Priority and emerging flame retardants in rivers: occurrence in water and sediment, Daphnia magna toxicity and risk assessment

Accumulation of microplastics and Tcep pollutants in agricultural soil: Exploring the links between metabolites and gut microbiota in earthworm homeostasis

Agricultural soil contamination with plastic film has become a critical global environmental problem, requiring greater research on the possible occurrence and biological risk of microplastics (MPs) and their additives in soil ecosystems. The presence of MPs and tris (2-chloroethyl) phosphate (Tcep) in agricultural soil was investigated at nine sites in the present study. Polyethylene MPs (PE-MPs) and Tcep were found at all nine sites. To study co-exposure effects on soil microbiota and earthworms, and to mimic a realistic exposure scenario, 0.05 % (w/w) PE-MPs with three particle size ranges were combined with Tcep (1.0 mg/kg). After 28 days of exposure, there was no indication that added PE-MPs and/or Tcep significantly affected the soil microbial community structure. In earthworms, size-selective intake, digestion and egestion of PE-MPs may occur, with Tcep co-exposure affecting the residual Tcep concentration in earthworm intestines (3.52-9.31 μg/g dw). Long-term earthworm PE-MPs intake caused intestinal damage, and Tcep co-exposure increased oxidative stress, thereby influencing their feeding behavior and growth, resulting in weight loss (3.42 %-14.96 %), especially for the most common PE-MPs sizes (0-300 μm). High performance liquid chromatography-mass spectrometry (LC-MS) was used for metabolomic analysis, revealing the significant up-regulation of citrate (p < 0.001) and down-regulation of l-glutamate (p < 0.05) in co-exposure groups. Co-exposure resulted in the alteration of most metabolic pathways, thereby impairing nervous, digestive and excretory systems in the earthworm, with an associated decrease in amino acid metabolism and changes in tricarboxylic acid (TCA) cycle intermediates. Gut microbiota, such as Proteobacteria (Verminephrobacter and Bradyrhizobium) and Firmicutes (Bacillus), are critically important in maintaining earthworm metabolic homeostasis, particularly for the TCA cycle and amino acid metabolism. Overall, MPs and Tcep co-exposure in agricultural soil enhanced their toxicity to earthworms and may potentially endanger the development of agricultural sustainability.

Genotoxic and Toxic Effects of The Flame Retardant Tris(Chloropropyl) Phosphate (TCPP) in Human Lymphocytes, Microalgae and Bacteria

Tris(chloropropyl) phosphate (TCPP) is a characteristic and widely used organophosphorus flame retardant. TCPP is comprised of four isomers and the most abundant is tris(1-chloro-2-propyl) phosphate. TCPP can be released into the environment, with potential impacts on living organisms and humans due to its extensive industrial use. Aiming to assess the potential risks of TCPP on human health and the environment, its toxic and genotoxic effects-using organisms from different trophic levels, i.e., bacteria, green microalgae, and human cells-were investigated. TCPP exposure at nominal concentrations of 10, 20, 30 and 40 μg mL^-1 was studied to identify the potential risk of inducing genotoxic effects in cultured human lymphocytes. Treatment with 30 and 40 μg mL^-1 of TCPP induced marginally significant micronuclei (MN) frequencies as well as cytotoxic effects. Freshwater microalgae species treated with TCPP (0.5, 1, 10, 20 and 50 μg L^-1) showed different growth rates over time. All the tested microalgae species were adversely affected after exposure to TCPP during the first 24 h. However, differences among the microalgae species' sensitivities were observed. In the case of the freshwater species, the most sensitive was found to be Chlorococcum sp. The marine algal species Dunaliella tertiolecta and Tisochrysis lutea were significantly affected after exposure to TCPP. The effects of TCPP on Aliivibrio fischeri that were observed can classify this flame retardant as a "harmful" compound. Our results suggest a potential risk to aquatic organisms and humans from the wide utilization of TCPP and its consequent release into the environment. These results highlight that further research should be conducted to investigate the effects of TCPP individually and in combination with other organophosphorus flame retardants in various organisms. In addition, the concern induced by TCPP points out that measures to control the introduction of TCPP into the environment should be taken.

Organophosphate flame retardants in Hangzhou tap water system: Occurrence, distribution, and exposure risk assessment

The usage of Organophosphorus flame retardants (OPFRs) is gradually increased as the ban on brominated flame retardants (BFRs) worldwide. The frequent accessibility of OPFRs in aquatic environment poses potential risk to human. Previous studies have concerned on surface water, while studies on tap water are limited. In this research, we aim to evaluate the removal efficiency of the tap water treatment process and investigate the exposure risk of OPFRs in tap water. Herein, we collected 14 samples from water source, 10 samples from water treatment plants and 47 from tap to analyze the concentrations and removal efficiency of OPFRs in Hangzhou tap water supply system. The results showed the concentrations of ∑OPFRs ranged from 9.25 to 224.74 ng/L in all samples, with Tris(1-chloro-2-propyl) Phosphate (TCPP), Tris(2-chloroethyl) phosphate (TCEP), Triphenyl phosphate (TPHP), and Tributyl phosphate (TBP) being the predominant compounds. Levels of the OPFRs had a 10.0 % - 50.4 % declination when compared samples after treatment with that before. The maximum exposure doses of ∑OPFRs via tap water for both adults and children were much lower than the reference dose (RfD). As a result, the hazard index (HI) and the carcinogenic risk (CR) pinpointed a negligible non-carcinogenic and carcinogenic risk for the residents. Even so, given the pervasive usage of OPFRs, the residual levels and the potential risk of OPFRs in watershed should be continuously concerned.

Antibacterial and Antibiofilm Potential of Microbial Polysaccharide Overlaid Zinc Oxide Nanoparticles and Selenium Nanowire

Here, we report on the synthesis of zinc oxide nanoparticles (ZnO NPs) and selenium nanowires (Se NWs) using microbial exopolysaccharides (EPS) as a mediator and then examine their antibacterial and ecotoxicity effects in vitro and in vivo, respectively. At 100 µg/mL, EPS, EPS-ZnO NPs, and EPS-Se NWs all exhibited potent in vitro antibacterial properties, drastically inhibiting the development of aquatic Gram(-) pathogens. In addition, antibiofilm studies using a microscope revealed that EPS, EPS-ZnO NPs, and EPS-Se NWs at 75 µg/mL prevented biofilm development. Furthermore, the in vivo toxicity was carried out via Danio rerio embryos and Ceriodaphnia cornuta. Danio rerio embryos were determined at different time intervals (6 hpf, 12 hpf, 24 hpf and 48 hpf). The maximum survival rate (100%) was obtained in a control group. Correspondingly, EPS, EPS-ZnO NPs and EPS-Se NWs treated embryos showed a considerable survival rate with 93.3%, 86.7% and 77.2%, respectively, at 100 µg/mL for 48 hpf. The total mortality of C. cornuta was seen at 100 µg/mL, with 56.7% in EPS, 60.0% in EPS-ZnO NPs, and 70.0% in EPS-Se NWs. For C. cornuta, the LC50 values for EPS, EPS-ZnO NPs, and EPS-Se NWs were 90.32, 81.99, and 62.99 µg/mL, respectively. Under a microscope, morphological alterations in C. cornuta were analyzed. After 24 h, an amount of dark substance was seen in the guts of C. cornuta exposed to 100 µg/mL, but in the control group, all of the living C. cornuta were swimming as usual. Our results show that EPS and EPS-ZnO NPs were less harmful than EPS-Se NWs, and that they were successfully employed to shield freshwater crustaceans from the toxins in aquatic environments.

Heterogeneous Fenton-like removal of tri(2-chloroisopropyl) phosphate by ilmenite (FeTiO3): Kinetic, degradation mechanism and toxic assessment

Tri(2-chloroisopropyl) phosphate (TCPP), a common organophosphate flame retardant, was frequently detected in the environment and posed threats to human health. In this work, the main component of ilmenite FeTiO₃ was synthesized by the sol-gel method and employed as the catalyst for the degradation of TCPP by activating persulfate (PS) under UV irradiation. The degradation processes were fitted by the pseudo-first-order kinetic. The k_obs value in UV/FeTiO₃/PS system was up to 0.0056 min^-1 and much higher than that in UV/PS (0.0014 min^-1), UV/FeTiO₃ (0.0012 min^-1) and FeTiO₃/PS (0.0016 min^-1) systems, demonstrating a distinct synergistic effect in TCPP removal. The degradation efficiency of TCPP increased with the increase of UV intensity, PS concentration and catalyst dosage, and with the decrease of pH. By quenching experiment and EPR analysis, ·OH was confirmed to be the dominant radical in the reaction of the UV/FeTiO₃/PS system. The possible degradation pathways of TCPP were dechlorination, dealkylation, and further oxidation of alkyl groups based on the theoretical calculation of frontier molecular orbits. The toxicity of degradation intermediates evaluated by luminescence inhibition rate of photoluminescence was higher than TCPP. Thus, TCPP can be degraded in the UV/FeTiO₃/PS system effectively at the premise of introducing controlling measures to reduce the toxicity of degradation intermediates.

Occurrence, distribution and risk assessment of organophosphate esters (OPEs) in water sources from Northeast to Southeast China

With the wide utilization of organophosphate esters (OPEs) in recent years, OPEs have been detected more frequently in the aquatic environment. However, the distribution of OPEs in drinking source water has rarely been investigated across a large region. In this study, the occurrence and distribution of 13 OPEs were investigated in 23 source water sites from Northeast to Southeast (spacing greater than 3320 km) with a direct injection ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method. Total OPEs ranged from 218.8 to 636.6 ng/L, with a mean of 380.8 ng/L. The average detected concentration of OPEs in southern cities was higher than that in northern cities. Chlorinated OPEs accounted for 64.74% of the total concentration. Triethyl phosphate (TEP), tri (2-chloroethyl) phosphate (TCEP), and tri (chloropropyl) phosphate (TCPP) were detected in all water samples. Rainfall is a significant factor that affects the OPE concentration (less rainfall, higher concentration). China's OPE concentrations have rapidly reached a median level when compared to those of other countries. Ecological risk assessment showed that most OPEs have no or low risk to organisms (fish, crustacea, algae), except tricresyl phosphate (TCP), which is medium risk. The risk of OPEs in less-rain regions needs to be of greater concern, especially TCP.

Organophosphate esters in the mariculture ecosystem: Environmental occurrence and risk assessments

Most investigations on organophosphate esters (OPEs) are conducted predominantly in a separate biological or abiotic medium, and few joint analyses have been performed in the mariculture ecosystem based on yearly sampling. Herein, we investigated the occurrence, load estimation, phase distribution, source diagnostics, and risks of 20 OPEs in seawater, sediment, and aquaculture organisms from a typical mariculture area in China. The total of these OPEs (∑_OPEs) ranged within 3.97-1068 ng/L, 0.39-65.5 ng/g (dw), and 4.09-16.3 ng/g (ww) in seawater, sediment and organisms, respectively. Chlorinated OPEs were the predominant congeners detected in seawater, whereas alkyl-OPEs were the leading contributors in sediment and biological samples. Seasonal variations of ∑_OPEs in seawater were more distinct than those in sedimentary environments. Load estimation indicated that approximately 70% of the OPEs in the study area existed in the water bodies. Source identification performed using the U.S. EPA positive matrix factorization indicated that polyurethane foam/plastics and hydraulic oil made the greatest contributions in seawater, whereas chemical production was the predominant source in sediment. Indices of ecological and health risks of OPEs were lower than their risk threshold, indicating that the OPEs detected in this study posed a low risk to the aquatic environment and human health.

Occurrence, distribution, source identification, and risk assessment of organophosphate esters in the coastal waters of Beibu Gulf, South China Sea: Impacts of riverine discharge and fishery

As emerging pollutants, the environmental geochemistry of organophosphate esters (OPEs) in the coastal zone with multiple functional areas are still less recognized. This study investigated spatiotemporal distribution, sources and risks of 11 widely used OPEs in surface waters from seagoing rivers and multiple coastal functional areas of the Beibu Gulf. The results indicated that significantly higher ∑₁₁OPEs (total concentrations of 11 OPEs, ng/L) occurred in summer (34.2-1227) than in winter (20.6-840), as a result of the high emission caused by climate reasons. In general, higher ∑₁₁OPEs occurred in rivers (41.2-1227) than in the coast (34.2-809) in summer, especially in the urban rivers, while in winter, higher ∑₁₁OPEs occurred in the coast (23.4-840 vs 20.6-319 in rivers) because of obviously higher ∑₁₁OPEs in marine fishery areas (99-840). Source identification revealed that fishery activity, especially fishing vessels, and urban rivers were the main sources of OPEs in the Beibu Gulf. For the individual OPE, only tri-n-butyl phosphate (TNBP) may have ecological risks to aquatic organisms in a few sites, but if considering the additive effects, the OPEs mixtures would pose a high risk to algae and low to medium threats to crustaceans and fish.

Distribution, partitioning, and health risk assessment of organophosphate esters in a major tributary of middle Yangtze River using Monte Carlo simulation

Globally, organophosphate esters (OPEs) have attracted substantial attention because of their ubiquity in the environment, toxicity, and potential ecological and health risks. This study comprehensively investigated the occurrence, partitioning, and spatial distribution of nine ordinary monomeric OPEs (m-OPEs) and three emerging oligomeric OPEs (o-OPEs) in a major tributary of the middle Yangtze River, which is the Zijiang River (ZR), and their associated potential health risks. Total OPE concentrations ranged from 18.8 to 439 ng L^-1, 1.40 to 19.1 ng L^-1, and 3.71 to 77.3 ng g^-1 dw in the surface water, suspended particulate matter (SPM), and sediment, respectively. Tris (2-chloroisopropyl) phosphate (TCPP) dominated the water (61.3%) and sediment (60.1%) samples, whereas tris (2-butoxyethyl) phosphate (TBOEP) was present in the SPM (59.0%) samples. The proportion of o-OPEs was low in all three media, ranging from 0.60% to 1.90%. Field-based log K_oc values of the frequently detected OPEs were higher than those predicted by EPI Suite and were negatively correlated with temperature. The spatial distribution of OPEs in the water and hierarchical cluster analysis suggested that sewage treatment plant effluents and the mining industry were the main sources of OPEs in the ZR. The total noncarcinogenic and carcinogenic risks of OPEs in the water were low at the detected concentrations, even in the high-exposure scenario.

IPPD-induced growth inhibition and its mechanism in zebrafish

N-isopropyl-N-phenyl-1,4-phenylenediamine (IPPD) is used as a ubiquitous antioxidant worldwide, it is an additive in tire rubber easily discharged into the surrounding environment. At present, there is no study concerning the subacute toxicity of IPPD on fish. We used zebrafish embryos (2 h post-fertilization) exposed to IPPD for 5 days at concentrations of 0, 0.0012, 0.0120 and 0.1200 mg/L to investigate its toxic effects of embryonic development, disruption of growth hormone/insulin-like growth factor (GH/IGF) and hypothalamic-pituitary-thyroid (HPT) axis. The results showed that IPPD exposure decreased hatchability, weakened movement ability, reduced body length, and caused multiple types of deformities in zebrafish embryos. The expression of genes involved to GH/IGF and HPT axis were altered after exposure to IPPD in zebrafish larvae. Meanwhile, exposure to IPPD significantly decreased thyroxine (T4) and 3,5,3'-triiodothyronine (T3) contents in larvae, which indicated that HPT axis was in a disturbed state. Moreover, treatment of IPPD decreased the enzymatic activities of superoxide dismutase (SOD) and catalase (CAT) as well as levels of glutathione (GSH). While the contents of malondialdehyde (MDA) were elevated after exposure to IPPD. The present study thus demonstrated that IPPD induced oxidative stress, caused developmental toxicity and disrupted the GH/IGF and HPT axis of zebrafish, which could be responsible for developmental impairment and growth inhibition.

A new and systematic review on the efficiency and mechanism of different techniques for OPFRs removal from aqueous environments

Organic phosphorus flame retardants (OPFRs), as a new type of emerging contaminant, have drawn great attention over the last few years, due to their wide distribution in aquatic environments and potential toxicities to humans and living beings. Various treatment methods have been reported to remove OPFRs from water or wastewater. In this review, the performances and mechanisms for OPFRs removal with different methods including adsorption, oxidation, reduction and biological techniques are overviewed and discussed. Each technique possesses its advantage and limitation, which is compared in the paper. The degradation pathways of typical OPFRs pollutants, such as Cl-OPFRs, alkyl OPFRs and aryl OPFRs, are also reviewed and compared. The degradation of those OPFRs depends heavily upon their structures and properties. Furthermore, the implications and future perspectives in such area are discussed. The review may help identify the research priorities for OPFRs remediation and understand the fate of OPFRs during the treatment processes.

Pilot monitoring scheme of water pollutants in Important Bird and Biodiversity Areas

In this study we have established a monitoring scheme to determine the presence and distribution of widely used pharmaceuticals, pesticides, organophosphate esters (OPEs) and perfluoroalkyl substances (PFAS) in water bodies from Important Bird and Biodiversity Areas (IBAs) from Spain. The monitoring scheme included the georeferenced sampling of rocky mountain, Atlantic forest, riparian forest, Mediterranean forest, agricultural, inland aquatic and coastal aquatic IBAs, with the aim to evaluate the impact of widely used chemicals in those aquatic resources. Water samples were extracted using a generic solid-phase extraction protocol and analyzed by 3 analytical methods based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Quality parameters such as compound recovery, intra and inter-day variation, linearity and limits of detection were calculated in order to validate the methods. In addition, the ionization conditions and the optimization of the most appropriate transitions permitted unequivocal identification. Once the sampling and analytical procedure was set-up, 59 target compounds were monitored in 63 samples. Pharmaceutical, followed by pesticides, OPEs and PFAS were widespread along all IBAs studied at concentrations from 0.5 to 41083 ng/L. Overall, this study highlights the need to monitor the presence of contaminants in areas of high ecological interest to contribute to pollution control and mitigation towards protection of biodiversity.

Toxicity of di-2-ethylhexyl phthalate and tris (2-butoxyethyl) phosphate to a tropical micro-crustacean (Ceriodaphnia cornuta) is higher in Mekong River water than in standard laboratory medium

Plasticizers such as di(2-ethylhexyl) phthalate (DEHP) and tris (2-butoxyethyl) phosphate (TBOEP) are manufactured chemicals produced in high volumes. These chemicals are frequently detected in the aquatic environment and cause toxic effects on organisms. In this study, we assessed the chronic impacts of DEHP and TBOEP, respectively, at the concentration of 100 µg L^-1 dissolved in the artificial medium (M4/4) and Mekong River water on life history traits of a tropical micro-crustacean, Ceriodaphnia cornuta, for 14 days. DEHP and TBOEP substantially reduced the survival of C. cornuta. In M4/4 medium, both plasticizers strongly enhanced reproduction but did not influence the growth of C. cornuta. Mekong River water, plasticizers-exposed C. cornuta produced less neonates than those in the control. The detrimental impacts of DEHP and TBOEP on the fitness of C. cornuta were much stronger in natural river water than in M4/4. Our results suggest that plasticizers can cause adverse effects on tropical freshwater cladocerans, particularly in natural water. These results are of a deep concern, as national and international regulatory guidelines which are based on ecotoxicological tests using standard media may not fully capture these effects.

Tricresyl phosphate inhibits fertilization in Japanese medaka (Oryzias latipes): Emphasizing metabolic toxicity

As tricresyl phosphate (TCrP) is commonly found in global water sources, its potential reproductive toxicity to fish is of increasing concern. Japanese medaka larvae were exposed to TCrP at 657.9, 1,511, and 4042 ng/L for 100 days. We identified significant fertilization inhibition (6.9%-12.8%) in all exposure groups. Intersex was significantly induced at 4042 ng/L, with an incidence of 22.0%. TCrP exposure also caused dilation of the efferent duct in the testes with maximum duct widths of 83.3, 93.2, and 149.7 μm in the 657.9, 1,511, and 4042 ng/L exposure groups, respectively. These widths were all significantly larger than that observed in the control group (37.7 μm) and likely contributed substantially to fertilization inhibition. The TCrP metabolites 4-OH-MDTP and 3-OH-MDTP, were detected at high concentrations in the liver and elicited 5.8-fold and 5.3-fold greater androgen receptor antagonistic activity than that elicited by TCrP (39.8 μM), which may explain the intersex observed in low exposure groups. 4-OH-MDTP and 3-OH-MDTP elicited anti-estrogenic activities by blocking the estrogen receptor, and the concentrations at which its responses were equal to the IC₂₀ of tamoxifen were 16.1 μM and 18.9 μM, respectively, as detected using the yeast two-hybrid assay. Such anti-estrogenic activities were likely the main driver of dilation of the efferent duct. Observed adverse outcomes after exposure to TCrP all occurred under environmentally relevant concentrations, suggesting considerable ecological risk to wild fish.

Organophosphate esters in surface waters of Shandong Peninsula in eastern China: Levels, profile, source, spatial distribution, and partitioning

Organophosphate ester (OPE) levels, profiles, sources, spatial distribution, and partitioning were firstly studied in the rivers of the Shandong Peninsula. A total of 53 water samples and 45 sediment samples were collected from the rivers and the sewage treatment plant in the peninsula to quantitate levels of 13 targeted OPEs. Total OPE concentrations ranged from 263 to 6676 ng L^-1 in the water, and 39.3-360 ng g^-1 in the sediment. TEP, TCPP, and TCEP together contributed more than 90% of total OPE content. TCEP and TCPP concentrations in the Xiaoqing River sediment were increased by approximately two and seven times from 2014 to 2019, respectively. Total OPE concentrations generally increased from upstream regions to the estuaries. The main OPE sources were municipal effluent in the Jiaozhou Bay (JZB) watershed and chemical industrial wastewater in the Laizhou Bay (LZB) watershed. TCPP, TEP, and TCEP were generally approaching equilibrium between sediment and overlying water, while TNBP, TIBP, and TBOEP effectively transferred from the overlying water to the sediment. The riverine OPE flux was 0.66 ton/year to JZB and 3.58 ton/year to the LZB. TCPP and TCEP in municipal effluent, and TEP in chemical industrial wastewater should be regulated to protect Shandong Peninsula waters.

Distribution of organophosphate esters influenced by human activities and fluvial-tidal interactions in the Dong Nai River System, Vietnam

Limited information is known about organophosphate esters (OPEs) in sediments of the Dong Nai River System (DNRS) in Vietnam and the influences of complex hydro-sedimentary dynamics on their fate. In this study, 48 surface sediment samples were collected from the Dong Nai-Soai Rap River and its tributary Vam Co River for the determination of 11 target OPEs, together with grain size and total organic carbon (TOC). The total concentrations of OPEs were in the range of 39.4 ng/g dw-373 ng/g dw (mean: 128 ng/g dw), and tris(1-chloro-2-propyl) phosphate (TCPP) was the predominant one with an average contribution of 81%, followed by tri-n-butyl phosphate (TNBP), tris(2-ethylhexyl) phosphate (TEHP). The composition profiles of OPEs at different locations of the DNRS showed no significant differences (p > 0.05). In addition, the distribution of OPEs had been influenced by both human activities and the fluvial-tidal interactions. The highly frequent and various human activities in Ho Chi Minh City (HCMC) leaded to the highest total concentration of OPEs in the midstream site. Based on our dataset, TOC content and grain size of sediments had significant correlation with certain OPEs (p < 0.05), and sediments with higher TOC content and finer grain size in the DNRS were more likely to be deposited in the downstream reach, contributing to the estuary of the DNRS was identified as another hotspot with the second highest concentration of OPEs. Furthermore, the distribution of OPEs in the transects had distinct characteristics, which reflected the joint influence of the human activities and fluvial-tidal interaction as well. However, the mechanism of their influence needed further investigation.

Occurrence, potential sources and risks of organophosphate esters in the high-elevation region, Tibet, China

Organophosphate esters (OPEs) are widely used flame retardants that are frequently released into the environment, causing potential harm to humans and ecosystems. Tibet is located on the Tibetan Plateau, known as the "roof of the world", but the occurrence of OPEs in Tibet remains unclear. This is the first report of the occurrence, potential sources and risks of 12 OPEs in water, soil, sediment and snow from Xainza, a typical town at high-elevation in Tibet (average elevation = 4700 m). Ten OPEs were observed, with ∑OPE concentrations of 46.45-1744.73 ng/L in surface water, 29.74-73.85 ng/g in soil, and 13.30-32.23 ng/g in sediment. Moreover, the mean ∑OPE concentration in snow was 413.90 ng/L. Tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCPP) were the main OPEs in surface water and snow, while 2-ethylhexyl diphenyl phosphate (EHDPP) was dominant in soil and sediment. Local human activities and long-distance atmospheric transport may be the main sources of OPEs in Xainza. The assessment of ecological risk indicated that EHDPP in soil poses potential risk. The occurrence of OPEs in Xainza showed that more attention should be paid to persistent organic pollutants in high-elevation regions.

Spatiotemporal Distribution and Analysis of Organophosphate Flame Retardants in the Environmental Systems: A Review

In recent times, there has been a cumulative apprehension regarding organophosphate flame retardants (OPFRs) owing to their high manufacturing and usage after brominated flame retardants were strictly regulated and banned from being distributed and used in many countries. OPFRs are known as the main organic pollutants in the terrestrial and aquatic environment. They are very dangerous to humans, plants and animals. They are also carcinogenic and some have been implicated in neurodevelopmental and fertility challenges. OPFRs are distributed into the environment through a number of processes, including the usage, improper disposal and production of materials. The solid phase extraction (SPE) method is suggested for the extraction of OPFRs from water samples since it provides high quality recoveries ranging from 67% to 105% and relative standard deviations (RSDs) below 20%. In the same vein, microwave-assisted extraction (MAE) is highly advocated for the extraction of OPFRs from sediment/soil. Recoveries in the range of 78% to 105% and RSDs ranging from 3% to 8% have been reported. Hence, it is a faster method of extraction for solid samples and only demands a reduced amount of solvent, unlike other methods. The extract of OPFRs from various matrices is then followed by a clean-up of the extract using a silica gel packed column followed by the quantification of compounds by gas chromatography coupled with a mass spectrometer (GC–MS) or a flame ionization detector (GC-FID). In this paper, different analytical methods for the evaluation of OPFRs in different environmental samples are reviewed. The effects and toxicities of these contaminants on humans and other organisms are also discussed.

Organophosphate esters in atmospheric particles and surface seawater in the western South China Sea

Seven organophosphate esters (OPEs) in atmospheric particles and surface seawater were observed during a cruise in the western South China Sea (SCS) in 2014. The median concentrations of ∑OPEs were 688 pg/m³ and 5.55 ng/L for particle and seawater samples, respectively. Total OPEs were dominated by tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP). The spatial distribution of OPEs indicates that the OPEs in particle phase were mainly influenced by the air masses originating from China, Indochina Peninsula and Malay Archipelago, showing the significant contribution of anthropogenic sources from these regions. Significant positive correlations between Tri-n-butylphosphate (TnBP) and organic carbon (P < 0.05) in particle phase over the western SCS suggests that it might be a potential tracer for the source regions of Indochina Peninsula and Malay Archipelago. The spatial distribution of OPEs in seawater was contributed by freshwater inputs associating with variations of human activities as well as salinity. Seawater pollution levels of OPEs in the eastern coast of Vietnam were increased compared to those measured in the northern SCS. The loadings of ∑OPEs transported to the vast area of western SCS vias atmospheric deposition and air-seawater gas exchange were estimated to be 59 tons/year and 105 tons/year, respectively. This work highlights the importance of transport processes and air-seawater interface behavior of OPEs in the oceanic area.

Insights into the sex-dependent reproductive toxicity of 2-ethylhexyl diphenyl phosphate on zebrafish (Danio rerio)

As a frequently detected organophosphate ester in various environmental media, the toxic effects of 2-ethylhexyl diphenyl phosphate (EHDPHP) on aquatic organisms of different sexes remain unclear. In this study, adult zebrafish were exposed to 2.5, 50, 250 µg/L of EHDPHP for 21 days to investigate its sex-dependent reproductive toxicity and related mechanisms. EHDPHP exposure significantly inhibited the reproduction of zebrafish, evidenced by the reduced spawning of females, depressed growth and development of their offspring. EHDPHP induced greater impacts on the changes of sex hormones and vitellogenin (VTG) in the males than females. For females, the synthesis of testosterone (T) was inhibited because of the down-regulated gnrhr2, gnrhr3, gnrhr4, gnrh3, gnrh2 and er2β in the brain, while 17β-estradiol (E2) increased in 250 µg/L due to up-regulated cyp19a. For males, the promotion of T was directly related to the up-regulation of fshr, 3βhsd, star, cyp11 and cyp17 in the gonad, and eventually led to the increase of E2. The decrease of plasma 11-KT in both sexes could be mainly attributed to the down-regulation of cyp11b and hsd11b. The plasma VTG decreased in females but increased in males, which was in accordance with the down and up regulation of erα and er2β in the females and males, respectively. All these indicated EHDPHP displayed reproductive toxicity on zebrafish in a sex dependent manner. Molecular docking analysis indicated stronger interaction of EHDPHP with the antagonisms of estrogen receptor (ER) and androgen receptor (AR), as well as the agonism of CYP19A1, which further revealed the sex-dependent reproductive toxicity mechanism of EHDPHP. This study highlights the importance of distinguishing males and females in toxicity evaluation of endocrine disruption chemicals.

Levels and Distribution of Organophosphate Esters (OPEs) in Typical Megacity Wetland Park Landscape Water Bodies in Southwest China

Human activities have led to the release of organophosphate esters (OPEs) into the environment. This study aims to investigate the levels and partitioning of OPEs in surface water, suspended particulate matter (SPM) and sediments of landscape waters across eleven parks in the city of Chengdu, a megacity in Southwest China. The average concentration of Σ₆OPEs in the SPM samples (median: 2.94 × 10³ ng/L, 6.88 × 10⁴ ng/g dry weight) was 1-3 orders of magnitude higher than that in the surface water (median: 359 ng/L) and sediment (median: 82.8 ng/g) samples. Tri-n-butyl phosphate (TnBP), tris-(2-chloroethyl)-phosphate (TCEP) and trichloropropyl phosphate (TCIPP) were the primary OPE pollutants in the surface water and SPM samples, while TnBP, tris-(2-butoxyethyl) phosphate (TBEP) and tris-(2-ethylhexyl) phosphate (TEHP) predominated the sediment samples. The higher log K_oc values of OPEs in park landscape water bodies estimated in the present study relative to previous studies could be explained by the environmental conditions, such as the sources of the inputs and the hydraulic retention times in these surface waters.

Organophosphate esters in inland and coastal waters in northern Greece

The occurrence and distribution of organophosphate esters (OPEs) in inland and coastal waters in Thessaloniki, Greece, were studied during the period 2019-2020. Samples from rivers and streams as well as coastal waters, were analyzed for the presence of 11 OPEs in dissolved and particulate fraction. OPEs were ubiquitous pollutants in the aquatic environment. Concentrations of dissolved fraction of ΣOPEs concentrations ranged from 400 to 2158 ng L^-1 in rivers, 400-1270 in coastal sites and 377-30,560 ng L^-1 in streams. TBOEP showed the highest concentrations followed by TPHP, TNBP and TClPP. Significant particulate fractions were determined for TNBP, TClPP TPHP and TCP. Field partition coefficients in inland waters were dependent on the concentration of total suspended solids. Risk assessment did not show potential threat due to OPEs in rivers and coastal sites, however, potential adverse effects were found in streams.

Spatiotemporal distribution and mass loading of organophosphate flame retardants (OPFRs) in the Yellow River of China (Henan segment)

During three sampling periods in 2014, systematic investigations were conducted into contamination profiles of ten organophosphate flame retardants (OPFRs) in both suspended particulate phase and water phase in the Yellow River (Henan Area). This research shows that OPFRs exist at lower concentrations in the suspended phase than in the water phase. The median concentration of 10 OPFRs (∑₁₀OPFRs) in the suspended particulate phase was 62.5 ng/g (fluctuating from ND to 6.17 × 10³ ng/g, dw), while their median concentration in the water phase was 109 ng/L (fluctuating from 35.6 to 469 ng/L). Among the selected 10 OPFRs, triethylphosphate (TEP), tris(1-chloro-2-propyl) phosphate (TCPP), and tris(2-chloroethyl) phosphate (TCEP) were the predominant compounds in the water phase (occupying 91.6% of the ∑₁₀OPFRs), while TCPP, TCEP, and tri-o-tolyl phosphate (o-TCP) were the most common in the suspended particulate phase, accounting for 90.1% of the ∑₁₀OPFRs. Across the three sampling periods, there was no significant seasonable variation for OPFRs either in the water phase or in the suspended particulate phase, except for TCEP and TCPP in the water phase. Compared with research findings relating to concentrations of OPFRs around China and abroad, the OPFRs of the Yellow River (Henan Area) in the water phase were at a moderate level. Suspended particles (SS) had a very important impact on the transportation of OPFRs in the studied area, with about 83.9% of ∑₁₀OPFRs inflow attributed to SS inflow and about 81.7% of ∑₁₀OPFRs outflow attributed to SS outflow. The total annual inflow and outflow of OPFRs were 7.72 × 10⁴ kg and 6.62 × 10⁴ kg in the studied area, respectively.

Organophosphate flame retardants, tetrabromobisphenol A, and their transformation products in sediment of e-waste dismantling areas and the flame-retardant production base

Due to the prohibition of polybrominated diphenyl ethers, organophosphate flame retardants (OPFRs) and tetrabromobisphenol A (TBBPA) have become emerging flame retardants. However, knowledge about their occurrence, especially their transformation products, is still limited. This study collected sediment samples from two rivers, i.e., Lianjiang River (located at an e-waste dismantling area) and Xiaoqing River (situated at a flame retardant production base), to investigate the occurrence, composition, and spatiality distribution of OPFRs, TBBPA, and their transformation products. Both targets were detected in the Lianjiang River in the range of 220-1.4 × 10⁴ and 108-3.1 × 10³ ng/g dw (dry weight) for OPFRs and TBBPA, and 0.11-2.35 and 4.8-414 ng/g dw for their respective transformation products, respectively. The concentrations of OPFRs and TBBPA in the Xiaoqing River ranged from 4.15 to 31.5 and 0.76-2.51 ng/g dw, respectively, and no transformation products were detected. Different compositional characteristics of OPFRs and distinct spatial distribution from mainstream and tributary observed between the two rivers are attributed to the difference in the local industries. Spatial distribution and principal component analysis indicated that e-waste dismantling activities could be a vital source of local pollution. Besides, the confluence of tributaries seemed to determine the contaminant levels in the Xiaoqing River. Also, concentration ratios and Spearman's correlation between metabolites and parent chemicals were analyzed. Low concentration ratios (3.6 ×10^-4 to 0.16) indicated a low transformation degree, and Spearman's correlation analysis suggested transformation products were partly stemming from commercial products. Considering the limited study of these transformation products, more studies on their sources, transform mechanism, and toxicity are required.

Organic pollutants in protected plain areas: The occurrence of PAHs, musks, UV-filters, flame retardants and hydrocarbons in woodland soils

Protected woodlands are rare and small portions of the plain territory of northern Italy, where agricultural, industrial and urban activities strongly dominate the landscape. Such natural areas are frequently set on river floodplains and are therefore potentially conditioned by the contamination brought by the surface waters. We investigated the occurrence of multiple categories of organic pollutants, including Polycyclic Aromatic Hydrocarbons (PAHs), Musk fragrances, UV-filters, organophosphorus and novel brominated Flame Retardants (FRs) and Total Petroleum Hydrocarbons (TPH) in woodland soils of eight different protected areas. The samples collected in the floodplains of the Po, Adige and Fratta rivers resulted more contaminated, with levels of PAHs up to 633 ng g^-1. Moreover, these samples for the first time revealed the presence of personal care products, primarily 2-ethylhexyl-4-methoxycinnamate (EHMC) and tonalide (AHTN), in soils of protected woodlands, reaching respectively 3.4 ng g^-1 and 5.0 ng g^-1, together with the occurrence of both organophosphorus and brominated FRs, with total concentrations up to 15 ng g^-1. Higher concentrations of hydrocarbons, with TPH in the range 5-65 μg g^-1, were instead reflecting the inputs of long chain n-alkanes from epicuticular waxes more than petrogenic contamination.

A review on organophosphate flame retardants in the environment: Occurrence, accumulation, metabolism and toxicity

Organophosphate flame retardants (OPFRs), as a substitute for brominated flame retardants (BFRs), are widely used in industrial production and life. The presence of OPFRs in the environment has an adverse effect on the ecological environment system. This review provides comprehensive data for the occurrence of OPFRs and their diester metabolites (OP diesters) in wastewater treatment plants, surface water, drinking water, sediment, soil, air and dust in the environment. In particular, the accumulation and metabolism of OPFRs in organisms and the types of metabolites and metabolic pathways are discussed for animals and plants. In addition, the toxicity of OP triesters and OP diesters in organisms is discussed. Although research on OPFRs has gradually increased in recent years, there are still many gaps to be filled, especially for metabolic and toxicity mechanisms that need in-depth study. This review also highlights the shortcomings of current research and provides suggestions for a basis for future research on OPFRs.

Occurrence, distribution, and ecological risk assessment of emerging and legacy contaminants in the Kadicha river in Lebanon

The Kadicha river basin in Northern Lebanon is an illustrative example of multiple pressures encountered in the Mediterranean region: it is a small coastal river affected by rapid urbanization, population growth (drastically impacted by the influx of Syrian refugees), and a chronic default of wastewater treatment. In this context, multiple classes of contaminants may attain the river accumulating in sediment. However, very little information is available in the literature on the contamination status in such stressed Mediterranean contexts. This study proposed a first contamination evaluation of a small Mediterranean river submitted to multiple pressures. Two sediment sampling campaigns along sites impacted by increasing urban gradient within the Kadicha river basin were performed to determine the occurrence and the environmental risks of both emerging and legacy contaminants. The results revealed the detection of the 41 studied compounds. The highest concentrations were attained by PAHs and polycyclic musks (up to 311.79, 94.22, and 81.13 ng/g of dry weight for PAH, cashmeran, and galaxolide, respectively). The discontinuous urbanized upstream area and the estuary were the most contaminated areas of the river. An environmental risk assessment showed a hazard quotient (HQ) higher than 1 for both legacy and emerging compounds (EHMC and 4-MBC), indicating a potential risk to benthic species. Monitoring campaigns and implementation of wastewater treatment plants should be encouraged as the anthropogenic pressure on small Mediterranean rivers will increase over the years.

Occurrence and risk assessment of organophosphate esters in urban rivers from Piracicaba watershed (Brazil)

Organophosphate esters (OPEs) are substances globally used as flame retardants and plasticizers that have been detected in all environmental compartments. This study aimed to evaluate the occurrence and sources of ten OPEs in the Piracicaba River Basin (Brazil). Twelve sampling sites were selected in five rivers with different pollution sources; six sampling campaigns were performed encompassing dry and wet seasons. ΣOPEs ranged from 0.12 to 6.2 μg L^-1; the levels in urban areas were higher than in rural and non-urban areas, but no overall tendency concerning the seasonal effect on OPEs concentrations was observed. Tris(2-butoxyethyl) phosphate (TBOEP), tris(2-chloroisopropyl) phosphate (TCIPP), and tris(1,3-dichloroisopropyl) phosphate (TDCIPP) were the most abundant and frequently detected compounds. Nine OPEs were detected at higher concentrations in a site affected by effluents from textile industries. An acute toxicity test using Daphnia similis was performed for tris(2-ethylhexyl) phosphate (TEHP) for the calculation of a preliminary predicted no effect concentration (PNEC). The risk quotient (RQ) approach was applied and risk to aquatic environment related to TEHP levels was observed in areas adjacent to textile industries, but more toxicity studies are required for the determination of a more reliable PNEC.

Human CYP enzyme-activated clastogenicity of 2-ethylhexyl diphenyl phosphate (a flame retardant) in mammalian cells

2-Ethylhexyl diphenyl phosphate (EHDPP) is a common flame retardant and environmental pollutant, exposing humans with endocrinal disrupting potentials. Its mutagenicity, especially following metabolism, remains unclear. In this study, molecular docking analysis indicated that EHDPP was a potential substrate for several human CYP enzymes except for CYP1A1. Among V79-derived cell lines genetically engineered for the expression of each CYP, EHDPP (6 h exposure/18 h recovery) did not induce micronuclei in the V79 or V79-derived cells expressing human CYP1A1, however, it was positive in V79-derived cell lines expressing human CYP2E1, 3A4, and 2B6. In a human hepatoma (HepG2) cell line, EHDPP (48 h exposure) moderately induced micronuclei, which was blocked by 1-aminobenzotriazole (ABT, 60 μM, inhibitor of CYPs); pretreating HepG2 cells with bisphenol AF, another organic pollutant as inducer of CYPs (0.1 μM for 16 h), significantly potentiated micronuclei formation by EHDPP, threshold being decreased from 10 to 1.25 μM. This effect was blocked by ABT, drastically reduced by ketoconazole (inhibiting CYP3A expression/activity), and moderately inhibited by trans-1,2-dichloroethylene (selective CYP2E1 inhibitor). Immunofluorescent centromere protein B staining indicated that EHDPP-induced micronuclei in V79-derived cell lines expressing human CYP2E1 and 3A4 were predominantly centromere-negative, and that in HepG2 cells pretreated with bisphenol AF (for inducing multiple CYPs) were purely centromere-negative. In bisphenol AF-pretreated HepG2 cells EHDPP potently induced DNA breaks, as indicated by the comet assay and Western blot analysis of γ-H2AX. In conclusion, our study suggests that EHDPP is potently clastogenic, following activation by several human CYP enzymes, CYP3A4 being a major one.

Distribution and sources of ordinary monomeric and emerging oligomeric organophosphorus flame retardants in Haihe Basin, China

With the banning of poly-brominated diphenyl ethers, organophosphorus flame retardants (OPFRs) have gained great development space as their alternatives. In this study, the concentration and partition of nine ordinary monomeric OPFRs and two emerging oligomeric OPFRs (Resorcinol bis(diphenyl phosphate) (RDP) and bisphenol A bis(diphenyl phosphate) (BDP) in the Haihe Basin of China were studied, and their possible sources were analyzed. The ƩOPFRs in the surface water, sediments and suspended particulate matters (SPMs) in Haihe Basin were 80.1-777 ng/L, 18.9-86.5 ng/g dw and 6.40-234 ng/g dw, respectively. The detection frequencies of both oligomeric OPFRs exceeded 85%, suggesting their environmental contamination was widespread. The mean concentrations of RDP and BDP were 2.09 and 6.03 ng/L in the surface water, 0.91 and 5.09 ng/g dw in the sediments, 1.08 and 2.61 ng/g dw in SPMs, respectively. With Cl-OPFRs being predominant in all the three media, the proportions of alkyl-OPFRs, aryl-OPFRs, and oligomeric OPFRs in the sediments and SPMs were remarkably higher than those in surface water, suggesting that non-halogenated OPFRs preferred to distribute in solid phases. The water-sediment/SPM partition coefficients, logK_oc, of the OPFRs were calculated based on the paired samples. The logK_oc values of RDP and BDP were reported for the first time, and their logK_{oc water-sediment} were 4.36 ± 0.47 and 4.76 ± 0.25 and their logK_{oc water-SPM} were 3.77 ± 0.45 and 4.00 ± 0.47, respectively. The obtained logK_oc values were correlated with their octanol-water partition coefficient (logK_ow) significantly. It suggested that their partition to sediment or SPM was dominated by hydrophobic interaction. Principal component analysis indicated that the emissions from manufacturing plants and airport operation might be two important sources of OPFRs in the Haihe Basin of China.

Severe contamination and time trends of legacy and novel halogenated flame retardants in multiple environmental media from Lake Shihwa, Korea: Effectiveness of regulatory action

Novel halogenated flame retardants (HFRs) were introduced to industrial markets as alternatives to legacy brominated FRs (BFRs), such as polybrominated diphenyl ethers (PBDEs). In the present study, PBDEs and their brominated and chlorinated alternatives, novel BFRs (NBFRs) and dechlorane plus (DP), were measured in multiple environmental matrices in a highly industrialized lake in Korea. Legacy and novel HFRs were detected in multiple samples, indicating ubiquitous contamination. Concentrations of HFRs in water and sediment observed in creeks running through machine, textiles, and automobile industrial complexes were significantly higher than those observed in inside and outside of the lake. Higher bioaccumulation levels of HFRs were observed in inshore compared with offshore waters. Results suggest that multi-matrix distribution of legacy and novel HFRs was dependent on the geographical proximity to industrial sources. Compared with previous studies, the highest levels of PBDEs and NBFRs were recorded in water samples on a global scale, implying on-going emissions from industrial activities. Decabromodiphenyl ethane (DBDPE) was a dominant compound in water samples, whereas the concentrations of PBDEs, NBFRs, and DP in sediment were similar to each other. This suggests a shift in consumption from legacy to novel HFRs, preferentially in water environments. A significant declining trend in PBDEs was observed in water and sediment collected between 2008 and 2015, indicating the effectiveness of regulatory actions. Based on their environmental occurrence and bioaccumulation potential, pentabromoethylbenzene and bis(2-ethylhexyl) tetrabromophthalate may pose emerging concerns regarding contamination of aquatic environments.

Occurrence, distribution and risk assessment of organophosphate ester flame retardants and plasticizers in surface seawater of the West Pacific

Twenty-eight samples of surface seawater were collected from the West Pacific Ocean during 2019 using a high-volume solid-phase extraction with high-throughput organic analysis (Hi-throat/Hi-volume SPE) method, and concentrations of 10 organophosphate ester flame retardants and plasticizers (OPEs) were determined. The total OPE concentration in the samples was 3.02-48.4 ng L^-1 (mean 25.0 ± 10.5 ng L^-1), with tris(2-chloroethyl) phosphate (TCEP) being the largest contributor. Cluster analysis results showed off-shore input from the coast of East and Southeast Asia was an important source of these chemicals. Tri-p-tolyl phosphate (TpTP) should also be considered for long-term monitoring, because of its high detection frequency. Results of a risk assessment indicated low ecological risk to species in the West Pacific Ocean for TPhP and ΣOPEs. Hazard quotients (HQs) were all <1, indicating that the health risk to humans from these chemicals was at acceptable levels.

Emerging contaminants and priority substances in marine sediments from Cartagena Bay and the Grand Marsh of Santa Marta (Ramsar site), Colombia

Emerging pollutants and priority substances are of growing concern due to their toxicity potential to aquatic organisms and human health. However, few reports on this issue in marine ecosystems in general and, more specifically, on the Colombian Caribbean coast are available. The aim of this study was to detect these compounds in sediments from Cartagena Bay (CB) and in the Grand Marsh of Santa Marta, GMSM (Ramsar site), in order to determine how they related to in vitro cytotoxicity assays on HepG2 cells of sediment extracts. A total of thirty compounds were detected using GC-MS/MS in fifteen stations during both the rainy and the dry seasons. Sediments from CB had a wide range of different toxicants, with polycyclic aromatic hydrocarbons (PAHs) being the most prevalent (12 PAHs, 5.5-881.6 ng/g). Total PCBs ranged from < LOD to 18.6 ng/g, with PCB 138 being the most common detected congener. Residues of p,p'-DDE, Chlorpyrifos and two organophosphate flame retardants, TEHP and ToTP, were found in most sampling locations. The UV filters 4MBC and homosalate were recurrently found in sediments, and the fragrance galaxolide appeared in all cases, with the greatest concentrations found on a touristic beach. In GMSM, with the exception of deltamethrin, all chemicals evaluated had lower average values than in CB. According to sediment quality guidelines, some sites in CB presented values of PAHs higher than the threshold effects level, while in the marsh, none of the stations exceeded it. HepG2 cells exposed to 1% sediment extracts presented reduced cell viability up to 26%. Cytotoxicity displayed a negative correlation with chlorpyrifos concentration. In short, these data suggest the bay and the marsh have specific contamination fingerprints related to anthropogenic interventions. This research highlights the need to further investigate the ecotoxicological implications of detected chemical stressors in these ecosystems.

A review on the occurrence of organophosphate flame retardants in the aquatic environment in China and implications for risk assessment

Organophosphate flame retardants (OPFRs), used extensively as substitutes for polybrominated diphenyl ethers, are ubiquitous environmental contaminants. OPFR pollution in aquatic environments, the main sink of pollutants, has been studied extensively over the past decade. Here, we review the current knowledge on the consumption and applications of OPFRs, and on their ecotoxicity in aquatic environments worldwide. We also synthesize the available evidence on the occurrence of OPFRs in aquatic environments in China (wastewater treatment plant influent and effluent, surface water, sediment, aquatic biota, and drinking water). Across China, the measured concentrations of OPFRs differ by more than three orders of magnitude. Risk assessments based on these measurements indicate a low level of ecological risk from OPFRs in most aquatic environments in China, and a low risk to human health from drinking water and aquatic products. Finally, we identify gaps in the current knowledge and directions for further research on OPFRs in aquatic environments.

Occurrence of organophosphate esters in surface water and sediment in drinking water source of Xiangjiang River, China

In this study, we investigated the occurrence of organophosphate esters (OPEs) in the surface water and sediments of the Xiangjiang (XJ) River, a drinking water source of Changsha City. The total concentrations of five detected OPEs (Σ₅OPEs) in surface water and tap water were 6.07-25.3 ng L^-1 (average 14.9 ± 4.98 ng L^-1), and 23.6 ng L^-1, respectively, and four detected OPEs (Σ₄OPEs) in sediments were 3.74-27.5 ng g^-1 dw (average 12.1 ± 6.48 ng g^-1 dw). Tris-2-chloroisopropyl phosphate (TCIPP) was the dominant contributor in water and sediment samples, accounting for over 40% of ΣOPEs. A particular flood event during July-August 2020 reduced the level of OPEs in river water, leading to generally uniform OPE concentrations in surface water and sediment samples from the upper, middle, and lower reaches of XJ. Principal component analysis-multiple linear regression (PCA-MLR) results indicated that the main sources of OPEs in the surface water and sediments of XJ were emissions of waste-water treatment plants and anthropocentric activities. The results of ecological and human health risk assessments indicated that all OPEs posed a low or negligible ecological risk for algae, daphnia, and fish, and negligible risk for human health. Interestingly, the concentration and human health risk of OPEs in a composite tap water sample was generally higher than those in river water samples, indicating possible OPE contamination from water treatment processes or transportation through pipe networks.

Long-Range Transport, Trophic Transfer, and Ecological Risks of Organophosphate Esters in Remote Areas

Organophosphate esters (OPEs) have been a focus in the field of environmental science due to their large volume production, wide range of applications, ubiquitous occurrence, potential bioaccumulation, and worrisome ecological and health risks. Varied physicochemical properties among OPE analogues represent an outstanding scientific challenge in studying the environmental fate of OPEs in recent years. There is an increasing number of studies focusing on the long-range transport, trophic transfer, and ecological risks of OPEs. Therefore, it is necessary to conclude the OPE pollution status on a global scale, especially in the remote areas with vulnerable and fragile ecosystems. The present review links together the source, fate, and environmental behavior of OPEs in remote areas, integrates the occurrence and profile data, summarizes their bioaccumulation, trophic transfer, and ecological risks, and finally points out the predominant pollution burden of OPEs among organic pollutants in remote areas. Given the relatively high contamination level and bioaccumulation/biomagnification behavior of OPEs, in combination with the sensitivity of endemic species in remote areas, more attention should be paid to the potential ecological risks of OPEs.

Occurrence and spatio-seasonal distribution of organophosphate tri- and di-esters in surface water from Dongting Lake and their potential biological risk

In this study, 24 surface water samples were collected from Dongting Lake, China, in the wet and dry seasons, then the concentrations, composition profiles and spatio-seasonal variations of nine organophosphate triesters (OPEs) and five organophosphate diesters (Di-OPs) were determined. Significantly higher total OPE concentrations (∑OPEs) were observed in the wet season (49.5-148 ng L^-1) than in the dry season (5.00-45.7 ng L^-1) suggesting higher input via tributaries discharge as well as wet deposition in the studied region. Whereas lower levels of TnBP and (triphenyl phosphate (TPHP) in wet season reflected their possible degradation under solar irradiation. Comparable levels of total Di-OPs (∑Di-OPs) were found in the wet season (3.41-13.9 ng L^-1) and dry season (1.01-12.3 ng L^-1). Tri(2-chloroethyl) phosphate and tris(2-chloroisopropyl) phosphate were the main OPE components, while diphenyl phosphate, di-n-butyl phosphate and bis(1,3-dichloro-2-propyl) phosphate were the main Di-OP components. High levels of OPEs and Di-OPs were found in Datong Lake suggesting possible local emissions potentially related to fishery activity in the land-locked lake. Samples at river mouths to the lake also have higher levels of target OPEs and Di-OPs, the results disclosed obvious discharges from tributaries in Hunan Province. Negligible non-carcinogenic and carcinogenic risks were determined based on the measured concentrations in source waters. A limited ecological risk aquatic organisms in the Dongting Lake was identified, with most risk from TPHP.

Occurrence, bioaccumulation, fate, and risk assessment of novel brominated flame retardants (NBFRs) in aquatic environments - A critical review

Novel brominated flame retardants (NBFRs), which have been developed as replacements for legacy flame retardants such as polybrominated diphenyl ethers (PBDEs), are a class of alternative flame retardants with emerging and widespread applications. The ubiquitous occurrence of NBFRs in the aquatic environments and the potential adverse effects on aquatic organisms have initiated intense global concerns. The present article, therefore, identifies and analyzes the current state of knowledge on the occurrence, bioaccumulation, fates, and environmental and health risks of NBFRs in aquatic environments. The key findings from this review are that (1) the distribution of NBFRs are source-dependent in the global aquatic environments, and several NBFRs have been reported at higher concentrations than that of the legacy flame retardants; (2) high bioaccumulative properties have been found for all of the discussed NBFRs due to their strong hydrophobic characteristics and weak metabolic rates; (3) the limited information available suggests that NBFRs are resistant to biotic and abiotic degradation processes and that sorption to sludge and sediments are the main fate of NBFRs in the aquatic environments; (4) the results of ecological risk assessments have indicated the potential risks of NBFRs and have suggested that source areas are the most vulnerable environmental compartments. Knowledge gaps and perspectives for future research regarding the monitoring, toxicokinetics, transformation processes, and development of ecological risk assessments of NBFRs in aquatic environments are proposed.

Establishment of a Target, Suspect, and Functional Group-Dependent Screening Strategy for Organophosphate Esters (OPEs): "Into the Unknown" of OPEs in the Sediment of Taihu Lake, China

Current environmental monitoring studies are generally confined to several target organophosphate esters (OPEs), and there is a lack of strategies for comprehensively screening all potential OPEs in environmental samples. Here, an effective and accurate strategy was developed for the target, suspect, and functional group-dependent screening of OPEs by the use of ultrahigh-performance liquid chromatography-Q Exactive hybrid quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap HRMS), and this strategy was applied for the analysis of n = 74 sediment samples (including 23 surface sediment samples and 51 sediment core samples) collected from Taihu Lake (eastern China) in 2019. In these analyzed samples, we successfully identified n = 35 OPEs, and 23 of them were reported in this region for the first time. In addition, this strategy also presented other interesting findings, i.e., (1) OPE concentrations decreased with increasing distance from the coast of the lake; (2) the newly identified 3-hydroxyphenyl diphenyl phosphate (meta-OH-TPHP) was not statistically significantly correlated with triphenyl phosphate (TPHP; r = 0.02494, p = 0.9101) but with resorcinol bis(diphenyl phosphate) (RDP) (r = 0.9271, p < 0.0001) and three other OPEs; and (3) the summed concentrations of aryl OPEs (∑_arylOPEs) in sediment core samples exhibited significantly increasing trends as the depth decreased. Collectively, this study provided an effective strategy that was successfully applied for comprehensive screening of OPEs in the sediments of Taihu Lake, and this strategy could have promising potential to be extended to other environmental matrices or samples.

Maternal Transfer of 2-Ethylhexyl Diphenyl Phosphate Leads to Developmental Toxicity Possibly by Blocking the Retinoic Acid Receptor and Retinoic X Receptor in Japanese Medaka (Oryzias latipes)

2-Ethylhexyl diphenyl phosphate (EHDPP) has been detected in wild fish with high concentrations, which may pose a risk in the embryo development considering its potential maternal transfer. In this study, EHDPP was demonstrated to elicit antagonistic activity to medaka retinoic acid receptor (mRAR) and retinoic X receptor (mRXR) with 50% inhibitory concentration of 18 and 36 μM, respectively. After adult female medaka were exposed to EHDPP at 156, 405, and 1161 ng/L for 35 days, the embryonic EHDPP concentrations (364-4824 ng/g lipid weight (lw)) were higher than those in the maternal tissues (15.0-4166 ng/g lw), showing notable maternal transfer. The embryonic concentration of EHDPP decreased limitedly during 1-2 day post-fertilization (dpf, the main developmental window of eye) but then decreased sharply after 2 dpf. The transcript abundance of cyp26a1 was inhibited and subsequent increasing embryonic all-trans RA level was observed in embryos, showing RAR/RXR antagonistic activity. These results may specifically contribute to the increased eye deformity incidences in all exposure groups (up to 8.0%; 51/637) relative to the control (1.0%, 7/733). The response behavior of the larvae to light stimulation was impaired in a dose-dependent manner, demonstrating a vision disorder. Because such developmental toxicities were observed at the environmental level, EHDPP may pose a threat to the survival of wild larvae and therefore a population risk for wild fish.

In vitro metabolic kinetics of cresyl diphenyl phosphate (CDP) in liver microsomes of crucian carp (Carassius carassius)

Cresyl diphenyl phosphate (CDP), as a kind of aryl substituted organophosphate esters (OPEs), is commonly used as emerging flame retardants and plasticizers detected in environmental media. Due to the accumulation of CDP in organisms, it is very important to discover the toxicological mechanism and metabolic process of CDP. Hence, liver microsomes of crucian carps (Carassius carassius) were prepared for in vitro metabolism kinetics assay to estimate metabolism rates of CDP. After 140 min incubation, the depletion of CDP accounted for 58.1%-77.1% (expect 0.5 and 2 μM) of the administrated concentrations. The depletion rates were best fitted to the Michaelis-Menten model (R² = 0.995), where maximum velocity (V_max) and Michaelis-Menten constant (K_m) were 12,700 ± 2120 pmol min^-1·mg^-1 protein and 1030 ± 212 μM, respectively. Moreover, the in vitro hepatic clearance (C_Lint) of CDP was 12.3 μL min^-1·mg^-1 protein. Log K_ow and bioconcentration factor (BCF) of aryl-OPEs were both higher than those of alkyl- and chlorinated-OPEs, indicating that CDP may easily accumulate in aquatic organisms. The results made clear that the metabolism rate of CDP was greater than those of other OPEs detected in liver microsomes in previous research. This paper was first of its kind to comprehensively investigate the in vitro metabolic kinetics of CDP in fish liver microsomes. The present study might provide useful information to understand the environmental fate and metabolic processes of these kinds of substances, and also provide a theoretical basis for the ecological risk assessment of emerging contaminants.

Exposure to organophosphate flame esters during early pregnancy and risk of spontaneous abortion: A case-control study

Prenatal exposure to organophosphate flame retardants (OPFRs) has been associated with adverse pregnancy outcomes including low birth weight and preterm birth. However, no study has addressed the impacts of OPFRs exposure on spontaneous abortion (SAB) and fetal chromosome abnormalities. We examined whether prenatal exposure to OPFRs was associated with increased risk of SAB and fetal chromosome abnormalities. A total of 272 pregnant women, including 136 SAB cases and 136 healthy controls, were enrolled in this case-control study. Urinary concentrations of 3 OPFRs metabolites (diphenyl phosphate (DPHP), bis (1,3-dichloro-2-propyl) phosphate (BDCIPP) and bis (1-chloro-2-propyl) phosphate (BCIPP)) were measured using ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). More than 70% of the urine samples detected quantifiable levels of 3 OPFRs metabolites. Concentrations of BCIPP were significantly higher in SAB cases than in healthy controls. Higher urinary BCIPP levels were associated with increased risk of SAB. Per unit increase in ln-transformed BCIPP concentrations was associated with 103% (OR = 2.03, 95% CI, 1.57, 2.63) increase in the odds of SAB. While higher BDCIPP levels were associated with increased risk of fetal chromosome abnormalities and the corresponding OR associated with a unit increase in ln-transformed BDCIPP concentrations were 2.34 (95% CI, 1.14, 4.81). Our results suggested the potential developmental toxicity and teratogenicity of some OPFRs.

Phthalates and organophosphate esters in surface water, sediments and zooplankton of the NW Mediterranean Sea: Exploring links with microplastic abundance and accumulation in the marine food web

In this study, surface seawater, sediment and zooplankton samples were collected from three different sampling stations in Marseille Bay (NW Mediterranean Sea) and were analyzed for both microplastics and organic plastic additives including seven phthalates (PAEs) and nine organophosphate esters (OPEs). PAE concentrations ranged from 100 to 527 ng L^-1 (mean 191 ± 123 ng L^-1) in seawater, 12-610 ng g^-1 dw (mean 194 ± 193 ng g^-1 dw) in sediment and 0.9-47 μg g^-1 dw (mean 7.2 ± 10 μg g^-1 dw) in zooplankton, whereas OPE concentrations varied between 9 and 1013 ng L^-1 (mean 243 ± 327 ng L^-1) in seawater, 13-49 ng g^-1 dw (mean 25 ± 11 ng g^-1 dw) in sediment and 0.4-4.6 μg g^-1 dw (mean 1.6 ± 1.0 μg g^-1 dw) in zooplankton. Microplastic counts in seawater ranged from 0 to 0.3 items m^-3 (mean 0.05 ± 0.05 items m^-3). We observed high fluctuations in contaminant concentrations in zooplankton between different sampling events. However, the smallest zooplankton size class generally exhibited the highest PAE and OPE concentrations. Field-derived bioconcentration factors (BCFs) showed that certain compounds are prone to bioaccumulate in zooplankton, including some of the most widely used chlorinated OPEs, but with different intensity depending on the zooplankton size-class. The concentration of plastic additives in surface waters and the abundance of microplastic particles were not correlated, implying that they are not necessarily good indicators for each other in this compartment. This is the first comprehensive study on the occurrence and temporal variability of PAEs and OPEs in the coastal Mediterranean based on the parallel collection of water, sediment and differently sized zooplankton samples.

Occurrence and risk evaluation of organophosphorus flame retardants in two urban rivers in Yangtze River Delta

The occurrence and profiles of organophosphate flame retardants (OPFRs) were investigated in the Huangpu and Shiwuli Rivers, two urban rivers in the Yangtze River Delta, China. The total concentrations of OPEs were found at part-per-trillion ranges, with average concentrations that ranged from 424 to 1.84 × 10³ ng L^-1 for Huangpu River and 221 to 1.84 × 10³ ng L^-1 for Shiwuli River. Three chlorinated OPFRs including tris(chloroethyl) phosphate (TCEP), tris(2-chloroisopropyl) phosphate (TCIPP), and tris(1,3-dichloroisopropyl) phosphate (TDCIPP) were the most abundant compounds among the investigated OPFRs, accounting for 90.6-99.8% of total concentrations. In Huangpu River, the OPFR concentrations were significantly higher in the dry season than in the wet season which indicates obvious seasonal variation. Chlorinated OPFR concentrations differed significantly between upstream and downstream reaches of the Shiwuli River, as the result of geographic features and wastewater discharge. Estimated risk was calculated to compare predicted no-effect concentrations (PNEC) to observed concentrations of OPFRs. The results indicated no significant acute adverse effects of OPFRs in the two urban rivers for fish, daphnia, or algae.

Embryotoxicity characterization of the flame retardant tris(1-chloro-2-propyl)phosphate (TCPP) in the invertebrate chordate Ciona intestinalis

Tris(1-chloro-2-propyl)phosphate (TCPP) is the most common chlorinated organophosphorus flame retardant in seawater. Due to its chemical features and abundance, TCPP has been classified as a high hazard, and restrictions of use have been set in multiple countries. Despite TCPP being highly present in the marine environment, only a few studies have explored the TCPP impact on the development of marine invertebrates. Ascidians are important invertebrate members of benthic marine communities and reliable model systems for ecotoxicological research. The aim of this study was to assess the adverse effects of TCPP exposure on the embryogenesis of the ascidian Ciona intestinalis. Our results showed that this pollutant affected both muscles and nervous system development. Malformations appeared similar to those reported in other animal models for other flame retardants, suggesting that these molecules could share a common mechanism of action and induce a mixture effect when simultaneously present in the aquatic environment even at sub-teratogenic concentrations.

Responses of the reproduction, population growth and metabolome of the marine rotifer Brachionus plicatilis to tributyl phosphate (TnBP)

The typical alkyl organophosphorus flame retardant tributyl phosphate (TnBP) can leak from common products into the marine environment, with potential negative effects on marine organisms. However, risk assessments for TnBP regarding zooplankton are lacking. In this study, a marine rotifer, Brachionus plicatilis, was used to analyze the effect of TnBP (0.1 μg/L, environmental concentration; 1 and 6 mg/L) on reproduction, population growth, oxidative stress, mitochondrial function and metabolomics. Mortality increased as the TnBP concentration rose; the 24-h LC50 value was 12.45 mg/L. All tested TnBP concentrations inhibited B. plicatilis population growth, with reproductive toxicity at the higher levels. Microstructural imaging showed ovary injury, the direct cause of reproductive toxicity. Despite elevated glutathione reductase activities, levels of reactive oxygen species and malonyldialdehyde increased under TnBP stress, indicating oxidative imbalance. TnBP induced mitochondrial malformation and activity suppression; the ROS scavenger N-acetylcysteine alleviated this inhibition, suggesting an internal connection. Nontargeted metabolomics revealed 398 and 583 differentially expressed metabolites in the 0.1 μg/L and 6 mg/L treatments relative to control, respectively, which were enriched in the pathways such as biosynthesis of amino acids, purine metabolism, aminoacyl-tRNA biosynthesis. According to metabolic pathway analysis, oxidative stress from purine degradation, mitochondrial dysfunction, disturbed lipid metabolism and elevated protein synthesis were jointly responsible for reproduction and population growth changes. This study echoes the results previously found in rotifer on trade-off among different life processes in response to environmental stress. Our systematic study uncovers the TnBP toxic mode of action.

Occurrence and trophic transport of organic compounds in sedimentation ponds for road runoff

Sedimentation ponds have been shown to accumulate several groups of contaminants, most importantly polycyclic aromatic compounds (PACs) and metals. But also, other urban organic pollutants have shown to be present, including polybrominated diphenyl ethers (PBDEs), organophosphate compounds (OPCs) and benzothiazoles (BTs). This investigation aimed at determining the occurrence of these four groups of contaminants in sedimentation ponds and determine their transport from water/sediment to organisms. PACs, including alkylated PACs, PBDEs; OPCs and BTs were determined in water, sediment, plants, dragonfly larvae and fish from two sedimentation ponds and one reference site. Fish were analysed for PAC metabolites. Overall, higher concentrations of all four pollutant groups were detected in water and sediment from sedimentation ponds compared to two natural lakes in rural environments (reference sites). The concentration difference was highest in sediments, and >20 higher concentration was measured in sedimentation ponds (3.6-4.4 ng/g ww) compared to reference (0.2 ng/g ww) for sum BDE6. For PACs and PBDEs a clear transport from water/sediment to organisms were observed. Fish were the highest trophic level organism (3.5-5) in our study, and all four pollutant groups were detected in fish. For PBDEs a trophic biomagnification (TMF) was found both in sedimentation ponds and reference, but higher concentrations in all matrices were measured in sedimentation ponds. TMF was not calculated for PACs since they are metabolised by vertebrates, but a transfer from water/sediment to organisms was seen. For BTs and OPCs, no consistent transfer to plants and dragonfly larvae could be seen. One OPC and two BTs were detected in fish, but only in fish from sedimentation ponds. It is therefore concluded that sedimentation ponds are hotspots for urban and traffic related contaminants, of which especially PACs and PBDEs are transferred to organisms living there.

Modified organophosphorus fire retardant with low toxicity/high flame retardancy using the pharmacophore model associated with Mamdani fuzzy inference approach

The bi-directional selective low toxicity/high flame retardancy organophosphorus fire retardants (OPFRs) derivatives were designed by a comprehensive effect 3D quantitative structure-activity relationship (QSAR) pharmacophore model, and the toxicity and flame retardancy mechanism of OPFR derivatives were explored. The 3D-QSAR comprehensive pharmacophore model was constructed using the toxicity/flame retardancy comprehensive evaluation values of OPFRs for molecular modifications, which were obtained by the Mamdani fuzzy inference approach. The environment-friendly OPFR derivatives (CDPP-F, CDPP-NO2, TPHP-F, TDCIPP-CH2CH3, and TDCIPP-Br) with high flame retardancy showed significantly reduced multi-toxicity effects (biotoxicity, reproductive toxicity, and neurotoxicity) in the comprehensive model. The spatial overlapping volumes of the toxicity/flame retardancy comprehensive effect model with the toxic effect and with flame retardant effect were 1 : 1. The trend (1 : 1) was similar to the degree of improvement of toxicity and flame retardancy of the OPFR derivatives. The toxicity and flame retardancy were decreased by more than 50%. This indicated that the spatial overlapping volumes in the comprehensive model with the toxic and flame retardant mono-models have significant effects. Based on the 2D-QSAR model, molecular docking, and density functional theory, it was found that, in molecular modification, the introduction of electronegative groups to improve the electronic parameters (q+) can reduce the toxicity of OPFRs. An increase in the bond length and bond angle of the molecular side chain increased the steric parameter (MR) that improved the molecular flame retardancy of OPFRs.

Legacy and novel flame retardants in water and sediment from highly industrialized bays of Korea: Occurrence, source tracking, decadal time trend, and ecological risks

Legacy and novel flame retardants (FRs) such as polybrominated diphenyl ethers (PBDEs), novel BFRs, and organophosphate flame retardants (OPFRs) were measured in water and sediment collected from highly industrialized bays of Korea. Predominant compounds in sediment were BDE 209, DBDPE, and BTBPE for BFRs, and TCPP and TBOEP for OPFRs, respectively. Higher alternative FR concentrations were observed compared to those reported for previous studies. The highest BFR concentrations were found in locations close to industrial complexes, while the OPFR concentrations were highest in locations close to domestic regions and a wastewater treatment plant. Different contamination sources were observed for BFRs and OPFRs. The ratio of DBDPE/BDE 209 in sediment ranged from 0.84 to 28, indicating a shift in consumption of BFRs. A significant decline in PBDEs suggests the effectiveness of domestic and global regulations. Despite this, sedimentary PBDE concentrations may pose adverse health risks to benthic organisms and humans.

Toxicity of tris(2-chloroethyl) phosphate in Daphnia magna after lifetime exposure: Changes in growth, reproduction, survival and gene transcription

In recent years, with the elimination of brominated flame retardants (BFRs), the product volume of tris(2-chloroethyl) phosphate (TCEP), as a main substitute of BFRs, was increasing and frequently detected in natural waters. However, the current toxicological studies on TCEP were mainly focused on the partial life stage assessment of model animals, and thus it might underestimate the impact of TCEP on environmental risks. Therefore, the whole-life-stage effects of TCEP on growth, reproduction, survival and gene transcription in Daphnia magna (D. magna) were studied in this study after exposure to environmentally relevant or greater concentrations (500 or 5000 ng/L). It was found that chronic exposure to TCEP at environmental relevant or greater concentrations promoted growth of D. magna and the expressions of genes involved in the pathways associated with growth were significantly up-regulated. TCEP did not affect reproduction of D. magna, but the expressions of some genes screened in reproduction stage were significantly changed. Furthermore, the expressions of genes involved in two heart disease-related pathways were down-regulated at the death stage of D. magna after TCEP exposure for 62 days, suggesting that TCEP delayed the death of D. magna by retarding their heart senility.