Bisphenol A Measurements Research Articles

Urinary Bisphenol A and Type-2 Diabetes in U.S. Adults: Data from NHANES 2003-2008

ObjectiveBisphenol A (BPA) is found in plastics and other consumer products; exposure may lead to insulin resistance and development of type-2 diabetes mellitus (T2DM) through over-activation of pancreatic β-cells. Previous studies using data from the National Health and Nutrition Examination Survey (NHANES) showed an inconsistent association between prevalence of self-reported T2DM and urinary BPA. We used a different diagnosis method of T2DM (hemoglobin A1c (HbA1c)) with a larger subset of NHANES.Methods and FindingsWe analyzed data from 4,389 adult participants who were part of a sub-study of environmental phenol measurements in urine from three NHANES cycles from 2003 to 2008. T2DM was defined as having a HbA1c ≥6.5% or use of diabetes medication. The weighted prevalence of T2DM was 9.2%. Analysis of the total sample revealed that a two-fold increase in urinary BPA was associated with an odds ratio (OR) of 1.08 of T2DM (95% confidence interval (CI), 1.02 to 1.16), after controlling for potential confounders. However, when we examined each NHANES cycle individually, we only found a statistically significant association in the 2003/04 cycle (n = 1,364, OR = 1.23 (95% CI, 1.07 to 1.42) for each doubling in urinary BPA). We found no association in either the NHANES cycle from 2005/06 (n = 1,363, OR = 1.05 (95% CI, 0.94 to 1.18)); or 2007/08 (n = 1,662, OR = 1.06 (95% CI, 0.91 to 1.23)). Similar patterns of associations between BPA and continuous HbA1c were also observed.ConclusionsAlthough higher urinary BPA was associated with elevated HbA1c and T2DM in the pooled analysis, it was driven by data from only one NHANES cycle. Additional studies, especially of a longitudinal design with repeated BPA measurements, are needed to further elucidate the association between BPA and T2DM.

THE UNIQUE PHARMACOKINETIC CHARACETERISTICS OF BISPHENOL A IN AMNIOTIC FLUID: THE IMPLICATION OF FETAL EXPOSURE

Background and Aims: Bisphenol A (BPA) is an estrogenic compound widely used in polycarbonate plastics and many household products. The placental β-glucuronidase may deconjugate BPA into its “free” active form, which has estrogenic, endocrine-disrupting properties. There are few data regarding BPA levels in the fetal compartment, and even sparser data regarding conjugated versus free BPA fractions. The effects of prolonged exposure of the fetus to the active form of BPA are unknown. Thus, we sought to quantify levels of conjugated and free BPA in second trimester amniotic fluid specimens to better define the role of the placenta in fetal exposure. Methods: Liquid chromatography/mass spectrometry was used to measure BPA concentrations in 20 prospectively collected second trimester amniotic fluid specimens. Concentrations were quantified using stable-isotope BPA. The total and free BPA were measured by direct analysis of samples with and without overnight enzymatic hydrolysis, respectively. The conjugated BPA concentrations were obtained by subtracting free BPA levels from the total BPA measurements. Results: Total BPA was detected in 17/20 samples, with levels ranging from non-detect to 0.75 ng/mL, with a median concentration of 0.44 ng/mL. Three samples contained no BPA, and 7 samples contained only conjugated BPA. Free BPA was detected in 10/20 samples, and levels ranged from non-detectable to 0.43 ng/mL, with a median concentration of 0.26 ng/mL. For those 10 amniotic fluid specimens that contained free BPA, it represented an average of 82% of the total BPA level. Discussion: Free BPA was detected in the fetal compartment in 50% of amniotic fluid specimens, and its concentration comprised 82% of total BPA levels. Because BPA is quickly conjugated in the adult liver once absorbed, our data suggest that BPA may be deconjugated in the placenta by β -glucuronidase, which leads to increasing potential fetal exposure to the active form, or free BPA.

Bisphenol A exposure reduces the estradiol response to gonadotropin stimulation during in vitro fertilization

To investigate associations between serum bisphenol A (BPA) concentrations and follicular response to exogenous ovary stimulation. Fasting serum was prospectively collected on the day of oocyte retrieval and assessed for unconjugated BPA using high-performance liquid chromatography with Coularray detection. Multivariable linear regression and negative binomial regression were used to assess associations between concentrations of BPA and outcome measures. Models were adjusted for race/ethnicity, antral follicle count at baseline, and cigarette smoking. A reproductive health center. Forty-four women undergoing IVF. None. Peak E(2) level and the number of oocytes retrieved during IVF. The median unconjugated serum BPA concentration is 2.53 ng/mL (range = 0.3-67.36 ng/mL). Bisphenol A is inversely associated with E(2) (β = -0.16; 95% confidence interval = -0.32, 0.01), as well as with E(2) normalized to the number of mature-sized follicles at the hCG trigger (β = -0.14; 95% confidence interval = -0.24, -0.03). No association is observed for BPA and the number of oocytes retrieved (adjusted risk ratio = 0.95; 95% confidence interval = 0.82, 1.10). Bisphenol A is associated with a reduced E(2) response during IVF. Although limited by the preliminary nature of this study, these results merit confirmation in a future comprehensive investigation.

Measurement of bisphenol A, bisphenol A ß-d-glucuronide, genistein, and genistein 4′-ß-d-glucuronide via SPE and HPLC-MS/MS

Bisphenol A (BPA) is a synthetic industrial reactant used in the production of polycarbonate plastics, and genistein is a natural phytoestrogen abundant in the soybean. Current studies investigating the endocrine-disrupting effects of concomitant exposures to BPA and genistein have warranted the development of an analytical method for the simultaneous measurement of BPA and genistein, as well as their primary metabolites, bisphenol A ß-D-glucuronide (BPA gluc) and genistein 4'-ß-D-glucuronide (genistein gluc), respectively. All four analytes were extracted from rat plasma via solid phase extraction (SPE). Three SPE cartridges and four elution schemes were tested. Plasma extraction using Bond Elut Plexa cartridges with sequential addition of ethyl acetate, methanol, and acetonitrile yielded optimal average recoveries of 98.1 ± 1.8% BPA, 94.9 ± 8.0% genistein, 91.4 ± 6.1% BPA gluc, and 103 ± 6.1% genistein gluc. Identification and quantification of the four analytes were performed by a validated HPLC-MS/MS method using electrospray ionization and selective reaction monitoring. This novel analytical method should be applicable to the measurement of BPA, genistein, BPA gluc, and genistein gluc in urine, cultures, and tissue following in vivo exposures. While reports of the determination of BPA and genistein independently exist, the simultaneous optimized extraction and detection of BPA, genistein, BPA gluc, and genistein gluc have not previously been reported.

The Social Epidemiology of Bisphenol A Exposure

ISEE-0385 Background and Objective: Socioeconomic disparities in exposure to endocrine-disrupting chemicals such as bisphenol A (BPA) have not been well characterized, nor has the complex relationship between socioeconomic position (SEP) and race/ethnicity. Studying these differences may reveal that certain groups bear a disproportionate burden of exposure and may generate useful hypotheses about sources of exposure. Methods: We conducted a cross-sectional study of 2,517 participants in the 2003-2004 National Health and Nutrition Examination Survey with urinary BPA measurements. Using multiple regression models and controlling for age, gender, and creatinine, we investigated the association between log-transformed BPA levels and numerous self-reported socioeconomic indicators, which capture slightly different aspects of social stratification. We attempted to disentangle effects of race/ethnicity and SEP. Results: Measuring SEP by income, education, and occupation revealed somewhat similar inverse relationships with BPA levels. Income showed the strongest association; people with poverty income ratios (PIR) less than one had BPA levels 23% (95% CI 11-37%) higher than those with PIRs greater than three. Income measures incorporating household size were better predictors, as was education compared to occupation. Education effects remained after controlling for income. Other indicators such as food security also had residual effects. In models not adjusted for SEP, Non-Hispanic Blacks had BPA levels that were 10% higher than Non-Hispanic Whites. With SEP adjustment, this difference dropped to 5%. Mexican Americans, on the other hand, had lower BPA levels than Non-Hispanic Whites, a difference that increased from 21 to 27% with control for SEP. Conclusion: Lower SEP, measured in different ways, was associated with higher urinary BPA levels. Dietary patterns, known to differ by SEP, may contribute to this disparity. For Non-Hispanic Blacks, SEP appeared to mediate some of the observed difference by race/ethnicity, but not for Mexican Americans, indicating possibly different sources of exposure in these two groups.

Development of a radioimmunoassay for the measurement of Bisphenol A in biological samples

Bisphenol A (BPA) is widely used in the manufacturing of polycarbonate plastic food and drink packaging. Possessing a weak estrogenic activity, BPA is listed among a growing list of endocrine disrupting compounds. In this study, a polyclonal anti-BPA antibody was obtained by immunization with BPA-monocarboxymethylether covalently linked to BSA. The antibody demonstrates negligible cross-reactivity with most analogous BPA phenolic structures, and no cross-reactivity with endogenous steroids. An extraction step with ethyl acetate minimized matrix effects and allowed the BPA measurement in plasma and other biological samples. Recovery after loading test was 96 ± 4% and dilution tests had a linear profile ( r 2 > 0.93). The limit of detection of the BPA RIA was 0.08 μg L −1 with an IC50 of 1.25 μg L −1. The intra- and inter-assay coefficients of variation were 5.6 and 8.6%, respectively at a BPA concentration of 0.7 μg L −1 and 6.9 and 5.7% at a BPA concentration of 1.3 μg L −1. A significant correlation was found between the values obtained by the RIA and HPLC–MS ( r 2 = 0.92) or HPLC coupled to a fluorescence detector ( r 2 = 0.80). In conclusion, we described a BPA-RIA that is a suitable tool for evaluating human exposure to BPA.

Bisphenol A and Risk Assessment

In a recent article, vom Saal and Hughes (2005) proposed that a new risk assessment on bisphenol A (BPA) is needed because of the availability of extensive new literature, including “recent epidemiologic evidence that BPA is related to disease in women.” Specifically, the only research that vom Saal and Hughes cited as evidence relating BPA to disease is a study by Takeuchi et al. (2004), which they describe as a case–control study that reports that ovarian disease in women is related to blood levels of BPA. Vom Saal and Hughes (2005) have misrepresented the Takeuchi study (Takeuchi et al. 2004): It is not a case–control study, and it does not demonstrate that BPA is specifically associated with ovarian disease. Takeuchi et al. (2004) conducted a small cross-sectional descriptive study that assessed 73 women with respect to serum BPA, hormone concentrations, and their clinical condition at a single point in time. Women were categorized clinically as normal (either obese or nonobese), or as having hyper-prolactinemia, hypothalamic amenorrhea, or polycystic ovary syndrome (PCOS) (again, either obese or nonobese). The six groups in the study each contained as many as 19 subjects (nonobese normal group) and as few as 6 subjects (PCOS obese group). The authors reported that serum BPA was higher in women with PCOS (both obese and not obese) and obese normal women than normal women who were not obese. There were also significant positive correlations between serum BPA and various androgens. Takeuchi et al. (2004) concluded that there is a strong relationship between serum BPA and androgen, and they noted that there are a number of possible explanations for this relationship. Takeuchi et al. (2004) appropriately acknowledged that their study was a hypothesis-generating study and they did not attempt to draw conclusions about causal relationships. Vom Saal and Hughes (2005) overstated the importance of this low-level epidemiologic evidence by referring to it as a case–control study. A case–control study is a more rigorous epidemiologic study in which a group of cases (i.e., with the disease of interest) is compared to a group of controls (i.e., without the disease of interest) with respect to exposures that occurred before the development of disease. Rather, Takeuchi et al. (2004) conducted a cross-sectional study in which both exposure and disease were assessed at a single point in time. When both exposure and outcome are assessed at a single point in time, it is not possible to determine whether the exposure preceded the clinical condition or whether the clinical condition affected the individual’s level of exposure. A cross-sectional study cannot test hypotheses; at most, it can merely examine correlations. Furthermore, cross-sectional studies cannot control for confounding factors that may obscure the true relationship between exposure and disease (Hennekens and Buring 1987). Vom Saal and Hughes (2005) overlooked the intended primary focus of the paper by Takeuchi et al. (2004), which is that there is a relationship between serum BPA and androgen levels. The exact nature of this relationship is not known at this time and Takeuchi et al. (2004) speculate that BPA may stimulate androgen production, or, more likely, androgen may suppress the metabolism of BPA. Consequently, women who have clinical conditions that are associated with elevated androgen (e.g., PCOS or obesity) may have elevated levels of BPA as a result of their elevated androgen. The cross-sectional study by Takeuchi et al. cannot shed light on the time course of events and, therefore, cannot address causal relationships among any of the variables studied in these women. In addition, a number of recent studies have reported that several of the ELISA kits available for measurement of serum BPA [the analytic method used by Takeuchi et al. (2004)] overestimate BPA concentrations and exhibit considerable cross-reactivity, calling into question the validity of results generated by such methods (Fukata and Mori 2004; Fukata et al. 2003; Kawaguchi et al. 2003). Furthermore, it is well known that BPA is metabolized and eliminated rapidly (Volkel et al. 2002), so serum levels provide only a snapshot of BPA exposure within the last day. It is not meaningful to correlate an acute exposure (serum BPA at one time-point) with a chronic disease that took years to develop. Chronic exposure to BPA would have to be demonstrated and not assumed. The Takeuchi et al. (2004) study suggests a hypothesis that could be further examined in an appropriately controlled analytic study. It should not be portrayed as recent epidemiologic evidence that demonstrates an association between blood levels of BPA and clinical disease in women.

Comparison of Elisa- and LC-MS-Based Methodologies for the Exposure Assessment of Bisphenol A

Several types of methods, mainly liquid chromatography (LC), have been used for the analysis and assessment of bisphenol A (BPA) in human biological samples. Enzyme-linked immunosorbent assay (ELISA) is also being used for BPA measurement. In this study, we verified whether ELISA is suitable for measuring human samples, namely, serum and urine, by comparing the ELISA results with those obtained by liquid chromatography with multichannel colometric electrochemical detection (LC/ECD) and liquid chromatography coupled to a mass spectrometer (LC/MS/MS). Results of the measurement with LC/ECD showed urinary BPA concentrations to be 1.92 [1.45] ± 1.99 (mean [median] ± standard deviation) ng BPA/mL without the correction of urine volume and 1.20 [0.90] ± 1.10 μg BPA/g creatinine; however, in serum, free and total BPA were not detected. In both samples, a good correlation of the values with the methods was not found. ELISA is one of the powerful measurement methods, since it is convenient and useful for screening bulk quantities. At this point, however, ELISA is not suitable for BPA measurement in human samples because of low levels of BPA in human samples, matrix effect, and specificity of anti-BPA antibody.

Absorption, Translocation and Metabolism of Bisphenol A, a Possible Endocrine Disruptor, in Rice Seedlings

Rice seedlings quickly absorbed bisphenol A (BPA), a possible endocrine disruptor, in culture medium, indicating that they are capable of improving water quality. Measurements of BPA extracted from roots with the stem base and leaves/stems indicated that BPA was translocated from the roots to the top of the plants. The recovery rate by MeOH extraction was very low even during the absorption period, indicating that BPA is not bioaccumulated in the seedlings. The roots and tops of the rice seedlings cultured in the medium containing deuterium-labeled BPA, [2H] BPA, were extracted with MeOH and hydrolyzed with HC1 and NaOH. The extracts and the hydrolyzates were analyzed by 2HNMR. The spectral data indicated that about 5% of the metabolites, as [2H] BPA equivalents, was found in the MeOH extracts and ca. 25% in the acidic and alkaline hydrolyzates. The rest (ca. 70%) could be polymerized and/or bound in the tissues as insoluble, unhydrolyzable forms. The signals in the 2H-NMR spectra of the extracts and the hydrolyzates indicated that BPA was metabolized by oxidation and skeletal rearrangement to several compounds.