Determination of free and conjugated forms of bisphenol A in human urine and serum by liquid chromatography-tandem mass spectrometry

Association between urinary levels of bisphenol A and its monochlorinated derivative and obesity

Population-based studies suggest the association between exposures to bisphenol A (BPA) and obesity. However, no human studies are available that link exposures to chlorinated derivatives of BPA with obesity biomarkers. The objective of this exploratory post hoc analysis of our cross-sectional study's dataset was to evaluate the association between urinary levels of BPA and monochlorinated BPA (mono-ClBPA) with body mass index (BMI) in a random sample of 223 adults (≥18 years) from the general population in Cyprus. Univariate analysis and multiple logistic regressions were performed for descriptive statistics and estimating odds ratio (OR) of above normal BMI, respectively. We observed a relatively weak positive association between urinary mono-ClBPA and BMI, such as (i) 76 ng g(-1) in participants with above normal BMI (≥25 kg m(-2)) versus 55 ng g(-1) in those with normal BMI (<25 kg m(-2)) (P for mean difference = 0.053) and (ii) higher percentage of participants with above normal BMI in the high urinary mono-ClBPA tertile (63% in tertile 3 and 57% in tertile 2 versus 50% in tertile 1, P for trend = 0.056). Similar tests of association between urinary BPA and BMI showed null outcome. A dichotomously-classified group analysis showed an increased odds ratio (OR) for higher BMI in the group with high creatinine-adjusted urinary levels of BPA and mono-ClBPA when compared with the participants group with low levels for both compounds [logistic model adjusted for gender and health status as potential confounders; adjusted OR (95% CI): 2.34 (1.10, 5.10), P = 0.027]. Measurements of both BPA and its trace chlorinated derivative in human matrices may be warranted for a comprehensive exposure assessment towards improving our understanding of their obesogenic effects.

Preliminary evidence of the association between monochlorinated bisphenol A exposure and type II diabetes mellitus: A pilot study

Evidence for the association of bisphenol A (BPA) with type II diabetes mellitus (T2DM) has been inconsistent in human studies. In-vitro and animal studies indicate that chlorinated BPA derivatives aggravate BPA health effects via higher estrogenic activity and alteration of membrane-initiating signaling pathways. We evaluated the association between urinary monochlorinated BPA (mono-ClBPA) concentrations and the incidence of T2DM. In our cross-sectional study, we identified 20 adult participants (≥18 yr) who reported having T2DM (doctor-diagnosed) and 131 adults with normal health. First morning void urine samples were analyzed for total BPA and mono-ClBPA. Detection limits of the analytical method were 95 ng L(-1) for BPA and 32 ng L(-1) for mono-ClBPA. Multivariable logistic regression analyses and additive Bayesian network modeling were performed. After adjusting for age, gender, BMI, urinary total BPA and other confounders, the odds of having T2DM was 3.29 times higher (95% confidence interval, CI: 1.10, 11.4; P < 0.05) per unit increase in log-transformed and creatinine-adjusted urinary mono-ClBPA levels (n = 151); this relation did not hold for total BPA. The globally optimum Bayesian model corroborated the results of the logistic regression by expressing mono-ClBPA in the pathway of T2DM, and not for total BPA. An age-matched sensitivity analysis confirmed the increase in OR of T2DM by 3.04 times (95% CI: 1.10, 11.0; P < 0.05) per unit increase in log-transformed and creatinine-adjusted urinary mono-ClBPA concentration (n = 68). The urinary monochlorinated BPA derivative was significantly associated with T2DM, whereas the parent compound (total BPA) was not. Caution should be applied in interpreting these findings, as this is the first study to report this association and the sample size of participants with T2DM is small. Additional research with a larger sample size coupled with relevant toxicological studies is warranted.

Evidence that bisphenol A (BPA) can be accurately measured without contamination in human serum and urine, and that BPA causes numerous hazards from multiple routes of exposure

There is extensive evidence that bisphenol A (BPA) is related to a wide range of adverse health effects based on both human and experimental animal studies. However, a number of regulatory agencies have ignored all hazard findings. Reports of high levels of unconjugated (bioactive) serum BPA in dozens of human biomonitoring studies have also been rejected based on the prediction that the findings are due to assay contamination and that virtually all ingested BPA is rapidly converted to inactive metabolites. NIH and industry-sponsored round robin studies have demonstrated that serum BPA can be accurately assayed without contamination, while the FDA lab has acknowledged uncontrolled assay contamination. In reviewing the published BPA biomonitoring data, we find that assay contamination is, in fact, well controlled in most labs, and cannot be used as the basis for discounting evidence that significant and virtually continuous exposure to BPA must be occurring from multiple sources.

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.

Holding thermal receipt paper and eating food after using hand sanitizer results in high serum bioactive and urine total levels of bisphenol A (BPA)

Bisphenol A (BPA) is an endocrine disrupting environmental contaminant used in a wide variety of products, and BPA metabolites are found in almost everyone's urine, suggesting widespread exposure from multiple sources. Regulatory agencies estimate that virtually all BPA exposure is from food and beverage packaging. However, free BPA is applied to the outer layer of thermal receipt paper present in very high (∼20 mg BPA/g paper) quantities as a print developer. Not taken into account when considering thermal paper as a source of BPA exposure is that some commonly used hand sanitizers, as well as other skin care products, contain mixtures of dermal penetration enhancing chemicals that can increase by up to 100 fold the dermal absorption of lipophilic compounds such as BPA. We found that when men and women held thermal receipt paper immediately after using a hand sanitizer with penetration enhancing chemicals, significant free BPA was transferred to their hands and then to French fries that were eaten, and the combination of dermal and oral BPA absorption led to a rapid and dramatic average maximum increase (Cmax) in unconjugated (bioactive) BPA of ∼7 ng/mL in serum and ∼20 µg total BPA/g creatinine in urine within 90 min. The default method used by regulatory agencies to test for hazards posed by chemicals is intra-gastric gavage. For BPA this approach results in less than 1% of the administered dose being bioavailable in blood. It also ignores dermal absorption as well as sublingual absorption in the mouth that both bypass first-pass liver metabolism. The elevated levels of BPA that we observed due to holding thermal paper after using a product containing dermal penetration enhancing chemicals have been related to an increased risk for a wide range of developmental abnormalities as well as diseases in adults.

Urinary levels of bisphenol analogues in residents living near a manufacturing plant in south China

The use of bisphenol A (BPA) has been restricted in many countries because of its potential health effects. As a result of these restrictions, a group of bisphenol analogues that are structurally similar to BPA have been developed as the alternatives for industrial applications. However, latest researches indicated that these chemicals have similar endocrine-disrupting effects as BPA in humans. Moreover, only a limited number of studies have attempted to monitor the exposure level in humans of other bisphenol analogues. In the present study, the concentrations of seven bisphenols, including bisphenol S (BPS), bisphenol F (BPF), bisphenol B (BPB), BPA, bisphenol AF (BPAF), tetrachlorobisphenol A (TCBPA) and tetrabromobisphenol A (TBBPA), in human urine samples were measured by liquid chromatography coupled to mass spectrometry (LC-MS/MS) following the enzymatic hydrolysis of glucuronidase/arylsulfatase and liquid-liquid extraction (LLE). Under the optimised conditions, high recoveries (81.6-116.8%) were obtained for all the analytes, and the relative standard deviations (RSD, %) were less than 16.4% (n=6). The isotopic internal standard calibration curves for each of the target compounds exhibited excellent linearity (r(2)>0.99) and the limit of quantification (LOQ) for the analytes in urine ranged from 0.024 to 0.310 ng mL(-1). The method was applied to investigate the urinary levels of these seven bisphenols in a cohort of residents living near a BPAF manufacturing plant in south China. BPS, BPF, BPA and BPAF were detected in urine samples at concentrations ranging from <LOQ to a few ng mL(-1), whereas BPB, TCBPA and TBBPA were not detected. This is the first study to report the occurrence of BPF and BPAF in human urine samples. The availability of rapid and simple analytical methods may be highly useful for the future biomonitoring of these compounds.

Influence of household cleaning practices on the magnitude and variability of urinary monochlorinated bisphenol A

Low-dose health effects of BPA have not been adequately explored in the presence of BPA metabolites of chlorinated structure that may exert larger estrogenic effects than those of their parent compound. We hypothesized that chlorine-containing cleaning products used in household cleaning activities could modify the magnitude of total urinary BPA concentration measurements via the production of chlorinated BPA (ClBPA) derivatives. Our objective was to investigate the influence of typical household cleaning activities (dishwashing, toilet cleaning, mopping, laundry, etc.) on the magnitude and variability of urinary total BPA and mono-ClBPA levels in the general adult population. A cross-sectional study (n=224) included an adult (≥18 years) pool of participants from the general population of Nicosia, Cyprus. First morning urine voids were collected, and administered questionnaires included items about household cleaning habits, demographics, drinking water consumption rates and water source/usage patterns. Urinary concentrations of total BPA (range: 0.2-82 μg L(-1)), mono-ClBPA (16-340 ng L(-1)), and total trihalomethanes (0.1-5.0 μg L(-1)) were measured using gas chromatography coupled with triple quadrupole mass spectrometry and large volume injection. Linear multiple regression analysis revealed that dishwashing along with age and gender (females) were able to predict urinary mono-ClBPA levels (ng g(-1)), even after adjusting for covariates; this was not the case for urinary total BPA levels (ng g(-1)). Significant (p<0.001) association was observed between urinary mono-ClBPA and THM levels, underlying the important role of disinfectant (chlorine) in promoting formation of both ClBPA and THM. Urinary mono-ClBPA levels were measured for the first time using an appreciable sample size, highlighting the co-occurring patterns of both total BPA and mono-ClBPA. Epidemiological studies and probabilistic BPA risk assessment exercises should consider assessing daily intake estimates for chlorinated BPA compounds, as well.

Determination of free Bisphenol A (BPA) concentrations in breast milk of U.S. women using a sensitive LC/MS/MS method

Bisphenol A (BPA) is a synthetic, endocrine-disrupting compound. Free BPA has been detected in human samples indicating that humans are internally exposed to estrogenically active BPA. The purpose of this study was to develop a sensitive method to detect free BPA in human breast milk. BPA was isolated from the milk of 21 nursing mothers in the U.S. by solid-phase extraction. It was then derivatized to improve sensitivity and subsequently analyzed by ultra high performance liquid chromatography-tandem mass spectrometry. Free BPA was detected in 62% of the milk samples (≤ 0.22-10.8 ng mL(-1), median 0.68 ng mL(-1), mean 3.13 ng mL(-1)). No statistical difference in BPA concentrations was observed between women with a low or high Body Mass Index (BMI) (<30 (n=11) and>30 (n=10), respectively). However, there was a significant association between BPA concentration and race. Caucasian women had significantly higher levels of free BPA in their breast milk than non-Caucasian women (mean=4.44 (n=14) and 0.52 (n=7), respectively; p<0.05). The difference between races could be attributed to variations in exposure, lifestyle or metabolism and suggests that certain populations should take extra precautions to limit BPA exposure, particularly during pregnancy and lactation.

Determination of bisphenol A, triclosan and their metabolites in human urine using isotope-dilution liquid chromatography-tandem mass spectrometry

Bisphenol A (BPA) and triclosan (TCS) are ubiquitous environmental phenols exhibiting endocrine disrupting activities that may be involved in various health disorders in humans. There is a need to measure separately free forms and conjugated metabolites because only the former are biologically active. We have developed sensitive methods using isotope-dilution liquid chromatography-tandem mass spectrometry for individual measurements of free BPA and TCS as well as their metabolites, BPA glucuronide (BPAG), BPA monosulfate (BPAS), BPA disulfate (BPADS), TCS glucuronide (TCSG) and TCS sulfate (TCSS) in urine. Comparative analyses of urine samples from 46 volunteers living in the Quebec City area using the new methods and a GC-MS/MS method previously used in our laboratory revealed very strong correlations for total BPA (Spearman's rs=0.862, p<0.0001) and total TCS concentrations (rs=0.942, p<0.0001). Glucuronide metabolites were the most abundant BPA and TCS species in urine samples (>94% of total urinary concentrations). Unconjugated TCS concentrations represented a small proportion of total TCS species (median=1.6%) but its concentration was likely underestimated due to losses by adsorption to the surface of polypropylene tubes used for sample storage. To our knowledge, we are the first to report levels of free, sulfated and glucuronidated TCS levels in human urine.

A round robin approach to the analysis of bisphenol A (BPA) in human blood samples

BACKGROUND

Human exposure to bisphenol A (BPA) is ubiquitous, yet there are concerns about whether BPA can be measured in human blood. This Round Robin was designed to address this concern through three goals: 1) to identify collection materials, reagents and detection apparatuses that do not contribute BPA to serum; 2) to identify sensitive and precise methods to accurately measure unconjugated BPA (uBPA) and BPA-glucuronide (BPA-G), a metabolite, in serum; and 3) to evaluate whether inadvertent hydrolysis of BPA-G occurs during sample handling and processing.

METHODS

Four laboratories participated in this Round Robin. Laboratories screened materials to identify BPA contamination in collection and analysis materials. Serum was spiked with concentrations of uBPA and/or BPA-G ranging from 0.09-19.5 (uBPA) and 0.5-32 (BPA-G) ng/mL. Additional samples were preserved unspiked as 'environmental' samples. Blinded samples were provided to laboratories that used LC/MSMS to simultaneously quantify uBPA and BPA-G. To determine whether inadvertent hydrolysis of BPA metabolites occurred, samples spiked with only BPA-G were analyzed for the presence of uBPA. Finally, three laboratories compared direct and indirect methods of quantifying BPA-G.

RESULTS

We identified collection materials and reagents that did not introduce BPA contamination. In the blinded spiked sample analysis, all laboratories were able to distinguish low from high values of uBPA and BPA-G, for the whole spiked sample range and for those samples spiked with the three lowest concentrations (0.5-3.1 ng/ml). By completion of the Round Robin, three laboratories had verified methods for the analysis of uBPA and two verified for the analysis of BPA-G (verification determined by: 4 of 5 samples within 20% of spiked concentrations). In the analysis of BPA-G only spiked samples, all laboratories reported BPA-G was the majority of BPA detected (92.2 - 100%). Finally, laboratories were more likely to be verified using direct methods than indirect ones using enzymatic hydrolysis.

CONCLUSIONS

Sensitive and accurate methods for the direct quantification of uBPA and BPA-G were developed in multiple laboratories and can be used for the analysis of human serum samples. BPA contamination can be controlled during sample collection and inadvertent hydrolysis of BPA conjugates can be avoided during sample handling.

Serum levels of unconjugated bisphenol A are below 0.2ng/ml in Swedish nursing women when contamination is minimized

In this study serum levels of bisphenol A (BPA) were investigated in primiparous women from Uppsala County, Sweden, sampled 3weeks after delivery 1996-2011, in both yearly pools of serum (n=39, temporal trend study) and in 208 individual samples also present in the pools. Possible contamination risks of BPA from blood sampling equipment and sample tubes, as well as from handling of the samples were evaluated. The unconjugated form of BPA was analyzed using a UPLC-MS/MS method with a limit of quantification (LOQ) of 0.2ng/ml. The results show that the levels of unconjugated BPA generally were <0.2ng/ml. The sampling equipment used when taking blood samples from the women and the tubes used for storage and processing of samples did not show any detectable BPA leakage. In the first analysis of the serum samples, unconjugated BPA levels ≥0.2ng/ml were found in 12% of the individual samples and in 21% of the trend samples. However, in reanalyses of individual serum samples from the same aliquot or from new aliquots, samples with BPA levels ≥0.2ng/ml in the first analysis did not have quantifiable BPA levels. Moreover, 11% of BPA spiked calibration samples (over 200) had higher levels than could be explained by the random error of the method. Thus BPA contamination of the biobanked samples probably occurred randomly during sample handling, pooling and processing. Equipment used for sampling of children and repeated blood sampling were leaking BPA. The results show the difficulties in analyzing compounds where samples are easily contaminated from exogenous sources. It also points out that it is questionable to use biobanked samples unless absence of BPA contamination from the sampling and storage materials, and during handling of the samples, can be proven.

Bisphenol A (BPA) pharmacokinetics with daily oral bolus or continuous exposure via silastic capsules in pregnant rhesus monkeys: Relevance for human exposures

We measured serum dBPA in non-pregnant and pregnant female rhesus monkeys, fetuses and amniotic fluid. dBPA was administered by a daily oral bolus or sc implantation of Silastic capsules; both resulted in daily average serum unconjugated dBPA concentrations of <1ng/ml. We observed lower serum concentrations of unconjugated dBPA in pregnant females relative to pre-pregnancy values, and generally lower concentrations in fetal serum than in maternal serum. Differences in pharmacokinetics of dBPA were evident between pre-pregnancy, early and late pregnancy, likely reflecting changes in maternal, fetal and placental physiology. The serum ratio of conjugated to unconjugated dBPA after continuous sc release of dBPA was similar to values reported in human biomonitoring studies and markedly lower than with oral administration, suggesting oral bolus exposure is not an appropriate human exposure model. We report elsewhere that there were numerous adverse effects on fetuses exposed to very low serum dBPA in these studies.

Biomonitoring method for bisphenol A in human urine by ultra-high-performance liquid chromatography-tandem mass spectrometry

An ultra-high-performance liquid chromatography-tandem mass spectrometry method for the measurement of total bisphenol A in human urine was developed and validated. The method utilized liquid/liquid extraction with 1-chlorobutane and a human urine aliquot size of 800μL. Chromatography was performed on an Acquity UPLC(®) system with a Kinetex(®) Phenyl-Hexyl column. Mass spectrometric analysis was with negative electrospray ionization on a Quattro Premier XE™. The surrogate matrix method was used for the preparation of calibration standards in synthetic urine due to the presence of BPA in control human urine. The validated calibration range was 0.75-20ng/mL with a limit of detection of 0.1ng/mL. The internal standard was d16-bisphenol A. Method validation utilized quality control samples at three concentrations in both synthetic urine and human urine. Bisphenol A mono-glucuronide was fortified in synthetic urine in each analytical run to monitor the enzymatic conversion of the glucuronide conjugate to BPA by β-glucuronidase. Validated method parameters included linearity, accuracy, precision, integrity of dilution, selectivity, re-injection reproducibility, recovery/matrix effect, solution stability, and matrix stability in human urine. Acceptance criteria for analytical standards and QCs were ±20% of nominal concentration. Matrix stability in human urine was validated after 24h at ambient temperature, after three freeze/thaw cycles, and after frozen storage at -20°C and -80°C for up to 218 days. The method has been applied to the analysis of over 1750 human urine samples from a biomonitoring study. The median and mean urine BPA concentrations were 2.71ng/mL and 4.75ng/mL, respectively.

Is drinking water a major route of human exposure to alkylphenol and bisphenol contaminants in France?

The main objective of this study was to evaluate potential exposure of a significant part of the French population to alkylphenol and bisphenol contaminants due to water consumption. The occurrence of 11 alkylphenols and bisphenols was studied in raw water and treated water samples from public water systems. One sampling campaign was performed from October 2011 to May 2012. Sampling was equally distributed across 100 French departments. In total, 291 raw water samples and 291 treated water samples were analyzed in this study, representing approximately 20 % of the national water supply flow. The occurrence of the target compounds was also determined for 29 brands of bottled water (polyethylene terephthalate [PET] bottles, polycarbonate [PC] reusable containers, and aluminum cans [ACs]) and in 5 drinking water networks where epoxy resin has been used as coating for pipes. In raw water samples, the highest individual concentration was 1,430 ng/L for bisphenol A (BPA). Of the investigated compounds, nonylphenol (NP), nonylphenol 1-carboxylic acid (NP1EC), BPA, and nonylphenol 2-ethoxylate (NP2EO) predominated (detected in 18.6, 18.6, 14.4, and 10 % of samples, respectively). Geographical variability was observed with departments crossed by major rivers or with high population densities being more affected by contamination. In treated water samples, the highest individual concentration was 505 ng/L for NP. Compared with raw water, target compounds were found in lower amounts in treated water. This difference suggests a relative effectiveness of certain water treatments for the elimination of these pollutants; however, there is also their possible transformation by reaction with chlorine. No target compounds were found in drinking water pipes coated with epoxy resin, in PET bottled water, or in water from ACs. However, levels of BPA in PC bottled water ranged from 70 to 4,210 ng/L with greater level observed in newly manufactured bottles. 4-Tert-butylphenol was only detected in recently manufactured bottles. The values observed for the monitored compounds indicate that drinking water is most likely not the main source of exposure.

Bisphenol a and its chlorinated derivatives in human colostrum

The health effects related to bisphenol A (BPA) and its exposure sources have undergone extensive investigation, but no consensus has been reached. Hitherto, the major source of human BPA exposure considered in the literature remains food-contact material. However, the chlorine present in drinking water may react with BPA to form chlorinated derivatives (ClxBPA), which have indeed been shown to have a heightened level of estrogenic activity. In this study, we have evaluated colostrum concentrations of BPA and ClxBPA in order to confirm our hypothesis according to which BPA water contamination leads to ClxBPA human exposure. BPA and its ClxBPA were assessed through online solid-phase extraction coupled to ultra high-performance liquid chromatography tandem mass spectrometry (SPE-UPLC-MS/MS) using the isotope dilution method in the colostrums of 21 women who had completed a water exposure questionnaire. BPA was detected in 19 colostrums and its ClxBPA in 21 colostrums. Mean concentrations were 1.87 ± 1.38 ng mL(-1) (n = 19) for BPA, 1.87 ± 1.23 ng mL(-1) (n = 7) and 1.56 ± 0.74 (n = 18) ng mL(-1) for 2,2'-Cl2BPA and 2,6-Cl2BPA, respectively, and 0.68 ng mL(-1) (n = 1) for trichloro-BPA. These findings confirm our hypothesis that ClxBPA should be taken into account in human health risk assessment.

A multi-class bioanalytical methodology for the determination of bisphenol A diglycidyl ethers, p-hydroxybenzoic acid esters, benzophenone-type ultraviolet filters, triclosan, and triclocarban in human urine by liquid chromatography-tandem mass spectrometry

A liquid-liquid extraction (LLE; ethyl acetate) protocol, followed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) methodology, was developed for the determination of 19 compounds, including bisphenol A diglycidyl ethers (BADGEs; industrial ethers), benzophenone-type UV filters (BP-UV filters; precursors and metabolites), p-hydroxybenzoic acid esters (parabens; preservatives), triclosan (TCS) and triclocarban (TCC) in human urine. Urine specimens were enzymatically deconjugated with β-glucuronidase (from Helix pomatia) and extracted by a LLE procedure for the measurement of total concentrations (i.e., free+conjugated forms) of target analytes. Absolute recoveries of BADGEs, BP-UV filters, parabens, TCS and TCC ranged 25-135%, 84-125%, 52-126%, 75-118% and 90-124%, respectively. Method precision (absolute values; N=5 replicate analyses at the fortification level of 10 ng, k=5 days) ranged from 5.8 (ethyl paraben) to 24.0% (TCS). The limits of quantification (LOQs) varied depending on the target compound and generally ranged from 0.2 to 2.0 ng/mL. The matrix effects ranged from +11 (2,3,4-trihydroxybenzophenone) to -86% (2,4-dihydroxybenzophenone). A total of 30 urine specimens collected from Athens, Greece, were analyzed for the 19 target compounds to demonstrate the applicability of the developed method. The concentrations of target chemicals in urine were presented on volume-, specific gravity (SG)-, and creatinine-normalization bases. MeP, EtP, PrP, OH-EtP, BADGE·2H2O, BP-1 and TCS were found frequently in urine at concentrations in the range of 2.7-436 ng/mL, <0.5-25.4 ng/mL, <0.5-575 ng/mL, <2-18.4 ng/mL, <0.5-13.8 ng/mL, <1-14.6 ng/mL and <0.5-95.3 ng/mL, respectively.

A systematic review of Bisphenol A "low dose" studies in the context of human exposure: a case for establishing standards for reporting "low-dose" effects of chemicals

Human exposure to the chemical Bisphenol A is almost ubiquitous in surveyed industrialized societies. Structural features similar to estrogen confer the ability of Bisphenol A (BPA) to bind estrogen receptors, giving BPA membership in the group of environmental pollutants called endocrine disruptors. References by scientists, the media, political entities, and non-governmental organizations to many toxicity studies as "low dose" has led to the belief that exposure levels in these studies are similar to humans, implying that BPA is toxic to humans at current exposures. Through systematic, objective comparison of our current, and a previous compilation of the "low-dose" literature to multiple estimates of human external and internal exposure levels, we found that the "low-dose" moniker describes exposures covering 8-12 orders of magnitude, the majority (91-99% of exposures) being greater than the upper bound of human exposure in the general infant, child and adult U.S. Population. "low dose" is therefore a descriptor without specific meaning regarding human exposure. Where human exposure data are available, for BPA and other environmental chemicals, reference to toxicity study exposures by direct comparison to human exposure would be more informative, more objective, and less susceptible to misunderstanding.

Blood and urinary bisphenol A concentrations in children, adults, and pregnant women from china: partitioning between blood and urine and maternal and fetal cord blood

Limited information exists on exposure to bisphenol A (BPA) by children, adults, and pregnant women in China. In the present study, we determined BPA concentrations in whole blood collected from 10 children (1-5 years), 40 women (30 pregnant and 10 nonpregnant), and 30 fetuses (i.e., cord blood). Further, to evaluate the relationship between urinary and blood BPA concentrations, paired specimens of blood and urine (n = 50 pairs) were collected from an adult population. BPA was found in 46% of all blood samples analyzed, with a geometric mean (GM) concentration of 0.19 ng/mL. BPA was found in 84% of urine samples from adults, with a GM concentration of 1.01 ng/mL [0.48 μg/g creatinine (Cr)]. Gender and age were not good predictors of blood BPA concentrations. However, we did find that the creatinine-adjusted urinary BPA concentrations in females were significantly higher (p < 0.05) than the concentrations found in males and that the blood BPA concentrations in children were significantly higher (p < 0.05) than the concentrations found in adults. Among all adults, unadjusted urinary BPA concentrations (i.e., volume-based) were inversely (r = -0.312, p < 0.05) correlated with age when an outlier value (8.70 ng/mL) was excluded from analysis. Concentrations of BPA in urine (creatinine-adjusted) and blood were significantly correlated (r = 0.571, p < 0.01), with concentrations measured in urine approximately an order of magnitude higher than the concentrations found in blood. The mean and GM values for ratios of concentration of BPA between blood and urine were 0.109 and 0.057, respectively. The ratio of mean concentrations of BPA between cord blood and maternal blood was 0.108. On the basis of urinary BPA levels, we estimated the total daily intake (EDI) of BPA by Chinese adults. The mean (range) EDIs of BPA by adult males and females in China were 0.041 (<0.005-0.224) and 0.048 (<0.005-0.151) ug/kg bw/day, respectively. The pregnant women who underwent intravenous drug administration immediately before delivery had significantly higher concentrations of BPA in their blood than did those who did not receive intravenous drug administration. This is the first study to document the occurrence of and human exposure to BPA by pregnant women and fetuses from China.

Surface-imprinted core-shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering

Surface-imprinted core-shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol-gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2 nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10 min owning to the advantage of ultrathin core-shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5-22.8 mg L(-1), with a detection limit of 0.12 mg L(-1) (blank±3×s.d.). When applied to SERS detection, the developed surface-imprinted core-shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples.

Fetal liver bisphenol A concentrations and biotransformation gene expression reveal variable exposure and altered capacity for metabolism in humans

Widespread exposure to the endocrine active compound, bisphenol A (BPA), is well documented in humans. A growing body of literature suggests adverse health outcomes associated with varying ranges of exposure to BPA. In the current study, we measured the internal dose of free BPA and conjugated BPA and evaluated gene expression of biotransformation enzymes specific for BPA metabolism in 50 first- and second-trimester human fetal liver samples. Both free BPA and conjugated BPA concentrations varied widely, with free BPA exhibiting three times higher concentrations than conjugated BPA concentrations. As compared to gender-matched adult liver controls, UDP-glucuronyltransferase, sulfotransferase, and steroid sulfatase genes exhibited reduced expression whereas β-glucuronidase mRNA expression remained unchanged in the fetal tissues. This study provides evidence that there is considerable exposure to BPA during human pregnancy and that the capacity for BPA metabolism is altered in the human fetal liver.

The contribution of diet to total bisphenol A body burden in humans: results of a 48 hour fasting study

Human biomonitoring studies measuring bisphenol A (BPA) in urine have shown widespread exposure in the general population. Diet is thought to be a major route of exposure. We studied urinary BPA patterns in five individuals over a 48-h period of fasting (bottled water only). Personal activity patterns were recorded with a diary to investigate non-dietary routes of exposure. All urine void events during the fast were collected, as well as events before and after the fast. The pattern of BPA concentrations was similar for all participants: they rose near the beginning of the fast (after the pre-fast meal), declined over the next 24h, fluctuated at lower levels during the second day, and then rose after the post-fast meal. Concentrations (~2 μg/g creatine) and calculated BPA intakes (~0.03 μg/kg-day) in these individuals during the first 24h were consistent with general population exposures. For the second 24h, concentrations and intakes declined by about two-thirds. One of the individuals had an extraordinary pre-fast exposure event with concentrations rising as high as 98 μg/g creatine but declining to <5 μg/g creatine by day 2. Given patterns found in day 1 and the subsequent decline to lower levels in day 2, we hypothesize that BPA exposures in these individuals were diet-driven. No events in the diary (use of personal care products, e.g.) appear associated with exposures. On day 2, non-dietary sources may still be present, such as from dust. Another hypothesis is that small reservoirs of BPA from past exposures are released from storage (lipid reservoirs, e.g.) and excreted.

Synthesis and characterization of bromophenol glucuronide and sulfate conjugates for their direct LC-MS/MS quantification in human urine as potential exposure markers for polybrominated diphenyl ethers

Bromophenol glucuronide and sulfate conjugates have been reported to be products of mammalian metabolism of polybrominated diphenyl ethers (PBDEs), a group of additive flame-retardants found ubiquitously in the environment. In order to explore their occurrence in human urine, four water-soluble bromophenol conjugates, namely, 2,4-dibromophenyl glucuronide, 2,4,6-tribromophenyl glucuronide, 2,4-dibromophenyl sulfate, and 2,4,6-tribromophenyl sulfate, were synthesized, purified, and characterized. An analytical protocol using solid-phase extraction and ion-paired liquid chromatography-electrospray tandem mass spectrometry (LC-ESI-MS/MS) quantification has been developed for the direct and simultaneous determination of these glucuronide and sulfate conjugates in human urine samples. The limit of detections for all analytes were below 13 pg mL(-1), with 73-101% analyte recovery and 7.2-8.6% repeatability. The method was applied to analyze 20 human urine samples collected randomly from voluntary donors in Hong Kong SAR, China. All the samples were found to contain one or more of the bromophenol conjugates, with concentration ranging from 0.13-2.45 μg g(-1) creatinine. To the best of our knowledge, this is the first analytical protocol for the direct and simultaneous monitoring of these potential phase II metabolites of PBDEs in human urine. Our results have also suggested the potential of these bromophenol conjugates in human urine to be convenient molecular markers for the quantification of population exposure to PBDEs.

Association between bisphenol A exposure and body mass index in Chinese school children: a cross-sectional study

BACKGROUND

There is increasing evidence suggesting that Bisphenol A (BPA), one of the highest volume chemicals produced worldwide, can interfere with the body's natural weight control mechanisms to promote obesity. However, epidemiological studies for this are limited, especially for children.

METHODS

A cross-sectional study was conducted to investigate the association between BPA exposure and body mass index (BMI) in school children. Three primary and three middle schools were randomly selected from 26 primary and 30 middle candidate schools in Changning District of Shanghai City in China. According to the BMI-based criteria by age and sex for screening of overweight or obese children, we randomly chose 20 obese, 10 overweight, and 30 normal weight children aged 8-15 years of age from each selected school. First morning urine was collected and total urine BPA concentrations were determined by ultra-performance liquid chromatography tandem mass spectrometry. Multiple linear regression analysis was conducted to examine the association of urine BPA concentrations and daily intake estimates with BMI.

RESULTS

BPA was detected in 84.9% of urine samples with a geometric mean of 0.45 ng/mL. The daily intake estimates ranged from 0.03 μg/day to 1.96 μg/day with a geometric mean of 0.37 μg/day. The average urine BPA concentrations and daily intake estimates were similar for boys and girls, but significantly higher in older children than younger ones, and showed an increasing trend with BMI. Multiple linear regression analyses showed that urine BPA concentrations were significantly associated with increasing BMI values in all subjects after adjustment for age and sex and the results were similar before and after corrected by urine specific gravity. When stratified by age or sex, the associations remained significant in females and in those 8-11 years of age before corrected by specific gravity. Similar results were shown for the association between BMI and daily intake estimates.

CONCLUSIONS

There is a possibility that BPA exposure increases BMI in school children. Given the cross-sectional nature of this study, longitudinal studies are warranted to confirm BPA exposure as a contributor to increased BMI in children.