effects of cfcs
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8/7/2019 Effects of CFCs
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Effects of CFCs
Environment
y CFCs, when released from the surface of the Earth, rise slowly into the stratosphere.
y They are bombarded by the incoming UV light from the Sun, releasing the chlorineatoms from the parent compound
y Which can then react with the ozone molecules (Figure 1)
y Eventually the chlorine atom is removed from the atmosphere by other reactions.
Figure 1: The destruction of stratospheric ozone (6) y Chlorofluorocarbons (which are used in aerosols, refrigerants, and other industrial
products) are remarkably inert and nonreactive.Indeed, it is because of these
characteristics---specifically because they are nontoxic and nonflammable---that they
were invented.
y But when they eventually rise into the stratosphere, they are
decomposed by solar ultraviolet radiations into free chlorine
atoms:
Chlorofluorocarbon Cl,
Cl + O3 ClO + O2,
ClO + O Cl + O2.
The chlorine atoms are recycled in these reactions, and are then free to attack other ozone
molecules. A single chlorine atom, released by the action of UV radiation on
chlorofluorocarbons, is capable of destroying catalytically tens of thousands of ozone
molecules during its residence in the stratosphere.It attributes to an increasing hole in the
ozone layer in the atmosphere above Antarctica, coupled with growing evidence of global
ozone depletion!
Health
Since the appearance of an ozone hole over the Antarctic in the early 1980s, Americans
have become aware of the health threats posed by ozone depletion, which decreases our
atmosphere's natural protection from the sun's harmful ultra-violet (UV) rays.
y Skin Cancer
- Basal Cell Carcinomas are the most common type of skin cancer tumors. They usually
appear as small, fleshy bumps or nodules on the head and neck, but can occur on other
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s
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Basal cell carc¡ ¢ ¦ §
a grows slowly ̈
and rarely s©
reads to
other parts of the body¥
It can, howeve r, penetrate to the bone and
cause cons ¡ derable damage ¥
- Squam
us C ell Car i
mas are tumors that may appear as nodules
or as red, scaly patches ¥
his cancer can develop into large masses,
and unlike basal cell carcinoma, it can spread to other parts of the
body ¥
y Catar acts and Other Ey e Damage
Cataracts are a form of eye damage in which a loss of transparency in the lens of the
eye clouds vision. If left untreated, cataracts can lead to blindness.
y I mmune Suppressi n
Scientists have found that overe posure to UV radiation may suppress proper
functioning of the body s immune system and the skin's natural def enses.
How to o o ?
Substitut s fo C Cs
y The only long term solution to solve the problem of depletion of th e ozone layer is to
phase out the use of CFCs (Montreal Protocol of 1987 and subsequent modifications
y Some CFCs can be replaced by HCFCs (hydrochlorofluorocarbons ! , compounds
containing at least 1 H atom.
y The C-H bond makes these compounds more reactive in the atmosphere so they are
destroyed more quickly and so are less able to diffuse into the stratosphere
Name Fo"
mula Code Uses
chlorodifluoromethane CHClF2 HCFC-22
air conditioning,
refrigeration,
foams
1-chloro-1,1-difluoroethane CClF2CH3 HCFC-142b aerosols
1,1-difluoroethane CHF2CH3 HCFC-152aaerosols,
refrigeration