The occurrence, tissue distribution, and PBT potential of per- and polyfluoroalkyl substances in the freshwater organisms from the Yangtze river via nontarget analysis

Multigeneration responses of Daphnia magna to short-chain per- and polyfluorinated substances (PFAS)

Short-chain per- and polyfluorinated substances (PFAS) are ubiquitous in the environment, but their chronic effects on aquatic organisms over multiple generations are often overlooked in environmental risk assessment. In this study, the ecotoxicity of perfluorobutane sulfonic acid (PFBS) and its precursor perfluorobutane sulfonamide (FBSA) to Daphnia magna was assessed under continuous exposure for six consecutive generations, with adult survival, reproduction, and population growth rate as endpoints. Observed effects were also related to internal PFAS concentrations in the daphnids. Compared to the first generation, both PFBS and FBSA showed intensified ecotoxicity over six generations, increasing by 1.8-3.0, and 3.6-6.4 times, respectively. Specifically, the EC50_r, water and LC50, water of PFBS decreased from 886 and > 1470 mg/L in the F0 generation to 470 and 483 mg/L, respectively in the F3 generation, while the EC50_r, water and EC50_repro, water of FBSA decreased from 12.4 and 7.08 mg/L in the F0 generation to 3.37 and 1.10 mg/L, respectively in the F5 generation. PFBS ecotoxicity increased as a result of elevated compound accumulation over generations, indicating a narcotic mode of action, whereas FBSA exerted specific reproductive toxicity, resulting in a more pronounced worsening of adverse effects over time. Compared to PFBS, FBSA was around 100 times more toxic in F0, escalating to over 435 times more toxic in F5, and also showed a higher bioaccumulation potential. These findings highlight that the conventional single-generation ecotoxicity tests underestimate PFAS ecotoxicity during multigeneration exposure, and that the environmental risks of PFAS cannot be reliably assessed by the current limited subset of studied compounds.

A systematic review for non-targeted analysis of per- and polyfluoroalkyl substances (PFAS)

This review follows the PRISMA guidelines to provide a systematic review of 115 peer reviewed articles that used non-targeted analysis (NTA) methods to detect per- and polyfluoroalkylated substances (PFAS). This literature highlights the significant positive impact of NTA in understanding PFAS in the environment. Within the literature a geographical bias exists, with most NTA studies (∼60 %) conducted in the United States and China. Future studies in other regions (such as South America and Africa) are needed to gain a more global understanding. More research is required in marine environments and the atmosphere, as current studies focus mainly on freshwater, groundwater, soil, and sediments. The majority of studies focus on measuring PFAS in the environment, rather than in commercial products (with the exception of AFFF). Non-lethal blood sampling has been successful for NTA in humans and wildlife, but additional biomonitoring studies are required on exposed cohorts to understand health risks and PFAS biotransformation pathways. NTA methods mostly use liquid chromatography and negative ionisation, which biases the literature towards the detection of specific PFAS. Despite improvements in data reporting and quality assurance and control (QA/QC) procedures, factors such as false negative and false positive rates are often overlooked, and many NTA workflows remain highly subjective. Perfluoroalkyl carboxylic acids (PFCAs) and perfluoroalkyl sulfonic acids (PFSAs) are the most detected PFAS classes, identified in over 80 % of NTA studies, and are common in routine monitoring. However, our review identified >1000 PFAS from a total of 382 different PFAS classes, with over 300 classes found in fewer than 5 % of studies. This highlights the variety of different PFAS present in the environment, and the limitations of relying solely on targeted methods. Future monitoring programs and regulations would benefit from considering NTA methods to provide more comprehensive information on PFAS present in the environment.

Influence of age on the concentrations of perfluoroalkyl acids (PFAA) in the tissues of perch (Percafluviatilis)

Globally, perfluoroalkyl acids (PFAA) are ubiquitous due to their almost unlimited applications in industry and households and are detected in a wide variety of matrices.Aquatic ecosystems are of particular importance due to the spread of PFAA via water fluxes. The majority of published studies describe PFAA concentrations in fish or aquatic mammals, but not the dependence of PFAA concentrations in tissues and organs in fish of different ages. Since this is very important for understanding the accumulation behavior of these substances our study systematically investigates the influence of age on the PFAA concentration in the tissues of 74 perches (Perca fluviatilis), a very popular edible fish. Fish are particularly suitable as indicators of PFAA contamination of water because of their uptake via water (gills and skin) and food (predominantly piscivorous diet). The mean total PFAA concentrations (as the sum of the individual concentrations of 11 compounds) were: 114 μg/kg (kidney), 112 μg/kg (heart), 79.9 μg/kg (liver), 78.4 μg/kg (spleen), 64.6 μg/kg (gills) and 21.7 μg/kg (muscle), with longer-chain compounds accounting for 90% of the substances. Perfluorooctanesulfoic acid (PFOS) accounted for the largest percentage of the total PFAA concentration in all tissues at 43-63%. With the exception of the heart and spleen, a significant increase in total concentrations was observed with increasing age of the perch. The strongest correlation was observed for the kidney, followed by the liver and gills. With regard to their consumption as human nutrition the tolerable weekly PFAA intake of 4.4 ng/kg bodyweight and week for the sum of the 4 EFSA PFAA in adults and children was exceeded many times over (860% and 1600% respectively) with an average fish consumption per week. The maximum PFAA levels set in the E.U. since January 2023 were exceeded five times.

Unveiling behaviors of 8:2 fluorotelomer sulfonic acid (8:2 FTSA) in Arabidopsis thaliana: Bioaccumulation, biotransformation and molecular mechanisms of phytotoxicity

8:2 fluorotelomer sulfonic acid (8:2 FTSA) has been commonly detected in the environment, but its behaviors in plants are not sufficiently known. Here, the regular and multi-omics analyses were used to comprehensively investigate the bioaccumulation, biotransformation, and toxicity of 8:2 FTSA in Arabidopsis thaliana. Our results demonstrated that 8:2 FTSA was taken up by A. thaliana roots and translocated to leaves, stems, flowers, and seeds. 8:2 FTSA could be successfully biotransformed to several intermediates and stable perfluorocarboxylic acids (PFCAs) catalyzed by plant enzymes. The plant revealed significant growth inhibition and oxidative damage under 8:2 FTSA exposure. Metabolomics analysis showed that 8:2 FTSA affected the porphyrin and secondary metabolisms, resulting in the promotion of plant photosynthesis and antioxidant capacity. Transcriptomic analysis indicated that differentially expressed genes (DEGs) were related to transformation and transport processes. Integrative transcriptomic and metabolomic analysis revealed that DEGs and differentially expressed metabolites (DEMs) in plants were predominantly enriched in the carbohydrate metabolism, amino acid metabolism, and lipid metabolism pathways, resulting in greater energy consumption, generation of more nonenzymatic antioxidants, alteration of the cellular membrane composition, and inhibition of plant development. This study provides the first insights into the molecular mechanisms of 8:2 FTSA stress response in plants.

Machine learning-enhanced molecular network reveals global exposure to hundreds of unknown PFAS

Unknown forever chemicals like per- and polyfluoroalkyl substances (PFASs) are difficult to identify. Current platforms designed for metabolites and natural products cannot capture the diverse structural characteristics of PFAS. Here, we report an automatic PFAS identification platform (APP-ID) that screens for PFAS in environmental samples using an enhanced molecular network and identifies unknown PFAS structures using machine learning. Our networking algorithm, which enhances characteristic fragment matches, has lower false-positive rate (0.7%) than current algorithms (2.4 to 46%). Our support vector machine model identified unknown PFAS in test set with 58.3% accuracy, surpassing current software. Further, APP-ID detected 733 PFASs in real fluorochemical wastewater, 39 of which are previously unreported in environmental media. Retrospective screening of 126 PFASs against public data repository from 20 countries show PFAS substitutes are prevalent worldwide.

Per- and polyfluoroalkyl substances (PFAS) exposure in plasma and their blood-brain barrier transmission efficiency-A pilot study

Per- and polyfluoroalkyl substances (PFAS) have been shown to penetrate the blood-brain barrier (BBB) and accumulate in human brain. The BBB transmission and accumulation efficiency of PFAS, as well as the potential health risks from human co-exposure to legacy and emerging PFAS due to differences in transport efficiency, need to be further elucidated. In the present pilot study, 23 plasma samples from glioma patients were analyzed for 17 PFAS. The concentrations of PFAS in six paired brain tissue and plasma samples were used to calculate the BBB transmission efficiency of PFAS (RPFAS). This RPFAS analysis was conducted with utmost care and consideration amid the limited availability of valuable paired samples. The results indicated that low molecular weight PFAS, including short-chain and emerging PFAS, may have a greater potential for accumulation in brain tissue than long-chain PFAS. As an alternative to perfluorooctane sulfonic acid (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) exhibited brain accumulation potential similar to that of PFOS, suggesting it may not be a suitable substitute concerning health risk in brain. The BBB transmission efficiencies of perfluorooctanoic acid, PFOS, and 6:2 Cl-PFESA showed similar trends with age, which may be an important factor influencing the entry of exogenous compounds into the brain. A favorable link between perfluorooctane sulfonamide (FOSA) and the development and/or progression of glioma may be implicated by a strong positive correlation (r2 = 0.94; p < 0.01) between RFOSA and Ki-67 (a molecular marker of glioma). However, a causal relationship between RFOSA and glioma incidence were not established in the present study. The present pilot study conducted the first examination of BBB transmission efficiency of PFAS from plasma to brain tissue and highlighted the importance of reducing and/or controlling exposure to PFAS.

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.