EDA U.S. Environmental Washington, DC
*-« " »»**—««- Agency EPA-SAB-CASAC-90-002
Report of the Clean Air Scientific
Advisory Committee (CASAC)
Review of the OAQPS Lead Staff Paper
and the ECAO Air Quality Criteria
Document Supplement
A SCIf NCf ADVISORY BOARD REPORT JANUARY 1990
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C. 20460
January 3, 1990
Honorable William K. Reilly
Administrator
U.S. Environmental Protection Agency
401 M street, sw
Washington, DC 20460
RE: National Ambient Air
Quality Standards for Lead
Dear Mr. Reilly:
I am pleased to transmit the advice of the Clean Air
Scientific Advisory Committee (CASAC) concerning the National
Ambient Air Quality standards (NAAQS) for Lead. The CASAC has
reviewed and offered comments directly to EPA Staff on the EPA Air
Criteria Document update, "Supplement to the 1986 EPA Air Quality
Criteria for Lead - Volume I Addendum (Pages Al - A67)M, and the
Office of Air Quality Planning and Standards (OAQPS) staff position
paper "Review of the National Ambient Air Quality Standards for
Lead: Assessment of Scientific and Technical Information", both
dated March 1989.
The Committee previously reached closure on the 1986 Air
Quality Criteria Document and Criteria Document Supplement. At a
meeting held on April 27, 1989, CASAC reviewed and was prepared to
close on the 1989 Criteria Document Addendum and the 1989 staff
Position Paper, but withheld closure pending receipt and
consideration of additional public comments. The public comment
period, scheduled to close 30 days following the CASAC meeting, was
extended through June 12, 1989, providing the interested public
further time to prepare comments. The additional comments received
as a result of the extended comment period were provided to the
Committee and taken into consideration before reaching closure.
The Committee concludes that these EPA documents, along with the
1986 documents previously clpsedf uffefc, provide a scientifically
balanced and defensible summary of our current knowledge of the
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effects of this pollutant, providing an adequate scientific basis
for EPA to retain or revise primary and secondary NAAQS for
airborne lead.
As part of this review process, the Committee considered and
approved the CASAC Exposure Subcommittee review of the August 1988
EPA document "Review of the National Ambient Air Quality Standards
for Leadi Exposure Analysis Methodology and Validation". That
approval is formally contained in the CASAC report transmitted to
you in April 1989 (EPA-SAB-CASAC-S9-Q18, April 1989),
In November 1988, the CASAC formed an ad hoc Joint Study Group
with the Science Advisory Board (SAB). The broad charge to this
Study Group included assessment of the weight of evidence
classification of lead and lead compounds as carcinogens? review
of lead-related health effects and exposure issues which cut across
EPA organizational lines? and an assessment of how the scientific
information concerning lead is applied to standard setting and
other regulatory decisions in the Agency. The report of that Joint
Study Group, based on their March 30, 1989 and April 28, 1989
meetings, is contained in their report (EPA-SAB-EC-9Q-QQ1, December
19S9), transmitted to you separately,
A key point of the Joint Study Group Report is the contrasting
nature of the data base for central nervous system versus
carcinogenic effects. The carcinogenic risk assessment is based
primarily on induction of kidney tumors in rodents administered
large quantities of lead. Use of these data for human risk
assessment involves two extrapolations; from rodents to people, and
from high doses to the low doses encountered in ambient exposures
of lead* In contrast, central nervous system effects are observed
directly in people and at exposures at or near the levels of
exposure relevant to setting the standard* Thus, and unless, more
quantifiable and relevant scientific evidence is available on the
carcinogenicity of lead, the Committee feels it appropriate to give
primary consideration to nervous system effects in setting the
national ambient air quality standard for lead.
During the course of the CASAC meeting several recommendations
were made to the EPA Staff as to actions that can be tafcen that
will provide an improved basis for setting the NAAQS for lead.
These include calculation of the distribution of blood lead levels
estimated to result from achieving an air lead concentration of
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0.25 ug/m3. In addition, it was suggested that it would be
appropriate to evaluate the estimated distribution of effects on
ehildrens intelligence at a given level of lead exposure.
While the Committee is willing to further advise you on the
lead standard, we see no need, in view of the extensive comments
provided, to review any proposed changes prior to their publication
in the Federal Register. The public comment period following
publication will provide sufficient opportunity for the Committee
to provide any additional comment or review, if needed*
The attached report contains the detailed analysis and
recommendations of the CASAC concerning its closure on the Criteria
Document Addendum and the EPA Staff Position Paper for airborne
lead. In considering the CASAC*s recommendations for the lead
NAAQS it is important to recognize that air is just one source of
exposure to lead; reducing the total population risk from lead will
require a concerted effort to reduce lead intake from all sources.
We appreciate the opportunity to provide advice on this
important issue and look forward to your response to our
recommendations.
Sincerely,
Roger 0. McClellan, D»V,M.
Chairman, Clean Air Scientific
Advisory Committee
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ABSTRACT
This is the report of the EPA's Clean Air Scientific Advisory
Committee (CASAC) on its review of the Agency's draft documents:
"Supplement to the 198S Air Quality Criteria for Lead - Volume I
Addendum (Pages Al - A67)", and "Review of the National Ambient Air
Quality Standards for Lead! Assessment of Scientific and Technical
Information", both dated March 1989, These documents were reviewed
in public session on April 27, 1989, with the Committee reaching
the conclusion that the documents provide an adequate scientific
and technical basis for EPA to retain or revise primary and
secondary national ambient air quality standards for lead.
Key Words: Lead; National Ambient Air Quality Standards; N&AQS;
Air Pollution
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M.OTICE
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 a 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 or other
agencies in the Federal government. Mention of trade names or
commercial products does not constitute a recommendation for use.
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U.S. Environmental Protection Agency
Science Advisory Board
Clean Air Scientific AdvisoryCommittee Lead Review Committee
Chairman
Dr. Roger O. McClellan*, Chemical Industry Institute of Toxicology,
Research Triangle Park, North Carolina
Co-jCh airman
Dr. Arthur Upton, New York University Medical Center, Department
of Environmental Medicine, New York, New York
Members
Dr. Gary Carlson, Department of Pharmacology and Toxicology,
School of Pharmacy, Purdue University, West Lafayette,
Indiana
Or. J. Julian chisolm, Jr., Johns Hopkins School of Medicine,
Francis Scott Key Medical Center, Baltimore, Maryland
Or, Robert Frank, The Johns Hopkins School of Hygiene and Public
Health, Baltimore, Maryland
Dr. Paul B. Hammond, Department of Environmental Health,
University of Cincinnati Medical Center, Kettering
Laboratory, Cincinnati, Ohio
Dr. Timothy Larson*, Environmental Engineering and Science
Program, Department of Civil Engineering, University of
Washington, Seattle, Washington
Dr. Ian von Lindern, President, Terragrahics Environmental
Engineering, Moscow, Idaho
Dr. Morton Lippmann, Institute of Environmental Medicine, New
York University Medical center, Tuxedo, New York
Dr. Kathryn R, Mahaffey, National Institute of Environmental
Health Sciences, University of Cincinnati Medical
Center, Cincinnati, Ohio
Dr. Paul Mushak, Consultant and Adjunct Professor, University
of North Carolina, Chapel Hill, North Carolina
Dr. Gilbert S, Omenn*, School of Public Health and community
Medicine, University of Washington, Seattle, Washington
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Or. Michael B. Rabinowitz, Marine Biological Laboratory, Wood's
Hole, Massachusetts
Dr. Marc B. Schenker*, occupational and Environmental Health Unit,
University of California, Davis, California
Dr, Ellen silbergeld, Environmental Defense Fund, Washington, DC
Dr* Mark J, utell*, Pulmonary Disease Unit, University of Rochester
School of Medicine, Rochester, New York
Dr. Bernard Weiss, Division of Toxicology, Department of EHSC,
School of Medicine, University of Rochester, Rochester, New
York
Dr. Jerome J* Wesolowski*, Air and Industrial Hygiene Laboratory,
California Department of Health, Berkeley, California
Dr. George T, Wolff*, General Motors Research Laboratories,
Environmental Science Department, Warren, Michigan
* Statutory CASAC Members
Science Advisory Board Staff
Mr. A. Robert Flaak, Designated Federal Official, Science Advisory
Board (A-101F), U.S. Environmental Protection Agency,
Washington, D.C. 20460
Ms. Carolyn Osborne, Staff Secretary, Science Advisory Board
(A-101F), U.S. Environmental Protection Agency, Washington,
DC 20460
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REPORT OF THE CLEAN AIR SCIENTIFIC ADVISORY COMMITTEE
ON ITS REVIEW OF
THE NATIONAL AMBIENT AIR QUALITY STANDARDS FOR LEAD
CASAC CLOSURE ON THI 1989 AIR QUALITY CRITERIA
DOCUMENT ADDENDUM AND 1989 STAFF POSITION PAPER
At a public meeting held on April 27, 1989, CASAC reviewed
the BFA Air Criteria Document update, Supplement to the 1986 EPA
Air Quality Criteria for Lead - Volume I Addendum (Pages Al - A671 .
and the Office of Air Quality Planning and Standards (OAQPS) staff
position paper Review of the National Ambient Air Quality Standards
for Lead; Assessment of Scientific and Technical Information, both
dated March 1989. The committee concluded that these documents,
along with the documents previously closed upon, provide a
scientifically balanced and defensible summary of the current basis
of our knowledge of the effects of this pollutant, providing an
adequate scientific basis for EPA to retain or revise primary and
secondary NAAQS for airborne lead.
In discussing blood lead levels used to assess alternative
standards, it is the consensus of CASAC that blood lead levels
above 10 ug/dl clearly warrant avoidance, especially for
development of adverse health effects in sensitive populations.
The value of 10 ug/dl refers to the maximum blood-lead level
permissible for all members of these sensitive groups, and not mean
or median values. The Committee concluded that the Agency should
seek to establish an air quality standard which minimizes the
number of children with blood lead levels above a target value of
10 ug/dl. In reaching this conclusion, the: Committee recognizes
that there is no discernible threshold for several lead effects and
that biological changes can occur at lower levels. In setting a
target value for blood lead (matched ultimately to air lead level)
the Committee emphasized the importance of always being mindful
that blood lead levels and health outcome measures are best
characterized as a distribution of values about mean or median
values. The importance of considering the distribution of values
about the mean or median is apparent from consideration of the
influence of lead exposure on I*Q. A seemingly modest decrease in
the mean or median value for I,Q. may result in significant changes
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at the outer limits of the distribution with both a reduction in
the number of bright children (I.Q. > 125) and an increase in the
number of children with I.Q. < 80,
In setting a blood lead target value (and the associated air
lead concentration) it is important to recognize that lead may
enter the body by both the inhalation and ingestion routes and that
oral intake may make significant contribution to a child's total
exposure to lead. For example, lead in food, water, soil and paint
are all contributors to total lead intake. Achieving a target
blood level will require an integrated approach with appropriate
standards for all routes of exposure, not just lead in air. The
Committee emphasized that assessment of risks of adverse health
effects is based on lead blood levels or body burden estimates, and
only indirectly on the air lead concentrations,
Lead is a toxic poison with no known beneficial function in
the human body. An individual exposed is at risk to a wide range
of effects in numerous organ systems and tissues. The EPA staff
have correctly identified the fetus and young children as
particularly sensitive population groups due to physiological
sensitivity during fetal development when the central nervous
system is undergoing its most pronounced growth, and due to early
developmental impairment associated with fetal exposure. In
addition, the Committee concurs with the staff's assessment of
risks associated with increased blood pressure related,to lead in
adult populations. As discussed below, quantitative exposure
analyses in the staff Position Paper were not done for populations
of pregnant women and their fetuses exposed under alternative
standards.
The Committee finds that the methodologies applied in the
staff paper case study analysis on young children and adult men
provide an appropriate tool to evaluate relative protection of
alternative lead NAAQS. Although these analyses are useful in
comparing standards, they should not be used to provide estimates
of absolute numbers of individuals at risk. In addition,
populations not evaluated quantitatively because of the lack of
valid data (e.g., pregnant women/fetuses) must be considered in
determining an appropriate margin of safety for the standard. The
Committee recognises, as noted by the CAS AC Exposure Subcommittee,
that valid modeling predictions are not possible at this time due
to a lack of relevant data.
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The EPA Staff recommended in the Staff Position Paper that
the lead NAAQS be expressed as a monthly standard in the range of
0.5 to 1.5 ug/m5 not to be exceeded more than once in three years.
The Committee concurs with the EPA Staff recommendation to express
the lead NAAQS as a monthly standard not to be exceeded more than
once in three years. The Committee strongly recommends that in
selecting the level of the standard you take into account, the
significance and persistence of the effects associated with lead
as well as those sensitive population groups for which valid
quantitative exposure/risk estimates could not be made at this
time. The Committee believes you should consider a revised
standard with a wide margin of safety, because of the risk posed
by lead exposures, particularly to the very young whose developing
nervous system may be compromised by even low level exposures. At
the upper level of the staff paper range (1.0-1,5 ug/m3), there is
relatively little, if any, margin of safety. Therefore, the
Committee recommends that in reaching a decision on the level of
the standard, greater consideration be given to air lead values
below 1,0 ug/m3. To provide perspective in setting the NAAQS for
lead it would be appropriate to have the EPA Staff compute the
distribution of blood-lead levels resulting from a monthly standard
of 0.25 ug/m3 for comparison with the values already computed for
higher levels. In setting the NAAQS for lead it is important to
recognize that airborne lead serves not only as a source of
inhalation exposures, but that lead in air deposits on soil and
plants becoming a potential source for intake into the body,
The CASAC agrees with the EPA staff recommendation for more
frequent sampling near point sources, but has reservations about
continued reliance on the hi-volume sampler for measuring airborne
lead. While the hi-volume sampler may be a reasonable indicator
for purposes of determining compliance with a monthly lead
standard, the Committee believes that more refined instruments for
characterizing airborne lead exposures are needed. The Committee
recommends that the Agency develop or validate lead instrumentation
that is capable of measuring both direct and indirect airborne lead
exposures so more refined air quality data will be available for
the next review. Finally, the Committee concurs with the staff
recommendation that the use of PM10 samplers be permitted in areas
where they produce similar results as the hi-volume sampler.
Given that lead has no biologic value, the Committee strongly
recommends that the Agency actively pursue a public health goal of
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minimizing the lead content of blood to the extent possible,
recognizing that as a naturally occurring element, lead will be
present at background levels. The air quality standard is an
important component of a strategy for achieving the goal, however,
the NAAQS for lead by itself is not sufficient to achieve the goal.
Instead, a concerted effort must be made to further reduce lead
exposures through all media of concern*
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