The Atmosphere 469

the Southern uteS, a Native American Indian tribe, live in southwestern Colorado, within sight of the La Plata Mountains. Besides being beautiful, this area is rich in natural gas. The removal and pro-cessing of this fuel provide income and work for people in the tribe and surrounding communities. However, faulty processing of natural gas can pollute the air.

The Southern Utes want to keep the air clean and safe to breathe. To do that, leaders of the tribe have worked with the state and federal governments to develop an air quality program. The program currently involves monitoring the air for pollutants and identifying point and nonpoint sources of air pollutants on the Southern Ute reservation. In addition, the program conducts inspections of industries and sees to it that industries fix any problems that arise. The Southern Ute Air Quality Program also includes many other activities, such as research into meth-ods of eliminating air pollution.

The Southern Utes are using technology, cooperation, creativity, and determination to preserve air quality. The Southern Ute Air Quality Pro-gram focuses on a relatively small area of land. At the national and global level, the United States and other nations are taking steps to deal with air pollution. We have a long way to go, but many of our efforts have been successful. You will read about some of those successes in this lesson.

LESS

ON 3Controlling Air Pollution

FIGURE 18 Monitoring Air Quality A scientist with the Southern Ute Air Quality Program examines a device that monitors air quality.

• Explain how the provisions of the Clean Air Act have reduced air pollution in the United States.

• Describe international efforts to reduce the ozone hole.

Reading Strategy After you read this lesson, write a sum-mary of the goals, provisions, and effects of the Clean Air Act.

Vocabulary Clean Air Act, catalytic converter, scrubber, ozone hole, chlorofluorocarbon (CFC), Montreal Protocol

Guiding Question: What measures can limit and prevent pollution of the atmosphere?

FOCUS Watch the ABC News video Ozone Layer Under Repair to learn about how the damage to the ozone layer was discovered and the progress that has been made to restore it. Use this video to launch a discussion on how changing human actions can help restore the environment.

15.3 LESSON PLAN PREVIEWDifferentiated Instruction Students create a three-column table to help them understand the goals, provisions, and ef-fects of the Clean Air Act.real World Students research changes to consumer goods in the effort to reduce damage to the ozone layer.

15.3 RESOURCESIn Your Neighborhood Activity, Using Your UV Index • Bellringer Video, Ozone Layer Under Repair • Graph It, Monitoring Major Air Pollutants • Real Data Online • Real Data Math Worksheet • Lesson 15.3 Worksheets • Lesson 15.3 Assessment • Chapter 15 Overview Presentation

470 Lesson 3

The Clean Air Act The Clean Air Act has provisions that have reduced air pollution

in the United States.

To address air pollution in the United States, Congress has passed a series of laws, including the Clean Air Act. The Clean Air Act was first passed in 1963 and has been revised several times since. Revisions in 1970 and 1990 were especially important. Those revisions set stricter standards for air quality and strengthened the government’s ability to enforce regulations.

Goal of the Clean Air Act The Clean Air Act protects and improves the quality of air in order to safeguard human health and the environ-ment. The law takes measures to reduce the emission of pollutants that cause health problems such as asthma and cancer. It also limits the release of pollutants responsible for environmental problems such as smog and acid deposition.

Provisions of the Clean Air Act Here are some of the measures taken by the Clean Air Act:•  The Act limits emissions of pollutants by motor vehicles and industries.•  It sets standards for air quality. The law limits the concentration of

some specific air pollutants, such as carbon monoxide and particulate matter. The upper limit of each pollutant is based on the maximum amount that humans can tolerate without harm.

•  It lets people sue industries that break the rules.•  It sets aside funds for research into pollution control.

Under the Clean Air Act, the U.S. Environmental Protection Agency (EPA) sets nationwide standards governing air pollutants and air qual-ity. However, the states and Native American tribes have the option of developing and enforcing specific regulations that are equivalent to—or exceed—those found in the Clean Air Act.

ReadingCheckpoint

What is the Clean Air Act?

FIGURE 19 Clean Air in the National Parks Air pollution is partly responsible for the haze over the Blue Ridge Mountains in Shenandoah National Park. The Clean Air Act has provisions that try to reduce haze in national parks.

How can we ensure everyone has clean air to breathe? Explanation Ask students to write a short newspaper-style article that explains the importance of one spe-cific provision of the Clean Air Act listed in the text. Remind students that their articles should not simply describe one of the provisions; they must include information to justify the importance of the provision.

BIG QUESTION

ANSWERS

Reading Checkpoint The Clean Air Act is a law that sets strict standards for air quality in order to safeguard human health and the environment.

Real Data

Declines in Five Major Pollutants

Carbonmonoxide

Nitrogenoxides

Volatile organic

compoundsAir Pollutant

Sulfurdioxide

Lead

200

150

100

50

0

100

80

60

40

20

0M

ass

Emit

ted

(mil

lion

s of

ton

s)

Mas

s Em

itte

d(t

hou

san

ds

of t

ons)(–56%)

Year19802008

(% change)

(–40%) (–47%) (–56%)

(–99%)

Data from U.S. EPA.

The Atmosphere 471

Reduction in Air Pollutants Since the Clean Air Act, the release of the worst air pollutants has gone down by 57 percent. This decrease in pollution has happened even though there are now many more people in the United States, and we use much more energy. The reduction of outdoor air pollution is one of the nation’s greatest accomplishments in protecting the environment.

▶ Motor Vehicles Cars and trucks now cause less pollution. Catalytic converters have helped bring this about. A catalytic converter is a device in a motor vehicle that reduces the amount of air pollutants in emissions. It changes harmful emissions, such as carbon monoxide, into substances that are less harmful, such as carbon dioxide and water. Catalytic convert-ers are usually located between the engine and the muffler of a car. Since 1975, all new cars in the United States have had catalytic converters.

▶ Cleaner Gasoline Gasoline once contained lead, and lead was part of the emissions from the exhaust systems of motor vehicles. Lead from vehicle emissions can settle to the ground and contaminate it. If lead gets into the bloodstream of a person—especially a young child—it can cause problems ranging from behavioral disorders to mental retardation. The EPA has been working to phase out lead in gasoline since 1973. Today gasoline used by cars and trucks contains almost no lead.

Effects of the Clean Air ActThe Clean Air Act has had major effects on the quality of the air we breathe. To monitor air quality, the EPA tracks emis-sions of several major air pollutants. The graph shows data for some air pollutants: carbon monoxide, nitrogen oxides, vola-tile organic compounds, sulfur dioxide, and lead. Look at the graph and then answer the following questions.1. Interpret Graphs What do the green

bars represent? 2. Interpret Graphs What do the purple

bars represent? 3. Analyze Data What trend does

the graph show? 4. Analyze Data Of the pollutants

shown on the graph, which has changed by the greatest percentage?

5. Interpret Graphs Why is the bar for lead shown separately from the bars for the other pollutants? (Hint: Look at the axis labels.)

6. Infer Do you think that the general trend shown in this graph is also true for the air in London between 1952 and now? Explain your answer.

Monitoring Major Air Pollutants

ANSWERS

Real Data1. The amount of pollutants emitted

in 19802. The amount of pollutants emitted

in 20083. The amount of pollutants emitted

into the air has decreased since 1980.

4. Lead5. The amount of lead is given in

thousands of tons; the amounts of the other pollutants are given in millions of tons.

6. Sample answer: Yes; after the smog catastrophe of 1952, London took measures to curb air pollution.

Air with pollutants enters the scrubber.

The dirty air passes throughclean water droplets.

Cleanwater

Clean air

Water andpollutants exit.

Cleaned air leaves the scrubber.

1

2

The water droplets capture pollutants and carry them to the bottom of the scrubber.

35

4

472 Lesson 3

FIGURE 20 Scrubber Scrubbers in a factory clean polluted air before it is released into the atmosphere.

▶ Industries and Power Plants As a result of the Clean Air Act, indus-tries and power plants have been required to reduce the amount of pol-lutants they release. Scrubbers are responsible for much of this reduction. A scrubber removes pollutants or changes them chemically before they leave factory smokestacks. Figure 20 shows one type of scrubber.

Ozone: A Success Story Nations have taken steps to deal with the problem of ozone

loss in the stratosphere.

Ozone is a pollutant in smog in the troposphere. However, recall that ozone is highly beneficial in the ozone layer of the lower stratosphere. Here, ozone absorbs ultraviolet radiation from the sun. UV radiation can harm living things. For example, it can cause skin cancer in humans by chemically changing the genetic material in skin cells.

The Ozone Hole Late in the twentieth century, scientists noticed that measurements of ozone in the stratosphere were lower than they should have been. By 1985, the level of ozone over Antarctica was 40 to 60 percent lower than it had been 10 years before. People began to use the term ozone hole for the area of lowered ozone concentration over Antarctica that occurs every year from August until October (Figure 21).

Chlorofluorocarbons Earlier, in 1974, two scientists, Sherwood Rowland and Mario Molina, had predicted ozone depletion, or loss, and had identified the probable cause. Rowland and Molina suggested that chemicals called chlorofluorocarbons could cause ozone deple-tion. Chlorofluorocarbons (CFCs) are a family of chemical compounds containing chlorine, fluorine, and carbon. In the 1970s and 1980s, CFCs were manufactured in large amounts. They were used in many ways—for example, in refrigerators and aerosol spray cans.

The Atmosphere 473

1. Relate Cause and Effect Overall, what has been the effect of the Clean Air Act? Give one reason why this has happened.

2. Predict As time passes, what will happen to the amount of ozone in the ozone layer in the stratosphere? Give a reason for your prediction.

3. You have just become mayor of your community, and the EPA has informed you that your county has failed to meet the air quality standards for sul-fur dioxide and nitrogen oxides. Your community includes an old coal-fired power plant that causes pollution but also provides employment for many people. What measures would you suggest that might deal with the pollution prob-lem but still keep people employed?

3

Molina and Rowland were correct in their prediction. CFCs were ris-ing into the stratosphere and then releasing chlorine atoms that react with ozone. The chemical reactions destroy ozone molecules in the strato-sphere. This destruction accounts for the ozone holes over Antarctica.

The Montreal Protocol Scientists and other people became con-cerned about the possible effects of ozone depletion. They were afraid, for example, that cases of skin cancer would increase. As a result of this con-cern, many nations, including the United States, began to work together to restrict production of CFCs and other ozone-depleting substances. In 1987, many nations signed the Montreal Protocol. The treaty, strength-ened by later amendments, called for major cuts in CFC manufacture. Today the production and use of ozone-depleting compounds has fallen by 95 percent since the late 1980s. Industry was able to shift to different chemicals to perform the functions that CFCs used to perform. The new chemicals have largely turned out to be cheaper and more efficient.

Evidence indicates that the ozone layer is beginning to recover. In the last few years, concentrations of stratospheric ozone have stabilized, and scientists expect that they will soon begin to increase to their former lev-els. The Montreal Protocol is widely considered the biggest success story in addressing a global environmental problem. The Montreal Protocol is a model for international cooperation in dealing with other worldwide environmental problems, such as climate change.

FIGURE 21 The Ozone Hole The dark blue areas in the photographs show the ozone hole over Antarctica. Notice how the size of the ozone hole grew between 1979 and 2000.

The ozone hole 1979 The ozone hole 2000

ANSWERS

Lesson 3 Assessment

1. Air pollution in the United States has been reduced. Sample reasons: Improved motor vehicle construc-tion; cleaner gasoline; reduced industrial and power plant pollut-ant release.

2. Stratospheric ozone should increase, because of the dramatic reduction in the production and use of CFCs.

3. Answers will vary but should include logical steps to balance the needs of the town and the environment. Sample answer: Public funds should be set aside to help the power plant modern-ize its technology and reduce the amount of pollutants it releases.