United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA/600/S3-85/074 Jan. 1986
&ER& Project Summary
Acute and Chronic Effects of
Water Quality Criteria Based
Metal Mixtures on Three
Aquatic Species
R. L Spehar and J. T. Fiandt
Acute and chronic toxicity tests were
conducted to determine the effects of
metals combined as mixtures at pro-
posed water quality criteria concentra-
tions and at multiples of the LC50 and
MATC obtained from tests on six
metals with three aquatic species.
These studies constituted the first part
of a larger U.S. EPA effort to derive
water quality criteria for combined pol-
lutants.
Arsenic, cadmium, chromium, cop-
per, mercury, and lead combined at
criterion maximum concentrations
caused nearly 100 percent mortality to
rainbow trout and daphnids after acute
exposure. Fathead minnows were not
adversely affected at this or two times
this concentration, although a mixture
of 4 to 8 times the maximum value
caused 15 to 60 percent mortality after
this time. Metals combined at the crite-
rion average concentrations signifi-
cantly reduced daphnid young produc-
tion and fathead minnow growth after
7 and 32 days, respectively. Embryo
hatchability and survival of rainbow
trout were reduced at 4 times this crite-
rion but not at the criterion average
concentration.
Acute tests with metals mixed at
multiples of the LC50 indicated that
their joint action was more than addi-
tive to fathead minnows and nearly
strictly additive to daphnids, based on
U.S. Environment! PwtectiontSftSHSp calculated from the individ-
O-i,:.^, ,, . .t uahJomponents of the mixture. Chronic
KeglOD V, Llor?uy tests showed that the joint action was
230 South Dearborn Street less than additive to fathead minnows
Illinois 60^04 but nearly strictly additive to daphnids.
indicating that long-term metal interac-
tions may be different in fish than in
lower invertebrates. Adverse effects
were observed at mixture concentra-
tions of 1/2 to 1/3 of the MATC in fat-
head minnows and daphnids, respec-
tively; this suggests that components
of mixtures at or below no effect con-
centrations may contribute signifi-
cantly to mixture toxicity on a chronic
basis. These results point out the need
for additional studies to determine the
type and degree of interaction of toxi-
cants, because single chemical water
quality criteria may not sufficiently pro-
tect some species when other toxicants
are present concurrently.
This Project Summary was devel-
oped by EPA's Environmental Research
Laboratory, Duluth, MN, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Much of the information in the litera-
ture on the toxicity of chemicals to
aquatic life deals with studies involving
single toxicants. Numerous toxicity
tests have been conducted to determine
the acute and chronic effects of toxi-
cants in order to provide data for the
derivation of water quality criteria. To
date, existing water quality criteria have
been derived for single toxicants, yet it
is rare to find natural waters in which
only single toxicants are present.
Aquatic organisms are more often ex-
posed to a wide variety of toxicants
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from direct effluent discharges or from
non-point source chemical runoff. For
this reason, the practice of setting water
quality criteria on single toxicants is
often questioned.
In an effort to establish more effective
water quality criteria and hazard assess-
ment programs, several mathematical
models have been developed which
predict the effect of mixtures of chemi-
cals on aquatic organisms.These meth-
ods, however, have generally applied to
acute lethality tests, and the chronic ef-
fects of sublethal concentrations of mix-
tures to aquatic organisms have
scarcely been investigated. Results
from these tests appear to be somewhat
contradictory and show no clear trend
as to how chemicals interact as mix-
tures during acute and chronic expo-
sure.
Due to the lack of adequate informa-
tion on the chronic effects of mixtures,
little guidance has been given for set-
ting water quality standards based on
chemical mixtures. An early, tentative
approach for evaluating joint toxicity
has been to assume that an additive ac-
tion occurs between diverse toxicants.
A similar approach has more recently
been taken by the Europeans. Based on
their review of the literature on the ef-
fects of mixtures on freshwater fish and
other aquatic organisms, they proposed
that for pollution control purposes, the
concentration addition model is ade-
quate to describe the acutely lethal joint
effect of commonly occurring con-
stituents of sewage and industrial
wastes. This proposal was based on the
rationale that the joint acute lethal toxic-
ity of chemicals to fish can be predicted
assuming simple addition of the pro-
portional contribution from each toxi-
cant, and that toxicity based on concen-
trations approaching no effect are less
than additive and probably do not con-
tribute to the toxicity of mixtures. It was
concluded, however, that more empiri-
cal studies are needed on the long-term
joint effect of mixtures of toxicants, es-
pecially, to determine the contribution
of small fractions of the toxic units of
the individual components.
The first objective of this research
was to determine if the single chemical
water quality criteria proposed by the
U.S. EPA in 1984 for selected inorganic
chemicals were sufficient to protect se-
lected aquatic species when these
chemicals were present as mixtures.
The criteria are not specific for individ-
ual species but are based on several
species from a variety of aquatic
families. The present studies would not
show the type and degree of interaction
of chemicals in these mixtures but
would indicate their interaction at pro-
posed criteria concentrations.
The second objective was to measure
the contribution of fractions of toxic
units of mixtures by using acute (LC50)
and chronic (MATC) values obtained
from tests with individual chemicals in
mixture tests at, above, and below these
concentrations. In addition to the
MATC, an estimate of the level of 50
percent reduction in growth and repro-
duction was used as the toxic unit in
chronic tests. Results from these tests
would be species specific and would in-
dicate the possibility of concentration
addition.
Inorganic chemicals, specifically ar-
senic, cadmium, chromium, copper,
mercury and lead were selected for this
study because of their importance to
EPA in deriving individual chemical
water quality criteria and because these
chemicals are found together as mix-
tures in commonly occurring sewage
and industrial wastes. Tests were con-
ducted with fathead minnows, rainbow
trout, and daphnids. Fathead minnows
and rainbow trout are important forage
and game fish, respectively, and are
representatives of both warm and cold
water aquatic organisms. Daphnids
were chosen for study because they are
among the most sensitive aquatic or-
ganisms to most of the selected chemi-
cals.
Conclusions
The above tests show that single
chemical water quality criteria for
metals may not be sufficient to protect
certain aquatic species if the chemicals
are combined as mixtures in solution.
Metals combined at both the criterion
maximum and average concentrations
proposed by EPA in 1984 caused signif-
icant adverse effects to the tested spe-
cies based on acute and chronic expo-
sure. Studies conducted to determine
the effects of metals combined at frac-
tions of LC50 and MATC suggest that
components of mixtures at or below no
effect concentrations may contribute
significantly to mixture toxicity on a
sublethal as well as on an acute basis.
These results point out the need for ad-
ditional studies to determine the type
and degree of interaction of toxicants at
proposed environmental levels. Such
studies are needed to identify general
characteristics or trends displayed by
chemical mixtures and would provide
for more effective hazard assessment.
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The EPA authors, R. L. Sp0har(also the EPA Project Officer, see below) andJ. T.
Fiandt, are with Environmental Research Laboratory, Duluth, MN 55804.
The complete report, entitled "A cute and Chronic Effects of Water Quality Criteria
Based Metal Mixtures on Three Aquatic Species," (Order No. PB 86-122
579/AS; Cost: $ 11.95, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Duluth, MN 55804
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S3-85/074
OC00329 PS
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