More homes in the South West are at risk from radioactive radon gas than previously thought.

New research shows the problem could affect heavily populated areas such as Plymouth, Torbay and Newton Abbot.

Radon - which is linked to an increased risk of lung cancer - is normally found in granite, but scientists have discovered a significant risk in areas with limestone rock.

Anyone worried about the gas is advised to get a radon test.

The NRPB has set a radon action level

Previously, areas at highest risk of radon were thought to be places like Bodmin Moor and Dartmoor.

But geologists now say water can move through rock layers from granite and carry uranium and radium, which give rise to radon.

Water can pool in limestone and that pooling can increase the risk of radon gas.

Plymouth, Torbay and Newton Abbot all have large areas of limestone.

Richard Scrivener, of the British Geological Survey, said: "If your property is situated over a fracture in limestone, then there's a possibility you'll have high radon levels.

"It really isn't a very big problem, but it does happen on a very much hit-and-miss basis."

Small amounts of radon are present in all buildings.

However, work to remove possible sources of radon gas from the home is fairly easy to complete.

Sometimes air pumps are installed in homes to drive out the gas.