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Layers of air extend high above the Earth’s surface. The air gets thinner the further away it is from the ground. Clouds float in many of these layers. Clouds at different heights tend to have different shapes. Thin, feathery clouds form high above the ground. Thick, gray clouds are lower.

Factory smoke is a major cause of air pollution. Factories release many types of gases into the air. These gases cause global warming and produce smog. Countries have made laws to limit this pollution. Many factories limit themselves, too. Some factories are switching to cleaner energy, such as solar power. They can also reduce air pollution by reducing trash they throw away. This results in less trash that might be burned.

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Making Connections


Have you ever seen smoke, smog, or other forms of air pollution? If so, where were you?


Have you read other books that mentioned pollution? What ways of reducing pollution did those books describe?


Air is just one natural resource that is affected by pollution. What are other resources near your home that could be affected by pollution?

Teacher Resources

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