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7.21: Reducing Air Pollution

Difficulty Level: Basic Created by: CK-12
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Can a car run on hydrogen?

Yes! But so far this is not feasible for more than just a few models. A major problem with hydrogen cars is the lack of hydrogen fuel. Many ways to reduce pollution are being developed. What can you do to help?

The Clean Air Act

Air quality is a measure of the pollutants in the air. More pollutants mean poorer air quality. Poor air quality started to become a serious problem after the Industrial Revolution. Factories burned coal for energy. Gasoline burned by cars and trucks added greatly to air pollution. By the mid-1900s, air quality in many big cities was very bad. Incidents in London and in U.S. cities alerted people to the extent of the problem. It was clear that air quality needed to be protected.

In 1970 in the U.S., the Clean Air Act was passed. It limits what can be released into the air. The air in the U.S. is much cleaner now than it was 50 years ago. But air pollution has not gone away. Vehicles, factories, and power plants still release more than 150 million tons of pollutants into the air each year.

Reducing Pollutants from Fossil Fuels

There are two basic types of strategies for reducing pollution from fossil fuels:

  1. Use less fossil fuel.
  2. Prevent pollutants from entering the air.

Use Less Fossil Fuel

We can reduce our use of fossil fuels in several ways:

  • Conserve fossil fuels. For example, turning out lights when we aren’t using them saves electricity. Why does this help? A lot of the electricity we use comes from coal-burning power plants.
  • Use fossil fuels more efficiently. For example, driving a fuel-efficient car lets you go farther on each gallon of gas. This can add up to a big savings in fossil fuel use.
  • Keep up with technology. Hybrid cars run on electricity that would be wasted during braking. These cars use gas only as a backup fuel. As a result, they produce just 10 percent of the air pollution produced by regular cars.

Keeping Pollutants out of the Air

Some of the pollutants from fossil fuels can be filtered out of exhaust before it is released into the air. Other pollutants can be changed to harmless compounds before they are released. Two widely used technologies are scrubbers and catalytic converters.

  • Scrubbers are used in factories and power plants. They remove particulates and waste gases from exhaust before it is released to the air. You can see how a scrubber works in Figure below.
  • Catalytic converters are used on motor vehicles. They break down pollutants in exhaust to non-toxic compounds. For example, they change nitrogen oxides to harmless nitrogen and oxygen gasses.

Before catalytic converters were required, cars spewed a lot of pollutants into the air. On the left is a car without a catalytic converter. The car on the right has one.

Increasing Alternative Energy Sources

Developing alternative energy sources is important. What are some of the problems facing wider adoption of alternative energy sources?

  • The technologies are still being developed. This includes sources of alternative energy, including solar and wind.
  • Solar and wind are still expensive relative to fossil fuels. The technology needs to advance so that the price falls.
  • Some areas get low amounts of sunlight and are not suited for solar. Others do not have much wind. It is important that regions develop what best suits them. The desert Southwest will need to develop solar. The Great Plains can use wind energy. Perhaps some locations will rely on nuclear power.

Ways You Can Reduce Air Pollution

Everyone can help to reduce air pollution. Just use less fossil fuels! How can you do this?

  • Ride a bike or walk instead of driving.
  • Take a bus or carpool.
  • Buy a fuel efficient car.
  • Turn off lights and appliances when they are not in use.
  • Use energy efficient light bulbs and appliances.
  • Buy fewer things that are manufactured using fossil fuels.

All these actions reduce the amount of energy that power plants need to produce.

National Geographic videos exploring energy conservation are found in Environment Videos, Energy: http://video.nationalgeographic.com/video/environment/energy-environment.

  • Alternative Energy
  • Fuel Cells
  • Solar Power

What you can do to your home to help reduce energy use: http://www.youtube.com/watch?v=6h8QjZvcp0I&feature=related.

A very simple thing you can do to conserve energy is discussed in “This Bulb”: http://www.youtube.com/watch?v=FvOBHMb6Cqc.


  • air quality: A measure of the pollutants in the air.


  • Catalytic converters reduce pollution from cars.
  • To reduce air pollution either use less fossil fuels or clean emissions before they enter the air.
  • Different types of clean energy can be developed for different locations. Some regions are suited for solar, others for wind, etc.


Use this resource to answer the questions that follow.


  1. How have lead levels changed in ambient air?
  2. How has reducing acid rain helped the environment?
  3. How much has acid deposition been reduced?
  4. How much have toxic emissions from industry been reduced?
  5. Explain the technologies that have improved vehicle emissions.


  1. Why is the Clean Air Act important?
  2. Why is it important to develop alternative energy sources?
  3. What can you do to reduce the amount of air pollution you produce?

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air quality Measure of the pollutants in the air.

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Jan 04, 2013
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