Dr Leah Feazel and colleagues from the University of Colorado analysed the genetic make-up of the microbes inside showerheads from 45 sites in the US. They discovered that levels of some bacteria were 100 times higher than normal background levels, including non-tuberculous mycobacteria. There were particularly high levels of Mycobacterium avium, the researchers found.
What is the risk?
Dr Feazel and colleagues said that showerheads may cause 'significant' exposure to microbes, including those known to cause disease.
'The detection of significant loads of Mycobacterium avium in many showerhead biofilms identifies a potential personal health concern,' they said.
Mycobacterium avium and other non-tuberculous mycobacteria have been shown to cause pulmonary disease in healthy people, as well as those predisposed to pulmonary infection, the researchers point out.
They suggest that consideration be given to contraindicating showering for people with compromised immune or pulmonary systems.
The researchers suggested that other home devices, such as humidifiers and evaporative cooling units, are likely to disperse bacteria. 'Little is known about the microbiology of such settings,' they said.
'There is need for further epidemiological investigations of potential sources of non-tuberculous mycobacteria infections, including showerheads.'
Do the findings warrant concern?
The Health Protection Agency said that the paper provides further information about the occurrence of opportunist organisms in the environment.
However, a spokeswoman pointed out that the organisms identified in the study were not often associated with pathogenic infections.
'These bacteria, which belong to the same family as tuber- culosis, can be found in the environment and occasionally in water supplies but rarely cause disease in healthy people,' she said.
She added that further work would be needed to see whether increased levels of these bacteria are actually associated with an increased risk of infection.
- Showerheads have levels of some bacteria 100 times background levels.
- Some of these bacteria are known to cause disease in healthy people.
- Research has yet to show that raised bacteria levels from showers increase infections.