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.

Assessment of BPA and BPS exposure in the general population in Guangzhou, China - Estimation of daily intakes based on urinary metabolites

Human exposure to bisphenol A (BPA) and bisphenol S (BPS) has garnered considerable global health concerns. In this paper, the daily intake (DI) of BPA and BPS in the general population of Guangzhou, China, were back-calculated using the biomarkers BPA glucuronides (BPA-G) and BPS glucuronides (BPS-G), respectively. The biomarkers are preferable to total BPA and BPS measurements because they are not susceptible to external contamination. A total of 1440 urine samples were gathered from the general population in Guangzhou, China, which were classified by age and sex into 36 pooled urine samples. 100% and 98% of pooled urine samples contained BPA-G and BPS-G at median values of 1.57 and 0.38 ng/mL, respectively. Based on urinary BPA-G and BPS-G concentrations, we determined the median DI of BPA and BPS to be 31.07 and 7.37 ng/(kg bw*d), respectively, and the highest values to be 106.77 ng/(kg bw*d) and 18.19 ng/(kg bw*d), respectively. Furthermore, our results showed that for the entire dataset, the DI of BPA and BPS were considerably greater in males than in females (p < 0.01)and declined significantly with age (p < 0.05). For risk assessment, the estimated DIs of BPA and BPS were much lower than the European Food Safety Authority^' s (EFSA) the temporary acceptable reference dose of 4 μg/(kg bw*d) advised for BPA, suggesting that the exposure risk of BPA and BPS for Guangzhou population is within a controllable safety range. This is the first study to investigate BPA and BPS exposure in the general population of Guangzhou, China, on the basis of urinary metabolites.

Biomonitoring of bisphenol A, 4-nonylphenol, and 4-t-octylphenol in Turkish population: exposure and risk assessment

Biomonitoring studies are important tools to understand the effects of endocrine-disrupting compounds on human health. Up to now, there have been no biomonitoring and risk assessment studies conducted in Turkish population in which urinary bisphenol A (BPA), 4-nonylphenol (4-NP), and 4-t-octylphenol (4-t-OP) levels were measured simultaneously. The aim of this study is to measure urinary BPA, 4-NP, and 4-t-OP on Turkish population and conduct a risk assessment using urinary levels of chemicals of interest. During the study, liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to measure urinary levels of above-mentioned chemicals, and human biomonitoring was used as a risk assessment tool in 103 volunteers, living in Mersin Region, Turkey. Urinary BPA, 4-NP, and 4-t-OP were founded as 0.0079 μg/g creatinine, 0.0177 μg/g creatinine, and 0.0114 μg/g creatinine, respectively. The obtained estimated daily intakes (EDIs) were calculated as 0.095 μg/kg bw/day, 0.041 μg/kg bw/day, and 0.091 μg/kg bw/day, for BPA, 4-NP, and 4-t-OP, respectively. In conclusion, although no potential health risk due to BPA and 4-NP exposure was observed, there might be health risks associated with 4-t-OP exposure in the Turkish population.

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.

Establishment of rapid, sensitive, and quantitative liquid chromatography-electrospray ionization-tandem mass spectrometry method coupled with liquid-liquid extraction for measurement of urinary bisphenol A, 4-t-octylphenol, and 4-nonylphenol

RATIONALE

Bisphenol A (BPA), 4-t-octylphenol (4-t-OP), and 4-nonylphenol (4-NP) are ubiquitous manufactured chemicals classified as endocrine disruptors. Now these substances are prevalent and found in a wide range of biological and environmental matrices globally. Acting as xenoestrogens, their target is to bind estrogen receptors and compete against natural hormones. Thus, there is an increasing concern on their negative health consequences.

METHODS

A rapid, sensitive, and robust method was established, validated, and used for the trace analysis of BPA, 4-t-OP, and 4-NP in human urine using liquid chromatography-electrospray ionization-tandem mass spectrometry.

RESULTS

The linear ranges for BPA, 4-t-OP, and 4-NP were 5.0-500 ng/mL. The correlation coefficient was higher than 0.996. The limit of detection and limit of quantitation for the compounds were 0.001, 0.007, and 0.005 ng/mL and 0.005, 0.023, and 0.180 ng/mL, respectively. The recoveries were as follows: 99.539%-108.557%, 97.780%-110.768%, and 99.694%-106.908% for BPA, 4-NP, and 4-t-OP respectively, with relative standard deviation <8.26%.

CONCLUSIONS

The established method was also applied effectively for the determination of BPA, 4-t-OP, and 4-NP levels in 15 human urine samples. This method was specifically developed for easy and precise analysis of BPA, 4-t-OP, and 4-NP in human urine. The method developed has been shown to be accurate, precise, and sensitive.

Investigating the glucuronidation and sulfation pathways contribution and disposition kinetics of Bisphenol S and its metabolites using LC-MS/MS-based nonenzymatic hydrolysis method

Despite showing serious health consequences and widespread exposure, the toxicokinetic information required to evaluate the health risks of BPS is insufficient. Thus, we aim to describe the comprehensive toxicokinetics of BPS and its glucuronide (BPS-G) and sulfate (BPS-S) metabolites in rats. Simultaneous quantification of BPS and its metabolites (authentic standards) was accomplished using UPLC-MS/MS method. BPS displayed rapid absorption, extensive metabolism and fast elimination after oral administration. Following intravenous administration, BPS exhibited CL (8.8 L/h/kg) higher than the rat hepatic blood flow rate suggesting the likelihood of extrahepatic clearance. The CL value differed from those reported previously (sheep and piglets) and the probable reason could be attributed to dose- and/or interspecies differences. BPS was extensively metabolized and excreted primarily through urine as BPS-G (∼56%). BPS and BPS-S exhibited a high protein binding capacity in comparison to BPS-G. In in vitro metabolic stability study, BPS was predominantly metabolized through glucuronidation. The predicted in vivo hepatic clearance of BPS suggested it to be a high and intermediate clearance chemical in rats and humans, respectively. The significant interspecies difference observed in the clearance of BPS between rats and humans indicated that toxicokinetics of BPS should be considered for health risk assessment in humans.

Bisphenol A and Metabolites in Meat and Meat Products: Occurrence, Toxicity, and Recent Development in Analytical Methods

Bisphenol A (BPA) is a commonly used compound in many industries and has versatile applications in polycarbonate plastics and epoxy resins production. BPA is classified as endocrine-disrupting chemical which can hamper fetal development during pregnancy and may have long term negative health outcomes in humans. Dietary sources, main route of BPA exposure, can be contaminated by the migration of BPA into food during processing. The global regulatory framework for using this compound in food contact materials is currently not harmonized. This review aims to outline, survey, and critically evaluate BPA contamination in meat products, including level of BPA and/or metabolites present, exposure route, and recent advancements in the analytical procedures of these compounds from meat and meat products. The contribution of meat and meat products to the total dietary exposure of BPA ranges between 10 and 50% depending on the country and exposure scenario considered. From can lining materials of meat products, BPA migrates towards the solid phase resulting higher BPA concentration in solid phase than the liquid phase of the same can. The analytical procedure is comprised of meat sample pre-treatment, followed by cleaning with solid phase extraction (SPE), and chromatographic analysis. Considering several potential sources of BPA in industrial and home culinary practices, BPA can also accumulate in non-canned or raw meat products. Very few scientific studies have been conducted to identify the amount in raw meat products. Similarly, analysis of metabolites and identification of the origin of BPA contamination in meat products is still a challenge to overcome.

Assessment of Bisphenol A Levels in Preschool Children: Results of a Human Biomonitoring Study in Ankara, Turkey

OBJECTIVE

There is general concern regarding environmental chemical exposure and the impact it may have on human health. This is particularly important for vulnerable populations such as infants and children during critical periods of development. Bisphenol A (BPA) is an endocrine disrupting chemical used worldwide over the last 30 years in many consumer products. Evidence points to widespread human exposure to BPA. The aim of this study was to evaluate the exposure of Turkish preschool children to BPA.

METHODS

This study was conducted as a preliminary investigation of BPA in urine, collected from 3-6 year old children living in Ankara. After spot urine samples were taken from preschool children, free BPA, β-D-glucuronide and total BPA were determined using high-performance liquid chromatography tandem mass spectrometry and adjusted by creatinine concentration.

RESULTS

Preschool children from Ankara (n=125; males n=70, females n=55; mean age: 4.50±1.26) were recruited. BPA was detected in 76.8% of children from Ankara city, with urinary concentrations ranging from < limit of quantification to 18.36 μg/g creatinine. Total BPA levels were not statistically different between boys (1.26 μg/g creatinine) and girls (2.24 μg/g creatinine) (p>0.05).

CONCLUSION

This study is an important contribution to the limited information about childhood exposure to BPA. The estimated daily BPA intake in this study is substantially lower than the European Food Safety Authority derived tolerable daily intake of 4 μg/kg BW/day.

Streamlined MRM method transfer between instruments assisted with HRMS matching and retention-time prediction

Multiple reaction monitoring (MRM) mode using liquid-chromatography tandem mass spectrometry (e.g., LC-QqQ-MS/MS) has been extensively employed in the small molecule analysis with trace levels in complex samples owing to its high sensitivity. However, most of the reported MRM methods are developed using authentic standards, which are often costly yet not readily available. To address this question, a practical platform for the MRM method transfer between different LC-QqQ-MS/MS instruments, assisted by the high-resolution mass spectrometry (LC-HRMS) and retention time (RT) prediction, has been developed in this study. The reported platform can take advantage of both the high sensitivity of LC-MRM method and ion transition pairs from the previous publications. LC-HRMS can provide the accurate mass measurement of the compounds, though high-quality MS/MS fragments are usually difficult to obtain for chemicals at trace levels. Retention time matching and peaks matching between both instrumental platforms rule out isobaric candidates. With an additional retention time prediction filter from quantitative structure retention relationship (QSRR) model based on random forest feature selection (Pearson r² = 0.63), identification of small molecules is achieved at a high confidence level without using authentic standards. The developed platform has been validated with robustness by examining spiked environmental chemicals in sludge water samples, biological urine, and cell extracts.

Glucuronide and Sulfate Conjugates of Bisphenol A: Chemical Synthesis and Correlation Between Their Urinary Levels and Plasma Bisphenol A Content in Voluntary Human Donors

Bisphenol A (BPA) glucuronide and sulfate conjugates are major products of Phase II metabolism of BPA in humans. In the past, their determination in body fluids usually involves tedious enzymatic hydrolysis and multiresidual analysis. The recent availability of authentic standards of these conjugates enables our better understand of the human metabolism of BPA and the distribution of their metabolites in body fluids. In this work, we report the chemical synthesis and purification of BPA mono- and di-glucuronide and BPA mono- and di-sulfate. Their levels, as well as that of BPA, in 140 paired human plasma and urine samples collected randomly from voluntary donors in Hong Kong SAR, China, were determined by solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS). BPA was found in more than 135 human plasma and urine samples. Its Phase II metabolites, ranging from N.D. to 36.7 µg g^-1-creatinine, also were detected in 139 of the 140 urine samples. Good correlation (r = 0.911) between molar concentration of BPA in the plasma and that of "total urinary BPA" (i.e., ln [(BPA + ∑ BPA phase II conjugate)_{molar concentration}]) was observed. Direct quantification of Phase II metabolites of BPA in human urine can be a useful assessment tool for population exposure to this potent endocrine disrupting chemical.

Recent advances in simultaneous analysis of bisphenol A and its conjugates in human matrices: Exposure biomarker perspectives

Human exposures to bisphenol A (BPA) has attained considerable global health attention and represents one of the leading environmental contaminants with potential adverse health effects including endocrine disruption. Current practice of measuring of exposure to BPA includes the measurement of unconjugated BPA (aglycone) and total (both conjugated and unconjugated) BPA; the difference between the two measurements leads to estimation of conjugated forms. However, the measurement of BPA as the end analyte leads to inaccurate estimates from potential interferences from background sources during sample collection and analysis. BPA glucuronides (BPAG) and sulfates (BPAS) represent better candidates for biomarkers of BPA exposure, since they require in vivo metabolism and are not prone to external contamination. In this work, the primary focus was to review the current state of the art in analytical methods available to quantitate BPA conjugates. The entire analytical procedure for the simultaneous extraction and detection of aglycone BPA and conjugates is covered, from sample pre-treatment, extraction, separation, ionization, and detection. Solid phase extraction coupled with liquid chromatograph and tandem mass spectrometer analysis provides the most sensitive detection and quantification of BPA conjugates. Discussed herein are the applications of BPA conjugates analysis in human exposure assessment studies. Measuring these potential biomarkers of BPA exposure has only recently become analytically feasible and there are limitations and challenges to overcome in biomonitoring studies.

The relation of urinary bisphenol A with kisspeptin in girls diagnosed with central precocious puberty and premature thelarche

BACKGROUND

Bisphenol A (BPA) is known as an endocrine disruptor and it is supposed to have a role on the development of central precocious puberty (CPP). Kisspeptin, a hypothalamic peptide, is a neuromodulator of gonadotropin releasing hormone and it has an important role on regulation of the onset of puberty. The BPA levels in girls with CPP and premature thelarche (PT) and its relation with kisspeptin levels were investigated.

METHODS

Twenty-eight girls with CPP, 28 girls with PT and 22 prepubertal girls as a control group were enrolled to the study. Urinary BPA and serum kisspeptin levels were compared in the groups. Bivariate correlations were performed to evaluate the relations of BPA with kisspeptin and estradiol.

RESULTS

There was no statistical difference between groups regarding BPA levels. Serum kisspeptin levels were higher in CPP group than controls [306.56 (interquartile range (IQR), 175.63-504.66) vs. 157.62 (IQR, 55.61-285.00) p: 0.008]. There were no correlations between BPA and kisspeptin levels (r: 0.088, p: 0.391) and between BPA and estradiol (r: -0.171, p: 0.144).

CONCLUSIONS

The BPA levels did not differentiate between groups and it seems that the exposed amount of BPA in daily life did not affect kisspeptin levels in girls with CPP and PT.

Determination of bisphenol A-glucuronide in human urine using ultrahigh-pressure liquid chromatography/tandem mass spectrometry

RATIONALE

Used widely as a plasticizer and as a monomer for plastics, bisphenol A (BPA) is under investigation as a possible endocrine disrupter. As an indication of systemic exposure, a fast and accurate assay was developed for the major BPA metabolite in human urine, BPA-monoglucuronide (BPA-G), using ultrahigh-pressure liquid chromatography/tandem mass spectrometry (UHPLC/MS/MS).

METHODS

Urine samples were prepared using solid-phase mixed-mode reversed-phase/anion-exchange extraction. BPA-G was measured using UHPLC/MS/MS with an amide UHPLC column interfaced to a triple-quadrupole mass spectrometer equipped with negative ion electrospray, collision-induced dissociation and selected reaction monitoring. [(13) C12 ]-BPA-G was used as a surrogate standard.

RESULTS

By measuring the glucuronide metabolite of BPA, potential interference due to BPA contamination from containers, solvents, pipette, etc., was avoided. The standard curve had a linear regression coefficient of 0.999, and the intra- and inter-assay variations were less than 10%. The assay was validated according to FDA guidelines.

CONCLUSIONS

A fast, accurate, and highly selective method for the determination of BPA-G in human urine was developed and validated using UHPLC/MS/MS. This method is suitable for assessing human exposure to BPA. Copyright © 2016 John Wiley & Sons, Ltd.

Determination of urinary levels of Bisphenol A in a Turkish population

Bisphenol A (BPA) is one of the environmental endocrine disrupting chemicals that is widely used in common consumer products. The aim of this study was to report the total urinary BPA concentrations (free plus conjugated) in 200 urine samples (children: 57; male: 74; female: 69) obtained from residents of a Mediterranean city, Mersin. Analyses were performed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) and for assessing environmental exposure to free BPA and its major metabolite bisphenol A glucuronide (BPAG) in human urine were determinated. Our results indicated that the free BPA and BPAG concentrations were in the range of 0.06-0.99 μg/g creatinine and 0.24-615 μg/g creatinine, respectively. No statistically significant difference obtained in BPA concentrations between genders (male and female) or domicile of residence (rural and urban) (p > 0.05). In our study, the mean level of detected free BPA was 0.46 μg/g creatinine in the urban area and 0.37 μg/g creatinine in the rural area. The average amount of BPAG was 60.56 μg/g creatinine in the urban area and 30.28 μg/g creatinine in the rural area. The data demonstrate that determined amount of total BPA in the present study is lower than the results of similar studies conducted in developed countries. There is no data about the levels of BPA in humans and environment in Turkey. Because of this reason, present study is very important since it is the first study in Turkey which determined the concentrations of free BPA and total BPA in human.