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Dust
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Dust is a general name for minute solid particles with diameters less than 20 thou (500 micrometers). Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution. Dust in homes, offices, and other human environments consists of human skin cells, plant pollen, human and animal hairs, textile fibers, paper fibers, minerals from outdoor soil, and many other materials which may be found in the local environment.
precise composition of domestic dust may vary widely:
According to the German Environmental Survey, approximately 6 mg/mē/day of house dust is formed in private households, depending primarily on the amount of time spent at home.
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Dust is a general name for minute solid particles with diameters less than 20 thou (500 micrometers). Particles in the atmosphere arise from various sources such as soil dust lifted up by wind, volcanic eruptions, and pollution. Dust in homes, offices, and other human environments consists of human skin cells, plant pollen, human and animal hairs, textile fibers, paper fibers, minerals from outdoor soil, and many other materials which may be found in the local environment.
Domestic dust
Composition and types
The precise composition of domestic dust may vary widely:
According to the German Environmental Survey, approximately 6 mg/mē/day of house dust is formed in private households, depending primarily on the amount of time spent at home. Nearly 1000 dust particles per square centimeter settle on domestic surfaces every hour. Some dust consists of human skin. Scientists estimate that humans shed the entire outer layer of skin every day or two, at a rate of 7 million skin flakes per minute, which corresponds to a mass emission rate of about 20 mg/minute. "Dust bunnies" are little clumps of fluff that form when sufficient dust accumulates.
Domestic dust and humans
Insects and other small fauna found in houses subtly interact with dust and may have adverse impact on the health of the regular occupants.
Dust may worsen hay fever. Circulating outdoor air through a house by keeping doors and windows open, or at least slightly ajar, may reduce the risk of hay fever causing dust. In colder climates, occupants seal even the smallest air gaps, and eliminate outside fresh air circulating inside the house. So it is essential to manage dust and airflow .
House dust mites exist on all indoor surfaces and even suspended in the air. They feed on minute particles of organic matter, the main constituent of house dust. Dust mites flourish in the fibers of bedding, furniture, and carpets. They excrete enzymes to digest the organic particles, and excrete feces, that together become part of the house dust, and may provoke allergic reactions in humans.
Alternately, the hygiene hypothesis posits that the modern obsession with cleanliness is as much a problem as house dust mites. The hygiene hypothesis argues that our prior pathogenic exposure, or lack thereof, may in fact encourage the development of ailments including hay fever and asthma.
Atmospheric dust
Airborne dust is considered an aerosol and can have a strong local radiative forcing on the atmosphere and significant effects on climate. In addition, if enough minute particles are dispersed within the air in a given area (such as flour or coal dust), under certain circumstances can cause an explosion hazard.
Coal dust is responsible for the lung disease known as Pneumoconiosis, including black lung disease, that occurs among coal miners. The danger of coal dust resulted in environmental legislation regulating work place air quality in some jurisdictions.
Road dust
Dust kicked up by vehicles travelling on roads may make up 33% of air pollution. Road dust consists of deposition of vehicle exhausts and industrial exhausts, tire and brake wears, dust from paved roads or potholes, and dust from construction sites. Road dust represents a significant source contributing to the generation and release of particulate matter into the atmosphere. Control of road dust is a significant challenge in urban areas, and also in other spheres with high levels of vehicular traffic upon unsealed roads such as mines and garbage dumps. Road dust may be suppressed by mechanical methods like sweeping vehicles, with vegetable oils, or with water sprayers.
Dust control
Dust control is the suppression of solid particles with diameters less than 500 micrometers. Dust in the airstream poses a serious health threat to children, older people, and those with respiratory illnesses.
Control of domestic dust
House dust can become airborne easily. Care should be exercised when removing dust to avoid causing the dust to become airborne. Some dust removing devices trap some dust, but broadcast some dust into the air, which may settle in the cleaner's lungs, and make the activity hazardous. One way to repel dust is with an electrical charge . Water-trap vacuums eliminate the risk of broadcasting dust by drowning the dust particles in water. Dust can't escape the container to fly back into the air.
Control of atmospheric dust
The U. S. Environmental Protection Agency (EPA) mandates facilities that generate dust minimize or mitigate the production of dust in their operation. The most frequent dust control violations occur at new residential housing developments in urban areas. United States Federal law requires that construction sites obtain permits to conduct earth moving, and include plans to control dust emissions. Control measures include such simple practices as spraying construction and demolition sites with water, and preventing the tracking of dust onto adjacent roads. US federal laws require dust control on sources such as vacant lots, unpaved parking lots, and unpaved roads. Dust in such places may be suppressed by mechanical methods , including paving or laying down gravel, or stabilizing the surface with water, vegetable oils or other dust suppressants, or by using water misters to suppress dust that is already airborne .
Dust in other contexts
Dust in outer space
Cosmic dust is widely present in space, where gas and dust clouds are primary precursors for planetary systems. The zodiacal light seen in the dark night sky, is produced by sunlight reflected from particles of dust in orbit around the Sun. The tails of comets are produced by emissions of dust and ionized gas from the body of the comet. Dust also covers solid planetary bodies, and vast dust storms occur on Mars that cover almost the entire planet. Interstellar dust is found between the stars, and high concentrations produce diffuse nebulae and reflection nebulae.
Dust is widely present in the galaxy. Ambient radiations heats dust and re-emits dust into the microwave band, which may distort the cosmic microwave background power spectrum. Dust in this regime has a complicated emission spectrum, and includes both thermal dust emission and spinning dust emission.
Dust samples returned from outer space may provide information about conditions in the early solar system. Several spacecraft have sought to gather samples of dust and other materials. Among these craft was Stardust, which flew past Comet Wild 2 in 2004, and returned a capsule of the comet's remains to Earth in January 2006. The Japanese Hayabusa spacecraft is on a mission to collect samples of dust from the surface of an asteroid.
See also
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