Organophosphate ester flame retardants and plasticizers in human placenta in Eastern China

Distribution Characteristics and Ecological Risk Assessment of Organophosphate Esters in Surface Soils of China

The chemical flame retardants represented by organophosphate esters (OPEs) are widely used and have a serious impact on the environment. In this study, we collected data on the exposure levels of ten OPEs in Chinese soils in recent years and performed an ecological risk assessment. The results showed that the levels of OPEs varied considerably throughout different regions of China, with high exposure levels in highly urbanized or industrialized areas such as Guangdong Province and Northeast China, where the mean value was >200 ng/g. The content of OPEs in the soil in industrial and commercial areas was significantly higher than in other regions, indicating that the concentration of OPEs in the soil is closely related to local economic development and the degree of industrialization. Meanwhile, the number of studies reporting on OPEs and their exposure concentrations have increased significantly since 2018. Through the ecological risk assessment, it was found that TCP, EHDPP and TEHP pose high ecological risks. Although some OPEs, such as TCIPP, have low ecological risk levels overall, their high exposure concentrations are still worthy of attention. This study details the general status of OPE contamination in Chinese soils, which can serve as a reference for ecological environmental supervision.

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 Role and Mechanism of Ambra1-Mediated Mitophagy in TDCPP-Exposed Mouse Hippocampal Neurons

Tri(1,3-dichloro-2-propyl)phosphate (TDCPP) is one of the most widely used organophosphorus flame retardants in consumer products. TDCPP has been confirmed to be neurotoxic, but its mechanism has not been clarified and may be related to mitophagy. AMBRA1 can promote neurological autophagy, but whether AMBRA1 is involved in the mechanism of TDCPP-induced neurotoxicity has not been elucidated. In this study, the optimal neuronal damage model was established by exposing mice hippocampal neurons to TDCPP. Furthermore, on the basis of this model, siRNA was used to knock down AMBRA1. Combined with qRT-PCR and Western blot techniques, we identified AMBRA1-mediated mitophagy-induced neuronal damage in vitro mechanism. The experimental results indicated that TDCPP treatment for 24 h led to a decrease in the cell viability of mouse hippocampal neurons, causing neuronal damage. Meanwhile, TDCPP exposure increased autophagy marker proteins p62 and LC3B, and down-regulated mitochondrial DNA ND1 damage and TOMM20 protein, suggesting that TDCPP exposure promoted mitophagy. In addition, TDCPP exposure led to changes in the expression of AMBRA1 and the key factors of mitophagy, FUNDC1, PINK1, and PARKIN, whereas mitophagy was inhibited after knockdown of AMBRA1. The research results indicated that exposure to TDCPP induced neuronal damage and promoted mitophagy. The mechanism may be that AMBRA1 promoted mitophagy in neuronal cells through the PARKIN-dependent/non-dependent pathway. This study revealed the toxic effects of TDCPP on the nervous system and its potential molecular mechanisms, which provided important clues for further understanding the mechanism of action of AMBAR1-mediated mitophagy.

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.

Seasonal variations of organophosphate esters (OPEs) in atmospheric deposition, and their contribution to soil loading

Organophosphate esters (OPEs) are ubiquitous in surface soil, and atmospheric deposition is considered to be the major pollution source. However, the research on the environmental transport behaviors of OPEs between atmospheric deposition and soil is very limited. In this study, we investigated the contamination levels and seasonal variations of OPEs in atmospheric deposition samples (n = 33) collected from an area of South China every month between February 2021 and January 2022, and evaluated the contribution of OPEs in atmospheric deposition to soil. The concentrations of ∑21target-OPEs ranged from 3670 to 18,600 ng/g dry weight (dw), with a mean of 8200 ng/g dw (median: 7600 ng/g dw). ∑21target-OPEs concentrations in all atmospheric deposition samples exhibited significant seasonal differences (p < 0.05) with higher concentrations observed in winter and lower concentrations in summer. Tris(2,4-di-tert-butylphenyl) phosphate (TDTBPP) was the most dominant target OPE in atmospheric deposition (4870 ng/g dw), and its seasonal variation trend was consistent with ∑21OPEs (p < 0.05). Simultaneously, in order to further explore the effect of atmospheric deposition on the levels of OPEs in soil of the study region, input fluxes and accumulation increments were estimated. Ten OPEs (including seven target OPEs and three suspect OPEs) exhibited high input flux means and accumulation increments, indicating that these compounds are prone to accumulate in soil via atmospheric deposition. It is noteworthy that the non-target phosphonate analyte bis(2,4-di-tert-butylphenyl) dibutyl ethane-1,2-diylbis(phosphonate) (BDTBPDEDBP) was detected at highest median concentration (8960 ng/g dw) in atmospheric deposition. Correspondingly, the average input flux and accumulation increment of BDTBPDEDBP were higher than those of all target and suspect OPEs. Collectively, this study quantifies the environmental transport behavior of OPEs between atmospheric deposition and soil, and provides new evidences for the fact that atmospheric deposition is the important pollution source of OPEs in soil.

Organophosphate flame retardants tris (2-butoxyethyl) phosphate (TBEP) and tris (2-chloroethyl) phosphate (TCEP) disrupt human motor neuron development by differentially affecting their survival and differentiation

Mounting evidence in animal experiments proves that early life stage exposure to organophosphate flame retardants (OPFRs) affects the locomotor behavior and changes the transcriptions of central nervous system genes. Unfortunately, their effect on human motor neuron (MN) development, which is necessary for body locomotion and survival, has not yet characterized. Here, we utilized a spinal cord MN differentiation model from human embryonic stem cells (ESCs) and adopted this model to test the effects of two typical OPFRs tris (2-butoxyethyl) phosphate (TBEP) and tris (2-chloroethyl) phosphate (TCEP), on MN development and the possible mechanisms underlying. Our findings revealed TBEP exerted a much more inhibitory effect on MN survival, while TCEP exhibited a stronger stimulatory effect on ESCs differentiation into MN, and thus TBEP exhibited a stronger inhibition on MN development than TCEP. RNA sequencing analysis identified TBEP and TCEP inhibited MN survival mainly by disrupting extracellular matrix (ECM)-receptor interaction. Focusing on the pathway guided MN differentiation, we found both TBEP and TCEP activated BMP signaling, whereas TCEP simultaneously downregulated Wnt signaling. Collectively, this is the first study demonstrated TBEP and TCEP disrupted human MN development by affecting their survival and differentiation, thereby raising concern about their potential harm in causing MN disorders.

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.

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

BACKGROUND

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

OBJECTIVES

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

METHODS

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

RESULTS

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

DISCUSSION

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

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.

Assessing developmental neurotoxicity of emerging environmental chemicals using multiple in vitro models: A comparative analysis

Newly synthesized chemicals are being introduced into the environment without undergoing proper toxicological evaluation, particularly in terms of their effects on the vulnerable neurodevelopment. Thus, it is important to carefully assess the developmental neurotoxicity of these novel environmental contaminants using methods that are closely relevant to human physiology. This study comparatively evaluated the potential developmental neurotoxicity of 19 prevalent environmental chemicals including neonicotinoids (NEOs), organophosphate esters (OPEs), and synthetic phenolic antioxidants (SPAs) at environment-relevant doses (100 nM and 1 μM), using three commonly employed in vitro neurotoxicity models: human neural stem cells (NSCs), as well as the SK-N-SH and PC12 cell lines. Our results showed that NSCs were more sensitive than SK-N-SH and PC12 cell lines. Among all the chemicals tested, the two NEOs imidaclothiz (IMZ) and cycloxaprid (CYC), as well as the OPE tris(1,3-dichloro-2-propyl) phosphate (TDCIPP), generated the most noticeable perturbation by impairing NSC maintenance and neuronal differentiation, as well as promoting the epithelial-mesenchymal transition process, likely via activating NF-κB signaling. Our data indicate that novel NEOs and OPEs, particularly IMZ, CYC, and TDCIPP, may not be safe alternatives as they can affect NSC maintenance and differentiation, potentially leading to neural tube defects and neuronal differentiation dysplasia in fetuses.

Triphenyl phosphate induces cardiotoxicity through myocardial fibrosis mediated by apoptosis and mitophagy of cardiomyocyte in mice

Triphenyl phosphate (TPHP) is an organophosphorus flame retardant, but its cardiac toxicity has not been adequately investigated. Therefore, in the current study, the effect of TPHP on the heart and the underlying mechanism involved was evaluated. C57BL/6 J mice were administered TPHP (0, 5, and 50 mg/kg/day) for 30 days. In addition, H9c2 cells were treated with three various concentrations (0, 50, and 150 μM) of TPHP, with and without the reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine or the mitochondrial fusion promoter M1. TPHP caused cardiac fibrosis and increased the levels of CK-MB and LDH in the serum. TPHP increased the levels of ROS, malondialdehyde (MDA), and decreased the level of superoxide dismutase (SOD) and Glutathione peroxidase (GSH-Px). Furthermore, TPHP caused mitochondrial damage, and induced fusion and fission disorders that contributed to mitophagy in both the heart of C57BL/6 J mice and H9c2 cells. Transcriptome analysis showed that TPHP induced up- or down-regulated expression of various genes in myocardial tissue and revealed enriched apoptosis pathways. It was also found that TPHP could remarkably increase the expression levels of Bax, cleaved Caspase-9, cleaved Caspase-3, and decreased Bcl-2, thereby causing apoptosis in H9c2 cells. Taken together, the results suggested that TPHP promoted mitophagy through mitochondria fusion dysfunction resulting from oxidative stress, leading to fibrosis by inducing myocardial apoptosis.

Typical neonicotinoids and organophosphate esters, but not their metabolites, adversely impact early human development by activating BMP4 signaling

Recent studies have highlighted the presence of potentially harmful chemicals, such as neonicotinoids (NEOs) and organophosphate esters (OPEs), in everyday items. Despite their potential threats to human health, these dangers are often overlooked. In a previous study, we discovered that NEOs and OPEs can negatively impact development, but liver metabolism can help mitigate their harmful effects. In our current research, our objective was to investigate the toxicity mechanisms associated with NEOs, OPEs, and their liver metabolites using a human embryonic stem cell-based differentiation model that mimics early embryonic development. Our transcriptomics data revealed that NEOs and OPEs significantly influenced the expression of hundreds of genes, disrupted around 100 biological processes, and affected two signaling pathways. Notably, the BMP4 signaling pathway emerged as a key player in the disruption caused by exposure to these pollutants. Both NEOs and OPEs activated BMP4 signaling, potentially impacting early embryonic development. Interestingly, we observed that treatment with a human liver S9 fraction, which mimics liver metabolism, effectively reduced the toxic effects of these pollutants. Most importantly, it reversed the adverse effects dependent on the BMP4 pathway. These findings suggest that normal liver function plays a crucial role in detoxifying environmental pollutants and provides valuable experimental insights for addressing this issue.

Exposure of male adult zebrafish (Danio rerio) to triphenyl phosphate (TPhP) induces eye development disorders and disrupts neurotransmitter system-mediated abnormal locomotor behavior in larval offspring

Triphenyl phosphate (TPhP) is a widely used organophosphorus flame retardant, which has become ubiquitous in the environment. However, little information is available regarding its transgenerational effects. This study aimed to investigate the developmental toxicity of TPhP on F1 larvae offspring of adult male zebrafish exposed to various concentrations of TPhP for 28 or 60 days. The findings revealed significant morphological changes, alterations in locomotor behavior, variations in neurotransmitter, histopathological changes, oxidative stress levels, and disruption of Retinoic Acid (RA) signaling in the F1 larvae. After 28 and 60 days of TPhP exposure, the F1 larvae exhibited a myopia-like phenotype with pathological alterations in the lens and retina. The genes involved in the RA signaling pathway were down-regulated following parental TPhP exposure. Swimming speed and total distance of F1 larvae were significantly reduced by TPhP exposure, and long-term exposure to environmental levels of TPhP had more pronounced effects on locomotor behavior and neurotransmitter levels. In conclusion, TPhP induced histological and morphological alterations in the eyes of F1 larvae, leading to visual dysfunction, disruption of RA signaling and neurotransmitter systems, and ultimately resulting in neurobehavioral abnormalities. These findings highlight the importance of considering the impact of TPhP on the survival and population reproduction of wild larvae.

Prenatal exposure to organophosphate esters and growth trajectory in early childhood

Maternal exposure to organophosphate esters (OPEs) has been linked to an increased risk of adverse birth outcomes. However, the impact of OPEs on childhood growth remains uncertain. This study assessed the associations between prenatal concentrations of OPE metabolites and the growth trajectory in early childhood. 212 singleton pregnant women were included in this study, and they were recruited between August 2014 and August 2016 in Wuhan, China. We measured the urinary concentrations of OPE metabolites during the 1st, 2nd, and 3rd trimesters. Standard deviation scores for weight and length were calculated for children at birth, 1, 6, 12, and 24 months. Trajectories of weight-for-age z-score (WAZ) and weight-for-length z-score (WLZ) were classified into four groups using group-based trajectory modeling. Trajectories of length-for-age z-score (LAZ) were classified into three groups with the same model. Then, we calculated odds ratios (ORs) and 95 % confidence interval (95%CI) using multinomial logistic regression to estimate increases in odds of different growth trajectories per doubling in OPE concentrations compared with moderate-stable trajectory. For average concentrations of OPE metabolites and growth trajectory, our results indicated that higher bis(2-butoxyethyl) phosphate, total aromatic OPE metabolites, and total OPE metabolites during pregnancy were associated with a higher likelihood of children falling into the low-stable and low-rising WAZ trajectory. Furthermore, compared to the moderate-stable LAZ trajectory, increased concentrations of 1-hydroxy-2-propyl bis(1-chloro-2-propyl) phosphate were linked to an elevated risk of a low-stable LAZ trajectory. Additionally, the 1st and 2nd trimesters may represent critical windows of heightened vulnerability to the effects of OPE metabolites on childhood growth. In conclusion, our study proves that prenatal exposure to OPE metabolites is inversely related to childhood growth. It is essential to conduct further research involving larger populations and to consider other compounds with known developmental toxicity to obtain more reliable and comprehensive results.

Organophosphate Esters in Building Materials from China: Levels, Sources, Emissions, and Preliminary Assessment of Human Exposure

Source characteristics and health risks of indoor organophosphate esters (OPEs) are limited by the lack of knowledge on emission processes. This study attempted to integrate the contents and emissions of OPEs from indoor building materials to assess human health effects. Thirteen OPEs were investigated in 80 pieces of six categories of building materials. OPEs are ubiquitous in the building materials and ∑13OPE contents varied significantly (p < 0.05) from 72.8 ng/g (seam agent) to 109,900 ng/g (wallpaper). Emission characteristics of OPEs from the building materials were examined based on a microchamber method. Depending on the sample category, the observed initial area-specific emission rates of ∑13OPEs varied from 154 ng/m2/h (carpet) to 2760 ng/m2/h (wooden floorboard). Moreover, the emission rate model was developed to predict the release levels of individual OPEs, quantify source contributions, and assess associated exposure risks. Source apportionments of indoor OPEs exhibited heterogeneities in multiple environmental media. The joint OPE contribution of wallpaper and wooden floorboard to indoor dust was up to 94.8%, while latex paint and wooden floorboard were the main OPE contributors to indoor air (54.2%) and surface (76.1%), respectively. Risk assessment showed that the carcinogenic risks of tris(2-chloroethyl) phosphate (3.35 × 10-7) were close to the acceptable level (1 × 10-6) and deserved special attention.

Cytotoxic and genotoxic effects of triphenyl phosphate on root tip cells of Allium cepa L

Triphenyl phosphate (TPhP) is a tri-ester of phosphoric acid and phenol. It is used in products such as polyvinyl chloride, hydraulic fluids, polymers, photographic films and printed circuit cards as a flame retardant. It is also widely used in consumer products like electric and electronic devices, textiles and building necessaries. TPhP can diffuse into its surrounding environment easily, because it does not form a chemical bond with polymeric materials. Therefore, bio-monitoring of such compounds is needed for possible environmental and human health effects. In this study, we evaluated genotoxicity and cytotoxicity of TPhP on Allium cepa on the cells of root tips. A 10 mg/mL stock solution of TPhP was dissolved in DMSO and dilutions of 2, 4, 6, 8 and 10 mg/mL was made in distilled water. Onion bulbs, rooted in test tubes, were exposed to these concentrations of TPhP for 24 h. Distilled water was used as a negative control, 0.7% hydrogen peroxide was used as positive control, and 0.5% DMSO was used as solvent control. Significant inhibition of onion root growth was observed following treatment with the 6, 8 and 10 mg/mL TPhP ranges in comparison with the negative and solvent control groups (p < 0.05). Furthermore, in the TPhP treatment groups, total chromosome aberration ratios were significantly high in comparison with the controls (p < 0.05). These results suggest that TPhP have cytotoxic and genotoxic effects on A. cepa root tips.

Astaxanthin activates the Nrf2/Keap1/HO-1 pathway to inhibit oxidative stress and ferroptosis, reducing triphenyl phosphate (TPhP)-induced neurodevelopmental toxicity

Triphenyl phosphate (TPhP) serves as a major organophosphorus flame retardant, and its induced neurodevelopmental toxicity has attracted widespread attention, but the mechanism remains unclear. In this study, we involved zebrafish to explore the new mechanism of TPhP inducing oxidative stress and ferroptosis to promote neurodevelopmental toxicity. The results suggested that TPhP affected the embryonic development, reduced the number of new neurons, and led to abnormal neural behavior in zebrafish larvae. TPhP also induced ROS accumulation, activated the antioxidant defense signal Nrf2 and Keap1, and significantly changed the activities of Acetylcholinesterase (AChE), Adenosine triphosphatase (ATPase) and glutathione S-transferase (GST). In addition, TPhP induced ferroptosis in zebrafish, which was reflected in the increase of Fe2+ content, the abnormal expression of GPX4 protein and genes related to iron metabolism (gpx4a, slc7a11, acsl4b, tfa, slc40a1, fth1b, tfr2, tfr1a, tfr1b and ncoa4). Astaxanthin intervention specifically inhibited ROS levels, and reversed SLC7A11 and GPX4 expression levels and Fe2+ metabolism thus alleviating ferroptosis induced by TPhP. Astaxanthin also partially reversed the activity of AChE, GST and the expression of neurodevelopmental-related genes (gap43, gfap, neurog1 and syn2a), so as to partially rescue the embryonic developmental abnormalities and motor behavior disorders induced by TPhP. More interestingly, the expression of mitochondrial apoptosis-related protein BAX, anti-apoptotic protein BCL-2, Caspase3 and Caspase9 was significantly altered in the TPhP exposed group, which could be also reversed by Astaxanthin intervention. In summary, our results suggested that TPhP exposure can induce oxidative stress and ferroptosis, thereby causing neurodevelopment toxicity to zebrafish, while Astaxanthin can partially reverse oxidative stress and reduce the neurodevelopmental toxicity of zebrafish larvae by activating Nrf2/Keap1/HO-1 signaling pathway.

Concentration identification and endpoint-oriented health risk assessments on a broad-spectrum of organic compounds in atmospheric fine particles: A sampling experimental study in Beijing, China

Understanding the complicate chemical components in atmospheric fine particulate matter (PM2.5) helps policy makers for pollutants control track progress and identify disparities in overall health risks. However, till now, information on accurate component detection, source identification, and effect-oriented risk assessment is scarce, especially for the simultaneous analysis of a broad-spectrum of compounds. In this study, a high-throughput target method was employed to distinguish the occurrence and characteristics of 152 chemicals: phthalate esters (PAEs), organophosphate esters (OPEs), carboxylic acid esters (CAEs), nitrophenols (NPs), nitrogen heterocyclic compounds (NHCs), per- and poly-fluoroalkyl substances (PFASs), triclosan and its derivatives (TCSs), and organosulfates (OSs) in ambient PM2.5 collected from Beijing, China. Detection frequencies of 77 targeted compounds were >50 %. Total concentrations of all compounds ranged from 33.1 to 745 ng/m3. The median concentration of ∑PAEs (108 ng/m3) was the highest, followed by ∑CAEs (12.2 ng/m3) and ∑NPs (10.1 ng/m3). Organophosphate diesters (di-OPEs) and TCSs were reported for the first time in ambient PM2.5. The pollutants mainly originated from the local industrial production, release of building materials, and environmental degradation of parent compounds. Based on absorption, distribution, metabolism, excretion, and toxicity (ADMET)-oriented risk evaluations, we found that bis (2-ethylhexyl) phthalate, diisobutyl phthalate, dibutyl phthalate, and di (2-ethylhexyl) adipate have high health risks. Additionally, the high oxidative stress potential of 4-nitrocatechol and the strong blood-brain barrier penetration potential of triclosan cannot be ignored. Our study will facilitate the evaluations of specific health outcomes and mechanisms of pollutants, and suggestion of pollutants priority control to reduce human health hazards caused by atmospheric particles.

Determinants of organophosphate esters exposure in pregnant women from East China

Organophosphate esters (OPEs) have been broadly used in various industrial and consumer products, resulting in global distribution and human exposure. Gestational exposure to OPEs may adversely affect the health of both pregnant women and their offspring. To better understand OPE exposure in pregnant women, our study determined eight urinary metabolites of major OPEs in pregnant women (n = 733) recruited at 12-16 weeks of gestation from Shanghai, China, and explored the determinants of OPE exposure among various sociodemographic characteristics, lifestyles, and dietary factors. Urinary metabolites of OPEs, including bis (1,3-dichloro-2-propyl) phosphate (BDCPP), bis (2-chloroethyl) phosphate (BCEP), bis (1-chloro-2-propyl) phosphate (BCIPP), dicresyl phosphate (DCP), diphenyl phosphate (DPP), dibutyl phosphate (DBP), bis (2-ethylhexyl) phosphate (BEHP), and bis (2-butoxyethyl) phosphate (BBOEP), exhibited a detection rate ranging from 69.30% to 99.32%. Multivariate linear regression models indicated that pregnant women who were multiparous, had a higher family income per capita, worked in white-collar jobs, and took nutritional supplements such as milk powder and fish oil tended to have higher urinary OPE metabolite concentrations. Besides, independent of sociodemographic characteristics and lifestyle factors, consumption of more aquatic products, soy products, pork, and puffed food, as well as drinking of purified tap water versus tap water, were associated with increased urinary OPEs metabolite concentrations. Our study demonstrated that OPE exposure was ubiquitous in pregnant women from Shanghai, and provided new insights into the potential factors influencing OPE exposure during pregnancy.

Associations of Organophosphate Ester Flame Retardant Exposures during Pregnancy with Gestational Duration and Fetal Growth: The Environmental influences on Child Health Outcomes (ECHO) Program

BACKGROUND

Widespread exposure to organophosphate ester (OPE) flame retardants with potential reproductive toxicity raises concern regarding the impacts of gestational exposure on birth outcomes. Previous studies of prenatal OPE exposure and birth outcomes had limited sample sizes, with inconclusive results.

OBJECTIVES

We conducted a collaborative analysis of associations between gestational OPE exposures and adverse birth outcomes and tested whether associations were modified by sex.

METHODS

We included 6,646 pregnant participants from 16 cohorts in the Environmental influences on Child Health Outcomes (ECHO) Program. Nine OPE biomarkers were quantified in maternal urine samples collected primarily during the second and third trimester and modeled as log 2 -transformed continuous, categorized (high/low/nondetect), or dichotomous (detect/nondetect) variables depending on detection frequency. We used covariate-adjusted linear, logistic, and multinomial regression with generalized estimating equations, accounting for cohort-level clustering, to estimate associations of OPE biomarkers with gestational length and birth weight outcomes. Secondarily, we assessed effect modification by sex.

RESULTS

Three OPE biomarkers [diphenyl phosphate (DPHP), a composite of dibutyl phosphate and di-isobutyl phosphate (DBUP/DIBP), and bis(1,3-dichloro-2-propyl) phosphate] were detected in > 85 % of participants. In adjusted models, DBUP/DIBP [odds ratio (OR) per doubling = 1.07 ; 95% confidence interval (CI): 1.02, 1.12] and bis(butoxyethyl) phosphate (OR for high vs. nondetect = 1.25 ; 95% CI: 1.06, 1.46), but not other OPE biomarkers, were associated with higher odds of preterm birth. We observed effect modification by sex for associations of DPHP and high bis(2-chloroethyl) phosphate with completed gestational weeks and odds of preterm birth, with adverse associations among females. In addition, newborns of mothers with detectable bis(1-chloro-2-propyl) phosphate, bis(2-methylphenyl) phosphate, and dipropyl phosphate had higher birth weight-for-gestational-age z -scores (β for detect vs. nondetect = 0.04 - 0.07 ); other chemicals showed null associations.

DISCUSSION

In the largest study to date, we find gestational exposures to several OPEs are associated with earlier timing of birth, especially among female neonates, or with greater fetal growth. https://doi.org/10.1289/EHP13182.

Toxicity assessment of organophosphate flame retardant triphenyl phosphate (TPHP) on intestines in mice

Triphenyl phosphate (TPHP), one widely used organophosphate flame retardant, has attracted accumulating attention due to its high detection rate in human biological samples. Up to date, the effects of TPHP exposure on intestinal health remain unexplored. In this study, BALB/c mice were used as a model and exposed to TPHP at dose of 2, 10, or 50 mg/kg body weight for 28 days. We observed Crohn's disease-like features in ileum and ulcerative colitis disease-like features in colon, such as shorter colon length, ileum/colon structure impairment, intestinal epithelial cell apoptosis, enrichment of proinflammatory cytokines and immune cells, and disruption of tight junction. Furthermore, we found that TPHP induced production of reactive oxygen species and apoptosis in intestinal epithelial Caco-2 cells, accompanied by disruption of tight junction between cells. To understand the molecular mechanism underlying TPHP-induced changes in intestines, we build the adverse outcome pathway (AOP) framework based on Comparative Toxicogenomics and GeneCards database. The AOP framework revealed that PI3K/AKT and FoxO signaling pathway might be associated with cellular apoptosis, an increase in ROS production, and increased inflammation response in mouse ileum and colon tissues challenged with TPHP. These results identified that TPHP induced IBD-like features and provided new perspectives for toxicity evaluation of TPHP.

Organophosphorus flame retardants and their metabolites in paired human blood and urine

Organophosphorus flame retardants (OPFRs) have been shown to be carcinogenic, neurotoxic, and endocrine disruptive, so it is important to understand the levels of OPFRs in human body as well as the modes of external exposure. In this study, we investigated the levels of 13 OPFRs and 7 phosphodiester metabolites in paired human blood and urine, as well as the influencing factors (region, age and gender), and studied the relationship between OPFRs and oxidative stress by urinary metabolites. We found that the concentrations of triphenyl phosphate (TPhP) and tris-(2-ethylhexyl) phosphate (TEHP) in the blood of urban populations were higher than those of rural populations, and that younger populations suffered higher TPhP and 2-ethylhexyl diphenyl phosphate (EHDPP) exposures than older populations. In addition, we found that tris-(2-chloroethyl) phosphate (TCEP), tributyl phosphate (TnBP), TPhP and EHDPP exposure induced oxidative stress. The results of the internal load principal component analysis indicated that dust ingestion, skin exposure, respiration and dietary intake may be the most important sources of TCEP, tris(2-butoxyethyl) phosphate (TBOEP), tri(2-chloroisopropyl) phosphate (TCIPP) and TEHP, respectively, and dust ingestion and skin exposure may be the main sources of TPhP for humans.

Developmental organophosphate flame retardant exposure disrupts adult hippocampal neurogenesis in Wistar rats

Organophosphate flame retardant (OPFR) contamination is ubiquitous and bio-monitoring studies have shown that human exposure is widespread and may be unavoidable. OPFRs bear structural similarities to known neurotoxicants such as organophosphate insecticides and have been shown to have both endocrine disrupting and developmental neurotoxic effects. The perinatal period in rodents represents a critical period in the organization of the developing nervous system and insults during this time can impart profound changes on the trajectory of neural development and function, lasting into adulthood. Adult hippocampal neurogenesis (AHN) facilitates dentate gyrus function and broader hippocampal circuit activity in adults; however, the neurogenic potential of this process in adulthood is vulnerable to disruption by exogenous factors during early life. We sought to assess the impact of OPFRs on AHN in offspring of dams exposed during gestation and lactation. Results indicate that developmental OPFR exposure has significant, sex specific impacts on multiple markers of AHN in the dentate gyrus of rats. In males, OPFR exposure significantly reduced the number of neural progenitors the number of new/immature neurons and reduced dentate gyrus volume. In females, exposure increased the number of neural progenitors, decreased the number of new/immature neurons, but had no significant effect on dentate gyrus volume. These results further elucidate the developmental neurotoxic properties of OPFRs, emphasize the long-term impact of early life OPFR exposure on neural processes, and highlight the importance of including sex as a biological variable in neurotoxicology research.

Effects of tris (2-chloroethyl) phosphate exposure on gut microbiome using the simulator of the human intestinal microbial ecosystem (SHIME)

Tris (2-chloroethyl) phosphate (TCEP) has been widely used, and its health risk has received increasing attention. However, the rare research has been conducted on the effects of TCEP exposure on changes in the structure of the human gut microbiome and metabolic functions. In this experiment, Simulator of the human intestinal microbial ecosystem (SHIME) was applied to explore the influences of TCEP on the human gut bacteria community and structure. The results obtained from high-throughput sequencing of 16S rRNA gene have clearly revealed differences among control and exposure groups. High-dose TCEP exposure increased the Shannon and Simpson indexes in the results of α-diversity of the gut microbiome. At phylum level, Firmicutes occupied a higher proportion of gut microbiota, while the proportion of Bacteroidetes decreased. In the genus-level analysis, the relative abundance of Bacteroides descended with the TCEP exposure dose increased in the ascending colon, while the abundances of Roseburia, Lachnospira, Coprococcus and Lachnoclostridium were obviously correlated with exposure dose in each colon. The results of short chain fatty acids (SCFAs) showed a remarkable effect on the distribution after TCEP exposure. In the ascending colon, the control group had the highest acetate concentration (1.666 ± 0.085 mg⋅mL-1), while acetate concentrations in lose-dose medium-dose and high-doseTCEP exposure groups were 1.119 ± 0.084 mg⋅mL-1, 0.437 ± 0.053 mg⋅mL-1 and 0.548 ± 0.106 mg⋅mL-1, respectively. TCEP exposure resulted in a decrease in acetate and propionate concentrations, while increasing butyrate concentrations in each colon. Dorea, Fusicatenibacter, Kineothrix, Lachnospira, and Roseburia showed an increasing tendency in abundance under TCEP exposure, while they had a negatively correlation with acetate and propionate concentrations and positively related with butyrate concentrations. Overall, this study confirms that TCEP exposure alters both the composition and metabolic function of intestinal microbial communities, to arouse public concern about its negative health effects.

Temporal trends and predictors of gestational exposure to organophosphate ester flame retardants and plasticizers

BACKGROUND

Organophosphate esters (OPEs), used as flame retardants and plasticizers, are chemicals of concern for maternal and infant health. Prior studies examining temporal trends and predictors of OPE exposure are primarily limited by small sample sizes.

OBJECTIVES

Characterize temporal trends and predictors of OPE exposure biomarkers.

METHODS

We determined urinary concentrations of eight biomarkers of OPE exposure at three timepoints during pregnancy for participants in the LIFECODES Fetal Growth Study (n = 900), a nested case-cohort recruited between 2007 and 2018. We examined biomarker concentrations, their variability during pregnancy, and temporal trends over the study period. In addition, we identified sociodemographic and pregnancy characteristics associated with biomarker concentrations. Analyses were conducted using both the within-subject pregnancy geometric means and biomarker concentrations measured at individual study visits.

RESULTS

Five OPE biomarkers were detected in at least 60% of the study participants. Biomarkers were not strongly correlated with one another and intraclass correlation coefficients, measuring within-subject variability during pregnancy, ranged from 0.27 to 0.51. Biomarkers exhibited varying temporal trends across study years. For example, bis(1-chloro-2-propyl) phosphate (BCIPP) increased monotonically, whereas bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP), displayed non-monotonic trends with concentrations that peaked between 2011 and 2014. We observed associations between sociodemographic characteristics and OPE biomarkers. In general, concentrations of most OPE biomarkers were higher among participants from racial and ethnic minority populations, participants who were younger, had higher pre-pregnancy body mass index (BMI), and less than a college degree. We observed consistent results using either averaged or visit-specific biomarker concentrations.

SIGNIFICANCE

We observed widespread exposure to several OPEs and OPE biomarkers displayed varying temporal trends in pregnant people from 2007 to 2018. Concentrations of most OPE biomarkers varied according to sociodemographic factors, suggesting higher burdens of exposure among participants with higher pre-pregnancy BMI, those belonging to racial and ethnic minority populations, and lower educational attainment.

Prenatal exposures to organophosphate ester metabolite mixtures and children's neurobehavioral outcomes in the MADRES pregnancy cohort

BACKGROUND

Evidence suggests organophosphate esters (OPEs) are neurotoxic; however, the epidemiological literature remains scarce. We investigated whether prenatal exposures to OPEs were associated with child neurobehavior in the MADRES cohort.

METHODS

We measured nine OPE metabolites in 204 maternal urine samples (gestational age at collection: 31.4 ± 1.8 weeks). Neurobehavior problems were assessed among 36-month-old children using the Child Behavior Checklist's (CBCL) three composite scales [internalizing, externalizing, and total problems]. We examined associations between tertiles of prenatal OPE metabolites (> 50% detection) and detect/non-detect categories (< 50% detection) and CBCL composite scales using linear regression and generalized additive models. We also examined mixtures for widely detected OPEs (n = 5) using Bayesian kernel machine regression.

RESULTS

Maternal participants with detectable versus non-detectable levels of bis(2-methylphenyl) phosphate (BMPP) had children with 42% (95% CI: 4%, 96%) higher externalizing, 45% (-2%, 114%) higher internalizing, and 35% (3%, 78%) higher total problems. Participants in the second versus first tertile of bis(butoxethyl) phosphate (BBOEP) had children with 43% (-1%, 109%) higher externalizing scores. Bis(1-chloro-2-propyl) phosphate (BCIPP) and child sex had a statistically significant interaction in internalizing (p = 0.02) and total problems (p = 0.03) models, with 120% (23%, 295%) and 57% (6%, 134%) higher scores in the third versus first BCIPP tertile among males. Among females, detectable vs non-detectable levels of prenatal BMPP were associated with 69% higher externalizing scores (5%, 170%) while the third versus first tertile of prenatal BBOEP was associated with 45% lower total problems (-68%, -6%). Although the metabolite mixture and each CBCL outcome had null associations, we observed marginal associations between di-n-butyl phosphate and di-isobutyl phosphate (DNBP + DIBP) and higher internalizing scores (0.15; 95% CrI: -0.02, 0.32), holding other metabolites at their median.

CONCLUSIONS

Our results generally suggest adverse and sex-specific effects of prenatal exposure to previously understudied OPEs on neurobehavioral outcomes in 36-month children, providing evidence of potential OPE neurotoxicity.

Maternal exposure to organophosphate flame retardants and neonatal anthropometric measures

BACKGROUND

Organophosphate flame retardants (OPFRs) are widely used as flame retardants and plasticizers. Laboratory evidence has suggested that maternal OPFR exposure may adversely affect fetal growth, but the epidemiological data are limited.

OBJECTIVES

To investigate the association of maternal OPFR exposure with neonatal anthropometric measures.

METHODS

This study included 354 mother-newborn pairs from the Laizhou Wan Birth Cohort (LWBC), China. Ten OPFR metabolites were measured in maternal urine samples collected before delivery. Neonatal anthropometric data was collected from medical records and standardized into z-scores using the WHO standards (2007), including the weight-for-age (WAZ), length-for-age (LAZ), body mass index-for-age (BMIZ), weight-for-length (WLZ), and head circumference-for-age z-score (HCZ). Multiple linear regression and weighted quantile sum (WQS) regression were used to estimate the associations of individual OPFR metabolites and their mixtures with neonatal anthropometrics, respectively. Stratified analysis by sex was performed.

RESULTS

The detection rates of BCEP, DPHP, BCIPP, BDCIPP, BBOEP, DnBP and DiBP were above 60%, with median concentrations ranging from 0.14 to 3.60 μg/g creatinine. Most OPFR metabolites (i.e., BCIPP, BDCIPP, DiBP, DnBP, or BBOEP) were associated with decreased offspring WAZ and HCZ. When using WQS analysis, the OPFR metabolite mixture was inversely associated with the WAZ, BMIZ and HCZ, whereas DnBP had the highest weights. After stratified by gender, the negative associations were more pronounced among males.

CONCLUSIONS

Maternal OPFR exposure was negatively associated with offspring WAZ, BMIZ, and HCZ, and males seemed to be more vulnerable to the developmental toxicity of certain OPFRs.

Lipid metabolic disturbance induced by triphenyl phosphate and hydroxy metabolite in HepG2 cells

Triphenyl phosphate (TPHP) has been widely used as flame retardants and been detected with increasing frequency in environment. TPHP can transform into mono-hydroxylated phosphate (OH-TPHP) and diester diphenyl phosphate (DPHP) through biotransformation. So far, information on the cytotoxicity and molecular regulatory mechanisms of TPHP metabolites are still limit. This study investigated the adverse effects of TPHP, OH-TPHP, and DPHP in HepG2 cells in terms of cell proliferation, lactate dehydrogenase release, reactive oxygen species generation, and mitochondrial membrane potential. The transcriptomic changes were measured using RNA sequencing, and bioinformatics characteristics including biological functions, signal pathways and protein-protein interaction were analyzed to explore the potential molecular mechanisms. Results displayed that the order of cytotoxicity was OH-TPHP> TPHP> DPHP. The prioritized biological functions changes induced by TPHP and OH-TPHP were correlated with lipid metabolism. Significant lipid accumulation was observed as confirmed by increased total cholesterol and triglycerides contents, and enhanced oil red O staining. Enrichment of PPARα/γ and down-stream genes suggested the participation of PPARs signal pathway in lipid metabolism disorder. In addition, TPHP and OH-TPHP induced endoplasmic reticulum stress (ERS), which was further confirmed by the ERS inhibitor experiment. In general, TPHP and OH-TPHP had obvious cytotoxic effects in HepG2 cells. PPARs signal pathway and endoplasmic reticulum stress may be involved in the lipid metabolism disorder induced by TPHP and OH-TPHP.

Sex-specific effects of prenatal organophosphate ester (OPE) metabolite mixtures and adverse infant birth outcomes in the maternal and developmental risks from environmental and social stressors (MADRES) pregnancy cohort

BACKGROUND

Organophosphate esters (OPEs) are used as flame retardants and plasticizers in various consumer products. Limited prior research suggests sex-specific effects of prenatal OPE exposures on fetal development. We evaluated overall and sex-specific associations between prenatal OPE exposures and gestational age (GA) at birth and birthweight for gestational age (BW for GA) z-scores among the predominately low-income, Hispanic MADRES cohort.

METHODS

Nine OPE metabolite concentrations were measured in 421 maternal urine samples collected during a third trimester visit (GA = 31.5 ± 2.0 weeks). We examined associations between single urinary OPE metabolites and GA at birth and BW for GA z-scores using linear regression models and Generalized Additive Models (GAMs) and effects from OPE mixtures using Bayesian Kernel Machine Regression (BKMR). We also assessed sex-specific differences in single metabolite analyses by evaluating statistical interactions and stratifying by sex.

RESULTS

We did not find significant associations between individual OPE metabolites and birth outcomes in the full infant sample; however, we found that higher bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) was associated with earlier GA at birth among male infants (p = 0.04), and a nonlinear, inverted U-shape association between the sum of dibutyl phosphate and di-isobutyl phosphate (DNBP + DIBP) and GA at birth among female infants (p = 0.03). In mixtures analysis, higher OPE metabolite mixture exposures was associated with lower GA at birth, which was primarily driven by female infants. No associations were observed between OPE mixtures and BW for GA z-scores.

CONCLUSION

Higher BDCIPP and DNBP + DIBP concentrations were associated with earlier GA at birth among male and female infants, respectively. Higher exposure to OPE mixtures was associated with earlier GA at birth, particularly among female infants. However, we saw no associations between prenatal OPEs and BW for GA. Our results suggest sex-specific impacts of prenatal OPE exposures on GA at birth.

Prenatal organophosphate ester exposure and executive function in Norwegian preschoolers

Organophosphate esters (OPEs) are ubiquitous chemicals, used as flame retardants and plasticizers. OPE usage has increased over time as a substitute for other controlled compounds. This study investigates the impact of prenatal OPE exposure on executive function (EF) in preschoolers.

Methods

We selected 340 preschoolers from the Norwegian Mother, Father, and Child Cohort Study. Diphenyl-phosphate (DPhP), di-n-butyl-phosphate (DnBP), bis(2-butoxyethyl) phosphate (BBOEP), and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) were measured in maternal urine. EF was measured using the Behavior Rating Inventory of Executive Functioning-Preschool (BRIEF-P) and the Stanford-Binet fifth edition (SB-5). EF scores were scaled so a higher score indicated worse performance. We estimated exposure-outcome associations and evaluated modification by child sex using linear regression.

Results

Higher DnBP was associated with lower EF scores across multiple rater-based domains. Higher DPhP and BDCIPP were associated with lower SB-5 verbal working memory (β = 0.49, 95% CI = 0.12, 0.87; β = 0.53, 95% CI = 0.08, 1.02), and higher BBOEP was associated with lower teacher-rated inhibition (β = 0.34, 95% CI = 0.01, 0.63). DPhP was associated with lower parent-reported BRIEF-P measures in boys but not girls [inhibition: boys: 0.37 (95% CI = 0.03, 0.93); girls: -0.48 (95% CI = -1.27, 0.19); emotional control: boys: 0.44 (95% CI = -0.13, 1.26); girls: -0.83 (95% CI = -1.73, -0.00); working memory: boys: 0.49 (95% CI = 0.03, 1.08); girls: -0.40 (95% CI = -1.11, 0.36)]. Fewer sex interactions were observed for DnBP, BBOEP, and BDCIPP, with irregular patterns observed across EF domains.

Conclusions

We found some evidence prenatal OPE exposure may impact EF in preschoolers and variation in associations by sex.

Occurrences and migration of organophosphite and organophosphate esters into food simulants from single-use food packaging in China

Organophosphite antioxidants (OPAs) and organophosphate esters (OPEs) are used as additives in food packaging. Because these chemicals have been found in various foods, they have caused increasing concern about potential health risks through food intake. Little information is available about the migration behaviors of OPAs and OPEs from single-use food packaging into food. In the present study, four OPAs and 23 OPEs were analyzed in paper and plastic single-use food packaging (n = 312), which are widely used for take-out food in China. The total concentrations of OPAs and OPEs in the packaging samples were 1966 and 189 ng/g, respectively. Tris (2,4-di-tert-butylphenyl) phosphite (AO168) was the dominant compound. OPAs and OPEs were present at higher concentrations in the plastic packaging than in the paper packaging. In a migration test, four OPAs and 15 OPEs were found in food simulants (4% acetic acid, 10% ethanol, and hexane). Higher levels of individual and total OPAs were found in hexane than the other food simulants, especially for AO168 migration from plastic packaging. The amounts of OPEs in the food simulants increased from the aqueous simulants (4% acetic acid and 10% ethanol) to the fatty food simulant (hexane). The migration efficiencies of the OPAs were higher than those of the OPEs. Preliminary calculations suggest that dietary exposure to OPAs and OPEs because of migration will be low for the population in China.

Organophosphate Flame Retardants in Pregnant Women: Sources, Occurrence, and Potential Risks to Pregnancy Outcomes

Organophosphate flame retardants (OPFRs) are found in various environmental matrixes and human samples. Exposure to OPFRs during gestation may interfere with pregnancy, for example, inducing maternal oxidative stress and maternal hypertension during pregnancy, interfering maternal and fetal thyroid hormone secretion and fetal neurodevelopment, and causing fetal metabolic abnormalities. However, the consequences of OPFR exposure on pregnant women, impact on mother-to-child transmission of OPFRs, and harmful effects on fetal and pregnancy outcomes have not been evaluated. This review describes the exposure to OPFRs in pregnant women worldwide, based on metabolites of OPFRs (mOPs) in urine for prenatal exposure and OPFRs in breast milk for postnatal exposure. Predictors of maternal exposure to OPFRs and variability of mOPs in urine have been discussed. Mother-to-child transmission pathways of OPFRs have been scrutinized, considering the levels of OPFRs and their metabolites in amniotic fluid, placenta, deciduae, chorionic villi, and cord blood. The results showed that bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) and diphenyl phosphate (DPHP) were the two predominant mOPs in urine, with detection frequencies of >90%. The estimated daily intake (EDI_M) indicates low risk when infants are exposed to OPFRs from breast milk. Furthermore, higher exposure levels of OPFRs in pregnant women may increase the risk of adverse pregnancy outcomes and influence the developmental behavior of infants. This review summarizes the knowledge gaps of OPFRs in pregnant women and highlights the crucial steps for assessing health risks in susceptible populations, such as pregnant women and fetuses.

Typical organic contaminants in hair of adult residents between inland and coastal capital cities in China: Differences in levels and composition profiles, and potential impact factors

The growing of urbanization, industrialization, and agricultural production have resulted in the increasing contamination of typical organic contaminants (OCs) in China. However, data on differences in exposure characteristics of typical OCs between the coastal and inland cities among residents in China are limited. In this study, hair samples were collected from adult residents in 10 and 17 provincial capital cities in coastal and inland China, respectively, to investigate the differences in the levels and composition profiles of typical OCs. The potential factors impacting the human exposure to OCs were also examined based on the relationship among the hair OC levels and the population characteristics and statistical indicators. The median concentrations of dichlorodiphenyltrichloroethane's (DDTs), polybrominated diphenyl ethers (PBDEs), and organophosphorus flame retardants (PFRs) in hair of coastal urban residents were 3.64, 5.58, and 268 ng/g, respectively, while their concentrations in samples from inland urban residents were 1.84, 3.85, and 202 ng/g, respectively. Coastal residents showed significantly higher hair OC concentrations than inland residents (p < 0.05). BDE209 and p,p'-DDE were the predominant chemicals for PBDEs and DDTs, respectively, in both coastal and inland cities. Tris(2-chloroisopropyl) phosphate (TCIPP) was the dominant PFR in coastal residents' hair, while triphenyl phosphate (TPHP) was the major PFR in inland residents' hair, possibly owing to the different usages of the PFRs. Significant gender differences were observed in the levels and composition profiles of OCs (p < 0.05). The levels of p,p'-DDE and TCIPP were significantly related to the gross domestic product (GDP), gross secondary industry product, and the per capita consumption of aquatic products (p < 0.05). This study provides scientific data for evaluating human exposure to OCs in urban residents at a large scale and its associations with statistical indicators including urbanization, industrialization, agricultural production, and diet in China.

Descriptive analysis of organophosphate ester metabolites in a pan-Canadian pregnancy cohort

Organophosphate esters (OPEs) are widely used in numerous consumer products for their flame retardant and plasticizing properties. Despite potential widespread exposure, biomonitoring data during critical windows of development are scarce and limited to the most widely studied metabolites. We quantified urinary concentrations of multiple OPE metabolites in a vulnerable Canadian population. Using data and biobanked specimens from the Maternal-Infant Research on Environmental Chemicals (MIREC) study (2008-2011), we measured first trimester urinary concentrations of 15 OPE metabolites as well as one flame retardant metabolite and quantified associations with sociodemographic and sample collection characteristics in 1865 pregnant participants. We applied 2 different analytical methods to quantify OPEs, one using UItra-Performance Liquid Chromatography coupled to tandem mass spectrometry (UPLC-MS/MS) and the other using Atmospheric Pressure Gas Chromatography coupled to mass spectrometry (APGC-MS/MS) with sensitive limits of detection (0.008-0.1 μg/L). We modelled associations between sociodemographic and sample collection characteristics and specific gravity-standardized chemical concentrations. Six OPE metabolites were detected in the majority (68.1-97.4 %) of participants. Bis-(2-chloroethyl) hydrogen phosphate had the highest detection rate (97.4 %). Diphenyl phosphate had the highest geometric mean concentration (0.657 μg/L). Metabolites of tricresyl phosphate were detected in few participants. Associations between sociodemographic characteristics varied according to each OPE metabolite. Pre-pregnancy body mass index tended to be positively associated with OPE metabolite concentrations whereas age tended to be inversely associated with OPE concentrations. OPE concentrations were, on average, higher in urine samples collected in the summer than other seasons the winter. We present the largest biomonitoring study of OPE metabolites in pregnant people to date. These findings demonstrate widespread exposure to OPEs and their metabolites and identify subpopulations who may experience heightened exposure.

Relationships of prenatal organophosphate ester exposure with pregnancy and birth outcomes: A systematic scoping review of epidemiological studies

Exposure to organophosphate esters (OPEs) during pregnancy has been suggested to be associated with adverse pregnancy and birth outcomes. However, relevant investigations are scarce, and the findings are inconsistent. We aimed to conduct a scoping review to provide an overview of these associations. Electronic databases, including MEDLINE (through PubMed), Web of Science, and CNKI (China National Knowledge Infrastructure), were searched from inception to March 2022 and updated in July 2022. A total of 8 studies (1860 participants) were included. Limited evidence indicates that OPE exposure during pregnancy may be negatively associated with both maternal and neonatal triiodothyronine and tetraiodothyronine concentrations but positively associated with thyroid-stimulating hormone concentrations. OPE exposure during pregnancy may be associated with lower insulin concentrations. OPE exposure during pregnancy was associated with gestational age in a sex-specific manner. Intrauterine OPE exposure might increase the risk of preterm birth in female infants but decrease the risk of preterm birth in male infants. Prenatal OPE exposure might be associated with an increased risk of low birth weight. The current scoping review suggests that OPE exposure during pregnancy may disturb pregnancy and birth health, including adverse thyroid function and birth size. Because of the limited evidence obtained for most associations, additional studies followed by a traditional systematic review are needed to confirm these findings.

Gestational organophosphate ester exposure and preschool attention-deficit/hyperactivity disorder in the Norwegian Mother, Father, and Child cohort study

BACKGROUND

Attention-deficit/hyperactivity-disorder (ADHD) is a leading neurodevelopmental disorder in children worldwide; however, few modifiable risk factors have been identified. Organophosphate esters (OPEs) are ubiquitous chemical compounds that are increasingly prevalent as a replacement for other regulated chemicals. Current research has linked OPEs to neurodevelopmental deficits. The purpose of this study was to assess gestational OPE exposure on clinically-assessed ADHD in children at age 3 years.

METHODS

In this nested case-control study within the Norwegian Mother, Father, and Child Cohort study, we evaluated the impact of OPE exposure at 17 weeks' gestation on preschool-age ADHD. Between 2007 and 2011, 260 ADHD cases were identified using the Preschool Age Psychiatric Assessment and compared to a birth-year-stratified control group of 549 children. We categorized bis(2-butoxyethyl) phosphate (BBOEP) and bis(1,3-dichloro-2-propyl) phosphate (BDCIPP) as values < limit of detection (LOD) (BBOEP N = 386, BDCIPP N = 632), ≥LOD but < limit of quantification (LOQ) (BBOEP N = 413; BDCIPP N = 75), or above LOQ (BBOEP N = 70; BDCIPP N = 102). Diphenyl phosphate (DPhP) and di-n-butyl phosphate (DnBP) were categorized as quartiles and also modeled with a log10 linear term. We estimated multivariable adjusted odds ratios (ORs) using logistic regression and examined modification by sex using an augmented product term approach.

RESULTS

Mothers in the 3rd DnBP quartile had 1.71 times the odds of having a child with ADHD compared to the 1st quartile (95%CI: 1.13, 2.58); a similar trend was observed for log10 DnBP and ADHD. Mothers with BDCIPP ≥ LOD but < LOQ had 1.39 times the odds of having a child with ADHD compared to those with BDCIPP < LOD (95%CI: 0.83, 2.31). Girls had lower odds of ADHD with increasing BBOEP exposure (log10 OR: 0.55 (95%CI: 0.37, 0.93), however boys had a weakly increased odds (log10 OR: 1.25 (95%CI: 0.74, 2.11) p-interaction = 0.01].

CONCLUSIONS

We found modest increased odds of preschool ADHD with higher DnBP and BDCIPP exposure.

A preliminary report on the association between maternal serum organophosphate ester concentrations and gestational diabetes mellitus

Organophosphate esters (OPEs) are extensively manufactured and used in China. Whether exposure to OPEs during pregnancy increases the risk of gestational diabetes mellitus (GDM) is unknown. Between 2011 and 2012, a case-control study including 130 and 67 women with and without GDM, respectively, was conducted in Hangzhou, China. The levels of 10 OPEs in maternal serum samples at delivery were quantified, and the relationships between the OPE concentrations and GDM risk were investigated. The results show that in all participants, tri-n-butyl phosphate (TNBP, median: 2.02 ng/mL) was the most common OPE present in the serum, followed by tri-phenyl phosphate (TPHP, median: 1.74 ng/mL) and tri-iso-butyl phosphate (median: 1.68 ng/mL). With one-unit elevation in the tris (2-chloroethyl) phosphate, TNBP, TPHP, and tris (2-butoxy ethyl) phosphate (TBOEP) concentrations in maternal serum, 1-h glucose levels increased by 0.19 (95% confidence interval (CI): -0.01, 0.29), 0.11 (95% CI: -0.18, 0.62), 0.29 (95% CI: 0.12, 0.58), and 0.20 units (95% CI: 0.01, 0.44), respectively. In addition, a unit increase in TBOEP levels in maternal serum was associated with an increase of 0.26 units (95% CI: 0.09, 0.61) in 2-h glucose levels. After adjusting for covariate factors, serum TNBP (odds ratio (OR) = 2.07; 95% CI: 1.27, 3.41), TBOEP (OR = 2.63; 95% CI: 1.68, 4.11), and TPHP (OR = 1.03; 95% CI: 1.05, 1.51) concentrations were associated with GDM incidence in pregnant women. Overall, TNBP, TBOEP, and TPHP exposure during pregnancy is associated with GDM risk and increased glucose levels.

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

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

Spleen Toxicity of Organophosphorus Flame Retardant TDCPP in Mice and the Related Mechanisms

Tris(1,3-dichloro-2-propyl) phosphate (TDCPP) is an organophosphorus flame retardant that has been utilized in recent years as a primary replacement for polybrominated diphenyl ethers (PBDEs) in a wide variety of fire-sensitive applications. However, the impact of TDCPP on the immune system has not been fully determined. As the largest secondary immune organ in the body, the spleen is considered to be an important study endpoint for determining immune defects in the body. The aim of this study is to investigate the effect of TDCPP toxicity on the spleen and its possible molecular mechanisms. In this study, for 28 consecutive days, TDCPP was administered intragastrically (i.g), and we assessed the general condition of mice by evaluating their 24 h water and food intake. Pathological changes in spleen tissues were also evaluated at the end of the 28-day exposure. To measure the TDCPP-induced inflammatory response in the spleen and its consequences, the expression of the critical players in the NF-κB pathway and mitochondrial apoptosis were detected. Lastly, RNA-seq was performed to identify the crucial signaling pathways of TDCPP-induced splenic injury. The results showed that TDCPP intragastric exposure triggered an inflammatory response in the spleen, likely through activating the NF-κB/IFN-γ/TNF-α/IL-1β pathway. TDCPP also led to mitochondrial-related apoptosis in the spleen. Further RNA-seq analysis suggested that the TDCPP-mediated immunosuppressive effect is associated with the inhibition of chemokines and the expression of their receptor genes in the cytokine-cytokine receptor interaction pathway, including four genes of the CC subfamily, four genes of the CXC subfamily, and one gene of the C subfamily. Taken together, the present study identifies the sub-chronic splenic toxicity of TDCPP and provides insights on the potential mechanisms of TDCPP-induced splenic injury and immune suppression.

High-throughput screening of toxicants that modulate extravillous trophoblast migration

Migration and subsequent invasion of extravillous trophoblasts into the uterus is essential for proper formation of the placenta. Disruption of these processes may result in poor pregnancy outcomes including preeclampsia, placenta accreta, fetal growth restriction, or fetal death. Currently, there are several methods for quantifying cell migration and invasion in vitro, each with limitations. Therefore, we developed a novel, high-throughput method to screen chemicals for their ability to alter human trophoblast migration. Human HTR8/SVneo trophoblast cells were cultured in Oris™ cell migration plates containing stopper barriers. After EVT cells attached and chemicals were added to media, stoppers were removed thereby creating a cell-free detection zone for migration. Entry of trophoblasts into this zone was monitored through imaging every 6 h and used to calculate a relative cell density. Chemicals known to increase (epidermal growth factor) and decrease (pertussis toxin and cadmium) trophoblast migration were used to validate this in vitro method. Next, a panel of environmental chemicals including bisphenols, mycoestrogens, and flame retardants, were screened for their ability to alter trophoblast invasion. In conclusion, a real-time method to track extravillous trophoblast migration offers potential for screening contaminants as placental toxicants.

Gestation and lactation triphenyl phosphate exposure disturbs offspring gut microbiota in a sex-dependent pathway

Triphenyl phosphate (TPhP) is an Organophosphate flame retardant (OPFR) that has been widely used in many commercial products. Following its widely usage, its health risk has been concerned. In this study, mice were exposed to TPhP (1 mg/kg) during pregnancy and lactation (E0-PND21), the effect of TPhP on gut microbiota and its role in TPhP mediated lipid metabolism disturbance of offspring was investigated. Our results showed that TPhP disturbed the gut microbiota in dam or offspring at different extent, with male offspring experiencing major effects. Both the composition, abundance or network of gut microbiome was affected in male offspring. In male offspring, expression of genes along gut-liver axis including FXR, CYP7A1, SREBP-1c and ChREBP was significantly up-regulated, and expression of SHP, FGF15 and ASBT was significantly down-regulated. Consistent with this, lipid accumulation in the liver, and increased level of triglyceride, total cholestrol and total bile acid in the serum was observed. The changed abundance of Ruminococcaceae, Clostridiaceae, and Bacteroidaceae shows strong correlation with disturbed lipid metabolism in male offspring. Our research showed that indirect TPhP exposure during early life stage could affect the gut microbiota and gene expression along gut-liver axis in offspring at sex-dependent pathways, with males experiencing more effects.

Seasonal and source characteristics of organophosphorus flame retardants in air and house dust in Taiwan residential microenvironments: Implications for young children's exposure and risk assessment using a probabilistic approach

Organophosphate flame retardants (OPFRs) are prevalent in multiple industries. They have gradually replaced brominated flame retardants in recent years. Eleven OPFRs were collected from indoor air and house dust in two primary activity spaces--bedrooms and living rooms. The aim of the present study was to explore the potential sources of, and health risks associated with, OPFR exposure in young children using integrated and probabilistic approaches. The level of 11 indoor air OPFRs (466 ng/m³) in the bedroom was greater than that measured in the living room (379 ng/m³), and these values contrasted with those detected in dust. The air OPFRs in the warmer season were higher than those measured in the cold season; the inverse was true for those detected in house dust. In both activity spaces, the composition profiles indicated that tris(1-chloro-2-propyl)phosphate in indoor air (39%) and tris(2-butoxyethyl)phosphate in house dust (67%) were the dominant congeners. The average daily exposure dose (ADD) of OPFRs via air inhalation and dust ingestion did not differ significantly between preschool and school-aged children or based on sex. The Monte-Carlo-simulated 95th percentile ADD of the OPFRs in dust ingested by preschool children was 1.4 times higher. The OPFR exposure from air inhalation and dust ingestion in Taiwanese children is currently an acceptable non-carcinogenic risk and a negligible carcinogenic risk to Taiwan residents.

Triphenyl phosphate proved more potent than its metabolite diphenyl phosphate in inducing hepatic insulin resistance through endoplasmic reticulum stress

Triphenyl phosphate (TPHP) is a widely used flame retardant and plasticizer and has been detected extensively in environmental media, wildlife and human bodies. Several epidemiological and animal studies have revealed that TPHP exposure is positively associated with glucose homeostasis disruption and diabetes. However, the effects of TPHP on hepatic glucose homeostasis and the underlying mechanisms remain unclear. The present work aimed to investigate the cytotoxicity and glucose metabolism disruption of TPHP and its metabolite diphenyl phosphate (DPHP) within hepatocytes. The cell viability assay undertaken on human normal liver (L02) cells showed that TPHP exhibited more potent hepatotoxicity than DPHP. RNA sequencing (RNA-seq) data showed that TPHP and DPHP presented different modes of toxic action. Insulin resistance is one of the predominant toxicities for TPHP, but not for DPHP. The insulin-stimulated glucose uptake and glycogen synthesis were impaired by TPHP, while DPHP exhibited no significant impairment on these factors. TPHP exposure induced endoplasmic reticulum (ER) stress, and the ER stress antagonist 4-PBA restored the impairment of insulin-stimulated glucose uptake and glycogen synthesis induced by TPHP. TPHP could also induce liver ER stress and insulin resistance in mice. Taken together, the results suggested that TPHP induces more potent insulin resistance through ER stress than its metabolite DPHP.

Neurodevelopmental toxicity of organophosphate flame retardant triphenyl phosphate (TPhP) on zebrafish (Danio rerio) at different life stages

As a substitute for polybrominated diphenyl ethers (PBDEs), organophosphate flame retardant triphenyl phosphate (TPhP) is widely used in our daily products and diffusely exists in our living surroundings, but there is a paucity of information concerning its neurodevelopmental toxicity. Herein, we investigated the effects of TPhP exposure on developmental parameters, locomotor behavior, oxidative stress, apoptosis and transcriptional levels in zebrafish at different developmental stages, so as to explore the effects of TPhP exposure on zebrafish neural development and the underlying molecular mechanisms. TPhP concentration gradient exposure reduced the survival rate, hatchability, heart rate, body length and eye distance of zebrafish embryos/larvae, and caused malformations of zebrafish larvae. TPhP also leads to abnormal locomotor behaviors, such as reduced swimming distance and swimming speed, and impaired panic avoidance reflex to high light stimulation. TPhP caused ROS accumulation in 96 hpf larvae and induced Nrf2-antioxidant response in zebrafish. In addition, TPhP further activated mitochondrial signaling pathways, which affected apoptosis in the zebrafish eye region, resulting in visual impairment. Neurodevelopmental (mbpa, syn2a, foxo3a and pax6a), Retinoid acid metabolism (cyp26a1, raraa, rbp5, rdh1, crabp1a and rbp2a) and apoptosis-related genes (bcl2a, baxa and casp9) revealed the molecular mechanism of abnormal behavior and phenotypic symptoms, and also indicated that 96 hpf larvae are more sensitive than 7 dpf larvae. Thus, in the present study, we revealed the neurotoxic effects of TPhP at different early life stages in zebrafish, and zebrafish locomotor behavior impairments induced by TPhP exposure are attributed to co-regulation of visuomotor dysfunction and neuro-related genes. These results suggest that the safety of TPhP in organisms and even in humans needs to be further studied.

Triphenyl phosphate induces clastogenic effects potently in mammalian cells, human CYP1A2 and 2E1 being major activating enzymes

As a new-type flame retardant and toxic substance, triphenyl phosphate (TPP) is a ubiquitous pollutant present even in human blood. TPP is transformed by human CYP enzymes to oxidized/dealkylated metabolites. The impact of TPP metabolism on its toxicity, however, remains unclear. In this study, the genotoxicity of TPP in several mammalian cell lines and its relevance to CYP/sulfortransferase (SULT) activities were investigated. The results indicated that TPP induced micronucleus formation at ≥1 μM concentrations in a human hepatoma (C3A, endogenous CYPs being substantial) cell line, which was abolished by 1-aminobenzotriazole (CYPs inhibitor). In cell line HepG2 (parental to C3A with lower CYP expression) TPP was inactive up to 10 μM, while pretreatment with ethanol (CYP2E1 inducer), PCB 126 (CYP1A inducer), or rifampicin (CYP3A inducer) led to micronucleus formation by TPP. In V79-Mz and V79-derived cells expressing human CYP1A1 TPP was inactive (up to 32 μM), and in cells expressing human CYP1B1, 2B6 and 3A4 it induced micronucleus weakly (positive only at 32 μM). However, TPP induced micronucleus potently in V79-derived cells expressing human CYP1A2, while this effect was drastically reduced by human SULT1A1 co-expression; likewise, TPP was inactive in cells expressing both human CYP2E1 and SULT1A1, but became positive with pentachlorophenol (inhibitor of SULT1) co-exposure. Moreover, in C3A cells TPP selectively induced centromere-free micronucleus (immunofluorescent assay), and TPP increased γ-H2AX (by Western blot, indicating double-strand DNA breaks). In conclusion, this study suggests that TPP is potently clastogenic, human CYP1A2 and 2E1 being major activating enzymes while SULT1A1 involved in detoxification.

Occurrence, correlation, and partitioning of organophosphate esters in soil and tree bark from a megacity, Western China

Concern over the influences of constant addition of emerging anthropogenic chemicals to the environment has become a public issue during the rapid urbanization. Here, we investigated the occurrence of organophosphate esters (OPEs) in soil and corresponding tree bark in a megacity, Western China. Our results showed levels of OPEs in tree bark (1250 ± 573 ng/g dry weight (dw)) were 1-2 orders of magnitude higher than those in soil (40.4 ± 30.8 ng/g dw). Rooster Mountain is a background mountain area, exhibiting significantly lower concentrations of OPEs in soil and tree bark than those in other sites with relatively high population density. This result highlights the effect of human activities on the distribution of OPEs in environmental matrices. Alkyl-OPEs were predominant compounds in soil, whereas halogenated- (Cl-) OPEs were characterized in tree bark. Furthermore, tris(2-chloroethyl) phosphate (TCEP) positively correlated with tris(2-chloroisopropyl) phosphate (TCIPP) in soil (r² = 0.43, P < 0.05) while negatively correlated with TCIPP in tree bark (r² = 0.31, P < 0.05). The ratios of logarithm concentrations of OPEs in tree bark to those in soil correlated well with logK_OA values of OPEs from 6 to 10, indicating the equilibrium status was achieved between OPE partitioning in soil and in tree bark. Nevertheless, tris (2-butoxyethyl) phosphate (TBEP) and tris(2-ethylhexyl) phosphate (TEHP) with high values of logK_OA deviated from this linear tendency, which was possibly due to the fact that they were subjected to the particle-bound deposition process, leading to partition into the soil.

Associations of gestational exposure to organophosphate esters with gestational age and neonatal anthropometric measures: The HOME study

Organophosphate esters (OPEs) are developmental toxicants in experimental studies of animals, but limited evidence is available in humans. We included 340 mother-infant pairs in the Health Outcomes and Measures of the Environment (HOME) Study (Cincinnati, Ohio, USA) for the analysis. We evaluated gestational exposure to OPEs with gestation age at birth and newborn anthropometric measures. We quantified four OPE urinary metabolites at 16 weeks and 26 weeks of gestation. We extracted gestational age at birth, newborn weight, length, and head circumference from the chart review. We calculated z-scores for these anthropometric measures and the ponderal index. We used multiple informant models to examine the associations between repeated OPE measurements and the outcomes. We used modified Poisson regression to estimate the association of gestational exposure to OPEs with preterm birth. We also explored effect modification by infant sex and the potential mediation effect by the highest maternal blood pressure and glucose levels. We found that bis(2-chloroethyl) phosphate (BCEP) at 16 weeks and diphenyl phosphate at 26 weeks of pregnancy were positively associated with gestational age and inversely associated with preterm birth. In female newborns, BCEP at 16 weeks was inversely related to birth weight and length z-scores. In male newborns, we observed negative associations of 26-week di-n-butyl phosphate with the ponderal index at birth. No mediation by the highest maternal blood pressure or glucose levels during pregnancy was identified. In this cohort, gestational exposure to some OPEs was associated with gestational age, preterm birth, and neonatal anthropometric measures. Certain associations tended to be window- and infant sex-specific.

Aryl-, halogenated- and alkyl- organophosphate esters induced oxidative stress, endoplasmic reticulum stress and NLRP3 inflammasome activation in HepG2 cells

Organophosphate esters (OPEs) are a group of extensively used man-made chemicals with diverse substituents that are ubiquitously detected in human-related samples including serum, breastmilk, food and house dust. The understanding of their toxicological effects and potential mechanisms on hepatocytes is still limited. In this study, nine most frequently detected OPEs were selected and divided into three subgroups (aryl-, halogenated- and alkyl-OPEs) based on their substituents. The cytotoxicity, apoptosis, oxidative stress, endoplasmic reticulum (ER) stress and NLRP3 inflammasome activation induced by OPEs were evaluated in human hepatocellular carcinomas HepG2 cells. All OPEs induced apoptosis likely through a caspase-dependent apoptotic pathway. The activities of anti-oxidative enzyme SOD and CAT exhibited sensitive responses after OPEs treatment for 6 h. The OPEs induced ROS overproduction, DNA damage, endoplasmic reticulum (ER) stress and NLRP3 inflammasome activation varied among aryl-, halogenated- and alkyl-OPEs. Halogenated- and alkyl- OPEs induced overproduction of ROS and DNA damage, and elevated ER stress and NLRP3 inflammasome activation are observed aryl-OPEs induced cytotoxicity.

Early life organophosphate ester exposures and bone health at age 12 years: The Health Outcomes and Measures of the Environment (HOME) Study

BACKGROUND

No human studies have evaluated early life organophosphate ester (OPE) exposures with bone health outcomes, despite evidence of osteotoxicity.

OBJECTIVES

We assessed associations of urinary OPE metabolites measured across early life with areal bone mineral density (aBMD) and bone mineral content (BMC) at age 12 years.

METHODS

Among 223 mother-child dyads enrolled in the Health Outcomes and Measures of the Environment (HOME) Study, we quantified concentrations of bis-2-chloroethyl phosphate (BCEP), bis-(1,3-dichloro-2-propyl) (BDCIPP), di-n-butyl phosphate (DnBP), and diphenyl phosphate (DPHP) in urine collected from mothers during pregnancy and children at ages 1, 2, 3, 5, and 8 years. At age 12 years, we performed dual energy x-ray absorptiometry and calculated aBMD and BMC z-scores at six skeletal sites. We estimated overall and sex-stratified BMD/BMC z-score differences per interquartile range (IQR) increase in OPE concentrations at multiple exposure timepoints: gestation (average) and 1-3 (average), 5, and 8 years.

RESULTS

In adjusted models, overall associations of BCEP and BDCIPP with total hip and 1/3rd distal radius aBMD and BMC varied significantly by exposure timepoint, as did BDCIPP with whole body aBMD. For example, differences (95 % CI) in total hip aBMD z-score per IQR increase in BDCIPP were 0.33 (0.01, 0.64), -0.10 (-0.34, 0.14), -0.18 (-0.40, 0.05), and 0.14 (-0.09, 0.38) for concentrations during gestation and at 1-3, 5, and 8 years, respectively. Overall DnBP and DPHP associations were generally null at all timepoints. We observed sex-specific associations for some timepoints and skeletal sites. For example, an IQR increase in 8-year DPHP was associated with a 0.21 (0.05, 0.38) greater total hip aBMD z-score among females but -0.19 (-0.43, 0.05) lower z-score among males.

DISCUSSION

Early life OPE exposures may be associated with sex- and exposure period-dependent alterations in early adolescent bone mineral accrual and strength.

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

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