One in five homes in Northern Ireland have been placed on an at-risk register after a survey published Friday showed the extent of cancer-causing radon gas seeping from the ground.

Health experts estimate there are about 1,000 lung cancer deaths a year across Great Britain linked to radon gas.

A new map covering Northern Ireland has on Friday highlighted more at-risk areas of the province than previously thought.

Public Health England, who published today's report, says households across Northern Ireland in at-risk areas should be tested for radon gas, with protective measures taken in the most affected areas.

In 2009 when the last survey was carried out, it was estimated 90,000 homes were at risk from radon gas, but today this number was significantly increased.

Neil McColl, head of radon at Public Health England's Center for Radiation, Chemical and Environmental Hazards, said: "We estimate some 155,000 homes, about one in five in Northern Ireland, are now in affected areas. These are places where some householders are exposed to radon at a level where we recommend protective action."

Radon is a naturally occurring radioactive gas that seeps into homes from the ground. Long term exposure has been linked to public health risks, but health experts in Britain say there are practical measures that can be taken to substantially cut the level of radon exposure.

The new map has been produced by radiation experts at Public Health England and the British Geological Survey, using geological information from the Geological Survey of Northern Ireland and radon measurements, including many made with support from the Northern Ireland Environment Agency.