The richer and more economically free a country, the fewer bacteria its banknotes carry, according to a study of paper money in 10 countries ranging from Burkina Faso to the U.S.
Researchers found a “strong correlation” between the amount of bacteria per square centimeter (0.16 square inch) on banknotes and a country’s ranking on the Index of Economic Freedom, Wageningen University in the Netherlands said on its website today. Currencies studied included the euro, U.S. dollar, British pound, Chinese yuan and Mexican peso.
Countries that rank lower on the economic freedom index presumably have older banknotes to which bacteria more easily cling, the university said. The indicator was developed by the Heritage Foundation and the Wall Street Journal to measure nations’ degree of economic freedom.
“The age of banknotes plays a role,” Wageningen University said. “The older banknotes are, the more wrinkled they are, which means dirt and bacteria can more easily settle into the folds of the bills.”
The material from which banknotes are made also plays a role in their cleanliness, and polymer-based bills such as euro notes contained a quarter of the bacteria on the cotton-based banknotes used by most countries, according to the research.