– We're among the world leaders in radon concentration

– This is due to both geological conditions, our climate and the way we build our homes, says senior adviser at the Department of Radiation Protection and Environment at the Norwegian Radiation and Nuclear Safety Authority, Maria Larsson.

Poses a significant health risk
With the cold comes the radioactive and harmful radon gas creeping in. The noble gas is formed in bedrock and can seep into buildings through cracks and gaps in the foundations. When we breathe in air containing radon, it causes irradiation of the lungs and airways, which over time can lead to lung cancer. It is estimated that radon in homes causes more than 400 cases of lung cancer annually in Norway. The risk increases with the radon concentration in the indoor air and with the amount of time spent in the building.
– The risk is greatest for those who actively smoke or have smoked. The risk from radon exposure is approximately 25 times greater for smokers than for people who have never smoked, says Larsson.
Radon in indoor air thus poses a significant health risk, and so naturally one wants radon levels to be as low as practically possible.
– The limit value for radon is 200 Bq/m³, and there is an action threshold of 100 Bq/m³, says Larsson.

Easy to get rid of?
We often talk about winter as the radon season, but Larsson explains that radon is present in the bedrock all year round.
– But when it is cold outside and buildings are heated, a negative pressure is created inside. Increased negative pressure in the building increases the influx of soil air and radon, says Larsson.
The good news is that it is often quite straightforward to get rid of radon gas once it has come inside the four walls of a building.
– There are good and effective measures. We divide them into three categories: sealing, pressure change in the ground (radon suction/well) and ventilation. Which type of measure, or combination of measures, is most appropriate must be assessed on a case-by-case basis, says Larsson.

She explains that the probability of measuring excessively high radon levels is often greater in older buildings than in new builds, as the Norwegian Building Regulations (TEK17) set requirements for preventive measures against radon.
– This entails a) a radon barrier against the ground and b) facilitation for pressure-reducing measures in the ground (radon suction/well) under the building, which can be activated when the radon concentration in the indoor air exceeds 100 Bq/m³, says Larsson.
She says that new builds should always be measured after they are taken into use, to ensure that the measures are working as intended. She refers to the website of the Norwegian Building Authority for more information:

https://www.dibk.no/regelverk/byggteknisk-forskrift-tek17/13/iii/13-5

Where do you find radon?
On this page: https://geo.ngu.no/kart/radon_mobil/ you will find a map showing where radon concentrations are highest in Norway. According to Larsson, however, one should not rely blindly on such a map.
– There is no specific radon belt in Norway. There are areas that are more exposed than others, but in this country there is potential for radon almost everywhere, she says, adding that indoor radon concentration is a combination of several different factors.
– In addition to geology, there are factors such as building technology, the technical condition of the building, climate, the use of the building and so on. Local variations can be large, and indoor radon levels in buildings in the same area can vary, even between neighbouring houses. A radon measurement is the only thing that can say anything definitive about the radon level in a single building.
– That is why we recommend that everyone measures radon, says Larsson.

How to measure radon: https://www.dsa.no/radon/slik-maler-du-radon