Our bodies are constantly exposed to radiation from a variety of natural sources. This natural background radiation is in the food we eat, it is in the soil, and reaches us from the stars via cosmic rays.

But the single biggest source of radiation in our lives is radon gas, which seeps into people’s homes from radioactive rocks buried deep underground.

A man test for radon

A test will establish the concentration of radon in the home

For most UK residents, radon will account for a half of their total annual radiation dosage.

Even so, this represents very little risk: the dosage is well within the safety limits set by the International Committee on Radiological Protection. But in some parts of the country radon levels are raised because of the local geological conditions.

It has been estimated that 50,000 people in Cornwall, Northamptonshire, Derbyshire and Scotland have higher than average concentrations of radon in their homes.

Lung cancer

Radon is seen as a silent threat: you cannot see, hear, feel or taste it. It is formed when atoms of uranium-238 decay. Radon will also decay, and, if it is inhaled, will emit alpha particles that can damage the internal lung surfaces.

A man closes a vent

Special vents can be built for radon

The alpha radiation dislodges the electrons that hold DNA together. This can trigger a series of chemical changes in the body that lead to cancer. Although the human cells are very good at repairing this damage, they cannot cope with high doses of radiation.

The radon concentration in the average UK home is about 20 becquerels per cubic metre. Action to deal with the problem is recommended when the concentration reaches 200 becquerels per cubic metre.

The most effective way to deal with radon is to fit an air pump to a property to vent the gas into the atmosphere. The pumps costs a few hundred pounds and are covered by local council grant schemes.

The dangers of radon became very apparent after World War Two when large uranium mines were opened around the world to feed the nuclear industry. Miners became exposed to high levels of radon and suffered increased rates of lung cancer.

In the big mines in the USA, the lung complaints caused by radon were referred to as “mountain sickness”.