Of all the phony scares the American Council on Science and Health wrestled with during its 40-year history, no chemical scare has been as resilient as bisphenol A, otherwise known as BPA.
So it should come as no surprise that even after the U.S. FDA’s unambiguous statement on February 23 from Deputy Commissioner Stephen Ostroff, MD, about the results of the two-year CLARITY-BPA Core Study that there are still holdouts calling for even more studies.
FDA concluded BPA is safe:
“One area that has been of significant consumer interest is the use of Bisphenol A (BPA) in food packaging. BPA is authorized for use in polycarbonate plastics and epoxy resins in certain food and beverage can linings. Given this interest, the FDA has routinely considered and evaluated the scientific evidence surrounding the use of BPA and continues to conclude that BPA is safe for the currently authorized uses in food containers and packaging.”
It is impossible to prove anything is completely safe, but at some point, you have to stop trying to concoct more far-fetched experiments and accept the best possible evidence. There is now plenty of evidence.
BPA is one of two chemicals that react to form polycarbonate plastic polymers, which have properties ideal for lining food containers, especially metal cans. Polycarbonate plastics are ubiquitous and very small quantities of BPA, which has been used for 60 years, can leach from the plastic into the food.
It’s not surprising that minuscule quantities of BPA (specifically, its metabolites) can be found in the urine of virtually everyone. But this is not due to the world being flooded with more BPA. It’s because of technology, or the power of modern analytical instrumentation. Concentrations of common chemicals, which used to be measured in parts per million can now be measured in parts per quadrillion range—a billion times less.
Chemicals that have been in our environment, food, and bodies all along can now be detected. As silly as it sounds, these chemicals have become scary simply because we know they’re present.
But this should not be entirely surprising; activist groups, most of which have little or no expertise in chemistry or toxicology, equate the presence of a chemical with harm from that chemical—a violation of the basic tenets of toxicology since it ignores dose or exposure.
The CLARITY-BPA was conducted by FDA senior scientists at the agency’s National Center for Toxicological Research. Studies in rodents were conducted at multiple doses of BPA. These doses were selected to mimic levels ranging from those far below to far higher than expected to be found in humans. A number of endpoints were selected in advance, including growth and weight of the rodents, and development of tumors.
With the exception of “minimal effects” on the development of tumors, nothing was found to suggest there was any cause for concern. These minimal effects can probably be dismissed outright because of the animal model chosen for the study—the Sprague-Dawley rat is known for spontaneous generation of tumors, regardless of whether the rats are exposed to a given test chemical. The “effect” noted was the increase in the occurrence of mammary gland tumors at one of the five doses, in one of the five groups, which is far from compelling.
Although these findings must still be subjected to peer review, Dr. Ostroff’s conclusion will almost certainly stand: “Overall, the study found ‘minimal effects’ for the BPA-dosed groups of rodents.”
Scientifically, it should come as no surprise nothing was found. The knock on BPA is it bears a structural similarity to the estrogen hormones and therefore acts as an “endocrine disruptor”—a term that is scientifically questionable.
Although structural similarity is subjective, receptor-binding affinity is not. Estradiol, the most important of the estrogens, binds about 12,000 times more tightly to estrogen receptors than to BPA. Thus, if BPA is an endocrine disruptor, it is a mighty poor one. This is the primary reason BPA scares are unfounded.
But there is another.
As the name implies, BPA is a member of a class of organic compounds called phenols—molecules that have a hydroxyl group attached to a benzene ring. Phenols are known to be notoriously difficult to work with for medicinal chemists, given they are tasked with discovering new drugs. Although an experimental phenol-containing drug may work very well in a “test tube,” the story in a living animal or human is quite different.
The reason phenols are poor candidates is the same reason BPA does not remain in our bodies. Phenols are known to rapidly undergo a particular type of metabolism called conjugation, in which the hydroxyl group is coupled to one of a small number of ubiquitous, highly water-soluble biomolecules. The resulting conjugate then becomes water-soluble and is excreted in the urine.
Conjugation is a very important mechanism for eliminating multiple chemicals, either natural or synthetic, that are exposed to our bodies. This is why when BPA is measured in studies it’s almost always sampled from urine.
As is the case with many other phenols, BPA is rapidly conjugated and eliminated; it does not accumulate in our bodies. That it’s found in urine simply means our livers are doing exactly what they are supposed to do. If it were not found in urine, it’s conceivable it could accumulate in the body and do harm.
It is more than a little ironic that the so-called “BPA Scare Industry” is making troubling claims, when, in fact, detection of BPA in urine is an indicator it is not doing harm.
The FDA has spoken. Science has spoken. Enough.
Dr. Bloom is the director of chemical and pharmaceutical sciences at the American Council on Science and Health. Reach him at email@example.com.
This column is being published with the permission of the American Council on Science and Health.