1. Atmosphere and Pollution
Ch. 18

2. Indoor air pollution can pose serious health risks, but they are risks that the individual can do much to minimize their exposure; outdoor air pollution on the other hand can only be addressed by government and regulation.

3. Guiding Questions
What is the composition, structure, and function of the atmosphere?
What are the major indoor and outdoor air pollutants?
What is ozone depletion and what are the steps being taken to address it?
How do weather and climate affect atmospheric conditions?

4. The atmosphere Atmosphere = the thin layer of gases around Earth
Provides oxygen
Absorbs radiation and moderates climate
Transports and recycles water and nutrients
78% N2, 21% O2
Human activity is changing the amount of some gases
CO2, methane (CH4), ozone (O3)

5. The first two layers of the atmosphere
Troposphere = bottommost layer (11 km [7 miles])
Air for breathing, weather
The air gets colder with altitude
Tropopause = limits mixing between troposphere and the layer above it
Stratosphere = 11–50 km (7–31 mi) above sea level
Drier and less dense, with little vertical mixing
Becomes warmer with altitude
Contains UV radiation-blocking ozone, 17–30 km (10–19 mi) above sea level

6. Atmospheric properties
Atmospheric pressure = the force per unit area produced by a column of air
Relative humidity = the ratio of water vapor air contains to the amount it could contain at a given temperature
High humidity makes it feel hotter than it really is
Temperature = varies with location and time
Atmospheric pressure decreases with altitude

7. Natural sources pollute: volcanoes
Release particulate matter, sulfur dioxide, and other gases
Can remain for months or years
Aerosols = fine droplets of sulfur dioxide, water, oxygen
Reflect sunlight back to space
Cool the atmosphere and surface
Volcanoes are one source of natural air pollution, as shown by the Mount Saint Helens eruption in 1980

8. Natural sources pollute: fires
Fires pollute the atmosphere with soot and gases
Over 60 million ha (150 million acres) of forests and grasslands burn per year
Human influence makes fires worse
Fuel buildup from fire suppression, development in fire-prone areas, “slash-and-burn” agriculture
Climate change will increase drought and fires
In 1997, unprecedented forest fires sickened 20 million and caused a plane to crash

9. We create outdoor air pollution
Air pollution comes from mobile or stationary sources
Point sources = specific spots where large quantities of pollutants are discharged (power plants and factories)
Non-point sources = more diffuse, consisting of many small sources (automobiles)
Primary pollutants = directly harmful and can react to form harmful substances (soot and carbon monoxide)
Secondary pollutants = form when primary pollutants interact or react with components of the atmosphere
Tropospheric ozone and sulfuric acid

10. The EPA sets standards
The EPA sets nationwide standards for emissions and concentrations of toxic pollutants
States monitor air quality
They develop, implement, and enforce regulations
They submit plans to the EPA for approval
The EPA takes over enforcement if plans are inadequate
Criteria pollutants = pollutants that pose especially great threats to human health
Carbon monoxide, sulfur dioxide, nitrogen dioxide, tropospheric ozone, particulate matter, lead

11. Criteria pollutants: CO and SO2
Carbon monoxide (CO) = colorless, odorless gas
Produced primarily by incomplete combustion of fuel
From vehicles and engines, industry, waste combustion, residential wood burning
Poses risk to humans and animals, even in small concentrations
Sulfur dioxide (SO2) = colorless gas with a strong odor
Coal emissions from electricity generation, industry
Can form acid precipitation

12. Criteria pollutants: NO2
Nitrogen dioxide (NO2) = a highly reactive, foul- smelling reddish brown gas
Nitrogen oxides (NOx) = formed when nitrogen and oxygen react at high temperatures in engines
Vehicles, industrial combustion, electrical utilities
Contribute to smog and acid precipitation

13. Criteria pollutants: tropospheric ozone
Tropospheric ozone (O3) = a colorless gas with a strong odor
Results from interactions of sunlight, heat, nitrogen oxides, and volatile carbon-containing chemicals
A secondary pollutant
A major component of smog
Participates in reactions that harm tissues and cause respiratory problems
The pollutant that most frequently exceeds EPA standards

14. Areas in the U.S. fail air quality standards
Many Americans live in areas with unhealthy levels of criteria pollutants

15. U.S. air pollution
In 2008, the U.S. emitted 123 million tons of the six monitored pollutants
The average U.S. driver emits 6 metric tons of CO2/yr as well as other pollutants!

16. We have reduced air pollution
Total emissions of the six monitored pollutants have declined 60% since the Clean Air Act of 1970
Despite increased population, energy consumption, miles traveled, and gross domestic product

17. We reduced emissions and improved the economy
Technology and federal policies
Cleaner-burning engines and catalytic converters
Permit-trading programs and clean coal technologies reduce SO2 emissions
Scrubbers = chemically convert or physically remove pollutants before they leave smokestacks
Phaseout of leaded gasoline

18. Industrializing nations suffer increasing pollution
Outdoor pollution is getting worse in developing nations
Factories and power plants pollute
Governments emphasize economic growth, not pollution control
People burn traditional fuels (wood and charcoal)
And more own cars
China has the world’s worst air pollution
Coal burning, more cars, power plants, factories
Causing over 300,000 premature deaths/year

19. Pollution in developing nations is high
More people own cars
Smog in Beijing surrounds an Olympic stadium

20. Smog: our most common air quality problem
Smog = an unhealthy mixture of air pollutants over urban areas
Sulfur in burned coal combines with oxygen to form sulfuric acid
Industrial (gray air) smog = industries burn coal or oil
Regulations in developed countries reduced smog
Coal-burning industrializing countries face health risks
Coal and lax pollution control
Smog in Donora killed 21 people and sickened 6,000

21. Photochemical (brown air) smog
Produced by a series of reactions
Formed in hot, sunny cities surrounded by mountains
Light-driven reactions of primary pollutants and atmospheric compounds
Morning traffic releases NO and VOCs
Irritates eyes, noses, and throats
Los Angeles smog kills 3,900/year and costs $28 billion/year
High levels of NO2 cause photochemical smog to form a brown haze over cities

22. Creation of industrial and photochemical smog
Industrial smog
Photochemical smog