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[00:01.00]The hole in the protective ozone layer over Antarctica has grown bigger this year than at any time since scientists began measuring it fifteen years ago.
[00:13.72]Ozone gas in the upper atmosphere blocks harmful ultraviolet radiation from the sun.
[00:21.89]Ozone helps protect people from the sun's harmful ultraviolet rays.
[00:28.01]Too much of this radiation can cause skin cancer or damage the eyes.
[00:35.14]U-V radiation can also threaten agriculture and the environment.
[00:41.30]Scientists say they are concerned that low ozone levels in the upper atmosphere could threaten heavily populated areas around the world.
[00:51.75]In the Nineteen-Seventies,scientists expressed concern about man-made chemicals called chlorofluorocarbons.
[01:00.90]They said these C-F-Cs were destroying the protective ozone layer.
[01:07.11]C-F-Cs destroy ozone in the presence of sunlight.
[01:13.28]They were once widely used in aerosol sprays and in cooling equipment.
[01:19.44]But most countries agreed to stop producing C-F-Cs after a worldwide ban in the late Nineteen-Eighties.
[01:29.60]Over the years,scientists have observed a huge loss in ozone over Antarctica.
[01:36.79]Antarctica is the ice-covered continent that covers and surrounds the South Pole.
[01:43.97]The loss of ozone takes place during its extremely cold winter season from June until September.
[01:52.10]Scientists believe that sunlight causes chemical reactions in the cold air over Antarcitica that can destroy ozone.
[02:02.28]This creates a huge ozone hole.
[02:05.57]The hole gets smaller as temperatures begin to rise in November.
[02:11.79]The temperature over Antarctica affects the size of the hole each year.
[02:18.92]The National Oceanic and Atmospheric Administration said that the ozone hole increased to more than twenty-seven-million square kilometers for a few days last month.
[02:33.11]Scientists say this is the largest size ever recorded.
[02:39.27]It is an area about the size of North Amercia.
[02:44.44]Record low temperatures in the upper atmosphere are believed to the cause.
[02:51.58]For several years,the hole has extended over populated areas at the southern end of South America.
[03:00.74]This year,cities in Chile and Argentina were hit with dangerous levels of ultraviolet radiation.
[03:09.99]And experts say it is possible that the situation could affect areas in South Africa,Australia or New Zealand.
