A
recent study
from French government researchers reported new results on the exposure of
pregnant women to more than 100 substances that might be a concern for the
health of a developing fetus.  The study
examined exposure to various metals (e.g., lead, mercury, arsenic) and many
common organic compounds that we might encounter in our daily lives.

 Included
in the study was bisphenol A (BPA),
which is used primarily as a building block to make polycarbonate plastic and
epoxy resins.  Although those names may be
unfamiliar to you, the materials are not; both are used in countless products
that we use every day.

 Polycarbonate
is a clear, durable and lightweight plastic that is used in a diverse range of
products from bicycle helmets to eyeglass lenses.  Epoxy resins are tough and chemically
resistant materials that excel in applications that require a protective
coating (e.g., anti-rust primer on automobile bodies) or a material that is
both high strength and lightweight (e.g., wind energy turbine blades).

 The
French researchers reported that the majority of women in their study were
exposed to BPA and provided quantitative data on the levels of exposure.  Missing from the paper was any context to
help us understand whether we should be alarmed or comforted by their findings.  In other words, are the exposure levels safe
or not?

 Coincidentally,
a group of Greek scientists recently published their assessment
of BPA in the peer-reviewed scientific literature and concluded that “exposure to BPA does not pose any
significant threat according to most realistic exposure scenarios.”  The conclusion is well supported by a set of
complementary analyses that specifically included pregnant women.  The conclusion of the Greek scientists is also
consistent with and further supports the science-based conclusions of
government bodies worldwide on the safety of BPA.

 New French Study on BPA Exposure to
Pregnant Women

An
increasingly accepted way to measure human exposure to chemicals is through
biomonitoring studies, which measure the level of a chemical in biological
samples such as urine or blood.  For BPA,
analysis of urine is most appropriate since BPA is rapidly eliminated from the
body in urine within hours of exposure.  By
measuring what comes out of the body, urine biomonitoring measures exposure to
BPA from all sources over the last day or so. 
When applied to a representative group of people, urine biomonitoring
provides a reasonable estimate of average exposure to BPA across a population.

 The
new study was conducted by a team of researchers from Santé publique France,
which is the French national public health agency and is responsible for the
French Human Biomonitoring Program.  In
this study, BPA was measured in the urine of more than 1,700 pregnant women who
gave birth in France in 2011.  Due to the
study design, the results provide an estimate of exposure that is
representative of the population of French pregnant women in that year.  The results are important since pregnant
women might generally be considered one of the most vulnerable subpopulations
for exposure to chemicals.

 Not
surprisingly, considering how widely it is used, BPA was quantified at low
levels in the urine of almost 74% of pregnant women, indicating that exposure
to BPA is common.  The median BPA level (0.75
micrograms/liter) is comparable to the results of a large-scale study
of pregnant women in Canada from a similar time period.  The BPA levels measured in the French study
are also comparable to the results of biomonitoring studies from
the same time period that are representative of the U.S. population.

Comparison
of the BPA levels with the levels of metals and other organic chemicals
measured in the French study reveals that the BPA levels are relatively low.  However, the French researchers did not
include information in their paper to help us understand whether the levels are
safe.

Credit: Shutterstock

How Can We Evaluate Safety?

With
thousands of studies published in the scientific literature, BPA is almost
certainly one of the best tested substances in commerce.  Many studies, including the new French
biomonitoring study, report that people are exposed to BPA at low levels, but
exposure studies alone can’t tell us whether the levels are safe.  After all, we’re exposed to many chemicals
that occur naturally in our diet, but we don’t conclude that our diet is unsafe
just because we can (and do) measure exposure to those chemicals.

 An
even larger number of studies, typically conducted on laboratory animals,
report various health effects that might be caused by exposure to BPA, but
these studies alone also can’t tell us whether BPA is safe.  Health effects have also been identified for
the chemicals that occur naturally in our diet, even for vitamins and other
essential nutrients, but that doesn’t make them unsafe.

 We
can evaluate safety by combining information on exposure and health effects in
a scientific process known as a safety or risk assessment.  Health effect information tells us what
effects can be caused by exposure to a chemical and, most critically, at what
exposure level the health effects might occur. 
Exposure information then tells us whether actual exposures are above or
below the critical level.

 What Do the New BPA Exposure Results
Mean?

Just
before the new biomonitoring study was published, a group of researchers in
Greece published their assessment of BPA. 
Jumping to the bottom line, they concluded that “exposure to BPA does not pose any significant threat according to most
realistic exposure scenarios.”  Since
their analysis explicitly included pregnant women, their conclusion is
particularly applicable to the exposure levels measured in pregnant women in
France.

 What
the Greek scientists did was focus on the exposure side of the safety
assessment equation with four complementary analyses.  Of particular relevance for the French
biomonitoring data is that they calculated a “biomonitoring equivalent” (BE)
based on the conservative safe intake level for BPA recently established by the
European Food Safety Authority.  The BE level
represents the estimated concentration of BPA in urine corresponding to intake
of BPA at the safe intake level.

 The
median BPA level measured in the French study is more than 400 times below the
BE level.  This indicates that not only
are the actual French exposure levels safe, but they’re safe with a wide margin
of safety.  It’s not even close.

 The
other three analyses from the Greek scientists gave consistent results and
provide further support for the safety of the French exposure levels.  The Greek scientists also stated that “there is no reason for concern based on either
individual or aggregate scenarios of BPA exposure.”  That conclusion is consistent with the views
of government bodies worldwide that have recently evaluated the safety of BPA,
for example the U.S.
Food and Drug Administration and the European Food
Safety Authority.

 What Else Does the French Study Tell
Us?

Careful
inspection of the data table in the French study reveals
another very important piece of information. 
Although we may frequently say that urine biomonitoring measures the
level of BPA in urine, as is stated above in this article, that’s not exactly
what is measured. 

 The
data table indicates that urine was monitored for both “unconjugated” and
“total” BPA.  Unconjugated BPA, which is
simply BPA itself, was found but could only be quantified at very low levels in
about 10% of the urine samples.

 Total
BPA consists almost entirely of a metabolized form of BPA.  From many other studies on laboratory animals
and, most importantly people,
we know that BPA is efficiently converted in the body to a biologically
inactive metabolite, which is then rapidly eliminated in urine.  It is this metabolized form of BPA that was
found in approximately 74% of the urine samples.

 The
urine biomonitoring data from the French study confirms that this important
metabolic process occurred in the French pregnant women.  As a result, since the metabolite is
biologically inactive and rapidly eliminated from the body, BPA is not likely
to cause health effects at the low exposure levels measured in the study.