The hygiene of wind

Hygiene in a hospital environment is very important. Medical staff with a cold are only allowed around critical patients with the necessary protection - or not at all. This is quite normal, as sneezing and coughing can spread diseases. So no wonder that a nurse working in an operating theatre asked a question in 2001 to Dr Karl on his radio show about the potential risk related to letting wind in a sterile environment.

Dr Karl Kruszelnickiis the real-life legend of science communication, and hails from Australia. I listen to one of his radio shows, available to non-Aussies via podcast. Basically, people call in with a science question, and either he answers, or, and that is really nice, he explains that he does not know. The question might then be answered by other people calling in, with sometimes even a follow-up weeks later. Just because the caller dares askinga question in public, Dr Karl (who is a medical doctor) calls the person "doctor". Especially encouraged are people doing multiple experiments (with written or photographic proof) or looking things up themselves in peer reviewed literature (e.g. via Google Scholar, which I mentioned elsewhere). You might also know him as an IgNobel laureate for his survey on belly button lint.

So one day a nurse asked if it was dangerous to the sterile environment in an operating room if she let fly some. Dr Karl was intrigued, and together with a colleague (Luke Tennent) went looking for an answer. The results were reported in the British Medical Journal of 22 December 2001. (Note: each year, the BMJ's Christmas number is more of a tongue-in-cheek edition that features science, but not necessarily "serious" science).

Basically, Tennent let someone rip above an agar plate, a petri dish with a bacterial growth medium. In the BMJ article, it is described that this was done by a colleague of Tennent, on the ABC site of Dr Karl this colleague seems to bethe 8-year old son of a colleague. Given that Dr Karl calls every caller "doctor", you can make the argument that this boy probablyis a colleague anyway, who should get proper credit if these results are ever published in a peer-reviewed article.

So this colleague was asked to "cut the cheese" twice 5 cm above an agar plate, once fully clothed (jeans) and once with pants down. The first plate, after incubation, was almost perfectly clean, and the second one, well, see for yourself:

Basically, as Tennent and Dr Karl describe it, there are two types of bacteria. In "ground zero" we have intestinal bacteria (and I assume you can guess how they got there), surrounded (described as "splatter ring") by skin bacteria. These probably got there from the skin by the sheer blast of the flatus.

The researchers do note that more investigation is needed concerning distances, effect of food, etc. So far, only the Naked Scientists have reproduced, but only varying the amount of clothing. They too confirmed that we should not worry too much: being clothed (as any medical staff probably is during the exercise of their profession) is enough to not risk the lives of patients when breaking wind. However, the sound and smell effects might influence how you got looked at, but hey ... science cannot solve everything!