UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, o.c.
SAB-EHO87-029
May 11, 1987
THE. A t?M ?M j^ r w A roK-
Honorable Lee M. Thomas
Jktainistrator
U. S. Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Dear Mr. Thomas:
The Drinking Water Subcommittee of the Science Advisory Board's
Environmental Health Committee has conpleted its review of the
Drinking Water Criteria Document for Nitrate and Nitrite and is
pleased to transmit its conclusions and recoianendations to you.
The Subconmi ttee advises that further technical changes are
warranted before finalizing the document. Specifically, the staff
should clarify the use of the Walton study, including the limitations
of the study and the weight assigned to its use for regulatory decision
roaking. Second, a clearer scientific rationale should be presented on
the selection of nargins of safety, these and other issues are
discussed in the attached report.
We
appreciate the opportunity to conduct this scientific review
est a formal response to the Subcommittee's report.
We apprecate te opportunty to conduct ths scent
and request a formal response to the Subcommittee's report.
Sincerely
Richard Griesemer, Chairman
Environmental Health Canmittee
Science Advisory Board
A
Norton Kfelson, Chairman
Executive Cecnmittee
Science Advisory Board
-------
UJNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, D.C, 20460
May 11, 1987
Dr. Richard A. Griesemer
OFFICE OF
THE
Environmental Health Conmittee
Science Advisory Board
U. S. Environmental Protection Agency
401 M Street, S. W.
Washington, D. C. 20460
Dear Dr. Griesemers
The Drinking Water Subcommittee of the Environmental Health Conaittee
has completed its review of the Office of Drinking Water Criteria Document
for Nitrate and Nitrite, The Subccraiittee concludes that the current
document merits further revision before a final version is prepared for use
as a technical basis for regulatory decision making. The two major reasons
for the Subcommittee's finding are stated below*
First, the documentation and its presentation are incomplete and
confusing, thus creating difficulties in reaching conclusions on matters of
scientific interpretation. For example, the observations of Walton are
used as a basis for determining acceptable levels for a ten-day health
advisory. The Subconmittee is particularly concerned about the weight
given the Walton study. The document describes the study in the summary
with little or no interpretation of the underlying study design, but its
importance merits an expert review by an epidemiologist. The study needs
to be fully described in the body of the document along with conclusions as
to its limitations and relative importance. Further, the same critical
approach should be followed for all studies that are crucial to the
development of proposed standards.
Second, public health standards setting involves the examination and
selection of appropriate margins of safety. The Safe Drinking Water Act
and its later Amendments specify that SPA address this issue* It is
especially critical here since the document cites the National Academy of
Sciences report (Drinking Water and Health, 1977) that remarks on the narrow
margin of safety for nitrates. In the Criteria Document for Nitrate and
Nitrite, the Agency selects a margin of safety that excludes, for all
practical purposes, protection of sensitive members of the population,
namely, infants with gastrointestinal disease. Ihe staff should clarify
its technical rationale for developing a margin of safety, as well as the
need to include or exclude particular subgroups of the population, for
example, those individuals who are genetically disposed to only slowly
reduce the methemoglobin. The Office of Drinking Water should set a
single public health standard for the contribution from both nitrate and
nitrite.
-------
„ 2 —
In addition, the Subcommittee notes that the document limits the
consideration of exposure to oral ingestion of drinking water. The
document should attempt to place into perspective the contributions of
drinking water to total human health exposure by age group (particularly
the endogenous sources); at present, there is little opportunity to determine
to what extent Agency actions for drinking water will provide overall public
health protection. The Subcommittee recommends that the Office of Drinking
Water also expand the chapter on alternate pathways and sources of exposure
to provide a more conprehensive analysis of relative exposure, and that the
section on the quantification of toxicological effects examine in detail
the contribution of nitrate and nitrite in drinking water to the risk of
disease in various populations. A data gap exists for reproductive and
developmental effects that the document should cite.
The Subcommittee concludes that the Agency can appropriately set a
proposed health advisory level on the basis of methemoglobin formation. In
addition, there is a carcinogenic potential of these inorganic ions in
chemical combination with naturally occurring substances. Ihe Subccnmittee
reeairoends that the Office of Drinking Water present a conclusion on the
current knowledge about the potential for impacts of nitrosated materials
from nitrate and nitrite in drinking water. The Criteria Document may
require further revision if new information arises about this subject.
Specifically, it is desirable to consider the case of splenic sarcomas
in male rats which appear to be related to compounds that produce
methemoglobemia. The Subcommittee also recommends that the nitrosamine
issue (endogenous formation) could warrant a separate EPA position paper
as seme nitrosamines are likely to be human carcinogens.
Finally, the Subcommittee wishes to address an issue that is applicable
not only to this document but to criteria documents or risk assessments in
general. If reproductive and developmental toxicity data are not available
from either reliable human epidemiolcgic studies, from concretely relatable
human experience, or frcm valid state-of-the-art animal studies, this fact
itself must be stated. Furthermore, when developmental toxicity data are
available from animal studies, then both the NOEL and the magnitude of the
most likely margin of safety between that animal NOEL and probable human
exposure needs to be stated. A second point is the relationship of the
vulnerability of the conceptus and the mother to the agent. If the agent
in question produces developmental toxicity only at, or very near to,
maternally toxic dose levels in an aniinal study, this needs to be stated as
does the pore hazardous situation wherein an agent produces adverse effects
on the conceptus in the absence of any maternal horaeostatic effect.
Sincere!'
Gary Carlson, Chairman
Drinking Water Subccnmittee
Robert Tardiff, Vice-Cbearman
Drinking Water Subccnmittee
------- |