The Washington Toxics Coalition tested cash register receipts and dollar bills for BPA.  Fifty percent of thermal paper receipts and most dollar bills tested in their study were tainted with Bisphenol A.  See more about the study here.

Of the 22 dollar bills tested in the study, 21 tested positive for BPA, but at lower levels than thermal paper receipts. The study attributed BPA on dollar bills to a handful of possible sources, including thermal receipts rubbing dollar bills in wallets and coming into contact with common house dust.

After holding thermal receipts for 17 minutes, participants in this study showed a 100-fold increase in BPA levels in their urine.