UN health agency seeks to minimize risks of cancer-causing radon gas

In an effort to reduce the rate of lung cancer worldwide, the United Nations health agency is launching an international project to help countries reduce the risks of radon, a natural radioactive gas that emanates from the ground into the air and is the second leading cause of the disease after tobacco.

“Radon poses an easily reducible health risk to populations all over the world, but has not up to now received widespread attention,” the coordinator of the World Health Organization (WHO) Radiation and Environmental Health Unit, Mike Repacholi, said in announcing the initiative in Geneva.

“Radon is all around us. Radon in our homes is the main source of exposure to ionizing radiation, and accounts for 50 per cent of the public's exposure to naturally-occurring sources of radiation in many countries,” he added.

The International Radon Project will identify effective strategies for reducing the health impact of the colourless, odourless and tasteless gas, promote sound policy options for countries and increase awareness of the consequences of exposure, setting up a global network of radon scientists, regulators and policy makers.

Radon in the air is present worldwide, its concentration depending on the highly variable uranium content of the soil. It is the second most important risk factor for lung cancer, causing between 6 and 15 per cent of all cases. Yet, there is little public awareness of radon as a threat to human health, which can be mitigated with relatively simple steps.

Although average exposure varies enormously, recent studies have shown that, when exposed to a concentration of 100 Bq (Becquerels)/m3, a non-smoker's risk of lung cancer by age 75 years increases by 1 in a 1,000 compared to non-exposed persons. Among those who smoke and are exposed to the same radon concentration, the risk of lung cancer is about 25 times greater.

On a global level, tens of thousands of lung cancer deaths annually can be attributed to radon. Most of those cases occur among smokers. For the average citizen, by far the greatest exposure to radon comes in the home, where concentration levels are higher than outdoors.

Exposure can be easily mitigated during construction of new homes, but existing buildings can also be protected. Most measures such as increasing under-floor ventilation and sealing cracks and gaps in the floor require simple alterations.

Radon is produced from radium in the decay chain of uranium, an element found in varying amounts in all rocks and soil. It escapes easily from the ground into the air and emits heavily ionizing radiation called alpha particles. These particles are electrically charged and attach to aerosols, dust and other particles in the air we breathe. As a result, radon progeny may be deposited on the cells lining the airways where the alpha particles can damage the DNA and potentially cause lung cancer.