Abstract 2520: Determination of free bisphenol A (BPA) concentrations in breast milk of U.S. women using a sensitive LC/MS/MS method

Bisphenol A (BPA) is a synthetic compound with structural similarities to the hormone 17β-estradiol. BPA is a major component of polycarbonate plastics and epoxy resins, which are used in the production of plastic containers, metal can linings, dental sealants, thermal receipt paper and household paper products. Incomplete polymerization of BPA as well as exposure to high temperatures and acidic or basic conditions can cause BPA monomers to leach from these products. Therefore, most people are exposed to BPA and levels have been quantified in human urine, blood, saliva, amniotic fluid, placental tissue, colostrum and breast milk. BPA is a weak estrogen and is considered a potential endocrine disrupting compound in humans. Initially it was thought that BPA was rapidly conjugated and excreted from the body. However, free BPA has been detected in human samples indicating that humans are internally exposed to estrogenically active BPA. The length of time that free BPA remains in circulation in the body and the extent to which it accumulates in tissues, such as the breast, is unknown. Given the known sources of BPA exposure, it is likely that lifestyle habits lead to varying levels of BPA exposure. Repeated use of products that contain or are packaged in materials with a high BPA content can lead to higher exposure rates. The same lifestyle choices resulting in high BPA exposure may also lead to high body mass index (BMI); for example, frequent consumption of carbonated soft drinks is associated with a high BMI in women and these beverages are often packaged in plastic bottles or metal cans that may contain BPA. Two recent studies have demonstrated a relationship between BPA levels in urine and obesity in adults and children. Because of the difficulty in measuring BPA in a complex fatty matrix such as milk, few studies have reported on BPA levels in breast milk, and none have examined the relationship between BMI and BPA. In the present study we optimized a sensitive method for assessing free BPA in breast milk and determined whether the levels of BPA were related to characteristics including age, race, BMI, child's age, and number of children nursed. BPA was separated from breast milk samples from 21 nursing women in the U.S. by solid-phase extraction and subsequently analyzed by HPLC-MS/MS. Free BPA was detected in 71% (15/21) of the breast milk samples. The method detection limit in water was determined to be 0.11 ng/mL. Free BPA concentrations were detected