Dangerous gas from underground

What is radon?

Radon is produced by the decay of uranium-238, which occurs naturally in Switzerland. This breakdown produces solid components like lead-214, which attach themselves to aerosols in the air. If inhaled, they irradiate the respiratory tract. "Radon is radioactive and was classed as 'definitely carcinogenic' by the International Agency for Research on Cancer in 1987. It is the main cause of lung cancer after smoking," Joëlle Goyette Pernot explains.

Does radon occur throughout Switzerland?

Radon seeps out of the ground and "all of Switzerland must be regarded as an at-risk area", our expert warns. The federal government has therefore created an interactive radon map on which you can check the risk at every location yourself. Buildings in the Alps and the Jura are particularly affected, although high levels can also be found on the Central Plateau.

This is partly due to geology, but also to our country's glacial history. The granite massifs found in Valais, Ticino and Grisons are rich in uranium-238. In addition, our glaciers have dragged moraines containing uranium-238 everywhere. For this reason, radon can also be found in varying quantities on the Central Plateau and in the Jura Arc.

How does radon get into homes?

It penetrates through leaks on the ground floor, such as clay cellars or cracked floor slabs. Once the gas has got into a building, it easily rises to the upper floors via open stairwells or laundry shafts. "However, radon dilutes in the air and its concentration decreases the higher it gets," the expert says.

How can you detect radon exposure?

"Radon is odourless and colourless and doesn't cause symptoms like headaches. The only way to detect it is through measurement," Joëlle Goyette Pernot says. This can be done using small devices known as dosimeters, which are typically placed in various places in the home for a year. Each dosimeter costs about CHF 100.

What level of exposure presents a risk?

The Radiation Protection Ordinance of 2017 set the reference value for buildings at 300 Becquerel per cubic metre. Anything above this concentration requires intervention. After all, living in a flat that exceeds this value for many years is hazardous to health. "However, there is no value below which there is no risk whatsoever," the expert adds. The FOPH therefore recommends keeping radon levels as low as possible in rooms that are used regularly (i.e. for at least 15 hours a week).

Does airing suffice to lower radon exposure in the home?

Ventilation is a temporary emergency measure that is effective in the short term. However, once the window is closed again, radon concentrations return to the same level within a few hours.

How can radon be eliminated permanently?

"You can, for example, install a self-closing, airtight cellar door or lay a drainage system below the foundations to extract radon-containing soil air and discharge it via the roof," Joëlle Goyette Pernot explains. As every house is unique, the best solution varies from case to case.

Is decontamination absolutely necessary?

With the exception of kindergartens and compulsory schools, there's no obligation to decontaminate buildings. There are only recommendations.