A friend bought a new electric kettle. But every time it boils he has to unplug the power, ask the reason, it turns out he is worried about not unplugging the power, the electric kettle will keep heating, the water is repeatedly boiled. According to past experience, the longer it is boiled, the more nitrite content in the water will increase – nitrite may cause cancer, harmful to the body – so the water is also known as “rolling water”. Nitrite, will not be “created from nothing” In fact, the nitrite in the water will not be created out of thin air, generally from the original nitrate in the water to transform. Qualified drinking water, nitrate is very little; but if the water source is contaminated with nitrogenous organic matter, nitrate content may increase. Generally speaking, repeated heating of drinking water leads to an increase in nitrite, mainly due to the evaporation and concentration of water, nitrite concentration increases, but the total amount does not increase; another possibility is that certain nitrates are decomposed into nitrite by heat. How much nitrite will be repeatedly boiled? China’s health standards for bottled water, the content of nitrite in water shall not exceed 2 micrograms / per liter. How much nitrite will there be in the repeatedly boiled water? In 2007, the Shanghai CDC conducted a study on this issue, after repeated heating of the water dispenser bucket of water, found that with the increase in the number of heating, nitrite content does rise, after repeated heating 52 times, the nitrite content of the water is 2.3 micrograms / liter. In 2011, Harbin Institute of Technology also tested this claim, researchers took six beakers, respectively, for the original water, boiled 1 to 5 times the water, to determine the nitrite, nitrate and other substances, the results found that the national standard of tap water repeatedly boiled without detecting the presence of nitrite, even if the artificial addition of a certain amount of nitrite, in the process of boiling water its content did not change. Some people have repeatedly heated the barrel of water 20 times and found that the nitrite content in the water exceeded the standard, reaching 2.1 micrograms / liter, only 0.1 micrograms over the standard. What if the number of heating more times? Some people put long-term continuous repeated heating of barrels of water with water fountains, heated to 181 times, the water nitrite ion content is 3.53 micrograms / per liter, 5 times the initial. See this “increased to 5 times”, there is no need to panic. This figure exceeds the health standards of our barrel water, but is still safe. You know, many people like to eat ham in the nitrite content is much higher than this: qualified ham in the allowable use of nitrite is 30,000 micrograms (30 mg) per kilogram. If ham is still safe, there is no need to worry about this nitrite in water. Besides, apart from doing scientific research, who boils water more than 180 times in daily life? And, in general, the home water fountain, ordinary electric kettle, the amount of water is not much, not yet heated a few times is estimated to have finished drinking. After boiling water, do not store for a long time However, it is worth reminding is that boiling water in the insulation pot for a long time to save placed in 5-6 days, due to the role of bacteria, coupled with some rural areas in the water nitrate content is relatively high, the content of nitrite does have the risk of rising. Therefore, it is recommended to boil water as soon as possible after drinking, do not store for a long time; really want to save, it is best to put in sealed preservation, to minimize the growth of bacteria reproduction. Of course, from the point of view of promoting energy conservation, water boiling after turning off the power is indeed a good habit, in addition to some electric kettles after the water is not timely unplugged may also have the risk of leakage, because the leakage of electricity and may cause fire, life safety and other dangers is more worthy of everyone’s attention, rather than the point of nitrite in the water. Therefore, from the safety of electricity and energy conservation, or recommend that we boil water after the power off in a timely manner.