Gary L. Phipps

Relationships of quantitative structure-activity to comparative toxicity of selected phenols in the Pimephales promelas and Tetrahymena pyriformis test systems

The relative toxic response of 27 selected phenols in the 96-hr acute flowthrough Pimephales promelas (fathead minnow) and the 48- to 60-hr chronic static Tetrahymena pyriformis (ciliate protozoan) test systems was evaluated. Log Kow-dependent linear regression analyses revealed that the data from each test system consisted of two linear equations. The less toxic chemicals form a relationship which models polar narcosis; these chemicals are slightly more active than the baseline toxicity of nonionic narcotic chemicals. The more toxic chemicals form a relationship which models uncoupling of oxidative phosphorylation. Regression analysis of fathead minnow toxicity (log LC50 (mol/liter] vs Tetrahymena toxicity (log BR (mmol/liter] showed good correlation between the two systems. An exception appears to be 4-nitrophenol, which is more active in the Tetrahymena system than in the fathead minnow and lies outside the 95% confidence interval. Reanalysis following deletion of 4-nitrophenol results in the equation log LC50 = -0.9192 (log BR) -3.5035; n = 26, r2 = 0.887.

Relative Sensitivity of Three Freshwater Benthic Macroinvertebrates to Ten Contaminants

The objective of this study was to determine the suitability of Hyalella azteca, Chironomus tentans and Lumbriculus variegatus as representative species for the assessment of sediment toxicity. Ten chemicals were tested at the U.S. EPA Environmental Research Laboratory-Duluth, always using H. azteca and C. tentans and, occasionally, L. variegatus. The exposures were water-only, flow-through tests with measured chemical concentrations, which were conducted for 10 days in Lake Superior water. Chemicals tested included five metals (copper, lead, zinc, nickel, cadmium) and five pesticides (chlorpyrifos, dieldrin, p,p′-DDD, p,p′-DDE, p,p′-DDT). The amphipod was quite sensitive to the metals, while the midge often was exceptionally sensitive to the pesticides. No one of the three species was most (or least) sensitive to the toxicants. Toxicity of the contaminants to the three species was compared to the genus mean acute and chronic data found in U.S. EPA Water Quality Criteria (WQC) documents, as well as information from the AQUIRE database. The results of these comparisons indicated that the three species reasonably represent the range of sensitivities of other aquatic test species, and occasionally are among the most sensitive species when compared to others in the WQC database.

Development and evaluation of test methods for benthic invertebrates and sediments: Effects of flow rate and feeding on water quality and exposure conditions

In order to ensure among-laboratory comparability in the results of sediment toxicity tests, it is necessary to characterize the influence of variations in test regimes on organism responses and exposure conditions. The objective of these studies was to develop and document an optimized combination of overlying water renewal (flow) and feeding rates for sediment tests with three commonly used benthic species (midges, Chironomus tentans; amphipods, Hyalella azteca; oligochaetes, Lumbriculus variegatus). Optimal conditions were defined by a number of chemical and biological considerations including: (1) flow rate through the system, (2) amount of food added, (3) acceptable responses (survival, growth, reproduction) of the organisms over the course of a 10-day test, and (4) maintenance of an adequate concentration of dissolved oxygen in overlying water. The goal was to minimize factors (1) and (2), while maximizing criteria (3) and (4). The major reason for minimizing (1) and (2) was the concern that excessive water flow or addition of food could reduce exposure of the test organisms to sediment-associated contaminants. To evaluate this, interstitial (pore) water concentrations of contaminants (ammonia, zinc, copper, dieldrin) were measured over the course of 10 day tests conducted with a number of different sediments under various flow and feeding regimes. The different combinations of flow/feeding had variable effects upon pore water concentrations of contaminants; for example under our optimized regime, in some instances slight decreases in interstitial water contaminant concentrations were observed, whereas in other cases contaminant concentrations remained constant or even increased. Overall, the use of minimal water renewal and feeding rates should result only in small changes in exposure of benthic organisms to contaminants in pore water over the course of 10-day tests.

Effects of light intensity on the phototoxicity of fluoranthene to a benthic macroinvertebrate.

Conceptual models suggest that the toxicity of photoactivated polycyclic aromatic hydrocarbons (PAHs) should be a direct function both of chemical (PAH) dose and intensity of the ultraviolet (UV) light to which the organism is exposed. However, there have been only limited studies with aquatic organisms to quantify the relationship between PAH dose and UV intensity in producing phototoxicity. In this study, oligochaetes (Lumbriculus variegatus) were exposed, via the water, to multiple concentrations of fluoranthene, a PAH known to be phototoxic, and then placed under UV light at three different intensities. The resultant phototoxicity clearly was a function both of PAH dose and light intensity. Time-dependent mortality of the oligochaetes could be accurately predicted through evaluation of the product of fluoranthene dose (in the tissue of the animal) and light intensity to which the organisms were exposed. These results indicate that criteria for phototoxic chemicals should incorporate consideration not only of xenobiotic exposure but also of light intensity in specific aquatic environments.

Acute toxicity of phenol and substituted phenols to the fathead minnow.

Because of the wide, high-volume usage of phenolics it behooves us to be aware of their toxicity in the environment. This awareness must include a knowledge of the effects on freshwater bodies and more specifically, an appreciation of the importance of differences in the physical properties of the water. The variability of the data on some phenolics makes it difficult to separate toxicity values that vary widely from others because of different test methods rather than different physical properties of the water. Data were lacking on some of the compounds we tested, and thus our data contribute significantly to the basic informtion on these chemicals. This acute test series was conducted with a variety (12) of phenolic compounds. Test conditions were kept as uniform as possible so that the toxicities of the compounds could be attributed to the differences in toxicity rather than to differences in test conditions. In addition, the tests provide data on the toxic effects in Lake Superior water, which is a major freshwater body in the USA.

Simultaneous multiple species testing: acute toxicity of 13 chemicals to 12 diverse freshwater amphibian, fish, and invertebrate families.

This test series developed methods for testing a compliment of aquatic organisms in a single test that satisfies the freshwater acute toxicity requirements for setting water quality criteria. Species tested included fathead minnowsPimephales promelas, rainbow troutSalmo gairdneri, bluegillLepomis macrochirus, channel catfishIctalurus punctatus, goldfishCarassius auratus, white suckerCatostomus commersoni, daphnidDaphnia magna, midgeTanytarsus dissimilis, crayfishOrconectes immunis, snailAplexa hypnorum, tadpoleXenopus laevis, and leechNephelopsis obscura. Five to nine of the preceding species were simultaneously exposed in individual tests. The chemicals tested were acrolein, aniline, dibutylfumarate, 2,4-dinitrophenol, Guthion®, nicotine sulfate, phenol, rotenone, silver, Systox®, 1,2,4-trichlorobenzene, 2,4,6-trichlorophenol, ando-xylene. This method of simultaneously exposing aquatic organisms in separate compartments of each exposure tank allows more accurate comparisons of species sensitivity with a tested chemical. Use of this method can also produce the minimum acute data set for the derivation of a water quality criterion in less time and with a substantial cost saving for labor, materials, and chemical analyses when compared with measured concentration tests conducted separately with each individual species.

A SEDIMENT TESTING INTERMITTENT RENEWAL SYSTEM FOR THE AUTOMATED RENEWAL OF OVERLYING WATER IN TOXICITY TESTS WITH CONTAMINATED SEDIMENTS

A sediment testing intermittent renewal (STIR) system (stationary or portable) for invertebrate toxicity testing with contaminated sediments has been successfully developed and thoroughly tested at ERL-Duluth. Both the stationary and portable systems enable the maintenance of acceptable water quality (e.g. DO) through the capability of automatically renewing overlying water in sediment tests at rates ranging from 1 to 21 volume renewals/day. The STIR system not only significantly reduces the labor associated with renewal of overlying water but also affords a gentle exchange of water that results in virtually no sediment resuspension. Both systems can also be installed in a compact vented enclosure to permit safe testing of hazardous contaminated sediments. To date the STIR system has been used extensively for conducting 10-day bulk sediment tests with Chironomus tentans, Hyalella azteca and Lumbriculus variegatus.

A method for aquatic multiple species toxicant testing: Acute toxicity of 10 chemicals to 5 vertebrates and 2 invertebrates

Abstract A method was developed to simultaneously ascertain 96 h LC50 values for seven freshwater species in a single flow through test with measured concentrations. It allows interspecific comparisons, easy determination of the most sensitive species, and cuts cost of labour, materials and chemical analysis for measured concentration tests. Species tested included fathead minnows Pimephales promelas, goldfish Carassius auratus, channel catfish Ictalurus punctatus, bluegill Lepomis macrochirus, rainbow trout Salmo gairdneri, crayfish Orconectes immunis and snails Aplexa hypnorum. Compounds tested were pentachlorophenol, 2-chloroethanol, 2,4-pentanedione, hexachloroethane, α-bromo-2′,5′-dimethoxyacetophenone, benzaldehyde, 1,3-dichloro-4,6-dinitrobenzene, dursban, sevin and cadmium chloride. The LC50 values from these multiple species tests compared favourably with those determined using single species tests at this laboratory, usually within 20%.

The acute toxicity of kelthane, dursban, disulfoton, pydrin, and permethrin to fathead minnows Pimephales promelas and rainbow trout Salmo gairdneri

Abstract Flow-through acute lethal toxicity tests were conducted with kelthane, dursban disulfoton, pydrin and permethrin using rainbow trout Salmo gairdneri and fathead minnows Pimephales promelas in Lake Superior water. Pydrin was the most toxic pesticide tested to both species of fish and was followed in order of decreasing toxicity by permethrin, dursban, kelthane and disulfoton. Rainbow trout were more sensitive than fathead minnows to all five pesticides. The 96-h LC 50 values (μg litre −1 ) for rainbow trout and fathead minnows, respectively, were: pydrin, 2·1 and 5·4; permethrin, 7·0 and 15·6; dursban, 8·0 and 203·0; kelthane, 210·0 and 510·0 and disulfoton, 3020·0 and 4000·0.

The acute toxicity of selected substituted phenols, benzenes and benzoic acid esters to fathead minnows Pimephales promelas

Abstract Flow-through acute toxicity tests were conducted with 24 organic compounds using fathead minnows Pimephales promelas as test organisms. The tested toxicants consisted of 11 substituted phenols, four substituted benzenes and nine esters. The 96-h LC 50 values determined for these compounds when tested against fathead minnows ranged from 0·135 mg litre −1 for nonylphenol to 117 mg litre −1 for nitrobenzene. Adverse sublethal effects were observed in fathead minnows at exposure concentrations below the 96-h LC 50 value with 14 of the 24 compounds tested. Acute toxicity tests were also conducted with 2,3,4,5-tetrachlorophenol using rainbow trout Salmo gairdneri ; with 1,4-dinitrobenzene, 2-ethoxyethylacetate, ethyl salicylate and phenyl salicylate using both channel catfish Ictalurus punctatus and snails Aplexa hypnorum ; and with 4-nitrophenol using channel catfish. The 96-h LC 50 for rainbow trout when tested against 2,3,4,5-tetrachlorophenol was 0·205 mg litre −1 , while 96-h LC 50 values for channel catfish ranged from 0·673 to 44·8 mg litre −1 with 1,4-dinitrobenzene and 2-ethoxyethylacetate, respectively. Snail 96-h LC 50 values ranged from 4·24 mg litre −1 for 1,4-dinitrobenzene to 65·2 mg litre −1 for 2-ethoxyethylacetate.