Saturday, January 30, 2010

Blowers vs Towels

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This is more microbiology than chemistry but it has been a subject that fascinated me. Electric hand dryers in public toilets have long been touted as more hygienic than paper towel.

Not so, it seems.

[Wikipedia] In 2008, a study was conducted by the University of Westminster, London, to compare the levels of hygiene offered by paper towels, warm air hand dryers and the more modern jet-air hand dryers .

The key findings were:
  • after washing and drying hands with the warm air dryer, the total number of bacteria was found to increase on average on the finger pads by 194% and on the palms by 254%
  • drying with the jet air dryer resulted in an increase on average of the total number of bacteria on the finger pads by 42% and on the palms by 15%
  • after washing and drying hands with a paper towel, the total number of bacteria was reduced on average on the finger pads by up to 76% and on the palms by up to 77%.

The scientists also carried out tests to establish whether there was the potential for cross contamination of other washroom users and the washroom environment as a result of each type of drying method. They found that:
  • the jet air dryer, which blows air out of the unit at claimed speeds of 400 mph, was capable of blowing micro-organisms from the hands and the unit and potentially contaminating other washroom users and the washroom environment up to 2 metres away
  • use of a warm air hand dryer spread micro-organisms up to 0.25 metres from the dryer
  • paper towels showed no significant spread of micro-organisms.
And, yes, the work has been replicated.
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Sunday, January 10, 2010

Potatoes

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When I worked at the Coroner's Court, I remember reading about a guy who had a whole lot of potatoes that had started to shoot and so he broke off all the shoots and stir-fried them.

May he rest in peace.

There is a toxic alkaloid called Solanine that is produced by shooting potatoes. It is very high in the shoots and is also high in the potato when it has a green skin.

This calls into question the ethics of supermarkets who sell potatoes in pink plastic bags, or under pink lighting, as it makes the green potatoes look brown.

Until you get them home.
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