Development of alginate beads for precise environmental release applications: A design of experiment based approach and analysis.

Controlled release of active ingredients are important for drug delivery and more recently environmental applications including modulated dosing of chemical and biological controls. This study demonstrates the importance of investigating various material science factors that can influence the diffusion rates of alginate beads to improve and tune their performance for marine environmental applications. This investigation aimed to design a rational workflow to aid in leveraging alginate bead use as a carrier matrix for releasing a specific active agent into water. Experiments were conducted to focus on the narrow a large list of relevant material formulation parameters, which included chitosan molecular weight, chitosan concentration, calcium concentration, drop height, and bead size. Once the most relevant material preparation methods were screened, a more robust statistic Design of Experiments approach was performed and results determined the important (and unimportant) factors for increasing dye release kinetics in marine water. The process was further streamlined by narrowing the critical experimental factors to a three-level based on the prior analysis: chitosan MW, chitosan concentration, and bead size. Analysis of the collected data indicated that while chitosan MW had a negligible impact (Fstatistic = 0.22), bead size (Fstatistic = 60.33) significantly influenced the diffusion rates based on surface area. However, chitosan MW had minor effects where lower chitosan MW enabled higher product release rates. This case investigation was a novel application of the design of experiment approach towards environmental applications to understand differences in release rates to marine waters for the first time and the workflow provided also serve as the basis for researchers to optimize other environmental applications requiring optimization when it is unknown how a large number of formulation variables will impact performance in different environmental scenarios.

Additives influence 3D printer emission profiles: Implications for working safely with polymer filament composites.

It is critical to thoroughly investigate, characterize, and understand the unique emission profiles of common and novel polymer feedstocks used in fused filament fabrication (FFF) 3D printers as these products become increasingly ubiquitous in consumer and industrial environments. This work contributes unique insights regarding the effects of polymer composite feedstocks with metal, ceramic, or carbonaceous particle additives on particulate emissions in a variety of filaments under various print conditions, including print temperature. In addition to active characterization of particulate size and concentration following the ANSI/CAN/UL 2904 method, particulate sampling and subsequent analysis by scanning electron microscopy revealed agglomeration behavior that may have important health implications. Specifically, fine particles (0.3-2.5 µm) generated by certain filaments including acrylonitrile butadiene styrene (ABS) and glycol-modified poly(ethylene terephthalate) (PETG) are shown to be formed via agglomeration of emitted ultrafine particles rather than composed of coherent primary particles; accordingly, transport and behavior of these particulates after inhalation may not follow expected patterns for micrometer-sized particles. Structures resembling carbonaceous additives (e.g., graphene and nanotubes) were also captured by airborne sampling during printing of filaments containing carbonaceous advanced materials.

Effect of Activated Carbon in Thin Sand Caps Challenged with Ongoing PCB Inputs from Sediment Deposition: PCB Uptake in Clams (Mercenaria mercenaria) and Passive Samplers.

Ongoing inputs, in the form of sediment deposition along with associated dissolved contaminants, have challenged the assessment of cap performance at contaminated sediment sites. To address this issue, thin 2-3 cm layer sand caps amended with activated carbon (AC) were investigated for the remediation of polychlorinated biphenyl (PCB) contaminated marine sediments using 90-day mesocosms. All treatments were challenged with (1) ongoing clean or marker-PCB-spiked sediment inputs and (2) bioturbation. Bioaccumulation in hard clams (filter feeding near the cap-water interface) was evaluated to best understand cap effectiveness, relative to sheepshead minnows (confined to the surface water) and sandworms (which burrowed through the caps). All caps (sand and AC amended sand) provided isolation of native bedded PCBs (i.e., PCBs sourced from the bed), reducing uptake in organisms. Total PCB bioaccumulation in clams indicated that AC addition to the cap provided no benefit with spiked influx, or some benefit (56% reduction) with clean influx. Spiked input PCBs, when added to the depositional input sediment, were consistently detected in clams and passive samplers, with and without AC in the cap. PCB uptake by passive samplers located in the caps did not reflect the performance of the remedy, as defined by clam bioaccumulation. However, PCB uptake by passive samplers in the overlying water reasonably represented clam bioaccumulation results.

Prevention through design: insights from computational fluid dynamics modeling to predict exposure to ultrafine particles from 3D printing.

Fused filament fabrication (FFF) 3D printers are increasingly used in industrial, academic, military, and residential sectors, yet their emissions and associated user exposure scenarios are not fully described. Characterization of potential user exposure and environmental releases requires robust investigation. During operation, common FFF 3D printers emit varying amounts of ultrafine particles (UFPs) depending upon feedstock material and operation procedures. Volatile organic compounds associated with these emissions exhibit distinct odors; however, the UFP portion is largely imperceptible by humans. This investigation presents straightforward computational modeling as well as experimental validation to provide actionable insights for the proactive design of lower exposure spaces where 3D printers may be used. Specifically, data suggest that forced clean airflows may create lower exposure spaces, and that computational modeling might be employed to predict these spaces with reasonable accuracy to assist with room design. The configuration and positioning of room air ventilation diffusers may be a key factor in identifying lower exposure spaces. A workflow of measuring emissions during a printing process in an ANSI/CAN/UL 2904 environmental chamber was used to provide data for computational fluid dynamics (CFD) modeling of a 6 m2 room. Measurements of the particle concentrations in a Class 1000 clean room of identical geometry were found to pass the Hanna test for agreement between model and experimental data, validating the findings.

Different as night and day: Behavioural and life history responses to varied photoperiods in Daphnia magna.

Nearly all animal species have utilized photoperiod to cue seasonal behaviours and life history traits. We investigated photoperiod responses in keystone species, Daphnia magna, to identify molecular processes underlying ecologically important behaviours and traits using functional transcriptomic analyses. Daphnia magna were photoperiod-entrained immediately posthatch to a standard control photoperiod of 16 light/ 8 dark hours (16L:8D) relative to shorter (4L:20D, 8L:16D, 12L:12L) and longer (20L:4D) day length photoperiods. Short-day photoperiods induced significantly increased light-avoidance behaviours relative to controls. Correspondingly, significant differential transcript expression for genes involved in glutamate signalling was observed, a critical signalling pathway in arthropod light-avoidance behaviour. Additionally, period circadian protein and proteins coding F-box/LRR-repeat domains were differentially expressed which are recognized to establish circadian rhythms in arthropods. Indicators of metabolic rate increased in short-day photoperiods which corresponded with broadscale changes in transcriptional expression across system-level energy metabolism pathways. The most striking observations included significantly decreased neonate production at the shortest day length photoperiod (4L:20D) and significantly increased male production across short-day and equinox photoperiods (4L:20D, 8L:16D and 12L:12D). Transcriptional expression consistent with putative mechanisms of male production was observed including photoperiod-dependent expression of transformer-2 sex-determining protein and small nuclear ribonucleoprotein particles (snRNPs) which control splice variant expression for genes like transformer. Finally, increased transcriptional expression of glutamate has also been shown to induce male production in Daphnia pulex via photoperiod-sensitive mechanisms. Overall, photoperiod entrainment affected molecular pathways that underpin critical behavioural and life history traits in D. magna providing fundamental insights into biological responses to this primary environmental cue.

Uptake Kinetics and Trophic Transfer of Tungsten from Cabbage to a Herbivorous Animal Model.

This investigation builds on previous studies on military-relevant tungsten (W) to more thoroughly explore environmental pathways and bioaccumulation kinetics during direct soil exposure versus trophic transfer and elucidate its relative accumulation and speciation in different snail organs. The modeled steady-state concentration and bioaccumulation factor (BAF) of W from soil into cabbage were 302 mg/kg and 0.55, respectively. Steady-state concentrations (34 mg/kg) and BAF values (0.05) obtained for the snail directly exposed to contaminated soil were lower than trophic transfer by consumption of W-contaminated cabbage (tissue concentration of 86 mg/kg; BAF of 0.36). Thus, consumption of contaminated food is the most important pathway for W mobility in this food chain. The highest concentrations of W compartmentalization were in the snail's hepatopancreas based on wet chemistry and synchrotron-based investigations. Chemical speciation via inductively couple plasma mass spectrometry showed a higher degree of polytungstate partitioning in the hepatopancreas relative to the rest of the body. Based on synchrotron analysis, W was incorporated into the shell matrix during exposure, particularly during the regeneration of damaged shell. This offers the potential for application of the shell as a longer-term biomonitoring and forensics tool for historic exposure.

Effects of Suspended Sediment on Early Life Stages of Smallmouth Bass (Micropterus dolomieu).

The resuspension of sediments caused by activities, such as dredging operations, is a concern in Great Lakes harbors where multiple fish species spawn. To address such concerns, smallmouth bass (Micropterus dolomieu) were exposed to uncontaminated suspended sediment (nominally 0, 100, 250, and 500 mg/L) continuously for 72 h to determine the effects on egg-hatching success and swim-up fry survival and growth. The test sediments were collected from two harbors: (1) fine-grained sediment in Grand Haven Harbor, Lake Michigan, and (2) coarser-grained sediment in Fairport Harbor, Lake Erie. Eggs exposed to total suspended solids (TSS) concentrations >100 mg/L resulted in decreased survival of post-hatch larval fish. Fry survival was >90 % at the highest exposure concentration (500 mg/L), but growth was decreased when the exposure concentration was >100 mg/L. Growth and survival of swim-up fry held for a 7- and 26-day post-exposure the grow-out period was variable suggesting that the sediment grain size and strain of fish may influence lingering effects after the cessation of exposure. The results suggest that exposed eggs hatched normally; however, newly hatched larvae, which are temporarily immobile, are more vulnerable to the effects of suspended sediment. The swim-up fry were found to be more sensitive to high TSS concentrations in sandy relative to silty sediment. These data represent a conservative exposure scenario that can be extrapolated to high-energy systems in the field to inform management decisions regarding the necessity for dredging windows or need to implement controls to protect M. dolomieu.

Daphnia magna's sense of competition: intra-specific interactions (ISI) alter life history strategies and increase metals toxicity.

This work investigates whether the scale-up to multi-animal exposures that is commonly applied in genomics studies provides equivalent toxicity outcomes to single-animal experiments of standard Daphnia magna toxicity assays. Specifically, we tested the null hypothesis that intraspecific interactions (ISI) among D. magna have neither effect on the life history strategies of this species, nor impact toxicological outcomes in exposure experiments with Cu and Pb. The results show that ISI significantly increased mortality of D. magna in both Cu and Pb exposure experiments, decreasing 14 day LC50 s and 95 % confidence intervals from 14.5 (10.9-148.3) to 8.4 (8.2-8.7) µg Cu/L and from 232 (156-4810) to 68 (63-73) µg Pb/L. Additionally, ISI potentiated Pb impacts on reproduction eliciting a nearly 10-fold decrease in the no-observed effect concentration (from 236 to 25 µg/L). As an indication of environmental relevance, the effects of ISI on both mortality and reproduction in Pb exposures were sustained at both high and low food rations. Furthermore, even with a single pair of Daphnia, ISI significantly increased (p < 0.05) neonate production in control conditions, demonstrating that ISI can affect life history strategy. Given these results we reject the null hypothesis and conclude that results from scale-up assays cannot be directly applied to observations from single-animal assessments in D. magna. We postulate that D. magna senses chemical signatures of conspecifics which elicits changes in life history strategies that ultimately increase susceptibility to metal toxicity.

Advancing Risk Analysis for Nanoscale Materials: Report from an International Workshop on the Role of Alternative Testing Strategies for Advancement.

The Society for Risk Analysis (SRA) has a history of bringing thought leadership to topics of emerging risk. In September 2014, the SRA Emerging Nanoscale Materials Specialty Group convened an international workshop to examine the use of alternative testing strategies (ATS) for manufactured nanomaterials (NM) from a risk analysis perspective. Experts in NM environmental health and safety, human health, ecotoxicology, regulatory compliance, risk analysis, and ATS evaluated and discussed the state of the science for in vitro and other alternatives to traditional toxicology testing for NM. Based on this review, experts recommended immediate and near-term actions that would advance ATS use in NM risk assessment. Three focal areas-human health, ecological health, and exposure considerations-shaped deliberations about information needs, priorities, and the next steps required to increase confidence in and use of ATS in NM risk assessment. The deliberations revealed that ATS are now being used for screening, and that, in the near term, ATS could be developed for use in read-across or categorization decision making within certain regulatory frameworks. Participants recognized that leadership is required from within the scientific community to address basic challenges, including standardizing materials, protocols, techniques and reporting, and designing experiments relevant to real-world conditions, as well as coordination and sharing of large-scale collaborations and data. Experts agreed that it will be critical to include experimental parameters that can support the development of adverse outcome pathways. Numerous other insightful ideas for investment in ATS emerged throughout the discussions and are further highlighted in this article.

Relating suborganismal processes to ecotoxicological and population level endpoints using a bioenergetic model.

Ecological effects of environmental stressors are commonly evaluated using organismal or suborganismal data, such as standardized toxicity tests that characterize responses of individuals (e.g., mortality and reproduction) and a rapidly growing body of "omics" data. A key challenge for environmental risk assessment is relating such information to population dynamics. One approach uses dynamic energy budget (DEB) models that relate growth and reproduction of individuals to underlying flows of energy and elemental matter. We hypothesize that suborganismal information identifies DEB parameters that are most likely impacted by a particular stressor and that the DEB model can then project suborganismal effects on life history and population endpoints. We formulate and parameterize a model of growth and reproduction for the water flea Daphnia magna. Our model resembles previous generic bioenergetic models, but has explicit representation of discrete molts, an important feature of Daphnia life history. We test its ability to predict six endpoints commonly used in chronic toxicity studies in specified food environments. With just one adjustable parameter, the model successfully predicts growth and reproduction of individuals from a wide array of experiments performed in multiple laboratories using different clones of D. magna raised on different food sources. Fecundity is the most sensitive endpoint, and there is broad correlation between the sensitivities of fecundity and long-run growth rate, as is desirable for the default metric used in chronic toxicity tests. Under some assumptions, we can combine our DEB model with the Euler-Lotka equation to estimate longrun population growth rates at different food levels. A review of Daphnia gene-expression experiments on the effects of contaminant exposure reveals several connections to model parameters, in particular a general trend of increased transcript expression of genes involved in energy assimilation and utilization at concentrations affecting growth and reproduction. The sensitivity of fecundity to many model parameters was consistent with frequent generalized observations of decreased expression of genes involved in reproductive physiology, but interpretation of these observations requires further mechanistic modeling. We thus propose an approach based on generic DEB models incorporating few essential species-specific features for rapid extrapolation of ecotoxicogenomic assays for Daphnia-based population risk assessment.

Gaining a Critical Mass: A Dose Metric Conversion Case Study Using Silver Nanoparticles.

Mass concentration is the standard convention to express exposure in ecotoxicology for dissolved substances. However, nanotoxicology has challenged the suitability of the mass concentration dose metric. Alternative metrics often discussed in the literature include particle number, surface area, and ion release (kinetics, equilibrium). It is unlikely that any single metric is universally applicable to all types of nanoparticles. However, determining the optimal metric for a specific type of nanoparticle requires novel studies to generate supportive data and employ methods to compensate for current analytical capability gaps. This investigation generated acute toxicity data for two standard species (Ceriodaphnia dubia, Pimephales promelas) exposed to five sizes (10, 20, 30, 60, 100 nm) of monodispersed citrate- and polyvinylpyrrolidone-coated silver nanoparticles. Particles were sized by various techniques to populate available models for expressing the particle number, surface area, and dissolved fraction. Results indicate that the acute toxicity of the tested silver nanoparticles is best expressed by ion release, and is relatable to total exposed surface area. Particle number was not relatable to the observed acute silver nanoparticle effects.

Adapting OECD Aquatic Toxicity Tests for Use with Manufactured Nanomaterials: Key Issues and Consensus Recommendations.

The unique or enhanced properties of manufactured nanomaterials (MNs) suggest that their use in nanoenabled products will continue to increase. This will result in increased potential for human and environmental exposure to MNs during manufacturing, use, and disposal of nanoenabled products. Scientifically based risk assessment for MNs necessitates the development of reproducible, standardized hazard testing methods such as those provided by the Organisation of Economic Cooperation and Development (OECD). Currently, there is no comprehensive guidance on how best to address testing issues specific to MN particulate, fibrous, or colloidal properties. This paper summarizes the findings from an expert workshop convened to develop a guidance document that addresses the difficulties encountered when testing MNs using OECD aquatic and sediment test guidelines. Critical components were identified by workshop participants that require specific guidance for MN testing: preparation of dispersions, dose metrics, the importance and challenges associated with maintaining and monitoring exposure levels, and the need for reliable methods to quantify MNs in complex media. To facilitate a scientific advance in the consistency of nanoecotoxicology test results, we identify and discuss critical considerations where expert consensus recommendations were and were not achieved and provide specific research recommendations to resolve issues for which consensus was not reached. This process will enable the development of prescriptive testing guidance for MNs. Critically, we highlight the need to quantify and properly interpret and express exposure during the bioassays used to determine hazard values.

Gill histopathologies following exposure to nanosilver or silver nitrate.

Fish gill is the site for many crucial physiological functions. It is among the first sites of xenobiotic exposure, and gill histopathological alterations may be detected soon after toxicant exposure. Silver (Ag) is one of the most toxic metals to aquatic organisms mainly due to its ability to disrupt ionic regulation. The goal of this study was to determine the effect of ionic and nanoscale Ag on fathead minnow gills by examining gill histology and Na(+)/K(+)-ATPase immunoreactivity. Fathead minnows were exposed to two measured concentrations of silver nitrate (AgNO3: 1.3 or 3.7 µg/L as Ag(+)), citrate silver nanoparticles (citrate-AgNP: 15 or 39 µg/L), and polyvinylpyrrolidone-AgNP (PVP-AgNP) (AgNP: 11 or 50 µg/L). Circulatory disturbances were the most prevalent gill alterations detected and were significantly increased in all Ag treatment groups compared to control. AgNO3 (1.3 µg/L) was the only treatment that significantly elevated the number of total mucous goblet cells present. In all other Ag treatments, the percent of degenerated goblet cells was significantly increased compared to control. When the sum of all histopathological abnormalities (weighted index) was calculated, all Ag groups displayed a significantly higher index, with citrate-AgNP having the highest toxicity (index of 10 ± 0.32 versus 2.4 ± 0.6 in controls). Gill Na(+)/K(+)-ATPase immunoreactivity was decreased by Ag. These results indicated that both AgNO3 and AgNP created similar disruptions in gill structure and ionic regulation, possibly due to the ionic Ag portion of each treatment.

SeqAssist: a novel toolkit for preliminary analysis of next-generation sequencing data.

BACKGROUND: While next-generation sequencing (NGS) technologies are rapidly advancing, an area that lags behind is the development of efficient and user-friendly tools for preliminary analysis of massive NGS data. As an effort to fill this gap to keep up with the fast pace of technological advancement and to accelerate data-to-results turnaround, we developed a novel software package named SeqAssist ("Sequencing Assistant" or SA). RESULTS: SeqAssist takes NGS-generated FASTQ files as the input, employs the BWA-MEM aligner for sequence alignment, and aims to provide a quick overview and basic statistics of NGS data. It consists of three separate workflows: (1) the SA_RunStats workflow generates basic statistics about an NGS dataset, including numbers of raw, cleaned, redundant and unique reads, redundancy rate, and a list of unique sequences with length and read count; (2) the SA_Run2Ref workflow estimates the breadth, depth and evenness of genome-wide coverage of the NGS dataset at a nucleotide resolution; and (3) the SA_Run2Run workflow compares two NGS datasets to determine the redundancy (overlapping rate) between the two NGS runs. Statistics produced by SeqAssist or derived from SeqAssist output files are designed to inform the user: whether, what percentage, how many times and how evenly a genomic locus (i.e., gene, scaffold, chromosome or genome) is covered by sequencing reads, how redundant the sequencing reads are in a single run or between two runs. These statistics can guide the user in evaluating the quality of a DNA library prepared for RNA-Seq or genome (re-)sequencing and in deciding the number of sequencing runs required for the library. We have tested SeqAssist using a synthetic dataset and demonstrated its main features using multiple NGS datasets generated from genome re-sequencing experiments. CONCLUSIONS: SeqAssist is a useful and informative tool that can serve as a valuable "assistant" to a broad range of investigators who conduct genome re-sequencing, RNA-Seq, or de novo genome sequencing and assembly experiments.

Differential effects and potential adverse outcomes of ionic silver and silver nanoparticles in vivo and in vitro.

Nanoparticles are of concern because of widespread use, but it is unclear if metal nanoparticles cause effects directly or indirectly. We explored whether polyvinylpyrrolidone-coated silver nanoparticles (PVP-AgNPs) cause effects through intact nanoparticles or dissolved silver. Females of the model species fathead minnow (Pimephales promelas) were exposed to either 4.8 µg/L of AgNO3 or 61.4 µg/L of PVP-AgNPs for 96h. Microarray analyses were used to identify impacted receptors and toxicity pathways in liver and brain tissues that were confirmed using in vitro mammalian assays. AgNO3 and PVP-AgNP exposed fish had common and distinct effects consistent with both intact nanoparticles and dissolved silver causing effects. PVP-AgNPs and AgNO3 both affected pathways involved in Na(+), K(+), and H(+) homeostasis and oxidative stress but different neurotoxicity pathways. In vivo effects were supported by PVP-AgNP activation of five in vitro nuclear receptor assays and inhibition of ligand binding to the dopamine receptor. AgNO3 inhibited ligand binding to adrenergic receptors α1 and α2 and cannabinoid receptor CB1, but had no effect in nuclear receptor assays. PVP-AgNPs have the potential to cause effects both through intact nanoparticles and metal ions, each interacting with different initiating events. Since the in vitro and in vivo assays examined here are commonly used in human and ecological hazard screening, this work suggests that environmental health assessments should consider effects of intact nanoparticles in addition to dissolved metals.

Survival, Growth, and Reproduction Responses in a Three-Generation Exposure of the Zebrafish (Danio rerio) to Perfluorooctane Sulfonate.

A prior multigenerational perfluorooctane sulfonic acid (PFOS) exposure investigation in zebrafish reported adverse effects at 0.734 µg/L, among the lowest aquatic effect levels for PFOS reported to date. The present three-generation PFOS exposure quantified survival, growth, reproduction, and vitellogenin (VTG; egg yolk protein) responses in zebrafish, incorporating experimental design and procedural improvements relative to the earlier study. Exposures targeting 0.1, 0.6, 3.2, 20, and 100 µg/L in parental (P) and first filial (F1) generations lasted for 180 days post fertilization (dpf) and the second filial generation (F2) through 16 dpf. Survival decreased significantly in P and F2 generation exposures, but not in F1, at the highest PFOS treatment (100 µg/L nominal, 94-205 µg/L, measured). Significant adverse effects on body weight and length were infrequent, of low magnitude, and occurred predominantly at the highest exposure treatment. Finally, PFOS had no significant effects on P or F1 egg production and survival or whole-body VTG levels in P or F1 male fish. Overall, the predominance and magnitude of adverse PFOS effects at <1 µg/L reported in prior research were largely nonrepeatable in the present study. In contrast, the present study indicated a threshold for ecologically relevant adverse effects in zebrafish at 117 µg/L (SE 8 µg/L, n = 10) for survival and 47 µg/L (SE 11 µg/L, n = 19) for all statistically significant negative effects observed. Environ Toxicol Chem 2024;43:115-131. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Extraction and analysis of silver and gold nanoparticles from biological tissues using single particle inductively coupled plasma mass spectrometry.

Expanded use of engineered nanoparticles (ENPs) in consumer products increases the potential for environmental release and unintended biological exposures. As a result, measurement techniques are needed to accurately quantify ENP size, mass, and particle number distributions in biological matrices. This work combines single particle inductively coupled plasma mass spectrometry (spICPMS) with tissue extraction to quantify and characterize metallic ENPs in environmentally relevant biological tissues for the first time. ENPs were extracted from tissues via alkaline digestion using tetramethylammonium hydroxide (TMAH). Method development was performed using ground beef and was verified in Daphnia magna and Lumbriculus variegatus . ENPs investigated include 100 and 60 nm Au and Ag stabilized by polyvynylpyrrolidone (PVP). Mass- and number-based recovery of spiked Au and Ag ENPs was high (83-121%) from all tissues tested. Additional experiments suggested ENP mixtures (60 and 100 nm Ag ENPs) could be extracted and quantitatively analyzed. Biological exposures were also conducted to verify the applicability of the method for aquatic organisms. Size distributions and particle number concentrations were determined for ENPs extracted from D. magna exposed to 98 µg/L 100 nm Au and 4.8 µg/L 100 nm Ag ENPs. The D. magna nanoparticulate body burden for Au ENP uptake was 613 ± 230 µg/kgww, while the measured nanoparticulate body burden for D. magna exposed to Ag ENPs was 59 ± 52 µg/kgww. Notably, the particle size distributions determined from D. magna tissues suggested minimal shifts in the size distributions of ENPs accumulated, as compared to the exposure media.

Fate and toxicity of CuO nanospheres and nanorods used in Al/CuO nanothermites before and after combustion.

Although nanotechnology advancements should be fostered, the environmental health and safety (EHS) of nanoparticles used in technologies must be quantified simultaneously. However, most EHS studies assess the potential implications of the free nanoparticles which may not be directly applicable to the EHS of particles incorporated into in-use technologies. This investigation assessed the aquatic toxicological implications of copper oxide (CuO) nanospheres relative to CuO nanorods used in nanoenergetic applications to improve combustion. Particles were tested in both the as-received form and following combustion of a CuO/aluminum nanothermite. Results indicated nanospheres were more stable in water and slowly released ions, while higher surface area nanorods initially released more ions and were more toxic but generally less stable. After combustion, particles sintered into larger, micrometer-scale aggregates, which may lower toxicity potential to pelagic organisms due to deposition from water to sediment and reduced bioavailability after complexation with sediment organic matter. Whereas the larger nanothermite residues settled rapidly, implying lower persistence in water, their potential to release dissolved Cu was higher which led to greater toxicity to Ceriodaphnia dubia relative to parent CuO material (nanosphere or rod). This study illustrates the importance of considering the fate and toxicology of nanoparticles in context with their relevant in-use applications.

Impact of organic carbon on the stability and toxicity of fresh and stored silver nanoparticles.

Studies investigating the impact of particle size and capping agents on nanosilver toxicity in pristine laboratory conditions are becoming available. However, the relative importance of known environmental mitigating factors for dissolved silver remains poorly characterized for nanosilver in context with existing predictive toxicity models. This study investigated the implications of freshly prepared versus stored 20 and 100 nm nanosilver stocks to freshwater zooplankton (Ceriodaphnia dubia) in presence and absence of dissolved organic carbon (DOC). Results indicated that while the acute toxicity of nanosilver decreased significantly with larger size and higher DOC, storage resulted in significant increases in toxicity and ion release. The most dramatic decrease in toxicity due to DOC was observed for the 20 nm particle (2.5-6.7 fold decrease), with more modest toxicity reductions observed for the 100 nm particle (2.0-2.4 fold) and dissolved silver (2.7-3.1 fold). While a surface area dosimetry presented an improvement over mass when DOC was absent, the presence of DOC confounded its efficacy. The fraction of dissolved silver in the nanosilver suspensions was most predictive of acute toxicity regardless of system complexity. Biotic Ligand Model (BLM) predictions based on the dissolved fraction in nanosilver suspensions were comparable to observed toxicity.

Assessment of chemical mixtures and groundwater effects on Daphnia magna transcriptomics.

Small organisms can be used as biomonitoring tools to assess chemicals in the environment. Chemical stressors are especially hard to assess and monitor when present as complex mixtures. Here, fifteen polymerase chain reaction assays targeting Daphnia magna genes were calibrated to responses elicited in D. magna exposed for 24 h to five different doses each of the munitions constituents 2,4,6-trinitrotoluene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, trinitrobenzene, dinitrobenzene, or 1,3,5-trinitro-1,3,5-triazacyclohexane. A piecewise-linear model for log-fold expression changes in gene assays was used to predict response to munitions mixtures and contaminated groundwater under the assumption that chemical effects were additive. The correlations of model predictions with actual expression changes ranged from 0.12 to 0.78 with an average of 0.5. To better understand possible mixture effects, gene expression changes from all treatments were compared using high-density microarrays. Whereas mixtures and groundwater exposures had genes and gene functions in common with single chemical exposures, unique functions were also affected, which was consistent with the nonadditivity of chemical effects in these mixtures. These results suggest that, while gene behavior in response to chemical exposure can be partially predicted based on chemical exposure, estimation of the composition of mixtures from chemical responses is difficult without further understanding of gene behavior in mixtures. Future work will need to examine additive and nonadditive mixture effects using a much greater range of different chemical classes in order to clarify the behavior and predictability of complex mixtures.