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September 15, 2009

BehindTheMedspeak: Is your shower killing you?


Long story short: showerheads are ideal places for bacterial biofilms to thrive, and may be covering you in a daily dose of bacteria that could make you sick.

Amazing that something so routine and accepted like a morning shower may have an effect precisely opposite that intended.

Here's Amy Norton's Reuters article.


Your shower may be blasting you with germs

Your shower may not be getting you as clean as you think with a U.S. study finding many showerheads are dirty and may be covering you in a daily dose of bacteria that could make you sick.

An analysis of 50 showerheads from nine U.S. cities found that about 30 percent harbored high levels of Mycobacterium avium — a group of bacteria that can cause lung infections when inhaled or swallowed. Researchers from the University of Colorado at Boulder found the levels of Mycobacterium avium were 100 times higher than those found in typical household 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," said researcher Norman Pace in a statement.

Mycobacterium avium is linked to pulmonary disease, causing symptoms such as a persistent drug cough, breathlessness and fatigue, and most often infects people with compromised immune system but can occasionally infect healthy people.

Pace said research at the National Jewish Hospital in Denver found that increases in pulmonary infections in the United States in recent decades from so-called "non-tuberculosis" mycobacteria species like Mycobacterium avium may be linked to people taking more showers and fewer baths.

He said water spurting from showerheads can distribute pathogenfilled droplets that suspend themselves in the air and can easily be inhaled into the deepest parts of the lungs.

The problem with showerheads is that the insides provide a moist, warm, dark haven where bacteria can form sticky "biofilms" that allow them to gain a foothold and eventually set up residence in the device.

The researchers, however, said it was still probably safe for most people to get into the shower and recommended people with compromised immune systems due to HIV or immune-suppressing drugs, use metal showerheads and change them regularly.

"This really shouldn't concern average, healthy people. The main concern is for people who are immune-compromised," researcher Leah Feazel told Reuters Health. The findings, published in Proceedings of the National Academy of Sciences on Monday, are based on tests of about 50 showerheads taken from nine U.S. cities, including New York, Denver and Chicago.

The researchers said showerheads are not the only potential bacterial dispersants in the home, however. Feazel said more research is needed to measure bacteria levels in household devices like humidifiers and evaporative coolers.


Here's the abstract of the paper whose findings are referred to above:


Opportunistic pathogens enriched in showerhead biofilms

The environments we humans encounter daily are sources of exposure to diverse microbial communities, some of potential concern to human health. In this study, we used culture-independent technology to investigate the microbial composition of biofilms inside showerheads as ecological assemblages in the human indoor environment. Showers are an important interface for human interaction with microbes through inhalation of aerosols, and showerhead waters have been implicated in disease. Although opportunistic pathogens commonly are cultured from shower facilities, there is little knowledge of either their prevalence or the nature of other microorganisms that may be delivered during shower usage. To determine the composition of showerhead biofilms and waters, we analyzed rRNA gene sequences from 45 showerhead sites around the United States. We find that variable and complex, but specific, microbial assemblages occur inside showerheads. Particularly striking was the finding that sequences representative of non-tuberculous mycobacteria (NTM) and other opportunistic human pathogens are enriched to high levels in many showerhead biofilms, >100-fold above background water contents. We conclude that showerheads may present a significant potential exposure to aerosolized microbes, including documented opportunistic pathogens. The health risk associated with showerhead microbiota needs investigation in persons with compromised immune or pulmonary systems.


FunFacts gleaned from related stories in today's New York TimesUSA Today and Wall Street Journal:

• Running the water for 30 seconds before stepping in is a good idea

• Metal showerheads are preferable to plastic because microbes cannot cling to them as easily

• Mycobacterium avium and its close cousins can cause a variety of exotic chest complaints including lifeguard lunghot tub lung and Lady Windermere's syndrome

Got you there, didn't I?

Come on — where else are you gonna find stuff like that?

September 15, 2009 at 04:01 PM | Permalink


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I've said for years that perhaps the most pleasant way to poison yourself is to take a nice long hot shower.

Posted by: Nick B | Sep 16, 2009 11:03:54 AM

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