1. THE OZONE LAYER Chrissi Williams Courtney Johnson Sarah Blankenship

2. WHAT IS OZONE AND WHAT DOES IT DO? Ozone, a gas, is a type of oxygen. Ozone molecules are made up of three oxygen atoms (0 3 ). Ozone is made by sunlight rays interacting with oxygen in the atmosphere. –Ozone photosynthesis is the process of creating ozone. When light splits oxygen atoms, ozone is formed. Ozone, though essential to our environment, can be detrimental to our health. Ozone is essential to our atmosphere because it protects Earth from harmful UV-B rays. Ozone absorbs these UV-B rays. Ozone is found in the stratosphere, 10-50 kilometers above the Earth’s surface. 90% of Earth’s ozone is located here. The remaining 10% is found in the troposphere. This is because of “wandering” ozone and ozone that is made by natural chemical reactions. (i.e., car exhaust, factory wastes)

3. WHAT ARE UV-B RAYS AND WHAT DO THEY DO? UV-B rays are a type of ultraviolet light. They come in wavelengths of 290-400 nanometers. This is shorter than visible light wavelengths. UV-B can cause sunburn, skin cancers, cataracts, and can even be harmful to the human immune system. UV-B rays are harmful to DNA. They are also harmful to crops and certain marine life: phytoplankton and surface dwelling fish. UV-B rays are harmful to crops because they interfere with the photosynthetic process. It can even cause changes in the current of the ocean; something that is dangerous to marine life. Ozone and UV-B rays have a “give and take” relationship. Just UV-B rays are attributed to the destruction of ozone, they are also needed to create ozone. This “give and take” creates an equilibrium of ozone levels.

4. WITHOUT OZONE Ozone is Earth’s natural sunscreen. Without it, Earth is susceptible to all of the harm of UV-B rays. Ozone also shields us from the solar winds. These winds, directed from the sun, are deadly to our planet. Only our atmosphere stand between us and the winds. Without ozone to protect us the following would suffer: –Crops, due to disruption of photosynthesis –Marine life –Humans, from skin cancers, cataracts, DNA mutations It has been estimated that even a 1% reduction in the amount of ozone in the stratosphere can cause significantly higher levels of radiation to reach Earth’s surface. The Scripps Institute of Oceanography have estimated that increased levels of radiation at the S. Pole have reduced phytoplankton growth by 1%.

5. OZONE DEPLETION Ozone depletion occurs naturally in the stratosphere, not only because of ultraviolet light, but because of natural chemicals in the atmosphere: volcanic eruptions, chlorine given off from oceans, & burning of trees. Natural occurrences, like the ones above, contribute to approximately 1/5 of ozone destroying chlorine. Chlorine, though a natural destroyer of ozone, has increased throughout the decades because of humans. Chlorofluorocarbons or CFCs are the primary depleters of ozone. They are man-made chemicals that are found in air conditioners (coolants), refrigerators, cleaning solvents and insulating foam. Once in the atmosphere, CFCs can last for 50-100 years. Another compound thought to be responsible for ozone depletion is bromine.

6. OZONE DEPLETION Other substances, such as carbon tetrachloride, which is used in dry cleaning, and methyl bromide, which is used as an insecticide, are believed to cause ozone depletion. Currently, replacements for ozone-depleting chemicals are being found. Some scientists argue that ozone depletion is natural, and that consequently ozone levels in our atmosphere fluctuate exceedingly. Because there are no records of ozone levels throughout the history of our planet, they say it is impossible to tell if the Earth often undergoes periods of ozone depletion. They also believe that ozone depletion could be caused not by humans, but by rises in methane of changes in the sun’s cycle. It was in the 1970s that it was first suggested that CFCs contributed to ozone depletion. However, it wasn’t until 1985, when members of the British Antarctic Survey first discovered the hole in the ozone. The hole is NOT an actual hole. It is an area of significantly reduced levels of ozone over the Antarctic (7-18 miles).

7. OZONE DEPLETION FACTS The amount of ozone lost over the Arctic is 6%; over the Antarctic there is more than 50% lost. One molecule of chlorine can destroy several molecules of ozone of the course of several years. UV-B rays have not been directly attributed to skin cancers or melanoma (the deadliest of skin cancers). The EPA has predicted an extra 200,000 skin cancer deaths in the U.S. by 2050

8. THE FIGHT AGAINST OZONE DEPLETION One of the first acts toward preventing further ozone depletion was in 1987, after the ’85 discovery of the ozone hole. The U.N. passed the ’87 Montreal Protocol on Substances That Deplete the Ozone Layer. This required all member nations of the U.N. to reduce CFC emissions by 50% by 1999. This act led to the need for complete banning of all CFCs by the year 2000, an agreement signed in 19991. Many European nations wanted complete phasing out of CFCs by 1997. Because most developing nations have a tendency to favor CFCs because of their cost-effectiveness, they have until 2010 to stop using CFCs entirely. $240 million dollars, in an international fund, is currently being used to help developing nations phase out CFCs entirely and find better substitutes. The cost has been estimated to be between $50-100 billion dollars.

9. OZONE RECOVERY The simplest ozone recovery plan is to do nothing. Many scientists feel optimistic that within 50-100 years all traces of CFCs will be gone from the atmosphere, and the ozone will begin to repair itself. Importing ozone to the stratosphere is out because ozone degrades once it come in contact with any surface. It wouldn’t get much farther than the troposphere, where “bad” ozone resides. Use of ozone depleting chemicals, such as CFCs have been banned throughout most of the world.

10. BIBLIOGRAPHY www.ozonelayer.noaa.gov www.epa.gov www.ecokids.org http://education.yahoo.com www.atm.eh.cam.ac.uk www.atmosphere.mpg.de www.bioshperical.com www.earthobservatory.nasa.gov All pictures courtesy of the internet http://www.epa.gov/airnow/- for up-to-date info on the ozone conditions across the globe!http://www.epa.gov/airnow/-