UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C. 20460
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
September 6, 2006
EPA-CASAC-06-010
Honorable Stephen L. Johnson
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, NW
Washington, DC 20460
Subject: Clean Air Scientific Advisory Committee's (CAS AC) Review of the 2nd Draft
Lead Air Quality Criteria Document
Dear Administrator Johnson:
In June, EPA's Clean Air Scientific Advisory Committee (CASAC), supplemented by
subject-matter-expert Panelists collectively referred to as the CASAC Lead Review Panel
(Lead Panel) reviewed EPA's Air Quality Criteria for Lead (Second External Review Draft),
Volumes I and II (EPA/600/R-05/144aB-bB, May 2006) (2nd Draft Lead AQCD). The
CASAC's report to you on this subject is found in a letter (EPA-CASAC-06-008) dated July 26,
2006. In this letter, the CASAC had requested to review an updated version of the integrative
synthesis (Chapter 7), which was only available as a first draft in the 2nd Draft Lead AQCD, and
the Executive Summary. The CASAC Lead Panel met in a public teleconference on August 15,
2006 to review these updated documents.
The Lead Panel found the two documents much improved, in response to the Panel's
previous recommendations. The Panel was pleased to see that the integrative synthesis chapter
was revised to include a discussion of the science to be considered for setting both the primary
and the secondary lead standards, and that the integrative synthesis was reordered in the Lead
AQCD to follow the environmental effects chapter. The Lead Panel also agreed that the newly-
available study by Schober et al. regarding lead-related mortality that was submitted by EPA's
Office of Research and Development (ORD) for the Panel's review was important enough to be
incorporated into both the integrative synthesis chapter and the Executive Summary of the Lead
AQCD. However, the study should be included with the appropriate caveats, as discussed in the
Lead Panel's teleconference and in individual comments of the panelists. The Panel also felt that
the Schober et al. paper should be mentioned, once again with appropriate caveats, in Chapter 6
(Epidemiologic Studies of Human Health Effects Associated with Lead Exposure).
Furthermore, the Panel felt that the interaction between air quality standards and the large
reservoirs of lead in other media such as water, soil, dust, plants and food, should be discussed in
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the Executive Summary in relation to Figure 7-1 regarding principal pathways of lead from the
environment to human consumption. In addition, the Panel notes that multimedia exposure
pathways are critical for the determination of projected human subject lead levels. Therefore, a
discussion of this topic, as well as Figure 7-1, should be included in both the integrative
synthesis chapter and the Executive Summary. Finally, the CASAC recommends that a number
of changes be made to the ecological section of the Executive Summary in order to more clearly
state the important findings of the Agency (see Lead Panel members' individual review
comments, particularly those of Dr. Andrew Friedland and Dr. Paul Mushak).
The Panel members agreed that the Lead AQCD will be adequate for rulemaking after
EPA incorporates the above recommendations and also makes a good-faith effort to address
Panel members' suggested changes as found in their individual review comments. The CASAC
Lead Panel was pleased to complete the review of the 2nd Draft Lead AQCD and looks forward
to the review of the 1st Draft Lead Staff Paper. As always, the CASAC wishes the Agency staff
well in this important endeavor.
Sincerely,
/Signed/
Dr. Rogene Henderson, Chair
Clean Air Scientific Advisory Committee
Appendix A - Roster of the Clean Air Scientific Advisory Committee
Appendix B - Roster of the CASAC Lead Review Panel
Appendix C - Review Comments from Individual CASAC Lead Review Panel Members
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Appendix A - Roster of the Clean Air Scientific Advisory Committee
U.S. Environmental Protection Agency
Science Advisory Board (SAB) Staff Office
Clean Air Scientific Advisory Committee (CASAC)
CHAIR
Dr. Rogene Henderson, Scientist Emeritus, Lovelace Respiratory Research Institute,
Albuquerque, NM
MEMBERS
Dr. Ellis Cowling, University Distinguished Professor-at-Large, North Carolina State
University, Colleges of Natural Resources and Agriculture and Life Sciences, North Carolina
State University, Raleigh, NC
Dr. James D. Crapo, Professor, Department of Medicine, National Jewish Medical and
Research Center, Denver, CO
Dr. Frederick J. Miller, Consultant, Cary, NC
Mr. Richard L. Poirot, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT
Dr. Frank Speizer, Edward Kass Professor of Medicine, Channing Laboratory, Harvard
Medical School, Boston, MA
Dr. Barbara Zielinska, Research Professor, Division of Atmospheric Science, Desert Research
Institute, Reno, NV
SCIENCE ADVISORY BOARD STAFF
Mr. Fred Butterfield, CASAC Designated Federal Officer, 1200 Pennsylvania Avenue, N.W.,
Washington, DC, 20460, Phone: 202-343-9994, Fax: 202-233-0643 (butterfield.fred@epa.gov)
(Physical/Courier/FedEx Address: Fred A. Butterfield, III, EPA Science Advisory Board Staff
Office (Mail Code 1400F), Woodies Building, 1025 F Street, N.W., Room 3604, Washington,
DC 20004, Telephone: 202-343-9994)
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Appendix B - Roster of the CASAC Lead Review Panel
U.S. Environmental Protection Agency
Science Advisory Board (SAB) Staff Office
Clean Air Scientific Advisory Committee (CASAC)
CASAC Lead Review Panel
CHAIR
Dr. Rogene Henderson*, Scientist Emeritus, Lovelace Respiratory Research Institute,
Albuquerque, NM
MEMBERS
Dr. Joshua Cohen, Faculty, Center for the Evaluation of Value and Risk, Institute for Clinical
Research and Health Policy Studies, Tufts New England Medical Center, Boston, MA
Dr. Deborah Cory-Slechta, Director, University of Medicine and Dentistry of New Jersey and
Rutgers State University, Piscataway, NJ
Dr. Ellis Cowling*, University Distinguished Professor-at-Large, North Carolina State
University, Colleges of Natural Resources and Agriculture and Life Sciences, North Carolina
State University, Raleigh, NC
Dr. James D. Crapo [M.D.]*, Professor, Department of Medicine, National Jewish Medical and
Research Center, Denver, CO
Dr. Bruce Fowler, Assistant Director for Science, Division of Toxicology and Environmental
Medicine, Office of the Director, Agency for Toxic Substances and Disease Registry, U.S.
Centers for Disease Control and Prevention (ATSDR/CDC), Chamblee, GA
Dr. Andrew Friedland, Professor and Chair, Environmental Studies Program, Dartmouth
College, Hanover, NH
Dr. Robert Goyer [M.D.], Emeritus Professor of Pathology, Faculty of Medicine, University of
Western Ontario (Canada), Chapel Hill, NC
Mr. Sean Hays, President, Summit Toxicology, Allenspark, CO
Dr. Bruce Lanphear [M.D.], Sloan Professor of Children's Environmental Health, and the
Director of the Cincinnati Children's Environmental Health Center at Cincinnati Children's
Hospital Medical Center and the University of Cincinnati, Cincinnati, OH
Dr. Samuel Luoma, Senior Research Hydrologist, U.S. Geological Survey (USGS), Menlo
Park, CA
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Dr. Frederick J. Miller*, Consultant, Cary, NC
Dr. Paul Mushak, Principal, PB Associates, and Visiting Professor, Albert Einstein College of
Medicine (New York, NY), Durham, NC
Dr. Michael Newman, Professor of Marine Science, School of Marine Sciences, Virginia
Institute of Marine Science, College of William & Mary, Gloucester Point, VA
Mr. Richard L. Poirot*, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT
Dr. Michael Rabinowitz, Geochemist, Marine Biological Laboratory, Woods Hole, MA
Dr. Joel Schwartz, Professor, Environmental Health, Harvard University School of Public
Health, Boston, MA
Dr. Frank Speizer [M.D.]*, Edward Kass Professor of Medicine, Channing Laboratory,
Harvard Medical School, Boston, MA
Dr. Ian von Lindern, Senior Scientist, TerraGraphics Environmental Engineering, Inc.,
Moscow, ID
Dr. Barbara Zielinska*, Research Professor, Division of Atmospheric Science, Desert Research
Institute, Reno, NV
SCIENCE ADVISORY BOARD STAFF
Mr. Fred Butterfield, CASAC Designated Federal Officer, 1200 Pennsylvania Avenue, N.W.,
Washington, DC, 20460, Phone: 202-343-9994, Fax: 202-233-0643 (butterfield.fred@epa.gov)
* Members of the statutory Clean Air Scientific Advisory Committee (CASAC) appointed by the EPA
Administrator
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Appendix C - Review Comments from
Individual CASAC Lead Review Panel Members
This appendix contains the preliminary and/or final written review comments of
the individual members of the Clean Air Scientific Advisory Committee (CASAC) Lead
Review Panel who submitted such comments electronically. The comments are included
here to provide both a full perspective and a range of individual views expressed by
Panel members during the review process. These comments do not represent the views
of the CASAC Lead Review Panel, the CASAC, the EPA Science Advisory Board, or
the EPA itself. The views of the CASAC Lead Review Panel and the CASAC as a
whole are contained in the text of the report to which this appendix is attached. Panelists
providing review comments are listed on the next page, and their individual comments
follow.
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Panelist Page#
Dr. Joshua Cohen C-3
Dr. James Crapo C-4
Dr. Andrew Friedland C-5
Dr. Robert Goyer C-6
Dr. Bruce Lanphear C-7
Dr. Samuel Luoma C-8
Dr. Paul Mushak C-9
Dr. Michael Rabinowitz C-12
Dr. Frank Speizer C-14
Dr. Ian von Lindern C-15
Dr. Barbara Zielinska C-16
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Dr. Joshua Cohen
Dr. Joshua Cohen
September 5, 2006
Comments on Chapter 4
EPA has made a number of clarifications to Chapter 4 (Lead Toxicokinetics and
Measurement/Modeling of Human Exposure Impacts on Internal Tissue Distribution of Lead)
that greatly enhance the report.
There is one issue that I would encourage the Agency to consider further. Section 4.4.4.2 of the
report cites a 1998 paper by Hogan et al. to support the contention that IEUBK model-predicted
PbB levels are close to empirically measured values. Although the report notes that Bowers and
Mattuck (2001) found the degree of agreement depends on various factors, EPA does not
mention or otherwise contend the finding by Bowers and Mattuck that the IEUBK model
predictions can substantially diverge from empirically measured PbB values.
More generally, consider the use of the IEUBK model to predict individual PbB values based on
child-specific environmental measurements. If the IEUBK model accurately reproduces the GM
and GSD PbB values for that population (as reported by Hogan et al., 1998) and if the correlation
between the empirical and lEUBK-predicted values is less than perfect, then it follows that the
low-end PbB values predicted by the IEUBK model will underestimate the corresponding
empirical values, while the high-end lEUBK-predicted values will overestimate the
corresponding empirical values. A simulation will demonstrate this phenomenon, which may
have regulatory implications.
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Dr. James Crapo
James D. Crapo, M.D.
Professor of Medicine
National Jewish Medical and Research Center
August 18,2006
Both Chapter 7 on Integrative Synthesis and the Executive Summary have been
substantially revised and have appropriately addressed the primary scientific concerns. Both
chapters are ready for closure with regard to the scientific data and issues required for this phase
of the Lead Review.
The Executive Summary is well written. The use of bullets provides clarity for the
presentation of the primary issues as well as highlighting the primary scientific data relevant to
lead air quality standards. My primary recommendation with regard to this chapter is that it
would benefit from including an additional section addressing the interaction between air lead
quality standards and the large reservoirs of lead in other media such as water, soil, dust, paint,
and foods. Multimedia exposure pathways are critical for the determination of projected human
subject lead levels. While airborne lead is a small component of this reservoir, it plays a central
role in the movement of lead between multimedia and the ultimate exposure of human subjects.
This topic needs to be more completely addressed in the Executive Summary to lay the
appropriate platform for consideration of the appropriate air quality standard for lead to be done
in the subsequent staff paper.
I compliment the EPA staff on preparing an outstanding document summarizing a very
complex field.
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Dr. Andrew Friedland
Andy Friedland, Ph.D.
Dartmouth College
16 August 2006
Brief specific comments related to the Executive Summary and Chapter 7 (Synthesis Chapter)
made after the 15 August 2006 conference call
Executive Summary
Page E-15, lines 32 forward: Methodologies Used in Terrestrial Ecosystem Research. We really
need to ask how much of this section on methods belongs in the Executive Summary. I would
say maybe one or two bullets including the material on BLM, but not all of this.
Page E-16 lines 28-29:1 want to draw attention to these lines as an important place to reorder the
sources of Pb based on the new information presented in the new table in Chapter 2. These lines
currently read: waste incineration first and coal-fired power plants last.
Page E-16 lines 35-39: We discussed this bullet as one that could be shortened or deleted. I
recommend that it read:
"Dry deposition can account for anywhere from 10% to 90% of total Pb deposition. Because
CAA Legislation has preferentially reduced Pb associated with fine particles, relative
contributions of dry deposition have changed in the last few decades."
Page E-17 line 18: "had" should be changed to "have".
Chapter 7
Page 7-86 lines 29-30:1 want to draw attention to these lines as an important place to reorder the
sources of Pb based on the information in Chapter 2. These lines currently read: waste
incineration first and then metal smelting and production...."
Page 7-88 line 8: "After deposition, most all Pb species are...." DELETE "all".
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Dr. Robert Goyer
Robert Goyer, M.D.
August 18,2006
The Integrative Synthesis Chapter (Chapter 7) is an accurate and comprehensive
synthesis of the 2nd draft of the Lead-AQCD update, particularly if comments make by various
panel members at the 8/15 teleconference are incorporated into the chapter. The integrative
synthesis of the Toxicological Effects of Lead as contained in chapter 5 is appropriately
summarized in Chapter 7. The major health effects are accurately presented particularly with
emphasis on the neurological, cardiovascular and renal effects and appropriate recognition of
other health effects.
I do not have expertise to comment on the Schober et al. paper but agree that it may
introduce a new dimension to the risk of lead exposure. Because of its significance it must be
corroborated and the data analyzed by others. I agree with the suggestion that the paper be
recognized but only with appropriate caveats.
The second draft of the Lead AQCD with suggested amendments and additions will
provide a accurate and up to date scientific basis for future EPA decisions
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Dr. Bruce Lanphear
Bruce Lanphear, M.D.
August 21,2006
Comments on Chapter 7 (Lanphear)
Page 7-15, line 28: It is true that "bone measurements likely constitute a better indication of
overall past cumulative exposure history" in adolescents and adults, but this sentence should be
modified because it is not a better biomarker in younger children (e.g., < 10 years of age).
Indeed, it cannot be measured reliably in these children.
Table 7-3, Page 7-24: The consensus of the CASAC advisory committee was that there was
evidence of lead-associated IQ deficits at blood lead concentrations of 5 |ig/dL. This table is
inconsistent with this consensus.
Page 7-37, line 25-27: A related problem is that the conclusion "possibly as low as 5 |ig/dL".
This statement is inconsistent with the consensus of the Committee. We indicated that there was
evidence of adverse consequences at blood lead levels of 5 |ig/dL and, although the data are less
certain, there is most likely adverse effects at blood lead levels below 5 |ig/dL.
Page 7-59, lines 26-27: The conclusion "and are of likely public health concern" sounds much
less definitive than the Committee's consensus. My understanding from the Committee meeting
is that "blood lead levels < 10 |ig/dL are a major public health concern".
Page 7-62: As written, the discussion about the Bowers & Beck manuscript was confusing and
inconclusive. The authors should refer to the commentaries by Joel Schwartz and Richard
Horning.
7-86, line 13-14: The term "risk-free" is not what was intended by the Committee. Please refer
to our August 15th, 2006 conference call minutes for the modified sentence suggested by Fred
Miller. This modified sentence should be the concluding sentence and the last sentence (lines
17-19), which doesn't fit in this paragraph, should be deleted.
Comments on Executive Summary (Lanphear)
Page E-8, lines 13-15: The reference to the animal studies should be deleted from this
paragraph; it belongs in the subsequent paragraph on animal studies.
Page E-15, lines 6-7: The term "risk-free" is not what was intended by the Committee. Please
refer to our August 15th, 2006 conference call minutes for the modified sentence suggested by
Fred Miller.
Page E-23: A concluding paragraph(s) would be extremely valuable to help the reader
understand the conclusions and implications of the CASAC recommendations. As written, the
reader is left hanging.
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Dr. Samuel Luoma
Samuel N. Luoma, Ph.D.
U.S. Geological survey (USGS)
August 18,2006
The updated versions of Chapter 7 and the Integrated Synthesis are both improved. The
agency has responded to some of the previous comments made by the panel, especially the
editorial comments. But they have not responded to others; perhaps some of the most important.
There are also contradictions between the new Chapter 7 and the Synthesis.
From the broadest view, EPA has missed an opportunity in these summaries to
characterize what is different between ecological risks of lead vs. other metals; and specifically
between atmospheric lead and other sources. I believe our subcommittee comments provided
some direction in that regard; to that there was little meaningful response. Characterizing the
unique aspects of the ecological risks of (atmospheric) lead could begin a basis for a more
informed generation of regulation; this document will not begin that transition. The iterations of
this document verify that agency is clearly comfortable with the simplistic source identification
and toxicity test approach they have used for decades as the basis for characterizing ecological
risk of a chemical; and uncomfortable with advanced testing techniques, models and field
evidence (multiple lines of evidence); even though the consensus in the scientific community is
that the latter is the only way to address the uncertainties in ALL approaches. Until that changes,
we can expect continued uneven treatment of these complex subjects and regulations that are at
least sometimes difficult to justify.
As I noted earlier, the report understated the uncertainties in the BLM and AVS
approaches. Chapter 7 responded to this by eliminating all mention of the BLM; but the
synthesis retains an endorsement of its development. The latter is appropriate under the heading
"developing area of research" (this is how AVS should be explained as well); but the summary
and the synthesis should be consistent with one another. Some detailed comments have also
been ignored. For example, their generic bioaccumulation model (three types of
bioaccumulation) is taken from a general metal model, as I noted in my first detailed comments;
all three models don't apply to lead. Lead also follows specific detoxification pathways in at
least some invertebrates (extra-cellular granule formation - Brown, -1977). The synthesis does
not include recognition of either of these points. This is not the most important flaw, by itself,
but it contributes to the general impression that the agency is not especially well informed about
important aspects of the ecological risks specific to this element. In short, I don't have any
comments to add to those I made in previous additions, other than the feeling of a missed
opportunity described above.
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Dr. Paul Mushak
CASAC PANEL REVIEW COMMENTS: POST TELECONFERENCE
Paul Mushak, Ph.D.
August 18,2006
I believe that the Executive Summary and the 2nd Draft of the Integrative Synthesis
Chapter 7 (Chapter 8 in the final) after changes indicated by members in the Panel's
teleconference review of 8/15 are made will be scientifically acceptable and can go forward to
complete the updated Pb AQCD.
I also believe the completed AQCD-Pb Update will not only serve as a scientific
underpinning for the needs of OAQPS and other Agency offices, but will also serve as the most
recent expert consensus treatise for use by the international scientific community.
Recapitulating some of my comments and those of others given Tuesday, for clarification
and emphasis:
The Executive Summary (ExSum) would benefit quite a bit from having EPA's
standard lead environmental cycling schematic, now appearing as Figure 7.1, also
appear in the ExSum.
I believe that the ExSum Figure should in fact reflect the nature of "air Pb" as a
multimedia pollutant rather than present all "Pb" per se in the Figure. There's a key
distinction here. Both the former and the latter obviously have multimedia
dimensions, but the former directly addresses ambient air Pb NAAQS assessment.
A key issue for air lead NAAQS facing OAQPS and the policy makers is the extent to
which regulating lead in air, for risks other than from direct inhalation, affects or does
not affect the total air Pb-driven exposure picture. Consequently, non-air Pb sources
such as paint lead should not appear in the Figure. The Figure legend, however,
should make it clear it is basically air Pb-driven.
The Figure should also be updated to show an arrow to local air Pb from dust Pb re-
entrainment.
Separating the Special Risk groups and the Potential Public Health Impacts from the
health effects summaries in the ExSum was a good move. These topics are given
better highlighting.
Chapter 7 should also separate out the public health impacts as a section for
highlighting. That is, make public health impacts, especially those impacts on the
known risk groups, a new section 7.6.
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Chapter 7, perhaps in the fate/transport and media lead levels section or even in the
section on measurement and modeling of human lead exposures as sprung from
Chapter 4, should include some Tables on dust lead loadings for both interior and
exterior hard surfaces as I did for illustration after the 2/28-3/1/06 CASAC Pb panel
meeting. Using equations already in EPA/NCEA documents, such as the '96 EPA
Integrated Report for the three-city soil lead abatement demonstration project, one
finds that even air Pb levels of 0.1 |ig/m3 produce dust lead loadings onto surfaces
such as floors in children's play areas that will become hazardous in the near term.
The newly published cardiovascular (CV) epidemiological study by Schober et al.
that had considerable discussion presumably could be handled in several ways. The
present proposed paragraph insert could include some qualifying statements. I leave
that to the regression jockeys on the Panel to thrash out with NCEA. EPA could do an
internal reanalysis, but it's doubtful time would allow that, using the data sets relied
upon by the authors along the lines discussed. Alternatively, the paper can be treated
as something requiring consideration as a factor that may have public health impact
without spelling our firm numbers. It could then be evaluated by OAQPS within the
confines of new information that, while not quantifiable as to risk enumerations, will
qualify as defining a need for "an adequate margin of safety" as spelled out in Sec.
109 of the CAA and the 1990 CAAA.
The need for replicating this study was noted. That would have to await a comparable
data set for analysis, which would in fact be another more recent NHANES survey.
NHANES surveys are unique national surveys in that they incorporate blood lead
levels within fairly rigid statistical designs and study execution for multiple national
health assessments. The only candidate for a new data set is the most recent
NHANES data segment, quasi-NHANES 4, spanning the period 1995 to 2004. The
Schober group followed 9757 individuals out to 2000 but there was only the single,
baseline Pb-B measured in the 88-94 time frame.
That alternative, however, requires years in the doing. The Schober et al. study did a
follow-up of subjects post-Pb-B at a median span of almost 9 years.
Does any more recent NHANES data set raise the potential biostatistical conundrum
that subjects in more recent NHANES testings (post-NHANES 3) will have
accumulated lower bone lead burdens and lower lead releases back to blood, given
the nature of the CV risk population as to age and exposure history? A null outcome
with any newer NHANES survey data analysis would arguably not rule out likelihood
that subjects in the Schober et al. analysis had a Pb-B vs. CV mortality association
and were presenting with a real risk for CV mortality. The extent to which there is
this lead release dependency or latency will depend on the cardiotoxic, vasoactive and
vasotoxic mechanisms operating in older humans.
Some quick comparisons can be made. First, for Schober et al., the youngest subjects
would have had the least amount of bone lead accumulation. The youngest subjects in
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Schober et al. were 40 years of age. At the midpoint of NHANES 3, i.e., 1991, 40
year olds tested that year were born in 1951. People born in 1951 were still to see the
peak of their lead exposures from various lead sources, and certainly from ambient air
levels linked to leaded gasoline consumption in the 1960s and 1970s, to, say, 1976.
This would be long after their somatic development reached the point, i.e., post-5
years of age, where their bone lead accumulations with net bone formation would
exceed bone lead releases from rapid turnover (e.g., O'Flaherty, 1993, 1995, 1998).
We would expect that even the youngest subjects in the Schober et al. study would
have had the opportunity to accumulate significant bone lead burdens and
endogenous lead releases over the period 1956 (5 years of age) to 1976, a span of 20
years.
For the period 1994-2004, a 40-year old at the mid-point would only have had a bit
more than half as much time for bone lead accumulation, all exposure factors
remaining the same. This might be enough reduction in the lead exposure biomarker
variable to reduce its statistical power. On the other hand, it is critical to keep in mind
that the shorter time frame of bone Pb accumulation is still capturing many of the
high lead exposure years applicable to the subjects in Schober et al.
The above applies to the youngest age defining a lower bound to bone lead release
rates to Pb-B and then any Pb-B vs. CV risk associations. Individuals in all the older
age bands, >40 years of age, would have increasingly more overlap of the highest
national lead exposure years for both Schober et al. and any newer NHANES data
sets. This assumes also that the subject numbers in the age cells used in the NHANES
strata are proportionately the same in NHANES III and NHANES IV.
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Dr. Michael Rabinowitz
Michael Rabinowitz, Ph.D.
August 15, 2006
Comments on 2nd Draft Pb AQCD
Having reviewed the Executive Summary and Chapter 7, my comments follow:
1- This is a much improved version. It should be sufficient as a basis for the regulation of
environmental lead exposure, assuming you have added the few concrete suggestions which I
offered previously dealing with earlier chapters, mostly related to blood lead trajectories.
2- It seems like a good time to offer suggestions about future research needs which would
improve our understanding of some critical areas. Let me suggest 3.
a) Lead as an independent risk factor for poor child development. Much data has
been collected from numerous human studies of lead burden and child development, and
more are in the pipeline. In every population, confounders are present. What I would like
to see is a clearer exposition of lead as an independent risk factor. Specifically I would
like to see the regression model of each study with and without the lead term, to assess
the models goodness of fit. Lead could be taken to be an independent risk factor if the
model fits significantly better with a lead term added, and also if adding the lead term
does not significantly change the coefficient of any of the other risk factors. From this
approach we could better see how important lead can be compared to the other risk
factors.
b) Transport of soil lead into dust and hence to humans. This topic has been
investigated, but since it has become a central feature of human exposure, we would
benefit from improved knowledge of those factors which influence the transport of lead
by this route: the range, amount, and form of lead. Those factors might be related to the
soil type, the chemical and physical forms of the lead pollution in the soil, and a host of
meteorological factors such as wind, humidity, and temperature. Factors related to the
residence might also be important. We should know more about how much and how far
the lead in soil can travel.
c) Lead as a factor in mortality. The recent examinations of the relationship
between adult blood lead and subsequent length of life deserve close attention. In that
population wide blood leads have fallen by an order of magnitude over the last
generation, we should have cause to expect longer lifes. Tobacco smoking is a strong
confounder in the general popultion; smoking causes premature deaths from heart
disease and cancers as well as elevating blood lead levels. Statistically adjusting for
smoking is a usefull tool in examining the popultion wide effects, but let me suggest that
to more exactly look at the role of lead as an independent risk factor, we should stratify
for smoking and look at the relationship between lead and age at death in a popultion of
non-smokers.
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3-1 must thank my fellow board members who have vigorously applied there varied expertise.
Because they have each done so much of the heavy lifting, I found my task was much easier.
Thank you.
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Dr. Frank Speizer
Dr. Frank Speizer
August 14, 2006
Comments on the Revised Chapter 7 Integrated summary and Executive Summary
In general I found both documents to be acceptable and with additions made ready for closure. I
am left with a few minor editorial changes, which are offered simply to add to clarity and set the
background straight.
Chapter 7
Page 7.2, line 30. End of historical background. This presents the facts as we heard them, but
does not give us any indication as to why, in the face of the data available, the administrator
chose not to change the standard. There clearly must be additional information to document
going against at least the recommendation to move to a 30 day average from the 120 day
average. The statement that air levels were already below the existing standard is part of the
answer but it seems incomplete. Perhaps additional administrative historical background should
be added. (In the final analysis it may have been a political decision, and if so, so be it. But
what we have here is only part of the history.)
Page 7.24, Table 7.3. For clarity I think the labels of effects at 5|ig/dl need to be moved down to
indicate that they are seen at the 5ug level and are uncertain (?) below that level. That is what
the footnote says, but not what might be interpreted by looking a t the table. Ditto for Table 7.4
for blood pressure.
Executive Summary
Page E.2, paragraph beginning line 23: Suggest somewhere in this paragraph indicate that the
averaging time for the standard is 3 month. Since this will be a consideration in a revised
standard it should be specified here.
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Dr. Ian von Lindern
Dr. Ian von Lindern
August 21,2006
Final Comments of Ian von Lindern re: Executive Summary and Synthesis Chapter
I have reviewed the latest draft of Section 7 and the Executive Summary of the 2nd Draft Air
Quality Criteria Document for lead and was a participant in the August 15, 2006 conference call
regarding these documents. I believe these Chapters are significantly improved and this
document is appropriate to meet the statutory, regulatory and scientific requirements of the
criteria process. Dr. Grant and his staff should be commended for a job well done,
notwithstanding the difficult schedules and sheer volume of material to be reviewed and
synthesized. I concur with the committee's recommendations and consensus agreements reached
on the call. My individual comments are minor and editorial.
I would like to see it explicitly stated in the Executive Summary, that the current standard of 1.5
|ig/m3 Pb is not protective of human health, due to subsequent deposition of lead dusts that
accumulate in acceptable amounts in homes (house dust) and soils.
As we were not able to review Chapter 2,1 accept Dr. Grant's explanation that references to
source and emissions inventories indicated in the Synthesis Chapter and the Executive Summary
are consistent with and reflective of modifications made since the June meeting. There were
some inconsistencies and caveats suggested for incorporation in the committee's and individual
comments that I trust have been addressed.
It might be worthwhile to double check that all points made in the Executive Summary can be
found in the Synthesis Chapter, as well, and are traceable to presentation and discussion in the
individual Chapters.
I believe a word may be missing in line 3, p E-6.
Perhaps section E-7 could point out that the lead accumulation, residence time and many of the
ecological effects resulting from past practices are likely to endure for decades or centuries, may
effectively permanently alter ecosystems, and that natural recovery processes will require several
human lifetimes.
C-15
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Dr. Barbara Zielinska
Dr. Barbara Zielinska
August 21,2006
Comments on Chapter 7 and Executive Summary of Lead AQCD - 2nd Draft
In my opinion, both the 2nd Draft of Chapter 7 on the Integrative Synthesis and the
Executive Summary are adequate and can be included in the final version of lead AQCD. I agree
with the other Lead Panel's members that the Executive Summary should emphasize the "air
lead" as a multimedia pollutant. The inclusion of updated Figure 7-1 in the Executive Summary
would be beneficial.
As far as Chapter 7 is concerned, I believe that it is important to list the current sources of
lead in the correct order (see also the memo from the Battery Council International regarding this
subject). Figure 7-1 should be updated to reflect the importance of soil and dust reentrainment as
sources of ambient and inhaled Pb. In the discussion of dry deposition (page 7-7) the size ranges
of "very small," "large" and "intermediate" particles should be given. Also, the sentence line 11-
13 on this page is not clear - the reference to the original paper or to Chapter 2 where the study
is discussed should be given.
C-16
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