Triphenyl phosphate interferes with the synthesis of steroid hormones through the PPARγ/CD36 pathway in human trophoblast JEG-3 cells

Triphenyl phosphate (TPhP), a chemical commonly found in human placenta and breast milk, has been shown to disturb the endocrine system. Our previous study confirmed that TPhP could accumulate in the placenta and interference with placental lipid metabolism and steroid hormone synthesis, as well as induce endoplasmic reticulum (ER) stress through PPARγ in human placental trophoblast JEG-3 cells. However, the molecular mechanism underlying this disruption remains unknown. Our study aimed to identify the role of the PPARγ/CD36 pathway in TPhP-induced steroid hormone disruption. We found that TPhP increased lipid accumulation, total cholesterol, low- and high-density protein cholesterol, progesterone, estradiol, glucocorticoid, and aldosterone levels, and genes related to steroid hormones synthesis, including 3βHSD1, 17βHSD1, CYP11A, CYP19, and CYP21. These effects were largely blocked by co-exposure with either a PPARγ antagonist GW9662 or knockdown of CD36 using siRNA (siCD36). Furthermore, an ER stress inhibitor 4-PBA attenuated the effect of TPhP on progesterone and glucocorticoid levels, and siCD36 reduced ER stress-related protein levels induced by TPhP, including BiP, PERK, and CHOP. These findings suggest that ER stress may also play a role in the disruption of steroid hormone synthesis by TPhP. As our study has shed light on the PPARγ/CD36 pathway's involvement in the disturbance of steroid hormone biosynthesis by TPhP in the JEG-3 cells, further investigations of the potential impacts on the placental function and following birth outcome are warranted.

Environmentally Relevant Concentrations of Triphenyl Phosphate (TPhP) Impact Development in Zebrafish

A common flame-retardant and plasticizer, triphenyl phosphate (TPhP) is an aryl phosphate ester found in many aquatic environments at nM concentrations. Yet, most studies interrogating its toxicity have used µM concentrations. In this study, we used the model organism zebrafish (Danio rerio) to uncover the developmental impact of nM exposures to TPhP at the phenotypic and molecular levels. At concentrations of 1.5-15 nM (0.5 µg/L-5 µg/L), chronically dosed 5dpf larvae were shorter in length and had pericardial edema phenotypes that had been previously reported for exposures in the µM range. Cardiotoxicity was observed but did not present as cardiac looping defects as previously reported for µM concentrations. The RXR pathway does not seem to be involved at nM concentrations, but the tbx5a transcription factor cascade including natriuretic peptides (nppa and nppb) and bone morphogenetic protein 4 (bmp4) were dysregulated and could be contributing to the cardiac phenotypes. We also demonstrate that TPhP is a weak pro-oxidant, as it increases the oxidative stress response within hours of exposure. Overall, our data indicate that TPhP can affect animal development at environmentally relevant concentrations and its mode of action involves multiple pathways.

Prenatal triphenyl phosphate exposure impairs placentation and induces preeclampsia-like symptoms in mice

Triphenyl phosphate (TPhP) is an organophosphate flame retardant that is widely used in many commercial products. The United States Environmental Protection Agency has listed TPhP as a priority compound that requires health risk assessment. We previously found that TPhP could accumulate in the placentae of mice and impair birth outcomes by activating peroxisome proliferator-activated receptor gamma (PPARγ) in the placental trophoblast. However, the underlying mechanism remains unknown. In this study, we used a mouse intrauterine exposure model and found that TPhP induced preeclampsia (PE)-like symptoms, including new on-set gestational hypertension and proteinuria. Immunofluorescence analysis showed that during placentation, PPARγ was mainly expressed in the labyrinth layer and decidua of the placenta. TPhP significantly decreased placental implantation depth and impeded uterine spiral artery remodeling by activating PPARγ. The results of the in vitro experiments confirmed that TPhP inhibited extravillous trophoblast (EVT) cell migration and invasion by activating PPARγ and inhibiting the PI3K-AKT signaling pathway. Overall, our data demonstrated that TPhP could activate PPARγ in EVT cells, inhibit cell migration and invasion, impede placental implantation and uterine spiral artery remodeling, then induce PE-like symptom and impair birth outcomes. Although the exposure doses used in this study was several orders of magnitude higher than human daily intake, our study highlights the placenta as a potential target organ of TPhP worthy of further research.

The flame retardant triphenyl phosphate alters the epigenome of embryonic cells in an aquatic in vitro model

Triphenyl phosphate (TPhP) is an organophosphate flame retardant and plasticizer that is added to a wide variety of consumer and industrial products. It is also a ubiquitous environmental pollutant. Exposure to TPhP has been shown to alter gene expression in metabolic and estrogenic signaling pathways in in vitro and in vivo models of a variety of species, and as such, is considered to be an endocrine disrupting chemical. Exposure to endocrine disrupting chemicals is increasingly being associated with changes to the epigenome, especially during embryonic development. The aim of this study was to evaluate whether TPhP exposure in aquatic ecosystems has the ability to alter the epigenome in two immortal cell lines derived from trout (Oncorhynchus mykiss). This study assessed whether 24 h exposure to TPhP resulted in changes to histone modification and DNA methylation profiles in steelhead trout embryonic cells and rainbow trout gill epithelial cells. Results show that several epigenetic modifications on histone H3 and DNA methylation are altered in the embryonic cells following TPhP exposure, but not in the gill epithelial cells. Specifically, histone H3 acetylation, histone H3 mono-methylation and global DNA methylation were found to be reduced. The alterations of these epigenetic modification profiles in the embryonic cells suggest that exposure to TPhP during fetal development may alter gene expression in the developing embryo, likely in metabolic and estrogenic pathways. The impacts to the epigenome determined in this study may even carry multigenerational detrimental effects on human and ecosystem health, which requires further investigation.

Endoplasmic reticulum stress participates in apoptosis of HeLa cells exposed to TPHP and OH-TPHP via the eIF2α-ATF4/ATF3-CHOP-DR5/P53 signaling pathway

Purpose

Triphenyl phosphate (TPHP) is a widely used organophosphate flame retardant, which can be transformed in vivo into diphenyl phosphate (DPHP) and 4-hydroxyphenyl phosphate (diphenyl) ester (OH-TPHP) through biotransformation process. Accumulation of TPHP and its derivatives in biological tissues makes it necessary to investigate their toxicity and molecular mechanism.

Methods

The present study evaluated the cellular effects of TPHP, DPHP, and OH-TPHP on cell survival, cell membrane damage, oxidative damage, and cell apoptosis using HeLa cells as in vitro model. RNA sequencing and bioinformatics analysis were conducted to monitor the differently expressed genes, and then RT-qPCR and Western bolt were used to identify potential molecular mechanisms and key hub genes.

Results

Results showed that OH-TPHP had the most significant cytotoxic effect in HeLa cells, followed by TPHP; and no significant cytotoxic effects were observed for DPHP exposure within the experimental concentrations. Biological function enrichment analysis suggested that TPHP and OH-TPHP exposure may induce endoplasmic reticulum stress (ERS) and cell apoptosis. The nodes filtering revealed that ERS and apoptosis related genes were involved in biological effects induced by TPHP and OH-TPHP, which may be mediated through the eukaryotic translation initiation factor 2α/activating transcription factor 4 (ATF4)/ATF3- CCAAT/ enhancer-binding protein homologous protein (CHOP) cascade pathway and death receptor 5 (DR5) /P53 signaling axis.

Conclusion

Above all, these findings indicated that ERS-mediated apoptosis might be one of potential mechanisms for cytotoxicity of TPHP and OH-TPHP.

Integrative analysis of triphenyl phosphate: contextual interpretation of bladder cancer cohort

In recent years, organophosphate ester flame retardants (OPFRs) have emerged as preferred alternatives to brominated flame retardants (BFRs) in materials such as building supplies, textiles, and furnishings. Simultaneously, a notable surge in bladder cancer incidences has been observed globally, particularly in developed nations, placing it as the 10th most prevalent cancer type. Among the extensive OPFRs, the linkage between triphenyl phosphate (TPP) and bladder cancer remains inadequately investigated. Hence, our study endeavors to elucidate this potential association. We sourced transcriptome profiles and TPP-related data from The Cancer Genome Atlas and Comparative Toxicogenomics databases. Using the ssGSEA algorithm, we established TPP-correlated scores within the bladder cancer cohort. Differentially expressed analysis enabled us to identify key genes in bladder cancer patients. We utilized the LASSO regression analysis, along with univariate and multivariate COX regression analyses to construct a prognostic prediction model. To uncover critical pathways involving key genes, we employed GSEA and GSVA enrichment analyses. Molecular docking analysis was performed to determine the binding capability between TPP and proteins. Our findings reveal that the TPP-centric risk model offers valuable prediction for bladder cancer cohorts. Furthermore, the reliability of this TPP-influenced risk model was verified through ROC curve analysis and survival studies. Intriguingly, TPP exposure appears to bolster the proliferation and invasiveness of bladder cancer cells. This study furnishes new insights into the possible benefits of minimizing TPP exposure for hindering bladder cancer progression.

Influence of Disinfection Methods on Cinematographic Film

Microbiological contamination of cinematographic films can cause damage and loss of image information. A large part of the films is made with the base of cellulose triacetate, which has been used from the 1940s until today. Cellulose triacetate is relatively resistant to common organic solvents, but some types of microorganisms can contribute to its faster degradation. In this work, we tested four types of disinfectants suitable for mass disinfection and sufficiently effective against various types of microorganisms. Butanol vapours, a commercial mixture of alcohols (Bacillol^® AF), Septonex^® (an aqueous solution of [1-(ethoxycarbonyl)pentadecyl] trimethylammonium bromide) and ethylene oxide applied as a gas mixed with carbon dioxide were tested. Samples of a commercial film made of cellulose triacetate were disinfected. The samples were aged for 56 days at 70 °C and 55% RH. Changes in optical, mechanical and chemical properties were studied. None of the disinfectants affected the change in the degree of substitution. For samples disinfected with Bacillol^® AF (alcohol mixture), part of the plasticiser (triphenyl phosphate) was extracted and the intrinsic viscosity of the cellulose triacetate solution was reduced after ageing. A slight decrease in intrinsic viscosity also occurred after disinfection with ethylene oxide. Compared to the non-disinfected samples, butanol vapours and Septonex^® appear to be the most gentle disinfectants for the cellulose triacetate film base, within the studied parameters.

Triphenyl phosphate-induced macrophages dysfunction by activation TLR4-mediated ERK/NF-κB pathway

Triphenyl phosphate (TPHP) is one of the most widely used organic phosphorus flame retardants and is ubiquitous in the environment. Studies have been reported that TPHP may lead to obesity, neurotoxicity and reproductive toxicity, but its impact on the immune system is almost blank. The present study was aimed to investigate the potential immunotoxicity of TPHP on macrophages and its underlying mechanism. The results demonstrated for the first time that TPHP (12.5, 25, and 50 μM)-induced F4/80⁺ CD11c⁺ phenotype of RAW 264.7 macrophages, accompanied by increased mRNA levels of inflammatory mediators, antigen-presenting genes (Cd80, Cd86, and H2-Aa), and significantly enhanced the phagocytosis of macrophage. Meanwhile, TPHP increased the expression of Toll-like receptor 4 (TLR4), and its co-receptor CD14, leading to significant activation of the downstream ERK/NF-κB pathway. However, co-exposure of cells to TAK-242, a TLR4 inhibitor, suppressed TPHP-induced F4/80⁺ CD11c⁺ phenotype, and down-regulated inflammatory mediators and antigen-presentation related genes, via blocked the TLR4/ERK/NF-κB pathway. Taken together, our results suggested that TPHP could induce macrophage dysfunction through activating TLR4-mediated ERK/NF-κB signaling pathway, and it may be the potential reason for health-threatening consequences.

Developmental exposure to the flame retardant, triphenyl phosphate, causes long-lasting neurobehavioral and neurochemical dysfunction

BACKGROUND

Human exposures to organophosphate flame retardants result from their use as additives in numerous consumer products. These agents are replacements for brominated flame retardants but have not yet faced similar scrutiny for developmental neurotoxicity. We examined a representative organophosphate flame retardant, triphenyl phosphate (TPP) and its potential effects on behavioral development and dopaminergic function.

METHODS

Female Sprague-Dawley rats were given low doses of TPP (16 or 32 mg kg^-1  day^-1 ) via subcutaneous osmotic minipumps, begun preconception and continued into the early postnatal period. Offspring were administered a battery of behavioral tests from adolescence into adulthood, and littermates were used to evaluate dopaminergic synaptic function.

RESULTS

Offspring with TPP exposures showed increased latency to begin eating in the novelty-suppressed feeding test, impaired object recognition memory, impaired choice accuracy in the visual signal detection test, and sex-selective effects on locomotor activity in adolescence (males) but not adulthood. Male, but not female, offspring showed marked increases in dopamine utilization in the striatum, evidenced by an increase in the ratio of the primary dopamine metabolite (3,4-dihydroxyphenylacetic acid) relative to dopamine levels.

CONCLUSIONS

These results indicate that TPP has adverse effects that are similar in some respects to those of organophosphate pesticides, which were restricted because of their developmental neurotoxicity.

Gestational exposure to triphenyl phosphate induces epigenetic modifications in C57Bl/6 fetal liver

INTRODUCTION

Triphenyl phosphate (TPHP) is a chemical flame retardant and plasticizer which is added to consumer and industrial products. The developmental origins of health and disease hypothesis postulate that in utero exposures can have later-in-life effects on the developing fetus and can alter fetal gene expression. This study aimed to determine whether epigenetic modifications occurred following in utero TPHP exposure in mice and whether these changes were dose and/or sex-dependent.

METHODS

Pregnant C57Bl/6 mice were treated with 0, 5, 25, or 50 mg/kg of TPHP on gestational days (GD) 8, 10, 12, and 14 via intraperitoneal injection and fetal livers were collected on GD 19. Changes in the levels of acetylation of H3 and H4, as well as methylation of H3K9 and global DNA methylation were assessed in the fetal livers by western blot.

RESULTS

Results showed that there was a significant decrease in fetal DNA methylation following in utero exposure to 50 mg/kg TPHP compared to the control (0 mg/kg) independent of the sex of the fetus. While there were no significant alterations compared to controls in any histone modifications at any dose or sex following in utero TPHP exposure, we did note a decrease (t test, p = .025) in the levels of acetylated H3 in males versus females following a maternal dose of 25 mg/kg. The monomethylated H3K9 levels were also increased in females versus males following exposure to TPHP at 5 mg/kg (p = .018) and 25 mg/kg (p = .027) when analyzed via unpaired t tests, although not significantly different from controls.

DISCUSSION

The results suggest that gestational TPHP exposure can induce epigenetic modifications in murine fetal tissue. Specifically, global DNA methylation levels were downregulated in response to TPHP. Additionally, males appear to be more sensitive to TPHP-induced histone modifications than females. These data support the need for further studies investigating the impacts of gestational TPHP exposure on the developing fetus.

[Degradation of Triphenyl Phosphate in Water by UV-driven Advanced Oxidation Processes]

As a type of emerging pollutant of concern, organophosphate esters (OPEs) have posed a moderate risk to the remote Antarctic waters. Triphenyl phosphate (TPHP) is a common type of OPEs in water, which has been proven to have toxic effects, bioaccumulation, and amplification effects and pose a great threat to the environment and human health. Fourier transform infrared spectroscopy (FT-IR) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) were used to investigate the degradation process of TPHP in three advanced oxidation processes (UV-AOPs), including ultraviolet-hydrogen peroxide (UV-H₂O₂), ultraviolet-titanium dioxide (UV-TiO₂), and ultraviolet-persulfate (UV-PS) systems. This was the first instance of using FT-IR for the online observation of the change in infrared characteristic peaks in the degradation process of TPHP, and its degradation reaction kinetics, photodegradation products, and degradation pathways were analyzed. The results showed that TPHP could be effectively degraded under UV-H₂O₂, UV-TiO₂, and UV-PS systems, and the photodegradation half-lives were 74, 150, and 89 min, respectively. The UV-H₂O₂ system had the best degradation effect on TPHP. Additionally, the degradation reactions of TPHP in three systems conformed to the first-order kinetics. When the concentration of H₂O₂ was 0-0.097 mol·L^-1, the increase in H₂O₂ concentration promoted the degradation of TPHP, and when the concentration of TiO₂ was 0-0.013 mol·L^-1, the increase in TiO₂ concentration promoted the degradation of TPHP. The photodegradation pathway of TPHP mainly included the P-O-C bond breaking, the C-H bond cleavage of the benzene ring structure and the hydrolysis reaction of TPHP. The UV-H₂O₂ system was used to degrade OPEs in the environmental water of Chengdu, and it was found that the removal rate of TPHP was 66% when the water samples of the park landscape water were degraded for 60 min.

Low concentration triphenyl phosphate fuels proliferation and migration of hepatocellular carcinoma cells

Organophosphate flame retardants (OPFRs) have been widely used due to their unique properties. The OPFRs are mainly metabolized in the liver. However, whether the plasma level of OPFRs was involved in the progression of liver cancer remains unclear. Triphenyl phosphate (TPP) is one of the OPFRs that are mostly detected in environment. In this study, we performed CCK8, ATP, and EdU analyses to evaluate the effect of TPP at the concentrations at 0.025-12.8 μM on the proliferation, invasion, and migration of Hep3B, a hepatocellular carcinoma (HCC) cell line. Tumor-bearing mouse model was used for in vivo validation. The results showed that low concentrations of TPP at (0.025-0.1 μM), which are obtained in the plasma of patients with cancers, remarkably promoted cell invasion and migration of Hep3B cells. Animal experiments confirmed that TPP treatment significantly enhanced tumor growth in the xenograft HCC model. To explore the possible molecular mechanisms that might mediate the actions of TPP on Hep3B cells, we profiled gene expression in groups treated with or without TPP at the concentrations of 0.05 and 0.1 μM using transcriptional sequencing. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment, and Protein-protein interaction (PPI) analyses demonstrated that pathways affected by differentially expressed genes (DEGs) were mainly in nuclear-transcribed mRNA catabolic processes, cytosolic ribosome, and ATPase activity. A 0.05 and 0.1 μM TPP led to up-regulation of a series of genes including EREG, DNPH1, SAMD9, DUSP5, PFN1, CKB, MICAL2, SCUBE3, and CXCL8, but suppressed the expression of MCC. These genes have been shown to be associated with proliferation and movement of cells. Taken together, our findings suggest that low concentration of TPP could fuel the proliferation, invasion, and migration of HCC cells. Thus, TPP is a risk factor in the progression of HCC in human beings.

Identification of biotransformation products of organophosphate ester from various aquatic species by suspect and non-target screening approach

Organic pollutants that are introduced into the aquatic ecosystem can transform by various mechanisms. Biotransformation is an important process for predicting the remaining structures of pollutants in the ecosystem, and their toxicity. This study focused on triphenyl phosphate (TPHP), which is a commonly used organophosphate flame retardant and plasticizer. Since TPHP is particularly toxic to aquatic organisms, it is essential to understand its biotransformation in the aquatic environment. In the aquatic ecosystem, based on consideration of the producer-consumer-decomposer relationship, the biotransformation products of TPHP were identified, and their toxicity was predicted. Liquid chromatography-high resolution mass spectrometry was used for target, suspect, and non-target analysis. The obtained biotransformation products were estimated for toxicity based on the prediction model. As a result, 29 kinds of TPHP biotransformation products were identified in the aquatic ecosystem. Diphenyl phosphate was detected as a common biotransformation product through a hydrolysis reaction. In addition, products were identified by the biotransformation mechanisms of green algae, daphnid, fish, and microorganism. Most of the biotransformation products were observed to be less toxic than the parent compound due to detoxification except some products (hydroquinone, beta-lyase products, palmitoyl/stearyl conjugated products). Since various species exist in a close relationship with each other in an ecosystem, an integrated approach for not only single species but also various connected species is essential.

[Characterization and 16S rRNA gene-based metagenomic analysis of the organophosphorous flame retardants degrading consortium YC-BJ1]

As flame retardants, organophosphate is recognized as a global environmental contaminant because of its wide application. This contaminant is hardly degradable by hydrolysis in the environment due to its special physicochemical properties. Therefore, it is of urgent needs to study the microbial degradation of organophosphate. Through continuous enrichment, we isolated one bacterial consortium, named YC-BJ1, from leachate of waste treatment plant in Beijing. The bacterial consortium YC-BJ1 could efficiently degrade 99.8% of triphenyl phosphate (TPhP) and 91.9% of tricresyl phosphate (TCrP) with the concentration of 100 mg/L within 4 days. Besides aryl phosphates, it could degrade chloro-phosphates, tris(1,3-dichloroisopropyl) phosphate (TDCPP) and tris(2-chloroethyl) phosphate (TCEP) by 16.5% and 22.0% respectively. The degradation of the consortium on TPhP was optimized through a broad range of temperature (15-40 ℃), pH (5.0-12.0) and salinity (0%-4%). 16S rRNA gene-based metagenomic analysis revealed that Hyphomicrobium (38.80%), Chryseobacterium (17.57%) and Sphingopyxis (17.46%) were the dominant genera of the consortium YC-BJ1. Compared with the reported organophosphorus flame retardants (OPFRs) degrading bacteria and microflora, the mixed microflora YC-BJ1 exhibited great advantages in degradation efficiency and environmental adaptability, demonstrating its wide application potential. The enrichment and isolation of highly efficient degrading flora can provide abundant microbial resources for the degradation of OPFRs and the bioremediation towards OPFRs-contaminated environments, and also lay a solid foundation for the exploration of its degradation mechanism.

Stable Covalent Organic Frameworks as Efficient Adsorbents for High and Selective Removal of an Aryl-Organophosphorus Flame Retardant from Water

A critical challenge in environmental remediation is the design of adsorbents with proper pore size for the removal of organic pollutants. Three covalent organic frameworks (COFs) with different pore sizes were successfully prepared by a room-temperature solution-suspension method and used to remove a typical aryl-organophosphorus flame retardant [triphenyl phosphate (TPhP)] from aqueous solution. The prepared COFs showed strong acid resistance and thermal stability. The 1,3,5-triformylphloroglucinol (TFP) reacted with benzidine (BD) (COF2) and exhibited the highest sorption capacity for TPhP, followed by the reaction of TFP and 4,4″-diamino- p-terphenyl (DT) (COF3), and the reaction of TFP and p-phenylenediamine (COF1). Their adsorption equilibriums were achieved within 12 h, and COFs with a larger pore size have higher initial sorption rate but longer time to reach sorption equilibrium. According to the Langmuir fitting, the maximum sorption capacities of three COFs for TPhP were 86.1, 387.2, and 371.2 mg/g, respectively. The density functional theory calculation verified that COF1 with a small pore size prevents TPhP molecules from entering the pores, resulting in extremely low sorption capacity, whereas a relatively too large pore size (COF3) will decrease the sorption energy, which is also not conducive to the adsorption of TPhP. Moreover, the prepared COFs can selectively adsorb TPhP in the presence of coexisting compounds and had high removal of TPhP from actual municipal wastewater, showing a promising application potential for selective removal of micropollutants from water by precisely controlling the COF structure.

Investigation of Daphnia magna Sub-Lethal Exposure to Organophosphate Esters in the Presence of Dissolved Organic Matter Using ¹H NMR-Based Metabolomics

Organophosphate esters (OPEs) are frequently detected in aquatic environments. Hydrophobic OPEs with high octanol-water partition coefficients (Log K_OW) will likely sorb to dissolved organic matter (DOM) and consequently alter OPE bioavailability and sub-lethal toxicity. ¹H nuclear magnetic resonance (NMR)-based metabolomics was used to evaluate how DOM (5 mg organic carbon/L) alters the metabolic response of Daphnia magna exposed to sub-lethal concentrations of three individual OPEs with varying hydrophobicity. D. magna exposed to the hydrophilic contaminant (Log K_OW = 1.43) tris(2-chloroethyl) phosphate (TCEP) did not have substantial metabolic changes and DOM did not alter the metabolic response. There were significant increases in amino acids and a decrease in glucose from exposure to the hydrophobic contaminant (Log K_OW = 3.65) tris(2-butoxyethyl) phosphate (TBOEP) which DOM did not mitigate, likely due to the high sub-lethal toxicity of TBOEP. Exposure to DOM and the hydrophobic contaminant (Log K_OW = 4.76) triphenyl phosphate (TPhP) resulted in a unique metabolic response which was unlike TPhP only exposure, perhaps because DOM may be an additional stressor with TPhP exposure. Therefore, Log K_OW values may not always predict how sub-lethal contaminant toxicity will change with DOM and there should be more consideration to incorporate DOM in sub-lethal ecotoxicology testing.

Gestational triphenyl phosphate exposure in C57Bl/6 mice perturbs expression of insulin-like growth factor signaling genes in maternal and fetal liver

Triphenyl phosphate (TPhP) is an organophosphorus flame retardant and plasticizer that has been added to numerous consumer products in recent years. TPhP is not overtly toxic, however recent studies have suggested that it may have metabolic disrupting effects following developmental exposure. The present study aimed to investigate the developmental and potential metabolic effects of TPhP in a murine model. C57Bl/6 dams were exposed on gestational days (GD) 8, 10, 12, and 14 to 0, 5, 25, or 50 mg/kg TPhP via intraperitoneal injection. Dams were euthanized on GD19, maternal organs excised and weighed, fetal measurements taken, and maternal and fetal livers retained for analysis. A significant increase in placenta size of TPhP exposed mice was found. Maternal and fetal liver gene expression of insulin-like growth factor (Igf) 1 and 2, as well as downstream genes involved in Igf signaling were measured. Additionally, Igf1 protein levels were measured in both maternal and fetal liver. A significant decrease in transcript levels of Igf1 and Irs2 was detected in maternal livers, whereas a significant increase in transcript levels of all genes measured was detected in fetal liver. A significant decrease in Igf1 protein levels was detected in maternal liver, however the increase in Igf1 protein levels in fetal livers was not found to be statistically significant. These results support previous findings that TPhP does not cause overt structural developmental toxicity. These data also support the hypothesis that TPhP could disrupt maternal and fetal metabolism, justifying the need for follow-up studies to investigate further.

Using silicone wristbands to evaluate preschool children's exposure to flame retardants

Silicone wristbands can be used as passive sampling tools for measuring personal environmental exposure to organic compounds. Due to the lightweight and simple design, the wristband may be a useful technique for measuring children's exposure. In this study, we tested the stability of flame retardant compounds in silicone wristbands and developed an analytical approach for measuring 41 flame retardants in the silicone wristband in order to evaluate exposure to these compounds in preschool-aged children. To evaluate the robustness of using wristbands to measure flame retardants, we evaluated the stability of 3 polybrominated diphenyl ethers (BDEs), and 2 organophosphate flame retardants (OPFRs) in wristbands over 84 days and did not find any evidence of significant loss over time at either 4 or -20°C (p>0.16). We recruited a cohort of 92 preschool aged children in Oregon to wear the wristband for 7 days in order to characterize children's acceptance of the technology, and to characterize their exposure to flame retardants. Seventy-seven parents returned the wristbands for analysis of 35 BDEs, 4 OPFRs, and 2 other brominated flame retardants although 5 were excluded from the exposure assessment due to protocol deviations (n=72). A total of 20 compounds were detected above the limit of quantitation, and 11 compounds including 4 OPFRs and 7 BDEs were detected in over 60% of the samples. Children's gender, age, race, recruitment site, and family context were not significantly associated with returning wristbands or compliance with protocols. Comparisons between flame retardant data and socio-demographic information revealed significant differences in total exposures to both ΣBDEs and ΣOPFRs based on age of house, vacuuming frequency, and family context. These results demonstrate that preschool children in Oregon are exposed to BDEs that are no longer being produced in the United States and to OPFRs that have been used as an alternative to polybrominated compounds. Silicone wristbands were well tolerated by young children and were useful for characterizing personal exposure to flame retardants that were not bound to particulate matter.

Urinary metabolites of organophosphate flame retardants and their variability in pregnant women

Organophosphate flame retardants (OPFRs) are commonly added to consumer products to reduce their flammability. Based on levels of OPFRs in indoor environments, human exposure is likely chronic and ubiquitous. Animal studies suggest that exposure to some OPFRs may result in adverse health impacts, particularly for Tris (1,3-dichloropropyl) phosphate (TDCPP); however, human data on the impacts of exposure to OPFRs are lacking. To design human studies, more information is needed on the stability of measured OPFRs in human samples over time. In this study, we sought to assess the degree of temporal variability of urinary TDCPP and triphenyl phosphate (TPP) metabolites throughout pregnancy in a cohort of women from central North Carolina. Eight pregnant women provided multiple urine samples: 3 during the 18th week of pregnancy, 1 during the 28th week, and 1 shortly after the child's birth. Bis (1,3-dichloropropyl) phosphate (BDCPP) and diphenyl phosphate (DPP), the respective metabolites of TDCPP and TPP, were measured in urine samples using liquid chromatography-tandem mass spectrometry. BDCPP and DPP were each detected in 38 of 39 urine samples and were not normally distributed. Geometric mean BDCPP and DPP concentrations were 1.3ng/mL (interquartile range (IQR): 0.8, 2.7ng/mL) and 1.9ng/mL (IQR: 0.9, 3.5ng/mL), respectively. BDCPP and DPP were moderately to strongly reliable over one week (intraclass correlation coefficient (ICC)=0.5; 95% confidence interval (CI): 0.4, 0.7 and ICC=0.7; 95% CI: 0.5, 0.8, respectively), and over the entire pregnancy (ICC=0.5 95% CI: 0.3, 0.7 and ICC=0.6; 95% CI: 0.4, 0.7, respectively). These data suggest that exposures to TDCPP and TPP are widespread and variable for pregnant women, and that a single measure of BDCPP or DPP, taken in the second trimester, likely captures information on the rank order of exposure throughout pregnancy.

Toxicity of new generation flame retardants to Daphnia magna

There is a tendency to substitute frequently used, but relatively hazardous brominated flame retardants (BFRs) with halogen-free flame retardants (HFFRs). Consequently, information on the persistence, bioaccumulation and toxicity (PBT) of these HFFRs is urgently needed, but large data gaps and inconsistencies exist. Therefore, in the present study the toxicity of a wide range of HFFRs to the water flea Daphnia magna was investigated. Our results revealed that four HFFRs were showing no effect at their Sw (saturated water concentration) and three had a low toxicity (EC50>10 mg L(-1)), suggesting that these compounds are not hazardous. Antimony trioxide had a moderate toxicity (EC50=3.01 mg L(-1), 95% CL: 2.76-3.25) and triphenyl phosphate and the brominated reference compound tetra bromobisphenol A were highly toxic to D. magna (EC50=0.55 mg L(-1), 95% CL: 0.53-0.55 and EC50=0.60 mg L(-1), 95% CL: 0.24-0.97 respectively). Aluminum trihydroxide and bisphenol A bis(diphenyl phosphate) caused limited mortality at Sw (26 and 25% respectively) and have a low solubility (<10 mg L(-1)). Hence, increased toxicity of these compounds may be observed when for instance decreasing pH could increase solubility. By testing all compounds under identical conditions we provided missing insights in the environmental hazards of new generation flame retardants and propose as best candidates for BFR replacements: APP, ALPI, DOPO, MHO, MPP, ZHS and ZS.

Urinary metabolites of organophosphate flame retardants: temporal variability and correlations with house dust concentrations

BACKGROUND

A reduction in the use of polybrominated diphenyl ethers (PBDEs) because of human health concerns may result in an increased use of and human exposure to organophosphate flame retardants (OPFRs). Human exposure and health studies of OPFRs are lacking.

OBJECTIVES

We sought to define the degree of temporal variability in urinary OPFR metabolites in order to inform epidemiologic study design, and to explore a potential primary source of exposure by examining the relationship between OPFRs in house dust and their metabolites in urine.

METHODS

Nine repeated urine samples were collected from 7 men over the course of 3 months and analyzed for bis(1,3-dichloro-2-propyl) phosphate (BDCPP) and diphenyl phosphate (DPP), metabolites of the OPFRs tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and triphenyl phosphate (TPP), respectively. Intraclass correlation coefficients (ICCs) were calculated to characterize temporal reliability. Paired house dust and urine samples were collected from 45 men.

RESULTS

BDCPP was detected in 91% of urine samples, and DPP in 96%. Urinary BDCPP showed moderate-to-strong temporal reliability (ICC range, 0.55-0.72). ICCs for DPP were lower, but moderately reliable (range, 0.35-0.51). There was a weak [Spearman r (r(S)) = 0.31] but significant (p = 0.03) correlation between urinary BDCPP and TDCPP concentrations in house dust that strengthened when nondetects (r(S) = 0.47) were excluded. There was no correlation between uncorrected DPP and TPP measured in house dust (r(S) < 0.1).

CONCLUSIONS

Household dust may be an important source of exposure to TDCPP but not TPP. Urinary concentrations of BDCPP and DPP were moderately to highly reliable within individuals over 3 months.

House dust concentrations of organophosphate flame retardants in relation to hormone levels and semen quality parameters

BACKGROUND

Organophosphate (OP) compounds, such as tris(1,3-dichloro-2-propyl) phosphate (TDCPP) and triphenyl phosphate (TPP), are commonly used as additive flame retardants and plasticizers in a wide range of materials. Although widespread human exposure to OP flame retardants is likely, there is a lack of human and animal data on potential health effects.

OBJECTIVE

We explored relationships of TDCPP and TPP concentrations in house dust with hormone levels and semen quality parameters.

METHODS

We analyzed house dust from 50 men recruited through a U.S. infertility clinic for TDCPP and TPP. Relationships with reproductive and thyroid hormone levels, as well as semen quality parameters, were assessed using crude and multivariable linear regression.

RESULTS

TDCPP and TPP were detected in 96% and 98% of samples, respectively, with widely varying concentrations up to 1.8 mg/g. In models adjusted for age and body mass index, an interquartile range (IQR) increase in TDCPP was associated with a 3% [95% confidence interval (CI), 5% to 1%) decline in free thyroxine and a 17% (95% CI, 432%) increase in prolactin. There was a suggestive inverse association between TDCPP and free androgen index that became less evident in adjusted models. In the adjusted models, an IQR increase in TPP was associated with a 10% (95% CI, 219%) increase in prolactin and a 19% (95% CI, 30% to 5%) decrease in sperm concentration.

CONCLUSION

OP flame retardants may be associated with altered hormone levels and decreased semen quality in men. More research on sources and levels of human exposure to OP flame retardants and associated health outcomes are needed.

Detection of organophosphate flame retardants in furniture foam and U.S. house dust

Restrictions on the use of polybrominated diphenyl ethers (PBDEs) have resulted in the increased use of alternate flame retardant chemicals to meet flammability standards. However, it has been difficult to determine which chemical formulations are currently being used in high volumes to meet flammability standards since the use of flame retardant formulations in consumer products is not transparent (i.e., not provided to customers). To investigate chemicals being used as replacements for PentaBDE in polyurethane foam, we analyzed foam samples from 26 different pieces of furniture purchased in the United States primarily between 2003 and 2009. Samples included foam from couches, chairs, mattress pads, pillows, and, in one case, foam from a sound-proofing system of a laboratory-grade dust sieve, and were analyzed using gas chromatography mass spectrometry. Fifteen of the foam samples contained the flame retardanttris(1,3-dichloro-2-propyl) phosphate (TDCPP; 1-5% by weight), four samples contained tris(1-chloro-2-propyl) phosphate (TCPP; 0.5 -22% by weight), one sample contained brominated chemicals found in a new flame retardant mixture called Firemaster 550 (4.2% by weight), and one foam sample collected from a futon likely purchased prior to 2004 contained PentaBDE (0.5% by weight). Due to the high frequency of detection of the chlorinated phosphate compounds in furniture foam,we analyzed extracts from 50 house dust samples collected between 2002 and 2007 in the Boston, MA area for TDCPP, TCPP, and another high volume use organophosphate-based flame retardant used in foam, triphenylphosphate (TPP). Detection frequencies for TDCPP and TPP in the dust samples were > 96% and were log normally distributed, similar to observations for PBDEs. TCPP was positively detected in dust in only 24% of the samples, but detection was significantly limited by a coelution problem. The geometric mean concentrations for TCPP, TDCPP, and TPP in house dust were 570, 1890, and 7360 ng/g, respectively, and maximum values detected in dust were 5490, 56,080 and 1,798,000 ng/g, respectively. These data suggest that levels of these organophosphate flame retardants are comparable, or in some cases greater than, levels of PBDEs in house dust. The high prevalence of these chemicals in foam and the high concentrations measured in dust (as high as 1.8 mg/g) warrant further studies to evaluate potential health effects from dust exposure, particularly for children.