Environmental radiation Environmental radiation

Environmental radiation

Environmental radiation

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