Re-boiling water has happened to everyone, maybe unintentionally or unconsciously. However you need to stop it right there as the composition of the water at boiling point is changed and this can be highly dangerous.
At boiling point water turns at boiling point. The steam is make of volatile compounds, burning out of water and turning into gasses, i.e. turn into steam. Once the water cools down and you re-boil it, the dissolved volatile gasses and minerals are subjected to the same process and the chemical components change their structure for the second time. This process is very harmful.
When the water is put for re-boiling, the dangerous compounds that need to get out from the water will stay aside. Re-boiled water contains nitrates, arsenic, and fluoride. The healthy minerals are retained in boiled water and if re-boiled, the healthy compounds create a dangerous situation to which we get exposed they become assumed in the re-boiled water. Calcium salts can contribute to kidney stones and gallstones if significant amount is consumed. Calcium salt can collect in the re-boiled water.
What are the negative effects of re-boiled water?
If you consume it, you expose yourself to toxic nitrates, excessive fluoride intake, and arsenic intoxication. When the nitrates are exposed to high temperatures and the water reaches boiling point and become toxic. The composition of the nitrates change and turn into nitrosamines and they are carcinogenic.
If you consume re-boiled water you are at risk of developing different types of cancer. Drinking it frequently will cause many health issues like infertility, heart disease, neurological issues, and cancer. Arsenic intoxication turns into invisible sediment and strays into the re-boiled water. The third thing which is dangerous is excessive intake of fluoride and it can cause neurological issues. Children who receive a lot of fluoride have been reported to suffer from cognitive delays.
You have to stop yourself from exposure of these toxins because you have decided to save a minute and not change the boiled and cooled down water in the kettle. You will need less than a minutes to fill your kettle with fresh water and it will keep your body toxin-free. It is worth to avoid harmful things.