Project-Based Inquiry ScienceAQ 128

Learning Set 3 • What Are Pollutants, and How Do They Get Into Air?

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Case Study: Pollution in Los Angeles

L.A. COURIERThe Most Polluted City in America

Los Angeles, California May 1, 2008

Once again, Los Angeles has topped the American Lung Association’s

Bad Air list of most polluted cities in America. The association found that the Los Angeles city area had the worst air in the United States.

“Nobody is surprised that LA has an air-pollution problem,” said Janice No-len of the American Lung Association. “The problems there are one of the reasons we have the Clean Air Act. But it is important for folks to know that there has been some improvement.”

The news wasn’t all bad for Los Angeles. Despite its poor ranking compared to other cities, the number of days residents breathed the nation’s worst air was fewer than in previous years. The association based the rankings on pollution levels when heat and sunlight come into contact with pollutants from power plants, cars and trucks, refineries, and other sources. The pollution released from these sources is made up of a mixture of tiny solid, liquid, and gas particles in the air.

Los Angeles under a heavy layer of smog. When Los Angeles has better air quality, the mountains can be seen in the distance, and people can breathe much easier.

AIR QUALITYAQ 129

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Understanding how pollution gets into the air in Los Angeles can help you understand how pollution might get into the air in your community. Los Angeles is a big city that has a big problem with air quality. It has the worst air quality of any United States city. The Los Angeles area is home to over 9 million people. It has the world’s largest marine port, one of the largest international airports, and almost 80,467 km (50,000 mi) of highways for car and truck traffic.

Stop and Think1. Think about what you know about the activities that produce the six

big pollutants. Which of these activities do you think are common in Los Angeles? Look back at the article on the previous page and at the paragraph above to help you answer this question.

2. What do you think might cause the air-pollution problem in Los Angeles? What do you think might make the problem so much greater in Los Angeles than in other large cities?

ConferenceShare with your group your ideas about what affects the air quality in Los Angeles. Discuss which sources of pollution you are sure about and which sources of pollution you are still unsure about. It is important for all the members of your group to discuss their ideas. As a group, use a Sources and Effects of Air Quality chart to create a list of possible sources and effects of air quality in Los Angeles. This chart should be similar to those you made earlier in the Unit when discussing your community.

Los Angeles highways stretch for almost 90,000 km.

Project-Based Inquiry Science

Learning Set 3 • What Are Pollutants, and How Do They Get Into Air?

AQ 130

Sources and Effects of Air Quality

Sources Effects Howto improvetheair

CommunicateShare your sources and effects with the class. If there is disagreement about the sources or effects, record those disagreements.

Factors That Affect the Air in Los AngelesYour class has determined several of the sources of pollution in Los Angeles. These might be the same sources you thought affected your own community. For example, you probably identified that cars on the road emit soot, carbon monoxide, and nitrogen oxides into the air.

Air pollution from vehicles is a particularly bad problem in Los Angeles. The city of Los Angeles grew very quickly. In 1870, only 5000 people lived in Los Angeles. After 30 years, that number grew to more than 170,000. In another 30 years, by 1930, the population was 1.2 million. Today, it has over 9 million people. Los Angeles has grown faster than almost any other city in the United States. As the city grew, the roads became more crowded with cars. Los Angeles built a very large network of roads and freeways to manage the traffic. That made the roads easier to drive on. This also made it easier for people to live far away from the center of the city and still drive to work in the city.

As more people moved to the Los Angeles area and more houses were built far from the center of the city, the roads became more crowded again. Most people who live in the Los Angeles area need to drive long distances to get from place to place. The large population and the long distances people drive in Los Angeles has resulted in a huge number of cars on the road. All these cars burn fuel. All of this combustion produces many of the pollutants that trouble Los Angeles.

AIR QUALITYAQ 131

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As the population grew in Los Angeles, more power plants were needed to supply electricity to all the houses and other buildings. The combustion in power plants adds more pollutants to the air in Los Angeles.

The geography and weather of Los Angeles also affect its air quality. Los Angeles is situated between the ocean and a mountain range. Combustion produces many air pollutants, and then the mountains trap these pollutants near the city.

The weather in Los Angeles keeps pollutants in the air. Los Angeles is very warm with very little rain. Rain washes pollutants out of the air. After a rain, the air is usually clearer than it was before the rain. However, because there is so little rain in Los Angeles, pollutants stay in the air for longer periods of time than they do in other places.

Stop and Think1. How did population growth affect the air quality of Los Angeles?

2. How does geography affect the air quality of Los Angeles?

3. How does weather affect the air quality of Los Angeles?

One factor that affects the air quality of Los Angeles is the mountains. They trap the air, keeping the wind from blowing away the polluted air.

Project-Based Inquiry Science

Learning Set 3 • What Are Pollutants, and How Do They Get Into Air?

AQ 132

What’s the Point?Los Angeles has many of the same pollution problems as other big cities. One factor that contributes to pollution in Los Angeles is the large number of cars, trucks, and buses that emit polluting gases and particulate matter. Another factor that contributes to pollution is its geography. The mountains trap air. The wind cannot easily blow the polluted air over the mountains, so the polluted air stays over the city. Another factor is the weather. Los Angeles generally has warm air with very little rain to wash the pollutants out of the air. The next few sections will help you better understand the impact of these factors. Then you will be able to determine how these factors may or may not also impact the air in your community.

The Los Angeles area has grown to over 9 million people since 1870.