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Chapter 3
chemicals are put into the air.When the air
is dirty, it becomes polluted.
Pittsburgh was a city with many
industrial plants and vehicles belching
harmful chemicals in the air. The air
became so dirty that the term “smog” was
invented to describe the type of air
surrounding Pittsburgh. Since the 1940s,
state and local laws have been passed to
control air pollution. Pittsburgh is a good
exampleof how the air environment canbe
made cleaner.
Harmful chemicals can also become
mixed in with types of moisture to form
acid rain
. Scientists think acid rain may
be slowly damaging our forests, streams,
soils, and animals. One solution is to save
energy. Another solution is to require
cleaner air. This can be done by having
industrial factories and vehicles put fewer
harmful chemicals into the air.
Keeping Our
Water Clean
O
ur planet Earth has plenty of
saltwater. Of course, animals and
plants who live in saltwater need
their environment clean. However, the
earth has a very limited supply of
freshwater. Many living things need clean
freshwater to live. When people in
factories, businesses, and homes use water,
it becomes dirty. Dirty water is called
wastewater
. One of the most common
kinds of wastewater is
sewage
. Sewage is
wastewater from sinks, showers, and toilets.
This water is collected by sewer pipes
coming fromhomes and other buildings.
Factories are not allowed to dump
polluted water into streams and rivers or
Industrial waste can pollute our rivers and streams.
