Wednesday January 7 2009
Sealing newly built homes against radon leaks could cut cancer deaths
The Daily Telegraph warns that “1,000 people die in the UK annually from preventable radon leaks in [the] home”. Radon is a naturally occurring radioactive gas that can enter buildings through cracks in the foundations, potentially damaging people’s lungs.
The current UK policy is to only install anti-radon measures in new homes built in areas with high radon levels. The newspaper says installing cheap anti-radon barriers into all new homes could cut deaths from radon-related lung cancer.
The story is based on a complex cost-effectiveness analysis which examined policies to control levels of radon in UK homes. By analysing data from other studies, researchers estimated that 3.3% of lung cancer deaths (1,100 per year) are linked to radon. They also found that measures such as the installation of radon-proof membranes in all new homes would be a cost-effective way to reduce lung cancer related to radon exposure. Installing anti-radon measures into existing homes was not found to be cost effective.
While a policy of anti-radon measures in all homes would appear to be beneficial, the vast majority of radon-related lung cancer deaths were found to also involve smoking. Ideally, these measures should be accompanied by people avoiding smoking.
Where did the story come from?
This research was carried out by Professor Alistair Gray and colleagues at University of Oxford. It was funded by Cancer Research UK, the Medical Research Council, the European Commission sixth framework programme, and the National Institute for Health Research. The study was published in the peer-reviewed British Medical Journal.
What kind of scientific study was this?
This was a cost-effectiveness analysis designed to investigate the number of lung cancer deaths that are related to radon gas in the home, and to look at the ‘value’ of alternative policies to control the radon.
Radon is considered to be the largest source of exposure to natural ionising radiation. Exposing sensitive bronchial cells to radon is known to cause damage in proportion to the number of cells exposed.
Radon concentration is highest indoors, particularly in houses and small buildings. In the UK, the policy is for action to be taken in the home when concentration is at or above 200 becquerels (Bq) per cubic metre. In some areas, such as Cornwall, the higher background level of radon means that all new homes built there are required to have an airtight membrane at floor level as well as through the walls.
Remedial action for existing homes includes installing low-speed fans to take air and radon out of the foundations. The study aimed to explore the cost-effectiveness of various policies to control indoor radon.
The researchers obtained data from a nationwide survey on the distribution of measured radon concentrations in UK homes. They estimated the size of annual radon concentration variability based on studies in which measurements were taken in the same home over several years.
The authors analysed data on smoking history and radon exposure for 7,000 people with lung cancer and 21,000 healthy controls across nine European countries. They calculated the percentage increase in risk of lung cancer per 100Bq/m3 increase in radon.
They also obtained data from two studies on absolute risk of death from lung cancer in non-smokers, and the percentage increase in risk of lung cancer from smoking.
The cost-effectiveness analysis involved constructing a model that estimated the lifetime risk of death from lung cancer before and after preventative measures to reduce radon. They looked at QALYs (quality adjusted life years) gained according to age and sex. They also looked at direct costs or savings made by homeowners and government departments, the Health Protection Agency, and the NHS.
The cost-effectiveness of intervention programmes was calculated as the ratio of net change in cost to net change in cancer deaths avoided (life years and QALYs gained). This allowed the different radon policies to be compared with one another. All policies were examined for their effectiveness over 100 years. This time period covered both the lifetimes of humans and the buildings.
They looked at the number of radon-related lung cancer deaths that would be avoided by full implementation of the policy throughout the UK.
What were the results of the study?
The average radon concentration in UK homes is 21Bq/m3. Each year, around 1,100 lung cancer deaths could be attributed to radon exposure in the home (3.3% of all deaths are the result of lung cancer).
Over 85% of these 1,100 deaths are at indoor concentrations of less than 100Bq/m3. However, most deaths are caused by the combination of cigarette smoking and radon exposure. Only one in seven of these deaths were caused by radon exposure alone, with six out of seven caused by smoking in combination with radon exposure.
For a non-smoker living in a home with average radon exposure, cumulative risk of death from lung cancer by age 75 was estimated to be 0.42% (compared to 15% for a smoker), reducing to 0.41% if they had no radon exposure, and increasing to 0.53% if there was a high 200Bq/m3 exposure (compared to 19% for a smoker).
Current UK policy is to employ basic preventative measures (e.g. sealed membrane at ground level) in newly built homes where levels are above 52Bq/m3. This was found to be highly cost-effective, and would have a cost per QALY gained of £11,400 if extended to the whole of the UK. After 10 years of the policy throughout the UK, 44 lung cancer deaths per year would be prevented, and this figure would increase by 4.4% each year the policy were continued.
Current policy in existing homes is to take repeated measurements when radon levels are above 64Bq/m3. It is recommended that homeowners remediate at their own expense when levels rise above 200Bq/m3. These measures were not found to be cost effective (£36,000 per QALY gained), nor would they reduce lung cancer deaths.
What interpretations did the researchers draw from these results?
The researchers conclude that it would be cost-effective to extend the policy of taking basic preventative measures to all newly built UK homes in areas of high radon concentration. This would complement campaigns to reduce smoking and lung cancer deaths.
Policies to remediate existing homes against high radon levels are not effective or cost-effective in reducing deaths linked to radon exposure.
What does the NHS Knowledge Service make of this study?
The study is a high-quality cost-effectiveness analysis, which has examined policies to control indoor levels of radon. This included a societal perspective, meaning that it has included the financial costs borne by home owners.
By looking at data from studies involving 7,000 people with lung cancer and 21,000 healthy individuals from nine countries, they found an estimated 3.3% of lung cancer deaths (1,100 per year) are linked to radon.
Current UK policies to reduce radon levels in newly built homes were found to be cost-effective and therefore recommended. However, remedial measures to monitor and reduce high radon levels in existing homes were not found to be effective in reducing lung cancer deaths.
Points to bear in mind:
- As demonstrated by the results, the greatest risk factor for lung cancer remains smoking. Risk of death from lung cancer in a lifelong non-smoker was negligible, and only marginally increased by radon exposure.
- As the authors say, if it were possible to measure radon concentrations across UK homes, 91% of them would be expected to have radon concentrations below 50Bq/m3,with an average of only 16Bq/m3. At these levels no monitoring, preventative or remedial action is considered necessary.
- Only 2% of homes would be in the 100-199Bq/m3 bracket, and 0.4% above 200Bq/m3. Therefore the public should be reassured that there are very few people living in the UK who are exposed to higher levels of radon in their homes. And even among them, the risk of death from lung cancer remains very small if they are a non-smoker.
- The study has only considered deaths from lung cancer and not the effects upon quality or duration of life of those living with lung cancer.
- Radon levels in places other than homes, e.g. workplaces, were not examined.
Indoor radon exposure remains a public health issue, particularly in other countries where concentrations, and hence radon-related lung cancer deaths, are thought to be higher. It is important that all existing policies and interventions are evaluated, and that existing policies be implemented if they are found to be effective, as has been demonstrated here.
The authors recommend a universal approach to prevention. They say that the impermeable membrane at ground level should be a requirement for all new homes, and its installation be enforced through building regulations, which are to be reconsidered soon.