Water pollution is contamination of streams, lakes, underground water, bays or oceans by substances harmful to any living thing. 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 pure, and they cannot survive if their water is loaded with toxic chemicals or harmful microorganisms. Some toxic chemicals that pollute water are sodium, mercury, lead, DDT, and PCB. Sodium …showed first 75 words of 1206 total…

…showed last 75 words of 1206 total…in the United States have been cleaned up. Many sewage plants are now filtering water that it can be used again. Surface waters are far cleaner than they were in 1972. A survey in 1990 of rivers and streams found that three-quarters of these waters were clean enough for swimming and fishing. We can help by not throwing our trash into the water. Another way to help prevent pollution is ride a bike instead of a car.