SAB-CASAC-86-024
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, o c. 20460
August 29, 1986
Honorable Craig Potter
Assistant Administrator for
Air and Radiation
U.S. Environmental Protection
Agency
Washington, D.C. 20460
Dear Mr. Potter;
At the March 11-12, 1986 Clean Air Scientific Advisory Committee
(CASAC) meeting, the Committee reviewed the second external review draft
of the Staff Paper for Lead. In general, the CASAC found the document
to be clear and appropriate. The major comments provided by the Committee
at that meeting along with the major written comments submitted afterwards
are formally summarized in this recommendation letter.
The Committee recommends that the Agency undertake the following
modifications to the Staff Paper for Lead;
1. jRevise the introduction to:
- Provide a systematic catalogue and ranking of air and
non-air sources of exposures.
- More clearly explain that because of the phase-down of
lead in gasoline, EPA's part of the lead problem, which
was originally a distributed source problem like other
ambient pollutants, is becoming a problem of specific,
well-localised sources.
Seme other parts of the lead problem, like the paint problem
over which EPA does not have authority, are still distributed
source problems. The Staff Paper should also clarify that the
primary mechanism of exposure for EPA's part of the problem
(airborne emissions) is via ingestion of lead in settled dust
and surface dirt, not via direct air e:xposure. This will require
better data on soil/dust fate and mass balance and children's
intake.
2, Revise the exposure assessment to make it clearer that the
primary sources for current and future exposures are point
sources. In particular the Staff Paper should:
- Critically discuss the problems of using knowledge
derived from area sources for studies of point
sources.
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- Focus and inf>rove the material covered in Appendix B
(especially Table B-2) since it drives the analysis of
the uncertainty.
- Raevaluate the point source exposure estimates.
- Discuss deposition and size distribution explicitly, both
in terms of the deposition on and resuspensiori from
ground surfaces, and in terms of the deposition in the
respiratory tract.
- Be more explicit about whom is being protected. The
99.91 approach, as now employed, is ambiguous.
3* Since, in the future, ambient air lead will be attributable to
a limited number of definable point sources, CASAC recommends
that EPA consider regulating lead through point source controls
rather than through the NMQS.
4. The discussion of measurement would be clearer if it were moved
to the end so that the preceeding discussions could motivate it.
Measurement poses two needs, with different data requirements
for each;
- Documenting the decline of the motor vehicle sources
problem.
- Controlling the problems of point sources.
5* Explicitly evaluate the degree of protection against cardiovascular
effects in adult males provided by the blood lead and air lead
levels developed to protect children against neurobehavioral
effects, if these levels do not provide adequate protection
against adverse cardiovascular effects in adult males, develop new
recommendations to provide such protection. This should include
an evaluation of the blood lead-blood pressure relationships in
adult males, and its implication to the incidence of cardiovascular
disease.
6. The perinate should be included as a population at increased
risk due to prenatal exposure of the fetus and postnatal exposure
of the lactating infant. This concern focuses on the fetus and
infant, not on the pregnant mother.
7, Emphasis should be increased on poetdepositional eixposures to
lead as the major route o£ exposure to airborne lead*
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8. The material on health effects should be moved forward so that
the discussion on sources and exposures proceeds without
interruption*
The cammsnts that form the basis for these recommendations were
provided informally to the staff of the Office of Air Quality Planning
and Standards after the close of the March 1986 meeting. This letter
constitutes the Committee's formal report to the Agency on this stage of
the review of the NMQS for Lead.
The Ccmmittee appreciates the opportunity to provide comments on
this important issue.
Sincerely, „,
Morton Lippmann, Ph.D.
Chairman
Clean Air Scientific Advisory
Committee
cc: Lee Thorns
A. James Barnes
Donald Ehreth
Gerald Emison
Lester Grant
John O'Connor
Terry Yosie
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