If you think it’s your keyboard that carries the most bacteria, think again!

Offices in the U.S. are brimming with more than 500 species of bacteria, a new study finds – and New York men’s offices are the worst according to a new study.

Research from University of California, San Diego found that not only were the men’s offices dirtier than women’s office, they found that their chairs and phones had the highest amounts of bacteria.

The study, led by Dr Scott Kelley from San Diego State University, and published in the journal PLoS One, examined 90 offices in New York, San Francisco and Tucson, Arizona found that office chairs and phones carried the most bacteria. Kelley and his team swabbed surfaces in the offices and analyzed the bacterial DNA.

San Francisco office had lower concentrations of bacteria than New York which had the most bacteria.

“Humans are spending an increasing amount of time indoors, yet we know little about the diversity of bacteria and viruses where we live, work and play,” said Dr. Scott Kelley in a statement. “This study provides detailed baseline information about the rich bacterial communities in typical office settings and insight into sources of these organisms.”

The study found significant differences in viable bacterial abundance between offices inhabited by men or women, among various surface types, and among cities. The most abundant bacteria tended to be common inhabitants of human skin, nasal, oral or intestinal cavities. Other types of bacteria were from environmental origins such as soils.

According to the findings, men are known to wash their hands and brush their teeth less frequently than women, and are on average larger than women, as well, they have a correspondingly greater skin surface area for bacterial colonization. Thus, in addition to being less hygienic, it is possible that men may shed more bacteria into their surrounding environment.

Humans were clearly the primary source of office bacterial contamination, according to the report, given that the study was similar to studies of airplane bacterial contamination, given that airplanes are not exposed to the outside, except for short periods of time.