Posted 6 December 2016
Older banknotes carry more bacteria compared to new polymer ones and in addition it was interesting to see that there was a general trend that the richer a nation; the cleaner its currency.
After the new plastic five pound note has been released in the UK, a project in to bacteria on currency has concluded that plastic, also known as polymer, banknotes are cleaner than cotton, cotton-linen and washi paper notes.
It’s not the only interesting result to come out of ten years of investigations, led by Professor Frank Vriesekoop.
He said: “We found that bacteria found on human hands are less capable of sticking to plastic banknotes compared to the old cotton-based UK pound notes; the linen-cotton mix based American dollar notes; and the washi paper based Japanese Yen notes.
“In addition, bacteria found on human hands die-off faster when on plastic banknotes.
“Older banknotes carry more bacteria compared to new polymer ones and in addition it was interesting to see that there was a general trend that the richer a nation; the cleaner its currency.
“Currently more than 30 countries are using the ‘cleaner’ plastic notes, now including the UK. Cotton-linen notes are only used in America and washi is only in Japan.
“We also carried investigations out on coins.
“We found that they also carry bacteria but many coins are actually toxic to bacteria. The composition of the coin influences the magnitude of its ‘coin toxicity’
“Despite coins being toxic, bacteria can adapt to a toxic environment. For this reason, there was still bacteria present on coins which we took out of circulation and tested.
“While writing up the report which has recently been published, I realised that I had one more question to answer. I had some coins in bags, which had come straight from the Royal Mint, and had never been in circulation. Would these have bacteria on them?
“There was much less bacteria on the non-circulated coins, but there was still bacteria. However, the bacteria which was present is known to survive a number of horrid situations, so it was no real surprise to find that kind of bacteria.
Being a professor in food biotechnology, it may originally appear that this research project falls outside the interest of Professor Vriesekoop, but there’s more similarities than originally thought. “This project originated from a question regarding food.
“I was lecturing in food microbiology in Australia. One of my students asked if someone preparing food and handling money with the same hand, and not washing it, could have a negative effect and have the ability to transfer bugs and make the consumer ill.
“At the time I said I didn’t know. I looked it up and at the time there were papers published but none of them could tell me. They all gave different results, had been done differently and none of them gave an answer to why.
“Next time I saw my class, I asked them if they wanted to do the research.
“We started on banknotes as they appeared to be the easiest. At the time when we did the first trial we got results but they were so low they didn’t compare at all to the previous studies. I contacted a colleague in Australia and she got almost the same results as we did.
“Then it dawned on me that we were using plastic money and all the published results were on cotton money. I got colleagues in other countries involved and it just snowballed from there.
“Even some of the equipment we have been using for this investigation is often used in food microbiology.
“It’s taken over ten years to get to this point but to me, this project is now over.
“One of the important things for me, is that every student who took part in the research has been an undergraduate.
“Some of them standardised methodology and then another came along and did the experiment.
“For those students, it showed how easily they could do a project which has real scientific meaning and be published.”