1. Composition of the Atmosphere
Primary Pollutants – methane, ozone, dust particles, microorganisms, and chlorofluorocarbons (CFC’s)
Causes of Primary Pollutants – factories, cars, wind and soil, volcanoes, forest fires, pollen, decaying plants, salt particles from the sea, and refrigerants.

2. 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.

3. Major Air Pollutants Nitrogen oxides and nitric acid:
Nitrogen oxide (NO) forms
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.

4. Major Air Pollutants Sulfur dioxide (SO2) and sulfuric acid:
About 1/3 of SO2 in the troposphere occurs naturally through the sulfur cycle.
2/3 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.

5. 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.

6. 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.

7. Major Air Pollutants Volatile organic compounds (VOCs):
Most are hydrocarbons 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.

8. 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.

9. Form when primary pollutants react
Secondary Pollutants
Form when primary pollutants react

10. Outdoor Air Pollution Secondary pollutants
Harmful chemical formed when primary pollutants react with one another or with the basic components of air.
Fig p. 421

11. URBAN OUTDOOR AIR POLLUTION
Industrial smog: 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.

12. Photochemical Reaction
any chemical reaction activated by light
Photochemical Smog
a mixture of primary and secondary pollutants formed under the influence of sunlight
Brown Air Smog
(N2 + O NO) high temps
(2NO + O NO2)
NO2 (yellowish brown gas)

13. Industrial Smog Gray Smog Comes from burning coal Sulfur Dioxide
Fig p. 426
Gray Smog
Comes from burning coal
Sulfur Dioxide
Sulfuric Acid
Particulates
Unburned Carbon

14. 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

15. 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)
high temperatures (promote photochemical reactions).

16. 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

17. 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

18. ACID DEPOSITION
Sulfur dioxides, nitrogen oxides, and particulates can react in the atmosphere to produce acidic chemicals

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

20. 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

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

22. Acid Deposition and Humans
Respiratory diseases
Toxic metal leaching into drinking water
Decreased atmospheric visibility
Damage to structures, especially containing limestone
Decreased productivity and profitability of fisheries, forests, and farms

23. Acid Deposition and Aquatic Systems
Fish declines
pH <4.5
Undesirable species
Aluminum toxicity
Acid Shock
Sudden runoff

24. Acid Deposition, Plants, and Soil
Fig p. 432
Nutrient leaching
Heavy metal release
Weakens trees

25. ACID DEPOSITION
Figure 19-8

26. 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

27. 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

28. Air Quality is better in US; EPA estimates since 1970
Particulate Matter (PM)- down 78%
Carbon Dioxide (CO2)- down 23%
Nitrogen Dioxide (Nox)- up 14%
Lead (Pb)- down 98%
Sulfur Dioxide (SO2)- down 32%
Air quality is worse in developing countries:
Mexico City & Beijing: air exceeds WHO standards 350 days/year

29. 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.

30. Indoor Air Pollution Sick Building Syndrome
Fig
p. 434
Chloroform Para-dichlorobenzene:
Source: Chlorine-treated water in hot showers Source: Air fresh., moth balls
Possible threat: Cancer Threat: cancer
1,1,1-Trichloroethane
Source: Aerosol sprays
Threat: Dizziness, irregular breathing
Nitrogen Oxides
Source: Unvented gas stoves and kerosene heaters, woodstoves
Threat: irritated lungs, children’s colds, headaches
Asbestos
Source: Pipe insulation, vinyl ceiling and floor tiles
Threat: Lung diseases
Caron Monoxide:
Faulty furnaces, unvented gas stoves and kerosene heaters, woodstoves
Threat: Headaches, drowsiness, irregular heartbeat, death
Methylene Chloride
Source: Paint strippers and thinners
Threat: Nerve disorders, diabetes
Radon-222
Source: Radioactive soil and rock surrounding foundation, water supply
Threat: lung cancer
Styrene
Source: Carpets, plastic products,
Threat: kidney and liver damage
Benzo-pyrene
Source: tobacco smoke, woodstoves
Formaldehyde
Source: Furniture stuffing, paneling, particle board, foam insulation
Threat: irritation of eyes, throat, skin, and lungs, nausea, dizziness
Tetrachloroethylene
Source: Dry-cleaning fluid fumes and clothes
Threat: nerve disorders, damage to liver and kidneys, possible cancer

31. 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

32. 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.

33. Radon
Fig
p. 436
Radon-222
Associated with uranium (U-238) and organic material in rocks
2nd leading cause of lung cancer
4 picocuries
EPA proposed standard

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

35. 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.

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

37. 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

38. Using the Marketplace to Reduce Outdoor Air Pollution
To help reduce SO2 emissions, the Clean Air Act authorized an 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.

39. 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.

40. 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.

41. 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.

42. 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

43. Can US Air Pollution Laws Be Improved….hmmm?
Continue to rely mostly on pollution cleanup rather than prevention.
Fail to increase fuel-efficiency standards for cars and light trucks.
Not adequately regulating emissions from inefficient two-cycle gasoline engines.
Do little to reduce emissions of carbon dioxide and other greenhouse gases.

44. The Next Steps
Integrating government policies for energy and air pollution.
Improving energy efficiency.
Relying more on lower-polluting and more climate-benign natural gas.
Increasing use of renewable energy.
Regulating the air quality for an entire region or airshed with primary emphasis on prevention.