2. • An area in the
stratosphere
where ozone is
highly
concentrated.
• Ozone (O3) absorbs
most of the UV
light that comes
from the sun.
WHAT IS THE OZONE LAYER?
3. Chlorofluorcarbons (CFCs)
• When first invented, were valued
because they are
• Nonpoisonous
• Nonflammable
• Do not corrode
• Were used for decades as
• Coolants in refrigerators & air
conditioners
• Component of Sytrofoam
• Propellant in hair spray,
deodorant, insecticides & paint
• In 1970’s it was discovered they may
be damaging the ozone layer.
WHAT CHEMICAL IS ATTRIBUTED WITH
CAUSING OZONE DEPLETION?
4. • At ground level, CFCs are
stable & do not cause
problems.
• When air currents carry them
to the stratosphere they can
deplete the ozone.
• Takes 10-20 years for the CFC’s to make
it to the stratosphere and they get
recycled while they are up there so they
are persistent for 60-120 years
• UV light from sun breaks CFC which
releases a chlorine atom.
• The chlorine atom breaks a molecule of
ozone (O3) into an O2 molecule and an
oxygen atom (O) which the chlorine
attaches to and creates chlorine
monoxide (ClO)
• Chlorine monoxide (ClO) hits another
ozone and the chlorine breaks off again
and attacks another ozone molecule.
• 1 chlorine from CFC can destroy
100,000 ozone molecules.
HOW DO CFC’S DEPLETE THE OZONE?
5. Ultraviolet light hits a chlorofluorocarbon
(CFC) molecule, such as CFCl3, breaking
off a chlorine atom and leaving
CFCl2.
UV radiation
Sun
Once free, the chlorine atom is off
to attack another ozone molecule
and begin the cycle again.
A free oxygen atom pulls
the oxygen atom off
the chlorine monoxide
molecule to form O2.
The chlorine
atom and the
oxygen atom join
to form a chlorine
monoxide molecule (ClO)
The chlorine atom attacks
an ozone (O3) molecule,
pulling an oxygen atom
off it and leaving
an oxygen
molecule (O2).
Cl
Cl
Cl
C
F
Cl
Cl
O
O
Cl
O
O
O
Cl
O
O
O
Cl
O
O
6. 1980’s scientists
working in Antarctica
noticed a thinning of the
ozone by 50-98% that
was occurring each
spring.
WHAT IS “THE OZONE HOLE”?
7. During the dark winter
months, VERY cold
strong winds called
polar vortex winds trap
CFC’s and convert them
to molecular Cl2
In the spring, UV rays
split Cl2 and the
individual Cl atoms
break ozone down
rapidly.
The thinning lasts for
several months.
HOW DOES THE OZONE HOLE FORM?
8. Ozone at ground
level is highly
reactive and reacts
with other molecules
of air pollution
before it can even
enter the
stratosphere.
WHY CAN’T OZONE CREATED AT GROUND
LEVEL (AKA- BAD OZONE) HELP HEAL THE
OZONE THINNING?
9. UV light can
Damage DNA
Premature aging
Weakened immune
system
Increase chance of
developing cataracts
Increase susceptibility
to skin cancer
WHAT ARE THE EFFECTS OF OZONE
THINNING ON HUMANS?
10. Oceans
Kills phytoplankton which is
the bottom of the marine food
chain.
Disrupts food chains
Phytoplankton removes CO2 so
if they die, CO2 levels would go
up in atmosphere (global
climate change)
Freshwater
Kill amphibian eggs
Survivors suffer birth defects
Populations decline
Land Plants
Interferes with photosynthesis
Reduces crop yield
WHAT ARE THE EFFECTS OF OZONE
THINNING ON ANIMALS & PLANTS?
11. Montreal Protocol
(1987)
Meeting of several nations
calling for reduction or
elimination of CFCs in
products.
Many manufacturers are
switching to non-CFC
propellants in aerosol
cans.
You can help by:
Not buying Styrofoam
products
If air conditioner leaks, fix it
to prevent release to air.
HOW CAN WE PROTECT THE OZONE
LAYER?
12. Describe the process by which chlorofluorcarbons destroy
ozone molecules in the stratosphere.
Describe the process by which the ozone hole forms over
Antarctica in the spring.
List five harmful effects that UV radiation could have on
plants or animals as a result of ozone thinning.
Explain why it will take years for the ozone layer to recover,
even though the use of CFCs has declined significantly.
YOU SHOULD BE ABLE TO…
