Download - Bisphenol A

Background information
Issue addressed in the study
Several large-scale urine biomonitoring studies have consistently demonstrated that human exposure
to BPA, from all sources, is extremely low with typical intake in the range of 25-50 nanograms/kg
bodyweight/day. These levels are more than 1,000 times below the safe intake limit (tolerable daily
intake, TDI) set by the European Food Safety Authority EFSA. Other studies, including several
controlled human volunteer studies, have shown that BPA is efficiently metabolized and rapidly
excreted in urine. Taken together, these studies provide a consistent and coherent understanding of
human exposure and metabolism.
In contrast, a number of smaller scale studies have reported significant levels of free (unmetabolized)
BPA in human blood. The levels reported are highly inconsistent with what is known about human
exposure and metabolism from the studies mentioned above. In addition, the validity of the data in
these blood biomonitoring studies is uncertain since other studies have suggested that sample
contamination may be a significant problem in trace level BPA analyses. Nevertheless, these studies
are used as evidence that people are exposed to high levels of BPA, with some claims that human
exposure is even higher than the TDI.
It was an objective of the Teeguarden-research team to contribute to understanding which of these
two sets of study data is valid.
What was done?
In the study, 20 human volunteers ate 3 meals in a day that were enriched in canned foods and
beverages to ensure that the participants were exposed to BPA. Based on how much total BPA was
found in urine, it was determined that the average exposure for all participants was 21% greater than
the 95 th percentile exposure determined by CDC’s population-scale urine biomonitoring data.
Blood and urine samples were collected from each participant hourly during the day of the study. The
blood samples were analyzed for both free BPA and total BPA, while urine samples were analyzed for
total BPA (previous data has shown that free BPA is not commonly found in urine), all with a sensitive
analytical method. This comprehensive set of data allows for a detailed analysis of the
pharmacokinetics of BPA.
Key Results
Total BPA was detected in only 14% of the 320 blood samples, only one of which was above 1 ppb.
Total BPA was below the sensitive limit of detection (0.3 ppb) for 86% of the samples.
Importantly, free BPA was below the limit of detection in all 320 blood samples analyzed by the CDC
lab, even for samples with detectable total BPA. Based on their results the authors note that reported
high levels of BPA in blood are unlikely to be valid: “Furthermore, the current results obtained using
analytical methodology 10-45 times more sensitive than the previous human study by Voelkel et al.
suggest that reported BPA concentrations in human blood of 1.4-19.2 nM [~0.3-4.4 ppb] (Vandenberg,
Chahoud et al. 2010) are highly unlikely in the general population exposed orally to amounts as much
as ~4 times greater than the 95 th upper percentile of aggregate exposure in the general U.S.
population.”
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