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Variability of bisphenol-A concentrations in first morning, bedtime, and 24-hour urine samples in 50 North Carolina adults over a six-week period
Citation:
Morgan, M., M. Nash, D. Barr, AND J. Sobus. Variability of bisphenol-A concentrations in first morning, bedtime, and 24-hour urine samples in 50 North Carolina adults over a six-week period. 2017 ISES Annual Meeting, Research Triangle Park, NC, October 15 - 19, 2017.
Impact/Purpose:
Presented at the 2017 ISES Annual Meeting
Description:
Bisphenol-A (BPA) is a high-production volume chemical that is used to make a number of consumer products and packaged goods. Many cross-sectional studies have frequently reported detecting BPA in urine. However, limited data exist on the temporal variability of urinary BPA concentrations. The major objectives of this study were to: 1) quantify the levels of BPA in first-morning void (FMV), bedtime, and 24-hour samples as concentration, specific gravity (SG) corrected, creatinine (CR) corrected, and excretion rate values for 50 adults over a six-week monitoring period; and 2) determine if these correction approaches decreased the variability in urinary BPA levels. In 2009–2011, a convenience sample of 50 adults (19–50 years old) was recruited from residential settings in North Carolina. Participants collected urine samples (FMV, bedtime, and 24-hour) during weeks 1, 2, and 6 of the six-week monitoring period. Urine samples (n=2335) were analyzed for total BPA concentrations by high-performance liquid chromatography/tandem mass spectrometry. The preliminary data show that BPA was frequently detected (98%) in all of the urine samples. Median levels of BPA were consistently the highest in 24-hour samples (2.08 ng/mL, 2.36 ng/mL-SG, 2.53 ng/mg-CR, and 2.64 ng/min) and the lowest in FMV samples (1.73 ng/mL, 1.61 ng/mL-SG, 1.64 ng/mg-CR, and 1.38 ng/min) across all four methods. Intraclass correlation coefficient (ICC) estimates for BPA showed poor reproducibility (< 0.40) for all urine sample types and methods over a day, week, and six weeks. The highest ICC value of 0.40 occurred for CR-corrected bedtime voids collected over a week. To obtain a reliable average biomarker estimate (ICC=0.80) for BPA, these results indicate that at least six bedtime urine measurements would be needed per adult over a week. In conclusion, these results suggest that bedtime voids may be the preferred sample type to collect in future studies to adequately assess BPA exposures in adults.
