Your daily shower may be getting you clean and making you sick at the same time.
A new study by University of Colorado researchers found that some showerheads may be shooting out a blast of pathogens that can trigger respiratory infections.
Scientists tested about 50 showerheads in nine cities in seven states, including Denver, New York and Chicago.
They found that 30 percent had high levels of Mycobacterium avium, a type of pathogen linked to pulmonary disease, which usually affects people with weaker immune systems.
Sometimes the pathogen infects healthy people but not frequently enough to spur an outbreak of showerphobia.
“For the average person, it’s not a huge concern,” said researcher Laura Baumgartner. “I take showers every day, and I’m not at all worried.”
This study is part of a larger project, funded by the Alfred P. Sloan Foundation, that examines the microbiology of the human environment — a detailed look at the air and water in schools, homes and public buildings.
New technology is providing a look into the world of microbes in these communities, one that’s been mostly invisible until recently.
In the past, studies depended on cell cultures, which identified only about 1 percent of the organisms in an environment.
But this study, which started as a project for a senior-level research class in molecular methods at CU, used DNA to identify organisms.
Norman Pace, a CU professor and the study’s lead author, developed a technology that uses molecular genetics to isolate DNA.
The students’ results were intriguing enough to merit a deeper investigation.
Scientists removed the showerhead from the pipe, swabbed the inside, and extracted DNA from that swab.
“We found a fairly high number (of M. avium),” said Baumgartner. “It was surprising how consistent it was.”
The risk of illness is lower for people who prefer baths to showers. That’s because showers act like aerosol sprays, and the pathogen-filled droplets are easily inhaled into the deepest part of the lungs.
Symptoms of M. avium infection are similar to those of tuberculosis: a chronic shallow cough, fever, fatigue and weight loss.
M. avium infections are on the rise, experts say. The reason, they hypothesize, is that more people are taking showers instead of soaking in the tub.
The disease cannot be transmitted from person to person, and healthy people can be exposed to these pathogens without developing symptoms.
But people with immune concerns — such as those who are pregnant, or who suffer from AIDS, substance abuse or cystic fibrosis — should change showerheads regularly.
Also, because microbes attach more easily to plastic showerheads, they should invest in all-metal showerheads, some of which have filters that can be changed weekly.
For most people, the answer is simple.
“Don’t stand in the shower when the first blast comes out,” Baumgartner said. “But most people don’t do that anyway, because that first blast is cold.”
Colleen O’Connor: 303-954-1083 or coconnor@denverpost.com
