A critical review of human exposure to organophosphate esters with a focus on dietary intake

Organophosphate flame retardants and their metabolites in paired dog food and urine: Pet exposure through food consumption

Companion dogs are exposed to various chemicals. However, our understanding of the sources and pathways of chemical exposure in pets remains limited. In this study, we collected urine samples from 47 dogs and corresponding samples of the food they consumed to analyze the concentrations and dietary exposure to organophosphate flame retardants (OPFRs) and their metabolites (mOPFRs). Triphenyl phosphate (TPHP) and its metabolite, diphenyl phosphate (DHPH), were the predominant compounds detected in dog food and urine samples. The concentration of mOPFRs in urine decreased as body weight increased; however, neither sex nor age significantly influenced mOPFR levels in dog urine. The estimated daily intake of OPFRs (343 ng/kg bw/day) through food consumption (EDIfood) was comparable to the previously reported levels of polycyclic aromatic hydrocarbons (324 ng/kg bw/day) and higher than those of pesticides (214 ng/kg bw/day), parabens (120 ng/kg bw/day), and polychlorinated biphenyls (103 ng/kg bw/day). By calculating the ratio of EDIfood to the cumulative daily intake based on urinary mOPFR concentrations, it was found that dietary sources contributed to 66% of the total TPHP exposure in dogs. This finding was further supported by Spearman's correlation analysis between parent OPFR concentrations in dog food and mOPFR levels in urine (p < 0.01), indicating that dietary intake may be one of the most significant exposure pathways for OPFRs in dogs. To the best of our knowledge, this is the first study to investigate the levels of OPFR exposure in paired dog food and urine samples.

Inhibition of platelet activation process upon tris (2-chloroethyl) phosphate exposure: Role of PFKP-mediated glycolysis and the pentose phosphate pathway

Tris (2-chloroethyl) phosphate (TCEP), recognized as an emerging pollutant, has been frequently detected in human blood. Maintenance of blood homeostasis is indispensable for regulating various physiological states and overall health, yet hematological toxicology of TCEP has not been extensively investigated. Platelets, a vital component of blood, are fundamental in the processes of hemostasis and thrombosis through their activation; thus, this study was designed to elucidate the effects and underlying mechanisms of TCEP on platelet activation. Utilizing an in vivo model, we conducted a proteomic analysis of platelets and found that TCEP exposure inhibited platelet activation. An ex vivo platelet evaluation system was employed to further dissect the processes of platelet activation, revealing that TCEP predominantly suppressed platelet aggregation, degranulation and clot retraction. These processes were highly dependent on energy metabolism, and TCEP was found to decrease ATP levels, primarily by impairing glycolysis and pentose phosphate pathways. Subsequent investigation into the molecular mechanisms revealed that TCEP decreased the activity of phosphofructokinase platelet (PFKP) by enhancing O-linked N-acetylglucosamine (O-GlcNAc) transferase interaction with PFKP. This study is the first to uncover the disruptive effects of TCEP on platelet activation process, providing valuable insights into the assessment of hematologic health risks associated with TCEP-like emerging pollutants exposure.

A comprehensive library of lifetime physiological equations for PBK models: Enhancing dietary exposure modeling with mercury as a case study

Dietary risk assessment of food contaminants requires a well-established understanding of the exposure in a heterogeneous population. There are many methods for estimating human exposure to food contaminants, such as intake calculations and internal biomarkers of exposure measured in individuals. However, those methods are expensive, partly invasive, and often provide a momentary exposure snapshot. Physiologically Based Kinetic (PBK) modelling is increasingly used to overcome those challenges that traditional human exposure methods encounter. Still, PBK models are often restricted to certain life stages (e.g., children, adolescents, adults). This study outlines a strategy for implementing nonlinear organ growths in age-specific PBK models to enhance dietary risk assessment from lifetime exposure. To this end, lifetime physiological equations calculating organ growth for both sexes were inventoried from literature and a library was established for 24 organs. We then assessed total lifelong mercury exposure via foodstuff by combining two existing age-specific PBK models for methylmercury (MeHg) and inorganic mercury (iHg) that simulated internal exposure to total mercury, the speciation typically measured in hair and urine. We implemented a set of physiological equations in the PBK model that fitted best the total mercury measured in individuals' organs, hair, and urine from heterogeneous populations. For refined dietary risk assessment, we ultimately estimated total mercury concentration in hair and urine based on i) maximum limits defined by the regulation for MeHg in seafood, ii) the health-based guidance values for MeHg and iHg, and iii) realistic intakes considering French demographic parameters and food consumption data. These exposure scenarios demonstrated that total mercury concentrations in hair and urine estimated from realistic intakes are below critical effect level measures at all ages. The result of this study is the creation of easily accessible tools in Excel and R that facilitate the implementation of physiological equations in Next Generation PBK models.

Cardiotoxicity of tris(2-chloroethyl) phosphate exposure: Insights into the role of oxygen sensor mediated energy metabolism remodeling

Tris(2-chloroethyl) phosphate, an extensively used organophosphorus flame retardant in consumer products, has caused pervasive environmental contamination and increased human exposure, raising concerns about its cardiotoxic potential. However, the detailed toxicological profile, particularly concerning the crucial cardiac energy metabolism, and the precise mechanisms remain poorly understood. This study in C57BL/6 J mice exposed to TCEP for 36 days at varying doses revealed cardiac dysfunction, structural abnormalities, and hypoxia. Analysis of energy metabolism indicated a shift from aerobic processes (tricarboxylic acid cycle, β-oxidation, and oxidative phosphorylation) to anaerobic metabolism (glycolysis). Further restoration of energy metabolism remodeling, which was achieved by activating oxidative phosphorylation and inhibiting glycolysis, mitigated TCEP-induced cardiotoxicity, highlighting the critical role of energy metabolism remodeling in TCEP-induced cardiac injury. Mechanistically, this metabolic remodeling was primarily driven by TCEP-enhanced hyperubiquitination and degradation of prolyl hydroxylase domain 2 (PHD2), leading to the accumulation and nuclear translocation of hypoxia-inducible factor-1α (HIF-1α). This study yields key insights into the cardiotoxicity of TCEP-like OPFRs exposure, and emphasizes the role of altered cardiac energy metabolism and the oxygen-sensing pathway, thereby proposing potential intervention strategies for OPFR-induced cardiac toxicity.

Declining trends and regional variations of organophosphate ester contamination in indoor dust from mainland China: Insights from a filed study and meta-analysis

This study investigated the presence of 20 organophosphate esters (OPEs) in indoor dust samples collected from the Chinese cities of Lanzhou, Xining, and Lhasa. The results demonstrate the ubiquitous presence of most OPEs in these three cities, with the highest concentrations of ΣOPEs found in Xining. We also summarized the occurrence of OPEs in indoor environments from 38 studies with 1875 samples collected across various regions of mainland China from 2012 to 2023. The weighted-median concentration of ΣOPEs in indoor dust exhibited region-specific variations, range from 381.9 to 6622.5 ng/g. Chloroalkyl-OPEs (Cl-OPEs) (e.g., tris(2-chloroethyl) phosphate (TCEP), tri(1-chloro-2-propyl) phosphate (TCIPP), and tri (1,3-dichloro-2-propyl) phosphate (TDCIPP)) predominated in all seven regions (range: 38.9 %-71.4 %). TCIPP was predominant in the Central China, North China, Northeast China, Northwest China, Southwest China, and Southwest China regions, while TCEP dominated in the Eastern China region. A significant downward trend in OPE concentrations in indoor environments was observed during the investigated period. Dust ingestion was identified as the predominant pathway of human exposure to OPEs indoors. The hazard quotients for Cl-OPEs were below the non-carcinogenic threshold, suggesting significant health risks are unlikely. This study underscores the widespread occurrence of OPEs in indoor dust across mainland China, emphasizing the necessity for ongoing monitoring and regulation of these chemicals.

An assessment of the levels of emerging and traditional organophosphate ester flame retardants in dairy products in China and their combined dietary risks

A comprehensive survey was conducted by investigating 25 emerging and traditional organophosphate esters (OPEs) in 182 dairy products collected in China. The concentrations of total OPEs (ΣOPEs) ranged from 0.0261 to 1178 ng/g wet weight (ww) in all the dairy samples. The major contaminants were triethyl phosphate (proportion: 94 %) and tris(1-chloro-2-isopropyl) phosphate (proportion: 2 %). Among types of dairy products, the concentrations of ΣOPEs decreased in the following order: milk powder (mean: 80.8 ng/g ww, proportion: 86 %) > cheese (9.43 ng/g ww, 10 %) > milk tablets (2.72 ng/g ww, 3 %) > liquid dairy (1.05 ng/g ww, 1 %). The significant correlation between emerging and traditional OPEs suggests that they likely share similar sources or are used together in commercial applications. OPEs contamination was related to the OPEs properties, local OPEs production and application, and dairy types. For the general Chinese population, the average and high estimated daily intakes of ΣOPEs via dairy products were 31.5 and 83.6 ng/kg bw/day, respectively. Dairy exposure in toddlers and children were higher than other age groups. Although the high-exposure risk of ΣOPEs was 3.50 × 10-3, potentially toxic tris(1-chloro-2-isopropyl) phosphate accounted for 38 % of the total hazard quotients.

Novel flame retardants (NFRs) in e-waste: Environmental burdens, health implications, and recommendations for safety assessment and sustainable management

Novel flame retardants (NFRs) have emerged as chemicals of environmental health concern due to their widespread use as an alternative to polybrominated diphenyl ethers (PBDE) in electrical and electronic devices. Humans and ecosystems are under threat because of e-waste recycling procedures that may emit NFRs and other anthropogenic chemicals into the e-waste workplace and the surrounding environment. The individual toxicity of NFRs including novel brominated flame retardants (NBFRs), their combined effects and the underlying mechanisms of toxicity have remained poorly understood. Exposure assessment as well as chemical safety testing should focus on prioritizing N(B)FRs for regulation and management. Here, the occurrence of N(B)FRs in the vicinity and surroundings of e-waste recycling sites are presented. Important knowledge gaps and prospects for a more integrated, harmonized, and mechanistically positioned risk assessment strategy for N(B)FRs as well as possible economically feasible and environmentally sustainable approaches for removing them from complex matrices are highlighted. Overall, data in the ng to µg-ranges of N(B)FR in soil, dust, sediment, water and fish were found. Dust and soil sample concentrations ranged from the low ng to low µg/g range while water concentrations were always in the low ng/L range (∼0.5 to ∼4 ng/L). Concentration in fish was usually in the range of 3- ∼300 ng/g with two substances in the low to medium-high µg/g range (DBDPE, BTBPE). From the 20 N(B)FR analysed in sediment samples only 10 were above detection limit. Most chemicals were found in a low ng/g range.

Metal heteroatoms significantly enhance efficacy of TiO2 nanomaterials in promoting hydrolysis of organophosphates: Implications for mitigating pollution of plastic additives

Organophosphate esters (OPEs) are prevalent pollutants in the aquatic environment. OPEs are released from many sources, particularly, from the breakdown and weathering of plastic wastes, as OPEs are commonly used plastic additives. Metal oxide mineral nanoparticles play critical roles in the hydrolytic transformation of OPEs. While natural minerals often contain metal impurities, it is unclear how metal heteroatoms affect the efficiency of mineral nanoparticles in mediating hydrolysis reactions. Herein, we show that transition metal-doped anatase titanium dioxide (TiO2) nanomaterials are more effective in catalyzing the hydrolysis of 4-nitrophenyl phosphate (pNPP), a model OPE compound, with the relative effects of the heteroatoms following the order of Fe > Cr > Mn ≈ Ni > Co > Cu. With multiple lines of evidence based on spectroscopic analysis, kinetics modeling, and theoretical calculations, we show that metal doping increases the Lewis acidity of the TiO2 nanomaterials by increasing the oxidation state of surface Ti atoms, inducing oxygen vacancies, and creating additional Lewis acid sites with stronger acidities. Moreover, the increased amounts of surface hydroxyl groups due to metal doping enhance inner-sphere complexation of pNPP through ligand exchange. The interesting observation that Fe-doped TiO2 exhibited the highest catalytic efficiency may have important implications for reducing the risks of organophosphate plastic additives, as iron is the most common heteroatom of naturally occurring TiO2 (nano)materials.

Tracking chemical feature releases from plastic food packaging to humans

Humankind are being exposed to a cocktail of chemicals, such as chemicals released from plastic food packaging. It is of great importance to evaluate the prevalence of plastic food packaging-derived chemicals pollution along the flow of food-human. We developed a robust and practical database of 2101 chemical features associated with plastic food packaging that combined data from three sources, 925 of which were acquired from non-target screening of chemical extracts from eight commonly used plastic food packaging materials. In this database, 625 features, especially half of the non-targets, were potential migrants who likely entered our bodies through dietary intake. Biomonitoring analysis of plastic chemical features in foodstuffs or human serum samples showed that approximately 78 % of the 2101 features were detectable and approximately half were non-targets. Of these, 17 plastic chemicals with high detection frequencies (DFs) in the human serum were confirmed to be functional chemical additives. Together, our work indicates that the number of plastic chemicals in our bodies could be far greater than previously recognized, and human exposure to plastic chemicals might pose a potential health risk.

Sex-specific effects on elements of the social brain neural network in Wistar rats from perinatal exposure to FireMaster 550 or its components

Developmental exposure to chemical flame retardants (FRs) has been linked to a variety of neurodevelopmental disorders and abnormal socioemotional behaviors in human and laboratory animal studies. We have previously shown in Wistar rats that gestational and lactational exposure to the FR mixture Firemaster 550 (FM 550) or its brominated or organophosphate ester (OPFR) components (at 2000 µg, 1000 µg, and 1000 µg oral to the dam respectively (absolute and not by bodyweight)) results in increased anxiety-like behaviors in females and decreased sociality in both sexes. Using their siblings, this study characterized sex and chemical specific targets of disruption in brain regions underlying each behavioral phenotype. Offspring were exposed across gestation and lactation then prepared for either immunohistochemistry or autoradiography at postnatal day 90 to quantify expression of serotonin, estrogen receptor α (ERα), and oxytocin receptor (OTR) in multiple brain regions. No effect of exposure was found in males for any biological target. In females, serotonin innervation was increased in the medial amygdala of FM 550 exposed animals while ERα expression in the bed nucleus of the stria terminalis (BNST) was reduced by FM 550 and OPFR. Evidence of disrupted OTR was observed in males, particularly the BNST but considered an exploratory finding given the small sample size. These results begin to shed light on the mechanisms by which developmental FR exposure alters socioemotional behaviors of relevance to neurodevelopmental disorders.

Migration patterns of organophosphate esters from plastic food packaging simulants to foods: Donors, behaviours, and influencing factors

In recent years, organophosphate esters (OPEs) have been widely produced and used as flame retardants and plasticizer additives, posing significant ecological and health risks. Dietary intake is considered to be the primary route of human exposure to OPEs. Plastic food packaging materials are considered a crucial source for contamination of OPEs in food. However, the migration behaviour of OPEs from plastic food packaging materials into foods has received limited attention. In this study, we employed a novel method to prepare migration donors containing 13 kinds of OPEs. The migration behaviours of OPEs from food packaging simulants (polypropylene) to foods (full-fat milk powder) were simulated, and factors influencing the migration of OPEs were examined, including the properties of the target compounds, migration temperature, fat content of the migration receptors, and mass transfer mode. The results indicated that OPEs exhibited a significant migration tendency. Low molecular weight OPEs (< 300 Da) had faster migration efficiency compared to high molecular weight OPEs. The mean migration efficiencies of various OPEs showed a significant negative correlation with their molecular weights (p < 0.01) and a significant positive correlation with temperature (p < 0.01). Except for resorcinol bis(diphenyl phosphate) (RDP), which showed almost no migration, the mean migration efficiencies of other OPEs at 25 °C, 40 °C, and 60 °C were 3.1-37.5 %, 9.0-60.0 %, and 23.9-80.4 %, respectively. Most of the OPEs demonstrated higher migration efficiency in high-fat content food than low-fat content food. The migration of OPEs from food packaging simulants to foods primarily occurred through contact rather than gas-phase mass transfer. Overall, this study uncovers the migration behaviours of OPEs from food packaging simulants to foods and scrutinized the relevant factors influencing the migration. It is expected that the research in terms of the contamination control of OPEs in food will benefit from this work.

Simultaneous analysis of several plasticizer classes in different matrices by on-line turbulent flow chromatography-LC-MS/MS

The development of methodologies for the determination of plasticizers is essential for assessing the environmental and human impact resulting from the use of plastics. A fast analytical method with on-line purification based on turbulent flow chromatography (TFC) coupled to tandem mass spectrometry (MS-MS) has been developed for the analysis of ten phthalates, four alternative plasticizers (including adipates and citrates), and 20 organophosphate esters (OPEs). The method has been validated for the determination of plasticizers across different matrices. Analytical parameters showed acceptable recoveries ranging between 50 and 125%, RSDs lower than 20%, and mLODs of 0.001-2.08 ng g-1 wet weight (ww), 0.002-0.30 ng g-1, and 0.001-0.93 ng m-3 for foodstuffs, face masks, and ambient air, respectively. These methodologies were applied to foodstuff samples purchased in grocery stores, reusable and self-filtering masks, and indoor air measured in different locations. Plasticizers were detected in all the analyzed samples, with values up to 22.0 μg g-1 ww, 6.78 μg g-1, and 572 ng m-3 for foodstuffs, face masks, and indoor air, respectively. The contribution of each family to the total plasticizer content varied between 1.3 and 87%, 0.5 and 98%, and 0.5 and 65% for phthalates, alternative plasticizers, and OPEs, respectively. These findings highlighted the need for analytical methodologies capable of simultaneously assessing a wide number of plasticizers with minimal extraction steps. This capability is crucial in order to obtain more conclusive insights into the impact of these pollutants on both the environment and human health, arising from different sources of exposure such as foodstuffs, plastic materials, and atmospheric air.

Organophosphate esters and their metabolites in eggs from Vietnam

Data on the occurrence of organophosphate tri-esters (tri-OPEs) and their metabolites (di-OPEs) in hen's eggs are scarce. Therefore, 200 egg samples were gathered in 2023 in Hanoi, Vietnam and analysed by UHPLC-Q-Exactive HRMS. The majority of these compounds were detected, with tris(2-ethylhexyl) phosphate (0.10-2.7 ng/g wet weight (ww)) and trihexyl phosphate (0.08-2.3 ng/g ww) being the most prevalent tri-OPEs. Significant differences in tri-OPE profiles were observed in egg samples from battery-cage and free-range farming (p < .05). Despite egg levels ranging from 0.05 to 11.2 ng/g ww, Σdi-OPE accumulation in yolk and egg white was not significantly different in (p > .05). Among di-OPEs, dibutyl phosphate was found at the highest levels in the egg white, while bis(2-ethylhexyl) phosphate had the highest levels in yolk. There was no carcinogenic human health risk associated with OPEs in eggs (HQs <1).

Exploring organophosphate ester contamination and distribution in food: A meta-analysis

This study examines the food safety risk of organophosphate esters (OPEs) by analyzing data from 23 studies with 14,915 data points. We found EDP contamination highest in cereals, dairy, and meats, and TEHP most prevalent in vegetables and fruits, with contamination levels reaching 4.54 ng/g and 1.46 ng/g, respectively. Food processing influences OPE contamination through complex and multifaceted, akin to a "double-edged sword.", as meta-analysis and Principal Component Analysis (PCA) revealed. Estimated Dietary Intakes (EDI) identified vegetables and cereals as primary OPE sources, contributing 33.3% and 23.8% of total intake, with EDI values of 44.74 ng/kg bw/day and 32.25 ng/kg bw/day, respectively. Current exposure levels are within U.S. EPA safety thresholds (HQ < < 1), but the heightened risk to infants and children necessitates revising safety standards and ongoing monitoring.

Comparison of the presence of high production volume chemicals in farmed and wild fish highly consumed in catalonia and their risk assessment

The decline in fish populations and the depletion of marine resources have sparked concerns about sustainable fish production, driving the innovation of new aquaculture methods. While some argue that wild fish are healthier than farmed fish due to less exposure to contaminants and pathogens, wild fish can accumulate contaminants from more contaminated water sources. The slower growth of wild fish and their longer exposure to the environment may contribute to higher pollutant levels in fish tissues. In this study, we focus on 25 contaminants considered as high production volume chemicals (HPVCs), such as organophosphate esters (OPEs), benzothiazoles (BTs), benzosulfonamides (BSAs) and phthalates (PAEs). The compounds were extracted from the edible part of the fish using the QuEChERS method and analysed by gas chromatography-tandem mass spectrometry. A total of 74 samples were analysed from three of the most commonly consumed species in Catalonia, Spain (turbot, sea bass and sea bream). Two samples of each species were collected each month, one form farmed and one from wild origin. In general, the compounds were found in all the samples in a wide concentrations range, although no significant differences were observed between the mean concentration of wild and farmed samples. Although similar mean concentrations for the OPEs, BTs and BSAs were found between farmed and wild origin samples, PAEs were more frequently detected in farmed samples. Di-n-octyl phthalate and diethyl phthalate showed the highest concentrations in all fish samples, with values up to 19505 and 17605 ng g-1 (d.w.), in sea bass and sea bream, respectively. Di-(2-ethylexyl)-adipate proved to be the most relevant carcinogenic compound, with no associated health risk. Despite the detection of the studied HPVCs, no health risk was associated with the consumption of these three fish species.

EHDPP induces proliferation inhibition and apoptosis to spermatocyte: Insights from transcriptomic and metabolomic profiles

BACKGROUND

2-ethylhexyldiphenyl phosphate (EHDPP) was used widespread in recent years and it was reported to impair reproductive behaviors and decrease fertility in male Japanese medaka. However, whether EHDPP causes spermatogenesis disturbance remains uncertain.

OBJECTIVES

We aimed to study the male reproductive toxicity of EHDPP and its related mechanism.

METHODS

Human spermatocyte cell line GC-2 was treated with 10 µM, 50 µM or 100 µM EHDPP for 24 h. Male CD-1 mice aged 6 weeks were given 1, 10, or 100 mg/kg/d EHDPP daily for 42 days and then euthanized to detect sperm count and motility. Proliferation, apoptosis, oxidative stress was detected in mice and cell lines. Metabolome and transcriptome were used to detect the related mechanism. Finally, anti-oxidative reagent N-Acetylcysteine was used to detect whether it could reverse the side-effect of EHDPP both in vivo and in vitro.

RESULTS

Our results showed that EHDPP inhibited proliferation and induced apoptosis in mice testes and spermatocyte cell line GC-2. Metabolome and transcriptome showed that nucleotide metabolism disturbance and DNA damage was potentially involved in EHDPP-induced reproductive toxicity. Finally, we found that excessive ROS production caused DNA damage and mitochondrial dysfunction; NAC supplement reversed the side effects of EHDPP such as DNA damage, proliferation inhibition, apoptosis and decline in sperm motility.

CONCLUSION

ROS-evoked DNA damage and nucleotide metabolism disturbance mediates EHDPP-induced germ cell proliferation inhibition and apoptosis, which finally induced decline of sperm motility.

Biotransformation, Bioaccumulation, and Bioelimination of Triphenyl Phosphate and Its Dominant Metabolite Diphenyl Phosphate In Vivo

Aryl phosphorus flame retardants (aryl-PFRs), such as triphenyl phosphate (TPHP) and diphenyl phosphate (DPHP), are widely used worldwide. Understanding the fates of aryl-PFRs in vivo is crucial to assessing their toxicity and the risks they pose. Seven TPHP metabolites, including Phase I hydrolysis and hydroxylation and Phase II glucuronidation products, were identified in C57BL/6J male mice following subacute dietary exposure to aryl-PFRs (70 μg/kg body weight (bw)/day) for 7 days. TPHP was almost completely metabolized by mice (∼97%), with DPHP the major metabolite formed (34%-58%). In addition, mice were exposed to aryl-PFRs (7 μg/kg bw/day) for 12 weeks. Both TPHP and DPHP occurred at higher concentrations in the digestive tract (intestine and stomach), liver and heart. The total concentration of DPHP in all organs was 3.55-fold greater than that of TPHP. Recovery analysis showed that the rate of TPHP elimination from mouse organs reached 38%, while only 3%-5% of DPHP was removed, suggesting that the rates of degradation and elimination of DPHP were slower than TPHP and its bioaccumulation potential was higher. These results highlight the critical role of DPHP in the biotransformation, bioaccumulation, and bioelimination of TPHP, providing valuable insights into the fate of aryl-PFRs in vivo.

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.

Organophosphate Esters in Raw Cow Milk and Cow's Drinking Water and Feed from China: Occurrence, Regional Distribution, and Dietary Exposure Assessment

Organophosphate esters (OPEs) have been widely produced and used, while little is known about their occurrence in the food chain and potential sources. In this study, raw cow milk, cow drinking water, and feed were collected from pastures across China, and OPEs were tested to explore the occurrence and transmission of OPEs in the food chain and to further assess daily OPE intakes for cows and humans via certain food consumption. The median level of ∑OPEs (sum of 15 OPEs) in raw milk was 2140 pg/mL, and tris(1-chloro-2-propyl) phosphate (TCIPP) was the most abundant OPE. Levels of OPEs in water were lower than those in raw milk except for triethyl phosphate (TEP), while levels of most OPEs in feed were significantly higher than those in raw milk (adjusted by dry weight). The estimated dietary intake of OPEs via feed for cows was 2530 ng/kg bw/day, which was much higher than that via water (742 ng/kg bw/day), indicating that feed was a more critical exposure source. For liquid milk consumers, the high-exposure (95th) estimated daily intakes (EDIs) of ∑15OPE were 20 and 7.11 ng/kg bw/day for 3-17 years and adults, respectively, and it is obvious that cows had much heavier OPE intake. Finally, the calculated hazard indexes (HIs) suggested that the intake of OPEs via cow milk consumption would not pose significant health risks to the Chinese population.

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.

Nationwide Investigation on Organophosphate Flame Retardants in Tea from China: Migration from Packaging Materials and Implications for Global Risk Assessment

In this study, we measured 15 common organophosphate flame retardants (OPFRs) in six categories of tea samples across China. OPFRs were found in all the tea samples, with the total concentrations of OPFRs (∑OPFRs) at 3.44-432 ng/g [geometric mean (GM): 17.6 ng/g]. Triphenyl phosphate (TPhP) was the dominant OPFR, accounting for 39.0-76.2% of ∑OPFRs across all tea categories. The potential factors influencing the residual OPFRs in tea were thoroughly examined, including the agricultural environment, fermentation, and packaging of teas. Tea packaging materials (TPMs) were then identified as the primary sources of OPFRs in teas. The migration test revealed that OPFRs with lower molecular weights and log Kow values exhibited a higher propensity for facilitating the migration of OPFRs from TPMs to teas. The estimated daily intakes of OPFRs from teas were relatively higher for the general populations in Mauritania, Gambia, Togo, Morocco, and Senegal (3.18-9.79 ng/kg bw/day) than China (3.12 ng/kg bw/day). The health risks arising from OPFRs in Chinese teas were minor. This study established a baseline concentration and demonstrated the contamination sources of OPFRs in Chinese tea for the first time, with an emphasis on enhancing the hygiene standards for TPMs.

Occurrence, spatial distribution and ecological risk assessment of Organophosphate Esters in surface water and sediments from the Ravi River and its tributaries

Organophosphate esters (OPEs) are widely used as substitutes for brominated flame retardants and characterized as emerging contaminants. Due to their toxicity and persistent nature, OPEs are becoming a matter of greater concern worldwide. However, information about the pollution profile of OPEs and associated ecological risks is still scarce in environmental matrices of the South Asian region, particularly Pakistan. Hence, the current study was conducted to investigate the occurrence, spatial distribution patterns, ecological risks and riverine flux of 10 organophosphate esters in surface water and sediments of Ravi River and its four tributaries. The concentrations of ∑10OPEs were in the range of 19.2 - 105 ng/L, with the dominance of chlorinated-OPEs (51 %) in surface water, whereas in case of sediments, the ∑10OPEs concentrations ranged from 20.7 to 149 ng/g dw, with high abundance of non - chlorinated alkyl-OPEs, which contributed about 56 % to total OPE concentration. The correlation analysis signified a strong positive relation of OPEs with TOC (p < 0.05, R = 0.76) in sediments; and in addition to this, field-based LogKoc values were estimated to be higher than predicted LogKoc. Moreover, a significantly positive correlation (p < 0.05, R = 0.88) was observed between LogKoc and LogKow, implying that hydrophobicity plays a significant role in OPE distribution in different environmental matrices. The global comparison revealed that contamination status of OPEs in the present study was comparatively lower than other regional findings, furthermore, principal component analysis suggested vehicular emissions, industrial discharges, household supplies and atmospheric deposition as main sources of OPEs occurrence in current study region. Furthermore, the riverine flux of ∑10OPEs was estimated to be 0.68 tons/yr and the ecological risk assessment indicated that all OPEs, except EHDPP and TCrP, showed negligible or insignificant ecological risks for aquatic organisms.

Profiling population-wide exposure to environmental chemicals: A case study of naphthalene

Long-term exposure to environmental chemicals can detrimentally impact human health, and understanding the relationship between age distribution and levels of external and internal exposure is crucial. Nonetheless, existing methods for assessing population-wide exposure across age groups are limited. To bridge this research gap, we introduced a modeling approach designed to assess both chronic external and internal exposure to chemicals at the population level. The external and internal exposure assessments were quantified in terms of the average daily dose (ADD) and steady-state blood concentration of the environmental chemical, respectively, which were categorized by age and gender groups. The modeling process was presented within a spreadsheet framework, affording users the capability to execute population-wide exposure analyses across a spectrum of chemicals. Our simulation outcomes underscored a salient trend: younger age groups, particularly infants and children, exhibited markedly higher ADD values and blood concentrations of environmental chemicals compared to their older counterparts. This observation is due to the elevated basal metabolic rate per unit of body weight characteristic of younger individuals, coupled with their diminished biotransformation kinetics of xenobiotics within their livers. These factors collectively contribute to increased intake rates of environmental chemicals per unit of body weight through air and food consumption, along with heightened bioaccumulation of these chemicals within their bodies (e.g., blood). Furthermore, we augmented the precision of the external and internal exposure assessment by incorporating the age distribution across the population. The simulation outcomes unveiled that, to estimate the central tendency of the population's exposure levels, employing the baseline value group (age group 21-30) or the surrogate age of 25 serves as a simple yet dependable approach. However, for comprehensive population protection, our recommendation aligns with conducting exposure assessments for the younger age groups (age group 0-11). Future studies should integrate individual-level exposure assessment, analyze vulnerable population groups, and refine population structures within our developed model.

EGFR and Hippo signaling pathways are involved in organophosphate esters-induced proliferation and migration of triple-negative breast cancer cells

The widespread application of organophosphate flame retardants has led to pervasive exposure to organophosphate esters (OPEs), prompting considerable concerns regarding their potential health risk to humans. Despite hints from previous research about OPEs' association with breast cancer, their specific effects and underlying mechanisms of triple-negative breast cancer (TNBC) remain unclear. In this study, we investigated the effects of four representative OPEs on cell proliferation, cell cycle regulation, migration, and the expression of genes and proteins associated with the epidermal growth factor receptor (EGFR) and Hippo signaling pathways in TNBC (MDA-MB-231) cells. Our findings revealed that treatment with 1-25 μM triphenyl phosphate (TPHP) and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) induced TNBC cell proliferation and accelerated cell cycle progression, with upregulation in MYC, CCND1, and BRCA1 mRNA. Moreover, exposure to 1-25 μM TPHP, 10-25 μM TDCIPP, and 1-10 μM tris (2-chloroethyl) phosphate (TCEP) induced MMP2/9 mRNA expression and enhanced migratory capacity, except for 2-ethylhexyl diphenyl phosphate (EHDPP). Mechanistically, four OPEs treatments activated the EGFR-ERK1/2 and EGFR-PI3K/AKT signaling pathways by increasing the transcript of EGFR, ERK1/2, PI3K, and AKT mRNA. OPEs treatment also suppressed the Hippo signaling pathway by inhibiting the expression of MST1 mRNA and phosphorylation of LATS1, leading to the overactivation of YAP1 protein, thereby promoting TNBC cell proliferation and migration. In summary, our study elucidated that activation of the EGFR signaling pathway and suppression of the Hippo signaling pathway contributed to the proliferation, cell cycle dysregulation, and migration of TNBC cells following exposure to OPEs.

Tris(2-ethylhexyl) phosphate induces cytotoxicity in TM3 Leydig cells by modulating autophagy and endoplasmic reticulum stress

Tris (2-ethylhexyl) phosphate (TEHP) is a frequently used organophosphorus flame retardant with significant ecotoxicity and widespread human exposure. Recent research indicates that TEHP has reproductive toxicity. However, the precise cell mechanism is not enough understood. Here, by using testicular mesenchymal stromal TM3 cells as a model, we reveal that TEHP induces apoptosis. Then RNA sequencing analysis, immunofluorescence, and western blotting results show that THEP inhibits autophagy flux and enhances endoplasmic reticulum (ER) stress. Moreover, the activation of the ER stress is critical for TEHP-induced cell injury. Interestingly, TEHP-induced ER stress is contributed to autophagic flux inhibition. Furthermore, pharmacological inhibition of autophagy aggravates, and activation of autophagy attenuates TEHP-induced apoptosis. In summary, these findings indicate that TEHP triggers apoptosis in mouse TM3 cells through ER stress activation and autophagy flux inhibition, offering a new perspective on the mechanisms underlying TEHP-induced interstitial cytotoxicity in the mouse testis.

Bioaccessibility of halogenated flame retardants and organophosphate esters in settled dust: Influences of specific dust matrices from informal e-waste and end-of-life vehicle processing areas in Vietnam

Bioaccessibility of halogenated flame retardants (HFRs) and organophosphorus esters (OPEs) is necessarily investigated to provide more accurate risk assessment and information about absorption behavior of these pollutants. In this study, total and bioaccessible concentrations of HFRs (including legacy and alternative substances) and OPEs were determined in settled dust samples collected from Vietnamese e-waste and end-of-life vehicle (ELV) processing areas. Concentrations of both HFRs and OPEs were significantly higher in the e-waste dust than ELV dust. Bioavailability of HFRs and OPEs in dust was determined by using an in vitro assay with human-simulated digestive fluids, dialysis membrane, and Tenax® TA sorptive sink. Bioaccessibility of HFRs was markedly lower than that of OPEs, which could be largely due to higher hydrophobicity of HFRs compared to OPEs. Bioaccessibility of almost hydrophobic compounds were markedly lower in the e-waste dust (containing micronized plastic debris) than in the ELV dust (containing oily materials), suggesting the influence of specific dust matrices on pollutant bioaccessibility. Although the daily uptake doses of selected HFRs and OPEs from dust were markedly higher in the e-waste sites compared to the ELV sites, the direct exposure risk was not significant. Our results suggest that bioaccessibility can partly explain the differences between dust and uptake profiles, which may relate to accumulation profiles of HFRs and OPEs in human samples.

Uptake, translocation, and metabolism of organophosphate esters (OPEs) in plants and health perspective for human: A review

Plant uptake, accumulation, and transformation of organophosphate esters (OPEs) play vital roles in their geochemical cycles and exposure risks. Here we reviewed the recent research advances in OPEs in plants. The mean OPE concentrations based on dry/wet/lipid weight varied in 4.80-3,620/0.287-26.8/12,000-315,000 ng g-1 in field plants, and generally showed positive correlations with those in plant habitats. OPEs with short-chain substituents and high hydrophilicity, particularly the commonly used chlorinated OPEs, showed dominance in most plant samples, whereas some tree barks, fruits, seeds, and roots demonstrated dominance of hydrophobic OPEs. Both hydrophilic and hydrophobic OPEs can enter plants via root and foliar uptake, and the former pathway is mainly passively mediated by various membrane proteins. After entry, different OPEs undergo diverse subcellular distributions and acropetal/basipetal/intergenerational translocations, depending on their physicochemical properties. Hydrophilic OPEs mainly exist in cell sap and show strong transferability, hydrophobic OPEs demonstrate dominant distributions in cell wall and limited migrations owing to the interception of Casparian strips and cell wall. Additionally, plant species, transpiration capacity, growth stages, commensal microorganisms, and habitats also affect OPE uptake and transfer in plants. OPE metabolites derived from various Phase I transformations and Phase II conjugations are increasingly identified in plants, and hydrolysis and hydroxylation are the most common metabolic processes. The metabolisms and products of OPEs are closely associated with their structures and degradation resistance and plant species. In contrast, plant-derived food consumption contributes considerably to the total dietary intakes of OPEs by human, particularly the cereals, and merits specifical attention. Based on the current research limitations, we proposed the research perspectives regarding OPEs in plants, with the emphases on their behavior and fate in field plants, interactions with plant-related microorganisms, multiple uptake pathways and mechanisms, and comprehensive screening analysis and risk evaluation.

Association between exposure to chemical mixtures and epigenetic ageing biomarkers: Modifying effects of thyroid hormones and physical activity

Evidence on the effects of internal chemical mixture exposures on biological age is limited. It also remains unclear whether hormone homeostasis and lifestyle factors can modify such a relationship. Based on the Biomarkers for Air Pollutants Exposure (BAPE) study, which involved healthy older adults aged 60-69 years in China, we found that chemical mixture exposures, including metals, polycyclic aromatic hydrocarbons (PAHs), per- and polyfluoroalkyl substances (PFASs), phthalates (PAEs), and organophosphate esters (OPEs), were significantly associated with shortened DNAmTL and accelerated SkinBloodClock, in which PFASs and OPEs in blood were the primary contributors to DNAmTL, while metals and PAEs had relatively higher contributions in urine. Furthermore, lower levels of thyroxin appeared to exacerbate the adverse effects of environmental chemicals on epigenetic ageing but relatively higher levels of physical activity had the beneficial impact. These findings may have important implications for the development of healthy ageing strategy and aged care policy, particularly in light of the global acceleration of population ageing.

Emerging organophosphite and organophosphate esters in takeaway food and the implications for human exposure

Takeaway food has become a prominent component of the diet in urban areas of China, especially for young people. Although dietary intake is a major pathway to contaminants for human exposure, studies on emerging organophosphite antioxidants (OPAs) and organophosphate esters (OPEs) in food are scarce. Here, we investigated four OPAs and 19 OPEs in takeaway foods (n = 99) and paired takeaway food packaging (n = 50) in China. AO168=O (mean: 14.9 ng/g ww), TPPO (mean: 1.05 ng/g ww), and TCIPP (mean: 0.579 ng/g ww) were dominant in the takeaway food. Some OPEs had significant correlations in takeaway food. Emerging OPAs and OPEs in takeaway food varied significantly depending on the packaging materials and food types. AO168 and AO168=O were widespread in the paired takeaway food packaging. The migration efficiencies of emerging OPAs and OPEs were low in takeaway food packaged in aluminum foil. Although the actual contamination of emerging OPAs and OPEs in takeaway food significantly differed from those of in food simulants migrated from paired takeaway food packaging, the results imply that food itself and takeaway food packaging are potential contamination sources of emerging OPAs and OPEs in takeaway food. The average estimated dietary intakes of emerging OPAs and OPEs were 465 ng/kg body weight (bw)/day and 91.9 ng/kg bw/day, respectively. The exposure risk of emerging OPAs and OPEs through takeaway food intake is low in China.

Prenatal exposure to a mixture of organophosphate flame retardants and infant neurodevelopment: A prospective cohort study in Shandong, China

BACKGROUND

Previous studies have suggested that prenatal exposure to organophosphate flame retardants (OPFRs) may have adverse effect on early neurodevelopment, but limited data are available in China, and the overall effects of OPFRs mixture are still unclear.

OBJECTIVE

This study aimed to investigate the association between prenatal exposure to OPFR metabolites mixture and the neurodevelopment of 1-year-old infants.

METHODS

A total of 270 mother-infant pairs were recruited from the Laizhou Wan (Bay) Birth Cohort in China. Ten OPFR metabolites were measured in maternal urine. Neurodevelopment of 1-year-old infants was assessed using the Gesell Developmental Schedules (GDS) and presented by the developmental quotient (DQ) score. Multivariate linear regression and weighted quantile sum (WQS) regression models were conducted to estimate the association of prenatal exposure to seven individual OPFR metabolites and their mixture with infant neurodevelopment.

RESULTS

The positive rates of seven OPFR metabolites in the urine of pregnant women were greater than 70% with the median concentration ranged within 0.13-3.53 μg/g creatinine. The multivariate linear regression model showed significant negative associations between bis (1-chloro-2-propyl) phosphate (BCIPP), din-butyl phosphate (DnBP), and total OPFR metabolites exposure and neurodevelopment in all infants. Results from the WQS model consistently revealed that the OPFR metabolites mixture was inversely associated with infant neurodevelopment. Each quartile increased in the seven OPFR metabolites mixture was associated with a 1.59 decrease (95% CI: 2.96, -0.21) in gross motor DQ scores, a 1.41 decrease (95% CI: 2.38, -0.43) in adaptive DQ scores, and a 1.08 decrease (95% CI: 2.15, -0.02) in social DQ scores, among which BCIPP, bis (1, 3-dichloro-2-propyl) phosphate (BDCIPP) and DnBP were the main contributors.

CONCLUSION

Prenatal exposure to a mixture of OPFRs was negatively associated with early infant neurodevelopment, particularly in gross motor, adaptive, and social domains.

Organophosphate esters in water and air: A minireview of their sources, occurrence, and air-water exchange

Organophosphate esters (OPEs) have received considerable attention in environmental research due to their extensive production, wide-ranging applications, prevalent presence, potential for bioaccumulation, and associated ecological and health concerns. Low efficiency of OPE removal results in the effluents of wastewater treatment plants emerging as a significant contributor to OPE contamination. Their notable solubility and mobility give OPEs the potential to be transported to coastal ecosystems via river discharge and atmospheric deposition. Previous research has indicated that OPEs have been widely detected in the atmosphere and water bodies. Atmospheric deposition across air-water exchange is the main input route for OPEs into the environment and ecosystems. The main processes that contribute to air-water exchange is air-water diffusion, dry deposition, wet deposition, and the air-water volatilization process. The present minireview links together the source, occurrence, and exchange of OPEs in water and air, integrates the occurrence and profile data, and summarizes their air-water exchange in the environment.

Organophosphate ester additives and microplastics in benthic compartments from the Loire estuary (French Atlantic coast)

We report the first empirical confirmation of the co-occurrence of organophosphate esters (OPEs) additives and microplastics (MPs) in benthic compartments from the Loire estuary. Higher median concentrations of MPs (3387 items/kg dw), ∑13tri-OPEs (12.0 ng/g dw) and ∑4di-OPEs (0.7 ng/g dw) were measured in intertidal sediments with predominance of fine particles, and under higher anthropogenic pressures, with a general lack of seasonality. Contrarily, Scrobicularia plana showed up to 4-fold higher ∑tri-OPE concentrations in summer (reaching 37.0 ng/g dw), and similar spatial distribution. Polyethylene predominated in both compartments. Tris(2-ethylhexyl) phosphate (TEHP), its degradation metabolite (BEHP) and tris-(2-chloro, 1-methylethyl) phosphate (TCIPP) were the most abundant OPEs in sediments, while TCIPP predominated in S. plana. The biota-sediment accumulation factors suggest bioaccumulation potential for chlorinated-OPEs, with higher exposure in summer. No significant correlations were generally found between OPEs and MPs in sediments suggesting a limited role of MPs as in-situ source of OPEs.

Occurrence and Health Risk Assessment of Phthalates in Municipal Drinking Water Supply of a Central Indian City

In this study, the occurrence of phthalates in the municipal water supply of Nagpur City, India, was studied for the first time. The study aimed to provide insights into the extent of phthalate contamination and identify potential sources of contamination in the city's tap water. We analyzed fifteen phthalates and the total concentration (∑15phthalates) ranged from 0.27 to 76.36 µg L-1. Prominent phthalates identified were di-n-butyl phthalate (DBP), di-isobutyl phthalate (DIBP), benzyl butyl phthalate (BBP), di (2-ethylhexyl) phthalate (DEHP), di-n-octyl phthalate (DNOP), and di-nonyl phthalate (DNP). Out of the fifteen phthalates analyzed, DEHP showed the highest concentration in all the samples with the median concentration of 2.27 µg L-1, 1.39 µg L-1, 1.83 µg L-1, 2.02 µg L-1, respectively in Butibori, Gandhibaag, Civil Lines, and Kalmeshwar areas of the city. In 30% of the tap water samples, DEHP was found higher than the EPA maximum contaminant level of 6 µg L-1. The average daily intake (ADI) of phthalates via consumption of tap water was higher for adults (median: 0.25 µg kg-1 day-1) compared to children (median: 0.07 µg kg-1 day-1). The hazard index (HI) calculated for both adults and children was below the threshold level, indicating no significant health risks from chronic toxic risk. However, the maximum carcinogenic risk (CR) for adults (8.44 × 10-3) and children (7.73 × 10-3) was higher than the threshold level. Knowledge of the sources and distribution of phthalate contamination in municipal drinking water is crucial for effective contamination control and management strategies.

Unravelling bioaccumulation, depletion and metabolism of organophosphate triesters in laying hens: Insight of in vivo biotransformation assisted by diester metabolites

Organophosphate triesters (tri-OPEs) threaten human health through dietary exposure, but little is known about their feed-to-food transfer and in vivo behavior in farm animals. Herein 135 laying hens were fed with contaminated feed (control group, low-level group and high-level group) to elucidate the bioaccumulation, distribution, and metabolism of the six most commonly reported tri-OPEs. The storage (breast muscle), metabolism and mobilization (liver and blood) and non-invasive (feather) tissues were collected. The exposure-increase (D1∼14) and depuration-decrease (D15∼42) trends indicated that feed exposure caused tri-OPE accumulation in animal tissues. Tissue-specific and moiety-specific behavior was observed for tri-OPEs. The highest transfer factor (TF) and transfer rate (TR) were observed in liver (TF: 14.8%∼82.3%; TR: 4.40%∼24.5%), followed by feather, breast muscle, and blood. Tris(2-chloroisopropyl) phosphate (TCIPP) had the longest half-life in feather (72.2 days), while triphenyl phosphate (TPhP) showed the shortest half-life in liver (0.41 days). Tri-OPEs' major metabolites (organophosphate diesters, di-OPEs) were simultaneously studied, which exhibited dose-dependent and time-dependent variations following administration. In breast muscle, the inclusion of di-OPEs resulted in TF increases of 735%, 1108%, 798%, and 286% than considering TCIPP, tributyl phosphate, tris(2-butoxyethyl) phosphate and tris(2-ethylhexyl) phosphate alone. Feather was more of a proxy of birds' long-term exposure to tri-OPEs, while short-term exposure was better reflected by di-OPEs. Both experimental and in silico modeling methods validated aryl-functional group facilitated the initial accumulation and metabolism of TPhP in the avian liver compared to other moiety-substituted tri-OPEs.

Tracing Organophosphate Ester Pollutants in Hadal Trenches─Distribution, Possible Origins, and Transport Mechanisms

Unraveling the mysterious pathways of pollutants to the deepest oceanic realms holds critical importance for assessing the integrity of remote marine ecosystems. This study tracks the transport of pollutants into the depths of the oceans, a key step in protecting the sanctity of these least explored ecosystems. By analyzing hadal trench samples from the Mariana, Mussau, and New Britain trenches, we found the widespread distribution of organophosphate ester (OPE) flame retardants but a complex transport pattern for the OPE in these regions. In the Mariana Trench seawater column, OPE concentrations range between 17.4 and 102 ng L-1, with peaks at depths of 500 and 4000 m, which may be linked to Equatorial Undercurrent and topographic Rossby waves, respectively. Sediments, particularly in Mariana (422 ng g-1 dw), showed high OPE affinity, likely due to organic matter serving as a transport medium, influenced by "solvent switching", "solvent depletion", and "filtering processes". Amphipods in the three trenches had consistent OPE levels (29.1-215 ng g-1 lipid weight), independent of the sediment pollution patterns. The OPEs in these amphipods appeared more linked to surface-dwelling organisms, suggesting the influence of "solvent depletion". This study highlights the need for an improved understanding of deep-sea pollutant sources and transport, urging the establishment of protective measures for these remote marine habitats.

Patterns of urinary organophosphate ester metabolite trajectories in children: the HOME Study

BACKGROUND

Organophosphate esters (OPEs) have replaced flame retardant polybrominated diphenyl ethers as flame retardants in consumer products, but few longitudinal studies have characterized childhood OPE exposure.

OBJECTIVE

We aimed to examine the exposure pattern of urinary OPE metabolites in children.

METHODS

We quantified three urinary OPE metabolites five times in children (1, 2, 3, 5, 8 years) from 312 mother-child pairs in the Health Outcomes and Measures of the Environment (HOME) Study, a prospective pregnancy and birth cohort in Cincinnati, Ohio, USA. We examined the associations of average maternal OPE metabolite concentrations with OPE metabolite concentrations in childhood, characterized childhood OPE trajectories with latent class growth analysis (LCGA), and examined factors related to trajectory membership.

RESULTS

Bis(2-chloroethyl) phosphate (BCEP) had the lowest median concentrations over time (0.66-0.97 mg/L) while the median concentrations of bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) increased with age (1.44-3.80 mg/L). The median concentrations of diphenyl phosphate (DPHP) fluctuated between 1.96 and 2.69 mg/L. Intraclass correlation coefficients for urinary metabolites measured at five time points indicated high variability within individuals (0.13-0.24). Average maternal urinary BCEP and BDCIPP were associated with concentrations in early childhood. Maternal education, the birth year of the child, and having a carpet in the main activity room were associated with BCEP and BDCIPP trajectory while none of the factors were associated with DPHP trajectory.

SIGNIFICANCE

The trajectory analysis showed different patterns of urinary OPE metabolite concentrations, suggesting the need to collect multiple samples to adequately reflect OPE exposure.

IMPACT STATEMENT

In this well-established cohort, we evaluated the patterns of urinary OPE metabolites in children ages 1-8 years. The number of repeated measures over childhood has not been achieved in prior studies. Our results suggested the high variability of urinary OPE metabolites within individuals. Maternal metabolite concentrations during pregnancy were related to child concentrations at ages 1-3 years. BCEP, BDCIPP, and DPHP demonstrated different trajectories in children, which suggests that multiple samples may be required to capture OPE exposure patterns in childhood.

Myriophyllum Biochar-Supported Mn/Mg Nano-Composites as Efficient Periodate Activators to Enhance Triphenyl Phosphate Removal from Wastewater

Transition metals and their oxide compounds exhibit excellent chemical reactivity; however, their easy agglomeration and high cost limit their catalysis applications. In this study, an interpolation structure of a Myriophyllum verticillatum L. biochar-supported Mn/Mg composite (Mn/Mg@MV) was prepared to degrade triphenyl phosphate (TPhP) from wastewater through the activating periodate (PI) process. Interestingly, the Mn/Mg@MV composite showed strong radical self-producing capacities. The Mn/Mg@MV system degraded 93.34% TPhP (pH 5, 10 μM) within 150 min. The experimental results confirmed that the predominant role of IO3· and the auxiliary ·OH jointly contributed to the TPhP degradation. In addition, the TPhP pollutants were degraded to various intermediates and subsequent Mg mineral phase mineralization via mechanisms like interfacial processes and radical oxidation. DFT theoretical calculations further indicated that the synergy between Mn and Mg induced the charge transfer of the carbon-based surface, leading to the formation of an ·OH radical-enriched surface and enhancing the multivariate interface process of ·OH, IO3, and Mn(VII) to TPhP degradation, resulting in the further formation of Mg PO4 mineralization.

Global patterns of human exposure to flame retardants indoors

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

Triphenyl phosphate exposure impairs colorectal health by altering host immunity and colorectal microbiota

Colorectal diseases such as colorectal cancer (CRC) and inflammatory bowel disease (IBD) have become one of the most common public health concerns worldwide due to the increasing incidence. Environmental factors are one of the important causes of colorectal diseases, as they can affect the intestinal barrier function, immune response and microbiota, causing intestinal inflammation and tumorigenesis. Triphenyl phosphate (TPHP), a widely used organophosphorus flame retardant that can leach and accumulate in various environmental media and biota, can enter the human intestine through drinking water and food. However, the effects of TPHP on colorectal health have not been well understood. In this study, we investigated the adverse influence of TPHP exposure on colorectal cells (in vitro assay) and C57BL/6 mice (in vivo assay), and further explored the potential mechanism underlying the association between TPHP and colorectal disease. We found that TPHP exposure inhibited cell viability, increased apoptosis and caused G1/S cycle arrest of colorectal cells. Moreover, TPHP exposure damaged colorectal tissue structure, changed immune-related gene expression in the colorectal transcriptome, and disrupted the composition of colorectal microbiota. Importantly, we found that TPHP exposure upregulated chemokine CXCL10, which was involved in colorectal diseases. Our study revealed that exposure to TPHP had significant impacts on colorectal health, which may possibly stem from alterations in host immunity and the structure of the colorectal microbial community.

Uptake mechanism, translocation, and transformation of organophosphate esters in water hyacinth (Eichhornia crassipes): A hydroponic study

Owing to their dominant wastewater origin, bioavailability, and toxicity, the occurrence and behavior of organophosphate esters (OPEs) in aquatic systems have attracted considerable attention over the past two decades. Aquatic plants can accumulate and metabolize OPEs in water, thereby playing an important role in their behavior and fate in waterbodies. However, their uptake, translocation and transformation mechanisms in plants remain incompletely characterized. We investigated the accumulation and transformation of OPEs in water hyacinth (Eichhornia crassipes) through a series of hydroponic experiments using three representative OPEs, tris(2-chloroethyl) phosphate (TCEP), tris(2-butoxyethyl) phosphate (TBEP), and triphenyl phosphate (TPP). These OPEs can not only be adsorbed onto and enter plant roots via passive diffusion pathways, which are facilitated by anion channels and/or aquaporins, but also can return to the solution when concentration gradients exist. After entry, hydrophilic TCEP showed a dominant distribution in the cell sap, strong acropetal transportability, and rapid translocation rate, whereas hydrophobic TPP was mostly retained in the root cell wall and therefore demonstrated weak acropetal transportability; TBEP with moderate hydrophilicity remained in the middle. All these OPEs can be transformed into diesters, which presented higher proportions in the cell sap and therefore have stronger acropetal transferability than their parent OPEs. TCEP exhibits the lowest biodegradability, followed by TPP and TBEP. These OPEs exerted apparent effects on plant growth, photosynthesis, and the diversity and composition of the rhizosphere microbial community.

Perinatal triphenyl phosphate exposure induces metabolic dysfunctions through the EGFR/ERK/AKT signaling pathway: Mechanistic in vitro and in vivo studies

Triphenyl phosphate (TPhP), a widely used organophosphate-flame retardant, is ubiquitously found in household environments and may adversely affect human health. Evidence indicates that TPhP exposure causes metabolic dysfunctions in vivo; however, the underlying mechanism of such adverse effects has not been comprehensively investigated. Herein, we utilized two in vitro models including mouse and human preadipocytes to delineate adipogenic mechanisms of TPhP. The results revealed that both mouse and human preadipocytes exposed to TPhP concentration-dependently accumulated more fat through a significant upregulation of epidermal growth factor receptor (EGFR). We demonstrated that TPhP significantly promoted adipogenesis through the activation of EGFR/ERK/AKT signaling pathway as evident by a drastic reduction in adipogenesis of preadipocytes cotreated with inhibitors of EGFR and its major effectors. Furthermore, we confirmed the mechanism of TPhP-induced metabolic dysfunctions in vivo. We observed that male mice perinatally exposed to TPhP had a significant increase in adiposity, hepatic triglycerides, insulin resistance, plasma insulin levels, hypotension, and phosphorylated EGFR in gonadal fat. Interestingly, an administration of a potent and selective EGFR inhibitor significantly ameliorated the adverse metabolic effects caused by TPhP. Our findings uncovered a potential mechanism of TPhP-induced metabolic dysfunctions and provided implications on toxic metabolic effects posed by environmental chemicals.

Accumulation of organophosphorus pollutants in adipose tissue of obese women - metabolic alterations

Organophosphorus pesticides (OPPs) and organophosphate esters (OPEs) are organophosphorus compounds created as substitutes for persistent environmental pollutants, namely organochlorines pesticides and brominated flame retardants, respectively. However, there is evidence that organophosphorus compounds are also widespread across the environment and have adverse effects on biota. In humans, OPPs and OPEs were reported to be carcinogenic, neurotoxic, hepatotoxic, nephrotoxic, amongst others. As lipophilic compounds, these accumulate in fat tissues as adipose tissue. Yet biomonitoring studies and analytical methodologies to assess these compounds in the human body are scarce, particularly in adipose tissue. In this study, the presence of six OPPs and seven OPEs was determined in samples of subcutaneous adipose tissue (scAT) and visceral adipose tissue (vAT) from 188 adult obese women. OPPs and OPEs were quantified by gas chromatography (GC) flame photometric detection and confirmed in GC tandem mass spectrometry. The detection frequencies ranged between 0.5-1.6% and 48-53%, respectively for OPPs and OPEs. Organophosphorus pollutants were present in both adipose tissues and median concentrations were 0.008 ± 0.020 μg/g scAT and 0.009 ± 0.020 μg/g vAT. A total of 32 Spearman's correlations were found between organophosphorus pollutants concentrations in adipose tissue and several biochemical parameters (18 positive and 14 negative). Our results show that anthropometric and hormonal parameters, cholesterol, glycaemia, macrominerals, urea and sedimentation velocity might be influenced by the presence of these compounds. The presence of organophosphorus pollutants in the environmental and their possible effect on female metabolic processes is concerning. Particularly because presently OPEs usage is not controlled or limited by any regulation. More studies are needed to fully understand these pollutants behaviour and hazard effects on human health, biota, and the environment so control regulations can be drawn to prevent and lessen their effects.

Triphenyl phosphate disrupts placental tryptophan metabolism by activating MAOA/ROS/NFκB

Triphenyl phosphate (TPhP) is an organophosphate flame retardant widely distributed in the environment. The neurodevelopmental toxicity of TPhP has been observed in animals and humans. Previously, we found that prenatal TPhP exposure disturbed placental tryptophan metabolism, impaired neurodevelopment in male offspring, and induced abnormal neurobehavior; however, the underlying mechanisms are unknown. In this study, using the trophoblast cell line JEG-3, we found that TPhP altered gene and protein expression in the tryptophan metabolism pathway, inhibited the tryptophan-serotonin pathway, and activated the tryptophan-kynurenine pathway. Meanwhile, TPhP induced oxidative stress by activating monoamine oxidase A (MAOA), promoting inflammatory factors including nuclear factor kappa-B (NFκB), interleukin-6, and tumor necrosis factor α. The NFκB inhibitor sulfasalazine could alleviate the effects of TPhP on tryptophan metabolism disturbance. The MAOA inhibitor clorgyline or the antioxidant N-acetylcysteine can mitigate oxidative stress and eliminate TPhP-induced inflammatory factors and tryptophan metabolism disturbances. The data above suggest that TPhP disturbed tryptophan metabolism by activating NFκB through MAOA-mediated oxidative stress. Finally, using the mouse intrauterine exposure model, the results confirmed that TPhP induced oxidative stress, activated inflammatory factors, disturbed tryptophan metabolism, and increased the levels of the tryptophan metabolites serotonin, kynurenine, 3-hydroxykynurenine, and 3-hydroxyanthranilic acid in the placenta during the second trimester of pregnancy. Overall, TPhP can disturb placental tryptophan metabolism by activating the inflammatory factor NFκB, which was induced by MAOA-induced oxidative stress. The results of this study confirm that indirect exposure to xenobiotic compounds at an early life stage can impair offspring development and provide a novel perspective on the neurodevelopmental toxicity of TPhP.

Assessment of Daily Exposure to Organophosphate Esters through PM2.5 Inhalation, Dust Ingestion, and Dermal Contact

Inhalation of airborne fine particulate matter (PM2.5), dust ingestion, and dermal contact with dust are important pathways for human exposure to different contaminants, such as organophosphate esters (OPE), compounds that are widely used as flame retardants and plasticizers. There are limited studies assessing the extent of the contamination of OPE in indoor airborne PM2.5. This study offers a novel approach by examining various indoor environments, such as homes, workplaces, and means of transport, where people typically spend their daily lives. The goal is to provide a comprehensive assessment of daily exposure to these pollutants. Both PM2.5 and dust samples were collected in order to determine the concentration levels of 17 different OPEs. Fifteen OPEs in PM2.5 and 16 in dust samples were detected. Concentration levels in indoor air ranged from 4.37 to 185 ng/m3 (median 24.4 ng/m3) and from 3.02 to 36.9 μg/g for the dust samples (median 10.2 μg/g). Estimated daily intakes (EDIs) of OPEs were calculated for adults, yielding median values of 3.97 ng/(kg bw × day) for EDIInhalation, 5.89 ng/(kg bw × day) for EDIDermal, and 1.75 ng/(kg bw × day) for EDIIngestion. Such levels lie below human health threshold risk limits, although in some cases they could be only 2 times below the threshold for carcinogenic risk, with a main contribution from tris(2-chloroethyl) phosphate (TCEP). Given this threshold proximity, additional exposure to these chemicals from other pathways, such as food ingestion, gas phase exposure, and/or inhalation of coarser particles (PM10-2.5), could therefore lead to health limit exceedances.

Assessing human internal exposure to chemicals at different physical activity levels: A physiologically based kinetic (PBK) model incorporating metabolic equivalent of task (MET)

Physical activity levels have the potential to impact human internal exposure to environmental chemicals. However, the current lack of simple modeling approaches hinders the high-throughput screening of chemical exposure at different physical activity levels. To address this gap, this study proposes a straightforward model for assessing human internal exposure to chemicals. Our approach is based on the physiologically based kinetic (PBK) model and utilizes the metabolic equivalent of task (MET) to characterize internal exposure to chemicals at varying activity levels. To facilitate the application of this model, we have developed an Excel-based operation tool, allowing users to easily modify the MET value and generate simulation results for different physical activity levels. The simulation results demonstrate that as physical activity levels increase, the biotransfer factors (BTFs) of chemicals decrease, suggesting that higher physical activity levels reduce the bioaccumulation potential of chemicals. The intensified physical activity enhances the overall elimination kinetics of chemicals from the human body. However, the simulated concentrations of chemicals in the human body increase with higher physical activity levels, due to the significantly increased external exposure to chemicals, such as through inhalation. Our proposed modeling approach, along with the operational tool, enables high-throughput simulation of human chronic internal exposure to chemicals at different physical activity levels, where the findings can assist in screening chemicals for further health risk assessment. To accomplish this, the model incorporates certain assumptions and utilizes generic model input values. However, due to the intricate nature of the interaction between external and internal exposures at different physical activity levels, validating the simulation through experimental studies becomes challenging and is not performed in this study. For future studies, we recommend incorporating more MET-related physiological input variables, improving energy balance estimates, comprehending external exposure estimates, and conducting cohort studies to enhance and validate the proposed modeling approach.

Occurrence, source apportionment, and ecological risk assessment of organophosphate esters in surface sediment from the Ogun and Osun Rivers, Southwest Nigeria

Organophosphate esters (OPEs) are synthetic chemicals widely used as e.g., flame retardants and plasticisers in various consumer products. Due to the toxicity of OPEs in aquatic ecosystems, exposure of fauna and flora to these compounds is of potential concern. In this study, the concentrations, profiles, sources, and ecological risk of eight OPEs were investigated in the sediments from the two major rivers in southwest Nigeria. Concentrations of ∑OPEs in surface sediments were in the range 13.1 - 2110 ng/g dry weight (dw) (median: 378 ng/g dw) in the Ogun River and 24.7-589 ng/g dw (median: 174 ng/g dw) in the Osun River. These concentrations are broadly within the range of those reported in surface sediment in previous studies conducted in other locations around the world. Tris (2-butoxyethyl) phosphate (TBOEP) was the dominant OPE in the sediment samples with a median concentration of 337 and 126 ng/g dw for the Ogun and Osun Rivers respectively, while tri-n-butyl phosphate (TnBP) was not detected in any sample. Excluding TBOEP, the chlorinated organophosphate esters: tris(2-chloroethyl) phosphate (TCEP), tris(2-chloro-propyl) phosphate (TCIPP), and tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) were the dominant OPEs in the Osun River, while the aryl-OPEs: triphenyl phosphate (TPHP), 2-ethylhexyl diphenyl phosphate (EHDPP), and tri-m-tolyl phosphate (TMTP) were dominant in the Ogun River. Under a median exposure scenario, moderate ecological risk was predicted from exposure to TCIPP in the Osun River. In contrast, under a high exposure scenario, concentrations of TDCIPP (risk quotient, RQ = 5.33-5.37) constituted a high ecological risk in both rivers, with moderate risks observed for TBOEP (RQ = 0.022-0.18) and TCIPP (RQ = 0.097 - 0.16). Therefore, the risk to aquatic organisms from concomitant exposure to mixtures of OPEs in freshwater ecosystems requires further investigation.

Anti-androgenic activity of novel flame retardants in mixtures: Newly identified contribution from tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO)

In recent decades, male infertility has been on the rise, largely attributed to exposure to chemicals with endocrine-disrupting properties. The adverse effects of disrupting androgen actions on the development and reproductive health of children and adolescents have been extensively studied. Flame retardants (FRs), used in consumer products to delay flammability, have been identified as antagonists of the androgen receptor (AR), potentially leading to adverse outcomes in male reproductive health later in life. This study examined the interaction of eight novel FRs with the AR, employing an in vitro AR-dependent luciferase reporter gene assay utilizing MDA-kb2 cells. The investigation revealed the anti-androgenic activity of tris(2,3-dibromopropyl) isocyanurate (TDBP-TAZTO), a frequently detected FR in the environment. Furthermore, TDBP-TAZTO contributed to anti-androgenic activity when combined with six other anti-androgenic FRs. The mixture effects were predicted by three commonly employed models: concentration addition (CA), generalized CA, and independent action, with the CA model showcasing the highest accuracy. This suggests that all FRs act through a similar mechanism, as further confirmed by in silico molecular docking, indicating limited synergy or antagonism. Importantly, in the mixtures, each FR contributed to the induction of anti-androgenic effects at concentrations below their individual effective concentrations in single exposures. This raises concern for public health, especially considering the co-detection of these FRs and their potential co-occurrence with other anti-androgenic chemicals like bisphenols. Therefore, our findings, along with previous research, strongly support the incorporation of combined effects of mixtures in risk assessment to efficiently safeguard population health.

Urinary phosphate is associated with cardiovascular disease incidence

INTRODUCTION

Elevated phosphate (P) in urine may reflect a high intake of inorganic P salts from food additives. Elevated P in plasma is linked to vascular dysfunction and calcification.

OBJECTIVE

To explore associations between P in urine as well as in plasma and questionnaire-estimated P intake, and incidence of cardiovascular disease (CVD).

METHODS

We used the Swedish Mammography Cohort-Clinical, a population-based cohort study. At baseline (2004-2009), P was measured in urine and plasma in 1625 women. Dietary P was estimated via a food-frequency questionnaire. Incident CVD was ascertained via register-linkage. Associations were assessed using Cox proportional hazards regression.

RESULTS

After a median follow-up of 9.4 years, 164 composite CVD cases occurred (63 myocardial infarctions [MIs] and 101 strokes). Median P (percentiles 5-95) in urine and plasma were 2.4 (1.40-3.79) mmol/mmol creatinine and 1.13 (0.92-1.36) mmol/L, respectively, whereas dietary P intake was 1510 (1148-1918) mg/day. No correlations were observed between urinary and plasma P (r = -0.07) or dietary P (r = 0.10). Urinary P was associated with composite CVD and MI. The hazard ratio of CVD comparing extreme tertiles was 1.57 (95% confidence interval 1.05, 2.35; P trend 0.037)-independently of sodium excretion, the estimated glomerular filtration rate, both P and calcium in plasma, and diuretic use. Association with CVD for plasma P was 1.41 (0.96, 2.07; P trend 0.077).

CONCLUSION

Higher level of urinary P, likely reflecting a high consumption of highly processed foods, was linked to CVD. Further investigation is needed to evaluate the potential cardiovascular toxicity associated with excessive intake of P beyond nutritional requirements.

Organophosphate esters in source, finished, and tap water in Wuhan, China

As important plasticizers and flame retardants, organophosphate esters (OPEs) have resulted in the contamination of various water bodies worldwide. However, their removal efficiency by different tap water treatment processes and seasonal variations in drinking water in China are not fully understood. In this study, source (n = 20), finished (n = 20), and tap (n = 165) water samples sourced from the Hanshui and the Yangtze River were collected in Wuhan, central China from July 2018 to April 2019 to measure selected OPE concentrations. The OPE concentrations in the source water samples ranged 10.5-113 ng/L (median: 64.6 ng/L). Most OPEs were not removed effectively by conventional tap water treatment, except for tris(2-chloroisopropyl) phosphate (TCIPP). Interestingly, trimethyl phosphate content was found to increase significantly during chlorination for water sourced from the Yangtze River. The OPEs could be removed more effectively by advanced processes with ozone and activated carbon (maximum removal efficiency of specific OPE was 91.0%). Similar cumulative OPE concentrations (ΣOPEs) values were found for the finished water and tap water in February rather than in July. The ΣOPEs (ng/L) in the tap water ranged 21.2-365 (median: 45.1). TCIPP and tris(2-chloroethyl) phosphate were the predominant OPEs in the studied water samples. Significant seasonal variations in the OPE residues in tap water were observed in this study. OPE exposure via tap water ingestion posed low health risks to human beings. This is the first study reporting the removal efficiencies of OPEs and the seasonal variations in tap water from central China. This is also the first study documenting the occurrence of cresyl diphenyl phosphate and 2,2-bis(chloromethyl)propane-1,3-diyltetrakis (2-chloroethyl) bisphosphate in tap water. Based on currently available data, the contamination of tap water by OPEs is in the order of Korea > eastern China > central China > New York State, the United States. Additionally, this study provides a method involving a trap column, to eliminate OPE contamination from the liquid chromatography system.

Independent and combined effects of exposure to organophosphate esters on thyroid hormones in children and adolescents

Toxicological studies suggest that organophosphate esters (OPEs) may impair thyroid function. Epidemiological evidence, related to children and adolescents, has not been reported, and little is known about the combined effects of exposure to OPE mixtures. In this study, we collected information of 1156 children and adolescents (aged 6-18 years, 48.4% males) from a cross-sectional study in Liuzhou, China, and measured the levels of 15 urinary OPE metabolites and 5 serum thyroid hormones. Multivariate linear regression and quantile g-computation (QGC) approach were used to examine the associations which adjusted for demographic and lifestyle characteristics. Few participants had levels of triiodothyronine (T3) and free thyroxine (FT4) outside age-specific pediatric ranges. QGC analyses showed that individuals in the second, third, and fourth quartiles (Q2-Q4) of exposure had 3.93% (2.14%, 5.75%), 8.01% (4.32%, 11.8%), and 12.3% (6.54%, 18.3%) higher T3 than those in the first quartile (Q1), with similar pattern for free triiodothyronine (FT3). Individuals in Q2 and Q3 had higher thyroid-stimulating hormone (TSH) than those in Q1, but no differences were observed in TSH between Q1-Q4. In contrast, compared to the lowest quartile, FT4 was lower for those in Q2 (- 1.54%; 95% CI: - 3.02%, -0.04%), Q3 (-3.07%; 95% CI: -5.95%, -0.09%), and Q4 (-4.56%; 95% CI: - 8.80%, - 0.13%). These associations were consistent with the results from multivariate linear regression. When stratified by sex, OPE exposure (individual or mixtures) was associated with increased T3 and FT3 in males and decreased FT4 in females. This study provides the first evidence to characterize the thyroid-disrupting effects of OPE exposure in children and adolescents.