1. The ozone hole © NOAANOAA O O O © 2007 Paul Billiet ODWSODWS

2. Ultra Violet light © 2007 Paul Billiet ODWSODWS

3. UV light and life  UV light is high energy light  When it strikes molecules it can cause them to beak into ions or free radicals  The free radicals in turn damage large molecules such as proteins and DNA  Damage to DNA causes mutations  It is a mutagen  Mutations can lead to cancer © 2007 Paul Billiet ODWSODWS

4. UV light and life  UV light can have beneficial effects too  It stimulates the transformation dietary steroids into Vit D (calciferol)  UV light is used to sterilise foods and medical equipment  Some animals can see UV light  Insects use it to guide them to nectar sources in flowers © 2007 Paul Billiet ODWSODWS

5. UV light & DNA  UV-B has a direct effect on DNA  DNA absorbs UV light of 260nm  The action of UV forms thymine dimers  This can cause a gene mutation when the DNA replicates UV-B Thymine dimer ACGCTGGCTTAGT TGCGACCGAATGA ACGCTGGCT=TAGT TGCGACCGAATGA DNA © 2007 Paul Billiet ODWSODWS

6. Specific damage by UV light  Sunburn  Clouding of the cornea and formation of cataract  Skin cancer (melanoma)  Reduced rates of photosynthesis © 2007 Paul Billiet ODWSODWS

7. Ozone in the atmosphere  Ozone (O 3 ) forms under the effect of UV light in the stratosphere  Ozone can also form in the troposphere  Naturally it forms from volcanic activity  It is produced by motor vehicules so it is a pollutant  Sunlight acts on NOx to produce O 3 © 2007 Paul Billiet ODWSODWS

8. © AirparifAirparif Ozone pollution in the troposphere Safety limit

9. The ozone layer  Ozone is an unstable gas  It rapidly breaks down  The ozone layer is only a few cm thick  If the rate of breakdown is faster than the rate of formation the ozone layer thins  This could develop into hole  An ozone hole was first observed over the Antarctic in 1985 © 2007 Paul Billiet ODWSODWS

10. The cause of the hole  Chlorofluorocarbons (CFCs)  The breakdown under the effect of UV light to release chlorine radicals (Cl)  Especially under cold conditions  The chlorine radicals react with O 3 converting it to O 2 and more radicals ClO © 2007 Paul Billiet ODWSODWS

11. What are CFCs?  Used as propellants in aerosol spray cans  Used as refrigerants in fridges, freezers and air conditioning units © 2007 Paul Billiet ODWSODWS

12. What can be done?  Reduce the use of CFCs  They are already banned in aerosols (1987)  BUT they are still used as refrigerants  Recycle fridges and air conditioning plants © 2007 Paul Billiet ODWSODWS

13. The current situation  The holes developing over the pole suggest that they may be show an improvement  BUT CFC molecules take 30 years to rise up to the stratosphere  The chlorine radicals last a long time  The peak ozone damage was supposed to be in 2000  Damage could go on another 50 years © 2007 Paul Billiet ODWSODWS

14. The biggest yet September 2006 © NASANASA