51 
Concentrations of man-made radioactivity 
in fish show generally decreasing trends, 
in agreement with trends in concentrations 
in seawater. Chernobyl-derived 137 Cs 
continued to be the most dominant man-made 
radionuclide in Baltic Sea fish. By the end of 
the reporting period, mean values of 1-10 Bq 
kg -1 wet weight were found in marine round 
fish (cod, herring, whiting) in various Baltic 
Sea basins, while the concentrations in pike 
were 10-25 Bq kg 1 wet weight on the Finnish 
coast. In marine flat fish (plaice, flounder, dab) 
slightly lower mean values were found than in 
marine round fish. 
The Baltic Sea has the highest concentrations 
of 137 Cs of any regional sea around the world, 
due to radioactive fallout from the Chernobyl 
accident. The Baltic Sea ranks third in the 
world with respect to 90 Sr in seawater, with 
only the Irish Sea and the Black Sea showing 
higher levels. Average concentrations of 137 Cs 
in fish from the Baltic Sea in 1990 were similar 
to those in the Irish Sea, about 4 times higher 
than in the Black Sea, and about 30 times 
higher than in the Mediterranean Sea. 
Radiation doses to humans from man-made 
radionuclides in the Baltic Sea are due mainly 
to ingestion of 137 Cs in fish. Doses from 3 H are 
lower by several orders of magnitude. During 
1999-2006 doses to members of the public 
from marine pathways have not exceeded an 
annual value of 0.02 mSv, which is well below 
the limit of 1 mSv for the general public set in 
the Basic Safety Standards of the European 
Council (EC 1996) and the IAEA (IAEA 1996). 
Concentrations of radioactive substances in 
the Baltic Sea are are not expected to cause 
harmful effects to wildlife in the foreseeable 
future. However, in line with international 
developments, the future work of HELCOM 
will continue to include assessments of the 
radiological risks to the environment from 
radioactive substances in the Baltic Sea. 
References 
EC (1996): Basic Safety Standards for the 
protection of the health of workers and the 
general public against the dangers arising 
from ionizing radiation. Council Directive 
96/29/EURATOM, European Council, 
Brussels. 
IAEA (1996): International Basic Safety 
Standards for Protection against 
Ionizing Radiation and for the Safety of 
Radiation sources, Safety Series No. 
115. International Atomic Energy Agency, 
Vienna. 
Baltic Sea Environment Proceedings No. 117