Working Report, 11/2006 – Radioactive isotopes in Danish drinking water

Radioactive isotopes in Danish drinking water

1 Background

Shortly before the revision of the 1980 European Council Directive for drinking water finished in 1998, a set of parameters on radioactivity was introduced. The parameters for radioactivity included tritium and Total Indicative Dose (TID). The Directive requirements on radioactivity are that the concentration of tritium in drinking water does not exceed 100 Bq/l and that the TID does not exceed 0.1 millisievert (mSv) per year. The TID is the sum of radiation doses from radioactive isotopes present in the drinking water excluding tritium, potassium-40, radon and radon decay products. The TID cannot be measured by a single method. To overcome this problem additional parameters and measuring principles were needed.

During the following years the EU Commission introduced proposals for monitoring the TID in the Article 12 Committee, elected to update the Drinking Water Directive for sampling and monitoring purposes. These changes of the Directive were used for the present investigation. Because the work on radioactivity was still under way in the Article 12 Committee when the Danish Statutory Order transferred the Drinking Water Directive into Danish regulation, the Order did not require monitoring of the TID by the water works. Instead it is stated in the Order that investigation of the TID is carried out by the Danish Environmental Protection Agency.

The present investigation of radioactivity in Danish drinking waters is the result of the work the Danish Environmental Protection Agency has carried out to meet this obligation. The investigation took place during 2001-2003 and has included investigation of nearly 300 water works and single wells.