Radioactivity in drinking water

STUK monitors artificial radioactivity in drinking water to be able to assess the resulting radiation exposure. Water samples are normally collected twice a year, directly from tap water. 

Concentrations of cesium (Cs-137), strontium (Sr-90) and tritium (H-3) in drinking water have been monitored on a regular basis since 1999. At first, samples were collected from three, now from five cities (Helsinki, Turku, Tampere, Oulu and Rovaniemi). The H-3 concentrations in samples were below the detection limit, or 1.4 Bq/l, in 2013. Thus, they were well below the limit of 100 Bq/l specified for tritium in household water by the Council Directive  98/83/EC.  According to the directive, the indicative total dose in water intended for human use must not exceed the value 0.10 mSv/year. 

In a fallout situation, short-lived radioactive materials disappear from drinking water in a couple of weeks. Radioactive materials in particle form are eliminated in filtration. Activated carbon filtration eliminates iodine, so I-131 may disappear depending on the water treatment system. Some long-lived substances, such as Cs-137, are removed at the water supply plant during aluminium sulphate precipitation. Sr-90 in soluble form is more difficult to eliminate than Cs-137; it is not significantly eliminated during normal water treatment.

More information on radioactive substances in drinking water is available in the report STUK-A241, Cs-137, Sr-90 and H-3 in freshwater environment and derived transfer factors for estimations in a radiation emergency situation.

H-3, Sr-90 and Cs-137 concentrations (Bq/l) in drinking water in 2014 in Helsinki, Oulu, Rovaniemi, Tampere and Turku.

  Sample collected 3H, Bq/l 90Sr, Bq/l 137Cs, Bq/l
Helsinki 9.4.2014 <2 0,005 0,011
  13.10.2014 <2 0,005 0,013
Oulu 8.4.2014 <2 0,003 0,003
  13.10.2014 <2 0,003 0,003
Rovaniemi 7.4.2014 <2 <0,0001 <0,0002
  15.10.2014 1,3 0,0003 <0,0004
Tampere 10.4.2014 <2 0,003 0,002
  12.10.2014 <2 0,006 0,003
Turku 8.4.2014 <2 <0,0001 <0,0006
  13.10.2014 1,2 0,001 <0,0003


Share this page



  • Kaisa Vaaramaa / Senior Inspector
    Tel. +358975988521