Characterization of the distribution, source, and potential ecological risk of perfluorinated alkyl substances (PFASs) in the inland river basin of Longgang District, South China

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

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

Occurrence of antibiotics, hormones and PFAs in surface water from a Nile tilapia aquaculture facility in a Brazilian hydroelectric reservoir

This study assessed the occurrence of five antibiotics, three hormones, caffeine, and long and short-chain perfluoroalkyl and polyfluoroalkyl substances (PFASs) in surface water and feedstuff samples obtained from aquaculture cages in Três Marias reservoir in Brazil. This is the first work to evaluate the presence of PFAS in surface water used for aquaculture in Brazil. Solid-phase extraction and low temperature partitioning extraction followed by liquid chromatography coupled to mass spectrometry (LC-MS) were performed to process and analyze surface water samples and feedstuff, respectively. The ecotoxicological risk quotient was calculated for target compounds detected in water. Ciprofloxacin and caffeine were detected in all surface water samples. Pharmaceutical drugs ranged from 0.7 ng L-1 (trimethoprim) to 389.2 ng L -1 (β-estradiol). Estrone (10.24 ng g-1) and β-estradiol (66.20 ng g-1) were also found in feedstuff. Four PFASs (PFOA, PFDoA, PFTeDA, and PFBS) were detected (9.40-15.2 μg L-1) at levels higher than reported in studies conducted worldwide. Ecotoxicological risk assessment indicated high risks for caffeine and PFOA, PFDoA, and PFTeDA with RQ values from 10 to 103. These findings reveal risks to biodiversity, ecosystem integrity and human health considering possible intake of these contaminants by fish consumption due to potential bioaccumulation of these substances. Hence, it is critical to conduct more studies in this direction in Brazil and other low and middle-low-income countries.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in water and edible fish species of Karun River, Ahvaz, Iran: spatial distribution, human health, and ecological risk assessment

Per- and polyfluoroalkyl substances (PFASs) such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are environmental contaminants with unfavorable impacts on human health and nature. This study aimed to determine the PFOA and PFOS concentration in water and fish samples from Karun, the largest river in Iran. According to the results, the PFOA and PFOS in water samples were 5.81-69.26 ng/L and not detected (n.d.)-35.12 ng/L, respectively. The dry season displayed higher concentrations in water samples than in the wet season. The maximum PFOS concentration measured was related to Barbus barbules sp. (27.89 ng/g). The human health risk assessment indicated minor risks (hazard ratio, HR < 1) from PFOA and PFOS through consuming contaminated drinking water and fish. Only HR value of PFOS in downstream area exceeded slightly 1.0, indicating potential health risk due to consumption of the river fish. Considering the average PFASs concentration, the risk quotients (RQs) showed low ecological risk.

Deriving aquatic PNECs of endocrine disruption effects for PFOS and PFOA by combining species sensitivity weighted distributions and adverse outcome pathway networks

Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), as emerging endocrine-disrupting chemicals (EDCs), pose adverse effects on aquatic organisms. Conventional ecological risk assessment (ERA) not fully considering the mode of toxicity action of PFOS and PFOA, may result in an underestimation of risks and confuse decision-makers. In the study, we developed species sensitivity weighted distribution (SSWD) models based on adverse outcome pathway (AOP) networks for deriving predicted no-effect concentrations (PNECs). Three kinds of weighting criteria (intraspecies variation, trophic level abundance, and data quality) and weighted log-normal distribution methods were adopted. The developed models considered the inter/intraspecies variation and integrated nontraditional endpoints of endocrine-disrupting effects. The PNECs of endocrine disruption effects were derived as 2.52 μg/L (95% confidence intervals 0.667-9.85 μg/L) for PFOS and 18.7 μg/L (5.40-71.0 μg/L) for PFOA, which were more conservative than those derived from the SSD method and were comparable with the values in the literature based on the chronic toxicity data. For PFOS, the effect of growth and development was the most sensitive; however, for PFOA, the effect of reproduction was the most sensitive in the effects of growth and development, reproduction, biochemistry and genetics, and survival. The endocrine-disrupting effects of PFOS and PFOA are significant and need to be fully recognized in the ERA. This study provided an ERA framework that can improve the ecological relevance and reduce the uncertainty of PNECs of EDCs.

Toxic effects of three perfluorinated or polyfluorinated compounds (PFCs) on two strains of freshwater algae: Implications for ecological risk assessments

Perfluorinated or polyfluorinated compounds (PFCs) continue entering to the environmental as individuals or mixtures, but their toxicological information remains largely unknown. Here, we investigated the toxic effects and ecological risks of Perfluorooctane sulfonic acid (PFOS) and its substitutes on prokaryotes (Chlorella vulgaris) and eukaryotes (Microcystis aeruginosa). Based on the calculated EC₅₀ values, the results showed that PFOS was significantly more toxic to both algae than its alternatives including Perfluorobutane sulfonic acid (PFBS) and 6:2 Fluoromodulated sulfonates (6:2 FTS), and the PFOS-PFBS mixture was more toxic to both algae than the other two PFC mixtures. The action mode of binary PFC mixtures on Chlorella vulgaris was mainly shown as antagonistic and on Microcystis aeruginosa as synergistic, by using Combination index (CI) model coupled with Monte Carlo simulation. The mean risk quotient (RQ) value of three individual PFCs and their mixtures were all below the threshold of 10^-1, but the risk of those binary mixtures were higher than that of PFCs individually because of their synergistic effect. Our findings contribute to enhance the understanding of the toxicological information and ecological risks of emerging PFCs and provide a scientific basis for their pollution control.

Per- and polyfluoroalkyl substances in Chinese surface waters: A review

The contamination of surface waters in China with Per- and polyfluoroalkyl (PFASs) has been extensively studied in recent decades, however, almost all studies have been conducted in small areas and/or limited samples, which are not representative of the nationwide contamination of surface water environments with PFASs. In this study, attempt was made to provide a comprehensive report about PFASs pollution in Chinese surface water based on the PRISMA. By analyzing 111 papers published between 2006 and 2022, we provide a systematic review of the pollution of PFASs in surface water environments in China. The results show that 26 PFASs contaminants were detected at least once in China's surface water environment and were mainly concentrated in the eastern part of China. Most surface water environments in China had mean PFASs concentrations below 100 ng/L. The most polluted place was the Xiaoqing River, where sampling results in 2020 showed PFASs concentrations as high as 25,429 ng/L, followed by the Tangxun Lake, the Xi River, the Daling River, the Majia River, the Baiyangdian Lake, the Liuxi River, the Jiaolai River, the Tuo River and the Zhimai River. The Xiaoqing River also has the highest concentration of the novel pollutant, with concentrations of HFPO-TA and HFPO-DA as high as 1039 ng/L and 164 ng/L. Based on the source analysis, fluoropolymer manufacturing plants are the main source of PFASs pollutants in surface water. The results of the base risk analysis using risk quotients value (RQ) method show that the RQ values of the Xiaoqing River, the surface water near Bohai Bay, the Majia River and the Tuo River PFOA are 36.9, 7.7, 3.6 and 2.1 respectively, which are high risk areas and require enhanced control. This study provides information on surface waters contaminated by PFASs nationwide, and the results can be used as a reference for the development of pollution control and management strategies for PFASs in surface waters in China.

Perfluorooctanoic acid (PFOA) exposure in relation to the kidneys: A review of current available literature

Perfluorooctanoic acid is an artificial and non-degradable chemical. It is widely used due to its stable nature. It can enter the human body through food, drinking water, inhalation of household dust and contact with products containing perfluorooctanoic acid. It accumulates in the human body, causing potential harmful effects on human health. Based on the biodegradability and bioaccumulation of perfluorooctanoic acid in the human body, there are increasing concerns about the adverse effects of perfluorooctanoic acid exposure on kidneys. Research shows that kidney is the main accumulation organ of Perfluorooctanoic acid, and Perfluorooctanoic acid can cause nephrotoxicity and produce adverse effects on kidney function, but the exact mechanism is still unknown. In this review, we summarize the relationship between Perfluorooctanoic acid exposure and kidney health, evaluate risks more clearly, and provide a theoretical basis for subsequent research.

Occurrence, fate, and risk assessment of antibiotics in typical pharmaceutical manufactories and receiving water bodies from different regions

This study aimed to investigate the presence and persistence of antibiotics in wastewater of four typical pharmaceutical manufactories in China and receiving water bodies and suggest the removal of antibiotics by the wastewater treatment process. It also evaluated the environmental impact of antibiotic residues through wastewater discharge into receiving water bodies. The results indicated that thirteen antibiotics were detected in wastewater samples with concentrations ranging from 57.03 to 726.79 ng/L. Fluoroquinolones and macrolides were the most abundant antibiotic classes found in wastewater samples, accounting for 42.5% and 38.7% of total antibiotic concentrations, respectively, followed by sulfonamides (16.4%) and tetracyclines (2.4%). Erythromycin-H2O, lincomycin, ofloxacin, and trimethoprim were the most frequently detected antibiotics; among these antibiotics, the concentration of ofloxacin was the highest in most wastewater samples. No significant difference was found in different treatment processes used to remove antibiotics in wastewater samples. More than 50% of antibiotics were not completely removed with a removal efficiency of less than 70%. The concentration of detected antibiotics in the receiving water bodies was an order of magnitude lower than that in the wastewater sample due to dilution. An environmental risk assessment showed that lincomycin and ofloxacin could pose a high risk at the concentrations detected in effluents and a medium risk in their receiving water bodies, highlighting a potential hazard to the health of the aquatic ecosystem. Overall, The investigation was aimed to determine and monitor the concentration of selected antibiotics in 4 typical PMFs and their receiving water bodies, and to study the removal of these substances in PMFs. This study will provide significant data and findings for future studies on antibiotics-related pollution control and management in water bodies.

Assessing the hepatotoxicity of PFOA, PFOS, and 6:2 Cl-PFESA in black-spotted frogs (Rana nigromaculata) and elucidating potential association with gut microbiota

Pollution caused by per- and polyfluoroalkyl substances (PFASs) has become a major global concern. The association between PFAS-induced hepatotoxicity and gut microbiota in amphibians, particularly at environmentally relevant concentrations, remains elusive. Herein we exposed male black-spotted frogs (Rana nigromaculata) to 1 and 10 μg/L waterborne perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) for 21 days; subsequently, liver histopathological, oxidative stress, molecular docking, gene/protein expression, and gut microbiome analyses were conducted. PFOS and 6:2 Cl-PFESA exposure enhanced serum alanine aminotransferase and aspartate aminotransferase activities, and markedly increased hepatic area of vacuoles and inflammatory cell infiltration, while PFOA exposure increased serum alanine aminotransferase but not aspartate aminotransferase activities and affected hepatic area of vacuoles and inflammatory cell infiltration to a lesser extent. All three PFASs elevated catalase, glutathione S-transferase, and glutathione peroxidase activities and glutathione and malondialdehyde contents in the liver, suggesting the induction of oxidative stress. Further, PFASs could bind to mitogen-activated protein kinases (p38, ERK, and JNK), upregulating not only their expression but also the expression of downstream oxidative stress-related genes and that of P-p38, P-ERK, and Nrf2 proteins. In addition, PFAS exposure significantly increased the relative abundance of Proteobacteria and Delftia and decreased that of Firmicutes and Dietzia, Mycoplasma, and Methylobacterium-Methylorubrum in the order of PFOS ≈ 6:2 Cl-PFESA > PFOA. Altogether, it appears that PFOS and 6:2 Cl-PFESA are more toxic than PFOA. Finally, microbiota function prediction, microbiota co-occurrence network, and correlation analysis between gut microbiota and liver indices suggested that PFAS-induced hepatotoxicity was associated with gut microbiota dysbiosis. Our data provide new insights into the role of gut microbiota in PFAS-induced hepatotoxicity in frogs.

A New Method for Environmental Risk Assessment of Pollutants Based on Multi-Dimensional Risk Factors

Pollutant discharge causing the deterioration of the watershed environment has seriously threatened human health and ecosystem function. The importance of improving the risk warning system is becoming more and more prominent. Traditional chemical risk assessment methods focused on toxicity and the exposure of pollutants without considering the impact of persistent pollutants in different environmental media. In this study, a new approach was proposed to reflect multi-dimensional evaluation with a synthetic risk factor (SRF) of pollutants. The integrating parameters of SRF include toxicity endpoint values, environmental exposure level, persistent properties, and compartment features. Selected pesticides, perfluorinated compounds, organophosphate esters and endocrine disruptors were analyzed by the proposed and traditional methods. The results showed a higher risk outcome using SRF analysis for PFOS, imazalil, testosterone, androstenedione and bisphenol A, which were different from those obtained by the traditional method, which were consistent with existing risk management. The study demonstrated that the SRF method improved the risk assessment of various pollutants in different environmental media in a more robust fashion, and also provided a more accurate decision basis for ecological environment protection.

Neurotransmission Targets of Per- and Polyfluoroalkyl Substance Neurotoxicity: Mechanisms and Potential Implications for Adverse Neurological Outcomes

Per- and polyfluoroalkyl substances (PFAS) are a group of persistent environmental pollutants that are ubiquitously found in the environment and virtually in all living organisms, including humans. PFAS cross the blood-brain barrier and accumulate in the brain. Thus, PFAS are a likely risk for neurotoxicity. Studies that measured PFAS levels in the brains of humans, polar bears, and rats have demonstrated that some areas of the brain accumulate greater amounts of PFAS. Moreover, in humans, there is evidence that PFAS exposure is associated with attention-deficit/hyperactivity disorder (ADHD) in children and an increased cause of death from Parkinson's disease and Alzheimer's disease in elderly populations. Given possible links to neurological disease, critical analyses of possible mechanisms of neurotoxic action are necessary to advance the field. This paper critically reviews studies that investigated potential mechanistic causes for neurotoxicity including (1) a change in neurotransmitter levels, (2) dysfunction of synaptic calcium homeostasis, and (3) alteration of synaptic and neuronal protein expression and function. We found growing evidence that PFAS exposure causes neurotoxicity through the disruption of neurotransmission, particularly the dopamine and glutamate systems, which are implicated in age-related psychiatric illnesses and neurodegenerative diseases. Evaluated research has shown there are highly reproduced increased glutamate levels in the hippocampus and catecholamine levels in the hypothalamus and decreased dopamine in the whole brain after PFAS exposure. There are significant gaps in the literature relative to the assessment of the nigrostriatal system (striatum and ventral midbrain) among other regions associated with PFAS-associated neurologic dysfunction observed in humans. In conclusion, evidence suggests that PFAS may be neurotoxic and associated with chronic and age-related psychiatric illnesses and neurodegenerative diseases. Thus, it is imperative that future mechanistic studies assess the impact of PFAS and PFAS mixtures on the mechanism of neurotransmission and the consequential functional effects.

Occurrence and Risk Assessment of Perfluorooctanoate (PFOA) and Perfluorooctane Sulfonate (PFOS) in Surface Water, Groundwater and Sediments of the Jin River Basin, Southeastern China

Perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) levels were determined in surface water, groundwater and sediments of the Jin River Basin, southeastern China. PFOA was detected in most of the samples, and its concentrations ranged from 0.53 to 8.77 ng/L, 0.26 to 15.1 ng/L and not detected (ND) to 23.9 ng/g in surface water, groundwater and sediments, respectively. Unlike PFOA, the detection frequency of PFOS was lower than 32%, and its concentrations ranged from ND to 2.56 ng/L, ND to 7.01 ng/L, ND to 11.1 ng/g in surface water, groundwater and sediments, respectively. The environmental risk assessment showed that PFOA could pose a high risk to surface water and groundwater, and both PFOA and PFOS posed a high risk to sediments. Moreover, the adults living in the Jin River Basin were at insignificant health risk to exposure to PFOA and PFOS through water consumption.