What's New

German Biomonitoring Data Confirms Very Low Human Exposure to Bisphenol A Around the World

September 26, 2005

Summary

A new study from a group of German researchers has provided the first direct evidence that human exposure to bisphenol A (BPA) in Europe is very low and is, at most, in a range similar to the levels reported in other parts of the world. The research was sponsored by UBA (Umweltbundesamt), which is the German Federal Environment Agency.

This study analyzed both urine and blood samples from a group of individuals with a rigorous analytical method and found no BPA at the limit of detection. The authors also noted that analytical methods used in other studies are prone to measure false positives due to the potential for contamination or interferences from other substances present in biological samples. The capability of the analytical method was further demonstrated by analysis of urine samples from a group of volunteers treated with a low oral dose of BPA, which confirmed that BPA is rapidly eliminated from the body with a half-life of about 4 hours.

The very low human exposure levels documented in this study are far below levels that have the potential to result in adverse health effects and support the conclusion that exposure to BPA from all sources poses no known risk to human health.

Human Exposure to Bisphenol A Confirmed Very Low Around the World

Biomonitoring is a scientific technique for directly measuring human exposure to natural or synthetic substances by analysis of human tissues and fluids. Recently published studies in which human urine samples were analyzed for BPA indicate that human exposure to BPA in Japan and the US is extremely low, with typical daily intake estimated in the range of 20-30 nanograms/kg-body weight/day. (1)

A high quality study from Germany has now provided the first direct evidence that human exposure to BPA in Europe is also very low.(2) The research was sponsored by UBA (Umweltbundesamt), which is the German Federal Environment Agency, and conducted at the University of Würzburg. In this study, urine and blood samples from a group of individuals were analyzed for both BPA and BPA-glucuronide, which is a metabolite of BPA. With a carefully validated analytical method, neither BPA nor BPA-glucuronide was found in any of the samples at the analytical limit of detection.

Based on the limit of detection in urine,(3) the authors estimate that daily intake of BPA for this group is less than 2.3 micrograms/person/day, corresponding to less than 38 nanograms/kg-body weight/day for a 60 kg individual. Since BPA was not detected, this represents the maximum level for any individual in the group and the typical level must be lower. As noted by the authors, their data suggest that human exposure to BPA in Europe is, at most, in a range similar to the levels reported in other parts of the world if not lower.

Analysis for both BPA and BPA-glucuronide adds considerable strength to this study since a previous study has shown that BPA is efficiently metabolized to BPA-glucuronide before it circulates in the body.(4) If any form of BPA is detected, the distinction between BPA and BPA-glucuronide is especially valuable for understanding any potential health implications since BPA-glucuronide has no known biological activity and, in particular, has been shown to be non-estrogenic. (5)

Bisphenol A Not Detected in Blood

Another strong point of this study is the analysis of both blood and urine from the same individuals. For substances such as BPA, which has a very short half-life in the body and is excreted by humans entirely in urine (see below), human exposure is best measured by analysis of urine where the concentration is expected to be highest. At the very low human exposure levels estimated in this study, the concentration of BPA in blood should be too low to detect by any available analytical method. The validity of the human exposure estimate is thus supported by the blood analyses, which confirmed that neither BPA nor BPA-glucuronide were present at the limit of detection. (6)

The rigorous analytical procedure used in this study also highlights the limitations of analytical methods that have been used for analysis of BPA in urine or blood in other studies. The authors note that many other methods are prone to false positives due to the potential for contamination or interference from other substances present in biological samples. Considering the very low human exposure levels demonstrated in this and other urine studies, it would not be expected to find BPA in blood at detectable levels. Any study reporting the presence of BPA in blood should be carefully examined to ensure that the analytical method employed is sufficiently rigorous to support the validity of the reported data.

Efficient Metabolism and Elimination of Bisphenol A Confirmed

The capability of the analytical method was also demonstrated by analysis of urine samples from a group of volunteers who were administered a single BPA dose of 25 micrograms/person. Consistent with an earlier study that tested a higher dose(4), this study confirms that BPA is efficiently converted to BPA-glucuronide and rapidly eliminated in urine with a half-life in the body of about 4 hours. With such a short half-life, essentially all BPA is eliminated from the body within a day after exposure with no potential for accumulation. For the short period of time when BPA is in the body, it is in the form of the BPA-glucuronide metabolite, which is not estrogenic(5) and has no known biological activity.

Low Human Exposure Levels Indicate Low Risk to Human Health

The very low human exposure levels documented in this study are far below levels that have the potential to result in adverse health effects. For example, these levels are below the lifetime daily intake levels set by the US Environmental Protection Agency(7) and the European Commission's Scientific Committee(8) on Food by a factor ranging from hundreds to thousands. Overall, the available biomonitoring data on BPA supports the conclusion that exposure to BPA from all sources poses no known risk to human health.

1. For a summary of biomonitoring and recent data on bisphenol A, see http://www.bisphenol-a.org/whatsNew/20050504.html.

2. "Quantitation of bisphenol A and bisphenol A glucuronide in biological samples by HPLC-MS/MS," W. Völkel, N. Bittner, and W. Dekant, Drug Metabolism and Disposition (2005), In Press; http://dx.doi.org/10.1124/dmd.105.005454.

3. The content of BPA in all urine samples was below the limit of detection of 1.14 micrograms/l (approximately 1.14 parts per billion).

4. "Metabolism and kinetics of bisphenol A in humans at low doses following oral administration," W. Völkel, T. Colnot, G. A. Csanady, et al., Chemical Research in Toxicology (2002), 15:1281-1287; http://dx.doi.org/10.1021/tx025548t.

5. "In vitro and in vivo interactions of bisphenol A and its metabolite, bisphenol A glucuronide, with estrogen receptors alpha and beta", J. B. Matthews, K. Twomey, and T. R. Zacharewski, Chemical Research in Toxicology (2001), 14:149-157; http://dx.doi.org/10.1021/tx0001833.

6. None of the plasma samples analyzed contained detectable concentrations of BPA or BPA-glucuronide, indicating plasma concentrations of BPA below 0.5 micrograms/l (approximately 0.5 parts per billion).

7. See http://www.epa.gov/iris.

8. See http://europa.eu.int/comm/food/fs/sc/scf/out128_en.pdf. ()