Research Comparison of Serum Bisphenol A Concentrations in Mice Exposed to Bisphenol A through the Diet versus Oral Bolus Exposure Paizlee T. Sieli,1,2 Eldin Jašarevic´,2,3,4 Denise A. Warzak,1,2 Jiude Mao,5 Mark R. Ellersieck,6 Chunyang Liao,7 Kurunthachalam Kannan,7 Séverine H. Collet,8,9 Pierre-Louis Toutain,8,9 Frederick S. vom Saal,3 and Cheryl S. Rosenfeld 1,2 1Department of Biomedical Sciences, 2Bond Life Sciences Center, 3Department of Biological Sciences, 4Interdisciplinary Neuroscience Program, 5Division of Animal Sciences, and 6Agricultural Experiment Station, University of Missouri, Columbia, Missouri, USA; 7Wadsworth Center, New York State Department of Health, and Department of Environmental Health Sciences, School of Public Health, State University of New York at Albany, Albany, New York, USA; 8INRA, UMR1331, Toxalim (Research Centre in Food Toxicology), Toulouse, France; 9Université de Toulouse, INP, ENVT, UPS, EIP, Toulouse, France Background : Bisphenol A (BPA) is a widely produced endocrine-disrupting chemical. Diet is a primary route of exposure, but internal exposure (serum concentrations) in animals and humans has been measured only after single oral bolus administration. o Bvitcej : We compared serum concentrations of BPA over a 24-hr period after oral bolus adminis- tration or ad libitum feeding in mice and assessed for buildup with dietary exposure. Methods : Adult female mice were administered [dimethyl-d6]-BPA (BPA-d6) as a single oral bolus (20 mg/kg body weight) or fed a diet containing 100 mg BPA-d6/kg feed weight ad libitum for 1 week. Serum concentrations were analyzed using isotope dilution liquid chromatography coupled with electrospray tandem mass spectrometry and compared between exposure groups over the first 23 hr and after 7 days of dietary exposure. r esult : Maximum concentration (Cmax) for BPA-d6 during the first 24 hr was reached at 1 hr and 6 hr for oral bolus and diet groups, respectively. Relative BPA-d6 bioavailability (unconjugated BPA-d6) was higher in diet-exposed mice than in the bolus group despite a relative lower absorp- tion, a phenomenon consistent with an inhibitory effect of food on first-pass hepatic metabolism. In mice with ongoing dietary exposure, unconjugated BPA-d6 was higher on day 7 than on day 1. words c onclusi : This is the first report of serum BPA concentrations in an animal model exposed to this chemical via the diet. Although bolus administration of BPA-d6 led to peak concentrations within 1 hr, Cmax for diet-exposed mice was delayed for several hours. However, bolus adminis- tration underestimates bioavailable serum BPA concentrations in animals—and presumably humans—than would result from dietary exposure. Exposure via diet is a more natural continuous exposure route than oral bolus exposure and is thus a better predictor of BPA concentrations in chronically exposed animals and humans. k ey : bioavailability, BPA, chronic exposure, deconvolution analysis, endocrine disrup- tor, food effect, oral bolus, pharmacokinetic analysis. Environ Health Perspect 119:1260–1265 (2011). http://dx.doi.org/10.1289/ehp.1003385 [Online 6 June 2011] (Vandenberg et al. 2010a) to reflect mount- ing evidence suggesting that human exposure to BPA can occur through routes other than diet and water consumption (Gies et al. 2009; Vandenberg et al. 2010b). A major hurdle in estimating human exposure to BPA is accounting for all of the potential routes of exposure, even though contaminated food and beverages are still considered the dominant source for this chemical (Galloway et al. 2010; Vandenberg et al. 2009; Willhite et al. 2008). For exam- ple, BPA exposure might also occur through less-explored routes, including dermal contact with thermal (carbonless) receipts, inhala- tion of household dusts, and cigarette smoke (Biedermann et al. 2010; Galloway et al. 2010; He et al. 2009). Only one published study to date has examined the elimination of BPA from blood after a single oral adminis- tration to volunteer human subjects, and this study failed to detect active BPA in the serum of these individuals (Volkel et al. 2002), most probably because concentrations fell below the detection limit of the relatively insen- sitive assay employed (Taylor et al. 2011; Vandenberg et al. 2009). Rather than recog- nize the potential limitation of that study, some investigators have used the data to Address correspondence to C.S. Rosenfeld, Department of Biomedical Sciences and Bond Life Sciences Center, University of Missouri, 440F Bond Life Sciences Center, 1201 East Rollins Rd., Columbia, MO 65211 USA. Telephone: (573) 882-5132. Fax: (573) 884- 9395. E-mail: rosenfeldc@missouri.edu Supplemental Material is available online (http:// dx.doi.org/10.1289/ehp.1003385). We thank J. Taylor and J. Keegan for provid- ing input and assistance for these experiments and V. Henige for assisting with the mouse husbandry. We are also grateful to R. Roberts for his critical review and editing of the manuscript. Funding for this research was provided by a National Institutes of Health Challenge Grant to C.S.R. (RC1 ES018195). F.S.v.S. consulted for an attorney involved in civil litigation regarding the health effects of BPA, but he has no financial interests related to plastics, products, or compounds that might serve as alternatives to BPA. The remaining authors declare they have no actual or potential competing financial interests. Received 25 December 2010; accepted 27 May 2011. ovlume 119 | number 9 | September 2011 • Environmental Health Perspectives Bisphenol A (BPA) was first developed in the 1930s and is presently used in the manufac- ture of many polycarbonate plastic containers (including baby bottles and reusable water bottles), dental sealants, metallic food cans, paper, and cardboard items (Biedermann et al. 2010; Galloway et al. 2010; He et al. 2009). Because this chemical was assumed to be relatively harmless, demand for these products has increased, and so has the manu- facture of BPA, which is now produced in amounts exceeding 8 billion pounds/year, with little signs of diminution of output (Bailin et al. 2008). BPA is stable in sediment and detectable in almost all bodies of water (Environment Canada 2008). Thus, expo- sure of wildlife and humans to BPA is inevi- table, likely to continue, and even to increase (Vandenberg et al. 2009). Human and ani- mal contact with BPA can occur through various sources, and whether diet is the pri- mary source of exposure remains unresolved (Stahlhut et al. 2009). Regardless, > 90% of people in the United States have measurable 1260 levels of BPA (Calafat et al. 2008), and there is no reason to suppose that the reach of BPA is not global (Vandenberg et al. 2010a). The overarching question concerns the total amount of BPA that most humans are subjected to on a daily basis. An attendant question is whether these exposures lead to adverse outcomes. Although a handful of studies have tried to address this question by measuring serum and urinary concentra- tions of BPA in human populations, great variability exists in the exact estimates [Food and Drug Administration (FDA) 2008; Vandenberg et al. 2007; vom Saal et al. 2007]. For instance, the FDA estimated that the daily BPA exposure for adults is 0.16 μg/kg/day (FDA 2008). However, based on the avail- able data at the time, a conference sponsored by the National Institute of Environmental Health Sciences in 2007 predicted that inter- nal exposure (plasma or serum concentrations) in humans is > 35 mg/day (~ 500 gμ/kg/day) (Vandenberg et al. 2007; vom Saal et al. 2007). This prediction has been updated