2. Radioactivity is natural. On earth it comes from rocks, but it also comes from space as cosmic rays. One of the sources of background radiation is radon gas from uranium in the ground. The two most common types of radon are radon-222 and radon-220. concentrations vary dramatically around the world.

3. New buildings in high radon areas are built with vented floors. When particularly high concentrations exist, extractor fans are fitted to draw out the gas before it can pass into the home. Another way of reducing radon levels is to use more impenetrable damp proof membranes on the ground floor.]

4. Radon-220 has a half life of 55.6 seconds. This means it is unlikely to be at risk as it decays before it has a chance to enter buildings. But radon-222 has a half life of just under 4 days. This means it has time to enter buildings. There are a total of 8 decays from radon-222 until a stable isotope is reached. Half are alpha emissions and half are beta. The emission of alpha or beta particles inside the lungs can lead to lung cancer. Around 5% of the 34,000 uk deaths each year from Lung cancer are attributed to radon.

5. Maps