Contribution of coplanar and non-coplanar polychlorinated biphenyls to the toxic equivalence of grey seal (Halichoerus grypus) milk.

We measured the concentration of coplanar polychlorinated biphenyl (PCB) congeners #77, #126 and #169 in the milk of 21 individual grey seals (Halichoerus grypus) from the same Scottish colony. Using the toxic equivalency factors (TEFs) of Ahlborg et al. (1994) we found TEQs ranged between 8.4 and 45.7 pg/g, with a mean of 22.3 +/- 9.3 pg/g on a lipid weight basis (n = 32). For some samples we also had concentrations of mono-ortho and di-orthochlorinated PCBs. Inclusion of these congeners approximately doubled the TEQ. There was a good correlation between the concentration of non-ortho PCBs and that of other congeners in the same sample.