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Sub-10 µm microplastics (MPs) in aquatic environments pose significant ecological and health risks due to their mobility and potential to carry harmful microcontaminants. Our effluent analysis from a Hong Kong Sewage Treatment Works shows that traditional treatment often fails to effectively remove these MPs. These small-sized MPs are commonly neglected due to challenges in accurate quantification, analysis, and removal. This study introduces a nanobubble-assisted flotation process that enhances the removal efficiency of both regular and irregular small-sized MPs from wastewater. The proposed process outperforms the traditional flotation process by fostering a more effective interaction between bubbles and MPs, increasing removal rates of MPs from 1 µm to 10 µm by up to 12% and providing a total efficiency boost of up to 17% for various particle sizes. Improvements are attributed to enhanced collision and adhesion probabilities, hydrophobic interactions, as well as better floc flotation. Supported by empirical evidence, mathematical models, and Molecular Dynamics simulations, this research elucidates the nanoscale mechanisms at play. The findings confirm the nanobubble-assisted flotation technique as an innovative and practical approach to removing sub-10 µm MPs in water treatment processes., (© 2024. The Author(s).)

Hydraulic fracturing (HF) has substantially boosted global unconventional hydrocarbon production but has also introduced various environmental and operational challenges. Understanding the interactions between abundant and diverse microbial communities and chemicals, particularly polymers used for proppant delivery, thickening, and friction reduction, in HF water cycles is crucial for addressing these challenges. This review primarily examined the recent studies conducted in China, an emerging area for HF activities, and comparatively examined studies from other regions. In China, polyacrylamide (PAM) and its derivatives products became key components in hydraulic fracturing fluid (HFF) for unconventional hydrocarbon development. The microbial diversity of unconventional HF water cycles in China was higher compared to North America, with frequent detection of taxa such as Shewanella, Marinobacter, and Desulfobacter. While biodegradation, biocorrosion, and biofouling were common issues across regions, the mechanisms underlying these microbe-polymer interactions differed substantially. Notably, in HF sites in the Sichuan Basin, the use of biocides gradually decreased its efficiency to mitigate adverse microbial activities. High-throughput sequencing proved to be a robust tool that could identify key bioindicators and biodegradation pathways, and help select optimal polymers and biocides, leading to more efficient HFF systems. The primary aim of this study is to raise awareness about the interactions between microorganisms and polymers, providing fresh insights that can inform decisions related to enhanced chemical use and biological control measures at HF sites., Competing Interests: Declaration of competing interest Cheng Zhong reports financial support was provided by Southwest Petroleum University. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The widespread occurrence of liquid crystal monomers (LCMs) in the environment has raised concerns about their persistence, bioaccumulation, and toxicity (PBT). Here we review the lifecycle of environmental LCMs, focusing on their occurrences, emission sources, human exposure routes, and toxicity. Industrial emissions from Liquid Crystal Display (LCD) manufacturing and e-waste recycling are the primary point sources of LCMs. In addition, emissions from LCD products, air conditioning units, wastewater treatment plants, and landfills contribute to environmental occurrence of LCMs as secondary sources. Dietary routes were identified as the primary exposure pathways to humans. E-waste dismantling workers and infants/children are vulnerable populations to LCMs exposure. Exposure to LCMs has been shown to potentially induce oxidative stress, metabolic disorders, and endocrine disruption. Accumulation of LCMs in the brain and liver tissues of exposed animals highlights the need for toxicokinetic studies., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Micro/nanoplastics can act as vectors for organic pollutants and enhance their toxicity, which has been attributed to the ingestion by organisms and the "Trojan horse effect". In this study, we disclosed a non-ingestion pathway for the toxicity enhancement effect of nanoplastics. Initially, the combined toxicity of polystyrene microplastics (40 μm) or nanoplastics (50 nm) with three disinfection byproducts (DBPs) to a marine polychaete, Platynereis dumerilii, was investigated. No toxic effect was observed for the micro/nanoplastics alone. The microplastics showed no effect on the toxicity of the three DBPs, whereas the nanoplastics significantly enhanced the toxicity of two aromatic DBPs when the polychaete was in its non-feeding early life stage throughout the exposure period. The microplastics showed no interaction with the P. dumerilii embryos, whereas the nanoplastics agglomerated strongly on the embryonic chorion and fully encapsulated the embryos. This could contribute to higher actual exposure concentrations in the microenvironment around the embryos, as the concentrations of the two aromatic DBPs on the nanoplastics were 1200 and 120 times higher than those in bulk solution. Our findings highlight an important and previously overlooked mechanism by which nanoplastics and organic pollutants, such as DBPs, pose a higher risk to marine species at their vulnerable early life stages. This study may contribute to a broader understanding of the environmental impacts of plastic pollution and underscore the necessity to mitigate their risks associated with DBPs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The microplastics and organic additives formed in routine use of plastic takeaway food containers may pose significant health risks. Thus, we collected plastic containers made of polystyrene, polypropylene, polyethylene terephthalate, polylactic acid and simulated two thermal usages, including hot water (I) and microwave treatments (M). Nile Red fluorescence staining was developed to improve accurate counting of microplastics with the aid of TEM and DLS analysis. The quantity of MPs released from thermal treatments was determined ranging from 285.7 thousand items/cm 2 to 681.5 thousand items/cm 2 in containers loaded with hot water with the following order: IPS>IPP>IPET>IPLA, while microwave treatment showed lower values ranging from 171.9 thousand items/cm 2 to 301.6 thousand items/cm 2 . In vitro toxicity test using human intestinal epithelial Caco-2 cells indicated decrease of cell viability in raw leachate, resuspended MPs and supernatants, which might further lead to cell membrane rupture, ROS production, and decreased mitochondrial membrane potential. Moreover, the leachate inhibited the expression of key genes in the electron transport chain (ETC) process, disrupted energy metabolism. For the first time, we isolate the actually released microplastics and organic substances for in vitro toxicity testing, and demonstrate their potential impacts to human intestine. SYNOPSIS: Plastic take-out containers may release microplastics and organic substances during daily usage, both of which can cause individual and combined cytotoxic effects on human colon adenocarcinoma cells Caco-2., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The Pearl River Estuary (PRE), one of the primary e-waste recycling centers in the world, has been suffering from the pollution of Liquid Crystal Monomers (LCMs), critical materials with persistent, bio-accumulative, and toxic substances used in electronic devices. It has been detected in seabed sediment with both high frequency and concentration near PRE - Hong Kong (HK) waters. In the same area, dredging operations with in-situ sediment have been frequently used in the last decades for coastal land reclamation projects. Dredging is known to cause a huge amount of sediment re-suspension into water columns, with potential damage to marine ecosystems and biodiversity. In this study, we proposed a new risk assessment strategy to estimate the secondary pollution due to the re-suspension sediment highly contaminated by LCMs. We formulate a robust and reliable probabilistic approach based on unsupervised machine learning and hydrodynamic and sediment transport numerical simulation. New risk indexes were also proposed to better quantify the impact of contaminated sediments. We applied the methodology to assess the potential impact of dredging operations in the PRE and Hong Kong waters on the local marine ecosystem. The results of the analysis showed how the potentially contaminated areas depended on the dredging locations., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dissolved organic matter (DOM) released from biochar (BDOM) can interact with microplastics (MPs) in the environment, inevitably affecting their environmental behaviour. Information regarding the influence of BDOM on MPs during photoaging and associated variations in the MP aging mechanism remains unclear. This study evaluated the effect of BDOM on the aging of polystyrene (PS) MPs. The results showed that among three pyrolysis temperatures, low-temperature BDOM significantly enhanced the photoaging process of PS MPs, with the smallest average particle size and highest carbonyl index value after 15 days of aging under light conditions. The DOM level decreased after 5 days, increased after 5-10 days, and stabilised after 15 d. BDOM accelerates PS MPs aging, leading to more DOM released from PS, which can be transformed into 1 O 2 via triplet-excited state ( 3 DOM ⁎ and 3 PS ⁎ ) to further enhance PS MPs aging, resulting in the realisation of the self-accelerated aging process of PS MPs. 1 O 2 plays a crucial role in the self-motivated accelerated aging process of PS MPs. These findings provide new insights into the effects of the DOM structure and composition on reactive oxygen species generation during MPs aging., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Understanding the molecular composition and fate of dissolved organic matter (DOM) during transport in estuaries is essential for gaining a comprehensive understanding of its role within the global biogeochemical cycle. In 2020, a catastrophic flood occurred in the Yangtze River basin. It is currently unknown whether differences in hydrologic conditions due to extreme flooding will significantly impact the estuarine to oceanic DOM cycle. We determined the DOM composition in the Yangtze River estuary (YRE) to the East China Sea by using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) during the high discharge and the flood period (monthly average discharge was 1.2 times higher) on the same trajectory. Our study found that the composition of DOM is more diverse, and more DOM molecules were introduced to the YRE during the flood, especially in the freshwater end member. The result revealed that the DOM was significantly labile and unstable during the flood period. A total of 1840 unique molecular formulas were identified during the flood period, most of which were CHON, CHONS, and CHOS compounds, most likely resulting from anthropogenic inputs from upstream. Only 194 of these molecules were detected in the seawater end member after transporting to the sea, suggesting that the YRE served as a 'filter' of DOM. However, the flood enhances the transport of a group of terrigenous DOM, that is resistant to photodegradation and biodegradation. As a result, YRE experienced ~1.6 times higher terrigenous DOC flux than high discharge period. Considering the increased frequency of future floods, our study provides a preliminary basis for further research on how floods affect the composition and characteristics of estuarine DOM. With the help of the FT-ICR MS technique, we can now better understand the dynamic of DOM composition and characteristics in large river estuaries., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Organic ultraviolet filters (OUVFs) have been used globally for the past 20 years. Given that OUVFs can be quickly released from sunscreens applied on human skins, they have been frequently detected in aquatic environments and organisms. Some byproducts of OUVFs might be more recalcitrant and toxic than their parent compounds. To further assess the toxicity and potential risk of OUVFs' byproducts, it is necessary to determine the fate of OUVFs and identify their transformation products. This review summarizes and analyzes pertinent literature and reports in the field of OUVFs research. These published research works majorly focus on the degradation mechanisms of OUVFs in aquatic environments, their intermediates/byproducts, and chlorination reaction. Photodegradation (direct photolysis, self-sensitive photolysis and indirect photolysis) and biodegradation are the main transformation pathways of OUVFs through natural degradation. To remove residual OUVFs' pollutants from aqueous environments, novel physicochemical and biological approaches have been developed in recent years. Advanced oxidation, ultrasound, and bio-based technologies have been proven to eliminate OUVFs from wastewaters. In addition, the disinfection mechanism and the byproducts (DBPs) of various OUVFs in swimming pools are discussed in this review. Besides, knowledge gaps and future research directions in this field of study are also mentioned., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Estuaries are hotspots where terrestrially originated dissolved organic matter (DOM) is modified in molecular composition before entering marine environments. However, very few research has considered nitrogen (N) modifications of DOM molecules in estuaries, limiting our understanding of dissolved organic nitrogen (DON) cycling and the associated carbon cycling in estuaries. This study integrated optical, stable isotopes (δ 15 N and δ 13 C) and molecular composition (FT-ICR MS) to characterize the transformation of DOM in the Yangtze River Estuary. Both concentration of dissolved organic carbon (DOC) and DON decreased with increasing salinity, while their δ 13 C and δ 15 N increased with the increasing salinity. A significant positive correlation was found between δ 15 N and δ 13 C during the transportation of DOM to marginal seas, indicating that the behavior of both DOC and DON are primarily controlled by the mixing of freshwater and the seawater in the YRE. During the mixing process, the DON addition was observed using the conservative mixing curves. In the view of molecular composition, DOM molecules became more aromatic as the number of N atoms increased. Spearman correlations reveal that DOM molecules with fewer N atoms exhibited a higher enrichment in protein-like components, while those with more N atoms were more enriched in humic-like components. In addition, the δ 15 N and δ 13 C tended to increase as the N content of DOM decreased. Therefore, DON molecules with fewer N atoms were likely to be transformed into those with more N atoms based on the isotopic fractionation theory. This study establishes a linkage between the molecular composition and the δ 15 N of DOM, and discovers the N transformation pattern within DOM molecules during the transportation to marginal seas., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

In indoor environments, liquid crystal monomers (LCMs) released from display devices is a significant concern, necessitating a comprehensive investigation into their distribution behaviors and potential health risks. Herein, we examined various LCMs in educational and workplace air and compared their associated health risks through inhalation and dermal absorption routes. 4-propyl-4'-vinylbicyclohexyl (3VbcH) and 4,4'-bis(4-propylcyclohexyl) biphenyl (b3CHB) with median concentrations of 101 and 1460 pg m -3 , were the predominant LCMs in gaseous and particulate phases, respectively. Composition and concentration of LCMs differed substantially between sampling locations due to the discrepancy in the quantity, types, and brands of electronic devices in each location. Three models were further employed to estimate the gas-particle partitioning of LCMs and compared with the measured data. The results indicated that the HB model exhibited the best overall performance, while the LMY model provided a good fit for LCMs with higher log K oa (>12.48). Monte Carlo simulation was used to estimate and compared the probabilistic daily exposure dose and potential health risks. Inhalation exposure of LCMs was significantly greater than the dermal absorption by approximately 1-2 orders of magnitude, implying that it was the primary exposure route of human exposure to airborne LCMs. However, certain LCMs exhibited comparable or higher exposure levels via the dermal absorption route due to the significant overall permeability coefficient. Furthermore, the particle size was discovered to impact the daily exposure dose, contingent on the particle mass-transfer coefficients and accumulation of LCMs on diverse particle sizes. Although the probabilistic non-carcinogenic risks of LCMs were relatively low, their chronic effects on human beings merit further investigations. Overall, this study provides insights into the contamination and potential health risks of LCMs in indoor environments, underscoring the importance of considering particle sizes and all possible exposure pathways in estimating human health risks caused by airborne organic contaminants., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Organic ultraviolet filters (OUVFs) are functional ingredients used in cosmetics to protect skin from the harmful effects of ultraviolet (UV) radiation. This study presents recent findings on the distribution of OUVFs in the Pearl River Estuary (PRE), located in southern China. This investigation was conducted during the early stages of the Covid-19 pandemic when the stay-at-home policy was implemented. Analysis revealed the presence of OUVFs in both the surface and bottom water samples collected from eight major outlets of the Pearl River. The OUVFs were detected in both the dissolved phase and suspended particulate matter, with a total concentration ranging from 7.19 ± 6.54 to 20.5 ± 9.62 ng/L. Notably, OUVFs' concentrations in the study period were significantly lower compared to those reported before the pandemic. This implies that effective reduction of OUVF emissions can be achieved through usage reduction combined with the management of direct discharge and appropriate treatment by urban wastewater treatment facilities. During the study period, the annual release of OUVFs was approximately 12.6 kg/1000 people/year, with the greatest contribution from the Hu Men outlet. Consequently, it is imperative to consider the potential ecological risks associated with the release of OUVFs from the PRE into the marine environment, particularly with the potential for an accompanying rebound in risk upon the lifting of restrictions on outdoor activities in the post Covid-19 time., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Liquid crystal monomers (LCMs), the essential substances used in the display screen of electronic devices, have been proposed as a class of emerging chemicals of concern. Despite their detection in various environmental matrices, little is known about the presence of LCMs in municipal sewage systems. This study aimed to investigate the occurrence, distribution, and fate of 64 LCMs released into the aqueous environment from a municipal wastewater treatment plant (WWTP) in Hong Kong, China. In total 14 LCMs were detected in WWTP samples. Specifically, the Σ 14 LCMs concentrations in crude influent, final effluent, and final sludge were found to be 16.8 ± 0.3 ng/L, 2.71 ± 0.05 ng/L, and 19.2 ± 1.0 ng/g dry weight, respectively. Among them, 10 fluorinated LCMs (F-LCMs) were determined to be present at concentrations of 8.90 ± 0.10 ng/L, 1.69 ± 0.05 ng/L, and 9.94 ± 1.00 ng/g dry weight, respectively. The predominant non-fluorinated LCMs (NF-LCMs) detected in all samples were 3OCB and EPhEMOB, while 2OdF3B was the dominant F-LCM. The overall removal rate of total LCMs was 83.8 ± 0.3 %, with 25.4 ± 4.8 % being removed by biodegradation and UV treatment. Compared to NF-LCMs, F-LCMs were more resistant to biodegradation. Despite the significant removal of LCMs through WWTP, the remaining LCMs in final effluent could result in an annual emission of 3.04 kg of total LCMs from the population of Hong Kong. This study provides the first evidence of LCMs contamination in municipal wastewater, possibly arising from routine electronic devices usage. Further investigation is needed to elucidate the potential impact of LCMs emission via WWTP effluent on the aquatic receiving ecosystem., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Organic ultraviolet filters (OUVFs) are extensively released into aquatic environments, where they undergo complex phototransformation. However, there is little knowledge regarding their transformation products (TPs) and associated endocrine disruption potentials. In the present study, we characterized the chemical and toxicological profiles of TPs for two common OUVFs, oxybenzone (BP3) and ethylhexyl methoxycinnamate (EHMC), by photooxidation under environmentally relevant conditions. It is hypothesized that TPs of the tested OUVFs will show varied estrogenicity at different reaction times. High-resolution liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) identified 17 TPs of 7 m / z for BP-3 and 13 TPs of 8 m / z for EHMC at confidence levels ≤2. Five novel TPs of 2 m / z were reported for the first time with structure-diagnostic MS/MS spectra. Estrogenicity assessment using the MCF-7- luc cell line showed discrepant estrogenic activities exhibited by OUVF-TPs over time. Specifically, BP3-TPs exhibited significantly greater estrogenicity than the parent at several reaction times, whereas EHMC-TPs displayed fluctuating estrogenicity with a declining trend. Correlation analysis coupled with molecular docking simulations further suggested several TPs of BP3 as potential endocrine disruptive compounds. These findings underscore the necessity of considering mixtures during chemical testing and risk assessment and highlight the potentially greater risks associated with post-transformation cocktails.

Indoor dust contaminated with liquid crystal monomers (LCMs) released from various commercial liquid crystal display (LCD) screens may pose environmental health risks to humans. This study aimed to investigate the occurrence of 64 LCMs in ventilation and air conditioning filters (VACF) dust, characterize their composition profiles, potential sources, and associations with indoor characteristics, and assess their in vitro toxicity using the human lung bronchial epithelial cells (BEAS-2B). A total of 31 LCMs with concentrations (ΣLCMs) ranging from 43.7 ng/g to 448 ng/g were detected in the collected VACF dust. Additional analysis revealed the potential interactions between indoor environmental conditions and human exposure risks associated with the detected LCMs in VACF dust. The service area and working time of the ventilation and air conditioning system, and the number of indoor LCD screens were positively correlated with the fluorinated ΣLCMs in VACF dust (r = 0.355 ∼ 0.511, p < 0.05), while the associations with the non-fluorinated ΣLCMs were not found (p > 0.05), suggesting different environmental behavior and fates of fluorinated and non-fluorinated LCMs in the indoor environment. Four main indoor sources of LCMs (i.e., computer (37.1%), television (28.3%), Brand A smartphone (21.2%) and Brand S smartphone (13.4%)) were identified by positive matrix factorization-multiple linear regression (PMF-MLR). Exposure to 14 relatively frequently detected LCMs, individually and in the mixture, induced significant oxidative stress in BEAS-2B cells. Among them, non-fluorinated LCMs, specifically 3cH2B and MeP3bcH, caused dominant decreased cell viability. This study provides new insights into the indoor LCMs pollution and the associated potential health risks due to the daily use of electronic devices., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Liquid crystal display (LCD) screens can release many organic pollutants into the indoor environment, including liquid crystal monomers (LCMs), which have been proposed as a novel class of emerging pollutants. Knowing the release pathways and mechanisms of LCMs from various components of LCD screens is important to accurately assess the LCM release and reveal their environmental transport behavior and fate in the ambient environment. A total of 47, 43, and 33 out of 64 target LCMs were detected in three disassembled parts of waste smartphone screens, including the LCM layer (LL), light guide plate (LGP), and screen protector (SP), respectively. Correlation analysis confirmed LL was the source of LCMs detected in LGP and SP. The emission factors of LCMs from waste screen, SP, and LGP parts were estimated as 2.38 × 10 -3 , 1.36 × 10 -3 , and 1.02 × 10 -3 , respectively. A mechanism model was developed to describe the release behaviors of LCMs from waste screens, where three characteristics parameters of released LCMs, including average mass proportion (AP), predicted subcooled vapor pressures ( P L ), and octanol-air partitioning coefficients ( K oa ), involving coexistence of absorption and adsorption mechanisms, could control the diffusion-partitioning. The released LCMs in LGP could reach diffusion-partition equilibrium more quickly than those in SP, indicating that LCM release could be mainly governed through SP diffusions.

Liquid crystal monomers (LCMs), an emerging group of organic pollutants related to electronic waste, have been frequently detected from various environmental matrices, including landfill leachate. The persistence of LCMs requires robust technology for remediation. The objectives of this study were to evaluate the feasibility, performance and mechanism of the remediation of a typical LCM 4-[difluoro(3,4,5-trifluorophenoxy)methyl]- 3,5-difluoro-4'-propylbiphenyl (DTFPB) via synchronized oxidation-adsorption (SOA) Fenton technology and verify its application in DTFPB-contaminated leachate. The SOA Fenton system could effectively degrade 93.5% of DTFPB and 5.6% of its total organic carbon (TOC DTFPB ) by hydroxyl radical oxidation (molar ratio of Fe 2+ to H 2 O 2 of 1/4 and pH 2.5-3.0) following a pseudo-first-order model under 0.378 h -1 . Additionally, synchronized adsorption of DTFPB and its degradation intermediates by in situ resultant ferric particles via hydrophobic interaction, complexation, and coprecipitation contributed to almost 100% of DTFPB and 33.4% of TOC DTFPB removal. Three possible degradation pathways involving eight products were proposed, and hydrophobic interactions might drive the adsorption process. It was first confirmed that the SOA Fenton system exhibited good performance in eliminating DTFPB and byproducts from landfill leachate. This study provides new insights into the potential of the Fenton process for the treatment of emerging LCMs contamination in wastewater., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Improving the sustainability of the hydraulic fracturing water cycle of unconventional oil and gas development needs an advanced water treatment that can efferently treat flowback and produced water (FPW). In this study, we developed a robust two-stage process that combines flocculation, and iron-carbon micro-electrolysis plus sodium persulfate (ICEPS) advanced oxidation to treat field-based FPW from the Sulige tight gas field, China. Influencing factors and optimal conditions of the flocculation-ICEPS process were investigated. The flocculation-ICEPS system at optimal conditions sufficiently removed the total organic contents (95.71%), suspended solids (92.4%), and chroma (97.5%), but the reaction stoichiometric efficiency (RSE) value was generally less than 5%. The particles and chroma were effectively removed by flocculation, and the organic contents was mainly removed by the ICEPS system. Fourier-transform infrared spectroscopy (FTIR) analysis was performed to track the changes in FPW chemical compositions through the oxidation of the ICEPS process. Multiple analyses demonstrated that PS was involved in the activation of Fe oxides and hydroxides accreted on the surface of the ICE system for FPW treatment, which led to increasing organics removal rate of the ICEPS system compared to the conventional ICE system. Our study suggests that the flocculation-ICEPS system is a promising FPW treatment process, which provides technical and mechanistic foundations for further field application., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

As microplastics and nanoplastics (MNPs) are widely distributed in the environment and can be transferred to human body through food chain, their potential impact on human health is of great concern. Perfluorooctane sulfonate (PFOS) is persistent, bioaccumulative and can be adsorbed by MNPs. However, there are few studies on the combined human health effects of MNPs with PFOS. In this study, the effects of polystyrene (PS) particles and PFOS on human colon adenocarcinoma cell Caco-2 were investigated in vitro to explore the combined toxicity from cellular level, and the toxic mechanism was further illustrated. Results showed that the presence of PFOS significantly increased the cell uptake of PS nanoparticles by >30 %, which is related to variations of the surface properties of PS particles, including the decrease of hydration kinetic diameter, the rise of surface potential and the adsorption of hydrophobic PFOS molecules. The toxic effect of PFOS was weakened in the presence of PS particles under low PFOS concentration (10 μg/mL), which is because the bioavailability of PFOS was reduced after adsorption. PS particles with small particle size (20 nm) showed higher cell uptake and ROS production, while PS particles with large particle size (1 μm) led to higher lipid oxidation degree and related membrane damage as well as mitochondrial stress. This study provides the first evaluation of combined toxicity of MNPs and PFOS on human intestinal cells, in order to support the risk assessment of combined pollution of MNPs and PFOS on human health., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Due to the prevalence of cardiovascular diseases, therapeutic drugs such as atenolol (ATE), metoprolol (MET), atorvastatin (ATO), and bezafibrate (BZB) have been widely used and thus frequently detected in surface water at ng·L -1 -μg·L -1 level. In this study, the developmental toxicity of these drugs (0.5 μg·L -1 -500 μg·L -1 ) to zebrafish, an aquatic model organism, was investigated; and the epigenetic toxicity of BZB was also explored. For all four drugs, the results showed that the drugs exposure could cause sublethal toxic effects on zebrafish larvae, such as decreases in hatching rate, body length, and heart rate. ATO also induced the swelling of the eyes of larvae by 5 %-15 %. Yolk sac edema, pericardial edema, bent spine, and tail malformation were observed in larvae exposed to the drugs, and yolk sac edema was the most common malformation. In addition, the spontaneous movement and free-swimming activity could be inhibited by the drugs. Combined with RNA-seq results, the adverse development of larvae in exposure groups may be caused by the disruption of lipid and carbohydrate metabolism, and the development and function of eye and nervous system. After a 30-day uptake period, the accumulation of BZB and the decrease of global DNA methylation level were observed in the liver, kidneys, gut, gills, and brain of adult zebrafish (4-month-old) exposed to 0.5 μg·L -1 to 500 μg·L -1 BZB. The liver was the main organ for BZB accumulation and the occurrence of DNA hypomethylation. In the liver, overexpression (1.5-7.6 times) of genes related to lipid metabolism (PPARα), DNA methylation (Dnmt1), and apoptosis (p53) was also observed. The results of the current study suggest that long-term exposure to low-concentrations of cardiovascular drugs may pose significant threats to aquatic ecosystems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

With the widespread use of sunscreen and other personal care products, organic ultraviolet filters (OUVFs) have become widely detected in the aquatic environment. Direct and indirect photolysis are important transformation pathways of OUVFs in aquatic environments, so their transformation products (TPs) are also chemicals of concern. Butyl methoxydibenzoylmethane (BMDBM) is one of the most commonly used OUVFs worldwide due to its ability to absorb ultraviolet light across a wide range of wavelengths, and it is ubiquitously detected in aquatic environments. In this study, we investigated the photodegradation of BMDBM through direct photolysis and hydroxyl radical (•OH) photooxidation. TPs were identified using ultrahigh performance liquid chromatography-high resolution mass spectrometry, and reaction mechanisms were proposed. Our results showed that the photodegradation rates for both enol and keto tautomer forms of BMDBM during direct photolysis and •OH photooxidation were similar. The formation of TPs resulted from α-cleavage and decarbonylation reactions involving the keto form of BMDBM. Comparisons of the kinetic data and TPs revealed that the direct photolysis mechanism was a significant sink for BMDBM even during •OH photooxidation. Evaluations of environmental properties based on the predicted physicochemical properties of BMDBM and TPs suggests that some of the TPs will have higher mobility than BMDBM. The quantitative structure-activity relationship (QSAR) approach was used to evaluate the ecotoxicity of BMDBM and the identified TPs. Most TPs were found to be less ecotoxic than BMDBM; however, TPs that had a diphenyl ring structure could be more ecotoxic than BMDBM. Overall, this study provides new insights into the photochemical behavior and ecotoxicity of BMDBM and its TPs, which are important for assessing the fate, persistence, accumulation, and adverse impacts of these compounds in aquatic environments., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Liquid crystal monomers (LCMs), commonly used in screens of electronic devices, have recently been identified as a group of emerging chemicals of concern associated with e-waste. They are potentially persistent, bioaccumulative, and toxic substances, and may pose a threat to the marine ecosystem. The Pearl River Estuary (PRE) receives organic contaminants discharged from the Pearl River Delta region, where primitive handling of e-waste is widespread. However, information on the pollution status of LCMs in the PRE is absent. Herein, a rapid and robust analytical method was established using ultrasonic extraction, solid phase extraction cleanup, and GC-Orbitrap-MS analysis. The spatial distribution of 39 target LCMs was investigated in 45 surface sediment samples from the PRE. Ten LCMs were detected, with ΣLCMs ranged from 0.9 to 31.1 ng/g dry weight. Our results demonstrated a widespread occurrence of LCMs in the sediments of the PRE, and a gradient of their contamination from inshore to offshore regions, indicating land-based origins. Our reported ΣLCMs concentrations were relatively higher compared to many other legacy and emerging pollutants found in the same investigated area. Preliminary risk assessment showed 3VbcH, Pe3bcH and tFMeO-3bcHP might be the top 3 risk contributors in the PRE. Further investigation on the ecological impact of LCMs on marine benthic ecosystems, as well as identification of their sources and control measures are warranted., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Per- and polyfluoroalkyl substances (PFAS) have been applied in numerous industrial and consumer products, the majority of which flow into waste management infrastructures (WMIs) at the end of their life cycles, but little is known about atmospheric releases of PFAS from these facilities. In this study, we addressed this key issue by investigating 49 PFAS, including 23 ionic and 26 neutral and precursor PFAS, in the potential sources (n = 4; within or adjacent to WMIs) and reference sites (n = 2; coastal and natural reserve sites) in urban and rural areas of Hong Kong, China. Duplicate samples of air and size-segregated particulate matter were collected for 48 h continuously using a 11-stage Micro-Orifice Uniform Deposit Impactor (MOUDI). In general, fluorotelomer alcohols (FTOHs) and perfluoroalkane sulfonamides were the predominant PFAS classes found across sampling sites. We also demonstrated the release of several less frequently observed semivolatile intermediate products (e.g., secondary FTOHs) during waste treatment. Except for perfluorooctane sulfonate, the size-segregated distributions of particulate PFAS exhibited heterogeneity across sampling sites, particularly in the WMIs, implying combined effects of sorption affinity and emission sources. A preliminary daily air emission estimation revealed that landfill was a relatively important source of PFAS relative to the wastewater treatment plant. A simplified International Commission on Radiological Protection model was used to estimate lung depositional fluxes, and the results showed that inhaled particulate PFAS were mainly deposited in the head airway while fine and ultrafine particles carried PFAS deeper into the lung alveoli. The cumulative daily inhalation dose of gaseous and particulate PFAS ranged from 81.9 to 265 pg/kg/d. In-depth research is required to understand the health effect of airborne PFAS on workers at WMIs., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

The consequences of soils exposed to hydraulic fracturing (HF) return fluid, often collectively termed flowback and produced water (FPW), are poorly understood, even though soils are a common receptor of FPW spills. Here, we investigate the impacts on soil microbiota exposed to FPW collected from the Montney Formation of western Canada. We measured soil respiration, microbial community structure and functional potentials under FPW exposure across a range of concentrations, exposure time and soil types (luvisol and chernozem). We find that soil type governs microbial community response upon FPW exposure. Within each soil, FPW exposure led to reduced biotic soil respiration, and shifted microbial community structure and functional potentials. We detect substantially higher species richness and more unique functional genes in FPW-exposed soils than in FPW-unexposed soils, with metagenome-assembled genomes (e.g. Marinobacter persicus) from luvisol soil exposed to concentrated FPW being most similar to genomes from HF/FPW sites. Our data demonstrate the complex impacts of microbial communities following FPW exposure and highlight the site-specific effects in evaluation of spills and agricultural reuse of FPW on the normal soil functions., (© 2022 Society for Applied Microbiology and John Wiley & Sons Ltd.)

The partitioning between phospholipids/proteins and water can be used to predict the bioaccumulation potential of chemicals with better accuracy compared with n-octanol-water partition coefficient. However, such partitioning is poorly understood for chiral chemicals, many of which exhibit differential bioaccumulation and toxicity potential between enantiomers. In this study, the enantiospecific liposome-water and bovine serum albumin (BSA)-water partition coefficients (Klip/w and KBSA/w, determined at 25 ℃ and 37 ℃, respectively) were measured by equilibrium dialysis for α-, β-, and γ-hexabromocyclododecane (HBCD) and three β-blockers (propranolol, metoprolol, and sotalol). Raman and fluorescence analyses and molecular docking were conducted to provide additional insights into the partitioning process. Results showed α- and β-HBCD displayed stronger enantioselective partitioning to liposomes with the (-)-form, while (-)-α-HBCD, R-(+)-propranolol, R-(+)-metoprolol, and E2-sotalol favored partitioning to BSA compared with their antipodes. Raman spectra revealed α- and γ-HBCD enhanced and reduced the organization of liposome acyl chains, respectively, and polar interactions enhanced the liposome partitioning of β-blockers. Fluorescence spectra indicated the changed tryptophan microenvironment might influence the BSA steric effect toward HBCD, and electrostatic interactions dominated the formation of BSA-β-blocker complexes. Molecular docking results supported the difference in the thermodynamic nature of interaction between the studied enantiomers and BSA., (Copyright © 2022 Elsevier B.V. All rights reserved.)

The unicellular freshwater green alga Haematococcus pluvialis has attracted much research attention due to its biosynthetic ability for large amounts of astaxanthin, a blood-red ketocarotenoid that is used in cosmetics, nutraceuticals, and pharmaceuticals. Recently, numerous studies have investigated the functions of natural astaxanthin; however, the high cost of the production of astaxanthin from H. pluvialis cultures restricts its commercial viability. There is an urgent need to fulfill commercial demands by increasing astaxanthin accumulation from H. pluvialis cultures. In this study, we discovered that treatment of H. pluvialis cultures at the beginning of the macrozooid stage (day 0) with 1 μM rac -GR24, a synthetic analogue of strigolactones (a class of phytohormones), led to significant increases in biomass [up to a maximum dry cell weight (DCW) of 0.53 g/L] during the macrozooid stage and astaxanthin (from 0.63 to 5.32% of DCW) during the hematocyst stage. We elucidated that this enhancement of biomass accumulation during the macrozooid stage by rac -GR24 is due to its increasing CO 2 utilization efficiency in photosynthesis and carbohydrate biosynthesis. We also found that rac -GR24 stimulated the overproduction of nicotinamide adenine dinucleotide phosphate (NADPH) and antioxidant enzymes in H. pluvialis cultures, which alleviated the oxidative damage caused by reactive oxygen species generated during the hematocyst stage due to the exhaustion of nitrogen supplies. Moreover, rac -GR24 treatment of H. pluvialis synergistically altered the activity of the pathways of fatty acid biosynthesis and astaxanthin esterification, which resulted in larger amounts of astaxanthin being generated by rac -GR24-treated cultures than by controls. In summary, we have developed a feasible and economic rac -GR24-assisted strategy that increases the amounts of biomass and astaxanthin generated by H. pluvialis cultures, and have provided novel insights into the mechanistic roles of rac -GR24 to achieve these effects.

The beta-blocker atenolol (ATE), and the selective serotonin and norepinephrine reuptake inhibitor, venlafaxine (VEN) are frequently detected in municipal wastewater effluents, but little is known about their ecotoxicological effect on aquatic animals. Herein, ATE and VEN were selected to explore their accumulation and global DNA methylation (GDM) in zebrafish tissues after a 30-day exposure. Molecular dynamics (MD) stimulation was used to investigate the toxic mechanism of ATE and VEN exposure. The results demonstrated that ATE and VEN could reduce the condition factor of zebrafish. The bioaccumulation capacity for ATE and VEN was in the order of liver > gut > gill > brain and liver > gut > brain > gill, respectively. After a 30-day recovery, ATE and VEN could still be detected in zebrafish tissues when exposure concentrations were ≥10 μg/L. Moreover, ATE and VEN induced global DNA hypomethylation in different tissues with a dose-dependent manner and their main target tissues were liver and brain. When the exposure concentrations of ATE and VEN were increased to 100 μg/L, the global DNA hypomethylation of liver and brain were reduced to 27% and 18%, respectively. In the same tissue exposed to the same concentration, DNA hypomethylation induced by VEN was more serious than that of ATE. After a 30-day recovery, the global DNA hypomethylations caused by the two drugs were still persistent, and the recovery of VEN was slower than that of ATE. The MD simulation results showed that both ATE and VEN could reduce the catalytic activity of DNA Methyltransferase 1 (DNMT1), while the effect of VEN on the 3D conformational changes of the DNMT1 domain was more significant, resulting in a lower DNA methylation rate. The current study shed new light on the toxic mechanism and potential adverse impacts of ATE and VEN on zebrafish, providing essential information to the further ecotoxicological risk assessment of these drugs in the aquatic environment., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

It is challenging to dependably keep the native distribution of arsenic (As) species before sample analysis in the laboratory. The on-site separation method can avoid sample contamination and species change in the process of sample collection and transportation from field to laboratory. In this study, As species distribution and variation of the extracted groundwater was first analyzed by an on-site species separation method in Jianghan Plain, China. Our study illustrated that: 1) high-As groundwater generally existed under mildly reducing conditions (Eh < 200 mV), weak alkaline conditions (pH < 7.2), elevated concentrations of dissolved Fe(II) and S(-II), and high proportions of As (III); 2) As species in the groundwater changed dramatically at room temperature in 36 hours post extraction (HPE). Fe-sulfide and Fe oxides minerals, which adsorbed As (V), were the main reasons influencing the As species concentration; 3) Acidification and strong complexing agents cannot preserve As species effectively. The average proportion of As (III) in the wells, where groundwater samples from the depth of 25 m exceed 10 μg L -1 As, can be reduced by 61% and 63% after HCl and EDTA were added, respectively. Accurate assessment of concentrations and distribution variation of As species in groundwater can guide the removal of As and the safe use of water resources, especially in drought areas relying on drinking well water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021. Published by Elsevier B.V.)

Liquid crystal monomers (LCMs) have been proposed as a class of emerging organic pollutants, which were recently detected in indoor dust and sediment samples collected near electronic devices recycling facilities. However, there is a knowledge gap for analytical method, occurrence, and distribution of LCMs in aqueous sample. Herein, a robust method was developed to determine 38 target LCMs in landfill leachate. A combined ultrasonic enhanced liquid-liquid extraction, saponification and silica/florisil packed column purification method achieved recoveries of 76.9~127.1%, 84.5~114.6% and 81.3~104.6% at spiking levels of 2 ng, 10 ng and 50 ng in leachate, respectively. The developed method was validated through determination of target LCMs in leachate samples collected from municipal landfills in Hong Kong (HK) and Shenzhen (SZ), China. There were 23 and 20 LCMs detected in the HK (ΣLCMs=1120 ng/L) and SZ (ΣLCMs=409 ng/L) sample, respectively, with 6 LCMs newly detected in the environment. This study provided the first evidence suggesting that landfill leachate might be a potential sink of LCMs emitted from e-waste. Future study is urged to investigate the potential migration of LCMs from landfill leachate as a point source, and their occurrence, distribution, fate, and ecotoxicological risk in aquatic environments on regional and global scales., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Phaeodactylum tricornutum, a model alga, is well known for its ability to accumulate intracellular omega-3 eicosapentaenoic acid (EPA). However, P.tricornutum cells need to have a higher EPA content if they are to be used for industrial applications. In this study, an auxin-like supermolecule (SM) was synthesised and used for the cultivation of P. tricornutum. Results show that the addition of 1 ppm of SM significantly increased the P. tricornutum cell density and boosted the P. tricornutum biomass. The experimental group treated with 5 ppm of SM, had an EPA content of 31.7%, which was a 2.09-fold increase over the EPA content in the untreated group. Overall, our results demonstrated that SM can significantly improve the microalgal growth and EPA accumulation in P. tricornutum, providing a feasible strategy to achieve efficient and cost-effective EPA production., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Hydraulic fracturing flowback and produced water (HF-FPW), which contains polyaromatic hydrocarbons (PAHs) and numerous other potential contaminants, is a complex wastewater produced during the recovery of tight hydrocarbon resources. Previous studies on HF-FPW have demonstrated various toxicological responses of aquatic organisms as consequences of combined exposure to high salinity, dissolved organic compounds and particle/suspended solids-bound pollutants. Noteworthy is the lack of studies illustrating the potentially toxic effects of the FPW suspended solids (FPW-SS). In this study, we investigated the acute and sublethal toxicity of suspended solids filtered from six authentic FPW sample collected from two fracturing wells, using a sediment contact assay based on early-life stages of zebrafish (Danio rerio). PAHs profiles and acute toxicity tests provided initial information on the toxic potency of the six samples. Upon exposure to sediment mixture at two selected doses (1.6 and 3.1 mg/mL), results showed adverse effects in larval zebrafish, as revealed by increased Ethoxyresorufin-O-deethylase (EROD) activity. Transcriptional alterations were also observed in xenobiotic biotransformation (ahr, pxr, cyp1a, cyp1b1, cyp1c1, cyp1c2, cyp3a65, udpgt1a1, udpgt5g1), antioxidant response (sod1, sod2, gpx1a, gpx1b) and hormone receptor signaling (esr1, esr2a, cyp19a1a, vtg1) genes. The results demonstrated that even separated from the complex aqueous FPW mixture, FPW-SS can induce toxicological responses in aquatic organisms' early life stages. Since FPW-SS could sediment to the bottom of natural wetland acting as a continuous source of contaminants, the current findings imply the likelihood of long-term environmental risks of polluted sediments on aquatic ecosystems due to FPW spills., (Copyright © 2021. Published by Elsevier Ltd.)

There is considerable debate about the sustainability of the hydraulic fracturing (HF) water cycle in North America. Recently, this debate has expanded to China, where HF activities continue to grow. Here, we provide a critical review of the HF water cycle in China, including water withdrawal practices and flowback and produced water (FPW) management and their environmental impacts, with a comprehensive comparison to the U.S. and Canada (North America). Water stress in arid regions, as well as water management challenges, FPW contamination of aquatic and soil systems, and induced seismicity are all impacts of the HF water cycle in China, the U.S., and Canada. In light of experience gained in North America, standardized practices for analyzing and reporting FPW chemistry and microbiology in China are needed to inform its efficient and safe treatment, discharge and reuse, and identification of potential contaminants. Additionally, conducting ecotoxicological studies is an essential next step to fully reveal the impacts of accidental FPW releases into aquatic and soil ecosystems in China. From a policy perspective, the development of China's unconventional resources lags behind North America's in terms of overall regulation, especially with regard to water withdrawal, FPW management, and routine monitoring. Our study suggests that common environmental risks exist within the world's two largest HF regions, and practices used in North America may help prevent or mitigate adverse effects in China.

The Advanced Oxidation System (AOS) is a novel electrochemical advanced oxidation process that effectively removes bacterial and organic contaminants from wastewater. However, potential formation of secondary oxidative species may pose additional hazards to aquatic organisms living in the receiving water affected by the post-treatment effluent. The effect of exposure to AOS treated water, especially the potential long-term effects on aquatic organisms, requires further investigation to demonstrate both efficacy and safety of this process. To examine the potential adverse effects of AOS treated water, three aquatic species, including daphnia, zebrafish, and rainbow trout, were exposed to treated and untreated municipal wastewater effluent (MWE) spiked with one of two model organic contaminants, benzo[a]pyrene (BaP) and 17β-estradiol (E2). The results indicated AOS treatment significantly reduced the adverse effects caused by exposure to MWE and model organic contaminants to baseline levels in daphnia (reduced fecundity), zebrafish embryo (elevated EROD activity), and rainbow trout (elevated plasma vitellogenin). The Ames test was also conducted to confirm the removal efficacy of carcinogenicity of BaP spiked in MWE. Overall, this study demonstrated that AOS treatment is a promising and environmentally friendly technology for wastewater treatment, remediation, and management., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Per- and polyfluoroalkyl substances (PFASs) have been manufactured and widely used for over 60 years. Currently, there are thousands of marketed PFASs, but only dozens of them are routinely monitored. This work involved target, nontarget, and suspect screening of PFASs in the liver of Indo-Pacific humpback dolphin ( Sousa chinensis ) and finless porpoise ( Neophocaena phocaenoides ), two resident marine mammals in the South China Sea, stranded between 2012 and 2018. Among the 21 target PFASs, perfluorooctane sulfonate and 6:2 chlorinated polyfluoroalkyl ether sulfonate (6:2 Cl-PFESA) predominated in the samples, accounting for 46 and 30% of the total PFASs, respectively. Significantly higher total target PFAS concentrations ( p < 0.05) were found in dolphin liver samples [3.23 × 10 3 ± 2.63 × 10 3 ng/g dry weight (dw)] than in porpoise liver samples (2.63 × 10 3 ± 1.10 × 10 3 ng/g dw). Significant increasing temporal trends ( p < 0.05) were found in the concentrations of two emerging PFASs, perfluoroethylcyclohexane sulfonate and 2,3,3,3-tetrafluoro-2-propanoate in porpoises, indicating increasing pollution by these emerging PFASs. Forty-four PFASs from 9 classes were additionally identified by nontarget and suspect screening, among which 15 compounds were reported for the first time in marine mammals. A primary risk assessment showed that the emerging PFAS 6:2 Cl-PFESA could have possible adverse effects in terms of reproductive injury potential on most of the investigated cetaceans.

Wastewater recovered from hydraulic fracturing is referred to as flowback and produced water (FPW), and is often saline, contains numerous organic and inorganic constituents, and may pose threats to groundwater resources. Hundreds of spills of FPW have been reported to the Alberta Energy Regulator each year. Recently, samples of FPW derived from hydraulic fracturing of the Duvernay Formation, AB, were found to contain a previously unidentified class of aryl phosphates, including diphenyl phosphate (DPP), triphenyl phosphate (TPP), and others. Aryl phosphates are also used in a variety of other industries and their constituents can be found in flame retardants, plasticizers, lubricants, hydraulic fluids, and oxidizers. Many of these aryl phosphates break down into DPP. Therefore, it is important to determine the environmental fate and potential impact of DPP if spilled in the near-surface, as DPP is an emerging contaminant in soil and groundwater systems. This study was aimed at determining 1) the sorption behavior of DPP onto various surficial sediments collected within the Fox Creek, AB region, and 2) the toxicity of DPP toward aquatic ecosystems. We report that the sorption of DPP onto both clay-rich soils and sandy sediment was low compared to that of other aryl phosphates, with an average log K OC value of 2.30 ± 0.42 (1σ). Therefore, the transport of DPP in groundwater would be rapid due to its low degree of sorption on surficial materials. We also determined the acute 96 h-LC 50 of DPP on zebrafish embryos to be 50.0 ± 7.1 mg/L. Su et al. (2014) studied the toxic effects of DPP and TPP on chicken embryonic hepatocytes and found that DPP had less cytotoxic effects than TPP but altered more gene transcripts. From the results our study, we infer that DPP may pose an environmental risk to aquatic ecosystems if released into the environment., (Crown Copyright © 2019. Published by Elsevier B.V. All rights reserved.)

Potential effects of horizontal drilling combined with high-volume hydraulic fracturing (HF) have drawn significant public concern, especially on the handling, treatment, and disposal of HF flowback and produced water (HF-FPW). Previous studies indicated HF-FPW could significantly disrupt biotransformation and expressions of genes related to the endocrine system. This study focused on effects of organic extracts of HF-FPW on receptor binding activity using several transactivation assays. Six HF-FPW samples were collected from 2 wells (Well A and Well B, 3 time points at each well). These were separated by filtration into aqueous (W) and particulate (S) phases, and organics were extracted from all 12 subsamples. Of all the tested fractions, sample B1-S had the greatest Σ 13 PAH (11,000 ng/L) and B3-S has the greatest Σ 4 alkyl-PAHs (16,000 ng/L). Nuclear receptor binding activity of all the extracts on aryl hydrocarbon receptor (AhR), estrogen receptor (ER), and androgen receptor (AR) were screened using H4IIE-luc, MVLN-luc, and MDA-kb2 cells, respectively. FPWs from various HF wells exhibited distinct nuclear receptor binding effects. The strongest AhR agonist activity was detected in B3-S, with 450 ± 20 μg BaP/L equivalency at 5 × exposure. The greatest ER agonist activity was detected in A1-W, with 5.3 ± 0.9 nM E2 equivalency at 10× exposures. There is a decreasing trend in ER agonist activity from A1 to A3 in both aqueous and particulate fractions from Well A, while there is an increasing trend in ER agonist activity from B1 to B3 in aqueous fractions from Well B. This study provides novel information on the sources of endocrine disruptive potentials in various HF-FPW considering both temporal and spatial variability. Results suggest that reclamation or remediation and risk assessment of HF-FPW spills likely requires multiple strategies including understanding the properties of each spill with respect to fractured geological formation and physiochemical properties of the injected fluid., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Hydraulic fracturing (HF) has emerged as a major recovery method of unconventional oil and gas reservoirs and concerns have been raised regarding the environmental impact of releases of Flowback and Produced Water (FPW) to aquatic ecosystems. To investigate potential effects of HF-FPW on fish embryo development, HF-FPW samples were collected from two different wells and the organic fractions were isolated from both aqueous and particle phases to eliminate the confounding effects of high salinity. Each organic extract was characterized by non-target analysis with HPLC-Orbitrap-MS, with targeted analysis for polycyclic aromatic hydrocarbons provided as markers of petroleum-affected water. The organic profiles differed between samples, including PAHs and alkyl PAHs, and major substances identified by non-target analysis included polyethylene glycols, alkyl ethoxylates, octylphenol ethoxylates, and other high molecular weight (C 49-79 ) ethylene oxide polymeric material. Zebrafish embryos were exposed to various concentrations of FPW organic extracts to investigate acute (7-day) and developmental toxicity in early life stages. The acute toxicity (LD 50 ) of the extracted FPW fractions ranged from 2.8× to 26× the original organic content. Each extracted FPW fraction significantly increased spinal malformation, pericardial edema, and delayed hatch in exposed embryos and altered the expression of a suite of target genes related to biotransformation, oxidative stress, and endocrine-mediation in developing zebrafish embryos. These results provide novel information on the variation of organic profiles and developmental toxicity among different sources and fractions of HF-FPWs.

Hydraulic fracturing flowback and produced water (FPW) is a wastewater produced during fracturing activities in an operating well which is hyper saline and chemically heterogeneous in nature, containing both anthropogenic and petrogenic chemicals. Determination of FPW associated toxicity to embryonic fish is limited, while investigation into how embryonic exposures may affect later life stages is not yet studied. Zebrafish embryos (24hrs post fertilization) were acutely exposed to 2.5% and 5% FPW fractions for either 24 or 48hrs and returned to freshwater. After either 24 or 48h exposures, embryos were examined for expression of 3 hypoxia related genes. Erythropoietin (epoa) but not hypoxia inducible factor (hif1aa) nor hemoglobin -ß chain (hbbe1.1) was up-regulated after either 24 or 48h FPW exposure. Surviving embryos were placed in freshwater and grown to a juvenile stage (60days post fertilization). Previously exposed zebrafish were analyzed for both swim performance (U crit and U max ) and aerobic capacity. Fish exposed to both sediment containing (FPW-S) or sediment free (FPW-SF) FPW displayed significantly reduced aerobic scope and U crit /U max values compared to control conditions. Our results collectively suggest that organics present in our FPW sample may be responsible for sub-lethal fitness and metabolic responses. We provide evidence supporting the theory that the cardio-respiratory system is impacted by FPW exposure. This is the first known research associating embryonic FPW exposures to sub-lethal performance related responses in later life fish stages., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Hydraulic fracturing to extract oil and natural gas reserves is an increasing practice in many international energy sectors. Hydraulic fracturing flowback and produced water (FPW) is a hyper saline wastewater returned to the surface from a fractured well containing chemical species present in the initial fracturing fluid, geogenic contaminants, and potentially newly synthesized chemicals formed in the fracturing well environment. However, information on FPW toxicological mechanisms of action remain largely unknown. Both cardiotoxic and respirometric responses were explored in zebrafish (Danio rerio) embryos after either an acute sediment-free (FPW-SF) or raw/sediment containing (FPW-S) fraction exposure of 24 and 48 h at 2.5% and 5% dilutions. A 48 h exposure to either FPW fraction in 24-72 h post fertilization zebrafish embryos significantly increased occurrences of pericardial edema, yolk-sac edema, and tail/spine curvature. In contrast, larval heart rates significantly decreased after FPW fraction exposures. FPW-S, but not FPW-SF, at 2.5% doses significantly reduced embryonic respiration/metabolic rates (MO 2 ), while for 5% FPW, both fractions reduced MO 2 . Expression of select cardiac genes were also significantly altered in each FPW exposure group, implicating a cardiovascular system compromise as the potential cause for reduced embryonic MO 2 . Collectively, these results support our hypothesis that organics are major contributors to cardiac and respiratory responses to FPW exposure in zebrafish embryos. Our study is the first to investigate cardiac and respiratory sub-lethal effects of FPW exposure, demonstrating that FPW effects extend beyond initial osmotic stressors and verifies the use of respirometry as a potential marker for FPW exposure., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Freshwater organisms actively take up ions from their environment to counter diffusive ion losses due to inhabiting hypo-osmotic environments. The mechanisms behind active Na + uptake are quite well understood in freshwater teleosts; however, the mechanisms employed by invertebrates are not. Pharmacological and molecular approaches were used to investigate Na + uptake mechanisms and their link to ammonia excretion in the ribbon leech Nephelopsis obscura At the molecular level, we identified a Na + channel and a Na + /H + exchanger (NHE) in the skin of N. obscura , where the NHE was up-regulated when acclimated to extremely low [Na + ] (0.05 mmol l -1 , pH 5) conditions. Additionally, we found that leeches in dilute freshwater environments use both a vacuolar-type H + -ATPase (VHA)-assisted uptake via a Na + channel and a NHE-based mechanisms for Na + uptake. Immunolocalization of VHA and Na + /K + -ATPase (NKA) indicated at least two cell types present within leech skin, VHA + and VHA - cells, where the VHA + cells are probably involved in Na + uptake. NKA was present throughout the epithelium. We also found that increasing ammonia excretion by decreasing water pH, ammonia loading leeches or exposing leeches to high environmental ammonia does not affect Na + uptake, providing indications that an NHE-Rh metabolon is not present and that ammonia excretion and Na + uptake are not coupled in N. obscura To our knowledge, this is the first study showing the mechanisms of Na + uptake and their links to ammonia excretion in a freshwater invertebrate, where results suggest an ammonia-independent Na + uptake mechanism relying on both Na + channels and NHEs., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

Hydraulic fracturing (HF) has emerged as a major method of unconventional oil and gas recovery. The toxicity of hydraulic fracturing flowback and produced water (HF-FPW) has not been previously reported and is complicated by the combined complexity of organic and inorganic constituents in HF fluids and deep formation water. In this study, we characterized the solids, salts, and organic signatures in an HF-FPW sample from the Duvernay Formation, Alberta, Canada. Untargeted HPLC-Orbitrap revealed numerous unknown dissolved polar organics. Among the most prominent peaks, a substituted tri-phenyl phosphate was identified which is likely an oxidation product of a common polymer antioxidant. Acute toxicity of zebrafish embryo was attributable to high salinity and organic contaminants in HF-FPW with LC50 values ranging from 0.6% to 3.9%, depending on the HF-FPW fractions and embryo developmental stages. Induction of ethoxyresorufin-O-deethylase (EROD) activity was detected, due in part to polycyclic aromatic hydrocarbons (PAHs), and suspended solids might have a synergistic effect on EROD induction. This study demonstrates that toxicological profiling of real HF-FPW sample presents great challenges for assessing the potential risks and impacts posed by HF-FPW spills., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Hydraulic fracturing is an industrial process allowing for the extraction of gas or oil. To fracture the rocks, a proprietary mix of chemicals is injected under high pressure, which later returns to the surface as flowback and produced water (FPW). FPW is a complex chemical mixture consisting of trace metals, organic compounds, and often, high levels of salts. FPW toxicity to the model freshwater crustacean Daphnia magna was characterized utilizing acute (48 h median lethal concentrations; LC 50 ) and chronic (21 day) exposures. A decrease in reproduction was observed, with a mean value of 18.5 neonates produced per replicate over a 21 day chronic exposure to 0.04% FPW, which was a significant decrease from the average of 64 neonates produced in the controls. The time to first brood was delayed in the highest FPW (0.04%) treatment. Neonates exhibited an LC 50 of 0.19% of full-strength FPW, making them more sensitive than adults, which displayed an LC 50 value of 0.75%. Quantitative PCR highlighted significant changes in expression of genes encoding xenobiotic metabolism (cyp4) and moulting (cut). This study is the first to characterize chronic FPW toxicity and will help with the development of environmental monitoring and risk assessment of FPW spills.

The effects of hydraulic fracturing (HF) flowback and produced water (HF-FPW), a complex saline mixture of injected HF fluids and deep formation water that return to the surface, was examined in rainbow trout (Oncorhynchus mykiss). Exposure to HF-FPWs resulted in significant induction of ethoxyresorufin-O-deethylase (EROD) activity in both liver and gill tissues. Increased lipid peroxidation via oxidative stress was also detected by thiobarbituric acid reactive substances (TBARS) assay. The mRNA expressions of a battery of genes related to biotransformation, oxidative stress, and endocrine disruption were also measured using quantitative real-time polymerase chain reaction (Q-RT-PCR). The increased expression of cyp1a (2.49 ± 0.28-fold), udpgt (2.01 ± 0.31-fold), sod (1.67 ± 0.09-fold), and gpx (1.58 ± 0.10-fold) in raw sample exposure group (7.5%) indicated elevated metabolic enzyme activity, likely through the aryl hydrocarbon receptor pathway, and generation of reactive oxygen species. In addition, the elevated vtg and era2 expression demonstrated endocrine disrupting potential exerted by HF-FPW in rainbow trout. The overall results suggested HF-FPW could cause significant adverse effects on fish, and the organic contents might play the major role in its toxicity. Future studies are needed to help fully determine the toxic mechanism(s) of HF-FPW on freshwater fish, and aid in establishing monitoring, treatment, and remediation protocols for HF-FPW.

Biochars have increasingly been used as adsorbents for organic and inorganic contaminants in soils. However, during the carbonization process of pyrolysis, contaminants, including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dioxins and furans (PCDD/DF) can be generated. In this study, biochars made from sawdust, were prepared at various temperatures ranging from 250 to 700 °C. The Microtox ® and rat hepatoma cell line H4IIE-luc assays were used to characterize the general toxic and effects, mediated through the aryl hydrocarbon receptor (AhR), or dioxin-like potencies of organic extracts of biochars. The greatest total concentrations of PAHs (8.6 × 10 2  μg kg -1 ) and PCDD/DF (6.1 × 10 2  pg g -1 ) were found in biochar generated at 400 °C and 300 °C, respectively. Results of the H4IIE-luc assay, which gives total concentrations of 2,3,7,8-TCDD equivalents (TEQ H4IIE-luc ), indicated that total potencies of aryl hydrocarbon receptor (AhR) agonists were in decreasing order: 300 °C > 250 °C > 400 °C > 500 °C > 700 °C. The 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ chem ) calculated as the sum of products of 16 PAHs and 17 PCDD/DF congers multiplied by their respective relative potencies (RePs) was less than that of TEQ H4IIE-luc determined by use of the bioanalytical method, with the H4IIE-luc assay, which measures the total dioxin-like potency of a mixtures. The ratio of TEQ chem /TEQ H4IIE-luc was in the range of 0.7%-3.8%. Thus, a rather small proportion of the AhR-mediated potencies extracted from biochars were identified by instrumental analyses. Results of the Microtox test showed similar tendencies as those of the H4IIE-luc test, and a linear correlation between EC50 of Microtox test and EC20 of H4IIE-luc test was found. The results demonstrated that biochars produced at higher pyrolysis temperatures (>400 °C) were less toxic and had lower potencies of AhR-mediated effects, which may be more suitable for soil application., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Arctic grayling (Thymallus arcticus) are salmonids that have a strict freshwater existence in post-glacial North America. Oil and gas development is associated with production of high volumes of hypersaline water. With planned industrial expansion into northern areas of Canada and the USA that directly overlap grayling habitat, the threat of accidental saline water release poses a significant risk. Despite this, we understand little about the responses of grayling to hypersaline waters. We compared the physiological responses and survivability of Arctic grayling and rainbow trout (Oncorhynchus mykiss) to tolerate an acute transfer to higher saline waters. Arctic grayling and rainbow trout were placed directly into 17 ppt salinity and sampled at 24 and 96 h along with control animals in freshwater at 24 h. Serum sodium, chloride and osmolality levels increased significantly in grayling at both 24 and 96 h time points, whereas trout were able to compensate for the osmoregulatory disturbance by 96 h. Sodium-potassium ATPase mRNA expression responses to salinity were also compared, demonstrating the inability of the grayling to up-regulate the seawater isoform nkaα1b. Our results demonstrated a substantially lower salinity tolerance in grayling. We also found a significant salinity-induced morphological gill remodelling by Arctic grayling, as demonstrated by the rapid growth of an interlamellar cell mass by 24 h that persisted at 96 h. We visualized and quantified the appearance of the interlamellar cell mass as a response to high salinity, although the functional significance remains to be understood fully. Compared with rainbow trout, which are used as an environmental regulatory species, Arctic grayling are unable to compensate for the osmotic stressors that would result from a highly saline produced water spill. Given these new data, collaboration between fisheries and the oil and gas industry will be vital in the long-term conservation strategies with regard to the Arctic grayling in their native habitat.

Oil sands-influenced process waters have been observed to cause reproductive effects and to induced CYP1A activity in fishes; however, little progress has been made in determining causative agents. Naphthenic acids (NAs) are the predominant organic compounds in process-affected waters, but due to the complexity of the mixture, it has been difficult to examine causal linkages in fishes. The aim of this study was to use in vitro assays specific to reproductive and CYP1A mechanisms to determine if specific acid extractable fractions of NAs obtained from oil sands-influenced water are active toward reproductive processes or interact with the Ah receptor responsible for CYP1A activity. NAs were extracted from aged oil sands-influenced waters by use of acid precipitation, and the mixture was fractionated into three acidic and one neutral fraction. The four fractions were examined for Ah receptor-mediated potency by use of the H4IIE-luc bioassay, effects on production of steroid hormones by use of the H295R steroidogenesis assay, and sex steroid receptor binding activity using the yeast estrogen screen and yeast androgen screen. The mixtures were characterized by high resolution mass spectrometry, (1)H nuclear magnetic resonance, and attenuated total reflectance infrared spectroscopy. The neutral fraction elicited Ah-receptor mediated activity after 24 h but not after 48 or 72 h. None of the fractions contained measurable levels of estrogen or androgen receptor agonists nor did they cause reductions in steroidogenesis. A number of fractions showed antiestrogenic or antiandrogenicity potency, with the neutral and main acidic fractions being the most potent. Neutral aromatic compounds are likely responsible for the CYP1A activity observed. Direct estrogenic, androgenic, or steroidogenic mechanisms are unlikely for NAs based on these results, but NAs act as potent antiandrogen or antiestrogens.

Oil sands process-affected water (OSPW) is produced by the oil sands industry in Alberta, Canada. OSPW has acute and chronic effects on aquatic organisms, but the suite of effects of OSPW, and mechanisms of effects, are not understood. The goal of this study was to use RNA sequencing (RNAseq) to quantify abundances of transcripts in livers of male fathead minnows exposed to untreated OSPW and ozone-treated OSPW to investigate sublethal effects of untreated OSPW and to determine whether ozonation imparts toxicity upon OSPW. A reference transcriptome of 25,342 contigs was constructed from RNA from livers of fathead minnows exposed to various experimental conditions. Exposure to untreated OSPW resulted in greater abundances of 104 transcripts and lesser abundances of 91 transcripts. Oxidative metabolism, oxidative stress, apoptosis, and immune function were identified as processes affected by OSPW. Exposure to ozone-treated OSPW resulted in greater abundances of 57 transcripts and lesser abundances of 75 transcripts. However, in general, putative pathways for effects of OSPW in fathead minnows exposed to untreated OSPW were not identified in minnows exposed to ozone-treated OSPW, and pathways by which ozone-treated OSPW might have effects were not identified., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Due to a policy of no release, oil sands process-affected water (OSPW), produced by the surface-mining oil sands industry in North Eastern Alberta, Canada, is stored on-site in tailings ponds. Currently, ozonation is considered one possible method for remediation of OSPW by reducing the concentrations of dissolved organic compounds, including naphthenic acids (NAs), which are considered the primary toxic constituents. However, further work was needed to evaluate the effectiveness of ozonation in reducing the toxicity of OSPW and to ensure that ozonation does not increase the toxicity of OSPW. This study examined effects of untreated, ozone-treated, and activated charcoal-treated OSPW (OSPW, O3-OSPW, and AC-OSPW) on the early life stage (ELS) of fathead minnow (Pimephales promelas). Success of hatching of eggs, spontaneous movement, and incidences of hemorrhage, pericardial edema, and malformation of the spine of embryos were examined. To elucidate the mechanism of toxicity, concentrations of reactive oxygen species (ROS) were measured, and the abundances of transcripts of genes involved in biotransformation of xenobiotics, response to oxidative stress, and apoptosis were quantified by real-time PCR. Compared to the control group, which had an embryo survival rate of 97.9 ± 2.08%, survival was significantly less when exposed to OSPW (43.8 ± 7.12%). Eggs exposed to untreated OSPW exhibited a significantly greater rate of premature hatching, and embryos exhibited greater spontaneous movement. Incidences of hemorrhage (50.0 ± 3.40%), pericardial edema (56.3 ± 7.12%), and malformation of the spine (37.5 ± 5.38%) were significantly greater in embryos exposed to OSPW compared to controls. These effects are typical of exposure to dioxin-like compounds, however, abundance of transcripts of cyp1a was not significantly greater in embryos exposed to OSPW. Significantly greater concentrations of ROS, and greater abundances of transcripts cyp3a, gst, sod, casp9, and apopen compared to controls, indicated that exposure to OSPW caused oxidative stress, which can result in damage to mitochondria and promote activation of caspase enzymes and apoptotic cell death. Removal of dissolved organic constituents by ozone treatment, or by activated charcoal, significantly attenuated all of the adverse effects associated with untreated OSPW. The results suggest that the organic fraction of OSPW can negatively impact the development of fathead minnow embryos through oxidative stress and apoptosis, and that ozonation attenuates this developmental toxicity., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Oil sands process-affected water (OSPW) produced by the surface mining oil sands industry in Alberta, Canada, is toxic to aquatic organisms. Ozonation of OSPW attenuates this toxicity. Altered concentrations of sex steroid hormones, impaired reproductive performance, and less prominent secondary sexual characteristics have been reported for fish exposed to OSPW. However, the mechanism(s) by which these effects occur and whether ozonation can attenuate these effects in fish was unknown. The objective of this in vivo study was to investigate the endocrine-disrupting effects of OSPW and ozone-treated OSPW on the abundances of transcripts of genes in the brain-gonad-liver (BGL) axis in male and female fathead minnows (Pimephales promelas). Abundances of transcripts of genes important for synthesis of gonadotropins were greater in brains from both male and female fish exposed to untreated OSPW compared to that of control fish. In gonads from male fish exposed to untreated OSPW the abundances of transcripts of gonadotropin receptors and several enzymes of sex hormone steroidogenesis were greater than in control fish. The abundances of transcripts of estrogen-responsive genes were greater in livers from male fish exposed to untreated OSPW than in control fish. In female fish exposed to untreated OSPW there was less abundance of transcripts of gonadotropin receptors in gonads, as well as less abundance of transcripts of estrogen-responsive genes in livers. Many effects were either fully or partially attenuated in fish exposed to ozone-treated OSPW. The results indicate that (1) OSPW has endocrine-disrupting effects at all levels of BGL axis, (2) OSPW has different effects in male and female fish, (3) ozonation attenuates the effects of OSPW on abundances of transcripts of some genes, and the attenuation is more prominent in males than in females, but effects of ozonation on endocrine-disrupting effects of OSPW were less clear than in previous in vitro studies. The results provide a mechanistic basis for the endocrine-disrupting effects of OSPW from other studies.

There is increasing environmental concern about the volume of oil sands process-affected water (OSPW) produced by the oil sands industry in Alberta, Canada. There is limited knowledge of the toxic effects of OSPW and one of the primary organic constituents, naphthenic acids (NAs), which are thought to be one of the toxic constituents of OSPW. OSPW and NAs can have endocrine disrupting potential. The NAs in OSPW are persistent, but ozonation can significantly reduce concentrations of NA, while increasing their biodegradability, and consequently reduce OSPW toxicity. However, it is of concern that OSPW ozonation might generate hydroxylated cycloaliphatics with endocrine disrupting potential. In this study, the estrogen receptor- (ER) and androgen receptor- (AR) mediated effects of OSPW and ozone-treated OSPW were investigated in vitro by use of T47D-kbluc (estrogen responsive) and MDA-kb2 (androgen responsive) cells. Ozonation neither attenuated nor intensified the estrogenicity of OSPW. The estrogenic responses to untreated OSPW and ozone treated OSPW were 2.58(±0.22)-fold and 2.48(±0.13)-fold greater than those of controls, respectively. Exposure to untreated OSPW produced significant antiandrogenicity in the presence of 0.01, 0.05, or 0.1 nM testosterone (T), while ozone-treated OSPW produced significant antiandrogenicity in the presence of 0.01 or 0.05 nM T. Exposure to untreated and ozone-treated OSPW also caused potentiation of androgen receptor-mediated effects of T. OSPW could cause estrogenic and antiandrogenic effects through receptor mediated pathways, and ozonation can partially mitigate the OSPW antiandrogenicity as well as androgen potentiating effect, without increasing estrogen potency.