Air Pollution
Chapter 18
The Asian Brown Cloud
Air Pollution in Shanghai, China, in 2004
The Atmosphere Consists of Several Layers
Atmosphere varies in• Density• Atmospheric pressure• Force, or mass, per unit area of a column of air
Air Movements in the Troposphere Play a Key Role in Earth’s Weather and Climate
Troposphere • 75–80% of the earth’s air mass• Surface to 17 kilometers up• Closet to the earth's surface• Chemical composition of air• 99% is nitrogen (78%) and oxygen (21%)
• Rising and falling air currents: weather and climate
• Involved in chemical cycling
The Stratosphere Is Our Global Sunscreen
Stratosphere• Similar composition to the troposphere, with 2
exceptions• Much less water
• O3, ozone layer, filters UV
• Location• 17 to 48 kilometers up
Natural Capital: The Earth’s Atmosphere Is a Dynamic System with Four Layers
Air Pollution Comes from Natural and Human Sources (1)
Air pollution
Natural sources• Dust blown by wind• Pollutants from wildfires and volcanoes• Volatile organics released by plants • Withdrawing groundwater
Air Pollution Comes from Natural and Human Sources (2)
Human sources: mostly in industrialized and/or urban areas• Stationary sources • Power and industrial plants
• Mobile sources• Motor vehicles
Case Study: Air Pollution in the Past: The Bad Old Days (1)
Discovery of fire
Middle Ages
Industrial Revolution
London, England• 1850s• 1952: yellow fog• Clean Air Act of 1956
Some Pollutants in the Atmosphere Combine to Form Other Pollutants
Primary pollutants• Are harmful chemicals emitted directly into the air from
natural processes and human activities
Secondary pollutants• When a primary pollutant reacts with normal air
components
Air quality improving in developed countries
Much more needs to be done in developing countries• Indoor pollution: big threat to the poor
Sources and Types of Air Pollutants
Indoor Air Pollution
What Are the Major Outdoor Air Pollutants? (1)
Carbon oxides • Carbon monoxide (CO)
• Carbon dioxide (CO2)
• Sources • Human health and environmental impact
What Are the Major Outdoor Air Pollutants? (2)
Nitrogen oxides (NO) and nitric acid (HNO3)
• Sources • Acid deposition• Photochemical smog• Human health and environmental impact
Sulfur dioxide (SO2) and sulfuric acid (H2SO4)
• Sources• Human health and environmental impact
What Are the Major Outdoor Air Pollutants? (3) Particulates
• Suspended particulate matter (SPM)• Consists of a variety of solid particles and liquid droplets small and
light enough to remain suspended in the air for long periods• Fine
• Most harmful• Less than 10 micrometers
• Ultrafine• Diameter less than 2.5 micrometers
• Sources• Dust, wild fires, sea salt• Coal-burning power and industrial plants, motor vehicles,
plowed fields, road construction, unpaved roads, tobacco smoke
• Human health and environmental impact• Mutations, reproductive problems, cancer• 60,000 to 70,000 premature deaths a year
What Are the Major Outdoor Air Pollutants? (4)
Ozone (O3)
• Sources• Human and environmental impact
• Coughing, breathing problems, aggravate lung and heart diseases
Volatile organic compounds (VOCs)• Hydrocarbons and terpenes• Sources
• Plants, wetlands, termites• Rice paddies, landfills, oil and natural gas wells, and cows
• Human and environmental impact• Leukemia, blood disorders
Chemical Reactions That Form Major Outdoor Air Pollutants
Statue Corroded by Acid Deposition and Other Forms of Air Pollution, RI, U.S.
Natural Capital: Lichen Species, Vulnerability to Air Pollutants
Burning Coal Produces Industrial Smog
Chemical composition of industrial smog • Sulfur dioxide, suspended droplets of sulfuric
acid, and solid particles Reduction of this smog in urban cities of the
United States • Large boilers with good pollution control• Tall smokestacks
China and smog• Human deaths (358,000 per year)
How Pollutants Are Formed from Burning Coal and Oil, Leading to Industrial Smog
Sunlight Plus Cars Equals Photochemical Smog Photochemical Smog• Chemical composition• Mixture of primary and secondary pollutants
formed under UV radiation
• Sources• Commuter vehicles releasing NO and VOCs
VOCs + NO2 + Heat + Sunlight yields
• Ground level O3 and other photochemical oxidants
• Aldehydes• Other secondary pollutants
Human health and environmental impact
A Model of How Pollutants That Make Up Photochemicals Are Formed
Global Outlook: Photochemical Smog in Santiago, Chile
Several Factors Can Decrease or Increase Outdoor Air Pollution (1)
Outdoor air pollution may be decreased by• Settling of particles due to gravity• Rain and snow• Salty sea spray from the ocean• Winds • Chemical reactions
Several Factors Can Decrease or Increase Outdoor Air Pollution (2)
Outdoor air pollution may be increased by• Urban buildings• Hills and mountains• High temperatures• Emissions of VOCs from certain trees and plants • Grasshopper effect• Occurs when volatile air pollutants are transported
by evaporation and winds from tropical and temperate areas through the atmosphere to the earth’s polar areas
• Temperature inversions
A Temperature Inversion
Acid Disposition Is a Serious Regional Air Pollution Problem
Acid deposition, acid rain• Formation• Excessive amounts of nitrogen oxides and sulfur
dioxide to the atmosphere• Local versus regional problems• Effects of prevailing winds• Buffers• Where is the worst acid deposition?
Natural Capital Degradation: Acid Deposition, Acid Rain
Current and Possible Future Acid Rain Problem Areas
Acid Deposition Has a Number of Harmful Effects (1)
Human respiratory disorders
Aquatic ecosystems affected
Release of toxic metals• Acid allows metals (lead and mercury) to leach
out into lakes used as water supplies
Acid Deposition Has a Number of Harmful Effects (2)
Leaching of soil nutrients• Allows essential nutrients to leach out and
harmful metals to take their place Loss of crops and trees
Damage to buildings, statues, and monuments
Natural Capital Degradation: Air Pollution Damage to Trees in North Carolina, U.S.
Indoor Air Pollution Is a Serious Problem (1)
Developing countries• Indoor burning• Poor suffer the greatest risk
Developed countries• Indoor air pollution is greater than outdoor air
pollution
Indoor Air Pollution Is a Serious Problem (2)
Why?• 11 of the common air pollutants higher inside
than outside• Greater in vehicles than outside• Health risks magnified: people spend 70–98% of
their time indoors
Indoor Air Pollution Is a Serious Problem (3)
Who are at greatest risk from indoor air pollution?• Children under 5 and the elderly• Sick• Pregnant women• People with respiratory disorders or heart
problems• Smokers• Factory workers
Indoor Air Pollution Is a Serious Problem (4)
Four most dangerous indoor air pollutants• Tobacco smoke• Formaldehyde• Radioactive radon-222 gas• Very small particles
Sources of these pollutants• Radon comes from radioactive decay of uranium,
phosphate, granite, and shale Human health risks
Indoor Air Pollution Is a Serious Problem (5)
Other possible indoor air pollutants• Pesticide residue• Pb particles• Living organisms and their excrements• E.g., Dust mites and cockroach droppings
• Airborne spores of molds and mildews
Sick-building syndrome• Studies have linked various air pollutants found in
buildings to a number of health effects
Some Important Indoor Air Pollutants
Science: Magnified View of a Household Dust Mite in a Dust Ball
Science: Sources and Paths of Entry for Indoor Radon-222 Gas
Your Body’s Natural Defenses against Air Pollution Can Be Overwhelmed
Respiratory system protection from air pollutants• Role of cilia, mucus, sneezing, and coughing
Effect of smoking and prolonged air pollution exposure• Chronic bronchitis• Emphysema
Air Pollution Is a Big Killer
3 Million deaths per year world-wide• Mostly in Asia• Main causes
EPA: proposed stricter emission standards for diesel-powered vehicles
Link between international trade and air pollution• Cargo ships and pollution
Premature Deaths from Air Pollution in the U.S.
Laws and Regulations Can Reduce Outdoor Air Pollution (1) United States• Clean Air Acts: 1970, 1977, and 1990• Enforced by states and major cities
EPA • National ambient air quality standards (NAAQs)
for 6 outdoor criteria pollutants• CO, NO, SO2, suspended particulate matter, ozone,
and lead• Primary standards were set to protect human health• Secondary standards were set to prevent
environmental and property damage
• National emission standards for 188 hazardous air pollutants (HAPs)• Toxic Release Inventory (TRI)
Laws and Regulations Can Reduce Outdoor Air Pollution (2)
Good news in U.S.• Decrease in emissions• Use of low-sulfur diesel fuel• Cuts pollution
Developing countries• More air pollution• Still a major problem
Case Study: U.S. Air Pollution Laws Can Be Improved (1)
Rely on cleanup more than prevention of pollution
Raise fuel-efficiency for cars, SUVs, and light trucks• Far behind European Union, Japan, and China
Better regulation of emissions of motorcycles and two-cycle gasoline engines
Regulate air pollution for oceangoing ships in American ports
Case Study: U.S. Air Pollution Laws Can Be Improved (2)
Why are airports exempt from many regulations?
Regulate greenhouse gas emissions
Ultrafine particles are not regulated
Urban O3 levels too high
Case Study: U.S. Air Pollution Can Be Improved (3)
What about indoor air pollution?
Better enforcement of the Clean Air Acts• Local governments are not getting the federal
funding required to enforce these regulations Is intense pressure needed from citizens to
make improvements?
We Can Use the Marketplace to Reduce Outdoor Air Pollution
Emission trading or cap-and-trade program• Mixed reactions to program
• SO2 emissions down significantly
• NO2 will be tried in the future
There Are Many Ways to Reduce Outdoor Air Pollution
1980 –2006
• SO2 emissions from U.S. electric power plants decreased by 66%
• NOx emissions by 41%
• Particulate emissions by 28%
Older plants not governed by the same regulations
New cars have better emissions
Reducing Indoor Air Pollution Should Be a Priority
Greater threat to human health than outdoor pollution
What can be done? • Prevention• Cleanup
We Need to Put More Emphasis on Pollution Prevention
Output approaches• What can we do about the air pollutants we
produce? New shift to preventing outdoor and indoor
pollution• Pressure from citizens
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