According to a recent study by researchers from the University of Colorado at Boulder, dirty showerheads in homes may well be a potential breeding ground for infectious bacteria - Mycobacterium avium, which can cause lung infections when inhaled or swallowed.

The study, funded by the National Institute of Occupational Safety and Health and the Alfred P. Sloan Foundation, is part of a larger effort that is analyzing the microbiology of the indoor environment and its role in spreading to illness within the house.

The researchers sampled the glop obtained from 50 showerheads in nine US cities - including New York City, and eight cities in Colorado, North Dakota, Tennessee, and Illinois -, and examined the ribosomal RNA gene sequences to find out more about the micro-organisms breeding in the samples.

Finding high levels of Mycobacterium avium in 30 percent of the showerhead glop samples, the researchers noted that these were 100 times more than the levels commonly found in typical household water.

Commenting on the findings, study's senior author Norman R. Pace, a distinguished professor of molecular, cellular and developmental biology, said: "We don't know a whole lot about Mycobacterium avium prevalence. It's hard to detect and largely ignored."

However, according to the Infectious Diseases Society of America, infections caused by Mycobacterium avium impede cellular immunity in patients of AIDS and chronic lung disease like emphysema.