Презентация по теме Pressing problems

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  Ecological problems
  

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  Atmospheric pollution raises problems of several types.
  First, there are local problems due to the production of smoke and offensive gases by factories.
  

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  Secondly, there are regional problems created by industrial agglomerations
  which may spread the same harmful effects over whole areas.
  

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  Thirdly, there are some types of pollution, such as those arising from nuclear explosives, which cover a considerable portion of the globe.
  

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  And lastly, there appeared one more type of pollution which is threatening the globe as a whole.
  

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  Recent scientific research suggests that the protective layer of ozone around our planet is under severe attack.
  

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  Alarm bells were sounded in 1982 when researchers in the Antarctic first identified a yawning hole over the Antarctic where the ozone layer is thinnest.
  

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  The major cause of this weakening of the ozone layer is believed to be the increasing
  amount of harmful chemicals that are being released into the atmosphere by humankind.
  

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  Environmentalists and scientists point out that a further one per cent drop in the overall ozone layer can cause an increase of skin cancer.
  

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  The appearance of the Antarctic hole has intensified the search for a cause. Strong evidence now suggests that it is the growing industrial use of chlorine compounds called chlorofluorocarbons (CFCs) which is responsible. CFC is a propel lent gas commonly used in aerosol sprays, air cooling systems in fridges and air-conditioning.
  

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  Researchers suggest that the level of CFCs in the atmosphere
  is actually increasing by 5 per cent each year.
  

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  Since 1969 the ozone level has fallen by 3 pen cent over the densely populated cities of the US,
  Canada and Europe and by 4 per cent over Australia and New Zealand.
  

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