Accumulation and distribution of organophosphate flame retardants (PFRs) and their di-alkyl phosphates (DAPs) metabolites in different freshwater fish from locations around Beijing, China

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.

Water temperature governs organophosphate ester dynamics in the aquatic food chain of Poyang Lake

Organophosphate esters (OPEs) are increasingly recognized as pervasive environmental contaminants, primarily from their extensive application in flame retardants and plasticizers. Despite their widespread presence, the intricacies of OPE bioaccumulation within aquatic ecosystems remain poorly understood, particularly the environmental determinants influencing their distribution and the bioaccumulation dynamics across aquatic food chains. Here we show that water temperature plays a crucial role in modulating the dispersion of OPE in the aquatic environment of Poyang Lake. We quantified OPE concentrations across various matrices, uncovering levels ranging from 0.198 to 912.622 ng L-1 in water, 0.013-493.36 ng per g dry weight (dw) in sediment, 0.026-41.92 ng per g wet weight (ww) in plankton, 0.13-2100.72 ng per g dw in benthic invertebrates, and 0.31-3956.49 ng per g dw in wild fish, highlighting a pronounced bioaccumulation gradient. Notably, the intestines emerged as the principal site for OPE absorption, displaying the highest concentrations among the seven tissues examined. Among the various OPEs, tris(chloroethyl) phosphate was distinguished by its significant bioaccumulation potential within the aquatic food web, suggesting a need for heightened scrutiny. The propensity for OPE accumulation was markedly higher in benthic invertebrates than wild fish, indicating a differential vulnerability within aquatic biota. This study lays a foundational basis for the risk assessment of OPEs as emerging contaminants and underscores the imperative to prioritize the examination of bioaccumulation effects, particularly in benthic invertebrates, to inform future environmental safeguarding strategies.

Organophosphate esters and their metabolites in silver pomfret (Pampus argenteus) of the Vietnamese coastal areas: Spatial-temporal distribution and exposure risk

A large number of studies on organophosphate esters (tri-OPEs) in marine organisms have not assessed the simultaneous occurrence of tri-OPEs and their metabolites (di-OPEs) in these species. This research investigated the concentration and geographical distribution of 15 tri-OPEs and 7 di-OPEs in 172 samples of Pampus argenteus that were collected annually from 2021 to 2023 at three distinct locations along the Vietnamese coast. As a result, tri-OPEs and di-OPEs were detected in numerous fish samples, indicating their widespread spatial and temporal occurrence in marine fish and pointing out the importance of monitoring their levels. The tri-OPEs and di-OPEs ranged within 2.1-38.9 ng g-1 dry weight (dw) and 3.2-263.4 ng g-1 dw, respectively. The mean concentrations of tri-OPEs ranged from 0.4 (TIPrP) to 5.4 ng g-1 dw (TBOEP), with TBOEP and TEHP having the highest mean values. In addition, the profiles of tri-OPEs in fish exhibited a descending order: Σalkyl OPEs > ΣCl-alkyl OPEs > Σaryl OPEs. The di-OPEs, namely BEHP and DMP, had the highest mean levels, measuring 33.4 ng g-1 dw and 23.8 ng g-1 dw, respectively. Furthermore, there have been significant findings of strong positive correlations between di-OPEs and tri-OPE pairs (p < 0.05). It is worth noting that there is a noticeable difference in the composition of tri-OPEs between the North and other regions. Despite these findings, the presence of OPE-contaminated fish did not pose any health risks to Vietnam's coastal population.

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.

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.

Organophosphorus flame retardants in fish from the middle reaches of the Yangtze River: Tissue distribution, age-dependent accumulation and ecological risk assessment

Two fish species from the middle reaches of the Yangtze River, China, were sampled to investigate the occurrence, tissue distribution, age-dependent accumulation and ecological risk assessment of 24 organophosphorus flame retardants (OPFRs). Seventeen OPFRs were detected in tissue samples with a total concentration ranging from not detected (ND) to 1092 ng g-1 dw. Cl-OPFRs were predominant in all tissues (mean: 145 ng g-1 dw, median: 72.9 ng g-1 dw) and the concentrations of OPFRs in brain were the greatest (crucian carp: 525 ng g-1 dw, silver carp: 56.0 ng g-1 dw) compared with the other three organs (e.g., liver, muscle and gonad). Furthermore, the total concentrations of OPFRs in crucian carp tissues were significantly greater than those in silver carp (P < 0.01). Age-dependent accumulation of OPFRs was observed in the two fish species, but the accumulation profiles in the two fish species were different. Ecological risk assessment demonstrated that both fish species were at medium to high risk, and TDCIPP was a main contributor (>50%).

Organophosphate esters in edible marine fish: Tissue-specific distribution, species-specific bioaccumulation, and human exposure

Although growing evidences have proved the wide presence of organophosphate esters (OPEs) in marine environments, information on the tissue- and species-specific accumulation characteristics of these emerging pollutants in wild marine fish and the associated human exposure risks are currently lacking. Eleven OPEs were comprehensively investigated for their occurrence and tissue accumulation in 15 marine fish species and their living environment matrices (seawater and sediment) from the Beibu Gulf. The OPE concentrations were statistically higher in the liver (17.6-177 ng/g ww, mean 90.9 ± 52.1 ng/g ww) than those of muscle tissues (2.04-22.9 ng/g ww, mean 10.6 ± 5.6 ng/g ww). Tris (phenyl) phosphate (TPHP) was the most predominant OPE congeners in fish liver, and tris(2-chloropropyl) phosphate (TCIPP) and tris(2-chloroethyl) phosphate (TCEP) were dominant OPEs in the muscle. The results suggested different OPE profiles occurred between the tissues. The median logarithmic bioaccumulation factors (BAFs) of TPHP in the muscle and liver, and TCEP in muscle were higher than the regulatory benchmark value (BCF >3.7), indicating very strong bioaccumulation. Carnivorous benthic fish appear to potentially accumulate TPHP, while pelagic and omnivory fish tend to accumulate TCIPP and TCEP. Except for proteins and phospholipids, no significant relationships were found between OPE levels and other biological properties of the studied fish. The results implied that the species-specific accumulation of OPEs mainly attributed to habitat and feeding habit rather than the difference of biochemical composition among species. Metabolism may have a significant effect on the bioaccumulation of OPEs in marine fish. The dietary risks of OPEs for consumers in different age groups ranged from 2.02 × 10-4 to 3.01 × 10-3, indicating relatively low human exposure risks from fish consumption.

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.

Optimization of the ultrasound-assisted extraction method for determining high production volume chemicals in fish liver and skin samples

The aquatic ecosystem is one of the most delicate environments, housing a diverse range of organisms, including fish, all of which are exposed to a wide variety of pollutants. The accumulation of these harmful substances in fish, which are part of the human diet, presents a significant health risk to humans. In our study, we have optimized an extraction technique to determine the presence of 25 high production volume chemicals in liver and skin samples taken from commonly consumed fish species. We have employed ultrasound-assisted extraction in conjunction with gas chromatography tandem mass spectrometry to achieve this goal. Apparent recoveries of the method ranged from 50% to 111% for both sample types with some exceptions such as most of the benzosulfonamides and benzothiazole. Additionally, the method's detection and quantification limits varied from 0.1 to 1.7 ng g-1 (dry weight, d.w) and 0.2-4.5 ng g-1 (d.w), respectively. Our investigation focused on three frequently consumed fish species in Tarragona: sea bass, sea bream, and turbot. Almost all of the samples we analysed contained traces of contaminants, with phthalates being the most commonly detected. The highest concentrations were observed for diethyl phthalate, with levels peaking at 8350 ng g-1 (d.w.). Organophosphate esters, such as triethyl phosphate and tributyl phosphate, also showed notable presence, with peak concentrations of 93.6 and 34.0 ng g-1 (d.w.), respectively.

Essential and non-essential elements in marine silverside Odontesthes argentinensis from southwestern Atlantic coast: Tissues bioaccumulation, biomagnification and public health risk assessment

In order to assess the metal pollution in the southwestern Atlantic coast, levels of eleven metals: Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, and Zn and one metalloid: As in water and tissues of Odontesthes argentinensis from the Samborombón Bay (SB) and Partido de La Costa (PC) were examined. Additionally, bioconcentration, and bioaccumulation factors, estimated daily intake (EDI) for adults and children, and the hazard risk for fishermen and general populations were evaluated. Cadmium, Cu and Zn levels in the water samples exceeded the limits established by international guidelines for the protection of aquatic life in marine environments (CCME). The liver showed the highest concentrations of As, Cu, Fe, and Zn, while muscle showed the least levels of all elements examined. Bioaccumulation of Cd, Cu, Mn, Pb and Zn were observed in all tissues, while Ba and Sr bioaccumulated significantly in the gills. The fish δ15N values significantly varied between sites, however, no biodilution or biomagnification was observed. The Target Hazard Quotients (THQ) and the Carcinogenic Risk (CR) indices suggest that there is no human health risk to the fishermen and general populations from the O. argentinensis consumption. Furthermore, As (27%) and Cr (33%) concentrations in silversides from PC and SB, respectively, exceeded the levels recommended by local and international guidelines.

Exposure, bioaccumulation, and risk assessment of organophosphate flame retardants in crayfish in the middle and lower reaches of the Yangtze River

Organophosphate flame retardants (OPFRs), a novel class of persistent pollutants, are widely distributed in the environment, and their potential health risks have garnered significant global attention in recent years. Crayfish is a popular freshwater crustacean product in China primarily sourced from the middle and lower reaches of the Yangtze River. The purpose of this study was to investigate the exposure levels of OPFRs in crayfish, assess the health and safety risks associated with crayfish consumption, and explore the bioaccumulation of OPFRs in environmental water and sediment on crayfish. Ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) was employed to analyze 7 common OPFRs in 106 crayfish samples and 76 environmental samples. The results revealed that OPFRs were detected at a high frequency of 100 % in crayfish, with tripropyl phosphate (TPP) being the predominant pollutant found in edible portions while also exhibiting secondary contamination within the crayfish food chain. Monte Carlo modeling combined with @risk risk assessment software demonstrated that TPP present in crayfish muscles had the most substantial impact on health effects, however, overall OPFR exposure did not pose significant risks to human health. Furthermore, analysis of OPFRs bioenrichment ability indicated that crayfish predominantly accumulated these compounds within their edible parts from surrounding environmental water sources, particularly highlighting TPP's potential for bioaccumulation.

Enrichment and distribution of 3,6-dichlorocarbazole in red crucian carp (Carassius auratus) and its hepatotoxicity

Polyhalogenated carbazoles (PHCZs) are a class of organohalogen compounds where the hydrogen atom on the carbazole ring is replaced by a halogen atom. In recent years, PHCZs have drawn increasing concern due to their persistence, dioxin-like toxicity, bioaccumulation, potential ecological hazards and widespread occurrence in the environment. Current research on the enrichment and depuration of PHCZs in biological tissues and organs is insufficient, and the liver toxicity is unclear. Herein, to understand the enrichment and elimination of 3,6-DCCZ in fish tissues and organs as well as the hepatotoxicity, we exposed the red crucian carp to 20 and 100 μg/L of 3,6-DCCZ for 20 days followed by a depuration period of 10 days. The 3,6-DCCZ enrichment in each organ tissue was classified from high to low: brain > liver, intestine, gill > muscle. For depuration, 3,6-DCCZ was quickly excreted in the various organs of the red crucian carp; however, the liver depuration was slow, with the concentration of 3,6-DCCZ was maintained at 0.25-0.35 μg/g. 3,6-DCCZ exposure at both tested concentrations induced oxidative stress in red crucian carp, causing lipid peroxidation and DNA damage, as well as some histopathological changes in the liver, such as cell vacuolization, nucleus pyknosis, nucleus pleomorphism, no nucleus areas. Additionally, the 3,6-DCCZ exposure at higher concentration (100 μg/L) caused more serious damage and abnormal lipid metabolism in the red crucian carp liver.

Organophosphate Triesters and Their Transformation Products in Sediments of Mangrove Wetlands in the Beibu Gulf, South China Sea

As emerging pollutants, organophosphate esters (OPEs) have been reported in coastal environments worldwide. Nevertheless, information on the occurrence and ecological risks of OPEs, especially the related transformation products, in mangrove wetlands is scarce. For the first time, the coexistence and distribution of OP triesters and their transformation products in three mangrove wetlands in the Beibu Gulf were investigated using ultrasonication and solid-phase extraction, followed by UHPLC-MS/MS detection. The studied OPEs widely existed in all the sampling sites, with the total concentrations ranging from 6.43 ng/g dry weight (dw) to 39.96 ng/g dw and from 3.33 ng/g dw to 22.50 ng/g dw for the OP triesters and transformation products, respectively. Mangrove wetlands tend to retain more OPEs than the surrounding coastal environment. Pearson correlation analysis revealed that the TOC was not the sole factor in determining the OPEs' distribution, and degradation was not the main source of the transformation products in mangrove sediments in the Beibu Gulf. The ecological risks of selected OPEs for different organisms were also assessed, revealing a medium to high risk posed by OP diesters to organisms. The levels or coexistence of OPEs and their metabolites in mangroves need constant monitoring, and more toxicity data should be further studied to assess the effect on normal aquatic organisms.

Tissue distribution and trophic transfer of organophosphate triesters and diesters in three marine mammals of the Liaodong Bay and the Northern Yellow Sea

Tissue (muscle, liver, kidney, lung, and heart) distribution and trophic transfer of organophosphate (OP) triesters and diesters in stranded 10 minke whales, 20 spotted seals and 27 East Asian finless porpoises from the Liaodong Bay and the Northern Yellow Sea were evaluated. The OP triesters and diesters were widely found in the tissues of the three marine mammals and their preys, with mean concentrations ranging from below the limits of detection (LOD) to 4342 μg/kg dry weight (dw) and from below the LOD to 1460 μg/kg dw, respectively. Tissue-specific distribution of the OP triesters or diesters were found in the investigated marine mammals with chemical-specific and species-specific. Log Kow negatively affect the accumulation of OP diesters in the marine mammals (p < 0.05), which related to their accumulation pathway in the tissues. The biological traits of the three marine mammals, body length, gender and age could affect the distribution of several OP triesters or diesters. Yet more concern is that significantly biological magnification was found for bis(2-chloroethyl) phosphate (BCEP) with trophic magnification factor (TMF) of 5.36 and for tris(2-ethylhexyl) phosphate (TEHP)(TMF:2.88) along with the finless porpoise food web. These results considerably contribute to expanding understanding of OP triesters or diesters pollution on the organisms in marine ecosystem.

Review on typical organophosphate diesters (di-OPEs) requiring priority attention: Formation, occurrence, toxicological, and epidemiological studies

The impact of primary metabolites of organophosphate triesters (tri-OPEs), namely, organophosphate diesters (di-OPEs), on the ecology, environment, and humans cannot be ignored. While extensive studies have been conducted on tri-OPEs, research on the environmental occurrence, toxicity, and health risks of di-OPEs is still in the preliminary stage. Understanding the current research status of di-OPEs is crucial for directing future investigations on the production, distribution, and risks associated with environmental organophosphate esters (OPEs). This paper specifically reviews the metabolization process from tri-OPEs to di-OPEs and the occurrence of di-OPEs in environmental media and organisms, proposes typical di-OPEs in different media, and classifies their toxicological and epidemiological findings. Through a comprehensive analysis, six di-OPEs were identified as typical di-OPEs that require prioritized research. These include di-n-butyl phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), bis(1,3-dichloro-2-propyl) phosphate (BDCIPP), bis(2-chloroethyl) phosphate (BCEP), bis(1-chloro-2-propyl) phosphate (BCIPP), and diphenyl phosphate (DPHP). This review provides new insights for subsequent toxicological studies on these typical di-OPEs, aiming to improve our understanding of their current status and provide guidance and ideas for research on the toxicity and health risks of di-OPEs. Ultimately, this review aims to enhance the risk warning system of environmental OPEs.

Organophosphate diesters (DAPs) and hydroxylated organophosphate flame retardants (HO-OPFRs) as biomarkers of OPFR contamination in a typical freshwater food chain

Organophosphate flame retardants (OPFRs) can rapidly biotransform into two types of metabolites in biota: (1) organophosphate diesters (DAPs) and (2) hydroxylated OPFRs (HO-OPFRs). Therefore, the levels of parent OPFRs alone are not sufficient to indicate OPFR pollution in biological organisms. This study analyzed 12 OPFR metabolites, including 6 DAPs and 6 HO-OPFRs, in a typical freshwater food chain consisted of crucian carp, catfish, mud carp, snakehead, and oriental river prawn. The total concentrations of OPFR metabolites were comparable to those of parent OPFRs, and ranged from 0.65 to 17 ng/g ww. Bis(2-butoxyethyl) 3'-hydroxy-2-butoxyethyl phosphate (14%-77%), di-n-butyl phosphate (DNBP) (6.7%-24%), bis(1-chloro-2-propyl) phosphate (BCIPP) (0.7%-35%), and 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate (BCIPHIPP) (6.0%-24%) were the major OPFR metabolites. Various aquatic species exhibited significant differences in their OPFR metabolite/parent ratios (MPR) (p < 0.05), indicating varying biotransformation potentials of different organisms for various OPFRs. The growth-independent accumulation of tri-n-butyl phosphate (TNBP), tris(chloro-2-propyl) phosphate (TCIPP), triphenyl phosphate, and 2-ethylhexyl diphenyl phosphate in mud carps could be explained by their biotransformation potential. A significant negative correlation was found between the concentration of bis(2-butoxyethyl) phosphate and δ15N values (p < 0.05), with a calculated trophic magnification factor (TMF) of 0.66. Significant positive correlations were observed between BCIPP and TCIPP (R2 = 0.25, p < 0.05), as well as between DNBP and TNBP (R2 = 0.30, p < 0.01), implying that these two DAPs could be used as biomarkers to quantitatively assess TCIPP and TNBP contamination in wild aquatic organisms.

Enhanced LC-ESI-MS/MS Sensitivity by Cationic Derivatization of Organophosphorus Acids

The chemical derivatization to enhance the signal intensity and signal-to-noise (S/N) of several organophosphorus (OP) acids in liquid chromatography tandem mass spectrometry (LC-ESI-MS/MS) is illustrated. The OP class of compounds represents the environmental degradants of OP nerve agents and pesticides. N-(2-(bromomethyl)benzyl)-N,N-diethylethanaminium bromide (CAX-B) was utilized to derivatize a panel of eight acids consisting of five alkyl methylphosphonic acids (ethyl-, isopropyl-, isobutyl-, cyclohexyl-, and pinacolyl-methylphosphonic acid) along with three dialkylphosphate analogs (diethyl-, dibutyl-, and diethyl thio-phosphate). The derivatization reaction with CAX-B was conducted in acetonitrile in the presence of potassium carbonate at 70 °C for 1 h. The resulting acid derivatives were analyzed with an LC-Orbitrap-ESI-MS/MS, and their dissociation processes were investigated. It was found that the derivatization procedure increased the limits of identification (LOIs) by one to over two orders of magnitude from the range of 1 to 10 ng/mL for the intact OP-acids to the range of 0.02-0.2 ng/mL for the derivatized acids utilizing an LC-MS(QqQ) in MRM mode, regardless of the sample matrix (hair, concrete, or plant extracts). The interpretation of the corresponding ESI-MS/MS spectra for each type of derivatized sub-OP family revealed the formation of characteristic neutral losses and a characteristic ion for the organophosphorus core. This derivatization is beneficial and useful for screening and identifying target and "unknown" OP acids.

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.

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.

Occurrence of some legacy and emerging contaminants in feed and food and their ranking priorities for human exposure

The "feed-to-food" pathway is one of the most important routes for human exposure to manmade contaminants. The contaminants could threaten human health through the "feed-to-food" route and have recently become of great public concern. This review selects the representative legacy and emerging contaminants (ECs), such as polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), organophosphate esters (OPEs), short-chain chlorinated paraffins (SCCPs), and per- and polyfluoroalkyl substances (PFASs), regarding their occurrence in feed and food, as well as their metabolites and transport in farming and livestock ecosystems. Factors that might influence their presence and behavior are discussed. This review raises an approach to rank the priority of ECs using the EC concentrations in feed and food and using the hazard quotient (HQ) method for human health. Although SCCPs have the highest levels in feed and food, their potential risks appear to be the lowest. PFASs have the highest HQs on account of human exposure risk. Future research should pay more attention to the combined effects of multiple ECs.

Direct evidence of the important role of proteins in bioconcentration and biomagnification of PFASs in benthic organisms based on comparison with OPEs

Despite the wide acceptance that bioconcentration and biomagnification of per/polyfluoroalkyl substances (PFASs) is related to proteins in organisms, few direct evidences are available. Here, bioconcentration and biomagnification of 9 organophosphate esters (OPEs) and 16 PFASs, which have similar range of log K_ow (octanol-water partitioning coefficient) values, were compared in the benthic food chain of biofilm-snail in Taihu Lake, China. The ∑OPEs level in water (150-23,036 ng/L) was significantly higher than ∑PFASs (57.3-351 ng/L). Although the logarithm of bioconcentration factors of both OPEs and PFASs in biofilm positively correlated with their log K_ow, the slope of PFASs was 4 times of that of OPEs, which might be due to the strong interactions of PFASs with biofilm extracellular proteins. Additionally, PFASs exhibited distinctly greater biomagnification factors from biofilm to snails (3.09-17.8) than OPEs (0.39-3.48). Significant correlations between the concentrations and protein contents in snails were observed for most long-chain PFASs, but not for any OPEs. Multiple receptor models identified polyurethane foam (77.9 %) and food packaging/metal plating (56.9 %) were the primary sources of OPEs and PFASs in Taihu Lake, respectively. We provided strong and direct evidences that proteins facilitated bioconcentration and biomagnification of PFASs.

Bioaccumulation and Trophic Transfer of Organophosphate Flame Retardants and Their Metabolites in the Estuarine Food Web of the Pearl River, China

The accumulation and trophodynamics of organophosphate flame retardants (OPFRs) and their metabolites were investigated in the estuarine food web of the Pearl River, China. The mean ∑OPFR concentration among the investigated species increased in the following order: fish [431 ± 346 ng/g lipid weight (lw)] < snail (1310 ± 621 ng/g lw) < shrimp (1581 ± 1134 ng/g lw) < crab (1744 ± 1397 ng/g lw). The di-alkyl phosphates (DAPs) of di-(n-butyl) phosphate (DNBP), bis(2-butoxyethyl) phosphate (BBOEP), and diphenyl phosphate (DPHP) were the most abundant metabolites, with concentrations same as or even higher than their corresponding parent compounds. The log bioaccumulation factors for most OPFRs were lower than 3.70, and significant biomagnification was only found for trisphenyl phosphate [TPHP, with the trophic magnification factors (TMFs) > 1]. The TMFs of OPFRs, except for TPHP and tributyl phosphate had a positive correlation with lipophilicity (log K_OW, p ≤ 0.05) and a negative correlation with the biotransformation rate (log K_M, p ≤ 0.05). The mean TMF > 1 was observed for all of the OPFR metabolites based on the bootstrap regression method. The "pseudo-biomagnification" of OPFR metabolites might be attributed to the biotransformation of OPFRs in organisms at high trophic levels.

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.

Occurrence, bioaccumulation and trophic transfer of organophosphate esters in marine food webs: Evidence from three bays in Bohai Sea, China

Due to the widespread use of organophosphate esters (OPEs), the occurrence and trophic transfer of OPEs have attracted attentions in ecosystems. However, as the final sink for these chemicals, the bioaccumulations and trophodynamics of OPEs in marine ecosystems are still not clear. In this study, seawater, sediment and marine organisms collected from Bohai Bay (BHB), Laizhou Bay (LZB), and Liaodong Bay (LDB) in Bohai Sea (BS), China were analyzed to investigate the occurrence, bioaccumulation and trophic transfer of typical OPEs. Total concentration of OPEs (∑₉ OPEs) in surface water in LZB (255.8 ± 36.44 ng/L) and BHB (209.6 ± 35.61 ng/L) was higher than that in LDB (170.0 ± 63.73 ng/L). Marine organisms in LZB accumulated the highest concentrations of OPEs among the 3 bays (∑₁₀OPEs, 70.56 ± 61.36 ng/g ww). Average bioaccumulation factor (BAF) of OPEs in marine organism in BHB, LZB, and LDB was ranged from -2.48 to 0.16, from -2.96 to 1.78, and from -2.59 to 0.59. We also found that trophic magnification factors (TMF) are generally <1, which suggested trophic dilutions of OPEs in BS, China. Nevertheless, the relatively high OPEs levels in BS still may bring potential risks to ecosystem and human health.

Adsorption behavior of hierarchical porous biochar from shrimp shell for tris(2-chloroethyl) phosphate (TCEP): Sorption experiments and DFT calculations

Tris(2-chloroethyl) phosphate (TCEP) as a new type of flame retardant exists in various water environments, causing great risks to humans and the environment. In this study, shrimp shell was used to prepare an economical and environmental-friendly adsorbent for the efficient removal of TCEP. The systematic studies including characterization, removal performance, and adsorption mechanism of shrimp shell biochar toward TCEP were carried out. Adsorption kinetics and thermodynamics showed that fast equilibrium reached within 30 min, the maximum adsorption capacity q_m was 108 μmol g^-1 at 298 K, and the adsorption process is spontaneous and exothermic. The environmental factor, such as temperature, pH, inorganic anions and organic matter hardly affected the adsorption performance. Structural characterization indicated that the hierarchical porous structure of shrimp shell biochar is the key to excellent adsorption performance. The adsorption mechanisms were further revealed using density functional theory (DFT) calculations, and the hydrogen bond, van der Waals interactions, Cl-H interactions, and pi-H interactions were identified as potential interaction mechanisms between TCEP and specific biochar structures. The calculated binding energy between TCEP and simplified biochar structure suggested that oxygen-containing groups especially carboxyl, hydroxyl and aldehyde facilitate the adsorption. Our work not only provides a novel strategy for the quick remediation of organophosphate-contaminated water environments but also offers new opportunities for crustacean waste biomass valorization.

Occurrence, distribution, and ecological risk of organophosphorus flame retardants and their degradation products in water and upper sediment of two urban rivers in Shenzhen, China

Organophosphorus flame retardants (OPFRs) are widely used in various industrial manufacturing processes; thus, their environmental impact in agglomerated industrial areas is of great concern. In this study, seventeen kinds of OPFRs and five kinds of organophosphate diesters (Di-OPs) in water and upper sediment samples from two urban rivers in the agglomerated industrial area of Shenzhen city, China, were investigated. The results showed that the total concentrations of detectable OPFRs ranged from 3438.83 to 12,838.87 ng/L with an average of 6494.94 ng/L in water samples and from 47.16 to 524.46 ng/g (dry weight, dw) with an average of 181.48 ng/g dw in sediment. The values were higher than those in other rivers worldwide. Tris(2-chloroethyl) phosphate (TCEP) is the predominant OPFRs in water and upper sediment, up to 10,664.23 ng/L in water and 414.12 ng/g dw in sediment. The total concentration of OPFRs of sediment samples in the Maozhou River was around twice as high as in the Guanlan River. The results indicated that the level of OPFRs was associated with the industrial activity intensity. Di-OPs exhibited lower concentrations than their parent compounds, and can be attributed to the degradation/metabolism of their parent compounds in the river. The sediment-water partition of OPFRs is significantly correlated with their log Kow values. Risk assessment revealed moderate ecological risks posed by OPFRs in water to aquatic organisms. The present study revealed the pollution status of OPFRs in rivers from agglomerated industrial and residential areas.

Integrating Physiologically Based Pharmacokinetic Modeling-Based Forward Dosimetry and in Vitro Bioassays to Improve the Risk Assessment of Organophosphate Esters on Human Health

The ability to accurately assess the health risks of contaminants is limited by the shortcomings of toxicological standards. Using organophosphate esters (OPEs) as an example, this study attempted to integrate physiologically based pharmacokinetic (PBPK)-based forward dosimetry and in vitro bioassays to assess the likelihood of contaminants inducing biological effects in humans. The total exposure level of OPEs for Chinese residents was 19.5 ± 8.71 ng/kg/day with inhalation being the main exposure pathway. Then, human PBPK models were developed for individual OPEs to predict their steady-state concentrations in human tissues, and the predicted median levels in blood were close to the measurements. The reference doses (RfDs) of OPEs based on in vitro bioassays were comparable to in vivo animal-derived RfDs, demonstrating the reliability of in vitro bioassays. Therefore, the likelihood of OPEs inducing bioactivities in humans (RQ_in-vitro) was calculated using in vitro toxicity data and OPE levels in human tissues. The RQ_in-vitros of tris(2-chloroisopropyl) phosphate, tris(1,3-dichloropropyl) phosphate, and triphenyl phosphate (7.68 × 10^-5-3.18 × 10^-3) were comparable to the risks assessed using traditional RfDs (5.22 × 10^-5-1.94 × 10^-3), indicating the credibility of the method proposed in this study. This study establishes a new framework to improve the health risk assessment of contaminants without sufficient toxicity data and minimize the need for animal experimentation.

Temporal trends and health risks of organophosphorus flame retardants in fishes in Taihu Lake from 2013 to 2018

Organophosphorus flame retardants (OPFRs) are synthetic, physical additive flame retardants widely detected in the environment. To investigate the temporal trends of OPFRs in Taihu regions and the associated health risks from fish consumption, 150 fish samples of five species were collected from Taihu Lake in China from 2013 to 2018. Eight OPFRs were measured, having 2-ethylhexyl diphenyl phosphate (90.7%) and tris (1,3-dichloro-2 propyl) phosphate (21.5%) as the most and least frequently detected OPFRs, respectively. Among the eight OPFRs, tris (chloropropyl) phosphate concentration (446 pg/g, wet weight) was higher than others. The maximum cumulative concentration of the OPFRs (∑₈OPFRs) was observed in large icefish (1.69 × 10³ pg/g), while silver carp (841 pg/g) had the lowest. For the temporal trends, higher levels of ∑₈OPFRs (1.91 × 10³ pg/g) were detected in 2013 than in other years, although no significant change in the trend occurred over time. The estimated daily intake of OPFRs from large icefish consumption was 1.20 × 10³ pg/kg-bw/day, higher than that of other fish species. The Monte Carlo simulations showed that ≤0.3% of adults and children would suffer non-cancer health risks from OPFRs via fish consumption. This study provides the first data on temporal trends of OPFRs in Taihu Lake.

Occurrence of emerging brominated flame retardants and organophosphate esters in marine wildlife from the Norwegian Arctic

To understand the exposure and potential sources of emerging brominated flame retardants (EBFR) and organophosphate esters (OPEs) in marine wildlife from the Norwegian Arctic, we investigated concentrations of EBFRs in 157 tissue samples from nine species of marine vertebrates and OPEs in 34 samples from three whale species. The samples, collected from a wide range of species with contrasting areal use and diets, included blubber of blue whales, fin whales, humpback whales, white whales, killer whales, walruses and ringed seals and adipose tissue and plasma from polar bears, as well as adipose tissue from glaucous gulls. Tris(2-ethylhexyl) phosphate (TEHP) and tris(2-chloroisopropyl) phosphate (TCIPP) ranged from <0.61 to 164 and < 0.8-41 ng/g lipid weight, respectively, in blue whales and fin whales. All other EBRFs and OPEs were below the detection limit or detected only at low concentration. In addition to the baseline information on the occurrence of EBFRs and OPEs in marine wildlife from the Arctic, we provide an in-depth discussion regarding potential sources of the detected compounds. This information is important for future monitoring and management of EBFRs and OPEs.

Determination of Organophosphate Ester Metabolites in Seafood Species by QuEChERS-SPE Followed by LC-HRMS

Organophosphate triesters are compounds widely used in industries and are ubiquitous in the environment, where they can be transformed into organophosphate diesters. Some organophosphate diesters are also used by industry. Several studies suggest organophosphate diesters can have toxic effects for reproduction, and hazardous and mutagenic properties. Due to the impact these compounds can have on marine biota and human beings through the consumption of fish and shellfish, it is necessary to study their presence in widely consumed seafood species. We therefore developed an analytical method for determining six of the most common organophosphate diesters in seafood. The procedure is based on the Quick, Easy, Cheap, Effective, Rugged and Safe extraction method and a solid phase extraction clean-up, followed by liquid chromatography coupled to high-resolution mass spectrometry. The method was optimised and validated for seafood with different lipid content, providing satisfactory relative recoveries (from 89 to 138%) and limits of detection (1.0-50 ng g^-1 dry weight), as well as repeatability values (RSD% (n = 5, 100 ng g^-1 (dry weight)) lower than 15%. Eight seafood species were analysed using this method and two organophosphate diesters were detected and quantified in all the samples, demonstrating the suitability of the method.

Exposure to tris(1,3-dichloro-2-propyl) phosphate for two generations aggravates the adverse effects on survival and growth of zebrafish at environmentally relevant concentrations

It was reported that tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) could inhibit the growth of F0-generation fish. However, multi-generation effects of TDCIPP on survival and growth of fish remain unknown. In this study, the effects of TDCIPP on survival and growth in F1 generation zebrafish were evaluated after two-generation exposure. Results demonstrated that TDCIPP inhibited the survival and growth of F1-generation zebrafish at 96 hpf and 30 dpf. Moreover, compared with the F0 generation, two-generation exposure resulted in a greater accumulation of TDCIPP in F1 generation zebrafish, and strongly down-regulated the expression of genes related to the GH/IGF axis (gh, igf1, igf2b) and HPT axis (tshβ). Taken together, for the first time, this study revealed that exposure to TDCIPP for two generations at environmentally relevant concentrations aggravated the adverse effects on growth and survival in zebrafish.

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.

Organophosphate esters and their diester metabolites in infant formulas and baby supplementary foods collected in Beijing, China: Occurrence and the implications for infant exposure

Organophosphate esters (OPEs) have been extensively used as flame retardants and/or plasticizers and they found to be ubiquitous in various environmental matrices along with the gradual phase-out of brominated flame retardants (BFRs). Moreover, their main metabolites, organophosphate di-esters (di-OPEs), were also frequently detected. However, few studies focused on the occurrence of OPEs and di-OPEs in foods. In this study, fourteen OPEs and five di-OPEs were measured in infant formula and baby supplementary food (BSF) collected in Beijing, China. Most OPEs and di-OPEs presented high detection frequencies, which indicated their ubiquity in baby foods. The concentrations of ∑₁₄OPEs in the 75 infant formula samples ranged from 0.79 to 159 ng/g, with a median of 23.2 ng/g, and in which triphenyl phosphate (TPhP) was the most abundant compound. The concentrations of ∑₁₄OPEs in the 32 BSF samples were 4.42-115 ng/g (median: 19.5 ng/g), and tri(3-chloropropyl) phosphate (TCIPP) was predominant. Moreover, no significant difference was observed between OPE levels in infant formula and BSF. The median concentrations of Σ₅di-OPEs in infant formula and BSF were 3.39 and 5.43 ng/g, respectively. However, no significantly correlation was observed between concentrations of di-OPEs and their parent compounds, which indicated they have different sources. The median estimated dietary intakes (EDIs) of the ∑₁₄OPEs were from 165 to 383 ng/kg bodyweight (bw)/day for infants via infant formula feeding, and were from 429 to 470 ng/kg bw/day via BSF feeding. A comparison to corresponding reference dose (RfD) suggested that dietary intakes of OPEs to Beijing infants via formula/BSF consumption were still unable to cause significant health concerns. However, EDIs of OPEs for infants were found to be significantly higher than that for Chinese adults, and dietary intake might be the predominant OPE intake pathway for infants. To our knowledge, this is the first study to investigate OPEs and their metabolites in baby foods.

Organophosphate esters in agro-foods: Occurrence, sources and emerging challenges

Safety and sustainable agro-food production is important for food and nutrition security. Agro-foods safety is challenged by various emerging environmental contaminants. Organophosphate esters (OPEs) have been reported to occur in various agro-food items worldwide, which has resulted in increasing concerns for effects on health of humans and wildlife, including through agriculture. However, information on presence, sources and transfer routes of OPEs in agro-foods, and consequent health risks remains scant. This review critically evaluates available information on concentrations of OPEs in various agro-foods, and discusses potential sources of OPEs in agro-foods, which are closely related to the ambient agri-environment, agricultural inputs, and agro-foods processing. Some directions for future research are suggested. First, since food is an important exposure pathway to OPEs, systematic monitoring of concentrations of OPEs in various categories of agro-foods is recommended. Second, surveillance of concentrations and characteristics of OPEs in agro-foods and ambient agri-environments, agricultural inputs or processing in the agro-food chain is needed to obtain a more complete description of exposure and transmission behavior of OPEs in agro-foods. Third, future comprehensive studies of transmission, metabolism and accumulation of OPEs in animals or plants, are required. Finally, measures to control emissions of OPEs as sources to agriculture should be taken.

Organophosphate esters in children and adolescents in Liuzhou city, China: concentrations, exposure assessment, and predictors

Dermal contact with dust is commonly considered an important pathway of exposure to organophosphate esters (OPEs), but the importance of OPE uptake from diet is unclear. Herein, we used hand wipes to estimate OPE exposure from indoor dust and examined whether urinary OPE metabolite concentrations were influenced by sociodemographic characteristics, OPE amount in hand wipes, and dietary factors. OPEs were measured in urine and hand wipes from 6 to 18-year-old children and adolescents (n=929) in Liuzhou, China. Sociodemographic and dietary factors were obtained from questionnaire. Six OPE metabolites were detected in >70% of the urine samples, and seven OPEs were detected in >50% of the hand wipes. Estimated daily intakes (EDIs) were calculated using urinary OPE metabolites to investigate the total daily intake of OPEs, in which 0.36-10.1% of the total intake was attributed to the exposure from dermal absorption. In multivariate linear regression models, sex, age, and maternal education were significant predictors of urinary OPE metabolite concentrations. Urinary diphenyl phosphate (DPHP) is positively associated with its parent compounds 2-ethylhexyl-diphenyl phosphate (EHDPP) and triphenyl phosphate (TPHP) in hand wipes. High versus low vegetable intake was associated with a 23.7% higher DPHP (95% confidence interval (CI): 0.51%, 52.1%). Barreled water drinking was associated with a 30.4% (95% CI: 11.8%, 52.0%) increase in bis(1-chloro-2-propyl) 1-hydroxy-2-propyl phosphate (BCIPHIPP) compared to tap water drinking. Our results suggested the widespread exposure to OPEs in children and adolescents. In addition to dermal absorption, dietary intake may be an important exposure source of certain OPEs.

Integrated passive sampling and fugacity model to characterize fate and removal of organophosphate flame retardants in an anaerobic-anoxic-oxic municipal wastewater treatment system

It is crucial to deeply understand the fate and removal mechanism of various organophosphate flame retardants (PFRs) in specified wastewater treatment processes. However, concentration fluctuation and matrix effect in wastewater challenge quantification of PFR flux for both field observation and model validation. We present measured seasonal distribution profiles of time-weighted average (TWA) concentrations by in situ hydrophobic and polar passive samplers and modeled mass transport and transformation by means of fugacity for 11 PFRs with varied structures in an anaerobic-anoxic-oxic (A-A-O) municipal wastewater treatment system, and provided a systematic approach to characterize fate and removal mechanism of PFRs in major compartments via various treatment processes. We find evidence that PFRs have a unique structural-dependent fate and removal in the A-A-O system. Hydrophilic chlorinated-PFRs present persistent in all major compartments and dominate in effluents with significant variations; alkyl-PFRs are majorly reduced by biodegradation; whereas hydrophobic aryl-PFRs have the highest removal percentage, contributed by both sorption on solids and biotransformation. Sensitive analysis shows the most influential operation parameters on removal efficiency varied among the PFRs with different properties. We also conclude passive sampling can be effectively applied to estimate TWA wastewater concentrations and to validate fugacity model prediction.

Bioaccumulation of organophosphorus flame retardants in the marine mussel Mytilus galloprovincialis

The bioaccumulation and depuration of seven organophosphorus flame retardants (OPFRs) in marine mussel Mytilus galloprovincialis were studied. OPFRs showed to be bioavailable in aquatic environments. When mussels are exposed to environmentally relevant concentrations of OPFRs, uptake kinetics fit well to a first-order model with a single compartment; in contrast depuration rates were generally underestimated by that model, most likely because it does not take into account the biotransformation of OPFRs by the organisms. The highest bioaccumulation rates were observed for tricresyl phosphate (TCrP), triphenyl phosphate (TPhP) and 2-ethylhexyldiphenylphosphate (EHDPP). This could be due to the presence of aryl groups in these compounds, their low solubility in water, and their affinity for fat tissues. According to these findings TCrP, with a BCF value of 4042 L kg^-1 wet weight, should be classified in environmental regulations as an accumulative chemical.

High-Resolution Mass Spectrometry Screening of Emerging Organophosphate Esters (OPEs) in Wild Fish: Occurrence, Species-Specific Difference, and Tissue-Specific Distribution

There is a dearth of information regarding the pollution status of emerging organophosphate esters (OPEs) in wild fish. Here, we optimized and validated a quick, easy, cheap, effective, rugged, and safe (QuEChERS) pretreatment method, which was further applied for target, suspect, and nontarget screening of OPEs in n = 48 samples of wild fishes from Taihu Lake (eastern China). This integrated technique allows us to fully identify 20 OPEs, and 9 out of them are emerging OPEs detected in wild fish for the first time. Importantly, some of the emerging OPEs, i.e., tris(2,4-di-tert-butylphenyl) phosphate (TDtBPP), 4-tert-butylphenyl diphenyl phosphate (BPDP), and 2-isopropylphenyl diphenyl phosphate (IPDP), exhibited greater or at least comparable contamination levels as compared to traditional ones. There were no statistically significant interspecies (n = 6) differences regarding OPE concentrations. However, we observed significant differences on OPE concentrations among different tissues of silver carp (Hypophthalmichthys molitrix), for which the intestine has the highest OPE mean concentration (46.5 ng/g wet weight (ww)), followed by the liver (20.1 ng/g ww) ≈ brain (20.0 ng/g ww) > gill (14.8 ng/g ww) > muscle (11.4 ng/g ww). An interesting exception is IPDP, which presents an unexpectedly high concentration in the brain (0.510 ng/g ww). Collectively, this study expands our understanding of OPE contamination in wild fish and clearly shows that emerging TDtBPP, IPDP, and BPDP could play an equally important role as traditional OPEs in contribution of OPE pollution in wild fish samples.

Comparison of extraction and clean-up methods for comprehensive screening of organic micropollutants in fish using gas chromatography coupled to high-resolution mass spectrometry

Monitoring the vast number of micropollutants in the environment by using comprehensive chemical screening is a major analytical challenge. The aim of this study was to evaluate a comprehensive analysis method for screening purposes of fish muscle samples by comparing sample preparation methods for a broad range of mid-to non-polar contaminants. Five extraction and three clean-up methods were evaluated for the analysis of 60 compounds with a log Kow range between 0.8 and 8.3 in fish. Both fresh and freeze-dried muscle tissue and extraction sodium sulphate blanks were included to assess recoveries and matrix effects. The performance of the different methods was evaluated using both comprehensive target and nontarget analysis using high resolution mass spectrometry (HRMS). The results showed that open-column and ultrasonication extractions (recoveries mostly between 20 and 160 %) resulted in higher recoveries than accelerated solvent extraction (ASE) (recoveries mostly between 20 and 80 %) and bead mixer homogenization extractions (recoveries between 0 and 50 % for the whole Kow range). Multilayer silica was the clean-up method resulting in the lowest matrix effects and highest recoveries, however some compounds (mostly pesticides) were denatured under the acidic conditions used. The convenient and time efficient ultrasonication extraction followed by deactivated silica clean-up proved to be promising for both target and nontarget approaches. The large difference in recoveries and number of detected peaks using target and nontarget approaches between fresh and freeze-dried fish seen for all methods calls for careful consideration, and further studies are needed to improve performance for screening of mid-to non-polar compounds in freeze-dried fish.

Organophosphate ester plasticizers in edible fish from the Mediterranean Sea: Marine pollution and human exposure

Concentrations of organophosphate esters (OPEs) plasticizers were analysed in the present study. Fifty-five fish samples belonging to three highly commercial species, European sardine (Sardina pilchardus), European anchovy (Engraulis encrasicolus), and European hake (Merluccius merluccius), were taken from the Western Mediterranean Sea. OPEs were detected in all individuals, except for two hake samples, with concentrations between 0.38 and 73.4 ng/g wet weight (ww). Sardines presented the highest mean value with 20.5 ± 20.1 ng/g ww, followed by anchovies with 14.1 ± 8.91 ng/g ww and hake with 2.48 ± 1.76 ng/g ww. The lowest OPE concentrations found in hake, which is a partial predator of anchovy and sardine, and the higher δ¹⁵N values (as a proxy of trophic position), may indicate the absence of OPEs biomagnification. Eleven out of thirteen tested OPEs compounds were detected, being diphenyl cresyl phosphate (DCP) one of the most frequently detected in all the species. The highest concentration values were obtained for tris(1,3-dichloro-2-propyl) phosphate (TDClPP), trihexyl phosphate (THP), and tris(2-butoxyethyl) phosphate (TBOEP), for sardines, anchovies, and hakes, respectively. The human health risk associated with the consumption of these fish species showing that their individual consumption would not pose a considerable threat to public health regarding OPE intake.

Seasonal variation, source identification, and risk assessment of organophosphate ester flame retardants and plasticizers in surficial sediments from Liao River estuary wetland, China

Organophosphate ester (OPE) flame retardants and plasticizers in surficial sediments were collected in Liao River estuarine wetland during the dry, flood, and level periods to understand the seasonal variation, potential sources, and environmental risks. The concentrations of ∑₁₃OPEs ranged from 19.5 to 67.0 ng g^-1 dry weight (dw), with an average concentration of 30.6 ng g^-1 dw. OPEs pollution displayed a seasonal variation, the concentrations of OPEs in dry period > level period > flood period. Tributyl-n-phosphate was the predominant OPEs, which accounts for 29.7% of ∑₁₃OPEs. Principal component analysis and positive matrix factorization suggested that the pollution sources of OPEs also varied seasonally. The ecological risk of OPEs to aquatic organisms was low, and the non-carcinogenic and carcinogenic risks to human beings were also far below the acceptable level. 2-Ethylhexyl diphenyl phosphate was the major compound causing ecological and non-carcinogenic risk, while tris-(2-chloroethyl) phosphate had the highest carcinogenic risk.

Organophosphate Esters in China: Fate, Occurrence, and Human Exposure

Organophosphate esters (OPEs) are widely used as flame retardants and plasticizers. OPEs have been released into various environments (e.g., water, sediments, dust and air, and soil). To investigate the occurrence and distribution of OPEs in various environments in China, this review collects and discusses the published scientific studies in this field. Chlorinated OPEs, as flame retardants, are the predominant OPEs found in the environment. The analysis of data revealed large concentration variations among microenvironments, including inflowing river water (range: 0.69-10.62 µgL^-1), sediments (range: 0.0197-0.234 µg/g), dust (range: 8.706-34.872 µg/g), and open recycling sites' soil (range: 0.122-2.1 µg/g). Moreover, OPEs can be detected in the air and biota. We highlight the overall view regarding environmental levels of OPEs in different matrices as a starting point to monitor trends for China. The levels of OPEs in the water, sediment, dust, and air of China are still low. However, dust samples from electronic waste workshop sites were more contaminated. Human activities, pesticides, electronics, furniture, paint, plastics and textiles, and wastewater plants are the dominant sources of OPEs. Human exposure routes to OPEs mainly include dermal contact, dust ingestion, inhalation, and dietary intake. The low level of ecological risk and risk to human health indicated a limited threat from OPEs. Furthermore, current challenges and perspectives for future studies are prospected. A criteria inventory of OPEs reflecting the levels of OPEs contamination association among different microenvironments, emerging OPEs, and potential impact of OPEs on human health, particularly for children are needed in China for better investigation.

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.

Organophosphate (OP) diesters and a review of sources, chemical properties, environmental occurrence, adverse effects, and future directions

Over the course of the continual phase-outs of toxic halogenated flame retardants (HFRs), there has been an increasing demand for organophosphate esters (OPEs) in global FR markets. OPE-FRs have largely been identified as OP triesters, which have a basic chemical structure of O = P(OR)₃. In addition to OP triesters, OPEs can refer to another class of related substances, namely, OP diesters that have a typical chemical structure of O = P(OR)₂(OH)). OP diesters are known as biotic or abiotic degradation products of OP triesters. In recent years, environmental scientists have proven that OP diesters widely exist in a variety of environmental matrices and biotic samples around the world, implying the potential risks from OP diester exposure to biota and humans in the environment. Here, we have reviewed the scientific literature for studies involving OP diesters and up to the end of 2020. The aim of the present review is to assess the present understanding of the physicochemical properties, sources (industrial production and degradation), environmental occurrence of OP diesters, and adverse effects to exposed organisms. Based on the literature in the Web of Science core collection, we found that at least 23 OP diesters have been reported as contaminants in various environments or as degradation products of OP triesters. The physicochemical properties of OP diesters vary depending on their specific chemical structures. OP diesters containing halogen atoms and aryl groups seem to be more persistent (with greater estimated half-life (t_1/2) values) in environmental matrices. There were multiple sources of OP diesters, including industrial production and biotic or abiotic degradation from OP triesters. Specifically, we found that ten OP diesters are produced somewhere in the world, and the total annual output was estimated to be 17,050 metric tons (this number is underestimated due to the limitation of the available information). In addition, the wide application of OP triesters worldwide makes the degradation of OP triesters another critical source of OP diesters to the environment and to organisms. Current monitoring studies have demonstrated that some OP diesters were detectable in the human body (via both blood and urine samples), indoor dust, wastewater, or sewage sludge worldwide. The highest concentrations of diphenyl phosphate (DPHP) in human urine have been reported as high as 727 ng/mL (children (aged 0-5 years) urine samples from Australia). In addition, adverse effects following direct or indirect exposure to 11 OP diesters in organisms (including animals, bacteria, and algae) have been reported, and the recorded adverse outcomes following exposure to OP diesters included developmental toxicity, alteration of gene expression, and disturbance of nuclear receptor activity. Biomonitoring studies regarding human samples have frequently reported statistically significant associations between the concentrations of OP diesters and markers of human health (mainly related to reproductive toxicity). Finally, on the basis of current knowledge on OP diesters, we propose prospects for related research directions in future studies.

A review of environmental occurrence, analysis, bioaccumulation, and toxicity of organophosphate esters

The ban and restriction of polychlorinated biphenyls (PCBs) and major brominated flame retardants (BFRs), including hexabromocyclododecane (HBCD) and polybrominated diphenyl ethers (PBDEs), due to their confirmed detrimental effects on wildlife and humans have paved the way for the wide application of organophosphate esters (OPEs). OPEs have been extensively used as alternative flame retardants, plasticizer, and antifoaming agents in various industrial and consumer products, which leads to an increase in production, usage, and discharge in the environment. We compile recent information on the production/usage and physicochemical properties of OPEs and discussed and compared the available sample treatment and analysis techniques of OPEs, including extraction, clean-up, and instrumental analysis. The occurrence of OPEs in sediment, aquatic biota, surface, and drinking water is documented. Toxicity, human exposure, and ecological risks of OPEs were summarized; toxicological data of several OPEs shows different adverse health effects on aquatic organisms and humans. Much attention was given to document evidence regarding the bioaccumulation and biomagnification potential of OPEs in aquatic organisms. Finally, identified research gaps and avenues for future studies are forwarded.

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.