Radon gas – what it is, the health risks, measurement and action levels

Radon gas is produced during the radioactive decay of radium which comes from uranium. It is also referred to as Radon-222 and is often described as the daughter of the radioactive decay of radium.

It occurs naturally through the presence of uranium in most rocks, soils, bricks and concrete.

Radon gas itself does not present too serious a radiological hazard when breathed in and immediately exhaled.  The problem lies with the decay products – the radon daughters – which behave like solids and can attach themselves to dust and moisture in the atmosphere. These solids can take up residence in lungs and airways and emit alpha particles which are known to cause cell damage.

We all breathe in radon to some extent and it accounts for half of the radiation dosage each of us receives. It is not possible to see, hear, smell or taste radon gas.

Outdoors, radon disperses harmlessly into the air, but once it finds its way indoors, through gaps and cracks in floors and walls, it may build up to potentially harmful levels.

The amount of gas released varies greatly depending on where you live and is more likely to be found in areas where the geology features concentrations of granite and limestone.

How radon gets into buildings
Generally radon rises up through cracks in the earth and simply disperses into the atmosphere. Warm air inside a house draws the gas in through flooring and any gaps or cracks in the building structure. Underground radon can collect in caves and mines. High concentrations of radon can also accumulate in confined spaces such as basements.

Health risks
Health data from nine European countries confirms that domestic exposure to radon increases the risk of lung cancer. In the UK between 1000 and 2000 deaths each year are estimated to be caused by exposure to radon. Results based on a European wide epidemiological study showed that the risk from radon is approximately 25 times higher for cigarette smokers than for non-smokers.

Measurement and action levels
Radon is measured in Becquerels per cubic meter of air (Bq m3). The Health Protection Agency (HPA), a government department that protects UK public health, has set the UK Action Level for radon at 200 Bq m3. Most homes in the UK have radon of around 20 Bq m3. A map showing the percentage of homes at or above the Action Level of 200 Bq m3can be viewed here.

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