With
the high level of attention to bisphenol
A (BPA) over the years, it’s easy to get the impression that
BPA is everywhere and we’re constantly being exposed to high and harmful levels
in our daily lives.  You might even have
seen BPA referred to as an “everywhere chemical.”   

Adding
to the confusion, the media is notorious for attaching pictures of products
that contain absolutely no BPA to articles about BPA.  Perhaps the most common examples are pictures
of bottled water.  Single-serve bottles
containing water, sports drinks or carbonated beverages are almost universally
made from a plastic known as polyethylene terephthalate (PET), which has no
connection to BPA at all.

Perhaps
stimulated by the controversy and confusion, scientists have been conducting
studies to look for BPA in various places and measure how much BPA we’re
actually exposed to.  It may be a
surprise to some, but many of these studies show that BPA is not present everywhere,
exposure levels are very low, and, most importantly, those levels are not
harmful.

How Is Exposure to BPA Measured?

An
entire field of science, known as exposure science, is dedicated to studying
exposure of people to chemicals that occur in their environment.  Several types of studies from this large and
growing field are particularly informative to understand human exposure to BPA.  These studies measure how much BPA goes in
the body, how much comes out and, most importantly, what happens in between.

What Goes In?  These studies measure BPA in products or
places that people contact, and estimate how much of that BPA could enter the
body.  Although exposure may only be estimated
and not directly measured, these studies can evaluate specific sources of
exposure.  Several studies published this
year focused on potential exposure to BPA from sources either known or
suspected of containing BPA.

Dental
sealants.  Many sealants
are based on a derivative of BPA known commonly as bis-GMA (bisphenol A
glycidyl methacrylate).  Because bis-GMA
could contain ultra-trace levels of residual BPA, the American Dental
Association analyzed 12 dental sealants from the U.S. market to determine how
much BPA could be released.  As reported
in ADA’s Professional
Product Review, the median amount of BPA released was
0.09 nanograms from the amount of sealant applied to four teeth.  That vanishingly small amount led ADA to
conclude, as summarized in the headline to its news
release, “BPA in dental
sealants safe.”

Hair
care products. 
For some time, concerns have been raised that hairdressers may be
exposed to unsafe levels of various chemicals from hair care products they use in
the salon.  To address these concerns,
the Finnish Institute of Occupational Health and the National Institute for
Health and Welfare conducted a study to measure exposure to BPA (and several
other chemicals).  As reported:  “According
to the results, hairdressers in Finland are not exposed to … bisphenol A … any
more than the rest of the population.” 
The result is important not only for hairdressers but also for
consumers.  If hairdressers, applying
hair care products throughout their workdays are not exposed to BPA, it seems
highly likely that consumers using the same products on their own hair would
also not be exposed to BPA.

Food
products.  It’s
well-known that BPA-based epoxy resins are commonly used as protective coatings
on food and beverage cans to help protect the contents from contamination.  The Food Safety Authority of Ireland (FSAI)
conducted a Total
Diet Study to measure levels of BPA (and other chemicals) in 147
foods and beverages representative of the normal Irish diet.  Not surprisingly, trace levels of BPA were
found in 30% of the samples analyzed.  Exposure
to BPA was then estimated based on food consumption data.  Comparison of estimated exposure to the
stringent health-based guidance value for BPA in Europe led FSAI to conclude
that “exposure to BPA is of low concern.”

The
studies listed above, along with many earlier studies, confirm that BPA is not
literally “everywhere.”  Where it is
present, the levels are very low and estimated exposures are well within
health-based guidance values for safety.

What Comes Out?  Since BPA is quickly eliminated from the body
through urine after exposure, analysis of BPA in urine provides a good measure
of total exposure to BPA from all sources combined.  Recent studies have focused on exposure to
BPA in the potentially sensitive subpopulations of reproductive-aged women and
reproductively active couples.

Reproductive-aged
couples.  A study
conducted by researchers at the University of Utah measured BPA in repeated
urine samples from couples planning pregnancy. The median BPA level (2.4
microgram BPA/L urine) was comparable to levels reported in large-scale studies
conducted by the U.S. Centers for Disease Control and Prevention (CDC) that are
representative of the U.S. population.

Reproductive-aged
women.  A similar study from
the U.S. National Institutes of Health and a team of researchers in the U.S.
and France measured BPA in repeated urine samples collected from
reproductive-aged women.  The median BPA
level (2.8 micrograms BPA/L urine) in this study was also comparable to levels
measured in the U.S. population.

A
separate series
of studies conducted by CDC (known as the National Health and
Nutrition Examination Survey, or NHANES) indicate that typical exposure to BPA
in the U.S. population is less than 50 nanograms BPA/kg bodyweight.  This level is more than 1,000 times below
safe intake levels set by U.S. government agencies based on extensive
scientific review.  The two new studies
indicate that exposure to reproductive-aged women and reproductively active
couples are also well within these safe limits.

What’s Inside the Body?  In contrast to the
studies above, which measure BPA outside the body, these studies measure how
much BPA is actually in the bloodstream where it could potentially cause
harm.  The studies are more challenging
to conduct, but are of high value for evaluating whether exposure to BPA is
harmful.  Two recent studies examined
levels of BPA in the blood of a potentially sensitive subpopulation and a
potentially more highly exposed group.

Pregnant
women.  A study
jointly conducted by researchers at the Pacific Northwest National Laboratory
and the U.S. Food and Drug Administration (FDA) measured BPA levels in urine
and blood from a group of pregnant women. 
Low levels of BPA were found in urine, indicating exposure similar to
levels found in the studies above.  More
importantly though, no BPA was detected in blood for most of the samples with a
very sensitive analytical method.  In
cases where BPA was detected, clear evidence was found that the trace levels
near the detection limit were the result of contamination and not indicative of
actual exposure.

Cashiers.  A minor use of BPA is as a component of the
heat-sensitive coating on some thermal receipt papers.  Since cashiers handle receipt paper
throughout the day in the course of their work, a U.S. National Toxicology
Program study measured
BPA levels in urine and blood from a group of cashiers before and after their
work shifts.  Although low levels of BPA
were detected in urine, no BPA was detected in most of the blood samples.  Similar to the study above, sample
contamination was suspected in most of the sample where trace levels of BPA
were detected.

These
studies are particularly informative in that they demonstrate that measureable
levels of BPA are not present in blood, even when low-level exposure to BPA is
confirmed by measurement of BPA in urine. 
This seeming contradiction is due to the efficient metabolism and
clearance of BPA from the body that has been demonstrated
in numerous studies on laboratory animals and human volunteers.  Any BPA to which we are exposed is converted
to a biologically inactive metabolite that is quickly eliminated from the body
in urine.  As a result, the potential for
BPA to be harmful at typical exposure levels is virtually eliminated.

BPA Is Safe Where It Is,
But It’s Not Everywhere

Although
no single study can answer all of our questions on BPA, results from these
studies taken together provide powerful evidence to evaluate the safety of
BPA.  These new results strongly support
the conclusions of government bodies worldwide that have reviewed the extensive
science on BPA.  A representative example
is FDA, which answers the question “Is
BPA safe?” with an unambiguous answer – “Yes.”