Dust (redirected from gather dust)

dust [dəst]

(geology)

Dry solid matter of silt and clay size (less than ¹⁄₁₆ millimeter).

(physics)

A loose term applied to solid particles predominantly larger than colloidal size and capable of temporary gas suspension.

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Dust 

an aerosol and disperse system that consists of small solid particles suspended in a gaseous medium. Separate particles and particle aggregates—from ultra-microscopic particles to those visible with the naked eye—have various shapes and compositions. In most cases, dust is formed as a result of the dispersion of solid bodies. It consists of particles that range in size from 10^-7 to 10^-4 m and that carry an electrical charge or are electrically neutral. Dust concentration, or dust content, is expressed by the number of particles or their total weight per unit volume of gas (air). Dust is unstable; its particles adhere during Brownian motion or during sedimentation.

The air always contains dust particles. The sources of dust include rock erosion, volcanic eruptions, fires, and wind erosion of arable lands. Droplets of seawater are carried into the atmosphere, where they evaporate and form dust. In industry, industrial dust is formed. The air also contains solid particles of cosmic and biological origin, such as plant pollens, spores, and microorganisms. Like other aerosols, dust affects the heat of the atmosphere and intensifies the scattering and absorption of light by the atmosphere.

Industry sometimes purposely resorts to atomization, for example, during the burning of pulverized fuel, during the air separation of powders, and during certain chemical engineering processes. The undesirable formation of dust occurs with the crushing and dry-grinding of hard rock, the mining of minerals, the processing and transportation of friable products and materials, and the burning of ashy organic fuel. Constant sources of increased dust concentration are the metallurgical, chemical, and textile industries, construction, many means of transportation, and some branches of agriculture, for example, fieldcrop farming. Industrial dust causes damage to equipment, lowers the quality of products, and causes the deterioration of working conditions. Dust from combustible or readily oxidized substances, such as coal, wood, flour, sugar, and aluminum, may be an explosive or fire hazard. The greater the dispersion and concentration of dust, the greater the probability of fire or explosion.

The collection of dust and the control of industrial dust formation pose important technical and health problems. Various types of dust collectors are widely used in industry, as well as complex systems of gas purification. The collection of dust is necessary in order to remove valuable products from the dust and is especially important in protecting the environment from air pollution in and around cities and industrial centers.

L. A. SHITS

Various characteristics of dust are significant in relation to health, including its chemical composition and concentration and the size, shape, and structure of its particles. The solubility, electrical charge, and radioactivity of dust are also significant. Dust has both a direct and indirect effect on the human body. Its direct effect may be the cause of atrophic, hypertrophic, suppurative, or ulcerous changes in the mucosa, bronchi, lung tissue, or skin. These changes can lead to such diseases as catarrh of the upper respiratory tract, ulceration of the nasal septum, bronchitis, pneumonia, pneumosclerosis, conjunctivitis, and dermatitis. Prolonged inhalation of dust leads to the development of pneumoconioses.

Some types of dust, for instance, lead, arsenic, and manganese dust, are poisonous. Organic dust of both natural and artificial origin, for example, grains and flower pollens and the dust from ursolic acid and a number of woods, may cause allergic diseases, including bronchial asthma. Dust may disseminate the causative agents of actinomycosis, anthrax, tuberculosis, diptheria, and ascariasis. Radioactive dust is a cause of radiation sickness. The indirect effect of dust on man is the specific result of the change that the intense dust concentration of the air causes in the spectrum and intensity of solar radiation; examples of changes in solar radiation include the absorption and scattering of ultraviolet rays and a decrease in illumination.

Prevention of industrial diseases includes the legislative regulation of healthy dust levels in the air and the administration of medical examinations. The control of dust formation and distribution is carried out by various methods. Organizational and technological measures that are extremely effective include replacing sandblasting of cast material with shotblasting and hydraulic spraying and dry boring and crushing with wet methods. Other measures include spraying with water and hermetically sealing equipment, moistening dust-producing materials, and using pneumatic tube transportation. The most effective means of removing dust from industrial and domestic premises is suction-and-exhaust ventilation and local ventilation with the use of air strainers. When there is a high dust concentration and an absence of ventilation, individual means of protection from the harmful effects of dust are used, such as respirators, pneumatic suits, helmeted suits, protective clothing, and goggles.

Biological methods of prevention against diseases caused by dust include ultraviolet irradiation of the body, alkaline inhalations, and a special diet.

REFERENCES

Fett, W. Atmosfernaia pyl’. Moscow, 1961. (Translated from German.)
Professional’nye bo/ezni, 3rd ed. Moscow, 1973.
Navrotskii, V. N. Gigiena truda, 2nd ed. Moscow, 1974.

A. A. KASPAROV