Radon is a radioactive gas given off by certain rocks. Unlike most radioactive materials it can be breathed in because it is a gas, and it produces the most dangerous type of radiation if ingested or inhaled – alpha radiation. Alpha radiation can damage cells and cause cancer. Radon inhalation is believed to be the second most common cause of lung cancer after smoking, causing about 5% of lung cancers.
Alpha radiation can build up in closed spaces and unventilated buildings. Some parts of the the United Kingdom are more prone to high radon concentration than others – Devon and Cornwall especially. This is shown in the 'radon map' of the UK below.
