BPA – Nothing New Under The Sun?
BY STEVE HENTGES | OCTOBER 16TH 2017 12:00 PM

It’s been shown that the primary route of human exposure to bisphenol A (BPA) isthrough the diet.

One source of BPA in the diet is the protective coating inside

many food and beverage cans, which helps to protect the safety and integrity of thefood. Epoxy resin-based coatings have been used for decades because they excel
in this application. Since epoxy resins are made from BPA, trace amounts ofresidual BPA can leach from the coatings into the food or beverage that we theningest.
An important factor that has a significant impact on whether exposure to BPA isharmful is what happens to BPA in the body after it is ingested, which falls within
the domain of the field of pharmacokinetics. For example, pharmacokinetic data
can tell us whether the level of BPA in the body is sufficiently high to cause effects– or so low as to be safe.
Very recently, researchers from Sweden and Canada published a humanpharmacokinetic study on BPA. In one phase of the study, a group of volunteers
ate a cookie that carried a dose of BPA that was higher than a typical consumerexposure. The researchers then monitored what happened to the BPA as it passed
through the bodies of their volunteers.
Importantly, even with a sensitive analytical method the researchers did not detect
any BPA in the blood of the volunteers after the exposure. However, they did finda biologically inactive metabolite of BPA in the volunteer’s urine very soon after theexposure.
These new results indicate that BPA is efficiently metabolized after oral exposureand quickly eliminated from the body in urine. Because of this normal process ofmetabolism, BPA is not likely to be harmful at the low levels to which we’re exposedsince our bodies are very good at metabolizing and eliminating BPA before it could
build up or do us any harm.
The new results also help to illustrate an important principle of the scientificmethod, specifically the principle of replication. If an experiment cannot bereplicated to get the same result, the original result may be an error. Conversely,

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if an experiment is replicated with the same result, we have more confidence thatthe result is valid.
In this case, the recent study was preceded by three other human pharmacokinetic
studies, each from a different group of researchers. The results from all fourstudies are substantially the same, which means we can have high confidence that
BPA is efficiently metabolized and eliminated from the body.

The new results provide further support to government bodies worldwide that havereviewed BPA and concluded that exposure to low levels of BPA is not a healththreat. With elegant simplicity, the U.S. Food and Drug Administration (FDA)
answers the question “Is BPA safe?” with a single, unambiguous word – “Yes.”
Nothing New Under the Sun?
Because BPA is weakly estrogenic, it has the potential to cause health effects byinterference with the endocrine system, which regulates many bodily functions
including reproduction and development. Whether BPA actually does or does notcause health effects in real life has been a controversial topic for quite a few years.
Human pharmacokinetic studies help to evaluate that potential by providing
important information on what happens to BPA when it enters the body. In
particular, pharmacokinetic studies address questions including where does BPA go

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in the body after it’s absorbed, in what form does it circulate, how long does it stayin the body and how is it eliminated?
On the surface, the new human pharmacokinetic data appears to be nothing
new. The close similarity with data from three earlier human studies might evenremind you of the world-weary complaint about life’s monotony as expressed in awell-known biblical verse:"What has been will be again, what has been done will be done again; there isnothing new under the sun." (Ecclesiastes 1:9, New International Version)
But there’s more to the story than meets the eye. It’s not always the case thatscientific data can be replicated in independent studies, and it’s also not always thecase than anyone even tries.
The story begins in 2002 with publication of the first human pharmacokinetic
study on BPA from a group of academic researchers in Germany. That landmark
study was the first to demonstrate that BPA is efficiently converted to a biologicallyinactive metabolite that is then quickly eliminated from the body in urine after oralexposure.
Even after an oral dose of 5 milligrams, which is hundreds of times higher thantypical human exposure from the diet, the researchers did not detect any BPA in
the participants’ blood. They did detect the inactive metabolite and confirmed thatelimination of the metabolite into urine was essentially complete within 24 hours.
The results suggested that BPA is not likely to be harmful after oral exposure due tothe efficient process by which BPA is metabolized and eliminated from thebody. Needless to say, these results did not go over so well with those who believethat BPA is harmful. In spite of the high quality of the study, it has been
repeatedly disparaged by true believers who refused to accept the scientific results.
The Scientific Method Worked As It Should!
At least partly because the results had been questioned, the U.S. National
Toxicology Program (NTP) undertook a larger- scale human study with an analyticalmethodology that is capable of detecting lower levels of BPA in blood. If you’re an
analytical chemist, you won’t be surprised that the methodology available today is3/5

quite a bit more sensitive than the methodology available 15 years ago. Lo andbehold, the results of the NTP study, published in 2015, corroborated the results ofthe earlier study from 2002.
But the story doesn’t end there. The results from a third human pharmacokinetic
study of oral exposure to BPA from a group of researchers at the Pacific Northwest
National Laboratory and FDA were also published in 2015. Once again, the results
were consistent with the results of the original study as well as the NTP study.
In light of the consistent results from three earlier studies, the results of the newstudy do not add much to our understanding of BPA. The results do, however,illustrate an important principle of the scientific method. We have much more
confidence in the validity of results that have been independently replicated,
especially multiple times.
With consistent results from four human studies, there can be little doubt that BPA
is efficiently metabolized and quickly eliminated from the body after oral
exposure. The disparagement of the original study from 2002 is just that,
disparagement with little scientific basis.
Now That We’re Sure of the Results, What Do They Mean?
Knowing that BPA is quickly and completely eliminated from the body in urine in theform of an inactive metabolite, we also know how to measure exposure to BPA. Infact, many biomonitoring studies have done just that by measuring the amount of
the metabolite in urine, which provides a reasonable estimate of daily intake ofBPA. These studies consistently show that human exposure to BPA around theworld is very low.
As noted above, the human pharmacokinetic results strongly suggest that oral
exposure to BPA at the low levels typically experienced by people is not likely to beharmful. Pharmacokinetic data cannot prove harm or lack thereof, but in this casethe data do provide strong supporting evidence for toxicity studies that do directly
assess the potential for harm.
Taken together, the many studies on human exposure, pharmacokinetics, andtoxicity provide a strong basis for the conclusions of government bodies that haveevaluated the scientific data and drawn conclusions on the safety of BPA. Similar

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to the perspective expressed by FDA, the European Food Safety Authority recently
concluded that “BPA poses no health risk to consumers of any age group (including
unborn children, infants and adolescents) at current exposure levels.” Like FDA,
they’ve got the data to back it up, and it’s been replicated.

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