Bulk and Mapping Speciation Analyses Unveil the Pattern and Heterogeneity of Cu Species during Organic Waste Treatment.

Organic wastes (OWs) can be a common source of copper (Cu) contamination of agricultural soils. Here we conducted a comprehensive study of 22 raw and treated OWs sampled at 6 different full-scale OW treatment plants. Bulk XANES analysis findings indicated that the Cu oxidation state was subject to changes throughout the OW treatment process, mostly depending on the anaerobic/aerobic conditions prevailing in each treatment stage. These changes were independent of the OW origin (agricultural, urban or industrial). Cu(I) prevailed in raw OWs and digestates (88-100%), whereas Cu(II) dominated in composts (46-100%). Bulk EXAFS analysis confirmed these observations and revealed that Cu(I) species in raw OWs and digestates consisted mainly of Cu(I)-sulfide (76-100%), while Cu(II) species (60-100%) in composts were Cu(II)-citrate, Cu(II)-carbonate and amorphous Cu(II)-phosphate. Interestingly, we observed that anaerobic digestion was conducive to the formation of crystallized Cu(I)-sulfides at the expense of nanosized and poorly crystalline Cu(I)-sulfide species, and that the recalcitrant Cu(I) species in composts was always crystallized Cu(I)-sulfide. XANES imaging analysis revealed Cu(II) species present in low proportions (2-4%) that were not detected using bulk XAS analysis in raw OWs and digestates. This demonstrated the potential of XANES imaging for probing minor species in complex matrices.

Size and Strain of Zinc Sulfide Nanoparticles Altered by Interaction with Organic Molecules.

Nanosized zinc sulfides (nano-ZnS) have size-dependent and tunable physical and chemical properties that make them useful for a variety of technological applications. For example, structural changes, especially caused by strain, are pronounced in nano-ZnS < 5 nm in size, the size range typical of incidental nano-ZnS that form in the environment. Previous research has shown how natural organic matter impacts the physical properties of nano-ZnS but was mostly focused on their aggregation state. However, the specific organic molecules and the type of functional groups that are most important for controlling the nano-ZnS size and strain remain unclear. This study examined the size-dependent strain of nano-ZnS synthesized in the presence of serine, cysteine, glutathione, histidine, and acetate. Synchrotron total scattering pair distribution function analysis was used to determine the average crystallite size and strain. Among the different organic molecules tested, those containing a thiol group were shown to affect the particle size and size-induced strain most strongly when added during synthesis but significantly reduced the particle strain when added to as-formed nano-ZnS. The same effects are useful to understand the properties and behavior of natural nano-ZnS formed as products of microbial activity, for example, in reducing environments, or of incidental nano-ZnS formed in organic wastes.

Cyto-Genotoxicity of Tritiated Stainless Steel and Cement Particles in Human Lung Cell Models.

During the decommissioning of nuclear facilities, the tritiated materials must be removed. These operations generate tritiated steel and cement particles that could be accidentally inhaled by workers. Thus, the consequences of human exposure by inhalation to these particles in terms of radiotoxicology were investigated. Their cyto-genotoxicity was studied using two human lung models: the BEAS-2B cell line and the 3D MucilAirTM model. Exposures of the BEAS-2B cell line to particles (2 and 24 h) did not induce significant cytotoxicity. Nevertheless, DNA damage occurred upon exposure to tritiated and non-tritiated particles, as observed by alkaline comet assay. Tritiated particles only induced cytostasis; however, both induced a significant increase in centromere negative micronuclei. Particles were also assessed for their effects on epithelial integrity and metabolic activity using the MucilAirTM model in a 14-day kinetic mode. No effect was noted. Tritium transfer through the epithelium was observed without intracellular accumulation. Overall, tritiated and non-tritiated stainless steel and cement particles were associated with moderate toxicity. However, these particles induce DNA lesions and chromosome breakage to which tritium seems to contribute. These data should help in a better management of the risk related to the inhalation of these types of particles.

Aquatic Mesocosm Strategies for the Environmental Fate and Risk Assessment of Engineered Nanomaterials.

In the past decade, mesocosms have emerged as a useful tool for the environmental study of engineered nanomaterials (ENMs) as they can mimic the relevant exposure scenario of contamination. Herein, we analyzed the scientific outcomes of aquatic mesocosm experiments, with regard to their designs, the ENMs tested, and the end points investigated. Several mesocosm designs were consistently applied in the past decade to virtually mimic various contamination scenarios with regard to ecosystem setting as well as ENMs class, dose, and dosing. Statistical analyses were carried out with the literature data to identify the main parameters driving ENM distribution in the mesocosms and the potential risk posed to benthic and planktonic communities as well as global ecosystem responses. These analyses showed that at the end of the exposure, mesocosm size (water volume), experiment duration, and location indoor/outdoor had major roles in defining the ENMs/metal partitioning. Moreover, a higher exposure of the benthic communities is often observed but did not necessarily translate to a higher risk due to the lower hazard posed by transformed ENMs in the sediments (e.g., aggregated, sulfidized). However, planktonic organisms were generally exposed to lower concentrations of potentially more reactive and toxic ENM species. Hence, mesocosms can be complementary tools to existing standard operational procedures for regulatory purposes and environmental fate and risk assessment of ENMs. To date, the research was markedly unbalanced toward the investigation of metal-based ENMs compared to metalloid- and carbon-based ENMs but also nanoenabled products. Future studies are expected to fill this gap, with special regard to high production volume and potentially hazardous ENMs. Finally, to take full advantage of mesocosms, future studies must be carefully planned to incorporate interdisciplinary approaches and ensure that the large data sets produced are fully exploited.

Elaboration of Cellulose Nanocrystal/Ge-Imogolite Nanotube Multilayered Thin Films.

Multilayered thin films combining two oppositely charged nanoparticles (NPs), i.e., cellulose nanocrystals (CNCs) and Ge-imogolites, have been successfully obtained by the layer-by-layer method. CNC/Ge-imogolite (NP/NP) film growth patterns were studied by comparing growth mode of all of the nanoparticles thin films to that of films composed of CNC or Ge-imogolites combined with polyelectrolytes (PEs), i.e., cationic poly(allylamine hydrochloride) and anionic poly-4-styrene sulfonate (NP/PE films). NP/NP and NP/PE films growth patterns were found to be different. To get a deeper understanding of the growth mode of NP/NP, impact of different parameters, such as imogolites aspect ratio, adsorption time, ionic strength, and repeated immersion/drying, was evaluated and influence of the drying step is emphasized. The aspect ratio of imogolites was identified as an important feature for the film's architecture. The short Ge-imogolites form denser films because the surface packing was more efficient.

Drastic Change in Zinc Speciation during Anaerobic Digestion and Composting: Instability of Nanosized Zinc Sulfide.

Zinc (Zn) is a potentially toxic trace element that is present in large amounts in organic wastes (OWs) spread on agricultural lands as fertilizer. Zn speciation in OW is a crucial parameter to understand its fate in soil after spreading and to assess the risk associated with agricultural recycling of OW. Here, we investigated changes in Zn speciation from raw OWs up to digestates and/or composts for a large series of organic wastes sampled in full-scale plants. Using extended X-ray absorption fine structure, we show that nanosized Zn sulfide (nano-ZnS) is a major Zn species in raw liquid OWs and a minor species in raw solid OWs. Whatever the characteristics of the raw OW, anaerobic digestion always favors the formation of nano-ZnS (>70% of zinc in digestates). However, after 1 to 3 months of composting of OWs, nano-ZnS becomes a minor species (<10% of zinc). In composts, Zn is mostly present as amorphous Zn phosphate and Zn sorbed to ferrihydrite. These results highlight (i) the influence of OW treatment on Zn speciation and (ii) the chemical instability of nano-ZnS formed in OW in anaerobic conditions.

Transformations of Nanoenabled Copper Formulations Govern Release, Antifungal Effectiveness, and Sustainability throughout the Wood Protection Lifecycle.

Here we compare the standard European benchmark of wood treatment by molecularly dissolved copper amine (Cu-amine), also referred to as aqueous copper amine (ACA), against two nanoenabled formulations: copper(II)oxide nanoparticles (CuO NPs) in an acrylic paint to concentrate Cu as a barrier on the wood surface, and a suspension of micronized basic copper carbonate (CuCO3·Cu(OH)2) for wood pressure treatment. After characterizing the properties of the (nano)materials and their formulations, we assessed their effects in vitro against three fungal species: Coniophora puteana, Gloeophyllum trabeum, and Trametes versicolor, finding them to be mediated only partially by ionic transformation. To assess the use phase, we quantify both release rate and form. Cu leaching rates for the two types of impregnated wood (conventional and nanoenabled) are not significantly different at 172 ± 6 mg/m2, with Cu being released predominantly in ionic form. Various simulations of outdoor aging with release sampling by runoff, during condensation, by different levels of mechanical shear, all resulted in comparable form and rate of release from the nanoenabled or the molecular impregnated woods. Because of dissolving transformations, the nanoenabled impregnation does not introduce additional concern over and above that associated with the traditional impregnation. In contrast, Cu released from wood coated with the CuO acrylate contained particles, but the rate was at least 100-fold lower. In the same ranking, the effectiveness to protect against the wood-decaying basidiomycete Coniophora puteana was significant with both impregnation technologies but remained insignificant for untreated wood and wood coated by the acrylic CuO. Accordingly, a lifecycle-based sustainability analysis indicates that the CuO acrylic coating is less sustainable than the technological alternatives, and should not be developed into a commercial product.

Respiratory hazard of Li-ion battery components: elective toxicity of lithium cobalt oxide (LiCoO2) particles in a mouse bioassay.

Rechargeable Li-ion batteries (LIB) are increasingly produced and used worldwide. LIB electrodes are made of micrometric and low solubility particles, consisting of toxicologically relevant elements. The health hazard of these materials is not known. Here, we investigated the respiratory hazard of three leading LIB components (LiFePO4 or LFP, Li4Ti5O12 or LTO, and LiCoO2 or LCO) and their mechanisms of action. Particles were characterized physico-chemically and elemental bioaccessibility was documented. Lung inflammation and fibrotic responses, as well as particle persistence and ion bioavailability, were assessed in mice after aspiration of LIB particles (0.5 or 2 mg); crystalline silica (2 mg) was used as reference. Acute inflammatory lung responses were recorded with the 3 LIB particles and silica, LCO being the most potent. Inflammation persisted 2 m after LFP, LCO and silica, in association with fibrosis in LCO and silica lungs. LIB particles persisted in the lungs after 2 m. Endogenous iron co-localized with cobalt in LCO lungs, indicating the formation of ferruginous bodies. Fe and Co ions were detected in the broncho-alveolar lavage fluids of LFP and LCO lungs, respectively. Hypoxia-inducible factor (HIF) -1α, a marker of fibrosis and of the biological activity of Co ions, was upregulated in LCO and silica lungs. This study identified, for the first time, the respiratory hazard of LIB particles. LCO was at least as potent as crystalline silica to induce lung inflammation and fibrosis. Iron and cobalt, but not lithium, ions appear to contribute to LFP and LCO toxicity, respectively.

Nanoparticle Uptake in Plants: Gold Nanomaterial Localized in Roots of Arabidopsis thaliana by X-ray Computed Nanotomography and Hyperspectral Imaging.

Terrestrial plants can internalize and translocate nanoparticles (NPs). However, direct evidence for the processes driving the NP uptake and distribution in plants is scarce at the cellular level. Here, NP-root interactions were investigated after 10 days of exposure of Arabidopsis thaliana to 10 mg·L-1 of negatively or positively charged gold NPs (∼12 nm) in gels. Two complementary imaging tools were used: X-ray computed nanotomography (nano-CT) and enhanced dark-field microscopy combined with hyperspectral imaging (DF-HSI). The use of these emerging techniques improved our ability to detect and visualize NP in plant tissue: by spectral confirmation via DF-HSI, and in three dimensions via nano-CT. The resulting imaging provides direct evidence that detaching border-like cells (i.e., sheets of border cells detaching from the root) and associated mucilage can accumulate and trap NPs irrespective of particle charge. On the contrary, border cells on the root cap behaved in a charge-specific fashion: positively charged NPs induced a higher mucilage production and adsorbed to it, which prevented translocation into the root tissue. Negatively charged NPs did not adsorb to the mucilage and were able to translocate into the apoplast. These observations provide direct mechanistic insight into NP-plant interactions, and reveal the important function of border cells and mucilage in interactions of plants with charged NPs.

Nanoscale Coloristic Pigments: Upper Limits on Releases from Pigmented Plastic during Environmental Aging, In Food Contact, and by Leaching.

The life cycle of nanoscale pigments in plastics may cause environmental or human exposure by various release scenarios. We investigated spontaneous and induced release with mechanical stress during/after simulated sunlight and rain degradation of polyethylene (PE) with organic and inorganic pigments. Additionally, primary leaching in food contact and secondary leaching from nanocomposite fragments with an increased surface into environmental media was examined. Standardized protocols/methods for release sampling, detection, and characterization of release rate and form were applied: Transformation of the bulk material was analyzed by Scanning Electron Microscopy (SEM), X-ray-tomography and Fourier-Transform Infrared spectroscopy (FTIR); releases were quantified by Inductively Coupled Plasma Mass Spectrometry (ICP-MS), single-particle-ICP-MS (sp-ICP-MS), Transmission Electron Microscopy (TEM), Analytical Ultracentrifugation (AUC), and UV/Vis spectroscopy. In all scenarios, the detectable particulate releases were attributed primarily to contaminations from handling and machining of the plastics, and were not identified with the pigments, although the contamination of 4 mg/kg (Fe) was dwarfed by the intentional content of 5800 mg/kg (Fe as Fe2O3 pigment). We observed modulations (which were at least partially preventable by UV stabilizers) when comparing as-produced and aged nanocomposites, but no significant increase of releases. Release of pigments was negligible within the experimental error for all investigated scenarios, with upper limits of 10 mg/m2 or 1600 particles/mL. This is the first holistic confirmation that pigment nanomaterials remain strongly contained in a plastic that has low diffusion and high persistence such as the polyolefin High Density Polyethylene (HDPE).

High-Energy Resolution Fluorescence Detected X-Ray Absorption Spectroscopy: A Powerful New Structural Tool in Environmental Biogeochemistry Sciences.

The study of the speciation of highly diluted elements by X-ray absorption spectroscopy (XAS) is extremely challenging, especially in environmental biogeochemistry sciences. Here we present an innovative synchrotron spectroscopy technique: high-energy resolution fluorescence detected XAS (HERFD-XAS). With this approach, measurement of the XAS signal in fluorescence mode using a crystal analyzer spectrometer with a ∼1-eV energy resolution helps to overcome restrictions on sample concentrations that can be typically measured with a solid-state detector. We briefly describe the method, from both an instrumental and spectroscopic point of view, and emphasize the effects of energy resolution on the XAS measurements. We then illustrate the positive impact of this technique in terms of detection limit with two examples dealing with Ce in ecologically relevant organisms and with Hg species in natural environments. The sharp and well-marked features of the HERFD-X-ray absorption near-edge structure spectra obtained enable us to determine unambiguously and with greater precision the speciation of the probed elements. This is a major technological advance, with strong benefits for the study of highly diluted elements using XAS. It also opens new possibilities to explore the speciation of a target chemical element at natural concentration levels, which is critical in the fields of environmental and biogeochemistry sciences.

Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier.

We assessed the potential of zerovalent-iron- (Fe(0)) based permeable reactive barrier (PRB) systems for arsenic (As) remediation in the presence or absence of microbial sulfate reduction. We conducted long-term (200 day) flow-through column experiments to investigate the mechanisms of As transformation and mobility in aquifer sediment (in particular, the PRB downstream linkage). Changes in As speciation in the aqueous phase were monitored continuously. Speciation in the solid phase was determined at the end of the experiment using X-ray absorption near-edge structure (XANES) spectroscopy analysis. We identified thio-As species in solution and AsS in solid phase, which suggests that the As(V) was reduced to As(III) and precipitated as AsS under sulfate-reducing conditions and remained as As(V) under abiotic conditions, even with low redox potential and high Fe(II) content (4.5 mM). Our results suggest that the microbial sulfate reduction plays a key role in the mobilization of As from Fe-rich aquifer sediment under anoxic conditions. Furthermore, they illustrate that the upstream-downstream linkage of PRB affects the speciation and mobility of As in downstream aquifer sediment, where up to 47% of total As initially present in the sediment was leached out in the form of mobile thio-As species.

Remote Biodegradation of Ge-Imogolite Nanotubes Controlled by the Iron Homeostasis of Pseudomonas brassicacearum.

The toxicity of high-aspect-ratio nanomaterials (HARNs) is often associated with oxidative stress. The essential nutrient Fe may also be responsible of oxidative stress through the production of reactive oxygen species. In the present study, it has been examined to what extent adding Fenton reaction promoting Fe impacted the toxicity of an alumino-germanate model HARN. Structural addition of only 0.95% wt Fe to Ge-imogolite not only alleviated the toxicity observed in the case of Fe-free nanotubes but also stimulated bacterial growth. This was attributed to the metabolization of siderophore-mobilized Fe from the nanotube structure. This was evidenced by the regulation of the homeostasis-monitoring intracellular Fe levels. This was accompanied by a biodegradation of the nanotubes approaching 40%, whereas the Fe-free nanomaterial remained nearly untouched.

Design Defines the Effects of Nanoceria at a Low Dose on Soil Microbiota and the Potentiation of Impacts by the Canola Plant.

Soils act as nanoceria sinks via agricultural spreading and surface waters. Canola plants were grown for one month in soil spiked with nanoceria (1 mg·kg(-1)). To define the role of nanomaterials design on environmental impacts, we studied nanoceria with different sizes (3.5 or 31 nm) and coating (citrate). We measured microbial activities involved in C, N, and P cycling in the rhizosphere and unplanted soil. Bacterial community structure was analyzed in unplanted soil, rhizosphere, and plant roots by 454-pyrosequencing of the 16S rRNA gene. This revealed an impact gradient dependent on nanomaterials design, ranging from decreased microbial enzymatic activities in planted soil to alterations in bacterial community structure in roots. Particle size/aggregation was a key parameter in modulating nanoceria effects on root communities. Citrate coating lowered the impact on microbial enzymatic activities but triggered variability in the bacterial community structure near the plant root. Some nanoceria favored taxa whose closest relatives are hydrocarbon-degrading bacteria and disadvantaged taxa frequently associated in consortia with disease-suppressive activity toward plant pathogens. This work provides a basis to determine outcomes of nanoceria in soil, at a dose close to predicted environmental concentrations, and to design them to minimize these impacts.

Meeting the Needs for Released Nanomaterials Required for Further Testing-The SUN Approach.

The analysis of the potential risks of engineered nanomaterials (ENM) has so far been almost exclusively focused on the pristine, as-produced particles. However, when considering a life-cycle perspective, it is clear that ENM released from genuine products during manufacturing, use, and disposal is far more relevant. Research on the release of materials from nanoproducts is growing and the next necessary step is to investigate the behavior and effects of these released materials in the environment and on humans. Therefore, sufficient amounts of released materials need to be available for further testing. In addition, ENM-free reference materials are needed since many processes not only release ENM but also nanosized fragments from the ENM-containing matrix that may interfere with further tests. The SUN consortium (Project on "Sustainable Nanotechnologies", EU seventh Framework funding) uses methods to characterize and quantify nanomaterials released from composite samples that are exposed to environmental stressors. Here we describe an approach to provide materials in hundreds of gram quantities mimicking actual released materials from coatings and polymer nanocomposites by producing what is called "fragmented products" (FP). These FP can further be exposed to environmental conditions (e.g., humidity, light) to produce "weathered fragmented products" (WFP) or can be subjected to a further size fractionation to isolate "sieved fragmented products" (SFP) that are representative for inhalation studies. In this perspective we describe the approach, and the used methods to obtain released materials in amounts large enough to be suitable for further fate and (eco)toxicity testing. We present a case study (nanoparticulate organic pigment in polypropylene) to show exemplarily the procedures used to produce the FP. We present some characterization data of the FP and discuss critically the further potential and the usefulness of the approach we developed.

Toxicity evaluation of manufactured CeO2 nanoparticles before and after alteration: combined physicochemical and whole-genome expression analysis in Caco-2 cells.

BACKGROUND: Engineered nanomaterials may release nanosized residues, by degradation, throughout their life cycle. These residues may be a threat for living organisms. They may be ingested by humans through food and water. Although the toxicity of pristine CeO2 nanoparticles (NPs) has been documented, there is a lack of studies on manufactured nanoparticles, which are often surface modified. Here, we investigated the potential adverse effects of CeO2 Nanobyk 3810™ NPs, used in wood care, and their residues, altered by light or acid. RESULTS: Human intestinal Caco-2 cells were exposed to residues degraded by daylight or in a medium simulating gastric acidity. Size and zeta potential were determined by dynamic light scattering. The surface structure and redox state of cerium were analyzed by transmission electronic microscopy (TEM) and X-ray absorption spectroscopy, respectively. Viability tests were performed in Caco-2 cells exposed to NPs. Cell morphology was imaged with scanning electronic microscopy. Gene expression profiles obtained from cells exposed to NPs before and after their alteration were compared, to highlight differences in cellular functions.No change in the cerium redox state was observed for altered NPs. All CeO2 NPs suspended in the culture medium became microsized. Cytotoxicity tests showed no toxicity after Caco-2 cell exposure to these various NPs up to 170 µg/mL (24 h and 72 h). Nevertheless, a more-sensitive whole-gene-expression study, based on a pathway-driven analysis, highlighted a modification of metabolic activity, especially mitochondrial function, by altered Nanobyk 3810™. The down-regulation of key genes of this pathway was validated by qRT-PCR. Conversely, Nanobyk 3810™ coated with ammonium citrate did not display any adverse effect at the same concentration. CONCLUSION: The degraded nanoparticles were more toxic than their coated counterparts. Desorption of the outside layer was the most likely cause of this discrepancy in toxicity. It can be assumed that the safe design of engineered nanoparticles could include robust protective layers conferring on them greater resistance to alteration during their life cycle.

Aged TiO2-based nanocomposite used in sunscreens produces singlet oxygen under long-wave UV and sensitizes Escherichia coli to cadmium.

TiO2-based nanocomposite (NC) are widely used as invisible UV protectant in cosmetics. These nanomaterials (NMs) end in the environment as altered materials. We have investigated the properties of T-Lite SF, a TiO2-NC used as sunscreen, after weathering in water and under light. We have examined the formation of ROS and their consequences on cell physiology of Escherichia coli. Our results show that aged-T-Lite SF produced singlet oxygen under low intensity long wave UV and formed hydroxyl radicals at high intensity. Despite the production of these ROS, T-Lite SF had neither effect on the viability of E. coli nor on mutant impaired in oxidative stress, did not induce mutagenesis and did not impair the integrity of membrane lipids, thus seemed safe to bacteria. However, when pre-exposed to T-Lite SF under low intensity UV, cells turned out to be more sensitive to cadmium, a priority pollutant widely disseminated in soil and surface waters. This effect was not a Trojan horse: sensitization of cells was dependent on the formation of singlet oxygen. These results provide a basis for caution, especially on NMs that have no straight environmental toxicity. It is crucial to anticipate indirect and combined effects of environmental pollutants and NMs.

Molecular insights of oxidation process of iron nanoparticles: spectroscopic, magnetic, and microscopic evidence.

Oxidation behavior of nano-Fe(0) particles in an anoxic environment was determined using different state-of-the-art analytical approaches, including high resolution transmission electron microscopy (HR-TEM) combined with energy filtered transmission electron microscopy (EFTEM), X-ray absorption spectroscopy (XAS), and magnetic measurements. Oxidation in controlled experiments was compared in standard double distilled (DD) water, DD water spiked with trichloroethene (TCE), and TCE contaminated site water. Using HR-TEM and EFTEM, we observed a surface oxide layer (∼3 nm) formed immediately after the particles were exposed to water. XAS analysis followed the dynamic change in total metallic iron concentration and iron oxide concentration for the experimental duration of 35 days. The metallic iron concentration in nano-Fe(0) particles exposed to water, was ∼40% after 35 days; in contrast, the samples containing TCE were reduced to ∼15% and even to nil in the case of TCE contaminated site water, suggesting that the contaminants enhance the oxidation of nano-Fe(0). Frequency dependence measurements confirmed the formation of superparamagnetic particles in the system. Overall, our results suggest that nano-Fe(0) oxidized via the Fe(0) - Fe(OH)2 - Fe3O4 - (γ-Fe2O3) route and the formation of superparamagnetic maghemite nanoparticles due to disruption of the surface oxide layer.

Nanometer-long Ge-imogolite nanotubes cause sustained lung inflammation and fibrosis in rats.

BACKGROUND: Ge-imogolites are short aluminogermanate tubular nanomaterials with attractive prospected industrial applications. In view of their nano-scale dimensions and high aspect ratio, they should be examined for their potential to cause respiratory toxicity. Here, we evaluated the respiratory biopersistence and lung toxicity of 2 samples of nanometer-long Ge-imogolites. METHODS: Rats were intra-tracheally instilled with single wall (SW, 70 nm length) or double wall (DW, 62 nm length) Ge-imogolites (0.02-2 mg/rat), as well as with crocidolite and the hard metal particles WC-Co, as positive controls. The biopersistence of Ge-imogolites and their localization in the lung were assessed by ICP-MS, X-ray fluorescence, absorption spectroscopy and computed micro-tomography. Acute inflammation and genotoxicity (micronuclei in isolated type II pneumocytes) was assessed 3 d post-exposure; chronic inflammation and fibrosis after 2 m. RESULTS: Cytotoxic and inflammatory responses were shown in bronchoalveolar lavage 3 d after instillation with Ge-imogolites. Sixty days after exposure, a persistent dose-dependent inflammation was still observed. Total lung collagen, reflected by hydroxyproline lung content, was increased after SW and DW Ge-imogolites. Histology revealed lung fibre reorganization and accumulation in granulomas with epithelioid cells and foamy macrophages and thickening of the alveolar walls. Overall, the inflammatory and fibrotic responses induced by SW and DW Ge-imogolites were more severe (on a mass dose basis) than those induced by crocidolite. A persistent fraction of Ge-imogolites (15% of initial dose) was mostly detected as intact structures in rat lungs 2 m after instillation and was localized in fibrotic alveolar areas. In vivo induction of micronuclei was significantly increased 3 d after SW and DW Ge-imogolite instillation at non-inflammatory doses, indicating the contribution of primary genotoxicity. CONCLUSIONS: We showed that nm-long Ge-imogolites persist in the lung and promote genotoxicity, sustained inflammation and fibrosis, indicating that short high aspect ratio nanomaterials should not be considered as innocuous materials. Our data also suggest that Ge-imogolite structure and external surface determine their toxic activity.

Comprehensive framework for overcoming scientific challenges related to assessing radioactive ultra-fine (nano/micro) particles transfer at the atmosphere-leaf interface.

Food products are prone into contamination after a nuclear emission of radionuclides. While the mechanisms of emission and deposition of ultrafine radioactive particles are well documented, the transfer of these species from the atmosphere into plants is poorly assessed. This is evident in the lack of quantification of particles distributed within plants, especially regarding particles physical-chemical criteria to plant of different properties. Such knowledge gaps raise the concern about the representativeness of risk assessment tools designed for the transfer evaluation of ionic/soluble species to be qualified for simulating insoluble species exposure and proposes a possible underestimation. This highlights the possible need for special particle codes development to be implemented in models for future emissions. In addition, the later tools utilize transfer factors aggregating relevant sub-processes, suggesting another weak point in their overall reliability. As researchers specialized in the nuclear safety and protection, we intend in this perspective, to develop a compressive analysis of the interaction of ultrafine particles with plants of different specificities at different level processes starting from particles retention and gradual translocation to sink organs. This analysis is leveraged in providing insights for possible improvements in the current modeling tools for better real-life scenarios representation.