RADON AND LUNG CANCER

Reducing Indoor Radon's Contribution to Deaths From Lung Cancer

January 7, 2009 — A new analysis of the contribution that indoor radon makes to deaths from lung cancer suggests that universal strategies to reduce radon in the home would be cost-effective and could make a "modest and worthwhile contribution" to reducing deaths from lung cancer, together with existing policies to reduce smoking. The report was published online January 6 in BMJ.

The new analysis, described by an accompanying editorial as the "most extensive and detailed evaluation to date," was carried out in the United Kingdom. However, the conclusions are likely to apply to most developed countries, many of which have higher mean radon concentrations, say the authors, headed by Alistair Gray, PhD, professor of health economics at Oxford University, in the United Kingdom.

Radon is a known lung carcinogen, and many countries already have policies to control radon within homes. Produced by the decay of uranium in the ground, radon seeps upward and enters buildings through cracks or holes in the foundation, the editorialists explain. Preventive measures involve installing a sealed membrane at ground level, under-floor ventilation, and a radon sump pump.

"Of course, smoking is by far the number 1 risk factor for lung cancer, and everything else comes far after it," said Anssi Auvinen, DMedSc, professor of epidemiology at the Tampere School of Public Health, in Finland, who coauthored the editorial. "But among the risk factors that come after smoking, indoor radon is a very close second, along with occupational exposure to asbestos and secondary exposure to smoking."

Indoor radon may account for about 5% of all lung cancer in the United Kingdom, and up to 10% of lung cancer in many other European countries, where radon levels are higher, Dr. Auvinen said in an interview with Medscape Oncology.

Reducing indoor radon levels is an important public-health issue, said Dr. Auvinen. Some authorities, such as radiation-protection agencies, believe that everything possible should be done to reduce radon levels, but there is an alternative view, and some public-health authorities advocate concentrating on tobacco, because most of the radon-induced lung cancers occur in smokers, he said. Radon increases the risk for lung cancer in everybody, but smokers have a much higher absolute risk because smoking substantially increases their baseline risk levels, Dr. Auvinen explained.

His view is that, "providing that we are doing pretty much all we can to combat smoking, we should also fight against indoor radon."

Contribution to Deaths From Lung Cancer

In their paper, Dr. Gray and colleagues used 2006 Cancer Research UK cancer statistics to calculate that radon is responsible for about 3.3% of all deaths from lung cancer, accounting for around 1100 deaths each year. Most of the deaths are caused jointly by radon and active smoking, the researchers comment (about 1 in 7 deaths is caused by radon and not active smoking).

The proportion of lung cancers attributable to radon could be higher in many other European countries, the editorialists comment, because the United Kingdom has relatively low radon concentrations. The mean indoor radon concentration in British homes is 21 becquerels per cubic meter (Bq/m³), the authors note. Dr. Auvinen said that the average indoor radon concentration in Nordic countries is 100 Bq/m³.

Universal Strategy to Reduced Indoor Radon

At present, many countries have policies to control radon only in areas where the concentrations are above a specified value, known as the "action level" or "reference level," Dr. Gray and colleagues comment. In the United Kingdom, this level currently stands at 200 Bq/m³, and current policy is mainly concerned with identifying existing homes with radon measurements above this level and implementing full preventive measures (including under-floor ventilation and a radon sump pump and associated pipework, in addition to the basic preventive measure of a ground-level membrane). There is also a policy of installing basic preventative measures in all new homes in geographic areas that have high radon levels.

In their paper, the authors outline calculations to show that this policy of identifying homes with high radon concentrations and then taking action in them is not cost effective.

They also question the logic behind the current policy. There is now direct evidence to show that indoor radon causes lung cancer in the general population, not only at high concentrations but also at concentrations below the current action level of 200 Bq/m³, they write. Only 0.4% of all homes in the United Kingdom have radon concentrations of 200 Bq/m³ or higher, and these are designated by the Health Protection Agency as "radon affected." However, they estimate that only 4% of all the radon-related lung cancer deaths would be found in these homes.

"Although people living in such homes have a greater risk than those living in homes with lower measurements, few such people exist," they point out. The great majority of the radon-related lung cancer deaths arise elsewhere, they say, estimating that 70% of these deaths are in homes where the radon concentrations are below 50 Bq/m³.

Dr. Gray and colleagues suggest that the second policy, installing anti-radon measures in all new houses, should be implemented universally, and not just in geographically high-radon areas, because it has more potential to reduce deaths from lung cancer. They outline calculations to show that it would be cost-effective.

During a period of 10 years, the current policy of taking action only in homes with high radon concentrations would avert only 5 deaths per year across the entire British population, whereas the suggested policy of basic measures in all new homes would avert 44 deaths from lung cancer per year, they write.

"We conclude that basic preventive measures against radon in new homes is likely to be a highly cost-effective public-health intervention measure, with the potential to make a modest but worthwhile contribution to reducing the annual number of deaths from lung cancer in the UK, alongside existing policies to reduce smoking," Dr. Gray and colleagues conclude. Because the concentrations of radon in the United Kingdom are lower than in most other countries, "similar policies are likely to be even more cost-effective elsewhere, depending on the extent of smoking-related lung cancer," they add.

Policies Need to Be Tailored Locally and Nationally

The editorialists point out that cost-effectiveness is context specific. "Policies for preventing lung cancer caused by radon should be tailored to the local or national distribution of radon concentrations in dwellings," they advise. For example, it may still be cost-effective to measure levels and take action in areas where there are a large proportion of homes with high indoor radon concentrations.

"The joint effect of radon and smoking is also important," they add. "Because 85% of radon-induced cancers occur in people who smoke, the deleterious effects of indoor radon on health could largely be avoided by eliminating smoking." This is reflected in the finding that reducing indoor concentrations of radon may not be cost-effective for people who have never smoked, the editorialists comment.