DDT contamination of fish and sediments from Lake Ørsjøen, Southern Norway: Comparison of data from 1975 and 1994

Long term DDT contamination is reported of a small lake which previously was recipient of the insecticide wastes from a plant nursery. 19 years after closing down of the outfall sum-DDT in perch and pike exceeds an assumed “high background level” by about 5–10 times. Gradient studies of sediments and perch indicated that deposits in the close vicinity of the former outfall still acted as a source for contamination of the more distant parts of the lake. Comparison with 1975 data nevertheless showed that DDT levels in fish had been reduced by about 90% and a rough estimate indicated a “half life” of DDT of 5–7 years.