Fortaleza, Joji Bryan Manongdo, Marc JulianMercado, Chino Karmelo Pilotin, Pamela Anne
Ozone Layer It is a layer in Earths atmosphere which contains relatively high concentrations of ozone (O3). The ozone layer resides in the stratosphere and surrounds the entire Earth. It was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson.
Ozone is constantly produced from O2 molecules because of its reaction with UV light. O2 molecules are more scattered because the stratosphere has less air. Stratospheric ozone protects us from excess UV but ozone in the lower atmosphere is an air pollutant with harmful effects on the respiratory systems of animals and will burn sensitive plants.
UV-B radiation (280- to 315- nanometer (nm) wavelength) from the Sun is partially absorbed in this layer. As a result, the amount of UV-B reaching Earth’s surface is greatly reduced. UV-A (315- to 400-nm wavelength) and other solar radiation are not strongly absorbed by the ozone layer.
Ozone Depletion The ozone layer can be depleted by free radical catalysts: nitric oxide (NO) nitrous oxide (N2O) hydroxyl (OH) atomic chlorine(Cl) atomic bromine (Br)
Concentrations of chlorine and bromine have increased in recent years due to the release of large quantities of man-made organohalogen compounds, especially chlorofluorocarbons (CFCs) and bromofluorocarbons (BFCs). CFCs and BFCs are capable of surviving the rise to the stratosphere due to their stability, where Cl and Br radicals are liberated by the action of ultraviolet light.
The Chlorofluorocarbons are expelled into the atmosphere by: Refrigeration Aerosol spray cans Air conditioning Foam insulation Cleaning agents Packing material CFCs were used in consumer products because they were chemically stable and non-toxic, thus it took decades before it was known to destroy the ozone layer.
Each radical is then free to initiate and catalyze a chain reaction capable of breaking down over 100,000 ozone molecules. The breakdown of ozone in the stratosphere results in the ozone molecules being unable to absorb ultraviolet radiation. Consequently, unabsorbed and dangerous UVB radiation is able to reach the Earth’s surface.
Though it is known that ozone is naturally decomposed to O2, the presence of Cl atoms in the stratosphere serves as a catalyst to the breakdown of ozone thus making the rate of decomposition faster.
The Ozone Hole The ozone "hole" is really a reduction in concentrations of ozone high above the earth in the stratosphere. It is defined geographically as the area wherein the total ozone amount is less than 220 Dobson Units. The ozone hole has steadily grown in size (up to 27 million sq. km.) and length of existence (from August through early December) over the past two decades.
Each spring in the stratosphere over Antarctica (Spring in the southern hemisphere is from September through November.), atmospheric ozone is rapidly destroyed by chemical processes. As winter arrives, a vortex of winds develops around the pole and isolates the polar stratosphere. When temperatures drop below - 78°C (-109°F), thin clouds form of ice, nitric acid, and sulphuric acid mixtures. Chemical reactions on the surfaces of ice crystals in the clouds release active forms of CFCs. Ozone depletion begins, and the ozone “hole” appears.
Over the course of two to three months, approximately 50% of the total column amount of ozone in the atmosphere disappears. At some levels, the losses approach 90%. This has come to be called the Antarctic ozone hole. In spring, temperatures begin to rise, the ice evaporates, and the ozone layer starts to recover.
Consequences of Ozone Depletion Every time 1% of the ozone layer is depleted, 2% more UV-B is able to reach the surface of the planet Human exposure to UV-B increases the risk of the following diseases: Skin cancer particularly in Caucasians Cataracts Increased rates of malaria and other infectious diseases. Suppressed immune system
The environment will also be negatively affected by ozone depletion. Physiological and developmental processes of plants are affected by UVB radiation. Effects on animals will also be severe, and are very difficult to foresee. Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms.
Solar UVB radiation has been found to cause damage to early developmental stages of fish, shrimp, crab, amphibians and other animals. The most severe effects are decreased reproductive capacity and impaired larval development. Other ecosystems such as forests and deserts will also be harmed Wind patterns could change, resulting in climatic changes throughout the world.
Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important trace gases e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere- atmosphere feedbacks that attenuate or reinforce the atmospheric buildup of these gases.
Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation. Any increase in solar UVB levels will therefore accelerate their breakdown, limiting the length of time for which they are useful outdoors. Ozone depletion will also magnify the effects of global warming.
The Montreal Protocol In 1985, the Vienna Convention established mechanisms for international co-operation in research into the ozone layer and the effects of ozone depleting chemicals (ODCs). The first discovery of the Antarctic ozone hole happened in 1985. The Montreal Protocol on Substances that Deplete the Ozone Layer was negotiated and signed by 24 countries and by the European Economic Community in September 1987.
The Protocol called for the Parties to phase down the use of CFCs, halons and other man-made ODCs. After a series of rigorous meetings and negotiations, the Montreal Protocol on Substances that Deplete the Ozone Layer was finally agreed upon on 16 September 1987 at the Headquarters of the International Civil Aviation Organization in Montreal.
The Montreal Protocol stipulates that the production and consumption of compounds that deplete ozone in the stratosphere-- chlorofluorocarbons (CFCs), halons, carbon tetrachloride, and methyl chloroform--are to be phased out by 2000 (2005 for methyl chloroform). Scientific theory and evidence suggest that, once emitted to the atmosphere, these compounds could significantly deplete the stratospheric ozone layer that shields the planet from damaging UV-B radiation.
The Montreal Protocol on Substances that Deplete the Ozone Layer is one of the first international environmental agreements that includes trade sanctions to achieve the stated goals of a treaty. It also offers major incentives for non-signatory nations to sign the agreement. The treaty negotiators justified the sanctions because depletion of the ozone layer is an environmental problem most effectively addressed on the global level.
Furthermore, without the trade sanctions, there would be economic incentives for non-signatories to increase production, damaging the competitiveness of the industries in the signatory nations as well as decreasing the search for less damaging CFC alternatives. At meetings in London (1990), Copenhagen (1992), Vienna (1995), Montreal (1997) and Beijing (1999) amendments were adopted that were designed to speed up the phasing out of ozone-depleting substances.
Summary of Montreal Protocol Control Measures ODS Developed Countries Developing Countries CFCs Phased out end of 1995 a Total phase out by 2010 Halons Phased out end of 1993 Total phase out by 2010 CCl4 Phased out end of 1995 a Total phase out by 2010 Methyl chloroform Phased out end of 1995 a Total phase out by 2015 HCFCs Freeze from 1996 b Freeze in 2016 35% reduction by 2004 Total phase out by 2040 65% reduction by 2010 90% reduction by 2015 Total phase out by 2020 c
HBFCs Phased out end of 1995 Phased out end of 1995 Methyl bromide Freeze in 1995 Freeze in 2002 at average at 1991 base level d 1995-1998 base level 25% reduction by 1999 20% reduction by 2005 e 50% reduction by 2000 Total phase out by 2015 70% reduction by 2001 Total phase out by 2005 a With the exception of a very small number of internationally agreed essential uses that are considered critical to human health and/or laboratory and analytical procedures. b Based on 1989 HCFC consumption with an extra allowance (ODP weighted) equal to 2.8% of 1989 CFC consumption. c Up to 0.5% of base level consumption can be used until 2030 for servicing existing equipment. d All reductions include an exemption for pre-shipment and quarantine uses. e Review in 2003 to decide on interim further reductions beyond 2005.
Becoming Ozone Friendly All parts of our daily lives have been touched by ozone-depleting substances. Prior to the 1980s, CFCs and other ozone-depleting substances were pervasive in modern life. But thanks to the work of individuals, businesses, organizations, and governments around the world, substitutes that are safer for the ozone layer continue to be developed for many ozone-depleting substances. The phase out of ozone-depleting substances has also made a substantial contribution toward the reduction in greenhouse gas emissions since their global warming potential is very high.
Then: Ozone-depleting substances were all around us.Now: More ozone-friendly products, better processes, and new equipment are in use.Computers Then: Solvents containing CFCs and methyl chloroform were used to clean circuit boards during their production. Now: Some companies have eliminated the need to clean circuit boards during their production. Others use water or have temporarily switched to HCFCs.
Polystyrene Cups and Packing Peanuts Then: Some polystyrene cups and foam packing “peanuts” were made using CFCs. Now: These products are made with materials that do not deplete the ozone layer.Aerosol Cans Then: CFCs were the propellant used in various spray cans. Now: Pumps and alternative propellants using hydrocarbons are being used.
Central Air Conditioners Then: CFCs were used as the coolant in household air conditioners. Now: HCFCs and HFCs have replaced CFCs.Degreasers Then: CFCs or methyl chloroform were used in many solvents for degreasing. Now: Water-soluble compounds and hydrocar- bon degreasers that do not deplete the ozone layer are available for many applications.
Refrigerators Then: CFCs were used in refrigerator coolants and foam insulation. Now: HFCs have replaced CFCs, and substitutes are on the horizon that will have reduced greenhouse gas impacts.Car Air Conditioners Then: CFCs were used as the coolant in automobile air conditioners. Now: HFCs have replaced CFCs.Fire Extinguishers
Fire Extinguishers Then: Halons were commonly used in hand-held fire extinguishers. Now: Conventional dry chemicals, which don’t deplete the ozone layer, and water have replaced halons. HFCs are also used.Furniture Then: Foam-blowing agents containing CFCs were used in furniture making. Now: Water-blown foam is being used.
Safety against UV Ultra-violet light (UV) is defined as electromagnetic radiation in the spectral region between 180 and 400 nanometers (nm). Immediate or prolonged exposure to UV light can result in painful eye injury, skin burn, premature skin aging, or skin cancer. Individuals who work with or in areas where UV sources are used are at risk for UV exposure if the appropriate shielding and protective equipment are not used.
Some Sources Welding operations Biological laboratories where gels are visualized Areas in which germicidal UV lights are used, including biological safety cabinets Libraries where UV light may be used to examine documents Science laboratories where Mineralights are used to cause fluorescence Mercury vapour lamps with broken or missing envelopes
The symptoms of UV overexposure to the skin are well known and characteristically called sunburn. However, the symptoms of overexposure to the eyes are not widely known. Symptoms are: a burning and painful sensation in the eye a sensitivity to light the sensation of a foreign object in the eye, sometimes described as sand in the eye tearing
Protection The purpose of the UV Light Safety Program is to ensure that the safeguards necessary to limit exposure have been implemented. The key to effectively reducing UV exposure is to properly shield the source and to require that users wear the appropriate personal protection. Personal protection that is appropriate includes welder’s masks, goggles and face shields.
Protection from ultraviolet (UV) radiation is important all year round, not just during the summer or at the beach. UV rays from the sun can reach you on cloudy and hazy days, as well as bright and sunny days. UV rays also reflect off of surfaces like water, cement, sand, and snow. Indoor tanning (using a tanning bed, booth, or sunlamp to get tan) exposes users to UV radiation. The hours between 10 a.m. and 4 p.m. daylight savings time are the most hazardous
Safety Measures Seek shade, especially during midday hours. Wear clothing to protect exposed skin. Wear a hat with a wide brim to shade the face, head, ears, and neck. Wear sunglasses that wrap around and block as close to 100% of both UVA and UVB rays as possible. Avoid indoor tanning.
Use sunscreen with sun protective factor (SPF) 15 or higher, and both UVA and UVB protection. Some make-up and lip balms contain some of the same chemicals used in sunscreens. If they do not have at least SPF 15, dont use them by themselves. To reduce the harm from UV radiation, the most important thing is to minimize direct exposure of the skin and the eyes to sunlight.