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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