Air Pollution
Chapter 18
The Asian Brown Cloud
18-1 What Is the Nature of the
Atmosphere?
 Concept 18-1 The atmosphere is structured in
layers, including the troposphere, which
supports life, and the stratosphere, which
contains the protective ozone layer.
Air Movements in the Troposphere Play a
Key Role in Earth’s Weather and Climate
 Troposphere
75–80% of the earth’s air mass
Closet to the earth's surface
Chemical composition of air
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
120
Atmospheric pressure (millibars)
1,000
200
400
600
800
75
0
110
100
90
Temperature
Thermosphere
65
Mesopause
55
Mesosphere
70
60
Stratopause
45
35
50
Stratosphere
40
25
30
Tropopause
Ozone layer
20
10 Pressure
(Sea 0
level)
Altitude (miles)
Altitude (kilometers)
80
–80
Troposphere
80
40
–40
0
Temperature (˚C)
120
15
5
Pressure =
1,000 millibars
at ground level
Fig. 18-3, p. 470
18-2 What Are the Major Outdoor
Pollution Problems?
 Concept 18-2 Pollutants mix in the air to form
industrial smog, mostly the result of burning
coal, and photochemical smog, caused by motor
vehicle, industrial, and power plant emissions.
Air Pollution Comes from Natural and
Human Sources
 Natural sources
• Dust blown by wind
• Pollutants from wildfires and volcanoes
• Volatile organics released by plants
 Human sources: mostly in industrialized and/or
urban areas
• Stationary sources
• Mobile sources
Primary Pollutants
CO CO2
SO2 NO NO2
Most hydrocarbons
Most suspended particles
Secondary Pollutants
SO3
HNO3 H2SO4
H2O2 O3 PANs
Most NO3− and SO42− salts
Sources
Natural
Stationary
Mobile
Fig. 18-4, p. 472
Air Quality Trends
Click for EPA air quality trends
Chemical Reactions That Form Major
Outdoor Air Pollutants
Major Air Pollutants
• Carbon oxides:
– Carbon monoxide (CO) is a highly toxic gas that
forms during the incomplete combustion of carboncontaining 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.
Sources CO
Click for more source information
CO trends
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. NOx form PANs.
– NO2 reacts with water vapor in the air to form nitric
acid (HNO3) and nitrate salts (NO3-) which are
components of acid deposition.
Sources NOx
Click for more NOx source information
NOx Trends
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.
Sources SOx
Click for more SOx source information
SO2 Trends
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.
Sources Particulate Matter
Click for more PM source information
PM-10 trends
PM-2.5 trends
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.
Ozone Trends
Click for more ozone information
Ventura County Ozone Trends
Click for Ventura County Air Pollution Control District
South Coast Air Basin Ozone Trend
Click here of California Air Resource Board
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.
Source Volatile Organics
Click more VOC source information
SOLUTIONS
Lead Poisoning
Prevention
Control
Phase out leaded
gasoline worldwide
Replace lead pipes and
plumbing fixtures
containing lead solder
Phase out waste
incineration
Remove leaded paint and
lead dust from older
houses and apartments
Ban use of lead solder
Ban lead glazing for
ceramicware used to
serve food
Sharply reduce lead
emissions from
incinerators
Remove lead from TV sets
and computer monitors
before incineration or land
disposal
Ban candles with lead
cores
Test for lead in existing
ceramicware used to
serve food
Test blood for lead by
age 1
Test existing candles for
lead
Ban use of lead in
computer and TV
monitors
Wash fresh fruits and
vegetables
Fig. 18-7, p. 476
How Pollutants Are Formed from Burning
Coal and Oil, Leading to Industrial Smog
Fig 18-8
A Model of How Pollutants That Make Up
Photochemicals Are Formed
Fig 18-9
Animation: Formation of photochemical
smog
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 – wind transports from
tropics/temperate to polar areas
• Temperature inversions
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 18-11
18-3 What Is Acid Deposition and
Why Is It a Problem?
 Concept 18-3 Acid deposition is caused mainly
by coal-burning power plant and motor vehicle
emissions, and in some regions, threatens
human health, aquatic life and ecosystems,
forests, and human-built structures.
Natural Capital Degradation: Acid
Deposition, Acid Rain
Fig 18-12
ACID DEPOSITION
 pH measurements in relation to major coalburning and industrial plants.
Figure 19-7
Current and Possible Future Acid Rain
Problem Areas
Fig 18-13
Acid Deposition Has a Number of
Harmful Effects






Human respiratory disorders
Aquatic ecosystems affected
Release of toxic metals
Leaching of soil nutrients
Loss of crops and trees
Damage to buildings, statues, and monuments
Statue Corroded by Acid Deposition and
Other Forms of Air Pollution, RI, U.S.
Natural Capital Degradation: Air Pollution
Damage to Trees in North Carolina, U.S.
Fig18-14
SOLUTIONS
Acid Deposition
Prevention
Cleanup
Reduce coal use
Add lime to
neutralize acidified
lakes
Burn low-sulfur coal
Increase natural gas use
Increase use of
renewable energy
resources
Add phosphate
fertilizer to
neutralize acidified
lakes
Remove SO2
particulates and NOx
from smokestack gases
Remove NOx from motor
vehicular exhaust
Tax emissions of SO2
Reduce air pollution by
improving energy
efficiency
Fig. 18-15, p. 483
Active Figure: Effect of air pollution in
forests
18-4 What Are the Major Indoor Air
Pollution Problems?
 Concept 18-4 The most threatening indoor air
pollutants are smoke and soot from wood and
coal cooking fires (a hazard found mostly in
developing countries) and chemicals used in
building materials and products.
Indoor Air Pollution Is a Serious
Problem
 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
 Four most dangerous indoor air pollutants
•
•
•
•
Tobacco smoke
Formaldehyde
Radioactive radon-222 gas
Very small particles
Indoor Air Pollution Is a Serious
Problem
 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
Chloroform
Source: Chlorine-treated
water in hot showers
Possible threat: Cancer
Para-dichlorobenzene
Source: Air
fresheners,
mothball crystals
Threat: Cancer
Tetrachloroethylene
Source: Dry-cleaning fluid
fumes on clothes
Threat: Nerve disorders,
damage to liver and
kidneys, possible cancer
1,1,1-Trichloroethane
Source: Aerosol sprays
Threat: Dizziness,
irregular breathing
Nitrogen oxides
Benzo- α -pyrene
Source: Tobacco
smoke, woodstoves
Threat: Lung cancer
Particulates
Source: Pollen, pet
dander, dust mites,
cooking smoke
particles
Threat: Irritated lungs,
asthma attacks, itchy
eyes, runny nose, lung
disease
Source: Pipe insulation,
vinyl ceiling and floor
tiles Threat: Lung
disease, lung cancer
Source: Furniture stuffing,
paneling, particleboard,
foam insulation
Threat: Irritation of eyes,
throat, skin, and lungs;
nausea; dizziness
Styrene
Source: Carpets,
plastic products
Threat: Kidney and
liver damage
Source: Unvented gas stoves
and kerosene heaters,
woodstoves
Threat: Irritated lungs,
children's colds, headaches
Asbestos
Formaldehyde
Carbon monoxide
Source: Faulty
furnaces, unvented gas
stoves and kerosene
heaters, woodstoves
Threat: Headaches,
drowsiness, irregular
heartbeat, death
Tobacco smoke
Source: Cigarettes
Threat: Lung cancer,
respiratory ailments,
heart disease
Methylene chloride
Radon-222
Source: Radioactive soil
and rock surrounding
foundation, water supply
Threat: Lung cancer
Source: Paint strippers
and thinners Threat:
Nerve disorders, diabetes
Fig. 18-16, p. 484
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.
Case Study: Radioactive Radon
Sources and paths of entry
for indoor radon-222 gas.
• Radon-222, a
radioactive gas
found in some
soils and rocks,
can seep into
some houses
and increase the
risk of lung
cancer.
Figure 18-18
18-5 What Are the Health Effects of
Air Pollution?
 Concept 18-5 Air pollution can contribute to
asthma, chronic bronchitis, emphysema, lung
cancer, heart attack, and stroke.
Premature Deaths from Air Pollution in
the U.S.
18-6 How Should We Deal with Air
Pollution?
 Concept 18-6 Legal, economic, and
technological tools can help to clean up air
pollution, but much greater emphasis should be
focused on preventing air pollution.
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 fuelefficiency 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.
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.
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
EPA cap and trade for acid rain report
California ARB on greenhouse gas cap and trade
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.
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
Wet Scrubber
 Can remove 98% of
SO2 and particulate
matter.
 Not very effective in
removing hazardous
fine and ultrafine
particles.
Integrated Gasification Combined-Cycle (IGCC)
systems
Gasifier uses heat and pressure to break apart
“feedstock” to produce “syngas” (hydrogen and CO)
Click for DOE information on gasification
SOLUTIONS
Stationary Source Air Pollution
Prevention
Burn low-sulfur coal
Remove sulfur from
coal
Convert coal to a
liquid or gaseous
fuel
Shift to less polluting
energy sources
Dispersion or
Cleanup
Disperse emissions
above thermal
inversion layer with tall
smokestacks
Remove pollutants
after combustion
Tax each unit of
pollution produced
Fig. 18-22, p. 491
SOLUTIONS
Motor Vehicle Air Pollution
Prevention
Use mass transit
Walk or bike
Cleanup
Require
emission
control devices
Use less polluting
fuels
Improve fuel
efficiency
Get older, polluting
cars off the road
Give large tax writeoffs or rebates for
buying low-polluting,
energy efficient
vehicles
Inspect car
exhaust
systems twice
a year
Set strict
emission
standards
Fig. 18-23, p. 491
SOLUTIONS
Prevention
Indoor Air Pollution
Cleanup or Dilution
Clean ceiling tiles and line
AC ducts to prevent
release of mineral fibers
Ban smoking or limit it to
well-ventilated areas
Set stricter formaldehyde
emissions standards for
carpet, furniture, and
building materials
Prevent radon
infiltration
Use office machines in
well-ventilated areas
Use less polluting
substitutes for harmful
cleaning agents, paints,
and other products
Use adjustable fresh air
vents for work spaces
Increase intake of outside
air
Change air more
frequently
Circulate a building’s air
through rooftop
greenhouses
Use efficient venting
systems for woodburning stoves
Use exhaust hoods for
stoves and appliances
burning natural gas
Fig. 18-24, p. 492
What Can You Do? Indoor Pollution:
Ways to Reduce Your Exposure
SOLUTIONS
Air Pollution
Outdoor
Indoor
Improve energy efficiency
to reduce fossil fuel use
Reduce poverty
Rely more on lowerpolluting natural gas
Distribute cheap and
efficient cookstoves or
solar cookers to poor
families in developing
countries
Rely more on
renewable energy
(especially solar cells,
wind, and solarproduced hydrogen)
Transfer energy
efficiency, renewable
energy, and pollution
prevention technologies
to developing countries
Reduce or ban
indoor smoking
Develop simple and
cheap tests for indoor
pollutants such as
particulates, radon, and
formaldehyde
Fig. 18-26, p. 493