Re: When and what would you say air pollution started with?

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