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.

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.

Interlaboratory Study of Polyethylene and Polydimethylsiloxane Polymeric Samplers for Ex Situ Measurement of Freely Dissolved Hydrophobic Organic Compounds in Sediment Porewater.

We evaluated the precision and accuracy of multilaboratory measurements for determining freely dissolved concentrations (Cfree ) of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in sediment porewater using polydimethylsiloxane (PDMS) and low-density polyethylene (LDPE) polymeric samplers. Four laboratories exposed performance reference compound (PRC) preloaded polymers to actively mixed and static ex situ sediment for approximately 1 month; two laboratories had longer exposures (2 and 3 months). For Cfree results, intralaboratory precision was high for single compounds (coefficient of variation 50% or less), and for most PAHs and PCBs interlaboratory variability was low (magnitude of difference was a factor of 2 or less) across polymers and exposure methods. Variability was higher for the most hydrophobic PAHs and PCBs, which were present at low concentrations and required larger PRC-based corrections, and also for naphthalene, likely due to differential volatilization losses between laboratories. Overall, intra- and interlaboratory variability between methods (PDMS vs. LDPE, actively mixed vs. static exposures) was low. The results that showed Cfree polymer equilibrium was achieved in approximately 1 month during active exposures, suggesting that the use of PRCs may be avoided for ex situ analysis using comparable active exposure; however, such ex situ testing may not reflect field conditions. Polymer-derived Cfree concentrations for most PCBs and PAHs were on average within a factor of 2 compared with concentrations in isolated porewater, which were directly measured by one laboratory; difference factors of up to 6 were observed for naphthalene and the most hydrophobic PAHs and PCBs. The Cfree results were similar for academic and private sector laboratories. The accuracy and precision that we demonstrate for determination of Cfree using polymer sampling are anticipated to increase regulatory acceptance and confidence in use of the method. Environ Toxicol Chem 2022;41:1885-1902. © 2022 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.

Effect of UV-light exposure duration, light source, and aging on nitroguanidine (NQ) degradation product profile and toxicity.

Previous studies have reported increased aquatic toxicity of UV-degraded nitroguanidine (NQ), but many details underlying the dynamics of NQ degradation and toxicity remain unknown. These data gaps represent critical barriers to assessing the environmental relevance of laboratory-generated UV-degradation results and extrapolation to environmental risk. In the present study, the toxicity of NQ increased with increasing proportional degradation of the parent compound. Specifically, while the LC50 of undegraded NQ was 1485 mg/L, the toxicity at the lowest degradation level examined (7% parent compound degraded) increased by nearly two-orders of magnitude (LC50 = 17.3 mg/L) and increased by nearly three-orders of magnitude (LC50 = 6.23 mg/L) in the highest percent NQ degradation (90%) treatment. Similar LC50 values between immediately tested and aged (8-13 days) NQ degradation products suggested the degradation product(s) causing the toxicity were stable, although concentrations of nitrite and nitrate increased after aging. Finally, experiments where NQ was degraded in natural sunlight confirmed increased toxicity in environmentally relevant D. pulex exposures; however, the two-order of magnitude increase in toxicity (LC50 = 21.3 mg/L) at 53% degradation was less than NQ degraded by a laboratory photoreactor by a similar percentage (46% degraded). Identification of principal toxic agents in the UV-degraded NQ product mixture remains a critical data gap. Mass balance calculations were generated for our experimental results and literature values revealing difficulty in accounting for all NQ degradation products. Products with suspected high potency in D. pulex were identified which require further testing including: nitrosoguanidine, nitrosourea, and hydroxylamine. SYNOPSIS: The toxicity of NQ increased with increasing UV-degradation where toxicity-inducing degradation products were stable over 1-2 weeks; increased toxicity was validated from natural-sunlight degradation of NQ, however toxicity was lower than UV-photoreactor degraded NQ; and the identity of specific toxic UV-degradation products remains elusive where carefully-designed mass-balance experiments and toxicity testing are needed to provide definitive identification.

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.

Comparative Toxicological Evaluation of UV-Degraded versus Parent-Insensitive Munition Compound 1-Methyl-3-Nitroguanidine in Fathead Minnow.

The US Army is replacing traditional munitions with insensitive munitions resistant to accidental detonation. Although the parent insensitive munition compound nitroguanidine (NQ) is generally not acutely toxic at concentrations >1000 mg/L in aquatic exposures, products formed by intensive ultraviolet (UV) degradation resulted in multiple-order of magnitude increases in toxicity. A methylated congener of NQ, 1-methyl-3-nitroguanidine (MeNQ), is also being assessed for potential use in insensitive munition explosive formulations; therefore, the present study investigated the hazard of parent versus UV-degraded MeNQ using fathead minnows (Pimephales promelas). Although up to 716 mg/L parent MeNQ caused no significant mortality or effects on growth in larval P. promelas fish in 7-d exposures, a similar concentration of MeNQ subjected to UV treatment resulted in 85% mortality. The UV treatment degraded only 3.3% of the MeNQ (5800 mg/L stock, UV-treated for 6 h), indicating that MeNQ degradation products have potentially high toxicity. The parent MeNQ exposure caused significantly decreased transcriptional expression of genes within the significantly enriched insulin metabolic pathway, suggesting antagonism of bioenergetics pathways, which complements observed, although nonsignificant, decreases in body weight. Significant differential transcriptional expression in the UV-degraded MeNQ treatments resulted in significant enrichment of pathways and functions related to the cell cycle, as well as erythrocyte function involved in O2 /CO2 exchange. These functions represent potential mechanistic sources of increased toxicity observed in the UV-degraded MeNQ exposures, which are distinct from previously observed mechanisms underlying increased toxicity of UV-degraded NQ in fish. Environ Toxicol Chem 2020;39:612-622. © 2019 SETAC.

Identifying degradation products responsible for increased toxicity of UV-Degraded insensitive munitions.

Degradation of insensitive munitions (IMs) by ultraviolet (UV) light has become a topic of concern following observations that some UV-degradation products have increased toxicity relative to parent compounds in aquatic organisms. The present investigation focused on the Army's IM formulation, IMX-101, which is composed of three IM constituents: 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ). The IM constituents and IMX-101 were irradiated in a UV photo-reactor and then administered to Daphnia pulex in acute (48 h) exposures comparing toxicities relative to the parent materials. UV-degradation of DNAN had little effect on mortality whereas mortality for UV-degraded NTO and NQ (and associated degradation products) increased by factors of 40.3 and 1240, respectively, making UV-degraded NQ the principle driver of toxicity when IMX-101 is UV-degraded. Toxicity investigations for specific products formed during UV-degradation of NQ, confirmed greater toxicity than the parent NQ for degradation products including guanidine, nitrite, ammonia, nitrosoguanidine, and cyanide. Summation of the individual toxic units for the complete set of individually measured UV-degradation products identified for NQ only accounted for 25% of the overall toxicity measured in the exposures to the UV-degraded NQ product mixture. From these toxic unit calculations, nitrite followed by CN- were the principal degradation products contributing to toxicity. Given the underestimation of toxicity using the sum toxic units for the individually measured UV-degradation products of NQ, we conclude that: (1) other unidentified NQ degradation products contributed principally to toxicity and/or (2) synergistic toxicological interactions occurred among the NQ degradation product mixture that exacerbated toxicity.

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.

Bioaccumulation in Functionally Different Species: Ongoing Input of PCBs with Sediment Deposition to Activated Carbon Remediated Bed Sediments.

Activated carbon-amended bed sediments reduced total polychlorinated biphenyl (PCB) accumulation in 3 functionally different marine species, sandworms (Alitta virens), hard clams (Mercenaria mercenaria), and sheepshead minnows (Cyprinodon variegatus), during both clean and contaminated ongoing sediment inputs. Mesocosm experiments were conducted for 90 d to evaluate native, field-aged bed sediment PCBs, and ongoing input PCBs added 3 times a week. Simulated in situ remediation applied an activated carbon dose equal to the native organic carbon content that was premixed into the bed sediment for 1 mo. The highest bioaccumulation of native PCBs was in worms that remained in and directly ingested the sediment, whereas the highest bioaccumulation of the input PCBs was in fish that were exposed to the water column. When periodic PCB-contaminated sediment inputs were introduced to the water column, the activated carbon remedy had minimal effect on the input PCBs, whereas the native bed PCBs still dominated bioaccumulation in the control (no activated carbon). Therefore, remediation of only the local bedded sediment in environmental systems with ongoing contaminant inputs may have lower efficacy for fish and other pelagic and epibenthic organisms. While ongoing inputs continue to obscure remedial outcomes at contaminated sediment sites, the present study showed clear effectiveness of activated carbon amendment remediation on native PCBs despite these inputs but no remediation effectiveness for the input-associated PCBs (at least within the present study duration). Environ Toxicol Chem 2019;38:2326-2336. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Sensitivity of the Marine Calanoid Copepod Pseudodiaptomus pelagicus to Copper, Phenanthrene, and Ammonia.

There are limited acute toxicity test methods for native North American marine species that are considered zooplankton for their entire life cycle. Examples of standardized marine zooplankton methods include mussel, bivalve, and echinoderm development tests that use a relatively short-lived planktonic larval stage, chronic life-cycle toxicity tests using epibenthic copepods, and a 24-h Acartia tonsa copepod test method. The objectives of the present study were to: 1) develop and evaluate a novel, 48-h acute toxicity test method using the marine North American copepod Pseudodiaptomus pelagicus that is planktonic for its entire life cycle, and 2) determine the sensitivity of P. pelagicus relative to commonly tested marine toxicity test species. The average (±1 standard deviation) median lethal concentrations (LC50s) for copper (Cu), phenanthrene, and un-ionized ammonia were 32 ± 15 µg/L, 161 ± 51 µg/L, and 1.08 ± 0.30 mg NH3 /L, respectively. These results placed P. pelagicus on the more sensitive end of Cu and phenanthrene species sensitivity distributions. The copepod was less sensitive to un-ionized ammonia than commonly tested marine species. This finding suggests that the acute P. pelagicus test method will allow a focus on assessing the impacts of persistent contaminants of concern with less confounding impact from naturally occurring ammonia released to the water from sources such as suspended sediments. Environ Toxicol Chem 2019;38:1221-1230. Published 2019 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Effects of soot by-product from the synthesis of engineered metallofullerene nanomaterials on terrestrial invertebrates.

The synthesis of carbon-based nanomaterials is often inefficient, generating large amounts of soot with metals as waste by-product. Currently, there are no specific regulations for disposal of engineered nanomaterials or the waste by-products resulting from their synthesis, so it is presumed that by-products are disposed of in the same way as the parent (bulk) materials. We studied the terrestrial toxicity of soot from gadolinium metallofullerene nanomanufacturing on earthworms (Eisenia fetida) and isopods (Porcellio scaber). The metallofullerene soot consisted of carbon particle agglomerates in the nanometer and submicrometer ranges (1-100 and 101-999 nm, respectively), with metals used during nanomanufacturing detectable on the particles. Despite high metal concentrations (>100 000 mg/kg) in the soot, only a relatively small amount of metals leached out of a spiked field soil, suggesting only moderate mobility. Seven- and 14-d exposures in field soil demonstrated that the soot was only toxic to earthworms at high concentrations (>10 000 mg/kg); however, earthworms avoided spiked soils at lower concentrations (as low as 500 mg/kg) and at lower soil pH. The presence of soot in food and soil did not cause isopod avoidance. These data demonstrate that metallofullerene soot from nanomanufacturing may only be toxic to earthworms at high concentrations representative of improper disposal or accidental spills. However, our results indicate that terrestrial invertebrates may avoid soils contaminated with soot at sublethal concentrations. Environ Toxicol Chem 2018;9999:1-12. Published 2018 Wiley Periodicals, Inc. on behalf of SETAC. This article is a US government work, and as such, is in the public domain in the United States of America.

Comparison of acute to chronic ratios between silver and gold nanoparticles, using Ceriodaphnia dubia.

As integration of nanoparticles (NPs) into products becomes more common, the need to address the paucity of chronic hazard information for aquatic environments required to determine risk potential increases. This study generated acute and chronic toxicity reference values for Ceriodaphnia dubia exposed to 20 and 100 nm silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) to generate and evaluate potential differences in acute-to-chronic ratios (ACR) using two different feeding methods. A modified feeding procedure was employed alongside the standard procedures to investigate the influence of food on organism exposure. An 8-h period before food was added allowed direct organism exposure to NP dispersions (and associated ions) without food-to-NP interactions. The AgNPs [chronic lethal median concentrations (LC50) between 18.7 and 31.9 µg/L] were substantially more toxic than AuNPs (LC50 = 21 507 to >26 384 µg/L). The modified chronic testing method resulted in greater sensitivity in AgNPs exposures. However, the modified feeding ration had less of an effect in exposures to the larger (100 nm) AgNPs compared to smaller particles (20 nm). The ACRs for AgNPs using the standard feeding ration were 1.6 and 3.5 for 20 nm and 100 nm, respectively. The ACRs for AgNPs using the modified feeding ration were 3.4 and 7.6 for 20 nm and 100 nm NPs, respectively. This supports that the addition of the standard feeding ration decreases C. dubia chronic sensitivity to AgNPs, although it must also be recognized organisms may be sensitized due to less access to food. The ACRs for 20 nm and 100 nm AuNPs (standard ration only) were 4.0 and 3.0, respectively. It is important to also consider that dissolved Ag+ ions are more toxic than AgNPs, based on both acute toxicity values in the cited literature and chronic toxicity thresholds generated in this study that support existing thresholds that Ag+ are likely protective of AgNPs effects.

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.

Integrate life-cycle assessment and risk analysis results, not methods.

Two analytic perspectives on environmental assessment dominate environmental policy and decision-making: risk analysis (RA) and life-cycle assessment (LCA). RA focuses on management of a toxicological hazard in a specific exposure scenario, while LCA seeks a holistic estimation of impacts of thousands of substances across multiple media, including non-toxicological and non-chemically deleterious effects. While recommendations to integrate the two approaches have remained a consistent feature of environmental scholarship for at least 15 years, the current perception is that progress is slow largely because of practical obstacles, such as a lack of data, rather than insurmountable theoretical difficulties. Nonetheless, the emergence of nanotechnology presents a serious challenge to both perspectives. Because the pace of nanomaterial innovation far outstrips acquisition of environmentally relevant data, it is now clear that a further integration of RA and LCA based on dataset completion will remain futile. In fact, the two approaches are suited for different purposes and answer different questions. A more pragmatic approach to providing better guidance to decision-makers is to apply the two methods in parallel, integrating only after obtaining separate results.

The increased toxicity of UV-degraded nitroguanidine and IMX-101 to zebrafish larvae: Evidence implicating oxidative stress.

Insensitive munitions (IMs) improve soldier safety by decreasing sympathetic detonation during training and use in theatre. IMs are being increasingly deployed, although the environmental effects of IM constituents such as nitroguanidine (NQ) and IM mixture formulations such as IMX-101 remain largely unknown. In the present study, we investigated the acute (96h) toxicity of NQ and IMX-101 to zebrafish larvae (21d post-fertilization), both in the parent materials and after the materials had been irradiated with environmentally-relevant levels of ultraviolet (UV) light. The UV-treatment increased the toxicity of NQ by 17-fold (LC50 decreased from 1323mg/L to 77.2mg/L). Similarly, UV-treatment increased the toxicity of IMX-101 by nearly two fold (LC50 decreased from 131.3 to 67.6mg/L). To gain insight into the cause(s) of the observed UV-enhanced toxicity of the IMs, comparative molecular responses to parent and UV-treated IMs were assessed using microarray-based global transcript expression assays. Both gene set enrichment analysis (GSEA) and differential transcript expression analysis coupled with pathway and annotation cluster enrichment were conducted to provide functional interpretations of expression results and hypothetical modes of toxicity. The parent NQ exposure caused significant enrichment of functions related to immune responses and proteasome-mediated protein metabolism occurring primarily at low, sublethal exposure levels (5.5 and 45.6mg/L). Enriched functions in the IMX-101 exposure were indicative of increased xenobiotic metabolism, oxidative stress mitigation, protein degradation, and anti-inflammatory responses, each of which displayed predominantly positive concentration-response relationships. UV-treated NQ had a fundamentally different transcriptomic expression profile relative to parent NQ causing positive concentration-response relationships for genes involved in oxidative-stress mitigation pathways and inhibited expression of multiple cadherins that facilitate zebrafish neurological and retinal development. Transcriptomic profiles were similar between UV-treated versus parent IMX-101 exposures. However, more significant and diverse enrichment as well as greater magnitudes of differential expression for oxidative stress responses were observed in UV-treated IMX-101 exposures. Further, transcriptomics indicated potential for cytokine signaling suppression providing potential connections between oxidative stress and anti-inflammatory responses. Given the overall results, we hypothesize that the increased toxicity of UV-irradiated NQ and the IMX-101 mixture result from breakdown products with elevated potential to elicit oxidative stress.

Assessing nanomaterial exposures in aquatic ecotoxicological testing: Framework and case studies based on dispersion and dissolution.

The unique behavior of engineered nanomaterials (ENM) in aqueous media and dynamic changes in particle settling, agglomeration and dissolution rates is a challenge to the consistency, reliability and interpretation of standard aquatic hazard bioassay results. While the toxicological endpoints (e.g., survival, growth, reproduction, etc.) in ecotoxicity bioassays are largely applicable to ENMs, the standard methods as written for dissolved substances are confounded by the dynamic settling, agglomeration and dissolution of particulate ENMs during the bioassay. A testing framework was designed to serve as a starting point to identify approaches for the consistent conduct of aquatic hazard tests that account for the behavior of ENMs in test media and suitable data collection to support representative exposure metrology. The framework was demonstrated by conducting three case studies testing ENMs with functionally distinct characteristics and behaviors. Pretests with a temporal sampling of particle concentration, agglomeration and dissolution were conducted on each ENM in test media. Results indicated that a silver nanoparticle (AgNP) powder was not dispersible, a nano-TiO2 powder was dispersible but unstable, and a polyvinylpyrrolidinone-coated AgNP was relatively stable in test media. Based on these functional results, Ceriodaphnia dubia bioassays were conducted to compare different exposure summary methods (nominal, arithmetic average, geometric average, time-weighted average) for calculating and expressing toxicity endpoints. Results indicated that while arithmetic means were effective for expressing the toxicity of more stable materials, time-weighted averaged concentrations were appropriate for the unstable nano-TiO2.

Aquatic toxicity of photo-degraded insensitive munition 101 (IMX-101) constituents.

Insensitive munitions are desirable alternatives to historically used formulations, such as 2,4,6-trinitrotoluene (TNT), because of their so-called insensitivity to unintended detonation. The insensitive munition IMX-101 is a mixture of 2,4-dinitroanisole (DNAN), 3-nitro-1,2,4-triazol-5-one (NTO), and nitroguanidine (NQ). Environmental releases of munitions may be from production wastewaters or training; these munitions may be exposed to ultraviolet (UV) light. Therefore, it is useful to understand the relative toxicity of IMX-101 and its constituents both before and after photodegradation. The intent of the present study was to generate relative hazard information by exposing the standard ecotoxicological model Ceriodaphnia dubia to each insensitive munition constituent individually and to IMX-101 before and after the exposure solution was irradiated in a UV photoreactor. Without photodegradation, DNAN was more toxic (median lethal concentration [LC50] = 43 mg/L) than the other 2 constituents and it contributed predominantly to the toxicity of IMX-101 (LC50 = 206 mg/L) based on toxic units. Toxicity was observed only at high levels of NQ (LC50 = 1174 mg/L) and pH-adjusted NTO (LC50 = 799 mg/L). The toxicity of IMX-101 is lower than literature-reported TNT toxicity. Photodegradation efficiency was greater at lower insensitive munition concentrations. The observed degradation was greatest for NQ (42-99%), which in turn corresponded to the greatest relative increase in toxicity (100-1000-fold). Modest percent of degradation (4-18%) and increases in phototoxicity (2-100-fold) were observed for NTO and DNAN. Photodegraded NQ products were the predominant source of toxicity of photodegraded IMX-101. Future work involves research to enable analytical and computational confirmation of the specific degradation compounds inducing the observed photoenhanced toxicity. Environ Toxicol Chem 2017;36:2050-2057. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

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.