Thermal paper often used in cash register receipts could be a potential source of exposure for the potentially-dangerous hormone disruptor bisphenol-A (BPA).

A recent study showed that when people handled the thermal receipt after using hand sanitizer a large amount of BPA was transferred from the paper onto their hands, and their blood levels rapidly rose upon handling, PLOS reported. This type of thermal paper is commonly used in restaurant receipts, which not only exposes cashiers to the chemicals but can lead to food contamination as well.

"Not taken into account when considering thermal paper as a source of BPA exposure is that some commonly used hand sanitizers, as well as other skin care products, contain mixtures of dermal penetration enhancing chemicals that can increase by up to 100 fold the dermal absorption of lipophilic compounds such as BPA," the researchers stated in their study abstract.

BPA is used in a number of common products containing epoxy resins and polycarbonate plastics, which are often used in containers that store food and beverages as well as other consumer goods, MayoClinic reported. The Food and Drug Administration (FDA) has said BPA is safe at low levels, but the research remains ongoing. Almost everyone has some level of BPA in their urine.

The outer layer of thermal receipt paper is covered in BPA or another estrogen-mimicking chemical called bisphenol S (BPS).

"The BPA blood levels caused by touching thermal paper are related to many diseases (for example obesity and diabetes) that are increasing in frequency as the use of BPA is increasing," said co-author Frederick S. vom Saal. "The use of BPA or other similar chemicals in thermal paper thus poses a threat to human health."

The findings were published in a recent edition of the journal PLOS ONE.