|MadSci Network: Environment & Ecology|
Jasmine- The start of air pollution depends upon what you consider air pollution. As with most environmental problems, change happens gradually rather than as one big event. There are a number of natural sources of "air pollution" such as volcanoes, which can emit large amounts of sulfur and nitrogen oxides, as well as particulate pollution (aerosols), which have been around for millions of years. Early anthropogenic (human-caused) sources of air pollution would have included the smelting of metals, fireplaces and burning of land. The next big step was probably when people started to burn coal instead of wood in cities that also had increasing population densities around the 12th and 13th century. It was already so bad in 1307 that the use of coal in London was banned (although that ban seemed to have a little effect). The invention of a more efficient (coal-powered) steam engine by James Watt in 1765 was one of the factors that kicked off the Industrial Revolution. This era saw a huge increase in factories and could definitely be viewed as the start of serious air pollution from industry. If you asked me to pick one date for the start of air pollution, this might be it, although it took many years for the implications to be felt. Soon after the industrial revolution, the first well documented urban smog events began to occur. A noxious fog appeared in London in 1873 that killed roughly 500 people. Another in 1880 was responsible for as many as 200 deaths. These severe air pollution events culminated in a particularly bad episode on December 5th, 1952 when as many as 4000 people may have died. The London smogs were dominated by the sulfur oxides produced by the burning of sulfur-rich coal. Modern urban air pollution is generally an oxidative photochemical smog that is caused by nitrogen oxides interacting with ozone and hydrocarbons. This type of smog (found in places like Los Angeles, Atlanta and Mexico City) became a serious problem after World War II when the use of automobiles increased greatly. That's a quick sketch. For the sake of brevity, I've omitted anything to do with acid rain, ozone depletion, emissions of heavy metals, and the generation of greenhouse gasses - all of which also pollute the atmosphere. I hope that helps! Alex References: A Green History of the World by Clive Ponting < href="http://www.met-office.gov.uk/education/historic/smog.html"> http://www.met-office.gov.uk/education/historic/smog.html http://www.epa.gov/history/topics/perspect/london.htm Big Smoke by Peter Brimblecombe
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