From Big Medical Encyclopedia

BACKGROUND RADIATION (the Russian Federation, a synonym a background of ionizing radiation) — ionizing radiation from natural sources of a space and terrestrial origin, and also from the artificial and natural radionuclides disseminated in the biosphere as a result of activity of the person.

The Russian Federation influences all population of the globe, having rather fixed level. The Russian Federation it is caused by environmental factors and does not include the radiation of the persons working with sources of ionizing radiation, radiation in diagnostic considered during the calculation of population doses and to lay down. the purposes, etc. (see. Radiation safety).

Distinguish natural background radiation, technologically changed natural background radiation, artificial background radiation and full background radiation.

The Natural Background Radiation (NBR) represents ionizing radiation (see) from natural sources of a space and terrestrial origin and quite often in literature it is identified with the concept Russian Federation.

The Technologically Changed Natural Background Radiation (TCNBR) represents ionizing radiation from the natural sources which underwent certain changes in result of activity of the person, napr, radiation from the natural radionuclides coming to the biosphere together with the minerals extracted on the Earth's surface from its subsoil (hl. obr. mineral fertilizers), as a result of receipt to the environment of products of combustion of organic fuel, radiation in the rooms built of the materials containing natural radionuclides. Here sometimes refer additional radiation due to flights by modern high-rise airplanes, and also radiation in life, napr, due to use of hours, the svetosostava of constant action containing natural radionuclides are applied on the dial to-rykh.

After the beginning of broad tests of nuclear weapon there was a global pollution of the biosphere artificial radionuclides. In recent years still very insignificant, but increasing pollution of local, regional and global character caused by waste of the enterprises of nuclear power and use of sources of ionizing radiation in the scientific purposes in medicine and in the national economy are added to it. The radiation caused by the artificial radionuclides disseminated in the biosphere represents the artificial background radiation (ABR) which adds only 1 — 3% to ERF now.

Set of ERF, TIERF and IRF makes full background radiation.

A measure of the Russian Federation is the power of an absorbed dose (see Doses of ionizing radiation; Radiation sizes, units). In geophysics at the same time the power of the dose absorbed in air on the area at the expense of external sources of radiation means. In medical and biol. to literature of the Russian Federation estimate, as a rule, on the power of an absorbed dose in body tissues. At the same time the doses caused by both external radiation, and internal at the expense of the radionuclides which got to an organism are considered.

For convenience of comparison biol. efficiency and assessment of risk of emergence of the remote effects at different types of radiation (see), including cases of uneven radiation, doses at the expense of the Russian Federation often express in indicators of an effective equivalent dose — the conditional concept characterizing the calculated dose of uniform external radiation of all body adequate on risk of emergence of the remote stochastic (probabilistic) effects to a real absorbed dose in this or that body.

Natural background radiation. ERF is the main Russian Federation component.

The natural sources of ionizing radiation creating ERF are subdivided into external sources of an extraterrestrial origin (space radiation); external sources of a terrestrial origin, i.e. the radionuclides which are present at crust, water, air; internal sources, i.e. the radionuclides of a natural origin which are contained in a human body.

The space radiation getting into the atmosphere of Earth from space represents the high energy radiation (primary space radiation), a cut interacts with atomic nuclei of the elements which are present at the atmosphere and generates the secondary space radiation reaching the Earth's surface consisting of nuclear particles and electromagnetic radiation (see. Space radiation). The annual effective equivalent dose at sea level at the expense of space radiation makes 30 mrem (3-10-4 Stars). The people living in conditions of highlands receive higher doses of external space radiation by 1,5 — 2 times.

External radiation at the expense of radionuclides of a terrestrial origin is caused 40K and elements of decay series 238U, 232Th, present at crust throughout all history of the planet (see Thorium, Uranium). Power of an absorbed dose, average on the globe, in air from natural radionuclides of a terrestrial origin out of rooms makes 5 mkrad / hour (0,05 mkgr / hour). In certain regions of the globe, napr, in the nek-ry regions of India, Brazil, France, these values are significantly higher. Accepting the coefficient considering mean time of stay of the person out of rooms, equal 0,2 it is possible to calculate that the annual effective equivalent dose at the expense of the gamma radiation of a terrestrial origin out of rooms makes 6 mrem (6-10“ ^ Stars). In rooms a dose from external radiation other as walls and overlappings, on the one hand, protect from the radiation generated by natural radionuclides of crust, and with another — become sources of additional radiation since building materials may contain the increased amounts of radionuclides. Wooden houses in weak degree protect from external radiation, without creating additional while houses from a brick and concrete effectively protect from radiation from the Earth's surface, and the dose created in such buildings is caused by hl. obr. the radionuclides which are contained in building materials. In modern buildings from a brick and concrete dosage rate in rooms is, as a rule, 1,5 — 2 times higher than dosage rate out of rooms. Taking into account a ratio of the buildings which are available on the globe from a tree, a brick and concrete the Scientific committee on action of atomic radiation at the UN estimates the power of an absorbed dose average on all globe in air in rooms at about 6 mkrad / hour (6-10-8 Gr / hour). Considering time of stay of the person in rooms expressed by coefficient 0,8 it is possible to count that the annual effective equivalent dose in rooms makes 29 mrem (2,9-10 ~ 4 Stars), and total (out of and in rooms) the annual effective equivalent dose due to external radiation by radionuclides of a terrestrial origin is equal 6 mberlg29 mrem = = 35 mrem (3,5 * 10 "4 Stars).

Internal radiation by radionuclides of a natural origin is caused by their receipt in a digestive tract with food and water, and also in lungs at breath. Radionuclides of a kosmogenny origin (3H, 7Be, 14C) cause an insignificant part of a dose of internal radiation, on average 1,5 mrem (0,015 mzv) in a year.

The radionuclides of a terrestrial origin getting to an organism create an annual effective equivalent dose at the level of 140 mrem (1400 μSv), from to-rykh 18 mrem (180 μSv) — for account 40K (see Potassium), the getting hl. obr. with food, 120 mrem (1200 μSv) — at the expense of isotopes 222Rn and 220Rn (thoron), and also the temporary products of their disintegration which are airborne preferential rooms owing to intake of thoron and 222Rn from building materials and soil of basements (see Radon). 238U arrives generally with food, it is significantly less — with water (except for certain regions, in particular in Helsinki where concentration 238U in nek-ry water sources reaches 5,4 nkyuri/l (200 Bq/l). Annual receipt 238U in a human body averages apprx. 140 pkyura (apprx. 5 Bq), concentration in a bone tissue — at the level of 2,7 — 5,4 pkyuri/kg (0,1 — 0,2 Bq/kg), annual absorbed doses on endosteal cells — 170 mkrad (1,7 • 10'6 Gr). 230Th owing to low absorption in went. - kish. a path gets into an organism preferential with inhaled air (about 0,27 pkyur, or

10 mbk in a year). Being osteotracks-nym an element and collecting in a skeleton, 230Th creates there doses at the level of 700 mkrad (7 • 10_6 Gr) in a year.

The main isotope of radium (see) — 226Ra gets to an organism of hl. obr. through a digestive tract — about 400 pkyur (15 Bq) a year. With air arrives (together with the inhaled dust) about 1000 times less than radium. The contribution of drinking water is small if water arrives from superficial water sources. The population using deep wells, mineral springs where concentration of radium is significantly higher as water sources can receive its most part with water. Apprx. 70 — 90% of the radium which came to an organism selectively

collects in a bone tissue. Average content 226Ra in a skeleton of the person makes apprx. 27 pkyura (1 Bq). The annual effective equivalent dose for the account 226Ra in regions with usual ERF is rather small and makes about 0,6 — 0,7 mrem (6 — 7 μSv).

Technologically changed natural background radiation. About a half of the effective equivalent dose received by an organism from the Russian Federation give 222Rn and the temporary products of its disintegration arriving through a respiratory organs in rooms. Worldwide average concentration of radon in air of rooms is about 10 times higher, than in the environment. Thereof receives a considerable share of all radiation of people as a result of stay in rooms. It gives the grounds to allocate a dose at the expense of this type of radiation from the dose caused by ERF and to consider it as a component technologically changed (in this case strengthened) background radiation.

to a telny measure are defined by socio-economic factors. Thereof they in various countries considerably vary. Their studying began rather recently and only over the certain countries by 1983 more or less full picture is received. The data characterizing specific population (averages individual) exposure doses of the population of the USSR at the expense of all wasps

Radiation in buildings at the expense of radon, thoron are presented in table 2 and are about 25% higher than products of their disintegration in midlatitudes, than on average on the globe that is explained by higher concentration of these radionuclides in rooms and rather more short-term stay of people in comparison with zones of tropical and subtropical climate in the open air. Key products of disintegration 222Rn, creating a considerable share of radiation of lungs, are the short-lived alpha radiating isotopes of lead (see) and polonium (218ro, 214Pb, 214Bi, 214ro). Besides, with air out of rooms comes to an organism in a year apprx. 108 pkyura (4 Bq) 210R and apprx. 27 pkyura (1 Bq) — 210ro, belonging to long-living decomposition products 222Rn. Smokers (20 cigarettes a day) in addition with tobacco smoke receive in a year apprx. 405 pkyura (15 Bq) 210R and 540 pkyur (20 Bq) 210ro. In the alimentary way of people receives in addition approximately for 1080 pkyur (40 B to) these nuclides. In northern areas owing to existence of specific food chains (see) the people consuming meat of rens receive with poor in a year apprx. 3,78 nkyur (140 Bq) 210R and 37,8 nkyur (1400 Bq) 210ro that causes increase in a dose of internal radiation. The generalized data on a contribution of various natural sources of ionizing radiation to formation of the Russian Federation are presented in table 1.

Exposure doses at the expense of technologically changed natural background radiation and full background radiation in znachi-

novny sources of radiation (on the published materials Ying-that biophysics of M3 of the USSR).

These tables 2 confirm a decisive contribution to a population dose of natural background radiation, technologically changed natural background radiation due to stay in buildings, and also X-ray and radio isotope diagnostic testings. Radiation, obuslov-

lenny the artificial radionuclides disseminated in the biosphere has much smaller specific weight.

Influence r and d and and c and about N-nogo of a background on health is a subject of studying of a physics health (see). In literature there are no established ideas of influence on health of the person of the small ionizing radiation doses characteristic of the Russian Federation yet. It is conventional that radiation at the expense of the Russian Federation even in regions where it is raised, does not cause to any specific radiation injuries. Statements about an important role are distributed, to-ruyu ERF played, being the mutagen factor participating in mechanisms of evolution of live organisms (see Radiogenetics). Nek-ry specialists believe that radiation in small doses plays a positive role, stimulating vital processes and, in any case, does not make harmful effects on an organism. as ERF exists since ancient times and to it people, animals and plants had to adapt. According to modern ideas of mechanisms and effects biol. actions of small doses of ionizing radiation, generalized in editions of the International commission on radiological protection and Scientific committee on action of atomic radiation at the UN, the Russian Federation does not exert positive impact on health of the person. Many specialists connect medical effect of radonic bathtubs rather with action of thermal, volumetric and other not radiation factors, but not with influence of the radon and its alpha-active decomposition products.

It is not necessary to revaluate a role of ERF and from the point of view of value for evolution. Ionizing radiation is not the only mutagen factor, there are also other mutagens — a rigid component At Physical spearing of the Sun, ions of metals, products of incomplete combustion of organic fuel, biogenic factors. In the light of modern ideas of mechanisms of a carcinogenesis (see) and the genetic damages induced by ionizing radiation there are all bases to consider that nek-paradise a part of the malignant tumors and hereditary diseases which are observed at people is caused by influence of small ionizing radiation doses, first of all at the expense of the Russian Federation and its such component as radon and its affiliated products. Owing to existence of long stage of latency and increase of probability of development of malignant tumors with increase in the saved-up ionizing radiation dose the tumors induced at the expense of the Russian Federation are shown, as a rule, aged when the person already has a posterity. This fact, and also very low probability of developing of malignant tumors and hereditary diseases under the influence of the Russian Federation demonstrate that the mankind is capable to exist also without development of adaptation of each individual to impact of ionizing radiation at the level of the Russian Federation. Thus, there are arguments in favor of existence certain, though small, dangers of the Russian Federation to health. At the same time the arguments testimonial of its beneficial influence on an organism are less convincing. The question of influence of small doses of ionizing radiation, and in particular components of the Russian Federation, on health still needs further researches.

In the USSR the National commission on radiation protection at the Ministry of Health of the USSR officially accepted the standards limiting admissible impact on the population of TIERF at the expense of natural radionuclides in building materials. At extremely small doses making the Russian Federation, the risk of developing of malignant tumors and hereditary diseases is even less — it is almost not detectable against the background of spontaneous incidence.

Theoretically expected frequency of developing of malignant tumors with a lethal outcome and hereditary diseases among the population of the USSR due to influence

of various sources of ionizing radiation is shown in table 3. Its data are calculated in Ying-those biophysics of M3 of the USSR according to the concept of linear nonthreshold action of ionizing radiation (see. Physics health).

Proceeding from data of table 3, and also using epidemiological and statistical data on prevalence of cancer and genetic disorders, it is possible to calculate that natural background radiation (without dose caused by stay in buildings) otvetstven approximately for 1% of the observed malignant tumors mortality.

The negative effects of radiation which do not have stochastic (probabilistic) character (see Postradiatsionny effects), are shown only at the capacities of the exposure doses surpassing background in tens and hundreds of times.

See also Radioecology.

Table 1


Table 2


Table 3


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