• Ozone molecules are natural substance in the upper
atmosphere known as the stratosphere. It is in between
19 to 30 kilometer above the Earth surface.
• The ozone layer helps shield harmful Ultraviolet Rays
from the sun.
• Ozone layer is measured in Dobson Unit. The normal
thickness of the ozone layer should be 300 Dobson Unit
• A slow and steady declination of the ozone layer is known
as ozone depletion
Cause of Ozone Depletion
• Doctor Molina and Rowland found out that
chlorofluorocarbon is depleting the ozone layer in
1974. However, no one believe them until the ozone
layer in Antarctic depletes in 1985
• Chlorofluorocarbon are man-made chemicals that
contains chlorine which depletes the ozone layer.
• Chlorofluorocarbon would be released to the
• The chlorofluorocarbon would release chlorine
when sunlight break them down
• The chlorine would change the ozone layer into
oxygen when the chlorine hit them
• Ozone depletion would happen if the ozone layer is
depleted faster than it can recover. There would be
an ozone hole if the ozone layer falls below 200 DU
• Chlorofluorocarbon can remain in the atmosphere
for 20 to 100 years
• The ozone layer is depleting at a rate of 3% from
1979 to 1991
• Places like North America, Europe, Russia,
Australia, New Zealand and South America is facing
• Global warming is predicted to let the hole in the
ozone layer at Antarctic grow larger in the decades
Consequence of Ozone Depletion
• The ozone layer help shield Ultraviolet Rays.
Without it, there will be dangers including
– Risk in human health
– Disruption of ecosystem in marine
– Disruption in plant growth
Risk in human health
• Ultraviolet rays can cause skin cancers. It is
predicted that more than 60000000 Americans will
get skin cancer because of the Ultraviolet rays
• Ultraviolet rays may also damage immune system.
People are prone to have infectious diseases. It can
even cause eyes disorder
Disruption of ecosystem in marine
• In the ocean, plankton is the foundation of marine
food webs. There are the main source of food in the
• The Plankton don’t have protective outer layers, so
they were highly sensitive to Ultraviolet rays. Marine
life would be disrupted if the plankton were killed.
• Marine animals will die when exposed to Ultraviolet
radiation. Food web is disrupted as predators have
no preys to prey on.
Disruption in plant growth
• The Ultraviolet rays can kill plants which are the
food producer. This would disrupt food web. Plants
also help redeem oxygen.
• Crops like rice would also die. This could cause
shortage of food