Vapors, gases, liquids, aerosols, chemical compounds, mixtures, when in contact with the human body, may cause changes in health or disease. Human exposure to hazardous substances can be accompanied by poisoning and injury.

Toxic substances enter the human body through Airways(inhalation penetration), gastrointestinal tract and skin. The degree of poisoning depends on their state of aggregation (gaseous and vaporous substances, liquid and solid aerosols) and on the nature technological process(heating the substance, grinding, etc.).

The overwhelming majority of occupational poisoning is associated with the inhalation of harmful substances into the body, which is the most dangerous, since the large suction surface of the pulmonary alveoli, intensively washed with blood, causes a very rapid and almost unhindered penetration of poisons to the most important vital centers.

Admission toxic substances through the gastrointestinal tract in a production environment is quite rare. This happens due to violation of personal hygiene rules, partial ingestion of vapors and dust penetrating the respiratory tract, and non-observance of safety rules when working in chemical laboratories. It should be noted that in this case, the poison enters the liver through the portal vein system, where it is converted into less toxic compounds.

Substances that are highly soluble in fats and lipoids can enter the bloodstream through intact skin. Severe poisoning is caused by substances with increased toxicity, low volatility, and rapid solubility in the blood. These substances include, for example, nitro and amino products of aromatic hydrocarbons, tetraethyl lead, methyl alcohol, etc.

Toxic substances are distributed unevenly in the body, and some of them are capable of accumulating in certain tissues. Here it is especially possible to highlight electrolytes, many of which very quickly disappear from the blood and are concentrated in individual bodies... Lead accumulates mainly in the bones, manganese - in the liver, mercury - in the kidneys and colon. Naturally, the peculiarity of the distribution of poisons can to some extent be reflected in their further fate in the body.

Entering the circle of complex and diverse life processes, toxic substances undergo various transformations in the course of oxidation, reduction and hydrolytic cleavage reactions. The general direction of these transformations is most often characterized by the formation of less toxic compounds, although in some cases more toxic products can be obtained (for example, formaldehyde during the oxidation of methyl alcohol).

The release of toxic substances from the body often occurs in the same way as the intake. Non-reactive vapors and gases are partially or completely removed through the lungs. A significant amount of poisons and products of their transformation are excreted through the kidneys. A certain role for the excretion of poisons from the body is played by the skin, and this process is mainly performed by the sebaceous and sweat glands.

The toxic effect of certain harmful substances can manifest itself in the form of secondary lesions, for example, colitis with arsenic and mercury poisoning, stomatitis with lead and mercury poisoning, etc.

The danger of harmful substances to humans is largely determined by their chemical structure and physicochemical properties. Of no small importance in relation to toxic effects is the dispersion of a chemical substance that penetrates into the body, and the higher the dispersion, the more toxic the substance.

By the nature of the effect on the human body, chemicals are divided into:

General toxic chemicals (hydrocarbons, alcohols, aniline, hydrogen sulfide, hydrocyanic acid and its salts, mercury salts, chlorinated hydrocarbons, carbon monoxide), which cause disorders of the nervous system, muscle cramps, disrupt the structure of enzymes, affect hematopoietic organs, interact with hemoglobin ...

· Irritants (chlorine, ammonia, sulfur dioxide, acid mists, nitrogen oxides, etc.) affect the mucous membranes, upper and deep respiratory tract.

Sensitizing substances (organic azo dyes, dimethylaminoazobenzene and other antibiotics) increase the body's sensitivity to chemicals, and in industrial conditions lead to allergic diseases

Carcinogenic substances (benz (a) pyrene, asbestos, nitroazo compounds, aromatic amines, etc.) cause the development of all cancer... This process can be remote from the moment of exposure to the substance for years and even decades.

· Mutagenic substances (ethyleneamine, ethylene oxide, chlorinated hydrocarbons, lead and mercury compounds, etc.) affect non-sex (somatic) cells that are part of all human organs and tissues, as well as reproductive cells (gametes). The effect of mutagenic substances on somatic cells causes changes in the genotype of a person in contact with these substances. They are found in the remote period of life and are manifested in premature aging, increased overall morbidity, and malignant neoplasms. When exposed to germ cells, the mutagenic effect affects the next generation, sometimes in very distant terms.

Chemicals that affect human reproductive function ( boric acid, ammonia, many chemicals in large quantities), cause the occurrence of congenital malformations and deviations from the normal structure in the offspring, affect the development of the fetus in the uterus, postpartum development and the health of the offspring.

The last three types of harmful substances (mutagenic, carcinogenic, and affecting reproductive capacity) are characterized by long-term consequences of their effect on the body. Their effect is not manifested during the period of exposure and not immediately after its end. And in remote periods, years and even decades later.

The maximum permissible concentration (MPC) of hazardous substances is the maximum concentration of a hazardous substance, which for a certain time of exposure does not affect the health of a person and his offspring, as well as the components of the ecosystem and the natural community as a whole.

Harmful substances according to the degree of impact on the human body are divided into four hazard classes:

- (> first class - extremely dangerous with MPC< 0,1 МГ/МЗ (свинец, ртуть - 0,001 мг/м з);

- (> second class - highly hazardous with MPC = 0.1 ... 1 mg / m3 (chlorine - 0.1 mg / m3; sulfuric acid - 1 mg / m3);

- (> third class - moderately hazardous with maximum permissible concentration = 1.1 ... 1 O mg / m3 (methyl alcohol - 5 mg / m3; dichloroethane - 10 mg / m3));

- (> fourth class - low-hazard with MPC> 1 O mg / m3 (for example, ammonia - 20 mg / m3; acetone - 200 mg / m3; gasoline, kerosene - 300 mg / m3; ethyl alcohol 1000 mg / m Z).

By the nature of the impact on the human body, harmful substances can be divided into groups: irritating (chlorine, ammonia, hydrogen chloride, etc.); asphyxiant (carbon monoxide, hydrogen sulfide, etc.); narcotic (nitrogen under pressure, acetylene, acetone, carbon tetrachloride, etc.); somatic, infringing activities of the body (lead, benzene, methyl alcohol, arsenic).

Measures for the prevention of occupational poisoning include hygienic rationalization of the technological process, its mechanization and sealing.

An effective remedy is to replace poisonous substances harmless or less toxic. Hygienic regulation is of great importance in improving working conditions, limiting the content of harmful substances by establishing maximum permissible concentrations in the air of the working area and on the skin. For this purpose, hygienic standardization of raw materials and products is carried out, which provides for the limitation of the content of toxic impurities in industrial raw materials and finished products, taking into account their harmfulness and danger.

A large role in the prevention of occupational intoxication belongs to the mechanization of the production process, which makes it possible to carry out it in a closed apparatus and minimizes the need for a worker to come into contact with toxic substances (mechanical loading and unloading of fertilizers, washing and detergents). Similar tasks are solved when sealing industrial equipment and premises that emit toxic gases, vapors and dust. A reliable means of combating air pollution is the creation of a certain vacuum, which prevents the release of toxic substances through the existing leaks.

The sanitary measures include the ventilation of working rooms. Operations with especially toxic substances should be carried out in special fume hoods with powerful suction or in closed equipment.

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Ministry of Education of the Russian Federation

Kazan National Technical University named after A.N. Tupolev

Department of General Chemistry and Ecology

abstract

Discipline: Toxicology

Topic: Ways of penetration of poisons into the body

Kazan, 2013

General concepts of poisons and poisoning

Poisoning is a disease caused by the introduction of toxic substances into the body.

Poison is a relative concept, since various poisonous substances, depending on their properties and quantities, can be not only useful, but also necessary for the body. However, the same substances, taken in large quantities, can cause health problems and even death. So, table salt, introduced in usual quantities, is a necessary food product, but 60 - 70 g of it cause the phenomena of poisoning, and 300 - 500 g - death; even ordinary water, taken in large quantities, can cause poisoning and death. When distilled water is ingested, poisoning phenomena are observed, its introduction into the blood can result in death. It is generally accepted that poisons include those substances that, when introduced into the body in minimal quantities, cause severe distress or death. In some cases, it is difficult to draw a sharp line between poison and medicine.

The study of poisoning is dealt with by the science of poisons - toxicology. She studies the physical and chemical properties of poisons, harmful effects, ways of entry, the transformation of poisons in the body, means of preventing and treating poisoning and the possibility of using the action of poisons in medicine and industry.

For the onset of poisoning, a number of conditions are necessary. One of them is the penetration of a poisonous substance into the blood, and through it into the cells of organs and tissues. This disrupts the course of normal processes, changes or destroys the structure of cells and entails their death. For poisoning to occur, a certain amount of poison must be injected. Symptoms, severity, duration of the course and outcome of poisoning depend on the amount of injected poison.

For all potent and toxic substances, the State Pharmacopoeia has established doses that doctors are guided by in their practice. The dose can be therapeutic, toxic, and lethal. A therapeutic dose is a certain minimum amount of a potent or poisonous substance that is used with therapeutic purpose; toxic - causes a health disorder, i.e. poisoning phenomena; the lethal dose is the minimum amount of poison per kilogram of weight that can cause death.

At the same dose, the concentration of the poison in the body is not the same: the greater the body weight, the lower the concentration of the poison, and vice versa. The same dose affects people in different ways. Injection of a certain amount of poison to a large, physically strong person can pass without any complications, but the dose taken by a thin and weak person can be toxic. With an increase in the dose, the toxic effect increases disproportionately: an increase in the dose by 2 times can increase the toxicity by 15 or more times.

The pharmacopoeia has established different doses for adults and children. Children are hypersensitive to poisons, in particular to drugs. Hypersensitivity to poisons is observed in the elderly, as well as in women, especially during menstruation or pregnancy. The course and outcome of poisoning worsens the presence of the victim various diseases internal organs, especially the liver, kidneys, heart. Thus, the development, course and outcome of poisoning depend not only on the dose of the poison, but also on the state of the organism.

One of the necessary conditions for the development of chronic poisoning is the so-called accumulation of poison, that is, its gradual accumulation in some organs and tissues. This can occur in cases where conditions are created for the constant intake of small doses of poison into the body. In this case, an important role is played by the violation of the processes of excretion of poison from the body, since the accumulation process is mainly expressed in the ratios between the intake of a poisonous substance and its excretion from the body.

A necessary condition for the development of poisoning is the physical state of the poison, which is of great importance in the process of its absorption and assimilation. Insoluble in water, in gastrointestinal tract poisonous substances, as a rule, are harmless to the body: they are not absorbed, or are absorbed into the blood in small quantities. Soluble toxic substances are quickly absorbed and therefore act much faster, for example, barium chloride salt, which is readily soluble in water, is very toxic, and barium sulfate, insoluble in water and body fluids, is harmless and is widely used in X-ray diagnostic practice. The strong poison of curare, introduced through the mouth, does not cause the phenomena of poisoning, since it is absorbed very slowly, and is excreted from the body much faster, but the same amount of poison introduced into the blood leads to death. Great importance has a concentration of poison. So, highly diluted hydrochloric acid almost harmless to the body, and concentrated is the strongest poison. Gaseous poisons act especially quickly; getting through the lungs into the blood, they are immediately carried throughout the body, showing their inherent properties.

One of the conditions for the development of poisoning is the quality of the poison, that is, its chemical purity. Often a poisonous substance is introduced into the body with various impurities that can enhance or weaken the effect of the poison, and sometimes even neutralize it.

Ways of entry of poisons into the body

Poisons can enter the human body through the respiratory system, digestive tract and skin. Moreover, the main ones are the respiratory tract. Poisons that penetrate through them have on the body more strong action than the poisons that penetrate the intestines, since in the first case they directly enter the bloodstream, and in the second they pass through the liver, which detains and partially neutralizes them.

In investigative and forensic practice, there are cases of the introduction of poison intravenously, subcutaneously, as well as into the vagina and rectum. In the stomach, the poison is absorbed relatively slowly due to the fact that the inner wall is covered with a mucous layer, which prevents the rapid penetration of the poison into the blood. But some poisons, such as hydrocyanic acid compounds, are absorbed very quickly. Poisons, being in the stomach, often cause irritation of its walls, as a result of which vomiting occurs and part or all of the poisonous substance is excreted. When the stomach is full, the poison is absorbed more slowly than when it is empty. The most complete absorption occurs in the small intestine.

Through the lungs, poisoning occurs with poisonous gases and vapors, such as carbon monoxide, hydrogen sulfide, and hydrocyanic acid vapor. At appropriate concentrations, poisoning occurs very quickly due to the ease of passage of the poison through the alveoli of the lungs and getting it into the blood.

Some poisons, for example, mercury preparations, easily penetrate the body through the skin, and the integrity of the surface layer of the skin - the epidermis; wounds, abrasions and, in general, places devoid of the epidermis are more vulnerable to the penetration of poisons into the body.

In the rectum and in the vagina, absorption occurs quickly enough. Vaginal poisoning can occur with the use of a poisonous substance for the purpose of a criminal abortion, as well as with medical errors.

The entry of the substance through the lungs

The huge surface of the pulmonary alveoli (about 80-90 m2) provides intensive absorption and a quick effect of the action of poisonous vapors and gases present in the inhaled air. In this case, in the first place, the lungs become the "gateway" for those of them that are readily soluble in fats. Diffusing through the alveolar-capillary membrane with a thickness of about 0.8 microns, which separates the air from the bloodstream, the molecules of the poison in the shortest way penetrate into the pulmonary circulation and then, bypassing the liver, through the heart reach blood vessels a large circle.

The possibility of a substance entering through the lungs is primarily determined by its state of aggregation (steam, gas, aerosol) This way of penetration of industrial poisons into the body is the main and most dangerous, since the surface of the pulmonary alveoli occupies a significant area (100-120 m2), and the blood flow in the lungs is sufficient intense.

The rate of absorption of chemicals into the blood depends on their state of aggregation, solubility in water and biological media, partial pressure in the alveolar air, the magnitude of pulmonary ventilation, blood flow in the lungs, the state of the lung tissue (the presence of inflammatory foci, transudates, exudates), the nature of the chemical interaction with biosubstrates of the respiratory systems.

The intake of volatile chemicals (gases and vapors) into the blood is subject to certain patterns. Non-reactive and reactive gases and vapors are absorbed differently. The absorption of non-reactive gases and vapors (hydrocarbons of the fatty and aromatic series and their derivatives) is carried out in the lungs according to the principle of simple diffusion in the direction of decreasing the concentration gradient.

For non-reactive gases (vapors), the distribution coefficient is constant. By its value, one can judge the danger of severe poisoning. Gasoline vapors (K - 2.1), for example, at high concentrations, can cause instant acute and even fatal poisoning. Acetone vapors, which have a high distribution coefficient (K = 400), cannot cause acute, especially fatal poisoning, since acetone, unlike gasoline, saturates the blood more slowly.

When reactive gases are inhaled, the saturation of body tissues does not occur due to their rapid chemical transformation. The faster the processes of biotransformation of poisons pass, the less they accumulate in the form of their products. Sorption of reacting gases and vapors occurs at a constant rate. The percentage of the sorbed substance is in direct proportion to the volume of respiration. As a result, the danger of acute poisoning is the more significant, the longer a person is in a polluted atmosphere, the development of intoxication can be promoted by physical work performed in a heated microclimate.

The point of application of the action of the reacting gases and vapors can be different. Some of them (hydrogen chloride, ammonia, sulfur (IV) oxide), which dissolve well in water, are sorbed mainly in the upper respiratory tract, substances (chlorine, nitric oxide (IV)), which are less soluble in water, penetrate into the alveoli and are sorbed into mostly there.

Penetration of poisons through the skin

The skin is one of the possible routes for the entry of poisons into the body. Only lipid-soluble substances penetrate the epidermis. Water-soluble substances penetrate through the skin only in small amounts. The penetration of water-soluble substances into the body is prevented by the fat layer formed on the surface of the skin as a result of the secretory activity of the sebaceous glands. Nicotine, tetraethyl lead, chlorine derivatives of hydrocarbons, chlorine-containing pesticides, aromatic amines, fatty hydrocarbons (from C 6 to C 10), finely ground salts of thallium, mercury and other metals easily penetrate through the skin. With mechanical damage to the skin, burns, the penetration of toxic substances through the skin increases.

The absorption of chemicals through the skin is complex. Their direct (transepidermal) penetration through the epidermis is possible, hair follicles and sebaceous glands, the ducts of the sweat glands. Different areas of the skin have a different ability to absorb industrial poisons; more suitable for the penetration of toxic agents is the skin on the medial surface of the thighs and arms, in the groin, genitals, chest and abdomen.

At the first stage, the toxic agent passes through the epidermis - a lipoprotein barrier that passes only for gases and fat-soluble organic substances. At the second stage, the substance enters the bloodstream from the dermis. This barrier is available for compounds that are readily or partially soluble in water (blood). The danger of skin-resorptive action increases significantly if the specified physicochemical properties of the poison are combined with high toxicity.

Industrial poisons that can cause intoxication in case of penetration through the skin include aromatic amino and nitro compounds, organophosphorus insecticides, chlorinated hydrocarbons, that is, compounds that do not dissociate into ions (not electrolytes). Electrolytes do not penetrate through the skin; they are retained, as a rule, in the stratum corneum or lustrous layer of the epidermis. The exception is heavy metals such as lead, tin, copper, arsenic, bismuth, mercury, antimony and their salts. Connecting with fatty acids and sebum on the surface or inside the stratum corneum of the epidermis, they form salts, are able to overcome the epidermal barrier.

Through the skin penetrate not only liquid substances that pollute it, but also volatile gaseous and vaporous non-electrolytes, the skin is an inert membrane through which they penetrate by diffusion.

The absorption of toxic substances from the digestive tract in most cases is selective, since its different parts have their own personal structure, innervation, chemical environment and enzyme glass.

Some toxic substances (all fat-soluble compounds, phenols, some salts, especially cyanides) are already absorbed in the oral cavity. In this case, the toxicity of substances increases due to the fact that they are not exposed to the action of gastric juice and, bypassing the liver, are not rendered harmless in it.

All fat-soluble substances and non-ionized molecules of organic substances are absorbed from the stomach by simple diffusion. The penetration of substances by filtration is possible through the pores of the cell membrane of the gastric epithelium. Many poisons, including lead compounds, dissolve better in gastric contents than in water, therefore they are better absorbed. Some chemicals, once in the stomach, completely lose their current toxicity, or it is significantly reduced through inactivation by gastric contents.

The nature and rate of absorption is significantly influenced by the degree of filling of the stomach, the solubility in the gastric contents and its pH. Substances taken on an empty stomach are absorbed, as a rule, more intensively.

Absorption through the digestive tract

poison poisoning epidermis blood

With poisoned food, water, as well as in "pure" form, toxic substances are absorbed into the bloodstream through the mucous membranes of the mouth, stomach and intestines. Most of them are absorbed into the epithelial cells of the digestive tract and further into the blood by the mechanism of simple diffusion. In this case, the leading factor for the penetration of poisons into the internal environments of the body is their solubility in lipids (fats), more precisely, the nature of the distribution between the lipid and water phases at the site of absorption. The degree of dissociation of poisons also plays a significant role.

As for fat-insoluble foreign substances, many of them penetrate the cell membranes of the mucous membranes of the stomach and intestines through the pores or spaces between the membranes. Although the pore area is only about 0.2% of the total membrane surface, it nevertheless allows the absorption of many water-soluble and hydrophilic substances. The blood stream from the gastrointestinal tract delivers toxic substances to the liver - an organ that performs a barrier function in relation to the vast majority of foreign compounds.

Absorption of toxic substances from the digestive tract occurs mainly in small intestine... Fat-soluble substances are well absorbed by diffusion. Lipophilic compounds quickly penetrate the intestinal wall, but are relatively slowly absorbed into the bloodstream. For fast absorption, the substance has good solubility in lipoids and water. Solubility in water promotes the absorption of poison from the intestinal wall into the blood. The rate of absorption of chemicals depends on the degree of ionization of the molecule. Strong acids and alkalis are absorbed slowly due to the formation of complexes with intestinal mucus. Substances similar in structure to natural compounds are absorbed through the mucous membrane by active transport, which ensures the supply of nutrients.

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The overwhelming majority of occupational poisoning is associated with the inhalation of harmful substances into the body, which is the most dangerous due to the large absorption surface of the pulmonary alveoli, intensively washed with blood, which causes very rapid penetration of poisons into the most important vital centers.

The ingestion of toxic substances through the gastrointestinal tract in the production environment is quite rare. This may be due to a violation of personal hygiene rules, partial splitting of vapors and dust entering through the respiratory tract, as well as non-compliance with safety when working in a chemical laboratory. It should be noted that in this case, the poison enters the liver through a vein, where it is converted into less toxic compounds.

Substances that are readily soluble in fats and lipids can enter the bloodstream through intact skin. Severe poisoning cause substances with high toxicity, low volatility and rapid blood solubility. Such substances include, for example, nitro and amino products of aromatic hydrocarbons, tetraethyl lead, methyl alcohol, etc.

Toxic substances are not evenly distributed in the body, some of them are capable of accumulating in certain tissues. These can be electrolytes, many of which quickly disappear from the blood and are concentrated in certain organs. Copper accumulates mainly in the bones, manganese - in the liver, mercury - in the kidneys and colon. Naturally, the distribution of poisons in organs can to some extent affect their further fate in the body.

Assuming a range of complex and varied life processes, toxic substances undergo various transformations in the process of oxidation, reduction and hydrolytic cleavage. As a result of these transformations, less toxic compounds are most often formed, although in some cases more toxic products are formed (for example, formaldehyde during the oxidation of methyl alcohol).

Workers in the chemical industry are systematically exposed to hazardous and harmful production factors (HHPF), leading to the development of a whole range of occupational diseases.

Working conditions at paint and varnish factories have their own specifics, due to the impact harmful factors specific to the chemical industry.

The assessment of working conditions was carried out at the largest paint and varnish plant in the Southern Federal District "Raduga", which produces a wide range of paint and varnish materials (LKM).

The main professions engaged in the production of paints and varnishes are machine operators and loaders. Apparatchiks serve various stages of the technological process of paint and varnish production, and also carry out quality control of semi-finished products and raw materials using control and measuring instruments.

The work of loaders is associated with the delivery of raw materials from the warehouse to the operator's workplace and the shipment of finished products to the warehouse using the simplest handling devices, as well as the intra-warehouse processing of packaged container units.

Table. Consistency in assessing the working conditions of workers in a paint and varnish plant

As a result of the assessment, it was concluded that the following harmful factors most often affect workers in paint and varnish industries: chemicals of hazard classes 2 and 3 (organic solvents, salts of heavy metals, finished paints and varnishes), moving parts of production equipment (dispersants, paint machines ), elevated level workplace noise (working bead mills, ventilation systems).

The next stage in the study of working conditions at the paint and varnish plant was the assessment of the degree of deviation of the identified factors of the working environment from their norm. The studies carried out made it possible to determine the degree of harmfulness of working conditions by the cumulative effect of physical, chemical, vibroacoustic factors.

Table. Comprehensive assessment of the harmfulness of working conditions for workers in paint and varnish industries

Analysis of the data in the table showed that the working conditions of all categories of workers in paint and varnish industries are harmful, but there are differences in the degree of harm and the factors that cause it. The harmfulness of working conditions largely depends on the type of paintwork materials in the production of which they are employed, as well as on the labor operations that they perform.

The harmfulness of working conditions (3 class 2 degree) of machine operators employed in the production of perchlorovinyl paints and varnishes is due to the excess of the maximum permissible concentration of harmful substances in the air of the working area, for the operators of the alkyd-acrylic paint shop - the excess of vibration and noise.

The working conditions of the apparatchiks involved in the production of oil paints and varnishes are also harmful, but the degree of harm is lower (class 3, degree 1). paint and varnish influence organism ecological

The harmfulness of the working conditions of loaders (3 class 1 degree) is due to the severity of the labor operations performed; for all other factors, working conditions are acceptable.

2.4.3. Ways of penetration of harmful substances into the human body

Toxic substances in the environment can enter the human body in three ways: inhalation, through the respiratory tract; oral, through the gastrointestinal tract (GIT); percutaneous, through intact skin.

Respiratory absorption

Absorption through the respiratory tract is the main route of entry of harmful substances into the human body at work. Inhalation poisoning is characterized by the most rapid entry of poison into the bloodstream.

The airway is an ideal system for gas exchange with a surface of up to 100 m 2 during deep breathing and a network of capillaries about 2000 km long. They can be divided into two parts:

a) upper respiratory tract: nasopharynx and tracheobronchial tree;

b) the lower part, consisting of bronchioles leading to air sacs (alveoli), collected in lobules.

From the point of view of absorption in the lungs, the alveoli are of greatest interest. The alveolar wall is lined with alveolar epithelium and consists of an interstitial framework consisting of basement membranes, connective tissue and capillary endothelium. Gas exchange takes place through this system having a thickness of 0.8 μm.

The behavior of gases and vapors within the respiratory tract depends on their solubility and chemical reactivity. Water-soluble gases dissolve easily in the water contained in the mucous membrane of the upper respiratory tract. Less soluble gases and vapors (eg nitrogen oxides) reach the alveoli, where they are absorbed and can react with the epithelium, causing local damage.

Fat-soluble gases and vapors diffuse through intact alveolar-capillary membranes. The absorption rate depends on their solubility in the blood, ventilation, blood flow and metabolic rate. Gaseous substances with a high solubility in the blood are easily absorbed, and those with a low solubility are easily expelled from the lungs with exhaled air.

The retention of particles in the airways depends on the physical and chemical properties of the particles, their size and shape, as well as anatomical, physiological and pathological characteristics. Soluble particles in the respiratory tract dissolve in the deposition zone. Insoluble materials can be removed in three ways, depending on the deposition zone:

a) with the help of the mucociliary cover both in the upper respiratory tract and in the lower part of the respiratory tract;

b) as a result of phagocytosis;

c) by passing directly through the alveolar epithelium.

It is possible to establish a quite definite regularity of the sorption of poisons through the lungs for two large groups of chemicals. The first group consists of the so-called unresponsive vapors and gases, which include vapors of all aromatic and fatty hydrocarbons and their derivatives. Poisons are called non-reactive due to the fact that they do not change in the body (there are few of them) or their transformation is slower than accumulation in the blood (most of them). The second group consists of reactive vapors and gases. These include poisons such as ammonia, sulfur dioxide, nitrogen oxides. These gases, quickly dissolving in body fluids, easily enter into chemical reactions or undergo other changes. There are also poisons that do not obey the laws established for these two groups of substances with respect to their sorption in the body.

Unresponsive vapors and gases enter the blood based on the law of diffusion, i.e., due to the difference in the partial pressure of gases and vapors in the alveolar air and blood.

At first, blood saturation with gases or vapors occurs quickly due to the large difference in partial pressure. Then it slows down and, finally, when the partial pressure of gases or vapors in the alveolar air and blood is equalized, it stops (Fig. 35).

Rice. 35. Dynamics of blood saturation with benzene and gasoline vapors

inhalation

* -After removing the victim from the polluted atmosphere, desorption of gases and vapors begins and their removal through the lungs. Desorption also occurs based on the laws of diffusion.

The established pattern allows us to draw a practical conclusion: if, at a constant concentration of vapors or gases in the air for a very short time, acute poisoning does not occur, it will not occur in the future, since when inhaling, for example, drugs, the equilibrium state of concentrations in the blood and alveolar air is established instantly. Removal of the victim from the polluted atmosphere is dictated by the need to create the possibility of desorption of gases and vapors.

The figure shows that, despite the same concentration of gasoline and benzene vapors in the air, the level of blood saturation with benzene vapors is much higher, and the saturation rate is much lower. It depends on the solubility, or, in other words, the distribution coefficient of benzene and gasoline vapors in the blood. The distribution coefficient (K) is the ratio of the concentration of vapors in arterial blood to their concentration in the alveolar air:

K = C blood / C alv. air ...

The lower the distribution coefficient, the faster, but at a lower level, the blood is saturated with vapors.

The distribution coefficient is a constant and characteristic value for each of the reacting vapors (gases). Knowing K for any substance, one can foresee the danger of quick and even fatal poisoning. Gasoline vapors, for example (K = 2.1), at high concentrations can cause instant acute or fatal poisoning, and acetone vapors (K = 400) cannot cause instant, especially fatal, poisoning, since inhalation of acetone vapors causes symptoms, acute poisoning can be prevented by removing the person from the polluted atmosphere.

The use of the distribution coefficient in blood in practice is facilitated by the fact that the coefficient of solubility, i.e., distribution in water (Ostwald coefficient), has approximately the same order of magnitude. If substances are readily soluble in water, then they are readily soluble in blood.

A different pattern is inherent in sorption by inhalation reacting gases: when these gases are inhaled, saturation never occurs (Table 10).

Table 10

Sorption of hydrogen chloride when inhaled by a rabbit

Sorption, as can be seen from the table, proceeds at a constant rate, and the percentage of sorbed gas is in direct proportion to the volume of respiration. As a result, the risk of poisoning is the more significant, the longer a person is in a polluted atmosphere.

This pattern is inherent in all reacting gases; differences can only be in the place of sorption. Some of them, for example, hydrogen chloride, ammonia, sulfur dioxide, are readily soluble in water and are sorbed in the upper respiratory tract; others, for example, chlorine, nitrogen oxides, dissolve worse in water, penetrate into the alveoli and are mainly absorbed there.

Sorption of chemicals in the form of dust of different dispersion occurs in the same way as the sorption of any non-toxic dust. The danger of poisoning from inhalation of dust depends on the degree of its solubility. Dust, which is highly soluble in water or fats, is already absorbed in the upper respiratory tract and even in the nasal cavity.

With an increase in the volume of pulmonary respiration and blood flow rate, sorption occurs faster, therefore, when performing physical work or staying in conditions of high temperature, when the volume of respiration and the speed of blood flow increases sharply, poisoning can occur faster.

Classification of harmful substances and ways of their entry into the human body
Irrational use of chemicals, synthetic materials adversely affects the health of workers.
A harmful substance (industrial poison), entering the human body during his professional activities, causes pathological changes.
The main sources of air pollution in industrial premises with harmful substances can be raw materials, components and finished products. Diseases arising from exposure to these substances are called occupational poisoning.
According to the degree of exposure to the body, harmful substances are divided into four hazard classes:

1st - extremely dangerous substances;
2nd - highly hazardous substances;
3rd - moderately hazardous substances;
4th - slightly hazardous substances.
The assignment of a harmful substance to a hazard class is carried out according to an indicator, the value of which corresponds to the highest hazard class.
Toxic substances enter the human body through the respiratory tract (inhalation penetration), gastrointestinal tract and skin. The degree of poisoning depends on their state of aggregation (gaseous and vaporous substances, liquid and solid aerosols) and on the nature of the technological process (heating the substance, grinding, etc.).
The overwhelming majority of occupational poisoning is associated with the inhalation of harmful substances into the body, the most dangerous, since the large suction surface of the pulmonary alveoli, intensively washed with blood, causes a very rapid and almost unhindered penetration of poisons to the most important vital centers.
The intake of toxic substances through the gastrointestinal tract in an industrial environment is quite rare. This happens due to violation of personal hygiene rules, partial ingestion of vapors and dust penetrating the respiratory tract, and non-compliance with safety rules when working in chemical laboratories. It should be noted that in this case, the poison enters the liver, where it turns into less toxic compounds.
Substances that are highly soluble in fats can enter the bloodstream through intact skin. Severe poisoning is caused by substances with increased toxicity, low volatility, and rapid solubility in the blood. These substances include, for example, nitro - and amino products of aromatic hydrocarbons, tetraethyl lead, methyl alcohol, etc.
Toxic substances are distributed unevenly in the body, and some of them are capable of accumulating in certain tissues. Here, electrolytes can be especially highlighted, many of which quickly disappear from the blood and are concentrated in individual organs. Lead accumulates mainly in the bones, manganese - in the liver, mercury - in the kidneys and colon. Naturally, the peculiarity of the distribution of poisons can, to some extent, be reflected in their further fate in the body.
Entering the circle of complex and diverse life processes, toxic substances undergo various transformations in the course of oxidation, reduction and hydrolytic cleavage reactions.The general direction of these transformations is most often characterized by the formation of less toxic compounds, although in some cases more toxic products can also be obtained (for example, formaldehyde with oxidation of methyl alcohol).
The release of toxic substances from the body often occurs in the same way as the intake. Non-reactive vapors and gases are partially or completely removed through the lungs. A significant amount of poisons and their products are excreted through the kidneys. A certain role for the excretion of poisons from the body is played by the skin, and this process is mainly done by the sebaceous and sweat glands.
It must be borne in mind that the release of some toxic substances is possible in the composition of human milk (lead, mercury, alcohol). This poses a risk of poisoning to infants. Therefore, pregnant women and nursing mothers should be temporarily suspended from production operations, toxic substances.
The toxic effect of certain harmful substances can manifest itself in the form of secondary lesions, for example, colitis with arsenic and mercury poisoning, stomatitis with lead and mercury poisoning, etc.
The danger of harmful substances to humans is largely determined by their chemical structure and physicochemical properties. Of no small importance in relation to toxic effects is the dispersion of a chemical substance that penetrates into the body, and the higher the dispersion, the more toxic the substance.
Environmental conditions can either enhance or weaken its effect. So, at high air temperatures, the risk of poisoning increases; poisoning with amido - and nitro compounds of benzene, for example, are more frequent in summer than in winter. High temperature also affects the volatility of the gas, the rate of evaporation, etc. It was found that air humidity increases the toxicity of some poisons (hydrochloric acid, hydrogen fluoride).

Ways of entry and distribution of harmful substances in the body
The main routes of entry of harmful substances into the body are the respiratory tract, digestive tract and skin.
Their entry through the respiratory system is of the greatest importance. Toxic dusts, vapors and gases released into the indoor air are inhaled by workers and penetrate into the lungs. Through the branched surface of the bronchioles and alveoli, they are absorbed into the blood. Inhaled poisons have an adverse effect almost throughout the entire time of work in a polluted atmosphere, and sometimes even after the end of work, since they are still being absorbed. The poisons that enter the bloodstream through the respiratory system are spread throughout the body, as a result of which their toxic effect can affect a wide variety of organs and tissues.
Harmful substances enter the digestive organs by ingesting toxic dusts that have settled on the mucous membranes of the oral cavity, or by bringing them there with contaminated hands.
The poisons that enter the digestive tract are absorbed through the mucous membranes into the blood throughout its entire length. Absorption mainly occurs in the stomach and intestines. The poisons that enter the digestive organs are sent to the liver by the blood, where some of them are retained and partially neutralized, because the liver is a barrier to substances entering through the digestive tract. Only after passing through this barrier, poisons enter the general bloodstream and are carried by them throughout the body.
Toxic substances with the ability to dissolve or dissolve in fats and lipoids can penetrate the skin when the latter is contaminated with these substances, and sometimes when they are present in the air (to a lesser extent). The poisons that penetrate the skin immediately enter the general bloodstream and are carried throughout the body.
Poisons that have entered the body in one way or another can be relatively evenly distributed over all organs and tissues, exerting on them toxic effect... Some of them accumulate mainly in some of the tissues and organs: in the liver, bones, etc. Such places of predominant accumulation of toxic substances are called the depot ida in the body. For many substances, certain types of tissues and organs are characteristic, where they are deposited. The delay of poisons in the depot can be both short-term and longer - up to several days and weeks. Gradually leaving the depot into the general bloodstream, they can also have a certain, usually mild toxic effect. Some unusual phenomena (alcohol intake, specific food, illness, injury, etc.) can cause more rapid elimination of poisons from the depot, as a result of which their toxic effect is more pronounced.
The excretion of poisons from the body occurs mainly through the kidneys and intestines; the most volatile substances are also excreted through the lungs with exhaled air.

The effect of harmful substances on the body
Harmful substances can have local and general effects on the body. Local action most often manifests itself in the form of irritation or chemical burn places of direct contact with poison; usually it is the skin or mucous membranes of the eyes, upper respiratory tract and mouth. It is a consequence of the chemical effect of an irritating or toxic substance on living cells of the skin and mucous membranes. V mild form it manifests itself in the form of redness of the skin or mucous membranes, sometimes in their swelling, itching or burning sensation; in more severe cases, the painful phenomena are more pronounced, and changes in the skin or mucous membranes can be up to their ulceration.
The general effect of the poison occurs when it penetrates the bloodstream and spreads throughout the body. Some poisons have a specific, that is, selective effect on certain organs and systems (blood, liver, nervous tissue, etc.). In these cases, penetrating the body in any way, the poison affects only a specific organ or system. Most of the poisons have a general toxic effect or effect simultaneously on several organs or systems,
The toxic effect of poisons can manifest itself in the form of acute or chronic poisoning - intoxication.
Acute poisoning occurs as a result of relatively short exposure to significant amounts of a harmful substance (high concentrations) and is characterized, as a rule, by the rapid development of painful phenomena - symptoms of intoxication.
There are several stages in the development of acute poisoning. The initial period of intoxication - prodromal - is characterized, as a rule, by some nonspecific phenomena, sometimes even slightly

The influence of harmful substances on the human body
By the nature of development and duration of the course, two main forms of occupational poisoning are distinguished - acute and chronic intoxication.
Acute intoxication occurs, as a rule, suddenly after short-term exposure to relatively high concentrations of poison and is expressed by more or less violent and specific clinical symptoms. In industrial conditions, acute poisoning is most often associated with accidents, equipment malfunction, or with the introduction of new materials with little-studied toxicity into the technology.
Chronic intoxication is caused by the ingestion of small amounts of poison into the body and is associated with the development of pathological phenomena only under the condition of prolonged exposure, sometimes determined by several years.
Most industrial poisons cause both acute and chronic poisoning. However, some toxic substances usually cause the development of predominantly the second (chronic) phase of poisoning (lead, mercury, manganese).
In addition to specific poisoning, the toxic effect of harmful chemicals can contribute to a general weakening of the body, in particular, a decrease in resistance to an infectious principle. For example, there is a known relationship between the development of influenza, tonsillitis, pneumonia and the presence in the body of such toxic substances as lead, hydrogen sulfide, benzene, etc. Poisoning with irritating gases can sharply exacerbate latent tuberculosis, etc.
The development of poisoning and the degree of exposure to the poison depend on the characteristics of the physiological state of the body. The physical stress accompanying work inevitably increases the minute volume of the heart and respiration, causes certain changes in metabolism and increases the need for oxygen, which inhibits the development of intoxication.
Sensitivity to poisons depends to a certain extent on the sex and age of the workers. It has been established that some physiological conditions in women can increase the sensitivity of their body to the effects of a number of poisons (benzene, lead, mercury). The undoubted poor resistance of female skin to the effects of irritating substances, as well as the high permeability of fat-soluble toxic compounds into the skin. As for adolescents, their developing organism has less resistance to the effects of almost all harmful factors of the working environment, including industrial poisons.
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