Does drinking boiled water many times cause cancer?

This rumor stems from the fear that there is nitrate in the water. When water is boiled many times, the nitrate will become more “concentrated” and can turn into nitrosamine, which is a carcinogen. In fact, the nitrate concentration in standard tap water is very low. Normal boiling does not produce significant amounts of nitrosamines. The risk is only a concern if the original water source is heavily polluted.

The World Health Organization (WHO) controls nitrate limits in drinking water very strictly. Currently, there is no reliable scientific evidence that repeatedly boiling water itself causes cancer.

If the water meets the original safety standards, it is not dangerous. Boil it again 1-2 times so it is still safe to drink. Do not leave the water in the kettle for too long (past the next day) because it can be contaminated with bacteria from the environment. Water that has a strange odor or unusual residue should be thrown away. Water contaminated with heavy metals is harmful whether boiled once or 5 times.

Note, untested drilled well water, water in arsenic contaminated areas should not be used. You should clean the kettle regularly to avoid white residue which is calcium residue.