High bacterial rates found in bottled water

More than 70 per cent of bottled water samples from Canada contain bacterial rates that exceed recommended limits in the U.S., suggests a study presented at the general meeting of the American Society of Microbiology.

In some Canadian water, results were more than 100 times U.S. limit

More than 70 per cent of bottled water samples from Canada contain bacterial rates that far exceed recommended limits in the U.S., suggests a study presented Tuesday at the general meeting of the American Society of Microbiology in San Diego.

"Heterotrophic bacteria counts in some of the bottles were found to be in revolting figures of 100 times more than the permitted limit," said Sonish Azam, a researcher on the study. Heterotrophic bacteria are a category which includes all bacteria that survive by consuming organic matter.

Montreal-based C-crest Laboratories Inc. conducted the research after a company employee complained of a foul taste and illness after drinking some bottled water.

The U.S. bacterial limit is no more than 500 colony-forming units of bacteria per millilitre of water. Health Canada does not have an equivalent standard for bacteria in bottled water. Canadian test samples showed results of more than 80,000 heterotrophic units.

"That's obviously problematic," said Greg Goss, a professor of biological science at the University of Alberta and a researcher with the Canadian Water Network.

But Goss said it's hard to pass a verdict on the finding without knowing which specific bacteria were found in the water.

"If there were fecal coliforms it would be a serious problem but if they're just a number of bacteria there isn't a significant health risk. The body can take quite a bit of other bacteria in our ingestion."

Researchers are still carrying out a second phase of the study that will determine the DNA of the bacteria involved. Researchers from the lab gathered samples of several major brands of bottled water from Montreal stores and tested the bacterial levels.

At a news conference in San Diego where the findings were announced, the researchers said the brands of water tested are commonly sold in Quebec and Ontario. They did not name any of the brands tested.

The samples were all tested about two months after bottling.

Industry not concerned

The executive director of the Canadian Bottled Water Association said she was neither surprised nor alarmed by the finding.

"My understanding is that heterotrophic plate count [bacterial level] is not pathogenic and does not pose a health risk," Elizabeth Griswold told CBC News.


All bacteria are single-celled organisms with no nucleus. Most bacteria are heterotrophic, though some, like algae, are autotrophic.


An organism that must consume organic material to survive (to gain carbon or nitrogen) is heterotrophic. All animals are heterotrophic because they must eat to survive.


Any organism that can create its own food, also called "biomolecules." For example, most plants are autotrophic because they create their own food through photosynthesis using energy from the sun and carbon dioxide.   

Heterotrophic bacteria

Examples of heterotrophic bacteria that can be harmful to humans: (

  • E. coli – causes gastrointestinal illness
  • Salmonella – gastrointestinal illness and fever
  • Group A streptococci – strep throat

More information

Not all bacteria are dangerous.

There are more bacterial cells in the human body than there are human cells. Bacterial flora is mainly found on the skin and in the digestive tract. A healthy immune system usually defends against any bacteria consumed through food and drink. 


She said bottled water is tested within 24 hours of the bottling process and the bacterial count is always below the 500 cfu/ml standard set in the United States.

But Goss pointed out bottled water does not contain chlorine, so bacteria in the water when it's bottled can reproduce later.

"If they're sitting around for a long time, it can build up fairly quickly," he said.

Researcher Ali Khamessan was surprised at how much bacteria built up in the water, especially some brands that had consistently high levels.

"It's like we're ingesting a cup of [bacterial] culture," he said at the news conference.

The C-crest team also tested samples of Canadian tap water and found the levels around 170 colony-forming units per millilitre of water — well below what was found in the bottled water.

"Despite having the cleanest tap water, a large number of Canadians are switching over to bottled water for their daily hydration requirements," said Azam. "Unsurprisingly, the consumer assumes that since bottled water carries a price tag, it is purer and safer than most tap water."

Azam said the bacteria likely don't cause disease, and the study did not confirm the presence of disease-causing bacteria in the water. Still, she cautioned that the bacteria could pose a risk to vulnerable people such as infants, pregnant women, the elderly and those with compromised immune systems.

The researchers are calling for limits on the amount of bacteria allowed in Canadian drinking water. C-crest offers product analysis and consulting services to the drug and food manufacturing industries.