I have often wondered why some people develop lung cancer when they have not smoked even one cigarette.

It has been suggested that it may be from 'passive smoking'.

However, I wonder, could it be the result of a silent killer - Radon?

Radon is a natural radioactive gas. You cannot see, hear, feel or taste it. It comes from the minute amounts of uranium that occur naturally in all rocks and soils.

Research has found that domestic exposure to radon gas is responsible for a significant number of lung cancer deaths, both in smokers and non-smokers.

The risk appears to be much higher for smokers, who have about 25 times the risk of developing lung cancer than those who do not smoke.

Radon gas from natural sources can accumulate in buildings and reportedly causes 21,000 lung cancer deaths per year in the United States alone. In the UK the figure is about 1,000 per year.

Radon is present in all parts of the UK, although the gas disperses outdoors so levels are generally very low.

However, geological conditions in certain areas can lead to higher than average levels. Some of the highest radon levels have been found in the southwest,particularly Cornwall. But levels well above average have been found in some other parts of the UK.

You can find a map of the incidence of ground Radon in England and Wales at:

http://www.hpa.org.uk/radiation/radon/radon_maps/index.htm

Radon seeps into your house from the earth beneath.

What can you do about it - apart from move?

High radon levels in existing houses can usually be reduced by changes to the ventilation system, such as improving underfloor air bricks and extracting radon from beneath the building with a fan, although this can cost up to £1,000 to install and £50 per year to run.

When constructing new buildings, however, low concentrations can usually be achieved by enhancing the damp-proof membrane across the full footprint of the building, at an extra cost of only around £100.

The only reliable guide to the level of radon in a building is a measurement over a period long enough to average out short term variations in radon levels - this should ideally be three months. The procedure recommended by the HPA is to use passive monitors as they are reliable, simple to use and can be sent by post. The individual result for each home is confidential and will not be given to anyone else without the prior consent of the householder at the time of the measurement. This service is available to any householder in the UK at a cost of £39.95 (including VAT). This includes the supply of two radon detectors, their subsequent analysis and the reporting of the result. All packaging and return postage are also included.

Go to: http://www.hpa.org.uk/radiation/services/radon/home.htm