Is it hygienic to eat after handling money?

20 November 2011



When someone buys chips (crisps I guess!) from a vending machine, they take their change, and then use the same hand to eat whats inside. Is this unwise?

I am a chemist, and really hope your show keeps growing.



Chris - I went looking at this because I think it's an interesting question, and I went to several sources. One of them was the book I wrote in Australia and it's called Stripping Down Science. It was out last year and I wrote a chapter in there called Sugar and Spice, and All Things Nice and E. coli. And the first line is "If girls are made of sugar and spice, and all things nice, then why are their hands covered in E. Coli? This is actually a report from a lady called Val Curtis from the London School of Hygiene and Tropical Medicine on the global hand washing day project she ran. This was back in 2008. They sent students who were doing a Masters with them to prowl up and down the lines of queuing commuters at train stations and public transport places all over Britain on this one day and they swabbed 400 sets of hands. And they wanted to see what they could grow. Now I just quote from the book because I could never remember all this in one go. So I'll just read you what I wrote: "Over 400 commuters consented to have their hands swabbed down to see what was lurking on them. The samples went to the microbiology laboratory for culture and identification. Nearly 30% of them tested positive for the presence of faecal bacteria including Enterococci and E. coli to common gut bugs. Yuck!" And then I say, "It actually stratified by what job you did. So manual workers tested positive 10% of the time, they were the best. And professionals, like you and me, they came up red handed in about a quarter of cases" and I say here, "The real Typhoid Mary's with a whopping 40% contamination rate turned out to be - do you know what? Either of you? What job?

Hannah - You're going to say scientists aren't you?

Chris - No, Administrators. How's that for justice? Anyway, also there's a geography here. If you go further up north in Britain, you're more likely to have these bugs on your hands than people in London, and the worst of all, the worst people are bus travellers apparently. "So, it's approximately one quarter of rail commuters were found to be carrying more than just their luggage", I said in that book.

Anyway, so that proves that people, just by going about their daily business, are covered in muck of a faecal variety. Now these bugs are not necessarily nasty in a sense that they won't give you very bad dose of gut rock, but they are a sign of bad hygiene being practiced, right, that's the first point. Then I went on, "If people handling money, we know that microorganisms will transfer easily between those hands that we now know. In 1/3 of cases are covered in stuff and the money". And so then I asked, "Well who's done research on what's on money?" So what I found ranges from 30% of bank notes through to 94% of bank notes are covered in the same sorts of bugs as reported in Val Curtis's study that I wrote about. And also, coins are slightly better than notes for obvious reasons. Metals, if they've got iron in them, iron tends to be toxic to some bacteria because it sets up oxidative reactions that breaks down the bugs. Copper also tends to be slightly lower carriage rate, paper money, really nasty, and there's also traces of drugs in there as well. So the answer is yeah, there's probably all kinds of nastiness all over those bank notes. Eat them at your peril. I mean, the point is being made, right? I find this funny...When you go to restaurants and things, or those fast food outlets, the people are wearing gloves, aren't they? And the idea here is I'll put gloves on because then I'm not touching the food I'm going to hand you. And then you hand them the money. Do they take their glove off? No. do they have someone separate who's collecting the money? They made your sandwich with this lovely gloved hand and when you give the money that they touched with their glove and they use till on everything, and then they go back and make another sandwich. So the bugs are basically going straight on the sandwich. No one has spotted the inconsistency in this!

Dave - How long are the bugs likely to survive on the money?

Chris - Not that long because it's quite dry and so, they do tend to perish quite quickly, but if you're using it merely as a sort of vector where it's on your skin, it goes on the money, it goes on the person's gloves, then on the food. Then the bug is very happy because it's now on the food. There's lots of Staph going on the food, there's lots of other things like E. coli going on the food. Staph is a bad one because Staphylococcus aureus makes a toxin and that toxin actually is heat stable. So if it gets in the food, the bugs grow and make lots of toxin, it goes in the food, and amplifies up. Then even if you heat the food up to kill the bug, the toxin is still there and you get gut right afterwards. That's bad. So you don't want that. So watch out. If they're wearing gloves and then they take money off you, make sure they change their gloves afterwards.

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