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Showerheads may spray germs at you

Sept. 14, 2009
Courtesy UC Boulder
and World Science staff

While bath­room show­ers can pro­vide an in­vig­or­ating cleans­ing, they al­so can de­liv­er a face full of po­ten­tially harm­ful bac­te­ria, ac­cord­ing to a sur­pris­ing new Un­ivers­ity of Col­o­rad­o at Boul­der stu­dy. 

The re­search­ers an­a­lyzed about 50 show­er­heads from nine cit­ies in sev­en U.S. states that in­clud­ed New York City, Chi­ca­go and Den­ver. 

A study has found that show­er­ing can give you face full of po­ten­tially harm­ful bac­te­ria. (Im­age: Glenn Asa­ka­wa, U. Co­lo­r­ado)


They found that about 30 per­cent of the de­vices har­bored sig­nif­i­cant lev­els of My­co­bac­te­r­ium avium, a germ linked to lung dis­ease that most of­ten in­fects peo­ple with weak­ened im­mune sys­tems but oc­ca­sion­ally al­so the healthy, said Nor­man Pa­ce, the stu­dy’s lead au­thor. 

The find­ings ap­peared in the Sept. 14 on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tional Acad­e­my of Sci­ences.

“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,” said Pa­ce. 

It’s not sur­pris­ing to find path­o­gens in mu­nic­i­pal wa­ters, he added. But the sci­en­tists found 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 nor­mal lev­els in mu­nic­i­pal wa­ter. 

Re­search at Na­tional Jew­ish Hos­pi­tal in Den­ver in­di­cates that in­creases in lung in­fec­tions in the Un­ited States in re­cent dec­ades from so-called “non-tuberculosis” my­co­bac­te­ria spe­cies like M. avi­um may be linked to peo­ple tak­ing more show­ers and few­er baths, said Pa­ce. Wa­ter spurt­ing from show­er­heads can dis­trib­ute path­o­gen-filled droplets that float in the air and can easily be in­haled in­to the deep­est parts of the lungs, he added.

Symp­toms of lung dis­ease caused by M. avi­um can in­clude tired­ness, a per­sist­ent, dry cough, short­ness of breath, weak­ness and “gen­erally feel­ing bad,” said Pa­ce. Immune-compromised peo­ple like preg­nant wom­en, the eld­erly and those who are fight­ing off oth­er dis­eases are more vul­ner­able, said Pa­ce, a pro­fes­sor in the mo­lec­u­lar, cel­lu­lar and de­vel­op­men­tal bi­ol­o­gy de­part­ment at the un­ivers­ity.

The researchers bleach-cleaned one show­erhead from Den­ver in at­tempt to kill its pro­fu­sion of the My­co­bac­te­ri­um gor­donae bac­teria, said Pa­ce. Tests on the show­erhead sev­er­al months lat­er showed the bleach treat­ment iron­ic­ally caused a three-fold in­crease in the germ, in­di­cat­ing a gen­er­al re­sist­ance of myco­bac­te­ria spe­cies to chlo­rine, he noted. 

So is it dan­ger­ous to take show­ers? “Probably not, if your im­mune sys­tem is not com­pro­mised,” said Pa­ce. “But it’s like an­y­thing else—there is a risk.” Pace said since plas­tic show­er­heads ap­pear to “load up” with more path­o­gen-enriched bio­films, met­al show­er­heads may be bet­ter. 

“There are lessons to be learn­ed here in terms of how we han­dle and mon­i­tor wa­ter,” said Pa­ce. “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.”


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While bathroom showers provide an invigorating cleansing, they also can deliver a face full of potentially harmful bacteria, according to a surprising new University of Colorado at Boulder study. The researchers analyzed about 50 showerheads from nine cities in seven U.S. states that included New York City, Chicago and Denver. They found that about 30 percent of the devices harbored significant levels of Mycobacterium avium, a bacterium linked to pulmonary disease that most often infects people with weakened immune systems but occasionally also healthy people, said Norman Pace, the study’s lead author. The study appeared in the Sept. 14 online edition of the research journal Proceedings of the National Academy of Sciences. “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,” said Pace. It’s not surprising to find pathogens in municipal waters, he added. But the scientists found 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. Research at National Jewish Hospital in Denver indicates that increases in lung infections in the United States in recent decades from so-called “non-tuberculosis” mycobacteria species like M. avium may be linked to people taking more showers and fewer baths, said Pace. Water spurting from showerheads can distribute pathogen-filled droplets that float in the air and can easily be inhaled into the deepest parts of the lungs, he added. Symptoms of pulmonary disease caused by M. avium can include tiredness, a persistent, dry cough, shortness of breath, weakness and “generally feeling bad,” said Pace. Immune-compromised people like pregnant women, the elderly and those who are fighting off other diseases are more prone to experience such symptoms, said Pace, a professor in the molecular, cellular and developmental biology department at the university. In addition to showerhead swabbing, Feazel took several individual showerheads, broke them into tiny pieces, coated them with gold, used a fluorescent dye to stain the surfaces and used a scanning electron microscope to look at the surfaces in detail. “Once we started analyzing the big metropolitan data, it suddenly became a huge story to us,” said Feazel, who began working in Pace’s lab as an undergraduate. In Denver, one showerhead with high loads of the pathogen Mycobacterium gordonae was cleaned with a bleach solution in an attempt to kill it, said Pace. Tests on the showerhead several months later showed the bleach treatment ironically caused a three-fold increase in M. gordonae, indicating a general resistance of mycobacteria species to chlorine. So is it dangerous to take showers? “Probably not, if your immune system is not compromised,” said Pace. “But it’s like anything else—there is a risk.” Pace said since plastic showerheads appear to “load up” with more pathogen-enriched biofilms, metal showerheads may be better. “There are lessons to be learned here in terms of how we handle and monitor water,” said Pace. “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.”