Pollution





Pollution is the relative increase in concentration in the environment of
undesireable substances caused by the activity of mankind. A similar
increase, when it occurs through causes not influenced by mankind, is not
considered to be pollution.

The term pollution can refer to both the polluting substances (such as
nitrogen oxides) as well as the effects brought about by those substances
(such as photochemical smog). Thus the algae blooms and low dissolved oxygen
content of eutrophic lakes are considered to be pollution because they are
the natural result of nutrient imbalances cause by industrial, agricultural,
and residential runoff and effluent.

There are a number of different types of pollution including air pollution,
water pollution, light pollution and noise pollution.

Although carbon dioxide is not toxic—and actually stimulates plant
growth—environmentalists labeled carbon dioxide a "pollutant" in the
1990s, because they believe that carbon dioxide emissions will lead to
harmful global warming (see greenhouse gas, global warming hypothesis).