IN SHORT
Both natural and artificial radioactive substances are present in the sea.
Radioactive substances can be transported by ocean currents over long distances.
Low levels of artificial radioactivity in the sea
Levels of radioactive contamination in marine fish and shellfish are generally very low. This also applies to caesium-137, which is one of the most problematic artificial radioactive substances in the environment. This is partly because the contamination is diluted in these large bodies of water, but also because the salt (potassium) content of the sea causes the animals to absorb less radioactive caesium from the environment. Along the coast and in fjords, the levels may be slightly higher than in the open sea.
Radioactive substances can be transported by ocean currents, and spread over large distances.
The DSA monitors levels of radioactive substances in seawater, sediment and living organisms, and takes part in research expeditions with the Institute of Marine Research every year. Although the levels of radioactive substances in seafood are low, it is important to document the situation and monitor the trends in Norwegian waters, also considering that fish are an important export industry.
The graph below shows caesium-137 concentrations (Bq/kg fresh weight) in Atlantic cod in the Barents Sea and in two coastal areas in Northern Norway (near Finnmark and in Vestfjorden).
Click on the blue arrows to make the picture larger.
Sources of radioactive contamination
The largest sources of radioactive contamination in the sea are the Chernobyl accident in 1986, the atmospheric nuclear tests of the 1950s and 60s and releases from reprocessing plants for spent nuclear fuel in Europe (such as Sellafield in the UK and La Hague in France).
Along the Norwegian coast, ocean currents mainly go north, carrying contamination from the Baltic Sea and Europe. Outflows from the Baltic Sea, which was particularly contaminated after Chernobyl, still affect the level of caesium-137 in our waters. In the 1990s, the Sellafield plant in the UK increased its releases of the radioactive substance technetium-99, and we saw an increase in Norwegian seas. The radioactive releases have recently decreased, and the levels in seawater are low.
Human activities that lead to increased concentrations of naturally occurring radioactive substances are also classed as radioactive contamination. One such example is radium-226 and radium-228 released in connection with offshore petroleum extraction. This requires permission from the DSA, and the companies report their releases.
There are also potential future sources of radioactive contamination in our vicinity, including the sunken Soviet nuclear submarine Komsomolets, which went down in 1989 southwest of Bjørnøya. The submarine is located at a depth of 1700 metres, and samples of sediment and seawater are taken nearby each year to investigate the situation and look for possible leaks of radioactive material.
Natural radioactivity in the sea
Natural radioactive substances have always been present in the sea, and originate mainly from the earth’s crust. The substance that usually contributes the most to the radiation dose from seafood is polonium-210. Levels of this substance are often somewhat higher in seafood than in food produced on land, but they vary widely between species. The DSA is working to survey the levels in the species of fish and shellfish that are commonly consumed in Norway.
Further reading:
- Institute of Marine Research: Radioactive substances in Norwegian farmed Atlantic salmon (pdf)
DSA-info 2:2021 Kan vi skille mellom forskjellige kilder til naturlig forekommende radioaktive stoffer i det marine miljø Teknisk dokument 15 Iodine-131 and other medical radioisotopes in Fucus vesiculous in the marine environment around Tromsøya and in sewage from the University Hospital of Tromsø DSA-rapport 04:2020 Radioactivity in the Marine Environment 2015, 2016 and 2017 StrålevernInfo 7:2018 No leakage from the sunken submarine K-159 StrålevernRapport 10:2017 Radioaktivitet i norsk mat StrålevernRapport 2017:13 Radioactivity in the Marine Environment 2012, 2013 and 2014 StrålevernInfo 5:2017 Joint Norwegian-Russian monitoring of radioactive contamination in Barent Sea area 2017 Teknisk dokument 12 Radionuklider i kommersielt høstede dyreplanktonarter fra Arktis og Antarktis StrålevernRapport 2015:3 Radioactivity in the Marine Environment 2011 StrålevernRapport 2012:10 Radioactivity in the Marine Environment 2010 StrålevernRapport 2011:4 Radioactivity in the Marine Environment 2008 and 2009 StrålevernRapport 2009:15 Radioactivity in the Marine Environment 2007 StrålevernRapport 2008:14 Radioactivity in the Marine Environment 2006 StrålevernRapport 2007:10 Radioactivity in the Marine Environment 2005 StrålevernRapport 2006:14 Radioactivity in the Marine Environment 2004 StrålevernRapport 2005:20 Radioactivity in the Marine Environment 2003 StrålevernRapport 2004:10 Radioactivity in the Marine Environment 2002 StrålevernRapport 2004:2 Radiological Environment of Svalbard StrålevernRapport 2003:8 Radioactivity in the Marine Environment 2000 and 2001 StrålevernRapport 2001:9 Radioactivity in the Marine Environment 1999 StrålevernRapport 2000:1 Artificial radionuclides North Europa Marine Environment 1995 StrålevernRapport 2000:7 Radioaktiv forurensing i marint miljø: 99Tc sjøvann/biota 98-99 StrålevernRapport 1999:6 Radioactive contamination in the marine environment (96-98) StrålevernRapport 1998:3 Tc-99 contamination North Sea/Costal areas 1996-97 StrålevernRapport 1997:3 Radioactive contamination in the marine environment (1995) StrålevernRapport 1995:1 Radioactive contamination in the marine environment (1993-94) Please contact us if you would like to have access to the publications that are not available online.Reports from the Norwegian Marine Monitoring Programme RAME