United States Science Advisory Board EPA-SAB-EHC-99-004
Environmental Washington, DC November 1998
Protection Agency www.epa.gfov/saii
AN SAB REPORT: TECHNICAL
REVIEW OF THE PROPOSED TSC
SECTION 403 REGULATION
(IDENTIFICATION OF
DANGEROUS LEVELS OF
LEAD)
PREPARED BY THE
ENVIRONMENTAL HEALTH
COMMITTEE (EHC) OF THE SCIENCE
ADVISORY BOARD (SAB)
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November 20, 1998
EPA-SAB-EHC-99-004
Honorable Carol M. Browner
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, DC 20460
Subject: Technical review of the proposed TSCA Section 403 regulations
(Identification of Dangerous Levels of Lead)
Dear Ms. Browner:
At the request of the EPA Office of Prevention, Pesticides and Toxic Substances
(OPPTS), Office of Pollution Prevention and Toxics (OPPT), the Environmental Health
Committee (EHC) conducted a technical review of the Lead 403 Rule. The EHC met on
September 8-9, 1998 in Arlington, Virginia. The EHC was charged to review the technical
aspects of the risk analysis which was presented in Risk Analysis to Support Standards for Lead
in Paint, Dust, and Soils, Volumes I and II, and on the net benefits (benefits minus cost) analysis
which was presented in Economic Analysis of Toxic Substances Control Act Section 403: Hazard
Standards. Subsequent to receipt of the charge, the EHC received the notice of the proposed lead
rule under authority of section 403 of the Toxic Substances and Control Act (TSCA), in the
Federal Register of June 3, 1998. The EHC found that some of the informative discussion in the
Federal Register notice was additional to that in the Agency reports. Therefore, some of the
recommendations relate to the information in the proposed rule.
The Agency is commended for the significant effort to provide a technical basis for the
proposed standards for lead levels in dust and soil and for the wealth of knowledge displayed
during the meeting. Overall, the EHC found many of the approaches used in the risk analysis to
be technically sound, appropriate, and scientifically defensible. Detailed comments are contained
in the full report.
The EHC has the following recommendations to improve and clarify the technical
approach for conducting the risk analysis:
a) The Agency should provide a clearer presentation on how Intelligence Quotient
(IQ) for risk and cost benefit analysis is used, the significance of lack of a
threshold, the impact of IQ shifts, the use of additional literature references for the
below 70 IQ scores, emphasis on IQ as a neurological surrogate, and the
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explanation that the IQ fractional point loss is valid for economic analysis but not
for interpretations for individual children;
b) The Agency should add more animal data since they support human data by
establishing causality, due to the absence of confounding variables, and potential
mechanisms for adverse health effects;
c) The Agency should clarify the discussion regarding the basis for setting the lead
standards given the marginal costs and marginal nets, including a plan for follow-
up to specific interventions;
d) The Agency should evaluate the potential role of education as an intervention
strategy;
e) The Agency should state, explicitly, the difference between a soil-lead standard
of 2000 parts per million (ppm) and the soil-lead level of concern of 400 ppm and
its impact on current practices by the Department of Housing and Development,
as well as some States; this difference should be explained along with the initial
presentation of the standards;
f) The sensitivity analysis should be expanded with a case study of a real community
that is highly susceptible to lead exposure and a presentation of the costs and
benefits associated with the case study; and
g) A plan should be developed for follow-up to evaluate the effectiveness of the
specific interventions and lead standards on public health.
The EHC concurs that available data have not identified a clear threshold for the health
effects from lead and with the rationale that the weight of scientific evidence shows that 10 |ig/dl
is a reasonable level of concern for childhood blood lead under the applicable statutory standard
of "poses a threat." It is recommended that the numerous health effects be brought forward to
emphasize that 10 |ig/dl is not a threshold value and to show the diversity of potential health
effects from lead.
There are critical differences in environmental lead-blood lead relationships found in
local communities that should be considered in interpreting the Agency's results at the national
level. These differences may be due to regional differences (especially lead in soil from non-
paint sources), differences in genetic susceptibility to lead health effects due to genetic
polymorphisms, and bioavailability differences for lead from different sources. These factors
should be acknowledged in the document, although it is recognized that their use in risk analysis
would require research. However, there is sufficient scientific evidence to indicate that delaying
rulemaking for additional research would leave a significant number of children unnecessarily at
risk. The Committee also provided several editorial comments on the Agency documents, Risk
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Analysis to Support Standards for Lead in Paint, Dust, and Soils, which are included in
Appendix D.
The Agency report documented that the most susceptible age range for children was 1-2
years and that the economic analysis was based on children aged zero to six years. The EHC felt
that it would be useful for the literature about the standards to consistently reference the broader
age range of 0-6 years. The EHC recommends this to eliminate the possible misconception that
the risk is only for the 1-2 year old child.
The Agency is highly commended for its stated intent to prepare and distribute
educational material tailored to specific circumstances for helping the public comply with the
lead standards of the Lead 403 Rule. The EHC feels that guidance is particularly important since
the requirement for homeowners to disclose a known lead risk may be a disincentive for testing.
The Committee appreciates the opportunity to review the Lead 403 Rule and looks
forward to receiving a written response from the Assistant Administrator for the Office of
Prevention, Pesticides and Toxic Substances.
Sincerely,
/signed/ /signed/
Dr. Joan A. Daisey, Chair Dr. Emil A. Pfitzer, Chair
Science Advisory Board Environmental Health Committee
Science Advisory Board
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NOTICE
This report has been written as part of the activities of the Science Advisory Board, a
public advisory group providing extramural scientific information and advice to the
Administrator and other officials of the Environmental Protection Agency. The Board is
structured to provide balanced, expert assessment of scientific matters related to problems facing
the Agency. This report has not been reviewed for approval by the Agency and, hence, the
contents of this report do not necessarily represent the views and policies of the Environmental
Protection Agency, nor of other agencies in the Executive Branch of the Federal government, nor
does mention of trade names or commercial products constitute a recommendation for use.
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ABSTRACT
The Environmental Health Committee (EHC) commends the Agency for its effort to
conduct a risk analysis for proposing standards for lead levels in dust and soil as required by the
Lead 403 Rule and for the wealth of knowledge on the Lead 403 risk analysis that the Agency
displayed during the meeting which was held on September 8-9, 1998. Overall, the EHC found
many of the approaches used in the risk analysis to be technically sound, appropriate, and
scientifically defensible.
The EHC offers several recommendations, including: a) providing a clearer presentation
on how IQ is used for risk and cost benefit analysis, the significance of lack of a threshold, the
impact of IQ shifts, the use of additional literature references for the below 70 IQ scores,
emphasis on IQ as a neurological surrogate, and improving the explanation that the IQ fractional
point loss is valid for risk and economic analysis but not for interpretations for individual
children; b) adding more animal data since they support human data by establishing causality,
due to the absence of confounding variables, and potential mechanisms for adverse health
effects; c) clarifying the discussion regarding the basis for setting the lead standards given the
marginal costs and marginal net benefits, d) including a plan for follow-up to specific
interventions; e) evaluating the potential role of education as an intervention strategy; f) stating,
explicitly, the difference between a soil-lead standard of 2000 parts per million (ppm) and the
soil-lead level of concern of 400 parts per million (ppm) and its impact on current practices by
the Department of Housing and Development, as well as some States; f) expanding the sensitivity
analysis with a case study of a real community that is highly susceptible to lead exposure and a
presentation of the costs and benefits associated with the case study; and h) developing a plan for
follow-up to evaluate the effectiveness of the specific interventions and lead standards on public
health.
Some of these recommendations will require further research. However, there is sufficient
scientific evidence to indicate that delaying rulemaking for additional research would leave a
significant number of children unnecessarily at risk.
The Agency is highly commended for its stated intent to prepare and distribute
educational material tailored to specific circumstances for helping the public comply with the
lead standards of the Lead 403 Rule.
KeyWords: Lead 403 Rule, cost benefit analysis, Intelligence Quotient (IQ), soil-lead
standard, soil-lead level of concern
11
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U.S. ENVIRONMENTAL PROTECTION AGENCY
SCIENCE ADVISORY BOARD
Environmental Health Committee
Lead 403 Review Panel Roster
CHAIR
Dr. Emil Pfitzer, Retired, Ramsey, NJ
MEMBERS
Dr. Cynthia Bearer, Assistant Professor, Case Western Reserve University, Cleveland, OH
Dr. John Doull, Professor Emeritus, Department of Pharmacology, Toxicology and
Therapeutics, University of Kansas Medical Center Kansas City, KS
Dr. Adolfo Correa, Associate Professor, Department of Epidemiology, The Johns Hopkins
University School of Hygiene and Public Health, Baltimore, MD (Did not attend meeting)
Dr. David G. Hoel, Distinguished University Professor, Department of Biometry and
Epidemiology, Medical University of South Carolina, Charleston, SC (Did not attend
meeting)
Dr. Abby A. Li, Toxicology Manager/Neurotoxicology Technical Leader, Monsanto Company,
St. Louis, MO
Dr. Michele Medinsky, Toxicology Consultant, Durham, NC (Did not attend meeting)
Dr. Frederica Perera, Professor of Public Health, Division of Environmental Health Sciences,
Columbia University, New York, NY (Did not attend meeting)
Dr. Lauren Zeise, Chief, Reproductive and Cancer Hazard Assessment Section, Office of
Environmental Health Hazard Assessment, California Environmental Protection Agency,
Berkeley, CA (Did not attend meeting)
Dr. Mark J. Utell, Acting Chairman, Department of Medicine, Director, Pulmonary Unit, and
Professor of Medicine and Environmental Medicine, University of Rochester Medical
Center, Rochester, NY (Did not attend meeting)
SAB Liaison from the SAB Environmental Economics Advisory Committee (EEAC)
Dr. Gloria Helfand, EEAC Consultant, Associate Professor of Environmental Economics,
School of Natural Resource and Environment, The University of Michigan, Ann Arbor,
MI
in
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SAB Liaison from the SAB Integrated Human Exposure Committee (IHEC)
Dr. Henry Anderson, IHEC Chair, Chief Medical Officer, Wisconsin Bureau of Public Health,
Madison, WI
CONSULTANTS
Dr. Bruce Fowler, Director, Program in Toxicology, University of Maryland, Baltimore, MD
Dr. Robert Goyer, Consultant, Chapel Hill, NC
Dr. Marinelle Payton, Instructor in Medicine and Occupational Medicine, Environmental and
Occupational Medicine, Harvard Medical School, Harvard School of Public Health,
Boston, MA
Dr. Bernard Weiss, Professor of Environmental Medicine and Pediatrics, Department of
Environmental Medicine, University of Rochester Medical Center, Rochester, NY
Science Advisory Board Staff
Ms. Roslyn A. Edson, Designated Federal Officer, U. S. Environmental Protection Agency,
Science Advisory Board (1400), 401 M Street, SW, Washington, DC 20460
Mr. Samuel Rondberg, Designated Federal Officer, U. S. Environmental Protection Agency,
Science Advisory Board (1400), 401 M Street, SW, Washington, DC 204601
Ms. Wanda Fields, Management Assistant, Environmental Protection Agency, Science
Advisory Board (1400), 401 M Street, SW, Washington, DC 20460
'Did not attend the public meeting but provided editorial support for this report.
iv
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TABLE OF CONTENTS
1. EXECUTIVE SUMMARY 1
2. INTRODUCTION 8
2.1 Background 8
2.2 The Review and Charge 10
3. RESPONSE TO CHARGE QUESTIONS 11
3.1 Specific Charge Question 1 11
3.2 Specific Charge Question 2 11
3.3 Specific Charge Question 3 12
3.4 Specific Charge Question 4 16
3.5 Specific Charge Question 5 17
3.6 Specific Charge Question 6 18
3.7 General Charge Question 1 19
3.8 General Charge Question 2 20
3.9 General Charge Question 3 20
3.10 General Charge Question 4 21
3.11 General Charge Question 5 22
4. SUMMARY OF RECOMMENDATIONS AND CONCLUSIONS 23
REFERENCES CITED R-l
APPENDIX A - ACRONYMS AND ABBREVIATIONS A-l
APPENDIX B - ANNOTATED OVERVIEW OF THE LEAD 403 RULE B-l
APPENDIX C - TABLE AND FIGURES ON IQ C-l
APPENDIX D - EDITORIAL COMMENTS ON EPA DOCUMENTS D-l
APPENDIX E - REVIEW OF THE ECONOMIC ANALYSIS E-l
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1. EXECUTIVE SUMMARY
At the request of the EPA Office of Prevention, Pesticides and Toxic Substances
(OPPTS), Office of Pollution Prevention and Toxics (OPPT), the Environmental Health
Committee (EHC) conducted a technical review of the Lead 403 Rule. The EHC met on
September 8-9, 1998 in Arlington, Virginia. The EHC was charged to review the technical
aspects of the risk analysis which was presented in Risk Analysis to Support Standards for Lead
in Paint, Dust, and Soils, Volumes I and n, and to review the net benefits (benefits minus cost)
analysis which was presented in Economic Analysis of Toxic Substances Control Act Section
403: Hazard Standards. Subsequent to receipt of the proposed rule for the identification of
dangerous levels of lead in the Federal Register of June 3, 1998, the EHC found that some of the
informative discussion in the Federal Register notice was additional to that in the Agency reports.
Therefore, some of the recommendations relate to the amount of information in the proposed
rule.
The EHC commends the Agency for its effort to conduct a risk analysis for proposing
standards for lead levels in dust and soil as required by the Lead 403 Rule and for the wealth of
knowledge on the Lead 403 risk analysis that the Agency displayed during the meeting. Overall,
the EHC found many of the approaches used in the risk analysis to be technically sound,
appropriate, and scientifically defensible.
The EHC addressed the following 6 specific charge questions and 5 general charge
questions:
a) Specific Charge Question 1: The HUD National Survey, conducted in 1989-90,
measured lead levels in paint, dust, and soil in 284 privately owned houses. Does
our use of these data constitute a reasonable approach to estimating the national
distribution of lead in paint, dust, and soil?
The use of the data from the HUD National Survey is a reasonable approach since
the data are the best currently available. The upcoming HUD survey should have
greater power and should therefore increase the accuracy of the database.
b) Specific Charge Question 2: The approach employs conversion factors to combine
data from studies that used different sample collection techniques. Is this
appropriate? Is the method for developing these conversion factors technically
sound?
Since both 'wipe' samples and 'vacuum' samples were used in different surveys,
it was necessary to be able to equate sampling methods before combining data.
The methods are considered to be appropriate, technically sound and well
described in clear language.
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c) Specific Charge Question 3: IQ point deficits.
(1) the approach characterizes IQ decrements in the baseline blood-lead
distribution, essentially implying that any blood-lead level above zero
results in IQ effects. Have we provided a sufficient technical justification
for this approach? Is this approach defensible and appropriate?
Since the available data do not demonstrate a clear threshold for relating
IQ decrements to blood-lead levels, there is sufficient technical justification to use
an empirical fit that assumes that any blood-lead level above zero results in IQ
effect, as long as it is used only for predictive models and economic analysis. The
EHC recommends that the justification should be improved by a clearer
presentation of: a) how IQ measures are used for risk and cost benefit analyses; b)
the significance of a lack of a threshold; c) the relevance to other methodologies
such as NOAEL and Benchmark Dose; and d) additional references to the
literature, particularly relevant animal data that support causality, due to the
absence of confounding variables, and mechanism. IQ should be described as a
surrogate for potential neurological deficits for which we lack adequate metrics
[and may not be the most sensitive marker]. The approach is defensible and
appropriate for descriptions of population effects suitable for predictive models
and economic analysis, but should not be used for predictions about an individual.
The EHC concurs that the available data have not identified a clear
threshold for the health effects from lead and with the rationale that the weight of
scientific evidence shows that 10 |ig/dl is a reasonable level of concern for
childhood blood lead under the applicable statutory standard of "poses a threat."
It is recommended that the list of numerous health effects presented on page
30316 of the Federal Register be brought forward to emphasize that 10 ng/dl is
not a threshold value and to show the diversity of potential health effects from
lead.
(2) the characterization of IQ point loss in the population includes the
summation of fractional IQ points over the entire population of children.
Have we provided a sufficient technical justification for this approach? Is
this approach defensible and appropriate?
With recognition of the principle that small effects distributed across a large
population exert large total health effects, the technical justification in the Agency
report needs a more direct explanation. Some readers may be confused because
they interpret the exercise as awarding fractional IQ points to individual children.
The relatively large test-retest variation for an individual measurement of IQ
should be acknowledged. Again, the approach is defensible and appropriate as
utilized for population predictions.
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(3) one of the IQ-related endpoints is incidence oflQ less than 70. Should
consideration be given to what the IQ score was, or would have been,
prior to the decrement (i.e., should different consideration be given to
cases where a small, or even fractional, point decrement causes the 70
occurrence vs. being 70 due to larger decrements)? If so, how might this
be done?
The Agency report relies on the probabilistic analysis devised by Wallsten
and Whitfield in 1986 for estimating IQ scores below 70 due to lead exposure.
This report by Wallsten and Whitefield which was not published in the peer-
reviewed literature was based on expert estimates as a substitute for data. Expert
judgment is no longer needed for such calculations because later publications with
data are available.
The issues of IQ shifts, complexities of IQ measurements, significance of
fractional IQ units, and potential influence of socioeconomic status require a more
complete and clear presentation. Several examples for alternative presentations
are provided.
d) Specific Charge Question 4: Are the assumptions regarding duration,
effectiveness, and costs of intervention activities reasonable?
Six interventions were defined for lead based paint (LBP) and for lead in soil and
dust. The interventions are dust cleaning, interior or exterior LBP maintenance,
interior or exterior LBP encapsulation/abatement, and soil removal. The expected
duration of effectiveness of these interventions as described in Table 6-1 of the
Agency report was considered reasonable. The EHC recommends that further
consideration be given to the selection of housing units that trigger intervention,
and the biases that affect the number of housing units triggered by pre-
intervention dust-lead loadings. Although education as an intervention strategy
has been reported to not work well in disadvantaged communities, it is
recommended that the potential role of education as an intervention strategy be
evaluated.
The major problems with the cost benefit analysis for interventions to lead
hazards are an overestimation of cost and an underestimation of benefits. These
divergent estimations tend to be additive to each other rather than negating each
other, however, the standards for lead were not based solely on the benefits and
costs. It is important to recognize that values derived from the cost benefit
analysis are only relative values that are not rigorous, scientifically defensible
numbers in and of themselves. It is also important to keep in mind that the risk
analysis is a tool to systematically compare various standards options in a uniform
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manner looking for the combination that maximizes net benefits. Whether the
calculated costs and benefits are highly accurate of what actual costs and benefits
will be is less important than the comparative relationships and the methodology's
ability to discriminate between standard options. Recommendations for
improving the cost benefit analysis include (a) clarifying the discussion regarding
the basis for setting the lead standards given the marginal costs and marginal nets,
and (b) including a plan for follow-up to specific interventions. A more detailed
review of the economic analysis is included as Appendix E which was written by
an EHC Consultant.
e) Specific Charge Question 5: Are the combinations of standards used in Chapter 6
of the risk analysis reasonably employed given the potential interrelationships
between levels of lead in different media? Are additional data available on the
interrelationship between lead levels in paint, dust, and soil prior to and after
abatement?
One might say, in an almost self-evident way, that the various
combinations of standards were reasonably employed in that they provided a basis
for the Agency to select specific standards for the proposed rule. The EHC would
like to have seen a table of the estimated distribution of health effect and blood-
lead concentration endpoints using the actual proposed standards and a more
complete discussion of implications of the predictions of the models. The EHC
was not aware of additional data on the interrelationships among lead levels in
paint, dust and soil prior to and after abatement. Subsequently, the EHC received
the publication by Ashley, et. al (1997) describing the use of stable lead isotopes
techniques to identify probable sources of lead and to design appropriate source
specific interventions.
f) Specific Charge Question 6: The approach for estimating health effect and blood-
lead concentration endpoints after interventions is based upon scaling projected
declines in the distribution of children's blood-lead concentrations to the
distribution reported in Phase 2 of the National Health and Human Nutrition
Examination Survey (NHANES) III. Under this approach, data collected in the
HUD National Survey are utilized to generate model-predicted distributions of
blood-lead concentrations prior to and after the rule making. The difference
between the pre section 403 and post section 403 model predicted distributions is
used to estimate the decline in the distribution of children's blood-lead
concentration. This decline is then mathematically applied to the distribution
reported in NHANES III. Is this adjustment scientifically defensible in general,
and in the specific case where the environmental data —from the HUD Survey —
and the blood lead data —from NHANES III — were collected at different times
(1989-90 vs. 1991-1994)?
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The EHC found the adjustment to be scientifically defensible given that
the various conversion factors are clearly delineated and well justified. The
Agency report provides a useful discussion of the assumptions and limitations of
each of the models. However, the EHC found the description of the approach in
the report to be very complex and difficult to understand and recommends the use
of the illustration in Appendix B, as was provided by the Agency at the meeting,
and annotated by the Agency after the meeting to further improve its clarity.
g) General Charge Question 1: In each of the specific areas identified above, have
we used the best available data? Have we used these data appropriately? Have
we fairly characterized the variability, uncertainties and limitations of the data
and our analyses?
The data sets are considered the best available in this area and the Agency
has used them in an appropriate manner for the task. The support documents go
to considerable length to characterize the variability, uncertainties and limitations
of the data, models used and analyses. The human epidemiological data seem to
have been chosen judiciously. A number of additional references are provided
that should support the data used.
With regard to fair characterization, the proposed standards for lead in dust
and soil, as presented on page 30303 of the Federal Register, do not make it clear
that the probability of exceeding a blood-lead level of 10 |ig/dl is higher for the
soil-lead standard than it is for the dust-lead standards. The EHC recommends
that this difference be explained along with the initial presentation of the
standards. It is also recommended that the soil-lead standard of 2,000 ppm and
the soil-lead level of concern of 400 ppm be explained with regard to the impact
on current practices of the Department of Housing and Urban Development
(HUD) and certain States.
h) General Charge Question 2: Are there alternative approaches that would improve
our ability to assess the relative risk impacts of candidate options for paint, dust,
and soil hazard standards?
The approaches taken were considered to be reasonable. While a variety
of alternatives are possible, most of them would require additional research. The
EHC felt that it would be useful for the literature about the standards to
consistently reference the broader age range of 0-6 years. The EHC makes this
recommendation to eliminate the possible misconception that the risk is only for
the 1-2 year old child.
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i) General Charge Question 3: The approach employs risk analysis models that
were primarily developed for use in site-specific or localized assessments. Has
the use and application of the Integrated Exposure Uptake Biokinetic Model
(IEUBK) and empirical model in this context been sufficiently explained and
justified? Is our use of these tools to estimate nationwide impacts technically
sound?
The general characteristics, uses and application of the IEUBK and
empirical models are well described, explained and justified. However, the
complexity presented in the Agency report was difficult to follow. The discussion
(page 30315 of the Federal Register notice) on the strengths and weaknesses of a
mechanistic model vs. a model based on empirical data was helpful and the EHC
recommends that it be included in the report. There is no perfect model. Thus the
use of two models (IEUBK and empirical) is appropriate and helpful, even though
both are flawed. Although each of the models has its limitations and
uncertainties, the estimates from these two complementary models overlap. To
that end, it would be helpful to provide greater emphasis upon the commonalties
found and when possible utilize the empirical data from the supportive studies to
validate the observations.
The EHC concluded that the Agency's use of these tools was technically
sound with the caveats noted in the responses to the specific questions above (e.g.,
10 |ig/dl is not a threshold). The EHC also concluded that the use of the tools to
estimate nationwide impacts is technically sound but that there are uncertainties
because the Agency is not using an absolute predictor.
j) General Charge Question 4: Are there any critical differences in environmental
lead-blood lead relationships found in local communities that should be
considered in interpreting our results at the national level?
There are differences in environmental lead-blood lead relationships found
in local communities. These differences may be attributable to factors such as
regional differences in the bioavailability of lead dependent on the source of the
lead (especially lead in soil from non-point sources), nutrition, age, and genetic
susceptibility. However, data on the effect of these factors on environmental lead-
blood lead relationships are limited and additional research would be required to
consider these factors in interpreting the Agency's results for lead-blood lead
relationships at the national level. The EHC acknowledges the Agency's plans for
flexibility at the regional level for complying with the lead standards.
k) General Charge Question 5: In view of the issues discussed and analyzed in
sensitivity analyses contained in the two documents, in what specific areas should
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we focus (e.g., refine our approach, gather additional data, etc.) between now and
the final rule?
The EHC recommends three specific projects for inclusion in the final
rule: (1) an expansion of the sensitivity analysis to include a case study of a real
community that is highly susceptible to lead exposure and a presentation of the
costs and benefits associated with that case study, (2) development of a plan for
follow-up to evaluate the effectiveness of the specific interventions, and (3)
sensitivity analyses that carry through all the way to cost for conversion factors
used to compare media loadings and for assumptions regarding the housing
industry.
In this report the EHC has made a number of recommendations for improving the
scientific basis for the standards in the Lead 403 Rule. Some of these recommendations will
require further research. However, there is sufficient scientific evidence to indicate that delaying
rulemaking for additional research would leave a significant number of children unnecessarily at
risk.
The Agency is highly commended for its stated intent to prepare and distribute
educational material to provide guidance for complying with the standards. This material should
be tailored to specific circumstances. The EHC feels that guidance is particularly important since
the requirement for homeowners to disclose a known lead risk may be a disincentive for testing.
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2. INTRODUCTION
2.1 Background
The Residential Lead-Based Paint Hazard Reduction Act of 1992 (42 U.S.C. 4851)
includes an amendment to the Toxic Substances Control Act (TSCA). This amendment requires
the EPA Administrator to enact a variety of activities to identify and reduce environmental
exposure to lead hazards. This amendment is referred to as Section 403 of TSCA and includes
the following language, "... the Administrator shall promulgate regulations which shall identify,
for purposes of this title and the Residential Lead-Based Paint Hazard Reduction Act of 1992,
lead-based paint hazards, lead-contaminated dust, and lead-contaminated soil."
The reports reviewed by the EHC were Risk Analysis to Support Standards for Lead in
Paint, Dust, and Soils, Volumes I and n, which presented the methods and findings of risk
analysis that provides the scientific foundation for the proposed standards and Economic Analysis
of Toxic Substances Control Act Section 403: Hazard Standards presenting a net benefits
(benefits minus cost) analysis. Subsequent to receipt of the charge, the EHC received the notice
of the proposed regulation for the Lead 403 Rule in the Federal Register of June 3, 1998. The
EHC found that some of the informative discussion in the Federal Register notice was additional
to that in the Agency reports. Therefore, some of the recommendations relate to the amount of
information in the proposed rule.
The population of interest for the risk analysis was U.S. children aged 1-2 years. To
characterize the health risk associated with lead exposures to children aged 1-2 years, the risk
analysis considered elevated blood-lead concentration and IQ point deficit as the health
endpoints. The national distribution of blood-lead concentration in children aged 1-2 years was
determined from data collected in Phase 2 of the third National Health and Nutrition
Examination Survey (NHANES III), conducted from 1991-1994. Environmental-lead levels in
the nation's housing stock were obtained from the National Survey of Lead-Based Paint in
Housing, conducted from 1989-1990 by the U.S. Department of Housing and Urban
Development (HUD). In analyzing data from the HUD National Survey, the Agency used
conversion factors to combine data from studies that used different sample collection techniques.
The Agency obtained data on the number of housing units and on children within specified
housing groups from the U.S. Bureau of the Census.
Two statistical models were used to characterize the risks posed by lead exposure to the
nation's population of children aged 1-2 years: the Agency's Integrated Exposure, Uptake,
Biokinetic (lEUBK) Model for Lead in Children (version 0.99D) and an empirical regression
model developed for the risk analysis. The IEUBK model was reviewed by the Science Advisory
Board Indoor Air Quality and Total Human Exposure Committee in March 1992 (SAB, 1992).
The empirical model, which was developed specifically for this study, is based on data collected
in a single lead exposure study (Lanphear et al., 1995). The empirical model was developed to
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address some aspects of lead exposure that were important to the risk management analyses but
could not be directly addressed by the IEUBK model. However, both models have their
limitations. For example, the empirical model can predict blood-lead concentration based on
dust-lead loadings rather than concentration, using data on lead loadings in window sill dust as
well as floor dust, and representing the effect of pica tendency in the presence of deteriorated
lead-based paint. The IEUBK model does not have this capability. On the other hand, the
empirical model uses data from one site as representative of a national level. Since neither of the
models is optimal for application within the risk analysis, the Agency used both models to obtain
two distributions of blood-lead concentration. Both models were used for obtaining blood-lead
distributions using floor-lead and soil-lead data, while only the empirical model was used for
window sills-lead data.
The Agency ultimately estimated the national distribution of blood-lead concentrations
that represented conditions after implementing the proposed Lead 403 rule and that was directly
comparable to the baseline distribution. The IEUBK model and a third statistical model, the
Rochester multimedia model, were used to determine "individual risks" which was defined by the
Agency as risks associated with children exposed to specified environmental-lead levels. The
Agency also estimated "population-based risks", the risk to an entire population of children aged
1-2 years, given exposure to baseline levels of lead in the nation's housing stock.
As part of the development of standards for lead dust and paint exposure under Section
403 of the Toxic Substances Control Act, the Economic and Policy Branch of OPPT performed a
benefit-cost analysis (BCA). The BCA is conducted from a national perspective, covering a 50-
year period. As soon as a child between 0 and 6 years of age enters a house where lead is
present, abatement activities are assumed to be conducted until the child reaches 6 years of age.
This process is repeated for as many times as a house has a child less than 6 years of age in it
over the 50 years. The optimal standards are those that maximize present net benefits of those
abatement activities. In conducting the net benefits analysis, the Agency used several default
assumptions including estimates for paint pica tendencies, the duration of repairing paint, and the
duration of encapsulation/abatement methodology.
The Agency has recognized that available data have not identified a clear threshold for
several lead effects and that biological changes can occur at lower levels. However, the Agency
has rejected a zero risk basis for dust- and soil-lead levels of concern for a variety of reasons.
For purposes of the proposed rule, 10 |ig/dl has been selected as a reasonable level of concern for
childhood blood-lead under the applicable statutory standard of "poses a threat." Thus the
proposed standards for lead in dust and soil were designed (based on the technical approaches of
the risk analysis) on the basis of predicting that children, living in a residence that had been
cleaned to these standards, would have a very low probability of having a blood-lead
concentration equal to or exceeding 10 |ig/dl.
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2.2 The Review and Charge
On September 8-9, 1998, the EHC met in Arlington, Virginia to conduct a technical
review of the Lead 403 Rule. The EHC was charged to respond to six specific and five general
questions. These charge questions and their responses by EHC are presented in the next section.
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3. RESPONSE TO CHARGE QUESTIONS
3.1 Specific Charge Question 1
The HUD National Survey, conducted in 1989-90, measured lead levels in paint, dust,
and soil in 284 privately owned houses. Does our use of these data constitute a
reasonable approach to estimating the national distribution of lead in paint, dust, and
soil?
Findings and Recommendations
The HUD National Survey of Lead-Based Paint in Housing is the only available
study designed specifically to provide nationally representative estimates of
environmental lead in dust and soil in private housing stock. The EHC considered that it
was a well-designed survey using appropriate methodologies. Although the study is more
than five years old, it is considered unlikely that the housing stock lead-based paint status
has either improved or deteriorated significantly to affect the estimates on a nationwide
basis. As with any survey, in retrospect, a larger sample size with more environmental
samples per dwelling would have provided more robust descriptive statistics, greater
confidence that the analysis of sample results were representative, and increased its utility
for the current modeling needs. Empirical data from the community studies discussed in
the support documents, and especially the HUD Lead Based Paint Hazard Control Grants,
add confidence that the National Survey data remain representative and the relationships
between environmental-lead data elements are still appropriate. The adjustments for loss
of housing stock (made to arrive at the 1997 estimates of pre-1980 housing stock) are
considered appropriate. The necessary conversion factors to account for technical
advances in methodology (see Specific Charge Question 2) may be more problematic
than the sampling design of a survey completed five years ago.
The upcoming HUD survey of 1,000 homes should have greater power and
should, therefore, increase the accuracy of the database used to estimate the national
distribution of lead in paint, dust, and soil.
3.2 Specific Charge Question 2
The approach employs conversion factors to combine data from studies that used
different sample collection techniques. Is this appropriate? Is the method for developing
these conversion factors technically sound?
Findings and Recommendations
Dust-lead measurements from floors and window sills in the HUD National
Survey were collected by the Blue Nozzle (BN) vacuum method. In addition the
Baltimore Repair and Maintenance (BRM) study used a BRM vacuum technique. Since
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standards for dust in the 403 Rule will be expressed as a measured lead loading collected
by a dust wipe sample, it was necessary to convert the BN and BRM vacuum data to
wipe-equivalent dust-lead loadings before combining data for risk analysis. Several
studies were presented that reported side-by-side wipe and vacuum dust-lead
measurements.
The EHC found that the specific conversion factors were appropriate, technically
sound, and well described in clear language in the review document.
3.3 Specific Charge Question 3
The three parts (a,b,c) of this question dealing with IQ point deficits are addressed
separately.
a) the approach characterizes IQ decrements in the baseline blood-lead distribution,
essentially implying that any blood-lead level above zero results in IQ effects.
Have we provided a sufficient technical justification for this approach? Is this
approach defensible and appropriate?
Findings and Recommendations
Because available data have not identified a clear threshold, the assumption of no
threshold for lead effects on IQ score is both defensible and appropriate statistically.
However, the EHC recommends that the technical justifications should be documented
more thoroughly. Because much of the public, and even some scientists, are confused
about what IQ scores measure, the document should clarify how IQ measures are used in
the risk and cost benefit analyses. It should state explicitly that, at least for the Agency's
purposes, IQ tests are not used to gauge some abstract quality called "intelligence," but,
instead, comprise a sample of performance with a defined degree of predictive power that
facilitates the economic analysis. Presenting IQ scores in this way might help avoid
misunderstandings on the part of some observers who convert the analyses into a claim
that "intelligence" determines earnings rather than as a description of an empirical
relationship. The document should clearly indicate the limitations of reliance on single
criterion that may not be the most sensitive response index, rather than the multiple
endpoints of neurotoxicity. (See Mendelson et al., 1998; Wasserman et al., 1998;
Needleman et al., 1996; and Sreissguth et al., 1996)
IQ should be recognized as a surrogate for potential neurological deficits for
which we lack adequate metrics. The complex relationships surrounding IQ scores
further argue for presenting IQ tests as samples of behavior rather than as measures of
some pure and unitary dimension. It also relates to the argument that the path between IQ
score and economic benefits is not necessarily one of direct causation. Despite their
universally acknowledged flaws, IQ scores are more readily translated into predictive
models to provide the basis for risk and threshold calculations.
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The EHC considered that the arguments about thresholds were somewhat
amorphous in the Agency report. The report should elaborate on the attempts to calculate
a threshold by testing the suitability of a linear fit to the dose response function (see Tong
et al., 1996; Hawk et al., 1986; Wyzga, 1990; and Schwartz, 1993). In addition the EHC
found the last paragraph on page 4-22 of the report to be unclear with regard to the
assumption that linear models reduce the likelihood of overestimating the number of
children at risk with low blood-lead concentrations. If this is an important point it may be
clarified with graphical illustrations. The EHC concurs that the available data have not
identified a clear threshold for the health effects from lead' and with the rationale that the
weight of scientific evidence shows that 10 |ig/dl is a reasonable level of concern for
childhood blood lead under the applicable statutory standard of "poses a threat." It is
recommended that the list of numerous health effects presented on page 30316 of the
Federal Register be brought forward to emphasize that 10 |ig/dl is not a threshold value
and to show the diversity of potential health effects from lead.
Human data, with all the intrinsic flaws of epidemiology, are generally given
precedence over animal data for risk analysis. Nevertheless, animal data are able to
establish causality (due to the absence of confounding variables) and mechanisms for
adverse health effects. This is certainly true for effects of lead and the animal data supply
confidence for the human data when the human data have large uncertainties. The EHC
recommends that additional animal data be included in the Agency report as support for
the use of the human data. Important references include: a) Cory-Slechta, 1997 (which
establishes relationships among lead exposure, biological indices, neurochemical systems
and behavior with significant effects at blood-lead levels of 10 - 20 |ig/dl), and b) Rice,
1996 (which indicates that functional deficits occur in monkeys with steady-state blood-
lead levels since infancy as low as 11 |ig/dl/.)
The EHC also considered that a discussion of the standard procedures involving
NOAEL, benchmark dose and uncertainty factors for risk analyses from animal data
should be presented. If the experimental animal data were to be treated by these
conventional standards, an acceptable level of lead exposure would likely be an order to
two orders of magnitude less. Clarifying the alternatives in this fashion may help the
public understand the course adopted by the Agency.
b) the characterization of IQ point loss in the population includes the summation of
fractional IQ points over the entire population of children. Have we provided a
sufficient technical justification for this approach? Is this approach defensible
and appropriate ?
Findings and Recommendations
The EHC considered that the Agency report should emphasize a core principle of
public health; namely, that small effects distributed across a large population exert large
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total health effects. Thus the characterization of IQ point loss by the summation of
fractional IQ points over the entire population of children is considered defensible and
appropriate. It was also considered that the technical justification needed to be explained
more clearly. In developing the final rule should be very careful when referencing effects
in individual children. Some readers, understandably, may be confused because they
interpret the exercise as awarding fractional IQ points to individual children. The
relatively large test-retest variation associated with any individual measure of IQ should
be clearly presented.
c) one of the IQ-related endpoints is incidence oflQ less than 70. Should
consideration be given to what the IQ score was, or would have been, prior to the
decrement (i.e., should different consideration be given to cases where a small, or
even fractional, point decrement causes the < 70 occurrence vs. being < 70 due to
larger decrements)? If so, how might this be done?
Findings and Recommendations
The EHC found this question to be the most problematic of all questions about the
Agency report, and recommends some reconsiderations.
The report relies on the probabilistic analysis devised by Wallsten and Whitfield
in 1986 for estimating IQ scores below 70 due to lead exposure. This report which was
not published in the peer-reviewed literature was based on expert estimates as a substitute
for data and appeared before the key papers of Bellinger et al. (1987), Dietrich et al.
(1987a, 1987b), and others used for Schwartz's (1994) analysis. Expert judgment is no
longer needed for such calculations.
The implications of shifts in IQ distribution should be expanded. If, based on the
Schwartz meta-analysis, the mean IQ decrement due to lead is 1.06, what does such a
shift do to the entire IQ distribution? The document is focused on IQ's below 70, but
corresponding changes occur at the other extreme of the distribution as well. An example
here would be useful; for instance, describe what would happen with a prototypical IQ
distribution (mean=100, SD=15) if the mean were to be displaced by 1% or 1 IQ point;
or, 3% or 3 IQ points. How many individuals would be classified as retarded, for
example? How many would be demoted from the superior category? In addition, what
are the implications for especially vulnerable, highly exposed subpopulations. Largely
low incomes and their associated health risks are common in these subpopulations. If
lead shifts IQ distributions toward lower scores, its effects are amplified in these
subpopulations because their distributions are already displaced toward lower scores.
Does including them in the population at large when calculating total IQ displacements
underestimate the effects of lead exposure?
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The Stanford-Binet and the Weschler Intelligence Scale for Children generally
assume a standard deviation of 15 (based on the validation population) and a mean of
100. The Bayley Scales of Infant Development generally conform to these figures. A
shift in the population mean of 1% means a shift in the original population mean of 1/15
standard deviation, and an increase in the proportion of scores below 70 from 0.0228 to
0.0266. In a population of 8,000,000 (about the size of the population of children 1-2
years of age), it means a rise from 182,400 to 212,800 children scoring below 70. A shift
of 3% would correspond to a rise from 182,400 to 287,200. A graphical depiction
appears in Figure 1 of Appendix C and may be useful in communicating this kind of
information to readers. Presenting the data in this way should make it unnecessary to deal
with the question of fractional point decrements as stated in the Charge Questions. If the
risk analysis calculates the mean IQ shift, which can involve fractional percentages, it
would provide the corresponding proportion of cases below an IQ of 70.
A second problem with the calculations is the assumption of a United States
(U.S.) population mean of 100. Although useful for illustrative purposes, and still in use
by schools for classification purposes, it is not considered a realistic assumption for risk
characterization. IQ scores around the world have been rising, at roughly 0.3 IQ points
annually. This is known as the Flynn Effect, named after James Flynn, a New Zealand
political scientist, and is extensively documented and a critical consideration in lead risk
analysis. Table 1 in Appendix C shows how the proportion of individuals scoring below
70 varies with mean IQ. If the rise observed during the past several decades continues,
standardized test scores will continue to lag this trend and the proportion below 70 will
continue to fall. As a result, the risks attributable to lead exposure will be
underestimated.
Because of the Flynn Effect, a more useful characterization of low IQ risk might
be to discuss it in terms of z-scores. That is, transform risk of IQ less than 70 to risk of
falling lower than -2 SD of the standard population which would make it independent of
mean population score. The present analysis, based on a mean equal to 100, would then
be used for illustrative purposed only. By adopting this approach, the basis for linking
lead exposure to IQ would then be expressed in terms of population and subpopulation
divergence. An example might compare a subpopulation with a mean blood-lead of 10.8
Hg/dl to one with a mean blood-lead of 3.0 |ig/dl. On the basis of the Schwartz meta-
analysis (one |ig/dl equates to 0.257 IQ units, See Schwartz (1994)), this would represent
a shift of 2 IQ points [(10.8 - 3.0)(0.257)]. The assessor would then calculate how many
children in the subpopulation have been displaced by 2 standard deviations or more below
the overall population mean.
A major thrust of the risk analysis is to elucidate the effects of diminished lead
exposure on populations with disadvantaged socioeconomic status (SES). As the report
notes, minority children in low SES households tend to exhibit higher lead levels. They
also tend to score lower on IQ tests. The result is that, for an equivalent displacement of
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mean IQ, such communities (in the aggregate, not as individuals) would experience a
relatively greater impact than those in higher SES groupings for indices such as
proportions of IQ scores below 70 or lower than -2 standard deviations. Even SES
represents only one of the many risk factors. The cumulative effects of many risk factors,
in combination with lead, would need to be determined to fully describe its adverse
effects (see Sameroff et al., 1987). Community characteristics pertaining primarily to
lead levels are available from several sources (see Lanphear et al., 1996). Among these
are race, population density, poverty, and education levels. It is particularly critical, for
lead, that these interactive variables are considered. Schwartz's (1994) analysis yielded a
lower mean loss in IQ scores attributable to lead in disadvantaged than in advantaged
populations. This finding, as noted by the paper, may be a product, if not an artifact, of
the greater cumulative risks to development suffered by such populations. The eventual
impact on earnings, however, might lie in the opposite direction due to the relationship
between IQ and opportunities for education (see Ceci and Williams, 1997) and because of
the actual impact of IQ losses on advantaged and disadvantaged populations.
In many surveys, the differences in mean IQ scores of these populations
approximate about 15 points. One may assume, then, for modeling purposes, that initial
IQ distributions will have respective means of 100 and 85, both with standard deviations
of 15. As an impact index, the number of scores below 70 can be calculated. With
population sizes of 100,000 each, as shown in Figure 2 of Appendix C, a loss of 1 IQ
point in the advantaged population will increase the number of individuals below 70 from
2,280 to 2,660. In the disadvantaged population, the loss assigns 17,530 rather than
15,870 individuals to the below 70 category. Although the proportional shift is greater in
the advantaged population (16.7%) than in the disadvantaged population (10.5%), the
number of individuals added to the developmentally disabled category is much larger in
the disadvantaged population (1,660) than in the advantaged population (380).
3.4 Specific Charge Question 4
Are the assumptions regarding duration, effectiveness, and costs of intervention activities
reasonable?
Findings and Recommendations
Six interventions were defined for lead based paint (LBP) and for lead in soil and dust.
The interventions are dust cleaning, interior or exterior LBP maintenance, interior or exterior
LBP encapsulation/abatement, and soil removal. The expected duration of effectiveness of these
interventions as described in Table 6-1 of the report was considered reasonable. The EHC
recommends that further consideration be given to the selection of housing units that trigger
intervention, and the biases that affect the number of housing units triggered by pre-intervention
dust-lead loadings. Although education as an intervention strategy has been reported to not work
well in disadvantaged communities, it is recommended that the potential role of education as an
intervention strategy be evaluated.
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As part of the development of standards for lead dust and paint exposure under Section
403 of the Toxic Substances Control Act, the Agency had a benefit-cost analysis (BCA)
performed. The BCA appears to have played a major, if not decisive, role in the choice of
standards; indeed, the Federal Register proposed rule notes that the legislation implicitly supports
the use of BCA in designating the proposed standards (pp. 30312-30314).
The EHC found the overall process used in the economic analysis to be reasonable. The
major problems with the cost benefit analysis for interventions to lead hazards are an
overestimation of cost and an underestimation of benefits. These divergent estimations tend to
be additive to each other rather than negating each other. The following two factors result in an
underestimation of benefits: 1) the use of IQ point deficit as an indicator of adverse health
effects, and 2) the exclusion of reduced inspection and abatement/remediation cost associated
with fewer children with blood levels exceeding 15 |ig/dl. The latter benefit should be applied
for universal screening and should be included in the cost benefit analysis. By not taking into
account the fact that people will undertake some of the abatement measure (such as repainting)
even in the absence of lead will probably result in an overestimation of cost since all painting
expenses (both lead abatement and non-lead abatement) are counted as lead abatement expenses.
The EHC supports the use of a discount rate of 3% rather than the OMB use of 7% for the
economic analysis. A more detailed review of the economic analysis is included as Appendix E
which was written by an EHC Consultant.
Most of the default assumptions used in the economic analysis were found to be
reasonable as discussed in the detailed review in Appendix E. The EHC recommends that the
discussion on the basis for setting the lead standards given the marginal costs and marginal nets
be rewritten because it was difficult to follow. It is important to recognize that values derived
from the cost benefit analysis are only relative values that are not rigorous, scientifically
defensible numbers in and of themselves. It is also important to keep in mind that the risk
analysis is a tool to systematically compare various standards options in a uniform manner
looking for the combination that maximizes net benefit. Whether the calculated costs and
benefits are highly accurate of what actual costs and benefits will be is less important than the
comparative relationships and the methodology's ability to discriminate between standard
options.
The EHC commends the Agency plans to develop educational material tailored to
specific circumstances for helping the public comply with the lead standards of the Lead 403
Rule. For example, a decision tree which answers questions regarding the regulation and
guidance should address differences in the age of the children residing in a house, the length of
stay in the house and the sensitivity of the children to other toxins. The EHC considers that such
guidance is particularly important since the requirement for homeowners to disclose a known
lead risk may be a disincentive for testing.
3.5 Specific Charge Question 5
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Are the combinations of standards used in Chapter 6 of the risk analysis reasonably
employed given the potential interrelationships between levels of lead in different media?
Are additional data available on the interrelationship between lead levels in paint, dust,
and soil prior to and after abatement?
Findings and Recommendations
The response to the second question above was straightforward in that the EHC was not
aware of additional data on the interrelationships among lead levels in paint, dust and soil prior
to and after abatement. Subsequently, the EHC received the publication by Ashley et al. (1997)
describing the use of stable lead isotope techniques to identify probable sources of lead and to
design appropriate source specific interventions.
The first question above was more troublesome for the EHC. One might say, in an
almost self-evident way, that the various combinations of standards were reasonably employed in
that they provided a basis for the Agency to select specific standards for the proposed rule. What
would have been of interest, then, would be a chart in the Federal Register like Table 6-8, but
using the actual proposed standards. The EHC thought the more relevant issues were the
implications of the predictions from the models based on the standards. For example, (1) what is
the contribution of natural lead (lead present not due to human interventions), or lead from water
and food as a function of different communities?, (2) should exposure sources in individual units
be identified and abated simultaneously?, (3) how often should blood-lead levels be monitored as
an indication of effectiveness?, and (4) when should a community's lead exposure be addressed
in a global fashion instead of one dwelling unit at a time.
3.6 Specific Charge Question 6
The approach for estimating health effect and blood-lead concentration endpoints after
interventions is based upon scaling projected declines in the distribution of children's
blood-lead concentrations to the distribution reported in Phase 2 of the National Health
and Human Nutrition Examination Survey (NHANES) III. Under this approach, data
collected in the HUD National Survey are utilized to generate model-predicted
distributions of blood-lead concentrations prior to and after the rule making. The
difference between the pre section 403 and post section 403 model predicted distributions
is used to estimate the decline in the distribution of children's blood-lead concentration.
This decline is then mathematically applied to the distribution reported in NHANES III.
Is this adjustment scientifically defensible in general, and in the specific case where the
environmental data —from the HUD Survey — and the blood lead data —from NHANES
III- were collected at different times (1989-90 vs. 1991-1994)?
Findings and Recommendations
While one would prefer to have all data sets contemporary to one another and the analytic
time frame, this rarely occurs. In this instance, the data sets are nearly contemporary to each
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other, as all large, complex national surveys are never truly cross-sectional point-in-time, but
rather, practicality necessitates implementation over a number of years. The survey design
protocols often include statistical sampling methods to minimize the impact of the duration of the
survey. The adjustments made to estimate 1997 housing status and the 1-2 year old population
blood lead distribution are likely to contribute more uncertainty than the fact that the data sets
were not gathered during the exact same periods. Using the geometric mean and geometric
standard deviation as the primary descriptive statistics should minimize any impact of outlier
shifts.
The EHC considered that the adjustment was scientifically defensible on the basis that the
various conversion factors were clearly delineated and justified. Mathematical transformation
factors are routinely used in many calculations where it is of scientific value to integrate or
compare data sets from two different sources which were collected at two different times. As
long as both data sets are scientifically valid, there is no reason why such adjustments cannot be
made in principle. The Lead 403 Rule document (Sections 4.1 - 4.3) provides a useful discussion
of assumptions and limitations of each of the models used for conversions. The application of
the HUD data set to the distribution of blood lead values observed in the NHANES HI was
appropriate since the NHANES in data set was the largest body of blood-lead data available
which is reflective of the general U.S. population. It should hence give the best distributional fit.
The available data and the risk analysis primary objectives (compare 1997 pre-403
standards baseline to post-403 implementation and select the environmental-lead measurements
that maximize the net benefit) made it necessary to design a multi-step, multi-model protocol to
achieve the necessary comparisons. However, it is difficult to devise a more simplistic approach
that would not interject other uncertainties for those removed. The EHC found the description of
the approach in the Agency report to be very complex and difficult to understand and
recommends the use of the illustration in Appendix B, as was provided by the Agency at the
meeting and annotated by the Agency after the meeting.
3.7 General Charge Question 1
In each of the specific areas identified above, have we used the best available data? Have
we used these data appropriately? Have we fairly characterized the variability,
uncertainties and limitations of the data and our analyses?
Findings and Recommendations
To the best knowledge of members of the EHC, the Agency report has used the best
available data sets for making its calculations. The NHANES in and HUD data sets are
considered the best available in this area and the Agency has used them in an appropriate manner
for the task. The support documents characterize, in considerable length, the variability,
uncertainties and limitations of the data, models used, and analyses. The human epidemiological
data seem to have been chosen judiciously and their limitations described at length except for the
reliance on expert estimates for calculations of IQ scores less than 70. Papers published since
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then make such reliance unnecessary. In the responses to the questions above, a number of
additional references are provided in the response to Specific Charge Question 3 that should
support the data used.
With regard to fair characterization, the proposed standards for lead in dust and soil, as
presented on page 30303 of the Federal Register, do not make it clear that the probability of
exceeding a blood-lead level of 10 |ig/dl is higher for the soil-lead standard than it is for the dust-
lead standards. The EHC recommends that this difference be explained along with the initial
presentation of the standards. It is also recommended that the soil-lead standard of 2,000 parts
per million (ppm) and the soil-lead level of concern of 400 parts per million (ppm) be explained
with regard to the impact on current practices of the Department of Housing and Urban
Development (HUD) and certain States.
3.8 General Charge Question 2
Are there alternative approaches that would improve our ability to assess the relative
risk impacts of candidate options for paint, dust, and soil hazard standards?
Findings and Recommendations
The EHC found the approaches taken to be reasonable. A variety of alternatives , most of
which would require additional research for use in the models for risk analysis, were discussed.
These included concern for variations in particle size of lead dust, the chemical form of the lead,
the variations in absorption from the gastrointestinal tract (50% for children vs. 10% for adults),
the potential influence of homes with porches, and the regional variation in climate that may
influence the time that windows are open.
The Agency report documented that the most susceptible age range for children was 1-2
years and that the economic analysis was based on children aged zero to six years. The EHC felt
that it would be useful for the literature about the standards to consistently reference the broader
age range of 0-6 years. The EHC recommends this to eliminate the possible misconception that
the risk is only for the 1-2 year old child.
3.9 General Charge Question 3
The approach employs risk analysis models that were primarily developed for use in site-
specific or localized assessments. Has the use and application of the Integrated
Exposure Uptake Biokinetic Model (IEUBK) and empirical model in this context been
sufficiently explained and justified? Is our use of these tools to estimate nationwide
impacts technically sound?
Findings and Recommendations
The general characteristics, uses and application of the IEUBK and empirical models are
well described, explained and justified. However, the complexity presented in the Agency report
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was difficult to follow. The discussion (page 30315 of the Federal Register notice) on the
strengths and weaknesses of a mechanistic model vs. a model based on empirical data was
helpful and the EHC recommends that it be included in the report. There is no perfect model.
Thus the use of two models (IEUBK and empirical) is appropriate and helpful, even though both
are flawed. Although each of the models has its limitations and uncertainties, the estimates from
these two complementary models overlap. To that end, it would be helpful to provide greater
emphasis upon the commonalties found and when possible utilize the empirical data from the
supportive studies to validate the observations. The EHC concluded that the Agency's use of
these tools was technically sound with the caveats noted in the responses to the specific questions
above (e.g., 10 |ig/dl is not a threshold). The EHC also concluded that the use of the tools to
estimate nationwide impacts is technically sound but that there are uncertainties because the
Agency is not using an absolute predictor.
3.10 General Charge Question 4
Are there any critical differences in environmental lead-blood lead relationships found in
local communities that should be considered in interpreting our results at the national
level?
Findings and Recommendations
It is important that the Agency define the term "local community" as a community with a
significant risk of lead-contaminated housing. There are differences in environmental lead-blood
lead relationships found in local communities. These differences may be attributable to factors
such as regional differences in the bioavailability of lead dependent on the source of the lead
(e.g., smelter vs. urban environment) and individual susceptibility (e.g., genetic polymorphisms
and nutritional status). There are also differences in the amount of lead paint applied during
painting which varied based on the harshness of the environment and when the paint was
manufactured (pre vs. post 1940). However, data on the effect of these factors on environmental
lead-blood lead relationships are limited and additional research would be required to consider
these factors in interpreting the Agency's results for lead-blood lead relationships at the national
level. Given that there are some regional differences in blood-lead lead relationships, the EHC
emphasizes the need for flexibility at the regional level for complying with the lead standards and
acknowledges the Agency's plans for flexibility as outlined on page 30344 of the Federal
Register notification of proposed rulemaking.
Since the particle size of lead paint dust is generally much finer than that of the larger
particles usually found in former mining sites, it is reasonable to assume that the lead component
from these particles is more biologically available and, hence, a conservative approach is
warranted. The question of whether this approach is technically sound for all soil environments
encountered across the U.S. should probably be discussed in relation to the nature of the soils.
Soils vary in their acidity and presence of other chelating minerals which could influence the
bioavailability of lead from a given soil type. It is possible that weighting factors may be
developed for some of these factors. This would in turn influence the predicted lead absorption
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coefficient inserted into a given model. This type of factoring would be a refinement of the
calculation not a substantive change in the model itself.
Other factors that may vary from community to community include age demographics of
the population of concern, diet, clusters of housing units, other toxic agents and perhaps genetic
susceptibility. These factors may exert a real influence on the actual measure of safety conferred
by interventions according to the proposed standards.
3.11 General Charge Question 5
In view of the issues discussed and analyzed in sensitivity analyses contained in the two
documents, in what specific areas should we focus (e.g., refine our approach, gather
additional data, etc.) between now and the final rule?
Findings and Recommendations
The sensitivity analyses provided are helpful in identifying the impact of critical factors.
Unfortunately, there is no one model or analytic methodology that is obviously superior. There
are always alternative approaches and additional factors to consider (see the multiple suggestions
in responses above). While gathering additional data would always be helpful, the EHC does not
believe that the Lead 403 rule should be delayed for any significant time. It would be useful to
have a discussion added on how the Lead 403 standards may relate to the state based activities to
investigate and order remediation of homes where lead poisoned children are found. These
investigations are, by definition, site specific, while the Lead 403 standards are more generic.
The EHC recommends three specific projects for inclusion in the final rule: a) an
expansion of the sensitivity analysis to include a case study of a real community that is highly
susceptible to lead exposure and a presentation of the costs and benefits associated with that case
study, b) the development of a plan for follow-up to evaluate the effectiveness of the specific
interventions (details should include the type of measurements to be made, the locations for the
measurements, and the timetable for the validation process), and c) sensitivity analyses that carry
through all the way to cost for conversion factors used to compare media loadings and for
assumptions regarding the housing industry.
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4. SUMMARY OF RECOMMENDATIONS AND CONCLUSIONS
In this report the EHC has made a number of recommendations for improving the
scientific basis for the standards in the Lead 403 Rule, including the following:
a) The Agency should provide a clearer presentation on how Intelligence Quotient
(IQ) is used for risk and cost benefit analysis, the significance of lack of a
threshold, the impact of IQ shifts, the use of additional literature references for the
below 70 IQ scores, emphasis on IQ as a neurological surrogate, and improving
the explanation that the IQ fractional point loss is valid for economic analysis but
not for interpretations for individual children;
b) The Agency should add more animal data since they support human data by
establishing causality, due to the absence of confounding variables, and potential
mechanisms for adverse health effects;
c) The Agency should clarify the discussion regarding the basis for setting the lead
standards given the marginal costs and marginal nets, including a plan for follow-
up to specific interventions;
d) The Agency should evaluate the potential role of education as an intervention
strategy;
e) The Agency should state, explicitly, the difference between a soil-lead standard
of 2000 parts per million (ppm) and the soil-lead level of concern of 400 parts per
million (ppm) and its impact on current practices by the Department of Housing
and Development, as well as some States; this difference should be explained
along with the initial presentation of the standards
f) The sensitivity analysis should be expanded with a case study of a real community
that is highly susceptible to lead exposure and a presentation of the costs and
benefits associated with the case study;
g) A plan should be developed for follow-up to evaluate the effectiveness of the
specific interventions and lead standards on public health.
Some of these recommendations will require further research. However, there is sufficient
scientific evidence to indicate that delaying rulemaking for additional research would leave a
significant number of children unnecessarily at risk.
The Agency is highly commended for its stated intent to prepare and distribute
educational material to provide guidance for complying with the standards. This material should
23
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be tailored to specific circumstances. The EHC feels that guidance is particularly important since
the requirement for homeowners to disclose a known lead risk may be a disincentive for testing.
24
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REFERENCES CITED
Ashley, P.J., Krogstad, E.J., Lees, P.S., Silbergeld, E., and D. Smith. 1997, "The use of stable
lead isotopes to identify and apportion sources of lead in urban house dust," In: Johnson, B.L.,
Xintaras, C., and Andrews, J.S. (Eds) Hazardous waste: Impacts on Human and Ecological
Health, Princeton Science Publishing
Bellinger, et al., 1987, "Longitudinal analyses of prenatal and postnatal lead exposure and early
cognitive developments," New England Journal of Medicine, 316(17): 1037-1043.
Calabrese, E.J., et al., 1997, "Soil ingestion: a concern for acute toxicity in children,"
Environmental Health Perspectives, 105:1354-1358.
Ceci, S.F., and Williams, W.W., 1997, "Schooling, intelligence, and income," American
Psychologist, 52:1051-10-58.
Centers for Disease Control, 1997, "Update: blood lead levels - United States, 1991-1994," U.S.
Department o/f Health and Human Services, Morbidity and Mortality Weekly Report 46(7): 141-
146.
Cory-Slecta, D.A., et al., 1997, "Relationships between lead-induced changes in neurotransmitter
function and behavioral toxicity," Neurotoxicology, 18:673-688.
Dietrich, K.N., Krafft, K.M., Bornschein, R.L., Hammond, P., Berger, O., Succop, B.A., and
Bier, M. 1987a, "Low-level fetal lead exposure effect on neurobehavioral development in early
infancy," Pediatrics, 80:721-730.
Dietrich, K.N., Krafft, K.M., Shukla, R., Bornschein, R.L., and Succop, P.A. 1987b, "The
neurobehavioral effects of early lead exposure," Monographs of the American Association on
Mental Deficiency, 8:71-95.
Hawk, B.A., Schroeder, S.R., Robinson, G., Otto, D., Mushak, P., Kleinbaum, D. And Dawson,
G. 1986, "Relation of lead and social factors to IQ of low-SES children: a partial replication,"
American Journal of Mental Deficiency, 91:178-193.
Lanphear, B.P., Winter, N.L., Apetz, L., Eberly, S. And Weitzman, M. 1996, "A randomized
trial of the effect of dust control on children's blood lead levels," Pediatrics, 98:35-40.
Lanphear, B.P., Emond, M., Jacobs, D.E., Weitzman, M., Tanner, M., Winter, N.L., Yakir, B.
And Eberly, S. 1995. "A side-by-side comparison of dust collection methods for sampling lead-
contaminated house dust," Environmental Research 68(2): 114-123.
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Lee, E., Daniels, R., Muha, D. and M. Booth. 1998, Review comments representing the Institute
of Real Estate Management, National Apartment Association, National Association of Home
Builders, National Leased Housing Association and the National Multihousing Council. August
7, 1998.
Mendelson, A.L., Dreyer, B.P., Fierman, A.H., Rosen, C.M., Legano, L.A., Kruger, H.A., Lim,
S.W., and Courtland, C.D. 1998, "Low-level lead exposure and behavior in early childhood,"
Pediatrics, 101:elO-el5.
Needleman, H.L. and Gatsonis, C. A.,1990, "Low-lead level exposure and the IQ of children. A
meta-analysis of modern studies" Journal of the American Medical Association, 263(5):673-8,
1990.
Needleman, H.L., Riess, J.A., Tobin, M.J., Biesecker, G.E., and Greenhouse, J.B. 1996, "Bone
lead levels and the delinquent behavior," , Journal of the American Medical Association,
275:363-369.
Rice, D., 1996, "Behavioral effects of lead: commonalities between experimental and
epidemiological data," Environmental Health Perspectives, 104(Suppl 2):337-351.
SAB. 1992. "An SAB Report: a review of the uptake biokinetic (UBK) model for lead, review,
by the Indoor Air Quality and Total Human Exposure Committee of the OSWER model to assess
total lead exposure and to aid in developing soil lead cleanup levels at residential
CERCLA/RCRA sites," USEPA, Science Advisory Board, Washington, DC, EPA-SAB-IAQC-
92-016. March 1992.
Sameroff, A.J., Seifer, R., Barocas, R., Zax, M., and Greenspan, S. 1987, "Intelligence quotient
scores of 4-year-old children: social-environmental risk factors," Pediatrics, 79:343-350.
Schwartz, J., 1993, "Beyond LOELs, p values and vote counting: methods for looking at the
shapes and strengths of associations," Neurotoxicology, 14:237-246.
Schwartz, J., 1994, "Low-level lead exposure and children's IQ: a meta-analysis and search for a
threshold," Environmental Research, 65:42-55.
Streissguth, et al., 1996, "A dose-response study of enduring effects of prenatal alcohol exposure:
birth to 14 years" In Spohr & Steinhausen, eds. Alcohol, Pregnancy and the Developing Child,
Cambridge University Press, pp. 141-168.
long, S., Baghurst, P., McMichael, A., Sawyer, M. and Mudge, J. 1996, "Lifetime exposure to
environmental lead and children's intelligence at 11-13 years: the Port Pirie cohort study,"
British Medical Journal, 312(Issue 7046):1569-1575.
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U.S. Environmental Protection Agency, 1995a, "Report on the National survey of lead-based
paint in housing: base report," Office of Pollution Prevention and Toxics, U.S. Environmental
Protection Agency, EPA 747-R-95-006, July 1995.
U.S. Environmental Protection Agency, 1995b, "Report on the National survey of lead-based
paint in housing: Appendix I: design and methodology," Office of Pollution Prevention and
Toxics, U.S. Environmental Protection Agency, EPA 747-R95-004, April 1995.
U.S. Environmental Protection Agency, 1995 b, "Report on the National survey of lead-based
paint in housing: Appendix U: analysis," Office of Pollution Prevention and Toxics, U.S.
Environmental Protection Agency, EPA 747-R95-005, April 1995.
U.S. Environmental Protection Agency. 1997. Conversion Equations for Use in Section 403
Rulemaking, Office of Pollution Prevention and Toxics, U.S. Environmental Protection Agency,
EPA747-R-96-0012.
U.S. Environmental Protection Agency. 1998a. Risk Analysis to Support Standards for Lead in
Paint, Dust, and Soil, Volume I and Volume II, Office of Pollution Prevention and Toxics, U.S.
Environmental Protection Agency, EPA 747-R97-006, June 1998.
U.S. Environmental Protection Agency. 1998b. Economic Analysis of Toxic Substances
Control Act Section 403: Hazard Standards , Economic and Policy Analysis Branch, Economics,
Exposure and Technology Division, Office of Pollution Prevention and Toxics, U.S.
Environmental Protection Agency, May 1998.
Wallsten, T.S. and R.G. Whitfield. 1986. "Assessing this risks to young children of three effects
associated with elevated blood-lead levels," Report by Argonne National Laboratory. Report No.
ANL/AA-32. Sponsored by the U.S. EPA Office of Air Quality Planning and Standards.
Wasserman, G.A., Staghezza-Jaramillo, B., Shrout, P., Popovic, D., and Graziano, J. 1998. "The
effect of lead exposure on behavior problems in preschool children," American Journal of Public
Health, 88:481-486.
Wyzga, R.E. 1990. "Towards quantitative risk analysis for neurotoxicity," Neurotoxicity,
11:199-207.
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APPENDIX A - ACRONYMS AND ABBREVIATIONS
BCA
BN
BRM
CDC
EHC
HUD
IEUBK
IQ
LBP
LOAEL
LOEL
NHANES
NOAEL
OMB
OPPT
OPPTS
ppm
SAB
SD
SES
TSCA
U.S.C.
benefit cost analysis
blue nozzle
Baltimore Repair and Maintenance
Centers for Disease Control
Environmental Health Committee
United States Department of Housing and Urban Development
Integrated Exposure Uptake Biokinetic Model
Intelligence Quotient
Lead based paint
lowest-observed-adverse-effect level
lowest-observed-effect level
National Health and Human Nutrition Examination Survey
no-observed-adverse-effect level
Office of Management and Budget
Office of Pollution Prevention and Toxics
Office of Prevention, Pesticides and Toxic Substances
parts per million
Science Advisory Board
standard deviation
socioeconomic status
Toxic Substances and Control Act
United States Code
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APPENDIX B - ANNOTATED OVERVIEW OF THE LEAD 403 RULE
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OS
QC
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APPENDIX C - TABLE AND FIGURES ON IQ
Table 1. Calculations of IQs below 70 based on SD=15 and different means
Proportion < 70
0.0475
0.0415
0.0359
0.0309
0.0266
0.0228
0.0194
0.0165
0.0139
0.0117
0.0098
Mean
95
96
97
98
99
100
101
102
103
104
105
Assume that SD=15 and z-score mean = 70; area is derived from tables of the normal curve.
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0.03-
c
'•§ 0.02-
o
o
BL 0.01 -
0.00-
40 60 80 100 120 140 160
IQ .
m
0.03-
c
H 0,02-
o
£ 0.01-
0.00-
40 60 80 100 120 140 160
IQ
Figure 1. Effects of a 3% (3-point) shift in mean IQ score on the-proportion
of a population with scores falling below 70. Upper chart shows an IQ
distribution with a mean of 10O and SD of 15. The dark area represents the
2.3%of the population below 7O. The light area represents those with IQs
below 100 and above 70. The lower chart depicts an IQ distribution with a
mean of 97. Here, 3.6% of the population falls below 7O. IQ of 100 is drawn
on both charts for orientation.
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25OOO
o
£ 20000
£ 15OOO
O
2 1OOOO
0>
.O
w
E 5OOO
El Mean of 1OO
DMean of 85
1 2
IQ Point Loss
Figure 2. Comparative effects of IQ point losses on an "Advantaged" population
with a mean IQ score of 1OO (SD=15) and a "Disadvantaged" population with a
mean IQ score of 85 (SD=15).
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APPENDIX D - EDITORIAL COMMENTS ON EPA DOCUMENTS
Page
ES-2
ES-4
2-6
2-10-11
2-12
2-13
2-13
2-19
2-20
3-64
3-66
5-4
5-9
5-25
5-26
Comment
Young children are acknowledged as a highly vulnerable subpopulation, but the document should also note the
recent data implicating the elderly as another vulnerable subpopulation.
Especially in the Executive Summary, the document should note that 10 ug/dL is not a threshold of toxicity, but
an action level, so to speak. The same ambiguity appears in the body of the document.
A target audience for the document was not specified, but the discussion of neurotoxic effects (Section 2.2.2) is
inappropriate for the non-specialist.
This section (2.3. 1) makes only passing reference to low birth weight and prematurity, but the medical literature
indicates that both are risk factors for reduced IQ. It needs more emphasis. In addition, the data indicating
correlations between blood lead and IQ in older children should be discussed more specifically in risk terms.
Performance IQ yields parts of the WISC score.
A question lurking below the surface of the risk assessment is the contribution of lead in context. That, is, lead
effects are small in magnitude compared to maternal IQ, SES, etc. This comparison leads some observers to
question the significance of lead hazards. The analysis should recognize these objections and note the
importance of the lead contribution as an independent factor.
It may be important to note that the Needleman (1979) data classified children with a blood lead mean of 24
ug/dL as "low lead," especially because on pages 2-15 and 2-17 "low" and "high" describe different
concentration ranges. Views of "low" and "high" have changed since the 1970's.
Table 2-1 uses the term "lead poisoning." It is not appropriate in this context because it implies a clinical
syndrome, not the purview of this risk assessment document.
The standard deviation associated with IQ tests is typically 15, not 5 points.
As noted in Table 3-36, children 3-5 seem to show a higher incidence of extreme values than children 1-2. The
full distributions might be edifying.
Table 3-38 shows different risks as a function of family income. The document might clarify the problem by
providing relevant IQ distributions for each income level. Also, as noted elsewhere, if IQ means are different in
different income groups, the proportion of scores less than 70 will also be different. Shouldn't disproportionate
impact be a part of risk characterization and management?
Plots of different IQ distributions based on different blood lead distributions would amplify portions of this
section.
Table 5-1 is unclear in some respects. It is difficult to determine how the IQ score less than 70 entry yields 9,130
children.
Define "tap weight" in Table 5-8.
In Table 509a, the calculation of the number of children with IQ<70 is unclear.
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APPENDIX E - REVIEW OF THE ECONOMIC ANALYSIS
(Prepared by Dr. Gloria E. Helfand)
The Scope of the Benefit-Cost Analysis
In many ways, it is peculiar for the Agency to conduct a benefit-cost analysis (BCA) of
proposed standards for which there is no required action. Typically, BCA is used to weigh the
advantages and disadvantages of taking a particular action, such as building a dam or requiring
new pollution abatement measures. In this case, the Agency's only action is to set the rule; the
Agency requires no action and undertakes little activity (other than some information provision).
Though there may well be legal ramification from that rule-setting; such as lenders becoming less
willing to finance mortgages for properties exceeding the standards, these actions are not under
the Agency's control. Instead, whether to act, as well as the levels of costs and benefits of any
actions, will be decided entirely in the private sector. Individuals, real estate owners and
managers, renters, lenders, and others involved in the housing markets are likely to want to
undertake their own BCAs of lead abatement, possibly in response to this rule, or possibly
independently. The Agency is not responsible in any obvious way for these actions.
The BCA is conducted from a national perspective, covering a 50-year period. As soon
as a child between 0 and 6 years of age enters a house where lead is present, abatement activities
are assumed to be conducted until the child reaches 6 years of age. This process is repeated for
as many times as a house has a child less than 6 years of age in it over the 50 years. The optimal
standards are those that maximize present net benefits of those abatement activities.
Since the actions and effects are virtually entirely private, it might be more appropriate
for the Agency to provide guidance to individual real estate owners or occupants on what the
activities that are desirable for their circumstances, rather than conduct a national-level, 50-year
analysis. That information could prove more useful to individuals in deciding whether and when
to act on lead hazards.
On the other hand, the Agency argues that one set of national standards is desirable for
clarity and simplicity (Federal Register, page 30307); while that decision could be debated, it is
not necessarily a bad idea. Then, in essence, the proposed standard is really an average guidance
on when it is efficient to undertake abatement activities. In this case, a critical issue is who will
undertake actions, and when. The assumption here is that all houses in violation of the standards
will undertake remedial action. As is noted in the BCA, this assumption is quite a strong one. It
seems more likely that some houses in violation of the standard will not comply than that houses
in compliance with the standard will abate anyway. As a result, the costs and benefits (at the
national level) are likely to be overstated, though it's hard to say whether costs or benefits are
more overstated. On the other hand, because it is very hard as well to identify any reasonable
alternative assumption on behaviors, it is hard to fault the analysis for using this assumption.
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Because this process develops, in essence, an average standard for when interventions
should be conducted, it does not provide guidance to specific individuals on whether or when to
abate for lead. Indeed, it does not even provide guidance on when an individual should test for
lead, possibly the most critical step in the process. There even appears to be a disincentive on the
part of property owners to test for lead, since they are required to disclose lead risk if it is known
(and are then likely to receive lower value for their property).
Despite all of the above comments, this approach to a national-scale benefit-cost analysis
with a 50-year time horizon has its usefulness. The current approach in essence provides an
average value for when abatement activities provide increased net benefits. This information
will be most valuable when the future occupants of a unit are unknown and the owner of the unit
is deciding whether to abate. For instance, HUD low-income housing may wish to use this
standard, since it is unlikely to be able to predict who will move into a specific unit. In that case,
a societal, long-term perspective makes sense.
At the same time, more specific guidance would be very valuable to individuals owning
or purchasing a unit. For instance, a family with several children under the age of 6, or with
children more sensitive to lead for some reason, should probably be encouraged to conduct
abatement activities that another family with one 5-year-old should not be so encouraged. The
Agency should provide a guidance document, perhaps in the form of a decision tree, to help
people decide whether or when to abate for their specific circumstances.
Regarding the comment by Lee et al. (1998) on whether the appropriate trigger should be
the "birth trigger" used by the Agency or real-estate transactions: the birth trigger is more
appropriate for the social BCA that the Agency has conducted, since, from a societal perspective,
that point is when interventions should be considered. The real estate trigger is what may
actually happen in some cases, but at that point the specific guidance suggested above should be
used, since specific circumstances are likely to be better known.
Estimation of Costs
Development of costs for different standards involved, first, relating treatment options
with reductions in exposure, and secondly, calculating costs of the treatment options; the result is
a cost associated with a specified standard. This procedure seems appropriate.
One serious concern is that the cost estimates do not take into account the fact that people
will undertake some of the abatement measure (such as repainting) even in the absence of lead.
If people do maintain their homes, then the appropriate measure of cost of lead abatement is the
cost over and above that associated with routine maintenance. It is impossible from the
information presented to determine how significant a cost overestimate results from the method
used here. Some very useful information, both to regulators and to owners of residences, would
be descriptions of what activities beyond routine maintenance are required for lead abatement,
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and the costs of those activities. The current approach of, e.g., counting all painting expenses as
lead abatement expenses is likely a significant overestimate of the costs of abatement.
One odd thing about the costs is that the marginal costs (the cost of increasing abatement
by one unit) do not increase as the standard is tightened for any of the potential standards;
instead, they bounce around. Typically marginal costs would be expected to be constant or
increase, an indication that it's easier to clean up lead when there's a lot of lead rather than when
there's only a little of it. The fluctuating marginal costs may be an artifact of very discrete
abatement measures, but it is a peculiarity.
Responses to a few points raised by Lee, et al.(1998) follow, including; first, 1) that real
estate transactions will become in fact the critical point of action; and 2) second, that costs do not
include changes in property values associated with identification of lead hazards in properties.
The first issue relates back to the scope of the BCA, and whether the analysis conducted by the
Agency really answers a question relevant to the policy process or to individual landowners.
There are no federal requirements; private markets are responding to the issuance of the
standards. Yet the analysis is conducted from a public policy perspective of net social benefits.
It is unclear as to whether or not there is a "right" answer to this issue. The Agency should
discuss this issue with the real estate industry and other affected parties, including mortgage
lenders to clarify the issue. On the second issue, there is disagreement. If a property is found to
have lead, the loss of property value is not a loss to society; rather, not incorporating the
existence of the lead into the property value is an implicit real estate subsidy to those properties
containing lead. Just as pollution is, in the economic framework, a cost of some business
activities that the businesses may not recognize, the cost of lead in a property is real and should
be reflected in the property's value
Estimation of Benefits
To estimate benefits, different standards were associated with changes in blood lead level
concentrations, which were then associated with changes in IQ, which were then assigned
monetary values. This procedure seems appropriate.
As with marginal costs, marginal benefits also show odd fluctuations. Typically marginal
benefits would be expected to decrease as the standard gets tighter: the greatest gains come from
controlling lead when there is a lot of it, and smaller gains are likely when there is little,
reflecting that the most important impacts result from the initial abatement, not the last units. In
Exhibits 6.1, 6.4, and 6.7 in the economic analysis document, marginal benefits not only appear
to increase as the standard tightens, but they increase and then decrease. Again, this oddity may
be due to these functions reflecting the nature of the housing stock. Tightening the standard
leads to more houses being recommended for abatement; the relationship between any standard
and the number of affected houses often has a relatively flat area (see Figures 6-4, 6-6, 6-8, 6-9 of
Risk Analysis to Support Standards for Lead in Paint Dust and Soil). That shape may lead to
the marginal benefits and cost curves having the shapes they do.
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The advantage of the typical shapes is that they indicate a unique level that maximizes net
benefits (where marginal benefits crosses marginal costs from above - to the left of that point,
the marginal net benefits are positive, while the marginal net benefits are negative to the right of
the standard). In this case, there is no unique set of standards that maximizes net benefits. There
is often a range where the net benefits are almost constant. The Federal Register discussion of
how standards were actually chosen indicates that those setting the standards understood the
implications of these strange functions and incorporated additional factors into their choice of the
lead standards. That procedure seems very appropriate in this case.
The economic analysis notes, validly, that reductions in IQ should probably not all be
valued the same: a 5-point IQ reduction from 150 is probably less significant than a 5-point IQ
reduction from 80. The economic analysis, however, values both these changes the same. Given
that there do not appear to be data to do any differently, one can't validly conclude that the
analysis was conducted incorrectly. Some discussions of whether the value of IQ used is likely
to correspond more to the high-IQ part of the scale or the low-IQ part of the scale, and therefore
whether it likely overstates or understates benefits, could be useful.
The value of an IQ point as developed here seems to be calculated appropriately.
Previous reviewers have asked why this value differs from the value used in an Agency study of
air quality. While sensitivity analysis is done on this point, there is no discussion of why these
two values differ and why the lower value is considered not appropriate. An explanation of these
points should be included.
The economic analysis assumes that distribution of blood-lead levels in the population, in
the absence of abatement activities, will stay constant over time (p. 5-3). Comments by Lee, et
al., (1998) that blood lead levels have shown a decrease over time due to reduction in lead from
other environmental sources seems to be an important one and should be considered. Ignoring
these reductions, if they are expected to continue, leads to an overstatement of benefits.
Lee et al. (1998) also claim that the analysis does not take into account that older houses
are being removed from the market. While it's not entirely clear from the economic analysis, it
appears that in fact the Agency has included changes in the housing stock in their analysis,
through the term et on page 5-20.
In sum, the benefit-cost analysis appears to have been done honestly and uses (for the
most part) the best available information and methods. It is considered that the costs are
overstated through ignoring the abatement activities that would normally be expected to be
conducted; that benefits may be understated through incorporating only IQ-related effects; and
that benefits may be overstated if there is expected to be a continuing reduction in blood lead
levels due to factors other than abatement under this rule. If these effects were incorporated, the
likely effect would be that the proposed standards ask for less abatement than is optimal (though,
"optimal" is hard to define here and needs to involve other factors).
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Calculating Net Present Value
Net present value, or net benefits, is merely the difference between benefits and costs.
Typically, if marginal costs increase with a tighter standard and marginal benefits decrease, there
is a unique point where marginal benefits equal marginal costs; at this point, net benefits are
maximized. Here, as noted, the marginal benefits and marginal costs are quite erratic in their
behavior; therefore, there is no unique value where marginal benefits equal marginal costs. The
Federal Register discussion of the choice of standards suggests that the maximum net benefits
values were considered as starting points; then other factors were brought to bear on the decision.
This approach seems reasonable.
The Discount Rate
The economic analysis uses a discount rate of 3%, with a sensitivity analysis using 7%.
Lee et al. (1998) believe that the economic analysis should be done using OMB's recommended
rate of 7%, representing the opportunity cost of capital in the long run. Chapter 3 of the
economic analysis (pp. 3-19 to 3-22) has a very nice discussion of the choice of the 3% discount
rate; I have no quarrel with the Agency's choice of that value.
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