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SNOW on the summit of Mont Blanc, western Europe鈥檚 highest mountain, is 80
times as radioactive as that anywhere else in the Alps, French scientists have
discovered. Radon gas seeping into the snow from crevasses in the rock is the
source of the radioactivity.

Radon is a decay product of uranium, traces of which occur naturally in
granite. Radon in turn decays into a radioactive isotope, lead-210, which is
monitored around the world to validate models of atmospheric lead pollution.

But when researchers led by Michel Pourchet from the French government鈥檚
Glaciology and Environmental Geophysics Laboratory in Grenoble took samples of
snow at the 4808-metre peak of Mont Blanc, they were surprised to discover 8400
becquerels of lead-210 per cubic metre. The average for other locations in the
Alps is 110 becquerels per cubic metre.

Pourchet also found high levels of radon in the snow and concluded that this
had leaked from fissures in the granite. He says that snow at the summit has not
been compressed into ice, which could block the flow of radon.

Pourchet warns pollution scientists monitoring lead-210 in snow to be wary of
unexpectedly high levels leaching from the ground. This could cause 鈥減otential
flaws鈥� in their models.

But the mountaineers who took the snow samples from Mont Blanc need not worry
about their health being damaged. 鈥淪cientifically these results are very
interesting,鈥� says Michael Clark from Britain鈥檚 National Radiological Protection
Board, 鈥渂ut the radiation dose anyone would receive from drinking litres of this
snow would be trivial.鈥�