Pallution

PULLUTION
Pollution is the introduction of contaminants into a natural environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or livingorganisms.[1] Pollution can take the form of chemical substances or energy, such as noise, heat, or light. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring;when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution. The Blacksmith Institute issuesannually a list of the world's worst polluted places. In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine, and Zambia.
Ancient cultures
Air pollution hasalways been with us. According to a 1983 article in the journal Science, "soot found on ceilings of prehistoric caves provides ample evidence of the high levels of pollution that was associated withinadequate ventilation of open fires."[3] The forging of metals appears to be a key turning point in the creation of significant air pollution levels outside the home. Core samples of glaciers inGreenland indicate increases in pollution associated with Greek, Roman and Chinese metal production.
Pollutants
A pollutant is a waste material that pollutes air, water or soil. Three factors determinethe severity of a pollutant: its chemical nature, the concentration and the persistence.
Pollution became a popular issue after World War II, due to radioactive fallout from atomic warfare andtesting. Then a non-nuclear event, The Great Smog of 1952 in London, killed at least 4000 people.[8] This prompted some of the first major modern environmental legislation, The Clean Air Act of 1956.Pollution began to draw major public attention in the United States between the mid-1950s and early 1970s, when Congress passed the Noise Control Act, the Clean Air Act, the Clean Water Act and the...