Water pollution, contamination (contaminate) of streams, lakes, underground (ground) water, bays, or oceans by substances, is harmful to living things. Water is necessary to life on earth. All organisms contain it; some live in it; some drink it. Plants and animals require water that is moderately (moderate) pure, and they can't survive if their water is loaded with toxic chemicals or harmful micro-organisms. If severe, water pollution can kill large numbers of fish, birds, and other animals. In some cases it may kill all members of a species in an affected (affect) area. Pollution makes streams, lakes, and coastal (coast) waters unpleasant (please) to look at, to smell, and to swim in. Fish and shellfish harvested from polluted waters may be unsafe (safe) to eat. People who ingest polluted water can become ill, and, with prolonged exposure (expose), may develop cancers or get children with birth defects. The major water pollutants (pollute) are chemical, biological, or physical materials that degrade (grade) water quality.

$1$. contamination

$2$. underground  

$3$. moderately

$4$. coastal

$5$. unpleasant  

$6$. unsafe

$7$. exposure

$8$. pollutants

$9$. degrade