Beware of dirty money

2011-12-08 10:54

If you get your hands on some money, wash them. Because all money is dirty – very dirty, say the experts.

Take a close look at coins: Some are tarnished, some are bright and shiny – but almost certainly any coin has passed through hundreds of hands before it got to you.

A coin issued in 2005, for example, has been in circulation for six years now. It has probably been passed between hundreds of people: beggars and millionaires, bankers and drug dealers, supermarket tills and vending machines.

Consider also the findings of a Global Hygiene Council survey in 2009, which estimated that 60% of South Africans do not wash their hands after going to the toilet or handling pets.

Theoretically, therefore, six of the last 10 people to handle that coin in your pocket could have left traces of faecal matter and accompanying germs on it.

Even if a coin has been sterilised at some point, “there is no such thing as a clean surface,” says Wits microbiology expert Professor Vincent Gray, who is also affiliated to the SA Society for Microbiology.

Press a coin between your fingers. It feels a bit sticky – why?

“Dirty fingers rub off on coins. Lipids (oils), amino acids (the building blocks of proteins), as well as bacteria, coat the surface of the coin and form a layer – like a skin,” Gray said.

Bacteria join to the lipids, dead skin cells and each other to form a living biomass or living biofilm, often seen accumulated in the recesses of a coin.

These oils and amino acids provide nutrients for bacteria, enabling them to survive and multiply on the coin’s surface.

Also, if a coin is kept in your pocket, your body heat can act as an incubator for the surface germs and accelerate the rate at which they multiply.

Bacteria are also surprisingly durable: they can survive for weeks, even months, on a surface, Gray said.

Common bacteria that could be lurking on your change include various staphylococcal species, E. coli, corynebacteria, and propionibacterium.

Less common pathogenic bacteria may also be transferred to the coin through handling.

These include mycobacterium tuberculosis (tuberculosis), salmonella, pathogenic strains of E. coli and vibrio cholerae (cholera) to name only a few.

“Bacteria are very abundant and account for a huge proportion of the world’s living biomass,” Gray said.

Viruses – like those that cause human infections such as hepatitis, herpes or influenza – can also be present on money, but are not likely to survive for long outside a host, he said.

Viruses tend to die when exposed to ultraviolet radiation, like sunlight, and therefore have limited survivability.

Bank notes, as well as coins, can carry some surprising nasties.

A study by the Institute of Public Health in Bangladesh analysed bank notes and found bacteria associated with a variety of throat, skin and bone diseases.

Igumbor et al (2007) conducted a study for the University of Venda, which found that banknotes of lower denomination (R10 and R20) had a higher concentration of germs on average than higher value notes.

The study, entitled Microbiological Analysis of Banknotes Circulating in the Venda Region of Limpopo Province, suggested this was because smaller notes circulate more quickly.

A British study conducted by Mass Spec Analytical found that 80% of bank notes were contaminated by drugs – especially cocaine. This figure rose to 99% in London bank notes.

It was hypothesised that this high rate of contamination might be caused by money counting machines, which spread traces of the drug to other notes.

But there are many other surfaces humans come into contact with on a daily basis that are even more likely to spread germs.

“Think of light switches, communal telephones, door handles and fridge doors ... just think of how dirty white computer keyboards get,” Gray said.

While it is theoretically possible to become sick from the germs spread via money, they are unlikely to affect people with healthy immune systems.

“Most of us have latent infections, but if the immune system is compromised, non-pathogenic infections can become pathogenic [sickness causing],” Gray said.

Exposure to small amounts of germs can actually be beneficial, he explained, as a healthy immune system is usually capable of adapting to otherwise harmful bacterial strains by building the body’s natural resistance.

Nonetheless, if you get your hands on some money, it is advisable to wash them.

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