1. Ozone – molecule made of 3 oxygen atoms.
The Ozone Shield
The ozone layer is an area in the stratosphere where ozone is highly concentrated. It absorbs most of the UV rays from the sun.
Ozone – molecule made of 3 oxygen atoms.

2. Ozone Depletion
Chlorofluorocarbons (CFCs) – human-made chemical once used as:
Coolants in refrigeration & air conditioning
Gassy fizz for making plastic foams
Propellant in spray cans
CFCs –break down in the stratosphere and destroy ozone molecules.
A single CFC can destroy 100,000 ozone molecules.
Remain active in the stratosphere for up to 120 years.

3. The Ozone Hole
The ozone hole is a thinning of stratospheric ozone that occurs over the poles during the spring.

4. Why is the ozone hole over the poles?
It is so cold at the poles during winter that clouds are able to form in the stratosphere (polar stratospheric clouds).
CFCs travel into the stratosphere on these clouds.

5. Negative Effects of Ozone Depletion
Humans & Land Animals
Skin cancers
Premature aging of skin
Cataracts
Weakened immune system
Amphibians
Death of eggs
Genetic mutations
Reduced Populations
Marine Life
Disruption of food chain (death of surface plankton & photosynthesizers)
Land Plants
Photosynthesis interference
Reduced crop yields

6. Protecting the Ozone Layer
Montreal Protocol – agreement among nations to limit the production of CFCs.
Developed nations agreed to eliminate CFCs by 1995.
Aerosol cans no longer use CFCs as propellants
Air conditioners and refrigerators are CFC-free