Prolonged Exposure to Bisphenol A from Single Dermal Contact Events

Bisphenol A and its potential mechanism of action for reproductive toxicity

Bisphenol A (BPA) is an organic synthetic chemical used worldwide. Billions of pounds of BPA are produced annually through industrial processes to be used in commercial products, making human exposure to BPA ubiquitous. Concerns have been raised due to the potential adverse health effects of BPA, specifically in vulnerable populations, such as pregnant persons and children. BPA is an endocrine-disrupting chemical, and through this function has been linked to reproductive toxicity. We review BPA's historical and current use, health and safety concerns and regulations, sources of exposure, and evidence for male and female reproductive toxicity. Evidence from epidemiological and animal studies idenfity that low- and high-exposure levels of BPA (prenatal, postnatal and adulthood exposure) can adversely affect male and female fertility and reproductive organs. While the cause of BPA-induced reproductive toxicity is not fully understood, we discuss BPA's estrogenic and androgenic activity, and its ability to disrupt the hypothalamic-pituitary-gonadal axis as a potential associated mechanism. There are significant differences in tolerable daily intakes of BPA set by global agencies, making interpretation of previous and emerging research findings challenging and inconsistent. Although BPA is deemed toxic by some government agencies, most do not currently consider it a health risk due to low populational exposure levels. However, we highlight evidence that even at acute, low exposure, BPA can adversely affect reproductive function. We recommend continuing research into the adverse effects of BPA on human health and revisiting the regulatory measures of BPA to limit exposure and promote public awareness of its potential to cause reproductive toxicity.

Infants exposure to chemicals in diapers: A review and perspective

Diapers are a staple care product for infants, yet concerns persist regarding the potential risks posed by dermal exposure to chemicals through their usage. This review provides a comprehensive summary of reported chemicals, highlighting the frequent detection of polychlorodibenzo-p-dioxins (PCDDs), phthalates (PAEs), volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), bisphenols (BPs), organotins, and heavy metals. Disposable diapers commonly exhibit higher concentrations of VOCs, PAEs, BPs, and heavy metals than other chemicals. Our estimation reveals formaldehyde as posing the highest dermal exposure dose, reaching up to 0.018 mg/kg bw/day. Conversely, perfluorooctanoic acid (PFOA) exhibits lower exposure, but its non-cancer hazard quotient (0.062) is the highest. In most scenarios, the risk of chemical exposure through diapers for infants is deemed acceptable, while the risk is higher under some extreme exposure scenarios. Using the cancer slope factor recently suggested by U.S. EPA, the cancer risk in diapers raised by PFOA is 5.5 × 10-5. It should be noted that our estimation is approximately 1000-10,000 folds lower than some previous estimations. The high uncertainties associated with exposure and risk estimations are primarily raised by unclear parameters related to chemical migration coefficients, absorption factors, concentrations, and toxicity data for skin exposure, which requires research attention in future. Besides that, future research endeavors should prioritize the identification of potential toxic chemicals and the development of hygiene guidelines and standards.

Bisphenols in daily clothes from conventional and recycled material: evaluation of dermal exposure to potentially toxic substances

Given the increasing concern about chemical exposure from textiles, our study examines the risks of dermal exposure to bisphenol A (BPA), bisphenol S (BPS), bisphenol B (BPB) and bisphenol F (BPF) from conventional and recycled textiles for adults, aiming to obtain new data, assess exposure, and evaluate the impact of washing on bisphenol levels. A total of 57 textile samples (33 from recycled and 24 from conventional material) were subjected to ultrasound-assisted extraction (UAE) followed by ultra-high performance liquid chromatography with tandem mass spectrometry analysis (UHPLC-MS/MS). The BPA and BPS concentrations varied widely (BPA: < 0.050 to 625 ng/g, BPS: 0.277-2,474 ng/g). The median BPA content in recycled textiles (13.5 ng/g) was almost twice as high as that of 7.66 ng/g in conventional textiles. BPS showed a median of 1.85 ng/g in recycled textiles and 3.42 ng/g in conventional textiles, indicating a shift from BPA to BPS in manufacturing practices. Simulated laundry experiments showed an overall reduction in bisphenols concentrations after washing. The study also assessed potential health implications via dermal exposure to dry and sweat-wet textiles compared to a tolerable daily intake (TDI) of 0.2 ng/kg bw/day for BPA set by the European Food Safety Authority (EFSA). Exposure from dry textiles remained below this threshold, while exposure from wet textiles often exceeded it, indicating an increased risk under conditions that simulate sweating or humidity. By finding the widespread presence of bisphenols in textiles, our study emphasises the importance of being aware of the potential risks associated with recycling materials as well as the benefits.

Critical role of endoplasmic reticulum stress on bisphenol A-induced cytotoxicity in human keratinocyte HaCaT cells

Bisphenol A (BPA) is widely used in plastic and paper products, and its exposure can occur through skin contact or oral ingestion. The hazardous effects of BPA absorbed through the skin may be more severe; however, few studies have investigated the skin toxicity of BPA. This study investigated the effects of BPA on human epidermal keratinocyte cell lines, which is relevant for skin exposure. BPA treatment reduced cell viability in a time- and concentration-dependent manner and elevated oxidative and endoplasmic reticulum (ER) stress. N-acetylcysteine (NAC), an oxidative stress inhibitor, reduced BPA-induced reactive oxygen species (ROS) levels. However, only 10% of the decreased cell viability was restored at the highest NAC concentration. Treatment with tauroursodeoxycholic acid (TUDCA), which is an ER stress inhibitor, effectively countered the increase in ER stress-related proteins induced by BPA. Moreover, TUDCA treatment led to a reduction in oxidative stress, as demonstrated by the decrease in ROS levels, maintenance of mitochondrial membrane potential, and modulation of stress signaling proteins. Consequently, TUDCA significantly improved BPA-induced cytotoxicity in a concentration-dependent manner. Notably, combined treatment using TUDCA and NAC further reduced the BPA-induced ROS levels; however, no significant difference in cell viability was observed compared with that for TUDCA treatment alone. These findings indicated that the oxidative stress observed following BPA exposure was exacerbated by ER stress. Moreover, the principal factor driving BPA-induced cytotoxicity was indeed ER stress, which has potential implications for developing therapeutic strategies for diseases associated with similar stress responses.

Penetration pathways, influencing factors and predictive models for dermal absorption of exobiotic molecules: A critical review

This review provides a comprehensive summary of the skin penetration pathways of xenobiotics, including metals, organic pollutants, and nanoparticles (NPs), with a particular focus on the methodologies employed to elucidate these penetration routes. The impacts of the physicochemical properties of exogenous substances and the properties of solvent carriers on the penetration efficiencies were discussed. Furthermore, the review outlines the steady-state and transient models for predicting the skin permeability of xenobiotics, emphasizing the models which enable realistic visualization of pharmaco-kinetic phenomena via detailed geometric representations of the skin microstructure, such as stratum corneum (SC) (bricks and mortar) and skin appendages (hair follicles and sebaceous gland units). Limitations of published research, gaps in current knowledge, and recommendations for future research are highlighted, providing insight for a better understanding of the skin penetration behavior of xenobiotics and associated health risks in practical application contexts.

Application of the Key Characteristics of Carcinogens to Bisphenol A

The ten key characteristics (KCs) of carcinogens are based on characteristics of known human carcinogens and encompass many types of endpoints. We propose that an objective review of the large amount of cancer mechanistic evidence for the chemical bisphenol A (BPA) can be achieved through use of these KCs. A search on metabolic and mechanistic data relevant to the carcinogenicity of BPA was conducted and web-based software tools were used to screen and organize the results. We applied the KCs to systematically identify, organize, and summarize mechanistic information for BPA, and to bring relevant carcinogenic mechanisms into focus. For some KCs with very large data sets, we utilized reviews focused on specific endpoints. Over 3000 studies for BPA from various data streams (exposed humans, animals, in vitro and cell-free systems) were identified. Mechanistic data relevant to each of the ten KCs were identified, with receptor-mediated effects, epigenetic alterations, oxidative stress, and cell proliferation being especially data rich. Reactive and bioactive metabolites are also associated with a number of KCs. This review demonstrates how the KCs can be applied to evaluate mechanistic data, especially for data-rich chemicals. While individual entities may have different approaches for the incorporation of mechanistic data in cancer hazard identification, the KCs provide a practical framework for conducting an objective examination of the available mechanistic data without a priori assumptions on mode of action. This analysis of the mechanistic data available for BPA suggests multiple and inter-connected mechanisms through which this chemical can act.

Bisphenols in Aquatic Products from South China: Implications for Human Exposure

In this study, 245 representative samples of aquatic products were selected from local markets in Shenzhen by stochastic sampling. The samples comprised eight species and fell into three aquatic product categories: fish, crustaceans, and bivalves. A total of eight BPs were determined by liquid chromatography coupled with mass spectrometry, namely, bisphenol A (BPA), bisphenol AF (BPAF), bisphenol AP (BPAP), bisphenol B (BPB), bisphenol S (BPS), bisphenol P (BPP), bisphenol Z (BPZ), and bisphenol F (BPF). All BPs were detected in aquatic products, except for BPAF, indicating pervasive contamination by BPs in aquatic products. BPS demonstrated the highest detection rate both before and after enzymatic hydrolysis, whereas BPAP exhibited the lowest detection rate before enzymatic hydrolysis and BPB displayed the lowest detection rate after enzymatic hydrolysis. The concentration difference before and after enzymatic hydrolysis proved to be statistically significant. Moreover, 49-96% of BPs in aquatic products were found in the combined state, underscoring the essentiality of conducting detections on aquatic product samples following enzymatic hydrolysis. While the health risks associated with ingesting BPs residues through aquatic product consumption were found to be minimal for residents at risk of exposure, the results suggest the necessity for more stringent regulations governing the consumption of aquatic products.

Nonspecific immune, histology and accumulation of marine worm, Urechis unicinctus in response to bisphenol A (BPA)

Bisphenol A (BPA) is one of the environmental endocrine disruptors, due to its chemical stability it exists in abundant concentrations in water and soil consequently accumulating in the food chain and causing many endocrine-related health problems. So far, studies on the effects of BPA on marine invertebrates have focused on acute toxicity, endocrine regulation, reproduction, and development. However, fewer studies have been conducted on marine benthos. The current study aimed to detect the accumulation of BPA and its impact on tissue structure, antioxidant capacity, and immune indexes in marine worm, Urechis unicinctus. U. unicinctus, as a common marine benthic animal, were exposed to different concentrations of BPA. Blood cells and intestinal tract were taken for tissue structure inspection, and supernatant of the coelomic fluid was collected for oxidative and antioxidant biomarkers. Results showed that the accumulation of BPA in muscles of U. unicinctus tended to increase with exposure time. BPA induced a rise in H2O2 and MDA content, and altered the activities of CAT, T-SOD, GST, LSZ and ACP, weaken the immune system functions. Moreover, pathological observation showed that BPA caused severe histopathology in the respiratory intestine, stomach, and midgut. These results will be helpful to understand the response mechanism of U. unicinctus under BPA exposure and provide a reference for controlling the aquaculture conditions and marine water quality of U. unicinctus.

Particle size-dependent and route-specific exposure to liquid crystal monomers in indoor air: Implications for human health risk estimations

In indoor environments, liquid crystal monomers (LCMs) released from display devices is a significant concern, necessitating a comprehensive investigation into their distribution behaviors and potential health risks. Herein, we examined various LCMs in educational and workplace air and compared their associated health risks through inhalation and dermal absorption routes. 4-propyl-4'-vinylbicyclohexyl (3VbcH) and 4,4'-bis(4-propylcyclohexyl) biphenyl (b3CHB) with median concentrations of 101 and 1460 pg m-3, were the predominant LCMs in gaseous and particulate phases, respectively. Composition and concentration of LCMs differed substantially between sampling locations due to the discrepancy in the quantity, types, and brands of electronic devices in each location. Three models were further employed to estimate the gas-particle partitioning of LCMs and compared with the measured data. The results indicated that the HB model exhibited the best overall performance, while the LMY model provided a good fit for LCMs with higher log Koa (>12.48). Monte Carlo simulation was used to estimate and compared the probabilistic daily exposure dose and potential health risks. Inhalation exposure of LCMs was significantly greater than the dermal absorption by approximately 1-2 orders of magnitude, implying that it was the primary exposure route of human exposure to airborne LCMs. However, certain LCMs exhibited comparable or higher exposure levels via the dermal absorption route due to the significant overall permeability coefficient. Furthermore, the particle size was discovered to impact the daily exposure dose, contingent on the particle mass-transfer coefficients and accumulation of LCMs on diverse particle sizes. Although the probabilistic non-carcinogenic risks of LCMs were relatively low, their chronic effects on human beings merit further investigations. Overall, this study provides insights into the contamination and potential health risks of LCMs in indoor environments, underscoring the importance of considering particle sizes and all possible exposure pathways in estimating human health risks caused by airborne organic contaminants.

The Role of Endocrine Disruptors Bisphenols and Phthalates in Obesity: Current Evidence, Perspectives and Controversies

Excess body weight constitutes one of the major health challenges for societies and healthcare systems worldwide. Besides the type of diet, calorie intake and the lack of physical exercise, recent data have highlighted a possible association between endocrine-disrupting chemicals (EDCs), such as bisphenol A, phthalates and their analogs, and obesity. EDCs represent a heterogeneous group of chemicals that may influence the hormonal regulation of body mass and adipose tissue morphology. Based on the available data from mechanistic, animal and epidemiological studies including meta-analyses, the weight of evidence points towards the contribution of EDCs to the development of obesity, associated disorders and obesity-related adipose tissue dysfunction by (1) impacting adipogenesis; (2) modulating epigenetic pathways during development, enhancing susceptibility to obesity; (3) influencing neuroendocrine signals responsible for appetite and satiety; (4) promoting a proinflammatory milieu in adipose tissue and inducing a state of chronic subclinical inflammation; (5) dysregulating gut microbiome and immune homeostasis; and (6) inducing dysfunction in thermogenic adipose tissue. Critical periods of exposure to obesogenic EDCs are the prenatal, neonatal, pubertal and reproductive periods. Interestingly, EDCs even at low doses may promote epigenetic transgenerational inheritance of adult obesity in subsequent generations. The aim of this review is to summarize the available evidence on the role of obesogenic EDCs, specifically BPA and phthalate plasticizers, in the development of obesity, taking into account in vitro, animal and epidemiologic studies; discuss mechanisms linking EDCs to obesity; analyze the effects of EDCs on obesity in critical chronic periods of exposure; and present interesting perspectives, challenges and preventive measures in this research area.

Bisphenols and alternative developers in thermal paper receipts from the U.S. market assessed by Fourier transform infrared spectroscopy

Cash register receipts made of thermal paper expose workers and shoppers to endocrine-disrupting chemicals and contaminate paper recycling streams. In 2022, 571 receipts were collected from retail stores in the United States and tested for developer chemicals using attenuated total reflection infrared spectroscopy. The results were compared to a 2017 study of 167 receipts to determine changes in color developer use over time. Receipts were tested as-is and a subset were additionally subjected to a simple extraction that improved detection of receipt chemicals. Bisphenol S was the most frequently detected developer (85% of tested receipts), followed by Pergafast 201 (12%), bisphenol A (1%); and Appvion Alpha Free, D-8, and NKK-1304 (each below 1%). NKK-1304 is reported here for the first time in a scientific journal. The frequency of bisphenol A usage in receipts decreased and the frequency of bisphenol S and Pergafast 201 increased between 2017 and 2022, particularly among large companies. National retailers were more likely than regional or local retailers to have adopted non-bisphenol alternatives. Potential health and environmental hazards of the detected developer chemicals and strategies for reduction are discussed.

Large-scale biomonitoring of bisphenol analogues and their metabolites in human urine from Guangzhou, China: Implications for health risk assessment

Bisphenol analogues (BPs) are ubiquitous in the environment and have gained significant attention regarding their associated health risks. However, there is a lack of comprehensive biomonitoring data on BPs and their metabolites in human urine. To address this, we conducted a study evaluate the exposure to BPs in the general population of Guangzhou, China. A total of 1440 urine samples were collected from volunteers and analyzed for the presence of BPs and their metabolites after being pooled into 36 groups based on age and gender. The findings revealed the common detection of ten free-form BPs, as well as the urinary metabolites of BPA and BPS, in the pooled urine samples. BPA was the predominant free-form compound, constituting 50% of the total BPs. The primary urinary metabolites of BPA and BPS are BPA-G and BPS-G, respectively, indicating glucuronidation as their primary metabolic pathway. The composition of urinary metabolites of BPA and BPS varied by age and sex, while the concentration of total BPs in urine was not significantly associated with age and sex. Enzymatic hydrolysis yielded a mean amplification of individual BPs concentrations in urine samples ranging from 1.8 times (BPA) to 4.6 times (BPS). Based on the outcomes, it was estimated that conjugated forms accounted for 96.9%, 96.2%, 94.7%, 94.1%, 92.6%, 89.1%, 87.3%, 87.2%, 87.1% and 85.8% of BPP, BPAF, BPZ, BPE, BPAP, BPF, BPA, BPC, BPS and BPF, respectively, in the pooled urine samples. Preliminary risk assessments indicated that the estimated daily intake of BPA was much higher than the latest proposed tolerable daily intake. Due to the unavailability of health-based guideline values for alternative BPs, some of them exhibit daily intakes comparable to BPA, implying that greater attention should be paid to health risks associated with exposure to BPs.

A review on immunomodulatory effects of BPA analogues

Bisphenol A (BPA) is a known endocrine disruptor found in many consumer products that humans come into contact with on a daily basis. Due to increasing concerns about the safety of BPA and the introduction of new legislation restricting its use, industry has responded by adopting new, less studied BPA analogues that have similar polymer-forming properties. Some BPA analogues have already been shown to exhibit effects similar to BPA, for example, contributing to endocrine disruption through agonistic or antagonistic behaviour at various nuclear receptors such as estrogen (ER), androgen (AR), glucocorticoid (GR), aryl hydrocarbon (AhR), and pregnane X receptor (PXR). Since the European Food Safety Authority (EFSA) issued a draft re-evaluation of BPA and drastically reduced the temporary tolerable daily intake (t-TDI) of BPA from 4 mg/kg body weight/day to 0.2 ng/kg body weight/day due to increasing concern about the toxic properties of BPA, including its potential to disrupt immune system processes, we conducted a comprehensive review of the immunomodulatory activity of environmentally abundant BPA analogues. The results of the review suggest that BPA analogues may affect both the innate and acquired immune systems and can contribute to various immune-mediated conditions such as hypersensitivity reactions, allergies, and disruption of the human microbiome.

The State of Research and Weight of Evidence on the Epigenetic Effects of Bisphenol A

Bisphenol A (BPA) is a high-production-volume chemical with numerous industrial and consumer applications. BPA is extensively used in the manufacture of polycarbonate plastics and epoxy resins. The widespread utilities of BPA include its use as internal coating for food and beverage cans, bottles, and food-packaging materials, and as a building block for countless goods of common use. BPA can be released into the environment and enter the human body at any stage during its production, or in the process of manufacture, use, or disposal of materials made from this chemical. While the general population is predominantly exposed to BPA through contaminated food and drinking water, non-dietary exposures through the respiratory system, integumentary system, and vertical transmission, as well as other routes of exposure, also exist. BPA is often classified as an endocrine-disrupting chemical as it can act as a xenoestrogen. Exposure to BPA has been associated with developmental, reproductive, cardiovascular, neurological, metabolic, or immune effects, as well as oncogenic effects. BPA can disrupt the synthesis or clearance of hormones by binding and interfering with biological receptors. BPA can also interact with key transcription factors to modulate regulation of gene expression. Over the past 17 years, an epigenetic mechanism of action for BPA has emerged. This article summarizes the current state of research on the epigenetic effects of BPA by analyzing the findings from various studies in model systems and human populations. It evaluates the weight of evidence on the ability of BPA to alter the epigenome, while also discussing the direction of future research.

Health Risks Posed by Dermal and Inhalation Exposure to High Concentrations of Chlorinated Paraffins Found in Soft Poly(vinyl chloride) Curtains

Chlorinated paraffins (CPs) are used in many products, including soft poly(vinyl chloride) curtains, which are used in many indoor environments. Health hazards posed by CPs in curtains are poorly understood. Here, chamber tests and an indoor fugacity model were used to predict CP emissions from soft poly(vinyl chloride) curtains, and dermal uptake through direct contact was assessed using surface wipes. Short-chain and medium-chain CPs accounted for 30% by weight of the curtains. Evaporation drives CP migration, like for other semivolatile organic plasticizers, at room temperature. The CP emission rate to air was 7.09 ng/(cm² h), and the estimated short-chain and medium-chain CP concentrations were 583 and 95.3 ng/m³ in indoor air 21.2 and 172 μg/g in dust, respectively. Curtains could be important indoor sources of CPs to dust and air. The calculated total daily CP intakes from air and dust were 165 ng/(kg day) for an adult and 514 ng/(kg day) for a toddler, and an assessment of dermal intake through direct contact indicated that touching just once could increase intake by 274 μg. The results indicated that curtains, which are common in houses, could pose considerable health risks through inhalation of and dermal contact with CPs.

Are human exposure assessment the same for non-persistent organic chemicals? -from the lens of urinary variability and predictability

Assessment of human exposure to mixtures of non-persistent chemicals from food matrices and consumer products requires accurate characterization and estimation of their preceding exposure levels, and assessment sampling approaches for these varying chemicals remain disputable. Here, we used high-throughput targeted method to quantify urinary concentrations of 59 most common non-persistent chemicals (6 parabens, 14 bisphenols, 1 triclosan, 7 benzophenones, 2 dichlorophenols, 13 phthalate metabolites and 16 antioxidants) in 158 consecutive spot samples from 11 participants over three consecutive days, 33 samples of which were first morning voids (FMVs). We found 49 chemicals with detection frequencies over 70 % in all urine samples. Principal component analyses showed greater inter-person variations than each person's inter-day variations. Intraclass correlation coefficient (ICC) to assess the reproducibility of targeted chemicals demonstrated that regardless of sampling approaches, dichlorophenols, most parabens, benzophenones and triclosan showed moderate to high reproducibility (0.445 < ICC < 0.969), with relatively high predictive power of FMVs for 24-h collections. Notably, most phthalates, bisphenols and antioxidants showed low ICC values. Together, our work demonstrates that FMV samples may be adequate for assessing human exposure to parabens, benzophenones, triclosan and dichlorophenols, whereas multiple consecutive urine collections may be advantageous for evaluating exposure to most phthalates, bisphenols and antioxidants.

Development of human dermal PBPK models for the bisphenols BPA, BPS, BPF, and BPAF with parallel-layered skin compartment: Basing on dermal administration studies in humans

Risk assessment of human exposure to bisphenols (BPs) including bisphenol A, S, F and AF (BPA, BPS, BPF and BPAF) have suggested that except for ingestion, health risk resulting from dermal contact is not negligible. However, the absorption kinetics of BPA substitutes in humans following dermal exposure have been poorly studied. This study aimed to address the knowledge gap in physiologically based pharmacokinetic (PBPK) modeling of BPA and its high-concerned substitutes (BPS, BPF and BPAF) following dermal administration. Parallel-layered skin compartmental model for dermal absorption of BPs was for the first time proposed and human dermal administration studies were conducted to determine dermal bio-accessibility of BPS from thermal paper (TP) (n = 4), BPF (n = 4) and BPAF (n = 5) from personal care products (PCPs). Further, pharmacokinetics of BPS and its metabolites following human handling TP were investigated and the dermal PBPK models for BPA and BPS were validated using the available human biomonitoring data. Overall, 28.03 % ± 13.76 % of BPS in TP was transferred to fingers followed by absorption of 96.17 % ± 2.78 % of that. The dermal bio-accessibilities of BPs in PCPs were 31.65 % ± 2.90 % for BPF and 12.49 % ± 1.66 % for BPAF. Monte Carlo analysis indicated that 90 % of the predicted variability fell within one order of magnitude, which suggested that the developed PBPK models had medium uncertainty. Global sensitivity analysis revealed that the model uncertainty is mainly attributed to the variabilities of dermal absorption parameters. Compared with the previous models for BPs, the developed dermal PBPK models were capable of more accurate predictions of the internal dose metric in target organs following human dermal exposure to BPs via TP and PCPs routes. These results suggested that the developed human dermal PBPK models would provide an alternative tool for assessing the risk of human exposure to BPs through dermal absorption.

Identification of risk for ovarian disease enhanced by BPB or BPAF exposure

The ban on bisphenol A (BPA) has led to a rapid increase in the use of BPA analogs, and they are increasingly being detected in the natural environment and biological organisms. Studies have pointed out that BPA analogs can lead to adverse health outcomes. However, their interference with ovarian tissue has not been fully elucidated. In this study, seven- to eight-week-old CD-1 mice were exposed to corn oil containing 300 μg/kg/day bisphenol B (BPB) or bisphenol AF (BPAF) through oral gavage, and ovarian tissues were collected at 14 and 28 days of exposure. Ovarian toxicity was evaluated by the ovarian index, ovarian area, and follicle number. mRNA-seq was used to identify differentially expressed genes (DEGs) and infer the association of DEGs with ovarian diseases. BPB or BPAF exposure induced morphological changes in ovarian tissue in CD-1 mice. In addition, Gene Ontology (GO) analysis revealed disturbances in biological processes (BP) associated with steroid biosynthetic process (GO:0006694) and cellular calcium ion homeostasis (GO:0006874). Subsequently, regulatory networks of BPA analogs (BPB or BPAF)-DEGs-ovarian diseases were constructed. Importantly, the expression levels of DEGs and transcription factors (TFs) associated with ovarian disease were altered. BPB or BPAF exposure causes damage to ovarian morphology through the synergistic effects of multiple biological processes and may be associated with altered mRNA expression profiles as a risk factor for ovarian diseases.

Handwipes as indicators to assess organophosphate flame retardants exposure and thyroid hormone effects in e-waste dismantlers

Dermal exposure is increasingly recognized as an important pathway for organic pollutant exposure. However, data on dermal exposure are limited, particularly with respect to the health effects. This study evaluated association between organophosphorus flame retardants (OPFRs) in handwipes and internal body burden on workers and adult residents in an electronic waste (e-waste) dismantling area. The impact of dermal exposure to OPFRs on thyroid hormones (THs) served as a biomarker for early effects. Triphenyl phosphate (TPhP) was the most detected compound in handwipes, with median levels of 1180, 200, and 24.0 ng in people identified as e-waste bakers, e-waste dismantlers, and adult residents. Among e-waste dismantlers, TPhP levels in handwipes were positively correlated with paired serum TPhP and urinary diphenyl phosphate (DPhP) levels. In multiple linear regression models controlling for sex, age and smoking, TPhP levels in handwipes of e-waste dismantlers were significantly negatively correlated with three THs used to evaluate thyroid function: serum reverse 3,3',5-triiodo-L-thyronine (rT3), 3,3'-diiodo-L-thyronine (3,3'-T2), and 3,5-diiodo-L-thyronine (3,5-T2). These findings suggest that handwipes can act as non-invasive exposure indicators to assess body burden of dermal exposure to TPhP and health effects on THs of e-waste dismantlers. This study highlights importance of OPFR effect on human THs through dermal exposure.

Bisphenol A and bisphenol S both disrupt ovine granulosa cell steroidogenesis but through different molecular pathways

BACKGROUND

Ovarian granulosa cells (GC) are essential for the development and maturation of a proper oocyte. GC are sensitive to endocrine disruptors, including bisphenol A (BPA) and its analogue bisphenol S (BPS), plasticisers present in everyday consumer products. BPA exhibits greater binding affinity for the membrane oestrogen receptor (GPER) than for the nuclear oestrogen receptors (ERα and ERβ). Here, we analysed the effects of BPA and BPS on the steroidogenesis of ovine GC in vitro, as well as their early mechanisms of action, the ovine being a relevant model to study human reproductive impairment. Disruption of GC steroidogenesis might alter oocyte quality and consequently fertility rate. In addition, we compared the effects of a specific GPER agonist (G-1) and antagonist (G-15) to those of BPA and BPS. Ewe GC were cultured with BPA or BPS (10 or 50 µM) or G-1 (1 µM) and/or G-15 (10 µM) for 48 h to study steroidogenesis.

RESULTS

Both BPA and BPS (10 µM) altered the secretion of progesterone, however, only BPS (10 µM) affected oestradiol secretion. RNA-seq was performed on GC after 1 h of culture with BPA or BPS (50 µM) or G-1 (10 µM), followed by real-time PCR analyses of differentially expressed genes after 12, 24 and 48 h of culture. The absence of induced GPER target genes showed that BPA and BPS did not activate GPER in GC after 1 h of treatment. These molecules exhibited mainly independent early mechanisms of action. Gene ontology analysis showed that after 1 h of treatment, BPA mainly disrupted the expression of the genes involved in metabolism and transcription, while BPS had a smaller effect and impaired cellular communications. BPA had a transient effect on the expression of CHAC1 (NOTCH signalling and oxidative balance), JUN (linked to MAPK pathway), NR4A1 (oestradiol secretion inhibition), ARRDC4 (endocytose of GPCR) and KLF10 (cell growth, differentiation and apoptosis), while expression changes were maintained over time for the genes LSMEM1 (linked to MAPK pathway), TXNIP (oxidative stress) and LIF (cell cycle regulation) after 12 and 48 h, respectively.

CONCLUSION

In conclusion, although they exhibited similar effects, BPA and BPS impaired different molecular pathways in GC in vitro. New investigations will be necessary to follow the temporal changes of these genes over time, as well as the biological processes involved.

Physiologically based modelling of dermal absorption and kinetics of consumer-relevant chemicals: A case study with exposure to bisphenol A from thermal paper

Bisphenol A (BPA) is one of the best studied industrial chemicals in terms of exposure, toxicity, and toxicokinetics. This renders it an ideal candidate to exploit the recent advancements in physiologically based pharmacokinetic (PBPK) modelling to support risk assessment of BPA specifically, and of other consumer-relevant hazardous chemicals in general. Using the exposure from thermal paper as a case scenario, this study employed the multi-phase multi-layer mechanistic dermal absorption (MPML MechDermA) model available in the Simcyp® Simulator to simulate the dermal toxicokinetics of BPA at local and systemic levels. Sensitivity analysis helped to identify physicochemical and physiological factors influencing the systemic exposure to BPA. The iterative modelling process was as follows: (i) development of compound files for BPA and its conjugates, (ii) setting-up of a PBPK model for intravenous administration, (iii) extension for oral administration, and (iv) extension for exposure via skin (i.e., hand) contact. A toxicokinetic study involving hand contact to BPA-containing paper was used for model refinement. Cumulative urinary excretion of total BPA had to be employed for dose reconstruction. PBPK model performance was verified using the observed serum BPA concentrations. The predicted distribution across the skin compartments revealed a depot of BPA in the stratum corneum (SC). These findings shed light on the role of the SC to act as temporary reservoir for lipophilic chemicals prior to systemic absorption, which inter alia is relevant for the interpretation of human biomonitoring data and for establishing the relationship between external and internal measures of exposure.

Impact of Extended and Combined Exposure of Bisphenol Compounds on Their Chromosome-Damaging Effect─Increased Potency and Shifted Mode of Action

Bisphenol (BP) compounds are important environmental pollutants and endocrine disruptors. BPs are capable of inducing DNA/chromosome breaks (clastogenesis, involved in carcinogenesis), which requires activation by human CYP1A1. We hypothesized that combined BPs and extended (from the standard two-cell cycle) exposure may enhance their genotoxicity via modulating CYP enzymes. In this study, individual and combined BPA/BPF/BPS/BPAF and a human hepatoma (HepG2) cell line were used for testing several genotoxicity end points. Exposing for a two-cell cycle period (48 h), each BP alone (0.625-10 μM) was negative in the micronucleus test, while micronucleus was formed under three- (72 h) and four-cell cycle (96 h) exposure; BP combinations further elevated the potency (with nanomolar thresholds). Immunofluorescence analysis of the centromere with formed micronucleus indicated that 48 h exposure produced centromere-negative micronucleus and phosphorylated histone H2AX (γ-H2AX) (evidencing clastogenesis), while extended (72 and 96 h) exposure formed centromere-positive micronucleus and phosphorylated histone H3 (p-H3) (indicating chromosome loss, i.e., aneugenesis); moreover, 1-aminotriabenzotriazole (CYP inhibitor) selectively blocked the formation of centromere-negative micronucleus and γ-H2AX, without affecting that of centromere-positive micronucleus and p-H3. This study suggests that the genotoxicity of BPs is potentiated by combined and extended exposure, the latter being specific for aneuploidy formation, a CYP activity-independent effect.

Twenty bisphenol analogues in take-out polystyrene-made food containers: concentration levels, simulated migration, and risk evaluation

Bisphenol A (BPA) is mainly used to produce polycarbonate consumer products. However, the occurrence of BPA and other bisphenol analogues (BPs) in polystyrene-made plastic products, such as white foam take-out containers (WFTOCs), has not been well investigated. In this study, occurrence of 20 BPs in WFTOC samples collected from China, Canada, and Poland were investigated with a sample size of 152. Results showed that 11 out of 20 BPs have been detected at least in one WFTOC sample. Among them, BPA was the most frequently detected BP, followed by bisphenol S (BPS) and bisphenol AF, while BPF was the least detected BP. Very high concentrations of BPA and BPS were detected in WFTOCs from China (mean 2694 and 552 ng/g), compared with Canada (81 and 45 ng/g, respectively) and Poland (95 and 16 ng/g). Other BPs, such as bisphenol TMC (BPTMC; detection frequency 65%, range < LOQ - 224 ng/g), bisphenol G (17%, < LOQ - 11 ng/g), and bisphenol BP (11%, < LOQ - 1.6 ng/g), were also detected in Chinese WFTOC samples. The mean partitioning coefficients of BPA, BPS, bisphenol AP, and BPTMC between WFTOCs and tap water, 10% ethanol, 50% ethanol, corn oil, or steamed rice were 0.22 - 2.9%, 0.16 - 5.1%, 0.11 - 7.5%, 2.3 - 6.5%, or 0.19 - 0.36%, respectively. The estimated daily intake of BPA, BPS, and BPTMC through using WFTOCs were 0.50 - 547, 0.054 - 229, and < 0.66 ng/kg bw/day, respectively, for general population in China, Canada, and Poland. Overall, this study first reveals the unexpected presence of BPs in WFTOCs made of polystyrene, which contributes to the better understanding of the sources of human exposure to BPs.

Bisphenol S Impairs Oestradiol Secretion during In Vitro Basal Folliculogenesis in a Mono-Ovulatory Species Model

Bisphenol S (BPS) affects terminal folliculogenesis by impairing steroidogenesis in granulosa cells from different species. Nevertheless, limited data are available on its effects during basal folliculogenesis. In this study, we evaluate in vitro the effects of a long-term BPS exposure on a model of basal follicular development in a mono-ovulatory species. We cultured ovine preantral follicles (180−240 μm, n = 168) with BPS (0.1 μM (possible human exposure dose) or 10 μM (high dose)) and monitored antrum appearance and follicular survival and growth for 15 days. We measured hormonal secretions (oestradiol (at day 13 [D13]), progesterone and anti-Müllerian hormone [D15]) and expression of key follicular development and redox status genes (D15) in medium and whole follicles, respectively. BPS (0.1 µM) decreased oestradiol secretion compared with the control (−48.8%, p < 0.001), without significantly impairing antrum appearance, follicular survival and growth, anti-Müllerian hormone and progesterone secretion and target gene expression. Thus, BPS could also impair oestradiol secretion during basal folliculogenesis as it is the case during terminal folliculogenesis. It questions the use of BPS as a safe BPA substitute in the human environment. More studies are required to elucidate mechanisms of action of BPS and its effects throughout basal follicular development.

Triglyceride profiles are associated with subacute exposure to bisphenol A in healthy young adults

Conflicted results from previous epidemiological studies call for mechanistic evidence to associate exposure to bisphenol A (BPA) with cardiometabolic diseases. In this natural experiment among healthy travelers from Los Angeles (LA) to Beijing, we collected paired urine and blood samples before their departure, 6-8 weeks after their arrival to Beijing, and 4-7 weeks after their return to LA for the assessment of urinary BPA and lipidome in the serum fraction of blood, to study the effects of drastically changed BPA exposure on the lipid metabolism in relation to the development of cardiometabolic disorders. We used linear mixed-effects models with random intercepts for participant and phase to examine the associations between urinary BPA and serum lipidome. Among 744 lipid species from seven classes, triglyceride (TGs) species showed the strongest associations with BPA exposure. The elevation in BPA exposure was associated with increases in TGs with short carbon chains or few double bonds, and decreases in TGs with long carbon chains or many double bonds. A significant linear relationship was observed between BPA-associated TG changes and the number of carbons and double-bonds in the acyl chain. No modification effects of gender but of body mass index (BMI) were observed on the associations between BPA exposure and TGs. This interdisciplinary environmental research substantiated the cardiometabolic effects of BPA according to the perturbations of TG profiling.

Association of bisphenol A, bisphenol F, and bisphenol S with ADHD symptoms in children

BACKGROUND

Bisphenol A (BPA) has been linked to attention-deficit/hyperactivity disorder (ADHD) symptoms, but the neurotoxic effects of bisphenol substitutes such as bisphenol F (BPF) and S (BPS) have not been well investigated. We investigated the associations between BPA, BPF, and BPS with ADHD symptoms at multiple time points in children.

METHODS

The levels of BPA (at ages 4, 6, and 8), BPF (at ages 6 and 8), and BPS (at ages 6 and 8) were measured in 619 children. Because of the low detection frequency of BPF and BPS levels, participants were divided into categories (<or ≥ limit of detection (LOD) for BPF; < LOD, ≥ LOD and < median, or ≥ median for BPS). ADHD symptoms were assessed using the ADHD Rating Scale IV (ARS). The relationship between bisphenols and ARS scores was analyzed using Poisson regression models, and generalized additive models and piecewise regression models were further explored for BPA.

RESULTS

BPA was detected in most participants (>97%), whereas BPF and BPS were less frequently detected (age 6: 17.5% for BPF and 42.0% for BPS; age 8: 51.6% for BPF and 73.3% for BPS). Doubling in BPA levels was associated with increased ARS scores by 4.7% (95% confidence intervals [CI]: 0.5, 9.2) at age 6. The association was greater with BPA levels higher than 3.0 μg/g creatinine (24.2% [95% CI: 15.5, 33.6] increase). The BPF ≥ LOD group had 10.8% (95% CI: 1.2, 21.4) higher ARS scores than the BPF < LOD group. The BPS ≥ median group had 11.4% (95% CI: 2.0, 21.7) higher ARS scores than the BPS < LOD group.

CONCLUSION

All bisphenols, in particular those at or above the LOD or median levels, were associated with ADHD symptoms at age 6. Further prospective studies are warranted to determine causal inference.

Toxicological profile of bisphenol F via comprehensive and extensive toxicity evaluations following dermal exposure

Bisphenol F (BPF) is classified as a harmful substance by the U.S. Environmental Protection Agency. Although previous studies focused on human exposure to BPF via direct consumption or inhalation, few investigators assessed potential toxicological effects following skin contact. The aim of this study was to examine (1) the degree and pattern by which BPF is absorbed onto the skin in vivo, and (2) determination of toxicity and safety using the following tests: acute dermal; a 28-day repeat dermal; a skin irritation; an eye irritation; and a skin sensitization. As indicated by the amount of BPF remaining in the epidermis or dermis, data demonstrated that BPF was absorbed through the skin at a 26.5% rate. BPF penetrated the subcutaneous layer at a "fast rate" (Kp: 2.2E-02). Although no toxicological changes or local irritation were observed following skin exposure, BPF induced potent sensitization. In summary, the findings of this study showed that BPF penetrated and was absorbed into the skin at a high rate which was associated with enhanced chemical-induced skin sensitization and this may have significant implications following exposure of skin to BPF.

Ultrasensitive and Highly Selective Detection of Bisphenol a Using Core-Shell Magnetic Molecularly Imprinted Quantum Dots Electrochemiluminescent Probe

The main aim of this work was to develop a magnetic molecularly imprinted polymer (MMIP)-based quantum dots electrochemiluminescent (ECL) probe for the ultrasensitive and highly selective detection of bisphenol A (BPA). The prepared core-shell Fe₃O₄@SiO₂ exhibited superparamagnetic properties, making them easy to separate. The MIP was fabricated by the self-polymerization of dopamine on the surface of amine-terminated Fe₃O₄@SiO₂ (Fe₃O₄@SiO₂-NH₂) magnetic nanoparticles and doped with quantum dots (QDs) to form an ECL system. The ECL intensity decrease with the concentration of BPA increased, due to the BPA molecules occupied molecularly imprinted sites and blocked the strong ECL emission of QDs. The prepared ECL sensor performed satisfactorily in the detection of BPA, with a wide linear range from 10^- 4 to 10^- 9 mol L^- 1 and a low detection limit of 3.4 × 10^- 10 mol L^- 1 (S/N = 3). The recoveries of BPA achieved were in the range 96%-107% in the detection of actual water samples. The proposed ECL sensor displayed high sensitivity and stability, and may provide an approach for determining other important analytes.

Overview of the Mechanisms of Action of Selected Bisphenols and Perfluoroalkyl Chemicals on the Male Reproductive Axes

Male fertility has been deteriorating worldwide for considerable time, with the greatest deterioration recorded mainly in the United States, Europe countries, and Australia. That is, especially in countries where an abundance of chemicals called endocrine disruptors has repeatedly been reported, both in the environment and in human matrices. Human exposure to persistent and non-persistent chemicals is ubiquitous and associated with endocrine-disrupting effects. This group of endocrine disrupting chemicals (EDC) can act as agonists or antagonists of hormone receptors and can thus significantly affect a number of physiological processes. It can even negatively affect human reproduction with an impact on the development of gonads and gametogenesis, fertilization, and the subsequent development of embryos. The negative effects of endocrine disruptors on sperm gametogenesis and male fertility in general have been investigated and repeatedly demonstrated in experimental and epidemiological studies. Male reproduction is affected by endocrine disruptors via their effect on testicular development, impact on estrogen and androgen receptors, potential epigenetic effect, production of reactive oxygen species or direct effect on spermatozoa and other cells of testicular tissue. Emerging scientific evidence suggests that the increasing incidence of male infertility is associated with the exposure to persistent and non-persistent endocrine-disrupting chemicals such as bisphenols and perfluoroalkyl chemicals (PFAS). These chemicals may impact men’s fertility through various mechanisms. This study provides an overview of the mechanisms of action common to persistent (PFAS) and nonpersistent (bisphenols) EDC on male fertility.

Interaction of prenatal bisphenols, maternal nutrients, and toxic metal exposures on neurodevelopment of 2-year-olds in the APrON cohort

BACKGROUND

Epidemiological studies suggest that Bisphenol-A (BPA) is a developmental neurotoxicant, but the modifying effects of maternal nutrient status or neurotoxicant metal co-exposures have not been reported. Bisphenol-S (BPS) is being used as a BPA-alternative, but few epidemiological studies have evaluated its effects.

OBJECTIVES

To examine if prenatal maternal BPA or BPS exposure are associated with children's neurodevelopment at two years of age while adjusting for effect-measure modification by sex, maternal nutrients, and co-exposure to neurotoxic metals.

METHODS

Total BPA and BPS concentrations were analyzed in spot maternal urine from the second trimester; metals and maternal nutrient status were analyzed in blood. Child neurodevelopment was evaluated with the Bayley Scales of Infant Development-III (Bayley-III) at age 2 (394 maternal-child pairs) and linear regression was used to investigate associations.

RESULTS

Among nutrients and neurotoxic metals, selenium (Se) and cadmium (Cd) were the most significant predictors of Bayley-III scale scores. Higher maternal Cd was significantly correlated with poorer motor performance (p < 0.01), and higher levels of maternal Se were significantly associated with poorer performance on the cognitive, motor, and adaptive behavior scales (p < 0.05). While maternal Cd did not modify relationships between bisphenol exposures and Bayley-III scores, both maternal Se and child sex were significant effect-measure modifiers. Associations between BPA exposure and social emotional scores were negative for boys (p = 0.056) but positive for girls (p = 0.046). Higher exposure to bisphenols was associated with lower motor scores among children with lower levels of maternal Se.

CONCLUSION

Higher maternal Cd was associated with poorer motor development, but it was not an effect-measure modifier of bisphenols' effects on motor development. Maternal Se may be protective against adverse effects of bisphenols, and additional nutrient-bisphenol interaction studies examining sex-specific effects of BPA and BPS on child development are warranted.

Human biomonitoring initiative (HBM4EU): Human biomonitoring guidance values (HBM-GVs) derived for bisphenol A

The "European Human Biomonitoring Initiative" (HBM4EU) derives human biomonitoring guidance values (HBM-GVs) for the general population (HBM-GV_GenPop) and/or for occupationally exposed adults (HBM-GV_Worker) for several priority substances and substance groups as identified by policy makers, scientists and stakeholders at EU and national level, including bisphenol A (BPA). Human exposure to BPA is widespread and of particular concern because of its known endocrine-disrupting properties. Unlike the conjugated forms of BPA circulating in the body, free BPA is known to interact with the nuclear estrogen receptors. Because free BPA is considered to be more toxicologically active than the conjugated forms (e.g. BPA-glucuronide (BPA-G) and BPA-sulfate (BPA-S)), its measurement in blood provides the superior surrogate of the biologically effective dose. However, considering the difficulty of implementing blood sampling in large HBM cohorts, as well as the current analytical capacities complying with the quality assurance (QA)/quality control (QC) schemes, total BPA in urine (i.e. the sum of free and conjugated forms of BPA measured after an hydrolysis of phase II metabolites) was retained as the relevant exposure biomarker for BPA. HBM-GV_GenPop for total BPA in urine of 230 µg/L and 135 µg/L for adults and children, respectively, were developed on the basis of toxicological data. To derive these values, the concentrations of urinary total BPA consistent with a steady-state exposure to the temporary Tolerable Daily Intake (t-TDI) of 4 µg/kg bw/day set in 2015 by the European Food Safety Authority (EFSA) were estimated. The BPA human physiologically-based pharmacokinetic (PBPK) model developed by Karrer et al. (2018) was used, assuming an oral exposure to BPA at the t-TDI level averaged over 24 h. Dermal uptake of BPA is suspected to contribute substantially to the total BPA body burden, which in comparison with the oral route, is generating a higher ratio of free BPA to total BPA in blood. Therefore, an alternative approach for calculating the HBM-GV_GenPop according to the estimated relative contributions of both the oral and dermal routes to the global BPA exposure is also discussed. Regarding BPA exposure at the workplace, the steady-state concentration of urinary total BPA was estimated after a dermal uptake of BPA that would generate the same concentration of free BPA in plasma (considered as the bioactive form) as would a 24 h-averaged intake to the European Chemicals Agency (ECHA)'s oral DNEL of 8 µg BPA/kg bw/day set for workers. The predicted concentration of urinary total BPA at steady-state is equivalent to, or exceeds the 95th percentile of total BPA in urine measured in different European HBM studies conducted in the general population. Thus, no HBM-GV_Worker was proposed, as the high background level of BPA coming from environmental exposure - mostly through food intake - is making the discrimination with the occupational exposure to BPA difficult.

Biomonitoring of occupational exposure to bisphenol A, bisphenol S and bisphenol F: A systematic review

Bisphenol A (BPA) and its substitutes bisphenol S (BPS) and bisphenol F (BPF) are endocrine disrupting chemicals widely used in the production of polycarbonate plastics, epoxy resins and thermal papers. The aim of the review was to identify occupational studies using human biomonitoring (HBM) as a tool for bisphenol exposure assessment and to characterize research gaps on the topic as part of the HBM4EU project. Hence, a systematic literature search using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology was conducted for articles published between 2000 and 27th March 2020 across three databases (PubMed, Scopus and Web of Science). Thirty studies on the occupational HBM of BPA met the inclusion criteria. Regarding BPS and BPF, only 4 and 2 publications were retrieved, respectively. Fifty-seven percent (57%) of the studies selected for BPA were conducted in Asia whereas half of BPS and BPF studies were undertaken in Europe. Studies on BPA in plastic and epoxy resin sectors were infrequent in Europe while Asian data showed higher exposure when the substance is employed as raw material. The main data on BPS were among cashiers while BPF data were available from incinerator workers. Several research gaps have been identified: (i) shortage of HBM studies on occupational exposure, especially to BPS and BPF; (ii) different methodological designs making suitable comparisons between studies difficult; and (iii) only few studies conducted on the industrial applications of bisphenols outside Asia. This review highlights the lack of recent occupational HBM studies on bisphenols and the need for a harmonized approach to acquire reliable data. Considering the increasing replacement of BPA by BPS and BPF, it is of relevance to evaluate the exposure to these substances and the impact of the available risk management measures on workers exposure and possible health risk.

Occurrence of Free-Form and Conjugated Bisphenol Analogues in Marine Organisms

Upon exposure, most bisphenol analogues (BPs) are rapidly metabolized to BP conjugates in organisms. Monitoring studies on BPs in aquatic organisms have been mainly focused on free-form BPs. However, the relative amount of conjugated BPs in organisms is still not well known, especially in marine organisms. In this study, we collected marine organisms (13 species; n = 74), as well as seawater (n = 15), from East China Sea, and analyzed them for bisphenol A (BPA) and its eight analogues. In seawater, BPA was the predominant BP (mean ± standard deviation (SD), 18 ± 9.7 ng/L), followed by bisphenol S (BPS; 3.7 ± 2.8 ng/L), bisphenol F (BPF; 0.31 ± 0.17 ng/L), and bisphenol AF (BPAF; 0.24 ± 0.15 ng/L). The whole body of each marine organism was used for BP analysis in this study. BPA (mean 3.8 ng/g, range 1.2-7.7 ng/g) and BPS (1.5 ng/g, 0.19-6.1 ng/g) were still the predominant BPs in marine organisms without hydrolysis. After enzymatic hydrolysis treatment, mean concentrations of BPs increased 1.8 (BPS)-3.7 (BPA) times in marine organisms. Correspondingly, on average, 74, 52, 49, 48, and 45% of BPA, bisphenol Z, BPF, BPS, and BPAF were present in conjugated forms, respectively, in marine organisms. Moreover, bioaccumulation and biomagnification of BPs were evaluated using pooled marine organism samples. We first found that the mean log BAF values of BPs increased 0.091 (BPAF) to 0.31 (BPA) times in marine organisms after hydrolysis. Overall, this study first determines the amount of BPs present in conjugated forms in marine organisms, which are helpful for better understanding the occurrence of BPs in organisms.

Bisphenol A in Africa: A review of environmental and biological levels

Bisphenol A (BPA) is a synthetic ubiquitous environmental toxicant present in many industrial and consumer products. BPA is recognized as an endocrine-disrupting chemical (EDC), and its mechanisms of perturbation of the physiological process include interference with hormone pathways and epigenetic modifications. An increase in industrial productions and food packaging across Africa has resulted in increased utilization of BPA-containing products with a concomitant increase in environmental bioaccumulation and human exposure. In order to assess the extent of this bioaccumulation, we identified, collated, and summarized the levels of BPA that have been reported across Africa. To achieve this aim, we performed a systematic search of four indexing databases to identify articles and extracted the necessary data from the selected articles. Of the 42 publications we retrieved, 42% were on water samples, 22% on food, 20% on human biological fluids, 10% on sediments, soils, and sludge and 6% on consumer and personal care products (PCPs). The highest level of BPA reported in literature across Africa was 251 ng/mL, 384.8 ng/mL, 937.49 ng/g, 208.55 ng/mL, 3,590 μg/g, and 154,820 μg/g for water, wastewater, food, biological fluids, consumer and PCPs, and semisolids, respectively. This review presented a comparative perspective of these levels relative to regulatory limits and levels reported from other continents. Finally, this review highlighted critical needs for the regulation of BPA across Africa in order to stem its environmental and toxicological impact. We hope that this review will stimulate further research in understanding the impact of BPA on health outcomes and wellbeing across Africa.

Exposure to phthalates and bisphenol analogues among childbearing-aged women in Korea: Influencing factors and potential health risks

Phthalates and bisphenol A (BPA), widely applied in industrial and consumer products, can affect hormones associated with the human reproductive system. Because the incidence of reproductive diseases is increasing, a comprehensive exposure assessment of phthalates and bisphenol analogues (BPs) is required for childbearing-aged women. Phthalate metabolites and BPs were measured in urine samples collected from 509 childbearing-aged women (20-48 years) in Korea to investigate their current exposure status, profiles, influencing factors, and potential health risks. DEHP metabolites and BPA were the dominant compounds found, indicating that they are highly consumed in daily life. Bisphenol S (BPS), as an alternative to BPA, was detected in most urine samples. Total concentrations of phthalate metabolites and BPs ranged from 3.42 to 3570 (GM: 45.6) ng/mL and from <LOQ to 80.3 (0.91) ng/mL, respectively, which were within the ranges observed in women in previous studies. Exposure to diethyl phthalate (DEP) was significantly associated with the use of cosmetics and personal care products such as perfume, body lotion, and sunscreen. Higher ratios of urinary BPS/BPA were observed in younger and more highly educated women and in women living in urbanized regions than others. This result suggests that a shift in consumption from BPA to BPS was preferentially occurring in urbanized regions. The assessment of the cumulative risk posed by phthalates and BPs showed that they pose only a small health risk to Korean women. This study provides baseline data on exposure levels, profiles, and influencing factors for phthalates and BPs in childbearing-aged women.

Pharmacokinetics of bisphenol A in humans following dermal administration

BACKGROUND

Human exposures to bisphenol A (BPA) are widespread. The current study addresses uncertainties regarding human pharmacokinetics of BPA following dermal exposure.

OBJECTIVE

To examine the absorption, distribution, metabolism and excretion of BPA in humans following dermal administration.

METHODS

We dermally administered deuterated BPA (d6-BPA) to 10 subjects (6 men and 4 women) at a dose of 100 µg/kg over a 12-hour period and conducted blood and urine analysis from the beginning of dosing through a three- or six-day period. We present time-course serum and urine concentrations of total and unconjugated ("free") d6-BPA and used this information to calculate terminal half-life and area under the curve.

RESULTS AND CONCLUSIONS

Detectable serum levels of total d6-BPA were observed at 1.4 h after the start of dosing, and a maximum serum concentration (C_max) of 3.26 nM was observed. Free d6-BPA was detectable in serum 2.8 h after start of dermal administration, with C_max of 0.272 nM. Beginning at approximately seven hours and continuing to 12 h (which corresponds to cessation of exposure), the concentration of free and total serum d6-BPA plateaued. The terminal half-lives of total d6-BPA and free d6-BPA in the body were 21.4 ± 9.81 h and 17.6 ± 7.69 h, respectively. Elimination from the body was rate-limited by kinetics in the dermal compartment. Free d6-BPA was a greater percentage of the area under the curve of total serum BPA (8.81%) compared to the 0.56% observed in our previously published oral study. Recovery of total d6-BPA in urine was <2% of the applied dose after six days. Analysis of the area under the curve for dermal and oral administration revealed that 2.2% of the dermal dose became systemically available. These data are in line with prior studies indicating how pharmacokinetics of BPA differ following oral and dermal exposures. Dermal exposure resulted in a longer apparent half-life and higher free:total d6-BPA ratio compared to oral.

Bisphenol A and its analogues: A comprehensive review to identify and prioritize effect biomarkers for human biomonitoring

Human biomonitoring (HBM) studies have demonstrated widespread and daily exposure to bisphenol A (BPA). Moreover, BPA structural analogues (e.g. BPS, BPF, BPAF), used as BPA replacements, are being increasingly detected in human biological matrices. BPA and some of its analogues are classified as endocrine disruptors suspected of contributing to adverse health outcomes such as altered reproduction and neurodevelopment, obesity, and metabolic disorders among other developmental and chronic impairments. One of the aims of the H2020 European Human Biomonitoring Initiative (HBM4EU) is the implementation of effect biomarkers at large scales in future HBM studies in a systematic and standardized way, in order to complement exposure data with mechanistically-based biomarkers of early adverse effects. This review aimed to identify and prioritize existing biomarkers of effect for BPA, as well as to provide relevant mechanistic and adverse outcome pathway (AOP) information in order to cover knowledge gaps and better interpret effect biomarker data. A comprehensive literature search was performed in PubMed to identify all the epidemiologic studies published in the last 10 years addressing the potential relationship between bisphenols exposure and alterations in biological parameters. A total of 5716 references were screened, out of which, 119 full-text articles were analyzed and tabulated in detail. This work provides first an overview of all epigenetics, gene transcription, oxidative stress, reproductive, glucocorticoid and thyroid hormones, metabolic and allergy/immune biomarkers previously studied. Then, promising effect biomarkers related to altered neurodevelopmental and reproductive outcomes including brain-derived neurotrophic factor (BDNF), kisspeptin (KiSS), and gene expression of nuclear receptors are prioritized, providing mechanistic insights based on in vitro, animal studies and AOP information. Finally, the potential of omics technologies for biomarker discovery and its implications for risk assessment are discussed. To the best of our knowledge, this is the first effort to comprehensively identify bisphenol-related biomarkers of effect for HBM purposes.

Different temporal trends of exposure to Bisphenol A among international travelers between Los Angeles and Beijing

Recent studies suggested a significant downward trend in population's exposure to bisphenol A (BPA) in the United States. However, the temporal trend of BPA exposure remains unclear in China - a populous country with substantial industrial activities but less efforts made to phase out BPA in consumer products. In addition, it is unclear to what extent a visit from the United States to China could affect human exposure to BPA. In this natural experiment, we measured the concentration of total BPA in 418 urine samples repeatedly collected from 55 Los Angeles residents before, during, and after they spent 10 weeks in Beijing from 2012 to 2017. We found that traveling from Los Angeles to Beijing led to a 2.91-fold (95% CI: 2.43 to 3.50) increase in urinary BPA levels, which fully returned to baseline after study participants came back to Los Angeles. From 2012 to 2017, urinary BPA concentrations decreased in Los Angeles by 25.5% per year (95% CI: -30.8% to -19.8%; p < 0.001) but did not change in Beijing (p = 0.24). Consequently, the concentration ratio of urinary BPA between Beijing and Los Angeles increased from 1.23 (95% CI: 0.82 to 1.85) in 2012 to 4.05 (95% CI: 2.75 to 5.97) in 2017. These results indicate that BPA exposures may increase among international travelers to China. Additional efforts are needed to reduce population's exposure to BPA in China.

Toxicokinetics of bisphenol-S and its glucuronide in plasma and urine following oral and dermal exposure in volunteers for the interpretation of biomonitoring data

The measurement of bisphenol-S (BPS) and its glucurono-conjugate (BPSG) in urine may be used for the biomonitoring of exposure in populations. However, this requires a thorough knowledge of their toxicokinetics. The time courses of BPS and BPSG were assessed in accessible biological matrices of orally and dermally exposed volunteers. Under the approval of the Research Ethics Committee of the University of Montreal, six volunteers were orally exposed to a BPS-d8 deuterated dose of 0.1 mg/kg body weight (bw). One month later, 1 mg/kg bw of BPS-d8 were applied on 40 cm² of the forearm and then washed 6 h after application. Blood samples were taken prior to dosing and at fixed time periods over 48 h after treatment; complete urine voids were collected pre-exposure and at pre-established intervals over 72 h postdosing. Following oral exposure, the plasma concentration-time courses of BPS-d8 and BPSG-d8 over 48 h evolved in parallel, and showed a rapid appearance and elimination. Average peak values (±SD) were reached at 0.7 ± 0.1 and 1.1 ± 0.4 h postdosing and mean (±SD) apparent elimination half-lives (t_½) of 7.9 ± 1.1 and 9.3 ± 7.0 h were calculated from the terminal phase of BPS-d8 and BPSG-d8 in plasma, respectively. The fraction of BPS-d8 reaching the systemic circulation unchanged (i.e. bioavailability) was further estimated at 62 ± 5% on average (±SD) and the systemic plasma clearance at 0.57 ± 0.07 L/kg bw/h. Plasma concentration-time courses and urinary excretion rate profiles roughly evolved in parallel for both substances, as expected. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 over the 0-72 h period postdosing was 1.72 ± 1.3 and 54 ± 10%. Following dermal application, plasma levels were under the lower limit of quantification (LLOQ) at most time points. However, peak values were reached between 5 and 8 h depending on individuals, suggesting a slower absorption rate compared to oral exposure. Similarly, limited amounts of BPS-d8 and its conjugate were recovered in urine and peak excretion rates were reached between 5 and 11 h postdosing. The average percent (±SD) of the administered dose recovered in urine as BPS-d8 and BPSG-d8 was about 0.004 ± 0.003 and 0.09 ± 0.07%, respectively. This study provided greater precision on the kinetics of this contaminant in humans and, in particular, evidenced major differences between BPA and BPS kinetics with much higher systemic levels of active BPS than BPA, an observation explained by a higher oral bioavailability of BPS than BPA. These data should also be useful in developing a toxicokinetic model for a better interpretation of biomonitoring data.

Toxicokinetics of Brominated Azo Dyes in the Early Life Stages of Zebrafish (Danio rerio) Is Prone to Aromatic Substituent Changes

Brominated azo dyes (BADs) have been identified as predominant indoor brominated pollutants in daycare dust; thus, their potential health risk to children is of concern. However, the toxicities of BADs remain elusive. In this study, the toxicokinetics of two predominant BADs, Disperse Blue 373 (DB373) and Disperse Violet 93 (DV93), and their suspect metabolite 2-bromo-4,6-dinitroaniline (BDNA) was investigated in embryos of zebrafish (Danio rerio). The bioconcentration factor of DV93 at 120 hpf is 6.2-fold lower than that of DB373. The nontarget analysis revealed distinct metabolism routes between DB373 and DV93 by reducing nitro groups to nitroso (DB373) or amine (DV93), despite their similar structures. NAD(P)H quinone oxidoreductase 1 (NQO1) and pyruvate dehydrogenase were predicted as the enzymes responsible for the reduction of DB373 and DV93 by correlating time courses of the metabolites and enzyme development. Further in vitro recombinant enzyme and in vivo inhibition results validated NQO1 as the enzyme specifically reducing DB373, but not DV93. Global proteome profiling revealed that the expression levels of proteins from the "apoptosis-induced DNA fragmentation" pathway were significantly upregulated by all three BADs, supporting the bioactivation of BADs to mutagenic aromatic amines. This study discovered the bioactivation of BADs via distinct eukaryotic enzymes, implying their potential health risks.

Correlates of exposure to phenols, parabens, and triclocarban in the Study of Environment, Lifestyle and Fibroids

We performed a cross-sectional analysis to identify correlates of urinary concentrations of seven phenols (bisphenols A, F, and S; 2,4-dichlorophenol; 2,5-dichlorophenol; benzophenone-3; triclosan), triclocarban, and four parabens (butyl, ethyl, methyl, and propyl). We analyzed baseline data from 766 participants in the Study of Environment, Lifestyle, and Fibroids, a prospective cohort study of 1693 Black women aged 23-34 years residing in Detroit, Michigan (2010-2012). We collected data on demographic, behavioral, and anthropometric factors via telephone interviews, clinic visits, and self-administered questionnaires. For each biomarker, we used linear regression models to estimate mean differences in log-transformed, creatinine-corrected concentrations across factors of interest. Each biomarker was detected in >50% of participants. Median creatinine-corrected concentrations were the highest for methyl paraben (116.8 μg/g creatinine), propyl paraben (16.8 μg/g creatinine), and benzophenone-3 (13.4 μg/g creatinine). Variables most strongly associated with biomarker concentrations included season of urine collection, education, and body mass index (BMI). BMI was positively associated with bisphenol A and S and triclocarban concentrations and inversely associated with butyl and methyl paraben concentrations. In this cohort of Black women, exposure to phenols, parabens, and triclocarban was prevalent and several factors were associated with biomarker concentrations.

An Evaluation of the Relationship among Urine, Air, and Hand Measures of Exposure to Bisphenol A (BPA) in US Manufacturing Workers

Background

Exposure to bisphenol A (BPA) can be assessed using external and internal exposure measures. We examined the relationship between two measures of external BPA exposure (air and hand-wipe samples) and one of internal exposure (total BPA in urine) for a group of US manufacturing workers.

Methods

During 2013-2014, we recruited 78 workers from six US companies that made BPA or made products with BPA. We quantified BPA in seven urine samples, two full-shift air samples and in pre- and end-shift hand-wipe samples collected from workers over 2 consecutive days. We examined correlations between creatinine-corrected urinary concentrations of total BPA (total BPACR) and BPA levels in air and hand wipes using Pearson's correlation coefficient. We also applied mixed-effects regression models to examine the relationship between total BPACR with BPA in air (urine~air model) and with BPA in end-shift hand wipes (urine~hand model), separately and together (urine~air+hand model), after adjusting for covariates.

Results

End-shift total BPACR strongly correlated with BPA in air (rp = 0.79, P < 0.0001) and nearly as strongly with BPA in end-shift hand wipes (rp = 0.75, P < 0.0001). In mixed-effect models, BPA air concentration and end-shift hand-wipe BPA level were significantly and positively associated with end-shift total BPACR (P < 0.0001 each). We found a significant effect of the Day 1 BPA air concentration on Day 2 total BPACR (P = 0.0104). When BPA air concentration and end-shift hand-wipe BPA level were in the same model, the air concentration (P < 0.0001) was more significant than the hand-wipe level (P = 0.0106).

Conclusion

BPA levels in air and end-shift hand wipes strongly correlated with total BPACR, suggesting that both inhalation and dermal contract were likely exposure routes; however, inhalation, on average, appeared to be a more dominant exposure route than dermal contact for these manufacturing workers.

Phthalate and BPA Exposure in Women and Newborns through Personal Care Product Use and Food Packaging

Phthalates and bisphenol A (BPA) are used in some personal care products (PCPs) and containers for food processing and packaging. The Plastics and Personal-Care Product use in Pregnancy (P4) Study (2009-10) explored the association between PCP use during pregnancy and the postpartum period among 80 pregnant women and 55 infants and BPA and phthalate concentrations in multiple maternal and infant urine specimens collected throughout the study (n = 1260 samples). The type, frequency, and timing of PCP and food packaging use 24 h before and during the urine collection period was collected at 5 time points for the mother using prospective diaries. Infant urine was collected up to 2 times before 3 months of age, and mothers answered questions about infant feeding and PCP use on their baby. In mothers, monoethyl phthalate (MEP) metabolite concentrations were significantly higher when women reported using makeup or body lotion in the last 24 h. MEP concentrations were consistently higher when the usage occurred within 0-6 h before the urine sample collection for almost all of the PCP categories. Infant lotion or baby powder application in the previous 24 h was associated with higher phthalate metabolite concentrations in infants. Total BPA metabolite concentrations were lower in exclusively breastfed infants compared to those who were exclusively formula fed or breastfed with supplementation. Given that PCPs tend to undergo frequent formulation changes, which could impact the relative importance of a certain product type as a source of exposure, continued research of this type is warranted.

The adverse health effects of bisphenol A and related toxicity mechanisms

Bisphenol A (BPA) is an industrial component commonly used in synthesis of polycarbonate plastics, epoxy resin and other polymer materials. Due to its mass productions and widespread applications, the presence of BPA is ubiquitous in the environment. BPA can enter the body via different ways such as digestive tract, respiratory tract and dermal tract. As an endocrine disruptor, BPA has estrogen-like and anti-androgen effects causing damages to different tissues and organs, including reproductive system, immune system and neuroendocrine system, etc. Recently, it has been shown that BPA could induce carcinogenesis and mutagenesis in animal models. Here, the underlying mechanisms of BPA-induced multi-organ toxicity were well summarized, involving the receptor pathways, disruption of neuroendocrine system, inhibition of enzymes, modulation of immune and inflammatory responses, as well as genotoxic and epigenetic mechanisms. The aim of this review is to compile the available current research data regarding BPA and provide an overview of the current status of BPA exposure and relevant health effects covering reproductive, developmental, metabolic, immuno, respiratory, hepatic and renal toxicity and carcinogenesis of BPA. This review provides comprehensive data of BPA toxicity on human health and related mechanisms. We also identify any missing data which should be addressed by further studies.

Direct analysis in real time accurate mass spectrometry determination of bisphenol A in thermal printing paper

Contact with thermal printing paper is a relevant source of dermal exposure to unbonded bisphenol A (BPA). In order to limit this exposure route, the European Union has introduced a drastic reduction in the maximum allowed concentration of BPA in thermal paper produced after beginning of year 2020. This study investigates the suitability of direct analysis in real time (DART), combined with accurate mass spectrometry, as a faster alternative to chromatography-based methods for the quantitative determination of BPA, and three analogues species, in receipts and tickets usually printed on thermal paper. The ionization efficiency of these compounds is evaluated under different conditions, and the effect of instrumental parameters of the DART source in the observed responses is discussed. The yield of the DART desorption-ionization process was greatly improved when compounds are previously converted into their acetyl derivatives; thereafter, the temperature of electronically excited helium atoms was the most relevant of the evaluated instrumental parameters. Under optimized conditions, the reported method provided recoveries in the range from 90 to 110%, a limit of quantification of 0.004% (w:w), well below the maximum concentration established after 2020 for BPA (0.02%, w:w), and permitted to perform duplicate determinations of each sample extract with a response time around 1 min. The accuracy of BPA levels found in non-spiked samples was confirmed using GC-EI-MS as reference technique. BPA was systematically noticed in the processed samples with concentrations ranging from 0.005% to more than 6%.

Comparison of Bisphenol A and Bisphenol S Percutaneous Absorption and Biotransformation

BACKGROUND

Bisphenol S (BPS) has been widely substituted for bisphenol A (BPA) on thermal papers, but little is known about its skin absorption.

OBJECTIVES

We compared the percutaneous absorption and biotransformation of BPS and BPA in vitro and in a controlled human trial.

METHODS

Absorption and biotransformation of BPS and BPA were monitored across reconstructed human epidermis at two environmentally relevant doses over 25 h. In the human trial, five male participants handled thermal receipts containing BPS and washed their hands after 2 h. Urine (0-48 h) and serum (0-7.5h) were analyzed for target bisphenols, and one participant repeated the experiment with extended monitoring. BPS data were compared with published data for isotope-labeled BPA ([Formula: see text]) in the same participants.

RESULTS

At doses of 1.5 and [Formula: see text] applied to reconstructed human epidermis, the permeability coefficient of BPS (0.009 and [Formula: see text], respectively) was significantly lower than for BPA (0.036 and [Formula: see text], respectively), and metabolism of both bisphenols was negligible. In participants handling thermal receipts, the quantities of BPS and [Formula: see text] on hands was significantly correlated with maximum urinary event flux ([Formula: see text]), but the slope was lower for BPS than BPA ([Formula: see text] and 1.1, respectively). As a proportion of total urinary bisphenol, free BPS [[Formula: see text]: [Formula: see text]] was higher than for free BPA ([Formula: see text]). Postexposure maximum urinary BPS concentrations (0.93 to [Formula: see text]; [Formula: see text]) were in the 93-98th percentile range of BPS in background Canadians ([Formula: see text]; [Formula: see text]).

CONCLUSION

Both the in vitro and human studies suggested lower percutaneous absorption of BPS compared with BPA, but a lower biotransformation efficiency of BPS should also be considered in its evaluation as a BPA substitute. https://doi.org/10.1289/EHP5044.

Determination of bisphenol A and bisphenol S concentrations and assessment of estrogen- and anti-androgen-like activities in thermal paper receipts from Brazil, France, and Spain

Bisphenol A (BPA) is a high-production-volume chemical with endocrine disrupting properties commonly used as color developer in thermal paper. Concerns about the potential hazards of human BPA exposure have led to the increasing utilization of alternatives such as bisphenol S (BPS) and bisphenol F (BPF). This study was designed to assess: (i) BPA, BPS, and BPF concentrations in 112 thermal paper receipts from Brazil, France, and Spain by liquid chromatography coupled to mass spectrometry (LC-MS); and (ii) hormone-like activities of these receipts using two receptor-specific bioassays, the E-Screen for (anti-)estrogenicity and PALM luciferase assay for (anti-)androgenicity. BPA was present in 95.3% of receipts from Spain, 90.9% of those from Brazil, and 51.1% of those from France at concentrations up to 20.27 mg/g of paper. Only two samples from Brazil, two from Spain, and ten from France had a BPS concentration ranging from 6.46 to 13.29 mg/g; no BPA or BPS was detected in 27.7% of French samples. No BPF was detected in any receipt. Estrogenic activity was observed in all samples from Brazil and Spain and in 74.5% of those from France. Anti-androgenic activity was observed in > 90% of samples from Brazil and Spain and in 53.2% of those from France. Only 25.5% of French samples were negative for both estrogenic and anti-androgenic activity. Estrogenic and anti-androgenic activities per gram of paper were up to 1.411 µM estradiol (E₂) equivalent units (E₂eq) and up to 359.5 mM procymidone equivalent units (Proceq), respectively. BPA but not BPS concentrations were positively correlated with both estrogenic and anti-androgenic activities. BPA still dominates the thermal paper market in Brazil and Spain, and BPS appears to be one of the main alternatives in France. There is an urgent need to evaluate the safety of alternatives proposed to replace BPA as developer in thermal printing. The large proportion of samples with hormonal activity calls for the adoption of preventive measures.