94. Direct LC-MS/MS and indirect GC–MS/MS methods for measuring urinary bisphenol A concentrations are comparable (lay summary)

Ashley-Martin J, Gaudreau E, Dumas P, Liang CL, Logvin A, Bélanger P, Provencher G, Gagné S, Foster WG, Lanphear BP, Arbuckle TE. Environment International 2021 Dec;157:106874. doi: 10.1016/j.envint.2021.106874

Bisphenol A (BPA) is a chemical found in numerous consumer products including plastics, receipt paper, and the lining of food cans.  This research addressed a controversy in the literature regarding measurement of urinary bisphenol A using the traditional indirect method vs the more recently developed direct method.  Statistical comparison of total BPA results using the direct and indirect methods is necessary to accurately interpret biomonitoring data for risk assessments of BPA.

This study compared urinary BPA concentrations estimated from the indirect and direct methods in duplicate first trimester urine samples collected from1,897 pregnant women enrolled in the MIREC study.  The Institut national de santé publique du Québec (INSPQ) measured urinary BPA concentrations using both methods. Researchers used statistical models to compare total BPA concentrations between the two methods in the whole sample of pregnant women as well as in subgroups with higher urinary specific gravity (density).

Median urinary BPA concentrations for the direct and indirect methods were 0.89 BPA µg equivalents/L and 0.81 µg/L respectively. Concentrations from the direct method were, on average, 8.6% higher than the indirect method. The differences between the two methods was highest in samples with more dense urines.

This study demonstrates, using the most rigorous statistical methods and largest population to date, that differences between the two methods for assessing urinary BPA concentrations are unlikely to influence interpretation of exposure and health outcome data.