Exposure to cerium dioxide nanoparticles differently affect swimming performance and survival in two daphnid species

The CeO2 NPs are increasingly used in industry but the environmental release of these NPs and their subsequent behavior and biological effects are currently unclear. This study evaluates for the first time the effects of CeO2 NPs on the survival and the swimming performance of two cladoceran species, Daphnia similis and Daphnia pulex after 1, 10 and 100 mg.L(-1) CeO2 exposures for 48 h. Acute toxicity bioassays were performed to determine EC50 of exposed daphnids. Video-recorded swimming behavior of both daphnids was used to measure swimming speeds after various exposures to aggregated CeO2 NPs. The acute ecotoxicity showed that D. similis is 350 times more sensitive to CeO2 NPs than D. pulex, showing 48-h EC50 of 0.26 mg.L(-1) and 91.79 mg.L(-1), respectively. Both species interacted with CeO2 NPs (adsorption), but much more strongly in the case of D. similis. Swimming velocities (SV) were differently and significantly affected by CeO2 NPs for both species. A 48-h exposure to 1 mg.L(-1) induced a decrease of 30% and 40% of the SV in D. pulex and D. similis, respectively. However at higher concentrations, the SV of D. similis was more impacted (60% off for 10 mg.L(-1) and 100 mg.L(-1)) than the one of D. pulex. These interspecific toxic effects of CeO2 NPs are explained by morphological variations such as the presence of reliefs on the cuticle and a longer distal spine in D. similis acting as traps for the CeO2 aggregates. In addition, D. similis has a mean SV double that of D. pulex and thus initially collides with twice more NPs aggregates. The ecotoxicological consequences on the behavior and physiology of a CeO2 NPs exposure in daphnids are discussed

Earthworm’s influence on phytoavailability and Human gastric bioaccessibility of metals

►Introduction : Le développement d’entreprises de recyclage des métaux comme la Société de Traitement Chimique des Métaux (STCM) participe à l’économie circulaire. Cependant, ces activités de recyclage ont durant plusieurs décennies également engendré des émissions de polluants dans l’environnement induisant une augmentation de sites pollués par les retombées atmosphériques de particules fines enrichies en métaux et métalloïdes. Par ailleurs, le ver de terre, organisme clé de l’écosystème sol, apparait comme un ingénieur physique et mécanique des sols, et fait désormais l’objet de nombreuses études environnementales. Pour cette étude, notre objectif était d’évaluer l’influence de la bioturbation des vers de terre sur la phytodisponibilité des métaux et les mécanismes en jeu en lien avec leur compartimentation, leur spéciation et leur écotoxicité. ►Mise en œuvre : Dans ce contexte, une expérience de 25 jours a été menée en microcosmes, avec ou sans vers de terre dans le sol et avec un gradient d’Eléments Traces Inorganiques (ETI) dû aux retombées des particules atmosphériques. L’influence de l’activité des vers de terre sur les transferts sol-plante des métaux a été étudiée au moyen de microcultures de laitues (dispositif RHIZOtests®) réalisées sur 3 conditions différentes de sols : sols non bioturbés (SNB), sols bioturbés (SB) et turricules (T, déjections des vers). Les concentrations en ETI dans les sols, les vers et les salades ont été mesurées et la bioaccessibilité gastrique humaine a été déterminée à partir du test in vitro BARGE. Par ailleurs, des analyses de spéciation chimique du plomb dans divers compartiments abiotiques (sols et turricules) et biotiques (divers organes du vers de terre) ont été réalisées par spectroscopie EXAFS au synchrotron de l’ESRF à Grenoble. ►Résultats & Discussions : L’activité des vers de terre n’est pas significativement impactée par les concentrations en ETI appliquées dans les sols. Mais, la bioturbation des vers augmente la concentration en ETI présents dans les feuilles de laitues (parties consommées par l’homme). La concentration en ETI dans les feuilles de salades peut augmenter avec l’activité des vers de terre, de plus de 45% et 36 % pour le Pb et le Zn respectivement. Généralement, dans les sols et les plantes, les concentrations mesurées en ETI pour les différentes conditions sont classées ainsi : SNB < SB et T. La bioaccessibilité gastrique humaine est fonction de la nature des ETI et augmente pour SB et T, dans le cas du Zn et du Cu notamment. Des changements de spéciation du plomb mettant en évidence l’effet des vers de terre sur le sol ont été observés par spectroscopie EXAFS, en comparant les sols SNB et T, et les tissus des vers de terre. La figure 1 présente les voies d’exposition des ETI pour les vers, et les mécanismes proposés pour expliquer l’augmentation de phytodisponibilité induite par la bioturbation. Figure 1. Voies d’exposition des vers de terre aux ETI et mécanismes potentiellement impliqués dans l’augmentation de phytodisponibilité du fait de la bioturbation. ►Conclusion : La bioturbation des vers de terre modifie le devenir des ETI dans les sols par des changements de spéciation pouvant augmenter la mobilité des métaux, et certainement aussi en raison de modifications de la distribution des matières organiques présentes dans le sol

Toxicity of CeO2 nanoparticles on a freshwater experimental trophic chain: A study in environmentally relevant conditions through the use of mesocosms

The toxicity of CeO2 NPs on an experimental freshwater ecosystem was studied in mesocosm, with a focus being placed on the higher trophic level, i.e. the carnivorous amphibian species Pleurodeles waltl. The system comprised species at three trophic levels: (i) bacteria, fungi and diatoms, (ii) Chironomus riparius larvae as primary consumers and (iii) Pleurodeles larvae as secondary consumers. NP contamination consisted of repeated additions of CeO2 NPs over 4 weeks, to obtain a final concentration of 1 mg/L. NPs were found to settle and accumulate in the sediment. No effects were observed on litter decomposition or associated fungal biomass. Changes in bacterial communities were observed from the third week of NP contamination. Morphological changes in CeO2 NPs were observed at the end of the experiment. No toxicity was recorded in chironomids, despite substantial NP accumulation (265.8±14.1mg Ce/kg). Mortality (35.3±6.8%) and a mean Ce concentration of 13.5±3.9mg/kg were reported for Pleurodeles. Parallel experiments were performed on Pleurodeles to determine toxicity pathways: no toxicity was observed by direct or dietary exposures, although Ce concentrations almost reached 100 mg/kg. In view of these results, various toxicity mechanisms are proposed and discussed. The toxicity observed on Pleurodeles in mesocosm may be indirect, due to microorganism’s interaction with CeO2 NPs, or NP dissolution could have occurred in mesocosm due to the structural complexity of the biological environment, resulting in toxicity to Pleurodeles. This study strongly supports the importance of ecotoxicological assessment of NPs under environmentally relevant conditions, using complex biological systems

Environmental release, fate and ecotoxicological effects of manufactured ceria nanomaterials

Recent interest in the environmental fate and effects of manufactured CeO2 nanomaterials (nanoceria) has stemmed from its expanded use for a variety of applications including fuel additives, catalytic converters, chemical and mechanical planarization media and other uses. This has led to a wave of publications on the toxicological effects of nanoceria in ecological receptor species, but only limited information is available on possible environmental releases, concentrations in environmental media, or environmental transformations. In this paper, we make initial estimates of likely environmental releases and exposure concentrations in soils and water and compare them to published toxicity values. Insufficient information was available to estimate aquatic exposures, but we estimated inputs to a hypothetical wastewater treatment plant that could result in effluent concentrations that would result in acute toxicity to the most sensitive aquatic organisms tested so far, cyanobacteria. The purpose of this exercise is to identify which areas are lacking in data to perform either regional or site specific ecological risk assessments. While estimates can be made for releases from use as a diesel fuel additive, and predicted toxicity is low in most terrestrial species tested to date, estimates for releases from other uses are difficult at this stage. We recommend that future studies focus on environmentally realistic exposures that take into account potential environmental transformations of the nanoceria surface as well as chronic toxicity studies in benthic aquatic organisms, soil invertebrates and microorgansims

Interactions between Magnetic Nanowires and Living Cells : Uptake, Toxicity and Degradation

We report on the uptake, toxicity and degradation of magnetic nanowires by NIH/3T3 mouse fibroblasts. Magnetic nanowires of diameters 200 nm and lengths comprised between 1 {\mu}m and 40 {\mu}m are fabricated by controlled assembly of iron oxide ({\gamma}-Fe2O3) nanoparticles. Using optical and electron microscopy, we show that after 24 h incubation the wires are internalized by the cells and located either in membrane-bound compartments or dispersed in the cytosol. Using fluorescence microscopy, the membrane-bound compartments were identified as late endosomal/lysosomal endosomes labeled with lysosomal associated membrane protein (Lamp1). Toxicity assays evaluating the mitochondrial activity, cell proliferation and production of reactive oxygen species show that the wires do not display acute short-term (< 100 h) toxicity towards the cells. Interestingly, the cells are able to degrade the wires and to transform them into smaller aggregates, even in short time periods (days). This degradation is likely to occur as a consequence of the internal structure of the wires, which is that of a non-covalently bound aggregate. We anticipate that this degradation should prevent long-term asbestos-like toxicity effects related to high aspect ratio morphologies and that these wires represent a promising class of nanomaterials for cell manipulation and microrheology.Comment: 21 pages 12 figure

Confounding experimental considerations in nanogenotoxicology

The development of novel nanomaterials with unique physico-chemical properties is increasing at a rapid rate, with potential applications across a broad range of manufacturing industries and consumer products. Nanomaterial safety is therefore becoming an increasingly contentious issue that has intensified over the past 4 years, and in response, a steady stream of studies focusing on nanotoxicology are emerging. However, it is becoming increasingly evident that nanomaterials cannot be treated in the same manner as chemical compounds with regards to their safety assessment, as their unique physico-chemical properties are also responsible for unexpected interactions with experimental components that generate misleading data-sets. In this report, we focus on nanomaterial interactions with colorimetric and fluorometric dyes, components of cell culture growth medium and genotoxicity assay components, and the resultant consequences on test systems are demonstrated. Thus, highlighting some of the potential confounding factors that need to be considered in order to ensure that in vitro genotoxicity assays report true biological impacts in response to nanomaterial exposure.status: publishe

Comparative Toxicity of Nanoparticulate CuO and ZnO to Soil Bacterial Communities

The increasing industrial application of metal oxide Engineered Nano-Particles (ENPs) is likely to increase their environmental release to soils. While the potential of metal oxide ENPs as environmental toxicants has been shown, lack of suitable control treatments have compromised the power of many previous assessments. We evaluated the ecotoxicity of ENP (nano) forms of Zn and Cu oxides in two different soils by measuring their ability to inhibit bacterial growth. We could show a direct acute toxicity of nano-CuO acting on soil bacteria while the macroparticulate (bulk) form of CuO was not toxic. In comparison, CuSO4 was more toxic than either oxide form. Unlike Cu, all forms of Zn were toxic to soil bacteria, and the bulk-ZnO was more toxic than the nano-ZnO. The ZnSO4 addition was not consistently more toxic than the oxide forms. Consistently, we found a tight link between the dissolved concentration of metal in solution and the inhibition of bacterial growth. The inconsistent toxicological response between soils could be explained by different resulting concentrations of metals in soil solution. Our findings suggested that the principal mechanism of toxicity was dissolution of metal oxides and sulphates into a metal ion form known to be highly toxic to bacteria, and not a direct effect of nano-sized particles acting on bacteria. We propose that integrated efforts toward directly assessing bioavailable metal concentrations are more valuable than spending resources to reassess ecotoxicology of ENPs separately from general metal toxicity

Nanoparticles within WWTP sludges have minimal impact on leachate quality and soil microbial community structure and function

One of the main pathways by which engineered nanoparticles (ENPs) enter the environment is through land application of waste water treatment plant (WWTP) sewage sludges. WWTP sludges, enriched with Ag and ZnO ENPs or their corresponding soluble metal salts during anaerobic digestion and subsequently mixed with soil (targeting a final concentration of 1400 and 140 mg/kg for Zn and Ag, respectively), were subjected to 6 months of ageing and leaching in lysimeter columns outdoors. Amounts of Zn and Ag leached were very low, accounting for <0.3% and <1.4% of the total Zn and Ag, respectively. No differences in total leaching rates were observed between treatments of Zn or Ag originally input to WWTP as ENP or salt forms. Phospholipid fatty acid profiling indicated a reduction in the fungal component of the soil microbial community upon metal exposure. However, overall, the leachate composition and response of the soil microbial community following addition of sewage sludge enriched either with ENPs or metal salts was very similar