Comparative acute freshwater hazard assessment and preliminary PNEC development for eight fluorinated acids

Short-term 48, 72 and 96-h aquatic toxicity tests were conducted to evaluate the acute toxicity of eight fluorinated acids to the cladoceran, Daphnia magna, the green alga, Pseudokirchneriella subcapitata, and the rainbow trout, Oncorhynchus mykiss or the fathead minnow, Pimephales promelas. The eight fluorinated acids studied were tridecafluorohexyl ethanoic acid (6:2 FTCA), heptadecafluorooctyl ethanoic acid (8:2 FTCA), 2H-dodecafluoro-2-octenoic acid (6:2 FTUCA), 2H-hexadecafluoro-2-decenoic acid (8:2 FTUCA), 2H,2H,3H,3H-undecafluoro octanoic acid (5:3 acid), 2H,2H,3H,3H-pentadecafluoro decanoic acid (7:3 acid), n-perfluoropentanoic acid (PFPeA) and n-perfluorodecanoic acid (PFDA). The results of the acute toxicity tests conducted during this study suggest that the polyfluorinated acids, 8:2 FTCA, 8:2 FTUCA, 6:2 FTCA, 6:2 FTUCA, 7:3 acid and 5:3 acid, and the perfluorinated acids PFPeA and PFDA, are generally of low to medium concern based on evaluation of their acute freshwater toxicity (EC/LC50s typically between 1 and >100 mg L⁻¹) using the USEPA TSCA aquatic toxicity evaluation paradigm. For the polyfluorinated acids, aquatic toxicity generally decreased as the number of fluorinated carbons decreased and as the overall carbon chain length decreased from 12 to 8. Acute aquatic toxicity of the 5 and 10 carbon perfluorocarboxylic acids (EC/LC50s between 10.6 and >100 mg L⁻¹) was greater or similar to that of the 6-9 carbon perfluorocarboxylic acids (EC/LC50s > 96.5 mg L⁻¹). This study also provides the first report of the acute aquatic toxicity of the 5:3 acid (EC/LC50s of 22.5 to >103 mg L⁻¹) which demonstrated less aquatic toxicity than the 7:3 acid (EC/LC50s of 0.4-32 mg L⁻¹). The cladoceran, D. magna and the green alga, P. subcapitata had generally similar EC50 values for a given substance while fish were typically equally or less sensitive with the exception that PFPeA was most toxic to fish. Predicted no-effect concentrations (PNECs) were estimated using approaches consistent with REACH guidance and when compared with available environmental concentrations, these PNECs suggest that the fluorinated acids tested pose little risk for aquatic organisms.     

Derivation of predicted no effect concentrations (PNEC) for 2,4,6-trichlorophenol based on Chinese resident species

2,4,6-Trichlorophenol (2,4,6-TCP) is a common chemical intermediate and a by-product of water chlorination and combustion processes, and is a priority pollutant of the aquatic environment in many countries. Although information on the toxicity of 2,4,6-TCP is available, there is a lack of information on the predicted no-effect concentration (PNEC) of 2,4,6-TCP, mainly due to the shortage of chronic and site-specific toxicity data. In the present study, acute and sub-chronic toxicity of 2,4,6-TCP on six different resident Chinese aquatic species were determined. PNEC values were calculated and compared by use of two approaches: assessment factor (AF) and species sensitivity distribution (SSD). Values for acute toxicity ranged from 1.1 mg L⁻¹ (Plagiognathops microlepis) to 42 mg L⁻¹ (Corbicula fluminea) and the sub-chronic no observed effect concentrations (NOECs) ranged from 0.05 mg L⁻¹ (Mylopharyngodon piceus) to 2.0 mg L⁻¹ (C. fluminea). PNECs obtained by the assessment factor approach with acute (AF = 1000, 0.001 mg L⁻¹) or chronic (AF = 10, 0.005 mg L⁻¹) toxicity data were one order of magnitude less than those from SSD methods (0.057 mg L⁻¹). PNEC values calculated using SSD methods with a 50% certainty for 2,4,6-TCP was less than those obtained by use of the USEPA recommend final chronic value (FCV) method (0.097 mg L⁻¹) and the one obtained by use of the USEPA recommend acute-to-chronic (ACR) methods (0.073 mg L⁻¹). PNECs derived using AF methods were more protective and conservative than that derived using SSD methods.     

The impact of an industrial effluent on the water quality,submersed macrophytes and benthic macroinvertebrates in a dammed river of Central Spain

This research was conducted in the middle Duratón River (Central Spain), in the vicinity of Burgomillodo Reservoir. An industrial effluent enters the river 300 m downstream from the dam. Fluoride and turbidity levels significantly increased downstream from the effluent, these levels being to some extent affected by differential water releases from the dam. The community of submersed macrophytes exhibited slighter responses and, accordingly, lower discriminatory power than the community of benthic macroinvertebrates, this indicating that metrics and indices based on macroinvertebrates may be more suitable for the biological monitoring of water pollution and habitat degradation in dammed rivers receiving industrial effluents. However, in relation to fluoride bioaccumulation at the organism level, macrophytes (Fontinalis antipyretica and Potamogeton pectinatus) were as suitable bioindicators of fluoride pollution as macroinvertebrates (Ancylus fluviatilis and Pacifastacus leniusculus). Fluoride bioaccumulation in both hard and soft tissues of these aquatic organisms could be used as suitable bioindicator of fluoride pollution (even lower than 1 mg F⁻ L⁻¹) in freshwater ecosystems. Echinogammarus calvus exhibited a great sensitivity to the toxicity of fluoride ions, with a 96 h LC₅₀ of 7.5 mg F⁻ L⁻¹ and an estimated safe concentration of 0.56 mg F⁻ L⁻¹. The great capacity of E. calvus to take up and retain fluoride during exposures to fluoride ions would be a major cause of its great sensitivity to fluoride toxicity. It is concluded that the observed fluoride pollution might be partly responsible for the absence of this native amphipod downstream from the industrial effluent.     

Toxicity and metabolism of copper pyrithione and its degradation product, 2,2'-dipyridyldisulfide in a marine polychaete

We conducted acute toxicity tests and sediment toxicity tests for copper pyrithione (CuPT) and a metal pyrithione degradation product, 2,2′-dipyridyldisulfide [(PS)₂], using a marine polychaete Perinereis nuntia. The acute toxicity tests yielded 14-d LC₅₀ concentrations for CuPT and (PS)₂ of 0.06 mg L⁻¹ and 7.9 mg L⁻¹, respectively. Sediment toxicity tests resulted in 14-d LC₅₀ concentrations for CuPT and (PS)₂ of 1.1 mg kg⁻¹ dry wt. and 14 mg kg⁻¹ dry wt., respectively. In addition to mortality, sediment avoidance behavior and decreases in animal growth rate were observed; growth rate was the most susceptible endpoint in the sediment toxicity tests of both toxicants. Thus, we propose lowest observed effect concentrations of 0.3 mg kg⁻¹ dry wt. and 0.2 mg kg⁻¹ dry wt. for CuPT and (PS)₂, respectively, and no observed effect concentrations of 0.1 mg kg⁻¹ dry wt. for both CuPT and (PS)₂. The difference in the toxicity values between CuPT and (PS)₂ observed in the acute toxicity test was greater than the difference in these values in the sediment toxicity test, and we attribute this to (PS)₂ being more hydrophilic than CuPT. In addition to the toxicity tests, we analyzed conjugation activity of several polychaete enzymes to the toxicants and marked activity of palmitoyl coenzyme-A:biocides acyltransferase and UDP-glucuronosyl transferase was observed.     

Toxicity of nanoparticulate and bulk ZnO, Al2O3 and TiO2 to the nematode Caenorhabditis elegans

Limited information is available on the environmental behavior and associated potential risk of manufactured oxide nanoparticles (NPs). In this research, toxicity of nanoparticulate and bulk ZnO, Al₂O₃ and TiO₂ were examined to the nematode Caenorhabditis elegans with Escherichia coli as a food source. Parallel experiments with dissolved metal ions from NPs were also conducted. The 24-h median lethal concentration (LC₅₀) and sublethal endpoints were assessed. Both NPs and their bulk counterparts were toxic, inhibiting growth and especially the reproductive capability of the nematode. The 24-h LC₅₀ for ZnO NPs (2.3 mg L⁻¹) and bulk ZnO was not significantly different, but significantly different between Al₂O₃ NPs (82 mg L⁻¹) and bulk Al₂O₃ (153 mg L⁻¹), and between TiO₂ NPs (80 mg L⁻¹) and bulk TiO₂ (136 mg L⁻¹). Oxide solubility influenced the toxicity of ZnO and Al₂O₃ NPs, but nanoparticle-dependent toxicity was indeed observed for the investigated NPs.     

Lethal effects of abamectin on the aquatic organisms Daphnia similis, Chironomus xanthus and Danio rerio

Abamectin is used as an acaricide and insecticide for fruits, vegetables and ornamental plants, as well as a parasiticide for animals. One of the major problems of applying pesticides to crops is the likelihood of contaminating aquatic ecosystems by drift or runoff. Therefore, toxicity tests in the laboratory are important tools to predict the effects of chemical substances in aquatic ecosystems. The aim of this study was to assess the potential hazards of abamectin to the freshwater biota and consequently the possible losses of ecological services in contaminated water bodies. For this purpose, we identified the toxicity of abamectin on daphnids, insects and fish. Abamectin was highly toxic, with an EC₅₀ 48 h for Daphnia similis of 5.1 ng L⁻¹, LC₅₀ 96 h for Chironomus xanthus of 2.67 μg L⁻¹ and LC₅₀ 48 h for Danio rerio of 33 μg L⁻¹.     

Distribution of Se and its species in Myriophyllum spicatum and Ceratophyllum demersum growing in water containing Se (VI)

The uptake of Se (VI) by two aquatic plants, Myriophyllum spicatum L. and Ceratophyllum demersum L., and its effects on their physiological characteristics have been studied. Plants were cultivated outdoors under semi-controlled conditions and in two concentrations of Na selenate solution (20 μg Se L⁻¹ and 10 mg Se L⁻¹). The higher dose of Se reduced the photochemical efficiency of PSII in both species, while the lower dose had no effect on PSII. Addition of Se had no effect on the amounts of chlorophyll a and b. The concentration of Se in plants grown in 10 mg Se L⁻¹, averaged 212 ± 12 μg Se g⁻¹ DM in M. spicatum (grown from 8-13 d), and 492 ± 85 μg Se g⁻¹ DM in C. demersum (grown for 31 d). Both species could take up a large amount of Se. The amount of soluble Se compounds in enzyme extracts ranged from 16% to 26% in control, and in high Se solution from 48% to 36% in M. spicatum and C. demersum, respectively. Se-species were determined using HPLC-ICP-MS. The main soluble species in both plants was selenate (∼37%), while SeMet and SeMeSeCys were detected at trace levels.     

Toxicity assessment of a common laundry detergent using the freshwater flagellate Euglena gracilis

Synthetic detergents are among the commonly used chemicals in everyday life. Detergents, reaching aquatic environments through domestic and municipal wastewater, can cause many different effects in aquatic organisms. The present study was aimed at the toxicity evaluation of a commonly used laundry detergent, Ariel, using the freshwater flagellate Euglena gracilis as a biotest organism. Different parameters of the flagellate like motility, swimming velocity, cell shape, gravitactic orientation, photosynthesis and concentration of light harvesting pigments were used as end points for the toxicity assessment. No Observed Effect Concentration (NOEC) and EC₅₀ values were calculated for the end point parameters at four different incubation times, i.e. 0, 6, 24 and 72 h. After 72 h incubation, swimming velocity of the cells was found to be the most sensitive parameter giving NOEC and EC₅₀ values of 10.8 and 34 mg L⁻¹, respectively. After 72 h exposure to the detergent, chlorophyll a and total carotenoids were significantly decreased in cultures treated with Ariel at concentrations of 50 mg L⁻¹ and above while chlorophyll b significantly decreased at concentrations above 750 mg L⁻¹. The maximum inhibitory effect on the quantum yield of photosystem II was observed after 24 h exposure and thereafter a recovery trend was observed. Motility, gravitaxis and cell shape were strongly impaired immediately upon exposure to the detergent, but with increasing exposure time these parameters showed acclimatization to the stress and thus the NOEC values obtained after 72 h were higher than those immediately after exposure.     

Acute effects of Fe₂O₃, TiO₂, ZnO and CuO nanomaterials on Xenopus laevis

Metal oxide nanomaterials have exhibited toxicity to a variety of aquatic organisms, especially microbes and invertebrates. To date, few studies have evaluated the toxicity of metal oxide nanomaterials on aquatic vertebrates. Therefore, this study examined effects of ZnO, TiO₂, Fe₂O₃, and CuO nanomaterials (20-100 nm) on amphibians utilizing the Frog Embryo Teratogenesis Assay Xenopus (FETAX) protocol, a 96 h exposure with daily solution exchanges. Nanomaterials were dispersed in reconstituted moderately hard test medium. These exposures did not increase mortality in static renewal exposures containing up to 1000 mg L⁻¹ for TiO₂, Fe₂O₃, CuO, and ZnO, but did induce developmental abnormalities. Gastrointestinal, spinal, and other abnormalities were observed in CuO and ZnO nanomaterial exposures at concentrations as low as 3.16 mg L⁻¹ (ZnO). An EC₅₀ of 10.3 mg L⁻¹ ZnO was observed for total malformations. The minimum concentration to inhibit growth of tadpoles exposed to CuO or ZnO nanomaterials was 10 mg L⁻¹. The results indicate that select nanomaterials can negatively affect amphibians during development. Evaluation of nanomaterial exposure on vertebrate organisms are imperative to responsible production and introduction of nanomaterials in everyday products to ensure human and environmental safety.     

Derivation of aquatic predicted no-effect concentration (PNEC) for 2,4-dichlorophenol: comparing native species data with non-native species data

2,4-Dichlorophenol (2,4-DCP) is known as an important chemical intermediate and an environmental endocrine disruptor. There is no paper dealing with the predicted no-effect concentration (PNEC) of 2,4-DCP, mainly due to shortage of chronic and site-specific toxicity data. In the present study, toxicity data was obtained from the tests using six Chinese native aquatic species. The HC₅ (hazardous concentration for 5% of species) was derived based on the constructed species sensitivity distribution (SSD), which was compared with that derived from literature toxicity data of non-native species. For invertebrates, the survival no-observed effect concentrations (NOECs) were 0.05 and 1.00 mg L⁻¹ for Macrobrachium superbum and Corbicula fluminea, respectively. NOECs based on fishes’ growth were 0.10, 0.20 and 0.40 mg L⁻¹ for Mylopharyngodon piceus, Plagiognathops microlepis and Erythroculter ilishaeformis, respectively. For aquatic plant Soirodela polyrhiza, NOEC based on concentration of chlorophyll was 1.00 mg L⁻¹. A final PNEC calculated using the SSD approach with a 50% certainty based on different taxa ranged between 0.008 and 0.045 mg L⁻¹. There is no significant difference between HC₅ derived from native and that from non-native taxa.     

Nano-TiO2 enhances the toxicity of copper in natural water to Daphnia magna

The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO₂ remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2 mg L⁻¹ nano-TiO₂, the (LC₅₀) of Cu²⁺ concentration observed to kill half the population, decreased from 111 μg L⁻¹ to 42 μg L⁻¹. Correspondingly, the level of metallothionein decreased from 135 μg g⁻¹ wet weight to 99 μg g⁻¹ wet weight at a Cu²⁺ level of 100 μg L⁻¹. The copper was found to be adsorbed onto the nano-TiO₂, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO₂ may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins.     

Comparative study of the accumulation and detoxification of Cu (essential metal) and Hg (nonessential metal) in the digestive gland and gills of mussels Mytilus galloprovincialis, using analytical and histochemical techniques

The aim of the present study is the comparative examination of accumulation and detoxification of Cu and Hg in digestive gland and gills of mussels Mytilus galloprovincialis, using atomic absorption spectrophotometry and autometallography. Mussels were exposed to 0.08 mg L⁻¹ Cu, 0.08 mg L⁻¹ Hg, as well as to a mixture of 0.08 mg L⁻¹ Hg and 0.08 mg L⁻¹ Cu for 11 d. After the experimental exposure, animals were kept under laboratory conditions for a detoxification period of 7 d. An antagonistic effect of Cu against to Hg accumulation was noted in the digestive gland of mussels after the experimental exposure, as well as after the detoxification period, supporting the protective role of Cu against to Hg toxicity in this tissue. Digestive gland was suggested as a main organ for Hg accumulation and gills as a target position for Cu accumulation. Additionally, lower time was evaluated for Hg detoxification in the digestive gland and gills of mussels, in relation to those addressed for Cu detoxification in the same tissues. The evaluation of black silver deposits (BSD) extent performed in digestive gland and gills was suggested as a less sensitive approach, in relation to atomic absorption spectrophotometry (AAS), to indentify the concentration of heavy metals in tissues of mussels. The toxic effects of Hg, Cu and a mixture of them on lysosomal system of the digestive cells are also discussed.     

Influence of Suwannee River humic acid on particle properties and toxicity of silver nanoparticles

Adsorption of natural organic matter (NOM) on nanoparticles can have dramatic impacts on particle dispersion resulting in altered fate and transport as well as bioavailability and toxicity. In this study, the adsorption of Suwannee River humic acid (SRHA) on silver nanoparticles (nano-Ag) was determined and showed a Langmuir adsorption at pH 7 with an adsorption maximum of 28.6 mg g⁻¹ nano-Ag. It was also revealed that addition of <10 mg L⁻¹ total organic carbon (TOC) increased the total Ag content suspended in the aquatic system, likely due to increased dispersion. Total silver content decreased with concentrations of NOM greater than 10 mg TOC L⁻¹ indicating an increase in nanoparticle agglomeration and settling above this concentration. However, SRHA did not have any significant effect on the equilibrium concentration of ionic Ag dissolved in solution. Exposure of Daphnia to nano-Ag particles (50 μg L⁻¹ and pH 7) produced a linear decrease in toxicity with increasing NOM. These results clearly indicate the importance of water chemistry on the fate and toxicity of nanoparticulates.     

Determination of hypoxia and dietary copper mediated sub-lethal toxicity in carp, Cyprinus carpio, at different levels of biological organisation

Hypoxic events frequently occur in the aquatic environment in association with micro pollutants, including heavy metals. Only a few studies are however available on the uptake and biological responses of heavy metals under hypoxic conditions. To elucidate the phenomenon, mirror carp Cyprinus carpio L. (16.13-16.22 g) were exposed chronically to dietary copper (Cu; 250 and 500 mg kg dry wt.⁻¹) for 30 d under normoxic (8.25 mg O₂ L⁻¹) and hypoxic (∼3 mg O₂ L⁻¹) conditions and adopting an integrated approach, sub-lethal biomarker responses were determined at different levels of biological organisation. Level of oxidative DNA damage (as determined by modified Comet assay) showed strong significant difference following exposure to dietary Cu level under normoxic (1.6-fold) as well as under hypoxic condition at both Cu levels (2.1 and 2.5-folds respectively). Significant difference was also observed for haematological parameters (i.e. increased red and white blood cells, haematocrit value and haemoglobin concentration). Quantitative histology revealed alterations in tissues (i.e. liver and gills) for hypoxic and all dietary Cu treatment groups under both normoxic and hypoxic conditions suggesting a compensatory response to these organs (p < 0.05). The order of Cu accumulation in tissues (as determined by ICP-OES) was liver > intestine > kidney > gill. Interestingly, SGR under both normoxic and hypoxic conditions reduced with elevating Cu levels (p = 0.019). Overall, the results provide evidence for enhanced toxicological responses in fish following exposure to Cu either alone or in combination with hypoxic condition and lends support to the evolving viewpoint that many water quality guidelines should be revisited in terms of new ecotoxicological criteria.     

Effects of the pharmaceuticals gemfibrozil and diclofenac on biomarker expression in the zebra mussel (Dreissena polymorpha) and their comparison with standardised toxicity tests

Pharmaceuticals, including the lipid regulator gemfibrozil and the non-steroidal anti-inflammatory drug diclofenac have been identified in waste water treatment plant effluents and receiving waters throughout the western world. The acute and chronic toxicity of these compounds was assessed for three freshwater species (Daphnia magna,Pseudokirchneriella subcapitata, Lemna minor) using standardised toxicity tests with toxicity found in the non-environmentally relevant mid mg L⁻¹ concentration range. For the acute endpoints (IC₅₀ and EC₅₀) gemfibrozil showed higher toxicity ranging from 29 to 59 mg L⁻¹ (diclofenac 47-67 mg L⁻¹), while diclofenac was more toxic for the chronic D. magna 21 d endpoints ranging from 10 to 56 mg L⁻¹ (gemfibrozil 32-100 mg L⁻¹). These results were compared with the expression of several biomarkers in the zebra mussel (Dreissena polymorpha) 24 and 96 h after exposure by injection to concentrations of 21 and 21,000 μg L⁻¹ corresponding to nominal concentrations of 1 and 1000 μg L⁻¹. Exposure to gemfibrozil and diclofenac at both concentrations significantly increased the level of lipid peroxidation, a biomarker of damage. At the elevated nominal concentration of 1000 μg L⁻¹ the biomarkers of defence glutathione transferase and metallothionein were significantly elevated for gemfibrozil and diclofenac respectively, as was DNA damage after 96 h exposure to gemfibrozil. No evidence of endocrine disruption was observed using the alkali-labile phosphate technique. Results from this suite of biomarkers indicate these compounds can cause significant stress at environmentally relevant concentrations acting primarily through oxidation pathways with significant destabilization of the lysosomal membrane and that biomarker expression is a more sensitive endpoint than standardised toxicity tests.     

The toxicity of phthalocyanines to the aquatic plant Lemna minor (duckweed) - testing of 31 compounds

Phthalocyanines are prospective chemicals that have applications in industry, medicine and biology due especially to their architectural flexibility and production of reactive oxygen species. Although they are used in so many areas of human activities nowadays, there is still little knowledge of their ecotoxicity. Here we present the first observation of their toxic effects on representatives of the aquatic plants Lemna minor. The tested phthalocyanines possess a wide spectrum of phytotoxicity ranging from seldom (>50 mg L⁻¹) to highly toxic 0.11 mg L⁻¹. Moreover, the potential of phthalocyanines to be used as selective cyanocides or herbicides is discussed as well.     

Ecotoxicity evaluation of selected sulfonamides

Sulfonamides (SAs) are a group of antibiotic drugs widely used in veterinary medicine. The contamination of the environment by these pharmaceuticals has raised concern in recent years. However, knowledge of their (eco)toxicity is still very basic and is restricted to just a few of these substances. Even though their toxicological analysis has been thoroughly performed and ecotoxicological data are available in the literature, a systematic analysis of their ecotoxicological potential has yet to be carried out. To fill this gap, 12 different SAs were chosen for detailed analysis with the focus on different bacteria as well as non-target organisms (algae and plants). A flexible (eco)toxicological test battery was used, including enzymes (acetylcholinesterase and glutathione reductase), luminescent marine bacteria (Vibrio fischeri), soil bacteria (Arthrobacter globiformis), limnic unicellular green algae (Scenedesmus vacuolatus) and duckweed (Lemna minor), in order to take into account both the aquatic and terrestrial compartments of the environment, as well as different trophic levels. It was found that SAs are not only toxic towards green algae (EC₅₀ = 1.54-32.25 mg L⁻¹) but have even stronger adverse effect on duckweed (EC₅₀ = 0.02-4.89 mg L⁻¹) than atrazine - herbicide (EC₅₀ = 2.59 mg L⁻¹).     

Root porosity and radial oxygen loss related to arsenic tolerance and uptake in wetland plants

The rates of radial oxygen loss (ROL), root porosity, concentrations of arsenic (As), iron (Fe) and manganese (Mn) in shoot and root tissues and on root surfaces, As tolerances, and their relationships in different wetland plants were investigated based on a hydroponic experiment (control, 0.8, 1.6 mg As L⁻¹) and a soil pot trail (control, 60 mg As kg⁻¹). The results revealed that wetland plants showed great differences in root porosity (9-64%), rates of ROL (55-1750 mmo1 O₂ kg⁻¹ root d.w. d⁻¹), As uptake (e.g., 8.8-151 mg kg⁻¹ in shoots in 0.8 mg As L⁻¹ treatment), translocation factor (2.1-47% in 0.8 mg As L⁻¹) and tolerance (29-106% in 0.8 mg As L⁻¹). Wetland plants with higher rates of ROL and root porosity tended to form more Fe/Mn plaque, possess higher As tolerance, higher concentrations of As on root surfaces and a lower As translocation factor so decreasing As toxicity.     

Toxic effects of chemical pesticides (trichlorfon and dimehypo) on Dunaliella salina

Dunaliella salina, a unicellular green alga of environmental tolerance, was employed as test organism to investigate the toxicity effects of trichlorfon and dimehypo widely used in agriculture and veterinary as pesticides. The influences of trichlorfon and dimehypo on cell growth, β-carotene level, cell morphology changes, and activities of superoxide dismutase (Sod) and catalase (Cat) were investigated. At the concentrations less than 0.050 g L⁻¹ trichlorfon or 0.0005 g L⁻¹ dimehypo, cell responses were similar to control. When treated with 0.075-0.100 g L⁻¹ trichlorfon or 0.001-0.004 g L⁻¹ dimehypo, cell growth and β-carotene levels declined at first and then revived. When concentrations were higher than 0.125 g L⁻¹ trichlorfon or 0.005 g L⁻¹ dimehypo, both cell growth and β-carotene levels decreased until they were undetectable. The 10-d IC50 of trichlorfon and dimehypo on D. salina were 0.179 g L⁻¹ and 0.032 g L⁻¹. Both pollutants could stimulate the increase of Cat activity at a low concentration. Tolerance of D. salina to trichlorfon was obviously higher than that of dimehypo.     

Effect of chronic exposure to acetaminophen and lincomycin on Japanese medaka (Oryzias latipes) and freshwater cladocerans Daphnia magna and Moina macrocopa, and potential mechanisms of endocrine disruption

Chronic toxicity of acetaminophen and lincomycin were evaluated using freshwater organisms including two crustaceans (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). H295R, a human adrenal cell was also used to understand the effects on steroidogenesis. In 21 d D. magna exposure, survival NOEC was found at 5.72 mg L⁻¹ and no reproduction related effects were noted at this level of exposure to acetaminophen, while 21 d survival or growth effects were not observed even at the highest exposure levels (153 mg L⁻¹) for lincomycin. In the chronic fish toxicity test, significant reduction in juvenile survival was observed at 30 d post-hatch (dph) at 95 mg L⁻¹ of acetaminophen, and 0.42 mg L⁻¹ of lincomycin. After the exposure to both pharmaceuticals, vitellogenin levels tended to increase in male fish at 90 dph. In the eggs which were prenatally exposed to 9.5 mg L⁻¹ of acetaminophen, reduced hatchability was observed. The results of H295R cell assay showed that both pharmaceuticals could alter steroidogenic pathway and increase estrogenicity. Endocrine disruption potentials and their ecological implication may deserve further studies. Our observations suggest however that ecological risks of both pharmaceuticals are negligible at the concentrations currently found in the environment.