Maternal urinary concentrations of free and total bisphenol A (BPA) and BPA-alternatives in the APrON birth cohort

Abstract

Introduction: Bisphenol A (BPA) has been widely used for manufacturing polycarbonate plastic and epoxy resins, and highly detectable in environmental and human samples. BPA is an endocrine disruptor in experimental models, and while epidemiological studies have examined BPA’s possible neurodevelopmental effects, results of these studies have been inconsistent. Biomonitoring data for BPA have mainly focused on total BPA in urine samples, with limited data on free BPA, and even less on BPA alternatives. Methods: In this study, in-line solid phase extraction – liquid chromatography – Orbitrap mass spectrometry was used to examine free and total BPA and BPA alternatives (bisphenol S (BPS), bisphenol F (BPF)) in urine samples collected in the 2nd trimester from 480 pregnant women in the APrON birth cohort (Alberta, Canada). Maternal nutrient status (i.e. folate, zinc, n-3 fatty acids) was also measured in maternal blood at the same time point. Neurodevelopment of children was assessed at 2 years of age using the Bayley-III and Child Behavior Checklist. Results: Total BPA was detectable in 93% of urine samples (GM: 1.23 ng/mL; <0.32 – 44 ng/mL), total BPS was detectable in 59% of urine samples (GM: 0.16 ng/mL; <0.10 – 243 ng/mL), and total BPF was detectable in 10% of urine samples (<1 – 390 ng/mL). The detection frequencies were less than 1% for free BPA, BPS and BPF in urine. Nevertheless, the highest free BPS and BPF concentrations were observed in urine that also contained the highest total BPS and BPF, and typically constituted <1% of the total concentration. Conclusion: The metabolites constituted the majority (>99%) of total BPA and BPA alternatives in urine samples. Mean population exposure to BPA was significantly higher than BPS, but maximum urinary levels of BPS (243 ng/mL) and BPF (390 ng/mL) were higher than maximum BPA (44 ng/mL). Preliminary associations among BPA, BPS, neurodevelopment and nutrient status will also be discussed.