The researchers conclude that radon in the home causes approximately 20,000 lung cancer deaths in the European Union each year, about 1,000 of which are in the UK.
The study – funded by Cancer Research UK and the European Commission – combines information from 13 smaller studies across Europe and is the largest ever to be conducted into the effects of radon exposure in the home.
The findings highlight the importance of people giving up smoking as soon as possible, as smokers are most at risk of lung cancer due to radon. In addition, for any given level of radon, smokers have about 25 times the risk of developing lung cancer as non-smokers. Radon can cause lung cancer in lifelong non-smokers but the risk is low.
Previous studies of radon in homes have not been large enough to assess the risks reliably. Nor have they been able to examine risks separately in smokers and non-smokers.Professor Sarah Darby at the University of Oxford, who led the collaboration, says: “By putting together many different studies we have shown that radon in ordinary homes is causing about nine per cent of lung cancer deaths each year in Europe, which is two per cent of all cancer deaths. In the UK, where radon levels are lower than in many European countries, radon in ordinary homes causes about 1000 deaths each year, which is about one per cent of all cancer deaths”
Professor Sir Richard Peto, also at Oxford University, adds: “On average in Europe, the absolute risks of getting lung cancer by age 75 years at usual radon concentrations of 0, 100, and 400 becquerels per cubic metre (Bq/m3)3 would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong non-smokers, and about 25 times greater (10%, 12%, and 16%) for cigarette smokers.”
This means that, on average, four lifelong non-smokers in every 1000 would develop lung cancer in the absence of radon, rising to seven in 1000 in the presence of radon at a concentration of 400 Bq/m3. In contrast, 100 in 1000 cigarette smokers would get lung cancer in the absence of radon, rising to 160 in 1000 at 400 Bq/m3 of radon.
Radon is formed from the natural disintegration of uranium, which is present in ordinary surface rocks and in soil. Radon that diffuses into the atmosphere usually disperses rapidly but it can accumulate indoors, especially in small buildings such as houses.
As radon decays it creates particles that can damage the cells lining the airways of the lung. This damage can lead to cancer and, as the lungs of smokers may have many cells that are already somewhat damaged, the extra risk from radon is much greater for them than it is for non-smokers.
Throughout Europe radon concentrations in houses vary widely. In most countries there are many homes with moderate levels, and a relatively small proportion of homes with very high levels.
High radon levels in existing houses can usually be reduced by changes to the ventilation system, such as improving underfloor air bricks and extracting radon from beneath the building with a fan, although this can cost up to £1000 to install and £50 per year to run.
When constructing new buildings, however, low concentrations can usually be achieved by enhancing the damp-proof membrane across the full footprint of the building, at an extra cost of only around £100.
The researchers found lung cancer risk to be raised by 16 per cent for every 100 Bq/m3 of radon present in the home. The additional risk is proportional to the usual radon level in the home.
Professor Darby adds: “We also found that there is a detectable risk even in homes with levels below 200 Bq/m3, which is the currently recommended ‘action level’ in the UK. Indeed we estimate that about ninety per cent of radon-induced lung cancers occurred in homes with levels of radon below 200 Bq/m3.
“Over the next few decades one of the most cost-effective ways of reducing the number of lung cancer deaths caused by radon may be for builders to incorporate low-cost radon-proof membranes into the foundations of all new homes, even in areas that are not currently designated as being particularly radon-affected.”
Professor Alex Markham, Chief Executive of Cancer Research UK, says: “The dangers of radon are much greater for smokers than for non-smokers. Most people who die from radon-induced lung cancer would not have developed the disease if they had not smoked. For smokers, the best way to reduce their risk of getting lung cancer, whether radon is present in their home or not, is to give up smoking. For the future, however, I hope these results will eventually lead to lower radon exposure for the whole population.”
- Radon is a naturally occurring, colourless, odourless, radioactive gas found at varying levels in all houses across the UK and Europe. Radon in homes accounts for about half of all non-medical radiation exposure
- Radon levels in homes are measured in becquerels per cubic metre (Bq/m3) – that is, radon disintegrations per second per cubic metre of air.
- The 13 European studies incorporated a total of 7000 people who had developed lung cancer and 14,000 without the disease.
- All 13 studies included individual smoking histories for each participant, and individual measurements of household radon in both current and previous homes.
- The 13 separate studies were conducted in the UK, Finland, Spain, France, Italy, Sweden, Germany, Austria and the Czech Republic.
- The researchers accounted in detail for the effects of smoking. This is necessary because in Europe people in cities are generally exposed to less radon but smoke more than people in rural areas. They also allowed for the extent to which radon levels in a home can fluctuate, which makes estimating the usual exposure level difficult.
- Radon has no taste, smell or colour. It can be detected only by using dedicated equipment. The gas is found in all soils and rocks to some degree, but the amount diffusing into homes varies between different parts of the country and from one house to the next.
- After radon atoms form they have a half-life of only four days, during which some of them diffuse through the soil and reach the atmosphere. In outdoor air radon disperses rapidly.
- The dangers of radon were first noticed in miners of minerals, some of whom in the past faced very high levels of radon while underground. Until now, however, there has been uncertainty about the implications of studies conducted in miners for the risk of radon in the home. This is because the miners were exposed under very different conditions, there was little information about their smoking habits, and many of them were also exposed to other lung carcinogens, such as arsenic.
- In Europe as a whole the average radon level in homes is about 59 Bq/m3 of air, which means 59 radon atoms disintegrating per second per cubic metre. Levels in the UK are only about one third as great, at 20 Bq/m3.
- People in the UK who want to know the radon level in their home can pay to have it measured by the National Radiological Protection Board, or by various companies. In some areas of the UK, free measurements are available.
- Overall, radon is responsible for about half of all non-medical exposure to ionising radiation in the UK, and for more than half in some other countries.
- In the UK, the work contributing to this study was carried out in the Clinical Trial Service Unit (CTSU) and in the Cancer Research UK Cancer Epidemiology Unit, both in Oxford University.