Multilaboratory evaluation of 15 bioassays for (eco)toxicity screening and hazard ranking of engineered nanomaterials: FP7 project NANOVALID

Within EU FP7 project NANOVALID, the (eco)toxicity of 7 well-characterized engineered nanomaterials (NMs) was evaluated by 15 bioassays in 4 laboratories. The highest tested nominal concentration of NMs was 100?mg/l. The panel of the bioassays yielded the following toxicity order: Ag?>?ZnO?>?CuO?>?TiO_2?>_?MWCNTs?>?SiO_2?>_?Au. Ag, ZnO and CuO proved very toxic in the majority of assays, assumingly due to dissolution. The latter was supported by the parallel analysis of the toxicity of respective soluble metal salts. The most sensitive tests/species were Daphnia magna (towards Ag NMs, 24-h EC_50?=_?0.003?mg Ag/l), algae Raphidocelis subcapitata (ZnO and CuO, 72-h EC_50?=_?0.14?mg Zn/l and 0.7?mg Cu/l, respectively) and murine fibroblasts BALB/3T3 (CuO, 48-h EC_50?=_?0.7?mg Cu/l). MWCNTs showed toxicity only towards rat alveolar macrophages (EC_50?=_?15.3?mg/l) assumingly due to high aspect ratio and TiO₂ towards R. subcapitata (EC_50?=_?6.8?mg Ti/l) due to agglomeration of TiO₂ and entrapment of algal cells. Finally, we constructed a decision tree to select the bioassays for hazard ranking of NMs. For NM testing, we recommend a multitrophic suite of 4 in vitro (eco)toxicity assays: 48-h D. magna immobilization (OECD202), 72-h R. subcapitata growth inhibition (OECD201), 30-min Vibrio fischeri bioluminescence inhibition (ISO2010) and 48-h murine fibroblast BALB/3T3 neutral red uptake in vitro (OECD129) representing crustaceans, algae, bacteria and mammalian cells, respectively. Notably, our results showed that these assays, standardized for toxicity evaluation of “regular” chemicals, proved efficient also for shortlisting of hazardous NMs. Additional assays are recommended for immunotoxicity evaluation of high aspect ratio NMs (such as MWCNTs).     

The influence of humic acid on the toxicity of nano‐ZnO and Zn2+ to the Anabaena sp.

This study explored the effects of humic acid (HA) on the toxicity of ZnO nanoparticles (nano‐ZnO) and Zn²⁺ to Anabaena sp. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse‐amplitude modulated fluorometer. Results showed that nano‐ZnO and Zn²⁺ could inhibit Anabaena sp. growth with the EC₅₀ (concentration for 50% of maximal effect) of 0.74 ± 0.01 and 0.3 ± 0.01 mg/L, respectively. In the presence of 3.0 mg/L of HA, EC₅₀ of nano‐ZnO increased to 1.15 ± 0.04 mg/L and EC₅₀ of Zn²⁺ was still 0.3 ± 0.01 mg/L. Scanning electron microscopy observation revealed that HA prevented the adhesion of nano‐ZnO on the algae cells due to the increased electrostatic repulsion. The generation of intracellular reactive oxygen species and cellular lipid peroxidation were significantly limited by HA. Nano‐ZnO had more damage to the cell membrane than Zn²⁺ did, which could be proven by the malondialdehyde content in Anabaena sp. cells. © 2014 Wiley Periodicals, Inc. Environ Toxicol 30: 895–903, 2015.     

Toxicity of seven phthalate esters to embryonic development of the abalone Haliotis diversicolor supertexta

The toxicity of seven phthalate esters (PAEs), dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), butylbenzyl phthalate (BBP), di-n-hexyl phthalate (DnHP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DOP) to embryogenesis and larval development of the marine univalve Haliotis diversicolor supertexta was examined by means of two-stage embryo toxicity test. At the blastula stage, the normal embryonic development of H. diversicolor supertexta showed a good dose-response decrease when exposed to DMP, DEP, DBP, BBP, and DnHP. 9-h EC₅₀ values of DMP, DEP, DBP, BBP, and DnHP were 55.71, 39.13, 8.37, 2.65, and 3.32 mg/l, respectively. 9-h EC₅₀ values of DEHP and DOP were not available due to their low solubility. The toxicity order of seven tested PAEs was BBP>DnHP>DBP>DEP>DMP>DOP>DEHP. With the completion of metamorphosis as an experimental endpoint, the 96-h no-observed effect concentration values of DBP, DEHP and the other five tested PAEs were 0.022, 0.021, and 0.020 mg/l, respectively. Due to simple obtainment, convenient stimulation to spawn in the lab, greater sensitivity than mature species, and short culture time, the embryos of H. diversicolor supertexta have the potential to be utilized in acute toxicity test for at least PAEs.     

Acute and chronic toxicity of nano-scale TiO2 particles to freshwater fish,cladocerans, and green algae,and effects of organic and inorganic substrate on TiO2 toxicity

This research evaluated the toxicity of TiO₂ nanoparticles to freshwater aquatic organisms and the effects of organic and inorganic material on TiO₂ toxicity. The fathead minnow was much less acutely sensitive to TiO₂ (LC50 500 mg/l and higher) than Ceriodaphnia dubia and Daphnia pulex (mean LC50 values 7.6 and 9.2 mg/l, respectively). Total organic carbon levels of 1.5 mg/l decreased TiO₂ acute toxicity to C. dubia (LC50 > 100 mg/l), but kaolinite clay decreased TiO₂ toxicity to a lesser extent. In chronic toxicity tests, the green algae Pseudokirchneriella subcapitata was more sensitive to TiO₂ (IC25 1–2 mg/l) than C. dubia (IC25 9.4–26.4 mg/l) and the fathead minnow (IC25 values over 340 mg/l). Study results indicate that the specific organisms exposed and the effects of water quality parameters on TiO₂ toxicity should be considered in hazard evaluations of this nanoparticle.     

The chronic toxicity of ZnO nanoparticles and ZnCl2 to Daphnia magna and the use of different methods to assess nanoparticle aggregation and dissolution

In this study, the effect of ZnO nanoparticles and ZnCl₂ on growth, reproduction and accumulation of zinc in Daphnia magna was determined in a 21-day chronic toxicity test. A variety of techniques were used to distinguish the free zinc ion, dissolved, nanoparticle and aggregated zinc fraction in the Daphnia test medium. The results showed similar chronic effects on growth, reproduction and accumulation for the ZnO nanoparticles (EC₁₀, ₂₀, ₅₀ reproduction: 0.030, 0.049, 0.112 mg Zn/l) and the ZnCl₂ (EC₁₀, ₂₀, ₅₀ reproduction: 0.014, 0.027, 0.082 mg Zn/l). A large fraction of the nanoparticles rapidly dissolved after introduction in the exposure medium. Aggregation of nanoparticles was also observed but within 48 h of exposure most of these ZnO aggregates were dissolved. Based on the combined dissolution kinetics and toxicity results, it can be concluded that the toxicological effects of ZnO nanoparticles at the chronic level can be largely attributed to the dissolved fraction rather than the nanoparticles or initially formed aggregates.     

Acute toxicity of nonylphenols and bisphenol A to the embryonic development of the abalone <Emphasis Type="Italic">Haliotis diversicolor supertexta</Emphasis>

Acute toxic effects and mechanisms of two typical endocrine disrupting chemicals, nonylphenols (NPs) and bisphenol A (BPA), to the embryonic development of the abalone Haliotis diversicolor supertexta, were investigated by the two-stage embryo toxicity test. The 12-h median effective concentrations (EC₅₀) of NPs and BPA to the trochophore development were 1016.22 and 30.72 μg L⁻¹, respectively, and the respective 96-h EC₅₀ values based on the completion of metamorphosis (another experimental endpoint) were reduced to 11.65 and 1.02 μg L⁻¹. Longer exposure time and magnified exposure concentrations in the benthic diatom, that serves as both food source and settlement substrate during the metamorphosis, via bioaccumulation, led to the higher sensitivity of metamorphosis to target EDCs compared with the trochophore development. The hazard concentrations for 5% of the species (HC₅) could be employed as the safety thresholds for the embryonic development of the abalone. The 12-h HC₅ values of NPs and BPA were 318.68 and 13.93 μg L⁻¹, respectively, and the respective 96-h HC₅ values were 0.99 and 0.18 μg L⁻¹, which were at environmentally relevant levels. Results of proteomic responses revealed that NPs and BPA altered various functional proteins in the abalone larvae with slight differences between each chemical and affected various physiological functions, such as energy and substance metabolism, cell signalling, formation of cytoskeleton and cilium, immune and stress responses at the same time, leading to the failure of metamorphosis.     

Synergistic toxicity of zno nanoparticles and dimethoate in mice: Enhancing their biodistribution by synergistic binding of serum albumin and dimethoate to zno nanoparticles

The extensive applications of ZnO nanoparticles (nano ZnO) and dimethoate (DM) have increased the risk of humans' co‐exposure to nano ZnO and DM. Here, we report the synergistic effect of nano ZnO and DM on their biodistribution and subacute toxicity in mice. Nano ZnO and DM had a synergistic toxicity in mice. In contrast, bulk ZnO and DM did not cause an obvious synergistic toxicity in mice. Although nano ZnO was low toxic to mice, coexposure to nano ZnO and DM significantly enhanced DM‐induced oxidative damage in the liver. Coadministration of nano ZnO with DM significantly increased Zn accumulation by 30.9 ± 1.9% and DM accumulation by 45.6 ± 2.2% in the liver, respectively. The increased accumulations of DM and Zn in the liver reduced its cholinesterase activity from 5.65 ± 0.32 to 4.37 ± 0.49 U/mg protein and induced hepatic oxidative stress. Nano ZnO had 3‐fold or 2.4‐fold higher binding capability for serum albumin or DM, respectively, than bulk ZnO. In addition, serum albumin significantly increased the binding capability of nano ZnO for DM by approximately four times via the interaction of serum albumin and DM. The uptake of serum albumin‐ and DM‐bound nano ZnO by the macrophages significantly increased DM accumulation in mice. Serum albumins play an important role in the synergistic toxicity of nano ZnO and DM. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1202–1212, 2017.     

In vivo acute toxicity of titanium dioxide nanoparticles to mice after intraperitioneal injection

Because of its excellent optical performance and electrical properties, TiO₂ has a wide range of applications in many fields. It is often considered to be physiologically inert to humans. However, some recent studies have reported that nano‐sized TiO₂ may generate potential harm to the environment and humans. In this paper the in vivo acute toxicity of nano‐sized TiO₂ particles to adult mice was investigated. Mice were injected with different dosages of nano‐sized TiO₂ (0, 324, 648, 972, 1296, 1944 or 2592 mg kg^–1). The effects of particles on serum biochemical levels were evaluated at various time points (24 h, 48 h, 7 days and 14 days). Tissues (spleen, heart, lung, kidney and liver) were collected for titanium content analysis and histopathological examination. Treated mice showed signs of acute toxicity such as passive behavior, loss of appetite, tremor and lethargy. Slightly elevated levels of the enzymes alanine aminotransferase and aspartate aminotransferase were found from the biochemical tests of serum whereas blood urea nitrogen was not significantly affected (P <0.05). The accumulation of TiO₂ was highest in spleen (P <0.05). TiO₂ was also deposited in liver, kidney and lung. Histopathological examinations showed that some TiO₂ particles had entered the spleen and caused the lesion of spleen. Thrombosis was found in the pulmonary vascular system, which could be induced by the blocking of blood vessels with TiO₂ particles. Moreover, hepatocellular necrosis and apoptosis, hepatic fibrosis, renal glomerulus swelling and interstitial pneumonia associated with alveolar septal thickening were also observed in high‐dose groups. Copyright © 2009 John Wiley & Sons, Ltd.     

Ecotoxicological assessment of effluents in the Basque country (Northern Spain) by acute and chronic toxicity tests using Daphnia magna straus

Acute pass/fail, multi-concentration tests, and 3-brood chronic toxicity tests with Daphnia magna Straus (Cladocera, Crustacea) were used to characterise industrial and municipal effluents from various sources. The effluents that “passed” the pass/fail tests had 48-h EC₅₀ values >100% and reproduction No Observed Effect Concentration (NOECs) ≥100%, except for one effluent that had a reproduction NOEC of 31.6%. The acute multi-concentration toxicity tests allowed a rapid classification of effluents from Very Toxic (48-h EC₅₀<25%), to Non-Toxic (48-h EC₅₀ >100%). The acute-to-chronic ratio (ACR: 48-h EC₅₀ divided by the NOEC for reproduction) in the studied effluents ranged from 5 to about 100. From these results, we propose a step-wise protocol for assessing effluent toxicity. First, effluent is evaluated by means of simple and rapid pass/fail acute toxicity tests, to discriminate Non-Toxic from potentially Toxic effluents, thus facilitating the establishment of priority actions. Second, 48-h EC _x is estimated to classify effluents on a toxicity scale from Non-Toxic to Very Toxic. Third, chronic multi-concentration tests are used to calculate reproduction NOECs. These parameters combined with data on effluent chemical composition, chemical and hydrological characteristics of receiving waters, and biological quality criteria can be jointly used for more rational regulatory practices and risk assessment of effluents.     

Assessment of the potential toxicity of a linear alkylbenzene sulfonate (LAS) to freshwater animal life by means of cladoceran bioassays

The acute and chronic toxic effects of LAS on the cladocerans Daphnia similis, Ceriodaphnia dubia and Ceriodaphnia silvestrii were tested. Both types of toxicity bioassays and the methods of culture and stock maintenance of the test organisms conformed to the recommendations of ABNT (Brazilian Society of Technical Standards), which closely follow the standard methods of USEPA. The results obtained for EC₅₀ (48 h) were: 14.17 mg L⁻¹ for D. similis, 11.84 mg L⁻¹ for C. dubia and 13.52 mg L⁻¹ for C. silvestrii. In the chronic toxicity tests performed on C. dubia and C. silvestrii, there was a significant decrease in the fecundity of the exposed animals; the value of NOEC for C. dubia and C. silvestrii were 1.00 mg L⁻¹ and 2.50 mg L⁻¹, respectively. Cladoceran bioassays provided evidence that LAS concentration as low as 1.00 mg L⁻¹ can damage invertebrate animal life in freshwaters, concentrations that can be found in many eutrophic rivers and reservoirs.     

Chemical composition and toxicity of waste dump leachates using Selenastrum capricornutum Printz (Chlorococcales,Chlorophyta)

Chemical composition and toxicity of leachates from a municipal waste dump in Buenos Aires Province were analyzed. Three sets of samples, obtained in 1996 and 1997, were compared. Levels of nitrogen, phosphorus, and organics (expressed as COD) were distinctly lower in 1997. Such differences were mainly attributed to higher rainfall in that year. The Selenastrum capricornutum assay showed a high sensitivity to heavy metals (Cd=0.049 mg L⁻¹; Cr hexavalent=0.247 mg L⁻¹ and Zn=0.037 mg L⁻¹). Cu, Zn, and Pb concentrations were toxic to algae in leachate samples of the first year, while the EC₅₀ leachates were slightly toxic (86.6 and 99.31%). Most likely, high levels of organics (COD=4640 and 3470 mg L⁻¹) form complex mixtures with metals reducing their toxicity. The EC₅₀ leachate=48.5% in the last year may be explained by high concentrations of Pb and Cu. © 2000 John Wiley & Sons, Inc. Environ Toxicol 15: 76–80, 2000     

Interactions of CuO nanoparticles with the algae Chlorella pyrenoidosa: adhesion,uptake, and toxicity

The potential adverse effects of CuO nanoparticles (NPs) have increasingly attracted attention. Combining electron microscopic and toxicological investigations, we determined the adhesion, uptake, and toxicity of CuO NPs to eukaryotic alga Chlorella pyrenoidosa. CuO NPs were toxic to C. pyrenoidosa, with a 72?h EC₅₀ of 45.7?mg/L. Scanning electron microscopy showed that CuO NPs were attached onto the surface of the algal cells and interacted with extracellular polymeric substances (EPS) excreted by the organisms. Transmission electron microscopy (TEM) showed that EPS layer of algae was thickened by nearly 4-fold after CuO NPs exposure, suggesting a possible protective mechanism. In spite of the thickening of EPS layer, CuO NPs were still internalized by endocytosis and were stored in algal vacuoles. TEM and electron diffraction analysis confirmed that the internalized CuO NPs were transformed to Cu₂O NPs (d-spacing, ～0.213?nm) with an average size approximately 5?nm. The toxicity investigation demonstrated that severe membrane damage was observed after attachment of CuO NPs with algae. Reactive oxygen species generation and mitochondrial depolarization were also noted upon exposure to CuO NPs. This work provides useful information on understanding the role of NPs–algae physical interactions in nanotoxicity.     

Cyst-based toxicity tests. VII. Evaluation of the 1-h enzymatic inhibition test (fluotox) with Artemia nauplii

The newly developed 1-h enzymatic inhibition bioassay (Fluotox) was applied to toxicity testing with the larvae of the brine shrimp Artemia. The method consists of visual observation of in vivo inhibition of an enzymatic process using a fluorigenic enzyme substrate. The 1-h Fluotox test and the conventional 24- and 48-h LC₅₀ toxicity tests were conducted in parallel on 8 different organic and inorganic chemicals. A good correlation was found between the 1-h EC₅₀ and the 24- and 48-h LC₅₀ data with r² s of 0.94 and 0.93 for each respective regression. Addition of the enzyme substrate did not influence the toxicity of the chemicals in the 24- and 48-h tests. The repeatability of the Fluotox test compares favorably with that of the conventional 24-h acute test; coefficients of variation (CV) ranged from 8 to 34% and from 1 to 39%, respectively. Investigations on the applicability of the Fluotox procedure for testing in brackish waters revealed that lowering the salinity from 35 to 15 ppt did not affect the fluorescence and mortality responses in the controls. The same decrease in salinity had no significant influence on the 1-h EC₅₀s except for NaLS and acetic acid. The ratio between the 1-h EC₅₀s at 35 and 15 ppt varied from 0.46 to 2.18 depending on the chemical. However, the same decrease in salinity significantly influenced (p < 0.05) the 24-h LC₅₀s (except NaPCP) and the 48-h LC₅₀ (except formaldehyde). In general, the ratio of the LC₅₀ values obtained at 35 and 15 ppt varied from 0.30 to 2.21 and from 0.48 to 2.53 for the 24- and 48-h exposures, respectively. In view of several inherent advantages such as rapidity, experimental simplicity, low cost of performance, and the use of dry cysts as biological starting material (which eliminates the maintenance of live stock culture) the 1-h Artemia Fluotox test offers promising potential for numerous ecotoxicological applications. © by John Wiley & Sons, Inc.     

Cytotoxicity of dental composite (co)monomers and the amalgam component Hg2+ in human gingival fibroblasts

Unpolymerized resin (co)monomers or mercury (Hg) can be released from restorative dental materials (e.g. composites and amalgam). They can diffuse into the tooth pulp or the gingiva. They can also reach the gingiva and organs by the circulating blood after the uptake from swallowed saliva. The cytotoxicity of dental composite components hydroxyethylmethacrylate (HEMA), triethyleneglycoldimethacrylate (TEGDMA), urethanedimethacrylate (UDMA), and bisglycidylmethacrylate (Bis-GMA) as well as the amalgam component Hg²⁺ (as HgCl₂) and methyl mercury chloride (MeHgCl) was investigated on human gingival fibroblasts (HGFs) at two time intervals. To test the cytotoxicity of substances, the bromodeoxyuridine (BrdU) assay and the lactate dehydrogenase (LDH) assay were used. The test substances were added in various concentrations and cells were incubated for 24 or 48 h. The EC₅₀ values were obtained as half-maximum-effect concentrations from fitted curves. Following EC₅₀ values were found [BrdU: mean (mmol/l); SEM in parentheses; n=12]: (24 h/48 h) HEMA 8.860 (0.440)/6.600(0.630), TEGDMA 1.810(0.130)/1.220(0.130), UDMA 0.120(0.010)/0.140(0.010), BisGMA 0.060(0.004)/0.040(0.002), HgCl₂ 0.015(0.001)/0.050(0.006), and MeHgCl 0.004(0.001)/0.005(0.001). Following EC₅₀ values were found [LDH: mean (mmol/l); SEM in parentheses; n=12]: (24 h/48 h) HEMA 9.490(0.300)/7.890(1.230), TEGDMA 2.300(0.470)/1.950(0.310), UDMA 0.200(0.007)/0.100(0.007), BisGMA 0.070(0.005)/0.100(0.002), and MeHgCl 0.014(0.006)/0.010(0.003). In both assays, the following range of increased toxicity was found for composite components (24 and 48 h): HEMA < TEGDMA < UDMA < BisGMA. In both assays, MeHgCl was the most toxic substance. In the BrdU assay, Hg²⁺ was about fourfold less toxic than MeHgCl but Hg²⁺ was about fourfold more toxic than BisGMA. In the BrdU test, a significantly (P<0.05) decreased toxicity was observed for Hg²⁺ at 48 h, compared to the 24 h Hg²⁺-exposure. A time depending decreased toxicity was observed only for Hg²⁺ which can then reach the toxic level of BisGMA.     

Influence of temperature and soil moisture on the toxic potential of clothianidin to collembolan Folsomia candida in a tropical field soil

Climate change can alter the toxic effects of pesticides on soil invertebrates. However, the nature and magnitude of the influence of climatic factors on clothianidin impacts in tropical soils are still unknown. The influence of increasing atmospheric temperature and the reduction in soil moisture on the toxicity and risk of clothianidin (seed dressing formulation Inside FS^®) were assessed through chronic toxicity tests with collembolans Folsomia candida in a tropical field soil (Entisol). The risk of clothianidin for collembolans was estimated using the Toxicity-Exposure Ratio (TER) approach. Organisms were exposed to increasing clothianidin concentrations at 20, 25 and 27?°C in combination with two soil moisture conditions (30 and 60% of the maximum water holding capacity—WHC). The effect of temperature and soil moisture content on clothianidin toxicity was verified through the number of F. candida juveniles generated after 28 days of exposure to the spiked soil. The toxicities estimated at 25?°C (EC₅₀__30%WHC?=?0.014?mg?kg^?1; EC_{50_60%WHC}?=?0.010?mg?kg^?1) and 27?°C (EC_{50_30%WHC}?=?0.006?mg?kg^?1; EC_{50_60%WHC}?=?0.007?mg?kg^?1) were 2.9–3.0-fold (25?°C) and 4.3–6.7-fold (27?°C) higher than those found at 20?°C (EC_{50_30%WHC}?=?0.040?mg?kg^?1; EC_{50_60%WHC}?=?0.030?mg?kg^?1), indicating that clothianidin toxicity increases with temperature. No clear influence of soil moisture content on clothianidin toxicity could be observed once the EC₅₀ values estimated at 30% and 60% WHC, within the same temperature, did not significantly differ. A significant risk was detected in all temperatures and soil moisture scenarios studied, and the TER values indicate that the risk can increase with increasing temperatures. Our results revealed that temperature could overlap with soil moisture in regulating clothianidin toxicity and reinforce the importance of including climatic factors in the prospective risk assessment of pesticides.

     

Toxicity of selenate and selenite to the potworm <Emphasis Type="Italic">Enchytraeus albidus</Emphasis> (Annelida: Enchytraeidae): a laboratory test

Little information is available about the toxicity of inorganic selenium forms in soil animals. Therefore, the effects of selenate and selenite on the mortality and reproduction of Enchytraeus albidus were examined in standard laboratory tests with chronic exposure. Total and available amount of selenate and selenite were tested in a calcareous loamy chernozem soil. The LC₅₀ of selenate was 5.69 (2.7–8.12) mg kg^-1 dry wt. for total Se and 4.74 (2.14–6.98) mg kg^-1 dry wt. for available Se. Selenite LC₅₀ was as high as 22.5 (19.6–25.7) mg kg^-1 dry wt. for total Se and 8.10 (6.8–9.6) mg kg^-1 dry wt. for available Se. The EC₅₀ of selenate was 0.41 (0.35–0.48) mg kg^-1 dry wt. for total Se and 0.28 (0.24–0.34) mg kg^-1 dry wt. for available Se. Selenite EC₅₀ was as high as 7.3 (6.2–8.5) mg kg^-1 dry wt. for total Se and 2.46 (2.05–2.91) mg kg^-1 dry wt. for available Se. The response in reproduction was more sensitive to Se toxicity than the response in mortality. Selenate proved to be more toxic than selenite. Available data show that E. albidus may function as a biological indicator for some inorganic selenium forms in the soil.     

Phytotoxicity and accumulation of copper oxide nanoparticles to the Cu-tolerant plant Elsholtzia splendens

The release of nanoparticles (NPs) to the environment poses an increasing potential threat to biological systems. This study investigated the phytotoxicity and accumulation of copper oxide (CuO) NPs to Elsholtzia splendens (a Cu-tolerant plant) under hydroponic conditions. The 50% effective concentration (EC₅₀) of CuO NPs to E. splendens was about 480 mg/L, implying the tolerance of E. splendens to CuO NPs. The Cu content in the shoots treated with 1000 mg/L CuO NPs was much higher than those exposed to the comparable 0.5 mg/L soluble Cu and CuO bulk particles. CuO NPs-like deposits were found in the root cells and leaf cells. Cu K-edge X-ray absorption near-edge structure analysis further revealed that the accumulated Cu species existed predominantly as CuO NPs in the plant tissues. All these results suggested that CuO NPs can be absorbed by the roots and translocated to the shoots in E. splendens.     

Transfer modelling and toxicity evaluation of the effluent from an installation of cleansing and uranium recovery using a battery of bioassays

On July 7, 2008, a leak of effluent from an Installation of Cleansing and Uranium Recovery (Tricastin, France) led to the spillage of uranium in a stream. The acute toxicity of the effluent was evaluated, and compared to the toxicity of uranium nitrate in bioassays using several organisms: Chlamydomonas reinhardtii, Daphnia magna, Chironomus riparius and Danio rerio. A sediment bioassay was also performed on C. riparius using water and sediment sampled along the river. Results showed that effluent EC₅₀ 72 h was 0.65 mg U/l for algae and LC₅₀ 48 h was 1.67 mg U/l for daphnia, while values obtained for uranium nitrate were higher. The LC₅₀ 96 h of effluent to C. riparius was 22.7 mg U/l, similar to value for uranium nitrate; the sediment collected was not toxic to C. riparius larvae. The LOEC of effluent and uranium nitrate on HT₅₀ of D. rerio were similar (0.03 mg U/l), but larvae were more sensitive to uranium nitrate than to effluent. Our results suggest that other substances contained in the effluent could potentially be toxic to wildlife in association with uranium. In parallel, the modelling of the transfers based on uranium measurements in the surface water was used to fill data gaps and assess the impact along the river. These results provided an estimate of exposure conditions that occurred along the river. This approach allowed us to see that the risk to ecosystem during this incident was certainly low and concerned a short period of time, but it could have existed at least for some species.     

Cytotoxicity of Au,ZnO and SiO2 NPs using in vitro assays with mussel hemocytes and gill cells: Relevance of size,shape and additives

Metal-bearing nanoparticles (NPs) possess unique physico-chemical characteristics that make them useful for an increasing number of industrial products and applications, but could also confer them a higher toxicity due to their higher reactivity compared to bulk forms of the same materials. There is a considerable interest in the use of in vitro techniques in environmentally relevant species, such as marine mussels, to evaluate NPs toxicity. In the present work, mussel hemocytes and gill cells were used to assess the potential toxic effects of Au, ZnO and SiO₂ NPs with different sizes and shapes in parallel with their respective ionic and bulk forms and additives used in the NPs preparations. Cytotoxicity (neutral red and MTT assays) was screened at a wide range of concentrations, and LC50 values were calculated. Uptake of fluorescently labeled SIO₂ NPs of 27?nm by hemocytes was also investigated. Au, ZnO and SiO₂ NPs were less toxic than the corresponding ionic forms but more toxic than the bulk forms. ZnO NPs were the most toxic NPs tested which could be related with their capacity to release free ions. SiO₂ NPs were not taken up by hemocytes and were not toxic to either hemocytes or gill cells. Size-dependent toxicity was found for Au NPs. Shape influenced the cytotoxicity of ZnO NPs. Finally, the presence of the additives Na-citrate and Ecodis P90 contributed to the toxicity of Au and ZnO NPs, respectively. As a general conclusion, solubility appears to play a key role in NPs toxicity to mussel cells.     

Effect of the test media and toxicity of LAS on the growth of <Emphasis Type="Italic">Isochrysis galbana</Emphasis>

In this paper, the toxicity of linear alkylbenzene sulfonate (LAS) was evaluated in the marine microalga Isochrysis galbana using data of growth inhibition toxicity tests at 96-h exposure time. Toxicity was examined in standard conditions and by means of the modification of two variables of the test media: (1) the dilution water and (2) the content of nutrients in the test medium. For this purpose, a total of 10 toxicity test were designed: five dilution waters, four natural marine waters and one synthetic seawater; each in two different nutritive conditions, saturated nutrient concentration (SC) by the addition of modified f/2 nutritive medium, and natural nutrient concentration (NC), i.e., without the addition of f/2. At threshold toxicity levels, the dilution waters used in the test and the nutrient concentrations did not affect the toxicity of LAS. At IC₅₀ concentrations, the toxicity of LAS is influenced by both variables: under SC conditions, the toxic effect of LAS diminishes, obtaining in all the tests IC₅₀ > 10 mg/L LAS. Under NC conditions, IC₅₀ concentrations ranging between 3.15 and 9.26 mg/L LAS have been obtained.