Pre- and post-natal exposure of children to organophosphate flame retardants: A nationwide survey in France

EHDPP impairs intestinal microbiota homeostasis and induces placental injury through choline mediated gut-placenta axis

2-Ethylhexyl-diphenyl phosphate (EHDPP) is an organophosphate ester (OPE) with roles of flame retardant and plasticizer. It is widely used in various applications, detected in environmental matrices and human body, threatening ecological environment and human health. Some OPEs have been reported to disturb the gut microbiota, the gut microbiota mediates placental function. Our previous study showed EHDPP causes placental toxicity and fetal weight loss, it is unknown that whether EHDPP affects fetal development through the gut-placenta axis and whether it is feasible to fight against EHDPP induced placental toxicity through the gut-placenta axis. Our study investigates and indicates that EHDPP disrupts normal gut function by disturbing the gut microbiota homeostasis and compromising the intestinal barrier integrity. The disruption of EHDPP leads to reduced choline transporter expression of the solute carrier family 44A2 (SLC44A2), impaired choline absorption and distribution in placenta. Gut microbiota depletion increases the choline level in placenta. Both gut microbiota depletion and choline supplementation alleviate the EHDPP induced fetal weight loss by increasing the expression and activation of LXRα. In addition, a mendelian randomization study indicates that choline transporter SLC44A2 expression reduction significantly increased the risk of low birth weight in human. In summary, EHDPP exposure exacerbates placental and fetal damage through attenuating the beneficial function of choline mediated gut-placental axis. Direct choline supplementation or indirect choline level upregulation by gut microbiota depletion are therapeutic strategies for EHDPP induced placental injury.

Effects of two typical organophosphate flame retardants on DNA damage of GT1-7 cells and relevant molecular mechanism

The tris (2-chloroethyl) phosphate (TCEP) and tri-n-butyl phosphate (TNBP) are two typical organophosphate esters (OPEs), which have estrogenic activity. However, fewer studies have been conducted on their genotoxicity and mechanisms. In this study, we evaluated the effects of TCEP and TNBP on cellular DNA damage in GT1-7 cells and examined the role of estrogen signaling in regulating DNA damage. The results showed that TCEP and TNBP significantly inhibited the cell viability and elevated intracellular reactive oxygen species (ROS) levels at higher exposure concentrations. TCEP and TNBP at test concentrations significantly increased comet tail length, comet tail DNA percentage (Tail DNA%), and Olive tail moment (OTM) values, indicating that TCEP and TNBP induced cellular DNA damage. In addition, TCEP and TNBP significantly upregulated the mRNA levels of target genes related to DNA damage-repair pathways, and elevated the expression of ataxia-telangiectasia mutated (ATM) and γ-H2AX proteins associated with DNA double-strand breaks. Furthermore, TCEP and TNBP significantly up-regulated the expression of membrane bound G-protein coupled estrogen receptor 1 (GPER) protein and increased the phosphorylation of extracellular signal-regulated kinases 1/2 (ERK1/2) at 10 µM. While the pretreatment of GPER1 inhibitor G15 and ERK1/2 inhibitor U0126 significantly inhibited the up-regulation of mRNA expression of the target genes associated with the DNA damage-repair pathways and decreased the DNA damage induced by TCEP and TNBP. These findings indicate that TCEP and TNBP activate GPER1/ERK1/2 signaling pathway which plays an important role in regulating DNA damage. The study will provide a novel insight into the genotoxicity mechanism of OPEs.

An assessment of organophosphate ester mixtures and the placental transcriptome

Prenatal exposure to organophosphate ester (OPE) chemicals, commonly used as flame retardants and plasticizers, has been associated with adverse birth outcomes. The placenta is a critical fetal organ and therefore may be involved in pathogenesis of birth outcomes. The goal of this study was to evaluate associations of 10 maternal urinary OPE metabolites, individually and as a mixture, with the placental transcriptome at birth in the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) study. Individual OPE metabolites were evaluated for associations with individual genes as well as co-expressed gene modules. Mixtures analysis was conducted using quantile g-computation. The analyses were performed with the entire data set (N = 737) as well as the sex-stratified subsets. Two genes (HAP1 and RAP1GAP) were associated with bis(1,3-dichloro-2-propyl) phosphate (BDCPP), and six genes were associated the mixture in the full data set. 3 genes were associated with diphenyl phosphate (DPHP) and 36 genes were associated with the mixture in a male stratified analysis. 2 genes were associated with DPHP, and 1 gene was associated with diethyl phosphate (DEP) in a female stratified analysis. Three gene modules were associated with BDCPP or diphenyl phosphate (DPHP) and one module was associated with the OPE mixture. 12 WGCNA modules were associated with individual OPE metabolites or the mixture in males, and 1 WGCNA module was associated with DEP in females. Five of the OPE-associated gene modules were enriched for a total of 17 KEGG pathways, and 11 modules were enriched with targets of 12 nuclear hormone receptor transcription factors. Overall, novel associations were identified between the placental transcriptome and OPE metabolites, individually and in mixture, including differences based on fetal sex. These findings highlight the need for additional research on mechanisms of OPE-associated gene expression changes in the placenta and associated health outcomes.

Identification of the associations between co-exposure to organophosphate flame retardants and thyroid dysfunction and exposure risk factors in residents of Shanghai, China

Toxicological studies indicate that organophosphate flame retardants (OPFRs) may cause thyroid dysfunction. However, population epidemiologic evidence is still limited and little is known about the effects of mixed exposures to OPFRs. This study included 436 community residents from Shanghai, China. We measured the levels of 9 OPFRs in 3 categories and 5 commonly used thyroid function indicators (TFIs) in serum samples from all participants. Multiple linear regression and restricted cubic spline model were used to examine the association between exposure to individual OPFRs and TFIs. Weighted quantile sum regression and Bayesian kernel-machine regression models were used to elucidate the joint impact of mixed OPFRs on thyroid function and the dose-response relationship. Machine learning combined with the SHapley Additive exPlanations algorithm identified important risk factors for exposure to OPFRs in the population. The results indicated that the residents were generally exposed to OPFRs. Exposure to either single or mixed OPFRs was significantly associated with TFI levels, particularly free thyroxine (FT4) and free triiodothyronine (FT3). Tri-n-butyl-phosphate (TBP), Tris-2-butoxy ethyl-phosphate (TBEP), and Tris-2-chloroethyl-phosphate (TCEP) were major contributors to the co-exposure effect. The dose-response relationship further revealed the trend in the impact of OPFRs on thyroid function. Education, occupation, age, body mass index, personal annual income, indoor time, and mollusk intake are noteworthy risk characteristics for population exposure to OPFRs. These findings suggest that OPFRs are environmental drivers of thyroid dysfunction in humans and provide clues for further risk management.

Adipogenic Effects of Cresyl Diphenyl Phosphate (Triphenyl Phosphate Alternative) through Peroxisome Proliferator-Activated Receptor Gamma Pathway: A Comprehensive Study Integrating In Vitro, In Vivo, and In Silico from Molecule to Health Risk

Cresyl diphenyl phosphate (CDP), a novel organophosphate ester (OPE), has been detected in various environmental and human samples. However, there is very limited knowledge regarding its toxicity, mechanisms of action, and potential health risks. Using new alternative methods (NAMs), across the molecular interactions, signaling pathways, cell functions, animal effects, and population risks, we investigated the potential adipogenic effects and associated risks of CDP and legacy OPE triphenyl phosphate (TPHP) by acting on peroxisome proliferator-activated receptor gamma (PPARγ). Among the 19 screened OPEs, CDP bound to PPARγ with the highest binding potency, followed by TPHP. CDP activated PPARγ through fitting into the binding pocket with strong hydrophobicity and hydrogen bond interactions; CDP exhibited higher potency compared to TPHP. In 3T3-L1 cells, CDP enhanced the PPARγ-mediated adipogenesis activity, exhibiting greater potency than TPHP. The intracellular concentration and receptor-bound concentrations (RBC) of CDP were also higher than those of TPHP in both HEK293 cells and 3T3-L1 cells. In mice, exposure to CDP activated the PPARγ-mediated adipogenic pathway, leading to an increased white adipose tissue weight gain. Overall, CDP could bind to and activate PPARγ, thereby promoting preadipocyte differentiation and the development of white adipose tissue. Its potential obesogenic risks should be of high concern.

Exposure to pesticides, persistent and non - persistent pollutants in French 3.5-year-old children: Findings from comprehensive hair analysis in the ELFE national birth cohort

INTRODUCTION

Exposure to endocrine disruptors during early childhood poses significant health risks. This study examines the exposure levels of French 3.5-year-old children to various persistent and non-persistent pollutants and pesticides using hair analysis as part of the ELFE national birth cohort. Differences in sex and geographical location among the children were investigated as ppossible determinants of exposure.

METHODS

Exposure biomarkers from 32 chemical families were analyzed using LC-MS/MS and GC-MS/MS in 222 hair samples from children in the ELFE cohort. Of these, 46 mother-child pairs from the same cohort provided unique insight into prenatal and postnatal exposure. Regressions, correlations and discriminate analysis were used to assess relationships between exposure and possible confounding factors.

RESULTS AND DISCUSSION

Among the biomarkers tested in children's hair samples, 69 had a detection frequency of ≥ 50 %, with 20 showing a 100 % detection rate. The most detected biomarkers belonged to the bisphenol, organochlorine and organophosphate families. Sex-specific differences were observed for 26 biomarkers, indicating the role of the child's sex in exposure levels. Additionally, regional differences were noted, with Hexachlorobenzene varying significantly across the different French regions. Nicotine presented both the highest concentration (16303 pg/mg) and highest median concentration (81 pg/mg) measured in the children's hair. Statistically significant correlations between the levels of biomarkers found in the hair samples of the mothers and their respective children were observed for fipronil (correlation coefficient = 0.32, p = 0.03), fipronil sulfone (correlation coefficient = 0.34, p = 0.02) and azoxystrobin (correlation coefficient = 0.29, p = 0.05).

CONCLUSIONS

The study highlights the elevated exposure levels of young children to various pollutants, highlighting the influence of sex and geography. Hair analysis emerges as a crucial tool for monitoring endocrine disruptors, offering insights into exposure risks and reinforcing the need for protective measures against these harmful substances.

Investigation of alkyl, aryl, and chlorinated OPFRs in sediments from estuarine systems: Seasonal variation, spatial distribution and ecological risks assessment

Estuaries in South Africa are very important for biodiversity conservation and serve as focal points for leisure and tourism activities. The organophosphate flame retardants (OPFRs) levels in these aquatic systems haven't been documented in any studies as of yet. Due to the negative effects of persistent organic pollutants in South African estuaries, we examined the occurrence of eight OPFRs in sediments of two estuaries by studying their spatiotemporal distribution, season variation, and ecological risks. The Sundays Estuary (SDE), a semi-urbanized agricultural surrounding system, recorded an ∑8OPFR concentration in sediments that ranged from 0.71 to 22.5 ng/g dw, whereas Swartkops Estuary, a largely urbanized system, recorded a concentration that ranged from 0.61 to 119 ng/g dw. Alkyl-OPFRs were the prevalent homologue in both estuaries compared to the chlorinated and aryl groups. While TBP, TCPP, and TCrP were the most abundant compounds among the homologue groups. There was no distinct seasonal trend of ∑8OPFR concentration in either estuary, with summer and autumn seasons recording the highest concentrations in SDE and SWE, respectively. Ecological risks in the majority of the study sites for the detected compounds were at low (RQ < 0.1) and medium levels (0.1 ≤ RQ < 1) for certain species of fish, Daphnia magna and algae. However, the cumulative RQs for all the compounds had ∑RQs ≥1 for most sites in both estuaries, indicating that these organisms, if present in both estuaries, may be exposed to potential ecological concerns due to accumulated OPFR chemicals. The scope of future studies should be broadened to include research areas that are not only focus on the bioaccumulation patterns of these compounds but also find sustainable ways to reduce them from these estuarine environments.

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.

Characterization of organic contaminants in hair for biomonitoring purposes

Biological monitoring is one way to assess human exposure to contaminants. Blood and urine are often used as biological matrices, but hair is an innovative and effective tool for quantifying more biomarkers over a wider exposure window. In order to improve the use of hair in exposure assessment, this article identifies relevant compounds in the literature to investigate hair contamination. Statistical analysis was performed to correlate the physical-chemical properties of the relevant compounds and their concentration levels in hair. Phthalates, pyrethroids and organophosphate flame retardants were chosen for further study of the interpretation of hair measurements for exposure assessment. No significant correlation was found between the average concentration levels in the literature and the physical-chemical properties of the selected compounds. This work also explores the properties of hair and the analytical process that may impact the quantification of organic contaminants in hair. The sample preparation method (sampling, storage, washing) were also studied and adaptations were suggested to improve the existing methods.

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.