From Big Medical Encyclopedia

AIR — mix of gases, from a cut consists the gas cover surrounding the globe. As a part of V. (tab.), except constant components atmospheres (see), various impurity of a natural origin and pollution brought by activity of the person contain.

Is physical century. mix, but not chemical compound of the gases making it in this connection at almost constant percentage of parts B. at different heights as a result of change of density of the atmosphere their weight concentrations and partial pressure change.

The great value in maintenance of gas composition of the atmosphere plays biosphere (see), biogeocenosis (see), ecological systems to-rykh are supported biol, cycle of matter.

Among constant components of V. major importance has the oxygen necessary for breath for all living beings except for the few anaerobic microorganisms. In the nature processes of consumption and recovery of oxygen are constantly carried out (see). The first occurs due to breath of the person and animals, processes of burning, oxidation. The only process of recovery of the normal oxygen content is photosynthesis (see), as a result to-rogo of carbonic acid, water and mineral substances during the use of energy of a sunlight is formed annually to 10 11 t of organic matters at simultaneous release approximately the same amount of free oxygen.

Transition of oxygen in blood and from blood in an intercellular lymph comes from alveolar V. under the influence of a difference in partial pressure (see). During the falling of partial pressure of oxygen at the person and animals the phenomena of air hunger develop (see the Hypoxia). The first signs of oxygen insufficiency are noted at decrease in partial pressure to 140 mm of mercury. (corresponds to height of 1000 m above sea-level); symptoms of a hypoxia or high-rise (mountain) disease are shown at 110 mm of mercury. (height of 3000 m above sea-level), decrease in partial pressure to 46 — 60 mm of mercury. it is life-threatening. At long accommodation in the high-rise area at people accustoming to a lack of oxygen due to adaptation gradually develops (see Adaptation to height). Small excess of oxygen is transferred by the person without any effects. Long inhalation of pure oxygen can lead to a fluid lungs.

The prevailing component of V. is nitrogen (see). In the nature continuously there is a process of a circulation of nitrogen, as a result to-rogo nitrogen of the atmosphere turns into organic compounds for the account biol, fixings, is recovered at their disintegration again and again communicates living beings.

Nitrogen belongs to to inert gases (see). Significant increase in content of nitrogen in V. can be followed by the phenomena of a hypoxia and asphyxia owing to decrease in partial pressure of oxygen. In the conditions of the open atmosphere such phenomena are not observed since fluctuations in the content of nitrogen are insignificant. Nitrogen is dissolved in blood in proportion to its partial pressure and upon bystry transition from high pressure to low excess of nitrogen is distinguished from blood in the form of vials of gas, causing a caisson disease (see. Compressed-air disease ).

Other inert gases (argon, neon, helium, krypton, xenon) on the nature of action on the person are similar to nitrogen.

The main sources of carbon dioxide gas in the atmosphere are the volcanic gases, hot water beating from the earth, breath of the person, animals, plants, processes of fermentation and rotting, and also products of combustion of natural minerals. The atmosphere contains approximately 2,3×10 12 t carbon dioxide gas (see).

Carbon dioxide gas assimilates plants in the course of photosynthesis, at the same time carbon is used on creation of organic matters. The large role in it is played by phytoplankton of the seas and oceans. The powerful regulator of content of carbon dioxide gas in V. is the hydrosphere of the earth, about a cut there is an intensive exchange. About 10 11 the t of carbon dioxide gas continuously is in an exchange state between the atmosphere and the ocean. Due to dependence of solubility of carbon dioxide gas on temperature in cold areas of the ocean there is preferential an absorption of carbon dioxide gas, and in tropics its allocation.

In air of a ground layer of the atmosphere there is no essential accumulation of carbon dioxide gas, but in a number of the industrial cities increase in its contents, especially in winter time due to fuel burning is noted. Observations and theoretical calculations demonstrate also global accumulation of carbon dioxide gas in connection with all the increasing volumes of the burned fuel. The amount of carbon dioxide gas in the atmosphere annually increases. Carbon dioxide intensively absorbs infrared beams of a solar range in this connection processes of accumulation of carbon dioxide gas can exert impact on a heat balance of the planet.

Accumulation of carbon dioxide gas can take place in V. of the enclosed space, being an indicator of its pollution. Carbon dioxide gas plays a large role in life activity of the person and animals, being the activator of a respiratory center. Falling of its concentration in V. does not constitute danger, increase — is not indifferent for the person. In premises from der-yakaniye of carbon dioxide it is regulated and shall not exceed 0,1%.

From other constant components B. is of interest ozone (see). Was considered that ozone is the natural making V. and is brought in a prizemny layer of the atmosphere from a stratosphere where it is continuously formed as a result of dissociation of oxygen under the influence of ultra-violet radiation. Presence of the ozone which is a strong oxidizer was considered as an indicator of purity of V. Issledovaniyami it is established that ozone is an intermediate product of the photochemical reactions proceeding under the influence of ultra-violet radiation between nitrogen dioxide and hydrocarbons — V.'s pollutants of the industrial cities. In this regard availability of ozone in V. of the cities can be considered as an indicator of its pollution. Biol, effect of ozone on the person is shown at concentration higher than 0,02 mg/mg.

Dust in V. can have a natural origin and arrive as a result of activity of the person. The role of space dust is insignificant, volcanic dust causes temporary pollution of V. after eruption of volcanoes. A little large role is played by land dust (soil, vegetable, from wildfires). Content of land dust fluctuates seasonally, existence of vegetation etc. Vegetable dust (pollen, disputes of fungi and other plants) is connected with a season of year; it can be the cause of allergic respiratory diseases. Industrial dust is characterized by a variety of qualitative and quantitative structure that defines it biol, action and a gigabyte. value (see. Dust ).

Except constant components, V. usually contain various gases arriving with emissions of the industrial enterprises, power plants and cars. From them sulfur dioxide gas, carbon monoxide, nitric oxides, hydrocarbons, hydrogen sulfide most often meet. Atmospheric V.'s pollution can exert adverse impact on living conditions and health of the population. In the atmosphere there is a gradual release of V. from foreign impurity, first of all for the account biol, circulation of the biosphere. However in connection with ever-increasing industrial production rates of self-cleaning of V. lag behind emissions that leads to disturbance of natural balance. Besides, nek-ry industrial emissions are not used by microorganisms and therefore are not utilized in biol, circulation. In the USSR much attention is paid to development and implementation on a nation-wide basis of actions on to sanitary protection of free air (see).

Air can contain various microorganisms, to-rye in the majority are saprophytes and do not cause diseases. Due to the development of nek-ry industries, in particular microbiological and medical drugs, local pollution of free air biol, products can make an adverse effect on the person. Causative organisms meet in the open atmosphere extremely seldom that connect with pernicious action on them ultraviolet rays. A source of pathogenic microorganisms in V. of the enclosed space are the saliva and slime emitted at a conversation and cough by patients or bacillicarriers.

Physical are of great importance for the person. properties B. — humidity, temperature and mobility.

The amount of water vapors, or V.'s humidity, fluctuates, averaging 0,42% on volume and 0,2% on weight. Content of water vapors falls with height; in the summer it is higher, than in the winter; V. in the equatorial zones is most wet (see. Humidity ).

For the person dressed easily and who is in rest V.'s temperature 18 — 20 ° is considered optimum. Lower temperatures are necessary for preservation of thermal balance during the performance of hard work. High humidity at low temperatures causes overcooling of a body in connection with bigger heat conductivity of wet V.; at high temperatures the overheat because of difficulty of evaporation of sweat is possible.

V.'s mobility can change a thermolysis of an organism and by that to influence a heat balance of the person.

In the USSR pollution and physical. properties B. are regulated by special standards. For atmospheric V. of the inhabited places and V. of production rooms maximum allowable concentrations of harmful substances are established, on a basis to-rykh recreational actions are developed and implemented.

For maintenance of a favorable microclimate in production rooms the norms considering the period of year and the nature of the performed work are established. Norms of temperature in residential buildings are stated in construction norms and rules; they consider the nature of use of rooms. Actions for pollution control of atmospheric V. include the technological, planning and other measures directed to respect for the established maximum allowable concentrations. Rational systems of ventilation, conditioning and V.'s cleaning (see. Ventilation , Air conditioning ) provide healthy working conditions in workrooms.

Free air also contains trace amounts of radioactive products of disintegration of uranium and thorium. One of them is the radon which is constantly diffusing from the soil and the products of its disintegration representing radioactive aerosols (see). Other isotopes of a number of uranium which are contained in atmospheric V. have a certain value. Concentration of natural radioactive materials in atmospheric V. is not identical, so, e.g., the content of radon-222 over the ocean is equal to 10 - 15 curie/l, and over the land — 5×10 - 13 curie/l; levels of thoron above the ground fluctuate ranging from 2×10 - 15 to 5×10 - 14 curie/l.

Atmospheric V.'s pollution by radioactive materials happens hl. obr. at the expense of the artificial radioisotopes coming to the atmosphere in the form of gases, aerosols or vapors.

Artificial radioisotopes receipts in V. of products nuclear (and thermonuclear) the explosions conducted for the purpose of testing of nuclear weapon, or industrial nuclear explosions with excavation of soil and also emissions are the reasons of pollution of the atmosphere radioactive waste (see).

At nuclear explosions fragmental cleavage products, radioactive products of activation («the induced activity») and a part of not reacted nuclear fuel come to atmospheric V. The radioactive gases arising at explosions (argon-41, xenon-135, krypton-85, etc.) under the influence of meteorological factors quickly dissipate in the atmosphere. Radioactive materials (see), passed at explosion into a vaporous state, in process of decrease in temperature in a radioactive cloud take the form of aerosols and are gradually besieged on the Earth's surface. The coarse particles which got at explosions to a stratosphere under the influence of gravity quickly settle on a surface of reservoirs and sushi. The finely dispersed aerosols bearing on themselves long-living radioisotopes of strontium, caesium, plutonium, etc. dissipate in the atmosphere under the influence of meteorological factors and are gradually besieged on the Earth's surface in a look radioactive fallout (see). The period of semi-clarification of the atmosphere from these radioisotopes makes apprx. 1 year.

The radioactive waste deleted in the atmosphere can be a source of local pollution of atmospheric V. Depending on character of sources where the specified waste is formed, systems of neutralization and removal waste may contain radioactive gases and aerosols. Main source of inert radioactive gases (argon-41, krypton-85, etc.) usually nek-ry types of atomic reactors are.

Atmospheric V.'s pollution by radioactive materials of a natural origin results from intake of volcanic dust, and also smokes and ashes from combustion of black coal, in Krom trace amounts of radium (from 0,001 to 1,3 nkyuri/kg), the cement dust which is also containing radium, dust of mineral (potash) fertilizers, etc. usually contain.

As the specified radioactive materials contain in solid particles, their behavior in the atmosphere is subordinated to the same patterns, as usual aerosols. Absolute levels of similar pollution depend on the content of natural radioactive materials in fuel or a feed stock (black coal, rocks), however similar pollution of atmospheric V. are not big and practically do not change a natural radioactive background of this area. Local pollution of the atmosphere natural radioactive gases, in particular radon, are possible in a zone of ventilating emissions from various mines. However the sphere of pollution of a ground layer of atmospheric V. even at adverse situations is limited to radon.

Concentration of radioactive materials in atmospheric V. are regulated in our country a dignity. the legislation adopted according to recommendations of the International commission on radiation protection and norms of the International agency but atomic energy (IAEA). For operating control sizes of annual average admissible concentration for each radioisotope in atmospheric Century are provided in standards.

Depending on properties of the radioisotopes coming to atmospheric V., ways of their impact on a human body can be various. So, the inert radioactive gases which are gamma-emitters at hit in atmospheric V. as a part of a radioactive cloud (at nuclear explosions) or in the form of a torch from pipes of reactors can be a source of external radiation of the people who are under a torch or under a cloud at the time of its passing. Other radioisotopes coming to the atmosphere in the form of aerosols and having beta and especially alpha radiation can make impact only at direct contact with an organism. Depending on properties of a radioisotope, degree of its solubility, ability to migrate on biol, to systems etc. in one cases the dominating role is played by an inhalation way of receipt from the atmosphere, in others — peroral.

In actual practice at long pollution of atmospheric V. radioactive materials of a way of their impact on the person are various, and, unlike toxicants, the inhalation way wins not first place.

Pollution of a ground layer of atmospheric V. radioactive materials is usually small that excludes need of use by the population of individual protection equipment.

The main protective measures come down to prevention of pollution: the termination of the nuclear explosions connected with receipt in the atmosphere of radioactive materials, the rational decision tekhnol. processes in atomic industry (see), careful cleaning of V. given to the reactor of any impurity, sealing of the equipment, deactivation of emissions (see. Deactivation ) etc. Check of performance of these actions is carried out in the course of precautionary a dignity. supervision at a design stage and by the current sanitarnodozimetrichesky control in the relevant institutions, and also at the enterprises of the atomic industry and nuclear power.

See also Atmosphere .

Bibliography: Vernadsky V. I. The biosphere, p.1 — 2, L., 1926; it, Biogeochemical sketches (1922 — 1932), M. — L., 1940; Vorobyov A. M. Methods of definition of radioactive materials in air, M., 1974, bibliogr.; Standards of radiation safety (NRB — 69), M., 1972; The Main standards of safety at protection against radiation, Mezhdunarodn. the agency on atomic energy, Vienna, 1968; Ryazanov V. A. Composition of free air and hygienic value of its main ingredients, the Guide to utility hygiene, under the editorship of F. G. Krotkov, t. 1, page 137, M., 1961; Solovyova T. V. and Crunch Leva V. A. The guide to methods of definition of harmful substances in free air, M., 1974; Monitoring behind the content of radioisotopes in air and water, the lane with English, M. * WHO, 197i, bibliogr.; X about l e y d and D. A., etc. A problem of radon in uranium mines, the lane with English, M., 1961.

K. A. Bushtuyeva; A. N. Marey (I am glad.).