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Should I be concerned if disposable water bottles freeze or overheat?
When disposable water bottles freeze or are exposed to heat (e.g. after being left in a car), chemicals may leach out of the container and into the water, increasing your cancer risk.
Drinking water from plastic water bottles that freeze or overheat does not increase your risk of cancer.
Some people are concerned about dioxins, a group of highly toxic substances that are known to cause cancer, leaching from the bottles into the water. But there is no evidence that plastic water bottles contain dioxins.
Some plastics contain substances known as plasticizers, such as DEHA, to make the plastic more flexible and less brittle. Rumours say that disposable plastic water bottles leach DEHA into the water, but DEHA is not used to manufacture these bottles and is not suspected of causing cancer.
When you should be concerned about disposable water bottles
Using plastic water bottles more than once can be harmful if they are not cleaned and dried properly or if they're left in warm areas where harmful germs can grow. These germs can make people sick, causing vomiting or diarrhea. This is true with other types of containers, not just disposable water bottles. But there is no evidence that using disposable plastic water bottles more than once can cause cancer.
The Canadian Cancer Society is committed to sharing important information about cancer risk to Canadians and will continue to monitor research in this area.