A five-fold increase in the number of homes officially designated at risk from a lethal gas that seeps out of the ground causing more than 1,000 deaths a year, was announced yesterday.
Homeowners are being urged to take extra precautions to protect themselves from radon, the naturally occurring radioactive gas produced by the decay of uranium 238 which is present throughout the Earth’s crust. Radon has been called the “worst environmental pollutant”.
The Health Protection Agency announced new standards yesterday to reduce exposure to radon, which causes an estimated 1,100 deaths from lung cancer annually.The new “target level” of exposure of 100 becquerels per cubic metre is half the existing “action level” of 200 becquerels.
Research over the last 20 years has shown that there is no safe level of radon. It exposes children in affected homes to higher levels of radiation than workers at the Sellafield nuclear re-processing plant. Scientists point out that if it were blue it would be the subject of widespread alarm but because it is odourless and colourless it is ignored.
Although the risks are higher in the worst affected homes, about 90 per cent of deaths from radon occur in homes below 200 becquerels because there are many more of them. About 100,000 UK homes have radon levels over 200 becquerels, and between 500,000 and 600,000 have levels over 100 becquerels.
The HPA says the new targets should also apply to all schools and to other buildings such as residential homes occupied by the public for more than 2,000 hours a year.
Neil Mccoll of the HPA’s Centre for Radiation, Chemicals and Environmental Hazards, said: “The scientific evidence has shown that the lung cancer risk is proportional to the long term exposure to radon. There is no safe or unsafe level. We want to keep our focus on homes above 200 becquerels - there are some above 1,000 and a handful above 10,000 - but we also want to make sure that people who are reducing the level should not think that below 200 they are safe. The risk is smaller but it is not zero - particularly if they are smokers or ex-smokers.”
When radon is inhaled it attaches itself to cells lining the lungs, and is especially harmful to smokers, whose cells are already partly damaged. Concentrations outdoors are low, but the gas can build up indoors, significantly increasing risks of cancer to the occupants. At 200 becquerels it is estimated to increase the risk of lung cancer by a third.
In the UK, radon levels are highest in houses on Dartmoor in Devon and in Cornwall, which are built on granite, in parts of Wales, the East Midlands and the Pennines. The gas seeps into buildings through cracks and holes in the foundations. In Devon and Cornwall it is difficult to sell a house without a certificate showing the radon level.
The current UK policy is to identify areas where radon levels are high and seal the foundations of new homes with gas-resistant membranes, which cost about £100. In existing buildings, owners are advised that a “radon sump” can be created by digging below the foundations and using a fan and pipe to blow the gas to the outside, but they have to meet the costs which average £1,000.
The policy was critcised by scientists from the University of Oxford last year in the British Medical Journal who said it was “costly” yet had a “minimal impact on radon-related deaths” because these mostly occurred in homes below the 200 becquerel limit.
The HPA has responded with its new two-level target, extending the number of homes falling within its remit. But the Oxford researchers proposed a more radical nationwide policy policy to install sealed membranes in all new homes, regardless of where they were built. At a cost of around £100 per house the measure would save around 1,000 lives over the first 20 years, they said.