Permissible radiation doses for humans

Radiation is a factor of influence on living organisms, which is not recognized by them in any way. Even people lack peculiar receptors that would sense the presence of a radiation background. Specialists have carefully studied the effect of radiation on human health and life. Instruments were also created with which you can record indicators. Doses of radiation characterize the level of radiation, under the influence of which a person was for a year.

What is radiation measured in?

On the World Wide Web you can find a lot of literature on radioactive radiation. In almost every source there are numerical indicators of exposure standards and the consequences of exceeding them. It is not immediately possible to understand incomprehensible units of measurement. The abundance of information characterizing the maximum permissible doses to the public can easily confuse a knowledgeable person. Consider the concepts in a minimal and more understandable volume.

What is radiation measured in? The list of values ​​is very impressive: curie, rad, gray, becquerel, rem - these are just the main characteristics of the radiation dose. Why so much? They are used for certain areas of medicine and environmental protection. For the unit of exposure to radiation on any substance, the absorbed dose is taken - 1 gray (Gy), equal to 1 J / kg.

When exposed to living organisms, they speak of an equivalent dose. It is equal to the dose absorbed by the tissues of the body, calculated on a unit mass, multiplied by the damage coefficient. A constant is allocated for each organ. As a result of calculations, a number with a new unit of measurement is obtained - sievert (Sv).

Based on the data already obtained on the effect of the received radiation on the tissues of a particular organ, the effective equivalent dose is determined. This indicator is calculated by multiplying the previous number in sievert by a coefficient that takes into account the different tissue sensitivity to radiation. Its value allows us to estimate the amount of energy absorbed, taking into account the biological reaction of the body.

What are permissible radiation doses and when did they appear?

Based on data on the effect of radiation on human health, radiation safety experts have developed maximum allowable energy values ​​that can be absorbed by the body without harm. Maximum allowable doses (SDA) are indicated for single or prolonged exposure. At the same time, radiation safety standards take into account the characteristics of persons exposed to the background radiation.

The following categories are distinguished:

• A - persons working with sources of ionizing radiation. In the course of the performance of their labor duties, they are exposed.
• B - the population of a certain area, workers whose duties are not associated with receiving radiation.
• In - the population of the country.

Two groups of personnel are distinguished: employees of the controlled area (radiation doses exceed 0.3 of the annual traffic regulations) and employees outside such a zone (0.3 of the traffic regulations are not exceeded). Within the limits of doses, 4 types of critical organs are distinguished, that is, those in whose tissues the greatest amount of destruction is observed due to ionized radiation. Given the above categories of people among the population and workers, as well as critical bodies, radiation safety sets traffic rules.

The limits of exposure first appeared in 1928. The annual absorption of the background radiation was 600 millisievert (mSv). It was installed for medical personnel - radiologists. With the study of the effect of ionized radiation on the duration and quality of life, traffic rules have been tightened. Already in 1956, the bar dropped to 50 millisievert, and in 1996 the International Commission on Radiation Protection reduced it to 20 mSv. It is worth noting that when establishing traffic rules, the natural absorption of ionized energy is not taken into account.

Natural radiation

If you can still avoid encountering radioactive elements and their radiation at least somehow, then you can’t hide from the natural background. Natural exposure in each of the regions has individual indicators. It has always been and over the years does not disappear, but only accumulates.

The level of natural radiation depends on several factors:

• height indicator above sea level (the lower the lower the background, and vice versa);
• soil, water, rock structures;
• artificial causes (production, nuclear power plants).

A person receives radiation through food, radiation from soils, the sun, during a medical examination. Additional sources of exposure are industrial enterprises, nuclear power plants, test sites and launch airfields.

Experts consider the most acceptable irradiation, which does not exceed 0.2 μSv in one hour. And the upper limit of the radiation norm is determined at 0.5 μSv per hour. After some time of continuous exposure to ionized substances, the permissible radiation doses for humans increase to 10 μSv / h.

According to doctors, in a lifetime a person can receive radiation in the amount of not more than 100-700 millisievert. In fact, people living in mountainous areas are exposed to radiation in somewhat larger sizes. The average absorption of ionized energy per year is about 2-3 millisievert.

How exactly does radiation affect cells?

A number of chemical compounds have the property of radiation. Active fission of atomic nuclei occurs, which leads to the release of a large amount of energy. This force is capable of literally pulling electrons from the atoms of the cells of a substance. The process itself is called ionization. An atom that undergoes such a procedure changes its properties, which leads to a change in the entire structure of the substance. For atoms, molecules change, for molecules, the general properties of living tissue. With an increase in the level of irradiation, the number of altered cells also increases, which leads to more global changes. In this connection, permissible radiation doses for humans were calculated. The fact is that changes in living cells also affect the DNA molecule. The immune system actively restores tissue and is even able to “repair” damaged DNA. But in cases of significant exposure or violation of the body's defenses, diseases develop.

It is difficult to predict the likelihood of developing diseases that occur at the cellular level with the usual absorption of radiation. If the effective dose of radiation (this is about 20 mSv per year for industrial workers) exceeds the recommended values ​​by hundreds of times, the overall health condition is significantly reduced. The immune system malfunctions, which entails the development of various diseases.

Huge doses of radiation that can be received as a result of an accident at a nuclear power plant or an atomic bomb explosion are not always compatible with life. Tissues under the influence of altered cells die in large numbers and simply do not have time to recover, which entails a violation of vital functions. If part of the tissues is preserved, then the person will have a chance of recovery.

Permissible exposure doses

According to radiation safety standards, the maximum permissible values ​​of ionizing radiation per year are established. Consider the indicators in the table.

As can be seen from the table, the permissible dose per year for workers in hazardous industries and nuclear power plants is very different from the indicators derived for the population of sanitary protection zones. The thing is that with prolonged absorption of permissible ionizing radiation, the body copes with the timely restoration of cells without compromising health.

Single doses of human exposure

A significant increase in the radiation background leads to more serious tissue damage, and therefore organs begin to function incorrectly or even fail. A critical state arises only when a huge amount of ionizing energy is received. A slight excess of the recommended doses can lead to diseases that can be cured.

A single receipt of a large amount of radiation negatively affects the state of the body: the cells are rapidly destroyed, not having time to recover. The stronger the impact, the more lesions occur.

The development of radiation sickness: causes

Radiation sickness is the general condition of the body caused by the influence of radioactive radiation in excess of traffic rules. Lesions are observed from all systems. According to statements by the International Commission on Radiological Protection, radiation doses causing radiation sickness start with indicators of 500 mSv at a time or more than 150 mSv per year.

The striking effect of high intensity (more than 500 mSv one-time) arises from the use of atomic weapons, their tests, the occurrence of technological disasters, and intensive irradiation procedures in the treatment of cancer, rheumatology and blood diseases.

The development of chronic radiation sickness is subject to medical workers located in the department of radiation therapy and diagnostics, as well as patients who are often subjected to radionuclide and radiological studies.

Classification of radiation sickness, depending on radiation doses

The disease is characterized on the basis of what dose of ionizing radiation the patient received and how long it took. A single exposure leads to an acute condition, and constantly repeating, but less massive, to chronic processes.

Consider the main forms of radiation sickness, depending on the received single exposure:

• radiation injury (less than 1 Sv) - reversible changes occur;
• bone marrow form (from 1 to 6 Sv) - has four degrees, depending on the dose received. Mortality with this diagnosis is more than 50%. Red bone marrow cells are affected. The condition may improve transplantation. The recovery period is long;
• the gastrointestinal (10–20 Sv) is characterized by a serious condition, sepsis, and gastrointestinal bleeding;
• vascular (20–80 Sv) - hemodynamic disturbances and severe intoxication of the body are observed;
• cerebral (80 Sv) - fatal outcome within 1-3 days due to cerebral edema.

A chance for recovery and rehabilitation are patients with a marrowy form (in half of the cases). More severe conditions cannot be treated. Death occurs within a few days or weeks.

The course of acute radiation sickness

After a high dose of radiation was received, and the radiation dose reached 1–6 Sv, acute radiation sickness develops. Doctors divide the states that replace each other into 4 stages:

1. Primary reactivity. It occurs in the first hours after exposure. It is characterized by weakness, lowering blood pressure, nausea and vomiting. When irradiated with more than 10 Sv, it immediately passes into the third phase.
2. Latent period. After 3-4 days from the moment of exposure to a month, the condition improves.
3. Detailed symptoms. It is accompanied by infectious, anemic, intestinal, hemorrhagic syndromes. The condition is serious.
4. Recovery.

An acute condition is treated depending on the nature of the clinical picture. In general, detoxification therapy is prescribed by administering agents that neutralize radioactive substances. If necessary, a blood transfusion, bone marrow transplantation is performed.

Patients who manage to survive the first 12 weeks of acute radiation sickness generally have a favorable prognosis. But even with full recovery, such people have an increased risk of developing cancer, as well as the birth of offspring with genetic abnormalities.

Chronic radiation sickness

With constant exposure to radioactive radiation at lower doses, but in total exceeding 150 mSv per year (not counting the natural background), a chronic form of radiation sickness begins. Its development goes through three stages: formation, restoration, outcome.

The first stage takes several years (up to 3). The severity of the condition can be determined from mild to severe. If you isolate the patient from the place of receipt of radioactive radiation, then within three years the recovery phase will begin. After that, a complete recovery is possible or, conversely, the progression of the disease with a quick fatal outcome.

Ionized radiation can instantly destroy the cells of the body and disable it. That is why compliance with radiation dose limits is an important criterion for work in hazardous production and life near nuclear power plants and test sites.