Water bottles, the perfect incubator?
So what happens when we refill our water bottles with this water then? It's not good news. One particular study assessing the bacterial quality of the water has shown that over 60% of water bottles had a HPC result higher than 500 CFU/mL, and over 70% had a HPC result higher than 100 CFU/mL.7
The same study also assessed the coliform concentration of the same bottles and 23% of them contained more coliform concentration than the standard of microbiological quality established by the FDA which is 1 CFU/100mL. Some bottles contained coliform counts greater than 150 CFU/100mL!
Coliforms are a particularly hazardous bacteria that grow in water. Examples include Escherichia coli (E. coli) and Staphylococcus aureus (more commonly known as golden staph). Strains of E. coli can cause infection and induce symptoms like diarrhea, stomach cramps, vomiting, fever, and in extreme cases, pneumonia and UTIs. Staph bacteria has a similar range of symptoms when digested and is one of the most common causes of food poising.
A similar study assessed the bacterial quality in the personal water bottles of elementary school children and yielded very similar results. Over 65% of bottles in this study have levels of bacteria that exceed 500 CLU/mL with only just over 15% having less than 1 CFU/mL.8 Likewise ~15% of bottles had coliform bacteria that exceeded the FDA standard of 1 CFU/100mL with over 9% of bottles having greater than 1,000 CFU/100mL!
A separate experiment on the bottles of gym-goers found 90% of the bottles had bacterial contamination.9,10 26% tested positive for S. aureus and 16% for E. coli, the two most frequent species detected.
So where does this bacteria come from?
Some of it is in our water bottles. According to experts in water quality, we need to wash our water bottles every single day thoroughly, not just rinse, but wash with soap, hot water and a bottle brush to eliminate biofilm build-up and get at all the nooks and crannies where bacteria could be happily residing.11,12,13 According to the FDA Food Code14, water is considered a food. Reusable bottles are therefore food-contact surfaces and require proper cleaning and sanitising.7
And some of it is from bacteria that's already present from our water supplies, whether that's straight from tap municipal water or filtered water which often harbours more germs. We also know that bacteria can grow even in treated & chlorinated water at room temperature as previously explained. Now add to that bacteria and nutrients that's newly introduced from our backwash. Whether we like it or not, and no matter how careful we are, backwash always occurs. Backwash not only provides the bacteria for transmission but also nutrients that allow the microorganisms to fruitfully multiply. We are the ones adding fuel to the fire that's happening in our bottles.7
Water bottles also check all the boxes for bacterial growth: moisture, nutrients, darkness, room temperature, low salinity, neutral pH, and time. It's hard to argue why water bottles aren't the perfect incubator for germs.