Between Bisphenol A Concentration Research Articles

Impact of bisphenol A exposure on the risk of gestational diabetes: a meta-analysis of observational studies.

A growing number of evidence have assessed the association between bisphenol A (BPA) as an endocrine-disrupting agent and the risk of gestational diabetes (GDM). This meta-analysis aimed to reassess the data on the association of BPA levels in women with GDM compared to the control. A comprehensive literature search was conducted in Medline, Embase, Scopus, and Web of Science to extract relevant published studies up to May 2024. 12 articles were included in the meta-analysis. DerSimonian and Liard random-effects model was used to estimate the pooled odds ratio (OR). Sensitivity analysis was conducted to assess the robustness of the pooled results by removing each study from the pooled effect size. Subgroup analyses were performed depending on the subgroups of gestational age, GDM trimester, BMI, study design and geographical area. The results showed that there was no significant association between circulating and urinary BPA concentrations with the risk of GDM (OR: 0.79; 95% CI 0.60-1.04; P = 0.095). No significant heterogeneity was found among the studies. Using Begg's correlation (P = 0.95) and Egger's linear regression (P = 0.86) tests, no publication bias was observed. The sensitivity analysis shows that our findings were completely robust and stable. Meta-regression indicated a significant association between BPA levels and study design and geometric mean as an index of the risk of GDM. The present meta-analysis demonstrates exposure to BPA was associated with a reduced risk of GDM. Further studies are needed for obtain the reliable results.

No Differences in Urine Bisphenol A Concentrations between Subjects Categorized with Normal Cognitive Function and Mild Cognitive Impairment Based on Montreal Cognitive Assessment Scores.

A link between bisphenol A (BPA) exposure and cognitive disorders has been suggested. However, the differences in BPA concentrations between subjects with and without cognitive impairment have not been analysed. Therefore, this observational study aimed to compare urine BPA levels in subjects with normal cognitive function (NCF) and mild cognitive impairment (MCI). A total of 89 MCI subjects and 89 well-matched NCF individuals were included in this study. Cognitive functions were assessed using the Montreal Cognitive Assessment (MOCA) scale. Urine BPA concentrations were evaluated by gas chromatography-mass spectrometry and adjusted for creatinine levels. Moreover, anthropometric parameters, body composition, sociodemographic factors, and physical activity were also assessed. Creatinine-adjusted urine BPA levels did not differ between the NCF and MCI groups (1.8 (1.4-2.7) vs. 2.2 (1.4-3.6) µg/g creatinine, p = 0.1528). However, there were significant differences in MOCA results between groups when the study population was divided into tertiles according to BPA concentrations (p = 0.0325). Nevertheless, multivariate logistic regression demonstrated that only education levels were independently associated with MCI. In conclusion, urine BPA levels are not significantly different between subjects with MCI and NCF, but these findings need to be confirmed in further studies.

Combined effects of bisphenol A and diabetes genetic risk score on incident type 2 diabetes: A nested case-control study

Observational studies reported inconsistent results on the association between bisphenol A (BPA) and type 2 diabetes (T2D) risk. Whether genetic factors modified the association remains unclear. The present nested case-control study prospectively investigated the association of BPA with T2D risk, and the interaction and combined effects of diabetes genetic risk score (GRS) and serum BPA on T2D risk. Based on the Dongfeng-Tongji cohort study, 995 incident diabetes cases and 1:1 age- and gender-matched controls were included. T2D was diagnosed based on the American Diabetes Association criteria. Serum BPA concentration was measured at baseline. Diabetes GRS was constructed by 88 diabetes-related SNPs selected from large-scale GWASs. A U-shaped association was observed between serum BPA levels and T2D risk, with the lowest odds of T2D at the serum BPA levels of 1.00 ng/mL (P = 0.001 for nonlinearity). Compared with the middle group, the multivariate-adjusted ORs of T2D in the lowest group and the highest group of serum BPA were 1.52 (95% CI: 1.04, 2.22) and 1.40 (95% CI: 1.08, 1.81), respectively. Both serum BPA levels (β = 0.107, P = 0.001) and weighted-GRS (w-GRS) (β = 0.072, P = 0.02) were significantly associated with baseline FPG levels. Participants with both highest w-GRS and serum BPA levels had highest risk of T2D (OR = 2.53, 95%CI: 1.49, 4.31, P = 0.001) and higher baseline FPG levels (β = 0.218, P = 0.01), compared with those with both lowest w-GRS and serum BPA levels. Non modified effects of serum BPA levels and w-GRS on T2D, baseline FPG levels, and 5-y changes of FPG levels were detected (All Pinteraction > 0.05). Our results suggested a U-shaped association between serum BPA levels and T2D risk. Participants with higher serum BPA levels and diabetes genetic risk had higher FPG levels and higher risk of T2D.

A Study on Impact of BPA in the Adipose Tissue Dysfunction (Adiposopathy) in Asian Indian Type 2 Diabetes Mellitus Subjects.

A surge to increase the production via usage of chemicals at both industrial and agricultural arena has forced humans to be routinely and imprudently exposed to a wide variety of endocrine disrupting chemicals. The overall aim of the study was to evaluate possible relation that might exist between bisphenol-A (BPA) and the adipose tissue hormones, and further impact on adiposopathy. In the present study, the role of BPA, an "endocrine disruptor" with respect to adiposopathy was evaluated in type 2 diabetes mellitus patients. For the study, 150 healthy control subjects and 150 newly diagnosed diabetes patients were recruited. Fasting venous blood samples was analyzed for several biochemical parameters such as serum glucose, lipid profile, insulin, adiponectin, leptin, TNF-α, IL-6, IL-1, free fatty acid. Concentrations of BPA were also measured both in control and diabetic subjects. Serum BPA concentration was found to be significantly higher in diabetic subjects in comparison to the control subjects. Levels of BPA were found to be positively correlated with BMI and WC in diabetic subjects. Also, it was found to be positively correlated with leptin and negatively correlated with adiponectin in diabetic subjects. Therefore, the current study suggested more deleterious effect of BPA on diabetes and its pathophysiology.

Associations between Maternal Exposure to Bisphenol A or Triclosan and Gestational Hypertension and Preeclampsia: The MIREC Study.

Little is known about the association between bisphenol A (BPA) or triclosan (TCS) exposure and hypertension in pregnancy. To investigate potential associations between maternal urinary concentrations of BPA or TCS and gestational hypertension (GH) and preeclampsia. Among 1,909 pregnant women participating in the maternal-infant research on environmental chemicals (MIREC) study, urinary concentrations of BPA and TCS were measured in the first trimester by liquid chromatography-tandem mass spectrometry using isotope dilution. Blood pressure was measured during each trimester. Multinomial regression was performed to estimate the adjusted odds ratio (aOR) and 95% confidence intervals (CI) for the associations between these phenols and GH and preeclampsia. BPA and TCS were not associated with GH or preeclampsia. However, in multiparous women, BPA (0.50-1.30 µg/L) was associated with decreased risk of GH (aOR =0.45; 95%CI: 0.21-0.98) while among nulliparous women, TCS was associated with an increased risk of GH (3.60-32.60 µg/L; aOR = 2.58; 95% CI: 1.09-6.13 and > 32.60 µg/L: aOR = 2.74; 95% CI: 1.15-6.51). BPA and TCS urinary concentrations were not associated with GH or preeclampsia; however, our results suggest an association between TCS and GH in nulliparous women. Additional studies are required to confirm our results.

Associations between Maternal Exposure to Bisphenol A or Triclosan and Gestational Hypertension and Preeclampsia: The MIIREC Study

Background: Little is known about the association between bisphenol A (BPA) or triclosan (TCS) exposure and hypertension in pregnancy.Objective: To investigate potential associations between maternal urinary concentrations of BPA or TCS and gestational hypertension and preeclampsia.Methods: Among 1909 pregnant women participating in the (Maternal-Infant Research on Environmental Chemicals (MIREC) Study, urinary concentrations of BPA and TCS were measured in the first trimester by liquid chromatography-tandem mass spectrometry using isotope dilution. Blood pressure was measured during each trimester. Multinomial regression was performed to estimate the adjusted odds ratio (aOR) and 95% confidence intervals (CI) for the associations between these phenols and gestational hypertension and preeclampsia.Results: BPA urinary concentrations were similar according to hypertension status: the median (interquartile range) concentrations were 0.97 µg/L (0.40, 2.00), 1.10 µg/L (0.40, 1.90), and 0.80 µg/L (0.35, 1.70) for women with gestational hypertension, those with preeclampsia and normotensive women, respectively (p = 0.075). For TCS, the values were 10.04 µg/L (2.56, 76.26) for the group with gestational hypertension, 6.48 µg/L (1.48, 67.94) for those with preeclampsia and 8.56 µg/L (2.16, 67.35) for normotensive women (p = 0.559). Compared with the lowest tertile, BPA and TCS were not associated with gestational hypertension (aOR for BPA > 1.30 µg/L = 1.00; 95% CI: 0.54-1.81 and aOR for TCS > 32.6 µg/L = 1.41; 95% CI: 0.83-2.37) or preeclampsia (aOR for highest tertiles were 1.26; 95% CI: 0.53-2.97 and 0.68; 95% CI: 0.31-1.48, respectively). Conclusion: BPA and TCS urinary concentrations measured during the first trimester of pregnancy were not associated with gestational hypertension or preeclampsia. Additional studies are required to confirm our results.

Bisphenol A is not associated with a 5-year incidence of type 2 diabetes: a prospective nested case-control study.

The relationship between bisphenol A (BPA) and diabetes remains controversial. This study aims to investigate whether serum BPA level could predict the 5-year incidence of type 2 diabetes (T2D). A nested case-control study was performed among Chinese who participated in the environment, inflammation and metabolic diseases study (2008-2013). Of the 3510 subjects who were free of diabetes, 232 subjects developed diabetes during the 5-year follow-up. Cases and controls were matched for age and gender by a ratio of 1:1. Homoeostasis model assessment was used to estimate basal β-cell function (HOMA-β) and insulin resistance (HOMA-IR). Participants were stratified into tertiles based on low, median and high baseline serum BPA levels. Regression models were used to analyze the relationship between serum BPA concentration and the incidence of T2D. At baseline, no significant difference in serum BPA concentration was observed between patients with T2D and controls [1.3 (0.3, 3.7) vs. 1.6 (0.4, 3.9)μmol/L, P=0.199]; serum BPA concentration was positively associated with fasting plasma glucose (r=0.27, P<0.001); however, neither HOMA-β nor HOMA-IR correlated with serum BPA concentration. During the follow-up, baseline BPA levels could not predict the 5-year T2D incidence, whether or not adjusted for the potential confounders such as body mass index and blood pressure. [Low BPA tertile was the reference, OR 0.66 (95% CI 0.30, 1.44) for median, OR 0.93 (95% CI 0.41, 2.13) for high.] CONCLUSION: BPA is not associated with a 5-year T2D incidence. These data do not support previous cross-sectional study that BPA exerted a detrimental effect on glucose metabolism.

Submicromolar bisphenol A induces proliferation and DNA damage in human hepatocyte cell lines in vitro and in juvenile rats in vivo

An association between bisphenol A (BPA) exposure and hepatic tumors was suggested, but the employment of high-dose levels raises questions about its relevance to human health. Here, we demonstrate that submicromolar concentrations of BPA induce the proliferation and DNA damage in human hepatocyte cell lines. In HepG2 and NKNT-3, undifferentiated and differentiated hepatocyte cell lines, respectively, submicromolar BPA concentrations promoted the cell proliferation, as indicated by enhanced DNA synthesis and elevated expression of cell-cycle proteins. At concentrations higher than 10 μM, these effects disappeared, reflecting a non-monotonic dose-response relationship. Notably, histone H2AX was activated following exposure to BPA, which is a sensitive marker of DNA damage. Importantly, proliferative foci and DNA damage were also observed in liver tissue of rats orally exposed to BPA at 0.5 mg/kg for 90 days, from juvenile age (postnatal day 9) through adulthood. Reactive oxygen species appeared to play a role in the BPA-induced proliferation and DNA damage, as evidenced by a partial reversal of both processes upon pretreatment with an antioxidant, N-acetylcysteine. Collectively, these results demonstrate that submicromolar BPA concentrations induce the DNA damage and promote the cell proliferation in the liver, which may support its role as a risk factor for hepatocarcinogenicity.

Bisphenol A and reproductive hormones and cortisol in peripubertal boys: The INMA-Granada cohort

IntroductionBisphenol A (BPA) is a well-known endocrine disrupting compound. Although several studies have investigated the effect of BPA exposure and reproductive hormones in humans, results have been inconsistent. ObjectiveTo explore the cross-sectional relationship between bisphenol A (BPA) exposure and reproductive hormones/cortisol among peripubertal boys. Material and methodsUrinary BPA and serum hormones were assessed in 172 boys belonging to the INMA “Environment and Childhood” Granada birth cohort in their follow-up at 9–11years of age. BPA concentrations were quantified by liquid chromatography-mass spectrometry, and levels of serum total testosterone (TT), luteinizing hormone (LH), follicle-stimulating hormone (FSH) and cortisol were measured by electrochemiluminescence immunoassay. Result(s)After adjustment for confounders, linear regression models showed that each natural-log unit increase in urinary BPA concentrations was associated with a 19% increase in geometric mean (GM) serum TT levels, and a 16% decrease in GM serum cortisol levels. When urinary BPA concentrations were categorized in tertiles, boys in the 3rd tertile showed 49% higher TT levels and 23% lower cortisol concentrations compared to boys in the 1st tertile. Additionally, urinary BPA concentrations were also significantly associated with higher TT:LH and TT:cortisol ratios, but not with serum LH or FSH levels. Conclusion(s)Our results suggest the possible endocrine disrupting potential of BPA during this important period of development. Although action at the testis or pituitary cannot be ruled out, our findings are compatible with a possible involvement of BPA at the adrenal gland, resulting in a differential production of androgens/cortisol. However, given the cross-sectional design of our study, the heterogeneous results reported in the literature, and the scant experimental research on BPA effects at the adrenal gland, the present findings should be interpreted with caution.

A study of the influence on diabetes of free and conjugated bisphenol A concentrations in urine: Development of a simple microextraction procedure using gas chromatography–mass spectrometry

The association between bisphenol A (BPA) exposure and adult health status is examined by measuring the urinary BPA concentration using a miniaturized technique based on dispersive liquid-liquid microextraction (DLLME) in combination with gas chromatography-mass spectrometry (GC–MS). Both the free bioactive and the glucuronide conjugated forms of BPA were measured, the glucuronide form usually being predominant. The main analogs of BPA, including bisphenol Z (BPZ), bisphenol F (BPF) and biphenol (BP) were also determined. Several parameters affecting enzymatic hydrolysis, derivatization by in-situ acetylation and the DLLME stages were carefully optimized by means of multivariate designs. DLLME parameters were 2mL urine, 1mL acetone and 100μL chloroform, and hydrolysis was performed using β-glucuronidase and sulfatase at pH 5. No matrix effect was observed and quantification was carried out by aqueous calibration with a surrogate standard. Detection limits were in the range 0.01–0.04ngmL−1. The intraday and interday precisions were lower than 11% in terms of relative standard deviation. Satisfactory values for all compounds were obtained in recovery studies (92–117%) at two concentration levels. Other bisphenols (BPF, BPZ and BP) were not detected in the urine samples, while BPA was the only bisphenol detected in the free form (creatinine adjusted) at concentration levels ranging from the detection limit to 15.9ngg−1, and total BPA was detected at concentrations ranging from 0.46 to 24.5ngg−1 levels. A comparison of the BPA content for both groups of patients revealed that slightly higher mean values were obtained for both free BPA and total BPA for diabetic patients, than for non-diabetic patients. However, a statistical comparison of the contents of BPA revealed that there were no significant differences. The procedure was validated using a certified reference material.

Influence of Bisphenol A on Thyroid Volume and Structure Independent of Iodine in School Children.

BackgroundAlthough several studies have evaluated the relationship between bisphenol A (BPA) and thyroid functions, their results are not entirely consistent. Little is known about BPA in relation to thyroid volume and structure.MethodsWe examined the association of BPA with thyroid volume and thyroid nodules using data from 718 Chinese children living in the East Coast of China in 2012. First morning urine samples were collected for the determination of urinary BPA, creatinine, and urinary iodine concentrations (UIC). Thyroid volume (TV) and nodules were assessed by thyroid ultrasonography.ResultsThe median of TV was 3.14ml. 459(63.9%) children took iodized salt at home and the median of UIC was 159μg/l. BPA was detected in 99.9% of the urine samples and the medians for boys and girls were 2.64 and 2.35μg/g creatinine, respectively. Of all participants 14.0% had thyroid nodules. Urinary BPA concentration was inversely associated with thyroid volume (β = -0.033, 95% CI: -0.053, -0.013) and the risk for multiple nodules (OR = 0.78; 95% CI: 0.63, 0.97). The associations above were similar for children who consumed iodized salt and those consumed non-iodized salt.ConclusionsThe data suggest that BPA may be one of the influencing factors for TV and thyroid nodules and its effects are independent of iodine nutrition status in children.

Associations between Bisphenol A Exposure and Reproductive Hormones among Female Workers.

The associations between Bisphenol-A (BPA) exposure and reproductive hormone levels among women are unclear. A cross-sectional study was conducted among female workers from BPA-exposed and unexposed factories in China. Women’s blood samples were collected for assay of follicle-stimulating hormone (FSH), luteinizing hormone (LH), 17β-Estradiol (E2), prolactin (PRL), and progesterone (PROG). Their urine samples were collected for BPA measurement. In the exposed group, time weighted average exposure to BPA for an 8-h shift (TWA8), a measure incorporating historic exposure level, was generated based on personal air sampling. Multiple linear regression analyses were used to examine linear associations between urine BPA concentration and reproductive hormones after controlling for potential confounders. A total of 106 exposed and 250 unexposed female workers were included in this study. A significant positive association between increased urine BPA concentration and higher PRL and PROG levels were observed. Similar associations were observed after the analysis was carried out separately among the exposed and unexposed workers. In addition, a positive association between urine BPA and E2 was observed among exposed workers with borderline significance, while a statistically significant inverse association between urine BPA and FSH was observed among unexposed group. The results suggest that BPA exposure may lead to alterations in female reproductive hormone levels.

Higher urinary bisphenol A concentration is associated with unexplained recurrent miscarriage risk: evidence from a case-control study in eastern China.

BackgroundEvidence about the association between Bisphenol A (BPA) and the risk of recurrent miscarriage (RM) in human being is still limited.ObjectiveWe evaluated the association of urinary BPA concentrations with RM in human being.MethodsA hospital-based 1:2 matched case-control study on RM was carried out in Suzhou and Kunshan in Jiangsu Province in China between August 2008 and November 2011. Total urinary BPA concentrations in 264 eligible urine samples (102 RM patients and 162 controls) were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The Wilcoxon test and conditional logistic regression were used to estimate the differences between the groups and odds ratios (OR) with 95% confidence intervals (CI), respectively.ResultsThe median ± IQR (interquartile range) (P 75-P 25) values of non-creatinine-adjusted total urinary BPA levels in the RM patients and the controls were 1.66±3.69ng/ml and 0.58±1.07ng/ml, respectively (0.98±2.67μg/g Cr (creatinine) and 0.40±0.77μg/g Cr. The adjusted BPA level was significantly higher in the RM patients than in the controls (Wilcoxon test, Z = 4.476, P<0.001). Higher level of urinary BPA was significantly associated with an increased risk of RM (P-trend <0.001). Compared to the groups with urinary BPA levels less than 0.16μg/g Cr, the women with levels of 0.40–0.93μg/g Cr and 0.93μg/g Cr or above had a significantly higher risk of RM (OR = 3.91, 95%CI: 1.23–12.45 and OR = 9.34, 95%CI: 3.06–28.44) that persisted after adjusting for confounding factors. The time from recently RM date to recruitment does not significantly influence the urinary BPA level (P = 0.090).ConclusionExposure to BPA may be associated with RM risk.

Relationship of serum bisphenol A with diabetes in the Thai population, National Health Examination Survey IV, 2009 在泰国人群中血清双酚丙烷与糖尿病的关系，2009年第4次全国健康调查研究

AbstractBackgroundEpidemiological studies of the association between bisphenol A (BPA) exposure and diabetes have been inconsistent. The present study determined serum BPA concentrations in the Thai population and their association with hyperglycemia and diabetes.MethodsIn all, 2581 serum samples from the Thai National Health Examination Survey (2009) were used to determine BPA levels. Impaired fasting glucose (IFG) was defined as fasting plasma glucose ≥100 and &lt;126 mg/dL. Diabetes was defined as a history of a physician's diagnosis or fasting plasma glucose ≥126 mg/dL. Multinomial logistic regression was used to examine the association of serum BPA with IFG and diabetes.ResultsOf 2581 samples tested, BPA was detected in 2135 samples (weighted percentage 78.1%), with a geometric mean concentration of 0.34 ng/mL BPA. Serum BPA levels were significantly higher among those with diabetes or IFG compared with normoglycemic individuals (0.52 and 0.38 vs 0.33 ng/mL, respectively; P &lt; 0.001). After adjusting for potential confounders, compared with the first quartile (≤0.071 ng/mL), the overall adjusted odds ratios (OR) of serum BPA concentration in the third and fourth quartiles (0.319–0.745 and ≥0.746 ng/mL, respectively) for IFG were 1.72 (95% confidence interval [CI] 1.19, 2.49) and 1.23 (95% CI 0.80, 1.89), respectively; for diabetes, the adjusted OR were 1.88 (95% CI 1.18, 2.99) and 1.83 (95% CI 1.12, 2.95), respectively, with a slightly stronger association among men than in women.ConclusionsSerum BPA concentrations were not associated with IFG, but were positively associated with diabetes in the Thai population. Further prospective studies are needed to confirm the relationship.

Behavior of cationic surfactants micellar solution solubilizing an endocrine disruptor bisphenol A

The interactions between bisphenol A (BPA) and cationic surfactant micelles have been studied by interfacial tension ( γ), conductivity ( κ) and pyrene fluorescence intensity ( I 1/ I 3) measurements. The following cationic surfactants have been investigated: decyltrimethylammonium bromide (DeTAB), dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and hexadecyltrimethylammonium bromide (HTAB). As the BPA concentration increases, the critical micelle concentration ( cmc) and the maximum surface excess ( Γ max) of surfactant decreases. Both the effects are more pronounced at smaller concentration of BPA, and also for the surfactant with a longer hydrocarbon tail. The degree of micelle dissociation ( α) tends to decrease with an increase of hydrocarbon tail length of surfactant molecule, except for the shortest chain DeTAB. Considering the ionic association constant ( K A), however, the K A value increases with the increase of hydrocarbon chain including DeTAB. That is to say, the anomalously small α value of DeTAB could be caused by its large cmc. As for the dependence of α value on BPA, the α value is increased by BPA addition in all the surfactants. The standard free energies of micellization ( Δ G m 0 ) and of interfacial adsorption ( Δ G ad 0 ) have also been determined. Those values indicate that BPA stabilizes the surfactant molecules in the micelle and at the air/water interface. These stabilizations are larger at the interface than in the micelle, which appears more significantly with the surfactant of longer hydrocarbon tail. From the fluorescence measurements, the I 1/ I 3 ratio shows almost no change with the increase of BPA concentration above the cmc. This means that the environmental polarity of pyrene is not affected by BPA in the micelle.

Interaction between bisphenol A and micelles of ionic surfactants

AbstractInteractions between bisphenol A (BPA) and ionic surfactants—cationic hexadecyltrimethylammonium bromide (HTAB) and anionic sodium dodecylsulfate (SDS)—were studied by measuring interfacial tensions and the intensities of pyrene fluorescence. The critical micellar concentrations (CMC) decreased with an increase in the BPA concentration, and the degree of that decrease was greater in HTAB than in SDS. In those micelles, BPA interacted more strongly with HTAB than with SDS. Conversely, BPA adsorbed on the air‐water interface cooperatively with the surfactants, even though almost no adsorption of BPA itself was observed. This cooperative adsorption was more enhanced with HTAB than with SDS. Thus, BPA worked on the surfactants to stabilize the micelles and interfacial adsorption. The stability gained by the addition of BPA was greater on the interface than in the micelle. This was evidence of decreased hydrophilicity of the head group of the ionic surfactant, which interacted with BPA, because this decrease acted on the surface activities of the surfactants more directly than on the micelle stabilities. Pyrene fluorescence measurements yielded identical results for the effect on micelle stabilities. It is noteworthy that the fluorescence intensity of peak 1, l1, decreased with an increase in BPA concentrations at constant concentrations of surfactant greater than the CMC, but the peak ratio, l1/l3, remained almost unchanged. This fact was also related to the interaction of BPA with the hydrophilic head groups in the surfactant micelle.