Time trends of organochlorine chemical residues in seven sedentary marine fish species from a Norwegian fjord during the period 1972-1982.

Abstract

The time trend in the DDT contamination of the marine environment in a Norwegian fjord where DDT has been used extensively in local fruitgrowing, has been studied for 10 years following the DDT ban. Residues of ∑-DDT (p,p′-DDT + 1.11p,p′-DDE + 1.11p,p′-TDE (DDD). The factor 1.11 is added to correct for the lower molecular weight) in 225 liver samples of seven sedentary fish species showed a downward trend during the period 1972 to 1982. The decrease in ∑-DDT illustrates the effectiveness of the 1970 ban on its use in Norway. The highest 1982 mean level of ∑-DDT was found in the liver of cod (Gadus morhua) (1237 μg/kg, wet weight, range 191–3845 μg/kg) and was about 1/3 of the corresponding 1972 residue level. The decrease of ∑-DDT was less rapid in the liver of the cod and the haddock (Melanogrammus aeglefinus) (half-life time 5.0 years with a 95% confidence limit of 2.3 years) than in the fish species sea scorpion (Myoxocephalus scorpius), cat fish (Anarhichas lupus), ballan wrasse (Labrus berggylta) and lemon sole (Microstomus kitt) (half-life time 2.6 years with a 95% confidence limit of 0.8 years). Cod and haddock have a substantially higher fat content in the liver compared to the other fish species. A half-life time of 3–5 years for biologically available DDT residues is suggested to apply generally to Nordic marine environments. Unmetabolized DDT constitute a smaller proportion of ∑-DDT in 1982 than in the previous years. However, a great variation between species and individuals was found. PCB contamination in the fish was low, and reflect a Norwegian baseline contamination. The highest 1982 mean level of PCB residues was found in cod liver (454 μg/kg, wet weight, range 175–1073 μg/kg) which was about 1/3 of the 1972 value. The levels of ∑-DDT and PCBs were correlated to fish weight in the cod. These two types of residues were mutually correlated over all weights. No correlation was found between the fat content of the liver and the residue level of organochlorine chemicals within the species. Only low levels of contamination by hexachlorobenzene (HCB), α-, γ-HCH and ∑-chlordane were found in 1982. The highest levels were found in cod liver (HCB 6–26; γ-HCH 6–16; α-HCH 4–140;∑-chlordane = oxychlordane + transnonachlor 38–220 μg/kg, wet weight). The levels of organochlorines in fish from a Norwegian fjord were generally low and not believed to have any toxicological implications.