BOULDER, CO — Researchers at the University of Colorado at Boulder have found that showerheads potentially deliver an unhealthy level of pathogenic bacteria when a shower is first turned on, according to September 14 University of Colorado news release.
The researchers used high-tech instruments and lab methods to analyze roughly 50 showerheads from nine cities in seven states that included New York City, Chicago and Denver. They concluded about 30 percent of the devices harbored 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, said CU-Boulder Distinguished Professor Norman Pace, lead study author.
Pace said it is not surprising to find pathogens in municipal waters. However, the CU-Boulder researchers 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.
“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 is quoted saying.
The study appeared in the September 14 online edition of the Proceedings of the National Academy of Sciences. The study is part of a larger effort by Pace and his colleagues to assess the microbiology of indoor environments and was supported by the Alfred P. Sloan Foundation.
During the early stages of the study, the CU team 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,” according to Leah Feazel, first author on the study. “Then we worked up the New York data and saw a lot of M. avium. It completely reinvigorated the study.”
New York City draws its water from surface water reservoirs in the Catskill Mountains, north of the city.
In addition to using a showerhead swabbing technique, 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.
In Denver, one showerhead in the study with high loads of the pathogen Mycobacterium gordonae was cleaned with a bleach solution in an attempt to eradicate 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.
Pace said since plastic showerheads appear to “load up” with more pathogen-enriched biofilms, metal showerheads may be a good alternative.
“There are lessons to be learned here in terms of how we handle and monitor water,” said Pace, a recipient of the National Academy of Sciences highest award in microbiology called the Selman Waxman Award. “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.”