Smog, air pollution

Smog Air pollution caused by the reaction of sunlight and chemical compounds such as nitrogen dioxide and hydrocarbons the compounds are usually produced by car exhaust and the release of gases from industries such as coal-fired power plants. 

Photochemical smog—Air pollution caused by complex reactions involving emitted chemicals, chemicals formed secondarily in the atmosphere, and sunlight. 

See smog air pollution Cottrell. (2) Wood smoke Light-colored particles of cellulose ash, pleasant aromatic odor. Smoke from special kinds of wood... 

Photochemical smog air pollution produced by the action of light on oxygen, nitrogen oxides, and unburned fuel from auto exhaust to form ozone and other pollutants. 

Photo smog Air pollution caused by ozone and other oxidizing compounds, which are formed in ambient air from the ozone precursors under the influence of sunlight. 

Materials The damage that air pollutants can do to some materials is well known ozone in photochemical smog cracks rubber, weakens fabrics, and fades dyes hydrogen sulfide tarnishes silver smoke dirties laundry acid aerosols ruin nylon hose. Among the most important effects are discoloration, corrosion, the soiling of goods, and impairment of visibility. 

Fig. 2-3. Grand average number (N), surface area (S), and volume (V) distribution of Los Angeles smog. The linear ordinate normalized by total number (NT), area (ST), or volume (VT) is used so that the apparent area under the curves is proportional to the quantity in that size range. Source Corn, M., Properties of non-viable particles in the air. In "Air Pollution," 3rd ed., Vol. I ( A. C. Stern, ed.). Academic Press, New York, 1976, p. 123.

The most widespread and persistent urban pollution problem is ozone. The causes of this and the lesser problem of CO and PMjq pollution in our urban areas are largely due to the diversity and number of urban air pollution sources. One component of urban smog, hydrocarbons, comes from automobile emissions, petroleum refineries, chemical plants, dry cleaners, gasoline stations, house painting, and printing shops. Another key component, nitrogen oxides, comes from the combustion of fuel for transportation, utilities, and industries. 

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

Although the original Clean Air Act of 1977 brought about significant improvements in air quality, the urban air pollution problems of ozone (known as smog), carbon monoxide (CO), and particulate matter (PM,o) persist. Currently, over 100 million Americans live in cities which are out of attaimnent with the public health standards for ozone. The most widespread and persistent urban... 

Ozone (Oj) a gas similar to oxygen that is a criteria air pollutant and a major constituent of smog. See also reactive organic compounds volatile organic compounds. 

Smog a mixture of air pollutants, principally ground-level ozone, produced by chemical reactions involving smog-forming chemicals. See also haze. 

Smog commonly refers to air pollution it implies an air mixture of smoke particles, mists, and fog droplets of such concentration and composition as to impair visibility, in addition to being irritating or harmful. Smog is often associated with temperature inversion in the atmosphere that prevent normal dispersion of contaminants. 

Burning fossil fuels can release air pollutants such as carbon dioxide, sulfur oxides, nitrogen oxides, ozone, and particulate matter. Sulfur and nitrogen oxides contribute to acid rain ozone is a component of urban smog, and particulate matter affects respiratory health. In fact, several studies have documented a disturbing correlation between suspended particulate levels and human mortality. It is estimated that air pollution may help cause 500,000 premature deaths and millions of new respiratory illnesses each year. 

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