____ is the introduction of harmful materials into the environment. These ____ materials are called pollutants. Pollutants can be natural, such as volcanic ____. They can also be created by human activity, such as ____ or ____ produced by factories. Pollutants damage the ____ of air, water, and land. Many things that are useful to people produce pollution. Cars spew ____ from their exhaust pipes. Burning coal to create ____ pollutes the air. Industries and homes generate ____ 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 ____ and ____. When these resources are polluted, all forms of life are threatened.

Pollution

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