Office workers -- especially men -- are marinating in their own bacteria, a new study shows.

In research funded in part by Clorox Corp. and appearing Wednesday in the journal PLoS ONE, scientists from San Diego State University and the University of Arizona took bacterial samples from 30 offices in New York, San Francisco, and Tucson, Ariz. They swabbed five surfaces in each office: chairs, phones, computer mice, computer keyboards, and desk surfaces.

Part of the sample was used to estimate the abundance -- how many total cells were present -- and part was genetically sequenced to determine how many kinds of bacteria were present.

The good news was that most of the bacteria the scientists found were natives to the human body, which harbors 10 times as many bacterial cells as human cells. Most of these bacteria are harmless, and some may even be helpful.

Since you're the one bringing them in, you probably don't have to worry, senior author and SDSU biologist, Scott Kelley, said in a telephone interview.

Interestingly, offices occupied by men seemed to have 10 to 20 percent more bacteria, on average, than offices occupied by women. There wasn't a significant difference between the sexes in terms of the diversity of bacteria, the team found.

It's not clear what the reason for the gender difference is, but Kelley and his colleagues think men might just not be washing their hands as often as women. They pointed to a 2008 paper from a University of Colorado team published in the Proceedings of the National Academy of Sciences that examined the difference in bacterial communities on the hands of men and women.

The authors of the PNAS paper said that women reported having washed their hands more recently than men, but also found there are still significant differences between the sexes once one accounts for different hand-washing routines.

Kelley and his colleagues also think body size might also factor in to the difference in bacterial abundance.

Since men are, on average, larger than women, they have a correspondingly greater skin surface area, as well as [larger] nasal and oral cavities and, therefore, a proportionally greater surface area for bacterial colonization, they wrote.

The bacterial communities in San Francisco and New York were more similar to each other than to Tucson, which seemed to have a higher proportion of bacteria originating from soil instead of the human body.

Of the five surfaces measured, the phone tended to have the most bacteria on it -- which makes sense, given that in addition to touching it with bacteria-covered hands, workers will be holding it close to their bacteria-spewing mouths all day. Interestingly, the second-most bacteria-rich surface was the office chair.

Kelley says this study is an attempt to establish a baseline for looking at bacteria in office environments, not a ploy to get office drones to obsessively start wiping down their telephones. He'd like to conduct future research looking at how the bacterial communities differ in buildings where workers tend to get sick, and how certain factors like communal spaces and air conditioning systems play a part in distributing bacteria.

I don't want people to be scared of their own office! Kelley joked.

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