<P> Modern smog, as found for example in Los Angeles, is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog . In certain other cities, such as Delhi, smog severity is often aggravated by stubble burning in neighboring agricultural areas . The atmospheric pollution levels of Los Angeles, Beijing, Delhi, Lahore, Mexico City, Tehran and other cities are increased by inversion that traps pollution close to the ground . It is usually highly toxic to humans and can cause severe sickness, shortened life or death . </P> <P> Coinage of the term "smog" is generally attributed to 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, "He 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 ." However, this is predated by a Los Angeles Times article of January 19, 1893, in which the word is attributed to "a witty English writer ." </P> <P> Coal fires, used to heat individual buildings or in a power - producing plant, can emit significant clouds of smoke that contributes to smog . Air pollution from this source has been reported in England since the Middle Ages . London, in particular, was notorious up through the mid-20th century for its coal - caused smogs, which were nicknamed' pea - soupers .' Air pollution of this type is still a problem in areas that generate significant smoke from burning coal . The emissions from coal combustions are one of the main causes of air pollution in China . Especially during autumn and winter when coal - fired heating ramps up, the amount of produced smoke forces some Chinese cities to close down roads, schools or airports . One prominent example for this was China's Northeastern city Harbin in 2013 . </P> <P> Traffic emissions--such as from trucks, buses, and automobiles--also contribute . Airborne by - products from vehicle exhaust systems cause air pollution and are a major ingredient in the creation of smog in some large cities . </P>

The smoke in london smog came primarily from
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