THE DANGERS OF SMOG

Sometimes urban authorities issue warning about the form of air pollution known as smog ( a made up word that combines smoke and fog). Though acute smog episodes are rare, they can be deadly Twenty people died and thousands fell ill during a smog alert in Donora, Pennsylvania, in 1948; and more than 4,000 people succumbed to london’s “killer smog” of 1952. Those who died in these dramatic incidents were primarily the very young , the very old, and those with chronic respiratory diseases. But many people in lower-risk categories may have been affected to some extent.

There are actually two types of smog; the London type and Los Angeles type. The London variety, blamed for thousands of deaths in Europe and the eastern United States. Is more correctly termed sulfur-dioxide smog. It is caused by the burning of fossil fuels (primarily coal with high sulfur content); high levels of sulfur dioxide and ozone result, combined with particulate matter and foggy air. Sulfur dioxide smog poses a special threat; it inhibits the sweeping action of the cilia that line our respiratory passages, allowing smog particles and chemicals impair breathing so markedly that people with chronic respiratory problem may die. Impaired breathing can also aggravate heart problems. Reduction of the use of high-sulfur fuels has significantly decreased the occurrence of London-type smoge.

Los Angeles –type smog, more properly called photochemical smog, result from the interaction of sunlight with temperature inversions and exhaust emission from automobiles. This type of smog occurs in areas with poor air circulation (Valleys, for example) , especially those where there in sunny weather and low humidity . In Los Angeles, a layer of cool ocean air may slip in under the normally warm, stable air above the city. This cool air becomes trapped by the warmer air , a phenomenon a called a temperature inversion . Motor vehicle emissionrise through the cool air but can not penetrate the warm layer, which acts like a lid on the Los Angeles basin. Thus p[pollutants are trapped and subjected to the action of sunlight , which produce additional pollutans (such as ozone). The pollutans do not disperse until the weather change and the inversion lifts.