Primary pollutants: are mixed vertically and horizontally and are
dispersed and diluted by the churning air in the troposphere.
Ex: CO, CO2, SO2, NO, NO2, most hydrocarbons, and most
Secondary pollutants: while in the troposphere, some of the
primary pollutants may react with one another or with the basic
compounds of air.
Ex: SO3, HNO3, H2SO4, H2O2, O3, and PANs
Six Principal Pollutants
- Carbon Monoxide (CO)
- Lead (Pb)
- Nitrogen Dioxide (NO2)
- Ozone (O3)
- Particulate Matter (PM-10)
- Sulfur Dioxide (SO2)
Ozone is formed by the action of sunlight on carbon-based
chemicals known as hydrocarbons, acting in combination
with a group of air pollutants called oxides of nitrogen.
Ozone reacts chemically ("oxidizes") with internal body
tissues that it comes in contact with, such as those in the
lung. Ozone (O3) in the troposphere causes more damage
to plants than all other air pollutants combined.
Sulfur dioxide belongs to the family of gases called sulfur
oxides (SOx ). These gases are formed when fuel
containing sulfur (mainly coal and oil) is burned, and
during metal smelting and other industrial processes.
The major health concerns associated with exposure to
high concentrations of SO2 include effects on breathing,
respiratory illness, alterations in pulmonary defenses, and
aggravation of existing cardiovascular disease.
In the past, motor vehicles were the biggest
source of lead. But since leaded gasoline has
been phased out, lead emissions have decreased by about
98 percent. Today, metal processing is the biggest source of
Lead can harm the kidneys, liver, nervous system and other
organs. It may cause neurological impairments such as
seizures, mental retardation and behavioral disorders. Even
at low doses, lead is associated with damage to the nervous
systems of fetuses and young children, resulting in lowered
IQ and learning problems.
Particulates is a general term used to describe tiny bits of
matter floating around in the atmosphere, such as certain
types of smoke (like diesel smoke), fine ash and dust. Larger
particles are caught by the hairs in your nose and your
breathing tubes, but smaller particles can get past these
defenses and cause lots of trouble.
Nitrogen dioxide belongs to a family of highly reactive
gases called nitrogen oxides (NOx). These gases form
when fuel is burned at high temperatures, and come
principally from motor vehicle exhaust and stationary
sources such as electric utilities and industrial boilers.
Nitrogen dioxide can irritate the lungs and lower resistance
to respiratory infections such as influenza.
Carbon Monoxide is produced by the
incomplete combustion of the fossil fuels
– gas, oil, coal and wood used in boilers,
engines, oil burners, gas fires, water heaters,
solid fuel appliances and open fires.
When carbon monoxide is present in the air you breath into
your lungs, it attaches itself to the hemoglobin.
The bond between hemoglobin and carbon monoxide is 250
times stronger than oxygen.
In the lungs carbon monoxide attaches to red blood cells in
place of oxygen.
The Four Most Dangerous
Indoor Air Pollutants
1. cigarette smoke
4. radioactive radon-222 gas
Formaldehyde is a colorless liquid or gas with a strong,
distinctive odor. It is found in furniture, new carpets,
particle board, plywood, rubber cement and adhesives.
Low levels of exposure can irritate the eyes, nose and
throat, cause skin problems, serious breathing problems
and can increase your risk of certain kinds of cancer.
Sources: Deteriorating of damaged insulation, fire-proofing,
or acoustical materials.
Health Effects: No immediate symptoms. Chest and
abdominal cancers and lung diseases. Smokers are at
higher risk of developing asbestos-induced lung cancer.
Sources: Earth, uranium and rock beneath home; well
water; building materials.
Health Effects: No immediate symptoms. Estimated to
cause about 10% of lung cancer deaths. Smokers are at
higher risk of developing radon-induced lung cancer.
Radon-222 can enter the house by diffusion
from soil and by emanation from building
materials, tap water and methane gas.
- an odorless, tasteless, invisible gas that mixes with air
- chemically inert and essentially non-reactive
- heaviest noble gas with highest melting and boiling point
- highly soluble in non-polar solvents
- moderately soluble in cold water
- able to diffuse through rock and soil
- decays by alpha particle emission (T 1/2 = 3.8 days)
The largest source of "indoor air
pollution"- in our homes, our schools or
workplaces- is car and truck pollution.
Electric vehicles are sometimes referred
to as "zero-emission vehicles" because
they produce essentially no pollution
from the tailpipe or through fuel
evaporation. This is important, for it
means that the use of electric vehicles
could greatly reduce emissions of
carbon monoxide and smog-forming
pollutants in cities with dirty air.
As many as 20 million Americans suffer from:
- chronic breathing problems
- sore throat
- eye irritation
Acid Deposition: the falling of acids and acid-forming
compounds from the atmosphere to earth’s surface. Acid
deposition is commonly known as acid rain, a term that refers
only to wet deposition of droplets of acids and acid-forming
Effects of Acid rain
- human respiratory disease (bronchitis and asthma)
- damages statues, buildings, metals, and car finishes
- depletion of calcium and magnesium ions in the soil
- damages trees
How to reduce acid deposition
1. Reduce energy use and thus air pollution by improving
2. Switch from coal to cleaner burning natural gas and
renewable energy resources
3. Remove sulfur from coal before it is burned
4. Burn low-sulfur coal
5. Remove SO2, particulates, and nitrogen oxides from
6. Remove nitrogen oxides from motor vehicle exhaust
A building is considered “sick” when at
least 20% of its occupants suffer persistent
symptoms that disappear when they go outside
At least 17% of the 4 million
commercial buildings in the U.S. are considered
Most ozone (about 90%)
exists in the stratosphere,
in a layer between 10 and
50km above the surface of
the earth. This ozone layer
performs the essential task
of filtering out most of the
sun's biologically harmful
Over Antarctica (and recently over the Arctic),
stratospheric ozone has been depleted over the last 15
years at certain times of the year. This is mainly due to
the release of manmade chemicals containing chlorine
such as CFC's (ChloroFluoroCarbons), but also compounds
containing bromine, other related halogen compounds and
also nitrogen oxides (NOx).
CFC's are chemicals that can be used in
the refrigerator to help keep food cold.
They can also be used in airconditioning and in products in spray
cans. CFC's rise into the air going into a layer called the
stratosphere. When this happens, the CFC's take part in
chemical reactions that can destroy parts of the ozone
which protects us from the sun's dangerous ultraviolet rays.
The Earth is kept warm by it's atmosphere, which
acts rather like a woolly coat - without it, the
average surface temperature would be about -18
degrees Centigrade. Heat from the sun passes
through the atmosphere, warming it up. As the
Earth warms up, it emits heat. Some of this heat is
trapped by the atmosphere, but the rest escapes into
space. The so-called "greenhouse gases" make the
atmosphere trap more of this radiation, so it
gradually warms up more than it should, like a
Where in the atmosphere
does it occur?
What process occurs?
Traps heat near the earth’s
Filters ultraviolet (UV)
radiation from the sun
What natural gases are
What are important
(CFCs), halons, carbon
What problems result?
Carbon dioxide is produced when any form of carbon or
almost any carbon compound is burned in an excess of
oxygen. For example, it is released into the atmosphere
during natural forest fires and the man-made combustion of
fossil fuels. Other natural sources of carbon dioxide include
volcanic eruptions, decay of dead plant and animal matter,
evaporation from the oceans and respiration (breathing).
Methane is a greenhouse gas that is creating a serious
problem for global warming. Methane gases are very
potent when trapping infrared heat in the atmosphere,
because one molecule of methane can trap infrared heat
twenty times more than carbon dioxide.
Methane the second most important
greenhouse gas is mostly produced
by the digestive system of cows.
Smog and particles certainly
trigger attacks in some people
who already have asthma. For
a long time it was thought that
air pollution could not cause
asthma to develop in
previously healthy people. Some recent
experiments challenge this belief. Scientists have shown
that people exposed to ozone or nitrogen dioxide are more
likely to react to allergens such as grass pollens and
housedust mites than those who are not exposed. Thus a
combination of air pollution and allergens could cause
some cases of asthma.
Lung cancer is more common in cities
than in the country. We know that over
90% of lung cancers are caused by
smoking cigarettes. A radioactive gas
called radon is thought to cause about
7% of lung cancers in North America.
87% of lung cancer cases are caused by smoking. 12
percent of all lung cancer deaths are linked to radon.
Another leading cause of lung cancer is on-the-job
exposure to cancer-causing substances or carcinogens.
Air pollution can make you
sick. It can cause burning eyes
and nose and an itchy, irritated
throat, as well as trouble in
breathing. Some chemicals
found in polluted air cause
cancer, birth defects, brain and
nerve damage and long-term
injury to the lungs and
breathing passages. Some air
pollutants are so dangerous
that accidental releases can
cause serious injury or even
According to the U.S. Environmental Protection Agency's
(EPA) latest Ten-Year Air Quality and Emissions Trends
report, there have been significant reductions in all 6 criteria
pollutants and reductions are expected to continue.
The 1990 Clean Air Act
Under this law, EPA sets limits on how much of a pollutant
can be in the air anywhere in the United States. This
ensures that all Americans have the same basic health and
environmental protections. The law allows individual states
to have stronger pollution controls, but states are not
allowed to have weaker pollution controls than those set for
the whole country.
Chapter 19: Global Warming
and Ozone Loss
The Greenhouse effect
• In the Greenhouse effect,
certain gases in the atmos
phere trap heat in the trop
osphere (lower atmospher
• If the atmospheric concent
rations of these gases rise
and arent removed by othe
r processes, the average t
emp of the lower atmosph
ere will gradually increase.
• The major greenho • These gases remai
use gases are wate
n in the atmospher
r vapor (H20), carb
e for 2,000-50,000
on dioxide (C20), o
zone (o3), methane
(CH4), nitrous oxid
• The two predomina
e (N2O), and chlor
nt gases are water
vapor (hyrologic cy
Cs), and a recently
cle) and carbon dio
xide (global carbon
• Measured atmospheric levels of certain gre
enhouse gases have risen substantially in r
ecent decades and are projected to enhan
ce the earth’s natural greenhouse effect, a
phenomenon called global warming
• Most of the increased levels of these green
house gases since 1958 have been caused
by human activities such as burning fossil f
uels, agricultue, deforestation, and use of
• Carbon dioxide (CO2):
– Responsible for 50-60% of the global warming fr
om greenhouse gases produced by human activit
– Main sources are fossil fuel burning (70-75%) an
d land clearing and burning (20-25%)
– Remains in atmosphere for 50-200 years
• Chloroflurocarbons (CFCs):
– Contribute to global warming in the troposphere
and also deplete ozone in the stratosphere
– Main sources are leaking ACs and fridges, evap
oration of industrial solvents, production of plas
tic foams, and aerosol propellants
– Trap 1,500- 7,000 times as much heat per mol
ecule as CO2 while they are in the troposphere.
• Methane (CH4):
– Accounts for about 20% of the overall warming eff
– Produced when anaerobic bacteria break down de
ad organic matter in moist places that lack oxygen
– Stays in the troposphere for 9-15 years
– Each CH4 molecule traps 20 times as much heat a
• Nitrous oxide (N2O):
– Can trap heat in the troposphere and also deplete oz
one in the stratosphere
– Released from nylon production, burning of biomass
and nitrogen-rich fuels, smog-fighting catalytic con
verters on motor vehicles, and the breakdown of nitr
ogen fertilizers in soil, livestock wastes, and nitratecontaminated groundwater.
– Stays in the troposphere about 120 years.
• According to EPA, emission of green
house gases by the US rose by 20%
between 1990 and 1996. Energy rela
ted activities accounted for about 86
% of these emissions in 1996, mostly
through burning fossil fuels.
• The atmospheric concentrations of C
O2 and other greenhouse gases are p
rojected to double from preindustrial l
evels sometimes during the next cent
ury and then continue to rise
The Earth’s past temperature
• Since 1860, mean global temperature
after correcting for excess heating ov
er urban areas has risen 0.3-0.6 degr
• Temperature rose about 0.3 degrees
between 1846 and 1997
• Since 1860, the thirteen warmest year
s occurred between 1979 and 1998,
with 1990, 1995, 1997, and 1998 bein
g the four hottest years.
Future global warming and its ef
• According to the la • According to the m
test climate models
odels, the northern
, the earth’s mean
warm more and fas
e should rise 1- 3.
5 degrees celsius b
n hemisphere beca
etween 1990 and 2
use the latter has
more heat- absorbi
• Model projects that
ng ocean than land
once the climate c
and because water
hanges, it will conti
nue for hundreds o
cools more slowly t
How Earth’s climate is affect
ed by various factors
• Solar output: ups and downs in solar
output can temporarily warm or cool t
he earth and thus affect the projectio
ns of climate models.
– Two studies showed that the projected
warming power of greenhouse gases sh
ould outweigh the climatic influence of t
he sun over at least the next 50 years.
• Oceans: the oceans mi
ght amplify global warm
ing by releasing more C
O2 into the atmosphere
or might dampen it by a
bsorbing more heat. T
he oceans currently hel
p moderate tropospheri
c temperature by remov
ing about 29% of the ex
cess CO2 pumped into
• Water vapor content and clouds: cha
nges in the atmosphere’s water vapor
content and the amount and types of
cloud cover also affect climate. Warm
er temperatures would increase evap
oration and the water-holding capacit
y of the air and create more clouds.
Significant increase in the water vapo
r, a potent greenhouse gas, could en
hance warming (positive feedback).
• Polar ice: the ability of the earth’s surface
to reflect light is called its albedo. Becaus
e of their albedo, light-colored Greenland
and Antarctic ice sheets act like enormous
mirrors, reflecting sunlight back into space
. If warmer temperatures melted some of t
his ice and exposed darker ground or ocea
n, more sunlight would be absorbed and w
arming would be accelerated.
• Air pollution: pollutants in the lower tropos
phere can either warm or cool the air depe
nding on the reflectivity of the underlying s
• It is hypothesized that SO2 and tiny particl
es in the troposphere attract enough water
molecules to form condensation nuclei, wh
ich leads to increased cloud formation
Some possible effects of a warmer
• Food production: a warmer global climat
e could increase food production in some
areas and lower it in others, depending o
n crop- growing capacity and climate bel
• Water supply: global warming would redu
ce water supply, shrinking or completely
drying up lakes, streams, and aquifers.
• Forests and biodiversity: global warming
would change the makeup and location o
f many of the worlds forests
• Sea levels: in a warmer world, sea levels a
re expected to rise, primarily because ocea
n water expands when heated and becaus
e some land-based glacial ice will melt
• Weather extremes: as more heat is retaine
d in the earth’s climate system, more air wi
ll move across the earth’s surface.
• Human health: global warming would bring
more heat waves, which would double or tr
iple heat-related deaths among the elderly
and people with heart disease; it would als
o increase suffering from respiratory ailme
nts such as asthma and bronchitis.
Solutions: dealing with global warm
• Stabilizing the Co2 levels at the curre
ct level would require reducing curren
t global CO2 emissions by 66-83%.
• Increased use of nuclear power to re
duce the amount of CO2 per unit of e
lectricity as coal
• Using natural gas could help make th
e 40 to 50 year transition to an age of
energy efficiency and renewable ener
• In a band of the stratosphere 17- 26 kms abov
e the earth’s surface, oxygen is continually con
verted to ozone and back to oxygen by a seque
nce of reactions initiated by UV radiation from t
• UV radiation reaching the stratosphere consists
of three bands: A, B, and C. The ozone layer b
locks out nearly all of the highest- energy and
biologically damaging UV-B band.
• Ozone depletion by certain chlorine- and bromi
ne- containing chemicals emitted into the atmo
sphere by human activities is a serious long-ter
m threat to human health, animal life, and the s
unlight drive promary producers that support th
• CFCs released into the air rise slowly into the st
ratosphere. There, under the influence of high
energy UV radiation, they break down and relea
se highly reactive chlorine atoms, which speed
up the breakdown of highly reactive ozone into
O2 and O. This causes ozone to be destroyed f
aster than it is formed.
Solutions: protecting the ozo
• It will take another 50-60 years for the ozo
ne layer to return to 1975 levels and anoth
er 100- 200 years to return to pre- 1950 r
• Substitutes are already available for most
uses of CFCs.
– Hydochlorofluorocarbons (HCFCs) contain fe
wer chlorine atoms per molecule than CFCs
• Because of their shorter lifetimes in the stratospher
e, these compounds should have only about 2.5%
of the ozone depleting potential of CFCs.