Radioactivity in drinking water

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 (in Finnish) (Julkari.fi).

H-3, Sr-90 and Cs-137 concentrations (Bq/l) in drinking water in 2018 in Helsinki, Oulu, Rovaniemi, Tampere and Turku. The Sr-90 and Cs-137 concentrations in all samples were low in 2018. The H-3 levels in the samples were below detection limit (less than 0.94 Bq/l), and thereby significantly below the maximum value of 100 Bq/l for H-3 under the Council Directive (98/83/EC) and Decree of the Ministry of Social Affairs and Health (1352/2015).

 

Date of sampling

3H, Bq/l

90Sr, Bq/l

137Cs, Bq/l

Helsinki

3.10.2018

<0,94

0,0045

0,012

Oulu

1.10.2018

<0,94

0,0030

0,0018

Rovaniemi

10.10.2018

<0,94

0,0002

<0,0002

Tampere

10.10.2018

<0,94

0,0039

0,0026

Turku

2.10.2018

<0,94

<0,0001

<0,0004

 

Contact

Contact

  • Kaisa Vaaramaa / Head of Laboratory
    Tel. +358975988521