The CSIRO Marine and Atmospheric Research's expert in ozone depletion, Dr Paul Fraser, said while the size of the ozone hole is large, it is more or less as expected.
"Its size is not a surprise because, other than year-to-year variability that mirrors temperature changes, Antarctic ozone depletion has remained at an approximately constant level for the past nine years," Dr Fraser said.
The 2005 ozone hole area reached 26.4 million square kilometres, about 3.5 times the area of Australia.
The ozone hole was biggest in the years 2003, 2000 and 1998.
The analysis is based on constant monitoring of ozone levels by NASA.
From August to December each year, about 2.5 trillion kilograms of ozone is broken down in the stratosphere above the Antarctic, with losses peaking in late September or early October.
Ozone depletion is caused by the effects of chlorine and bromine, which are released in summer when sunlight acts on CFCs, solvents, HCFCs, halons and methyl bromide.
Ozone depletion is especially severe over the Antarctic in spring.
Ozone depletion is showing a pattern of recovery similar to 2000, which implies that this year's hole should decrease by the end of November.
Dr Fraser said that despite a decrease in the chemicals that deplete ozone, this Antarctic ozone hole is larger than last year because of lower temperatures in the stratosphere.
While not significantly larger or deeper in comparison to those of the past decade, the Antarctic ozone hole is not showing any signs of a recovery.
"Due to their long lifetime, ozone depleting gases remain in the Earth's upper atmosphere for about 50 years," Dr Fraser said.
"Ozone depletion, and the resultant human health and environmental
problems from exposure to increased UV levels, will therefore be an
issue of concern for several decades to come.
"Half a century or more may pass before the Antarctic ozone hole is repaired and the first clear signs of recovery may not be apparent for
five to 10 years," Dr Fraser said.