The concentration of bisphenol A in urine is affected by specimen collection, a preservative, and handling.

In urine specimens that were collected from pregnant women in a large cohort, 24% contained more than 10 ng/ml of total bisphenol A (BPA), suggesting external contamination. Therefore, we conducted an investigation of the source(s) of extraneous BPA in the specimens. We found that under the conditions used to collect urine specimens in the epidemiologic study, contamination with BPA occurred, and by two separate mechanisms.