smog

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smog

(smŏg) [smoke+fog], dense, visible air pollutionair pollution,
contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health. The major sources of air pollution are transportation engines, power and heat generation, industrial processes, and the
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. Smog is commonly of two types. The gray smog of older industrial cities like London and New York derives from the massive combustion of coal and fuel oil in or near the city, releasing tons of ashes, soot, and sulfur compounds into the air. The brown smog characteristic of Los Angeles and Denver in the late 20th cent. is caused by automobiles. Nitric oxide from automobile exhaust combines with oxygen in the air to form the brown gas nitrogen dioxide. Also, when hydrocarbons and nitrous oxides from auto emissions are exposed to sunlight, a photochemical reaction takes place that results in the formation of ozone and other irritating compounds. In some instances, atmospheric pollutants accumulate and become concentrated when air movement is stopped by a temperature inversiontemperature inversion,
condition in which the temperature of the atmosphere increases with altitude in contrast to the normal decrease with altitude. When temperature inversion occurs, cold air underlies warmer air at higher altitudes.
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: Usually the air is warmer at the earth's surface and colder above; in a temperature inversion a layer of warm air forms above and holds down a layer of cool air at the ground. Smog usually results in reduced visibility, irritation of the eyes and respiratory system, and damage to paint, metal, rubber, and other materials. Prolonged smogs (generally caused by temperature inversions) are often lethal to persons with respiratory ailments. As the result of an unremitting smog in 1948 in Donora, Pa., more than 5,000 persons were reported ill and the deaths of 20 persons were recorded. In London, smog accounted for the deaths of more than 4,000 persons in 1952 and 106 persons in 1962.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Smog

 

the severe air pollution over large cities and industrial centers. There are two types of smog. One is a thick fog that contains smoke or gaseous industrial wastes as, for example, in London; the other is a pall of corrosive gases and aerosols in high concentrations (without fog). The latter type arises under the effect of ultraviolet solar radiation in the atmosphere as a result of photochemical reactions occurring in the exhausts of motor vehicles and the gaseous wastes of chemical plants as, for example, in Los Angeles. Smog is usually observed when there is low atmospheric turbulence and, consequently, an even distribution of air temperature with height, especially in temperature inversions during a calm or a slight wind.

Smog, which reduces visibility and accelerates the corrosion of metals and man-made structures, is also harmful to human health. Intense and prolonged smog can be a cause of increased morbidity and mortality.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

smog

[smäg]
(meteorology)
Air pollution consisting of smoke and fog.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

smog

A condition in which the surface visibility is reduced because of smoke particles suspended in the moist air.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved

smog

a mixture of smoke, fog, and chemical fumes
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
In a seesawing battle, Houston and Los Angeles continue to vie for the dubious distinction of having the smoggiest sky in the nation.
That day, Deer Park registered 251 parts of ozone per billion, more than twice the federal standard, and Houston surpassed Los Angeles as the smoggiest city in the United States.
In Houston, which recently surpassed Los Angeles as the nation's smoggiest city and is under a federal mandate to dramatically reduce ozone levels, more accurate emissions estimates might scuttle the plan to clean up the city's air now being considered by the EPA.
During 1999, Texas led the nation in Clean Air Act violations, and Houston replaced Los Angeles as our "smoggiest city." Like many environmentalists, former Texas Air Control Board pollution investigator Neil Carmen cites Bush's environmental policies as the source of Texas' foul air.
If the air around Sacramento--the smoggiest city in Northern California--looks a bit clearer these days, it may be thanks to Raley's new "Clean Air Machines." Eight of the supermarket company's semi trucks and two yard tractors use liquefied natural gas (LNG), which reportedly reduces smog-producing nitrous oxide emissions by 60%, compared with diesel fuel.
The legislation promised to reduce ground-level ozone in the nation's smoggiest metropolitan areas by requiring the use of cleaner burning reformulated gasolines.
The settlement will require the nine smoggiest cities -- accounting for 25 percent of U.S.
But now Houston is the smoggiest city in America, Come home, George W.