Many of us have heard that flushing toilets could result in airborne particles of "poo" making their way onto our toothbrushes. In recent years, the idea of traveling water droplets with "poo" in them has been cast as a sort of urban myth, thanks largely to a segment on the psuedo-science "Mythbusters" show. The yucky truth is that what Mythbusters found in no way disproved the idea of particles traveling from the toilet to toothbrushes and what they actually found was no reason for assurance that it is OK to leave toothbrushes out in the bathroom.

When you flush your toilet it does indeed result in water droplets traveling through the air. Have you ever flushed the toilet while sitting on it? Odds are you sometimes feel droplets of water hitting your bottom - and those droplets contain parts of whatever you are flushing. Similarly, a man who urinates standing up can produce similar droplets that travel outside the toilet, some of which he can feel if his legs and/or feet are bare. Anyone who has had the "pleasure" of cleaning on and around a toilet bowl knows that what is going in the toilet also goes outside the toilet.

The spread of toilet water droplets is not limited to just those large enough to feel. Thanks to "the aerosol effect", a veritable cloud of tiny droplets travels far outside the toilet when it is flushed. The aerosol effect was first brought to light by University of Arizona environmental microbiologist Charles Gerba when he published a scientific article in 1975 describing the disturbing results of his tests on bacterial and viral aerosols due to toilet flushing. He conducted tests by placing pieces of gauze in different locations around the bathroom and measuring the bacterial and viral levels on them after a toilet flush. His results were more than a little disturbing: he found that the aerosols traveled as far as six to eight feet away from the toilet.

"Droplets are going all over the place—it's like the Fourth of July," said Gerba. "One way to see this is to put a dye in the toilet, flush it, and then hold a piece of paper over it"

In the Mythbusters segment which has been cited to disprove the idea of particles of poo traveling outside the toilet, what they actually found was that bacteria from feces can be found everywhere - including on a pair of "control" toothbrushes they put away in a medicine cabinet in another room. That is hardly reassuring nor is it in any way proof that particles do not travel from the toilet to exposed toothbrushes. Plus, the Mythbusters team only tested for bacteria and not actual particles nor viruses.

It is true that fecal coliform bacteria are not considered to be a health risk since they are found naturally in the human body. However, that does not mean that it is a good idea to introduce the bacteria into the mouth. Also, the presence of fecal bacteria is an indication that other bacteria which are known to be dangerous may also be present. Fecal coliform grows in an environment similar to other waterborne bacteria, and thus their presence outside of the body means that other bacteria like hepatitis A or dysentery could also be present.

The bottom line is that it is not a healthy idea to leave toothbrushes exposed in the bath room. Besides the fact that fecal matter can travel to exposed toothbrushes, exposed toothbrushes are more susceptible to multiple forms of bacteria, including dangerous ones. Toothbrushes should be covered and protected and the toilet lid should be closed before flushing. To better protect against the presence of bacteria and viruses, clean toothbrushes with an item like a UV device made for that purpose and/or spritz some colloidal silver on the toothbrushes prior to use. Another very good idea would be using a natural antiseptic toothpaste product such a one which contains tea tree oil.

Sources included:

http://www.suite101.com/content/do-poop-particles-get-on-toothbrushes-a266122
http://www.youtube.com/watch?v=TeAOC3A0xJ8
http://serendip.brynmawr.edu/exchange/node/1839
http://serendip.brynmawr.edu/biology/b103/f02/web2/stan.html#2

See also:

Make Your Own Safe, Natural and Healthy Tooth Pastes and Tooth Cleansers