Comparison of developmental toxicity induced by PFOA, HFPO-DA, and HFPO-TA in zebrafish embryos

Small-molecule intercalation induces defective generation of bromine-doped bismuth oxychloride to enhance photocatalytic degradation and detoxification of tetracycline

Photocatalysts are one of the effective methods to degrade antibiotic contamination, but the efficiency is low and the toxicity is not well recognized. Deep lattice doping to induce defect generation is an effective way to improve the performance of photocatalysts. Here, defect-rich bromine-doped BiOCl-XBr photocatalysts were constructed with the help of small molecules inserted into the interlayer. The photocatalytic degradation performance of BiOCl-XBr was significantly enhanced, and its degradation rate was up to about 12 times that of BiOCl monomer. The main reasons for the stronger photocatalytic performance of BiOCl-XBr include Br doping to enhance visible light absorption, surface defects, and Bi valence changes to improve charge transport. The degradation of tetracycline (TC) produced more toxic intermediates, and the biotoxicity experiments also confirmed that the toxicity showed a trend of increasing and then decreasing, indicating that the more toxic intermediates were also mineralized during the degradation process. However, the mortality and hatching rate of zebrafish in the exposed group after degradation recovered but changed their activity pattern under light and dark conditions. This further warns us to focus on the toxicity changes after antibiotic degradation. Finally, based on the free radical analysis, the mechanism of photocatalytic degradation and detoxification of TC by BiOCl-XBr was proposed.

Fractionation and tidal characteristics of per- and polyfluoroalkyl substances in the estuarine maximum turbidity zone

Complex tidal processes and suspended particulate matter (SPM) behavior influence the land-sea transport of terrestrial contaminants in estuaries. Contaminants are generally trapped within the estuarine maximum turbidity zone (MTZ), where SPM concentrations peak, misleading flux estimation. Here, we conducted high-resolution continuous sampling over two tidal cycles within the MTZ of a semidiurnal estuary. Tidal variations of per- and polyfluoroalkyl substances (PFAS), a class of persistent organic pollutants, were analyzed in dissolved water and size-fractionated SPM. Results showed that variations in dissolved PFAS may related to the mixing of upstream and downstream. The predominant size range for SPM was found in 1-31 μm (75 %, mainly 10-31 μm), but the PFAS tended to be sorbed by 0.22-1 μm (60 %) and > 31 μm (37 %) fractions. Except during periods of sediment resuspension when particulate PFAS concentration decreased, the PFAS concentration in the 1-31 μm increased during flood tides and decreased during ebb tides, which may not be related to organic carbon/elemental carbon levels. The hourly dynamic flux of dissolved-phase and particulate-phase PFAS transport to the sea in the MTZ was calculated by combining it with a hydrodynamic model. This study first highlights the size-fractionated PFAS transport under tidal influences and provides hourly flux estimation with a hydrodynamic model.

Adverse outcome pathway for the neurotoxicity of Per- and polyfluoroalkyl substances: A systematic review

Per- and polyfluoroalkyl substances (PFAS) are endocrine disruptors with unambiguous neurotoxic effects. However, due to variability in experimental models, population characteristics, and molecular endpoints, the elucidation of mechanisms underlying PFAS-induced neurotoxicity remains incomplete. In this review, we utilized the adverse outcome pathway (AOP) framework, a comprehensive tool for evaluating toxicity across multiple biological levels (molecular, cellular, tissue and organ, individual, and population), to elucidate the mechanisms of neurotoxicity induced by PFAS. Based on 271 studies, the reactive oxygen species (ROS) generation emerged as the molecular initiating event 1 (MIE1). Subsequent key events (KEs) at the cellular level include oxidative stress, neuroinflammation, apoptosis, altered Ca2+ signal transduction, glutamate and dopamine signaling dyshomeostasis, and reduction of cholinergic and serotonin. These KEs culminate in synaptic dysfunction at organ and tissue levels. Further insights were offered into MIE2 and upstream KEs associated with altered thyroid hormone levels, contributing to synaptic dysfunction and hypomyelination at the organ and tissue levels. The inhibition of Na+/I- symporter (NIS) was identified as the MIE2, initiating a cascade of KEs at the cellular level, including altered thyroid hormone synthesis, thyroid hormone transporters, thyroid hormone metabolism, and binding with thyroid hormone receptors. All KEs ultimately result in adverse outcomes (AOs), including cognition and memory impairment, autism spectrum disorders, attention deficit hyperactivity disorders, and neuromotor development impairment. To our knowledge, this review represents the first comprehensive and systematic AOP analysis delineating the intricate mechanisms responsible for PFAS-induced neurotoxic effects, providing valuable insights for risk assessments and mitigation strategies against PFAS-related health hazards.

Are HFPO-TA and HFPO-DA safe substitutes for PFOA? A comprehensive toxicity study using zebrafish (Danio rerio) embryos and adults

Due to the multiple biotoxicity caused by perfluorooctanoic acid (PFOA), the application and production of PFOA is regulated globally. PFOA substitutes including hexafluoropropylene oxide trimer acid (HFPO-TA) and hexafluoropropylene oxide dimer acid (HFPO-DA) have been applied to industrial processes and subsequently detected in surface and groundwater, yet there is a lack of comprehensive assessment of their toxicity to aquatic organisms. Therefore, under the same time and same experimental conditions, the toxic effects and differences of PFOA, HFPO-TA, and HFPO-DA on zebrafish adults and embryos were assessed from oxidative damage, apoptosis, immune function impairment, and protein interactions. The HFPO-TA and HFPO-DA caused more severe oxidative damage than PFOA. While PFOA only disrupted immune function in adults, HFPO-TA and HFPO-DA affected immune homeostasis in both adults and embryos. Integrated biomarker response results showed that superoxide dismutase (SOD) activity and reactive oxygen species content could be used as early warning indicators of toxicity in adults and embryos, respectively. Molecular docking simulations identified HFPO-TA as having the lowest binding energy with SOD proteins, thereby exerting the greatest effect on SOD activity. Compared to PFOA, HFPO-TA and HFPO-DA exhibited a greater toxicological response and, therefore, may not be suitable substitutes for PFOA.

Impact of hexafluoropropylene oxide trimer acid (HFPO-TA) on sex differentiation after exposures during different development stages of zebrafish (Danio rerio)

Hexafluoropropylene oxide trimer acid (HFPO-TA), a novel alternative to perfluorooctanoic acid (PFOA), has been widely used and ubiquitously detected in aquatic environments. However, its potential effects on sex differentiation of aquatic organisms are not well known. Therefore, in this study, zebrafish were exposed to HFPO-TA at different development stages (0-21, 21-42, and 42-63 dpf) to investigate the effects on sex differentiation and its underlying mechanisms. All three exposures to HFPO-TA resulted in the feminization of zebrafish, and the impact of Stage II was most significant. The transcription levels of key genes related to female differentiation (bpm15, cyp19a1a, esr1, vtg1, and sox9b) were up-regulated, while those of key genes related to male differentiation (dmrt1, gata4, amh, and sox9a) were down-regulated, which could lead to the feminization. In addition, it was found that the dysregulations of these genes were prolonged in adult zebrafish even through a long recovery, which could cause sex imbalance in populations. Therefore, HFPO-TA might not be a safe alternative to PFOA, and more evidences from multi- and transgenerational toxicology are warranted.

Hexafluoropropylene oxide trimer acid (HFPO-TA) disrupts sex differentiation of zebrafish (Danio rerio) via an epigenetic mechanism of DNA methylation

Hexafluoropropylene oxide trimer acid (HFPO-TA), an alternative to perfluorooctanoic acid, has been shown to have estrogenic effects. However, its potential to disrupt fish sex differentiation during gonadal development remains unknown. Therefore, this study exposed zebrafish to HFPO-TA from approximately 2 hours post fertilization (hpf) to 60 days post fertilization (dpf) to investigate its effects on sex differentiation. Results indicated that HFPO-TA disrupted steroid hormone homeostasis, delayed gonadal development in both sexes, and resulted in a female-skewed sex ratio in zebrafish. HFPO-TA exposure up-regulated gene expressions of cyp19a1a, esr1, vtg1 and foxl2, while down-regulated those of amh, sox9a and dmrt1. These suggested that HFPO-TA dysregulated the expressions of key genes related to sex differentiation of zebrafish, promoted the production and activation of estrogen, and further induced the feminization. Interestingly, we observed promoter hypomethylation of cyp19a1a and promoter hypermethylation of amh in male zebrafish, which were negatively associated with their gene expressions. These suggested that HFPO-TA dysregulated these key genes through DNA methylation in their promoters. Therefore, the HFPO-TA disrupted the sex differentiation of zebrafish through an epigenetic mechanism involving DNA methylation, ultimately skewing the sex ratio towards females. Overall, this study demonstrated adverse effects of HFPO-TA on fish sex differentiation and provided novel insights into the underlying epigenetic mechanism.

Disruption of zebrafish sex differentiation by emerging contaminants hexafluoropropylene oxides at environmental concentrations via antagonizing androgen receptor pathways

As alternatives of perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimeric acid (HFPO-DA) and trimeric acid (HFPO-TA) have been detected increasingly in environmental media and even humans. They have been shown to exhibit reproductive toxicity to model species, but their effects on human remain unclear due to the knowledge gap in their mode of action. Herein, (anti-)androgenic effects of the two HFPOs and PFOA were investigated and underlying toxicological mechanism was explored by combining zebrafish test, cell assay and molecular docking simulation. Exposure of juvenile zebrafish to the chemicals during sex differentiation promoted feminization, with HFPO-TA acting at an environmental concentration of 1 μg/L. The chemicals inhibited proliferation of human prostate cells and transcriptional activity of human and zebrafish androgen receptors (AR), with HFPO-TA displaying the strongest potency. Molecular docking revealed that the chemicals bind to AR in a conformation similar to a known AR antagonist. Combined in vivo, in vitro and in silico results demonstrated that the chemicals disrupted sex differentiation likely by antagonizing AR-mediated pathways, and provided more evidence that HFPO-TA is not a safe alternative to PFOA.

Evaluating potential developmental toxicity of perfluoroalkyl and polyfluoroalkyl substances in Xenopus laevis embryos and larvae

As part of the US Environmental Protection Agency's perfluoroalkyl and polyfluoroalkyl substances (PFAS) Action Plan, the agency is committed to increasing our understanding of the potential ecological effects of PFAS. The objective of these studies was to examine the developmental toxicity of PFAS using the laboratory model amphibian species Xenopus laevis. We had two primary aims: (1) to understand the developmental toxicity of a structurally diverse set of PFAS compounds in developing embryos and (2) to characterize the potential impacts of perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonic acid (PFHxS), perfluorooctanoic acid (PFOA), and hexafluoropropylene oxide-dimer acid (HFPO-DA a.k.a. GenX), on growth and thyroid hormone-controlled metamorphosis. We employed a combination of static renewal and flow-through exposure designs. Embryos were exposed to 17 structurally diverse PFAS starting at the midblastula stage through the completion of organogenesis (96 h). To investigate impacts on PFOS, PFOA, PFHxS, and HFPO-DA on development and metamorphosis, larvae were exposed from premetamorphosis (Nieuwkoop Faber stage 51 or 54) through pro metamorphosis. Of the PFAS tested in embryos, only 1H,1H,10H,10H-perfluorodecane-1,10-diol (FC10-diol) and perfluorohexanesulfonamide (FHxSA) exposure resulted in clear concentration-dependent developmental toxicity. For both of these PFAS, a significant increase in mortality was observed at 2.5 and 5 mg/L. For FC10-diol, 100% of the surviving embryos were malformed at 1.25 and 2.5 mg/L, while for FHxSA, a significant increase in malformations (100%) was observed at 2.5 and 5 mg/L. Developmental stage achieved was the most sensitive endpoint with significant effects observed at 1.25 and 0.625 mg/L for FC10-diol and FHxSA, respectively. In larval studies, we observed impacts on growth following exposure to PFHxS and PFOS at concentrations of 100 and 2.5 mg/L, respectively, while no impacts were observed in larvae when exposed to PFOA and HFPO-DA at concentration of 100 mg/L. Further, we did not observe impacts on thyroid endpoints in exposed larvae. These experiments have broadened our understanding of the impact of PFAS on anuran development.

Synergistic developmental effects of zebrafish exposed to combined perfluorooctanoic acid and atrazine

Perfluorooctanoic acid (PFOA) and atrazine are two endocrine disruptors that are widely found in waters. Negative effects of PFOA and atrazine have been studied individually, but few data have focused on their combined effects. Here, zebrafish embryos were used as model to investigate the combined toxicity of PFOA and atrazine. The acute toxicity of atrazine (11.9 mg/L) to zebrafish embryos was much higher than that of perfluorooctanoic acid (224.6 mg/L) as shown by the 120h-LC50 value. Developmental effects, including delayed yolk sac absorption, spinal curvature, and liver abnormalities, were observed in both one- and two-component exposures. Notably, the rate of embryonic malformations in the co-exposure group was more than twice as high as that of single component exposure in the concentration range of 1/8-1/2 EC50, which indicated a synergistic effect of the binary mixture. The synergistic effect of PFOA-atrazine was further validated by combinatorial index (CI) modeling. In addition, changes of amino acid metabolites, reactive oxygen species and superoxide dismutase indicated that oxidative stress might be the main pathway for enhanced toxicity under co-exposure condition. Overall, co-exposure of PFOA and atrazine resulted in stronger developmental effects and more complicated amino acid metabolic response toward zebrafish, compared with single component exposure.

Maternal or Paternal Antibiotics? Intergenerational Transmission and Reproductive Toxicity in Zebrafish

Despite the known direct toxicity of various antibiotics to aquatic organisms, the potential chronic impact through intergenerational transmission on reproduction remains elusive. Here, we exposed zebrafish to a mixture of 15 commonly consumed antibiotics at environmentally relevant concentrations (1 and 100 μg L-1) with a cross-mating design. A high accumulation of antibiotics was detected in the ovary (up to 904.58 ng g-1) and testis (up to 1704.49 ng g-1) of F0 fish. The transmission of antibiotics from the F0 generation to the subsequent generation (F1 offspring) was confirmed with a transmission rate (ki) ranging from 0.11 to 2.32. The maternal transfer of antibiotics was significantly higher, relative to paternal transfer, due to a greater role of transmission through ovarian enrichment and oviposition compared to testis enrichment. There were similar impairments in reproductive and developmental indexes on F1 eggs found following both female and male parental exposure. Almost all antibiotics were eliminated in F2 eggs in comparison to F1 eggs. However, there were still reproductive and developmental toxic responses observed in F2 fish, suggesting that antibiotic concentration levels were not the only criterion for evaluating the toxic effects for each generation. These findings unveil the intergenerational transmission mechanism of antibiotics in fish models and underscore their potential and lasting impact in aquatic environments.

Hexafluoropropylene oxide trimer acid exposure triggers necroptosis and inflammation through the Wnt/β-catenin/NF-κB axis in the liver

Hexafluoropropylene oxide trimer acid (HFPO-TA), an emerging alternative to perfluorooctanoic acid (PFOA), has recently been identified as a significant environmental pollutant. Nevertheless, there is a scarcity of studies regarding the hepatotoxic effects of HFPO-TA. Here, we investigated the types and potential mechanisms of liver damage caused by HFPO-TA. Initially, we validated that the introduction of HFPO-TA resulted in the Wnt/β-catenin signaling (W/β signaling) activation, as well as the induction of necroptosis and inflammation, both in the liver of mice and in HepG2 cells. Subsequently, we established that the W/β signaling mediated the necroptosis and inflammation observed in the liver and HepG2 cells exposed to HFPO-TA. Finally, we demonstrated that the phosphorylated form of NF-κB p65 (p-NF-κB p65) played a role in mediating the necroptosis and inflammation, and its activity could be regulated by the W/β signaling pathway in the liver of mice and HepG2 cells exposed to HFPO-TA. In conclusion, our investigation elucidates the role of HFPO-TA in inducing necroptosis and inflammation in the liver, which is facilitated through the activation of the W/β/NF-κB axis.

Activation of estrogen-related receptor: An alternative mechanism of hexafluoropropylene oxide homologs estrogenic effects

Perfluorooctanoic acid (PFOA) alternatives such as hexafluoropropylene oxide homologs (HFPOs) cause concern due to increased occurrence in the environment as well as potential bioaccumulation and toxicity. HFPOs have been demonstrated to activate the estrogen receptor (ER) pathway. The ER pathway is homologous and connected to the estrogen-related receptor (ERR) pathway, but HFPOs effects on the ERR pathway have not been studied. Hence, we assessed the potential estrogenic effects of HFPOs via ERRγ pathway. In vitro assays revealed that HFPO dimeric, trimeric, and tetrameric acids (HFPO-DA, -TA, and -TeA, respectively), acted as ERRγ agonists, activating the transcription of both human and zebrafish ERRγ at low concentrations, but inhibiting zebrafish ERRγ at high concentrations. We also found that HFPO-TA promoted the human endometrial cancer cells (Ishikawa cells) proliferation via ERRγ/EGF, Cyclin D1 pathway. The HFPO-TA-induced proliferation of Ishikawa cells was inhibited by co-exposure with a specific antagonist of ERRγ, GSK5182. In vivo exposure of female zebrafish to HFPO-TA disturbed sex hormone levels, interfered with the gene expression involved in estrogen synthesis and follicle regulation, and caused histopathological lesions in the ovaries, which were similar to those induced by a known ERRγ agonist GSK4716. Taken together, this study revealed a new mechanism concerning the estrogenic effect of HFPOs via activation of the ERRγ pathway.

Dose Response, Dosimetric, and Metabolic Evaluations of Replacement PFAS Perfluoro-(2,5,8-trimethyl-3,6,9-trioxadodecanoic) Acid (HFPO-TeA)

Few studies are available on the environmental and toxicological effects of perfluoroalkyl ether carboxylic acids (PFECAs), such as GenX, which are replacing legacy PFAS in manufacturing processes. To collect initial data on the toxicity and toxicokinetics of a longer-chain PFECA, male and female Sprague Dawley rats were exposed to perfluoro-(2,5,8-trimethyl-3,6,9-trioxadodecanoic) acid (HFPO-TeA) by oral gavage for five days over multiple dose levels (0.3-335.2 mg/kg/day). Clinically, we observed mortality at doses >17 mg/kg/day and body weight changes at doses ≤17 mg/kg/day. For the 17 mg/kg/day dose level, T3 and T4 thyroid hormone concentrations were significantly decreased (p < 0.05) from controls and HFPO-TeA plasma concentrations were significantly different between sexes. Non-targeted analysis of plasma and in vitro hepatocyte assay extractions revealed the presence of another GenX oligomer, perfluoro-(2,5-dimethyl-3,6-dioxanonanoic) acid (HFPO-TA). In vitro to in vivo extrapolation (IVIVE) parameterized with in vitro toxicokinetic data predicted steady-state blood concentrations that were within seven-fold of those observed in the in vivo study, demonstrating reasonable predictivity. The evidence of thyroid hormone dysregulation, sex-based differences in clinical results and dosimetry, and IVIVE predictions presented here suggest that the replacement PFECA HFPO-TeA induces a complex and toxic exposure response in rodents.

Perfluorooctanoic acid induces behavioral impairment and oxidative injury in Nauphoeta cinerea nymphs

Perfluorooctanoic acid (PFOA) is a persistent organic contaminant with potential health threats to both animals and humans. However, the impact of PFOA on insects, which play significant roles in ecosystems, is understudied. We evaluated the toxicological impact of ecologically relevant concentrations of PFOA (0, 25, 50, 100, and 200 µg L-1) on Nauphoeta cinerea nymphs following exposure for 42 consecutive days. We analyzed the behavior of the insects with automated video-tracking software and processed the head, midgut, and fat body for biochemical assays. PFOA-exposed insects exhibited significant reductions in locomotory abilities and an increase in freezing time. Furthermore, PFOA exposure reduced acetylcholinesterase activity in the insect head. PFOA exposure increased the activities of superoxide dismutase, glutathione peroxidase, and catalase in the head and midgut, but decreased them in the fat body. PFOA also significantly increased glutathione-S transferase activity, while decreasing glutathione levels in the head, midgut, and fat body. Additionally, PFOA exposure increased reactive oxygen and nitrogen species, nitric oxide, lipid peroxidation, and protein carbonyl contents in the head, midgut, and fat body of the insects. In conclusion, our findings indicate that PFOA exposure poses an ecological risk to Nauphoeta cinerea.

Significant Variability in the Developmental Toxicity of Representative Perfluoroalkyl Acids as a Function of Chemical Speciation

Current toxicological data of perfluoroalkyl acids (PFAAs) are disparate under similar exposure scenarios. To find the cause of the conflicting data, this study examined the influence of chemical speciation on the toxicity of representative PFAAs, including perfluorooctanoic acid (PFOA), perfluorobutane carboxylic acid (PFBA), and perfluorobutanesulfonic acid (PFBS). Zebrafish embryos were acutely exposed to PFAA, PFAA salt, and a pH-negative control, after which the developmental impairment and mechanisms were explored. The results showed that PFAAs were generally more toxic than the corresponding pH control, indicating that the embryonic toxicity of PFAAs was mainly caused by the pollutants themselves. In contrast to the high toxicity of PFAAs, PFAA salts only exhibited mild hazards to zebrafish embryos. Fingerprinting the changes along the thyroidal axis demonstrated distinct modes of endocrine disruption for PFAAs and PFAA salts. Furthermore, biolayer interferometry monitoring found that PFOA and PFBS acids bound more strongly with albumin proteins than did their salts. Accordingly, the acid of PFAAs accumulated significantly higher concentrations than their salt counterparts. The present findings highlight the importance of chemical forms to the outcome of developmental toxicity, calling for the discriminative risk assessment and management of PFAAs and salts.

Toxicological Mechanisms of Emerging Per-/poly-fluoroalkyl Substances: Focusing on Transcriptional Activity and Gene Expression Disruption

Environmental and human monitoring studies have witnessed increasing occurrence of emerging per-/poly-fluoroalkyl substances (ePFASs) worldwide. Three classes of ePFASs, namely chlorinated polyfluoroalkylether sulfonic acids, hexafluoropropylene oxide homologues and short-chain perfluoroalkyl acids attracted the most attention. It is, therefore, the goal of this review to systematically and critically analyse the toxicity and toxicological mechanisms of these ePFASs based on the papers published between 2017 and 2022. The review summarized the main findings from both in vivo and in vitro studies, covering the hepatotoxicity of ePFASs and their interference with the endocrine system, including reproductive, developmental and thyroid toxicity. It also summarized the changes in gene expression in the hypothalamic-pituitary-thyroid axis and hypothalamic-pituitary-gonad axis of the model organisms after ePFASs exposure. The changes in gene expression in vitro and in vivo provide a clearer understanding of the toxicological mechanisms of ePFASs interference on hormonal levels (i.e., estradiol, testosterone, and thyroid hormones), developmental disturbance (e.g., swim bladder dysfunction) and lipid metabolism disruption (e.g., lipid droplet accumulation and hepatomegaly). In the end, future research directions on the toxicological mechanisms of ePFASs are suggested.

Persistent oxidative injury and neurobehavioral impairment in adult male and female Nauphoeta cinerea exposed to perfluorooctanoic acid

This study aimed to elucidate if the toxicity of perfluorooctanoic acid (PFOA), an emerging persistent organic contaminant, is reversible or not in adult male and female Nauphoeta cinerea. Both sexes of Nauphoeta cinerea were separately exposed to 0, 1 and 5 mg/L PFOA in drinking water for 21 consecutive days. PFOA-exposed Nauphoeta cinerea exhibited significant deficits in the locomotor and exploratory capabilities with concomitant increase in anxiogenic behaviors which persisted after cessation of PFOA exposure. Moreover, PFOA-induced decrease in acetylcholinesterase activity persisted after cessation of PFOA exposure in both insects' sexes. Catalase and superoxide dismutase activities were increased in the midgut but restored to control following cessation of PFOA exposure. The increased reactive oxygen and nitrogen species, nitric oxide and hydrogen peroxide levels persisted in the head whereas they were abated in the midgut after cessation of PFOA exposure. However, PFOA-induced persistent increase in lipid peroxidation and protein carbonyl levels in the head and midgut of insects. Collectively, PFOA exposure elicited persistent neurobehavioral and oxidative injury similarly in both sexes of adult Nauphoeta cinerea during this investigation.

Short-chain per- and polyfluoralkyl substances (PFAS) effects on oxidative stress biomarkers in human liver, kidney, muscle, and microglia cell lines

Long-chain per- and polyfluoralkyl substances (PFAS) are ubiquitous contaminants implicated in the induction of intracellular reactive oxygen species (ROS), compromising antioxidant defense mechanisms in vitro and in vivo. While a handful of studies have assessed oxidative stress effects by PFAS, few specifically address short-chain PFAS. We conducted an evaluation of oxidative stress biomarkers in vitro following exposures to low (1 nM) and high (1 μM) concentrations of five short-chain PFAS compounds: perfluorobutanesulfonic acid (PFBS), perfluorohexanoic acid (PFHxA), [undecafluoro-2-methyl-3-oxahexanoic acid (HFPO-DA)], 6:2 fluorotelomer alcohol (6:2 FTOH) and perfluorohexanesulfonic acid (PFHxS). We conducted experiments in human kidney (HEK293-hTLR2), liver (HepaRG), microglia (HMC-3), and muscle (RMS-13) cell lines. Fluorescence microscopy measurements in HepaRG cells indicated ROS generation in cells exposed to PFBS and PFHxA for 24 h. Antioxidant enzyme activities were determined following 24 h short-chain PFAS exposures in HepaRG, HEK293-hTLR2, HMC-3, and RMS-13. Notably, exposure to PFBS for 24 h increased the activity of GPX in all four cell types at 1 μM and 1 nM in HepaRG and RMS-13 cells. Every short-chain PFAS evaluated, except for PFHxS, increased the activity of at least one antioxidant enzyme. To our knowledge, this is the first study of its kind to explore antioxidant defense alterations to microglia and muscle cell lines by PFAS. The findings of this study hold great potential to contribute to the limited understanding of short-chain PFAS mechanisms of toxicity and provide data necessary to inform the human health risk assessment process.

The metabolites could not be ignored: A comparative study of the metabolite norfluoxetine with its parent fluoxetine on zebrafish (Danio rerio)

The ubiquitous pharmaceuticals in aquatic environments have attracted huge attention due to their significant risks to humans and ecosystems. However, even though the knowledge of the negative effects induced by the parent pharmaceuticals is quite extensive, little is known about their metabolites for a long time. This study provides systematical knowledge about the potential toxicity of metabolite norfluoxetine and its parent fluoxetine on zebrafish (Danio rerio) at the early life stage. The results showed that the metabolite norfluoxetine had similar acute toxicity in fish with the parent fluoxetine. For the altered fish development, there was no significant difference in most cases between the two pharmaceuticals. Compared to the control, the metabolite markedly inhibited the locomotor behavior under light-to-dark transitions, which was comparable to the parent. Norfluoxetine could easily accumulate but hardly eliminate from fish, relative to fluoxetine. In addition, the accumulated fluoxetine in zebrafish may rapidly metabolize to norfluoxetine and then be eliminated through different metabolic pathways. The functional genes related to serotonergic process (5-ht1aa, 5-ht2c, slc6a4b, and vmat), early growth (egr4), and circadian rhythm (per2) were downregulated by both the norfluoxetine and fluoxetine, indicative of the same mode-of-action of norfluoxetine with its parent in these functions. Meanwhile, the alterations caused by norfluoxetine were more pronounced than that of fluoxetine in the genes of 5-ht2c, slc6a4b, vmat, and per2. The molecular docking also confirmed that norfluoxetine could bind with serotonin transporter protein in the same as fluoxetine with a lower binding free energy. Overall, the metabolite norfluoxetine could induce similar and even more toxic effects on zebrafish with the same mode of action. The different and binding energy of the metabolite norfluoxetine and its parent fluoxetine on zebrafish may be responsible for the differentiated effects. It highlights the risks of the metabolite norfluoxetine in the aquatic environment could not be ignored.

Transport and transformation of perfluoroalkyl acids, isomer profiles, novel alternatives and unknown precursors from factories to dinner plates in China: New insights into crop bioaccumulation prediction and risk assessment

Perfluoroalkyl acids (PFAAs) are contaminants of global concern, and the inadvertent consumption of PFAA-contaminated crops may pose a threat to public health. Therefore, systematically studying their source tracing, bioaccumulation prediction and risk assessments in crops is an urgent priority. This study investigated the source apportionment and transport of PFAAs and novel fluorinated alternatives (collectively as per- and polyfluoroalkyl substances, PFASs) from factories to agricultural fields in a fluorochemical industrial region of China. Furthermore, bioaccumulation specificities and prediction of these chemicals in different vegetables were explored, followed by a comprehensive risk assessment from agricultural fields to dinner plates which considered precursor degradation. A positive matrix factorization model revealed that approximately 70 % of PFASs in agricultural soils were derived from fluorochemical manufacturing and metal processing. Alarming levels of ∑PFASs ranged 8.28-84.3 ng/g in soils and 163-7176 ng/g in vegetables. PFAS with short carbon chain or carboxylic acid group as well as branched isomers exhibited higher environmental transport potentials and bioaccumulation factors (BAFs) across a range of vegetables. The BAFs of different isomers of perfluorooctanoic acid (PFOA) decreased as the perfluoromethyl group moved further from the acid functional group. Hexafluoropropylene oxide dimer acid (GenX) showed relatively low BAFs, probably related to its ether bond with a high affinity to soil. Vegetables with fewer Casparian strips (e.g., carrot and radish), or more protein, possessed larger BAFs of PFASs. A bioaccumulation equation integrating critical parameters of PFASs, vegetables and soils, was built and corroborated with a good contamination prediction. After a total oxidizable precursors (TOP) assay, incremental perfluoroalkyl carboxylic acids (PFCAs) were massively found (325-5940 ng/g) in edible vegetable parts. Besides, precursor degradation and volatilization loss of PFASs was firstly confirmed during vegetable cooking. A risk assessment based on the TOP assay was developed to assist the protection of vegetable consumers.