Evaluation of estrogenic activities and mechanism of action of perfluorinated chemicals determined by vitellogenin induction in primary cultured tilapia hepatocytes

Ecotoxicological effects of per- and polyfluoroalkyl substances in aquatic organisms: A review

Per- and polyfluoroalkyl substances (PFAS) are found throughout the environment due to their chemical stability. Their widespread use in industrial and consumer products has resulted in their frequent detection in aquatic environments, making them contaminants of significant concern. Recent studies focus on the adverse effects of PFAS on aquatic organisms in an effort to elucidate their toxic mechanisms and physiological changes. Here, we comprehensively review the major effects of PFAS on aquatic organisms, including general toxicity, metabolic disruption, and microbiome alterations, and explore how these changes affect biological function and ecosystem balance. In addition to toxic responses in aquatic organisms reported previously, PFAS disrupt metabolic pathways, causing abnormalities in carbohydrate metabolism, lipid homeostasis, and hormonal regulation. They also cause gut microbiome imbalances and reduce the prevalence of beneficial bacteria while promoting pathogen proliferation, which contributes to physiological dysfunction and damages liver and other organ tissues. Experimental evidence emphasizes the multifaceted threats PFAS pose to aquatic health and ecosystem stability and provide a crucial foundation for understanding their long-term impacts from both physiological and ecological perspectives.

Specific and potent inhibition of steroid hormone pre-receptor regulator AKR1C2 by perfluorooctanoic acid: Implications for androgen metabolism

Per- and polyfluoroalkyl substances (PFAS) are ubiquitous environmental pollutants that are highly stable synthetic organofluorine compounds. One congener perfluorooctanoic acid (PFOA) can be detected in nearly all humans and is recognized as an endocrine disrupting chemical (EDC). EDCs disrupt hormone synthesis and metabolism and receptor function. One mechanism of steroid hormone action is the pre-receptor regulation of ligand access to steroid hormone receptors by aldo-keto reductases. Here we report PFOA inhibition of AKR family 1 member C2 (AKR1C2), leading to dysregulation of androgen action. Spectrofluorimetric inhibitor screens identified PFOA as a competitive and tight binding inhibitor of AKR1C2, whose role is to inactivate 5α-dihydrotestosterone (5α-DHT). Further site directed mutagenesis studies along with molecular docking simulations revealed the importance of residue Valine 54 in mediating AKR1C2 inhibitor specificity. Binding site restrictions were explored by testing inhibition of other related PFAS chemicals, confirming that steric hinderance is a key factor. Furthermore, radiochromatography using HPLC and in line radiometric detection confirmed the accumulation of 5α-DHT as a result of PFOA inhibition of AKR1C2. We showed that PFOA could enhance the transactivation of AR in reporter genes assays in which 5α-DHT metabolism was blocked by AKR1C2 inhibition in HeLa cells. Taken together, these data suggest PFOA has a role in disrupting androgen action through inhibiting AKR1C2. Our work identifies an EDC function for PFOA not previously revealed.

A novel approach based on supramolecular solvents microextraction for quick detection of perfluoroalkyl acids and their precursors in aquatic food

Per-and polyfluoroalkyl substances (PFASs) have garnered significant attention owing to their prevalence and adverse effects on humans. The direct dietary intake of perfluoroalkyl acids (PFAAs) and PFAAs precursors (pre-PFAAs) biotransformation are considered major contributors to human exposure to PFASs. However, little information is available on analytical methods for the simultaneous detection of PFAAs and pre-PFAAs. In the present study, a single-step sample-treatment-based supramolecular solvents-dispersed liquid-liquid microextraction (SUPRASs-DLLME) technique was established for the analysis of 16 PFAAs and 7 pre-PFAAs in aquatic food. SUPRASs were synthesized using 1-heptanol (3 mL) and tetrahydrofuran (4 mL), which were self-assembled in water. The parameters for microextraction, such as extraction method and enrichment capacity, were optimized. Under the optimum conditions, the limit of detection (LOD) and limit of quantification (LOQ) were 0.03-0.15 ng·g-1 and 0.1-0.5 ng·g-1, respectively. Good linearities (R2 > 0.996) were obtained for all the target compounds, and the recoveries ranged 81.1-120 % with relative standard deviations (RSDs) lower than 20 %. This method was applied to the analysis of 16 PFAAs and 7 pre-PFAAs in aquatic food samples (crabs, prawns, and fish). This study provides a new idea for analyzing other pollutants in biological samples.

Perfluoroalkyl substances exposure and the risk of breast cancer: A nested case-control study in Jinchang Cohort

BACKGROUND

As persistent organic pollutants (POPs), perfluoroalkyl substances (PFAS) may potentially impact human health. Our study aimed to investigate the prospective association between PFAS exposure and the incidence risk of breast cancer in females.

METHODS

By fully following the Jinchang Cohort after a decade, we conducted this nested case-control study with 135 incidence cases of breast cancer (BC) and 540 bias-paired controls. The PFAS levels were tested by baseline serum samples. Conditional logistic regression and a restricted cubic spline model were employed to investigate the BC incidence risks and the dose-response associated with single PFAS component exposure. Furthermore, the Quantile g-computation model (Qgc), random forest model (RFM), and bayesian kernel machine regression models (BKMR) were integrated to estimate the mixed effects of PFAS exposure on the incidence risk of BC.

RESULTS

Exposures to specific PFAS components were positively associated with an increased incidence risk of breast cancer. By grouping the study population into different baseline menopausal statuses, PFHxS, PFNA, PFBA, PFUdA, PFOS, and PFDA demonstrated a similarly positive correlation with BC incidence risks. However, the increased incidence risks of BC associated with PFOA, PFOS, PFUdA, and 9CL-PF3ONS exposure were exclusively found in the premenopausal population. Both BKMR and Qgc revealed that exposure to mixed PFAS was associated with an increased risk of breast cancer, with Qgc specifically indicating an odds ratio (OR) of 2.21 (95% CI: 1.53, 3.19). Random forests showed that PFBA, PFOS, PFHxS, and PFDA emerged as predominant factors potentially influencing breast cancer incidence.

CONCLUSION

Our findings suggest a strong association between PFAS exposure and the incidence of breast cancer. Premenopausal women should exercise more caution regarding PFAS exposure.

Interaction of Per- and Polyfluoroalkyl Substances with Estrogen Receptors in Rainbow Trout (Oncorhynchus mykiss): An In Silico Investigation

Fresh water sources, including lakes, such as the Great Lakes, are some of the most important ecosystems in the world. Despite the importance of these lakes, there is increasing concern about the presence of per- and polyfluoroalkyl substances (PFAS)─among the most prevalent contaminants of our time─due to the ability of PFAS to bioaccumulate and persist in the environment, as well as to its linkages to detrimental human and animal health effects. In this study, PFAS exposure on rainbow trout (Oncorhynchus mykiss) is examined at the molecular level, focusing on the impact of PFAS binding on the alpha (α) and beta (β) estrogen receptors (ERs) using molecular dynamics simulations, binding free energy calculations, and structural analysis. ERs are involved in fundamental physiological processes, including reproductive system development, muscle regeneration, and immunity. This study shows that PFAS binds to both the estrogen α and estrogen β receptors, albeit via different binding modes, due to a modification of an amino acid in the binding site as a result of a reorientation of residues in the binding pocket. As ER overactivation can occur through environmental toxins and pollutants, this study provides insights into the influence of different types of PFAS on protein function.

Individual and joint associations of per- and polyfluoroalkyl substances (PFAS) with gallstone disease in adults: A cross-sectional study

Disturbances in the enterohepatic circulation are important biological mechanisms for causing gallstones and also have important effects on the metabolism of Per- and polyfluoroalkyl substances (PFAS). Moreover, PFAS is associated with sex hormone disorder which is another important cause of gallstones. However, it remains unclear whether PFAS is associated with gallstones. In this study, we used logistic regression, restricted cubic spline (RCS), quantile g-computation (qg-comp), Bayesian kernel machine regression (BKMR), and subgroup analysis to assess the individual and joint associations of PFAS with gallstones and effect modifiers. We observed that the individual associations of perfluorodecanoic acid (PFDeA) (OR: 0.600, 95% CI: 0.444 to 0.811), perfluoroundecanoic acid (PFUA) (OR: 0.630, 95% CI: 0.453 to 0.877), n-perfluorooctane sulfonic acid (n-PFOS) (OR: 0.719, 95% CI: 0.571 to 0.906), and perfluoromethylheptane sulfonic acid isomers (Sm-PFOS) (OR: 0.768, 95% CI: 0.602 to 0.981) with gallstones were linearly negative. Qg-comp showed that the PFAS mixture (OR: 0.777, 95% CI: 0.514 to 1.175) was negatively associated with gallstones, but the difference was not statistically significant, and PFDeA had the highest negative association. Moreover, smoking modified the association of perfluorononanoic acid (PFNA) with gallstones. BKMR showed that PFDeA, PFNA, and PFUA had the highest groupPIP (groupPIP = 0.93); PFDeA (condPIP = 0.82), n-perfluorooctanoic acid (n-PFOA) (condPIP = 0.68), and n-PFOS (condPIP = 0.56) also had high condPIPs. Compared with the median level, the joint association of the PFAS mixture with gallstones showed a negative trend; when the PFAS mixture level was at the 70th percentile or higher, they were negatively associated with gallstones. Meanwhile, when other PFAS were fixed at the 25th, 50th, and 75th percentiles, PFDeA had negative associations with gallstones. Our evidence emphasizes that PFAS is negatively associated with gallstones, and more studies are needed in the future to definite the associations of PFAS with gallstones and explore the underlying biological mechanisms.

Perfluoroalkyl substances (PFAS) occurrence, concentrations and spatial distribution along the French Mediterranean coast and lagoons, based on active biomonitoring

Tracking PFAS in ecosystems is challenging. In this context, monitoring programs are crucial to fill data gaps, especially in marine environments, which are the ultimate outlets for these forever chemicals. The 2021 chemical contamination monitoring campaign along the French Mediterranean coast established a baseline for PFAS concentrations in mussels, with 90 % of measurements below quantification limits. When detected, long-chain PFCA's were predominant. Spatial distribution patterns suggested continuous PFAS inputs and complex dynamics, shaped by the influence of large watersheds and rivers (Rhône, Aude, Huveaune). Lapeyrade shallow lagoon stood out as the most contaminated site. Similar PFAS profiles in connected sites implied shared sources but raised questions about accumulation processes in mussels. While certain sites had evident sources (e.g., military airbase for Palo lagoon), others remained uncertain (e.g., Toulon bay). Coastal stations (Banyuls, Cap Agde, Brégançon, Pampelonne) showed PFAS contamination without clear onshore sources, possibly due to insufficient transportation process understanding.

An Integrated Approach of Bioassays and Non-Target Screening for the Assessment of Endocrine-Disrupting Activities in Tap Water and Identification of Novel Endocrine-Disrupting Chemicals

The safety of drinking water is a significant environmental issue of great concern for human health since numerous contaminants are often detected in drinking water and its sources. Boiling is a common household method used to produce relatively high-quality drinking water in some countries and regions. In this study, with the aid of an integrated approach of in vitro bioassays and non-target analysis based on high-resolution mass spectrometry coupled with liquid chromatography, alterations in endocrine-disrupting activities in tap water samples without and with boiling were revealed, as well as the potential endocrine-disrupting chemicals (EDCs) contributing to these alterations were identified. The organic extracts of tap water had no significant (ant)agonistic activities against an estrogen receptor (ER), progesterone receptor (PR), glucocorticoid receptor (GR), and mineralocorticoid receptor (MR) at enrichment concentrations of ≤10 times, posing no immediate or acute health risk to humans. However, the presence of agonistic activities against PR and MR and antagonistic activities against ER, PR, GR, and MR in OEs of tap water at relatively higher enrichment concentrations still raise potential health concerns. Boiling effectively reduced antagonistic activities against these steroid hormone receptors (SHRs) but increased estrogenic and glucocorticoid activities in drinking water. Four novel potential EDCs, including one UV filter (phenylbenzimidazole sulfonic acid, PBSA) and three natural metabolites of organisms (beta-hydroxymyristic acid, 12-hydroxyoctadecanoic acid, and isorosmanol) were identified in drinking water samples, each of which showed (ant)agonistic activities against different SHRs. Given the widespread use of UV filters in sunscreens to prevent skin cancer, the health risks posed by PBSA as an identified novel EDC are of concern. Although boiling has been thought to reduce the health risk of drinking water contamination, our findings suggest that boiling may have a more complex effect on the endocrine-disrupting activities of drinking water and, therefore, a more comprehensive assessment is needed.

Proposing Effective Ecotoxicity Test Species for Chemical Safety Assessment in East Asia: A Review

East Asia leads the global chemical industry, but environmental chemical risk in these countries is an emerging concern. Despite this, only a few native species that are representative of East Asian environments are listed as test species in international guidelines compared with those native to Europe and America. This review suggests that Zacco platypus, Misgurnus anguillicaudatus, Hydrilla verticillata, Neocaridina denticulata spp., and Scenedesmus obliquus, all resident to East Asia, are promising test species for ecotoxicity tests. The utility of these five species in environmental risk assessment (ERA) varies depending on their individual traits and the state of ecotoxicity research, indicating a need for different applications of each species according to ERA objectives. Furthermore, the traits of these five species can complement each other when assessing chemical effects under diverse exposure scenarios, suggesting they can form a versatile battery for ERA. This review also analyzes recent trends in ecotoxicity studies and proposes emerging research issues, such as the application of alternative test methods, comparative studies using model species, the identification of specific markers for test species, and performance of toxicity tests under environmentally relevant conditions. The information provided on the utility of the five species and alternative issues in toxicity tests could assist in selecting test species suited to study objectives for more effective ERA.

Perfluorooctane Sulfonate (PFOS) Negatively Impacts Prey Capture Capabilities in Larval Zebrafish

Per- and polyfluoroalkyl substances (PFAS) are widely used in many industrial and domestic applications, which has resulted in unintentional human exposures and bioaccumulation in blood and other organs. Perfluorooctane sulfonate (PFOS) is among the most prevalent PFAS in the environment and has been postulated to affect brain functions in exposed organisms. However, the impacts of PFOS in early neural development have not been well described. We used zebrafish larvae to assess the effects of PFOS on two fundamental complex behaviors, prey capture and learning. Zebrafish exposed to PFOS concentrations ranging from 2 to 20 µM for differing 48-h periods were viable through early larval stages. In addition, PFOS uptake was unaffected by the presence of a chorion. We employed two different experimental paradigms; first we assessed the impacts of increasing organismal PFOS bioaccumulation on prey capture and learning, and second, we probed stage-specific sensitivity to PFOS by exposing zebrafish at different developmental stages (0-2 vs. 3-5 days post fertilization). Following both assays we measured the amount of PFOS present in each larva and found that PFOS levels varied in larvae from different groups within each experimental paradigm. Significant negative correlations were observed between larval PFOS accumulation and percentage of captured prey, whereas nonsignificant negative correlations were observed between PFOS accumulation and experienced-induced prey capture learning. These findings suggest that PFOS accumulation negatively affects larval zebrafish's ability to perform complicated multisensory behaviors and highlights the potential risks of PFOS exposure to animals in the wild, with implications for human health. Environ Toxicol Chem 2024;00:1-9. © 2023 SETAC.

Perfluorooctanoic acid (PFOA) affects steroidogenesis and antioxidant defence in granulosa cells from swine ovary

PFOA is mainly employed in products with water and oil repellent properties. Due to its persistence, bioaccumulation and critical effects on health, its use has been restricted in several countries. This research was intended to explore PFOA action on the main functions of swine ovarian granulosa cells, a valuable model for translational medicine. Moreover, since we previously demonstrated a disruptive effect on free radical generation we sought to explore PFOA effects on the main antioxidant enzymes. PFOA inhibited cell proliferation (p < 0.001), assessed by BrdU uptake. Steroidogenesis was disrupted: PFOA also stimulated 17β-estradiol production (p < 0.05), increased progesterone production (p < 0.05) at the lowest dose while it displayed an inhibitory effect at higher concentrations (p < 0.05). SOD (p < 0.001), catalase (p < 0.05) and peroxidase (p < 0.01) activities were stimulated. Therefore, our study supports a disruptive effect of PFOA in cultured swine granulosa cells.

Perfluorooctane sulfonic acid modulates expression of placental steroidogenesis-associated genes and hormone levels in pregnant rats

Perfluorooctane sulfonate (PFOS) is a widespread and persistent chemical in the environment. Reports show that PFOS is a potential endocrine disruptor; however, the possible effects of PFOS on placental endocrine function are unclear. This study aimed to investigate the endocrine-disrupting effects of PFOS on the placenta in pregnant rats and its potential mechanism. Pregnant rats from gestational days 4-20 were exposed to 0, 10, and 50 μg/mL PFOS through drinking water followed by analysis of various biochemical parameters. PFOS dose-dependently decreased fetal and placental weight in both sexes, with a specific decrease in weight of labyrinth but not junctional layer. Plasma progesterone (↑166%), aldosterone (↑201%), corticosterone (↑205%), testosterone (↑45%), luteinizing hormone (↑49%) levels were significantly increased, while estradiol (↓27%), prolactin (↓28%) and hCG (↓62%) levels were reduced in groups exposed to higher doses of PFOS. Real-time quantitative reverse transcriptase-polymerase chain reaction analysis revealed a significant increase in mRNA levels of placental steroid biosynthesis enzymes, including Cyp11A1 and 3β-HSD1 in male placenta and StAR, Cyp11A1, 17β-HSD1 and 17β-HSD3 in female placenta of PFOS dams. Cyp19A1 expression in ovaries was significantly decreased in PFOS dams. mRNA levels for placental steroid metabolism enzyme UGT1A1 increased in male but not in female placenta of PFOS dams. These results suggest that the placenta is a target tissue of PFOS and PFOS-induced dysregulation in steroid hormone production might be related to the altered expression of hormone biosynthesis and metabolism enzyme genes in the placenta. This hormone disruption might affect maternal health and fetal growth.

Association between polyfluoroalkyl substances exposure and sex steroids in adolescents: The mediating role of serum albumin

BACKGROUND

Polyfluoroalkyl substances (PFASs) are an emerging class of contaminants with endocrine disrupting hazards. The impact of PFASs exposure on sex steroids remain inconclusive.

METHODS

This study used data from the 2013-2016 National Health and Nutrition Examination Survey (NHANES), including 525 adolescents aged 12-19. We explored the association between serum PFASs and sex steroids using multiple linear regression, weighted quantified sum (WQS) regression, and Bayesian kernel machine regression (BKMR). Mediation analyses were performed to assess whether serum albumin mediates the effects of PFASs on sex steroids.

RESULTS

Single exposure to perfluorohexane sulfonic acid (PFHxS) or n-perfluorooctanoic acid (n-PFOA) was found to be inversely associated with sex hormone binding protein (SHBG) after adjustment for confounders. Results from both the WQS and BKMR models showed that mixed exposure to the five PFASs was negatively associated with SHBG and testosterone (TT) in all adolescents, while only in the WQS model, the mixed exposure to PFASs was negatively correlated with E₂ and FAI in boys and negatively correlated with TT and SHBG in girls. Serum albumin was found to possibly mediate 9.7 % of the association between mixed PFAS exposure and TT, and 9.7 % of the association between mixed PFAS exposure and SHBG.

CONCLUSION

Our study demonstrates a negative association between mixed exposure to PFASs and adolescent TT and SHBG levels, and suggests that albumin may merit further study as a potential target for PFAS harm reduction.

Verification of In Vivo Estrogenic Activity for Four Per- and Polyfluoroalkyl Substances (PFAS) Identified as Estrogen Receptor Agonists via New Approach Methodologies

Given concerns about potential toxicological hazards of the thousands of data-poor per- and polyfluorinated alkyl substances (PFAS) currently in commerce and detected in the environment, tiered testing strategies that employ high-throughput in vitro screening as an initial testing tier have been implemented. The present study evaluated the effectiveness of previous in vitro screening for identifying PFAS capable, or incapable, of inducing estrogenic responses in fish exposed in vivo. Fathead minnows (Pimephales promelas) were exposed for 96 h to five PFAS (perfluorooctanoic acid [PFOA]; 1H,1H,8H,8H-perfluorooctane-1,8-diol [FC8-diol]; 1H,1H,10H,10H-perfluorodecane-1,10-diol [FC10-diol]; 1H,1H,8H,8H-perfluoro-3,6-dioxaoctane-1,8-diol [FC8-DOD]; and perfluoro-2-methyl-3-oxahexanoic acid [HFPO-DA]) that showed varying levels of in vitro estrogenic potency. In agreement with in vitro screening results, exposure to FC8-diol, FC10-diol, and FC8-DOD caused concentration-dependent increases in the expression of transcript coding for vitellogenin and estrogen receptor alpha and reduced expression of insulin-like growth factor and apolipoprotein eb. Once differences in bioconcentration were accounted for, the rank order of potency in vivo matched that determined in vitro. These results provide a screening level benchmark for worst-case estimates of potential estrogenic hazards of PFAS and a basis for identifying structurally similar PFAS to scrutinize for putative estrogenic activity.

Association between perfluoroalkyl substances exposure and the prevalence of nonalcoholic fatty liver disease in the different sexes: a study from the National Health and Nutrition Examination Survey 2005-2018

There is evidence that perfluoroalkyl substances (PFASs) have effects on liver toxicity, and the effects may exhibit sex differences. Our study aims to explore the association between exposure to four PFASs (perfluorooctanoic acid, PFOA; perfluorooctane sulfonate, PFOS; perfluorohexane sulfonate, PFHxS; and perfluorononanoate, PFNA) and the risk of nonalcoholic fatty liver disease (NAFLD) in adults ≥ 20 years old in the US population. The data were based on the National Health and Nutrition Examination Survey (NHANES) 2005-2018. We used Poisson regression to explore the association between the four PFASs and NAFLD. We included 3464 participants; of these, 1200 (34.64%) individuals were defined as having NAFLD, and the prevalence of NAFLD was 39.52% in men and 30.40% in women. After Poisson regression, among the premenopausal and postmenopausal and total women, PFOA had a significantly positive association with NAFLD (p < 0.05). After principal component analysis, the "composite PFAS" was associated with NAFLD in postmenopausal and total women, and the RRs (95% CIs) were 1.306 (1.075, 1.586) and 1.161 (1.007, 1.339), respectively. In adults, we found that PFASs were associated with NAFLD, and the associations varied by sex, particularly for PFOA and PFNA, which had a positive association with NAFLD in women.

A Recent Progress in the Leachate Pretreatment Methods Coupled with Anaerobic Digestion for Enhanced Biogas Production: Feasibility, Trends, and Techno-Economic Evaluation

Landfill leachate (LFL) treatment is a severe challenge due to its highly viscous nature and various complex pollutants. Leachate comprises various toxic pollutants, including inorganic macro/nano components, xenobiotics, dissolved organic matter, heavy metals, and microorganisms responsible for severe environmental pollution. Various treatment procedures are available to achieve better effluent quality levels; however, most of these treatments are nondestructive, so pollutants are merely transported from one phase to another, resulting in secondary contamination. Anaerobic digestion is a promising bioconversion technology for treating leachate while producing renewable, cleaner energy. Because of its high toxicity and low biodegradability, biological approaches necessitate employing other techniques to complement and support the primary process. In this regard, pretreatment technologies have recently attracted researchers' interest in addressing leachate treatment concerns through anaerobic digestion. This review summarizes various LFL pretreatment methods, such as electrochemical, ultrasonic, alkaline, coagulation, nanofiltration, air stripping, adsorption, and photocatalysis, before the anaerobic digestion of leachate. The pretreatment could assist in converting biogas (carbon dioxide to methane) and residual volatile fatty acids to valuable chemicals and fuels and even straight to power generation. However, the selection of pretreatment is a vital step. The techno-economic analysis also suggested the high economic feasibility of integrated-anaerobic digestion. Therefore, with the incorporation of pretreatment and anaerobic digestion, the process could have high economic viability attributed to bioenergy production and cost savings through sustainable leachate management options.

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.

Long-term trends of fluorotelomer alcohols in a wastewater treatment plant impacted by textile manufacturing industry

Fluorotelomer alcohols (FTOHs) are important precursors and substitutes of perfluoroalkyl carboxylic acids (PFCAs). This study investigated the long-term trends of FTOHs in a municipal wastewater treatment plant impacted by textile manufacturing industry (T-WWTP) in Wuxi city from 2013 to 2021. For comparison, four domestic wastewater treatment plants (D-WWTPs) were also selected for the investigation. The total concentrations of FTOHs, which were 9.8-43 ng/L, 5.9-29 ng/L and 10-50 ng/g in influent, secondary effluent, and sludge samples from the T-WWTP, were significantly higher than those of the D-WWTPs (p < 0.01). The significant correlation between decrease of mass loads for FTOHs and the increase for PFCAs was observed, suggesting the potential biotransformation of FTOHs to PFCAs. Concentration variation in FTOH concentrations was observed for the T-WWTP, which was in accord with the variation in annual output of textile products in Wuxi city (p = 0.005). The predominance of 8:2 FTOH in the influents of T-WWTP between 2013 and 2016 switched over to 6:2 FTOH in 2020-2021. This work highlighted the textile manufacturing industry as a significant discharge route for FTOHs to municipal WWTP, as well as the dramatic change in the usage of FTOHs in the textile manufacturing industry in Wuxi.

Comparison of the mechanisms of estrogen disrupting effects between triphenyl phosphate (TPhP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP)

As the typical aryl-organophosphate flame retardants (OPFRs), triphenyl phosphate (TPhP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were reported to be estrogen disruptors. However, estrogen receptor α (ERα) binding experiments could not explain their biological effects. In this study, their action on ERα, G protein-coupled estrogen receptor (GPER) and the synthesis of 17β-estradiol (E2) were investigated using in vitro assays and molecular docking. The results showed that TPhP acted as an ERα agonist and recruited steroid receptor co-activator 1 (SRC1) and 3 (SRC3), which was found for the first time. Unlike TPhP, TDCIPP acted as an ERα antagonist. However, both TPhP and TDCIPP activated the estrogen pathway by GPER in SKBR3 cells which were lack of ERα. Although molecular docking results revealed that both TPhP and TDCIPP could dock into ERα and GPER, their substituent groups and combination mode might affect the receptor activation. In addition, by using estrogen biosynthesis assay in H295R cells, both of TPhP and TDCIPP were found to promote E2 synthesis and E2/T ratio involving their different alteration on levels of progesterone, testosterone and estrone, and expression of various key genes. Our data proposed estrogen-disrupting mechanism frameworks of TPhP and TDCIPP. Moreover, our results will contribute to future construction of adverse outcome pathway (AOP) framework of endocrine disruptors.

Exposure to per- and polyfluoroalkyl substances associates with an altered lipid composition of breast milk

The composition of human breast milk is highly variable inter- and intra-individually. Environmental factors are suspected to contribute to such compositional variation, however, their impact on breast milk composition is currently poorly understood. We sought to (1) define the impact of maternal exposure to per- and polyfluoroalkyl substances (PFAS) on lipid composition of human breast milk, and (2) to study the combined impact of maternal PFAS exposure and breast milk lipid composition on the growth of the infants.In a mother-infant study (n = 44) we measured the levels of PFAS and lipids in maternal serum and conducted lipidomics analysis of breast milk collect 2-4 days after the delivery and at 3 months of infant age, by using ultra high performance liquid chromatography combined with quadrupole-time-of-flight mass spectrometry. Gastrointestinal biomarkers fecal calprotectin and human beta defensin 2 were measured in the stool samples at the age of 3, 6, 9, and 12 months. Maternal diet was studied by a validated food frequency questionnaire. PFAS levels were inversely associated with total lipid levels in the breast milk collected after the delivery. In the high exposure group, the ratio of acylated saturated and polyunsaturated fatty acids in triacylglycerols was increased. Moreover, high exposure to PFAS associated with the altered phospholipid composition, which was indicative of unfavorable increase in the size of milk fat globules. These changes in the milk lipid composition were further associated with slower infant growth and with elevated intestinal inflammatory markers. Our data suggest that the maternal exposure to PFAS impacts the nutritional quality of the breast milk, which, in turn, may have detrimental impact on the health and growth of the children later in life.

Umbilical cord serum concentrations of perfluorooctane sulfonate, perfluorooctanoic acid, and the body mass index changes from birth to 5 1/2 years of age

Prenatal exposure to perfluoroalkyl substances (PFAS) has been reported to affect body weight from birth to childhood, but the results remain inconclusive. We investigated whether umbilical cord blood concentrations of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) are associated with children’s risk trajectory for obesity. 600 children were randomly selected from the Hamamatsu Birth Cohort for Mothers and Children (HBC study) and their umbilical cord serum PFAS concentrations were quantified. Participants underwent BMI measurements at ages 1, 4, 10, 18, 24, 32, 40, 50, and 66 months. Growth curve modeling with random intercept was performed with standardized BMI as outcome variable. PFOS was negatively associated with standardized BMI (β =  − 0.34; p = 0.01), with a marginally significant interaction with the child’s age (β = 0.0038; p = 0.08). PFOA was negatively associated with standardized BMI (β =  − 0.26, 95% CI − 0.51, 0; p = 0.05), with a significant interaction with the child’s age (β = 0.005; p = 0.01). Stratified analysis by sex revealed that these effects were significant only among girls. Prenatal exposure to PFAS initially was associated with lower standardized BMI during infancy, but this effect dissipated over time and reversed in direction during later childhood. The effects of prenatal PFAS on higher standardized BMI is stronger in girls.

Perfluorooctane sulfonate and bisphenol A induce a similar level of mast cell activation via a common signaling pathway, Fyn-Lyn-Syk activation

Perfluoroalkyl compounds (PFCs) as food contaminants are widely distributed persistent organic pollutants (POPs) and have been suggested to induce immune dysfunction. However, their effects on immune function are not conclusive. Mast cells play a central role in allergic and non-allergic inflammatory responses. Therefore, we have examined the effects of PFCs (PFHxS, PFOA, PFOS) on mast cell-mediated inflammatory responses using in vitro mouse bone marrow-derived mast cells (BMMCs) and human mast cells (HMC-1) and in vivo mice model. The effects of PFCs were compared with those of bisphenol A (BPA), a well-studied environmental pollutant. Among PFCs tested, PFOS had the highest effects. Both PFOS and BPA increased degranulation and production of inflammatory eicosanoids in mast cells at a similar level, which subsequently led to increased skin edema and serum LTC₄ and PGD₂ in mice. Both PFOS and BPA increased not only downstream signaling (PLCγ1, AKT, ERK), but also upstream signaling (Fyn, Lyn, Syk/LAT) in mast cells. Taken together, PFOS and BPA induce mast cell-mediated inflammatory responses via a common signaling pathways. Our results may help establish the scientific basis for understanding the etiology of mast cell-mediated inflammatory responses and improve the immune dysfunction risk assessment for emerging POPs such as PFCs.

Environmental exposure to per- and polyfluoroalkyl substances mixture and male reproductive hormones

BACKGROUND

Previous epidemiological studies on the relationship between per- and polyfluoroalkyl substances (PFAS) exposure and male reproductive hormones were mainly limited to a few legacy PFAS and ignored the possible mixture effects.

OBJECTIVES

To assess the associations of PFAS mixture, branched isomers and emerging alternatives of PFAS with male reproductive hormones.

METHODS

A total of 902 men (mean age: 31.3 years) were recruited in this cross-sectional study. We quantified 24 targeted PFAS, including 7 branched PFOS isomers, 2 branched PFOA isomers and 2 components of F-53B, in blood plasma. Five reproductive hormones, including total testosterone (TT), estradiol (E₂), follicular stimulating hormone (FSH), luteinizing hormone (LH) and insulin like factor 3 (INSL3), and sex hormone binding globulin (SHBG) were measured in serum. Associations were first assessed by confounder-adjusted multiple linear regression while correcting for multiple comparisons. Bayesian kernel machine regression (BKMR) and adaptive elastic net (AENET) were further used to assess mixture effects and the adjusted exposure response (ER) relationship of individual PFAS.

RESULTS

After adjusting for confounders, we found that PFAS mixture was significantly and inversely associated with E₂ and E₂/TT, with perfluoro-n-undecanoic acid (PFuDA) being the major contributor. Although the associations between PFAS mixture and other hormones were non-significant, certain individual PFAS presented significant associations. Notably, perfluoro-n-tridecanoic acid (PFTrDA) and perfluoro-n-dodecanoic acid (PFDoA) were found to be significantly and inversely associated with INSL3, a unique indicator of Leydig cells function. Meanwhile, significant positive associations were found between perfluorobutane sulfonic acid (PFBS) and FSH and between PFuDA and LH. But the associations with branched isomers or F-53B were sporadic and inconsistent.

CONCLUSIONS

Our findings provided the evidence that PFAS mixture may reduce E₂ level, and certain PFAS (i.e., PFTrDA and PFDoA) may have negative effects on Leydig cells function among young men. Additional studies are much needed to confirm our results and elucidate potential mechanisms.

Maternal exposure to perfluoroalkyl chemicals and anogenital distance in the offspring: A Faroese cohort study

Exposure to perfluoroalkyl substances (PFASs) has in some studies been associated with reduced anogenital distance (AGD) in newborns as a sensitive indicator of prenatal anti-androgenic exposure. The aim of this study was to investigate the association between maternal PFAS exposure and offspring AGD in a population with wide ranges of PFAS exposures. Participants were recruited in the Faroe Islands in 2007-2009, and information on AGD and PFAS exposure was obtained from 463 mother-infant pairs. Perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), perfluorononanoic acid (PFNA) and perfluorodecanoic acid (PFDA) were measured in maternal serum. Data were analyzed using multiple linear regression analysis adjusted for birth weight, child age at examination, parity, and maternal education level. Among boys, higher maternal serum concentrations of PFOA, PFOS, PFNA and PFDA were significantly associated with a longer AGD, both with the exposure entered as a continuous variable and as quartiles. Boys in the highest quartile of PFOA, PFOS, PFNA and PFDA exposure had an increase in AGD of 1.2 mm (95 % CI 0.1;2.2), 1.3 mm (95 % CI 0.3;2.3), 1.0 mm (95 % CI 0.0:2.0) and 1.3 mm (95 % CI 0.3;2.4), respectively, when compared to boys in the lowest quartile of exposure (p < 0.05). No significant association was found between male AGD and PFHxS. No association was found for girls. In conclusion, elevated maternal exposure to major PFASs was significantly associated with a longer AGD in boys. No significant associations were found among girls, thus suggesting a sex-dimorphic effect of PFAS exposure.

Dietary exposure and accumulation of per- and polyfluoroalkyl substances alters growth and reduces body condition of post-metamorphic salamanders

Per- and polyfluoroalkyl substances (PFAS) are contaminants of concern due to their persistence, potential to bioaccumulate, and toxicity. While dietary exposure is the primary route of exposure for terrestrial species, data on dietary PFAS uptake and adverse effects are largely restricted to mammals. As such, substantial data gaps exist that hinder ecological risk assessment, including environmentally relevant exposure levels and taxa. Using a 30-d laboratory experiment, we examined the effects of dietary PFAS-exposure on post-metamorphic tiger salamanders (Ambystoma tigrinum). We fed salamanders crickets exposed to perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), or 6:2 fluorotelomer sulfonate (6:2 FTS) at low (<1.0), medium (2-5), or high (16-62) ng PFAS/g/d (wet weight) dose rates. We found that only PFOS resulted in substantial biomagnification. Despite limited evidence for biomagnification, PFAS altered growth and generally reduced body condition. Salamanders with the highest burdens of PFOS grew less and had lower body conditions, while burdens of PFHxS and PFOA were only associated with reduced growth. There was no evidence that environmentally relevant doses of PFAS increase liver size in salamanders. Our results demonstrate that dietary exposure and accumulation of PFAS can impact fitness-related traits in amphibians and contribute to trophic transfer in terrestrial food webs.

Resolving unknown isomers of emerging per- and polyfluoroalkyl substances (PFASs) in environmental samples using COSMO-RS-derived retention factor and mass fragmentation patterns

Chromatographic retention factors (k) and mass spectral fragmentation patterns of per- and polyfluoroalkyl substances (PFASs) were determined using the optimized parameters in liquid chromatography with tandem high-resolution mass spectrometry (LC-HRMS) analysis. Characteristic fragment ions obtained at various collision energies (MS² fragmentation) were used to determine the structures of newly discovered (emerging) PFASs detected from industrial effluent and surface water samples. Moreover, COnductor-like Screening MOdel for Realistic Solvents (COSMO-RS) derived octanol-water partition coefficients (K_ow), along with mean isotropic polarizabilities calculated from Density Functional Theory (DFT), of known PFASs were plotted against their experimental k values (k_exp) to obtain a multivariable regression model that can be used to predict k values of unknown PFASs. The k values of different structural isomers of unknown PFASs were calculated and compared to k_exp. The predicted k value for the isomer that matches the MS² fragmentation observed was found to be within 4.2 % of k_exp. This study demonstrates the applicability of an approach that combines the observed MS² fragmentation patterns and k values, together with computationally-derived log K_ow and polarizabilities, in assigning the structures of unknown PFASs at environmentally relevant conditions when no reference standards are available.

Perfluorooctane sulfonate exposure alters sexual behaviors and transcriptions of genes in hypothalamic-pituitary-gonadal-liver axis of male zebrafish (Danio rerio)

BACKGROUND

Perfluorooctane sulfonate (PFOS) has been reported to be widely distributed in the environment and wildlife with persistence. PFOS has various biological toxicity, especially disturbing the endocrine system. However, few studies have systematically evaluated its effect on sexual behaviors alteration and reproduction-related genes. This study was performed to assess the effect of PFOS exposure on sexual behaviors and genes in hypothalamic-pituitary-gonadal-liver (HPGL) axis in adult zebrafish.

METHODS

Male adult zebrafish were exposed to PFOS (0, 2, 20, and 200 μg/L) and 5 μg/L estradiol (E₂) continuously for 21 days. Sexual behaviors were analyzed by zebrafish behavior tracking system and the mRNA levels of HPGL-related genes was detected by RT-qPCR.

RESULTS

Body weight of the fish was increased in 2, 200 μg/L PFOS and E₂ groups, and body length was increased with exposure to 2 μg/L PFOS and E₂. The hepatic-somatic index was decreased significantly after 2 and 20 μg/L PFOS treatments. Highest PFOS (200 μg/L) and E₂ exposure impaired standard zebrafish sexual behaviors significantly such as chasing, nose-tail and tail-touching. In brains, the genes gonadotropin-releasing hormone (GnRH), gonadotropin-releasing hormone receptor (GnRHr) were down-regulated with exposure to PFOS with linear trend and E₂ exposure, and follicle-stimulating hormone and luteinizing hormone were also down-regulated with exposure to 20 and 200 μg/L PFOS. In livers, the genes vitellogenin 1 and 3 were upregulated with some concentrations of PFOS and E₂, but estrogenic receptor α, β2 were upregulated in any concentration of PFOS and E₂. In testes, the expressions of follicle-stimulating hormone receptor, luteinizing hormone receptor, and androgen receptor genes were all significantly down-regulated with any exposure concentration of PFOS and E₂.

CONCLUSIONS

PFOS may alter the zebrafish reproductive system by disrupting endocrine activity and impairing sexual behaviors.

Evaluation of the Estrogenic/Antiestrogenic Activities of Perfluoroalkyl Substances and Their Interactions with the Human Estrogen Receptor by Combining In Vitro Assays and In Silico Modeling

The potential estrogenic activities of perfluoroalkyl substances (PFASs) are controversial. Here, we investigated the estrogenic/antiestrogenic activities of PFASs and explored the corresponding interaction mode of PFASs with the estrogen receptor (ER) by combining in vitro assays and in silico modeling. We found that three PFASs (perfluorobutanoic acid, perfluorobutane sulfonate, and perfluoropentanoic acid) exerted antiestrogenic effects by inhibiting luciferase activity, whereas perfluorohexane sulfonate (PFHxS) and perfluorooctane sulfonate (PFOS) exerted estrogenic effects by inducing luciferase activity. When coexposed to 17β-estradiol (E2), all tested PFASs attenuated the E2-stimulated luciferase activity; unexpectedly, each PFAS could further attenuate the luciferase activity generated by the cotreatment with ICI 182,780 and E2, with a minimal effective concentration comparable to that found in human serum. PFHxS and PFOS significantly induced the gene expression of TFF1; additionally, all PFASs inhibited the E2-induced gene expression of TFF1 and EGR3. Furthermore, the results of the blind docking analyses suggested that the interaction with the coactivator-binding region on the ER surface should be included as a pathway through which PFASs exert estrogenic and antiestrogenic activities. Finally, we revealed the critical molecular property of the zero-order molecular connectivity index (MCI) (⁰χ) that affects the antiestrogenic activity of PFASs.

Proteomics and lipidomics analyses reveal modulation of lipid metabolism by perfluoroalkyl substances in liver of Atlantic cod (Gadus morhua)

The aim of the present study was to investigate effects of defined mixtures of polycyclic aromatic hydrocarbons (PAHs) and perfluoroalkyl substances (PFASs), at low, environmentally relevant (1× = L), or high (20× = H) doses, on biological responses in Atlantic cod (Gadus morhua). To this end, farmed juvenile cod were exposed at day 0 and day 7 via intraperitoneal (i.p.) injections, in a two-week in vivo experiment. In total, there were 10 groups of fish (n = 21-22): two control groups, four separate exposure groups of PAH and PFAS mixtures (L, H), and four groups combining PAH and PFAS mixtures (L/L, H/L, L/H, H/H). Body burden analyses confirmed a dose-dependent accumulation of PFASs in cod liver and PAH metabolites in bile. The hepatosomatic index (HSI) was significantly reduced for three of the combined PAH/PFAS exposure groups (L-PAH/H-PFAS, H-PAH/L-PFAS, H-PAH/H-PFAS). Analysis of the hepatic proteome identified that pathways related to lipid degradation were significantly affected by PFAS exposure, including upregulation of enzymes in fatty acid degradation pathways, such as fatty acid β-oxidation. The increased abundances of enzymes in lipid catabolic pathways paralleled with decreasing levels of triacylglycerols (TGs) in the H-PFAS exposure group, suggest that PFAS increase lipid catabolism in Atlantic cod. Markers of oxidative stress, including catalase and glutathione S-transferase activities were also induced by PFAS exposure. Only minor and non-significant differences between exposure groups and control were found for cyp1a and acox1 gene expressions, vitellogenin concentrations in plasma, Cyp1a protein synthesis and DNA fragmentation. In summary, our combined proteomics and lipidomics analyses indicate that PFAS may disrupt lipid homeostasis in Atlantic cod.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) and their effects on the ovary

BACKGROUND

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are found widespread in drinking water, foods, food packaging materials and other consumer products. Several PFAS have been identified as endocrine-disrupting chemicals based on their ability to interfere with normal reproductive function and hormonal signalling. Experimental models and epidemiologic studies suggest that PFAS exposures target the ovary and represent major risks for women's health.

OBJECTIVE AND RATIONALE

This review summarises human population and toxicological studies on the association between PFAS exposure and ovarian function.

SEARCH METHODS

A comprehensive review was performed by searching PubMed. Search terms included an extensive list of PFAS and health terms ranging from general keywords (e.g. ovarian, reproductive, follicle, oocyte) to specific keywords (including menarche, menstrual cycle, menopause, primary ovarian insufficiency/premature ovarian failure, steroid hormones), based on the authors' knowledge of the topic and key terms.

OUTCOMES

Clinical evidence demonstrates the presence of PFAS in follicular fluid and their ability to pass through the blood-follicle barrier. Although some studies found no evidence associating PFAS exposure with disruption in ovarian function, numerous epidemiologic studies, mostly with cross-sectional study designs, have identified associations of higher PFAS exposure with later menarche, irregular menstrual cycles, longer cycle length, earlier age of menopause and reduced levels of oestrogens and androgens. Adverse effects of PFAS on ovarian folliculogenesis and steroidogenesis have been confirmed in experimental models. Based on laboratory research findings, PFAS could diminish ovarian reserve and reduce endogenous hormone synthesis through activating peroxisome proliferator-activated receptors, disrupting gap junction intercellular communication between oocyte and granulosa cells, inducing thyroid hormone deficiency, antagonising ovarian enzyme activities involved in ovarian steroidogenesis or inhibiting kisspeptin signalling in the hypothalamus.

WIDER IMPLICATIONS

The published literature supports associations between PFAS exposure and adverse reproductive outcomes; however, the evidence remains insufficient to infer a causal relationship between PFAS exposure and ovarian disorders. Thus, more research is warranted. PFAS are of significant concern because these chemicals are ubiquitous and persistent in the environment and in humans. Moreover, susceptible groups, such as foetuses and pregnant women, may be exposed to harmful combinations of chemicals that include PFAS. However, the role environmental exposures play in reproductive disorders has received little attention by the medical community. To better understand the potential risk of PFAS on human ovarian function, additional experimental studies using PFAS doses equivalent to the exposure levels found in the general human population and mixtures of compounds are required. Prospective investigations in human populations are also warranted to ensure the temporality of PFAS exposure and health endpoints and to minimise the possibility of reverse causality.

A sensitive method for simultaneous determination of 12 classes of per- and polyfluoroalkyl substances (PFASs) in groundwater by ultrahigh performance liquid chromatography coupled with quadrupole orbitrap high resolution mass spectrometry

Per- and polyfluoroalkyl substances (PFASs) comprise a large group of chemicals with diverse physicochemical properties, which make their simultaneous determination a challenging task. A trace analytical method based on ultrahigh performance liquid chromatography-quadrupole Orbitrap high resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS) was developed for simultaneous determination of 54 PFASs belonging to 12 classes in groundwater, including 24 perfluorocarbons and 30 precursors. This method provided good linearity of calibration standards (R² > 0.99), excellent method limits of quantification (MLOQs) (0.5-250 pg/L), satisfactory matrix spiking recoveries (63%-148%), high precision (intra-day relative standard deviations (RSDs) 1.4-11.4%, inter-day RSDs 1.6-12.9%, and inter-week RSDs 2.1-12.7%), and short runtime (13 min), suitable for high throughput studies. The newly established method was successfully applied to detect PFASs in the groundwater samples collected from Hebei Province, China. Twenty PFASs were detected with the total concentration of 0.3-32.9 ng/L, indicating the contamination level similar to that in drinking water. The dominant PFASs were perfluorobutanesulfonate (PFBS), perfluorobutanoic acid (PFBA), perfluoropentanoic acid (PFPeA) and perfluorooctanoic acid (PFOA). In addition, 6:2 fluorotelomer phosphate diester (6:2 diPAP) and 6:2 fluorotelomer sulfonate (6:2 FTS) were found as the major precursors. The total PFAS concentrations were lower than the cumulative permissible limit of 70 ng/L for PFOS and PFOA recommended by the United States Environmental Protection Agency (USEPA) for drinking water in 2016. In a nutshell, this study provided a fast and sensitive method based on HRMS for the simultaneous analysis of a wide range of PFASs, present at trace levels in groundwater samples.

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.

Effects of perfluorooctanoic acid (PFOA) on the thyroid status, vitellogenin, and oxidant-antioxidant balance in the Murray River rainbowfish

Perfluorooctanoic acid's (PFOA) widespread use, presence and persistence in the aquatic environment has led to an increasing number of studies focusing on its toxicological effects. In Australia, PFOA has been detected in the aquatic environment, however its effects on Australian native fauna are unknown. In this study, male Australian native fish Murray River rainbowfish (Melanotaenia fluviatilis) were exposed to four different concentrations of PFOA (0.01, 0.1, 1 and 10 mg L^-1). Variations in thyroid hormones (Triiodothyronine (T3)/Thyroxine (T4)) and the presence of vitellogenin were determined in plasma. Oxidative stress responses were evaluated in gills and liver. Exposure of male fish to PFOA resulted in altered T3/T4 ratios and the presence of vitellogenin in the plasma. Activities of catalase (CAT) and glutathione- S-transferase (GST) were significantly increased in the gills and significantly reduced in the liver. Lipid peroxidation was observed in both tissues showing that vital organs could not neutralize the peroxides generated by oxidative stress resulting from exposure to PFOA. In natural populations exposed to PFOA, such hormonal disturbances can have negative effects, notably through altered capacity to respond to changes in environmental conditions.

Contaminant levels and endocrine disruptive effects in Clarias gariepinus exposed to simulated leachate from a solid waste dumpsite in Calabar, Nigeria

Solid waste dumpsites (SWDs) and landfills are significant sources of emerging contaminants to terrestrial and aquatic ecosystems. We have studied the endocrine disruptive effects of simulated leachate from a solid waste dumpsite in Calabar, Nigeria. Juvenile C. gariepinus were exposed to simulated leachate, diluted to 0:0 (control), 1:10, 1:50, 1:100 for 3, 7 and 14 days. In addition, 17β-estradiol (E2: 100 μg/L)-exposed positive control group was included. Hepatic transcripts for the genes encoding vitellogenin (vtg), estrogen receptor-α (er-α), and aromatase (cyp19a1) were analyzed by real-time PCR. Protein expression for Vtg and Cyp19 were measured by immunoblotting and plasma steroid hormones (testosterone: T and E2) were measured using enzyme immunoassay (EIA). Soil samples from the dumpsite were analyzed for selected group of contaminants showing that DEHP was the only detected phthalate ester (PE) at 1300 ± 400 ng/g. Further, perfluoroalkyl substances (PFASs) such as PFBS, PFOS, PFHxA, PFOA, PFNA, PFDA, PFUnDA and PFDoDA were detected in the soil samples from the dumpsite. We observed significant and apparent concentration-dependent increases in mRNA (vtg, er-α, and cyp19a1) and their corresponding functional protein products, after exposure to the simulated leachates. Further, the simulated leachate produced concentration-specific changes in plasma E2 and T levels. In general, the estrogenic endocrine and reproductive alterations in the exposed fish may directly be attributed to the PFASs and DEHP detected at the dumpsites. However, in addition to PFASs and DEHP, there could be other estrogenic contaminants in the leachate. Given the rapid utilization, for residential purposes, and increases in human settlement in areas around the Lemna SWDs, this study provides a direct cause-and-effect evidence of the potential contaminants at the dumpsite with significant environmental and human health consequences.

Inhibitory effect of metals on animal and plant glutathione transferases

Glutathione transferases (GSTs) represent a widespread enzyme superfamily in eukaryotes and prokaryotes catalyzing different reactions with endogenous and xenobiotic substrates such as organic pollutants. The latter are often found together with metal contamination in the environment. Besides performing of essential functions, GSTs protect cells by conjugation of glutathione with various reactive electrophiles. The interference of toxic metals with this functionality of GSTs may have unpredictable toxicological consequences for the organisms. In this review results from the recent literature are summarized and discussed describing the ability of metals to inhibit intracellular detoxification processes in animals and plants.

Stronger estrogenic and antiandrogenic effects on zebrafish larvae displayed by 6:2 polyfluoroalkyl phosphate diester than the 8:2 congener at environmentally relevant concentrations

Polyfluoroalkyl phosphate esters (PAPs) are one kind of emerging polyfluoroalkyl substances in the environment. However, their in vivo toxicities are largely unknown, especially at environmental relevant concentrations. To fill this gap, zebrafish embryos were exposed to 6:2 or 8:2 diPAP at environmentally relevant concentrations (0.5, 5, 50 ng/L) for 7 d. 6:2 and 8:2 diPAPs upregulated the mRNA and protein levels of aromatase in the exposed larvae, and elevated estradiol (E2) and vitellogenin (VTG) levels, but reduced testosterone (T) and 11-ketotestosterone (11-KT) levels, demonstrating estrogenic and antiandrogenic effects. Among the three ER subtypes, ERβ2 displayed the highest in vivo mRNA expression and the lowest in silico binding energies, suggesting that it was the main target ER subtype responsible for the estrogenic effect. Molecular simulation results indicated that diPAPs and E2 could bind to one common residue, arginine (Arg) 87, in the binding pocket of ERβ2, inducing similar estrogenic disruption mechanisms as E2. Both compounds could form hydrophobic interaction with glutamic acid (Glu) 12 and tryptophan (Trp) 80 and two hydrogen bonds with Arg81 of androgen receptor (AR) ligand-binding domains (LBDs) in antagonistic mode, resulting in a reduced level of AR upon exposure. The in silico binding energies of 6:2 diPAP with both ER and AR were lower than 8:2 diPAP, explaining the observed greater in vivo estrogenic and antiandrogenic activities of 6:2 diPAP. This study provided the first line of evidences that diPAPs could display adverse effects on the endocrine functions of fish species.

Perfluorooctanoic Acid Exposure Assessment on Common Carp Liver through Image and Ultrastructural Investigation

Perfluorooctanoic acid (PFOA) poses particular concern as an emerging pollutant in both surface and ground waters. Fish, as a natural inhabitant of these waters and being highly representative of vertebrates, represents an ideal animal model to assess the toxic effects of PFOA. Hereby, liver microscopic texture was comparatively evaluated in individuals of common carp subchronically exposed to PFOA using grayscale differential box counting, a fractal analysis method. Furthermore, liver cytoplasmic glycogen areas and ultrastructure were also evaluated and compared to the image analysis findings. Redundancy Analysis was performed to assess, in summary, how much the variation of fractal dimension and lacunarity was explained by the concentration of PFOA in liver, the mass of liver and the number of proliferating cell nuclear antigen (PCNA)-immunoreactive nuclei. Treatment group ordination was better determined by fractal dimension than lacunarity. Interestingly, a significant complexity increase was associated with the modification of liver microscopic texture due to PFOA exposure. This complexity increase was related to "cloudy swelling", possibly representing a primarily adaptive strategy against PFOA challenge, rather than a slight, reversible form of degeneration as traditionally proposed. The occurrence of endoplasmic reticulum stress, unfolded protein reaction and hormetic response was proposed and discussed.

Impact of Perfluorooctane Sulfonate on Reproductive Ability of Female Mice through Suppression of Estrogen Receptor α-Activated Kisspeptin Neurons

Perfluorooctane sulfonate (PFOS) is used extensively in industrial and household applications. High exposure to PFOS has been associated with increased odds of irregular and long menstrual cycles in women. However, the underlying mechanisms remain to be elucidated. Herein, we show that adult female mice appeared prolongation of diestrus and reduction of corpora luteum within a week of oral administration of PFOS (10 mg/kg), which are associated with decreases in the levels of serum progesterone, LH and hypothalamic GnRH. The number of AVPV-kisspeptin neurons and the AVPV-kisspeptin expression were increased in proestrus mice or OVX-mice treated with high-dose estradiol benzoate (0.05 mg/kg), which were suppressed by the administration of PFOS. The administration of PFOS or GPR54 antagonist P234 prevented the generation of LH-surge in OVX-mice treated with high-dose E2. In hypothalamic slices incubated in 100 nM E2 for 4 h, the AVPV-kisspeptin expression was significantly enhanced, which was inhibited by PFOS in a dose-dependent manner or estrogen receptor α (ERα) antagonist MPP, but not ERβ antagonist PHTPP. The incubation of ERα agonist PPT rather than ERβ agonist DPN could increase the level of AVPV-kisspeptin expression, which was sensitive to the treatment with PFOS. The administration of GPR54 agonist kisspeptin-10 in PFOS-mice could correct the prolongation of diestrus and reduction of corpora luteum, and recover the LH-surge and the levels of LH and GnRH. The results indicate that exposure to PFOS suppressed ERα-induced activation of AVPV-kisspeptin neurons leads to diestrus prolongation and ovulation reduction.

Fluorinated diiodine alkanes exert developmental toxicity on embryo-larval stages of zebrafish strain AB via regulating the expression of the specific endocrine-related genes

Fluorinated diiodine alkanes (FDIAs) are environmental pollutants, including octafluoro-1,4-diiodobutane (PFBDI), hexadecafluoro-1,8-diiodooctane (PFODI) and dodecafluoro-1,6-diiodohexane (PFHxDI). They showed an estrogenic effect in in vitro studies. However, little information is currently available regarding the toxicity of FDIAs in in vivo studies. Zebrafish (Danio rerio) is a vertebrate animal model that is increasingly used for toxicity and efficacy screening as well as for assessing the toxicity and safety of novel compounds, pollutants and pharmaceuticals. In the present study, we investigated the developmental toxicity of FDIAs (PFBDI, PFHxDI and PFODI) and the specific endocrine-related gene expression in zebrafish embryos. The results revealed that all three FDIAs showed developmental toxicity on zebrafish embryos. The half-maximal effective concentration values for PFBDI, PFHxDI and PFODI were 0.89 ± 0.07, 0.53 ± 0.04 and 0.04 ± 0.007 mm, respectively. PFHxDI exhibited the highest developmental toxicity compared with the other FDIAs. In addition, all three FDIAs significantly upregulated the expression of estrogen receptor (esr)1 and cytochrome P450 (CYP) 19b (CYP19b), but did not significantly affect the expression of esr2b, CYP17 and CYP19a in zebrafish. The upregulation effect of PFHxDI was greater than the effect of PFBDI and PFODI. This study furthers our knowledge on the effects of FDIAs on the developmental toxicity and the specific endocrine-related gene expression in the embryo-larval stages of zebrafish. Our results provided a preliminary insight into the toxicity of FDIAs in zebrafish, which will be of great relevance regarding future studies on FDIAs in the environment.

Perfluoroalkyl substances (PFASs) in the marine environment: Spatial distribution and temporal profile shifts in shellfish from French coasts

Perfluoroalkyl substances (PFASs) were investigated in filter-feeding shellfish collected from 2013 to 2017 along the English Channel, Atlantic and Mediterranean coasts of France. PFOS (perfluorooctane sulfonate), PFTrDA (perfluorotridecanoic acid), PFTeDA (perfluorotetradecanoic acid), PFDoDA (perfluorododecanoic acid) and PFUnDA (perfluoroundecanoic acid) were detected in more than 80% of samples, thus indicating widespread contamination of the French coastal environment by these chemicals. The distribution of PFAS concentrations showed differences according to sampling locations and years. PFOS was the predominant PFAS in most samples collected from English Channel and Atlantic coasts until 2014, but the opposite was observed in 2015, 2016 and 2017, while perfluoroalkyl carboxylic acids (PFCAs) prevailed in Mediterranean samples in all study years. Among PFCAs, PFTrDA showed the highest maximum (1.36 ng g^-1 ww) and median (0.077 ng g^-1 ww) concentrations in 2016-2017. Other PFAS median concentrations were within the 0.014 (PFNA) - 0.055 (PFTeDA) ng g^-1 ww range. The profiles determined each year in most Mediterranean samples suggest distinctive sources. PFOS median concentrations showed a significant decrease over the study years, from 0.118 to 0.126 ng g^-1 ww in 2013-2015 to 0.066 ng g^-1 ww in 2016 and 2017. ∑PFCAs showed no trends in concentration ranges over the same years. The shift in PFAS profiles from PFOS to long-chain PFCAs over the study period reflects PFOS production phase-out, combined with continuous inputs of PFCAs into the marine environment. These results provide reference data for future studies of the occurrence of contaminants of emerging concern on European coasts.

Modulation of Neuro-Dopamine Homeostasis in Juvenile Female Atlantic Cod ( Gadus morhua) Exposed to Polycyclic Aromatic Hydrocarbons and Perfluoroalkyl Substances

The dopaminergic effect of PAH and PFAS mixtures, prepared according to environmentally relevant concentrations, has been studied in juvenile female Atlantic cod ( Gadus morhua). Benzo[a]pyrene, dibenzothiophene, fluorene, naphthalene, phenanthrene, and pyrene were used to prepare a PAH mixture, while PFNA, PFOA, PFOS, and PFTrA were used to prepare a PFAS mixture. Cod were injected intraperitoneally twice, with either a low (1×) or high (20×) dose of each compound mixture or their combinations. After 2 weeks of exposure, levels of plasma 17β-estradiol (E2) were significantly elevated in high PAH/high PFAS treated group. Brain dopamine/metabolite ratios (DOPAC/dopamine and HVA+DOPAC/dopamine) changed with E2 plasma levels, except for high PAH/low PFAS and low PAH/high PFAS treated groups. On the transcript levels, th mRNA inversely correlated with dopamine/metabolite ratios and gnrh2 mRNA levels. Respective decreases and increases of drd1 and drd2a after exposure to the high PAH dose were observed. Specifically, high PFAS exposure decreased both drds, leading to high plasma E2 concentrations. Other studied end points suggest that these compounds, at different doses and combinations, have different toxicity threshold and modes of action. These effects indicate potential alterations in the feedback signaling processes within the dopaminergic pathway by these contaminant mixtures.

Sex-specific endocrine-disrupting effects of three halogenated chemicals in Japanese medaka

Several halogenated chemicals are found in an array of products that can cause endocrine disruption. Human studies have shown that endocrine responses are sex specific, with females more likely to develop hypothyroidism and males more likely to have reproductive impairment. The objective of this study was to assess sex differences on thyroid and estrogenic effects after exposure of Japanese medaka (Oryzias latipes, SK2MC) to halogenated compounds. This strain is an excellent model for these studies as sex can be determined non-destructively a few hours postfertilization. Medaka embryos were exposed to sublethal concentrations of Tris(1,3-dichloro-2-propyl) phosphate (TDCPP, 0.019 mg/L), perfluorooctanoic acid (PFOA, 4.7 mg/L) and its next generation alternative, perfluorobutyric acid (PFBA, 137 mg/L). Methimazole (inhibits thyroid hormone synthesis) and the thyroid hormone triiodothyronine served as reference controls. Fish were exposed throughout embryo development until 10 days postfertilization. Females displayed significantly larger swim bladders (which are under thyroid hormone control) after exposure to all chemicals with the exception of triiodothyronine, which caused the opposite effect. Females exposed to TDCPP and PFOA had increased expression of vitellogenin and exposure to PFOA upregulated expression of multiple thyroid-related genes. Upregulation of estrogenic-regulated genes after exposure to TDCPP, PFOA and methimazole was only observed in males. Overall, our results suggest that females and males show an estrogenic response when exposed to these halogenated chemicals and that females appear more susceptible to thyroid-induced swim bladder dysfunction compared with males. These results further confirm the importance of considering sex effects when assessing the toxicity of endocrine-disrupting compounds.

Protonation state effects of estrogen receptor α on the recognition mechanisms by perfluorooctanoic acid and perfluorooctane sulfonate: A computational study

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have been reported to cause adverse health effects on wildlife as well as humans. Numerous studies demonstrated that PFOA and PFOS could interfere with the transcriptional activation of estrogen receptor α (ERα) by mimicking the function of endogenous ligand, whereas some reports suggested that the two compounds present non-estrogenic activities. These conflicting results bring a confusion to understand their molecular mechanism on the ERα-mediated signaling pathway. To address this issue, we performed the molecular docking and molecular dynamics simulations to elaborate the structural characteristics for the binding of PFOA and PFOS to ERα. Our results indicated that the two opposite binding orientations were modulated by the protonation states of key residue His524. In sub-acidic condition, PFOA and PFOS prefer to form the H-bonding interactions with the protonated His524, whereas Arg394 provided the H-bonding interactions for stable binding in sub-alkaline condition. Conformational analyses implied that the diverse binding modes were closely related to the conformational propensity of ERα for subsequent coactivator recruitment and transcription activation. Generally, our findings provide a flexible strategy to assess the pH impacts of microenvironment on the toxicities of perfluoroalkyl acids by their interactions with proteins.

Perfluorooctanoic acid (PFOA) and perfluooctane sulfonate (PFOS) induce different modes of action in reproduction to Japanese medaka (Oryzias latipes)

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) have widely and frequently used in many industrial sectors, and thus have been frequently found in the environment. These chemicals may act as endocrine disrupting chemicals (EDCs), although the molecular mechanisms are still debated. In this study, Japanese medaka (Oryzias latipes) were exposed to 10 mg/l PFOA and 1 mg/l PFOS for 21 days, and the reproductive responses, such as the fecundity, secondary sexual characteristics and transcriptional levels of vitellogenin (vtg1 and vtg2) and choriogenin (chgh, chghm and chgl), were time-dependently evaluated (day 7, 14 and 21). PFOA and PFOS significantly reduced fecundity, and caused expression changes in the genes with time, although the patterns were different for each chemical and each sex. Different transcriptional regulations of vitellogenin and choriogenin in male suggest that PFOA and PFOS have different mode of actions in reproductive effects despite their similar chemical structure.

Estrogenic effects of fluorinated diiodine alkanes in MCF-7 cells, H295R cells and zebrafish embryo assays

Fluorinated diiodine alkanes (FDIAs), important industrial intermediates in the synthesis of various perfluorinated compounds, which are distributed widely in wildlife and humans. Recent studies showed that FDIAs had in vitro estrogenic effects. However, to date, little information is available regarding the in vivo estrogenic effects of FDIAs and the mechanisms are unclear. In this study, a combination of in vitro and in vivo assays was used to investigate the estrogenic effects of FDIAs. We tested the in vitro estrogenic effects and estrogen receptor-related gene expression via MCF-7 cell assay. The hormone level of estradiol and the expression of estrogenic synthesis genes were measured in the H295R cell assay. Finally, the in vivo effects of FDIAs on development and estrogen-related gene expression were assessed in the zebrafish embryos assay. The results demonstrated that FDIAs could exhibit estrogenic activity through inducing cell proliferation (1.6-6.7-fold of the control) and estrogen receptor alpha gene expression (1.07-1.39-fold of the control), altering estradiol production (1.14-1.22-fold of the control) and the major estrogenic synthesis gene expression of CYP19 (1.22-1.31-fold of the control), disrupting the estrogen-related genes (esr1 and cyp19b) levels in zebrafish (1.52-2.99-fold and 2.95-5.00-fold of the control for esr1 and cyp19b, respectively). The current findings indicated the potential estrogenic effects of FDIAs and provided novel information for human risk assessment.

8:2 fluorotelomer alcohol inhibited proliferation and disturbed the expression of pro-inflammatory cytokines and antigen-presenting genes in murine macrophages

Fluorotelomer alcohols (FTOHs, F(CF₂)_nCH₂CH₂OH) are members of per- and polyfluoroalkyl substances (PFASs) and are increasingly used in surfactant and polymer industries. FTOHs pose hepatotoxicity, nephrotoxicity and endocrine-disrupting risks. Nevertheless, there is limited research on the immunotoxic effects of FTOHs. In this study, we examined the immunotoxicity of 8:2 FTOH (n = 8) on murine macrophage cell line RAW 264.7. The results showed that 8:2 FTOH exposure reduced cell viability in dose- and time-dependent manners, inhibited cell proliferation and caused cell cycle arrest. Exposure to 8:2 FTOH downregulated the mRNA expression of some cell cycle-related genes, including Cdk4, Ccnd1, Ccne1, and p53, but also upregulated the mRNA expression of other cell cycle related genes, including Ccna2, p21, and p27. Additionally, exposure to 8:2 FTOH under unstimulated and LPS-stimulated conditions downregulated the mRNA expression of pro-inflammatory genes, including Il1b, Il6, Cxcl1, and Tnfa, and secreted levels of IL-6 and TNF-α. Treatment with 8:2 FTOH upregulated the mRNA expression of antigen-presenting-related genes, including H2-K1, H2-Ka, Cd80, and Cd86. The abovementioned immunotoxic effects caused by 8:2 FTOH in RAW 264.7 cells were partially or completely blocked by co-treatment with hydralazine hydrochloride (Hyd), a reactive carbonyl species (RCS) scavenger. However, exposure to 8:2 FTOH did not exhibit any effects on intracellular reactive oxygen species (ROS) level with or without LPS stimulation. Taken together, these results suggest that 8:2 FTOH may have immunotoxic effects on macrophages and RCS may underlie the responsible mechanism. The present study aids in understanding the health risks caused by FTOHs.