More than a dozen houses in Brittany have been found to have up to six times the alert levels of radon, the colourless, odourless, radioactive gas which can cause cancer.
Although radon occurs naturally in the decay chain of uranium into lead – and especially in granite rocks such as those found in Morbihan and Finistère – the homes in question are thought to be built on spoil heaps from old uranium mines near Persquen.
Homes in other regions may also have problems as the gas seeps out of underlying volcanic rock and can make under-ventilated rooms dangerous. Areas where the gas is found in high concentration include Brittany, Normandy, the Massif Central and Corsica.
Tests are being carried out on the Brittany homes. If natural radon seepage is the cause it may be costly for owners – and the health risk is significant as continuing high-level radon exposure can cause lung cancer.
France’s Institut de Radioprotection et de Sûreté Nucléaire says radon has a 3-12% risk of causing cancer and this is calculated to mean 3,000 lung cancer deaths a year. The affected houses showed levels up to six times in excess of France’s ‘alert’ levels – at 2,500 becquerels per cubic metre of air (Bq/m3) against the reference level for public spaces of 400Bq/m3 (there is no set level for homes).
If uranium spoil is identified as the cause the former mine operator, the nuclear power company Areva, must organise and pay to clear it from the site, but if it is natural the property owner must fund any remedial action.
Remedies can be simple or complicated – with complication resulting in extra expense.
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Radon is common, we breathe it each day and it is, to all intents and purposes, harmless as it is diluted in the open air. It is when it seeps into poorly ventilated rooms that it can become a health hazard.
The simple remedy is to fit proper ventilation but if a living area is affected it could be more expensive. Other solutions include installing a pressurisation system to draw outside air into the attic and blow it into the house to stop radon from seeping inside or a specialised depressurisation system.
The Ecology Ministry called in Areva to survey the area near the Brittany homes to identify where uranium spoil from Prat Merien mine (stériles miniers) was deposited. As this was usually done within 50km of a mine, it means areas with similar geology and radiation levels.
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Nuclear safety authority ASN oversees the operations. Yoann Terliska, deputy head of the ASN division in Brittany and Pays-de-la-Loire, said: “When the mines operated people could collect spoil to use on local roads, house courtyards and farmyards but we now know this can cause problems when people live close to it.
“We asked the old mine operator, now Areva, to identify the areas where stériles miniers had been used. They flew over the area and followed up with tests on the ground and then residents and businesses affected were given dosimeters, to measure radioactivity.”
However, only one in two of those involved returned their dosimeters for testing and the affected properties, which were above French 400Bq/m3 guidelines with levels of more than 2,500Bq/m3, were identified.
These 400Bq/m3 levels are being reduced to 300Bq/m3 at the start of 2018 to meet European regulations (the UK action level is 200Bq/m3).
Although Areva acts as ‘judge and jury’ to identify the radon source it is known that removing spoil waste may not make radon levels fall, as there may still be a high background effect so radon seeps into homes.
Mr Terliska added: “If the level of radon is due to background effect the owner will, if they go ahead, have to pay for remedial work – and there is no state aid – but our experience is that the simplest methods often provide acceptable results.”
You can find out if you live in an area with a high radon exposure, using the radiation risk agency IRSN’s interactive map at tinyurl.com/y92o292v
The Brittany residents are still in their homes and it is not known what future they face.
Three years ago in Haute-Vienne a family had to leave their home after an ‘abnormal amount’ of radon gas was discovered in the basement.
The house had been built on illegal waste from the treatment of uranium ore at a nearby uranium processing plant.
It has now been demolished, the site grassed over and fenced off and the family rehoused.
Dr Suzanne Déoux, of Angers University and president of Bâtiment Santé Plus, said: “The World Health Organisation estimates radon plays a role in 6% to 15% of all lung cancer deaths worldwide.”
Only smoking causes more, although radon is a major cause among non-smokers – and is also suspected in childhood leukaemia and skin cancer.
“This risk is 25 times higher for smokers. About 60% of deaths from lung cancer associated with radon occur in smokers, 30% in ex-smokers and 10% in non-smokers.”
Dr Déoux said homeowners and building professionals did not know enough about the value of efficient ventilation.
“During the build, it is possible to reduce radon entry by better sealing of the ground / building interface.
“The rules are there. Good building site practice must be better applied.”
Sealing foundations in new properties with gas-resistant membranes will stop radon build-up before it starts.
Existing buildings can have a ‘radon sump’ fitted by digging under the foundations to install a fan and a pipe to push the gas into the open air, to dissipate.
Technically, since July 1 this year, anyone selling or renting a home must provide information on a property’s radon risk; but the regulation, set out in a decree in February 2016, has not yet been implemented.
Testing is simple and dosimeter kits can be bought online for €25 for one, €39 for three. They should be used over two months in winter in main rooms. (The IRSN site above has links to dosimeter manufacturers).
