Nitrates and nitrites. Decomposition of nitrates. Nitrates in foods and water. Nitrates are ...

Each of us at least once in my life encountered the unpleasant consequences of eating products with nitrates. For someone, such a meeting continued with a slight intestinal disorder, and someone managed to get into the hospital and for a long time looked with apprehension at any fruits and vegetables bought on the market. A pseudo-scientific approach and lack of awareness makes of a saltpeter a monster capable of even killing, but it is worth getting acquainted with these concepts closer.

Nitrates and nitrites

Nitrites are nitric acid salts that look like crystals. They dissolve well in water, especially in hot water. On an industrial scale, they are obtained by absorbing nitrous gas. Used to produce dyes, as an oxidant in the textile and metal processing industry, as a preservative.

Nitrates are nitric acid salts, formerly called nitrates. They are obtained after exposure to nitric acid metals, and in themselves they are very strong oxidants. They readily dissolve in water. The decomposition of nitrates occurs at temperatures above 300 degrees Celsius. The main field of application of nitrates is agriculture, but some compounds use pyrotechnics as explosives, and also as components of rocket fuel.

The role of nitrates in plant life

One of the four basic elements that make up a living organism is nitrogen. It is necessary for the synthesis of protein molecules. Nitrates are salt molecules that contain the amount of nitrogen a plant needs. Absorbed by the cell, the salts are reduced to nitrites. The latter, in turn, reach the ammonia chain in a chain of chemical transformations. And it, in turn, is necessary for the formation of chlorophyll.

Natural sources of nitrates

The main source of nitrates in nature is the soil itself. When organic substances, which are contained in it, are mineralized - nitrates are formed. The speed of this process depends on the nature of land use, weather and the type of soil. The earth does not contain a lot of nitrogen, so environmentalists are not worried about the formation of a significant amount of nitrates. Moreover, agricultural works (harrowing, disking, constant use of mineral fertilizers) reduce the amount of organic nitrogen.

Therefore, natural sources can not be considered a factor in the pollution of groundwater and the accumulation of nitrates in plants.

Anthropogenic sources

Conditionally anthropogenic sources can be divided into agricultural, industrial and communal. The first category includes fertilizers and livestock waste, to the second - industrial wastewater and industrial wastes. Their impact on environmental pollution varies and depends on the specifics of each specific region.

The determination of nitrates in organic materials gave the following results:

- More than 50 percent is the result of harvesting campaign;
- about 20 percent - manure;
- municipal waste is approaching 18 percent;
- all the rest is industrial rubbish.

The most serious harm is caused by nitrogen fertilizers, which are introduced into the soil to increase the yield. The decomposition of nitrates in the soil and plants forms a sufficient number of nitrites for food poisoning. Intensification of agriculture only aggravates this problem. The highest level of nitrates is noticed in the main drains, which collect water after irrigation.

Effects on the human body

Nitrates and nitrites first compromised themselves in the mid-seventies. Then in Central Asia, doctors recorded an outbreak of poisoning by watermelons. In the course of the investigation, it was found that the fruit was treated with ammonium nitrate and, apparently, overdid it a little. After this case, chemists and biologists have taken up the study of the interaction of nitrates with living organisms, in particular man.

1. In the blood, nitrates interact with hemoglobin and oxidize the iron that enters it. Thus, methhemoglobin is formed, which can not transfer oxygen. This leads to disruption of cellular respiration and oxidation of the internal environment of the body.
2. Disrupting homeostasis, nitrates contribute to the growth of harmful microflora in the intestine.
3. In plants, nitrates reduce the content of vitamins.
4. An overdose of nitrates can lead to an abortion or a violation of sexual function.
5. With chronic nitrate poisoning, there is a decrease in the amount of iodine and a compensatory increase in the thyroid gland.
6. Nitrates are a trigger factor for the development of tumors in the digestive system.
7. A large dose of nitrates at one time can lead to collapse due to the sharp expansion of small vessels.

Metabolism of nitrates in the body

Nitrates are derivatives of ammonia, which, getting into a living organism, are built into the metabolism and change it. In small quantities, they do not cause concern. With food and water, nitrates are absorbed in the intestines, pass with blood flow through the liver and are excreted from the body by the kidneys. In addition, in nursing mothers, nitrates enter the breast milk.

In the process of metabolism, nitrates are converted into nitrites, oxidizes iron molecules in hemoglobin and breaks the respiratory chain. In order to form twenty grams of methaemoglobin, only one milligram of sodium nitrite is sufficient . Normally, the concentration of methemoglobin in blood plasma should not exceed a couple of percent. If this figure rises above thirty, there is poisoning, if above fifty - it is almost always deadly.

To control the level of methaemoglobin in the body, there is methemoglobin reductase. It is a hepatic enzyme that is produced in the body, beginning with three months of life.

The permissible norm of nitrates

Of course, the ideal option for a person is to avoid getting nitrates and nitrites into the body, but in real life it does not happen. Therefore, the doctors of the Sanitary and Epidemiological Station established the norms of these substances, which can not damage the body.

For an adult weighing more than seventy kilograms, a dose of 5 milligrams per kilogram of weight is acceptable. Without serious health consequences, an adult can swallow up to half a gram of nitrate. In children, this indicator is more average - 50 milligrams, regardless of weight and age. At the same time, a fifth of this dose will be enough for a baby to be poisoned.

Ways of Penetration

You can get poisoning with nitrates through an alimentary route, that is, through food, water and even medicines (if they contain nitrate salts). More than half the daily dose of nitrates falls in a person with fresh vegetables and canned food. The remaining dose comes from baking, dairy products and water. In addition, an insignificant portion of nitrates is a metabolic product and is formed endogenously.

Nitrates in water are an occasion for a separate conversation. It is a universal solvent, therefore, it contains not only useful minerals and microelements necessary for normal human activity, but also toxins, poisons, bacteria, helminths, which are the causative agents of dangerous diseases. According to the World Health Organization, because of poor water every year, about two billion people get sick, and more than three million of them die.

Chemical fertilizers containing ammonium salts leak through the soil and enter underground lakes. This leads to accumulation of nitrates, and sometimes their number reaches two hundred milligrams per liter. Artesian water is cleaner, as it is extracted from deeper layers, but toxins can also enter it. Residents of the countryside, along with well water, receive eighty milligrams of nitrate daily from each liter of drinking water.

In addition, the content of nitrates in tobacco is high enough to cause long-term smokers to cause chronic poisoning. This is another reason for fighting the bad habit.

Nitrates in products

During the culinary processing of products, the amount of nitrates in them is significantly reduced, but at the same time, a violation of the storage rules can lead to the opposite effect. Nitrites, the substances most toxic to humans, are formed at a temperature of ten to thirty-five degrees, especially if the storage location of products is poorly ventilated, and the vegetables are damaged or they begin to rot. Nitrites are formed in unfrozen vegetables, on the other hand, deep freezing prevents the formation of nitrites and nitrates.

Under optimum storage conditions, it is possible to reduce the amount of nitrate in products to fifty percent.

Nitrate poisoning

Symptoms of nitrate poisoning:

- blue lips, face, nails;
- nausea and vomiting, there may be pain in the abdomen;
- icterus of eye whites, stools with blood;
- headache and drowsiness;
- noticeable shortness of breath, palpitations and even loss of consciousness.

Sensitivity to this poison manifests itself more strongly in conditions of hypoxia, for example high in the mountains or in case of poisoning with carbon monoxide or strong alcohol intoxication. Nitrates enter the intestine, where the natural microflora metabolizes them to nitrites. Nitrites are absorbed into the systemic circulation and affect hemoglobin. The first signs of poisoning can be replaced after an hour at a large initial dose or six hours later, if the amount of nitrates was small.

It should be remembered that acute poisoning with nitrates in its manifestations is similar to alcohol intoxication.

It is impossible to separate our life from nitrates, because this will affect all spheres of human life: from nutrition to production. However, you can try to protect yourself from excessive consumption, following simple rules:

- wash vegetables and fruits before consumption;
- store products in refrigerators or in specially equipped rooms;
- drink purified water.