This was true even in areas with high levels of both radon gas and gamma radiation.

BBC: Radon cancer fears dismissed

Radon is a gas, a product of decaying radium and an emitter of particles.

FORBES: A Pinch of Poison

Dr Siegfried believes the hormone may exacerbate the effects of exposure to tobacco smoke - and to other substances known to be linked to lung cancer such as the gas radon.

BBC: Lung cancer risk greater for women

The most effective way to deal with radon is to fit an air pump to a property to vent the gas into the atmosphere.

BBC: Radon