Industrial dust is one of the most common harmful factors in human work. Numerous technological processes and operations in industry and construction, transport and agriculture are accompanied by the formation and release of dust, and a significant number of workers are exposed to it.
For example, in the mining industry, dust formation is associated with the processes of drilling, blasting, sorting, and the operation of mining machinery - combines, excavators, bulldozers, etc. At processing plants, dust enters the air when rock is crushed and broken. In the building materials industry, all technological processes are associated with crushing, grinding, displacement and transportation of dusty raw materials and products (cement, brick, fireclay, silica, etc.). In mechanical engineering, dust formation processes take place in foundries during the preparation of molding soil, during knocking, stripping, blowing molds and cleaning castings, as well as in machine shops during grinding and polishing of products.
Many processes in metallurgy, electric welding, plasma and electric spark processing of metal are accompanied by the release of dust and vapors into the air, condensing into aerosols. In textiles, dust can occur during cleaning and sorting of wool and other types of fabric.
In agriculture, industrial dust is formed during loosening and fertilizing the soil, using powdered pesticides (pesticides), cleaning grain and seeds, cotton, flax, etc.
In various industries, numerous processes are associated with dust formation. These include crushing, grinding of bulk materials, excavation and loading of rock mass, blasting.
In the oil and gas industry, dust is generated during drilling, operation and repair of wells. The composition of this dust includes potassium, sodium or calcium aluminosilicates, barite (barium sulfate), slaked and quicklime, and cements of various compositions.
At oil refineries and petrochemical enterprises, many technological processes use catalysts, the dust from which may contain nickel, aluminum components, chromium and iron oxides, etc.
At gas processing plants, solid sulfur is produced as a by-product, which forms highly dispersed dust during transportation.
Incomplete combustion of solid fuel produces waste - sols and slags, which consist of 80-90% silicon dioxide, iron oxides, calcium, magnesium. When they are processed and buried, dust of a similar composition is formed.
When carrying out electric gas welding work, an aerosol is generated, which is dangerous because it contains manganese and chromium oxides.
One has to deal with dust of natural origin mainly when solving problems of cleaning the supply air before entering it into ventilated rooms. Industrial dust arises during the production process. Almost every type of production, every material or type of raw material is accompanied by a certain type of dust.
Many technological processes are aimed at producing various materials consisting of small particles, for example, cement, building gypsum, flour, etc. The collection of these particles is correctly called dusty material. The corresponding dust (for example, cement, flour, etc.) is usually called the smallest particles of these materials, carried by air currents.
Most types of dust arise as a result of processes associated with the processing of materials (cutting, grinding, etc.), their sorting and transportation (loading, unloading, etc.).
A significant part of industrial dust is of mixed origin, that is, it consists of inorganic and organic particles or, being organic, includes particles of mineral and metal dust. For example, grain dust, in addition to particles formed during grain grinding, also contains mineral particles that got into the grain mass during growing and harvesting. Dust released during grinding of metal products, in addition to metal particles, contains mineral particles formed during the interaction of the metal being processed and the tools for its processing (abrasive wheel, etc.). This must be taken into account when choosing cleaning methods and dust collection equipment.
Industrial dust is one of the most common adverse factors. occupational hazard. It occurs in the vast majority of industries, where a wide variety of technological processes and operations are accompanied by the formation and release of dust into the zone of influence on large contingents of workers.
In the mining industry, significant amounts of dust are generated during drilling and blasting operations. In the coal industry - during the operation of combines and rock loading machines, when sorting coal, etc. At processing plants, dust enters the air during crushing and grinding of rock. The entire building materials industry is associated with the processes of crushing, grinding, mixing and transporting dusty raw materials and products (cement, brick, fireclay, silica, etc.). In the engineering industry, dust formation processes take place in foundries during the preparation of molding soil, during knocking, stripping, blowing molds and cleaning castings, as well as in machine shops - mainly during grinding and polishing of products. Many processes in metallurgy, electric welding, plasma and electric spark processing of metal are accompanied by the release of dust and vapors into the air, condensing into aerosols. With incomplete combustion of fuel, soot and soot, which are also aerosols in the form of smoke and dust, can enter into the air of workplaces, along with sublimation products and resinous substances. In the chemical industry, many processes are also associated with dust formation. In agriculture, dust is formed when loosening and fertilizing the soil, using powdered pesticides, cleaning grain and seeds, cotton, flax, etc.
Industrial dust are suspended in the air, slowly settling solid particles ranging in size from several tens to fractions of microns. Dust is an aerosol, i.e. a dispersed system in which the dispersed phase is solid particles and the dispersion medium is air.
Industrial dust is classified by origin, method of formation and particle size(dispersity). --.---
By origin dust is divided into: organic, inorganic And mixed. Organic dust can be natural - animal or plant origin (wood, cotton, linen, jute, bone, wool, etc.) and artificial (dust from plastics, rubber, resins, dyes and other synthetic products). Inorganic dust can be mineral (quartz, silicate, asbestos, cement, emery, porcelain, etc.) and metal (zinc, iron, copper, lead, manganese). Mixed types of dust include dust generated in the metallurgical industry, in many chemical and other industries.
Depending on the way of education differentiate aerosols of disintegration and condensation. Disintegration aerosols are formed during mechanical grinding, crushing and destruction of solids (drilling, grinding, rock blasting, etc.), during mechanical processing of products (cleaning castings, polishing, etc.). Condensation aerosols are formed during thermal processes of sublimation of solids (melting, electric welding, etc.) due to cooling and condensation of vapors of metals and non-metals, in particular polymeric materials - plastics, as a result of thermal treatment of which vapor-gas-aerosol mixtures are formed containing solid, liquid particles, gases and vapors of complex chemical composition.
Depending on the dispersion there are: visible dust (more than 10 microns), microscopic(from "0.25 to 10 microns), ultramicroscopic(less than 0.25 microns).
The dispersion of aerosols determines the rate at which particles settle in the external environment. The smallest particles (0.01-0.1 microns) can remain in the air for a long time in a state of Brownian motion. Larger ones settle from the air at a rate determined by their size and specific gravity. The settling speed of large particles is determined by Newton's law (with the acceleration of gravity), small ones (from 0.1 to 100 microns) by Stokes' law (with the acceleration of gravity).
Currently, the fight against dust, which is the most common unfavorable factor in the working environment, seems to be an extremely urgent problem facing occupational medicine in general and, including hygienic science. A huge number of technological processes and operations in industry, transport, and agriculture are accompanied by the formation and release of dust, and large contingents of workers are exposed to it.
Dust characteristics. Knowledge of the origin and conditions of formation of industrial dust, its physical and chemical properties and the characteristics of its effect on the human body are important not only in improving the working conditions of working contingents, but also in the subsequent diagnosis and treatment of respiratory diseases, as well as the development of comprehensive engineering and technical sanitary and hygienic preventive measures.
Dust- These are solid particles suspended in the air, slowly settling, ranging in size from several tens to fractions of microns. Dust is an aerosol, i.e. a dispersed system in which the dispersed phase is solid particles and the dispersion medium is air.
The most widely used classification of dust is by method of formation, origin, dispersion and nature of action (Table No. 18).
Table No. 18. Classification of aerosols.
Organic dust can be of animal or plant origin (wool, feed, bone, wood, cotton, linen, etc.); inorganic dust can be mineral and metal (quartz, silicate, cement, zinc, iron, copper, lead, etc.); With mixed dust widely found in the metallurgical, mining and chemical industries; artificial dust(dust of rubber, resins, dyes, plastics, etc.) is typical for petrochemical, paint and varnish enterprises and other types of industrial production.
Of primary importance for the hygienic characteristics of industrial dust is the particle size or degree of dispersion of aerosols, which determine not only the rate of dust settling, but also its retention and depth of penetration into the respiratory system. According to dispersion, dust is divided into finely dispersed And ultramicroscopic(dust particle size up to 0.25 microns); medium-disperse or microscopic(size from 0.25 to 10 microns); coarse(size greater than 10 microns).
The physical, physicochemical and chemical properties of dust largely determine the nature of its toxic, irritant and fibrogenic effect on the human body. The main role in the nature of the general toxic and specific effects of dust is played not only by its concentration in the air of the working area or atmospheric air, but also by the density and shape of dust particles, its adsorption properties, the solubility of dust particles and electrical charge.
Industrial aerosols, according to their damaging resulting effects, can be divided into aerosols of predominantly fibrogenic action (APFA) and aerosols with predominantly general toxic, irritating, carcinogenic and mutagenic effects. According to the classification (1996), depending on the pneumofibrogenic activity of dust, pneumoconiosis is divided into three groups: pneumoconiosis from exposure to highly fibrogenic and moderately fibrogenic dust; pneumoconiosis from exposure to weakly fibrogenic dust; pneumoconiosis caused by exposure to toxic-allergenic aerosols.
Clinical and morphological studies have proven that fibrogenic dust can cause diseases of the upper respiratory tract in the respiratory organs, the formation of nodular and diffuse sclerotic forms of pulmonary dust fibrosis - pneumoconiosis and chronic bronchitis.
According to the etiology, the following forms of pneumoconiosis have been identified: silicosis, which develops as a result of inhalation of dust containing free silicon dioxide; silicates that occur when dust enters the lungs, in which silicon dioxide is in a bound state with other compounds (asbestosis, talcosis, polyvinosis, neferenosis, etc.); carboconiosis caused by exposure to carbon-containing dusts (coal, coke, soot, graphite); metalloconiosis, which develops under the influence of metal dust and their oxides (beryllosis, siderosis, aluminosis, baritosis, staniosis, etc.); pneumoconiosis, developing as a result of inhalation of organic dust of animal, plant and synthetic origin (byssinosis, bagassosis, mycosis, etc.); pneumoconiosis caused by exposure to mixed dust containing free silicon dioxide (anthracosilicosis, siderosilicosis, silicosilicosis) and not containing it or with an insignificant content.
The mechanisms of pathological reactions that develop in the body when exposed to metal dust, mixed and organic dust have a number of features. Thus, when inhaling metal dust with toxic properties, along with the development of fibrosis in the lung tissue, symptoms of chronic intoxication are revealed. Pneumoconiosis, which occurs under the influence of mixed dust, is characterized mainly by interstitial changes in the lung tissue, and the development of nodular forms of fibrosis is possible. Pneumoconiosis caused by exposure to organic dust is characterized by moderately severe pulmonary fibrosis, combined with allergic, bronchospastic and inflammatory changes in the bronchopulmonary system. It should be noted that the clinical course of the above forms of pneumoconiosis is milder than that of silicosis.
In addition to silicosis and pneumoconiosis, chronic bronchitis, pneumonia, asthmatic rhinitis and bronchial asthma can develop under the influence of industrial dust. Certain types of fibrogenic dust can lead to the development of malignant neoplasms. Thus, prolonged inhalation of asbestos dust is accompanied not only by the development of dust fibrosis (asbestosis), but also by the development of pleural tumors (mesathelioma) and bronchial cancer. The irritating, sensitizing and photodynamic effects of dust lead to the development of allergic dermatitis, eczema, and folliculitis. Dust can affect the organ of vision and lead to inflammatory processes in the conjunctiva (conjunctivitis), and in some cases to the development of cataracts.
Unfavorable microclimatic conditions and exposure to a number of biological and physical factors in the working environment can potentiate the adverse effect of the dust factor on the body and lead to the development of respiratory diseases.
For aerosols of predominantly fibrogenic action containing free silicon dioxide, the hygienic regulations (MPC) for the air of the working area are 1 mg/m 3 (with a SiO 2 content of 10% or more) and 2 mg/m 3 (with a SiO 2 content of less than 10 %). For other types of dust, the maximum permissible concentrations in the air of the working area are set from 2 to 10 mg/m3. For dust containing natural asbestos, the average shift concentration is 0.5 mg/m3, and the maximum single concentration is 2.0 mg/m3. Currently, maximum permissible concentrations have been approved for more than 100 types of dust that have a fibrogenic effect.
To characterize real working conditions, obtain objective information about harmful factors in the working environment and indicators of the health status of workers at industrial enterprises, it is advisable to determine both maximum single-time concentrations (MSC) and average shift concentrations of air in industrial premises.
RTO– aerosol concentration, determined from the results of continuous or discrete aerosol sampling in the breathing zone of workers or the working area over a period of time equal to 30 minutes, with a process technology accompanied by maximum dust formation.
Where C mrk is the concentration of all dust floating in the air, mg/m 3, M 0 is the weight of the filter before collecting dust samples, mg; M 1 – weight of the filter after collecting dust samples, mg; V – volume of air passed through the filter and reduced to normal conditions (V 0);
The value of the MRC of dust (C 0) with discrete measurements of equal duration of individual measurements for 30 minutes is calculated as the arithmetic mean of single concentrations using the formula:
Where C 1, C 2, …, C n – measurement results, n – number of measurements.
Determining the maximum single concentration, unfortunately, does not make it possible to establish the relationship between the dose of dust absorbed by the body and the degree of damage to the body. To establish the dose-time-effect relationship, it is necessary to determine the average shift concentration, which most fully reflects the presence of a biological connection between the concentration of the dust factor and the state of human health.
When conducting a sanitary examination in the field of working conditions related to determining the dust content in the air of the working area, and if the average shift concentration is exceeded, an assessment of the dust load (LO) on the worker’s body is necessary.
on the worker's respiratory system - this is the real or predicted value of the total exposure to the dose of dust that the worker inhales over the entire period of actual or expected professional contact with the dust factor.PN for the respiratory organs of a worker (or a group of workers, if they perform similar work under the same conditions) is calculated based on the actual K s APFD in<воздухе рабочей зоны, объема легочной вентиляции (зависящего от тяжести труда) и продолжительности контакта с пылью:
PN= K ss ÍNÍTÍQ
WhereКсс – actual average shift concentration in the worker’s breathing zone; N – number of work shifts in a calendar year (for example, 248); T – number of years of contact with APFD; Q – volume of pulmonary ventilation per shift, m3.
According to SanPiN “Sanitary and epidemiological requirements for the air of industrial premises” No. 355 dated July 14, 2005, SanPiN “Hygienic requirements for the microclimate of industrial premises” No. 355 dated July 14, 2005, the Ministry of Health of the Republic of Kazakhstan recommends the use of the following average values of pulmonary ventilation volumes, which depend on the level of energy consumption and, accordingly, the categories of work. For work of category Ia-Ib, pulmonary ventilation per shift is 4 m3, for category IIa-IIb - 7 m3 and category III - 10 m3.
To obtain the actual or predicted value of the dust load, the latter can be calculated for any period of work in contact with dust.
The obtained values of the actual dust load are compared with the value of the control dust load (CPL), the value of which is calculated depending on the actual or expected work experience, the maximum permissible concentration of dust and the category of work:
CPN = maximum permissible concentration ss, N. T. Q,
Where MPC ss – shift average MPC, mg/m3; N – number of workers in a calendar year; T – number of years of contact with APDF; Q – volume of pulmonary ventilation per shift, m3.
When developing an algorithm for a system of health measures (Figure No. 18), basic hygienic requirements must be applied not only to knowledge of the physical and chemical properties of dust, its toxicity and danger, but also to technological processes and equipment, ventilation, construction and planning solutions, rational maintenance of workplaces , use of personal protective equipment. In this case, it is necessary to be guided by sanitary and hygienic rules and regulations, which determine the relevant requirements for technological processes and production equipment.
Preventive actions. Measures to limit the adverse effects of dust on workers in production conditions should include technological, sanitary, medical, preventive and organizational measures. An important role in the system of preventive measures is played by regulations that regulate the values of maximum permissible concentrations of aerosols in the air of the working area, define sanitary rules for the design and maintenance of industrial enterprises, formulate methodological recommendations for the prevention of occupational respiratory diseases, and many others.
Technological measures that ensure the fight against industrial dust include closed and semi-closed cycles and waste-free production, ensured by sanitary ventilation (Figure No. 19).
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Preliminary, before starting work, and periodic medical examinations are the main medical and preventive measures to protect workers from exposure to industrial dust. Important importance in the system of therapeutic and preventive measures aimed at increasing the reactivity and resistance of the body is given to providing working contingents with therapeutic and preventive nutrition and milk, vitamin supplementation, and rational organization of work and rest regimes. In industries associated with exposure to dust, measures must be taken to diagnose, treat, examine the ability to work, and provide employment to sick people.
Industrial dust (or aerosols) are small solid particles of organic or mineral origin that are in the air of a work area and gradually settle. The size of one speck of dust can reach from 0.0001 to 0.1 mm in diameter.
Manufacturing operations that generate dust are very diverse. These include the process of crushing and grinding solids, sifting, drying, grinding, polishing various surfaces, and working with bulk materials. The dust released during these operations, according to the method of formation, belongs to the category of disintegration aerosols. Therefore, industries with intense dust generation include enterprises in the mining, coal, porcelain and earthenware, textile and flour milling industries.
Dust can also form during the melting and sublimation of a certain substance. As a result, vapors of this substance will be released, which, when air interacts with them, will begin to condense into small solid particles. According to the method of formation, such dust belongs to condensation aerosols.
Types of dust
There are so many types of industrial dust that it became necessary to classify it. The classification according to the method of aerosol formation is generally accepted.
- 1. Organic:
- · vegetable (grain, etc.);
- · animal (wool, etc.);
- · protein (production of protein-vitamin concentrates).
- 2. Inorganic:
- · mineral (silica, etc.);
- metal (iron dust, etc.);
- 3. Mixed:
- · mineral-metallic (a mixture of iron dust and silicon compounds, etc.);
- · a mixture of organic and inorganic (dust from cereals and soil, etc.).
There is also a classification of dust by dispersion:
- 1. Visible (?10 µm);
- 2. Microscopic (from 10 to 0.25 microns);
- 3. Ultramicroscopic (? 0.25 microns).
By origin, dust is divided into:
- 1. Soluble (sugar, etc.);
- 2. Insoluble (bleach dust).
Industrial dust is particles of solid matter suspended in the air. According to its physicochemical properties, it belongs to the category of aerosols.
In industrial conditions, the sources of aerosols entering the air of working premises are a variety of technological processes: crushing and grinding of solid materials, sifting, drying, loading and unloading of bulk substances, grinding, turning, polishing of metal and other surfaces, sandblasting, mining and drilling operations, carding - scattering work in textile factories and many others. All these production operations are accompanied by the release of industrial dust, which, according to the method of formation, belongs to the category of disintegration aerosols. On the other hand, the sources of aerosol formation can be the processes of melting and sublimation of certain substances, as a result of which vapors of these substances are released, which, when the air is oversaturated with them, condense into tiny solid particles suspended in the air (for example, zinc oxide in copper foundries), called aerosols condensation
The wide variety of types of industrial dust has led to the need to classify it. It is generally accepted to classify dust by origin and divide it into two groups: organic and inorganic. Organic dust includes: plant dust (linen, wood, flour, etc.), animal dust (wool, bristle, horn, etc.) and artificial (plastic); to inorganic - mineral (quartz, asbestos, talc, gypsum, etc.) and metal (iron, cast iron, steel, copper, etc.). Mixed dusts are often encountered, containing particles of different groups (for example, coal and soil in coal mines, metal and mineral when processing metal products on emery wheels, etc.).
The dust content in the air of industrial enterprises depends mainly on two factors: the amount of dust generated and its stability, i.e., on the duration of its stay in the air in suspension. While the amount of dust generated depends on the nature of the technological process, the stability of dust in the air is associated mainly with its physicochemical properties: the degree of particle dispersion and their electrical charge.
The degree of dust dispersion depends on the conditions of its formation during the technological process. It has been established that in industrial premises there are mainly particles up to 10 μ in size, and of this number, 60-70% of dust has sizes up to μ.
The electric charge of particles arises during grinding due to friction against machine parts, during mutual friction of particles against each other, or due to the adsorption of ions from the air. Dust particles with opposite charges are mutually attracted, thereby turning into larger particles and settle faster, while those with like charges, on the contrary, repel and remain suspended longer. Thus, the smaller the particle size and the greater the number of particles with the same charge, the greater the stability of dust in the air.
A number of other factors also influence the stability of dust in the air. In industrial conditions, due to the movement of people, the operation of machines, convection currents, etc., the air is in constant motion. This delays the settling of dust, as a result of which particles smaller than 2 μ in size (i.e., which are the largest in the air) practically do not settle.
The combination of all these factors determines the degree of dust in the air, which, like gas pollution, is assessed by the value of its concentration.
Naturally, the higher the concentration of dust, the more likely it is to enter the respiratory tract. At the same time, not only the amount of dust entering the body is significant, but also the depth of its penetration and the degree of retention in the body. In these processes, the main role belongs to the dispersion of particles and the protective properties of the body.