Organophosphorous flame retardants in biota from Svalbard, Norway

Effects of 2-ethylhexyl diphenyl phosphate (EHDPP) on glycolipid metabolism in male adult zebrafish revealed by targeted lipidomic analyses

The present study aims to evaluate the effects of 2-ethylhexyldiphenyl phosphate (EHDPP) on glycolipid metabolism in vivo. Adult male zebrafish were exposed to various concentrations (0, 1, 10, 100 and 250 μg/L) of EHDPP for 28 days, and changes in lipid and glucose levels were measured. Results indicated significant liver damages in the 100 and 250 μg/L EHDPP groups, which both exhibited significant decreases in hepatic somatic index (HSI), elevated activities of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum and liver, as well as hepatocyte vacuolation and nuclear pyknosis. Exposure to 100 and 250 μg/L EHDPP led to significant reductions in serum and liver cholesterol (TC), triglycerides (TGs), and lipid droplet deposition, indicating a significant inhibition of EHDPP on hepatic lipid accumulation. Lipidomic analyses manifested that 250 μg/L EHDPP reduced the levels of 103 lipid metabolites which belong to glycerides (TGs, diglycerides, and monoglycerides), fatty acyles (fatty acids), sterol lipids (cholesterol, bile acids), sphingolipids, and glycerophospholipids, and downregulated genes involved in de novo synthesis of fatty acids (fas, acc, srebp1, and dagt2), while upregulated genes involved in fatty acid β-oxidation (pparα and cpt1). KEGG analyses revealed that EHDPP significantly disrupted glycerolipid metabolism, steroid biosynthesis and fatty acid biosynthesis pathways. Collectively, the results showed that EHDPP induced lipid reduction in zebrafish liver, possibly through inhibiting lipid synthesis and disrupting glycerolipid metabolism. Our findings provide a theoretical basis for evaluating the ecological hazards and health effects of EHDPP on glycolipid metabolism.

Exposure to organophosphate esters among Inuit adults of Nunavik, Canada

Halogenated organophosphate esters (OPEs) are increasingly used as flame retardants to replace polybrominated diphenyl ethers (PBDEs), which have been phased out due to their confirmed persistence, toxicity, and ability to undergo long range atmospheric transport. Non-halogenated OPEs are primarily used as plasticizers. While human exposure to PBDEs in the Canadian Arctic is well documented, it is not the case for OPEs. To assess the exposure to OPEs in Inuit living in Nunavik (northern Québec, Canada), we measured 16 metabolites of halogenated and non-halogenated OPEs in pooled urine samples from the last population health survey conducted in Nunavik, the Qanuilirpitaa? 2017 Inuit Health Survey (Q2017). Urine samples (n = 1266) were pooled into 30 pools by sex (female; male), age groups (16-19; 20-29; 30-39; 40-59; 60+ years old) and regions (Hudson Bay; Hudson Strait; Ungava Bay). Q2017 geometric means and 95 % confidence intervals were compared with data from the Canadian Health Measures Survey Cycle 6 (2018-2019) (CHMS). Halogenated OPEs were systematically detected and generally found at higher concentrations than non-halogenated OPEs in both Q2017 and CHMS. Furthermore, urinary levels of BCIPP and BDCIPP (halogenated) were lower in Q2017 compared to CHMS while concentrations of DPhP, DpCP and DoCP (non-halogenated) were similar between Q2017 and CHMS. Across the 16 metabolites measured in Q2017, BCIPHIPP (halogenated) had the highest levels (geometric mean: 1.40 μg/g creatinine). This metabolite was not measured in CHMS and should be included in future surveys. Overall, our results show that Inuit in Nunavik are exposed to lower or similar OPEs levels than the rest of the general Canadian population suggesting that the main current exposure to OPEs may be from consumer goods containing flame retardants and imported from the south rather than long-range atmospheric transport to the Arctic.

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.

Organophosphate ester flame retardants and plasticizers affect the phenotype and function of HepG2 liver cells

Exposure to the organophosphate esters (OPEs), used as flame retardants and plasticizers, is associated with a variety of adverse health effects including an increase in the incidence of fatty liver diseases. The goal of this study was to investigate the effects of six OPEs, all detected in Canadian house dust, on the phenotype and function of HepG2 liver cells. We used high-content imaging to investigate the effects of these OPEs on cell survival, mitochondria, oxidative stress, lipid droplets, and lysosomes. Effects on the autophagy/lipophagy pathway were evaluated using confocal microscopy. The triaryl OPEs (isopropylated triphenylphosphate [IPPP], tris(methylphenyl) phosphate [TMPP], and triphenyl phosphate [TPHP]) were more cytotoxic than non-triaryl OPEs (tris(2-butoxyethyl) phosphate [TBOEP], tris(1-chloro-2-propyl) phosphate [TCIPP], and tris(1,3-dichloro-2-propyl) phosphate [TDCIPP]). Exposure to most OPEs increased total mitochondria, reduced reactive oxygen species, and increased total lipid droplet areas and lysosomal intensity. Potency ranking was done using the lowest benchmark concentration/administered equivalent dose method and toxicological prioritization index analyses to integrate all phenotypic endpoints. IPPP, TBOEP, and TPHP ranked as the most potent OPEs, whereas TMPP, TCIPP, and TDCIPP were relatively less bioactive. Confocal microscopic analysis demonstrated that IPPP reduced the colocalization of lipid droplets (PLIN2), lysosomes (LAMP1), and autophagosomes (p62), disrupting autophagy. In contrast, TBOEP rescued cells from bafilomycin A1-induced inhibition of autophagy and/or increased autophagic flux. Together, these data demonstrate that OPEs have adverse effects on HepG2 cells. Further, OPE-induced dysregulation of autophagy may contribute to the association between OPE exposure and adverse effects on liver lipid homeostasis.

Tris(1,3-dichloro-2-propyl) phosphate induces endoplasmic reticulum stress and mitochondrial-dependent apoptosis in mouse spermatocyte GC-2 cells

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is a frequently detected organophosphorus flame retardants (OPFRs) in various environmental media, and has been evidenced as reproductive toxicity. However, its adverse effects on spermatogenic cells are unknown. In this study, mouse spermatocyte GC-2spd (GC-2) cells were selected as an in vitro model, and the impact of mitochondrial structure and function, endoplasmic reticulum (ER) stress, cell apoptosis and the related molecular mechanisms were investigated. Our study indicated that cell viability was decreased significantly in a dose-dependent manner after TDCIPP treatment with the half lethal concentration (LC50) at 82.8 μM, 50.0 μM and 39.6 μM for 24 h, 48 h and 72 h, respectively. An apoptosis was observed by Annexin V-FITC/PI stain. In addition, fragmentation of mitochondrial structure, an increase of mitochondrial membrane potential (MMP), reduction of cellular adenosine triphosphate (ATP) content, release of cytochrome c and activation of Caspase-3 and Caspase-9 activity implicated that Caspase-3 dependent mitochondrial pathway might play a key role in the process of GC-2 cell apoptosis. Furthermore, ER stress induction was convinced by altered morphology of ER and up-regulation of ER targeting genes, including (Bip, eIF2α, ATF4, XBP1, CHOP, ATF6 and Caspase-12). Taken together, these results demonstrate that both mitochondrial apoptotic pathways and ER stress apoptotic pathways might play important roles in the process of apoptosis in GC-2 cells induced by TDCIPP treatment. Therefore, the potential reproductive toxicity of TDCIPP should not be ignored.

Bioaccumulation and thyroid endcrione disruption of 2-ethylhexyl diphenyl phosphate at environmental concentration in zebrafish larvae

2-ethylhexyl diphenyl phosphate (EHDPP) strongly binds to transthyretin (TTR) and affects the expression of genes involved in the thyroid hormone (TH) pathway in vitro. However, it is still unknown whether EHDPP induces endocrine disruption of THs in vivo. In this study, zebrafish (Danio rerio) embryos (< 2 h post-fertilization (hpf)) were exposed to environmentally relevant concentrations of EHDPP (0, 0.1, 1, 10, and 100 μg·L-1) for 120 h. EHDPP was detected in 120 hpf larvae at concentrations of 0.06, 0.15, 3.71, and 59.77 μg·g-1 dry weight in the 0.1, 1, 10, and 100 μg·L-1 exposure groups, respectively. Zebrafish development and growth were inhibited by EHDPP, as indicated by the increased malformation rate, decreased survival rate, and shortened body length. Exposure to lower concentrations of EHDPP (0.1 and 1 μg·L-1) significantly decreased the whole-body thyroxine (T4) and triiodothyronine (T3) levels and altered the expressions of genes and proteins involved in the hypothalamic-pituitary-thyroid axis. Downregulation of genes related to TH synthesis (nis and tg) and TH metabolism (dio1 and dio2) may be partially responsible for the decreased T4 and T3 levels, respectively. EHDPP exposure also significantly increased the transcription of genes involved in thyroid development (nkx2.1 and pax8), which may stimulate the growth of thyroid primordium to compensate for hypothyroidism. Moreover, EHDPP exposure significantly decreased the gene and protein expression of the transport protein transthyretin (TTR) in a concentration-dependent manner, suggesting a significant inhibitory effect of EHDPP on TTR. Molecular docking results showed that EHDPP and T4 partly share the same mode of action of binding to the TTR protein, which might result in decreased T4 transport due to the binding of EHDPP to the TTR protein. Taken together, our findings indicate that EHDPP can cause TH disruption in zebrafish and help elucidate the mechanisms underlying EHDPP toxicity.

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.

Upregulation of oxidative stress by triphenyl phosphate (TPhP) exposure causes antioxidant insult and apoptotic process in Epithelioma papulosum cyprini (EPC) cells

Triphenyl phosphate (TPhP) is the predominant compound of organophosphate flame retardants (OPFRs), which can elicit a toxicological effect on physiological response and tissue development of fish. In this study, we investigated the effect of TPhP exposure on cell viability, antioxidant capacities, and apoptosis in EPC cells. Current study revealed that TPhP exposure could decrease cell viability and promote intracellular oxidative stress in EPC cells. In addition, high-dose TPhP exposure could facilitate antioxidant insults and cause mitochondrial collapse in a dose-dependent manner, along with increased gene expressions involved in apoptosis and unfolded protein response (UPR). These results indicated that reactive oxygen species (ROS)-induced cytotoxic stress and cell death were involved in antioxidant insults and apoptotic activation in TPhP-exposed fish cells.

2-Ethylhexyl Diphenyl Phosphate Causes Obesity in Zebrafish by Stimulating Overeating via Inhibition of Dopamine Receptor D2

Obesity is a popular public health problem worldwide and is mainly caused by overeating, but little is known about the impacts of synthetic chemicals on obesity. Herein, we evaluated the obesogenic effect caused by 2-ethylhexyl diphenyl phosphate (EHDPHP) on zebrafish. Adult zebrafish were exposed to 5, 35, and 245 μg/L of EHDPHP for 21 days. Results showed that EHDPHP exposure significantly promoted the feeding behavior of zebrafish, as evidenced by shorter reaction time, increased average food intake, feeding rate, and intake frequency (p < 0.05). Transcriptomic, real-time quantitative PCR, and neurotransmitter analyses revealed that the dopamine (DA) receptor D2 (DRD2) was inhibited, which interfered with the DA neural reward regulation system, thus stimulating food addiction to zebrafish. This was further verified by the restored DRD2 after 7 days of Halo (a DRD2 agonist) treatment. A strong interaction between EHDPHP and DRD2 was identified via molecular docking. As a consequence of the abnormal feeding behavior, the exposed fish exhibited significant obesity evidenced by increased body weight, body mass index, plasma total cholesterol, triglyceride, and body fat content. Additionally, the pathways linked to Parkinson's disease, alcoholism, and cocaine addiction were also disrupted, implying that EHDPHP might cause other neurological disorders via the disrupted DA system.

Trends of legacy and emerging organic contaminants in a sediment core from Cienfuegos Bay, Cuba, from 1990 to 2015

Legacy and emerging organic pollutants pose an ever-expanding challenge for the marine environment. This study analysed a dated sediment core from Cienfuegos Bay, Cuba, to assess the occurrence of polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), alternative halogenated flame retardants (aHFRs), organophosphate esters (OPEs), and phthalates (PAEs) from 1990 to 2015. The results evidence the continuing presence of historical regulated contaminants (PCBs, OCPs, and PBDEs) in the southern basin of Cienfuegos Bay. PCB contamination declined since 2007, likely in response to the gradual global phasing out of PCB containing materials. There have been relatively consistent low accumulation rates for OCPs and PBDEs at this location (in 2015 approximately 1.9 and 0.26ng/cm²/year, respectively, with 2.8ng/cm²/year for Σ₆PCBs), with indications of recent local DDT use in response to public health emergencies. In contrast, sharp increases are observed between 2012 and 2015 for the contaminants of emerging concern (PAEs, OPEs, and aHFRs), and in the case of two PAEs (DEHP and DnBP) the concentrations were above the established environmental effect limits for sediment dwelling organisms. These increasing trends reflect the growing global usage of both alternative flame retardants and plasticizer additives. Local drivers for these trends include nearby industrial sources such as a plastic recycling plant, multiple urban waste outfalls, and a cement factory. The limited capacity for solid waste management may also contribute to the high concentrations of emerging contaminants, especially plastic additives. For the most recent year (2015), the accumulation rates for Σ₁₇aHFRs, Σ₁₉PAEs, and Σ₁₇OPEs into sediment at this location were estimated to be 10, 46 000, and 750ng/cm²/year, respectively. This data provides an initial survey of emerging organic contaminants within this understudied region of the world. The increasing temporal trends observed for aHFRs, OPEs, and PAEs highlights the need for further research concerning the rapid influx of these emerging contaminants.

Tris(1,3-dichloro-2-propyl) Phosphate Inhibits Early Embryonic Development by Binding to Gsk-3β Protein in Zebrafish

Recently, several studies have reported that exposure to tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) results in abnormal development of zebrafish embryos in blastocyst and gastrula stages, but molecular mechanisms are still not clear. This lacking strongly affects the interspecific extrapolation of embryonic toxicity induced by TDCIPP and hazard evaluation. In this study, zebrafish embryos were exposed to 100, 500 or 1000 μg/L TDCIPP, and 6-bromoindirubin-3'-oxime (BIO, 35.62 μg/L) was used as a positive control. Results demonstrated that treatment with TDCIPP or BIO caused an abnormal stacking of blastomere cells in mid blastula transition (MBT) stage, and subsequently resulted in epiboly delay of zebrafish embryos. TDCIPP and BIO up-regulated the expression of β-catenin protein and increased its accumulation in nuclei of embryonic cells. This accumulation was considered as a driver for early embryonic developmental toxicity of TDCIPP. Furthermore, TDCIPP and BIO partly shared the same modes of action, and both of them could bind to Gsk-3β protein, and then decreased the phosphorylation level of Gsk-3β in TYR·216 site and lastly inhibited the activity of Gsk-3β kinase, which was responsible for the increased concentrations of β-catenin protein in embryonic cells and accumulation in nuclei. Our findings provide new mechanisms for clarifying the early embryonic developmental toxicity of TDCIPP in zebrafish.

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.

Effects of 2-ethylhexyl diphenyl phosphate exposure on the glucolipid metabolism and cardiac developmental toxicity in larval zebrafish based on transcriptomic analysis

2-Ethylhexyl diphenyl phosphate (EHDPP) is an organophosphorus type of flame retardant. It is mainly used as a flame-retardant plasticizer in the production of flexible polyvinyl chloride. EHDPP is widely present in environment, particularly in aquatic environment. In this study, we reported that EHDPP exposure significantly affected glucose and lipid metabolism in zebrafish larvae, which was reflected by changes in the transcription of relevant genes and decreased levels of glucose, pyruvate, and triglycerides. In addition, the transcriptomic analysis revealed that the differentially expressed genes could enrich various endpoints in zebrafish larvae. Interestingly, EHDPP exposure could not only change the transcription of genes related to glucolipid metabolism but also cause cardiotoxicity by affecting the transcription of genes related to calcium signaling pathways in zebrafish larvae. To support these findings, we confirmed that these genes involved in cardiac morphology and development were significantly upregulated in zebrafish larvae after EHDPP exposure. More importantly, the distance and overlapping area of the atrium and ventricle were also changed in the EHDPP-exposed zebrafish larvae of transgenic Tg (myl7: EGFP). Overall, our study revealed that EHDPP exposure could affect various endpoints related to glucolipid metabolism and cardiac development in the early developmental stages of zebrafish.

The regulatory roles of DDIT4 in TDCIPP-induced autophagy and apoptosis in PC12 cells

Tris (1,3-dichloro-2-propyl) phosphate (TDCIPP) is a commonly used organophosphate-based flame retardant and can bio-accumulate in human tissues and organs. As its structure is similar to that of neurotoxic organophosphate pesticides, the neurotoxicity of TDCIPP has raised widespread concerns. TDCIPP can increase neuronal apoptosis and induce autophagy. However, its regulatory mechanism remains unclear. In this study, we found that the expression upregulation of the DNA Damage-Inducible Transcript 4 (DDIT4) protein, which might play essential roles in TDCIPP-induced neuronal autophagy and apoptosis, was observed in TDCIPP-treated differentiated rat PC12 cells. Furthermore, we determined the protective effect of the DDIT4 suppression on the autophagy and apoptosis induced by TDCIPP using Western blot (WB) and Flow cytometry (FACS) analysis. We observed that TDCIPP treatment increased the DDIT4, the autophagy marker Beclin-1, and the microtubule-associated protein light chain 3-II (LC3II) expressions and decreased the mTOR phosphorylation levels. Conversely, the suppression of DDIT4 expression increased the p-mTOR expression and decreased cell autophagy and apoptosis. Collectively, our results revealed the function of DDIT4 in cell death mechanisms triggered by TDCIPP through the mTOR signaling axis in differentiated PC12 cells. Thus, this study provided vital evidence necessary to explain the mechanism of TDCIPP-induced neurotoxicity in differentiated PC12 cells.

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.

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.

Accumulations and equilibrium conditions of organophosphate esters (OPEs) in the indoor window film and the estimation of concentrations in air

The study of the fate of organophosphate esters (OPEs) in the interior environment is vital because of the growing use of OPEs. Organic films on glass are both sink and sources of indoor pollutants. Indoor window films have been employed as passive air samplers to collect OPEs in the indoor air. Nevertheless, little is known about the development and equilibrium condition of OPEs on indoor window films during the film formation process. In this study, the concentrations of twelve OPEs in indoor window films from different buildings on a university campus and the growth thickness of the films as a function of sampling time were investigated in different seasons. Ten out of the 12 OPEs were detected in window film with >50 % frequency. Tris (2-chloroethyl) phosphate (TCEP) and tris (1-chloro-2-propyl) phosphate (TCPP), which are chlorinated and toxic OPEs, were the dominant OPEs found in the winter. The majority of OPEs in window films exhibited linear growth patterns within 77 days. Temperature, humidity, ventilation, and seasonality all affected the concentrations of various OPEs in the window films. Low molecular weight OPEs, such as tri-n-butyl phosphate and TCEP, attained equilibrium between indoor air and window films within 49 or 77 days. The indoor air concentrations of OPEs were estimated from their film concentrations based on the theoretical approach for the passive air sampler. In winter, the predicted gas-phase air concentrations of OPEs (3.7 ng/m³ for TECP) were significantly lower than or comparable to summer (11 ng/m³, p < 0.05). To the best of our knowledge, this is the first attempt to combine uncertainty and sensitivity analysis to understand the behaviors of OPEs in indoor film and air.

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.

Co-contaminants of microplastics in two seabird species from the Canadian Arctic

Through ingestion and subsequent egestion, Arctic seabirds can bioaccumulate microplastics at and around their colony breeding sites. While microplastics in Arctic seabirds have been well documented, it is not yet understood to what extent these particles can act as transport vehicles for plastic-associated contaminants, including legacy persistent organic pollutants (POPs), trace metals, and organic additives. We investigated the occurrence and pattern of organic and inorganic co-contaminants of microplastics in two seabird species from the Canadian Arctic - northern fulmar (Fulmarus glacialis) and black-legged kittiwake (Rissa tridactyla). We found that fulmars had higher levels of plastic contamination and emerging organic compounds (known to be plastic additives) than kittiwakes, whereas higher concentrations of legacy POPs were found in kittiwakes than the fulmars. Furthermore, fulmars, the species with the much larger foraging range (∼200 km), had higher plastic pollution and overall contaminant burdens, indicating that birds may be acting as long-range transport vectors for plastic-associated pollution. Our results suggest a potential connection between plastic additive contamination and plastic pollution burdens in the bird stomachs, highlighting the importance of treating plastic particles and plastic-associated organic additives as co-contaminants rather than separate pollution issues.

Legacy and emerging organic contaminants in the polar regions

The presence of numerous emerging organic contaminants (EOCs) and remobilization of legacy persistent organic pollutants (POPs) in polar regions have become significant concerns of the scientific communities, public groups and stakeholders. This work reviews the occurrences of EOCs and POPs and their long-range environmental transport (LRET) processes via atmosphere and ocean currents from continental sources to polar regions. Concentrations of classic POPs have been systematically monitored in air at several Arctic stations and showed seasonal variations and declining trends. These chemicals were also the major POPs reported in the Antarctica, while their concentrations were lower than those in the Arctic, illustrating the combination of remoteness and lack of potential local sources for the Antarctica. EOCs were investigated in air, water, snow, ice and organisms in the Arctic. Data in the Antarctica are rare. Reemission of legacy POPs and EOCs accumulated in glaciers, sea ice and snow may alter the concentrations and amplify their effects in polar regions. Thus, future research will need to understand the various biogeochemical and geophysical processes under climate change and anthropogenic pressures.

Toxic effect of triphenyl phosphate (TPHP) on Cyprinus carpio and the intestinal microbial community response

Triphenyl phosphate (TPHP) is a kind of organophosphorus flame retardants, and its use is increasing annually. However, the toxic effect associated with exposure to it has not been adequately investigated. Therefore, in this study, we determined the toxic dose of TPHP in the economic fish species, Cyprinus carpio. Acute and subacute toxicity tests were conducted, and the enrichment of TPHP in the gills, brain, intestines, and liver were determined by Liquid Chromatography-Mass Spectrometry, and the response of carp gut microbial community to TPHP stress was determined using 16 S rRNA gene high-throughput sequencing. Results showed that the 96-h LC₅₀ of TPHP in carp was 7 mg/L. At the 7 d, the order of TPHP absorption was as follows (from highest to lowest): gills > intestine > liver > brain, but at the 28 d and the purification period, the order of TPHP absorption was brain > gills > intestine > liver. TPHP exposure at 3.5 mg/L decreased α-diversity of the intestinal microbial community (p < 0.05), and altered community composition, in particular the relative abundance of dominant microbial populations. Functional profiles of the microbial communities predicted based on 16 S rRNA gene data showed upregulation in the degradation of exogenous substances and energy metabolism of the TPHP-treated groups (p < 0.05), suggesting that intestinal microbial taxa play a role in reducing TPHP toxicity. The results provide insights that could facilitate risk assessments of TPHP pollutants in aquatic environments and the management of associated water pollution.

Comprehensive screening of polar emerging organic contaminants including PFASs and evaluation of the trophic transfer behavior in a freshwater food web

Bioaccumulation and trophic transfer of persistent legacy contaminants have been intensively characterized, but little is known on the contaminants of emerging concern (CECs) in freshwater food webs. Herein, we comprehensively screened CECs with a focus on polar substances and further evaluated their trophic transfer behavior in selected items from the food web of Lake Templin, Germany. Weselected one plankton, two mussel, and nine fish samples covering three trophic levels. With an effective multi-residue sample preparation method and high-resolution mass spectrometry-based target, suspect, and non-target screening, we characterized 477 targets and further screened unknown features in complex biota matrices. Of the 477 targets, 145 were detected and quantified in at least one species (0.02-3640 ng/g, dry weight). Additionally, the suspect and non-target analysis with experimental mass spectra libraries and in silico techniques (MetFrag and SIRIUS4/CSI:FingerID) enabled further identification of 27 unknown compounds with 19 confirmed by reference standards. Overall, the detected compounds belong to a diverse group of chemicals, including 71 pharmaceuticals, 27 metabolites, 26 pesticides, 16 per- and polyfluoroalkyl substances (PFASs), 4 plasticizers, 3 flame retardants, 11 other industrial chemicals and 14 others. Moreover, we determined the trophic magnification factor (TMF) of 34 polar CECs with >80% detection frequency, among which 6 PFASs including perfluorooctane sulfonic acid (PFOS), perfluorodecanoic acid (PFDA), perfluorohexane sulfonic acid (PFHxS), perfluorotridecanoic acid (PFTrA), perfluorotetradecanoic acid (PFTeA), and perfluoroundecanoic acid (PFUnA), exhibited biomagnification potential (TMF =1.8 - 4.2, p < 0.05), whereas 5 pharmaceuticals (phenazone, progesterone, venlafaxine, levamisole, and lidocaine) and 1 personal care product metabolite (galaxolidone) showed biodilution potential (TMF = 0.4 - 0.6, p < 0.05).

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.

Atmospheric deposition, seasonal variation, and long-range transport of organophosphate esters on Yongxing Island, South China Sea

The South China Sea (SCS), surrounded by developing countries/regions with a huge consumption of flame retardants, is generally contaminated by organophosphate esters (OPEs). However, studies on the occurrence, deposition and long-range atmospheric transport (LRAT) process over the SCS of OPEs compounds are still limited. In this work, 10 OPEs were measured in 100 atmospheric samples collected from Yongxing Island (YXI) in the SCS. The total OPEs concentrations ranged from 1508 to 1968 pg/m³ with 28.6-1416.9 pg/m³ in gas and 95.2-1066.2 pg/m³ in particle partition. The three chlorinated OPEs are present at higher concentrations than the other seven non-chlorinated OPEs. Most OPEs had clear seasonal variations that followed the order: spring>summer≈winter>autumn except for tri-isobutyl phosphate (TIBP) and tris-(2-ethylhexyl) phosphate (TEHP). The particle-bound fraction of the total OPEs had little seasonal variations with a mean value of 0.35. Comparing J-P model and Koa model, it was found that the gas/particle partition in the study area was in non-equilibrium condition. LRAT, controlled by seasonal wind direction, was the predominated factor that led to the seasonal variations of OPEs on YXI. The average daily deposition flux of total OPEs was 13.0 ng/m² with an annual total deposition of 15.06 g.

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 the mechanisms of estrogen disrupting effects between triphenyl phosphate (TPhP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP)

As the typical aryl-organophosphate flame retardants (OPFRs), triphenyl phosphate (TPhP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were reported to be estrogen disruptors. However, estrogen receptor α (ERα) binding experiments could not explain their biological effects. In this study, their action on ERα, G protein-coupled estrogen receptor (GPER) and the synthesis of 17β-estradiol (E2) were investigated using in vitro assays and molecular docking. The results showed that TPhP acted as an ERα agonist and recruited steroid receptor co-activator 1 (SRC1) and 3 (SRC3), which was found for the first time. Unlike TPhP, TDCIPP acted as an ERα antagonist. However, both TPhP and TDCIPP activated the estrogen pathway by GPER in SKBR3 cells which were lack of ERα. Although molecular docking results revealed that both TPhP and TDCIPP could dock into ERα and GPER, their substituent groups and combination mode might affect the receptor activation. In addition, by using estrogen biosynthesis assay in H295R cells, both of TPhP and TDCIPP were found to promote E2 synthesis and E2/T ratio involving their different alteration on levels of progesterone, testosterone and estrone, and expression of various key genes. Our data proposed estrogen-disrupting mechanism frameworks of TPhP and TDCIPP. Moreover, our results will contribute to future construction of adverse outcome pathway (AOP) framework of endocrine disruptors.

Bioaccumulation and potential risk of organophosphate flame retardants in coral reef fish from the Nansha Islands, South China Sea

Organophosphate flame retardant (OPFR) pollution in marine environment has attracted increasing attention in recent years. Coral reefs are regarded as significant marine ecosystems, however, research on OPFR contamination in coral reefs is limited. In the present work, 9 OPFR compounds were analyzed in fish samples collected from the Zhubi Reef and Yongshu Reef of the Nansha Islands, South China Sea, to evaluate the biomagnification and potential threats of OPFRs in the coral reef ecosystems. ∑OPFR concentrations in the coral reef fish ranged from 38.7 to 2090 ng/g lipid weight (lw), with an average of 420 ± 491 ng/g lw. Alkyl OPFRs were more abundant than chlorinated OPFRs and aryl OPFRs. Individually, TBEP and TCPP were the two most abundant OPFR compounds. Biomagnification potential was indicated for TCPP, TCEP, TBP, TBEP and TEHP along the marine food web, with trophic magnification factors being greater than one. The estimated dietary intakes of OPFRs via coral fish consumption were 0-1.11 ng/kg bw/d and 0.01-2.06 ng/kg bw/d, respectively, for rural and urban residents. Additionally, the hazard quotients of OPFR compounds ranged from 2 × 10^-7 to 7.41 × 10^-5 for rural residents and from 4 × 10^-7 to 1.37 × 10^-4 for urban residents. Although the risk to human health from exposure to OPFRs via consuming coral reef fish from the South China Sea was low, further investigation of these chemicals is still recommended.

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.

Effects of tris(1,3-dichloro-2-propyl) phosphate on epididymal sperm parameters in adult male rats

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is widely used as a flame retardant and is known to exhibit anti-androgenic effects in vitro and in vivo. To assess the reproductive toxicity potency of TDCIPP, we investigated the effects of 7 days of TDCIPP oral administration on epididymal sperm motion and concentration in adult male Wistar-Imamichi rats. Thirty-five days after the final administration, sperm parameters were evaluated by computer-assisted sperm analysis. Results showed that sperm swimming progression and vigor and sperm concentration in TDCIPP-treated rats were unexpectedly higher than those in control rats. TDCIPP did not significantly affect the percentage of motile sperms or sperm swimming pattern. These results contribute to the understanding of the biological effects of TDCIPP.

Tris(1,3-dichloro-2-propyl)phosphate Induces Mass Mortality of Crucian Carp (Carassius carassius) Embryos in Taihu Lake

Global fishery resources have been declining for decades, leading some fisheries to collapse. Although the decline is partly due to man-made chemical contamination, causal chemicals have been identified in only a few cases. We conducted consecutive 3-year investigations of embryonic mortality in Taihu Lake, China, including heavily contaminated northern areas, including Zhushan (ZS), Meiliang (ML), and Gonghu (GH), and the less polluted southeastern Suzhou (SZ). In 2016, 65.8% of crucian carp (Carassius carassius) embryos collected from ZS died before hatching, a substantially higher mortality rate than those observed in ML (21.7%), GH (15.2%), and SZ (2.2%). In 2017, the embryonic mortality rates were 38.8% in ZS, 1.3% in ML, 6.9% in GH, and 3.5% in SZ, and these rates strongly correlated with the concentrations of tris(1,3-dichloro-2-propyl)phosphate (TDCIPP): 104.2, 1.8, 4.6, and 4.1 ng/g lipid weight (lw) in embryos from ZS, ML, GH, and SZ, respectively. In 2018, embryonic mortality decreased to 4.0% in ZS and 1.2% in GH, consistent with decreases in embryonic TDCIPP concentrations to 17.1 and 1.5 ng/g lw, respectively. Moreover, the TDCIPP concentrations in dead embryos (70.5-216.8 ng/g lw) were much higher than those in live embryos (1.2-10.5 ng/g lw). Embryonic mortality was also observed in well-controlled laboratory experiments in which wild crucian carp were exposed to TDCIPP at concentrations similar to those measured in embryos collected from Taihu Lake, thus confirming TDCIPP as a causal factor in mass crucian carp embryo mortality in Taihu Lake. TDCIPP thus poses a threat to the sustainability of fisheries worldwide, given the high worldwide production volume of this chemical and its embryonic lethal toxicity.

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.

First study on the presence of plastic additives in loggerhead sea turtles (Caretta caretta) from the Mediterranean Sea

Loggerhead turtles (Caretta caretta) voluntarily ingest floating plastic debris and hence are chronically exposed to plastic additives, but very little is known about the levels of these compounds in their tissues. This work studied the presence of organophosphate esters (OPEs) on sea turtles collected from two different areas in the western Mediterranean, some of their prey and some floating plastic debris. OPEs were detected in all the samples analysed and ∑OPEs ranged from 12.5 to 384 ng/g wet weight (ww) in the turtles from the Catalan coasts, with a mean value of 21.6 ng/g ww, and from 6.08 to 100 ng/g ww in the turtles the Balearic Islands, with a mean value of 37.9 ng/g ww. Differences in ∑OPEs were statistically significant, but turtles from the two regions did not differ in their OPE profiles. As per turtle's prey, ∑OPEs ranged from 4.55 to 90.5 ng/g ww. Finally, marine plastic litter showed ∑OPEs concentrations between 10.9 and 868 ng/g. Although most compounds were present in both potential sources of contamination, prey and plastic debris, the OPE profiles in loggerhead turtles and these sources were different. Some OPEs, such as tris(2-isopropylphenyl) phosphate (T2IPPP), tripropyl phosphate (TPP) and tris(2-butoxyethyl) phosphate (TBOEP), were detected in plastic debris and turtle muscle but not in their prey, thus suggesting that ingestion of plastic debris was their main source. Contrarily, the levels of triethyl phosphate (TEP), diphenyl cresyl phosphate (DCP), 2-isopropylphenyl diphenyl phosphate (2IPPDPP) and 4-isopropylphenyl diphenyl phosphate (4IPPDPP) in turtle muscle were much higher than in jellyfish, their main prey, thus indicating a biomagnification potential. Regular ingestion of plastic debris and contamination from their prey may explain why ∑OPEs in loggerhead turtles is much higher than the values reported previously for teleost fishes and marine mammals from the western Mediterranean.

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.

Lifetime bioaccumulation, gender difference, tissue distribution, and parental transfer of organophosphorus plastic additives in freshwater fish

Plastic pollution has been a growing global issue. Various plastic additives may enter the environment with plastic debris, which could also become contaminants. Lifetime bioaccumulation, gender difference, tissue distribution, and parental transfer potential of commonly applied organophosphorus plastic additives (OPPAs) were investigated in wildlife fish of the Pearl River system, China. The OPPAs were widely detected in 7 consumable fish species. Tris (2-chloropropyl) phosphate was the predominant compound, with a median concentration of 18.8 ng/g lipid weight. The total OPPA concentrations (ΣOPPAs) were higher in the livers and swimming bladders, suggesting important roles of lipophilicity on the OPPAs accumulation in the fish. Besides, the livers were more abundant in the non-chlorinated OPPAs relative to the other tissues, indicating potentially stronger metabolism of the chlorinated OPPAs in the livers. Redbelly tilapia contained obviously lower ΣOPPAs than the other species. On the other hand, proportions of the chlorinated OPPAs were obviously lower in barbel chub and Guangdong black bream. For an individual species, higher ΣOPPAs were usually detected in the female than in the male fish. Furthermore, the females contained higher proportions of the non-chlorinated OPPAs. These results suggested potentially more accumulation of the OPPAs, particularly the non-chlorinated OPPAs in the female than in the male fish. Body weight dependence of the OPPAs accumulation showed varied patterns depending on species, tissue, and compound. Species-specific characteristics affected by both ecology and organisms' physiology should be considered in combination in assessing bioaccumulation of the OPPAs. The OPPAs were slightly bioaccumulative with LogBAFs of 1.2-3.3. The OPPAs did not show obvious inclination to be partitioned to biota from sediment. Omnipresence of the OPPAs in both egg/ovary and testis of the fish suggested potential transgenerational transfer of these chemicals, which can be a serious ecological issue and warrants further research.

Tris(1,3-dichloro-2-propyl)phosphate Reduces Growth Hormone Expression via Binding to Growth Hormone Releasing Hormone Receptors and Inhibits the Growth of Crucian Carp

Tris(1,3-dichloro-2-propyl)phosphate (TDCIPP) has commonly been used as an additive flame retardant and frequently detected in the aquatic environment and in biological samples worldwide. Recently, it was found that exposure to TDCIPP inhibited the growth of zebrafish, but the relevant molecular mechanisms remained unclear. In this study, 5 day-old crucian carp (Carassius auratus) larvae were treated with 0.5, 5, or 50 μg/L TDCIPP for 90 days; the effect on growth was evaluated; and related molecular mechanisms were explored. Results demonstrated that 5 or 50 μg/L TDCIPP treatment significantly inhibited the growth of crucian carp and downregulated the expression of growth hormones (ghs), growth hormone receptor (ghr), and insulin-like growth factor 1 (igf1). Molecular docking, dual-luciferase reporter gene assay, and in vitro experiments demonstrated that TDCIPP could bind to the growth hormone releasing hormone receptor protein of crucian carp and disturb the stimulation of growth hormone releasing hormone to the expression of ghs, resulting in the decrease of the mRNA level of gh1 and gh2 in pituitary cells. Our findings provide new perceptions into the molecular mechanisms of developmental toxicity of TDCIPP in fish.

Hepatic Gene Expression Profiling of Atlantic Cod (Gadus morhua) Liver after Exposure to Organophosphate Flame Retardants Revealed Altered Cholesterol Biosynthesis and Lipid Metabolism

Since the phasing out and eventual ban on the production of organohalogen flame retardants, the use of organophosphate flame retardants (OPFRs) has increased rapidly. This has led to the detection of OPFRs in various environments including the Arctic. Two of the most prevalent OPFRs found in the Arctic are tris(2-chloroisopropyl) phosphate (TCPP), and 2-ethylhexyl diphenyl phosphate (EHDPP). The impacts of exposure to OPFRs on Arctic organisms is poorly understood. The objective of the present study was to determine the effects of exposure to TCPP, EHDPP, and a mixture of OPFRs on gene expression patterns in Atlantic cod, Gadus morhua. Precision-cut liver slices from Atlantic cod in vitro were exposed to either TCPP or EHDPP alone or in a mixture and sampled at 2 different time points to quantify gene expression patterns using RNA sequencing. We exposed the liver slices to 2 concentrations of TCPP and EHDPP, one of which was chosen based on the levels found in the Arctic environment. The RNA sequencing results demonstrated differential expression of hundreds of genes in response to exposure. The genes representing cholesterol biosynthesis and lipid metabolism pathway were significantly enriched in all the treatment groups. Almost all the cholesterol biosynthesis genes were significantly down-regulated in response to OPFR exposure. The effects on these pathways could involve various physiological processes including reproduction, growth, and behavior as well as adaptation to changing temperatures. Membrane fluidity is an important adaptive mechanism among aquatic organisms. Altered cholesterol homeostasis could have long-term consequences by altering the adaptive potential of aquatic organisms to changing water temperatures, particularly those living in polar environments. These results suggest that OPFRs could have unique effects on the organisms living in the Arctic compared with other environments. Further studies are needed to understand the long-term impacts of exposure to environmentally realistic concentrations using laboratory and field-based studies. Environ Toxicol Chem 2021;40:1639-1648. © 2021 SETAC.

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

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

Extractable organochlorine (EOCl) and extractable organobromine (EOBr) in GPC-fractionated extracts from high-trophic-level mammals: Species-specific profiles and contributions of legacy organohalogen contaminants

Previous studies have suggested that unidentified compounds constitute a large proportion of extractable organochlorine (EOCl) and extractable organobromine (EOBr) in the crude extracts without fractionation; however, the proportion of unidentified EOX (X = chlorine, bromine) associated with high-/low-molecular-weight compounds is still unknown. In this study, we applied gel permeation chromatography to fractionate extracts from archived liver samples of high-trophic marine and terrestrial mammals (striped dolphins, cats, and raccoon dogs), for which concentrations of legacy organohalogen contaminants (polychlorinated biphenyls, organochlorine pesticides, and polybrominated diphenyl ethers [PBDEs]) had been previously reported. EOX in high- (>1000 g/mol) and low- (≤1000 g/mol) molecular-weight fractions (EOX-H and EOX-L) were determined by neutron activation analysis. Comparison of EOCl and EOBr enabled the characterization among species. Despite small differences in the concentrations and molecular-weight profiles of EOCl among species, the contribution of chlorine in identified compounds to EOCl-L varied from 1.5% (cats) to 79% (striped dolphins). Considerable species-specific variations were observed in the concentrations of EOBr: striped dolphins exhibited significantly greater concentrations of both EOBr-H and EOBr-L than cats and/or raccoon dogs. Moreover, the contribution of bromine in PBDEs to EOBr-L was >50% in two cats, while it was <6% in other specimens. This is the first report on EOBr mass balance in cetaceans and on EOX mass balance in terrestrial mammals living close to humans. These results suggest the need for analysis of unidentified chlorinated compounds in terrestrial mammals and unidentified brominated compounds in marine mammals.

Organohalogen compounds of emerging concern in Baltic Sea biota: Levels, biomagnification potential and comparisons with legacy contaminants

While new chemicals have replaced major toxic legacy contaminants such as polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT), knowledge of their current levels and biomagnification potential in Baltic Sea biota is lacking. Therefore, a suite of chemicals of emerging concern, including organophosphate esters (OPEs), short-chain, medium-chain and long-chain chlorinated paraffins (SCCPs, MCCPs, LCCPs), halogenated flame retardants (HFRs), and per- and polyfluoroalkyl substances (PFAS), were analysed in blue mussel (Mytilus edulis), viviparous eelpout (Zoarces viviparus), Atlantic herring (Clupea harengus), grey seal (Halichoerus grypus), harbor seal (Phoca vitulina), harbor porpoise (Phocoena phocoena), common eider (Somateria mollissima), common guillemot (Uria aalge) and white-tailed eagle (Haliaeetus albicilla) from the Baltic Proper, sampled between 2006 and 2016. Results were benchmarked with existing data for legacy contaminants. The mean concentrations for ΣOPEs ranged from 57 to 550 ng g^-1 lipid weight (lw), for ΣCPs from 110 to 640 ng g^-1 lw for ΣHFRs from 0.42 to 80 ng g^-1 lw, and for ΣPFAS from 1.1 to 450 ng g^-1 wet weight. Perfluoro-4-ethylcyclohexanesulfonate (PFECHS) was detected in most species. Levels of OPEs, CPs and HFRs were generally similar or higher than those of polybrominated diphenyl ethers (PBDEs) and/or hexabromocyclododecane (HBCDD). OPE, CP and HFR concentrations were also similar to PCBs and DDTs in blue mussel, viviparous eelpout and Atlantic herring. In marine mammals and birds, PCB and DDT concentrations remained orders of magnitude higher than those of OPEs, CPs, HFRs and PFAS. Predator-prey ratios for individual OPEs (0.28-3.9) and CPs (0.40-5.0) were similar or somewhat lower than those seen for BDE-47 (5.0-29) and HBCDD (2.4-13). Ratios for individual HFRs (0.010-37) and PFAS (0.15-47) were, however, of the same order of magnitude as seen for p,p'-DDE (4.7-66) and CB-153 (31-190), indicating biomagnification potential for many of the emerging contaminants. Lack of toxicity data, including for complex mixtures, makes it difficult to assess the risks emerging contaminants pose. Their occurence and biomagnification potential should trigger risk management measures, particularly for MCCPs, HFRs and PFAS.

Occurrence, analysis and risk assessment of organophosphate esters (OPEs) in biota: A review

Due to their widespread use, organophosphate esters (OPEs) are commonly detected in various environmental matrices and have been identified as emerging contaminants. In this review article, the occurrence and analytical techniques of OPEs in the biotic environment have been compiled and reviewed. Data from studies published the last decade all over the world covering a variety of species in trophic chain have been synthesized and evaluated. OPEs are among the most frequent detected flame retardants and high concentrations are detected in biota to date. Knowledge gaps and recommendations for future research are discussed emphasizing on further monitoring, advanced analytical methodologies, and risk assessment studies to completely understand the science of OPEs in biota.

Novel toxicity of tris(1,3-dichloro-2-propyl) phosphate in adult male rats

The widespread use of tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) as a flame retardant has led to its release to the environment. Thus, the toxicological effects of TDCIPP on humans and animals are of importance. For better understanding of its potential toxicities, TDCIPP (250, 500, or 650 mg/kg/day) or vehicle control was administrated orally to adult male Wistar-Imamichi rats for 7 days. After the final administration of compounds, organ weights, histopathology, blood biochemistry, and hematology were examined. Hepatic toxicity was observed at doses ≥ 500 mg/kg/day of TDCIPP, and renal toxicity was observed at 650 mg/kg/day. The anti-androgenic activity of TDCIPP was previously confirmed in vitro and in vivo, but weights of epididymis, an androgen-dependent organ, were not affected by TDCIPP treatment in adults. Serum alkaline phosphatase activity was significantly decreased in all TDCIPP-treated rats independent of dose. Hemoglobin concentration, hematocrit, red blood cell count, and reticulocyte count were decreased in all TDCIPP-treated rats, but mean corpuscular volume, total iron-binding capacity, and serum iron were normal, suggesting that renal anemia was caused by TDCIPP. Together with previous reports on effects of anti-androgenic substances on red blood cell indices, anemia caused by TDCIPP could be due to its anti-androgenic activity. These considerations will contribute to further assessment of the toxicity of the compound.

Distribution, sources and transport of organophosphorus flame retardants in the water and sediment of Ny-Ålesund, Svalbard, the Arctic

Organophosphorus flame retardants (PFRs) are contaminants of emerging concern which have been detected globally. However, little information on PFRs in the Arctic freshwater environment is currently available. In this study, both hydrophilic and hydrophobic PFRs in the water and sediment of four areas (town, surroundings, coastal marine water, and glacier melt runoff) near Ny-Ålesund Svalbard were investigated by time-integrated passive sampling (water) and grab sampling (sediment). Seven kinds of PFRs were found in the Arctic waters with individual freely dissolved concentrations from 0.007 ng L^-1 to 355 ng L^-1, and the concentrations of chlorinated PFRs were 3-4 orders of magnitude higher than those of non-chlorinated PFRs. The distribution of different PFRs in freshwater showed significant spatial differences among the different areas, and the town was found to have most kinds of PFRs and highest PFRs concentrations. The sources and transport of different kinds of PFRs were explored based on a spatial overlay analysis of the contaminant distributions, environmental conditions, and PFR applications. As a result, human settlements, industrial activities, atmospheric deposition, and transportation in Ny-Ålesund were proposed to be related to the pollution of different PFRs at Ny-Ålesund. The PFRs in the inshore marine water were found to be affected by both local ship contamination and ocean current transport. Furthermore, nine PFRs were detected in the sediments of Ny-Ålesund. Accumulation of different PFRs in the Arctic sediment was found to be dominated by their physico-chemical properties (polarity).

Occurrence, distribution, air-seawater exchange and atmospheric deposition of organophosphate esters (OPEs) from the Northwestern Pacific to the Arctic Ocean

Eleven organophosphate esters (OPEs) in air and seawater were investigated from the Northwestern Pacific to the Arctic Ocean. The concentration of Σ₁₁OPEs in air and seawater ranged from 231.56 to 1884.25 pg/m³ and from 8.47 to 143.45 ng/L, respectively. Halogenated OPEs dominated in both two media. The slight decreasing trend was observed for OPEs in gaseous air, no obvious trend for particle-bound OPEs and in seawater. The net air-seawater exchange flux ranged from -792.68 to 590.29 pg/m²/day. The dry deposition flux ranged from 16.4 to 185 ng/m²/day with high value observed at the Bering Strait (64.70 ng/m²/day). The relationship between temperature and OPEs particle-bound fractions suggests that temperature might be a driving factor of OPEs long-range atmospheric transport (LRAT). This research highlighted that OPEs are subject to LRAT from the Asian continent to the northwestern Pacific and Arctic Oceans and demonstrated the "sink" in polar regions of OPEs atmospheric transportation.

Assessment of organophosphate flame retardants in Mediterranean Boops boops and their relationship to anthropization levels and microplastic ingestion

Plastic litter pollution is increasing in the seas and oceans worldwide, raising concern on the potential effects of plasticizer additives on marine fauna. In this study, muscle samples of 30 bogues (Boops boops; Linneaus, 1758) from the North Western Mediterranean Sea were analysed to assess the concentrations of 19 organophosphate flame retardant (OPFR) compounds and to inspect any relationship with microplastic ingestion and relative levels of anthropization. Out of the 19 OPFRs analysed, 6 compounds were detected, being tri-n-butyl phosphate (TNBP), 2-ethylhexyldiphenyl phosphate (EHDPP) and triphenylphosphine oxide (TPPO) the most abundant. As expected, OPFR concentrations were higher in samples collected off the most anthropized area of the city of Barcelona than in those from the Cap de Creus Marine Protected Area, while no significant correlation was detected between OPFR concentrations and microplastic ingestion. The results of this manuscript provide a first evidence of OPFR presence in the muscle of the bogue and identify the coastal area off Barcelona as a possible concentration area for contaminants, further supporting the use of the bogue as an indicator species of plastic pollution in the Mediterranean Sea.

2-Ethylhexyl Diphenyl Phosphate and Its Hydroxylated Metabolites are Anti-androgenic and Cause Adverse Reproductive Outcomes in Male Japanese Medaka (Oryzias latipes)

Although high concentrations of 2-ethylhexyl diphenyl phosphate (EHDPP) have been detected in wild fish, its reproductive toxicity in fish remains unclear. In this study, we for the first time observed that EHDPP elicited androgen receptor (AR) antagonistic activity with a 50% inhibitory concentration of 37.5 μM. 2-Ethyl-5-hydroxyhexyl diphenyl phosphate was proved to be the dominant metabolite of EHDPP in Japanese medaka and elicited 3.1-fold stronger AR antagonistic activity than that of EHDPP. Medaka larvae (0-day post hatching) were exposed to EHDPP for 100 days, and intersex was observed in males from all exposure groups with significantly increased incidence (13.5-48.6%). 17β-E₂ was promoted at 104 ng/L, and androgens were suppressed at 434 ng/L, which account for the intersex incidence in the high-exposure groups but do not explain the significant incidence of intersex in the 29.9 ng/L exposure group. The AR antagonistic activity of EHDPP and its metabolites must therefore play a key role in intersex incidence. EHDPP also significantly (p < 0.05) repressed reproductive behaviors of males in the 434 ng/L group and decreased fertility in high-exposure groups compared with the control. All the adverse outcomes were observed under environmentally relevant concentrations, implying that EHDPP poses an ecological risk for wild fish populations.

Organophosphate contaminants in North Atlantic fin whales

Pollution of the marine environment by litter composed of plastics is a growing concern. Chemical additives such as organophosphate flame retardants (OPFRs), which are added to plastics to improve their qualities, are in focus because they allegedly cause adverse effects on marine fauna. Here we analyse OPFR levels in the muscle of fin whales because, as a mysticete, this cetacean obtains its food by filter-feeding and is thus highly vulnerable to marine litter. Moreover, the fin whale performs long-range migrations from low-latitude areas in winter to high-latitude areas in summer, a trait that makes it a potentially good large-scale biomonitor of pollution. We also analyse OPFR levels in its main prey, the krill Meganyctiphanes norvegica, to assess transfer through diet. The samples analysed consisted of muscle tissue from 20 fin whales and whole-body homogenates of 10 krill samples, all collected off West Iceland. From the 19 OPFRs analysed, we detected 7 in the fin whale and 5 in the krill samples. Tri-n-butyl phosphate (TNBP), Isopropylated triphenyl phosphate (IPPP) and Triphenylphosphine oxide (TPPO) were the most abundant compounds found in both species. Mean ∑OPFR concentration, expressed on a lipid weight basis, was 985 (SD = 2239) ng g^-1 in fin whale muscle, and 949 (SD = 1090) ng g^-1 in krill homogenates. These results constitute the first evidence of the presence of OPFRs in the tissues of fin whales. Furthermore, they seem to support the non-significance of bioaccumulation of OPFRs through lifespan and of biomagnification trough the food web.

Adipogenic activity of 2-ethylhexyl diphenyl phosphate via peroxisome proliferator-activated receptor γ pathway

Recent studies have shown that exposure to some organophosphates, such as triphenyl phosphate (TPHP) and diphenyl phosphate (DPHP), can affect adipogenesis in preadipocytes. 2-Ethylhexyl diphenyl phosphate (EHDPP), an organophosphate, is frequently detected in various environmental media. However, there is less information about the toxicity effects and the mechanism by which EHDPP affects preadipocytes. In the present study, we investigated whether EHDPP could induce differentiation in 3T3-L1 preadipocytes through the peroxisome proliferator-activated receptor γ (PPARγ) signaling pathway. The fluorescence competitive binding assay and the dual-luciferase reporter gene assay were used to assess the binding affinity and activation of PPARγ, and the results showed that EHDPP can bind to the ligand binding domain of PPARγ (PPARγ-LBD) and activate PPARγ in vitro. Exposure to EHDPP for 10 days extensively induced adipogenesis in 3T3-L1 preadipocytes as assessed by lipid accumulation and gene expression of adipogenic markers of fatty acid binding protein 4 (FABP4), lipoprotein lipase (Lpl), adiponectin (Adip), and fatty acid synthase (Fasn). Furthermore, the preadipocytes differentiation was blocked by the PPARγ-specific antagonist GW9662, indicating that the PPARγ signaling pathway plays an important part in 3T3-L1 cell differentiation induced by EHDPP. Taken together, EHDPP can bind to PPARγ-LBD, activate PPARγ receptor, and induce cell differentiation via the PPARγ signaling pathway in 3T3-L1 preadipocytes.

Uptake, Deposition, and Metabolism of Triphenyl Phosphate in Embryonated Eggs and Chicks of Japanese Quail (Coturnix japonica)

The toxicokinetics of triphenyl phosphate (TPHP) in vivo including the uptake, deposition, and biotransformation into the metabolite diphenyl phosphate (DPHP) is presently reported in embryonated eggs and chicks of Japanese quail. Quail were dosed with TPHP at 3 concentrations by air cell egg injection on embryonic day 0, followed by daily oral dosing after chicks hatched (5 d). Vehicle-only exposed controls were also used. In dosed eggs, only 33% of the TPHP remained 2 d after injection (no hepatic development); after 10 d (post-hepatogenesis), only 2% remained. The estimated TPHP half-lives in the eggs ranged from 1.1 to 1.8 d for the 3 dosed groups. In all exposed eggs and chicks, DPHP significantly increased with dose (0.001 < p < 0.044). It appears that DPHP is an important metabolite in quail, making up 41 to 74% of all metabolites formed in embryonated eggs. In chicks, at medium and high doses, DPHP concentrations significantly exceeded those of TPHP (p ≤ 0.007), making up 67 and 76% of the total burden, respectively. Our findings suggest that rapid TPHP metabolism occurred in chicks and embryonated quail eggs but that this may vary with the age of the embryonated egg and the stage of embryo development, which should be considered when evaluating concentrations of TPHP and DPHP measured in eggs of wild birds. Environ Toxicol Chem 2020;39:565-573. © 2019 Her Majesty the Queen in Right of Canada. Environmental Toxicology and Chemistry © 2019 SETAC.

Ny-Ålesund-oriented organic pollutants in sewage effluent and receiving seawater in the Arctic region of Kongsfjorden

Ny-Ålesund, one of four permanent settlements on Spitsbergen in Svalbard, is a research town that includes scientific institutes from many countries. Because of daily-used chemicals (e.g., pharmaceutical and personal care products (PPCPs)) used by residents in the area, generated sewage is considered as a point source in the Kongsfjorden. The aim of the present study was to identify and quantify organic pollutants in the effluent and along the shoreline and offshore via target, suspect, and non-target screening using liquid chromatography-high-resolution mass spectrometry. We tentatively identified 30 compounds using the suspect and non-target screening methods in effluent samples from our first visit to the settlement in 2016. Among these, 3 were false positive, 24 were confirmed, and the 3 remaining compounds were not confirmed because of a lack of reference standards. Of the confirmed, 21 were quantifiable and considered target compounds for the 2nd year study. The quantified compounds in the effluent samples in 2017 totaled 17, including PPCPs, pesticides, perfluorinated compounds, and their metabolites. Some of the compounds, such as caffeine, paraxanthine/theophylline, acetaminophen, cetirizine, diethyl toluamide (DEET), and icaridin, were also detected in the receiving seawater. The concentration range was from 4 to 280,000 ng/L in the effluent and 2-98 ng/L in the seawater. Other 24 compounds were tentatively identified in the second-year effluent samples. Five were further confirmed using reference standards. Prioritization was performed on the 47 substances screened in Ny-Ålesund using the exposure and toxicity index. As the result, the top seven substances of concern present were perfluorooctanesulfonic acid (PFOS), triphenyl phosphate (TPHP), irbesartan, DEET, acetaminophen, caffeine, and paraxanthine/theophylline. As the effluent was identified as a source of the concerned organic pollutants, an emission reduction strategy should take place for protection of Arctic Fjorden environment.