# Study: Human Exposure to BPA 'Grossly Underestimated'



## Ernest Nagel (Sep 22, 2010)

I can't help but wonder if the proliferation of BPA usage and escalating obesity rates aren't connected in some way? Is something closely akin to synthetic estrogen really the only viable way to get the the things we use BPA for done?

http://www.nytimes.com/gwire/2010/0...pa-grossly-underestima-4581.html?pagewanted=1

*Study: Human Exposure to BPA 'Grossly Underestimated'*
By GAYATHRI VAIDYANATHAN of Greenwire
Published: September 20, 2010

Americans are likely to be exposed at higher levels than previously thought to bisphenol A, a compound that mimics hormones important to human development and is found in more than 90 percent of people in the United States, according to new research.

U.S. EPA says it is OK for humans to take in up to 50 micrograms of BPA per kilogram of body weight each day. The new study, published in the journal Environmental Health Perspectives, suggests that we are exposed to at least eight times that amount every day.

"Our data raise grave concern that regulatory agencies have grossly underestimated current human exposure levels," states the study.

The study also gives the first experimental support that some BPA is likely cleared at similar rates in mice, monkeys and humans, making it possible to extrapolate health studies in mice to humans.

Despite decades of research, questions about BPA have lingered and recently become politicized. Sen. Dianne Feinstein (D-Calif.) hopes to add an amendment to the "FDA Food Safety Modernization Act," currently under consideration in the Senate, banning the chemical from children's food and drink packaging. Republicans and industry representatives have been averse, saying that research has not shown conclusively that the chemical is harmful.

Hormones are essential during development and can determine, among other things, a child's gender. BPA, since it mimics estrogen, is an "endocrine disrupter," according to Thomas Zoeller, a biology professor at the University of Massachusetts, Amherst. And amazingly, BPA has the ability to bind to not one, but three receptors -- the estrogen, the male hormone and the thyroid hormone receptors, Zoeller said.

*Controversy over method*

Some scientists question whether the ability of BPA to bind receptors translates to a health effect. Detractors say that most of the chemical does not circulate in blood long enough to have health effects. All scientists agree that BPA resembles estrogen, and indeed, it was first synthesized as a man-made estrogen substitute before being used widely in the linings of canned goods and polycarbonate plastics.

Within the scientific world, the controversy hinges on the seemingly obscure question: Does the liver detox the chemical completely enough to secrete most of it out in urine, or does BPA get into human blood where it can mimic important hormones?

Feeding human volunteers a fixed dose of BPA and sampling their blood to check for the chemical would answer some of these questions, according to Zoeller. But such an experiment throws up ethical issues. The only human study of this nature was conducted in 2002 by the German researcher Wolfgang Völkel at the University of Würzburg.

Völkel found the liver removes more than 99 percent of BPA from the blood, and humans excrete it within six hours. He did find some BPA in the blood of his volunteers but found this level to be insignificant.

It is at this point that science breaks down into controversy. Some researchers say the method Völkel used to measure BPA in the blood was not sensitive enough and that he likely overestimated the ability of the chemical to pass through without causing harm.

The new study, led by Julia Taylor, a biologist at the University of Missouri, uses a more sensitive test for measuring the compound. She fed mice and monkeys a fixed amount of BPA daily. She took blood samples and found that the animals had "biologically active" amounts of the estrogen-like chemical, according to the study.

The study suggests that BPA is not completely removed by the liver and does circulate in the blood and in amounts that are cause for concern, according to Taylor.

"For those of us who work with BPA, no one has actually directly compared mice and monkeys before, and monkeys and humans before," Taylor said. "For those of us who work with it in an academic sense at least, this is confirmation of what we believe."

This study suggests that all the possible ways in which humans are exposed to BPA are not yet known, Taylor said. It also makes it possible to compare studies of BPA in mice and extrapolate it to monkeys and humans since they all clear BPA at similar rates, she said.

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## Tad (Sep 22, 2010)

I'm not totally sold on the dangers of BPA, but one important thing to keep in mind is that with hormones you don't get much of a dose effect beyond some very low level. That is, you have that low level, that will essentially saturate the appropriate receptors. Anything above that doesn't really matter. This is different from toxins, where generally a bigger dose is more of a problem. 

What I've not seen determined in any sort of at conclusive way is what level of BPA in the blood actually causes much effect. If it does what it is feared to do, the required dose will be very small....but how small?

ETA: there has also apparently been generally dropping sperm counts in the western world, another thing that could potentially trace back to BPA?


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## Ernest Nagel (Sep 22, 2010)

Tad said:


> I'm not totally sold on the dangers of BPA, but one important thing to keep in mind is that with hormones you don't get much of a dose effect beyond some very low level. That is, you have that low level, that will essentially saturate the appropriate receptors. Anything above that doesn't really matter. This is different from toxins, where generally a bigger dose is more of a problem.
> 
> What I've not seen determined in any sort of at conclusive way is what level of BPA in the blood actually causes much effect. If it does what it is feared to do, the required dose will be very small....but how small?
> 
> ETA: there has also apparently been generally dropping sperm counts in the western world, another thing that could potentially trace back to BPA?



Tad, I'm completely with you re dosage but it's exactly the _very low_ presence of BPA that concerns some qualified researchers. I've been following this guy vom Saal's work on the topic for several years. Fetal and infant exposure has some pretty scary developmental implications. See this link for some overview. Lots more. If you're interested IM me. I'm clear the majority of my posts on the health board bore the crap out of most people. Just because it's tedious and inconclusive doesn't mean it's unimportant though. :happy:

http://stats.org/stories/2007/washington_obesity_mar12_07.htm


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