Regulatory and academic studies to derive reference values for human health: The case of bisphenol S

In silico analysis of endocrine-disrupting potential of triclosan, bisphenol A, and their analogs and derivatives

Owning to the increasing body of evidence about the ubiquitous exposure to endocrine disruptors (EDCs), particularly bisphenol A (BPA), and associated health effects, BPA has been gradually substituted with insufficiently tested structural analogs. The unmanaged excessive use of antimicrobial agents such as triclosan (TCS) during the COVID-19 outbreak has also raised concerns about its possible interferences with hormonal functions. The similarity of BPA and estradiol, as well as TCS and non-steroidal estrogens, imply that endocrine-disrupting properties of their analogs could be predicted based on the chemical structure. Hence, this study aimed to evaluate the endocrine-disrupting potential of BPA substitutes as well as TCS derivatives and degradation/biotransformation metabolites, in comparison to BPA and TCS based on their molecular properties, computational predictions of pharmacokinetics and binding affinities to nuclear receptors. Based on the obtained results several under-researched BPA analogs exhibited higher binding affinities for nuclear receptors than BPA. Notable analogs included compounds detected in receipts (DD-70, BTUM-70, TGSA, and BisOPP-A), along with a flame retardant, BDP. The possible health hazards linked to exposure to TCS and its mono-hydroxylated metabolites were also found. Further research is needed in order to elucidate the health impacts of these compounds and promote better regulation practices.

Human in vitro percutaneous absorption of bisphenol S: Assessment of the skin reservoir and occlusion effects

Bisphenol S (BPS) was introduced in many industrial and commercial applications as a presumed safer alternative to bisphenol A. However, concerns have been raised surrounding skin absorption and potential persistence of BPS and its related toxic effects in humans. A previous study revealed the likelihood of a reservoir building up in exposed skin. Here, we studied the interactions of BPS solubilized in acetone, ultrapure water, or artificial sebum with freshly excised human skin samples. In vitro tests were performed in static Franz diffusion cells, to explore reservoir and occlusion effects, absorption and metabolism. Most BPS passed through the skin without metabolization - <10% was recovered as glucuronide or sulfate conjugates. Importantly, a substantial amount of BPS persisted in the skin, especially in the stratum corneum. This reservoir could lead to prolonged diffusion into the body after surface cleaning. Occlusion, that may occur with protective clothing, amplified BPS absorption up to six-fold. These findings have implications for occupational settings, highlighting the persistence of BPS contamination even after washing the skin's surface and the need to ensure protective equipment is correctly maintained and used.

High Levels of BPA and BPF Exposure during Pregnancy Are Associated with Lower Birth Weight in Shenyang in Northeast China

Animal studies indicate that bisphenol A (BPA) has obesogenic effects. Recent experiments reported similar endocrine-disrupting effects of bisphenol F (BPF) and bisphenol S (BPS), which are substitutes of BPA. The aim of this study was to investigate the exposure levels of these bisphenols in pregnant women and their effects on the physical development of infants aged 0-12 months. This study recruited pregnant women who gave birth at a hospital between February 2019 and September 2020. Urine samples from these pregnant women in the third trimester of pregnancy were detected by using ultrahigh-performance liquid chromatography-triple quadruple mass spectrometry. Follow-ups at 6 and 12 months of age were conducted by telephone by pediatricians using a structured questionnaire. Multiple linear regressions were used to determine the associations between bisphenol concentrations and infant weight. A total of 113 mother-child pairs had complete questionnaires and urine samples as well as data on newborns aged 6 months and 12 months. The detection rates of urinary BPA, BPF, and BPS in pregnant women were 100, 62.83, and 46.02%, respectively. Their median levels are 5.84, 0.54, and 0.07 μg/L, respectively. Increased urinary BPA and BPF concentrations during pregnancy were significantly associated with lower birth weight (standardized regression coefficients [β] = -0.081 kg, 95% confidence interval [CI]: -0.134 to -0.027; β = -0.049 kg, 95% CI: -0.097 to -0.001). In addition, urinary BPA and BPF concentrations during pregnancy were positively associated with weight growth rate from 0 to 6 months (β = 0.035 kg/mouth, 95% CI: 0.00-0.064; β = 0.028 kg/mouth, 95% CI: 0.006-0.050), especially in female infants (β = 0.054 kg/mouth, 95% CI: 0.015-0.093; β = 0.035 kg/mouth, 95% CI: 0.005-0.065). Therefore, maternal BPA and BPF levels during pregnancy were negatively correlated with birth weight and positively correlated with the growth rate of infant weight at 0-6 months of age, especially in female infants.

Drivers of divergent assessments of bisphenol-A hazards to semen quality by various European agencies, regulators and scientists

The downward revision of the bisphenol A (BPA) Health-based Guidance Value (HBGV) by the European Food Safety Authority (EFSA) has led to disagreements with other regulatory agencies, among them the German Federal Institute for Risk Assessment (BfR). The BfR has recently published an alternative Tolerable Daily Intake (TDI), 1000-times higher than the EFSA HBGV of 0.2 ng/kg/d. While the EFSA value is defined in relation to immunotoxicity, the BfR alternative TDI is based on declines in sperm counts resulting from exposures in adulthood. Earlier, we had used semen quality deteriorations to estimate a BPA Reference Dose (RfD) of 3 ng/kg/d for use in mixture risk assessments of male reproductive health. We derived this estimate from animal studies of gestational BPA exposures which both EFSA and BfR viewed as irrelevant for human hazard characterisations. Here, we identify factors that drive these diverging views. We find that the fragmented, endpoint-oriented study evaluation system used by EFSA and BfR, with its emphasis on data that can support dose-response analyses, has obscured the overall BPA effect pattern relevant to male reproductive effects. This has led to a disregard for the effects of gestational BPA exposures. We also identify problems with the study evaluation schemes used by EFSA and BfR which leads to the omission of entire streams of evidence from consideration. The main driver of the diverging views of EFSA and BfR is the refusal by BfR to accept immunotoxic effects as the basis for establishing an HBGV. We find that switching from immunotoxicity to declines in semen quality as the basis for deriving a BPA TDI by deterministic or probabilistic approaches produces values in the range of 2.4-6.6 ng/kg/d, closer to the present EFSA HBGV of 0.2 ng/kg/d than the BfR TDI of 200 ng/kg/d. The proposed alternative BfR value is the result of value judgements which erred on the side of disregarding evidence that could have supported a lower TDI. The choices made in terms of selecting key studies and methods for dose-response analyses produced a TDI that comes close to doses shown to produce effects on semen quality in animal studies and in human studies of adult BPA exposures.

Comparison of the Effect of BPA and Related Bisphenols on Membrane Integrity, Mitochondrial Activity, and Steroidogenesis of H295R Cells In Vitro

Bisphenol A (BPA) is an endocrine-disruptive chemical that is widely utilized in the production of polycarbonate plastic and epoxy resin, which are used to make a wide range of consumer products, food and drink containers, and medical equipment. When the potential risk of BPA emerged, it was substituted by allegedly less harmful substitutes such as bisphenols S, F, B, and AF. However, evidence suggests that all bisphenols can have endocrine-disruptive effects, while the extent of these effects is unknown. This study aimed to determine effect of BPA, BPAF, BPB, BPF, and BPS on viability and steroidogenesis in human adrenocortical carcinoma cell line in vitro. The cytotoxicity of bisphenols was shown to be considerable at higher doses. However, at low concentrations, it improved viability as well as steroid hormone secretion, indicating that bisphenols have a biphasic, hormetic effect in biological systems. The results are consistent with the hypothesis that bisphenols selectively inhibit some steroidogenic enzymes. These findings suggest that bisphenols have the potential to disrupt cellular steroidogenesis in humans, but substantially more detailed and systematic research is needed to gain a better understanding of the risks associated with bisphenols and their endocrine-disrupting effect on humans and wildlife.

Gestational exposure to bisphenol S induces microvesicular steatosis in male rat offspring by modulating metaflammation

Prenatal exposure to endocrine-disrupting bisphenol A (BPA) shows a long-lasting programming effect on an organ's metabolic function and predisposes it to the risk of adult metabolic diseases. Although a reduced contaminant risk due to "BPA-free" exposure is proposed, limited data on a comparative assessment of gestational exposure to BPS and BPA and their effects on metaflammation in predisposing liver metabolic disease is reported. Pregnant Wistar rats were exposed to BPS and BPA (0.0, 0.4, 4.0 μg/kg bw) via gavage from gestational day 4 to 21, and effects were assessed in the 90 d male offspring. Prenatal BPS-exposed offspring showed a more obesogenic effect than BPA, including changes in body fat distribution, feed efficiency, and leptin signalling. The BPS exposure induced the adipocyte hypertrophy of visceral adipose to a greater extent than BPA. The adipose hypertrophy was augmented by tissue inflammation, endoplasmic reticulum (ER) stress, and apoptosis due to increased expression of pro-inflammatory (IL6, IL1β, CRP, COX2) cytokines, ER stress modulator (CHOP), and apoptotic effector (Caspase 3). The enlarged, stressed, inflamed adipocytes triggered de novo lipogenesis in the bisphenol-exposed offspring liver due to increased expression of cholesterol and lipid biogenesis mediators (srebf1, fasn, acaca, PPARα) concomitant with elevated triacylglycerol (TG) and cholesterol (TC), resulted in impaired hepatic clearance of lipids. The lipogenic effects were also promoted by increased expression of HSD11β1. BPS exposure increased absolute liver weight, discoloration, altered liver lobes more than in BPA. Liver histology showed numerous lipid droplets, and hepatocyte ballooning, upregulated ADRP expression, an increased expression of pro-inflammatory mediators (IL6, CRP, IL1β, TNFα, COX2), enhanced lipid peroxidation in the BPS-exposed offspring's liver suggest altered metaflammation leads to microvesicular steatosis. Overall, gestational BPS exposure demonstrated a higher disruption in metabolic changes than BPA, involving excess adiposity, liver fat, inflammation, and predisposition to steatosis in the adult male offspring.

SMAD signaling pathway is disrupted by BPA via the AMH receptor in bovine granulosa cells†

Significant events that determine oocyte competence occur during follicular growth and oocyte maturation. The anti-Mullerian hormone, a positive predictor of fertility, has been shown to be affected by exposure to endocrine disrupting compounds, such as bisphenol A and S. However, the interaction between bisphenols and SMAD proteins, mediators of the anti-Mullerian hormone pathway, has not yet been elucidated. AMH receptor (AMHRII) and downstream SMAD expression was investigated in bovine granulosa cells treated with bisphenol A, bisphenol S, and then competitively with the anti-Mullerian hormone. Here, we show that 24-h bisphenol A exposure in granulosa cells significantly increased SMAD1, SMAD4, and SMAD5 mRNA expression. No significant changes were observed in AMHRII or SMADs protein expression after 24-h treatment. Following 12-h treatments with bisphenol A (alone or with the anti-Mullerian hormone), a significant increase in SMAD1 and SMAD4 mRNA expression was observed, while a significant decrease in SMAD1 and phosphorylated SMAD1 was detected at the protein level. To establish a functional link between bisphenols and the anti-Mullerian hormone signaling pathway, antisense oligonucleotides were utilized to suppress AMHRII expression with or without bisphenol exposure. Initially, transfection conditions were optimized and validated with a 70% knockdown achieved. Our findings show that bisphenol S exerts its effects independently of the anti-Mullerian hormone receptor, while bisphenol A may act directly through the anti-Mullerian hormone signaling pathway providing a potential mechanism by which bisphenols may exert their actions to disrupt follicular development and decrease oocyte competence.

Neonatal exposure to bisphenol analogues disrupts genital development in male mice

The public concern and governmental regulations on bisphenol A (BPA) have stimulated the development and production of alternative analogues to replace BPA in a myriad of applications. Given the endocrine disrupting activities of BPA and potentially other analogues, the present study investigated and compared the effects of neonatal exposure to BPA, BPB, BPE, BPF, and BPS on the genital development in male mice. Pups were injected subcutaneously on the right shoulder in the mornings of postnatal days P0.5, P2, P4, and P6, resulting in a low dose of 0.05 μg/g body weight (bw)/day and a high dose of 10 μg/g bw/day. Mice were sacrificed at predetermined time and evaluated for gene expression levels (3 days after birth or P3), steroid hormone levels (P5), and morphological changes (P21). The results demonstrated that BPA, BPB, BPE, or BPF significantly shortened glans penis length and anogenital distance, while BPS didn't. Testis weight and anogenital distance were also significantly affected by BPA, BPE or BPF. The results also revealed that bisphenol analogues exposure significantly reduced testosterone levels, and altered the expression levels of developmental genes networks in developing penis of mice. Our data demonstrate that selected bisphenol analogues may possess similar endocrine disrupting effects compared to BPA, and exposure to these analogues could affect reproductive development of male mice. This raises the concern on the environmental and health safety of bisphenol analogues applied as industrial BPA replacements.

Multigenerational Effects of a Complex Human-Relevant Exposure during Folliculogenesis and Preimplantation Embryo Development: The FEDEXPO Study

Animal toxicological studies often fail to mimic the complexity of the human exposome, associating low doses, combined molecules and long-term exposure. Since the reproductive potential of a woman begins in the fetal ovary, the literature regarding the disruption of its reproductive health by environmental toxicants remains limited. Studies draw attention to follicle development, a major determinant for the quality of the oocyte, and the preimplantation embryo, as both of them are targets for epigenetic reprogramming. The "Folliculogenesis and Embryo Development EXPOsure to a mixture of toxicants: evaluation in the rabbit model" (FEDEXPO) project emerged from consideration of these limitations and aims to evaluate in the rabbit model the impacts of an exposure to a mixture of known and suspected endocrine disrupting chemicals (EDCs) during two specific windows, including folliculogenesis and preimplantation embryo development. The mixture combines eight environmental toxicants, namely perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), dichlorodiphenyldichloroethylene (DDE), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), 2,2'4,4'-tetrabromodiphenyl ether (BDE-47), di(2-ethylhexyl) phthalate (DEHP) and bisphenol S (BPS), at relevant exposure levels for reproductive-aged women based on biomonitoring data. The project will be organized in order to assess the consequences of this exposure on the ovarian function of the directly exposed F0 females and monitor the development and health of the F1 offspring from the preimplantation stage. Emphasis will be made on the reproductive health of the offspring. Lastly, this multigenerational study will also tackle potential mechanisms for the inheritance of health disruption via the oocyte or the preimplantation embryo.

Importance of relative binding of bisphenol A and bisphenol S to plasma proteins for predicting their in vivo potencies

Many studies suggest that the potential impact of bisphenol S (BPS) as an endocrine disruptor is comparable to that of bisphenol A (BPA). However, in vitro-to-in vivo and from animal to human extrapolations require knowledge of the plasma free fraction of the active endocrine compounds. The present study aimed to characterise BPA and BPS binding to plasma proteins both in humans and different animal species. The plasma protein binding of BPA and BPS was assessed by equilibrium dialysis in plasma from adult female mice, rats, monkeys, early and late pregnant women as well as paired cord blood, early and late pregnant sheep and foetal sheep. The fraction of free BPA was independent of plasma concentrations and ranged between 4% and 7% in adults. This fraction was 2 to 3.5 times lower than that of BPS in all species except sheep, ranging from 3% to 20%. Plasma binding of BPA and BPS was not affected by the stage of pregnancy, BPA and BPS free fractions representing about 4% and 9% during early and late human pregnancy, respectively. These fractions were lower than the free fractions of BPA (7%) and BPS (12%) in cord blood. Our results suggest that similarly to BPA, BPS is extensively bound to proteins, mainly albumin. The higher fraction of free BPS compared to BPA may have implications for human exposure assessment since BPS free plasma concentrations are expected to be 2 to 3.5 times higher than that of BPA for similar plasma concentration.

RNA binding protein YTHDF1 mediates bisphenol S-induced Leydig cell damage by regulating the mitochondrial pathway of BCL2 and the expression of CDK2-CyclinE1

Bisphenol S (BPS) causes reproductive adverse effects on humans and animals. However, the detailed mechanism is still unclear. This research aimed to clarify the role of RNA binding protein YTHDF1 in Leydig cell damage induced by BPS. The mouse TM3 Leydig cells were exposed to BPS of 0, 20, 40, and 80 μmol/L for 72 h. Results showed that TM3 Leydig cells apoptosis rate markedly increased in BPS exposure group. Meanwhile, the apoptosis-related molecule BCL2 protein level decreased significantly, and Caspase9, Caspase3, and BAX increased significantly. Moreover, the cell cycle was blocked in the G1/S phase, CDK2 and CyclinE1 were considerably down-regulated in BPS exposure groups, and the protein level of RNA binding protein YTHDF1 decreased sharply. Furthermore, after overexpression of YTHDF1, the cell viability significantly increased, and the apoptosis rate significantly decreased in TM3 Leydig cells. In the meantime, BCL2, CDK2, and CyclinE1 were significantly up-regulated, and BAX, Caspase9, and Caspase3 were significantly down-regulated. Conversely, interference with YTHDF1 decreased cell proliferation and promoted apoptosis. Importantly, overexpression of YTHDF1 alleviated the cell viability decrease induced by BPS, and interference with YTHDF1 exacerbated the situation. RIP assays showed that the binding of YTHDF1 to CDK2, CyclinE1, and BCL2 significantly increased after overexpressing YTHDF1. Collectively, our study suggested that YTHDF1 plays an essential role in BPS-induced TM3 Leydig cell damage by regulating CDK2-CyclinE1 and BCL2 mitochondrial pathway at the translational level.

Human biomonitoring guidance values (HBM-GVs) for priority substances under the HBM4EU initiative - New values derivation for deltamethrin and cyfluthrin and overall results

The European Initiative HBM4EU aimed to further establish human biomonitoring across Europe as an important tool for determining population exposure to chemicals and as part of health-related risk assessments, thus making it applicable for policy advice. Not only should analytical methods and survey design be harmonized and quality assured, but also the evaluation of human biomonitoring data. For the health-related interpretation of the data within HBM4EU, a strategy for deriving health-based human biomonitoring guidance values (HBM-GVs) for both the general population and workers was agreed on. On this basis, HBM-GVs for exposure biomarkers of 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), phthalates (diethyl hexyl phthalate (DEHP), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DiBP), butyl benzyl phthalate (BBzP), and bis-(2-propylheptyl) phthalate (DPHP)), bisphenols A and S, pyrethroids (deltamethrin and cyfluthrin), solvents (1-methyl-2-pyrrolidone (NMP), 1-ethylpyrrolidin-2-one (NEP), N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC)), the heavy metal cadmium and the mycotoxin deoxynivalenol (DON) were developed and assigned a level of confidence. The approach to HBM-GV derivations, results, and limitations in data interpretation with special focus on the pyrethroids are presented in this paper.

Critical Overview on Endocrine Disruptors in Diabetes Mellitus

Diabetes mellitus is a major public health problem in all countries due to its high human and economic burden. Major metabolic alterations are associated with the chronic hyperglycemia that characterizes diabetes and causes devastating complications, including retinopathy, kidney failure, coronary disease and increased cardiovascular mortality. The most common form is type 2 diabetes (T2D) accounting for 90 to 95% of the cases. These chronic metabolic disorders are heterogeneous to which genetic factors contribute, but so do prenatal and postnatal life environmental factors including a sedentary lifestyle, overweight, and obesity. However, these classical risk factors alone cannot explain the rapid evolution of the prevalence of T2D and the high prevalence of type 1 diabetes in particular areas. Among environmental factors, we are in fact exposed to a growing amount of chemical molecules produced by our industries or by our way of life. In this narrative review, we aim to give a critical overview of the role of these pollutants that can interfere with our endocrine system, the so-called endocrine-disrupting chemicals (EDCs), in the pathophysiology of diabetes and metabolic disorders.

Bisphenol A and its substitutes in the aquatic environment: Occurrence and toxicity assessment

Bisphenol A is classified as a high production volume chemical commonly used in the manufacture of polycarbonate plastics, epoxy resins and thermal paper. The endocrine disrupting properties of this xenobiotic have led to the restriction and prohibition of its use in many consumer products. To date, many chemical compounds with a chemical structure similar to bisphenol A have been used in consumer products as its replacement. The ubiquitous occurrence of bisphenol A and its substitutes in the environment and their endocrine activity as well as adverse effects on aquatic organisms is a global concern, especially because many available literature reports show that many substitutes (e.g. bisphenol AF, bisphenol AP, bisphenol B, bisphenol C, bisphenol F, bisphenol G, bisphenol FL, tetrabromobisphenol A) exert adverse effects on aquatic organisms, similar to, or even stronger than bisphenol A. Therefore, the objective of this paper is to provide a comprehensive overview of the production, sources, occurrence and associated toxicity, as well as the endocrine activity of bisphenol A and its substitutes on aquatic species. The environmental levels and ecotoxicological data presented in this review allowed for a preliminary assessment and prediction of the risk of bisphenol A and its substitutes for aquatic organisms. Furthermore, the data collected in this paper highlight that several compounds applied in bisphenol A-free products are not safe alternatives and regulations regarding their use should be introduced.

Application of AOPs to assist regulatory assessment of chemical risks - Case studies, needs and recommendations

While human regulatory risk assessment (RA) still largely relies on animal studies, new approach methodologies (NAMs) based on in vitro, in silico or non-mammalian alternative models are increasingly used to evaluate chemical hazards. Moreover, human epidemiological studies with biomarkers of effect (BoE) also play an invaluable role in identifying health effects associated with chemical exposures. To move towards the next generation risk assessment (NGRA), it is therefore crucial to establish bridges between NAMs and standard approaches, and to establish processes for increasing mechanistically-based biological plausibility in human studies. The Adverse Outcome Pathway (AOP) framework constitutes an important tool to address these needs but, despite a significant increase in knowledge and awareness, the use of AOPs in chemical RA remains limited. The objective of this paper is to address issues related to using AOPs in a regulatory context from various perspectives as it was discussed in a workshop organized within the European Union partnerships HBM4EU and PARC in spring 2022. The paper presents examples where the AOP framework has been proven useful for the human RA process, particularly in hazard prioritization and characterization, in integrated approaches to testing and assessment (IATA), and in the identification and validation of BoE in epidemiological studies. Nevertheless, several limitations were identified that hinder the optimal usability and acceptance of AOPs by the regulatory community including the lack of quantitative information on response-response relationships and of efficient ways to map chemical data (exposure and toxicity) onto AOPs. The paper summarizes suggestions, ongoing initiatives and third-party tools that may help to overcome these obstacles and thus assure better implementation of AOPs in the NGRA.

Multi-omics approaches for remediation of bisphenol A: Toxicity, risk analysis, road blocks and research perspectives

In this "plastic era" with the increased use of plastic in day today's life the accumulation of its degraded products like microplastics or plastic additives such as Bisphenol A(BPA) is also increasing. BPA is an endocrine-disrupting chemical used as a plasticizing agent in clear plastic, building materials, coatings, and epoxy resin. Several enzymes including laccases and lipases have been studied for the reduction of BPA toxicity. Over the decades of encountering these toxicants, microorganisms have evolved to degrade different classes of plastic additives. Since the degradation of BPA is a long process thus meta-omics approaches have been employed to identify the active microbiota and microbial dynamics involved in the mitigation of BPA. It is also necessary to investigate the impact of processing activities on transit of BPA in food items and to limit its entrance in food world. This review summarizes a comprehensive overview on BPA sources, toxicity, bio-based mitigation approaches along with a deeper understanding of multi-omics approaches for its reduction and risk analysis. Knowledge gaps and opportunities have been comprehensively compiled that would aid the state-of-the-art information in the available literature for the researchers to further address this issue.

Cytotoxic and genotoxic evaluation of bisphenol S on onion root tips by Allium cepa and comet tests

Bisphenol S (BPS) is an analog of bisphenol A, which is used as substitute of BPA in many products like airport luggage tags, baby bottles, plastics, and epoxy resins etc. Bisphenol S can cause toxic effects in different organisms, i.e., mice, rat, zebrafish, and C.elegans, etc. Bisphenol S is also known as "endocrine disruptor" due to its ability to mimic the endocrine receptors. So, the aim of this study was to evaluate the cytotoxic and genotoxic effects of bisphenol S on meristematic cells present in onion root tips through Allium cepa (A.cepa) and comet tests. Root growth inhibition was evaluated by root growth inhibition assay. Mitotic index (MI) and chromosomal aberrations (CAs) were assessed by A.cepa assay. DNA damage was evaluated by comet assay. Root growth of A.cepa was inhibited due to bisphenol S. LC50 value calculated by root growth inhibition assay for bisphenol S was (2.6±0.63, 50 μg/ml). Mitotic index was reduced, and chromosomal aberrations were observed, i.e., stickiness, polyploidy, and disturbed ana-telophase in anaphase and telophase stages of mitosis. In case of comet assay, DNA damage was increased in statistically significant manner (p ≤ 0.05). It was concluded that bisphenol S constitutes cytotoxic and genotoxic effects on A. cepa root meristematic cells. Moreover, it is suggested to explore more toxicity studies of bisphenol S at molecular level.

Exposure to either Bisphenol A or S Represents a Risk for Crucial Behaviors for Pup Survival, Such as Spontaneous Maternal Behavior in Mice

INTRODUCTION

Maternal behavior depends on a multitude of factors, including environmental ones, such as Endocrine Disrupting Chemicals (EDCs), which are increasingly attracting attention. Bisphenol A (BPA), an EDC present in plastic, is known to exert negative effects on maternal behavior. Bisphenol S (BPS), a BPA substitute, seems to share some endocrine disrupting properties. In this study, we focused on the analysis of the effects of low-dose (i.e., 4 µg/kg body weight/day, EFSA TDI for BPA) BPA or BPS exposure throughout pregnancy and lactation in mice.

METHODS

We administered adult C57BL/6 J females orally BPA, BPS, or vehicle from mating to offspring weaning. We assessed the number of pups at birth, the sex ratio, and the percentage of dead pups in each litter, and during the first postnatal week, we observed spontaneous maternal behavior. At the weaning of the pups, we sacrificed the dams and analyzed the oxytocin system, known to be involved in the control of maternal care, in the hypothalamic magnocellular nuclei.

RESULTS

At birth, pups from BPA-treated dams tended to have a lower male-to-female ratio compared to controls, while the opposite was observed among BPS-treated dams' litters. During the first postnatal week, offspring mortality impacted differentially in the BPA and BPS litters, with more female dead pups among the BPA litters, while more male dead pups in the BPS litters, sharpening the difference in the sex ratio. BPA- and BPS-treated dams spent significantly less time in pup-related behaviors than controls. Oxytocin immunoreactivity in the paraventricular and supraoptic nuclei was increased only in the BPA-treated dams.

DISCUSSION/CONCLUSIONS

Alterations in maternal care, along with the treatment itself, may affect, later in life, the offspring's physiology and behavior. Exposure to BPs during sensitive developmental periods represents a risk for both dams and offspring, even at low environmentally relevant doses, through the functional alteration of neural circuits controlling fundamental behaviors for pup survival, such as maternal behaviors.

Combined exposures to bisphenols, polychlorinated dioxins, paracetamol, and phthalates as drivers of deteriorating semen quality

BACKGROUND

Semen quality in men continues to decline in Western countries, but the contours of the issue remain obscure, in relation to contributing chemicals.

OBJECTIVES

To obtain more clarity about the chemicals that drive the deterioration of semen quality, we conducted a mixture risk assessment based on European exposures.

METHODS

We included chemicals capable of affecting semen quality after prenatal exposures, among them androgen receptor antagonists, substances that disrupt prostaglandin signalling, suppress testosterone synthesis, inhibit steroidogenic enzymes or activate the aryl hydrocarbon receptor. We employed the Hazard Index approach (HI), based on risk quotients of exposures in Europe and reference doses for reductions in semen quality. By summing up the risk quotients of the 29 chemicals included in the assessment we examined fold-exceedances of "acceptable" mixture exposures relative to an index value of 1. For bisphenols A, F, S, phthalates DEHP, DnBP, BBzP, DiNP, n-butyl paraben and paracetamol we relied on biomonitoring studies in which these 9 chemicals were measured together in the same subjects. This allowed us to construct personalised Hazard Indices.

RESULTS

Highly exposed subjects experienced combined exposures to the 9 chemicals that exceeded the index value of 1 by more than 100-fold; the median was a 17-fold exceedance. Accounting for median background exposures to the remaining 20 chemicals added a Hazard Index of 1.39. Bisphenol A made the largest contribution to the HI, followed by polychlorinated dioxins, bisphenols S and F and DEHP. Eliminating bisphenol A alone would still leave unacceptably high mixture risks. Paracetamol is also a driver of mixture risks among subjects using the drug.

CONCLUSIONS

Tolerable exposures to substances associated with deteriorations of semen quality are exceeded by a large margin. Bisphenols, polychlorinated dioxins, phthalates and analgesics drive these risks. Dedicated efforts towards lowering exposures to these substances are necessary to mitigate risks.

Human Biomonitoring Guidance Values (HBM-GVs) for Bisphenol S and Assessment of the Risk Due to the Exposure to Bisphenols A and S, in Europe

Within the European Joint Programme HBM4EU, Human Biomonitoring Guidance Values (HBM-GVs) were derived for several prioritised substances. In this paper, the derivation of HBM-GVs for the general population (HBM-GVGenPop) and workers (HBM-GVworker) referring to bisphenol S (BPS) is presented. For the general population, this resulted in an estimation of the total urinary concentration of BPS of 1.0 µg/L assuming a 24 h continuous exposure to BPS. For workers, the modelling was refined in order to reflect continuous exposure during the working day, leading to a total urinary concentration of BPS of 3.0 µg/L. The usefulness for risk assessment of the HBM-GVs derived for BPS and bisphenol A (BPA) is illustrated. Risk Characterisation Ratios (RCRs) were calculated leading to a clear difference between risk assessments performed for both bisphenols, with a very low RCR regarding exposure to BPA., contrary to that obtained for BPS. This may be due to the endocrine mediated endpoints selected to derive the HBM-GVs for BPS, whereas the values calculated for BPA are based on the temporary Tolerable Daily Intake (t-TDI) from EFSA set in 2015. A comparison with the revised TDI recently opened for comments by EFSA is also discussed. Regarding the occupational field, results indicate that the risk from occupational exposure to both bisphenols cannot be disregarded.

Bisphenol S exposure induces intestinal inflammation: An integrated metabolomic and transcriptomic study

As a typical substitute for bisphenol A (BPA), bisphenol S (BPS) is raising concerns due to the potential adverse effects on human health. Limit evidence is available to understand the toxicity of BPS to the digestive system, especially for intestine. In this study, we aimed to investigate the potential effects and underlying mechanisms of BPS exposure on human colon mucosal epithelial cells (NCM460). Our results showed that BPS exposure significantly increased the production of pro-inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ) and interleukin-17A (IL-17A). The tight junctions of the cells has been destroyed by BPS exposure, which was characterized by a down-regulation of the tight junction proteins (Claudin1 and zonula occluden 1 (ZO1)). A multi-omics study explored the underlying mechanisms based on the metabolomic and transcriptomic responses. A variety of neurotransmitters increased significantly after exposure to BPS. The top enriched pathway was "glutamatergic synapse", which was activated by BPS exposure, resulting in the up-regulation of l-glutamine. Links were observed among the altered metabolites, genes and cytokines. Our results indicate that exposure to BPS may disturb the balance of gut-brain axis, leading to the production of inflammatory cytokines and the destruction of tight junction in NCM460 cells. It provides new clue for the development of intestinal inflammation in terms of the environmental pollutants.

Bisphenols A and F, but not S, induce apoptosis in bovine granulosa cells via the intrinsic mitochondrial pathway

With the gradual decline in global fertility rates, there is a need to identify potential contributing factors, their mechanisms of actions and investigate possible solutions to reverse the trend. Endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), are environmental toxicants that are known to negatively impact reproductive functions. As such, the use of BPA in the manufacturing industry has slowly been replaced by analogs, including bisphenol S (BPS) and bisphenol F (BPF), despite limited knowledge available regarding their impact on health and their safety. The following study investigates the effects of BPA, BPS and BPF at a concentration of 0.5 μg/mL and 50 μg/mL on bovine granulosa cell apoptosis, with the ultimate goal of determining how they may impact oocyte competence and, thus, overall fertility. The underlying hypothesis is that bisphenols disrupt the granulosa cell environment surrounding the oocyte inducing excessive apoptosis via the intrinsic mitochondrial pathway. To test this hypothesis, apoptosis was measured following a time- and dose-dependent exposure to all three bisphenols by flowcytometry paired with annexin V/PI staining as well as by quantification of key genes belonging to the intrinsic apoptotic pathway both at the mRNA and protein levels. The results of this study report that BPA and BPF reduce cell viability through reduced cell counts and increased apoptosis. This increase is due, in part, to the induction of apoptotic genes of the intrinsic pathway of apoptosis. Additionally, this study also suggests that BPS may not act on the intrinsic mitochondrial apoptotic pathway in bovine granulosa cells. Overall, this study allows us to establish potential apoptotic pathways activated by bisphenols as well as compare the relative apoptotic activities of BPA to its most widespread analogs.