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Radon is invisible, odourless and can only be detected with a special air sampling kit. It decays naturally to inhalable radioactive dust which can damage the lungs and cause cancer. Radon can affect both domestic and workplace premises. There are several approaches to reducing its concentration to a safe level.

Frequently Asked Questions

Radon is a chemical element, formed by the radioactive decay of uranium which occurs naturally in all rocks and soils. Radon exists as a colourless, odourless gas. It is itself radioactive, like the uranium it comes from. Radioactive elements decay into elements of lower atomic weight, emitting radiation as they do so. There are three forms of radiation emitted by radioactive decay of elements: alpha particles, beta particles and gamma radiation. The first two are, as the name suggests, particles of matter, while gamma radiation is part of the electromagnetic spectrum, which also includes visible light, radio waves and ultraviolet radiation.

Radon is everywhere. Outdoors, levels are low because they are diluted by the air. Indoors, higher levels may build up depending upon the area you are in, and the way the building has been constructed. The highest levels of radon tend to occur in underground spaces such as caves, mines and basements. The Health Protection Agency and the British Geological Survey have compiled a free map of England and Wales which shows areas where higher levels of radon are likely. In the least affected areas, the risk of having a higher level of radon in a building is less than one in 100. In the most affected areas, this risk rises to higher than one in three. Any type of building – home, office or school – may be affected by a high level of radon. However, just because you live or work in a radon affected area, it does not necessarily follow that you are exposed to a high level of the element. The South West and parts of Wales and Scotland tend to have the highest levels of radon.

Radon levels are measured in Becquerels (Bq) per cubic metre. The Bq is a unit of radioactive emission and 1 Bq is one radioactive disintegration per second. The more radon there is in a building, the greater the number of Bqs emitted. In the UK, the average level of radon is around 20 Bqs per cubic metre. Levels below 100 Bq per cubic metre are not thought to pose any particular health risk. For levels above 200 Bq per cubic metre, the Health Protection Agency advises taking action to reduce levels.

The HPA recommends that anyone living or working in a radon-affected area should have radon levels measured in their building. The test kit, available from UK Radon, consists of two detectors, one each for the two busiest rooms of the building (i.e Bedroom and Living room) which are posted to the tester. The detector consists of a film which respond to the presence of alpha particles. The kit is returned after three months for analysis and the results are posted to the tester. It is advised that another test should be taken if corrective work is carried out, to see whether the work has been successful in reducing radon levels

Studies of the health of uranium miners who (if not protected) would be exposed to high radon levels have shown a link with lung cancer. Research funded by Cancer Research UK and the European Commission also shows that the presence of radon in the home increases the risk of lung cancer. It is estimated that radon causes around 1,100 deaths from lung cancer every year in the UK, half of which occur in people who smoke. A smoker's risk from radon is 25 times that of a non-smoker. To put this into context, the total annual number of deaths from lung cancer in the UK every year is about 35,000. A non-smoker living in a building where the radon level is 20 Bq per cubic metre has a one in 200 chance of developing lung cancer, while the risk is as high as one in three for a smoker living in a building where radon levels are 800 Bq per cubic metre. There is no evidence that radon causes any other type of cancer or any other health risk.

It is not the radon gas itself which poses the health risk; when the gas is breathed in, it is breathed straight out again, without doing any particular damage. But the radioactive decay products of radon, which are themselves radioactive, behave more like particles, attaching themselves to dust particles or water droplets in the air. These radioactive particles are inhaled and the radiation they emit causes damage to lung tissue which sets the scene for cancer. All three forms of radiation pose a cancer risk.

Everyone is exposed to a certain (usually low) level of exposure to radiation, of which around 84% is naturally-occurring, with the rest coming from sources such as medical applications (14%) and tiny amounts from nuclear fallout and occupational exposures. At the average radon level of 20 Bq per cubic metre, radon accounts for around 50% of total radiation exposure. Higher levels – i.e in affected areas – push this percentage up considerably.

An employer has a legal duty to protect the health and safety of staff and this means, first of all, testing workplace premises that are in one of the UK's radon affected areas. The employer must take action if the level exceeds 400 Bq per cubic metre (it would be responsible to take action if it exceeded 200 Bq per cubic metre). The Health Protection Agency recommends a five-point plan to employers in an affected area, namely:

  1.  Test for radon on the ground floor and in any occupied basements 
  2.  Continue monitoring during and after any remediation work 
  3.  Do a risk assessment based on radon levels 
  4.  Complete your remedial work within 6 months 
  5.  Continue with periodic testing and routine checks 
  6.  Staff members have a right to be informed of their radon exposure risk

The aim should be to prevent radon from entering the building. It is not a pollutant like a house dust mite or mould, which can be removed once it is inside. The main methods used for radon reduction are:

  • Radon sump. A sump is a pit or hollow fitted with a fan which is used under a solid floor to remove radon seeping in from the ground beneath. 
  • Underfloor ventilation. Ventilation of space beneath the ground floor of a building can stop radon building up inside. 
  • Positive ventilation. A fan blows fresh air from the roof space into the house, stopping radon from being sucked up from below. 
  • Active under-floor ventilation. A fan is used to either blow air into or extract air from a space beneath the ground floor.

The method chosen depends upon how the building is designed and constructed.