Ms. Pride
Regents Biology
Human Impact Presentation
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Ozone (O3) : The ozone layer is a layer of the
upper atmosphere that blocks out harmful UV
rays.
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Between 20 and 50 kilometers above the Earth’s
surface
Absorbs most of the harmful UV light from sunlight
before it reaches the Earth’s surface
Ozone depletion: the gradual thinning of the
ozone layer and the decline of the total amount
of ozone remaining in the Earth's atmosphere
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The main cause of ozone layer depletion was the
emission of CFCs (Chloroflurocarbons) containing
chlorine.
CFCs escape into the atmosphere from refrigeration
and propellant devices and other chemical processes
CFCs eventually end up in the stratosphere, where UV
light breaks the bond holding chlorine atoms (Cl) to the
CFC molecule.
A free chlorine atom goes on to participate in a series
of chemical reactions that both destroy ozone and
return the free chlorine atom to the atmosphere to
cause more damage.
These are all the major forms
of chlorine being put into the
stratosphere.
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Predictions of
chlorine
concentrations in the
stratosphere.
These predictions
lead to policy
reform.
Extent of the Problem:
Average yearly size of the ozone hole
This shows how the size of the ozone hole varies year to year, and
that recently the trend has been that the hole has fluctuated in size.
Health Effects as a Result of
Ozone Layer Depletion
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UV light is a major factor to skin cancer:
 UV light damages DNA
 Hole is centered over Antarctica and over the Artic
 If holes start to form over areas like cities and
beaches, there will be a rapid increase in the number
of patients with skin cancer.
UV light also affects plant vascular tissue.
Plankton is one of the most important parts of a
fundamental aquatic food chain.
 If plankton were to become extinct because eof an
inability to reproduce and pass in genetic
information, then almost all the other organisms in
the aquatic ecosystem would be effected.
Solutions and Policy Reform
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Montreal Protocol (meeting of forty-six
nations) called for the immediate resduction in
production and use of CFCs by the year 2000.
US passed law to ban use of CFCs in aerosol
cans by 2000.
Check to ensure aerosols and refrigeration
chemicals are CFC-free.
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http://ozonewatch.gsfc.nasa.gov/index.html
http://www.cpc.ncep.noaa.gov/products/stratosphere/winter_b
ulletins/sh_07/Fig_3.gif
http://en.wikipedia.org/wiki/Image:Sources_of_stratospheric_c
hlorine.png
http://www.epa.gov/ozone/
http://www.atm.ch.cam.ac.uk/tour/part3.html
http://www.nas.nasa.gov/About/Education/Ozone/history.htm
l
http://www.cpc.ncep.noaa.gov/products/stratosphere/winter_b
ulletins/sh_07/Fig_3.gif