The population of the earth is increasing
very fast. Humans must make the earth support the increasing
population. This has made it necessary for agriculture and industry to
develop rapidly.
Such a rapid development produces more and more
waste, which goes into the water, the soil and the air. Some of it is
made harmless. However, where there is too much of it, the poisonous
waste may do great harm to the things around the people.
When
farmers add fertilizer to the soil to make plants grow better, or use
poison to kill pests, poison is sent into the air, the water and the
soil. When birds, fish and people eat the grain, drink the water or
breath the air, harm will be done to their health.
The air in
big cities is often made very dirty by cars and factories. Millions of
tons of waste and poisonous gases are sent into the air with the smoke.
In some places, little is done to make the smoke clean before it goes
into the air.
Fortunately, people are beginning to realize just
how serious the whole situation is. In many countries, laws have been
made to stop factories from sending out poisonous gases.
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