Bacteria Growth in Water Bottles

Plastic water bottles can harbor many different kinds of bacteria. Although reused bottles are at the highest risk, even bottles that are unopened can harbor potentially harmful bacteria. Knowledge, prevention and instruction are the best ways to limit bacteria in water bottles and eliminate this health risk.

Water Origins

• Most bottled water originates from local tap water sources that run the water through additional filters to purify it. Since many brands of bottled water import from out of state, the water quality of the state where the water was bottled may be less than that of your state.

Bacteria Potential

• Although there is a small chance that unsafe levels of bacteria are present in freshly bottles water, there is a higher potential for bacteria in a reused plastic bottle. A 1999 study by the Natural Resources Defense Council showed that about one third of the brands of water studied contained unsafe levels of chemicals or bacteria when freshly bottled. These findings were confirmed by Canadian research company C-crest Laboratories in 2010. Seventy percent of the bottles studied by C-crest contained bacteria above U.S. recommended levels (less than 500 colony-forming bacteria per milliliter of water)--some had 100 times the recommended levels, though the type of bacteria found in the study may not have been harmful.

  A study conducted by the University of Calgary in 2003 investigated disposable plastic bottles that were reused for water consumption by children. On these reused bottles, researchers found coliform bacteria (bacteria found in fecal matter) present in 9 percent of the bottles, while high levels of heterotrophic bacteria (bacteria that eats organic matter) were founding 13 percent of the bottles.

Reusing Bottles

• Any bottle has the potential for collecting bacteria. No matter the measures taken, bacteria will find its way into almost any container. The best bottles for reuse are bottles made from thicker plastics, glass and metal. According to a 2003 article by Suzanne Driessen, Regional Extension Educator of Food Science at the University of Minnesota, these types of bottles offer a wider neck, which makes for easier cleaning. One-use plastic bottles should not be reused.

Prevention and Solution

• It is possible to prevent much of the harmful bacteria that collects in reusable bottles. Other than discarding disposable bottles made of thin plastic, daily washing of reusable bottles is also a necessity. Hot, soapy water scrubbed inside the bottle with a bottle brush is the most effective cleaning method. The narrow opening of some reusable bottles makes them difficult to clean in the dishwasher.

Warning

• Much of the bacteria present on plastic water bottles comes from bacteria resting on people's hands. It is important to wash your hands thoroughly before opening any water bottle, especially the kind of bottle with a screw-off top. If children use reusable bottles, instruct them on proper sanitation methods, such as washing hands after using the bathroom and keeping the bottles from touching surfaces such as water fountains.