Scientists Say: Pollution

Pollution is any harmful substance or form of energy released into the environment

Pollution includes trash, chemicals or other substances that contaminate the air, water or land.

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Pollution (noun, “Puh-LOO-shun”)

Pollution is any harmful substance or form of energy released into the environment. Some pollution is natural. Volcanic eruptions blow ash and toxic gases into the air. Some oil naturally seeps into oceans through the seafloor. But pollution usually refers to contamination caused by people. Human activity dirties air, water and land alike.

Cars and factories, for instance, send pollutants such as nitrogen oxide and sulfur dioxide into the air. These chemicals give rise to smog. That haze of pollution can lead to health problems and make it hard to breathe. Burning fossil fuels also releases greenhouse gases like carbon dioxide and methane. These gases are warming Earth’s climate.

Chemicals such as lawn and farm fertilizers, meanwhile, seep into streams and lakes. Those chemicals can feed harmful algal blooms. This overgrowth of algae can make water unsafe plants and animals. Other pollutants can make water dangerous for people to drink. Plastic trash causes trouble in the oceans, where animals may mistake it for food.

Recycling materials such as glass, metals, paper and plastic can reduce this trash. Laws and agreements between nations can also limit how much pollution people and companies create. In 1987, for instance, nearly 200 countries agreed to the Montreal Protocol. This agreement phased out chemicals called chlorofluorocarbons, or CFCs. These chemicals were eating a hole in Earth’s ozone layer. Since then, the ozone layer has started to recover.

Some types of pollution are not physical. Light pollution, for example, is human-made light in places that should be dark. Light from cars, buildings and streetlamps are sources of light pollution. This glow can mess up the sleep cycles of people and animals. Similarly, noise pollution is disruptive sound. Noise from construction and transportation can make it harder for birds to communicate. And ship noise may drive fish and whales away from their feeding grounds. Noise pollution can also cause hearing loss in people.

In a sentence

Recent research suggests that worldwide, air pollution lowers people’s average life span by a year.

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Maria Temming is the assistant editor at Science News for Students. She has bachelor's degrees in physics and English, and a master's in science writing.

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