The reason for this is that there are more and more organic pollutants in water, some of which are volatile and will evaporate with water vapor when heated. So when the water is about to boil, open the lid of the kettle and cook for two or three minutes after the water boils, so as to volatilize these substances to the maximum extent. On the other hand, if the water is boiled for too long, it will also cause water aging and form harmful substances. Therefore, healthy water that meets human needs should be fresh.
In addition, if the water is left for too long after boiling, it will also become aged water, and the toxic substances in aged water will increase with the increase of water storage time. So it's best to drink the water that was cooked that day. Experiments show that drinking boiled water for no more than 6 hours after natural cooling is most beneficial to human health!