Air Pollution

The growth of population centers coupled with the switch from wood-burning to coal-burning fires created clouds of smoke over cities as early as the eleventh century. Air pollution regulations first appeared in England in 1273, but for the next several centuries, attempts at controlling the burning of coal met with notable failure. The problem was not confined to London, nor was it confined to England. As the Industrial Revolution swept across countries, and as coal became common in private residences, smoke and industrial pollution claimed more and more lives. In the United States, Donora, Pennsylvania, became famous for a tragedy that symbolized the dangers of industrial air pollution. On October 26, 1948, a thick, malodorous fog enveloped the small industrial town. Unlike usual fogs, it did not burn off as the day progressed. Instead, it stayed on the ground for five days. Twenty people died in Donora and 7,000 were hospitalized with respiratory problems. The cause was a weather anomaly that trapped toxic waste emissions from the town's zinc smelting plant close to the ground. The Donora disaster brought air pollution into focus in the United States, and paved the way for the Clean Air Act, enacted in 1963 and strengthened in 1970.

Between December 5 and 9, 1952, 4,000 people died in London as a result of smog trapped in a thermal inversion (a condition where the air close to the ground is colder than the layer above it, and is therefore unable to rise above it). This incident brought about England's Clean Air Act in 1956.

Smoke from coal-fired power plants creates the related problem of acid rain. Gases (sulfur dioxide and nitrogen oxides) released by burning fossil fuels make the rain more acidic and therefore corrosive. Acid rain kills plants and trees and damages structures. It also accumulates in rivers and streams, and has resulted in lakes that are already devoid of life in large parts of eastern North America and Scandinavia.

All around the world, the advent of the internal combustion engine-powered vehicles compounded air pollution, adding particulate and gaseous contaminate to the air people breath. The use of leaded gasoline raised lead levels in populations around the world. Leaded gasoline was phased out in the U.S. starting in 1976, but is still in use in many parts of the world In 1987, scientists discovered a hole in the ozone layer and recognized a serious threat to the layer that protects the earth from the sun's ultraviolet radiation. The Montréal Protocol, drafted in 1987, addressed the damage caused to the ozone layer by a chemical group known as CFCs, which were common in aerosol spray containers and air conditioners. The Montréal Protocol set as a goal the elimination of CFCs in consumer and industrial products. The global climate change accord signed in Rio de Janeiro, Brazil, in 1992 addressed the so-called "greenhouse gases," gases which trap heat in the atmosphere and lead to a global warming trend. The Rio Accord, and the Kyoto Protocol (1997) call for a reduction in greenhouse gases emissions but little progress has been made as the United States, a major generator of greenhouse gases, never signed the treaty and President George W Bush has rejected the Kyoto Protocol outright.

Corbis Bettmann First Day
Woman planting flowers in New York's Union Square Park on the first Earth Day. (©Bettmann/Corbis. Reproduced by permission.)

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