From Big Medical Encyclopedia

DUST — the aerosol, a dispersed phase to-rogo represents solid particles of the crushed substances which are in suspension in a gaseous fluid. The item represents unequigranular unstable system. Particle sizes P., as a rule, fluctuate ranging from 0,1 to 100 microns and more. Ability of particles to get into upper respiratory tracts and lungs and speed of their sedimentation, forms, the specific weight of the crushed material, the size of electric charge significantly depend on their sizes (see. Aerosols ). Vitaniye of P.'s particles in air is considered not only in connection with a possibility of their influence on health, but also ability of particles to enter atmospheric chemical and photochemical reactions and also as a factor of visibility reduction.

Among the reasons of pollution of free air dust the important place is taken wind soil erosion and rocks, by drilling-and-blasting works, volcanic eruptions, deleting of pavings as moving transport and so forth. A significant amount of P. comes to free air as a part of industrial emissions of the enterprises of ore mining industry, steel, cement works, combined heat and power plant and kotelen. In the atmosphere there can be also P. space and biol, origins. The space P. containing iron, nickel and other elements gets into the atmosphere under the influence of forces of gravitation, the electromagnetic field of Earth and light pressure (photophoresis). The item biol, origins consists of vegetable P. (cotton, linen, grain, formula-feed, etc.), and also P. of animal origin (woolen, etc.).

Free air of the cities differs in higher dust content, than free air of rural areas. The main component city P. are products of incomplete combustion of fuel (firm, liquid, gaseous) in the form of soot and resinous substances adsorbed on it containing 3,4 benzpyrene. Near metallurgical, mining, cement, chemical and other companies P. can come to the atmosphere owing to imperfection of separate treatment facilities and during the transportation of loose loads. Such P. contains in the basic of a particle of starting materials. Besides, it includes the resinous substances which are formed from deleting of a paving (asphalt, tar, etc.). To the enclosed space of P. can get with an induced air.

The item possesses more often alkali reaction since consists generally of oxides of silicon, calcium, aluminum, magnesium and other elements which with water vapors of air form hydroxides. Motes of a metal origin and the main oxides bear on themselves negative charges, and motes of non-metallic materials and acid oxides — positive. Existence of opposite charges promotes P. Zapylennost's coagulation increases in the cities in cold season, and in rural areas — in summertime. During the day in connection with household and productions the maximum concentration of P. is observed in the morning and in the evening. Vertical stability of the atmosphere in the form of convection, inversions and isothermies is of great importance for P.'s distribution.

Specific weight of P. depends on its chemical structure. Low specific weight and small particle sizes promote a long vitaniye of P. in air and to distribution on a long distance. Time of a vitaniye of suspended particles in the atmosphere and them biol, activity depend on physical. - chemical properties, disperse structure of P. and meteorological factors. P.'s removal from the atmosphere results from sedimentation of particles by gravity. It depends on the speed of the movement of air and level of humidity.

With reduction of particle sizes P. its specific surface, chemical activity and sorption ability increases. Dust particles occlude the surface the gases, vapors, radioactive materials, ions and free radicals which are formed at processes of burning under the influence of radoactive radiation and as a result of photochemical effect.

The contaminated free air (see) can make an adverse effect on flora and fauna. The interrelation between the level of pollution of free air and incidence of the population, first of all pulmonary and allergic diseases is proved. Toxicants in the atmosphere, napr, sulfur dioxide gas, phenol, etc., can strengthen action on an organism of carcinogenic substances.

In our country much attention is paid to questions of environmental control (see), improvements of working conditions, life and rest of the Soviet people. In resolutions of Party and Government the attention to the correct placement of the new cities and territorialnoproizvodstvenny complexes, to reduction of pollution of free air is paid. Systematic moistening of roads, transportation of loose loads in a tight container, gardening of territories also promote decrease in maintenance of P. in free air (see. Sanitary protection of free air ).

For the characteristic of level of pollution of P. of free air and assessment of efficiency of pyleochistny installations the greatest distribution in practice a dignity. supervision received a gravimetric (weight) method of definition of concentration of P. Maksimalno one-time to maximum allowable concentration of non-toxic dust in free air it is equal to 0,5 mg/m 3 , and average daily — 0,15 mg/m 3 .

Production (industrial) dust

Production (industrial) dust it is formed in the course of performance of labor operations at the industrial enterprises and in agriculture. The number of productions at which there can be an intensive pylevydeleniye is extremely big. Such processes at the enterprises of the ore mining, metal-working, woodworking, textile industry, in brick and ceramic, farforo-faience, cement, foundry and other productions are most frequent.

Industrial P. is classified by a way of education, chemical structure and the sizes of dust particles. Depending on a way of education distinguish P. in the form of an aerosol of disintegration which is allocated as a result of mechanical crushing of solid matter (crushing, drilling, grinding, cleaning of casting, processing of a tree, wool, cotton, etc.) willows a type of an aerosol of condensation, formed during the cooling of vapors of substances (zinc oxide, copper, iron etc.).

On chemical structure of P. can be organic and inorganic. Carry vegetable P. to organic (wood, grassy, flour, tobacco, etc.), P. of animal origin (woolen, fur, hair, feather) and P. of synthetics. The miner P. consisting of oxides of metals, silicon dioxide, etc. components can be an example of inorganic P. The item of complex structure call mixed.

In the atmosphere and air of a working zone of production rooms, in addition to P., in the form of aerosols of disintegration there can be finely divided aerosols of condensation — smokes (see). Smoke is formed at combustion of various substances as a result of sublimation and condensation of their vapors, and also owing to chemical and photochemical reactions (at combustion of liquid and solid fuel, smelting of metals, electric welding, spraying of solutions with the subsequent drying of droplets etc.). Smoke as well as P., contains firm parts of substances. However much smaller (0,1 — 0,001 microns) and they practically do not settle their sizes by gravity.

The item and smoke can be present at free air and the air environment of production rooms at the same time in this connection a concept industrial (production) dust and combines both kinds of aerosols.

Depending on the sizes of dust particles distinguish visible P. (particle size more than 10 microns), microscopic (particle size from 0,25 to 10 microns) and ultramicroscopic (particle size less than 0,25 microns). The greatest danger to the person is constituted, as a rule, by P. with particle sizes from 0,25 to 5 microns; it deeply gets into respiratory tracts and reaches alveoluses. Particles more than 5 microns in size are late a mucous membrane of upper respiratory tracts and bronchial tubes.

Important gigabyte. the form and hardness of dust particles matter. The particles which are formed as a result of disintegration of substances (a grinding, grinding, crushing, etc.), have, as a rule, uneven keen edges and injure a mucous membrane of respiratory tracts. Long soft and flexible motes of a plant, animal and mineral (asbestos) origin easily are late a mucous membrane of respiratory tracts and quite often cause development hron, inflammatory processes: a nasopharyngitis (see. Rhinitis , Pharyngitis ), tracheitis (see), mechanic bronchitis (see).

Production P. can render the fibrogenny, inflammatory, irritating, toxic and allergenic action on an organism (see. Dust allergy ). Fibrogenny action is shown at long inhalation of highly disperse P. (see. Pneumoconiosis ), inflammatory — during the work in the conditions of the increased dust content of air, especially coarse-dispersion the Item. Some types of P. (manganese ore, potassium bichromate, etc.), getting into a respiratory organs, can cause development of pneumonia (see), render irritant action on mucous membranes (dust of hromovoshchelochny salts, limes, arsenic, soda, calcium carbide, superphosphate, etc.), to cause diseases of skin (dermatitis). Toxic action of P. depends on its chemical structure and solubility in fluid mediums of an organism. The item, having allergic properties (dust is lame, a box, mahogany, etc.), is an origin of astmoidny states, bronchial asthma, eczema.

For prevention occupational diseases of a dust etiology implementation radical technological, a dignity is necessary. - those. and to lay down. - the prof. of the actions directed to reduction of dust formation. Effective measures are sealing of the equipment and the processes connected with crushing, a grinding, weighing, loading, unloading and movement of the raising dust substances and products; replacement of dry processes of processing of materials wet (drilling with washing, conducting clearing and driving works in the coal industry by combines with irrigation, wet sanding of products, a wet mandrel of china, etc.); use of effective positive-pressure ventilation (see). In ore mining industry (see) drilling with washing, irrigation of the raising dust materials during the handling works in combination with correctly organized ventilation allowed to reduce dust content of the miner atmosphere to the levels close to maximum allowable concentration and to sharply reduce incidence of a pneumoconiosis. Use of the local sucking-away ventilation during the welding works, sifting of powder materials and other manufacturing operations allows to reduce P.'s concentration in a working zone. Implementation of hydrocoal mining, replacement in textile, chemical and pharm. the industries of a number of powdery products pastes and solutions excluded danger of impact of a dust factor on an organism of working. Automation and mechanization of the manufacturing operations connected with the increased dust formation allow not only to facilitate work, but also to reduce number of the persons working in potentially dangerous conditions. In prevention of occupational diseases of a dust etiology also social and legal actions — the shortened working hours, additional issue, the privilege to treatment and rest in the conditions of sanatoria, dispensaries and rest houses are important, earlier retirement, etc.

the Dust inseminated by microorganisms

the Source of infection of P. is the soil, in a cut sporous forms of bacteria and fungi, the steadiest against an adverse effect of environmental factors, and also pathogenic and opportunistic microorganisms of a zoogene origin live. In the enclosed space (residential, public buildings and to lay down. - professional, institutions) the main source of microbic planting of P. is the patient or the bacillicarrier.

Pathogenic and opportunistic microorganisms a long time survive on dust particles. So, pathogenic staphylococcus more than 20 days, and in air survive more than 10 days on scattered light. Long survival in P. of causative agents of diphtheria and tuberculosis, a dispute of mold fungi is noted. By means of P. causative agents of flu, measles, chicken and natural pox, tuberculosis and many other diseases can be transferred.

The infected P. is the cornerstone of an air and dust way of transfer of the activators steady against adverse environmental factors (insolation, drying, action of Uv-radiation, etc.). In natural and experimental conditions the main patterns of circulation of causative agents of the infections told with P. Ustanovleno that the infected P. in rooms can repeatedly rise in air are studied circulate on all building, settle on a surface of objects, get into a human body together with air. Infection of people is most often observed in the enclosed space (inhabited, public, hospital, etc.), and also under production conditions (processing of page - x. raw materials, microbiological laboratories, etc.).

For inhabited and public places the admissible maintenance of P. shall not exceed 0,15 mg/m 3 , however the direct quantity of microorganisms is normalized only in air of surgery blocks and delivery rooms — 500 bacteria in 1 m 3 , at the same time golden staphylococcus — one of the main activators of pyoinflammatory complications — in samples of air of 250 l shall be absent.

Under production conditions bacterial. SES laboratories carry out systematic microbiological control of objects of the production environment. In surgery blocks control of the intrahospital environment shall be carried out systematically and according to indications, and under production conditions — according to the schedule of the controlling services (veterinary, sanitary and epidemiologic, etc.).

Allocation of microorganisms from P., their identification is made according to the practical standards (see Identification of microbes). Sampling of air is carried out by Krotov's device or other samplers.

Architectural planning solutions, systems of ventilation, cleaning and disinfecting of air belong to the actions providing restriction of circulation of microorganisms with P. E.g., the optimal solutions allowing to limit circulation of pathogenic and opportunistic microorganisms in rooms to lay down. - the prof. of institutions, locks with the exhaust ventilation at chambers are, locks at an entrance to ward section with forced ventilation and neutral zones (rooms between ward sections and lestnichnoliftovy nodes) with the device of positive-pressure ventilation. For an exception of transfer of microorganisms via channels of the exhaust ventilation (see) these channels shall be designed separately for each room intended for long stay of people.

For disinfecting of objects of use and air of the rooms infected with pathogenic bacteriums, intestinal and respiratory viruses the most effective is uses of short-wave ultraviolet radiation (see). - For disinfecting of surfaces of objects of use and air of rooms concerning bacterial and virus pollution use of aerosols of disinfecting substances is shown (hydrogen peroxide, chloroamine, hexylresorcin, etc.). Systematic wet cleaning of rooms with use of disinfecting detergents is important.

See also articles devoted to separate types of productions of which P.'s allocation is characteristic, e.g. Ore mining industry , Ceramic-metal production , Flour-grinding production etc.

Bibliography: Bagdasaryan G. A., etc. Fundamentals of sanitary virology, M. of 1977; E. B Boletus. Hygienic aspects of prevention of intrahospital infections, Gigabyte. and dignity., No. 4, page 9, 1981; Fight against a silicosis, under the editorship of G. A. Pozdnyakov and E. I. Vorontsova, t. 11, M., 1982; Vlodavets V. V. Fundamentals of aerobiology, page 118, M., 1972; Intrahospital infections, under the editorship of M. T. Parker, the lane with English, M., 1979; Hygienic aspects of environmental control, under the editorship of E. I. Korenevskaya, century 3, page 14, M., 1976; Izrael Yu. A., etc. Implementation in the USSR systems of monitoring of pollution of the environment, page 15, 62, L., 1978; Lashchenkov P. N. Guide to experimental hygiene, page 8, Tomsk, 1927; Methodological questions of hygienic rationing of production factors, under the editorship of N. F. Izmerov and A. A. Kasparov, page 87, M., 1976; Nemyria V. I. and Vlodavets V. V. Environmental control from emissions of the enterprises of the microbiological industry, M., 1979; Occupational diseases, under the editorship of. A. A. De-taveta, etc., page 351, M., 1973; The Guide to hygiene of free air, under the editorship of K. A. Bushtuyeva, page 5, 349, M., 1976; With and-dorenko G. I. Topical issues of hygiene of free air, Gigabyte. and dignity., No. 12, page 3, 1975; The Reference book on professional pathology, under the editorship of L. N. Gratsianskaya and V. E. Kovshilo, L., 1981; X about-tsyanov L. K., Leite about R. G. and Martsinkovsky B. I. Occupational health, page 455, M., 1958.

E. I. Vorontsova; G. A. Bagdasaryan (the dust inseminated by microorganisms).