We’ve mentioned several times already on this blog about
bisphenol A (BPA) and how this endocrine disrupting chemical is present in all
sorts of plastics from water bottles, baby bottles, and dental sealants. What may not be inherently obvious is where
else BPA can be found in everyday products.
One example is with thermal printing paper: were you aware that thermal printing paper
contains BPA and once touched could possibly transfer onto your fingers?
Who Uses Thermal Paper?
Thermal paper is found in many places, though most commonly
it is found in the receipt paper at a store, or the paper used in certain
recorders in various laboratories. Could
employees working the cash register or even the customer handling the receipt
to file away in their records be exposed to BPA through the thermal paper? Could researchers working with recorders be
exposed to BPA when handling the paper to analyze their results?
What exactly IS thermal paper?
I already mentioned that thermal paper is the paper that’s
used often in cash registers as well as recorders in the laboratory. Breaking it down even further, imagine a
piece of thermal cash register paper. On
the side to be printed, there is a layer of printing ink covering the entire
surface. The color used to print
contains a leuco dye, which is a chemical that can exist in two forms: a
colored form and a colorless form. When
it comes time to print, the thermal head of the printer causes the leuco dye
and other chemicals on the surface to melt and react with one another, which
results in the dye taking on its dark colored form. These chemicals, in combination with the
heating and melting process, result in chemical products including the
endocrine disruptor, BPA.
Could the BPA on the thermal paper transfer to our skin?
This is certainly an interesting question, and one that has
not been studied too often. Those few
studies in animals examining absorption of BPA by the skin found that BPA can
be absorbed by the udders of cows, as well as through pig skin. What about humans? Is handling this thermal paper on our
receipts a cause for concern? Can the
BPA on this paper be absorbed through our skin as it has been shown to occur in
cows and pigs?
Preliminary Findings
In a study by a team of researchers from the Official Food
Control Authority of the Canton of Zürich in Switzerland, they examined whether
or not BPA can be transferred from thermal paper to the skin, and if there are
certain conditions that are better or worse for this transfer than others. Several interesting results came out of this
study.
First, holding thermal paper transferred on average 1.13ug
of BPA onto the fingers. If the fingers
were humid or greasy, then 10 times more BPA was transferred from the paper to
the fingers (on average 23ug/finger). The
greatest amount of BPA transferred onto the fingers was when the fingers were
so wet that some of the particulates from the paper itself stuck on to the
fingers.
Second, when touching the paper in multiple spots with “normal”
(i.e. dry) skin, no more BPA was transferred that had been after the first
initial touch. Basically, this means
that having regular contact with this type of paper throughout the day results
in a mostly consistent level of BPA on the fingers the entire day. If all
10 fingers were in contact with the paper, then on average 11ug of BPA would be
transferred onto the skin. If the paper
is crumpled up, theoretically a greater surface area could touch the fingers
and thus more BPA could be absorbed (not tested).
Wash those hands!
What happens if you immediately wash your hands after coming
in contact with BPA-laden thermal paper?
The Swiss researchers took a look at this as well, and found that
immediately washing ones hands after coming into contact with the thermal paper
was very helpful in reducing BPA levels on the skin. Somewhere around 90% of
the BPA was washed away when the hands were immediately washed, but it’s
important to note that some of the BPA still remained and was unable to be
washed off, perhaps due to its absorbance too deep into the skin.
It was noted that if the hands were wet, for example when
the BPA was applied in this experiment using ethanol, a significant increase in
absorption of BPA into the skin was observed.
So much so, that after 1 hour, it was already absorbed into the skin and
it could not be washed away. If the
fingers were completely dry prior to touching the thermal paper, it was found
that most of the BPA could still be washed away, even at 2 hours. Though a lot could be washed away, it is important
to note that 2 hours after thermal paper contact with dry skin, 27% of the BPA
could NOT be washed off and was already absorbed by the skin.
How much BPA in a day?
Based on the results of this paper, you can calculate just
how much BPA would be absorbed into your skin if you were say working the
register at a busy store, or maybe taking a lot of readings and doing a lot of
analysis on your laboratory recorder.
Luckily for me, the Swiss researchers already did this math, so I don’t
have to.
Let’s say you work the cash register at a store for a 10
hour shift. Based on the results of this
preliminary study, each one of your fingers should absorb about 0.09ug of BPA
per hour. Let’s say you touch the
thermal paper enough so that you maintain about 3ug of BPA on your fingertips
throughout the day. Assuming your
washing your hands periodically throughout the day, your skin would absorb
roughly 41ug of BPA. If you don't wash
your hands at all, even more BPA would be absorbed into your skin, resulting in
a worst-case scenario of 71ug of BPA that day.
Note: if you were wearing lotion
or your hands were somehow frequently wet (perhaps you like your fingers to
help grab at the paper), the results of this study would indicate that even
more BPA could be absorbed, perhaps by a factor of 10!
How to avoid BPA exposure via thermal paper?
Well, the results of this study would indicate that washing your
hands frequently should remove a significant amount of the BPA transferred onto
your fingers from the thermal paper.
Also, try not to wear any hand lotions, creams, or anything else that
might give your hands extra moisture, as this moisture seems to act as a vector
for even more BPA to be quickly absorbed into your body.
Sponge-Bob BPA-Pants
Think about it-> if you spill some liquid on the floor
and try to clean it up with a bone dry sponge, it takes forever for the liquid
to be absorbed into the porous material.
On the other hand, if you dampened the sponge prior to cleaning up the
mess, you’ll notice the liquid is much more readily absorbed into the sponge
and you have the surface cleaned in no time!
Something similar is likely happening with your skin: Dry skin = Very little BPA absorption. Damp skin = you may as well install a BPA IV
into your veins (well, OK, not THAT much, but it’ll get absorbed real fast).
The next step in this research would be to determine if the
levels of BPA absorbed actually cause any damage to the person that is handling
the thermal paper. Are the levels of BPA
absorbed by the skin enough to cause harm?
Technically, the levels observed are actually lower than the allowed
amount by US and European entities, however, many studies have shown that there
can be significant “low dose effects” of BPA at levels much lower than allowed.
In the meantime, wash your hands, and don’t slather yourself
with lotion if you’re going to be working with thermal paper all day.
Source: Biedermann,
S., Tschudin, P., Grob, K. 2010. Transfer of bisphenol A from thermal paper tothe skin. Analytical and Bioanalytical
Chemistry 398: 571-576.
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