232
P
ollution comes in many
forms, ranging from toxins
in the air to trash at the
bottom of the sea. Any substances
or forms of energy that spoil the
quality of the atmosphere, oceans,
water, or soil are pollutants. They
may be chemicals or biological
contaminants (including human
waste), products (such as plastics),
or noise, light, or heat. The effects
of pollution on life of all kinds
can be far-reaching, spreading
thousands of miles beyond its
original source. Pollution can
spread through the food chain andbe carried through air and water,
affecting all life. Contaminants such
as plastics can facilitate the invasion
of nonindigenous species, as
discovered by Australian marine
biologist Emma Johnston. There is
also a direct effect on human health:
it is estimated that exposure to
polluted air, water, and soil caused
9 million premature deaths—one in
six of all deaths—in 2015.Pollution through the ages
Human-made pollution has a long
history. The presence of soot on
the walls of caves, dating backPOLLUTION
thousands of years, indicates
that early humans generated air
pollution from their fires. Analysis
of 2,500-year-old ice cores in
Greenland has shown evidence of
air pollution from copper smelting
thousands of miles away, in the
center of the Roman Empire.
However, such impacts were
on a small scale. With the start
of the Industrial Revolution in
Europe, air and water pollution
became serious. Factory chimneys
pumped smoke out into the air;
toxic chemicals poured into rivers.
Cities expanded quickly and hadIN CONTEXT
KEY FIGURE
Emma Johnston (1973–)BEFORE
1272 King Edward I of
England bans the burning
of sea coal in London because
of the smoke it produces.19th century Coal-burning
during Britain’s Industrial
Revolution stunts children’s
growth and raises death rates
from respiratory diseases.AFTER
1956 The Clean Air Act is
introduced in the UK, bringing
the thick smogs that plagued
its major cities to an end.1963 The Clean Air Act
is passed in the US.1972 The Clean Water Act
is fully ratified in the US.1984 Toxic gas leaks from the
Union Carbide India factory
in Bhopal kill thousands and
injure many more.Effects of pollution on health
Polluted air and water cause the deaths of millions of
people every year. This illustration describes the specific
damage caused to different organs of the human body.The brain. Mental
development in
children is delayed,
and the brains of
adults are affected.The heart. Pollution
increases the risk
of heart disease
and stroke.The reproductive
system. During
pregnancy, the
fetus’s brain
development can
be affected.The lungs. Air
pollution can
cause cancer,
and is linked
to asthma.The pancreas.
Air pollution has
been linked to
Type 2 diabetes
in adults.US_230-235_Pollution.indd 232 12/11/18 6:25 PM