Urine and serum biomonitoring of exposure to environmental estrogens I: Bisphenol A in pregnant women.

Despite its very low oral bioavailability and rapid elimination, multiple reports of unexpectedly high bisphenol A (BPA) concentrations in the serum of pregnant mothers or cord blood have raised questions about BPA exposures during pregnancy. Thirty healthy pregnant women recruited to the study were evaluated for total BPA exposure over a 30-h period comprising one-half day in the field and one day in a clinical setting. BPA and its metabolites were measured in serum and total BPA was measured in matching urine samples. The mean total exposure was similar to the 50(th) percentile of exposure for U.S. women and pregnant women in a large North American cohort. Twenty volunteers had total daily exposures equal to or exceeding the U.S. mean, and six volunteers had exposures exceeding the 75th percentile. Women working as cashiers did not have higher total BPA exposure. BPA was detected in some serum samples (0.25-0.51 ng/ml), but showed no relationship to total BPA in corresponding urine samples, no relationship to total BPA exposure, and had unconjugated BPA fractions of 60-80%, consistent with established criteria for sample contamination. We conclude that typical exposures of North American pregnant women produce internal exposures to BPA in the picomolar range.