Recently the Kantonales Labor Zürich found Bisphenol A BPA in relevant concentrations in some thermal paper receipts of swiss retailers. These are mg BPA / kg thermal paper:
The lab also did some preliminary trials on what happens, once we touch these receipts. Because the work is not published in a journal, here some explaining statements by Sandra Biedermann, of the gaschromatography group headed by Konrad Grob, who did the tests:
How did you do measure the BPA in the receipts?
Translation: "For extracting the Bisphenol A from the paper we add a solvent. We used Methanol, because we know that Bisphenol A dissolves very well in Methanol. The Bisphenol A is extracted from the paper over night at 60 degrees celsius. Then we analyzed the methanol using liquid chromatography, HPLC. (...)"
How did you test what happens when we touch the receipts?
Translation: "We basically simulated a checkout-operator. We took a receipt, held it in our hands for 5 seconds. Then I extracted my fingers in a solvent (this time ethanol). and then measured the content using HPLC. This way I could see, how much coming from the receipt had landed on my fingers."
How much did you find?
Translation: "We measured that on average there were 2 micrograms of Bisphenol A on the fingers."
What influences the quantity?
Translation: "It doesn't matter much if you touch the paper for a longer time or less long. It depends rather on the consistency of the fingers. If they are wet or oily. with wet or oily fingers you can get out easily ten times more."
What happens if I hold the receipt in my hands for a longer period?
Translation: "We also varied the time of touching. Whether I hold the receipt 5 seconds or 60 seconds doesn't make a big difference."
Any idea what happens, once the BPA is on my skin?
Translation: "We did a kind of pre-trial. We put a defined amount on the finger and measured again after one and a half hours. we hardly found anything anymore of it. After that one has to assume that it was taken up, because we know, that it does not evaporate in large amounts. So, yes, we assume, it is taken up."
The KLZH emphasizes that these are just preliminary tests and that the evaluation of the dermal uptake of substances is outside of its field of competences.