TUCSON – What’s dirtier: a public toilet seat, door handle or your empty washing machine?

Your washing machine, according to UA microbiologist Dr. Chuck Gerba, a research professor who also has been interviewed on CBS’s “The Early Show” about his ongoing study of germs. “People think we’re too clean, but we’re not,” Gerba said. “Clothes are a good example. Clothes have more germs than ever.”

Gerba, in a study published in the July 2007 edition of Applied and Environmental Microbiology, wanted to find out if certain viruses and bacteria could survive in a load of laundry after being washed in detergent with and without bleach. So he added several different types of bacteria, such as salmonella, and viruses, such as hepatitis A, to loads of laundry.“

(We found) viruses can live up to a month after being washed (in non-bleach detergent) and bacteria can live up to a few days,” Gerba said.

He said these germs could cause several kinds of illnesses, such as diarrhea, meningitis or a cold.

“Hepatitis A can cause infections, and if you are infected with that, it can kill you,” he added.

The amount of germs in household washing machines and public facility machines are “probably about the same, but it depends on how frequently someone is using hot water and bleach,” Gerba said.

The study also found that certain germs, such as the flu, couldn’t survive easily in washing machines.

“Certain ones, like influenza, are not an issue,” he said. “The flu is killed easily with detergent.”

However, Gerba said non-bleach detergents wouldn’t kill most germs because they “are only largely designed to remove dirt, not microorganisms.”

His study found that the most common germ the average household washing machine contains is E. coli bacteria.

“The average laundry load has about 100 million E. coli in the water when you do a load of undergarments,” he said. “The E. coli is from fecal matter.”

Undeclared sophomore Juliana Campbell, who shares an apartment off campus, called Gerba’s findings “kind of gross. It makes me want to go home and sanitize my machine. You figure it would be clean.”

While Campbell said she’s going to start using bleach more often, she’ll probably continue to wash her clothes with cold water because she doesn’t want to shrink them.

Gerba said the best way to prevent illness from washing machines is to first run a load of undergarments with bleach detergent and hot water to sanitize the machine before washing other clothing. He also said clothes should be put in the dryer for at least 45 minutes.

“Water should be at about 140 degrees (Fahrenheit) when hot and should reduce viruses by 99.99 percent if used with bleach,” he said. “The dryer will kill up to another 99 percent if it goes for 45 minutes.”

Clothes are now germier than ever because of the invention of cold-water detergent in the last 20 years, Gerba said.

“Hot water is really critical in killing those bacteria,” he said.

He said the reason toilet seats and bathroom door handles are cleaner than most washing machines is because people wipe off toilet seats and between 70 and 80 percent of the public wash their hands.

Gerba couldn’t say how many people get sick from washing machines because he said there is no way to track that information. 

UA anthropology freshman Orrin Frederick, who lives in Cochise Residence Hall, called Gerba’s findings “surprising. I actually did my laundry today. The more I think about it, it seems plausible.”

Frederick said that while he sometimes uses bleach and always uses the dryer, he usually doesn’t use hot water.

“I’ll probably use bleach more often,” he said. “Not all the time, but more than normal.”

Undeclared freshman Pavel Borisenko, who does his laundry at his girlfriend’s house, added, “I don’t like doing laundry anyway, though, so that’s a good excuse not to do it.”

The original version of this story appeared in the Arizona Daily Wildcat on Nov. 9, 2009.