Radon 'more dangerous than previously thought'

Radon may be more dangerous than had previously been thought.

The radioactive gas, caused by uranium decaying in granite and soil, spreads more easily than experts believed.

Radon can seep from the ground into homes and can be fatal if allowed to build up.

Now a study by researchers at Columbia University in New York shows that damage from irradiated cells spreads to neighbouring cells.

Gerhard Randers-Pehrson, who led the study, said it's: "a reason for concern but not panic. We're talking about the acceptable level of radon changing perhaps by a factor of two, not 100."

Even this change could mean many houses currently on the borderline of acceptable limits need attention.

The results so far are for cells in culture. Radon exposure may not have the same effect on bodies, Barry Michael of the Gray Cancer Institute in London, says. "The mix of cell types in living organisms might lead to a very different picture," he adds.

Radon causes around 17,000 lung cancer cases in the US each year, the journal Nature reports.

"It seems that when a cell is irradiated, it sends a signal to neighbour cells that causes them to get damaged too," says Randers-Peterson. "We don't know why this happens."