UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, o.c. 20460
IPA-SAB-EHC-89-036
September 19, 1989
OFFICE
fNE AOiM i wiS
Honorable William K. Reilly
Administrator
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, B.C. 20460
Subject! Science Advisory Board's preliminary review of mixture
issues relating to, some Phase II drinking water regulations of
the Office of Drinking Water
Dear Mr. Reilly,
The Halogenated Qrganics Subcommittee of the Science
Advisory Board's Environmental Health Committee has completed its
preliminary review of mixture issues relating to three
contaminants for which regulations are currently being developed.
This review was conducted early in the deliberations of the
Office of Drinking Water (ODW) with the objective of providing
them with some general directions for their thinking about the
state of knowledge of the scientific background concerning how to
estimate the health effects of complex chemical mixtures. The
three contaminants of immediate interest to QDW were; polycyclie
aromatic hydrocarbons, plasticiiers (including phthalates and
adipate esters) and gasoline. This review was based on a
briefing paper presented to the Subcommittee which met in
Washington, D.C., November 9-10, 1988. The subcommittee reached
conclusions resulting in suggestions for both the plasticizers
and gasoline, some informal suggestions and comments were given
at the meeting for all three contaminants.
Regarding the plasticizers, the Subcommittee concluded that
the health assessments for diethyl hexyl phthalate (DEEP) and
diethyl hexyl adipate (DEHA) should be conducted separately,
This suggestion is based on the lack of adequately defined
mechanisms that would provide a rationale for treating these
substances eguivalently. DEHP is classified as a group B2
carcinogen in the EPA weight of evidence scheme, while DEHA is
tentatively classified as a group C carcinogen. Results from
future mechanistic studies may necessitate reexamination of this
recommendation. A thorough literature search might resolve the
question of whether any additional phthalates or adipates should
be of concern.
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There was a clear agreement among the Subcommittee members
that only a few of the many components of gasoline are of major
health significance. Since benzene is invariably a component of
gasoline, and is generally the most soluble component, and is a
known carcinogen which is already regulated, and since there are
no known synergistic or antagonistic effects betwefen the •
components of gasoline/ the Subcommittee sugges€s that benzene is
the most appropriate component for risk assessment. The toxicity
of water soluble contaminants (xylenes, toluene, ethylbenzene, n-
hexane) could be evaluated using EPA's mixtures guidelines.
Gasoline additives, such as methyl tributyl ether, could be
considered on an individual component basis.
We appreciate the opportunity to conduct this particular
scientific review. Since this is only preliminary advice, the
Agency may wish to respond formally at this time or wait until
the time of its proposed regulations for these contaminants.
Sincerely,
Raymond Loehr
Chairman
Executive committee
Arthur Upton
chairman
""Environmental Health
Committee
Martha Ri
Vice-chairman
Halogenated Organics
Subcommittee
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U.S. Environmental Protection Agency
Science Advisory Board
Haloganated Organios subcommittee
November 9-10, 1988 Meeting
CHAIRMAN
Dr. John Doull
University of Kansas Medical Center
Kansas City, KS 66103
VICE CHAIRMAN
Dr. Martha RadiKe
University of Cincinnati Medical College
Department of Environmental Health
3223 Eden Avenue, M.L.056
Cincinnati, OH 45267
CONSULTANT^
Dr. George T, Bryan
Department of Human Onconolgy
University of Wisconsin
K4/528, Clinical Science Center
600 Highland Avenue
Madison, WI 53792
Dr. James M. Gentile, Professor
Biology Department
Hope College
Holland, Michigan 49423
Dr. Ronald D. Hood, Professor
Department of Biology
The University of Alabama
P.O. Box 870344
Tuscaloosa, Alabama 35487-0344
Dr. Larry Kaminsky, chief
Biochemical and Genotoxicology Laboratory
Wadsworth Center for Laboratories and Research
New York State Department of Health
Albany, NY 12201
Dr. Curtis Klaassen
Professor of Pharmacology and Toxicology
University of Kansas Medical Center
39th and Rainbow Boulevard
Kansas city, KS 66103
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SOiC-PASB TWO
Dr. Eugene McConnell *
Box 348-25 '
Route 6
Raleigh, N.C. 27613
Dr. Don E. McMiHian
Chairman, Department of Pharmacology
Mail 1638, University of Arkansas Medical Sciences
4301 West Markham street
Little RoaJc, AR 72205
Dr. Myron Mehlman
Director, Mobil
Environmental & Health Science Laboratory
P.O. Box 1029'
Princeton, NJ 08540
Dr. Stephen Safe
Department of Veterinary,Physiology and Pharmacology
College of Veterinary Medicine
Texas, _A & M University
College"*Station, TX 77843-4466
Dr. Thomas Starr
CUT
P.O. Box 12137
Research Triangle park, NC 27709
Dr. Robert Squire
1515 Labelle Avenue
Ruxton, MD 21204
Executive secretary - (for this meeting)
Dr, K. Jack Kooyoorajian
Environmental Protection Agency
Science Advisory Board
499 South Capitol Street, S.W.
Washington, D.C, 20460
Executive secretary
Dr. C. Richard Cothern
Environmental Protection Agency
Science Advisory Board
499 South Capitol Street, S.W,
Washington, D.c. 20460
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