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Ozone Depletion
Formation of Ozone
O2 + UV O + O
O + O2 O3 (Ozone)
Chlorofluorocarbons - CFC’s
Principle Cause of Ozone Depletion
Once used in: •Air conditioners •Refrigerators •Aerosol Sprays •Plastic Foams
CFCs are used in aerosol sprays CFCs were used as refrigerants in the past
Chemical Reactions
* CFCl3 + UV ➔ Cl• + CFCl2
* ClO• + O• ➔ O2 + Cl• * Cl• + O3 ➔ O2 + ClO•
Other Ozone-Destroying Chemicals
Methyl Bromide – Pesticide
Halons -Fire Extinguishers
HCFC’s - Refrigerants
Carbon Tetrachloride & Methyl Chloroform – Solvents
Present situation
� Stratospheric ozone over Antarctica:– Has been depleted over the last 15 years– The ozone hole:
� enlarging� large enough to cover most of the North America� would take at least 50 years to restore
Effects of Air Pollution Summary • Respiratory Problems - coughing, bronchitis,
asthma, emphysema, cancer • Cardiovascular Problems - CO • Nerve Damage - Hg and Pb• Tree damage • Acidify lakes • Damage concrete, statues
Effects of UV
• Sunburn• Accelerated Aging (wrinkles, sun spots)• Depresses immune system • Cataracts Clouding of Lens of Eye
(400,000 new cases/year US (1 in 49 people)
Causes of ozone depletion� Details are not fully understood� Catalyzed by halocarbons (carbon compounds
containing fluorine, chlorine, bromine and iodine)– Examples: CFCs and ClONO2
� Halogen atoms catalyze ozone layer depletion by destroying ozone molecules and forming oxygen molecules.
� Much more serious in Antarctica than other regions on the planet
Consequences of less ozone
� Because CFCs has long life span and very stable, it continuous to attack the ozone layer and more UV reach our earth.
Food supply
� Reduce photosynthesis - crops affected.
� Kills plankton fish ↓
Ozone Depletion ≠ Global Warming