[Polychlorinated biphenyls: determination of individual components in raw milk and contaminated fodder].

Since 1980, 2145 samples of raw milk from producers in the district of Freiburg have been analysed for polychlorinated biphenyls (PCB) during a monitoring programme. In 1983, we started to search for the source of PCB, whenever milk was contaminated above the average value (above 0.2 mg/kg fat, calculated as Clophen A60). In 7 cases, previous coats of paint in the silos proved to be the cause of the PCB contamination. Five samples of milk and 4 corresponding silages as well as 1 sample of wood (from a cowshed) were investigated for all of the individual PCB components included in the technical mixtures of Clophen A30 and A60. Two samples of silages contained both low and high chlorinated biphenyls, whereas low chlorinated biphenyls (di-, tri-, and tetrachlorinated biphenyls) were not detected in the corresponding milk samples. Pentachlorinated biphenyls were only detected in the range of 1%-2%. In the samples of wood and corresponding milk, a different PCB pattern appeared. There were remarkably high percentages of hepta- and octachlorinated biphenyls as well as a lower percentage of hexachlorinated biphenyls. The exact PCB content of the milk, determined by the addition of all single components, proved to be approximately half the value obtained by the usual calculation based on the evaluation of the three main peaks of the technical PCB mixture (Clophen A60). During 1984-1987, 607 samples of raw milk were analysed for six single PCB components, for which legal tolerance levels became valid in 1988.(ABSTRACT TRUNCATED AT 250 WORDS)