatic 

32 organisms? 

33 4. Is there new evidence that contributes to a better understanding of the nature and 

34 magnitude of the potential effects of Pb on aquatic ecosystem services? 

35 
March 2011 4-15 Draft – Do Not Quote or Cite

1 4.4 CAUSAL DETERMINATIONS 

2 In evaluating and integrating the different types of evidence from recent studies with that 

3 available during the previous reviews, the ISA will draw conclusions regarding the strength of 

4 the evidence in describing causal relationships between relevant blood Pb, bone Pb or other 

5 exposure metrics and health effects and relevant Pb concentrations and environmental effects. 

6 Since the last Pb NAAQS review, EPA has developed a framework that is intended to provide a 

consistent and transparent basis for drawing such conclusions.15 7 Briefly, the framework includes 

8 the following considerations for drawing conclusions of causality for specific endpoints: 

9 consistency of findings for an endpoint across studies in which it was examined, coherence of the 

10 results related to a specific endpoint among different study types or disciplines, the coherence of 

11 results with characterized mechanisms of action (biological plausibility), and evidence of a 

12 concentration- or dose-response relationship for an endpoint. In the ISA, in considering the 

13 strength of the evidence with regard to demonstrating that exposure to ambient air-related Pb, in 

14 particular, causes specific health effects, EPA will give particular attention to studies that 

15 examine Pb exposures relevant to those currently occurring in the U.S. population or ecosystems. 

16 4.5 SUPPLEMENTARY MATERIALS 

17 Previous science assessments conducted to support NAAQS reviews included 

18 supplementary materials, which were designed to provide detailed supporting information and 

19 more comprehensive coverage of the research areas summarized in the ISA. NCEA intends to 

20 change the form, while maintaining the relevant content, of the materials that were formerly 

21 contained within the Annexes to the ISA. 

22 As discussed previously, studies included in the text of the ISA will be those deemed 

23 informative to the NAAQS review process (e.g. policy-relevant) and of adequate quality. The 

24 ISA text, tables and figures will highlight and summarize key study details that are needed to 

25 understand and interpret the results of a study. This information, which was described in the text 

26 as well as reiterated in the annex tables of previous documents, includes the air quality system 

27 (AQS) data; studies of fate and transport in air, water, and soil; human exposure and dosimetry 

28 studies; blood Pb, bone Pb or other exposure metrics corresponding to adverse health effects and 

29 dose and duration of exposure in toxicological studies; and, effect estimates, study location and 

30 time period, population, exposure metric and time window, as well as the characteristics of the 

31 exposure/dose distribution for epidemiologic studies. In addition, supplementary materials will 

32 be provided in the form of output from the Health and Environmental Research Online (HERO) 

33 database. A key function of the HERO output will be to document the base of evidence 

 15 Use of this framework in the recent science assessment for particulate matter is described in chapter 1 of 

that ISA (EPA, 2009a). 
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1 containing publications evaluated for the Pb review, including any publications considered but 

2 not included in the ISA. This information will be presented as links to lists of references in the 

3 HERO database, which include bibliographic information and abstracts. In addition, certain 

4 study characteristics of epidemiologic studies, including location, ages investigated, outcomes, 

5 and health endpoints, will be summarized in tables developed from HERO extracted study data. 

6 4.6 SCIENTIFIC AND PUBLIC REVIEW 

7 Drafts of the ISA will be reviewed by the CASAC Pb Review Panel and made available 

8 for public comment, as indicated in Figure 4-1 above. The CASAC Pb Review Panel will review 

9 the first draft ISA and discuss their comments in a public meeting announced in the Federal 

10 Register. Based on CASAC’s past practice, EPA anticipates that key CASAC advice and 

11 recommendations for revision of the first draft ISA will be summarized by the CASAC Review 

12 Panel in a letter to the EPA Administrator. In revising the first draft ISA, EPA will take into 

13 account any such recommendations. EPA will also consider comments received from CASAC 

14 or from the public at the meeting itself and any written public comments. Additionally, EPA has 

established a public docket for development of the ISA.16 15 EPA will prepare a second draft ISA 

16 for CASAC review and public comment. The CASAC Pb Review Panel will review the second 

17 draft ISA and discuss their comments in a public meeting announced in the Federal Register. 

18 Again, based on CASAC’s past practice, EPA anticipates that key CASAC advice and 

19 recommendations for revision of the second draft ISA will be summarized by the CASAC Pb 

20 Review Panel in a letter to the EPA Administrator. In finalizing the ISA, EPA will take into 

21 account any such recommendations. EPA will also consider comments received from CASAC or 

22 from the public at the meeting itself and any written public comments. After appropriate 

23 revision, the final document will be made publicly available on an EPA website and in hard 

24 copy. A notice announcing the availability of the final ISA will be published in the Federal 

25 Register. 

 26 

 16 The ISA docket for the current Pb review is identified as EPA-HQ-ORD-2011-0051. The draft and final 

ISAs and CASAC letters will be placed into this docket by EPA and the public may submit materials to it for EPA 

consideration in development of the ISA. This docket and the rulemaking docket described in chapter 7 below are 

publicly accessible at www.regulations.gov. 
March 2011 5-1 Draft – Do Not Quote or Cite

1 5 QUANTITATIVE RISK AND EXPOSURE 

2 ASSESSMENTS 

3 Quantitative risk and exposure assessments are generally designed to estimate human 

4 exposure and health risk, as well as environmental exposures and risks, when appropriate. 

5 Development of the risk/exposure assessments (REAs) draws upon the information presented in 

6 the ISA and its supplemental materials. This includes information on atmospheric chemistry, air 

7 quality, human and environmental exposures, including biokinetic information, and health and 

8 welfare effects of concern. In particular, the availability of concentration-response and dose9 response data from the health and welfare effects literature influences the types of exposure 

10 assessment and risk characterization that are performed. The health and welfare assessments 

11 focus on exposures and dose metrics that are consistent with effects of concern, with available 

12 measurement and modeled data, where appropriate, used to generate estimates of exposure. 

13 Characterization of risks may include conducting air quality analyses to support quantitative 

14 exposure and risk assessments in specific locations to the extent warranted by new information, 

15 taking into consideration available resources. The results of such assessments are generally put 

16 into a broader public health and public welfare perspective, for example, with a particular 

17 emphasis on exposures and health risks in susceptible populations, such as children. 

18 This phase generally begins with the preparation of a planning document. This document 

19 considers the extent to which newly available scientific evidence and tools/methodologies 

20 provide support for conducting quantitative risk and exposure assessments. To the extent 

21 warranted, the scope and methods for components of exposure/risk assessments are described. 

22 This document is the subject of a consultation with the CASAC Panel and is made available to 

23 the public for review and comment. If warranted, one or more drafts of an REA are then 

24 prepared and released for CASAC review and public comment prior to completion of a final 

25 REA subsequent to completion of the final ISA. 

26 The information newly available in this review is considered in light of the 

27 comprehensive, complex and resource-intensive quantitative assessments of human exposure and 

28 health risks performed for the last review. This information is considered with regard to the 

29 extent to which it indicates the potential for development of an REA from which substantially 

30 different conclusions might be drawn with regard to the health risks associated with air-related 

31 Pb under conditions associated with the current standard. The REA planning document will 

32 describe this consideration of the available scientific evidence, tools and methodologies by EPA 

33 staff in light of areas of uncertainty in the REA prepared for the last review and of the potential 

34 for a new REA to provide notably different exposure and risk estimates, with lower associated 
March 2011 5-2 Draft – Do Not Quote or Cite

1 uncertainty. The timeline for collection of ambient air Pb data under the recently revised 

2 monitoring requirements is also recognized as a consideration for this document. Consultation 

3 with the CASAC Pb Panel and comments from the public on this draft IRP, as well as the 

4 availability of resources, will also inform development of the REA planning document. 

5 5.1 OVERVIEW OF ASSESSMENTS IN LAST REVIEW 

6 In the last review, EPA designed and developed a full-scale human exposure and health 

7 risk assessment as well as a screening-level ecological risk assessment. These assessments are 

8 summarized below. 

9 5.1.1 Human Exposure and Health Risk Assessments 

10 In the last review, EPA developed and applied models to estimate human exposures to 

11 air-related Pb and associated health risk. Estimates were developed for various air quality 

12 scenarios and alternative standards to provide additional information and insights that could help 

13 to put judgments about risk associated with exposure to air-related Pb in a broader public health 

14 context and inform decisions on the standards. The exposure and risk analyses to estimate blood 

15 Pb and associated IQ loss in children exposed to air-related Pb were conducted in the context of 

16 five case studies that generally represent two types of population exposures: (1) more highly air17 pathway exposed children (as described below) residing in small neighborhoods or localized 

18 residential areas with air concentrations somewhat near the standard being evaluated, and (2) 

19 location-specific urban populations with a broader range of air-related exposures. The case 

20 studies representing the more highly air-pathway exposed children included a general urban case 

21 study and a primary Pb smelter case study. The three location-specific urban case studies 

22 focused on specific residential areas within three U.S. cities to provide representations of urban 

23 populations with a broader range of air-related exposures due to spatial gradients in both ambient 

24 air Pb levels and population density. The air quality scenarios assessed included (a) the current 

25 NAAQS (for all five case studies) ; (b) current conditions for the location-specific and general 

26 urban case studies (which are below the current NAAQS); and (c) a range of alternate standard 

27 levels (for all case studies). 

28 Exposure and associated blood Pb levels were simulated using the Integrated Exposure 

29 and Uptake Biokinetic (IEUBK) model, as more fully described and presented in the Risk 

30 Assessment Report (USEPA, 2007a). The assessment incorporated a number of innovative 

31 design elements intended to support a probabilistic characterization of risk with consideration for 

32 the multi-pathway nature of lead exposure. In generating risk estimates, empirical data were 

33 combined with mechanistic modeling to increase the representativeness of the risk estimates 

34 generated. Some of the more important design elements included in the risk model were: (a) use 

35 of monitor data as the basis for characterizing Pb levels in ambient air for the case studies and in 
March 2011 5-3 Draft – Do Not Quote or Cite

1 outdoor soil, (b) use of a combination of empirically-derived ratios and more complex empirical2 mechanistic hybrid modeling to predict indoor dust Pb levels associated with ambient (outdoor) 

3 air Pb levels and Pb levels in other related media such outdoor soil, (c) use of empirical data 

4 characterizing Pb exposure for some pathways such as dietary intake, (d) use of IEUBK to 

5 predict central tendency blood Pb (PbB) levels for study populations given pathway-specific 

6 intake rates (e) use of empirical PbB variability data combined with the IEUBK-based estimates 

7 of central-tendency PbB levels to generate population distributions of PbB levels and (f) use of 

8 epidemiological study-based concentration-response functions for IQ loss in children (given 

9 specified PbB levels) to generate risk distributions. The risk model that was developed allowed 

10 us to estimate IQ loss estimates for various percentiles of each study population and furthermore, 

11 to partition that risk between various pathways of interest (although with varying degrees of 

12 overall confidence, as noted below). 

13 Although the assessment utilized a number of innovative modeling elements in order to 

14 generate representative estimates of risk for our study populations, like all risk models there was 

15 uncertainty associated with the model and its output. For example, because of the evidence for a 

16 nonlinear response of blood Pb to exposure and also the nonlinearity reflected in the C–R 

17 functions for estimation of IQ loss, the assessment first estimated total blood Pb levels and 

18 associated risk (i.e., for air- and nonair-related exposure pathways), and then separated out those 

19 estimates of blood Pb and associated risk associated with the pathways of interest in this review. 

20 We separated out the estimates of total (all-pathway) blood Pb and IQ loss into a background 

21 category and two air-related categories. However, significant limitations in our modeling tools 

22 and data resulted in an inability to parse specific risk estimates into specific pathways, such that 

23 we approximated estimates for the air-related and background categories. We believe these 

24 limitations led to slight overestimation of the risks in the one of the air-related categories and 

25 under representation of air-related pathways in the second category. Thus, we characterized the 

26 risk attributable to air-related exposure pathways to be bounded by the estimates developed for 

27 the two air-related categories. 

28 Additional limitations, assumptions and uncertainties, which were recognized in various 

29 ways in the assessment and presentation of results, are listed below, beginning with those related 

30 to design of the assessment or case studies, followed by those related to estimation of Pb 

31 concentrations in ambient air, indoor dust, outdoor soil/dust, and blood, and estimation of Pb32 related IQ loss. 

33  Temporal Aspects: During the 7-year exposure period, media concentrations remain 

34 fixed and the simulated child remains at the same residence (while exposure factors and 

35 physiological parameters are adjusted to match the age of the child). 
March 2011 5-4 Draft – Do Not Quote or Cite

1  General Urban Case Study: The design for this case study employs assumptions 

2 regarding uniformity that are reasonable in the context of a small neighborhood 

3 population, but would contribute uncertainty to extrapolation of these estimates to a 

4 specific urban location, particularly a relatively large one. 

5  Location-specific Urban Case Studies: Limitations in the ambient air monitoring 

6 network limit characterization of spatial gradients of ambient air Pb in these case studies. 

7  Air Quality Simulation: The proportional roll-up and roll-down procedures used in some 

8 case studies to simulate the then-current NAAQS and alternate NAAQS levels, 

9 respectively, assume proportional changes in air concentrations across the study area in 

10 those scenarios for those case studies. 

11  Outdoor Soil/Dust Pb Concentrations: Uncertainty regarding soil/dust Pb levels and the 

12 inability to simulate the influence of changing air Pb levels related to lowering the 

13 NAAQS contributes uncertainty to air-related risk estimates. 

14  Indoor Dust Pb Concentrations: Limitations and uncertainty in modeling of indoor dust 

15 Pb levels, including the impact of reductions in ambient air Pb levels, contributes 

16 uncertainty to air-related risk estimates. 

17  Interindividual Variability in Blood Pb Levels: Uncertainty related to population 

18 variability in blood Pb levels, and limitations in our ability to model it, introduces 

uncertainty into blood Pb and IQ loss estimates for the 95th 19 percentile of the population. 

20  Pathway Apportionment for Higher Percentile Blood Pb and IQ Loss: Limitations in 

21 data, modeling tools and assessment design introduce uncertainty into estimates of air22 related blood Pb and IQ loss for the upper ends of population distribution. 

23  IQ Loss Concentration-response Functions: Specification of the quantitative relationship 

24 between blood Pb level and IQ loss is subject to significant uncertainty at lowest blood 

25 Pb levels (e.g., below 5 μg/dL concurrent blood Pb). 

26 The assumptions, limitations and uncertainties noted above are areas for consideration as 

27 to any advances in available data and or risk characterization methods with regard to the extent 

28 to which they might substantially address areas of largest uncertainty with regard to estimation of 

29 health risks associated with ambient air-related Pb. 

30 
March 2011 5-5 Draft – Do Not Quote or Cite

1 5.1.2 Ecological Risk Assessment 

2 A screening level risk assessment was performed by EPA for the last review to estimate 

the potential for ecological risks associated with exposures to Pb emitted into ambient air.17 3 This 

4 assessment built upon the environmental concentrations modeling performed for the human 

5 exposure and health risk assessment described above. A case study approach was used which 

6 included areas surrounding a primary Pb smelter and a secondary Pb smelter, as well as a 

7 location near a nonurban roadway. Soil, surface water, and/or sediment concentrations were 

8 estimated for each of the three initial case studies from available monitoring data or modeling 

9 analysis, and then compared to ecological screening benchmarks to assess the potential for 

10 ecological impacts from Pb that was emitted into the air. A national-scale screening assessment 

11 was also used to evaluate surface water and sediment monitoring locations across the United 

12 States for the potential for ecological impacts associated with atmospheric deposition of Pb. All 

13 three case studies and the national-scale assessment considered current or recent environmental 

14 conditions. In all cases but the primary Pb smelter case study, current air quality conditions were 

15 below the then-current NAAQS. The current air quality conditions for the primary Pb smelter 

16 case study exceeded the NAAQS. An additional case study was identified to look at gasoline17 derived Pb effects on an ecologically vulnerable ecosystem but various limitations precluded any 

18 analyses. 

19 Ecological screening values, developed from the Eco-SSLs methodology, EPA’s 

20 recommended ambient water quality criteria, and sediment screening values developed by 

21 MacDonald and others (2000, 2003) were used to estimate the potential for ecological risk. A 

22 Hazard Quotient (HQ) was calculated for various receptors to determine the potential for risk to 

23 that receptor. The HQ was calculated as the ratio of the media concentration to the ecotoxicity 

24 screening value. For each case study, HQ values were calculated for each location where either 

25 modeled or measured media concentrations were available. Separate soil HQ values were 

26 calculated for each ecological receptor group for which an ecotoxicity screening value has been 

27 developed (i.e., birds, mammals, soil invertebrates, and plants). HQ values less than 1.0 were 

28 concluded to suggest that Pb concentrations in a specific medium were unlikely to pose 

29 significant risks to ecological receptors, while HQ values greater than 1.0 indicated that the 

30 expected exposure exceeded the ecotoxicity screening value, which was concluded to indicate a 

31 potential for adverse effects. 

32 Several uncertainties that apply across case studies were identified: 

 17 The assessment is described in detail in Lead Human Exposure and Health Risk Assessments and 

Ecological Risk Assessment for Selected Areas, Pilot Phase (ICF, 2006). Various limitations precluded 

performance of a full-scale ecological risk assessment. 
March 2011 5-6 Draft – Do Not Quote or Cite

1  The ecological risk screen was limited to specific case study locations and other locations 

2 for which Pb data were available. Efforts were made to ensure that the Pb exposures 

3 assessed were attributable to airborne Pb and not dominated by nonair sources. However, 

4 there was uncertainty as to whether other sources might have actually contributed to the 

5 Pb exposure estimates. 

6  A limitation to using the selected ecotoxicity screening values is that they might not be 

7 sufficient to identify risks to some threatened or endangered species or unusually 

8 sensitive aquatic ecosystems (e.g., 2006 AQCD, p. AX7–110). 

9  The methods and database from which the surface water screening values (i.e., EPA10 recommended ambient water quality criteria for Pb) were derived is somewhat dated. 

11 New data and approaches (e.g., use of pH as indicator of bioavailability) may now be 

12 available to estimated the aquatic toxicity of Pb (2006 AQCD, sections X7.2.1.2 and 

13 AX7.2.1.3). 

14  No adjustments were made for sediment-specific characteristics that might affect the 

15 bioavailability of Pb in sediments in the derivation of the sediment quality criteria used 

16 for this ecological risk screen (2006 AQCD, sections 7.2.1 and AX7.2.1.4; Appendix M, 

17 ICF, 2006). Similarly, characteristics of soils for the case study locations were not 

18 evaluated for measures of bioavailability. 

19  Although the screening value for birds used in this analysis is based on reasonable 

20 estimates for diet composition and assimilation efficiency parameters, it was based on a 

21 conservative estimate of the relative bioavailability of Pb in soil and natural diets 

22 compared with water soluble Pb added to an experimental pellet diet (Appendix L, ICF, 

23 2006). 

24 For the case studies, the concentrations of Pb in soil and sediments in various locations 

25 exceeded screening values for these media indicating potential for adverse effects to terrestrial 

26 organisms (plants, birds and mammals) and to sediment dwelling organisms. While the 

27 assessment was limited in that it was not possible to dissect the contributions of air Pb emissions 

28 from other sources, it is likely that, at least for the primary smelter, that the air contribution is 

29 significant. For the other case studies, the contributions of current air emissions to the Pb 

30 burden, is less clear. The national-scale screen of surface water data initially identified 15 areas 

31 for which water column levels of dissolved Pb were greater than hardness adjusted chronic 

32 criteria for the protection of aquatic life indicating a potential for adverse effect if concentrations 

33 were persistent over chronic periods. Acute criteria were not exceeded at any of these locations. 

34 The extent to which air emissions of Pb had contributed to these surface water Pb concentrations 

35 is unclear. In the national-scale screen of sediment data associated with the 15 surface water 

36 sites described above, threshold effect concentration-based HQs at nine of these sites exceeded 
March 2011 5-7 Draft – Do Not Quote or Cite

1 1.0. Additionally, HQs based on probable effect concentrations exceeded 1.0 at five of the sites, 

2 indicating probable adverse effects to sediment dwelling organisms. Thus, sediment Pb 

3 concentrations at some sites are high enough that there is a likelihood that they would cause 

4 adverse effects to sediment dwelling organisms. However, the contribution of air emissions to 

5 these concentrations is unknown. 

6 5.2 CONSIDERATION OF QUANTITATIVE ASSESSMENTS FOR THIS 

7 REVIEW 

8 To the extent that new research and/or improved methodologies are identified to inform 

9 updates to the design of Pb exposure and risk assessments or new scientific evidence is available 

10 to substantially inform our ability to characterize and/or reduce uncertainties identified in the 

11 assessments performed for the last review, EPA may design and conduct quantitative 

12 assessments for this review. Drawing on the evaluation of evidence in the first draft ISA, a 

13 planning document will systematically discuss the available scientific evidence, tools and 

14 methodologies pertaining to each of the key aspects of an assessment, with particular attention to 

15 evidence and tools newly available in this review. This discussion will focus particularly on 

16 areas of uncertainty in the REA prepared for the last review and the potential for a new REA to 

17 provide notably different exposure and risk estimates, with lower associated uncertainty. Some 

18 key areas for staff analysis, including types of data, methodology and tools to be considered, are 

19 summarized below. 

20 5.2.1 Human Exposure and Health Risk Assessments 

21 5.2.1.1 Air Quality and Environmental Media Concentrations 

22 Generally speaking, and as addressed in the last review, Pb concentrations in air and 

23 indoor dust, and to some extent outdoor dust/soil, are particularly key components in the 

24 assessment of air-related Pb health risk. In the case studies included in the assessment for the 

25 last review, a mixture of modeling and monitoring approaches were used to estimate these 

26 concentrations. For example, in the location-specific urban case studies, air concentrations were 

27 estimated based on the assignment of ambient monitor concentrations to U.S. Census units 

28 according to proximity. The limited number of monitors in relation to sources contributed 

29 uncertainty to our characterization of spatial gradients in ambient air concentration. Limitations 

30 and uncertainty in modeling the associated Pb concentrations in indoor dust was another area of 

31 uncertainty. In considering the extent to which new information or insights might be gained 

32 from a new assessment, we will consider the availability of new information or methods in these 

33 areas. 
March 2011 5-8 Draft – Do Not Quote or Cite

1 To the extent more spatially detailed information on air Pb concentrations in the urban 

2 context is available, this could reduce this area of uncertainty in the risk assessment completed 

3 for the last review. Specifically, more spatially-refined air concentration estimates or 

4 measurements might allow us to more accurately define spatial gradients around ambient 

5 monitors, potentially differentiating gradients around source-oriented monitors from those 

6 associated with nonsource oriented monitors. This might in turn improve the representativeness 

7 of the characterization of ambient air Pb concentrations for exposed populations in urban study 

8 areas. If these types of more refined ambient data are available, an initial step to consider the 

9 impact of their inclusion in the assessment could be a sensitivity analysis-oriented calculation for 

10 one study area to determine the degree to which this type of refined ambient Pb spatial gradient 

11 data could impact exposure (and ultimately risk) estimates. 

12 An additional area of uncertainty recognized in the last assessment concerned the 

13 procedures for simulating conditions for alternative NAAQS levels. The availability of more 

14 refined ambient air Pb data or other information providing insights into the spatial pattern 

15 associated with reductions in ambient Pb levels (i.e., spatial pattern of rollbacks in ambient air Pb 

16 levels) could address another important source of uncertainty with regard to estimation of air Pb 

17 concentrations in the previous risk assessment. 

18 With regard to media related to indoor dust Pb modeling, any newly available urban 

19 residential datasets with matched measurements useful in evaluating the relationship between 

20 ambient outdoor air Pb and indoor dust Pb may be important to consider with regard to 

21 evaluation of this source of uncertainty in the risk assessment completed for the last review. 

22 Specifically, having outdoor ambient air Pb data matched to outdoor soil Pb, indoor ambient air 

23 Pb and indoor dust Pb data, for a set of residential locations, might improve our ability to 

24 evaluate and possibly further calibrate performance of the hybrid indoor dust Pb model 

25 developed and used in the last review. The availability of multiple matched media 

26 concentrations over an extended period (e.g., allowing for characterization of daily, weekly or 

27 monthly levels) would further improve their utility in this regard. This reflects the fact that the 

28 dust Pb model is a dynamic model which combines mechanistic and empirical elements to 

29 generate a near-steady state estimate of indoor dust Pb concentrations given various loading 

30 rates. Therefore, having data which are temporally refined would allow us to evaluate the degree 

31 to which the model tracks the temporal profile of these media concentrations. 

32 The characterization of soil Pb levels and their relationship to air Pb levels, particularly in 

33 urban areas is another area contributing to the exposure characterization in which uncertainty 

34 might be reduced with new information or methods. For example, the identification of more 

35 current data characterizing Pb soil levels in the urban residential context which could be further 

36 differentiated to capture any regional trends and potentially more importantly, differences in 
March 2011 5-9 Draft – Do Not Quote or Cite

1 housing age (as a surrogate for information on leaded paint usage) might further reduce 

2 uncertainty associated with modeling this pathway, characterizing contributions from air-related 

3 and nonair-related sources, and potentially in modeling total exposure and total risk. 

4 Considering housing age in characterizing outdoor soil Pb levels is potentially important because 

5 in some cases (i.e., older houses with Pb exterior paint), soil Pb levels can be elevated due to 

6 historical loading from weathered exterior Pb paint. Furthermore, older houses are also more 

7 likely to have higher concentrations of indoor dust Pb contributed by older indoor Pb paint. 

8 Together these two factors mean that background (nonair) exposures to Pb can be elevated for 

9 residents of older houses, a factor important to reflect in our risk assessment to the extent that 

10 data allow. 

11 An additional policy-relevant aspect of the environmental characterization component of 

12 the last assessment concerned the identification of air-related and nonair-related (background) 

13 environmental Pb concentrations. For example, as described in the documents prepared for the 

14 last review, while conceptually indoor Pb paint contributions to indoor dust Pb would be 

15 considered nonair or background, technical limitations precluded us from parsing out the indoor 

paint contributions from historic air-related Pb in indoor dust (73 FR 66980).18 16 Similarly we 

17 were unable to separate the air contribution to dietary or drinking water Pb from the nonair 

18 contributions, such that Pb in these pathways was identified as “background” yet recognized 

19 qualitatively to also include air-related Pb. The availability of information and methods that 

20 might improve our characterization of distinctions between these air and nonair-related pathways 

21 will also be an important consideration with regard to the potential for impact on REA results. 

22 5.2.1.2 Human Exposure Assessment 

23 The exposure assessment completed as part of the risk assessment for the last review 

24 focused on characterizing population-level distributions of blood Pb levels, including (a) 

25 estimates of high-end percentile estimates of that distribution and (b) estimation of the 

26 apportionment of total PbB levels associated with a given percentile among air- and nonair27 related pathways of Pb. As noted in the last review and earlier in this section, there is 

28 considerable uncertainty associated with apportioning total Pb exposure (and hence total risk) to 

29 the air- and nonair-related pathways. 

30 One aspect of the uncertainty in apportioning exposure and risk among exposure 

31 pathways concerns uncertainty regarding the specific contribution of different Pb exposure 

32 pathways to total exposure for individuals with widely differing total exposure. In the last 

33 assessment we applied the same relative contributions to all individuals in the population. 

 18 Indoor dust Pb derived from lead recently emitted to the air was quantified separate from this combined 

historic Pb of paint or air origin. 
March 2011 5-10 Draft – Do Not Quote or Cite

1 Uncertainty in this area reflects the fact that we do not have comprehensive data on exposure 

2 levels matched with PbB measurements for a larger set of individuals, which prevents us from 

3 assessing how contributions of different Pb exposure pathways to total PbB may vary across 

4 percentiles in the population distribution (of total PbB). If such data are now available, we could 

5 be in a position to reduce this potentially important source of uncertainty. These types of data 

6 could take the form of matched data on PbB levels and dietary exposure (for a set of study 

7 subjects). 

8 Furthermore, we plan to consider the extent to which data are now available that 

9 characterize key areas of variability in the inputs to modeling total PbB levels (e.g., soil Pb, 

10 outdoor and indoor dust Pb, dietary food Pb) which might support a probabilistic simulation of 

11 the full range of exposure and risk for a given study population. An important aspect to this 

12 consideration will be the availability of data characterizing the degree of correlation between 

13 these modeling inputs (e.g., degree to which indoor dust Pb levels and outdoor soil Pb levels are 

14 correlated). As available, the extent to which these types of data characterizing variability in 

15 pathway-specific Pb concentrations (and correlations between those distributions) might provide 

16 the basis for a Monte Carlo simulation-based estimation of population variability in PbB levels 

17 with pathway apportionment for the simulated PbB levels will also be considered, with regard to 

the ability to estimate, for example, the 95th 18 population percentile PbB levels and the fractional 

19 contribution to that PbB level by the underlying Pb exposure pathways. Another area for 

20 consideration with regard to population variability will be the availability of more recent 

21 information on PbB variability in study populations relevant for an assessment (e.g., the 

22 availability of an updated estimate of population PbB variation such as geometric standard 

23 deviation, potentially differentiated by region and possibly by housing stock or by the SES 

24 attributes of the underlying study population). 

25 5.2.1.3 Health Risk Assessment 

26 In analyzing newly available information pertaining to the health risk assessment step, we 

27 plan to consider newly available studies with regard to the support they might provide for 

28 assessment of health endpoints and risk metrics other than childhood IQ and, as available, the 

29 extent to which they indicate the potential to lead to risk estimates for notably different from 

30 those of the last assessment. Focusing specifically on the step of translating childhood exposure 

31 estimates into IQ loss estimates, as the risk metric, a key source of uncertainty in the last 

32 assessment was the specification of the IQ loss function, specifically, the portion of the function 

33 predicting IQ loss at lower exposure levels (e.g., below PbB levels of approximately 3-5 ug/dL). 

34 If we identify either new cohort studies, or pooled/meta analyses based on existing studies which 

35 describe the nature of the function at these lower exposure levels, then we might be in a position 
March 2011 5-11 Draft – Do Not Quote or Cite

1 to reduce uncertainty in the risk assessment. To the extent such newly available information is 

2 identified, we will consider the potential for it to impact REA results and the size and 

3 characterization of such impact. One other source of uncertainty that might be reduced with new 

4 information, involves the type of PbB metric to use (concurrent, lifetime averaged etc). For 

5 example, if newly available study data clearly point to the importance of a PbB metric other than 

6 the concurrent metric used in the last review, then, depending on the associated concentration7 response function, this could impact the risk estimates generated. 

8 5.2.2 Ecological Risk Assessment 

9 In considering the extent to which the currently available information warrants 

10 development of an ecological risk assessment in this review, we will consider both the 

11 availability of new air quality data and data or estimates for other media that might inform 

12 consideration of the current Pb standards, as well as any newly available scientific evidence that 

13 indicates a more refined understanding of the direct and indirect effects of deposited ambient Pb 

14 on ecosystems and organisms. We intend to focus most specifically on 1) the ability of current 

15 data sets to characterize exposure of ecosystems to ambient Pb currently being deposited and 2) 

16 any new evidence that would allow the current review to arrive at different conclusions as to the 

17 causality or degree of effect than the last review. 

18 In considering air quality information, availability of monitoring data from the newly 

19 designed Pb monitoring network, discussed below in chapter 6, will be considered. For example, 

20 available ambient data may be evaluated with regard to its adequacy for determining ambient 

21 concentrations of Pb in potentially vulnerable ecosystems. The availability of methods or 

22 models to estimate the amount of deposition occurring in those areas will also be considered. 

23 Additionally, it will be important to consider the available information with regard to its 

24 usefulness for apportioning sources of deposited Pb to ambient sources (as compared to nonair 

25 sources of Pb in ecosystems). A key consideration will be with regard to the extent to which 

26 information is available to support a quantitative analysis of ambient Pb-related effects 

27 associated with current ambient conditions or at conditions meeting the current standard. 

28 In the last review, the scientific evidence of direct effect from current ambient levels of 

29 Pb to specific ecosystems or organisms was limited. In considering the scientific evidence on 

30 which a risk assessment might be based, staff plans to evaluate whether there is sufficient 

31 scientific evidence to causally link deposited atmospheric lead with adverse ecological effects 

32 under the current standard. Information relating to critical loads for Pb in ecosystems was 

33 lacking in the last review. Staff plans to evaluate the adequacy of any new scientific evidence on 

34 critical loads that might be used in assessing ecosystems potentially vulnerable to Pb on a 

35 national-scale. Staff also plans to look at any new scientific evidence that might be available to 
March 2011 5-12 Draft – Do Not Quote or Cite

1 apportion specific ecological effects to ambient air Pb as opposed to other sources of current and 

2 historic Pb in the environment, as well as to provide additional insight into the responsiveness of 

3 ecosystems to changes in Pb deposition. 

4 5.3 SCIENTIFIC AND PUBLIC REVIEW 

5 The REA planning document will be distributed to the CASAC Pb Panel for their 

6 consideration and provided to the public for review and comment. The document will be the 

7 subject of a consultation with the CASAC Pb Panel at a public meeting that will be announced in 

8 the Federal Register. 

9 If upon consideration of CASAC and public comments, EPA concludes that development 

10 of a new REA, or updating or expanding the last assessment, is warranted, staff will take into 

11 account comments received from CASAC and the public in designing and conducting the 

12 assessments. In such a case, staff would prepare at least one draft of the assessments for CASAC 

13 review and public comment. Review would be conducted by the CASAC Pb Review Panel and 

14 discussed at public meetings that would be announced in the Federal Register. Based on past 

15 practice by CASAC, EPA expects that key advice and recommendations for revision of the 

16 document would be summarized in a letter to the EPA Administrator. In revising the draft REA 

17 document, EPA would take into account any such recommendations, and also consider 

18 comments received, from CASAC or from the public, at the meeting itself and any written 

19 comments received. A final document would then be made available on an EPA website, with 

20 its public availability announced in the Federal Register. 

21 If upon consideration of CASAC and public comments on the REA planning document, 

22 EPA concludes that development of a new REA is not warranted, a REA will not be developed 

23 and the Policy Assessment for this review will draw from the REA developed in the last review 

24 in light of analyses or assessments made in the REA planning document with regard to the 

25 current evidence pertaining to exposure and risk, as well as the evidence presented in the ISA 

26 and other documents prepared for the review. Review steps for the PA are described in section 

27 7.1 below. 
March 2011 6-1 Draft – Do Not Quote or Cite

1 6 AMBIENT AIR MONITORING CONSIDERATIONS 

2 In the course of NAAQS reviews, aspects of the methods for sampling and analysis of the 

3 NAAQS pollutant are reviewed, and the current network of monitoring locations with the 

4 associated data is considered. The methods for sampling and analysis of each NAAQS pollutant 

5 are generally reviewed in conjunction with consideration of the indicator element for each 

6 NAAQS. Consideration of the ambient air monitoring network generally informs the 

7 interpretation of current data on ambient air concentrations, and helps identify if the monitoring 

8 network is adequate to determine compliance with a potentially revised Pb NAAQS. This 

9 chapter describes plans for considering these aspects of the ambient air monitoring program for 

Pb. 19 10 

11 6.1 CONSIDERATION OF SAMPLING AND ANALYSIS METHODS 

12 In order to be used in attainment designations, ambient Pb concentration data must be 

13 obtained using either the Federal Reference Method (FRM) or a Federal Equivalent Method 

14 (FEM). As described in section 1.3 above, the indicator for the current Pb NAAQS is Pb-TSP. 

15 However, in some situations (described below), ambient Pb-PM10 concentrations may be used in 

16 judging nonattainment. Accordingly, FRMs have been established for Pb-TSP and for Pb-PM10. 

17 The current FRM for the measurement of Pb-TSP is provided in 40 CFR part 50 

18 Appendix G. This FRM includes sampling using a high-volume TSP sampler that meets the 

19 design criteria identified in 40 CFR part 50 Appendix B and sample analysis for Pb content using 

flame atomic adsorption. There are 24 FEMs currently approved for Pb-TSP.20 20 All 24 FEMs are 

21 based on the use of high-volume TSP samplers and a variety of approved equivalent analysis 

22 methods. 

23 During the review of the Pb NAAQS completed in 2008, CASAC noted the variability in 

24 high-volume TSP sample measurements associated with the effects of wind speed and wind 

25 direction on collection efficiency in their comments regarding the indicator. However, at the 

26 time of the 2008 review, no alternative TSP sampler designs were identified that had an adequate 

27 characterization of their collection efficiency over a wide range of particle sizes. The existing 

28 high volume sampler was retained as the sampling approach for the Pb-TSP FRM and FEMs. 

 19 The code of federal regulations (CFR) at parts 50, 53 and 58 specifies required aspects of the ambient 

monitoring program for NAAQS pollutants. The federal reference methods (FRMs) for sample collection and 

analysis are specified in 40 CFR part 50, the procedures for approval of FRMs and federal equivalent methods 

(FEMs) are specified in 40 CFR part 53 and the rules specifying requirements for the planning and operations of the 

ambient monitoring network are specified in 40 CFR part 58. 

20 A complete list of FEM can be found at the following webpage - 

http://www.epa.gov/ttn/amtic/files/ambient/criteria/reference-equivalent-methods-list.pdf 
March 2011 6-2 Draft – Do Not Quote or Cite

1 Due to reduced availability of laboratories capable of performing flame atomic 

2 adsorption analyses and general advances in analysis methods, the EPA has initiated an effort to 

3 replace atomic adsorption with a more modern analysis method such as inductively coupled 

4 plasma mass spectroscopy (ICP-MS). A consultation with the CASAC Ambient Air Monitoring 

5 and Methods Subcommittee was held on September 15, 2010 and the EPA plans to propose a 

6 new FRM based on a more modern analysis method in the fall of 2011. 

7 In addition to maintaining the existing FRM for Pb-TSP, a new FRM for Pb in PM10 (Pb8 PM10) was promulgated as part of the 2008 review. This new FRM is based on the PM10 sampler 

9 defined in 40 CFR part 50 Appendix J coupled with x-ray fluorescence (XRF) analysis. The Pb10 PM10 measurements may be used as an alternative to Pb-TSP measurements in certain conditions 

11 defined in 40 CFR part 58 Appendix D paragraph 2.10.1.2. These conditions include where Pb 

12 concentrations are not expected to equal or exceed 0.10 micrograms per cubic meter on an 

13 arithmetic 3-month mean and where the source of Pb emissions is expected to emit a substantial 

14 majority of its Pb in the PM10 size fraction. 

15 Sampling and analysis issues to be considered during this review include the following: 

16  Are new TSP samplers available and adequately characterized for use in Pb-TSP 

17 sampling? 

18  Are new data on Pb size distributions available that would better inform the need for Pb19 TSP or the adequacy of Pb measurements in PM10 or other size fractions (e.g., Pb-PM15 

20 or Pb-PM20) in characterizing total Pb concentrations? 

21  If an alternative size fraction is identified that may adequately characterize total Pb 

22 concentrations, are there samplers for that size fraction that have been adequately 

23 characterized that can be used as the basis for a new FRM sampling method? 

24 

25 6.2 CONSIDERATION OF AIR MONITORING NETWORK 

26 REQUIREMENTS 

27 The majority of data used to determine compliance with the Pb NAAQS are obtained 

28 from monitors operated by state, local, and tribal monitoring agencies (“monitoring agencies”). 

29 These monitors are either required due to federal regulations (40 CFR part 58, Appendix D) and 

30 state regulations, or are operated voluntarily by the monitoring agency. A review of the 

31 available lead monitoring data and then-existing Pb monitoring network was performed as part 

32 of the 2008 Pb NAAQS review (USEPA, 2007b). This review indicated that the Pb monitoring 

33 network existing at that time was inadequate to assess compliance and determine the extent of all 

34 the areas that may violate the revised NAAQS. Many states had no ambient air Pb monitors in 

35 place, such that there were large portions of the country with no data being collected on Pb 

36 concentrations in ambient air. In addition, many of the largest Pb emitting sources in the country 
March 2011 6-3 Draft – Do Not Quote or Cite

1 did not have nearby ambient Pb air monitors. Due to these findings, the EPA promulgated 

2 revised Pb monitoring network design requirements along with the revised Pb NAAQS (73 FR 

3 66964). The Pb monitoring network design requirements were revised again in December 2010 

4 as a result of EPA’s decision to grant a petition to reconsider the prior network design 

5 requirements that was filed by several environmental and public health organizations (75 FR 

6 81126). 

7 The current Pb monitoring network design requirements (40 CFR part 58, Appendix D, 

8 paragraph 4.5) include two types of monitoring sites – source-oriented monitoring sites, and non9 source-oriented monitoring sites. Source-oriented monitoring sites are required near sources of 

10 air Pb emissions which are expected to or have been shown to contribute to ambient air Pb 

11 concentrations in excess of the NAAQS. At a minimum, there must be one source-oriented site 

12 located to measure the maximum Pb concentration in ambient air resulting from each non-airport 

13 Pb source which emits 0.50 or more tons of Pb per year and from each airport which emits 1.0 or 

more tons of Pb per year.21 14 In addition, one year of monitoring is required near 15 specific 

15 airports in order to gather additional information on the likelihood of NAAQS exceedances near 

16 airports due to the combustion of leaded aviation gasoline (75 FR 81126). 

17 Monitoring agencies are required to conduct non-source-oriented Pb monitoring at the 

18 multipollutant monitoring sites (referred to as NCore sites, required under 40 CFR part 58 

19 Appendix D, paragraph 3) in Core Based Statistical Areas (CBSA) with a population of 500,000 

or more.22 20 While non-source-oriented monitoring data can be used for designation purposes, the 

21 main objective for non-source-oriented monitoring is to gather information on neighborhood22 scale lead concentrations that are typical in urban areas so to better understand ambient air23 related Pb exposures for the general population. 

24 Following the implementation of the December 2010 Pb network requirements, the Pb 

25 monitoring network will consist of approximately 270 required monitors including 

26 approximately 210 source-oriented monitors and 60 non-source-oriented monitors. Figure 6.1 

27 shows the estimated geographic distribution of monitors associated with these new requirements. 

 21 The Regional Administrator may waive the requirement in paragraph 4.5(a) for monitoring near Pb 

sources if the State or, where appropriate, local agency can demonstrate the Pb source will not contribute to a 

maximum Pb concentration in ambient air in excess of 50 percent of the NAAQS (based on historical monitoring 

data, modeling, or other means). 

22 Defined by the US Census Bureau - http://www.census.gov/population/www/metroareas/metroarea.html 
March 2011 6-4 Draft – Do Not Quote or Cite

1 

Figure 6-1. Map of Required Lead Monitors based on 2005 National Emission Inventory 

Estimates. 

2 

3 Sampling and analysis issues to be considered during this review include the following: 

4  Is the current emission threshold of 0.50 tons per year for industrial sources and 1.0 tons 

5 per year for airports appropriate and adequate for determining compliance with the 

6 current or alternative NAAQS considered? 

7  The current monitoring requirements specify source emissions thresholds intended to 

8 identify situations where these emissions may result in exceedances of the current 

9 NAAQS (e.g., near stationary sources or airports) and also provide for the identification 

10 of areas of historic industrial activity from which emissions may also result in 

11 exceedances. Is there recent, newly available information indicating other situations 

12 where exceedances to the current NAAQS are likely to occur? To the extent that 

13 revisions to the NAAQS are considered during this review, at what alternative levels 

14 and/or averaging times would other types of Pb sources be likely to cause exceedances to 

15 the alternative NAAQS considered? 

16 

17 
March 2011 7-1 Draft – Do Not Quote or Cite

1 7 POLICY ASSESSMENT AND RULEMAKING 

2 7.1 POLICY ASSESSMENT 

3 The PA, like the previous OAQPS Staff Paper, is a document that provides a transparent 

4 OAQPS staff analysis and staff conclusions regarding the adequacy of the current standards and 

5 potential alternatives that are appropriate to consider prior to the issuance of proposed and final 

6 rules. The PA integrates and interprets the information from the ISA and REA(s) to frame policy 

7 options for consideration by the Administrator. The PA is also intended to facilitate CASAC’s 

8 advice to the Agency and recommendations to the Administrator on the adequacy of the existing 

9 standards or revisions that may be appropriate to consider, as provided for in the Clean Air Act. 

10 Staff conclusions will be based on the information contained in the ISA, and, as available, the 

REA23 11 , and any additional staff evaluations and assessments discussed in the PA. In so doing, 

12 the discussion in the PA will be framed by consideration of a series of the policy-relevant 

13 questions drawn from those outlined in chapter 3, including the fundamental questions associated 

14 with the adequacy of the current standards and, as appropriate, consideration of alternative 

15 standards in terms of the specific elements of the standards: indicator, averaging time, level, and 

16 form. 

17 The PA will identify conceptual evidence-based and risk/exposure-based approaches for 

18 reaching public health and welfare policy judgments. It will discuss the implications of the 

19 science and quantitative assessments for the adequacy of the current standards, and for any 

20 alternative standards under consideration. The PA will also describe a broad range of policy 

21 options for standard setting, identifying the broadest range for which the staff identifies support 

22 within the available information. In so doing, the PA will describe the underlying interpretations 

23 of the scientific evidence and risk/exposure information that might support such alternative 

24 policy options that could be considered by the Administrator in making decisions for the Pb 

25 standards. 

26 In identifying a range of primary standard options for the Administrator to consider, it is 

27 recognized that the final decision will be largely a public health policy judgment. A final 

28 decision must draw upon scientific information and analyses about health effects and risks, as 

29 well as judgments about how to deal with the range of uncertainties that are inherent in the 

30 scientific evidence and analyses. Staff’s approach to informing these judgments is based on a 

31 recognition that the available health effects evidence generally reflects a continuum consisting of 

32 ambient levels at which scientists generally agree that health effects are likely to occur through 

 23 The quantitative risk and exposure assessments from the last review may be considered in light of current 

air quality analyses if new quantitative risk and exposure assessments are not developed for this review. 
March 2011 7-2 Draft – Do Not Quote or Cite

1 lower levels at which the likelihood and magnitude of the response become increasingly 

2 uncertain. This approach is consistent with the requirements of the NAAQS provisions of the 

3 Act and with how EPA and the courts have historically interpreted the Act. These provisions 

4 require the Administrator to establish primary standards that are requisite to protect public health 

5 and are neither more nor less stringent than necessary for this purpose. The provisions do not 

6 require that primary standards be set at a zero-risk level, but rather at a level that avoids 

unacceptable risks to public health, including the health of sensitive groups.24 7 

8 In identifying a range of secondary standard options for the Administrator to consider, 

9 staff recognizes that the final decision will be largely a public policy judgment. A final decision 

10 must draw upon scientific evidence and analyses about effects on public welfare, as well as 

11 judgments about how to deal with the range of uncertainties that are inherent in the relevant 

12 information. This approach is consistent with the requirements of the NAAQS provisions of the 

13 Act and with how EPA and the courts have historically interpreted the Act. These provisions 

14 require the Administrator to establish secondary standards that are requisite to protect public 

15 welfare from any known or anticipated adverse effects associated with the presence of the 

16 pollutant in the ambient air. In so doing, the Administrator seeks to establish standards that are 

17 neither more nor less stringent than necessary for this purpose. The provisions do not require 

18 that secondary standards be set to eliminate all welfare effects, but rather at a level that protects 

19 public welfare from those effects that are judged to be adverse. 

20 Staff will prepare at least one draft of the PA document for CASAC review and public 

21 comment. The draft PA document will be distributed to the CASAC Pb Panel for their 

22 consideration and provided to the public for review and comment. Review by the CASAC Pb 

23 Panel will be discussed at public meetings that will be announced in the Federal Register. Based 

24 on past practice by CASAC, EPA expects that key advice and recommendations for revision of 

25 the document would be summarized by the CASAC in a letter to the EPA Administrator. In 

26 revising the draft PA document, OAQPS will take into account any such recommendations, and 

27 also consider comments received, from CASAC and from the public, at the meeting itself, and 

28 any written comments received. The final document will be made available on an EPA website, 

29 with its public availability announced in the Federal Register. 

 24 The sensitive population groups identified in a NAAQS review may be comprised of low income or 

minority groups. Where low income/minority groups are among the sensitive groups, the rulemaking decision will 

be based on providing protection for these and other sensitive population groups. To the extent that low 

income/minority groups are not among the sensitive groups, a decision based on providing protection of the 

sensitive groups would be expected to provide protection for the low income/minority groups (as well as any other 

less sensitive population groups). 
March 2011 7-3 Draft – Do Not Quote or Cite

1 7.2 RULEMAKING 

2 Following issuance of the final PA and EPA management consideration of staff analyses 

3 and conclusions presented therein, and taking into consideration of CASAC advice and 

4 recommendations, the Agency will develop a notice of proposed rulemaking. The proposed 

5 rulemaking notice conveys the Administrator’s proposed conclusions regarding the adequacy of 

6 the current standards and any revision that may be appropriate. A draft notice of proposed 

7 rulemaking will be submitted to the Office of Management and Budget (OMB) for interagency 

8 review, in which OMB and other federal agencies are provided the opportunity for review and 

9 comment. After the completion of interagency review, EPA will publish the notice of proposed 

10 rulemaking in the Federal Register. Monitoring rule changes associated with review of the Pb 

11 standards, and drawing from considerations outlined in chapter 6 above, will be developed and 

12 proposed, as appropriate, in conjunction with this NAAQS rulemaking. 

13 At the time of publication of the notice of proposed rulemaking, all materials on which 

the proposal is based are made available in the public docket for the rulemaking.25 14 Publication 

15 of the proposal notice is followed by a public comment period, generally lasting 60 to 90 days, 

16 during which the public is invited to submit comments on the proposal to the rulemaking docket. 

17 Taking into account comments received on the proposed rule, the Agency will then develop a 

18 notice of final rulemaking, which again undergoes OMB-coordinated interagency review prior to 

19 issuance by EPA of the final rule. In the notice of final rulemaking, and generally also through 

20 the use of an accompanying document, the Agency responds to all significant comments on the 

proposed rule.26 21 Publication of the final rule in the Federal Register completes the rulemaking 

22 process.

 25 The rulemaking docket for the current Pb review is identified as EPA-HQ-OAR-2010-0108. This docket 

has incorporated the ISA docket (EPA-HQ-ORD-2011-0051) by reference. Both dockets are publicly accessible at 

www.regulations.gov. 

26 For example, Agency responses to all substantive comments on the 2008 notice of proposed rulemaking 

in the last review were provided in the preamble to the final rule and in a document titled “Response to Responses to 

Significant Comments on the 2008 Proposed Rule on the National Ambient Air Quality Standards for Lead (May 

20, 2008; 73 FR 29184)”, which is available at: 

http://www.epa.gov/ttn/naaqs/standards/pb/data/20081015_responsetocomments.pdf. 
March 2011 8-1 Draft – Do Not Quote or Cite

1 8 REFERENCES 

2 ICF International. (2006) Lead Human Exposure and Health Risk Assessments and Ecological Risk 

3 Assessment for Selected Areas. Pilot Phase. Draft Technical Report. Prepared for the U.S. 

4 EPA's Office of Air Quality Planning and Standards, Research Triangle Park, NC. 

5 December. 

6 Jackson, L. (2009) Memorandum from Administrator Lisa Jackson, Subject: Development of 

7 regulations and policies. September 11, 2009. Available at: 

8 http://www.epa.gov/ttn/naaqs/pdfs/NAAQSReviewProcessMemo52109.pdf 

9 MacDonald, D.D., Ingersoll, C.G., and Berger, T.A. (2000) Development and evaluation of 

10 consensus-based sediment quality guidelines for freshwater ecosystems. Archives of 

11 Environmental Contamination and Toxicology. 39:20-31. 

12 MacDonald, D.D., Ingersoll, C.G., Smorong, D.E., Lindskoog, R.A., Sloane, G., and Biernacki, T. 

13 (2003) Development and Evaluation of Numerical Sediment Quality Assessment Guidelines 

14 for Florida Inland Waters. British Columbia: MacDonald Environmental Sciences, Lt. 

15 Columbia, MO: U.S. Geological Survey. Prepared for: Florida Department of 

16 Environmental Protection, Tallahassee, FL. January. 

17 U.S. Environmental Protection Agency. (1977) Air quality criteria for lead. Research Triangle Park, 

18 NC: Health Effects Research Laboratory, Criteria and Special Studies Office; EPA report 

19 no. EPA-600/8-77-017. Available from: NTIS, Springfield, VA; PB-280411. 

20 U.S. Environmental Protection Agency. (1986a) Air quality criteria for lead. Research Triangle 

21 Park, NC: Office of Health and Environmental Assessment, Environmental Criteria and 

22 Assessment Office; EPA report no. EPA-600/8-83/028aF-dF. 4v. Available from: NTIS, 

23 Springfield, VA; PB87-142378. 

24 U.S. Environmental Protection Agency. (1986b) Lead effects on cardiovascular function, early 

25 development, and stature: an addendum to U.S. EPA Air Quality Criteria for Lead (1986). 

26 In: Air quality criteria for lead, v. 1. Research Triangle Park, NC: Office of Health and 

27 Environmental Assessment, Environmental Criteria and Assessment Office; pp. A1-A67; 

28 EPA report no. EPA-600/8-83/028aF. Available from: NTIS, Springfield, VA; PB87-

29 142378. 

30 U.S. Environmental Protection Agency. (1989) Review of the national ambient air quality standards 

31 for lead: Exposure analysis methodology and validation: OAQPS staff report. Research 

32 Triangle Park, NC: Office of Air Quality Planning and Standards; report no. EPA-450/2-

33 89/011. Available on the web: 

34 http://www.epa.gov/ttn/naaqs/standards/pb/data/rnaaqsl_eamv.pdf 

35 U.S. Environmental Protection Agency. (1990a) Air quality criteria for lead: supplement to the 1986 

36 addendum. Research Triangle Park, NC: Office of Health and Environmental Assessment, 

37 Environmental Criteria and Assessment Office; report no. EPA/600/8-89/049F. Available 

38 from: NTIS, Springfield, VA; PB91-138420. 
March 2011 8-2 Draft – Do Not Quote or Cite

1 U.S. Environmental Protection Agency. (1990b) Review of the national ambient air quality 

2 standards for lead: assessment of scientific and technical information: OAQPS staff paper. 

3 Research Triangle Park, NC: Office of Air Quality Planning and Standards; report no. EPA4 450/2-89/022. Available from: NTIS, Springfield, VA; PB91-206185. Available on the 

5 web: http://www.epa.gov/ttn/naaqs/standards/pb/data/rnaaqsl_asti.pdf 

6 U.S. Environmental Protection Agency. (1991) U.S. EPA Strategy for Reducing Lead Exposure. 

7 Available from U.S. EPA Headquarters Library/Washington, D.C. (Library Code EJBD; 

8 Item Call Number: EAP 100/1991.6; OCLC Number 2346675).. 

9 U.S. Environmental Protection Agency. (2005) Project Work Plan for Revised Air Quality Criteria 

10 for Lead. Research Triangle Park, NC: National Center for Environmental Assessment-RTP 

11 Report no. NCEA-R-1465. CASAC Review Draft. 

12 U.S. Environmental Protection Agency. (2006a) Plan for Review of the National Ambient Air 

13 Quality Standards for Lead. Office of Air Quality Planning and Standards, Research 

14 Triangle Park, NC. Available online at: 

15 http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_cr_pd.html 

16 U.S. Environmental Protection Agency. (2006b) Air Quality Criteria for Lead. Washington, DC, 

17 EPA/600/R-5/144aF. Available online at: www.epa.gov/ncea/ 

18 U.S. Environmental Protection Agency. (2006c) Analysis Plan for Human Health and Ecological 

19 Risk Assessment for the Review of the Lead National Ambient Air Quality Standards. 

20 Office of Air Quality Planning and Standards, Research Triangle Park, NC. Available online 

21 at: http://www.epa.gov/ttn/naaqs/standards/pb/s_pb_cr_pd.html

22 U.S. Environmental Protection Agency. (2007a) Lead: Human Exposure and Health Risk 

23 Assessments for Selected Case Studies, Volume I. Human Exposure and Health Risk 

24 Assessments – Full-Scale and Volume II. Appendices. Office of Air Quality Planning and 

25 Standards, Research Triangle Park, NC. EPA-452/R-07-014a and EPA-452/R-07-014b. 

26 U.S. Environmental Protection Agency. (2007b) Review of the National Ambient Air Quality 

27 Standards for Lead: Policy Assessment of Scientific and Technical Information, OAQPS 

28 Staff Paper. EPA-452/R-07-013. Office of Air Quality Planning and Standards, Research 

29 Triangle Park, NC. 

30 U.S. Environmental Protection Agency. (2010) Integrated Science Assessment for Carbon 

31 Monoxide. EPA/600/R-09/019F. National Center for Environmental Assessment-RTP 

32 Division, Research Triangle Park, NC. 
March 2011 A-1 Draft – Do Not Quote or Cite 

Appendix A 

Integrated Science Assessment for Lead – Outline 

 
March 2011 A-2 Draft – Do Not Quote or Cite 

Integrated Science Assessment for Lead 

Chapter 1 Introduction 

1.1 Legislative Requirements 

1.2 History of Reviews of the NAAQS for Pb 

1.3 ISA Development 

1.4 Document Organization 

1.5 Document Scope 

1.6 EPA Framework for Causal Determination 

1.7 Summary 

Chapter 2 Integrative Overview 

2.1 Ambient Pb Sources and Concentrations 

2.2 Exposure to Ambient Pb 

2.3 Kinetics, Biomarkers, and Models Relating Pb Exposure to Dose Metrics 

2.4 Mode of Action 

2.5 Pb Health Effects 

2.6 Policy Relevant Considerations 

2.7 Ecological and Other Welfare Effects 

2.8 Integration of Health and Ecosystem Effects of Pb 

Chapter 3 Ambient Pb Source to Concentration 

3.1 Introduction 

3.2 Sources of Atmospheric Pb 

3.3 Fate and Transport of Pb 

3.4 Monitoring of Ambient Pb 

3.5 Ambient Pb Air Pb Concentrations 

3.6 Ambient Pb Concentrations in Non-Air Media and Biota 

3.7 Summary 

Chapter 4 Toxicokinetics, Biomarkers and Models of Pb Burden in Humans 

4.1 Pb Exposure Assessment 

4.2 Kinetics of Pb 

4.3 Biomarkers of Pb 

4.4 Empirical Models of Pb Exposure-Blood Pb Relationships 

4.5 Biokinetic Models of Pb Exposure-Blood Pb Relationships 

Chapter 5 Integrated Health Effects of Pb Exposure 

5.1 Introduction 

5.2 Modes of Action 

5.3 Neurotoxic Effects of Pb 

5.4 Cardiovascular Effects of Pb 

5.4.1 Mortality Effects 

5.5 Renal Effects 

5.6 Effects of Pb on the Immune System 

5.7 Carcinogenic and Genotoxic Potential of Pb 
March 2011 A-3 Draft – Do Not Quote or Cite 

5.8 Effects of Pb on Heme Synthesis and RBC Function 

5.9 Effects of Pb on the Reproductive System 

5.10 Effects of Pb on Other Organ Systems 

5.11 Summary 

Chapter 6 Susceptible Populations 

6.1 Susceptibility Factors and Biomarkers of Pb Exposure 

6.2 Susceptibility Factors Related to Pb-induced Health Effects 

6.3 Summary 

Chapter 7 Ecological Effects and Other Welfare Effects of Pb 

7.1 Introduction to Ecological Concepts 

7.2 Terrestrial Ecosystem Effects 

7.3 Aquatic Ecosystem Effects 

7.4 Summary
United States 

Environmental Protection Agency 

Office of Air Quality Planning and Standards 

Health and Environmental Impacts Division 

Research Triangle Park, NC 

Publication No. EPA-452/D-11-001

March 2011