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

•A sensitive method was developed to detect free BPA in human breast milk.•Free BPA was detected in 62% of the milk samples (range⩽0.22–10.8ngmL−1).•Caucasian women had significantly higher levels of free BPA in their breast milk.•This is the first study to find that BPA levels in breast milk may vary with race. 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 (⩽0.22–10.8ngmL−1, median 0.68ngmL−1, mean 3.13ngmL−1). No statistical difference in BPA concentrations was observed between women with a low or high Body Mass Index (BMI) (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