Perch from Helsinki’s Vanhankaupunginlahti have highest tin content of all fish in Finland

Levels as high as in the Elbe in the 1990s

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Extremely high levels of organic tin have been measured in perch caught from Helsinki’s Vanhankaupunginlahti, a bay in the northern part of the capital.
      According to a survey organised by the Finnish Food Safety Authority Evira, the bay has the highest level of tin pollution of all of Finland’s sea areas and lakes.
      Tin compounds have been used, among other things, in paints covering the hulls of ships and boats to prevent the growth of algae and microbes.
      Research professor Anja Hallikainen of Evira compares the discovered toxin contents to those measured in the 1990s from bream living in the Elbe River, the water of which was polluted by German industrial plants.
     
Already last year Evira recommended that people avoid excessive consumption of perch from the Vanhankaupunginlahti bay. The recommendation was given after the high tin compound concentrations were first discovered.
      According to European Food Safety Authority recommendations, a person weighing 60 kilograms should not be exposed to more than 15 micrograms of such compounds per day. In the bay perch, accumulations of 181 micrograms of tin compounds per kilogram have been measured.
      “In other words, a hundred grams of perch a day already exceeds the ill-effect limit”, Hallikainen describes.
      The highest concentrations noted were in excess of 500 milligrams per kilogram. Such high toxin contents were typically found in old and large fish.
     
The researchers also examined zander (pike-perch, Sander lucioperca) and roach. In these fish the concentrations were significantly lower.
      The differences between the various species of fish are explained by their living environments. The contents are lower with the fish that typically thrive further out, away from the harbours. The Baltic herring and salmon, which live in the open sea, typically accumulate dioxins and PCBs (polychlorinated biphenyls), but hardly any tin compounds.
     
The organic tin compounds are suspected of weakening the human body’s immune system, among other things.
      Acting department head Hannu Komulainen from the National Public Health Institute says that in animal tests exposure to tin compounds increased the risk of infections and possibly lowered fertility. For the fish themselves, the compounds cause disturbances in their hormonal action.
      “There is no absolute evidence, though, of the tin compounds from eaten fish having caused health hazards to people. If one consumes fish normally, one should be able to avoid the risks”, Komulainen says.
      At the beginning of the year the use of hull paint containing tin compounds was forbidden altogether in vessels registered in the European Union.
      It is not thought likely that the ban will have any immediate marked effect on concentrations. As Jaakko Mannio of the Finnish Environment Institute pointed out, seals in the Baltic Sea are still having reproductive problems even though PCBs and DDT were put on the banned list over a decade ago.


Previously in HS International Edition:
  Baltic Sea panel calls for tighter emission restrictions (19.5.2008)
  Pike, Baltic salmon and herring to be eaten in moderation (29.4.2004)

See also:
  Finland considers more intensive fishing to reduce dioxins in Baltic Sea fish (4.8.2008)

Links:
  Finnish Food Safety Authority (EVIRA): Organic tin compounds in Finnish fresh and saltwater fish
  European Food Safety Authority

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