What is the effect of ionizing radiation on the human body. The effect of ionizing radiation on the human body

The degree of exposure to ionizing radiation on the human body depends on the dose of radiation, its power, ionization density of radiation, type of radiation, duration of exposure, individual sensitivity, physiological state of the body, etc. Under the influence of ionizing radiation in living tissue , as in any medium, energy is absorbed and excitation and ionization of the atoms of the irradiated substance arise. As a result, primary physicochemical processes arise in the molecules of living cells and the surrounding substrate and, as a consequence, a violation of the functions of the whole organism. Primary effects at the cellular level are manifested in the form splitting a protein molecule, oxidizing them with OH and H radicals, breaking the least strong bonds, as well as damaging the mitosis mechanism and chromosomal apparatus, blocking the processes of cell renewal and differentiation.

The most sensitive to the action of radiation are the cells of constantly renewing tissues and organs. (bone marrow, sex glands, spleen, etc.).

These changes at the cellular level and cell death can lead to disruption of the functions of individual organs and systems, interorgan connections, disruption of the normal life of the organism and its death.

Irradiation of the body can be external when the radiation source is outside the body, and internal - when a radioactive substance (radionuclides) gets into the body through the digestive tract, respiratory organs and through the skin.

With external exposure, the most dangerous are gamma, neutron and x-ray radiation. Alpha and beta particles, due to their low penetrating power, mainly cause skin lesions.

Internal radiation is dangerous the fact that it causes long-lasting ulcers on various organs. Exposure of people to ionizing radiation can lead to somatic, somato-stochastic and genetic consequences..

Somatic effects are manifested in the form of acute or chronic radiation sickness of the whole organism, as well as in the form of local radiation injuries.

Somato-stochastic effects are manifested in the form of a reduction in life expectancy, malignant changes in hematopoietic cells (leukemia), tumors of various organs and cells. These are long-term consequences.

Genetic effects manifest themselves in subsequent generations in the form of gene mutations as a result of the effect of radiation on germ cells at dose levels that are not dangerous for a given individual.

Acute radiation sickness characterized by a cyclical course with the following periods:

period of primary reaction;

latent period; the period of formation of the disease; recovery period; the period of long-term consequences and outcomes of the disease.

Chronic radiation sickness is formed gradually with prolonged and systematic irradiation with doses exceeding the permissible for external and internal exposure.Chronic illness maybe easy ( I stage), medium (II stage) and heavy (III stage).

The first stage of radiation sickness manifests itself in the form of a minor headache, lethargy, weakness, sleep and appetite disturbances, etc.

Middle or second stage characterized by an increase in these symptoms and neuro-regulatory disorders with the appearance of functional insufficiency of the digestive glands, cardiovascular and nervous systems, impairment of some metabolic processes, persistent leuko- and thrombocytopenia.

With severe degree , in addition, anemia develops, sharp leuko- and thrombopenia appears, atrophic processes occur in the mucous membrane of the gastrointestinal tract, etc. (changes in the central nervous system, hair loss).

Long-term consequences of radiation sickness are manifested in an increased predisposition of the body to malignant tumors and diseases of the hematopoietic system.

The danger of radionuclides entering the body is due to a number of reasons , - the ability of some of them to selectively accumulate in individual organs, an increase in the irradiation time before the excretion of a nuclide from an organ and its radioactive decay, an increase in the danger of highly ionizing alpha and beta particles, which are ineffective with external irradiation.

Critical organs are divided into three groups :

I- whole body, reproductive organs (gonads), red bone marrow;

II - muscles, thyroid gland, adipose tissue, liver, kidneys, spleen, gastrointestinal tract, lungs, lens of the eye;

III- bone tissue, skin, arms, forearms, feet.

IONIZING RADIATION, THEIR NATURE AND EFFECT ON THE HUMAN ORGANISM

Radiation and its varieties

Ionizing radiation

Sources of radiation hazard

The device of ionizing radiation sources

Ways of penetration of radiation into the human body

Measures ionizing effects

The mechanism of action of ionizing radiation

Radiation consequences

Radiation sickness

Ensuring safety when working with ionizing radiation

Radiation and its varieties

Radiation is all types of electromagnetic radiation: light, radio waves, the energy of the sun and many other radiations around us.

Sources of penetrating radiation that create a natural background of irradiation are galactic and solar radiation, the presence of radioactive elements in soil, air and materials used in economic activities, as well as isotopes, mainly potassium, in the tissues of a living organism. One of the most significant natural sources of radiation is radon, a gas that is tasteless and odorless.

Of interest is not any radiation, but ionizing radiation, which, passing through the tissues and cells of living organisms, is able to transfer its energy to them, breaking chemical bonds inside molecules and causing serious changes in their structure. Ionizing radiation arises during radioactive decay, nuclear transformations, deceleration of charged particles in matter and forms ions of different signs when interacting with the environment.

Ionizing radiation

All ionizing radiation is divided into photonic and corpuscular.

Photonic ionizing radiation includes:

a) Y-radiation emitted by decay of radioactive isotopes or annihilation of particles. Gamma radiation is inherently shortwave electromagnetic radiation, i.e. flux of high-energy quanta of electromagnetic energy, the wavelength of which is much less than the interatomic distances, i.e. y< 10 см. Не имея массы, Y-кванты двигаются со скоростью света, не теряя её в окружающей среде. Они могут лишь поглощаться ею или отклоняться в сторону, порождая пары ионов: частица- античастица, причём последнее наиболее значительно при поглощении Y- квантов в среде. Таким образом, Y- кванты при прохождении через вещество передают энергию электронам и, следовательно, вызывают ионизацию среды. Благодаря отсутствию массы, Y- кванты обладают большой проникающей способностью (до 4- 5 км в air environment);

b) X-ray radiation that occurs when the kinetic energy of charged particles decreases and / or when the energy state of the electrons of an atom changes.

Corpuscular ionizing radiation consists of a stream of charged particles (alpha, beta particles, protons, electrons), the kinetic energy of which is sufficient to ionize atoms in a collision. Neutrons and other elementary particles do not directly ionize, but in the process of interacting with the medium, they release charged particles (electrons, protons) that can ionize the atoms and molecules of the medium through which they pass:

a) neutrons are the only uncharged particles formed in some reactions of fission of uranium or plutonium atoms. Since these particles are electrically neutral, they penetrate deeply into any substance, including living tissues. Distinctive feature neutron radiation is its ability to convert atoms of stable elements into their radioactive isotopes, i.e. create induced radiation, which sharply increases the danger of neutron radiation. The penetrating power of neutrons is comparable to Y-radiation. Depending on the level of the carried energy, one can conditionally distinguish between fast neutrons (with energies from 0.2 to 20 MeV) and thermal (from 0.25 to 0.5 MeV). This difference is taken into account when carrying out protective measures. Fast neutrons are slowed down, losing ionization energy, by substances with low atomic weight (the so-called hydrogen-containing ones: paraffin, water, plastics, etc.). Thermal neutrons are absorbed by materials containing boron and cadmium (boric steel, boral, boric graphite, cadmium-lead alloy).

Alpha, beta particles and gamma quanta have energies of only a few megaelectronvolts, and cannot create induced radiation;

b) beta particles - electrons emitted during the radioactive decay of nuclear elements with intermediate ionizing and penetrating ability (range in air up to 10-20 m).

c) alpha particles - positively charged nuclei of helium atoms, and in outer space and atoms of other elements, emitted during the radioactive decay of isotopes of heavy elements - uranium or radium. They have a low penetrating power (range in the air - no more than 10 cm), even human skin is an insurmountable obstacle for them. They are dangerous only if they enter the body, since they are able to knock electrons out of the shell of a neutral atom of any substance, including the human body, and turn it into a positively charged ion with all the ensuing consequences, which will be discussed later. Thus, an alpha particle with an energy of 5 MeV forms 150,000 ion pairs.

Penetration characteristic different types ionizing radiation

The quantitative content of radioactive material in a human body or substance is defined by the term "activity of a radioactive source" (radioactivity). A unit of radioactivity in the SI system is a becquerel (Bq) corresponding to one decay in 1 s. Sometimes in practice the old unit of activity is used - curie (Ki). This is the activity of such an amount of matter in which 37 billion atoms decay in 1 s. For translation, use the dependence: 1 Bq = 2.7 x 10 Ci or 1 Ci = 3.7 x 10 Bq.

Each radionuclide has a constant, inherent only half-life (the time required for a substance to lose half of its activity). For example, for uranium-235 it is 4,470 years, while for iodine-131 it is only 8 days.

Sources of radiation hazard

1. The main cause of the danger is a radiation accident. Radiation accident - loss of control of an ionizing radiation source (IRS) caused by equipment malfunction, improper actions of personnel, natural disasters or other reasons that could lead or have led to the exposure of people above the established standards or to radioactive contamination of the environment. In accidents caused by the destruction of the reactor vessel or melting of the core, the following are discharged:

1) Fragments of the core;

2) Fuel (waste) in the form of highly active dust, which can be in the air for a long time in the form of aerosols, then, after passing the main cloud, fall out in the form of rain (snow) precipitation, and when it enters the body, cause a painful cough, sometimes in severity similar to an asthma attack;

3) lavas, consisting of silicon dioxide, as well as molten concrete as a result of contact with hot fuel. The dose rate near such lavas reaches 8000 R / hour, and even a five-minute stay near such lavas is fatal to humans. In the first period after the precipitation of radioactive substances, the greatest danger is posed by iodine-131, which is a source of alpha and beta radiation. Its half-life from the thyroid gland is: biological - 120 days, effective - 7.6. This requires the fastest implementation of iodine prophylaxis for the entire population caught in the accident zone.

2. Enterprises for the development of deposits and enrichment of uranium. Uranium has an atomic weight of 92 and three natural isotopes: uranium-238 (99.3%), uranium-235 (0.69%) and uranium-234 (0.01%). All isotopes are alpha emitters with negligible radioactivity (2800 kg of uranium are equivalent in activity to 1 g of radium-226). The half-life of uranium-235 = 7.13 x 10 years. Artificial isotopes uranium-233 and uranium-227 have half-lives of 1.3 and 1.9 minutes. Uranium is a soft metal similar in appearance to steel. The uranium content in some natural materials reaches 60%, but in most uranium ores it does not exceed 0.05-0.5%. During the extraction process, upon receipt of 1 ton of radioactive material, up to 10-15 thousand tons of waste are generated, and during processing from 10 to 100 thousand tons. From the waste (containing insignificant amounts of uranium, radium, thorium and other radioactive decay products), a radioactive gas is released - radon-222, which, when inhaled, causes irradiation of lung tissues. When enriching ore, radioactive waste can get into nearby rivers and lakes. During the enrichment of uranium concentrate, some leakage of gaseous uranium hexafluoride from the condensation-evaporation plant into the atmosphere is possible. Some uranium alloys, shavings, sawdust obtained during the production of fuel elements can ignite during transportation or storage, as a result, significant amounts of burned uranium waste can be released into the environment.

3. Nuclear terrorism. Cases of theft of nuclear materials suitable for the manufacture of nuclear weapons, even in an artisanal way, have become more frequent, as well as threats to disable nuclear enterprises, ships with nuclear installations and nuclear power plants in order to obtain a ransom. The danger of nuclear terrorism also exists at the household level.

4. Tests of nuclear weapons. Recently, miniaturization of nuclear test charges has been achieved.

The device of ionizing radiation sources

According to the device, there are two types of IRS - closed and open.

Sealed sources are placed in sealed containers and pose a hazard only in the absence of proper control over their operation and storage. Military units are also making their contribution, transferring decommissioned devices to sponsored educational institutions. Lose written off, destruction as unnecessary, theft with subsequent migration. For example, in Bratsk, at a building structure plant, radiation sources, enclosed in a lead sheath, were stored in a safe together with precious metals. And when the robbers broke into the safe, they decided that this massive blank of lead was also precious. They stole it, and then honestly divided it by sawing in half a lead "shirt" and an ampoule with a radioactive isotope sharpened in it.

Working with open IRS can lead to tragic consequences if you do not know or violate the relevant instructions on the rules for handling these sources. Therefore, before starting any work using IRS, it is necessary to carefully study all job descriptions and safety regulations and strictly follow their requirements. These requirements are set out in the "Sanitary Rules for the Management of Radioactive Waste (SPO GO-85)". The enterprise "Radon", upon request, performs individual control of persons, territories, objects, checks, dosages and repairs of devices. Work in the field of IRS treatment, radiation protection equipment, mining, production, transportation, storage, use, maintenance, disposal, disposal is carried out only on the basis of a license.

Ways of penetration of radiation into the human body

To correctly understand the mechanism of radiation damage, it is necessary to have a clear idea of ​​the existence of two ways by which radiation penetrates into the tissues of the body and affects them.

The first way is external irradiation from a source located outside the body (in the surrounding space). This radiation can be associated with X-rays and gamma rays, as well as some high-energy beta particles that can penetrate the surface layers of the skin.

The second way is internal radiation caused by the ingress of radioactive substances into the body in the following ways:

In the first days after a radiation accident, the most dangerous are radioactive isotopes of iodine, which enter the body with food and water. There are a lot of them in milk, which is especially dangerous for children. Radioactive iodine accumulates mainly in the thyroid gland, the mass of which is only 20 g. The concentration of radionuclides in this organ can be 200 times higher than in other parts of the human body;

Through damage and cuts on the skin;

Absorption through healthy skin with prolonged exposure to radioactive substances (RV). In the presence of organic solvents (ether, benzene, toluene, alcohol), the skin permeability for RS increases. Moreover, some radioactive substances that enter the body through the skin enter the bloodstream and, depending on their chemical properties, are absorbed and accumulated in critical organs, which leads to high local doses of radiation. For example, growing limb bones absorb radioactive calcium, strontium, radium, kidneys - uranium well. Other chemical elements, such as sodium and potassium, will spread more or less evenly throughout the body, since they are found in all cells of the body. In this case, the presence of sodium-24 in the blood means that the body was additionally exposed to neutron irradiation (i.e., the chain reaction in the reactor at the time of irradiation was not interrupted). It is especially difficult to treat a patient who has been exposed to neutron irradiation, therefore, it is necessary to determine the induced activity of the body's bioelements (P, S, etc.);

Through the lungs when breathing. The penetration of solid radioactive substances into the lungs depends on the degree of dispersion of these particles. Tests carried out on animals have shown that dust particles less than 0.1 micron in size behave in the same way as gas molecules. When inhaled, they enter the lungs with air, and when exhaled, they are removed with air. Only a small fraction of solid particles can remain in the lungs. Large particles larger than 5 microns are retained by the nasal cavity. Inert radioactive gases (argon, xenon, krypton, etc.) that enter the blood through the lungs are not compounds that make up tissues, and are eventually removed from the body. Do not stay in the body long time and radionuclides of the same type with the elements that make up the tissues and are consumed by humans with food (sodium, chlorine, potassium, etc.). Over time, they are completely removed from the body. Some radionuclides (for example, radium, uranium, plutonium, strontium, yttrium, zirconium deposited in bone tissues) enter into a chemical bond with elements of bone tissue and are hardly eliminated from the body. During a medical examination of residents of areas affected by the accident at the Chernobyl nuclear power plant, in the All-Union Hematological Center of the Academy of Medical Sciences, it was found that with a total irradiation of the body with a dose of 50 rad, some of its cells were irradiated with a dose of 1,000 or more rad. At present, standards have been developed for various critical bodies that determine the maximum permissible content of each radionuclide in them. These norms are set out in section 8 “ Numerical values permissible levels "Norm radiation safety NRB - 76/87.

Internal exposure is more dangerous, and its consequences are more severe for the following reasons:

The radiation dose is sharply increased, determined by the residence time of the radionuclide in the body (radium-226 or plutonium-239 throughout life);

The distance to the ionized tissue is practically infinitely small (the so-called contact irradiation);

The radiation involves alpha particles, the most active and therefore the most dangerous;

Radioactive substances do not spread evenly throughout the body, but selectively, they are concentrated in individual (critical) organs, increasing local exposure;

It is impossible to use any protective measures applied during external exposure: evacuation, personal protective equipment (PPE), etc.

Measures for ionizing exposure

The measure of the ionizing effect of external radiation is exposure dose, determined by air ionization. The unit of exposure dose (De) is considered to be x-ray (R) - the amount of radiation at which 1 cc. air at a temperature of 0 C and a pressure of 1 atm 2.08 x 10 pairs of ions are formed. According to the guidance documents of the International Company for Radiological Units (ICRU) RD - 50-454-84, after January 1, 1990, it is not recommended to use such values ​​as the exposure dose and its power in our country (it is accepted that the exposure dose is the absorbed dose in air). Most of the dosimetry equipment in the Russian Federation is calibrated in X-rays, X-rays / hours, and these units have not yet been abandoned.

A measure of the ionizing effect of internal radiation is absorbed dose. Accepted as a unit of absorbed dose. This is the dose of radiation transferred to the mass of the irradiated substance in 1 kg and measured by the energy in joules of any ionizing radiation. 1 rad = 10 J / kg. In the SI system, the unit of absorbed dose is gray (Gy), equal to 1 J / kg energy.

1 Gr = 100 glad.

1 rad = 10 Gr.

To convert the amount of ionizing energy in space (exposure dose) into absorbed by the soft tissues of the body, the proportionality coefficient K = 0.877 is used, i.e.:

1 x-ray = 0.877 rad.

Due to the fact that different types of radiation have different efficiency (with equal energy consumption for ionization produce a different effect), the concept of "equivalent dose" was introduced. Its unit of measurement is rem. 1 rem is a dose of radiation of any kind, the effect of which on the body is equivalent to the effect of 1 rad of gamma radiation. Therefore, when assessing the overall effect of radiation exposure on living organisms with total exposure to all types of radiation, a quality factor (Q) is taken into account, equal to 10 for neutron radiation (neutrons are about 10 times more effective in terms of radiation damage) and 20 - for alpha radiation. In the SI system, the unit of the equivalent dose is the sievert (Sv), equal to 1 Gy x Q.

Along with the amount of energy, type of radiation, material and mass of the organ important factor is the so-called biological half-life a radioisotope - the length of time required for elimination (with sweat, saliva, urine, feces, etc.) from the body of half of the radioactive substance. Already 1-2 hours after the entry of radioactive substances into the body, they are found in its secretions. The combination of a physical half-life with a biological one gives the concept of "effective half-life" - the most important in determining the resulting amount of radiation to which the body is exposed, especially critical organs.

Along with the concept of "activity" there is the concept of "induced activity" (artificial radioactivity). It arises from the absorption of slow neutrons (products nuclear explosion or nuclear reaction), the nuclei of atoms of non-radioactive substances and their transformation into radioactive potassium-28 and sodium-24, which are formed mainly in the soil.

Thus, the degree, depth and form of radiation injuries developing in biological objects (including humans) when exposed to radiation depend on the amount of absorbed radiation energy (dose).

The mechanism of action of ionizing radiation

A fundamental feature of the action of ionizing radiation is its ability to penetrate into biological tissues, cells, subcellular structures and, causing simultaneous ionization of atoms, due to chemical reactions damage them. Any molecule can be ionized, and hence all structural and functional destruction in somatic cells, genetic mutations, effects on the embryo, illness and death of a person.

The mechanism of this effect consists in the absorption of ionization energy by the body and the rupture of the chemical bonds of its molecules with the formation of highly active compounds, the so-called free radicals.

The human body is 75% water, therefore, the indirect effect of radiation through the ionization of the water molecule and subsequent reactions with free radicals will be of decisive importance in this case. When a water molecule is ionized, a positive HO ion and an electron are formed, which, having lost energy, can form a negative HO ion. Both of these ions are unstable and decay into a pair of stable ions, which recombine (are reduced) with the formation of a water molecule and two free OH radicals and H, characterized by extremely high chemical activity. Directly or through a chain of secondary transformations, such as the formation of a peroxide radical (hydrated water oxide), and then hydrogen peroxide HO and other active oxidants of the OH and H groups, interacting with protein molecules, they lead to tissue destruction mainly due to vigorous processes oxidation. In this case, one active molecule with high energy involves thousands of molecules of living matter in the reaction. In the body, oxidative reactions begin to prevail over reductive ones. Payback comes for the aerobic method of bioenergetics - saturation of the body with free oxygen.

Human exposure to ionizing radiation is not limited to changes in the structure of water molecules. The structure of the atoms that make up our body is changing. The result is the destruction of the nucleus, cell organelles and rupture of the outer membrane. Since the main function of growing cells is the ability to divide, its loss leads to death. For mature non-dividing cells, destruction causes the loss of certain specialized functions (production of certain products, recognition of foreign cells, transport functions, etc.). Radiation-induced cell death occurs, which, unlike physiological death, is irreversible, since the implementation of the genetic program of terminal differentiation in this case is carried out against the background of multiple changes in the normal course of biochemical processes after irradiation.

In addition, the additional supply of ionization energy to the body disturbs the balance of the energy processes occurring in it. After all, the presence of energy in organic substances depends primarily not on their elementary composition, but on the structure, location and nature of the bonds of atoms, i.e. those elements that are most susceptible to energetic influence.

Radiation consequences

One of the earliest manifestations of irradiation is the massive death of lymphoid tissue cells. Figuratively speaking, these cells are the first to receive the radiation hit. The death of lymphoids weakens one of the main life support systems of the body - the immune system, since lymphocytes are cells that are able to respond to the appearance of antigens foreign to the body by developing strictly specific antibodies to them.

As a result of exposure to the energy of radiation radiation in low doses, changes in the genetic material (mutations) occur in the cells, threatening their viability. As a result, degradation (damage) of chromatin DNA (breaks of molecules, damage) occurs, which partially or completely block or distort the function of the genome. There is a violation of DNA repair - its ability to restore and heal cell damage with an increase in body temperature, exposure to chemicals, etc.

Genetic mutations in germ cells affect the life and development of future generations. This is the case, for example, if a person has been exposed to small doses of radiation during medical exposure. There is a concept - when a dose of 1 rem is received by the previous generation, it gives an additional 0.02% of genetic anomalies in the offspring, i.e. in 250 babies per million. These facts and long-term studies of these phenomena have led scientists to the conclusion that there is no safe dose of radiation.

The effect of ionizing radiation on the genes of germ cells can cause harmful mutations that will be passed on from generation to generation, increasing the "mutational burden" of humanity. Conditions that double the genetic load are life-threatening. Such a doubling dose is, according to the conclusions of the UN Scientific Committee on Atomic Radiation, a dose of 30 rad for acute exposure and 10 rad for chronic exposure (during the reproductive period). With increasing dose, it is not the severity that increases, but the frequency of the possible manifestation.

Mutational changes also occur in plant organisms. In the forests that have been exposed to radioactive fallout near Chernobyl, as a result of mutation, new absurd plant species have arisen. Rusty-red coniferous forests have appeared. In a wheat field near the reactor, two years after the accident, scientists discovered about a thousand different mutations.

Influence on the embryo and fetus due to irradiation of the mother during pregnancy. Cell radiosensitivity changes at different stages of the division process (mitosis). The most sensitive cell is at the end of dormancy and at the beginning of the first month of division. The zygote, an embryonic cell formed after the fusion of a sperm with an egg, is especially sensitive to radiation. In this case, the development of the embryo during this period and the effect of radiation, including X-ray, irradiation on it can be divided into three stages.

Stage 1 - after conception and before the ninth day. The newly formed embryo dies under the influence of radiation. Death in most cases goes unnoticed.

2nd stage - from the ninth day to the sixth week after conception. This is the formation period internal organs and limbs. At the same time, under the influence of a radiation dose of 10 rem, a whole spectrum of defects appears in the embryo - cleft palate, arrest of limb development, impaired brain formation, etc. At the same time, growth retardation of the body is possible, which is reflected in a decrease in body size at birth. Irradiation of the mother during this period of pregnancy can also result in the death of the newborn at the time of childbirth or some time after it. However, the birth of a living child with gross defects is probably the biggest misfortune, much worse than the death of an embryo.

3rd stage - pregnancy after six weeks. The radiation doses received by the mother cause persistent growth retardation. In an irradiated mother, the child is smaller than normal at birth and remains below average height for the rest of her life. Pathological changes in the nervous, endocrine systems, etc. are possible. Many radiologists assume that a greater chance of having a defective baby warrants termination of pregnancy if the dose received by the embryo during the first six weeks after conception is greater than 10 rads. This dose was included in the legislative acts of some Scandinavian countries. For comparison, during fluoroscopy of the stomach, the main areas of the bone marrow, the abdomen, and the chest receive a radiation dose of 30-40 rad.

Sometimes a practical problem arises: a woman goes through a series of x-rays, which include images of the stomach and pelvic organs, and is subsequently discovered that she is pregnant. The situation is aggravated if radiation exposure occurred in the first weeks after conception, when pregnancy may go unnoticed. The only solution to this problem is not to expose the woman to radiation during the specified period. This can be achieved by having a woman of reproductive age undergo a stomach x-ray or abdominal cavity only during the first ten days after the onset of the menstrual period, when there is no doubt about the absence of pregnancy. In medical practice, this is called the "ten days" rule. In an emergency, X-ray procedures cannot be rescheduled for weeks or months, but it is prudent for a woman to tell her doctor before taking an X-ray that she may be pregnant.

In terms of the degree of sensitivity to ionizing radiation, cells and tissues of the human body are not the same.

The testes are especially sensitive organs. A dose of 10-30 rad can reduce spermatogenesis over the course of a year.

The immune system is highly sensitive to radiation.

In the nervous system, the retina of the eye turned out to be the most sensitive, since deterioration of vision was observed under irradiation. Disturbances in taste sensitivity occurred when radiation therapy chest, and repeated irradiation with doses of 30-500 R reduced tactile sensitivity.

Changes in somatic cells can contribute to cancer. A cancerous tumor occurs in the body at the moment when the somatic cell, out of control of the body, begins to divide rapidly. The root cause of this is mutations in genes caused by repeated or strong single irradiation, leading to the fact that cancer cells lose their ability, even in the event of an imbalance, to die physiological, or rather programmed death. They become, as it were, immortal, constantly dividing, increasing in number and dying only from a lack of nutrients. This is how the tumor grows. Leukemia (blood cancer) develops especially rapidly - a disease associated with the excessive appearance in the bone marrow, and then in the blood of defective white cells - leukocytes. However, it has recently emerged that the relationship between radiation and cancer is more complex than previously thought. So, in a special report of the Japanese-American Association of Scientists, it is said that only some types of cancer: tumors of the mammary and thyroid glands, as well as leukemia, develop as a result of radiation damage. Moreover, the experience of Hiroshima and Nagasaki showed that thyroid cancer is observed with irradiation of 50 or more rad. Breast cancer, from which about 50% of cases die, is observed in women who have undergone repeated x-ray examinations.

A characteristic feature of radiation injuries is that radiation injuries are accompanied by severe functional disorders and require complex and long-term (more than three months) treatment. The viability of the irradiated tissues is significantly reduced. In addition, complications arise many years and decades after the injury. Thus, there were cases of benign tumors in 19 years after irradiation, and the development of radiation cancer of the skin and breast in women - in 25-27 years. Often, injuries are found against the background or after exposure to additional factors of a non-radiation nature (diabetes, atherosclerosis, purulent infection, thermal or chemical injuries in the radiation zone).

It should also be borne in mind that people who survived a radiation accident experience additional stress for several months and even years after it. Such stress can trigger a biological mechanism that leads to the onset of malignant disease. For example, in Hiroshima and Nagasaki, a large outbreak of thyroid cancer was observed 10 years after the atomic bombing.

Studies carried out by radiologists on the basis of data from the Chernobyl accident indicate a decrease in the threshold of consequences from exposure to radiation. Thus, it has been established that exposure to 15 rem can cause disturbances in the activity of the immune system. Already after receiving a dose of 25 rem, the liquidators of the accident showed a decrease in the blood of lymphocytes - antibodies to bacterial antigens, and at 40 rem, the likelihood of infectious complications increased. Cases of neurological disorders caused by changes in the structures of the brain were often observed under the influence of constant irradiation with a dose of 15 to 50 rem. Moreover, these phenomena were observed long after irradiation.

Radiation sickness

Depending on the dose and time of exposure, three degrees of the disease are observed: acute, subacute and chronic. In the lesions (when receiving high doses), acute radiation sickness (ARS) usually occurs.

There are four degrees of ARS:

Easy (100 - 200 rad). The initial period - the primary reaction as in ARS of all other degrees - is characterized by bouts of nausea. Headache, vomiting, general malaise, a slight increase in body temperature, in most cases - anorexia (lack of appetite, up to aversion to food), infectious complications are possible. The primary reaction occurs 15 to 20 minutes after exposure. Its manifestations gradually disappear after a few hours or days, or may be absent altogether. Then comes the latent period, the so-called period of imaginary well-being, the duration of which is determined by the dose of radiation and the general condition of the body (up to 20 days). During this time, erythrocytes reach their end of life, ceasing to supply oxygen to the cells of the body. ARS of mild degree is curable. Negative consequences are possible - blood leukocytosis, skin redness, decreased performance in 25% of those affected 1.5-2 hours after irradiation. There is a high content of hemoglobin in the blood within 1 year from the moment of irradiation. Recovery time is up to three months. In this case, the personal attitude and social motivation of the victim, as well as his rational employment, are of great importance;

Average (200 - 400 rad). Short bouts of nausea that resolve 2–3 days after exposure. The latent period is 10-15 days (may be absent), during which the leukocytes produced by the lymph nodes die and stop rejecting the infection that enters the body. Platelets stop clotting blood. All this is the result of the fact that the bone marrow, lymph nodes and spleen killed by radiation do not produce new erythrocytes, leukocytes and platelets to replace the spent ones. Edema of the skin, blisters develop. This state of the body, called "bone marrow syndrome", leads 20% of those affected to death, which occurs as a result of damage to the tissues of the hematopoietic organs. Treatment consists of isolating patients from the external environment, administering antibiotics and blood transfusion. Young and elderly men are more susceptible to moderate ARS than middle-aged men and women. Disability occurs in 80% of the affected in 0.5 - 1 hour after irradiation and after recovery remains reduced for a long time. Perhaps the development of cataracts of the eyes and local defects of the limbs;

Heavy (400 - 600 glad). Symptoms typical for gastrointestinal upset: weakness, drowsiness, loss of appetite, nausea, vomiting, prolonged diarrhea. The latent period can last 1 - 5 days. After a few days, signs of dehydration of the body appear: loss of body weight, exhaustion and complete exhaustion. These phenomena are the result of the death of the villi of the intestinal walls, which absorb nutrients from the incoming food. Their cells under the influence of radiation are sterilized and lose the ability to divide. There are foci of perforation of the walls of the stomach, and bacteria enter the bloodstream from the intestine. Primary radiation ulcers and purulent infection from radiation burns appear. Loss of working capacity 0.5-1 hour after irradiation is observed in 100% of victims. In 70% of those affected, death occurs within a month from dehydration and stomach poisoning (gastrointestinal syndrome), as well as from radiation burns with gamma irradiation;

Extremely heavy (over 600 glad). Severe nausea and vomiting occur within minutes after exposure. Diarrhea - 4-6 times a day, in the first 24 hours - impaired consciousness, skin edema, severe headaches. These symptoms are accompanied by disorientation, loss of coordination of movements, difficulty swallowing, upset stools, seizures, and eventually death. The immediate cause of death is an increase in the amount of fluid in the brain due to its release from small vessels, which leads to an increase in intracranial pressure. This condition is called central disorder syndrome. nervous system».

It should be noted that the absorbed dose causing damage separate parts organism and death, exceeds the lethal dose for the whole body. The lethal doses for individual parts of the body are as follows: head - 2,000 glad, lower abdomen - 3,000 glad, upper abdomen - 5,000 glad, chest - 10,000 glad, limbs - 20,000 glad.

The level of effectiveness of ARS treatment achieved to date is considered to be the limiting one, since it is based on a passive strategy - the hope for independent recovery of cells in radiosensitive tissues (mainly bone marrow and lymph nodes), for support of other body systems, platelet transfusion to prevent hemorrhage, erythrocyte - to prevent oxygen starvation. After that, it remains only to wait until all the systems of cellular renewal start working and eliminate the disastrous consequences of radiation exposure. The outcome of the disease is determined by the end of 2-3 months. In this case, the following may occur: complete clinical recovery of the victim; recovery, in which his ability to work in one way or another will be limited; an unfavorable outcome with the progression of the disease or the development of complications leading to death.

The transplantation of a healthy bone marrow is hampered by an immunological conflict, which is especially dangerous in an irradiated organism, since it depletes the already undermined strength of the immune system. Russian scientists-radiologists propose a new way of treating patients with radiation sickness. If a part of the bone marrow is taken from the irradiated person, then in the hematopoietic system after this intervention, the processes of earlier recovery begin than in natural development events. The extracted part of the bone marrow is placed in artificial conditions, and then after a certain period of time is returned to the same organism. Immunological conflict (rejection) does not occur.

At present, scientists are carrying out work, and the first results have been obtained on the use of pharmaceutical radioprotectors, which allow a person to tolerate radiation doses that are approximately twice the lethal dose. These are cysteine, cystamine, cystophos and a number of other substances containing sulfidehydryl groups (SH) at the end of a long molecule. These substances, like "scavengers", remove the formed free radicals, which are largely responsible for the intensification of oxidative processes in the body. However, a major drawback of these protectors is the need to introduce it into the body intravenously, since the sulfidehydryl group added to them to reduce toxicity is destroyed in the acidic environment of the stomach and the protector loses its protective properties.

Ionizing radiation also has a negative effect on fats and lipoids (fat-like substances) contained in the body. Irradiation disrupts the process of emulsification and promotion of fats in the cryptal region of the intestinal mucosa. As a result, drops of non-emulsified and coarsely emulsified fat, absorbed by the body, enter the lumen of the blood vessels.

An increase in the oxidation of fatty acids in the liver leads to increased liver ketogenesis in insulin deficiency, i.e. an excess of free fatty acids in the blood lowers the activity of insulin. And this, in turn, leads to the widespread disease of diabetes mellitus today.

The most typical diseases associated with radiation damage are malignant neoplasms (thyroid gland, respiratory organs, skin, hematopoietic organs), metabolic and immune disorders, respiratory diseases, complications of pregnancy, congenital anomalies, mental disorders.

Recovery of the body after irradiation is a complex process, and it proceeds unevenly. If the restoration of erythrocytes and lymphocytes in the blood begins after 7 - 9 months, then the restoration of leukocytes - after 4 years. The duration of this process is influenced not only by radiation, but also by psychogenic, social, household, professional and other factors of the post-radiation period, which can be combined into one concept of "quality of life" as the most capacious and fully expressing the nature of human interaction with biological factors of the environment, social and economic conditions.

Ensuring safety when working with ionizing radiation

When organizing the work, the following basic principles of ensuring radiation safety are used: selection or reduction of the power of sources to minimum values; reducing the time of working with sources; increasing the distance from the source to the worker; shielding radiation sources with materials that absorb or attenuate ionizing radiation.

In the premises where work is carried out with radioactive substances and radioisotope devices, the intensity of various types of radiation is monitored. These rooms should be isolated from other rooms and equipped with supply and exhaust ventilation... Other collective means of protection against ionizing radiation in accordance with GOST 12.4.120 are stationary and mobile protective screens, special containers for transportation and storage of radiation sources, as well as for collection and storage of radioactive waste, protective safes and boxes.

Stationary and mobile protective screens are designed to reduce the radiation level at the workplace to an acceptable level. Protection against alpha radiation is achieved by using plexiglass with a thickness of several millimeters. To protect against beta radiation, screens are made of aluminum or plexiglass. Water, paraffin, beryllium, graphite, boron compounds, concrete protects from neutron radiation. Lead and concrete protect against X-rays and gamma radiation. For viewing windows use lead glass.

When working with radionuclides, special clothing should be used. In case of contamination of the working space with radioactive isotopes, over the cotton overalls, film clothing should be worn: a dressing gown, suit, apron, trousers, arm ruffles.

Film clothes are made of plastics or rubber fabrics that can be easily cleaned from radioactive contamination. In the case of using film clothing, it is necessary to provide for the possibility of supplying air under the suit.

The workwear kits include respirators, air helmets and other personal protective equipment. For eye protection, glasses with glasses containing tungsten phosphate or lead should be worn. When using personal protective equipment, it is necessary to strictly adhere to the sequence of putting on and taking off, and dosimetric control.

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Under normal conditions, each person is continuously exposed to ionizing radiation as a result of cosmic radiation, as well as due to the radiation of natural radionuclides found in the earth, food, plants and in the human body itself.

The level of natural radioactivity caused by the natural background is low. This level of radiation is familiar to the human body and is considered harmless to it.

Technogenic exposure arises from technogenic sources both under normal and emergency conditions.

Different kinds radioactive radiation can cause certain changes in the tissues of the body. These changes are associated with the ionization of atoms and molecules of cells of a living organism that occurs during irradiation.

Working with radioactive substances in the absence of appropriate protective measures can lead to exposure to doses that have a harmful effect on the human body.

Contact with ionizing radiation is a serious hazard to humans. The degree of danger depends both on the amount of absorbed radiation energy and on the spatial distribution of the absorbed energy in the human body.

The radiation hazard depends on the type of radiation (radiation quality factor). Heavy charged particles and neutrons are more dangerous than X-rays and gamma rays.

As a result of the effect of ionizing radiation on the human body, complex physical, chemical and biological processes can occur in tissues. Ionizing radiation causes the ionization of molecules and atoms of the substance, as a result of which the molecules and cells of the tissue are destroyed.

Ionization of living tissues is accompanied by the excitation of cell molecules, which leads to the rupture of molecular bonds and to a change in the chemical structure different connections.

It is known that 2/3 of the total composition of human tissue is water. In this regard, the processes of ionization of living tissue are largely determined by the absorption of radiation by water of cells, ionization of water molecules.

Hydrogen (H) and hydroxyl group (OH) formed as a result of water ionization, either directly or through a chain of secondary transformations, form products with high chemical activity: hydrated oxide (HO2) and hydrogen peroxide (H2O2), which have pronounced oxidizing properties and high toxicity in relation to to the fabric. Entering into compounds with molecules of organic substances, and above all with proteins, they form new chemical compounds that are not characteristic of healthy tissue.

When exposed to neutrons in the body, radioactive substances can be formed from the elements contained in it, forming induced activity, that is, radioactivity created in a substance as a result of the effect of neutron fluxes on it.

Ionization of living tissue, depending on the energy of radiation, mass, the magnitude of the electric charge and the ionizing ability of radiation, leads to the rupture of chemical bonds and a change in the chemical structure of various compounds that make up tissue cells.

In turn, changes in the chemical composition of tissue, resulting from the destruction of a significant number of molecules, lead to the death of these cells. Moreover, many radiation penetrates very deeply and can cause ionization, and therefore damage to cells in deeply located parts of the human body.

As a result of exposure to ionizing radiation, the normal course of biological processes and metabolism in the body are disrupted.

Depending on the radiation dose and duration of exposure and on individual characteristics the organism, these changes can be reversible, in which the affected tissue restores its functional activity, or irreversible, which will lead to damage to individual organs or the whole organism. Moreover, the greater the dose of radiation, the greater its effect on the human body. It was noted above that along with the processes of damage to the body by ionizing radiation, protective and restorative processes also occur.

The duration of the irradiation has a great influence on the effect of the irradiation, and it should be considered that not even the dose, but the dose rate of the irradiation is of decisive importance. With increasing dose rate damaging effect increases. Therefore, fractional exposure to lower doses of radiation is less destructive than receiving the same radiation dose during a single exposure to the total dose of radiation.

The degree of damage to the body by ionizing radiation increases with an increase in the size of the irradiated surface. The effect of ionizing radiation is different depending on which organ is being irradiated.

The type of radiation affects the destructive ability of radiation when exposed to organs and tissues of the body. This influence takes into account the weighting factor for the given type of radiation, which was noted earlier.

The individual characteristics of the organism are strongly manifested at low doses of radiation. With an increase in the radiation dose, the influence of individual characteristics becomes insignificant.

A person is most resistant to radiation between the ages of 25 and 50. Young people are more sensitive to radiation than middle-aged people.

The biological effect of ionizing radiation largely depends on the state of the central nervous system and internal organs. Nervous diseases, as well as diseases of the cardiovascular system, hematopoietic organs, kidneys, endocrine glands reduce a person's endurance to radiation.

Features of the impact of radioactive substances that have entered the body are associated with the possibility of their long-term presence in the body and direct impact on internal organs.

Radioactive substances can enter the human body through inhalation of air contaminated with radionuclides, through the digestive tract (when eating, drinking, smoking), through damaged and intact skin.

Gaseous radioactive substances (radon, xenon, krypton, etc.) easily penetrate through the respiratory tract, are quickly absorbed, causing general damage. Gases are relatively quickly excreted from the body, most of them are excreted through the respiratory tract.

The penetration of atomized radioactive substances into the lungs depends on the degree of dispersion of the particles. Particles larger than 10 microns, as a rule, are retained in the nasal cavity and do not penetrate into the lungs. Particles less than 1 micron in size, trapped inside the body during inhalation, are removed with air during exhalation.

The degree of danger of injury depends on the chemical nature of these substances, as well as on the rate of elimination of the radioactive substance from the body. Less dangerous radioactive substances:

quickly circulating in the body (water, sodium, chlorine, etc.) and not lingering in the body for a long time;

not assimilated by the body;

does not form compounds that make up fabrics (argon, xenon, krypton, etc.).

Some radioactive substances are almost not excreted from the body and accumulate in it, while some of them (niobium, ruthenium, etc.) are evenly distributed in the body, others are concentrated in certain organs (lanthanum, anemones, thorium - in the liver, strontium, uranium, radium - in bone tissue), leading to their rapid damage.

When assessing the effect of radioactive substances, one should also take into account their half-life and the type of radiation. Substances with a short half-life quickly lose activity and are therefore less hazardous.

Each dose of radiation leaves a deep mark on the body. One of the negative properties of ionizing radiation is its overall, cumulative effect on the body.

The cumulative effect is especially strong when radioactive substances that are deposited in certain tissues enter the body. At the same time, being present in the body from day to day for a long time, they irradiate nearby cells and tissues.

There are the following types of radiation:

chronic (constant or intermittent exposure to ionizing radiation for a long time);

acute (single, short-term radiation exposure);

general (irradiation of the whole body);

local (irradiation of a part of the body).

The result of exposure to ionizing radiation in both external and internal irradiation depends on the radiation dose, duration of exposure, type of radiation, individual sensitivity and the size of the irradiated surface. In case of internal irradiation, the effect of exposure also depends on the physicochemical properties of radioactive substances and their behavior in the body.

Based on a large experimental material with animals, as well as by generalizing the experience of people with radionuclides in general outline it was found that when a person is exposed to certain doses of ionizing radiation, they do not cause significant irreversible changes in the body. Such doses are called limiting doses.

Dose limit - the value of the effective annual or equivalent dose of technogenic exposure, which should not be exceeded under normal operating conditions. Compliance with the annual dose limit prevents the occurrence of deterministic effects, while the probability of stochastic effects remains at an acceptable level.

Deterministic radiation effects - clinically detectable harmful biological effects caused by ionizing radiation, in relation to which a threshold is assumed, below which there is no effect, and above which the severity of the effect depends on the dose.

Stochastic radiation effects are harmful biological effects caused by ionizing radiation that do not have a dose threshold of occurrence, the probability of occurrence of which is proportional to the dose and for which the severity of manifestation does not depend on the dose.

In connection with the above, the issues of protecting workers from the harmful effects of ionizing radiation are of a multifaceted nature and are regulated by various legal acts.

Ionizing radiation is any radiation that causes ionization of the medium , those. 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 ionizing radiation

Sources of ionizing radiation are radioactive elements and their isotopes, nuclear reactors, particle accelerators, etc. X-ray installations and high-voltage direct current sources are X-ray sources. It should be noted here that during normal operation, the radiation hazard is negligible. It occurs when an emergency occurs and can manifest itself for a long time in case of radioactive contamination of the area.

The population receives a significant part of the exposure from natural sources of radiation: from space and from radioactive substances in the earth's crust. The most significant of this group is the radioactive gas radon, which occurs in almost all soils and constantly escapes to the surface, and most importantly, penetrates into industrial and residential premises. It almost does not manifest itself, as it is odorless and colorless, which makes it difficult to detect.

Ionizing radiation is divided into two types: electromagnetic (gamma radiation and X-ray radiation) and corpuscular, which is a- and β-particles, neutrons, etc.

Types of ionizing radiation

Ionizing radiation is called radiation, the interaction of which with the environment leads to the formation of ions of different signs. Sources of these radiation are widely used in nuclear energy, engineering, chemistry, medicine, agriculture etc. Work with radioactive substances and sources of ionizing radiation poses a potential threat to the health and life of people who are involved in their use.

Ionizing radiation includes two types of radiation:

1) corpuscular (α- and β-radiation, neutron radiation);

2) electromagnetic (γ-radiation and X-rays).

Alpha radiation- This is a stream of helium atomic nuclei emitted by a substance during the radioactive decay of a substance or during nuclear reactions. A significant mass of α-particles limits their speed and increases the number of collisions in matter; therefore, α-particles have a high ionizing ability and low penetrating ability. The range of α-particles in air reaches 8 ÷ 9 cm, and in living tissue - several tens of micrometers. This radiation is not dangerous as long as the radioactive substances emitting a- particles that will not enter the body through a wound, with food or inhaled air; then they become extremely dangerous.

Beta radiation- This is the flow of electrons or positrons arising from the radioactive decay of nuclei. Compared to α-particles, β-particles have a much lower mass and lower charge, therefore β-particles have a higher penetrating power than α-particles, and their ionizing power is lower. The range of β-particles in air is 18 m, in living tissue - 2.5 cm.

Neutron radiation- This is a stream of nuclear particles that do not have a charge, emitted from the nuclei of atoms in some nuclear reactions, in particular during the fission of uranium and plutonium nuclei. Depending on the energy, a distinction is made between slow neutrons(with energy less than 1 keV), intermediate energy neutrons(from 1 to 500 keV) and fast neutrons(from 500 keV to 20 MeV). In the case of inelastic interaction of neutrons with the atomic nuclei of the medium, secondary radiation arises, consisting of both charged particles and γ-quanta. The penetrating power of neutrons depends on their energy, but it is significantly higher than that of α-particles or β-particles. For fast neutrons, the path length in air is up to 120 m, and in biological tissue - 10 cm.

Gamma radiation represents electromagnetic radiation emitted during nuclear transformations or particle interactions (10 20 ÷ 10 22 Hz). Gamma radiation has a low ionizing effect, but a high penetrating power and propagates at the speed of light. It freely passes through the human body and other materials. This radiation can only be trapped by a thick lead or concrete slab.

X-ray radiation also represents electromagnetic radiation arising from the deceleration of fast electrons in matter (10 17 ÷ 10 20 Hz).

The concept of nuclides and radionuclides

The nuclei of all isotopes of chemical elements form a group of "nuclides". Most nuclides are unstable, i.e. they turn into other nuclides all the time. For example, the uranium-238 atom occasionally emits two protons and two neutrons (a-particles). Uranium turns into thorium-234, but thorium is also unstable. Ultimately, this chain of transformations ends with a stable lead nuclide.

The spontaneous decay of an unstable nuclide is called radioactive decay, and such a nuclide itself is called a radionuclide.

With each decay, energy is released, which is transmitted further in the form of radiation. Therefore, we can say that, to a certain extent, the emission by the nucleus of a particle consisting of two protons and two neutrons is a-radiation, the emission of an electron is β-radiation, and, in some cases, g-radiation arises.

The formation and dispersion of radionuclides leads to radioactive contamination of air, soil, water, which requires constant monitoring of their content and the adoption of measures to neutralize.

The effect of ionizing radiation on the body

The main effect of all ionizing radiation on the body is reduced to the ionization of the tissues of those organs and systems that are exposed to their irradiation. The charges acquired as a result are the cause of the occurrence of oxidative reactions in cells that are unusual for the normal state, which, in turn, cause a number of responses. Thus, a series of chain reactions occurs in the irradiated tissues of a living organism, disrupting the normal functional state of individual organs, systems and the organism as a whole. There is an assumption that as a result of such reactions in the tissues of the body, harmful products are formed - toxins, which have an adverse effect.

When working with products with ionizing radiation, the pathways of exposure to the latter can be twofold: through external and internal radiation. External exposure can occur when working on accelerators, X-ray machines and other installations emitting neutrons and X-rays, as well as when working with sealed radioactive sources, that is, radioactive elements sealed in glass or other blind ampoules, if the latter remain intact. Sources of beta and gamma radiation can pose a risk of both external and internal radiation. In practice, alpha-radiation is dangerous only with internal irradiation, since due to the very low penetrating power and small range of alpha-particles in the air, a slight distance from the radiation source or small shielding eliminate the danger of external radiation.

With external irradiation with rays with a significant penetrating ability, ionization occurs not only on the irradiated surface of the skin and other integuments, but also in deeper tissues, organs and systems. The period of direct external exposure to ionizing radiation - exposure - is determined by the exposure time.

Internal irradiation occurs when radioactive substances enter the body, which can occur when vapors, gases and aerosols of radioactive substances are inhaled, introduced into the digestive tract or enter the blood stream (in cases of contamination of damaged skin and mucous membranes). Internal irradiation is more dangerous, because, firstly, in direct contact with tissues, even radiation of insignificant energies and with a minimal penetrating ability still have an effect on these tissues; secondly, when a radioactive substance is in the body, the duration of its exposure (exposure) is not limited by the time of direct work with sources, but continues continuously until it is completely disintegrated or excreted from the body. In addition, if ingested, some radioactive substances, possessing certain toxic properties, in addition to ionization, have a local or general toxic effect (see "Harmful chemicals").

In the body, radioactive substances, like all other products, are carried by the bloodstream to all organs and systems, after which they are partially excreted from the body through the excretory systems (gastrointestinal tract, kidneys, sweat and mammary glands, etc.), and some of them are deposited in certain organs and systems, exerting a preferential, more pronounced effect on them. Some radioactive substances (for example, sodium - Na 24) are distributed throughout the body relatively evenly. Preferential deposition various substances in certain organs and systems is determined by their physicochemical properties and functions of these organs and systems.

The complex of persistent changes in the body under the influence of ionizing radiation is called radiation sickness. Radiation sickness can develop as a result of chronic exposure to ionizing radiation and short-term exposure to significant doses. It is characterized mainly by changes in the central nervous system (depression, dizziness, nausea, general weakness, etc.), blood and hematopoietic organs, blood vessels (bruising due to fragility of blood vessels), endocrine glands.