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Dublin: 13°C Monday 4 July 2022

How much bacteria lives on a pedestrian crossing button?

Despite the stainless steel surface, they’re thriving.

A pedestrian crossing at Ulster Bank.
A pedestrian crossing at Ulster Bank.
Image: James Horan/Photocall Ireland

EVERY DAY ACROSS the country, the button on a pedestrian crossing could be pressed by dozens of people.

Seeing as people’s hands are often not the cleanest, something people are conscious of now with the current flu outbreak, are germs being transferred to the button?

A BT Young Scientist project by students from Castleknock Community College in Dublin found there is a significant amount of bacteria there – but that doesn’t mean you should be avoiding them at all costs.

Alison Egan, Caoimhe Harrington, and Áine Morgan took swabs from six pedestrian crossings in spring and summer, and used catalase and Gram staining tests to figure out if anything was living there.

They found “significant” colonies, with only three of their tests coming back negative.

students Source: TheJournal.ie

They found diphtheroid, staphylococcus, bacillus. You might recognise these names from their nasty derivatives, with some being the cause of everything from diphtheria to food poisoning – however, it’s not a guarantee.

Bacteria lives everywhere, and further, more complex testing would be required to say for sure if these could cause harm.

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However, they were able to make themselves at home on the stainless steel surface, and would sometimes secret a sticky substance in order to cling on better. With a different material, such as copper, they would struggle to survive.

Wiping the crossing with alcohol wipes didn’t kill off all strains, but would actually boost some as it allowed them to become more dominant.

The Dublin students said that while it’s probably better to not rub your hand all over your face after touching a pedestrian crossing, further research is needed.

Debunked: Does pressing the pedestrian crossing button more than once make any difference? >

About the author:

Nicky Ryan

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