Lecture Outlines
Chapter 17
The Science behind the Stories
4th Edition
© 2011 Pearson Education, Inc.
This lecture will help you understand:
• The Earth’s atmosphere
• Weather, climate, and
atmospheric conditions
• Outdoor pollution and
• Stratospheric ozone
• Acidic deposition and
• Indoor air pollution and
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Central Case: L.A. and its sister cities
struggle for a breath of clean air
• Vehicles caused smog in Los
Angeles from 1970s to 1990s
• Policies and technologies
improved its air qualities
- But its “sister cities” are not
as clean
• 3,600/month die in Tehran from
air pollution
- Old cars use cheap gas
- Topography, immigration,
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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
• Minute concentrations of permanent (remain at stable
concentrations) gases
- Variable gases = varying concentrations across time
and place
• Human activity is changing the amount of some gases
- CO2, methane (CH4), ozone (O3)
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The atmosphere’s composition
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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
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The two highest levels of the atmosphere
• Mesosphere = 50–80 km (31–56 mi) above sea level
- Extremely low air pressure
- Temperatures decrease with altitude
• Thermosphere = atmosphere’s top layer
- Extends upward to 500 m (300 mi)
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The atmosphere’s four layers
• Atmospheric layers
have different
- Temperatures
- Densities
- Composition
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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
- High humidity makes it
feel hotter than it really is
• Temperature = varies with
location and time
Atmospheric pressure
decreases with altitude
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Solar energy heats the atmosphere
• Energy from the sun:
- Heats and moves air
- Creates seasons
- Influences weather
and climate
• Solar radiation is highest
near the equator
• The spatial relationship between the Earth and sun
determines how much solar energy strikes the Earth
• Microclimate = a localized pattern of weather conditions
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Solar energy creates seasons
• Because the Earth is tilted, each hemisphere tilts
toward the sun for half the year
- Results in a change of seasons
Equatorial regions are
unaffected by this tilt, so
days average 12 hours
throughout the year
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Solar energy causes air to circulate
• Air near Earth’s surface is
warm and moist
• Convective circulation =
less dense, warmer air rises
- Creating vertical currents
- Rising air expands and
- Cool air descends and
becomes denser
- Replacing rising warm
Convection influences
weather and climate
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The atmosphere drives weather and climate
• Weather and climate involve the physical properties of
the troposphere
- Temperature, pressure, humidity, cloudiness, wind
• Weather = specifies atmospheric conditions over short
time periods and within small geographic areas
• Climate = patterns of atmospheric conditions across
large geographic regions over long periods of time
• Mark Twain said, “Climate is what we expect; weather
is what we get”
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Air masses produce weather
• Front = the boundary between
air masses that differ in
temperature, moisture, and
• Warm front = boundary
where warm, moist air
replaces colder, drier air
• Cold front = where colder,
drier air displaces warmer,
moister air
Warm fronts produce
light rain
Cold fronts produce
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Air masses have different pressures
• High-pressure system = air that descends because it is
- It spreads outward as it nears the ground
- Brings fair weather
• Low-pressure system = warm air rises and draws air
inward toward the center of low pressure
- Rising air expands and cools
- It brings clouds and precipitation
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Thermal (temperature) inversion
• Air temperature decreases as altitude increases
- Warm air rises, causing vertical mixing
• Thermal inversion = a layer of
cool air occurs beneath warm
• Inversion layer = the band of
air where temperature rises with
- Denser, cooler air at the
bottom of the layer resists
• Inversions trap pollutants in
cities surrounded by mountains
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Circulation systems produce climate patterns
• Convective currents contribute to climatic patterns
• Hadley cells = convective cells near the equator
- Surface air warms, rises, and expands
- Causing heavy rainfall near the equator
- Giving rise to tropical rainforests
• Currents heading north and south are dry
- Giving rise to deserts at 30 degrees
• Ferrel cells and polar cells = lift air and create
precipitation at 60 degrees latitude north and south
- Conditions at the poles are dry
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Global wind patterns
• Atmospheric cells interact with Earth’s rotation to
produce global wind patterns
- As Earth rotates, equatorial regions spin faster
• Coriolis effect = the apparent north-south deflection of
air currents of the convective cells
- Results in curving global wind patterns called the
doldrums, trade winds, and westerlies
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Climate patterns and moisture distribution
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Global wind patterns
• Doldrums = a region near the equator with few winds
• Trade winds = between the equator and 30 degrees
- Blow from east to west
- Weaken periodically, leading to El Niño conditions
• Westerlies = from 30 to 60 degrees latitude
- Blow from west to east
• People used these winds to sail across the ocean
• Wind and convective circulation in ocean water maintain
ocean currents
- And can create violent storms
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Storms pose hazards
• Atmospheric conditions can produce dangerous storms
• Hurricanes = form when winds rush into areas of low
- Warm, moist air over the topical oceans rises
• Typhoons (cyclones) = winds turn counterclockwise in
the Northern Hemisphere
- Drawing up huge amounts of water vapor
- Which falls as heavy rains
• Tornadoes = form when warm air meets cold air
- Quickly rising warm air forms a powerful convective
current (spinning funnel)
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Hurricanes and tornadoes
• Understanding how the atmosphere works helps us to:
- Predict violent storms and protect people
- Comprehend how pollution affects climate,
ecosystems, and human health
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Outdoor air pollution
• Air pollutants = gases and particulate material added to
the atmosphere
- Can affect climate or harm people or other organisms
• Air pollution = the release of pollutants
• Outdoor (ambient) air pollution = pollution outside
- Has recently decreased due to government policy and
improved technologies in developed countries
- Developing countries and urban areas still have
significant problems
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Natural sources pollute: volcanoes
• Release particulate matter,
sulfur dioxide, and other
- Can remain for months or
• Aerosols = fine droplets of
sulfur dioxide, water, oxygen
- Reflect sunlight back to
- Cool the atmosphere and
Volcanoes are one source
of natural air pollution, as
shown by the Mount Saint
Helens eruption in 1980
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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
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Natural sources pollute: dust storms
• Wind over arid land sends
huge amounts of dust aloft
- Even across oceans
• Businesses, schools, and
governments close
• Unsustainable farming and
grazing promote:
- Erosion
- Desertification
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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
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Pollutants exert local and global effects
• Residence time = the time a pollutant stays in the
• Pollutants with brief residence times exert localized
impacts over short time periods
- Particulate matter, automobile exhaust
• Pollutants with long
residence times exert
regional or global impacts
- Pollutants causing
climate change or
- ozone depletion
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Legislation addresses pollution
• Air Pollution Control Act (1963) funded research and
encouraged emissions standards
• The Clean Air Act of 1970
- Set standards for air quality, limits on emissions
- Provided funds for pollution-control research
- Allowed citizens to sue parties violating the standards
• The Clean Air Act of 1990 strengthened regulations for
auto emissions, toxic air pollutants, acidic deposition,
stratospheric ozone depletion
- Introduced emissions trading for sulfur dioxide
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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
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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
• Sulfur dioxide (SO2) = colorless gas with a strong odor
- Coal emissions from electricity generation, industry
- Can form acid precipitation
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Criteria pollutants: NO2
• Nitrogen dioxide (NO2) = a highly reactive, foulsmelling 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
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Criteria pollutants: tropospheric ozone
• Tropospheric ozone (O3) = a colorless gas with a strong
- 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
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Criteria pollutants: particulate matter and
• Particulate matter = suspended solid or liquid particles
- Primary pollutants: dust and soot
- Secondary pollutants: sulfates and nitrates
- Damages respiratory tissue when inhaled
- From dust and combustion processes
• Lead = in gasoline and industrial metal smelting
- Bioaccumulates and damages the nervous system
- Banned in gasoline in developed, but not in
developing, countries
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Areas in the U.S. fail air quality standards
Many Americans live in areas with
unhealthy levels of criteria pollutants
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Agencies monitor emissions
• State and local agencies monitor, calculate, and report to
the EPA the emissions of these pollutants:
- Carbon monoxide, sulfur dioxide, particulate matter,
lead, and all nitrogen oxides
• Tropospheric ozone has no emissions to monitor
- It is a secondary pollutant
• Agencies monitor volatile organic compounds (VOCs)
= carbon-containing chemicals
- Used and emitted by engines and industrial processes
- VOCs can react to produce ozone
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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!
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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
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We reduced emissions and improved the
• Technology and federal
• 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
• Phaseout of leaded gasoline
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Toxic substances pose health risks
• Toxic air pollutants = substances that cause:
- Cancer, reproductive defects
- Neurological, developmental, immune system, or
respiratory problems
• The EPA regulates 188 toxic air pollutants from metal
smelting, sewage treatment, industry, etc.
• Include heavy metals, VOCs, diesel, urban hazards
• Clean Air Act regulations helped reduce emissions by
more than 35% since 1990
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U.S. health risks vary geographically
Nationwide cancer risks
Non-cancerous respiratory
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Industrializing nations suffer increasing
• 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
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Pollution in developing nations is high
More people own cars
Smog in Beijing surrounds
an Olympic stadium
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Air pollution in China
• The government is trying to decrease pollution
- Shutting down heavily polluting factories and mines
- Phasing out some subsidies for polluting industries
- Installing pollution controls in factories
- Encouraging renewable and nuclear energy
- Mandating cleaner burning fuels
• Air is improving in Beijing but not in other places
• Asian (Atmospheric) Brown Cloud = a 2-mile-thick layer
of pollution over southern Asia
- Decreased plant productivity, increased flooding, etc.
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Air quality is a rural issue, too
• Airborne pesticides from farms
• Industrial pollutants from cities, factories, and power
• Feedlots, where cattle, hogs, or chickens are raised in
dense concentrations
- Voluminous amounts of dust, methane, hydrogen
sulfide, and ammonia
- Also create objectionable odors
- People living or working nearby have high rates of
respiratory illness
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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
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Smog in Donora
killed 21 people
and sickened 6,000
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
High levels of NO2 cause
photochemical smog to
form a brown haze over
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Creation of industrial and photochemical
Industrial smog
Photochemical smog
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We can reduce smog
• Regulations require new cars to have catalytic converters
• Require cleaner industrial facilities
- Close those that can’t improve
• Financial incentives to replace aging vehicles
- Restricting driving
• Vehicle inspection programs (“smog checks”)
• Reduce sulfur in diesel; remove lead in gasoline
• Electronic pollution indicator boards raise awareness
• But increased population and cars can wipe out advances
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Synthetic chemicals deplete stratospheric
• Ozone layer = ozone in the lower stratosphere
- Blocks incoming ultraviolet (UV) radiation
- Protecting life from radiation’s damaging effects
• Ozone-depleting substances = human-made chemicals
that destroy ozone by splitting its molecules apart
• Halocarbons = human-made compounds made from
hydrocarbons with added chlorine, bromine, or fluorine
• Chlorofluorocarbons (CFCs) = a halocarbon used as
refrigerants, in fire extinguishers, in aerosol cans, etc.
- Releases chlorine atoms that split ozone
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CFCs destroy ozone
• CFCs are inert (don’t react)
• CFCs remain in the
stratosphere for a century
• UV radiation breaks CFCs
into chlorine and carbon
• The chlorine atom splits
• Ozone hole = decreased
ozone levels over Antarctica
One chlorine atom can
destroy 100,000 ozone
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The Antarctic ozone hole
• High-altitude polar stratospheric clouds form during the
dark, frigid winter
• Nitric acid in clouds splits chlorine off of CFCs
- A polar vortex (swirling winds) traps chlorine
- UV radiation in September (spring) sunshine dissipates
the clouds and releases the
- The chlorine destroys the
- December’s warmer air
shuts down the polar vortex
- Ozone-poor air diffuses,
while ozone-rich air enters
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The Montreal Protocol
• Montreal Protocol = 196 nations agreed to cut CFC
production in half by 1998
• Follow-up agreements deepened cuts, advanced
timetables, and addressed other ozone-depleting
- Industry shifted to safer, inexpensive, and efficient
• Challenges still face us
- CFCs will remain in the stratosphere for a long time
- Nations can ask for exemptions to the ban
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The Montreal Protocol is a success
• It is considered our biggest environmental success story
• Research developed rapidly, along with technology
• Policymakers included industry in helping solve the
• Implementation of the plan allowed an adaptive
management strategy
- Strategies responded to new scientific data,
technological advances, and economic figures
• The Montreal Protocol can serve as a model for
international environmental cooperation
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Protecting the ozone layer
International agreements
reduced ozone-depleting
The hole in the ozone has
stopped growing
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Acid deposition
• Acid deposition is another transboundary issue
• Acidic deposition = the deposition of acid, or acidforming pollutants from the atmosphere onto Earth’s
• Acid rain = precipitation containing acid
- Rain, snow, sleet, hail
• Atmospheric deposition = the wet or dry deposition on
land of pollutants (mercury, nitrates, organochlorines)
- From automobiles, electric utilities, industrial facilities
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Burning fossil fuels produces acid rain
• Burning fossil fuels releases sulfur dioxide and nitrogen
- These compounds react with water, oxygen, and
oxidants to form sulfuric and nitric acids
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Impacts of acid deposition
• Nutrients are leached from topsoil
• Soil chemistry is changed
• Metal ions (aluminum, zinc, etc.) are converted into
soluble forms that pollute water
• Affects surface water and kills fish
• Damages agricultural crops
• Erodes stone buildings, corrodes cars, erases writing on
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pH of precipitation in the U.S.
• The acid-neutralizing capacity of soil, rock, or water
impacts the severity of acid rain’s effects
Many regions of acidification are downwind
of major sources of pollution
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We have begun to address acid deposition
• Reducing acid deposition involves reducing the pollution
that contributes to it
• The Clear Air Act of 1990 established an emissions
trading program for sulfur dioxide
- Benefits outweighed costs 40:1
• New technologies such as scrubbers have helped
• Acid deposition is worse in the developing world
- Especially in China, which burns coal in factories
lacking pollution control equipment
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Indoor air pollution
• Indoor air pollution = in workplaces, schools, and homes
- Health effects are greater than from outdoor pollution
• The average U.S. citizen spends 90% of the time indoors
- Exposed to synthetic materials that have not been
comprehensively tested
• Being environmentally prudent can make it worse
- To reduce heat loss and improve efficiency, ventilation
systems were sealed off
- Windows do not open, trapping pollutants inside
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Indoor air pollution in the developing world
• Stems from burning wood,
charcoal, dung, crop
wastes with little to no
• Fuel burning pollution
causes 1.6 million
- Soot and carbon monoxide
- Pneumonia, bronchitis, lung cancer, allergies,
cataracts, asthma, heart disease, etc.
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Tobacco smoke and radon
• The most dangerous indoor pollutants in developed
• Secondhand smoke from cigarettes is very dangerous
- Contains over 4,000 chemical compounds
- Causes eye, nose, and throat irritation
- Smoking has declined in developed nations
• Radon causes 21,000 deaths a year in the U.S.
- A radioactive gas resulting from natural decay of rock,
soil, or water that can seep into buildings
- New homes are being built that are radon resistant
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Radon risk across the U.S.
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VOCs pollute indoor air
• The most diverse group of indoor air pollutants
- Released by everything from plastics and oils to
perfumes and paints
- Most VOCs are released in very small amounts
• Unclear health implications due to low concentrations
• Formaldehyde leaking from pressed wood and insulation
irritates mucous membranes and induces skin allergies
• Pesticides seep through floors and walls
- Are brought in on shoe soles
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Sources of indoor air pollution
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Living organisms can pollute indoors
• Dust mites and animal dander worsen asthma
• Fungi, mold, mildew, airborne bacteria cause allergies,
asthma, other respiratory ailments, and diseases
• Building-related illness = a sickness produced by indoor
• Sick building syndrome = a sickness produced by
indoor pollution with general and nonspecific symptoms
- Reduced by using low-toxicity building materials and
good ventilation
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We can reduce indoor air pollution
• In developed countries:
- Use low-toxicity materials, limit use of plastics and
treated wood, monitor air quality, keep rooms clean
- Provide adequate ventilation
- Limit exposure to known toxicants
- Test homes and offices and use CO detectors
• In developing countries:
- Dry wood before burning
- Cook outside
- Use less-polluting fuels (natural gas)
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• Indoor air pollution is a potentially serious health threat
- We can significantly minimize risks
• Outdoor air pollution has been addressed by government
legislation and regulation in developed countries
• Reduction in outdoor air pollution represents some of the
greatest strides in environmental protection
- There is still room for improvement, especially in
developing countries
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The major component of Earth’s atmosphere is:
Nitrogen gas
Oxygen gas
Argon gas
Water vapor
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Ozone in the _________ is a pollutant, but in the ______
is vital for life.
Stratosphere, troposphere
Troposphere, stratosphere
Troposphere, tropopause
Stratosphere, thermosphere
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With convective circulation:
Less dense, cooler air rises
Denser, warmer air rises
Less dense, warmer air rises
Denser, cooler air rises
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If you were on a sailing ship going from the United
States to Europe, you would want to be in the area of
the _____.
Trade winds
Polar cell
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The Clean Air Act does all of the following, EXCEPT:
Forbid emissions trading
Provide funds for pollution-control research
Allow citizens to sue violators
Set standards for air quality
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Which criteria pollutant is highly reactive, foul smelling,
and has a reddish brown color?
Sulfur dioxide
Nitrogen dioxide
Tropospheric ozone
Carbon monoxide
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Why is the Montreal Protocol considered our greatest
environmental success story?
It has stopped global warming.
It decreased criteria pollutants.
It successfully stopped ozone depletion.
It slowed acid deposition.
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QUESTION: Viewpoints
Think of a major city near you. Do you think drivers
should have to pay to drive downtown?
a) Yes, if mass transit is available.
b) Yes, but only charge people who do not live in
the downtown area.
c) No, it’s my right to drive wherever I want to.
d) I don’t care, because I don’t own a car.
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QUESTION: Viewpoints
Should the government be able to force industries to put
pollution-control devices on their factories?
Yes, I don’t want to be exposed to pollution.
Yes, only if the people in the area agree.
No, let the factory owner decide.
No, in these tough economic times, we need to leave
businesses alone.
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QUESTION: Interpreting Graphs and Data
What does this graph show about the stratosphere?
a) It contains the most
b) It is a very thin layer.
c) Temperature decreases
with increasing altitude.
d) Temperature is not
affected with increasing
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QUESTION: Interpreting Graphs and Data
Which conclusion can you draw from this graph?
a) Even though population and
consumption increased,
emissions have decreased.
b) Emissions have decreased
but population has increased.
c) People have increased
emissions, but only slightly.
d) The United States no longer
needs the Clean Air Act.
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Atmospheric Science and Air Pollution