THOUSANDS of householders are being targeted in a Health Protection Agency (HPA) campaign to cut exposure to a cancer-causing gas.

It is thought thousands of homes in West Oxfordshire could be exposed to dangerously high levels of radioactive radon, which the HPA says can cause lung cancer.

Now the agency is writing to the 9,000 homes which it believes to be most at risk.

Properties in Chipping Norton, Enstone and Charlbury are thought to be of most concern.

Radon occurs naturally and is present all over the UK, but high levels are linked with Cotswold stone, a limestone which allows the gas to seep to the surface more easily.

The gas cannot be seen, heard, smelled or tasted, but may lead to 1,000 UK lung cancer deaths a year, including 12 in Oxfordshire.

The existence of high levels of radon in West Oxfordshire has been recorded before, but the agency has now stepped up its campaign following more in-depth research.

Neil McColl, head of radon at the HPA, insisted there was no need to panic, but also said it was being taken seriously.

He said: “It is a radioactive decay product of uranium. High levels of radon exposure are clearly linked to increased risk of lung cancer.

“There is no need for panic. The risk comes from long-term exposure, year after year.”

For years, HPA scientists have run testing campaigns where levels of the gas are believed to be high, including Scotland and Cornwall.

Ten years ago, 8,500 homes in the Cherwell area were told they were in potential danger.

Radon is measured in becquerels per metre cubed of air (Bq m3). The HPA recommends steps are taken to reduce exposure when radon is at a concentration of 200 Bq m3, but in some areas of West Oxfordshire and Cherwell the reading has topped 2,500 Bq m3.

So far, 820 homes in West Oxfordshire have been tested and 42 were found to be above the level where householders should take action.

The HPA will now spend £100,000 to offer free tests to concerned residents.

Barry Palmer, 69, of Cleveley Road, Enstone, said: “We need to know what the problem is and the only way to do that is to do the testing.”

Radon testing involves placing two biscuit-sized plastic detectors around the home for three months.

The HPA then notes the levels. If levels are high, householders will be advised to cut them. Advice sessions are planned.

Householders can choose to install a sump under their homes to pump out the gas, but that can cost several hundreds of pounds.