Showerhead 'Slime' Linked to Lung Disease, Study Reveals

A lung disease has been linked to the most common group of germs which populate the average household showerhead. The biofilm on metal showerheads was more likely to contain mycobacteria than those on plastic units, according to the authors of a study published in MBio.

Breathing in aerosols of a specific type of mycobacteria can cause nontuberculous mycobacterial (NTM). Most people do not fall ill if they inhale mycobacteria. However, if the organisms attack the lungs, it can trigger inflammation. Left untreated, a chronic lung infection can occur, bringing coughing, shortness of breath, weight loss and tiredness. Treatment can involve taking antibiotics for at least 12 months.

In the U.S., more than 80,000 people have NTM​, most of whom are older adults, according to the American Lung Association.

Read more: What do probiotics do? Gut health could be harmed by 'good' bacteria

The authors warned that NTM infections were "increasingly recognized as a threat to public health" as they can be difficult to treat, and that rates were on the rise in the U.S. and other developed countries.

The "hot spots" of mycobacteria were found where NTM was most common, the authors found. Past research showed the disease is most prevalent in Hawaii, southern California, Florida and New York City.

Dr. Noah Fierer, study author and Cooperative Institute for Research in Environmental Sciences (CIRES) fellow and professor of ecology and evolutionary biology at the University of Colorado at Boulder, said in a statement: "There is a fascinating microbial world thriving in your showerhead, and you can be exposed every time you shower.

"Most of those microbes are harmless, but a few are not, and this kind of research is helping us understand how our own actions—from the kinds of water treatment systems we use to the materials in our plumbing—can change the makeup of those microbial communities," he said.

To conduct the study, scientists at the University of Colorado at Boulder and CIRES analyzed swabs taken from 656 household showers across the U.S., as well as 13 countries in Europe.

The team sequenced the DNA of the biofilm and pinpointed which and how many forms of bacteria lived in showerheads.

Mycobacteria was most commonly found in the United States. That's probably because chlorine-based disinfectants—which mycobacteria are more resistant to than other bacteria—are more widely used there than in Europe, the authors believed. Bathrooms which received water from the municipal system rather than a well were more prone to the germs.

Plastic heads contain chemicals that enable a wider range of bacteria to grow compared to metal heads, which means mycobacteria may not be able to dominate the ecosystem, the authors surmised. That might explain why more mycobacteria is found on metal showerheads, the authors said.

Matt Gebert, lead author of the study and researcher at CIRES, said in a statement: "It's important to understand routes of mycobacterial exposure, especially in the household. We can learn a lot from studying the biofilm that accumulates inside your showerhead, and the associate water chemistry."

The research was the latest to investigate the microscopic germs that populate the surfaces around us. A recent study published in the journal BMC Infectious Diseases revealed the plastic bins used during security checks were the dirtiest places in an airport.