1. Ozone Depletion

2. Ozone Layer Ozone layer absorbs 97% to 99% of ultraviolet (UV) radiation from the sunOzone layer absorbs 97% to 99% of ultraviolet (UV) radiation from the sun 78% nitrogen gas 78% nitrogen gas 21% oxygen gas 21% oxygen gas 1% other gases 1% other gases OZONE DEPLETION

3. Ozone  a 3-atom molecule of oxygen (O 3 ) This is a completely different compound than the oxygen we breathe (O 2 ). Ozone is actually a toxic gas when given off at ground level. OZONE DEPLETION

4. Chlorofluorocarbons (CFCs)  The major problem: After a chlorine (Cl) atom removes an oxygen molecule from O 3 it is able to separate from the lone oxygen atom and combine with another O 3 molecule, so the process continues over and over and over again (up to 100 years). Chemicals once used in aerosol cans, plastics, and refrigerators that are now mostly banned. CFCs break up the ozone layer. OZONE DEPLETION CAUSES:

5. After breaking down an ozone molecule, the chlorine atom frees itself from the oxygen atom to restart the reaction. OZONE DEPLETION

6. Without the ozone layer larger amounts of UV rays can reach the earth and potentially cause cancer in humans, cause cataracts (damage eye-sight), and affect crop growth. UV induces skin cancer by causing mutations in DNA.UV induces skin cancer by causing mutations in DNA. The United Nations Environment Program estimates that a sustained 1 percent depletion of ozone will ultimately lead to a 2-3 percent increase in the incidence of non-melanoma skin cancer.The United Nations Environment Program estimates that a sustained 1 percent depletion of ozone will ultimately lead to a 2-3 percent increase in the incidence of non-melanoma skin cancer. OZONE DEPLETION

7. Overexposure to UV radiation can change the flowering times of some kinds of plants and therefore will affect the animals that depend on them. Marine organisms living in shallow water experience damaging levels of UV radiation. A healthy green sea urchin embryo appears above left. A UV-irradiated green sea urchin embryo (above right) displays an abnormal, extruded gut. UV radiation also impairs the process of photosynthesis in plants.

8. Since the Montreal Protocol, is the ozone layer completely back to normal? OZONE DEPLETION SOLUTIONS: The good news is that CFCs have been banned and can no longer damage the ozone layer Montreal Protocol treaty including over 200 countries has banned the use of CFCs. The ozone layer is predicted to make a recovery to what it was in 1980 by 2050

9. UV INDEX http://www2.epa.gov/sunwise/uv-index CLIP http://www.epa.gov/ozone/science/movies/f orecastearth_3_300.wmvhttp://www.epa.gov/ozone/science/movies/f orecastearth_3_300.wmv OZONE DEPLETION