Radioactivity of household water

Artificial radioactivity in household water intended for human consumption is monitored in order to assess the internal radiation exposure of humans caused by household water.

The cesium-137 (Cs-137) and strontium-90 (Sr-90) concentrations in drinking water mainly originate from the Chernobyl fallout and the tritium (H-3) concentrations from nuclear weapon tests carried out in the atmosphere. The man-made radioactive materials analyzed from samples as part of the monitoring programme are usually present only in household water sourced from surface waters. A more significant radiation exposure in Finland is caused by naturally occurring radioactive materials in household water. The maximum concentrations of them in the water distributed by waterworks are restricted by Decree of the Ministry of Social Affairs and Health (1352/2015). The Decree Relating to the Quality and Monitoring of Water Intended for Human Consumption was amended by the amending Regulation 683/2017.

The household water samples are taken once a year, alternating in spring/autumn. The samples are taken from the tap water of Oulu, Rovaniemi, Tampere, Turku and Vantaa. The sample of the Helsinki Metropolitan Area was taken from Helsinki until 2021.

The Sr-90 and Cs-137 concentrations in all samples were low in 2023. In 2023, the H-3 concentrations were between 1.2 and 1.5 Bq/l or below the limit of quantification. In all years, the concentrations were below the maximum value for H-3 in household water, i.e. 100 Bq/l, set in the Council of Europe Directive (98/83/EC) and in the Decree of the Ministry of Social Affairs and Health (1352/2015).

The variation in radionuclides between localities are due to both differences in the level of Chernobyl fallout in the region as well as the amounts of surface and ground water used as raw water. The raw water in Tampere consists of both surface and ground water. In Rovaniemi, only ground water is used. In the Helsinki Metropolitan Area and Oulu, drinking water is almost exclusively surface water. Since autumn 2012, drinking water in Turku has been sourced from artificial recharge. Raw water consists of both surface and ground water. In Rovaniemi, only ground water is used. In the Helsinki Metropolitan Area and Oulu, drinking water is almost exclusively surface water. Since autumn 2012, the drinking water in Turku has been sourced from artificial recharge.

Activity concentrations of Cs-137, Sr-90 and H-3 in drinking water samples in 2023 (Bq/l)