IStockPhoto 2024539 © Christian Point

Most of the women who attend games at Turner Field in Atlanta wash their hands after using the restroom. Just 1 in 20 neglect to lather and rinse. Male baseball fans, by contrast, are about nine times less hygienic. The odds a man was observed not washing his hands after using the facilities are 1 in 2.32, or 43%. It is equally likely (1 in 2.33) that an adult living in Dane County, Wisconsin, admits to public nose-picking.

The observations from Turner Field are extreme, but they are in line with national trends. In 2007, the American Society for Microbiology and The Soap and Detergent Association monitored behavior in six public bathrooms in four major cities: Atlanta, Chicago, New York, and San Francisco. Only one location, the Shedd Aquarium in Chicago, showed comparable rates of washing between men and women. Researchers found that, nationwide, an overwhelming majority of women (1 in 1.14) (88%) diligently wash their hands, and that a great number of men (1 in 2.99) do not. Both sexes claim to be cleaner than they are. Almost 92% of adults (1 in 1.09) report routinely washing their hands in public restrooms.

It is not clear why men are so much less likely to wash—apathy, laziness, a flawed understanding of germ theory. Yet just as mysterious is why women are no more sanitary than men. A recent study (PDF) from the University of Colorado found that men and women carry similar numbers of microbes on their hands. The study identified 4,742 distinct species of bacteria on 102 palms. The average person’s hand was colonized by over 150 different types of organisms.

Most resident germs are not harmful. Given the right circumstances, however, their growth sometimes becomes problematic. Bacteria living on the hand can cause acne, conjunctivitis, pneumonia, staph infection, strep throat, gonorrhea, meningitis, and in extreme cases, flesh-eating disease, toxic shock syndrome, or brain abscesses. More common than most of these, and more worthy of concern, is influenza. Though it does not live on the hands as many bacteria do, the flu is spread primarily through hand contact. Situated on a hard, moist surface (such as the doorknob of a public restroom), the virus can remain infectious for up to 72 hours.

Click here for an interview with the research director (Harris Interactive) of this study.