The thermal printing paper that is commonly used for cash register receipts contains bisphenol A, the chemical that has generated a great deal of controversy because of concerns that it may have an effect on our health even at very low concentrations. That controversy has generated a great deal of ink in newspapers and magazines, and that ink too is often formulated with BPA. Is it possible that just handling cash receipts or newspapers or magazines can transfer BPA to the skin and that from there it can find its way into the bloodstream? Science can quite readily answer those questions, and it has. Indeed, BPA can be absorbed by the skin through handling paper that contains BPA and it can then pass into the bloodstream. Of course whether the amount that ends up in the bloodstream is consequential or not is a totally different question and one that is much more difficult to answer.
How do we know that BPA is absorbed by the skin? Sometimes pigs’ ears come in handy for more than serving as tasty chews for dogs. Pig ear skin is a widely used model for human skin. Dr. Daniel Zalko at the French National Institute for Agricultural Research treated pig skin with radioactively labeled bisphenol A and followed the movement of the chemical through the skin by monitoring radioactivity. About 65% of the BPA diffused through the pig skin. This prompted experiments with human skin, which showed that about 46% of the chemical made it through. That still left the question of whether or not this can lead to an increase in blood levels since the possibility remained that passage through the skin allowed for BPA to be metabolized. It turns out, however, that the compound does make it through the skin intact. Dr. Joe Braun at Harvard looked at the concentration of BPA in the urine of 389 pregnant women who worked as cashiers, teachers or had industrial jobs. The cashiers who handled a lot of thermal paper had the highest levels of BPA, suggesting that BPA is absorbed through the skin and does end up in the circulatory system, eventually to be eliminated in the urine.
Researchers in Switzerland added some corroborative evidence when they had volunteers hold thermal printing paper for five seconds and then analyzed the skin for BPA. About 1 microgram was transferred, with the amount depending on whether the fingers were dry, wet or greasy. Wetness or greasiness was associated with ten times greater transfer of BPA to the skin. In an attempt to monitor the fate of the BPA, the researchers investigated whether the BPA absorbed into the skin was extractable with alcohol after 2 hours. It turned out that after holding the thermal paper, the BPA was extractable from the skin after two hours, but when applied in an alcohol solution it was no longer extractable. This suggests that BPA can pass into the bloodstream depending on skin conditions. Based on the amount that was not extractable, the researchers concluded that exposure to someone touching thermal paper for 10 hours a day could lead to the absorption of 70 micrograms of BPA per day, which is some 42 times less than the present tolerable daily intake. However if there is cream on the hands, the margin of safety could be less.
There is also the question of where the thermal paper eventually ends up. Much of it heads for recycling, meaning that facial tissues and toilet paper could also lead to BPA exposure. It should also be noted that in thermal papers and in recycled papers BPA is a free compound, as opposed to its presence in polycarbonate plastics or can liners where it is incorporated into polymers. Absorption from paper therefore is easier. The bottom line is that it is not a bad idea, especially for young women working as accountants or cashiers who may become pregnant to wear latex gloves when handling receipts. Then all they have to worry about is latex allergy.
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