Environmental Engineering Reference
In-Depth Information
50
Washington
Oregon
Montana
South
Dakota
Vermont
Wisconsin
Delaware
DC
40
New Mexico
Kansas
Tex a s
30
Florida
20
Annual deaths from skin cancer per 100,000 people
Figure 10.3
Annual deaths from skin cancer per 100,000 white males in the United States, compiled
before thinning of the ozone layer. A latitudinal control is evident. (Department of Health
and Human Services)
carbons (CFCs). They have been extensively used as refrigerants in
refrigerators and air conditioners, for cleaning electronic circuit boards,
in the manufacture of foams used for insulation, in insecticide and hair
spray cans as propellants, and in rigid polystyrene plastic drinking cups.
Liquid CFCs are volatile chemicals and leak easily into the air. They
rise in the atmosphere, and in a few years, they reach the ozone layer,
where they remain for many decades, even under bombardment by UV
radiation. Some types of CFCs can last in the ozone layer for more than
a hundred years. They are destroyed very slowly by the UV rays, which
separate the chlorine atoms from the rest of the CFC molecule. There
are now fi ve times more chlorine atoms in the upper atmosphere than
before CFCs were invented. Chlorine attacks ozone, and each chlorine
