I was recently directed by my fiancé to this article by a non-profit organization called STATS. The article is called “Science suppressed: How America became obsessed with BPA” and focuses on the controvery over health impacts of Bisphenol-A (BPA).
Background on the BPA debate
BPA is chemical found in many products, including medical supplies, dental fillings, water bottles, baby bottles, CD’s, DVD’s, and food containers. BPA leaches out of these products over time and is frequently ingested.
When bisphenol-A is found in the blood, it acts as a weak endocrine disruptor, which means that its structure is similar enough to natural hormones (in this case, estrogen) to be capable of binding to hormone receptors. Studies on animal models suggest that BPA consumption can lead to numerous negative outcomes, including reproductive health problems, the early onset of puberty, obesity, increased rates of mammary and prostate cancers and neurological problems (to name a few).
The article written by STATS was particularly interesting because it presented a side of the debate about which I wasn’t familiar. It pointed out that numerous regulatory agencies including the European Food Safety Authory as well as agencies in Japan, Australia, New Zealand and the United States have reviewed the available literature and determined that BPA does NOT pose a significant health threat.
The literature on the health impacts of BPA is divided. Independent researchers often determine that BPA has harmful health effects while industry scientists decide that there are no harmful health effects at the levels in which people are currently encountering BPA. So how did the government agencies decide which body of literature to base their findings on?
The agencies determined that the independent researchers often used experimental methods that were unsound. For example, the route of BPA introduction for many of these studies was by injection rather than by ingestion. This is a significant problem because when BPA is ingested it is processed by the gastrointestinal tract. In the liver, enzymes add a sugar molecule to BPA, which makes it easy to pass from the body and (most importantly) makes it unable to bind to estrogen receptors (so it is no longer an endocrine disrupter). Because most ingested BPA is made inert by this process, studies which inject BPA will dramatically overestimate the negative health effects associated with consuming the same concentration of the chemical orally.
The STATS article also points out that many of the discarded studies had low sample sizes, which means that there were too few animals in the study to draw any reliable conclusions.
A final complaint against the independent studies was that they only administered one dose concentration to the animals in their study. Administering different dose concentrations (for example, using a control saline solution, a low dose, and a high dose) gives you a better idea of how the compound effects human health. The impacts could be linear, meaning that the more you get the the worse the health effects or non-linear, meaning that small doses may cause no ill effects but passing a threshold concentration could induce serious effects (an all-or-nothing kind of effect).
An additional problem with administering only one dose is that you might mask an impurity in your BPA solution. If you administer two different doses and your BPA solution was well-manufactured, then there should be a difference in the magnitude of health effects if BPA is causing problems. If the solution was not made well and some impurity in the solution is causing health problems, then hopefully the concentration of the impurity will be the same in the two doses and the health effects will be of the same magnitude in each treatment.
Based on these concerns, government agencies threw out much of the independent research and made their decisions based on industry research.
Commentary on the STATS article
The remainder of the STATS article discusses how The Journal Sentinel reported only one side of the story and began America’s hysteria over the use of BPA in food and beverage containers. I’m more interested in the actual science on BPA than I am about how reporters misrepresented the story (which is clearly important as well), so I won’t be commenting on that aspect of the STATS article.
The website claims that the STATS organization is non-partisan, which I took to mean that they would present both side of the argument in a balanced manner. Perhaps the point of this article was to scold The Journal Sentinel and not to present both sides of the debate, but the tone of the paper was definitely anti anyone who thinks BPA has negative health effects.
Frederick vom Saal, a prominent researcher on the negative health effects of BPA, is set up at the beginning of the article as being an overzealous fool. Many government agencies decided did not consider vom Saal’s findings in their official decisions because of unsound scientific methods (likely for the reasons outlined above) and vom Saal has taken a fairly extreme stance on the BPA debate. He has likened BPA to the “biological equivalent of global warming” and his extreme stance sets him up to look like an unreliable source.
It should be noted, however, that vom Saal’s research is funded by the National Institute of Health. This means that a number of prominent medical researchers read vom Saal’s experimental protocol and determined that it was sound enough to be funded. His findings were then published in high-end, peer-reviewed journals, again attesting to the fact that vom Saal’s standing in the scientific community is sound.
But fine, I’ll buy that vom Saal’s opinion shouldn’t be the final word on the BPA debate. After setting vom Saal up to look like a zealous loony, they then attempt to discredit numerous other BPA researchers by noting any association with vom Saal that they may have had in the past.
For example, National Public Radio aired a Living on Earth episode which relied heavily on the input of Ana Soto. The STATS article is quick to note that Ana Soto collaborated with vom Saal in 1993 on one of the first papers to propose that BPA may be an endocrine disrupter (which it is). This is mentioned as a way to insinuate that Soto is as unreliable as vom Saal, which is an unfair conclusion to draw. First of all, collaborators can agree on results but disagree on their broader implications, suggesting that Soto could take a more down to earth stance on the BPA debate than vom Saal has taken. Additionally, Soto has not collaborated with vom Saal again in 16 years. A lot can happen in a decade and a half and it’s possible that they haven’t collaborated again in that span of time because of differences in opinion.
The STATS article also tries to discredit a large group of independent researchers who signed a document called the Chapel Hill Consensus by pointing out that, you guessed it, vom Saal played a big role in the development of the document (he was the lead author). You can’t discard the opinion of 38 prominent researchers because one researcher with whom you disagree was involved in the drafting of the document. All 38 of these researchers hail from respectable institutions across the country where they run successful research labs.
A big general problem with the BPA debate is that independent researchers often determine that BPA has negative effects on human health while industry researchers (with a vested interest in keeping BPA on the market) find that BPA is not harmful to human health (at least at the levels in which we currently ingest it). The STATS article rightly points out that immediately discrediting industry research is foolish and that lots of high quality research is conducted by industry groups. This still, however, doesn’t reconcile the problem with the fact that a large group of independent researchers are not coming to the same conclusions as the industry scientists.
The article writes off this discrepancy by refering to the experimental method issues described above (e.g., injecting and not feeding BPA to animal subjects). While it is certaintly true that some experiments may not be very informative due to experimental design issues, there are plenty of experiments conducted by independent researchers that are finding harmful effects of BPA when conducting sound research. For example, I mentioned an experiment in an earlier post in which BPA was fed (not injected) to a pregnant mouse, having a significant impact on the pup’s epigenome (see slide show explaining the research here).
If there is a discrepancy between industry and independent research findings, then we should give money to independent researchers who are employing sound experimental methods. Because BPA has the potential to be such a huge public health issue, it’s imperative that we get independent researchers to run the same test that industry researchers are running and compare their results. With so much at stake, we can’t afford to rely entirely on the findings of a group with vested interests.
Additionally, it seems to me as though there is a lot about potential effects of BPA that we don’t yet understand. For example, perhaps BPA is safe in adults and safe in children, but can have major effects on a developing embryo. The tone of the STATS article would lead you to believe that everyone should conclude that BPA is totally safe at current exposure levels, but clearly there is a lot of work left to do.
I would certainly suggest reading the STATS article (if you have time, it’s 24 pages long) to get the often unheard other side of the story. It makes a good case that our panic over the use of BPA may be overblow, but I think that we still have a long road ahead of us before we can say with certaintly that BPA really isn’t a health hazard.