Data challenges the APB on BPA

BOSTON -- A controversial component of plastic bottles and canned food linings that have helped make the world’s food supply safer has recently come under attack: bisphenol A. Widely known as BPA, it has the potential to mimic the sex hormone estrogen if blood and tissue levels are high enough. Now, an analysis of almost 150 BPA exposure studies shows that in the general population, people's exposure may be many times too low for BPA to effectively mimic estrogen in the human body.

The analysis*, presented at the American Association for the Advancement of Science's annual meeting by toxicologist Justin Teeguarden of the Department of Energy's Pacific Northwest National Laboratory (Richland, Washington), shows that BPA in the blood of the general population is many times lower than blood levels that consistently cause toxicity in animals. The result suggests that animal studies might not reflect the human BPA experience appropriately.

"Looking at all the studies together reveals a remarkably consistent picture of human exposure to BPA with implications for how the risk of human exposure is interpreted," said Teeguarden. "At these exposure levels, exposure to BPA can’t be compared to giving a baby the massive dose of estrogens found in a birth control pill, a comparison made by others.”

‘Low dose’ studies

In addition to evaluating the likelihood of BPA mimicking estrogen in humans, Teeguarden also analyzed another set of BPA studies that looked at the chemical’s toxicity in animals and cells in the lab. These 130 studies are significant as a group because they refer to the exposures as "low dose," implying they are very relevant to human exposures.

According to his analysis, however, the "low doses" actually span an immense range of concentrations, a billion-fold. In addition, only a small fraction of the exposures in these self-described “low dose” studies are in the range of human exposures, from 0.8 to 7 percent, depending on the study.

"The term low-dose cannot be understood to mean either relevant to human exposures or in the range of human exposures. However, this is in fact what it has come to mean to the public, as well as many in the media," said Teeguarden.

Analysis of 150 exposure studies

The first analysis covered 30,000 individuals, including women and infants, in 19 countries. Human blood concentrations were calculated multiple ways using many kinds of exposure data.

Teeguarden looked to see if BPA concentrations were sufficiently high to be a significant source of estrogen-like activity in the blood. Researchers have long known that BPA can bind to the same proteins that estrogen does -- called estrogen receptors -- when estrogen is doing its job in the body. However, in most cases, BPA does so much more weakly than estrogen. To trigger biological effects thNike Air Max 95