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However, these precautions will become more important as ozone depletion worsens. UVB has been linked to many harmful effects , including skin cancers, cataracts, and harm to some crops and marine life. Scientists have established records spanning several decades that detail normal ozone levels during natural cycles.
Ozone concentrations in the atmosphere vary naturally with sunspots, seasons, and latitude. These processes are well understood and predictable. Each natural reduction in ozone levels has been followed by a recovery.
Beginning in the s, however, scientific evidence showed that the ozone shield was being depleted well beyond natural processes. When chlorine and bromine atoms come into contact with ozone in the stratosphere, they destroy ozone molecules.
One chlorine atom can destroy over , ozone molecules before it is removed from the stratosphere. Ozone can be destroyed more quickly than it is naturally created. Some compounds release chlorine or bromine when they are exposed to intense UV light in the stratosphere.
These compounds contribute to ozone depletion, and are called ozone-depleting substances ODS ODS A compound that contributes to stratospheric ozone depletion. ODS include chlorofluorocarbons CFCs , hydrochlorofluorocarbons HCFCs , halons, methyl bromide, carbon tetrachloride, hydrobromofluorocarbons, chlorobromomethane, and methyl chloroform. ODS are generally very stable in the troposphere and only degrade under intense ultraviolet light in the stratosphere.
When they break down, they release chlorine or bromine atoms, which then deplete ozone. ODS that release chlorine include chlorofluorocarbons chlorofluorocarbons Gases covered under the Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone.
These gases are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol.
All these substances are also greenhouse gases. See hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, ozone depleting substance. CFCs , hydrochlorofluorocarbons hydrochlorofluorocarbons Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons CFCs.
They have been introduced as temporary replacements for CFCs and are also greenhouse gases. See ozone depleting substance. HCFCs , carbon tetrachloride carbon tetrachloride A compound consisting of one carbon atom and four chlorine atoms. Carbon tetrachloride was widely used as a raw material in many industrial uses, including the production of chlorofluorocarbons CFCs , and as a solvent. Solvent use ended when it was discovered to be carcinogenic.
It is also used as a catalyst to deliver chlorine ions to certain processes. Its ozone depletion potential is 1. Methyl chloroform is used as an industrial solvent. Its ozone depletion potential is 0. ODS that release bromine include halons halons Compounds, also known as bromofluorocarbons, that contain bromine, fluorine, and carbon. They are generally used as fire extinguishing agents and cause ozone depletion. Bromine is many times more effective at destroying stratospheric ozone than chlorine.
Methyl Bromide is an effective pesticide used to fumigate soil and many agricultural products. But more work is needed to address other substances, in particular methyl bromide and HCFCs. More than 99 percent of ODS have been phased out by the Montreal Protocol over the last 30 years, and the ozone layer is on track to recover by mid-century. Up to 2 million cases of skin cancer may be prevented globally each year by Importantly, more than billion tonnes of carbon dioxide equivalent emissions have been averted, making the Montreal Protocol an important force to combat climate change.
The GEF has responded to new chemicals conventions and the movement towards integration and synergies among the conventions by evolving its strategy to accommodate these transitions. The Chemicals and Waste Focal Area will support the reduction of POPs that are controlled by the Stockholm Convention on Persistent Organic pollutants, mercury and mercury compounds that are controlled by the Minamata Convention on Mercury, Ozone Depleting Substances and other chemicals controlled by the Montreal Protocol on Substances that deplete the Ozone Layer, lead in paints, chemicals of global concern in the supply chain of commercial and domestic products and highly hazardous pesticides that enter the global food supply.
A fully integrated focal area that is better aligned with sectoral investments in countries to address pollution, agriculture, and industrial efficiency can better attract the private sector and link to efforts on increasing environmental sustainability in these sectors, since the actions will be based on sectors rather than targeting a single chemical.
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