1. Chapter 19
Air Pollution

2. Chapter Overview Questions
What layers are found in the atmosphere?
What are the major outdoor air pollutants, and where do they come from?
What are two types of smog?
What is acid deposition, and how can it be reduced?
What are the harmful effects of air pollutants?
How can we prevent and control air pollution?

3. Updates Online
The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at to access InfoTrac articles.
InfoTrac: Indoor air pollution. Eva Rehfuess, Carlos Corvalan, Maria Neira. Bulletin of the World Health Organization, July 2006 v84 i7 p508(1).
InfoTrac: Risks of cleaning house disclosed. San Jose Mercury News (San Jose, CA), May 23, 2006.
InfoTrac: Pollution From Chinese Coal Casts Shadow Around Globe. Keith Bradsher, David Barboza. The New York Times, June 11, 2006 pA1(L).
American Industrial Hygiene Association: Do I Work in a Sick Building?
PBS: Deadly Smog
EPA: Toxic Air Pollutants

4. Video: Air Pollution
This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

5. Video: Smog Pollution
This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

6. Core Case Study: When Is a Lichen Like a Canary?
Lichens can warn us of bad air because they absorb it as a source of nourishment.
Figure 19-1

7. Core Case Study: When Is a Lichen Like a Canary?
Some lichen species are sensitive to specific air-polluting chemicals.
After Chernobyl, more than 70,000 reindeer had to be killed because they ate highly radioactive lichens.
Because lichens are widespread, long-lived, and anchored in place, they can help track pollution to its source.

8. STRUCTURE AND SCIENCE OF THE ATMOSPHERE
The atmosphere consists of several layers with different temperatures, pressures, and compositions.
Figure 19-2

9. Atmospheric pressure (millibars)
Temperature
Pressure
Thermosphere
Mesopause
Heating via ozone
Mesosphere
Altitude (kilometers)
Stratopause
Altitude (miles)
Stratosphere
Figure 19.2
Natural capital: the earth’s atmosphere is a dynamic system that consists of four layers. The average temperature of the atmosphere varies with altitude (red line). Most UV radiation from the sun is absorbed by ozone (O3), found primarily in the stratosphere in the ozone layer 17–26 kilometers (10–16 miles) above sea level. QUESTION: How did living organisms lead to the formation of the ozone layer?
Tropopause
Ozone “layer”
Heating from the earth
Troposphere
Pressure = 1,000 millibars at ground level
(Sea level)
Temperature (˚C)
Fig. 19-2, p. 440

10. STRUCTURE AND SCIENCE OF THE ATMOSPHERE
The atmosphere’s innermost layer (troposphere) is made up mostly of nitrogen and oxygen, with smaller amounts of water vapor and CO2.
Ozone in the atmosphere’s second layer (stratosphere) filters out most of the sun’s UV radiation that is harmful to us and most other species.

11. AIR POLLUTION
Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants.
Figure 19-3

12. Most suspended particles H2O2 O3 PANs
Primary Pollutants CO
CO2
Secondary Pollutants
SO2 NO
NO2
Most hydrocarbons
SO3
HNO3
H3SO4
Most suspended particles
H2O2 O3
PANs
Most NO3– and SO42– salts
Sources
Natural
Stationary
Figure 19.3
Natural capital degradation: sources and types of air pollutants. Human inputs of air pollutants may come from mobile sources (such as cars) and stationary sources (such as industrial and power plants). Some primary air pollutants may react with one another or with other chemicals in the air to form secondary air pollutants.
Mobile
Fig. 19-3, p. 442

13. Major Air Pollutants Carbon oxides:
Carbon monoxide (CO) is a highly toxic gas that forms during the incomplete combustion of carbon-containing materials.
93% of carbon dioxide (CO2) in the troposphere occurs as a result of the carbon cycle.
7% of CO2 in the troposphere occurs as a result of human activities (mostly burning fossil fuels).
It is not regulated as a pollutant under the U.S. Clean Air Act.

14. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should carbon dioxide be regulated as an air pollutant?
a. No. Because funds are limited, they should be spent on regulating and reducing more toxic air pollutants, such as mercury.
b. Yes. Carbon dioxide is a serious greenhouse gas and its emissions must be regulated and reduced.

15. Major Air Pollutants Nitrogen oxides and nitric acid:
Nitrogen oxide (NO) forms when nitrogen and oxygen gas in air react at the high-combustion temperatures in automobile engines and coal-burning plants. NO can also form from lightening and certain soil bacteria.
NO reacts with air to form NO2.
NO2 reacts with water vapor in the air to form nitric acid (HNO3) and nitrate salts (NO3-) which are components of acid deposition.

16. Major Air Pollutants Sulfur dioxide (SO2) and sulfuric acid:
About one-third of SO2 in the troposphere occurs naturally through the sulfur cycle.
Two-thirds come from human sources, mostly combustion (S+ O2  SO2) of sulfur-containing coal and from oil refining and smelting of sulfide ores.
SO2 in the atmosphere can be converted to sulfuric acid (H2SO4) and sulfate salts (SO42-) that return to earth as a component of acid deposition.

17. Major Air Pollutants Suspended particulate matter (SPM):
Consists of a variety of solid particles and liquid droplets small and light enough to remain suspended in the air.
The most harmful forms of SPM are fine particles (PM-10, with an average diameter < 10 micrometers) and ultrafine particles (PM-2.5).
According to the EPA, SPM is responsible for about 60,000 premature deaths a year in the U.S.

18. Major Air Pollutants Ozone (O3):
Is a highly reactive gas that is a major component of photochemical smog.
It can
Cause and aggravate respiratory illness.
Can aggravate heart disease.
Damage plants, rubber in tires, fabrics, and paints.

19. Major Air Pollutants Volatile organic compounds (VOCs):
Most are hydorcarbons emitted by the leaves of many plants and methane.
About two thirds of global methane emissions comes from human sources.
Other VOCs include industrial solvents such as trichlorethylene (TCE), benzene, and vinyl chloride.
Long-term exposure to benzene can cause cancer, blood disorders, and immune system damage.

20. Major Air Pollutants Radon (Rn):
Is a naturally occurring radioactive gas found in some types of soil and rock.
It can seep into homes and buildings sitting above such deposits.

21. URBAN OUTDOOR AIR POLLUTION
Industrial smog is a mixture of sulfur dioxide, droplets of sulfuric acid, and a variety of suspended solid particles emitted mostly by burning coal.
In most developed countries where coal and heavy oil is burned, industrial smog is not a problem due to reasonably good pollution control or with tall smokestacks that transfer the pollutant to rural areas.

22. Case Study: South Asia’s Massive Brown Cloud
A huge dark brown cloud of industrial smog, caused by coal-burning in countries such as China and India, stretches over much of southeastern Asia.
In areas beneath the cloud, photosynthesis is reduced interfering with crop development.
Fine particles and droplets in the cloud appear to be changing regional climates (including rainfall).
May have contributed to floods in 2002 and 2005 which killed thousands of people.

23. Sunlight plus Cars Equals Photochemical Smog
Photochemical smog is a mixture of air pollutants formed by the reaction of nitrogen oxides and volatile organic hydrocarbons under the influence of sunlight.

24. Sunlight plus Cars Equals Photochemical Smog
Mexico City is one of the many cities in sunny, warm, dry climates with many motor vehicles that suffer from photochemical smog.
Figure 19-4

25. Animation: Formation of Photochemical Smog
PLAY
ANIMATION

26. Factors Influencing Levels of Outdoor Air Pollution
Outdoor air pollution can be reduced by:
settling out, precipitation, sea spray, winds, and chemical reactions.
Outdoor air pollution can be increased by:
urban buildings (slow wind dispersal of pollutants), mountains (promote temperature inversions), and high temperatures (promote photochemical reactions).

27. Temperature Inversions
Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left).
Areas with sunny climate, light winds, mountains on three sides and an ocean on the other (right) are susceptible to inversions.
Figure 19-5

28. Descending warm air mass Warmer air
Inversion layer
Inversion layer
Sea breeze
Increasing altitude
Figure 19.5
Natural capital degradation: two sets of topography and weather conditions that lead to prolonged temperature inversions, in which a warm air layer sits atop a cooler air layer. Air pollutants can build to harmful levels during an inversion. A temperature inversion can occur during cold, cloudy weather in a valley surrounded by mountains (left). Frequent and prolonged temperature inversions can also occur in an area with a sunny climate, light winds, mountains on three sides, and the ocean on the other (right). A layer of descending warm air from a high-pressure system prevents ocean-cooled air near the ground from ascending enough to disperse and dilute pollutants. Because of their topography, Los Angeles, California and Mexico City, Mexico (Figure 19-4) have frequent temperature inversions, many of them prolonged during the summer. QUESTION: Do you live in an area that suffers from fairly frequent thermal inversions?
Decreasing temperature
Fig. 19-5, p. 447

29. Animation: Thermal Invasion and Smog
PLAY
ANIMATION

30. ACID DEPOSITION
Sulfur dioxides, nitrogen oxides, and particulates can react in the atmosphere to produce acidic chemicals that can travel long distances before returning to the earth’s surface.
Tall smokestacks reduce local air pollution but can increase regional air pollution.

31. Animation: Acid Deposition
PLAY
ANIMATION

32. ACID DEPOSITION
Acid deposition consists of rain, snow, dust, or gas with a pH lower than 5.6.
Figure 19-6

33. Lakes in deep soil high in limestone are buffered
Wind
Transformation to sulfuric acid (H2SO4) and nitric acid (HNO3)
Windborne ammonia gas and particles of cultivated soil partially neutralize acids and form dry sulfate and nitrate salts
Wet acid depostion (droplets of H2SO4 and HNO3 dissolved in rain and snow)
Nitric oxide (NO)
Sulfur dioxide (SO2) and NO
Dry acid deposition (sulfur dioxide gas and particles of sulfate and nitrate salts)
Acid fog
Farm
Lakes in shallow soil low in limestone become acidic
Ocean
Figure 19.6
Natural capital degradation: acid deposition, which consists of rain, snow, dust, or gas with a pH lower than 5.6, is commonly called acid rain. Soils and lakes vary in their ability to buffer or remove excess acidity.
Lakes in deep soil high in limestone are buffered
Fig. 19-6, p. 448

34. ACID DEPOSITION
pH measurements in relation to major coal-burning and industrial plants.
Figure 19-7

35. ACID DEPOSITION
Acid deposition contributes to chronic respiratory disease and can leach toxic metals (such as lead and mercury) from soils and rocks into acidic lakes used as sources for drinking water.

36. ACID DEPOSITION
Figure 19-8

37. ACID DEPOSITION
Air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater.
Figure 19-9

38. Emissions Lake Groundwater Acid deposition SO2 NOx H2O2 O3 PANs Others
Susceptibility to drought, extreme cold, insects, mosses, & disease organisms
Direct damage to leaves & bark
Reduced photo-synthesis and growth
Soil acidification
Tree death
Figure 19.9
Natural capital degradation: air pollution is one of several interacting stresses that can damage, weaken, or kill trees and pollute surface and groundwater.
Leaching of soil nutrients
Release of toxic metal ions
Root damage
Reduced nutrient & water uptake
Acids
Lake
Groundwater
Fig. 19-9, p. 451

39. Animation: Effects of Air Pollution in Forests
PLAY
ANIMATION

40. Solutions Acid Deposition Prevention Cleanup
Reduce air pollution by improving energy efficiency
Add lime to neutralize acidified lakes
Reduce coal use
Add phosphate fertilizer to neutralize acidified lakes
Increase natural gas use
Increase use of renewable energy resources
Burn low-sulfur coal
Figure 19.10
Solutions: methods for reducing acid deposition and its damage. QUESTION: Which two of these solutions do you think are the most important?
Remove SO2 particulates & NOx from smokestack gases
Remove NOx from motor vehicular exhaust
Tax emissions of SO2
Fig , p. 452

41. INDOOR AIR POLLUTION
Indoor air pollution usually is a greater threat to human health than outdoor air pollution.
According to the EPA, the four most dangerous indoor air pollutants in developed countries are:
Tobacco smoke.
Formaldehyde.
Radioactive radon-222 gas.
Very small fine and ultrafine particles.

42. Tobacco Smoke Carbon Monoxide Methylene Chloride
Para-dichlorobenzene
Chloroform
Tetrachloroethylene
Formaldehyde
1, 1, 1-
Trichloroethane
Styrene
Nitrogen Oxides
Benzo-a-pyrene
Particulates
Tobacco Smoke
Radon-222
Asbestos
Carbon Monoxide
Methylene Chloride
Fig , p. 453

43. INDOOR AIR POLLUTION
Household dust mites that feed on human skin and dust, live in materials such as bedding and furniture fabrics.
Can cause asthma attacks and allergic reactions in some people.
Figure 19-12

44. Case Study: Radioactive Radon
Radon-222, a radioactive gas found in some soils and rocks, can seep into some houses and increase the risk of lung cancer.
Sources and paths of entry for indoor radon-222 gas.
Figure 19-13

45. Clothes dryer Sump pump Radon-222 gas
Outlet vents for furnaces and dryers
Open window
Openings around pipes
Cracks in wall
Slab joints
Wood stove
Cracks in floor
Clothes dryer
Sump pump
Furnace
Slab
Radon-222 gas
Figure 19.13
Science: sources and paths of entry for indoor radon-222 gas. QUESTION: Have you tested the indoor air where you live for radon-222? (Data from U.S. Environmental Protection Agency)
Uranium-238
Soil
Fig , p. 454

46. HEALTH EFFECTS OF AIR POLLUTION
Your respiratory system can help protect you from air pollution, but some air pollutants can overcome these defenses.
Figure 19-14

47. Goblet cell (secreting mucus)
Epithelial cell
Cilia
Goblet cell (secreting mucus)
Nasal cavity
Oral cavity
Pharynx (throat)
Mucus
Trachea (windpipe)
Bronchioles
Bronchus
Alveolar duct
Right lung
Figure 19.14
Major components of the human respiratory system.
Alveoli
Alveolar sac (sectioned)
Bronchioles
Fig , p. 455

48. HEALTH EFFECTS OF AIR POLLUTION
Normal human lungs (left) and the lungs of a person who died of emphysema (right).
Figure 19-15

49. Air Pollution is a Big Killer
Each year, air pollution prematurely kills about 3 million people, mostly from indoor air pollution in developing countries.
In the U.S., the EPA estimates that annual deaths related to indoor and outdoor air pollution range from 150,000 to 350,000.
According to the EPA, each year more than 125,000 Americans get cancer from breathing diesel fumes.

50. Air Pollution is a Big Killer
Spatial distribution of premature deaths from air pollution in the United States.
Figure 19-16

51. PREVENTING AND REDUCING AIR POLLUTION
The Clean Air Acts in the United States have greatly reduced outdoor air pollution from six major pollutants:
Carbon monoxide
Nitrogen oxides
Sulfur dioxides
Suspended particulate matter (less than PM-10)

52. PREVENTING AND REDUCING AIR POLLUTION
Environmental scientists point out several deficiencies in the Clean Air Act:
The U.S. continues to rely on cleanup rather than prevention.
The U.S. Congress has failed to increase fuel-efficiency standards for automobiles.
Regulation of emissions from motorcycles and two-cycle engines remains inadequate.
There is little or no regulation of air pollution from oceangoing ships in American ports.

53. PREVENTING AND REDUCING AIR POLLUTION
Airports are exempt from many air pollution regulations.
The Act does not regulate the greenhouse gas CO2.
The Act has failed to deal seriously with indoor air pollution.
There is a need for better enforcement of the Clean Air Act.

54. PREVENTING AND REDUCING AIR POLLUTION
Executives of companies claim that correcting these deficiencies would cost too much, harm economic growth, and cost jobs.

55. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access the “Polls Clicker Questions” from the PowerLecture main menu.
Should the 1990 U.S. Clean Air Act be strengthened?
a. No. Strengthening the Act would be too expensive and would harm the economy.
b. Yes. Strengthening the Act would improve the environment and people's health, save energy, and ultimately save money.

56. Using the Marketplace to Reduce Outdoor Air Pollution
To help reduce SO2 emissions, the Clean Air Act authorized and emission trading (cap-and-trade) program.
Enables the 110 most polluting power plants to buy and sell SO2 pollution rights.
Between , the emission trading system reduced emissions.
In 2002, the EPA reported the cap-and-trade system produced less emission reductions than were projected.

57. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access the “Polls Clicker Questions” from the PowerLecture main menu.
Should emissions trading be used to help control emissions of all major air pollutants?
a. No. Emissions trading has no system for verifying compliance and eliminating "hot spots" of air pollution.
b. Yes. Emissions trading is an efficient and effective way of reducing air pollution.

58. Video: Clean Air Act
PLAY
VIDEO
From ABC News, Environmental Science in the Headlines, 2005 DVD.

59. Solutions: Reducing Outdoor Air Pollution
There are a of ways to prevent and control air pollution from coal-burning facilities.
Electrostatic precipitator: are used to attract negatively charged particles in a smokestack into a collector.
Wet scrubber: fine mists of water vapor trap particulates and convert them to a sludge that is collected and disposed of usually in a landfill.

60. Electrostatic Precipitator
Can remove 99% of particulate matter
Does not remove hazardous ultrafine particles.
Produces toxic dust that must be safely disposed of.
Uses large amounts of electricity
Figure 19-18

61. Negatively charged electrode Positively charged precipitator wall
Clean gas out
Negatively charged electrode
Positively charged precipitator wall
Dirty gas (smoke) in
Dust falls off into collector
Figure 19.18
Solutions: an electrostatic precipitator (left) and a wet scrubber (right) are used to reduce SO2 and particulate emissions from coal-burning power and industrial plants.
Taken to landfill
Fig a, p. 460

62. Wet Scrubber Can remove 98% of SO2 and particulate matter.
Not very effective in removing hazardous fine and ultrafine particles.
Figure 19-18

63. Polluted liquid (sludge) out
Clean gas out
Separator
Liquid water in
Dirty gas (smoke) in
Polluted liquid (sludge) out
Figure 19.18
Solutions: an electrostatic precipitator (left) and a wet scrubber (right) are used to reduce SO2 and particulate emissions from coal-burning power and industrial plants.
Fig b, p. 460

64. Stationary Source Air Pollution
Solutions
Stationary Source Air Pollution
Prevention
Dispersion or Cleanup
Burn low-sulfur coal
Disperse emissions above thermal inversion layer with tall smokestacks
Remove sulfur from coal
Remove pollutants after combustion
Convert coal to a liquid or gaseous fuel
Figure 19.17
Solutions: methods for reducing emissions of sulfur oxides, nitrogen oxides, and particulate matter from stationary sources such as coal-burning electric power plants and industrial plants. QUESTION: Which two of these solutions do you think are the most important?
Tax each unit of pollution produced
Shift to less polluting fuels
Fig , p. 459

65. Solutions: Reducing Outdoor Air Pollution
In 2003, fourteen states and a number of U.S. cities sued the EPA to block new rules that would allow older coal-burning power plants to modernize without having to install the most advanced air pollution controls.

66. How Would You Vote?
To conduct an instant in-class survey using a classroom response system, access “JoinIn Clicker Content” from the PowerLecture main menu for Living in the Environment.
Should older coal-burning power and industrial plants have to meet the same air pollution standards as new facilities?
a. No. The private sector should not have to upgrade existing facilities every time the regulations change.
b. Yes. All facilities should comply with current regulations so that the environment and human health are effectively protected.

67. Solutions: Reducing Outdoor Air Pollution
There are a of ways to prevent and control air pollution from motor vehicles.
Because of the Clean Air Act, a new car today in the U.S. emits 75% less pollution than did pre-1970 cars.
There is and increase in motor vehicle use in developing countries and many have no pollution control devices and burn leaded gasoline.

68. Video: Air Pollution in China
PLAY
VIDEO
From ABC News, Environmental Science in the Headlines, 2005 DVD.

69. Motor Vehicle Air Pollution
Solutions
Motor Vehicle Air Pollution
Prevention
Cleanup
Mass transit
Emission control devices
Bicycles and walking
Less polluting engines
Less polluting fuels
Car exhaust inspections twice a year
Improve fuel efficiency
Figure 19.19
Solutions: methods for reducing emissions from motor vehicles. Go to to find out how dirty your car is. QUESTION: Which two of these solutions do you think are the most important?
Get older, polluting cars off the road
Give buyers large tax write-offs or rebates for buying low-polluting, energy efficient vehicles
Stricter emission standards
Fig , p. 460

70. Indoor Air Pollution
Little effort has been devoted to reducing indoor air pollution even though it poses a much greater threat to human health than outdoor air pollution.
Environmental and health scientists call for us to focus on preventing air pollution (especially indoor) in developing countries.

71. Use adjustable fresh air vents for work spaces
Solutions
Indoor Air Pollution
Prevention
Cleanup or Dilution
Cover ceiling tiles & lining of AC ducts to prevent release of mineral fibers
Use adjustable fresh air vents for work spaces
Increase intake of outside air
Ban smoking or limit it to well ventilated areas
Change air more frequently
Set stricter formaldehyde emissions standards for carpet, furniture, and building materials
Circulate a building’s air through rooftop green houses
Figure 19.20
Solutions: ways to prevent and reduce indoor air pollution. QUESTION: Which two of these solutions do you think are the most important?
Prevent radon infiltration
Use exhaust hoods for stoves and appliances burning natural gas
Use office machines in well ventilated areas
Use less polluting substitutes for harmful cleaning agents, paints, and other products
Install efficient chimneys for wood-burning stoves
Fig , p. 461

72. • Do not buy furniture and other products containing formaldehyde.
What Can You Do?
Indoor Air Pollution
• Test for radon and formaldehyde inside your home and take corrective measures as needed.
• Do not buy furniture and other products containing formaldehyde.
• Remove your shoes before entering your house to reduce inputs of dust, lead, and pesticides.
• Test your house or workplace for asbestos fiber levels and for any crumbling asbestos materials if it was built before 1980.
• Don't live in a pre-1980 house without having its indoor air tested for asbestos and lead.
• Do not store gasoline, solvents, or other volatile hazardous chemicals inside a home or attached garage.
Figure 19.21
Individuals matter: ways to reduce your exposure to indoor air pollution. QUESTION: Which three of these actions do you think are the most important?
• If you smoke, do it outside or in a closed room vented to the outside.
• Make sure that wood-burning stoves, fireplaces, and kerosene- and gas-burning heaters are properly installed, vented, and maintained.
• Install carbon monoxide detectors in all sleeping areas.
Fig , p. 461

73. Improve energy efficiency to reduce fossil fuel use Reduce poverty
Solutions
Air Pollution
Outdoor
Indoor
Improve energy efficiency to reduce fossil fuel use
Reduce poverty
Distribute cheap & efficient cookstoves or solar cookers to poor families in developing countries
Rely more on lower-polluting natural gas
Rely more on renewable energy (especially solar cells, wind, & solar-produced hydrogen)
Reduce or ban indoor smoking
Figure 19.22
Solutions: ways to prevent outdoor and indoor air pollution over the next 30–40 years. QUESTION: Which two of these solutions do you think are the most important?
Transfer technologies for latest energy efficiency, renewable energy, & pollution prevention to developing countries
Develop simple and cheap tests for indoor pollutants such as particulates, radon, and formaldehyde
Fig , p. 462