Remember Mom's advice about washing your hands thoroughly after using the restroom?
A new study by Michigan State University researchers found that only 5 percent of people who used the bathroom washed their hands long enough to kill the germs that can cause infections.
What's more, 33 percent didn't use soap and 10 percent didn't wash their hands at all. Men were particularly bad at washing their hands correctly.
The study, based on observations of 3,749 people in public restrooms, appears in the Journal of Environmental Health.
"These findings were surprising to us because past research suggested that proper hand washing is occurring at a much higher rate," said Carl Borchgrevink, associate professor of hospitality business and lead investigator on the study.
Hand washing is the single most effective thing one can do to reduce the spread of infectious diseases, according to the Centers for Disease Control and Prevention. Failing to sufficiently wash one's hands contributes to nearly 50 percent of all foodborne illness outbreaks
It takes 15 to 20 seconds of vigorous hand washing with soap and water to effectively kill the germs, the CDC says, yet the study found that people are only washing their hands, on average, for about 6 seconds.
Borchgrevink and colleagues trained a dozen college students in data collection and had them observe hand washing in restrooms in bars, restaurants and other public establishments. The student researchers were as unobtrusive as possible - by standing off to the side and entering results on a smart phone, for example.
The study is one of the first to take into account factors such as duration of the hand washing and whether people used soap.
Specific findings include:
Fifteen percent of men didn't wash their hands at all, compared with 7 percent of women.
When they did wash their hands, only 50 percent of men used soap, compared with 78 percent of women.
People were less likely to wash their hands if the sink was dirty.
Hand washing was more prevalent earlier in the day. Borchgrevink said this suggests people who were out at night for a meal or drinks were in a relaxed mode and hand washing became less important.
People were more likely to wash their hands if a sign encouraging them to do so was present.
Borchgrevink, who worked as a chef and restaurant manager before becoming a researcher, said the findings have implications for both consumers and those who operate restaurants and hotels.
"Imagine you're a business owner and people come to your establishment and get foodborne illness through the fecal-oral route - because people didn't wash their hands - and then your reputation is on the line," he said. "You could lose your business."
Borchgrevink's co-authors were Jae Min Cha and Sung Hyun Kim. All three are faculty members in MSU's School of Hospitality Business.