Nanosafety: a Perspective on Nano-Bio Interactions.

Engineered nanomaterials offer numerous benefits to society ranging from environmental remediation to biomedical applications such as drug or vaccine delivery as well as clean and cost-effective energy production and storage, and the promise of a more sustainable way of life. However, as nanomaterials of increasing sophistication enter the market, close attention to potential adverse effects on human health and the environment is needed. Here a critical perspective on nanotoxicological research is provided; the authors argue that it is time to leverage the knowledge regarding the biological interactions of nanomaterials to achieve a more comprehensive understanding of the human health and environmental impacts of these materials. Moreover, it is posited that nanomaterials behave like biological entities and that they should be regulated as such.

Aging of Copper Nanoparticles in the Marine Environment Regulates Toxicity for a Coastal Phytoplankton Species.

Environmental conditions in aquatic ecosystems transform toxic chemicals over time, influencing their bioavailability and toxicity. Using an environmentally relevant methodology, we tested how exposure to seawater for 1-15 weeks influenced the accumulation and toxicity of copper nanoparticles (nano-Cu) in a marine phytoplankton species. Nano-Cu rapidly agglomerated in seawater and then decreased in size due to Cu dissolution. Dissolution rates declined during weeks 1-4 and remained low until 15 weeks, when the large agglomerates that had formed began to rapidly dissolve again. Marine phytoplankton species were exposed for 5-day periods to nano-Cu aged from 1 to 15 weeks at concentrations from 0.01 to 20 ppm. Toxicity to phytoplankton, measured as change in population growth rate, decreased significantly with particle aging from 0 to 4 weeks but increased substantially in the 15-week treatment due apparently to elevated Cu dissolution of reagglomerated particles. Results indicate that the transformation, fate, and toxicity of nano-Cu in marine ecosystems are influenced by a highly dynamic physicochemical aging process.

Nanomaterials in sunscreens: Potential human and ecological health implications.

Inorganic nanomaterials such as TiO2 and ZnO provide significant benefits in terms of UV protection, and their use generally has increased in commercial sunscreens. However, more recently there have been concerns about their potential human and ecological health implications, mostly driven by perception rather than by formal assessments. The large and increasing body of literature on these nanomaterials indicates that in most circumstances their risk are minimal. Penetration of the human epidermis is minimal for these nanomaterials, significantly reducing the potential effects that these nanomaterials may pose to internal organs. The excess Zn ion dose is very small compared to normal dietary consumption of Zn, which is a necessary element. The levels of residual nanomaterials or released ions in public swimming pools is also low, with minimal effect in case this water is ingested during swimming or bathing. In natural environments with significant water flow due to wind and water currents, the concentrations of nanomaterials and released ions are generally well below levels that would cause effects in aquatic organisms. However, sensitive habitats with slow currents, such as coral reefs, may accumulate these nanomaterials. The number of studies of the levels and effects of nanomaterials in these sensitive habitats is very small; more research is needed to determine if there is an elevated risk to these ecosystems from the use of sunscreens with these nanomaterials.

Les nanomatériaux inorganiques, comme le dioxyde de titane (TiO2 ) et l'oxyde de zinc (ZnO), offrent des avantages significatifs en ce qui concerne la protection UV, et leur utilisation a généralement augmenté dans les protections solaires commerciales. Cependant, plus récemment, il y a eu des préoccupations concernant leurs implications potentielles sur la santé humaine et écologique, motivées principalement par la perception plutôt que par des évaluations formelles. L'importante quantité croissante de littérature sur ces nanomatériaux indique que dans la plupart des circonstances, leur risque est minime. La pénétration dans l'épiderme humain est minimale pour ces nanomatériaux, ce qui réduit significativement les effets potentiels de ces nanomatériaux sur les organes internes. La dose d'ions Zn en excès est très faible par rapport à la consommation alimentaire normale de Zn, qui est un élément nécessaire. Les niveaux de nanomatériaux résiduels ou d'ions libérés dans les piscines publiques sont également faibles, avec un effet minime dans le cas où cette eau est ingérée pendant la natation ou la baignade. Dans les environnements naturels caractérisés par un flux d'eau important en raison de courants éoliens et de courants aquatiques, les concentrations de nanomatériaux et d'ions libérés sont généralement nettement inférieures aux niveaux qui pourraient avoir des effets sur les organismes aquatiques. En revanche, des habitats sensibles à courants lents, comme les récifs coralliens, peuvent accumuler ces nanomatériaux. Le nombre d'études sur les niveaux et les effets des nanomatériaux dans ces habitats sensibles est très faible. Des recherches supplémentaires sont nécessaires pour déterminer s'il existe un risque élevé pour ces écosystèmes lié à l'utilisation de crèmes solaires comportant ces nanomatériaux.

Removal of pharmaceuticals and personal care products from wastewater via anodic oxidation and electro-Fenton processes: current status and needs regarding their application.

This review provides a current opinion on the most recent works that have been published toward the application of electrochemical advance oxidation processes (EAOPs) for the degradation of pharmaceutical and personal care products (PPCPs) in water streams. Advances in the application of anodic oxidation (AO)- and electro-Fenton (EF)-based processes are reported, including operational conditions, electrode performance, and removal. Although AO- and EF-based processes can easily reach 100% removal of PPCPs, mineralization is desirable to avoid the generation of potential toxic byproducts. The following section exploring some techno-economic aspects of the application of EAOPs is based on electrode selection, operational costs as well as their use as cotreatments, and their synergistic effects. Finally, this short review ends with perspectives about the emerging topics that are faced by these technologies applied for the degradation of PPCPs in research and practice.

Dissolution and Aggregation of Metal Oxide Nanoparticles in Root Exudates and Soil Leachate: Implications for Nanoagrochemical Application.

Knowledge of dissolution, aggregation, and stability of nanoagrochemicals in root exudates (RE) and soil leachate will contribute to improving delivery mechanisms, transport in plants, and bioavailability. We characterized aggregation, stability, and dissolution of four nanoparticles (NPs) in soybean RE and soil leachate: nano-CeO2, nano-Mn3O4, nano-Cu(OH)2, and nano-MoO3. Aggregation differed considerably in different media. In RE, nano-Cu(OH)2, and nano-MoO3 increased their aggregate size for 5 days; their mean sizes increased from 518 ± 43 nm to 938 ± 32 nm, and from 372 ± 14 nm to 690 ± 65 nm, respectively. Conversely, nano-CeO2 and nano-Mn3O4 disaggregated in RE with time, decreasing from 289 ± 5 nm to 129 ± 10 nm, and from 761 ± 58 nm to 143 ± 18 nm, respectively. Organic acids in RE and soil leachate can be adsorbed onto particle surfaces, influencing aggregation. Charge of the four NPs was negative in contact with RE and soil leachate, due to organic matter present in RE and soil leachate. Dissolution in RE after 6 days was 38%, 1.2%, 0.5%, and <0.1% of the elemental content of MoO3, Cu(OH)2, Mn3O4, and CeO2 NPs. Thus, the bioavailability and efficiency of delivery of the NPs or their active ingredients will be substantially modified soon after they are in contact with RE or soil leachate.

Drilling into the Metabolomics to Enhance Insight on Corn and Wheat Responses to Molybdenum Trioxide Nanoparticles.

Metabolomics is an emerging tool to understand the potential implications of nanotechnology, particularly for agriculture. Although molybdenum (Mo) is a known plant micronutrient, little is known of its metabolic perturbations. Here, corn and wheat seedlings were exposed to MoO3 nanoparticles (NPs) and the corresponding bioavailable Mo6+ ion at moderate and excessive levels through root exposures. Physiologically, corn was more sensitive to Mo, which accumulated up to 3.63 times more Mo than wheat. In contrast, metabolomics indicated 21 dysregulated metabolites in corn leaves and 53 in wheat leaves. Five more metabolomic pathways were perturbed in wheat leaves compared to corn leaves. In addition to the overall metabolomics analysis, we also analyzed individual metabolite classes (e.g., amino acids, organic acids, etc.), yielding additional dysregulated metabolites in plant tissues: 7 for corn and 7 for wheat. Most of these were amino acids as well as some sugars. Additional significantly dysregulated metabolites (e.g., asparagine, fructose, reduced glutathione, mannose) were identified in both corn and wheat, due to Mo NP exposure, by employing individual metabolite group analysis. Targeted metabolite analysis of individual groups is thus important for finding additional significant metabolites. We demonstrate the value of metabolomics to study early stage plant responses to NP exposure.

Metabolomic Responses of Green Alga Chlamydomonas reinhardtii Exposed to Sublethal Concentrations of Inorganic and Methylmercury.

Metabolomics characterizes low-molecular-weight molecules involved in different biochemical reactions and provides an integrated assessment of the physiological state of an organism. By using liquid chromatography-mass spectrometry targeted metabolomics, we examined the response of green alga Chlamydomonas reinhardtii to sublethal concentrations of inorganic mercury (IHg) and monomethylmercury (MeHg). We quantified the changes in the levels of 93 metabolites preselected based on the disturbed metabolic pathways obtained in a previous transcriptomics study. Metabolites are downstream products of the gene transcription; hence, metabolite quantification provided information about the biochemical status of the algal cells exposed to Hg compounds. The results showed that the alga adjusts its metabolism during 2 h exposure to 5 × 10-9 and 5 × 10-8 mol L-1 IHg and MeHg by increasing the level of various metabolites involved in amino acid and nucleotide metabolism, photorespiration, and tricarboxylic acid (TCA) cycle, as well as the metabolism of fatty acids, carbohydrates, and antioxidants. Most of the metabolic perturbations in the alga were common for IHg and MeHg treatments. However, the exposure to IHg resulted in more pronounced perturbations in the fatty acid and TCA metabolism as compared with the exposure to MeHg. The observed metabolic perturbations were generally consistent with our previously published transcriptomics results for C. reinhardtii exposed to the comparable level of IHg and MeHg. The results highlight the potential of metabolomics for toxicity evaluation, especially to detect effects at an early stage of exposure prior to their physiological appearance.

Unraveling Metabolic and Proteomic Features in Soybean Plants in Response to Copper Hydroxide Nanowires Compared to a Commercial Fertilizer.

Mechanistic understanding of the interaction of copper-based nanomaterials with crops is crucial for exploring their application in precision agriculture and their implications on plant health. We investigated the biological response of soybean (Glycine max) plants to the foliar application of copper hydroxide nanowires (CNWs) at realistic exposure concentrations. A commercial copper based-fungicide (Kocide), dissolved copper ions, and untreated controls were used for comparison to identify unique features at physiological, cellular, and molecular levels. After 32 d of exposure to CNW (0.36, 1.8, and 9 mg CNW/plant), the newly developed tissues accumulated significantly high levels of Cu (18-60 µg/g) compared to Kocide (10 µg/g); however, the rate of Cu translocation from the site of CNW treatment to other tissues was slower compared to other Cu treatments. Like Kocide, CNW exposure at medium and high doses altered Co, Mn, Zn, and Fe accumulation in the tissues and enhanced photosynthetic activities. The proteomic and metabolomic analyses of leaves from CNW-treated soybean plants suggest a dose-dependent response, resulting in the activation of major biological processes, including photosynthesis, energy production, fatty acid metabolism, lignin biosynthesis, and carbohydrate metabolism. In contrast to CNW treatments, Kocide exposure resulted in increased oxidative stress response and amino acid metabolism activation.

Magnesium Oxide Nanomaterial, an Alternative for Commercial Copper Bactericides: Field-Scale Tomato Bacterial Spot Disease Management and Total and Bioavailable Metal Accumulation in Soil.

Copper (Cu) is the most extensively used bactericide worldwide in many agricultural production systems. However, intensive application of Cu bactericide have increased the selection pressure toward Cu-tolerant pathogens, including Xanthomonas perforans, the causal agent of tomato bacterial spot. However, alternatives for Cu bactericides are limited and have many drawbacks including plant damage and inconsistent effectiveness under field conditions. Also, potential ecological risk on nontarget organisms exposed to field runoff containing Cu is high. However, due to lack of alternatives for Cu, it is still widely used in tomato and other crops around the world in both conventional and organic production systems. In this study, a Cu-tolerant X. perforans strain GEV485, which can tolerate eight tested commercial Cu bactericides, was used in all the field trials to evaluate the efficacy of MgO nanomaterial. Four field experiments were conducted to evaluate the impact of intensive application of MgO nanomaterial on tomato bacterial spot disease severity, and one field experiment was conducted to study the impact of soil accumulation of total and bioavailable Cu, Mg, Mn, and Zn. In the first two field experiments, twice-weekly applications of 200 µg/mL MgO significantly reduced disease severity by 29-38% less in comparison to a conventional Cu bactericide Kocide 3000 and 19-30% less in comparison to the water control applied at the same frequency (p = 0.05). The disease severity on MgO twice-weekly was 12-32% less than Kocide 3000 + Mancozeb treatment. Single weekly applications of MgO had 13-19% higher disease severity than twice weekly application of MgO. In the second set of two field trials, twice-weekly applications of MgO at 1000 µg/mL significantly reduced disease severity by 32-40% in comparison to water control applied at the same frequency (p = 0.05). There was no negative yield impact in any of the trials. The third field experiment demonstrated that application of MgO did not result in significant accumulation of total and bioavailable Mg, Mn, Cu, or Zn in the root-associated soil and in soil farther away from the production bed compared to the water control. However, Cu bactericide contributed to significantly higher Mn, Cu, and Zn accumulation in the soil compared to water control (p = 0.05). This study demonstrates that MgO nanomaterial could be an alternative for Cu bactericide and have potential in reducing risks associated with development of tolerant strains and for reducing Cu load in the environment.

Low Concentrations of Silver Nanoparticles and Silver Ions Perturb the Antioxidant Defense System and Nitrogen Metabolism in N2-Fixing Cyanobacteria.

Although toxic effects of silver nanoparticles (AgNPs) on aquatic organisms have been extensively reported, responses of nitrogen-fixing cyanobacteria to AgNPs/Ag+ under environmentally relevant concentrations are largely unknown. Here, cyanobacteria were exposed to different concentrations of AgNPs (0.01, 0.1, and 1 mg/L) or Ag+ (0.1, 1, and 10 µg/L) for 96 h. The impacts of AgNPs and Ag+ on photosynthesis and N2 fixation in cyanobacteria (Nostoc sphaeroides) were evaluated. In addition, gas chromatography-mass spectrometry (GC-MS)-based metabolomics was employed to give an instantaneous snapshot of the physiological status of the cells under AgNP/Ag+ exposure. Exposure to high doses of AgNPs (1 mg/L) or Ag+ (10 µg/L) caused growth inhibition, reactive oxygen species overproduction, malondialdehyde accumulation, and decreased N2 fixation. In contrast, low doses of AgNPs (0.01 and 0.1 mg/L) and Ag+ (0.1 and 1 µg/L) did not induce observable responses. However, metabolomics revealed that metabolic reprogramming occurred even at low concentrations of AgNP and Ag+ exposure. Levels of a number of antioxidant defense-related metabolites, especially phenolic acid and polyphenols (gallic acid, resveratrol, isochlorogenic acid, chlorogenic acid, cinnamic acid, 3-hydroxybenzoic acid, epicatechin, catechin, and ferulic acid), significantly decreased in response to AgNPs or Ag+. This indicates that AgNPs and Ag+ can disrupt the antioxidant defense system and disturb nitrogen metabolism even at low-dose exposure. Metabolomics was shown to be a powerful tool to detect "invisible" changes, not observable by typical phenotypic-based endpoints.

C60 Fullerols Enhance Copper Toxicity and Alter the Leaf Metabolite and Protein Profile in Cucumber.

Abiotic and biotic stress induce the production of reactive oxygen species (ROS), which limit crop production. Little is known about ROS reduction through the application of exogenous scavengers. In this study, C60 fullerol, a free radical scavenger, was foliar applied to three-week-old cucumber plants (1 or 2 mg/plant) before exposure to copper ions (5 mg/plant). Results showed that C60 fullerols augmented Cu toxicity by increasing the influx of Cu ions into cells (170% and 511%, respectively, for 1 and 2 mg of C60 fullerols/plant). We further use metabolomics and proteomics to investigate the mechanism of plant response to C60 fullerols. Metabolomics revealed that C60 fullerols up-regulated antioxidant metabolites including 3-hydroxyflavone, 1,2,4-benzenetriol, and methyl trans-cinnamate, among others, while it down-regulated cell membrane metabolites (linolenic and palmitoleic acid). Proteomics analysis revealed that C60 fullerols up-regulated chloroplast proteins involved in water photolysis (PSII protein), light-harvesting (CAB), ATP production (ATP synthase), pigment fixation (Mg-PPIX), and electron transport ( Cyt b6f). Chlorophyll fluorescence measurement showed that C60 fullerols significantly accelerated the electron transport rate in leaves (13.3% and 9.4%, respectively, for 1 and 2 mg C60 fullerols/plant). The global view of the metabolic pathway network suggests that C60 fullerols accelerated electron transport rate, which induced ROS overproduction in chloroplast thylakoids. Plant activated antioxidant and defense pathways to protect the cell from ROS damaging. The revealed benefit (enhance electron transport) and risk (alter membrane composition) suggest a cautious use of C60 fullerols for agricultural application.

Short Total Synthesis of [15N5]-Cylindrospermopsins from 15NH4Cl Enables Precise Quantification of Freshwater Cyanobacterial Contamination.

Fresh water cyanobacterial algal blooms represent a major health risk because these organisms produce cylindrospermopsin, a toxic, structurally complex, zwitterionic uracil-guanidine alkaloid recognized by the EPA as a dangerous drinking water contaminant. At present, the ability to detect and quantify the presence of cylindrospermospin in water samples is severely hampered by the lack of an isotopically labeled standard for analytical mass spectrometry. Herein, we present a concise, scaled total synthesis of 15N cylindrospermosin from 15N ammonium chloride, which leverages a unique stereoselective intramolecular double conjugate addition step to assemble the tricyclic guanidine core. In addition to providing the first pure isotopically labeled probe for precise quantification of this potent biotoxin in fresh water sources, our results demonstrate how unique constraints associated with isotope incorporation compel novel solutions to synthesis design.

Metabolomics Reveals the Molecular Mechanisms of Copper Induced Cucumber Leaf ( Cucumis sativus) Senescence.

Excess copper may disturb plant photosynthesis and induce leaf senescence. The underlying toxicity mechanism is not well understood. Here, 3-week-old cucumber plants were foliar exposed to different copper concentrations (10, 100, and 500 mg/L) for a final dose of 0.21, 2.1, and 10 mg/plant, using CuSO4 as the Cu ion source for 7 days, three times per day. Metabolomics quantified 149 primary and 79 secondary metabolites. A number of intermediates of the tricarboxylic acid (TCA) cycle were significantly down-regulated 1.4-2.4 fold, indicating a perturbed carbohydrate metabolism. Ascorbate and aldarate metabolism and shikimate-phenylpropanoid biosynthesis (antioxidant and defense related pathways) were perturbed by excess copper. These metabolic responses occur even at the lowest copper dose considered although no phenotype changes were observed at this dose. High copper dose resulted in a 2-fold increase in phytol, a degradation product of chlorophyll. Polyphenol metabolomics revealed that some flavonoids were down-regulated, while the nonflavonoid 4-hydroxycinnamic acid and trans-2-hydroxycinnamic acid were significantly up-regulated 4- and 26-fold compared to the control. This study enhances current understanding of copper toxicity to plants and demonstrates that metabolomics profiling provides a more comprehensive view of plant responses to stressors, which can be applied to other plant species and contaminants.

Metabolomics Reveals How Cucumber ( Cucumis sativus) Reprograms Metabolites To Cope with Silver Ions and Silver Nanoparticle-Induced Oxidative Stress.

Due to their well-known antifungal activity, the intentional use of silver nanoparticles (AgNPs) as sustainable nanofungicides is expected to increase in agriculture. However, the impacts of AgNPs on plants must be critically evaluated to guarantee their safe use in food production. In this study, 4-week-old cucumber ( Cucumis sativus) plants received a foliar application of AgNPs (4 or 40 mg/plant) or Ag+ (0.04 or 0.4 mg/plant) for 7 days. Gas chromatography-mass spectrometry (GC-MS)=based nontarget metabolomics enabled the identification and quantification of 268 metabolites in cucumber leaves. Multivariate analysis revealed that all the treatments significantly altered the metabolite profile. Exposure to AgNPs resulted in metabolic reprogramming, including activation of antioxidant defense systems (upregulation of phenolic compounds) and downregulation of photosynthesis (upregulation of phytol). Additionally, AgNPs enhanced respiration (upregulation of tricarboxylic acid cycle intermediates), inhibited photorespiration (downregulation of glycine/serine ratio), altered membrane properties (upregulation of pentadecanoic and arachidonic acids, downregulation of linoleic and linolenic acids), and reduced inorganic nitrogen fixation (downregulation of glutamine and asparagine). Although Ag ions induced some of the same metabolic changes, alterations in the levels of carbazole, lactulose, raffinose, citraconic acid, lactamide, acetanilide, and p-benzoquinone were AgNP-specific. The results of this study offer new insight into the molecular mechanisms by which cucumber responds to AgNP exposure and provide important information to support the sustainable use of AgNPs in agriculture.

Interactions, Transformations, and Bioavailability of Nano-Copper Exposed to Root Exudates.

Due to the potential for interactions between crop plants and engineered nanomaterials (ENMs), there is increasing interest in understanding the bioavailability and effects of ENMs released into soil systems. Here, we investigate the influence of root exudates on the fate of ENMs from a thermodynamic perspective. Nano isothermal titration calorimetry was applied to determine thermodynamic parameters for the interaction between nanocopper (nCu) and synthetic root exudate (SRE) and its components (including sugars, organic acids, amino acids, and phenolic acids), as well as Cu2+ and SRE. The measured binding constant (Kd = 5.645 × 103 M-1) indicated strong interactions between nCu particles and SRE, as well as with individual organic acids. The interaction between Cu2+ and SRE was stronger (Kd = 7.181 × 104 M-1) but varies for the individual SRE components. nCu dissolution in the presence of SRE was the predominant interaction. In addition, SRE resulted in a complex transformation of nCu, where Cu2+, Cu+, and Cu0 were formed via oxidation and reduction. Plant-nCu exposure experiments indicate that the binding of SRE with nCu and dissolved Cu ions can significantly decrease Cu uptake and bioaccumulation in plants. nITC provides a fundamental thermodynamic understanding of interactions between nCu and plant root exudates, providing an important tool for understanding plant NP-interactions.

Rapid Life-Cycle Impact Screening Using Artificial Neural Networks.

The number of chemicals in the market is rapidly increasing, while our understanding of the life-cycle impacts of these chemicals lags considerably. To address this, we developed deep artificial neural network (ANN) models to estimate life-cycle impacts of chemicals. Using molecular structure information, we trained multilayer ANNs for life-cycle impacts of chemicals using six impact categories, including cumulative energy demand, global warming (IPCC 2007), acidification (TRACI), human health (Impact2000+), ecosystem quality (Impact2000+), and eco-indicator 99 (I,I, total). The application domain (AD) of the model was estimated for each impact category within which the model exhibits higher reliability. We also tested three approaches for selecting molecular descriptors and identified the principal component analysis (PCA) as the best approach. The predictions for acidification, human health, and the eco-indicator 99 model showed relatively higher performance with R2 values of 0.73, 0.71, and 0.87, respectively, while the global warming model had a lower R2 of 0.48. This study indicates that ANN models can serve as an initial screening tool for estimating life-cycle impacts of chemicals for certain impact categories in the absence of more reliable information. Our analysis also highlights the importance of understanding ADs for interpreting the ANN results.

Metabolomics Reveals Cu(OH)2 Nanopesticide-Activated Anti-oxidative Pathways and Decreased Beneficial Antioxidants in Spinach Leaves.

While the use of nanopesticides in modern agriculture continues to increase, their effects on crop plants are still poorly understood. Here, 4 week old spinach plants grown in an artificial medium were exposed via foliar spray to Cu(OH)2 nanopesticide (0.18 and 18 mg/plant) or Cu ions (0.15 and 15 mg/plant) for 7 days. A gas chromatography-time-of-flight-mass spectrometry metabolomics approach was applied to assess metabolic alterations induced by Cu(OH)2 nanopesticide in spinach leaves. Exposure to Cu(OH)2 nanopesticide and copper ions induced alterations in the metabolite profiles of spinach leaves. Compared to the control, exposure to 18 mg of Cu(OH)2 nanopesticide induced significant reduction (29-85%) in antioxidant or defense-associated metabolites including ascorbic acid, α-tocopherol, threonic acid, ß-sitosterol, 4-hydroxybutyric acid, ferulic acid, and total phenolics. The metabolic pathway for ascorbate and aldarate was disturbed in all exposed spinach plants (nanopesticide and Cu2+). Cu2+ is responsible for the reduction in antioxidants and perturbation of the ascorbate and aldarate metabolism. However, nitrogen metabolism perturbation was nanopesticide-specific. Spinach biomass and photosynthetic pigments were not altered, indicating that metabolomics can be a rapid and sensitive tool for the detection og earlier nanopesticide effects. Consumption of antioxidants during the antioxidant defense process resulted in reduction of the nutritional value of exposed spinach.

Assessing the Risk of Engineered Nanomaterials in the Environment: Development and Application of the nanoFate Model.

We developed a dynamic multimedia fate and transport model (nanoFate) to predict the time-dependent accumulation of metallic engineered nanomaterials (ENMs) across environmental media. nanoFate considers a wider range of processes and environmental subcompartments than most previous models and considers ENM releases to compartments (e.g., urban, agriculture) in a manner that reflects their different patterns of use and disposal. As an example, we simulated ten years of release of nano CeO2, CuO, TiO2, and ZnO in the San Francisco Bay area. Results show that even soluble metal oxide ENMs may accumulate as nanoparticles in the environment in sufficient concentrations to exceed the minimum toxic threshold in freshwater and some soils, though this is more likely with high-production ENMs such as TiO2 and ZnO. Fluctuations in weather and release scenario may lead to circumstances where predicted ENM concentrations approach acute toxic concentrations. The fate of these ENMs is to mostly remain either aggregated or dissolved in agricultural lands receiving biosolids and in freshwater or marine sediments. Comparison to previous studies indicates the importance of some key model aspects including climatic and temporal variations, how ENMs may be released into the environment, and the effect of compartment composition on predicted concentrations.

Dynamic Model for the Stocks and Release Flows of Engineered Nanomaterials.

Most existing life-cycle release models for engineered nanomaterials (ENM) are static, ignoring the dynamics of stock and flows of ENMs. Our model, nanoRelease, estimates the annual releases of ENMs from manufacturing, use, and disposal of a product explicitly taking stock and flow dynamics into account. Given the variabilities in key parameters (e.g., service life of products and annual release rate during use) nanoRelease is designed as a stochastic model. We apply nanoRelease to three ENMs (TiO2, SiO2 and FeOx) used in paints and coatings through seven product applications, including construction and building, household and furniture, and automotive for the period from 2000 to 2020 using production volume and market projection information. We also consider model uncertainties using Monte Carlo simulation. Compared with 2016, the total annual releases of ENMs in 2020 will increase by 34-40%, and the stock will increase by 28-34%. The fraction of the end-of-life release among total release flows will increase from 11% in 2002 to 43% in 2020. As compared to static models, our dynamic model predicts about an order of magnitude lower values for the amount of ENM released from this sector in the near-term while stock continues to build up in the system.

Interactions between Algal Extracellular Polymeric Substances and Commercial TiO2 Nanoparticles in Aqueous Media.

The implications of engineered nanomaterials (ENMs) in the environment are often investigated using pristine particles. However, there are several biogenic and geogenic materials in natural waters that interact with and modify the surface of ENMs, thereby influencing their fate and effects. Here we studied the influence of soluble extracellular polymeric substances (sEPS) produced by freshwater and marine algae on the surface properties and fate of three commercial TiO2 nanoparticles (nTiO2) with different coatings. Adsorption of sEPS by the various nTiO2 is dependent on particle surface area, intrinsic nTiO2 surface charge, and hydrophobicity. Interactions between sEPS and nTiO2 were driven by electrostatic interactions and chemical bonding (bridge-coordination) between the COO- group of sEPS and nTiO2. Charge reversal of positively charged nTiO2 was observed at pH 7 in the presence of 0.5 mg-C/L sEPS. In addition, the critical coagulation concentration (CCC) of nTiO2 increased in the presence of sEPS-from both freshwater and marine sources. CCC of all nTiO2 increased as sEPS concentrations increased. This study shows that naturally occurring sEPS can modify the surface properties and fate of nTiO2 in natural waters, and should be accounted for when predicting the fate and effects of engineered nanomaterials in the environment.