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 ------- 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. ------- 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 U S ENVIR PROTECTION AGENCY REGION 5 LIBRARY 230 S DEARBORN STREET CHICAGO 1L 60604 ------- |