Soil is a huge natural laboratory in which a wide variety of complex processes of destruction and synthesis of organic substances continuously occur, new inorganic compounds are formed, and pathogenic bacteria, viruses, protozoa, and helminth eggs die off. The soil is used for purification and neutralization of household wastewater, liquid and solid waste generated in populated areas. Soil has a significant impact on the climate of the area, the nature of vegetation, the layout and development of populated areas and individual buildings, their improvement and operation.
In agricultural production conditions, a large number of various pesticides, mineral fertilizers, soil structure formers, and plant growth stimulants are purposefully introduced into the soil. With liquid and solid household and industrial waste, wastewater, emissions from industrial enterprises and vehicles, surfactants (surfactants), polycyclic aromatic hydrocarbons (PAHs), large amounts of heavy metals, petroleum products, etc. enter the soil with subsequent migration into underground and surface reservoirs are sources of water supply, and from there into drinking water, agricultural plants, and atmospheric air. Soil can be a factor in the transmission of infectious diseases and invasions. Thus, it has a major impact on public health.
Even in ancient times, a distinction was made between “healthy” and “unhealthy” soils. Areas located on hills, with dry soils, well ventilated and insolated were considered “healthy”. The “unhealthy” areas included areas located in lowlands, cold, flooded, damp, and with frequent fogs. Therefore, the soil is of great hygienic importance for public health and the improvement of populated areas and is:
1) the main factor in the formation of natural and artificial biogeochemical provinces, which play a leading role in the occurrence and prevention of endemic diseases among the population;
2) the environment that ensures circulation in the system environment - people of chemical and radioactive substances used in the national economy, as well as exogenous chemicals that enter the soil with emissions from industrial enterprises, aircraft and vehicles, wastewater, and therefore a factor affecting public health;
3) one of the sources of chemical and biological pollution of atmospheric air, ground and surface water, as well as plants used by humans for food;
4) a factor in the transmission of infectious diseases and invasions;
5) natural, most suitable environment for the neutralization of liquid and solid waste. R
Endemic importance of soil. Soil is the environment in which solar energy transformation processes occur. According to V.A. However, plants annually accumulate almost 0.5 x 1015 kW of solar energy.
Humanity uses only 7 x 1012 kW in the form of fuel, food and livestock feed. It has been proven that today and in the future the soil - plants - animals system in people's lives will remain the main supplier of transformed solar energy.
Soil is the element of the biosphere that forms the chemical composition of food products, drinking water and partly atmospheric air. Every year, 8.3 x 1010 tons of living matter, represented mainly by plant phytomass, is produced on Earth. Over the entire history of the biosphere, the total mass of living matter produced by it was almost 2 times greater than the inorganic mass of the earth's crust. Over the course of a year, humanity on our planet uses about 3.6 x 108 tons of living plant matter for food, which is 0.5% of what is produced on Earth. Naturally, phytobiomass consumed by humans through food, directly or through food products of animal origin, should be harmless in chemical composition.
It is scientifically proven that the chemical composition of phytobiomass depends on the natural chemical composition of the soil, i.e. endogenous chemicals present in the soil, as well as on the quality and quantity of exogenous chemicals that enter the soil accidentally or are purposefully introduced to increase crop yields . Cases of poisoning of people and animals who consumed plant phytomass grown on land in endemic areas, which contained increased concentrations of certain chemicals, have been described. There are also known diseases associated with insufficient content of certain microelements in the soil, and accordingly, in the daily diet.
Thus, plants that grew in areas where selenium is endemic in the soil can accumulate up to 5000 mg/kg of this microelement. The consumption of such phytomass, obtained on alkaline lands of the USA, Canada, and Ireland, led to poisoning of people and mass death of farm animals. Selenium toxicosis is called "alkaline" disease. At the same time, selenium is a biomicroelement, and it must enter the human body in a physiologically optimal daily dose (0.05-0.2 mg). In some regions of China, Egypt and Sweden, the selenium content in soils is significantly less than the clarke (the average content in the earth's crust). Such a low content of selenium in the soil and, accordingly, in plant products is the cause of Keshan disease - selenium hypomicroelementosis, in which juvenile cardiopathy is observed, the risk of developing atherosclerosis, hypertension, endocrinopathies, neoplasms is increased, chronic dermatitis (itching, peeling of the skin) occurs, arthralgia.
A connection has been established between increased molybdenum content in soil and the incidence of molybdenum gout, esophageal cancer, and reproductive dysfunction. Molybdenum gout (molybdenum hypermicroelementosis) is an endemic disease in some regions of Armenia (Ankavan and Kadrazhan). Excessive intake of molybdenum into the human body (daily requirement is 0.1-0.3 mg) leads to increased xanthine oxidase activity and increased formation of uric acid and its salts (urates).
In some areas of Transbaikalia, Eastern Siberia (Chita, Amur, Irkutsk regions), Korea and China, the so-called Urov disease, or Kashin-Bek disease, has been registered. In the soils of these regions, the content of many microelements (strontium, iron, manganese, zinc, lead, silver, fluorine) is increased against the background of low calcium content. Kashin-Beck disease (endemic polyhypermicroelementosis) occurs in the form of osteodeforming osteoarthritis, especially of the interphalangeal (bear paw), hip joints and spine (duck gait).
An extremely pressing problem in Ukraine was endemic goiter, which was registered in people living for a long time in the Carpathians and Poltava region. The soils of these areas have a very low natural iodine content, which led to insufficient iodine intake (the daily human requirement is 0.2-0.3 mg) into the body with local food products. Lack of iodine caused hyperplasia of the thyroid gland due to hypertrophy of the connective tissue and atrophy of the glandular tissue, i.e., there were signs of hypothyroidism (decreased metabolism, increased body temperature, obesity, passivity, apathy, decreased ability to work, hair loss). Congenital developmental defects and mental retardation were observed in children.
Arsenic contamination of soil leads to hoof disease, which was first recorded in Japan. Over 12 thousand people fell ill, of which 120 children died. The disease manifested itself with signs of hyperkeratosis, hair loss, brittle nails, neuritis, paralysis, blurred vision, and liver damage were observed. A link has been proven between arsenic levels in soil and the incidence of stomach cancer.
At present, in addition to natural soil regions endemic for one or another chemical element, artificial biogeochemical regions and provinces have appeared. Their appearance is associated with the use of various pesticides, mineral fertilizers, plant growth stimulants, as well as with the entry of industrial emissions, wastewater and waste into the soil.
The population living in these provinces for a long time is constantly exposed to the adverse effects of exogenous chemicals. In such artificial geochemical provinces, there is an increase in the incidence rate, the number of cases of congenital deformities and developmental anomalies. In addition, the soil's ability to self-purify is reduced. In addition to long-term consequences, in artificial geochemical provinces there are cases of not only chronic, but also acute poisoning due to the use of manual labor and mechanized work in agricultural fields, household plots, gardens treated with pesticides, as well as on land contaminated with exogenous chemicals contained in atmospheric emissions from industrial enterprises. For example, soil contamination with fluoride due to emissions from industrial enterprises led to necrosis of the leaves of grapevines and apricot trees in the Rhone Valley (Switzerland). Product consumption
Plant origin grown in soil with high fluoride content led to the development of fluorosis. Disorders of hematopoiesis in children, as well as phosphorus-calcium metabolism, and an increase in the number of patients with liver and kidney damage and gastritis were recorded.
A pollutant such as nickel is toxic to plants, soil microorganisms and humans. It inhibits hydrolytic enzymes in coarse humus podzolized forest soil. Technogenic contamination of soil with nickel had a negative impact on public health, resulting in an increased incidence of schizophrenia, lung and stomach cancer.
Increased boron content in the soil due to industrial emissions led to the occurrence of boron enteritis.
In uncontaminated soil, mercury is usually found in trace form. The entry of even small amounts of mercury into the soil affects its biological properties. Mercury reduces amonifying and nitrifying activity and the action of dehydrogenases. High levels of mercury have an adverse effect on the human body. There is an increase in the incidence of diseases of the nervous and endocrine systems, genitourinary organs in men, and a decrease in fertility.
In lead artificial biogeochemical provinces, the number of cases of diseases of the hematopoietic and reproductive systems, internal secretion organs increased, and cases of malignant neoplasms of various localizations became more frequent. In addition, lead inhibits the activity of not only nitrifying bacteria, but also microorganisms - antagonists of Escherichia coli and dysentery bacilli Flexner and Sonne, and increases the time of soil self-purification. Microelements, the increased content of which in the soil leads to unfavorable changes, also include vanadium, thallium, tungsten, etc.
Similar to the accumulation of inorganic chemical elements and substances in the soil, the excess content of organic chemical compounds leads to the formation of artificial geochemical provinces. These include primarily pesticides.
The use of environmentally persistent polychlorinated biphenyls as insecticides in agriculture has led to significant contamination of soils in Japanese rice fields. It was here that Yusho disease, or oil disease, was first recorded in Kyushu. More than 1,000 people fell ill then. The cause of the disease was the consumption of rice oil containing polychlorinated biphenyls. Poisoning was accompanied by nausea, vomiting, weakness, skin hyperkeratosis, chloracne, bronchitis, hepatitis, and neurological disorders. Polychlorinated biphenyls have the ability to overcome the transplacental barrier and enter milk. Therefore, the disease was recorded even in newborns whose mothers consumed contaminated vegetable oil during pregnancy. The carcinogenic effect of polychlorinated biphenyls has been proven.
In artificially created endemic provinces, due to the migration of exogenous chemicals from the soil into the atmospheric air, water or plants, cases of acute and chronic poisoning and allergic diseases are observed. There is also an increase in the blastomogenic danger of soil, which is associated with an increased content of benzpyrene and similar compounds in it. This usually happens near airfields, as well as along “corridors” of aircraft movement. Artificial geochemical provinces with a high content of carcinogenic substances in the soil are also observed near thermal power plants with ineffective ash collectors, highways, after forest fires, etc.
Soil is a medium that determines the circulation of exogenous chemicals in the environment-human system and can become a source of pollution of atmospheric air, water, and food products. Soil is the leading link in the cycle of substances in nature, an environment in which various complex processes of destruction and synthesis of organic substances continuously occur. Organic substances entering the soil under natural conditions in the form of plant and animal remains, as well as their metabolic products, are destroyed by various saprophytic soil microorganisms: bacteria, actinomycetes, fungi, algae, protozoa, etc. In the presence of oxygen, aerobic microorganisms decompose carbohydrates into carbon dioxide and water.
Under aerobic conditions, fats are broken down into glycerol and fatty acids, which break down into carbon dioxide and water. The breakdown of protein compounds occurs in 2 stages. At the first stage - ammonification - proteins break down into amino acids, which, in turn, break down into ammonia and ammonium salts, as well as fatty and aromatic acids. Under aerobic conditions, the second stage of mineralization of nitrogen-containing compounds occurs in parallel - nitrification, when ammonia is oxidized to nitrites, and the latter to nitrates. Thus, thanks to the processes of destruction, organic compounds are converted into those forms of inorganic substances in which they can become nutritious material for plants and again enter the cycle of substances in nature.
Soil is the leading link in the migration of chemicals on our planet. In addition, migration processes include substances of both natural and anthropogenic (technogenic) origin. Migration is carried out along short (soil - plant - soil; soil - water - soil; soil - air - soil) and long (soil - plant - animal - soil; soil - water - plant - soil; soil - water - plant - animal - soil; soil - air - water - plant - soil, etc.) migration chains. Food chains can be extremely complex. Chemicals can accumulate and concentrate in them. For example, as a result of the use of DDT in agriculture as an insecticide and its further migration, the concentration of this substance in the water of Lake Michigan was 2 x 10"6 mg/l, in silt - 1.4 x 10"2 mg/kg, in shrimp tissues - 0.41 mg/kg, in fish meat - 6 mg/kg, in seagull tissues - 99 mg/kg.
The same migration chains include a person who drinks drinking water, food products of plant and animal origin, and breathes atmospheric air.
Natural abnormally high or low content of endogenous chemical substances in the soil, their migration from the soil into adjacent environments (water of reservoirs, atmospheric air, plants) and along food chains determines the formation of natural biogeochemical provinces and the occurrence of endemic diseases. Exogenous chemicals that enter the soil accidentally (with wastewater and solid waste, industrial emissions into the atmosphere, vehicle emissions) or are introduced intentionally (chemical plant protection products, mineral fertilizers, soil structure formers) circulate in the environment along the same migration chains . The formation of artificial biogeochemical provinces is associated with them.
Consequently, soil is the main element of the biosphere, where the processes of migration, transformation and exchange of all chemical substances on our planet occur.
Soil, as a leading element of the biosphere, plays an important role in shaping the water quality of domestic drinking water supply sources, which primarily include groundwater (groundwater, interstratal pressure and non-pressure water), as well as surface water bodies (rivers, lakes, reservoirs). The chemical composition of water in surface and underground reservoirs is closely related to the chemical composition of the soil (see p. 60).
The soil affects the qualitative composition of the atmosphere. Chemical compounds of various physical and chemical properties, with which the soil is oversaturated due to technogenic pollution, enter the atmospheric air through evaporation, accumulate in the ground layer in concentrations exceeding the maximum permissible, i.e., they reach levels dangerous to human health. The interaction of soil with atmospheric air is an extremely complex process.
It should be noted that the soil has pores, and if it is dry, then they are filled with soil air. The concentrations of gases and vapors in soil air differ from those in the atmosphere. Therefore, diffusion constantly occurs, i.e. movement along a concentration gradient: gaseous substances, which are abundant in the soil air (for example, carbon dioxide), enter the surface layer of the atmosphere and, conversely, gases whose partial pressure in the atmosphere is higher (for example, oxygen ), move into the soil. In addition, there is the so-called soil respiration, which is associated with the simultaneous entry of the entire mixture of gases and vapors that form soil air into the ground layer of the atmosphere when the soil temperature increases and the barometric pressure decreases.
An example of the influence of the chemical composition of the soil on the quality of atmospheric air is the natural mercury biogeochemical province of the Altai Mountains, located in the area where mercury-containing ores occur. The soils of this province contain mercury in concentrations from 0.3 to 12.0 mg/kg, although in the soils of other areas it ranges from 0.04 to 0.12 mg/kg. The level of mercury in the atmospheric air of the province is 7-13 μg/m3, which is also significantly higher than the average background level for mercury vapor in the ground layer of the atmosphere - 0.002 μg/m3. The mercury content in the urine of residents of this area is also increased. In addition, it increased with increasing duration of contact: among preschool children it was 0.014 mg/l, among schoolchildren - 0.021 mg/l, among adults - 0.033 mg/l. There was an increase in the morbidity of the population (diseases of the nervous and endocrine systems, the genitourinary system in men), and a decrease in fertility.
Another example of the influence of soil on the state of atmospheric air is the formation of so-called toxic fog in agricultural fields treated with pesticides. It should be noted that from soil treated with pesticides, especially highly volatile organophosphates, a certain amount of pesticide constantly evaporates. This process lasts until a dynamic equilibrium is reached between the pesticide, which is in the soil, and its vapors in the ground layer of air. As a result, certain concentrations of pesticides are formed in the ground layer of dry air, which in the long term (1-2 weeks) after processing the fields are in most cases low and safe for health. But under certain meteorological conditions that contribute to the formation of fog in the fields, the concentrations of pesticides in the ground air layer can increase significantly. It goes like this. Due to previous rains, the soil is abundantly moistened. During the night the air temperature drops. The soil has a high heat capacity and retains heat better. Therefore, in the morning the soil is warmer than the air. Moisture from the warm surface of the soil evaporates and enters the cold air in the form of steam. It condenses to form a fine water mist (aerosol), which does not dissipate for some time under unfavorable meteorological conditions (temperature inversion, low wind speeds). Pesticide molecules that were in the form of vapor in the ground layer of dry air are sorbed on the surface of tiny droplets of water mist. The surface area of water mist droplets is very large. Now there is no vapor phase of the pesticide in the air. This disrupts the dynamic equilibrium, to achieve which a new portion of the pesticide evaporates from the soil into the air and depends on its physical parameters: water content and dispersity. Water particles of fog are small in size, but are characterized by a large total surface area per unit volume on which pesticide vapors are adsorbed. Due to the adsorption of pesticide molecules on the surface of water mist droplets, their vapor pressure decreases, and to restore equilibrium, an additional portion of pesticides evaporates from the soil surface until adsorption equilibrium and equilibrium vapor pressure are achieved. As a result, the concentration of pesticides in the surface layer of the atmosphere may exceed the MPC by one to several orders of magnitude. Such concentrations are already hazardous to health and can cause acute poisoning.
The above examples indicate that atmospheric air polluted with chemicals migrated from the soil can be hazardous to human health.
Soil as a factor in the transmission of pathogens of infectious diseases and human invasions (epidemiological significance of soil). The epidemiological significance of soil is that in it, despite the antagonism of soil saprophytic microflora, pathogens of infectious diseases can remain viable, virulent and pathogenic for quite a long time. Thus, in the soil, especially in its deep layers, typhoid Salmonella can survive up to 400 days. During this time, they can contaminate underground water supplies and infect humans. Not only pathogenic microorganisms, but also viruses can persist in the soil for quite a long time (Table 46).
Spores of anaerobic microorganisms, which are constantly found in the soil of populated areas, persist in the soil for a particularly long time (20-25 years). These include the causative agents of tetanus, gas gangrene, botulism, and anthrax. A long stay in the soil of these pathogenic microorganisms and their spores is the cause of the occurrence of corresponding infectious diseases when contaminated soil enters a human wound or the consumption of contaminated food products.
Contaminated soil can act as a factor in the transmission of pathogens of both anthroponotic and zoonotic infections to humans. Among anthroponotic ones are intestinal infections of a bacterial nature (typhoid fever, paratyphoid fevers A and B, bacterial and amoebic dysentery, cholera, salmonellosis, escherichiosis), viral etiology (hepatitis A, enteroviral infections - polio, Coxsackie, ECHO) and protozoal nature (amoebiasis, giardiasis). Zooanthroponoses that can spread through the soil include: leptospirosis, in particular the anicteric form, water fever, infectious jaundice, or Vasiliev-Weil disease, brucellosis, tularemia, anthrax. Mycobacterium tuberculosis can also be transmitted through soil. The role of soil in the transmission of helminthic infestations (ascariasis, trichocephalosis, diphyllobothriasis, hookworm disease, strongyloidiasis) is especially great. These infections and infestations are characterized by a fecal-oral transmission mechanism, which is the leading one for intestinal infections, and one of the possible ones for others.
TABLE 46 Survival of some pathogenic microorganisms in soil
The fecal-oral mechanism of transmission of infectious diseases through soil is a multi-stage process characterized by a sequential alternation of three phases: release of the pathogen from the body into the soil; presence of the pathogen in the soil; the introduction of a pathogen into a species-determined organism of a biological host and comes down to the following. Pathogenic microorganisms or eggs of geohelminths with the excrement of a sick person or carrier of infection or a sick animal (in zooanthroponotic infections) enter the soil, in which they retain viability, pathogenic and virulent properties for some time. While in the soil, pathogens of infectious diseases can enter the water of underground and surface sources, and from there into drinking water, from which they enter the human body. In addition, pathogens can get from the soil onto vegetables, berries and fruits, and onto your hands. They are also spread by rodents, flies and other insects. Transmission of infection can occur in the following ways:
There is a known case of an epidemic of typhoid fever that affected 60% of kindergarten students in 36 days. Sand on playgrounds turned out to be contaminated. Typhoid fever pathogens entered children's bodies through sand-contaminated hands. There is evidence of the penetration of typhoid and dysentery pathogens from contaminated soil into groundwater, which led to outbreaks of intestinal infections in the population who used well water.
It should be noted that anthrax spores, mycobacterium tuberculosis, polio viruses, Coxsackie and ECHO, and the causative agents of some other respiratory tract infections can spread with soil dust, i.e., by airborne dust, causing corresponding infectious diseases. In addition, people can become infected with anthrax through direct contact with contaminated soil (through broken skin).
Spore-forming clostridia (Cl. botulinum, Cl. tetani, Cl. perfringens, Cl. histolyticum, etc.) enter the soil mainly with the excrement of animals and people. Clostridium botulism spores are found not only in cultivated but also in uncultivated soil. They were isolated in soil samples from California (70% of cases), the North Caucasus (40%), they were found in the coastal zone of the Azov Sea, in silt and sea water, on the surface of vegetables and fruits, in the intestines of healthy animals, fresh red fish (sturgeon, beluga, etc.), in the intestines (15-20%) and in the tissues (20%) of sleeping fish. Violation of food processing technology at food industry enterprises and at home, especially canned vegetables, meat and fish, as well as when smoking and salting fish, making sausages, leads to the proliferation of botulism bacillus and the accumulation of botulinum toxin. Eating such foods leads to the development of a serious illness with symptoms of damage to the central nervous system.
Spores of the causative agents of tetanus and gas gangrene enter the human body through damaged skin and mucous membranes (small, usually puncture wounds, abrasions, splinters, through necrotic tissue in burns). Soil and soil dust in tetanus are one of the factors of transmission of infection.
Soil plays a specific role in the spread of geohelminthiasis - ascariasis, trichuriasis, hookworm, strongyloidiasis. The (immature) eggs of Ascaris lumbricoides, Trichiuris trichiura, Ancylostoma duodenale and Stronguloides stercoralis released into the soil are not capable of causing invasion. Optimal conditions for the development (ripening) of eggs in the soil are created at a temperature of 12 to 38 ° C, sufficient humidity and the presence of free oxygen. Depending on the conditions, the maturation of geohelminth eggs lasts from 2-3 weeks to 2-3 months. Only after this do they become invasive, that is, capable of causing illness when entering the human body through contaminated hands, vegetables, fruits and other food products. Geohelminth eggs, falling on the soil surface, die, but at a depth of 2.5 to 10 cm, protected from insolation and drying, they remain viable, according to the latest data, for up to 7-10 years.
The epidemiological significance of soil also lies in the fact that soil contaminated with organic substances is a habitat and breeding place for rodents (rats, mice), which are not only carriers, but also sources of many dangerous zooanthroponoses - plague, tularemia, leptospyrosis, rabies.
In addition, flies live and breed in the soil, which are active carriers of pathogens of intestinal and other infectious diseases.
Finally, natural disinfection of wastewater and waste from the pathogenic microorganisms and helminths they contain can occur in the soil.
Soil is a natural environment for the neutralization of liquid and solid household and industrial waste. This is the life support system of the Earth, that element of the biosphere in which detoxification (neutralization, destruction and transformation into non-toxic compounds) of the bulk of exogenous organic and inorganic substances entering it occurs. According to the famous hygienist of the 19th century. Rubner, soil is "... the only place that satisfies all the requirements and is given by nature itself for the neutralization of pollution. But its detoxification ability has a limit, or threshold, of ecological adaptive capacity."
When the threshold of the ecological adaptive capacity of the soil is exceeded, the values of natural self-purification processes characteristic of a given type of soil are violated, and it begins to release biological and chemical pollutants into plants, atmospheric air, surface and groundwater, which can accumulate in environments in contact with the soil in quantities dangerous to the soil. health of people, animals and plants.
Organic substances that enter the soil (proteins, fats, carbohydrates of plant residues, excrement or carcasses of animals, liquid or solid household waste, etc.) decompose until the formation of inorganic substances (mineralization process). In parallel, in the soil there is a process of synthesis from organic waste substances of a new complex organic substance of the soil - humus. The described process is called humification, and both biochemical processes (mineralization and humification), aimed at restoring the natural state of the soil, are its self-purification. This term also refers to the process of liberating soil from biological contaminants, although in this case we should talk about natural processes of its disinfection. As for the processes of self-purification of soil from ECS, it is more correct to call them processes of soil detoxification, and all processes together - processes of soil neutralization.
The process of soil self-purification from foreign organic matter is very complex and is carried out mainly by saprophytic soil microorganisms. Penetration of nutrients necessary for existence into the microbial cell occurs due to osmotic absorption through small pores in the cell wall and cytoplasmic membrane. The pores are so small that complex molecules of proteins, fats and carbohydrates do not penetrate through them. Only when complex substances are broken down into simpler molecules (amino acids, monosaccharides, fatty acids) can nutrients enter the microbial cell.
To implement this method of nutrition, in the process of evolution, microorganisms have developed the ability to release hydrolytic enzymes into the environment, which prepare the complex substances contained in it for assimilation by the microbial cell. All enzymes of microorganisms are divided into two groups according to the place of their action: exoenzymes that act outside the cell, and endoenzymes that act inside the cell. Exoenzymes are involved in preparing nutrients for entry into the cell, and endoenzymes contribute to their absorption. The nature of the action of enzymes is different. Esterases (lipases), which break down fats, are found in many molds and bacteria. Proteases that break down protein molecules are secreted by many putrefactive bacteria, etc.
Carbohydrates (polysaccharides) that enter the soil with waste are converted by exoenzymes (carbohydrases) into di- and monosaccharides, which are absorbed by the microbial cell. Under aerobic conditions, under the influence of endoenzymes, most of the monosaccharides are oxidized during endogenous respiration, and a small part is used for the synthesis of glycogen (see p. 272).
Under anaerobic conditions, the biochemical process of carbohydrate breakdown is much more complex and consists of the formation of fatty acids, followed by their breakdown to organic alcohols, carbon dioxide, methane, hydrogen and other gaseous substances with the release of energy. In this case, microorganisms receive energy. Anaerobic respiration occurs without the participation of free oxygen, but the amount of energy generated is much less than with oxygen respiration.
The breakdown of fats (see p. 273) occurs very slowly, since they are little susceptible to biochemical destruction processes. Under the action of exoenzymes (lipases, esterases), fats are broken down into fatty acids and glycerol, which under aerobic conditions are decomposed by endoenzymes into carbon dioxide and water, releasing energy. Under anaerobic conditions, fatty acids and glycerol are broken down in approximately the same way as carbohydrates, to carbon dioxide, methane, and hydrogen. Volatile fatty acids with an unpleasant odor are also formed. A certain amount of fatty acids is not destroyed, but is used for the synthesis of microbial cell lipids.
The breakdown of proteins also occurs with the participation of saprophytic soil microorganisms, for which protein-containing substances are a source of nitrogen. Under the influence of exoenzymes secreted by microorganisms, complex protein molecules (polypeptides) are broken down into albumins and peptones, and then into amino acids. Many bacteria contain the enzyme tryptase, which directly breaks down proteins into amino acids, bypassing the peptone stage. and
Most of the amino acids, after entering the microbial cell, are used as plastic and energy material by reproducing saprophytic soil microorganisms. Subsequently, after the death of these microorganisms, humus is formed - an organic substance that is part of the soil. The composition of humus, in addition to protein complexes, includes organic acids, hemicellulose, and fats formed as a result of microbial synthesis. Humus contains many saprophytic soil microorganisms; there are no pathogenic microorganisms, with the exception of spore-forming ones. Despite the presence of organic compounds in humus, it does not rot, does not emit gases with an unpleasant odor and does not attract flies.
Humus can be used as an organic fertilizer because it decomposes slowly, gradually releasing nutrients to plants. The process of humus formation is called humification.
Some amino acids undergo deamination to form ammonia, carbon dioxide and water. The process of breaking down proteins into ammonia is called ammonification. Under aerobic conditions, ammonia, dissolving in water, turns into ammonium hydroxide, which, when combined with carbon dioxide, turns into ammonium carbonate.
In addition, ammonium carbonate is also formed due to the autoxidation of protein substances of saprophytic soil microorganisms.
Ammonium carbonate, formed both during deamination and during the death of microorganisms and during the hydrolysis of urea and other products of nitrogen metabolism, undergoes biochemical oxidation with the participation of aerobic bacteria. This process, called nitrification, is carried out in two phases: in the first phase of biochemical oxidation, ammonium salts are converted into nitrogenous compounds (nitrites) by bacteria of the genus Bac. nitrosomonas, and in the second - into nitrogen compounds (nitrates) by bacteria of the genus Vas. nitrobacter.
Nitric acid in the form of minerals (nitrates) is a residual product of the oxidation of protein compounds and their metabolic products.
Simultaneously with oxidation processes in the soil, reduction processes also occur, which are called denitrification. Denitrification is understood as the reduction of nitrates by microorganisms, regardless of whether nitrites, lower nitrogen oxides, ammonia or free nitrogen are formed.
The degree of the restorative effect of bacteria depends not only on their biochemical characteristics, but also on the composition of the environment, its active reaction (pH) and other conditions. Thus, in an alkaline environment under aerobic conditions, the reduction process proceeds until the formation of nitrous acid salts (nitrites); in an acidic environment under anaerobic conditions - to ammonia.
Denitrification in a narrower sense of the word refers to the decomposition of nitrates and nitrites with the release of free nitrogen. If there is no oxygen in the environment or its content is limited, denitrifying bacteria take it from salts of nitric and nitrous acids and simultaneously oxidize nitrogen-free organic compounds, thereby obtaining energy. They also use nitrate nitrogen to build the cytoplasm. This complex process is both reducing and oxidizing (see p. 275).
The hygienic importance of denitrification is very important due to the fact that this process during the operation of soil treatment facilities can become predominant when the air permeability of the soil is disrupted, for example, during the initial period of operation of irrigation fields. The positive thing about this process is that when there is a deficiency of oxygen in the air, nitrate oxygen can be used, and this process prevents them from polluting groundwater. Some of the nitrates formed during the biochemical oxidation of organic substances are absorbed by the root system of plants, and some are denitrified. Nitrate nitrogen can also be used for synthetic processes by microorganisms.
Under conditions conducive to the proliferation of anaerobic microorganisms, intermediate products of protein breakdown are formed (indole, skatole, mercaptans, volatile fatty acids, carbon disulfide, etc.). They are characterized by an unpleasant strong odor. Such conditions are created as a result of soil overload with organic waste, especially in the case of its heavy mechanical composition (medium and heavy sandy loam, loam, clay) and high humidity.
As the soil self-purifies itself from organic contaminants, pathogenic microflora, mainly non-spore-forming microorganisms, also die off. Factors that contribute to the death of pathogenic microorganisms and helminth eggs include bacteriophages and antibiotics present in the soil, solar radiation, and drying out of the soil. All of the above indicates the great hygienic importance of soil self-purification processes, which can be used and even reproduced on artificial structures intended for
Soil is one of the main elements of the natural environment, which can negatively affect human health and living conditions as a result of the migration of various chemical compounds, biological organisms and their metabolic products. Moreover, this influence is carried out indirectly, since, unlike water and atmospheric air, direct human contact with soil in modern conditions is limited, with the exception of the possibility of wound infection.
Soil value:
1. Epidemiological.
The point is that in the soil, despite the antagonism of soil microflora, pathogens of many infectious diseases can remain viable and virulent for a long time. For example, in the soil, especially in its deep layers, the pathogens of typhoid fever can survive up to 400 days, the dysentery bacillus up to 40-57 days. Spores of pathogenic anaerobic microorganisms (spores of tetanus bacillus, the causative agent of gas gangrene, botulism and anthrax) can persist for a long time, up to 20-25 years.
Human infection through contaminated soil can occur in different ways. For example, infection with tetanus and gas gangrene is possible when contaminated soil comes into direct contact with mechanically damaged skin during field work.
Pathogens of intestinal infections can be transmitted in 2 ways: 1) the body of a sick person - soil - groundwater - susceptible organism (outbreaks of typhoid fever, dysentery caused by drinking well water); 2) the patient’s body – soil – food products of plant origin – susceptible organism.
Soil dust can spread pathogens of a number of infectious diseases (mycobacterium tuberculosis, polio viruses, etc.), which are contracted when healthy people inhale such dust.
2. Soil is the environment that determines the circulation of chemicals in the external environment - human system. It is the element of the earth’s biosphere that forms the chemical composition of food, drinking water and atmospheric air consumed by humans. It affects the body through direct contact or through media in contact with the soil along ecological chains.
There are several ways soil can affect the human body:
Through drinking water. Chemical compounds found in the soil with surface runoff enter from the surface into open bodies of water or migrate into the depths of the soil, penetrating into underground horizons (ground and interstratal waters). Contamination of water from surface and underground water sources used in water supply to populated areas may be due to the accumulation of various compounds in the soil. For example, it is possible that nitrates may appear in groundwater due to excessive use of nitrogen mineral fertilizers or organic soil pollution;
Through food (soil – plant – food – man; soil – plant – animals – food – man). Soil is an element of the biosphere that forms the chemical composition of food consumed by humans, since substances that fall into it can accumulate in plants, be included in food chains and thus affect human health;
Through atmospheric air. Chemical substances entering the soil undergo evaporation and sublimation, enter the atmospheric air and can accumulate in it to concentrations exceeding the maximum permissible concentration and reach levels hazardous to humans. This is primarily due to changes in the composition of soil air (accumulation of carbon dioxide, methane, hydrogen in it as a result of soil contamination with organic substances), which can lead to intoxication.
The unfavorable indirect influence of soil on the human body manifests itself in the form of diseases.
The composition of the soil can be determined by natural processes occurring in the earth's crust or by technogenic influence on it. There are territories in which the soil composition is characterized by increased or decreased content of microelements and a violation of their optimal relationship with each other. Such regions are called biogeochemical provinces (natural and artificial).
Natural biogeochemical provinces– these are territories characterized by an anomalous level of content and ratio of microelements, which is caused by natural processes occurring in the earth’s crust. This leads to a corresponding change in the chemical composition of water and food grown in a given area. Populations living in such regions develop endemic diseases.
A low level of iodine in the soil leads to a low iodine content in plants, and then in animal meat, as well as in water. As a result, the population's diet turns out to be deficient in iodine, which becomes the cause of endemic goiter. This disease is associated with the development of endemic cretinism, deafness and mental retardation.
Urovsky disease is also an endemic disease. This is deforming osteoarthritis, which begins at the age of 8-20 years, occurs chronically without characteristic changes in the internal organs. An increased content of strontium and a decreased content of calcium in the soil and plants was revealed, with a lesser deficiency of barium, phosphorus, copper, iodine and cobalt. Microelementosis caused by selenium deficiency (Keshan disease), caries, and fluorosis have also been described.
Artificial (technogenic) provinces– these are territories that are characterized by abnormal content and ratio of macro- and microelements in connection with human economic activity. Their appearance is associated with the use of pesticides, mineral fertilizers, plant growth stimulants, and the release of industrial emissions and wastewater into the soil.
The population living in these provinces for a long time is constantly exposed to the adverse effects of exogenous chemicals, therefore, in these territories there is an increase in the level of morbidity, congenital deformities and developmental anomalies, disorders of physical and mental development.
3. Soil is a natural environment for waste disposal, since it is characterized by a self-purification process. Soil is the element of the biosphere in which detoxification of exogenous organic and inorganic substances entering it occurs.
Sources of soil pollution are divided into chemical (inorganic and organic) and biological (viruses, bacteria, protozoa, helminth eggs, etc.).
Chemicals are divided into the following groups:
1. chemicals introduced into the soil systematically, purposefully (agrochemicals - pesticides, mineral fertilizers, soil structure formers, plant growth stimulants). Agrochemicals are necessary to improve the agrotechnical properties of the soil, increase its fertility and protect cultivated plants from pests. Only in case of excessive application of these drugs do they become soil pollutants;
2. chemical substances that enter the soil accidentally, with man-made liquid, solid and gaseous waste (substances that enter the soil along with domestic and industrial wastewater, atmospheric emissions from industrial enterprises, exhaust gases from vehicles). These compounds can have toxic, allergenic, mutagenic, embryotropic and other effects.
Soil self-cleaning ability
The self-cleaning ability of soil is determined by mechanical, physicochemical, biochemical and biological processes occurring in the soil. The process of neutralizing organic matter is very complex and is carried out mainly by natural soil microflora, represented mainly by saprophytic microorganisms. Since microorganisms do not have special digestive organs, all substances necessary for life enter the cell by osmotic absorption through the smallest pores of the membrane. These pores are so small that complex molecules (proteins, fats, carbohydrates) do not penetrate through them. In the process of evolution, microorganisms have developed the ability to release hydrolytic enzymes into the environment, which prepare the complex substances contained in it for assimilation by the microbial cell. All microbial enzymes are divided into two groups according to the nature of their action: exoenzymes, which act outside the cell, and endoenzymes, which act inside the cell. Exoenzymes are involved in the preparation of nutrients for their absorption by the cell. Endoenzymes promote the absorption of food.
The self-purification process occurs in two directions:
1. mineralization.
Mineralization can occur under aerobic conditions with sufficient oxygen availability and anaerobic conditions.
Under aerobic conditions, the organic substrate decomposes to carbon dioxide, water, nitrates, and phosphates. Polysaccharides that enter the soil are converted into monosaccharides, which are then partially used for the synthesis of glycogen in various microbial cells, and most of them are broken down into carbon dioxide. Fats are broken down into fatty acids with the release of energy. Proteins are broken down into amino acids. Most amino acids are used as plastic material for biosynthesis by microorganisms. The other part undergoes deamination to form ammonia, water and carbon dioxide. Nitrogen-containing organic substances enter the soil not only in the form of protein, but also amino acids and products of protein metabolism (urea). They undergo a process of nitrification - urea, under the influence of urobacteria and their enzyme urease, is hydrolyzed and also forms ammonium carbonate, which is then converted into nitrogenous compounds (nitrites) by bacteria of the genus Bac. Nitrosomonos, and then into nitrogen compounds (nitrates) by bacteria Bac. Nitrobacter. Nitrates are the final product of the breakdown of protein substances and in this form they serve as plant nutrition. In the same way, hydrogen sulfide is converted into sulfuric acid and sulfuric acid salts (sulfates), carbon dioxide into carbon dioxide salts (carbonates), phosphorus into phosphoric acid (phosphates).
Under anaerobic conditions, the decomposition of carbohydrates and fats occurs to hydrogen, carbon dioxide, methane and other gases.
2. humification is a complex biochemical anaerobic process of transformation of a dead organic substrate into a complex organic complex of great agrotechnical and hygienic importance.
From an agrotechnical point of view, humus determines soil fertility. Humus is obtained as a result of the vital activity of microorganisms and is a mass of complex chemical composition rich in organic matter (humin, lignin, carbohydrates, fats, proteins). Humification occurs under natural conditions in the soil and during the neutralization of waste in composts. At a certain stage of decomposition of organic matter, humus becomes stable, slowly decomposes, gradually releasing nutrients to plants. Although humus contains a lot of organic matter, it is not capable of rotting, does not emit an odor, and does not attract flies. During the process of humification, many pathogenic microorganisms die, although the causative agents of some infectious diseases (spores of anthrax bacilli) remain viable for a long time.
(according to K.D. Pyatkin)
The danger of infection undoubtedly exists when a person comes into direct contact with the soil. In such cases, diseases of tetanus and gas gangrene are possible, the causative agents of which are among the spore-bearing anaerobes and are permanent inhabitants of the soil. Tetanus spores are most often found in garden soil fertilized with manure, as well as in other places contaminated with animal excrement. In case of various traumatic injuries to the skin, together with soil particles and dust, tetanus spores enter the damaged tissue and can cause a serious illness, releasing a potent toxin. For the purpose of prevention, it is necessary, even for minor injuries, scratches and abrasions contaminated with soil and dust, to immediately administer anti-tetanus serum.
Athletes should be well aware of this, since skin damage is possible during athletics, football and other sports. When exercising in gyms with contaminated floors, there is also a risk of skin lesions becoming infected.
Soil contaminated by the excretions of animals with anthrax or their carcasses may contain anthrax spores that persist for years. Once in the human body, they germinate and most often cause a skin form of the disease, less often pulmonary and intestinal.
The importance of soil is especially great as a specific factor in the transmission of a number of helminthic diseases, so-called geohelminthiases (ascariasis, hookworm infection, etc.).
Bacterial contamination of soil in populated areas should be taken into account when choosing sites for the construction of outdoor sports facilities. It is often necessary to remove the surface layer of soil and replace it with a new one that satisfies not only sports and technical, but also sanitary and epidemiological requirements. In rural settlements, it is strictly forbidden to allocate areas that were previously used for keeping livestock for sports grounds.
A rational system for the removal and neutralization of sewage and waste plays a decisive role in preventing soil pollution in cities and towns.
Chemical and radioactive soil contamination
In connection with the increasing chemicalization of agriculture, the issue of soil contamination with chemicals used to fertilize the soil and control pests and diseases of agricultural plants and weeds has acquired urgent hygienic importance. Chemicals used as mineral fertilizers, as a rule, have little toxicity. However, on soil oversaturated with fertilizers, root crops grow that contain excessive concentrations of nitrates, causing various serious problems with human health.
Pesticides used to control plant pests and diseases and increase crop yields are, in most cases, highly toxic substances that sometimes have carcinogenic and other harmful properties. Their negative effect on the human body can manifest itself not only through direct contact with them during work, but also as a result of their accumulation in the soil, penetration from it into groundwater, into plants, and with them into the body of animals and then with plant and vegetable products. of animal origin - into the human body. Pesticides cause various acute and chronic poisonings.
In order to prevent their adverse effects on the human body, the Russian Federation has established a list and doses of pesticides allowed for use in agriculture (hexochlorane, metaphos, etc.) and developed rules for their use.
The soil, as already noted, may be subject to radioactive contamination. Subsequently, radioactive isotopes enter the plants, and through them into the body of herbivores.
Hygienic justification for choosing soils for sports facilities
The mechanical, physical and chemical properties of soil are important for physical education and sports. Even in ancient times, people understood the advantages of non-swampy, dry and elevated areas over low-lying, swampy and damp ones. The water, thermal and air regimes of the soil have a great influence on the state of human health and those involved in sports and physical education. High standing soil water causes dampness in sports facilities, high air humidity and, therefore, affects the microclimate of the area. The thermal properties of the ground layer of air depend on the thermal regime of the soil.
At the same time, the soil (a complex of physicochemical properties and structure - the lithosphere) participates in the creation of not only vital conditions of the external environment (biosphere), but also the dispersed environment of the atmosphere. As a result of air movement, soil microelements are dispersed in the external environment. They are vitally important for the normal functioning of the human body and especially physical education and sports activities. When choosing a site for construction of a sports facility, it is necessary to be guided by the basic hygienic requirements for the soil of the sports site:
The area should not be flooded with rain or melt water;
The soil should be dry;
Groundwater must be at a depth of at least 0.7 m;
For the construction of sports facilities, coarse-grained soil is most preferable;
The soil must be epidemically and toxicologically safe.
Test questions and assignments
1 What is soil?
2 Indicate the basic properties of the soil.
3 Indicate the composition and physical properties of the soil
4 What types of soils do you know?
5 Give a hygienic characteristic of the soil
6 What is the epidemiological significance of soil?
7 What hygienic requirements are imposed on the soil when planning and constructing sports facilities?
Chapter 6 HYGIENE OF HARDENING
Hardening is one of the most powerful and effective health-improving means of physical education. It allows you not only to maintain and improve your health, but also to increase your performance.
Under hardening is understood as increasing resilience - adaptation of the human body to the action of various unfavorable climatic factors (cold, heat, solar radiation) due to the use of a set of systematic and targeted measures.
Hardening is organized for a professional (production) purpose (preparation for work in certain climatic conditions in the north, south, in the mountains); for the purpose of general health promotion; increasing mental and physical performance; increasing the human body’s resistance to adverse environmental factors.
Physiological basis of hardening
Hardening is based on training the central and peripheral parts of the thermoregulatory apparatus, improving the mechanisms that regulate the release and generation of heat. Constant systematic and targeted strictly dosed exposure to irritating factors leads to the development of adaptive adaptive reactions that reduce the body's sensitivity to their effects. This increases the human body’s resistance to changing environmental factors. The leading role in this belongs to the human central nervous system.
In the process of onto- and phylogenesis, the human body has developed certain physiological and biochemical mechanisms that ensure its resistance to the effects of a complex of unfavorable meteorological factors. The human body is able to effectively adapt to changes in meteorological and temperature conditions, withstand even significant fluctuations in air temperature, while maintaining the thermal balance of the body.
The body's heat balance is achieved as a result of complex thermoregulatory processes. On the one hand, there is an optimal dynamic fluctuation in the volume and intensity of heat production due to changes in the intensity of redox processes that ensure the formation of thermal energy; on the other hand, there is a simultaneous restructuring of the body’s heat exchange through its heat transfer to the external environment.
At low temperatures, the mechanisms of heat production in the human body are enhanced, while the diameter of skin vessels and the redistribution of blood flow between the skin and internal organs decrease.
The range of functional capabilities of human thermoregulation mechanisms can be significantly expanded after using a set of targeted, systematic hardening procedures.
The mechanism of the healing effect of hardening at the subcellular level is identical to the mechanism of action of physical training: a deficiency of ATP and creatine phosphate is created and the phosphorylation potential increases. The genetic apparatus of cells is activated, the production of mitochondria, the energy “factories” of the cell, increases.
The energy power of the cell (mitochondrial power), the production of ATP per unit of tissue mass increase, its deficiency is eliminated, therefore, adaptation to cold, hypoxia and physical activity develops.
As a result of hardening, not only thermoregulation is improved, but also some changes occur in the morphological structure and physicochemical properties of various body tissues. Repeated temperature irritations cause thickening of the epidermis, a decrease in water content in the skin, compaction of biological calloids, etc. This increases the body’s resistance to adverse meteorological environmental factors.
Activation of energy processes helps normalize fat and carbohydrate metabolism and plays a positive role in the prevention of atherosclerosis, hypertension, diabetes and obesity.
During hardening, immune mechanisms are sharply activated. Through the central nervous system and its subcortical formations (hypothalamus), the functional state of the pituitary gland, an endocrine gland that controls the action of all endocrine glands, is activated. Of primary importance in increasing immunity during hardening procedures is the effect of the pituitary gland on the thymus (thymus) gland and adrenal glands. The functioning of the main immune mechanisms - lymphocytes and antibodies - depends on this gland, as a result of which the body’s resistance to various infections caused by bacteria and viruses is significantly increased, control over the appearance of foreign malignant cells is improved, they are destroyed, which creates an obstacle to the development of cancer.
The functioning of the adrenal cortex is accompanied by an increase in the formation of its hormone - cortisone. This enhances the action of immune mechanisms, reduces the possibility of allergic reactions and diseases, increases the body’s adaptive abilities to stress and, in particular, to such factors as excessive physical activity, climatic factors, mental irritants, and excessive neuro-emotional stress.
Thus, cold hardening improves health, increases mental and physical performance, resistance to infectious, allergic, malignant diseases, atherosclerosis, obesity, and diabetes. Hardening allows athletes to quickly adapt to training loads, achieving a more effective impact. The risk of adverse effects on the body from physical and mental stress is reduced, and the risk of decreased immune defense at the peak of athletic form is reduced.
The result depends on the type of hardening factor (air, water, sun), the method of its application (rubbing, bathing, showering, swimming), physical activity during this period, the intensity and duration of the procedures, and the level of hardening. The local effect of procedures is especially important, for example, hardening of the nasopharynx, legs, and chest for the prevention of upper respiratory tract infections.
The intensity of the procedures should increase gradually, as the body quickly adapts to the hardening measures. Therefore, their use should be systematic, daily or even twice a day.
If hardening is irrational, acute and chronic diseases of the upper respiratory tract (runny nose, sinusitis, bronchitis, tonsillitis, pneumonia), kidneys (nephritis), and joints (arthritis) may develop. This most often occurs when the principle of matching the strength of the stimulus with the age-sex functional capabilities and individual characteristics of the body is violated.
Hygienic principles of hardening
The principle of complexity. The greatest healing effect of hardening is possible only with the simultaneous targeted use of a complex of various hardening agents (sun, air, water).
The principle comes from the physiological essence of hardening. The physiological effects on the body of each agent used are complementary during the hardening process, which expands the range of compensatory and adaptive reactions of the body and enhances the healing effects of hardening.
The principle of systematicity. The hardening agent will have a healing effect only if it is used regularly, without long breaks. Repeated and systematic short-term thermal effects with a gradual increase in the strength of irritation lead to the formation of a stable adaptation of the human body to a specific stimulus. Response reflex reactions change significantly during the hardening process, and some of them fade away, and in their place new ones arise that have a greater adaptive effect. In establishing new functional relationships between the body and the environment, the leading role is played by the formation of conditioned reflex nerve connections, ensuring the effective adaptability of the body to changing temperature conditions. Hardening procedures must be applied day after day, and not from time to time, since trace reactions that occur after individual procedures are not properly fixed. In case of forced long breaks, hardening is resumed with weaker procedures compared to those used the previous time.
The principle of gradualism: stepwise increase in the strength of the influencing stimuli. For example, when starting water procedures, you need to start with cool water and gradually move to colder water.
The principle of optimal dosing of procedures. The correct dosage is the one that best suits the functional characteristics and capabilities of a particular person, including his state of health. Therefore, all hardening procedures and techniques are strictly age-specific. When choosing a hardening agent, the main thing is the strength of the stimulus, and not the duration of its effect. In this regard, hardening sessions should not be excessively increased.
Hardening using low temperatures
Physiological basis of cold hardening. The main hygienic significance of different ambient temperatures is their effect on the body’s heat exchange with the environment: high temperatures make it difficult to return, while low temperatures, on the contrary, increase it. Thanks to the perfection of thermoregulatory mechanisms integrated and controlled by the central nervous system, a person is able to adapt to different temperature conditions and can briefly tolerate even significant deviations from optimal temperatures.
Changes in external temperature activate the physiological mechanisms of heat production and its release into the environment: a person, on the one hand, changes the conditions of heat loss, and on the other, effectively adapts to the external temperature, changing the amount of heat generated.
The change in heat production is explained by chemical thermoregulation. At low air temperatures (starting from +15°C), the breakdown of nutrients in the body, which serves as a source of thermal potential energy, increases, while at high temperatures (above +25°C) it decreases. Activation of metabolism at low temperatures also occurs due to involuntary muscle contraction (muscle tremors).
Heat transfer occurs on the basis of physical thermoregulation. With temperature stimulation of skin thermoreceptors, the lumen of the peripheral vessels of the skin changes. If the temperature is low, they narrow, blood moves to deep-lying tissues, to the internal organs, protecting them from cooling. At the same time, the skin temperature decreases, and the difference between it and the ambient temperature becomes smaller, which reduces heat transfer. If the air temperature is high, blood vessels dilate, blood flow to the periphery increases, skin temperature rises and increased heat transfer occurs. The bulk of heat is lost from the surface of the skin as a result of:
radiation to colder surrounding objects (about 45%);
convection, i.e. layer-by-layer heating of air adjacent to the body and usually in some movement (about 30%);
evaporation of moisture from the skin and mucous membranes of the respiratory tract (about 25%).
The rest of the heat is spent on warming food, inhaled air and is lost through excretions - up to 10%. In a state of rest and thermal comfort, heat loss by convection is 15.3%, by radiation - 55.6, by evaporation - 29.1%.
The given values of heat losses are approximate and typical for a state of rest at room temperature. At high or low ambient temperatures and during physical work, they change significantly. Starting from a temperature of +30°C, heat transfer through radiation and convection decreases and evaporation increases, which becomes the only way of heat transfer at temperatures above +37°C. Heat transfer by convection also occurs upon contact with soil or other colder surfaces.
Thanks to the regulation of heat generation and heat transfer, the human body is able to maintain a constant body temperature even with significant fluctuations in ambient temperature, but the limits of thermoregulation are far from unlimited.
Hardening is carried out when the skin and mucous membranes of the upper respiratory tract are exposed to low ambient temperatures.
The skin consists of two layers: the upper - epidermis (epithelial cells with an outer layer of keratinized scales) and the lower - dermis, which is a conglomerate of blood and lymphatic vessels, sweat glands, hair follicles, nerve receptors located in the supporting connective tissue.
There are three phases in the body’s reaction to the action of a temperature stimulus (air or water procedure).
In the first phase (when inhaling cold air), a spasm of small arteries (arterioles) occurs in the skin and mucous membranes of the upper respiratory tract, blood supply and skin temperature decrease, due to which heat transfer decreases. Thus, a constant body temperature is maintained. In less hardened people, the first phase is more pronounced both in terms of the degree of decrease in the temperature of the skin and mucous membranes, and in the duration of this reaction.
This feature of the body’s reaction is used to determine the degree of hardening. A vessel with cold water (for example, 4 °C) is applied to the skin and the degree of decrease in local temperature at the site of contact and the duration of its recovery are determined.
The first phase of the reaction to cold serves as a trigger for the development of the second phase. Reflexively, through the neuroendocrine system, metabolism increases, energy production by skeletal muscles, liver, and internal organs increases, blood supply increases, skin vessels dilate, and the number of capillaries functioning in the skin increases.
In the second phase, the body maintains a constant body temperature due to more intense heat production. These processes are especially important in the hardening mechanism.
When carrying out each hardening procedure, it is necessary to achieve this phase and prevent the development of the third phase, since it appears due to overstrain and disruption of regulatory and protective mechanisms and serves as a sign of an overdose of the hardening procedure. In this phase, the blood flow in the skin slows down, it acquires a bluish tint, “goose bumps” appear, and the person feels an unpleasant chill.
The hardening effect is manifested in a faster onset and persistent retention of the second phase of the reaction. As hardening occurs, the intensity of cold irritation increases. However, there is specificity in the development of physiological mechanisms of hardening depending on the strength of cold irritation.
The body can adapt to the action of predominantly moderate, but long-term cooling factors (long stay in the air with a moderate decrease in temperature, long-term swimming in moderately cold water) or to strong, but relatively short-term cold factors (swimming in ice water - winter swimming).
The first type of hardening obviously plays a more important role in preserving and improving human health, increasing its resistance to the action of infectious and non-infectious environmental factors. And not only because of the characteristics of physiological reactions, but also due to the greater prevalence of these factors in everyday life and industrial conditions and due to the availability of hardening.
Hygienic standards for air hardening
Air baths begin to be taken at a room temperature of +18...+20°C, fully or partially exposing the body (up to panties, a bathing suit). Starting with a 10-minute duration of the procedure, it is increased daily by 3-5 minutes and up to 30-50 minutes. Depending on age and health status, hardening is stopped at a temperature of +12...+15° C. The criterion for the adequacy of the procedure to the functional capabilities of the body is well-being. The appearance of a feeling of chills, “goose bumps” indicates an overdose of hardening procedures.
It is very effective to combine air hardening with simultaneous physical exercises (Tables 20, 21).
Epidemiological significance of soil is that in it, despite the antagonism of soil saprophytic microflora, pathogens of infectious diseases can remain viable, virulent and pathogenic for quite a long time. Thus, in the soil, especially in its deep layers, typhoid Salmonella can survive up to 400 days. During this time, they can contaminate underground water supplies and infect humans. Not only pathogenic microorganisms, but also viruses can persist in the soil for quite a long time.
Spores of anaerobic microorganisms, which are constantly found in the soil of populated areas, persist in the soil for a particularly long time (20-25 years). These include the causative agents of tetanus, gas gangrene, botulism, and anthrax. A long stay in the soil of these pathogenic microorganisms and their spores is the cause of the occurrence of corresponding infectious diseases when contaminated soil enters a human wound or the consumption of contaminated food products.
Contaminated soil can act as a factor in the transmission of pathogens of both anthroponotic and zoonotic infections to humans. Among anthroponotic ones are intestinal infections of a bacterial nature (typhoid fever, paratyphoid A and B, bacterial and amoebic dysentery, cholera, salmonellosis, escherichiosis), viral etiology (hepatitis A, enteroviral infections - polio, Coxsackie, ECHO) and protozoal nature (amoebiasis , giardiasis). Zooanthroponoses that can spread through the soil include: leptospirosis, in particular the anicteric form, water fever, infectious jaundice, or Vasiliev-Weil disease, brucellosis, tularemia, anthrax. Mycobacterium tuberculosis can also be transmitted through soil. The role of soil in the transmission of helminthic infestations (ascariasis, trichocephalosis, diphyllobothriasis, hookworm disease, strongyloidiasis) is especially great. These infections and invasions are characterized by a fecal-oral transmission mechanism, which is the leading one for intestinal infections, and one of the possible ones for others.
Fecal-oral mechanism of transmission of infectious diseases through the soil - a multi-stage process characterized by a sequential alternation of three phases: release of the pathogen from the body into the soil; presence of the pathogen in the soil; the introduction of a pathogen into a species-determined organism of a biological host and comes down to the following. Pathogenic microorganisms or eggs of geohelminths with the excrement of a sick person or carrier of infection or a sick animal (in zooanthroponotic infections) enter the soil, in which they retain viability, pathogenic and virulent properties for some time. While in the soil, pathogens of infectious diseases can enter the water of underground and surface sources, and from there into drinking water, from which they enter the human body. In addition, pathogens can get from the soil onto vegetables, berries and fruits, and onto your hands. They are also spread by rodents, flies and other insects.
There is a known case of an epidemic of typhoid fever that affected 60% of kindergarten students in 36 days. Sand on playgrounds turned out to be contaminated. Typhoid fever pathogens entered children's bodies through sand-contaminated hands. There is evidence of the penetration of typhoid and dysentery pathogens from contaminated soil into groundwater, which led to outbreaks of intestinal infections in the population who used well water.
It should be noted that anthrax spores, mycobacterium tuberculosis, polio viruses, Coxsackie and ECHO, and the causative agents of some other respiratory tract infections can spread with soil dust, i.e., by airborne dust, causing corresponding infectious diseases. In addition, people can become infected with anthrax through direct contact with contaminated soil (through broken skin).
Spore-forming clostridia enter the soil mainly with animal and human excrement. Clostridium botulism spores are found not only in cultivated but also in uncultivated soil. They were isolated in soil samples from California (70% of cases), the North Caucasus (40%), they were found in the coastal zone of the Azov Sea, in silt and sea water, on the surface of vegetables and fruits, in the intestines of healthy animals, fresh red fish (sturgeon, beluga, etc.), in the intestines (15-20%) and in the tissues (20%) of sleeping fish. Violation of food processing technology at food industry enterprises and at home, especially canned vegetables, meat and fish, as well as when smoking and salting fish, making sausages, leads to the proliferation of botulism bacillus and the accumulation of botulinum toxin. Eating such foods leads to the development of a serious illness with symptoms of damage to the central nervous system.
Spores of the causative agents of tetanus and gas gangrene enter the human body through damaged skin and mucous membranes (small, usually puncture wounds, abrasions, splinters, through necrotic tissue in burns). Soil and soil dust in tetanus are one of the factors of transmission of infection.
Soil plays a specific role in the spread of geohelminthiasis - ascariasis, trichuriasis, hookworm, strongyloidiasis. The (immature) eggs of Ascaris lumbricoides, Trichiuris trichiura, Ancylostoma duodenale and Stronguloides stercoralis released into the soil are not capable of causing invasion. Optimal conditions for the development (ripening) of eggs in the soil are created at a temperature of 12 to 38 ° C, sufficient humidity and the presence of free oxygen. Depending on the conditions, the maturation of geohelminth eggs lasts from 2-3 weeks to 2-3 months. Only after this do they become invasive, that is, capable of causing illness when entering the human body through contaminated hands, vegetables, fruits and other food products. Geohelminth eggs, falling on the soil surface, die, but at a depth of 2.5 to 10 cm, protected from insolation and drying, they remain viable, according to the latest data, for up to 7-10 years.
The epidemiological significance of soil also lies in the fact that soil contaminated with organic substances is a habitat and breeding place for rodents (rats, mice), which are not only carriers, but also sources of many dangerous zooanthroponoses - plague, tularemia, leptospirosis, rabies.
In addition, flies live and breed in the soil, which are active carriers of pathogens of intestinal and other infectious diseases.
Finally, natural disinfection of wastewater and waste from the pathogenic microorganisms and helminths they contain can occur in the soil.
Soil is a natural environment for the neutralization of liquid and solid household and industrial waste. This is the life support system of the Earth, that element of the biosphere in which detoxification (neutralization, destruction and transformation into non-toxic compounds) of the bulk of exogenous organic and inorganic substances entering it occurs. According to the famous hygienist of the 19th century. Rubner, soil is "... the only place that satisfies all the requirements and is given by nature itself for the neutralization of pollution. But its detoxification ability has a limit, or threshold, of ecological adaptive capacity." When the threshold of the ecological adaptive capacity of the soil is exceeded, the values of natural self-purification processes characteristic of a given type of soil are violated, and it begins to release biological and chemical pollutants into plants, atmospheric air, surface and groundwater, which can accumulate in environments in contact with the soil in quantities dangerous to the soil. health of people, animals and plants.
Organic substances that enter the soil (proteins, fats, carbohydrates of plant residues, excrement or carcasses of animals, liquid or solid household waste, etc.) decompose until the formation of inorganic substances (mineralization process). In parallel, in the soil there is a process of synthesis from organic waste substances of a new complex organic substance of the soil - humus. The described process is called humification, and both biochemical processes (mineralization and humification), aimed at restoring the natural state of the soil, are its self-purification. This term also refers to the process of liberating soil from biological contaminants, although in this case we should talk about natural processes of its disinfection. As for the processes of self-purification of soil from ECS, it is more correct to call them processes of soil detoxification, and all processes together - processes of soil neutralization. G
Soil self-purification process removal of foreign organic matter is very complex and is carried out mainly by saprophytic soil microorganisms. Penetration of nutrients necessary for existence into the microbial cell occurs due to osmotic absorption through small pores in the cell wall and cytoplasmic membrane. The pores are so small that complex molecules of proteins, fats and carbohydrates do not penetrate through them. Only when complex substances are broken down into simpler molecules (amino acids, monosaccharides, fatty acids) can nutrients enter the microbial cell. To implement this method of nutrition, in the process of evolution, microorganisms have developed the ability to release hydrolytic enzymes into the environment, which prepare the complex substances contained in it for assimilation by the microbial cell. All enzymes of microorganisms are divided into two groups according to the place of their action: exoenzymes that act outside the cell, and endoenzymes that act inside the cell. Exoenzymes are involved in preparing nutrients for entry into the cell, and endoenzymes contribute to their absorption. The nature of the action of enzymes is different. Esterases (lipases), which break down fats, are found in many molds and bacteria. Proteases that break down protein molecules are secreted by many putrefactive bacteria, etc.
1. The reason for the development of methemoglobinemia in humans may be the introduction into the soil of:
a) potash fertilizers
b) phosphate fertilizers
c) nitrogen fertilizers
d) pesticides
2. If contaminated soil gets into a human wound, it can cause the development of:
a) cholera
b) salmonellosis
c) gas gangrene
d) tetanus
3. Indicators of the sanitary condition of the soil are:
a) sanitary number
b) coli titer
c) titer of anaerobes
d) the number of helminth eggs per gram of soil
e) number of earthworms per square meter of soil
4. The following pathogens cannot remain viable in the soil for a long time:
a) Bac.anthracis
c) Cl.perfringens
d) Cl.Botulinum
5. “Healthy soil” should be:
a) coarse-grained, wet, highly porous
b) coarse-grained, dry, with low porosity
c) fine-grained, dry, low porosity
d) fine-grained, wet, with high porosity
6.Soil has a great influence on:
a) microclimate of the area
b) microrelief of the area
c) construction and improvement of populated areas
d) development of vegetation
7.Transmission of pathogens of intestinal diseases to humans from soil occurs:
a) through food products
b) through damaged skin
c) with water from underground sources
d) from surface waters
8.Select the appropriate indicators of standards characteristic of clean soil:
9. Soil is a transmission factor for which infectious diseases:
a) tuberculosis
c) typhoid fever
d) dysentery
e) diphtheria
e) anthrax
10. An increased content of nitrates in the soil with a low amount of chlorides indicates:
a) about long-standing soil contamination
b) about recent soil contamination
c) about constant soil pollution
d) about periodic soil contamination
11.Find the logically correct endings of the statements:
12.Select the appropriate characteristics:
13.Choose the correct conclusions:
14. Choose the correct conclusions.