Pollution

  Pollution Pollution  is the introduction of  harmful  materials into the  environment . These harmful materials are called  pollutants . Pollutants can be natural, such as  volcanic ash . They can also be created by human activity, such as trash or  runoff  produced by factories. Pollutants damage the quality of air, water, and land. Many things that are useful to people produce pollution. Cars  spew  pollutants from their  exhaust  pipes. Burning  coal  to create  electricity  pollutes the air. Industries and homes  generate  garbage and  sewage  that can pollute the land and water.  Pesticides —chemical  poisons  used to kill weeds and insects— seep  into  waterways  and harm  wildlife . All living things—from one-celled  microbes  to blue whales—depend on  Earth ’s supply of air and water. When these  resources  are pol...