Assessment of organophosphorus flame retardants and plasticizers in aquatic environments of China (Pearl River Delta, South China Sea, Yellow River Estuary) and Japan (Tokyo Bay)

Biodegradation pathway and mechanism of tri (2-chloropropyl) phosphate by Providencia rettgeri

Tri (2-chloropropyl) phosphate (TCPP) was an emerging contaminant of global concern because of its frequent occurrence, potential toxic effects, and persistence in the environment. Microbial degradation might be an efficient and safe removal method, but limited information was available. In this study, Providencia rettgeri was isolated from contaminated sediment and showed it could use TCPP as unique phosphorus source to promote growth, and decompose 34.7% of TCPP (1 mg/L) within 5 days. The microbial inoculation and the initial concentration of TCPP could affect the biodegradation efficient. Further study results indicated that TCPP decomposition by Providencia rettgeri was mainly via phosphoester bond hydrolysis, evidenced by the production of bis (2-chloropropyl) phosphate (C6H13Cl2PO4) and mono-chloropropyl phosphate (C3H8ClPO4). Both intracellular and extracellular enzymes could degrade TCPP, but intracellular degradation was dominant in the later reaction stage, and the presence of Cu2+ ions had a promoting effect. These findings developed novel insights into the potential mechanism of TCPP microbial degradation.

A review of the present methods used to remediate soil and water contaminated with organophosphate esters and developmental directions

Organophosphate esters (OPEs) are widely used commercial additives, but their environmental persistence and toxicity raise serious concerns necessitating associated remediation strategies. Although there are various existing technologies for OPE removal, comprehensive screening for them is urgently needed to guide further research. This review provides a comprehensive overview of the techniques used to remove OPEs from soil and water, including their related influencing factors, removal mechanisms/degradation pathways, and practical applications. Based on an analysis of the latest literature, we concluded that (1) methods used to decontaminate OPEs include adsorption, hydrolysis, photolysis, advanced oxidation processes (AOPs), activated sludge processes, and microbial degradation; (2) factors such as the quantity/characteristics of the catalysts/additives, pH value, inorganic ion concentration, and natural organic matter (NOM) affect OPE removal; (3) primary degradation mechanisms involve oxidation induced by reactive oxygen species (ROS) (including •OH and SO4•-) and degradation pathways include hydrolysis, hydroxylation, oxidation, dechlorination, and dealkylation; (5) interference from the pH value, inorganic ion and the presence of NOM may limit complete mineralization during the treatment, impacting practical application of OPE removal techniques. This review provides guidance on existing and potential OPE removal methods, providing a theoretical basis and innovative ideas for developing more efficient and environmentally friendly techniques to treat OPEs in soil and water.

Organophosphate ester in surface water of the Pearl River and South China Sea, China: Spatial variations and ecological risks

This study focused on investigating the concentrations, compositional profiles, partitioning behaviors and spatial variations of organophosphate esters (OPEs) in the Pearl River (PR), South China Sea (SCS) region, to evaluate their environmental risks. ∑OPEs concentrations in the surface water of the PR ranged from 117.5 to 854.8 ng/L in the dissolved phase and from 0.5 to 13.3 ng/L in the suspended particulate matter. In the surface seawaters of the northern and western parts of the SCS, ∑OPEs concentrations were 1.3-17.6 ng/L (mean: 6.7 ± 5.2) and 2.3-24.4 ng/L (mean: 7.6 ± 5.5), respectively. The percentage of chlorinated OPEs in surface water samples from the PR to the SCS was 79 ± 15%. Tripentyl phosphate (TPeP) (average: 28.3%) and triphenylphosphate (TPhP) (average: 9.6%) exhibited significant particulate fraction. A significant negative correlation (p < 0.05) between salt concentration and OPE congeners in seawater suggested that river runoff predominantly introduced OPEs into the coastal waters of the SCS. The findings also showed higher levels of OPEs in the PR and estuary than in offshore waters. The OPE loading from the PR into the SCS was estimated to be ∼119 t y-1. The presence of TCEP (RQmax = 2.1), TnBP (RQmax = 0.48) and TPhP (RQmax = 0.3) in PR water samples pose a high risk to aquatic organisms, whereas OPEs (RQ < 0.1) in SCS water samples do not pose a threat to aquatic organisms. This research emphasizes the environmental fate and impact of OPEs on surface waters of the PR and SCS.

Organophosphate esters (OPEs) pollution characteristics, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, China

As the substitutes of polybrominated diphenyl ethers, organophosphate esters (OPEs) with high concentrations have accumulated in the estuaries, bays, and harbors. However, limited information is available about the OPEs in the estuary organism categories, especially under the multiple industrial pressure. This study investigated the occurrence, bioaccumulation and human consumption implication in wild marine organisms from the Yellow River Estuary, where located many petroleum and chemical manufacturing industries. This study found that concentrations of Σ13OPEs ranged from 547 ng/L to 1164 ng/L in seawater (median: 802 ng/L), from 384 to 1366 ng/g dw in the sediment (median: 601 ng/g dw), and from 419 to 959 ng/g dw (median: 560 ng/g dw) in the marine organisms. The congener compositions in the organisms were dominated by alkyl-OPEs (80.7 %), followed by halogenated-OPEs (18.8 %) and aryl-OPEs (0.5 %). Based on the principal component analysis, petrochemical pollution, and industrial wastewater discharge were distinguished as the main plausible sources of OPEs to the YRE ecosystem. Most OPEs had potential or strong bioaccumulation capacity on the organisms, with a positive correlation between log BAF (Bioaccumulation Factor) and log Kow of OPEs. The highest estimated daily intake value of OPEs was tri-n-propyl phosphate, exceeding 300 ng/kg·bw/day via consuming fish. The highest hazard quotients from OPEs ranged from 0.001 to 0.1, indicating a low risk to human health by consuming marine organisms in the YRE. As the consumption of OPEs increases year by year, the risks of OPEs still cannot be ignored.

Metabolic activity of gut microbial enrichment cultures from different marine species and their transformation abilities to plastic additives

The role of the gut microbiota in host physiology has been previously elucidated for some marine organisms, but little information is available on their metabolic activity involved in transformation of environmental pollutants. This study assessed the metabolic profiles of the gut microbial cultures from grouper (Epinephelus coioides), green mussel (Perna viridis) and giant tiger prawn (Penaeus monodon) and investigated their transformation mechanisms to typical plastic additives. Community-level physiological profiling analysis confirmed the utilization profiles of the microbial cultures including carbon sources of carbohydrates, amines, carboxylic acids, phenolic compounds, polymers and amino acids, and the plastic additives of organophosphate flame retardants, tetrabromobisphenol A derivates and bisphenols. Using in vitro incubation, triphenyl phosphate (TPHP) was found to be rapidly metabolized into diphenyl phosphate by the gut microbiota as a representative ester-containing plastic additive, whereas the transformation of BPA (a representative phenol) was relatively slower. Interestingly, all three kinds of microbial cultures efficiently transformed the hepatic metabolite of BPA (BPA-G) back to BPA, thereby increasing its bioavailability in the body. The specific enzyme analysis confirmed the ability of the gut microbiota to perform the metabolic reactions. The results of 16S rRNA sequencing and network analysis revealed that the genera Escherichia-Shigella, Citrobacter, and Anaerospora were functional microbes, and their collaboration with fermentative microbes played pivotal roles in the transformation of the plastic additives. The structure-specific transformations by the gut microbiota and their distinct bioavailability deserve more attention in the future.

Organophosphate esters (OPEs) in corals of the South China Sea: Occurrence, distribution, and bioaccumulation

Organophosphate esters (OPEs) have garnered significant attention in recent years. In view of the enormous ecosystem services value and severe degradation of coral reefs in the South China Sea, this study investigated the occurrence, distribution, and bioaccumulation of 11 OPEs in five coral regions: Daya Bay (DY), Weizhou Island (WZ), Sanya Luhuitou (LHT), Xisha (XS) Islands, and Nansha (NS) Islands. Although OPEs were detected at a high rate, their concentration in South China Sea seawater (1.56 ± 0.89 ng L-1) remained relatively low compared to global levels. All OPEs were identified in coral tissues, with Luhuitou (575 ± 242 ng g-1 dw) showing the highest pollution levels, attributed to intense human activities. Coral mucus, acting as a defense against environmental stresses, accumulated higher ∑11OPEs (414 ± 461 ng g-1 dw) than coral tissues (412 ± 197 ng g-1 dw) (nonparametric test, p < 0.05), and their compositional characteristics varied greatly. In the case of harsh aquatic environments, corals increase mucus secretion and then accumulate organic pollutants. Tissue-mucus partitioning varied among coral species. Most OPEs were found to be bioaccumulative (BAFs >5000 L kg-1) in a few coral tissue samples besides Triphenyl phosphate (TPHP). Mucus' role in the bioaccumulation of OPEs in coral shouldn't be ignored.

Global responses to tris(1-chloro-2-propyl) phosphate and tris(2-butoxyethyl) phosphate in Escherichia coli: Evidences from biomarkers, and metabolic disturbance using GC-MS and LC-MS metabolomics analyses

Tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-butoxyethyl) phosphate (TBEP) as pollutants of emerging concern have aroused the rising attention due to their potential risks on aquatic ecosystem and public health. Nevertheless, there is a lack of toxicological mechanisms exploration of TCPP and TBEP at molecular levels. Herein, the toxicity effects and molecular mechanism of them were fully researched and summarized on Escherichia coli (E.coli). Acute exposure to them significantly activated antioxidant defense system and caused lipid peroxidation, as proved by the changes of antioxidant enzymes and MDA. The ROS overload resulted in the drop of membrane potential as well as the downregulated synthesis of ATPase, endorsing that E. coli cytotoxicity was ascribed to oxidative stress damage induced by TCPP and TBEP. The combination of GC-MS and LC-MS based metabolomics validated that TCPP and TBEP induced metabolic reprogramming in E.coli. More specifically, the responsive metabolites in carbohydrate metabolism, lipids metabolism, nucleotide metabolism, amino acid metabolism, and organic acids metabolism were significantly disturbed by TCPP and TBEP, confirming the negative effects on metabolic functions and key bioprocesses. Additionally, several biomarkers including PE(16:1(5Z)/15:0), PA(17:1(9Z)/18:2(9Z,12Z)), PE(19:1(9Z)/0:0), and LysoPE(0:0/18:1(11Z)) were remarkably upregulated, verifying that the protection of cellular membrane was conducted by regulating the expression of lipids-associated metabolites. Collectively, this work sheds new light on the potential molecular toxicity mechanism of TCPP and TBEP on aquatic organisms, and these findings using GC-MS and LC-MS metabolomics generate a fresh insight into assessing the effects of OPFRs on target and non-target aquatic organisms.

Combined Computational and Experimental Study Reveals Complex Mechanistic Landscape of Brønsted Acid-Catalyzed Silane-Dependent P═O Reduction

The reaction mechanism of Brønsted acid-catalyzed silane-dependent P═O reduction has been elucidated through combined computational and experimental methods. Due to its remarkable chemo- and stereoselective nature, the Brønsted acid/silane reduction system has been widely employed in organophosphine-catalyzed transformations involving P(V)/P(III) redox cycle. However, the full mechanistic profile of this type of P═O reduction has yet to be clearly established to date. Supported by both DFT and experimental studies, our research reveals that the reaction likely proceeds through mechanisms other than the widely accepted "dual activation mode by silyl ester" or "acid-mediated direct P═O activation" mechanism. We propose that although the reduction mechanisms may vary with the substitution patterns of silane species, Brønsted acid generally activates the silane rather than the P═O group in transition structures. The proposed activation mode differs significantly from that associated with traditional Brønsted acid-catalyzed C═O reduction. The uniqueness of P═O reduction originates from the dominant Si/O═P orbital interactions in transition structures rather than the P/H-Si interactions. The comprehensive mechanistic landscape provided by us will serve as a guidance for the rational design and development of more efficient P═O reduction systems as well as novel organophosphine-catalyzed reactions involving P(V)/P(III) redox cycle.

Occurrence, bioaccumulation and trophodynamics of organophosphate esters in the marine biota web of Laizhou Bay, Bohai Sea

The trophodynamic of organophosphate esters (OPEs) has not been known well despite their widespread occurrence in the aquatic environments. In this study, ten species of crustacean, seven species of mollusk, and 22 species of fish were collected in the Laizhou Bay (LZB) to examine the occurrence, bioaccumulation, and trophic transfer, and health risk of eight traditional OPEs and three emerging oligomeric OPEs. The results showed that total concentration of OPEs was 2.04 to 28.6 ng g-1 ww in the muscle of crustacean, mollusk, and fish and 2.62 to 60.6 ng g-1 ww in the fish gill. Chlorinated OPEs averagely contributed to over 85% of total OPEs while oligomeric OPEs averagely accounted for approximate 4%. The average log apparent bioaccumulation factor (ABAF) ranged from - 0.4 L kg-1 ww for triethyl phosphate to 2.4 L kg-1 ww for resorcinol-bis (diphenyl) phosphate. Apparent trophic magnification factors (ATMF) of individual OPE were generally less than 1, demonstrating the biodilution effect of the OPEs in the organism web of LZB. Additionally, the log ABAF and ATMF of OPEs were significantly positively correlated to their log Kow but negatively correlated to their biotransformation rate constant (BRC). Therefore, the OPEs with high Kow and low BRC tend to more accumulate in the marine organisms. The health risks associated with OPEs through the consumption of the seafood from the bay were low, even at high exposure scenario.

Behavioral toxicity of TDCPP in marine zooplankton: Evidence from feeding and swimming responses, molecular dynamics and metabolomics of rotifers

As new organic flame retardants, chlorinated organophosphate esters (Cl-OPEs) have high water solubility and structural similarity to organophosphate pesticides, posing risks to aquatic organisms. The potential neurotoxicity of Cl-OPEs has attracted attention, especially in marine invertebrates with a relatively simple nervous system. In this study, a marine rotifer with a cerebral ganglion, Brachionus plicatilis, was exposed to tris (1,3-dichloro-2-propyl) phosphate (TDCPP) (two environmental concentrations and one extreme level), and the changes in feeding and swimming behaviors and internal mechanism were explored. Exposure to 1.05 nM TDCPP did not change the filtration and ingestion rates of rotifers and average linear velocity. But 0.42 and 4.20 μM TDCPP inhibited these three parameters and reduced unsaturated fatty acid content, reproduction and population growth. All TDCPP test concentrations suppressed AChE activity, causing excessive accumulation of acetylcholine within rotifers, thereby disturbing the neural innervation of corona cilia. Molecular docking and molecular dynamics revealed that this inhibition was because TDCPP can bind to the catalytic active site of rotifer AChE through van der Waals forces and electrostatic interactions. TRP420 was the leading amino residue in the binding, and GLY207 contributed to a hydrogen bond. Nontargeted metabolomics using LC-MS and GC-MS identified differentially expressed metabolites in TDCPP treatments, mainly from lipid and lipid-like molecules, especially sphingolipids. TDCPP decreased ganglioside content but stimulated ceramide generation and the expression levels of 3 genes related to ceramide de novo synthesis. The mitochondrial membrane potential (MMP) and ATP content decreased, and the electron respiratory chain complex and TCA cycle were deactivated. An inhibitor of ceramide synthase, fumonisin, alleviated MMP and ATP, implying a critical role of ceramide in mitochondrial dysfunction. Thus, TDCPP exposure caused an energy supply deficit affecting ciliary movement and ultimately inhibiting rotifer behaviors. Overall, this study promotes the understanding of the neurotoxicity of Cl-OPEs in marine invertebrates.

Typical neonicotinoids and organophosphate esters, but not their metabolites, adversely impact early human development by activating BMP4 signaling

Recent studies have highlighted the presence of potentially harmful chemicals, such as neonicotinoids (NEOs) and organophosphate esters (OPEs), in everyday items. Despite their potential threats to human health, these dangers are often overlooked. In a previous study, we discovered that NEOs and OPEs can negatively impact development, but liver metabolism can help mitigate their harmful effects. In our current research, our objective was to investigate the toxicity mechanisms associated with NEOs, OPEs, and their liver metabolites using a human embryonic stem cell-based differentiation model that mimics early embryonic development. Our transcriptomics data revealed that NEOs and OPEs significantly influenced the expression of hundreds of genes, disrupted around 100 biological processes, and affected two signaling pathways. Notably, the BMP4 signaling pathway emerged as a key player in the disruption caused by exposure to these pollutants. Both NEOs and OPEs activated BMP4 signaling, potentially impacting early embryonic development. Interestingly, we observed that treatment with a human liver S9 fraction, which mimics liver metabolism, effectively reduced the toxic effects of these pollutants. Most importantly, it reversed the adverse effects dependent on the BMP4 pathway. These findings suggest that normal liver function plays a crucial role in detoxifying environmental pollutants and provides valuable experimental insights for addressing this issue.

Bioaccumulation and Potential Endocrine Disruption Risk of Legacy and Emerging Organophosphate Esters in Cetaceans from the Northern South China Sea

Despite the increasing health risks shown by the continuous detection of organophosphate esters (OPEs) in biota in recent years, information on the occurrence and potential risks of OPEs in marine mammals remains limited. This study conducted the first investigation into the body burdens and potential risks of 10 traditional OPEs (tOPEs) and five emerging OPEs (eOPEs) in 10 cetacean species (n = 84) from the northern South China Sea (NSCS) during 2005-2021. All OPEs, except for 2-ethylhexyl diphenyl phosphate (EHDPHP), were detected in these cetaceans, indicating their widespread occurrence in the NSCS. Although the levels of the ∑10tOPEs in humpback dolphins remained stable from 2005 to 2021, the concentrations of the ∑5eOPEs showed a significant increase, suggesting a growing demand for these new-generation OPEs in South China. Dolphins in proximity to urban regions generally exhibited higher OPE concentrations than those from rural areas, mirroring the environmental trends of OPEs occurring in this area. All OPE congeners, except for EHDPHP, in humpback dolphins exhibited a maternal transfer ratio >1, indicating that the dolphin placenta may not be an efficient barrier for OPEs. The observed significant correlations between levels of OPEs and hormones (triiodothyronine, thyroxine, and testosterone) in humpback dolphins indicated that OPE exposures might have endocrine disruption effects on the dolphin population.

Occurrence, distribution, sources, and risk assessment of organophosphate esters in typical coastal aquaculture waters of China

This study monitored 20 organophosphate esters (OPEs) in water and sediment from three typical mariculture bases (Yunxi Marine Ranching (YX), Hangzhou Bay (HZB), and Zhelin Bay (ZLB)) and Meiliang Bay (MLB) of Taihu Lake in China, focusing on the spatial distribution and sources of OPEs. Moreover, the occurrence and risk of OPEs in fishes from ZLB were evaluated. The ∑OPE concentrations in waters followed the order MLB (591 ng/L) > YX (102 ng/L) > HZB (70.0 ng/L) > ZLB (37.4 ng/L), with tri(1-chloro-2-propyl) phosphate (TCIPP), triethyl phosphate (TEP), and tri(2-chloroethyl) phosphate (TCEP) being the dominant OPEs. Significantly higher ∑OPE concentrations were found in sediment in MLB compared to the other three areas with similar levels. The decreasing concentrations of OPEs from nearshore to offshore areas in HZB and MLB indicated that terrigenous input is the main source of OPEs. The even distribution of OPEs in YX and ZLB combined with PCA analysis suggested ship traffic or aquaculture activities are also potential sources. The ∑OPE concentrations in fishes ranged from 0.551-2.45 ng/g wet weight, with TCIPP, tri-phenyl phosphate (TPHP), and TCEP being the main OPEs. Hydrophobicity was a key factor affecting the sediment-water distribution coefficients and the bioaccumulation factors of OPEs. The human exposure to OPEs through consumption of fishes from ZLB had a low health risk.

Fate of organophosphate esters from the Northwestern Pacific to the Southern Ocean: Occurrence, distribution, and fugacity model simulation

Eleven organophosphate esters (OPEs) in the air and seawater were investigated from the northwestern Pacific Ocean to the Southern Ocean during the 2018 Chinese 34th Antarctic Scientific Expedition. The concentration of total OPEs ranged from 164.82 to 3501.79 pg/m3 in air and from 4.54 to 70.09 ng/L in seawater. Two halogenated OPEs, tri(chloropropyl) phosphate (TCPP) and tri (2-chloroethyl) phosphate (TCEP), were generally more abundant than the non-halogenated OPEs. A level III fugacity model was developed to simulate the transfer and fate of seven OPEs in the air and seawater regions of the central Ross Sea. The model results indicate that OPEs are transferred from the air to the seawater in the central Ross Sea in summer, during which the Ross Sea acts as a final OPE sink. Dry and wet deposition dominated the processes involving OPE transfer to seawater. The OPE degradation process was also found to be more pervasive in the atmosphere than in the seawater region. These findings highlights the importance of long-range transport of OPEs and their air-seawater interface behavior in the Antarctic.

Global patterns of human exposure to flame retardants indoors

To fill the knowledge gaps regarding the global patterns of human exposure to flame retardants (FRs) (i.e., brominated flame retardants (BFRs) and organophosphorus flame retardants (OPFRs)), data on the levels and distributions of FRs in external and internal exposure mediums, including indoor dust, indoor air, skin wipe, serum and urine, were summarized and analysed. Comparatively, FR levels were relatively higher in developed regions in all mediums, and significant positive correlations between FR contamination and economic development level were observed in indoor dust and air. Over time, the concentration of BFRs showed a slightly decreasing trend in all mediums worldwide, whereas OPFRs represented an upward tendency in some regions (e.g., the USA and China). The occurrence levels of FRs and their metabolites in all external and internal media were generally correlated, implying a mutual indicative role among them. Dermal absorption generally contributed >60% of the total exposure of most FR monomers, and dust ingestion was dominant for several low volatile compounds, while inhalation was found to be negligible. The high-risk FR monomers (BDE-47, BDE-99 and TCIPP) identified by external exposure assessment showed similarity to the major FRs or metabolites observed in internal exposure mediums, suggesting the feasibility of using these methods to characterize human exposure and the contribution of indoor exposure to the human burden of FRs. This review highlights the significant importance of exposure assessment based on multiple mediums for future studies.

Organophosphate flame retardants and their metabolites in the Pearl River Estuary: Occurrence, influencing factors, and ecological risk control strategies based on a mass balance model

Estuaries serve as crucial filters for land-based pollutants to the open sea, but there is a lack of information on the migration and fate of organophosphate flame retardants (OPFRs) within estuaries. This study focused on the Pearl River Estuary (PRE) by examining the co-occurrence of OPFRs and their metabolites and quantifying their transport fluxes using a mass balance model. The seawater concentrations of OPFRs and their metabolites exhibited significant seasonal variations (p < 0.01), while the sediment concentrations of OPFRs reflected the long-term distributional equilibrium in the PRE. The concentration of Σ9OPFRs in seawater showed a relentless dilution from the entrance to the offshore region in the normal and wet seasons, which was significantly in accordance with the gradients of pH, dissolved oxygen (DO), and salinity (p < 0.05). Furthermore, horizontal migration dominated the transport of OPFRs, and the inventory assessment revealed that both the water column and sediment were important reservoirs in the PRE. According to the estimated fluxes from the mass balance model, riverine input emerged as the principal pathway for OPFR entry into the PRE (1.55 × 105, 6.28 × 104, and 9.00 × 104 kg/yr in the normal, dry and wet seasons, respectively), whereas outflow to the open sea predominantly determined the main fates of the OPFRs. The risk quotient (RQ) results showed that EHDPHP (0.835) in water posed medium ecological risk, while other OPFRs and metabolites presented relatively lower risk (RQ < 0.1). The risk control effects were evaluated through scenario simulations of mathematical fitting between controllable source factors and the RQ of risky OPFR. The risk of EHDPHP in the PRE could be effectively reduced by restricting its concentrations in entrance region (<9.31, 8.67, and 12.7 ng/L in the normal, dry and wet seasons, respectively) of the PRE. This research offers foundational insights into environmental management and pollution control strategies for emerging pollutants in estuaries.

Organophosphate esters in seawater and sediments from the low-latitude tropical sea

Little is known about the distribution, transport and fate of organophosphate esters (OPEs) in the low-latitude tropic sea. Fourteen OPEs were measured in seawater and sediments from the Pearl River Estuary (PRE) and South China Sea (SCS). The concentrations of OPEs in seawater and sediments ranged from 7.65-270 ng/L and 9.02-44.9 ng/g dw, respectively. The concentrations of OPEs in surface seawater from the PRE (93.4 ± 16.5 ng/L) were significantly higher than those in SCS (23.6 ± 2.17 ng/L, p < 0.001). OPEs in water from the PRE showed a decreasing trend from upstream to downstream. The salinity of water was an important factor to determine the concentrations of OPEs in the PRE. The annual input of OPEs from the PRE to the SCS was about 304 tons. The concentrations of OPEs in seawater column from the SCS decreased during 5-800 m and showed an increasing pattern from 800 m to 3400 m, indicating that OPEs can transport into deep seawater. TCPP was the most abundant OPEs in water and sediments from the PRE and TCEP was the predominant OPEs in the SCS. This work highlights long-range transport of OPEs by seawater to the deep sea environment.

Interannual variation and machine learning simulation of organophosphate esters in Taihu Lake

Organophosphate esters (OPEs) are widespread in water bodies and have attracted public attention due to their hazards. This study investigated the presence of OPEs in surface water of Taihu Lake from 2012 and 2021-2022. The OPEs concentration was compared ten years ago and ten years later. Water and meteorological parameters were ranked using the random forest (RF) model, and OPEs concentration in lakes was simulated using selected parameters as inputs. The concentration of Σ7OPEs was higher ten years ago compared to ten years later. There was no significant seasonal difference in Σ7OPEs from 2021-2022, while the concentration of Σ7OPEs in 2012 was lower in summer than in other seasons. The spatial distribution of the two interannual Σ7OPEs exhibited a decreasing trend from the northwest region. The results of RF importance ranking and redundancy analysis showed that NH3-N, TN, TP, water temperature and relative humidity were the most influential factors affecting OPEs concentrations. RF models performed better for TnBP, as indicated by training R and test R values are excellent and relatively low errors. Our results demonstrated that machine learning models were useful in facilitating efficient monitoring and assessment of OPEs contamination in lakes.

Deriving seawater quality criteria of tris(2-chloroethyl) phosphate for ecological risk assessment in China seas through species sensitivity distributions

Tris(2-chloroethyl) phosphate (TCEP), one of the widely used organophosphorus flame retardants (OPFRs), has been frequently detected in the marine environment in the seas off China. The existing freshwater biotoxicity data are not suited to derivation of the seawater quality criteria of TCEP and evaluating the associated ecological risks. This study aimed at deriving water quality criteria (WQC) of TCEP for marine organisms based on species sensitivity distribution (SSD) approach using the acute toxicity data generated from multispecies bioassays and chronic toxicity data by converting acute data with the acute-to-chronic ratios (ACRs); the derived WQC were then used to evaluate the ecological risk for TCEP in China Seas. According to median effective concentration (EC50) and median lethal concentration (LC50), TCEP had a moderate or low toxicity to eight marine species selected, among which mysid Neomysis awatschensis (96h-LC50 of 39.65 mg/L) and green alga Platymonas subcordiformis (96-h EC50 of 395.42 mg/L) were the most sensitive and the most tolerant, respectively. The acute and chronic hazardous concentrations of TCEP for 5% of marine species (HC5) were estimated to be 29.55 and 2.68 mg/L, respectively. The short-term and long-term WQC were derived to be 9.85 and 0.89 mg/L, respectively. The risk quotient (RQ) values indicated that TECP at current levels poses a negligible risk to marine ecosystems in China. These results will provide valuable reference for the government to establish a seawater quality standard for TCEP.

Spatial and temporal variability and risk assessment of organophosphate esters in seawater and sediments of the Yangtze River estuary

Organophosphate esters (OPEs) as substitutes for PBDEs have been widely detected in the marine environment, while little is known about the pollution characteristics and variation of OPEs in estuarine environments with complex hydrodynamic conditions and land-based input. Yangtze River Estuary (YRE) is a typical highly urbanized and industrialized estuary, with a complex hydrological environment and geochemical behavior. This study found that the concentrations of OPEs in both seawater and sediments in the YRE were higher in spring than in summer. Alkyl OPEs were the first contributor, with TnBP and TiBP as the main components, where the contribution of alkyl OPEs had exceeded 75 % in both seawater and sediments in spring, and 60 % in summer seawater, and even 80 % in sediments. In spring, OPEs peaked in the central to southern region near the YRE. In summer, OPEs were mainly concentrated in the southern branch waterway and southern nearshore area of the YRE and showed a decreasing trend to the northeast. The OPEs in the sediments were mainly concentrated in the Yangtze River Mud Area (YREMA) and the Zhe-Min Coastal Mud Area (ZMCMA). Based on the fugacity model and principal component analysis, sediments could be released into the aquatic environment as an endogenous source, and exogenous sources were mainly municipal and industrial sewage discharge sources, urban and marine traffic discharge sources, and atmospheric deposition sources. The ecological risk analysis showed that the Σ14OPEs had exhibited a low to moderate ecological risk in the southern branch waterway and the south-central region offshore.

Prenatal exposure to emerging and traditional organophosphate flame retardants: Regional comparison, transplacental transfer, and birth outcomes

During gestation, organophosphate flame retardants (OPFRs) have the potential to pose health risks to fetuses due to their ability to cross the placental barrier. However, data are scarce regarding the transplacental transfer of these compounds, particularly concerning emerging OPFRs and regional variations. In this study, we analyzed 14 traditional OPFRs and 5 emerging OPFRs in maternal and cord serum samples from Mianyang and Hangzhou, two cities in eastern and western China, respectively. The results revealed marked disparities in the overall levels of OPFRs between the two cities (p < 0.05), with the average concentration in maternal serum being higher in Hangzhou (14.55 ng/mL) than in Mianyang (8.28 ng/mL). The most abundant compounds found in both cities were tris (2-chloroethyl) phosphate (TCEP), Triphenyl phosphate (TPHP), and Tri-n-butyl phosphate (TnBP). Additionally, this study marked the first detection of novel OPFRs, including resorcinol bis (diphenyl phosphate) (RDP), isodecyl diphenyl phosphate (IDDPP), cresyl diphenyl phosphate (CDP), and bisphenol A bis (diphenyl phosphate) (BPA-BDPP) in maternal and cord serum simultaneously with the detection frequencies higher than 45%. This study also found that transplacental transfer efficiencies for OPFRs varied by ester group, with Aryl-OPFRs exhibiting the highest transfer rates (0.90-1.11) and Alkyl-OPFRs exhibiting the lowest (0.66-0.83). Transfer efficiencies exhibited a positive correlation with log Kow values (p < 0.05), suggesting that hydrophobic OPFRs with higher log Kow values are more likely to permeate the placental barrier. Moreover, the exposure levels of Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP), Tri (Chloropropyl) Phosphate (TCIPP), TPHP, and CDP in cord serum were negatively associated (p < 0.05) with birthweight of newborns. This research adds to our understanding of the transplacental transfer of OPFRs and the possible health risks associated with prenatal exposure.

Organophosphate esters (OPEs) in a heavily polluted river in South China: Occurrence, spatiotemporal trends, sources, and phase distribution

In the past decade, organophosphate esters (OPEs) undergo rapid increase in production and use. Meanwhile, owing to their additive property, OPEs exhibit liability to escape from related products and therefore ubiquity in various environments. Moreover, numerous researches verify their bioavailability and negative effects on biota and human, hence their occurrence and associated risks have caught much concern, particularly those in aquatic systems. So far, however, OPEs in water are generally investigated as a whole, their phase distribution and behavior in waterbodies are incompletely characterized. We examined 25 OPEs in water (including dissolved and particulate phases), sediment, and sediment core samples from the Lian River, which flows through the Guiyu e-waste recycling zone and Shantou specific economic zone in South China. Compared to most global waterbodies, the Lian River showed high or ultrahigh OPE levels in both water and sediments, particularly in the reaches surrounded by e-waste recycling and plastic-related industries, which were the top two greatest OPE sources. Non-industrial and agriculture-related anthropogenic activities also contributed OPEs. Sediment core data suggested that OPEs have been present in waters in Guiyu since the 1960s and showed a temporal trend consistent with the local waste-recycling business. The phase distribution of OPEs in the Lian River was significantly correlated with their hydrophobicity and solubility. Owing to their wide range of physicochemical properties, OPE congeners showed significant percentage differences in the Lian River water and sediments. Generally, OPEs in water reflect their dynamic real-time inputs, while those in sediment signify their accumulative deposition, which is another cause of their phase distribution disparities in the Lian River. The physicochemical parameters of OPEs first imposed negative and then positive influences on their dissolved phase-sediment distribution, indicating the involvement of both the adsorption of dissolved OPEs and the deposition of particle-bound OPEs.

New Perspective to Understand and Prioritize the Ecological Impacts of Organophosphate Esters and Transformation Products in Urban Stormwater and Sewage Effluents

Due to their prevalence in urban contaminated water, the driving factors of organophosphate esters (OPEs) need to be well examined, and their related ecological impacts should include that of their transformation products (TPs). Additionally, a robust framework needs to be developed to integrate multiple variables related to ecological impacts for improving the ecological health assessment. Therefore, OPEs and TPs in urban stormwater and wastewater in Hong Kong were analyzed to fill these gaps. The results revealed that the total concentrations of OPEs in stormwater were positively correlated with the area of transportation land. Individual TP concentrations and the mass ratios of individual TPs/OPEs were somewhat higher in sewage effluents than that in stormwater. OPEs generally showed relatively higher risk quotients than TPs; however, the total risk quotients increased by approximately 38% when TPs were factored in. Moreover, the molecular docking results suggested that the investigated TPs might cause similar endocrine disruption in marine organisms as their parent OPEs. This study employed the Toxicological-Priority-Index scheme to successfully integrate the ecological risks and endocrine-disrupting effects to refine the ecological health assessment of the exposure to OPEs and their TPs, which can better inform the authority on the prioritization for regulating these contaminants of emerging concern in urban built environments.

Tertiary Amine-Mediated Reductions of Phosphine Oxides to Phosphines

The reduction of phosphine oxides without the use of highly reactive reductants represents a safer and more sustainable solution for recycling of organophosphorus compounds. Herein, we disclose an N,N,N',N'-tetramethylethylenediamine (TMEDA)-mediated reduction via an unusual intermolecular hydride transfer. Mechanistic studies suggest that TMEDA serves as a hydride donor, while the P(V) halophosphonium salt acts as the hydride acceptor. This methodology provides a scalable and efficient protocol to reduce phosphine oxides under mild conditions.

Environmental occurrence and ecotoxicity of aquaculture-derived plastic leachates

Plastic products such as fishing nets and foam buoys have been widely used in aquaculture. To enhance the desirable characteristics of the final equipment, plastic gear for aquaculture is mixed with a wide range of additives. Recent studies have shown that additives could be leached out to the environment with a long-term use of aquaculture plastics, forming aquaculture-derived plastic leachates. It should be emphasized that some leachates such as phthalic acid esters (PAEs) and organophosphate esters (OPEs) are endocrine disruptors, which could increase the exposure risk of aquatic products and subsequently display potential threats to human health via food chain. However, systematic studies on the release, occurrence, bioaccumulation, and toxic effects of aquaculture-derived plastic leachates are missing, overlooking their potential sources and ecotoxicological risks in aquatic environments. We have reviewed and compared the concentrations of major plastic leachates in the water environment and organisms of global aquaculture and non-farmed areas, confirming that aquaculture leachate is an important source of contaminants in the environment. Moreover, the toxic effects of aquaculture-derived plastic additives and the related mechanisms are summarized with fish as a representative, revealing their potential health risk. In addition, we proposed current challenges and future research needs, which provides scientific guidance for the use and management of plastic products in aquaculture industries.

Organophosphate esters in the seawater of the Bohai Sea: Environmental occurrence, sources and ecological risks

Organophosphate esters (OPEs) are widely distributed in surface water systems, but limited information was available on the spatial occurrence and ecological risks of OPEs in the Bohai Sea. In this study, 89 water samples in the Bohai Sea and the five surrounding rivers were investigated for the determination of 15 OPEs. The concentration of ∑₁₅OPEs ranged from 373.20 to 2931.27 ng·L^-1 in the river water and 137.81 to 2641.30 ng·L^-1 in the seawater, with high levels of OPEs in Liaodong Bay. Tris(2-chloroethyl) phosphate (TCEP, 10- 92 %) and triethyl phosphate (TEP, 5- 64 %) were dominant for OPEs. The correlation analysis, principal component analysis and hierarchical cluster analysis suggested the conjunction of municipal wastewater via river input and maritime shipping was the main source of OPEs in the Bohai Sea. The ecological risk assessment indicated that the individual OPEs arise low ecological risks in the Bohai Sea, while medium ecological risks of ∑₁₅OPEs are in minority river samples.

Exposure to environmentally relevant concentrations of TnBP results in tissue-specific bio-accumulation and inhibits growth of silver carp (Hypophthalmichthys molitrix)

Tri-n-butyl phosphate (TnBP) is commonly used as flame retardant and rubber plasticizer, and has been widely detected in aquatic organisms and natural waters. However, the potential toxicity of TnBP in fish remains unclear. In the present study, silver carp (Hypophthalmichthys molitrix) larvae were treated with environmentally relevant concentrations (100 or 1000 ng/L) of TnBP for 60 d and then they were depurated in clean water for 15 d, and the accumulation and depuration of the chemical in six tissues of silver carp were measured. Furthermore, effects on growth were evaluated and potential molecular mechanisms were explored. Results indicated that TnBP could be rapidly accumulated and depurated in silver carp tissues. In addition, the bio-accumulation of TnBP displayed tissue-specificity, where intestine contained the greatest and vertebra had the smallest level of TnBP. Furthermore, exposure to environmentally relevant concentrations of TnBP led to time- and concentration-dependent growth inhibition of silver carp, even though TnBP was completely depurated in tissues. Mechanistic studies suggested that exposure to TnBP up- and down-regulated the expression of ghr and igf1 in liver, respectively, and increased GH contents in plasma of silver carp. TnBP exposure also up-regulated the expression of ugt1ab and dio2 in liver, as well as decreased T4 contents in plasma of silver carp. Our findings provide direct evidence of health hazards of TnBP to fish in natural waters, calling for more attention of environmental risks of TnBP in aquatic environment.

Occurrence and risk assessment of organophosphate esters in global aquatic products

Organophosphate esters (OPEs), as an important class of new pollutants, have been pervasively detected in global aquatic products, arousing widespread public concern due to their potential bioaccumulative behavior and consequent risks. With the continuous improvement of living standards of citizens, there have been constant increment of the proportion of aquatic products in diets of people. The levels of OPEs exposed to residents may also be rising due to the augmented consumption of aquatic products, posing potential hazards on human health, especially for people in coastal areas. The present study integrated the concentrations, profiles, bioaccumulation, and trophic transfer of OPEs in global aquatic products, including Mollusca, Crustacea, and fish, evaluated health risks of OPEs through aquatic products in daily diets by Mont Carol Simulation (MCS), and found Asia has been the most polluted area in terms of the concentration of OPEs in aquatic products, and would have been increasingly polluted. Among all studied OPEs, chlorinated OPEs generally showed accumulation predominance. It is worth noting that some OPEs were found bioaccumulated and/or biomagnified in aquatic ecosystems. Though MCS revealed relative low exposure risks of residents, sensitive and special groups such as children, adolescents, and fishermen may face more serious health risks than the average residents. Finally, knowledge gaps and recommendations for future research are discussed encouraging more long-term and systematic global monitoring, comprehensive studies of novel OPEs and OPEs metabolites, and more toxicological studies to completely evaluate the potential risks of OPEs.

Organophosphate tri- and diesters in source water supply and drinking water treatment systems of a metropolitan city in China

The water contaminations with organophosphate triesters (tri-OPEs) and diesters (di-OPEs) have recently provoked concern. However, the distributions of these compounds in natural water sources and artificial water treatment facilities are poorly characterized. A comprehensive study was therefore performed to measure their concentrations in a water source, a long-distance water pipeline, and a drinking water treatment plant (DWTP). Eight tri-OPEs and 3 di-OPEs were found to be widely distributed, with total concentrations in source water and pipelines ranging from 290.6 to 843.9 ng/L. The most abundant pollutants were tris(1-chloro-2-propyl) phosphate (TCPP), triethyl phosphate, tri-n-butyl phosphate (TnBP), and diphenyl phosphate (DPhP). Di-OPEs appeared to be removed less efficiently in the DWTP than the parent tri-OPEs, and the elimination efficiencies of tri-OPEs were structure-dependent. Long-distance pipeline transportation had no significant effect on the distributions of tri- and di-OPEs. Statistical analysis suggested that the sources of di-OPEs and the corresponding tri-OPEs differed, as did those of DPhP and di-n-butyl phosphate. A risk analysis indicated that tri-OPEs present limited ecological risks that are mainly due to TnBP and TCPP, and that the human health risks of tri-OPEs are negligible. However, di-OPEs (especially DPhP) may increase these risks. Further studies on the risks posed by di-OPEs in aquatic environments are therefore needed.

Emission and gas-particle partitioning characteristics of atmospheric halogenated and organophosphorus flame retardants in decabromodiphenyl ethane-manufacturing functional areas

The emission and gas-particle partitioning characteristics in various functional areas of production lines are still unknown. However, flame-retardant manufacturing activities are the primary emission source of flame retardants. Thus, fine particles and gases were investigated in three functional areas of a decabromodiphenyl ethane production line, i.e., polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), dechlorane plus (DPs), and organophosphorus flame retardants (OPFRs) in a flame-retardant manufacturing factory. High levels of PBDEs (8.02 × 10³-4.16 × 10⁴ pg/m³), NBFRs (6.05 × 10³-1.92 × 10⁵ pg/m³), and DPs (89.5-5.20 × 10³ pg/m³) were found in various functional areas, suggesting manufacturing activities were a primary emission source. In contrast, OPFRs were derived from long-range transport or other non-industrial sources. Varied concentrations of PBDEs, NBFRs, and DPs were observed in different production lines, higher in the reaction zone area than others. As the predominant compounds, decabromodiphenyl ether, decabromodiphenyl ethane, syn-DP, and tris(chloropropyl) phosphate accounted for 54.7%, 89.3%, 93.4%, and 34.7% of PBDEs, NBFRs, DPs, and OPFRs, respectively. Three models were used to predict the gas-particle partitioning of the halogenated flame retardants emitted from manufacturing activities. The Li-Jia Empirical Model predicted the gas-particle partitioning behavior well. This research shows that the adsorption-desorption process of the halogenated flame retardants between the gaseous and particulate phases did not reach equilibrium.

Evaluating the spatial and temporal distribution of emerging contaminants in the Pearl River Basin for regulating purposes

Little information is available on how the types, concentrations, and distribution of chemicals have evolved over the years. The objective of the present study is therefore to review the spatial and temporal distribution profile of emerging contaminants with limited toxicology data in the pearl river basin over the years to build up the emerging contaminants database in this region for risk assessment and regulatory purposes. The result revealed that seven groups of emerging contaminants were abundant in this region, and many emerging contaminants had been detected at much higher concentrations before 2011. Specifically, antibiotics, phenolic compounds, and acidic pharmaceuticals were the most abundant emerging contaminants detected in the aquatic compartment, while phenolic compounds were of the most profound concern in soil. Flame retardants and plastics were the most frequently studied chemicals in organisms. The abundance of the field concentrations and frequencies varied considerably over the years, and currently available data can hardly be used for regulation purposes. It is suggested that watershed management should establish a regular monitoring scheme and comprehensive database to monitor the distribution of emerging contaminants considering the highly condensed population in this region. The priority monitoring list should be formed in consideration of historical abundance, potential toxic effects of emerging contaminants as well as the distribution of heavily polluting industries in the region.

Spatiotemporal variations and the ecological risks of organophosphate esters in Laizhou Bay waters between 2019 and 2021: Implying the impacts of the COVID-19 pandemic

Organophosphate esters (OPEs) are a group of synthetic chemicals used in numerous consumer products such as plastics and furniture. The Coronavirus Disease 2019 (COVID-19) pandemic significantly slowed anthropogenic activities and reduced the emissions of pollutants. Meanwhile, the mismanagement of large quantities of disposable plastic facemasks intensified the problems of plastic pollution and leachable pollutants in coastal waters. In this study, the joint effects of the COVID-19 outbreak on the occurrence of 12 targeted OPEs in the waters of Laizhou Bay (LZB) were investigated. The results showed that the median total OPE concentrations were 725, 363, and 109 ng L^-1 in the sewage treatment plant effluent, river water, and bay water in 2021, decreased significantly (p < 0.05) by 67%, 68%, and 70%, respectively, compared with those before the COVID-19 outbreak. The release potential of targeted OPEs from disposable surgical masks in the LZB area was ∼0.24 kg yr^-1, which was insufficient to increase the OPE concentration in the LZB waters. The concentrations of most individual OPEs significantly decreased in LZB waters from 2019 to 2021, except for TBOEP and TNBP. Spatially, a lower concentration of OPEs was found in the Yellow River estuary area in 2021 compared with that before the COVID-19 pandemic due to the high content of suspended particulate matter in the YR. A higher total OPE concentration was observed along the northeastern coast of LZB, mainly owing to the construction of an artificial island since 2020. The ecological risks of the OPE mixture in LZB waters were lower than those before the COVID-19 outbreak. However, TCEP, TNBP, and BDP should receive continuous attention because of their potential ecological risks to aquatic organisms.

Occurrence and treatment effect assessment of organophosphorus flame retardants in source and drinking water, Jinan, China

The occurrence and removal efficiencies of organophosphorus flame retardants (OPFRs) by traditional treatment processes (pre-flocculation, sand filtration, and post-chlorination processes) and advanced treatment processes (i.e., ozone and granular activated carbon (GAC), ultraviolet/hydrogen peroxide (UV/H₂O₂), GAC alone, ultrafiltration membrane, nanofiltration membrane) were examined in two municipal plants and a pilot plant in Jinan, China. The concentrations of six OPFRs in raw waters were at levels of 16.8-100.0 ng/L, and three OPFRs were below the detection limits. The traditional treatment processes could not effectively remove the OPFRs (the removal efficiency was - 12.0-15.4%). The advanced oxidation with ozone and GAC (the removal efficiency was 35.6-60.3%) or UV/H₂O₂ and GAC processes (the removal efficiency was 68.0-86.7%) were more effective than the traditional water treatment processes. The removal efficiencies of ultrafiltration process for the OPFRs was 11.2-69.8% which were positively correlated with the logKow values of OPFRs. The nanofiltration membrane process with ultrafiltration membrane process as the pretreatment was the most effective process (the removal efficiencies were almost to 100%). These results imply that the combination of ultrafiltration membrane and nanofiltration membrane is an effective measure in the treatment of OPFRs in municipal drinking water plants.

Insights into the geographical distribution, bioaccumulation characteristics, and ecological risks of organophosphate esters

Organophosphate esters (OPEs), as flame retardants and plasticizers, have been numerously explored regarding the occurrence and ecotoxicology. Given their toxicity, persistency and bio-accumulative potential, however, they may pose negative effects on ecosystems, regarding which is a growing global concern. Accordingly, the present review systematically analyses the recent literature to (1) elucidate their worldwide distribution, bioaccumulation, and biomagnification potential, (2) determine their interim water quality criteria (i.e., effect thresholds), and (3) preliminarily assess the ecological risks for 32 OPEs in aquatic ecosystems. The results showed that the spatiotemporal distribution of OPEs was geographically specific and closely related to human activities (i.e., megacities), especially halogenated-OPEs. We also found that precipitation of airborne particulates could affect the concentrations of OPEs in soil, and there was a positive correlation between the bioaccumulation and hydrophobicity of OPEs. Tris(2-ethylhexyl) phosphate may exhibit high bioaccumulation in aquatic organisms. A substantial difference was found among interim water quality criteria for OPEs, partly attributable to the variation of their available toxicity data. Tris(phenyl) phosphate (TPHP) and tris(1,3-dichloroisopropyl) phosphate with the lowest predicted no-effect concentration showed the strongest toxicity of growth and reproduction. Through the application of the risk quotient and joint probability curve, TPHP and tris(chloroethyl) phosphate tended to pose moderate risks, which should receive more attention for risk management. Future research should focus on knowledge gaps in the mechanism of biomagnification, derivation of water quality criteria, and more precise assessment of ecological risks for OPEs.

Bioaccumulation of organophosphorus flame retardants in marine organisms in Liaodong Bay and their potential ecological risks based on species sensitivity distribution

Although organophosphorus flame retardants (OPFRs) in aquatic environments have received increasing concern, little information is available on their bioaccumulation and trophic transfer in marine food webs. Consequently, the risks of OPFRs to marine ecosystems are unknown. In this study, seven OPFR compounds in marine biological samples collected from Liaodong Bay, Bohai Sea, were analyzed to evaluate their level and biological amplification effect in the marine food web. The total OPFRs of marine organisms in Liaodong Bay ranged from 2.60 to 776 ng/g ww, and lipids were critical factors affecting the concentration of OPFRs in marine species. Tris (2-ethylhexyl) phosphate (TEHP) and tris(1-chloro-2-propyl) phosphate (TCIPP) were the OPFRs most frequently detected in marine species. Still, tris(2-chloroethyl) phosphate (TCEP) was dominant in most marine species (16/24), and the content of chlorinated OPFRs was highest. At the same time, alkyl OPFRs and aryl OPFRs accounted for the same proportion. No correlation between OPFR concentration and the trophic level was observed in marine organisms from Liaodong Bay. It was shown in the results of the species sensitivity distribution that TCIPP in Chinese seawater does not pose a potential ecological risk to marine species. However, much work remains to be done on accumulating information and the ecological risks of OPFRs in different marine food webs.

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.

Occurrence and removal of organophosphate esters in municipal wastewater treatment plants in Thessaloniki, Greece

An integrate study regarding the occurrence and fate of eleven organophosphate esters (OPEs) was conducted at two wastewater treatment plants (WWTPs) in the area of Thessaloniki, Greece. Both plants employed conventional activated sludge process whereas as last treatment step the first unit use chlorination and the second one ozonation. OPEs were determined in dissolved fraction, total suspended solids and sludge from various treatment stages of WWTPs. Tris (2-butoxyethyl) phosphate (TBOEP), tris (1-chloro-2-propyl) phosphate (TClPP) and triphenylphosphine oxide (TPPO) were the most abundant compounds in influent and treated effluent. Triphenyl phosphate (TPHP) was also abundant in suspended solids and sludge. Total concentrations of ∑₁₁OPEs ranged from 2144 to 9743 ng L^-1 in influents, 1237-2909 ng L^-1 in effluents and 3332-14294 ng g^-1 dw in sludge. Removal rates from 55% to 80% were observed for most OPEs, whereas chlorinated OPEs, especially for tris(2-chloroethyl) phosphate (TCEP) exhibited low removal efficiency. Mass balance analysis showed that biodegradation was the dominant removal mechanism contributing up to 85%. Sorption onto sludge was also relevant removal pathway for most compounds. Emissions of OPEs through effluents and sludge did not pose considerable risk to the aquatic and terrestrial environment.

Non-target screening and risk assessment of organophosphate esters (OPEs) in drinking water resource water, surface water, groundwater, and seawater

By use of an integrated target, suspect, and non-target screening strategy, we investigated occurrence and spatial distribution of organophosphate esters (OPEs) in four types of water (drinking water resource water, surface water, groundwater, and seawater) collected from Jiangsu Province (China) in 2021 (n = 111). Eighteen out of 23 target OPEs were detectable at least once in these analyzed samples, and the total concentrations (Σ18OPEs) of OPEs in various water samples exhibited a descending order following as: groundwater (67026 ng/L) > surface water (35803 ng/L) > drinking water resource water (21055 ng/L) > seawater (17820 ng/L). The highest concentration detected in groundwater may be ascribed to pollution from surrounding factories. Among the target OPEs, triethyl phosphate (TEP), tris(chloroethyl) phosphate (TCEP), and tris (1-chloro-2-propyl) phosphate (TCIPP) were the most abundant congeners with the average concentrations of 407 ng/L, 143 ng/L, and 475 ng/L, respectively. Besides of 18 target OPEs, we further identified 17 suspect OPEs (3 of them were fully identified by authentic standards) on the basis of in-house suspect screening OPE database, and 2 non-target organophosphates (OPs) on the basis of feature fragments. One of these 2 non-target OPs was fully identified as bis(2-chloroethyl) 2-chloroethylphosphonate (B2CE2CEPP) by matching the retention time and MS/MS data with authentic standard, and the other one was preliminarily identified as 2,4,8,10-tetra-tert-butyl-6-methoxydibenzo[d,f][1,3,2]dioxaphosphepin-6-one (TTBMDBDOPPO). We also observed that B2CE2CEPP shared a similar structure with TCEP, suggesting that they may have similar toxicological characteristics and commercial sources. The ecological and human health risk assessments indicated that all OPEs posed a low or negligible ecological risk to aquatic organisms (algae, crustacean, and fish), and negligible risk to human health except for trimethyl phosphate (TMP) in drinking water resource water.

Development of a new methodology for multifaceted assessment, analysis, and characterization of soil contamination

It is important to identify key performance and core progress features of soil contamination management practices. Traditional research currently focuses on numerical statistics of contaminated sites but exhibits structural limitations regarding cross-assessment and in-depth analysis of published findings. Herein, we report a multidimensional perspective to assess the environmental management performance of soil contamination via systematic and historical development of construction land risk control and remediation lists (RCRLs). The considered contaminated sites are mainly concentrated in Northern China, Yangtze River Delta, Pearl River Delta, and Sichuan-Chongqing regions. Monthly historical overviews indicate that most lists are updated 4-5 times within 32 months. Direct chemical-related industrial production results in the largest number of contaminated sites. Arsenic and lead are the most common heavy metals of concern in soil contamination. The fiscal revenue index exhibits the best positive performance in terms of the number of contaminated sites. By employing the site number, update frequency, and published contents of different calculation proportions, ten types of integrated assessment indicators (IAIs) are established to evaluate the environmental achievements in various provincial regions in regard to soil contamination protection. This multifaceted strategy can provide advanced guidance for Chinese environmental management and expand the application of soil pollution risk control and remediation in a wide range of countries.

Contaminant occurrence, spatiotemporal variation, and ecological risk of organophosphorus flame retardants (OPFRs) in Hangzhou Bay and east China sea ecosystem

Occurrence, spatiotemporal variation, sources, and ecological risks of 20 organophosphorus flame retardants (OPFRs) in water and sediments from Hangzhou Bay (HZB) and its adjacent East China Sea (ECS) were investigated in this study. The concentrations of OPFRs (∑OPFR) in water ranged from 0.51 ng/L to 885 ng/L, with chlorinated OPFRs having the highest value. For sediments, ∑OPFR ranged from 2.93 ng/g, dry weight (dw) to 37.8 ng/g, dw. The ∑OPFR in the water and sediments of HZB in summer was significantly (p < 0.05) higher than that in autumn. Additionally, the pollution of OPFRs in HZB was higher than that in ECS, and the high-concentration areas appeared in the north and south banks of HZB and near the coast of ECS. Principal component analysis-multiple linear regression showed that the OPFRs in this region were mainly from industrial products (e.g., polyurethane foam/paint/coating/textiles/product processing). In terms of aquatic environments, ecological risks were in a low (∑RQs<0.1) to moderate (0.1<∑RQs<1) level, with regard to median exposure levels, a moderate risk (0.1<∑RQs<1) was found in the sediments during autumn. This study can provide new insights into the OPFR pollution characteristic and ecological risk in a specific eco-environment.

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.

Toxicity of triphenyl phosphate toward the marine rotifer Brachionus plicatilis: Changes in key life-history traits, rotifer-algae population dynamics and the metabolomic response

Triphenyl phosphate (TPhP) is used as a flame retardant that gradually leaks from products into the marine environment and thus may threaten low-trophic-level marine organisms, such as zooplankton. To assess the effect of TPhP on these taxa, we treated the marine rotifer Brachionus plicatilis as a target and examined the changes in key life history parameters and the metabolome after exposure to TPhP at 0.02, 1 and 5 mg/L. Additionally, the rotifer-Phaeocystis population dynamics (a simulation of the prey-predator relationship) were studied under TPhP stress. Our results showed that TPhP at 1 and 5 mg/L reduced the average lifespan and the total offspring number and prolonged the prereproductive time, suggesting damage to survival and fecundity. In the 0.02 mg/L group, no obvious damage occurred in the overall condition of rotifers, but the volume of parental rotifers after the first brood decreased. This implied that rotifers sacrificed somatic growth to reproduction in the initial period of TPhP exposure at the low concentration. All the tested TPhP concentrations altered the rotifer-Phaeocystis population dynamic changes, especially that 1 mg/L TPhP reduced the ability of rotifers to remove this harmful alga, as evidenced by the decrease in the maximum population density of rotifers and the extended time to P. globosa extinction. At the molecular level, metabolomics identified 84 and 206 differentially expressed metabolites, most of which were enriched in glycerophospholipid metabolism, steroid biosynthesis and sphingolipid metabolism. Nile red staining showed a decrease in neutral lipids in rotifers, further indicating a disorder of lipid metabolism induced by TPhP. Moreover, the balance between ROS production and the defense system was disrupted by TPhP, which contributed to its toxicity. This finding will promote the understanding of the ecological risk and mode of action of TPhP in aquatic environments.

Simultaneous determination of 16 urinary metabolites of organophosphate flame retardants and organophosphate pesticides by solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry

Organophosphate flame retardants (OPFRs) and organophosphate pesticides (OPPs), pertaining to organophosphate esters, are ubiquitous in environment and have been verified to pose noticeable risks to human health. To evaluate human exposures to OPFRs and OPPs, a fast and sensitive approach based on a solid phase extraction (SPE) followed by the ultra-high-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) detection has been developed for the simultaneous analysis of multiple organophosphorus metabolites in urine. The method allows the identification and quantification of ten metabolites of the most common OPFRs and all six dialkylphosphates (DAPs) of OPPs concerning the population exposure characteristics. The method provided good linearities (R² = 0.998-0.999), satisfactory method detection limits (MDLs) (0.030-1.129 ng/mL) and only needed a small volume (200 μL) of urine. Recovery rates ranged 73.4-127.1% at three spiking levels (2, 10 and 25 ng/mL urine), with both intra- and inter-day precision less than 14%. The good correlations for DAPs in a cross-validation test with a previous gas chromatography-mass spectrometry (GC-MS) method and a good inter-laboratory agreement for several OPFR metabolites in a standard reference material (SRM 3673) re-enforced the precision and validity of our method. Finally, the established method was successfully applied to analyze 16 organophosphorus metabolites in 35 Chinese children's urine samples. Overall, by validating the method's sensitivity, accuracy, precision, reproducibility, etc., data reliability and robustness were ensured; and the satisfactory pilot application on real urine samples demonstrated feasibility and acceptability of this method for being implemented in large population-based studies.

Sources, behaviors, transformations, and environmental risks of organophosphate esters in the coastal environment: A review

The rapid growth in the global production of organophosphate esters (OPEs) has resulted in their high environmental concentrations. The low removal rate of OPEs makes the effluents of wastewater treatment plants be one of the major sources of OPEs. Due to relatively high solubility and mobility, OPEs can be carried to the coastal environment through river discharge and atmospheric deposition. Therefore, the coastal environment can be an important OPE sink. Previous studies have shown that OPEs were widely detected in coastal atmospheres, water, sediments, and even aquatic organisms. OPEs can undergo various environmental processes in the coastal environment, including adsorption/desorption, air-water exchange, and degradation. In addition, bioaccumulation of OPEs was observed in coastal biota but current concentrations would not cause significant ecological risks. More efforts are required to understand the environmental behaviors of OPEs and address resultant environmental and health risks, especially in the complicated environment.

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.

Biodegradation of tricresyl phosphates isomers by a novel microbial consortium and the toxicity evaluation of its major products

A novel microbial consortium ZY1 capable of degrading tricresyl phosphates (TCPs) was isolated, it could quickly degrade 100% of 1 mg/L tri-o-cresyl phosphate (ToCP), tri-p-cresyl phosphate (TpCP) and tri-m-cresyl phosphate (TmCP) within 36, 24 and 12 h separately and intracellular enzymes occupied the dominated role in TCPs biodegradation. Additionally, triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), bisphenol-A bis (diphenyl phosphate) (BDP), tris (2-chloroethyl) phosphate (TCEP) and tris (1-chloro-2-propyl) phosphate (TCPP) could also be degraded by ZY1 and the aryl-phosphates was easier to be degraded. The TCPs reduction observed in freshwater and seawater indicated that high salinity might weak the degradability of ZY1. The detected degradation products suggested that TCPs was mainly metabolized though the hydrolysis and hydroxylation. Sequencing analysis presented that the degradation of TCPs relied on the cooperation between sphingobacterium, variovorax and flavobacterium. The cytochrome P450/NADPH-cytochrome P450 reductase and phosphatase were speculated might involve in TCPs degradation. Finally, toxicity evaluation study found that the toxicity of the diesters products was lower than their parent compound based on the generation of the intracellular reactive oxygen (ROS) and the apoptosis rate of A549 cell. Taken together, this research provided a new insight for the bioremediation of TCPs in actual environment.

Occurrence and distribution of organophosphate flame retardants in seawater and sediment from coastal areas of the East China and Yellow Seas

Organophosphates (OPEs) are manmade organic pollutants that are widely used as flame retardants, plasticizers, and antifoaming and hydraulic agents. In this study, seven OPEs in seawater and sediment from the Yellow Sea and East China Sea were determined to study the distribution and diffusion behavior, and to evaluate the environmental risks. The ΣOPEs in the seawater and sediments ranged from below the method detection limit (<MDL) to 497.40 ng/L and from < MDL to 66.50 ng/g dw, respectively. Tri-n-butyl phosphate (TnBP), tris-(1, 3-Dichloro-2-Propyl) phosphate (TDCPP), and tri-meta-cresyl phosphate (TmCP) were the dominant OPEs in the seawater and sediments. OPEs were mainly distributed in coastal areas and the South Yellow Sea, indicating that they are mainly affected by land-based pollution and ocean currents. Fugacity analysis shows that tri-para-cresyl phosphate (TpCP) was in a state of equilibrium, while TDCPP, TnBP, and TmCP other OPEs tended to diffuse from sediment to water. The diffusion behavior of OPEs is mainly affected by their chemical properties. Hazard quotient (HQ) values of TmCP and TpCP in sediment samples were >1.0, indicating high ecological risks to aquatic organisms.

Ecological risk assessment for organophosphate esters in the surface water from the Bohai Sea of China using multimodal species sensitivity distributions

Organophosphate esters (OPEs) as the foremost substitutes of brominated flame retardants have been ubiquitously found in the aquatic environment around the world. However, the information on the community-level risks induced by OPEs to the marine ecosystem remains scarce. This study adopted ten commonly used species sensitivity distribution (SSD) parametric statistical approaches coupled with the acute-to-chronic transformation for the toxicity data to fit the sensitivity distributions of different species to four major OPE congeners including triethyl phosphate (TEP), tri-n-butyl phosphate (TnBP), tri(2-chloroethyl) phosphate (TCEP), and tris(1-chloro-2-propyl) phosphate (TCPP) in the surface water of the Bohai Sea. All SSD models except Exponential for TnBP, TCEP, and TCPP fitted well the chronic toxicity data for the four OPE congeners. Discrepancies appeared among the best fitting models for different congeners, which also happened to the fitting results from the multiple SSD models for each congener. Based on the best fitting models, the hazard concentrations corresponding to the cumulative probability of 5% were 3.58 mg/L, 0.116 mg/L, 1.30 mg/L, and 1.44 mg/L for TEP, TnBP, TCEP, and TCPP, respectively. The risks induced by the four OPE congeners to the Bohai Sea ecosystem were negligible during the monitoring period because of both the risk quotients and the hazard indexes far <0.1. This study drew a clear picture of the joint ecological risks of TEP, TnBP, TCEP, and TCPP to the Bohai Sea environment. The application of multimodal SSD statistical methods will benefit the accurate derivation of water quality criteria and the community-level ecological risk assessment for pollutants.

Terrigenous export and ocean currents' diffusion of organophosphorus flame retardants along China's adjacent seas

High demands for but strict regulatory measures on Organophosphorus Flame Retardants (OPFRs) have resulted in mainland China transitioning from the region that imports OPRFs to one that exports these substances. Simultaneously, large quantities of terrigenous OPFRs have been exported to adjacent seas by the major river systems, particularly the Yangtze River. This study examined the presence of ten OPFRs in China's adjacent seas. High levels of OPFRs were observed in seas south of mainland China, with Tris (2-chloroethyl) phosphate (TCEP) and Tris (1,3-dichloro-2-propyl) phosphate (TDCPP) dominant. The terrigenous OPFRs were redistributed by the ocean surface currents, with OPFRs tending to accumulate in regions with lower current speed. The producers of OPFRs are mainly distributed along the Haihe, Yellow, and Yangtze river systems. The application of OPFRs to electric vehicle charging stations, charging connectors, and 5G infrastructure in the Chinese mainland will likely drive rapid growth in OPFR related industry in the future. The diffusion trend map of OPFR indicated that the Bohai Sea and the central northern Yellow Sea are at high risk of ecological damage in the spring. The offshore region of the north of the South China Sea tended to aggregate more OPFRs in summer. Regions of the OPFR aggregation effect were at a higher risk of ecological damage.