PFOA accumulation in the leaves of basil (Ocimum basilicum L.) and its effects on plant growth, oxidative status, and photosynthetic performance.

BACKGROUND: Perfluoroalkyl substances (PFASs) are emerging contaminants of increasing concern due to their presence in the environment, with potential impacts on ecosystems and human health. These substances are considered "forever chemicals" due to their recalcitrance to degradation, and their accumulation in living organisms can lead to varying levels of toxicity based on the compound and species analysed. Furthermore, concerns have been raised about the possible transfer of PFASs to humans through the consumption of edible parts of food plants. In this regard, to evaluate the potential toxic effects and the accumulation of perfluorooctanoic acid (PFOA) in edible plants, a pot experiment in greenhouse using three-week-old basil (Ocimum basilicum L.) plants was performed adding PFOA to growth substrate to reach 0.1, 1, and 10 mg Kg- 1 dw. RESULTS: After three weeks of cultivation, plants grown in PFOA-added substrate accumulated PFOA at different levels, but did not display significant differences from the control group in terms of biomass production, lipid peroxidation levels (TBARS), content of α-tocopherol and activity of ascorbate peroxidase (APX), catalase (CAT) and guaiacol peroxidase (POX) in the leaves. A reduction of total phenolic content (TPC) was instead observed in relation to the increase of PFOA content in the substrate. Furthermore, chlorophyll content and photochemical reflectance index (PRI) did not change in plants exposed to PFAS in comparison to control ones. Chlorophyll fluorescence analysis revealed an initial, rapid photoprotective mechanism triggered by PFOA exposure, with no impact on other parameters (Fv/Fm, ΦPSII and qP). Higher activity of glutathione S-transferase (GST) in plants treated with 1 and 10 mg Kg- 1 PFOA dw (30 and 50% to control, respectively) paralleled the accumulation of PFOA in the leaves of plants exposed to different PFOA concentration in the substrate (51.8 and 413.9 ng g- 1 dw, respectively). CONCLUSION: Despite of the absorption and accumulation of discrete amount of PFOA in the basil plants, the analysed parameters at biometric, physiological and biochemical level in the leaves did not reveal any damage effect, possibly due to the activation of a detoxification pathway likely involving GST.

Research Needs Regarding the Vapor Intrusion Potential of Volatile Per- and Polyfluoroalkyl Substances.

Certain per- or polyfluoroalkyl substances [e.g., fluorotelomer alcohols (FtOHs), perfluorooctane sulfonamides (FOSAs), and perfluorooctane sulfonamidoethanols (FOSEs)] have sufficient volatility to merit investigation of the vapor intrusion pathway on a site-specific basis, when they occur as subsurface contaminants in sufficient concentrations near occupied buildings. This perspective summarizes some of the evidence that these categories of per- or polyfluoroalkyl substances are volatile and offers specific research questions and objectives, for purposes of further assessing whether FtOHs, FOSAs, and/or FOSEs can pose indoor exposures via soil vapor intrusion and under what circumstances.

PFASs in Cerebrospinal Fluids and Blood-CSF Barrier Permeability in Patients with Cognitive Impairment.

Attention has been drawn to the associations between PFASs and human cognitive decline. However, knowledge on the occurrence and permeability of PFASs in the brains of patients with cognitive impairment has not been reported. Here, we determined 30 PFASs in paired sera and cerebrospinal fluids (CSFs) from patients with cognitive impairment (n = 41) and controls without cognitive decline (n = 18). We revealed similar serum PFAS levels but different CSF PFAS levels, with lower CSF PFOA (median: 0.125 vs 0.303 ng/mL, p < 0.05), yet higher CSF PFOS (0.100 vs 0.052 ng/mL, p < 0.05) in patients than in controls. Blood-brain transfer rates also showed lower RCSF/Serum values for PFOA and higher RCSF/Serum values for PFOS in patients, implying potential heterogeneous associations with cognitive function. The RCSF/Serum values for C4-C14 perfluoroalkyl carboxylates exhibited a U-shape trend with increasing chain length. Logistic regression analyses demonstrated that CSF PFOS levels were linked to the heightened risk of cognitive impairment [odds ratio: 3.22 (1.18-11.8)] but not for serum PFOS. Toxicity inference results based on the Comparative Toxicogenomics Database suggested that PFOS in CSF may have a greater potential to impair human cognition than other PFASs. Our results contribute to a better understanding of brain PFAS exposure and its potential impact on cognitive function.

Prediction of the Interactions of a Large Number of Per- and Poly-Fluoroalkyl Substances with Ten Nuclear Receptors.

Per- and poly-fluoroalkyl substances (PFASs) are persistent, toxic chemicals that pose significant hazards to human health and the environment. Screening large numbers of chemicals for their ability to act as endocrine disruptors by modulating the activity of nuclear receptors (NRs) is challenging because of the time and cost of in vitro and in vivo experiments. For this reason, we need computational approaches to screen these chemicals and quickly prioritize them for further testing. Here, we utilized molecular modeling and machine-learning predictions to identify potential interactions between 4545 PFASs with ten different NRs. The results show that some PFASs can bind strongly to several receptors. Further, PFASs that bind to different receptors can have very different structures spread throughout the chemical space. Biological validation of these in silico findings should be a high priority.

Impacts of Perfluoroalkyl Substances on Aqueous and Nonaqueous Phase Liquid Dechlorination by Sulfidized Nanoscale Zerovalent Iron.

Per- and poly fluoroalkyl substances (PFASs) are often encountered with nonaqueous phase liquid (NAPL) in the groundwater at fire-fighting and military training sites. However, it is unclear how PFASs affect the dechlorination performance of sulfidized nanoscale zerovalent iron (S-nFe0), which is an emerging promising NAPL remediation agent. Here, S-nFe0 synthesized with controllable S speciation (FeS or FeS2) were characterized to assess their interactions with PFASs and their dechlorination performance for trichloroethylene NAPL (TCE-NAPL). Surface-adsorbed PFASs blocked materials' reactive sites and inhibited aqueous TCE dechlorination. In contrast, PFASs-adsorbed particles with improved hydrophobicity tended to enrich at the NAPL-water interface, and the reactive sites were re-exposed after the PFASs accumulation into the NAPL phase to accelerate dechlorination. This PFASs-induced phenomenon allowed the materials to present a higher reactivity (up to 1.8-fold) with a high electron efficiency (up to 99%) for TCE-NAPL dechlorination. Moreover, nFe0-FeS2 with a higher hydrophobicity was more readily enriched at the NAPL-water interface and more reactive and selective than nFe0-FeS, regardless of coexisting PFASs. These results unveil that a small amount of yet previously overlooked coexisting PFASs can favor selective reductions of TCE-NAPL by S-nFe0, highlighting the importance of materials hydrophobicity and transportation induced by S and PFASs for NAPL remediation.

Persistence of PFOA Pollution at a PTFE Production Site and Occurrence of Replacement PFASs in English Freshwaters Revealed by Sentinel Species, the Eurasian Otter (Lutra lutra).

Concentrations of 33 PFASs were determined in 20 Eurasian otters, sampled 2015-2019, along a transect away from a factory, which used PFOA in PTFE manufacture. Despite cessation of usage in 2012, PFOA concentrations remained high near the factory (>298 µg/kg ww <20 km from factory) and declined with increasing distance (<57 µg/kg ww >150 km away). Long-chain legacy PFASs dominated the Σ33PFAS profile, particularly PFOS, PFOA, PFDA, and PFNA. Replacement compounds, PFECHS, F-53B, PFBSA, PFBS, PFHpA, and 8:2 FTS, were detected in ≥19 otters, this being the first report of PFBSA and PFECHS in the species. Concentrations of replacement PFASs were generally lower than legacy compounds (max: 70.3 µg/kg ww and 4,640 µg/kg ww, respectively). Our study underscores the utility of otters as sentinels for evaluating mitigation success and highlights the value of continued monitoring to provide insights into the longevity of spatial associations with historic sources. Lower concentrations of replacement, than legacy, PFASs likely reflect their lower bioaccumulation potential, and more recent introduction. Continued PFAS use will inevitably lead to increased environmental and human exposure if not controlled. Further research is needed on fate, toxicity, and bioaccumulation of replacement compounds.

Assessment of Fetal Exposure and Elimination of Perfluoroalkyl and Polyfluoroalkyl Substances: New Evidence from Paired Serum, Placenta, and Meconium Samples.

Multiple pieces of evidence have shown that prenatal exposure to perfluoroalkyl and polyfluoroalkyl substances (PFASs) is closely related to adverse birth outcomes for infants. However, difficult access to human samples limits our understanding of PFASs transport and metabolism across the human placental barrier, as well as the accurate assessment of fetal PFASs exposure. Herein, we assess fetal exposure to 28 PFASs based on paired serum, placenta, and meconium samples. Overall, 21 PFASs were identified first to be exposed to the fetus prenatally and to be metabolized and excreted by the fetus. In meconium samples, 25 PFASs were detected, with perfluorooctane sulfonate and perfluorohexane sulfonic acid being the dominant congeners, suggesting the metabolism and excretion of PFASs through meconium. Perfluoroalkyl sulfonic acids might be more easily eliminated through the meconium than perfluorinated carboxylic acids. Importantly, based on molecular docking, MRP1, OATP2B1, ASCT1, and P-gp were identified as crucial transporters in the dynamic placental transfer of PFASs between the mother and the fetus. ATSC5p and PubchemFP679 were recognized as critical structural features that affect the metabolism and secretion of PFASs through meconium. With increasing carbon chain length, both the transplacental transfer efficiency and meconium excretion efficiency of PFASs showed a structure-dependent manner. This study reports, for the first time, that meconium, which is a noninvasive and stable biological matrix, can be strong evidence of prenatal PFASs exposure.

Distribution of Per- and Polyfluoroalkyl Substances (PFASs) in a Waste-to-Energy Plant─Tracking PFASs in Internal Residual Streams.

Per- and polyfluoroalkyl substances (PFASs) constitute a diverse group of man-made chemicals characterized by their water- and oil-repellent properties and persistency. Given their widespread use in consumer products, PFASs will inevitably be present in waste streams sent to Waste-to-Energy (WtE) plants. We have previously observed a subset of PFASs in residual streams (ashes, treated process water, and flue gas) from a WtE plant. However, the transport and distribution of PFASs inside the WtE plant have remained unaddressed. This study is part of a comprehensive investigation to create a synoptic overview of the distribution of PFASs in WtE residues. PFASs were found in all sample types except for boiler ash. The total levels of 18 individual PFASs (Σ18PFASs) in untreated flue gas ranged from 5.2 to 9.5 ng m-3, decreasing with 35% ± 10% after wet flue gas treatment. Σ18PFASs in the condensate ranged from 46 to 50 ng L-1, of which perfluorohexanoic acid (PFHxA) made up 90% on a ng L-1 basis. PFHxA was also dominant in filter ash, where Σ18PFASs ranged from 0.28 to 0.79 ng g-1. This study shows that flue gas treatment can capture some PFASs and transfer them into WtE residues.

Four Decades of Spatiotemporal Variability of Per- and Polyfluoroalkyl Substances (PFASs) in the Baltic Sea.

Temporal and spatial variability of per- and polyfluoroalkyl substances (PFASs) in herring, cod, eelpout, and guillemot covering four decades and more than 1000 km in the Baltic Sea was investigated to evaluate the effect of PFAS regulations and residence times of PFASs. Overall, PFAS concentrations responded rapidly to recent regulations but with some notable basin- and homologue-specific variability. The well-ventilated Kattegat and Bothnian Bay showed a faster log-linear decrease for most PFASs than the Baltic Proper, which lacks a significant loss mechanism. PFOS and FOSA, for example, have decreased with 0-7% y-1 in the Baltic Proper and 6-16% y-1 in other basins. PFNA and partly PFOA are exceptions and continue to show stagnant or increasing concentrations. Further, we found that Bothnian Bay herring contained the highest concentrations of >C12 perfluoroalkyl carboxylic acids (PFCAs), likely from rivers with high loads of dissolved organic carbon. In the Kattegat, low PFAS concentrations, but a high FOSA fraction, could be due to influence from the North Sea inflow below the halocline and possibly a local source of FOSA and/or isomer-specific biotransformation. This study represents the most comprehensive spatial and temporal investigation of PFASs in Baltic wildlife while providing new insights into cycling of PFASs within the Baltic Sea ecosystem.

The Total Mass of Per- and Polyfluoroalkyl Substances (PFASs) in California Cosmetics.

Cosmetics make up one of the consumer product categories most widely known to contain perfluoroalkyl and polyfluoroalkyl substances (PFASs), including precursors to perfluorooctanoic acid (PFOA) and other perfluoroalkyl acids (PFAAs). Because of the way cosmetics are used, most of the PFASs present in these products are likely to reach wastewater treatment plants (WWTPs), which suggests that cosmetics may contribute significantly to the load of PFOA and other PFASs at WWTPs. However, the majority of PFASs present as intentional ingredients in cosmetics cannot be quantified with the available analytical methods. To address this issue, we developed a methodology to estimate the total PFAS mass in cosmetics as well as the corresponding mass of total organic fluorine and of fluorinated side chains associated with PFAA precursors, using various ingredient databases and ingredient concentrations reported by manufacturers. Our results indicate that the cosmetics sold in California during a one-year period cumulatively contain 650-56 000 kg of total PFASs, 370-37 000 kg of organic fluorine, and 330-20 000 kg of fluorinated side chains associated with PFAA precursors. Among the 16 product subcategories considered, >90% of the PFAS mass came from shaving creams and gels, hair care products, facial cleansers, sun care products, and lotions and moisturizers, while the sum of all nine makeup subcategories accounted for <3%. Comparing our estimates to available WWTP influent data from the San Francisco Bay Area suggests that cosmetics may account for at least 4% of the precursor-derived PFAAs measured in wastewater. As the first study ever to estimate the total mass of PFASs contained in cosmetics sold in California, our results shed light on the significance of certain cosmetics as a source of PFASs to WWTPs and can inform effective source reduction efforts.

Contamination status, partitioning behavior, ecological risks assessment of legacy and emerging per- and polyfluoroalkyl substances in a typical heavily polluted semi-enclosed bay, China.

The contaminant status, spatial distribution, partitioning behavior, and ecological risks of 26 legacy and emerging perfluoroalkyl and polyfluoroalkyl substances (PFASs) in Laizhou Bay, China were investigated. The concentrations of ∑PFASs in surface and bottom seawater ranged from 37.2 to 222 ng/L and from 34.2 to 305 ng/L with an average of 116 ± 62.7 and 138 ± 93.8 ng/L, respectively. There were no significant differences in the average concentrations between the surface and bottom seawater (P > 0.05). Perfluorooctanoic acid (PFOA) and short-chain PFASs dominated the composition of PFASs in seawater. The concentrations of ∑PFASs in sediments ranged from 0.997 to 7.21 ng/g dry weight (dw), dominated by perfluorobutane sulfonate (PFBS), perfluorobutanoic acid (PFBA), and long-chain PFASs. The emerging alternatives of perfluoro-1-butane-sulfonamide (FBSA) and 6:2 fluorotelomer sulfonic acid (6:2 FTSA) were detected for the first time in Laizhou Bay. The ∑PFASs in seawater in the southwest of the bay were higher than those in the northeast of the bay. The ∑PFASs in sediments in the northeast sea area were higher than those in the inner area of the bay. Log Kd and log Koc values increased with increasing carbon chain length for PFASs compounds. Ecological risk assessments indicated a low ecological risk associated with HFPO-DA but a moderate risk associated with PFOA contamination in Laizhou Bay. Positive matrix factorization (PMF) analysis revealed that fluoropolymer manufacturing, metal plating plants, and textile treatments were identified as major sources contributing to PFASs contamination.

Roles of varying carbon chains and functional groups of legacy and emerging per-/polyfluoroalkyl substances in adsorption on metal-organic framework: Insights into mechanism and adsorption prediction.

Metal-organic frameworks (MOFs) are promising adsorbents for legacy per-/polyfluoroalkyl substances (PFASs), but they are being replaced by emerging PFASs. The effects of varying carbon chains and functional groups of emerging PFASs on their adsorption behavior on MOFs require attention. This study systematically revealed the structure-adsorption relationships and interaction mechanisms of legacy and emerging PFASs on a typical MOF MIL-101(Cr). It also presented an approach reflecting the average electronegativity of PFAS moieties for adsorption prediction. We demonstrated that short-chain or sulfonate PFASs showed higher adsorption capacities (µmol/g) on MIL-101(Cr) than their long-chain or carboxylate counterparts, respectively. Compared with linear PFASs, their branched isomers were found to exhibit a higher adsorption potential on MIL-101(Cr). In addition, the introduction of ether bond into PFAS molecule (e.g., hexafluoropropylene oxide dimeric acid, GenX) increased the adsorption capacity, while the replacement of CF2 moieties in PFAS molecule with CH2 moieties (e.g., 6:2 fluorotelomer sulfonate, 6:2 FTS) caused a decrease in adsorption. Divalent ions (such as Ca2+ and SO42-) and solution pH have a greater effect on the adsorption of PFASs containing ether bonds or more CF2 moieties. PFAS adsorption on MIL-101(Cr) was governed by electrostatic interaction, complexation, hydrogen bonding, π-CF interaction, and π-anion interaction as well as steric effects, which were associated with the molecular electronegativity and chain length of each PFAS. The average electronegativity of individual moieties (named Me) for each PFAS was estimated and found to show a significantly positive correlation with the corresponding adsorption capacity on MIL-101(Cr). The removal rates of major PFASs in contaminated groundwater by MIL-101(Cr) were also correlated with the corresponding Me values. These findings will assist with the adsorption prediction for a wide range of PFASs and contribute to tailoring efficient MOF materials.

Occurrence, source apportionment, and ecological risk of legacy and emerging per- and poly-fluoroalkyl substances (PFASs) in the Dahei river basin of a typical arid region in China.

Per- and poly-fluoroalkyl substances (PFASs) are artificial chemicals with broad commercial and industrial applications. Many studies about PFASs have been conducted in densely industrial and populated regions. However, fewer studies have focused on the PFASs' status in a typical arid region. Here, we investigated 30 legacy and emerging PFASs in surface water from the mainstream and tributaries of the Dahei River. Our results revealed that total PFASs concentrations (∑30PFASs) in water ranged from 3.13 to 289.1 ng/L (mean: 25.40 ng/L). Perfluorooctanoic acid (PFOA) had the highest mean concentration of 2.44 ng/L with a 100% detection frequency (DF), followed by perfluorohexanoic acid (PFHxA) (mean concentration: 1.34 ng/L, DF: 59.26%). Also, perfluorohexane sulfonate (DF: 44.44%), perfluorobutane sulfonate (DF: 88.89%), and perfluorooctane sulfonate (PFOS) (DF: 92.59%) had mean concentrations of 12.94, 2.00, and 1.05 ng/L, respectively. Source apportionment through ratio analysis and principal component analysis-multiple linear regression analysis showed that treated or untreated sewage, aqueous film-forming foam, degradation of precursors, and fluoropolymer production were the primary sources. The PFOS alternatives were more prevalent than those of PFOA. Conductivity, total phosphorus, and chlorophyll a positively correlated with Σ30PFASs and total perfluoroalkane sulfonates concentrations. Furthermore, ecological risk assessment showed that more attention should be paid to perfluorooctadecanoic acid, perfluorohexadecanoic acid, perfluorooctane sulfonate, perfluorohexane sulfonate, and (6:2 and 6:2/8:2) polyfluoroalkyl phosphate mono- and di-esters. The mass load of PFASs to the Yellow River was 1.28 kg/year due to the low annual runoff in the Dahei River in the arid region. This study provides baseline data for PFASs in the Dahei River that can aid in the development of effective management strategies for controlling PFASs pollution in typical arid regions in China.

Per- and polyfluoroalkyl substances in waterbird feathers around Poyang Lake, China: Compound and species-specific bioaccumulation.

As a nondestructive means of environmental monitoring, bird feathers have been used to analyze levels of per- and polyfluoroalkyl substances (PFASs) in specific environments. In this study, feather samples from 10 waterbird species around Poyang Lake were collected, and a pretreatment method for PFASs in feathers was optimized. The results showed that a combined cleaning method using ultrapure water and n-hexane effectively removed external PFASs. Twenty-three legacy and emerging PFASs were identified in the feathers of waterbirds, of which hexafluoropropylene oxides (HFPOs), chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs), and sodium p-perfluorinated noneoxybenzene sulfonate (OBS) were reported for the first time, with their concentrations ranging from 0.060-2.4 ng·g-1 dw, 0.046-30 ng·g-1 dw, and lower than the method detection limit to 30 ng·g-1 dw, respectively. Compound- and species-specific bioaccumulation of PFASs was observed in the feathers of different waterbird species, suggesting that different PFAS types can be monitored through the selection of different species. Moreover, the concentrations of most PFCAs (except perfluorobutyric acid), perfluorooctane sulfonate (PFOS), and perfluorooctane sulfonamide (FOSA) were significantly positively correlated with δ15N (p < 0.05), while the concentrations of HFPOs, Cl-PFESAs, and OBS had significant positive correlations with δ13C. This indicates that the bioaccumulation of legacy and emerging PFASs in waterbird feathers is affected by their trophic level, feeding habits, and foraging area.

Review of Recent Computational Research on the Adsorption of PFASs with a Variety of Substrates.

The widespread use and impervious nature of per- and polyfluorinated alkyl substances (PFASs) is leading to potentially harmful exposure in numerous environments. One avenue to explore remediation of PFAS-contaminated environments involves investigating how well PFASs adsorb onto various substrates. In the current review, we focus on summarizing recent computational research, largely involving density functional theory (DFT) and molecular dynamics (MD), into the adsorption and interaction of PFASs with a variety of substrates with an aim to provide insight and inspire further research that may lead to solutions to this critical problem that impacts the environment and human health.

Distribution of per- and polyfluoroalkyl substances in blood, serum, and urine of patients with liver cancer and associations with liver function biomarkers.

Studies have shown that per- and polyfluoroalkyl substances (PFASs) may be hepatotoxic in animals or humans. However, data on clinical epidemiology are very limited. In this study, 21 PFASs were determined in patients with liver diseases, with the highest median concentrations detected in the serum sample (26.7 ng/mL), followed by blood (10.7 ng/mL) and urine (5.02 ng/mL). Higher total PFAS concentrations were found in hepatocellular carcinoma (HCC) patients compared to non-HCC patients, with significant discrepancies in serum and blood samples. Besides, significant correlations were also found among PFAS concentrations and age, gender, body mass index (BMI), and liver function biomarkers levels. For example, PFAS concentrations are significantly higher in males than in females; Several serum PFASs concentrations increase with age and BMI, while the serum perfluorohexane sulfonic acid (PFHxS) concentrations are negatively correlated with age. In addition, multiple regression models adjusted for age, gender and BMI found that increased serum perfluorobutane sulfonic acid (PFBS), perfluoroheptane sulfonic acid (PFHpS) and perfluorohexylphosphonic acid (PFHxPA) conentrations are correlated with elevated alkaline phosphatase (ALP), aspartate aminotransferase (AST), and alpha-fetoprotein (AFP) (p < 0.05). Our results provide epidemiological support for the future study on the potential clinical hepatotoxicity of PFAS.

Unrecognized risk of perfluorooctane sulfonate in promoting conjugative transfers of bacterial antibiotic resistance genes.

Antibiotic resistance is a major global health crisis facing humanity, with horizontal gene transfer (HGT) as a principal dissemination mechanism in the natural and clinical environments. Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse effects on humans. However, it is unknown whether PFASs affect the HGT of bacterial antibiotic resistance. Using a genetically engineered Escherichia coli MG1655 as the donor of plasmid-encoded antibiotic resistance genes (ARGs), E. coli J53 and soil bacterial community as two different recipients, this study demonstrated that the conjugation frequency of ARGs between two E. coli strains was (1.45 ± 0.17) × 10-5 and perfluorooctane sulfonate (PFOS) at environmentally relevant concentrations (2-50 µg L-1) increased conjugation transfer between E. coli strains by up to 3.25-fold. Increases in reactive oxygen species production, cell membrane permeability, biofilm formation capacity, and cell contact in two E. coli strains were proposed as major promotion mechanisms from PFOS exposure. Weighted gene co-expression network analysis of transcriptome data identified a series of candidate genes whose expression changes could contribute to the increase in conjugation transfer induced by PFOS. Furthermore, PFOS also generally increased the ARG transfer into the studied soil bacterial community, although the uptake ability of different community members of the plasmid either increased or decreased upon PFOS exposure depending on specific bacterial taxa. Overall, this study reveals an unrecognized risk of PFOS in accelerating the dissemination of antibiotic resistance. IMPORTANCE Perfluoroalkyl substances (PFASs) are emerging contaminants of global concern due to their high persistence in the environment and adverse health effects. Although the influence of environmental pollutants on the spread of antibiotic resistance, one of the biggest threats to global health, has attracted increasing attention in recent years, it is unknown whether environmental residues of PFASs affect the dissemination of bacterial antibiotic resistance. Considering PFASs, often called "forever" compounds, have significantly higher environmental persistence than most emerging organic contaminants, exploring the effect of PFASs on the spread of antibiotic resistance is more environmentally relevant and has essential ecological and health significance. By systematically examining the influence of perfluorooctane sulfonate on the antibiotic resistance gene conjugative transfer, not only at the single-strain level but also at the community level, this study has uncovered an unrecognized risk of PFASs in promoting conjugative transfers of bacterial antibiotic resistance genes, which could be incorporated into the risk assessment framework of PFASs.

Poly- and Perfluoroalkyl Substances Induce Immunotoxicity via the TLR Pathway in Zebrafish: Links to Carbon Chain Length.

Previous studies have reported the immunotoxicity of per- and polyfluoroalkyl substances (PFASs), but it remains a significant challenge to assess over 10,000 distinct PFASs registered in the distributed structure-searchable toxicity (DSSTox) database. We aim to reveal the mechanisms of immunotoxicity of different PFASs and hypothesize that PFAS immunotoxicity is dependent on the carbon chain length. Perfluorobutanesulfonic acid (PFBA), perfluorooctanoic acid (PFOA), and perfluorononanoic acid (PFNA) representing different carbon chain lengths (4-9) at environmentally relevant levels strongly reduced the host's antibacterial ability during the zebrafish's early-life stage. Innate and adaptive immunities were both suppressed after PFAS exposures, exhibiting a significant induction of macrophages and neutrophils and expression of immune-related genes and indicators. Interestingly, the PFAS-induced immunotoxic responses were positively correlated to the carbon chain length. Moreover, PFASs activated downstream genes of the toll-like receptor (TLR), uncovering a seminal role of TLR in PFAS immunomodulatory effects. Myeloid differentiation factor 88 (MyD88) morpholino knock-down experiments and MyD88 inhibitors alleviated the immunotoxicity of PFASs. Overall, the comparative results demonstrate differences in the immunotoxic responses of PFASs due to carbon chain length in zebrafish, providing new insights into the prediction and classification of PFASs mode of toxic action based on carbon chain length.

Sex-Specific Bioaccumulation, Maternal Transfer, and Tissue Distribution of Legacy and Emerging Per- and Polyfluoroalkyl Substances in Snakes (Enhydris chinensis) and the Impact of Pregnancy.

The effects of sex and pregnancy on the bioaccumulation and tissue distribution of legacy and emerging per- and polyfluoroalkyl substances (PFASs) in Chinese water snakes were investigated. The bioaccumulation factor of PFASs showed a positive correlation with their protein-water partition coefficients (log KPW), and steric hindrance effects were observed when the molecular volume was > 357 Å3. PFAS levels in females were significantly lower than those in males. The chemical composition of pregnant females was significantly different from that of non-pregnant females and males. The maternal transfer efficiencies of perfluorooctane sulfonic acid were higher than those of other PFASs, and a positive correlation between the maternal transfer potential and log KPW was observed for other PFASs. Tissues with high phospholipid content exhibited higher concentrations of ∑PFASs. Numerous physiological changes occurred in maternal organ systems during pregnancy, leading to the re-distribution of chemicals among different tissues. The change in tissue distribution of PFASs that are easily and not-so-easily maternally transferred was in the opposite direction. The extent of compound transfer from the liver to the egg determined tissue re-distribution during pregnancy.

Perfluoroalkyl Substances in Seabird Eggs from Canada's Pacific Coast: Temporal Trends (1973-2019) and Interspecific Patterns.

Whether perfluoroalkyl sulfonates (PFSAs) and perfluoroalkyl carboxylates (PFCAs) are responding to legislative restrictions and showing decreasing trends in top marine predators that range across the eastern North Pacific Ocean is unclear. Here, we examined longer-term temporal trends (1973-2019) of 4 PFSAs and 13 PFCAs, as well stable isotopes of δ13C and δ15N, in the eggs of 4 seabird species sampled along a nearshore-offshore gradient; double-crested cormorants (Nannopterum auritum), pelagic cormorants (Urile pelagicus), rhinoceros auklets (Cerorhinca monocerata), and Leach's storm-petrels (Hydrobates leucorhous) from the Pacific coast of British Columbia, Canada. PFOS was the most abundant PFSA (79-94%) detected in all eggs regardless of colony and year, with the highest concentrations, on average, measured in auklet eggs (mean = 58 ng g-1, range = 11-286 ng g-1 ww). Perfluoroundecanoic acid (PFUdA) and perfluorotridecanoic acid (PFTriDA) were the dominant long-chain PFCAs (≥30% combined). The majority of PFSAs (including PFOS) are statistically declining (p < 0.001) in the eggs of all 4 species with PFOS half-lives ranging from 2.6 to 7.8 years. Concentrations of long-chain PFCAs exhibited a trajectory comprised of linear increases and second-order declines, suggesting that the rate of uptake of PFCAs is slowing or leveling off. These trends are consistent with the voluntarily ceased production of PFSAs by 3M circa 2000-2003 and are among the first from the northeast Pacific to indicate a positive response to several regulations and restrictions on PFCAs from facility emissions and product content.