Researchers from Australia's University of Ballarat said they have dispelled a myth by showing that banknotes do not carry dangerous levels of bacteria.
But they found that polymer banknotes, such as those used in Australia, carry the least quantity of contamination.
Australia's notes are manufactured and marketed by Melbourne-based Securency International Pty. Ltd., a joint venture established in 1996 between the Reserve Bank of Australia and U.K.-based polymer film maker Innovia Films Ltd.
The biaxially oriented polypropylene substrate has been used in Australian banknotes since 1988 and the technology was sold to about 30 other countries.
University of Ballarat food microbiologist Frank Vriesekoop led a global team analyzing banknotes from at least 10 nations.
“The richer and more developed countries had fewer bacteria on their money than poorer countries,” he said.
“Importantly, nowhere in the world were alarming levels of pathogenic bacteria found on money. We also found the age of the banknotes, and the material of which they are made, will affect the extent of contamination of that money.”
The international study collected a total of 1,280 banknotes from food outlets, such as food shops and cafeterias, and tested them for bacteria.
The research was conducted in Australia, the U.S., the United Kingdom, China, Ireland, Mexico, the Netherlands, New Zealand, Nigeria and Burkina Faso.
The findings were published in the U.S. scientific journal Foodborne Pathogens and Disease.
Vriesekoop said: “Older notes are more wrinkled, so dirt and bacteria can easily nestle in the folds of the notes. The material the banknotes are made of was also found to be important.
“In most countries, banknotes are made from a cotton-based material, while in Australia, New Zealand and Mexico the notes are made from polymer. We found notes made from polymer carried significantly less bacteria compared to notes based on cotton.”
The researchers also found that the lower a country scored on the Index of Economic Freedom, the more bacteria were on the banknotes.
“It is also likely that, in a country that scores low on this index, the banknotes might be older than in countries with a higher score,” Vriesekoop said.
“We found only very low levels of pathogenic bacteria in any banknotes and never in alarming numbers.”
The researchers still recommend that food handling be separated from money collection.