Acute and chronic toxicity of short chained perfluoroalkyl substances to Daphnia magna

Comparative toxicity assessment of alternative versus legacy PFAS: Implications for two primary trophic levels in freshwater ecosystems

Perfluoroalkyl substances (PFAS) are common environmental pollutants, but their toxicity framework remains elusive. This research focused on ten PFAS, evaluating their impacts on two ecotoxicologically relevant model organisms from distinct trophic levels: the crustacean Daphnia magna and the unicellular green alga Raphidocelis subcapitata. The results showed a greater sensitivity of R. subcapitata compared to D. magna. However, a 10-day follow-up to the 48 h immobilisation test in D. magna showed delayed mortality, underlining the limitations of relying on EC50 s from standard acute toxicity tests. Among the compounds scrutinized, Perfluorodecanoic acid (PFDA) was the most toxic to R. subcapitata, succeeded by Perfluorooctane sulfonate (PFOS), Perfluorobutanoic acid (PFBA), and Perfluorononanoic acid (PFNA), with the latter being the only one to show an algicidal effect. In the same species, assessment of binary mixtures of the compounds that demonstrated high toxicity in the single evaluation revealed either additive or antagonistic interactions. Remarkably, with an EC50 of 31 mg L-1, the short-chain compound PFBA, tested individually, exhibited toxicity levels akin to the notorious long-chain PFOS, and its harm to freshwater ecosystems cannot be ruled out. Despite mounting toxicological evidence and escalating environmental concentrations, PFBA has received little scientific attention and regulatory stewardship. It is strongly advisable that regulators re-evaluate its use to mitigate potential risks to the environmental and human health.

The effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana pipiens) tadpole development

Short-chain perfluoroalkyl carboxylic acids (PFCAs) have been detected in the environment globally. The presence and persistence of these compounds in the environment may lead to chronic wildlife exposure. We used northern leopard frog (Rana pipiens) tadpoles to investigate the chronic toxicity and the bioconcentration of two short-chain PFCAs, perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA). We exposed Gosner stage 25 tadpoles to PFBA and PFHxA (as individual chemicals) at nominal concentrations of 0.1, 1, 10, 100, and 1000 µg/L for 43-46 days. Tadpoles exposed to 0.1 to 100 µg/L of PFBA and PFHxA had significantly higher mean snout-to-vent lengths, mean masses, and scaled mass indexes than control tadpoles. These results indicate that exposure to short-chain PFCAs influences tadpole growth. Further investigation into the mechanism(s) causing the observed changes in tadpole growth is warranted. We observed a significantly higher proportion of males in the PFBA 1 µg/L treatment group, however further histological analyses are required to confirm visual sex identification before making concrete conclusions on the effects of PFCAs on amphibian sex ratios. PFBA concentrations in tissues were higher than PFHxA concentrations; a pattern that contrasts with previously published studies using fish, suggesting potential differences between taxa in PFBA and PFHxA bioconcentration. Bioconcentration factors were <10 L/kg wet weight, indicating low bioconcentration potential in tadpoles. Our results suggest that PFBA and PFHxA may have effects at environmentally-relevant concentrations (0.1-10 µg/L) and further investigation is required before these compounds can be deemed a "safe" alternative to their long-chain counterparts.

The untold story of PFAS alternatives: Insights into the occurrence, ecotoxicological impacts, and removal strategies in the aquatic environment

Due to increasing regulations on the production and consumption of legacy per- and polyfluoroalkyl substances (PFAS), the global use of PFAS substitutes increased tremendously, posing serious environmental risks owing to their bioaccumulation, toxicity, and lack of removal strategies. This review summarized the spatial distribution of alternative PFAS and their ecological risks in global freshwater and marine ecosystems. Further, toxicological effects of novel PFAS in various freshwater and marine species were highlighted. Moreover, degradation mechanisms for alternative PFAS removal from aquatic environments were compared and discussed. The spatial distribution showed that 6:2 chlorinated polyfluorinated ether sulfonate (6:2 CI-PFAES, also known as F-53B) was the most dominant emerging PFAS found in freshwater. Additionally, the highest levels of PFBS and PFBA were observed in marine waters (West Pacific Ocean). Moreover, short-chain PFAS exhibited higher concentrations than long-chain congeners. The ecological risk quotients (RQs) for phytoplankton were relatively higher >1 than invertebrates, indicating a higher risk for freshwater phytoplankton species. Similarly, in marine water, the majority of PFAS substitutes exhibited negligible risk for invertebrates and fish, and posed elevated risks for phytoplanktons. Reviewed studies showed that alternative PFAS undergo bioaccumulation and cause deleterious effects such as oxidative stress, hepatoxicity, neurotoxicity, histopathological alterations, behavioral and growth abnormalities, reproductive toxicity and metabolism defects in freshwater and marine species. Regarding PFAS treatment methods, photodegradation, photocatalysis, and adsorption showed promising degradation approaches with efficiencies as high as 90%. Finally, research gaps and future perspectives for alternative PFAS toxicological implications and their removal were offered.

An integrated assessment of ecological and human health risks of per- and polyfluoroalkyl substances through toxicity prediction approaches

Per- and polyfluoroalkyl substances (PFAS) are also known as "forever chemicals" due to their persistence and ubiquitous environmental distribution. This review aims to summarize the global PFAS distribution in surface water and identify its ecological and human risks through integrated assessment. Moreover, it provides a holistic insight into the studies highlighting the human biomonitoring and toxicological screening of PFAS in freshwater and marine species using quantitative structure-activity relationship (QSAR) based models. Literature showed that PFOA and PFOS were the most prevalent chemicals found in surface water. The highest PFAS levels were reported in the US, China, and Australia. The TEST model showed relatively low LC50 of PFDA and PFOS for Pimephales promelas (0.36 and 0.91 mg/L) and high bioaccumulation factors (518 and 921), revealing an elevated associated toxicity. The risk quotients (RQs) values for P. promelas and Daphnia magna were found to be 269 and 23.7 for PFOS. Studies confirmed that long-chain PFAS such as PFOS and PFOA undergo bioaccumulation in aquatic organisms and induce toxicological effects such as oxidative stress, transgenerational epigenetic effects, disturbed genetic and enzymatic responses, perturbed immune system, hepatotoxicity, neurobehavioral toxicity, altered genetic and enzymatic responses, and metabolism abnormalities. Human biomonitoring studies found the highest PFOS, PFOA, and PFHxS levels in urine, cerebrospinal fluid, and serum samples. Further, long-chain PFOA and PFOS exposure create severe health implications such as hyperuricemia, reduced birth weight, and immunotoxicity in humans. Molecular docking analysis revealed that short-chain PFBS (-11.84 Kcal/mol) and long-chain PFUnDA (-10.53 Kcal/mol) displayed the strongest binding interactions with human serum albumin protein. Lastly, research challenges and future perspectives for PFAS toxicological implications were also discussed, which helps to mitigate associated pollution and ecological risks.

Environmental exposure and ecotoxicological properties of a new-generation fluorosurfactant (cC6 O4 ): A comparison with selected legacy perfluoroalkyl acids

Cyclic C6 O4 (cC6 O4 , CAS number 1190931-27-1) is a new-generation polyfluorinated alkyl substance (PFAS) used as a polymerization aid in the synthesis of fluoropolymers, which has been produced in Italy since 2011. A review of the properties of cC6 O4 , focused on environmental distribution and ecotoxicology, was conducted. The EQuilibrium Criterion model was applied, using default environmental scenarios, to estimate environmental distribution and fate. In a situation of static thermodynamic equilibrium in a closed system (Level I), cC6 O4 distributes mainly to water (97.6%) and in a minimal amount to soil (2.3%). In a more realistic scenario (Level III), with dynamic conditions in an open system, with advection in air and water and with equal emissions in air and water, the major amount of the compound is transported through water advection. Monitoring data, mainly referring to surface and groundwater, are available for water bodies close to the production sites (maximum measured concentration 52 μg/L) as well as for a wider area in the river Po watershed with concentrations generally lower than 1 μg/L. Few values are also available for concentration in biota. Effect data indicate low toxicity on all tested organisms with no observed effect concentration (NOEC) values always higher than the maximum concentrations tested (100 mg/L for acute tests). Bioaccumulation potential is also very low. A comparison with selected widely used PFAS with five to eight C atoms indicates that cC6 O4 is substantially less dangerous to aquatic organisms. For the time being, an ecological risk for the aquatic ecosystem may be excluded even in directly exposed ecosystems. However, for a complete assessment of the suitability of cC6 O4 as a substitute for other PFAS (namely, perfluorooctanoic acid), more comprehensive chronic experiments are necessary, to produce realistic NOEC, as well as higher tier experiments (e.g., mesocosms) capable of providing ecologically relevant endpoints. Moreover, a more accurate evaluation of the environmental persistence would be necessary. Integr Environ Assess Manag 2023;19:1636-1648. © 2023 SETAC.

Environmental exposure and ecological risk of perfluorinated substances (PFASs) in the Shaying River Basin, China

There have been concerns raised about the environmental effects of perfluoroalkyl substances (PFASs) because of their toxicity, widespread distribution, and persistence. Understanding the occurrences and ecological risk posed by PFASs is essential, especially for the short-chain replacements perfluorobutanoic acid (PFBA) and perfluorobutane sulfonic acid (PFBS), which are now becoming predominant PFASs. The lack of aquatic life criteria (ALC), however, prevents an accurate assessment of the ecological risks of PFBA and PFBS. This study thus investigated the occurrence of 15 PFASs at 29 sampling sites in Shaying River Basin (in China) systematically, conducted the toxicity tests of PFBA and PFBS on eight resident aquatic organisms in China, and derived the predicted non-effect concentration (PNEC) values for PFBA and PFBS for two environmental media in China. The results showed that the total PFASs concentrations (ΣPFASs) ranged from 5.07 to 20.32 ng/L (average of 10.95 ng/L) in surface water, whereas in sediment, ΣPFASs ranged from 6.46 to 20.05 ng/g (dw) (average of 11.51 ng/g). The presence of PFBS was the most prominent PFASs in both water (0.372-8.194 ng/L) and sediment (4.54-15.72 ng/g), demonstrating that short-chain substitution effects can be observed in watersheds. The PNEC values for freshwater and sediment were 6.60 mg/L and 8.30 mg/kg (ww), respectively, for PFBA, and 14.04 mg/L, 37.08 mg/kg (ww), respectively, for PFBS. Ecological risk assessment of two long-chain PFASs, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), and two short-chain PFASs, PFBA and PFBS, using the hazard quotient method revealed that Shaying River and other major River Basins in China were at risk of PFOS contamination. This study contributes to a better understanding of the presence and risk of PFASs in the Shaying River and first proposes the ALCs for PFBA and PFBS in China, which could provide important reference information for water quality standards.

Synthesis and Performance Analysis of Green Water and Oil-Repellent Finishing Agent with Di-Short Fluorocarbon Chain

A novel fluorine-containing water-repellent agent (OFAE-SA-BA) was designed and synthesized by emulsion copolymerization, which was used to replace the commercial long fluorocarbon chain water-repellent agent. To improve water repellency, the intermediate and monomer containing two short fluoroalkyl chains were successfully synthesized and characterized by ¹H NMR, ¹³C NMR and FT-IR, respectively. After being treated by the water-repellent agent, the surface chemical composition, molecular weight, thermal stability, surface morphology, wetting behavior, and durability of the modified cotton fabrics were characterized using X-ray photoelectron spectrophotometry (XPS), gel permeation chromatography (GPC), thermal degradation (TG), scanning electron microscopy (SEM), and video-based contact angle goniometry, respectively. The cotton fabric demonstrated water contact angle of 154.1°, both the water and oil repellency rating were grade 4. The durability of water repellency of the treated fabrics only decreased slightly after 30 times, which represented very good washing durability. The finishing agent did not affect the whiteness of the fabric.

Tissue Bioconcentration Pattern and Biotransformation of Per-Fluorooctanoic Acid (PFOA) in Cyprinus carpio (European Carp)—An Extensive In Vivo Study

The perfluoroalkyl substances (PFAS) represent a persistent class of synthetic chemicals that spread in the environment as a result of industrialization. Due to their bioaccumulative and endocrine disruption implications, these chemicals can affect food quality and human health, respectively. In the present study, the bioconcentration and biotransformation of perfluorooctanoic acid (PFOA) in common carp (Cyprinus carpio) were evaluated in a biphasic system (exposure and depuration). Carp were continuously exposed, under laboratory conditions, to 10 (Experiment 1) and 100 (Experiment 2) µg/L PFOA for 14 weeks, followed by a wash out period of 3 weeks. Fish organs and tissues were collected at 8, 12, 14 weeks of exposure and at week 17, after the depuration period. The results obtained from the LC-MS/MS analysis showed the presence of PFOA in all studied organs. The highest values of PFOA were identified in the gallbladder (up to 2572 ng/g d.w.) in Experiment 1 and in the gallbladder (up to 18,640 ng/g d.w.) and kidneys (up to 13,581 ng/g d.w.) in Experiment 2. The average BCF varied between 13.4 and 158 L/Kg in Experiment 1 and between 5.97 and 80.3 L/Kg in Experiment 2. Four biotransformation products were identified and quantified in all organs, namely: PFBA, PFPeA, PFHxA, and PFHpA. PFBA was proven to be the dominant biotransformation product, with the highest values being determined after 8 weeks of exposure in the kidney, gallbladder, brain, liver, and gonads in both experiments. Because freshwater fish are an important food resource for the human diet, the present study showed the fishes’ capacity to accumulate perfluoroalkyl substances and their metabolites. The study revealed the necessity of monitoring and risk studies of new and modern synthetic chemicals in aquatic resources.

Isomer-specific perfluoroalkyl acids accumulation, excretion and maternal transfer to eggs in chickens around a fluorochemical manufactory in China

The co-existing of multiple Per- and polyfluoroalkyl substances (PFASs) might pose more complicated situation for the exposure risk of environment and biota, especially for the surrounding area of the contaminated communities. In this study, tissues and organs of free-ranged chickens, paired eggs, corresponding feces, water, soil/dust, and feed samples around a fluorochemical manufactory were collected to investigate the tissue-isomer-specific accumulation, elimination and maternal transfer to eggs of PFASs. Free-ranged chickens had much higher ∑PFASs concentrations than farm chickens, and PFBA and PFOS were the predominant PFASs in tissues and organs, which is consistence with the electrochemical fluorination (ECF) production pattern of this manufactory. This result implied that PFASs released from manufactory production is a direct exposure source to the chickens. ∑PFASs concentrations in yolk samples were higher than other tissues and organs, while the concentrations in albumen were lowest. Isomer profiles analysis indicated that n-PFOS proportions in tissues, organs, yolk, and albumen ranged from 85.3 %-98.1 %, whereas in the feces with the percentage of 72.9 %, indicating that the branched PFOS isomers showed faster excretion rate than n-PFOS for chickens. Resident's estimated daily intakes (EDIs) of ∑PFASs via chicken were in the range of 6.41 to 107.18 ng/kg·bw/d. Notably, the EDIs of the sum of four PFASs were higher than the TDI of EFSA in 2020, indicating potential health risks.

Acute toxicity and risk assessment of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in tropical cladocerans Moina micrura

Per- and polyfluoroalkyl substances (PFAS) are gaining worldwide attention because of their toxicity, bioaccumulative and resistance to biological degradation in the environment. PFAS can be categorised into endocrine disrupting chemicals (EDCs) and identified as possible carcinogenic agents for the aquatic ecosystem and humans. Despite this, only a few studies have been conducted on the aquatic toxicity of PFAS, particularly in invertebrate species such as zooplankton. This study evaluated the acute toxicity of two main PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), by using freshwater cladocerans (Moina micrura) as bioindicators. This study aimed to assess the adverse effects at different levels of organisations such as organ (heart size and heart rate), individual (individual size and mortality) and population (lethal concentration, LC₅₀). PFOA was shown to be more hazardous than PFOS, with the LC₅₀ values (confidence interval) of 474.7 (350.4-644.5) μg L^-1 and 549.6 (407.2-743.9) μg L^-1, respectively. As the concentrations of PFOS and PFOA increased, there were declines in individual size and heart rate as compared to the control group. The values of PNECs acquired by using the AF method (PNEC_AF) for PFOA and PFOS were 0.4747 and 0.5496 μg L^-1, respectively. Meanwhile, the PNEC values obtained using the SSD method (PNEC_SSD) were 1077.0 μg L^-1 (PFOA) and 172.5 μg L^-1 (PFOS). PNEC_AF is more protective and conservative compared to PNEC_SSD. The findings of this study have significant implications for PFOS and PFOA risk assessment in aquatic environments. Thus, it will aid freshwater sustainability and safeguard the human dependency on water resources.

An unexpected synergistic toxicity caused by competitive bioconcentration of perfluoroalkyl acid mixtures to Daphnia magna: Further promoted by elevated temperature

The mixed pollution of the global water environment by perfluoroalkyl acids (PFAAs) and their ecological risks have aroused widespread concern. However, the relationship between the combined toxicity of PFAA mixtures and their accumulation in aquatic organisms is not well understood in the context of global warming. Here, we study the bioconcentration and combined toxicity of three PFAA mixtures (PFOA, PFDA, PFDoA) to Daphnia magna (D. magna) under different exposure concentrations and temperatures. The results show that although competitive bioconcentration exists, the combined toxicity of the PFAA mixtures to D. magna is synergistic. These contradictory phenomena occur because although the longer-chain PFDoA inhibits the bioconcentration of the shorter-chain PFOA and PFDA, the bioconcentration of PFDoA itself is promoted, and PFDoA is more toxic to D. magna than PFOA and PFDA. The toxic equivalent concentration for the PFAA mixture is 1.38-1.67 times higher than that obtained from simple addition for the three PFAAs when exposed separately. Moreover, elevated temperature promotes not only the bioconcentration of each PFAA and the competition of bioconcentration between shorter-chain and longer-chain PAFF, but also the synergistic toxicity of PFAA mixtures to D. magna. This study suggests that the effect of the interactions among different PFAAs on their bioconcentration and toxicity under different water environmental conditions, such as temperature, should be considered for ecological risk assessment of PFAA mixtures.

Differing behavioral changes in crayfish and bluegill under short- and long-chain PFAS exposures: Field study in Northern Michigan, USA

The emergent contaminant family, per- and poly-fluorinated alkyl substances (PFAS) has gained research attention due to their widespread detection and stability within the environment. Despite the growing amount of research on perfluorooctanesulfonic acid (PFOS) and perfluoro-n-octanoic acid (PFOA) in aquatic organisms, investigations detailing behavioral and physiological effects of aquatic organisms exposed to a mixture of PFAS analytes in the wild have been limited. The objective of this study was to evaluate the potential behavioral and histological effects of environmental exposure to PFAS compounds within multiple trophic levels of aquatic ecosystems. The current study investigates effects of environmentally relevant PFAS concentration exposures in crayfish (Faxonius immunis, F. rusticus, F. virilis) and bluegill (Lepomis macrochirus) sourced from four water bodies in Northern Michigan. Antipredator response and foraging behavioral assays were used to investigate potential effects on crayfish; a swimming speed behavioral assay and liver and gill histology analysis were used to investigate potential effects on fish. Linear mixed model and multiple regression analyses resulted in significant relationships between tissue accumulation levels of long chain PFAS compounds and crayfish foraging and fish critical swimming speed responses. Crayfish foraging decreased and fish critical swim speeds increased with PFAS exposure which may lead to energetic and population concerns. Antipredator response in crayfish and liver and gill histology in fish were not significantly related to PFAS tissue or water concentrations. The sensitivity of crayfish and bluegill behavior contributes to the growing body of research regarding the differential toxicity of short-chain and long-chain PFAS compounds. The sensitivity of some aquatic organism behaviors to PFAS accumulated in tissue may have implications for PFAS transfer and alterations to ecosystem functioning; based on the results of this field study, further laboratory research is recommended to further evaluate these relationships.

Broad toxicological effects of per-/poly- fluoroalkyl substances (PFAS) on the unicellular eukaryote, Tetrahymena pyriformis

Per-/Poly- fluoroalkyl substances represent emerging persistent organic pollutants. Their toxic effects can be broad, yet little attention has been given to organisms at the microscale. To address this knowledge shortfall, the unicellular eukaryote Tetrahymena pyriformis was exposed to increasing concentrations (0-5000 μM) of PFOA/PFOS and monitored for cellular motility, division and function (i.e., phagocytosis), reactive oxygen species generation and total protein levels. Both PFOA/PFOS exposure had negative impacts on T. pyriformis, including reduced motility, delayed cell division and oxidative imbalance, with each chemical having distinct toxicological profiles. T. pyriformis represents a promising candidate for assessing the biological effects these emerging anthropogenically-derived contaminants in a freshwater setting.

Combined toxicity of polystyrene microplastics and ammonium perfluorooctanoate to Daphnia magna: Mediation of intestinal blockage

Microplastics (MPs) have worldwide accumulated in aquatic environments and coexisted with various water contaminants including perfluorinated compounds (PFCs) that are frequently detected. The adverse effects of individual MPs or PFCs on aquatic organisms have been extensively reported; however, the combined toxicity of MPs and PFCs remains unknown. This study evaluated the combined toxicity of MPs [pristine and aged polystyrene (PS)] and a PFC [ammonium perfluorooctanoate (APFO)] to Daphnia magna under different concentration ratios by three classic methods: toxicity unit, additive index, and mixed toxicity index. The adsorption kinetics of APFO on MPs, aggregation of MPs in exposure medium, MP gut fullness of daphnids, intestinal histology, and lipid peroxidation were analyzed to reveal the mechanism underlying the combined toxicity. Our results showed that the combined toxic modes varied with the concentration ratios of MPs to APFO (antagonism at 4:1 and 1:4, synergism at 3:1, 1:2, and 1:3, and partial addition/antagonism at 2:1 and 1:1 for pristine PS + APFO; antagonism at all ratios except partial addition/antagonism at 3:1 and 1:3 for aged PS + APFO), which could be attributed to the alteration of MP aggregation and thus MP gut fullness in the daphnids. The combined toxicity was further confirmed to occur in the daphnid's gut, which was reflected in physiological and biochemical responses mediated by intestinal blockage. Observable intestinal damages under co-exposures at μg•L^-1 levels indicated the risks from future long-term exposure to MPs and PFCs in aquatic environments. This work demonstrates the necessity of assessing combined toxicity with different concentration ratios and provides new insights into the potential risks of MPs in aquatic environments.

Next generation per- and poly-fluoroalkyl substances: Status and trends, aquatic toxicity, and risk assessment

Widespread application of poly- and per-fluoroalkyl substances (PFAS) has resulted in some substances being ubiquitous in environmental matrices. That and their resistance to degradation have allowed them to accumulate in wildlife and humans with potential for toxic effects. While specific substances of concern have been phased-out or banned, other PFAS that are emerging as alternative substances are still produced and are being released into the environment. This review focuses on describing three emerging, replacement PFAS: perfluoroethylcyclohexane sulphonate (PFECHS), 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFAES), and hexafluoropropylene oxide dimer acid (HFPO-DA). By summarizing their physicochemical properties, environmental fate and transport, and toxic potencies in comparison to other PFAS compounds, this review offers insight into the viabilities of these chemicals as replacement substances. Using the chemical scoring and ranking assessment model, the relative hazards, uncertainties, and data gaps for each chemical were quantified and related to perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) based on their chemical and uncertainty scores. The substances were ranked PFOS > 6:2 Cl-PFAES > PFOA > HFPO-DA > PFECHS according to their potential toxicity and PFECHS > HFPO-DA > 6:2 Cl-PFAES > PFOS > PFOA according to their need for future research. Since future uses of PFAS remain uncertain in the face of governmental regulations and production bans, replacement PFAS will continue to emerge on the world market and in the environment, raising concerns about their general lack of information on mechanisms and toxic potencies.

Persistent Water Repellency of Syndiotactic Polymethylene with Perfluoroethyl Hexyloxycarbonyl Side Chains

Polyacrylates bearing long fluoroalkyl (Rf) side chains are known to have ultralow surface energies that are appropriate for functional coating and fabric finishing. However, these long Rf chains cause health concerns because of the risk of toxic and bioaccumulative perfluoroalcanoic acid emission via oxidative degradation. This work demonstrates that incorporating a short Rf chain of perfluoroethylene at the end of the side chains of syndiotactic poly(substituted methylene) (PM) produces hydrophobicity. A contact angle of 105° of PM remains constant for more than 50 s, whereas that of the polyacrylate (PA) with the same side chain rapidly decreases from 85° to 44° over the same period. Such persistent water repellency of the PM is ascribed to a liquid crystal structure comprised the main chains arranged in a 2D hexagonal lattice and side chains that extend perpendicularly from these main chains.

LC-HRMS screening of per- and polyfluorinated alkyl substances (PFAS) in impregnated paper samples and contaminated soils

High per- and polyfluorinated alkyl substance (PFAS) concentrations have been detected in agricultural soils in Southwest Germany. Discharges of PFAS-contaminated paper sludge and compost are suspected to be the cause of the contamination. Perfluorinated carboxylic acids (PFCAs) have been detected also in groundwater, drinking water, and plants in this area. Recently, previously unknown compounds have been identified by high-resolution mass spectrometry (HRMS). Major contaminants were polyfluorinated dialkylated phosphate esters (diPAPs) and N-ethyl perfluorooctane sulfonamide ethanol–based phosphate diester (diSAmPAP). In this study, HRMS screening for PFAS was applied to 14 soil samples from the contaminated area and 14 impregnated paper samples which were from a similar period than the contamination. The paper samples were characterized by diPAPs (from 4:2/6:2 to 12:2/12:2), fluorotelomer mercapto alkyl phosphates (FTMAPs; 6:2/6:2 to 10:2/10:2), and diSAmPAP. In soil samples, diPAPs and their transformation products (TPs) were the major contaminants, but also FTMAPs, diSAmPAP, and their TPs occurred. The distribution patterns of the carbon chain lengths of the precursor PFAS in soil samples were shown to resemble those in paper samples. This supports the hypothesis that paper sludge is a major source of contamination. The presence of major degradation products like PFCAs, FTSAs, or PFOS and their distribution of carbon chain lengths indicate the activity of biotic or abiotic degradation processes and selective leaching processes from the upper soil horizons.

Bioaccumulation, Biodistribution, Toxicology and Biomonitoring of Organofluorine Compounds in Aquatic Organisms

This review is a survey of recent advances in studies concerning the impact of poly- and perfluorinated organic compounds in aquatic organisms. After a brief introduction on poly- and perfluorinated compounds (PFCs) features, an overview of recent monitoring studies is reported illustrating ranges of recorded concentrations in water, sediments, and species. Besides presenting general concepts defining bioaccumulative potential and its indicators, the biodistribution of PFCs is described taking in consideration different tissues/organs of the investigated species as well as differences between studies in the wild or under controlled laboratory conditions. The potential use of species as bioindicators for biomonitoring studies are discussed and data are summarized in a table reporting the number of monitored PFCs and their total concentration as a function of investigated species. Moreover, biomolecular effects on taxonomically different species are illustrated. In the final paragraph, main findings have been summarized and possible solutions to environmental threats posed by PFCs in the aquatic environment are discussed.

Exposure to perfluorooctanesulfonate (PFOS) but not perflurorooctanoic acid (PFOA) at ppb concentration induces chronic toxicity in Daphnia carinata

Widespread environmental contamination of per- and polyfluoroalkyl substances (PFAS) is well established. Nevertheless, few studies have reported on the aquatic toxicity of PFAS, especially in indicator species such as Daphnia. In this study, the toxicity of two major PFAS, namely perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS), was investigated on water flea (Daphnia carinata) using a battery of comprehensive toxicity tests, including a 48 h acute and a 21-day chronic assays. The survival, growth, and reproduction of D. carinata were monitored over a 21-day life cycle. PFOS exhibited higher toxicity than PFOA. The 48 h LC₅₀ values (confidence interval) based on acute toxicity for PFOA and PFOS were 78.2 (54.9-105) mg L^-1 and 8.8 (6.4-11.6) mg L^-1, respectively. Chronic exposure to PFOS for 21 days displayed mortality and reproductive defects in D. carinata at a concentration as low as 0.001 mg L^-1. Genotoxicity assessment using comet assay revealed that exposure for 96 h to PFOS at 1 and 10.0 mg L^-1 significantly damaged the organism's genetic makeup. The results of this study have great implications for risk assessment of PFOS and PFOA in aquatic ecosystems, given the potential of PFOS to pose a risk to Daphnia even at lower concentrations (1 μg L^-1).

Per- and Polyfluoroalkyl Substances (PFAS) in Surface Water Near US Air Force Bases: Prioritizing Individual Chemicals and Mixtures for Toxicity Testing and Risk Assessment

Per- and polyfluoroalkyl substances (PFAS) are a large class of persistent chemicals used for decades in industrial and commercial applications. A key challenge with regard to estimating potential risk to ecological (and human) receptors associated with PFAS exposure lies in the fact that there are many different PFAS compounds and several to many can co-occur in any given environmental sample. We applied a data science approach to characterize and prioritize PFAS and PFAS mixtures from a large dataset of PFAS measurements in surface waters associated with US Air Force Installations with a history of the use of aqueous film-forming foams (AFFFs). Several iterations of stakeholder feedback culminated in a few main points that advanced our understanding of a complex dataset and the larger ecotoxicological problem. First, perfluorooctane sulfonate (PFOS) was often a dominant PFAS in a given surface water sample, frequently followed by perfluorohexane sulfonate (PFHxS). Second, a 4-chemical mixture generally accounted for >80% of the sum of all routinely reported PFAS in a sample, and the most representative 4-chemical mixture was composed of PFOS, PFHxS, perfluorohexanoic acid (PFHxA), and perfluorooctanoic acid (PFOA). We suggest that these results demonstrate the utility of formalized data science analysis and assessment frameworks to address complex ecotoxicological problems. Specifically, our example dataset results can be used to provide perspective on toxicity testing, ecological risk assessments, and field studies of PFAS in and around AFFF-impacted sites. Environ Toxicol Chem 2021;40:871-882. © 2020 SETAC.

Acute effects of CH3NH3PbI3 perovskite on Scenedesmus obliquus and Daphnia magana in aquatic environment

CH₃NH₃PbI₃ is one of the most widely studied and most promising photoelectric conversion materials for large-scale application. However, once it is discharged into the aquatic environment, it will release a variety of lethal substances to the aquatic organisms. Herein, two typical aquatic pollution indicators, Scenedesmus obliquus (a typical phytoplankton) and Daphnia magna (a typical zooplankton), were used to assess the acute effects of CH₃NH₃PbI₃ perovskite on aquatic organisms. The results showed that, when the initial CH₃NH₃PbI₃ perovskite level (CPL) was 40 mg L^-1 or higher, the growth of S. obliquus would be remarkably inhibited with significant decreases of chlorophyll content and protein content. And when the CPL was over 5 mg L^-1, the survival of D. magna would be notably threatened. Specifically, the 72 h EC-50 of CH₃NH₃PbI₃ perovskite to S. obliquus was calculated as 37.21 mg L^-1, and the 24 h LC-50 of this perovskite to D. magna adults and neonates were calculated as 37.53 mg L^-1 and 18.55 mg L^-1, respectively. Moreover, remarkably solution pH declination and large amounts of lead bio-accumulation was observed in the both acute experiments, which could be the main reasons causing the above acute effects. Considering the strong acute effects of these CH₃NH₃PbI₃ perovskite materials and their attractive application prospect, more attentions should be paid on their harmness to the environment.

Lethal and sublethal toxicity of perfluorooctanoic acid (PFOA) in chronic tests with Hyalella azteca (amphipod) and early-life stage tests with Pimephales promelas (fathead minnow)

Perfluoroalkyl substances (PFAS), including perfluorooctanoic acid (PFOA), are industrial chemicals that are of concern due to their environmental presence, persistence, bioaccumulative potential, toxicity, and capacity for long-range transport. Despite a large body of research on environmental exposure, insufficient chronic aquatic toxicity data exist to develop water quality targets for clean-up of federal contaminated sites in Canada. Thus, our objective was to assess the aqueous toxicity of PFOA in chronic tests with Hyalella azteca (amphipod) and early-life stage tests with Pimephales promelas (fathead minnow). Toxicity data were analyzed based on measured PFOA concentrations. Amphipod exposures were 42 d (0.84-97 mg/L) and examined survival, growth, and reproduction. Fathead minnow exposures were 21 d (0.010-76 mg/L), which encompassed hatching (5 d) and larval stages until 16 d post-hatch; endpoints included hatching success, deformities at hatch, and larval survival and growth. Amphipod survival was significantly reduced at 97 mg/L (42-d LC50 = 51 mg/L), but growth and reproduction were more sensitive endpoints (42-d EC50 for both endpoints = 2.3 mg/L). Fathead minnows were less sensitive than amphipods, exhibiting no significant effects in all endpoints with the exception of uninflated swim bladder, which was significantly higher at 76 mg/L (15%) than controls (0%). Maximum concentrations of PFOA are generally in the ng/L range in global surface waters, but can reach the μg/L range in close proximity to major source inputs; therefore, environmental concentrations are well below those that caused toxicity in the current study. Our data will provide valuable information with which to assess the risk of PFOA at contaminated sites, and to set a target for site remediation.

Liposome-mediated delivery of challenging chemicals to aid environmental assessment of Bioaccumulative (B) and Toxic (T) properties

Standard aquatic toxicity tests of chemicals are often limited by the chemicals’ water solubility. Liposomes have been widely used in the pharmaceutical industry to overcome poor pharmacokinetics and biodistribution. In this work, liposomes were synthesized and used in an ecotoxicological context, as a tool to assure stable dosing of technically challenging chemicals to zooplankton. Three chemicals with distinctly different characteristics were successfully incorporated into the liposomes: Tetrabromobisphenol A (TBBPA, log K_ow 5.9, pK_a1 7.5, pK_a2 8.5), chlorinated paraffin CP-52 (log K_ow 8–12) and perfluorooctanoic acid (PFOA, pK_a 2.8). The size, production yield and stability over time was similar for all blank and chemical-loaded liposomes, except for when the liposomes were loaded with 10 or 100 mg g⁻¹ PFOA. PFOA increased the size and decreased the production yield and stability of the liposomes. Daphnia magna were exposed to blank and chemical-loaded liposomes in 48 hour incubation experiments. A dose-dependent increase in body burden in D. magna and increased immobilization (LD₅₀ = 7.6 ng CPs per individual) was observed. This confirms not only the ingestion of the liposomes but also the successful internalization of chemicals. This study shows that liposomes can be a reliable alternative to aid the study of aquatic toxicity of challenging chemicals.

Adverse effects of perfluoroalkyl acids on fish and other aquatic organisms: A review

Perfluoroalkyl acids (PFAAs) have been widely used in many industrial and consumer products. They have been detected ubiquitously in ambient water along with other environmental matrices, and their adverse effects on aquatic organisms have been a subject of active investigation. Here, we intended to summarize and synthesize the existing body of knowledge on PFAA toxicity through an extensive literature review, and shed light on areas where further research is warranted. PFAA toxicity appears to be influenced by the sex and developmental stages of aquatic organisms, but not significantly by exposure route. PFAA-induced aquatic toxicity could be classified as metabolism disturbance, reproduction disruption, oxidative stress, developmental toxicity, thyroid disruption, etc. At the molecular level, these responses can be initiated by key events, such as nuclear receptor activation, reactive oxygen species induction, or interaction with a membrane, followed by a cascade of downstream responses. PFAA-induced toxicity involves diverse metabolic processes, and therefore elucidating crosstalk or interactions among diverse metabolic pathways is a challenging task. In the presence of other chemicals, PFAAs can function as agonists or antagonists, resulting in different directions of combined toxicity. Therefore, mixture toxicity with other groups of chemicals is another research opportunity. Experimental evidence supports the trans-generational toxicity of PFAAs, suggesting that their long-term consequences for aquatic ecosystems should become of concern. A recent global ban of several PFAAs resulted in an increasing dependence on PFAA alternatives. The lack of sufficient toxicological information on this emerging group of chemicals warrant caution and rigorous toxicological assessments.

On the Ability of Perfluorohexane Sulfonate (PFHxS) Bioaccumulation by Two Pseudomonas sp. Strains Isolated from PFAS-Contaminated Environmental Matrices

PFASs (perfluoroalkyl and polyfluoroalkyl substances) are highly fluorinated, aliphatic, synthetic compounds with high thermal and chemical stability as well as unique amphiphilic properties which make them ingredients in a range of industrial processes. PFASs have attracted consideration due to their persistence, toxicity and bioaccumulation tendency in the environment. Recently, attention has begun to be addressed to shorter-chain PFASs, such as perfluorohexane sulfonate [PFHxS], apparently less toxic to and more easily eliminated from lab animals. However, short-chain PFASs represent end-products from the transformation of fluorotelomers whose biotic breakdown reactions have not been identified to date. This means that such emergent pollutants will tend to accumulate and persist in ecosystems. Since we are just learning about the interaction between short-chain PFASs and microorganisms, this study reports on the response to PFHxS of two Pseudomonas sp. strains isolated from environmental matrices contaminated by PFASs. The PFHxS bioaccumulation potential of these strains was unveiled by exploiting different physiological conditions as either axenic or mixed cultures under alkanothrofic settings. Moreover, electron microscopy revealed nonorthodox features of the bacterial cells, as a consequence of the stress caused by both organic solvents and PFHxS in the culturing substrate.

Two PBDEs exposure inducing feeding depression and disorder of digestive and antioxidative system of Daphnia magna

2,2',4,4'-tetrabrominated diphenyl ether (BDE-47) and 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) are two typical polybrominated diphenyl ethers (PBDEs), and studies have proven that these PBDs can disrupt the behaviors and physical function of aquatic organisms. However, little is known about the compositional impacts of BDE-47/BDE-99 compound pollution on the feeding behavior of Daphnia magna. In this study, a response surface methodology (RSM) was introduced into the combined toxicity assessment of BDE-47 and BDE-99 on the feeding depression of D. magna. Low concentrations of BDE-47 (9.2 μg/L) and BDE-99 (5.4 μg/L) had no effect on the feeding behavior of D. magna; nevertheless, the feeding depression was strengthened, and a concentration-dependent effect was observed with increasing concentrations of BDE-47 and BDE-99. The results of RSM indicated that the mixture of BDE-47 and BDE-99 can enhance their toxicity on the feeding behavior of D. magna. Moreover, real-time PCR (qPCR) analysis showed that the down-regulation of α-amylase (AMS) appeared in most of the exposed D. magna. However, there were significant different in the gene expression of trypsin, superoxide dismutase (SOD) and catalase (CAT) between the exposure and control groups. The change in the enzyme activity of AMS, trypsin, SOD and CAT implied that BDE-47 and BDE-99 cause damage to the digestive and antioxidative systems of D. magna. Correlation analysis indicated that a significant positive correlation existed between the gene expression and enzyme activity of SOD and CAT. Our results contribute to the understanding of toxicity caused by BDE-47/BDE-99 compound pollution in D. magna and help to improve traditional toxicity assessment methods for aquatic environments.

Potential of biochar filters for onsite wastewater treatment: Effects of active and inactive biofilms on adsorption of per- and polyfluoroalkyl substances in laboratory column experiments

This study investigated the potential of biochar filters as a replacement for, or complement to, sand filters for removal of per- and polyfluoroalkyl substances (PFASs) from wastewater in on-site wastewater treatment systems (OWTSs). Concentrations and removal of nine perfluoroalkyl carboxylates (PFCAs; C_3-11) and three perfluoroalkane sulfonates (PFSAs; C₄, ₆, ₈) and one perfluorooctanesulfonamide (FOSA; C₈) were investigated over 22 weeks in four treatments with column filters: biochar (BC) without biofilm (BC-no-biofilm), biochar with active biofilm (BC-active-biofilm), biochar with inactive biofilm (BC-inactive-biofilm) and sand with active biofilm (Sand-active-biofilm). The filters were operated under hydraulic loading (50 L m^-2 day^-1) to mimic the loading rate in on-site filtration beds. The initial concentrations of the ΣPFASs in the influent were in the range of 1500-4900 ng L^-1. In BC-no-biofilm, the removal efficiency (20-60%) and adsorption capacity (0-88 ng ΣPFASs g^-1 BC) of short-chain PFCAs (C_3-6) and PFSA (C₄) was low, whereas the removal efficiency (90-99%) and the adsorption capacity (73-168 ng g^-1) was high for C₇-C₁₁ PFCAs, C₆, C₈ PFSAs and FOSA. The relative removal was generally lower for C_3-9 PFCAs and C₄, C₆, C₈ PFSAs using BC-active-biofilm and BC-inactive-biofilm compared with BC-no-biofilm. This can be explained by the presence of biofilm and solids in BC-active-biofilm and the presence of wastewater solids in BC-inactive-biofilm, which decreased the availability and number of adsorption sites for PFASs compared with BC-no-biofilm. On the other hand, inactivation of the biofilm resulted in lower removal efficiencies for C_5-11 PFCAs, C₄, C₆, C₈ PFSAs and FOSA, probably because the biofilm degraded organic matter and thus increased the availability and number of adsorption sites compared with BC-inactive-biofilm. Sand-active-biofilm showed poor removal (0-70%) for all PFASs except FOSA (90%) and its adsorption capacity was low (0.0-7.5 ng g^-1). In general, for all biochar treatments, shorter-chain PFASs were more resistant to removal than longer-chain PFASs. In addition, C₄, C₆ and C₈ PFSAs showed 10-30%, 10-50% and 20-30% higher average removal efficiency, respectively, than PFCAs with corresponding perfluoroalkyl chain length. In conclusion, biochar is a promising filter medium for removal of PFASs in OWTSs, especially for PFASs with a perfluorocarbon chain longer than C₆.

Selection of organosilicone surfactants for tank-mixed pesticides considering the balance between synergistic effects on pests and environmental risks

In this study, the bioactivities of binary mixtures of organosilicone surfactants and indoxacarb against two Lepidopteran pests were investigated along with their environmental risks. All of the tested organosilicone surfactants had obvious synergistic effects on the contact toxicity of indoxacarb against Spodoptera exigua and Agrotis ipsilon. However, all of the organosilicone surfactants exhibited certain antagonism for indoxacarb against S. exigua in terms of stomach & contact toxicity; both Silwet-408 and Silwet-806 exhibited additivity against A. ipsilon, whereas Silwet-618 and Silwet-DRS-60 exhibited synergism and slight antagonism, respectively. All of the tested chemicals were highly toxic to Daphnia magna, among which Silwet-DRS-60 had the lowest acute toxicity (EC₅₀ of 94.91 μg/L). However, these chemicals were less toxic to Brachydanio rerio. Silwet-DRS-60 had a low toxicity to B. rerio, while Silwet-408, Silwet-806 and Silwet-618 were moderately toxic to B. rerio. For the joint toxicity evaluation of organosilicone surfactants and indoxacarb to D. magna and B. rerio, the additive index method, concentration addition method and toxicity unit method were robust in judging synergism or antagonism, whereas other methods were more conservative; the V-value method and equilibrium curve method exhibited high robustness and viability in evaluating the combined effects of binary mixtures. Overall, we should carefully select organosilicone surfactants for premixed or tank-mixed pesticides in agriculture to obtain a balance between synergistic effects on pests and environmental risks.

Membrane-Water Partition Coefficients to Aid Risk Assessment of Perfluoroalkyl Anions and Alkyl Sulfates

This study determined the sorption affinity to artificial phospholipid membranes ( K_MW) for series of perfluorinated carboxylates (PFCAs), perfluorinated sulfonates (PFSAs), alkyl sulfates (C _xSO₄), and 1-alkanesulfonates (C _xSO₃). A sorbent dilution assay with solid supported lipid membranes (SSLM) showed consistent CF₂ unit increments of 0.59, and CH₂ unit increments of 0.53, for the log K_MW of perfluorinated and hydrogenated anions, respectively. PFSAs sorbed 0.90 log units stronger than analogue PFCAs; C _xSO₄ sorbed 0.75 log units stronger than analogue C _xSO₃ anions. The log K_MW values for the octyl analogues increase in the order H(CH₂)₈SO₃^- (1.74) < H(CH₂)₈SO₄^- (2.58) < F(CF₂)₈CO₂^- (PFNA, 4.04) < F(CF₂)₈SO₃^- (PFOS, 4.88). Intrinsic partition ratios determined on a phospholipid coated HPLC column (IAM-HPLC) closely aligned with SSLM K_MW values. COSMO-RS based molecular calculations of K_MW aligned with SSLM K_MW values for hydrogenated anions with C₈-C₁₄ alkyl chains but strongly underestimated CF₂ and CH₂ unit increments for C₄-C₈ based anions. Dividing the critical narcotic membrane burden of 100 mmol/kg by the experimental K_MW predicts lethal baseline toxicity concentrations (LC_50,narc). The LC_50,narc coincides with the lowest reported acute LC₅₀ values for several anionic surfactants but were on average about an order of magnitude lower.

Solubility Constraints on Aquatic Ecotoxicity Testing of Anionic Surfactants

In order to develop models that can predict the environmental behavior and effects of chemicals, reliable experimental data are needed. However, for anionic surfactants the number of ecotoxicity studies is still limited. The present study therefore aimed to determine the aquatic ecotoxicity of three classes of anionic surfactants. To this purpose we subjected daphnids (Daphnia magna) for 48 h to alkyl carboxylates (C_xCO₂^-), alkyl sulfonates (C_xSO₃^-), and alkyl sulfates (C_xSO₄^-) with different carbon chain lengths (x). However, all surfactants with x > 11 showed less than 50% immobility at water solubility. Hence, EC₅₀ values for only few surfactants could be gathered: C₉CO₂^- (16 mg L^-1), C₁₁CO₂^- (0.8 mg L^-1) and C₁₁SO₄^- (13.5 mg L^-1). Data from these compounds showed an increase in ecotoxicity with a factor 4.5 per addition of a hydrocarbon unit to the alkyl chain, and a factor 20 when replacing the sulfate head group by a carboxylate head group. Unfortunately, we could not test carboxylates with a broader variety of chain lengths because solubility limited the range of chain length that can be tested.

Echogenicity enhancement by end-fluorinated polylactide perfluorohexane nanocapsules: Towards ultrasound-activable nanosystems

Polylactide (PLA) polymers containing five distinct lengths of fluorinated (from C₃F₇ to C₁₃F₂₇) and non-fluorinated (C₆H₁₃) end-groups were successfully synthesized by ring-opening polymerization of d,l-lactide. Fluorination was expected to increase the encapsulation efficiency of perfluorohexane (PFH). 150 nm nanocapsules were obtained and ¹⁹F nuclear magnetic resonance revealed that nanocapsules formulated with fluorinated polymers increased by 2-fold the encapsulation efficiency of PFH compared with non-fluorinated derivatives, without any effect of fluorine chain length. Fluorination of the polymers did not induce any specific in vitro cytotoxicity of nanocapsules towards HUVEC and J774.A1 cell lines. The echogenicity of fluorinated-shelled nanocapsules was increased by 3-fold to 40-fold compared to non-fluorinated nanocapsules or nanoparticles devoid of a perfluorohexane core for both conventional and contrast-specific ultrasound imaging modalities. In particular, an enhanced echogenicity and contrast-specific response was observed as the fluorinated chain-length increased, probably due to an increase of density and promotion of bubble nucleation. When submitted to focused ultrasound, both intact and exploded nanocapsules could be observed, also with end-group dependency, indicating that PFH was partly vaporized. These results pave the way to the design of theranostic perfluorohexane nanocapsules co-encapsulating a drug for precision delivery using focused ultrasound.

STATEMENT OF SIGNIFICANCE

We have synthesized novel fluorinated polyesters and formulated them into nanocapsules of perfluorohexane as ultrasound contrast agents. This nanosystem has been thoroughly characterized by several techniques and we show that fluorination of the biodegradable polymer favors the encapsulation of perfluorohexane without producing further reduction of cell viability. Contrary to nanocapsules of perfluoroctyl bromide formulated with the fluorinated polymers [32], the presence of the fluorinated moieties leads to an increase of echogenicity that is dependent of the length of the fluorinated moiety. Morevover, the ability of nanocapsules to explode when submitted to focused ultrasound also depends on the length of the fluorinated chain. These results pave the way to theranostic perfluorohexane nanocapsules co-encapsulating a drug for precision delivery using focused ultrasound.

Effects of three diamides (chlorantraniliprole, cyantraniliprole and flubendiamide) on life history, embryonic development and oxidative stress biomarkers of Daphnia magna

The diamides have become one of the most promising new classes of insecticides. In this study, we evaluated the toxicity of three diamides (chlorantraniliprole, cyantraniliprole and flubendiamide) to Daphnia magna. The acute toxicity test showed that the 48-h EC₅₀ of chlorantraniliprole, cyantraniliprole and flubendiamide were 8.5, 23.9 and 63.5 μg/L, respectively. Biochemical measurements revealed a significant increase in reactive oxygen species (ROS) in D. magna after acute exposure to the three diamides. A significant decrease in activities of antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) was observed, which was consistent with the down-regulated transcription of antioxidant genes sod and gpx. Catalase (CAT) activity exhibited a significant increase while the related gene cat showed no obvious change in daphnids acutely exposed to the three diamides. The chronic test revealed that the three diamides could cause lethal and sub-lethal effects on daphnids within constricted range of concentrations at μg/L level. The 21-d EC₅₀ of chlorantraniliprole, cyantraniliprole and flubendiamide for mobility were 5.0, 13.6 and 36.8 μg/L, respectively. The chronic LOEC of chlorantraniliprole, cyantraniliprole and flubendiamide based on survival, growth and reproduction of D. magna were 4.05, 10.24 and 19.36 μg/L, respectively. Moreover, these three diamides can induce severe developmental abnormalities in D. magna embryos including underdeveloped second antennae, curved tail spine and abnormal body region after acute exposure and the 48-h EC₅₀ were 6.2, 14.1 and 30.8 μg/L for chlorantraniliprole, cyantraniliprole and flubendiamide respectively. Our findings indicate that even low levels of diamides can pose ecological risks to aquatic ecosystems.

End-chain fluorination of polyesters favors perfluorooctyl bromide encapsulation into echogenic PEGylated nanocapsules

Fluorination of polyesters favors the encapsulation efficiency of perfluorooctyl bromide into nanocapsules.

Novel Fluorinated Polymers Containing Short Perfluorobutyl Side Chains and Their Super Wetting Performance on Diverse Substrates

Because the emission of perfluorooctanoic acid (PFOA) was completely prohibited in 2015, the widely used poly- and perfluoroalkyl substances with long perfluoroalkyl groups must be substituted by environmentally friendly alternatives. In this study, one kind of potential alternative (i.e., fluorinated polymers with short perfluorobutyl side chains) has been synthesized from the prepared monomers {i.e., (perfluorobutyl)ethyl acrylate (C4A), (perfluorobutyl)ethyl methacrylate (C4MA), 2-[[[[2-(perfluorobutyl)]sulfonyl]methyl]amino]ethyl acrylate (C4SA), and methacrylate (C4SMA)}, and the microstructure, super wetting performance, and applications of the synthesized fluorinated polymers were systematically investigated. The thermal and crystallization behaviors of the fluoropolymer films were characterized by differential scanning calorimetry and wide-angle X-ray diffraction analysis, respectively. Dynamic water-repellent models were constructed. The stable low surface energy and dynamic water- and oil-repellent properties of these synthesized fluorinated polymers with short perfluorobutyl side chains were attributed to the synergetic effect of amorphous fluorinated side chains in perfluoroalkyl acrylate and crystalline hydrocarbon pendant groups in stearyl acrylate. Outstanding water- and oil-repellent properties of fabrics and any other substrates could be achieved by a facile dip-coating treatment using a fluorinated copolymer dispersion. As a result, we believe that our prepared fluorinated copolymers are potential candidates to replace the fluoroalkylated polymers with long perfluorinated chains in nonstick and self-cleaning applications in our daily life.

Aquatic acute toxicity assessments of molybdenum (+VI) to Daphnia magna

Generally, molybdenum (Mo) metals in the environment are very rare, but wastewater discharges from industrial processes may contain high concentrations of Mo, which has the potential to contaminate water or soil if not handled properly. In this study, the impact of three common compounds of hexavalent Mo (sodium molybdate (Na2MoO4‧2H2O), ammonium molybdate ((NH4)6Mo7O24‧4H2O) and molybdenum trioxide (MoO3)) in an aquatic system were assessed based on 48-h exposure acute toxicity to Daphnia magna (D. magna). The LC50 toxicities for associated conjugate ions including Na(+), Cl(-), SO4(2-), and NH4(+) were determined. Furthermore, the LC50 values for the three forms of hexavalent Mo were determined, and the acute toxicities of the Mo forms were found to follow the order: (NH4)6Mo7O24‧4H2O > MoO3 > Na2MoO4‧2H2O in solution. (NH4)6Mo7O24‧4H2O exhibited the lowest LC50 of 43.3 mg L(-1) (corresponding to 23.5 mg Mo L(-1)) among the three molybdenum salts. The research confirmed that the toxicity of molybdenum in the aquatic system is highly dependent on the form of molybdenum salts used, and is also associated with the influence of the background water quality.

Modeling and Classification of Kinetic Patterns of Dynamic Metabolic Biomarkers in Physical Activity

The objectives of this work were the classification of dynamic metabolic biomarker candidates and the modeling and characterization of kinetic regulatory mechanisms in human metabolism with response to external perturbations by physical activity. Longitudinal metabolic concentration data of 47 individuals from 4 different groups were examined, obtained from a cycle ergometry cohort study. In total, 110 metabolites (within the classes of acylcarnitines, amino acids, and sugars) were measured through a targeted metabolomics approach, combining tandem mass spectrometry (MS/MS) with the concept of stable isotope dilution (SID) for metabolite quantitation. Biomarker candidates were selected by combined analysis of maximum fold changes (MFCs) in concentrations and P-values resulting from statistical hypothesis testing. Characteristic kinetic signatures were identified through a mathematical modeling approach utilizing polynomial fitting. Modeled kinetic signatures were analyzed for groups with similar behavior by applying hierarchical cluster analysis. Kinetic shape templates were characterized, defining different forms of basic kinetic response patterns, such as sustained, early, late, and other forms, that can be used for metabolite classification. Acetylcarnitine (C2), showing a late response pattern and having the highest values in MFC and statistical significance, was classified as late marker and ranked as strong predictor (MFC = 1.97, P < 0.001). In the class of amino acids, highest values were shown for alanine (MFC = 1.42, P < 0.001), classified as late marker and strong predictor. Glucose yields a delayed response pattern, similar to a hockey stick function, being classified as delayed marker and ranked as moderate predictor (MFC = 1.32, P < 0.001). These findings coincide with existing knowledge on central metabolic pathways affected in exercise physiology, such as β-oxidation of fatty acids, glycolysis, and glycogenolysis. The presented modeling approach demonstrates high potential for dynamic biomarker identification and the investigation of kinetic mechanisms in disease or pharmacodynamics studies using MS data from longitudinal cohort studies.

Human metabolism is controlled through basic kinetic regulatory mechanisms, where the overall system aims to maintain a state of homeostasis. In response to external perturbations, such as environmental influences, nutrition or physical exercise, circulating metabolites show specific kinetic response patterns, which can be computationally modeled. In this work, we searched for dynamic metabolic biomarker candidates and analyzed specific kinetic mechanisms from longitudinal metabolic concentration data, obtained through a cycle ergometry stress test. In total, 110 metabolites measured from blood samples of 47 individuals were analyzed using tandem mass spectrometry (MS/MS). Dynamic biomarker candidates could be selected based on the amplitudes of changes in metabolite concentrations and the significance of statistical hypothesis testing. We were able to characterize specific kinetic patterns for groups of similarly behaving metabolites. Kinetic shape templates were identified, defining basic kinetic response patterns to physical exercise, such as sustained, early, late and other shape forms. The presented approach contributes to a better understanding of (patho)physiological biochemical mechanisms in human health, disease or during drug therapy, by offering tools for classifying dynamic biomarker candidates and for modeling and characterizing kinetic regulatory mechanisms from longitudinal experimental data.