Your trusty reusable water bottle could be teeming with deadly bacteria, even if you wash it every day, researchers have warned.
As mountains of research have linked plastic water bottles to everything from high blood pressure to developmental delays and infertility, more Americans are opting for reusable ones to lower their exposure to toxic forever chemicals.
In fact, as many as 155million Americans, or 60 percent, say they own at least one reusable bottle.
And the market for reusable water bottles in the US alone has reached about $2billion as of last year.
However, a resurfaced study from Purdue University found the inside of reusable bottles are prime ‘breeding grounds’ for colonies of bacteria.
The researchers swabbed the inside and outside of 90 bottles owned and used regularly by college students.
They found roughly seven in 10 bottles had levels of bacteria above safe drinking water limits, and 60 percent exceeded the maximum safety threshold.
And about one in five sampled bottles had traces of coliform bacteria, or fecal matter. One of the most common forms of coliform bacteria is E. coli, which sickens 265,000 Americans every year and leads to bloody diarrhea, vomiting and muscle aches.
A resurfaced study from Purdue University found reusable water bottles could harbor harmful fecal bacteria (stock image)
Dr Yuriko Fukuta, now an associate professor at Baylor College of Medicine in Texas, told Earth.com: ‘We’re constantly touching our water bottles with our mouths and hands, so it’s easy to transmit bacteria to them, and then it just grows.
‘In some cases this can make you sick, especially if you have a weaker immune system.’
The study was published in the journal Food Protection Trends in 2017 but recently resurfaced online.
The researchers collected 90 water bottles from Purdue University students and asked them how long they had the bottles, how often they used them and how regularly they cleaned them.
About 85 percent of bottles were made from reusable plastic, while 11 percent were metal and the remainder were glass.
One in 10 bottles also had a built-in carbon filter, which is meant to remove contaminants.
Researchers swabbed the outer surfaces of the bottles with an ATP test, which lights up when it detects organic residue.
Bottles were considered ‘clean’ if they had residue levels at or below 10 relative light units (RLUs). RLUs between 11 and 20 were ‘inadequately cleaned’ and above 30 indicated a ‘dirty’ bottle.
They then rinsed the insides with water and counted the amount of bacteria that clung to surfaces that came into contact with water.
The team found the outside of all water bottles tested were considered ‘dirty,’ including two that were purchased from a local retailer as controls that had not been used.
Bottles refilled more often were more frequently were also associated with higher RTU levels, which the researchers said could be because each refill adds touchpoints like hands, the cap, the edge of counters and faucet areas.
The researchers found about 20 percent of tested water bottles had coliform bacteria, or fecal matter. The most common type is E. coli (pictured in the above stock image)
The safe limit of bacterial colonies is at or below 100 to 500 colony forming units (CFU) per milliliter, according to the CDC.
About seven in 10 bottles tested exceeded 100 CFU/ml, two in three topped 200 CFU/ml and three in five exceeded 500 CFU/ml.
Additionally, about 20 percent of bottles had detectable levels of coliform, or fecal, bacteria. It’s unclear exactly which types of coliform they found, but E. coli is the most common type, living almost exclusively in the intestines of humans and animals.
While E. coli is most often harmless, in some cases it can trigger bloody diarrhea, vomiting, nausea and muscle aches. In severe but rare cases, it can spiral into a life-threatening kidney infection called hemolytic-uremic syndrome (HUS).
The researchers also suggested bacteria in water bottles could include staphylococcus (staph), which live on the skin and are generally harmless. But if the bacteria enters the body through an opening like a wound, it can lead to a staph infection.
Left untreated, staph infections can poison the blood and travel to vital organs, leading to death.
The researchers said frequently cleaning reusable water bottles is key for eliminating harmful bacteria. They recommended using hot water and dish soap and scrubbing the walls of the bottle with a brush.
All parts should also dry completely, as drying prevents bacteria from clinging on to moisture.