The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish. Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48-h Daphnia magna median effective concentration (EC50) was 390 microg/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 microg/L, respectively. A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 microg/L and 71.3 microg/L, respectively, were determined with an early life-stage toxicity test with Oncorhynchus mykiss. During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 microg/L and the 96-h NOEC was 0.69 microg/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five-week test period was 4,157 at 3 microg/L and 2,532 at 30 microg/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS-containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment.
The aquatic toxicity of triclosan (TCS), a chlorinated biphenyl ether used as an antimicrobial in consumer products, was studied with activated-sludge microorganisms, algae, invertebrates, and fish. Triclosan, a compound used for inhibiting microbial growth, was not toxic to wastewater microorganisms at concentrations less than aqueous solubility. The 48-h Daphnia magna median effective concentration (EC50) was 390 microg/L and the 96-h median lethal concentration values for Pimephales promelas and Lepomis macrochirus were 260 and 370 microg/L, respectively. A no-observed-effect concentration (NOEC) and lowest-observed-effect concentration of 34.1 microg/L and 71.3 microg/L, respectively, were determined with an early life-stage toxicity test with Oncorhynchus mykiss. During a 96-h Scenedesmus study, the 96-h biomass EC50 was 1.4 microg/L and the 96-h NOEC was 0.69 microg/L. Other algae and Lemna also were investigated. Bioconcentration was assessed with Danio rerio. The average TCS accumulation factor over the five-week test period was 4,157 at 3 microg/L and 2,532 at 30 microg/L. Algae were determined to be the most susceptible organisms. Toxicity of a TCS-containing wastewater secondary effluent to P. promelas and Ceriodaphnia was evaluated and no observed differences in toxicity between control and TCS-treated laboratory units were detected. The neutral form of TCS was determined to be associated with toxic effects. Ionization and sorption will mitigate those effects in the aquatic compartment.
In previous work, the toxicity of several anionic and nonionic surfactants to rotifer (Brachionus calyciflorus) was shown to be highly correlated with interfacial activity. In this study, the relationship between interfacial properties of surfactants and their effects on aquatic organisms is extended to include the toxicity of the cationic surfactant class (homologues of alkyl trimethylammonium chloride and alkyl hydroxyethyl dimethylammonium chloride) to green algae (Selenastrum capricornutum) and the bioconcentration of linear alkylbenzene sulfonate (LAS) isomers and homologues by fish (Pimephales promelas and Ictalurus punctatus). In each case, the interfacial activity is expressed by the physicochemical parameter, delta G0ad/Amin, where delta G0ad is the standard free energy of adsorption of the surfactant at the air/solution interface and Amin is the minimum cross sectional area of the surfactant, or the analogous parameter, delta 1sG0ad/1sAmin, at the solid/liquid interface, where the solid is an immobilized artificial membrane (IAM) that mimics a biological cell membrane. The general nature of the relationship between interfacial activity of surfactants and their biological effects in aquatic systems indicates that sorption to biological membranes is a critical parameter for predicting and understanding environmental effects. While specific interactions probably occur once a surfactant has penetrated a membrane bilayer, nonspecific hydrophobic interactions appear to be driving the sorption process.
Species sensitivity distributions (SSD) require a large number of measured toxicity values to define a hazard level protective of multiple species. This investigation comprehensively evaluated the accuracy of SSDs generated from toxicity values predicted from interspecies correlation estimation (ICE) models. ICE models are log-log correlations of multiple chemical toxicity values for a pair of species that allow the toxicity of multiple species to be predicted from a single measured acute toxicity value for a surrogate species. ICE SSDs were generated using four surrogate species (fathead minnow, Pimephales promelas; rainbow trout, Oncorhynchus mykiss; sheepshead minnow, Cyprinodon varigatus; and water flea, Daphnia magna). ICE-based hazard concentrations (HC5s) from the 5th percentile of the log-logistic distribution of toxicity values were compared to HC5s determined from the acute toxicity of 55 chemicals from the United States Environmental Protection Agency Ambient Water Quality Criteria (AWQC). Measured fish and invertebrate acute toxicity data and HC5s from the AWQC data sets were compared to ICE-based HC5s. Surrogate species choice was found to be an important consideration in developing predictive HC5s. These results illustrated that fish predict fish betterthan invertebrates and D. magna predicted invertebrates better than most fish. For example, a mixed model of predicted fish and invertebrates from fathead minnow and D. magna as surrogate species provided predictive relationships with an average factor of 3.0 (+/- 6.7) over 7 orders of toxic magnitude and several chemical classes (HC5(predicted)/HC5(measured)). The application of ICE models is recommended as a valid approach for generating SSDs and hazard concentrations for chemicals with limited toxicity data.
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