Radiation is the ionizing radiation of microscopic particles and physical fields. Radiation does not include ultraviolet rays and the range of visible light. Radio waves and microwaves do not possess the ability to ionize the oncoming substance, this is not radiation. The lethal dose for humans is not artificially created by chemical processes, radiation refers to the physical action.
Power and Dose
The power of radiation is the amount of ionization for a certain time period. For power, there is a unit of measurement - microroentgen per hour.
The received dose is measured by the total dose, determined by the radiation power multiplied by the duration of the microparticles, thus, a lethal dose of radiation for a person is calculated, which leads to death. The sievert (Sv) is used to measure the equivalent dose, the power for calculation is determined in sievert per hour (Sv / h).
To calculate the equivalent dose from exposure to various types of rays, the intensity of the desired radiation with respect to the sievert is taken into account. For example, when determining the total dose from the action of gamma rays, 100 x-rays are equated to 1 Sv. Small doses less than 1 Sv are calculated in relation to:
- 1 mSv (millisievert) is equal to 1/1000 sievert;
- 1 μSv (microsievert) is equal to 1/1000 millisievert or 1/1000000 sievert.
Radiation meter
The standard common device for determining the dose rate or the power directed to the device and to the device operator is the dosimeter. Dosimetry is carried out during the exposure to radiation, for example, a shift or the time of rescue work.
The lethal dose of radiation for a person in x-rays depends on the radiation intensity at the location of the employee, if the total figure is more than 600 units, then such exposure is life-threatening. The transported goods, objects are examined, the background from buildings and buildings is measured. Each person visiting places with the danger of radiation pollution acquires a dosimeter for permanent personal use.
When going to an unfamiliar area, for example, mountains, lakes, going on a hike or for berries and mushrooms, they take a device for examining the area before a long stay. The radiation intensity of the site is determined before construction or when buying land. The radiation background does not decrease and is not removed from the walls of buildings and objects, therefore, a hazard is previously detected using a dosimeter.
The concept of radioactivity
Some atoms contain unstable nuclei that can transform or decay. This process promotes the release of free ions. Radioactive radiation arises, energetically powerful, capable of acting on the surrounding substance and provoking the appearance of new ions of negative and positive charge. A lethal dose of radiation in rad occurs when a person is exposed to 600 rad, with 100 rad (an extra-systemic unit) = 100 x-rays.
Causes of radioactive contamination
The action of various factors and circumstances causes an increased radiation background:
- fallout of a radioactive substance from a nuclear cloud in an explosion;
- in the event of induced radiation, obtained by the formation of isotopes of a radioactive type under the instant action of gamma rays and neutrons released during a nuclear explosion;
- the action of external radiation of gamma and beta rays;
- a lethal dose of radiation occurs with internal exposure after radioactive isotopes enter the human body from the air or with food;
- Radioactive contamination is provoked in peacetime by man-made disasters at nuclear facilities, improper transportation and disposal of nuclear waste.
Type of radiation
Dangerous to humans is the emission of microparticles, leading to diseases of the body and deaths. The magnitude of the effect depends on the variety of rays, duration of action and frequency:
- heavy alpha particles positively charged after nuclear decay (these include thoron, cobalt-60, uranium, radon);
- beta particles are ordinary electrons of strontium-90, potassium-40, cesium-137;
- gamma radiation is represented by particles with high penetrating power (cesium-137, cobalt-60);
- hard X-ray radiation, resembling gamma particles, but less energetic, provides americium-241, the sun is a constant source of occurrence;
- neutrons result from the decay of plutonium nuclei, their accumulation is observed in the environment of atomic reactors.
Variety of doses
An equivalent fixed effective dose is the determination of radiation doses to the body as a result of the intake of a certain amount of a harmful substance. This indicator takes into account the sensitivity of internal organs and the time spent by a radioactive substance in the body (sometimes throughout life). In some cases, a lethal dose of radiation in x-rays is measured for one selected organ.
The ambident dose equivalent is determined by the amount that a person could receive if he were present in the territory where dosimetry is done, the indicator is measured in sievert.
The effects of radiation pollution on the human body
Any radiation that leads to the formation in the environment of electric particles with different signs is considered ionizing. The scattered radiation background constantly accompanies a person, it is created by cosmic radiation, the influence of the sun, natural sources of radionuclides, and other components of the biosphere.
For work in hazardous conditions, personnel are protected with special suits, comply with safety standards. The body receives radiation at the workplace during physical and chemical experiments, flaw detection, medical research, geological surveys, etc.
Radiation mutation
The lethal dose of radiation for a person in rad is over 600 units and leads to death. Irradiation in a dose of 400 to 600 rad contributes to the appearance of radiation sickness and can cause gene mutation. The effect of ionized transformation of the body is poorly understood, mutations manifest themselves through generations. The scatter of time gives the right to doubt whether a mutation has arisen from a radioactive effect or is caused by other reasons.
Mutations by type are divided into dominant, appearing in a short period after exposure to radiation and recessive. The second type manifests itself if the mother and child have the same mutant gene. A mutation does not wake up for several generations or does not bother a person at all. Fetal degeneration is difficult to determine in the case of premature birth, if the mutation does not allow the embryo to reach birth age.
Radiation sickness. Leukemia
Radiation is a major contributor to the diagnosis of radiation sickness. A lethal dose of radiation leads to death, but radiation levels from 200 to 600 r that cause radiation sickness are no less dangerous. Radiation affects a person after a single powerful exposure or with the constant penetration of radiation of low power. An example is the work of radiologists who do not withstand constant exposure and fall ill with characteristic diseases.
The most dangerous is the effect of radiation on a fragile body up to 15 years. There is no consensus on the dose size, the researchers cite different tolerance doses of 50, 100 and 200 r. Pathogenesis is being studied at research institutes; radiation leukemia is becoming more accessible for treatment.
Oncological diseases
The study of the effect of radiation on humans is hindered by the fact that large groups of people are studied for the appearance of generalized data, which is impossible without a special experiment. What lethal dose of radiation is lethal, and what levels cause human oncological tumors can not be judged by an experiment on animals.
In the sense of highlighting a dangerous dose that causes cancerous tumors, there is no definite data. Any dose of radiation received gives an impetus to the body to begin the division of aggressive cells. The frequency of manifestations of the disease is divided as follows:
- the most common is the manifestation of leukemia;
- out of 1000 women at risk, 10 patients develop breast cancer;
- the same statistics for thyroid cancer.
Severity of radiation sickness
Symptoms of radiation sickness are persistent headache, impaired movement, gesture coordination, nausea, vomiting, dizziness, and indigestion. What dose of radiation is fatal to humans:
- the first degree appears after a latency period of two weeks, the disease is caused by irradiation from 100 to 200 x-rays;
- for the manifestation of the second degree after exposure to a dose of 200 to 400 x-rays, death occurs in a fourth of exposed;
- the third stage of radiation sickness is mortality in 50% of cases; a dose of 400 to 600 x-rays is sufficient for the occurrence;
- the fourth, most dangerous stage, also causes radiation. The lethal dose is more than 600 x-rays, death occurs in 100% of cases.
