The Nordic countries use slightly different methods to prevent radon harm

A report by Nordic-Nat (Nordic Working Group on Natural Ionizing Radiation) states that radon is an issue that poses a threat to health, especially in Finland, Norway and Sweden. These countries have similar concentrations of radon in indoor air of apartments and in drinking water. In Denmark, the situation is less problematic, and in Iceland the radon-active concentrations in both indoor air and drinking water are very low overall.

In Finland, the reference value for radon level in the design and construction of buildings is 200 becquerels per cubic metre of air (Bq/m ³⁾ and 300 Bq/m³ for existing buildings. If the radon level in indoor air exceeds these values, it is recommended to take corrective measures. In Denmark, the reference value is 100 Bq/m³ and in Sweden 200 Bq/m³. In Norway, the action level for radon is 100 Bq/m³ and the maximum allowed concentration is 200 Bq/m³.

There are also differences between the countries in the interpretation of the measurement results. In Finland and Norway, the measurement results are used to estimate the annual average radon level, which is then compared with the reference value. In other countries, the comparison is made directly with the measurement result. In Denmark and Sweden, the reference value is compared to the average of measurements carried out in the apartment, whereas in Norway the value only applies to measurements taken in the living room and bedroom.

Tuukka Turtiainen, Senior Inspector at the Radiation and Nuclear Safety Authority, says that the comparison of the different Nordic countries demonstrates that the differences in regulations and measurement methods are understandable and in accordance with the Basic Safety Standards Directive adopted by the European Union in 2013. 

“Finland has a higher reference value for radon in workplaces than other Nordic countries, but we carry out significantly more radon monitoring in workplaces than the other Nordic countries and actively organise random checks,” says Tuukka Turtiainen.

Significant differences in limit values for drinking water

Recommendations and requirements for drinking water quality also differ between the Nordic countries. The absolute quality requirements for radon levels imposed on waterworks are either 100 becquerels per litre (Bq/l) or 1,000 Bq/l. The quality target, on the other hand, is either below 100 or 300 Bq/l. There are no actual requirements for private wells, but the quality recommendations vary between 500 and 1,000 Bq/l. In Finland, the recommendations and requirements for drinking water are the most permissible among the Nordic countries.

Senior Inspector Tuukka Turtiainen says that one explanation for the differences is that the EU directive on the radioactivity of drinking water gives the maximum value a range of 100—1000 Bq/l. The current understanding is that radon in drinking water causes only a little radiation exposure to the digestive system. The lungs are the most exposed to radiation even in drinking water as radon is released from the water into the indoor air, such as in the shower, when washing laundry or in other water use. Turtiainen emphasises that the radiation exposure of most Finns is definitely from radon in indoor air.

Founded in 2016, Nordic-Nat’s (Nordic Working Group on Natural Ionizing Radiation) mission is to identify common challenges related to the monitoring of natural radiation, implement development projects and draw up joint position statements. The group offers a platform for exchanging experiences in order to promote monitoring work and communications. Collaboration also facilitates the efficient sharing of expensive laboratory resources. The members of the working group come from the radiation safety authorities of Finland (STUK), Sweden (SSM), Denmark (SSI), Iceland (GR) and Norway (DSA).