You are probably guilty of doing the same thing I do each morning, when I turn the kettle on for my cup of tea or coffee. While the water boils I start seeing to some other things, then I realize I have forgotten about the kettle. So there I go and re-boil the water all over again. But, it never occurred to me that this foolish routine was detrimental to my health until I was warned about the adverse effects. Here's what you need to know:
Why reboiling water is harmful
The composition of water changes when boiled. This beneficially releases volatile compounds and gases, making boiled water a safe drink.
But when ordinary water is over boiled or reboiled, the chemical compounds change for the worse. Instead of dissolving, dangerous substances accumulate, increasing the risk of consuming certain chemicals and harmful substances like nitrates, arsenic and fluoride (see more in the section below). Healthy minerals may also turn for the worse when 'amassed': in large quantities, calcium salts, for instance, can lead to kidney stones and gallstones.
The damaging effects of reboiled water
Nitrates that are exposed to high heat become highly toxic. High temperatures transform nitrates to nitrosamines, which are carcinogenic (having the potential to cause cancer). Nitrates have also been linked to diseases like leukemia, non-Hodgkin lymphoma, ovarian, colon, rectal, bladder, stomach, pancreatic and thyroid cancer.
In addition, over the years, an accumulation of arsenic (a chemical element that occurs in many minerals) can lead to arsenic intoxication, which has been shown to cause numerous health issues including cancer, cardiovascular disease, neurological issues, infertility, and developmental disorders.
Furthermore, being exposed to too much fluoride can have damaging effects on neurological and cognitive development, particularly in children, according to data collected at Harvard University.
So, take precautions today! If you must reboil your water, be sure to change it first. Happily, however, reboiling is fine if you are using perfectly pure distilled deionized water, where no ill-effects have yet been noted.