CONGENER-SPECIFIC EXPOSURE OF GREY SEAL (HALICHOERUS-GRYPUS) PUPS TO CHLORINATED BIPHENYLS DURING LACTATION

We determined total and daily exposure of young grey seals (Halichoeru s grypus) to 25 chlorinated biphenyl (CB) congeners in their mothers' milk at the Isle of May, Scotland, in 1990, 1991, and 1992. Total expo sure for 36 pups born to 13 different females varied between 8.8 and 5 8.9 mg, IUPAC congeners CB-153 and CB-138 were the dominant components in milk, accounting for 42.1% of total CB exposure. The quantity of m ilk consumed by pups each day and the lipid content of that milk incre ased during lactation. As a result, daily exposure to CBs increased sh arply in the first half of the 18-day lactation period. There were sig nificant among-female differences in milk CB concentrations and in the relative contribution of individual congeners to total CB exposure. W hen the effects of among-female variation were removed, there were sig nificant changes in concentrations of less chlorinated CBs during lact ation and among years. A grey seal pup's exposure to CBs can be accura tely estimated from its mother's identity, its mass at weaning, and th e CB concentration in a single milk sample taken towards the end of la ctation.