Monitoring and asssessment of radioactive substances in marine organisms

Lead Institute FI Institute of Fisheries Ecology

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Measuring task as a Federal Coordinating Office according to §4 Abs. 1 IMIS Competence Act (IMIS-Zuständigkeitsverordnung) connected with § 161 paragraph 1 number 1 letter c Federal Radiation Protection Act (Strahlenschutzgesetz)

The Thünen-Institute of Fisheries Ecology is the national competent authority for survey and assessment of radioactive substances in marine organisms in the North and Baltic Sea including coastal waters and the continental shelf according to §4 paraph Abs. 1 IMIS Competence Act (IMIS-Zuständigkeitsverordnung) in connection with §161 Radiation Protection Act.

Background and Objective

Germany established a network for monitoring and assessment of radioactive substances in the environment after ratification of the EURATOM treaty in 1957. This task was fulfilled by setting up an isotope laboratory and establishment of methods for analysis of marine organisms in an ancestor of the Thünen Institute of Fisheries Ecology in 1959. The monitoring of alpha- beta and gamma emitters in selected encironmental media was restructured and implemented in the Precautionary Radiation Protection Act and its by-law in 1986. Since then, the Thünen-Institue of Fisheries Ecology and its ancestor is speciefied as Federal coordinating office for fish and fishery products, crustacean, shell fish and aquatic plants.

Our Research Questions

Are and to which extent are aquatic organisms in the North and the Baltic Sea contaminated with radioactive substances?
Are there differences in the extent and do regional trends of the contamination exist?
Bestehen zeitliche Trends bezüglich der Kontaminationshöhe?
Is it possible to identify the source of the contamination?
Are risks emerging for aquatic organisms or humans emerging from the contamination?

Preliminary Results

Marine organisms always contain a mixture of natural and artufucial radioactive substances. This means that around 100 Bq/kg fresh weight (FW) of the natural radionuclide Patassium-40 (K-40) are included in fish. Potassium is required as essential trace element for metabolic processes. The long-lived isotope caesium-137 (Cs-137) is a marker for artificial radionuclides. This compound is comparingly easy to measure and due to its long halflife of around30 years and therefore a good marker for monitoring and assessment of a contamination with artificial radioactive.

The distribution of Cs-137 in fish of the Baltic and the North Sea differs significantly.

Whereas in fish of North Sea actually a mean of 0,1 Bq/kg FW are determined, the specific activity in fish of the western Baltic Sea (Kiel bight to Rügen) is around 1,5 Bq/kg FW; the values are increasing in easterly direction.

Since the beginning of our date series in year 1985, the Cs-137 in fish oft he North Sea increased from 2 Bq/kg FW to 3 Bq/kg FW and afterwards declined continously. A similar effect was observed for the Baltic Sea, but at a higher level: The Cs-137 activity increased from 4 Bq/kg FW in 1985, increased to a mean of 12 Bq/kg FW, but decreased afterwards to a mean of 1,5 Bq/kg FW.

The sources of the Cs-137 are mostly known. A part of the contamination of both seas originate from the Global Fallout from atmospheric nuclear weapons testing in the 1950ies and 1960ies.The North Sea was additionally affected by long-distance transport of releases from the European nuclear reprocessing plants for nuclear fuel in Sellafield, UK, and La Hague, France. Although the emissions of both installations ,significantly decreased since the beginning of the 1980ies, the Caesium bound to sediments in times of higher emissions is released, now.

The interim highly increased specific activities of Cs-137 in both seas originate from the accident in the Chernobyl nuclear power plant in year 1986. While around 5% of the releases came down as fallout in region of the eastern Baltic, the North Sea was minor affected. Through the lower water exchange oft he Baltic Sea compared to the North Sea, radioactive substances are diluted to a smaller extent resulting in a slower decrease of concentrations in water and fish.

For assessment of hazards to human and marine organisms from radioactive substances, radiation doses are calculated from measured values of specific activities and compared with guidelines and maximum permitted levels.

This examination leads tot he conclusion that doses from artificial radionuclides in the western Baltic Sea have always been below the maximum permitted levels and are nowadays even below the exemption criterion of annually 10µSv (humans) or 10µGy (other organisms). In comparison: the mean annual radiation dose from natural and artificial sources to a German resident is 2000µSv, each. Therefore, considering the actual state of research, no risk existed or exists to humans and marine organisms from radioactive substances in fish in the German exclusive economic zone.

All results mentioned above include those of measurement facilities oft he federal states and are published in the annual reports „Environmental radioactivity and radioation exposure" (in German, Summary in English) des BMUV veröffentlicht. Additionally, the assessments are published on a three-annual basis on the series „Reports of the Federal coordinating offices for surveillance of environmental radioactivity“ (in German), which additionally highlight actual topics. Furthermore, the data are important for the assessment of the status of the marine enviroment; Cs-137 is an indicator fort he assessment of the EU Marine Strategy Framwork Directive and therefore part of the reports to the European Commission (in German). Our data are also reported to the international marine protection conventions HELCOM and OSPAR and we are involved in the large-scale assessments (actually HELCOM BSEP 151).