Biological effects of radiation on the human body. Biological effect of radioactive radiation. Learn more about how radiation affects the human body
The biological effect of radiation on a person is to ionize the cells of the tissues of his body and the appearance of radiation sickness. The course of the disease will depend on many factors: on the area of damage, on the dose of ionizing radiation, on the time during which this dose was received.
ionizing radiation
When high-energy particles, or photons, pass through matter, they form pairs of charged particles on their way, which are called ions. Therefore, it is ionizing radiation that is considered dangerous. The biological effect of radiation affects living matter to a greater extent. living tissue- these are cells that are constantly updated, this is a dynamic process. And for him, ionizing radiation is doubly painful.
In part, radiation damage is associated with mechanical damage to molecular structures, such as chromosomes. Partly with chemical processes occurring with the released radicals. Since a person is 75% water, it is water cells that absorb radiation first, forming OH, HO2, H types. Subsequently, chain reactions of oxidation of protein molecules by these radicals occur. Further, functional changes appear in the biological patterns of cell life.
The following changes occur in cells:
- the mechanism of division and the chromosome apparatus of the damaged cell is damaged;
- the process of cell renewal and differentiation is blocked;
- the process of tissue proliferation and regeneration is blocked.
Most of all, the biological effect of radiation affects the constantly renewing cells of the bone marrow, spleen, gonads, etc.
Acute radiation sickness
A very high dose of ionizing radiation (more than 600 rad) leads to a rapid death of a person (if no treatment is carried out). At a dose of 400-600 rad, about 50% of people die. Starts acute radiation sickness, which collapses and dies hematopoietic system and the body's defense system stops working.
The first week of acute radiation sickness is asymptomatic - this is the so-called latent period of the disease. Then the immune system fails, everything starts to worsen chronic diseases and new infections appear. By about the fourth week, anemia develops, the blood stops clotting, and the risk of bleeding increases.
The current level of medicine allows you to save people who have received a dose of up to 1000 rad. Previously, the biological effects of radiation in such quantities were not amenable to treatment. Radiation sickness is an extreme degree of damage. Smaller doses can cause leukemia and various malignant tumors.
Radiation sources and types of exposure
A person can receive a dangerous dose of radiation from a passing radiation cloud or from a contaminated surface of buildings, structures, and the earth. This is called external exposure. Internal exposure occurs when a person inhales contaminated aerosols (an inhalation hazard) or consumes contaminated food and water. Radioactive substances can get on the skin and clothing. Such irradiation is called contact.
The biological effect of radiation can cause following effects:
- Somatic-stochastic. They are difficult to detect and may not appear for decades.
- Somatic. They affect only the irradiated person, they do not affect the offspring.
- Genetic. Sexual cell structures of irradiated people are disturbed, which will affect the offspring that appears with congenital deformities and mutations.
The degree of exposure depends not only on the dose, but also on the time of exposure. grave consequences. Acute radiation sickness can develop with a single dose of 100 rad.
abstract
Topic:
Plan:
Introduction
1 Direct and indirect effects of ionizing radiation
2 The impact of ionizing radiation on individual organs and the body as a whole
3 Mutations
4 Effect of high doses of ionizing radiation on biological objects
5. Two types of irradiation of the body: external and internal
Conclusion
Literature
BIOLOGICAL EFFECTS OF RADIATION
The radiation factor has been present on our planet since its formation, and as further studies have shown, ionizing radiation, along with other phenomena of a physical, chemical and biological nature, accompanied the development of life on Earth. However, the physical effects of radiation began to be studied only in late XIX centuries, and its biological effects on living organisms - in the middle of the XX. Ionization radiation refers to those physical phenomena that are not felt by our senses, hundreds of specialists, working with radiation, received radiation burns from high doses of radiation and died from malignant tumors caused by overexposure.
However, today world science knows more about the biological effects of radiation than about the effects of any other factors of physical and biological nature in the environment.
When studying the effect of radiation on a living organism, the following features were determined:
The effect of ionizing radiation on the body is not perceptible by a person. People do not have a sense organ that would perceive ionizing radiation. There is a so-called period of imaginary well-being - the incubation period for the manifestation of the action of ionizing radiation. Its duration is reduced by irradiation in high doses.
· Action from small doses can be summed up or accumulated.
· Radiation acts not only on a given living organism, but also on its offspring - this is the so-called genetic effect.
Various organs of a living organism have their own sensitivity to radiation. With a daily dose of 0.002-0.005 Gy, changes in the blood already occur.
· Not every organism as a whole perceives radiation in the same way.
· Irradiation is frequency dependent. A single high-dose irradiation causes more profound consequences than fractionated irradiation.
1. DIRECT AND INDIRECT EFFECTS OF IONIZING RADIATION
Radio waves, light waves, the thermal energy of the sun - all these are varieties of radiation. However, radiation will be ionizing if it is able to break the chemical bonds of the molecules that make up the tissues of a living organism, and, as a result, cause biological changes. The action of ionizing radiation occurs at the atomic or molecular level, regardless of whether we are exposed to external radiation, or receive radioactive substances from food and water, which upsets the balance biological processes in the body and lead to adverse effects. The biological effects of the influence of "radiation on the human body are due to the interaction of radiation energy with biological tissue. The energy directly transferred to the atoms and molecules of biological tissues is called direct the action of radiation. Some cells, due to the uneven distribution of radiation energy, will be significantly damaged.
One direct effect is carcinogenesis or the development of cancer. Cancer occurs when somatic cell gets out of control of the body and begins to actively divide. The root cause of this is a violation in the genetic mechanism, called mutations. When a cancer cell divides, it only produces cancer cells. One of the most sensitive organs to the effects of radiation is the thyroid gland. Therefore, the biological tissue of this organ is the most vulnerable in terms of cancer development. The blood is no less susceptible to the influence of radiation. Leukemia or blood cancer is one of the common effects of direct exposure to radiation. charged particles penetrate into the tissues of the body, lose their energy due to electrical interactions with the electrons of atoms electrical interaction accompanies the process of ionization (pulling out an electron from a neutral atom)
Physico-chemical changes accompany the occurrence in the body of extremely dangerous " free radicals".
In addition to direct ionizing radiation, there is also an indirect or indirect effect associated with the radiolysis of water. During radiolysis, there are free radicals - certain atoms or groups of atoms with high chemical activity. The main feature of free radicals are excess or unpaired electrons. Such electrons are easily displaced from their orbits and can actively participate in a chemical reaction. The important thing is that very small external changes can lead to significant changes. biochemical properties cells. For example, if an ordinary oxygen molecule captures a free electron, then it turns into a highly active free radical - superoxide. In addition, there are active compounds such as hydrogen peroxide, hydroxide and atomic oxygen. Most free radicals are neutral, but some may have a positive or negative charge.
If the number of free radicals is low, then the body has the ability to control them. If there are too many of them, then the work of protective systems, the vital activity of individual functions of the body, is disrupted. Damage caused by free radicals increases rapidly in a chain reaction. Getting into the cells, they disrupt the balance of calcium and the coding of genetic information. Such phenomena can lead to malfunctions in protein synthesis, which is vital. important function of the whole organism, tk. defective proteins disrupt the immune system. The main filters of the immune system - The lymph nodes work in an overstressed mode and do not have time to separate them. Thus, protective barriers are weakened and the body creates favorable conditions for the multiplication of viruses, microbes and cancer cells.
Free radicals that cause chemical reactions, involve in this process many molecules not affected by radiation. Therefore, the effect produced by radiation is determined not only by the amount of absorbed energy, but also by the form in which this energy is transmitted. No other type of energy absorbed by a biological object in the same amount leads to such changes as ionizing radiation causes. However, the nature of this phenomenon is such that all processes, including biological ones, are balanced. Chemical changes arise as a result of the interaction of free radicals with each other or with "healthy" molecules Biochemical changes happen like in the moment of irradiation, and for many years, which leads to cell death.
Our body, in contrast to the processes described above, produces special substances that are a kind of "cleaners".
These substances (enzymes) in the body are able to capture free electrons without turning into free radicals. AT normal condition the body maintains a balance between the appearance of free radicals and enzymes. Ionizing radiation disrupts this balance, stimulates the growth of free radicals and leads to negative consequences. You can activate the processes of absorption of free radicals by including antioxidants, vitamins in the diet. A, E, C or preparations containing selenium. These substances neutralize free radicals by absorbing them in large quantities.
2. IMPACT OF IONIZING RADIATION ON INDIVIDUAL ORGANIS AND THE ORGANISM AS A WHOLE
In the structure of the body, two classes of systems can be distinguished: control (nervous, endocrine, immune) and life-supporting (respiratory, cardiovascular, digestive). All major metabolic (metabolic) processes and catalytic (enzymatic) reactions occur at the cellular and molecular levels. The levels of organization of the organism function in close interaction and mutual influence on the part of the control systems. Majority natural factors act first on higher levels, then through certain bodies and tissues - to the cellular-molecular levels. After that, the response phase begins, accompanied by adjustments at all levels.
The interaction of radiation with the body begins at the molecular level. Direct exposure to ionizing radiation is therefore more specific. An increase in the level of oxidizing agents is also characteristic of other influences. It is known that various symptoms (temperature, headache, etc.) occur in many diseases and their causes are different. This makes it difficult to make a diagnosis. Therefore, if as a result harmful effects no radiation to the body certain disease, establish the reason for more long-term effects difficult as they lose their specificity.
The radiosensitivity of various body tissues depends on biosynthetic processes and the enzymatic activity associated with them. Therefore, cells of the bone marrow, lymph nodes, and germ cells are distinguished by the highest radioactivity. The circulatory system and red bone marrow are the most vulnerable to radiation and lose their ability to function normally already at doses of 0.5-1 Gy. However, they have the ability to recover and if not all cells are affected, circulatory system can restore its functions. reproductive organs, for example, the testes, are also characterized by increased radiosensitivity. Irradiation above 2 Gy results in permanent sterility. Only after many years they can fully function. The ovaries are less sensitive at least, in adult women. But a single dose of more than 3 Gy still leads to their sterility, although large doses with repeated irradiation do not affect the ability to bear children.
RADIO SENSITIVITY. LAWBERGONIER-TRIBONDO.
Radiosensitivity - sensitivity of biological objects to the damaging effects of ionizing radiation. Quantification radiosensitivity produced by measuring the absorbed doses of ionizing radiation that cause a certain effect. In many studies, it is based on measuring the dose of ionizing radiation that causes the death of 50% of irradiated objects (the so-called 50% lethal dose, or LD 50).
Many reactions to radiation are specific to certain tissues and systems. For example, such a universal response of cells to irradiation as a delay in division is easily detected in actively proliferating tissues and cannot be detected in tissues where cell division weak or absent. Therefore, to evaluate radiosensitivity usually use such clearly recorded reactions as the survival (or death) of cells or organisms.
The study of the mechanisms of the damaged action of ionizing radiation and the mechanisms of recovery of organisms from radiation damage has great importance to develop methods of radiation protection and increase the effectiveness of radiation therapy for tumors.
Range of species differences radiosensitivity organisms is very wide and measured by several orders of magnitude. No less difference radiosensitivity observed in different cells and tissues. Along with radiosensitive (blood system, intestines and sex glands), there are so-called radioresistant or radioresistant systems and tissues(bone, muscle and nerve).
The radiosensitivity varies within one type depending on age - age radiosensitivity(thus, young and old animals are the most radiosensitive, sexually mature and newborns are the most radioresistant), from sex - sexual radiosensitivity(as a rule, males are more radiosensitive) and individual radiosensitivity in different individuals of the same population.
On the population The level of radiosensitivity depends on the following factors:
features of the genotype (in the human population, 10 - 12% of people are characterized by increased radiosensitivity). This is due to a hereditarily reduced ability to eliminate DNA breaks, as well as to a reduced accuracy of the repair process. Increased radiosensitivity accompanies such hereditary diseases as ataxia-telangiectasia, pigment xeroderma.);
physiological (for example, sleep, alertness, fatigue, pregnancy) or pathophysiological state of the body (chronic diseases, burns);
gender (men are more radiosensitive);
age (people of mature age are the least sensitive).
The degree of radiosensitivity varies not only within the species. Within the same organism, cells and tissues also differ in their radiosensitivity. Therefore, for correct assessment consequences of exposure of the human body, it is necessary to assess the radiosensitivity at various levels.
On the cellular The level of radiosensitivity depends on a number of factors: the organization of the genome, the state of the DNA repair system, the content of antioxidants in the cell, the intensity of redox processes, the activity of enzymes that utilize the products of water radiolysis (for example, catalase, which destroys hydrogen peroxide, or superoxide dismutase, which inactivates the superoxide radical).
On the tissue level is performed Bergonier's rule–Tribondo:the radiosensitivity of a tissue is directly proportional to the proliferative activity and inversely proportional to the degree of differentiation of its constituent cells. Consequently, the most radiosensitive in the body will be rapidly dividing, rapidly growing and little specialized tissues, for example, hematopoietic cells of the bone marrow, the epithelium of the small intestine and skin. The least radiosensitive will be specialized, weakly renewing tissues, for example, muscle, bone, and nervous. The exception is lymphocytes, which are highly radiosensitive. At the same time, tissues that are resistant to the direct action of ionizing radiation are very vulnerable to long-term effects.
At the level of organs, radiosensitivity depends not only on the radiosensitivity of the tissues that make up the given organ, but also on its functions. Most adult tissues are relatively insensitive to the action of radiation.
Biological effect of ionizing radiation. Factors that determine the damage to the body.
There are two types of effect of exposure to ionizing radiation on the body: somatic and genetic. With a somatic effect, the consequences are manifested directly in the irradiated person, with a genetic effect, in his offspring. Somatic effects may be early or delayed. Early ones occur in the period from several minutes to 30-60 days after irradiation. These include redness and peeling of the skin, clouding of the lens of the eye, damage to the hematopoietic system, radiation sickness, death. Long-term somatic effects appear several months or years after irradiation in the form of persistent skin changes, malignant neoplasms, decreased immunity, and reduced life expectancy.
The biological effect of ionizing radiation is characterized by a number of general patterns:
1) Deep violations of vital activity are caused by negligible amounts of absorbed energy.
2) The biological effect of ionizing radiation is not limited to the exposed organism, but can extend to subsequent generations, which is explained by the effect on the body's hereditary apparatus.
3) The biological effect of ionizing radiation is characterized by a latent (latent) period, i.e., the development of radiation injury is not observed immediately. The duration of the latent period can vary from several minutes up to tens of years, depending on the dose of radiation, the radiosensitivity of the body. Thus, when irradiated in very high doses (tens of thousands of glad) can cause "death under the beam", while long-term irradiation in small doses leads to a change in the state of the nervous and other systems, to the appearance of tumors years after irradiation.
Age, physiological state, intensity of metabolic processes of the body, as well as irradiation conditions are also of great importance. At the same time, in addition to the dose of irradiation of the body, the following play a role: the power, rhythm and nature of irradiation (single, multiple, intermittent, chronic, external, general or partial, internal), its physical features that determine the depth of energy penetration into the body (X-ray, gamma- radiation, alpha and beta particles) , ionization density (under the influence of alpha particles it is greater than under the action of other types of radiation). All these features of the acting radiation agent determine the relative biological effectiveness of radiation. If radioactive isotopes that have entered the body are the source of radiation , then of great importance for the biological effect of ionizing radiation emitted by these isotopes is their chemical characteristics, which determine the participation of the isotope in the metabolism, the concentration in a particular organ, and, consequently, the nature of the irradiation of the body.
Factors that determine the damage to the body:
1. Type of radiation. All types of ionizing radiation can have an impact on health. The main difference lies in the amount of energy that determines the penetrating power of alpha and beta particles, gamma and X-rays.
2. The amount of the dose received. The higher the dose of radiation received, the higher the likelihood of biomedical consequences.
3. duration of exposure to radiation. If a dose is received within days or a week, the effects are often not as severe if a similar dose is received within minutes.
4 . Part of the body affected. Limbs such as arms or legs get large quantity radiation with less pronounced damage than the blood that forms the organs located in the lower back.
5. Age of a person. As a person ages, cell division slows down and the body is less sensitive to the effects of ionizing radiation. Once cell division has slowed down, the effects of radiation are somewhat less damaging than when cells were rapidly dividing.
6. biological differences. Some people are more sensitive to the effects of radiation than others.
Features of damage to the body as a whole are determined by two factors: 1) radiosensitivity of tissues, organs and systems directly exposed to radiation; 2) absorbed radiation dose and its time distribution. Individually and in combination, these factors determine predominant type of radiation reactions(local or general), specificity and time of manifestation(immediately after irradiation, shortly after irradiation or in the long term) and their importance for the body.
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The biological effect of radiation
1. Direct and indirect action of ionizing radiation
Radio waves, light waves, the thermal energy of the sun - all these are varieties of radiation. However, radiation will be ionizing if it is able to break the chemical bonds of the molecules that make up the tissues of a living organism, and, as a result, cause biological changes. The action of ionizing radiation occurs at the atomic or molecular level, regardless of whether we are exposed to external radiation, or receive radioactive substances from food and water, which upsets the balance of biological processes in the body and leads to adverse consequences. The biological effects of the influence of "radiation on the human body are due to the interaction of radiation energy with biological tissue. The energy directly transferred to the atoms and molecules of biological tissues is called direct the action of radiation. Some cells, due to the uneven distribution of radiation energy, will be significantly damaged.
One of the direct effects is carcinogenesis or the development of oncological diseases. A cancerous tumor occurs when a somatic cell gets out of control of the body and begins to actively divide. The root cause of this is a violation in the genetic mechanism, called mutations. When a cancer cell divides, it produces only cancer cells. One of the most sensitive organs to the effects of radiation is the thyroid gland. Therefore, the biological tissue of this organ is the most vulnerable in terms of cancer development. The blood is no less susceptible to the influence of radiation. Leukemia or blood cancer is one of the common effects of direct exposure to radiation. charged particles penetrate into the tissues of the body, lose their energy due to electrical interactions with the electrons of atoms. electrical interaction accompanies the process of ionization (pulling out an electron from a neutral atom).
Physico-chemical changes accompany the emergence of extremely dangerous "free radicals" in the body.
In addition to direct ionizing radiation, there is also an indirect or indirect effect associated with the radiolysis of water. During radiolysis, there are free radicals- certain atoms or groups of atoms with high chemical activity. The main feature of free radicals are excess or unpaired electrons. Such electrons are easily displaced from their orbits and can actively participate in a chemical reaction. It is important that very slight external changes can lead to significant changes in the biochemical properties of cells. For example, if an ordinary oxygen molecule captures a free electron, then it turns into a highly active free radical - superoxide. In addition, there are active compounds such as hydrogen peroxide, hydroxide and atomic oxygen. Most free radicals are neutral, but some may have a positive or negative charge.
If the number of free radicals is low, then the body has the ability to control them. If there are too many of them, then the work of protective systems, the vital activity of individual functions of the body, is disrupted. Damage caused by free radicals increases rapidly in a chain reaction. Getting into the cells, they disrupt the balance of calcium and the coding of genetic information. Such phenomena can lead to failures in the synthesis of proteins, which is a vital function of the whole organism, because. defective proteins disrupt the immune system. The main filters of the immune system - the lymph nodes work in an overstressed mode and do not have time to separate them. Thus, protective barriers are weakened and favorable conditions are created in the body for the reproduction of viruses, microbes and cancer cells.
Free radicals, which cause chemical reactions, involve in this process many molecules that are not affected by radiation. Therefore, the effect produced by radiation is determined not only by the amount of absorbed energy, but also by the form in which this energy is transmitted. No other type of energy absorbed by a biological object in the same amount leads to such changes as ionizing radiation causes. However, the nature of this phenomenon is such that all processes, including biological ones, are balanced. Chemical changes arise as a result of the interaction of free radicals with each other or with “healthy” molecules Biochemical changeshappen like in the moment of irradiation, and for many years, which leads to cell death.
Our body, in contrast to the processes described above, produces special substances that are a kind of "cleaners".
These substances (enzymes) in the body are able to capture free electrons without turning into free radicals. In a normal state, the body maintains a balance between the appearance of free radicals and enzymes. Ionizing radiation disrupts this balance, stimulates the growth of free radicals and leads to negative consequences. You can activate the processes of absorption of free radicals by including antioxidants, vitamins A, E, C or preparations containing selenium in the diet. These substances neutralize free radicals by absorbing them in large quantities.
2. The impact of ionizing radiation on individual organs and the body as a whole
In the structure of the body, two classes of systems can be distinguished: control (nervous, endocrine, immune) and life-supporting (respiratory, cardiovascular, digestive). All major metabolic (metabolic) processes and catalytic (enzymatic) reactions occur at the cellular and molecular levels. The levels of organization of the organism function in close interaction and mutual influence on the part of the control systems. Most of the natural factors act first on the higher levels, then through certain organs and tissues - on the cellular and molecular levels. After that, the response phase begins, accompanied by adjustments at all levels.
The interaction of radiation with the body begins at the molecular level. Direct exposure to ionizing radiation is therefore more specific. An increase in the level of oxidizing agents is also characteristic of other influences. It is known that various symptoms (temperature, headache, etc.) occur in many diseases and their causes are different. This makes it difficult to make a diagnosis. Therefore, if a specific disease does not occur as a result of the harmful effects of radiation on the body, it is difficult to establish the cause of more distant consequences, since they lose their specificity.
The radiosensitivity of various body tissues depends on biosynthetic processes and the enzymatic activity associated with them. Therefore, the cells of the bone marrow, lymph nodes, and germ cells are distinguished by the highest radioactivity. The circulatory system and red bone marrow are the most vulnerable to radiation and lose their ability to function normally already at doses of 0.5-1 Gy. However, they have the ability to recover and if not all cells are affected, the circulatory system can restore its functions. Reproductive organs, such as the testicles, are also characterized by increased radiosensitivity. Irradiation above 2 Gy results in permanent sterility. Only after many years they can fully function. The ovaries are less sensitive, at least in adult women. But a single dose of more than 3 Gy still leads to their sterility, although large doses with repeated irradiation do not affect the ability to bear children.
The lens of the eye is very susceptible to radiation. Dying, the cells of the lens become opaque, growing, leading to cataracts, and then to complete blindness. This can happen at doses around 2 Gy.
The radiosensitivity of an organism depends on its age. Small doses of radiation in children can slow or even stop their bone growth. How less age child, the more skeletal growth is inhibited. Irradiation of a child's brain can cause changes in his character, lead to memory loss. The bones and brain of an adult can withstand much higher doses. Relatively large doses are able to withstand most organs. The kidneys withstand a dose of about 20 Gy received within a month, the liver - about 40 Gy, bladder- 50 Gy, and mature cartilage tissue - up to 70 Gy. How younger body, all other things being equal, it is more sensitive to the effects of radiation.
Species radiosensitivity increases with the complexity of the organism. This is explained by the fact that in complex organisms more weak links causing chain reactions of survival. This is facilitated by more complex control systems (nervous, immune), which are partially or completely absent in more primitive individuals. For microorganisms, the doses that cause 50% of mortality are thousands of Gy, for birds - tens, and for highly organized mammals - units.
3. Mutations
Every cell in the body contains a DNA molecule that carries the information for the proper reproduction of new cells.
DNA- is deoxyribonucleic acid consisting of long, rounded molecules in the form of a double helix. Its function is to ensure the synthesis of most of the protein molecules that make up amino acids. The chain of the DNA molecule consists of separate sections that are encoded by special proteins, forming the so-called human gene.
Radiation can either kill the cell or distort the information in the DNA so that defective cells eventually appear. Change genetic code cells are called mutations. If the mutation occurs in the egg of the sperm, the consequences can be felt in the distant future, because. during fertilization, 23 pairs of chromosomes are formed, each of which consists of complex substance called deoxyribonucleic acid. Therefore, a mutation that occurs in a germ cell is called a genetic mutation and can be passed on to subsequent generations.
According to E.J. Hall, such disorders can be attributed to two main types: chromosomal aberrations, including changes in the number or structure of chromosomes, and mutations in the genes themselves. Gene mutations are further subdivided into dominant (which appear immediately in the first generation) and recessive (which can occur if the same gene is mutated in both parents). Such mutations may not show up for many generations, or may not show up at all. A mutation in a samotic cell will only affect the individual himself. Mutations caused by radiation do not differ from natural ones, but the scope of harmful effects increases.
The reasoning described is based only on laboratory studies of animals. There is no direct evidence of radiation mutations in humans yet, tk. full identification of all hereditary defects occurs only over many generations.
However, as John Hoffman emphasizes, the underestimation of the role chromosomal disorders based on the statement "their meaning is unknown to us" is a classic example of decisions made by ignorance. Permissible doses exposures were established long before the advent of methods to establish those sad consequences to which they can lead unsuspecting people and their descendants.
4. Effect of high doses of ionizing radiation on biological objects
A living organism is very sensitive to the action of ionizing radiation. The higher a living organism is on the evolutionary ladder, the more radiosensitive it is. Radiosensitivity is a multilateral characteristic. The "survival" of a cell after irradiation simultaneously depends on a number of factors: on the volume of genetic material, the activity of energy-providing systems, the ratio of enzymes, and the intensity of the formation of free radicals H and OH.
When irradiating complex biological organisms it is necessary to take into account the processes occurring at the level of interconnection of organs and tissues. Radiosensitivity various organisms varies quite widely.
The human body, as a perfect natural system, is even more sensitive to radiation. If a person has undergone total exposure to a dose of 100-200 rad, then after a few days he will have signs of radiation sickness in mild form. Its sign can be a decrease in the number of white blood cells, which is determined by a blood test. The subjective indicator for a person is possible vomiting on the first day after irradiation.
The average severity of radiation sickness is observed in persons exposed to radiation of 250-400 rad. They have a sharp decrease in the content of leukocytes (white blood cells) in the blood, nausea and vomiting are observed, and subcutaneous hemorrhages appear. Fatal outcome observed in 20% of those exposed 2-6 weeks after exposure.
When irradiated with a dose of 400-600 rad, a severe form of radiation sickness develops. Numerous subcutaneous bleedings appear, the number of leukocytes in the blood decreases significantly. The lethal outcome of the disease is 50%.
A very severe form of radiation sickness occurs when exposed to a dose above 600 rad. Leukocytes in the blood completely disappear. Death occurs in 100% of cases.
The consequences of radiation exposure described above are typical for cases where there is no medical care.
For the treatment of an irradiated organism modern medicine widely uses such methods as blood substitution, bone marrow transplantation, administration of antibiotics, as well as other methods intensive care. With such treatment, it is possible to exclude a fatal outcome even with irradiation with a dose of up to 1000 rad. The energy emitted by radioactive substances is absorbed by the environment, including biological objects. As a result of the impact of ionizing radiation on the human body, complex physical, chemical and biochemical processes can occur in the tissues.
The ionizing effect destroys first of all normal course biochemical processes and metabolism. Depending on the magnitude of the absorbed radiation dose and individual characteristics the organism caused by changes can be reversible or irreversible. At small doses, the affected tissue restores its functional activity. Large doses for long-term exposure can cause permanent damage individual bodies or the whole organism. Any type of ionizing radiation causes biological changes in the body both with external (the source is outside the body) and with internal exposure (radioactive substances enter the body, for example, with food or inhalation). Consider the effect of ionizing radiation when the radiation source is outside the body.
The biological effect of ionizing radiation in this case depends on the total dose and time of exposure to radiation, its type, the size of the irradiated surface and the individual characteristics of the organism. With a single irradiation of the entire human body, biological disturbances are possible depending on the total absorbed dose of radiation.
When exposed to doses 100-1000 times the lethal dose, a person can die during exposure. Moreover, the absorbed dose of radiation, causing damage to individual parts of the body, exceeds the lethal absorbed dose of radiation of the whole body. Lethal absorbed doses for individual parts of the body are as follows: head - 20 Gy, Bottom part belly - 30 Gy, top part belly - 50 Gy, rib cage- 100 Gr, limbs - 200 Gr.
The degree of sensitivity of different tissues to radiation is not the same. If we consider the tissues of organs in order of decreasing their sensitivity to the action of radiation, we get the following sequence: lymphatic tissue, lymph nodes, spleen, thymus, bone marrow, germ cells. Great sensitivity hematopoietic organs to radiation is the basis for determining the nature of radiation sickness.
With a single irradiation of the entire human body with an absorbed dose of 0.5 Gy, a day after irradiation, the number of lymphocytes can sharply decrease. The number of erythrocytes (red blood cells) two weeks after irradiation. At healthy person there are about 10 4 red blood cells, and 10 4 patients with radiation sickness reproduce daily, this ratio is disturbed and as a result the organism dies.
An important factor in the impact of ionizing radiation on the body is the exposure time. With increasing dose rate, the damaging effect of radiation increases. The more fractional the radiation in time, the less its damaging effect (Fig. 2.17).
External exposure to alpha as well as beta particles is less dangerous. They have a small run in the tissue and do not reach hematopoietic and other internal organs. With external irradiation, it is necessary to take into account gamma and neutron irradiation, which penetrate into the tissue for great depth and destroy it, as described in more detail above.
5. Two types of irradiation of the body: external and internal
Ionizing radiation can affect a person in two ways. First way - external exposure from a source located outside the body, which mainly depends on the radiation background of the area where the person lives or on other external factors. Second - internal radiation, due to the ingestion of a radioactive substance into the body, mainly with food.
Food products that do not meet radiation standards have increased content radionuclides are incorporated with food and become a source of radiation directly inside the body.
Food and air containing isotopes of plutonium and americium, which have high alpha activity, are of great danger. Plutonium, which fell out of the Chernobyl disaster, is the most dangerous carcinogen. Alpha radiation has a high degree of ionization and, therefore, a large damaging ability for biological tissues.
The ingestion of plutonium, as well as americium through the respiratory tract, into the human body causes oncology of pulmonary diseases. However, it should be taken into account that the ratio of the total amount of plutonium and its equivalents americium, curium to total plutonium inhaled into the body insignificantly. As Bennett found, when analyzing nuclear tests in the atmosphere, in the United States, the ratio of fallout and inhalation is 2.4 million to 1, that is, the vast majority of alpha-containing radionuclides from nuclear weapons tests went into the ground without affecting humans. Particles of nuclear fuel, the so-called hot particles with a size of about 0.1 microns, were also observed in the emissions from the Chernobyl trace. These particles can also be inhaled into the lungs and pose a serious hazard.
External and internal exposures require different precautions to be taken against dangerous action radiation.
External exposure is mainly generated by gamma-containing radionuclides, as well as x-rays. Its striking ability depends on:
a) radiation energy;
b) the duration of the radiation action;
c) distance from the radiation source to the object;
d) protective measures.
There is a linear relationship between the duration of exposure time and the absorbed dose, and the effect of distance on the result of radiation exposure has a quadratic relationship.
For protective measures against external radiation, mainly lead and concrete protective screens are used along the radiation path. The effectiveness of a material as an X-ray or gamma ray shield depends on the density of the material as well as the concentration of electrons it contains.
If it is possible to protect oneself from external radiation by special screens or other actions, then it is not possible to do this with internal radiation.
There are three possible ways through which radionuclides can enter the body:
a) with food
b) through the respiratory tract with air;
c) through damage to the skin.
It should be noted that the radioactive elements plutonium and americium enter the body mainly with food or inhalation, and very rarely through skin lesions.
As J. Hall notes, human organs react to substances that enter the body based solely on the chemical nature of the latter, regardless of whether they are radioactive or not. Chemical elements such as sodium and potassium are part of all body cells. Therefore, their radioactive form, introduced into the body, will also be distributed throughout the body. Other chemical elements tend to accumulate in individual organs, as happens with radioactive iodine in the thyroid gland or calcium in the bone tissue.
The penetration of radioactive substances with food into the body depends significantly on their chemical interaction. It has been established that chlorinated water increases the solubility of plutonium and, as a consequence, its incorporation into internal organs.
After a radioactive substance has entered the body, the amount of energy and type of radiation, the physical and biological half-life of the radionuclide should be taken into account. biological half-life called the time it takes to remove half of the radioactive substance from the body. Some radionuclides are excreted from the body quickly, and therefore do not have time to apply great harm, while others persist in the body for a considerable time.
The half-life of radionuclides depends significantly on physical condition person, his age and other factors. The combination of a physical half-life with a biological half-life is called effective half-life- the most important in determining the total amount of radiation. The organ most exposed to the action of a radioactive substance is called critical. For various critical organs, standards have been developed that determine the permissible content of each radioactive element. Based on these data, documents have been created that regulate the permissible concentrations of radioactive substances in the atmospheric air, drinking water, food products. In Belarus, in connection with the accident at the Chernobyl nuclear power plant, the Republican acceptable levels content of cesium and strontium radionuclides in food products and drinking water (RDU-92). In the Gomel region, some food products nutrition, such as children's, more stringent standards. Taking into account all the above factors and standards, we emphasize that the average annual effective equivalent human exposure dose should not exceed 1 mSv per year.
Literature
1. Savenko V.S. Radioecology. - Minsk: Design PRO, 1997.
2. M.M. Tkachenko, "Radiology (promeneva diagnostics and promeneva therapy)"
3. A.V. Shumakov A Brief Guide to Radiation Medicine Lugansk -2006
4. Beckman I.N. Nuclear Medicine Lectures
5. L.D. Lindenbraten, L.B. Naumov. Medical radiology. M. Medicine 1984
6. P.D. Khazov, M.Yu. Petrov. Fundamentals of medical radiology. Ryazan, 2005
7. P.D. Khazov. Radiation diagnostics. Cycle of lectures. Ryazan. 2006
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Radioactivity is the emission by the nuclei of certain elements of various particles, accompanied by the transition of the nucleus to another state and a change in its parameters. The phenomenon of radioactivity was discovered by the French scientist Henri Becquerel in 1896 for uranium salts.
In 1899, under the guidance of the English scientist Ernst Rutherford, an experiment was carried out that made it possible to discover the complex composition radioactive radiation.
THREE components of radiation Beta - particles are a stream of fast electrons flying at speeds close to the speed of light. They penetrate the air up to 20 m. Alpha particles are streams of nuclei of helium atoms. The speed of these particles is 20,000 km/s, which exceeds the speed of a modern aircraft (1000 km/h) by 72,000 times. Alpha - rays penetrate the air up to 10 cm. Gamma radiation is an electromagnetic radiation emitted during nuclear transformations or the interaction of particles
Each type of radiation has its own penetrating power, that is, the freedom to pass through matter. The greater the density of a substance, the worse it transmits radiation.
Alpha radiation - has a low penetrating power; - delayed by a sheet of paper, clothing, human skin; - alpha particles that have got into the body are very dangerous.
-radiation According to their properties, -particles have a low penetrating ability and do not pose a danger until radioactive substances emitting -particles enter the body through a wound, with food or inhaled air; then they become extremely dangerous.
Beta radiation - has a much greater penetrating power; - can pass in the air a distance of up to 5 meters, is able to penetrate into the tissues of the body; - a layer of aluminum a few millimeters thick can trap beta particles.
-radiation - particles can penetrate into the tissues of the body to a depth of one to two centimeters.
Gamma radiation - has even greater penetrating power; - delayed by a thick layer of lead or concrete.
-radiation -radiation that propagates at the speed of light has a large penetrating power; only a thick lead or concrete slab can hold it back.
Basic concepts, terms and definitions Radiation is a phenomenon that occurs in radioactive elements, nuclear reactors, during nuclear explosions, accompanied by the emission of particles and various radiations, resulting in harmful and hazards that affect people. Penetrating radiation should be understood as a damaging factor of ionizing radiation that occurs, for example, during the explosion of a nuclear reactor. Ionizing radiation is any radiation that causes ionization of the environment, i.e. the flow of electric currents in this environment, including in the human body, which often leads to cell destruction, changes in blood composition, burns and other serious consequences.
Sources of external exposure 1. Cosmic rays (0.3 m Sv/year) give slightly less than half of all external exposure received by the population. 2. Finding a person, the higher he rises above sea level, the stronger the exposure becomes. 3. Terrestrial radiation comes mainly from those rocks of minerals that contain potassium - 40, rubidium - 87, uranium - 238, thorium - 232.
Internal exposure of the population Ingestion with food, water, air. The radioactive gas radon is an invisible, tasteless, odorless gas that is 7.5 times heavier than air. Alumina. Industrial wastes used in construction, such as red clay bricks, blast-furnace slag, fly ash When coal is burned, a significant part of its components are sintered into slag, where radioactive substances are concentrated.
When working with any source of radiation, it is necessary to take measures for the radiation protection of all people who can get into the zone of radiation. Human beings are not able to detect any doses of radioactive radiation with the help of the senses. Dozimeters are used to detect ionizing radiation, measure their energy and other properties. Radiation measurement
Equivalent dose 1 Sv. = 1 J/kg Sievert is the unit of absorbed dose multiplied by a factor that takes into account the unequal radioactive hazard to the body different types ionizing radiation.
Equivalent dose of radiation: H=D*K K — quality factor D — absorbed dose of radiation Absorbed dose of radiation: D=E/m E — energy of the absorbed body m — body mass
Radiation dose absorption E of ionizing radiation to the mass of matter In SI, the absorbed dose of radiation is expressed in grays Natural background radiation (cosmic rays, radioactivity environment and human body) amounts to a radiation dose of about 2 * 10 -3 Gy per year. A radiation dose of 3 -10 Gy received in a short time is lethal
Exposure to ionizing radiation Any type of ionizing radiation causes biological changes in the body. A single irradiation causes biological disturbances that depend on the total absorbed dose. So at a dose up to 0, 25 Gy. visible violations no, but already at 4 - 5 Gy. deaths account for 50% of the total number of victims, and at 6 Gy. and more - 100% of the victims. The main mechanism of action is associated with the processes of ionization of atoms and molecules of living matter, in particular water molecules contained in cells. The degree of impact of ionizing radiation on a living organism depends on the dose rate of radiation, the duration of this exposure and the type of radiation and radionuclide that has entered the body.
The mechanism of action of radiation: ionization of atoms and molecules occurs, which leads to a change in the chemical activity of cells. Biological effect of radioactive radiation
Due to the fact that at radioactive exposure the biological susceptibility of the organs of the human body or individual systems of the body is not the same, they are divided into groups: I (the most vulnerable) - the whole body, gonads and red bone marrow (hematopoietic system); II - lens of the eye, thyroid gland ( endocrine system), liver, kidneys, lungs, muscles, adipose tissue, spleen, gastrointestinal tract, as well as other organs that are not included in groups I and III; III - skin covering, bone tissue, hands, forearms, feet and lower legs.
Sensitivity of individual organs to radioactive radiation Tissues Equivalent dose % Bone 0, 03 Thyroid 0.03 Red bone marrow 0.12 Lungs 0.12 Mammary gland 0.15 Ovaries, testes 0.25 Other tissues 0.3 Body as a whole
Radioactive radiation has a strong biological effect on the tissues of a living organism, which consists in the ionization of atoms and molecules of the medium. Biological effect of radioactive radiation
living cell - complex mechanism unable to continue normal activity even with minor damage to its individual sections. Even weak radiation can cause significant damage to cells and cause dangerous diseases(radiation sickness). At high radiation intensity, living organisms die. The danger of radiation lies in the fact that they do not cause any pain even when lethal doses. Biological effect of radioactive radiation
Biological effect of radioactive radiation Changes in the cell: - Destruction of chromosomes - Violation of the ability to divide - Change in permeability cell membranes— Swelling of cell nuclei
Irradiation can also some benefit The rapidly proliferating cells cancerous tumors more sensitive to radiation. This is the basis for the suppression of a cancerous tumor by γ-rays of radioactive preparations, which are more effective for this purpose than X-rays.
Cell nuclei most sensitive to radiation: 1. Bone marrow cells (the process of blood formation is disturbed) 2. Damage to cells of the digestive tract and other organs. Biological effect of radioactive radiation
The genetic consequences of radiation are manifested in the form of gene mutations, as well as changes in the number or structure of chromosomes. A dose of 1 Gy, received at low radiation levels in males (estimates are less certain for females), causes the appearance of 1000 to 2000 mutations leading to serious consequences, and between 30 and 1000 chromosomal rearrangements (aberrations) for every million live births.
Radioactive waste RW Waste containing radioactive isotopes of chemical elements and having no practical value. These are nuclear materials and radioactive substances, the further use of which is not foreseen.
Classification of radioactive waste state of aggregation: Liquid Solid Gaseous According to the composition of radiation: α - radiation β - radiation γ - radiation neutron radiation By lifetime: short-lived (less than 1 year) medium-lived (from a year to 100 years) long-lived (more than 100 years) By activity: Low active Medium active Highly active
accident on Chernobyl nuclear power plant showed the great danger of radioactive radiation. All people should be aware of this danger and the measures to protect against it. April 26, 1986
Methods and means of protection against ionizing radiation increasing the distance between the operator and the source; reduction of the duration of work in the radiation field; radiation source shielding; remote control; use of manipulators and robots; full automation technological process; use of personal protective equipment and warning with a sign of radiation hazard; constant control radiation levels and personnel exposure doses.
The simplest method of protection is the removal of personnel from the source of radiation at a sufficiently large distance. Therefore, all volumes with radioactive preparations should not be taken by hand. It is necessary to use special tongs with a long handle. If the distance from the radiation source to a sufficiently large distance is not possible. Barriers made of absorbing materials are used to protect against radiation.
