The UN World Meteorological Organization (WMO) says the long-term outlook for the healing of the Earth's ozone layer is good.  But, WMO scientists say they expect the ozone hole to get worse over the next few years, before it gets better. 

The World Meteorological Organization says the ozone hole over Antarctica usually does not reach its maximum size until mid to late September.  But, it says scientists already are seeing the first signs of ozone destruction.  It says the ozone hole is expected to deepen and may become worse than last year, but depletion probably will not reach record levels as it did in 2003.

WMO ozone expert, Geir Braathen, says the thinning of the ozone layer is likely to continue for as long as ozone-depleting substances, mainly chlorofluorocarbons and halons, remain in the atmosphere. 

"We see that the atmospheric concentrations of ozone depleting substances have leveled off and is about to decline.  But, it will still take several decades before these substances have disappeared from the atmosphere before they are broken down.  They have a long lifetime in the atmosphere, so they will stay there for decades.  So, we expect annually recurring ozone holes to take place until maybe the middle of this century," he said.

Chlorofluorocarbons used as refrigerants, in aerosol sprays and as solvents are responsible for the destruction of the ozone, which filters out harmful ultra-violet radiation from the sun.   Scientists attribute the rise in global skin cancers and cataracts to the loss of ozone.

These harmful man-made chemicals are banned under an international treaty known as the Montreal Protocol.  Mr. Braathen says western industrialized countries have phased them out.  However, he notes, the treaty allows developing countries to phase out these substances over a longer period of time.

The WMO scientist says loss will continue as long as the stratosphere contains an excess of ozone depleting substances.  He says recovery is occurring, but slowly.

"We still expect ozone holes to appear annually and that they actually might be a little bit worse over the next five to 10 years and then, the situation will start to improve?In the long-term, the problem is probably solved.  So, if we think, let us say 50 years ahead, the ozone hole problem might actually be solved," he added.

Mr. Braathen says the large ozone hole over Antarctica poses no problem to human health because the continent is so sparsely populated.  But, he says the dangers increase when the ozone hole develops over the Arctic, which is surrounded by densely populated regions, especially in Europe and Asia.