Background radiation: the radiation dose for a person
Permissible dose of radiation for humans
Cosmic radiation the Earth, and anthropogenic and natural radionuclides participate in the formation of background radiation. Background radiation is radiation from man-made and natural sources that affects the person is.
After the Chernobyl catastrophe, the atmosphere was thrown about 40 types of artificial radionuclides. The greatest danger to humans substances such as strontium, cesium, plutonium, iodine. The half-life of some of them reaches 25 thousand years.
According to the organization, which is engaged in the problems of the environment, radionuclides are recognized as the most toxic substances. On the territory of the former USSR have long existed nuclear test sites, where testing of nuclear weapons, and also stored hazardous waste. The most well known are «Mayak» and the polygon in Semipalatinsk.
The person receives a radiation dose from an external, cosmic sources, also under the influence of radionuclides present in the body. The average dose of radiation from external and internal exposure sources is about 200 mrem/year.
Industrial human activity directly affects the education in the atmosphere of radionuclides and isotopes. They are extracted from the earth in the process of getting coal, oil, gas, and mineral fertilizers.
Be exposed to natural radionuclides is possible even at home. Materials such as brick, wood, concrete, release small quantities of radon.
Being a long time in an unventilated room, the person risks to get a big dose of the radionuclide. Negative impact on health have potassium-40, radium-226, polonium-210, radon-222, -220.
The impact of space radiation on humans depends on the area in which he resides. People living in the mountains, have a higher risk of exposure than those who live in the lowlands. It is known that those who live low on the sea level of 300 µsv/year. The reason filmed the properties of water. The average amount of radiation coming from the cosmos, to which man is exposed per year, equal to 350 mSv.
Background radiation and its types
The composition of the background radiation of natural origin include cosmic radiation and natural radionuclides that are present on the water surface, earth’s crust, the atmosphere in General. Its value has remained unchanged for many thousands of years. There are several areas where the magnitude of the impact of radiation on human beings is much higher. This is because shallow soil underlain by thorium or uranium ore out radon sources.
Natural background radiation is radiation that comes from space, due to the recycling of radioactive elements found in the bowels of the Earth, in building materials, food. The most dangerous ones are the radionuclides 40K and 222Rn. Natural background radiation was formed and developed simultaneously with the development of the biosphere. Cosmogenic radionuclides involved in the process of formation of the crust of the Earth. Shifts and troughs in it – places where radionuclides were released to the earth’s surface, the power of ionizing radiation increased. Over time the level of radioactivity decreased.
Natural background radiation can be technologically changed because of the transformation of ionizing radiation. Artificial background radiation is a consequence of the collapse of the nuclear waste energy.
The impact of artificial radiation sources illustrated in the table below:
|The type of radiation source||The amount of radiation (mrem/year)|
|The use of everyday objects||4|
|Radiation from TVs and monitors||0.1|
Human activity as the source of the manifestation of radiation
Since the mid XX century the level of radiation from anthropogenic impact has increased to the level of 15 Mr/h. This happened for several reasons:
- the testing of nuclear weapons;
- the burning of fossil fuels;
- redistribution of mineral substances that are mined out of the earth;
- emissions of harmful substances due to accidents at nuclear power plants and enterprises.
To include various anthropogenic sources of ionizing radiation:
- apparatus for medical diagnosis;
- x-ray equipment;
- installation power and research profile;
- radiation defectoscopy.
As a result of nuclear reactions are formed transuranic radionuclides. They are characterized by high toxicity. The most dangerous are plutonium, americium.
The degree of toxicity of the radionuclides are divided into 4 groups:
- very high toxicity;
- high toxicity;
- the average toxicity;
- low toxicity (do not bear serious danger to humans).
Measurement of level of radiation exposure
The concept of «normal background radiation» appeared in the 20-ies of the last century. The allowable level of radiation was around 600 mSv/year. By the mid-twentieth century, this value fell to 50 mSv/year, and in 1996 the 20 mSv/year. Indicator norms were introduced for examination of medical staff, particularly radiologists.
People experiencing the effects of radiation everywhere. Radioactive dose in a certain amount present in the body always. When the rate of radiation in the body is exceeded many times, death can occur.
The permissible rate of radiation to humans (exposure to natural background) is from 0.05 µsv/h 0.5 µsv/h. Particularly dangerous to be exposed to technogenic radiation in large volume. Radionuclides and isotopes accumulate in the human body, causing diseases, primarily cancer.
The radiation level is the maximum allowable dosage levels of ionizing radiation (measured in microsieverts). The allowable radiation level indoors is 25 Mr/h radiation Unit of radiation microsieverts per hour. The likelihood of developing cancer rises dramatically if a person is exposed to a radiation dose in excess of 11.42 Μsv/h. More than half of people obluchinskaya dose over 570.77 MSv at one time, die in 3-4 weeks. The maximum permissible level of radiation from sources of natural origin is considered normal in the range of 0.57 µsv/hour. Normal background radiation, excluding the impact of radon is 0.07 MK/h.
A particular danger the radiation poses to persons whose professional activity involves a constant clash with irradiation. Measures to prevent exposure among the medical staff are reduced to the permissible limit of radiation.
Maximum permissible concentration (MPC) of radioactive radiation is calculated from data about the type and period of decay of the ionizing particles.
If the person is regularly in contact with radioactive elements, it is necessary to know how to defend themselves. Developed and put into practice acceptable levels of contamination of clothing and means of protection after disinfection. The maximum allowable level of pollution is reflected in the table below.
|The object of pollution||The number of particles in 1 minute|
|Alpha radiation||Beta radiation|
|Before cleaning||After cleaning||Before cleaning||After cleaning|
|Linen and towels||75||background||5000||background|
|Overalls from a cotton fabric||500||100||25000||5000|
|Clothing from the film||500||200||25000||10000|
There is an average daily rate for a human. It is equal 0,0027 mlsv per day.
The risk of exposure to radiation on the body
Normal background radiation does not prejudice the life and health of a person. The most harmful consequences of radiation exposure are somatic diseases, and genetic, which are reflected at the DNA level.
It is established that systematic radiation has on the human body in a more gentle action than a single, because radiation damage tends to recover.
Hazardous substances accumulate in the body unevenly. The immune system is inhibited under the influence of radionuclides, which is reflected in the increased susceptibility of a person to certain diseases, especially cancer. Digestive and respiratory system suffer the most. Through them comes primarily radionuclides. The concentration of absorbed harmful substances in them is 2-3 times higher than in other organs. Normal safe level of background radiation is 50 Mr/HR.
Major Russian cities and cities have higher background radiation. This is due to the effects of the Chernobyl accident, the movement of radioactive dust, continuous operation of large industrial enterprises, transport emissions and CHP. Adverse effects from radiation for a person becomes unwell, the development of cancer, different mutations at the gene level, which lead to an overall reduction in quality of life.