Acute and Chronic Toxicity of Uncured Resin Feedstocks for Vat Photopolymerization 3D Printing to a Cladoceran (Ceriodaphnia Dubia).

The accessibility and popularity of additive manufacturing (AM) has increased over the past decade. Environmental hazard assessment and safety data sheets for 3D printer feedstocks has lagged technology development. Vat photopolymerization may have unique risks relative to other AM technologies due to mishandling of uncured monomers/oligomer feedstocks and its decreasing cost enabling uninformed residential use. The acute and chronic toxicity of six uncured resins to Ceriodaphnia dubia was explored. Two-day acute toxicity (LC50) ranged from 2.6 to 33 mg/L and inhibition concentrations (IC25) values for reproduction ranged from 0.33 to 16 mg/L. Cleaning and waste management procedures recommended in user guides could be the most hazardous handling scenario as use of isopropyl alcohol increases miscibility and thus the fate, transport and bioavailability of the uncured resins. Residential users may often be poorly informed about potential toxicity and the need for a plan for use, handling, and waste management of uncured resins.

Radio Frequency Heating of Washable Conductive Textiles for Bacteria and Virus Inactivation.

The ongoing COVID-19 pandemic has increased the use of single-use medical fabrics such as surgical masks, respirators, and other personal protective equipment (PPE), which have faced worldwide supply chain shortages. Reusable PPE is desirable in light of such shortages; however, the use of reusable PPE is largely restricted by the difficulty of rapid sterilization. In this work, we demonstrate successful bacterial and viral inactivation through remote and rapid radio frequency (RF) heating of conductive textiles. The RF heating behavior of conductive polymer-coated fabrics was measured for several different fabrics and coating compositions. Next, to determine the robustness and repeatability of this heating response, we investigated the textile's RF heating response after multiple detergent washes. Finally, we show a rapid reduction of bacteria and virus by RF heating our conductive fabric. 99.9% of methicillin-resistant Staphylococcus aureus (MRSA) was removed from our conductive fabrics after only 10 min of RF heating; human cytomegalovirus (HCMV) was completely sterilized after 5 min of RF heating. These results demonstrate that RF heating conductive polymer-coated fabrics offer new opportunities for applications of conductive textiles in the medical and/or electronic fields.

Selecting an Optimal Faraday Cage To Minimize Noise in Electrochemical Experiments.

The ubiquitous Faraday cage, an experimental component particularly essential for nanoelectrochemical measurements, is responsible for neutralizing noise introduced by electromagnetic interference (EMI). Faraday cage designs abound in the literature, often exhibiting varying thicknesses, mesh sizes, and base materials. The fact that the Faraday cage composition most often goes unreported underscores the fact that many electrochemical researchers assume a 100% EMI reduction for any given design. In this work, this assumption is challenged from a theoretical and empirical perspective by highlighting the physical principles producing the Faraday effect. A brief history of the Faraday cage and a simplified theoretical approach introduce fundamental considerations regarding optimal design properties. In practice, time-domain noise profiles and corresponding Fourier transform frequency domain information for custom-built Faraday cages reveal that maximally conductive cages provide more optimal EMI exclusion.

Toward bioinspired polymer adhesives: activation assisted via HOBt for grafting of dopamine onto poly(acrylic acid).

The design of bioinspired polymers has long been an area of intense study, however, applications to the design of concrete admixtures for improved materials performance have been relatively unexplored. In this work, we functionalized poly(acrylic acid) (PAA), a simple analogue to polycarboxylate ether admixtures in concrete, with dopamine to form a catechol-bearing polymer (PAA-g-DA). Synthetic routes using hydroxybenzotriazole (HOBt) as an activating agent were examined for their ability in grafting dopamine to the PAA backbone. Previous literature using the traditional coupling reagent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) to graft dopamine to PAA were found to be inconsistent and the sensitivity of EDC coupling reactions necessitated a search for an alternative. Additionally, HOBt allowed for greater control over per cent functionalization of the backbone, is a simple, robust reaction, and showed potential for scalability. This finding also represents a novel synthetic pathway for amide bond formation between dopamine and PAA. Finally, we performed preliminary adhesion studies of our polymer on rose granite specimens and demonstrated a 56% improvement in the mean adhesion strength over unfunctionalized PAA. These results demonstrate an early study on the potential of PAA-g-DA to be used for improving the bonds within concrete.

ACEstat: A DIY Guide to Unlocking the Potential of Integrated Circuit Potentiostats for Open-Source Electrochemical Analysis.

Miniaturization of analytical instrumentation is paramount to enabling convenient in-field sensing. The recent thrust in potentiostat miniaturization for electrochemical sensing and general use has led to the development of commercial application specific integrated circuits (ASICs) that pack all the power of a benchtop instrument into one 5 mm × 5 mm chip. While the capabilities of these integrated circuits far exceed those of open-source potentiostats in the literature, the activation barrier for their implementation requires extensive electrical and software engineering expertise to overcome. In order to more rapidly bring the utility of ASIC potentiostats to researchers, we present a low size, weight, power, and cost (Low SWaP-C) Army Corps of Engineers potentiostat (ACEstat) based on the widely available ADuCM355 offered by Analog Devices. This potentiostat is a streamlined and fully programmable device that leverages industry-leading integrated hardware to perform electrochemical measurements such as cyclic voltammetry, pulse voltammetry, and electrochemical impedance spectroscopy. The ACEstat enables control over a wide range of test parameters and displays results through an intuitive, open-source graphical user interface available on mobile devices and computers. In this report, we present an approachable, do-it-yourself guide to unlocking the capabilities of this integrated circuit potentiostat by outlining the fabrication and programming details necessary to facilitate electroanalysis. Furthermore, we demonstrate the practicality of this device by detecting 2,4,6-trinitrotoluene (TNT) in water at sub-mg/L detection limits, highlighting its potential for in-field use.

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.

Analytical Methods Incorporating Molecularly Imprinted Polymers (MIPs) for the Quantification of Microcystins: A Mini-Review.

Harmful algal blooms (HABs) negatively impact numerous natural waterways worldwide and have significant socioeconomic and health-related ramifications for local populations. In order to better detect, characterize, and mitigate bloom events, novel field deployable analytical technologies capable of quantifying common HAB toxins (e.g., microcystins) are of paramount importance. Toward this end, molecularly imprinted polymer (MIP) transducing elements used in conjunction with sensitive analytical techniques may be a useful tool for microcystin detection and quantification. Indeed, several efforts have been undertaken in the last decade (2010-2020) to combine the selectivity provided by MIPs with various analytical methods, many of which are adaptable for in-field analysis. This review presents a summary of the current state of microcystins detection methods incorporating MIPs with a focus on potentiometry, photoelectrochemistry, liquid chromatography, quartz crystal microbalance, competitive ELISA, interferometry, and immunochromatography. Furthermore, a perspective detailing trends and observations from the current body of literature is provided to guide future MIP-based microcystin and other HAB toxin detection efforts with a specific focus on deployable analytical platforms.

Green MIP-202(Zr) Catalyst: Degradation and Thermally Robust Biomimetic Sensing of Nerve Agents.

Rapid and robust sensing of nerve agent (NA) threats is necessary for real-time field detection to facilitate timely countermeasures. Unlike conventional phosphotriesterases employed for biocatalytic NA detection, this work describes the use of a new, green, thermally stable, and biocompatible zirconium metal-organic framework (Zr-MOF) catalyst, MIP-202(Zr). The biomimetic Zr-MOF-based catalytic NA recognition layer was coupled with a solid-contact fluoride ion-selective electrode (F-ISE) transducer, for potentiometric detection of diisopropylfluorophosphate (DFP), a F-containing G-type NA simulant. Catalytic DFP degradation by MIP-202(Zr) was evaluated and compared to the established UiO-66-NH2 catalyst. The efficient catalytic DFP degradation with MIP-202(Zr) at near-neutral pH was validated by 31P NMR and FT-IR spectroscopy and potentiometric F-ISE and pH-ISE measurements. Activation of MIP-202(Zr) using Soxhlet extraction improved the DFP conversion rate and afforded a 2.64-fold improvement in total percent conversion over UiO-66-NH2. The exceptional thermal and storage stability of the MIP-202/F-ISE sensor paves the way toward remote/wearable field detection of G-type NAs in real-world environments. Overall, the green, sustainable, highly scalable, and biocompatible nature of MIP-202(Zr) suggests the unexploited scope of such MOF catalysts for on-body sensing applications toward rapid on-site detection and detoxification of NA threats.

A Generalized Potentiostat Adaptor for Multiplexed Electroanalysis.

Electrochemical measurements over an array of electrodes may be accomplished with one of three potentiostat architectures: a single-channel device which averages the signal from a number of interconnected electrodes, a multichannel device with dedicated circuits for each electrode, or a single-channel device with a multiplexer interface to isolate the signal from specific electrodes. Of these three architectures, the use of a multiplexer interface is best suited to facilitate measurements over individual electrodes without the need for large numbers of dedicated potentiostat channels. We present a versatile strategy for the development of flexible printed circuit (FPC) electrode arrays with accompanying multiplexing hardware to interface with single-channel potentiostats. The FPC array was fabricated with 78 individually addressable 0.3 mm diameter gold working electrodes and characterized using optical and scanning electron microscopy, energy dispersive spectroscopy, profilometry, impedance spectroscopy, and cyclic voltammetry to investigate the morphology, elemental composition, height profile, impedance characteristics, and electrochemical response, respectively. Interfacing the FPC array via a simple connector with three 32-channel ADG731 multiplexers permitted electrochemical measurements using single-channel commercial potentiostats. Voltammetric experiments were conducted to demonstrate the reliability, stability, and reproducibility of the FPC array and interfacing hardware. The combination of these devices represents an accessible hardware platform with robust, functionalizable electrodes, a simple connection interface with commercial potentiostats, and a low cost through the use of off-the-shelf components. Our reported strategy holds great promise to facilitate multiplexed electroanalysis in next-generation sensors to increase statistical sample size and multianalyte detection capabilities.

Textile-based wearable solid-contact flexible fluoride sensor: Toward biodetection of G-type nerve agents.

Rising global concerns posed by chemical and biological threat agents highlight the critical need to develop reliable strategies for the real-time detection of such threats. While wearable sensing technology is well suited to fulfill this task, the use of on-body devices for rapid and selective field identification of chemical agents is relatively a new area. This work describes a flexible printed textile-based solid-contact potentiometric sensor for the selective detection of fluoride anions liberated by the biocatalytic hydrolysis of fluorine-containing G-type nerve agents (such as sarin or soman). The newly developed solid-contact textile fluoride sensor relies on a fluoride-selective bis(fluorodioctylstannyl)methane ionophore to provide attractive analytical performance with near-Nernstian sensitivity and effective discrimination against common anions, along with excellent reversibility and repeatability for dynamically changing fluoride concentrations. By using stress-enduring printed inks and serpentine structures along with stretchable textile substrates, the resulting textile-based fluoride sensor exhibits robust mechanical resiliency under severe mechanical strains. Such realization of an effective textile-based fluoride-selective electrode allowed biosensing of the nerve-agent simulant diisopropyl fluorophosphate (DFP), in connection to immobilized organophosphorus acid anhydrolylase (OPAA) or organophosphorus hydrolase (OPH) enzymes. A user-friendly portable electronic module transmits data from the new textile-based potentiometric biosensor wirelessly to a nearby smartphone for alerting the wearer instantaneously about potential chemical threats. While expanding the scope of wearable solid-contact anion sensors, such a textile-based potentiometric fluoride electrode transducer offers particular promise for effective discrimination of G-type neurotoxins from organophosphate (OP) pesticides, toward specific field detection of these agents in diverse defense settings.

In Situ Preconcentration and Quantification of Cu2+ via Chelating Polymer-Wrapped Multiwalled Carbon Nanotubes.

Trace analysis of heavy metals in complex, environmentally relevant matrices remains a significant challenge for electrochemical sensors employing stripping voltammetry-based detection schemes. We present an alternative method capable of selectively preconcentrating Cu2+ ions at the electrode surface using chelating polymer-wrapped multiwalled carbon nanotubes (MWCNTs). An electrochemical sensor consisting of poly-4-vinyl pyridine (P4VP)-wrapped MWCNTs anchored to a poly(ethylene terephthalate) (PET)-modified gold electrode (r = 1.5 mm) was designed, produced, and evaluated. The P4VP is shown to form a strong association with Cu2+ ions, permitting preconcentration adjacent to the electrode surface for interrogation via cyclic voltammetry. The sensor exhibited a detection limit of 0.5 ppm with a linear range of 1.1-13.8 ppm (16.6-216 µM) and a relative standard deviation (RSD) of 4.9% at the Environmental Protection Agency (EPA) limit of 1.3 ppm. Evaluation in tap water, lake water, ocean water, and deionized water rendered similar results, highlighting the generalizability of the presented preconcentration strategy. The advantages of electrochemical analysis paired with polymeric chelation represent an effective platform for the design and deployment of heavy metal sensors for continuous monitoring of natural waters.

Multi-species Aquatic Toxicity Assessment of 1-Methyl-3-Nitroguanidine (MeNQ).

The Army is replacing traditional munitions with insensitive munitions (IM) resistant to accidental detonation. The aquatic toxicity of 1-methyl-3-nitroguanidine (MeNQ), which is being assessed for potential use in IM formulations, remains largely untested. The present study fills a number of critical data gaps for MeNQ aquatic toxicity by evaluating effects across two vertebrate and five invertebrate species. Specifically, responses in larval Pimephales promelas, Rana pipiens tadpoles, Chironomus dilutus, Lumbriculus variegatus, Hydra littoralis, Hyalella azteca, and Daphnia pulex were assessed in MeNQ exposures across various acute, subchronic, and chronic bioassays. Overall, survival was unaffected in most of the MeNQ exposures where significant lethal effects were only observed in D. pulex, H. littoralis, and C. dilutus and only at concentrations ≥ 2186 mg/L. Significant sublethal effects on growth were observed for C. dilutus at 903 mg/L and H. azteca at 1098 mg/L in 10-d assays. Significantly decreased reproduction was observed at 2775 mg/L for H. azteca in a chronic 35-d assay and at 174 mg/L for D. pulex in the 11-d three-brood assay representing a sublethal effect one order of magnitude more sensitive than the effective lethal concentration for D. pulex (2987 mg/L). Degradation of MeNQ in ultraviolet light (UV) greatly increased toxicity to D. pulex. Specifically, exposure to a MeNQ solution that was completely UV-degraded prior to D. pulex exposures resulted in an 11-d LC50 of 6.1 mg/L and a 50% reduction in reproduction at 3.125 mg/L, based on the original MeNQ parent-compound concentrations.

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.

Regioselectivity of Hydroxyl Radical Reactions with Arenes in Nonaqueous Solutions.

The regioselectivity of hydroxyl radical addition to arenes was studied using a novel analytical method capable of trapping radicals formed after the first elementary step of reaction, without alteration of the product distributions by secondary oxidation processes. Product analyses of these reactions indicate a preference for o- over p-substitution for electron donating groups, with both favored over m-addition. The observed distributions are qualitatively similar to those observed for the addition of other carbon-centered radicals, although the magnitude of the regioselectivity observed is greater for hydroxyl. The data, reproduced by high accuracy CBS-QB3 computational methods, indicate that both polar and radical stabilization effects play a role in the observed regioselectivities. The application and potential limitations of the analytical method used are discussed.

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.

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.