Bisphenol A in 24 h urine and plasma samples of the German Environmental Specimen Bank from 1995 to 2009: a retrospective exposure evaluation.

Human exposure to Bisphenol A (BPA) is omnipresent. Both the extent of the exposure and its toxicological relevance are controversially discussed. We aim to reliably determine and evaluate the extent of BPA body burden in the German population from 1995 to 2009 based on 600 24 h urine samples and corresponding plasma samples from the Environmental Specimen Bank. We determined total and unconjugated BPA in urine and plasma using on-line solid-phase extraction high-performance liquid chromatography coupled to isotope dilution tandem mass spectrometry with a limit of quantification (LOQ) of 0.1 μg/l. In the stored urines, total BPA was quantifiable in >96% (median: 1.49 μg/l; 95th percentile: 7.37 μg/l), whereas unconjugated BPA was quantifiable only in <15% of the samples. Total BPA concentrations decreased over time, but 24 h urine volumes increased. Therefore, daily intakes calculated from the 24 h urines remained rather constant at a median of 0.037 and a 95th percentile of 0.171 μg BPA/kg body weight/day. In 60 corresponding plasma samples, total BPA levels were generally below the LOQ of 0.1 μg/l and, if quantifiable, most BPA was unconjugated, thus hinting to external contamination. We see total BPA in urine as the most appropriate and robust marker for BPA exposure assessment (if controlled for BPA contamination). Unconjugated BPA in urine and unconjugated or total BPA in plasma where contamination or breakdown of the glucuronide cannot be ruled out are of no value for human exposure assessment.