Your bathroom showers are hazardous to health

That invigorating relief and good cleansing from daily bathroom showers may bring along a face full of potentially pathogenic bacteria, warn researchers at the University of Colorado at Boulder.

Using high-tech instruments and lab methods, the researchers analysed roughly 50 showerheads from nine cities in seven states that included New York City, Chicago and Denver.

CU-Boulder Distinguished Professor Norman Pace, lead study author, says that about 30 percent of the devices were found to harbour significant levels of Mycobacterium avium, a pathogen linked to pulmonary disease that most often infects people with compromised immune systems, but which can occasionally infect healthy people.

The study showed that some M. avium and related pathogens 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.

He pointed out that research at National Jewish Hospital in Denver indicated that increases in pulmonary infections in the US in recent decades from so-called "non-tuberculosis" mycobacteria species, such as M. avium, could be attributed to people taking more showers and fewer baths.

He said that water spurting from showerheads could distribute pathogen-filled droplets that suspend themselves in the air, and could easily be inhaled into the deepest parts of the lungs.

"There have been some precedents for concern regarding pathogens and showerheads. But until this study we did not know just how much concern," said Pace.

In Denver, according to the researcher, one showerhead with high loads of Mycobacterium gordonae was cleaned with a bleach solution in an attempt to eradicate it, but tests conducted several months later showed that the bleach treatment ironically caused a three-fold increase in the pathogen, indicating a general resistance of mycobacteria species to chlorine.

Ask Pace whether it is dangerous to take showers, and he says: "Probably not, if your immune system is not compromised in some way. But it's like anything else -- there is a risk associated with it."

He stresses that plastic showerheads appear to "load up" with more pathogen-enriched biofilms, and thus metal showerheads may be a good alternative.

"There are lessons to be learned here in terms of how we handle and monitor water. Water monitoring in this country is frankly archaic. The tools now exist to monitor it far more accurately and far less expensively that what is routinely being done today," said Pace.

A research article on his study has been published in the online edition of the Proceedings of the National Academy of Sciences.