Levels of organic tin compounds in Baltic sea and Finnish fresh water fish

The decision to launch an extensive study on the levels of organic tin compounds (OTC) in Finnish fresh water and sea fish was made when high levels of OTC were found in fish and in the sediment in connection with the construction project of the new harbour in Helsinki in 2005. The study focused on the fresh water and sea fish species that Finns mainly use as food. Samples were collected both in harbour and industrial areas with OTC contamination and in areas with no local contamination. OTC content in fresh water fish usually remained under 10 μg/kg fresh weight (fw), but contents measured in four municipalities (Varkaus, Lohja, Jyväskylä and Tampere) were 19–28 μg/kg. OTC content of as high as 35,000 μg/kg (dry weight) was measured in the sediment in Huruslahti Bay, Varkaus, at the depth of 2–6 cm. Sea fish showed OTC levels about ten times higher than fresh water areas. OTC content in fish was under 20 μg/kg fw in sea areas with no local contamination. Contents in contaminated areas exceeded 40 μg/kg. Contents of 150–500 μg/kg were found in severely contaminated areas. The highest OTC contents (28–528 μg/kg) were found in perch caught in Vanhankaupunginlahti Bay in Helsinki. In this case, both the length and weight of fish correlated with the OTC content. High OTC levels were also found in the Naantali Harbour where the level decreased rapidly when moving towards the open sea. The OTC levels in fish caught in the same area varied between different species. Levels found in perch, bream and pike-perch, the preferred habitats of which are in the archipelago and inland bays, were on average higher than levels found in herring, salmon and sprat, which live in the open sea. 
For additional information, please contact: Research professor Anja Hallikainen, tel. +358 20 77 24277, email anja.hallikainen@evira.fi