If
you’ve ever heard of the chemical bisphenol A
(BPA), and who hasn’t, you probably have the distinct impression that it’s
highly toxic. After a steady drumbeat of
more than 15 years suggesting that BPA is linked to virtually every health
effect known to man, how could you think any differently?
There
are literally thousands of studies on BPA in the scientific literature, many of
which report biological effects of one sort or another. But separate from the sheer volume of data,
what the data mean is the key question.
The consensus of government bodies worldwide, based on their independent
evaluations
of the data, has been that BPA is safe for use.
Nevertheless the conventional wisdom is the opposite: that BPA is
dangerous.
In
light of that conventional wisdom, you might be puzzled by recent headlines
such as “BPA
unlikely to be harmful, federal study shows” and “Plastic
Additive BPA Not Much Of A Threat, Government Study Finds.” Clearly there is some sort of a disconnect
between the recent headlines and the conventional wisdom.
Unless
you’ve been paying very close attention to the scientific literature, you
probably didn’t know that U.S. government scientists have been conducting an in-depth research
program on BPA for more than 10 years. This multi-million dollar sustained effort
was aimed at resolving any remaining uncertainties about the safety of BPA.
What
led to these headlines is that the U.S. National Toxicology Program (NTP) just released
the findings of the capstone study of that research program. Known as the CLARITY Core study, it’s the
largest study ever conducted on BPA. The
study successfully resolved uncertainties as intended and the results indicate
that BPA has very little potential to cause health effects even when people are
exposed to it throughout their lives.
As
stated in the conclusion of the study
report, “BPA produced
minimal effects that were distinguishable from background.” In a statement released in
conjunction with the report, Dr. Steven Ostroff, Deputy Commissioner for Foods
and Veterinary Medicine at the U.S. Food and Drug Administration (FDA)
noted: “our initial review supports our determination that currently
authorized uses of BPA continue to be safe for consumers.”
What’s All the Controversy Been About?
It’s
been known for many decades that BPA is weakly estrogenic. By itself that biological property doesn’t
mean much and it didn’t attract much interest until about 20 years ago. From that point forward scientists worldwide
have been fascinated by BPA and have conducted thousands of studies of every
type imaginable. Of particular interest
is the potential for BPA to cause health effects at low levels of exposure, for
example even in the very low dose range of typical consumer exposure.
The
conclusions of scientific
assessments by government bodies worldwide consistently support the safety
of BPA. The most straightforward
conclusion is the one from FDA, which is summarized with their Q&A: “Is
BPA safe? Yes.” To address residual controversy, FDA worked
in conjunction with other U.S. federal government agencies to design a research
program that would resolve any remaining uncertainties.
How the U.S. Government Set Out to Resolve
the Controversy
To
comprehensively understand the safety of BPA, several complementary types of
scientific data are necessary. In
particular, we need to understand levels of exposure, what happens to BPA when
it enters the body, and the potential for actual exposures to cause health
effects.
To
fill the first need, the U.S. Centers for Disease Control and Prevention (CDC) has
conducted biennial
biomonitoring studies of the U.S. population since 2003 to monitor consumer
exposure to BPA (and many other substances).
From these studies we know that human exposure to BPA is quite low,
typically below 0.1 micrograms BPA/kilogram bodyweight/day.
From
a comprehensive set of pharmacokinetic studies conducted by FDA and NTP
scientists on rodents,
non-human primates
and human volunteers,
we know that BPA is quickly eliminated from the body after exposure. Even more importantly, as BPA is absorbed
into the body after oral exposure it is efficiently converted into a
metabolite, which is the biologically inactive form of BPA that actually enters
the body and is then quickly eliminated in urine.
Based
on the pharmacokinetic and exposure data, we can predict that BPA is unlikely
to cause health effects at typical consumer exposure levels. The results of the CLARITY Core study, which
was conducted by FDA senior scientists in FDA’s research laboratory,
resoundingly confirm that prediction.
The
scope and magnitude of the CLARITY Core study are unprecedented, but size alone
is not what makes the results so compelling.
The laboratory animals in the CLARITY Core study were exposed to BPA
from pregnancy, through early-life development, and continuing through their
entire lifetime. The exposure levels
ranged from very low to an upper level that is more than 250,000 higher than
typical consumer exposure levels.
Exposure
occurred during all developmental stages of life, which are likely to be the
most sensitive life stages. Potential
health effects were monitored throughout the animals’ lifetimes, which ensured
that any delayed effects from early-life exposure would be found.
Because
of this comprehensive and rigorous
study design, FDA can confidently reaffirm their perspective that “currently authorized uses of BPA continue to
be safe for consumers.” The
perspective of FDA is fully supported by solid scientific evidence, just as it
should be.
What’s Next?
The
study will next undergo peer-review
by a panel of experts selected by NTP. That
will actually be the second peer-review since the pathology results have
already been peer-reviewed through an earlier NTP process known as a Pathology
Working Group. Comments from that
process have already been addressed in the report that was recently released.
The
upcoming peer-review process includes a public
meeting scheduled for April 26, after which the NTP draft report will be
released in final form with responses to any peer-review comments. The study will also be published in the
scientific literature, which will add a third layer of peer-review as part of
the normal publication process.
Without
a doubt, the results of the CLARITY Core study will be of high interest to
government bodies worldwide that have assessed the safety of BPA. Similar to the perspective of FDA, we can
anticipate that other government bodies will also rely on the CLARITY Core
study finding to conclude, again, that BPA is safe.
So
going back to the top, when exactly did BPA stop being toxic? Based on the collective results from the
CLARITY Core study and the in-depth U.S. government research program, that’s a
trick question. It never was toxic.
