BEWARE the Ides of March, as the saying goes, but what about the rays of February? That blood-red sun may have banished winter over much of Ireland this past week but it also posed one of the biggest health threats of the year - or of a lifetime, some scientists say.

Last month international experts predicted that a record hole in the ozone layer would open up over part of the northern hemisphere.

Destruction of the layer - the protective shield against ultra-violet (UV) radiation - is running at record levels. Last week's cloudless sky will have significantly increased the risk of skin cancer and eye cataracts.

An ozone hole is so named when less than 50 per cent of the protective layer is measured. A series of conditions, including the passage of a polar vortex over northern Scotland late last month, is expected to contribute to significant ozone destruction in the stratosphere this spring.

These polar stratospheric clouds trigger a sequence of chemical reactions which lead to rapid ozone depletion.

Recent statistics from the World Meteorological Organisation (WMO) are already worrying, according to Dr Paul Dowding, environmental scientist and lecturer at Trinity College Dublin.

During the Antarctic "spring" months of August to September the ozone hole was reported to be the biggest, and depletion the greatest, on record. Unusual weather last winter may have contributed to the worst ozone loss ever over the northern hemisphere with a 10 per cent depletion over Europe and a startling 35 per cent over Siberia, according to the New Scientist.

"So these spring months - particularly towards the end of March - in this hemisphere represent the greatest risk period," Dr Dowding said. "The danger is not the ozone, but the ultra-violet rays penetrating through a lack of ozone during a high-pressure weather spell. This sunlight is much riskier now than in high summer".

Apart from increased risk of eye cataracts and skin cancer, ultraviolet light on skin suppresses the immune system generally. "People should never look at the sun directly. Ultra-violet protecting spectacles are recommended."

Should we be warned? This has been a grey area, to date, with the Department of Health stating that it is not its responsibility. The Meteorological Service has not regarded it as part of its brief, although occasional mention is made in forecasts of the risk of sunburn during high summer.

It does contribute to the very different monitoring of low-level ozone - ground-level pollution - by the Environmental Protection Agency (EPA), which now plans to develop a warning system for high-level ozone based on monitoring at Valentia, Co Kerry.

As for the cause, it's all our own fault, of course - or that of the developed world. Ten years ago, the world produced a million tonnes a year of chlorofluorocarbons (CFCs), the chemicals that wreak most destruction on the ozone layer.

International action has reduced this to about 360,000 tonnes annually, in spite of a ban on CFC production. This is because the 1985 Vienna Convention for the Protection of the Ozone Layer allows developing countries to continue producing and importing CFCs and other hazardous chemicals until 2010.

Part of the concession to the developing countries, led by China and India, involved subsidies from rich countries to help pay for alternatives to CFC-emitting fridges and suchlike. However, the multilateral fund has run short of money.

Italy, which owes $19 million, has paid nothing, although its refrigeration industry is said to be the biggest single beneficiary of fund purchases. Ireland contributed over £200,000 to the fund in 1995, according to the Department of the Environment.

The outlook is still bleak. An upper atmosphere research satellite controlled by the US National Aeronautics and Space Administration (NASA) in Washington has recently detected an increase of almost 100 per cent on average concentrations of chlorine monoxide, a product of CFC gases which attacks ozone in the presence of sunlight.

Before the end of the century, "fine weather" may come to be a dark, cloudy, radiation-shielding spring.