What is radon?
Radon (Rn) is a radioactive gas generated during the radioactive decay of naturally occurring uranium and thorium present in minerals in the ground. Radon has no taste, smell or colour.
How does radon get into homes?
Whilst it disperses rapidly in the air radon can accumulate in some buildings. This is because it can seep out of the soil and find its way through any cracks in the flooring, or gaps around pipes and cables and between joints. Once inside, it tends to get trapped because the air pressure inside a building is generally slightly lower than outside. In this way, harmful concentrations can build up.
Why is radon harmful?
Harm is caused because radon emits a type of radioactivity called alpha particles which, if breathed in, can cause lung cancer by damaging cell DNA. Radon is believed to be the second greatest cause of lung cancer in the UK after smoking.
How dangerous is radon?
Radon concentration is measured in units of Becquerels per cubic metre of air (Bq m-³). This is a measure of how many radon atoms in each cubic metre of air are undergoing radioactive decay and emitting alpha particles each second. The average level in UK homes is 20 Bq m-³. To reduce the risk to health, the government has set a Radon Action Level of 200 Bq m-³ and recommends people to take positive steps to reduce the level in their homes below this. For employers, the level above which action must be taken to protect workers in industrial and commercial premises is 400 Bq m-³.
Radon is believed to be the second most important cause of lung cancer after smoking (active smoking accounts for 30 of every 1000 deaths; passive smoking 3 per every thousand deaths; radon 0.3 per every thousand deaths).
The National Radiological Protection Board (NRPB) has estimated that living in a house with radon at the Action Level increases a person’s lifetime risk of developing lung cancer ten-fold compared to living in a house with an average concentration. Radon has a greater effect on people who smoke cigarettes, and their risk of developing lung cancer is estimated as about twenty-five times higher than non-smokers.
In Europe, the absolute risks of getting lung cancer by age 75 years at radon concentrations of 0, 100, and 400 Becquerels per cubic metre (Bq m-³) in the home would be about 0.4%, 0.5%, and 0.7%, respectively, for lifelong non-smokers. However, for cigarette smokers the risks are about 25 times greater - 10%, 12% and 16%.
Reassuringly a major study of radon and childhood cancer has shown that there is no evidence of a link between levels of radon in homes and childhood cancer.