UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D C. 20460
July 19,1988
OFFICE OF
SAB-EHC-88-034
Honorable Lee M. Thomas
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.c. 20460
Subject: Science Advisory Board's review of the MERCURY health
criteria document
Dear Mr. Thomas:
The Metals Subcommittee of the Science Advisory Board's'
Environmental Health Committee has completed its review of the
Drinking Water Health' Criteria Document for Mercury dated
February 1987. The review was conducted January 14-15, 1988, at
the St. James Hotel in Washington, D.C.
The Subcommittee recommended that: the document focus
clearly on inorganic rather than organic mercury, the exposure
section be made more realistic, a rationale be given for the
choice of end-point used to develop the standard and the existing
analysis be extended,
The Subcommittee concludes that the report adequately
summarizes the available information on the health effects of
inorganic mercury. However, the report is confusing. It states,
correctly, that almost all mercury in drinking water is the
inorganic form, and contains calculations for a Drinking Water
Equivalent Level (DWEL) for inorganic mercury. Much of the
report, however, concerns organic mercury. The extensive
attention given methylmercury and other alkyl mercurials is
unwarranted. The subcommittee recommends that this material
either be deleted, placed in an Appendix or used to calculate a
DWEL for organic mercury. If this material is deleted, the title
of the document should indicate that it considers only inorganic
mercury 4
The estimates of mercury intake from drinking water are
probably too high and may reflect the use of the analytical
detection limit as a substitute for actual mercury
concentrations. Also, some of the reported values of mercury in
drinking water are suspiciously high. The Subcommittee
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recommends that these numbers be validated. In addition, it
recommends that the exposure section be 'expanded to consider
mercury dental amalgams, which may be a much more important human
source of inorganic mercury exposure than drinking water.
Certainly this source needs to be considered in developing the
Maximum Contaminant Level Goal.
The calculation of the DWEL in the document correctly
includes the differences in absorption between subcutaneously-
injected and orally-ingested mercury. It is stated without
justification in the document that auto-immune irregularities are
a more sensitive endpoint that proteinuria for establishing a
DWEL for inorganic mercury. The Subcommittee recommends that the
Agency provide the rationale for this choice of endpoint.
Three animal studies are used in the derivation of the DWEL.
The most important is that of Druet et al which used several dose
groups. The other two studies used only one exposed group at
relatively high levels of exposure. All three studies had very
small numbers of animals in the exposed groups. The Subcommittee
concludes that the calculation of the DWEL from the animal
studies is correct given the current EPA guidelines. The
Subcommittee recommends, however, that additional methods to
assess the risks of systemic toxicants be applied to the animal
data. The addition of more analyses will give a better sense of
the robustness of the DWEL estimates, as well as help to
highlight the differences between alternative methods.
The Subcommittee noted that calculations of a NQAEL for
inorganic mercury based upon human exposure to mercury vapor
were presented at the Workshop in Cincinnati, Additional
calculations were derived from kidney NQAELs in both humans and
animals. We recommend that these calculations be included in the
final document. It would help confirm the use of short-term
animal and subcutaneous injection data in deriving the DWEL.
Additional specific comments have been forwarded to the
program offices.
Sincerely,
Norton Nelson, chairman
Executive Committee
Richard A. Griesemer, Chairman
Environmental Health Committee
Bernard Weiss, chairman
Metals Subcommittee
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..,b a'A'iroraritir.Cd-
Science Advisory Board
Environmental Health Conroittee
Petals Subconranittee
Dr. Bernard Weiss i,Chairj, Professor, Division of Toxicology, P.O. box
RBB, University or Rochester, School of hedicine, Rochester, WY 1^642
(71b) 275-3791
ur. Ronaiu Wyzga [Vice-chairj, Electric Power Research Institute, 3412
Hiilview Avenue, P.O. Box 1041, Palo Alto, California 94303 (415) 855-2577
Dr. Thomas Clarkson, Professor ana Head, Division of Toxicology, University
ot Rochester, School ot iieaicine, Post Office Box EBB, Rochester, New York
14642 (716) 275-3911
Ur. Gary Diamond, Assistant Professor of Pharmacology, University ot
Rochester School of tfedicine, Kccdester, New York 14642 (716) 275-5250
ur. Phil Interline [ENVlKUMlENlAL hhALTh CUIilITEE], Departnsent of Biostatistics,
Graduate School of Public Health, University ot Pittsburg, 130 Desoto Street,
Pittsburgh, PA 1i>261 (4!2) 624-3U32
Ur. KoDerc usyer, Deparonenc ot Pathology, Health Sciences Centre, University
of Western Ontario, Lyndon, Untario, Canada N6A5C1
L>r. tiarvin Kuschner, Dean, School of Iledicine, Health Science Center,
Level 4, State University or New York, Stony Brook, New YorK 11794
(516) 444-208U
Dr. Brooke T. tiossman, Departn^ent ot Pathology, The university oŁ Vermont,
Medical Alunni Building, Burlington, Vermont 05405-0066 (602) 656-2210
Dr. Gunter Oberdoerster, Associate Professor, Radiation Biology and
Biophysics Division, University ot Rochester, School ot Medicine, 400
Elrawod Avenue, Rochester, U.Y. 14642 (716) 275-3BU4
Dr. F, William Sunderraan, Professor of Laboratory tiedicine and Pharmacology
and Head, Department of Laboratory tiedicine. University of Connecticut
Health Center, Room C 2021, Farmington, Connecticut 06032 (203) 674-2328
Executive Secretary
Ur. Richard Cothern, Executive Secretary, Environmental health committee,
Science Advisory Board [A-1Q1FJ, U.S. Environmental Protection Agency,
Washington, D,C. 20460 (202)382-2552
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