Showering may be bad for your health, say US scientists, who have shown that
dirty shower heads can deliver a face full of harmful bacteria.
Tests revealed nearly a third of devices harbour significant levels of a bug
that causes lung disease.
Levels of Mycobacterium avium were 100 times higher than those found in typical
household water supplies.
M. avium forms a biofilm that clings to the inside of the shower head, reports
the National Academy of Science.
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
Researcher Professor Norman Pace
In the Proceedings journal, the study authors say their findings might explain
why there have been more cases of these lung infections in recent years, linked
with people tending to take more showers and fewer baths.
Water spurting from shower heads can distribute bacteria-filled droplets that
suspend themselves in the air and can easily be inhaled into the deepest parts
of the lungs, say the scientists from the University of Colorado at Boulder.
Potential threat
Lead researcher Professor Norman Pace, said: "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."
While it is rarely a problem for most healthy people, those with weakened
immune systems, like the elderly, pregnant women or those who are fighting off
other diseases, can be susceptible to infection.
They may develop lung infection with M. avium and experience symptoms including
tiredness, a persistent, dry cough, shortness of breath and weakness, and
generally feel unwell.
When the researchers swabbed and tested 50 shower heads from nine cities in
seven different states in the US, including New York City and Denver, they
found 30% of the devices posed a potential risk.
Since plastic shower heads appear to "load up" with more bacteria-rich
biofilms, metal shower heads may be a good alternative, said Professor Pace.
Showers have also been identified as a route for spreading other infectious
diseases, including a type of pneumonia called Legionnaires' disease and chest
infections with a bacterium called Pseudomonas aeruginosa.
Hot tubs and spa pools carry a similar infection risk, according to the Health
Protection Agency.
A HPA spokesperson said: "This is an interesting paper which provides further
information about the occurrence of opportunist organisms - germs which do not
usually cause infections in humans - in the environment.
"These bacteria, which belong to the same family as TB, can be found in the
environment and occasionally in water supplies but rarely cause disease in
healthy people.
"Further work will need to look at whether finding these organisms is
associated with any increased risk of infection."