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The objective of this study was to determine whether the water effect ratio (WER) or biotic ligand model (BLM) could be applied to efficiently develop water quality criteria (WQC) in Korea. Samples were collected from 12 specific sites along the Yeongsan River (YSR), Korea, including two sewage treatment plants and one estuary lake. A copper toxicity test using Daphnia magna was performed to determine the WER and to compare to the BLM prediction. The results of the WER from YSR samples also indicated significantly different copper toxicities in all sites. The model-based predictions showed that effluent and estuary waters had significantly different properties in regard to their ability to be used to investigate water characteristics and copper toxicity. It was supposed that the slight water characteristics changes, such as pH, DOC, hardness, conductivity, among others, influence copper toxicity, and these variable effects on copper toxicity interacted with the water composition. The 38% prediction was outside of the validation range by a factor of two in all sites, showing a poor predictive ability, especially in STPs and streams adjacent to the estuary, while the measured toxicity was more stable. The samples that ranged from pH 7.3–7.7 generated stable predictions, while other samples, including those with lower and the higher pH values, led to more unstable predictions. The results also showed that the toxicity of Cu in sample waters to D. magna was closely proportional to the amounts of acidity, including the carboxylic and phenolic groups, as well as the DOC concentrations. Consequently, the acceptable prediction of metal toxicity in various water samples needs the site-specific results considering the water characteristics such as pH and DOC properties particularly in STPs and estuary regions. [ABSTRACT FROM AUTHOR]

Natural and artificial heavy metal exposure to the environment requires finding thresholds to protect aquatic ecosystems from the toxicity of heavy metals. The threshold is commonly called a predicted no effect concentration (PNEC) and is thought to protect most organisms in an ecosystem from a chemical. PNEC is derived by applying a large assessment factor (AF) to the toxicity value of the most sensitive organism to a chemical or by developing a species sensitivity distribution (SSD), which is a cumulative distribution function with many toxicity data for a chemical of diverse organisms. This study developed SSDs and derived PNECs using toxicity data of organisms living in Korea for four heavy metals: copper (Cd), cadmium (Cu), lead (Pb), and zinc (Zn). Five distribution models were considered with log-transformed toxicity data, and their fitness and uncertainty were investigated. As a result, the normal distribution and Gumbel distribution fit the data well. In contrast, the Weibull distribution poorly accounted for the data at the lower tails for all of the heavy metals. The hazardous concentration for 5% of species (HC5) derived from the most suitable model for each heavy metal was calculated to be the preferred PNEC by AF 2 or AF 3. PNECs, obtained through a suitable SSD model with resident species and reasonable AF, will help protect freshwater organisms in Korea from heavy metals. [ABSTRACT FROM AUTHOR]

A high throughput toxicity biosensor has been designed and constructed using recombinant Escherichia coli cells, containing stress specific promoters (recA, fabA, or katG) or constitutive promoters (lac) fused to luciferase genes originating from Vibrio fisheri. These genetically engineered cells were immobilized in 96 well plates. By optimizing cell immobilization conditions and the strains’ response specificity to toxic chemicals, bioluminescent outputs decreased or increased dose-dependently upon adding test chemicals. However, to date the toxicity data obtained using this biosensor have not been compared with the results of other toxicity tests. Phenolics were chosen to evaluate the correlation between the LD50 and the EC50 (GC2) or EC120 (DPD2540) of Daphnia magna and E. coli, respectively. Toxicity data obtained from constitutive strains by bioluminescent level decrements were compared with the results from D. magna as a standard. LD50 values were used as parameters of D. magna toxicity and EC50 of EC120 values were used for the immobilized biosensor. In the DPD2540 test, phenolics, membrane damaging toxic chemicals, for testing immobilized stress specific bacterial strains trigger dose-dependant bioluminescence increase within specific concentration. Although the stress specific responsiveness from the strains could not be compared with D. magna''s LD50 values, these responses offer additional information, such as upon the mode of toxic action in the sample, in addition to the cellular toxicity results as indicated by the EC50. This novel high throughput toxicity biosensor can be implemented to investigate the toxicity of any other soluble materials, and can be used as a standardization tool for the evaluation of toxicity. [Copyright &y& Elsevier]

Per- and polyfluoroalkyl substances (PFAS) are gaining worldwide attention because of their toxicity, bioaccumulative and resistance to biological degradation in the environment. PFAS can be categorised into endocrine disrupting chemicals (EDCs) and identified as possible carcinogenic agents for the aquatic ecosystem and humans. Despite this, only a few studies have been conducted on the aquatic toxicity of PFAS, particularly in invertebrate species such as zooplankton. This study evaluated the acute toxicity of two main PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), by using freshwater cladocerans (Moina micrura) as bioindicators. This study aimed to assess the adverse effects at different levels of organisations such as organ (heart size and heart rate), individual (individual size and mortality) and population (lethal concentration, LC 50). PFOA was shown to be more hazardous than PFOS, with the LC 50 values (confidence interval) of 474.7 (350.4–644.5) μg L−1 and 549.6 (407.2–743.9) μg L−1, respectively. As the concentrations of PFOS and PFOA increased, there were declines in individual size and heart rate as compared to the control group. The values of PNECs acquired by using the AF method (PNEC AF) for PFOA and PFOS were 0.4747 and 0.5496 μg L−1, respectively. Meanwhile, the PNEC values obtained using the SSD method (PNEC SSD) were 1077.0 μg L−1 (PFOA) and 172.5 μg L−1 (PFOS). PNEC AF is more protective and conservative compared to PNEC SSD. The findings of this study have significant implications for PFOS and PFOA risk assessment in aquatic environments. Thus, it will aid freshwater sustainability and safeguard the human dependency on water resources. [Display omitted] • Toxicity and environmental risks of PFOA and PFOS on M. micrura were elucidated. • LC 50 , HC 5 and PNEC values of PFOA and PFOS to M. micrura were established. • PFOA LC 50 toxicity is more than PFOS. • Exposed M. micrura showed shorter lifespan, lower heart rate and smaller body size. [ABSTRACT FROM AUTHOR]

Abstract: The transmission and toxicity of metals and metalloids were initially investigated with various nanofiltration (NF) and seawater reverse osmosis (SWRO) membranes, under oxic condition, using wastewater effluent and seawater samples. Various metals and metalloids were categorized into three groups according to their properties, such as specific gravity and concentration level, as well as others. The levels of various transition metals and metalloids included in the wastewater effluent and seawater samples were within ng/L–μg/L range; the concentrations of almost all compounds were substantially reduced to ng/L or a few μg/L levels after membrane filtrations, as measured by ICP-MS. Toxicity measurements were performed using bioassays, including both the Microtox and daphnia methods, for raw and membrane treated samples of wastewater effluent and seawater. The results indicated that (1) the SWRO membrane exhibited very good removal efficiencies for all metals and metalloids tested, (2) most metals and metalloids tested were efficiently removed by the tight NF membranes employed; however, some metals and metalloids included in seawater were not efficiently removed by the relatively loose NF membrane, (3) based on the Microtox measurements, only the seawater sample treated using the relatively loose NF membrane provided a relatively high toxic unit close to 1.0; otherwise, all other samples (both raw and membrane treated samples) exhibited relatively low toxicities. [Copyright &y& Elsevier]

The sorption characteristics of 10 organic chemicals, categorized as pharmaceuticals, estrogens and phenols, onto synthetic suspended particle (i.e., alumina) coated with humic acid were investigated according to their octanol–water partition coefficient (K ow). Chemical analyses were performed with gas chromatography and mass spectrometry (GC/MS) and high performance liquid chromatography (HPLC). The effects of particles on the toxicity reduction were evaluated using bioassay tests, using Daphnia magna and Vibrio fisheri for phenols and pharmaceuticals, and the human breast cancer cell MCF-7 for estrogens. Sorption studies revealed that 22 and 38% of octylphenol and pentachlorophenol, respectively, were removed by suspended particle, whereas 2,4-dichlorophenol was not removed, which was directly proportional to the logK ow value. Similar to the sorption tests, suspended particles significantly reduced the acute toxicities of octylphenol and pentachlorophenol to D. magna and V. fisheri (p <0.01), but there was no significant difference in the toxicity of 2,4-dichlorophenol to D. magna (p =0.8374). Pharmaceuticals, such as ibuprofen, gemfibrozil and tolfenamic acid, showed no discernible sorption to the suspended particle, with the exception of diclofenac, which revealed 11% sorption. For estrogens, such as estrone, 17β-estradiol and 17α-ethynylestradiol, the results indicated no reduction in the sorption test. This may be attributed to the polar interaction by functional groups in sorption between pharmaceuticals and estrogens and suspended particles. In the bioassays, presence of suspended particles did not significantly modify the toxicity of pharmaceuticals (regardless of their K ow values) to D. magna, V. fisheri or E-screen. [Copyright &y& Elsevier]