Organophosphate Ester, 2-Ethylhexyl Diphenyl Phosphate (EHDPP), Elicits Cytotoxic and Transcriptomic Effects in Chicken Embryonic Hepatocytes and Its Biotransformation Profile Compared to Humans

Estrogenic and anti-estrogenic assessment of the flame retardant, 2-ethylhexyl diphenyl phosphate (EHDPP), and its metabolites: Evidence from in vitro, in silico, and transcriptome studies

2-Ethylhexyl diphenyl phosphate (EHDPP) is a replacement flame-retardant commonly found in several environmental matrices and human biospecimens. Although some adverse effects of EHDPP have been identified, the endocrine-disrupting effects of EHDPP and its key metabolites on the human estrogen receptor (ER) are largely unknown. Herein, we report for the first time that EHDPP, at concentrations found in the environment and humans, significantly promoted estrogenic activity and synergized with 17β-estradiol-induced ER transactivation. However, two major EHDPP metabolites 2-ethyl-3-hydroxyhexyl diphenyl phosphate (3-OH-EHDPP) and 2-ethyl-5-hydroxyhexyl diphenyl phosphate (5-OH-EHDPP), inhibited the ER through a non-competitive binding mechanism. Molecular docking showed that Pi-Pi stacking, hydrogen, and hydrophobic bonds primarily stabilize intermolecular interactions between EHDPP and the binding pockets of human ERα and ERβ. Moreover, transcriptome analysis confirmed the estrogenic effects of EHDPP, revealing notable enrichments in ER-mediated signaling and breast cancer pathways, consistent with the validated estrogenic gene expression profile. Intriguingly, EHDPP markedly promoted the clonogenic growth of two ER+ breast cancer cell lines, corroborating the expression levels of ERα protein. Our findings indicate that the common flame-retardant EHDPP activates the ER and downstream signaling, providing far-reaching implications for environmental and health risks associated with estrogen-related adversities such as the development of ER+ breast cancer.

Developmental toxicity of an emerging organophosphate ester Bis-(2-ethylhexyl)-phenyl phosphate on embryonic zebrafish: Comparison to 2-ethylhexyl diphenyl phosphate

Bis-(2-ethylhexyl)-phenyl phosphate (BEHPP) and its structural analog, 2-ethylhexyl diphenyl phosphate (EHDPP), are widely present in the environment. However, their toxic effects, particularly developmental toxicity, remain poorly understood. In this study, we evaluated the impacts of BEHPP and EHDPP on multiple developmental endpoints in zebrafish. BEHPP did not lead to mortality and malformations of embryos within the test concentration range (0.5-4.0 μM). In contrast, EHDPP had significant lethal effects, with an LC50 of 2.44 μM, and induced malformations, notably pericardial edema (PE), with an EC50 of 1.77 μM. In addition, BEHPP induced cardiac dysfunctions in embryos to a similar degree as EHDPP. Both stroke volume and cardiac output were significantly increased at BEHPP concentrations of 1.8 nM and above and at EHDPP concentrations of 4.3 nM and above. Transcriptomic analysis further corroborated the similar disturbance at the molecular level for both substances and revealed the Key Events (KEs) in the cardiac toxic regulation, including the focal adhesions, ECM-receptor interaction, cardiac muscle contraction, and the adrenergic signaling in cardiomyocytes. Taken together, the present study provided novel insights into the adverse effects of these emerging organophosphate esters and highlighted their potential risks to embryonic development in both ecosystems and humans.

The Role of Human Adiponectin Receptor 1 in 2-Ethylhexyl Diphenyl Phosphate Induced Lipid Metabolic Disruption

Epidemiological evidence links exposure to 2-ethylhexyl diphenyl phosphate (EHDPP) with lipid metabolic disruption, typically attributed to nuclear receptors, while the role of membrane receptors remains underexplored. This study explored the role of adiponectin receptor 1 (AdipoR1) in EHDPP-induced lipid metabolic disturbances. We examined EHDPP's binding affinity and transcriptional impact on AdipoR1. AdipoR1 knockdown (AdipoR1kd) human liver cells and coculture experiments with AdipoR1 activator (AdipoRon) were used to investigate the effect and the mechanism. EHDPP disrupted triglyceride and phospholipid synthesis and altered corresponding gene expression, mirroring effects in AdipoR1kd cells but diminishing in EHDPP-treated AdipoR1kd cells. RNA sequencing revealed that EHDPP primarily disrupted oxidative phosphorylation and insulin signaling dependent on AdipoR1. Mechanistically, EHDPP interacted with AdipoR1 and reduced AdipoR1 protein levels at 10-7 mol/L or higher, weakening the activation of the calmodulin dependent protein kinase β (CaMKKβ)/AMPK/acetyl CoA carboxylase pathway. Furthermore, EHDPP pretreatment blocked the increase in Ca2+ flux and the corresponding kinase CaMKKβ, as well as liver kinase B1 (LKB1) activation induced by AdipoRon, which is necessary for AMPK activation. Collectively, these findings demonstrate that EHDPP-induced lipid imbalance is partially dependent on AdipoR1, expanding the understanding of environmental metabolic disruptors beyond nuclear receptors.

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.

Dermal exposure assessment of formal e-waste dismantlers to flame retardants and plasticizers using passive sampling methodologies

The recycling of e-waste can lead to the release of organic chemicals when materials containing additives are subjected to dismantling and grinding. In this context, the exposure of workers from a Catalonian e-waste facility to flame retardants and plasticizers (including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs) and dechloranes) was assessed using T-shirts and wristbands as passive samplers. The study area includes an area exclusively dedicated to cathodic ray-tube (CRT) TVs dismantling, and a grinding area where the rest of e-waste is ground. All the families of compounds were detected in both T-shirts and wristbands, with the highest concentration levels corresponding to OPEs, followed by PBDEs, NBFRs, and dechloranes. The CRT area presented higher concentration levels than the grinding area. The compounds with higher concentrations in T-shirts were 2-ethylhexyl diphenyl phosphate (EHDPP), diphenyl cresyl phosphate (DCP) and triphenyl phosphate (TPHP), and the total concentration of all groups ranged between 293 and 8324 ng/dm2-h (hour). In the case of the wristbands, the most abundant compounds were DCP, TPHP, and BDE-209, with total concentrations between 188 and 2248 ng/dm2-h. The two sampling methods appear to be complementary, as T-shirts collect coarser particles, while wristbands also capture volatile compounds. Based on normalized surface and time concentrations, the estimated daily intake (EDI) through dermal contact was calculated and carcinogenic and non-carcinogenic risks (CR and non-CR) associated with this activity assessed. The results show median CR 29 and 16 times below the threshold in CRT and grinding areas respectively. The non-CR medians were 2 and 3 times below the threshold, although in the CRT area one exceptional value surpassed the threshold, suggesting that risk can exist for some workers in the facility.

Metabolic perturbation and oxidative damage induced by tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) and tris(2-ethylhexyl) phosphate (TEHP) on Escherichia coli through integrative analyses of metabolome

Organophosphate esters (OPEs) are one of the emerging environmental threats, causing the hazard to ecosystem safety and human health. Yet, the toxic effects and metabolic response mechanism after Escherichia coli (E.coli) exposed to TDCIPP and TEHP is inconclusive. Herein, the levels of SOD and CAT were elevated in a concentration-dependent manner, accompanied with the increase of MDA contents, signifying the activation of antioxidant response and occurrence of lipid peroxidation. Oxidative damage mediated by excessive accumulation of ROS decreased membrane potential and inhibited membrane protein synthesis, causing membrane protein dysfunction. Integrative analyses of GC-MS and LC-MS based metabolomics evinced that significant perturbation to the carbohydrate metabolism, nucleotide metabolism, lipids metabolism, amino acid metabolism, organic acids metabolism were induced following exposure to TDCIPP and TEHP in E.coli, resulting in metabolic reprogramming. Additionally, metabolites including PE(16:1(5Z)/15:0), PA(17:0/15:1(9Z)), PC(20:2(11Z,14Z)/12:0), LysoPC(18:3(6Z,9Z,12Z)/0:0) were significantly upregulated, manifesting that cell membrane protective molecule was afforded by these differential metabolites to improve permeability and fluidity. Overall, current findings generate new insights into the molecular toxicity mechanism by which E.coli respond to TDCIPP and TEHP stress and supply valuable information for potential ecological risks of OPEs on aquatic ecosystems.

2-ethylhexyl diphenyl phosphate exposure induces duodenal inflammatory injury through oxidative stress in chickens

2-ethylhexyl diphenyl phosphate (EHDPHP) is a widely used organophosphorus flame retardant and plasticizer, which is commonly found in the environment. EHDPHP not only potentially harms the environment but also causes different degrees of damage to the organism. In this study, the duodenum of chicks was selected as the potential toxic target organ to explore the mechanism of duodenal injury induced by EHDPHP exposure. Ninety one-day-old healthy male chicks were selected and randomly divided into C1(control group), C2(solvent control group), L(800 mg/kg), M(1600 mg/kg), H(3200 mg/kg) according to different doses of EHDPHP after one week of environmental adaptation. The chicks were given continuous gavage for 14 d, 28 d, and 42 d. It was found that constant exposure to EHDPHP caused an increase in duodenal MDA content, a decrease in P-gp, SOD, GSH-Px activities, and a decrease in duodenal mucosal immune factor (sIgA, GSH-Px). The expression of sIgM and mucosal link proteins (CLDN, OCLN, ZO-1, JAM) decreased, and the expression of the inflammatory protein (NF-κB, COX2) in duodenal tissues was up-regulated. The results showed that continuous exposure to EHDPHP could cause duodenal oxidative stress, inflammation, and mucosal barrier damage in chicks, which provided a basis for studying the mechanism of toxic damage caused by EHDPHP in poultry.

Comprehensive dietary exposure assessment of the Chinese population to organophosphate esters (OPEs): Results of the sixth China total diet study

Organophosphate esters (OPEs) are emerging pollutants, while data on their occurrence in foods and human dietary intake are limited. Based on the 6th China total diet study conducted in 2016-2019, this study implemented a comprehensive survey of OPEs in plant-derived foods of cereals, potatoes, legumes, fruits, vegetables, and further assessed dietary exposure from both plant- and animal-derived food. The sum concentrations of 15 OPEs in the plant-derived samples ranged from 0.567 to 106 ng/g ww. 2-Ethylhexyl diphenyl phosphate (EHDPP) (median: 1.14 ng/g ww) had the highest level in plant-derived foods, with a proportion of 35.6% in the total median OPEs. Regional distribution analysis showed a higher contamination of OPEs in plant-derived food from northern area of China. Estimated dietary intakes (EDIs) of ∑OPEs for Chinese population were from 109 ng/kg bw/day in Beijing to 1164 ng/kg bw/day in Gansu province, with mean and median of 296 and 222 ng/kg bw/day, respectively. Although animal-derived foods had higher levels of OPEs, plant-derived foods, specifically cereals, was the major source of dietary OPE intake. The EDIs were much lower than reference doses, which suggested the intakes of OPEs via food consumption could not cause significant health risks to the Chinese population at present.

Effects of organophosphorus flame retardant EHDPP on mouse retinal photoreceptor cells: Oxidative stress, apoptosis, and proinflammatory response

2-Ethylhexyl diphenyl phosphate (EHDPP) is a frequently utilized organophosphorus flame retardant (OPFR) and has been extensively detected in environmental media. Prolonged daily exposure to EHDPP has been linked to potential retinal damage, yet the adverse impacts on the retina are still generally underexplored. In this research, we explored oxidative stress, inflammation, and the activating mechanisms initiated by EHDPP in mouse retinal photoreceptor (661 W) cells following a 24 h exposure period. Our research demonstrated that EHDPP led to a decline in cell viability that was directly proportional to its concentration, with the median lethal concentration (LC50) being 88 µM. Furthermore, EHDPP was found to elevate intracellular and mitochondrial levels of reactive oxygen species (ROS), trigger apoptosis, induce cell cycle arrest at the G1 phase, and modulate the expression of both antioxidant enzymes (Nrf2, HO-1, and CAT) and pro-inflammatory mediators (TNF-α, IL-1β, and IL-6) within 661 W cells. These findings indicate that retinal damage triggered by EHDPP exposure could be mediated via the Nrf2/HO-1 signaling pathway in these cells. Collectively, our investigation revealed that oxidative stress induced by EHDPP is likely a critical factor in the cytotoxic response of 661 W cells, potentially leading to damage in retinal photoreceptor cells.

Melatonin improves mouse oocyte quality from 2-ethylhexyl diphenyl phosphate-induced toxicity by enhancing mitochondrial function

2-Ethylhexyl diphenyl phosphate (EHDPP) is a representative organophosphorus flame retardant (OPFR) that has garnered attention due to its widespread use and potential adverse effects. EHDPP exhibits cytotoxicity, genotoxicity, developmental toxicity, and endocrine disruption. However, the toxicity of EHDPP in mammalian oocytes and the underlying mechanisms remain poorly understood. Melatonin is a natural free radical scavenger that has demonstrated cytoprotective properties. In this study, we investigated the effect of EHDPP on mouse oocytes in vitro culture system and evaluated the rescue effect of melatonin on oocytes exposed to EHDPP. Our results indicated that EHDPP disrupted oocyte maturation, resulting in the majority of oocytes arrested at the metaphase I (MI) stage, accompanied by cytoskeletal damage and elevated levels of reactive oxygen species (ROS). Nevertheless, melatonin supplementation partially rescued EHDPP-induced mouse oocyte maturation impairment. Results of single-cell RNA sequencing (scRNA-seq) analysis elucidated potential mechanisms underlying these protective effects. According to the results of scRNA-seq, we conducted further tests and found that EHDPP primarily disrupts mitochondrial distribution and function, kinetochore-microtubule (K-MT) attachment, DNA damage, apoptosis, and histone modification, which were rescued upon the supplementation of melatonin. This study reveals the mechanisms of EHDPP on female reproduction and indicates the efficacy of melatonin as a therapeutic intervention for EHDPP-induced defects in mouse oocytes.

Exposure to organophosphate esters and maternal-child health

Organophosphate esters (OPEs) are a class of chemicals now widely used as flame retardants and plasticizers after the phase-out of polybrominated diphenyl ethers (PBDEs). However, OPEs carry their own risk of developmental toxicity, which poses concern for recent birth cohorts as they have become ubiquitous in the environment. In this review, we summarize the literature evaluating the association between OPE exposure and maternal, perinatal, and child health outcomes. We included original articles investigating associations of OPE exposure with any health outcome on pregnant women, newborns, children, and adolescents. We found 48 articles on this topic. Of these, five addressed maternal health and pregnancy outcomes, 24 evaluated prenatal OPE exposure and child health, 18 evaluated childhood OPE exposure and child/adolescent health, and one article evaluated both prenatal and childhood OPE exposure. These studies suggest that OPE exposure is possibly associated with a wide range of adverse health outcomes, including pregnancy loss, altered gestational duration and smaller birthweight, maternal and neonatal thyroid dysfunction, child metabolic dysregulation and abnormal growth, impaired neurodevelopment, and changes in immune response. Many of the reported outcomes associated with OPE exposure varied by child sex. Findings also varied substantially by OPE metabolite and exposure time. The OPEs most frequently measured, detected, and found to be associated with health outcomes were triphenyl phosphate (TPHP, metabolized to DPHP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP, metabolized to BDCIPP). The extensive range of health outcomes associated with OPEs raises concern about their growing use in consumer products; however, these findings should be interpreted considering the limitations of these epidemiological studies, such as possible exposure misclassification, lack of generalizability, insufficient adjustment for covariates, and failure to consider chemical exposures as a mixture.

House dust-derived mixtures of organophosphate esters alter the phenotype, function, transcriptome, and lipidome of KGN human ovarian granulosa cells

Organophosphate esters (OPEs), used as flame retardants and plasticizers, are present ubiquitously in the environment. Previous studies suggest that exposure to OPEs is detrimental to female fertility in humans. However, no experimental information is available on the effects of OPE mixtures on ovarian granulosa cells, which play essential roles in female reproduction. We used high-content imaging to investigate the effects of environmentally relevant OPE mixtures on KGN human granulosa cell phenotypes. Perturbations to steroidogenesis were assessed using ELISA and qRT-PCR. A high-throughput transcriptomic approach, TempO-Seq, was used to identify transcriptional changes in a targeted panel of genes. Effects on lipid homeostasis were explored using a cholesterol assay and global lipidomic profiling. OPE mixtures altered multiple phenotypic features of KGN cells, with triaryl OPEs in the mixture showing higher potencies than other mixture components. The mixtures increased basal production of steroid hormones; this was mediated by significant changes in the expression of critical transcripts involved in steroidogenesis. Further, the total-OPE mixture disrupted cholesterol homeostasis and the composition of intracellular lipid droplets. Exposure to complex mixtures of OPEs, similar to those found in house dust, may adversely affect female reproductive health by altering a multitude of phenotypic and functional endpoints in granulosa cells. This study provides novel insights into the mechanisms of actions underlying the toxicity induced by OPEs and highlights the need to examine the effects of human relevant chemical mixtures.

Prenatal organophosphate esters exposure and neurodevelopment trajectory in infancy: Evidence from the Shanghai Maternal-Child Pairs Cohort

BACKGROUND

Concerns remain about the neurotoxic properties of the ubiquitous organophosphate esters (OPEs), the replacement of the toxicant polybrominated diphenyl ethers.

OBJECTIVES

We examined the associations of prenatal exposure to OPEs and their mixtures with early-life neurodevelopment trajectories.

METHODS

Totally 1276 mother-child pairs were recruited from the Shanghai Maternal-Child Pairs Cohort. A high-performance liquid chromatography-triple quadrupole mass spectrometer was used to measure the levels of 7 OPEs in cord serum. Ages and Stages Questionnaires was used to examine children's neuropsychological development at 2, 6, 12, and 24 months of age. Group-based trajectory models were applied to derive the neurodevelopmental trajectories. Multiple linear regression and logistic regression model were performed to assess the relationships between OPEs exposure and neurodevelopment and trajectories. Mixtures for widely detected OPEs (n = 4) were investigated using quantile-based g-computation.

RESULTS

Tributyl phosphate (TBP), tris (2-butoxy ethyl) phosphate (TBEP), tris(1,3-dichloro-2-propyl) phosphate (TDCPP), and 2-ethylhexyl diphenyl phosphate (EHDPP), had detection rates >50 %. TDCPP had the highest median concentration (1.02 μg/L) in cord serum. EHDPP concentrations were negatively associated with scores in most domains at 12 months of age, with effect values (β) ranging from -1.89 to -0.57. EHDPP could negatively affect the total ASQ (OR = 1.07, 95 % CI: 1, 1.15) and gross-motor (OR = 1.09, 95 % CI: 1.02, 1.17) trajectory in infancy. Joint exposure to OPEs was associated with decreased scores in the total ASQ, gross-motor, fine-motor and problem-solving domain of 12-month-old infants, with β ranging from -5.93 to -1.25. In addition, the qgcomp models indicated significant positive associations between the concentrations of OPEs mixtures and risks of the persistently low group of the total ASQ, gross-motor and fine-motor development in early childhood. The impact of OPEs was more pronounced in boys.

DISCUSSION

Our findings suggested OPEs, especially EHDPP, had a persistently negative effect on neurodevelopment during the first 2 years.

Biomarkers of Organophosphate and Polybrominated Diphenyl Ether (PBDE) Flame Retardants of American Workers and Associations with Inhalation and Dermal Exposures

This study evaluated workers' exposures to flame retardants, including polybrominated diphenyl ethers (PBDEs), organophosphate esters (OPEs), and other brominated flame retardants (BFRs), in various industries. The study aimed to characterize OPE metabolite urinary concentrations and PBDE serum concentrations among workers from different industries, compare these concentrations between industries and the general population, and evaluate the likely route of exposure (dermal or inhalation). The results showed that workers from chemical manufacturing had significantly higher (p <0.05) urinary concentrations of OPE metabolites compared to other industries. Spray polyurethane foam workers had significantly higher (p <0.05) urinary concentrations of bis(1-chloro-2-propyl) phosphate (BCPP) compared to other industries. Electronic scrap workers had higher serum concentrations of certain PBDE congeners compared to the general population. Correlations were observed between hand wipe samples and air samples containing specific flame-retardant parent chemicals and urinary metabolite concentrations for some industries, suggesting both dermal absorption and inhalation as primary routes of exposure for OPEs. Overall, this study provides insights into occupational exposure to flame retardants in different industries and highlights the need for further research on emerging flame retardants and exposure reduction interventions.

Neurotoxic effects of 2-ethylhexyl diphenyl phosphate exposure on zebrafish larvae: Insight into inflammation-driven changes in early motor behavior

The extensive utilization and potential adverse impacts of the replacement flame-retardant 2-Ethylhexyl Diphenyl Phosphate (EHDPP) have raised concerns. Currently, there is limited knowledge regarding the developmental, neurological, and immunotoxic consequences of EHDPP exposure, as well as its potential behavioral outcomes. In this study, we undertook a comprehensive examination and characterization of the toxic effects over the EHDPP concentration range of 14-1400 nM. Our findings unveiled that EHDPP, even at an environmentally relevant concentration of 14 nM, exhibited excitatory neurotoxicity, eliciting a 13.5 % increase in the swimming speed of zebrafish larvae. This effect might be attributed to the potential influence of EHDPP on the release of neurotransmitters like serotonin and dopamine, which, in turn, mediated anxiety-like behavior in the zebrafish larvae. Conversely, sublethal dose EHDPP (1400 nM) exposure significantly suppressed the swimming vigor of zebrafish larvae, accompanied by morphological changes, abnormal behaviors, and alterations in intracerebral molecules. Transcriptomics revealed the underlying mechanism. The utilization of pathway inhibitors reshaped the inflammatory homeostasis and alleviated the toxicity induced by EHDPP exposure, anchoring the pivotal role played by the TLR4/NF-κB signaling pathway in EHDPP-induced adverse changes in zebrafish behavior and neurophysiology. This study observed the detrimental effects of EHDPP on fish sustainability at environmentally relevant concentrations, highlighting the practical significance for EHDPP risk management. Elucidating the toxic mechanisms of EHDPP will contribute to a deeper comprehension of how environmental pollutants can intricately influence human health.

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.

The Regulatory Role of MicroRNAs in Obesity and Obesity-Derived Ailments

Obesity is a condition that is characterized by the presence of excessive adipose tissue in the body. Obesity has become one of the main health concerns worldwide since it can lead to other chronic ailments, such as type 2 diabetes or fatty liver disease, and it could be an aggravating factor in infections. MicroRNAs (miRNAs) are small, non-coding RNA molecules that regulate gene expression and can play an important role in controlling crucial biological processes involved in the onset of obesity, such as lipogenesis, adipogenesis, lipid metabolism, or the regulation of cytokines and chemokines. Moreover, chemical compounds present in food or food packaging can alter miRNA expression and regulate the aforementioned biological mechanisms related to diabetes onset and progression. Furthermore, therapies, such as bariatric surgery and aerobic exercise training, can also influence the expression profile of miRNAs in obesity. Therefore, the present review provides insight into the current research on the role of miRNAs in obesity and obesity-derived ailments, intending to develop novel therapies to effectively manage these disorders.

Toxicological Mechanisms and Potencies of Organophosphate Esters in KGN Human Ovarian Granulosa Cells as Revealed by High-throughput Transcriptomics

Despite the growing number of studies reporting potential risks associated with exposure to organophosphate esters (OPEs), their molecular mechanisms of action remain poorly defined. We used the high-throughput TempO-Seq™ platform to investigate the effects of frequently detected OPEs on the expression of ∼3000 environmentally responsive genes in KGN human ovarian granulosa cells. Cells were exposed for 48 h to one of five OPEs (0.1 to 50 μM): tris(methylphenyl) phosphate (TMPP), isopropylated triphenyl phosphate (IPPP), tert-butylphenyl diphenyl phosphate (BPDP), triphenyl phosphate (TPHP), or tris(2-butoxyethyl) phosphate (TBOEP). The sequencing data indicate that four OPEs induced transcriptional changes, whereas TBOEP had no effect within the concentration range tested. Multiple pathway databases were used to predict alterations in biological processes based on differentially expressed genes. At lower concentrations, inhibition of the cholesterol biosynthetic pathway was the predominant effect of OPEs; this was likely a consequence of intracellular cholesterol accumulation. At higher concentrations, BPDP and TPHP had distinct effects, primarily affecting pathways involved in cell cycle progression and other stress responses. Benchmark concentration (BMC) modelling revealed that BPDP had the lowest transcriptomic point of departure. However, in vitro to in vivo extrapolation modeling indicated that TMPP was bioactive at lower concentrations than the other OPEs. We conclude that these new approach methodologies provide information on the mechanism(s) underlying the effects of data-poor compounds and assist in the derivation of protective points of departure for use in chemical read-across and decision-making.

Activation of LXRα attenuates 2-Ethylhexyl diphenyl phosphate (EHDPP) induced placental dysfunction

2-Ethylhexyl diphenyl phosphate (EHDPP) is one of the typical organophosphate flame retardants (OPFRs) and has been widely detected in environmental media. Exposure to EHDPP during pregnancy affects placental development and fetal growth. Liver X receptor α (LXRα) is essential to placental development. However, finite information is available regarding the function of LXRα in placenta damages caused by EHDPP. In present study we investigated to figure out whether LXRα is playing roles in EHDPP-induced placenta toxicity. While EHDPP restrained cell viability, migration, and angiogenesis dose-dependently in HTR-8/SVneo and JEG-3 cells, overexpression or activation by agonist T0901317 of LXRα alleviated the above phenomenon, knockdown or inhibition by antagonist GSK2033 had the opposite effects in vitro. Further study indicated EHDPP decreased LXRα expression and transcriptional activity leading to mRNA, protein expression levels downregulation of viability, migration, angiogenesis-related genes Forkhead box M1 (Foxm1), endothelial nitric oxide synthase (eNos), matrix metalloproteinase-2 (Mmp-2), matrix metalloproteinase-9 (Mmp-9), vascular endothelial growth factor-A (Vegf-a) and upregulation of inflammatory genes interleukin-6 (Il-6), interleukin-1β (Il-1β) and tumor necrosis factor-α (Tnf-α) in vitro and in vivo. Moreover, EHDPP caused decreased placental volume and fetal weight in mice, treatment with LXRα agonist T0901317 restored these adverse effects. Taken together, our study unveiled EHDPP-induced placenta toxicity and the protective role of LXRα in combating EHDPP-induced placental dysfunction. Activating LXRα could serve as a therapeutic strategy to reverse EHDPP-induced placental toxicity.

Sex-specific effects of organophosphate ester exposure on child growth trajectories in the first two years

The connections between urinary organophosphate ester (OPE) metabolites and child growth have been identified in prior research, but there is currently a dearth of epidemiological evidence regarding the sex-specific impact of OPEs on child growth trajectories. This study enrolled 804 maternal–child pairs, and five OPE congeners were quantified in maternal serum during pregnancy. In this study, the impact of prenatal OPE exposure on child growth trajectories was assessed using linear mixed-effect models and a group-based trajectory model (GBTM), with consideration given to sex-specific effects. Fetuses were frequently exposed to OPEs in utero, and tris(2-butoxyethel) phosphate (TBEP) exhibited the highest concentration levels in maternal serum. Among male children, an increase of 2.72 ng/g lipid in TBEP concentration was associated with a 0.11-unit increase in head circumference-for-age z-score (HCAZ), and the effect was mainly concentrated at 1 and 2 months of age. Among female children, an increase of 2.72 ng/g lipid in tris(2-chloro-1-(chloromethyl) ethyl) phosphate (TDCPP) concentration was associated with a 0.15-unit increase in length-for-age z-score (LAZ) and a 0.14-unit increase in weight-for-age z-score (WAZ), and the effects were mainly concentrated at 9 months of age. For HCAZ trajectories, higher prenatal TBEP exposure was associated with higher odds for the fast growth group in male children. For the LAZ and WAZ trajectories, higher prenatal TDCPP exposure was associated with higher odds for the fast growth group in female children. The trajectory analysis approach provided insight into the complex associations between OPE exposure and child growth.

•Organophosphate ester (OPEs) were detected in serum samples of pregnant women, and tributyl phosphate (TBP) was the most frequently detected OPEs. •Prenatal exposure to TBP, tris(2-butoxyethyl) phosphate (TBEP), and tris(2-chloro-1-(chloromethyl) ethyl) phosphate (TDCPP) were positively associated with infant growth trajectories. •Female infants were more sensitive to OPE exposure than males.

First insight into the sex-dependent accumulation, tissue distribution and potential toxicities of 2-ethylhexyl diphenyl phosphate and its metabolites in adult zebrafish

The 2-ethylhexyl diphenyl phosphate (EHDPHP), a primary organophosphorus flame retardant used in various industrial products, is prone to biotransformation. However, there is a knowledge gap on the sex- and tissue-specific accumulation and potential toxicities of EHDPHP (M1) and its metabolites (M2-M16). In this study, adult zebrafish (Danio rerio) were exposed to EHDPHP (0, 5, 35 and 245 µg/L) for 21-day, which was followed by 7-day depuration. The bioconcentration factor (BCF) of EHDPHP in female zebrafish was 26.2 ± 7.7% lower than in males due to the lower uptake rate (k_u) while higher depuration rate (k_d) in the females. The regular ovulation and higher metabolic efficiency promoted elimination from female zebrafish, thus leading to much less (28-44%) accumulation of ∑(M1-M16) in female zebrafish. They exhibited the highest accumulation in the liver and intestine in both sexes, which might be regulated by tissue-specific transporters and histones evidenced by molecular docking results. Intestine microbiota analysis further revealed that female zebrafish were more susceptible to EHDPHP exposure, with more significant changes in phenotype number and KEGG pathways in female than male fish. Disease prediction results suggested that EHDPHP exposure might cause cancers, cardiovascular diseases as well as endocrine disorders in both sexes. These results provide a comprehensive understanding of the sex-dependent accumulation and toxicity of EHDPHP and its metabolites.

Glyphosate-induced autophagy inhibition results in hepatic steatosis via mediating epigenetic reprogramming of PPARα in roosters

Glyphosate (Gly) is the most widely used herbicide with well-defined hepatotoxic effects, but the underlying mechanisms of Gly-induced hepatic steatosis remain largely unknown. In this study, a rooster model combined with primary chicken embryo hepatocytes was established to dissect the progresses and mechanisms of Gly-induced hepatic steatosis. Data showed that Gly exposure caused liver injury with disrupted lipid metabolism in roosters, manifested by significant serum lipid profile disorder and hepatic lipid accumulation. Transcriptomic analysis revealed that PPARα and autophagy-related pathways played important roles in Gly-induced hepatic lipid metabolism disorders. Further experimental results suggested that autophagy inhibition was involved in Gly-induced hepatic lipid accumulation, which was confirmed by the effect of classic autophagy inducer rapamycin (Rapa). Moreover, data substantiated that Gly-mediated autophagy inhibition caused nuclear increase of HDAC3, which altered epigenetic modification of PPARα, leading to fatty acid oxidation (FAO) inhibition and subsequently lipid accumulation in the hepatocytes. In summary, this study provides novel evidence that Gly-induced autophagy inhibition evokes the inactivation of PPARα-mediated FAO and concomitant hepatic steatosis in roosters by mediating epigenetic reprogramming of PPARα.

Exposure to novel brominated and organophosphate flame retardants and associations with type 2 diabetes in East China: A case-control study

The alternative flame retardants, novel brominated flame retardants (NBFRs) and organophosphate flame retardants (OPFRs) are ubiquitous in the environment and biota and may induce endocrine disruption effects. Associations between traditional endocrine-disrupting chemicals and type 2 diabetes have been extensively reported in epidemiological studies. However, the effects of NBFRs and OPFRs in humans have not been reported to date. This paper reports a case-control study of 344 participants aged 25-80 years from Shandong Province, East China, where potential associations between serum NBFR and OPFR concentrations and type 2 diabetes are assessed for the first time. After adjusting for covariates (i.e., age, sex, body mass index, smoking status, alcohol consumption, triglycerides, and total cholesterol), serum concentrations of pentabromotoluene, 2,3-dibromopropyl 2,4,6-tribromophenyl ether, tri-n-propyl phosphate, triphenyl phosphate, and tris (2-ethylhexyl) phosphate were significantly positively associated with type 2 diabetes. In the control group, decabromodiphenyl ethane and triphenyl phosphate were significantly positively associated with fasting plasma glucose, triglycerides, and high-density lipoprotein cholesterol. In the quantile g-computation model, significant positive mixture effect was found between the flame retardants mixtures and high-density lipoprotein cholesterol levels, and decabromodiphenyl ethane contributed the largest positive weights to the mixture effect. Overall, these findings suggest that exposure to NBFRs and OPFRs may promote type 2 diabetes.

Plastic packaging-associated chemicals and their hazards - An overview of reviews

Plastic packaging contains residues from substances used during manufacturing, such as solvents, as well as non-intentionally added substances (NIAS), such as impurities, oligomers, or degradation products. By searching peer-reviewed literature, we found that at least 10,259 chemicals were related to plastic packaging materials, which include chemicals used during manufacturing and/or present in final packaging items. We then summarized and discussed their chemical structures, analytical instruments, migration characteristics, and hazard categories where possible. For plastic packaging chemicals, examination of the literature reveals gas and liquid chromatography hyphenated to a variety of accurate mass analyzers based on the use of high-resolution mass spectrometry is usually used for the identification of unknown migrants coming from plastic packaging. Chemical migration from food packaging is affected by several parameters, including the nature and complexity of the food, contact time, temperature of the system, type of packaging contact layer, and properties of the migrants. A review of the literature reveals that information on adverse effects is only available for approximately 1600 substances. Among them, it appears that additives are more toxic than monomers to wildlife and humans. Neurotoxicity accounted for the highest proportion of toxicity of all types of chemicals, while benzenoids, organic acids, and derivatives were the most toxic types of chemicals. Furthermore, studies have demonstrated that hydrocarbon derivatives, organic nitrogen compounds, and organometallic compounds have the highest proportions of dermatotoxicity, and organohalogen compounds have the highest proportions of hepatotoxicity. The main contributors to skin sensitization are organic salts. This study provides a basis for comprehensively publicizing information on chemicals in plastics, and could be helpful to better understand their potential risks to the environment and humans.

Human exposure to organophosphate esters in water and packed beverages

Drinks are an essential part of human diet, which makes them a source of human exposure to plasticizers such as organophosphate esters (OPEs). The current study provides new information about sixteen OPE levels in 75 different samples (tap water, packed water, cola drinks, juice, wine and hot drinks). Tap water mean levels (40.9 ng/L) were statistically higher than packed water mean levels (4.82 ng/L), mainly due to the contribution of tris(2-chloroisopropyl) phosphate (TCIPP) and tris(2-butoxyethyl) phosphate (TBOEP) that may come from PVC water pipes. Over 90% of samples presented at least one OPE, where regular cola drinks had the highest mean concentrations (2876 ng/L). There was a significantly higher presence of OPEs in added sugar beverages than sugar free drinks, especially for 2-ethylhexyl diphenyl phosphate (EHDPP), which might be related not only to packaging materials but to the added sugar content. Estimated daily intakes (EDIs) in normal and high-exposure scenarios were 2.52 ng/kg bw/day and 7.43 ng/kg bw/day, respectively. Human risk associated with beverages ingestion showed regular cola drinks, juice and tap water as the groups with the highest hazard quotients (HQs). Although OPE exposure was below to safety limits, it should be noted that EHDPP values for regular cola group must be cause of concern, and other routes of exposure such as food ingestion or air inhalation should be also considered.

Downregulation of miRNA-155-5p contributes to the adipogenic activity of 2-ethylhexyl diphenyl phosphate in 3T3-L1 preadipocytes

2-Ethylhexyl diphenyl phosphate (EHDPP) is a commonly used organophosphorus flame retardant and food packaging material. Because of its high lipophilic and bioaccumulative properties, adipocytes are the primary target of EHDPP. However, the toxicity of EHDPP on preadipocytes and the potential mechanism have not been fully elucidated. MicroRNAs (miRNAs) are thought to be an important mediator that contribute to the toxicity of environmental contaminants. To identify the miRNAs specifically responsible for EHDPP exposure and their role in EGDPP's toxicity in preadipocytes, the adipogenic effects and miRNA expression profiling were performed on 3T3-L1 preadipocytes exposed to EHDPP. EHDPP at concentrations of 1-10 μM promoted adipocyte differentiation, as evidenced by lipid staining, triglyceride content, and expression of adipogenesis markers. MiRNA-seq analysis revealed that 7 differentially expressed miRNAs were recognized under EHDPP exposure, with miR-155-5p being the top down-regulated miRNA. Quantitative reverse transcription PCR (RT-qPCR) analysis showed that miR-155-5p level fell sharply during the first 2 days and continued to fall dose-dependently throughout the EHDPP exposure period. MiR-155-5p inhibition promotes adipocyte differentiation, whereas its overexpression counteracted EHDPP-induced adipogenesis. Luciferase reporter assay identified CCAAT/enhancer-binding protein beta (C/EBPβ) as a target of miR-155-5p in 3T3-L1 preadipocytes in response to EHDPP. Taken together, EHDPP exposure down-regulated miR-155-5p, which then increased C/EBPβ and peroxisome proliferator-activated receptor γ (PPARγ) expression and promoted adipogenesis in preadipocytes.

Replacement Flame-Retardant 2-Ethylhexyldiphenyl Phosphate (EHDPP) Disrupts Hepatic Lipidome: Evidence from Human 3D Hepatospheroid Cell Culture

The present study aims to evaluate the effects of repeated exposure to 2-ethylhexyldiphenyl phosphate (EHDPP) on human liver cells. In vitro three-dimensional (3D) hepatospheroid cell culture was utilized to explore the potential mechanisms of EHDPP-mediated metabolic disruption through morphological, transcriptional, and biochemical assays. Lipidomics analysis was performed on the individual hepatospheroids to investigate the effects on intracellular lipid profiles, followed by hepatospheroid morphology, growth, functional parameters, and cytotoxicity evaluation. The possible mechanisms were delineated using the gene-level analysis by assessing the expression of key genes encoding for hepatic lipid metabolism. We revealed that exposure to EHDPP at 1 and 10 μM for 7 days alters the lipid profile of human 3D hepatospheroids. Dysregulation in several lipid classes, including sterol lipids (cholesterol esters), sphingolipids (dihydroceramide, hexosylceramide, ceramide, sphingomyelin), glycerolipids (triglycerides), glycerophospholipids, and fatty acyls, was noted along with alteration in genes including ACAT1, ACAT2, CYP27A1, ABCA1, GPAT2, PNPLA2, PGC1α, and Nrf2. Our study brings a novel insight into the metabolic disrupting effects of EHDPP and demonstrates the utility of hepatospheroids as an in vitro cell culture model complemented with omics technology (e.g., lipidomics) for mechanistic toxicity studies.

Biotransformation of Organophosphate Esters by Rice and Rhizosphere Microbiome: Multiple Metabolic Pathways, Mechanism, and Toxicity Assessment

The biotransformation behavior and toxicity of organophosphate esters (OPEs) in rice and rhizosphere microbiomes were comprehensively studied by hydroponic experiments. OPEs with lower hydrophobicity were liable to be translocated acropetally, and rhizosphere microbiome could reduce the uptake and translocation of OPEs in rice tissues. New metabolites were successfully identified in rice and rhizosphere microbiome, including hydrolysis, hydroxylated, methylated, and glutathione-, glucuronide-, and sulfate-conjugated products. Rhizobacteria and plants could cooperate to form a complex ecological interaction web for OPE elimination. Furthermore, active members of the rhizosphere microbiome during OPE degradation were revealed and the metagenomic analysis indicated that most of these active populations contained OPE-degrading genes. The results of metabolomics analyses for phytotoxicity assessment implied that several key function metabolic pathways of the rice plant were found perturbed by metabolites, such as diphenyl phosphate and monophenyl phosphate. In addition, the involved metabolism mechanisms, such as the carbohydrate metabolism, amino acid metabolism and synthesis, and nucleotide metabolism in Escherichia coli, were significantly altered after exposure to the products mixture of OPEs generated by rhizosphere microbiome. This work for the first time gives a comprehensive understanding of the entire metabolism of OPEs in plants and associated microbiome, and provides support for the ongoing risk assessment of emerging contaminants and, most critically, their transformation products.

First Insight into the Formation of In Vivo Transformation Products of 2-Ethylhexyl diphenyl phosphate in Zebrafish and Prediction of Their Potential Toxicities

As a frequently detected organophosphorus flame retardant in the environment, 2-ethylhexyl diphenyl phosphate (EHDPHP) is vulnerable to biotransformation, while the transformation mechanisms and potential toxicities of its transformation products remain unclear. In the present study, in vivo transformation products of EHDPHP in exposed zebrafish for 21d were analyzed by suspect screening and identified by mass spectrometry. Fifteen metabolites were identified, including 10 phase I and 5 phase II products with monohydroxylated products being primary, among which 5-OH-EHDPHP was the most predominant. Two sulfation products and one terminal desaturation metabolite of EHDPHP were reported for the first time. A density functional calculation coupled with molecular docking disclosed that the specific conformation of EHDPHP docked in the protein pockets favored the primary formation of 5-OH-EHDPHP, which was fortified to be a more suitable biomarker of EHDPHP exposure. The in vitro tests suggested that EHDPHP transformation took place not only in liver but also in intestine, where gut microbes played an important role. Due to lack of standards, in silico toxicity prediction combined with molecular docking indicated that several metabolites potentially cause higher toxicities than EHDPHP. The results provide deep insight into the potential health risks due to specific in vivo transformation of EHDPHP.

Prenatal Exposure of Organophosphate Esters and Its Trimester-Specific and Gender-Specific Effects on Fetal Growth

The toxicity of organophosphate esters (OPEs) on embryonic development is well noted in animal experiments, but epidemiological studies are still lacking. This study evaluated the prenatal exposure of OPEs and its trimester-specific and gender-specific effects on fetal growth. The correlations between OPE exposure and fetal growth were investigated by linear mixed-effect models and multivariable linear regression analyses. Prenatal exposure to tributyl phosphate (TBP) was negatively associated with a z-score of fetal abdominal circumference (AC), biparietal diameter (BPD), femur length (FL), and head circumference (HC). In the second trimester, the serum concentration of TBP was inversely related to the z-score of AC, BPD, and HC. In the third trimester, serum concentration of TBP was inversely related to AC, BPD, and FL z-scores. Prenatal exposure to tri-m-cresyl phosphate (TMCP) was inversely related to the z-score of AC, BPD, and HC. In the second trimester, TMCP was negatively correlated with AC, BPD, FL, and HC z-scores. After stratification by gender, male fetuses were more sensitive to OPE exposure. The above results remained robust after excluding pregnant women who gave preterm birth or those with low or high pre-pregnancy BMI. Our findings suggested that health effects of typical OPEs, particularly TBP and TMCP, should be taken into consideration in future works.

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.

Occurrence, seasonal variation, potential sources, and risks of organophosphate esters in a cold rural area in Northeast China

Organophosphate esters (OPEs) in the environment have been the focus of increasing attention due to their ubiquity and potential toxicity. However, there is little information on the occurrence and characteristics of OPEs in rural areas, especially those with cold year-round temperatures and frozen soil in winter. In this study, environmental samples were collected, in summer and winter, from villages and towns in Northeast China differing in the types and intensities of their anthropogenic activities. The samples were analyzed for 12 OPEs. The results showed the widespread presence of alkyl-OPEs, Cl-OPEs, and aryl-OPEs in the water, soil, snow, and ice of the study sites. In summer, tris(1-chloro-2-propyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the primary compounds in water and soil, respectively. The ∑₁₂OPE concentration in three villages varied from 46.26 to 257.37 ng/L in water, and from 6.62 to 19.46 ng/g in soils. The ∑₁₂OPE concentrations in water were lower in winter than summer, but conversely, ∑₁₂OPE concentrations in frozen soils in winter were higher than those in soils in summer. In winter, there was a shift in the predominant OPEs in water and frozen soils, with dominance of TCEP and complex compounds, respectively. Obvious seasonal characteristics of the potential sources and ecological risks of OPEs in these areas were also determined, with more complex sources of OPEs seen in summer than winter. In summer, only 2-ethylhexyl diphenyl phosphate (EHDPP) in water posed a potential risk, while in summer and, especially, in winter, EHDPP and tris(2-ethylhexyl) phosphate posed potential risks in soils. The high ∑₁₂OPE concentration in snow (56.77 ng/L) implied that wet deposition can amplify OPEs in other environmental compartments. This is the first systematic report on OPEs in a cold rural area. Our findings highlight the need for seasonal monitoring of OPEs in similar areas.

Exposure of men living in the greater Montreal area to organophosphate esters: Association with hormonal balance and semen quality

Exposure to organophosphate esters (OPEs) is extensive, yet few studies have investigated their association with hormone levels or semen quality. Here, we studied the association between urinary concentrations of OPEs and their metabolites with hormone levels and semen parameters in men (n = 117) predominantly in the 20-29 years age range who were recruited from the greater Montreal area between 2009 and 2012. Urine, serum, and semen samples were analyzed for OPEs, hormones, and semen quality, respectively. Bis(2-ethylhexyl) phosphate (BEHP), bis(2,4-di-tert-butylphenyl) hydrogen phosphate (B2,4DtBPP), tris(2-chloroisopropyl) phosphate (TCIPP), diphenyl phosphate (DPHP), bis (2-butoxyethyl) phosphate (BBOEP) and di-cresyl phosphate (DCPs) were detected in urine at a frequency ≥ 95%. The highest geometric mean concentration was observed for DPHP (18.54 ng/mL) and the second highest was B2,4DtBPP (6.23 ng/mL). Associations between a doubling in analyte concentrations in urine and hormone levels and semen quality parameters were estimated using multivariable linear regression. B2,4DtBPP levels were positively associated with total T3 (β = 0.09; 95% CI: 0.01, 0.17). DPHP was inversely associated with estradiol (β = -2.56; 95% CI: -5.00, -0.17), and TCIPP was inversely associated with testosterone (β = -0.78; 95% CI: -1.40, -0.17). Concentrations of BCIPP were inversely associated with sperm concentrations (β = -7.76; 95% CI: -14.40, -0.61), progressive motility (β = - 4.98; 95% CI: -8.71, -1.09), and the sperm motility index (β = -9.72; 95% CI: -17.71, -0.96). In contrast, urinary DPHP concentrations were positively associated with the sperm motility (β = 4.37; 95% CI: 0.76, 8.12) and fertility indices (β = 6.64; 95% CI: 1.96, 11.53). Thus, OPE detection rates were high and exposure to several OPEs was associated with altered hormone levels and semen parameters. The possibility that OPEs affect male reproduction warrants further investigation.

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.

Industrial Production of Organophosphate Flame Retardants (OPFRs): Big Knowledge Gaps Need to Be Filled?

Since the phase-out of traditional halogenated flame retardants (HFRs), interests of research are gradually being shifted to organophosphate flame retardants (OPFRs), and this can be reflected by the increasing number of publications on OPFRs year by year. Here, an extensive survey is conducted in an attempt to generate a list of OPFRs that are being produced in factories, and to investigate the annual production volume (APV). This survey suggests that at least n = 56 OPFR monomers and n = 62 OPFR mixtures are being currently produced in 367 factories around the world, and 201 out of them are in Mainland China. APV of OPFRs was estimated as 598,422 metric tons, and this number could be underestimated due to the limitation of available information. We also notice that current researches are confined to a limited number of OPFRs, especially for OP esters (OPEs), and other OPFRs with different structures from OPEs has been rarely studied. Based on all the collected datasets, we provide five recommendations for how to proceed with future research to more comprehensively understand the currently-produced OPFRs in the environment.

Disruption by stealth - Interference of endocrine disrupting chemicals on hormonal crosstalk with thyroid axis function in humans and other animals

Thyroid hormones (THs) are important regulators of growth, development, and homeostasis of all vertebrates. There are many environmental contaminants that are known to disrupt TH action, yet their mechanisms are only partially understood. While the effects of Endocrine Disrupting Chemicals (EDCs) are mostly studied as "hormone system silos", the present critical review highlights the complexity of EDCs interfering with TH function through their interactions with other hormonal axes involved in reproduction, stress, and energy metabolism. The impact of EDCs on components that are shared between hormone signaling pathways or intersect between pathways can thus extend beyond the molecular ramifications to cellular, physiological, behavioral, and whole-body consequences for exposed organisms. The comparatively more extensive studies conducted in mammalian models provides encouraging support for expanded investigation and highlight the paucity of data generated in other non-mammalian vertebrate classes. As greater genomics-based resources become available across vertebrate classes, better identification and delineation of EDC effects, modes of action, and identification of effective biomarkers suitable for HPT disruption is possible. EDC-derived effects are likely to cascade into a plurality of physiological effects far more complex than the few variables tested within any research studies. The field should move towards understanding a system of hormonal systems' interactions rather than maintaining hormone system silos.

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

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

Life Cycle Exposure to Environmentally Relevant Concentrations of Diphenyl Phosphate (DPhP) Inhibits Growth and Energy Metabolism of Zebrafish in a Sex-Specific Manner

Due to commercial uses and environmental degradation of aryl phosphate esters, diphenyl phosphate (DPhP) is frequently detected in environmental matrices and is thus of growing concern worldwide. However, information on potential adverse effects of chronic exposure to DPhP at environmentally realistic concentrations was lacking. Here, we investigated the effects of life cycle exposure to DPhP on zebrafish at environmentally relevant concentrations of 0.8, 3.9, or 35.6 μg/L and employed a dual-omics approach (metabolomics and transcriptomics) to characterize potential modes of action. Exposure to DPhP at 35.6 μg/L for 120 days resulted in significant reductions in body mass and length of male zebrafish, but did not cause those same effects to females. Predominant toxicological mechanisms, including inhibition of oxidative phosphorylation, down-regulation of fatty acid oxidation, and up-regulation of phosphatidylcholine degradation, were revealed by integrated dual-omics analysis and successfully linked to adverse outcomes. Activity of succinate dehydrogenase and protein content of carnitine O-palmitoyltransferase 1 were significantly decreased in livers of male fish exposed to DPhP, which further confirmed the proposed toxicological mechanisms. This study is the first to demonstrate that chronic, low-level exposure to DPhP can retard growth via inhibiting energy output in male zebrafish.

Human internal exposure to organophosphate esters: A short review of urinary monitoring on the basis of biological metabolism research

As alternatives to traditional brominated flame retardants, organophosphate flame retardants (OPFRs), especially for organophosphate esters (OPEs) -- the most widely used and investigated OPFRs, have raised people's concern on their environmental and health-related risks over the years. Considering their extensive environmental occurrence and potential adverse effects, precise estimation on the human body burden of OPEs will be conducive to the restrictions on the usage of these compounds scientifically. Biomonitoring research can provide precise information on human exposure to OPEs as it reveals the degree of external exposure from all exposure routes. Knowledge on biotransformation and metabolism of OPEs in the biosystems is of great significance for our understanding of the internal exposure to these compounds. In this study, the biological metabolic processes of nine OPEs prevalent in the environment, involving tris(2-chloroethyl) phosphate (TCEP), tris(1-chloro-2-propyl) phosphate (TCIPP), tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), tripropyl phosphate (TPrP), tri-n-butyl phosphate (TnBP), tris(2-butoxyethyl) phosphate (TBOEP), triphenyl phosphate (TPhP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tricresyl phosphate (TCrP), are comprehensively reviewed. Specifically, the metabolic pathway, kinetics and mechanism of OPEs are depicted in detail. Under this context, the advances and limitations on biomonitoring of OPE metabolites in human urine are summarized. The requirements of specificity, quantitative stability, high detection frequency/concentration are needed for OPE metabolites to be considered and validated as biomarkers. Thus far, deeper elucidations on the metabolic processes and identification of biomarkers of OPEs are urgently required, given that some OPEs have no suitable biomarkers in human biomonitoring. For better assessment of the body burden of OPEs in humans, reliable and effective methodologies for urine sampling and estimation on internal exposure to OPEs need to be further developed in the future.

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

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

Exposure of children and mothers to organophosphate esters: Prediction by house dust and silicone wristbands

Ubiquitous human exposure to organophosphorus tri-esters (tri-OPEs) has been reported worldwide. Previous studies investigated the feasibility of using house dust and wristbands to assess human OPE exposure. We hypothesized that these two approaches could differ in relative effectiveness in the characterization of children and adult exposure. In the participants recruited from Guangzhou, South China, urinary levels of major OPE metabolites, including diphenyl phosphate (DPHP) and bis(butoxyethyl) phosphate (BBOEP), were significantly higher in children than their mothers (median 6.6 versus 3.7 ng/mL and 0.11 versus 0.06 ng/mL, respectively). The associations of dust or wristband-associated OPEs with urinary metabolites exhibited chemical-specific patterns, which also differed between children and mothers. Significant and marginally significant associations were determined between dust concentrations of triphenyl phosphate (TPHP), tris(2-butoxyethyl) phosphate (TBOEP), trimethylphenyl phosphate (TMPP), or tris(1-chloro-2-propyl) phosphate (TCIPP) and their metabolites in children urine and between dust tris(1,3-dichloroisopropyl) phosphate (TDCIPP), TPHP or TMPP and urinary metabolites in mothers. By contrast, wristbands exhibited better efficiency of predicting internal exposure to TDCIPP. While both house dust and wristbands exhibited the potential as a convenient approach for assessing long-term OPE exposure, their feasibility requires better investigations via larger-scale studies and standardized sampling protocols.

Evaluation of hepatotoxicity induced by 2-ethylhexyldiphenyl phosphate based on transcriptomics and its potential metabolism pathway in human hepatocytes

Increasing use of organophosphorus flame retardants (OPFRs) has aroused great concern to their uncertain environment risk, especially to human health risk. In our study, hepatotoxicity screening of six aryl-OPFRs, potential hepatotoxicity mechanism of 2-ethylhexyldiphenyl phosphate (EHDPP) using RNA-sequencing and its metabolites were investigated in human hepatocytes (L02). The toxicity results demonstrated that EHDPP should be prioritized for further research with the highest toxicity. Further RNA-seq results through GO and KEGG enrichment analysis indicated that exposure to 10 mg/L of EHDPP significantly affected energy homeostasis, endoplasmic reticulum (ER) stress, apoptosis, cell cycle, and inflammation response in cells. The top 12 hub genes were validated by RT-qPCR and conformed to be mainly related to glycolysis and ER stress, followed by cell cycle and inflammation response. Western blot, apoptosis detection, glycolysis stress test, and cell cycle analysis were further performed to verify the above main pathways. Additionally, it was found in the metabolism experiment that detoxification of EHDPP by phase I and phase II metabolism in cells wasn't significant until 48 h with a metabolic rate of 6.12%. EHDPP was stable and still dominated the induction of toxicity. Overall, this study provided valuable information regarding the toxicity and potential metabolism pathway of EHDPP.

Characterizing exposures to flame retardants, dioxins, and furans among firefighters responding to controlled residential fires

Firefighters may encounter items containing flame retardants (FRs), including organophosphate flame retardants (OPFRs) and polybrominated diphenyl ethers (PBDEs), during structure fires. This study utilized biological monitoring to characterize FR exposures in 36 firefighters assigned to interior, exterior, and overhaul job assignments, before and after responding to controlled residential fire scenarios. Firefighters provided four urine samples (pre-fire and 3-h, 6-h, and 12-h post-fire) and two serum samples (pre-fire and approximately 23-h post-fire). Urine samples were analyzed for OPFR metabolites, while serum samples were analyzed for PBDEs, brominated and chlorinated furans, and chlorinated dioxins. Urinary concentrations of diphenyl phosphate (DPhP), a metabolite of triphenyl phosphate (TPhP), bis(1,3-dichloro-2-propyl) phosphate (BDCPP), a metabolite of tris(1,3-dichloro-2-propyl) phosphate (TDCPP), and bis(2-chloroethyl) phosphate (BCEtP), a metabolite of tris(2-chloroethyl) phosphate (TCEP), increased from pre-fire to 3-hr and 6-hr post-fire collection, but only the DPhP increase was statistically significant at a 0.05 level. The 3-hr and 6-hr post-fire concentrations of DPhP and BDCPP, as well as the pre-fire concentration of BDCPP, were statistically significantly higher than general population levels. BDCPP pre-fire concentrations were statistically significantly higher in firefighters who previously participated in a scenario (within the past 12 days) than those who were responding to their first scenario as part of the study. Similarly, firefighters previously assigned to interior job assignments had higher pre-fire concentrations of BDCPP than those previously assigned to exterior job assignments. Pre-fire serum concentrations of 2,3,4,7,8-pentachlorodibenzofuran (23478-PeCDF), a known human carcinogen, were also statistically significantly above the general population levels. Of the PBDEs quantified, only decabromodiphenyl ether (BDE-209) pre- and post-fire serum concentrations were statistically significantly higher than the general population. These results suggest firefighters absorbed certain FRs while responding to fire scenarios.

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.

First insight on in vitro metabolism of three newly identified aryl organophosphate esters via a suspect coupled with nontarget screening approach

The ubiquity of organophosphate esters (OPEs) in the environment has triggered research into metabolic pathways of OPEs. Using liquid chromatography coupled with a hybrid quadrupole Orbitrap high-resolution mass spectrometer, a suspect and characteristic fragment ion-based nontarget screening strategy for the identification of unknown OPE metabolites was developed and evaluated. Then, this integrated approach was successfully used for investigation of three newly identified organophosphate esters (NOPEs), namely 2-biphenylol diphenyl phosphate (BPDPP), tris(2-biphenyl) phosphate (TBPHP), and naphthalen-2-yl diphenyl phosphate (NDPHP), in human liver microsomes (HLMs). The results demonstrated that BPDPP, TBPHP, and NDPHP were effectively metabolized by HLMs, with zero-order kinetics (R² = 0.48-0.94) within the time frame of the assay. The suspected approach identified a considerable number of dearylated phosphate (DP), and hydroxylated metabolites for each of NOPEs after incubation with HLMs for 2 h. In addition, the nontarget approach further identified 9 novel metabolites including 2 epoxide intermediates and 7 oxidative ring-opening compounds, which were first reported in the Phase I metabolism of OPEs. Collectively, this study provided a novel suspect coupled with nontarget screening approach and was successfully used to screen metabolites of three NOPEs. For the first time, we observed direct evidence that oxidative ring-opening might serve as another primary metabolic pathway regarding the metabolism of aryl OPEs.

Newly discovered bis-(2-ethylhexyl)-phenyl phosphate (BEHPP) was a ubiquitous contaminant in surface soils from a typical region, South China

The organophosphate ester (OPE), bis-(2-ethylhexyl)-phenyl phosphate (BEHPP), was recently identified as an abundant contaminant in indoor dust samples; however, its pollution status in other matrices remains unknown. Here, n = 95 surface soil samples were collected from a prefecture-level city (hereafter referred to as D city) in South China during 2019, and further analyzed to accurately determine the concentrations of BEHPP and eight other OPEs, including tris(2-chloroethyl) phosphate (TCEP), tris(1,3-dichloro-isopropyl) phosphate (TDCIPP), triphenyl phosphate (TPHP), tris(2-butoxyethyl) phosphatetris (TBOEP), 2-ethylhexyl diphenyl phosphate (EHDPP), tris(2-ethylhexyl) phosphate (TEHP), 4-biphenylol diphenyl phosphate (BPDPP), and tris(2-biphenyl) phosphate (TBPHP). BEHPP was detected in all six functional areas (agricultural, scenic, commercial, industrial, and residential areas) of this region, and exhibited a high detection frequency of 67.4%, with a median concentration of 0.455 ng/g dry weight (DW range: nd-7.05 ng/g dw), regardless of the functional area. Samples from commercial, industrial, and residential areas contained significantly greater BEHPP concentrations than those from agricultural and scenic areas. Furthermore, strong and statistically significant correlations were observed between BEHPP and other OPE congeners, particularly for TEHP (r = 0.764, p < 0.001), TBOEP (r = 0.687, p < 0.001), and TPHP (r = 0.709, p < 0.001), indicating that BEHPP may have similar commercial applications and sources to these compounds in surface soil. Collectively, this study provides the first evidence of the presence of BEHPP in soil samples, and indicates that this emerging contaminant is widely distributed across all five functional areas of a typical region (South China).

Assessment of triphenyl phosphate (TPhP) exposure to nail salon workers by air, hand wipe, and urine analysis

Triphenyl phosphate (TPP or TPhP) is commonly used as an additive plasticizer or organophosphate flame retardant (OPFR) in consumer products including nail polish. We evaluated exposure to TPhP from 12 nail salon technicians working at four nail salons located in California over a period of two work days. Bulk samples of 15 nail polishes and other nail products were collected. Study participants also provided two personal air samples, two hand wipe samples (pre- and post-shift on day two), and two urine samples (pre-shift day one and post-shift day two). The geometric mean (GM) of TPhP air sampling concentrations was 7.39 ng/m³. Post-shift TPhP hand wipe concentrations (GM 1.35 μg/sample) were significantly higher (p = 0.024) than pre-shift hand wipe concentrations (GM 0.29 μg/sample). Diphenyl phosphate (DPP or DPhP), a urinary metabolite of TPhP used in this study as a biomarker of exposure, was detected in all post-shift urine samples and 75% of urine pre-shift samples. DPhP post-shift concentrations (GM 1.35 μg/g creatinine) were significantly higher than pre-shift concentrations (GM 0.84 μg/g creatinine; p = 0.012). In addition, DPhP post-shift concentrations were correlated with TPhP post-shift hand wipe concentrations, suggesting dermal contact may be a relevant exposure pathway for nail salon workers.

Cytotoxic Screening and Transcriptomics Reveal Insights into the Molecular Mechanisms of Trihexyl Phosphate-Triggered Hepatotoxicity

Mounting evidence shows that organophosphate flame retardants (OPFRs), especially aryl- and halogenated-OPFRs, exert various adverse health effects on living organisms. This study evaluated the hepatotoxic effect of trihexyl phosphate (THP) as a long-chain alkyl-OPFR on human hepatocyte cells (LO2) and mouse hepatocyte cells (AML12) by performing screening of cytotoxicity in vitro. In combination with transcriptomic analysis, toxicological mechanisms in vitro were further investigated. Results showed that THP triggered hepatotoxicity in vitro by altering four signaling pathways: endoplasmic reticulum (ER) stress, apoptosis, cell cycle, and the glycolysis signaling pathway. Exposure of LO2 and AML12 liver cells to THP (25 μg/mL) significantly induced ER stress-mediated apoptosis and cell cycle arrest. Meanwhile, downregulation of glycolysis caused the blockage of energy metabolism. Furthermore, the high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS/MS) revealed that much of THP was absorbed into the cells and displayed stability in the two liver cell lines. In vivo assays using a mouse model demonstrated that exposure to THP at 400 mg/kg induced the ballooning degeneration of hepatocytes in liver tissue, whereas exposure to THP at 800 mg/kg caused acute liver injury with high alanine aminotransferase levels. This study provides novel insights into the impact of THP on hepatotoxicity in vitro and in vivo and uncovers the underlying toxicological mechanisms, which may serve as a guide for further ecological risk assessment and reasonable application of alkyl-OPFRs.

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.