Showerheads spew bacteria

In a story ripe for fright matching Alfred Hitchcock’s famous shower scene, researchers at the University of Colorado at Boulder have discovered that taking a shower can deliver a face full of potentially dangerous bacteria.

Researchers analyzed roughly 50 showerheads from nine cities in seven states that included New York City, Chicago and Denver. The result? Thirty percent of the devices harbored significant levels of Mycobacterium avium, a bacteria linked to pulmonary disease that most often infects people with compromised immune systems but which can occasionally infect healthy people, said Professor Norman Pace, who lead the study.

Bacteria levels more than 100 time municipal water

While it’s not surprising to find bacteria in municipal waters, researchers found that some bacteria were clumped together in slimy “biofilms” that clung to the inside of showerheads at more than 100 times the “background” levels of municipal water. “If you are getting a face full of water when you first turn your shower on, that means you are probably getting a particularly high load of Mycobacterium avium, which may not be too healthy,” Pace said.

During the early stages of the study, researchers tested showerheads from smaller towns and cities, many of which were using well water rather than municipal water. “We were starting to conclude that pathogen levels we detected in the showerheads were pretty boring,” said Boulder researcher Leah Feazel, first author on the study. “Once we started analyzing the big metropolitan data, it suddenly became a huge story to us.”

Researchers sampled showerheads in homes, apartment buildings and public places in New York, Illinois, Colorado, Tennessee and North Dakota.

Bleach not effective to clean showerheads

While chlorine bleach is almost universally thought of as a one-stop shop for killing harmful bacteria, using it to clean showerheads in the study had almost the opposite effect. In Denver, one showerhead was cleaned with a bleach solution in an attempt to eradicate it. Tests on the showerhead several months later showed the bleach treatment ironically caused a three-fold increase indicating a general resistance of this type of bacteria to chlorine.

So is it dangerous to take showers? “Probably not, if your immune system is not compromised in some way,” said Pace. “But it’s like anything else — there is a risk associated with it.”

So how do you reduce your risk of getting sick? See these showerhead cleaning tips provided by Laura K. Baumgartner, Ph.D., a researcher who worked the project. You can also listen to an audio interview with Baumgartner about the showerhead bacteria study.