Tap water is not sterile, and using it in home medical devices can result in serious and even deadly infections. But in a study published Wednesday in the journal Emerging Infectious Diseases, one-third of respondents to a survey incorrectly answered that tap water does not contain bacteria or other living organisms.
In the August 2021 survey, more than half of 1,004 survey participants incorrectly said that tap water can be used for nasal rinsing, 50% believed is appropriate for rinsing contact lenses and 42% trusted it is safe for use in respiratory devices such as humidifiers or CPAP – continuous positive airway pressure – machines, which are used to treat sleep apnea.
Shanna Miko, an author of the study and Epidemic Intelligence Service officer at the US Centers for Disease Control and Prevention, says these findings highlight misconceptions about the safe use of nonsterile tap water for medical devices at home.
“While tap water is generally safe to drink, it is not OK for other uses,” Miko said.
Although US tap water is treated to meet safe drinking standards, it may contain low levels of microorganisms.
These microbes are generally harmless when ingested during drinking and cooking because they are killed by stomach acid. However, when irrigating the nose or eyes, they may cause serious and even deadly infections.
“With the aging infrastructure, our aging pipes, there are some new waterborne challenges that have emerged, and those are basically these pathogens or these germs that can live in these protective areas that like to stick to pipes called biofilm pathogens,” Miko said.
Harmless to drink, risky in medical devices
Pathogens found in tap water systems – including Pseudomonas aeruginosa, nontuberculous mycobacteria, Legionella, Acanthamoeba and Naegleria fowleri – can invade the lungs, brain, eyes or skin.
Several cases of brain-eating amoeba have been reported from neti pots, devices used to flush nasal passages. There have also been multi-state outbreaks of Acanthamoeba from improper contact lens rinsing, which can cause blindness and other permanent eye damage.
“They might not be the most frequent things to be occurring each year,” Miko said, “but to the people that do acquire the infections, it has a significant impact.”
Most healthy people exposed to these microbes will not get sick. However, certain groups of people may be at a higher risk of serious infection. These include older people, infants younger than 6 months, and those with weakened immune systems or other chronic health issues such as cancer, HIV or lung disease.
“We want them to know that even though they’re at higher risk for infections of these waterborne associated pathogens, there are simple steps that they can take to reduce their risks,” Miko said.
How to stay safe
The CDC recommends individuals using at-home medical devices like CPAP machines, humidifiers and neti pots only use water free from microbes such as distilled or sterile water, which can be bought in stores. Boiled and cooled water may also be used.
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In addition to using distilled, sterile or previously boiled water, individuals can decrease their exposure to microbes by regularly cleaning and disinfecting at-home medical devices.
For populations at higher risk, Miko recommends flushing plumbing systems regularly and applying special filters on faucets or showers. She notes that most pitcher, refrigerator and sink water filters are not designed to remove germs from water.
“This data isn’t meant to scare anybody. We have one of the best public water drinking systems in the world,” Miko said.
She encourages people to follow guidance on safe water practices for at-home medical devices which can be found on the CDC website.
“If we can just do something as simple as boiling water or using sterile distilled water to reduce the risk, that’s something we’d like to share with people,” Miko said.