Determination of free and total bisphenol A in human urine to assess daily uptake as a basis for a valid risk assessment.

Bisphenol A (BPA) is widely distributed and exhibits weak estrogenic activity. In contrast to BPA, the corresponding glucuronide metabolite is not estrogenic. Therefore, free and total BPA were determined in human urine samples to assess the significance of free BPA for risk assessment. In only 10% of 474 samples from 287 subjects was free BPA detected in a range from <LOD (0.3 microg/l) to 2.5 microg/l. Due to sample contamination with low amounts ( approximately 1 microg/l) of BPA, house dust samples were independently collected in homes but not from persons who provide urine samples and analysed for BPA to check for potential sources of contamination. BPA was found in the range from 117 to 1 486 microg/kg (median: 553 microg/kg) dust. Additionally, BPA and d(16)-BPA were administered to a volunteer to demonstrate the problem of contamination. In comparison to low levels of free BPA (<1.25 microg/l), no free d(16)-BPA was observed. Therefore, the maximal concentration of 2.5 microg/l observed here may be considered as an exaggerated value as a result of contamination. Nevertheless, for risk assessment a concentration of 2.5 microg/l was used and this value is 800-fold below the tolerable daily intake (TDI) of 50 microg/kg. Total BPA was determined in 147 urine samples with concentrations between <LOD and 9.3 microg/l.