The ozone hole is larger in 2008 than the previous year but is not expected to reach the size seen two years ago, the World Meteorological Organisation said Tuesday.

"In 2008, the ozone hole appeared relatively late. However, during the last couple of weeks it has grown rapidly and has now passed the maximum size attained in 2007," the WMO said in a statement.

The hole in the layer over the Antarctic was discovered in the 1980s. It regularly tends to form in August, reaching its maximum size late September or early October before it fills again in mid-December.

The size it reaches is dependent on weather conditions.

Experts warned that such is the damage to the ozone layer, which shields the Earth from harmful ultra-violet rays, it will only attain full recovery in 2075.

"It would take decades for the hole to disappear and for it to return to the situation before 1980. We are looking at 2075," Geir Braathen, who is the World Meteorological Organisation's expert on the subject told AFP.

On September 13, the hole covered an area of 27 million square kilometers, while in 2007, the maximum reached was 25 million square kilometers, said the WMO.

"Since the ozone hole is still growing, it is too early to determine how large this year's ozone hole will be," it added.

Ozone provides a natural protective filter against harmful ultra-violet rays from the sun, which can cause sunburn, cataracts and skin cancer and damage vegetation.

Its depletion is caused by extreme cold temperatures at high altitude and a particular type of pollution, from chemicals often used in refrigeration, some plastic foams, or aerosol sprays, which have accumulated in the atmosphere.

Most of these chemicals, chlorofluorocarbons (CFCs), are being phased out under the 1987 Montreal Protocol, but they linger in the atmosphere for many years.