The quantity of ozone in the Antarctic stratosphere, more than 40,000 feet (12,000m) up, has fallen to only 40 per cent of its usual level, according to measurements at the British Antarctic Survey's Faraday and Halley research stations. A German research station claims levels have dropped to 30 per cent.
Since the late 1970s, a hole has opened in the layer each Antarctic spring, which happens at this time of year. 'This year it has happened much earlier . . . and the rate of depletion of the ozone is higher,' Jonathan Shanklin, a meteorologist at the survey's Cambridge headquarters, said.
Industrial chemicals, notably chlorofluorocarbons (CFCs), are to blame for the loss of the ozone gas which prevents the sun's harmful ultraviolet radiation reaching the earth's surface.
The CFCs drift up to the stratosphere and, in a complex series of reactions, release chlorine which breaks down the ozone.
Scientists believe that the eruption of Mount Pinatubo in the Philippines last year is partly to blame for this year's record hole. Tiny particles of sulphuric acid released by the volcano provide surfaces on which the ozone-depleting chemical reactions take place.
But the fact that the situation is still worsening after two international agreements to control CFCs puts pressure on ministers to agree much stronger controls when they meet in Denmark in November to renegotiate the Montreal Protocol for protecting the ozone layer.Reuse content