Accumulation, Biotransformation, and Endocrine Disruption Effects of Fluorotelomer Surfactant Mixtures on Zebrafish

Using Zebrafish to Screen Developmental Toxicity of Per- and Polyfluoroalkyl Substances (PFAS)

Per- and polyfluoroalkyl substances (PFAS) are found in many consumer and industrial products. While some PFAS, notably perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are developmentally toxic in mammals, the vast majority of PFAS have not been evaluated for developmental toxicity potential. A concentration-response study of 182 unique PFAS chemicals using the zebrafish medium-throughput, developmental vertebrate toxicity assay was conducted to investigate chemical structural identifiers for toxicity. Embryos were exposed to each PFAS compound (≤100 μM) beginning on the day of fertilization. At 6 days post-fertilization (dpf), two independent observers graded developmental landmarks for each larva (e.g., mortality, hatching, swim bladder inflation, edema, abnormal spine/tail, or craniofacial structure). Thirty percent of the PFAS were developmentally toxic, but there was no enrichment of any OECD structural category. PFOS was developmentally toxic (benchmark concentration [BMC] = 7.48 μM); however, other chemicals were more potent: perfluorooctanesulfonamide (PFOSA), N-methylperfluorooctane sulfonamide (N-MeFOSA), ((perfluorooctyl)ethyl)phosphonic acid, perfluoro-3,6,9-trioxatridecanoic acid, and perfluorohexane sulfonamide. The developmental toxicity profile for these more potent PFAS is largely unexplored in mammals and other species. Based on these zebrafish developmental toxicity results, additional screening may be warranted to understand the toxicity profile of these chemicals in other species.

Association between exposure to per- and perfluoroalkyl substances (PFAS) and reproductive hormones in human: A systematic review and meta-analysis

BACKGROUND

Per- and polyfluoroalkyl substances (PFAS) is persistent endocrine disrupting chemicals. Previous evidence suggests that exposure to PFAS is associated with reproductive hormone levels, but the results of relevant studies are inconsistent. The objective of our study is to determine the association between exposure to PFAS and reproductive hormone levels in gender-specific general population.

METHOD

Based on scientific search strategies, we systematically searched PubMed, Web of Science, Embase, Medline, and Scopus to obtain the eligible studies published before January 21, 2023. The quality of the included articles was assessed using the Office of Health Assessment and Translation (OHAT) Risk of Bias tool. We combined the β coefficient and 95% confidence intervals (CI) using Stata.17 with random-effect model or fixed-effect model. We also performed subgroup analysis, sensitivity analysis, and Begger's and Egger's tests.

RESULTS

Eleven studies involving 7714 participants were included. Meta-analysis showed that PFHxS exposure was positively associated with estradiol (E2) levels in female [β = 0.030, 95% CI: (0.013, 0.046), P = 0.000]. A negative association was found between PFOA [β = -0.012, 95% CI: (-0.023, -0.002), P = 0.017] and PFOS [β = -0.011; 95% CI: (-0.021, -0.000), P = 0.042] exposure with male testosterone (TT) levels. In the subgroup analysis, there were stronger associations in children than in adults. And the high heterogeneity was mainly due to the cross-sectional studies. Publication bias was not found in most of the analyses.

CONCLUSION

Our study showed that PFAS exposure was significantly associated with reproductive hormone levels. Further related studies are needed to identify the association and potential mechanism in the future.

Synthesis, Surface Activity, and Foamability of Two Short-Chain Fluorinated Sulfonate Surfactants with Ether Bonds

Fluorinated surfactants are widely used in many fields because of their excellent surface active properties, but their high stability has caused many environmental problems. With the ban and restriction of classical long-chain fluorinated surfactants such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) worldwide, the development and replacement of their alternatives is now a major challenge. How to reduce environmental persistence, bioaccumulation, and biotoxicity while maintaining high surface activity has become an important issue in the development of fluorinated surfactants. Using short-chain fluorinated surfactants is one of the important solutions to resolve the pollution of organic fluorinated compounds. In this article, we synthesized two short-chain fluorinated surfactants with ether bonds. One of them 6:2 FTESNa (2) used the perfluoroalkyl chain (n-C6F13-) and the other C72 FEESNa (4) used the fluoroether segment with six fluorinated carbons and two oxygens (CF3OCF(CF3)CF2OCF(CF3)). The surface activity, foam performance, and wettability of the two molecules were measured. The surface tensions at critical micelle concentration (γcmc) and the critical micelle concentration (cmc) of 2 and 4 were 17.6 mN/m (2.2 g/L) and 20.2 mN/m (4.6 g/L), respectively. Both of them were significantly superior to the surface activity of 6:2 FTSNa (7) which is one of the current alternatives for PFOS. Additionally, the foamability and foam stability of both 2 and 4 were better than that of 7. In the aspect of wettability on PTFE, that of 4 was greater than those of 2 and 7. In summary, this work provided a new choice for alternatives of PFOS and PFOA.

Association between Serum Per- and Polyfluoroalkyl Substance Levels and Risk of Central and Peripheral Precocious Puberty in Girls

Concerns about the endocrine-disrupting effects of per- and polyfluoroalkyl substances (PFASs) have raised questions about their potential influence on precocious puberty in girls, which is an emerging concern in some populations. However, epidemiological evidence is lacking. In this study, 882 serum samples were collected from girls with central precocious puberty (CPP, n = 226), peripheral precocious puberty (PPP, n = 316), and healthy controls (n = 340) in 2021 in Shanghai, China. The serum levels of 25 legacy and emerging PFASs and 17 steroids were measured. Results showed that PFAS exposure was positively associated with estradiol levels. Eleven PFASs were significantly or marginally associated with the higher odds of the overall precocious puberty. Across subtypes, PFASs were more clearly associated with PPP, while the associations with CPP were consistent in direction but did not reach statistical significance. These findings were consistent with the assessment of PFAS mixtures using quantile-based g-computation (qgcomp) and Bayesian kernel machine regression, with perfluorobutane sulfonate and 6:2 polyfluorinated ether sulfonate showing the highest contribution to joint effects. Although changes in serum estradiol could arise from various factors, our results suggest that the PFAS exposure may contribute to the increase in estradiol secretion, thereby increasing the risk of precocious puberty, especially PPP. The potential effects of PFASs on precocious puberty warrant further investigation, given the associated complications of public health concern, including psychological distress and increased risk of multiple diseases.

Does contaminant exposure disrupt maternal hormones deposition? A study on per- and polyfluoroalkyl substances in an Arctic seabird

Maternal effects are thought to be essential tools for females to modulate offspring development. The selective deposition of avian maternal hormones could therefore allow females to strategically adjust the phenotype of their offspring to the environmental situation encountered. However, at the time of egg formation, several contaminants are also transferred to the egg, including per- and polyfluoroalkyl substances (PFAS) which are ubiquitous organic contaminants with endocrine disrupting properties. It is, however, unknown if they can disrupt maternal hormone deposition. In this study we explored relationships between female PFAS burden and maternal deposition in the eggs of steroids (dihydrotestosterone, androstenedione and testosterone), glucocorticoids (corticosterone) and thyroid hormones (triiodothyronine and thyroxine) in a population of the Arctic-breeding black-legged kittiwake (Rissa tridactyla). Egg yolk hormone levels were unrelated to female hormone plasma levels. Second-laid eggs had significantly lower concentrations of androstenedione than first-laid eggs. Triiodothyronine yolk levels were decreasing with increasing egg mass but increasing with increasing females' body condition. Testosterone was the only transferred yolk hormone correlated to maternal PFAS burden: specifically, we found a positive correlation between testosterone in yolks and circulating maternal perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDcA) and perfluoroundecanoic acid (PFUnA) in first-laid eggs. This correlative study provides a first insight into the potential of some long-chain perfluoroalkyl acids to disrupt maternal hormones deposition in eggs and raises the question about the consequences of increased testosterone deposition on the developing embryo.

Impacts of PFOAC8, GenXC6, and their mixtures on zebrafish developmental toxicity and gene expression provide insight about tumor-related disease

Concerns about per- and polyfluoroalkyl substances (PFASs) have grown in importance in the fields of ecotoxicology and public health. This study aims to compare the potential effects of long-chain (carbon atoms ≥ 7) and short-chain derivatives and their mixtures' exposure according to PFASs-exposed (1, 2, 5, 10, and 20 mg/L) zebrafish's (Danio rerio) toxic effects and their differential gene expression. Here, PFOA_C8, GenX_C6, and their mixtures (v/v, 1:1) could reduce embryo hatchability and increase teratogenicity and mortality. The toxicity of PFOA_C8 was higher than that of GenX_C6, and the toxicity of their mixtures was irregular. Their exposure (2 mg/L) caused zebrafish ventricular edema, malformation of the spine, blood accumulation, or developmental delay. In addition, all of them had significant differences in gene expression. PFOA_C8 exposure causes overall genetic changes, and the pathways of this transformation were autophagy and apoptosis. More importantly, in order to protect cells from PFOA_C8, GenX_C6, and their mixtures' influences, zebrafish inhibited the expression of ATPase and Ca²⁺ transport gene (atp1b2b), mitochondrial function-related regulatory genes (mt-co2, mt-co3, and mt-cyb), and tumor or carcinogenic cell proliferation genes (laptm4b and ctsbb). Overall, PFOA_C8, GenX_C6, and their mixtures' exposures will affect the gene expression effects of zebrafish embryos, indicating that PFASs may pose a potential threat to aquatic biological safety. These results showed that the relevant genes in zebrafish that were inhibited by PFASs exposure were related to tumorigenesis. Therefore, the effect of PFASs on zebrafish can be further used to study the pathogenesis of tumors.

PFAS Biotransformation Pathways: A Species Comparison Study

Limited availability of fish metabolic pathways for PFAS may lead to risk assessments with inherent uncertainties based only upon the parent chemical or the assumption that the biodegradation or mammalian metabolism map data will serve as an adequate surrogate. A rapid and transparent process, utilizing a recently created database of systematically collected information for fish, mammals, poultry, plant, earthworm, sediment, sludge, bacteria, and fungus using data evaluation tools in the previously described metabolism pathway software system MetaPath, is presented. The fish metabolism maps for 10 PFAS, heptadecafluorooctyl(tridecafluorohexyl)phosphinic acid (C6/C8 PFPiA), bis(perfluorooctyl)phosphinic acid (C8/C8 PFPiA), 2-[(6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl)oxy]-1,1,2,2-tetrafluoroethanesulfonic acid (6:2 Cl-PFESA), N-Ethylperfluorooctane-1-sulfonamide (Sulfuramid; N-EtFOSA), N-Ethyl Perfluorooctane Sulfonamido Ethanol phosphate diester (SAmPAP), Perfluorooctanesulfonamide (FOSA), 8:2 Fluorotelomer phosphate diester (8:2 diPAP), 8:2 fluorotelomer alcohol (8:2 FTOH), 10:2 fluorotelomer alcohol (10:2 FTOH), and 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB), were compared across multiple species and systems. The approach demonstrates how comparisons of metabolic maps across species are aided by considering the sample matrix in which metabolites were quantified for each species, differences in analytical methods used to identify metabolites in each study, and the relative amounts of metabolites quantified. Overall, the pathways appear to be well conserved across species and systems. For PFAS lacking a fish metabolism study, a composite map consisting of all available maps would serve as the best basis for metabolite prediction. This emphasizes the importance and utility of collating metabolism into a searchable database such as that created in this effort.

The effects of exposure to environmentally relevant PFAS concentrations for aquatic organisms at different consumer trophic levels: Systematic review and meta-analyses

Per-and polyfluoroalkyl substances (PFAS) is a collective name for approximately 4700 synthetic chemicals ubiquitous in the aquatic environment worldwide. They are used in a wide array of products and are found in living organisms around the world. Some PFAS have been associated with cancer, developmental toxicity, endocrine disruption, and other health effects. Only a fraction of PFAS are currently monitored and regulated and the presence and effects on aquatic organisms of many PFAS are largely unknown. The aim of this study is to investigate the health effects of environmentally relevant concentrations of PFAS on aquatic organisms at different consumer trophic levels through a systematic review and meta-analysis. The main result shows that PFAS in concentrations up to 13.5 μg/L have adverse effects on body size variables for secondary consumers. However, no significant effects on liver or gonad somatic indices and neither on fecundity were found. In addition, the results show that there are large research gaps for PFAS effects on different organisms in aquatic environments at environmentally relevant concentrations. Most studies have been performed on secondary consumers and there is a substantial lack of studies on other consumers in aquatic ecosystems.

First Evidence of Prenatal Exposure to Emerging Poly- and Perfluoroalkyl Substances Associated with E-Waste Dismantling: Chemical Structure-Based Placental Transfer and Health Risks

Limited information is available about prenatal exposure to per- and polyfluoroalkyl substances (PFAS) in electronic waste (e-waste) recycling sites. In this study, we determined 21 emerging PFAS and 13 legacy PFAS in 94 paired maternal and cord serum samples collected from an e-waste dismantling site in Southern China. We found 6:2 fluorotelomer sulfonate (6:2 FTSA), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA), and perfluorooctanephosphonate (PFOPA) as the major emerging PFAS, regardless of matrices, at median concentrations of 2.40, 1.78, and 0.69 ng/mL, respectively, in maternal serum samples, and 2.30, 0.73, and 0.72 ng/mL, respectively, in cord serum samples. Our results provide evidence that e-waste dismantling activities contribute to human exposure to 6:2 FTSA, 6:2 Cl-PFESA, and PFOPA. The trans-placental transfer efficiencies of emerging PFAS (0.42-0.94) were higher than that of perfluorooctanesulfonic acid (0.37) and were structure-dependent. The substitution of fluorine with chlorine or hydrogen and/or hydrophilic functional groups may alter trans-placental transfer efficiencies. Multiple linear regression analysis indicated significant associations between maternal serum concentrations of emerging PFAS and maternal clinical parameters, especially liver function and erythrocyte-related biomarkers. This study provides new insights into prenatal exposure to multiple PFAS in e-waste dismantling areas and the prevalence of emerging PFAS in people living near the sites.

Health-related toxicity of emerging per- and polyfluoroalkyl substances: Comparison to legacy PFOS and PFOA

Per- and polyfluoroalkyl substances (PFAS) are highly persistent, manufactured chemicals used in various manufacturing processes and found in numerous commercial products. With over 9000 compounds belonging to this chemical class, there is increasing concern regarding human exposure to these compounds due to their persistent, bioaccumulative, and toxic nature. Human exposure to PFAS may occur from a variety of exposure sources, including, air, food, indoor dust, soil, water, from the transfer of PFAS from non-stick wrappers to food, use of cosmetics, and other personal care products. This critical review presents recent research on the health-related impacts of PFAS exposure, highlighting compounds other than Perfluorooctanoic acid (PFOA) and Perfluoroctane sulfonate (PFOS) that cause adverse health effects, updates the current state of knowledge on PFAS toxicity, and, where possible, elucidates cause-and-effect relationships. Recent reviews identified that exposure to PFAS was associated with adverse health impacts on female and male fertility, metabolism in pregnancy, endocrine function including pancreatic dysfunction and risk of developing Type 2 diabetes, lipid metabolism and risk of childhood adiposity, hepatic and renal function, immune function, cardiovascular health (atherosclerosis), bone health including risk for dental cavities, osteoporosis, and vitamin D deficiency, neurological function, and risk of developing breast cancer. However, while cause-and-effect relationships for many of these outcomes were not able to be clearly elucidated, it was identified that 1) the evidence derived from both animal models and humans suggested that PFAS may exert harmful impacts on both animals and humans, however extrapolating data from animal to human studies was complicated due to differences in exposure/elimination kinetics, 2) PFAS precursor kinetics and toxicity mechanism data are still limited despite ongoing exposures, and 3) studies in humans, which provide contrasting results require further investigation of the long-term-exposed population to better evaluate the biological toxicity of chronic exposure to PFAS.

Bioaccumulation of per- and polyfluoroalkyl substance in fish from an urban river: Occurrence, patterns and investigation of potential ecological drivers

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous in aquatic environments and a recent shift toward emerging PFAS is calling for new data on their occurrence and fate. In particular, understanding the determinants of their bioaccumulation is fundamental for risk assessment purposes. However, very few studies have addressed the combined influence of potential ecological drivers of PFAS bioaccumulation in fish such as age, sex or trophic ecology. Thus, this work aimed to fill these knowledge gaps by performing a field study in the Seine River basin (France). Composite sediment and fish (European chub, Squalius Cephalus) samples were collected from four sites along a longitudinal transect to investigate the occurrence of 36 PFAS. Sediment molecular patterns were dominated by fluorotelomer sulfonamidoalkyl betaines (i.e. 6:2 and 8:2 FTAB, 46% of ∑PFAS on average), highlighting the non-negligible contribution of PFAS of emerging concern. C₉-C₁₄ perfluoroalkyl carboxylic acids, perfluorooctane sulfonic acid (PFOS), perfluorooctane sulfonamide (FOSA) and 10:2 fluorotelomer sulfonate (10:2 FTSA) were detected in all fish samples. Conversely, 8:2 FTAB was detected in a few fish from the furthest downstream station only, suggesting the low bioaccessibility or the biotransformation of FTABs. ∑PFAS in fish was in the range 0.22-3.8 ng g^-1 wet weight (ww) and 11-140 ng g^-1 ww for muscle and liver, respectively. Fish collected upstream of Paris were significantly less contaminated than those collected downstream, pointing to urban and industrial inputs. The influence of trophic ecology and biometry on the interindividual variability of PFAS burden in fish was examined through analyses of covariance (ANCOVAs), with sampling site considered as a categorical variable. While the latter was highly significant, diet was also influential; carbon sources and trophic level (i.e. estimated using C and N stable isotope ratios, respectively) equally explained the variability of PFAS levels in fish.

Behaviors of 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) in wheat seedlings: Bioaccumulation, biotransformation and ecotoxicity

As a new alternative to perfluorooctane sulfonate (PFOS), 6:2 fluorotelomer sulfonamide alkylbetaine (6:2 FTAB) has been currently used in industrial and consumer applications, which has been frequently detected in environment media. However, the behaviors of 6:2 FTAB in plants are still unclear. This study investigated the bioaccumulation, biotransformation and ecotoxicity of 6:2 FTAB in wheat (Triticum aestivum L.) by hydroponic exposure. 6:2 FTAB was easily taken up by roots with the root concentration factor (RCF) as high as 94.8, but difficult to be acropetally translocated in the shoots with the translocation factor (TF) as low as 0.058. Two intermediates and six terminal perfluorocarboxylic acid (PFCA) metabolites were detected in roots and shoots. The detected metabolites included 6:2 fluorotelomer sulfonic acid (6:2 FTSA), 6:2 fluorotelomer carboxylic acid (6:2 FTCA), perfluoroheptanoic acid (PFHpA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), perfluorobutyric acid (PFBA), pentafluoropropionic acid (PFPrA) and trifluoroacetic acid (TFA), and 6:2 FTSA was the main metabolite. 6:2 FTAB significantly reduced the biomass of plant and prevented chlorophyll (Chl) accumulation, while caused no significant change in malondialdehyde (MDA) content. Significant reduction in glutathione (GSH) contents, excess production of reactive oxygen species (ROS), and obvious inhibition of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione-s-transferase (GST) activities were observed, suggesting damage of antioxidant defense systems and failure to detoxication of 6:2 FTAB in wheat. These findings provide important knowledge for the fate of 6:2 FTAB in plants.

Transport and fate of aqueous film forming foam in an urban estuary

The deployment of aqueous film forming foams (AFFF) used for firefighting during emergencies and training often releases per- and polyfluoroalkyl substances (PFAS) into the environment. In October 2018, first responders in Providence, RI, USA applied an AFFF during a fuel spill. Due to the proximity of the incident to the upper reaches of Narragansett Bay (NB), an unknown quantity of gasoline and AFFF entered the estuary via surface runoff and stormwater drains. Water samples near the spill were collected approximately 15 h after the incident and analyzed for 24 PFAS. Minor increases in measured PFAS concentrations were observed relative to pre- and post-spill samples at monitoring sites near the incident, except 6:2-fluorotelomer sulfonate (6:2-FTS) that peaked post-spill (max 311 ng/L). After performing the total oxidizable precursor (TOP) assay on water samples and the AFFF concentrate, significant increases in perfluorocarboxylic acids (PFCAs) were observed. One compound, 6:2 fluorotelomer mercaptoalkylamido sulfonate (6:2-FTSAS), was identified as a major component of the AFFF used. Peak areas of 6:2-FTSAS and the degradation product 6:2-FTSAS-sulfoxide corresponded to observed increases in the TOP assay results and were useful as tracers of AFFF in surrounding waters. Elevated levels of PFAS at the time of sampling were limited to a confined area of the Providence River due to river flow and tidal action. Observed concentrations were also compared to hydrodynamic model results, and results confirmed rapid dissipation of AFFF components with distance from the spill. However, modeled results did not capture possible secondary releases of AFFF from local municipal stormwater and sewer infrastructure, as observational data suggest. The multiple lines of evidence of PFAS present in surface waters permitted a better assessment of the potential environmental impacts from products such as AFFF for which the chemical composition is largely unknown.

Novel and legacy per- and polyfluoroalkyl substances (PFAS) in freshwater sporting fish from background and firefighting foam impacted ecosystems in Eastern Canada

Emerging PFAS were recently reported at sites impacted by aqueous film-forming foams (AFFFs) and near major manufacturing centers; however, few studies have evaluated whether these can occur far from release sites. Here, newly identified PFAS were investigated in wild sporting fish from boreal freshwater ecosystems (background sites, 2013-2014 summer seasons), compared to fish impacted by a major AFFF release (summer 2013 and autumn 2014). Different freshwater wild sporting fish species (Esox lucius, Esox masquinongy, Micropterus dolomieu, Sander vitreus, Perca flavescens, and Semotilus corporalis, n = 74) were collected from 13 ecosystems (lakes, reservoirs, and rivers) across Eastern Canada. Of 29 quantitative PFAS, 15 compounds were detected in fish from background sites, including perfluorocarboxylates (C_6,8-14), perfluoroalkane sulfonates (C_6,8,10), perfluorooctane sulfonamide (FOSA), 6:2 fluorotelomer sulfonate (6:2 FTSA), 7:3 fluorotelomer carboxylic acid (7:3 FTCA), and a zwitterionic PFAS-perfluorooctane sulfonamidoalkyl betaine (PFOSB). To our knowledge, this is the first report of PFOSB in biota. It is also one of the first reports of anionic fluorotelomers (6:2 FTSA, 7:3 FTCA, 9:3 FTCA) in wildlife from background sites. Long-chain fluorotelomer sulfonamidoalkyl betaines (e.g., 8:2 and 10:2 FTAB), fluorotelomer betaines (e.g., 9:3 and 9:1:2 FTB), and fluorotelomer sulfone propanoic acids (e.g., 8:2 FT(SO₂)-PA, 10:2 FT(SO₂)-PA)) were solely prevalent (up to 97% of summed suspect PFAS) in Smallmouth Bass (M. dolomieu) from the AFFF-impacted site. Perfluorobutane sulfonamide (FBSA), perfluorohexane sulfonamide (FHxSA), 6:2 FTSA and 7:3 FTCA were detected in at least one Smallmouth Bass sample both at the AFFF-impacted and background sites. According to the estimated chronic daily intake and current tolerable daily intake suggested by national agencies, the observed PFOS levels would not pose a health risk to anglers who might consume these wild-caught fish.

Pyriproxyfen induced impairment of reproductive endocrine homeostasis and gonadal histopathology in zebrafish (Danio rerio) by altered expression of hypothalamus-pituitary-gonadal (HPG) axis genes

Pyriproxyfen (PPF), a broad-spectrum insecticide known to cause reproductive and endocrine disruption in invertebrates, while the data is scarce in aquatic vertebrates. The goal of this study is to investigate the impact of PPF on reproductive endocrine system of male and female zebrafish along hypothalamus-pituitary-gonadal (HPG) axis. In brain, PPF caused significant alteration in the transcripts of erα, lhβ, and cyp19b genes in male and fshβ, lhβ, and cyp19b genes in female zebrafish. The downstream genes of steroidogenic pathway like, star, 3βhsd, 17βhsd, and cyp19a expression were significantly altered in gonad of both sexes. Subsequent changes in circulatory steroid hormone levels lead to imbalance in hormone homeostasis as revealed from estradiol/testosterone (E₂/T) ratio. Further, the vitellogenin transcript level was enhanced in hepatic tissues and their blood plasma content was increased in male (16.21%) and declined in female (21.69%). PPF also induced histopathological changes in gonads such as, reduction of mature spermatocytes in male and vitellogenic oocytes in female zebrafish. The altered E₂/T ratio and gonadal histopathology were supported by the altered transcript levels of HPG axis genes. Overall, these findings provide new insights of PPF in zebrafish reproductive system and highlights for further investigations on its potential risks in aquatic environment.

Per- and Polyfluoroalkyl Substances (PFAS) Neurotoxicity in Sentinel and Non-Traditional Laboratory Model Systems: Potential Utility in Predicting Adverse Outcomes in Human Health

Per- and polyfluoroalkyl substances (PFAS) are a class of chemicals that were widely used in manufacturing and are now present in the environment throughout the world. It is known that various PFAS are quantifiable in human in blood, but potential adverse health outcomes remain unclear. Sentinel and non-traditional model species are useful to study potential toxicity of PFAS in order to understand the relationship between environmental and human health. Here, we present a critical review of studies on the neurotoxicity of PFAS in sentinel and non-traditional laboratory model systems, including Caenorhabditis elegans (nematode), Dugesia japonica (planarian), Rana pipiens (frogs), Danio rerio and Oryzias melastigma (fish), and Ursus maritimus (polar bears). PFAS have been implicated in developmental neurotoxicity in non-traditional and traditional model systems as well as sentinel species, including effects on neurotransmitter levels, especially acetylcholine and its metabolism. However, further research on the mechanisms of toxicity needs to be conducted to determine if these chemicals are affecting organisms in a similar manner. Overall, findings tend to be similar among the various species, but bioaccumulation may vary, which needs to be taken into account in future studies by quantifying target organ concentrations of PFAS to better compare different species. Furthermore, data on the majority of PFAS is lacking in neurotoxicity testing, and additional studies are needed to corroborate findings thus far.

Alternatives to Animal Use in Risk Assessment of Mixtures

Risk assessment of chemical mixtures has emerged as a focus of research efforts, but traditional toxicology testing in mammals is costly, time-consuming, and subject to ethical scrutiny in the context of recent trends to reduce reliance on animal testing. In this review, which is a summary of presentations given at a workshop in Havana, Cuba, in April 2019, we survey the utility of zebra fish as an alternative laboratory model in whole-mixture and component-based testing, as well as in vitro modeling in 3-dimensional organotypic cultures from primary human cells cultured at the air-liquid interface and organ-on-a-chip platforms. Finally, we discuss the complexities of assessing the dynamics and delivery of multispecies liquid aerosol mixtures along the human respiratory tract, with examples of alternative and computational approaches to aerosol dosimetry. The workshop contributed to the professional development of Cuban toxicologists, an underserved segment of the global scientific community, delivering a set of tools and recommendations that could potentially provide cost-effective solutions for scientists with limited research resources.

Bioaccumulation of Zwitterionic Polyfluoroalkyl Substances in Earthworms Exposed to Aqueous Film-Forming Foam Impacted Soils

Critical knowledge gaps remain regarding the fate and effects of zwitterionic, cationic, and anionic perfluoroalkyl and polyfluoroalkyl substances (PFASs), including assessment of their bioaccumulation potential. Here, biota soil accumulation factors (BSAFs) were assessed in earthworms (Eisenia fetida) exposed to soil microcosms amended with zwitterionic fluorotelomers and anionic perfluoroalkyl acids. The 6:2 fluorotelomer sulfonamidoalkyl betaine (6:2 FTAB) bioaccumulated in earthworms [BSAF ∼ 2.5-5.4 (g_dw,worm/g_dw,soil)^-1] but to a lesser extent than perfluorooctane sulfonate (PFOS: BSAF ∼ 21-29). The BSAF of perfluorocarboxylates increased from ∼2.0 for C₄-C₆ analogues to ∼92 for perfluorotridecanoate (C₁₃). In earthworms exposed to Ansulite and Arctic Foam aqueous film-forming foams (AFFFs), the BSAF was related to perfluorinated chain length for n:3 fluorotelomer betaines (FtBs), n:1:2 FtB, and n:2 FTAB. Earthworms were also collected in situ from a fire-equipment testing site at a major Canadian airport. Summed PFAS concentrations were between 65 000 and 830 000 ng g^-1 wet weight, possibly the highest burden recorded in terrestrial biota. Fluorotelomer sulfonates (6:2 FTS, 8:2 FTS, and 10:2 FTS) and FtB were particularly prevalent. Field worms also displayed elevated concentrations of n:3 acids (n = 3-11), but not those from laboratory microcosms exposed to fluorotelomer-based AFFFs. The findings provide an important confirmation to recent data suggesting that fluorotelomer compounds may accumulate in invertebrate species with limited metabolization.

l-aspartic acid promotes fish survival against Vibrio alginolyticus infection through nitric oxide-induced phagocytosis

Bacterial infection severely impairs aquaculture development throughout the world. Despite the use of antibiotics to control bacterial infection, few other options are available especially in the area of complex ecosystem and various types of fish. In search for novel approaches in controlling bacterial infection, we adopt zebrafish, Danio reiro, as infection host and the bacteria, Vibrio alginolyticus, as pathogen to explore potential metabolites that boost host's capability to eliminate bacterial infection. By comparing the metabolome of dying fish, l-aspartic acid is a metabolite of differential abundance between the dying fish and surviving fish upon Vibrio alginolyticus infection. Exogenous l-aspartic acid increases fish survival rate from 46.67% to 76.67%. We further demonstrated that l-aspartic acid drives the production of nitrogen oxide that promotes phagocytosis. Whereas the inhibition of nitrogen oxide synthase would abolish l-aspartic acid-triggered phagocytosis as well as in vivo protective ability to V. alginolyticus. The importance of nitrogen oxide production in fish survival is also consistent with the observation in the dying fish that showed increased urea production but not nitrogen oxide. Thus, our results exemplify a novel approach in promoting fish survival in an eco-friendly way.