Radon in Finland

Radon is a colourless and odourless noble gas that is present in the indoor air in buildings. Radon prevention in the construction phase is easier and less expensive than implementing mitigation measures afterwards. Radon-bearing air from the soil seeps into the building through openings and gaps in the base floor. Finland has higher indoor air radon concentrations than most other countries. This can be explained by geology, construction technology and the climate.

The average radon concentration in Finnish homes is approximately 94 becquerels per cubic metre (Bq/m3). This equals an annual radiation dose of approximately four millisieverts. 

According to the decree of the Ministry of Social Affairs and Health on ionising radiation, the reference level for indoor radon concentration in dwellings is 300 becquerels per cubic metre (Bq/m3) of air. The reference level for the design and construction of new buildings is 200 Bq/m3.

Radon (Rn-222) is a radioactive gas in the uranium series. Radon is produced from uranium (U-238) through a series of decay steps. The element preceding radon in the decay chain is radium (Ra-226). Radon further decays into a series of daughters; the final product is stable lead (Pb-206).

The uranium concentration in our granitic bedrock and soil is higher than the global average.  In Finland, the regions of Lahti, Eastern Uusimaa and Kymenlaakso have the highest uranium concentrations, while North Karelia, Kainuu and Northern Lapland have the lowest.

Moraines and sandy ridges that are very permeable and let the radon-bearing air easily move there. Therefore, in buildings built on ridges, radon concentrations are clearly higher compared with buildings in the same area that are built on other types of soil.

STUK recommends radon measurements in all areas in Finland, as high concentrations have been measured in all types of areas.

Between the sand, gravel and clay grains of soil there is air. The radon concentration of this air usually varies from 10,000 to 100,000 Bq/m3. In the worst areas, measured radon concentrations have exceeded one million becquerels per cubic metre.

Radon causes lung cancer

Prolonged exposure to high levels of radon significantly increases the risk of lung cancer. It is estimated that around 150 to 270 people in Finland develop lung cancer from radon each year. The current understanding is that radon does not cause any other health effects than lung cancer.

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Radon regulation of workplaces

The goal of radon regulation of workplaces is to prevent employees' excessive exposure of radon. Read more on the radon regulation at Radon at workplaces page.