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Smog

2007 Schools Wikipedia Selection. Related subjects: Environment

   Victorian London was notorious for its thick smogs, or "pea-soupers", a
   fact that is often recreated to add an air of mystery to a period
   costume drama.
   Victorian London was notorious for its thick smogs, or "pea-soupers", a
   fact that is often recreated to add an air of mystery to a period
   costume drama.

   Smog is a kind of air pollution; the word "smog" is a portmanteau of
   smoke and fog. Classic smog results from large amounts of coal burning
   in an area and is caused by a mixture of smoke and sulphur dioxide.

Photochemical smog

   In the 1950s a new type of smog, known as photochemical smog, was first
   described. This is a noxious mixture of air pollutants including the
   following:
     * nitrogen oxides, such as nitrogen dioxide
     * tropospheric ozone
     * volatile organic compounds (VOCs)
     * peroxyacyl nitrates (PAN)
     * aldehydes (R'O)

   All of these chemicals are usually highly reactive and oxidizing. Due
   to this fact, photochemical smog is considered to be a problem of
   modern industrialization.

   Photochemical smog is a concern in most major urban centres but,
   because it travels with the wind, it can affect sparsely populated
   areas as well. Smog is caused by a reaction between sunlight and
   emissions mainly from human activity. Photochemical smog is the
   chemical reaction of sunlight, nitrogen oxides (NOx) and volatile
   organic compounds (VOC's) in the atmosphere, which leaves airborne
   particles (called particulate matter) and ground-level ozone. Nitrogen
   oxides are released in the exhaust of fossil fuel-burning engines in
   cars, trucks, coal power plants, and industrial manufacturing
   factories. VOC's are vapors released from anthropogenic (man-made)
   sources such as gasoline, paints, solvents, pesticides, and biogenic
   sources, such as pine and citrus tree emissions.

Origin of term

   Smog in New York City viewed from the World Trade Center in 1988.
   Smog in New York City viewed from the World Trade Centre in 1988.

   The term "smog" was first coined by Dr. Henry Antoine Des Voeux in his
   1905 paper, “Fog and Smoke,” for a meeting of the Public Health
   Congress. The 26 July 1905 edition of the London newspaper Daily
   Graphic quoted Des Voeux, “[H]e said it required no science to see that
   there was something produced in great cities which was not found in the
   country, and that was smoky fog, or what was known as ‘smog.’” The
   following day the newspaper stated that “Dr. Des Voeux did a public
   service in coining a new word for the London fog.”

Areas affected

   A comparison of Beijing air on a day after rain and a sunny but smoggy
   day
   A comparison of Beijing air on a day after rain and a sunny but smoggy
   day
   Smog in Santiago, Chile
   Smog in Santiago, Chile

   Smog can form in almost any climate where industries or cities release
   large amounts of air pollution. However, it is worse during periods of
   warmer, sunnier weather when the upper air is warm enough to inhibit
   vertical circulation. It is especially prevalent in geologic basins
   encircled by hills or mountains. It often stays for an extended period
   of time over densely populated cities or urban areas, such as London,
   New York, Los Angeles, Mexico City, Houston, Toronto, Athens, Beijing,
   Hong Kong, the Randstad or Ruhr Area and can build up to dangerous
   levels.

London

   London has been known for smog since Roman times. In 1273, concerns
   over air pollution were sufficient for Edward I to (briefly) ban coal
   fires in London. In 1661, John Evelyn's Fumifugium suggested burning
   fragrant wood instead of mineral coal, which he believed would reduce
   coughing. The Ballad of Gresham College the same year describes how the
   smoke "does our lungs and spirits choke, Our hanging spoil, and rust
   our iron."

   Severe episodes of smog continued in the 19th century and were
   nicknamed "pea-soupers". The Great Smog of 1952 darkened the streets of
   London and killed approximately 4,000 people in the short term (a
   further 8,000 died from its effects in the following weeks and months).
   Initially a flu epidemic was blamed for the loss of life. In 1956 the
   Clean Air Act introduced smokeless zones in the capital. Consequently,
   reduced sulphur dioxide levels made the intense and persistent London
   smog a thing of the past. It was after this the great clean-up of
   London began and buildings recovered their original stone façades
   which, during two centuries, had gradually blackened. Smog caused by
   traffic pollution, however, does occur in modern London.

Mexico City

   Due to its location in a highland 'bowl', cold air sinks down onto the
   urban area of Mexico City, trapping industrial and vehicle pollution
   underneath, and turning it into the most infamous smog-plagued city of
   Latin America. Within one generation, the city has changed from being
   known for some of the cleanest air of the world into one with some of
   the worst pollution, with pollutants like nitrogen dioxide breaching
   international health standards by 2-3 times.

Tehran

   In December 2005, schools and public offices had to close in Tehran,
   Iran and 1600 people were taken to hospital, in a severe smog blamed
   largely on unfiltered car exhaust.

Health effects

   Smog is a problem in a number of cities and continues to harm human
   health. Ground-level ozone is especially harmful for senior citizens,
   children, and people with heart and lung conditions such as emphysema,
   bronchitis, and asthma. It can inflame breathing passages, decreasing
   the lungs' working capacity, and causing shortness of breath, pain when
   inhaling deeply, wheezing, and coughing. It can cause eye and nose
   irritation and it dries out the protective membranes of the nose and
   throat and interferes with the body's ability to fight infection,
   increasing susceptibility to illness. Hospital admissions and
   respiratory deaths often increase during periods when ozone levels are
   high .

   The U.S. EPA has developed an Air Quality index to help explain air
   pollution levels to the general public. 8 hour average ozone
   concentrations of 85 to 104 ppbv are described as "Unhealthy for
   Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to
   404 ppb as "very unhealthy" . The "very unhealthy" range for some other
   pollutants are: 355 μg m^-3 - 424 μg m^-3 for PM10; 15.5 ppbv - 30.4ppb
   for CO and 0.65 ppbv - 1.24
   Characteristic coloration for smog in California in the beige cloud
   bank behind Golden Gate Bridge
   Characteristic coloration for smog in California in the beige cloud
   bank behind Golden Gate Bridge

Natural causes

   An erupting volcano can also emit high levels of sulphur dioxide,
   creating volcanic smog, or vog.

   The burning of forests in Indonesia has on a number of occasions
   created prolonged smog-like haze, which have extended to parts of
   Malaysia, Philippines, Singapore and Thailand although a lot of the
   times these fires are started by farmers who want to clear away land
   for the start of the new planting season.
   Retrieved from " http://en.wikipedia.org/wiki/Smog"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
