The next time students step into the shower, they may have some uninvited guests.

Research led by a professor at the University of Colorado-Boulder showed that trillions of microorganisms could be living on a single shower curtain.

UC-Boulder biology professor Norman Pace spoke about microbes that thrive on swimming pools and shower curtains at the American Association for the Advancement of Science conference Feb. 14.

Pace and three of his former graduate students, Ulrike Theison, Allison St. Amand and Largus Angenent, as well as Scott Kelly, a researcher at San Diego State University, conducted a study on five shower curtains to identify the types and quantities of microbes that could be found on it. The first curtain analyzed was Pace’s own.

“Most microbial life is stuck to a surface someplace,” Pace said, calling these places “bio-films.”

His team estimated about 1 billion microbes, referred to as “soap scum,” reside in every square inch of a shower curtain.

“We found no identical organisms, but there were similar kinds,” Pace said. He called many of the organisms “adventitious pathogens.”

Two commonly found bacteria were Sphingomonas and Methylobacterium.

In most cases, he said, these types of pathogens would only pose a threat to those with already suppressed immune systems, such as people with AIDS or those undergoing chemotherapy for cancer.

“People need to be aware of public cleanliness,” Pace said.

UW professor of medicine Jeffery Glassroth agreed, saying, “We need to keep things clean and be careful, but we shouldn’t go crazy.”

Despite his findings, Pace said he continues to take showers but makes sure to pay more attention to their cleanliness.

“I do [still] take showers,” Pace said. “But since I did the study, I clean the shower curtain every few weeks.”

The second study Pace and his team conducted was at a Midwest indoor swimming pool and hot tub. Many of the microbes were found just above the surface of the water. This is especially the case in hot tubs or pools that are only filtered and treated with UV radiation, such as many therapeutic pools.

A disease he referred to as “Lifeguard Lung” can occur in pool workers who are in contact with these pathogens. This disease can affect their lungs and breathing patterns. Pace said these findings were quite scary.

“I would not get into a public hot tub,” Pace said. “They are breeding grounds for microbial problems.

Glassroth also said warm-water areas such as heated pools are common breeding grounds for bacteria.

“This isn’t as though pools are unique,” Glassroth said, adding that lakes have certain amounts of bacteria as well. “I think in general, advice is that pools (and hot tubs) should be maintained.”

In order to prevent these problems, Pace suggests increased attention to pool and hot-tub maintenance.

He also feels humans need to perform risk assessments because not all microbes will cause a threat. He said public cleanliness is very important in combating microbes that can cause potential illness or harm.

“We live in a world where we are constantly exposed to things, sometimes in places we don’t expect them,” Glassroth said. “We live and cohabitate our planet with microbes of all kinds. We have to understand them and be prudent and thoughtful in the way we understand them.”