Cloud of radiation alarms France

SCIENTISTS are baffled by a cloud of radioactivity which passed over the south of France and parts of Switzerland and Italy 10 days ago. On the 2 and 3 June, the amount of caesium 137 in the atmosphere over the French Mediterranean coast rose to 2,000 times normal. None of the pollution reached the ground and safety authorities insist that there was no threat to human health. But there is deep concern in France that the source of the pollution should be identified.

A leak, or a fire, at a nuclear power station has been ruled out because such an incident would have released a mixture of radioactive materials, not a cloud of pure caesium 137. Contamination of the atmosphere from the Indian and Pakistani nuclear tests has also been excluded. "At present, we are confronted with a scientific enigma," Professor Jean-Francois Lacronique, president of the French nuclear safety institute, said yesterday. "We can only speculate."

Caesium 137 is used in some industrial processes and in hospitals. One theory is that a batch of it might have been accidentally dumped into an incinerator. Another possibility, given the direction of the wind, is an undeclared accident aboard a ship in the Mediterranean.

To put the pollution in perspective, Swiss authorities said it was 10,000 times less dense than the contamination from the Chernobyl nuclear accident in 1986. French nuclear safety agencies have launched an investigation with the French meteorological office and the World Health Organisation to try to identify the likely source of the pollution.