With the improvement of modern living standards, almost every household uses electric kettles and water dispensers. However, if you forget to unplug these appliances, it is inevitable that the water will be repeatedly heated. What harm does repeatedly heated water, also known as "thousand boiling water," have on the human body?
What is "thousand boiling water"?
"Thousand boiling water" refers to water that has been repeatedly boiled. Due to long-term boiling, the levels of non-volatile substances, such as calcium and magnesium, as well as nitrite, increase in the water. Since "thousand boiling water" contains carcinogenic nitrite, it is generally believed to be harmful to the body.
Sources of nitrite in water
Water contains a certain amount of nitrate, which decomposes into nitrite after a period of time. Repeatedly heating the water is the cause of increased nitrite levels. This is mainly due to water evaporation and concentration, resulting in an increase in nitrite concentration without an overall increase in quantity.
Nitrite content in "thousand boiling water"
According to the hygiene standards for bottled water in China, the nitrite content should not exceed 2 micrograms per liter. How much nitrite is present in water that has been repeatedly boiled? Some experimental data shows that it takes heating the water 20 times before the nitrite exceeds the standard, reaching 2.1 micrograms per liter. It has been found that after repeatedly heating the water in a water dispenser 181 times, the nitrite content reaches 3.53 micrograms per liter. This is still lower than the nitrite content found in commonly consumed processed meat products such as ham sausages. Therefore, there is no need to worry about the nitrite content in water.
Water quality determines nitrite content in "thousand boiling water"
The harm of "thousand boiling water" to the human body is related to the quality of the water. Generally, qualified drinking water has a low nitrate content. However, if the water source is contaminated with nitrogenous organic substances, the nitrate content will increase. A set of data shows that lake water has a high ammonia nitrogen content, while groundwater and purified water have almost zero ammonia nitrogen content. After repeated boiling, the nitrite content in poorly quality lake water increases significantly, while there is little change in nitrite content in groundwater and purified water.
Boiled water should not be stored for a long time
After being stored in a thermos for 5-6 days, boiled water can have an increased nitrite content due to bacterial action, as well as the naturally high nitrate content in some regions. Therefore, it is recommended to drink boiled water as soon as possible after it has been boiled and not to store it for a long time. If you must store it, it is best to keep it sealed to minimize bacterial growth and reproduction.
