Possible Association Between Dental Sealants and Urinary Bisphenol A Levels in Children Warrants Additional Biomonitoring and Safety Research

Bisphenol A as a Factor in the Mosaic of Autoimmunity

The population worldwide is largely exposed to bisphenol A (BPA), a commonly used plasticizer, that has a similar molecular structure to endogenous estrogens. Therefore, it is able to influence physiological processes in human body, taking part in the pathophysiology of various endocrinopathies, as well as, cardiovascular, neurological and oncological diseases. BPA has been found to affect the immune system, leading to the development of autoimmunity and allergies, too. In the last few decades, the prevalence of autoimmune diseases has significantly increased, that could be explained by a rising exposure of the population to environmental factors, such as BPA. BPA has been found to play a role in the pathogenesis of systemic autoimmune diseases and also organ-specific autoimmunity (thyroid autoimmunity, diabetes mellitus type 1, myocarditis, inflammatory bowel disease, multiple sclerosis, encephalomyelitis etc), but the results of some studies remain still controversial, so further research is needed.

Prenatal bisphenol A exposure, fetal thyroid hormones and neurobehavioral development in children at 2 and 4 years: A prospective cohort study

Findings about the association between prenatal Bisphenol A (BPA) exposure and neurobehavioral development in children are still inconsistent. In addition, whether fetal thyroid hormones (THs) mediate the reported association remains unclear. The present study aimed to examine the association between prenatal BPA exposure and risks of child behavioral problems at 2 and 4 years of age and whether the association could be explained by alteration of fetal THs as measured in cord plasma. Using the Shanghai-Minhang Birth Cohort Study (S-MBCS), BPA concentration was measured in maternal urine samples collected at 12-16 weeks of gestation. Children's neurobehavioral development was assessed using the Child Behavior Checklist/1.5-5 (CBCL), at 2 and 4 years of age. Using generalized estimating equation (GEE) models, 745 mother-pairs were included to examine associations of BPA with CBCL scores, Using multiple linear regression models, 348 mother-pairs were included to evaluate the association between maternal BPA and THs in cord plasma. A mediation analysis was conducted to explore the potential mediating role of THs. After adjusting for potential confounders, prenatal BPA level was associated with increased risks of Emotionally Reactive problem, Anxious/Depressed problem, having Somatic Complaints, exhibiting Aggressive Behavior, and Internalizing and Externalizing Problems: compared to the lowest tertile, the risks in the highest tertile and middle tertile, ranged between 1.55-fold (95% CI: 1.09, 2.21) and 2.59-fold (95% CI: 1.52, 4.42). The association was more pronounced among boys. None of the associations reached statistical significance among girls. An inverse association between prenatal BPA and fetal TH level was also observed. However, the observed neurotoxic effects of prenatal BPA exposure did not appear to be mediated by THs levels. The current findings suggest that prenatal exposure to BPA may disrupt fetal THs levels and may induce long-lasting behavioral alterations, especially in boys.

Prenatal bisphenol A exposure is associated with language development but not with ADHD-related behavior in toddlers from the Odense Child Cohort

Bisphenol A (BPA) is a non-persistent chemical with endocrine disrupting abilities widely used in a variety of consumer products. The fetal brain is particularly sensitive to chemical exposures due to its rapid growth and complexity. Some studies have reported associationbetween maternal BPA exposure and behavior but few have assessed impact on cognitive development, and to our knowledge no studies have specifically assessed the impact on language development. We therefore assessed whether maternal urinary BPA concentration during pregnancy was associated with language development and attention-deficit and hyperactivity disorder (ADHD) symptoms in offspring aged 18-36 months in the prospective Odense Child Cohort. BPA was analyzed in 3rd trimester maternal fasting urine spot samples. Language development was addressed among 535 children using the Danish adaptation of the MacArthur-Bates Communicative Development Inventories at median age 21 months; ADHD traits were assessed by parents of 658 children using the Child Behavior Checklist for ages 1½-5 years at mean age 2.7 years. Associations were assessed using logistic regression models comparing children below the 15th percentile score for language and above the 85 percentiles score for ADHD with the other children while stratifying by sex and adjusting for maternal education, duration of breastfeeding and maternal urine phthalates. BPA was detected in 85.3% of the urine samples (median 1.2 ng/ml). Boys of mothers with BPA exposure in the highest tertile had an odds ratio of 3.70 (95% CI 1.34-10.21) of being in the lowest 15th percentile of vocabulary score compared to boys of mothers within the lowest tertile of BPA exposure after adjustment, whereas no association was found in girls. No clear dose-response relationship between maternal BPA and ADHD scores above the 85th percentile was found for either sex. Since early language development is a predictor of future reading skills and educational success, more epidemiological studies assessing BPA exposure and language skills are needed to confirm our findings.

The Association of Serum Bisphenol A with Thyroid Autoimmunity

Introduction: Data on the association of bisphenol A (BPA) exposure and autoimmunity in humans is unclear. Objective: To elucidate the influence of BPA on thyroid autoimmunity, in the present study we assessed the association between serum BPA and thyroid autoantibodies. Methods: Serum samples from 2361 subjects, aged ≥15 years, from the Thai 4th National Health Examination Survey were measured for BPA, antithyroglobulin (TgAb), antithyroperoxidase (TPOAb) and antithyrotrophin receptor (TRAb) antibodies. Results: The proportion of subjects positive for TgAb, TPOAb and TRAb were 11.1%, 14.9% and 1.9%, respectively. With regard to BPA, 51.9% had serum BPA levels exceeding the detection limit of the assay (0.3). There was a significant increasing trend for subjects with TgAb (p < 0.05) and TPOAb (p < 0.001) positivity as BPA quartiles increased, particularly in the highest quartile. In contrast, no relationship between BPA quartiles and TRAb was found. Logistic regression analysis showed that age, gender and BPA quartiles were determinants of TPOAb or TgAb positivity, independent of BMI. However, only the association between BPA and TPOAb positivity was consistent in both men and women. Conclusions: BPA was independently associated with TPOAb positivity. However, its mechanism related to TPOAb positivity, subsequently leading to autoimmune thyroid disease, needs further investigation.

Changes in urinary bisphenol A concentrations associated with placement of dental composite restorations in children and adolescents

BACKGROUND

Bisphenol A-glycidyl methacrylate (bis-GMA)-based dental composite restorations may release bisphenol A (BPA). The authors assessed changes in urinary BPA concentrations over a 6-month follow-up period in children and adolescents who received bis-GMA-based restorations.

METHODS

The authors collected data from 91 study participants aged 3 to 17 years who needed composite restorations. Participants provided urine samples and information on BPA-related exposures before and at approximately 1 day, 14 days, and 6 months after treatment. The authors used multivariable linear regression models to test associations between the number of surface restorations placed and the changes in urinary BPA concentrations.

RESULTS

Participants had a mean (standard deviation [SD]) of 1.4 (1.0) for surfaces restored with composite at the first treatment visit and 2.3 (1.6) for surfaces restored during the entire study period. Mean (SD) change in urinary BPA concentrations between pretreatment and day 1 was 1.71 (9.94) nanograms per milliliter overall and 0.87 (5.98) after excluding 1 participant who had 8 surfaces restored at the visit. Overall, the authors observed an association between a greater number of composite surface restorations placed and higher urinary BPA concentrations in the 1-day sample (posterior-occlusal exponentiated coefficients [e(β)] = 1.47; 95% confidence interval [CI], 1.18-1.83; P < .001), but the association was attenuated after the authors restricted the sample to the 88 participants who had up to 4 restorations (e(β) = 1.19; 95% CI, 0.86-1.64), and they did not observe any association using 14-day (e(β) = 0.94; 95% CI, 0.75-1.18) or 6-month (e(β) = 0.88; 95% CI, 0.74-1.04) samples.

CONCLUSIONS

Placement of bis-GMA-based restorations in children and adolescents may produce transient increases in urinary BPA concentrations that are no longer detectable in urine samples taken approximately 14 days or 6 months after treatment. After placement of a few restorations, increases in urinary BPA concentrations may not be detectable, owing to a high level of variation in background BPA exposure.

PRACTICAL IMPLICATIONS

These results suggest that leaching of BPA from newly placed composite restorations ceases to be detectable in urine within 2 weeks after restoration placement. The potential human health impact of such short-term exposure remains uncertain.