A sudden rise in the level of harmful ultraviolet radiation has renewed fears about the low ozone levels over Britain last week.
The strength of harmful ultraviolet B (UVB) rays in sunshine were as much as double those normally recorded for early March, the Government's National Radiological Protection Board said yesterday.
"It is the first time we've seen anything like this in Britain," Professor Roger Clarke, the board's director, said last night. "It seems that last week's ozone depletion was so severe that we actually saw significant effects on ultraviolet."
High levels of these rays are known to cause skin cancers and may cause cataracts in people. They can also harm crops, wild plants and plankton which lie at the base of food chains. It is the ozone gas in the stratosphere, above 40,000 feet, which absorbs much of the UVB from the sun.
Last week, the Independent reported that ozone levels had dropped to the lowest levels ever recorded over Britain, due to a combination of intense cold at high altitude and chlorine and bromine-containing pollutants.
Through early March the peak strength of UVB measured in Cornwall, Leeds and Glasgow was equal to that normally found on a sunny day in late April or early May. Only the Chilterns, with persistent cloud cover, registered no high levels.
Professor Clarke stressed that UVB levels twice those experienced last week were normal in midsummer: "The extra ultraviolet last week is not considered to represent a serious health hazard. They are short term and only contribute a very small amount to the annual dose."
Although since last week ozone levels over Britain have risen towards normal due to changing weather patterns at high altitude, the World Meteorological Organisation yesterday published figures showing an average ozone decline of 30 per cent over Britain and Scandinavia during January, February and the early part of March.
The ozone layer has been deteriorating for several decades due to the action of chemicals containing chlorine and bromine used in refrigeration and air conditioning.