National Ambient Air Quality Standards for Lead, 71488-71544 [E7-23884]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 72, Number 241 (Monday, December 17, 2007)]
[Proposed Rules]
[Pages 71488-71544]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-23884]



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Part II





Environmental Protection Agency





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40 CFR Part 50



National Ambient Air Quality Standards for Lead; Proposed Rule

Federal Register / Vol. 72 , No. 241 / Monday, December 17, 2007 / 
Proposed Rules

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 50

[EPA-HQ-OAR-2006-0735; FRL-8503-8 ]
RIN 2060-AN83


National Ambient Air Quality Standards for Lead

AGENCY: Environmental Protection Agency (EPA).

ACTION: Advance notice of proposed rulemaking (ANPR).

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SUMMARY: EPA is issuing this ANPR to invite comment from all interested 
parties on policy options and other issues related to the Agency's 
ongoing review of the national ambient air quality standards (NAAQS) 
for lead (Pb). Consistent with recent modifications the Agency has made 
to its process for reviewing NAAQS, we are seeking broad public comment 
at this time to help inform the Agency's future proposed decisions on 
the adequacy of the current Pb NAAQS and on any revisions of the Pb 
NAAQS that may be appropriate. EPA is also soliciting comment on 
retaining Pb on the list of criteria pollutants and on maintaining 
NAAQS for Pb.
    As part of this review, the Agency has released several key 
documents that will inform the Agency's rulemaking. These documents 
include the Air Quality Criteria for Lead, released in 2006, which 
critically assesses and integrates relevant scientific information; 
risk assessment reports including the most recent report, Lead: Human 
Exposure and Health Risk Assessment for Selected Case Studies, which 
documents quantitative exposure analyses and risk assessments conducted 
for this review; and a recently released Staff Paper, Review of the 
National Ambient Air Quality Standards for Lead: Policy Assessment of 
Scientific and Technical Information, which presents an evaluation by 
staff in EPA's Office of Air Quality Planning and Standards (OAQPS) of 
the policy implications of the scientific information and quantitative 
assessments and OAQPS staff conclusions and recommendations on a range 
of policy options for the Agency's consideration.
    Under the terms of a court order, the Administrator will sign by 
September 1, 2008 a Notice of Final Rulemaking for publication in the 
Federal Register. To meet this schedule, we anticipate the 
Administrator will sign a Notice of Proposed Rulemaking in March 2008 
for publication in the Federal Register, at which time further 
opportunity for public comment will be provided.

DATES: Comments must be received by January 16, 2008.

ADDRESSES: Submit your comments, identified by Docket ID No. EPA-HQ-
OAR-2006-0735 by one of the following methods:
     https://www.regulations.gov: Follow the on-line 
instructions for submitting comments.
     E-mail: a-and-r-Docket@epa.gov.
     Fax: 202-566-9744.
     Mail: Docket No. EPA-HQ-OAR-2006-0735, Environmental 
Protection Agency, Mail code 6102T, 1200 Pennsylvania Ave., NW., 
Washington, DC 20460. Please include a total of two copies.
     Hand Delivery: Docket No. EPA-HQ-OAR-2006-0735, 
Environmental Protection Agency, EPA West, Room 3334, 1301 Constitution 
Ave., NW., Washington, DC. Such deliveries are only accepted during the 
Docket's normal hours of operation, and special arrangements should be 
made for deliveries of boxed information.
    Instructions: Direct your comments to Docket ID No. EPA-HQ-OAR-
2006-0735. The EPA's policy is that all comments received will be 
included in the public docket without change and may be made available 
online at https://www.regulations.gov, including any personal 
information provided, unless the comment includes information claimed 
to be Confidential Business Information (CBI) or other information 
whose disclosure is restricted by statute. Do not submit information 
that you consider to be CBI or otherwise protected through https://
www.regulations.gov or e-mail. The https://www.regulations.gov Web site 
is an ``anonymous access'' system, which means EPA will not know your 
identity or contact information unless you provide it in the body of 
your comment. If you send an e-mail comment directly to EPA without 
going through https://www.regulations.gov, your e-mail address will be 
automatically captured and included as part of the comment that is 
placed in the public docket and made available on the Internet. If you 
submit an electronic comment, EPA recommends that you include your name 
and other contact information in the body of your comment and with any 
disk or CD-ROM you submit. If EPA cannot read your comment due to 
technical difficulties and cannot contact you for clarification, EPA 
may not be able to consider your comment. Electronic files should avoid 
the use of special characters, any form of encryption, and be free of 
any defects or viruses. For additional information about EPA's public 
docket, visit the EPA Docket Center homepage at https://www.epa.gov/
epahome/dockets.htm.
    Docket: All documents in the docket are listed in the https://
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., CBI or other information 
whose disclosure is restricted by statute. Certain other material, such 
as copyrighted material, will be publicly available only in hard copy. 
Publicly available docket materials are available either electronically 
in https://www.regulations.gov or in hard copy at the Air and Radiation 
Docket and Information Center, EPA/DC, EPA West, Room 3334, 1301 
Constitution Ave., NW., Washington, DC. The Public Reading Room is open 
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744 and the telephone number for the Air and Radiation Docket and 
Information Center is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: Dr. Deirdre Murphy, Health and 
Environmental Impacts Division, Office of Air Quality Planning and 
Standards, U.S. Environmental Protection Agency, Mail code C504-06, 
Research Triangle Park, NC 27711; telephone: 919-541-0729; fax: 919-
541-0237; e-mail: Murphy.deirdre@epa.gov.

SUPPLEMENTARY INFORMATION: 

General Information

What Should I Consider as I Prepare My Comments for EPA?

    1. Submitting CBI. Do not submit this information to EPA through 
https://www.regulations.gov or e-mail. Clearly mark the part or all of 
the information that you claim to be CBI. For CBI information in a disk 
or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM 
as CBI and then identify electronically within the disk or CD ROM the 
specific information that is claimed as CBI. In addition to one 
complete version of the comment that includes information claimed as 
CBI, a copy of the comment that does not contain the information 
claimed as CBI must be submitted for inclusion in the public docket. 
Information so marked will not be disclosed except in accordance with 
procedures set forth in 40 CFR part 2.
    2. Tips for Preparing Your Comments. When submitting comments, 
remember to:
     Identify the rulemaking by docket number and other 
identifying

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information (subject heading, Federal Register date and page number).
     Follow directions--the agency may ask you to respond to 
specific questions or organize comments by referencing a Code of 
Federal Regulations (CFR) part or section number.
     Explain why you agree or disagree, suggest alternatives, 
and substitute language for your requested changes.
     Describe any assumptions and provide any technical 
information and/or data that you used.
     If you estimate potential costs or burdens, explain how 
you arrived at your estimate in sufficient detail to allow for it to be 
reproduced.
     Provide specific examples to illustrate your concerns, and 
suggest alternatives.
     Explain your views as clearly as possible, avoiding the 
use of profanity or personal threats.
     Make sure to submit your comments by the comment period 
deadline identified.

Availability of Related Information

    A number of documents relevant to this rulemaking, including the 
Air Quality Criteria for Lead (Criteria Document) (USEPA, 2006a), the 
Staff Paper, related risk assessment reports, and other related 
technical documents are available on EPA's Office of Air Quality 
Planning and Standards (OAQPS) Technology Transfer Network (TTN) Web 
site at https://www.epa.gov/ttn/naaqs/standards/pb/s_pb_index.html. 
These and other related documents are also available for inspection and 
copying in the EPA docket identified above.

Table of Contents

    The following topics are discussed in this preamble:

I. Introduction
II. Background
    A. Legislative Requirements
    B. History of Lead NAAQS Reviews
    C. Current Related Lead Control Programs
    D. Current Lead NAAQS Review
    E. Implementation Considerations
III. The Primary Standard
    A. Health Effects Information
    1. Internal Disposition--Blood Lead as Dose Metric
    2. Nature of Effects
    3. Lead-Related Impacts on Public Health
    a. At-Risk Subpopulations
    b. Potential Public Health Impacts
    4. Key Observations
    B. Human Exposure and Health Risk Assessments
    1. Overview of Risk Assessment From Last Review
    2. Design Aspects of Exposure and Risk Assessments
    a. CASAC Advice
    b. Health Endpoint, Risk Metric and Concentration-Response 
Functions
    c. Case Study Approach
    d. Air Quality Scenarios
    e. Categorization of Policy-Relevant Exposure Pathways
    f. Analytical Steps
    g. Generating Multiple Sets of Risk Results
    h. Key Limitations and Uncertainties
    3. Summary of Results
    a. Blood Pb Estimates
    b. IQ Loss Estimates
    C. Considerations in Review of the Standard
    1. Background on the Current Standard
    a. Basis for Setting the Current Standard
    b. Policy Options Considered in the Last Review
    2. Approach for Current Review
    3. Adequacy of the Current Standard
    a. Evidence-Based Considerations
    b. Exposure- and Risk-Based Considerations
    c. CASAC Advice and Recommendations
    d. Policy Options
    4. Elements of the Standard
    a. Indicator
    b. Averaging Time and Form
    c. Level
IV. The Secondary Standard
    A. Welfare Effects Information
    B. Screening Level Ecological Risk Assessment
    1. Design Aspects of the Assessment and Associated Uncertanties
    2. Summary of Results
    C. Considerations in Review of the Standard
    1. Background on the Current Standard
    2. Approach for Current Review
    3. Adequacy of the Current Standard
    a. Evidence-Based Considerations
    b. Risk-Based Considerations
    c. CASAC Advice and Recommendations
    d. Policy Options
    4. Elements of the Standard
V. Considerations for Ambient Monitoring
    A. Sampling and Analysis Methods
    B. Network Design
    C. Sampling Schedule
    D. Data Handling
    E. Monitoring for the Secondary NAAQS
VI. Solicitation of Comment
VII. Statutory and Executive Order Reviews
     References

I. Introduction

    In the past year EPA has instituted a number of changes to the 
process that the Agency uses in reviewing the NAAQS to help to improve 
the efficiency of the process while ensuring that the Agency's 
decisions are informed by the best available science and broad 
participation among experts in the scientific community and the public 
(described at https://www.epa.gov/ttn/naaqs/). These changes apply to 
the four major components of the NAAQS review process: planning, 
science assessment, risk/exposure assessment, and policy assessment/
rulemaking. The process improvements will help the Agency meet the goal 
of reviewing each NAAQS on a 5-year cycle as required by the Clean Air 
Act (CAA) without compromising the scientific integrity of the process. 
These changes are being incorporated into the various ongoing NAAQS 
reviews being conducted by the Agency, including the current review of 
the Pb NAAQS.
    The issuance of this ANPR is one of the key features of the new 
NAAQS review process. Historically, a policy assessment that evaluates 
the policy implications of the available scientific information and 
risk/exposure assessments has been presented in the form of a Staff 
Paper, prepared by staff in EPA's OAQPS, which included OAQPS staff 
conclusions and recommendations on a range of policy options for the 
Agency's consideration. The new process will enable broader 
participation of the scientific community and the public early in the 
NAAQS review by providing scientific information, risk/exposure 
assessments, and policy options in an ANPR rather than a Staff Paper. 
The purpose of the ANPR is to identify conceptual evidence- and risk-
based approaches for reaching policy judgments, discuss what the 
science and risk/exposure assessments say about the adequacy of the 
current standards, and describe a range of options for standard 
setting, in terms of indicators, averaging times, forms, and ranges of 
levels for any alternative standards. Discussion of alternative 
standards is to include a description of the underlying interpretations 
of the scientific evidence and risk/exposure information that might 
support such alternative standards and that could be considered by the 
Administrator in making NAAQS decisions. The issuance of an ANPR 
provides the opportunity for the Clean Air Scientific Advisory 
Committee (CASAC) \1\ and the public to evaluate and provide comment on 
a broad range of policy options being considered by the Administrator.
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    \1\ As discussed below in section II, CASAC is the independent 
scientific review committee that provides advice and recommendations 
to the EPA Administrator related to periodic reviews of NAAQS, as 
mandated by the Clean Air Act.
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    In the case of this Pb NAAQS review, which was initiated well 
before changes were instituted to the NAAQS review process, both an 
OAQPS Staff Paper and an ANPR are being issued. As discussed below in 
section II, the issuance of both documents reflects the terms of a 
court order that governs this review and requires that a final OAQPS 
Staff Paper be issued. As a consequence, in addition to soliciting 
comment, this ANPR summarizes information from the OAQPS Staff Paper 
(referred to as Staff Paper throughout this notice) and from

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the Agency's risk assessment and Criteria Document. This ANPR is 
structured such that policy options on adequacy of the current 
standards and aspects of potential alternative standards are discussed 
in Sections III.C and IV.C. Preceding those policy discussions are 
sections focused on health and welfare effects in Sections III.A and 
IV.A, respectively, and on human exposure and risk and ecological risk 
in Sections III.B and IV.B, respectively.

II. Background

A. Legislative Requirements

    Two sections of the Clean Air Act (Act) govern the establishment 
and revision of the NAAQS. Section 108 (42 U.S.C. 7408) directs the 
Administrator to identify and list each air pollutant that ``in his 
judgment, cause or contribute to air pollution which may reasonably be 
anticipated to endanger public health and welfare'' and whose 
``presence * * * in the ambient air results from numerous or diverse 
mobile or stationary sources'' and to issue air quality criteria for 
those that are listed. Air quality criteria are to ``accurately reflect 
the latest scientific knowledge useful in indicating the kind and 
extent of all identifiable effects on public health or welfare which 
may be expected from the presence of [a] pollutant in ambient air * * 
*''. Section 108 also states that the Administrator ``shall, from time 
to time * * * revise a list'' that includes these pollutants, which 
provides the authority for a pollutant to be removed from or added to 
the list of criteria pollutants.
    Section 109 (42 U.S.C. 7409) directs the Administrator to propose 
and promulgate ``primary'' and ``secondary'' NAAQS for pollutants 
listed under section 108. Section 109(b)(1) defines a primary standard 
as one ``the attainment and maintenance of which in the judgment of the 
Administrator, based on [air quality] criteria and allowing an adequate 
margin of safety, are requisite to protect the public health.'' \2\ A 
secondary standard, as defined in Section 109(b)(2), must ``specify a 
level of air quality the attainment and maintenance of which, in the 
judgment of the Administrator, based on 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.'' \3\
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    \2\ 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)
    \3\ 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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    The requirement that primary standards include an adequate margin 
of safety was intended to address uncertainties associated with 
inconclusive scientific and technical information available at the time 
of standard setting. It was also intended to provide a reasonable 
degree of protection against hazards that research has not yet 
identified. Lead Industries Association v. EPA, 647 F.2d 1130, 1154 (DC 
Cir 1980), cert. denied, 449 U.S. 1042 (1980); American Petroleum 
Institute v. Costle, 665 F.2d 1176, 1186 (D.C. Cir. 1981), cert. 
denied, 455 U.S. 1034 (1982). Both kinds of uncertainties are 
components of the risk associated with pollution at levels below those 
at which human health effects can be said to occur with reasonable 
scientific certainty. Thus, in selecting primary standards that include 
an adequate margin of safety, the Administrator is seeking not only to 
prevent pollution levels that have been demonstrated to be harmful but 
also to prevent lower pollutant levels that may pose an unacceptable 
risk of harm, even if the risk is not precisely identified as to nature 
or degree.
    In selecting a margin of safety, EPA considers such factors as the 
nature and severity of the health effects involved, the size of the 
sensitive population(s) at risk, and the kind and degree of the 
uncertainties that must be addressed. The selection of any particular 
approach to providing an adequate margin of safety is a policy choice 
left specifically to the Administrator's judgment. Lead Industries 
Association v. EPA, supra, 647 F.2d at 1161-62.
    In setting standards that are ``requisite'' to protect public 
health and welfare, as provided in section 109(b), EPA's task is to 
establish standards that are neither more nor less stringent than 
necessary for these purposes. In so doing, EPA may not consider the 
costs of implementing the standards. See generally Whitman v. American 
Trucking Associations, 531 U.S. 457, 471, 475-76 (2001).
    Section 109(d)(1) of the Act requires that ``Not later than 
December 31, 1980, and at 5-year intervals thereafter, the 
Administrator shall complete a thorough review of the criteria 
published under section 108 and the national ambient air quality 
standards promulgated under this section and shall make such revisions 
in such criteria and standards and promulgate such new standards as may 
be appropriate in accordance with section 108 and subsection (b) of 
this section. The Administrator may review and revise criteria or 
promulgate new standards earlier or more frequently than required under 
this paragraph.'' Section 109(d)(2)(A) requires that ``The 
Administrator shall appoint an independent scientific review committee 
composed of seven members including at least one member of the National 
Academy of Sciences, one physician, and one person representing State 
air pollution control agencies.'' Section 109(d)(2)(B) requires that, 
``Not later than January 1, 1980, and at five-year intervals 
thereafter, the committee referred to in subparagraph (A) shall 
complete a review of the criteria published under section 108 and the 
national primary and secondary ambient air quality standards 
promulgated under this section and shall recommend to the Administrator 
any new national ambient air quality standards and revisions of 
existing criteria and standards as may be appropriate under section 108 
and subsection (b) of this section.'' \4\ Since the early 1980's, this 
independent review function has been performed by the Clean Air 
Scientific Advisory Committee (CASAC) of EPA's Science Advisory Board.
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    \4\ In addition to the provisions of Section 109(d)(2)(B), 
concerning the role of CASAC in providing advice and recommendations 
to the Administrator on the criteria and standards, Section 
109(d)(2)(C) provides that CASAC shall also, ``(i) advise the 
Administrator of areas in which additional knowledge is required to 
appraise the adequacy and basis of existing, new, or revised 
national ambient air quality standards, (ii) describe the research 
efforts necessary to provide the required information, (iii) advise 
the Administrator on the relative contribution to air pollution 
concentrations of natural as well as anthropogenic activity, and 
(iv) advise the Administrator of any adverse public health, welfare, 
social economic, or energy effects which may result from various 
strategies for attainment and maintenance of such national ambient 
air quality standards.''
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B. History of Lead NAAQS Reviews

    On October 5, 1978 EPA promulgated primary and secondary NAAQS for 
Pb 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 ([mu]g/m\3\), measured as Pb in total suspended particulate 
matter (Pb-TSP), not to be exceeded by the maximum arithmetic mean 
concentration averaged over a calendar quarter. This standard was based 
on the 1977 Air Quality Criteria for Lead (USEPA, 1977).

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    A review of the Pb standards was initiated in the mid-1980s. The 
scientific assessment for that review is described in the 1986 Air 
Quality Criteria for Lead (USEPA, 1986a), the associated Addendum 
(USEPA, 1986b) and the 1990 Supplement (USEPA, 1990a). As part of the 
review, the Agency designed and performed human exposure and health 
risk analyses (USEPA, 1989), the results of which were presented in a 
1990 Staff Paper (USEPA, 1990b). Based on the scientific assessment and 
the human exposure and health risk analyses, the 1990 Staff Paper 
presented options for the Pb NAAQS level in the range of 0.5 to 1.5 
[mu]g/m\3\, and suggested the second highest monthly average in three 
years for the form and averaging time of the standard (USEPA, 1990b). 
After consideration of the documents developed during the review and 
the significantly changed circumstances since Pb was listed in 1976, as 
noted above, the Agency did not propose any revisions to the 1978 Pb 
NAAQS. In a parallel effort, the Agency developed the broad, multi-
program, multimedia, integrated U.S. Strategy for Reducing Lead 
Exposure (USEPA, 1991). As part of implementing this strategy, the 
Agency focused efforts primarily on regulatory and remedial clean-up 
actions aimed at reducing Pb exposures from a variety of nonair sources 
judged to pose more extensive public health risks to U.S. populations, 
as well as on actions to reduce Pb emissions to air.

C. Current Related Lead Control Programs

    States are primarily responsible for ensuring attainment and 
maintenance of ambient air quality standards once EPA has established 
them. Under section 110 of the Act (42 U.S.C. 7410) and related 
provisions, States are to submit, for EPA approval, State 
implementation plans (SIP's) that provide for the attainment and 
maintenance of such standards through control programs directed to 
sources of the pollutants involved. The States, in conjunction with 
EPA, also administer the prevention of significant deterioration 
program (42 U.S.C. 7470-7479) for these pollutants. In addition, 
Federal programs provide for nationwide reductions in emissions of 
these and other air pollutants through the Federal Motor Vehicle 
Control Program under Title II of the Act (42 U.S.C. 7521-7574), which 
involves controls for automobile, truck, bus, motorcycle, nonroad 
engine, and aircraft emissions; the new source performance standards 
under section 111 of the Act (42 U.S.C. 7411); and the national 
emission standards for hazardous air pollutants under section 112 of 
the Act (42 U.S.C. 7412).
    As Pb is a multimedia pollutant, a broad range of Federal programs 
beyond those identified above that focus on air pollution control 
provide for nationwide reductions in environmental releases and human 
exposures. The Centers for Disease Control and Prevention (CDC) 
programs provide for the tracking of children's blood Pb levels 
nationally and provide guidance on levels at which medical and 
environmental case management activities should be implemented (CDC, 
2005a; ACCLPP, 2007).\5\ In 1991, the Secretary of the Health and Human 
Services (HHS) characterized Pb poisoning as the ``number one 
environmental threat to the health of children in the United States'' 
(Alliance to End Childhood Lead Poisoning. 1991). And, in 1997, 
President Clinton created, by Executive Order 13045, the President's 
Task Force on Environmental Health Risks and Safety Risks to Children 
in response to increased awareness that children face disproportionate 
risks from environmental health and safety hazards (62 FR 19885).\6\ By 
Executive Orders issued in October 2001 and April 2003, President Bush 
extended the work for the Task Force for an additional three and a half 
years beyond its original charter (66 FR 52013 and 68 FR 19931). The 
Task Force set a Federal goal of eliminating childhood Pb poisoning by 
the year 2010 and reducing Pb poisoning in children was the Task 
Force's top priority.
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    \5\ As described in Section III below the CDC stated in 2005 
that no ``safe'' threshold for blood Pb levels in young children has 
been identified (CDC, 2005a).
    \6\ Co-chaired by the Secretary of the HHS and the Administrator 
of the EPA, the Task Force consisted of representatives from 16 
Federal departments and agencies.
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    Federal abatement programs provide for the reduction in human 
exposures and environmental releases from in-place materials containing 
Pb (e.g., Pb-based paint, urban soil and dust and contaminated waste 
sites). Federal regulations on disposal of Pb-based paint waste help 
facilitate the removal of Pb-based paint from residences (See 
``Criteria for Classification of Solid Waste Disposal Facilities and 
Practices and Criteria for Municipal Solid Waste Landfills: Disposal of 
Residential Lead-Based Paint Waste; Final Rule'' EPA-HQ-RCRA-2001-
0017). Further, in 1991, EPA lowered the maximum levels of Pb permitted 
in public water systems from 50 parts per billion (ppb) to 15 ppb (56 
FR 26460).
    Federal programs to reduce exposure to Pb in paint, dust and soil 
are specified under the comprehensive federal strategy developed under 
the Residential Lead-Based Paint Hazard Reduction Act (Title X). Under 
Title X and Title IV of the Toxic Substances Control Act, EPA has 
established regulations in the following four categories: (1) Training 
and certification requirements for persons engaged in lead-based paint 
activities; accreditation of training providers; work practice 
standards for the safe, reliable, and effective identification and 
elimination of lead-based paint hazards; (2) Ensuring that, for most 
housing constructed before 1978, lead-based paint information flows 
from sellers to purchasers, from landlords to tenants, and from 
renovators to owners and occupants; (3) Establishing standards for 
identifying dangerous levels of lead in paint, dust and soil; and (4) 
Providing information on lead hazards to the public, including steps 
that people can take to protect themselves and their families from 
lead-based paint hazards.
    Under Title X of TSCA, EPA established dust lead standards for 
residential housing and soil dust in 2001. This regulation supports the 
implementation of other regulations which deal with worker training and 
certification, lead hazard disclosure in real estate transactions, lead 
hazard evaluation and control in federally-owned housing prior to sale 
and housing receiving Federal assistance, and U.S. Department of 
Housing and Urban Development grants to local jurisdictions to perform 
lead hazard control. In addition, this regulation also establishes, 
among other things, under authority of TSCA section 402, residential 
lead dust cleanup levels and amendments to dust and soil sampling 
requirements (66 FR 1206). The Title X term ``lead-based paint hazard'' 
implemented through this regulation identifies lead-based paint and all 
residential lead-containing dusts and soils regardless of the source of 
lead, which, due to their condition and location, would result in 
adverse human health effects. One of the underlying principles of Title 
X is to move the focus of public and private decision makers away from 
the mere presence of lead-based paint, to the presence of lead-based 
paint hazards, for which more substantive action should be undertaken 
to control exposures, especially to young children. In addition the 
success of the program will rely on the voluntary participation of 
states and tribes as well as counties and cities to implement the 
programs and on property owners to follow the standards and EPA's 
recommendations. If EPA

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were to set unreasonable standards (e.g., standards that would 
recommend removal of all lead from paint, dust and soil), States and 
Tribes may choose to opt out of the Title X lead program and property 
owners may choose to ignore EPA's advice believing it lacks credibility 
and practical value. Consequently, EPA needed to develop standards that 
would not waste resources by chasing risks of negligible importance and 
that would be accepted by States, Tribes, local governments and 
property owners.
    On January 10, 2006, EPA issued a Notice of Proposed Rulemaking 
covering renovations performed for compensation in target housing. The 
2006 Proposal contains requirements designed to address lead hazards 
created by renovation, repair, and painting activities that disturb 
lead-based paint. The 2006 Proposal includes requirements for training 
renovators, other renovation workers, and dust sampling technicians; 
for certifying renovators, dust sampling technicians, and renovation 
firms; for accrediting providers of renovation and dust sampling 
technician training; for renovation work practices; and for 
recordkeeping. The 2006 Proposal proposes to make the rule effective in 
two stages. Initially, the rule proposes to apply to all renovations 
for compensation performed in target housing where a child with an 
increased blood lead level resided and rental target housing built 
before 1960. The proposed rule also proposes application to owner-
occupied target housing built before 1960, unless the person performing 
the renovation obtained a statement signed by the owner-occupant that 
the renovation would occur in the owner's residence and that no child 
under age 6 resided there. As proposed, the rule would take effect one 
year later in all rental target housing built between 1960 and 1978 and 
owner-occupied target housing built between 1960 and 1978. EPA also 
proposes to allow interested States, Territories, and Indian Tribes the 
opportunity to apply for and receive authorization to administer and 
enforce all of the elements of the new renovation provisions.
    A significant number of commenters observed that the proposal did 
not cover buildings where children under age 6 spend a great deal of 
time, such as day care centers and schools. Commenters noted that the 
risk posed to children from lead-based paint hazards in schools and 
day-care centers is likely to be equal to, if not greater than, the 
risk posed from these hazards at home. These commenters suggested that 
EPA expand its proposal to include such places, and several suggested 
that EPA use the existing definition of ``child-occupied facility'' in 
40 CFR Sec.  745.223 to define the expanded scope of coverage. EPA felt 
that these comments had merit, and, because adding child-occupied 
facilities was beyond the scope of the 2006 Proposal, an expansion of 
the 2006 Proposal was necessary to give this issue full and fair 
consideration. Accordingly, on June 5, 2007, EPA issued a Supplemental 
Notice of Proposed Rulemaking to add child-occupied facilities to the 
universe of buildings covered by the 2006 Proposal. EPA is working 
expeditiously to finalize this rulemaking and expects to do so in the 
first calendar quarter of 2008.
    Programs associated with the Comprehensive Environmental Response, 
Compensation, and Liability Act (CERCLA or Superfund) and Resource 
Conservation Recovery Act (RCRA) also implement abatement programs, 
reducing exposures to Pb and other pollutants. For example, EPA 
determines and implements protective levels for Pb in soil at Superfund 
sites and RCRA corrective action facilities. Federal programs, 
including those implementing RCRA, provide for management of hazardous 
substances in hazardous and municipal solid waste (e.g., ``Hazardous 
Waste Management System; Identification and Listing of Hazardous Waste: 
Inorganic Chemical Manufacturing Wastes; Land Disposal Restrictions for 
Newly Identified Wastes and CERCLA Hazardous Substance Designation and 
Reportable Quantities; Final Rule'', https://www.epa.gov/epaoswer/
hazwaste/state/revision/frs/fr195.pdf and https://www.epa.gov/epaoswer/
hazwaste/ldr/basic.htm). For example, Federal regulations concerning 
batteries in municipal solid waste facilitate the collection and 
recycling or proper disposal of batteries containing Pb (e.g., See 
``Implementation of the Mercury-Containing and Rechargeable Battery 
Management Act'' https://www.epa.gov/epaoswer/hazwaste/recycle/
battery.pdf and ``Municipal Solid Waste Generation, Recycling, and 
Disposal in the United States: Facts and Figures for 2005'' https://
www.epa.gov/epaoswer/osw/conserve/resources/msw-2005.pdf). Similarly, 
Federal programs provide for the reduction in environmental releases of 
hazardous substances such as Pb in the management of wastewater (http:/
/www.epa.gov/owm/).
    A variety of federal nonregulatory programs also provide for 
reduced environmental release of Pb containing materials through more 
general encouragement of pollution prevention, promote reuse and 
recycling, reduce priority and toxic chemicals in products and waste, 
and conserve energy and materials. These include the Resource 
Conservation Challenge (https://www.epa.gov/epaoswer/osw/conserve/
index.htm), the National Waste Minimization Program (https://
www.epa.gov/epaoswer/hazwaste/minimize/leadtire.htm), ``Plug in to 
eCycling'' (a partnership between EPA and consumer electronics 
manufacturers and retailers; https://www.epa.gov/epaoswer/hazwaste/
recycle/electron/crt.htm#crts), and activities to reduce the practice 
of backyard trash burning (https://www.epa.gov/msw/backyard/pubs.htm).
    Efforts such as those programs described above have been successful 
in that blood Pb levels in all segments of the population have dropped 
significantly from levels around 1990. In particular, blood Pb levels 
for the general population of children 1 to 5 years of age have dropped 
to a median level of 1.6 [mu]g/dL and a level of 3.9 [mu]g/dL for the 
90th percentile child in the 2003-2004 NHANES as compared to median and 
90th percentile levels in 1988-1991 of 3.5 [mu]g/dL and 9.4 [mu]g/dL, 
respectively (https://www.epa.gov/envirohealth/children/body_burdens/
b1-table.htm). These levels (median and 90th percentile) for the 
general population of young children \7\ are at the low end of the 
historic range of blood Pb levels for general population of children 
aged 1-5 years and are below a level of 5 [mu]g/dL--a level that has 
been associated with adverse effects with a higher degree of certainty 
in the published literature (than levels such as 2 [mu]g/dL) and is a 
level where cognitive deficits were identified with statistical 
significance (Lanphear et al., 2000). The decline in blood Pb levels in 
the United States has resulted from coordinated, intensive efforts at 
the national, state and local levels. The Agency has continued to 
grapple with soil and dust Pb levels from the historical use of Pb in 
paint and gasoline and other sources. In doing so, the agency has faced 
the difficulty of determining the level at which to set standards for 
residential dust levels given the uncertainties at what environmental 
levels and in which specific medium may actually cause particular blood 
Pb levels that are

[[Page 71493]]

associated with adverse effects (66 FR 1206).\8\
---------------------------------------------------------------------------

    \7\ It is noted that although the 95th percentile value for the 
2003-2004 NHANES is not currently available, that value for 2001-
2002 was 5.8 [mu]g/dL. Also, as discussed in Section III.A.1 
(including footnote 15), levels have been found to vary among 
children of different socioeconomic status and other demographic 
characteristics (CD, p. 4-21).
    \8\ See 2001 regulation to establish standards for lead-based 
paint hazards in most pre-1978 housing and child-occupied facilities 
(66 FR 1206).
---------------------------------------------------------------------------

    EPA's research program, with other Federal agencies defines, 
encourages and conducts research needed to locate and assess serious 
risks and to develop methods and tools to characterize and help reduce 
risks. For example, EPA's Integrated Exposure Uptake Biokinetic Model 
for Lead in Children (IEUBK model) for Pb in children and the Adult 
Lead Methodology are widely used and accepted as tools that provide 
guidance in evaluating site specific data. More recently, in 
recognition of the need for a single model that predicts Pb 
concentrations in tissues for children and adults, EPA is developing 
the All Ages Lead Model (AALM) to provide researchers and risk 
assessors with a pharmacokinetic model capable of estimating blood, 
tissue, and bone concentrations of Pb based on estimates of exposure 
over the lifetime of the individual. EPA research activities on 
substances including Pb focus on better characterizing aspects of 
health and environmental effects, exposure and control or management of 
environmental releases (see https://www.epa.gov/ord/
researchaccomplishments/).

D. Current Lead NAAQS Review

    EPA initiated the current review of the air quality criteria for Pb 
on November 9, 2004 with a general call for information (69 FR 64926). 
A project work plan (USEPA, 2005a) for the preparation of the Criteria 
Document was released in January 2005 for CASAC and public review. EPA 
held a series of workshops in August 2005, with invited recognized 
scientific experts to discuss initial draft materials that dealt with 
various lead-related issues being addressed in the Pb air quality 
criteria document. The first draft of the Criteria Document (USEPA, 
2005b) was released for CASAC and public review in December 2005 and 
discussed at a CASAC meeting held on February 28-March 1, 2006.
    A second draft Criteria Document (USEPA, 2006b) was released for 
CASAC and public review in May 2006, and discussed at the CASAC meeting 
on June 28, 2006. A subsequent draft of Chapter 7--Integrative 
Synthesis (Chapter 8 in the final Criteria Document), released on July 
31, 2006, was discussed at an August 15, 2006 CASAC teleconference. The 
final Criteria Document was released on September 30, 2006 (USEPA, 
2006a; cited throughout this preamble as CD). While the Criteria 
Document focuses on new scientific information available since the last 
review, it integrates that information with scientific criteria from 
previous reviews.
    In February 2006, EPA released the Plan for Review of the National 
Ambient Air Quality Standards for Lead (USEPA 2006c) that described 
Agency plans and a timeline for reviewing the air quality criteria, 
developing human exposure and risk assessments and an ecological risk 
assessment, preparing a policy assessment, and developing the proposed 
and final rulemakings.
    In May 2006, EPA released for CASAC and public review a draft 
Analysis Plan for Human Health and Ecological Risk Assessment for the 
Review of the Lead National Ambient Air Quality Standards (USEPA, 
2006d), which was discussed at a June 29, 2006 CASAC meeting 
(Henderson, 2006). The May 2006 assessment plan discussed two 
assessment phases: a pilot phase and a full-scale phase. The pilot 
phase of both the human health and ecological risk assessments was 
presented in the draft Lead Human Exposure and Health Risk Assessments 
and Ecological Risk Assessment for Selected Areas (ICF, 2006; 
henceforth referred to as the first draft Risk Assessment Report) which 
was released for CASAC and public review in December 2006. The first 
draft Staff Paper, also released in December 2006, discussed the pilot 
assessments and the most policy-relevant science from the Criteria 
Document. These documents were reviewed by CASAC and the public at a 
public meeting on February 6-7, 2007 (Henderson, 2007a).
    Subsequent to that meeting, EPA conducted full-scale human exposure 
and health risk assessments, although no further work was done on the 
ecological assessment due to resource limitations. A second draft Risk 
Assessment Report (USEPA, 2007a), containing full-scale human exposure 
and health risk assessments, was released in July 2007 for review by 
CASAC at a meeting held on August 28-29, 2007. Taking into 
consideration CASAC comments (Henderson, 2007b) and public comments on 
that document, we conducted additional human exposure and health risk 
assessments. A final Risk Assessment Report (USEPA, 2007b) and final 
Staff Paper (USEPA, 2007c) were released on November 1, 2007.
    The final Staff Paper presents OAQPS staff's evaluation of the 
policy implications of the key studies and scientific information 
contained in the Criteria Document and presents and interprets results 
from the quantitative risk/exposure analyses conducted for this review. 
Further, the Staff Paper presents OAQPS staff recommendations on a 
range of policy options for the Administrator to consider concerning 
whether, and if so how, to review the primary and secondary Pb NAAQS. 
Such an evaluation is intended to help ``bridge the gap'' between the 
scientific assessment contained in the Criteria Document and the 
judgments required of the EPA Administrator in determining whether it 
is appropriate to retain or revise the NAAQS for Pb. In evaluating the 
adequacy of the current standard and a range of policy alternatives, 
the Staff Paper considered the available scientific evidence and 
quantitative risk-based analyses, together with related limitations and 
uncertainties, and focused on the information that is most pertinent to 
evaluating the basic elements of air quality standards: Indicator,\9\ 
averaging time, form,\10\ and level. These elements, which together 
serve to define each standard, must be considered collectively in 
evaluating the health and welfare protection afforded by the Pb 
standards. The information, conclusions, and OAQPS staff 
recommendations presented in the Staff Paper were informed by comments 
and advice received from CASAC in its reviews of the earlier draft 
Staff Paper and drafts of related risk/exposure assessment reports, as 
well as comments on these earlier draft documents submitted by public 
commenters.
---------------------------------------------------------------------------

    \9\ The ``indicator'' of a standard defines the chemical species 
or mixture that is to be measured in determining whether an area 
attains the standard.
    \10\ 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.
---------------------------------------------------------------------------

    The schedule for completion of this review is governed by a 
judicial order resolving a lawsuit filed in May 2004, alleging that EPA 
had failed to complete the current review within the period provided by 
statute. Missouri Coalition for the Environment, v. EPA (No. 
4:04CV00660 ERW, Sept. 14, 2005). The order that now governs this 
review, entered by the court on September 14, 2005, provides that EPA 
finalize the Staff Paper no later than November 1, 2007, which we have 
done. The order also specifies that EPA sign, for publication, notices 
of proposed and final rulemaking concerning its review of the Pb NAAQS 
no later than May 1, 2008 and September 1, 2008, respectively. To 
ensure that the ordered final rulemaking deadline will be met, EPA has 
set an interim target date for a proposed rulemaking of March 2008.

[[Page 71494]]

    The EPA invites general, specific, and/or technical comments on all 
issues discussed in this ANPR, including issues related to the Agency's 
review of the primary and secondary Pb NAAQS (sections III and IV 
below) and associated monitoring considerations (section V below). EPA 
also invites comments on all information, findings, and recommendations 
presented in this notice (section VI below).
    A public meeting of the CASAC will be held on December 12-13, 2007 
for the purpose of providing advice and recommendations to the 
Administrator based on its review of this ANPR and the recently 
released final Staff Paper and Risk Assessment Report. Information 
about this meeting was published in the Federal Register on November 
20, 2007 (72 FR 65335-65336).

E. Implementation Considerations

    Currently only two areas in the United States are designated as 
non-attainment of the Pb NAAQS. If the Pb NAAQS is significantly 
lowered as a result of this review, it is likely (based on a review of 
the current air quality monitoring data) that many more areas would be 
classified as non-attainment (see section 2.3.2.5 of the Staff Paper 
for more details). States with Pb non-attainment areas would be 
required to develop ``State Implementation Plans'' that identify and 
implement specific air pollution control measures that would reduce the 
ambient Pb concentrations to below the Pb NAAQS. If the Pb NAAQS is 
revised to a lower level, States may be able to attain the revised 
NAAQS by implementing air pollution controls on lead emitting 
industrial sources. These controls include such measures as fabric 
filter particulate controls and fugitive dust controls. However, at 
some of the lower Pb concentration levels that have been identified for 
consideration in this review, it may become necessary in some areas to 
implement controls on nonindustrial sources such as dust from roadways, 
dust from construction, and/or demolition sites.
    As described in further detail in the Staff Paper (see Section 
2.2), Pb is emitted from a wide variety of source types. The top five 
categories of sources of Pb emissions included in the EPA's 2002 
National Emissions Inventory (NEI) include: Mobile sources; \11\ 
industrial, commercial, institutional and process boilers; utility 
boilers; iron and steel foundries; and primary Pb smelting (see Staff 
Paper Section 2.2).
---------------------------------------------------------------------------

    \11\ The emissions estimates identified as mobile sources in the 
current NEI are currently limited to combustion of general aviation 
gas in piston-engine aircraft. Lead emissions estimates for other 
mobile source emissions of Pb (e.g., brake wear, tire wear, and 
others) are not included in the current NEI.
---------------------------------------------------------------------------

III. The Primary Standard

    This section presents information relevant to the review of the 
primary Pb NAAQS, including information on the health effects 
associated with Pb exposures, results of the human exposure and health 
risk assessment, and considerations related to evaluating the adequacy 
of the current standard and alternative standards that might be 
appropriate for the Administrator to consider.

A. Health Effects Information

    The following summary focuses on health endpoints associated with 
the range of exposures considered to be most relevant to current 
exposure levels and makes note of several key aspects of the health 
evidence for Pb. First, because exposure to atmospheric Pb particles 
occurs not only via direct inhalation of airborne particles, but also 
via ingestion of deposited particles (e.g., associated with soil and 
dust), the exposure being assessed is multimedia and multi-pathway in 
nature, occurring via both the inhalation and ingestion routes. In 
fact, ingestion of indoor dust can be recognized as a significant Pb 
exposure pathway, particularly for young children, for which dust 
ingested via hand-to-mouth activity can be a more important source of 
Pb exposure than inhalation, although dust can be resuspended through 
household activities and pose an inhalation risk as well (CD, p. 3-27 
to 3-28).\12\ Some studies have found that dietary intake of Pb may be 
a predominant source of Pb exposure among adults, greater than 
consumption of water and beverages or inhalation (CD, p. 3-43).\13\ 
Second, the exposure index or dose metric most commonly used and 
associated with health effects information is an internal biomarker 
(i.e., blood Pb). Additionally, the exposure duration of interest 
(i.e., that influencing internal dose pertinent to health effects of 
interest) may span months to potentially years, as does the time scale 
of the environmental processes influencing Pb deposition and fate. 
Lastly, the nature of the evidence for the health effects of greatest 
interest for this review, neurological effects in young children, are 
epidemiological data substantiated by toxicological data that provide 
biological plausibility and insights on mechanisms of action (CD, 
sections 5.3, 6.2 and 8.4.2).
---------------------------------------------------------------------------

    \12\ For example, the Criteria Document states the following: 
``Given the large amount of time people spend indoors, exposure to 
Pb in dusts and indoor air can be significant. For children, dust 
ingested via hand-to-mouth activity is often a more important source 
of Pb exposure than inhalation. Dust can be resuspended through 
household activities, thereby posing an inhalation risk as well. 
House dust Pb can derive both from Pb-based paint and from other 
sources outside the home. The latter include Pb-contaminated 
airborne particles from currently operating industrial facilities or 
resuspended soil particles contaminated by deposition of airborne Pb 
from past emissions.'' (CD, p. E-6)
    \13\ Some recent exposure studies have evaluated the relative 
importance of diet to other routes of Pb exposure. In reports from 
the NHEXAS, Pb concentrations measured in households throughout the 
Midwest were significantly higher in solid food compared to 
beverages and tap water (Clayton et al., 1999; Thomas et al., 1999). 
However, beverages appeared to be the dominant dietary pathway for 
Pb according to the statistical analysis (Clayton et al., 1999), 
possibly indicating greater bodily absorption of Pb from liquid 
sources (Thomas et al., 1999). Dietary intakes of Pb were greater 
than those calculated for intake from home tap water or inhalation 
on a [mu]g/day basis (Thomas et al., 1999). The NHEXAS study in 
Arizona showed that, for adults, ingestion was a more important Pb 
exposure route than inhalation (O'Rourke et al., 1999). (CD, p. 3-
43)
---------------------------------------------------------------------------

    In recognition of the multi-pathway aspects of Pb, and the use of 
an internal exposure metric in health risk assessment, the next section 
describes the internal disposition or distribution of Pb, and the use 
of blood Pb as an internal exposure or dose metric. This is followed by 
a discussion of the nature of Pb-induced health effects that emphasizes 
those with the strongest evidence. Potential impacts of Pb exposures on 
public health, including recognition of potentially susceptible or 
vulnerable subpopulations, are then discussed. Finally, key 
observations about Pb-related health effects are summarized.
1. Internal Disposition--Blood Lead as Dose Metric
    The health effects of Pb are remote from the portals of entry to 
the body (i.e., the respiratory system and gastrointestinal tract). 
Consequently, the internal disposition and distribution of Pb is an 
integral aspect of the relationship between exposure and effect. This 
section briefly summarizes the current state of knowledge of Pb 
disposition pertaining to both inhalation and ingestion routes of 
exposure as described in the Criteria Document.
    Inhaled Pb particles deposit in the different regions of the 
respiratory tract as a function of particle size (CD, pp. 4-3 to 4-4). 
Lead associated with smaller particles, which are predominantly 
deposited in the pulmonary region, may, depending on solubility, be 
absorbed into the general circulation or transported to the 
gastrointestinal tract (CD, pp. 4-3). Lead associated with larger 
particles, which are predominantly deposited in the head and conducting 
airways (e.g., nasal

[[Page 71495]]

pharyngeal and tracheobronchial regions of respiratory tract), may be 
transported into the esophagus and swallowed, thus making its way to 
the gastrointestinal tract (CD, pp. 4-3 to 4-4), where it may be 
absorbed into the blood stream. Thus, Pb can reach the gastrointestinal 
tract either directly through the ingestion route or indirectly 
following inhalation.
    Once in the blood stream, where approximately 99% of the Pb 
associates with red blood cells, the Pb is quickly distributed 
throughout the body (e.g., within days) with the bone serving as a 
large, long-term storage compartment, and soft tissues (e.g., kidney, 
liver, brain, etc) serving as smaller compartments, in which Pb may be 
more mobile (CD, sections 4.3.1.4 and 8.3.1.). Additionally, the 
epidemiologic evidence indicates that Pb freely crosses the placenta 
resulting in continued fetal exposure throughout pregnancy, and that 
exposure increases during the later half of pregnancy (CD, section 
6.6.2).
    During childhood development, bone represents approximately 70% of 
a child's body burden of Pb, and this accumulation continues through 
adulthood, when more than 90% of the total Pb body burden is stored in 
the bone (CD, section 4.2.2). Accordingly, levels of Pb in bone are 
indicative of a person's long-term, cumulative exposure to Pb. In 
contrast, blood Pb levels are usually indicative of recent exposures. 
Depending on exposure dynamics, however, blood Pb may--through its 
interaction with bone--be indicative of past exposure or of cumulative 
body burden (CD, section 4.3.1.5).
    Throughout life, Pb in the body is exchanged between blood and 
bone, and between blood and soft tissues (CD, section 4.3.2), with 
variation in these exchanges reflecting ``duration and intensity of the 
exposure, age and various physiological variables'' (CD, p. 4-1). Past 
exposures that contribute Pb to the bone, consequently, may influence 
current levels of Pb in blood. Where past exposures were elevated in 
comparison to recent exposures, this influence may complicate 
interpretations with regard to recent exposure (CD, sections 4.3.1.4 to 
4.3.1.6). That is, higher blood Pb concentrations may be indicative of 
higher cumulative exposures or of a recent elevation in exposure (CD, 
pp. 4-34 and 4-133).
    In several recent studies investigating the relationship between Pb 
exposure and blood Pb in children (e.g., Lanphear and Roghmann 1997; 
Lanphear et al., 1998), blood Pb levels have been shown to reflect Pb 
exposures, with particular influence associated with exposures to Pb in 
surface dust. Further, as stated in the Criteria Document ``these and 
other studies of populations near active sources of air emissions 
(e.g., smelters, etc.), substantiate the effect of airborne Pb and 
resuspended soil Pb on interior dust and blood Pb'' (CD, p. 8-22).
    Blood Pb levels are extensively used as an index or biomarker of 
exposure by national and international health agencies, as well as in 
epidemiological (CD, sections 4.3.1.3 and 8.3.2) and toxicological 
studies of Pb health effects and dose-response relationships (CD, 
Chapter 5). The prevalence of the use of blood Pb as an exposure index 
or biomarker is related to both the ease of blood sample collection 
(CD, p. 4-19; Section 4.3.1) and by findings of association with a 
variety of health effects (CD, Section 8.3.2). For example, the U.S. 
Centers for Disease Control and Prevention (CDC), and its predecessor 
agencies, have for many years used blood Pb level as a metric for 
identifying children at risk of adverse health effects and for 
specifying particular public health recommendations (CDC, 1991; CDC, 
2005a). In 1978, when the current Pb NAAQS was established, the CDC 
recognized a blood Pb level of 30 [mu]g/dL as a level warranting 
individual intervention (CDC, 1991). In 1985, the CDC recognized a 
level of 25 [mu]g/dL for individual child intervention, and in 1991, 
they recognized a level of 15 [mu]g/dL for individual intervention and 
a level of 10 [mu]g/dL for implementing community-wide prevention 
activities (CDC, 1991; CDC, 2005). In 2005, with consideration of a 
review of the evidence by their advisory committee, CDC revised their 
statement on Preventing Lead Poisoning in Young Children, specifically 
recognizing the evidence of adverse health effects in children with 
blood Pb levels below 10 [mu]g/dL and the data demonstrating that no 
``safe'' threshold for blood Pb had been identified, and emphasizing 
the importance of preventative measures (CDC, 2005a, ACCLPP, 2007).\14\
---------------------------------------------------------------------------

    \14\ With the 2005 statement, CDC identified a variety of 
reasons, reflecting both scientific and practical considerations, 
for not lowering the 1991 level of concern, including a lack of 
effective clinical or public health interventions to reliably and 
consistently reduce blood Pb levels that are already below 10 [mu]g/
dL, the lack of a demonstrated threshold for adverse effects, and 
concerns for deflecting resources from children with higher blood Pb 
levels (CDC, 2005a). CDC's Advisory Committee on Childhood Lead 
Poisoning Prevention recently provided recommendations regarding 
interpreting and managing blood Pb levels below 10 [mu]g/dL in 
children and reducing childhood exposures to Pb (ACCLPP, 2007).
---------------------------------------------------------------------------

    Since 1976, the CDC has been monitoring blood Pb levels nationally 
through the National Health and Nutrition Examination Survey (NHANES). 
This survey has documented the dramatic decline in mean blood Pb levels 
in the U.S. population that has occurred since the 1970s and that 
coincides with regulations regarding leaded fuels, leaded paint, and 
Pb-containing plumbing materials that have reduced Pb exposure among 
the general population (CD, Sections 4.3.1.3 and 8.3.3; Schwemberger et 
al., 2005). The Criteria Document summarizes related information as 
follows (CD, p. E-6).

    In the United States, decreases in mobile sources of Pb, 
resulting from the phasedown of Pb additives created a 98% decline 
in emissions from 1970 to 2003. NHANES data show a consequent 
parallel decline in blood-Pb levels in children aged 1 to 5 years 
from a geometric mean of ~15 [mu]g/dL in 1976-1980 to 1-2 [mu]g/dL 
in the 2000-2004 period.

While levels in the U.S. general population, including geometric mean 
levels in children aged 1-5, have declined significantly, mean levels 
have been found to vary among children of different socioeconomic 
status (SES) and other demographic characteristics (CD, p. 4-21).\15\
---------------------------------------------------------------------------

    \15\ For example, while the 2001-2004 median blood level for 
children aged 1-5 of all races and ethnic groups is 1.6 [mu]g/dL, 
the median for the subset living below the poverty level is 2.3 
[mu]g/dL and 90th percentile values for these two groups are 4.0 
[mu]g/dL and 5.4 [mu]g/dL, respectively. Similarly, the 2001-2004 
median blood level for black, non-hispanic children aged 1-5 is 2.5 
[mu]g/dL, while the median level for the subset of that group living 
below the poverty level is 2.9 [mu]g/dL and the median level for the 
subset living in a household with income more than 200% of the 
poverty level is 1.9 [mu]g/dL. Associated 90th percentile values for 
2001-2004 are 6.4 [mu]g/dL (for black, non-hispanic children aged 1-
5), 7.7 [mu]g/dL (for the subset of that group living below the 
poverty level) and 4.1 [mu]g/dL (for the subset living in a 
household with income more than 200% of the poverty level). (https://
www.epa.gov/envirohealth/children/body_burdens/b1-table.htm_then 
click on ``Download a universal spreadsheet file of the Body Burdens 
data tables'').
---------------------------------------------------------------------------

    Bone measurements, as a result of the generally slower Pb turnover 
in bone, are recognized as providing a better measure of cumulative Pb 
exposure (CD, Section 8.3.2). The bone pool of Pb in children, however, 
is thought to be much more labile than that in adults due to the more 
rapid turnover of bone mineral as a result of growth (CD, p. 4-27). As 
a result, changes in blood Pb concentration in children more closely