Water is an essential and indispensable substance for human survival. A person can go a day without food, but not a day without water. However, not all water is safe for drinking. The following five types of water, to some extent, can form nitrites and other toxic and harmful substances, which can pose certain hazards to the human body and therefore require people's attention. One, Aged Water:
Commonly known as "stagnant water," it is water that has been stored for a long time without moving. Drinking this water often can significantly slow down the metabolism of cells in minors, affecting physical development; in middle-aged and elderly people, it can accelerate aging. The incidence of esophageal and stomach cancer is increasing in many places, and according to medical research, it may be related to long-term consumption of aged water. Relevant data indicates that the toxic substances in aged water also increase with the length of storage time. Two, Re-boiled Water:
Re-boiled water is water that has been boiling on a stove all night or for a long time, as well as water in an electric water heater that has been boiled repeatedly. Due to prolonged boiling, this water has high levels of non-volatile substances, such as heavy metals like calcium and magnesium, and high nitrite content. Drinking this water for a long time can interfere with a person's gastrointestinal function, causing temporary diarrhea and bloating; toxic nitrites can also cause hypoxia in the body, and in severe cases, it can lead to coma, convulsions, or even death. Three, Steamer Water:
Steamer water is the leftover water from cooking foods like steamed buns, especially steamer water that has been used repeatedly, which has a very high concentration of nitrites. Drinking this water often or using it to cook porridge can cause nitrite poisoning; scale often enters the human body with the water, which can also cause diseases of the digestive, nervous, urinary, and hematopoietic systems, and even cause premature aging. Four, Unboiled Water:
The tap water people drink is sterilized by chlorination. Chlorinated water can separate 13 harmful substances, of which halogenated hydrocarbons and chloroform have carcinogenic and teratogenic effects. When the water temperature reaches 90°C, the content of halogenated hydrocarbons increases from 53 micrograms per kilogram to 177 micrograms, exceeding the national drinking water hygiene standard by 2 times. Experts point out that drinking unboiled water increases the risk of bladder cancer and rectal cancer by 21% to 38%. When the water temperature reaches 100°C, these two harmful substances will greatly reduce with the evaporation of steam; if boiling continues for 3 more minutes, it is safe to drink. Five, Re-boiled Water:
Some people are in the habit of re-boiling the remaining warm water from a thermos to drink, with the aim of saving water, coal (gas), and time. However, this kind of "saving" is not advisable. Because the water is boiled again, the water evaporates again, and nitrites increase. Drinking this water often can cause nitrites to accumulate in the body, leading to poisoning.