(3) Air Pollution

10 Most Polluted Cities


Burning Coal Produces Industrial Smog

Fifty years ago, cities such as London, England, and Chicago and Pittsburgh in the United States burned large amounts of coal in power plants and factories, for heating homes, and often for cooking food.

During the winter, people in such cities were exposed to industrial smog consisting mostly of sulfur dioxide, suspended droplets of sulfuric acid, and a variety of suspended solid particles that give the resulting smog a gray color, explaining why it is sometimes called gray air smog. During the 1940s, the air over some industrialized cities in the United States (such as Chattanooga, Tennessee) was so polluted that people had to use their automobile headlights during the day.

Today, urban industrial smog is rarely a problem in most developed countries where coal and heavy oil are burned only in large boilers with reasonably good pollution control or with tall smokestacks that transfer the pollutants to downwind rural areas. However, industrial smog remains a problem in industrialized urban areas of China, India, Ukraine, and some eastern European countries, where large quantities of coal are burned in houses and in factories with inadequate pollution controls.

Because of its heavy reliance on coal, China has some of the world’s highest levels of industrial smog and 16 of the world’s 20 most polluted cities. In 2006, China’s Environmental Protection Administration estimated that each year, air pollution (mostly from coal burning) prematurely kills 358,000 Chinese-an average of 981 deaths per day.

In 2006, a U.S. satellite tracked the spread of a dense cloud of pollutants from northern China to Seoul, South Korea, and then across the Pacific Ocean to the United States. The EPA estimates that on certain days nearly one-fourth of the particulate matter in the skies above Los Angeles, California, can be traced to coal-fired power plants, smelters, diesel trucks, and dust storms (due to drought and deforestation) in China.

The history of air pollution control in Europe and the United States shows that industrial smog can be cleared up fairly quickly by setting standards for coal burning industries and utilities and by shifting from coal to cleaner-burning natural gas in urban industries and dwellings. China and India are slowly beginning to take such steps, but they have a long way to go.



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