What's the deal with Dust?
Dust, tiny particles that are carried by air currents. Dust is present throughout the lower atmosphere. It is most common in city air, and the smallest concentrations are in the air over mountains and oceans.
Although water most often condenses around particles that are not dust, the condensation of water around dust particles does contribute to the formation of clouds, mist, haze, and fog.
Dust particles are mainly mineral substances, but they may also contain organic matter. The largest particles of dust settle out, while the smaller particles remain suspended in the air. About 43 million tons of dust settle over the United States each year.
Q: If you don't dust, how high will it build up?
A: It won't. Dust settles only on places that have been freshly dusted. The reason for this might be because it is afraid of heights.
Sources of Dust
Most dust in the atmosphere comes from natural sources. Winds that blow against the surface of the earth pick up tiny particles of soil and rock and carry them into the air. In dry areas with only sparse vegetation, winds sometimes pick up huge quantities of dust and create dust storms. In the United States this process caused widespread dust storms during the 1930's in the Dust Bowl, which included parts of Colorado, Kansas, Texas, Oklahoma, and New Mexico.
Volcanic eruptions are another major natural source of dust. They often throw up great amounts of dust that may remain in the atmosphere for years before settling out. Minor sources of dust include meteors, comets, and plants.
Large quantities of man-made dust are added to the air in heavily populated urban and industrial areas. Smoke from houses, factories, and incinerators pollutes the air with soot and ash. Other sources of man-made dust include automotive exhausts, mining, industrial operations, and construction work, such as digging and road building.
Problems Caused by Dust
Dust may cause both health and industrial problems. Dust often carries disease-producing bacteria, as well as pollen and spores that cause hay fever, asthma, and other allergic conditions.
Respiratory diseases and even death may be caused by heavy concentrations of industrial waste materials in the air. In London, for example, nearly 4,000 persons died in December 1952 as a result of their being exposed to such contaminants.
Some industrial dusts, such as arsenic and lead dust, can produce poisoning. Others, such as asbestos dust, may cause chronic lung ailments. Silicosis, a respiratory disease caused by the dust of quartz and other silicates, was common among miners and stonecutters until they began using protective masks.
The risk of dust explosions is one of the greatest dangers of dust in industry. When fine particles of a combustible material became suspended in the air, a slight spark or flame may ignite them and cause a violent explosion.
Some materials, including metals (such as magnesium), are combustible when in the form of dust, although they are not so when in large pieces. Dust explosions are especially likely to occur in coal mines, sawmills, paper mills, and grain elevators.
To reduce the hazard of dust explosions, ventilating systems, dust collectors, water sprays, and other devices have been developed either to eliminate the explosive material or to reduce its flammability.