8273

• UCREFRP Catalog Number: 8273
• Author: U.S. Bureau of Reclamation, U.S. Fish and Wildlife Service, U.S. Geological Survey and U.S. Bureau of Indian Affairs.
• Title: Guidelines for Interpretation of the Biological Effects of Selected Constituents in Biota, Water, and Sediment.
• USFW Year: 1998.
• USFW - Doc Type: \
• Copyright Material: NO

National Irrigation Water Quality Program Guidelines

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a particular compound to a particular
species without consulting the more
detailed information presented later in
each chapter and, when possible, the
original studies.

(4) Results from many recent studies could
not be included here. Most of the
research for these chapters was completed
by mid-1996, and only the literature pub-
lished prior to that time was system-
atically surveyed. During subsequent
review and preparation of this volume,
more recent results that came to our
attention were added opportunistically,
not systematically.

(5) Legally enforceable standards are not
presented here, with two exceptions. The
U.S. Environmental Protection Agency
has established "maximum contaminant
levels," applicable only to drinking water,
for most of these constituents, and the
U.s. Food and Drug Administration has
"action levels for human consumption" for
two of them (DOT and mercury). These
legal standards are noted near the end of
each chapter, in the section "Regulatory
standards." Note, however, that even in
those sections, values identified as "goals"
or "criteria" do not have the force of law.

Individual States may set legal standards that
are stricter than those of the Federal
Government, and many have chosen to do
so. State standards are too variable and
voluminous to be listed here; however,
Appendix I lists addresses and phone
numbers for the offices responsible for water
quality standards in each of the 17 Western
States.

The Need for Caution in
Interpreting Toxicological Data

The contents of this report are described as
guidelilles, rather than rules or standards,
because toxicological effects vary greatly in

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natural ecosystems. Many variables can cause
individual constituents to be more or less toxic
at other sites or for other species. This section
describes some of the better known factors
that may complicate the interpretation of
toxicity data.

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Unnatural Laboratory Settings

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Most laboratory studies test toxicity under
completely unnatural conditions: they test the
effect of a single compound on a single
species, delivered by only one pathway under
carefully controlled conditions. In the wild,
organisms are exposed to many different
chemical and physical agents simultaneously.
(See "Interactions," below.)

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Generally, laboratory specimens in an
experimentally contaminated environment are
given food from outside, uncontaminated
sources, whereas wild creatures must eat food
that has grown in the same environment and
that may have accumulated, through
bioconcentration, lethal levels of whatever
toxins are present. Thus, for instance, fish or
waterfowl could end up dying in areas where
waterborne toxin concentrations are at levels
that caused no harm to laboratory specimens.

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On the other hand, most laboratory specimens
are taken from uncontaminated populations,
which have no previous history of exposure to
the toxin being tested. In the wild, organisms
living in a contaminated environment may
have acclimated or adapted to the toxin,
especially if the contamination developed
gradually. In this case, one might find fish
and waterfowl thriving in areas where
waterborne concentrations are at levels
experimentally determined to be lethal.

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Laboratory specimens are rarely threatened by
predators or challenged by others of their own
kind in mating competitions, whereas their
undomesticated cousins deal with both
conflicts. These conflicts can add to the
overall stress on the organisms, making them

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