The document summarizes information about the ozone layer, including: 1) The ozone layer is a layer in the stratosphere that protects the Earth from harmful UV radiation. It is formed when oxygen molecules interact with solar radiation. 2) Chlorofluorocarbons (CFCs) released from products like aerosol sprays are the primary cause of ozone layer depletion, as chlorine atoms from CFCs destroy ozone molecules. 3) Depletion of the ozone layer leads to increased UV radiation reaching the Earth's surface, which can cause skin cancer, eye damage, and harm plants and plankton. International agreements have led to a ban on CFCs to allow

1. Presentation on
OZONE LAYER DEPLETION

2. What is the ozone layer?
The ozone layer is a deep layer in the stratosphere, encircling the Earth, that has
large amounts of ozone in it. The layer shields the entire Earth from much of the
harmful ultraviolet radiation that comes from the sun.

3. Where is the ozone layer ?
The ozone layer lies between 10
and 50 kilometres above the
Earth's surface.
It is in a region of the atmosphere
called the Stratosphere. The
Stratosphere completely surrounds
the Earth with a thickness of about
33 kilometers in most places.

4. Formation of the Ozone
Layer
One billion years ago, early aquatic organisms called blue-green algae began using energy from the
Sun to split molecules of H2O and CO2 and recombine them into organic compounds and molecular
oxygen (O2).
This solar energyconversion process is known as photosynthesis.Some of the photosynthetically
created oxygen combined with organic carbon to recreate CO2 molecules.
The remaining oxygen accumulated in the atmosphere, touching off a massive ecological disaster
with respect to early existing anaerobic organisms.As oxygen in the atmosphere increased,
CO2 decreased.
High in the atmosphere, some oxygen (O2) molecules absorbed energy from the Sun's ultraviolet
(UV) rays and split to form single oxygen atoms.These atoms combined (27k jpeg) with remaining
oxygen (O2) to form ozone (O3) molecules, which are very effective at absorbing UV rays.The thin
layer of ozone that surrounds Earth acts as a shield, protecting the planet from irradiation by UV
light.

6. Advantages of ozone layer
 Primarily, it blocks "UV-B", which other components of the atmosphere do
not touch..
 Helps to mitigate temperature, so that nights are a little warmer, and days a
little cooler.

7. Different chemicals are responsible for the destruction of
the ozone layer
 Topping the list :
chlorofluorocarbons (CFC’s) Catalyzed by halocarbons (carbon compounds containing
fluorine, chlorine, bromine and iodine)
– Examples: CFCs and ClONO2
– man-made, non-toxic and inert in the troposphere
– In the stratosphere are photolysed, releasing reactive
chlorine atoms that catalytically destroy ozone

8. Ozone-Depleting
Substance(s) (ODS):
CFCs,
HCFCs,
halons,
methyl bromide,
carbon tetrachloride, and
methyl chloroform.
dangerous

9. Chlorine atoms from CFCs attack the ozone, taking away ozone and forming
chlorine monoxide (ClO).
O3 + Cl  O2 + ClO
Chlorine monoxide then combines with another oxygen atom to form a new
oxygen molecule and a chlorine atom.
ClO + O  Cl + O2
The chlorine atom is free to destroy up to 100,000 ozone molecules

10. Depletion process

11. Effect of depletion
On Human being/Animal /plants–
UV-B damages DNA, which results in cancer, mutation and reduced crop yield from any Earth-
surface-dwelling organism
 Skin cancer
 Eye damage such as cataracts
 Immune system damage
 Reduction in phytoplankton
 Damage to the DNA in various life-forms
– this has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultra-
violet light (they've never needed them before)
 Possibly other things too that we don't know about at the moment.

12. Effects of UV radiation on biological organisms
DNA damage…Maximum effect on small and single cell organism
Impaired growth and photosynthesis ...poor crop yields
Phytoplankton: ………………………...Reduced uptake of CO2
…………………………………………..mortality
…………………………………………..Impaired reproductive capacity
Nitrogen-fixing soil bacteria…………. Reduced, damaged
Human health effects:
Suppressed immune system……………..Enhanced susceptibility to infection
…………………………………………..Increase risk of Cancer
Dermatology (skin)……………………...Sunburn
…………….………………………….....Loss of skin elasticity (Premature aging)
…………….…………………………… Photosensitivity
Neoplasia (cancer)……………………....Melanocytic (malignant melanoma)
…………….………………………….....Squamous cell skin – cancer
…………….……………………………Basal skin – cancer
Still questionable if causes lip cancer or cancer of
the salivary glands
Oculur (Eye)….…………………….......Cataract
…………….…………………………....Pterygium

13. DNA & UV-B
 DNA absorbs UV-B radiation
 Changes shape in DNA
– Changes in the DNA molecule mean that
enzymes cannot “read” the DNA code
– Results in mutated cells or the cells die
 Cells have developed the ability to
repair DNA
– A special enzyme arrives at the damage
site
– removes the damaged section of DNA
– replaces it with the proper components
 This makes DNA somewhat resilient
to damage by UV-B

14. Aquatic Ecosystems

15. PLANTS

16. The influence of the UV-B radiation
on plant process.

17. Flowering
 UV-B radiation can alter
both the time of flowering
as well as the number of
flowers in certain species.
 Differences in timing of
flowering may have
important consequences
for the availability of
pollinators.
 The reproductive parts of
plants, such as pollen and
ovules are well shielded
from solar UV-B radiation.

18. Amphibians

19. UV-B Effects on Human Over exposure may:
– Increase risk of non-
melanoma and malignant
melanoma skin cancer
 Higher risks of
malignant melanoma
from severe
sunburns –
especially in
childhood
 Risk of malignant
melanoma has
increased 10%
 Risk of
nonmalignant
melanoma has
increased 26%
malignant
Non-malignant
www.ldeo.columbia.edu/.../ lectures/ozone_health/

20. -Suppress immune system
-Accelerate aging of skin due high exposure
-Cause an outbreak of rash in fair skin

21. Skin Protection
 Protect the skin against the solar radiation
using skin creams with SPF
– The greater the numerical value of the SPF the
greater the protection
 Use lip balm with SPF
 Cover up

22. cornea is encountered first
then the lens
vitreous humor
 Increases the risk of
cataracts
– Induces type of
protein that provokes
cleaving (splitting) in
the lens
– Leading cause of
blindness
– The prevalence of
cataract after age 30
is doubling each
decade
 Causes pterygium
Over Exposure to UV B….

23. Manifestations
of…
Cataracts
Pterygium
Cancer
brought on by
over exposure to
UV-B

24. Protection
 Sunglasses with 100% UV block
 Wrap around sunglasses
 Eye protection for children
 Hats

25. Images of Antarctica Taken Indicate A Slow
Recovery

26. Suggestions

27. What can an individual do to
reduce Ozone depletion
You can make a difference by these actions:
 Unplug electronics from the wall when not in use
 Don't use regular incandescent light bulbs
 Switch to compact fluorescent light bulbs
 Follow 3R Rule - Recycle, Reduce, and Reuse
 Avoid heavily packaged products
 Carpool, bike, or walk instead of driving alone
 Plant a tree
 Buy fresh produce at you local farmer's market
 Use energy efficient appliances
 Limit private vehicle driving
 Use eco-friendly household cleaning products
 Avoid using pesticides
 Developing stringent regulations for rocket launches
 .Banning the use of dangerous nitrous oxide

28. - PRESENTED by. Mr.P.R.TAMBE
- MMS IV sem.