Denmark is bringing new meaning to the phrase ‘dirty money.’ According to tests from Oxford University that measured the amount of bacteria present on European currencies, the Danish krone is the dirtiest money on the continent.

Researchers tested bank notes across six European countries, and found that kroner banknotes were the dirtiest, containing 40,266 bacteria on average. In comparison, banknotes across the other countries averaged 26,000 bacteria. The euro note contained 11,066 on average, while the cleanest, newest bills tested contained 2,400 bacteria.

The findings, commissioned by MasterCard, come in conjunction with a survey carried out by the credit card company that asked Europeans in 15 countries to identify the least hygienic item they come into contact with on a daily basis. In each of the countries surveyed, respondents found cash to be the dirtiest item – even more so than escalator handrails or library books.

And according to Gaetano Carboni of MasterCard Europe, this may be changing the way Europeans handle their money.

“It’s interesting to see a majority of Europeans prefer paying by card and find it a simpler, more straightforward way of paying,” Carboni said in a press release. “It’s now true to say that the majority also find it more hygienic.”