Low organotin levels in lake fish
The most significant organic tin compound releases in terms of the environment originate from antifoulants used on ships and boats to inhibit the attachment of marine organisms. The suspected harmful effects of organic tin compounds include at least immunotoxicity. The National Food Agency has previously issued recommendations for eating fish. If warranted by the results of the research project, these recommendations will be reviewed also in this respect.
At the first stage, a total of 268 samples were collected. One fifth of them, or 55 samples, have now been analysed, so at this point the results are only indicative. The assessment of the results will continue after half of the samples have been analysed, or if the samples show high levels of OT compounds.
All in all, almost 800 sample fish will be collected in the research project. By August 2006, about 90% of the samples had been collected.
- Samples from sea areas: average levels were relatively low, with ca. 4 nanograms of tributyltin (TBT) per gram and ca. 4 ng of triphenyltin (TPhT) per gram of fresh weight. In previous studies, both TBT and TPhT have been found in levels several times higher than these in fish caught in contaminated sea areas.
- In lake areas that were expected to be free from contaminants, the levels of organotin compounds in fish were clearly lower than in fish from sea areas, with TBT in most cases below the determination limit (ca. 0.2 ng/g of fresh weight).
- TPhT has been found in all fish samples collected so far from lakes that have previously been assumed to be uncontaminated, but the levels were very low, in the range of 1 ng/g of fresh weight.
- The average levels of TBT in contaminated lake areas were ca. 2 ng/g and the levels of TPhT ca. 9 ng/g of fresh weight.
- In contaminated areas, the highest levels of TPhT were found in the vicinity of large cities (Jyväskylä, Tampere), typically 15 - 20 ng/g of fresh weight.
The fish samples are provided by the Finnish game and Fisheries Research Institute, and analysed by the National Public Health Institute. The collection of samples focuses on areas in which fish are caught for sale as human food. The samples have been collected according to the season of the various species. The selected areas include the most important fishing areas from the eastern Gulf of Finland to the Bothnian Bay, Lake Oulujärvi, and Tehinselkä in lake Päijänne. In sea areas samples are taken of 12 fish species: Baltic herring, spratt, salmon, burbot, pike-perch, perch, pike, flounder, whitefish, roach, bream, and vendace, as well as lamprey.
Inland lakes: burbot, bream, pike-perch, perch, pike, vendace, and whitefish, as well as signal crayfish. Farmed fish are also analysed.
In order to establish the sources of releases, perch samples were also collected from so-called problem areas near harbours, shipyards and certain industrial facilities, in both sea and lake areas.
Senior Officer Anja Hallikainen, Finnish Food Safety Authority Evira, tel. +358 (0) 50 386 8433