Radon is a chemically inert, naturally occurring, radioactive gas. It has no smell, colour, or taste, and is produced from the natural radioactive decay of uranium which is found in rocks and soil.

Radon gas escapes easily from rocks and soils into the air and tends to concentrate in enclosed spaces, such as underground mines, houses, and other buildings.

Soil gas infiltration is recognized as the most important source of residential radon. Other sources of radon include building materials and water extracted from wells, but are of less importance.

Exposure to radon in the home and workplace is one of the main risks of ionizing radiation causing tens of thousands of deaths from lung cancer each year globally. In order to reduce this burden it is important that national authorities have methods and tools based on solid scientific evidence and sound public health policy. The public needs to be aware of radon risks and the means to reduce and prevent these.

Recent findings from case-control studies on lung cancer and exposure to radon in homes completed in many countries allow for substantial improvement in risk estimates and for further consolidation of knowledge by pooling data from these studies. The consistency of the findings from the latest pooled analyses of case-control studies from Europe and North America as well as China provides a strong argument for an international initiative to reduce indoor radon risks.

WHO has formed a network of key partner agencies from over 40 Member States. This network is the basis for the WHO International Radon Project (IRP) which was launched in 2005. Working groups collect and analyse information on radon risk, radon policies, radon mitigation and prevention as well as radon risk communication.

The key elements of the International Radon Project include:

• developing evidence-based public health guidance for Member States to formulate policy and advocacy strategy including the establishment of radon levels;
• provision of guidance on methods for radon measurements and mitigation;
• development of approaches for radon risk communication.