Chapter 18
Air Pollution
Chapter Outline
CORE CASE STUDY South Asia’s Massive Brown Clouds
18-1 What Is the Nature of the Atmosphere?
18-2 What Are the Major Outdoor Air Pollution Problems?
SCIENCE FOCUS The South Asian Brown Clouds, Melting Glaciers, and Climate Change
CASE STUDY Lead Is a Highly Toxic Pollutant
SCIENCE FOCUS Detecting Air Pollutants
18-3 What Is Acid Deposition and Why Is It a Problem?
18-4 What Are the Major Indoor Air Pollution Problems?
CASE STUDY Radioactive Radon Gas
18-5 What Are the Health Effects of Air Pollution?
18-6 How Should We Deal with Air Pollution?
18-7 How Have We Depleted Ozone in the Stratosphere and What Can We Do About It?
Individuals matter: Sherwood Rowland and Mario Molina—A Scientific Story of Expertise, Courage, and
Persistence
TYING IT ALL TOGETHER The South Asian Brown Clouds and Sustainability
Key Concepts
18-1 The two innermost layers of the atmosphere are the troposphere, which supports life, and the
stratosphere, which contains the protective ozone layer.
18-2 Pollutants mix in the air to form industrial smog, primarily as a result of burning coal, and to form
photochemical smog, caused by emissions from motor vehicles, industrial facilities, and power plants.
18-3 Acid deposition is caused mainly by coal-burning power plants and motor vehicle emissions, and in
some regions it threatens human health, aquatic life and ecosystems, forests, and human-built structures.
18-4 The most threatening indoor air pollutants are smoke and soot from the burning of wood and coal in
cooking fires (mostly in less-developed countries), cigarette smoke, and chemicals used in building
materials and cleaning products.
18-5 Air pollution can contribute to asthma, chronic bronchitis, emphysema, lung cancer, heart attack,
and stroke.
18-6 Legal, economic, and technological tools can help us to clean up air pollution, but the best solution
is to prevent it.
18-7A Our widespread use of certain chemicals has reduced ozone levels in the stratosphere and allowed
more harmful ultraviolet radiation to reach the earth’s surface.
18-7B To reverse ozone depletion, we must stop producing ozone-depleting chemicals and adhere to the
international treaties that ban such chemicals.
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Key Questions and Case Studies
CORE CASE STUDY: South Asia’s Massive Brown Clouds
Air pollution is no longer a localized phenomenon. South Asian Brown Clouds, containing dust, smoke,
ash, soot, acidic compounds and particles of toxic metals, can cover areas the size of the continental
United States and drift across oceans. Such pollution can be reduced fairly quickly with new standards
and enforcement, but the worst polluting nations have a long way to go.
18-1 What Is the Nature of the Atmosphere?
The atmosphere consists of several layers with different temperatures, pressures, and composition.
Density and atmospheric pressure vary throughout the atmosphere due to gravitational forces that
pull the gas molecules toward the earth’s surface. Air at sea level has a higher density than air at the
top of a mountain.
A. About 75–80% of the earth’s air mass is found in the troposphere, the atmospheric layer closest
to the earth’s surface. This layer extends about 11 miles above sea level at the equator and about
5 miles above the poles. About 99% of the volume of air is made up of nitrogen (78%) and
oxygen (21%) with the rest consisting of water vapor, argon, carbon dioxide, and traces of
several other gases.
B. The stratosphere is the second layer of the atmosphere and extends from 11–30 miles above the
earth’s surface. The concentration of ozone in this layer is much higher than in the troposphere.
Ozone is produced when oxygen molecules interact with ultraviolet radiation (3 O2 + UV  2
O3). This “global sunscreen” keeps about 95% of the sun’s harmful UV radiation from reaching
the earth’s surface.
18-2 What Are the Major Outdoor Air Pollution Problems?
A. Air pollutants come mostly from natural sources and from burning fossil fuels. Primary
pollutants are pollutants emitted into the air. They can react with one another and/or with air to
form secondary pollutants.
B. Outdoor air pollution comes mostly from natural sources and burning fossil fuels in vehicles and
power and industrial plants.
C. Major air pollutants include:
1. Carbon oxides
2. Nitrogen oxides and nitric acid
3. Sulfur dioxide and sulfuric acid
4. Particulates
5. Ozone
6. Volatile Organic Compounds (VOCs)
SCIENCE FOCUS: The South Asian Brown Clouds, Melting Glaciers, and Climate Change.
Air pollution is not localized. South Asia’s brown clouds affect glaciers in the Himalayas, which in
turn affects global climate.
CASE STUDY: Lead is a Highly Toxic Pollutant.
Lead is a pollutant found in air, water, soil, plants and animals. It is a neurotoxin that is especially
dangerous for children. The United States has phased out lead in gasoline and paint with the effect
of a dramatic decrease in the percentage of children with blood lead levels above safety standards.
Other nations however have not yet made this transition.
D. Industrial smog is a mix of sulfur dioxide, sulfuric acid, and suspended particles. China has the
world’s highest levels of industrial smog.
SCIENCE FOCUS: Detecting Air Pollutants
Air pollutants can be detected and measured remotely with the use of unmanned aircraft, remote
laboratories, and lasers. Other methods rely on biological indicators such as lichens.
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E. Photochemical smog is formed by the reaction of nitrogen oxides and volatile hydrocarbons
under the influence of sunlight. All cities have some photochemical smog, though it is more
common in places with sunny, warm and dry climates.
F. Factors that reduce air pollution include particles heavier than air settling out, rain and snow
cleansing the air, salty sea spray washing out pollutants, winds sweeping pollutants away, and
chemical reactions.
G. Factors that increase air pollution include buildings obstructing the wind, hills and mountains,
high temperatures, emissions of VOCs, the movement of air pollutants to polar areas, and
temperature inversions.
H. Air pollution is influenced by atmospheric conditions. A temperature inversion, where a layer of
warm air sits over a layer of cold air, prevents the mixing and dense, colder air becomes stagnant
and accumulates more pollutants. This is a particular problem for cities in a valley (e.g., Los
Angeles).
18-3 What Is Acid Deposition and Why Is It a Problem?
A. Acid deposition: Sulfur dioxide, nitrogen oxides, and particulates react in the atmosphere to
produce acidic chemicals that travel long distances before coming back to earth. Acidic particles
remain in the atmosphere for 2–14 days, depending on the prevailing winds, precipitation, and
other weather patterns. The acidic substances return to the earth in one of two forms:
1. Wet deposition: acidic rain, snow, fog, and cold vapor with a pH less than 5.6.
2. Dry deposition: acidic particles.
B. Acid deposition can cause or worsen respiratory disease, attack metallic and stone objects,
decrease atmospheric visibility, and kill fish.
C. Acid deposition can deplete some soil nutrients, release toxic ions into soil, and weaken plants
that become susceptible to other stresses. Effect of acid deposition on plants is caused partly by
chemical interaction in the soils.
18-4 What Are the Major Indoor Air Pollution Problems?
A. Indoor air pollution is usually a much greater threat to human health than outdoor air pollution.
1. Pesticides and lead residues can collect in carpets and on furnishings
2. Living organisms and the excrement can pollute indoor air
3. Airborne spores of molds and mildews can be a source of indoor air pollution
B. The four most dangerous indoor air pollutants in more-developed countries are tobacco smoke,
formaldehyde, radioactive radon-222 gas and very small particles from emissions.
CASE STUDY: Radioactive Radon Gas.
Radon-222 gas is found in some soils and rocks, and can seep into some homes and increase the risk
of lung cancer. Radon is produced by the radioactive decay of uranium-238. Radon gas tends to be
pulled into homes because of the slightly lower atmospheric pressure inside most homes. Radon is
thought to be the second leading cause of lung cancer deaths each year in the U.S.
18-5 What Are the Health Effects of Air Pollution?
A. Prolonged or acute expose to air pollutants can overload or break down the natural defenses.
Several respiratory diseases can develop such as asthma, lung cancer, chronic bronchitis, and
emphysema. People with respiratory diseases, older adults, infants, pregnant women, and people
with heart disease are especially vulnerable to air pollution.
B. Each year, air pollution kills about 2.4 million people, mostly from indoor air pollution in
developing countries. Air pollution deaths in the U.S. range from 150,000 to 350,000 people per
year.
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18-6 How Should We Deal with Air Pollution?
A. Clean Air Acts in the United States have greatly reduced outdoor air pollution from six major
pollutants. The U.S. Congress passed Clean Air Acts in 1970, 1977, and 1990. National air
quality standards (NAAQS) were established for six outdoor criteria pollutants. Two limits were
established: a primary standard is set to protect human health, and a secondary standard is set to
prevent environmental and property damage.
B. Allowing producers of air pollutants to buy and sell government air pollution allotments in the
marketplace can help reduce emissions. The Clean Air Act of 1990 allows an emissions trading
policy that permits companies to buy and sell SO2 pollution rights.
1. Success of these programs is dependent upon how low the initial cap is set, and how often it
is lowered.
D. There are a number of ways to prevent and control air pollution from coal-burning facilities and
motor vehicles. Indoor air pollution is a greater threat to human health, but little effort has been
spent on reducing it.
Teaching Tips
Large Lecture Classes:
Start the lecture by asking how many students live in basement apartments, and then asking how many of
them have had the apartment tested for radon. Ask how many live in a location near a furnace and how
many have CO monitors installed. When you reach the radon section, revisit the results and ask whether a
landlord should have responsibility to test for radon. You can also highlight that Radon is an alpha emitter
and therefore particularly dangerous when attached to particles—mention that this is particularly a
problem for smokers since the particulates can carry radon into the lungs.
Smaller Lecture Classes:
Ask students to characterize sources of indoor and outdoor air pollution on campus before coming to
class. They should arrive with a list of five potential sources of air pollution and the types of pollution
that would be generated by these sources. Organize the lists and ask the class to rank the types of
pollution from highest potential risk to lowest risk. Use the list to generate a discussion about prioritizing
air pollution control measure, costs of air pollution control, and who should bear the responsibility for air
pollution control.
Key Terms
acid deposition
air pollution
atmospheric pressure
carbon oxides
industrial smog
nitrogen oxides
nitric acid
ozone
ozone layer
particulates
photochemical smog
primary pollutants
secondary pollutants
stratosphere
sulfur dioxide
sulfuric acid
temperature inversion
troposphere
volatile organic compounds
(VOCs)
Term Paper Research Topics
1.
Outdoor air pollution: the geographic distribution of air quality problems; air pollution and major
ecosystem disruption; fine particulates as a health hazard; the history of air pollution; the air
pollution disaster in Donora, Pennsylvania; reducing urban heat island effects.
2.
Indoor air pollution: radon gas; asbestos; second-hand smoke; formaldehyde: sources, health effects,
and control measures for each.
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3.
Acid deposition: tall smokestacks and acid deposition; acid deposition in the northeastern United
States; Germany's waldsterben; liming lakes; acid deposition and freshwater ecosystems.
4.
Smog: how and where it is formed, and what can be done to reduce it.
5.
How much air pollution should we tolerate and what criteria should we use to decide?
6.
Methods of assessing and cleaning up air pollution: scientific methods for measuring indoor and
outdoor air pollutants; methods for measuring automobile emissions; stack scrubber technology;
catalytic converters and their problems; electric automobiles.
7.
National Policy: The Clean Air Act; the EPA's record on enforcement of the Clean Air Acts; changes
in regulations on smoking in public places over the last decade; emissions trading policy.
8.
International Policy: the London air pollution cleanup; air pollution in Eastern Europe; joint
responsibility of Canada and the United States for acid deposition in the Great Lakes region.
9.
Cap and Trade approaches to air quality.
10. Comparison of European versus U.S. approaches to air pollution regulation.
Discussion Topics
1.
How does the idea of environmental justice apply to air pollution? What are the issues?
2.
What are the particular local air quality problems?
3.
Who should pay for air quality regulation?
4.
How much effort should we put into clean air technologies? How much would you be willing to
pay?
5.
Would your perspective on air pollution be different if you had respiratory problems? What if you
lived next to a major highway?
Attitudes and Values
1.
Is clean air a basic right?
2.
Who is responsible for air pollution?
3.
What obligation is there to reduce the ecological impacts of air pollution? Why?
4.
What role should the federal, state, and local government play in regulating air pollution?
5.
Would privatizing the atmosphere be logistically feasible? How might privatization of the
atmosphere improve/deteriorate the quality of the air we breathe?
Instructor's Manual: Chapter 18