Can't drink "Thousand Boiling Water"?

In daily life, everyone must have heard such a saying, "water that is repeatedly boiled is'thousand boiling water', which cannot be drunk", because "the nitrite content in the thousand boiling water exceeds the standard, and regular drinking will cause poisoning and even cancer.
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"Is it true? Yesterday, the reporter bought drinking water samples of different brands and sent them to the Xi'an Nutrition Society for testing by experts
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Experimental location : Xi'an Nutrition SocietyLaboratory staff : Member of Xi'an Nutrition Society, National First-level Nutritionist Zhou Ping, Du Yuchun LaboratoryAssistant : Member of Xi'an Nutrition Society Zhang Jingzhi ExperimentalConsultant : Vice President of Xi'an Nutrition Society Wang YongjianLaboratory Supplies : Nitrite Rapid Test Reagent , drinking water sample one, two, three, four, induction cooker and so on
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Experimental principleThe nitrite in the food reacts with the chromogenic agent to generate colored compounds.
The visual colorimetric analysis method is used to directly read the nitrite content in the food on the nitrite rapid detection color scale card
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Experimental process1.
Take 500ml each of tap water, a certain brand of pure drinking water, a certain brand of natural mineral water, and a certain brand of drinking mineral water, and pour them into a milk pot and place them on an induction cooker to heat them
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2.
After the water of each sample is boiled, put 1ml of each sample into the corresponding colorimetric tube, drop in the nitrite rapid detection reagent, close the lid, and shake it well
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3.
Compare with the colorimetric card of nitrite rapid detection reagent
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Let the four sample liquids boiled before airing for 10 minutes, and then heat them for the second time.
After boiling, perform the same operation as after the first heating
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Wait 10 minutes before proceeding with the same operation for the third time
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Experimental results: After boiling different drinking water samples several times, a total of 12 sample liquids were obtained.
After rough testing, it was found that the liquids in the final 12 colorimetric tubes did not change in color or properties, and they were compared by colorimetric cards.
Later, the nitrite readings all showed 0, and the above experiment did not detect the nitrite component in the thousand boiling water
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　　Experts explain　　Zhou Ping said that nitrite refers to a general term for a class of inorganic compounds.
Studies have reported that a one-time intake of 0.
2-0.
5g of nitrite can cause acute poisoning, and 3 grams can lead to death
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JACFA (Joint Expert Committee on Food Additives) allows the daily intake of nitrite to be 0.
07 mg per kilogram of body weight
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The potential harm of nitrite is that frequent contact with nitrite-rich foods can easily form nitrosamines with intestinal methamines.
Nitrosamines are recognized as carcinogens in the world
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In fact, drinking water comes from natural source water.
The main source of nitrite in natural water is organic pollutants, such as manure, urine, domestic sewage and wastewater from nitrogen fertilizer plants, but they are decomposed into ammonia under the action of microorganisms and oxygen.
, Nitrite, nitrate, so as to purify the water quality
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Because nitrite is very unstable, it is converted into ammonia in the absence of oxygen and in the presence of reducing substances, and converted into nitrate in the presence of oxygen and oxides to reduce toxicity.
Generally, there is sufficient oxygen in natural water, so nitrite The nitrogen content is far below 0.
1mg/L (standard for drinking natural mineral water)
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In drinking water, there should be no nitrite nitrogen, so the drinking water sanitary standard does not determine its limit
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　　Zhou Ping said that although nitrite was not detected in the test samples, some research reports showed that the heating of metal containers would increase the nitrite content, and mineral water would increase more than tap water
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Compared with tap water, mineral water contains more mineral elements
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Analysis of this phenomenon may be caused by a certain mineral element participating in the reduction of part of nitrate to nitrite under heating conditions, but the specific mechanism of action still needs further study
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Therefore, shortening the heating time in daily life to avoid repeated boiling of drinking water is still a feasible measure to reduce the harm of nitrite
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　　Are these claims about drinking water reliable? 　　Listen to what the experts say 　　 The　　water is boiled and then boiled for 3 minutes to remove chloride? It should continue to boil but it does not take that long.
　　Zhou Ping said that after the tap water is boiled, it should continue to boil, but there is no need to wait for 3 minutes, almost a minute or two
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Because the tap water is chlorinated and disinfected during processing, it will be helpful for the volatilization of residual chlorine after it is boiled and then burned on a low fire
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　　Can’t drink “overnight water”? 　　This is a reliable statement　　Zhou Ping introduced that how long the water will deteriorate after being boiled is not suitable for drinking.
In fact, there is no fixed time because it is also affected by the objective environment, such as the outside temperature
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In summer, the temperature exceeds 30°C, the air humidity is high, bacteria multiply quickly, and the water is easily polluted, which can cause human diarrhea
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Therefore, the boiled water should not be left for too long, even if there is no fixed shelf life of the number of days, it is best not to drink the boiled water after the night
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　　Drinking "hard water" often causes stones? 　　There is no scientific basis for the claim.
　　Zhou Ping said that the "hard water" we often say refers to water with a high content of calcium and magnesium ions
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Hard water is harmless to the human body.
Calcium and magnesium are both essential elements for the human body, and most people's intake is low.
In this sense, water with high hardness can also replenish some minerals
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Of course, this amount is far from enough for daily needs.
The right way to supplement minerals is to have a balanced diet.
As for the fact that regular drinking of "hard water" can cause stones, there is still no conclusion in the medical field
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