Scientific proof: Money is dirty.

Aug 18, 2011

Liao, C, and K Kannan. 2011. High levels of bisphenol-A in paper currencies from several countries, and implications for dermal exposure. Environmental Science and Technology

Synopsis by Steven Neese and Wendy Hessler

Tai Machado/flickr
Paper money from countries all around the world carry a chemical hitchhiker – the hormone-active substance known as bisphenol A (BPA). Paper bills are the latest addition to a growing list of items tainted with the ubiquitous chemical that has been linked to adverse reproductive, metabolic and behavioral effects.

The study identifies cash as another source of human exposure to BPA, report the researchers who found that BPA can transfer to the bills from thermal cash receipts stored next to them in wallets.

The levels measured in the 50 bills from different governments varied widely – from almost nothing to considerably high amounts. Still, more research is needed to understand human exposures and possible health effects.



BPA is a high production chemical, used in the production of a variety of plastic products and the epoxy resin linings of canned food. This chemical can escape from these products and contaminate the packaged food (Schecter et al. 2010). More than 90 percent of the U.S. population is chronically exposed to BPA (Calafat et al. 2008), and diet is considered a major source of this exposure.

Contact and absorption through the skin is another potential source of exposure. BPA is found in some types of thermal papers that are used in a variety of applications, including cash register receipts, luggage tags and faxes (Mendum et al. 2010), all products that require handling.

BPA is loosely bound to the thermal papers – most notably cash register receipts – allowing for easy transfer to hands, money and other products touched in a complementary setting. Household dust also contains this chemical (Loganathan and Kanna 2011), and may be another source from which BPA can be transferred to other items.

To date, only one study has measured for the chemical in paper money. The Washington Toxic Coalition detected BPA in 21 of 22 U.S. dollar bills. No research has examined paper currency from other countries or tested if BPA can be deposited on money from other sources. Researchers do not know whether paper money is made with BPA.

Identifying sources of exposure is important because BPA has endocrine disrupting effects, meaning it can interfere with the actions of hormones in the body. Animal studies have linked developmental BPA exposures to reproductive and neurobehavioral problems, obesity and immune system changes.

What did they do?

In the study, paper currency was collected from several different countries, including the United States, Canada, Czech Republic, Russia, Turkey, Australia, Brazil, Egypt, South Africa, China, India, Japan, Korea, Kuwait, Malaysia, the Philippines, Singapore, Thailand, Vietnam and the United Arab Emirates.

Bills were graded as "fresh" or "used" based upon appearance. They were collected from different years of release. Three circle punches from each bill – the lower left corner, middle and upper right hand corner – were analyzed for BPA.

To test if currencies can collect BPA from other sources, several bills – two from the Philippines, two from Thailand and one each from Vietnam, Brazil and the Czech Republic – were placed in direct contact with a thermal register receipt and kept in a wallet for 24 hours.

What did they find?

All 52 paper bills tested contained a detectable level of BPA in at least one of the punches. Levels ranged from almost nothing – 0.001 micrograms per gram (µg/g) – to very high amounts of almost 83 µg/g.

Concentrations varied on the bill itself and across countries. Higher levels were detected away from the edges in the bill's interior. Of the countries, Brazil's bills had the highest levels. No relationship was found between currency value and BPA levels.

BPA concentrations in paper money with low initial levels – including the Philippines, Thailand and Vietnam – were increased 100- to 1,000-fold when placed alongside a receipt in a wallet for 24 hours. A more modest two-fold increase was seen in paper money from Brazil and the Czech Republic that had a high initial BPA content. These results clearly suggest the possibility of transfer from thermal receipts to paper money, with quantity shifted dependent upon the initial concentration in the currency.

Older bills from some countries (including the United States, China and the Philippines) had consistently higher levels of this chemical than newer bills. These findings further suggest potential transfer from other BPA-containing products, an effect that can result in an accumulation of this chemical in paper money across years of circulation.

What does it mean?

Paper currency is another in a long list of everyday products contaminated with BPA. The results suggest people around the world can be exposed to the endocrine-active chemical through yet another ubiquitous source: money.

Yet, how it ends up tainting the bills is not altogether clear.

The researchers did find that the BPA can rub off onto paper money from thermal receipt papers kept in the same wallet. BPA is not chemically bound to the receipts, and in this study it easily migrated to nearby items.

BPA and BPA-containing products may also be used to produce paper money, including ink developers and recycled paper. While these products can contain BPA, it is not know whether paper money is manufactured with them. Its use could explain the contaminant found in paper currencies around the world and account for some of the differences measured in the various currencies.

These results are important because BPA can be absorbed through the skin. Little is known of human exposures through this route, but research suggests up to 27 percent can be transported to the bloodstream within two hours of dermal exposure (Biedermann et al. 2010).

Exposure could also occur through breathing air and dust. Cashiers and others who spend long periods of time handling the thermal receipts and money may be at most risk for this type of exposure.

Overall, the results of this study suggest the need for additional research regarding the transfer of BPA to and from money and the potential human exposure and health effects that may accompany frequent contact with the paper money.


Biedermann, S, P Tschudin and K Grob. 2010. Transfer of bisphenol A from thermal printer paper to the skin. Analytical and Bioanalytical Chemistry 398:571-576.

Calafat, AM, X Ye, LY Wong, JA Reidy and LL Needhman. 2008. Exposure of the U.S. population to bisphenol A and 4-tertiary-octylphenol: 2003-2004. Environmental Health Perpectives 116:39-44.

Loganathan, SN and K Kannan. 2011. Occurrence of bisphenol A in indoor dust from two locations in the eastern United States and implications for human exposures. Archives of Environmental Contamination and Toxicology 61:68-73.

Mendum T, E Stoler, H VanBenschoten and JC Warner. 2011. Concentration of bisphenol A in thermal paper. Green Chemistry Letters and Reviews 4:81-86.

Schecter, A, N Malik, D Haffner, S Smith, TR Harris, O Paepke and L Birnbaum. 2010. Bisphenol A (BPA) in U.S. food. Environmental Science and Technology 44:9425-9430.



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