Chronic Toxicity Data Research Articles

Acute/chronic ratios to estimate chronic toxicity from acute data

Acute toxicity of 25 narcotic compounds to D. magna was determined in this paper. Acute/ Chronic Ratios (ACRs), which are often used to estimate chronic toxicity from acute toxicity data, are discussed based on Quantitative Structure‐Activity Relationships (QSARs) of the compounds between both acute and chronic toxicity data and n‐octanol/water partition coefficients, and an improved equation is derived to estimate chronic toxicity data from acute toxicity data. Application of the improved equation and ACRs is illustrated for D. magna and fathead minnow to estimate chronic toxicity from acute toxicity.

Evaluation of aquatic toxicity and bioaccumulation of C8‐ and C9‐alkylphenol ethoxylates

AbstractThe extensive database of acute and chronic aquatic toxicity data for alkylphenol ethoxylates (APEs) and selected biodegradation intermediates was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish inhabiting cold and warm water bodies. Most acute toxicity studies that tested APE‐9 and APE‐10, the most common commercially relevant APEs, reported results that ranged from about 1,000 to 10,000 μg/L. Results from studies testing alkylphenols, intermediate by‐products of APE biodegradation, ranged from about 20 to 3,000 μg/L. Chronic values are a factor of about 2 to 10 lower. Although most studies used one of several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This toxicological database encompasses virtually all important types of aquatic habitats and classes of aquatic species. Bioaccumulation data from both laboratory and field studies indicate that alkylphenols have a low to moderate bioaccumulation potential. Fresh weight, nonlipid‐based bioconcentration factors (BCFs) measured in the laboratory ranged from < 1 to 1,250 for fish and 1 to 3,400 for invertebrates, whereas field bioaccumulation factors (BAFs) ranged from 6 to 487, with most values < 100. Overall, these data provide an extensive and useful database to support environmental risk assessment activities.

慢性毒性の生命表評価法と生態リスク分析

For the ecological risk assessment, extrapolation from toxicological data obtained at the individual level into effects at the population level is required. We review the analytical methods for translating chronic toxicity data into the effect on propensity of populations (population growth rate or intrinsic rate of population increase). Actual ecotoxicological data have two major problems, i.e., 1) only a very small fraction of chemicals-species combinations has been examined for chronic toxicity, and 2) it is not feasible for many test species to execute the life-cycle test. As analytical methods in order to circumvent these limitations of data, we focus on the extrapolation method and the life history sensitivity analysis, and discuss these methods in the context of ecological risk assessment. The cxtrapolation method is to infer missing chronic toxicity data from regression of known chronic data to acute data, or from regression of chromic data between different species or life stages. From the inferred and the directly estimated chronic toxicity data, the effect of chemicals to population growth rate is estimated. The life history sensitivity analysis estimates the relative importance of life stages in terms of intrinsic rate of natural increase, and reduces the life table evaluation by excluding the unimportant life stages. These analytical methods that apply the ecological theory may be important for future ecotoxicological data analysis embedded in the ecological risk assessment.

Derivation of Australian tropical marine water quality criteria for the protection of aquatic life from adverse effects of petroleum hydrocarbons

The use of data on the water concentration of total petroleum hydrocarbons (TPH) in hazard evaluation for marine biota is hindered by the lack of justified water quality criteria for TPH. Using ecotoxicology data for marine organisms and U.S. EPA guidelines (1985, 1994), numerical criteria for TPH were derived. Acute and chronic toxicity data for marine organisms exposed to water-soluble fractions of oil products were obtained from published materials and the author's investigations. Out of 310 data reviewed and sorted, 82 data for the test temperatures of 20–32°C were selected and analyzed. The genus mean acute values (GMAV) were calculated for 15 animal genera belonging to the phyla Chordata, Arthropoda, Mollusca, Annelida. Plant values were obtained for six species of the algae classes Diatom, Chlorophyta and Dinophyta. The GMAVs ranged from 0.2 to 13.1 mg/L TPH. The considerable variability of data was attributed to differences in toxicity test designs. The EC50 values were adjusted by taking into account the fact that average test concentrations drop during courses of static-renewal and static toxicity tests. These adjustments resulted in a GMAV range of 0.2–5.2 mg/L with acceptable intergeneric variability. The final acute value derived as the fifth percentile of the set of 15 GMAVs for animals was in the range of 0.168–0.198 mg/L for the triangular, logistic, and normal distribution models. The advisory water quality criterion (AWQC) derived from these values was 0.007 mg/L. According to the criterion definition, to protect warm water marine organisms from unacceptable effects, an ambient concentration of TPH must not exceed AWQC of 0.007 mg/L. © 1998 John Wiley & Sons, Inc. Environ Toxicol Water Qual 13: 273–284, 1998

Aquatic toxicity of eighteen phthalate esters

AbstractThe extensive database of acute and chronic aquatic toxicity data for 18 phthalate esters was reviewed and summarized for freshwater and saltwater aquatic microorganisms, algae, invertebrates, and fish. Phthalate esters have been tested with six species of microorganisms, including bacteria and protozoans. Fifteen algal species have been tested, including green and bluegreen algae in both freshwater and saltwater. Nineteen freshwater and saltwater invertebrate species inhabiting surface waters and sediments and 21 freshwater and saltwater fish inhabiting cold and warm water bodies have been tested. The results of most studies indicate that acute and chronic toxicity to microorganisms, algae, aquatic invertebrates, and fish are limited to the lower molecular weight phthalate esters (i.e., dimethyl‐, diethyl‐, diallyl‐, dipropyl‐, dibutyl‐, diisobutyl‐, and butylbenzylphthalate). In contrast, higher molecular weight phthalate esters are not acutely or chronically toxic to aquatic organisms. Although conflicting data on chronic effects for high molecular weight phthalate esters have been reported for daphnids, these inconsistencies are attributed to physical effects imposed on daphnids when exposed to test concentrations in excess of true water solubilities. Altogether, nearly 400 test results covering more than 60 species of microorganisms, algae, invertebrates, and fish are reported for both freshwater and saltwater aquatic species. While most investigators used several common species and standard protocols to assay conventional endpoints, many nontraditional species and toxicological endpoints were also used. This has created a toxicological database of both sufficient depth to compare many similar tests and sufficient breadth to encompass virtually all important types of aquatic habitats and classes of aquatic species.

Development of a chronic toxicity structure-activity relationship for alkyl sulfates

Much of the historical data regarding the toxicity of alkyl sulfate (AS) surfactants to aquatic organisms have been compromised due to excessive loss of the parent material via biodegradation and precipitation—processes especially important during chronic tests. To minimize these issues, a novel flow-through system for Ceriodaphnia dubia was developed and acute and chronic toxicity data were obtained for several AS structures. Acute toxicity increased linearly with increased alkyl chain length (CL) from C12AS to C16AS. However, a parabolic response was observed for reproduction where toxicity increased with alkyl chainlength from C12AS to C14AS, but decreased with increased chain length from C14AS to C18AS. Soluble vs precipitated forms of AS contribute to the parabolic relationship. A quadratic approach using the chronic end points no observed effect concentration, lowest observed effect concentration, maximum acceptable toxicant concentration, EC50, and EC20 yielded the best fit for EC20 (R2=0.99). Quantitative structure–activity relationships for AS, based on acute toxicity alone, overpredict chronic toxicity at chainlengths greater than C14AS. Use of the quadratic model [EC20(M)=5.12×10−7(CL)2−1.49×10−5(CL)+11.1×10−5] is advocated for use in environmental risk assessment. © 1997 John Wiley & Sons, Inc. Environ Toxicol Water Qual 12: 295–303, 1997

Conversion Factors Estimating Indicative Chronic No-Observed-Adverse-Effect Levels from Short-Term Toxicity Data

Data on chronic toxicity are generally required to derive a health-based acceptable exposure limit, such as the acceptable daily intake. However, only acute and/or subacute toxicity data are available for many compounds. In this study, we assessed conversion factors (CFs) to estimate a chronic no-observed-adverse-effect-level (NOAELchronic) from these short-term toxicity data. We evaluated distributions of ratios between (sub)acute and chronic toxicity data for 332 compounds. By defining the CF as the upper 95% confidence limit of the 95th percentile for the relevant ratio distribution, both the variation between compounds (95th percentile) and the estimation error (upper 95% confidence limit) could be taken into account. Dividing a NOAELsubacuteor LD50by the corresponding CF results in a conservative estimate of the chronic NOAEL. We assessed a CF of 87 for a NOAELsubacuteand a CF of 1.7 × 104for an LD50. We found the NOAELsubacuteto be a better predictor of the NOAELchronicthan the LD50. Moreover, the added value of an LD50in estimating a NOAELchronicappeared to be limited when a NOAELsubacutewas available.

Food chain analysis of exposures and risks to wildlife at a metals-contaminated wetland.

A food chain analysis of risks to wetland receptors was performed in support of a baseline ecological risk assessment at the Milltown Reservoir Sediments Superfund site in Montana. The study area consisted of over 450 acres of primarily palustrine wetland contaminated with metals from mining wastes transported from upstream sources (average of 465 mg/kg for Cu in sediments, and 585 mg/kg in soils). The food chain analysis focused on several species of terrestrial and semiaquatic animals indigenous to montane wetlands of the northern Rocky Mountains. Receptors consisted of mice, voles, muskrats, beaver, various waterfowl species, osprey, bald eagles, and deer. Samples of aquatic and terrestrial invertebrates, small mammal tissues, fish tissue, aquatic and terrestrial vegetation, soils, sediment, and surface water were collected and analyzed for As, Cd, Cu, and Zn. A linear multimedia food-chain model was constructed to estimate daily intakes of the metals for each receptor, with assumed values for ingestion of aquatic and terrestrial food items, ingestion of local surface water, and incidental ingestion of soils and/or sediments. Evaluation of health risks to the receptors was performed by comparison of exposures expressed as daily intakes to a suite of toxicity values. The range of values consisted of the lower end of chronic toxicity data found in toxicology databases or the literature for the same or similar species, modified to account for extrapolation uncertainties. Daily intakes of chemicals of concern were below or within the range of toxicity values for all receptors. The weight of evidence from the food chain analysis and earlier bioassessment and ecological studies suggest that the health of the wetland receptors is at minimal risk due to the presence of elevated metals in sediments, upland soils, water, or food items at the site.

Aquatic Toxicology and Chemistry of Some Surfactants

Surfactants are one of the major components of detergent or household cleaning products. Several are commonly found in river waters and consequently, their impact on the aquatic environment has been discussed in the U.S.A, Western Europe and Japan. This paper reviewed the studies on the environmental monitoring, environmental fate, acute, chronic and sublethal toxicity, and environmental risk assessment of anionic surfactants. The reported acute and chronic toxicity data overlapped with some worse case of LAS environmental concentrations in rivers in Japan for a lack of adequate treatment of household gray water. Aquatic safety of other surfactants was considered preliminary and limited until validated with corresponding exposure measurements and chronic toxicity data for test species. Life-Cycle Assessment on surfactants was also reviewed.

A risk‐based protocol to develop acceptable concentrations of bioaccumulative organic chemicals in sediments for the protection of piscivorous wildlife

Abstract Environmental quality guidelines are benchmarks that indicate whether or not environmental concentrations present measureable risks to ecosystem health. This paper outlines an approach for the development of guidelines for concentrations of bioaccumulative organic chemicals in sediments that would be protective of wildlife at the top of the food chain an aquatic ecosystem. The proposed method uses risk assessment techniques that integrate information on relevant exposure pathways from sediments to top predators and toxicity assessment for avian and mammalian species. The method requires biota‐to‐sediment bioaccumulation factors (BSAFs) for various ecosystems and food webs and knowledge of the predator‐prey relationships and physiological parameters of piscivores. The proposed method is considered to be an improvement to existing regulatory methods for the derivation of water quality guidelines that are based on acute and chronic toxicity data generated primarily from waterborne exposure assays of aquatic species, and recent efforts to develop sediment quality guidelines on the basis of acute and chronic toxicity of contaminated sediments to benthic invertebrates and benthic community structure. Neither of these existing methodologies adequately address the potential for food chain transfer of persistent bioaccumulative organic chemicals through relevant exposure pathways from sediments.

Tests for bioequivalence of control media and test media in studies of toxicity

AbstractStatistical tests of the classical (null) hypothesis–that there is no difference in effects of control media and test media– are commonly used to make statistical inferences toward the no‐observed‐adverse‐effect concentration. However, failing to reject this hypothesis is not considered as scientific proof the hypothesis is true. An effect may exist, but high variation due to inadequate replication, variation in experimental units, or imprecise measurement techniques may yield data for which the hypothesis is not rejected. An experiment may also be too precise, yielding effects that are statistically significant but not biologically important. We propose the use of tests of bioequivalence of control media and test media to alleviate these unsatisfactory characteristics of tests of the classical hypotheses for regulatory decisions. We review and illustrate the test for bioequivalence using acute and chronic toxicity data. We also define a procedure for determining the level of effect at which there will be high power to refute the hypothesis that there is a lack of bioequivalence if in fact the biological response in the control media is identical to the response in the test media.

Aqatic toxicity equivalency factors for chlorinated phenolic compounds present in pulp mill effluents

Aquatic toxicity equivalency factors (TEFs) for chlorinated phenolic compounds present in blached kraft mill effluents were estimated using published chronic toxicity data for fathead minnows, rainbow trout, zebra fish, American flagfish, and sea urchins. To provide the most consistent and reliable approach for estimating relative toxicity, each set of toxicity data employed for TEF determination encompassed only data relating to a common toxic end point, a single aquatic test species, and a common method of testing and of statistical analysis. The TEF values were determined as a ratio of the chronic threshold values for the mono-to pentachloro-substituted phenolics to that for pentachlorophenol, where the threshold values were obtained from linear regression equations relating chronic toxicity to the number of chlorine substituents for a given chlorinated phenolic. Using this approach, the TEF values for monochloro-, dichloro-, trichloro-, tetrachloro-, and pentachloro-substituted phenolic compounds were determined to be 0.04, 0.1, 0.2, 0.5, and 1.0, respectively.

Toxicity of cobalt to freshwater indicator species as a function of water hardness

Although generally rare in natural aquatic systems, cobalt concentrations can be elevated through ore and coal mining operations and discharges of certain textile dyes. The U.S. Environmental Protection Agency does not have an ambient water quality criterion for cobalt due to a lack of toxicological data. The present study determined whether freshwater acute and chronic cobalt toxicity were dependent on dilution water hardness. We specifically examined the relative toxicity of cobalt at high water hardness (≥ 200 mg/l as CaCO 3) because cobalt often occurs in carbonate ores. Acute and chronic toxicity tests using both Ceriodaphnia dubia and Pimephales promelas were performed using four different synthetic waters: 50,200. 400, and 800 mg/l hardness as CaCO 3. Diluent hardness appeared to have no effect on measured cobalt concentrations. Dissolved cobalt in water samples during testing was similar to the corresponding total recoverable cobalt in this study suggesting that most of the cobalt was in a soluble and presumably bioavailable form. LC 50 values for P. promelas could not be calculated owing to their low sensitivity to high cobalt concentrations (≥ 5 mg/l) over a 48 h period. Regression analysis of P. promelas acute NOEC values and test water hardness indicated an R 2 = 0.94 suggesting a direct relationship between water hardness and acute toxicity to cobalt for this species. C. dubia acute tests indicated water hardness effects after 48 h of exposure and non-linear dose responses in hard water (≥ 200 mg/l). Regression analysis of C. dubia 24 h LC 50 values and test water hardness indicated an R 2 = 0.91. For both cases, a simple power function gave the best regression fit. C. dubia appeared to be more sensitive than P. promelas at hardness ≥ 200 mg/l but the reverse was true in soft water ( ≤ 50 mg/l). The 7 d P. promelas chronic NOEC increased from 1232 μg/l cobalt (50 mg/l hardness) to ≥ 3833 μg/ l (800 mg/l hardness). Effects were on fish survival and not growth. Regression analysis yielded an R 2 = 0.97 based on the fish survival NOECs and the natural log of hardness. C. dubia chronic tests were inconclusive due to poor survival and reproduction in the synthetic waters. Available data suggest that within 50–200 mg/l water hardness, cobalt acute toxicily is inversely related to water hardness. Tentative cobalt acute criteria, based on power functions, are 288 μg/l and 873 μg/l for soft and hard water, respectively. Available chronic toxicity data suggest that daphnids are more sensitive to cobalt than other genera. Chronic endpoints for both P. promelus and D. magna were similar in soft and hard water (≤ 400 mg/l hardness) suggesting that chronic toxicity is not hardness-dependent over this range. However, chronic cndpoints at 800 mg/l hardness were 3.1 and ≥ 12 times higher than endpoints observed under soft water conditions for P. promelas and C. dubia respectively suggesting that very hard waters may significantly reduce chronic toxicity potential of cobalt.

An environmental risk assessment for DTDMAC in The Netherlands

The environmental safety of the cationic surfactant, ditallow dimethyl ammonium chloride (DTDMAC), has been determined from usage rates and fate data from The Netherlands and standard, well accepted assessment techniques. An environmental concentration model was developed using DTDMAC tonnages for 1990, actual per capita waste flow, and measured removal rates in wastewater treatment plants. This model incorporated a state of the art dilution model, instream removal and background DTDMAC concentrations. Based on this model, the 90 th percentile river concentration of DTDMAC below wastewater treatment plant outfalls was estimated as 0.021 mg/L (i.e., 90% of Dutch surface waters receiving wastewater effluents have environmental concentrations less than 0.021 mg/L). This estimated concentration agrees well with the maximum measured DTDMAC concentrations in Dutch surface waters. Toxicity values for the risk assessment were derived from a study which used an environmentally relevant dosing system (i.e., effluent from an activated sludge treatment system) to measure commercial DTDMAC toxicity. Based on chronic toxicity data for Ceriodaphnia dubia and Selenastrum capricornutum from this study, a no effect level of 4.53 mg/L was determined for use in the risk assessment. Thus, the DTDMAC safety factor for aquatic organisms is 215 (4.53/0.021). It is concluded that DTDMAC poses a low risk to aquatic life based on testing of sensitive species and environmental concentrations predicted by state-of-the-art assessment methods.

Environmental concentrations and aquatic toxicity data on diflubenzuron (dimilin).

The insecticide diflubenzuron (DFB) is commonly used in various mid-Atlantic states for suppression of gypsy moths in hardwood forests. DFB is potentially toxic to nontarget biota because it can enter aquatic systems through aerial application or runoff after precipitation events. Based on this concern, the objectives of this study were to: (1) compile, review, and synthesize literature on the fate, persistence, and environmental concentrations of DFB in both freshwater and saltwater environments; (2) compile, review, and synthesize acute and chronic aquatic toxicity data on DFB effects on freshwater and saltwater organisms; (3) assess possible risk to aquatic biota associated with the use of this insecticide in one specific area (Maryland); and (4) recommend future research based on the data gaps identified from this study. DFB has low solubility in water and exists as a technical grade (TG) and wettable powder (WP) formulation. The toxicity of both formulations is similar at concentrations less than 10 micrograms/l. Organic matter is a major factor influencing the adsorption and degradation of DFB in freshwater, saltwater, and sediment. The half-life of this insecticide in freshwater is approximately 3 days at a pH of 10 and temperature of 36 degrees C. At lower pH conditions of 6 and at the same temperature, DFB is more persistent since half-life values of approximately 9 days have been reported. The half-life of DFB in soil is less than 14 days when the particle size was approximately 2 microns. The half-life is generally greater in cool, dry soil than in hot, wet soil. Aquatic vegetation acts as a sink for DFB by gradually adsorbing the chemical and releasing it over a period of time. Freshwater organisms demonstrated a wide range of sensitivity to DFB. Sensitivity was dependent on body composition (i.e., exo- vs. endoskeleton), trophic level, and life stage. During acute exposures, aquatic invertebrates were more than 25,000 times as sensitive to DFB than fishes. The most acutely sensitive species tested was the Amphipod, Hyallela azteca (96-h LC50 = 1.84 micrograms/l). A mature Plecopteran, Skwala sp., was the most resistant invertebrate species tested in acute tests (96-h LC50 greater than 100,000 micrograms/l). In chronic tests, DFB concentrations of 1 microgram/l or greater were reported to eliminate populations of various Plecopteran (stoneflies) and Ephemeropteran (mayflies) species after 1 month of exposure. A 30-day LC50 of 0.1 micrograms/l DFB was also reported for the Tricopteran, Clistorinia magnifica.(ABSTRACT TRUNCATED AT 400 WORDS)

Utilization of quantitative structure-activity relationships (QSARs) in risk assessment: Alkylphenols

Alkylphenols are a class of environmentally pervasive compounds, found both in natural (e.g., crude oils) and in anthropogenic (e.g., wood tar, coal gasification waste) materials. Despite the frequent environmental occurrence of these chemicals, there is a limited toxicity database on alkylphenols. We have therefore developed a “toxicity equivalence approach” for alkylphenols which is based on their ability to inhibit, in a specific manner, the enzyme cyclooxygenase. Enzymeinhibiting ability for individual alkylphenols can be estimated based on the quantitative structure-activity relationship developed by Dewhirst (1980) and is a function of the free hydroxyl group, electron-donating ring substituents, and hydrophobic aromatic ring substituents. We evaluated the toxicological significance of cyclooxygenase inhibition by comparison of the inhibitory capacity of alkylphenols with the inhibitory capacity of acetylsalicylic acid, or aspirin, a compound whose low-level effects are due to cyclooxygenase inhibition. Since nearly complete absorption for alkylphenols and aspirin is predicted, based on estimates of hydrophobicity and fraction of charged molecules at gastrointestinal pHs, risks from alkylphenols can be expressed directly in terms of “milligram aspirin equivalence,” without correction for absorption differences. We recommend this method for assessing risks of mixtures of alkylphenols, especially for those compounds with no chronic toxicity data.

Comparison of the critical concentration and critical volume hypotheses to model non-specific toxicity of individual compounds

The critical concentration and critical volume hypotheses for non-specific toxicity require the molar concentration (CC) and volume fraction (VF) of toxicant in target tissue to be constant. Thus these factors should be independent of the octanol-water partition coefficient ( K ow) for individual compounds. CC and VF values were calculated based on acute sub-lethal, acute and chronic lethal toxicity data, K ow and pure component molar volume (MV) data. When these values were plotted against log K ow, the slopes of the regression equations were significantly different to zero but were not significantly different from each other. The observed slight increase in CC and VF with increasing log K ow was attributed predominantly, to the use of K ow values which overestimate the target tissue-water partition coefficient ( K ttw. An additional error associated with the volume fraction calculations was the use of the molar volume instead of partial molar volume. VF and CC values were calculated correcting for both these factors and regressed against log K ow. The resulting for VF had a gradient not significantly different from zero, while that for CC was, thus indicating the superiority of the critical volume hypothesis in modelling non-specific toxicity of individual compounds.

Chronic and sublethal toxicities of surfactants to aquatic animals: A review and risk assessment

Surfactants are one of the major components (10–18%) of detergent and household cleaning products and are used in high volumes. Several are commonly found in natural waters and consequently, their impact on the environment has been, and continues to be, discussed in the U.S.A., Western Europe and Japan. The chronic and sublethal toxicities of commercially important surfactants to aquatic animal life have not been summarized in the available scientific literature. Based on the summary provided here scientific understanding of the chronic and sublethal toxicities of cationic surfactants is less than that for the other surfactant groups. Chronic toxicity of anionic and nonionic surfactants occurs at concentrations usually greater than 0.1 mg/l. Effects of these same surfactants on several behavioral and physiological parameters range from 0.002 to 40.0 mg/l. The available toxicity data base is largely comprised of laboratory-derived toxicity data for a few surfactants, predominantly LAS, and single freshwater planktonic species such as Daphnia magna and the fathead minnow and a benthic midge. Community effect levels have been reported only for linear alkylbenzene sulfonate (LAS) and effects on single freshwater and saltwater test species and on natural biotic communities are largely unknown for many commercially important surfactants. Based on a comparison of the reported chronic toxicity data and measured environmental levels in rivers, the aquatic safety of the anionic LAS is indicated, more so than for any other surfactant. Safety assessments for other major surfactants in saltwater and freshwater should be considered preliminary and limited until validated with corresponding exposure measurements and additional laboratory and field-derived chronic toxicity data for animal test species.

Interacting Effects of pH Acclimation, pH, and Heavy Metals on Acute and Chronic Toxicity to Ceriodaphnia dubia (Cladocera)

Understanding the factors that modify the sensitivity of the zooplankton Ceriodaphnia dubia to toxicants is important to the interpretation of chronic toxicity data generated for granting industrial permits. Early reports of high sensitivity of Ceriodaphnia to brief pH excursions led toxicologists to question the use of C. dubia as a test organism. Acute and chronic toxicity of pH and heavy metals, pH acclimation to acidic and alkaline conditions and the role of pH in modifying heavy metal (copper and zinc) toxicities were investigated. Ceriodaphnia dubia acclimated near neutral pH had acute (48-hr) lethal concentrations of 4.6 and 10.3 SU. Reproduction and mortality were not impaired between pH 6.14-8.99 regardless of pH acclimation history. Reproduction was significantly impaired beyond these extremes. Acute exposures to both heavy metals at pH 6, 8 and 9 and in water hardness of 180, 110 and 100 mg/L showed C dubia was consistently most sensitive in low pH and low hardness waters. Reproduction and mortality were not so affected by pH in chronic exposures. Similar concentrations of metals at all pH levels resulted in equivalent reductions in offspring per female. The results strongly suggest that effluent guidelines for pH at 6-9 are sound, and that toxicantmore » activity in chronic time frames is directed primarily by concentration and water hardness, not by pH. 34 refs., 2 figs., 8 tabs.« less

The toxicity of aluminum to aquatic species in the US

In August 1988 the US Environmental Protection Agency (EPA) published an ambient water quality criteria document for the protection of aquatic organisms from the toxic effects of aluminum. The EPA water quality criteria were developed utilizing procedures described in theGuidelines for Deriving Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their Uses, and after careful analysis of the latest toxicological information available to EPA on the adverse effects of aluminum on aquatic vertebrates, invertebrates and plants.The EPA criteria recommend that the four-day average concentration of aluminum not exceed 87 μg L(-1) more than once every three years on the average when the ambient pH is between 6.5 and 9.0 to provide protection from chronic toxicity. The criteria also recommend that the one-hour average concentration of aluminum not exceed 750 μg L(-1) more than once every three years on the average when the ambient pH is between 6.5 and 9.0 to provide protection from acute toxicity.Acute toxicity data for 20 species of freshwater aquatic organisms and chronic toxicity data for five species of freshwater aquatic organisms were utilized to develop the EPA water quality criteria. Striped bass and brook trout were observed to be the two most sensitive North American species to the toxic effects of aluminum. Aluminum toxicity was also observed to be increased at lower pH.