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17
Atmospheric Science and
Air Pollution
Chapter Objectives
This chapter will help students:
Describe the composition, structure, and function of Earth’s atmosphere
Outline the scope of outdoor air pollution and assess potential solutions
Explain stratospheric ozone depletion and identify steps taken to address it
Define acidic deposition and illustrate its consequences
Characterize the scope of indoor air pollution and assess potential solutions
Lecture Outline
I. Central Case: Charging toward Cleaner Air in London
A. Thick and blinding smog first settled over the city on December 5,
1952, when many residents stoked their coal stoves because of
unusually cold temperatures.
B. A wind finally relieved Londoners of the smog on Tuesday, December
9, but by that time thousands of people had died from lung ailments.
C. Many similar events have taken place in Pennsylvania, New York,
Mexico, and Malaysia.
D. We have improved, however, as declines in air pollution represent
some of the biggest successes of environmental policy.
E. Much remains to be done because there are hundreds of people who
die prematurely each year due to vehicle emissions.
II. The Atmosphere
A. The atmosphere is a thin layer of gases that surrounds Earth.
B. The atmosphere consists of several layers.
1. The bottommost layer is the troposphere, where temperature
decreases with altitude.
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C.
D.
E.
F.
2. The stratosphere extends from 11 km to 50 km above sea level,
with its temperature rising gradually with altitude.
3. A portion of the stratosphere between 17 and 30 km above sea
level contains most of the atmosphere’s ozone and is called the
ozone layer; this layer greatly reduces the amount of UV
radiation that reaches Earth’s surface. The protection of the ozone
layer is vital for life on Earth.
4. Above the stratosphere lies the mesosphere, which extends from
50 to 90 km above sea level.
5. From the outer mesosphere, the thermosphere extends upward to
an altitude of 500 km, where solar rays produce temperatures over
1,700 degrees Celsius.
Atmospheric properties include temperature, pressure, and humidity.
1. Atmospheric pressure measures the weight per unit area
produced by a column of air and decreases with altitude.
2. Relative humidity is the amount of water vapor a given volume
of air holds relative to the maximum amount it could contain for a
given temperature.
3. The temperature of air varies with location and time, and these
temperature differences affect air circulation.
Solar energy heats the atmosphere, helps create seasons, and causes
air to circulate.
1. Energy from the sun plays a major role in our atmosphere by
driving most of its air movements.
2. The spatial relationship between Earth and the sun determines the
amount of solar radiation that strikes each point of Earth’s
surface.
3. Because Earth is tilted on its axis by about 23.5 degrees, the
Northern and Southern Hemispheres each face the sun for onehalf of the year.
4. Land and surface waters absorb solar energy, reradiating some
heat and causing some water to evaporate.
5. The difference in air temperatures at different altitudes sets into
motion convective circulation, as warm air rises, cools, and
expands, and then descends past other warm air that is rising.
The atmosphere drives weather and climate.
1. Weather consists of the local physical properties over short time
periods in relatively small geographic areas.
2. Climate describes the pattern of atmospheric conditions found
across a relatively large geographic region over a long period.
Weather is produced by interacting air masses.
1. The boundary between two air masses that differ in temperature
and density is called a front.
a. A mass of warmer, moister air replacing a mass of colder,
drier air is a warm front.
b. A mass of colder, drier air displacing a warmer, moister air
mass is a cold front.
2. Opposing air masses may also differ in atmospheric pressure.
a. Air moving outward away from a center of high pressure as it
descends is a high-pressure system.
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b. Air moving toward a low atmosphere pressure at the center of
a rising system is a low-pressure system.
3. One type of weather event has implications for environmental
health.
a. If a layer of cool air occurs beneath a layer of warmer air, this
is known as a temperature inversion, or thermal inversion.
b. The band of air in which temperature rises with altitude is
called an inversion layer.
G. Global climate patterns result from large-scale circulation systems.
1. Sunlight near the equator produces pairs of convection cells called
Hadley cells.
2. Two pairs of similar but less intense convective cells, Ferrel cells
and polar cells, lift air and create precipitation around 60 degrees
latitude north and south and cause air to descend at around 30
degrees latitude and in the polar regions.
3. These three pairs of cells account for the latitudinal distribution of
moisture across Earth’s surface.
4. As Earth rotates on its axis, north–south air currents of convective
cells appear to be deflected from a straight path; this is called the
Coriolis effect.
III. Outdoor Air Pollution
A. Air pollutants are gases and particulate material added to the
atmosphere that can affect climate and/or harm organisms, including
ourselves.
B. Natural sources can pollute.
1. Winds sweeping over arid terrain can send huge amounts of dust
aloft.
2. Volcanic eruptions release large quantities of particulate matter,
as well as sulfur dioxide and other gases, into the troposphere and
can even cause global cooling by a fraction of a degree.
3. Sulfur dioxide reacts with water and oxygen and condenses into
fine particles called aerosols.
4. The burning of vegetation pollutes the atmosphere with smoke
and soot.
C. We create various types of outdoor air pollution.
1. Since the onset of industrialization, outdoor air pollution from
human activity can originate from stationary or mobile sources.
2. Once in the air, a pollutant may do harm directly or may induce
chemical reactions that produce harmful compounds.
a. Primary pollutants, such as soot and carbon monoxide, are
pollutants emitted into the troposphere in a form that can be
directly harmful or that can react to form harmful substances.
b. Secondary pollutants are harmful substances produced when
primary pollutants interact or react with constituents of the
atmosphere.
D. Clean Air Acts legislation has addressed pollution in the United
States.
1. Congress has passed a number of laws dealing with pollution.
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E.
F.
G.
H.
I.
J.
a. The Clean Air Act of 1970 set strict standards for air quality,
imposed limits on emissions, provided funds for research, and
allowed citizens to sue parties violating the standards.
b. The Clean Air Act of 1990 sought to strengthen regulations
pertaining to air quality standards, auto emissions, toxic air
pollution, acidic deposition, and ozone depletion, while
introducing market-based incentives.
c. In 1995, businesses and industry were allocated permits to
release sulfur dioxide that they could buy, sell, or trade among
one another. This market-based incentive program reduced
sulfur dioxide levels.
The EPA sets standards for “criteria pollutants.”
1. The EPA gives special attention to several pollutants judged to
pose especially great threats to human health and welfare.
2. For six criteria pollutants, the EPA has established maximum
allowable concentrations.
a. Carbon monoxide is a colorless, odorless gas produced
primarily by the incomplete combustion of fuels.
b. Sulfur dioxide is a colorless gas with a pungent odor that is
released when coal is burned and contributes to acid rain.
c. Nitrogen dioxide is a highly reactive, foul-smelling reddish
gas that contributes to smog and acid rain.
d. Tropospheric ozone results from the interaction of sunlight,
heat, nitrogen oxides, and volatile organic compounds.
e. Particulate matter is any solid or liquid particle small
enough to be carried aloft; it may cause damage to respiratory
tissues when inhaled.
f. Lead is a metal that enters the atmosphere as a particulate
pollutant released by industrial processes and fuel
combustion.
Agencies monitor pollutants that affect air quality.
1. Volatile organic compounds (VOCs) are a large group of
potentially harmful organic chemicals emitted by vehicle engines
and used in solvents and industrial processes such as dry cleaning,
household chemicals, and manufacturing.
2. Human activity accounts for about half of U.S. VOC emissions,
but many tons of VOCs are released from natural sources (plants
and animals) each year.
Air pollution has decreased markedly since 1970.
1. Reduction in air pollutants have occurred despite population
increases.
2. New technologies such as catalytic converters, electrostatic
precipitators, and scrubbers helped to reduce pollutants.
Toxic substances also pollute.
1. Other chemicals known to cause serious health or environmental
problems are classified as toxic air pollutants.
Recent policy proposals have been contentious.
1. The George Bush administration has vigorously advocated
proposals that would overturn key provisions of the Clean Air
Act.
Burning fossil fuels produces industrial smog.
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K. Photochemical smog is produced by a complex series of atmospheric
reactions.
L. Air quality is a rural issue too.
1. Pesticide drift contributes to poor air quality in rural areas.
2. Huge confined animal feeding operations with their associated
manure add methane, sulfur dioxide, hydrogen sulfide, and
ammonia to rural areas. These pollutants have harmful effects on
humans and animals.
M. Industrializing nations are suffering increasing air pollution.
1. Chinese cities suffer the worst air pollution as they industrialize
rapidly.
N. Synthetic chemicals deplete stratospheric ozone.
1. Ozone molecules are considered a pollutant at low altitudes, but at
altitudes of 25 km (15 mi) they are highly effective at absorbing
incoming ultraviolet radiation from the sun, thus protecting life on
Earth’s surface.
2. Starting in the 1960s, atmospheric scientists began wondering
why their measurements of ozone were lower than theoretical
models predicted.
3. In 1974, Sherwood Rowland and Mario Molina broke the news
that chlorofluorocarbons (CFCs) depleted stratospheric ozone
by splitting ozone molecules and creating O2 molecules from
them.
4. In 1985, scientists from the British Antarctic Survey announced
that stratospheric ozone levels over Antarctica had declined 40 to
60% in the previous decade, leaving behind a thinned ozone
concentration that was soon dubbed the “ozone hole.”
O. The Montreal Protocol addressed ozone depletion.
1. The world community came together in 1987 to design the
Montreal Protocol, which has been signed by 180 nations.
2. The production and use of ozone-depleting compounds has fallen
95% since the late 1980s.
3. Environmental scientists have attributed the success of the
Montreal Protocol to two factors.
a. Policymakers engaged industry in helping to solve the
problem.
b. The process after 1987 successfully followed an adaptive
management approach, which allows for altering strategies
midstream in response to new scientific data, technological
advances, or economic figures.
4. Due to the lag time between policy implementation and desired
effect, scientists often advocate a proactive approach, following
the precautionary principle.
P. Acidic deposition represents another transboundary pollution
problem.
1. Acidic deposition refers to the deposition of acidic or acidforming pollutants from the atmosphere onto Earth’s surface.
2. Acidic deposition is one type of atmospheric deposition, which
is the wet or dry deposition on land of a wide variety of pollutants.
3. Because the pollutants leading to acid rain may travel long
distances, their effects can be felt far from their point sources.
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4. Acid deposition can also mobilize toxic metal ions from the soil
and convert them from insoluble to soluble molecules where they
hinder nutrient uptake by plants.
5. Acid water running off the land is toxic to many aquatic life forms
and has led to the death of ecosystems.
Q. Acid deposition has not been reduced as much as scientists had hoped.
IV. Indoor Air Pollution
A. Indoor air pollution in the developing world arises from fuelwood
burning.
B. Tobacco and radon gas are the two most dangerous indoor air
pollutants in the developed world.
1. Secondhand smoke has been found to cause many of the same
problems as directly inhaled cigarette smoke.
2. After cigarette smoke, radon gas is the second-leading cause of
lung cancer for Americans.
C. Many VOCs pollute indoor air.
1. Products that emit VOCs surround us; VOCs are emitted in very
small amounts.
2. The implications for human health of chronic exposure to VOCs
are far from clear. There are so many, at such low levels, that it is
difficult to study their effects.
D. Living organisms can pollute indoor air.
1. Dust mites, animal dander, fungi, mold, mildew, and bacteria can
all cause health problems.
2. These organisms may be the most widespread source of indoor air
pollution in the developed world.
3. Microbes that induce allergic responses are thought to be one
frequent cause of building-related illness.
E. We can reduce indoor air pollution.
1. The 1970 U.S. Clean Air Act did not even mention indoor air
pollution; rather, indoor spaces were assumed to be safe havens
from outdoor pollution.
2. Today we know far less about indoor air pollution than we do
about outdoor air pollution.
V. Conclusion
A. Indoor air pollution is a potentially serious health threat but one that
we can do a great deal to minimize for ourselves and our families.
B. Outdoor air pollution has been addressed more effectively by
government legislation and regulation.
C. Much room for improvement remains, particularly in reducing acidic
deposition and photochemical smog.
Key Terms
acidic deposition
aerosols
air pollutant
air pollution
atmospheric deposition
atmospheric pressure
carbon monoxide
chlorofluorocarbons (CFCs)
Clean Air Act of 1970
Clean Air Act of 1990
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climate
cold front
convective circulation
Coriolis effect
criteria pollutant
Ferrel cell
Hadley cell
high-pressure system
industrial smog
inversion layer
lead
low-pressure system
Montreal Protocol
nitrogen dioxide
ozone layer
particulate matter
photochemical smog
polar cell
primary pollutant
radon
relative humidity
secondary pollutant
stratosphere
sulfur dioxide
temperature inversion
thermal inversion
toxic air pollutant
troposphere
tropospheric ozone
volatile organic compounds (VOCs)
warm front
weather
Teaching Tips
1. Use the AirData website made available by the U.S. Environmental Protection
Agency (www.epa.gov/air/data/index.html). This website provides air
pollution data for the entire United States and produces reports and maps
using criteria that you specify. Air data are acquired from two EPA databases,
Air Quality System (AQS) and National Emission Inventory (NEI).
Present students with air data from your geographic area or ask them to
retrieve data themselves. The database will generate tables showing the
facilities within a state or a county that emit various particulates, in the order
of total amount of emission.
2. Assign students to read papers about air pollution and environmental justice at
the University of Michigan’s website (www.umich.edu/~snre492/cases.html).
You can have groups of students each choose a paper from the website that
relates to air pollution. Have them read the paper and then do follow-up
research to find out the current status of the problem. You can have the groups
write reports, do poster projects, or do PowerPoint presentations to the class or
an invited assembly.
Ask students to begin by considering the following questions:

What was the initial discovery?

What was the source of the problem?

What lawsuits have been filed? What were the outcomes?

What health effects have been documented?

What do you think can be done to prevent similar problems?
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3. As a classroom demonstration or student assignment, go to Smog City at
www.smogcity.com, developed by the Sacramento Metropolitan Air Quality
Management District. Smog City is an interactive air pollution simulator that
shows how population, environmental factors, and land use contribute to air
pollution. Smog City allows the user to adjust these factors to see the effect on
ground-level ozone formation. Ask students to consider the following
questions:

Does one factor seem to affect smog formation more than others?

How do weather variables affect smog formation?

How does population affect smog formation?

What can you do as an individual to reduce smog?
4. To find out about pollution in your community, go to Scorecard: The
Pollution Information Site (www.scorecard.org/). Have students enter their
ZIP codes to learn about toxic chemicals released into the air by local sources.
5. A poster project can be an exercise in learning good communication skills.
Students must summarize a great deal of information, use principles of color
and design, and have both graphic impact and a presentation style that draws
and holds interest. A short presentation to use in class, or to have students
access on their own, can be found at dv.pima.edu/~jduek. Click on “Education
Power Points” and from that page choose “Poster Projects.” It includes an
outline for students to follow and for instructors to use in grading projects:
20% content: written material and visual material
20% accuracy: content, grammar, and spelling
20% neatness: lettering, visuals, and use of color/design/layout
20% layout: tips are given about colors, lettering, placement, shape, and
decoration
20% creativity: written, visual, layout, humor, and other creative directions
6. Provide white or light-colored cotton squares to students for an outdoor
activity that will answer the question: “Is there particulate matter in the
atmosphere around campus that I am unable to see?” Be sure that all swatches
are the same size. Ask students if they can predict where there might be higher
levels of air quality impact. If in urban areas, regions near the ground that are
subject to diesel fumes provide interesting collecting sites. If possible, leave
the swatches outdoors secured to trees, posts, or even the building. Retrieve
the material after 24 hours and examine the swatches against a control swatch
kept inside the classroom in an airtight container. Ask students if any of their
predictions match the visual results.
Additional Resources
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Websites
1. AIRNow, U.S. Environmental Protection Agency (airnow.gov)
This interagency and international website provides air quality forecasts,
information, and reports on air quality to the general public.
2. Air and Radiation: Where You Live, U.S. Environmental Protection Agency
(www.epa.gov/air/where.html)
This resource has general information about air quality and regulation,
including criteria on air pollutants, air quality trends, and toxic air pollution.
3. Encyclopedia of the Atmospheric Environment, Manchester Metropolitan
University (www.ace.mmu.ac.uk/eae/english.html)
Published by the Atmosphere, Climate, and Environment Information
Programme, this website is supported by the United Kingdom Department for
Environment, Food, and Rural Affairs. It is a source of information on air
quality, ozone depletion, acid rain, and global warming.
4. The Great Smog of 1952, Met Office Education Service, United Kingdom,
(www.met-office.gov.uk/education/secondary/students/smog.html)
This website has a detailed summary of London’s Killer Smog of 1952.
5. The Hubbard Brook Ecosystem Study, Hubbard Brook Research Station
(www.hubbardbrook.org)
The home page of the Hubbard Brook Ecosystem Study (HBES) provides
access to its three main resources: Research and Data, Hubbard Brook
Research Foundation, and Educational Resources.
Audiovisual Materials
1. Ozone: Cancer of the Sky, 1994, produced by Television New Zealand Natural
History, distributed by The Video Project (www.videoproject.com)
This video presents general information about the ozone layer. The program
follows scientists as they convene in Antarctica to study the ozone hole that
forms there each spring.
2. Assault on the Ozone Layer, distributed by Films for the Humanities and
Sciences (www.films.com)
This program shows how the ozone layer is depleted and how its depletion is
stunting, mutating, and destroying life.
3. What’s Up with the Weather? NOVA video, distributed by WGBH
(shop.wgbh.org)
This program examines today’s extreme weather patterns, such as flooding,
hurricanes, and high temperatures. It addresses the question as to whether
these are natural phenomena or whether they are indicators of global warming.
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4. The Air We Breathe, 1997, produced by Hamm Productions and the National
Film Board of Canada, distributed by Bullfrog Films
(www.bullfrogfilms.com)
In two videos, this program shows the connection between suburban sprawl,
air pollution, and increases in asthma and other respiratory diseases.
5. What’s in Our Air, 1999, produced and distributed by Rainbow Video and
Film Productions (www.rainbowvideoandfilm.com)
This 25-minute video documents community members in Oregon,
Washington, and California using low-tech bucket monitors to sample the air
for 43 hazardous air pollutants.
Weighing the Issues: Facts to Consider
Your County’s Air Quality
Facts to consider: In order to determine local air quality, the instructor could
suggest websites for county departments of environmental quality or some
equivalent state agency that monitors air quality. For national comparisons,
the instructor may recommend the first website in the Additional Resources,
AIRNow (www.airnow.gov), as a source of comparative information. The
Internet has numerous websites that have ideas for air pollution reduction,
from international to local and personal perspectives. Ideas and opinions about
the causes of local air pollution and solutions for reducing air pollution will
vary, depending on the social, economic, and industrial context of the county
being investigated and the experience, knowledge, and priorities of the
student.
International Cooperation to Solve Global Problems
Facts to consider: Substantive action on issues such as organic pollutants,
climate change, and biodiversity loss will require definitive proof of direct
harm to human health. The human health consequences of the Antarctic ozone
hole were straightforward, and governments and industry had no choice but to
act accordingly. Negative environmental effects, and even more specifically
negative human health effects, are not as straightforward in many other
situations. A relatively easy fix, such as CFCs in the case of ozone depletion,
is more palatable to politicians than complex lifestyle changes. Organic
pollutants are plentiful, and global climate change and biodiversity crises
appear to have multiple causes. Developing sufficient viable alternatives to the
significant causal agents would be enormously difficult.
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Fortunately, there have been some other large-scale environmental success
stories. Most lead sources have been eliminated in the United States. Urban air
quality has improved significantly in the United States and Britain due to the
results of clean air legislation. Exposure to tobacco smoke, an indoor
pollutant, has decreased in the United States and some other nations. Growing
awareness of naturally emitted radon has resulted in over a million homes
being built with radon-resistant features. In the future, the use of low-toxicity
building materials and good ventilation hold promise for reducing indoor air
pollution. Indoor air pollution in developing countries can also be reduced in
the near term by drying wood before burning and using less-polluting fuels
and cleaner-burning stoves.
How Safe Is Your Indoor Environment?
Facts to consider: This question requires an individual response, but
responses should consider a wide range of potential sources of air pollution, as
designated by the EPA, including asbestos; biological pollutants such as mold,
mildew, or pollen; carbon monoxide from gas appliances or woodstoves;
formaldehyde used in building materials; organic chemicals used in cleaning
products, dry cleaning, or hobbies; lead from old paint; nitrogen dioxide from
gas or kerosene heaters; pesticides to control indoor insects or
microorganisms; naturally occurring radon gas; combustion products from
fireplaces or woodstoves; and secondhand smoke. Generally applicable ways
to make indoor spaces safer from pollution include limiting use of plastics and
treated wood where possible, increasing ventilation, having the space tested
for radon gas, and storing cleansers and other household products in a garage
or shed.
The Science behind the Stories: Thinking Like
a Scientist
How Scientists Identified CFCs as the Main Cause of
Ozone Depletion
Observation: By the 1970s, industrial chemicals known as
chlorofluorocarbons (CFCs) were being produced in vast quantities. However,
in 1974, F. Sherwood Rowland and Mario Molina published a paper whose
main point was that the inertness of CFCs could have disastrous consequences
for the ozone layer.
Hypothesis: CFCs were causing significant decreases in global stratospheric
ozone. Rowland and Molina hypothesized that CFCs would not be broken
down in the lower atmosphere and would reach the stratosphere undamaged.
Intense ultraviolet light would break down CFCs into chlorine and carbon
atoms. The chlorine atoms would catalyze the destruction of ozone molecules.
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Experiment: Several experiments had to be conducted to provide data to
support this hypothesis. Richard Stolarski and Ralph Cicerone showed that
chlorine atoms acted as catalysts for ozone molecule destruction. James
Lovelock devised an instrument to measure extremely low concentrations of
atmospheric gases. James Farman and his colleagues reported that Antarctic
atmospheric ozone levels had been dramatically falling since the 1970s. Paul
Crutzen showed that the Antarctic ozone hole was the result of a combination
of Antarctic weather conditions and the presence of CFCs in the stratosphere.
Results: By the mid-1980s, scientists had conclusive evidence that global
ozone levels were declining, particularly over Antarctica, and that those
declines were due primarily to CFCs and other human-made chemicals.
Acid Rain at Hubbard Brook Research Forest
Observation: Long-term studies of water flow and nutrient cycling are
important to understanding the interplay between abiotic and biotic portions of
any ecosystem.
Study: The 7,800 acre Hubbard Research Forest was established in New
Hampshire in 1955 as a long-term hydrological study and was augmented in
1963 by Dartmouth University researchers to include the study of nutrient
cycling. Precipitation was collected in clean plastic bottles from funnels with a
30-cm opening. These bottles were retrieved each week and measured for
acidity and electrical conductivity. Concentrations of specific compounds
were also measured by other labs.
Results: In the 1960s, Gene Likens, F. Herbert Bormann, and others found
that the pH of the Hubbard Brook precipitation was several hundred times
more acidic than natural rainwater. Other studies in the 1970s supported this
finding, eventually showing that the precipitation from Pennsylvania to Maine
was averaging a pH of 4.0, with some precipitation measured as low as 2.1.
The result of this study was the implementation of the National Atmospheric
Deposition Program to measure precipitation and dry deposition across the
United States. This program developed a nationwide pH map that showed that
the northeast United States had the worst acid deposition problem. It was
hypothesized that the fossil-fuel burning plants of the Midwest provided the
compounds that increased the acidity of the soil in the northeast United States.
The Clean Air Act of 1970 was amended in 1990 to restrict acidic compounds
from these Midwest factories and power plants. In 1996, researchers also
found that acidic deposition was leaching calcium and magnesium out of the
soil while increasing the amount of aluminum in the soil. These nutrient
deficiencies and surpluses weakened trees and slowed forest growth, making
trees more vulnerable to drought and insect damage.
Causes and Consequences
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The following answers for the Causes and Consequences features are
examples, and are not intended to represent a comprehensive list. In addition,
the sequence of items is not meant to connote relative importance.
Issue: Indoor Air Pollution
Causes:
radon seepage into homes
the need to burn fuelwood in developing nations
cigarette smoking
volatilization from manufactured products
bacteria, viruses, mildew, etc.
poor ventilation
Consequences:
lung cancer: 20,000 deaths per year in the United States
various other illnesses and health impacts
deaths from chronic or acute exposure
Solutions:
measure radon with a test kit; increase ventilation
replace indoor wood fires with stoves
keep ducts clean
quit smoking
minimize chemicals in one's house
Unintended consequences:
Increasing ventilation increases energy expenditure for heating and cooling a
home.
Buying stoves is more expensive for poor families—and they are the ones
who need them.
…and New solutions:
Ventilate at times of day when temperature is moderate; improve insulation
and other energy-saving features of home.
Government can assist in purchases, or can enact other measures to attempt
to relieve poverty.
InvestigateIt Case Studies and Videos
Case Studies
Something (and Lots of It)
Is in the Air
Critics Say Clean-Air Plan
May Be a Setback for
Parks
Trucks Soil Mont Blanc's
Sparkling Slopes
Indonesia's Yearly Smoke
Location
Topic
Connecticut
Air Pollution
Tennessee
Air Pollution
France
Malaysia
Air Pollution
Air Pollution
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Region
Cloud Reaches Malaysia
and Thailand
Parents and Health
Experts Unite in Effort to
Ease Pollution in Northern
Italy
Bangkok Journal:
Breathing Easier as the
Battle for Blue Skies Pays
Off
As China Roars, Pollution
Reaches Deadly Extremes
Fitness: For Athletes, An
Invisible Traffic Hazard
Milan, Italy
Air Pollution
Italy
Bangkok,
Thailand
Air Pollution
Thailand
China
Air Pollution
China
California
Toxicology
California
Answers to End-of-Chapter Questions
Testing Your Comprehension
1. The Earth’s atmosphere is about 500 km (300 mi) thick, consisting of four
layers: the bottommost layer, the troposphere, is only 11 km (7 mi) thick but
contains three-quarters of the atmosphere’s mass; the stratosphere extends
from 11–50 km (7–31 mi) above sea level and contains most of the
atmosphere’s UV-absorbing ozone; the mesosphere is a zone of declining
temperatures and extremely low pressures, extending 50–90 km (31–56 mi)
above sea level; finally, the thermosphere is the outermost layer of the
atmosphere, extending from 90–500 km (56–300 mi) above sea level. In this
layer, infrequent molecular collisions allow the atmosphere to become
chemically stratified, with lighter hydrogen and helium rising to the top of the
layer, and the heavier oxygen and nitrogen sinking toward the bottom.
2. The ozone layer is concentrated 17–30 km (10–19 mi) above sea level in the
stratosphere. Stratospheric ozone absorbs UV radiation, which is harmful to
life. Tropospheric ozone can contact living organisms, and react chemically
with their tissues, causing harmful oxidation to occur. This oxidation can
chemically alter a cell’s DNA, leading to mutations and the possibilities of
cell death or cancer.
3. Solar energy heats air, causing pressure gradients that drive Earth’s
atmospheric circulation. This circulation distributes heat and moisture over
Earth’s surface (i.e., determines the main factors of climate). Hadley, Ferrel,
and polar cells are convection patterns in the atmosphere, driven by the sun’s
energy, that produce predictable bands of precipitation and wind direction
over the globe. These factors in turn control the distribution of Earth’s biomes.
4. The London smog event of 1952 was caused by the exhaust of coal-burning
power plants and of home fireplaces/furnaces being trapped in a layer of
colder, denser air near the surface—a so-called thermal inversion.
5. Natural sources of outdoor pollution include plant metabolism, dust storms,
volcanoes, and forest fires. Anthropogenic sources include industrial
combustion processes, home fireplaces, and automobile exhaust, among other
sources.
6. A primary pollutant, such as soot, is emitted into the atmosphere in a form that
is directly harmful. A secondary pollutant is produced in the atmosphere by
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7.
8.
9.
10.
means of a chemical reaction occurring there. For example, the nitric acid in
acid rain is produced by reaction of the primary pollutant NO2 and water vapor
in the air.
The term “smog” was coined from the combination of “smoke” and “fog,” and
today refers to unhealthy mixes of air pollutants that often occur over urban
areas, especially when the air pollutants are trapped there by a temperature
inversion. Photochemical smog is caused by secondary pollutants and other
chemicals, often including ozone and NO2. Industrial smog is caused by the
by-products of industrial combustion, especially soot, CO, CO2, SO2, and NO2,
resulting in a characteristically gray, acidic mixture.
CFCs split O3 to produce O2. Because CFCs persist in the atmosphere for
years, are mixed all over the world regardless of their source, and destroy UVprotective stratospheric ozone, they are considered a long-term international
problem. Many nations of the world came together to create the Montreal
Protocol, which limited the production of CFCs and similar chemicals
internationally.
Acidic deposition, an example of a secondary pollutant, can occur far from the
source of its precursor pollutants because of the long-range atmospheric
transport that occurs while the atmospheric chemical reactions are occurring.
Acidic deposition can change soil chemistry, kill trees, acidify lakes, harm
aquatic organisms, eat away at buildings, and cause other impacts.
Common indoor air pollution sources include tobacco smoke, radon gas,
volatile organic compounds, living organisms from mites to bacteria, and
smoke from indoor fires. Exposure can be reduced for each (in the order of the
factors just mentioned) by not smoking indoors, ventilating confined spaces in
basements, choosing alternative products for floor coverings or cleaning
compounds, minimizing sources of standing water in the building’s HVAC
system, and limiting wood fires to the outdoors, or at least proving a working
chimney and adequate ventilation.
Interpreting Graphs and Data
1. Relative to 1970, GDP is up 203%, vehicle miles traveled is up 177%, energy
consumption is up 49%, population is up 46%, and aggregate emissions are
down 54%. GDP per capita is up 105%, vehicle miles traveled per capita is up
94%, energy consumption per capita is up 5%, and aggregate emissions per
capita are down 67%.
2. Relative to 1970, aggregate emissions per unit of energy consumed is down
69% for 2006.
3. Technological advances will continue to be made, but to date, those advances
have accounted for virtually all of the decreased emissions. Note that the
change in aggregate emissions per capita and the change in aggregate
emissions per unit of energy consumed are nearly identical. Significant
decreases could be made if we changed our behavior and drove our modern,
efficient cars only as many miles per person as we did in 1970.
Calculating Ecological Footprints
IG-261
You
Your Class
Your State
United States
Total NOx emissions
(lb)
NOx emissions
due to light-duty
vehicles (lb)
146.4
Answers will vary
Answers will vary
42,204,000,000
24.9
Answers will vary
Answers will vary
7,166,000,000
1. The U.S. population increase from 2002 to 2010 is projected to be 7.1%. NOx
emissions have decreased slightly during the past decade, even as the
population has grown, largely the result of improved technology. Unless
unexpected technological breakthroughs occur, or unless fuel demand surges,
we may expect these trends to continue.
2. By reducing your vehicle miles traveled by one-half, 12.45 pounds of NOx
emissions could be avoided, which would be an 8.5% reduction in your total
NOx emissions.
3. Answers will vary. Anything that would reduce your combustion of fossil
fuels would also reduce your amount of NOx emissions (e.g., setting your
thermostat lower in the winter and higher in the summer; using only those
lights necessary; taking cooler, shorter showers). Reducing the per capita
share of vehicle miles traveled is as easy as carpooling, combining several
errands into one trip, or walking/biking when possible.
IG-262